Index: E2-E3 Consumer Mobility Index

E2-E3 Consumer Mobility Index
INDEX
1 CELLULAR CONCEPT, GSM ARCHITECTURE AND GSM RADIO ...... 2
2 MAINTENANCE ISSUES OF BTS, NODE-B, AND E-NODE-B ................. 23
3 3G RADIO NETWORK .................................................................................... 31
4 3G CORE NETWORK ...................................................................................... 43
5 3G CALL PROCESSING (VOICE AND DATA) ........................................... 49
6 3G RADIO NETWORK OPTIMIZATION .................................................... 61
7 BACKHAUL MEDIA FOR MOBILE RADIO NETWORK (OFC/ OFC

SYSTEMS/ MINI LINK) AND RRH ............................................................... 68
8 HSPA,HSPA+ AND MIGRATION TO 4G (REL5 TO REL8)....................... 78
9 4G AND 5G NETWORK ARCHITECTURE ................................................. 90
10 KPI REPORTS FOR 2G/3G/4G ..................................................................... 107
11 CONCEPT OF SON ......................................................................................... 132
12 NETWORK OPTIMIZATION USING DTT REPORTS AND SON DATA

MANAGEMENT .............................................................................................. 151
13 SITE PLANNING, RELOCATION AND RRH ............................................ 163
E2-E3 CM Version 3.0 April 2021 Page 1 of 174

For Restricted Circulation
E2-E3 Consumer Mobility Cellular Concept, GSM Architecture and GSM Radio
1 CELLULAR CONCEPT, GSM ARCHITECTURE AND

GSM RADIO
1.1 LEARNING OBJECTIVE

After completion of this chapter participant will able to understand about:
 Cellular Concept
 Cells, Cluster, Concept of frequency reuse
 Types of Cell
 GSM Architecture
 GSM Radio
1.2 CELLULAR CONCEPT

Traditional mobile service was structured similar to television broadcasting. One
very powerful transmitter located at the highest spot in an area would broadcast in a
radius of up to fifty kilometers. The Cellular concept structured the mobile telephone
network in a different way. Instead of using one powerful transmitter many low-powered
transmitter were placed throughout a coverage area. In a cellular system, the covering
area of an operator is divided into cells. A cell corresponds to the covering area of one
transmitter or a small collection of transmitters. The cellular concept employs variable
low power levels, which allows cells to be sized according to subscriber density and
demand of a given area. As the population grows, cells can be added to accommodate that
growth. Frequencies used in a cell will be reused several cells away. The distance
between the cells using the same frequency must be sufficient to avoid interference. The
frequency reuse will increase considerably the capacity in number of users.
Conversations can be handed over from cell to cell to maintain constant phone
service as the user moves between cells. The cellular system design was pioneered by
during‟70s by Bell Laboratories in the United States, and the initial realization was
known as AMPS (Advanced Mobile Phone Service). The AMPS cellular service was
available in United States in 1983. AMPS is essentially generation 1 analog cellular
system in contrast to generation 2 digital cellular systems of GSM and CDMA (1S-95).
1.2.1 CELLS
A cell is the basic geographic unit of cellular system. The term cellular comes
from the honeycomb areas into which a coverage region is divided. Cells are base stations
transmitting over small geographic areas that are represented as hexagons as shown in
Figure. Each cell size varies depending upon landscape. Because of constraint imposed by
natural terrain and man-made structures, the true shape of cell is not a perfect hexagon. In
order to work properly, a cellular system must verify the following two main conditions:
 The power level of a transmitter within a single cell must be limited in
order to reduce the interference with the transmitters of neighboring cells.
The interference will not produce any damage to the system if a distance
of about 2.5 to 3 times the diameter of a cell is reserved between
transmitters.
 Neighboring cells can not share the same channels. In order to reduce the
interference, the frequencies must be reused only within a certain pattern.

Figure 1: Cellular Network

1.2.2 CLUSTER
The spectrum allocated for a cellular network is limited. As a result there is a limit
to the number of frequencies or channels that can be used. The cells are grouped into
clusters. Group of cells in which no frequencies are reused is termed as a cluster.
Figure 2: Cell Clustering and Co-channel cells

The number of cells in a cluster must be determined so that the cluster can be
repeated continuously within the covering area of an operator. A cellular network can
only provide service to a large number of subscribers, if the channels allocated to it can
be reused. Channel reuse is implemented by using the same channels within cells located
at different positions in the cellular network service area. Cells using the same channel set
are called co-channel cells. Cell clustering and co-channel cells (Shaded cells) are shown
in Figure.
Within the service area (PLMN), specific channel sets are reused at a different
location (another cell). In the Figure, there are 7 channel sets: A through G. Neighboring
cells are not allowed to use the same frequencies. For this reason all channel sets are used
in a cluster of neighboring cells. As there are 7 channel sets, the PLMN can be divided
into clusters of 7 cells each. The figure shows three clusters.
The number of channel sets is represented by K. K is also called the reuse factor.
In the figure, K=7. Valid values of K can be found using equation (where i and j are
integers):
;
Here cells are shaped ideally (hexagons). The distance between cells using the
same channel set is always the same. The typical clusters contain 4, 7, 12 or 21 cells. The

number of cells in each cluster is very important. The smaller the number of cells per
cluster is, the bigger the number of channels per cell will be. The capacity of each cell
will be therefore increased. However a balance must be found in order to avoid the
interference that could occur between neighboring clusters. This interference is produced
by the small size of the clusters (the size of the cluster is defined by the number of cells
per cluster). The total number of channels per cell depends on the number of available
channels and the type of cluster used.
Signal attenuation with distance
Frequencies can be reused throughout a service area because radio signals

typically attenuate with distance to the base station (or mobile station). When the distance
between cells using the same frequencies becomes too small, co-channelInterference
might occur and lead to service interruption or unacceptable quality of service.
As long as the ratio

Frequency reuse distance = D
Cell radius R
is greater than some specified value, the ratio
Received radio carrier power =C

Received interferer radio carrier power I
will be greater than some given amount for small as well as large cell sizes when
all signals are transmitted at the same power level.
Relationship between K and D/R
There is a relationship between K and ratio D/R, shown by the following equation:
D/R=  3K
Relationship between K and Performanc
The performance of a cellular network can be expressed in quality of service. An

acceptable quality of service means a low (co-channel) interference level in the network.
The relationship between the reuse factor K and the network performance is: if K
increases, then the co-channel interference decreases, and so the performance increases
(note that there is a fixed relationship between K and ratio D/R).
Relationship between K and Cell Capacity
The other key relationship in cellular networks is the one between the reuse factor
K and call capacity. First of all, call capacity depends on the number of available
channels. In GSM, a limited number of frequencies is available (for GSM: 124
frequencies, and for GSM-1800: 374 frequencies). The frequencies are grouped into
frequency sets. If K increases, the number of frequencies per set (and so per cell)
decreases, and so the call capacity per cell.

Capacity/Performance Trade-offs
 If K increases, then performance increases
 If K increases, then call capacity decreases per cell
The number of sites to cover a given area with a given high traffic density, and
hence the cost of the infrastructure, is determined directly by the reuse factor and the
number oftraffic channels that can be extracted from the available spectrum. These two
factors are compounded in what is called spectral efficiency of the system.
Many techniques are used to reduce interference and enhance spectral efficiency
like-
 Power Control
 Use if directional Antennas (3 sector configuration)
 Mobile Assisted Handover (MAHO).
1.3 TYPES OF CELLS

The density of population in a country is so varied that different types of cells are
used:
1.3.1 MACRO CELLS
The macro cells are large cells for remote and sparsely populated areas.
1.3.2 MICRO CELLS
These cells are used for densely populated areas. By splitting the existing areas
into smaller cells, the number of channels available is increased as well as the capacity of
the cells. The power level of the transmitters used in these cells is then decreased,
reducing the possibility of interference between neighboring cells.
1.3.3 PICO CELLS
Pico cells are small cells whose diameter is only few dozen meters; they are used
mainly in indoor applications. It can cover e.g. a floor of a building or an entire building
like shopping centers, Airports etc.
1.3.4 SELECTIVE CELLS
It is not always useful to define a cell with a full coverage of 360 degrees. In some
cases, cells with a particular shape and coverage are needed. These cells are called
selective cells. Typical examples of selective cells are the cells that may be located at the
entrances of tunnels where coverage of 360 degrees is not needed. In this case, a selective
cell with coverage of 120 degrees is used.

1.3.5 UMBRELLA CELLS
A freeway crossing very small cells produces an important number of handovers

among the different small neighboring cells in case of a fast moving mobile subscriber. In
order to solve this problem, the concept of umbrella cells is introduced. An umbrella cell
covers several micro cells. The power level inside an umbrella cell is increased
comparing to the power levels used in the micro cells that form the umbrella cell. When
the speed of the mobile is too high, the mobile is handed over to the umbrella cell. The
mobile will then stay longer in the same cell (in this case the umbrella cell). This will
reduce the number of handovers and the work of the network.
1.3.6 CELL SECTORISING
One way of reducing the level of interference is to use directional antenna at base
stations, with each antenna illuminating a sector of the cell, and with a separate channel
set allocated to each sector. There are two commonly used methods of Sectorisation either
using 120˚ sector or 60˚ sector, both of which reduce the number of prime interference
sources. The three sector case is generally used with a seven cell pattern, giving an
overall requirement for 21 channel sets as shown in Figure. The main drawbacks of cell
sectoring are increase in number of antennas at each base station. The number of
handovers increases as the mobile move from one sector to another.
f
3
1
3 f
21
f
2
Figure 3: Cell Sectoring
Concept of Frequency Assignment

The cell layout (4-Cell, 3-Sectored) and the corresponding frequency planning is
shown in Figure.
Frequency Planning Aspects

A1 B1 C1 D1 A2 B2 C2 D2 A3 B3 C3 D3
1 2 3 4 5 6 7 8 9 10 11 12
13 14 15 16 17 18 19 20 21 22 23 24
25 26 27 28 29 30 31 32 33 34 35 36

A1
A2
A3
D1 B1
D2 B2
D3 C1 B3
C2
C3
Figure 4: Frequency Planning in Sectored Cells

1.3.7 FEATURES OF DIGITAL SYSTEM
Small cells: A cellular system uses many base stations with relatively small
coverage radii (on the order of a 100 m to 30 km).
Frequency reuse: The spectrum allocated for a cellular network is limited. As a

result there is a limit to the number of channels or frequencies that can be used. For this
reason each frequency is used simultaneously by multiple base-mobile pairs. This
frequency reuse allows a much higher subscriber density per MHz of spectrum than other
systems.
Small, battery-powered handsets: In addition to supporting much higher

densities than previous systems, this approach enables the use of small, battery-powered
handsets with a radio frequency that is lower than the large mobile units used in earlier
systems.
Performance of handovers: In cellular systems, continuous coverage is achieved

by executing a “handover” (the seamless transfer of the call from one base station to
another) as the mobile unit crosses cell boundaries. This requires the mobile to change
frequencies under control of the cellular network.
1.4 GSM ARCHITECTURE

A GSM system is basically designed as a combination of three major subsystems:
the network subsystem, the radio subsystem, and the operation support subsystem. In
order to ensure that network operators will have several sources of cellular infrastructure
equipment, GSM decided to specify not only the air interface, but also the main interfaces
that identify different parts. There are three dominant interfaces, namely, an interface
between MSC and the base Transceiver Station (BTS), and an Um interface between the
BTS and MS.

Um Interface A-bis Interface A-Interface

Figure 5: GSM Architecture
1.4.1 GSM NETWORK STRUCTURE
Every telephone network needs a well-designed structure in order to route

incoming called to the correct exchange and finally to the called subscriber. In a mobile
network, this structure is of great importance because of the mobility of all its subscribers.
In the GSM system, the network is divided into the following partitioned areas.
 GSM service area;
 PLMN service area;
 MSC service area;
 Location area;
 Cells.
The GSM service is the total area served by the combination of all member
countries where a mobile can be serviced. The next level is the PLMN service area. There
can be several within a country, based on its size. The next level of division is the
MSC/VLR service area. In one PLMN there can be several MSC/VLR service areas.
MSC/VLR is a sole controller of calls within its jurisdiction.
The next division level is that of the LA‟s within a MSC/VLR combination. There
are several LA‟s within one MSC/VLR combination. A LA is a part of the MSC/VLR
service area in which a MS may move freely without updating location information to the
MSC/VLR exchange that control the LA.
Lastly, a LA is divided into many cells. A cell is an identity served by one BTS.
1.4.2 MOBILE STATION
The MS includes radio equipment and the man machine interface (MMI) that a
subscribe needs in order to access the services provided by the GSM PLMN. MS can be
installed in Vehicles or can be portable or handheld stations. The MS includes provisions
for data communication as well as voice. A mobile transmits and receives messages to
and from the GSM system over the air interface to establish and continue connections
through the system.

Each MS is identified by an IMEI that is permanently stored in the mobile unit.

Upon request, the MS sends this number over the signaling channel to the MSC. The
IMEI can be used to identify mobile units that are reported stolen or operating incorrectly.
Just as the IMEI identities the mobile equipment, other numbers are used to
identity the mobile subscriber. Different subscriber identities are used in different phases
of call setup. The Mobile Subscriber ISDN Number (MSISDN) is the number that the
calling party dials in order to reach the subscriber. It is used by the land network to route
calls toward an appropriate MSC. The international mobile subscribe identity (IMSI) is
the primary function of the subscriber within the mobile network and is permanently
assigned to him. The GSM system can also assign a Temporary Mobile Subscriber
Identity (TMSI) to identity a mobile. This number can be periodically changed by the
system and protect the subscriber from being identified by those attempting to monitor
the radio channel.
Functions of MS
The primary functions of MS are to transmit and receive voice and data over the
air interface of the GSM system. MS performs the signal processing function of
digitizing, encoding, error protecting, encrypting, and modulating the transmitted signals.
It also performs the inverse functions on the received signals from the BS.
In order to transmit voice and data signals, the mobile must be in synchronization
with the system so that the messages are the transmitted and received by the mobile at the
correct instant. To achieve this, the MS automatically tunes and synchronizes to the
frequency and TDMA timeslot specified by the BSC.
MS monitors the power level and signal quality, determined by the BER for
known receiver bit sequences (synchronization sequence), from both its current BTS and
up to six surrounding BTSs. This data is received on the downlink broadcast control
channel. The MS determines and send to the current BTS a list of the six best-received
BTS signals. The measurement results from MS on downlink quality and surrounding
BTS signal levels are sent to BSC and processed within the BSC. The system then uses
this list for best cell handover decisions.MS keeps the GSM network informed of its
location during both national and international roaming, even when it is inactive. This
enables the System to page in its present LA. The MS includes an equalizer that
compensates for multi-path distortion on the received signal. This reduces inter-symbol
interface that would otherwise degrade the BER.
Finally, MS can store and display short received alphanumeric messages on the
liquid crystal display (LCD) that is used to show call dialing and status information.
These messages are limited to 160 characters in length.
SIM Card
GSM subscribers are provided with a SIM card with its unique identification at
the very beginning of the service. The subscriber is identified in the system when he
inserts the SIM card in the mobile equipment. This provides an enormous amount of
flexibility to the subscribers since they can now use any GSM-specified mobile
equipment.

The SIM is a removable SC, the size of a credit card, and contains an integrated
circuit chip with a microprocessor, random access memory (RAM), and read only
memory (ROM). It is inserted in the MS unit by the subscriber when he or she wants to
use the MS to make or receive a call.
International Mobile Subscriber Identity (IMSI)
An IMSI is assigned to each authorized GSM user. It consists of a mobile country

code (MCC), mobile network code (MNC), and a PLMN unique mobile subscriber
identification number (MSIN).
Temporary Mobile Subscriber Identity (TMSI)
A TMSI is a MSC-VLR specific alias that is designed to maintain user

confidentiality. It is assigned only after successful subscriber authentication.
The Mobile Station Roaming Number (MSRN)
The MSRN is allocated on temporary basis when the MS roams into another
numbering area. The MSRN number is used by the HLR for rerouting calls to the MS. It
is assigned upon demand by the HLR on a per-call basis.
International Mobile Equipment Identity (IMEI)
The IMEI is the unique identity of the equipment used by a subscriber by each
PLMN and is used to determine authorized (white), unauthorized (black), and
malfunctioning (gray) GSM hardware. In conjunction with the IMSI, it is used to ensure
that only authorized users are granted access to the system. An IMEI is never sent in
cipher mode by MS.
1.4.3 BASE STATION SYSTEM
The BSS is a set of BS equipment (such as transceivers and controllers) that is in

view by the MSC through a single A interface as being the entity responsible for
communicating with MSs in a certain area. The radio equipment of a BSS may be
composed of one or more cells. A BSS may consist of one or more BS. The interface
between BSC and BTS is designed as an A-bis interface. The BSS includes two types of
machines: the BTS in contact with the MSs through the radio interface and the BSC, the
latter being in contact with the MSC.
A BTS is a network component that serves one cell and is controlled by a BSC.
BTS is typically able to handle three to five radio carries, carrying between 24 and 40
simultaneous communication. Reducing the BTS volume is important to keeping down
the cost of the cell sites.
An important component of the BSS that is considered in the GSM architecture as

a part of the BTS is the Transcoder/Rate Adapter Unit (TRAU). The TRAU is the
equipment in which coding and decoding is carried out as well as rate adoption in case of
data. Although the specifications consider the TRAU as a subpart of the BTS, it can be
sited away from the BTS (at MSC), and even between the BSC and the MSC.

The interface between the MSC and the BSS is a standardized SS7 interface (A-
interface). This allows the system operator to purchase switching equipment from one
supplier and radio equipment and the controller from another. The interface between the
BSC and a remote BTS likewise is a standard the A-bis.
1.4.4 FUNCTIONS OF BTS

The primary responsibility of the BTS is to transmit and receive radio signals
from a mobile unit over an air interface. To perform this function completely, the signals
are encoded, encrypted, multiplexed, modulated, and then fed to the antenna system at the
cell site. Transcoding to bring 13-kbps speech to a standard data rate of 16 kbps and then
combining four of these signals to 64 kbps is essentially a part of BTS, though, it can be
done at BSC or at MSC.
Random access detection is made by BTS, which then sends the message to BSC.
The channel subsequent assignment is made by BSC. Timing advance is determined by
BTS. BTS signals the mobile for proper timing adjustment. Uplink radio channel
measurement corresponding to the downlink measurements made by MS has to be made
by BTS.
1.4.5 TRANSCODER
The transcoder is the device that takes 13-Kbps speech or 3.6/6/12Kbps data
multiplexes and four of them to convert into standard 64-Kbps data. First, the 13 Kbps or
the data at 3.6/6/12 Kbps are brought up to the level of 16 Kpbs by inserting additional
synchronizing data to make up the difference between a 13-Kbps speech or lower rate
data, and then four of them are combined in the transcoder to provide 64 Kpbs channel
within the BSS. Four traffic channels can then be multiplexed on one 64-Kpbs circuit.
Thus, the TRAU output data rate is 64 Kpbs. Then, up to 30 such 64-Kpbs channels are
multiplexed onto a 2.048 Mpbs if a CEPT1 channel is provided on the A-bis interface.
This channel can carry up to 120-(16x 120) traffic and control signals. Since the data rate
to the PSTN is normally at 2 Mbps, which is the result of combining 30-Kbps by 64-
Kbph channels, or 120- Kbps by 16-Kpbs channels.
1.4.6 BSC
The BSC, as discussed, is connected to the MSC on one side and to the BTS on
the other. The BSC performs the Radio Resource (RR) management for the cells under its
control. It assigns and release frequencies and timeslots for all MSs in its own area. The
BSC performs the intercell handover for MSs moving between BTS in its control. It also
reallocates frequencies to the BTSs in its area to meet locally heavy demands during peak
hours or on special events. The BSC controls the power transmission of both BSSs and
MSs in its area. The minimum power level for a mobile unit is broadcast over the BCCH.
The BSC provides the time and frequency synchronization reference signals broadcast by
its BTSs.
1.4.7 SWITCHING SUBSYSTEMS: MOBILE SWITCHING CENTER AND

GATEWAY SWITCHING CENTER
The main role of the MSC is to manage the communications between the GSM
users and other telecommunication network users. The basic switching function of
performed by the MSC, whose main function is to coordinate setting up calls to and from
GSM users. The MSC has interface with the BSS on one side (through which MSC VLR

is in contact with GSM users) and the external networks on the other
(ISDN/PSTN/PSPDN). The main difference between a MSC and an exchange in a fixed
network is that the MSC has to take into account the impact of the allocation of RRs and
the mobile nature of the subscribers and has to perform, in addition, at least, activities
required for the location registration and handover.
The MSC is a telephony switch that performs all the switching functions for MSs
located in a geographical area as the MSC area. The MSC must also handle different
types of numbers and identities related to the same MS and contained in different
registers: IMSI, TMSI,ISDN number, and MSRN. In general identities are used in the
interface between the MSC and the MS, while numbers are used in the fixed part of the
network, such as, for routing.
1.4.8 FUNCTIONS OF MSC
The main function of the MSC is to coordinate the set up of calls between GSM
mobile and PSTN users. Specifically, it performs functions such as paging, resource
allocation, location registration, and encryption.
This is ensured if the two BSSs are connected to the same MSC but also when
they are not. In this latter case the procedure is more complex, since more than one MSC
in involved. The MSC performs billing on calls for all subscribers based in its areas.
When the subscriber is roaming elsewhere, the MSC obtains data for the call billing from
the visited MSC. Encryption parameters transfers from VLR to BSS to facilitate ciphering
on the radio interface are done by MSC. The exchange of signaling information on the
various interface toward the other network elements and the management of the interface
themselves are all controlled by the MSC. Finally, the MSC serves as a SMS gateway to
forward SMS messages from Short Message Service Centers (SMSC) to the subscribers
and from the subscribers to the SMSCs. It thus acts as a message mailbox and delivery
system.
1.4.9 VLR
The VLR is collocated with an MSC. A MS roaming in an MSC area is controlled

by the VLR responsible for that area. When a MS appears in a LA, it starts a registration
procedure. The MSC for that area notices this registration and transfers to the VLR the
identity of the LA where the MS is situated. A VLR may be in charge of one or several
MSC LA‟s. The VLR constitutes the databases that support the MSC in the storage and
retrieval of the data of subscribers present in its area. When an MS enters the MSC area
borders, it signals its arrival to the MSC that stores its identity in the VLR. The
information necessary to manage the MS is contained in the HLR and is transferred to the
VLR so that they can be easily retrieved if so required.
1.4.10 DATA STORED IN VLR
The data contained in the VLR and in the HLR are more or less the same.
Nevertheless the data are present in the VLR only as long as the MS is registered in the
area related to that VLR. Data associated with the movement of mobile are IMSI,
MSISDN, MSRN, and TMSI.

1.4.11 HOME LOCATION REGISTER
The HLR is a database that permanently stores data related to a given set of
subscribers. The HLR is the reference database for subscriber parameters. Various
identification numbers and addresses as well as authentication parameters, services
subscribed, and special routing information are stored. Current subscriber status including
a subscriber‟s temporary roaming number and associated VLR if the mobile is roaming,
are maintained.
The HLR maintains record of which supplementary service each user has
subscribed to and provides permission control in granting services. The HLR stores the
identification of SMS gateways that have messages for the subscriber under the SMS
until they can be transmitted to the subscriber and receipt is knowledge.
1.4.12 AUTHENTICATION CENTER
The AUC stores information that is necessary to protect communication through

the air interface against intrusions, to which the mobile is vulnerable. The legitimacy of
the subscriber is established through authentication and ciphering, which protects the user
information against unwanted disclosure. Authentication information and ciphering keys
are stored in a database within the AUC, which protects the user information against
unwanted disclosure and access.
1.4.13 EQUIPMENT IDENTIFY REGISTER
EIR is a database that stores the IMEI numbers for all registered ME units. The
IMEI uniquely identifies all registered ME. There is generally one EIR per PLMN. It
interfaces to the various HLR in the PLMN. The EIR keeps track of all ME units in the
PLMN. There are three classes of ME that are stored in the database, and each group has
different characteristics.
 White List: contains those IMEIs that are known to have been assigned to
valid MS‟s. This is the category of genuine equipment.
 Black List: contains IMEIs of mobiles that have been reported stolen.
 Gray List: contains IMEIs of mobiles that have problems (for example,
faulty software and wrong make of the equipment). This list contains all
MEs with faults not important enough for barring.
1.4.14 INTERWORKING FUNCTION
The IWF, which in essence is a part of MSC, provides the subscriber with access
to data rate and protocol conversion facilities so that data can be transmitted between
GSM Data Terminal Equipment (DTE) and a land-line DTE.
1.4.15 ECHO CANCELER (EC)
EC is used on the PSTN side of the MSC for all voice circuits. The EC is required
at the MSC PSTN interface to reduce the effect of GSM delay when the mobile is
connected to the PSTN circuit. The total round-trip delay introduced by the GSM system,
which is the result of speech encoding, decoding and signal processing, is of the order of
180 ms. Normally this delay would not be an annoying factor to the mobile, except when
communicating to PSTN as it requires a two-wire to four-wire hybrid transformer in the

circuit. This hybrid is required at the local switching office because the standard local
loop is a two-wire circuit. Due to the presence of this hybrid, some of the energy at its
four-wire receive side from the mobile is coupled to the four-wire transmit side and thus
retransmitted to the mobile. This causes the echo, which does not affect the land
subscriber but is an annoying factor to the mobile. The standard EC cancels about 70 ms
of delay.
During a normal PSTN (land-to-land call), no echo is apparent because the delay
is too short and the land user is unable to distinguish between the echo and the normal
telephone “side tones” However, with the GSM round-trip delay added and without the
EC, the effect would be irritating to the MS subscriber.
1.4.16 OPERATION AND MAINTENANCE CENTER (OMC)
The OMC provides alarm-handling functions to report and log alarms generated
by the other network entities. The maintenance personnel at the OMC can define that
criticality of the alarm. Maintenance cover both technical and administrative actions to
maintain and correct the system operation, or to restore normal operations after a
breakdown, in the shortest possible time.
The OMC provides system change control for the software revisions and
configuration data bases in the network entities or uploaded to the OMC. The OMC also
keeps track of the different software versions running on different subsystem of the GSM.
1.5 GSM RADIO

The radio interface is the interface between the mobile stations and the fixed
infrastructure. It is one of the most important interfaces of the GSM system. One of the
main objectives of GSM is roaming. Therefore, in order to obtain a complete
compatibility between mobile stations and networks of different manufacturers and
operators, the radio interface must be completely defined. The spectrum efficiency
depends on the radio interface and the transmission, more particularly in aspects such as
the capacity of the system and the techniques used in order to decrease the interference
and to improve the frequency reuse scheme. The specification of the radio interface has
then an important influence on the spectrum efficiency.
The specifications of GSM radio interface:

 Frequency Band
 FDMA and TDMA
 Uplink and Downlink
 Physical and Logical Channel
 Multiplexing Logical Channels
 Frame Types in Radio Interface
 GSM Radio Link Processes
 Low Bit Rate Speech coding
 Channel coding
 Bit Interleaving
 Burst assembling

1.5.1 FREQUENCY ALLOCATION

GSM 900 MHz
Two frequency bands, of 25 MHz each one, have been allocated for the GSM
system:
The band 890-915 MHz has been allocated for the uplink direction (transmitting
from the mobile station to the base station).
The band 935-960 MHz has been allocated for the downlink direction
(transmitting from the base station to the mobile station).
But not all the countries can use the whole GSM frequency bands. This is due
principally to military reasons and to the existence of previous analog systems using part
of the two 25 MHz frequency bands.
GSM 1800 MHz
Two frequency bands, of 75 MHz each one, have been allocated for the GSM
system:
The band 1710 to 1785 MHz has been allocated for the uplink direction
(transmitting from the mobile station to the base station).
The band 1805 to 1880 has been allocated for the downlink direction (transmitting
from the base station to the mobile station). 1.3.2 FDMA and TDMA methods
To achieve a high spectral efficiency in the cellular network a combination of

FDMA (Frequency Division Multiple Access) and TDMA (Time Division Multiple
Access) is used. The FDMA part involves the division by frequency of the 25 MHz
bandwidth into 124 carrier frequencies spaced 200 KHz for GSM-900. For GSM-1800
the frequency spectrum of the 75 MHz bandwidth is divided into 374 carrier frequencies
spaced 200 KHz. One or more frequencies are assigned to each BTS. Each of these
carrier frequencies is then divided in time, using a TDMA scheme to increase the number
of channels per carrier frequency.
1.5.2 UPLINK AND DOWNLINK
In the frequency range specified for the GSM-900 mobile radio networks, 124
frequency channels with a bandwidth of 200 KHz are available for both the uplink and
downlink direction. The uplink (mobile station to BTS) uses the frequencies between 890
MHz and 915 MHz and the downlink (BTS to mobile station) uses the frequencies
between 935 MHz and 960 MHz. The duplex spacing, the spacing between the uplink and
downlink channel, is 45 MHz.
GSM-1800 uses a similar scheme. The difference is that for GSM-1800 the uplink
uses the frequencies between 1710 MHz and 1785 MHz and the downlink the frequencies
between 1805 MHz and 1880 MHz. The duplex spacing is 95 MHz.
1.5.3 PHYSICAL AND LOGICAL CHANNEL
One GSM carrier of 200 KHz is divided in 8 time slots and access by various
users is in TDMA mode. Calls to and from subscribers in a cell coverage area are

facilitated by various logical channels. Logical channels are mapped onto physical
channel which is one time slot of a GSMcarrier.
A physical channel is determined by the carrier frequency (or a number of carrier

frequencies and a defined hopping sequence) and the timeslot number. A mobile station
can transmit speech data only during its assigned timeslot.
Types of Logical Channels:

 Traffic channel
 Broadcast channels
 Common control channels
 Dedicated control channels
Note that the first channel type carries speech and data, and the other types control
information (signaling).
1.5.4 TRAFFIC CHANNELS
The traffic channels are used to send speech or data services. There are two types
of traffic channels. They are distinguished by their transmission rates.
The following traffic channels are provided:
 TCH/F (Traffic Channel Full rate) : The TCH/F carries information at a

gross bit rate of 22.8 kbit/s (after channel coding). The net (or effective) bit
rate at the TCH/F is for speech 13 kbit/s and for data 12, 6 or 3.6 kbit/s (before
channel coding). The transmission rates of the data services allow services
which are compatible to the existing, respectively, 9.6, 4.8 and 2.4 kbit/s
PSTN and ISDN services.
 TCH/H (Traffic Channel Half rate): The TCH/H carries information at a

gross bit rate of 11.4 kbit/s. The net bit rate at the TCH/H is for speech 5.6
kbit/s and for data 6 or 3.6kbit/s.
A TCH/F or a TCH/H may also be used to send signaling information (for

example call forwarding and short messages). In that case a small portion of the time slot
is used.
1.5.5 BROADCAST CHANNELS
The information distributed over the broadcast channels helps the mobile stations
to orient themselves in the mobile radio network.
The broadcast channels are point-to-multipoint channels which are only defined
for the downlink direction (BTS to the mobile station). They are divided into:
 BCCH (Broadcast Control Channel) :Via the BCCH the mobile station is
informed about the system configuration parameters (for example Local Area
Identification, Cell Identity and Neighbor Cells). Using this information the
mobile stations can choose the best cell to attach to.The BCCH is also known
as beacon.

 FCCH (Frequency Correction Channel) :To communicate with the BTS the
mobile station must tune to the BTS. The FCC transmits a constant frequency
shift of the radio frequency carrier that can be used by the mobile station for
frequency correction.
 SCH (Synchronization Channel) :The SCH is used to time synchronize the

mobile stations. The data on this channel carries the TDMA frame number and
the BSIC (Base Station Identity Code).
 CBCH (Cell Broadcast Channel) :The CBCH is used for the transmission of
generally accessible information (Short Message Service messages) in a cell,
which can be polled by the mobile station.
1.5.6 COMMON CONTROL CHANNEL
Common control channels are specified as point-to-multipoint channels which

only operate in one direction of transmission, either in the uplink or downlink direction.
The following channels are provided:
 PCH (Paging Channel) : The PCH is used in the downlink direction for
paging the mobile stations.
 AGCH (Access Grant Channel) : The AGCH is also used in the downlink
direction. A logical channel for a connection is allocated via the AGCH if the
mobile station has requested such a Channel via the RACH.
 RACH (Random Access Channel) : The RACH is used in the uplink

direction by the mobile stations for requesting a channel for a connection. It is
an access channel that uses the slotted Aloha access scheme.
1.5.7 DEDICATED CONTROL CHANNELS
Dedicated control channels are full-duplex, point-to-point Channels. They are

used for signaling between the BTS and a certain mobile station. They are divided into:
 SACCH (Slow Associated Control Channel) :The SACCH is a duplex

Channel which is always allocated to a TCH or SDCCH. The SACCH is used
for transmission of signaling data, radio link supervision measurements,
transmit power control and timing advance data. Note that the SACCH is only
used for non- urgent procedures.
 FACCH (Fast Associated Control Channel) :The FACCH is used as a main

signaling link for the transmission of signaling data (for example handover
commands). It is also required for every call set-up and release. During the
call the FACCH data is transmitted over the allocated TCH instead of traffic
data; this is marked by a flag called a stealing flag. The process of stealing a
TCH for FACCH data is called pre-emption.
 SDCCH (Stand-alone Dedicated Control Channel) :The SDCCH is a

duplex, point-to-point Channel which is used for signaling in higher layers. It
carries all signaling between the BTS and the mobile station when no TCH is

allocated. The SDCCHs are used for service requests (for example Short
Message Service), location updates, subscriber authentication, ciphering
initiation, equipment validation and assignment to a TCH. The net SDCCH bit
rate is about 0.8kbit/s.
1.5.8 MULTIPLEXING LOGICAL CHANNELS ONTO PHYSICAL

CHANNELS
Several of the above-mentioned types of logical channels can be transmitted over

one single physical channel (timeslot). The GSM specifications 05.02 specify several
combinations of channel types (the sequence of logical channels is fixed).The order of the
logical channels depends on the channel combination.
Channel Combination
The channel combinations are:

 TCH/F + FACCH/F + SACCH/F
 TCH/H + FACCH/H +SACCH/H
 (TCH/F + FACCH/F + SACCH/F) or (TCH/H + FACCH/H +SACCH/H)
 FCCH + SCH + CCCH +BCCH
 FCCH + SCH + CCCH + BCCH + SDCCH/4 +SACCH/4
 CCCH +BCCH
 SDCCH/8 +SACCH/8
The CCCH is a channel that carries both the PCH and the AGCH on the downlink,
and the RACH on the uplink. The extensions “/4” and “/8” in the above mentioned terms
mean, respectively, that four and eight logical channels are mapped onto one physical
channel (timeslot).Note that the BCCH is always transmitted in timeslot 0 on the first
defined frequency.
1.5.9 FRAME TYPES ON THE RADIO INTERFACE
The GSM specifications define several types of frames, which are:
 TDMA frame:A TDMA frame consists of eight timeslots (physical channels).

The length of a timeslot is 0.577 ms. The length of a TDMA frame is therefore
4.62 ms.
Note: because data on a timeslot is transmitted in bursts, the length of a

timeslot is often expressed in BP (Burst Period); 1 BP represents the length of
1timeslot.
 26-TDMAmultiframe :This multiframe is defined as a succession of 26

TDMA frames, and corresponds to the 26 x 8 BP or 120 ms cycle used in the
definition of the TCH/F and TCH/H.
 51-TDMAmultiframe :This multiframe is defined as a succession of 51

TDMA frames, and corresponds to the 51 x 8 BP cycle used in the definition
of the TCH/F, TCH/H and of the common channels.

 Superframe : The superframe is a succession of 51 x 26 TDMA frames (6.12

sec), and corresponds to the smallest cycle for which the organization of all
channels is repeated.
 Hyperframe : The hyperframe is the numbering period. It is 2048 x 51 x 26 x

8 BP long, or 3 hours, 28 minutes, 53 seconds and 760 milliseconds. It is a
multiple of all previously cited cycles, and determines all the cycles in the
transmission of the radio path. It is in particular the smallest cycle for
frequency hopping and for ciphering.
1.5.10 BURST ASSEMBLING
 The burst assembling procedure is in charge of grouping the bits into bursts.
 GSM radio transmission is accomplished by sending data in burst.
 Burst is the physical content of a time slot.
 Each burst consists of 148 usable bits of each 3.69 msec.
 Guard period between the bursts is 30.5 msec. (=8.25 bits) to distinguish
consecutive burst.
 Hence each time slot has a fixed length of 156.25 bits (0.577 m sec.)
 Different parts of a burst have special function.
 E.g. of burst part are training sequence, encrypted bits, tail bit, guard period &
stealing bit.
Figure 6: Organization of a burst

 Training sequence bitsFixed (26 or 41 or 64) bit pattern to train the MS in
predicting and correcting signal distortions (due to multi path effects) in the
demodulation process.
 Encrypted bits - Represents the useful bits of speech, data or signaling to

transmit.
 Tail bits - To indicate the start (3bits) and end (3bits) of a burst.
 Stealing Flag bits -Two bits (Hl and Hu) are located just before and after the
TSC in normal burst. To identify the data contained in the bursts Indicate

whether adjacent 57 bits in associated data field contain speech/data or are

„stolen‟ from the traffic channel for carrying FACCH signaling Information.
 Guard period (8.25 bits) - Necessary for switching the transmitter on and
off for MS. (Switching off will reduce interference to RF channel)
1.5.11 BURST TYPES
Normal Burst - Two Packets Of 58 encrypted bits (57 data bits+1 stealing bit) are
carried for the traffic channel (TCH) or for the control channel (BCCH and CCCH)
Dummy Burst - Transmitted in idle Time slots on the BCCH carrier which ensures
that the BCCH is always present. This makes it easier for the MS to find the BCCH
carrier and permits assessment of the neighbor cell. It provides two packets of fixed bit
pattern without information content.
Synchronization burst - First Burst in the down link direction that a MS needs to
process, used on the SCH. Provides a unique 64 bit TSC in order to facilitate the initial
demodulation for the MS. The encrypted bit field contain Base Station Identity Code
(BSIC) and the TDMA frame Number. Frame Number continuously counted in a Hyper
Frame are run from (0 to 2715647)
Access Burst - Short burst used by MS in the Uplink direction at an initial phase
of a call when the propagation delay between MS and BTS is not known. Occurs during
a first access on the RACH and sometimes upon a hand over to a new cell.
Frequency Correction Burst - Used by the MS to correct its Transmit and Receive
Frequency. Sent in down link direction as FCCH. Consists of a bit string of all logical 0‟s
1.6 RADIO RESOURCE MANAGEMENT

GSM network has adopted various Radio Resource management techniques such
as Discontinuous Transmission, Discontinuous Reception, Power Control, Timing
Advance and Frequency Hopping.
1.6.1 DISCONTINUOUS TRANSMISSION (DTX)
This is another aspect of GSM that could have been included as one of the
requirements of the GSM speech codec. The function of the DTX is to suspend the radio
transmission during the silence periods. This can become quite interesting if we take into
consideration the fact that a person speaks less than 40 or 50 percent during a
conversation. The DTX helps then to reduce interference between different cells and to
increase the capacity of the system. It also extends the life of a mobile's battery. The DTX
function is performed thanks to two main features:
The Voice Activity Detection (VAD), which has to determine whether the sound
represents speech or noise, even if the background noise is very important. If the voice
signal is considered as noise, the transmitter is turned off producing then, an unpleasant
effect called clipping.
The comfort noise, an inconvenient of the DTX function is that when the signal is
considered as noise, the transmitter is turned off and therefore, a total silence is heard at

the receiver. This can be very annoying to the user at the reception because it seems that
the connection is dead. In order to overcome this problem, the receiver creates a
minimum of background noise called comfort noise. The comfort noise eliminates the
impression that the connection is dead.
1.6.2 TIMING ADVANCE
The timing of the bursts transmissions is very important. Mobiles are at different
distances from the base stations. Their delay depends, consequently, on their distance.
The aim of the timing advance is that the signals coming from the different mobile
stations arrive to the base station at the right time. The base station measures the timing
delay of the mobile stations. If the bursts corresponding to a mobile station arrive too late
and overlap with other bursts, the base station tells, this mobile, to advance the
transmission of its bursts.
1.6.3 POWER CONTROL
This is a feature of the GSM air interface which allows the network provider to
not only compensate for the distance from MS to BTS as regards timing, but can also
cause the BTS and MS to adjust their power output to take account of that distance also.
The closer the MS is to the BTS, the less the power it and the BTS will be required to
transmit. This feature saves radio battery power at the MS, and helps to reduce co-channel
and adjacent channel interference. Both uplink and downlink power settings can be
controlled independently and individually at the discretion of the network provider. Initial
power setting for the MS is set by the information provided on the Broadcast Control
Channel (BCCH) for a particular cell. The BSS controls the transmit power of both the
MS and the BTS. The received MS power is monitored by the BSS and the receive BTS
power is monitored by the MS and then reported to the BSS. Using these measurements
the power of both MS and BTS can be adjusted accordingly
1.6.4 DISCONTINUOUS RECEPTION
DRX allows the MS to effectively “switch off” during times when reception is
deemed unnecessary. By monitoring the Broadcast Control Channel (BCCH), the
Frequency Correction Control Channel (FCCH) and the Synchronization Control Channel
(SCCH) the MS is aware of the Frame Number and repetition format for Frame
Synchronization. It can therefore, after initially locking on to a BCCH, determine when
the next relevant information is to be transmitted. This allows the MS to „go to sleep‟ and
listen-in only when necessary, with the effective saving in power usage. DRX may only
be used when a MS is not in a call. When DRX is employed, the MS using information
broadcast on the BCCH determines its “paging group”. The paging group may appear
once during a control channel multiframe, or may only be scheduled to appear once over
several multiframes – the rate of repetition is determined by the network provider and it is
this information which is broadcast over the BCCH, which allows the MS to determine its
paging group
1.6.5 FREQUENCY HOPPING
Frequency hopping allows the RF channel used for carrying signaling channel
timeslots or traffic channel (TCH) timeslots to change frequency every frame (or 4.615

msec). This capability provides a high degree of immunity to interference, due to the
effect of interference averaging, as well as providing protection against signal fading.
The effective “radio channel interference averaging” assumes that radio channel
interference does not exist on every allocated channel and the RF channel carrying TCH
timeslots changes to a new allocated RF channel every frame. Therefore, the overall
received data communication experiences interference only part of the time.
All mobile subscribers are capable of frequency hopping under the control of the
BSS.
To implement this feature, the BSS software must include the frequency hopping
option. Cyclic or pseudo random frequency hopping patterns are possible, by network
provider selection
1.6.6 MULTIPATH AND EQUALISATION
At the GSM frequency bands, radio waves reflect from buildings, cars, hills, etc.
So not only the 'right' signal (the output signal of the emitter) is received by an antenna,
but also many reflected signals, which corrupt the information, with different phases.
An equalizer is in charge of extracting the 'right' signal from the received signal. It
estimates the channel impulse response of the GSM system and then constructs an inverse
filter. The receiver knows which training sequence it must wait for. The equalizer will
then, comparing the received training sequence with the training sequence it was
expecting, compute the coefficients of the channel impulse response. In order to extract
the 'right' signal, the received signal is passed through the inverse filter.
1.7 CONCLUSION
GSM is very successful technology due to its robust radio network design. By
virtue of TDMA and frequency reuse the capacity of GSM system is increased
tremendously. But with the introduction of Data on mobile GSM has lost its shine as it
deliveries very less data rates. Thus GSM has been migrated to newer technologies such
as GPRS and EDGE.

E2-E3 Consumer Mobility Maintenance Issues of BTS , Node-B and e-Node-B
2 MAINTENANCE ISSUES OF BTS, NODE-B, AND E-

NODE-B

 Functioning of BTS, Node-B, e Node-B
 Common faults in base stations
 Resolution of common fault such as VSWR, Cable Swamping etc
 VSWR Meter functioning
 Alarm Handling
 E node B Troubleshooting
2.2 INTRODCTION
Traditional mobile service was structured similar to television broadcasting. One
very powerful transmitter located at the highest spot in an area would broadcast in a
radius of up to fifty kilometers. The Cellular concept structured the mobile telephone
network in a different way. Instead of using one powerful transmitter many low-powered
transmitters were placed throughout a coverage area. For example, by dividing
metropolitan region into one hundred different areas (cells) with low power transmitters
using twelve conversations (channels) each, the system capacity could theoretically be
increased from twelve conversations using one hundred low power transmitters.
The cellular concept employs variable low power levels, which allows cells to be
sized according to subscriber density and demand of a given area. As the populations
grow, cells can be added to accommodate that growth. Frequencies used in one cell
cluster can be reused in other cells. Conversations can be handed over from cell to cell to
maintain constant phone service as the user moves between cells.
2.3 CELLS
A cell is the basic geographic unit of cellular system. The term cellular comes
from the honeycomb areas into which a coverage region is divided. Cells are base stations
transmitting over small geographic areas that are represented as hexagons. Each cell size
varies depending upon landscape. Because of constraint imposed by natural terrain and
man-made structures, the true shape of cell is not a perfect hexagon.
A group of cells is called a cluster. No frequencies are reused in a cluster. Features
of Digital Cellular Systems:
 Small cells
 Frequency reuse
 Small, battery-powered handsets
 Performance of handovers
2.4 FUNCTIONS OF BTS

 The BTS provides the physical connection of an MS to the network in
form of the Air-interface.
 On the other side, toward the NSS, the BTS is connected to the BSC via
the Abis-interface.
 The GSM recommendations allow for one BTS to host up to 18 TRXs.

 Each frequency is given a number called as ARFCN (Absolute Radio

Frequency Carrier Number).
 In the field, the majority of the BTSs host between one and twelve TRXs.
(4+4+4) (3 Sector each with 3 frequencies).
 Radio transmission & reception (TRX).
 Modulation, demodulation, equalization and digitalization of voice and
data signals coming from air interface.
 Combining and coupling of RF Signals to antenna.
 Mapping & Transmission of information from BTS to BSC side.
 Alarms generation and Control of over all BTS system.
2.5 MAINTENANCE
STEP-1
 Enter into the BTS room or the shelter (outdoor BTS).
 Do Physical examination of the environment of BTS, Check for fire,
smoke, humidity and physical damage to BTS or infrastructure. (Also
check alarms).
 If OK proceeds further.
STEP-2
 If alarms are available, go to subsequent step or go sequence by sequence.
 First check the control card and its LEDs. Generally, it contains the media
termination also. So, check for media LED if media is down.
 Verify by giving the loop in both the directions.
 If OK, go to check TRX step
STEP-3
 If Control Card itself is faulty, replace it with new one or tested card from
other site. Also try to reset the control card so that software can be
reloaded to it. If possible, locally access the control card and try to identify
the fault.
STEP-4
 If media and control card both is OK, then proceed to the TRX cards.
 Check the LEDs on TRX card (on all cards).
 Mark the TRX card which is showing fault.
STEP-5
 If TRX Card itself is faulty then only in one sector some frequency will
not work or sector will not work if BCCH carrier is down, replace it with
new one or from tested card from other site.
 If not possible, replace it with other TRX card of same BTS of other sector
or same sector but it should not contain the BCCH channel carrier. Also
check the cable connection of TRX card and coupler.
 If this occurs frequently check the temperature.
STEP-6
 If TRX Cards are OK, check the coupler card and also the status of RF
jumper cable connecting the output of TRX or coupler to the antenna.
Look out for VSWR reports.

 Consult with the OMC-R team for physical test and media test. Now if
configuration is proper, the BTS should be up and radiating.
 Look out for all LEDs and alarms and take subsequent action.
STEP-7
 If BTS is radiating and calls are not landing
 Check whether BCCH channel is assigned or not.
 If not assigned, assign it. Also check the BCCH channel should not be on
hopping frequency.
 Check the availability of SDCCH channel. Sometime TRX is also faulty.
STEP-8
 If BTS is radiating, calls land but are not maturing, there is crosstalk, call
drop, interference.
 Check whether BCCH channel is assigned or not. If not assigned, assignit.
 Also check the BCCH channel should not be on hopping frequency and
whether the cable has not been swapped. Also check HSN & MAIO with
adjacent sector.
2.6 ALARMS IN BTS

There are two classes of alarms in BTS.
 External Alarms: These alarms are external in nature and are caused due
to environmental conditions or infrastructural failure.
 Internal Alarms: They are internal to the BTS system.
2.6.1 EXTERNAL ALARMS
 Power plant &Battery: Generally BTS are inside other exchanges so they
take power from existing power plant. If not at least 25-50 A module
power plant with 200 AH battery set must be provided. The health of the
battery is very crucial as at most of the site it is seen that BTS is off due to
no battery backup and DG.
 Engine Alternator: Ensure the working of engine alternator. Make sure that
battery of DG set is working properly and ensure the starting of DG when
mains fail. Timely check the DG (periodically test).
 Air-conditioning: Check the site condition. Recommended Temperature is
23oC+ 3oC.
 Fire detection system should be available.
 Tower earthing should be proper and separated from DC earth.
 Earthing: Measure earth resistance range <0.5ohms.
 Media: Check the PCM. If possible, give a redundant PCM (optional).
 Shelter: Cleaning of shelter. It should be dust free. No additional items
should be available in shelter as it causes troubles.
 VSWR
2.6.2 INTERNAL ALARMS
 BTS fail
 TRX card faulty
 Combiner faulty
 Combiner loss
 Swapping of feeder cable with adjacent sector

 BCCH TRX failure

 High BER in PCM
 Power failure
 Media failure
 Fan failure
2.7 MAINTENANCE ISSUES OF NODE-B

Node B is the telecommunications node in particular mobile communication
networks, namely those that adhere to the UMTS standard. The Node B provides the
connection between mobile phones (UEs) and the wider telephone network. Node
B corresponds to BTS (Base Transceiver station) in GSM. e Node Bs have minimum
functionality, and are controlled by an RNC (Radio Network Controller). However, this is
changing with the emergence of High-Speed Downlink Packet Access (HSDPA), where
some logic (e.g., retransmission) is handled on the Node B for lower response times. A
full cell site has a cabinet, an antenna mast and actual antenna. An equipment cabinet
contains e.g. RF power amplifiers, digital signal processors and backup batteries. A Node
B can serve several cells, also called sectors, depending on the configuration and type of
antenna. Common configuration is 3 sectors (3×120°).
2.7.1 LOCATING FAULTY EQUIPMENTS
 If RNC has fault, usually it will affect some Sites or all of Sites.
 If NodeB has fault, usually it just affects itself and the handover successful
rate of adjacent cells.
 During implementation or expansion, we can “Interchange” NodeB and
judge the fault is because of RNC or NodeB
 During maintenance, RNC faults don‟t just affect one NodeB.
2.7.2 COMMON FAULT TYPES
RAN fault
 Cell
 Traffic
 Link
 Interconnection
 Clock
 Antenna & Feeder
 Transmission
Operation and maintenance fault
 OMC
 Software Loading
RNO fault
 Access
 Call drop
 Congestion
 Handover
Operation and Maintenance System Faults
Fundamental knowledge of Node-B provides two modes of operation and
maintenance.
 Near end operation and maintenance
 Far end operation and maintenance

Case1: Downloading Software Package Lasts Too Long, Sometimes Software

Downloading Fails
In the course of software upgrading, it takes several hours to download the
software package , and sometimes, the software downloading procedure fails.
Troubleshooting methods
 For maintenance over IPoA through RNC, check whether the IPoA
bandwidth on RNC Operation and Maintenance system is too narrow.
 Increase the IPoA bandwidth to speed up software downloading progress
based on the actual situation.
Case2: Fail to Log in to NodeB by Near End Mode
In near end maintenance mode, the Operation and Maintenance system can log in
to NodeB normally before downloading data configuration file. When NodeB restarts
after the data configuration file downloading procedure finishes, the Operation and
Maintenance system cannot log in to NodeB by near end mode, but can log in to it over
IPoA. In this case, board indicators are normal.
The reason for this fault may be incorrect setting of IP address of near end
maintenance channel.
 Step 1: Log into NodeB over IPoA link through Operation and
Maintenance system, configure IP for near end maintenance channel by
using the MML command SET IP. Query whether the setting is successful
by using the MML command LST IP.
 Step 2: Open the data configuration file on the configuration management
system to modify the NodeB property. Modify the local IP address as the
value demanded, download the data configuration file again, and then
restart the NodeB.
Cell Faults
Case1: No CELL SETUP REQUEST Message from RNC While NodeB in Normal
State
The logical cell cannot be setup. When you perform query with MML command
on NodeB Operation and Maintenance system, the local cell resources are available, and
both NCP and CCP states are normal. Upon receipt the request of resource audit from
NodeB Operation and Maintenance system by MML command ADT RES, RNC delivers
only a resource audit command but no CELL SETUP REQUEST message.
 Step 1:Check whether the maximum downlink power reported by NodeB
in the audit message is smaller than the value configured by RNC.
 Step 2:On NodeB Operation and Maintenance system, use the MML
command DSP CELL to view whether the local cell ID is consistent with
that specified in RNC.
Case2: Cell Deleted and Setup Repeatedly, RNC Multi-Frame Out-of-
Synchronization Alarm Occurs, Cell SetupFails
From the message traced by Iub interface, cell is deleted and setup repeatedly. At
the same time, there are multi-frame out-of-synchronization alarms unable to be cleared
in RNC. But E1 cable state is available when queried by the MML command DSP E1T1
on NodeB Operation and Maintenance system.
The most possible cause for this fault is that E1 working mode for NodeB is not
consistent with that for RNC, dual-frame for NodeB, and multi-frame for RNC.

Case3: Only One Cell Can Be Setup due to Modification of Cell Radius
Originally, cell 0 and cell 2 can be setup normally. After the radius of both cell 0
and cell 2 is modified from 256*78 m to 1536*78 m, cell 2 is failed to setup. The local
cell is unavailable due to lack of baseband resources according to the query result with
the corresponding MML command.
The fault must be caused by lack of access resources. A set of access resources
includes an access ASIC and an access DSP. When the cell radius is smaller than or equal
to 384*78 m, a set of access resources can support three cells. When the cell radius is
greater than 384*78 m, it can support only one cell.
Case4: RNC Deletes Cell after NodeB Responds with Cell and Common Transport
Channel Setup
RNC sends a CELL SETUP REQUEST message to NodeB, and NodeB reports a
CELL SETUP RESPONSE message to RNC. Then RNC sends two COMMON
TRANSPORT CHANNEL SETUP REQUEST messages. Upon receipt of the two
COMMON TRANSPORT CHANNEL SETUP RESPONSE messages from NodeB, the
RNC sends a CELL DELETION REQUEST message instead of a SYSTEM
INFORMATION UPDATE REQUEST message. There is no alarm in NodeB or RNC.
The fault may be relative to Iub interface user plane. In this case, it is necessary to
check the user plane of NodeB and RNC in data configuration and hardware connection
to see whether they are consistent.
2.7.3 NODE B FAULT PREVENTION
Hardware installation specifications are most important
 Pay more attention to E1 connector
 Pay more attention to feeder connector
 Pay more attention to the waterproofed of antenna and feeder system
 Confirm the grounding and lightning protection
Checking Running status
 Node B maintenance console.
 First, do “multi-site fault query”.
 Then, try to remove the fault according to the alarm description and
suggestion.
 If you cannot remove the fault provisionally, confirm the reason of every
fault at least.
2.8 LTE E NODE B TROUBLESHOOTING

Troubleshooting process

2.8.1 LTE SERVICE FAULTS

Service faults are further classified into the following types:
 Access faults
– User access fails.
– The access success rate is low.
 Handover faults
– The intra-frequency handover success rate is low.
– The inter-frequency handover success rate is low.
 Service drop faults
– Service drops occur during handovers.
– Services are unexpectedly released.
 Inter-RAT interoperability faults
– Inter-RAT handovers cannot be normally performed.
 Rate faults
– Data rates are low.
– There is no data rate.
– Data rates fluctuate.

2.8.2 LTEQUIPMENT FAULTS

Equipment faults are further classified into the following types:
 Cell faults
– Cell setup fails.
– Cell activation fails.
 Operation and maintenance channel (OMCH) faults
– The OMCH is interrupted or fails intermittently.
– The CPRI link does not work properly.
– The S1/X2/SCTP/IPPATH links do not work properly.
– IP transport is abnormal.
 Clock faults
– The clock source is faulty.
– The IP clock link is faulty.
– The system clock is out of lock.
 Security faults
– The IPSec tunnel is abnormal.
– SSL negotiation is abnormal.
– Digital certificate processing is abnormal.
 Radio frequency faults
– The standing wave is abnormal.
– The received total wideband power (RTWP) on the RX channel is
abnormal. The antenna line device (ALD) link does not work
properly.
 License faults
– License installation fails.
– License modification fails.
2.8.3 RECTIFYING THE FAULT
To troubleshoot a fault, take proper measures to eliminate the fault and restore the
system, including checking and repairing cables, replacing boards, modifying
configuration data, switching over the system, and resetting boards. Maintenance
personnel need to clear different faults using proper methods.
After the fault is cleared, be sure to perform the following:
o Perform testing to confirm that the fault has been rectified.
o Record the troubleshooting process and key points.
o Summarize measures of preventing or decreasing such faults. This
helps to prevent similar faults from occurring in the future.
2.9 CONCLUSION
For proper working of network maintenance of radio network is very important.
Day to day resolution of fault is of prime importance.

E2-E3 Consumer Mobility 3G Radio Network
3 3G RADIO NETWORK

 3G Standers and Releases
 CDMA/WCDMA Concept
 WCDMA Codes
 Handovers in 3G
 WCDMA Channels
3.2 INTRODUCTION
3G refers to the 3rd generation of mobile telephony (that is cellular) technology.
The 3rd generations the name suggests, follow two earlier generations. The 1st generation
(1G) began in the early80‟s with commercial development of advanced mobile phone
service (AMPS) cellular networks. Early AMPS network used frequency division
multiplex access (FDMA) to carry analogy voice over channels in the 800MHZ frequency
band. The 2nd generation (2G) emerged in the 90‟s when mobile generators deployed two
competing digital voice standards. In the North America, some operators adopted IS-95,
which uses CDMA to multiplex up to 64 calls per channel in the 800MHZ band. Across
the world, many operators adopted the global system for mobile communication (GSM)
standard, which used the time division multiple accesses (TDMA) technique to multiplex
up to 8 calls per channel in the 900MHZ and 1800MHZ spectrum bands.
The international telecommunication union (ITU) defined the 3rd generation (3G)
of mobile telephony standards IMT-2000 to facilitate growth, increase bandwidth and
support more diverse applications. Some of the limitations of 2Gsystems, it‟s only voice
oriented, it has limited data capabilities, no worldwide (WW) roaming and incompatible
system in different countries. Despite the extension of 2G system i.e. 2.5G such as GPRS
and EDGE, which provides the enhanced facilities and much improved data rates, but
there was still incompatibility issues and WW-roaming problems. Therefore, there was a
need of a system that could provide more advanced services. Some of the features of the
3G systems are:
 Bit rates up to 2Mbps.
 Variable bit rate to offer bandwidth on demand.
 Multiplexing of services with different Qos requirements on a single connection.
 Quality requirements from 10% frame error rate to 10-6 bit error rate.
 Co-existence with different systems and inter-system handovers for coverage
enhancement sand loading balancing.
 Uplink and downlink asymmetry e.g. web browsing causes more loading to
downlink than to uplink.
 High spectrum efficiency.
 Co-existence of FDD (Frequency division duplex) and TDD (time division
duplex) modes.
3.3 3G STANDARDS AND WCDMA RELEASES

Universal Mobile Telecommunication System (UMTS) is the standard for
European 3G based WCDMA systems which turned out to be the preferred solution for
countries with 2G because of its high data capability. The 3rd Generation Partnership

Project (3GPP) manages the UMTS and has assumed responsibility for the continued
standardization of GSM since July 2000. If we recall the first commercial UMTS network
was deployed in 2001 by NTT Do Como in Japan after since then other countries soon
took the same step in deploying the network including Germany, UK, France etc. During
the development of the UMTS specifications for the WCDMA systems within the3GPP,
it went through a series of phases and continuous update for instance the first UMTS
specification released which is known as the 3GPP Release-99 which was functionally
frozen in December 1999, which then implemented similar services with those of GSM
phase 2+(GPRS/EDGE). However the 3G network might still offer additional services
which are not available on the GSM platform e.g. video call. In the second phase brought
about the3GPP Release- 4 which would introduce mainly an all IP-Core Network which
would allow for the separation of call signalling and control from all actual connections
i.e. within the core network the flow of data will pass through a media gateway (MGW)
which would in turn maintain the connection and perform other switching functions this
approach was known as Soft Switching, however release-4 became frozen in march
2001because of newer releases to be introduced. After a while there was another release
termed as the 3GPP Release 5 which introduced the IP Multimedia Subsystem (IMS)
which would unify and perform all IP based multiservice i.e. a combination of more than
one service on a physical channel to a user e.g. voice & video or image. The introduction
of HSDPA and wide band AMR services are evolution of the Air Interface in order to
enhance the speed of the data rate, which was done by integrating the voice data on the
dedicated channel and data on the downlink shared channel are all multiplexed and
carried on the same carrier which allows for speed up to 14Mbps.
However release 5 specifications were soon frozen in 2002, nevertheless
subsequent releases within the specifications occur mainly with the transport technology;
basically the changes are made to improve the flexibility and efficiency of the operating
network.
3.4 CODE DIVISION MULTIPLE ACCESS AND WCDMA

Code Division Multiple Access (CDMA) is a multiple access technology where
the users are separated by unique codes, which means that all users can use the same
frequency and transmit at the same time. With the fast development in signal processing,
it has become feasible to use the technology for wireless communication, also referred to
as WCDMA and CDMA2000. In CDMA One and CDMA2000, a 1.25 MHz wide radio
signal is multiplied by a spreading signal (which is a pseudo-noise code sequence) with a
higher rate than the data rate of the message. The resultant signal appears as seemingly
random, but if the intended recipient has the right code, this process is reversed and the
original signal is extracted. Use of unique codes means that the same frequency is
repeated in all cells, which is commonly referred to as a frequency re-use of 1.
WCDMA is a step further in the CDMA technology. It uses a 5 MHz wide radio
signal and a chip rate of 3.84 Mcps, which is about three times higher than the chip rate of
CDMA2000 (1.22 Mcps). The main benefits of a wideband carrier with a higher chip rate
are:
• Support for higher bit rates
• Higher spectrum efficiency
• Higher QoS
Further, experience from second-generation systems like GSM and CDMA One
has enabled improvements to be incorporated in WCDMA. Focus has also been put on
ensuring that as much as possible of WCDMA operators‟ investments in GSM equipment
can be reused. Examples are the re-use and evolution of the core network, the focus on

co-siting and the support of GSM handover. In order to use GSM handover the
subscribers need dual mode handsets.
3.5 WCDMA CONCEPTS

Wideband Code Division Multiple Access is used for transmission and reception
in release 99. It concentrates on the air interface‟s physical layer, and the procedures used
in higher layers. The action takes place in the air interface‟s transport protocols. In the
transmitter, the radio link control and medium access control protocols handle tasks such
as retransmissions and control of the transmitted data rate. The physical layer then
manipulates the data in three stages. In the first stage, the data are processed one bit at a
time, to carry out tasks such as error correction coding. In the second stage, the coded bits
are divided into shorter units called chips, and the chips are processed at a time using the
techniques of CDMA. Finally, the chips are converted from digital to analogue form for
transmission over the air interface.
Figure 7: Architecture of the air interface’s transport protocols

When the data enter the physical layer, the data rate is typically 12.2 kbps. Using
error correction coding and another process called rate matching; the bit rate processor
increases the bit rate by a factor between 2 and 3, to 30 kbps. The chip rate processor then
divides each coded bit into 128chips, to produce a chip rate of 3.84 million chips per
second(Mcps). The same chip rate is used throughout UMTS FDD mode, but the other
numbers can vary from one data stream to another, and between the uplink and downlink.
Figure 8: Downlink channelisation and de-channelisation, from a Base Station to a

single mobile

Figure shows the chip rate processing that is carried out on the downlink, in a
network containing one mobile and one cell. At the top of the figure, the base station‟s
chip rate transmitter is handling a stream of bits that it wishes to send to the mobile. The
base station assigns the mobile a code that is known either as a channelisation code or a
spreading code: this is made of chips and has a length equal to the bit duration, so that the
code is repeated every bit. It then multiplies the symbol representations of the bits and
chips together, and sends the resulting chips to the analogue processor for transmission.
The bits and chips both have values of 0 and 1, but we have represented them
using binary phase shift keyed (BPSK) symbols of +1 and –1. In UMTS FDD mode, the
chip rate is fixed at 3.84 Mcps, so the chip duration is about 0.26µs. The number of chips
per bit is called the spreading factor: in this example, the spreading factor is 8. The bit
rate equals the chip rate divided by the spreading factor, so here the bit rate is 480kbps.
Note that error correction has already been applied to these bits, so the underlying
information rate is typically one third to one half.
If we ignore problems like noise and propagation loss, then the mobile‟s chip rate
processor receives an exact replica of the transmitted chips. We now assume that the base
station has previously told the mobile about the channelisation code that it will use, so
that the mobile can use this information to undo the effect of channelisation. It does this
by multiplying the incoming chips by the channelisation code. The mobile now has to
convert the chips into bits, which it does by adding together the chips that comprise each
bit. The result is a set of soft decisions, each of which has a sign corresponding to the
mobile‟s best estimate of the transmitted bit, and a magnitude corresponding to the
mobile‟s confidence in that estimate. Finally, the mobile converts the soft decisions into
hard decisions by taking the sign and it recovered the original bits.
Figure 9: Downlink channelisation &de-channelisation, from a base station to two

mobiles

Figure shows what happens if there are two mobiles in the cell. Here, the base
station assigns a different channelisation code to the second mobile, with the condition
that the two codes must be orthogonal: if we multiply them together chip-by-chip and add
up the results, the total must be zero. The base station multiplies the incoming bits by the
irrespective channelisation codes as before, and then adds the two streams together, chip-
by-chip. The transmitted chip stream contains signal levels of +2, 0 and –2, where each
chip has contributions for both of the two mobiles. The receive processing is unchanged:
each mobile multiplies the incoming stream of chips by its own channelisation code, adds
together the chips that comprise each bit, and calculates a set of hard decisions. In the
figure, the two mobiles have successfully recovered the bits that were intended for them,
despite the fact that the transmitted stream contained information for both mobiles. This
works because the two channelisation codes are orthogonal.
The complete processing procedures of a WCDMA system is shown in figure .
Source coding can increase the transmission efficiency of the input service signal. Error
detection and correction capabilities are introduced through channel coding to make the
transmission more reliable. Multi- level spreading is done to increase the capability of
overcoming interference. Through the modulation technique, the signals are then
converted to radio signals from digital form for transmission through the channel. At the
receiver, reverse of all these processes are carried out to recover the information signal
back.
Processing Procedure of WCDMA System

Transmitter
Service Source Channel

Spreading Modulation Transmission
Signal Coding Coding
symbol modulated
bit chip Radio
signal
Channel
Service Source Channel Reception

Despreading Demodulation
Signal Decoding Decoding
Receiver
Figure 10: A WCDMA System
3.6 WCDMA CODES

Two categories of codes used with UMTS WCDMA systems are Channelisation
codes and scrambling codes. Channelisation codes are orthogonal codes, based on
Orthogonal Variable Spreading Factor (OVSF) technique. The codes are fully orthogonal,
i.e., they do not interfere with each other, if they are time synchronized. Thus,
channelisation codes can separate the transmissions from a single source. In the downlink,
it can separate different users within one cell/sector. The OVSF channelisation codes are

picked from the code tree shown in Figure. We can think of the figure as a family tree in
which each channelisation code has two children, one made by repeating it, and the other
by repetition and inversion. The codes on each spreading factor are all mutually
orthogonal, while codes on different spreading factors are orthogonal too, so long as they
are not ancestors or descendants of each other.
The number of orthogonal codes available is equal to the spreading factor i.e.
eight orthogonal codes at a spreading factor of eight. The spreading factors are implicitly
restricted to integer powers of 2: in release 99, we only use spreading factors from 4 to
512 on the downlink, and 4 to 256 on the uplink. The channelisation code tree can only
accommodate a limited number of mobiles, so we want to re-use it in every cell. This
causes a problem if two nearby cells are transmitting on the same frequency and the same
channelisation code, because of cross-talk between the two transmissions. This problem
can be solved by introducing a second set of codes, known as scrambling codes, and
labeling each nearby cell with a different scrambling code.
Figure 11: Code Tree
3.7 CHANNELISATION CODES USED BY UMTS (ADAPTED

FROM 3GPP TS 25.213.)
The scrambling codes are made of chips, but they have a much longer repetition
period than the channelisation codes: 10ms, which is 38400 chips. In UMTS, there are
enough scrambling codes to label 512 different cells. This number is large enough that
cells on the same scrambling code are a large distance apart, and the cross-talk between
them is minimal. Ideally, the scrambling codes would be orthogonal to each other, but
here all the orthogonal codes are used in making the tree of channelisation codes. So
codes are created using a pseudo-random number generator, which makes the scrambling
codes uncorrelated. If we multiply two scrambling codes together and add up the results
as before, then the total is zero on the average, but it is not identically zero.
The effect of using uncorrelated codes is shown in figure which has four cells with
different scrambling codes, each transmitting to a different mobile. In this figure, the
spreading factor is four, so take the first four chips from each scrambling code. Here each

mobile receives a signal from its corresponding Node B, and interference from the other
three. The channelisation codes are left out for clarity: Choose channelisation codes of
1111 throughout, which would leave all the other numbers unchanged. Also assume that
each mobile receives equally strong signals from the four cells; this is a rather artificial
situation, but it serves to illustrate the point. Each cell applies its scrambling codes by a
chip-by-chip multiplication, and the process is reversed in the mobile receiver. Because
the scrambling codes are uncorrelated and not orthogonal, the mobiles receive some
interference from neighboring cells.
Figure 12: Scrambling and de-scrambling on the downlink

This perturbs the soft decisions away from their expected values, and occasionally
causes errors in the hard decisions. The receiver can correct most of these errors later on
using error correction and retransmissions, but some of them will leak through and
degrade the performance of the application. The interference and the resultant errors are a
very important issue in UMTS, and will ultimately limit the capacity of the system.
In the uplink, the processing steps are exactly the same, but the channelisation and
scrambling codes are used differently. The reason is that, in FDD mode, the transmissions
from different mobiles are not time synchronised in any way. This simplifies the design
of the system, but it has a disadvantage: it is impossible to distinguish the mobiles by the
use of different channelisation codes, because those codes are only orthogonal if they are
time synchronised with each other. Instead, the network distinguishes different mobiles
by assigning different scrambling codes to them, which ever cell they are in. The
channelisation codes are only used for two purposes: to set the data rate by means of the
spreading factor, and to distinguish different transmissions from a single mobile.
3.8 WCDMA RADIO ACCESS NETWORK:

The main purpose of the WCDMA Radio Access Network is to provide a
connection between the handset and the core network and to isolate all the radio issues

from the core network. The advantage is one core network supporting multiple access
technologies. The WCDMA Radio Access Network consists of two types of nodes:
Figure 13: WCDMA Radio Access Network
3.9 RADIO BASE STATION (NODE B)

The Radio Base Station handles the radio transmission and reception to/from the
handset over the radio interface (Uu). It is controlled from the Radio Network Controller
via the Iub interface. One Radio Base Station can handle one or more cells.
Figure 14: WCDMA Node B

3.9.1 FUNCTIONS OF NODE B:
 Radio transmission and reception handling
 Involved in the mobility management
 Involved in the power control
 Modulation / Demodulation
 Closed loop power control
3.10 RADIO NETWORK CONTROLLER (RNC)

The Radio Network Controller is the node that controls all WCDMA Radio
Access Network functions. It connects the WCDMA Radio Access Network to the core
network via the Iu interface. There are two distinct roles for the RNC, to serve and to
control. The Serving RNC has overall control of the handset that is connected to
WCDMA Radio Access Network. It controls the connection on the Iu interface for the
handset and it terminates several protocols in the contact between the handset and the
WCDMA Radio Access Network. The Controlling RNC has the overall control of a
particular set of cells, and their associated base stations.
Figure 15: Radio Network Controller
Main Functions of this Intelligent part of UTRAN System includes;
 Radio resource management (code allocation, Power Control,
congestion control, admission control)
 Call management for the users
 Connection to CS and PS Core Network
 Radio mobility management

When a handset must use resources in a cell not controlled by its Serving RNC,
the Serving RNC must ask the Controlling RNC for those resources. This request is made
via the Iur interface, which connects the RNCs with each other. In this case, the
Controlling RNC is also said to be a Drift RNC for this particular handset. This kind of
operation is primarily needed to be able to provide soft handover throughout the network.
3.11 RADIO ACCESS BEARERS

The main service offered by WCDMA RAN is the Radio Access Bearer (RAB).
To establish a call connection between the handset and the base station a RAB is needed.
Its characteristics are different depending on what kind of service/information to be
transported. The RAB carries the subscriber data between the handset and the core
network. It is composed of one or more Radio Access Bearers between the handset and
the Serving RNC, and one Iu bearer between the Serving RNC and the core network.
3GPP has defined four different quality classes of Radio Access Bearers:
 Conversational (used for e.g. voice telephony) – low delay, strict ordering
 Streaming (used for e.g. watching a video clip) – moderate delay, strict
ordering
 Interactive (used for e.g. web surfing) – moderate delay
 Background (used for e.g. file transfer) – no delay requirement
3.12 RADIO NETWORK FUNCTIONALITY

For optimal operation of a complete wireless system i.e. from handset to radio
access network (RAN) several functions are needed to control the radio network and the
many handsets using it. All functions described in this section, except for Handover to
GSM, are essential and therefore necessary for a WCDMA system.
Figure 16: WCDMA Architecture

3.12.1 POWER CONTROL
The power control regulates the transmit power of the terminal and base station,
which results in less interference and allows more users on the same carrier. Transmit
power regulation thus provides more capacity in the network. With a frequency re-use of
1, it is very important to have efficient power control in order to keep the interference at a
minimum. For each subscriber service the aim is that the base station shall receive the
same power level from all handsets in the cell regardless of distance from the base station.
If the power level from one handset is higher than needed, the quality will be excessive,
taking a disproportionate share of the resources and generating unnecessary interference
with the other subscribers in the network. On the other hand, if power levels are too low
this will result in poor quality. In order to keep the received power at a suitable level,
WCDMA has a fast power control that pdates power levels 1500 times every second. By
owing that the rapid change in the radio channel is handled. To ensure good performance,
power control is implemented in both the up-link and the down-link, which means that
both the output powers of the handset and the base station are frequently updated. Power
control also gives rise to a phenomenon called “cell breathing”. This is the trade-off
between coverage and capacity, which means that the size of the cell varies depending on
the traffic load. When the number of subscribers in the cell is low (low load), good
quality can be achieved even at a long distance from the base station. On the other hand,
when the number of users in the cell is high, the large number of subscribers generates a
high interference level and subscribers have to get closer to the base station to achieve
good quality.
3.12.2 SOFT AND SOFTER HANDOVER
With soft handover functionality the handset can communicate simultaneously

with two or more cells in two or more base stations. This flexibility in keeping the
connection open to more than one base station results in fewer lost calls, which is very
important to the operator. To achieve good system performance with a frequency re-use
of 1 and power control, soft and softer handover is required. Soft and softer handover
enables the handset to maintain the continuity and quality of the connection while moving
from one cell to another. During soft or softer handover, the handset will momentarily
adjust its power to the base station that requires the smallest amount of transmit power
and the preferred cell may change very rapidly. The difference between soft and softer
handover is that during soft handover, the handset is connected to multiple cells at
different base stations, while during softer handover, the handset is connected to multiple
cells at the same base station. A drawback with soft handover is that it requires additional
hardware resources on the network side, as the handset has multiple connections. In a
well-designed radio network, 30–40 % of the users will be in soft or softer handover.
Figure 17: Soft and Softer Handover

3.12.3 HANDOVER TO GSM (INTER-SYSTEM HANDOVER)
When WCDMA was standardized a key aspect was to ensure that existing
investments could be re-used as much as possible. One example is handover between the
new (WCDMA) network and the existing (GSM) network, which can be triggered by
coverage, capacity or service requirements. Handover from WCDMA to GSM, for
coverage reasons, is initially expected to be very important since operators are expected
to deploy WCDMA gradually within their existing GSM network. When a subscriber
moves out of the WCDMA coverage area, a handover to GSM has to be conducted in
order to keep the connection. Handover between GSM and WCDMA can also have a
positive effect on capacity through the possibility of load sharing. If for example the
numbers of subscribers in the GSM network is close to the capacity limit in one area,
handover of some subscribers to the WCDMA network can be performed. Another
function that is related to inter-system handover is the compressed mode. When
performing handover to GSM, measurements have to be made in order to identify the
GSM cell to which the handover will be made. The compressed mode is used to create the
measurement periods for the handset to make the required measurements. This is
typically achieved by transmitting all the information during the first 5 milliseconds of
the frame with the remaining 5 milliseconds being used for measurements on the other
systems.
Figure 18: Inter System Handover
3.12.4 INTER-FREQUENCY HANDOVER (INTRA-SYSTEM HANDOVER)
The need for inter-frequency handover occurs in high capacity areas where
multiple 5 MHz WCDMA carriers are deployed. Inter-frequency handover, which is
handover between WCDMA carriers on different frequencies, has many similarities with
GSM handover, for example the compressed mode functionality.
3.13 CONCLUSION
WCDMA is very successful technology due to its robust radio network design.3G
has got an add-on feature with the introduction of HSPA and HSPA+.

E2-E3 Consumer Mobility 3G Core Network
4 3G CORE NETWORK

 UMTS Network Component
 3G Core Network
 Elements of 3G Core
 Functionalities of 3G Core Network Elements
4.2 UMTS NETWORK COMPONENT

UMTS is regarded as a third generation (3G) wireless communication system
based on WCDMA and is an evolved version of GSM GPRS and EDGE .The first release
of the UMTS system was called release 99.
A UMTS network consists of three interacting domains:
 User Equipment (UE)
 UMTS Terrestrial Radio Access Network (UTRAN)
 Network (CN)
These three elements all have interfaces that connect to one element to the
otherwhich are denoted as Iu and Uu, the Iu is the interface between the core network and
the UTRAN, while the Uu is the interface between the UTRAN and the User equipment,
Figure 19: UMTS Release 99 Architecture
4.3 3G CORE NETWORK (CN)

The 3G UMTS core network architecture is a migration of that used for GSM with
further elements overlaid to enable the additional functionality demanded by UMTS.The
core network provides all the central processing and management for the system. The CN
is similar to the network and switching subsystem (NSS) of the GSM architecture. The
main function of the CN is to perform packet routing, connection of users, security,
billing etc. The core network is the overall entity that interfaces to external networks
including the public phone network and other cellular telecommunications networks.
The UMTS Core Network elements can be categorised into two domains depending on
the type of traffic and functions they handle.

 Circuit switched elements: These elements are primarily based on the

GSM network entities and carry data in a circuit switched manner, i.e. a
permanent channel for the duration of the call.
 Packet switched elements: These network entities are designed to carry
packet data. This enables much higher network usage as the capacity can
be shared and data is carried as packets which are routed according to their
destination.
Figure 20: UMTS Core Network
4.4 CIRCUIT SWITCHED CORE NETWORK

The circuit switched elements of the UMTS core network architecture include the
following network entities:
4.4.1 MOBILE SWITCHING CENTRE (MSC)
The MSC is the interface between the Radio Access Network (RAN) and fixed
networks. It provides mobility management, call control and switching functions to
enable circuit-switched services to and from mobile stations.
4.4.2 GATEWAY MSC (GMSC)
The GMSC interfaces with the fixed networks, handles subscriber location
information from the HLR and performs routing functions to and from mobile stations.
GMSC functionality can be contained in all or some of the MSCs of the network,
depending on network configuration.
4.5 PACKET SWITCHED ELEMENTS

Packet Switched core network includes elements that support packet switching
technology. Packet-switching technology routes packets of user data independently of one
another. No dedicated circuit is established. Each packet can be sent along different
circuits depending on the network resources available. The packet switched elements of
the 3G UMTS core network architecture include the following network entities:

4.5.1 SERVING GPRS SUPPORT NODE (SGSN)

As the name implies, this entity was first developed when GPRS was introduced,
and its use has been carried over into the UMTS network architecture. The SGSN
provides a number of functions within the UMTS network architecture.
 Mobility Management: When a UE attaches to the Packet Switched domain of
the UMTS Core Network, the SGSN generates MM information based on the
mobile's current location.
 Session Management: The SGSN manages the data sessions providing the
required quality of service and also managing what are termed the PDP (Packet
data Protocol) contexts, i.e. the pipes over which the data is sent.
 Interaction with other areas of the network: The SGSN is able to manage its
elements within the network only by communicating with other areas of the
network, e.g. MSC and other circuit switched areas.
 Billing: The SGSN is also responsible billing. It achieves this by monitoring the
flow of user data across the GPRS network. CDRs (Call Detail Records) are
generated by the SGSN before being transferred to the charging entities
(Charging Gateway Function, CGF).
4.5.2 GATEWAY GPRS SUPPORT NODE (GGSN)

Like the SGSN, this entity was also first introduced into the GPRS network. The
Gateway GPRS Support Node (GGSN) is the central element within the UMTS packet
switched network. It handles inter-working between the UMTS packet switched network
and external packet switched networks, and can be considered as a very sophisticated
router. In operation, when the GGSN receives data addressed to a specific user, it checks
if the user is active and then forwards the data to the SGSN serving the particular UE.
4.5.3 BORDER GATEWAY (BG)
The BG provides connectivity, and interworking and roaming capabilities between
two different PLMNs.
4.6 SHARED ELEMENTS

Some network elements, particularly those that are associated with registration are
shared by both domains and operate in the same way that they did with GSM. The shared
elements of the 3G UMTS core network architecture include the following network
entities:
4.6.1 HOME LOCATION REGISTER (HLR)
This database contains all the administrative information about each subscriber
along with their last known location. In this way, the UMTS network is able to route calls
to the relevant RNC / Node B. When a user switches on their UE, it registers with the
network and from this it is possible to determine which Node B it communicates with so
that incoming calls can be routed appropriately. Even when the UE is not active (but
switched on) it re-registers periodically to ensure that the network (HLR) is aware of its
latest position with their current or last known location on the network.

4.6.2 VISITOR LOCATION REGISTER(VLR)

The VLR manages mobile subscribers in the home PLMN and those roaming in a
foreign PLMN. The VLR exchanges information with the HLR.
4.6.3 EQUIPMENT IDENTITY REGISTER (EIR)
The EIR is the entity that decides whether a given UE equipment may be allowed
onto the network. Each UE equipment has a number known as the International Mobile
Equipment Identity. This number, as mentioned above, is installed in the equipment and
is checked by the network during registration.
4.6.4 AUTHENTICATION CENTRE (AUC)
The AuC is a protected database that contains the secret key also contained in the
user's USIM card.
4.6.5 EQUIPMENT IDENTITY REGISTER (EIR)
The EIR stores information on mobile equipment identities.
4.6.6 SMS MSCS
SMS MSCs enable the transfer of messages between the Short Message Service
Center and the PLMN.
4.7 ENHANCEMENT IN UMTS ARCHITECTURE IN FUTURE

RELEASES
The first enhancement was the bearer independent circuit switched core network
in release 4. In this architecture, the mobile switching centre is split in two. The circuit
switched media gateway (CS-MGW) handles the traffic functions of the MSC, but uses
different transport protocols that we will see in the next section. It also includes a media
conversion function, which allows it to communicate with networks that are using other
types of transport protocol. The MSC server combines the signalling functions of the
MSC with those of the VLR, and also controls the CS-MGW over a signalling interface
that lies between them. A GMSC server is built in the same way.
The main network enhancement in release 5 is the IP multimedia subsystem
(IMS). This is an extra network which interfaces with the packet switched domain, and
which provides users with real time packet switched services that cannot be supplied
using the packet switched domain alone. The home subscriber server (HSS) was also
introduced in release5, and combines the functions of the HLR and the AuC. The third
release5 enhancement (not shown in the figure) is an architectural feature known as
IuFlex. In earlier releases, each radio network controller was connected to just one MSC
and one SGSN. IuFlex introduces a more flexible architecture in which each RNC can be
connected to multiple MSCs and multiple SGSNs.
The main release 6 enhancement is wireless local area network (WLAN)
interworking. This allows users to access the network operator‟s packet switched services
using a wireless LAN. The services are supplied either by the IMS, or by data servers that
are controlled by the network operator and directly connected to a GGSN. The connection
uses some extra core network components that are not shown in the figure, known as the
WLAN access gateway (WAG) and packet data gateway (PDG).

Figure 21: 3GPP Releases
4.8 3GPP RELEASE 4 (R4) ARCHITECTURE

3GPP Release 4 implements the NGN architecture in the core network, separating
the control and user planes. This enables a true separation of control and connection
operations, and provides the independence of applications and services from basic
switching and transport technologies. 3GPP Release 4 (R4) introduces the following new
network elements in addition to R99 elements:

4.8.1 MSC SERVER
The MSC server provides call control and mobility management functions for an
MSC. It also holds subscriber service data information and provides connection control
for media channels in a CS-MGW.

4.8.2 GMSC SERVER

The GMSC server provides call control and mobility management functions for a
GMSC.
4.8.3 CIRCUIT-SWITCHED-MEDIA GATEWAY (CS-MGW)
The CS-MGW is an interface between the UTRAN and the Core Network. The
CS- MGW supports both UMTS and GSM media. CS-MGW terminates bearer channels
from circuit-switched networks and media streams from packet networks. It supports
media conversion, bearer control and payload processing. See figure for an illustration of
3GPP Release 4 network architecture.
4.9 3GPP RELEASE 5 (R5)

3GPP Release 5 implements a unified IP backbone infrastructure which enables
high performance services and functions. 3GPP Release 5 (R5) introduces the following
new network elements in addition to R99 and R4 elements:
Common Core Network elements:
 Home Subscriber Server (HSS)
 Internet protocol Multimedia (IM) subsystem.
The IM subsystem consists of all Core Network elements that use the services
provided by the PSCN to offer multimedia services. The IM subsystem primarily includes
the Call ServerControl Function (CSCF), Media Gateway Control Function (MGCF) and
the Multimedia Resource Function (MRF).
4.10 CONCLUSION
The 3G Network is designed for data delivery , but upto release 4 legacy network
is also accommodated in the same. After release 5 core network is converted to complete
IP based network

E2-E3 Consumer Mobility 3G Call Proessing (Voice and Data)
5 3G CALL PROCESSING (VOICE AND DATA)

 3G Mobile Originated Call
 3G Terminated Voice Call
 Data Attach/Detach processes
 3G Data Call Flow.
5.2 ARCHITECTURE FOR UMTS 3G CALL HANDLING

The architecture for handling a basic Mobile Originated (MO) call and a basic
Mobile Terminated Call (MT) are shown in Fig. A basic mobile-to-mobile call is treated
as the concatenation of an MO call and an MT call.
5.2.1 ARCHITECTURE FOR AN MO CALL
A basic mobile originated call involves signaling between the MS and its Visiting
MSC (VMSC) via the BSS, between the VMSC and the VLR and between the VMSC
and the destination exchange, as indicated in figure
Radio I/F signalling Iu or A I/F signalling IAM (ISUP)

BSSA VMSCA
MS
SIFOC
Complete call
VPLMNA VLRA
Figure 24: Architecture for a basic mobile originated call

The term BSS is used to denote a UTRAN BSS. The term ISUP is used to denote
the telephony signaling system used between exchanges. In a given network, any
telephony signaling system may be used.
When the user of an MS wishes to originate a call, the MS establishes
communication with the network using radio interface signaling, and sends a message
containing the address of the called party. VMSCA requests information to handle the
outgoing call (SIFOC) from VLRA, over an internal interface of the MSC/VLR. If VLRA
determines that the outgoing call is allowed, it responds with a Complete Call. VMSCA:
 establishes a traffic channel to the MS; and
 constructs an ISUP IAM using the called party address and sends it to the
destination exchange.
5.2.2 ARCHITECTURE FOR AN MT CALL
A basic mobile terminated call involves signaling as indicated in figure below.
Communication between VMSCB and the MS is via the BSS, as for the mobile originated
case. If VPLMNB supports GPRS and the Gs interface between VLRB and the SGSN is
implemented and there is an association between VLRB and the SGSN for the MS, the

paging signal towards the MS goes from VMSCB via VLRB and the SGSN to the BSS.
The IPLMN(Interrogating PLMN ) , containing GMSCB, is in principle distinct from
HPLMNB (Home Public Land Mobile Network B ), containing HLRB, but the practice
for at least the majority of current UMTS or GSM networks is that a call to an MS will be
routed to a GMSC in HPLMNB.
Radio I/F
IAM signalling
IPLMN (ISUP) VMSCB BSSB
IAM
(ISUP)
GMSCB SIFIC
MS
Page/ack
Complete call
VLRB VPLMNB
Send Routeing
Inf o/ack
Provide Roaming
Number/ack
IMLMN : Interrogating PLMN
VMSC : Visiting MSC
HPLMN : Home PLMN
HLRB
HPLMNB
Figure 25: Architecture for a basic mobile terminated call

When GMSCB receives an ISUP IAM, it requests routing information from
HLRB using the MAP protocol. HLRB requests a roaming number from VLRB, also
using the MAP protocol, and VLRB returns a roaming number in the Provide Roaming
Number Ack. HLRB returns the roaming number to GMSCB in the Send Routing Info
ack. GMSCB uses the roaming number to construct an ISUP IAM, which it sends to
VMSCB. When VMSCB receives the IAM, it requests information to handle the
incoming call (SIFIC) from VLRB, over an internal interface of the MSC/VLR. If VLRB
determines that the incoming call is allowed, it requests VMSCB to page the MS.
VMSCB pages the MS using radio interface signaling. When the MS responds, VMSCB
informs VLRB in the Page ack message. VLRB instructs VMSCB to connect the call in
the Complete call, and VMSCB establishes a traffic channel to the MS.
5.2.3 ARCHITECTURE FOR A TO CALL
A basic trunk originated call involves signaling between the PSTN and the
PLMN"s MSC, as indicated in figure. The originating exchange may also be another
MSC of the same or different PLMN.
The MSC may also be connected to PBX but that is outside the scope of this
document. In the PBX case same modelling applies but the PBX signaling is different to
ISUP.

IAM GMSCB/
(ISUP/ internal) VMSCB
IAM
Originating IAM
(ISUP) MSC
exchange (ISUP)
PSTN
sw itch
IAM
(ISUP)
Other
PLMN
Figure 26: Architecture for a basic trunk originated call

The term ISUP is used to denote the telephony signaling system used between
exchanges. In a given network, any telephony signaling system may be used.
The MSC receives a setup (IAM) message from the originating exchange. The
MSC analyses the called party number and routes the call to an appropriate destination. If
the called party number is an MSISDN the gateway MSC functionality is activated. If the
MSISDN belongs to another PLMN (or is ported out), the call is routed to another
PLMN. If the called number is a PSTN number then the call is routed to (appropriate)
PSTN operator. There may be other destinations also.
5.2.4 INFORMATION FLOW FOR AN MO CALL
An example information flow for an MO call is shown in figure; many variations
are possible. Signaling over the radio interface between MSA and BSSA or VMSCA is
shown by dotted lines; signaling over the Iu interface (for UMTS) or the A interface (for
GSM) between BSSA and VMSCA is shown by dashed lines; signaling over the B
interface between VMSCA and VLRA is shown by chain lines; and ISUP signaling
between VMSCA and the destination exchange is shown by solid lines.
Figure 27: Information flow for a basic mobile originated call

NOTE 1: Authentication may occur at any stage during the establishment of an

MO call; its position in this message flow diagram is an example.
NOTE 2: Security procedures may be initiated at any stage after authentication;
the position in this message flow diagram is an example.
NOTE 3: If ciphering is not required for a GSM connection, the MSC may send a
CM service accept towards the MS; optionally it may instead send a "start ciphering"
request indicating that no ciphering is required. This option is not available for a UMTS
connection.
NOTE 4: The network may request the IMEI from the MS, and may check the
IMEI, at any stage during the establishment of an MO call, either as part of the procedure
to start security procedures or explicitly after security procedures have started; this is not
shown in this message flow diagram.
When the user wishes to originate a call, MSA establishes a signalling connection
with BSSA, and sends a Connection Management (CM) service request to BSSA, which
relays it to VMSCA. VMSCA sends a Process Access Request to VLRA. VLRA may
then initiate authentication, as described in 3GPP TS 33.102 [32] for UMTS and3GPP TS
43.020 [1] for GSM. VLRA may also initiate security procedures at this stage, as
described in3GPP TS 33.102 [32] for UMTS 3GPP TS 43.020 [1] for GSM. If the user
originates one or more new MO calls in a multicall configuration, MSA sends a CM
service request through the existing signalling connection for each new call.
If the MS has performed the Connection Management (CM) service request in a
CSG cell, VLRA shall control if the CSG cell is allowed by the CSG subscription data
stored in VLRA. If the CSG cell is not allowed, VLRA shall reject the Process Access
Request.
If the MS has performed the Connection Management (CM) service request in a
hybrid cell, VLRA shall set the CSG membership status in the Process Access Request
ack according to the CSG subscription data stored in VLRA.
If VLRA determines that MSA is allowed service, it sends a Process Access
Request ack to VMSCA. If VMSCA has received a Start security procedures message
from VLRA, the Process Access Request ack message triggers a Start security procedures
message towards BSSA; otherwise VMSCA sends a CM Service Accept message
towards BSSA.
If BSSA receives a Start security procedures message from VMSCA, it initiates
security procedures as described in 3GPP TS 33.102 [32] for UMTS and 3GPP TS 43.020
[1] for GSM; when security procedures have been successfully initiated, MSA interprets
this in the same way as a CM Service Accept. If security procedures are not required at
this stage, BSSA relays the CM Service Accept to MSA.
When MSA has received the CM Service Accept, or security procedures have
been successfully initiated, MSA sends a Set-up message containing the B subscriber
address via BSSA to VMSCA. MSA also uses the Set-up message to indicate the bearer
capability required for the call; VMSCA translates this bearer capability into a basic
service, and determines whether an interworking function is required. VMSCA sends to
VLRA a request for information to handle the outgoing call, using a Send Info For
Outgoing Call (SIFOC) message containing the B subscriber address.
If VLRA determines that the call should be connected, it sends a Complete Call
message to VMSCA. VMSCA sends a Call Proceeding message via BSSA to MSA, to
indicate that the call request has been accepted, and sends an Allocate channel message to
BSSA, to trigger BSSA and MSA to set up a traffic channel over the radio interface. The
Call Proceeding message includes bearer capability information if any of the negotiable
parameters of the bearer capability has to be changed. When the traffic channel

assignment process is complete (indicated by the Allocation complete message from

BSSA to VMSCA), VMSCA constructs an ISUP IAM using the B subscriber address,
and sends it to the destination exchange.
When the destination exchange returns an ISUP Address Complete Message
(ACM), VMSCA sends an Alerting message via BSSA to MSA, to indicate to the calling
user that the B subscriber is being alerted.
When the destination exchange returns an ISUP ANswer Message (ANM),
VMSCA sends a Connect message via BSSA to MSA, to instruct MSA to connect the
speech path.
The network then waits for the call to be cleared.
For an emergency call, a different CM service type (emergency call) is used, and
the mobile may identify itself by an IMEI. It is a network operator option whether to
allow an emergency call when the mobile identifies itself by an IMEI.
5.2.5 INFORMATION FLOW FOR RETRIEVAL OF ROUTING INFO FOR

AN MT CALL
The information flow for retrieval of routing information for an MT call is shown
in figure ISUP signalling between the originating exchange and GMSCB, and between
GMSCB and VMSCB is shown by solid lines; signalling over the MAP interfaces
between GMSCB and HLRB and between HLRB and VLRB, and over the B interface
between VLRB and VMSCB is shown by chain lines; signalling over the Iu interface (for
UMTS) or the A interface (for GSM) between VMSCB and BSSB is shown by dashed
lines; and signalling over the radio interface between BSSB and MSB is shown by dotted
lines.
Figure 28: Information flow for retrieval of routing information for a basic mobile
terminated call

NOTE 1: If pre-paging is used, paging is initiated after VLRB has accepted the
PRN message.
NOTE 2: VMSCB starts the timer for the release of radio resources after it sends
the Process Access Request message to VLRB. VMSCB releases the radio resource
allocated for the MT call if the timer expires before the IAM is received, and when the
MAP RELEASE_RESOURCES message is received from the GMSC.
NOTE 3: If an ISUP REL message is received at the GMSC between sending of
SRI and receiving of SRI ack, the GMSC does not send IAM to the VMSC. Instead a
MAP Release_ Resources message may be sent to the VMSC.
When GMSCB receives an IAM, it analyses the called party address. If GMSCB
can derive an HLR address from the B party address, it sends a request for routeing
information (SRI) to HLRB. If GMSCB supports pre-paging (i.e. it is prepared to wait
long enough for the SRI ack to allow pre-paging to be completed), it indicates this by an
information element in the SRI message.
HLRB decides whether pre-paging is supported according to the following
criteria:
GMSCB has indicated that it supports pre-paging; and
HLRB supports pre-paging (i.e. it is prepared to wait long enough for the PRN ack
to allow pre-paging to be completed).
HLRB sends a request for a roaming number (PRN) to VLRB; if pre-paging is
supported, it indicates this by an information element in the PRN message. If Paging Area
function is supported in HLRB then HLRB sends the paging area if stored in HLR. VLRB
returns the roaming number in the PRN ack, and HLRB relays the roaming number to
GMSCB in the SRI ack. GMSCB constructs an IAM using the roaming number, and
sends it to VMSCB.
If the GMSC performs domain selection through HLR interrogation and the HLR
supports domain selection functionality, HLRB executes domain selection functionaility.
The HLR shall:
send PRN to VLRB as defined in this section , if the result of domain selection is
to handle the call in CS domain; or
reply with SRI ack without sending PRN to VLRB, if the result of domain
selection is to transfer the call from CS domain to IMS domain.
5.2.6 INFORMATION FLOW FOR AN MT CALL
An example information flow for an MT call is shown in figure ; many variations
are possible. ISUP signalling between GMSCB and VMSCB is shown by solid lines;
signalling over the B interface between VMSCB and VLRB is shown by chain lines;
signalling over the Iu interface (for UMTS) or the A interface (for GSM) between
VMSCB and BSSB is shown by dashed lines; and signalling over the radio interface
between VMSCB or BSSB and MSB is shown by dotted lines. NOTE 1: Security
procedures may be initiated at any stage after the network has accepted the page response;
the position in this message flow diagram is an example.
NOTE 2: If Security procedures are not required, the MSC may send a Start
security procedures message indicating that no ciphering is required.
NOTE 3: This message flow diagram assumes that the MS has already been
authenticated on location registration. If this is not so (for the first MT call after VLR
restoration), the network may initiate authentication after the MS responds to paging.
NOTE 4: The network may request the IMEI from the MS, and may check the
IMEI, at any stage after the MS responds to paging, either as part of the procedure to start

security procedures or explicitly after security procedures have been started; this is not
shown in this message flow diagram.
NOTE 5: If a connection between MSCB and MSB has been established as a
result of pre-paging, the paging procedure is not performed.
NOTE 6: If a connection between MSCB and MSB has been established as a
result of pre-paging, VLRB sends the Call arrived message to MSCB to stop the guard
timer for the release of the radio connection.
Figure 29: Information flow for a basic mobile terminated call

When VMSCB receives an IAM from GMSCB it sends to VLRB a request for
information to handle the incoming call, using a Send Info For Incoming Call (SIFIC)
message containing the roaming number received in the IAM.
If VLRB recognizes the roaming number, and MSB is allowed service, it sends a
request to VMSCB to page MSB. If a radio connection between the network and MSB is
already established, VMSCB responds immediately to the page request. If no radio
connection exists, VMSCB sends a page request to BSSB, and BSSB broadcasts the page
on the paging channel. If VPLMNB supports GPRS and the Gs interface between VLRB
and the SGSN is implemented (see 3GPP TS 23.060 [9]) and there is a valid association
between VLRB and the SGSN for the MS, the paging signal towards the MS goes from
VMSCB via VLRB and the SGSN to the BSS.

If MSB detects the page, it sends a channel request to BSSB, which responds with
an immediate assignment command, to instruct MSB to use the specified signalling
channel. MSB then sends a page response on the signalling channel; BSSB relays this to
VMSCB. VMSCB sends a Process access request message to VLRB to indicate that MSB
has responded to paging. VLRB may then initiate authentication, as described in 3GPP
TS 33.102 [32] for UMTS and 3GPP TS 43.020 [1] for GSM. VLRB may also initiate
security procedures at this stage, as descry bed in3GPP TS 33.102 [32] for UMTS and
3GPP TS 43.020 [1] for GSM.
If the MS is paged in a CSG cell, VLRB shall control if the CSG cell is allowed
by the CSG subscription data stored in VLRB. If the CSG cell is not allowed, VLRB shall
reject the Process Access Request.
If the MS is paged in a hybrid cell, VLRA shall set the CSG membership status in
the Process Access Request ack according to the CSG subscription data stored in VLRA.
VLRB may restore CSG data from CSS for a MT call after a VLRB restart.
If VLRB determines that MSB is allowed service, it sends a Process access
request ack to VMSCB. The Process access request ack message triggers a Start security
procedures message towards BSSB; if VMSCB has not received a Start security
procedures message from VLRB, the Start security procedures message indicates no
ciphering.
VLRB then sends a Complete call message to VMSCB. VMSCB sends a Set-up
message towards MSB. The Set-up message may include bearer capability information
for the call.
When MSB receives the Set-up message from BSSB, it responds with a Call
confirmed message. The Call Confirmed message includes bearer capability information
if any of the negotiable parameters of the bearer capability has to be changed. When
VMSCB receives the Call confirmed message via BSSB, it sends an Allocate channel
message to BSSB. BSSB instructs MSB to tune to a traffic channel by sending an
Assignment command. When MSB has tuned to the specified traffic channel it responds
with an Assignment complete, message, which BSSB relays to VMSCB as an Allocation
complete, and sends an Alerting message to indicate that the called user is being alerted.
VMSCB sends an ACM to GMSCB, which relays it to the originating exchange.
When the called user answers, MSB sends a Connect message, which BSSB
relays to VMSCB. VMSCB:
 responds with a Connect ack message towards MSB.
 sends an ANM to GMSCB, which relays it to the originating exchange.
 sends a Complete call ack to VLRB.
 the network then waits for the call to be cleared.
5.3 DETAILS CALL FLOW DIAGRAM

5.3.1 BASIC MOBILE ORIGINATINGIRCUIT SWITCHED CALL
DIAGRAM
A 3G UMTS originating voice call setup involves complex signalling to setup and
release the call.
In this Procedure the UE is attached to the Network in Idle mode. The following
steps need to be executed in order for a MO call to complete:
 RRC Connection Setup
 Service Request
 Security Procedures (Identity / Authentication / Security mode)

 Call Setup Request

 Radio Link and RAB Configuration
 Call Connection
Figure 30: Mobile Originated Circuit Switched Call flow

Call Control (CC) Messages exchanged between CC entity of UE and CC entity
of network are summarized below for MO call establishment:
(UE) SETUP >>>(NETWORK)
(UE)<<< CALL PROCESSING (NETWORK)
(UE)<<< ALERTING (NETWORK)
(UE)<<< CONNECT (NETWORK)
(UE) CONNECT ACK >>>(NETWORK)
5.3.2 BASIC MOBILE TERMINATING CIRCUIT SWITCHED CALL
FLOW
The following steps need to be executed in order for a MT call to complete:
 RRC Paging
 RRC Connection setup
 Call confirmed
 Radio bearer setup

 Alerting
 Connect
Call Control (CC) Messages exchanged between CC entity of UE and CC entity
of network are summarized below for MT call establishment:
(UE)<<< SETUP (NETWORK)
(UE) CALL CONFIRMED >>> (NETWORK)
(UE) ALERTING >>> (NETWORK)
(UE) CONNECT >>> (NETWORK)
(UE)<<< CONNECT ACK (NETWORK)
Figure 31: Mobile Terminated Circuit Switched Call flow

5.3.3 MOBILE ORIGINATED PACKET SWITCHED CALL FLOW

General packet switched call flow(PS call/Data call) between Mobile(UE) and
network compatible with WCDMA covers messages exchanged between Layer 3 entities
at both side. It includes channels used at layer 1 to carry these messages over the air.
At the start of this Procedure the UE is RRC Idle, PMM Detached and SM
Inactive.
The following steps need to be executed in order for a mo call to complete;
Establish an RRC connection to the UTRAN
Establish an Iu connection to the CN
Make an Attach Request
Carry out Security Procedures
Complete the Attach
Request PDP context activation
Set-up RAB‟s for the connection
Create GTP connections and activate PDP Context at the GGSN
Data Transfer
Figure 32: Mobile Originated Packet Switched Call flow

5.3.4 MOBILE TERMINATED PACKET SWITCHED CALL FLOW

The following steps need to be executed in order for a MT Packet switched call to
complete:
 RRC Paging
 RRC Connection setup
 Service Requiest
 PDP Context activation
 Radio bearer setup
 Data Transfer
Figure 33: Mobile Terminated Packet Switched Call flow
5.4 CONCLUSION
In this chapter we have understood regarding various types of 3G calls i.e. circuit
switched and packet switched in detail.

E2-E3 Consumer Mobility 3G Radio Network Optimization
6 3G RADIO NETWORK OPTIMIZATION

 WCDMA Radio Network Optimization
 WCDMA Optimization and monitoring
 Challenges in WCDMA Optimization
 WCDMA Drive Test
 WCDMA Parameters
6.2 INTRODUCTION
The overall planning goal in any wireless system is to maximize coverage and
capacity while meeting the KPIs (key performance indicators) and QoS (quality of
service). The UMTS radio system planning process is similar to the GSM planning
process. The phases of the planning process are:
 Dimensioning
 Configuration planning
 Coverage and capacity planning
 Code and frequency planning
 Parameter planning
 Optimization and monitoring
Figure shows the UMTS planning process. In particular, the figure shows the one
key issue in UMTS coverage and capacity planning, namely that the traffic level has to be
considered continuously in UMTS radio planning.
Figure 34: The UMTS Planning and Optimization process
6.3 WCDMA OPTIMIZATION AND MONITORING

Network optimization can initially be seen as a very involving task as a large
number of variables are available for tuning, impacting different aspect of the network
performance. To simplify this process a step by step approach is proposed in Figure. This
approach divides the optimization in simpler steps, each step focusing on a limited set of
parameters:
 RF optimization will focus mainly on RF configuration and in a lesser
extent on reselection parameters.

 Voice optimization will focus on improving the call setup (Mobile

Originated and Mobile Terminated) and call reliability thus focusing
mainly on access and handover parameters.
 Advance services optimization will rely extensively on the effort
conducted for voice. The initial part of the call setup are similar for all
type of services and vendor have not at this point defined different set of
handover parameters for different services. Consequently, optimizing these
services will focus on a limited set of parameters, typically power
assignment, quality target, and Radio Link Control (RLC) parameters.
 Inter-system (also known as inter-RAT) change (both reselection and
handover) optimization is considered once the WCDMA layer is fully
optimized. This approach will ensure that inter-system parameters are set
corresponding to finalize boundaries rather than set to alleviate temporary
issues due to sub-optimal optimization.
Even after careful RF planning, the first step of optimization should concentrate
on RF. This is necessary as RF propagation is affected by so many factors (e.g.,
buildings, terrain, vegetation…) that propagation models are never fully accurate. RF
optimization thus takes into account any difference between predicted and actual
coverage, both in terms of received signal (RSCP) and quality of the received signal
(Energy per chip / Noise spectral density( Ec/No)).In addition, the same qualitative
metrics defined for planning should be considered: cell overlap, cell transition, and
coverage containment of each cell. At the same time, assuming that a UE (User
Equipment) is used to measure the RF condition in parallel with a pilot scanner,
reselection parameters can be estimated considering the dynamics introduced by the
mobility testing: during network planning dynamics cannot be considered, as network
planning tools are static by nature, only simulating at one given location at a time,
irrespectively of the surrounding. In addition, once the RF conditions are known,
dynamic simulation can be used to estimate the handover parameters, even before placing
any calls on the network.
Service optimization is needed to refine the parameter settings (reselection,
access, and handover). Because the same basic processes are used for all types of
services, it is best to set the parameters while performing the simpler and best understood
of all services: voice. Either for access or for handover, the main difference between
voice and other service is the resource availability. Testing with voice service greatly
simplifies the testing procedure and during analysis limits the number of parameters, or
variable, to tune. During this effort, parameter setting will be the main effort.
Different set of parameters are likely to be tried to achieve the best possible
trade-offs: coverage vs. capacity, call access (Mobile Originated and Mobile Terminated)
reliability vs. call setup latency, call retention vs. Active Set size to name only a few. The
selection of the set of parameter to leave on the network will directly depend on the
achieved performance and the operator priority (coverage, capacity, access performance,
call retention performance…).

Figure 35: step by step approach

Once the performance targets are reached for voice, optimizing advanced services
such as video-telephony and packet switched (PS) data service will concentrate on a
limited set of parameters: power assignment, quality target (BLER target), and any bearer
specific parameters (RLC -Radio Link Control or channel switching parameters for
example). During the optimization of PS data service the importance of good RF
optimization will be apparent when channel switching is considered. Channel switching
is a generic term referring to the capability of the network to change the PS data bearer to
a different data rate (rate switching) or a different state (type switching). Channel
switching is intended to adapt the bearer to the user needs and to limit the resource
utilization. Saving resource will be achieved by reducing the data rate when the RF
conditions degrade. By reducing the data rate, the spreading gain increases, resulting in
lower required power to sustain the link.
Once the basic services are optimized, i.e., the call delivery and call retention
performance targets are met, the optimization can focus on service continuity, through
inter-system changes, and application specific optimization. Inter-system changes, either
reselection or handover, should be optimized only once the basic WCDMA optimization
is completed to ensure that the WCDMA coverage boundary is stable.

Application optimization can be seen as a final touch of service optimization and

is typically limited to the PS domain. In this last effort, the system parameters are
optimized not to get the highest throughput or the lowest delay, but to increase the
subscriber experience while using a given application. A typical example would be the
image quality for video-streaming. The main issue for this application based optimization
might be that different applications may have conflicting requirements. In such case, the
different applications and their impacts on the network should be prioritized. Irrespective
of the application considered, the main controls available to the optimization engineer are
the RLC parameters, target quality and channel switching parameters. The art in this
process is to improve the end user perceived quality, while improving the cell or system
capacity
6.4 OPTIMIZATION CHALLENGES FOR WCDMA

Three particularly important optimization challenges for WCDMA cell sites are
examined: traffic load balancing, handoff overhead management, and interference
control. The fundamental problem of traffic loading is that cellular traffic is distributed
unevenly among different geographical areas of the network. In fact, even within cells
traffic tends to be distributed unevenly among the sectors. Such imbalance has the effect
of locking up network capacity in under-utilized sectors while causing blocking problems
in the most heavily used sectors. Balancing the traffic load among the sectors of a cell
alleviates the blocking and creates headroom for traffic growth. And by creating
headroom at network hot spots, a targeted traffic load-balancing strategy allows more
traffic growth and more efficient use of infrastructure and spectrum across the entire
network. One way of achieving load balancing is to modify the antenna orientation and
angular beam width of each sector to unify the traffic. This is possible using smart array
antennas, as shown in Figure. Another aspect of WCDMA optimization that directly
affects cell site capacity is the management of handoff overhead. The soft/softer handoff
feature of the CDMA air interface improves the quality and reliability of CDMA calls.
However, because a given mobile may be in contact with two or more cells or sectors at
any given time, as in areas A and B in Figure , soft/softer handoff implies a significant
cost in capacity. After measuring the pilot strength in the area, the size of handoff zones
within the cell footprint should be decreased. Handoff zones should be shifted from high-
traffic areas to low-traffic areas. Interference directly limits capacity of CDMA cell sites.
One of the biggest interference problems in WCDMA networks is pilot pollution. Pilot
pollution is often caused due to high-elevation sites with RF coverage footprints much
larger than normal. The solution is to reduce the size of the coverage footprint. This can
be accomplished by reducing the elevation of offending antennas, introducing down tilt,
or reducing the transmitted power.
Figure 36: Balancing Traffic Load

Figure 37: Inefficient Design
6.5 INTER-RAT HANDOVER (INTER RADIO ACCESS

TECHNOLOGY HANDOVER)
The 2G/3G inter-RAT handover involves the handover from GSM to UMTS and
the handover from UMTS to GSM. The handover is controlled mainly by the network.
For MSs in dedicated mode, inter-RAT handovers can be performed, including the
emergency handover, better cell handover, inter-RAT load handover, and inter-RAT
service handover.
6.5.1 INTER-RAT HANDOVER FROM UMTS TO GSM
MSs in dedicated mode can be handed over from a UMTS cell to a GSM cell. The
handover decision and handover procedure are controlled by the RNC. The BSS
considers the incoming handover from UMTS to GSM as a common inter-BSC handover.
The parameter Inter-RAT In BSC Handover Enable determines whether inter-RAT
handover from UMTS to GSM is enabled. If Inter-RAT In BSC Handover Enable is
set to No, the BSS rejects all the requests for the handover from UMTS to GSM.
6.5.2 INTER-RAT HANDOVER FROM GSM TO UMTS
The parameter Inter-RAT In BSC Handover Enable determines whether the
inter-RAT handover from GSM to UMTS is enabled. If Inter-RAT In BSC Handover
Enable is set to NO (No), the BSS rejects all the requests for the handover from GSM to
UMTS and does not select a UMTS cell as the target cell.
In dedicated mode, an MS obtains the list of neighbouring UMTS cells and other
information from the Measurement Information. Then, the MS reports the measurement
result to the BSS through the measurement report. After receiving the measurement
result, the BSS determines whether to initiate the inter-RAT handover from GSM to
UMTS based on the measurement result and the handover algorithm.

6.6 BASIC WCDMA DRIVE TEST PARAMETERS

6.6.1 CPICH EC/NO:
Chip Energy by Noise- Common Pilot channel Ec/No (CPICH Ec/No) is the
ratio of the energy of the chip and the combined power of all the signals including the
specific pilot channel. It also shows the level of Noise disrupting the specific CPICH.
Ranges for Ec/No:(Unit is dB)
 0 to -7 Good
 to -10 Acceptable
 -10 to -36 Bad
6.6.2 CPICH RSCP:
Received signal Code Power is the level of the signal received by the U.E. or in
simple RSCP is the total power of the entire cell or a specific Common Pilot Channel
received by the user Equipment.
Ranges of RSCP: (Unit is dbm)
 -30 to -75 Good
 -75 to -85 Acceptable
 -85 to -140 Bad
6.6.3 TX POWER:
Tx Power is the transmitting power of the mobile station. Its value can vary from
50 to -50. The minimum the Tx Power of the mobile station the better it is for call quality.
Tx Power is the power of mobile station measured in the dedicated mode. If you are in a
low coverage area the mobile will increase its Tx power to avoid your call from being
dropped.
6.6.4 RSSI:
Received Signal Strength Indicator is the total power of the entire common pilot
channel received by the Mobile station Including Neighbors interference and noise as
well of neighbors and itself also.
RSSI= RSCP + Ec/No
RSSI Ranges:
 0 to -75 Good
 -75 to -85 Acceptable
 -85 to -140 Bad
6.6.5 SIR:
Signal to Interference ratio is the ratio of energy in the DPCC (Dedicated Physical
control channel) to that of the interference and noise received by the User Equipment.
6.6.6 SQI:
It is the speech quality index which is a parameter to rate the voice quality on that
particular call. It ranges from 0 to 30. While 30 being the Best Value. Adaptive Multi
Rate (AMR) is also used to enhance the speech or the voice quality of the specific call.
WCDMA use AMR source Coding. AMR vary with different Ranges Highest
AMR Value is 12.20 and lowest AMR value is 4.75.
6.6.7 RRC STATE:
It tells the current state and channel as in idle or dedicated.

6.6.8 CELL NAME:

Specific Name of the Node B allotted by the Operator according to its location
and Serial value.
6.6.9 SCRAMBLING CODES:
Scrambling Codes are usually used to identify different cells of a node B.
They are of two types.
1- Secondary Scrambling Code
2- Primary Scrambling Code

Secondary Scrambling Code are used in Beam forming cases.
Primary Scrambling codes (0 to 511) are actually the Scrambling codes usually
used to identify different sectors. They totally lies from 0 to 8191. More over 512 PSC are
divided into a group of 64.Each contains 8PSC.
Total Down link Scrambling Codes 16*8=512.
6.6.10 AS (ACTIVE SET):

Set of scrambling codes on which the user equipment is currently latched on.
Generally,there can be maximum three scrambling codes in an Active Set.
6.6.11 MN (MONITORED NEIGHBOR):
Neighbor cell that is detected by user equipment as a neighbor.
6.6.12 DN (DETECTED NEIGHBOR):
Detected Neighbor are cells detected by UE, which are neither in the Active set
nor in the Monitored set. (Missing Neighbor Definitions). Hence the U.E does not
handover onto these cells. It can be because of Overshooting, incomplete neighbor list or
in case of a new site. It is very important to optimize a network and have no DN‟s as they
are one of the major reasons of call drops in 3G.
6.7 CONCLUSION
3G Radio Network is very important and its parameter and planning plays a vital
role in network performance.

E2-E3 Consumer Mobility Backhaul Media for Mobile Radio Network
7 BACKHAUL MEDIA FOR MOBILE RADIO NETWORK

(OFC/ OFC SYSTEMS/ MINI LINK) AND RRH

 Importance of backhaul media in 3G
 Various type of Backhaul media
 Choice of backhauling
 Concept of Cloud RAN
7.2 INTRODUCTION
The physical part of a communications network between the central backbone and
the individual local networks is known as backhaul. Mobile backhaul refers to the
transport network that connects the core network and the RAN (Radio Access Network)
of the mobile network. Recently, the introduction of small cells has given rise to the
concept of front haul, which is a transport network that connects the macro cell to the
small cells. Whilst mobile backhaul and front haul are different concept, the term mobile
backhaul is generally used to encompass both concepts.
Figure 38: Backhaul Concept

Cell phones communicating with a single cell tower constitute a local subnetwork;
the connection between the cell tower and the rest of the world begins with a backhaul
link to the core of the internet service provider's network (via a point of presence). A
backhaul may include wired, fiber optic and wireless components. Wireless sections may
include using microwave bands and mesh and edge network topologies that may use a
high-capacity wireless channel to get packets to the microwave or fiber links.
7.3 MOBILE BACKHAUL N/W

 Mobile backhaul is the transport network that connects the core network
and the RAN/Cell Site.

 The connection between the cell tower and the rest of the world begins
with a backhaul link to the core N/w.
 A backhaul may include wired, fiber optic and wireless components.
 Wireless sections may include using microwave bands and mesh and edge
network topologies
 Interconnection b/n core network elements is done through backbone N/w.
7.3.1 FRONT HAUL VS BACKHAUL
 Split RAN architecture has reshaped the traditional definitions of front

haul and backhaul.
 In its earliest incarnation, backhaul was simply described as the connection

between Cell Site to BSC/RNC (In 2G/3G)
 Front haul became a necessary addition when a new link connected

centralized BBU to individual RRH.
 Front haul is connection in RAN infrastructure between the Baseband Unit

(BBU) and Remote Radio Head (RRH).
 Front haul originated with LTE networks when operators first moved their
radios closer to the antennas.
 This new link was established to supplement to the backhaul connection

between the BBU and central network core.
7.4 IMPORTANCE OF MOBILE BACKHAUL

Wireless and fixed-line backhaul infrastructure is an essential component of the
mobile telecommunications network. Mobile networks are ubiquitous and support a mix
of voice, video, text and data traffic originating from and terminating to mobile devices.
All of this traffic must be conveyed between the mobile cellular base stations and the core
network. The 3G and 4G Long-Term Evolution (LTE) strive for more network capacity,
latency reduction, and the need to deliver an enhanced user experience. In the era of 5G,
where a network will be densified and more stringent requirement will be imposed,
mobile backhaul will become even more important.
7.5 MOBILE BACKBONE NETWORK

Mobile backbone network refers to the interconnection of core elements situated
at separate geographic locations. As the requirement of bandwidth is large, typically,
OFC is used in the backbone network. However, MW is also sometimes used in the
backbone network, particularly in those areas where laying fibre is not a feasible option
due to difficult terrain, time constraints or economic viability.

7.6 TECHNOLOGY CHOICES FOR MOBILE BACKHAUL

The most common network type in which backhaul is implemented is a mobile
network. A backhaul of a mobile network, also referred to as mobile-backhaul connects a
cell site towards the core network. The two main methods of mobile backhaul
implementations are fiber-based backhaul and wireless point-to-point backhaul. Other
methods, such as copper-based wire line, satellite communications and point-to-
multipoint wireless technologies are being phased out as capacity and latency
requirements become higher in 4G and 5G networks.
Figure 39: Mobile Backhaul Network Choices

The technological solutions used for backhaul, including both wireline and
wireless solutions are given below:
7.6.1 COPPER-LINE
Copper-based backhaul was the primary backhaul technology for 2G/3G. At the
heart of copper-based backhaul is the T1/E1 protocol, which supported 1.5 Mbps to 2
Mbps. This bandwidth can be boosted by using DSL over the copper pair and DSL is still
an option for mobile backhaul for indoor small cells, in-building and public venue small
cell networks.
7.6.2 FIBRE-OPTIC IN BACKHAUL MEDIA FOR MOBILE RADIO

NETWORK (OFC/OFC SYSTEMS)
This technology is the mainstay wired backhaul in MNO networks and second
overall only to microwave backhaul. Even though fibre has significant inherent
bandwidth carrying capability, several additional techniques can be used to offset any
bandwidth constraints and essentially rendering the fibre assets future-proof.

Figure 40: OFC Media and System Mobile Network Backhaul

These techniques include Wavelength Division Multiplexing (WDM) technology
which enables multiple optical signals to be conveyed in parallel by carrying each signal
on a different wavelength or colour of light. WDM can be divided into Coarse WDM
(CDWM) or Dense WDM (DWDM). CWDM provides 8 channels using 8 wavelengths,
while DWDM uses close channel spacing to deliver even more throughput per fibre.
Modern systems can handle up to 160 signals, each with a bandwidth of 10 Gbps for a
total theoretical capacity of 1.6 Tbps per fibre.
The traffic generated by LTE has accelerated the demand for Fiber to the Tower
(FTTT) and has required Mobile Network Operators (MNOs) to upgrade many aspects of
their backhaul networks to fibre-based Carrier Ethernet. The main limitations of fibre are
the cost and logistics of deploying fibre (ducts etc.). Also it can take several months to
provision a cell site with fibre optic backhaul. Fibre optic will remain as the main choice
for backhaul.
7.6.3 WIRELESS BACKHAUL (MICROWAVE MINI-LINK)
Despite fibre being the preferred choice for 3G/4G/5G backhaul, microwave
backhaul is the most used technology due to a combination of its capability and relative
ease of deployment (i.e. no need for trenches/ducting) making it a low-cost option that
can be deployed in a matter of days. Microwave backhaul solutions in the 7 GHz to 40
GHz bands, in addition to higher microwave bands such as V-band (60 GHz) and the E-
band (70/80 GHz) can be relied. Backhaul links using the V-band or the E-band are well
suited to supporting 5G due to their 10 Gbps to 25 Gbps data throughput capabilities.

Figure 41: Microwave Mini-Links for Mobile Communications

Microwave can be used in LOS or NLOS mode which makes it ideal to be used in
a chain, mesh or ring topologies to enable resilience and/or reach.
7.6.4 LOS VS. NLOS
LOS backhaul has the advantage of using a highly directed beam with little fading
or multi-path dispersion and enables efficient use of spectrum as multiple transceivers can
be located within a few feet of each other and use the same frequency to transmit different
data streams.
NLOS backhaul is much more “plug and play” and so take less time with less
skilled labour to set up. NLOS backhaul OFDM technology (Orthogonal Frequency
Division Multiplexing) to relay information back to a central base station. NLOS
backhaul needs only to be within a range of the receiver unit with OFDM providing a
level of tolerance to multi-path fading not possible with LOS
7.6.5 SATELLITE BACKHAUL
Satellite Backhaul is a niche solution and used in fringe areas (e.g. remote rural
areas) and sometimes as an emergency/temporary measure (e.g. a disaster area. This
backhaul is used in developing markets and as a complementary role in developed
markets. The technology can deliver 150Mbps/10Mbps (downlink/.uplink). However,
latency is a challenge as there a round trip delay of circa 500-600ms for a geostationary
satellite. LEO (Low Earth Orbit) satellites have tried to address the latency issue (i.e.
using a much lower orbit of 1500km versus 36000km and resulting in a one way trip of
circa 50ms). However, LEO satellites are not geostationary and thus there is sometimes a
need to route traffic via multiple satellites.
7.6.6 FREE SPACE OPTICS (FSO)
Free Space Optics (FSO) is a newer low-latency technology that offers speeds
comparable to fibre optics that transmit voice, video and data with up to 1.5Gbps, and can
be deployed as backhaul to expand mobile network footprint with building-to-building
connectivity. The high bandwidth can be provided with a reception of light by deploying
free space optics technology.

BSNL is likely to use free space optics, a new line-of-sight outdoor wireless
technology, to overcome backhaul constraints in large arid areas of Rajasthan and Gujarat
plains.
7.6.7 WIFI BACKHAUL
There is marginal use of this technology for macrocell backhaul. The unlicensed
nature of the technology combined with the growing interference from increasing public
and private WLANs plus poor transmission ranges severely limits its deployment.
7.7 CHALLENGES IN MOBILE BACKHAUL

There are a number of market trends that result in new challenges and
requirements that must be met by the backhaul.
7.7.1 EVOLUTION OF LTE
Technical innovations occurring on LTE, which is known as LTE-Advanced Pro

or 4.5G which enable enhancements such as improved peak bandwidth and greater energy
efficiency for IoT connections. The peak bandwidth of 4.5G is around 1Gbps which is 8-
10x higher than standard LTE, and will enable (inter alia) support of video traffic at 4K
resolution to mobile devices.
7.7.2 EMERGENCE OF 5G
The 5G network will comprise both NR (New Radio) as well as a new 5G

Core Network (5GC). The advent of NR offers a leap in bandwidth speeds in comparison
to 3G and 4G via the utilisation of higher frequency spectrum. The higher frequencies
enable wider channel bandwidths at the access but also result in smaller cell sizes. Both
have implications for backhaul.
7.7.3 NETWORK SLICING
In 5G Network, one concept of “network slicing” is introduced whereby the

physical network infrastructure can be partitioned into bespoke logical networks
(“slices”) in the RAN and 5G core which are targeted to the needs of a specific
application or use case. Slicing will impact on the backhaul network.
7.7.4 SUBSCRIBER GROWTH
Backhaul strategy/evolution must cope with both an increase in subscriptions as

well as a large number of those subscriptions being “high bandwidth” users.
7.7.5 MOBILE DATA TRAFFIC GROWTH
The increasing subscriber total plus increased access bandwidth usage of those
subscribers results in mobile data traffic increasing at a rate.
7.7.6 STRINGENT LATENCY REQUIREMENTS
Both 5G mission-critical applications and increased video streaming will result in

more stringent end-end latency requirements and impact on the backhaul latency budget.

If higher latency backhaul links are deployed (e.g. satellite links), then such backhaul
would only carry 2G/3G and non-latency sensitive LTE services.
7.7.7 NETWORK DENSIFICATION:
The increased demand for mobile broadband results in the number of macrocell.
The new macrocells include both 4G and 5G technologies. This results in extra traffic to
backhaul as well as additional challenges due to the smaller cell size for 5G NR.
7.8 ALTERNATIVE ARCHITECTURES FOR MOBILE

BACKHAUL OPTIMISATION
7.8.1 MULTI ACCESS EDGE COMPUTING
MEC (Multi-access edge computing) is where computing and intelligence

capabilities that were mostly centralized in the core network are provided at the edge of
the access network. MEC enables high bandwidth and ultra-low latency access to cloud
computing/IT services at the edge to be accessed by applications developers and content
providers.
MEC, while incurring a cost to implement core functions at the edge, can provide
opportunities to optimise backhaul demand via caching and/or local breakout. Caching
reduces the load on mobile backhaul and enhances the customer experience by storing
frequently accessed contents in the edge network. Customers can access the contents at a
lower latency (with less distance for signal to travel) and backhaul demand is reduced as
there is no need to reach further to the external network to obtain the contents. Local
breakout also enables the mobile backhaul to be optimised as the contents do not need to
travel to the core network and then to the internet. The caveat with local breakout is that
the transport network to connect the edge to the internet needs to be in place and therefore
won‟t optimise cost in certain scenarios.
7.8.2 CLOUD RAN
Cloud RAN is where some layers of radio access network are centralized to an
edge site rather than at the cell site, which allows some (or all) of the processing
capabilities to be focused at the edge site reducing the complexities at the cell site. This
architecture is suitable in the small cell era, where only a little space and cost constraint is
affordable at the cell site. While the architecture may not be suitable for traditional macro
cell base stations as they would need to process significant load of signal transmitted
from/received by various radio elements, heterogeneous networks with many small cells
would benefit from this architecture.
As shown in the figure below, Cloud RAN in its two forms (low-level and high-
level splits) significantly reduces complexities and capabilities at the cell site to be
concentrated in the edge site. The low-level split is where only the physical layer is
processed at the edge site while all the electronics are concentrated in the edge site. This
architecture allows easy installation and very low complexity at the cell site but comes at
a higher front haul cost as baseband signals would need to be transferred. On the other
hand, high-level split brings relatively less front haul cost but comes with more
complexity at the cell site than low-level split.

Figure 42: Cloud RAN Architecture

7.8.3 RRH
A remote radio head (RRH), also called a remote radio unit (RRU) in wireless
networks, is a remote radio transceiver that connects to radio base station unit via
electrical or wireless interface.
The RRH is termed “Remote” as it is usually installed on a mast-top, or tower-top

location that is physically some distance away from the base station hardware which is
often mounted in an indoor rack-mounted location. In wireless system technologies such
as GSM, CDMA, UMTS, LTE this Radio equipment is remote to the
BTS/NodeB/eNodeB, and is also called Remote Radio Head.
This equipment will be used to extend the coverage of a BTS/NodeB/eNodeB like

rural areas or tunnels. They are generally connected to the BTS/NodeB/eNodeB via a
fibre optic cable using Common Public Radio Interface protocols.
Figure 43: RRH

Using Wireless (Microwave, Millimetre Wave, MMW, Free Space Optics, and
FSO) links instead of fibre allows the Remote Radio Head (RRH) to be connected
without need for fibre optics. By avoiding the needs for digging, trenches, leased circuits

from telcos, dark fibre or way-leaves for disrupting busy city streets, 4G/LTE networks
can be realised very quickly with installation taking hours rather than days, weeks or
months.
Figure 44: Backhaul for RRH

7.8.4 IMPORTANCE OF RRH
RRHs have become one of the most important subsystems of today's new
distributed base stations. The RRH contains the base station's RF circuitry plus analog-to-
digital/digital-to-analog converters and up/down converters. RRHs also have operation
and management processing capabilities and a standardized optical interface to connect to
the rest of the base station. This will be increasingly true as LTE and WiMAX are
deployed. Remote radio heads make MIMO operation easier; they increase a base
station's efficiency and facilitate easier physical location for gap coverage problems.
RRHs will use the latest RF component technology including Gallium nitride (GaN) RF
power devices and envelope tracking technology within the RRH RF power amplifier
(RFPA).
7.8.5 RRH PROTECTION IN FIBER TO THE ANTENNA SYSTEMS
Fourth generation (4G) and beyond infrastructure deployments will include the
implementation of Fiber to the Antenna (FTTA) architecture. FTTA architecture has
enabled lower power requirements, distributed antenna sites, and a reduced base station
footprint than conventional tower sites. The use of FTTA will promote the separation of
power and signal components from the base station and their relocation to the top of the
tower mast in a Remote Radio Head (RRH).
According to the Telcordia industry standard that establishes generic requirements

for Fiber to the Antenna (FTTA) protection GR-3177,the RRH shifts the entire high-
frequency and power electronic segments from the base station to a location adjacent to
the antenna. The RRH will be served by optical fiber and DC power for the optical-to-
electronic conversion at the RRH.
RRHs located on cell towers will require Surge Protective Devices (SPDs) to
protect the system from lightning strikes and induced power surges. There is also a

change in electrical overstress exposure due to the relocation of the equipment from the
base station to the top of the mast.
7.8.6 PROTECTION FROM LIGHTNING DAMAGE
RRHs can be installed in a low-profile arrangement along a rooftop, or can

involve a much higher tower arrangement. When installed at the highest point on a
structure (whether a building or a dedicated cell tower), they will be more vulnerable to
receiving a direct lightning strike and higher induced lightning levels, compared with
those installed in a lower profile manner below the upper edges of the building.
As noted in GR-3177, while surges can be induced into the RRH wiring for
lightning striking the nearby rooftop or even the base station closure, the worst case will
occur when a direct strike occurs to the antenna or its supporting structure. Designing the
electrical protection to handle this situation will provide protection for less damaging
scenarios... it can also be use in optical fiber communication but different type.
7.9 CONCLUSION
In order to have best of Network and throughput from it backhaul is of at most
importance. Introduction of cloud RAN has open the path for low latency network and
path for future radio technologies.

E2-E3 Consumer Mobility HSPA , HSPA+ and Migration to 4G(Rel 5 to Rel 8)
8 HSPA,HSPA+ AND MIGRATION TO 4G (REL5 TO REL8)

 HSAP and HSPA+ Standards
 Various releases
 HSPA and HSPA+ technology
 Migration to 4G
8.2 UMTS HSPA AND 3GPP STANDARDS

3G HSPA provides a major improvement in performance to the 3G UMTS mobile
telecommunications system. It provides additional facilities that are added on to the basic
3GPP UMTS standard. The top data rates for HSPA compete well with the 4G LTE
technology. As such the 3G infrastructure usage was prolonged and enabled many
operators to maximise the use of their investment before having to add the capability for
4G.
The evolution of UMTS-HSPA happens in stages referred to as 3GPP Releases.

The upgrades and additional facilities were introduced at successive releases of the 3GPP
standard.
Figure 45: 3GPP UMTS Evolution
 Release 4: This release of the 3GPP standard provided for the efficient use of IP,
a facility that was required because the original Release 99 focussed on circuit
switched technology. Accordingly this was a key enabler for 3G HSDPA.
 Release 5: This release included the core of HSDPA itself. It provided for
downlink packet support, reduced delays, a raw data rate (i.e. including payload,
protocols, error correction, etc) of 14 Mbps and gave an overall increase of
around three over the 3GPP UMTS Release 99 standard.

 Release 6: This included the core of HSUPA with an enhanced uplink with
improved packet data support. This provided reduced delays, an uplink raw data
rate of 5.74 Mbps and it gave an increase capacity of around twice that offered
by the original Release 99 UMTS standard. Also included within this release was
the MBMS, Multimedia Broadcast Multicast Services providing improved
broadcast services, i.e. Mobile TV.
 Release 7: This release of the 3GPP standard included downlink MIMO

operation as well as support for higher order modulation up to 64-QAM in the
downlink and 16-QAM in the uplink. However it only allows for either MIMO
or the higher order modulation. It also introduced protocol enhancements to
allow the support for Continuous Packet Connectivity (CPC).
 Release 8: This release of the standard occurred during the course of 2008 and it
defines dual carrier operation as well as allowing simultaneous operation of the
high order modulation schemes and MIMO. Further to this, latency is improved
to keep it in line with the requirements for many new applications being used.
 Release 9: 3GPP Release 9 occurred during 2009 and included facilities for
HPSA including 2x2MIMO in the uplink and a 10MHz bandwidth in the
downlink. The uplink carriers may be from different bands.
 Release 10: HSPA Release 10 utilises up to 4-carriers, i.e. 20 MHz bandwidth

which may be from two separate bands. In addition to this 2x2 MIMO in the
downlink provides data rates up to 168 Mbps. This figure equates to that
obtained for LTE Release 8 when using comparable bandwidth and antennas
configurations.
 Release 11: Release 11 occurred during 2011 / 2012. It provided the facility for
40MHz bandwidth in the uplink along with up to 4x4 MIMO. The downlink was
upgraded to accommodate 64-QAM modulation and MIMO.
8.3 HSPA: HIGH SPEED PACKET ACCESS

High speed packet access, HSPA is an upgrade to 3G UMTS to provide very high
higher data rates in both uplink and downlink.3G UMTS enabled mobile communications
to move from voice-centric systems to data centric ones. However the speeds that could
be supported wee nowhere near sufficient to enable Internet surfing and video downloads.
To overcome this 3G UMTS was upgraded with high speed packet access, HSPA to
provide a major leap in performance and make it suitable to cover its requirements.
Initially the downlink was addressed using high speed downlink packet access,
HSDPA and then upgrades were added to the uplink with high speed uplink packet
access.
Further upgrades were added later with dual carrier and MIMO capabilities to
raise the data speeds hugely above those first envisaged for 3G.

8.3.1 HSPA BENEFITS
The system provides an enhancement on the basic 3G WCDMA / UMTS cellular

system, providing data transfer rates that are considerably in excess of those originally
envisaged for 3G as well as much greater levels of spectral efficiency.
The system provides many advantages for users over the original UMTS system.
3G HSPA SPEED & HIGHLIGHT FEATURES
3GPP RELEASE TECHNOLOGY DOWNLINK UPLINK

SPEED (MBPS) SPEED
(MBPS)
Rel 5 HSDPA 14.4 0.384
Rel 6 HSUPA 14.4 5.7
Rel 7 2xdata capacity 28 11
2x voice capacity
Rel 8 Multi-carrier 42 11
Rel 9 Multicarrier, 10 MHz, 2x2 84 23
MIMO UL,
10 MHz & 16-QAM D/L
Rel 10 20 MHz 2x2 MIMO in UL, 10 168 23
Rel 11 40 MHz 2x2 / 4x4 MIMO UL, 336 - 672 70

10 MHz 64-QAM MIMO DL
Table 1. 3G HSPA SPEED & HIGHLIGHT FEATURES

8.3.2 3G HSPA FEATURES
The UMTS cellular system as defined under the 3GPP Release 99 standard was
orientated more towards switched circuit operation and was not well suited to packet
operation. Additionally greater speeds were required by users than could be provided with
the original UMTS networks. Accordingly the changes required for HSPA were
incorporated into many UMTS networks to enable them to operate more in the manner
required for current applications.
HSPA provides a number of significant features that enable the new service to
provide a far better performance for the user. While 3G UMTS HSPA offers higher data
transfer rates, this is not the only feature, as the system offers many other improvements
as well:
1. Use of higher order modulation: 16QAM is used in the downlink instead of
QPSK to enable data to be transmitted at a higher rate. This provides for
maximum data rates of 14 Mbps in the downlink. QPSK is still used in the
uplink where data rates of up to 5.8 Mbps are achieved. The data rates quoted are
for raw data rates and do not include reductions in actual payload data resulting
from the protocol overheads.

2. Shorter Transmission Time Interval (TTI): The use of a shorter TTI reduces
the round trip time and enables improvements in adapting to fast channel
variations and provides for reductions in latency.
3. Use of shared channel transmission: Sharing the resources enables greater
levels of efficiency to be achieved and integrates with IP and packet data
concepts.
4. Use of link adaptation: By adapting the link it is possible to maximize the
channel usage.
5. Fast Node B scheduling: The use of fast scheduling with adaptive coding and
modulation (only downlink) enables the system to respond to the varying radio
channel and interference conditions and to accommodate data traffic which tends
to be "bursty" in nature.
6. Node B based Hybrid ARQ: This enables 3G HSPA to provide reduced
retransmission round trip times and it adds robustness to the system by allowing
soft combining of retransmissions.
For the network operator, the introduction of 3G HSPA technology brings a cost
reduction per bit carried as well as an increase in system capacity. With the increase in
data traffic, and operators looking to bring in increased revenue from data transmission,
this is a particularly attractive proposition. A further advantage of the introduction of 3G
HSPA is that it can often be rolled out by incorporating a software update into the system.
This means its use brings significant benefits to user and operator alike.
8.3.3 3G UMTS HSPA CONSTITUENTS
There are two main components to 3G UMTS HSPA, each addressing one of the
links between the base station and the user equipment, i.e. one for the uplink, and one for
the downlink.
The two technologies were released at different times through 3GPP. They also
have different properties resulting from the different modes of operation that are required.
In view of these facts they were often treated as almost separate entities. The two
technologies are summarised below:
 HSDPA - High Speed Downlink Packet Access: HSDPA provides packet
data support, reduced delays, and a peak raw data rate (i.e. over the air) of 14
Mbps. It also provides around three times the capacity of the 3G UMTS
technology defined in Release 99 of the 3GPP UMTS standard.
 HSUPA - High Speed Uplink Packet Access: HSUPA provides improved
uplink packet support, reduced delays and a peak raw data rate of 5.74 Mbps.
This results in a capacity increase of around twice that provided by the Release
99 services.
8.3.4 HSDPA : HIGH SPEED DOWNLINK PACKET ACCESS
High Speed Downlink Packet Access enables high speed packet data up to 14.4
Mbps to be carried in the downlink of 3G UMTS. 3G HSDPA High Speed Downlink
Packet Access provides additional capability to the basic 3G UMTS cellular
telecommunications system.
HSDPA was the first upgrade along the path to HSPA which enabled high speed
data to be carried in both directions. However as much more data was carried in the

downlink direction, HSDPA was standardised and implemented first to provide the
maximum benefit as soon as possible.
8.4 HSDPA TECHNOLOGIES

The 3G HSDPA upgrade includes several changes that are built onto the basic
3GPP UMTS standard. While some are common to the companion HSUPA technologies
added to the uplink, others are specific to HSDPA High Speed Downlink Packet Access,
because the requirements for the each direction differ.
 Additional channels: In order to be able to transport the data in the required
fashion, and to provide the additional responsiveness of the system, additional
channels have been added.
To achieve the high speed data HSDPA uses new channels including: High
Speed Downlink Shared Channel (HS-DSCH), High Speed Signalling Control
Channel(HS-SCCH), High Speed Dedicated Physical Control Channel (HS-
DPCCH).
 Modulation: One of the keys to the operation of HSDPA is the use of an

additional form of modulation. Originally W-CDMA had used only QPSK as
the modulation scheme, however under the new system16-QAM which can
carry a higher data rate, but is less resilient to noise is also used when the link
is sufficiently robust. The robustness of the channel and its suitability to use
16-QAM instead of QPSK is determined by analyzing information fed back
about a variety of parameters. These include details of the channel physical
layer conditions, power control, Quality of Service (QoS), and information
specific to HSDPA.
 Improved scheduling: Further advances have been made in the area of

scheduling. By moving more intelligence into the base station, data traffic
scheduling can be achieved in a more dynamic fashion. This enables variations
arising from fast fading can be accommodated and the cell is even able to
allocate much of the cell capacity for a short period of time to a particular user.
In this way the user is able to receive the data as fast as conditions allow.
 Fast HARQ: Fast HARQ (hybrid automatic repeat request), has also been
implemented along with multi-code operation and this eliminates the need for a
variable spreading factor. By using these approaches all users, whether near or
far from the base station are able to receive the optimum available data rate.
HSDPA provided a significant improvement in performance for 3G. With peak
user data rates of around 10 Mbps and peak raw data rates of 14.4 Mbps, the system gave
a marked improvement over what was available with basic 3G UMTS. When combined
with HSUPA and other HSPA upgrades, the system was able to provide performance that
rivalled that of the next generation networks.
8.5 HSUPA : HIGH SPEED UPLINK PACKET ACCESS

HSUPA, High Speed Uplink Packet Access, provided a considerable
improvement in performance in the uplink for 3G UMTS networks.High Speed Uplink

Packet Access, HSUPA provides a major increase in data rate and overall performance
for 3G UMTS networks.As the name indicates, HSUPA applies to the uplink, and as such
it is the companion to HSDPA which is applied to the downlink.
With both HSDPA and HSUPA active, the overall scheme is referred to as HSPA
- high speed packet access.Although when using HSUPA, there is a considerable increase
in performance, the overall data rate in the uplink is not as fast as that available in the
downlink. This is because the majority of data is passed in the downlink rather than the
uplink.
In addition to this there are additional difficulties providing the same performance
from the UE in view of some of the restrictions imposed by the fact that a large number of
UEs are communicating with the NodeB.
8.5.1 HSUPA TECHNOLOGIES
HSUPA brings enhanced performance through the addition of new features that sit
on top of the existing UMTS technology.
The key specification parameters that are introduced by the use of HSUPA are:
 Increased data rate: The use of HSUPA is able to provide a significant

increase in the data rate available. It allows peak raw data rates of 5.74 Mbps.
 Lower latency: The use of HSUPA introduces a TTI of 2 ms, although a

10ms TTI was originally used and is still supported.
 Improved system capacity: In order to enable the large number of high data
rate users, it has been necessary to ensure that the overall capacity when using
HSUPA is higher.
 Modulation order: Originally only BPSK modulation, that adopted for

UMTS, was used. Accordingly it did not support adaptive modulation schemes.
Higher order modulation was introduced in Release 7 of the 3GPP standards
when 64QAM was allowed.
 Hybrid ARQ: In order to facilitate the improved performance the Hybrid

ARQ (Automatic Repeat request) used for HSDPA is also employed for the
uplink, HSUPA.
 Fast Packet Scheduling: In order to reduce latency, fast packet scheduling

has been adopted again for the uplink as for the downlink, although the
implementation is slightly different.
With these specification parameters enable HSUPA to complement the

performance of HSDPA, providing an overall performance improvement for systems
incorporating HSPA.
The addition of HSUPA to the 3G UMTS network enabled the uplink as well as
the downlink to provide much improved performance. With both HSDPA (downlink) and
HSUPA (uplink) active the complete package was called HSPA - high speed packet
access. Although most of the data is passed int he downlink, many users found the uplink

without HSUPA very slow and it degraded the overall user experience. With HSUPA
active the overall experience was much improved.
8.6 EVOLVED HSPA / HSPA+

Once the basic HSPA was running, further evolutions were implemented in the
form of Evolved HSPA / HSPA+ / HSPA Evolution. As data usage increased still further,
HSPA was improved in a series of revisions to provide what was termed Evolved HSPA,
HSPA+ or even HSPA Evolution.
The overall Evolved HSPA / HSPA+ involved a series of enhancements that

improved not only the data speed, but also reduced latency and gave an overall
improvement in performance.
To achieve these enhancements were made to the radio access network as well as
backhaul along with an on-going improvement to the network itself.
8.6.1 HSPA+ IN 3GPP RELEASES
The definition of HSPA+ / Evolved HSPA have been included in Releases 7 and 8
of the 3GPP standards.
 3GPP Release 7: This release of the 3GPP standard included downlink

MIMO operation as well as support for higher order modulation up to 64 QAM
in the uplink and 16 QAM in the downlink. However it only allows for either
MIMO or the higher order modulation. It also introduced protocol
enhancements to allow the support of more users that are in a "continuously
on" state.
 3GPP Release 8: This release of the standard defines dual carrier operation as
well as allowing simultaneous operation of the high order modulation schemes
and MIMO. Further to this, latency is improved to keep it in line with the
requirements for many new applications being used.
8.6.2 EVOLVED HSPA / HSPA+ HIGHLIGHT FEATURES
There are a number of major new features as well as some enhancements to

existing capabilities that enable HSPA+ or Evolved HSPA to provide a significant
improvement in performance over that provided by the standard HSPA systems.
Some of the major features include:
 Higher Order Modulation: Although MIMO provides some significant

improvements in throughput, where the multiple antennas needed for MIMO
are not available, and where signal strength is relatively high, it is possible to
increase the order of the modulation to enable higher throughput rates.
However this can only be achieved when signal levels are sufficiently high
otherwise data errors increase.
 MIMO: Many other systems have utilised MIMO and so too, HSPA+ is able
to gain significant advantages from its use.

 Layer 2 protocol enhancements: In order to benefit from the higher data

rates over the HS-DSCH enhancements to the RLC and MAC-hs protocols
have been introduced.
 Continuous packet connectivity: With much of the data traffic being in the
form of IP data, continuous connectivity is an increasing requirement. To
achieve the HS-DSCH and E0DCH channels have been reconfigured to enable
them to be rapidly able to transmit user data.
 Enhanced CELL_FACH operation: This enhanced operation is required to

assist in maintaining the always-on packet connectivity during periods when
there have been little or no activity.
8.6.3 HSPA+ DATA RATE COMPARISON WITH LTE
The next migration of the cellular services beyond HSPA+ is known as LTE.
Using a completely new air interface based around the use of OFDM rather than W-
CDMA which is used for UMTS, HSPA and HSPA+, it offers even higher data traffic
rates. It is then anticipated that it will be used as the basis for the next generation, i.e. 4G
systems.
It is however worth comparing the maximum data rates offered by both HSPA+
and LTE.
CHANNEL HSPA+ DATA RATE LTE DATA RATE

BANDWIDTH (MBPS) (MBPS)
(MHZ)
5 42 37
10 84 73
20 -- 150
Table 2. HSPA+ data rate comparison
Although the basic comparisons appear to show that LTE will offer few
advantages, there are several other features of LTE that mean that it is a preferable option
for the long term. LTE enables wider bandwidths and the OFDM modulation enables data
transmissions to be made more resilient to multipath and other propagation effects.
8.7 LTE: LONG TERM EVOLUTION

LTE Long Term Evolution was the 4G successor to 3G UMTS that provided
improved speeds and performance. Providing much higher data speeds and greatly
improved performance as well as lower operating costs, the scheme started to be deployed
in its basic form around 2008.
Initial deployments gave little improvement over 3G HSPA and were sometimes
dubbed 3.5G or 3.99G, but soon the full capability of LTE was realised it provided a full
4G level of performance.

The first deployments were simply known as LTE, but later deployments were
designated 4G LTE Advanced and later still 4G LTE Pro.
Not only was the radio access network improved for 4G LTE, but the network
architecture was overhauled enabling lower latency and much better interconnectivity
between elements of the radio access network, RAN.
8.7.1 LTE EVOLUTION
It was 3GPP release 8 when LTE was introduced for the very first time. All the
releases following only enhanced the technology.
Although there are major step changes between LTE and its 3G predecessors, it is
nevertheless looked upon as an evolution of the UMTS / 3GPP 3G standards. Although it
uses a different form of radio interface, using OFDMA / SC-FDMA instead of CDMA,
there are many similarities with the earlier forms of 3G architecture and there is scope for
much re-use.
In determining what is LTE and how does it differ from other cellular systems, a
quick look at the specifications for the system can provide many answers. LTE can be
seen for provide a further evolution of functionality, increased speeds and general
improved performance.
COMPARISON WITH OTHER MOBILE COMMUNICATIONS
TECHNOLOGIES
WCDMA HSPA HSPA+ LTE
(UMTS) HSDPA / HSUPA
Max downlink 384 k 14 M 28 M 100M
speed
bps
Max uplink speed 128 k 5.7 M 11 M 50 M
bps
Latency 150 ms 100 ms 50ms (max) ~10 ms
round trip time
approx
3GPP releases Rel 99/4 Rel 5 / 6 Rel 7 Rel 8
Approx years of 2003 / 4 2005 / 6 HSDPA 2008 / 9 2009 / 10
initial roll out 2007 / 8 HSUPA
Access CDMA CDMA CDMA OFDMA / SC-
methodology FDMA
Table 3. Comparison With Other Mobile Communications Technologies
In addition to this, LTE is an all IP based network, supporting both IPv4 and IPv6.
8.7.2 LTE SPECIFICATION OVERVIEW
It is worth summarizing the key parameters of the 3G LTE specification. In view

of the fact that there are a number of differences between the operation of the uplink and
downlink, these naturally differ in the performance they can offer.

These highlight specifications give an overall view of the performance that LTE
will offer. It meets the requirements of industry for high data download speeds as well as
reduced latency - a factor important for many applications from VoIP to gaming and
interactive use of data. It also provides significant improvements in the use of the
available spectrum
LTE BASIC SPECIFICATIONS
PARAMETER DETAILS
Peak downlink speed 100 (SISO), 172 (2x2 MIMO), 326 (4x4 MIMO)
64QAM
(Mbps)
Peak uplink speeds 50 (QPSK), 57 (16QAM), 86 (64QAM)
(Mbps)
Data type All packet switched data (voice and data). No circuit switched.
Access schemes OFDMA (Downlink)
SC-FDMA (Uplink)
Modulation types QPSK, 16QAM, 64QAM (Uplink and downlink)
supported
Spectral efficiency Downlink: 3 - 4 times Rel 6 HSDPA
Uplink: 2 -3 x Rel 6 HSUPA
Channel bandwidths 1.4, 3, 5, 10, 15, 20
(MHz)
Duplex schemes FDD and TDD
Mobility 0 - 15 km/h (optimised),
15 - 120 km/h (high performance)
Latency Idle to active less than 100ms
Small packets ~10 ms
Table 4. LTE Basic Specifications
8.8 4G : LTE ADVANCED

The basic LTE, long term evolution cellular services were launched around 2010
with some advance deployments well before this. It was never envisaged that this initial
form of LTE would provide the full performance intended. This required some additional
elements that were in what was termed LTE Advanced.
LTE Advanced, LTE-A incorporated a number of new techniques that enabled the
system to provide very much higher data rates, and also much better performance,
particularly at cell edges and other areas where performance would not normally have
been so good.
LTE Advanced took a few more years to fully develop and roll out across the
networks, but when introduced it enabled its many advanced features to provide
significant improvements over basic LTE.

International Telecommunication Union using Radio (ITU-R) defined 4G mobile

technology as IMT-Advanced (International Mobile telecommunication Advanced).
LTE-Advanced specifications in release 10 includes significant features and
improvements to fulfil ITU IMT-Advanced requirements which sets higher speeds than
what UE can achieve from 3GPP release 8 specifications.
Figure 46: IMT 2000 & IMT Advanced

Some key requirements laid down by IMT-Advanced are as below
Figure 47: Key Requirement of IMT-Advanced

8.8.1 RADIO TECHNOLOGY EVOLUTION TO 4G
OFDM forms the basis of the radio access technology. Along with it there is
OFDMA (Orthogonal Frequency Division Multiple Access) along with SC-FDMA
(Single Channel Orthogonal Frequency Division Multiple Access). These will be used in
a hybrid format. However the basis for all of these access schemes is OFDM.
LTE uses separate multiple-access technologies for the downlink (base station to
mobile) and the uplink (mobile to base station). It employs Orthogonal FDMA (OFDMA)
for the downlink and Single-Carrier FDMA (SC-FDMA) for the uplink.
Figure 48: Radio Technology Evolution
8.8.2 NETWORK ARCHITECTURE EVOLUTION
Figure 49: Network Architecture Evolution
8.9 CONCLUSION
In this chapter we have studied about HSPA and HSPA+, along with LTE
Technologies. Carrier aggregation is the way for future radio technologies. HSPA+ plays
a important role in delivering high speed data over 3G Network.

E2-E3 Consumer Mobility 4G and 5G Network Architecture
9 4G AND 5G NETWORK ARCHITECTURE

 4G Network Architecture
 LTE Architecture goals
 LTE Radio Network E UTRAN
 LTE Network Elements
 5G Network Architecture
9.2 4G NETWORK ARCHITECTURE

9.2.1 4G LTE SYSTEM ARCHITECTURE
LTE has a flat architecture which minimizes the number of network elements.
LTE is optimized for Packet Switched (PS) services but includes functionality to handle
Circuit Switched (CS) services, e.g. CS fallback to UMTS/ LTE also supports the speech
service using Voice over IP.
The high-level architecture of LTE is known as evolved packet system (EPS).

There are three main components, namely the user equipment (UE), the evolved UMTS
terrestrial radio access network (E-UTRAN) and the evolved packet core (EPC). In turn,
the evolved packet core communicates with packet data networks in the outside world
such as the internet, private corporate networks or the IP multimedia subsystem.
Figure 50: LTE System Architecture

LTE uses a flat architecture without a Radio Network Controller (RNC). LTE
equivalent of a UMTS Node B is an 'evolved' Node B or eNode B. eNode B are
connected to the Evolved Packet Core (EPC) using a Mobility Management Entity
(MME) for control plane signaling and a Serving Gateway for user plane data.

9.2.2 LTE ARCHITECTURE GOAL
Figure 51: LTE Architecture Goal

9.2.3 LTE RADIO NETWORK : THE E-UTRAN
The radio access network of LTE is known as Evolved UMTS Terrestrial Radio
Access Network which is evolved version of UMTS access network. The E-UTRAN is
comprised of
 User Equipment (UEs)
 Evolved Node B (eNodeB)
 The Evolved Universal Terrestrial Radio Access (E-UTRA)
The UE can be a device such as: mobile phone, laptop, tablet, computer, etc., used
by a subscriber for communication. eNodeB is the base station and its radio interface is
the E-UTRA, the Evolved Universal Terrestrial Radio Access.
Figure 52: LTE Radio Network

9.2.4 E-UTRA
The E-UTRA is the air interface of an LTE network and is the equivalent of the
UTRA air interface in UMTS networks. The E-UTRA enables a latency decrease, allows
high bandwidth capabilities and is optimized for packet data.

The E-UTRA uses Orthogonal frequency-division multiple access (OFDMA) in

the downlink and Single-Carrier Frequency-Division Multiple Access (SC-FDMA) in the
uplink. OFDM splits data into small sub-carriers on neighboring frequencies, over a
single channel. OFDM handles phenomena such as interference, noise or multipath
significantly more efficiently than other modulation methods.
SC-FDMA is also a frequency division multiple access scheme and usually

represents and alternative to OFDM. Its main advantage is a lower peak-to-average power
ration, which is proven to be more efficient in networks where the transmit power is most
important.
The E-UTRA also uses the MIMO technology and enables the simultaneous
support of more users and a lower processing power required for each UE. In the case of a
2×2 MIMO antenna system, the two transmitters send different parts of the same data
stream simultaneously, while the receivers have to piece them back together.
9.2.5 ENODEB
The eNodeB is a part of the E-UTRAN radio access network and is the component
that allows UEs to connect to the LTE network. An eNodeB typically communicates with
the UE, with other eNodeBs, and with the EPC through various interfaces: the Uu, X2
and S1.
Figure 53: eNodeB

The eNodeB performs the following functions:
Radio resource management, which includes:
 Radio bearer control – is responsible for the setup, maintenance and the
release of radio bearers and its resource configuration
 Mobility management – handles the radio resource management for UEs in
both idle and connected modes
 Admission control – allows or denies radio bearer setup requests
 Dynamic resource allocation, covering the release and allocation of radio
resources in both the user plane and the control plane
Routing of user plane packets towards the S-GW
MME selection, which includes:
 Enabling the UE to be served by an MME while the UE is in the “attach”
procedure

Enabling the UE to be served by a different MME while being in a

network
 The establishment of the route towards an MME, based on the information
provided by the UE when the routing information is not available
Packet compression and ciphering, which includes:
 Encryption and decryption of packets through ciphering algorithms
 Header compression for downlink packets and header decompression for
uplink packets
Message scheduling and transmission, which includes:
 The transmission of paging messages, OM messages or broadcast
information via the Uu interface
 The reception of broadcast information and paging messages from an
MME and the OM messages from the operation and maintenance center.
9.2.6 INTERFACES OF THE ENODEB
LTE-Uu Interface
The LTE-Uu is the radio interface that connects the UEs to the eNodeBs, eNodeB
with the UE. It handles all the signalling messages between the eNodeB and the MME as
well as the data traffic between the UE and the S-GW.
S1 Interface
The S1 interface connects the E-UTRAN and the EPC for both the user and the
control planes. It has two parts: the S1-AP, belonging to the control plane and the S1-U
(GTP-U), belonging to the user plane.The S1-AP connects the eNodeB to the MME and
is based on IP transmission. It transmits signalling messages of the radio network layer of
the E-UTRAN through the Stream Control Transmission Protocol (SCTP)/IP stack.
Figure 54: S1 Interface

Therefore, when the eNodeB has to connect to an MME, it does so through the S1
interface seeking each MME node in the corresponding pool area. The next step is that of
setting up the Transport Network Layer (TNL). One eNodeB and one MME can set up a
single Stream Control Transmission Protocol (SCTP) connection. Once the TNL has been
established, the eNodeB starts an S1 interface, which has the purpose of managing the
configuration data for the operation exchange between the ENB and the MME.

The S1-U connects the eNodeB to the S-GW through the GTP/UDP5/IP stack. In
the user plane, the S1-U (GTP) is based on the GTP/UDP5/IP protocol stack from
previous UMTS and GPRS networks. The GPRS Tunnelling Protocol User plane (GTP-
U) is responsible for tunnelling the user plane bearers, acts as a reference point for inter-
eNodeB handover, and allows intra-3GPP mobility.
X2 Interface
The X2 interface provides connectivity between two or more eNodeBs. There are
two parts of the X2 interface, the X2-C, the interface between the control planes of
eNodeBs, and the X2-U, the interface between the user planes of eNodeBs. The X2-C and
the X2-U have the same structure as the S1 interface. as seen below. The only difference
consists of the X2-AP replacing the S1-AP.Two or more eNodeBs exchange information
related to load, interference or handover.
Figure 55: X2 Interface

Two or more eNodeBs can exchange signalling information through the X2
interface. The main roles of the X2 interface are the following:
 Mobility management
 Load management
 Inter-cell interference management
 Inter-eNodeB handover
 Tracing function
 X2 interface management and error handling

9.2.7 4G LTE EPC ARCHITECTURE
Figure 56: Mobile Core (Evolved Packet Core).
The 4G Mobile Core, which 3GPP officially refers to as the Evolved Packet Core
(EPC), consists of five main components.
 MME (Mobility Management Entity)
 HSS (Home Subscriber Server)
 PCRF (Policy & Charging Rules Function
 SGW (Serving Gateway)
 PGW (Packet Gateway)
Although specified as distinct components, in practice the SGW (RAN-facing)
and PGW (Internet-facing) are often combined in a single device, commonly referred to
as an S/PGW.
The first three run in the Control Plane (CP) and the second two run in the User
Plane (UP).
Figure 57: 4G Mobile Core (Evolved Packet Core).

9.2.8 MME (MOBILITY MANAGEMENT ENTITY)
Tracks and manages the movement of UEs throughout the RAN.
Figure 58: MME

The mobility management entity (MME) controls the high-level operation of the
mobile, by sending it signalling messages about issues such as security and the
management of data streams that are unrelated to radio communications. As with the
serving gateway, a typical network might contain a handful of MMEs, each of which
looks after a certain geographical region. Each mobile is assigned to a single MME,
which is known as its serving MME , but that can be changed if the mobile moves
sufficiently far. The MME also controls the other elements of the network, by means of
signalling messages that are internal to the EPC.
9.2.9 HSS (HOME SUBSCRIBER SERVER)
A database that contains all subscriber-related information.
Figure 59: HSS

9.2.10 PCRF (POLICY & CHARGING RULES FUNCTION)
Tracks and manages policy rules and records billing data on subscriber traffic.
9.2.11 SGW (SERVING GATEWAY)
Forwards IP packets to and from the RAN. Anchors the Mobile Core end of the
bearer service to a (potentially mobile) UE, and so is involved in handovers from one
base station to another.
The serving gateway (S-GW) acts as a router, and forwards data between the base
station and the PDN gateway. A typical network might contain a handful of serving
gateways, each of which looks after the mobiles in a certain geographical region. Each
mobile is assigned to a single serving gateway, but the serving gateway can be changed if
the mobile moves sufficiently far.
Figure 60: SGW (Serving Gateway)

9.2.12 PGW (PACKET GATEWAY)
Essentially an IP router, connecting the Mobile Core to the external Internet.

Supports additional access-related functions, including policy enforcement, traffic
shaping, and charging. The packet data network (PDN) gateway (P-GW) is the EPC‟s
point of contact with the outside world. Through the SGi interface, each PDN gateway
exchanges data with one or more external devices or packet data networks, such as the
network operator‟s servers, the internet or the IP multimedia subsystem. Each packet data
network is identified by an access point name (APN). A network operator typically uses a
handful of different APNs, for example one for its own servers and one for the internet.
Each mobile is assigned to a default PDN gateway when it first switches on, to
give it always-on connectivity to a default packet data network such as the internet. Later

on, a mobile may be assigned to one or more additional PDN gateways, if it wishes to
connect to additional packet data networks such as private corporate networks. Each PDN
gateway stays the same throughout the lifetime of the data connection.
Figure 61: PGW (Packet Gateway)
9.3 5G NETWORK ARCHITECTURE

9.3.1 5G SYSTEM ARCHITECTURE
The 5G System (SGS) includes the 5G Core Network (CN), the 5G Access
Network (AN) and the User Equipment (UE).The 5G Core Network provides
connectivity to the internet and to application servers. The 5G Access Network can be a
3GPP Next Generation Radio Access Network (NG RAN), or a non-3GPP Access
Network.
Figure 62: 5G System Architecture

3GPP has specified both 'Reference Point' and 'Service based' architectures for
the 5G System (SGS).
Figure 63: Architectures for the 5G System (Actual).
Concept of Reference Point Architecture

The 'Reference Point' architecture is based upon a set of Network Elements (NE)
which uses point-to-point interfaces to inter-connect those Network Elements. Signalling
procedures are specified for each point-to-point interface.
The 'Reference Point' architecture can lead to repetition within the specifications
if the same signalling procedure is used across multiple interfaces
Figure 64: Reference Point architecture

Concept of Service based system architecture

The 'Service based' architecture replaces the set of Network Elements with a set of
Network Functions (NF). Each Network Function can provide services to other Network
Functions, i.e. each Network Function is a service provider. This type of architecture is
service based architecture. The point-to-point interfaces are replaced by a common bus
which inter- connects all Network Functions. Services are specified for the Network
Function providing them, rather than for each pair of providing and consuming Network
Functions.
Figure 65: SBA
Figure 66: 5G Network Architecture Evolution

9.3.2 5G NEXTGEN NG CORE NETWORK REQUIREMENT
The requirements for the network for 5G will be particularly diverse. In one
instance, very high bandwidth communications are needed, and in other applications there
is a need for exceedingly low latency, and then there are also requirements for low data
rate communications for machine to machine and IoT applications.
In amongst this there will be normal voice communications, Internet surfing and
all the other applications that we have used and become accustomed to using.

As a result the 5G NextGen network will need to accommodate a huge diversity in

types of traffic and it will need to be able to accommodate each one with great efficiency
and effectiveness. Often it is thought that type suits all approach does not give the
optimum performance in any application, but this is what is needed for the 5G network.
To achieve the requirements for the 5G network a number of techniques are being
employed. These will make the 5G network considerably more scalable, flexible and
efficient.
 Software defined networking, SDN: Using software defined networks, it is

possible to run the network using software rather than hardware. This provides
significant improvements in terms of flexibility and efficiency
 Network functions virtualisation, NFV: When using software defined networks

it is possible to run the different network function purely using software. This
means that generic hardware can be reconfigured to provide the different functions
and it can be deployed as required on the network.
 Network slicing: As 5G will require very different types of network for the
different applications, a scheme known as network slicing has been devices. Using
SDN and NFV it will be possible to configure the type of network that an individual
user will require for his application. In this way the same hardware using different
software can provide a low latency level for one user, whilst providing voice
communications for another using different software and other users may want
other types of network performance and each one can have a slice of the network
with the performance needed.
The performance required for the 5G NextGen network has been defined by the
NGMN (Next Generation Mobile Network Alliance). The Next Generation Mobile
Networks Alliance is a mobile telecommunications association of mobile operators,
vendors, manufacturers and research institutes and by using the experience of all parties,
it is able to develop the strategies for the next generation mobile networks, like that for
5G.
As such the 5G NG, NextGen core network will be able to utilise far greater levels
of flexibility to enable it to serve the increased and diverse requirements placed upon it by
the radio access network and the increased number of connections and traffic.
9.3.3 5G CORE NETWORK ARCHITECTURE
5G core Network is called the Next Generation Core (NG-Core). 5G Mobile Core
divided into a Control Plan and a User Plane, an architectural feature known as CUPS:
Control and User Plane Separation
The Service Based architecture is applicable to the control plane section of the 5G
Core Network.
The Reference Point architecture remains for the user plane section of the 5G
Core Network.

Figure 67: LTE System Architecture
Core Network Architecture Evolution to 5G
Service Based Core Network

The 5G Mobile Core, which 3GPP calls the NG-Core, adopts Service Based
architecture which specifies a set of Network Functions (NF)and a common bus which
inter-connects those Network Functions.
Figure 68: SBA Terminology

The following organizes the set of functional blocks into three groups.
Figure 69: functional blocks

The first group runs in the Control Plane (CP) and has a counterpart in the EPC.
 AMF (Core Access and Mobility Management Function): Responsible for

connection and reachability management, mobility management, access
authentication and authorization, and location services. Manages the
mobility-related aspects of the EPC‟s MME.
 SMF (Session Management Function): Manages each UE session, including
IP address allocation, selection of associated UP function, control aspects of
QoS, and control aspects of UP routing. Roughly corresponds to part of the
EPC‟s MME and the control-related aspects of the EPC‟s PGW.
 PCF (Policy Control Function): Manages the policy rules that other CP
functions then enforce. Roughly corresponds to the EPC‟s PCRF.
 UDM (Unified Data Management): Manages user identity, including the
generation of authentication credentials. Includes part of the functionality in
the EPC‟s HSS.
 AUSF (Authentication Server Function): Essentially an authentication server.
Includes part of the functionality in the EPC‟s HSS.
The second group also runs in the Control Plane (CP) but does not have a direct
counterpart in the EPC:
 SDSF (Structured Data Storage Network Function): A “helper” service used
to store structured data. Could be implemented by an “SQL Database” in a
microservices-based system.
 UDSF (Unstructured Data Storage Network Function): A “helper” service
used to store unstructured data. Could be implemented by a “Key/Value
Store” in a microservices-based system.
 NEF (Network Exposure Function): A means to expose select capabilities to
third-party services, including translation between internal and external
representations for data. Could be implemented by an “API Server” in a
microservices-based system.
 NRF (NF Repository Function): A means to discover available services.
Could be implemented by a “Discovery Service” in a microservices-based
system.
 NSSF (Network Slicing Selector Function): A means to select a Network
Slice to serve a given UE. Network slices are essentially a way to partition

network resources in order to differentiate service given to different users. It

is a key feature of 5G that we discuss in depth in a later chapter.
The third group includes the one component that runs in the User Plane (UP):
 UPF (User Plane Function): Forwards traffic between RAN and the Internet,
corresponding to the S/PGW combination in EPC. In addition to packet
forwarding, it is responsible for policy enforcement, lawful intercept, traffic
usage reporting, and QoS policing.
9.3.4 5G NR NEW RADIO
5G NR or 5G New Radio is the new radio air interface being developed for 5G
mobile communications. Unlike Previous Generation Core Network of 5G is design to
work seamlessly with more than one access technology.
The 5G NR has been defined with no backward compatibility with the existing
LTE and LTE- Advanced systems.
Figure 70: Next Generation Radio Access Network NG-RAN

An NG-RAN node is either:
 A gNB, providing NR user plane and control plane protocol terminations
towards the UE; or
 An ng-eNB, providing E- UTRA user plane and control plane protocol
terminations towards the UE.
 eNodeB (eNB) :LTE access network from 3GPP Rel-8 up to 3GPP Rel-14
 Next generation eNodeB (ng-eNB) : LTE access network from 3GPP Rel- 15
onwards node providing E-UTRA user plane and control plane protocol
terminations towards the UE, and connected via the NG interface to the 5GC.
 Next generation NodeB (gNB) : 5G access network from 3GPP Rel-15
onwards.
5G/NR - RAN Architecture

Figure 71: gNodeB Architecture

5G NR gNodeB is splited into two part; gNB-Cu 9 central unit and gNB-DU(
Distributed unit. Split helps to virtualize the network functionalities.At least as of now, it
would be difficult to virtualize the lower layer of gNB(PHY/MAC/RLC), but you would
be able to put higher layer protocol stack (PDCP and above) into a open hardware and
software-based protocol stack.
Figure 72: NR Architecture

9.3.5 5G DEPLOYMENT OPTIONS
With an already deployed 4G RAN/EPC in the field and a new 5G RAN/NG-Core

deployment underway, we can‟t ignore the issue of transitioning from 4G to 5G (an issue

the IP-world has been grappling with for 20 years). 3GPP officially spells out multiple
deployment options, which can be summarized as follows.
 Standalone 4G / Stand-Alone 5G
 Non-Standalone (4G+5G RAN) over 4G‟s EPC
 Non-Standalone (4G+5G RAN) over 5G‟s NG-Core
The second of the three options, which is generally referred to as “NSA“, involves
5G base stations being deployed alongside the existing 4G base stations in a given
geography to provide a data-rate and capacity boost. In NSA, control plane traffic
between the user equipment and the 4G Mobile Core utilizes (i.e., is forwarded through)
4G base stations, and the 5G base stations are used only to carry user traffic. Eventually,
it is expected that operators complete their migration to 5G by deploying NG Core and
connecting their 5G base stations to it for Standalone (SA) operation. NSA and SA
operations are illustrated in Figure
Figure 73: SA and Non SA Deployment
Figure 74: 5G Deployment Options
9.4 CONCLUSION
The 5G Network is the need of hour, as 4G Network has reached to its maximum
capabilities and it is difficult to manage latency in it, 5G is required for AI services. The
5G deployment option can be exercised as per availability of existing network. New
operator may directly go to 5G Deployment.

E2-E3 Consumer Mobility KPI Reports for 2G/3G/4G
10 KPI REPORTS FOR 2G/3G/4G

Telecom Service Providers use Key Performance Indicators (KPIs) to judge their
network performance and evaluate the Quality of Service (QoS). Regulatory authority
also uses KPIs to monitor Quality of Service of different operator. The KPIs are actually
the statistical measure of network quality and encompass all the QoS parameters related
to Network Accessibility, Service Accessibility, and Network Retain-ability. This chapter
deals with Key Performance Indicators used in GSM, UMTS, HSPA, and LTE networks.
10.2 INTRODUCTION
Key Performance Indicators are a set of quantifiable measures used in GSM,
UMTS, HSPA, and LTE networks to gauge or compare performance in terms of meeting
mobile network‟s strategic and operational goals. KPIs vary between management,
marketing, operations and network engineering people depending on their priorities,
perspectives or performance criteria sometimes referred to as “key success indicators
(KSI)”.
10.3 KPI OF GSM

In GSM all the events being occurred over air interface are triggering different
counters in the Base Station Controller (BSC). The KPIs are derived with the help of
these counters using different formulations. RF Optimizer makes frequent use of
statistical data for routine optimization activities. This raw data, which is actually based
on counters, makes optimization tasks quite cumbersome as counters are in thousands.
So, to make the tasks simpler, counters are appended into formulae, whereas, each
formula reflects a specific performance indicator. All major performance indicators are
categorized as Key Performance Indicators (KPIs). The KPIs are available in report form
through OMC.
Following 2G network KPI optimizations are covered in this chapter:
 SDCCH congestion Rate
 SDCCH drop Rate
 TCH congestion/Blocking Rate
 Call Setup Success Rate
 TCH (call) drop Rate
 Handover Success Rate
 Paging Success Rate
 RACH Success Rate
 Data KPI improvement
10.3.1 SDCCH CONGESTION RATE
During Location Update and set up of MO and MT calls, MS usually seizes SDCCH
to exchange signalling. SMS is also sent/delivered through SDCCH channel in idle mode.
When BSC receives SDCCH request from MS, it checks SDCCH resource. If all
SDCCHs are occupied at that moment, SDCCH congestion takes place. Its day average
value should be ≤ 1%.

Causes and solutions:

(a) Large traffic volume exceeding network capacity
Solution: Increase cell capacity by adding more TRXs.
(b) Too many location update at LAC boundaries
Solution: (i) Adjust LAC selection and/or modify LAC boundaries
(ii) Adjust CRH (Cell Reselection Hysteresis)
(iii) Adjust parameter setting of periodic location update timer (T3212)
(c) Too much SMS traffic
Solution: (i) Implement dynamic SDCCH allocation mode
(ii) Increase SDCCH channels
(d) Hardware fault in TRX or transmission system (Abis link etc.)
Solution: (i) Replace the faulty hardware
(ii) Check and repair the transmission system
(e) Unreasonable setting of system parameters and RACH parameters
Solution:
(i) Increase RACH access threshold appropriately to cope with interference
(ii) Reduce Max Retrans appropriately
10.3.2 SDCCH DROP RATE:
When MS is already on SDCCH and in-between communication with Base station
SDCCH channel got disconnected abruptly then SDCCH Drop has occurred.
Process for Optimization:
Identify the Bad performing Cells for SDCCH Drop Rate. Then follow the below
mentioned Process after Analyzing detailed report
a) The Main Reasons for High SDCCH Drop Rate are improper Parameters
Configuration and Bad RF & Environmental factors.
b) First Audit for any parameters related discrepancies and define as per standard
parameters set.
c) Check for Neighbour Relations and correct if it is not proper.
d) Low Coverage: Through Drive Test Find out the low coverage patched and try to
improve the coverage.
e) Interference: Check for interference from repeaters, Intra-Network interference
due to aggressive reuse or improper Freq., Inter-Network can also be the case.
Find out the actual cause and rectify it.
f) Antenna System: High VSWR due to feeders, improper antenna configuration
(Ex. Sector cable Swap)
g) Check for Hardware Issue and rectify if you found any.
h) After the activity check the subsequent days report and repeat the procedure for
pin pointing the actual cause.
10.4 TCH CONGESTION/BLOCKING RATE

If during call attempt MS is not getting a TCH as all the available TCH in the cell
are already occupied, TCH congestion/blocking occurs. Its day average value should be ≤
2%.
Process for Optimization:

 Check TRX/Hardware Fault in the affected cell
 Check carried Traffic (Erlang) from BH Report and increase no. of TRX in
the cell (If possible). No. of TCH required according to traffic can be
analyzed from Erlang-B table (please see the table)

 Implement Half Rate/AMR-Half Rate if already maximum no. of TRX is

equipped.
Explore possibilities of sharing the traffic of affected cell with neighbouring cell
by:
 Antenna azimuth/tilt/height adjustment of affected/ neighbouring cells.
 HO margin adjustment for making logical slope to neighbouring cells.
 Directed Retry/Traffic handover may be enabled.
 In very exceptional cases power of affected cell may be reduced.
 Additional sector may be installed in the affected BTS.
 Dual band may be implemented in the affected BTS to increase no. of
TRX.
 Last option: Introduction of new BTS in the affected area
Table 5. Erlang B Table

10.4.1 CALL SETUP SUCCESS RATE (CSSR)
CSSR indicates the probability of successful calls initiated by MS. It is an
important KPI for evaluating the network performance. If CSSR is too low, the
subscribers are not likely to make calls successfully. Its value should be ≥95%
CSSR value depends on
I. SDCCH Assignment success Rate
II. SDCCH Drop Rate
III. TCH Assignment Success Rate

Process of optimisation
Find out the causes of a low CSSR.(Check whether a low CSSR is caused by
SDCCH/Immediate Assignment Success Rate problems, SDCCH Drop Rate problems, or
TCH Assignment Success Rate problems.) and accordingly following actions may be
taken
a) Minimise SDCCH Congestion (Refer SDCCH Congestion in the same chapter)
b) Minimise SCDDH Drop (Refer SDCCH Drop in the same chapter)
c) Minimise TCH Congestion (Refer TCH Congestion in the same chapter)
d) Check Hardware/Transmission Faults and Feeder Cable Swap (if any)
e) Check value of parameters like RXLEV_ACCESS_MIN/RACH Min Access
Level/Tx-integer etc.
10.4.2 CALL DROP RATE
Call drops are identified through SACCH messages. A Radio Link Failure counter
(RLT) value is broadcast on the BCH. The counter value may vary from network to
network. At the establishment of a dedicated channel, the counter is set to the broadcast
value (which will be the maximum allowable for the connection). The mobile decrements
the counter by 1 for every FER (unrecoverable block of data) detected on the SACCH and
increases the counter by 2 for every data block that is correctly received (up to the initial
maximum
value). If this counter reaches zero, a radio link failure is declared by the mobile and it
returns back to the idle mode.
If the counter reaches zero when the mobile is on a SDCCH then it is an SDCCH Drop. If
it happens on a TCH, it is a TCH drop.
Sometimes an attempted handover, which may in itself have been an attempt to
prevent a drop, can result in a dropped call.
When the quality drops, a mobile is usually commanded to perform a handover.
Sometimes however, when it attempts to handover, it finds that the target cell is not
suitable. When this happens it jumps back to the old cell and sends a Handover Failure
message to the old cell. At this stage, if the handover was attempted at the survival
threshold, the call may get dropped anyway. If on the other hand the thresholds were
somewhat higher, the network can attempt another handover. Call Drop Rate should be ≤
2%.
Causes of call drop
a) Blind spot, low coverage level.
b) Unavoidable interference can be the inter network interference, interference from
repeaters, or intra network interference resulting from aggressive frequency reuse.
c) Poor transmission quality and unstable transmission links over the Abis interface end
other interfaces.
d) Faulty hardware/high VSWR/ Feeder Cable swap
e) Unreasonable settings of handover parameters/during inter BSC/MSC handover.
f) If pre-emption is used in MSC then lower priority MS will face call drop.
g) Unreasonable setting of radio parameters.
a) Check radio parameters. Adjust unreasonable settings of radio parameters.
b) Proper frequency plan viz. achieve minimum interference level by proper BCCH
planning, HSN, MAIO planning.
c) Minimizing coverage holes by physical optimization (Orientation, Height, E.Tilt,
M.Tilt).

d) Setting Radio link timeout parameter as per inter site distance viz. for rural sites RLT
can be of higher value.
e) Similar for Rural site where uplink quality is poor, Rxlev Access min, Rach Access
min parameter can be set appropriately. Proper balance should be maintained for this
parameter else path imbalance will result and TCH drop will increase.
f) Minimize Abis and other interface fluctuation – Link stability plays very vital role.
g) Check and remove BTS/BSC hardware fault and Cable swap/high VSWR (if any).
h) During HO to neighbour cells should be having free TCH resources else call drop may
increase. For this proper half rate thresholds should be defined as per traffic pattern,
decongestion of these cells by capacity argument.
i) Proper Neighbour definition should be maintained – some handovers cannot be
performed and thus call drops.
10.4.3 HANDOVER SUCCESS RATE (HOSR)
Handovers are meant for maintaining call continuity when subscriber crosses over from
one cell to another cell. KPI to be monitored for handover performance in GSM is
“Handover Success Rate”.
Handover Process: The overall handover process is implemented in the MS, BSS &
MSC.
 Measurement of radio subsystem downlink performance and signal strengths received
from surrounding cells, is made in the MS.
 These measurements are sent to the BSS for assessment.
 The BSS measures the uplink performance for the MS being served and also assesses
the signal strength of interference on its idle traffic channels.
 Initial assessment of the measurements in conjunction with defined thresholds and
handover strategy may be performed in the BSS. Assessment requiring measurement
results from other BSS or other information resident in the MSC, may be perform. In
the MSC.
 The MS assists the handover decision process by performing certain measurements.
 When the MS is engaged in a speech conversation, a portion of the TDMA frame is
idle while the rest of the frame is used for uplink (BTS receive) and downlink (BTS
transmit) timeslots.
 During the idle time period of the frame, the MS changes radio channel frequency and
monitors and measures the signal level of the six best neighbour cells.
 Measurements which feed the handover decision algorithm are made at both ends of
the radio link.
a) Identify the Bad performing Cells for HOSR
b) Take the detailed report showing cause & target cell
c) Check whether HO parameters are defined correctly.
d) BCCH & BSIC confusion i.e. check whether same BCCH and BSIC combination
is repeated in nearby cells.
e) Minimise TCH Congestion as TCH congestion in target cell results HO fail.
f) Unnecessary Handovers – more number of handovers, higher risk of facing
quality problem and even in call drop
g) Missing neighbour – Best server is not in there in neighbour list
h) Feeder cable swap
i) One way neighbour handover

j) If neighbour is defined through external cells (between cells in different OMC

servers e.g. 2G-3G HO/HO b/w cells of different vendors) - need to define correct
CGI, BCCH, BSIC etc. in external cells.
10.4.4 PAGING SUCCESS RATE
Paging Success rate is the percentage of valid page responses received by the system.
Paging Channel Congestion should be ≤ 1%.
a) Removal of non existing Cell site database created in BSCs
b) Correct LAC dimensioning; split LA if paging discard is due to big LA.
c) Define correct channel configuration for CCCH. Avoid combining SDCCH in the
BCH+CCCH timeslot.
d) Remove SDCCH congestion in network as page response is sent to network
through SDCCH.
e) Eliminate Abis /A interface congestion/error.
f) Correcting the various Paging/Location Update timers/parameters in
MSC/BSC/Cell.
g) Poor Paging Success rate is also observed due to poor RF environment (Site
outage/ Poor Signal Level etc.).
h) Use correct paging strategy according to network size and topology.
10.4.5 RACH SUCCESS RATE
Random Access Channel (RACH) is used by the MS on the “uplink” to request for
allocation of an SDCCH. This request from the MS on the uplink could either be as a
page response (MS being paged by the BSS in response to an incoming call) or due to
user trying to access the network to establish a call. For all services there will CH REQ
(Channel Request) from MS and in the response of CH REQ if MS will get the IMM ASS
CMD (Signalling Ch) Access to system is successful. Nature of this Access REQ is
random so it is call Random Access Channel Request.
a) Identify the Bad performing Cells for RACH Success Rate
b) Take detailed report and analyze for no of failure of Request and failures.
c) The main reasons for bad RACH success rate could be access from very distant
place with very low coverage; Parameters Configuration discrepancies.
d) First Check for Parameters Configuration discrepancies and correct as per
standard parameter set.
e) The main parameters to be verified are:
I. “MS MAX Retrans” allows the MS to retransmit again for AGCH by not
incrementing the RACH access failure counter. It can set depending upon Traffic
and Clutter.
II. “Tx-Interger” will reduce the RACH collision and can improve RACH success
rate.
III. “T3122” waiting time for next network access.
IV. “RACH Min.Access Level (dbm)” very important parameter for low coverage
rural areas.
V. “CCCH conf” & “BS_AG_BLKS_RES” check properly defined or not? Because
if you have overload with AGCH “IMM ASS” can‟t be send in the response of
CH REQ.
f) Check for Hardware Issues (Ex. BTS sensitivity has very crucial role to play here)
g) Check for Uplink Interference and quality.

i) Check for UL-DL imbalance and correct if any problem.
10.5 DATA KPI IMPROVEMENT
10.6 TBF SUCCESS RATE

Temporary Block Flow (TBF) is a physical connection used by the two Radio
Resource entities to support the unidirectional transfer of PDUs on packet data physical
channels. The TBF is allocated radio resource on one or more PDCHs and comprises a
number of RLC/MAC blocks carrying one or more LLC PDU. TBF Success Rate is when
during a data session, TBFs are successfully established on UL and DL.
a) Identify the Bad performing Cells for TBF Success Rate.
b) Identify the bifurcation of Poor TBF Success Rate: whether UL or DL is poor or it
is poor in both directions.
c) Take the detailed report showing (Ex. Total TBF Requests, Total TBF Success,
Failure reasons)
d) Identify the failure reasons after analyzing detailed report and follow the below
mentioned process.
Failure is mainly due to TBF Congestion or MS No response.
10.6.1 TBF CONGESTION:
i. Check the Static and Dynamic PDCH definition from BSC Configuration data) If you
find Zero Static or Dynamic PDCH, define the same.
ii. If PDCH definition is sufficient as per the guidelines, then check whether the TBF
requests are high. If requests are high, then we need to define more PDCHs in the
cell. But before defining more PDCHs, check whether the Voice Utilization is not
high and there is no TCH Congestion in the cell.
iii. Check Hardware/TRX alarms; Resolve if find any.
iv. Audit for any parameters related discrepancies and define as per standard parameters
set.
MS No Response: RF and Environmental Factors:
i. Low Coverage Areas (Try to reduce low coverage patches with physical
optimization; New sites)
ii. Interference/ Bad quality/ UL-DL Imbalance;
iii. Check the states for TRx on which PDCH is configured can be issue of TRx also;
Change TRx if you found random behavior of TRx.
10.6.2 AVERAGE GPRS/EDGE RLC THROUGHPUT
Throughput is the amount of data uploaded/downloaded per unit of time.
a) Identify the Bad performing Cells for Poor GPRS/EDGE Throughput.
b) Identify the bifurcation of Poor Throughput: whether UL or DL is poor or it is poor in
both directions.
c) Take the detailed report showing (Ex. Total TBF Requests, Coding Scheme
Utilization)
d) Identify the cells after analyzing detailed report and follow the below mentioned
process.
e) Take the configuration dump of the poor cells:
I.Check The Static and Dynamic PDCH definition from BSC Configuration data)
II.If you find Zero Static or Dynamic PDCH, define the same.

III.If PDCH definition is sufficient as per the guidelines, then check whether the TBF
requests are high. If requests are high, then we need to define more PDCHs in the cell.
But before defining more PDCHs, check whether the Voice Utilization is not high and
there is no TCH Congestion in the cell.
IV.Check whether there are enough Idle TS defined at the site. If not, definition to be
done.
f) Check whether it is due to poor radio conditions/interference; check C/I. Perform a
drive test to analyze the cell in more detail.
g) Check Gb Congestion/Utilization at the BSC/PCU.
h) Check Hardware/TRX alarms; Resolve if find any.
i) Audit for any parameters related discrepancies and define as per standard parameters
set.
10.6.3 DOWNLINK MULTI SLOT ASSIGNMENT SUCCESS RATE
User timeslot request based on traffic types and MS multi-timeslot capability and
the actual timeslot allocated by the system which can also be termed as Downlink
Multislot Assignment Success rate.
a) Identify the Bad performing Cells for Poor Poor DL Multislot Assignment.
b) Take the detailed report showing (Ex. Total TBF Requests, Failure in terms of TS
requests)
c) Identify the cells after analyzing detailed report and follow the below mentioned
process.
d) Take the configuration dump of the poor cells:
I. Check The Static and Dynamic PDCH definition from BSC Configuration
data)
II. If you find Zero Static or Dynamic PDCH, define the same.
III. If PDCH definition is sufficient as per the guidelines, then check whether the
TBF requests are high. If requests are high, then we need to define more
PDCHs in the cell. But before defining more PDCHs, check whether the Voice
Utilization is not high and there is no TCH Congestion in the cell.
IV. Check the multiplexing thresholds and upgrade/downgrade reports.
e) Check whether it is due to poor radio conditions/interference; check C/I. Perform a
drive test to analyze the cell in more detail.
f) Check Gb Congestion/Utilization at the BSC/PCU.
g) Check Hardware/TRX alarms; Resolve if find any.
h) Audit for any parameters related discrepancies and define as per standard parameters
set.

10.7 3G UMTS KPI

10.7.1 3G KPIS ARCHITECTURE
Figure 75: 3G KPI Structure

RAN KPI Class :
Figure 76: 3G KPI Class

10.7.2 RAB ESTABLISHMENT SUCCESS RATE
This KPI describes the ratio of all successful RAB establishments to RAB
establishment attempts for UTRAN network and is used to evaluate service accessibility
across UTRAN. This KPI is obtained by the number of all successful RAB
establishments divided by the total number of attempted RAB establishments.

RAB Assignment is the last step of the service connection. If it is successfully

assigned, the connection to the user plane is successfully setup.
RAB setup procedure is the process that establishes the higher-layer connection
between UE and CN that is used to transfer the user data only (not signalling). When the
RNC receives the RAB ASSIGNMENT REQUEST allocates the necessary resources for
the requested service, after successful call admission. Resources include Codes, CE,
Power, IUB bandwidth. Then the RB is setup which is the UTRAN part of the RAB.
Upon successful completion of the RB setup, the RNC responds to the CN with
the RAB ASSIGNMET RESPOND message.
Figure 77: RAB Establishment

10.7.3 RRC CONNECTION ESTABLISHMENT SUCCESS RATE
This KPI describes the ratio of all successful RRC establishments to RRC
establishment attempts for UTRAN network, and is used to evaluate UTRAN and RNC or
cell admission capacity for UE and/or system load. This KPI is obtained by the number of
all successful RRC establishments divided by the total number of attempted RRC
establishments.

Figure 78: RRC Establishment

RRC setup procedure is the process that establishes the L3connection between UE
and RNC that is used for signalling traffic only. After RNC receives the RRC
CONNECTION
REQUEST, processes it and allocates relevant resources on L1, L2 and L3 ofthe air
interface for this signalling connection. The RNC notifies the UE for the prepared
configuration with the RRC CONNECTION SETUP message. The UE reports its
capabilities to the RNC with the RRCCONNECTION SETUP COMPLETE
10.7.4 CALL SETUP SUCCESS RATE/ SERVICE ACCESS SUCCESS RATE:
This KPI describes the ratio of successful call establishments. It is based on the
Successful RRC Connection Establishment Rate for callsetup purposes and the RAB
Establishment Success Rate for all RAB types. Both KPIs are multiplied.
Figure 79: RAB & RRC Establishment

The Call Set up Success Rate (CSSR) is one of the most important Key
Performance Indicators (KPIs) used by all mobile operators. The CSSR in general is a
term in telecommunications denoting the fraction of the attempts to make a call which
result in a connection to the dialled number.
10.7.5 UTRAN SERVICE ACCESS SUCCESS RATE
UTRAN service access success rate for idle mode UEs describes the ratio of all
successful UTRAN access to UTRAN access attempts for UTRAN network and is used
to evaluate service accessibility provided by UTRAN. Successful RRC set up repetition
and/or cell re-selections during RRC setup should be excluded, namely only service
related RRC setup should be considered.
This KPI is obtained by the Successful RRC Connection Establishment Rate for
UTRAN access purposes multiplied by the RAB Establishment Success Rate for all RAB
types.
10.7.6 UMTS PDP CONTEXT ACTIVATION SUCCESS RATE
This KPI describes the ratio of the number of successfully performed PDP context
activation procedures to the number of attempted PDP context activation procedures for
UMTS PS core network and is used to evaluate service accessibility provided by UMTS
and network performance to provide GPRS.
This KPI is obtained by successful PDP context activation procedures initiated by

MS divided by attempted PDP context activation procedures initiated by MS.
10.7.7 CALL DROP RATE
It is the most important indicators of the customers experience. It reflects the

retain ability of the network.
The Call Drop Rate (CDR) is the fraction of the telephone calls which, due to
technical reasons, were cut off before the speaking parties had finished their conversation
and before one of them had hung up (dropped calls), this fraction is usually measured as a
percentage of all calls. This KPI describes the ratio of RAB release requests related to the
number of successful RAB establishment (per CS/PS domain).
Figure 80: Call Drop
Drops are derived from "IU Release Request" and "RAB Release Request
“messages sent from UTRAN to the CN as calculated by the formula:

10.7.8 CALL BLOCKING RATE :
This KPI indicate rate of blocked calls due to resource shortage. This KPI partially
reflects the degree of congestion in the cell.
10.8 MOBILITY KPI

10.8.1 SOFT HANDOVER SUCCESS RATE
This Indicate Radio link addition success rate. This KPI describes the ratio of
number of successful radio link additions to the total number of radio link addition
attempts.
This KPI is obtained by the number of successful radio link additions divided by
the total number of radio link.
Figure 81: Soft Handover

This indicator reflects the soft handover mobility in the RNC control area.

10.8.2 OUTGOING INTER RAT HANDOVER SUCCESS RATE (CS)
This KPI describes the ratio of number of successful inter RAT handover to the
total number of the attempted inter RAT handover from UMTS to GSM for CS domain.
This KPI is obtained by the number of successful inter RAT handover divided by
the total number of the attempted inter RAT handover from UMTS to GSM for CS
domain.
Figure 82: CS Outgoing Inter RAT Handover ( UMTS to GSM )

10.8.3 OUTGOING INTER RAT HANDOVER SUCCESS RATE (PS)
This KPI describes the ratio of number of successful inter RAT handover to the
total number of the attempted inter RAT handover from UMTS to GSM for PS domain.
This KPI is obtained by the number of successful inter RAT handover divided by
the total number of the attempted inter RAT handover from UMTS to GSM/GPRS for PS
domain respectively.

Figure 83: PS Outgoing Inter RAT Handover ( UMTS to GSM )

10.8.4 INTER RAT INCOMING HANDOVER ( PS )
This indicates the Inter-RAT handover mobility, the handover is from GPRS
system to UMTS system.
Figure 84: Incoming Inter RAT Handover ( GPRS to UMTS)

10.9 UTILISATION KPI

10.9.1 CS SERVICE TRAFFIC ERLANG
This indicator reflects the traffic Erlang of CS conversation service.
10.9.2 PS SERVICE THROUGHPUT
This indicator reflects total throughput of PS service.
10.9.3 UTRAN CELL AVAILABILITY.
A KPI that shows Availability of UTRAN Cell.Percentage of time that the cell is
considered available.
10.10 4G LTE KPI

As specified in the 3GPP TS 32.451 document, there are several types of KPI
parameters that are integral to any LTE network, depending on the target they measure:
 Accessibility
 Retainability
 Integrity
 Availability
 Mobility
Others can be added depending on the the network‟s need, such as:
 Utilization
 Traffic
 Latency
Accessibility
Accessibility is a measurement that allows operators to know information related
to the mobile services accessibility for the subscriber. The measurement is performed
through E-UTRAN‟s E-RAB service.

Retainability
Retainability measures how many times a service was interrupted or dropped
during use, thus preventing the subscriber to benefit from it or making it difficult for the
operator to charge for it. Therefore, a high retainability is very important from a business
stand point.The measurement is performed through E-UTRAN‟s E-RAB service.
Integrity
Integrity measures the high or low quality of a service while the subscriber is
using it.The measurement is performed through E-UTRAN‟s delivery of IP packets.
Availability
Availability measures a service‟s availability for the subscriber. The measurement
is performed by determining the percentage of time that the service was available for the
subscribers served by a specific cell. The measurement can also aggregate data from more
cells or from the whole network.
Mobility
Mobility measures how many times a service was interrupted or dropped during a
subscriber‟s handover or mobility from on cell to another. The measurement is performed
in the E-UTRAN and will include Intra E-UTRAN and Inter RAT handovers.
KPIs for LTE RAN (Radio Access Network)
LTE KPI INDICATORS
 RRC setup success rate

 ERAB setup success rate
 Call Setup Success Rate
Accessibility KPI
Are used to measure properly of whether services requested
by users can be accessed in given condition, also refers to the
quality of being available when users needed. eg. user request
to access the network, access the voice call, data call, ......
 Call drop rate

 Service Call drop rate
Retainability KPI
Are used to measure how the network keep user's possession
or able to hold and provide the services for the users
 Intra-Frequency Handover Out Success Rate
 Inter-Frequency Handover Out Success Rate
 Inter-RAT Handover Out Success Rate (LTE to
Mobility WCDMA)
KPI
Are used to measure the performance of network which can
handle the movement of users and still retain the service for
the user, such as handover,...
Integrity  E-UTRAN IP Throughput
KPI  IP Throughput in DL

 E-UTRAN IP Latency
Are used to measure the character or honesty of network to

its user, such as what is the throughput, latency which users
were served.
 E-UTRAN Cell Availability
Partial cell availability (node restarts excluded)
Availability
KPI
Are used to measure how the network keep user's possession
or able to hold and provide the services for the users
 Mean Active Dedicated EPS Bearer Utilization
Utilization
KPI
Are used to measure the utilization of network, whether the
network capacity is reached its resource.
Table 6. LTE KPI
10.10.1 RRC SETUP SUCCESS RATE
RRC setup success rate is calculated based on the counter at the e-NodeB when
the e-NodeB received the RRC connection request from UE. Number of RRC connection
attempt is collected by the e-NodeB to the measurement at point A, and the number of
successful RRC connection calculated at point C. Here's an illustration:
Figure 85: RRC Setup
Table 7. RRC Setup Success Rate

10.10.2 ERAB SETUP SUCCESS RATE
ERAB setup success rate KPI shows the probability of success ERAB to access all
services including VoIP in a cell or radio network. KPI is calculated based counter ERAB
connection setup attempt (point A) and successful ERAB setup (point B). The
explanation is as given in the following illustration:
Figure 86: ERAB Setup
Table 8. ERAB Setup Success Rate

10.10.3 CALL SETUP SUCCESS RATE
Call Setup Success Rate KPI call setup indicates the probability of success for all
service on the cell or radio network. KPI is calculated by multiplying the RRC setup
success rate KPI, S1 signalling connection success rate KPI, and ERAB success rate KPI.
The table below describes the definition Call Setup Success Rate:
Table 9. CSSR

10.10.4 CALL DROP
VoIP call drop arise when VoIP ERAB release is not normal. Each ERAB
associated with QoS information. Here's an illustration of two procedures being done to
release ERAB namely: ERAB release indication and the UE context release request:
Figure 87: ERAB Release
Table 10. Call Drop

10.10.5 INTRA-FREQUENCY HANDOVER OUT SUCCESS RATE
Intra-Frequency Handover Success Rate Our KPI shows intra-frequency handover

success rate of local cell or radio network to the intra-frequency neighboring cell or radio
network. Intra-frequency HO included in a single cell e-NodeB or different e-NodeB.
Intra-frequency HO scenario shown in the figure below:
Figure 88: Intra-Frequency Handover Out

No attempt HO calculations at point B. When E-NodeB sending RRC connection
reconfiguration message to the EU, he will do the handover. E-NodeB will count the
number of times the HO attempt at the source cell. HO calculation of success is at point

C. The HO E-NodeB count the number of the source cell when E-NodeB receive RRC
connection reconfiguration message complete of the EU. Here's a scenario intra-
frequency handover inter E-NodeB
Figure 89: Intra-Frequency Handover inter E-NodeB

Handover attempt occurs at point B, when the source E-NodeB (S-e-NodeB)
sends RRC connection reconfiguration message to the UE. He decided to conduct inter E-
NodeB HO. in this KPI, the source and the target cell work on the same frequency. The
number of the attempt HO calculated at the source cell. The number of successful HO
occurs at point C. During HO, HO amount which success is measured in the cell sauce.
This measurement appears typing S-e-NodeB received a UE context release message
from the target eNode B (T-e-NodeB), or the UE context release command from the
MME, which shows that the UE-e-NodeB T has successfully attach at the T-e-NodeB.
The following scenarios illustrate intra frequency B HO - inter E-NodeB:
Figure 90: Intra-Frequency Handover inter E-NodeB

Following the definition of Intra Frequency Out Handover Success Rate KPI:
Table 11. Intra-Frequency Handover Out Success Rate
10.10.6 INTER-RAT HANDOVER OUT SUCCESS RATE (LTE TO WCDMA)
Inter RAT Handover Out Success rate shows the success rate KPI HO from LTE
cell or radio network to a WCDMA cell.
Here's a scenario out inter RAT handover success rate:
Figure 91: out inter RAT handover

Inter RAT handover success rate out

Table 12. Inter-RAT Handover Out Success Rate
10.10.7 E-UTRAN IP THROUGHPUT
A KPI that shows how E-UTRAN impacts the service quality provided to an end-
user. Payload data volume on IP level per elapsed time unit on the Uu interface. IP
Throughput for a single QCI:
Figure 92: E-UTRAN IP Throughput

To achieve a throughput measurement that is independent of bursty traffic pattern,

it is important to make sure that idle gaps between incoming data is not included in the
measurements. That shall be done as considering each burst of data as one sample.
ThpVolDl is the volume on IP level and the ThpTimeDl is the time elapsed on Uu for
transmission of the volume included in ThpVolDl.
Figure 93: E-UTRAN IP Throughput

10.10.8 E-UTRAN IP LATENCY
A measurement that shows how E-UTRAN impacts on the delay experienced by

an end-user. Time from reception of IP packet to transmission of first packet over the Uu.
To achieve a delay measurement that is independent of IP data block size only the first
packet sent to Uu is measured. To find the delay for a certain packet size the IP
Throughput measure can be used together with IP Latency (after the first block on the Uu,
the remaining time of the packet can be calculated with the IP Throughput measure).
Figure 94: E-UTRAN IP Latency

T_Lat is defined as the time between receiption of IP packet and the time when
the e-NodeB transmits the first block to Uu. Since services can be mapped towards
different kind of E-RABs, the Latency measure shall be available per QoS group.
AVAILABILITY KPI:
10.10.9 E-UTRAN CELL AVAILABILITY.
A KPI that shows Availability of E-UTRAN Cell.Percentage of time that the cell is
considered available.
As for defining the cell as available, it shall be considered available when the e-
NodeB can provide E-RAB service in the cell.
10.11 CONCLUSION
It is very important to manage KPI of radio network in order to have best of radio
network performance.

E2-E3 Consumer Mobility Concept of SON
11 CONCEPT OF SON

 Concept of SON
 SON Implementation
 Issues in SON implementation
 SON Data Creation
 Automatic handover in SON
11.2 INTRODUTION
Self Organising Network (SON) is a collection of procedures (or functions) for
automatic configuration, optimization, diagnostication, and healing of cellular networks.
It is considered to be a major necessity in future mobile networks and operations mainly
due to possible savings in capital expenditure (CAPEX) and operational expenditure
(OPEX) by introducing SON.
The drivers for SON are:

 The number and complexities of networks, nodes, elements and
parameters
 Existence of multi-technology, multi-vendor and multi-layer operations
within the network
 Traffic growth and capacity management
 Consistent quality and service availability
 The need for knowledge-based and interactive networks
Figure 95: Network without SON Capability
Figure 96: Network with SON Capability

Figure 97: Benefits of SON

The main benefits of introducing SON functions in cellular networks are as
follows.
 Reduced installation time and costs.
 Reduced OPEX due to reductions in manual efforts in connection with
monitoring, optimizing, diagnosing, and healing of the network.
 Reduced CAPEX due to more optimized use of network elements and
spectrum.
 Improved user experience.
 Improved network performance
11.3 SELF ORGANIZING NETWORKS (SON) CONCEPT

The SON functions are usually categorized into three main groups: Self-
configuration, self-optimization, and self-healing. It should be noted that a given SON
function can belong to more than one of these categories.
Figure 98: Functions of SON

Figure 99: 3GPP SON FRAMEWORK
Network Lifecycle
Planning Deployment Optimization Maintenance
Self-Planning Self-Configuring Self-Optimizing Self-Healing

- Automatically derive - Plug-n-Play Hardware - Automatic Neighbor - Auto Cell
few Radio - Self-Configuration Relation Outage
parameters for eNBs Radio Parameters Optimization Detection
which will be . Initial PCI, - Mobility - Auto Cell
established. Robustness Outage
. Initial NR,
- Reduce amount of . Initial PRACH configuration Optimization Compensation
- Mobility Based
manual pre- - Automatic IP Acquisition Load balancing
planning - Automatic Neighbor Lists
Activities - RACH optimization
- Automatic - Energy Cost
- Reduce self- Connectivity
configuration Optimizatio
establishment n
errors - Self-test and - Coverage &
S/W download Capacity
Optimization
Figure 100: SON Technology
11.3.1 SELF CONFIGURATION
The Self-configuration SON is a collection of algorithms that aims at reducing the

amount of human intervention in the overall installation process by providing “plug and
play” functionality in network elements such as the E-UTRAN NodeBs (eNBs). This will
result in faster network deployment and reduced costs for the operator in addition to a
more integral inventory management system that is less prone to human errors. This
process involves three key operations: set-up, authentication and radio configuration.

Self-configuration is a broad concept which involves several distinct functions

that are covered through specific SON features, such as automatic software management,
self test, Physical cell ID configuration (PCI), and automatic neighbor relations (ANR).
The latter function is not only used during installation but is also an important part during
normal operations.
The self-configuration should take care of all soft- configuration aspects of an

eNB once it is commissioned and powered up for the first time. It should detect the
transport link and establish a connection with the core network elements, download and
upgrade to the latest software version, set up the initial configuration parameters
including neighbor relations, perform a self-test, and finally set itself to operational mode.
In order to achieve these goals, the eNB should be able to communicate with several
different entities.
Figure 101: Self Configuration Procedure

The self-configuration actions will take place after the eNBs physically installed,
plugged to the power line and to the transport link. When it is powered on, the eNB will
boot and perform a self test, followed by a set of self-discovery functions, which include
the detection of the transport type, tower-mounted amplifier (TMA), antenna, antenna
cable length and auto-adjustment of the receiver-path.
After the self-detection function, the eNB will configure the physical transport link
autonomously and establish a connection with the DHCP/DNS (dynamic host
configuration protocol/domain name server) servers, which will then provide the IP
addresses for the new node and those of the relevant network nodes, including serving
gateway, mobility management entity (MME), and configuration server. After this, the
eNB will be able to establish secure tunnels for operations administration and
maintenance (OAM), S1, and X2 links and will be ready to communicate with the
configuration server in order to acquire new configuration parameters.
One of the OAM tunnels created will communicate the eNB with a dedicated
management entity, which contains the software package that is required to be installed.
The eNB will then download and install the corresponding version of the eNB software,
together with the eNB configuration file. Such configuration file contains the

preconfigured radio parameters that were previously planned. A finer parameter

optimization will take place after the eNB is in operational state (self-optimization
functions).
The self-configuration SON functions were among the first standardized by 3GPP
(release 8) and have been more or less stable since then. From the roadmaps of different
vendors it can be concluded that self-configuration SON is available and mature. These
SON features will be extremely useful in the rollout phase to reduce the installation time
compared with ordinary installation procedures, and also later when new eNBs are added
to increase the network capacity. The actual decrease in OPEX is not easy to give since
the corresponding installation without any (self) automatic features is difficult to foresee.
The self configuration procedures for LTE presents three automated processes:
Self configuration of eNB, Automatic Neighbor Relations (ANR) and Automatic
Configuration of Physical Cell ID (PCI).
11.3.2 SELF CONFIGURATION OF ENB
This is relevant to a new eNB trying to connect to the network. It is a case where
the eNB is not yet in relation to the neighbour cells, but to the network management
subsystem and the association of the new eNB with the serving gateway (S-GW). It is the
basic set-up and initial radio configuration. The stepwise algorithm for self configuration
of the eNB is outlined:
1. The eNB is plugged in/powered up.
2. It has established transport connectivity until the radio frequency transmission is
turned on.
3. An IP address is allocated to it by the DHCP/DNS server.
4. The information about the self configuration subsystem of the Operation and
Management (O & M) is given to the eNB.
5. A gateway is configured so that it connects to the network. Since a gateway has
been connected on the other side to the internet, therefore, the eNB should be able
to exchange IP packets with the other internet nodes.
6. The new eNB provides its own information to that self configuration subsystem
so that it can get authenticated and identified.
7. Based on these, the necessary software and information for configuration (radio
configuration) are downloaded.
8. After the download, the eNB is configured based on the transport and radio
configuration downloaded.
9. It then connects to the Operation Administration Management (OAM) for any other
management functions and data-ongoing connection.
10. The S1 and X2 interfaces are established.
11.3.3 AUTOMATIC NEIGHBOUR RELATIONS (ANR)
ANR is an automated way of adding/deleting neighbour cells. ANR relies on user

equipment (UE) to detect unknown cells and report them to eNBs. Its operation can be
summarized into: measurements, detection, reporting, decision (add/delete cell) and
updating.

Figure 102: ANR with help of UE Measurement

The step-by-step ANR procedure is outlined:
1. During measurements, the UE detects PCI from an unknown cell.
2. The UE reports the unknown PCI to the serving eNB via Radio Resource
Controller (RRC) reconfiguration message.
3. The serving eNB requests the UE to report the E-UTRAN Cell Global ID (ECGI)
of the target eNB. The eNB is able to detect devices faster that way.
4. The UE reports ECGI by reading the broadcast channel (BCCH) channel.
5. Based on the ECGI, the serving eNB retrieves the IP address from the Mo- bility
Management Entity (MME) to further set-up the X2 interface, since an initial X2
interface set-up would have happened during the target eNB‟s self configuration.
6. Function is extended to inter-RAT and inter-frequency cases with suitable
messaging.
11.3.4 ANR WITH OPERATION ADMINISTRATION & MANAGEMENT
(OAM) SUPPORT
ANR with OAM support is a more centralized system of operation. The OAM is
the management system of the network. ANR procedures with OAM support are outlined:
 The new eNB registers with OAM and downloads the neighbour
information table which includes the PCI, ECGI and IP addresses of the
neighbouring eNBs.
 The neighbours update their own tables with the new eNB information.
 The UE reports the unknown PCI to the serving eNB.
 The eNB sets-up the X2 interface using the neighbour information table
formed previously.

11.3.5 AUTOMATIC CONFIGURATION OF PHYSICAL CELL

IDENTIFICATION (PCI).
The automatic configuration of physical cell ID (PCI) for eNBs in LTE was
standardised in 3GPP release 8 as part of “eNB self configuration.” PCI is a locally
defined identifier for eNBs with a restricted range (up to 504 values) and must be reused
throughout the network. The PCI numbering of eNBs must locally be unique so that the
UEs may be able to communicate and possible perform handovers. The goal of PCI
configuration is to set the PCI of a newly introduced cell. The PCI is contained in the
SCH (synchronization channel) for user equipment (UE) to synchronize with the cell on
the downlink. When a new eNB is established, it needs to select PCIs for all the cells it
supports. Since the PCI parameters have a restricted value range, the same value needs to
be assigned to multiple cells throughout the network and must be configured collision
free, that is, the configured PCI needs to be different from the values configured in all the
neighbouring cells.
In today‟s algorithms for automatic PCI assignments, conflicts may occur in the
way they are allocated. Therefore, to achieve the aim of SON, work is currently being
done to ensure automatic configuration of PCIs become a part of the standardized
configuration.
PCI configuration must satisfy two rules:

 Collision Free: The PCI of one cell should not be the same as those of his
neighbor cells.
 Confusion Free: The PCI of the neighbor cells should not be the same.
PCI B PCI B
PCI A PCI A PCI A PCI B
PCI A PCI A PCI B PCI C
Collision Based Collision Free Confusion Based Confusion Free

Figure 103: PCI Solution
11.3.6 SELF OPTIMIZATION
SON self-optimization functions are aiming at maintaining network quality and

performance with a minimum of manual intervention from the operator. Self-optimization
functions monitors and analyzes performance data and automatically triggers
optimization action on affected network element(s) when necessary. This significantly
reduces manual interventions and replaces them with automatic adjustments keeping the
network optimized at all times. Self-optimizing SON functions make it possible to
introduce new automatic processes that are too fast, and/or too complex to be
implemented manually. This will improve the network performance by making the

network more dynamic and adaptable to varying traffic conditions and improve the user
experience.
Self configuration alone is not sufficient to guarantee effective management of the

end-to-end network, the need for knowledge-based end-to-end monitoring is also very
crucial. After configurations, automated processes/algorithms should be able to regularly
compare the current system status parameters to the target parameters and execute
corrective actions when required. This process ensures optimum performance at all times.
This process is known as Self Optimization.
Some of the most important self-optimization SON use cases are:
(i) Physical cell ID(PCI);
(ii) Automatic neighbour relations(ANR);
(iii) Inter-cell Interference coordination(ICIC);
(iv) Mobility robustness optimization(MRO);
(v) Mobility load balancing optimization (MLB).
The two first use cases, PCI and ANR, may as well be categorized as self-
configuration algorithms since they will be part of initial configuration procedures, but
will also play an important part in normal operation and therefore may be viewed as being
self optimization procedures.
11.3.7 PHYSICAL CELL ID CONFIGURATION (PCI)
The PCI automatic configuration was one of the first SON functions to be
standardized by 3GPP. The self- configuration feature seems to be quite mature and all of
the main vendors have this function implemented in their eNBs. Some vendors report
tests with 100% handover success rate in networks where new eNB are introduced and
the Automatic PCI Optimization are applied. The physical cell ID configuration is a SON
function that should be implemented at eNB rollout.
11.3.8 AUTOMATIC NEIGHBOUR RELATIONS (ANR)
One of the more labour intense areas in existing radio technologies is the handling
of neighbour relations for handover. A neighbour relation is information that a neighbour
cell is a neighbour to an eNB. Each eNB holds a table of detected neighbour cells which
are used in connection with handovers. Updating automatic neighbour relations (ANR) is
a continuous activity that may be more intense during network expansion, but is still a
time consuming task in mature networks. The task is multiplied with several layers of
cells when having several networks to manage. With LTE, one more layer of cells is
added; thus, optimization of neighbour relations may be more complex. Due to the size of
the neighbouring relation tables in radio networks, it is a huge task to maintain the
neighbour relations manually. Neighbour cell relations are therefore an obvious area for
automation, and ANR is one of the most important features for SON. To explore its full
potential, ANR must be supported between network equipment from different vendors.
ANR was therefore one of the first SON functions to be standardized in 3GPP.

11.3.9 INTER-CELL INTERFERENCE COORDINATION (ICIC).
The main idea behind inter-cell interference coordination (ICIC) is to coordinate

transmissions in different cells in such a way that the inter-cell interference and/or the
effect of it is reduced. With the currently proposed solutions this is achieved by letting
each cell omit using some of the spectrum resources (frequency/time slots/power) in order
to reduce interference. Omitting to use spectrum resources implies that some capacity is
lost, so the gains obtained by operating in an environment with less interference must
more than compensate for this loss. The most important gain that can be achieved by
ICIC is the ability to provide a more homogeneous service to users located in different
regions of the network, especially by improving the cell-edge performance.
Mutual interference may occur between the cells in an LTE network. Interference
unattended to leads to signal quality degradation. Inter-cell interference in LTE is
coordinated based on the Physical Resource Block (PRB). It involves coordinating the
utilization of the available PRBs in the associated cells by introducing restrictions and
prioritization, leading to significantly improved Signal to Interference Ratio (SIR) and the
associated throughput. This can be accomplished by adopting ICIC RRM (Radio
Resource Management) mechanisms through signalling of Overload Indicator (OI), High
Interference Indicator (HII), or downlink transmitter power indicator.
Multi-layer heterogeneous network layout including small cell base stations are
considered to be the key to further enhancements of the spectral efficiency achieved in
mobile communication networks. It has been recognized that inter-cell interference has
become the limiting factor when trying to achieve not only high average user satisfaction,
but also a high degree of satisfaction for as many users as possible.
Figure 104: ICIC Use Case

The servicing operator for each cell carries out interference coordination, by
configuring the ICIC associated parameters such as reporting thresholds/periods and
prioritized resources. The ICIC SON algorithm is responsible for the automatic setting
and updating of these parameters.
The ICIC SON algorithm work commenced in Release 9 but was not completed
here. It is targeted at self configuration and self optimization of the control parameters of
ICIC RRM strategies for uplink and downlink. To achieve interference coordination, the
SON algorithm leverages on exchange of messages between eNBs in different cells
through the X2 interface. The SON algorithm enables automatic configuration/adaptation
with respect to cell topology, it requires little human intervention and leads to optimized
capacity in terms of satisfied users.
11.3.10 MOBILITY ROBUSTNESS / HANDOVER OPTIMIZATION (MRO).
Handover coordination is very necessary in ensuring seamless mobility for user

devices within a wireless network. In 2G/3G systems, setting handover parameters is a
manual and time consuming task and sometimes too costly to update after initial
deployment. Mobility Robustness Optimization (MRO) automates this process to
dynamically improve handover operations within the network, provide enhanced end user
experience and improved network capacity.
To achieve this aim, the question to be critically answered is “What triggers

handover?” Therefore, 3GPP categorize handover failures into:
 Failures due to too late handover triggering
 Failures due to too early handover triggering
 Failures due to handover to a wrong cell
Figure 105: Too Late Handover

Figure 106: Too Early Handover
Figure 107: Wrong Handover

Also, unwanted handovers may occur subsequent to connection set-up, when cell-
reselection parameters are not in agreement with the handover parameters.
Therefore, the MRO algorithm is aimed at detecting and minimizing these failures
as well as reducing inefficient use of network resources caused by unnecessary handovers
and also reducing handovers subsequent to connection set-up.
As specified by 3GPP, enabling MRO requires that:
a) The relevant mobility robustness parameters should be automatically
configurable by the eNB SON entities;
b) OAM should be able to configure a valid range of values for these parameters;
and
c) The eNB should pick a value from within this configured range, using vendor-
specific algorithms for handover parameter optimization.

For efficient/effective MRO, there must be linkage to policies to ensure other

parameters/QoE is not affected. This implies that all parameter modifications must align
with other similar interacting SON algorithms (such as Load Balancing). Therefore, there
is a need for communication between SON algorithms to resolve probable conflicts and
ensure stability.
During roll-out of an LTE network, there will be areas having limited LTE
coverage. Enabling handover from LTE to existing 2G/3G systems will therefore become
an important feature. In this scenario, it will be very important to maintain a low drop rate
for UEs moving from LTE to 2G/3G.
A SON MRO mechanism was introduced in release 10 for the purpose of

detecting unnecessary inter-RAT handover. During the handover preparation the source
RAT (LTE) requests optionally the target RAT (GSM/UMTS) to perform UE
measurements of the source RAT. The measurements start following the successful
handover, and the measurement duration is one of the parameters provided by the source
RAT (max 100 seconds). The measurements stop if a new inter-RAT HO takes place
during this time interval.
If during this period the UE measurements shows that the source RAT quality
remains better than a configurable threshold, the target RAT will report to the source
RAT that the handover could have been avoided. The source RAT may then take
corrective action, for example, adjust the handover threshold or increase time-to-trigger
setting for handovers to the concerned inter-RAT target cell.
MRO is very useful in the LTE network deployment process, reducing the need
for extensive drive-testing. Since the LTE coverage often will be spotty in the beginning,
inter- RAT MRO will also be very useful. For networks in operation MRO will ensure
that the handover thresholds are optimal at all times and remove the need for manual task
such as drive- testing, detailed system log, and post processing.
The benefits of MRO will be especially useful in HetNets, which are more
dynamic where small cells appear and disappear. However, MRO solutions for HetNets
are still not fully developed.
MRO is not critical for the operation of LTE networks today. The networks are
usually stable macro networks with low to moderate traffic load, and most of the
terminals are PC dongles and hence usually stationary when used. However, MRO will
become more important as the penetra- tion of handheld terminals becomes larger, the
traffic load increases and micro-, pico-, and femto-cells are introduced in the network. It
will be beneficial to include MRO in LTE networks from the start but it will not be a
critical function when the network is a stable macro network, but will offer reduced
installation time and reduced OPEX costs. As the number of small cells in the network
increase, MRO will be become more important and an MRO function capable of handling
HetNet scenarios should be included.
11.3.11 MOBILITY LOAD BALANCING OPTIMIZATION (MLB)
The objective of mobility load balancing (MLB) is to intelligently spread user

traffic across the system‟s radio resources in order to optimize system capacity while
maintaining quality end-user experience and performance. Additionally, MLB can be

used to shape the system load according to operator policy, or to empty lightly loaded
cells which can then be turned off in order to save energy. The automation of this
minimizes human intervention in the network management and optimization tasks.
Basic functionality of mobility load balancing was defined in Release 9. Release

10 added enhancements that addressed inter-RAT scenarios and inter-RAT information
exchange.
Support for mobility load balancing consists of one or more of following

functions:
(i) load reporting;
(ii) load balancing action based on handovers;
(iii) adapting handover and/or reselection configuration.
Figure 108: Mobility Load Balancing

Triggering of each of these functions is optional and depends on implementation.
Current implementations of the MLB function are relatively simple. Moving load
between cells are achieved by adjusting the handover thresholds and hence the position
of the cell boundaries. As this can affect the handover performance, this must be
coordinated with the MRO SON function. This can, for example, be achieved by letting
the MRO function define an allowed interval for the handover threshold. The MLB
function can then adjust the handover threshold within this interval.
One of the weaknesses of current MLB implementations is that the UEs that are
moved from one cell to another do not usually constitute the optimal choice and can even
cause problems in the target cell. For example, moving an UE that uses a lot of capacity
can cause overloading in the target cell. This will lead to new MLB-based handovers and,
if necessary precautions are not taken, even to ping-pong effects.

It should be notated that estimating what load an UE will represent in the new cell
is not straightforward. The radio conditions in the new cell will be different from what it
was in the original cell, hence the radio resources (i.e., the air time) required for a certain
capacity will also be different. In the downlink the estimation can be done based on
RSRP/RSRQ (reference signal received quality) reports from the UE. However, similar
information is not available for uplink and extended information exchange between the
eNBs is required.
MLB of idle mode UEs is more difficult than for active mode UEs. There is
currently no way to know exactly on which cell an idle mode UE is camping. The only
time the system becomes aware of the exact cell an UE is in, while in idle mode, is
when the tracking area of the user changes and a tracking area update message is sent by
the UE. Therefore, while parameters that control how and when a UE performs cell
reselection (idle handover) are modi- fiable, there is no direct measurement mechanism
for the system to determine when there are “too many” idle users. In current
implementations the idle mode load balancing is usually done by adjusting the cell
reselection parameters for the idle users based on the current active user condition.
The load balancing can be operated in different ways. One possibility is to only
activate MLB when a cell becomes congested. Another possibility is to let MLB be a
more continuous process trying to keep the load in different cells balanced at all times. In
the latter case careful consideration should be given to the network signalling load.
Currently, the rear eliminated knowledge on the advantages and disadvantages of
operating MLB in different ways, and further studies and field trials should be performed.
The way of operation should be configurable by the operator through the network
management system.
To increase the effectiveness of the MLB function, especially in HetNet scenarios

with many small cells, it will be necessary to develop more advanced algorithms. One
potential improvement is to choose which UEs should be moved from one cell to another
more carefully. The choice could be based on such parameters as capacity and QoS
requirements, possibly including predicted values for these parameters based on historical
information. The decision on what cells UEs should be moved to and from could also be
performed more optimally, for example, based on current and historical statistical data on
the load in different cells.
Basing the MLB related decisions on more information requires extended

exchange of data between eNBs, which requires standardization of the necessary
signalling support. Another area for improvement of MLB is its interworking with other
SON functions, especially with MRO. In most cur-rent MLB implementations, MRO has
priority and MLB has to adapt to the adjustments done by MRO. This significantly limits
the MLB operation. For inter-RAT and inter-frequency handovers, MLB should probably
have priority over MRO.
MLB also significantly overlap with the traffic steering and must be coordinated
closely with this function.
In newly deployed LTE networks the traffic load will be modest and there will be
little need for load balancing between LTE cells and between LTE and 2G/3G cells. As
traffic increases, the usefulness of the MLB function also increases. It is therefore not
necessary to include MLB in LTE deployments from the start. The usefulness of MLB

increases as the network load increase and becomes important when the network develops
in to a HetNet with many small cells.
11.3.12 COVERAGE AND CAPACITY OPTIMIZATION.
Coverage and Capacity Optimization (CCO) is a self optimization technique used

in managing wireless networks according to coverage and capacity. CCO measures the
health of the network and compares with performance target and policies as defined by
individual operators. It has been identified by 3GPP as a crucial optimization area in
which the SON algorithm determines the optimum antenna configuration and RF
parameters (such as UL power control parameters) for the cells that serve a particular area
and for a defined traffic situation, after the cells have been deployed.
For successful implementation of CCO SON algorithms, there is need to take into
serious consideration, the difference between coverage optimization and capacity
optimization. Coverage optimization involves identifying a “hole” in the network and
then adjusting parameters of the neighbouring cells to cover the hole. However, in-
creasing cell coverage affects spectral efficiency negatively due to declining signal
power, which results in lesser capacity. It is therefore not possible to optimize coverage
and capacity at the same time, but a careful balance and management of the trade- offs
between the two will achieve the optimization aim.
Adapting to network changes (such as addition/removal of eNBs and change in

user distribution) manually is costly and time consuming. Hence, the CCO algorithms
operate endlessly, gathering measurements and executing actions if needed. CCO is a
slow process in which decisions are made based on long-run statistics.
Below is a list of functions the CCO algorithm is to perform as identified by

3GPP; but 3GPP does not specify how to perform these functions but are operator-
defined:
• E-UTRAN coverage holes with 2G/3G coverage.
• E-UTRAN coverage holes without any other coverage.
• E-UTRAN coverage holes with isolated island coverage.
• E-UTRAN coverage holes with overlapping sectors.
11.3.13 RANDOM ACCESS CHANNEL (RACH) OPTIMIZATION.
RACH configuration within a network has major effects on the user experience
and the general network performance. RACH configuration is a major determinant for
call setup delays, hand-over delays and uplink synchronized state data resuming delays.
Consequently, the RACH configuration significantly affects call setup success rate and
hand-over success rate. This configuration is done in order to attain a desired balance in
the allocation of radio resources between services and the random accesses while
avoiding extreme interference and eventual degradation of system capacity. Low
preamble detection probability and limited coverage also result from a poorly configured
RACH. The automation of RACH configuration contributes to excellent performance
with little/no human intervention; such that the algorithm monitors the current conditions
(e.g. change in RACH load, uplink interference), and adjusts the relevant parameters as
necessary. RACH parameter optimization provides the following benefits to the net-
work:
• Short call setup delays resulting in high call setup rates

• Short data resuming delays from UL unsynchronized state

• Short handover delays resulting in high handover success rate
More generally, RACH optimization provides reduced connection time, higher
throughput, and better cell coverage and system capacity. All the UE and eNB
measurements are provided to the SON entity, which resides in the eNB. An eNB ex-
changes information over the X2 interface with its neighbors for the purpose of RACH
optimization. The PRACH Configuration is exchanged via the X2 setup and eNB
configuration update procedures. An eNB may also need to communicate with the O&M
in order to perform RACH optimization.
11.3.14 ENERGY SAVING
Mobile network operators are very keen on finding network energy saving
solutions to minimize power consumption in telecommunication networks as much as
possible. This will lead to reduced OPEX (since energy consumption is a major part of an
operator‟s OPEX) and enable sustainable development on the long- run. Energy saving is
very crucial today, especially with the increasing deployment of mobile radio network
devices to cope with the growing user capacity.
OPEX due to energy consumption within a network can be significantly

controlled by: a) the design of low-powered network elements; b) temporarily powering
off un- used capacity; and c) working on the power amplifiers, since they consume
majority of the available energy in a wireless network.
The normal practice is the use of modems to put the relevant network elements in
stand-by mode. These modems have a separate management system. To achieve an
automated system of saving energy, the network elements should be able to remotely
default into stand-by mode using the minimum power possible when its capacity is not
needed, and also switch-off stand-by mode remotely when needed, without affecting user
experience.
The energy saving solutions in the E-UTRAN, which are being worked on by
3GPP, to be used as the basis for standardization and further works are: Inter-RAT energy
savings; Intra-eNB energy savings; and Inter-eNB energy savings 3GPP has also
stipulated the following conditions under which any energy saving solutions should
operate, since energy savings should ideally not result in service degradation or network
incompetence:
 User accessibility should be uncompromised when a cell switches to
energy saving mode.
 Backward compatibility and the ability to provide energy savings for Rel-
10
 Network deployment that serves several legacy UEs should be met.
 The solutions should not impact the physical layer.
 The solutions should not impact the UE power consumption negatively.
11.3.15 SELF-HEALING
Self-healing functionality was not initially defined a part of the 3GPP SON
functionality, but it was taken into the SON standards in release 9 and 10, by 3GPP .

Self-healing is a collection of SON procedures which detects problems and solves

or mitigates these to avoid user impact and to significantly reduce maintenance costs. Self
healing involves automatic detection and localization of failures and the application of the
necessary algorithms to restore system functionality. Self- healing is triggered by alarms
generated by the faulty network elements. If it finds alarms that it might be able to correct
or minimize the effects of, it gathers more necessary correlated information (e.g.,
measurements, testing results, and so forth), does deep analysis, and then trigger the
appropriate actions.
The two major areas where the self-healing concept could be applied are as
follows.
(1) Self-diagnosis: create a model to diagnose, learning from past experiences.
(2) Self-healing: automatically start the corrective actions to solve the
problem.
Making use and analyzing data from the current optimization tools (alarm
supervision system, OAM system, network consistency checks), optimizers can decide
if network degradation occurs, which is the most likely cause, and then perform the
needed corrections to solve the problem. The experience of optimizers in solving such
problems in the past, and the access to a database of historic solved problems is very
useful to improve the efficiency in finding solutions.
This whole optimization process could be enhanced in two steps as follows.

(i) Diagnosis model creation based on the experience of already solved
problems, using a database with faults and their symptoms. Automatic
troubleshooting action can be done without human intervention.
(ii) Self-test results from the periodic execution of consistency checks would
help during the self diagnosis phase, to address better the healing process.
In the recommendation three different Self-healing SON functions are defined:
(i) cell outage,
(ii) self-recovery of network element (NE) software and
(iii) self-healing of board faults.
11.3.16 CELL OUTAGE.
This SON function has two basic components, namely, Cell Outage Detection
(COD) and Cell Outage Compensation (COC) .
COD uses a collection of evidence and information to determine if a particular

cell is not working correctly. The equipment usually detects faults in itself automatically.
But in a situation where the detection system itself is faulty and has therefore failed to
notify the OAM, such unidentified faults of the eNBs are referred to as sleeping cells.
Cell Outage Detection and Compensation automatically handles these eNB failures by
combining several individual mechanisms to determine if an outage has occurred, and
then compensating for the failures after soft recovery techniques fail to restore normal
service. The automated detection mechanism ensures the operator knows about the fault
before the end user. The SON compensation system temporarily mitigates the problem.

11.4 3GPP SON EVOLUTION

Self Organizing Networks (SON) developed by 3GPP, using automation, ensures
operational efficiency and next generation simplified network management for a mobile
wireless network. The introduction of SON in LTE therefore brings about optimum
performance within the network with very little human intervention.
3GPP standardization in line with SON features has been targeted at favouring
multivendor network environments. Many works are on-going within 3GPP to define
generic standard interfaces that will support exchange of common information to be
utilized by the different SON algorithms developed by each vendor. The SON
specifications are being developed over the existing 3GPP network management
architecture defined over Releases 8, 9, 10 and beyond.
Release 8 marked the first LTE network standardization; therefore, the SON
features here focused on processes involved with initial equipment installation and
integration. Release 8 SON activities include:
 eNB Self Configuration: This involves Automatic Software Download and
dynamic configuration of X2 and S1 interfaces.
 Automatic Neighbour Relation (ANR)
 Framework for PCI selection
 Support for Mobility Load Balancing
Release 9 marked enhancements on Release 8 LTE network; therefore, SON tech-
niques in Release 9 focused on optimization operations of already deployed networks.
Release 9 SON activities include:
 Automatic Radio Network Configuration Data Preparation
 Self optimization management
 Load Balancing Optimization
 Mobility Robustness/Handover optimization (MRO)
 Random Access Channel (RACH) Optimization
 Coverage and Capacity optimization (CCO)
 Inter-Cell Interference Coordination (ICIC)
Release 10 SON in LTE activities include enhancements to existing use cases and
definition of new use cases as follows:
 Self optimization management continuation: CCO and RACH
 Self healing management: Cell Outage Detection and Compensation
 OAM aspects of Energy saving in Radio Networks
 LTE self optimizing networks enhancements
 Enhanced Inter-Cell Interference Coordination (eICIC)
 Minimization of Drive Testing
 UTRAN SON management: ANR
 LTE SON coordination management
 Inter-RAT Energy saving management
 Further self optimizing networks enhancements: MRO, support for Energy
saving.


 Enhanced Network-Management-Centralized CCO
 Multi-vendor plug and play eNB connection to the network.
 The 3GPP SON standardization is a work in progress and is expected to
cover all focus areas of wireless technology evolution, as it relates to
network management, optimization and troubleshooting in multi-tech,
multi-cell, multi-actor and heterogeneous networks.
11.5 CONCLUSION
Manual tuning of radio network is not possible as it involve lot parameter
management and leads to false decision and poor network. SON is the best practice, but
data inputted must be correct.

E2-E3 Consumer Mobility Network Opt. Using DTT reports and SON Data Mgmt
12 NETWORK OPTIMIZATION USING DTT REPORTS

AND SON DATA MANAGEMENT

 Radio Network Optimization
 Drive Test Tool and its Setup
 LTE Drive Test Parameters
 UMTS Drive Test Parameters
 GSM Drive Test Parameters
 SON Architecture
12.2 RADIO NETWORK OPTIMIZATION

Once some hundreds of sites are on air, it becomes necessary to perform
optimization on the network in order to maximize benefits while minimizing capital and
operation costs for operators. This section, in fact, deals with all aspects of optimizing a
GSM network starting from standard operations and ending with specific trials, studies
and fine-tuning. Before the network is commercially launched, the radio network
optimization process starts and then continues during the life of the network.
Depending on the type of network management system, either in the BSC or in the
BTS, each cell reports thousands of statistics about all relevant behaviors (number of
attempts, failures, successes, during call, handover, setup, etc.). These statistics are
reported to the Network Management System (NMS) as counters. To facilitate
interpretation of the behavior, a set of key performance indicators (KPIs) is defined out of
formulas using pure counters. Each operator chooses its own KPIs and sets, according to
specific criteria, some objectives to be met in order to achieve a good end user perception
of the service offered and also in order to benchmark one network with other operators.
Another aspect that is important in the optimization phase deals with drive tests.
In fact, while statistics give a general idea of the cell‟s behavior at a certain period, field
measurements give a one instant scenario of one area‟s behavior during a call. Different
tools can be used to perform drive tests. Each specific tool is able to standard reporting at
the signal level, quality and site information (cell identity, BCCH, mobile allocation list,
best neighbors, etc.).
Statistics and drive tests are the main methods used to monitor the network‟s
performance. However, other specific methods can also be used. Tracing catches one
object‟s behavior (TRX, cell, BTS or BSC) during a certain period and regardinga
specific event (SDCCH allocation, conversation phase of a voice call, etc.) or a set of
successful events (IMSI attach, paging, call setup, location update, etc.). Alarm
monitoring, transmission network auditing and network switching subsystem (NSS)
performance follow-up are also important in the sense that they give an idea of hardware
problems or parameter errors.
After deep analysis, actions are then taken to correct and improve performance.
All the above-described methods help the optimization engineers to identify the origin of
the problem from the office while applying several analysis methods. Another aspect is,

however, very important: field knowledge. Correct site re-engineering is the basis for a
good performing network. Frequency planning review is also a key step in the process.
Network planning optimization consists of various operations, all leading to the

improvement of KPIs. input data for starting optimization are KPI values in a certain area.
Depending on whether the area KPI is greater or less than the target, troubleshooting on a
cell basis starts and statistics can be extracted weekly, daily or even on an hourly basis
from the NMS. The Call Setup Success Rate (CSSR) and dropcall rate (DCR) are the
main KPIs relevant to operator losses.
12.3 DRIVE TESTING

12.3.1 WHAT IS DRIVE TEST
Drive Testing is a method of measuring and assessing the coverage, capacity and
Quality of Service (QoS) of a mobile radio network. Drive testing is principally applied in
both the planning and optimization stage of network development. Drive tests are the
most common measurement tool used by operators, to probe the quality status and solve
network problems.
12.3.2 DRIVE TESTING
The technique consists of using a motor vehicle containing mobile radio network
air interface measurement equipment that can detect and record a wide variety of the
physical and virtual parameters of mobile cellular service in a given geographical area.
It is conducted for checking the coverage criteria of the cell site with the RF drive
test tool.
The data collected by drive test tool in form of Log files are assessed to evaluate
the various RF parameters of the network.
12.3.3 DATA ACQUIRED FROM DRIVE TEST:
The dataset collected during drive testing field measurements can include
information such as
 Signal intensity
 Signal quality
 Interference
 Dropped calls
 Blocked calls
 Call statistics
 Service level statistics
 QoS information
 Handover information
 Neighbouring cell information
 GPS location co-ordinates
12.3.4 TYPES OF DRIVE TESTING
 Network Benchmarking

 Optimization & Troubleshooting

 Service Quality Monitoring
Network Benchmarking
Sophisticated multi-channel tools are used to measure several network

technologies and service types simultaneously to very high accuracy and collect accurate
competitive data on the true level of their own and their competitors technical
performance and quality levels
Optimization & Troubleshooting
Optimization and troubleshooting information is more typically used to aid in

finding specific problems during the rollout phases of new networks or to observe
specific problems reported by consumers during the operational phase of the network
lifecycle.
Service Quality Monitoring
Service quality monitoring typically involves making test calls across the network
to a fixed test unit to assess the relative quality of various services using Mean opinion
score (MOS).Service quality monitoring is typically carried out in an automated fashion.
The results produced by drive testing for each of these purposes is different.
12.3.5 DRIVE TEST EQUIPMENT
Following Resources/Equipments are required for drive test

 A Laptop
 Drive Test software with Dongle/License Key
 GPS (Global Positioning system) to provide location information
 One or Multiple Handsets Compatible with the Drive Test Software
 Scanner (Optional)
 Database of Existing Network (Cell site database)
 A Suitable Vehicle
12.3.6 CONNECTIVITY OF DRIVE TEST TOOL
As shown in figure, all the equipments (GPS, Mobile Handsets, Dongle) are
connected to Laptop via USB ports. Normally antenna type GPS (with magnetic base to
stick on top of vehicle) is used with drive test tool.

Figure 109: Connectivity of Drive Test Tool

12.3.7 DRIVE TEST TOOLS
Data Collection Tools
 TEMS Investigation
 Nemo Outdoor
 JDSU E6474A
 Accuver XCAL
Post-processing tools
 Actix Analyzer/Spotlight
 Accuver XCAP
 TEMS Discovery LTE
12.3.8 LTE DRIVE TEST PARAMETERS
 RSRP: Reference Signal Received Power.
 RSRQ: Reference Signal Received Quality.
 RSSI: Received Signal Strength Indicator.
 SINR : Signal to Interference Noise Ratio
 CQI: Channel Quality Index.
 PCI: Physical Cell Identity.
 BLER: Block Error Ratio.
 DL Throughput: Down Link Throughput.
 UL Throughput : Up Link Throughput
This is the common key performance parameters for LTE drive test parameter we
have to work out for LTE drive test task.
RSRP:
It indicates coverage. RSRP is the average power received from a single
Reference signal, and its typical range is around -44dbm (good) to -140dbm (bad).
RSRQ:
RSRQ – Indicates quality of the received signal and its range is typically -19.5dB
(bad) to -3dB (good).
RSSI:
RSSI (Received Signal Strength Indicator) is a parameter which provides
information about total received wide-band power (measure in all symbols) including all
interference and thermal noise.
RSSI = wideband power = noise + serving cell power + interference power
RSSI is related to the other parameters through the following formula:

RSRQ=N*(RSRP/RSSI)

Where N is the number of Resource Blocks of the E-UTRA carrier RSSI

measurement bandwidth.
SINR:
SINR is the reference value used in the system simulation and can be defined:
 Wide band SINR
 SINR for a specific sub-carriers (or for a specific resource elements)
All measured over the same bandwidth!
RSSP vs RSRQ vs RSSI vs SINR
Below is a chart that shows what values are considered good and bad for the LTE
signal strength values:
Table 13. LTE signal strength values

CQI:
The Channel Quality Indicator (CQI) contains information sent from a UE to the
eNode-B to indicate a suitable downlink transmission data rate, i.e., a Modulation and
Coding Scheme (MCS) value. CQI is a 4-bit integer and is based on the observed signal-
to-interference-plus-noise ratio (SINR) at the UE. The CQI estimation process takes into
account the UE capability such as the number of antennas and the type of receiver used
for detection. This is important since for the same SINR value the MCS level that can be
supported by a UE depends on these various UE capabilities, which needs to be taken into
account in order for the eNode-B to select an optimum MCS level for the transmission.
The CQI reported values are used by the eNode-B for downlink scheduling and link
adaptation, which are important features of LTE.
In LTE, there are 15 different CQI values ranging from 1 to 15 and mapping
between CQI and modulation scheme, transport block size is defined as follows :

Table 14. 15 different CQI values
Table 15. 15 different CQI values

BLER:
A Block Error Ratio is defined as the ratio of the number of erroneous blocks
received to the total number of blocks sent. An erroneous block is defined as a Transport
Block, the cyclic redundancy check (CRC) of which is wrong.

12.3.9 WCDMA (3G) DRIVE TEST PARAMETERS

RSCP (Received Signal Code Power)
The received power on one code measured on the Primary CPICH. Unit is dbm. It
shows signal strength of a cell. It Indicates Coverage.
RSSI (Received Signal Strength Indicator)
It is the wide-band received power within the relevant channel bandwidth. It is a
parameter in dbm that describes the total signal strength of a UTRA carrier frequency i.e.
signal strength of all cells of same frequency at a certain location.
Ec/No
It is a parameter in dB that describes the received energy per chip divided by the
power density in the band. Measurement shall be performed on the Primary CPICH.It
shows signal quality. Value of Ec/No>-15dB is considered good, between -15db and -18
dB is poor and less than -18dB is very poor.
Main reasons of poor Ec/Io are poor RSCP, missing neighbours, overshooting,
pilot pollution etc.
12.3.10 ACTIVE, MONITORED AND DETECTED SETS
Cells that the UE is monitoring are grouped in the UE into three mutually
exclusive categories:
 Active Set: Active Set is defined as the set of cells the UE is
simultaneously connected to (i.e., the UTRA cells currently assigning a
downlink DPCH to the UE constitute the active set).
 Monitored Set: Cells, which are not included in the active set, but are
included in the CELL_INFO_LIST belong to the Monitored Set i.e. shows
probable candidate sectors for handovers. If one of the active cells
becomes weak, it is replaced by a candidate cell having highest signal
strength from monitored set.
 Detected Set: Cells detected by the UE, which are neither in the
CELL_INFO_LIST nor in the active set belong to the Detected Set. All the
missing neighbors appear in detected set. These must not have high signal
strengths otherwise they will degrade the aggregate Ec/No & lead to call
drops.
Pilot Pollution
When the number of strong cells exceeds the active set size, there is
“Pilot Pollution” in the area. Pilot pollution is the detection of many high power pilots as
compared to Best Serving Pilot that do not contribute to improve the signal strength. It
ultimately degrades the aggregate Ec/Io leading to call drop. All other strong signals
received when Active Set Size is full, act as interference which degrades the performance
of the system. Physical optimization should be done so that there should not be many
Pilots available at same spot with equally high signal strengths.
12.3.11 GSM (2G) DRIVE TEST PARAMETERS
 Rx level : Indicates received signal strength in dbm
 Rx Quality: Indicates Quality of voice, which is measured on the basis of
BER (Range 0-7 where value 0 denotes minimum BER.
 C/I: The carrier-over-interference ratio is the ratio between the signal
strength of the current serving cell and the signal strength of undesired
(interfering) signal components (Unit is dB)

 FER: Frame Erasure Rate it represents the percentage of frames being

dropped due to high number of bit errors in the frame. It is indication of
voice quality in network.
Figure 110: Screenshot of a Drive test window
12.4 SON ARCHITECTURE

The SON architecture defines the location of SON within the network. When
implemented at a high level in the network (OAM), it is called Network Management
System (NMS); while implementation at lower levels (network elements) like the eNBs is
called Element Management System (EMS). For self-configuration techniques of SON, a
self configuration subsystem is created in the OAM which handles the self configuration
process. For self optimization, the subsystem can be created in the OAM or the eNB or
both. Therefore, depending on the location of SON algorithms, SON architecture may be
described as being centralized, distributed or hybrid (a combination of centralized and
distributed).
Centralized SON Distributed SON
NMS Operator OSS NMS

Operator OSS
EMS Equipment vendor OSS Equipment vendor OSS EMS
Commands, Policies,
parameter Measure- high Reports
settings ments, level
KPIs KPIs
Hybrid SON
Operator
NMS OSS Commands
Reports SON related

Equipment vendor messages
EMS OSS
Commands,
parameter Measurements,
setting s, policies, KPIs, reports
high level KPIs
Commands
SON related
messages
Figure 111: SON Architecture

12.4.1 CENTRALIZED SON
In a centralized SON architecture, the algorithms are executed at the network

management level. Commands, requests and parameter settings data flow from the
network management level to the network elements, while measurement data and reports
flow in the opposite direction.
This is an example of the Network Management System (NMS) where the

algorithms are created and executed in the OAM . In this type of SON architecture, the
algorithms are present in just a few locations thereby making it simple and easy to
implement.
The main benefit of this approach is that the SON algorithms can take information
from all parts of the network into consideration. This means that it is possible to jointly
optimize parameters of all centralized SON functions such that the network becomes
more globally optimized, at least for slowly varying network characteristics. Also,
centralized solutions can be more robust against network instabilities caused by the
simultaneous operation of SON functions having conflicting goals. Since the control of
all SON functions is done centrally, they can easily be coordinated. Another advantage is
that multivendor and third party SON solutions are possible, since functionality can be
added at the network management level and not in the network elements where vendor
specific solutions are usually required.
Figure 112: Centralized SON Architecture

The main drawbacks of the centralized SON architecture are longer response
times, increased backbone traffic, and that it represents a single point of failure. The
longer response time limits how fast the network can adapt to changes and can even cause
network instabilities. The backbone traffic increase since measurement data have to be
sent from the network elements to the network management system and instructions must

be sent in the opposite direction. This traffic will increase as more cells are added to the
network. If there are many pico- and femto-cells this traffic will be very significant. Also,
the centralized processing power needed will be large.
12.4.2 DISTRIBUTED SON
In a distributed SON architecture, the SON algorithms are run in the network
nodes and the nodes exchange SON related messages directly with each other. This
architecture can make the SON functions much more dynamic than centralized SON
solutions, so that the network can adapt to changes much more quickly. It is also a
solution that scales very well as the number of cells in the network increases.
The main drawbacks are that the sum of all the optimizations done at cell level do
not necessarily result in optimum operation for the network as a whole and that it is more
difficult to ensure that network instabilities do not occur. Another drawback is that the
implementation of the SON algorithm in the network elements will be vendor specific, so
third party solutions will be difficult. Even if the algorithms themselves are executed in
the network elements, the network management system is usually able to control the
behavior of the SON function, for example, by setting the optimization criteria, receiving
periodic reports, and being able to turn it off if necessary.
An example of the EMS in which the algorithms are deployed and executed at the
eNBs is distributed SON. Therefore the SON automated processes may be said to be
present in many locations at the lower level of the architecture. Due to the magnitude of
deployment to be carried out caused by a large number of eNBs, the distributed SON
cannot support complex optimization algorithms.
Figure 113: Distributed SON Architecture

In order to fully benefit from this architecture type, work is being done towards
extending the X2 interface (interface between the eNBs). However, distributed SON
offers quick optimization/ deployment when concerned with one/two eNBs. An example
of this is in ANR and load balancing optimizations.

12.4.3 HYBRID SON
An architecture in which the optimization algorithms are executed in both OAM

and the eNBs is called Hybrid SON. Hybrid SON solution means that part of the SON
algorithm is run on the network management level and part is run in the network
elements. The solution represents an attempt to combine the advantages of centralized
and distributed SON solutions: centralized coordination of SON functions and the ability
to respond quickly to changes at the network element level.
The hybrid SON solves some of the problems posed by other architecture
alternatives. The simpler optimization processes are executed at the eNBs while the
complex ones are handled by the OAM; therefore, it supports various optimization
algorithms and also supports optimization between different vendors. However, the
hybrid SON is deployment intensive and requires several interface extensions.
Figure 114: Hybrid SON Architecture

Unfortunately, the drawbacks of both centralized and distributed SON are also
inherited. The SON related traffic in the backbone will be proportional to the number of
network elements in the network, which means that it might not scale well. The same
holds for the SON related processing required at the network management level. Also,
since parts of the SON algorithms are running in the network elements and the interface
between the centralized and distributed SON functions will be proprietary, third party
solutions will be difficult.
It should be noted that the term “Hybrid SON” is not clearly defined and is used
differently by different vendors. Some vendors classify their solutions as “hybrid” if the
network management system can control the SON function by setting main
parameters/policies, receiving reports and being able to turn it off if necessary.
12.5 CONCLUSION
RF Planning and Optimization plays a vital role in mobile radio network without
it is merely impossible to rollout and manage radio network. RF Planning and
optimization plays an important role in Network health as it gives health as well as
monitoring of current network conditions.


E2-E3 Consumer Mobility Site Planning , Relocation and RRH
13 SITE PLANNING, RELOCATION AND RRH
13.1 LAERNING OBJECTIVE

After completion of this chapter the participant will be able to understand about
Site planning process, RRH and its utility, C-RAN architecture and its deployment.
13.2 SITE PLANNING :

cell sizes and types, heterogeneous networks (HetNets), energy efficiency, self-
organizing network features, control and data plane split architectures (CDSA), massive
multiple input multiple out (MIMO), coordinated multipoint (CoMP), cloud radio access
network, and millimetre-wave-based cells plus the need to support Internet of Things
(IoT) and device-to-device (D2D) communication require a major paradigm shift in the
way cellular networks have been planned in the past.
13.2.1 SITE PLANNING PROCESS
The cell planning process consists of three phases: preplanning, or dimensioning;
detailed planning; and post planning, or optimization. The output of the dimensioning
phase is an approximate number of BSs required to cover an area of interest. The detailed
planning phase allows determining the actual positions of the BSs within the area to be
served. In the optimization phase, which occurs after the network has been deployed and
is running, the network performance is analysed, potential problems detected, and
improvements made to enhance network operation.
Figure 115: Cell planning process
13.3 CELL PLANNING OBJECTIVES

The objectives of CP heavily depends on the business strategy of the operators.
The coverage target for different services, the pricing and throughput policies, regulatory
constraints, market share goals and competition are some factors among many that dene
the CP objectives. Ultimately, CP objectives can be boiled down to the following set of
optimization targets identified in the cell planning problem:
1) Minimize TCO : In addition to minimizing the overall network cost, this objective
may also include minimizing economic costs related to deployment costs and parameter
optimization.
2) Maximize capacity: For a single service, this objective can be defined as the number
of users who can be served at one time. In the case of multi-service traffic, capacity can
be approximated in terms of global throughput.

3) Maximize Coverage: This includes satisfying coverage policy requirements for

various services. Up Link (UL) and Down Link (DL) coverage must be balanced. Both
traffic channels and coverage of common channels must be considered.
4) Minimize Power Consumption: Health concerns have motivated the radiated power
minimization objective. However, recent awakening of a desire for greener wireless
systems has added more depth to this objective. Consequently, power consumption,
including fixed circuit power as well as variable transmission power, must be minimized.
5) Optimise handover (HO) zones: In a well-planned cellular system, a certain
proportion of the area of each cell should overlap with neighbouring cells to satisfy HO
conditions. HO zones are essential to guarantee continuity of service between the sectors.
It also strengthens the radio link against fast fading and shadowing.
However, too much overlap may result in wastage of power, and radio resources, and
increase in interference and electro-smog, making it a tricky planning objective.
13.3.1 CELL PLANNING INPUTS
Different inputs are required to solve the cell planning difficulty depending on objectives
in focus and phase of planning. Usually, the following inputs need to be known :
1) Traffic Models: User traffic distribution is a main factor that ultimately determines the
cellular system plan and, hence, is a key input in the CP process. In GSM (mono-service
systems), for instance, geographical characterisation of traffic distribution is sufficient.
However, with multi-service systems supporting data, traffic characterisation based on
types and level of service is needed . Test point based traffic models are often used for CP
traffic modelling, for the sake of practicality . In this model, an area is characterized over
a time interval and all located mobile terminals are bundled into a single test point. This
point represents the cumulative traffic, or traffic intensity from all these terminals, over
the determined interval.
2) Potential Site Locations: Theoretically, a base station can be installed anywhere.
However in the real world, a set of candidate sites is first pre-determined and used as
input to the CP, to incorporate the real estate constraints. The objective, thus, is to find the
optimum subset of BS locations. These potential BS locations are determined by taking
into account the constraints such as, socio-economic feasibility and availability of site(s),
traffic density, building heights,
terrain height(s) and pre-existence of a site(s) by the same or other operators.
3) BS Model: There are many parameters that dente the BS model such as: antenna type
and height, receiver sensitivity, load capacity, transmit power and capital and operational
cost. Moreover, heterogeneous networks necessitate modelling of new types of nodes; for
instance relay stations (RS), pico-cells, femto-cells, and small cells.
4) Propagation Prediction Models/Maps: A key input to the planning process is the
signal propagation model. The potential of this model is to incorporate reflection,
differentiation, absorption, and propagation of the signal in real environment. Taking into
account the natural
and man-made structures, vegetation and topography of an area, highly determines the
accuracy of the CP outcomes [38]. Very sophisticated planning tools rely on actual
measurement based propagation maps, or ray tracing based complex analysis, to predict
the propagation. However, obtaining complete propagation maps of a large area using
these methods is a very cumbersome, time consuming, and expensive process. For this
reason, different empirical models have been proposed in the literature. Such models
abstract the experimental and statistical data in the form of deterministic expressions, that
can easily be used in the CP. Okumura Hata and COST 231 are a few examples of such
well known propagation models used in CP to depict propagation loss in different

environments and scenarios. A fine tuning of these models is done by setting parameters
within these models to
recent the real-world conditions as closely as possible. While propagation models for sub
5 GHz frequencies are well established, research on developing such models for higher
frequencies such as mm Waves is still in progress.
13.4 CELL PLANNING OUTPUTS

The goal of the CP process is to provide one or more of the following outputs:
1) The optimal number of base stations;
2) The best locations to install base stations;
3) The types of base station optimal for each location;
4) The configuration of parameters such as antenna height, number of sectors and
sector orientation, tilt, power;
5) Frequency reuse pattern;
6) Capacity dimensioning, e.g. number of carriers or carrier components per sector.
13.4.1 TYPES OF CELL PLANNING AND OTHER COMPLEXITY
The objectives, input and output of the CP process also depend on the type of
planning. There are generally two types of CP, roll out and incremental, as explained
below:
1) Roll-out CP: This is the CP where no prior networks exists and a plain state approach
can be used to meet all the objectives of interest. In terms of input parameters, in this
phase the traffic distribution is not exactly known yet. Estimates of traffic based on geo-
marketing forecasts are used for planning in this phase
2) Incremental Planning: This type of CP is generally carried out after the first roll-out
planning to meet the increasing demand. Unlike the plane state approach, planning in this
phase is bounded by additional constraints imposed by existing sites. However, in this
phase the traffic distribution can be modelled now with much better accuracy using the
measurements from existing network reports. It is anticipated that 5G deployment will
mostly require incremental planning by building on LTE/UMTS/GSM network.
Figure 116: Cell planning Steps

13.5 SITE RELOCATION AND RRH

To answer the need for more throughput at lower cost, wireless network providers
are moving to using a remote radio head (RRH) where the radio equipment is connected
to the baseband unit (BBU) by a fiber optic cable. This provides a new level of flexibility
in how the cell site is deployed, including siting the RRH at the masthead (for low RF
losses) or locating the BBU at a remote location (for improved operational efficiencies).
Remote radio heads (RRHs) have become one of the most important subsystems
of today‟s new distributed base stations. The RRH concept constitutes a fundamental part
of a state-of-the-art base station architecture. The move to RRH based cell sites has
delivered flexibility, performance improvements and cost savings.
13.5.1 RRH TECHNOLOGY

The remote radio head contains the base station‟s RF circuitry plus analog-to-
digital/digital-to-analog converters and up/down converters. RRHs also have operation
and management processing capabilities and a standardized optical interface to connect to
the rest of the base station. Modern interfaces standards for RRH interconnect are Open
Base Station Architecture Initiative (OBSAI) and Common Public Radio Interface (CPRI)
which enable interoperability between hardware items and faster time-to-market for
complete solutions. Remote radio heads make MIMO operation easier; they increase a
base station‟s efficiency and facilitate easier physical location for gap coverage problems.
Figure 117: Remote radio Head

RRH is sitting on top of cell tower that mainly performs following functions:
 Convert optical signal to electrical signal and vice versa using CPRI
 In transmitter section of RRH, it converts digital signal to RF and
amplifies that signal to the desire power level and Antenna connected to it,
radiates the RF signal in air
 In Receiver section of RRH, it receives the desired band of signal from
antenna and amplify it.
 And convert RF signal back to digital signal in the receiver chain.

Figure 118: RRH Architecture

The RRH is connected to the Base band unit (BBU) via fibre optical cable which
uses CPRI format signals. Optical cable is used because it has less loss and it is cheaper
as compared to RF Coaxial cable, especially at the CPRI bit rates which can be 6Gbps up
to 10Gbps or more. One base-band unit is connected to multiple RRHs depending upon
the capability of base-band unit. The following example shows 3 RRH‟s connected to
one baseband unit to provide 3 sectors of coverage:
Figure 119: RRH Connectivity

The key advantages of using RRHs are listed in below
 Smaller footprint : Easier installation, reduced wind load, lower site rental
costs, optimized coverage.

 Flexibility in Software : Remote upgrades and frequency-agile operations,

easier capacity upgrades.
 Higher performance: High power efficiency, spectral emissions
requirements, sensitivity, capacity
 Multi-mode operations: Combined and concurrent multi-standard
operations reduce equipment needs.
 Flexible multi-carrier capability: Frequency agility, easier capacity
upgrades
13.5.2 THE EVOLUTION OF CELL SITES AND RRH
Mobile data traffic has been soaring ever since smartphones were first introduced
and spread throughout the world. Mobile base stations are being transformed accordingly.
RRHs are more commonly used because they can minimize radio transmission loss by
allowing radio parts, which used to be installed indoor, to be placed closer to antennas.
Most RRHs and antennas today are placed pretty close to each other on a
building's rooftop, tower, etc., but they still need a 2~3-meter-long connection cable
between them to exchange signals with each other. As RRHs are moved out of a building
and onto a rooftop, where only antennas used to be placed, operators are facing new
challenges - securing space for a variety of products from different manufacturers that are
run by different operators for different frequency bands, and achieving reliability of the
frame structures where those products are mounted.
Figure 120: Evolution of base station and RRH tower

Particularly installing RRHs and antennas on building rooftops or small towers in
big cities can be not only undesirable from an aesthetic point of view, but also an obstacle
in building a network from operators' point of view.
To solve these issues in distributed cell sites, antenna-integrated RRH solution
was introduced. Fourth-generation (4G) and beyond infrastructure deployments will
include the implementation of Fiber to the Antenna (FTTA) architecture. FTTA
architecture has enabled lower power requirements, distributed antenna sites, and a
reduced base station footprint than conventional tower sites. The use of FTTA will

promote the separation of power and signal components from the base station and their
relocation to the top of the tower mast in a Remote Radio Head (RRH).
13.5.3 FEATURES OF ANTENNA-INTEGRATED RRH
These types of antenna-integrated RRHs have the following four characteristics:
Figure 121: Antenna Integrated RRH
Less signal transmission loss between antenna and RRH

In a conventional cell cite, an antenna and RRH are connected usually with a
2~3-meter-long connection cable, and this contributes to transmission loss of about
0.6~0.7 dB. An antenna-integrated RRH solution however can eliminate this loss,
resulting in more energy savings.
Less CAPEX/OPEX burden on operators
In conventional structures, antennas and RRHs have to be installed separately,
which means higher installation costs and more space to lease. On the other hand, an
antenna-integrated RRH gives operators advantage of lower costs of installation and
space lease because it only takes one installation of an antenna.
Reduction of physical load on frame structures
Frame structures on towers or rooftops of a building are affected not only by
weight of the installed products, but also by wind loads. Because RRA allows RRHs to be
attached right to the back of an antenna, wind loads on the face of RRHs can be
eliminated. This can help to install more RRHs in limited space on towers or rooftops of
buildings.
Passive Inter-modulation (PIMD) quality
Connecting an antenna with RRHs in a tower is a pretty demanding and dangerous
job that can be done by only those with experiences. Improper connection by a less-
experienced person can cause poor PIMD and waterproofing issues. When more than two
frequencies are combined, a new unwanted frequency can be generated as a result of the
synthesis of fundamental and harmonic waves of the two original frequencies. This
distortion is called PIMD. Distorted signals detected within the receiving frequency band
can affect the receiving performance of system. This is why PIMD is considered as an
important factor in RF products. So, if we can just skip this whole troublesome
connecting process, there will be no problem to take care of at all.
13.5.4 CLOUD RAN AND RRH :
In recent years, cellular networks are facing extreme traffic loads because of sharp
increasing in connected smart devices (e.g., smart phone, tablet, Internet of Things (IoT)
devices, etc.) and the introduction of new applications and services. This increasing is a

considerable challenge for the mobile network that will lead to increase the complexity of
management and operation of network, as well as high upgrade costs, and slow time-to-
market for new innovations and services.
Therefore, the cellular companies should increase the network capacity to meet
the demand of growing user data rate. Furthermore, Long Term Evolution (LTE) is used
as an approach to increase network capacity by either, creating a complex structure of
Heterogeneous and Small Cell Networks (HetSNets), adding more cells or by
implementing techniques such as multi user Multiple Input Multiple Output (MIMO) and
3D Massive MIMO.
Figure 122: Distributed Base Station in C-RAN

Cloud RAN is a specific concept that is rapidly being developed and prepared for
commercial deployment. This aims to centralize the functions of the RAN network (e.g.
eNodeB for LTE, NodeB & RNC for 3G) within the cloud servers, such that only the
physical transceiver and antenna elements of the eNodeB need to be physically located at
the cell site. This provides for a more cost efficient deployment, especially for “small
cells” or local cell sites used to boost capacity or fill gaps in coverage. The Cloud RAN
concept is taking advantage of technologies such as CPRI, that allow the baseband to
TRX link of the base station to be carried on dedicated high speed optical fiber links. This
technology has already been developed for Remote Radio Head use (RRH), where the
TRX/ Antenna is separated from the base station baseband by several meters (top and
bottom of cell site mast) up to separation of hundreds of meters or of kilometers (e.g. for
in building or shopping mall deployment, where a single baseband serves all
TRX/antenna sites). So Cloud RAN is extending the same concept further such that all
TRX/Antenna sites in a network region can be connected by a fiber ring to a centralized
baseband server. Off course this technology currently relies on having dedicated fiber
access to each cell site, and this can limit deployment in some scenarios.
In C-RAN, Base Band Unit (BBU) is centralized in a BBU pool and connected to
the RRHs. Therefore, few BBUs are needed in C-RAN compared to the traditional
architecture. C-RAN has ability to decrease the cost of network operation and power
consumption compared to the traditional architecture. A new architecture can be upgraded
easily, that lead to improving the scalability also enabling network maintenance easy.
Recently, virtualization technology is used in the BBU pool to decrease power
consumption. Generally, it consists of two parts; physical servers working with a set of
hardware components, and software platform applied by the operating system. Virtualized

BBU pool can be shared the resources, as well as can be shared by different network
operators by letting them rent Radio Access Network (RAN) as a cloud service. For
example, BBUs from different operators are placed in one cloud service. They can
interact with increased spectral efficiency, lower delays, and throughput. Furthermore, the
performance of the network is improved, by reducing handover delay during intra-BBU
pool. Additionally, the virtualization technology has many benefits in C-RAN
architecture, such as reducing costs, minimizing the investment capital, reducing power
consumption as well as more reliability and flexibility in utilizing the server/network
resource.
13.5.5 BASE STATION ARCHITECTURE EVOLUTION
C-RAN architecture can be defined as centralized different BBUs of deployed
traditional BSs together to form of a single pool. Therefore, they can be managed and
dynamically share resources on demand among all BBUs. C-RANs have many benefits
over traditional cellular networks, such as low power consumption, increased resource
utilization efficiency, better hardware utilization and light interference. Centralized
processing has many methods and technology to turn RRHs on/off in the in a time-
varying data traffic in different scenarios. However, this section explains the basic
concept of C-RAN as well as the traditional BS evolution. The BS functions can be
divided into radio functionalities and baseband processing. Furthermore, the baseband
processing functions are Modulation, Coding, Mapping, Fast Fourier Transform (FFT),
etc. However, the radio unit is the response to frequency, digital processing, and power
amplification.
Traditional Cellular Network Architecture
In the traditional architecture the functions of the radio and BBU processing are co-
located in BS (i.e. in the same cell site). Generally, the antenna is located near to the radio
unit, the coaxial cables are used to connect the antenna with radio unit. Furthermore, X2
interface and S1 are used between BSs and connect the BSs to the mobile core network,
respectively.
Figure 123: Traditional architecture of cellular network

13.5.6 C-RAN ARCHITECTURE
In this context, the BS is separated into two parts; a baseband signal processing unit
and a radio unit. The radio unit is called an RRH, and it has many functions such as
Digital to Analogue Conversion (DAC), Analogue to Digital Conversion (ADC), digital

processing, filtering, power amplification and interface to the fibre . The baseband signal
processing is called a BBU, which is located in a central unit called BBU pool. The
Interconnection and split function between the BBU and RRH depend on type of the
network deployment. The distance between an RRH and a BBU pool is up to 40 km [28],
distance limitation is coming from the propagation delay of fibre and processing signal in
BBU. However, a fronthaul can be optical fibre or microwave. Generally, the optical fibre
is a candidate to be used in the next generation to meet the requirements of data rate
demands. Moreover, RRHs designed to be small and light, so easy to install on poles or
rooftops with very efficient cooling. Open Base Station Architecture Initiative (OBSAI)
[29] and Common Public Radio Interface (CPRI)are the radio interface candidate
protocols to use between RRHs and BBUs.
Figure 124: C-RAN Architecture based on Virtualization

In C-RAN, the BBUs are centralized into one place that is called a BBU pool to
optimize BBU utilization between light and heavy data traffic demand to save energy. In
this architecture, virtualization technology is used, where the BBU‟s functions installed as
software on the physical servers called the virtual BS.
Furthermore, the fronthaul interface is used as a medium to connect the RRHs
with the BBU pool within high-performance processors, low latency, and high bandwidth
optical fibre medium. The backhaul interface is used as a medium to connect the BBU
pool with the mobile core network .
C-RAN Components
In general C-RAN architecture comprises of three main parts, namely (i) BBU
pool which consists of a large number of BBUs with centralized processors located at the
CO, (ii) RRHs with antennas system located at the cell sites, and (iii) fronthaul transport
link which connects the BBU pool to the RRHs and needs low latency and high
bandwidth to meet the 5G requirements.
1. Base Band Unit Pool
BBU pool consists of multiple BBUs in a form of a cloud, each capable to serve
many RRHs. BBUs can be located at Central Office (CO) or Data Centres (DCs) of
system. BBUs operate as virtual base stations which comprise of parts that process and
schedule the incoming signals from different RRHs and optimizing radio resource
allocation . BBUs are responsible for functions from layer 1 to layer 3 depending on
functional split between the BBUs and RRHs that used in level of C-RAN architecture.
Based on data traffic demand and time varying environment, the signal processing
radio resources can be fully shared among different BBUs in the BBU pool. The BBU
pool is connected by optical fibre to RRHs using Radio over Fibre (RoF) technology. In
term of power consumption in the BBU pool, the power consumption model for the BBU

pool is calculated as a sum of the active BBUs. Computing resources and processing of
the BBU can be measured in by Million Operations Per Time-Slot (MOPTS) or Giga
Operations Per Second (GOPS) translated into power figures. Many components and
functions in BBU have significant effect in power consumption calculation such as the
frequency and time domain processing, central processing units (CPU), Forward Error
Correction (FEC) and processing related to CPRI.
2. Remote Radio Head
RRH is located at the cell site, it provides the wireless signal coverage for the cell
site area and comprises of Analogue to Digital Conversion (ADC) and Digital to
Analogue Conversion (DCA), Power Amplifier (PA), antennas system, interface
adaptation, voltage suppliers and Low Noise Amplifier (LNA). By moving most of the
baseband processing from cell site to BBU pool to reduce both CAPEX and OPEX,
which allows a more optimized energy consumption as well as less complexity and of
course lowers their price.
Therefore, RRH can significantly help cellular network operators to resolve
performance, cost, and efficiency challenges when deploying new base stations in 5G
networks. Moreover, RRHs distributed in certain areas such as urban areas with high
traffic loads offer efficient cost. They are located at the cell sites and used to transmit the
RF signals to users and forward the baseband signals from the users to the BBU pool.
3. Front haul Network
It can be defined as a connection between RRHs and BBUs to provide low latency
and high capacity. C-RAN front haul is realized by different technologies such as
wireless, and wire represented by optical fibre networks. Generally, Wireless front haul
link are cheaper and faster to deploy than optical fiber front haul links.
13.5.7 C-RAN DEPLOYMENT
C-RAN is a candidate architecture to implement for next generation of cellular
network instead of traditional cellular network like LTE Advanced (LTE-A), LTE and
UMTS. In C-RAN architecture, BSs can be implemented by separating BBUs and RRHs,
and baseband processing resources for multiple BBUs in a CO can be scheduled in carrier
level. Easy to deploy the RRHs due to they are light weight and small size. RRHs
transmit and receive radio signals from and to the BBUs via optical fiber front haul links.
RRHs can be installed in cell sites far from the BBU pool (e.g. 1- 40 km) . The front haul
network between BBUs and RRHs can be standardized like CPRI or OBRI. The
centralized BBUs should have a low latency, high bandwidth, corresponding protocol and
switch matrix to support the effective cooperation among multiple BBUs in BBU pool.
The radio signals from deployed RRHs can be switched to any BBU in the BBU
pool. Thus, the centralized concepts can use load balance technique to avoid overloading
in some BBUs during peak hours while some BBUs operate in low load. This can reduce
power consumption, improve the usage efficiency of devices, and improve system
reliability. Deployment of C-RAN will be an unique scenarios for micro, macro, picocell,
and indoor as well as the deployment candidate to be a heterogeneous arrangement.
Generally, C-RAN supports many significant scenarios such as greenfield deployments,
C-RAN for capacity boosting and different stages of C-RAN deployment. C-RAN
deployment still is limited by the maximum distance between RRH and BBU (up to 40
km) due to propagation signals in front haul link and processing delays in BBU. The path
towards complete C-RAN deployment, where BBUs are pooled to support RRHs, and
how many pool needed to serve specific network becomes required. Multiple BBU pools
may be needed to serve a metropolitan area.

• Green Field Deployment: In term of this field, the placement of the RRH and
BBU pool is subjected to network planning. The transport solution and physical medium
can be designed with respect to C-RAN architecture requirements. In general, the main
aim of the network deployment is to reduce cost of deployment and minimize Total Cost
of Ownership (TCO) a ratio with high system performance. However, C-RAN
architecture is promising for small scale deployments for metropolitan areas with high
density RRHs.
• Small Cell Deployment: A small coverage area cells are most likely for C-RAN
architecture for capacity boosting. Release 13 of cellular network standards provide
enhancement of small cell deployment. Adding new small cells to cellular network is
promising to increase network capacity. Small cell deployment scenarios are candidate to
be used with C-RAN. It also supports both user deployed cells and operator, co-existence
operators, Self-Organizing Networks (SONs) mechanisms, and networking between
different RATs. The small cells deployment scenario with C-RAN reduces signalling
resources because they are supported by one central BBU pool, not many BSs as in
tradition network . In future cellular networks many small cells can be deployed to
improvements network capacity and quality in offices, public spaces and homes. When a
user will move out from small cell to the other, the system needs to handover the user to
the new small cell. In this case, the system needs a special coordination technique
between small cells.
13.6 CONCLUSION
As the need of network is changing on day to day basis and the need of site
reallocation will always be there. Proper Site Planning will remove the problem of
relocation of site. RRH is an important network element for extension of network.


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E2-E3 Consumer Mobility Index

1 CELLULAR CONCEPT, GSM ARCHITECTURE AND GSM RADIO ...... 2

2 MAINTENANCE ISSUES OF BTS, NODE-B, AND E-NODE-B ................. 23

3 3G RADIO NETWORK .................................................................................... 31

4 3G CORE NETWORK ...................................................................................... 43

5 3G CALL PROCESSING (VOICE AND DATA) ........................................... 49

6 3G RADIO NETWORK OPTIMIZATION .................................................... 61

7 BACKHAUL MEDIA FOR MOBILE RADIO NETWORK (OFC/ OFC

8 HSPA,HSPA+ AND MIGRATION TO 4G (REL5 TO REL8)....................... 78

9 4G AND 5G NETWORK ARCHITECTURE ................................................. 90

10 KPI REPORTS FOR 2G/3G/4G ..................................................................... 107

11 CONCEPT OF SON ......................................................................................... 132

12 NETWORK OPTIMIZATION USING DTT REPORTS AND SON DATA

13 SITE PLANNING, RELOCATION AND RRH ............................................ 163

E2-E3 CM Version 3.0 April 2021 Page 1 of 174

1 CELLULAR CONCEPT, GSM ARCHITECTURE AND

1.1 LEARNING OBJECTIVE

1.2 CELLULAR CONCEPT

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Figure 1: Cellular Network

Figure 2: Cell Clustering and Co-channel cells

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Signal attenuation with distance

Frequencies can be reused throughout a service area because radio signals

As long as the ratio

Received radio carrier power =C

Relationship between K and D/R

The performance of a cellular network can be expressed in quality of service. An

Relationship between K and Cell Capacity

E2-E3 CM Version 3.0 April 2021 Page 4 of 174

 If K increases, then performance increases

 If K increases, then call capacity decreases per cell

 Use if directional Antennas (3 sector configuration)

 Mobile Assisted Handover (MAHO).

1.3 TYPES OF CELLS

1.3.1 MACRO CELLS

1.3.2 MICRO CELLS

1.3.3 PICO CELLS

1.3.4 SELECTIVE CELLS

E2-E3 CM Version 3.0 April 2021 Page 5 of 174

1.3.5 UMBRELLA CELLS

A freeway crossing very small cells produces an important number of handovers

1.3.6 CELL SECTORISING

Concept of Frequency Assignment

Frequency Planning Aspects

E2-E3 CM Version 3.0 April 2021 Page 6 of 174

Figure 4: Frequency Planning in Sectored Cells

Frequency reuse: The spectrum allocated for a cellular network is limited. As a

Small, battery-powered handsets: In addition to supporting much higher

Performance of handovers: In cellular systems, continuous coverage is achieved

1.4 GSM ARCHITECTURE

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Um Interface A-bis Interface A-Interface

Every telephone network needs a well-designed structure in order to route

1.4.2 MOBILE STATION

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Each MS is identified by an IMEI that is permanently stored in the mobile unit.

E2-E3 CM Version 3.0 April 2021 Page 9 of 174