Henry2020 - 5G Is Real - Evaluating The Compliance of The 3GPP 5G New Radio System With The ITU IMT 2020 Requirements
Henry2020 - 5G Is Real - Evaluating The Compliance of The 3GPP 5G New Radio System With The ITU IMT 2020 Requirements
Henry2020 - 5G Is Real - Evaluating The Compliance of The 3GPP 5G New Radio System With The ITU IMT 2020 Requirements
154
1. introduction to 5G..........................................................................................................154
1.1 5G Evolution toward 6G................................................................................154
1.2 Release 15............................................................................................................164
1.3 Release 16............................................................................................................164
1.4 Release 17............................................................................................................164
1.5 NR air interface.................................................................................................165
1.6 NR provides a flexible air interface........................................................165
1.8 Network slicing..................................................................................................171
1.9 5G Core Network Functions........................................................................173
1.10 Edge computing..............................................................................................174
Salient Features of 5G...........................................................................................175
1.11 Key benefits with 5G....................................................................................176
1.12 Speed upgrades..............................................................................................176
1.13 Low Latency.....................................................................................................177
1.14 Enhanced capacity........................................................................................177
1.15 increased bandwidth....................................................................................178
1.16 5G availability and network coverage................................................178
1.17 5G LAN.................................................................................................................180
1.19 Critical Medical Applications..................................................................183
1.20 5G V2X.................................................................................................................185
1.21 Unmanned Aerial Vehicle or UAV.........................................................187
1.22 Audio-visual production..............................................................................188
1.23 Cyber-Physical Control Applications...................................................189
1.24 Haptic Service...............................................................................................194
1.25 Miscellaneous services..............................................................................195
1.26 NR Enhanced 15.............................................................................................197
1.27 NR Unlicensed (NRU)...................................................................................199
1.28 URLLC enhancements.................................................................................201
1.29 Industrial Internet of Things (IIoT).......................................................203
1.30 New frequency band.....................................................................................204
Chapter 2................................................................................................................................210
2. New Radio: Architecture...............................................................................................210
2.1 Overview of the NG-RAN Architecture..................................................210
2.2. Architecture Options and Migration Paths........................................212
2.3 NR gNB Connected to the 5GC (Option 2)...........................................213
2.5 Multi-RAT DC with the 5GC, NR as Master (Option 4)...................214
2.6 LTE ng-eNB with to the 5GC (Option 5)................................................214
2.7 Multi-RAT DC with the 5GC, E-UTRA as Master (Option 7)........214
2.8 Migration Considerations.............................................................................215
2.9 G NR Base Station (gNB) Architecture.................................................216
2.10 Higher Layer Split (HLS) of the gNB....................................................217
2.11 Separation of CP and UP with Higher Layer Split (HLS)...........220
2.12 Xx Interface Family.......................................................................................221
2.13 NR Radio Interface Protocol....................................................................222
2.14.1 Service data adaptation protocol (SDAP)............................................................223
2.15 Control plane....................................................................................................225
Chapter 3................................................................................................................................228
3. NR Radio Access Technology........................................................................................228
3.1 overview of the NR radio access technology....................................228
3.2 NR KEY FEATURES..........................................................................................229
3.2.1Higher frequencies and spectrum flexibility......................................................229
3.2.2 Ultra-lean design..................................................................................................230
3.2.3 Transmission scheme, bandwidth parts, and frame structure........................231
3.2.4 Duplex schemes....................................................................................................235
3.2.5 Low latency support............................................................................................237
3.2.6 Scheduling and data transmission......................................................................238
3.2.7 Control channels..................................................................................................240
3.2.8 Beam-centric design and multi-antenna transmission.....................................242
3.2.9 Initial access........................................................................................................245
3.3 Interworking and LTE coexistence..................................................246
Chapter 4................................................................................................................................249
4.1 Introduction to VoNR......................................................................................249
4.3 Voice services in an NSA.............................................................................262
4.4 Voice services using EPS fallback..........................................................265
4.4.1 Network interworking requirements supporting voice services......................265
4.4.2Registration procedure – aspects for voice support..........................................268
4.4.3 5G IMS support...................................................................................................272
4.4 .4 EPS fallback........................................................................................................282
4.5 Voice services using NG-eNB....................................................................290
4.6 Voice services with RAT fallback............................................................292
4.7 Voice over NR (VoNR)..............................................................................295
4.7.1 VoNR radio parameter support recommendation............................................298
4.8 Network deployment and connectivity options supporting voice
............................................................................................................................................301
4.10 Supplementary Voice Service, Emergency Call and SMS........311
4.10.1 Supplementary Voice Service...........................................................................311
4.10.2 SMS in 5G...................................................................................................312
5G Evolution
Chapter 1
1. introduction to 5G
The evolution of mobile networks by analog cellular systems in 1980
transformed mobile network technologies into network services. This radio
technology evolution in telecommunication networks improves network
connectivity, latency, and devices' mobility.5G, the fifth-generation mobile
network, is the current evolution in mobile networks. It is a unique global
wireless communication standard after the 4 G LTE (Long term Evolution)
mobile network standard. The 5G, the novel mobile network, allows connection
to everyone, everything and everywhere, including machines, objects, and
devices. It provides high speed, low latency, wide coverage, more connectivity,
and flexible wireless services for everyone. Furthermore, it offers more network
capacity, better availability, and a consistent user experience. 5G network
performance and efficiency empower connects to new industries. The 5G
mobile network is a complete transformation of telecommunication networks
and provides benefits that pave the way for new capabilities and support
connectivity for the latest applications like smart cities, autonomous vehicles,
remote healthcare, and more. It also enables wireless services and technologies
in various sectors, such as agriculture, medical and educational domains.
The 3GPP introduced 5G Phase 1 (R15) to frame policies for 5G. The Phase 1
(R15) lays a solid foundation for future releases of 5GWith NR air interface
and network architecture. The air interface connects two mobile stations in the
wireless communication networks. It works with both the physical and data link
layers (layers 1 and 2) of the OSI model for a connection. R16 and later
releases in 3GPP expand applications of wireless communications. The 3GPP
releases several 5G designed standards like R15, R16 and others. The eMBB
based R15, R16 and later releases expand the supported services of 5G.
5Gbenefits the lifestyle with faster download speeds, low latency, and high
network capacity. There are vast network capacity and connectivity for billions
of devices in Virtual reality (VR), IoT and Artificial Intelligence (AI) 5G LAN
replaces wireless LAN with flexibility and higher performance. 5G applications
in seaports use case: Normally, seaports have challenges such as complex
turnarounds, a large and diverse workforce, and many moving assets.5G
solution for these challenges is an integrated seaport management solution
based on a 5G private network. It benefits operational efficiency, enhances
safety, and increases security. 5G enables prompt communication without
categorizing between vehicles, humans, and implanted sensors, as they share
the same access technology. In non-terrestrial networks, satellites use 5G to
provide service ubiquity, service continuity and service scalability.
Figure 1.1: 5G Radio Access Network gNB
The novel 5G mobile network transforms the early industry standard into the
existing advanced industry standard 4.0. So, it boosts manufacturing, production
and related industrial activities and value creation processes. New Radio (NR)
based positioning in the mmWave band, a 5G radio link behaves partially as an
optical wave and possesses optical properties such as reflection, refraction, and
diffraction. The optical wave properties, along with beam forming in 5G, are
used to locate objects and their position accurately. This NR positioning
supports many use cases like emergencies, UAV operations, AR/VR/XR and
factory automation.
Haptic communication with the haptic sense improves the user experience to a
large extent NR-New radio on unlicensed spectrum, improves many features
and supports carrier aggregation and dual connectivity after R16.
IAB implementation used IAB concepts in the stand-alone (SA) and non-
standalone (NSA) networks. The IAB concept works equally well for NSA
(Non-Standalone) operations. An IAB-Node could provide the 5G access for the
NSA device. In Figure 1.3, the device is in NSA operation, i.e., using the EPC
(evolved packet core). However, in this example, the IAB-Node itself, which
also has a USIM (Universal Subscriber Identity module) or eSIM (embedded
SIM), operates in SA mode, i.e., it is using the 5GC (5G Core). It is very
flexible, supporting both “in-band” (using the same band as the 5G access) or
“out-of-band” (using a different band).
Figure 1.3: Using IAB and interworking with NSA Operation
Frequency bands in 5G networks: The frequency bands for 5G networks are two
ranges, FR1 and FR2. The frequency range, FR1, ranges from 450 MHz to 6
GHz, including the LTE frequency range. Frequency range 2 (FR2) ranges from
24.25 GHz to 52.6 GHz. The sub-6 GHz range is the name for FR1, and the
mmWave spectrum is the name for FR2. these bands support many use cases
such as densification, industrial IoT, backhaul, fronthaul and an intelligent
transportation system ITS. The new radio NR significantly improves MIMO
operation, mobility concept, positioning, and UE power savings. Release R15
significantly defines virtualization-friendly service-based architecture (SBA).
This enhanced architecture is suitable for the vehicle to any (V2X), network
automation, CLI / RIM, eCAPIF, and IMS.
The fundamental elements in the 5g system are a New Radio (NR) air interface,
new radio, core network architectures, Virtualization, automation technologies
and new types of devices. These building blocks enable 5G to offer targeted 5G
services. When Release 15 provides a solid framework for enhanced network
performance and mass offering of excellent services, 3GPP actively enhances
the framework, as shown in Fig. 1.5.
1.2 Release 15
3GPP stands for Third Generation Partnership Project. 3GPP has specifications
for the third-generation mobile system, Universal Mobile Telecommunication
System (UMTS) and fourth-generation mobile systems, long-term evolution
(LTE). International Mobile Telecommunications (IMT)-2020 defined 5G
performance requirements in release 15 pahase1. Key features of R15 include
the New Radio (NR) air interface, new radio network architecture called next-
generation radio access network (NG-RAN), new core network architecture
called next-generation core (NGC) or 5G core (5GC), service-based architecture
(SBA), network slicing and edge computing.
Figure1. Non-Standalone 5G
R15 fully presents two deployment options for the network architecture: non-
standalone (NSA) NR and standalone (SA) NR. So, non-standalone NR with the
EPC uses the LTE eNB like the master node and uses a gNB's NR radio
resources when possible. Standalone NR with the NGC does not rely on the
LTE eNB at all the time and permits direct communications between the UE
and the gNB.
Figure1. 5G RAN
Salient Features of 5G
5the generation mobile network is revolutionary in 5G mobile technology. Its
features and mobility are beyond the expectation of the human being. The high
speed in the 5G data increases the usability of cell phones. With several
innovative features, an intelligent cell phone replaces the laptop now. The 5G
network technology implements significant features in smart mobile devices
such as gaming options, more comprehensive multimedia options, connectivity
everywhere, zero latency, faster response time, and high-quality sound and HD
video, improving multimedia services and user experience.
The mobile phone at 5G caters for most network users. We list the few key
benefits of 5 G below.
1.11 Key benefits with 5G
The 5G network features lower latency, higher capacity, and increased
bandwidth compared to 4G.
It redefines 5G and IoT with an increased 5g network capacity with internet and
wireless network. With 5G devices communicating capacity, applications for
cities, factories, farms, schools, and homes are growing, and 5G applications
bring thousands of sensors on hundreds of different machines, automating
supply chain management processes and ensuring just-in-time delivery of
materials while using predictive maintenance to minimize work stoppages.
Smart homes and cities also take a giant leap forward in the future of 5G. Using
more connected devices, AI to place, has no edge on computing. From houses
that give personalized energy-saving suggestions, maximize the environmental
impact of traffic lights that change their patterns based on traffic flow. 5G
applications relying on added network capacity affect everyone.
Figure1. : Evolution to 5G
3gpp focussed more on eMBB usage scenarios’ in R15, but most of the work in
R15 is helpful for URLLC and mMTC usage scenarios. Fig 3.0 explains the
extended service scenarios beyond eMBB by 3gpp in R16. The 3gpp focuses on
different industries. Many of these services that related to different industries.
They are not distinctively different but overlap each other to some extent. We
describe these services in sections 3.1 to 3.10.
1.17 5G LAN
Figure 1.22 shows the key concepts related to 5Glocal area network (LAN)
services [TR22.821]. Like fixed or wireless LAN's, 5G LAN provides reliable
communications between a group of restricted UEs in residential, commercial,
or industrial environments. The 5G system can enhance, supplement the
existing fixed wireless local area network, or completely replace such a local
area network. Uses the 5G system to create a virtual private network (PVN).
Compared to traditional LAN, based on 5G.
5G LAN redefines 5G, and the Internet of Things increases the capacity of the
5G network in virtual private networks for internet and wireless networks and
provides benefits such as superior performance, remote access, mobile support,
and enhanced security. In a residential environment, different devices in a single
house or different users in an apartment building can get enhanced 5G QoS and
maintain privacy and isolation of communications when needed.
5G LAN helps connect computers, printers, scanners, and servers in the
enterprise setting and supports access to private and secure settings across a
wide area or even across distant sites.
Figure 1.22: key Concepts Related to 5G Local Area Network (LAN) Services
The 5G LAN connects controllers, actuators, and sensors without wires and low
latency communications in the industrial environment. Reliable 5G wireless
connectivity cancels Ethernet cables in a hazardous environment or in moving
or rotating parts and facilitates factory reconfiguration to improve productivity.
Use case categories are service ubiquity, service continuity and service
scalability. These categories are not mutually exclusive; a use case may belong
to over one category.
```
Figure1.23:5G Access
Medical experts are in various places. We can further divide this category into
"static-remote" or "mobile-remote" according to whether the equipment or
person is moving while providing care. Since this type of care takes place on a
large scale, PLMN 5G provides communication services.
►5G PLMN uses cases. In emergencies, distance is usually a key factor. When
providing intensive care for patients, 5G can help overcome these distance
limitations. In the emergency care case, an ambulance nurse can perform an
ultrasound at the accident scene and take actions under remote guidance (for
example, applying pressure to a specific part of the body to prevent bleeding or
injury) as a medical expert. The most suitable medical institution (such as a
heart hospital) can be selected according to the patient's situation. We can place
various sensors on the patient's body and the emergency room (ER) is prepared
even before the patient is transported to the emergency room. Without an
exceptional surgeon present in person, remote surgery or remote, we can also
perform surgery, which significantly expands medical care to remote areas. In
another case, from the moment the ambulance arrives at the accident site to the
moment the patient is taken to the operating table in the operating room, a
networked ambulance can transmit essential patient data to the emergency
room. Come to receive patients. In another case, a sensor was installed on a
recently discharged patient from the hospital to track essential measurement
data and notify the appropriate medical institution. If necessary, medical
assistance can be provided to the patient immediately.
1.20 5G V2X
Although LTE can solve some Internet vehicles (V2X) use cases, the 5G V2X
significantly expands the types of use cases supported by 5G's high data rate,
ultra-low latency, and high reliability. Please note that the NR-based V2X is a
supplement to the LTE-based V2X, not a replacement. For example, the LTE-
based V2X can be used to send important security messages, and scenarios that
require stricter SOS requirements (for example, delay, reliability, and data rate)
can benefit from the NR-basedThe V2XV2X is a subcategory of side-chain
communication, supporting vehicles and supporting public safety through EU-
to-EU communication. R17 will solve the unresolved V2X problems in R15 and
R16 and introduce research projects to expand NR side link communication
capabilities and applications. We expect R17 to contribute to energy saving,
reliability, and latency. Figure 1.24 summarizes 3GPP's use case group for 5G
V2X [TR22.886].
► Extended sensors. Vehicles can share their raw or processed sensor data with
other vehicles and MSW to create situational awareness. This exchange of
information allows vehicles to make tactical or manoeuvring decisions. For
example, the exchange of sensor data, including high-resolution video, can
detect objects that local sensors cannot see directly (such as behind other
vehicles, in curves, or behind building corners).
►Live video. They can equip the drone with a 360˚ spherical camera. The
drone can communicate with the gNB on the ground and send 4k / 8k video to
the cloud server. People wearing augmented reality glasses can enjoy live video
broadcasts as if they were in a stadium.
► Mission-critical.
► Rail and maritime transport. Asset tracking in rail and marine applications
can improve transportation efficiency, reduce the possibility of container loss or
theft, and facilitate logistics.
Measurements. The air pressure sensor method uses an air pressure sensor to
determine the vertical component of the UE position. In the WLAN positioning
method, the access point identifier (AP), the WLAN measurement performed by
the UE, and the database are used to find the UE. The Bluetooth® positioning
method involves measurement using beacon identifiers and Bluetooth®
beacons. In the TBS positioning method, the UE measures the TBS signal. TBS
comprises a network of terrestrial transmitters that broadcast signals only for
positioning purposes. TBS signals include Metro Beacon System (MBS) signals
and Positioning erence Signals (PRS). The motion sensor method uses various
sensors such as accelerometers, gyroscopes, and magnetometers to determine
the displacement of the UE.
► Personalized alarms. This service replaces the default or custom alarm tones
with multi-modal tones that combine custom haptic alarms with sound, video,
and other senses. When the calling party attempts to establish a call with the
caller party, customized tactile alert information and specific information about
the incoming call will be sent to the UE of the called party. The called party UE
generates customized tactile alert feedback suitable for the user.
► Call waiting for a sign. When a subscriber takes part in an active call or a
call on hold, we can notify them of incoming calls using tactile feedback. We
can customize this tactile feedback for different callers. By avoiding
interruptions, haptic feedback can lead to a smoother communication
experience.
► Accident or health crisis. The elderly may fall, thus alerting the server and
allowing timely help. Even if a person cannot move, the rescue will be on the
road because of autonomous driving during a crisis.
1.26 NR Enhanced 15
3GPP has created an ultra-flexible and high-performance NR air interface in
R15. I expected the NR air interface to become a solid foundation for later
versions. As the picture shows. 3.1 lists the enhancements of NR 5) in R16 and
higher to support the various new services described in section 2.0. I explain
these NR characteristics in Sections following. Figure 1.26: NR enhancement
beyond 5G Phase 1 Integrated Access and Backhaul.
(IAB) Integrated Access and Backhaul (IAB) means that spectrum can be
shared between (i) wireless access service UE and (ii) wireless backhaul to
achieve a station core network connectivity base. In the future, we can use IAB
for small cell deployments outdoors, indoors, and even on mobile relays (for
example, on buses or trains). We can view IAB as a cost-effective deployment
solution that simplifies radio core connections and reduces the complexity of
Fiber-based transmission networks. IAB also reduced the total implementation
time. As the picture shows. Adapted from [TR38.874] 3.2 illustrates an example
of IAB implementation. 5) 3GPP has extensively studied an adventurous
multiple access scheme called non-orthogonal multiple access (NOMA) but
decided not to continue. This means that OFDMA (and optional SCFDMAjF)
will soon continue to be the p erred multiple access scheme.
.
In Figure 1.26, two base stations, IAB node X and IAB node Z use the spectrum
to provide wireless access to their UEs and communicate with the IAB donor
base station that provides connectivity to the network centre (CN). The IAB
node is not directly connected to the CN, and the IAB donor has a CN
connection. In addition, IAB donors can provide wireless access to their own
UEs. 5G gNB can decompose into a central unit (CU) and distributed unit (DU)
specified in R15. IAB also supports multi-hop links, where the IAB node A
base station is connected to the IAB donor through the IAB node Y
► Return in and out of band. In-band backhaul means that the access link and
the backhaul link overlap at least partially in frequency. There is no such
frequency overlap for out-of-band backhaul. Supports spectrum below 6 GHz
and spectrum above 6 GHz.
► RAT and SA and NSA modes. Although NR-based backhaul is the primary
concern, LTE-based backhaul can be supported. The IAB node can operate in
independent NR mode or non-independent NR mode.
In R15, 3GPP initially defined FR1 to cover 450 MHz to 6 GHz and FR2 to
cover 24.250 GHz to 52.6 GHz. FR1 was later extended in R15 to cover 410
MHz to 7.125 GHz to include the unlicensed 6 GHz spectrum at the highest
frequency and any spectrum available around 400 MHz (for example, GSM 410
or GSM link system from about 410 MHz to about 410 MHz). 430 MHz). 3GPP
is exploring further increases in the 7.125 GHz to 24.250 GHz range and
frequency bands above 52.6 GHz. The 7.125 GHz to 24.250 GHz frequency
band can be divided into multiple frequency bands, such as 7.125 GHz to about
1013 GHz, 101618 GHz to 101618 GHz and 1618 GHz to 24.250 GHz.
Existing FR1/FR2 can be extended, or new FR can be defined. At higher
frequencies (for example, 52.6 GHz to 71 GHz), new OFDM parameter sets can
be defined. Higher propagation path loss, higher phase noise, higher insertion
loss at the RF interface characterizes higher frequencies (for example, higher
low-noise amplifier noise (LNA) and more analogue-to-digital converters. The
challenge of (ADC) noise and lower power amplifier efficiency compared to
lower frequencies 8). 8) 3GPP is studying various waveforms that differ from
the currently used OFDM waveforms. These new waveforms may be better
suited for higher frequencies. However, these higher frequencies provide the
benefits of high channel bandwidth and the high throughput, low latency, and
high capacity that come with it. Figure 1.29 shows an example use case that can
be supported using a spectrum above 52.6 GHz. Figure 1.29: Example use case
for spectrum above 52.6 GHz.
Figure1.29 Example use cases for the spectrum above 52.6 GHz
► CLI and RIM. In a TDD system, when two gNBs use the same slot format
on a carrier frequency, co-channel interference and adjacent channel
interference are minimized. However, if dynamic TDD is implemented and
gNBs independently choose their slot
Network densification. With the ultrahigh definition displays, AR/VR apps and
mobile 3D projects, data traffic demand is expected to soar even further.
Network densification is an effective mechanism to meet the ever-increasing
data traffic demand. Higher frequency bands are suitable for the small cell
deployments needed for network densification. Backhaul and fronthaul. The
availability of large bandwidth at higher frequencies makes these frequencies
suitable for wireless backhaul. Decomposition or disaggregation of the gNB
requires two logical parts of the gNB to communicate with each other. In one
scenario, baseband and RF portions can communicate using wireless fronthaul
—indoor hotspots and stadiums. Deploying large bandwidth and high-frequency
hotspots meets heavy indoor or outdoor data traffic demand. Higher frequency
reuse is possible because of small cells. ITS. Large bandwidths enable wireless
transfer of high-definition videos and sensor data between the vehicles and
high-definition maps from the infrastructure to the vehicles. Industrial IoT.
Factory automation can benefit from private 5G networks using a high-
frequency spectrum in a local area with significant frequency reuse thanks to
small cells. Larger sub-carrier spacing can reduce latency, and wider channel
bandwidths can achieve high data rates and high reliability.
5G New Radio
Chapter 2
The gNBs and ng-eNBs are connected employing the NG interfaces to the 5G
Core (5GC), to the AMF (Access and Mobility Management Function)
employing the NG-C interface and to the UPF (User Plane Function) employing
the NG-U interface. Both the user plane and control plan for NG-RAN same as
the same high-level architecture scheme, as depicted in Figure 2.1 below.
NG-RAN provides NR and LTE radio access services. An NG-RAN node (base
station) is a gNB (i.e., a 5G base station), services both NR e services, and an
ng-eNB, providing LTE/E-UTRAN services towards the UE.
The gNBs and ng-eNBs using the Xn interface. The gNBs and ng-eNBs are also
connected using NG interfaces to the 5G Core (5GC), more specifically to the
AMF (Access and Mobility Management Function) using the NG-C interface
and to the UPF (User Plane Function) using the NG-U interface. The overall
relation of NG-RAN with the overall 5G system is shown in Figure 2.1. The
user plane and control plane architectures for NG-RAN follow the same high-
level architecture scheme, as depicted in Figure 2.2 below.
The prime reason for selecting this option was the close similarity to the
protocol stack split applied in Dual Connectivity: in a DC configuration, the
Master Node (MN) and the Secondary Node (SN) are “split” along the same
point as Option 2.
. In addition, they divide F1 interface functions into F1-C and F1-U functions.
F1-C (Control Plane) Functions: • F1 Interface Management Functions: F1
setup, gNB-CU Configuration Update, gNB-DU Configuration Update, error
indication and reset function. • System Information Management Functions: The
gNB-DU is responsible for the scheduling and broadcasting of system
information. For system information broadcasting, the encoding of NR-MIB
and SIB1 is performed by the gNB-DU, while the gNB-CU performs the
encoding of other SI messages. The F1 interface also provides signalling
support for on-demand SI delivery, enabling UE energy saving. • F1 UE
Context Management Functions: These functions are responsible for the
establishment and modification of the necessary UE context. The gNB-CU
initiates the establishment of the F1 UE context, and the gNB-DU can accept or
reject the establishment based on admission control criteria (e.g., the gNB-DU
can reject a context setup or modification request in case resources are not
available). In addition, an F1 UE context modification request can be initiated
by either gNB-CU or gNB-DU. The receiving node may accept or reject the
modification. The F1 UE context management function can also be used to
establish, modify, and release Data Radio Bearers (DRBs) and Signalling Radio
Bearers (SRBs). • RRC Message Transfer Function: This function is responsible
for transferring RRC messages from the gNB-CU to the gNB-DU and vice
versa. F1-U (User Plane) Functions: • Transfer of User Data: This function
allows to transfer of user data between gNB-CU and gNB-DU. • Flow Control
Function: This function allows to control the downlink user data transmission
towards the gNB-DU. Several functionalities are introduced for improved
performance on
The main functions of the PDCP protocol are to provide header compression
and decompression using RoHC (Robust Header Compression), security
functions including ciphering/deciphering and integrity protection, duplication
of transmitted PDCP PDUs, and reordering and duplicate detection of received
PDCP PDUs. The most significant differences in NR PDCP compared to LTE
are introducing the data duplication over different transmission paths to achieve
extremely high reliability for URLLC (Ultra-Reliable Low Latency)
applications and introducing integrity protection for user plane data.
The other significant additions relative to LTE RRC are the support of an ’on
demand’ system information mechanism that enables the UE to request when
specific system information is required instead of the NG-RAN consuming
radio resources to provide frequent periodic system information broadcast, and
the extension of the measurement reporting framework to support beam
measurements for handover within a high-frequency beam-based deployment.
Figure 2.9 shows the control plane protocol stack. The Non-Access Stratum
(NAS) protocols terminate in the UE and the AMF of the 5G core network and
are used for core network-related functions such as registration, authentication,
location updating and session management. The Radio Resource Control (RRC)
protocol terminates in the UE and the 5G-RAN and is used to control and
configuration the radio-related functions in the UE
The NG-RAN so that transitions to/from RRC Connected are faster and incur
less signalling overhead. See Figure 2.10 above. The other significant additions
relative to LTE RRC are the support of an ’on demand’ system information
mechanism that enables the UE to request when specific system information is
required instead of the NG-RAN consuming radio resources to provide frequent
periodic system information broadcast, and the extension of the measurement
reporting framework to support beam measurements for handover within a high-
frequency beam-based deployment.
Summary
3GPP has taken several steps to specify interfaces and protocols that ease the
migration of LTE-based cellular networks to 5G and NR. It is expected that
these steps will help the uptake of NR and 5GC while making it easier to evolve
networks in the most cost-efficient manner possible. Enhancements beyond
phase-1 will address requirements and functions needed for industries beyond
cellular mobile broadband: automated driving, industry automation, e-health
services, etc. The 5G platform is promising to deliver the foundation for the
next decade in the digital age.
5G New Radio
Chapter 3
they cause interference to other cells, thereby reducing the achievable data rates.
The ultra-lean-design principle aims at minimizing the always-on transmissions,
thereby enabling higher network energy performance and higher achievable
data rates.
In LTE, all devices support the maximum LTE carrier bandwidth of 20 MHz.
However, given the extensive maximum bandwidth, it is not reasonable to
require all NR devices to support the maximum NR carrier bandwidth.
Furthermore, NR allows for device-side receiver-bandwidth adaptation to
reduce the device energy consumption. Bandwidth adaptation ers to using a
modest bandwidth for monitoring control channels and receiving medium data
rates and dynamically open a wideband receiver only when needed to support
extremely high data rates.To handle this, NR defines bandwidth parts that
indicate the bandwidth over which a device is currently assumed to receive
transmissions of specific numerology.
few OFDM symbols can be sufficient to carry the available payload. This is
especially beneficial in conjunction with analog beamforming, where
transmissions to multiple devices in different beams must be separated in time.
The spectrum allocation typically gives the duplex scheme at hand. For lower
frequency bands, allocations are often paired, implying frequency-division
duplex (FDD). At higher frequency bands, unpaired spectrum allocations are
increasingly common, calling for time-division duplex (TDD). Given the
significantly higher carrier frequencies supported by support for unpaired
spectrum is thus even more pronounced in NR compared to LTE. In contrast to
LTE, NR can operate in paired and unpaired spectrums using a standard frame
structure. The basic frame structure supports both half-duplex and full-duplex
operations. In half-duplex, the device cannot transmit and receive at the same
time. Examples hereof are TDD and half-duplex FDD. In full-duplex operation,
on the other hand, simultaneous transmission and reception are possible with
FDD as a typical example.
The basic approach to dynamic TDD is for the device to monitor for downlink
control signalling and follow the scheduling decisions. It instructed if the device
to transmit; it transmits in the uplink. Otherwise, it will attempt to receive any
downlink transmissions. The uplink-downlink allocation is then entirely under
the scheduler's control, and any traffic variations can be dynamically tracked.
There are deployment scenarios where dynamic TDD may not be helpful, but it
is much simpler to restrict the dynamics of a dynamic scheme in those scenarios
when needed rather than trying to add dynamics to a Fundamentally semi-static
design as LTE. For example, in a wide-area macro network with above-rooftop
antennas, the inter-cell interference situation requires coordination of the
uplink-downlink allocation between the cells. In such situations, a semi-static
allocation is appropriate with an operation like LTE.
The requirements on the device (and network) processing times are significantly
tighter in NR compared to LTE. For example, a device is assumed to respond
with a HARQ acknowledgement one slot (or even less for some device
categories) after receiving downlink data. The time from a scheduling grant to
uplink data transfer is in the same range. The higher-layer protocols MAC and
RLC have also been designed with low latency in mind, with header structures
chosen to enable processing without knowing the amount of data to transmit.
This is especially important in the uplink direction as the device may only have
a few OFDM symbols after receiving the uplink grant until the transmission
occurs.
Given the extremely high data rates supported by NR, channel coding for data
transmission is based on low-density parity-check (LDPC) codes [2]. LDPC
codes are attractive from an implementation perspective, especially at higher
code rates where they can offer a lower complexity than the Turbo codes used
in LTE.
last one or two symbols of a slot and can support high-speed feedback of
hybrid-ARQ acknowledgements to realize so-called self-contained slots where
the delay from the end of the data transmission to the reception of the
acknowledgement from the device is in the order of an OFDM symbol,
corresponding to a few ten microseconds depending on the numerology used.
This can be compared to 3 ms in LTE and is yet another example of how the
focus on low latency in NR has impacted the design. For situations when the
duration of the short PUCCH is too short of providing sufficient coverage, there
are also possibilities for longer PUCCH durations.
NR channels and signals, including those used for control and synchronization,
have been designed to support beamforming. Channel-state information (CSI)
for the operation of massive multi-antenna schemes can be obtained by the
feedback of CSI reports based on the transmission of CSI erence signals in the
downlink and uplink measurements exploiting channel reciprocity. NR is
deliberately supporting functionality to support analog beamforming and digital
preceding/beamforming to provide implementation flexibility. At high
frequencies, analog beamforming, where the beam is shaped after digital-to-
analogue conversion, may be necessary from an implementation perspective, at
least initially. It can only form analog beamforming results in the constraint that
a receive or transmit beam in one direction at a given time instant and requires
beam-sweeping where the same signal is repeated in multiple OFDM symbols,
but different transmit beams. By having beam-sweeping possibility, they
ensured that it could transmit any signal with a high gain beamformed to reach
the entire intended coverage area.
With a massive number of antenna elements also for lower frequency bands, the
possibility to separate uses spatially increases both in uplink and downlink but
requires that the transmitter has channel knowledge. For NR, extended support
for such multi-user spatial multiplexing is introduced, either by using high-
resolution channel-state-information feedback using a linear combination of
DFT vectors or uplink sounding erence signals targeting the utilization of
channel reciprocity.
Initial access is when a device finds a cell to camp on, receives the necessary
system information, and requests a connection through random access. The
basic structure of NR initial access is like the corresponding functionality of
LTE [3] with a Primary Synchronization Signal (PSS) and Secondary
Synchronization Signal (SSS) used to find, synchronize to, and identify a
network and a Physical Broadcast Channel (PBCH) that carries a minimum
amount of system information. In the context of NR, the PSS, SSS, and PBCH
are jointly erred to as a Synchronization Signal (SS) block.
LTE/NR spectrum coexistence, that is, the possibility for an operator to deploy
NR in the same spectrum as an already existing LTE deployment, has been
identified to enable early NR deployment in lower frequency spectrum without
reducing the amount of spectrum available to LTE.In the second scenario, there
is coexistence only in the uplink transmission direction, typically within the
uplink part of lower frequency paired spectrum, with NR downlink transmission
taking place in spectrum dedicated to NR, typically at higher frequencies.This
scenario attempts to address the uplink-downlink imbalance discussed above.
Dual connectivity within NR and NR will be added in a later release.
However, the lower frequency bands are often already occupied by current
technologies, primarily LTE. Furthermore, an additional low-frequency
spectrum is planned to be deployed with LTE soon. LTE/NR spectrum
coexistence, that is, the possibility for an operator to deploy NR in the same
spectrum as an already existing LTE deployment, has the ore been identified to
enable early NR Deployment in lower frequency spectrum without reducing the
amount of spectrum available to LTE.
In the second scenario (right part of Figure 2.12), it is coexistence only in the
uplink transmission direction, typically within the uplink part of the lower
frequency paired spectrum, with NR downlink transmission do in the spectrum
dedicated to NR at higher band frequencies. This scenario attempts to address
the uplink-downlink imbalance discussed above. NR supports a supplementary
uplink (SUL) to handle this scenario specifically.
DELETE
NRNR
Figure3.
[1] Note that the first releases of LTE did not support uplink spatial
multiplexing
[2] In release 15, dual connectivity is only supported between NR and LTE.
Dual connectivity within NR and NR will be added in a later release.
It is simple to keep the existing voice services already in place, but this
achievement requires solving some complex technical challenges. Any solution
implementation must adapt to existing network deployment, so a single solution
is not viable.
The recent 5G implementation has adopted option 3, which means that the
network provider owns the existing 4G LTE network and has implemented a 5G
network alongside it. As a result, 5G NR is a secondary cell, and the core
technology remains the Evolved Packet Core (EPC). During Option 3 operation,
the UE registers with the IMS through the Evolved Packet System (EPS). When
a 5G UE initiates (or receives) a voice call, the EPS system follows the typical
VoLTE procedure. When the service provider chooses option 2, they implement
the 5G network as an SA network without depending on In this option, the IMS
core provides voice as a 5G application service. Voice services on such
networks are called Voice for New Radio (VoNR). Even option 2 has
challenges. In the initial stages of 5G, the geographic coverage of 5G will be
incomplete. When the mobile device moves out of the 5G NR coverage area,
the ongoing VoNR voice call will need to be switched to use VoLTE on the 4G
network. It Needs meticulous network planning and coverage. In the early
VoLTE systems, circuit-switched reservations (CSFB) caused delays and
interrupted calls. The process discussed in detail in this article is called "EPS
support for IMS voice." This process avoids such dropped calls by instructing
the UE to call on the EPS immediately after initiating any voice call. EPS
reservation will cause a handover during the initial setup rather than during a
call. To avoid affecting the user's call experience. With the support of EPS, the
European Union will adopt the highest priority 5G RAT. Since full 5GC support
is not currently needed, EPS can be used as an intermediate step to accelerate
market voice services.
The benefits of 5G VoNR for pure voice calls are the call quality and ultra-high
definition. However, as we noted above, and most importantly, 5G VoNR can
also play a key role in the data services provided by 5G.
This section explains the architecture the NG-RAN architecture builds on the
success of the 4G LTE radio architecture while introducing several keys,
revolutionary and forward-looking concepts both on the overall architecture
front and protocols.
The sparse SS-block raster enables significantly reduced time for initial cell
search, at the same time as it can significantly improve the network energy
performance due to the longer SS-block period. At the end of the section, how
to make NR voice successful in testing and measurement is solved. The
consideration was done in laboratory tests and field tests and briefly described
the actual settings that allowed testing of NR voice.
While long term evolution (LTE) uses a few nodes in the evolved packet core
(EPC), 5G defines more network functions managed by network function
virtualization (NFV) include network security and firewalls, network address
translation (NAT), domain name services (DNS), caching, intrusion detection
and more.5G has more NFs that have fewer responsibilities. The next-
generation radio access network (NG-RAN) architecture builds on the success
of the 4G LTE radio architecture while introducing several keys, revolutionary
and forward-looking concepts both on the overall architecture front and
protocols. The technical work on NR was started in the spring of 2016, with the
first release, being part of the 3GPP release 15 of the NR specifications
finalized by the end of 2017. It limited this first release to non-standalone NR
operation, implying that NR devices rely on LTE for initial access and mobility.
The sparse Synchronization Signal (SS)-block raster enables significantly
reduced time for initial cell search, at the same time as it can significantly
improve the network energy performance due to the longer SS-block period.
The analyst says that the number of global voice subscriptions will double by
2025. Mobile users demanding voice services ensure these services are still part
of the service provider's package and business model. However, 5G network
voice is more than just satisfying. Customers: voice can also play a role in the
new data services provided by 5G.
It is simple to keep the existing voice services already in place, but this
achievement requires solving some difficult technical challenges. Any solution
implementation must adapt to existing network deployment, so a single solution
is not viable.
It is simple to keep the existing voice services already in place, but this
achievement requires solving some complex technical challenges. Any solution
implementation must adapt to existing network deployment, so a single solution
is not viable.
The benefits of 5G VoNR for pure voice calls are the call quality and ultra-high
definition. However, as we noted above, and Most importantly, 5G VoNR can
also play a key role in the new data services provided by 5G.
This article develops the technical details of how 5G networks support voice
services. Unfortunately, the 5G system will not provide a single technical
solution for voice services, including radio access technology, infrastructure
deployment, and the protocol layer. The purpose here is to describe the
technological evolution required to support voice services and to ensure that the
introduction of 5G will not restrict these services.
The purpose of this article is to introduce various 5G voice services and some
evolution paths in more detail, to explain how the voice services provided will
change with the evolution of the 5G system (5GS) and 5G access network
(5GAN). The realization of equipment (UE). Finally, some complimentary
support services are considered, such as emergency services, SMS or eCall car
emergency services. NR voice is voice over IP using the IP Multimedia
Subsystem (IMS) infrastructure from a high-level perspective. The advantage of
using IMS is establishing and guaranteeing the quality of Service (QoS) for
each application. The task of IMS is to establish, control and maintain protocol
data unit (PDU) sessions, including all relevant data bearers with corresponding
QoS flows, to obtain the best quality experience for the end-user. Compared
with the data PDU session in 5G, one difference is that through the PDU session
establishment request of the no-access stratum signalling process (NAS), the
UE requests the PDU session to signal IMS. Like Voice for Long Term
Evolution (VoLTE), IMS voice in 5GS also supports QoS. This is a significant
difference compared to voice services provided by external applications, such as
so-called OTH voice services (OTT).
So, there is a question about how to connect IMS to the next generation 5GC
network. The evolution path describes whether EUTRA only supports the voice
on the NSA connection and whether the synchronous NR data connection can
be maintained or suspended. This option is called Voice over LTE (VoLTE) in
the ENDC configuration.
The Evolved Packet System fallback use case describes a situation where 5GC
does not provide voice services. If necessary, it will transfer the connection to
the EPS (VoLTE) connection. Another backup mode is RAT backup. The
current core network is supposed to support voice services, but the current RAT,
which is NR, does not. Here, the connection is only transferred from NR to
EUTRA.NR Voice (VoNR) indicates that the NR network supports voice
services, and the 5GC provides a connection to the IMS. Usually, VoNR is
independent of dual connection so that it can be used with ENDC. However, the
focus is on NR SA, where 5GC is connected to IMS that supports voice
services. Since LTE is running in parallel here, intersystem handover is
mandatory to ensure UE mobility and avoid dropped calls and take advantage of
high-quality key performance indicators (KPIs). Please note that in 3GPP
Release 15, the switch between 5G and 3G/2G is not defined. The ore, no
circuit switch flyback scheme (CSFB) is also possible. 2G / 3G circuit
switching can only be completed in two steps by temporarily connecting to 4G.
In the 16th release of 3GPP, Single Radio Voice Call Continuity (SRVCC) was
introduced, in which VoNR connections can be transferred to 3G. The goal is to
avoid dropped calls when the coverage of 5G services is weakened, and LTE
coverage is unavailable. See Figure 4.1 for related settings. Besides the terminal
capabilities, support for voice services in 5G NR must consider the various
network deployment options. Critical questions are, for example, which RAT to
use (EUTRA or NR), which core network is available (EPC or 5GC) and
whether the evolved NodeB (eNB) is a next generation evolved NodeB
(NGeNB) or just a legacy eNB. We may speak about EPS fallback, RAT
fallback, voice-over NGeNB (NGENDC) or standalone VoNR. The frequency
band allocation applies to such voice call deployment options, i.e., network
operators plan to orm legacy frequency bands in the lower frequencies from
LTE to 5G. With such enhanced coverage, services like VoNR also become
feasible.NR Voice (VoNR) indicates that the NR network supports voice
services and the 5GC provides a connection to the IMS. Normally, VoNR is
independent of dual connection, so it can be used with ENDC. However, the
focus is on NR SA, where 5GC is connected to IMS that supports voice
services. Since LTE is running in parallel here, intersystem handover is
mandatory to ensure UE mobility and avoid dropped calls and take advantage of
high-quality key performance indicators (KPIs). Please note that in 3GPP
Release 15, the switch between 5G and 3G/2G is not defined. The ore, no
circuit switch flyback scheme (CSFB) is also possible. 2G / 3G circuit
switching can only be completed in two steps by temporarily connecting to 4G.
In the 16th release of 3GPP, Single Radio Voice Call Continuity (SRVCC) was
introduced, in which VoNR connections can be transferred to 3G. The goal is to
avoid dropped calls when the coverage of 5G services is weakened and LTE
coverage is unavailable. See Figure 4.1 for related settings. Besides the terminal
capabilities, support for voice services in 5G NR must consider the various
network deployment options. Critical questions are, for example, which RAT to
use (EUTRA or NR), which core network is available (EPC or 5GC) and
whether the evolved NodeB (eNB) is a next generation evolved NodeB
(NGeNB) or just a legacy eNB. We may speak about EPS fallback, RAT
fallback, voice-over NGeNB (NGENDC) or standalone VoNR. The frequency
band allocation applies to such voice call deployment options, i.e., network
operators plan to orm legacy frequency bands in the lower frequencies from
LTE to 5G. With such enhanced coverage, services like VoNR also In addition
to the technological evolution of RAT and core network from 4G to 5G, we
have also witnessed an evolution, especially introducing more complex and
higher-quality voice and video services. The accompanying term for VoNR is
Enhanced Voice Service (EVS), which has a broader audio capacity, higher
sampling rate, better quantization, and higher resolution. become
The EVS voice codec has been introduced into various networks with LTE, but
5G voice services rely more widely on this advanced voice coding algorithm. It
also briefly introduces the principles of EVS and the corresponding voice codec.
Due to the interoperability of N3IWF, you can even choose to establish voice
calls via IMS on access networks other than 3GPP (such as WLAN) and switch
to VoNR. For brevity, the details of this process are omitted here but can be
found in TS 23.502.
feasible.
5G uses the mid-frequency band, and LTE uses the lower frequency band,
which can cause some coverage limitations
Thanks to these interworking and erence points, one can ensure an IP flow
controlled via UPF and SMF independent of whether the UE is camping on
LTE or NR.Regardless of whether the 5G deployment is based on the NSA or
SA mode, the lessons learned from the introduction of traditional networks have
shown that the initial deployment will not have full coverage. The ore, 5GC
must be tightly coupled with EPC, especially the existing IMS VoLTE
supporting infrastructure, to provide seamless voice services throughout the
network, with an acceptable quality of experience (QoE) as a KPI. The goal is
to register UEs on 5G networks, even if voice services are not supported and
need to be switched to LTE. This method is independent of RAT and IMS. The
support for voice services can be obtained through EPC. UEs residing in NR
will be redirected to EPC as the core, and the serving RAT can also be changed
from NR to EUTRA.
Please note that only the backup process of changing the RAT from NR to
EUTRA is called RAT backup voice service. To achieve a tight coupling
between EPC and 5GC, the goal is first to introduce an additional interface
between the entities and functions of the core network. Note that your
implementation depends on the deployment strategies of the infrastructure
providers and operators. Some of these new connections include the following.
► The N6 interface is used to connect the 5GC user plane function (UPF) to the
IMS. TS 23.501 defines N6 as the erence point between UPF and the data
network. For voice support, the data network is now represented by the IMS
signalling system. PDU connections can be established using the QoS flows
required for voice services. N6 is also a prerequisite for full VoNR support.
► S5 interface, used for the control and connection of the user plane between
the session management function (SMF) / UPF that represents the 5GC entity
and the service gateway (SGW) that represents the EPC entity. From an EPC
perspective, the S5U interface replaces the public data network (PGW) gateway
for voice services because they are now established through UPF logic.
► The N26 interworking interface between the mobility management entity
(MME) and the mobility and access management function (AMF) to implement
context transmission and network-controlled mobility scenarios, such as
handover between LTE and 5G. N26 means optional network implementation.
As a primary benefit, TS 23.501 indicates that the interworking process with
N26 provides IP address continuity for mobility between systems for UEs that
support 5GC Non-Access Stratum (NAS) and EPC NAS and operate in single
sign-on mode. Without the N26 interface, assuming the UE is in single
registration mode, the control coordination between MME and AMF must be
routed through SMF and PGW.
Figure4. : erence points between EPC, 5GC and IMS to ensure tight interworking
for voice support
transmission in accordance with service provider policy (for details, see TS.
Thanks to these interworking and erence points, one can ensure an IP flow
controlled via UPF and SMF independent of whether the UE is camping on
LTE or NR. In addition, mobile terminated connections initiated by IMS can be
routed properly. Even in a single registration situation, due to the optional N26
interworking it is possible to maintain the IP address allocated to the UE.
The first important process in a possible 5GS voice service product is the
registration process. In this process, the UE and the network exchange the
intentions and capabilities of the two entities. More detailed information about
the NAS message flow registration process is provided in TS 24.501. Through
the registration request message, the UE displays its usage settings to the
network. Use settings can be data-centric or voice-centric. If the UE intends to
use voice, the UE usage setting must indicate a voice-centric mode. Another
important indicator in this control message is the S1 mode indicator contained
in the 5G Mobility Management Capability Element (5GMM). Using this flag,
the UE indicates whether the possible downgrade process from EPS's IMS voice
from 5GS to EPC is feasible. Through the exchange of capacity information, the
UE reveals its IMS-related parameters. Common IMS parameters that the UE
can support include, for example, the voice bearer indication on EUTRA, the
voice bearer on the secondary cell group (SCG) bearer, and the echo indication
in EPS. The voiceOverNR parameter indicates the UE's support for NR voice. If
the UE does not support Voice over NR and only supports EPS fallback, it is
recommended to set the parameter flag to voiceOverNR = False and
voiceFallbackIndicationEPSr16 = True. Please note that UE capability is a
process between the UE and the NG Radio Access Network (NGRAN) (TS
38.331). When 5GC receives a registration request, it must provide an
appropriate response based on the network's capabilities or quotation.
Obviously, one of them is the support of the network part for voice services. By
registering to accept the message, the network not only confirms the successful
transition to the 5GMM_REGISjected state, but also confirms the compatibility
with the voice call-related functions. The 5GS network function support
information element that registers to receive messages deserves to be mentioned
in more detail. This information element (IE) contains indicators such as
support for "IMS packet-switched (PS) voice session for 3GPP access", "non-
3GPP voice support", "emergency call service" or "emergency call reservation
support", and whether to support the presence or absence of network interface
N26. In the figure 4.4 below, the registration process focuses only on voice-
specific control information. More detailed information about the NAS
registration procedure is provided in TS 24.501.
TS 23.501 defines some interworking scenarios between 5GS and EPC and
provides more information about N26 and other interfaces. S1 mode means EPS
connection is successful, N1 mode means 5GC connection is successful. The
definition in TS 24.501 is that in N1 mode, the UE accesses the 5G core
network through the 5G access network. Single or double registration means
that the mobile status is processed at the same time. In single sign-on mode,
there is only one mobile state active at any one time. The UE remains in 5GC
NAS mode or EPC NAS mode. Regarding the UE identifier [ . [Figure 20],
during the movement between EPC and 5GC, the UE maps the globally unique
temporary ID EPC (EPCGUTI) to 5GGUTI. As mentioned above, if the
network supports the N26 interface, the UE will maintain the 5G context, such
as IP address allocation, for reuse when moving from 5GC to EPC. To interact
with the EUTRAN connected to the EPC, UEs that support both S1 mode and
N1 mode can work in single registration mode or dual registration mode. For
UEs that support both S1 mode and N1 mode, the first mode (single registration
mode) is mandatory. The dual registration mode requires the UE to
independently process 5GMM and EMM contexts at the same time. In this
mode, the UE independently maintains the identifiers 5GGUTI and EPCGUTI.
The UE can use the corresponding GUTI to perform a new 5GC or EPC
registration/TAU.
Initially, IMS was an all-IP system designed to help mobile operators cost-
effectively provide next-generation interactive and interoperable services on an
architecture that provides Internet flexibility.
Session Initiation Protocol (SIP) was selected as the IMS signalling mechanism,
allowing voice, text, and multimedia services to traverse all connected
networks. 3GPP works closely with IETF experts to ensure maximum reuse of
Internet standards and avoid fragmentation of IMS standards. For more
information on the general aspects of IMS, see TS 22.228 and TS 23.228.
Since 5G voice service is not mandatory for the UE and the network, 3GPP has
agreed a general implementation and training strategy to ensure the normal
operation of the voice service when it is provided. The GSM Association
(GSMA) has issued a permanent erence document [ . 8] to define a
configuration file using the minimum set of mandatory features defined in the
3GPP and GSMA specifications. Wireless devices and networks must
implement these features to ensure high-quality, interoperable IMS-based
communication services for voice, video, and messaging are delivered over 5GC-
connected Next Generation Radio (NG) access.
The network that provides voice services in 5GS must support IMS with the
following functions:
► Tell the UE if it should support voice sessions over IMS PS ► The ability to
transfer the address of the call session control function Proxy (PCSCF) to UE
► IMS
Initiated Session
serves the Public Land Mobile Network (PLMN) AMF should send an
indication to UE via 3GPP access during registration process to indicate if IMS
voice sessions are compatible with 3GPP access and non-3GPP access. The UE
usage setting applies to UE with voice capabilities in 5GS and indicates whether
the UE p ers voice services or data services. When the UE chooses to use the
setting as "voice-centric", this includes the IMS voice. When the UE chooses to
use the setting as "data centric", the data service includes any type of user data
transmission without voice media components (TS 24.501).
Mobile devices providing voice services on 5GS must support the IMS
functions required by the Gm and Ut benchmarks. The Gm erence point
supports communication related to session registration and control between UE
and IMS. The Ut erence point helps to manage subscriber information related
to services and configurations [ . 9]. To ensure the normal operation of IMS-
based services, 3GPP and GSMA recommend a set of 11 common IMS
functions that should be supported. More details can be found in [ . 8].
1. SIP registration
UE needs to register with IMS via the SIP protocol, and must support and
implement certain aspects of this registration process:
► Two separate IMS registries use different APN / DNNs, each of which
supports a subset of IMS services. The app can register with IMS at IMS APN /
DNN and at the same time register with Home Operator Service (HOS) APN /
DNN to combine voice services with Rich Communication Services (RCS).
This depends on the RCS VoLTE single register parameter [ . 10] and applies
if at least one of the rich calling services based on the RCS messaging service or
the Message Session Relay Protocol (MSRP) is enabled. If this parameter is set
to zero, the UE processes two separate IMS records. If set to 1, the UE uses a
single record. If set to 2, if the UE is registered in the home network, the only
IMS registration is used; otherwise, it processes two IMS records.
► SIP registration procedure. The UE and IMS network must follow the SIP
registration process defined in TS 24.229. To protect privacy, the UE should
include the user part in the contact address URI, so that the user part is globally
unique and does not reveal any private information. Note that the UE can
perform two separate IMS registration procedures for the default DNN
► Register in IMS with specific services. During the registration process, if the
UE registers for the MMTEL service, the UE will display information related to
the service, such as the IMS Communication Service Identifier (ICSI), to
indicate IMS multimedia phone and multimedia feature labels, such as "audio"
or "video." Similar information disclosure is defined as services such as SMS,
call editor, or RCS (see [ erence 8]).
2. Identity verification:
To ensure secure access to the network, IMS also requires verification of the
identity of the device and the user. GSMA requirements in [ erences]. 8] It
implies the support of two authentication mechanisms (IMSAKA defined in TS
33.203 or SIP authentication through the summary method defined in GSMA [
erence 10]) and provides more details and requirements for these authentication
procedures. The last authentication method includes mandatory UE and optional
network support for HTTP content server authentication. Protecting the integrity
of the network and the UE is mandatory, while protecting the confidentiality of
SIP signalling is optional for the network, depending on whether radio link
layer security is enabled.
3. Addressing
Regarding IMS call processing parameters, 5G needs the same strategy as LTE,
TS 24.229 defines the exact details. Optionally, domestic operators can
configure a timer for the UE to estimate the round-trip time (T1), the maximum
retransmission time of INVITE responses (T2), or the maximum duration of
messages in the network (T4) (see TS 24.167). The slight difference is that
when the connection is terminated by a CANCEL or BYE message, the UE
includes the reason information as the reason. If available, the UE shall insert
Paccess network info [ . 8]. To take advantage of user availability, some
connection extensions and modification services are also required. For example,
the UE and the network should be able to add video calls to the voice session by
transmitting SDP messages during session establishment. If available, the UE
must support the service provided by the MMTEL call combiner and the RCS
message service defined by GSMA [ erence. 10].
6. Initial Media and Notification UE must support the reception of voice and
video media related to the initial dialogue, for example. When the SIP 180
message follows the SIP INVITE, and the UE must support the Pearly media
header field. TS 24.628 provides more details on how the UE presents the
locally generated communication progress information.
7. Fork
As a reminder, SIP fork represents a mechanism for dividing SIP calls into
multiple clones of multiple endpoints. This increases usability, for example an
incoming call can ring at multiple endpoints at the same time. With SIP
branching, your desk phone can ring simultaneously with your softphone or SIP
phone on your mobile device. The fork of the
network is determined by the operator. For reasons of interoperability and
forward compatibility, the UE must be prepared to receive the response
generated by the fork request and operate according to the procedures specified
in TS 24.229. In addition, the UE should be able to maintain at least 40 parallel
early conversations until a final response is received in one of the early
conversations, and the UE should support media reception in one of these early
conversations [ erence 8].
8. Signalling Compression
[ . [8] indicates that when the initial IMS registration is completed on the 5G
RAN, the UE should not use methods such as Signaling Compression
(SIGCOMP).
To enable connection flow and handle unexpected timeouts and timeouts, the
UE must handle the session timeout timer during the INVITE process, such as
RFC 4028 [ . 15].
Like traditional networks, the upper layers describe voice services and other
applications such as Multimedia Telephony Services (MTSI) or MMTEL. We
define them in TS 26.980. Voice or video is an application layer that is
transmitted through the User Datagram Protocol (UDP) / IP protocol through
the Real Time Protocol (RTP) [ . 13]. In this protocol layer view, the RAT
layer can be EUTRAN on VoLTE or 5G NR on VoNR. Besides transmitting
audio visual content via RTP, the Real Time Control Protocol (RTCP) also adds
additional information about the corresponding RTP stream, such as the
calculated jitter value. IMS uses RTP as a media transmission protocol
independent of the radio layer. RTP and RTCP are in IETF RFC 3550 [ . 13].
The primary purpose of RTP is to allow the receiver to play the received media
at an appropriate rate, because IP networks will introduce delay and packet loss
and jitter. For example, if two IP packets are sent to the same destination with a
delay of 10 milliseconds, there is no guarantee that these two packets will also
reach the destination with a delay of 10 milliseconds. IP packet number 2 can
arrive immediately after packet number 2.1, or later or even earlier. The RTP
timestamp is used to restore the correct time relationship between the IP data
packets.
Since voice or video can be run using streaming media services, the Internet
Engineering Working Group (IETF) is a network control protocol in RFC 2326
[ . 19] designed for entertainment and communication systems to control
streaming media servers. The transmission of streaming data itself is not the job
of RTSP. Most RTSP servers combine RTP with the RTP Control Protocol
(RTCP) for streaming media. In the control plane, there are two main protocols,
namely SIP and Session Description Protocol (SDP). Since some SIP messages
can be transmitted through an IPsec tunnel, an optional IP key exchange (IKE)
can be additionally performed.
This section describes the PDU session details related to IMS connection
configuration. First, we assume that the UE has registered and established a
5GMM context as a prerequisite. The PDU session establishment message is
transmitted to the AMF through the uplink non-access layer transport container
message (UL NAS). Here, the parameter message type indicates the NAS
message PDU session establishment request as the initial request, and the DNN
is set as the name of the corresponding IMS network. SMF connects to IMS, so
the PDU session establishment request contains parameters indicating the IMS
connection request (see TS 24.501). For example, the SSC mode should be set
on the request for SSC mode 1 by the UE. The PDU IE session type shows
whether the UE p ers IPv4 or IPv6 addresses, or one of the two. In the 5GSM
capability, the UE should indicate support for S1 mode and lected QoS. Using
the extended protocol configuration option (PCO), the UE can indicate that an
IMS session should be established (TS 24.008). If the UE establishes a PDU
session for the IMS and the UE is configured to discover the PCSCF address
during connection establishment, the UE must include an indicator in the
Session Management Container (SM) IE (TS 23.502) that it is requesting the
PCSCF IP address. Upon success with establishing a PDU session, the network
responds with the configuration of the PCSCF address in the session
establishment acceptance message, and the network uses the QoS flow 5QI = 5
that inherits the IMS signalling QoS profile to activate the PDU session. IMS
support is clearly a prerequisite for VoNR.
From a protocol layer perspective, the EPS fallback scenario is shown in Figure
4.6. First, the UE camps on 5G NR and establishes a 5G connection. 5GC
provides at least one SIP control connection to recognize that the UE requests a
voice connection. The connection is moved from 5G NR to EUTRA through
rerouting or switching procedures.
The advantage of EPS reservation is that UE or NodeB (gNB) only needs to
support IMS signalling channel (SIP over NR, low real-time requirements) and
does not need to support IMS voice / video communication channels (RTP or
RTCP over NR, high requirements in real time)). and the network. RTP or
RTCP over NR requires lower latency and better 5G NR radio coverage [ .
two]. The ore, it can be considered as an intermediate step to provide VoNR,
depending on the maturity of the equipment backup solution Once all the
necessary voice functions are installed on the network, the migration to VoNR
can be completed. When inputting NR voice, the device input before this step
will still be on site. The capabilities of these devices will determine whether
these devices use NR voice or continue to rely on EPS support. The ore, the
network will support NR voice, including EPS support [ . 1] for a long time.
Figure4. : EPS
When attempting to establish a QoS flow for voice media on NR during call
setup, NGRAN used to establish a QoS flow to SMF and indicated that the
move was in progress.
If the UE has at least one PDU session to support session continuity during
interworking, the UE performs the tracking area update process, i.e., the UE has
an EPS bearer ID and QoS parameters mapped EPS.
If the UE does not register a PDU session in the 5GC, or the UE only registers a
PDU session and does not support session continuity during interworking with
the EPC, the UE performs the initial connection procedure, and the UE or EPC
does not support attaching a PDN connection.
When the UE is served by 5GC, the UE has one or more PDU sessions in
progress, and each session includes one or more QoS flows. The serving PLMN
AMF sends a sign to support the IMS Voice over PS session to the UE during
the registration process, triggering the IMS registration. During this registration
process, the network will show whether it supports the N26 interface. The
signalling flow of EPS backhaul is shown in Figure 4.8 (TS 23.502):
interface and configure the QoS flow to 5QI=1 to make the voice reach
NGRAN.
3. NGRAN is configured to support EPS support for IMS voice and decides to
enable EPS support, considering the capabilities of the UE. During the initial
context configuration (TS 38.413), AMF indicated that "EPS backup voice can
be redirected". In addition, it provides network settings (such as N26
availability) and radio conditions. NGRAN can initiate measurement report
requests from UEs, including EUTRAN as a target.
4. NGRAN establishes a QoS flow for the IMS voice received in step 2
indicating the rejection of the PDU session modification and sends a response
message to the PDU session modification to PGWC + SMF via AMF and
indicates that mobility due to IMS voice reservation is in progress.
5. Considering the capabilities of the UE, NGRAN initiates the access network
handover or release (AN release) through inter-system redirection to EPS.
6. 6a. In the case of the transfer from 5GS to EPS and in the case of redirecting
to EPS with N26 interface between systems, the UE initiates the monitoring
area update process (TAU).
Figure4. : EPS
The IMS registration process in step 4 provides some specific voice details.
Like a general IMS session, the network assigns an IP address for the UE and
informs the PCSCF of the address. SIP REGISTRAR and SUBSCRIBE
signalling messages contain the main access network information (PANI)
[ erence. 16] Such as "3GPPNRFDD" or "3GPPNRTDD" and the SIP
definition of cellular network, with parameters such as mobile country code
(MCC), mobile network code (MNC), tracking area code (TAC) and NR cell
identity (NCI) (TS 24.229). In the above example, the UE is registered in IMS
via 5G; the ore, the length of TAC is 6 hexadecimal digits (for example, the
length in LTE is 4), and there is also NCI. The UE requests the establishment of
a voice call based on the Enhanced Voice Service (EVS) audio codec through
the SDP. To indicate the pending response, IMS sends a session 183 in progress
message. During the dedicated QoS flow establishment and resource
reservation, since VoNR cannot be established, 5GC decides the EPS
reservation of the voice call. The decision is based on the UE's earlier request
for EPS rollback or triggered due to lack of VoNR support for 5GC. The ore,
NRRAN initiates the release of the radio resource control (RRC) connection
(via the RRC Release command or transfer request) and redirects to the
EUTRAN information to return to EPS. In our example, we assume that the
N26 interface is compatible between 5GC and EPC. This enables the TAU
process and the continuation of the DNN and IMS PDU session; the ore, the
UE and PCSCF IP addresses are reserved. In the TAU message, several
parameters are set to specific values: the field containing the oldGUTI is set to
the value "5GGUTI", and the EPS bearer status is set to "Internet and IMS
PDU" as description and "active" as status information. Through the SIP
REREGISTER message, the UE sets the new PANI equal to
"3GPPEUTRAFDD" as the new network access identifier. The last step 6 of
this call establishment process is to establish a voice bearer that inherits QCI =
1. As an example of a real message record, the following figure contains two
excerpts from the signalling procedure of the EPS reservation scenario using the
R & S®CMX500 radio communications tester [ erence]. twenty-four]. First,
the message on the right indicates the establishment of a PDU session. The
excerpt provided here actually indicates two PDU sessions: one with default
5QI and the second with IMS signalling 5QI details. Through the RRC message
(not shown in this excerpt), the 5G NR network triggers the RC RC Release
message with a redirect indication to EUTRA.
the RAT backup procedure can be used to trigger RAT changes (not necessarily
EUTRA, because RAT changes from NR to NR are also possible). The
prerequisites are like the EPS reservation scheme; the UE is served by 5GC and
there are one or more PDU sessions in progress, with each session including one
or more QoS flows. The PLMN AMF service indicates support for the IMS
Voice over PS session during the registration process and activates the IMS
registration. The following figure shows the message flow.
2. The network initiated PDU session is modified and the QoS flow is
established so that the IMS voice reaches the NGRAN source through the N2
interface.
Figure4. : IMS Voice RAT Delay
3. If the source NGRAN is configured to support RAT support for IMS voice,
the source NGRAN decides to enable RAT fallback, considering UE
capabilities, network configuration, and radio conditions. To ensure reliable
mobility scenarios, the source NGRAN can initiate measurement report requests
from UEs that include the destination NGRAN. 4. The source NGRAN
responds with a PDU session response message to SMF via AMF indicating the
rejection of the PDU session modification to establish a QoS flow for the IMS
voice and indicates that the mobility due to IMS voice reservation is ongoing. 5.
Initiate NGRAN to initiate Xn-based handover between NGRAN or N2-based
handover or redirection between NGRAN and EUTRA connected to 5GC.
Voice processing requires that both NR and UE support the QoS flow of the
wireless access voice, that is, the establishment of the QoS flow must be
supported by gNB. VoNR QoS considers non-GBR voice or video QoS
transmissions that support conversational voice and video, IMS signalling, and
MSRP services. It is worth mentioning that the UE can have two IMS registers
according to the configuration of the RCS support parameters .To meet the
voice gap KPI and avoid dropped calls, a certain relationship and
interconnection between 5GS and EPS needs to exist to support mobile
scenarios, that is, the traditional handover between systems from VoNR to
VoLTE. Although
Optionally, if the UE wants to change the QoS rules, it can request PDU session
modification. Based on the selected media or voice or video codec, the network
sends a complete session modification with negotiated QoS parameters, and the
UE will confirm with a complete modification message. Following these QoS
and media configuration protocols, the UE and UPF use the agreed audio or
video codec on the N3 interface to initiate a user plane data session.
-strong header compression method. One function provided by the PDCP layer
is RoHC defined in TS 38.323. At least the UE and the network must support
the "RTP / UDP / IP" configuration file (0x0001) to compress RTP packets and
the "UDP / IP" configuration file (0x0002) to compress RTCP packets. The UE
and the network must support these profiles for IPv4 and IPv6 address
assignment.
Radio bearer: To support 5G voice and video services, the UE and the network
establish signalling and data radio bearers with specific QoS profiles. The RLC
layer provides transmission services in recognized mode (AM) and
unrecognized mode (UM). For the transmission of IMS signalling, the UE and
the network establish an AM data radio bearer (DRB) with 5QI = 5. An
additional AM DRB and 5QI as one of the 6/7/8/9 values are likely to be set for
non-guaranteed bit rate (non-GBR) services at the same time. Depending on
whether the service is voice or video recommended by 3GPP, the UE and the
network configure the UM DRB to 5QI = 1 for voice and/or 5QI = 2 for video.
One suggestion to avoid timeouts is to let NGRAN set a discard Timer (discard
Timer) for IMS and set DRB to an "infinite" value.
1 or 2 IMS registration:
UE PDCP must support RTP and RTCP RoHC compression and the UE MAC
layer will support DRX.
Optionally, for RCS service support, the UE can register with the IMS DNN of
the Home Operator (HOS) at the same time. We can use the second QoS flow
using the same 5QI for home operator specific HTTP signalling messages with
XCAP or HTTP content. According to the service, [ erence. 8] We recommend
that 5QI = 1 for voice, 5QI = 2 for video, and 5QI = 6 to 9 for non-GBR voice /
video. Note that emergency services and conversational voice share the same
QoS flow. A detailed description of other IMS signalling parameters and
characteristics for voice services can be found in [ erences]. 8].
Option 3 ENDC is the implementation of NSA in 5G. The ore, the LTE
connection is mandatory. With this option 3, the EUTRA and EPC core
networks support voice services. According to TS 37.340, the primary cell
group (PCG) (or primary carrier) supports the LTE PDCP or NR PDCP protocol
layer. The ore, there are two ways to implement voice services in Network
Option 3 mode: Traditional VoLTE or Enhanced VoLTE using NR PDCP
. The following figure simplifies these voice service implementations; only the
logical voice flow is described, and the coded voice is summarized as user plane
data and SIP signalling. Dual connectivity between LTE and 5G is only
described symbolically. The advantage of this voice implementation is that it
does not require any upgrades to the existing voice support infrastructure,
except for the slight transition from PDCP to NR PDCP.
The focus of this section is on the speech codec. Other popular modern cellular
communication systems include video communication. This requires support
and definition of video codecs. In TS 26.114, 3GPP stipulates those networks
and UEs supporting Video over NR (ViNR) services must support IUT
Recommendation H.264 as a video codec. There are multiple video codecs, and
due to their evolution, GSMA has issued a list of requirements. To ensure
interoperability, these video codecs must be compatible with the UE [ . 8]:
4.10.2 SMS in 5G
The concept of short message service (SMS) introduced in the early days of 2G
is still an important use case for 5G. There are two ways to transmit SMS
messages through 5G access (like LTE). The first method is to use IMS as SMS
(SMSoIP) on the IP of the management and coordination network to ensure
correct data transmission. The second method is SMS over 5G NAS
(SMSoNAS), which is a method of encapsulating SMS data containers in 5G
control messages. In SMSoNAS, initiated and terminated SMS messages are
transmitted between UE and AMF through NAS messages. According to [ . 8],
for UEs claiming to be SMS capable, both SMS transmission methods are
mandatory, and the network can choose which options to provide. For the sake
of completeness, we must mention that it is also possible to transmit short
messages through the RCS message service, but this is not the focus of this
section. The Short Message Service Function (SMSF) is defined in 5GS, which
is used to use the traditional MAP transmission protocol or Diameter [ . 12] It
is used for SMS exchange between UE and SMS Service Center (SMSSC). In
SMSoIP, an SMS Service Gateway for SMS over IP (IPSMGW) must exist to
start and end SMS. The IPSMGW can also perform the MT domain selection
for other accesses (4G, 3G, 2G), and the transmission of SMS between
5GS UE support voice should support SMS on NAS and SMS on IP, and each
operator can freely decide whether to support SMS on NAS, SMS on IP or both.
These SMS solutions can be used in combination or in the case of EPS backup
for voice [ . 1]. During the 5GS registration process, the UE includes an
indication of "SMS support" in the registration request, indicating the ability of
the UE to transmit SMS via NAS. TS 23.502 provides more detailed
information about the registration process and various SMS connection
scenarios involving MS messages initiated or terminated on the mobile device
when the UE is in the CM_IDLE or CM_CONNECTED state.
Figure4. : SMS in 5G [ . 1]
By way of example, the message flow for a mobile originating SMS over NAS
in the CM_IDLE state is illustrated in Figure4.25. The main function applied to
the 5G system is the short message service function (SMSF). This represents the
5G function that provides the ability to deal with SMS and interconnect to the
legacy SMS interworking MSC (SMSIWMSC). The SMSIWMSC ensures
delivery of the SMS to the endpoint regardless of the RAT of the destination
UE.
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