Advanced Mobile Phone System (AMPS)

AMPS facts
• Analog FM modulation
• RF bandwidth 30 kHz. The band can accommodate 832 duplex channels, among which 21 are
reserved for call setup, and the rest for voice communication.
• Frequency allocated by FCC on 824-849 MHz for downlink and 869-894 MHz for uplink traffic.
• Uses the same system throughout the US
• Available in U.S., Canada, Hong Kong, New Zealand, Thailand
• A narrowband versus exists with a 10 kHz channel spacing, such that 2496 channels can be
assigned, in stead of 832 for the normal AMPS mode.

Digitization of AMPS
The uniformity of the analogue AMPS system throughout the US highly contributed to its success of
capturing 2/3 of the analog cellular subscribers worldwide. Around 1995, AMPS had an estimated 13
Million subscribers in the U.S.. US manufacturers and operators have been divided about the operational
merits of various technologically advanced options for radio channel access and digital modulation, in
particular the choice between Code Division Multiple Access (CDMA) and Time Division Multiple
Access (TDMA) transmission formats for cellular telephony. For the migration towards all-digital
operation, the objective of the Federal Communication Commission (FCC) has been to introduce a digital
system that was fully compatible with the existing analog AMPS system, i.e., the FCC was looking for a
new system that uses the same radio spectrum as the old analog system, but at least ten times more
efficient in spectrum use. By 1988, the Cellular Telecommunications Industry Association (CTIA) defined
a full set of User Performance Requirements (UPR).

Two different solutions have come up. US cellular network operators are implementing a narrowband
TDMA version of AMPS, known as IS-54. Meanwhile, the Californian company Qualcomm promotes a
CDMA concept, presenting scientific and experimental evidence to academic fora about the technical
superiority of CDMA over TDMA. Experimental CDMA systems are in operation in several cities, based
on the IS-95 standard. Expectations are that AMPS product shipments reached its top in 1996 with
Motorola, Nokia, NEC and Ericsson dominating the market. Digital systems including PCS are expected
to become cost effective with analog AMPS in the time frame 1997-2000.

PCS: AMPS 1900

A 1900 MHz version of AMPS has been developed, which allows dual-band/dual-mode 800/1900 MHz
systems. It allows operators to provide identical PCS applications and services in both bands. Seamless
inter-working between 800 and 1900 MHz networks is possible through dual-band/dualmode mobile
stations. Subscribers on a D-AMPS 1900 channel can handoff both to/from a D-AMPS channel on 800
MHz as well as to/from an analog AMPS channel.
Existing 800 MHz D-AMPS operators can use the 1900 MHz spectrum to increase capacity and develop
new user segments in their 800 MHz networks. For example, 800 MHz cells can provide wide-area
coverage (through macro-cells) and act as umbrellas for 1900 MHz micro- and picocells. The small cells
can cover the indoor office environment, shopping malls, airports and hot spot coverage. The umbrella
cells would carry the signals for fast-moving subscribers and fill in gaps in between two isolated
microcells.

D-AMPS 1900 mobile phones will be marketed initially in single-band 1900 MHz as well as dual-band
800/1900 MHz versions. In the long run, dual-band versions may prove themselves able to replace single-
band versions at both 800 and 1900 MHz.

AMPS Network Layout

The D-AMPS 800/1900 system architecture is similar to most other cellular system architectures (e.g.
GSM network architecture). It contains a Switching System, an Operation and Support System, base
stations and mobile station.

The switching system

The Switching System contains five main functional entities:

• The Mobile Switching Center (MSC) performs the telephony switching functions for the network.
It controls calls to and from other telephone and data communications networks such as Public
Switched Telephone Networks (PSTN), Integrated Services Digital Networks (ISDN), Public Land
Mobile Networks (PLMN) and Public Data Networks.
• The Visitor Location Register (VLR) database contains all temporary subscriber information
needed by the MSC to serve visiting subscribers who are temporarily in the area of the MSC.
• The Home Location Register (HLR) database stores and manages user subscriptions. It contains all
permanent subscriber information including the their service profile, location information and
activity status.
• The Authentication Center (AC) supports authentication and encryption functionality. It verifies
the user’s identity (by authitication) and ensures the confidentiality of each call (by encryption) .
This protects network operators against fraud.
• The Message Center (MC) supports messaging services.

The base station

The Base Station is the radio equipment needed to serve each cell in the network. One base station site
may serve more than one cell.

The Operation and Support System

The Operation and Support System supports operation and maintenance activities in the network to allow
for reliable and cost-efficient operation.

The mobile station

IS-54 and IS-136 (Digital AMPS)

IS-54 is the standard for the digital version of the US AMPS system. Recently IS-54 has been replaced by
the IS-136 standard. The system uses and hybrid Frequency Division Multiple Access and Time Division
Multiple Access concept as it accepts 3 users per carrier. The carrier spacing 30 kHz, similar to the analog
AMPS. Thus, assuming that the analog and digital system use the same frequency reuse pattern, the digital
version can accommodate three times more users. In terms frequency planning the digital system behaves
similar to analog AMPS. Carrier frequencies are in the 800 and 1900 MHz bands.

Although the digital system has advantages for the operator, marketers found it difficult to convince
subscribers to go digital, i.e., to buy a new phone. The advantages of improved security in a digital system
were intentionally not used, to avoid that subscribers would be alerted that the analog AMPS system had
less security.

Radio Aspects
• Channel bit rate 48.6 kbit/s
• Frame duration 40 ms, divided into six 6.67 ms slots. If follows that for usual carrier frequencies,
on the average one fade per bursts occur. See Spreadsheet v = 27 m/s, fc = 1900 MHz, fade margin
6 .. 10 dB)
• Each slot: 324 bits, 260 user data
• Full rate and half rate codebook excited linear predictive coding:
Vector Sum Excited Linear Prediction (VSELP)
Source rate 7.95 kbit/s, transmitted at 13 kbit/s
• Differential QPSK (not constant envelope: power penalty) pi/2 shifted, root cosine roll-off
filtering, roll-off factor 0.35
• 1.62 bit/s/Hz
• Idle voice channels can be used for CDPD packet data transmission.
• Equalization was initially not included in the standard, but appears useful for delay spreads larger
than T/8, with T the symbol time. This corresponds to delay spreads of a few microseconds.

EXTENDED AMPS
• Proposed by Hughes
• Digital Speech Interpolation (DSI): Speech pauses are exploited to enhance user capacity.
Typically speech activity is about 0.4. Compare with PRMA.
 • Frame of six slots; dynamically assigned to different users Example of DSI performance:
o No DSI: E-AMPS has 6 times capacity of analogue AMPS
o DSI on 1 RF carrier: 6 times analogue
o 3 RF carriers: 7 times analogue
o 8 RF carriers: 9 times analogue
o 19 RF carriers: 11 time analogue
o Many RF carriers: Law of large numbers:
o ultimately 6 / 0.4 = 15 times analogue AMPS
• DSI in forward link: multiplexing
DSI in reverse link: random access: throughput loss because of collisions
• Slow frequency hopping: mitigates effect of fading

Generations of Mobile Wireless Technologies

Mobile wireless industry has started its technology creation, revelution and evolution since early 1970s. In
the past few decades, mobile wireless technologies have experience 4 or 5 generations of technology
revolution and evelution, namely from 0G to 4G. The cellular concept was intoduced in the 1G technology
which made the large scale mobile wireless communicaton possible. Digital communication has replaced
the analogy technology in the 2G which significantly improved the wireless communication quality. Data
communication, in addition to the voice communication, has been the main focus in the 3G technologies
and a converged network for both voice and data communication is emerging. With continued R&D, there
are many killer application opportunities for the 4G as well as technological challengies. We briefly listed
all the key technologies and protocols used in each generation of the mobile wireless communications in
th following table.

0G 0G refers to pre-cellular mobile telephony technology in 1970s. These mobile telephones

were usually mounted in cars or trucks, though briefcase models were also made.
PTT Push to talk
MTS Mobile Telephone System
IMTS Improved Mobile Telephone Service
AMTS Advanced Mobile Telephone System
0.5G 0.5G is a group of technologies with improved feature than the basic 0G technologies.
Autotel/PALM Autotel, or PALM (Public Automated Land Mobile)
ARP Autoradiopuhelin, Car Radio Phone
HCMTS High Capacity Mobile Telephone System
1G 1G (or 1-G) is the first-generation wireless telephone technology, cellphones. These are
the analog cellphone standards that were introduced in the 1980s.
NMT Nordic Mobile Telephone
AMPS Advanced Mobile Phone System
TAGS Total Access Communication System (TACS) is the European version of AMPS.
JTAGS Japan Total Access Communication System
2G 2G (or 2-G) is the second-generation wireless telephone, which is based on digital
technologies. 2G networks is basically for voice communications only, except SMS
messaging is also available as a form of data transmission for some standards.
GSM Global System for Mobile Communications
iDEN Integrated Digital Enhanced Network
D-AMPS Digital Advanced Mobile Phone System based on TDMA
cdmaOne Code Division Multiple Access technology defined by IS-95
PDC Personal Digital Cellular
TDMA Time Division Multiple Access
2.5G 2.5G is a group of bridging technologies between 2G and 3G wireless communication. It
is a digital communication allowing e-mail and simple Web browsing, in addition to
voice.
GPRS General Packet Radio Service
WiDEN Wideband Integrated Dispatch Enhanced Network
2.75G 2.75G refer to the technologies which don't meet the 3G requirements but are marketed
as if they do.
CDMA2000 CDMA-2000 is a TIA standard (IS-2000) that is an evolutionary outgrowth of cdmaOne.
1xRTT CDMA2000 with 1xRTT is slight weaker than 3G requirements.
EDGE Enhanced Data rates for GSM Evolution
3G 3G stand for the third generation of wireless communication technologies, which support
broadband voice, data and multi-media communications over wireless networks.
W-CDMA Wideband Code Division Multiple Access
UMTS Universal Mobile Telecommunications System
FOMA Freedom of Mobile Multimedia Access
CDMA2000 More advanced CDMA2000 with 1xEV technology satisfy 3G requirements.
1xEV
TD-SCDMA Time Division Synchronous Code Division Multiple Access
3.5G The 3.5G generally refer to the technologies beyond the well defined 3G wireless/mobile
technologies.
HSDPA High-Speed Downlink Packet Access
3.75G The 3.75G refer to the technologies beyond the well defined 3G wireless/mobile
technologies.
HSUPA High-Speed Uplink Packet Access
4G 4G is the name of technologies for high-speed mobile wireless communications designed
for new data services and interactive TV through mobile network.
3G: Third Generation Wireless Technologies and Services
Third Generation Wireless(3G) contains a group of standards to support broadband voice, data and multi-
media communications over wireless networks. IMT-2000, the 3G standards developed by ITU, will
specify no less than five means of multiple access – CDMA2000, WCMA, a time division duplex version
of WCDMA, 136HS (based on the UWCC's recommendation), and Digital Enhanced Cordless Telephone
(DECT). The "family of standards" will be required to interoperate with both GSM MAP and IS-41
networks. Namely, the WCDMA specification will be required to allow interconnection with IS-41 and
CDMA2000 will be required to interface with GSM MAP.

Currently, the second generation (2G) of wireless networks, such as GSM, CDMA (IS-95) and TDMA
(IS-136) networks, are widely used in the wireless communications. The 2G networks can provide narrow
band (up to 144kbps) voice and data services using circuit switching techniques. To conduct a smooth
evolution from the 2G to 3G wireless networks, some transitional technologies, such as GPRS for GSM,
136 high-speed for TDMA or IS-95B for CDMA, are defined, which are sometimes called 2.5G wireless
technologies.

The following table lists the comparison and evolution of Wireless Systems from 1G, 2G to 3G:

1G 2G 3G
System Analogue Digital Digital
Major AMPS, NMT and WCDMA, CDMA-2000 and
GSM, CDMA and TDMA
Systems TACS TD-SCDMA
Application Voice Voice + little Circuit- switch Data Voice + Packet-switch Data
Local
Less than 500k About 5.9M More than 5M (Estimated)
Subscriber
Depends on Analogue 384kbps for mobile & 2Mbps
Speed 9.6kbps - 14.4kbps
Signal for stationary
More secure, data services
Unstable, incomplete Multimedia data, positioning
available, broader coverage, more
Properties coverage and poor capability, connection to
stable, allow more user, better
sound quality Internet, always connected
sound quality
3G: Third Generation Wireless Technologies and Services