McGraw Hill - 2002 - W-CDMA and cdma2000 for 3G Mobile Networks_5 potx

Because the ward traffic channel associated with this pilot is no longer usable,the base station sends a release request to the MSC, which forwards for-Chapter 4136 Pilot added to candid

message to the base station that uses this particular pilot (that is,the target base station) The target base station may then proceed tojoin the handoff process and thus exchange necessary messages with

the MSC The mobile station receives the Direction message at t3,transfers that pilot to the active set, properly updates the candidateset as well, and sends a Handoff Complete message to the primarybase station

From instant t3, the mobile station continues in the soft handoff

state At instant t4, when the signal level of an active pilot begins tofall below the pilot drop threshold T_DROP, a timer with a fixedtimeout setting is started If the signal begins to improve back again

so that it exceeds T_DROP, the timer is stopped and reset, indicatingthat this pilot will continue to be active If, however, the timer

expires at instant t5, and if the signal remains below the threshold

for the entire duration from t4 to t5 as indicated in the figure, themobile station sends a pilot strength measurement message to theprimary base station

On receiving the message, say, at instant t6, the base station sends

a Handoff Direction message to the mobile station Because the ward traffic channel associated with this pilot is no longer usable,the base station sends a release request to the MSC, which forwards

for-Chapter 4136

Pilot added to candidate set BTS sends handoff message Pilot moved to active set

Drop timer started Timer expires, MS sends measurement data BTS sends handoff message

Pilot moved to neighbor set

Figure 4-7

Soft handoff in

IS-95

it to the target base station as part of the process to drop it from thesoft handoff.

The mobile station receives the Handoff Direction message at

time t7, removes the pilot from the active set, adds it to the neighborset, and sends a Handoff Complete message to the base station.CDMA allows for an idle handoff as well If a mobile station, while

in the idle state, detects a pilot channel from another base station to

be significantly stronger than the pilot channel of the current basestation, it may decide to initiate a handoff

cdma2000 System Features

Traffic Types Broadly speaking, cdma2000, like all other 3G nologies, is expected to support the following types of traffic Thedata rates may vary from 9.6 kb/s to 2 Mb/s:

tech-■ Traditional voice and voice over IP (VoIP)

■ Data services

■ Packet data These services are IP-based with the

Transmission Control Protocol (TCP) or User Datagram Protocol (UDP) at the transport layer Included in this category

are the Internet applications, H.323-type multimedia services,and so on

■ Circuit-emulated broadband data Examples of this kind oftraffic include fax, asynchronous dial-up access, H.321-basedmultimedia services where audio, video, data, and control andindication are transmitted using circuit emulation over

Asynchronous Transfer Mode (ATM), and so on.

In addition, there are, of course, signaling services

3G systems are intended for indoor and outdoor environments,pedestrian or vehicular applications, and fixed environments such as

wireless local loops Cells sizes may range from a few tens of meters(say, less than 50 m for picocells) to a few tens of kilometers (inexcess of 35 km for large cells).

Bandwidth A cdma2000 system may operate at different widths with one or more carriers In a multicarrier system, adjacentcarriers should be separated by at least 1.25 MHz as shown in Fig-ure 4-8(a) In an actual multicarrier system, each individual carrierusually has a bandwidth of 1.25 MHz and is separated from an IS-

band-95 carrier by means of orthogonal codes However, when three riers are being used in a multicarrier system, the bandwidthrequired is 5 MHz To provide high-speed data services of the typediscussed previously, a single channel may have a nominal band-width of 5 MHz as indicated in Figure 4-8(b) with a chip rate of3.6864 Mc/s (that is, 3  1.2288 Mc/s).5The bandwidth BW in Fig-

car-ure 4-8(b), outside of which the power density is negligible, depends

Chapter 4138

BW

5 MHz

1.25 MHz 1.25 MHz

on the pulse-shaping filter at the baseband.6If a raised cosine filter

is used, BW  R c(1  a), where R cis the chip rate and a is the off factor If a 0.25, BW  4.6 MHz, and so the guard band G 

roll-200 kHz Clearly, an advantage of a wider bandwidth lies in the factthat it provides more resolvable paths that can be used in a multi-path diversity receiver to improve the system performance

Quality of Service (QoS) At any time, multiple applications mayrun on a mobile station A user may request a desired QoS depend-ing on the application, and the network is expected to guarantee therequested quality without any (noticeable) degradation in the QoScontracted by other active users

Packet Mode Data Services cdma2000 supports packet modedata services [1] Starting from an initial state, if there is a packet

to send, the user attempts to establish the dedicated and commoncontrol channels using the multiple-access slotted Aloha scheme.7In

6 Recall that the purpose of this filter is to reduce out-of-band energy at the RF stage and minimize the intersymbol interference.

7 The Aloha system is a wireless computer communication network that was oped in the late 1960s at the University of Hawaii In this system, multiple user ter- minals could access a central computer over a radio link using a random access scheme, whereby any terminal could seize the channel at any time and transmit a packet of a fixed length If there was no contention from other terminals, the central computer would receive the packet error-free, and send an acknowledgment If a user terminal did not receive the acknowledgment, it would wait for a random period of time, and retransmit the packet A terminal would repeat this process until

devel-it was successful or until devel-it had attempted three times The radio link operated in the FDD mode, where the two frequencies used were 413.350 MHz and 413.475 MHz The bandwidth in either direction was 100 kHz The data rate was 24,000 bauds.

Since this access is purely random, transmissions form two or more terminals may completely or partially overlap, thereby significantly reducing the throughput In the slotted Aloha scheme, where synchronized time slots are used for transmission pur- poses, a user can transmit only at the beginning of a slot Thus, in case of contention, transmissions from multiple users would completely overlap This approach, there- fore, improves the throughput considerably For a detailed description, see N Abram-

son, “The Throughput of Packet Broadcasting Channels,” IEEE Trans Commun., Vol.

COM-25, No 1, pp 117–128, Jan 1977.

this scheme, a reference clock is used to create a sequence of timeslots of equal duration When a user has a packet to send, it canbegin to transmit, but only at the beginning of a time slot ratherthan at any arbitrary instant of time Notice that although users aresynchronized via the reference clock, there is some probability thattwo or more users could begin to transmit at the same time.

When these channels are established, the user may send thepacket(s) over the dedicated control channel, and may also request atraffic channel of a desired bandwidth Once this traffic channel hasbeen assigned, the user transmits the packet(s), maintaining syn-chronization and power control as necessary, and releasing the traf-fic channel either immediately following transmission or after afixed time-out period If there are no more packets to send, the dedi-cated control channel is also released after a while, but the networkand link layer connections are maintained for a certain length oftime so that newly arrived packets, if any, may be sent without anychannel setup delays At the end of that time period, short, infre-quent data packets may be sent over a common control channel Theuser may either disconnect at this point, continue in this state indef-initely, or reestablish the dedicated control and traffice channels ifthere are large or frequents packets to send

Transmit Diversity One of the advantages of W-CDMA is thepossibility of transmit diversity This may be accomplished in twoways First, with a 5 MHz, direct-spread CDMA system, the userdata may be divided into two or more streams, each spread with anorthogonal code, and then transmitted to mobile stations Because

of multipath diversity, the forward channel performance mayimprove significantly Second, if it is a multicarrier system, user datastreams may be transmitted over different carriers on differentantennas (see Figure 3-5)

The Protocol Stack

cdma2000 takes the information—user data and signaling—fromthe higher layers and adds two lower-layer protocols before trans-

Chapter 4140

ferring the data over the air interface This is shown in Figure 4-9.

The link layer consists of the link access control (LAC) and media access control (MAC) layers The MAC layer is divided into two sub- layers: the physical layer-independent convergence function (PLICF) and physical layer-dependent convergence function (PLDCF) [7], [5].

The various layers and sublayers perform the following functions.Each traffic type coming from the higher layer has a different QoSrequirement in terms of delays, delay variations, and error rates Thefunction of the LAC is to ensure that various types of traffic aretransferred over the air interface according to their QoS require-

ments The link layer protocols used for this purpose include an matic repeat request (ARQ) as well as an acknowledged data transfer procedure using acknowledgment/negative acknowledgment (ACK/

auto-NACK) and sequence numbering for retransmission The MAC layeralso provides a certain degree of transmission reliability However,when it does not meet the requirements of an application, the LACmay call for an appropriate link layer procedure Notice that forsome traffic, such as circuit-switched voice, the LAC layer functionmay be null In other words, associated packets from the higher lay-ers are passed directly to the MAC layer

Packet Data

Voice over IP Voice

Circuit Data Signaling

Link Access Control

PLICF

PLDCF

Physical Layer

MAC Layer

A MAC sublayer performs the following functions:

■ It controls user access to the physical layer (that is, themedium) by resolving, if necessary, contention among multipleapplications from the same user or among multiple users, andscheduling its resources so as to ensure efficient utilization ofbandwidth Resources include buffers, spreading codes,convolutional encoders, and so on

■ User data and signaling information from the upper layers (that

is, the LAC layer and the higher layers) are multiplexed,mapped into different physical channels, and delivered to thephysical layer on a best-effort basis, providing a basic level oftransmission reliability.8

The MAC layer is divided into two sublayers:

■ Functions that are independent of the physical layer, such ascontrolling access to the medium so as transmit packets, areperformed by the sublayer called PLICF The user data andcontrol information are passed to the lower sublayer over a set

of logical channels, such as a dedicated traffic channel, commontraffic channel, dedicated signaling channel, common signalingchannel, dedicated MAC channel carrying MAC messages,forward common MAC channel, and reverse common MACchannel

■ The second sublayer is the PLDCF Functions performed at thissublayer when transmitting over the air interface includemultiplexing logical channels coming from PLICF, mappingthem into physical channels, assigning proper priorities to eachaccording to its QoS requirement, and delivering them to thephysical layer The best-effort delivery of data services is

performed at this layer using a radio link protocol (RLP) for streaming-mode user data, and a radio burst protocol (RBP) for

Chapter 4142

8 In the best-effort service, the user specifies the maximum and minimum data rates The amount of bandwidth allocated to a user may vary during the life of a call depend- ing on the congestion experienced by the network.

short bursts of user data over a common traffic channel TheRLP uses an ARQ-based retransmission scheme The

corresponding protocols for handling signaling information are

the signaling radio link protocol (SRLP) and signaling radio burst protocol (SRBP).

Physical Channels

Forward Physical Channels As in IS-95, the pilot channel tinuously transmits a carrier modulated with an all-zero patttern sothat mobile stations can achieve initial cell synchronization Amobile station may use the received signal as a reference carrier forcoherent demodulation, or measure the received signal strength andreport the measurement to a base station for handoff purposes

con-A common auxiliary pilot channel has been added to cdma2000 sothat adaptive antennas can be used for beamforming to extend cov-erage, increase capacity, and provide higher data rates, among otherthings Because beamforming is accomplished by combining signalsfrom different locations in the antenna’s aperture in an optimalmanner using an adaptation algorithm that requires as accurate achannel estimate as possible, it is necessary that the pilot and datasignals travel along the same path to the receiver [3], [4]

A dedicated auxiliary pilot channel is dedicated to a given mobilestation (or a group of mobile stations) for the purpose of beam steer-ing using an adaptive antenna array

A sync channel operates at 1200 b/s, transmitting synchronizationmessages so that mobile stations in the coverage area of a base sta-tion can acquire frame synchronization after cell acquisition For asingle carrier system with a channel bandwidth of 1.25 MHz, thechannel encoder used is of rate 1/2 If the system consists of multiplecarriers or a single carrier with a bandwidth of 5 MHz or more, theconvolution code used is of rate 1/3

The paging channel is used to transmit paging and overhead sages directed to mobile stations in the coverage area of a basestation There are two data rates: 9.6 and 4.8 kb/s For a singlecarrier system with a channel bandwidth of 1.25 MHz, the convolu-tional encoder used is of rate 1/2 If the system consists of multiple

mes-carriers, or a single carrier with a bandwidth of 5 MHz or more, theencoder used is of rate 1/3.

The quick paging channel has been added so that a base stationcan send a quick paging message to a mobile station operating in theslotted mode This message actually consists of a single bit, which isfollowed by a regular paging message in the slot that has been allo-cated to the particular mobile

Next is the broadcast common channel Instead of combining head and paging messages on a paging channel, the system perfor-mance can be improved to some extent by separating overheadmessages and sending them over this channel

over-The common control channel is used to send layer 3 and MAClayer messages to mobile stations at 9.6 kb/s using frame sizes of 5,

5 ms frames are permissible

Supplementary channel 1 and 2 are designed for higher datarates Rates supported are shown in Table 4-1 Frames are usually

20 ms long

Reverse Physical Channels The reverse pilot channel is similar

in concept to the forward pilot channel Used in conjunction withreverse dedicated channels, it enables a base station to acquire ini-tial time synchronization and recover a phase-coherent carrier forcoherent demodulation in a rake receiver It also includes a powercontrol subchannel, which sends one bit in each 1.25 ms power con-trol group or 16 bits in each 20 ms frame The base station can usethis bit to adjust its power level when necessary

Chapter 4144

9 This is after adding the frame quality indicator bits to incoming frames.

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The access channel transmits layer 3 and MAC layer messagesfrom different mobile stations to a base station Multiple usersaccess this channel using a mechanism that is very similar to theslotted Aloha scheme The data rate supported is 9.6 kb/s There may

be more than one access channel, each identified by a unique onal code

orthog-The common control channel, like the reverse access channel justdescribed, also carries layer 3 and MAC messages, and is accessed bymobile stations using the same multiple access scheme Data ratessupported include 9.6, 19.2, and 38.4 kb/s

The dedicated control channel, like the reverse fundamental orsupplementary channels, carries user data packets at 9.6 kb/s or14.4 kb/s in 5 ms or 20 ms frames

The fundamental channel is similar to the forward fundamentalchannel It supports a data rate of 9.6 kb/s and its subrates (4.8,2.7, and 1.5 kb/s), or 14.4 kb/s and its subrates (7.2, 3.6, and 1.8kb/s) For these rates, convolutional codes are used A frame is usu-ally 20 ms long However, in some cases, a 5 ms frame may also beused Note that only a fundamental channel supports a 5 msframe

Supplementary channel 1 and 2, which are similar to the forwardsupplementary channels, provide higher data rates: (1) 9.6, 19.2,

Single-carrier cdma2000 M  9.6 kb/s, M  1, 2, M  14.4 kb/s, M  1, 2, with a bandwidth of 4, 8, 16, and 32 Uses 4, 8, and 16 Uses

rate 1 / 2 rate 1 / 2 Multicarrier cdma2000 M  9.6 kb/s, M  1, 2, M  14.4 kb/s, M  1, 2, where each channel has 4, 8, 16, 32, and 64 4, 8, 16, 32, and 64.

a bandwidth of 1.25 Uses channel encoder Uses channel encoder MHz, or a single-carrier of rate 1 / 3 of rate 1 / 4

system with a bandwidth

of 5 MHz or multiples thereof

38.4, 76.8, and 153.6 kb/s, and (2) 14.4, 28.8, 57.6, 115.2, and 230.4kb/s Only 20 ms frames are supported For these data rates, turbocoding may be used.

Forward Channel Transmit Functions

As an aid to understand the technology used in the tion of physical layer functions of a typical W-CDMA system, a sim-plified block diagram of the transmit functions of a multicarriercdma2000 base transceiver station was presented in Chapter 3,

implementa-“Principles of Wideband CDMA,” (see Figure 3-5 of that chapter).Figure 4-10 shows a similar diagram of the transmit functions ofthe forward channels of a direct-spread, single-carrier cdma2000system For simplicity, only a subset of the forward physical chan-nels is included in this figure Notice the similarity betweencdma2000 and IS-95 (refer to Figure 4-4) forward channel transmitfunctions Some of the differences are as follows

cdma2000 has two traffic channel types—the fundamental andsecondary A number of data rates are supported Depending uponthe data rate, convolutional codes of rate 1/2,3/8,1/3, or 1/4may be used.Both 10 ms and 5 ms frames are supported

I- and Q-channel symbols are multiplied by gain factors

to provide some additional power control As in IS-95, cells areseparated by different pilot PN sequence offsets.10 However, now,complex spreading is used by, first, adding the real-valued I and Qsequences in quadrature (so that the result is a complex number)

and then multiplying it with a another complex number S I  jS Q,

where S I and S Qare, respectively, the I-channel and Q-channel pilot

PN sequences The output of this multiplication is a complex tity whose in-phase and quadrature components are as shown in thelower part of the figure With complex spreading, the output of thewave-shaping filter goes through zero only with low probability, thusleading to improved power efficiency

quan-Chapter 4146

10 The period of these sequences is 2 15  1 chips.

Reverse Channel Transmit Functions

The functional block diagram of direct-spread, reverse-channeltransmit functions in cdma2000 is shown in Figure 4-11 Consider,first, the fundamental channel The incoming data on this channel isprocessed in the usual way Depending on the user data rate, a vari-able number of frame-quality indicator bits in the form of CRC areadded to a frame A few tail bits are appended to ensure proper oper-ation of the channel encoder, which may be either a convolutional

W0

X X

X X

carrier W

Q

Complex Spreading Code

Walsh Code for Paging Channel Block

Interleaver

Paging Channel

Wave-Shaping Filter X

X

t A

cos

Output

Symbol Mapper

Long Code Mask

Long Code Generator Decimator

+

o

o MUX P/S

I Q

Channel Gain

Channel Gain

Block Interleaver Sync

Channel

k = 9

r = 1/2

Symbol Repettion +

Walsh Code for Sync Channel

+

Block Interleaver Fundamental or

Secondary Channel

Conv.

Encoder

Symbol Repettion Long Code Mask

Long Code Generator Decimator

+

Add CRC and Encoder

Decimator

PC Bits MUX

carrier W

Wave-Shaping Filter

t A

coder or a turbo coder Code symbols are repeated, but dependingupon the rates, some of them are also deleted The output of theinterleaver is spread with a Walsh code, mapped into modulationsymbols, and multiplied by gain factors, resulting in a signal labeled

A fund.The supplementary channels 1 and 2 and control channels areprocessed in the same way, although details might vary in somecases For example, symbol puncturing is not done on a reverse ded-icated control channel Similarly, the reverse pilot channel, whichconsists of a string of zeros (that is, real values of 1), is treated dif-ferently because it is not encoded into a channel code, interleaved in

a block interleaver, or multiplied by a Walsh code However, a powercontrol bit is inserted into the pilot channel for each power controlgroup or 16 power control bits per frame For simplicity, we haveomitted these repetitions and merely indicated the processed out-

puts of these channels as Asub1, Asub2, A cont , and A pilot.The fundamental channel and supplementary channel 1 aresummed together giving an output Q Similarly, the remaining chan-nels are summed separately, giving I as the output Notice that inthis case, the I- and Q-channel sequences formed for QPSK modula-tion are independent of each other because they are derived from dif-ferent channels and not by splitting the data stream of a given

Chapter 4148

Wave-Shaping Filter X

X

t A

cos

IS IQS Q

QS IIS Q I

S

Reverse Fundamental Channel

Conv or Turbo Encoder

User m

Long Code Mask

+

Add CRC and Encoder

Wave-Shaping Filter

t A

sin

Symbol Mapper

Walsh Code

Gain

Symbol Repettion &

Puncture if Needed

Interleaver A fund

1 sup

A

2 sup

A cont A pilot A

I Q

Complex Spreading I

Q

I-Channel

PN Sequence Q-Channel

PN Sequence

Walsh Code

Q S

Complex Code Generator

channel into two sub-streams The I and Q sequences are spread by

a complex code of the type S I  jS Q , where S I and S Qare user-specificbecause they are obtained from a 42-bit long code mask for the givenuser, I- and Q-channel pilot PN sequences, and a Walsh code

Summary

In this chapter, we have described the fundamental aspects ofcdma2000, which is one of the systems specified by IMT-2000.Because cdma2000 is an evolved version of the current CDMA sys-tem known as cdmaOne, a brief description of this system is alsoincluded The basic features and service capabilities of cdma2000 arediscussed To provide services in cdma2000, a new link layer proto-col has been defined that consists of a LAC layer and a MAC layer.The functions performed by the different sublayers are brieflydescribed This is followed by a description of the physical layer interms of the physical channels and the forward and reverse channeltransmit functions

The distinctive features of a cdma2000 system may be rized as follows:

summa-■ Wider bandwidth and higher chip rate For a direct-spreadCDMA system, the nominal bandwidth is 5 MHz While IS-95Bsupports data rates in the range of 64 to 115 kb/s, much higherdata rates—from 144 kb/s to 2.0 Mb/s—are possible in

cdma2000 CDMA in general is inherently resistant to fades.However, the improvement in the bit error rate performance issignificantly greater for a 5 MHz system than for 1.25 MHz.Because the chip rate is three times as high as in IS-95, for agiven power delay profile, there are many more resolvable paths

in direct-spread cdma2000 that can be utilized in a rakereceiver Furthermore, as we discussed before, transmit diversity

is a distinct possibility here that will significantly improve thedownlink performance

■ Multicarrier system cdma2000 may consist of a single, spread, 5 MHz carrier, or multiple carriers, each with a

direct-bandwidth of 1.25 MHz In a multicarrier system, because eachcarrier is orthogonally spread, W-CDMA can be overlaid on anexisting IS-95 system Also, a multicarrier system is inherentlycapable of providing transmit diversity because high-speed userdata may be divided into two or more streams and transmitted

on multiple carriers over different antennas

■ Spreading codes In both IS-95 and cdma2000, the spreading ofdownlink channels is similar For example, different cells areseparated by means of different offsets of the I- and Q-channelpilot PN sequences Similarly, traffic channels directed to a givenuser are spread by user-specific long codes

On uplinks, however, there are some differences In cdma2000,physical channels are separated by Walsh codes, and mobilestations by long codes, whereas in IS-95, long codes are used toseparate the access and traffic channels

■ Variable length Walsh codes Because a traffic channel of acdma2000 system is required to support many data rates, it isnecessary to use variable-length Walsh codes This length variesfrom 4 to 128 chips On fundamental channels, Walsh codeshave a fixed length But on the secondary channels, as the datarates increase, the code length decreases (which, in essence,reduces the process gain and thus the number of simultaneoususers on a CDMA channel)

■ Complex spreading In cdma2000, complex spreading is usedthat reduces the amplitude variations of the baseband filteroutput, thus making the signal more suitable for nonlinearpower amplifiers

■ Additional pilot channels Many new physical channels havebeen defined in cdma2000 that have the potential for improvingthe system performance For example, in the downlink, there is

an auxiliary pilot that may be code-multiplexed to providebeamforming and beam steering with adaptive antenna arrays.Similarly, there is a pilot channel in the uplink, which again iscode-multiplexed, enabling a base station to recover the carrierfor coherent demodulation in a rake receiver

Chapter 4150

■ New traffic channels There are two types of traffic channels:fundamental and supplementary, both of which are code-multiplexed A fundamental channel is used for lower data ratessuch as 9.6 and 14.4 kb/s and their subrates The supplementarychannels provide higher data rates Also, two channel codes areused—convolutional codes on fundamental channels or

supplementary channels with a data rate of 14.4 kb/s At higherdata rates on a supplementary channel, turbo codes of constraintlength 4 and rate 1/4are recommended Fundamental channelssupport both 20 ms and 5 ms frames, while secondary channelsuse only 20 ms frames

■ Packet mode data services cdma2000 supports a highly flexiblepacket mode data service The multiple-access procedure isbased upon the slotted Aloha scheme The physical channels thatmay be used for this purpose include dedicated traffic channels,dedicated control channels, and common control channels

■ Quality of service The support of multimedia services atvariable data rates with user-specified QoS is unique towideband systems

References

[1] T Ojanpera and R Prasad, “An Overview of Air Interface

Multiple Access for IMT-2000/UMTS,” IEEE Commun Mag.,

Vol 36, No 9, September 1998, pp 82–95

[2] E Dahlman, B Gudmundson, M Nilsson, and J Skold,

“UMTS/IMT-2000 Based on Wideband CDMA,” IEEE

Com-mun Mag., Vol 36, No 9, September 1998, pp 70–80.

[3] F Adachi, M Sawahashi, and H Suda, “Wideband DS-CDMA

for Next Generation Mobile Communications System,” IEEE

Commun Mag., Vol 36, No 9, September 1998, pp 56–69.

[4] G Tsoulos, M Beach, and J McGeehan, “Wireless PersonalCommunications for the 21st Century: European Technolog-

ical Advances in Adaptive Antennas,” IEEE Commun Mag.,

Vol 35, No 9, September 1998, pp 102—109

[5] TIA TR 45.5, “The cdma2000 ITU-RTT Candidate sion,” TR 45-ISD/98.06.02.03, May 15, 1998.

Submis-[6] TIA/EIA/IS-95-A: Mobile Station-Base Station CompatibilityStandard for Dual-Mode Wideband Spread Spectrum Cellu-lar System, May 1995

[7] V.K Garg, IS-95 CDMA and cdma2000 New Jersey: Prentice

Hall, 1999

Chapter 4152

The GSM System and General Packet Radio Service

(GPRS)

5

Copyright 2002 M.R Karim and Lucent Technologies Click Here for Terms of Use.

We mentioned in Chapter 1 that core networks of UMTS are monized with GSM The UMTS core network is also compliant with

har-the Mobile Application Part (MAP) protocol of Signaling System 7 (SS7) that provides signaling between a Mobile Switching Center (MSC), the Visitor Location Registers (VLR), the Home Location Register (HLR), and the Authentication Center (AC) in GSM Simi-

larly, the packet mode data services in UMTS and the associatednetwork entities and protocols have been harmonized with those ofGPRS, which is now being offered as an upgrade of GSM The readermay recall from Chapter 1 that ETSI has also defined another stan-

dard called Enhanced Data Rates for GSM Evolution (EDGE) to

support data rates up to 384 kb/s in GSM networks The widebandTDMA system IS-136 HS for outdoor/vehicular applications isdesigned to use this protocol in the access network Thus, eventhough there are significant differences in the air interface stan-dards of UTRAN and GSM, a description of GSM and GPRS isappropriate in this context

GSM was first deployed in a few countries of Europe in 1991 sequently, it was adopted in most of Europe, Australia, much of Asia,South America, and the United States Today, it is the fastest grow-ing technology in many parts of the world and is being continuallyevolved to provide advanced features, particularly in areas of datacommunications

Sub-GSM supports voice, circuit-switched data, and short messagingservices The standards work on a packet mode data service in GSMstarted in 1994, and was completed in 1997 The new system speci-fied by these standards was called GPRS A number of references areavailable in the literature that describe the GSM system in greatdetail See, for example, [23], [1], and [2] Reference [9] gives adetailed description of GPRS and discusses its performance based onsimulation GPRS services are described in [11] An overall descrip-tion of the GPRS radio interfaces appears in Reference [12] Details

of the radio link control and medium access control protocols are vided in Reference [13] Our goal in this chapter is to present anoverview of GSM and GPRS systems

pro-Chapter 5154

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