Comparison of W-CDMA and Cdma2000

Contents

Executive Summary 2

Introduction 3

Understanding the technologies 4

A comparison of W-CDMA and cdma2000 6

Upgrading your existing network towards 3G 9

Economical advantages of W-CDMA 10

Siemens’ value proposition 11

Conclusion 11

Glossary 12

Comparison of W-CDMA and cdma2000

Data services are becomingmore and more dominant and the race towards 3Gmobility has already begun.2G operators are looking forthe best technology and themost lucrative road to thisdestination. UMTS, consistingof W-CDMA and TD-SCDMA,is the most promising 3Gcandidate, proposed by theGSM community, whereascdma2000 is the alternative3G approach emerging fromthe IS-95 path.

This Siemens White Paperreviews and discusses thesetwo 3G technologies from avariety of perspectives suchas air interface performance,costs, and ease of evolution.The comparative investigationof these 3G alternativesreveals that system capacitiesare more or less in the samerange, with slight advantageof W-CDMA when usingcomparable transmissiontechnologies and channelconditions. This advantage of W-CDMA mainly resultsfrom the higher coverage of high-bit-rate services.cdma2000’s 1xEV systemsare technologically exhaustedwhen capacity is concerned,while W-CDMA still holdspotential by introducingHSDPA.

Moreover, the investigationshows that the cdma2000evolution is not as clean andcost efficient as often claimed.There is an obvious breakbetween 1xRTT and 1xEV-DOregarding compatibility of theradio transmission technologiesand the network topology,which requires a separateoverlay network with massiveadditional investment costs.

However, the most strikingfactors for the right 3G choiceare economic aspects likeeconomies of scales, terminalcost as well as the geo-graphical footprint for globalroaming facilities. From thoseperspectives, GSM and itssuccessors are clearly makingthe race, and the smooth 2G-3G migration strategy also offers a gradual capitalinvestment in line with thecontinuously increasing datathroughput demands.Thus, the GSM/GPRS/EDGE/W-CDMA path appears tohave significant advantagesby providing immediate andlong-term revenue and profitopportunities for GSM,TDMA,and even IS-95 operators.

– 2 –The best choice towards 3G: W-CDMA

Executive Summary

Wireless operators are lookingfor the right choice to upgradetheir 2G networks to 3G,dealing with upcoming dataand non-voice related services(circuit and package switched)more efficiently. Today, themobile user is used to settingup a voice call anytime andanywhere. Tomorrow, he willexpect the same flexibility for access to Internet andmultimedia services. Mobileapplications will have toevolve to today’s realities ofwired data communication(e.g. high speed wiredInternet access via xDSL).

Based on the IMT-2000requirements for 3G systems,five terrestrial air interfacestandards have been approved.EDGE and UMTS with W-CDMA as FDD mode andTD-(S)CDMA as TDD mode arethe three standards developedby 3GPP. Introduced as multi-carrier CDMA (MC-CDMA) andcurrently standardized in 3GPP2,cdma2000 is the competing3G approach from the IS-95camp. An upgraded DECTversion is the fifth standard.

Operators in Europe havesecured new 3G spectrumand have extended theirGSM network to the packetswitched GPRS system. Theyare already on the migrationpath towards W-CDMA.However, the situation in theAmericas differs from Europeand the rest of the world dueto multiple competing 2G radiotechnologies and in particularthe strong political impact ofthe CDMA (IS-95) community.With the decision of the UWCCto desist from the UWC-136HSapproach, the TDMA operatorshave the choice of 3G evolution: They can either choose – asalready done by AT&T Wirelessand Cingular – to migrate to 3G through the GSM familyending up in EDGE and laterin W-CDMA technology, – orthey can consider thecdma2000 family.


Introduction


The cdma2000 family

The cdma2000 system consistsof several branches or phasesto support additional enhancedservices in terms of increasedvoice capacity or packet-orienteddata services. In general,cdma2000 is a multi-carrierapproach for n times 1.25 MHzcarriers operating in FDD mode.But the standardization work isfocused on a single 1.25 MHzcarrier solution (1x) with thesame chip rate as IS-95.

� cdma2000 1xRTT

The first phase of cdma2000,variously called 1xRTT, 3G1x,or just 1x, is designed toimprove voice capacity of IS-95b (cdmaOne) and to support data transmission ofup to 307.2 kbps peak rate.However, the first commercial1x terminals will only allow153.6 kbps peak data rate.Improvements over IS-95 areachieved with the introductionof some advanced technologiessuch as QPSK modulationand turbo encoding for dataservices as well as a fast(800 Hz) downlink powercontrol and transmit diversity.

� cdma2000 1xEV-DO

1xEV-DO, conceived fromQualcomm’s HDR (High DataRate), was ratified under thisname as a 3G standard inAugust 2001 and signifies anevolution of the single carriersolution for exclusive packetdata transmission.The philosophy behind this system is splitting voice andhigh-data-rate services intodifferent carriers. 1xEV-DOcan only be realized as a dataoverlay network that requiresa separate carrier. In order touse both voice and packet calls

in such an overlay structure,dual mode 1x and 1xEV-DOdevices are needed.

The downlink transmissiontechnique is not compatiblewith 1xRTT. 1xEV-DO isemploying a shared channelapproach in downlink in aTDMA-based manner, i.e.downlink packet transmissionis time multiplexed withinslots of 1.67 ms length. Onlya single user is served at anyinstant and thus maximumtransmission power of thebase station can be spent toone single user. The CDMAtechnology, including softhandoff, is suspended indownlink.

Theoretically, downlink peakrates of up to 2.4 Mbps canbe achieved using high-valuemodulation schemes(16QAM), best base stationselection, turbo encoding,and exclusive usage of thetime slot with maximumtransmission power in closebase station proximity. Theuplink with data rates up to153.6 kbps is kept accordingto cdma2000 1xRTT.

� cdma2000 1xEV-DV

Knowing about the vastnessof resources of 1xEV-DOresulting from a fixed separation of the resourcesfor data and voice while traffic and service mixes are temporarily varying, theCDG (CDMA developmentgroup) initiated a the thirdphase of cdma2000 bringingvoice and data services backinto one 1.25 MHz carrierand retaining once more thebackward-compatibility to1xRTT. The downlink baselineframework of 1xEV-DV is bebased on the L3NQS (LGE,

LSI, Lucent, Nortel Networks,QUALCOMM, and Samsung)proposal.

The maximum user dataannounced for L3NQS is upto 3.1 Mbps correspondingto the data packet size of3840 bit with 1.25ms trans-mission duration. Qualcommproposed a modification ofthe existing packet sizes toincrease the RLP efficiencywith lower overhead, butthis is also still being dis-cussed.

Although the principal transmission technique hasbeen identified, there arestill multiple componenttechnology proposals pendingfor inclusion in the final 1xEV-DV downlink specifications.The final 1xEV-DV specifica-tions are expected to beready for publication in allSDOs by mid 2002.

� cdma2000 3x (MC-CDMA)

cdma2000 3x, or 3xRTT, refersto the original multi carrier (MC)option of the cdma2000 radioconfigurations and is termedas MC-CDMA (IMT-MC) withinIMT-2000. It involves the useof 3 1x carriers to increase thedata rate and is designed for a5 MHz frequency band (3x1.25 MHz channels).The multicarrier option is only applied inthe downlink transmissiondirection.The uplink is directlyspread, similar to W-CDMAwith a slightly lower chip rateof 3.6864 Mcps (three times1.2288 Mcps).

This approach has recentlybecome less significant due tothe definition of the 1xEVolutionbranches. A commercialdeployment of 3xRTT is currently not planned and,

therefore, not regarded in thisanalysis paper.

The GSM / UMTS family

�GPRS

GPRS (General Packet RadioService) is a 2.5G radio system, but a 3G system interms of the core network. Itenhances GSM data servicessignificantly by providing genuine end-to-end packet-switched data connections,offers data transmissionspeeds up to 171.2 kbps(peak data rate) and supportsthe leading Internet protocolsTCP/IP and X.25.

The integration of GPRS intoGSM is a rather straightforwardprocess. A subset of time slotson the air interface are definedfor GPRS allowing scheduledpacket data multiplexing ofseveral mobile stations. Thebase station subsystem needsa minor modular upgradeassociated with the packetcontrol unit (PCU) to providea routing path for packet databetween the mobile terminaland gateway node. A minorsoftware upgrade becomesnecessary to employ the different channel codingschemes.

The GSM core network con-structed for circuit-switchedconnections has to beextended with new packetdata switching and gatewaynodes, the so-called GGSN(Gateway GPRS SupportNode) and SGSN (ServingGPRS Support Node).However this acquisitionendures the migration towards3G, since the high-speedpacket switching core networkprovided by GPRS and EDGEcan be used for UMTS almost

Understanding the technologies

completely and, therefore,represents a secure investmentfor the operator. GPRS is amature technology and a fullystandardized solution withopen interfaces.

� EDGE

EDGE (Enhanced Data rates forGlobal Evolution) is an approved3G transmission technique thatcan be deployed in existingspectrum of TDMA and GSMoperators. EDGE reuses theGSM carrier bandwidth andtime slot structure and wasdesigned to enhance user datarates of GPRS or HSCSD byusing higher-level modulationschemes and other advancedtechnologies such as incremental redundancy.Thus, EDGE-capable infra-structure and terminals arefully compatible with GSMand GPRS.

Due to adaptive modulation/coding schemes optimal bitrates are achieved for all channel qualities. The maxi-mum user peak data rate thatcan be achieved in a 200 kHzcarrier with the most sensitivemodulation/coding schemeand combining of all 8 time-slots is 473.6 kbps.

�W-CDMA or UMTS/FDD

W-CDMA (Wideband CodeDivision Multiple Access) isthe radio interface technologyof UMTS for paired bandoperation. It operates in FDDmode and is based on thedirect sequence (DS) spreadspectrum (CDMA) technologyusing a chip rate of 3.84 Mcpswithin a 5 MHz frequencyband. A higher bandwidthand higher spreading providean increase of processinggain and a higher receivermulti-path resolution, whichwas a decisive point for theIMT-2000 bandwidth fixing.

W-CDMA fully supports bothcircuit and packet-switchedhigh-bit-rate services andensures the simultaneousoperation of mixed serviceswith an efficient packetmode. Moreover, W-CDMAsupports highly variable userdata rates based on the ratematching procedure, wheredata capacity among theusers can change from frameto frame (frame length 10ms)as demonstrated in Figure 1.

The current W-CDMA standardis equipped with QPSK, a morerobust modulation schemethan 8-PSK, which provides apeak data rate of 2 Mbps with

good transmission quality in alarge coverage area.

W-CDMA is the new radiotransmission technology witha new radio access network(RAN) called UTRAN, consistingof the network elements RNC(radio network controller) andNodeB (name for base stationin UMTS).

But it should be noted that theGPRS/EDGE core network canbe reused, that multi-modeterminals capable of support-ing GSM/GPRS/EDGE and W-CDMA are specified, and thathandover and cell re-selectionwill be established betweenthese systems.

�UMTS/TDD

With increasing shortage ofspectrum it may be more likelythat unpaired spectrum blockscan be cleared and, therefore,TDD systems may becomemore important in the nearfuture. The IMT-2000 standardforTDD, called IMT-TC, definestwo types of air interfaces:UTRA-TDD and TD-SCDMA.Within 3GPP they are standardized as TDD hcr (highchip rate) and TDD lcr (lowchip rate), respectively. Bothtechnologies use a hybridaccess technology combiningTDMA and CDMA.

The consequent harmonizationof the TDD transmission tech-niques with W-CDMA and theefficient usage of the existingunpaired bands make theTDD-based standard (IMT-TC)of the IMT-2000 family, aninteresting proposition forwireless operators, andSiemens offers both UMTSmodes, FDD and TDD, in itsproduct portfolio.

�HSDPA

All the advanced transmissiontechnologies such as adaptivemodulation and incrementalredundancy are not exploitedin W-CDMA yet. Therefore,the next logical evolutionarystep of W-CDMA in terms ofhigher downlink data rates isbeing standardized in 3GPPwith the working title HSDPA(High Speed Downlink PacketAccess). HSDPA will improvethe average throughput of thecell and, furthermore, the enduser access speed of up to10 Mbps.

This upgrade in terms ofadvanced transmission technologies is comparable tothose from GPRS to EDGE orfrom 1xRTT to 1xEV-DV,respectively. HSDPA is fullycompatible with current 3GPPreleases and the standard has been completed in theRelease 5 (R5) timeframe.


Figure 1: Variable bandwidth allocation in W-CDMA

Time

Variable bit-rate user dueto variable spreading

Low-bit-rate user

High-bit-rate user

Frequency

Power

frame10 ms

5 MHz

Only the cdma2000 1x singlecarrier system with its variousevolution phases is used forcomparison here, since themulti-carrier approach hasbeen relegated from thecdma2000 evolution path(Figure 6).

Both W-CDMA and cdma2000meet the overall technicalrequirements set forth by theIMT-2000 including the supportof high-bit-rate multimediaservices, packet data and IPaccess. Also the radio trans-mission technology of bothsystems is based on DS-CDMAas multi user access tech-nology, but there are alsosome basic differences:

Main differences

�Chip rate

W-CDMA uses more thanthree times the bandwidthand chip rate of the cdma20001x evolution family. Hence, thehigher chip rate of 3.84 Mcpsin W-CDMA gives more multi-path diversity, especially insmall urban cells. Multi-pathdiversity combats critical fadesand improves coverage. Thehigher chip rate furthermoreprovides higher trunking gainand smaller signaling overhead,especially for high-bit-rateservices.

The higher the bandwidth,the better the coverage forhigh-data-rate services of 384kbps and beyond. This is whythe wider bandwidth of 5 MHzhas been chosen for IMT-2000.Moreover, the higher chip rateimproves the receiver’s abilityto resolve multi-path effects.

�Cell site synchronization

As in the IS-95 system thecdma2000 base stations are

synchronized typically via GPS.The need for a GPS signalmakes the deployment of theindoor and small urban (withantenna below rooftop) cellsrather difficult as GPS doesnot work properly withoutline-of-sight connection to thesatellites. In contrast, W-CDMAis designed to operate withasynchronous base stations(node B).

� TDM access for 1xEV-DO

The 1xEV-DO system employsa shared, time-multiplexeddownlink where only a singleuser is served at any instant,i.e. an introduction of a strictTDMA technology in order toavoid power sharing and multiple access interference(MAI).This approach allows anoperation at maximum outputpower in downlink needed forvery high peak rates.

This downlink channel structure with fixed timeslotsfor shared access is differentto IS-95 / cdma2000 1x andmeans a break of the physicallayer compatibility. In uplinkstill CDMA is applied as for1xRTT.

�Mixed services

1xEV-DO is a data-only solution designed as overlayfor cdma2000 1x systems, i.e.it needs a separate 1.25 MHzcarrier for data services. Inmixed service scenarios thisseparation of resources mayresult in an inefficient spectrumusage (Figure 2). For instance,a low loaded carrier reservedfor data only cannot be usedfor voice traffic.

W-CDMA in contrast is veryflexible in handling mixedvoice and data services.Therefore, the next cdma2000

phase 1xEV-DV was initiatedto overcome this drawback.

� Power control frequency

A fast closed-loop powercontrol solution is applied toboth systems in both trans-mission directions. However,in W-CDMA power control isalmost twice as frequentlyexecuted with a rate of 1500times per second (1.5 kHz) ascdma2000, which uses 800power control updates persecond. The faster the powercontrol is, the better theneeded signal quality can beguaranteed and the moreusers can be admitted.

�Common channel overhead

The power consumption of thecommon channels (e.g. pilot,sync and paging channels) havean impact on the coverage areaof the base station and, there-fore, on the system capacity.While the downlink pilot structure of W-CDMA is basedon dedicated and commonpilot symbols, cdma2000 1x isbased on a common continuouspilot sequence.The pilot channelof cdma2000 needs about20% of the total downlinktransmission power in contrastto W-CDMA with about 10%.

Moreover, due to the wide-band nature of W-CDMA thecommon channels requireproportionally less capacitythan needed in cdma2000and the traffic channels experience higher trunkinggain efficiency.

�Underlying core network

The UMTS core network islogically separated into circuit-switched and packet-switcheddomains. The circuit switcheddomain basically correspondswith GSM networks deployedin Europe and throughout the world utilizing a mobility management protocoldefined as GSM MobileApplication Part (GSM-MAP).

The packet-switched domainutilizes the GPRS core network with the two basicinfrastructure nodes GGSNand SGSN and is based onInternet Protocol version 6(IPv6) (Figure 3).

GPRS subscription data androuting information is held ina common HLR that is sharedbetween GPRS and the circuitswitched functions of GSM.

As UMTS shares a commonpacket core with GPRS/EGDE,all services like billing, security,


Time

Speechblocking

cdma2000 1x and 1xEV-DO

1xData

1xVoice

1xVoiceTh

ree

1.25

MHz

� Reduced datathroughput� Unused

capacity� Optimal adaptionon the traffic mix☺

Time

W-CDMA

One

5 M

Hz

voicedataSource: NOKIA

Figure 2: Handling of mixed voice/data traffic in an overlay network of

cdma2000 1x and 1xEV-DO in comparison to W-CDMA

A comparison of W-CDMAand cdma2000

and roaming deployed to support GSM-based GPRSservices will also support W-CDMA services.

Figure 4 illustrates the under-lying network for cdma20001x.The circuit-switched domainutilizes the same core networkelements around the MobileSwitching Center (MSC) asGSM running a differentmobility management protocolcalled ANSI-41. Since packetservices in IS-95 have beenrealized as short circuit-switched connections, aninter-working function (IWF) is required between MSC and Internet. However, thissolution is not practicable forhigher bit rates served in theupcoming third generation.

To complete the newcdma2000 1x data/voice network, additional networkelements have to be added.The anchor point in a privateIP-centric environment is the so-called PDSN (PacketData Serving Node), whichterminates the point-to-pointprotocol (PPP) data link withmobile terminal and is con-nected via the radio packet(R-P) interface to the basestation subsystem (BSS). ThePDSN is also responsible forthe mobility management and

acts as a foreign agent (FA) forMobile IP (MIP) functionality.A home agent (HA) is neededto terminate the IP tunnelsinitiated by PDSN/FA and tomaintain the MIP session. AnAAA (Accounting, Authen-tication, and Authorization)server, which is based onRemote Authorization Dial-InService (RADIUS), containsthe subscriber packet-data-provisioning information andis used for authentication.

The packet control function(PCF) is one of the new entities within the BSS neededfor upgrades to support thepacket-switched network viathe R-P interface. The data-only version (1xEV-DO) doesnot use the R-P interface tothe radio access point andneeds additional network elements as the 1xEV-DOaccess router.

The evolution to 1xEV-DOrequires a second overlay network with once more newradio equipment, the 1xEV-DOaccess points (AP), whichemploy a TDM access schemein downlink and CDMA inuplink. It is called accesspoint, since it also containsfunctionalities beyond a 1xRTTbase station transforming thereceived RF signals into IP

communications that are forwarded to the accessrouter (another new networkelement needed in the coredomain). It receives andaggregates IP-encapsulatedinformation and routes trafficto PDSN. Moreover, a serveris necessary to provide net-work control services, whichagain are required to operatea network of access points.

Performance issues

� Peak rate, throughput andsystem capacity

The terms "peak rate” and"throughput” are solely relatedto packet switched data serv-ices. For a circuit switchedconnection the bit rate is constant and exclusivelyassigned for the user duringthe complete call duration.

Peak rate is the maximumtransmission speed a connection may experienceunder ideal conditions, i.e. oneuser can exclusively use allresources of one cell withoutany interference and noiserestrictions, and – mostimportant – only a momentarytime instance is regarded.One should be aware that thedazzling peak data rates often

used to highlight a technologyare theoretical and will benever reached in a cellularenvironment. Thus, peak daterates are of small importancefor the operator.

Throughput is defined as theamount of data transferredsuccessfully from one placeto another in a given timeperiod, e.g. for the packet callduration or a complete WWWsession. For instance, thethroughput decreases if packets need to be retrans-mitted several times.

System capacity is the mostinteresting performance issuefor the network operator.It is the average throughputfor all users in a multi-cellularenvironment taking trafficloading, interference and noiseimpairments into account,associated to the bandwidth,which is needed to operatethe mobile communicationsystem over the completeserving area (sum of all carriersin case of frequency reuse).

As system capacity increasesdue to advanced radio trans-mission technology and radioresource managementschemes, each cell site canhandle a higher traffic volume,and that in turn results in a


Core Network

HLR

MSC/VLR

SGSN GGSN

2.5GRadio Access

Network

3GRadio Access

Network

PSTN / ISDN

Internet,x.25, private

networks

Gc

Gn

Gb

Iups

Iucs

A

Gs

MAP-D

Gr

Figure 3: GPRS / W-CDMA core network architecture

Core Network

IWF

1xEV-DOAR

AAA(RADIUS)

1xRTTRadio Access

Network

1xEV-DOAccessPoints

PSTN / ISDN

InternetR-P

AHLR

HA

ANSI-41

MSC/VLR

PDSN

FAPrivate

IP network

Figure 4: cdma2000 1x core network infrastructure


higher revenue streams andhigher return on operator’sinvestment spent for radioinfrastructure (cell cites) andspectrum acquisition.

� Evaluation results

Due to the different requiredbandwidths, a W-CDMA systemcannot directly be comparedto cdma2000. However, acomparable situation existswhen three 1.25 MHzcdma2000 carriers aredeployed in 5 MHz bandwidth.

As described above, there are some basic technical differences between the W-CDMA and cdma2000 suchas chip rate, power control, andcommon channels that attestW-CDMA a better systemperformance. But there arealso other comprehensive,multi-cellular system aspectsthat have an impact on systemcapacity. Those capacity-determining aspects can only be derived from dynamic,multi-cell system-level simulations, which are rathercomputing-intensive, even for packet data.

Results from computer simu-lations with realistic channeland propagation models in a

multi-cellular environmentshow that the system capacityof the different 3G standardsthat are currently available islocated in the same range.Figure 5 shows the capacityfigures for non-real-time(NRT) data services (likeInternet browsing) in a 5 MHzdeployment.The good systemperformance of EDGE on onehand results from its TDMAnature – through the back-doorintroduced in 1xEV-DO aswell – and on the on the handfrom advanced features suchas incremental redundancyand link adaptation, which willbe implemented in HSDPA,the W-CDMA evolution step.

These performance figurescan still be improved whenapplying more sophisticatedradio transmission technologiesto both W-CDMA and 1xEV,but it is very likely that theywill remain in the same order.However, in terms of mixed-voice and data traffic, W-CDMAwill clearly be superior. All inall, the system performancewill not be the dominant factorthat will affect the operator’sdecision about the right tech-nology. Other quite importantaspects such as marketissues, terminals, applications,service creation platforms,etc. may play a striking role in

building a successful businessmodel for a 3G network.

� Evolution of the standards

Figure 6 shows that all major2G standards with exceptionof IS-95 have selected EDGE/W-CDMA as their 3G pathindicating a EDGE/W-CDMAmarket share of more than85% (see also Figure 9). GSMis the 2G system with thehighest penetration worldwideand its pathway towards 3G –clearly defined over GPRS(EDGE) towards W-CDMA – istherefore becoming the mostpopular evolution route. Sincethe core network is enabledfor packet switching withGPRS or EDGE by integratingthe corresponding network elements (i.e. SGSN andGGSN), they may representthe natural but not mandatoryintermediate step towards W-CDMA. EDGE, an improvedGPRS radio technology for highdata rates, is approved as a 3Gstandard and as the best wayto serve 3G services in existing2G spectrum resources. Thenew 3G technology W-CDMAwill not necessarily replace theprevious ones, but will in factco-exist with them.

In January 2000, the IS-136(TDMA) operators, represented

by the Universal WirelessCommunication Consortium(UWCC), decided to desistfrom a separate 3G path andto work together with theGSM camp for EDGE dataevolution based on GPRS.Thus, they will transit overGPRS-capable networks toEDGE and afterwards on to W-CDMA when havingadditional 3G spectrum.

In Japan, W-CDMA has beenset-up as a stand-alone systemin the first role out. Dual-modePDC/W-CDMA handsets havebeen ordered, however they willonly be applicable for roamingand not for handover as it hasbeen planned in co-existingGERAN/W-CDMA networks.

For the IS-95 community, thetransition to 3G and the deliveryof higher data rates will bemet with 1xRTT and the 1xEVtechnologies.The forking of thepath behind 1xRTT indicatesthat 1xEV-DV, the final versionthat once more combines dataand voice, is not a real evolutionfrom the data-only version(1xEV-DO), but a effort to findback to the 1x compatibility.1xEV-DO consists of a differentair interface optimized fornon-real-time packet data.

0cdma2000

1xRTTEDGE W-CDMA

50

100

150

200

400

kbps

/MHz

/cel

l

HSDPA cdma20001xEV-DO

350

300

250

Source: Siemens (BASED ON ITU-R)

GSM

TDMA

IS-95

GPRS W-CDMA

EDGE

HSDPA

1xEV-DV

TD-SCDMA

1xEV-DO

UMTS

1xRTT

PDC

Figure 5: Downlink system capacity for NRT packet data transmission

for different radio technologies in a 5 MHz deployment

Figure 6: 3G evolution of the different standard


GSM operators on the tracktowards W-CDMA

The GSM operators are alreadyon the right track towards W-CDMA when deployingGPRS, which introduces packet-switching capabilities.Building the GPRS infra-structure is fast and cost-efficient as it is basically anadd-on to the GSM network.

The capabilities and systemperformance of the GSM/GPRSnetworks can be enhancedby further introducing EDGEand – within new IMT-2000frequency bands – W-CDMA.The GSM/GPRS packet corenetwork becomes the base-ment for W-CDMA in orderto deliver the full set of 3Gservices and applications.

TDMA operators migratingtowards W-CDMA

The first step in this evolutionstrategy is the migration toGSM/GPRS. Of course,the operator can start witheach evolution phase, but the advantage of a smoothmigration is a reduced andstaged investment adapted to the continuous increase of bandwidth demands.

Figure 7 shows the evolution

steps from TDMA to W-CDMAboth for the core and radioaccess part together with thecorresponding new equipmentacquisitions as well asupgrades indicated by thearrows "new” and "modified”.A GSM/GPRS overlay networkrequires new equipment incore and radio domain whileEDGE only comprises softwareupgrades. Due to the change inradio technology, the migrationstep to W-CDMA needs a HWupgrade with new radioaccess network elements.However, the core network isconsistent with GPRS.

� TDMA operators choosingcdma2000

In spite of the UWCCendorsement for the EDGE/W-CDMA migration the TDMAoperator may principally alsochoose the cdma2000 track.Which of the new equipmentacquisitions and upgrade possibilities will lay beforehim? Comparing the migrationto cdma2000, it is evident thatthe migration path is not ascheap and, in particular, the1xEVolution is not as smoothas often claimed (Figure 8). Toinstall a cdma2000 1xRTToverlay network, a completenew radio and packet coreequipment is needed.

Furthermore, the MSC, run-ning the same IS-41 mobilitymanagement protocol, mustbe upgraded. Obviously, thisfact does not offer appreciablesavings for the operator, as themajor costs stem from thepurchase of radio equipment.

A notable new investment isneeded in both radio and coredomain when installing 1xRTTand once more when evolvingfrom 1xRTT towards 1xEV-DO.The different air link, the missingR-P interface to PDSN, andthe philosophy of separatingdata services require a secondoverlay network. Thus, new1xEV-DO access points areneeded on the radio side, andnew 1xEV-DO access routerstogether with a control serverare required in the core domain.

A third notable investmentwill arise through furthermigration to 1xEV-DV. So it is estimated that the GPRS/EDGE/W-CDMA radio andpacket core upgrade will beabout 30% cheaper than the1xRTT/1xEV-DO1xEV-DVupgrade for both TDMA andCDMA operators.

The IS-95 operator

Regarding the limitations ofIS-95 in terms of inter-frequency

handover and reduced roamingcapabilities as well as themoderate performance ofcdma2000 1xRTT in somepractical environments (e.g.for fast moving users or inindoor deployments due tomissing GPS connection),IS-95 operators should alsoconsider an early shift to theGSM/EDGE/W-CDMA path.

For an upgrade to cdma20001xRTT, the IS-95 operator hasto raise almost the sameinvestment for acquiring newnetwork equipment. There areseveral new packet core elements such as PDSN/FA,AAA-server, and HA in combi-nation with the R-P interfacein the BSS, which replace theIWF. New channel cards arerequired at the base stationto provide new radio con-figurations that include variablespreading, variable coding,and code aggregation.

Since new network elementsare needed in any case toinstall a packet-switched corenetwork, the economies ofscale associated with GSMhold an interesting pricingproposition for an affordableshift towards GSM/GPRS.

Upgrading your existingnetwork towards 3G

Core

�Completepacket corenetwork*

* PDSN, AAA,HA/FA, DCN

�BTS�BSC including

RCF and R-P I/F

�PDSNupgrade

�EV-DO accesspoint**

Standardization is in progress.1xEV-DV is not an evolution from 1xEV-DO � big changes

** contains BTS, BSC andpartly MSC functionality

RAN

New Modified New

1xRTT

1xEV-DO

1xEV-DV

TDMA

Migration

�EV-DOaccess router�Control Server

�MSCupgrade

Figure 8: cdma2000 migration forTDMA operators

Core

�Completecorenetwork*

* packet andcircuit switched

�BTS�BSC**

�Minor SWupgrade

�SW upgrade

�SW upgrade� Iu I/F for MSC

and SGSN

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*** in BTS prepared forGSM/UMTS Collocation

RAN

New Modified New Modified

GSM/GPRS

EDGE

W-CDMA

TDMA

Migration

or

Figure 7: GERAN/W-CDMA Migration forTDMA operators


Building on success of GSM

GSM has become the mostpopular standard in the world,with more than 646 millionsubscribers (January 2002,source GSM Association) in400 networks in 171 countriesworldwide. Based thereupon,it is also apparent that UMTS,the 3G evolution of GSM(based on W-CDMA for FDD)will be the globally mostaccepted standard for 3Gmobile communications.

With the recent migration ofTDMA operators (e.g. Cingular,AT&T Wireless) to GSM,developing their 3G networkevolution based on EDGE and the conversion of IS-95operators (e.g. MobileOne(Singapore)), the number ofsubscribers associated withthe GSM/GPRS/EDGE evolutionto W-CDMA is reaching 85%of all cellular subscribers inthe near future (Figure 9).

The GSM market success isalso a result of its standard-ization success ensuringinteroperability of terminalsand infrastructure. These standards allow operators toselect radio equipment offeredby a number of competingvendors. Moreover, GSM isoperable in all open 2G

frequency bands, 800, 900,1800 and 1900 MHz, whichsupports global networkdeployments and globalroaming for subscribers. Bothvoice and data services canroam with the subscriber, whichbecomes important whenconsidering the increasingamount of SMS associated withincreasing operator revenue.

Economies of scale

GSM has establishedunmatched economies ofscale, which have become amajor element in driving downthe cost of infrastructure andterminals. For sure, its evolvingproducts will tremendouslybenefit from this fact as well,as the volume of devices andinfrastructure equipment willmost likely reach the sameorder. The dominant marketshare and the huge footprintof GPRS/EDGE/W-CDMA willdrive down the prices forinfrastructure equipment andterminals. Affordable handsetprices and services will benecessary for a widespreadmass market.

The broad coverage of GERAN/W-CDMA will generate yet aanother positive momentum:more end users will want to

buy services that can beapplied anywhere in the worldand will thus drive up thecustomer base. Also, depend-ing on the broad coverage,applications and services forEDGE/W-CDMA systems willbe the first in the marketwhile resulting in a highlycompetitive pricing systemfor subscribers.

W-CDMA – the dominant3G technology throughoutthe world

In Japan the W-CDMA rollouthas already started in October2001 and it is evident that W-CDMA will be deployed inEurope in the near future.

More and more non-GSMoperators are joining theGSM/W-CDMA alliance. AfterAT&T Wireless’ chose tomove towards GPRS/EDGE,Cingular also announced toconsolidate its TDMA networkwith an EDGE data-capableoverlay network. In theU.S.A., the way to W-CDMAwill be paved as soon as oneof these operators can addspectrum to its existingcapacity in the upcoming US3G auctions. The roll out willbe a lot easier as EDGE andW-CDMA work off the samegeneral core network.

Even IS-95 operators likeMobileOne in Singapore haveindicated intentions to convertto the GSM/W-CDMA alliance.MobileOne is planning to shutdown its entire CDMA networkand offer GSM services to itscustomers – while possiblyevolving towards W-CDMA.

01999 2001 2003

400

800

1200

1600

Num

ber o

f sub

scrib

ers

(milli

ons)

2005

TDMAGSM/GPRS/EDGE/W-CDMAPDCIS-95/cdma2000Analog

Source: GSA

Figure 9: Global cellular subscribers per technology

Economical advantages of W-CDMA


Siemens mobile is numberthree in the world for GSMnetworks and has over 180GSM customers in over 90countries – more than any othersupplier of infrastructures.Siemens mobile is also in anexcellent position in the racefor 3G awards and has con-tracts with all major globalmobile network operators.

Cingular Wireless, the secondlargest operator in the U.S.,has chosen Siemens as itsinfrastructure supplier for asignificant portion of the GSM/EDGE network. Under theterms of this contract, Siemenswill supply GSM/GPRS/EDGEradio network equipment.Furthermore, Siemens isdeveloping dual-mode TDMA-GSM handsets to guarantee aseamless usage of both net-works by America’s end-users.

In 3G market share terms,Siemens mobile holds positionthree when regarding thenumber of contracts weightedby country population (Figure 10).

Due to the partnership withNEC, W-CDMA expertise anddevelopment resources can bepooled while reducing bothcosts and time-to-market of3G infrastructure. Siemens

mobile has several trial systemsand two quasi-commercialUMTS networks in operationin Monaco and Isle of Man.

Siemens mobile networksgroup is a premier player inradio and core networks forall generations of mobilecommunication systems.Moreover, it is also operatingin the top categories solutionsand devices, allowing Siemensmobile to provide a completesolution package to operatorsmigrating optimally towards 3G.

Almost all practical issuessuch as performance, costsand ease of evolution, whichcan make or break a businesscase have been discussed.TheGSM/EDGE/W-CDMA approachshows clear advantages inthe race while providing significant revenue and profitopportunities for GSM,TDMA,and – regarded objectively –also for IS-95 operators.

The system performancederived from network capacity,which by the way is the operator’s pivotal issue, iscomparable with both 3Gtechnologies W-CDMA andcdma2000 1xEV. In respect tothe coverage area, W-CDMAis clearly superior to the 1xEVfamily by supporting high-bit-rate services and hencerequiring guaranteed QoS(Quality of Service). With tuning downlink packet trans-mission (HSDPA), W-CDMAhas additional potential toprovide capacity and accessspeed enhancements overcdma2000. But there is also anumber of other advantagesthat make W-CDMA and EDGEthe optimum technologychoices for 3G networks.

Another system performancecriterion considered by theconsumer is global roaming:GSM/EDGE/W-CDMA,together with TDMA inAmerica, is clearly superior dueto its worldwide dominance.EDGE is the coupling tech-nology of GSM and TDMA.EDGE is the best 3G choicefor operators to deploy existingspectrum allocations and W-CDMA for new IMT-2000or re-farmed spectrum.

The broad coverage of the GSM/EDGE/W-CDMA technology offers the opportunity to leverage powerful economies of scaledriving down network build-outand management costs as wellas guaranteeing reasonably-priced handsets. Global roaming and the possibility touse services anywhere in theworld will especially appealcustomers to subscribe these3G services, and at the sametime drive up customer base,delivering higher economies ofscale as well as reducing costsand prices. It is evident thatall these factors will deliver agreater benefit and value tocustomers and operators.

ConclusionSiemens’ value proposition

Figure 10: Percentage of 3G market share

Lucent 4%

Nortel 17%

Alcatel 7%

Source: Yankee Group

Motorola 2%

Siemens 19%

Ericsson 29%

Nokia 22%

Glossary and abbreviations

1xEV-DO Evolution of cdma2000 operating with one1.25 MHz RF carrier for data only

1xEV-DV Evolution of cdma2000 operating with one1.25 MHz RF carrier integrating voice and data

1xRTT The first cdma2000 phase as upgradefrom IS-95 for providing 3G services inone 1.25 MHz RF carrier.

2G Second generation of cellular mobile systems. In contrast to first generationsystems based on digital transmissiontechnique and primarily designed for voicecommunication. Typical 2G radio systemsare GSM, IS-95, and D-AMPS.

3G Third generation of mobile communicationsystem featuring higher data rates (up to 2Mbps) and packet switched services forwireless Internet. 3G radio standard arefor instance W-CDMA and cdma2000.

3GPP Third Generation Partnership Project3GPP2 Third Generation Partnership Project 2AMPS Advanced Mobile Phone Service;

US analog standardCDMA Code Division Multiple AccessD-AMPS Digital AMPS; 2G US radio standard based

on TDMAEDGE Enhanced Data Rates for GSM/Global

EvolutionFDD Frequency Division DuplexGERAN GSM EDGE Radio Access NetworkGPRS General Packet Radio ServiceGSM Global Standard for Mobile; worldwide 2G

radio standardGGSN Gateway GPRS Support NodeHSDPA High Speed Downlink Packet Access;

advanced W-CDMA technology fordownlink peak data rate of 10 Mbps.

Visit our website at www.siemens.com/3G

IS-136 Interim Standard #136; 2G US radio standard based on TDMA, also known as D-AMPS

IS-95 Interim Standard #95; 2G US radio standard based on CDMA

MC-CDMA Multi carrier CDMA; 3G radio standardfrom cdma2000 family operating withthree 1.25 MHz carrier and also referred to as 3xRTT

PDC Personal Digital Cellular; Japanese 2Gradio standard

SDO Standard Development OrganizationSGSN Serving GPRS Support NodeTD-CDMA Hybrid Time Division / Code Division

Multiple Access; 3G radio technologyused for operation in unpaired IMT-2000bands that is referred to as high chip rateUTRA-TDD with 3GPP standardization

TD-SCDMA Time Division / Synchronous Code DivisionMultiple Access; 3G radio technologyused for operation in unpaired IMT-2000bands that is referred to as low chip rateUTRA-TDD with 3GPP standardization

TDMA Time Division Multiple Access; primarily a multi user access techniques, but oftenused as synonym for D-AMPS

TDD Time Division DuplexUMTS Universal Mobile Telecommunications

SystemsUTRA(N) UMTS Radio Access (Network)UWCC Universal Wireless Communications

ConsortiumW-CDMA Wideband CDMA; 3G radio standard that

is referred to as UTRA-FDD with 3GPPstandardization

Order No. A50001-N3-P112-1-7600 • Printed in Germany • D01402A 06023. • © Copyright • Siemens AG 2002 • Information and Communication Mobile • Networks • Hofmannstr. 51 •81359 Munich • Germany • This publication is issued to provide information only and is not to form part of any order or contract.

The products and services described herein are subject to availability and to change without notice. Information contained in this document is subject to change without notice. Allother trademarks or registered trademarks are properties of their respective owners. All other companies, product or service names referenced in this brochure are used for identifi-cation purpose only and may be trademarks of their respective owners. Data and/or information used in screens and samples output are fictitious unless otherwise noted.

Any statements in this document that are not historical facts are forward-looking statements that involve risks and uncertainties; actual results may differ from the forward-lookingstatements. Siemens AG undertakes no obligation to publicly release the results of any revisions to these forward-looking statements that may be made to reflect events or circum-stances after the date hereof or to reflect the occurrence of unanticipated events.

Comparison of W-CDMA and Cdma2000

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