2g and 3g bts bandwidth requirments

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Huawei Technologies

MAR 2008.

ISSUE 39 3

Can Abis optimization really pay off?The rapid development of mobile services has increased pressure on mobile backhaul bandwidth,

especially in terms of 3G service provision. Abis optimization can to some extent ameliorate this situation

by enhancing transport efciency, but how great is the value generated?By Chen Ni

Abis optimization in 2Gand 3G networks

ncluding some well known Europeanoperators, many in the industry have already adopted leased lines ormicrowave technology to construct

mobile backhaul networks, which incursvery high per unit bandwidth costs. As3G traic grows, operators are aced

with gr eater de mands on bandw idt h

resources, and this has resulted in hugenetwork capacity expansion investment.Tereore, various bandwidth optimizationtechnologies have been developed andapplied in orientation to mobile backhaul,amongst which Abis optimization is anoption.

Voice services remain a dominantcommercial interest or mobile operators.Since GSM systems dier rom 3GUMS systems in terms o voice serviceprocessing, Abis optimization technology

presents diferent unctions or them.GSM systems utilize ull-rate codes toprocess voice services, and transmissionbandwidth is occupied even in the muteperiod o the communication process.he Abis interace, which is locatedbetween the base transceiver station (BS)and the base station controller (BSC),has to support two major bandwidthrequirements or both voice service andmute rames. According to the generaltraic model, mute rames in a GSM

I

system normally occupy 50% to 60% o all BS uplink bandwidths.

Abis op t imizat ion technology i sdeveloped to delete mute rames throughthe BS’s Abis interace and to multiplex

the unused timeslots. he mute ramesare then recovered beore reaching theBSC. It can enhance 2G service transporteciency by an average o 60%, and even80% in best case scenarios.

3G systems employ adaptive multi-rate (AMR) technology to process voiceservices. As voice activation actors areintroduced in coding, no mute rames existin service bandwidth and thus 3G servicetransport eciency cannot be improved by their deletions.

Limited bandwidthsavings

Although Abis optimization technology

creates little value or 3G systems, it seemsto be an eective solution to mobilebackhaul bandwidth optimization, givenits 60% bandwidth optimization eciency in GSM systems.

However, the actual situation is notso simple. Operators are challenged by bandwidth pressures not just rom GSM,but also rom the whole mobile backhaulsystem that supports both GSM and 3G.

As such, an evaluation o Abis optimizationtechnology should consider the value



HOW TO OPERATE

MAR 2008.

ISSUE 39

generated rom bandwidth optimizationacross the entire mobile backhaul, ratherthan in GSM systems only.

At early phase o 3G services: at most 20%

When 3G services are initially provided,operators’ existing transmission networksare able to support the requirements o 2Gservices, and new added bandwidth or 3G

services can drive mobile backhaul capacity expansion. In this instance, Node B coverageis similar to that provided by a BS, with95% o all Node Bs sharing the samesites as GSM BSs. Uplink bandwidthcomprises both Abis and Iub services.

In each GSM system the uplink transmission resources o individual BSsshould be conigured according to themaximum bandwidth needed by the BStype, the major ones being S1/1/1, S2/2/2and S3/3/3. able 1 lists the transmissionbandwidths r equi r ed by BS Abi s

interaces, in which Abis optimizationtechnology is able to optimize all Abisinteraces in the GSM system.

Each 3G network can be congured by reerring to the typical 3G traic model

BTS type TRX OML RSL 64K Time Slots Trafc

S1/1/1 3 1 3 9.4 0.60 Mbps

S2/2/2 6 1 6 17.8 1.14 Mbps

S3/3/3 9 1 9 26.2 1.68 Mbps

Table 1 Transmission bandwidth requirements of Abis interfaces network by 3 to 5 times. N DoCoMoin Japan, or example, began constructing its 3G network with approximately 15,000Node Bs in place, but the maturity o iMode services based on 3G broadbandapplications has to date stimulated anincrease in the quantity o Node Bs toaround 50,000.

In mobile networks, only 20% - 25% o the base stations are 2G, and each requires1×E1 uplink bandwidth. he remaining 80% o 3G Node Bs require 3×E1 uplink bandwidth or each, which is consistent

with in it ia l phase spec i icat ions. GSMservices demand 7.7% o all bandwidthrequirements (1×20%/(3×80%+1×20%)).

When Ab is opt imiz ati on te ch nolog y is employed to optimize these services

across an entire mature 3G network, anoperator can save only 4.62% (7.7%×60%)bandwidth at most.

How great is theapplication value?

An assessment o Abis optimizationtechnology’s application in a network should not be conined to proits gainedby decreased bandwidth in base stations.Consideration should also be given to

bandwidth provision ability and mobilebackhaul costs, which in turn determinethe application o Abis optimizationtechnology. he selection o mobilebackhaul optimization or reconstruction

Can Abis optimization really pay off

and the service planning requirements o 3GPP. he calculations listed in able 2show that each 3G BS calls or an uplink bandwidth o 5.61M in the early phase,

which is 3.3 times the uplink bandwidthrequired by an S3/3/3 BS, and 9.4 timesthe amount needed by an S1/1/1 BS.

hi s ana lys i s demonst r a t es tha tmost bandwidth pressures encounteredby operators derive rom 3G services.GSM services occupy 20% o the total

bandwidth in mobile backhaul and, asit is assumed that Abis optimizationtechnology can save 60% bandwidth, 12%can be saved across the whole network,considerably less than 20%. his isinsigniicant in terms o reducing overalltransmission capacity expansion costs.

At mature phase o 3G services: lessthan 5%

When data services, espec ially thosebased on high-speed data packet access

(HSDPA), become mainstream, voiceservice-based Node Bs/BSs are incapableo covering data service subscribers, withthe number o Node Bs in a 3G network exceeding the number o BSs in a 2G

Trafc model

Voice (mErl) 25

CS 64 data (mErl) UDI 18

PS 64/64 (bps) 100PS 384 Trafc 150

HSDPA (bps) 1024

HSDPA minimum throughput per cell 1 Mbps

Voice activity factor 50%

Voice penetration 100%

Voice data penetration 20%

PS data penetration 40%

HSDPA penetration 50%

Subscriber per Node B 1000

Bandwidth dimension

Voice trafc 0.33 Mbps

CS data trafc 0.37 Mbps

PS 64K trafc 0.06 MbpsPS 384K trafc 0.08 Mbps

HSDPA minimum throughput per cell(HSDPA trafc)

3.00 Mbps(0.92 Mbps)

CCH trafc 0.41 Mbps

Signaling & OM 0.43 Mbps

Engineering margin 0.94 Mbps

Trafc 5.61Mbps

Table 2 Bandwidth requirements of various 3G services

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Huawei Technologies

MAR 2008.

ISSUE 39

requires an analysis based on actualnetwork conditions in terms o 3Gnetwork construction.

For leased line backhaul: just a supplementary

Fig. 1 illustrates that the booming d e m a n d o r b a n d w i d t h i n c r e a s e sleased circuit costs by tens or evenhundreds o t imes in terms o new network construction costs. While Abisoptimization equipment can garneran extra 4.6% proits rom bandwidthoptimization, this remains inadequate

when compared with leased lines’ long-term OPEX. In this case, necessary measures to remove the pressure rombandwidth capacity expansion involvetransmission network construction and thereduction o leased line use.

In typical environments or remote areas where transmission networks cannot beconstructed, Abis optimization technology can be adopted to supplement a decreasein bandwidth lease costs.

For microwave backhaul: only restricted unctions

Microwave mobile backhaul generally adopts a tree networking mode in which

the SDH microwave is adopted at theRNC/BSC, while PDH is utilized at theNode Bs/BS and or tributary links. As3G services require greater bandwidth,the 4.6% extra bandwidth prots derived

rom Abis optimization does not obviatethe necessity or microwave network reconstruct ion, which incurs highexpenditure levels.

At present, microwave backhaul ollowsthree major trends. Firstly, the PDHmicrowave that supports 2 - 4 E1 channelsgradually disappears at the network end,and is replaced by a microwave thatsupports 8 - 16 E1 channels. Secondly, theSDH microwave is progressively extendedto base stations until it accounts or 40% (ormore) in the network, up rom the existing 20%. Tirdly, the SDH microwave, whichis close to the RNC/BSC, is gradually transormed to optical iber networking

with a capacity exceeding 2×SM-1.During microwave network reconstruction

or expansion, maintenance and labor ormthe major portion o expenditure, as opposedto equipment. Current microwave sotmodulation technology supports sotwareupgrades rom 1×E1 to SM-1, thuseectively controlling equipment hardwareand maintenance upgrade costs. For example,in order to upgrade a microwave system thatsupports 4×E1 to a system that supports16×E1, legacy expansion methods requireUSUSD9,000 or equipment migration andengineering. However, present developmentsallow the microwave network to be upgraded

by sotware at almost no cost.Due to improvements in microwave

technology and eicient network costcontrol measures, the value o Abisoptimization is rather limited in terms o

LL w/o optimization

LL after optimization

MW w/o optimizationFiber

2×E1 4×E1 6×E1 8×E1 10×E1 12×E1 14×E1 16×E1 STM-1 STM-4 STM-16

Times

Fig. 1 Comparison of capacity expansion costs among various networking modes

microwave bandwidth cost savings.

For optical fber backhaul: a temporary means also

O p t i c a l i b e r m o b i l e b a c k h a u lconstruction can efectively improve network quality or mobile operators, and providealmost limitless bandwidth. he unit bittransmission cost o an optical transmissionnetwork is ar less than the cost o deploying

Abis optimization technology, demonstrating that in this case Abis optimization possessesnegligible value.

Al though much time is requ ir ed toextend optical ibers to all Node Bs/BSs, doing so is increasingly popular

with numerous related projects currently

underway. As Fx projects are carriedout throughout the world, the opticalcable price per kilometer is alling, witha unit cost in France, or example, o between EUR150 and EUR200.

Since the acquisition o optical ibersbecomes easier, uplink bandwidth capacity has become unrestricted by transmissionmedia, and Abis optimization no longerorms an expedient option or operators.

Conclusion

Abis optimization plays an importantrole in GSM systems and under generalconditions leads to 60% bandwidthoptimizat ion e ic iency. In spec ia lc i r c ums t anc e s , s u c h a s i n r emot emountainous areas, Abis optimizationcan remarkably improve the transporteciency o 2G voice services.

As 3G services develop, the value o Abis optimization has grew insignicant. Itis insucient to ully mitigate transmission

bandwidth pressures, and can only beapplied as a supplementary or temporary measure. hus, the primary means o solving backhaul network bandwidthpressures lies in the construction o sel -bui lt t ransport networks, suchas microwave with sot modulationtechnology or optical iber backhaul.Optical ber backhaul represents the mostefective means or operators to drastically release bandwidth pressure.

Editor: Liu Zhonglin [email protected]

3MAR 2008.

ISSUE 39

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2g and 3g bts bandwidth requirments

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