7/28/2019 07-Main Topic--Backhaul Technology in the IP Era

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MainTopic

JUN 2009.

ISSUE 5025

Backhaul technology in the IP eraAs base station backhaul transforms to IP, transmission is switched from circuits to packets in order to

efciently carry multiple mobile broadband services and reduce operators OPEX ready for the IP era.

By Liu Xiheng

its continuous technological and protocoloptimization. Indeed, most operatorscurrently deploy MPLS PN devices ormobile backhaul networks.

PWE3 tunnel is adopted in the MPLSPN to ensure that the bearer layer is uniedand compatible with the DM and AMservices o traditional mobile 2G/3G basestations. PWE3 transmits DM, AM, orEthernet services in backhaul and simpliesbase station access to IP bearer networks.

Te PN is structured in a similar wayto the hierarchical rings o SDH networks,

which reduces overa l l maintenancecomplexity. For services , the PNutilizes star path planning with DiServtechnology to implement cross-serviceQoS between base stations. PNs use thesimple and reliable 1:1 LSP protectionmode.

he PN uses a hierarchical OAMdesign that covers Ethernet or POS links,MPLS tunnels, PWE3 tunnels, and Ethernetservices, providing OAM inormation ateach level o the entire network. he PNsupports uture-oriented LE, large-capacitypacket convergence and IEEE 1588v2 clocks.For the X2 interaces o the LE eNB, PNprovides L2/L3 switching. Visualized endto end (E2E) network management enablesrapid E2E service coniguration and, withthe OAM mechanism, the PN can quicklylocate board and port aults within minutes.

MPLS already transports packets ontelecom networks due to improved telecomeatures. PN is in act an extension oMPLS at the base station access layer or

Backhaul technology in the IP era

Backhaul goes IP

P-based multi-service applications arepervading mobile communications.Bottlenecks are created in SDHbackhaul networks as broadband

access become dominant in base stationbackhaul; SDHs insucient capacity, loweciency, and costly data service interaceare gradually becoming evident.

he transormation o base stationbackhaul to IP marks both network evolution

and a technological revolution. Te capacityand eiciency o base stations are greatlyexpanded and improved ater IP bearernetwork access is achieved, and resultingcosts are easily controllable. In this scenario,per shel capacity ranges rom 500G to 1,network transmission is raised to 40GE, andstatistical division multiplexing improveseciency by 50%.

However, IP base station backhaul presentssome risks, and minimizing these is a currentindustry priority. An IP network requires aree and open inormation structure, whichthreatens the immediacy, reliability, andmanageability o base station backhaul.

One leading European operator decidedto replace its legacy SDH/PDH networkswith Huaweis customized IP bearer networksolution or base station access, as opposedto a pure Ethernet or router solution. heoperator reasoned that IP transormationwould deploy 300,000 base stations globally,and that these should ulill a number ounctions: improve eiciency; be uture-

oriented, and guarantee service provision,stability, and ease o management.

A detailed study o IP bearer networkcharacteristics in terms o base station accessreveals that uniied bearer, hierarchicaland multi-domain networking, and visualmanagement are preconditions or the largescale deployment o IP bearer networks withmobile base station access. Compared with aDSLAM metropolitan broadband network,these characteristics are more important thanthe IP protocols used or multiple serviceprovision. Nevertheless, many ocus only on

technical maturity and ignore the inherentattributes o mobile IP bearer networks. Tisdoes not help operators avoid risks in basestation backhaul IP transormation.

MPLS hits themainstream

IP/MPLS or Ethernet switching canbe employed to realize IP transormation.MPLS, transport MPLS (MPLS) andprovider backbone transport (PB) are majortransport technologies that can be identiedas PN technologies. hese technologiesimplement QoS management or base stationbackhaul, hierarchical and multi-domainnetworking, and visualized management.

Each technology has its own advantagesand disadvantages. Commercial circumstanceshave restricted the development o MPLSand PB or IP bearer networks thatdeliver mobile base station access. MPLSis now the dominant technology thanks to

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7/28/2019 07-Main Topic--Backhaul Technology in the IP Era

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Huawei Communicate

JUN 2009.

ISSUE 50 2

large-scale networking in terms o hierarchicaland multi-domain networks, visualizedmanagement, and clock systems. he PNuses MPLS routers to meet the needs o IPbearer networks with mobile base stationaccess, which eliminates mobile operators

concerns regarding IP transmission.PN devices are now the leading choice

or customized IP bearer networks withmobile base station access. Xu Rong, aresearcher or China Mobile, believes thatPN provides a variety o carrier-classnetwork eatures and greatly reduces CAPEXand OPEX. Tus, PN has emerged as theonly option or the IP transportation o basestation backhaul.

Future transformation

strategies

he rapid development o mobilebroadband services has encouraged manyoperators plan to deploy LE networks,and some are already constructing FMCnetworks. In this sense, IP transormation omobile base station backhaul must considerLE and FMC development.

LTE backhaul

Te centralized control o radio networkcontrollers (RNCs) diminishes in the LEphase and communication services existbetween eNBs and access gateways (AGWs).Base station switchover can be perormedbetween eNBs through X2 interaces.

Some industry insiders maintain that LEbandwidth inherits xed DSLAM bandwidthto support mass P2P services, and thatlat IP switching between eNBs transmitsservices through a large number o routingprotocols instead o through carrier-classmanagement. However, this is not entirelycorrect and is common misunderstanding oIP technological application in the telecomeld.

he scale o the Internet and its accessscope continue to grow rapidly. Servicedevelopment demonstrates that MAN basestation services are increasingly integrated toenter the Internet backbone network romMAN core nodes. his is also the majorreason why LE standards deine that allvoice, data, and video service fows enter the

AGW with the S1 interace. Te X2 interaceis only responsible or switching traicbetween base stations. Base station backhaulwith fat P2P IP switching is not necessarilyrequired or LE. I P2P traic is notconsidered, a two-level service model o star

(S1 trac) and mesh (X2 trac) is ormed.Te trac o X2 interaces eatures mesh

distribution that is transmitted through L2MAC or L3 IP switching. X2 interaceshave a logical mesh structure, but the servicevolume on the X2 interace is relativelylow (3% to 5% o network bandwidth)due to the short duration o base stationbandwidth switchover. In this case, the costo independent network-wide L2 or L3switching is quite high and the network iscomplex to be managed, leading to integratedL2/L3 switching as the preerred mechanism.In this case, L2/L3 switching usually occursin the central nodes when X2 services havearrived through designated MPLS tunnels.

In a new backhaul network betweenbase stations and AGWs, service tunnelsare thus S1 and X2. L2/L3 switchingis implemented in easily controlledconvergence nodes that are less costsensitive or operators. Te mesh-structuretrac o X2 interaces is realized throughlogical links. Te star links and integratedL2/L3 switching solution ameliorate cost,

management, and complex service lowissues in the mobile backhaul network.

-Mobile has begun to build its LE-oriented mobile IP backhaul network basedon comprehensive research and analysis.he operator will deploy MPLS routers inthe central nodes with L2/L3 switching,and deploy end-to-end VLL provisioningor base station access to simpliy thebackhaul network. his will help to reducenetwork costs, improve management, andensure carrier-class control and uture LEdevelopment.

FMC bearer network

Numerous mobile operators have soughtto increase their competitiveness in variousways; or example, by constructing large-scaleWi-Fi networks, acquiring small or mediumbroadband operators, or by applying or xedlicenses in the drive to become ull serviceoperators. Operators avor combining mobilebearer networks with broadband MANs to

reduce the overall cost o bearer networks, butto do so requires that IP bearer networks withbase station access can support uture FMCservice development, such as IPV and IPVPN. Tis poses higher requirements on thetraditional backhaul network o mobile base

stations.Notably, FMC bearer network in this

situation does not reer to the FMC bearernetwork or each base station as each MANincorporates many base stations. FMC bearernetwork generally reers to combined multi-play IP convergence bearer networks andIP backhaul networks (the PNs) o basestations.

As PNs ocus too much on tunnel ,stability, and management, current PNscannot bear multi-play services. raditionalMPLS routers are recommended toimplement IP convergence centering onservice provision. Tese convergence routersadopt dynamic or static multicast or IPVservices, implement L2 switching or Ethernetservices rom xed networks, provide VPLSand IP VPN dedicated lines or commercialusers, and evaluate base station backhaulservices as VPN dedicated line services.

he number o base stations is aboutten times greater than that ound atconvergence nodes. I MPLS routersare used or such a large-scale network

maintained through command lines,the costs are high, reliability is notguaranteed, and management is complex.hus, PN technology is recommendedbased on service requirements. Te entirenetwork can be built with router-based IPaggregation layer and PN-based mobilebase station access, and be managed bya uniied network management system(NMS).

By selecting optimum technologies basedon services and uniying management, themost eective FMC bearer solution in an

FMC MAN combines MPLS routers andthe PN. One leading European operatorsRomanian and Belgian networks employ thissolution. MPLS routers improve the IP metroaggregation networks multi-service provisioncapability. he IP transormation o basestation backhaul enhances service provision,orties management, and acilitates low-costbase station expansion; mobile bandwidthcompetitiveness is thus greatly improved.

Editor: Xu Pengxupeng@huawei.com