UMTS High-Speed Railway (HSR)Coverage SolutionZTE University

ContentsChallenge of HSR Coverage Strategy of HSR CoverageZTE UMTS HSR Coverage SolutionSuccess Stories

The HSR Era is Coming By 2025, the total length of HSR will reach 37,000km in the world Train running on the current HSR with speed of over 200km/hFast development of HSR, more requirement for HSR coverage

High Speed Influence the Communication PerformanceHigh speedPoor user experienceWorse profitWorse brandWorse KPIHigher penetration lossDoppler effectLonger overlap regionHigher call drop rateLower access success rateLower handover success rateCall dropWorse voice qualityInstable data connectionLower trafficHigher user complaint

HSR Coverage Face ChallengeEvident Doppler EffectHigher carriagepenetration lossInfluenced communication processIn the high speed railway coverage, the main challenge include:

High Speed Introduces Doppler OffsetV: train speed; C: velocity of light; f: system working frequency.f0-fdf1-2fdf1+2fdf0+fd is the change in frequency of a wave for an observer moving relative to the source of the wave.Doppler EffectCalculation Formula Compared with the frequency offset in UE, there is twice in Node B.

Doppler Effect Influence on Node B Performance

Doppler Effect Influence on UE PerformancesceneTwo RRU facing each other and merging UE at the middle of two sitesLogical cellFor UMTS network with 2.1GHz, UE performance result in the limited application of multi RRU of one cell in open place scenario of HSR, only 2RRU back to back can be used.At the middle of logical cell, UE will receive two different direction signal with plus-minus frequency offset of one cell, and the performance will be affected except Qualcomm UE.

Higher Penetration Loss with New TrainBombardier trainCRH3 trainDifferent train, different penetration lossBetter carriage tightness, higher penetration lossOvercoming the most penetration loss is the target of coverage design

T-type trainK-type trainCRH2 train24dB14dB12dB

Communication Procedure is AffectedCell SelectionCell ReselectionHandoverCall ProcedureWith the same cell reselection delay, faster mobile speed, larger reselection overlap area.For faster movement, UE resident time in single cell is less than cell selection time.With the same handover delay, faster mobile speed, larger handover overlap area.For longer each procedure delay, call procedure may be managed in the different cell.

ContentsChallenge of HSR Coverage Strategy of HSR CoverageZTE UMTS HSR Coverage SolutionSuccess Stories

Introduction of Network Deployment StrategyPublic CoverageDedicated CoverageDefinition Utilize public RNC and Node B Cover HSR area and other areas synchronously Same frequency Same parametersDefinition Independent RNC , Node B, transmission and feeder system Cover area along the HSR only Independent frequency Independent parameters

The Problem of Public CoverageRNCnRNC1LAC1LACnCNRNC2LAC2Too many LACs, Too many location updateStationRNC border may be at high speed area, lower handover successful ratio

Solution for Problem 1 RNC1RNC2LAC2LAC1CNRNC3Configure high speed scenario coverage cells under the same RNC/LACBuild new RNC for HSR by administrative region respectively, and set a single LACLANReduce RNC/LAC Number

Solution for Problem 2For a long time delay of Inter-RNC handover, handover in RNC border cell may not complete when UE is at a high speed.Set RNC/LAC border at the low speed area , like as station.Set Rational RNC/LAC Border

Solution for Problem 3 Larger Waiting RoomLarger waiting room, covered by many cellsEntrance: F1/F2 dual frequency cell Higher priority of indoor F2 cell Outdoor F1 cell indoor F1 cell, bi-directional reselection/handover Indoor F1 cell -> indoor F2 cell, uni-directional reselection/handover Indoor F1 cell is used for transition from outdoor to indoor onlyExit: F2 cell Indoor F2 cell outdoor F1 cell, bi-directional reselection/handover

Exit passenger flowSet handover or reselection overlap at waiting room only

Solution for Problem 3 Smaller Waiting Room Smaller waiting room, covered by one cellEntrance: F1/F2 dual frequency cellHigher priority of indoor F2 cellOutdoor F1 cell indoor F1 cell, bi-directional reselection/handoverIndoor F1 cell -> indoor F2 cell, uni-directional reselection/handoverIndoor F1 cell is used for transition from outdoor to indoor onlyExit: F1/F2 dual frequency cellIndoor F2 cell -> outdoor F1 cell, uni-directional reselection/handover

Set handover or reselection overlap at waiting room only

Solution for Problem 4Dont influence public network performance Overcoming the most penetration loss is the target of coverage designInside the train, the pilot signal strength is -95dBm generallyAdjusting the pilot signal strength for different HSR grade

Dedicated Coverage Absorb all HSR Services

Solution for Problem 5 - Network Planning StrategyExploit existing siteAntenna heighthigher than target coverage area visible distanceVertical distance less than 300mVertical distanceLess than 100m33antenna preferablyLess than 300m65antenna preferablyLonger tunnelLeak cable preferably

Rational planningAntenna SelectionDistance between SitesSite SelectionOverlap AreaCell RadiusVertical DistanceDistance between SitesThree principlesThe shortest distancelink estimationpropagation modelRational overlap areaReselection areaHandover area

Solution for Problem 5 - Site Selection StrategyTargetExploit existing site efficientlyBuild new site rationallyOptimizing the selection of HSR siteBBUBBUcell1cell2Build new siteShare site resourceNew equipment: BBU + RRUNew antennaNew cell1RRU: power splitting2RRU: back to back

Dedicated Coverage, Better SelectionPublic Coverage AreaDedicated Coverage AreaDedicated coverage, dedicated application for HSR usersSententious signal distribution, easier network optimization, better coverage qualityExclusive reselection/handover sequence, smoother reselection/handoverLesser RNC/LAC number, lesser signaling interactive, better network performanceZTE Suggest: dedicated coverage for HSR area

Blind Area influence User Experience Complex environment and difficult construction condition may be bring in blind area in the HSR coverage.

Repeater Cover Blind AreaRadio Repeater Theory: a radio signal amplifier actually Defect Raise background noise Unbalance forward/back coverageLower transmission powerCoupling signal from donor Node BNo Capacity variationHigher fault rateLower reliabilityQuality bottleneck of systemCapacityCoverageReliabilityRepeater is only used for unimportant and smaller area now

RRU Cover Blind AreaBBURRUDistributed Node B supports fast deployment and flexible networkingBBU aggregated, RRU distributed, Infrastructure & equipment room shared, saving costRRU close to antenna, reduce feeder loss and zero room space

Same Resource Requirement, Higher Performance Same resource requirement: Site, fiber, power Higher performance: capacity, coverage radius Remote RRU is more suitable for the high speed scenario of less site space , weak ground load, or antenna far from site.Fiber RepeaterRemote Radio Unit

ContentsChallenge of HSR Coverage Strategy of HSR CoverageZTE UMTS HSR Coverage SolutionSuccess Stories

End to End HSR Coverage SolutionHSPA data cardSDR Series Node BsIP based RNCMobile soft-switchService platformSGSNGGSNCNMSCIuCSIuPSIubIubIuPSIuCSIurNode BRNCUTRANGn

ZTE SDR Based Series BTSs FamilyMulti-Mode SupportedGSM/UMTS/HSPAHSPA+/LTEMulti-Band SupportedG/U900M, G/U1800MU/L2100M, U/L2600M Long term TCO Saving50% HPA TechnologySmart Carrier On/OffSmooth Evolution64QAM HSPA+MIMO HSPA+LTEBased on SDR hardware platform, all IP and multiple carriers capableAll base stations share same components, higher integration and less sparesBaseband UnitB8200R8860ER8840Indoor MacroZXSDR BS8800Outdoor MicroZXSDR BS8906Distributed MacroZXSDR BS8700RSU40RSU60ERSU82Outdoor MacroZXSDR BS8900ARadio UnitRSU40RSU60ERSU82R8880AOutdoor MicroZXSDR BS8908R8882Embedded Indoor MacroZXSDR BS8800

ZTE Advanced High Speed Data TerminalIn March, 2009, Hong Kong CSL HSPA+ actual test result in the streetIn June, 2010, DC-HSDPA service testing & demo based on CSL commercial networkFilm download from internet Average:39.1MbpsUDP download from the intranet PDN server, Average:41.6MbpsHSPA+ Data Card3G Modem(HSPAWiFi)

Core Technology of ZTE HSR SolutionNetworking Technology in High Speed Scenario MRRU Combination based on Baseband combination

Patent Frequency Offset Compensation Algorithm Theory Trace frequency offset variety rapidly Compensate efficiently Guarantee the network performanceEffect The compensation range: 1800Hz Node B support: 450km/hSupport all the high speed railway coverage requirement

Theory of MRRU Combination Based on Baseband*Dont raise the noise and dont decrease uplink receive sensitivityProvide better handling ability than radio combinationBBUBBUUplink Baseband CombinationUplink Radio Combination

RRU

RRU

RRU

RAKE Mltipath Demodulation

Mltipath search and selection

Maximal Ratio Combination

Symbol and high level Handling

RNC

BBU

Creating Downlink Signal

Copying Downlink Signal

...

...

MRRU Combination Mode1RRU Power Splitting2RRU Back to Back6RRU CombinationMRRU CombinationEnhance single RRUs coverageScenario: urban areasSite resources: abundantEnhance sites coverage furtherScenario: open placeSite resource: lesserScenario: longer tunnelTunnel face: RRU close to tunnel faceDont set handover overlapInside tunnel1RRU power splitting antenna - leak cable

RRU4

RRU1

RRU6

RRU5

6RRU Cell

RRU2

RRU3

MRRU Combination Converge with Other TechnologyImprove DL coverageHigher Antenna HeightFlexible Mode40w / 1Carrier Reduce feeder loss : 3dB (typical)Enlarge coverage radius: 30%Provide enough DL power to support HSDPA throughputImprove DL pilot signal coverage obviouslyAdapt to different scene 200km/h - 2RRU 200km/h - MRRUInside tunnel - MRRU1RRU Power SplittingCarrier added by softwareEnlarge capacity smoothlyEnlarge single cell coverage and distance between sites, reduce investmentReduce handover, raise the network performanceImprove 45% comparing with 20m Improve 18% comparing with 30m Suggestion: higher than 40mRRU Top Tower

Networking Technology at High Speed SceneTargetBroaden the dedicated network coverage area by antenna and site selectionConfigure better coverage and chain network by cooperation with public networkGuarantee fast and smooth transition along high speed railway with optimized RRM algorithm

Antenna selectionWide horizontal beamBroaden the coverage area along HSRScenario: urban, hill, open country Narrow horizontal beam, higher gainGuarantee the radial coverageScenario: bridge, mountain area or area with shelter forest Coverage ability decided by leak cable typeLesser loss, longer coverage distance 2m high, flushed with train window, 20cm spacing at leastNarrow area33antenna tunnelLeak cableGeneral area65antenna

Zigzag Site LayoutSite LayoutDistance between SitesInterleaving layout along line, balance coverageVertical distance decided by penetration lossSuggestion:14dB(penetration loss): 600m 24dB(penetration loss): 300m other train decided by actual

Decided by propagation model and link estimation Suggestion:250km/h (train speed): 3.5km350km/h (train speed): 2kmother train decided by actual line grade, train type, coverage standard Generally, pilot strength -95dBm Adjusted with different line gradeAssociated factorCoverage Standard

Cooperation with Public Network Along the HSR lineDont configure reselection/handover relationship between public cell and HSR cell.Public network users cant engross dedicated network resource.HSR users reside in dedicated network always and enjoy better QoS service.Waiting roomIndoor: F1, F2 dual frequency coverageIndoor F1 cell is used for transition while users move from outdoor to indoorIndoor F2 cell absorbs service of waiting room/station

Fast Directional Handover AlgorithmChain networkImprove neighbour cell priority of adjacent cell to achieve directional handoverFast cell reselectionQuicken reselection at high speedguarantee call success ratioTotal 1.8sTreselection : 1s Identify new cell: 0.8sReselection overlap (360km/h)Uni-direction: 180mBi-direction: 360mFast handover Enhance handover speedGuarantee handover success ratioHandover parameter:add easily and delete hardlyHandover overlap (360km/h):Normal handover: 0.8s, 80mSignalling handover: 1.3s, 130mDirectional handover parameterImprove handover directionalityswitch to target cell exactlyDirectional handover

DefaultHSR ValueSintraSearchPreyesnoQHyst2S2dB2dBQoffset2SNSib110dB0dBQHyst1S10dB4dBQoffset1SNSib110dB0dB

DefaultHSR ValueMeasQuantityCpihc EcNoCpihc EcNoRptRange for 1A3dB4dBRptRange for 1B5dB7dBHysteresis for 1C4dB2dBTrig Time for 1A200ms100msTrig Time for 1B640ms1280ms

Neighbor cell priorityDefaultHSR Valueadjacent HSR cell1 or 20other HSR cell1common cell1 or 2

ContentsChallenge of HSR Coverage Strategy of HSR CoverageZTE UMTS HSR Coverage SolutionSuccess Stories

China Hefei Nanjing HSR TEST (250km/h) Clear voice and videoHSDPA average rate: 2.45MbpsHSUPA average rate:1.2MbpsOKIn Dec 2009, China Unicom arranged test on the Hefei-Nanjing HSR

DirectionServiceTypeRSCP>-95dBmEc/Io>-12dBHefei to NanjingVCHolding98.55%94.65%Hefei to NanjingVPHolding92.71%93.98%Nanjing to HefeiVCHolding86.57%93.04%Nanjing to HefeiVPHolding97.83%96.43%

Calling NumberHandover NumberCS Service Try/SuccessTry/SuccessCS 12.2K holding test1/1122/122CS 12.2K dialing test7/770/70CS64K holding test1/191/91CS 64K dialing test7/777/77

China Zhengzhou Xian HSR (350km/h)Tunnel face: no handoverRRU close to tunnel face1RRU power splittingCoverage: 1km single hole, dual railLow loss leak cable6RRU cell, coverage 6kmOpen CountryEnlarge site distanceSave investment2RRU: back to backAntenna height: 45mAntenna gain: 20dBiRRU top towerSite distance: 2kmVertical distance: 300mLarge-span BridgeBuild site at every end of bridgeAchieve bridge coverage 2.4km bridgeEnhance antenna height33narrow beam antenna2.9km bridgePilot strength: -97.5dBmBalance coverage and qualityLonger TunnelTunnel face: smooth transitionInside tunnel: reduce handoverBy multi technology, achieve the balance among coverage, site distance and quality

Solution1.SDR based BBU + RRU solution2. Patent Algorithm3.MRRU Combination based on Baseband4. Special Networking Technology

Case1. China Hefei-Nanjing HSR 2. China Zhengzhou-Xian HSRRequirement1 . Evident Doppler Frequency Offset2. Higher Penetration Loss3. Affected Communication ProcessBenefit1. Fast delivery, smooth capacity expansion 2. Higher performance3. Cost saving 4. simple O&M

Summary

The relative increase in frequency can be explained as follows. When the source of the waves is moving toward the observer, each successive wave crest is emitted from a position closer to the observer than the previous wave. Therefore each wave takes slightly less time to reach the observer than the previous wave. Therefore the time between the arrival of successive wave crests at the observer is reduced, causing an increase in the frequency. While they are traveling, the distance between successive wavefronts is reduced; so the waves "bunch together". Conversely, if the source of waves is moving away from the observer, each wave is emitted from a position farther from the observer than the previous wave, so the arrival time between successive waves is increased, reducing the frequency. The distance between successive wavefronts is increased, so the waves "spread out".

*while two RRUs configured as two cells (STSR), UE will receive single-path signal from different cell. The frequency offset demodulation performance of each UE can be up to 1000Hz.

**SDRSDRSoftware Defined RadioRU SDR***