HSDPA技术简介和分析课件

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1、HSDPAHSDPA技术简介和分析技术简介和分析2001年9月HSDPA技术简介和分析ContentlOverviewlTechnical Details（Including Characteristic，Performance and Complexity）AMC，H-ARQ，FCS lImpacts on R99（Including radio protocols，UE，NodeB，RNC，MAC，Interfate Iub&Iur）lConclusionsHSDPA技术简介和分析What is HSDPA?lHSDPA is abbreviation of High Speed down

2、link packet access.lIt can apply to UTRA in order to provide very high speed downlink packet access.lHSDPA is extending UTRA with a new transport channel HS-DSCH(High Speed Downlink Shared Channel).HSDPA技术简介和分析Why Introduced HSDPA?lUse of HS-DSCH will enhance the UTRA support for interactive,backgro

3、und,and,to some extent,streaming services,in terms of Higher peak data rates Improved overall cell throughput kbps/MHz/cell Reduced delay HSDPA技术简介和分析HS-DSCH L1 Structure in Code Domain HSDPA技术简介和分析SharingHSDPA技术简介和分析Technologies to support HSDPAlAdaptive Modulation and CodinglHybrid ARQlFast Cell S

4、electionlMultiple Input Multiple Output Antenna techniqueslStand alone DSCHHSDPA技术简介和分析AMC（Adaptive Modulation and Coding）lWhy introduce AMC?无线链路的信道质量是时变的，任何对链路变化进无线链路的信道质量是时变的，任何对链路变化进行的适应都有易于接收信号的质量。行的适应都有易于接收信号的质量。lLink adapation FunctionPower controlAMC HSDPA技术简介和分析AMC Basic PrinciplelPrinciple

5、of changing MCSusers in favorable positions e.g.users close to the cell site are typically assigned higher order modulation with higher code rates(e.g.64 QAM with R=3/4 Turbo Codes)users in unfavorable positions e.g.users close to the cell boundary,are assigned lower order modulation with lower code

6、 rates(e.g.QPSK with R=1/2 Turbo Codes)HSDPA技术简介和分析MCS（Modulation and Coding Scheme）MCS LevelInfo Rate（Mbps）Code RateModulation710.83/464QAM67.23/416QAM54.81/216QAM45.43/48PSK33.63/4QPSK22.41/2QPSK11.21/4QPSKHSDPA技术简介和分析AMC Physical Layer StructureHSDPA技术简介和分析AMC benefitslMain benefits处于有利位置的用户可以得到更

7、高的数据速率，提高处于有利位置的用户可以得到更高的数据速率，提高小区平均吞吐量；小区平均吞吐量；链路自适应基于改变调制编码方案代替改变发射功率链路自适应基于改变调制编码方案代替改变发射功率减小干扰，减小干扰，AMC在不使用快速下行功率控制的条件在不使用快速下行功率控制的条件下允许达到较高的频谱利用率和高的数据速率。下允许达到较高的频谱利用率和高的数据速率。HSDPA技术简介和分析选择选择MCS的方法的方法 MCS的选择基于下行信道的质量。的选择基于下行信道的质量。l根据根据UE的反馈信息的反馈信息 UE对下行信道质量进行测量，有两种可能：对下行信道质量进行测量，有两种可能：UE估计估计/预测下

8、行信道质量并计算合适的传输格式报告给预测下行信道质量并计算合适的传输格式报告给Node-B；UE估计估计/预测下行信道质量并报告给预测下行信道质量并报告给Node-B；l不根据不根据UE的反馈信息的反馈信息Node-B不通过来自不通过来自UE的反馈决定传输格式，而通过其他信息的反馈决定传输格式，而通过其他信息估计下行信道质量。估计下行信道质量。HSDPA技术简介和分析下行信道质量估计下行信道质量估计l基于基于C/I方法：使用方法：使用CPICH RSCP/ISCP测量下行信道质量。测量下行信道质量。缺点：缺点：公共导频问题公共导频问题，不知道如何和自适应天线和波束成形很好不知道如何和自适应天线

9、和波束成形很好的一起工作的一起工作 。l基于基于TPC方法：使用下行方法：使用下行DPCH的的TPC估计下行信道质量。估计下行信道质量。优点：不增加优点：不增加UE的复杂度，的复杂度，DPCH和和HS-DSCH采用同一个波束采用同一个波束。不存在公共导频问题。不存在公共导频问题。缺点：不适于在软切换情况下的工作。缺点：不适于在软切换情况下的工作。HSDPA技术简介和分析Some challenge¬icelrequire more advanced receiver techniques and more advanced receiver structures lsensitive t

10、o measurement error Errors in the channel estimate will cause the scheduler to select the wrong data rate and either transmit at too high a power,wasting system capacity,or too low a power,raising the block error rate lsensitive to measurement delay Delay in reporting channel measurements also reduc

11、es the reliability of the channel quality estimate.HSDPA技术简介和分析Discuss FocuslIs 8PSK needed?lIs 64QAM needed?l7 level MCS or 5 level MCS?HSDPA技术简介和分析 Hybrid ARQHSDPA技术简介和分析HARQ的分类的分类l按选择机制按选择机制selective repeat(SR)stop-and-wait(SAW)l按实现方法按实现方法 HARQ Type HARQ Type (Incremental Redundancy scheme)HARQ T

12、ype (Incremental Redundancy scheme)lmultiple redundancy versionslmultiple redundancy versionsHSDPA技术简介和分析HARQ的分类的分类lTypeH-ARQ The ARQ method used in current 3GPP specifications is referred to as HARQ type I;the CRC is added and the data is encoded with a forward error correction(FEC)code;lType II H-

13、ARQ additional redundant information is incrementally transmitted if the decoding fails on the first attempt;Neednt to repeat information bits if transmission is unseccessful;（type need）HSDPA技术简介和分析HARQ的分类的分类lType H-ARQLike type II hybrid ARQ,type III hybrid ARQ also belongs to the incremental redun

14、dancy ARQ schemes;each retransmission is self-decodable which is not the case with H-ARQ-type II;lChase combining(also called H-ARQ-type-III with one redundancy version)the same FEC coding is used for each retransmission,similar to the operation of HARQ type I;the erroneous packets are stored in the

15、 receiver and combined with retransmissions of the packet;Diversity(time)gain is thus obtained;HSDPA技术简介和分析Hybrid ARQ Type HSDPA技术简介和分析Hybrid ARQ Type-HSDPA技术简介和分析SR(1/2)characteristiclA common type of ARQ protocol employed by many systems including RLC R99 linsensitive to delaylOnly erroneous block

16、s are re-transmitted lA sequence number is required to identify the block lThe greater the feedback delay the larger the maximum sequence number must be.HSDPA技术简介和分析SR(2/2)Two difficultieslUE memory requirements are high the mobile needs to store soft samples for each partially received block.lRequi

17、res the receiver to reliably determine the sequence number of each transmission.HSDPA技术简介和分析SAW HARQ(1/4)lCharacteristicStop-and-wait is one of the simplest forms of ARQ.In stop-and-wait,the transmitter operates on the current block until the block has been received successfully.stop-and-wait protoc

18、ol&Hybrid ARQ protocol HSDPA技术简介和分析SAW HARQ(2/4)lAdvantagerequire very little overhead;control overhead is minimal;Acknowledgement overhead is minimal;memory requirements at the UE are minimized;HSDPA技术简介和分析SAW HARQ(3/4)lmajor drawback -acknowledgements are not instantaneous and therefore after ever

19、y transmission,the transmitter must wait to receive the acknowledgement prior to transmitting the next block.-the channel remains idle and system capacity goes wasted.HSDPA技术简介和分析SAW HARQ(4/4)RobustessHSDPA技术简介和分析N channel SAW HARQ lno system capacity goes wasted lthe receiver has to store N blocks

20、HSDPA技术简介和分析Timing relations for 2-channel HARQ process HSDPA技术简介和分析Chase CombininglThe simplest form of Hybrid ARQ scheme was proposed by Chase,also called H-ARQ-type-III with one redundancy version.lThe basic idea in Chases combining scheme is to send a number of repeats of each coded data packet

21、and allowing the decoder to combine multiple received copies of the coded packet weighted by the SNR prior to decoding.HSDPA技术简介和分析Combining SchemesHSDPA技术简介和分析Combining SchemesThe second is the best.HSDPA技术简介和分析RCPT codes in HARQ HSDPA技术简介和分析Complexity Evaluation(1/2)lProcessing timeThe time requir

22、ed for processing the tasks depends on the number of timeslots in the HSDPA TTI(number of bits to be processed).The shorter the HSDPA TTI the less time there is available for processing.HSDPA技术简介和分析Complexity Evaluation(2/2)lRequired memory of UE receiver windows.The longer the HSDPA TTI the more me

23、mory is required of UE.The UE buffer size is likely to be a UE capability.HSDPA技术简介和分析Tasks to be introduced(1/2)lNode B processing tasksDecode the ACK/NACK transmitted in uplink Make a scheduling decision on which UE is due to receive data among the UEs having data in the transmission buffer Set TF

24、CI and other information fields on downlink control channels HSDPA技术简介和分析Tasks to be introduced(2/2)lUE processing tasks Decode TFCI,HSDPA TTI sequence info etc Despreading and demodulation Soft combine retransmitted HSDPA TTI in the receiver buffer for the correct subchannel Decode HSDPA TTI for th

25、e subchannelCheck CRC to decide whether the HSDPA TTI was received correctly Generate ACK/NACK signaling for uplink HSDPA技术简介和分析Discuss FocuslHARQ Scheme-IR or Chase Combining?More proposals are Chase combining for its simplicity.lSynchronous vs Asynchronous SAW HARQ lNumber of SAW Subchannels?N=4 o

26、r N=5 is proposedlHow to porform with AMC?Not to change MCS between retransmissions is proposed.HSDPA技术简介和分析FCS（Fast Cell Selection）lFast Cell Selection implies that the UE should decide on the“best”cell for HSDPA transmission and signal this to the network.lThe physical layer requirements of Fast C

27、ell Selection is conceptually similar to physical layer aspect of Site Selection Diversity Transmission(SSDT)included in Release 99.HSDPA技术简介和分析FCSl分类分类Intra-Node B FCSInter-Node B FCSlTwo schedulersRound Robin MAX C/IlMain benefit improves throughput and residual FER for UEs in multi-coverage regio

28、ns HSDPA技术简介和分析FCSlCompare with SSDT in R99In case of SSDT,the“best”cell(the so-called“primary cell”)is selected based on measurements of CPICH RSCP for the cells in the active set.The same measurements can be used as a basis for fast cell selection.In case of SSDT,the best cell is reported to the n

29、etwork using physical-layer(DPCCH)signalling with a maximum rate of 500 Hz.Basically identical signalling could be used for fast cell selection.HSDPA技术简介和分析FCSlImpact on InterfacesIubIurlDiscuss Focuspotential performance increaseIntra-Node B FCS vs Inter-Node B FCSHSDPA技术简介和分析MIMOlDiversity techniq

30、ues based on the use of multiple downlink transmit antennas are well known.lMultiple input multiple output(MIMO)processing employs multiple antennas at both the base station transmitter and terminal receiver,providing several advantages over transmit diversity techniques with multiple antennas only

31、at the transmitter and over conventional single antenna systems.HSDPA技术简介和分析MIMO BenefitlIf multiple antennas are available at both the transmitter and receiver,the peak throughput can be increased using a technique known as code re-use.lWith code re-use,each channelization/scrambling code pair allo

32、cated for HS-DSCH transmission can modulate up to M distinct data streams,where M is the number of transmit antennas.HSDPA技术简介和分析Stand alone DSCHlDefinitionA standalone DSCH is a DSCH on a downlink carrier that is different from the WCDMA carrier that carries its companion DPCH lBenefitBy assigning

33、up to whole carrier for the HS-DSCH,the maximum power and code space available for HS-DSCH transmission would be increased as no resource has to be set aside for DCH or common channels.HSDPA技术简介和分析Stand alone DSCHlPerform schemeBase W-CDMABase OFDMHSDPA技术简介和分析Stand alone DSCH ImpactlThe introduction

34、 of the Stand-alone DSCH would lead to some modifications of the physical layer structure as far as physical channel characteristics are concerned.lImpact is mostly on the UE,as a double receiver would be needed due to the simultaneous reception on two carriers.HSDPA技术简介和分析Impact On R99&R4lRadio Int

35、erface ArchitecturelUplink SignallinglDownlink SignallinglUE CapabilitylMAC lIub&IurHSDPA技术简介和分析Impact on ArchitecturelIn R99 scheduling is perfermed at the SRNC.lIn order to support fast scheduling and reduce UE memory requirements,it is proposed to include a new entity called MAC HS-DSCH terminate

36、d in Node B.lthe transport format selection and scheduling are located in MAC HS-DSCH entity.HSDPA技术简介和分析Radio Interface ArchitectureHSDPA技术简介和分析UE CapabilitylNumber of codeslNumber of channels N lModulation level supportlMemory in UElShould be included in TS 25.306HSDPA技术简介和分析MAClMAC-hs at UE sideT

37、he HARQ entity is responsible for handling the HARQ protocol.generating ACKs and/or NACKs.lMAC-hs at UTRAN sideFlow Control HARQ Scheduling/Priority Handling TFC selection HSDPA技术简介和分析Iub&IurlDiscuss in RAN3HSDPA技术简介和分析ConclusionslHSDPA allows the increase of throughput and peak data rates with reduction in concomitant delay.lHS-DSCH will be specified for both the UTRA/FDD and UTRA/TDD modes.HSDPA技术简介和分析