電信認(rèn)證CDMA原理基礎(chǔ)知識(shí)44a:反向業(yè)務(wù)信道

課程目標(biāo)

了解CDMA反向業(yè)務(wù)信道.理解反向業(yè)務(wù)信道是如何生成的.理解反向碼分信道的概念及其與前向碼分信道的區(qū)別.了解數(shù)據(jù)突發(fā)隨機(jī)化的概念.論述反向信道的解調(diào).CDMA反向業(yè)務(wù)信道用于在呼叫期間發(fā)送：用戶的話音業(yè)務(wù)用戶對(duì)來自基站的命令和查詢的響應(yīng)用戶對(duì)基站請(qǐng)求支持可變速率操作8Kbps聲碼器速率集1-9600,4800,2400和1200bps13Kbps聲碼器速率集2-14400,7200,3600,1800bps反向業(yè)務(wù)信道反向業(yè)務(wù)信道的生成

采用8kb語音編碼9600bps4800bps2400bps1200bps28.8kspsR=1/3,K=91.2288McpsUserAddress

MaskLongPNCodeGenerator28.8kspsOrthogonalModulationDataBurstRandomizer307.2kcps1.2288McpsQPN(nooffset)I

PN(nooffset)D1/2PNChipDelayDirectSequenceSpreadingConvolutionalEncoder&RepetitionBlockInterleaver1/3速率卷積編碼器+++g0g1g2Informationbits(INPUT)CodeSymbols(OUTPUT)CodeSymbols(OUTPUT)CodeSymbols(OUTPUT)12345678反向業(yè)務(wù)信道塊交織28.8kspsFromCoding&SymbolRepetition20ms符號(hào)塊被按序重新排列抵抗快衰落的影響4800bps和4800bps以下速率的重復(fù)符號(hào)被隔離開來改善了符號(hào)數(shù)據(jù)對(duì)衰落的抵抗性能分散了突發(fā)干擾的影響輸入陣列(正常序列)32x18輸出陣列(重排序序列)32x1828.8kspstoOrthogonalModulation反向業(yè)務(wù)信道：

64階正交調(diào)制每輸入六個(gè)符號(hào)，輸出64個(gè)沃氏比特片六個(gè)符號(hào)被轉(zhuǎn)換為一個(gè)0-63的十進(jìn)制數(shù)對(duì)應(yīng)該數(shù)的64位沃氏碼被輸出101100100011Symbols3544WalshLookupTable10001...1101064ChipPatternofWalshCode#35反向業(yè)務(wù)信道:

數(shù)據(jù)突發(fā)隨機(jī)化造成可變速率傳輸一些重復(fù)的符號(hào)被刪除交織器的輸出受一個(gè)時(shí)間濾波器的控制進(jìn)行選通傳輸門控的周期隨傳輸數(shù)據(jù)率變化用一個(gè)偽隨機(jī)屏蔽模式屏蔽掉碼由符號(hào)重復(fù)所產(chǎn)生的冗余數(shù)據(jù)1.2288McpsUserAddress

MaskLongCodePNGeneratorDataBurstRandomizer307.2kcpsFromOrthogonalModulationFrameDataRateToDirectSequenceSpreading數(shù)據(jù)突發(fā)隨機(jī)化:How&WhyHOW所有符號(hào)均以全速率傳輸在門控電路不選通期間，傳輸功率至少降低20dB每一個(gè)輸入到碼重復(fù)處理的碼符號(hào)只傳輸一次WHY反向鏈路的功率控制必須更緊密配合基站收信機(jī)可以更快地確定符號(hào)強(qiáng)度，因?yàn)椴恍枰ㄙM(fèi)時(shí)間去整合重復(fù)符號(hào)(與前向鏈路處理不同)快速判決可以更準(zhǔn)確地在前向鏈路發(fā)送功率控制比特(反向閉環(huán)功率控制)隨機(jī)化傳輸數(shù)據(jù)使得基站從移動(dòng)臺(tái)接收的功率在時(shí)間上是分散開的因此干擾信號(hào)少，易于恢復(fù)出原始信號(hào)反向業(yè)務(wù)信道:

直接序列擴(kuò)頻隨機(jī)器的輸出用長(zhǎng)碼進(jìn)行直序擴(kuò)頻移動(dòng)臺(tái)可以使用兩種長(zhǎng)碼掩碼基于ESN的公共長(zhǎng)碼掩碼專用長(zhǎng)碼掩碼1.2288McpsUserAddress

MaskLongCodePNGeneratorDataBurstRandomizer307.2kcpsToQuadratureSpreading1.2288Mcps反向業(yè)務(wù)信道:

偏置正交擴(kuò)頻和基帶濾波反向業(yè)務(wù)信道用零偏置導(dǎo)頻PN序列擴(kuò)頻基帶濾波可確保波形包含在要求的頻率限值范圍內(nèi)基帶信號(hào)進(jìn)一步轉(zhuǎn)換為800MHz或1900MHz范圍內(nèi)的射頻信號(hào)1.2288McpsI-ChannelPilotPNSequence1.2288McpsPNIQIQcos(2pfct)sin(2pfct)PNchip1.2288McpsFromDataBurstRandomizerRFConvertersD1/2PNChipTimeDelayBasebandFilterBasebandFilter反向業(yè)務(wù)信道的生成

采用13kb語音編碼14400bps7200bps3600bps1800bpskspsR=1/2,K=9McpsUserAddress

MaskLongPNCodeGeneratorkspsOrthogonalModulationDataBurstRandomizerkcpsMcpsQPN(nooffset)I

PN(nooffset)D1/2PNChipDelayDirectSequenceSpreadingConvolutionalEncoder&RepetitionBlockInterleaver反向信道解調(diào)IS-95A/J-STD-008移動(dòng)臺(tái)調(diào)制過程的反過程多徑分量有益于CDMA處理來自多個(gè)接收單元的信號(hào)可以被矢量合并以改善總的接收信號(hào)質(zhì)量U/D

CommandDe-InterleaverSpeechOutputCombinerBTSReceiverBSCDemodulatorSearchCorrelatorDemodulatorSearchCorrelatorDemodulatorSearchCorrelatorDemodulatorSearchCorrelatorPowerControl

DecisionViterbiDecoder聲碼器CDMA概述第四課:CDMA反向信道4a:反向業(yè)務(wù)信道復(fù)習(xí)

4a:ReviewQuestions1.WhatisthesizeoftheblockinterleavingarraysusedintheReverseCDMAChannelsTheirsizeis32rowsby18columns(576modulationsymbols).2.WhatisthemodulationsymbolrateinputtotheOrthogonalModulationstep,whatisthechiprateout,andhowdoesthisratechangehappen28.8kspskcpsout.EverysixmodulationsymbolsareinterpretedasaWalshindex(0-63),andtheyarereplacedbythecorresponding64-bitWalshcode.CDMA概述第四課:CDMA反向信道4b:接入信道4b:接入信道

課程目標(biāo)論述接入信道的作用明確接入信道的主要調(diào)制參數(shù)了解接入信道的產(chǎn)生了解接入信道和尋呼信道的關(guān)系接入信道移動(dòng)臺(tái)用接入信道：與基站建立初始通信對(duì)尋呼信道消息作出響應(yīng)固定數(shù)據(jù)率：4800bps每個(gè)接入信道僅與一個(gè)尋呼信道相關(guān)每個(gè)尋呼信道最多可支持32個(gè)接入信道(0-31)4800bps接入信道的生成請(qǐng)求消息被隨機(jī)化以降低沖突的可能性兩類消息:響應(yīng)消息(響應(yīng)基站的消息)請(qǐng)求消息(移動(dòng)臺(tái)自動(dòng)發(fā)送)kspsConvolutionalEncoder&RepetitionR=1/3McpsAccessChannel

LongCodeMaskLongPNCode

GeneratorkspsOrthogonalModulationkcpsMcpsQPN(NoOffset)I

PN(NoOffset)D1/2PNChipDelayBlockInterleaverAccessChannelInformation(88bits/Frame)4.8kpbsDirectSequenceSpreading接入信道試探Seq2Seq3SeqMAX_REQ_SEQ(15max)PDRequestmessagereadyfortransmissionAccessAttemptSystemTimeAccessProbeSequence1REQUESTATTEMPTRSPDRSPDACCESSPROBESEQUENCEIP(InitialPower)TARTTARTTARTPITAAccessProbe1AccessProbe2AccessProbe3AccessProbe4AccessProbe1+NUM_STEP(16max)PIPISystemTimeCDMA概述

第四課:CDMA反向信道4b:接入信道復(fù)習(xí)4b:ReviewQuestions1.

WhatareAccessChannelsusedfor?

AccessChannelsareusedbymobilestationstoinitiatecommunicationwiththebasestationortorespondtoPagingChannelmessages.2.HowmanyAccessChannelsarethere,andhowaretheydifferentiatedfromotherforwardandreversechannelsonthesameCDMAfrequency?

Upto32AccessChannelsforeveryPagingChannelcanbesupportedonaCDMAfrequency.EachAccessChannelisdifferentiatedfromallotherforwardandreversechannelsonthatfrequencybythemaskappliedtothelongPNcodebeforetheorthogonalmodulationstep.ThismaskcombinestheAccessandPagingChannelnumberswiththebasestation-specificBASE_IDandPILOT_PNparameters.