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SPRUGK1–March2009
TMS320C6457Turbo-DecoderCoprocessor2
Channeldecodingofhighbit-ratedatachannelsfoundinthird-generation(3G)cellularstandardsrequires
decodingofturbo-encodeddata.Theturbo-decodercoprocessor(TCP2)insomeofthedigitalsignal
processor(DSPs)oftheTMS320C6000EDSPfamilyhasbeendesignedtoperformthisoperationfor
IS2000and3GPPwirelessstandards.Thisdocumentdescribestheoperationandprogrammingofthe
TCP2.
TheTCP2provides:
•Highperformance:
–Very-low-processingdelaybecauseofthehighlyparalleledarchitectureallowing8iterationsofa2
Mbps3GPPchanneltobedecodedinlessthan1.2msandanIS2000channelinlessthan1.2ms.
–Processingdelaycanbefurtherreducedbyenablingastoppingcriteriaalgorithmwhileachieving
optimalBERperformance.
–TCP2andtheDSPcanrunfullspeedinparallel.
•Systemcostoptimization:
–Reducesboardspaceandpowerconsumptionbyperformingon-chipturbo-decoding.
–CommunicationbetweentheDSPandtheTCP2isperformedthroughahighperformanceDMA
engine,theenhancedDMA(EDMA3).
–TCP2usesitsownoptimizedmemories,reducingsystemmemoryoverheadandyieldinghigher
overallperformance.
–Increasedprogrammability.
–Powerefficientandmodulepower-savercapabilities.
•Highflexibilitytocopewithstandardevolutions:
–AcceptsallIS2000,3GPPrates,andpolynomials.
–Acceptsanyframelengthfrom40(3GPPminimumframesize)upto20730forstandalone
processing.Framesizesgreaterthan20730canbeprocessedbybreakingthemupintosmaller
subframesforprocessinginsharedprocessingmode.
–Supportsallinterleavercombinationsviainterleavertable.
–Frees-upDSPresources.
•ImprovementsoverTCP:
–Standalonemodeframelengthincreasedfrom5114to20730.
–Coderates1/2,1/3,1/4and1/5(otherratesviade-puncturingmaybeachieved).
–Prologreduction.
–Cyclicredundancycheck(CRC)stoppingcriteria.
–Channelre-encoding.
–Max-LogMaximumaPosteriori(MAP)optionaddedtoTCP2(Max*-LogMAPstillavailable).
–Inputsignprogrammable.
–DebugmodeaddedtoallowpausingaftereachMAP.
–DecisionorderingprogrammableasMSBfirstorLSBfirst.
–ExtrinsicscalingaddedforMax-LogMAP.
SPRUGK1–March2009TMS320C6457Turbo-DecoderCoprocessor29
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