Efficient automatic repeat request methods and app.docx

Efficient automatic repeat request methods and app.docx

《Efficient automatic repeat request methods and app.docx》由会员分享，可在线阅读，更多相关《Efficient automatic repeat request methods and app.docx（35页珍藏版）》请在冰豆网上搜索。

Efficientautomaticrepeatrequestmethodsandapp

Efficientautomaticrepeatrequestmethodsandapparatus

FIELDOFTHEINVENTION

Thepresentinventionisdirectedtoimprovedmethodsofcommunicatinginawirelesscommunicationssystemandmorespecificallytoimprovedmethodsofautomaticrepeatrequestsinamultipleaccesswirelesscommunicationssystem.

BACKGROUND

Cellularcommunicationssystemsarebecomingevermorecommon.Incellularsystems,acommunicationsareaisdividedintoapluralityofcells.Eachcellnormallyincludesatleastonebasestation.Thebasestationineachcellcommunicateswithapluralityofdevices,e.g.,mobileterminals,locatedwithinthesamecellasthebasestation.Thebasestationusuallyservesasamobileterminal'spointofattachmenttoacommunicationsnetworkwhichincludesthebasestation.Sinceaccesstothecommunicationsnetworkisobtainedbyamobileterminalthroughthebasestationtowhichitiscoupled,e.g.,byawirelesslink,basestationsaresometimesknownasaccessnodes.

Incellularwirelessdatacommunicationsystems,dataisoftentransportedbetweenabasestationandamobileterminalviaaquantumofresourcecalledatrafficsegment.Insuchsystems,theavailableresourcefordatacommunicationinacell,e.g.,atrafficchannel,isoftenpartitionedintomultipletrafficsegments.Controlinformationmaybetransmittedviaotherchannels,e.g.,acknowledgmentchannels.Downlinktrafficsegmentstransportdatatrafficfromabasestationtooneormorewirelessterminals,whileuplinktrafficsegmentstransportdatatrafficfromoneormorewirelessterminalstoabasestation.

Acknowledgmentchannelsincludeacknowledgmentsegmentswhichcanbeusedtoindicatewhetherornotinformationinoneormorecorrespondingtrafficsegmentswassuccessfullyreceived.Anuplinkacknowledgmentchannelcanbeusedbyamobiledevicetosignalthatinformationtransmittedbythebasestationwassuccessfullyreceived,e.g.,wasabletobedecodedbythemobileterminal.ThismaybeachievedbysendinganAcknowledgement（Ack）inasegmentoftheuplinkacknowledgmentchannel.Failuretosuccessfullyreceiveinformationmaybecommunicatedbysendinganegativeacknowledgement（NAK）insteadofanACK.TheACKandNAKcanberepresentedusingasinglebit,e.g.,a1torepresentanACKanda0torepresentaNAK.Adownlinkacknowledgmentchannelcanbeusedbyabasestationtosignalwhetherornotinformationtransmittedbythemobileinanuplinktrafficchannelwassuccessfullyreceived,e.g.,wasabletobedecodedby,thebasestationinthesamemannerthattheuplinkacknowledgementchannelisusedbythemobileterminals.Thetransmitter,e.g.basestationormobileterminal,uponreceivingaNAKcanchoosetoretransmitthesamedata.

Theretransmissionofthepreviouslytransmittedinformationrepresentsthetransmissionofredundantinformation.Whileretransmissioncanleadtoimprovedtransmissionsuccess,itcanbearelativelycostlyprocesssincetransmissionresourcesareconsumedbytheneedtotransmitthesamedatamultipletimes.Theselectiveretransmissionprocesscanalsoleadtodelaysinachievingasuccessfultransmissionresult.

Themechanismbywhichadeterminationismadeastowhetherornotredundantinformation,e.g.,previouslytransmittedinformation,needstobetransmittedissometimescalledanautomaticrepeatrequest（ARQ）mechanism.

Inordertoincreaseerrorresiliencyandreducetheneedfortheretransmissionofdata,errorcorrectioncodingmaybeused.Errorcorrectioncodes（ECCs）resultintheadditionofredundantinformation,e.g.,oneormoreECCs,beingaddedinaselectivemannertothetransmittedinformation.Byusingtheredundantinformation,itmaybepossibletorecovertransmittedinformationevenwhensomeerrorsoccurduringthetransmissionprocess.

Inordertoprovideefficientutilizationofcommunicationbandwidth,itisgenerallydesirabletominimizetheamountofredundantinformation,e.g.,errorcorrectioncodes,transmittedalongwiththeinformationtobecommunicated.Asaresult,evenwhenerrorcorrectioncodingtechniquesareused,asaresultoftransmissionerrors,theremaystillremainaneedforanARQmechanism.

Inviewoftheabovediscussion,itshouldbeappreciatedthatimprovedARQmechanismsandmethodsofcommunicatingredundantinformationtoincreasetheefficientutilizationoflimitedamountsofbandwidthavailabletocommunicatedataarebothneededanddesired.

SUMMARYOFTHEINVENTION

Themethodsandapparatusofthepresentinventionaredirectedtotechniqueswhichmaybeusedincombinationwitherrorcorrectioncodes,tominimizetheamountofredundantinformationthatneedstobere-transmitted,e.g.,intheeventofcommunicationserrors.Theinventionisalsodirectedtonewandnovelautomaticrepeatrequest（ARQ）mechanismsandmethodsofimplementingsuchmechanisms.ImprovedARQmechanismswhichcanbeusedwithLowDensityParityCheckCodes（LDPCs）,whichdifferfrom,andoffervariousadvantagesover,otherwellknownerrorcorrectioncodesincludingReed-Solomoncodesaredescribedandusedinvariousembodiments.

MethodsandapparatusoftheinventionuseNAK（negativeacknowledgement）signalsthataretransmittedtoindicateatransmissionfailure,e.g.,uncorrectableerrorsinadecodedsignaland/oranunsatisfactorylevelofreliabilitywithregardtodecodedinformation.Anunsatisfactorylevelofreliabilitymaybedeterminedfromoneormorereliabilitystatisticsmaintainedbyadecoder,e.g.,acountofuncorrectableerrorand/orsoftinformationvalues.

Incaseswheredecodingissuccessful,anACK（acknowledgment）signalistransmittedtothedevicefromwhichthesuccessfullydecodedsignalwasreceived.

Inaccordancewiththepresentinvention,NAKsignalsmayassumeanyofapluralityofvalues,e.g.,valuesinasetofpre-selectedvaluesoravalueinarangeofcontinuousvalues.ThevalueofaNAKsignalisusedtoconveyinformationusefulindeterminingtheamountofredundantinformationthatshouldbetransmittedtofacilitatedecodingoftheoriginallytransmittedinformationsignal.TheNAKsignalvaluemaybedetermined,inaccordancewiththepresentinvention,basedondecodererrorstatistics,e.g.,acountofdetectederrorsinadecodedsignalorotherinformation,suchassoftinformationvaluesindicativeofthereliabilityofdecodedvaluesgeneratedfromthetransmittedsignalaspartofadecodingprocess.Suchstatisticsprovideameasureofthedecodingsuccess,e.g.,fewerunrecoverableerrorsindicategreaterdecodingsuccessthanalargernumberofunrecoverableerrors.Sincedecodingerrorratesareafunctionofthequalityofthereceivedencodedsignal,theNAKsignalvaluesgeneratedinaccordancewiththeinventionareindicativeofthereceivedencodedsignalquality.

Aspartoftheencodingprocessusedinvariousembodimentsofthepresentinvention,anencodedinformationsignalisgeneratedalongwithasetofredundantinformation,e.g.,additionalerrorcorrectionbitswhichneednotbetransmittedwiththeoriginalencodedinformationsignal.Insomecases,theoriginalencodedinformationsignalincludessomeerrorcorrectionbitsbutthisnumberisusuallyfarsmaller,e.g.,lessthanhalf,thenumberoferrorcorrectionbitsincludedinthesetofredundantinformationwhichisnottransmittedwiththeencodedinformationsignal.Theredundantinformationisstoredforaperiodoftimeaftertransmissionoftheencodedinformationsignal,e.g.,intheeventaNAKisreceived.InthecasewhereanACKisreceived,theredundantinformationbitscan,andnormallyare,discardedwithoutbeingtransmitted.

Thedevicewhichtransmittedtheoriginalencodedinformationsignal,determinesfromthevalueofareceivedNAKsignaltheamountofredundantinformationthatshouldbetransmittedtofacilitatedecodingoftheoriginalinformationsignal.DifferentamountsofredundantinformationwillnormallybeselectedfordifferentNAKsignalvalues.Thisprovidesanefficientrepeatmechanismwhichavoidstheneedtosendafixedamountofredundantinformationregardlessofthequalityofthereceivedsignalwhichcouldnotbedecoded.Byvaryingtheamountofredundantinformationtoreflecttherelativelevelofdecodingsuccess,transmissionefficienciescanbeachievedwithouttheneed,inmostcases,toretransmittheentireoriginalsignal.

Insomecases,e.g.,whereacontinuesrangeofNAKsignalvaluesaresupported,thegranularityofthetransmittedNAKsignalsmaybefinerthanthegranularityatwhichdifferentamountsofredundantinformationareselectedfortransmission.Accordingly,insuchcasesmultipleNAKsignalvaluesmaycorrespondtothesamesizeportionofredundantinformationbutatleastsomeNAKsignalvalueswillcorrespondtodifferentsizedportionsofredundantinformation.

TheselectedportionofredundantinformationistransmittedfollowingreceiptofaNAKsignal.Thedevicereceivingtheredundantinformationusesitincombinationwithinformationobtainedfromtheoriginalreceivedsignalinanattempttosuccessfullydecodethepreviouslyreceivedsignal.

SuccessfuldecodingofthepreviouslyreceivedsignalthroughuseoftheredundantinformationresultsinanACKbeingtransmittedinresponsetoreceivingtheredundantinformation.However,ifthedevicereceivingtheredundantinformationisstillunabletosuccessfullydecodethereceivedinformationaNAKistransmittedinresponsetoreceivingtheredundantinformation.ThevalueoftheNAKisselectedtoindicatethecurrentlevelofdecodingsuccess.Thus,theNAKtransmittedinresponsetoreceivingredundantinformationwillnormallybeadif