Concept
Thegenerationoferrorcodesisduetothedecaychangingthevoltageofthesignalduringsignaltransmission,whichcausesthesignaltobedestroyedduringtransmissionandgenerateerrorcodes.Noise,pulsescausedbyalternatingcurrentorlightning,transmissionequipmentfailure,andotherfactorscancausebiterrors(forexample,thetransmittedsignalis1andthereceivedis0;viceversa).Variousdevicesofdifferentspecificationshavestrictdefinitionsofbiterrorrate.Forexample,thebiterrorrateoftheusualvideo/audiotwo-wayopticaltransceivershouldbe:(BER)≤10E-9.
Biterrorrateisthemostcommonlyuseddatacommunicationtransmissionqualityindex.Itexpressesthetransmissionqualityofthedigitalsystemas"howmanybitsofdatahasonebiterroroccurred".Forexample,ifonebiterroroccursin10,000bitsofdata,thebiterrorrateis1in10,000,thatis,10E-4.Errorrate=numberoferrorsymbols/totalnumberoftransmittedsymbols.Thecalculationformulais:
BitErrorRate=NumberofErrorBits/TotalNumberofTransmissionBits.
Detection
Inthebinarydigitalfrequencybandtransmissionsystem,thebiterrorrateisrelatedtothesignalform(modulationmethod),statisticalcharacteristicsofnoise,demodulationanddecodingdecisionmethod.Thebiterrorrateofthemulti-arydigitalmodulationsystemisrelatedtotheaveragesignal-to-noiseratioandthenumberofdigits.
Forabinarydigitalfrequencybandtransmissionsystem,nomatterwhatmethodordetectionmethodisadopted,thecommonpointisthatastheinputsignal-to-noiseratioincreases,thesystem'sbiterrorratedecreases;onthecontrary,Whentheinputsignal-to-noiseratiodecreases,thebiterrorrateofthesystemincreases.ForbroadcastandtelevisionindustryMPEG-HformatTSstreamanalysis,therearemainlystreamprotocol,streamstructure,SItableinformationanalysis,EPGprogramguide,TR101290real-timetest,bitratetest,clockPCRanalysis,QAManalysis,etc.TScodestreamreal-timetestisclassifiedaccordingtoTR101290errorpriorityasfollows:
Firstpriority-decodabilityerrors(6intotal):transmissionstreamsynchronizationloss(TSsyncloss);synchronizationbyteerror(Syncbyteerror);programrelatedtableerror(PATerror);programmaptableerror(PMTerror);continuouscountingerror(Continutyeounterror);programidentificationtableerror(PIDerror).
Secondpriority-impaireddecodabilityerrors(6intotal):transportpacketerror(Transporterror);programclockreferenceerror(PCRerror);programclockreferenceaccuracyerror(PCRaccuracyerror);cyclicredundancyDetectionerror(CRCerror);PTStableerror(PCRerror);Conditionalacceptanceerror(CATerror).
Thethirdpriority-errorsthatdonotaffectthedecodability(10intotal):NITerror(NITerror);SIrepetitionerror(SIrepetitiomerror);Buffererror;PIDerrornotquoted(UnrererencedPID);SDTerror(SDTerror);EITerror(EITerror);RSTerror(RSTerror);TDTerror(TDTerror);emptybuffererror(Emptybuffererror);datadelayerror(Datadelayerror).
BitErrorRate
Indatatransmission,thenumberofbiterrors(English:biterrors)isreceivedThenumberofbitschangedinthedatastreamduetonoise,interference,loss,orbitsynchronizationerrorsinthechannel.Biterrorprobability(i.e.errorprobability,English:biterrorprobability)peistheexpectedvalueofthebiterrorrate.Thebiterrorratecanberegardedasaroughestimateofthebiterrorprobability.Forlongtimeperiodsandhigherrorbits,thisestimateismoreaccurate.
Calculation
Biterrorrateistheprobabilitythattheamountofsymbolinformationislostinthetransmissionsystem.Whentransmittingbinarysymbols,biterrorrate=biterrorrate.Fordigitalcommunicationsystems,thelowertheerrorrate,thehigherthereliability.Thecalculationformulaofthebiterrorrateis:
Biterrorrate=theamountofinformationtransmittedbythesysteminaunittime(numberofbits)/thetotalamountofinformationtransmittedbythesysteminaunittime(thetotalnumberofbits)
Example
Foranexample,supposethetransmittedbitserialis0110001011
andthereceivedbitserialis0010101001,
Inthisexample,thenumberoferrorbits(underlinedbits)is3.Thebiterrorrateisthenumberoferrorbits3dividedbythenumberoftransmittedbits10,whichis0.3or30%.
Influencingfactors
Incommunicationsystems,thebiterrorrateatthereceivingendwillbeaffectedbytransmissionchannelnoise,interference,loss,bitsynchronizationproblems,attenuation,wirelessmultipathfading,etc..