协同通信和AF和DF中继协议样本.doc

协同通信和AF和DF中继协议样本 协同通信和F AF和和F DF中继协议本文档所提供的信息仅供参考之用，不能作为科学依据，请勿模仿。 文档如有不当之处，请联系本人或网站删除。 Abstract Nowadays,there is a trendfor munication system that the wholework systemis beingdynamic so that there are alwayshaving devicesshould beembedded andremoved.Conventional wiredmunication,due to the plexityof cabling,does notadapt to the modernmunicationsystem.Wireless techniquehas beenused widelybecause devicescan beconnected by electromagism wavewithout cabling.However,low transmittingreliablity becauseof inter-interference betweenele ctromagismwaves is the keyproblem ofwireless munication.Based onthis,this thesisinvestigates one of thetechnique calledcooperative munication and itcooperative protocols.Cooperative munication is avirtual multiple-input multiple-ou tput(MIMO)system.To increase the reliabilityof signal transmitted without increasing theamount ofmunication devices,this technologytries tomake each antennas haveone ormore partnersthat assist them to transmit the signal.In wirelesswork,the devicesnot onlytransmit theirown signalbut alsoassist their“partner”to transmittheir signalfor savingthe cost of installationof additional antennas atboth receiverand senderIn this thesis,we focuson introducingthree mainprotocols incooperative munication:Amplify-andForward(AF),Decode-and-Forward(DF)and Coded Cooperation(CC).The performanceand mathematicalequations of AF and DF areanalysed,and thenMATLAB programswere createdto simulate the performance of thesetwo protocols.About thethree protocols,the mainprocedures arealso introduced.The performance parison forAF and DF in different signal-to-noise(SNR)are本文档所提供的信息仅供参考之用，不能作为科学依据，请勿模仿。 文档如有不当之处，请联系本人或网站删除。 demonstrated.The resultpresents that the DFprotocols hasbetter performancethan AF.Finally,s omeremendations andfuture workare mentionedat theend of the thesis.本文档所提供的信息仅供参考之用，不能作为科学依据，请勿模仿。 文档如有不当之处，请联系本人或网站删除。 文档如有不当之处，请联系本人或网站删除。 文档如有不当之处，请联系本人或网站删除。 文档如有不当之处，请联系本人或网站删除。 文档如有不当之处，请联系本人或网站删除。 文档如有不当之处，请联系本人或网站删除。 文档如有不当之处，请联系本人或网站删除。 文档如有不当之处，请联系本人或网站删除。 ListofAbbreviations andSymbols MIMOMultiple input multiple outputSISO Single input single output AFAmplify-and-Forward DFDecode-and-Forward CCCodedCooperationBER Biterror rateQPSK Quadraturephase-shift keyingi.i.d independently and identically distribution MLMaximum likelihoodSNR Signalnoise-ratio本文档所提供的信息仅供参考之用，不能作为科学依据，请勿模仿。 文档如有不当之处，请联系本人或网站删除。 1Introduction BackgroundWireless municationis,recently,the fastestimproving segmentand mostwidely usedway of the municationindustry.For utilizingthe broadcastproperty ofelectromagism wave,the informationcan betransmitted inwireless environment,which savesmuch costfor cablingand makesthe changeof workstructure easily.On theother hand,as wirelesstechnique is used morewidely,there arealso manyproblems appearing.For example,the wirelesssig nalcan be affected a lot bythe transmittingmedium andinterfered withother signal and the destination will receive not only thedirect wavebut also some extrawaves.These sortsof wavesignal willgenerate andform the received signalat the destinat ion,which willresult insharply differingwith the original signalso thatdecreases the quality of signal andreliability.This iscalled multipath fading11.To solvethese problems,cooperative municationis oneof the methods.Cooperativemunication technique is amethod based on MIMO(multiple-inputmultiple-output)system.MIMO systemis amodel thatinstalling morethan oneantennas inboth thesender andreceiver,which achieveone signal is transmittedby differentchannels.In practical,d ueto thelimitation ofsize,power wasteand hardware,it is hard toinstall alotofantennas inone municationdevice sothat MIMOtechniqueishard toutilize inpractical directly.Thus,cooperative municationis amodel thatbuilds avirtual MIMOsystemamong existing antennas instead of buildingadditionalantennasbut achievesthe gain of MIMOsystem8.本文档所提供的信息仅供参考之用，不能作为科学依据，请勿模仿。 文档如有不当之处，请联系本人或网站删除。 Compared withtraditional transmittingmethod,cooperative munication builds a cooperative workrelationship betweeneachantennawhich means eachantenna willhave ahelper toassistthemtotransmitsignal and these helperantennas willtake somemeasures tooptimize the quality ofsignal.Therefore,at the destination,lots ofsignals will be received sothat receiver can have gain of diversity.Some protocolsdescribe whatfunctions sthese antennasapply foroptimiz ingsignal.In this report,some explanationsand literaturereviews focusedon amplify and forward protocol,decoded and forwardprotocol and coded cooperative protocolare demonstrated.Otherwise,simulation resultfor amplifyand forwardand decoded and forwardprotocol ismade.Objectives Thepurpose ofthis projectis toanalyse theadvantages of cooperative municationby analysisof threemain cooperative protocols.In thishalf year,this projectcan havea conclusionabout threeobjectives:1.Trying tounderstand the concept ofcooperative municationand itsworking systemmodels s.Research forhow the signal deliveredthrough nodes.2.F Finding thethree cooperativeprotocols thatantennas obeyAF(amplifyand-forward),DF(decode-and-forward)and CC(coded cooperation)protocols and how theyworks.3.Use theMATLAB to simulatethe performanceofAF andDF anddo aparison aboutthem.Approaches本文档所提供的信息仅供参考之用，不能作为科学依据，请勿模仿。 文档如有不当之处，请联系本人或网站删除。 Firstly,analy yzz ingtheconceptofcooperative municationandfind ingthe fundamentalprotocols sabout it.Secondly,finding theimportant describedequations and the usedcoefficients.Finally,use MATLABtosimulatethe proceduresofAFandDF and tryto get the BER(bit error rate)-SNR(signal-Noise ratio)diagram andpare thetheir performance.Thesis outlineThis reportincludes fiveparts:first partintroduce thebackground ofcooperative munication.Second partexplains sseveral literaturereviews sabout wireless,diversity technology,MIMO and cooperativeprotocols.Third andforth partsdemonstrate thesimulation aboutAFandDFandget theresult diagram.Additional,the forthpart alsoincludes theperformanceparisonbetweenAFandDF.Last partmake essaconclusion and the futurework aboutthe project.本文档所提供的信息仅供参考之用，不能作为科学依据，请勿模仿。 文档如有不当之处，请联系本人或网站删除。 2Literature ReviewOverview Toovere thelack ofmulti pleantennas limited by sizeor hardwareplexity,cooperativemunicationis proposed.Cooperative municationcan beunderstood avirtual multi ple inputmultipleoutput(MIMO)system between source anddest ination.In anotherwords,the cooperativemunicationbuildacooperativerelationship amongexistingantennas.For utilizingthe broadcastproperty ofelect romagismwave,notonlythe destination,there arealsosomeother antennasreceive the source signal.Instead ofdiscarding thissignal,this relationshipasks theseantennas to take somemeasures to process thissignal and retransmit it to theappoint eddestination.本文档所提供的信息仅供参考之用，不能作为科学依据，请勿模仿。 文档如有不当之处，请联系本人或网站删除。 FigurevirtualMIMOsystemTo decreasethe bit error rateand recover the source signal well,there arethree monprotocols for the helperantennas applying:amplifyandforward(AF)protocol,decodedandforward(DF)protocola nd codedcooperative(CC)protocol.本文档所提供的信息仅供参考之用，不能作为科学依据，请勿模仿。 文档如有不当之处，请联系本人或网站删除。 Figure Cooperative munication Spatialdiversity technologyCooperativemunicationutilizes the spatial diversity technology.Diversity is an idea that transmittinga signalthrough manyind ependentchannels,it isdescribed in1.When sourcesends onesignal indifferent independentchannels,the destinationwillreceivemany formatsabout thissignal.In thisway,it canincrease the signal-to-noise ratio(SNR)at the receiver whichresult inrecovering the source signalbetter.There arethree mondiversity technologies:time diversity,frequency diversityand spatial diversity.Spatial technologyis to build manyrelays toretransmit the signal whichcreates additionalchannels inspac e.The cooperativemunication appliesthespatialdiversitytechnologymainly4.Basic Modelfor WirelessSingleinput and singleoutput(SISO)system Singleinputandsingleoutputis thetradition modelwhich bothtransmitter andreceiver haveo neantenna tosend orreceive signal.In thisway,the informationis transmittedbyelectromagismwave inthe air.Due to the effect of multiple pathfading,the destinationishardto recover the source signal fromreceiver signal.Multiple inputandmultiple output(MIMO)system As the namesaid,MIMO allowsboth the source and destination tohave multipleantennas tosend andreceive signal9.Due to the effectof本文档所提供的信息仅供参考之用，不能作为科学依据，请勿模仿。 文档如有不当之处，请联系本人或网站删除。 multiplepathfading,thequality ofsignalwill be decreased.However,by buildingadditional waysbetween sourceand destination,more informationwill betransmitted atthe sametime andfor the destination manyformats of sourcesignalwill bereceivedsothat MIMOcan greatlyimprove thespectrum utilizationand channelcapacity withoutincreasingthe bandwidth.But moreantennas meanmore municationdevices inboth sourceand destination.It hasto costalottobuildenormous systemto supportthe multiplexingtechnology9.Figure MIMOsystem Cooperativemodel Theba siooperative modelis the source-relay-destination model.Here wedefined thecooperative antennaas relay.This modelis naturallyrepresented bythe graphbelow3.Here we set the source-to-relay channelgain toH1,noise isN1;the gainof source-ttoo-destination toH2,noise isN2;the gainof relay-to-destination toH3,noise isN3.At the first time slot,the sourcesent thesourcesignalX1to the relay anddestination:本文档所提供的信息仅供参考之用，不能作为科学依据，请勿模仿。 文档如有不当之处，请联系本人或网站删除。 Y2=H1*X1+N1Y3=H2*X1+N2At the second timeslot,the relaytakes somemeasures toprocess the received signalY2,we setthe processto C:X2=C*Y2.Then,the relayretransmitted theX2tothe destination:Y4=H3*X2+N3.As aresult,atthe destination Y4and Y3are received:Y3=H2*X1+N2Y4=C*H3*H1*X1+C*H3*N1+N2The destinations taskis recoveringX1from Y3and Y4.Cooperative schemesAlthough thespatialdiversitytechnology canincreasetherate ofsuessful packetreceipt andthereceiverSNR,during the signal transmittingthrough the channel(Rayleigh fadingchannel),the signalstill sufferfrom the fading likenoise.Due tothe negativeeffectof本文档所提供的信息仅供参考之用，不能作为科学依据，请勿模仿。 文档如有不当之处，请联系本人或网站删除。 Rayleigh fading,the signaldensity andphase willbe changed.To weakenedthis effect,the relaynode needtotakesome cooperativecoding strategies.Amplify-and-forwa rdmethod(AF)In practical,during the signaltransmitted in channel,oneof thefadingproblems is amplitude fading,which maylead topackets lossand powerefficiency decreasing4.Amplify-and-forward method is quitesimple.After the relay received the signal from source,the relayjust amplifiesthe signaland retransmitsit tothe destination.Although the noise partis amplifiedas well,the destinationcanhavegainofdiversity8.However,the amplify coefficient shouldmeet theconstraint of power.Here,we setthe power of sourcesending signal to P,the powerof noisebetweensourceand relay is n1.The powerof retransmittingis P1.We canget(the energyis amplified,not the power):sqrt*P1=B*sqrt*(P+n1)?B=sqrt*(P1/(P+n1)Figur eRelayamplifymodel本文档所提供的信息仅供参考之用，不能作为科学依据，请勿模仿。 文档如有不当之处，请联系本人或网站删除。 Decoded-and-forward(DF)method Thereis anothermethod forthe relaytoprocessthereceived signal.Compared tothe AF,this method is moreplex.In thismethod the relay attemptsto detectthereceivedsignal from source.At the firsttimeslot,thesourcesends the signal torelay andsource in50%of totalpower respectively.At thesecond timeslot,after the relay receivedthe signal fromsource,it willdecode itand detectif errorhappens duringsource-to-relay channel.If thereare errors,therelaywill staysilent andthesourcewill send the signal tothe destination in50%of totalpower again.If noerrors,therelaywill encodethesignalandretransmitit tothedestination.In thisway,because therelay onlyretransmits theright signalthe error bits willbedecreased.However,it shouldnotice thatDF islimitedbythequalityofsource-to-relay channel8.本文档所提供的信息仅供参考之用，不能作为科学依据，请勿模仿。 文档如有不当之处，请联系本人或网站删除。 Figure Decodedandforwardmodel Codedcooperation Insteadof simpleprocessing signalby relay inthe AFor DFmethod,coded cooperationis abination ofchannel codingandcooperativemunication6.Codedcooperationis aideathatby twoindependentlyandidenticallydistributionchannels transmittingone hosts differentparts ofdata bits.Its basicidea is that eachhosts transmittheir incrementalredundancy to their partner.If thequalityofchannel betweenhosts isbad,it willchange tonon-cooperative model.本文档所提供的信息仅供参考之用，不能作为科学依据，请勿模仿。 文档如有不当之处，请联系本人或网站删除。 Figure Codedcooperative modelThe municationamong usersis withno feedbackforthetransmission operatedautomatically throughthe codedesign.The signalto betransmitted willbe divided into blocksand eachblock willbe sentin twoframes6.Figure Codedcooperation dataallocation Inthefirstframe,each usertries todecode partners data.If decoded suessfully,it willsend partners second part data.If not,sendthesecondpartdata ofits own.Due tono feedbackamong users,each userdoes本文档所提供的信息仅供参考之用，不能作为科学依据，请勿模仿。 文档如有不当之处，请联系本人或网站删除。 not knowif partnerdecoded itsfirst datapart suessfullyor notso thereare fourpossible situations.Each userdecoded partners datasuessfully,no userdecodedsuessfully.One ofusers decodedsuessfully.Figure Fourcases incodedcooperative6For recoveringthe original signal from the correspondingusers,thedestinationneeds toknow which case is ourred.One ofthemethodsisthatdestination thinksabout andchecks everycase aordingtotheiremergence possibilitiesuntil theCRC bitspresent correctresult.The othermethodiseach userattaches anadditional informationbits intheir secondpart codewordthat includeswhichcaseisourred6.The firstmethod takestoo muchtime andthesecondmethod makesthe wholeprocess plex.本文档所提供的信息仅供参考之用，不能作为科学依据，请勿模仿。 文档如有不当之处，请联系本人或网站删除。 3Simulations andAnalyses ofAF OverviewAmplify andforward methodisasimple method to decreasethe biterrorrateatreceiverbasedondiversitytechnology.Its mainidea istoamplify thesignaland noise.Then thissignal isretransmitted tothedestination.The本文档所提供的信息仅供参考之用，不能作为科学依据，请勿模仿。 文档如有不当之处，请联系本人或网站删除。 challenge ishow torecoverthe original signalatthereceiver.The MaximumLikelihood method(ML)can meetthe requirement.Maximum likelihoodmethod Asthedestination receivesmuch signalwith noise,it is thedestinations responsibilityfor recoveringthe original signalfromreceivedsignal.Maximum likelihoodmethodisjust anestimation methodinsteadofgetting auratesignal,which isdescribed in7.Th edata setandthestatistical modelare known.The taskis toestimate themodels parameters.Always,the maximumlikelihood makesa approximatemodel withsome selectedparameters toforecast thewanted value.Here weconsider QPSK signal.For adiscre tetime blockandthesignalis transmitted through Rayleigh fadingchannel.The receivedsignal can be:y=Hx+n,where Hisaknown channelmatrix andnisthe noise.The fadingcoefficients are.To recoverthe original signal x,where xi i is oneof(1,-11,-i,i),then minimizes|y-Hx|2210.Simulation andAnalysis The wholeprocedureandanalysisBefore sourcebroadcasting thesignal,thesourcewill modulatethe digital signal intoQuadrature PhaseShift Keying(QPSK)signal Xs(1,-1,i,-ii).Thewholeprocedure isdividedintotwo timeslot.At thefirsttimeslot,thesourcesent thesignaltotherelay anddestination respectively.The mathematicalequation canbe presentas below:Source torelay:Y1=sqrt(P*1/2)*h1*S+n1()本文档所提供的信息仅供参考之用，不能作为科学依据，请勿模仿。 文档如有不当之处，请联系本人或网站删除。 Source to destination:Y2=sqrt(P*1/2)*h2*S+n2()Where Pmeans thesignal power,h1andh2istheRayleigh channelgainofsource torelay anddestinationrespectively.n1andn2are theadditive Gaussiannoise during eachchannel.The figurebelow describesthe behaviourofthesource atthefirsttimeslot.At thesecond timeslot,therelayreceive thenoisy signalY1fromsourceand amplifiesit byamplifycoefficientB.For efficientB,therearesome constraints forit.It isimpossible that thesignalwill notbe amplifiedinfinite.To ensurethepoweroftherelayislimited,B needsto satisfythe condition:B=sqrt(P/(P*|h1|22+N00)()Where N00isthepowerofthe noise.After amplified,thesignalwillbe:Y3=b*Y1=sqrt(P/(P*|h1|22+N00)*(sqrt(P*1/2)*h1*S+n1)()本文档所提供的信息仅供参考之用，不能作为科学依据，请勿模仿。 文档如有不当之处，请联系本人或网站删除。 The Y3istransmitted todestinationthroughRayleigh channel Y4=sqrt(P)*h3*Y3+n3=sqrt(P)*h3*sqrt(P/(P*|h1|22+N00)*(sqrt(P)*h1*S+n1)+n3=sqrt(P)*h3*sqrt(P/(P*|h1|22+N00)*sqrt(P)*h1*S+sqrt(P)*h3*sqrt(P/(P*|h1|22+N00)*n1+n3()So far,thedestinationreceived Y4and Y3two signal.The destinationsresponsibility hereis torecover“S”by Y4and Y3used MaximumLikelihood(ML)method.After thedigitalsignaltransmittedtoQPSK signal,every symbolofthesignal hasfour differentvalues dh=1-1i-i()B By selectingthe valueof“S(i)”fromthedh thatminimums theD3,constitute astring ofsignal whichis likelytotheoriginalsignal.D1=|Y4-sqrt(P)*h3*sqrt(P/(P*|h1|22+N00)*sqrt(P)*h1*S|22()D2=|Y2-sqrt(P)*h2*S|22()本文档所提供的信息仅供参考之用，不能作为科学依据，请勿模仿。 文档如有不当之处，请联系本人或网站删除。 D3=D1+D2()(which Sselected fromdh)Using thismethod,we cangettheprocessed signal“S“.Finally,thedestinationwill use the QPSKdemodulation methodto gettheoriginalsignal“s“.To judgetheperformanceofAFprotocol,a parameter“biterrorrate(BER)”isused.BER=E/N()Which Eisthe errorbits of processedsignal paredwith theoriginal,N isthe numberbitsoforiginalsignal.The B