数字通信第5章-加性高斯白噪声的最佳接收机

第5章加性高斯白噪声信道的最佳接收机５.1受加性高斯白噪声恶化信号的最佳接收机相关解调器结论最佳AWGN接收机的实现形式5.2无记忆调制的最佳接收机性能分析二进制调制的错误概率1、2PAM2、正交信号BinarysignalsExercises5-4,5-8,•M=2,equalstotheantipodalsignals•kincreasebyone,4dBSNRisrequired•UseGraycoding,MbPkP1UseGraycoding,MbPkP14PSKand4QAMarecomparableWhenM4,M-aryQAMisbetterthanM-aryPSK021011exp1|NrNsrps0201exp1|NrNsrpmmThepdfoffirstcorrelationisTherestofcorrelation111111312|,...,drsrpsrnrnrnPPMcdxxdxsrpsrnPNrrmmmm01122112exp21|TheprobabilityofcorrectdecisionisForeachterm11122012exp21drrpdxxPMNrccMPP1ThecorrectdecisionSymbolerrorrate121kMMPMPMkkkMknPkPnk122121121221MkMkbPPPForthebiterrorrateOrthogonalsignalsM-arybiorthogonalsignalsConstructedfromM/2orthogonalsignalsDemodulation:UseM/2orthogonalcrosscorrelationormatchedfiltersTx:s1(t)222211...MMsnrnrnrCrosscorrelation2/,...2,1,21MmsrCMkmkkmmsrsr,Thesignusedtodetermines(t)or-s(t)wastransmittedThecorrectdecisionfors1(t)•r10•r1rm=nmThus,-r1nmr1,correctdxxdxNxNrrnPNrNrrrm222020110101112exp21exp10Theprobabilityofcorrectdecisionis0111222201012exp21drrpdxxPMNrNrccMPP1BiorthogonalsignalsDifferentialPSK•Thereceivedsignaliscomparedwithphaseoftheprecedingsignal•nocarrierinformationneededkksknjrexp111expkksknjr*11*11*1expexpexpkkkkskkskkskknnnjnjjrrNonoise,-k-k-1Nonoise,-rkr*kisindependentofcarrierphaseErrorprobabilityestimationofDPSKAssumption:k-k-1=0kjexp-comparedwithnk-1andnk*1*1kkskknnnn*1*1*1kkkksskknnnnrr*1*1ImRekkkksnnynnxx,yaretheuncorrelatedGaussianrandomvariable,N0xyr1tan•SimilartoPSK•noiseistwicelarger•DPSKhas3dBpoorerperformance0exp21NPbb•BinaryPSKandDPSK-lessthan3dBdifferences•Pbgetsmaller,differencesbecomessmall•BPSK&4PSKhavethesameBER•4phaseDPSKworsethan2phaseDPSK数字调制方式的比较带宽和频带利用率（归一化数据速率R/W）给定的错误概率情况下，R/W和比特SNR的关系曲线带宽受限区域功率受限区域信道容量限5.5有线和无线通信系统性能分析本节内容再生中继器无线通信中链路预算分析