数字通信第5章_加性高斯白噪声的最佳接收机课件

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1、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,equalstotheantipodalsignalskincreasebyone,4dBSNRisrequiredUseGraycoding,UseGraycoding,4PSKand4QAMarecomparableWhenM>4,M-aryQAMisb

2、etterthanM-aryPSKThepdfoffirstcorrelationisTherestofcorrelationTheprobabilityofcorrectdecisionisForeachtermThecorrectdecisionSymbolerrorrateForthebiterrorrateOrthogonalsignalsM-arybiorthogonalsignalsConstructedfromM/2orthogonalsignalsDemodulation:UseM/2orthogonalcr

3、osscorrelationormatchedfiltersTx:s1(t)CrosscorrelationThesignusedtodetermines(t)or-s(t)wastransmittedThecorrectdecisionfors1(t)r1>0r1>rm=nmThus,-r1<nm

4、phaseoftheprecedingsignalnocarrierinformationneededNonoise,->k-k-1Nonoise,->rkr*kisindependentofcarrierphaseErrorprobabilityestimationofDPSKAssumption:k-k-1=0->comparedwithnk-1andnkx,yaretheuncorrelatedGaussianrandomvariable,N0SimilartoPSKnoiseistwicelargerDPSK

5、has3dBpoorerperformanceBinaryPSKandDPSK->lessthan3dBdifferencesPbgetsmaller,differencesbecomessmallBPSK&4PSKhavethesameBER4phaseDPSKworsethan2phaseDPSK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