數(shù)字通信第5章-加性高斯白噪聲的最佳接收機

第5章加性高斯白噪聲信道的最佳接收機1234５.1受加性高斯白噪聲惡化信號的最佳接收機

5678相關(guān)解調(diào)器91011121314151617181920結(jié)論2122232425最佳AWGN接收機的實現(xiàn)形式2627282930313233343536375.2無記憶調(diào)制的最佳接收機

性能分析

38二進制調(diào)制的錯誤概率1、2PAM2、正交信號3940414243444546Binarysignals47Exercises5-4,5-8,4849505152M=2,equalstotheantipodalsignalskincreasebyone,4dBSNRisrequiredUseGraycoding,535455565758UseGraycoding,5960616263644PSKand4QAMarecomparableWhenM>4,M-aryQAMisbetterthanM-aryPSK6566Thepdfoffirstcorrelationis

Therestofcorrelation67TheprobabilityofcorrectdecisionisForeachterm68Thecorrectdecision

Symbolerrorrate69Forthebiterrorrate

70Orthogonalsignals71M-arybiorthogonalsignalsConstructedfromM/2orthogonalsignalsDemodulation:UseM/2orthogonalcrosscorrelationormatchedfiltersTx:s1(t)72CrosscorrelationThesignusedtodetermines(t)or-s(t)wastransmittedThecorrectdecisionfors1(t)r1>0r1>rm=nmThus,-r1<nm<r1,correct73Theprobabilityofcorrectdecisionis

74Biorthogonalsignals75DifferentialPSKThereceivedsignaliscomparedwithphaseoftheprecedingsignalnocarrierinformationneeded76Nonoise,->k-k-1Nonoise,->rkr*kisindependentofcarrierphase77ErrorprobabilityestimationofDPSKAssumption:k-k-1=0

->comparedwithnk-1andnk78x,yaretheuncorrelatedGaussianrandomvariable,N0SimilartoPSKnoiseistwicelargerDPSKhas3dBpoorerperformance79BinaryPSKandDPSK->lessthan3dBdifferencesPbgetsmaller,differencesbecomessmall80BPSK&4PSKhavethesameBER4phaseDPSKworsethan2phaseDPSK81數(shù)字調(diào)制方式的比較帶寬和頻帶利用率（歸一化數(shù)據(jù)速率R/W）給定的錯誤概率情況下，R/W和比特SNR的關(guān)系曲線帶寬受限區(qū)域功