数字通信第5章-加性高斯白噪声的最佳接收机PPT课件.ppt

.,*,单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,第5章加性高斯白噪声信道的最佳接收机,.,.,.,.,.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、2PAM,2、正交信号,.,.,.,.,.,.,.,.,Binary signals,.,Exercises,5-4,5-8,.,.,.,.,.,M=2,equals to the antipodal signals,k increase by one,4dB SNR is required,Use Gray coding,.,.,.,.,.,.,Use Gray coding,.,.,.,.,.,.,4PSK and 4QAM are comparable,When M4,M-ary QAM is better than M-ary PSK,.,.,The pdf of first correlation is,The rest of correlation,.,The probability of correct decision is,For each term,.,The correct decision,Symbol error rate,.,For the bit error rate,.,Orthogonal signals,.,M-ary biorthogonal signals,Constructed from M/2 orthogonal signals,Demodulation:Use M/2 orthogonal cross correlation or matched filters,Tx:s,1,(t),.,Cross correlation,The sign used to determine s(t)or-s(t)was transmitted,The correct decision for s1(t),r,1,0,r,1,r,m,=n,m,Thus,-r,1,n,m,k,-,k,-1,No noise,-,r,k,r,*,k,is independent of carrier phase,.,Error probability estimation of DPSK,Assumption:,k,-,k-1,=0,-compared with n,k-1,and n,k,.,x,y,are the uncorrelated Gaussian random variable,N,0,Similar to PSK,noise is twice larger,DPSK has 3 dB poorer performance,.,Binary PSK and DPSK-less than 3dB differences,Pb,get smaller,differences becomes small,.,BPSK&4PSK have the same BER,4 phase DPSK worse than 2 phase DPSK,.,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,.,.,.,.,.,.,.,.,.,.,