数字通信第5章_加性高斯白噪声的最佳接收机课件

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: s1(t) Cross correlation The sign used to determine s(t) or -s(t) was transmitted The correct decision for s1(t) r1 0 r1 rm=nm Thus, -r1 k-k-1 No noise, - rkr*k is independent of carrier phase Error probability estimation of DPSK Assumption: k-k-1=0 - compared with nk-1 and nk x, y are the uncorrelated Gaussian random variable , N0 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 n带宽和频带利用率（归一化数据速率R/W） n给定的错误概率情况下，R/W和比特SNR