用matlab仿真DFE均衡器

1、DFE均衡器1. 基本原理均衡器用来消除码间干扰， DFE 即判决均衡器的主要思路是：一旦一个信息符号被检测并被判定后，就可在检测后续符号之前预测并消除由这个信息符 号带来的码间干扰。其基本功能是消除当前估计中的符号间干扰，这个干扰 是由前面检测的符号流引起的。2仿真程序(1) DFE主程序如下：clear allclose allclcglobal cir_matrix_tglobal Nglobal flagflag = 1;snr = 6:16;iter_num = 10;N = 1000;ber = ;for snr_index=1:length(snr)err = 0;lambda

2、= power(10,-snr(snr_index)/20);for iter =1:iter_numequal_bit = ;bit_signal = randint(1,N)；% bit_signal 为 1000 列的随机矩阵，矩阵的元素为 0 和 1 modul_signal = mod_4PSK(bit_signal); rx_sym = Through_channel(modul_signal,N/2); rx_signal = awgn(rx_sym,snr(snr_index);% rx_signal = rx_sym equal_signal = equalizer(rx_s

3、ignal,lambda);for k=1:N/2if real(equal_signal(1,k) equal_bit = equal_bit 0 0;elseif real(equal_signal(1,k) equal_bit = equal_bit 1 0;else equal_bit = equal_bit 0 1 ; endenderrr = sum(abs(equal_bit-bit_signal);err = err+ errr;enderr/(N*iter_num);snr_index;ber = ber err/(N*iter_num);endbersemilogy(snr

4、,ber,*-)hold ongrid on2) equalizer 子程序如下：function equal_out = equalizer(in_signal,lambda)global cir_matrix_tglobal Nglobal flagNf = 16;Nb = 8;len = length(in_signal);b_signal = zeros(1,Nb);for k = 1:N/2cir = cir_matrix_t(:,k).;cir_len = length(cir);Hff = convmtx(cir,Nf);Hfb = Hff(:,end-cir_len+2:end

5、);Hfb = Hfb,zeros(16,Nb-cir_len+1);Vff = eye(Nf+cir_len-1);Vff(Nf+1:end,Nf+1:end) = zeros(cir_len-1);Sff = Hff(:,Nf);Fffn = in v(Hff*Vff*Hff+(lambdaA2)*eye(Nf)*Sff;Ffb = -Hfb*Fffn;f_signal=zeros(1,max(0,k+Nf-1-len)in_signal(min(len,k+Nf-1):-1:k) .;out_sym = Fffn*f_signal+Ffb*b_signal.;equal_out(1,k)

6、 = hard_4QAM_demodul(out_sym);b_signal = equal_out(1,k) b_signal(1:end-1);end(3) hard_4QAM_demodu子程序如下：function symb_hard =hard_4QAM_demodul(in_signal)in_signal = in_signal*exp(j*pi/4);if real(in_signal)0if imag(in_signal)0symb_hard = 1;else symb_hard = -1*i;endelseif imag(in_signal)0symb_hard = i;e

7、lse symb_hard = -1;endend( 4)Through_channel 子程序如下：function rx_signal = Through_channel(tx_signal,signal_len) global cir_matrix_tglobal flagcir_matrix = ;if flag = 0C2= 0 ; 0 ; 0 ; 0 ; 0 ;C2= 1 .;C2= C2/norm(C2);endc_end = 1 .;% .;c_end = c_end/norm(c_end);% cir_cir = C2 ;cir_len = length(c_end); ci

8、r_matrix = cir_matrix C2;for k=1:signal_len+cir_len-1cir_matrixcir_matrixC2+(c_end-C2)/(2*(signal_len+cir_len-1);end cir_matrix_t = cir_matrix; cir_len , conv_len = size(cir_matrix) ; tx_temp=zeros(1,cir_len);for k=1:conv_lenif ksignal_len+1 tx_temp = tx_signal(1,k) tx_temp(1,1:end-1);else tx_temp = 0 tx_temp(1,1:end-1); endcir = cir_matrix(:,k);cir = cir/norm(cir); rx_signal(1,k) = tx_temp * cir;end(5) mod_4PS子程序如下：fun ctio n y=mod_4PSK(x)% 4PSK Modulator% x - binary input bits. The length of x must be multiples of 4. % y - complex output. vect