fading-channel-qpsk-SIMULATION.zip_QPSK 信道均衡_QPSK信道均衡_多径 信道均衡_多径

clear;clc; %成型滤波器参数设置 R = 0.5; %平方根升余弦_滚降系数beta P = 10; %平方根升余弦_扩展周期span %信号参数设置 N = 8000; Bd = 512; %码速率 CarryFreq = 2048; %载波频率 fs = 2048*16; %采样频率 L = round(1/Bd*fs);%每个码元的长度 %信道参数 h_multitrace = [0.02 0.05 0.1 -0.2 1 -0.2 0.1 0.06 0.01]; %均衡器参数 M = 5; %抽头系数 C_equalization = force_zero(h_multitrace,M)';%确定迫零调整的抽头系数 %低通滤波器系数 load('lowpass.mat') [a,b]=tf(Hd); %误码率参数设置 EbNoxlabel = 20:1:52; %一般取20:1:40可以较好作图 errorprobability = zeros(1,length(EbNoxlabel)); SNRxlabel = EbNoxlabel + 10*log10(4) - 10*log10(N); %循环求误码率 for i = 1:length(SNRxlabel) snr = SNRxlabel(i); error = 0;count = 0; while error < 1 symbolbit = randi([0 1],1,N); symbol = 2*symbolbit-1; %1为1，0为-1 symbolreflect = symbol(1:2:N-1)+1i*symbol(2:2:N); %成型滤波 h = rcosdesign(R,P,L); %根升余弦滤波器 h_len = length(h); %内插零 symbolreflect_insert = zeros(1,N*L/2); symbolreflect_insert(1:L:N*L/2-1) = symbolreflect; symbolreflect_h = conv(symbolreflect_insert,h); %过滤波器并且内插零 cut = floor(h_len/2); %截取适当的长度，使长度变为bit数乘以L symbolreflect_h = symbolreflect_h(cut+1:length(symbolreflect_h)-cut); t=(0:length(symbolreflect_h)-1)/fs; Carrysignal = exp(1i*2*pi*CarryFreq*t); %载波，复数表示 %subplot(322);plot(faxis,abs(fft(Carrysignal,fftn))); xlim([0 fs]); %一定要注意i在之前的变量里有没有用到 frequencysignalup = real(symbolreflect_h.*Carrysignal);%正交上变频 %subplot(323);plot(faxis,abs(fft(frequencysignalup,fftn)));xlim([0 fs]); %多径信道参数设置 symbolmultitrace = conv(frequencysignalup,h_multitrace); cut = floor(length(h_multitrace)/2); symbolmultitrace = symbolmultitrace(cut+1:length(symbolmultitrace)-cut); %加性高斯信道 symbolawgn = awgn(symbolmultitrace,snr); %正交下变频 frequencysignaldown = symbolawgn.*conj(Carrysignal); %subplot(325);plot(faxis,abs(fft(frequencysignaldown,fftn)));xlim([0 fs]); %低通滤波 frequencysignaldown_lpf = conv(a,frequencysignaldown); %a为滤波器系数 %subplot(326);plot(faxis,abs(fft(frequencysignaldown_lpf,fftn)));xlim([0 fs]); alen_cut = length(a)/2; frequencysignaldown_lpf = frequencysignaldown_lpf(alen_cut+1:length(frequencysignaldown_lpf)-alen_cut); %接受匹配滤波 symbolreceive = conv(frequencysignaldown_lpf,h); cut = floor(length(h)/2); symbolreceive = symbolreceive(cut+1:length(symbolreceive)-cut); %均衡 symbolequal =conv(symbolreceive,C_equalization); cut = floor(length(C_equalization)/2); symbolreceive = symbolequal(cut+1:length(symbolequal)-cut); symboldetect = zeros(1,N); symboldetect(1:2:N-1) = (real(symbolreceive(1:L:end))>0); symboldetect(2:2:N) = (imag(symbolreceive(1:L:end))>0); error = sum(symboldetect~=symbolbit)+error; %计算错误比特数 count = count + 1; end errorprobability(i) = error/(count*N); end semilogy(EbNoxlabel,errorprobability);grid on; xlabel('EbNo');ylabel('error');