基于MATLAB实现的OFDM系统中抗多径衰落的仿真+使用说明文档.zip

% ofdm_mod.m function [qam_out] = Qam4_mod(qam_in) %% 4QAM 调制函数 %% 输入： 矩阵，列数必须是4的倍数，01序列 %% 输出： 矩阵，4qam调制后的矩阵 global QamTable global bitPerSymbol; QamTable = [ -1-i, 1-i, -1+i, 1+i ]; [ m, n ] = size(qam_in); qam_out = zeros(m,n/bitPerSymbol); for k = 1:m QamTmp = reshape(qam_in(k,:),bitPerSymbol,n/bitPerSymbol)'; QamTmpTmp = bi2de( QamTmp, 'left-msb'); qam_out(k, :) = QamTable( QamTmpTmp+1 ); end ofdm_demod.m function [qam_out] = Qam4_demod(qam_in) %% 4QAM 解调函数 %% 输入： 矩阵，列数必须是的的倍数 %% 输出： 矩阵，解调后的01序列矩阵 %% 之前必须调用过 global QamTable; global bitPerSymbol ; [m,n] = size(qam_in); qam_out = zeros(m,n*bitPerSymbol); % 判决 for k = 1:m delt = abs(reshape(qam_in(k,:), n, 1)*ones(1,4) - ones(n,1)*QamTable); %求最近的点 [tmp, index] = min(delt,[],2); %得到索引值 qam_outTmp = de2bi(index-1,bitPerSymbol,'left-msb'); qam_out(k,:) = reshape(qam_outTmp',1,bitPerSymbol*n); end ofdm_mod_neq.m function [s_out] = ofdm_mod_neq( s_in ) %% ofdm 调制，无均衡 %% 输入：二进制序列 %% 输出：ofdm调制后符号 %global CP_len; global nSubC global ifft_len; global symbolPerCarrier; global bitPerSymbol; global CP_len; global carriers; len = length(s_in); SQam = reshape(s_in, nSubC,len/nSubC); %串并转换 PQam = Qam4_mod(SQam); carriers = (1: nSubC) + (floor( ifft_len/4) - floor(nSubC/2)); conj_carriers = ifft_len - carriers + 2; P_IFFT = zeros(ifft_len, symbolPerCarrier ); % 一个符号块，含4列训练序列，1列 0 P_IFFT(carriers,:) = PQam; P_IFFT(conj_carriers,:)=conj(PQam); % 构造共轭矩阵 PCh = real(ifft( P_IFFT )); PCh2 = cat(1, PCh((ifft_len-CP_len+1):ifft_len,:), PCh); % 添加 CP s_out = reshape(PCh2, 1, (ifft_len+CP_len)*(symbolPerCarrier)); %并串转换 ofdm_mod_eq.m function [s_out] = ofdm_mod_eq( s_in ) %% ofdm 调制，带均衡 %% 输入：二进制序列 %% 输出：ofdm调制后符号 %global CP_len; global nSubC global ifft_len; global symbolPerCarrier; global bitPerSymbol; global trainingSymbols; global trainingSymbols_len; global CP_len; global carriers; len = length(s_in); SQam = reshape(s_in, nSubC,len/nSubC); %串并转换 PQam = Qam4_mod(SQam); tmpTable = [-1,1,i,-i]; trainingSymbols_len = 10; trainingSymbols = (tmpTable(floor( 4*rand(trainingSymbols_len,nSubC))+1 ))'; PQam = cat(2,zeros(nSubC,1),PQam); PQam = cat(2,trainingSymbols,PQam); carriers = (1: nSubC) + (floor( ifft_len/4) - floor(nSubC/2)); conj_carriers = ifft_len - carriers + 2; P_IFFT = zeros(ifft_len,1 + symbolPerCarrier + trainingSymbols_len); P_IFFT(carriers,:) = PQam; P_IFFT(conj_carriers,:)=conj(PQam) ; PCh = (ifft( P_IFFT ,ifft_len,1)); PCh2 = cat(1, PCh((ifft_len-CP_len+1):ifft_len,:), PCh); % 添加 CP s_out = reshape(PCh2, 1, (ifft_len+CP_len)*(symbolPerCarrier +trainingSymbols_len + 1)); %并串转换 channel.m function [s_out] = channel(s_in, SNR) %% 信道函数 % 模拟多径信道 global fade; Len = length(s_in);f_len = length(fade); sch = s_in; for m = 1:f_len sch(1+m:Len) = sch(1+m:Len) + fade(m)*(s_in(1:Len-m)); end % 高斯信道 Tx_signal_power = var(sch); % 方差 linear_SNR = 10^( SNR /10) ; noise_sigma = Tx_signal_power / linear_SNR; noise_scale_factor = sqrt(noise_sigma) ; noise = randn(1, length(sch) )*noise_scale_factor; %模拟信道噪声,为随机数,即高斯白噪 s_out = sch + noise; ofdm_demod_neq.m function [s_out] = ofdm_demod_neq(s_in) %% ofdm 解调 %% 输入为二进制序列 global ifft_len; global CP_len; global bitPerSymbol; global symbolPerCarrier; global carriers; global s_len; P_S = reshape(s_in, ifft_len+CP_len, symbolPerCarrier); % 接收 ，进行串并转换 PDeCP = P_S(1+CP_len:ifft_len+CP_len,:); %去CP P_FFT = fft(PDeCP); P_FFT2 = P_FFT(carriers,:); SQam = Qam4_demod(P_FFT2); s_out = reshape(SQam,1,s_len); % 并串转换 ofdm_demod_eq.m function [s_out] = ofdm_demod_eq(s_in) %% ofdm 解调 %% 输入为二进制序列 global trainingSymbols; global trainingSymbols_len; global ifft_len; global CP_len; global bitPerSymbol; global symbolPerCarrier; global carriers; global s_len % 接收 ，进行串并转换 P_S = reshape(s_in, ifft_len+CP_len, symbolPerCarrier + trainingSymbols_len + 1); PDeCP = P_S(1+CP_len:ifft_len+CP_len,:); %去C P P_FFT = fft(PDeCP,ifft_len,1); P_FFT2 = P_FFT(carriers,:); RxTrainSymbols = P_FFT2(:, (1: trainingSymbols_len)); %RxTrainSymbols = P_FFT2(:, (1: trainingSymbols_len),size(P_FFT2,2)-trainingSymbols_len+1:size(P_FFT2,2)); %信道均衡 H = RxTrainSymbols./ trainingSymbols; H_2 = H.^2; H_2 = sum(H_2,2); H_C2 = sum(H,2); H_C2 = conj(H_C2); H = H_C2./H_2 ; % 1/H = conj(H)/H^2 P_FFT3 = H*ones(1,size(P_FFT2,2)).*P_FFT2 ; P_FFT4 = P_FFT2(:,(trainingSymbols_len+2:size(P_FFT3,2))); SQam = Qam4_demod(P_FFT4); s_out = reshape(SQam,1,s_len); % 并串转换 test1.m %% 本测试为 不同信道环境下系统误码率曲线 %% close all;clear all; clc; tic ; %计时开始 global CP_len; global nSubC; global ifft_len; global bitPerSymbol; global symbolPerCarrier; global s_len; global fade; %信道衰弱 %% 测试参数 %SNR = 40; % dB CP_len = 0;nSubC = 48;ifft_len = 256;bitPerSymbol = 2;symbolPerCarrier = 50; % 开始测试 s_len = nSubC*bitPerSymbol* symbolPerCarrier; SNR = 0:2:20; ber1 = zeros(1,length(SNR));ber2 = zeros(1,length(SNR));ber3 = zeros(1,length(SNR)); for kk = 1:length(SNR) max = floor((2^kk)/10)+10; fprintf('仿真信噪比： %d\n', SNR(kk)); fprintf('仿真点数： %d\n', max*bitPerSymbol*symbolPerCarrier*nSubC); fade = [0]; % 信道参数，下标为延时点数，值为衰减系数 ber = 0; for m = 1:max % 生成用于测试的随机比特 s_in = floor( rand(1, s_len )*2 ); sch = ofdm_mod_eq(s_in); sch = channel(sch,SNR(kk)); s_out = ofdm_demod_eq(sch); %计算误比特率 err_count = sum(abs(s_in-s_out)); ber = ber + err_count/s_len; end ber1(kk) = ber/max; fade = [0, 0, 0, 0, 0.4]; % 信道参数 ber = 0; for m = 1:max s_in = floor( rand(1, s_len )*2 ); sch = ofdm_mod_eq(s_in); sch = channel(sch,SNR(kk)); s_out = ofdm_demod_eq(sch); %计算误比特率 err_count = sum(abs(s_in-s_out)); ber = ber + err_count/s_len; end ber2(kk) = ber/max ; fade = [0, 0, 0, 0, 0.4, 0.3]; % 信道参数，下标为延时点数，值为衰减系数 ber = 0; for m = 1:max % 生成用于测试的随机比特 s_in = floor( rand(1, s_len )*2 ); sch = ofdm_mod_eq(s_in); sch = channel(sch,SNR(kk)); s_out = ofdm_demod_eq(sch); %计算误比特率 err_count = sum(abs(s_in-s_out)); ber = ber + err_count/s_len; end ber3(kk) = ber/max ; end figure(2); semilogy(SNR,ber1,'o-'); hold on;semilogy(SNR,ber2,'r*-');hold on; semilogy(SNR,ber3,'gv-');xlabel('SNR in dB');ylabel('Bit Error Rate'); legend('AWGN','AWGN + 2 path','AWGN + 3 path');grid; toc test2.m %% 多径信道下，有无添加CP的系统误码率曲线 close all;clear all; clc; tic ; %计时开始 global CP_len; global nSubC; global ifft_len; global bitPerSymbol; global symbolPerCarrier; global s_len; global fade; %信道衰弱 %% 测试参数 CP_len = 0;nSubC = 48;ifft_len = 256;bitPerSymbol = 2;symbolPerCarrier = 50; fade = [0, 0, 0, 0.4, 0.3]; % 信道参数 % 开始测试 s_len = nSubC*bitPerSymbol* symbolPerCarrier; SNR = 0:2:30; ber1 = zeros(1,length(SNR));ber2 = zeros(1,length(SNR)); for kk = 1:length(SNR) max = floor((2^(kk))/50)+10; fprintf('仿真信噪比： %d\n', SNR(kk)); fprintf('仿真点数： %d\n', max*nSubC*bitPerSymbol*symbolPerCarrier); CP_len = 0; ber = 0; for m = 1:max % 生成用于测试的随机比特 s_in = floor( rand(1, s_len )*2 ); sch = ofdm_mod_neq(s_in); sch = channel(sch,SNR(kk)); s_out = ofdm_demod_neq(sch); %计算误比特率 err_c