毕业论文：OFDM通信系统抗多径衰落性能仿真

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

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%% 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_count = sum(abs(s_in-s_out));

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ber = ber + err_count/s_len ; end

ber1(kk) = ber/max;

fprintf('cp=0 :%f\\n',ber1(kk)); CP_len = 16; 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_count = sum(abs(s_in-s_out)); ber = ber + err_count/s_len; end

ber2(kk) = ber/max ;

fprintf('cp=16 :%f\\n\\n',ber2(kk)); end

figure(2);semilogy(SNR,ber1,'o-');hold on;

semilogy(SNR,ber2,'r*-');xlabel('SNR in dB');ylabel('Bit Error Rate'); legend('no CP','CP');grid; toc test3.m

%% 本测试为 有无使用均衡情况下的系统误码率曲线 %%

close all;clear all; clc; tic ; %计时开始 global CP_len; global nSubC;

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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 = 16;nSubC = 48;ifft_len = 256;bitPerSymbol = 2;symbolPerCarrier = 50; fade = [0, 0, 0, 0.4, 0.3]; % 信道参数，下标为延时点数，值为衰减系数 % 开始测试

s_len = nSubC*bitPerSymbol*symbolPerCarrier; SNR = 0:2:20;

ber1 = zeros(1,length(SNR));ber2 = 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); CP_len = 16 ; 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_count = sum(abs(s_in-s_out)); ber = ber + err_count/s_len; end

ber1(kk) = ber/max;

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fprintf('无均衡 BER = %f\\n',ber1(kk)); CP_len = 16; 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

ber2(kk) = ber/max ;

fprintf('均衡和CP BER = %f\\n\\n',ber2(kk)); end

figure(2);semilogy(SNR,ber1,'o-');hold on;

semilogy(SNR,ber2,'r*-');xlabel('SNR in dB');ylabel('Bit Error Rate'); legend('without equilizer','with equlizer');grid; toc

参考文献：

[1] 吕爱琴，等，基于MATLAB的OFDM系统仿真及性能分析[A]，计算机仿真，2005，10－0164－05

[2] 徐发强，等，OFDM系统在短波宽带信道上均衡方法 [3] 尹泽明，等，精通MATLAB6[M]，清华大学出版社，2002 [4] 王文播，等，宽带无线通信OFDM技术，人民邮电出版社，2003 [5] 尹长川，等编，多载波宽带无线通信技术，北京邮电大学出版社，2004

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