卷积码的matlab仿真

clear all; clc; snr_db = 0:10; %信息源 msg = randint(1,1e3); ber0 = zeros(1,length(snr_db)); ber1 = zeros(1,length(snr_db)); % Trellises trel = poly2trellis(3,[7 5]); %Define trellis for rate 1/2 code. for n=1:length(msg)/2; for x=1:length(snr_db) % Code words code = convenc(msg,trel); % Encode. state = 20; inter = randintrlv(code,state); % BPSK 调制 s0 = sign(msg-0.5); s1 = sign(inter-0.5); % AWGN Channel add_noise0=awgn(s0,snr_db(x),'measured'); add_noise1=awgn(s1,snr_db(x),'measured'); % Deinterleaver with noise for soft decoding deinter_noise = randdeintrlv(add_noise1,state); % 解调 r_0 = 0.5*sign(add_noise0) + 0.5; r_1 = 0.5*sign(add_noise1) + 0.5; % Deinterleaver deinter_1 = randdeintrlv(r_1,state); % Traceback length tblen = 5; % vitdec 判决 decoded1 = vitdec(deinter_1,trel,tblen,'cont','hard'); % vitdec 判决 % 比较误码率 [num0,rat0] = biterr(r_0,msg); [num1,rat1] = biterr(double(decoded1(tblen+1:end)),msg(1:end-tblen)); ber0(n,x) = rat0; ber1(n,x) = rat1; end end ber0 = mean(ber0); ber1 = mean(ber1); ber2 = zeros(1,length(snr_db)); ber3 = zeros(1,length(snr_db)); % Trellises trel2= poly2trellis(3,[1 6 5]); %Define trellis for rate 1/3 code. for n=1:length(msg)/2; for x=1:length(snr_db) % Code words code2 = convenc(msg,trel2); % Encode. state = 20; inter2 = randintrlv(code2,state); % BPSK 调制 s2 = sign(msg-0.5); s3 = sign(inter2-0.5); % AWGN Channel add_noise2=awgn(s2,snr_db(x),'measured'); add_noise3=awgn(s3,snr_db(x),'measured'); % Deinterleaver with noise for soft decoding deinter_noise = randdeintrlv(add_noise1,state); % 解调 r_2 = 0.5*sign(add_noise2) + 0.5; r_3 = 0.5*sign(add_noise3) + 0.5; % Deinterleaver deinter_3 = randdeintrlv(r_3,state); % Traceback length tblen2 = 5; % vitdec 判决 decoded2 = vitdec(deinter_3,trel2,tblen2,'cont','hard'); % vitdec 判决 % 比较误码率 [num2,rat2] = biterr(r_2,msg); [num3,rat3] = biterr(double(decoded2(tblen2+1:end)),msg(1:end-tblen2)); ber2(n,x) = rat2; ber3(n,x) = rat3; end end ber2 = mean(ber2); ber3 = mean(ber3); figure; semilogy(snr_db,ber1,'b-o',snr_db,ber3,'r-s'); xlabel('SNR (dB)'); ylabel('BER'); legend('(2,1,3)','(3,1,3)'); title('不同码率下的编码性能');