📄 turbo_sys_demo.html
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"><html xmlns:mwsh="http://www.mathworks.com/namespace/mcode/v1/syntaxhighlight.dtd"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> <!--This HTML is auto-generated from an M-file.To make changes, update the M-file and republish this document. --> <title>turbo_sys_demo</title> <meta name="generator" content="MATLAB 7.6"> <meta name="date" content="2008-11-10"> <meta name="m-file" content="turbo_sys_demo"><style>body { background-color: white; margin:10px;}h1 { color: #990000; font-size: x-large;}h2 { color: #990000; font-size: medium;}/* Make the text shrink to fit narrow windows, but not stretch too far in wide windows. */ p,h1,h2,div.content div { max-width: 600px; /* Hack for IE6 */ width: auto !important; width: 600px;}pre.codeinput { background: #EEEEEE; padding: 10px;}@media print { pre.codeinput {word-wrap:break-word; width:100%;}} span.keyword {color: #0000FF}span.comment {color: #228B22}span.string {color: #A020F0}span.untermstring {color: #B20000}span.syscmd {color: #B28C00}pre.codeoutput { color: #666666; padding: 10px;}pre.error { color: red;}p.footer { text-align: right; font-size: xx-small; font-weight: lighter; font-style: italic; color: gray;} </style></head> <body> <div class="content"><pre class="codeinput"><span class="comment">% This script simulates the classical turbo encoding-decoding system.</span><span class="comment">% It simulates parallel concatenated convolutional codes.</span><span class="comment">% Two component rate 1/2 RSC (Recursive Systematic Convolutional) component encoders are assumed.</span><span class="comment">% First encoder is terminated with tails bits. (Info + tail) bits are scrambled and passed to</span><span class="comment">% the second encoder, while second encoder is left open without tail bits of itself.</span><span class="comment">%</span><span class="comment">% Random information bits are modulated into +1/-1, and transmitted through a AWGN channel.</span><span class="comment">% Interleavers are randomly generated for each frame.</span><span class="comment">%</span><span class="comment">% Log-MAP algorithm without quantization or approximation is used.</span><span class="comment">% By making use of ln(e^x+e^y) = max(x,y) + ln(1+e^(-abs(x-y))),</span><span class="comment">% the Log-MAP can be simplified with a look-up table for the correction function.</span><span class="comment">% If use approximation ln(e^x+e^y) = max(x,y), it becomes MAX-Log-MAP.</span><span class="comment">%</span><span class="comment">% Copyright Nov 1998, Yufei Wu</span><span class="comment">% MPRG lab, Virginia Tech.</span><span class="comment">% for academic use only</span>clear <span class="string">all</span><span class="comment">% Write display messages to a text file</span>diary <span class="string">turbo_logmap.txt</span><span class="comment">% Choose decoding algorithm</span>dec_alg = input(<span class="string">' Please enter the decoding algorithm. (0:Log-MAP, 1:SOVA) default 0 '</span>);<span class="keyword">if</span> isempty(dec_alg) dec_alg = 0;<span class="keyword">end</span><span class="comment">% Frame size</span>L_total = input(<span class="string">' Please enter the frame size (= info + tail, default: 400) '</span>);<span class="keyword">if</span> isempty(L_total) L_total = 400; <span class="comment">% infomation bits plus tail bits</span><span class="keyword">end</span><span class="comment">% Code generator</span>g = input(<span class="string">' Please enter code generator: ( default: g = [1 1 1; 1 0 1 ] ) '</span>);<span class="keyword">if</span> isempty(g) g = [ 1 1 1; 1 0 1 ];<span class="keyword">end</span><span class="comment">%g = [1 1 0 1; 1 1 1 1];</span><span class="comment">%g = [1 1 1 1 1; 1 0 0 0 1];</span>[n,K] = size(g);m = K - 1;nstates = 2^m;<span class="comment">%puncture = 0, puncturing into rate 1/2;</span><span class="comment">%puncture = 1, no puncturing</span>puncture = input(<span class="string">' Please choose punctured / unpunctured (0/1): default 0 '</span>);<span class="keyword">if</span> isempty(puncture) puncture = 0;<span class="keyword">end</span><span class="comment">% Code rate</span>rate = 1/(2+puncture);<span class="comment">% Fading amplitude; a=1 in AWGN channel</span><span class="comment">% a = 1;</span><span class="comment">% Number of iterations</span>niter = input(<span class="string">' Please enter number of iterations for each frame: default 5 '</span>);<span class="keyword">if</span> isempty(niter) niter = 5;<span class="keyword">end</span><span class="comment">% Number of frame errors to count as a stop criterior</span>ferrlim = input(<span class="string">' Please enter number of frame errors to terminate: default 15 '</span>);<span class="keyword">if</span> isempty(ferrlim) ferrlim = 15;<span class="keyword">end</span>EbN0db = input(<span class="string">' Please enter Eb/N0 in dB : default [2.0] '</span>);<span class="keyword">if</span> isempty(EbN0db) EbN0db = [2.0];<span class="keyword">end</span>fprintf(<span class="string">'\n\n----------------------------------------------------\n'</span>);<span class="keyword">if</span> dec_alg == 0 fprintf(<span class="string">' === Log-MAP decoder === \n'</span>);<span class="keyword">else</span> fprintf(<span class="string">' === SOVA decoder === \n'</span>);<span class="keyword">end</span>fprintf(<span class="string">' Frame size = %6d\n'</span>,L_total);fprintf(<span class="string">' code generator: \n'</span>);<span class="keyword">for</span> i = 1:n <span class="keyword">for</span> j = 1:K fprintf( <span class="string">'%6d'</span>, g(i,j)); <span class="keyword">end</span> fprintf(<span class="string">'\n'</span>);<span class="keyword">end</span><span class="keyword">if</span> puncture==0 fprintf(<span class="string">' Punctured, code rate = 1/2 \n'</span>);<span class="keyword">else</span> fprintf(<span class="string">' Unpunctured, code rate = 1/3 \n'</span>);<span class="keyword">end</span>fprintf(<span class="string">' iteration number = %6d\n'</span>, niter);fprintf(<span class="string">' terminate frame errors = %6d\n'</span>, ferrlim);fprintf(<span class="string">' Eb / N0 (dB) = '</span>);<span class="keyword">for</span> i = 1:length(EbN0db) fprintf(<span class="string">'%10.2f'</span>,EbN0db(i));<span class="keyword">end</span>fprintf(<span class="string">'\n----------------------------------------------------\n\n'</span>);fprintf(<span class="string">'+ + + + Please be patient. Wait a while to get the result. + + + +\n'</span>);<span class="keyword">for</span> nEN = 1:length(EbN0db) en = 10^(EbN0db(nEN)/10); <span class="comment">% convert Eb/N0 from unit db to normal numbers</span><span class="comment">% L_c = 4*a*en*rate; % reliability value of the channel</span> sigma = 1/sqrt(2*rate*en); <span class="comment">% standard deviation of AWGN noise</span><span class="comment">% Clear bit error counter and frame error counter</span> errs(nEN,1:niter) = zeros(1,niter); nferr(nEN,1:niter) = zeros(1,niter); nframe = 0; <span class="comment">% clear counter of transmitted frames</span> <span class="keyword">while</span> nferr(nEN, niter)<ferrlim h =(randn(1,1)+j*randn(1,1)); a = abs(h); L_c = 4*a*en*rate; <span class="comment">% reliability value of the channel</span> nframe = nframe + 1; x = round(rand(1, L_total-m)); <span class="comment">% info. bits</span> [temp, alpha] = sort(rand(1,L_total)); <span class="comment">% random interleaver mapping</span> en_output = encoderm( x, g, alpha, puncture ) ; <span class="comment">% encoder output (+1/-1)</span> r = h*en_output+sigma*randn(1,L_total*(2+puncture)); <span class="comment">% received bits</span> yk = demultiplex(r,alpha,puncture); <span class="comment">% demultiplex to get input for decoder 1 and 2</span><span class="comment">% Scale the received bits</span> rec_s = 0.5*L_c*yk;<span class="comment">% Initialize extrinsic information</span> L_e(1:L_total) = zeros(1,L_total); <span class="keyword">for</span> iter = 1:niter<span class="comment">% Decoder one</span> L_a(alpha) = L_e; <span class="comment">% a priori info.</span> <span class="keyword">if</span> dec_alg == 0 L_all = logmapo(rec_s(1,:), g, L_a, 1); <span class="comment">% complete info.</span> <span class="keyword">else</span> L_all = sova0(rec_s(1,:), g, L_a, 1); <span class="comment">% complete info.</span> <span class="keyword">end</span> L_e = L_all - 2*rec_s(1,1:2:2*L_total) - L_a; <span class="comment">% extrinsic info.</span><span class="comment">% Decoder two</span> L_a = L_e(alpha); <span class="comment">% a priori info.</span> <span class="keyword">if</span> dec_alg == 0 L_all = logmapo(rec_s(2,:), g, L_a, 2); <span class="comment">% complete info.</span> <span class="keyword">else</span> L_all = sova0(rec_s(2,:), g, L_a, 2); <span class="comment">% complete info.</span> <span class="keyword">end</span> L_e = L_all - 2*rec_s(2,1:2:2*L_total) - L_a; <span class="comment">% extrinsic info.</span><span class="comment">% Estimate the info. bits</span> xhat(alpha) = (sign(L_all)+1)/2;<span class="comment">% Number of bit errors in current iteration</span> err(iter) = length(find(xhat(1:L_total-m)~=x));<span class="comment">% Count frame errors for the current iteration</span> <span class="keyword">if</span> err(iter)>0 nferr(nEN,iter) = nferr(nEN,iter)+1; <span class="keyword">end</span> <span class="keyword">end</span> <span class="comment">%iter</span><span class="comment">% Total number of bit errors for all iterations</span> errs(nEN,1:niter) = errs(nEN,1:niter) + err(1:niter); <span class="keyword">if</span> rem(nframe,3)==0 | nferr(nEN, niter)==ferrlim<span class="comment">% Bit error rate</span>⌨️ 快捷键说明
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