如何解码LDPC
如何解码LDPC
提问于 2019-10-17 21:37:20
我生成一个奇偶校验矩阵，并使用comm.LDPCEncoder对码字进行编码。但是，当我使用comm.LDPCDecoder对LLR码进行解码时，解码后的字与信源不同。你能帮我找出哪里出了问题吗？
K = 4;N = 8;
H1 = [0 0 0 1 1 0 1 1;
0 0 0 0 1 1 0 0
1 1 0 0 0 0 0 1
0 0 1 0 0 1 0 1];
H = sparse(H1);
hEnc = comm.LDPCEncoder(H);
hDec = comm.LDPCDecoder(H);
msg_source = logical(randi([0 1], K, 1));
msg_coded = step(hEnc, msg_source);
LLR = double(msg_coded);
msg_decoded = step(hDec,LLR);
errors = (sum(xor(msg_source,msg_decoded)));非常感谢。
回答 2
Stack Overflow用户
发布于 2019-10-18 00:50:33
看起来LLR = double(msg_coded);是问题的根源。
我不是一个通信专家，也从未使用过LDPC编码器和解码器。
我尝试了MATLAB代码样本，发现经过调制和解调后，1s (1)为负值，0s (0)为正值。
代替LLR = double(msg_coded);
您可以使用以下转换：LLR = 1 - double(msg_coded)*2;。
0 --> 1
1 --> -1
修改后的代码如下：
K = 4;N = 8;
H1 = [0 0 0 1 1 0 1 1;
0 0 0 0 1 1 0 0
1 1 0 0 0 0 0 1
0 0 1 0 0 1 0 1];
H = sparse(H1);
hEnc = comm.LDPCEncoder(H);
hDec = comm.LDPCDecoder(H);
msg_source = logical(randi([0 1], K, 1));
msg_coded = step(hEnc, msg_source);
%LLR = double(msg_coded);
%Convert from logical to double where 0 goes to -1 and 1 goes to 1.
LLR = 1 - double(msg_coded)*2;
msg_decoded = step(hDec,LLR);
errors = (sum(xor(msg_source,msg_decoded)));下面是我用来查找问题的调制解调代码(基于MATLAB示例)：
K = 4;N = 8;
H1 = [0 0 0 1 1 0 1 1;
0 0 0 0 1 1 0 0
1 1 0 0 0 0 0 1
0 0 1 0 0 1 0 1];
H = sparse(H1);
hEnc = comm.LDPCEncoder(H);
hDec = comm.LDPCDecoder(H);
hMod = comm.PSKModulator(4, 'BitInput',true);
hChan = comm.AWGNChannel(...
'NoiseMethod','Signal to noise ratio (SNR)','SNR',10);
hDemod = comm.PSKDemodulator(4, 'BitOutput',true,...
'DecisionMethod','Approximate log-likelihood ratio', ...
'Variance', 1/10^(hChan.SNR/10));
msg_source = logical(randi([0 1], K, 1));
msg_coded = step(hEnc, msg_source);
modSignal = step(hMod, msg_coded);
receivedSignal = step(hChan, modSignal);
demodSignal = step(hDemod, receivedSignal);
msg_decoded = step(hDec, demodSignal);
errors = (sum(xor(msg_source,msg_decoded)));Stack Overflow用户
发布于 2019-10-21 19:35:59
为什么要将逻辑编码数据转换为双精度？尝试在编码后立即解码：
K = 4;N = 8;
H1 = [0 0 0 1 1 0 1 1;
0 0 0 0 1 1 0 0
1 1 0 0 0 0 0 1
0 0 1 0 0 1 0 1];
H = sparse(H1);
hEnc = comm.LDPCEncoder(H);
hDec = comm.LDPCDecoder(H);
msg_source = logical(randi([0 1], K, 1));
msg_coded = step(hEnc, msg_source);
msg_decoded = step(hDec,LLR);
errors = (sum(xor(msg_source,msg_decoded)));页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/58434030
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