2010年本科毕业论文：LDPC码的编译码算法研究

参考文献

[1] [2] [3] [4] [5] [6] 版社,2006

[7] [8]

张德丰. MATLAB/Simulink建模与仿真. 电子工业出版社,2009 邵玉斌. MATLAB/SIMULINK通信系统建模与仿真实例分析. 清华大学贺鹤云. LDPC码基础与应用. 人民邮电出版社,2009 袁东风, 张海刚. LDPC码理论与应用, 人民邮电出版社,2008 符初生,周亮,文红. LDPC码原理与应用. 电子科技大学出版社,2006 （美）传特. 通信系统仿真原理与无线应用. 机械工业出版社,2005 周建兴. MATLAB从入门到精通. 人民邮电出版社, 2008

（美）亨塞尔曼，（美）利特菲尔德. 精通Matlab 7. 清华大学出

出版社,2008

[9]

张建国.LDPC码的应用研究[J].通信技术.2003年11期2

[10] 李水平,刘玉君,王云鹤.串行级联LDPC码[J].信息工程大学学报.2004年02期

[11] 苏杰,王琳,赵春雨.规则LDPC码在瑞利平坦衰落信道下的设计和仿真[J].电讯技术.2004年05期

[12] 王鹏,王新梅.LDPC码的快速编码研究[J].西安电子科技大学学报.2004年06期

[13] 仲海梅,王锐华.4G中的纠错编码技术LDPC码及其新进展[J].广东通信技术.2004年12期

[14] J Chen, A Dholakia, E Eleftheriou. “Reduced-complexity decoding of LDPC codes”. 2005.

21

代码

% Bit error rate of BPSK modulated LDPC codes under AWGN channel clc; clear all;

% LDPC matrix size, rate must be 1/2

% Warning: encoding - decoding can be very long for large LDPC matrix! M = 1000; N = 2000;

% Method for creating LDPC matrix (0 = Evencol; 1 = Evenboth) method = 1;

% Eliminate length-4 cycle noCycle = 1;

% Number of 1s per column for LDPC matrix onePerCol = 3;

% LDPC matrix reorder strategy (0 = First; 1 = Mincol; 2 = Minprod) strategy = 2;

% EbN0 in dB

EbN0 = [0 0.5 1 1.5];

% Number of iteration; iter = 5;

% Number of frame (N bits per frame) frame = 10;

% Make the LDPC matrix

H = makeLdpc(M, N, 1, 1, onePerCol);

for i = 1:length(EbN0)

ber1(i) = 0; ber2(i) = 0;

% Make random data (0/1)

dSource = round(rand(M, frame));

for j = 1:frame

fprintf('Frame : %d\\n', j);

% Encoding message

[c, newH] = makeParityChk(dSource(:, j), H, strategy); u = [c; dSource(:, j)];

% BPSK modulation bpskMod = 2*u - 1;

% Additional white gaussian noise N0 = 1/(exp(EbN0(i)*log(10)/10));

tx = bpskMod + sqrt(N0/2)*randn(size(bpskMod));

22

% Decoding (select decoding method)

%vhat = decodeProbDomain(tx, H, newN0, iter); vhat1 = decodeLogDomain(tx, newH, N0, iter); vhat2 = decodeLogDomainSimple(tx, newH, iter); %vhat = decodeBitFlip(tx, newH, ter);

% Get bit error rate (for brevity, BER calculation includes parity bits) [num1, rat1] = biterr(vhat1', u); ber1(i) = (ber1(i) + rat1);

[num2, rat2] = biterr(vhat2', u); ber2(i) = (ber2(i) + rat2);

end % for j

% Get average of BER ber1(i) = ber1(i)/frame; ber2(i) = ber2(i)/frame;

end % for i

% Plot the result

semilogy(EbN0, ber1, 'o-'); hold;

semilogy(EbN0, ber2, 'o--'); grid on; hold off;

function H = makeLdpc(M, N, method, noCycle, onePerCol) % Create R = 1/2 low density parity check matrix %

% M : Number of row % N : Number of column

% method : Method for distributing non-zero element

% {0} Evencol : For each column, place 1s uniformly at random

% {1} Evenboth: For each column and row, place 1s uniformly at random % noCyle : Length-4 cycle

% {0} Ignore (do nothing) % {1} Eliminate

% onePerCol: Number of ones per column %

% H : Low density parity check matrix % %

% Copyright Bagawan S. Nugroho, 2007 % http://bsnugroho.googlepages.com

% Number of ones per row (N/M ratio must be 2) if N/M ~= 2

fprintf('Code rate must be 1/2\\n'); end

onePerRow = (N/M)*onePerCol;

fprintf('Creating LDPC matrix...\\n');

23

switch method % Evencol case {0}

% Distribute 1s uniformly at random within column for i = 1:N

onesInCol(:, i) = randperm(M)'; end

% Create non zero elements (1s) index

r = reshape(onesInCol(1:onePerCol, :), N*onePerCol, 1); tmp = repmat([1:N], onePerCol, 1); c = reshape(tmp, N*onePerCol, 1);

% Create sparse matrix H H = full(sparse(r, c, 1, M, N));

% Evenboth case {1}

% Distribute 1s uniformly at random within column for i = 1:N

onesInCol(:, i) = randperm(M)'; end

% Create non zero elements (1s) index

r = reshape(onesInCol(1:onePerCol, :), N*onePerCol, 1); tmp = repmat([1:N], onePerCol, 1); c = reshape(tmp, N*onePerCol, 1);

% Make the number of 1s between rows as uniform as possible

% Order row index [r, ix] = sort(r);

% Order column index based on row index for i = 1:N*onePerCol cSort(i, :) = c(ix(i)); end

% Create new row index with uniform weight tmp = repmat([1:M], onePerRow, 1); r = reshape(tmp, N*onePerCol, 1);

% Create sparse matrix H

% Remove any duplicate non zero elements index using logical AND S = and(sparse(r, cSort, 1, M, N), ones(M, N)); H = full(S);

end % switch

% Check rows that have no 1 or only have one 1 for i = 1:M

n = randperm(N);

% Add two 1s if row has no 1 if length(find(r == i)) == 0 H(i, n(1)) = 1;

24