Matlab programms for encoding and decoding of LDPC codes over GF(2^m).(600 KB)

There is an example of how to use the LDPC encode/decode with AWGN channel model in files .\ldpc_decode.m and .\GFq\ldpc_decode.m. There are a few parity check matrices available in the code but you can use other matrices provided you have enough memory to load them. I suggest checking out matrices in Alist format available on David MacKay's web site.You will need to have access to a MEX compiler to be able to use a few functions written in C. A sample code of LDPC encode/decode is shown below:

% Example:
% We assume G is systematic G=[A|I] and therefore mod(G*H',2)=0
sigma = 1; % AWGN noise deviation
x = (sign(randn(1,size(G,1)))+1)/2; % random bits
y = mod(x*G,2); % coding
z = 2*y-1; % BPSK modulation
z=z + sigma*randn(1,size(G,2)); % AWGN transmission
f1=1./(1+exp(-2*z/sigma^2)); % likelihoods
f0=1-f1;
[z_hat, success, k] = ldpc_decode(z,f0,f1,H);
x_hat = z_hat(size(G,2)+1-size(G,1):size(G,2));
x_hat = x_hat'; % result of decoding

Matlab programms for Wavelet image denoising(670 KB)

The matlab functions (dn1, dn2, dn3 and dn4) implement ML and MAP procedures for image denoising in wavelet domain using local Gaussian model for an image (and exponential prior in the case of MAP). For details refer to the paper, our ICASSP 1999 presentation and Kivanc's webpage.

Low-Complexity Image Denoising Based on Statistical Modeling of Wavelet Coefficients
Kivanc Mihcak, M.; Kozintsev, I.; Ramchandran, K.; Moulin, P., IEEE Signal Processing Letters, Volume: 6 Issue: 12, Dec. 1999
PDF

I recommend trying dn2. This denoising method uses several sizes for estimation window to predict the local variance and chooses the smallest one. You will need to implement your favorite wavelet transform and create function fwt_image.m or email me and I will forward you my version. Other assumptions: grayscale 512x512 image (a few examples are provided) in raw format and 6 level orthogonal wavelet transform. Please see headers and test.m for example usage.