Decode and recover message from RS codeword

This example shows how to use RS Decoder block to decode and recover a message from a Reed-Solomon (RS) codeword. In this example, a set of random inputs are generated and provided to the comm.RSEncoder function and its output is provided to the RS Decoder block. The output of the RS Decoder block is compared with the input of the comm.RSEncoder function to check whether any errors are encountered. The example model supports HDL code generation for the RS Decoder subsystem.

Set Up Input Data parameters

Specify the input variables.

n = 255;
k = 239;
primPoly = [1 0 0 0 1 1 1 0 1];
B = 1;
nMessages = 4;
data = zeros(k,nMessages);
inputMsg = (zeros(n,nMessages));
startSig = [];
endSig = [];

Generate Random Input Samples

Generate random samples based on n,k, and m values and provide them as input to the comm.RSEncoder function. Here, n is the codeword length, k is the message length, and m is the gap between the frames.

hRSEnc = comm.RSEncoder;
hRSEnc.CodewordLength = n;
hRSEnc.MessageLength = k;
m=0;

for ii = 1:nMessages
data(:,ii) = randi([0 n],k,1);
[inputMsg(1:n,ii)] = hRSEnc(data(:,ii));
inputMsg1(1:n,ii) = inputMsg(1:n,ii);
[inputMsg(n+1:n+m,ii)] = zeros(m,1);
validIn(1:n,ii) = true;
validIn(n+1:n+m) = false;

endSig = [endSig [false(n-1,1); true;false(m,1);]];
startSig = [startSig [true;false(n+m-1,1)]];

end

refOutput = data(:);

Import Encoded Random Input Samples to the Simulink® Model

Provide the output of the comm.RSEncoder function as input to the Simulink model.

simDataIn = inputMsg(:);
simStartIn = startSig(:);
simEndIn = endSig(:);
simValidIn = validIn(:);

Run the Simulink Model

Run the Simulink model to export the decoded samples of the Simulink block to the MATLAB® workspace.

modelname = 'RSDecoder';
open_system(modelname);
out = sim(modelname);
simOutput = out.dataOut(out.validOut);

Compare Simulink Block Output with MATLAB Function Input

Compare the output of the Simulink block with the input provided to the comm.RSEncoder function.

fprintf('\nHDL RS Decoder\n');
difference = double(simOutput) - double(refOutput);
fprintf('\nTotal number of samples differed between Simulink block output and MATLAB function output is: %d \n',sum(difference));

HDL RS Decoder

Total number of samples differed between Simulink block output and MATLAB function output is: 0