Encode message to RS codeword

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This example shows how to use the RS Encoder block to encode a message to a Reed-Solomon (RS) codeword. In this example, a set of random inputs frames are generated and provided to the comm.RSEncoder System object. Using the whdlFramesToSamples function, these frames are converted into samples and provided as input to the RS Encoder block. The output of the RS Encoder block is then compared with the output of the comm.RSEncoder System object to check whether the encoded output codeword for the given input message is same. By default, the puncturing option is disabled in this example. To enable puncturing, set the puncturing value to true. This example model supports HDL code generation for the RS Encoder subsystem.

Set Up Input Data Parameters

Set up these workspace variable for the models to use. These variables configure the RS Encoder block inside the model.

nMessages = 3;
n = 255;                               % Specify codeword length
k = 239;                               % Specify message length
m = n-k;                               % Parity length
inDataType = fixdt(0,ceil(log2(n)),0);
puncturing = false;                    % true for puncturing
puncturePattern = randsrc(m,1,[0 1]);  % Considered, when punturing is true
shortMsg = false;                      % true for shortened message
k1 = k-1;                              % Considered when shortMsg is true

Generate Random Input Samples

Generate random samples using n, k, and m variables and provide those generated samples as input to the comm.RSEncoder System object.

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

if isequal(shortMsg,true)
    hRSEnc.ShortMessageLength = k1;
else
    k1 = k;
end

if isequal(puncturing,true)
    hRSEnc.PuncturePatternSource = "Property";
    hRSEnc.PuncturePattern = puncturePattern;
    puncLen = n-k-sum(hRSEnc.PuncturePattern);
else
    puncLen = 0;
end

data = cell(1,nMessages);
refData = (zeros(k1+m-puncLen,nMessages));

for ii = 1:nMessages
    data{ii} = randi([0 n],k1,1);
    refData(:,ii) = hRSEnc(data{ii});
end

refOutput = refData(:);

Generate Input Control Samples for the Simulink® Model

gapBetweenFrames = n-k;
gapBetweenSamples = 0;

[simDataIn, ctrlIn] = whdlFramesToSamples(data,gapBetweenSamples,gapBetweenFrames);
simStart = ctrlIn(:,1);
simEnd = ctrlIn(:,2);
simValidIn = ctrlIn(:,3);
stopTime = length(simValidIn);

Run Simulink Model

Run the Simulink model. The block imports the workspace variables and generates the output.

modelname = 'HDLRSEncoder';
open_system(modelname);
if isequal(puncturing,true)
    set_param([modelname '/RS Encoder/RS Encoder'],'PuncturePatternSource','on');
    set_param([modelname '/RS Encoder/RS Encoder'],'PuncturePattern',['[' num2str(puncturePattern') ']']);
end
out = sim(modelname);

Export the Simulink Block Output to the MATLAB® Workspace

The encoded samples from the RS Encoder block are exported to the MATLAB workspace.

simOutput = dataOut(validOut);

Compare the Simulink Block Output with the MATLAB Function Output

Capture the output of the RS Encoder block. Compare that output with the output of the comm.RSEncoder System object.

fprintf('\nHDL RS Encoder\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 Encoder

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