ccsdsRSDecode

Generate a full-length encoded Reed-Solomon (RS) codeword, introduce random errors, and decode the result using a Consultative Committee for Space Data Systems (CCSDS) RS decoder.

Generate a random message of length k.

k = 223;
msg = randi([0 255],k,1);

Encode the message by using a CCSDS RS encoder.

code = ccsdsRSEncode(msg,k);

Generate 15 random error symbols and 15 unique random locations to insert these errors.

err = randi([1 255],15,1);
errLoc = randperm(255,15);
errVec = zeros(255,1);
errVec(errLoc) = err;

Introduce error symbols in the encoded message.

rxBytes = bitxor(code,errVec);

Decode the encoded symbols introduced with errors by using CCSDS RS decoder.

[decoded,v,ccode] = ccsdsRSDecode(rxBytes, k);

Display the number of corrected errors.

disp(v)

    15

Generate an full-length encoded Reed-Solomon (RS) codeword, introduce burst of errors, and decode the result using a Consultative Committee for Space Data Systems (CCSDS) RS decoder.

Specify the message length k and interleaving depth, i.

k = 239;
i = 5;

Generate a column vector of random message bits. Encode the message by using a CCSDS RS encoder.

msg = randi([0 255],k*i,1);
code = ccsdsRSEncode(msg,k,i);

Generate 30 random error symbols.

err = randi([1 255],30,1);
errVec = zeros(255*i,1);

Introduce burst errors from location 52 to 81.

errVec(52:81) = err;
rxBytes = bitxor(code,errVec);

Decode the encoded symbols introduced with burst errors by using a CCSDS RS decoder.

[decoded,v,ccode] = ccsdsRSDecode(rxBytes,k,i);

Display the number of corrected errors.

disp(v)

    30

Encode-decode a bit-input shortened CCSDS RS encoded codeword with interleaving, in the presence of additive white Gaussian noise (AWGN) channel.

Encode the bit-input shortened message using CCSDS RS encoder.

k = 239;  % Message length
s = 219;  % Shortened message length
i = 5;    % Interleaving depth
msg = logical(randi([0 1],s*i*8,1)); % Datatype is logical for bit input
codeBits = ccsdsRSEncode(msg,k,i,s);

QAM modulate a signal, add AWGN, and then demodulate to get the LLR bits.

M = 4;
txSig = qammod(double(codeBits),M, ...
     InputType="bit",UnitAveragePower=true);  % QAM modulation
snr = 10;                                     % SNR in dB
rxSig = awgn(txSig,snr,"measured",0);        % AWGN addition
llr = qamdemod(rxSig,M,"OutputType", ...
   "approxllr","UnitAveragePower",true, ...
   NoiseVariance=10.^(-snr/10));              % LLR demapper

Demodulate the RS encoded codeword using the CCSDS RS decoder.

[decoded,v,ccode] = ccsdsRSDecode(llr<0,k,i,s);

Calculate the BER.

berCalc = comm.ErrorRate;
errInfo = berCalc(msg,decoded);
numErr = int32(errInfo(2));      % Number of erroneous bits

Display the error information.

fprintf('Number of errors after decoding = %d.\n', numErr);

Number of errors after decoding = 0.

fprintf('Number of errors corrected = %d.\n', int32(v));

Number of errors corrected = 7.