Estimate BER of QPSK in AWGN with Reed-Solomon (240,224) Coding

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Anouar Nechi
Anouar Nechi 2023-9-12
回答： Balaji 2023-9-22
Ran in:
I want to make a BER estimate of QPSK in AWGN with RS(240.224) as depicted in this paper. So I began with something working like the MATLAB example and I just made parameter changes as follows:
rng(1993); % Seed random number generator for repeatable results
M = 4; % Modulation order
bps = log2(M); % Bits per symbol
N = 240; % RS codeword length
K = 224; % RS message length
rsEncoder = comm.RSEncoder( ...
BitInput=true, ...
CodewordLength=N, ...
MessageLength=K);
rsDecoder = comm.RSDecoder( ...
BitInput=true, ...
CodewordLength=N, ...
MessageLength=K);
ebnoVec = (3:0.5:8)';
ebnoVecCodingGain = ...
ebnoVec + 10*log10(K/N); % Account for RS coding gain
errorStats = zeros(length(ebnoVec),3);
for i = 1:length(ebnoVec)
awgnChannel.EbNo = ebnoVecCodingGain(i);
reset(errorRate)
while errorStats(i,2) < 100 && errorStats(i,3) < 1e7
data = randi([0 1],1500,1);
encData = rsEncoder(data);
modData = pskmod(encData,M,InputType='bit');
rxSig = awgnChannel(modData);
rxData = pskdemod(rxSig,M,OutputType='bit');
decData = rsDecoder(rxData);
errorStats(i,:) = errorRate(data,decData);
end
end
Unrecognized function or variable 'errorRate'.
berCurveFit = berfit(ebnoVecCodingGain,errorStats(:,1));
semilogy(ebnoVecCodingGain,errorStats(:,1),'b*', ...
ebnoVecCodingGain,berCurveFit,'c-')
ylabel('BER')
xlabel('Eb/No (dB)')
legend('RS coded BER','Curve Fit')
grid
I keep getting this error:
Error using comm.RSEncoder/setupImpl
the dimensions of the Input X must be consistent with the BitInput property value, the message and Codeword lengths, and primitive polynomial. ...
Could someone help me please fixing this issue. Thank you

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采纳的回答

Balaji
Balaji 2023-9-22
Hi Anour
I understand that you are facing an error in using the ‘comm.RSEncoder’.
When the ‘BitInput’ property is set to 1, the message length should be be an integer multiple of (MessageLength×M)  bits.
Where ‘MessageLength’ is ‘K’ and N = 2M -1. The current code doesn’t follow that property.
A group of M bits represents an integer in the range [0, (2M – 1)] that belongs to the finite Galois field gf(2M)
For more information on ‘comm.RSEncoder’ I suggest you refer to the following documentation:
https://www.mathworks.com/help/comm/ref/comm.rsencoder-system-object.html
Hope this helps
Thanks
Balaji

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