BCH DVB-S2 codes for short code length LDPC

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george masters
george masters 2023-4-29
评论： george masters 2023-5-3
Ran in:
i am trying to create a BCH encoder for a DVB-S2 code based on Final draft ETSI EN 302 307 V1.2.1 (2009-04) table 5b (16200 ldpc code legnth). So i have used the following parmaters to generate the generator polynomials (g)
R = 8/9, Kbch = 14232, Nbch = 14400, t = 12, nldpc = 16200
R = 0.8889
Kbch = 14232
Nbch = 14400
t = 12
nldpc = 16200
g = x^12 + x^10 + x^9 + x^7 + x^6 + x^5 + x^3 + x^2 + x + 1
Accoridng to MATLAB, i can use this in comm.BCHEncode/comm.BCHDecode.
bchEnc = comm.BCHEncoder(Nbch,Kbch,'x^12 + x^10 + x^9 + x^7 + x^6 + x^5 + x^3 + x^2 + x + 1');
msg = randi([0 1],Kbch,1);
EncodedData = bchEnc(msg)
Error using comm.BCHEncoder/setParameters
The generator polynomial must evenly divide X^n+1, where n is the length of a full length code
However when i try this i get this error:
Error using comm.BCHEncoder/setParameters The generator polynomial must evenly divide X^n+1
So either i am using the wrong BCH encoder or ive got the polynomials wrong.

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采纳的回答

Sathvik
Sathvik 2023-5-2
Ran in:
Hi George
By setting a generator polynomial, you are shortening the BCH code to a message length of 5 (since the default ShortMessageLength property is set to 5), which may not be ideal for your parameters. I would suggest you to set the Parameters as follows.
enc = comm.BCHEncoder(Nbch,Kbch);
This way, the generator polynomial would be created automatically
Here is an example code to verify the BCH Encoder
Kbch = 14232;
Nbch = 14400;
% Encoding
msg = randi([0 1], Kbch, 1);
enc = comm.BCHEncoder(Nbch,Kbch);
y=enc(msg);
% Decoding
dec = comm.BCHDecoder(Nbch,Kbch);
z=dec(y);
isequal(msg,z)
ans = logical
1
You can refer to the following documentation for more information on how you can implement your BCH code
https://www.mathworks.com/help/comm/ref/comm.bchencoder-system-object.html
Hope this helps!

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