Date: Dec 18, 2010 10:37 AM
Author: Spiros
Subject: commBCHEncoder/commBCHDecoder

Hi to all, 
This question is considered with the use of Communications
Toolbox/Blockset.

I am trying to write a m-file that uses the comm.BCHEncoder/comm.Decoder in MATLAB R2010b for the DVB-T2 (DVB-S2 are the same) standard?.

In the DVB-S.2 model in Simulink the compiler doesn't complaint for any LDPC rate and everything seems OK.
In my code,if I try to use comm.BCHEncoder with any code rate other than 1/2 again everything is OK.
When I try Kbch=32208 and Nbch=32400,
I get an error:The values for N and K do not produce a valid narrow-sense BCH code.

%-----------------BCH encoding.... --------------------------------------
%
% Constrution of BCH_Encoder and BCH_Decoder
N_BCH=32400;
K_BCH=32208;
BBFrame=round(rand(32208,1));
BCH_Encoder=comm.BCHEncoder('CodewordLength',N_BCH,'MessageLength',K_BCH,'GeneratorPolynomial',g);
BCH_Decoder=comm.BCHDecoder('CodewordLength',N_BCH,'MessageLength',K_BCH,'GeneratorPolynomial',g);

BCHFrame=step(BCH_Encoder
Where BBframe is a random 32400 binary vector, and g the generator polynomial exactly the same as in the Simulink model DVB.S2 (can be found under "dvb stuct".
P.S. I also tried to use the PrimitivePolynomial with no success.

Hope for help
kindly regards Spiros