BCH Primitive Polynomial Edit

[jstarustka]

I have two questions, but first a little background.  I am using the modulation toolkit which comes with a BCH Encode and Decode vi.  I am reproducing a signal that was BCH encoded using 31,21,2 values and a generator polynomial of g(x)=x^10 + x^9 + x^8 + x^6 + x^5 + x^3 + 1.  My first question is does the BCH encode vi that comes with the modulation toolkit use this polynomial or some other polynomial.  I believe that the vi is using g(x)=x^5 + x^2 + 1, is this correct?  If my assumption is correct is there a way to edit the BCH Encode vi so that it will be forced to use the first polynomial when I select the 31,21,2 option.

Thanks

Joe

[David L.]

Hi jstarustka,

I am looking into the algorithm and polynomial a bit further, and will post back. If I understand the question correctly, you want to use the 31,21,2 input to the ‘BCH encoder.vi’, but change the polynomial it will use, correct?

Regards,

[jstarustka]

That is correct. I would like to change the generator polynomial in the 31,21,2 option thereby bypassing the primitive polynomial and LCM derivation along with the error checking that the vi uses.  I need to make some custom block codes for the system that I am working on.  After digging through the vi I think that the primitive polynomial used for the 31,21,2 option is g(x)= x^5 + x^2 + 1 and the generator polynomial is g(x)=x^10 + x^9 + x^8 + x^6 + x^5 + x^3 + 1, but I am not sure so if you could verify this I would greatly appreciate it.

Thanks

Joe

[Yardov]

Hi Joe,

You are correct in those values. You can see if you dig in the program the arrays for p(x) and g(x).
You can see that they match the ones that you will find in a BCH table of coefficients in a textbook. I am not sure why you need to change those (since they are defined) but probably that is your current experiment.
Best of luck,