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https://github.com/jhshi/openofdm.git
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74 lines
2.0 KiB
Python
74 lines
2.0 KiB
Python
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# Authors: Veeresh Taranalli <veeresht@gmail.com>
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# License: BSD 3-Clause
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from fractions import gcd
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from numpy import array, arange, concatenate, convolve
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from commpy.channelcoding.gfields import GF, polymultiply, poly_to_string
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from commpy.utilities import dec2bitarray, bitarray2dec
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__all__ = ['cyclic_code_genpoly']
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def cyclic_code_genpoly(n, k):
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"""
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Generate all possible generator polynomials for a (n, k)-cyclic code.
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Parameters
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----------
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n : int
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Code blocklength of the cyclic code.
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k : int
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Information blocklength of the cyclic code.
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Returns
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-------
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poly_list : 1D ndarray of ints
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A list of generator polynomials (represented as integers) for the (n, k)-cyclic code.
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"""
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if n%2 == 0:
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raise ValueError("n cannot be an even number")
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for m in arange(1, 18):
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if (2**m-1)%n == 0:
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break
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x_gf = GF(arange(1, 2**m), m)
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coset_fields = x_gf.cosets()
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coset_leaders = array([])
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minpol_degrees = array([])
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for field in coset_fields:
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coset_leaders = concatenate((coset_leaders, array([field.elements[0]])))
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minpol_degrees = concatenate((minpol_degrees, array([len(field.elements)])))
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y_gf = GF(coset_leaders, m)
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minpol_list = y_gf.minpolys()
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idx_list = arange(1, len(minpol_list))
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poly_list = array([])
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for i in range(1, 2**len(minpol_list)):
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i_array = dec2bitarray(i, len(minpol_list))
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subset_array = minpol_degrees[i_array == 1]
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if int(subset_array.sum()) == (n-k):
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poly_set = minpol_list[i_array == 1]
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gpoly = 1
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for poly in poly_set:
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gpoly_array = dec2bitarray(gpoly, 2**m)
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poly_array = dec2bitarray(poly, 2**m)
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gpoly = bitarray2dec(convolve(gpoly_array, poly_array) % 2)
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poly_list = concatenate((poly_list, array([gpoly])))
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return poly_list.astype(int)
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if __name__ == "__main__":
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genpolys = cyclic_code_genpoly(31, 21)
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for poly in genpolys:
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print(poly_to_string(poly))
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