Abstract: For finding the optimal period interleaver, we rearrange the information polynomial of Turbo codes as a matrix based on the divisibility between the information polynomial and the feedback polynomial. Any column of the matrix can be permuted randomly, and the permutation between columns should satisfy the form which is the automorphism group of the binary cyclic Turbo code generated by the feedback polynomial. According to this idea a method to find the form of the optimal period interleaver is given. From the computer simulation we find that such an interleaver can improve the BER performance of Turbo codes.

Key words: Turbo codes, the optimal period interleaver, the divisibility of polynomial