On turbo code interleavers optimized by bit error rate evolution and free distance evolution

Since their appearance in 1993, first approaching the Shannon limit, turbo codes gave a new direction in the channel encoding field, especially since they have been adopted for multiple telecommunication norms. To obtain an excellent performance, it is necessary to design a robust turbo code interleaver. We are using genetic algorithms as an optimization method to find a well-performing interleaver for large frame sizes. In this paper, we introduce a novel evolutionary method for interleaver optimization, compare the proposed method with several previous approaches and present experimental results. We compare the results obtained for two fitness functions: the bit error rate measured after simulated transmission of information and the analytically estimated maximum free distance.