A Study on Performance Evaluation of the Asymmetric Turbo Codes

It is well known the fact that the turbo codes has better performance as the number of iterations and the interleaver size increase in an AWGN channel environment. However, if the number of iterations and the interleaver size are increased, it is required much delay and computation for an iterative decoding. And it is caused the flattening effect phenomenon which is very little BER performance improvement at the arbitrary SNR. This paper proposes the new asymmetric turbo codes, which is consisted of the parallel concatenated turbo codes, that uses the mixed types of the component codes with different not only the constraint length but also the generator polynomial. It analyzes the BER performance for the log-MAP decoding algorithm with the frame sizes of 128, 256, 512 and 1024 bits, and the coding rate of 1/3. The simulation result shows that the BER performance of the proposal asymmetric turbo codes is superior to the conventional symmetric turbo codes. It can be also observed that the flattening effect phenomenon is very reduced by applying the proposal asymmetric turbo codes.