AWGN and Rayleigh channels response for turbo codes and iterative decoding

Designing a channel code is always a tradeoff between the complexity of encoder and decoder in conjunction with efficient energy and bandwidth goals. 'Turbo codes' code with mostly high-weight Code Words (hwCW), eventually make the task of the decoder easier. Through a parallel concatenation of two codes separated by an interleaver, turbo codes usually correct significant errors. In this paper, we provide an extended mathematical description for AWGN and Rayleigh channel response for turbo codes. The robustness of description is verified for a 3G communication system to show the effectiveness of iterative processing in extrinsic information. Performance comparison of the optimal decoding technique have been presented which shows that turbo codes have near Shannonian limit over AWGN channel but fading environment is still a challenging task for further improvement.