Improvement of interleaver for Turbo codes in wireless communication

Performance of Turbo code in wireless communications depends critically. on the efficient design of interleaver. This paper describes improvement of interleaver design based on the distance spectrum, of the code. This paper analyzes the impact of weight-2, 3, 4 and 5 input sequences on the codewords. Considering all these low weight inputs, a set of condition is developed and this constraint set is suggested to be used with the S-random interleaving algorithm. This improved algorithm can eliminate or decrease the low free distance of codewords. The improvement is presented in terms of interleaver gain by using Bit Error Rate (BER) performance curve. Impact of frame size, number of shift registers of the encoder on interleaver gain is shown. Increased complexity for this improvement is shown in terms of simulation time.