Efficient Selection of Circular and Random Interleaver for Turbo Codes Multiuser CDMA System with Hadamard Spreading code in AWGN and Rayleigh Fading Channels

Abstract

Recently, turbo codes have attracted many researchers because of the codes astonishing performance at low signal to noise ratio SNR. The interleaver types and lengths is an important part in the design of a turbo code. In this paper, the performance of turbo codes with efficient selection length for random and circular interleaver is studied with various issues related to the turbo code performance are investigated. These include the effect of number of decoding iteration used in iterative decoding algorithm, the effect of number of states used in a convolutional code, the effect of interchanges the interleaver type and the effect of the interleaver length for Multiuser-CDMA system. Simulation results show that the BER performance of random interleavers is better than circular interleavers for all SNR and the efficient performance gained for turbo coded 16 user CDMA system in AWGN or Rayleigh fading channels when using Random interleaver of length 512 or Circular interleaver of length 1024. The BER performances are evaluated using MATLAB R2009a computer simulation software.