Comprehensive evaluation of chip interleaving effect on turbo-coded DS-SS in a Rayleigh fading channel with antenna diversity reception

In this paper, we present a comprehensive performance evaluation of chip interleaving effect on turbo coded direct sequence spread spectrum (DS-SS) system in a frequency non-selective Rayleigh fading channel with antenna diversity reception. At the transmitter, chip interleaver scrambles the SF (spreading factor) chips associated with a data symbol and transforms the transmission channel into a highly time-selective or highly memoryless channel at the chip level. The use of chip interleaving is equivalent to using SF-antenna diversity reception with correlated fading among the branches and with reduced average received signal power per antenna by a factor of SF. We theoretically analyze how chip interleaving alters the received signal statistics. Then, the effect of the various parameters, viz. interleaver size, interleaving depth, information sequence length, spreading factor and the fading maximum Doppler frequency, are also evaluated. It is found that the bit error rate (BER) performance improves with increasing spreading factor and increasing frame length. Chip interleaving is found to be effective in the presence of receive antenna diversity as well. Copyright # 2005 John Wiley & Sons, Ltd.