Chip interleaved turbo codes for DS-CDMA in a Rayleigh fading channel with diversity reception

A new channel interleaving method, called chip interleaving, for direct sequence code division multiple access (DS-CDMA) mobile radio is proposed. Chip interleaver scrambles the chips and transforms the transmission channel into a highly time-selective or highly memoryless channel. It was found that the turbo decoding performance which degrades in a fading channel is significantly improved with chip interleaving. It was also found that the bit error rate (BER) performance improves with increasing spreading factor (SF) and increasing frame length. Chip interleaving is effective in the presence of antenna diversity as well, however the improvement decreases with the increase in the number of antennas.