Differential parallel combinatorial CDMA systems in multipath fading channels

This paper investigates the error rate performance of differential parallel combinatorial CDMA (DP/CDMA) systems in frequency-nonselective and frequency-selective Rician fading channels. The DPC/CDMA system is one of the multi-code DS/CDMA techniques using orthogonal pseudo-noise (PN) sequences. The information data are conveyed by the combination of pre-assigned PN sequences and by the polarity the transmitting PN sequences. Multiple information bits are conveyed by the combination of the pre-assigned PN sequences set, so that they are capable of making the data rate higher with longer PN sequences. The bit error rate (BER) performance of uncoded and coded DPC/CDMA systems are analyzed by the standard Gaussian approximation for co-channel interference analysis. The effect of diversity and error control coding are considered throughout the analysis. Numerical results show that the coded DPC/CDMA systems provide substantial BER improvement compared with conventional DPSK-DS/CDMA systems. Using explicit diversity enhances the advantage of coded DPC/CDMA systems. If stronger line-of-sight signals are available in Rician fading channels, the coded DPC/CDMA systems are more advantageous even though the available spreading factor is small