Performance of a STBC-CDMA system in a fading channel

Space-time coding is known to be a potential technique for improving the reliability of wireless communication over fading channels. In this paper, we investigate the performance of a space-time coded CDMA system in a fading channel. Although significant amount of related work is found in literature, not much reported work exists on the use of Gold codes as spreading sequences in such systems. In this paper, we investigate the performance of a space-time block-coded CDMA system for different chip lengths, ranging from 31-chip to 511-chip Gold codes. Results show that at low signal-to-noise ratio, the coding gain provided by the codes surpasses the diversity advantage provided by the use of the multiple antennas. The results also show that coding gain between no-diversity link and its Gold-coded counterpart is the same as that between the transmit-diversity link and its Gold-coded counterpart. The independence of the diversity advantage provided by multiple transmit antennas and the coding gain obtainable from the use of the spreading sequences enables the prediction of the performance of composite space-time block-coded CDMA systems.