High performance phase rotated FD-MC-CDMA to exploit full diversity

FD-MC-CDMA is an attractive frequency domain CDMA system that provides high performance in multi-path fading channels by exploiting both diversity gain and multi-user detection (MUD) gain. In FD-MC-CDMA, by decomposing the entire subcarrier set into multiple non-contiguous subcarrier sets, the number of interfering users within each subcarrier set is significantly reduced. As a direct result, an optimal maximum likelihood MUD receiver can be implemented at low complexity. In this paper, we first revisit previously developed phase rotation spreading code design to bring signal space diversity to conventional MC-CDMA systems. Similarly, due to the binary nature of the spreading codes, full diversity is not always exploited in FD-MC-CDMA system. Then we combine the phase rotated spreading code design scheme with FD-MC-CDMA system to exploit full diversity. With the phase rotated spreading codes and the exploitation of full diversity, the new FD-MC-CDMA system offers significant performance enhancement compared with the original FD-MC-CDMA system along with conventional MC-CDMA system. Simulation results over multi-path fading channels confirm the performance gain of the proposed scheme.