A Unified Analysis of Diversity Exploitation in Multicarrier CDMA

Since the introduction of multicarrier code-division multiple access (MC-CDMA), several publications have presented various detection concepts for efficient and robust multiuser communications in the up- and downlink. System concepts, which either exploit channel knowledge at the transmitter or at the receiver, have been investigated. The approach, which exploits channel knowledge at the transmitter and at the receiver simultaneously, referred to as combined-equalization, is a new approach that targets a common optimization of data transmission and reception. In this paper, we introduce a unified analysis for optimally exploiting diversity. We apply this analysis exemplarily to MC-CDMA systems exploiting any of the aforementioned concepts. It should be noted that this analysis could be applied to numerous other systems that exploit diversity. The presented approach analytically derives the theoretical lower performance bounds for pre-, post-, and combined-equalization achievable with MC-CDMA in up- and downlink. This fundamental investigation of lower bounds will serve as a benchmark for future optimization of MC-CDMA in multiuser scenarios. Moreover, we exemplarily present multiuser performance results with combined-equalization for the uplink which approach the lower bound derived in this paper.