Zero-forcing and minimum mean-square error multiuser detection in generalized multicarrier DS-CDMA systems for cognitive radio

Abstract

In wireless communications, multicarrier direct-sequence code-division multiple access (MC DS-CDMA) constitutes one of the highly flexible multiple access schemes. MC DS-CDMA employs a high number of degrees-of-freedom, which are beneficial to design and reconfiguration for communications in dynamic communications environments, such as in the cognitive radios. In this contribution, we consider the multiuser detection (MUD) in MC DS-CDMA, which motivates lowcomplexity,high flexibility, and robustness so that the MUD schemes are suitable for deployment indynamic communications environments. Specifically, a range of low-complexity MUDs are derivedbased on the zero-forcing (ZF), minimum mean-square error (MMSE), and interference cancellation(IC) principles. The bit-error rate (BER) performance of the MC DS-CDMA aided by the proposedMUDs is investigated by simulation approaches. Our study shows that, in addition to the advantagesprovided by a general ZF, MMSE, or IC-assisted MUD, the proposed MUD schemes can beimplemented using modular structures, where most modules are independent of each other. Dueto the independent modular structure, in the proposed MUDs one module may be reconfiguredwithout yielding impact on the others. Therefore, the MC DS-CDMA, in conjunction with theproposed MUDs, constitutes one of the promising multiple access schemes for communications inthe dynamic communications environments such as in the cognitive radios.