An adaptive multiuser detector for MC-CDMA systems in frequency-selective multipath-fading channels

The multi-carrier code-division multiple access (MC-CDMA) system is characterized by implementing the spectral spreading operation in the frequency domain, however, it can be also viewed as a special form of DS-CDMA in the time domain. In this paper, a time-domain adaptive centralized decision-feedback multiuser detector (MUD) is proposed for a synchronous MC-CDMA system in a frequency-selective multipath-fading channel. The suggested receiver employs a nonlinear centralized decision-feedback equalizer to suppress both intersymbol interference (ISI) and multi-access interference (MAI). The recursive least-squares (RLS) algorithm is employed to optimize the receiver parameters by minimizing the time-average weighted squared error. The performance of the proposed receiver architecture is evaluated in a multipath-fading channel exhibiting four propagation paths. Uniform and exponential multipath intensity profiles (MIP) are investigated. Computer simulation results demonstrate that the overall performance of the considered system which uses the proposed MUD outperforms both the conventional equal gain and maximum ratio combiner (EGC, MRC), as well as the single-user detector (SUD).