Performance of asynchronous multicarrier CDMA multiuser receiver over frequency selective fading channels

An asynchronous multicarrier code division multiple access (MC-CDMA) scheme over frequency selective multipath Rayleigh fading channels for the reverse link of a mobile communication system is investigated when the delay spread is in excess of a symbol interval. An architecture of a centralized decision feedback equalizer (CDFE) based on the minimum mean-square-error (MMSE) criterion is suggested to reduce both inter-symbol-interference (ISI) and multiple access interference (MAI) due to the multi-path propagation, and the MAI due to the effect of the reverse asynchronous reception mode at the base station. The receiver architecture is for multi-user detection (MUD) consisting of a multiple-layer feed-forward filter (ML-FFF) and a centralized feed back filter (CFBF). Results indicate that an enhancement in capacity and good interference resistance are obtained by the proposed multi-user detection scheme over the structure without CFBF (NCDFE), which only uses ML-FFF and FBF. Additionally, it is demonstrated that the structure performs multi-path energy Rake combining.