Uplink spectral efficiency of multiuser distributed MIMO-CDMA systems using loosely synchronised spreading codes

We consider a multiuser distributed MIMO system under multipath fading channels with wideband code-division multiple-access (CDMA) technology. The spreading codes of the CDMA system are assumed to employ loosely synchronized (LS) spreading codes. LS codes exhibit a so-called interference free window (IFW), where both the auto-correlation and cross-correlation of the codes become zero. Therefore LS codes have the promise of mitigating the effects of intersymbol interference (ISI) and multiple access interference (MAI) in multipath fading channels. The uplink spectral efficiency of the system is studied carefully when single-user detectors with different assumptions of interference knowledge are used at the receiver. Simulation results show that the uplink spectral efficiency of the distributed MIMO-CDMA system using LS codes can significantly outperform that of the system using random spreading codes.