Multichannel adaptive beamforming and interference mitigation in multiuser CDMA systems

In CDMA systems, multiple users produce cochannel interference that is only partially mitigated by user-dependent spreading codes. Limitations in any closed-loop transmitter power control can create received power variations at the base station that are potentially large. Multichannel multiuser detectors are data-adaptive receivers that provide interference mitigation as well as spatial and temporal diversity. These receivers are discussed in the context of CDMA applications. A maximum likelihood formulation of multiuser detection with antenna arrays is introduced to provide motivation and intuition. The proposed multiuser receiver incorporates space-time beamforming and time-domain interference cancellation. Performance examples using simulated and experimental data are given along with comparisons with a variety of receiver types.