A space-time multiuser receiver with turbo partial parallel interference cancellation and adaptive beamforming for DS-CDMA systems

Direct-sequence code-division multiple access (DS-CDMA) is an important technique for third-generation and beyond wireless mobile communication systems. In DS-CDMA uplink systems, the multiple access interference (MAI) may cause serious degradation of the system performance and a multiuser detector is usually required for the receiver. By placing an antenna array at the base station and employing a beamforming technique for a partial parallel interference cancellation (PPIC) based multiuser detector, we can enhance the system performance appropriately; however, due to the steering vectors and channel fading gains being needed for the reconstruction of MAI in a PPIC-based multiuser detector, the system complexity may be increased by an additional estimation mechanism. For DS-CDMA uplink systems, we present a space-time PPIC-based multiuser receiver with adaptive beamforming based on the normalized least mean-squares algorithm. Using this adaptive mechanism, the channel information can easily be estimated from the beamforming weights. Computer simulation results show that the proposed multiuser receiver structure reaches acceptable performance with reasonable computational complexity in wireless environments.