Interference management for CDMA systems through power control, multiuser detection, and beamforming

Among the ambitious challenges to be met by the third-generation systems is to provide high-capacity flexible ser,ices, Code-division multiple access (CDMA) emerges as a promising candidate to meet these challenges. It is wel l known that CDMA systems are interference-limited, and interference manage ment is needed to maximally utilize the potential gains of this access sche me, Several methods of controlling and/or suppressing the interference thro ugh power control, multiuser detection (temporal filtering), and receiver b eamforming (spatial filtering) have been proposed to increase the capacity of CDMA systems up to date. We investigate the capacity increase that is po ssible by combining power control with intelligent temporal and spatial rec eiver filter design. The signal-to-interference ratio maximizing joint temp oral-spatial receiver filters in unconstrained and constrained filter space s are derived, Two-step iterative power control algorithms that converge to the optimum powers and the joint temporal and spatial receiver filters in the corresponding filter domains are given. A power control algorithm with a less complex filter update procedure is also given. We observe that signi ficant savings in total transmit power are possible if filtering in both do mains is utilized compared with conventional power control and joint optima l power control and filtering in only one domain.