SINR, power efficiency, and theoretical system capacity of parallel interference cancellation

This paper analytically derives exact expressions for the SINR of the two-stage linear parallel interference cancellation (LPIC) and two-stage hard-decision parallel interference cancellation (HPIC) multiuser detectors in a synchronous, nonorthogonal, binary, CDMA communication system with deterministic short spreading sequences. We consider approximations to the SINR expressions that are justified in typical operating scenarios to obtain a more intuitive understanding of the SINR performance of the HPIC detector. We consider the case where a specific SINR requirement is given for each user in the system and derive expressions for the set of transmit powers necessary to meet this requirement when two-stage LPIC or HPIC detection is used. We also derive expressions for a measure of the theoretical system capacity using LPIC and HPIC detection, defined as the maximum number of users possible in a system with finite available transmit power. Numerical results are presented that compare the HPIC and LPIC detectors to the hard-decision successive interference cancellation (SIC) detector and matched filter (MF) detector. Our results suggest that HPIC detection may offer the best SINR and power efficiency performance when the number of users in the system is low to moderate and that SIC detection may offer superior performance when the number of users in the system is large.