Statistical PIC in Multirate DS-CDMA Systems Over Dispersive Fading Channels

Statistical parallel interference cancellation (STPIC) is a reduced complexity IC technique in which IC is performed only on a small percentage of "unreliable" bits. In this paper, we extend our previous STPIC analysis for single rate direct sequence-code division multiple access (DS-CDMA) systems over flat fading channels to multi-rate systems with variable spreading gain (VSG) over dispersive fading channels. We show that with STPIC, both low rate (LR) and high rate (HR) users can achieve performance similar to or better than full PIC, but with reduced computational complexity. We also show that for LR users STPIC BER analysis based on the Gaussian approximation (GA) matches simulated results well at low signal-to-noise ratios (SNRs) and is slightly optimistic at high SNRs; whereas for HR users with small processing gains, the GA analysis can be either optimistic or pessimistic depending on SNRs, the IC threshold u, and loading factors.