Parallel interference cancellation (PIC) improvements for CDMA multiuser receivers using partial cancellation of MAI estimates

We study the improvement technique for multistage parallel interference cancellation (PIC) DS-CDMA multiuser receivers, which cancel only a fraction of the estimated multiple access interference (MAI) at each receiver stage. This technique takes into account the fact that the MAI estimate, especially in the earlier stages, contains substantial error, and a relatively conservative strategy of using the estimate may lead to better system performance (i.e., lower average bit error rate). We start with simulating the BER performance as a function of the fraction of cancellation, which shows that the fraction can make a significant difference and a "best" fraction can be far less than one. Then the PIC with partial cancellation and the standard PIC are compared under various near-far effects, channel SNR, and number of users. The simulations indicate how the partial cancellation technique can provide significant improvement over the standard PIC.