A hybrid interference cancellation scheme for multiuser systems in multipath fading channels

A new hybrid interference cancellation (IC) scheme is proposed for the uplink of multirate direct-sequence code division multiple access (DS-CDMA) systems communicating over mobile radio channels. The hybrid IC scheme includes both non-decision directed and decision directed IC, together with a modified RAKE combiner to utilize the diversity in a frequency-selective channel. The performance is evaluated via computer simulations for the two multiple data rate schemes, mixed modulation and multicode, in a multipath environment. Both known channel parameters and channel estimation using pilot symbols are considered. The results show that multicode or a combination of multicode and mixed modulation are preferable when handling multirate system and the loss in performance compared to the single-user bound is small.