This document discusses techniques for improving multiuser detection in DS-CDMA systems using successive interference cancellation. It begins with an introduction to the multiple access interference problem in CDMA systems and how multiuser detection can help address this issue. It then provides the system model for a CDMA uplink and describes the matched filter receiver structure. Next, it discusses multiuser detection algorithms and focuses on successive interference cancellation as a suboptimal but lower complexity method. The document describes the successive interference cancellation algorithm and introduces the groupwise successive interference cancellation technique, which provides cancellation in groups to handle multirate users. It provides a block diagram of the groupwise successive interference cancellation receiver and discusses how it works to sequentially detect and cancel the strongest user signals