System Performance Gain by Interference Cancellation in WCDMA Dedicated and High-Speed Downlink Channels

A large number of the existing and planned 3G networks rely on the 3GPP WCDMA standard. Since the downlink of WCDMA systems is usually interference limited, interference cancellation algorithms that reduce the interference on the desired signal can significantly improve the system capacity. In this paper, the system-level performance gain that can be achieved by interference cancellation on the terminal side is investigated. Two downlink channels are considered: the dedicated downlink channel, which is already part of the WCDMA standard, and the new high-speed downlink channel for packet-data support, which will be part of Release 5 of the WCDMA standard. In the analysis, four receiver classes are compared: the standard Rake receiver, a Rake receiver with pilot subtraction, a linear MMSE equalizer, and a non-linear iterative successive cancellation algorithm. The resulting performance gains and the necessary implementation complexity are discussed.