Groupwise successive interference cancellation for multirate CDMA based on MMSE criterion

In this work, groupwise successive interference cancellation scheme for multirate CDMA signals is proposed. The proposed detector operation is based on the minimum mean square error (MMSE) criterion. It has the promise of decision feedback interference cancellation for superior performance compared to the linear MMSE detection at the cost of a moderate increase in complexity. In groupwise detection, users are grouped according to their processing gain or data rate, i.e., users with the same processing gain or data rate are grouped together, then detected. Users with the lowest processing gain or highest data rate are detected first, neglecting the presence of the other users in the system. Interference between the groups is cancelled in a successive order. The BER of the groupwise successive MMSE interference canceler is compared with the BER multirate linear MMSE detector and multirate decorrelating detector. The results show that the groupwise successive MMSE interference canceler yields better performance than the multirate linear MMSE detector and multirate decorrelating detector. When the system is highly loaded, the groupwise successive MMSE interference canceler can offer a better performance than the multirate linear MMSE detector and the multirate conventional detector