Optimal power allocation for multirate CDMA systems with interference cancellation

We derive the optimal (minimal) power allocation and capacity for a multirate DS/CDMA system with various QoS requirements. Most of the previous work on power allocation only dealt with the conventional matched filter (MF) receiver and no multiuser detection (MUD) was considered. It is well known that MUD and in particular interference cancellation (IC) can be used to improve the system performance significantly. Hence, after proposing a novel graph-aided method to do optimal power allocation with the conventional MF receiver, parallel IC (P/C) is considered in multirate systems. We propose an iterative approach for optimal power allocation with PIC in multirate systems. It is shown that the proposed power allocation algorithm can converge to the optimal solution quickly. Furthermore, it is demonstrated that when PIC is combined with optimal power allocation, the power dissipation decrease and the system capacity increase significantly