Capacity optimization by using cancellation-error-ascending decoding order in multimedia CDMA networks with imperfect successive interference cancellation

In this paper, we study the influence of decoding order on the capacity of multimedia DS-CDMA systems with imperfect successive interference cancellation. In contrast to previous studies, cancellation errors are assumed to be different for different users in this work. For any given decoding order, we derive the necessary power allocation that guarantees the QoS of the multimedia traffic. Based on this result, we prove that instead of by descending order of data rate as suggested in some literature, the system capacity is maximized by decoding users according to the ascending order of cancellation errors. We also prove that this capacity-optimal decoding order makes total residual interference minimum at the same time. Out results are verified by numerical example.