Downlink Power Allocation for Multi-class CDMA Wireless Networks

In this paper we consider the downlink power allocation problem for multi-class CDMA wireless networks. We use a utility based power allocation framework to treat multi-class services in a unified way. The goal of this paper is to obtain a power allocation which maximizes the total system utility. In the wireless context, natural utility functions for each mobile are non-concave. Hence, we cannot use existing techniques on convex optimization problems to derive a social optimal solution. We propose a simple distributed algorithm to obtain an approximation to the social optimal power allocation. The proposed distributed algorithm is based on dynamic pricing and allows partial cooperation between mobiles and the base station. The algorithm consists of two stages. At the mobile selection stage, the base station selects mobiles to which power is allocated, considering the partial-cooperative nature of mobiles. This is called partial-cooperative optimal selection, since in a partial-cooperative setting and pricing scheme considered in this paper, this selection is optimal and satisfies system feasibility. At the power allocation stage, the base station allocates power to the selected mobiles. This power allocation is a social optimal power allocation among mobiles in the partial-cooperative optimal selection, thus, we call it a partial-cooperative optimal power allocation. We compare the partial-cooperative optimal power allocation with the social optimal power allocation for the single class case. From these results, we infer that the system utility obtained by the partial-cooperative optimal power allocation is quite close to the system utility obtained by the social optimal allocation.