Joint admission and power control for quality-of-service in the wireless downlink

This paper addresses the problem of joint admission and power control in the downlink of a single-cell code-division-multiple-access (CDMA) wireless network. The objective is to maximize the user-capacity (or base station revenue), while meeting the quality-of-service (QoS) requirements of each admitted user. This paper considers bounded maximum delay and bounded minimum data rate as the QoS measures. For applications with strict QoS requirements, we show that the joint problem can be solved to optimality by performing admission control and power allocation separately. To solve the admission control problem, we give an exact polynomial-time algorithm for user-capacity maximization, and an efficient approximation algorithm with guaranteed performance for base station revenue maximization. To solve the power control problem, we provide two simple power allocation heuristics. For applications with soft QoS requirements, we consider the problem of allocating transmit powers to all users such that the minimum fraction of QoS requirement satisfied for any user is maximized. Regardless of the number of users in the system, we show that the problem always reduces to one-dimensional search. This leads an efficient power control algorithm that provides, in O(1) iterations, solutions arbitrarily close to the optimal one.