Opportunistic scheduling for utility maximization under QoS constraints

Opportunistic scheduling provides an important capability of resource management for wireless systems by taking advantage of multiuser diversity, allowing delay variation in delivering data packets. Our opportunistic scheduling aims at maximizing the utility which is usually expressed as a function of user throughput. In this paper we derive an off-line optimal scheduling policy by optimization theory, and show that the policy is also optimal in opportunistic scheduling. We extend the scheduling policy by adding QoS requirements for each user. To do so, we classify opportunistic schedulers according to QoS constraints. Their optimalities are also proved through mathematical analysis. To obtain optimal scheduling policy, the parameters related to QoS should be computed, so we propose a practical algorithm for parameter adaptation and verify its performance through simulations. The results confirm that our considered opportunistic schedulers show good fairness performance and guarantee each user's QoS without any difficulty in implementation.