QoS-Aware Cooperative and Opportunistic Scheduling Exploiting Multi-user Diversity for Rate Adaptive Ad Hoc Networks

Abstract

The recent researches in wireless networks prompt the opportunistic transmission that exploiting channel fluctuations to improve the overall system performance. In wireless ad hoc networks, nodes may have packets destined to multiple neighboring nodes. We consider an opportunistic scheduling that takes advantage of time-varying channel among different receivers to improve system performance. Maximizing overall throughput and satisfying QoS requirements for transmission flows are two important objectives that need to be considered. In literature, many opportunistic scheduling policies for ad hoc networks have been proposed, in which each transmitter schedules the transmission indepen-dently. However, due to co-channel interference, the decisions of neighboring transmitters are highly correlated. Moreover, to achieve the QoS requirements, nodes have to be cooperative to share the common wireless channel. In this paper, we formulate the opportunistic scheduling problem taking the interaction among the neighboring transmitters into account. We present an optimal scheduling policy which maximizes the overall network performance while satisfying QoS requirements of individual flows. We also proposed COS, a distributed Cooperative and Opportunistic Scheduling algorithm, which modifies IEEE 802.11 protocol to implement the optimal scheduling policy by exchanging average channel conditions and QoS factors among 2-hop neighboring nodes. Simulation results indicate that our implementation achieves higher network throughput and provides better QoS support than existing work.