Scheduling Algorithms for Performance and Fairness over IEEE 802.11 Multi-Hop Wireless Ad Hoc Networks

摘要

IEEE 802.11 MAC protocol for medium access control in wireless Local Area Networks (LANs) is the de facto standard for wireless ad hoc networks, however, it does not perform well in terms of delay, throughput, and specially, fairness in multihop wireless ad hoc networks. The problems are due to MAC and link layer contention. Many researches have been published in this area. Among them, a modification of IEEE 802.11 MAC protocol was proposed to achieve per-node fairness, but the modification of MAC layer requires a change of hardware, so, it is difficult to implement. Moreover, it still faces up per-flow unfairness problem. As another solution, the Round Robin (RR) scheduling was introduced to overcome the per-flow unfairness problem caused by the First In First Out (FIFO) scheduling. Those solutions are based on the assumption that MAC layer gives the ideal fairness of bandwidth allocation, but IEEE 802.11 MAC protocol fails to ensure MAC layer fairness in multihop ad hoc network. In this paper, we propose a new scheduling method, Probabilistic Control on Round robin Queue (PCRQ) scheduling, aiming to achieve per-flow fairness in multihop ad hoc networks. In PCRQ scheduling, a new link layer scheduling is proposed without assuming the fairness of MAC layer. Our proposed method achieves good performance results in both UDP and TCP traffics.