Distributed Fair Scheduling with Variable Transmission Lengths

The fairness of 802.11 wireless networks is hard to predict and control because of the randomness and complexity of the MAC contentions and dynamics. Moreover, asymmetric channel conditions such as those caused by capture and channel errors often lead to severe unfairness among stations. In this paper we propose a novel distributed scheduling algorithm that we call VLS, for “variable-length scheduling”, that provides weighted fairness to all stations despite the imperfections of the MAC layer and physical channels. Distinct features of VLS include the utilization of variable transmission lengths based on distributed observations, compatibility with 802.11’s contention window algorithm, opportunistic scheduling to achieve high throughput under noisy and time-varying wireless channel conditions, and flexibility and ease of implementation.