A Novel Backoff Algorithm Based on the Tradeoff of Efficiency and Fairness for Ad hoc Networks

Since the wireless medium is a scarce resource, design of efficient medium access control (MAC) protocols with both high throughput and high fairness is significantly important for distributed ad hoc networks. Many current MAC protocols use an exponential backoff mechanism. In that mechanism, a node picks a random backoff time uniformly in an interval that doubles in size after a collision or decreases to the minimum value after a successful transmission. It can cause unfairness problem to some nodes. In this paper, we propose a novel and efficient contention-based backoff mechanism for wireless ad hoc networks, namely, the adaptive efficiency-fairness tradeoff (AEFT) backoff algorithm, which provides not only a higher throughput and a larger fairness index, but also a tradeoff between efficiency and fairness. We increase the contention window when the channel is busy, and use an adaptive window to fast decrease the backoff time when the channel is idle by fair scheduling. The fair scheduling mainly adopts maximum successive transmission and collision limit to finish the fairness.