wireless local area networks, WLAN, IEEE 802.11, Distributed Coordination Function, DCF, medium access control, MAC, contention window, backoff algorithm
In the IEEE 802.11 Wireless Local Area Networks (WLANs), network nodes experiencing collisions on the shared channel need to backoff for a random period of time, which is uniformly selected from the Contention Window (CW ). This contention window is dynamically controlled by the Binary Exponential Backoff (BEB) algorithm. The BEB scheme, as shown in some studies in the literature, suffers from a fairness problem and low throughput under high traffic load. In this paper, we propose a new backoff algorithm, termed the Linear/Multiplicative Increase and Linear Decrease (LMILD) backoff algorithm, for use with the IEEE 802.11 Distributed Coordination Function. In the LMILD scheme, colliding nodes increase their contention windows multiplicatively, while other nodes overhearing the collisions increase their contention windows linearly. After successful transmissions, all nodes decrease their contention windows linearly. Our preliminary study shows that the LMILD scheme out-performs the BEB scheme employed in the IEEE 802.11 MAC standard and the Multiplicative Increase Linear Decrease (MILD) scheme over a wide range of network sizes.
Deng, Jing; Varshney, Pramod K.; and Haas, Zygmunt J., "A New Backoff Algorithm for the IEEE 802.11 Distributed Coordination Function" (2004). Electrical Engineering and Computer Science. Paper 85.