Dynamic Distributed Contention Window Control in Wireless Ad Hoc LANs

The IEEE DCF 802.11 is currently used as WLAN standard. The standard specifies the contention-based MAC mechanism, Distributed Coordination Function (DCF), which allows to share the wireless channel. In the DCF each node picks a random contention slot from the uniform distribution over the [lower bound, upper bound] interval, where the lower bound always equals 0 and the upper bound equals an integer called Contention Window (CW). We propose three algorithms that modify the distribution of the CW size (lower bound, upper bound and both) based on the number of 1-hop neighbors and the number of transmission attempts. All algorithms achieve a better throughput and significantly reduce the number of collisions and prolong the lifetime of the network compared to the IEEE 802.11 DCF standard.