Spatial backoff contention resolution for wireless networks

Traditional medium access control (MAC) protocols utilize temporal mechanisms such as access probability or backoff interval adaptation for contention resolution. They typically take the set of competing nodes as a given, and address the problem of adapting each node\´s channel access behavior to the given channel contention level. This is a temporal approach for contention resolution, which aims to separate transmissions from different nodes in time to achieve successful transmissions. We explore an alternative approach for wireless networks-named "spatial backoff-that adapts the "space" occupied by the transmissions. Each transmission in a wireless network competes for a certain space. By adapting the space occupied by transmissions, the set of "locally" competing nodes, and thus, the channel contention level, can be adjusted to reach a suitable level. There are different ways to realize spatial backoff. In this paper, we propose a dynamic spatial backoff algorithm using the joint control of carrier sense threshold and transmission rate. Our results suggest that spatial backoff can lead to a substantial gain in channel utilization.