Section: New Results

Algorithms: Channel Access algorithms in wireless networks

Participants : Mathieu Feuillet, Philippe Robert.

This is a collaboration with Thomas Bonald (Telecom ParisTech) and Alexandre Proutière (Microsoft Research). In wireless networks, to share available bandwidth between users is necessary. The bandwidth can be divided in several channels (frequency division) or the users can share the whole bandwidth by transmitting in different time slots (time division). We are studying different algorithms that allow users of a wireless network to access the channel. Those algorithms must avoid collisions and use the available bandwidth in the most efficient way. More and more wireless networks are decentralized and those algorithms must be distributed. Moreover, in order to use bandwidth in an efficient way, it is necessary to take the network topology into account. Recent studies have shown that it is possible to use the available bandwidth in a distributed and efficient way without message passing.

We studied a simplified version of the 802.11 channel access algorithm: CSMA/CA (Carrier Sense Multiple Access With Collision Avoidance). We proved that this algorithm does not use the bandwidth in the most efficient way and we proposed in 2010 a modification of this algorithm that is efficient. This result has been extended to multi-channels networks in [8] and its extended version [12] .