An opportunistic IEEE 802.11 medium access control protocol

In a wireless network, the signals transmitted between a source station and different receiver users most often have different channel fluctuation characteristics. This diversity that exists between users is named multiuser diversity (MUD) and can be exploited to improve the capacity of wireless networks. One way of exploiting MUD is by opportunistic scheduling of users, i.e. giving priority to users having the best channel conditions. To be able to take advantage of the MUD, a feedback protocol has to be deployed to notify the source station about the Carrier to Noise Ratio (CNR) or the channel gain of the mobile user with the finest channel conditions. In this paper, we are inspired from the splitting algorithm [1] to provide IEEE 802.11 with an opportunistic scheduling. We describe the new opportunistic MAC protocol and we give an overview of its implementation in NS-2. We show that the simulation of the splitting algorithm gives the same average feedback time as the analysis study. We compare the native IEEE 802.11 scheduling to the opportunistic one and prove that exploiting MUD increases the network capacity. We also show that this increase is higher with increasing the number of users. Finally, we studied the influence of the observed number of packets in the queue and we prove that maximizing this number does increase the network capacity and the medium access fairness.