Multiple access protocol misbehavior in WLANs

Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) is probably the most widespread multiple access protocol in use today, mainly due to the tremendous success of the IEEE 802.11 suite of standards. Until now most of the studies done about the protocol have focused on maximizing the performance. However as the bands become more crowded and the user terminals become easier to reconfigure, it is reasonable to assume that users will try to modify their equipment in order to achieve better performance, even if this may be in expense of the other users. The focus of this paper is from an overall network point of view, where two competing networks are considered. The competing network scenarios are modeled by the use of game theory, applying simple and repeated form games. The outcome of the games is described by the Nash Equilibrium (NE). We argue that by modifying the contention window, based on respective network parameters and by simple interaction between the contending networks, a superior performance than provided by the standard can be obtained. In the first part of the paper we compare the performance of a network following the standard to a network that is maximizing its throughput. The result is that by modifying the contention window size it is actually possible to achieve better performance than for a network that adheres to the standard. We then continue on analyzing the case where both networks try to achieve maximum performance in a selfish manner.