A Fuzzy Logic Based Scheme to Detect Adaptive Cheaters in Wireless LAN

The most commonly used medium access mechanism in WLAN is based on the CSMA/CA protocol. This protocol schedules properly the access to the medium among all competing nodes. However, in a hostile environment, such as wireless local area networks (WLANs), selfish or greedy behaving nodes may prefer to decline the proper use of the protocol´s rules in order to increase their bandwidth shares at the expense of well behaving nodes. In this paper, we focus on one such misbehavior and in particular on the adaptive greedy misbehavior of a node in the context of wireless local area network environment. In such environment, wireless nodes compete to gain access to the medium and communicate directly with an access point (AP). In this case, a greedy node may violate the common rules in order to earn extra bandwidth upon its neighbors. In order to avoid its detection, this node may adopt intelligently different techniques and switch dynamically between each of them. To counter such a misbehavior, we propose the use of a fuzzy logic technique in a new detection scheme. This scheme, implemented in the access point, monitors the behavior of associated wireless nodes and reports any deviation from the proper use of the CSMA/CA protocol. The simulation results of the proposed scheme show its robustness and ability to detect and identify quickly most of the deviations of an adaptive cheater.