A RANDOM ACCESS PROTOCOL UNDER BACKOFF ATTACK: PERFORMANCE AND GAME-THEORETIC DETERRENT

摘要

The IEEE 802.11 medium access control protocol is vulnerable to selfish backoff attacks consisting in the selection of shorter-than-random backoff times by some stations. Administrative punishment and reputation-based prevention of such attacks fail in wireless ad-hoc networks which lack any means of mandating stations' behavior. In this paper, we take an incentive-oriented approach whereby stations are allowed to act so as to maximize their payoffs (obtained bandwidth shares). An approximate Markovian model is proposed to calculate the payoffs under saturation load. The payoff structure specific to CSMA/CA permits to define a two-player game of perfect information, one of the players launching a backoff attack and the other defending itself via a simple jamming mechanism. It is shown that under some conditions, not launching a backoff attack is a weakly best-response strategy against a certain strategy that the defending player may commit herself to.