Solvability of a Markovian model of an IEEE 802.11 LAN under a backoff attack
Jerzy Konorski · Modeling, Analysis, and Simulation On Computer and Telecommunication Systems · 2005
Ad-hoc IEEE 802.11 LANs employ CSMA/CA at the MAC layer. CSMA/CA selects a random backoff time from a contention window that grows from w/sub min/ to w/sub max/ upon consecutive frame collisions. A selfish backoff attack by configuring small w/sub min/ and/or w/sub max/ (i.e., systematic selection of short backoff times) brings the attacking station an unfairly large long-term bandwidth share. To evaluate the impact of backoff attacks we use Bianchi's model of a saturated CSMA/CA network. So far, its solvability has been rigorously established only for identical w/sub min/ and w/sub max/ at all stations. We ask whether the model remains solvable for a general backoff attack scenario, where w/sub min/ and w/sub max/ differ from station to station. Although we find the answer negative, we formulate a sufficient condition for solvability that covers realistic backoff attacks. Based on the obtained bandwidth distribution and power efficiency we point to several features of CSMA/CA under a backoff attack.