QoS provisioning in a single-cell ad hoc WLAN via queuing and stochastic games

Selfish manipulation of the binary exponential backoff scheme in an ad hoc IEEE 802.11 WLAN leads to a noncooperative CSMA/CA game with a payoff structure characteristic of a multiplayer Prisoners’ Dilemma. For a simple QoS sensitivity model, assuming elastic traffic flows with a minimum bandwidth share requirement R, we modify the payoffs to define a QoS game. In an ideal scenario, WLAN stations take actions (switch to selfish play) sequentially, in which case for R large enough the game changes into a queuing game with multiple unfair Nash equilibria. Even if the stations are allowed to act simultaneously, these equilibria predict the outcome of the QoS game fairly accurately, depending on the schedule and limits on the number of actions. However, a station can selfishly depart from a common schedule of actions; to account for that, we propose a Markovian stochastic game model and prove the existence of a fair Markov perfect Nash equilibrium.