Selfishness, Not Always A Nightmare: Modeling Selfish MAC Behaviors in Wireless Mobile Ad Hoc Networks

In wireless mobile ad hoc networks where nodes are selfish and non-cooperative, a natural and crucial question is how well or how bad the MAC layer protocol IEEE 802.11 DCF performs. In this paper, we study this question by modeling the selfish MAC protocol as a non- cooperative repeated game where players follow the TIT- FOR-TAT (TFT) strategy which is regarded as the best strategy in such environments. We show for single-hop ad hoc networks the game admits a number of Nash Equilibria (NE). We then perform NE refinement to eliminate the inefficient NE and show that there exists one efficient NE maximizing both local and global payoff. We also propose an algorithm to approach the efficient NE. We then extend our efforts to multi-hop case by showing that the game converges to a NE which may not be globally optimal but quasi- optimal in the sense that the global payoff is only slightly less than the optimal case. As conclusion, we answer the posed question by showing that selfishness does not always lead to network collapse. On the contrary, it can help the network operate at a NE globally which is optimal or quasi-optimal under the condition that players are long-sighted and follow the TFT strategy.