Transmission costs, selfish nodes, and protocol design

We study the influence of transmission costs on the behavior of selfish nodes in wireless local area networks. Intuitively, it seems that transmission costs should have a stabilizing effect as (rational) nodes will defer packet transmissions when congestion develops and the cost for (successfully) transmitting a packet becomes high. In this paper we investigate whether this intuition is true. We use the slotted Aloha to model the communication channel where we capture the interaction among nodes as a non-cooperative game. For this game, we study the existence and properties of a (symmetric) Nash equilibrium. We show that the existence of a transmission cost is not always sufficient to guarantee stability. In particular, a stable equilibrium strategy will not exist if the transmission cost is too small. We then propose and analyze a price-based mechanism to guarantee stability and to optimize system performance in terms of throughput and delay.