Reservation-Based Distributed Medium Access in Wireless Collision Channels

We consider an uplink wireless collision channel, shared by multiple mobile users. As part of the medium access protocol, channel reservation is carried out by using request-to-send (RTS) and clear-to-send (CTS) control packets. Consequently, collisions are reduced to the relatively short periods where mobiles request channel use. In our model, users are free to schedule their individual channel requests, while the objective of each user is to minimize its own power investment subject to a minimum-throughput demand. Our analysis reveals that for feasible throughput demands, there exist exactly two Nash equilibrium points in stationary strategies, with one being superior to the other uniformly for all users. We then show how this better equilibrium point can be obtained through a distributed mechanism. Finally, we discuss the optimal design of the reservation periods, while considering capacity, power and delay tradeoffs.