Sender-initiated reservations for reducing collisions in 802.11 MAC

The IEEE 802.11 MAC adopted a collision avoidance mechanism in which contending stations should wait a random backoff time before sending a frame. While the algorithm reduces the collision probability in general, a large number of stations may still experience heavy collisions and thus decrease the throughput. In this paper, we propose a simple reservation scheme for enhancing the performance of multiple access in 802.11 MAC: when a transmitter sends a frame, if it has another frame to send in its output queue, it may reserve an additional time that is needed to send the next frame and receive an ACK for the frame. Thus one can occupy the medium for two data frames, while reducing the collision probability through the reservation. We develop a mathematical model to analyze the performance of proposed scheme, and perform simulations to show its performance compared with the original MAC.