Optimal physical carrier sensing to defend against exposed terminal problem in wireless ad hoc networks

Abstract

Physical carrier sensing (PCS) is an effective mechanism to reduce the collision and interference caused by hidden terminals in wireless ad hoc networks, which allows nodes to be separated by a silent margin. However, potential simultaneous transmissions may be suppressed in this silent margin due to exposed terminal problem. As a consequence, PCS mechanism affects the network performance in two opposite ways. In this paper, we present an analytical model for deriving the optimal carrier sensing threshold to make a tradeoff between hidden terminal and exposed terminal problems for given network topology. Our model takes into account the potential throughput loss of exposed terminals, which previous studies have ignored. Based on the model, an adaptive and iterative algorithm is proposed to obtain the optimal sensing threshold and dynamically adjust the physical carrier sensing threshold through periodic estimation of channel condition. Simulation results demonstrate that the proposed scheme outperforms IEEE 802.11 protocol in terms of average network throughput.