IEEE 802.11 MAC having two methods for medium reservation. 1) virtual carrier sensing and 2) physical carrier sensing. VCS having many drawbacks in wireless ad hoc networks. Physical carriersensing is more advantage than the virtual carriersensing in terms of throughput, spatial reuse and probability of collisions and its playing important role to remove hidden terminal problem and exposed terminal problem. Choice of physical carriersensing threshold is trade-off between the amount of spatial reuse and probability of packet collisions in a wireless ad hoc network. In this mechanism no need of extra amount of packets to reserve the medium and its somehow removing hidden terminal problem and exposed terminal problem compared to virtual carriersensing. we present a new analytical approach for optimizing the PCS threshold as measured by probability of packet collisions and the aggregate one-hop throughput. The goal of this work lies in developing an analytical model lor PCS tuning to evaluate its impact on network metrics such as the saturation throughput and the probability of collisions. We developed a markov chain model for each node to estimate the optimal physical carriersensing threshold for a network.

Keywords: Throughput, Physical Carrier Sensing, MAC, Ad hoc Network, IEEE 802.11, Threshold