Physical Carrier Sensing Outage in Single Hop IEEE 802.11 Ad Hoc Networks with Slowly Moving Stations

Physical Carrier Sensing plays a crucial role in the effectiveness of CSMA-based MAC protocols, yet its properties and impact on the system performance under slow fading channel have not been well understood. We demonstrate that carrier sensing can be highly unreliable even within the "carrier sensing range" and the channel is largely stable during a transmission between slowly moving mobile stations. Then we formulate the carrier sensing outage probability between competing mobile stations and propose a model to estimate the frame error rate and normalized throughput of a saturated IEEE 802.11 DCF single-hop ad-hoc network. Our model is validated via extensive simulations using Qualnet. The numerical and simulation results reveal substantial degradation in system performance with a small amount of carrier sensing outage.