A Liberal Carrier Sensing for Increased Spatial Reuse in Multi-Hop Wireless Ad Hoc Networks

Recent experimental results have shown that the minimum signal-to-interference ratio required at a receiver (CPth ) depends on the order of arrival of the overlapping frames. For a given sender-receiver distance, this differential capture capability of a receiver leads to two distinct interference ranges (ri ) around the receiver, and its value is much smaller when the sender's frame arrives earlier. This feature also suggests a possibility of increased spatial reuse by allowing the (secondary) nodes outside the primary receiver's ri to communicate concurrently once the primary receiver starts its DATA reception. In this paper, we propose a liberal carrier sensing (LCS) scheme wherein some already available information at an otherwise 'exposed' receiver are exploited to help decide when it is safe to respond to a secondary transmission request. The proposed modification in the carrier sensing approach results in a significantly improved spatial reuse, thereby increasing overall system throughput. Our simulation studies show that, compared to the conventional carrier sensing scheme with differential capture capable receivers, the end-to-end TCP throughput with LCS can be improved by more than 20% in regular topologies and up to about 9% in random topologies.