Mitigation of exposed terminals problem with differential capture capable receivers

Recent experimental studies on physical layer capture in 802.11 based networks have demonstrated that the minimum signal-to-interference ratio required for successful reception of a frame depends upon the order of arrivals of the sender's frame and the interference, and it is much less when the sender's frame arrives earlier. This differential capture capability (DCC) leads to a very small interference range around the receiver once it starts receiving a frame, and hence it allows considerable reduction in the required carrier sensing range. While the DCC feature of receivers helps alleviate some hidden and exposed terminal problems, there still remains many exposed nodes. In this paper, we further exploit the DCC feature to mitigate the problem of these exposed terminals that remain even after optimum reduction in carrier sensing range. We propose a liberal carrier sensing scheme that helps identify some of the exposed prospective receivers by using some already available local information and allow them to initiate secondary sessions. Through extensive simulations we demonstrate that the proposed scheme offers significant throughput gain over the conventional carrier sensing scheme that ignores the DCC feature.