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Abstract : |
This paper presents ' the first analytical model to derive the saturation throughput of collision avoidance protocols' in multi-hop ad hoc networks ' with nodes randomly placed according to a two-dimensional Poisson distribution. We show that the sender-initiated collision-avoidance scheme performs much better than the ideal CSMA scheme with a separate channel for acknowledgments'. More importantly, we show that the collision-avoidance scheme can accom-modate much fewer competing nodes within a region in a network infested with hidden terminals ' than in those cases without hidden terminals ' or with just a few, if reasonable throughput is to be maintained. Simulations of the popular IEEE 802.11 MAC protocol show that it cannot ensure collision-free transmission of data packets ' and thus throughput can degrade well below what is predicted by the analysis ' of a correct collision avoidance protocol. Based on these results', a number of improvements ' are proposed for the IEEE 802.11 MAC protocol., |
