Throughput Improvement in 802.11 WLANs Using Collision Probability Estimates in Link Adaptation

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The 802.11 standard includes several modulation rates, each of which is optimal for a different channel condition. However, there are no simple and reliable methods for nodes to determine their current channel conditions. Existing link adaptation techniques use packet losses as an indication of poor channel conditions; however, when there is a significant probability of collision, this assumption fails, leading to degraded throughput. In this paper, the authors show that an estimate of the probability of collision can be used to improve link adaptation in 802.11 networks with hidden terminals, and significantly increase throughput by up to a factor of five. They demonstrate this through NS-2 simulations of a few link adaptation techniques including a new algorithm, called SNRg.