Improving energy efficiency via probabilistic rate combination in 802.11 multi-rate wireless networks

Energy efficiency is one of the most important concerns in wireless networks because wireless clients usually have limited battery power. The aim of this work is to reduce energy consumption by exploiting multi-rate diversity in 802.11 wireless networks. An important observation is that “probabilistic rate combination” in transmission can significantly reduce power consumption. We formulate the energy efficient rate combination as a non-convex optimization problem. A non-cooperative rate adaptation scheme is presented to reduce power consumption without information exchange. Each node selects rate combination strategy and computes its transmission probability based on the weighted average interface queue length. Due to the well-known “rate anomaly” problem, selfish nodes may choose to transmit at a lower rate free ride from the other nodes. To mitigate this problem, we propose a joint consecutive packet transmission (CPT) and contention window adaptation mechanism (CWA). We prove the stability of our proposed algorithm, and to the best of our knowledge, this is the first control theoretical analysis on 802.11 “multi-rate” wireless networks. Simulation results show that the probabilistic rate combination can greatly save battery power, even up to 700% times compared with standard 802.11a/h protocol.