Distributed Cooperative Rate Adaptation for Energy Efficiency in IEEE 802.11-Based Multihop Networks

In this paper, we study the problem of using the rate adaptation technique to achieve energy efficiency in an IEEE 802.11-based multihop network. Specifically, we formulate it as an optimization problem, i.e., minimizing the total transmission power over transmission data rates, subject to the traffic requirements of all the nodes in a multihop network. Interestingly, we can show that this problem is actually a well-known multiple-choice knapsack problem, which is proven to be an NP-hard problem. Therefore, instead of finding an optimal solution, which is NP-hard, we seek a suboptimal solution. Our key technique to attack this problem is distributed cooperative rate adaptation (CRA). Here, we promote node cooperation due to our observation that the inequality in noncooperative channel contention among nodes caused by hidden terminal phenomenon in a multihop network tends to result in energy inefficiency. Under this design philosophy, we propose a distributed CRA scheme and prove that it converges. Simulation results show that our CRA scheme can reduce power consumption up to 86% as compared to the existing (noncooperative) algorithm.