Rate control in the mac80211 framework: Overview, evaluation and improvements

Abstract

From version 2.6.22, the mac80211 framework has been incorporated as part of the stock kernel in Linux. This means millions of Linux based devices depend on this framework to provide wireless networking. The framework provides functionalities and interfaces for wireless device drivers (e.g., ath5k) to delegate common tasks to the kernel and to exchange information between physical and upper layers. One of these tasks is rate control at the MAC layer, which uses a metric to evaluate the channel conditions and an algorithm to select a transmission rate that achieves the best performance objective (e.g., max throughput) for the given conditions. To the best of our knowledge, a comprehensive analysis of this framework and its rate control mechanisms does not exist. This paper is the first comprehensive study on rate control mechanisms supported by the mac80211 framework, including overview, evaluation and potential improvements of these mechanisms. In addition to proposing a way to solve the oscillation problem in one of the mechanisms, we propose and evaluate an adaptive and low-cost solution to address collisions due to the hidden terminal problem that has not been considered by both mechanisms. The results show more than 40% improvement if the proposed solution is used when hidden terminals are present.