Robust Active Queue Management for Wireless Networks

Active Queue Management (AQM) algorithms have been extensively studied in the literature in the context of wired networks. In this paper, we study AQM for wireless networks. Unlike a wired link, which is assumed to have a fixed capacity, a wireless link has a capacity that is time-varying due to fading. Thus, the controller is required to meet performance objectives in the presence of these capacity variations. We propose a robust controller design that maintains the queue length close to an operating point. We treat capacity variations as an external disturbance and design a robust controller using H_∞ control techniques. We also consider the effect of round-trip time in our model. Our method of incorporating the delay into the discretized model simplifies controller design by allowing direct use of systematic controller design methods and/or design packages. We demonstrate the robustness of the controller to changes in the load condition and in the round-trip time through ns-2 simulations.