Self-tuning PI rate controller for AQM router supporting best-effort traffic

In this paper, we propose a self-tuning PI (proportional-integral) rate controller for an AQM (active queue management) router that would support best-effort traffic in the Internet. Our design employs classical control theory that allows the users to achieve good stability robustness of AQM control system by assigning a proper interval of gain and phase margins. Our self-tuning PI controller will self-tune only when the gain margin or phase margin drifts outside the specified interval. Every controlled source node always sends the data to the network at the maximum allowed transmission rate, thus maximizing the utilization of network resources. The self-tuning PI controller located in the router can calculate the advertised transmission rate for source nodes based on the instantaneous queue length of the buffer. Our simulations demonstrate good stability robustness of AQM control system with our self-tuning PI controller.