Self-tuning PI TCP flow controller for AQM routers with interval gain and phase margin assignment

We propose a self-tuning proportional-integral (PI) controller for active queue management (AQM) in the Internet. Classical control theory is applied in the controller design. We assign a proper interval of gain and phase margins to achieve good AQM performance while adapting the AQM control system to great traffic load changes very well. Based on the knowledge of the queue size, our PI controller can regulate the TCP source window size to clamp the steady value of queue size to specified target buffer occupancy. OPNET simulations demonstrate that, with our self-tuning PI controller applied, the network shows good stability robustness.