A PI Controller for AQM Routers Supporting TCP Flows

Y. Hong, Q. Chen, and O.W.W. Yang (Canada)


Active Queue Management, PI control, Phase Margin.


We propose a proportional-integral (PI) controller for TCP flows in the Internet. Classical control theory is applied in the design to meet frequency domain specification – phase margin. The PI controller can regulate the source window size based on the knowledge of the queue size to clamp the steady value of queue length to the specified reference value. The user can specify proper phase margin to achieve good performance of AQM. Our PI controller is verified via simulation using OPNET. It is shown to outperform RED significantly.

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