Design of an H∞ Based PI controller for AQM routers supporting TCP flows

The active queue management (AQM) schemes implemented in the routers of communication networks supporting transmission control protocol (TCP) flows can be modeled as a feedback control system. Based on a linearized TCP/AQM model, a new PI controller is designed analytically using H_∞ optimal control theory in this paper. The most important feature of the proposed controller is that it is tuned by a single parameter for the nominal performance and robustness of AQM control system. The proposed PI controller is verified and compared with other existing AQM schemes using ns-2 simulator. The results show the advantage of the new PI controller for AQM routers supporting TCP flows.