Design of an adaptive Pl rate controller for streaming media traffic based on gain and phase margins

An adaptive proportional-integral (PI) rate controller for best-effort streaming media traffic in the Internet is proposed. Classical control theory is employed in the control design, which allows the user to achieve good performance of active queue management (AQM) in the router by specifying the proper gain and phase margins. The proposed adaptive PI rate controller will self-tune only when the number of active controlled source nodes changes or the average round trip time becomes longer. The adaptive PI rate controller located in the router can calculate the advertised source transmission rate for the streaming media traffic based on the instantaneous queue length of the buffer, which clamps the steady value of the queue length around the target buffer occupancy. Every controlled source node always transmits streaming media traffic through IP packets into the network at the maximum allowed transmission rate, thus providing the best-effort service traffic and maximising the bandwidth utilisation of the Internet. Our OPNET simulations demonstrate that the rate-based AQM control system can adapt to the fluctuation of the uncontrolled guaranteed traffic very well, thus providing the network with good stability robustness.