Improved Variable Structure Proportional–Integral Controller for TCP/AQM Network Systems

Abstract

This study proposes the design of a new variable structure proportional-integral (VSPI) controller, which combines the advantages of a proportional-integral (PI) controller with the more flexible variable structure (VS) controller for transmission control protocol (TCP) router-based active queue management (AQM) network systems. The objective of the proposed controller is to improve the performance of routers by reducing packet loss and queuing delay and increasing throughput. The performance of the VSPI controller is verified and compared with the PI controller using Network Simulator 2 (NS–2). The results demonstrate that the proposed controller is stable and robust under various scenarios and is a suitable design approach for TCP/AQM network systems. Moreover, the VSPI controller is flexible and easy to use owing to the trade-off between stability and performance of the AQM control system.