Article

# Design of robust active queue management controllers for a class of TCP communication networks

Department of Engineering Science, National Cheng Kung University, Tainan 701, Taiwan, ROC; Department of Computer and Communication, Shu-Te University, Kaohsiung 824, Taiwan, ROC

Information Sciences 12/2002; DOI: 10.1016/j.ins.2007.02.044 Source: DBLP

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**ABSTRACT:**This paper is concerned with the design of a robust AQM control scheme for congestion control in Internet. The design of efficient control schemes is challenging since the TCP congestion window model presents both time-varying time delay, appearing in the state and the control signal, and model uncertainties, due to variations of network characteristic parameters. Hence, our paper begins firstly by giving sufficient conditions for stability and stabilizability for the class of systems whose dynamic is similar to the TCP congestion window one, in term of LMI. After, the general results obtained are applied to congestion control, resulting in a new AQM which is implemented in NS2 and compared to other ones in the literature, as PI and REM. The simulations emphasized the effectiveness of our AQM and its improvements with respect to the other control schemes.Simulation Modelling Practice and Theory. 01/2011; 19:301-313. - [Show abstract] [Hide abstract]

**ABSTRACT:**Although passive queue management is defective, it is simpler than active queue management algorithm, so it is still widely used in Internet. In order to improve the deficiencies, the multi-dropping packets passive queue management algorithm is proposed. When the queue is full, randomly multi-dropping packets. Simulation results show that this algorithm develops the transmission performance of the network, improves the RTT fairness and speed fairness effectively, and the computation is small, so it is suitable for Internet.01/2011; - [Show abstract] [Hide abstract]

**ABSTRACT:**Active Queue Management (AQM) algorithms have been proposed to address performance degradations of end-to -end congestion control. However, these AQM algorithms present weaknesses for stabilizing delays in heavy loaded networks. In this paper, we describe a novel T-S fuzzy control algorithm to improve best effort TCP/IP Networks performance. In TCP networks, the packet-dropping probability function is considered as a control input. Thus, a TCP/AQM controller is modeled as a time-delay system. The robust observer-based controller is designed to achieve the desired queue size and guarantee the asymptotic stability of the operating point. For the particular TCP network mode, the Lyapunov-Krasovskii function is defined, and the system can be stabilize with the obtained the fuzzy state feedback control law by using linear matrix inequality (LMI). Simulation results show that the derived control strategy is validated.American Control Conference (ACC), 2010; 08/2010

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