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

Department of Computer and Communication, Shu-Te University, Kaohsiung 824, Taiwan, ROC
Information Sciences (Impact Factor: 4.04). 12/2002; 177(19):4059-4071. DOI: 10.1016/j.ins.2007.02.044
Source: DBLP


This paper describes the design of active queue management (AQM) controllers for a class of TCP communication networks. In TCP/IP networks, the packet-dropping probability function is considered as a control input. Therefore, a TCP AQM controller was modeled as a time-delayed system with a saturated input. The objective of the work described here was to design robust controllers capable of achieving the desired queue size and guaranteeing asymptotic stability of the operating point. To achieve this aim, we have proposed two control strategies, namely a static state feedback controller and an observer-based controller. By applying the Lyapunov–Krasovskii functional approach and the linear matrix inequality technique, control laws and delay-independent stability criteria for the AQM controllers were derived. The performance of the two control schemes was evaluated in various network scenarios via a series of numerical simulations. The simulation results confirm that the proposed schemes outperform other AQM schemes.

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    • "Window size, as one of the state variables in TCP dynamic models, is not accessible at the router's side in real networks. To overcome this constraint, some researchers proposed an observer design to estimate this state (Hollot, et al. 2002; Chen, et al. 2007). Zeng, et al. (2007) expressed the window size as a function of the rate mismatch at routers, which can be estimated. "
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    ABSTRACT: This paper presents a new PID congestion controller design for transmission control protocol (TCP) networks. It would be possible to efficiently control the TCP traffic in the proposed control scheme. This would be done via the use of only the queue length at router needless to know the TCP window size which is not accessible at the routers side. The stability condition is presented by applying linear matrix inequality (LMI). The proposed approach is laid out via numerical results by ns2 software. The usability and advantage of the proposed method is shown compared with other control schemes such as PI, RED and GMV.
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    • "In [7], a model of the TCP congestion window was proposed; allowing to use common controllers such as proportional-integral (PI) [1], proportional-integral-derivative (PID) [8] [9], robust control [10] [11] [12] [13] and Lyapunov theory [14] [15] [16]. The LMI approach was also used as in [17], where authors used a state feedback, and gave necessary conditions to insure asymptotic stability of the linearized model of TCP congestion window. However, they neglected the delay on the feedback signal. "
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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(1):301-313. DOI:10.1016/j.simpat.2010.07.001 · 1.38 Impact Factor
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    • "The study of congestion problem in time delay systems framework is not new and has been successfully exploited. Nevertheless, most of these works have been dedicated to the stability analysis of networks composed of homogeneous sources (see for example [25], [31], [9], [28] and [37]). "
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    ABSTRACT: This paper investigates the overload problem of a single congested router in TCP (Transmission Control Protocol) networks. To cope with the congestion phenomenon, we design a feedback control based on a multiple time-delays model of the set TCP/AQM (Active Queue Management). Indeed, using robust control tools, especially in the quadratic separation framework, the TCP/AQM model is rewritten as an intercon- nected system and a structured state feedback is constructed to stabilize the network variables. Finally, we illustrate the proposed methodology with a numerical example and simulations using NS-2 simulator.
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