Browsing by Subject "Active queue management (AQM)"

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    H∞-performance analysis of robust controllers designed for AQM
    (IEEE, 2003) Yan, P.; Özbay, Hitay
    It has been shown that the TCP connections through the congested routers with the Active Queue Management (AQM) can be modeled as a nonlinear feedback system. In this paper, we design H∞ robust controllers for AQM based on the linearized TCP model with time delays. For the linear system model exhibiting LPV nature, we investigate the H∞-performance with respect to the uncertainty bound of RTT (round trip time). The robust controllers and the corresponding analysis of H∞-performance are validated by simulations in different scenarios.
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    On the design of AQM supporting TCP flows using robust control theory
    (IEEE, 2004) Quet, P-F.; Özbay, Hitay
    Recently it has been shown that the active queue management 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 delay differential equations model of TCPs congestion-avoidance mode different control schemes have been proposed. Here a robust controller is designed based on the known techniques for H∞ control of systems with time delays.
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    A variable structure control approach to active queue management for TCP with ECN
    (Institute of Electrical and Electronics Engineers, 2005) Yan, P.; Gao, Y.; Özbay, Hitay
    It has been shown that the transmission control protocol (TCP) connections through the congested routers can be modeled as a feedback dynamic system. In this paper we design a variable structure (VS) based control scheme in active queue management (AQM) supporting explicit congestion notification (ECN). By analyzing the robustness and performance of the control scheme for the nonlinear TCP/AQM model, we show that the proposed design has good performance and robustness with respect to the uncertainties of the round-trip time (RTT) and the number of active TCP sessions, which are central to the notion of AQM. Implementation issues are discussed and ns simulations are provided to validate the design and compare its performance to other peer schemes' in different scenarios. The results show that the proposed design significantly outperforms the peer AQM schemes in terms of packet loss ratio, throughput and buffer fluctuation.