Anti-windup Compensator Synthesis for Sampled-Data Delay Systems

J Control Autom Electr Syst

Haoussi

et al. 2020

Self Cite

A methodology for designing congestion controllers, based on active queue management (AQM), is presented here. The congestion control law is derived using sampled-data H ∞ systems theory. More precisely, a sampled-data state feedback that guarantees the stability of the closed-loop system and satisfies a H ∞ disturbance attenuation level is derived here, based on sufficient conditions expressed in terms of linear matrix inequalities. The effectiveness of the developed technique is validated on two examples. Keywords AQM • Network congestion control • Sampled-data controller • Saturating input 1 Introduction Network congestion in communication networks is being paid significant attention because of their wide range of applications, from Web servers to industrial control systems. In order to manage network congestion, active queue management (AQM) (Braden et al. 1998) techniques are frequently used, which aim to reduce packet drops and improve the overall network utilization. One of the most well-known AQM policies are random early detection (RED) (Floyd and Jacobson 1993), adaptive RED (ARED) (La et al. 2003) and nonlinear RED (NLRED) (Rastogi and Zaheer 2016). Moreover, the fundamentals of control theory have been used to analyze new AQM schemes, such as proportional integral (PI) (Hollot et al. 2002), proportional integral derivative (PID) (Zhang and Papachristodoulou 2014), adaptive PI (Zhang et al. 2003) and PI enhanced (PIE) (Pan et al. 2013). Also, in Bender (2013) it has proposed the use of a dynamic anti-windup gain matrix to improve the performance of a designed controller used to AQM in congested TCP/IP routers, and it was developed in El Fezazi et al.

Section: Remarkmentioning

confidence: 99%

Congestion Control in TCP/IP Routers Based on Sampled-Data Systems Theory

Lamrabet

J Control Autom Electr Syst

Haoussi

et al. 2020

Self Cite

“…Step 3. Substitute the new matrix variables into (28). If the result is feasible, then set = + Δ and repeat Step 2; otherwise, = − Δ, which is the desired estimate and finish.…”

Section: Maximization Ofmentioning

confidence: 99%

“…Since the control actions in AQM are the discarding probabilities, AQM approaches that ignore the input saturation are not adequate because saturations are known to deteriorate performance and might lead to unacceptable losses of stability. In order to mitigate the saturation effect on the stability of such systems, local/global stabilization in a specified domain of attraction has been studied previously, [12][13][14][15][16][17][18][19][20][21][22] and antiwindup techniques have been proposed in other works [23][24][25][26][27][28] where the emphasis was on the transient performance caused by the saturation. In this sense, the aforementioned works [23][24][25][26] proposed delay dependent antiwindup techniques to ensure the closed-loop stability of TCP/IP AQM routers.…”

mentioning

confidence: 99%

Multiclass AQM on a TCP/IP router: A control theory approach

Intl J Robust & Nonlinear

Haoussi

Tissir

et al. 2019

Self Cite

Summary Active queue management (AQM) is a well‐known technique to improve routing performance under congested traffic conditions. It is often deployed to regulate queue sizes, thus aiming for constant transmission delay. This work addresses AQM using an approach based on control theory ideas. Compared with previous results in the literature, the novelty is the consideration of heterogeneous traffic, ie, multiclass traffic. Thus, each traffic class may have different discarding policies, queue sizes, and bandwidth share. This feature brings the proposal nearer to real network management demands than previous approaches in the literature. The proposed technique assumes that each class already has a simple controller, designed a priori, and focuses on designing a static state‐feedback controller for the multiclass system, where the design is based on using LMIs for the calculations. For this, optimization problems with LMI constraints are proposed to compute the state‐feedback gains that ensure stability for a large set of admissible initial conditions. These conditions ensure not only closed‐loop stability but also some level of performance. As far as we know, this is the first control theory based approach for the AQM problem on TCP/IP routers that allows a multiclass AQM while also considering time‐varying delays and input saturation. This is an important step to frame AQM in a more formal, yet realistic context, enabling it to address important service level agreement (SLA) directives. The proposal is tested on a simulated system at the end of this paper, showing the feasibility and performance of the approach in the presence of multiclass traffic.

“…Since the control actions in AQM are the discarding probabilities (real numbers bounded between [0, 1]), the AQM approaches that ignore the input saturation are not adequate because saturations might deteriorate the control system's performance and frequently lead to unacceptable losses of stability. Then, to mitigate the saturation effects on stability of such systems, local/global stabilization in a specified region of attraction (Cao et al 2002;El Fezazi et al 2017, 2019cEl Fezazi 2019;Naamane et al 2017) and anti-windup techniques where the emphasis is on the transient performance caused by the saturations (Bender 2013(Bender , 2014Lamrabet et al 2017Lamrabet et al , 2018 is studied. The drawback of some proposed approaches is the computing resources demanded to implement them in a real network, which may yield it unfeasible.…”

Section: Introductionmentioning

confidence: 99%

AQM Congestion Controller for TCP/IP Networks: Multiclass Traffic

J Control Autom Electr Syst

Elfakir

Bender

et al. 2020

Active queue management (AQM) is a congestion control mechanism for the early notification of the incipient congestion pursued by dropping/marking packets. The novelty in our result is that we are able to consider heterogeneous traffic (i.e., multiclass traffic) where each class has its own packet discarding policy, queue size, and bandwidth share. Then, this is so far the first control theory-based approach for the AQM problem on the TCP/IP routers that allows multiclass AQM. Our proposed technique assumes that each class has already a controller, designed a priori, and focuses on designing a static state feedback controller where the proposed design approach is based on the solution of linear matrix inequalities (LMIs). From the theoretical conditions, a new controller design methodology for discrete time systems with multi-delays, saturated inputs, and disturbances is proposed to overcome the obstacle of bilinearity which leads to a quite simple LMI condition that is numerically tractable with any convex optimization algorithm. A numerical example is provided at the end of this paper to show the effectiveness and performances of the proposed approach in the presence of multiclass traffic.