The Experts below are selected from a list of 3210 Experts worldwide ranked by ideXlab platform
Robert Shorten - One of the best experts on this subject based on the ideXlab platform.
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Stochastic Frequency Control of Grid-Connected Microgrids
IEEE Transactions on Power Systems, 2018Co-Authors: Pietro Ferraro, Emanuele Crisostomi, Robert Shorten, Federico MilanoAbstract:This paper proposes a stochastic control strategy, namely the unsynchronized Addictive Increase Multiplicative Decrease (AIMD) algorithm, to manage the power flow of interconnected microgrids (MGs). The proposed control aims at achieving a tradeoff between the individual utility function of each MG while ensuring the stability of the grid. Both centralized and decentralized AIMD approaches are considered and compared. Extensive Monte Carlo simulations are performed on the IEEE 39-bus system, and show that the proposed control strategy is able to provide the sought tradeoff.
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ECC - Asynchronous algorithms for network utility maximisation with a single bit
2015 European Control Conference (ECC), 2015Co-Authors: Fabian Wirth, Sonja Stuedli, M. Corless, Robert ShortenAbstract:We present a convergence result for a nonhomogeneous Markov chain that arises in the study of networks employing the additive-increase Multiplicative Decrease (AIMD) algorithm. We then use this result to solve the network utility maximisation (NUM) problem.
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CDC - On the modified AIMD algorithm for distributed resource management with saturation of each user's share
2015 54th IEEE Conference on Decision and Control (CDC), 2015Co-Authors: Sonja Studli, Martin Corless, Richard H Middleton, Robert ShortenAbstract:Recently the additive increase Multiplicative Decrease (AIMD) algorithm has been applied in fields other than congestion control in communications networks. A major attribute of these new applications is that the share of each user is bounded. Simulations suggest that AIMD performs well, even in the case of individual constraints on each user. In this paper, we provide a formal proof of exponential convergence to a unique fixed-point for the AIMD algorithm under individual user constraints.
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Distributed Load Management Using Additive Increase Multiplicative Decrease Based Techniques
Plug In Electric Vehicles in Smart Grids, 2014Co-Authors: Sonja Studli, Emanuele Crisostomi, Richard H Middleton, Julio H. Braslavsky, Robert ShortenAbstract:Due to the expected increase in penetration levels of Plug-in Electric Vehicles (PEVs), the demand on the distribution power grid is expected to rise significantly during PEV charging. However, as PEV charging in many cases may not be time critical, they are suitable for load management tasks where the power consumption of PEVs is controlled to support the grid. Additionally, PEVs may also be enabled to inject power into the grid to lower peak demand or counteract the influence of intermittent renewable energy generation, such as that produced by solar photovoltaic panels. Further, PEV active rectifiers can be used to balance reactive power in a local area if required, to reduce the necessity for long distance transport of reactive power. To achieve these objectives, we adapt a known distributed algorithm, Additive Increase Multiplicative Decrease, to control both the active and reactive power consumption and injection. Here, we present this algorithm in a unified framework and illustrate the flexibility of the algorithm to accommodate different user objectives. We illustrate this with three scenarios, including a domestic scenario and a workplace scenario. In these scenarios the various objectives allow us to define a type of “fairness” for how the PEVs should adapt their power consumption, i.e. equal charging rates, or charging rates based on energy requirements. We then validate the algorithms by simulations of a simple radial test network. The simulations presented use the power simulation tool OpenDSS interlinked with MATLAB.
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On the higher moments of TCP
Linear Algebra and its Applications, 2013Co-Authors: Arieh Schlote, Fabian Wirth, Avi Berman, Robert ShortenAbstract:Abstract In this paper we describe the moments of a stochastic model of the Additive Increase Multiplicative Decrease (AIMD) algorithm. AIMD is the algorithm that underpins the Transmission Control Protocol (TCP), which is used extensively in the internet. We prove that the Markov chain describing TCP has the remarkable property that all moments converge to their asymptotes at exactly the same rate. Further, we illustrate how a closed form solution can be obtained from the network properties, and this formula is explicitly calculated for the case of the third moment.
Saverio Mascolo - One of the best experts on this subject based on the ideXlab platform.
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Mathematical analysis of Westwood+TCP congestion control
IEE Proceedings - Control Theory and Applications, 2005Co-Authors: Luigi Alfredo Grieco, Saverio MascoloAbstract:TCP congestion control is based on an additive-increase/Multiplicative-Decrease (AIMD) probing paradigm aimed at adapting the sending rate of TCP data sources to match the Internet time-varying available bandwidth. Westwood+ TCP has been recently proposed to improve the tracking of available bandwidth of classic TCP. It is based on an end-to-end estimate of the available bandwidth, which is obtained by properly counting and filtering the stream of acknowledgement packets. The estimate is used to adaptively Decrease the congestion window and slow start threshold after congestion so that it can be said that Westwood+ TCP substitutes the classic Multiplicative Decrease with an adaptive Decrease paradigm. The authors propose a mathematical analysis of the additive-increase/adaptive-Decrease (AIADD) paradigm to analyse the steady-state throughput provided by Westwood+ TCP and investigate the intra-protocol fairness of the AIADD paradigm and the inter-protocol friendliness between AIADD and AIMD algorithms. It is shown that (i) both classic and Westwood+ TCP provide a throughput that is proportional to 1/√p, where p is the segment drop probability, that is they are friendly to each other; and (ii) the throughput of Westwood+ TCP is proportional to 1/√RTT, where RTT is the round trip time, whereas the throughput of Reno TCP is proportional to 1/RTT, i.e. Westwood+ TCP improves the intra-protocol fairness. Finally, Ns-2 simulations are reported in order to validate the mathematical model in the presence of a wide range of network loads, loss probabilities and round trip times.
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ICC - Linux 2.4 implementation of Westwood+ TCP with rate-halving: a performance evaluation over the Internet
2004 IEEE International Conference on Communications (IEEE Cat. No.04CH37577), 2004Co-Authors: A. Dell'aera, Luigi Alfredo Grieco, Saverio MascoloAbstract:The additive increase/Multiplicative Decrease probing paradigm is at the core of TCP congestion control. To improve the classic Reno/New Reno congestion control algorithms, the recent Westwood+ TCP proposes to substitute the Multiplicative Decrease phase with an adaptive Decrease phase, which takes into account an end-to-end estimate of the available bandwidth obtained by filtering the stream of returning ACKs. This paper aims at evaluating the performance of Westwood+ TCP over the real Internet. For that purpose, a Linux 2.4.19 implementation of Westwood+ TCP has been developed and compared with an implementation of New Reno. More than 4000 files, with different sizes, have been uploaded via ftp from a host at the Politecnico of Bari (South of Italy) to three remote servers, which are located at Parma (North of Italy), Uppsala University (Sweden) and University of California Los Angeles (UCLA, California). Experimental results indicate that Westwood+ TCP improves the goodput with respect to New Reno TCP over paths with a bandwidth delay product larger than few segments. In particular, goodput improvements up to 40-50% have been measured when transmitting data from Politecnico of Bari to Uppsala or UCLA servers. Currently, Westwood+ TCP support is available in the official Linux kernel. It was included both in the kernel 2.4.x from version 2.4.26-prel on and in the kernel 2.6.x from version 2.6.3-rcl on.
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A mathematical model of westwood+ TCP congestion control algorithm
Providing Quality of Service in Heterogeneous Environments Proceedings of the 18th International Teletraffic Congress - ITC-18, 2003Co-Authors: Luigi Alfredo Grieco, Saverio MascoloAbstract:Classic TCP congestion control implements the Additive-Increase/Multiplicative-Decrease (AIMD) probing paradigm to track the Internet time varying available bandwidth. The recent Westwood+ TCP is a sender-side only enhancement of the classic Tahoe/Reno/NewReno TCP that proposes to estimate the bandwidth available for a TCP connection by properly counting and filtering the stream of ACK packets. The estimate is used to adaptively Decrease the congestion window and slow start threshold after congestion. In this way Westwood+ TCP substitutes the classic Multiplicative Decrease paradigm with an adaptive Decrease paradigm. This paper proposes a mathematical analysis of the new Additive-Increase/Adaptive-Decrease (AIAD) paradigm. In particular, three equation models have been derived to predict the steady-state throughput of Westwood+ with different degree of approximations. Based on these models, we have shown: (1) the global and exponential stability of the steady-state equilibrium point; (2) the friendliness of the AIAD towards the AIMD algorithm and (3) the improved fairness provided by the AIAD paradigm w. r. t. AIMD paradigm. Finally, the three throughput equation models have been validated using ns -2 simulations in the presence of a wide range of network loads and loss probabilities. Results have shown that the proposed models predict the throughput of AIAD controlled flows with an average error within 15%.
Fabian Wirth - One of the best experts on this subject based on the ideXlab platform.
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ECC - Asynchronous algorithms for network utility maximisation with a single bit
2015 European Control Conference (ECC), 2015Co-Authors: Fabian Wirth, Sonja Stuedli, M. Corless, Robert ShortenAbstract:We present a convergence result for a nonhomogeneous Markov chain that arises in the study of networks employing the additive-increase Multiplicative Decrease (AIMD) algorithm. We then use this result to solve the network utility maximisation (NUM) problem.
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On the higher moments of TCP
Linear Algebra and its Applications, 2013Co-Authors: Arieh Schlote, Fabian Wirth, Avi Berman, Robert ShortenAbstract:Abstract In this paper we describe the moments of a stochastic model of the Additive Increase Multiplicative Decrease (AIMD) algorithm. AIMD is the algorithm that underpins the Transmission Control Protocol (TCP), which is used extensively in the internet. We prove that the Markov chain describing TCP has the remarkable property that all moments converge to their asymptotes at exactly the same rate. Further, we illustrate how a closed form solution can be obtained from the network properties, and this formula is explicitly calculated for the case of the third moment.
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Brief paper: Modelling TCP congestion control dynamics in drop-tail environments
Automatica, 2007Co-Authors: Robert Shorten, Fabian Wirth, Christopher King, Douglas J. LeithAbstract:In this paper we study communication networks that employ drop-tail queueing and additive-increase Multiplicative-Decrease (AIMD) congestion control algorithms. We show that the theory of non-negative matrices may be employed to model such networks and to derive basic theorems concerning their behaviour.
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ACC - On the ergodicity of AIMD networks
2007 American Control Conference, 2007Co-Authors: Robert Shorten, Fabian Wirth, Christopher King, Douglas J. LeithAbstract:In this paper we study communication networks that employ drop-tail queueing and Additive-Increase Multiplicative- Decrease (AIMD) congestion control algorithms. A basic assumption in the study of such networks is that the underlying stochastic process is ergodic. In this paper we present a proof of ergodicity for such networks under very general assumptions.
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A positive systems model of TCP-like congestion control: Asymptotic results
IEEE/ACM Transactions on Networking, 2006Co-Authors: Robert Shorten, Fabian Wirth, Douglas LeithAbstract:We study communication networks that employ drop-tail queueing and Additive-Increase Multiplicative-Decrease (AIMD) congestion control algorithms. It is shown that the theory of nonnegative matrices may be employed to model such networks. In particular, important network properties, such as: 1) fairness; 2) rate of convergence; and 3) throughput, can be characterized by certain nonnegative matrices. We demonstrate that these results can be used to develop tools for analyzing the behavior of AIMD communication networks. The accuracy of the models is demonstrated by several NS studies
Luigi Alfredo Grieco - One of the best experts on this subject based on the ideXlab platform.
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Mathematical analysis of Westwood+TCP congestion control
IEE Proceedings - Control Theory and Applications, 2005Co-Authors: Luigi Alfredo Grieco, Saverio MascoloAbstract:TCP congestion control is based on an additive-increase/Multiplicative-Decrease (AIMD) probing paradigm aimed at adapting the sending rate of TCP data sources to match the Internet time-varying available bandwidth. Westwood+ TCP has been recently proposed to improve the tracking of available bandwidth of classic TCP. It is based on an end-to-end estimate of the available bandwidth, which is obtained by properly counting and filtering the stream of acknowledgement packets. The estimate is used to adaptively Decrease the congestion window and slow start threshold after congestion so that it can be said that Westwood+ TCP substitutes the classic Multiplicative Decrease with an adaptive Decrease paradigm. The authors propose a mathematical analysis of the additive-increase/adaptive-Decrease (AIADD) paradigm to analyse the steady-state throughput provided by Westwood+ TCP and investigate the intra-protocol fairness of the AIADD paradigm and the inter-protocol friendliness between AIADD and AIMD algorithms. It is shown that (i) both classic and Westwood+ TCP provide a throughput that is proportional to 1/√p, where p is the segment drop probability, that is they are friendly to each other; and (ii) the throughput of Westwood+ TCP is proportional to 1/√RTT, where RTT is the round trip time, whereas the throughput of Reno TCP is proportional to 1/RTT, i.e. Westwood+ TCP improves the intra-protocol fairness. Finally, Ns-2 simulations are reported in order to validate the mathematical model in the presence of a wide range of network loads, loss probabilities and round trip times.
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ICC - Linux 2.4 implementation of Westwood+ TCP with rate-halving: a performance evaluation over the Internet
2004 IEEE International Conference on Communications (IEEE Cat. No.04CH37577), 2004Co-Authors: A. Dell'aera, Luigi Alfredo Grieco, Saverio MascoloAbstract:The additive increase/Multiplicative Decrease probing paradigm is at the core of TCP congestion control. To improve the classic Reno/New Reno congestion control algorithms, the recent Westwood+ TCP proposes to substitute the Multiplicative Decrease phase with an adaptive Decrease phase, which takes into account an end-to-end estimate of the available bandwidth obtained by filtering the stream of returning ACKs. This paper aims at evaluating the performance of Westwood+ TCP over the real Internet. For that purpose, a Linux 2.4.19 implementation of Westwood+ TCP has been developed and compared with an implementation of New Reno. More than 4000 files, with different sizes, have been uploaded via ftp from a host at the Politecnico of Bari (South of Italy) to three remote servers, which are located at Parma (North of Italy), Uppsala University (Sweden) and University of California Los Angeles (UCLA, California). Experimental results indicate that Westwood+ TCP improves the goodput with respect to New Reno TCP over paths with a bandwidth delay product larger than few segments. In particular, goodput improvements up to 40-50% have been measured when transmitting data from Politecnico of Bari to Uppsala or UCLA servers. Currently, Westwood+ TCP support is available in the official Linux kernel. It was included both in the kernel 2.4.x from version 2.4.26-prel on and in the kernel 2.6.x from version 2.6.3-rcl on.
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A mathematical model of westwood+ TCP congestion control algorithm
Providing Quality of Service in Heterogeneous Environments Proceedings of the 18th International Teletraffic Congress - ITC-18, 2003Co-Authors: Luigi Alfredo Grieco, Saverio MascoloAbstract:Classic TCP congestion control implements the Additive-Increase/Multiplicative-Decrease (AIMD) probing paradigm to track the Internet time varying available bandwidth. The recent Westwood+ TCP is a sender-side only enhancement of the classic Tahoe/Reno/NewReno TCP that proposes to estimate the bandwidth available for a TCP connection by properly counting and filtering the stream of ACK packets. The estimate is used to adaptively Decrease the congestion window and slow start threshold after congestion. In this way Westwood+ TCP substitutes the classic Multiplicative Decrease paradigm with an adaptive Decrease paradigm. This paper proposes a mathematical analysis of the new Additive-Increase/Adaptive-Decrease (AIAD) paradigm. In particular, three equation models have been derived to predict the steady-state throughput of Westwood+ with different degree of approximations. Based on these models, we have shown: (1) the global and exponential stability of the steady-state equilibrium point; (2) the friendliness of the AIAD towards the AIMD algorithm and (3) the improved fairness provided by the AIAD paradigm w. r. t. AIMD paradigm. Finally, the three throughput equation models have been validated using ns -2 simulations in the presence of a wide range of network loads and loss probabilities. Results have shown that the proposed models predict the throughput of AIAD controlled flows with an average error within 15%.
Eitan Altman - One of the best experts on this subject based on the ideXlab platform.
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Orchestrating parallel TCP connections: Cyclic and probabilistic polling policies
Performance Evaluation, 2011Co-Authors: Omer Czerniak, Eitan Altman, Uri YechialiAbstract:The standard Transmission Control Protocol (TCP) is based on an additive rate increase in the absence of congestion, and on Multiplicative Decrease triggered by congestion signals. However, it does not scale well as the distances, or as the speed of the network, increase. Thus, we study some of the solutions that have been proposed to encounter this problem. These solutions include (i) splitting the transmission from a source to its destination into several parallel connections, and (ii) using Scalable TCP, which is a more aggressive version of TCP. The connection whose rate Decreases when a signal arrives is chosen either at random or according to a round robin policy. Our analysis concentrates on a centrally controlled TCP system having N connections. We consider both Additive Increase Multiplicative Decrease (AIMD) and Multiplicative Increase Multiplicative Decrease (MIMD) control mechanisms. The Laplace-Stieltjes Transforms (LST) of the transmission rate of each connection at a polling instant, as well as at an arbitrary moment, are derived. Explicit results are obtained for the mean transmission rate and (in contrast to most polling models) for its second moment. For the AIMD procedure under the cyclic visit policy we show that, for both dynamic (Hamiltonian-type) and static visit orders in each cycle, the connections should be visited following a simple index rule in order to achieve maximum throughput. For the probabilistic visit policy we obtain the set of optimal probabilities that maximizes mean throughput. The analysis of the probabilistic MIMD models uses transformations yielding a system's law of motion equivalent to that of an M/G/1 queue with batch service. The MIMD control mechanism with probabilistic strategy is further analyzed for the case where the transmission rate is bounded above.
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Analysis of scalable TCP congestion control algorithm
Computer Communications, 2010Co-Authors: R. El Khoury, Eitan Altman, R. El AzouziAbstract:In recent years, several more aggressive versions of TCP have been proposed which leave the Additive Increase Multiplicative Decrease (AIMD) paradigm. The motivation is to adapt TCP to networks with very large bandwidth delay products. In this paper, we study the scalable TCP (STCP) which is designed to be a Multiplicative Increase Multiplicative Decrease (MIMD) protocol. We analyze how it shares a bottleneck link with other CBR flows. We identify conditions under which the time varying queueing delay transforms the whole Multiplicative increase dynamics of the window size into an additive increase dynamics, which implies that window evolution of STCP behaves as an AIMD protocol. In addition, we analyze and derive expressions for the case of very small buffer. Finally, we validate our results using ns-2 simulations.
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VALUETOOLS - Analysis of a TCP system under polling-type reduction-signal procedures
Proceedings of the 4th International ICST Conference on Performance Evaluation Methodologies and Tools, 2009Co-Authors: Omer Czerniak, Eitan Altman, Uri YechialiAbstract:The performance of a Transmission Control Protocol (TCP) for a system with N connections sharing a common Active Queue Management (AQM) is analyzed for both Additive-Increase Multiplicative-Decrease (AIMD) and Multiplicative-Increase Multiplicative-Decrease (MIMD) control mechanisms, where reduction signals follow either a cyclic or a probabilistic polling-type procedure. The Laplace-Stieltjes Transforms (LST) of the transmission rate of each connection at a polling instant, as well as at an arbitrary moment, are derived. Explicit results are calculated for the mean rate and (in contrast to most polling models) for its second moment. The analysis of the probabilistic MIMD models uses transformations yielding a system's law of motion equivalent to that of an M/G/1 queue with bulk service.
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Analysis of MIMD congestion control algorithm for high speed networks
Computer Networks, 2005Co-Authors: Eitan Altman, Konstantin Avrachenkov, Chadi Barakat, Arzad A. Kherani, B.j. PrabhuAbstract:Proposals to improve the performance of TCP in high speed networks have been recently put forward. Examples of such proposals include High Speed TCP, Scalable TCP, and FAST. In contrast to the additive increase Multiplicative Decrease algorithm used in the standard TCP, Scalable TCP uses a Multiplicative increase Multiplicative Decrease (MIMD) algorithm for the window size evolution. In this paper, we present a mathematical analysis of the MIMD congestion control algorithm in the presence of random losses. Random losses are typical to wireless networks but can also be used to model losses in wireline networks with a high bandwidth-delay product. Our approach is based on showing that the logarithm of the window size evolution has the same behaviour as the workload process in a standard G/G/1 queue. The Laplace-Stieltjes transform of the equivalent queue is then shown to directly provide the throughput of the congestion control algorithm and the higher moments of the window size. Using ns-2 simulations, we validate our findings using Scalable TCP.
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Time-averaging of high-speed data transfer protocols
IEEE Transactions on Automatic Control, 2005Co-Authors: Richard Marquez, Eitan Altman, S. Sole-alvarezAbstract:We propose two modeling approaches of additive-increase/Multiplicative-Decrease (AIMD) congestion control mechanisms. The first separates the increase and Decrease parts whereas the second describes the rate evolution of the congestion window as a continuous process governed by a differential equation. We relate these approaches and show that the second (fluid-flow) model results from deterministic time averaging of the first (discontinuous) model. A generalized class of nonlinear protocols, which includes Floyd's HighSpeed TCP, is then proposed and analyzed. Our findings are validated by simulation.
