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Biplab Sikdar - One of the best experts on this subject based on the ideXlab platform.
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modeling queueing and channel access delay in unsaturated ieee 802 11 random access mac based wireless networks
IEEE ACM Transactions on Networking, 2008Co-Authors: Omesh Tickoo, Biplab SikdarAbstract:In this paper, we present an analytic model for evaluating the queueing delays and channel access Times at nodes in wireless networks using the IEEE 802.11 Distributed Coordination Function (DCF) as the MAC protocol. The model can account for arbitrary arrival patterns, packet size Distributions and number of nodes. Our model gives closed form expressions for obtaining the delay and queue length characteristics and models each node as a discrete Time G/G/1fs queue. The Service Time Distribution for the queues is derived by accounting for a number of factors including the channel access delay due to the shared medium, impact of packet collisions, the resulting backoffs as well as the packet size Distribution. The model is also extended for ongoing proposals under consideration for 802.11e wherein a number of packets may be transmitted in a burst once the channel is accessed. Our analytical results are verified through extensive simulations. The results of our model can also be used for providing probabilistic quality of Service guarantees and determining the number of nodes that can be accommodated while satisfying a given delay constraint.
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a queueing model for finite load ieee 802 11 random access mac
International Conference on Communications, 2004Co-Authors: Omesh Tickoo, Biplab SikdarAbstract:This paper presents an analytic model for evaluating the MAC layer queueing delays at wireless nodes using the distributed coordination function of IEEE 802.11 MAC specifications. Our model is valid for finite loads and can account for arbitrary arrival patterns, packet size Distributions and number of nodes. Each node is modeled as a discrete Time G/G/1 queue and we obtain closed form expressions for the delay and queue length characteristics at each node. We derive the Service Time Distribution for the packets at each node while accounting for a number of factors including the channel access delay due to the shared medium, impact of packet collisions, the resulting backoffs as well as the packet size Distribution. Our analytical results are verified through extensive simulations and are more accurate than existing models.
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queueing analysis and delay mitigation in ieee 802 11 random access mac based wireless networks
International Conference on Computer Communications, 2004Co-Authors: Omesh Tickoo, Biplab SikdarAbstract:We present an analytic model for evaluating the queueing delays at nodes in an IEEE 802.11 MAC based wireless network. The model can account for arbitrary arrival patterns, packet size Distributions and number of nodes. Our model gives closed form expressions for obtaining the delay and queue length characteristics. We model each node as a discrete Time G/G/1 queue and derive the Service Time Distribution while accounting for a number of factors including the channel access delay due to the shared medium, impact of packet collisions, the resulting backoffs as well as the packet size Distribution. The model is also extended for ongoing proposals under consideration for 802.11e wherein a number of packets may be transmitted in a burst once the channel is accessed. Our analytical results are verified through extensive simulations. The results of our model can also be used for providing probabilistic quality of Service guarantees and determining the number of nodes that can be accommodated while satisfying a given delay constraint.
Samuel Rota Bulò - One of the best experts on this subject based on the ideXlab platform.
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explicit solutions for queues with hypo or hyper exponential Service Time Distribution and application to product form approximations
Performance Evaluation, 2014Co-Authors: Andrea Marin, Samuel Rota BulòAbstract:Abstract Queueing systems with Poisson arrival processes and Hypo- or Hyper-exponential Service Time Distribution have been widely studied in the literature. Their steady-state analysis relies on the observation that the infinitesimal generator matrix has a block-regular structure and, hence, the matrix analytic method may be applied. Let π n k be the steady-state probability of observing the k th phase of Service and n customers in the queue, with 1 ≤ k ≤ K , and K the number of phases, and let π n = ( π n 1 , … , π n K ) . Then, it is well-known that there exists a rate matrix R such that π n + 1 = π n R . In this paper, we give a symbolic expression for such a matrix R for both cases of Hypo- and Hyper-exponential queueing systems. Then, we exploit this result in order to address the problem of approximating a M / HYPO K / 1 queue by a product-form model. We show that the knowledge of the symbolic expression of R allows us to specify the approximations for more general models than those that have been previously considered in the literature and with higher accuracy.
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explicit solutions for queues with hypo exponential Service Time and applications to product form analysis
Performance Evaluation Methodolgies and Tools, 2011Co-Authors: Andrea Marin, Samuel Rota BulòAbstract:Queueing systems with Poisson arrival processes and Hypo-exponential Service Time Distribution have been widely studied in literature. Their steady-state analysis relies on the observation that the infinitesimal generator matrix has a block-regular structure and, hence, matrix-analytic method may be applied. Let πnk be the steady-state probability of observing the k-th stage of Service busy and n customers in the queue, with 1 ≤ k ≤ K, and K the number of stages, and let πn = (πn1,..., πnK). Then, it is well-known that there exists a rate matrix R such that πn+1 = πnR. In this paper we give a symbolic expression for such a matrix R. Then, we exploit this result in order to address the problem of approximating a M/HypoK/1 queue by a model with initial perturbations which yields a product-form stationary Distribution. We show that the result on the rate matrix allows us to specify the approximations for more general models than those that have been previously considered in literature and with higher accuracy.
Omesh Tickoo - One of the best experts on this subject based on the ideXlab platform.
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modeling queueing and channel access delay in unsaturated ieee 802 11 random access mac based wireless networks
IEEE ACM Transactions on Networking, 2008Co-Authors: Omesh Tickoo, Biplab SikdarAbstract:In this paper, we present an analytic model for evaluating the queueing delays and channel access Times at nodes in wireless networks using the IEEE 802.11 Distributed Coordination Function (DCF) as the MAC protocol. The model can account for arbitrary arrival patterns, packet size Distributions and number of nodes. Our model gives closed form expressions for obtaining the delay and queue length characteristics and models each node as a discrete Time G/G/1fs queue. The Service Time Distribution for the queues is derived by accounting for a number of factors including the channel access delay due to the shared medium, impact of packet collisions, the resulting backoffs as well as the packet size Distribution. The model is also extended for ongoing proposals under consideration for 802.11e wherein a number of packets may be transmitted in a burst once the channel is accessed. Our analytical results are verified through extensive simulations. The results of our model can also be used for providing probabilistic quality of Service guarantees and determining the number of nodes that can be accommodated while satisfying a given delay constraint.
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a queueing model for finite load ieee 802 11 random access mac
International Conference on Communications, 2004Co-Authors: Omesh Tickoo, Biplab SikdarAbstract:This paper presents an analytic model for evaluating the MAC layer queueing delays at wireless nodes using the distributed coordination function of IEEE 802.11 MAC specifications. Our model is valid for finite loads and can account for arbitrary arrival patterns, packet size Distributions and number of nodes. Each node is modeled as a discrete Time G/G/1 queue and we obtain closed form expressions for the delay and queue length characteristics at each node. We derive the Service Time Distribution for the packets at each node while accounting for a number of factors including the channel access delay due to the shared medium, impact of packet collisions, the resulting backoffs as well as the packet size Distribution. Our analytical results are verified through extensive simulations and are more accurate than existing models.
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queueing analysis and delay mitigation in ieee 802 11 random access mac based wireless networks
International Conference on Computer Communications, 2004Co-Authors: Omesh Tickoo, Biplab SikdarAbstract:We present an analytic model for evaluating the queueing delays at nodes in an IEEE 802.11 MAC based wireless network. The model can account for arbitrary arrival patterns, packet size Distributions and number of nodes. Our model gives closed form expressions for obtaining the delay and queue length characteristics. We model each node as a discrete Time G/G/1 queue and derive the Service Time Distribution while accounting for a number of factors including the channel access delay due to the shared medium, impact of packet collisions, the resulting backoffs as well as the packet size Distribution. The model is also extended for ongoing proposals under consideration for 802.11e wherein a number of packets may be transmitted in a burst once the channel is accessed. Our analytical results are verified through extensive simulations. The results of our model can also be used for providing probabilistic quality of Service guarantees and determining the number of nodes that can be accommodated while satisfying a given delay constraint.
Hayriye Ayhan - One of the best experts on this subject based on the ideXlab platform.
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cyclic queueing networks with subexponential Service Times and finite buffers
IEEE Transactions on Automatic Control, 2015Co-Authors: Jungkyung Kim, Hayriye AyhanAbstract:In this technical note, we consider closed tandem queueing networks with finite buffers and blocking. We assume that at least one station has subexponential Service Time Distribution. We analyze this system under communication blocking and manufacturing blocking rules. Our objective is to derive expressions for the tail asymptotics of transient cycle Times and waiting Times. Furthermore, we study under which conditions on system parameters these tail asymptotics also hold for their stationary counter parts. Finally, we provide numerical examples to understand the convergence behavior of the tail asymptotics.
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cyclic queueing networks with subexponential Service Times
Report Eurandom, 2002Co-Authors: Hayriye Ayhan, Zbigniew Palmowski, Sabine SchlegelAbstract:For a K-stage cyclic queueing network with N customers and general Service Times, we provide bounds on the nth departure Time from each stage. Furthermore, we analyze the asymptotic tail behavior of cycle Times and waiting Times given that at least one Service-Time Distribution is subexponential.
Ward Whitt - One of the best experts on this subject based on the ideXlab platform.
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a diffusion approximation for the g gi n m queue
Operations Research, 2004Co-Authors: Ward WhittAbstract:We develop a diffusion approximation for the queue-length stochastic process in theG/GI/n/m queueing model (having a general arrival process, independent and identically distributed Service Times with a general Distribution,n servers, andm extra waiting spaces). We use the steady-state Distribution of that diffusion process to obtain approximations for steady-state performance measures of the queueing model, focusing especially upon the steady-state delay probability. The approximations are based on heavy-traffic limits in whichn tends to infinity as the traffic intensity increases. Thus, the approximations are intended for largen.For theGI/M/n/8 special case, Halfin and Whitt (1981) showed that scaled versions of the queue-length process converge to a diffusion process when the traffic intensity? napproaches 1 with (1 -? n )v n ? I for 0
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an operational calculus for probability Distributions via laplace transforms
Advances in Applied Probability, 1996Co-Authors: Joseph Abate, Ward WhittAbstract:In this paper we investigate operators that map one or more probability Distributions on the positive real line into another via their Laplace-Stieltjes transforms. Our goal is to make it easier to construct new transforms by manipulating known transforms. We envision the results here assisting modelling in conjunction with numerical transform inversion software. We primarily focus on operators related to infinitely divisible Distributions and Levy processes, drawing upon Feller (1971). We give many concrete examples of infinitely divisible Distributions. We consider a cumulant-moment-transfer operator that allows us to relate the cumulants of one Distribution to the moments of another. We consider a power-mixture operator corresponding to an independently stopped Levy process. The special case of exponential power mixtures is a continuous analog of geometric random sums. We introduce a further special case which is remarkably tractable, exponential mixtures of inverse Gaussian Distributions (EMIGs). EMIGs arise naturally as approximations for busy periods in queues. We show that the steady-state waiting Time in an M/G/1 queue is the difference of two EMIGs when the Service-Time Distribution is an EMIG. We consider several transforms related to first-passage Times, e.g. for the M/M/1 queue, reflected Brownian motion and Levy processes. Some of the associated probability density functions involve Bessel functions and theta functions. We describe properties of the operators, including how
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heavy traffic asymptotic expansions for the asymptotic decay rates in the bmap g 1 queue
Stochastic Models, 1994Co-Authors: Gagan L. Choudhury, Ward WhittAbstract:In great generality, the basic steady-state Distributions in theBMAP/G/l queue have asymptotically exponential tails. Here we develop asymptotic expansions for the asymptotic decay rates of these tail probabilities in powers of one minus the traffic intensity. The first term coincides with the decay rate of the exponential Distribution arising in the standard heavy-traffic limit. The coefficients of these heavy-traffic expansions depend on the moments of the Service-Time Distribution and the derivatives of the Perron-Frobenius eigenvalue δ(z) of the BMAP matrix generating function D (z) at z = 1. We give recursive formulas for the derivatives δ(κ) (1). The asymptotic expansions provide the basis for efficiently computing the asymptotic decay rates as functions of the traffic intensity, i.e., the caudal characteristic curves. The asymptotic expansions also reveal what features of the model the asymptotic decay rates primarily depend upon. In particular, δ(z) coincides with the limiting Time-average of the ...
