Search results for "Queueing theory"
showing 10 items of 33 documents
Proposal of a neuro-fuzzy model of a WWW server
2005
This paper presents the ways of designing simulation models of Web servers. At the beginning queuing network models are introduced, those models are generally known and often used in the initial phase of research on particular technical solutions. Next, an entirely new approach to the issue discussed is presented - neuro-fuzzy models, thanks to which, it is possible to automate the process of designing simulation models. The results of comparative tests of these two models are presented. Based on these results it can be concluded that neuro-fuzzy models are accurate and can be used in simulation research.
Providing QOS in 3G-WLAN environment with RSVP and DIFFSERV
2006
Here we present the end-to-end QoS mechanism in 3G-multiaccess network environment. As multi-access wireless WLAN and wired xDSL wideband multi-access technologies has emerge and become more popular a need for interoperability with different technologies and domains has become necessity. There is also a need for end-to-end QoS management. We show a scenario where the UE-GGSN connection is covered by RSVP and RAN network part uses partial over dimensioning and real-time controlled ATM queuing. DiffServ covers WLAN-Core QoS and radio interface between WLAN AP and WLAN UE uses IEEE's 802.11e. Our interest is to find out how well 3G traffic classes can survive in different traffic conditions in…
About the stability of active queue management mechanisms
2004
In this paper, we discuss the influence of multiple bottlenecks on the stability of active queue management (AQM) controllers, usually configured on a single bottleneck basis. To see this, we consider a network scenario where RED is configured at each router according to previously developed control theoretic techniques. These configuration rules assure stability in a single bottleneck scenario. Yet, we show that instability may arise when two links become congested. We justify this result through a multiple bottleneck model.
AQM Stability in Multiple Bottleneck Networks
2004
In this paper, we highlight that multiple bottlenecks can affect the performance of active queue management controllers, which are usually configured on a single bottleneck basis, as if each controller were the only element regulating the TCP traffic along its path. To see this, we consider a network scenario where RED is configured at each router, according to previously developed control theoretic techniques. These configuration rules assure stability in a single bottleneck scenario. Yet, we show that instability may arise when two link become congested. We justify this result through a multiple bottleneck model and give guidelines for new cooperative AQM controllers.
Computer networks stability independence of the queuing delays
2015
Communication in intelligent computer networks is an indispensible attribute of the dataflow quality in Web traffic. We propose a model that investigates intelligent computer networks stability while specifying its limits. Packet queuing delay affects the performance of the network, and especially its stability. If the network is presented as a dynamic system in block diagram form, we compute a transfer function and determine the quasi-polynomial system. The characteristic polynomial distribution of zeros of complex variable quasi-plane determines the boundaries of the network stability. The approach relies on estimation of the network system's transfer functions and its quasi-polynomial. C…
Performance Evaluation of a new Adaptive Packet Marking Scheme for TCP over DiffServ Networks
2004
In differentiated services (DiffServ) networks, packets may receive a different treatment according to their differentiated services code point (DSCP) label. As a consequence, packet marking schemes can be devised to differentiate packets belonging to the same TCP flow, with the goal of improving the experienced performance. The paper presents an extensive performance evaluation of a new adaptive packet marking scheme, applied to a traffic scenario composed of TCP flows with different lengths. The proposed marking scheme is most efficient when applied to a scenario composed of all long-lived flows. In a realistic mixed traffic scenario, composed of both long-lived and short-lived TCP flows,…
Spectrum Occupancy and Residual Service Analysis in CRNs Using a Multi-Server Queueing Model
2015
Cognitive radio technology enables secondary users (SUs) to opportunistically access the unused or sparsely utilized spectrum by primary users (PUs) without causing any harmful interference to PUs. Consequently, spectrum occupancy modeling appears as an essential task in cognitive radio networks (CRNs). In this paper, we model spectrum occupancy using a queueing theory based approach in order to evaluate the performance of CRNs in terms of network capacity and number of cognitive radio users waiting for services etc. The queue adopted in this model has variable service capacity and can be considered as a multi-service queue with server failure where each channel acts as a server. When a cha…
Bayesian hierarchical models in manufacturing bulk service queues
2006
In this paper, Queueing Theory and Bayesian statistical tools are used to analyze the congestion of various manufacturing bulk service queues with the same characteristics that are working independently of one another and in equilibrium. Hierarchical models are discussed in order to develop the whole inferential process for the parameters governing the system. Markov Chain Monte Carlo methods and numerical inversion of transforms are addressed to compute the posterior predictive distributions of the usual measures of performance in practice.
Bayesian design in queues: An application to aeronautic maintenance
2007
We exploit Bayesian criteria for designing M/M/c//r queueing systems with spares. For illustration of our approach we use a real problem from aeronautic maintenance, where the numbers of repair crews and spare planes must be sufficiently large to meet the necessary operational capacity. Bayesian guarantees for this to happen can be given using predictive or posterior distributions.
Analysis of the renal transplant waiting list in the País Valencià (Spain).
2005
In this paper we analyse the renal transplant waiting list of the Pais Valencia in Spain, using Queueing theory. The customers of this queue are patients with end-stage renal failure waiting for a kidney transplant. We set up a simplified model to represent the flow of the customers through the system, and perform Bayesian inference to estimate parameters in the model. Finally, we consider several scenarios by tuning the estimations achieved and computationally simulate the behaviour of the queue under each one. The results indicate that the system could reach equilibrium at some point in the future and the model forecasts a slow decrease in the size of the waiting list in the short and mid…