Cell Loss Probability Research Articles

Estimating Tail Probability in MMPP/D/1 Queue with Importance Sampling by Service Rate Adjustments

The Asynchronous Transfer Mode (ATM) is an efficient technology for call relays, and it transmits information from multiple services including data, video, or voice. This information is conveyed at ATM multiplexers in small fixed-size packets called cells. The acceptable cell loss probability at ATM multiplexers is about 10−12. Important Sampling (IS) is an efficient method for estimating tiny probabilities that cannot be achieved by traditional Monte Carlo (MC) methods. This research presents a novel approach for evaluating the tail probability in the MMPP/D/1 queue system utilizing importance sampling simulation in the ATM network. To generate more rare events, a virtual queue is implemented in the dequeue process by decreasing the processing rate in the queue. In this way, the tail probability can be estimated on a real-time network.

Micro-flow cell washing technique combined with single-cell Raman spectroscopy for rapid and automatic antimicrobial susceptibility test of pathogen in urine

Facing the rapid spread of antimicrobial resistance, methods based on single-cell Raman spectroscopy have proven their advances in reducing the turn-around time (TAT) of antimicrobial susceptibility tests (AST). However, the Raman-based methods are still hindered by the prolonged centrifugal cell washing procedure, which may require complex labor operation and induce high mechanical stress, resulting in a pretreatment time of over 1 h as well as a high cell-loss probability. In this study, we developed a micro-flow cell washing device and corresponding Raman-compatible washing chips, which were able to automatically remove the impurities in the samples, retain the bacterial cell and perform Raman spectra acquisition in situ. Results of washing the 5- and 10-μm polymethyl methacrylate (PMMA) microspheres showed that the novel technique achieved a successful removal of 99 % impurity and an 80 % particle retention rate after 6 to 10 cycles of washing. The micro-flow cell washing technique could complete the pretreatment for urine samples in a 96-well plate within 10 min, only taking 15 % of the handling time required by centrifugation. The AST profiles of urine sample spiked with E. coli 25922, E. faecalis 29212, and S. aureus 29213 obtained by the proposed Raman-based approach were found to be 100 % consistent with the results from broth micro-dilution while reducing the TAT to 3 h from several days which is required by the latter. Our study has demonstrated the micro-flow cell washing technique is a reliable, fast and compatible approach to replace centrifuge washing for sample pretreatment of Raman-AST and could be readily applied in clinical scenarios.

Applying switching and multiple access model for reducing packet loss and network overheads in watm

As an effectual simple wireless equivalent created in the telecommunications (telephone) industry, Wireless Asynchronous Transfer Mode (WATM) is utilized to stream unified traffics like video, data, and voice data. In the asynchronous data transfer mode, voice data transfer a packet with the same medium, and data share the networks and burst data. Effective WATM data transmission requires an extensive array of designs, techniques used for control, and simulation methodologies. The congestion of the network is among the key challenges that lower the entire WATM performance during this procedure, in addition to the delay in cell and the overload of traffic. The congestions cause cell loss, and it requires expensive switches compared to the LAN. Consequently, in this current study, the application of an effectual switching model together with a control mechanism that possesses multiple accesses is employed. The multiple access process and switching model are utilized to establish an effective data sharing process with minimum complexity. The switching model uses the synchronous inputs and output ports with buffering to ensure the data sharing process. The traffic in the network is decreased, and the loss of packets in the cells is efficiently kept to a minimum by the proposed technique. The system being discussed is employed through the utilization of software employed using OPNET 10.5 simulation, with the valuation of the WATM along with the investigational outcomes accordingly. The system's efficiency is assessed by throughput, latency, cell loss probability value (CLP), overhead network, and packet loss. Thus, the system ensures the minimum packet loss (0.1 %) and high data transmission rate (96.6 %)

Analytical Modeling of RRM-ATM Switch for Linear Increment and Exponential Decay of Source Data Rate

This paper describes analytical modeling of relative rate marking (RRM) switch for available bit rate (ABR) ATM service considering linear increment and exponential decay of data rate(s) of the source(s) to achieve faster congestion control of the network through resource management of the RRM switch. Theoretical performance of the switch has been evaluated in respect of link utilization factor and cell loss probability. It is shown that the switch achieves faster control over source(s) along with improved link utilization factor. This is particularly attractive for congestion control in ABR-ATM networks. The developed switch model can find potential application in the design of RRM switch specific to a network environment.

Clinical Outcomes in Cytomegalovirus-Positive Posner-Schlossman Syndrome Patients Treated With Topical Ganciclovir Therapy

To evaluate the clinical characteristics and therapeutic outcomes of cytomegalovirus (CMV)-positive Posner-Schlossman syndrome patients undergoing topical ganciclovir treatment. Retrospective, comparative, and interventional case series. One eye of each of 126 consecutive Posner-Schlossman syndrome patients was investigated using aqueous polymerase chain reaction (PCR) between January 2006 and June 2013. The initial presentations and follow-up data of the CMV-positive patients (68 eyes) and CMV-negative patients (58 eyes) were compared. Severe endothelial cell loss (P < .001) and a higher number of eyes requiring glaucoma filtering surgery (P = .017) were observed in CMV-positive Posner-Schlossman syndrome patients. All CMV-infected eyes treated with continual topical 2% ganciclovir exhibited an undetectable CMV level at the following taps. During follow-up, the average number of antiglaucomatous agents decreased, and a similar frequency of intraocular pressure (IOP) spikes was observed in both groups (P = .358). Patients with CMV-positive eyes with a disease duration over 5 years were likely to require glaucoma surgery (P = .024, log-rank test). All patients receiving surgery exhibited CMV-negative PCR during the IOP attack, but experienced severe peripheral anterior synechiae and pigment clogging. Both groups exhibited a similar endothelial cell decrease (P = .243) and probability of progressive endothelial cell loss (P = .219, log-rank test). Ganciclovir treatment was effective for clearing the viral load, assisting the IOP control, and preserving the corneal endothelium of CMV-positive Posner-Schlossman syndrome patients. Early diagnosis and proper treatment could decrease the risk of advanced glaucoma and avoid glaucoma surgery in long-lasting cases.

Dimensioning Hierarchical Access Modules

Network dimensioning has been in the center of interest ever since the earliest networking architectures were put to use in the seventies. Since then service providers try to serve an ever increasing traffic with a given QoS. As a result, one of the main challenges of network dimensioning is how to design minimum capacity and minimum HW complexity network access modules which can carry a given amount of traffic with some predefined QoS parameters. The QoS is usually measured by cell loss probabilities and average cell delays. In this paper we provide dimensioning algorithms for Hierarchical Access Modules (HAMs) built up by subracks in a hierarchical manner and developed to provide different types of user-access to internet. The main objective is to design minimum complexity HAMs, which can serve a given population of users with a pre-negotiated level of QoS. Since the complexity and cost are measured by the number of racks and the link capacities used in HAM, optimal design is defined here as constructing a HAM which contains the smallest possible number of racks (cards) and the lowest capacity links. However, there are plentiful various topologies and corresponding link capacity arrangements which can serve a given population of users with a predefined QoS. As a result - when HAM is described as a multidimensional vector representing the topology the number of subracks and the corresponding link capacities - the optimal solution is to be sought in a large vector space. This casts dimensioning as a combinatorial optimization problem and we refer to this task as Node and Capacity Arrangement Problem (NCAP). In this paper, we develop such algorithms and provided numerical results for typical traffic loads and QoS parameters which can occur while using HAMs.

The special cell effects and somatic consequences of exposure to low-dose radiation

The present work presents the peculiar form of a tissue post-irradiation reaction, characterised by a massive dose-independent transition of cell populations to the steady-state modification with increased cell damage and cell loss probability compared with the probability level of the same alterations in control. The X-ray irradiation at a dose of 0.5 Gy as well as at higher doses, 2.25 and 4.5 Gy, produces in rat myocardium capillary endotheliocytes specific potential changes: a long-term increase of the yield of cells with signs of an irreversible damage. The experimental data suggest that epigenetic mechanisms occur in the induction and preservation of these alterations. The discovered form of cellular reaction observed in different biological objects may be considered as a general biological tendency. This effect does not increase with the dose, and is not subjected to reparation throughout the most part of the animal lifespan. It is suggested that the changes revealed might play a role in the development of remote vascular pathology after effects of low-dose irradiation (including that in post-accident situations).

Improving the Quality of Service Guarantee in an Asynchronous Transfer Mode (ATM) Network

This study presents a technique for improving the quality of service (QoS ) guarantee in an ATM network. In the proposed model, it was assumed that high priority traffic have been allocated a switch resource to guarantee a given QoS and low priority cells are allowed to enter the buffer, to improve the exploitation of reserved resources. The proposed technique was backed up with an exact analytical model for evaluating the cell loss probability of high and low priority cells. The performance of the proposed model was evaluated using C++ programming language. The results of the simulation shows that the loss probability of both high and low cells reduces as the buffer capacity increase and that the performance of high priority cell is better than that of low priority cell.

Performance analysis and evaluation for multi-traffic networks with priority control

In this paper, we consider a multi-traffic network system for next generation communication networks with a transmission link shared by an Available Bit Rate (ABR) application for non-real time traffic and a Variable Bit Rate (VBR) application for real time traffic. It is assumed that the VBR traffic has a higher transmission priority than the ABR traffic. We propose a new feedback control method to control the flow of the ABR traffic. In this method, the ABR source has multiple states and the number of cells transmitted by the ABR source is controlled by the feedback based on the congestion state of the buffer. By using the Markov chain method, we establish a tractable analytical model for the system. We give some iterative formulas for calculating the transition probabilities. Then, based on the analysis, we calculate the cell loss probability and the utilization of the network system. The impact of several parameters on the system performance is presented through some numerical results.

An approximate analysis of shared‐buffer channel‐grouped ATM switches under imbalanced traffic

AbstractGrouping output channels in a shared‐buffer ATM switch has shown to provide great saving in buffer space and better throughput under uniform traffic. However, uniform traffic does not represent a realistic view of traffic patterns in real systems. In this paper, we extend the queuing analysis of shared‐buffer channel‐grouped (SBCG) ATM switches under imbalanced traffic, as it better represent real‐life situations. The study focuses on the impact of the grouping factor and other key switch design parameters on the performance of such switches as compared to the unichannel allocation scheme in terms of cell loss probability, throughput, mean cell delay and buffer occupancy. Numerical results from both the analytical model and simulation are presented, and the accuracy of the analysis is presented. Copyright © 2005 John Wiley &amp; Sons, Ltd.

Traffic splitting in a network: split traffic models and applications

The contemporary high-speed networks, e.g. the Internet and asynchronous transfer mode (ATM) networks provide a convenient and cost-effective communication platform to carry the emerging multimedia applications. However, problems, such as network congestion caused by overloaded traffic get worse day by day. Thus, how to properly control the system while maintaining the quality of service (QoS) for users becomes an important and challenging issue. To reach the goal of QoS guarantee, load sharing or traffic balancing is one of important techniques to improve the whole network performance. In this paper, we focus on the probabilistic routing policy and analyze split traffic models under such a probabilistic routing policy with input traffic models of the batch Markovian arrival process (BMAP) and discrete-time BMAP (D-BMAP) which can be employed to characterize the multimedia traffic in current and future networks. We successfully show that the split traffic on each routing path from an original BMAP (D-BMAP) input is still a BMAP (D-BMAP). The detailed traffic structure is also acquired. Applying traffic splitting along with the output process characterization, we propose a network-wise performance evaluation method suitable for mesh networks with a probabilistic routing algorithm to get the end-to-end delay, delay variance, and cell loss probability. With numerical experiments, we show that (i) the probabilistic routing policy with a random routing matrix performs well for systems; (ii) the proposed method of network-wise performance analysis has good accuracy.

Measurement-based virtual queue (VQ): to estimate the real-time bandwidth demand under loss constraint

We study a traffic measurement issue for active queue management and dynamic bandwidth allocation at a single network node under the constraint of Cell Loss Probability (CLP) or buffer overflow probability. Using the concept of measurement-based Virtual Queue (VQ) and frequency-domain traffic filtering, we propose an online algorithm to estimate the real-time bandwidth demand under both short- and long-term cell loss constraint. The algorithm is adaptive and robust to the piece-wise stationary traffic dynamics. The VQ runs in parallel to the real queueing system and monitors the latter in a non-intrusive way. It captures a proper traffic sampling interval T c. Simulation and analysis show its critical role in achieving higher utilization of bandwidth and buffer resource without violating QoS requirement. Given an appropriate T c, we argue that network controls, such as the Call Admission Control (CAC) and dynamic bandwidth allocation, are facilitated with accurate information about traffic loading and QoS status at the smallest timescale.

Traffic splitting in a network: split traffic models and applications

The contemporary high-speed networks, e.g. the Internet and asynchronous transfer mode (ATM) networks provide a convenient and cost-effective communication platform to carry the emerging multimedia applications. However, problems, such as network congestion caused by overloaded traffic get worse day by day. Thus, how to properly control the system while maintaining the quality of service (QoS) for users becomes an important and challenging issue. To reach the goal of QoS guarantee, load sharing or traffic balancing is one of important techniques to improve the whole network performance. In this paper, we focus on the probabilistic routing policy and analyze split traffic models under such a probabilistic routing policy with input traffic models of the batch Markovian arrival process (BMAP) and discrete-time BMAP (D-BMAP) which can be employed to characterize the multimedia traffic in current and future networks. We successfully show that the split traffic on each routing path from an original BMAP (D-BMAP) input is still a BMAP (D-BMAP). The detailed traffic structure is also acquired. Applying traffic splitting along with the output process characterization, we propose a network-wise performance evaluation method suitable for mesh networks with a probabilistic routing algorithm to get the end-to-end delay, delay variance, and cell loss probability. With numerical experiments, we show that (i) the probabilistic routing policy with a random routing matrix performs well for systems; (ii) the proposed method of network-wise performance analysis has good accuracy.

A shared buffer memory switch with multicast function using generalized two‐level priority control

AbstractIn the future, various multicast applications are anticipated for ATM networks, and many studies have examined ATM switches having the multicast function. In a shared buffer switch, the cell loss performance is clearly improved by unicast priority control that gives send priority to the unicast cell in an address copy switch. However, if the multicast traffic increases, a reduction in the priority control effect becomes a problem. To solve this unicast priority control problem, in this paper, we propose two generalized two‐level priority control schemes (deterministic‐threshold scheme and adaptive‐threshold scheme) that give priority to cells having the number of copies below some threshold. The deterministic‐threshold scheme sets the optimum threshold when the traffic state is known, and clearly reduces the cell loss probability even when the ratio of multicast cells in the input traffic is high. The problem becomes what to set the threshold to because the optimum threshold changes depending on the traffic state in this scheme. The adaptive‐threshold scheme always maintains the priority control effect by automatically changing the threshold in response to traffic variations based on the result obtained from the deterministic‐threshold scheme. We use simulations to compare the adaptive scheme to conventional schemes and demonstrate the effectiveness of the adaptive‐threshold scheme. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 87(8): 63–70, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10111

Estimation of cell loss probability for self-similar traffic in ATM networks—a fuzzy approach

Abstract Estimating cell loss probability (CLP) in real time for achieving satisfactory call admission control (CAC) remains an important research problem. In estimating CLP which are often specified to be less than 10−9, fuzzy-based techniques have been found to be more promising over crisp statistical techniques. In this paper, we propose a novel fuzzy logic algorithm based on the α-cuts of equivalence relation to estimate CLP in real time for self-similar traffic in ATM networks. The α-cuts of fuzzy sets are used to construct the membership functions of the input and output variables, and to induce necessary fuzzy rules. The proposed fuzzy approach is validated by comparing the estimated values of CLP with the theoretical values. The new approach not only estimates accurate real time CLP, but also achieves it by using fewer appropriate theoretical data.

Pushout with virtual thresholds buffer management scheme in a shared buffer ATM switch

AbstractIn this paper we investigate the performance metrics of buffer management schemes. In general, the selective pushout (SP) scheme can support very low loss probability of the high‐priority cells, but it may cause unfairness of buffer allocation among different output queues and high overall cell loss probability. In order to fit the dynamic required performance metrics of ATM switches, a novel buffer management scheme called pushout with virtual thresholds (PVT) is proposed. In the PVT scheme, each output queue is guaranteed to increase in length until its virtual threshold (VT). Simulation results show the PVT can dynamically achieve the fairness and low overall cell loss probability or very low loss probability of the high priority cells by adequately adjusting the VT. Specially, when the VT = 0, the PVT control can be viewed as the SP control. Copyright © 2003 John Wiley &amp; Sons, Ltd.

A Multi-Agent Architecture for QoS Management in Multimedia Networks

Increasing interest in the transmission of audiovisual applications over best-effort networks (i.e., IP and ATM ABR, and UBR services) and efficient video-aware congestion control techniques have to be designed in order to improve the video quality in the presence of cell loss. This paper presents a new slice-based discard scheme to be used with Guaranteed Frame Rate service (formerly UBR+). The scheme adaptively and selectively adjusts discard levels to the switch's buffer occupancy, video cell payload types, and Forward Error Correction Drop Tolerance. To improve its performance, we introduce a distributed multiagent system that provides a self-regulating network control management by means of automatic adjustment of congestion control parameters. The control agents are distributed in the network and operate on a local scope referred to as a “domain” consisting of two adjacent ATM switches. The aim of the overall Intelligent Quality-of-Service (QoS) control framework is twofold. First, to ensure graceful picture quality degradation by minimizing the cell loss probability for critical video data while guaranteeing a bounded cell transfer delay. Second, to optimize the network effective throughput by reducing the transmission of “nonuseful” data. Performance evaluations show significant improvement over traditional approaches.

Fault tolerance in Clos–Knockout multicast ATM switch

AbstractIn this paper, we propose a new architecture for multicast ATM switches with fault tolerant capability based on the Clos–Knockout switch. In the new architecture, each stage has one more redundant switch module. If one switch module is faulty, the redundant module would replace the faulty one. On the other hand, under the fault‐free condition, the redundant modules in the second and third stages will provide additional alternative internal paths, and hence improve the performance. The performance analysis shows that the cell loss probability is lower than the original architecture when all modules are fault free, and the reliability of the original architecture is improved. Copyright © 2002 John Wiley &amp; Sons, Ltd.

A measurement-based call admission control scheme for ATM networks based on the diffusion approximation

We present a dynamic call admission control method based on the diffusion approximation method. The diffusion approximation method is traditionally used for calculating the effective bandwidth for a number of connections having a certain cell loss requirement. The proposed method has a low implementation overhead since it performs measurements on the aggregate traffic stream at a particular ATM switch as opposed to other methods that need to perform per-source measurements. We provide a study of the performance of the method for specific traffic types using simulation and compare with the performance of the static diffusion approximation effective bandwidth method. We also study the influence of variation in traffic parameters such as the source traffic descriptors, the buffer capacity, and the required cell loss probability on the performance of the method.

Numerical Queueing Analysis of Loss Priority for Large Buffer in Atm Networks

In this paper, a new method to analyze the cell loss behavior of partial buffer sharing priority mechanism is proposed. The traffic model is based on the fluid queue and normal stochastic process and the analytical technique is simple and general, only requiring mean arrival rate and autocovariance function. Some typical sources (such as voice, video and heavy tail sources) are applied to the proposed method. Performance results obtained show that the method is valid and useful. The proposed method has the merits that it can easily solve cell loss probability especially with large buffer and avoid huge state space problem comparing with classical state transition matrix method. In particular, the computational gain is substantial regardless of buffer size. Also, the traffic sources can be homogeneous and heterogeneous, bursty and correlated.