1,720,968 research outputs found
Performance analysis of the DAR(1)/D/c priority queue under partial buffer sharing policy
Full text linkWe analyze a multi-server priority queueing system with partial buffer sharing, where the input is a discrete autoregressive process of order 1 (DAR(1)) which is known as a good mathematical model for a VBR-coded teleconference video traffic. We assume that arriving packets are classified into two priority classes, say, high priority class and low priority class based on their importance. A threshold T is set to limit the accessibility of low priority packets to the buffer. When the partial buffer sharing is applied to the real time traffic such as teleconference video traffic, it is known that it can decrease the queueing delay at the expense of the loss of low priority packets which is less important. Since the queueing delay is more important than the loss probability for real time traffic, it is important to analyze the queueing delay of DAR(l) arrivals under the partial buffer sharing policy. Based on the Wiener-Hopf factorization of the GI/GI/1 queue, we obtain the waiting time distribution of a packet which is not discarded at its arrival in the steady state. Numerical examples are provided to show the feasibility of our analysis. We also show that the partial buffer sharing policy significantly decreases the waiting time as the value of threshold increases. (C) 2003 Elsevier Ltd. All rights reserved.This work was supported by Korea Research Foundation Grant (KRF-2001-
042-D00009). The authors would like to thank Dr. D. H. Han for his
careful reading and comments on the paper. They also thank the anonymous
reviewer for his valuable comments on the earlier version of the paper
Performance analysis of priority leaky bucket scheme with queue-length-threshold scheduling policy
No full textThe leaky bucket scheme is a promising method that regulates input traffic for preventive congestion control in ATM networks. One of the important problems in ATM networks is meeting the quality of service requirements for real-time and non-real-time traffics. The authors propose a priority leaky bucket scheme with queue-length-threshold scheduling policy. The motivation of this proposed leaky bucket scheme is to meet the quality of service for real-time traffic while providing more improved services for non-realtime traffic. Using the embedded Markov chain method, the authors obtain the joint distribution of the queue lengths, the loss probability and the mean waiting time. Numerical results show the effects of the system parameters such as the buffer size and the token pool size on the performance of the proposed scheme
Decay rate approximation of queue in packet switched networks
No full textThe authors refine their previous result for calculating the decay rare of a queue arising in packet switched networks such as ATM. The input process is assumed to be a (or a number of) two-state Markovian source(s). The improvement of the refined formula will be shown by numerical examples.This work was supported by Korea Resarch Foundation Grant KRF-99-015-DI0016
Priority queueing system with fixed-length packet-train arrivals
No full textA discrete-time priority queueing system is studied, in which two different classes of fixed-length packet-trains arrive according to independent batch geometric streams. The packets in each packet-train arrive at the rate of one packet per slot (train arrivals), resulting in st correlated arrival stream. The service time of one packet is deterministic of one slot. The motivation for the work comes from ATM networks with diverse traffic sources and correlated packet arrival stream. Using the probability generating function method, the joint distribution of queue lengths and the waiting time distribution are obtained for each class. Numerical results are presented. Comparision is made with the case of 'batch arrivals', where all packets of a packet-train arrive simultaneously at the buffer
Performability analysis of common-channel signaling networks, based on signaling system #7
No full textWithin integrated services digital networks (ISDN), all inter-exchange signaling messages for ISDN and intelligent network (IN) call controls are carried through a common channel signaling network (CCSN) as a backbone signaling network. Since CCSN usually have very strict reliability requirements as well as good performance objectives, performance and reliability of CCSN need to be jointly analyzed. This paper evaluates the mean end-to-end delay of a single-mated pair (SMP) CCSN for various call-arrival rates in a normal state and several failure states, as a performance index. As a performability index, this paper also analyzes the mean time to unreliable operation (MTUO) of a given network for various call- arrival rates at each signaling end point (SEP) and the failure rate of each signaling transfer point (STP). These results can be used in the design of common-channel signaling networks. This performability evaluation can be further studied for varying the failure rates of SEP and linksets, and the Various threshold Values of the unreliable operation
An application of Markovian arrival process (MAP) to modeling superposed ATM cell streams
No full textFirst, we propose a new modeling method for superposed ATM traffic by the MMPP(2), which is a special case of the MAP(2). In this new method, we measure the mean and autocorrelation of cell interarrival times, and the histogram of the number of arrivals during measurement windows of fixed size. The MMPP(2) has interarrival times with the second-order hyper-exponential distribution with coefficient of variation c(v) > 1. However, superposed traffic is often observed to have c(v) < 1. To cover this situation, we extend the MMPP(2) to a MAP(3) by adding a new state with inter-state transition accompanied by an arrival. For the MAP(3) model, we take into account the second moment of the interarrival times. From numerical examples, we observe that both the proposed MMPP(2) and MAP(3) yields very good estimation of the cell loss ratio (CLR) for usual superpositions of voice and/or VBR video sources. However, when we have superpositions from CBR video sources together with other VBR sources, c(v) is much less than 1, and the MAP(3) outperform the MMPP(2), as expected. The proposed MAP(3) well characterizes the cell scale component as well as the burst scale component of superposed traffic streams
An analysis of M,MMPP/G/1 queues with QLT scheduling policy and Bernoulli schedule
No full textWe analyze M, MMPP/G/1 finite queues with queue-length-threshold (QLT) scheduling policy and Bernoulli schedule where the arrival of type-1 customers (nonreal-time traffic) is Poisson and the arrival of type-2 customers (real-time traffic) is a Markov-modulated Poisson process (MMPP). The next customer to be served is determined by the queue length in the buffer of type-1 customers. We obtain the joint queue length distribution for customers of both types at departure epochs by using the embedded Markov chain method, and then obtain the queue length distribution at an arbitrary time by using the supplementary variable method. From these results, we obtain the loss probabilities and the mean waiting times for customers of each type. The numerical examples show the effects of the QLT scheduling policy on performance measures of the nonreal-time traffic and the bursty real-time traffic in ATM networks
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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