Queueing Performance Research Articles

A tollbooth tandem queue with heterogeneous servers

We study a tandem queueing system with K servers and no waiting space in between. A customer needs service from one server but can leave the system only if all down-stream servers are unoccupied. Such a system is often observed in toll collection during rush hours in transportation networks, and we call it a tollbooth tandem queue. We apply matrix-analytic methods to study this queueing system, and obtain explicit results for various performance measures. Using these results, we can efficiently compute the mean and variance of the queue lengths, waiting time, sojourn time, and departure delays. Numerical examples are presented to gain insights into the performance and design of the tollbooth tandem queue. In particular, it reveals that the intuitive result of arranging servers in decreasing order of service speed (i.e., arrange faster servers at downstream stations) is not always optimal for minimizing the mean queue length or mean waiting time.

Based on regular expression matching of evaluation of the task performance in WSN: a queue theory approach.

Due to the limited resources of wireless sensor network, low efficiency of real-time communication scheduling, poor safety defects, and so forth, a queuing performance evaluation approach based on regular expression match is proposed, which is a method that consists of matching preprocessing phase, validation phase, and queuing model of performance evaluation phase. Firstly, the subset of related sequence is generated in preprocessing phase, guiding the validation phase distributed matching. Secondly, in the validation phase, the subset of features clustering, the compressed matching table is more convenient for distributed parallel matching. Finally, based on the queuing model, the sensor networks of task scheduling dynamic performance are evaluated. Experiments show that our approach ensures accurate matching and computational efficiency of more than 70%; it not only effectively detects data packets and access control, but also uses queuing method to determine the parameters of task scheduling in wireless sensor networks. The method for medium scale or large scale distributed wireless node has a good applicability.

Waiting time distributions in the accumulating priority queue

We are interested in queues in which customers of different classes arrive to a service facility, and where performance targets are specified for each class. The manager of such a queue has the task of implementing a queueing discipline that results in the performance targets for all classes being met simultaneously. For the case where the performance targets are specified in terms of ratios of mean waiting times, as long ago as the 1960s, Kleinrock suggested a queueing discipline to ensure that the targets are achieved. He proposed that customers accumulate priority as a linear function of their time in the queue: the higher the urgency of the customer's class, the greater the rate at which that customer accumulates priority. When the server becomes free, the customer (if any) with the highest accumulated priority at that time point is the one that is selected for service. Kleinrock called such a queue a time-dependent priority queue, but we shall refer to it as the accumulating priority queue. Recognising that the performance of many queues, particularly in the healthcare and human services sectors, is specified in terms of tails of waiting time distributions for customers of different classes, we revisit the accumulating priority queue to derive its waiting time distributions, rather than just the mean waiting times. We believe that some elements of our analysis, particularly the process that we call the maximum priority process, are of mathematical interest in their own right.

Large Deviation Delay Analysis of Queue-Aware Multi-User MIMO Systems With Two-Timescale Mobile-Driven Feedback

Multi-user multi-input-multi-output (MU-MIMO) systems transmit data to multiple users simultaneously using the spatial degrees of freedom with user feedback channel state information (CSI). Most of the existing literatures on the reduced feedback user scheduling focus on the throughput performance, while the user queueing delay is usually ignored. As the delay is very important for real-time applications, a low feedback queue-aware user scheduling algorithm is desired for the MU-MIMO system. This paper proposes a two-stage queue-aware user scheduling algorithm, which consists of a queue-aware mobile-driven feedback filtering stage and a user scheduling stage, where the feedback filtering policy is obtained from optimizations. We evaluate the queueing performance of the proposed scheduling algorithm by using the sample path large deviation analysis. We show that the large deviation decay rate for the proposed algorithm is much larger than that of the CSI-only user scheduling algorithm. The numerical results also demonstrate that the proposed algorithm performs much better than the CSI-only algorithm, while requiring only a small amount of feedback.

Critically Loaded Time-Varying Multiserver Queues: Computational Challenges and Approximations

In this paper, we consider time-varying multiserver queues with abandonment and retrials. For their performance analysis, fluid and diffusion limits utilizing strong approximations have been widely used in the literature. Although those limits are asymptotically exact, they may not accurately approximate performance of multiserver queues even if the number of servers is large. To address that concern, this paper focuses on developing a methodology by taking fluid and diffusion limits in a nontraditional fashion. We show that our approximation is significantly more accurate and also asymptotically true. We illustrate the effectiveness of our methodology by performing several numerical experiments.

On the Performance of Underlay Cognitive Radio Networks Using M/G/1/K Queueing Model

Motivated by a realistic scenario for cognitive radio systems, we model the underlay cognitive radio network (CRN) under interference power constraint imposed by the primary network as an M/G/1/K queueing system. The respective embedded Markov chain is provided to analyze several key queueing performance measures. In particular, the equilibrium probabilities of all states are derived and utilized to evaluate throughput, blocking probability, mean packet transmission time, mean number of packets in the system, and mean waiting time of an underlay CRN with Nakagami-m fading channels.

Asymptotic Queuing Analysis for Dynamic Spectrum Access Networks in the Presence of Heavy Tails

The heavy tailed nature exhibited in both primary and secondary users' traffic fundamentally challenges the performance limit of dynamic spectrum access (DSA) networks under the conventional light tailed assumptions. This paper provides an asymptotic analysis of the steady-state queue length distribution of secondary users (SUs) under the heavy tailed network environment. Specifically, two network scenarios are investigated. In the first scenario where each SU has its exclusive access to a primary user (PU) channel, it is shown that the heavy tailed nature of either the PU traffic or the SU traffic can make SUs experience heavy tailed queue length with unbounded moments. In the second scenario where multiple SUs share a single PU channel, the queuing performance under throughput optimal scheduling policies is studied. It is proven that if the PU traffic has a heavier tail than any SU traffic, the queue length of each SU is at least one order heavier than the PU traffic under any scheduling policy. Otherwise, if the traffic from at least one of the SUs has a heavier tail than the PU traffic, it is proven that the celebrated throughput-optimal maximum weight scheduling leads to the worst possible asymptotic queuing performance for SUs by letting each SU queue have the heaviest possible tail. On the contrary, it is shown that there always exists a feasible set of β parameters such that the maximum weight-β scheduling yields the best asymptotic performance for the SU queues by letting each queue have the lightest possible tail.

Transient analysis of machining systems with service interruption, mixed standbys and priority

Spare support plays an important role in improving the reliability of multi-component repairable machining systems in many industries as well as in day-to-day real-time embedded systems. This paper is concerned with the reliability analysis of embedded machining system consisting of two types of units along with warm and cold standbys support under the priority concepts. The Markov model is developed by constructing the transient equations using birth death process. Various queueing and reliability performance measures are established in terms of transient probabilities of the system states which are evaluated using numerical technique based on Runge-Kutta method. To illustrate the tractability of the proposed method, a numerical example is worked out. Further neuro-fuzzy inference approach is employed to compare some performance indices which are also obtained numerically.

Computing performance measures of fuzzy non-preemptive priority queues using robust ranking technique

This paper put forward a procedure to find the various performance measures in term of crisp values for fuzzy non- preemptive priority queues with 3-priorities. Here the inter arrival time and service time are Trapezoidal as well as Triangular fuzzy numbers.The basic idea is to convert the fuzzy inter arriva l rates and service rates into crisp values by applying Robust ranking technique.Then apply the crisp values in the traditional queuing performance measure formulas. Ranking fuzzy numbers is an important aspect of decision making in a fuzzy environment.This ranking technique is a systematic procedure ,easy to apply and can be utilized for all types of queuing problems .An illustration is given to establish the performance measures for 3-priority queues.

Agent-Based Simulation Tool for Evaluating Pooled Queue Performance at Marine Container Terminals

Truck queuing at marine container terminal gates is one of the main sources of delay at terminals and is an area of concern because delays increase the logistical cost of transporting a container. Previous studies on terminal gates focused on the performance of strategies such as the appointment system and extended gate hours. However, no study has yet evaluated the performance of pooling trucks into a single queue at the gates. Previous studies on pooling offered mixed opinions on whether pooling was beneficial, but none of those studies attempted to model the movements of the entities in the queue. In a human system (no vehicles), the movements are not as important because the time to move up one space in the queue is negligible; however, because of the size and weight of the trucks at the gates, the time to move is significant and should be considered. A study was conducted with agent-based simulation to model the terminal gate system with two queuing strategies, a pooled queue and nonpooled queues, because analytical solutions could not capture vehicle movements within the queue. In the study, a car-following model was used to capture a realistic representation of how vehicles move within the queue. The developed simulation model was used to evaluate queuing strategies in various conditions. Results indicate that the use of a pooled queue yields significantly lower average queuing times and lower variability in queuing times.

An On-Demand Queue Management Architecture for a Programmable Traffic Manager

A queue manager (QM) is a core traffic management (TM) function used to provide per-flow queuing in access and metro networks; however current designs have limited scalability. An on-demand QM (OD-QM) which is part of a new modular field-programmable gate-array (FPGA)-based TM is presented that dynamically maps active flows to the available physical resources; its scalability is derived from exploiting the observation that there are only a few hundred active flows in a high speed network. Simulations with real traffic show that it is a scalable, cost-effective approach that enhances per-flow queuing performance, thereby allowing per-flow QM without the need for extra external memory at speeds up to 10 Gbps. It utilizes 2.3%-16.3% of a Xilinx XC5VSX50t FPGA and works at 111 MHz.

Queue Performance in Presence of Long-Range Dependencies – an Empirical Study

The queuing, as an inherent feature of each real system, plays a very important role in teletraffic networks as well. It is known that the queuing system consists of three basic components: the input stream of requests, the service processes and the queue discipline. The optimal performance of system can be achieved only in the case when all components are “matched” together. The teletraffic models that describe the early telephone services (e.g. Poisson and Markov) have been very successful. One of the main reasons for this success with models, which accurately resembles the real-world behavior, has been due to the highly static, low varying nature of early development phase of telephone voice traffic. This means that the whole environment of early telephone networks can be treated as a simple system. The main features of such systems can be described by: thermodynamic quasi-equilibrium, homogenous topologies, random graph theory, short-range dependencies, Poisson distribution, circuit switching, etc. However, the evolution of teletraffic from voice to new data traffic and integrated services inevitably leads to the vastly different statistical characteristics that are much more irregular and variable and as a result undermine the basis for the traditional traffic models. In this paper we show that taking into account the complex systems approach the existence of long-range dependencies (expressed by 1/f noise) influence queue performance. This is done basing on analytical approach with presentation of long-range dependent queue model and also by experimental study of traffic behavior in computer network during daily workload generated by computer user.

Fourth Stage of Voice Priority Queue for VoIP over WLANs

Voice over Internet Protocol (VoIP) is growing rapidly during this decade. VoIP is seen as a short-term and long-term transmission for voice and audio traffic and is moving on Wireless Local Area Networks (WLANs) based on IEEE 802.11 standards. Currently, packet scheduling algorithms like Weighted Fair Queuing (WFQ), was mainly designed to provide the bandwidth reservation. The Strict Priority (SP) is low-cost to maintain the delay sensitive voice traffic. Also, a number of research scheduling solutions have been proposed like General processor sharing (GPS), Deficit Round Robin (DRR), Contention-Aware Temporally fair Scheduling (CATS). Unfortunately, the current scheduling won’t be able to handle the VoIP packets properly and they have drawbacks over real-time applications. The objective of this research is to propose a Fourth Stage of Voice Priority Queue (VPQ) packet scheduling and algorithm to ensure more throughput, fairness and efficient packet scheduling for VoIP performance of queues and traffics. A new scheduler flexible which is capable of satisfying the VoIP traffic flows. Experimental topologies on NS-2 network simulator were analyzed for voice traffic.

Loss probability estimation for OFDM/TDMA-based wireless systems considering a cascade-based multifractal traffic model

In this paper, we analyze the queueing performance in terms of byte loss rate of an orthogonal frequency-division multiplexing/time division multiple access based wireless system taking into account the multifractal behaviour of the wireless traffic flows. To this end, first, we show evidences of multifractal characteristics on wireless traffic traces. These findings motivated us to derive a loss probability equation for wireless traffic flows that can be applied to an orthogonal frequency-division multiplexing/time division multiple access based wireless system. Simulations and comparisons to other methods are carried out to verify the accuracy of the proposed loss probability estimation approach in describing real traffic queueing behaviour. Copyright © 2012 John Wiley & Sons, Ltd.

Optimal design for dynamic spectrum access in cognitive radio networks under Rayleigh fading

We consider a time slotted cognitive radio network under Rayleighfading where multiple secondary users (SUs) contend for spectrumusage over available primary users' channels. Weanalyze the performance of a channel access policy where each SU stochasticallydetermines whether to access a wireless channel or not based on agiven access probability. In the analysis, we focus on the queueing performance ofan arbitrary SU with the channel access policy.To improve the queueing performance of SUs, theaccess probability in our channel access policy is adapted to theknowledge on the wireless channel information, e.g., the number of available channels andthe nonfading probability of channels.It is then important to obtain the optimalaccess probabilities from the queueing performance perspective.  &nbsp In this paper we consider three scenarios. In the first scenario,all SUs have full information on wireless channel status andfading channel conditions. In the second scenario, all SUs havethe information on wireless channel status but do not know theirfading channel conditions, and in the last scenario all SUs do nothave any information on wireless channel status and conditions. Foreach scenario we analyze the queueing performance of anarbitrary SU and show how to obtain the optimal accessprobabilities with the help of the effective bandwidth theory.From our analysis we provide an insight on how to design an optimalchannel access policy in each scenario. We also show how the optimal channel accesspolicies in three scenarios are related with each other. Numericalresults are provided to validate our analysis. In addition, weinvestigate the performance behaviors of the optimal channel access policies.

Study about effects of self-similar IP network traffic on queuing and network performance

The paper examines self-similar properties of real communication network traffic data over a wide range of time scales. These self-similar properties are very different from the properties of traditional models based on Poisson and Markov-modulated Poisson processes. Advanced self-similar models of sequentional generators and fixed-length sequence generators, and efficient algorithms that are used to simulate self-similar behaviour of IP network traffic processes are developed and applied. Simulations and numerical results are shown and analysed. Furthermore, simulations with stochastic and long range dependent traffic source models are conducted; and efficient algorithms for buffer overflow simulation in finite buffer single server model under self-similar traffic load are developed and applied. Simulations and numerical results are shown and analysed.

Queuing Analysis for IEEE 802.11e Networks in Non-Saturation Environments

This paper presents an analytical model for the performance evaluation of an IEEE 802.11e network in non-saturation environments. We first characterize the probability distribution of the MAC layer packet service time. Based on the probability distribution model of the MAC layer packet service time, we then study the queuing performance of the wireless local area networks (WLANs) at different traffic loads based on the IEEE 802.11e MAC protocol. The numerical results show that we can choose a feasible number and bandwidth of the node which determines the system performance that a user demands.

The Unreliable M/M/1 Retrial Queue in a Random Environment

We examine an M/M/1 retrial queue with an unreliable server whose arrival, service, failure, repair, and retrial rates are all modulated by an exogenous random environment. Provided are conditions for stability, the (approximate) orbit size distribution, and mean queueing performance measures which are obtained via matrix-analytic methods. Additionally, we consider the problem of choosing arrival and service rates for each environment state with the objective of minimizing the steady state mean time spent in orbit by an arbitrary customer, subject to cost and revenue constraints. Two numerical examples illustrate the main results.

The VPQ Scheduler In Access Point For VoIP Over WLAN

The Voice over Internet Protocol (VoIP) application has observed the fastest growth in the world of telecommunication. VoIP is seen as a short-term and long-trem transmission for voice and audio traffic. Meanwhile, VoIP is moving on Wireless Local Area Networks (WLANs) based on IEEE 802.11 standards. Currently, there are many packet scheduling algorithms for real-time transmission over network. Unfortunately, the current scheduling will not be able to handle the VoIP packets with the proper manner and they have some drawbacks over real-time applications. The objective of this research is to propose a new Voice Priority Queue (VPQ) packet scheduling and algorithm to ensure more throughput, fairness and efficient packet scheduling for VoIP performance of queues and traffics. A new scheduler flexible which is capable of satisfying the VoIP traffic flows. Experimental topologies on NS-2 network simulator wereanalyzed for voice traffic. Preliminary results show that this can achieve maximum and more accurate VoIP quality throughput and fairness index in access point for VoIP over WLANs. We verified and validated VPQ an extensive experimental simulation study under various traffic flows over WLANs.

Mobility of Mobile Station in Voice Priority Queue Scheduler for VoIPWLANs

Voice over Internet Protocol (VoIP) is growing rapidly during this decade. VoIP is seen as a short-term and long-trem transmission for voice and audio traffic. Meanwhile, VoIP is moving on Wireless Local Area Networks (WLANs) based on IEEE 802.11 standards. Currently, many packet scheduling algorithms like Weighted Fair Queuing (WFQ), was mainly designed to provide the bandwidth reservation. The Strict Priority (SP) is low-cost to maintain the delay sensitive voice traffic. Also, a number of research scheduling solutions have been proposed like General processor sharing (GPS), Deficit Round Robin (DRR), Contention-Aware Temporally fair Scheduling (CATS). Unfortunately, the current scheduling will not be able to handle the VoIP packets with the proper manner and they have some drawbacks over real-time applications. The objective of this research is to propose a new Voice Priority Queue (VPQ) packet scheduling and algorithm to ensure more throughput, fairness and efficient packet scheduling for VoIP performance of queues and traffics. A new scheduler flexible which is capable of satisfying the VoIP traffic flows. Experimental topologies on NS-2 network simulator were analyzed for voice traffic. Preliminary results show that this can achieve maximum and more accurate VoIP quality throughput and fairness index in mobility of mobile station. We verified and validated VPQ an extensive experimental simulation study under various traffic flows over WLANs.