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Sample records for active queue management

  1. Performance Comparison of Active Queue Management Techniques

    Directory of Open Access Journals (Sweden)

    T. B. Reddy

    2008-01-01

    Full Text Available Congestion is an important issue which researchers focus on in the Transmission Control Protocol (TCP network environment. To keep the stability of the whole network, congestion control algorithms have been extensively studied. Queue management method employed by the routers is one of the important issues in the congestion control study. Active Queue Management (AQM has been proposed as a router-based mechanism for early detection of congestion inside the network. In this study, we are comparing AQM two popular queue management methods, Random Early Detection (RED and droptail, in different aspects, such as throughput and fairness Index. The comparison results indicate RED performed slightly better with higher throughput and higher fairness Index than droptail. Simulation is done by using Network Simulator (NS2 and the graphs are drawn using X- graph.

  2. A Robust Algorithm in Active Queue Management

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    A variable structure based control scheme was proposed for Active Queue Management (AQM) by using sliding model algorithm and reach law method. This approach aims toaddress the tradeoff between good performance and robustness with respect to the uncertainties of the round-trip time and the number of active connections. Ns simulations results show that the proposed design significantly outperforms the peer AQM schemes in terms of fluctuation in the queue length, packet throughput, and loss ratio. The conclusion is that proposed scheme is in favor of the achievement to AQM objectives due to its good transient and steady performance.

  3. Comparison of load-based and queue-based active queue management algorithms

    Science.gov (United States)

    Kwon, Minseok; Fahmy, Sonia

    2002-07-01

    A number of active queue management algorithms have been studied since Random Early Detection (RED) was first introduced in 1993. While analytical and experimental studies have debated whether dropping/marking should be based on average or instantaneous queue length or, alternatively, based on input and output rates (or queue length slope), the merits and drawbacks of the proposed algorithms, and the effect of load-based versus queue-based control have not been adequately examined. In particular, only RED has been tested in realistic configurations and in terms of user metrics, such as response times and average delays. In this paper, we examine active queue management (AQM) that uses both load and queuing delay to determine its packet drop/mark probabilities. This class of algorithms, which we call load/delay controllers (LDC), has the advantage of controlling the queuing delay as well as accurately anticipating incipient congestion. We compare LDC to a number of well-known active queue management algorithms including RED, BLUE, FRED, SRED, and REM in configurations with multiple bottlenecks, round trip times and bursty Web traffic. We evaluate each algorithm in terms of Web response time, delay, packet loss, and throughput, in addition to examining algorithm complexity and ease of configuration. Our results demonstrate that load information, along with queue length, can aid in making more accurate packet drop/mark decisions that reduce the Web response time.

  4. An Active Queue Management Algorithm: CRED

    Institute of Scientific and Technical Information of China (English)

    LI Shi-ning; SUN En-chang; QIN Zheng

    2006-01-01

    By applying the method of average and variance, a new queue management algorithm named the Classified-Random Early Detection (CRED) algorithm is presented which can identify the media streaming, TCP traffic and other UDP traffic at the edge routers. The algorithm discriminates the slow start and the congestion control phase of the TCP traffic and combines the TCP congestion control with the IP congestion control to alleviate the congestion effectively. Simulation shows that CRED can not only make the media streaming obtain the resources needed but also protect the TCP traffic transmitted effectively and reliably.

  5. MRED: A New Adaptive Active Queue Management Algorithm

    Institute of Scientific and Technical Information of China (English)

    JIANGMing; WUChunming; ZHUMiaoliang

    2004-01-01

    To address the problems of TCP (Transport control protocol) end-to-end congestion control mechanism, the IETF (Internet engineering task force) advocates deploying active queue management mechanisms in the network. RED is a popular AQM algorithm. It uses average queue size to detect the incipient network congestion. RED can effectively resolve the problems of traditional Drop-Tail. However, there are still some problems with RED. RED is too sensitive to its parameters and the changes of the number of active TCP connections. On the other hand, the congestion notification sending rate of RED algorithm is determined by maxp and the value of maxp is fixed. As a result, these will lead to queue size oscillation which causes queuing delay and jitter. This paper proposes a new adaptive AQM algorithm named “MRED”(Modified RED). Our goal is to stabilized the queue size in a wide variety of traffic scenarios. MRED can adjust the value of maxp to the changes of the traffic load so that the congestion notification can be sent to sufficient TCP sources to mitigate the congestion level. Simulation results indicate that MRED can effectively avoid the queue overfiow and stabilize the queue occupation independent of the number of active TCP connections thus resulting in a more predictable packet delay in the network.

  6. Some Improvements on Active Queue Management Mechanism Based on Adaptive Fuzzy Control

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    Nguyen Kim Quoc

    2015-11-01

    Full Text Available Active queue management operates at network nodes to control the number of packets in the queue of nodes, by actively receiving packets when the queue is not full, removing packets when the queue is full or notifying bottlenecks even in the embryonic period of the bottlenecks due to to-be-full queue. In recent years, scientists have used fuzzy logic to improve queue management mechanisms. Overall, these improvements have used Mamdani fuzzy system with a fixed structure with triangular functions for input and output variables, so they do not adapt to the changing state of the network. We propose a adaptive fuzzy control (AFC model to improve the effectiveness of active queue management mechanisms.

  7. Design and Analysis of a Multiscale Active Queue Management Scheme

    Institute of Scientific and Technical Information of China (English)

    Qi-Jin Ji; Yong-Qiang Dong

    2006-01-01

    Since Internet is dominated by TCP-based applications, active queue management (AQM) is considered as an effective way for congestion control. However, most AQM schemes suffer obvious performance degradation with dynamic traffic. Extensive measurements found that Internet traffic is extremely bursty and possibly self-similar. We propose in this paper a new AQM scheme called multiscale controller (MSC) based on the understanding of traffic burstiness in multiple time scale. Different from most of other AQM schemes, MSC combines rate-based and queue-based control in two time scales. While the rate-based dropping on burst level (large time scales) determines the packet drop aggressiveness and is responsible for low and stable queuing delay, good robustness and responsiveness, the queue-based modulation of the packet drop probability on packet level (small time scales) will bring low loss and high throughput. Stability analysis is performed based on a fluid-flow model of the TCP/MSC congestion control system and simulation results show that MSC outperforms many of the current AQM schemes.

  8. WSAP: provide loss rate differentiation with active queue management

    Institute of Scientific and Technical Information of China (English)

    Zhang Miao; Wu Jianping; Xu Ke

    2005-01-01

    How to provide service differentiation in the Internet is a hot research topic. One proposal is to provide loss rate differentiation by assigning levels of dropprecedence to IP packets. This paper proposes a new Active Queue Management (AQM) mechanism, Weighted SAP (WSAP) to achieve this goal. WSAP is based on a new AQM algorithm called Simple Adaptive Proportional (SAP). WSAP can approximate proportional loss rate differentiation, while keeping high link utilization and short queuing delay. Compared with Weighted RED(WRED) and RED In and Out (RIO), WSAP is easier to configure and can provide better performance. Furthermore, an architecture for differentiated service is proposed. In the design of this architecture, more attention is paid to the characte of network traffic in the Internet and an attempt is made to preserve the Internet's oringinal design principles.

  9. Performance study of Active Queue Management methods: Adaptive GRED, REDD, and GRED-Linear analytical model

    Directory of Open Access Journals (Sweden)

    Hussein Abdel-jaber

    2015-10-01

    Full Text Available Congestion control is one of the hot research topics that helps maintain the performance of computer networks. This paper compares three Active Queue Management (AQM methods, namely, Adaptive Gentle Random Early Detection (Adaptive GRED, Random Early Dynamic Detection (REDD, and GRED Linear analytical model with respect to different performance measures. Adaptive GRED and REDD are implemented based on simulation, whereas GRED Linear is implemented as a discrete-time analytical model. Several performance measures are used to evaluate the effectiveness of the compared methods mainly mean queue length, throughput, average queueing delay, overflow packet loss probability, and packet dropping probability. The ultimate aim is to identify the method that offers the highest satisfactory performance in non-congestion or congestion scenarios. The first comparison results that are based on different packet arrival probability values show that GRED Linear provides better mean queue length; average queueing delay and packet overflow probability than Adaptive GRED and REDD methods in the presence of congestion. Further and using the same evaluation measures, Adaptive GRED offers a more satisfactory performance than REDD when heavy congestion is present. When the finite capacity of queue values varies the GRED Linear model provides the highest satisfactory performance with reference to mean queue length and average queueing delay and all the compared methods provide similar throughput performance. However, when the finite capacity value is large, the compared methods have similar results in regard to probabilities of both packet overflowing and packet dropping.

  10. Researches on Active Queue Management%主动队列管理机制研究

    Institute of Scientific and Technical Information of China (English)

    李方敏; 叶澄清; 李仁发

    2001-01-01

    Currently,there are two methods suggested to handle congestion. The first approach uses packet or link scheduling on multiple logical or physical queues to explicitly reserve and allocate output bandwidth to each class of traffic. The second approach,called Active Queue management,uses advanced packet queuing disciplines on an outbound queue of a router to actively avoid congestion with the help of cooperative traffic sources. On the basis of analyzing the two approaches ,in order to efficiently support flow-controlled contnuous multimedia flows,we compare and analyze RED,FRED,CBT,D-CBT. Finally,we point out the shortcomings and the next research topic.

  11. A FUZZY-LOGIC CONTROL ALGORITHM FOR ACTIVE QUEUE MANAGEMENT IN IP NETWORKS

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Active Queue Management (AQM) is an active research area in the Internet community. Random Early Detection (RED) is a typical AQM algorithm, but it is known that it is difficult to configure its parameters and its average queue length is closely related to the load level. This paper proposes an effective fuzzy congestion control algorithm based on fuzzy logic which uses the predominance of fuzzy logic to deal with uncertain events. The main advantage of this new congestion control algorithm is that it discards the packet dropping mechanism of RED, and calculates packet loss according to a preconfigured fuzzy logic by using the queue length and the buffer usage ratio. Theoretical analysis and Network Simulator (NS) simulation results show that the proposed algorithm achieves more throughput and more stable queue length than traditional schemes. It really improves a router's ability in network congestion control in IP network.

  12. Model Integrating Fuzzy Argument with Neural Network Enhancing the Performance of Active Queue Management

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    Nguyen Kim Quoc

    2015-08-01

    Full Text Available The bottleneck control by active queue management mechanisms at network nodes is essential. In recent years, some researchers have used fuzzy argument to improve the active queue management mechanisms to enhance the network performance. However, the projects using the fuzzy controller depend heavily on professionals and their parameters cannot be updated according to changes in the network, so the effectiveness of this mechanism is not high. Therefore, we propose a model combining the fuzzy controller with neural network (FNN to overcome the limitations above. Results of the training of the neural networks will find the optimal parameters for the adaptive fuzzy controller well to changes of the network. This improves the operational efficiency of the active queue management mechanisms at network nodes.

  13. Active Queue Management in TCP Networks Based on Fuzzy-Pid Controller

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    Hossein ASHTIANI

    2012-01-01

    Full Text Available We introduce a novel and robust active queue management (AQM scheme based on a fuzzy controller, called hybrid fuzzy-PID controller. In the TCP network, AQM is important to regulate the queue length by passing or dropping the packets at the intermediate routers. RED, PI, and PID algorithms have been used for AQM. But these algorithms show weaknesses in the detection and control of congestion under dynamically changing network situations. In this paper a novel Fuzzy-based proportional-integral derivative (PID controller, which acts as an active queue manager (AQM for Internet routers, is proposed. These controllers are used to reduce packet loss and improve network utilization in TCP/IP networks. A new hybrid controller is proposed and compared with traditional RED based controller. Simulations are carried out to demonstrate the effectiveness of the proposed method and show that, the new hybrid fuzzy PID controller provides better performance than random early detection (RED and PID controllers

  14. MRIO: A New Active Queue Management Algorithm for Differentiated Services

    Institute of Scientific and Technical Information of China (English)

    WUChunming; JIANGMing; ZHUMiaoliang

    2005-01-01

    The DiffServ (Differentiate service) architecture has recently become the preferred service model for addressing QoS (Quality of service) issues in IP networks due to its simplicity and scalability. In DiffServ domain, the core routers use RIO (Red with in and out) algorithm, which performs different packets dropping schemes when congestion occurs. But RIO algorithm cannot stabilize the queue size and therefore, leads to unpredictable queuing delay and jitter. Furthermore, RIO has the “bandwidth skew” problem. The object of MRIO (MRED with in and out) algorithm is to stabilize the queue size and mitigate the ""bandwidth skew"" problem. MRIO is based on RED (Random early detection) for IN packets and MRED (Modified RED) algorithm for OUT packets. The simulation results indicate that compared with RIO, MRIO performs better in stabilizing queue size and mitigating “bandwidth skew” problem.

  15. A GA-based PID active queue management control design for TCP/IP networks

    Science.gov (United States)

    Kuo, H.-H.; Chen, C.-K.; Yan, J.-J.; Liao, T.-L.

    2008-02-01

    In this paper, a genetic algorithm-based (GA-based) proportional-integral-derivative (PID) controller as an active queue manager for Internet routers is proposed to reduce packet loss and improve network utilization in TCP/IP networks. Based on the window-based nonlinear dynamics, the TCP network was modeled as a time-delayed system with a saturated input due to the limitations of packet-dropping probability and the effects of propagation delays in TCP networks. An improved genetic algorithm is employed to derive optimal or near optimal PID control gains such that a performance index of integrated-absolute error (IAE) in terms of the error between the router queue length and the desired queue length is minimized. The performance of the proposed control scheme was evaluated in various network scenarios via a series of numerical simulations. The simulation results confirm that the proposed scheme outperforms other AQM schemes.

  16. Design and analysis of a model predictive controller for active queue management.

    Science.gov (United States)

    Wang, Ping; Chen, Hong; Yang, Xiaoping; Ma, Yan

    2012-01-01

    Model predictive (MP) control as a novel active queue management (AQM) algorithm in dynamic computer networks is proposed. According to the predicted future queue length in the data buffer, early packets at the router are dropped reasonably by the MPAQM controller so that the queue length reaches the desired value with minimal tracking error. The drop probability is obtained by optimizing the network performance. Further, randomized algorithms are applied to analyze the robustness of MPAQM successfully, and also to provide the stability domain of systems with uncertain network parameters. The performances of MPAQM are evaluated through a series of simulations in NS2. The simulation results show that the MPAQM algorithm outperforms RED, PI, and REM algorithms in terms of stability, disturbance rejection, and robustness.

  17. Multicast Services of QoS-Aware Active Queue Management over IP Multimedia Applications

    Science.gov (United States)

    Hwang, I.-Shyan; Hwang, Bor-Jiunn; Chang, Pen-Ming

    2010-10-01

    Recently, the multimedia services such as IPTV, video conference emerges to be the main traffic source. When UDP coexists with TCP, it induces not only congestion collapse but also unfairness problem. In this paper, a new Active Queue Management (AQM) algorithm, called Traffic Sensitive Active Queue Management (TSAQM), is proposed for providing multimedia services. The TSAQM comprise Dynamic Weight Allocate Scheme (DWAS) and Service Guarantee Scheme (SGS), the purpose of DWAS is to allocate resource with fairness and high end-user utility, and the purpose of SGS is to determine the satisfactory threshold (TH) and threshold region (TR). Several objectives of this proposed scheme include achieving high end-user utility for video service, considering the multicast as well as unicast proprieties to meet inter-class fairness and achieving the QoS requirement by adjusting the thresholds adaptively based on traffic situations.

  18. Improving Internet Quality of Service through Active Queue Management in Routers

    Directory of Open Access Journals (Sweden)

    Gamal Attiya

    2012-01-01

    Full Text Available The traffic characteristics of real-time and non real-time applications require a certain Quality of Service (QoS from the Internet in terms of bandwidth, delay, packet loss, fairness and jitter. However, most of the current Active Queue Management (AQM algorithms at the internet routers do not guarantee QoS for real time traffics such as video and audio. This is because; most of the algorithms handle different packets of different traffics by the same strategy. In this paper, we propose a new AQM strategy to guarantee QoS for real time traffics. The proposed strategy uses three queues at the internet routers, each of which handles a single class of traffic. Where, the arriving packets are queued according to their class type. Additionally, the queued packets are scheduled according to a predefined weight. The proposed algorithm is evaluated and compared with the most recent algorithms by using the Network simulator NS-2.

  19. Predictive functional control for active queue management in congested TCP/IP networks.

    Science.gov (United States)

    Bigdeli, N; Haeri, M

    2009-01-01

    Predictive functional control (PFC) as a new active queue management (AQM) method in dynamic TCP networks supporting explicit congestion notification (ECN) is proposed. The ability of the controller in handling system delay along with its simplicity and low computational load makes PFC a privileged AQM method in the high speed networks. Besides, considering the disturbance term (which represents model/process mismatches, external disturbances, and existing noise) in the control formulation adds some level of robustness into the PFC-AQM controller. This is an important and desired property in the control of dynamically-varying computer networks. In this paper, the controller is designed based on a small signal linearized fluid-flow model of the TCP/AQM networks. Then, closed-loop transfer function representation of the system is derived to analyze the robustness with respect to the network and controller parameters. The analytical as well as the packet-level ns-2 simulation results show the out-performance of the developed controller for both queue regulation and resource utilization. Fast response, low queue fluctuations (and consequently low delay jitter), high link utilization, good disturbance rejection, scalability, and low packet marking probability are other features of the developed method with respect to other well-known AQM methods such as RED, PI, and REM which are also simulated for comparison.

  20. Optimal Tracking Controller Design for Active Queue Management Routers via LQ-Servo

    Science.gov (United States)

    Lee, Kang Min; Yang, Ji Hoon; Suh, Byung Suhl

    2009-01-01

    This paper proposes the LQ-Servo controller for AQM (Active Queue Management) routers. The proposed controller structure is made by taking a traditional servo mechanism based on Linear Quadratic approach and by augmenting a new state variable to the feed forward loop. Since the controller structure is consists of a standard optimal feedback regulator and a feed forward controller, it is able to enhance the usefulness of resources and to reduce unnecessary memory reservations such as RAM (Random Access Memory) or SMA (Shared Memory Area) on ordinary router systems, respectively.

  1. Evaluation of Performance of Background Traffic-based CMT-SCTP with Active Queue Management Algorithms

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    Meifang Shen

    2012-11-01

    Full Text Available Existing researches on performance analysis of SCTPs Concurrent Multipath Transfer (CMT-SCTP usually use DropTail algorithm as queue management algorithm without considering the impact of the background traffic. However, the background traffic of realistic network environments has an important impact on the QoS of SCTP. Besides, more and more Active Queue Management (AQM algorithms have been proposed as a router-based mechanism for early congestion detection to keep the stability of the whole network. This paper investigates the effect of background traffic on the performance of CMT-SCTP, and evaluates the performance of CMT-SCTP under two realistic simulation topologies with reasonable background traffic and different AQM algorithms in NS-2. The simulation results show that: 1 the performance of CMT-SCTP depends on characteristic of background traffic; and 2 the different AQM algorithms used as queue management algorithm under same background traffic have the different effects. Finally, this paper summarizes the proposals to satisfy the QoS requirements in terms of throughput, end-to-end packet delay and loss rate. Since CMT-PF2 is recommended by RFC4960 but without taking impact of cross traffic into account. In the second part, we use the most promising topology which meets the developing network and base on result of analysis mentioned in the first part to analyze the performance CMT-PF1/2/3/4 played respectively, in this part, the most common scenario, symmetric CMT-SCTP, is adopted and CMT-PF algorithm is turned on. A conclusion had been nailed down that, CMT-PF3 can get more advantage in terms of average throughput than CMT-PF2 which is recommended by RFC4960. Per reasonable analyzing, we lastly recommend a more reasonable resolution for realistic network in order to reaching more satisfied QoS.

  2. Survival of the Fittest: An Active Queue Management Technique for Noisy Packet Flows

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    Shirish S. Karande

    2007-01-01

    Full Text Available We present a novel active queue management (AQM technique to demonstrate the efficacy of practically harnessing the predictive utility of SSR indications for improved video communication. We consider a network within which corrupted packets are relayed over multiple hops, but a certain percentage of packets needs to be dropped at an intermediate node due to congestion. We propose an AQM technique, survival of the fittest (SOTF, to be employed at the relay node, within which we use packet state information, available from SSR indications and checksums, to drop packets with the highest corruption levels. On the basis of actual 802.11b measurements we show that such a side information (SI aware processing within the network can provide significant performance benefits over an SI-unaware scheme, random queue management (RQM, which is forced to randomly discard packets. With trace-based simulations, we show the utility of the proposed AQM technique in improving the error recovery performance of cross-layer FEC schemes. Finally, with the help of H.264-based video simulations these improvements are shown to translate into a significant improvement in video quality.

  3. Design of Active Queue Management for Robust Control on Access Router for Heterogeneous Networks

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    Åhlund Christer

    2011-01-01

    Full Text Available The Internet architecture is a packet switching technology that allows dynamic sharing of bandwidth among different flows with in an IP network. Packets are stored and forwarded from one node to the next until reaching their destination. Major issues in this integration are congestion control and how to meet different quality of service requirements associated with various services. In other words streaming media quality degrades with increased packet delay and jitter caused by network congestion. To mitigate the impact of network congestion, various techniques have been used to improve multimedia quality and one of those techniques is Active Queue Management (AQM. Access routers require a buffer to hold packets during times of congestion. A large buffer can absorb the bursty arrivals, and this tends to increase the link utilizations but results in higher queuing delays. Traffic burstiness has a considerable negative impact on network performance. AQM is now considered an effective congestion control mechanism for enhancing transport protocol performance over wireless links. In order to have good link utilization, it is necessary for queues to adapt to varying traffic loads. This paper considers a particular scheme which is called Adaptive AQM (AAQM and studies its performance in the presence of feedback delays and its ability to maintain a small queue length as well as its robustness in the presence of traffic burstiness. The paper also presents a method based on the well-known Markov Modulated Poisson Process (MPP to capture traffic burstiness and buffer occupancy. To demonstrate the generality of the presented method, an analytic model is described and verified by extensive simulations of different adaptive AQM algorithms. The analysis and simulations show that AAQM outperforms the other AQMs with respect to responsiveness and robustness.

  4. Fuzzy variable structure algorithms for active queue management with delay compensation

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Based on the linearized model of the TCP connections through the congested routers, this paper puts forward an active queue management algorithm (FVS-T). The algorithm utilizes the fuzzy variable structure control algorithm with delay factor to compensate time varying round-trip times (RTT) and uncertainties with respect to the number of active TCP sessions. By analyzing the robustness and performance of the control scheme for the nonlinear TCP/AQM model, we show that the proposed design has good performance and robustness, which are central to the notion of AQM. Implementation issues were discussed and ns simulations were provided to validate the design and compare its performance to other peer schemes in different scenarios. The results show that the proposed design significantly outperforms the other congestion schemes in terms of packet loss ratio, throughput and buffer fluctuation.

  5. Performance Analysis Of Active Queue Management AQM In VOIP Using Different Voice Encoder Scheme

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    Samir Eid Mohammed

    2015-08-01

    Full Text Available Abstract Voice over Internet Protocol VoIP is a rapidly growing technology that enables transport of voice over data networks such as Ethernet Wide area networks WANs due to this important different codec scheme is developed to meet the QoS requirements. This thesis presents a comprehensive study about the impact of active queue management AQM on Voice over Internet Protocol VoIP quality of service using different codec scheme such as G711 G723 G729 and GSM using simulations tools. The evaluation is done using the OPNET Modeler which provides a convenient and easy-to-use platform for simulating large scale networks and this also give a power to go through different levels of designing a network even with the ability to program the mechanism you want which is used here to implement two types of AQM mechanism which is not included by default in the OPNET and these two mechanisms are ARED and GRED. The performance metrics used in the study are jitter throughput and delay. The study shows that G.711 and G729 codecs in a simulation gives a significant result for the performance of VoIP that codec G711 and G.729A has acceptable throughput and less deviation of received to transmit packet as compared to GSM and G.723 also average delay like end to end delay and Voice jitter is lesser in codec G711 and G.729 as compared to the other two referenced codecs.

  6. GPID:变速PID主动队列管理算法%Gearshift PID-based Active Queue Management Algorithm

    Institute of Scientific and Technical Information of China (English)

    刘琳琅; 王万良; 姚信威; 陈伟杰

    2012-01-01

    Active queue management (AQM) is one of the hot research field in network congestion. In this paper, a congestion control algorithm Gearshift integral PID( GPID) is proposed, which tends to address the problem of overshoot and big jitter of PID in AQM. The algorithm is characteristic of dynamic changes of the integral role on PID in accordance with the deviation of stimutaneous queue length, that is, the larger the deviation in queue length is, the smaller the integral coefficients are, the faster the convergence rate is and the bigger the overshoot is and vice versa. This algorithm can effectively control the deviation of the queue length so that it can attain the expected length. The simulation result shows that GPID has a faster convergence speed, a higher rate of link utilization and that the average queue length is closer to the expected length.%主动队列管理(Active Queue Management,简称AQM)是网络拥塞控制领域的一个热点.针对主动队列管理中PID算法超调量大,抖动大的问题,提出一种GPID(Gearshift PID)的拥塞控制算法.该算法特点是:积分作用大小跟随瞬时队列长度的偏差大小变动而变动,队列长度的偏差越大,则积分系数值越小,收敛速度越慢,超调量越大;反之,偏差越小,积分系数值越大,收敛速度越快,超调量越大.该算法可以有效的控制队列长度的偏差变化,调节瞬时队列长度趋于队列期望值收敛.仿真实验结果表明,该算法收敛速度快,链路利用率高,平均队列长度更趋于期望值.

  7. An Enhanced Active Queue Management Algorithm%一种改进的主动队列管理算法

    Institute of Scientific and Technical Information of China (English)

    陈建孝; 易勇; 周驰岷

    2007-01-01

    传统的主动队列管理算法(AQM:Active Queue Management)存在响应时间较长等问题,PID(Proportional Integral Differentia1) 主动队列管理算法对此作出了一定改进,然而在时延较大时也不能使队列长度收敛到期望值.本文利用BP神经网络自适应控制的特点,针对无线信道(TCP Westwood)提出了一种基于BP神经网络整定的PID主动队列管理算法.

  8. Improved Active Queue Management Algorithm Based on ARED%基于ARED的主动队列管理改进算法

    Institute of Scientific and Technical Information of China (English)

    饶刚; 周井泉

    2014-01-01

    随机早期检测(Random Early Detection,RED)是IETF推荐部署的主动队列管理(Active Queue Management,AQM)算法。 RED存在参数难以配置、无法适应动态网络环境的缺点。 ARED( Adaptive RED)是RED的自适应版本,通过平均队列长度来动态调整最大丢弃概率,从而达到稳定平均队列长度的目的,但是存在瞬时队列长度振荡的问题。文中研究了拥塞控制中的主动队列管理,对ARED算法进行了改进,优化丢弃概率计算函数,提出TTS-ARED算法,实现在动态网络环境下队列长度的稳定以及丢包率降低。 NS2的仿真结果表明,TTS-ARED算法显著地降低了丢包率,队列长度稳定性比ARED算法更优越。%Random Early Detection ( RED) is the Active Queue Management ( AQM) algorithm recommended by IETF. RED is difficult to configure its parameters,and can't adapt to dynamic network. ARED is an improved adaptive RED,by measuring average queue size to dynamically adjust maximum drop rate,achieving stable average queue size. But it may cause instantaneous queue size oscillation. It re-searched the active queue management in congestion control,and some improvements are made based on ARED algorithm. It optimized the calculation of dropping probability and a new algorithm TTS-ARED is proposed,low drop rate and the stable queue size in dynamic network are realized. The simulation results indicate that the drop rate can be decreased significantly by using TTS-ARED,and in the area of stabilizing queue size,TTS-ARED algorithm is superior to RED algorithm.

  9. Improved Active Queue Management Algorithm%一种改进的主动队列管理算法

    Institute of Scientific and Technical Information of China (English)

    王新生; 袁小波

    2011-01-01

    From the angle whether maintaining flow state information, this paper presents an improved Active Queue Management(AQM)Single Flow-AQM(SF-AQM).SF-AQM only maintenances data flow state information which has high transmission rate in order to reduce the router overhead identifies the non-adaptive flow by comparing packet the arrival intervals of different flow, improves the fairness of the algorithm, and controls the queue length under the target value to ensure the stability of the algorithm.Simulation results show SF-AQM algorithm has good performance in fairness and stability, and it is an effective algorithm in high performance communication networks congestion control.%从是否维护数据流状态信息的角度出发,提出一种改进的主动队列管理算法--SF-AQM.SF-AQM算法只维护发送速率大的数据流状态信息以降低路由器的开销,通过比较不同数据流的包到达时间间隔衡量流到达速率,识别出非适应性数据流,提高算法公平性,并使队列长度控制在目标值附近,保证算法稳定性.仿真结果表明,SF-AQM算法具有较好的公平性和稳定性,且对抑制网络拥塞有明显效果.

  10. New Adaptive Active Queue Management Algorithm with Kalman Filter%自适应卡尔曼滤波的主动队列管理算法

    Institute of Scientific and Technical Information of China (English)

    闫巧; 胡晓娟; 雷琼钰

    2012-01-01

    controller accelerates the regulation speed of the controller through differential factor. But the parameters of PID controller are fixed,they can't be adapted with dynamic network,so the stability of the queue can't be controlled effectively. A new adaptive active queue management(AQM) algorithm with Kalman filter was presented according to the adaptivity of the neural network The new algorithm combines Kalman filter law with neural network, which has the merits of both. It can determinate future queue length based on queue lengths and some rates of change in the queue length. The results of simulation show that the new AQM algorithm is superior to the typical PID controller on the queue stability, time delay and link utilization.%PID控制器通过微分环节加快了控制器的调节速度,但PID的参数是固定的,不能根据动态的网络自调整参数,故不能有效控制队列的稳定性.由于神经元网络有自适应性,提出了一种自适应卡尔曼滤波的主动队列管理算法(adaptive-KF-AQM).它结合卡尔曼滤波和神经元网络方法,根据队列长度及其变化率来估计下一时刻的队列长度,使队列长度在期望值附近波动.仿真结果表明,该算法在队列稳定性、收敛速度、延时和链路利用率等方面都明显优于传统的PID算法.

  11. STUDY THE EFFECTIVENESS APPLICATIONS OF FUZZY CONTROLLER WITH TWO ENTRANCES IN THE SYSTEM OF ACTIVE QUEUE MANAGEMENT THE PACKETS IN TCP/IP NETWORKS

    Directory of Open Access Journals (Sweden)

    O. V. Nevdachyna

    2016-01-01

    Full Text Available The paper presents an approach to solving the overloading problem in TCP/IP networks. Offered fuzzy controller with two inputs for system of active queue management packages in TCP/IP networks, and investigated its use in these systems with a random change of traffic load. Proposed controller has two inputs, one of which is the value of the difference between the current queue length and the second – the difference between the current level of usage of the buffer. The output of the fuzzy controller calculates the probability of discarding packet.Mathematical model system of active queue management that is studied is presented in an interactive MATLAB system, in wherein also is demonstrated the processes occurring in the system with a random change of traffic load. The research results show that the AQM-system with fuzzy controller with two entrances stable enough maintains the desired current length the queue for sufficiently small values of the probability of dropping/marking packets (at acceptable size of queue q0= 200 packets, the average probability of dropping / marking is not more than 3,5×10–3 or less 0,35% packets is discarded or marked from the total number of incoming packets. The results obtained will help improve the efficiency of the functioning and operation of TCP / IP networks by increasing data transmission quality. this happens due introduction of the proposed controller at the design of new, more efficient routers for networks to minimize the delay of information.

  12. Research on active queue management algorithm based on cellular ant%基于元胞蚁群的主动队列管理算法研究

    Institute of Scientific and Technical Information of China (English)

    张春琴; 谢立春

    2012-01-01

    order to mitigate the network congestion phenomenon, a novel active queue management algorithm (Drop Front algorithm based on Cellular Ant, DFCA) is proposed by Drop Front. In this algorithm, the maximum of actual network queue length is build by cellular ant. And the dropping N-pack-ets method from queue head is presented by comparing the relationship between network queue length and threshold. Then, with the long-rang dependence data, a simulation was conducted to study DFCA and RED, as well as DROP-TAIL algorithm. The results show that DFCA has better adaptability.%针对网络拥塞现象,基于弃头方式提出了一种新的主动队列管理算法.该算法首先利用元胞蚁群建立了实际网络队长最大值的计算方法,同时通过判断网络队长与阈值的关系,采取从队列头部丢弃N个数据包的方法.最后,以长相关数据进行仿真实验,对比分析了DFCA与RED、DROP-TAIL之间的优劣,结果表明该算法具有较好的适应性.

  13. The WorkQueue project - a task queue for the CMS workload management system

    Science.gov (United States)

    Ryu, S.; Wakefield, S.

    2012-12-01

    We present the development and first experience of a new component (termed WorkQueue) in the CMS workload management system. This component provides a link between a global request system (Request Manager) and agents (WMAgents) which process requests at compute and storage resources (known as sites). These requests typically consist of creation or processing of a data sample (possibly terabytes in size). Unlike the standard concept of a task queue, the WorkQueue does not contain fully resolved work units (known typically as jobs in HEP). This would require the WorkQueue to run computationally heavy algorithms that are better suited to run in the WMAgents. Instead the request specifies an algorithm that the WorkQueue uses to split the request into reasonable size chunks (known as elements). An advantage of performing lazy evaluation of an element is that expanding datasets can be accommodated by having job details resolved as late as possible. The WorkQueue architecture consists of a global WorkQueue which obtains requests from the request system, expands them and forms an element ordering based on the request priority. Each WMAgent contains a local WorkQueue which buffers work close to the agent, this overcomes temporary unavailability of the global WorkQueue and reduces latency for an agent to begin processing. Elements are pulled from the global WorkQueue to the local WorkQueue and into the WMAgent based on the estimate of the amount of work within the element and the resources available to the agent. WorkQueue is based on CouchDB, a document oriented NoSQL database. The WorkQueue uses the features of CouchDB (map/reduce views and bi-directional replication between distributed instances) to provide a scalable distributed system for managing large queues of work. The project described here represents an improvement over the old approach to workload management in CMS which involved individual operators feeding requests into agents. This new approach allows for a

  14. An Effective Queue Management Scheme for Data Communication

    Directory of Open Access Journals (Sweden)

    Sheela Thavasi

    2011-01-01

    Full Text Available Problem statement: The growth in the needs of Internet applications that transmit massive amount of data has led to the emergence of Effective Queue Management. Approach: Queues were used to smooth spikes in incoming packet rates and to allow the router sufficient time for packet processing. When the waiting time is less a better queue management is ensured thereby resulting in increased flow in the queue. When the incoming packet rate was higher than the router's outgoing packet rate, the queue size was increased, eventually exceeding the available buffer space. With respect to TCP’s RED queue management, the problem was that the buffer size was reduced to half and the packets were dropped abruptly. The congestion was detected early and the packets were dropped. The merit may be that congestion was detected early but the adverse effect was loss of packets. Results: The sender had to retransmit causing delay onto the network. This caused adverse effects on the network performance. In proposed system queue was extended whenever the number of packets present in the queue exceeds queue threshold. Packet drops were insignificantly even during network congestion. When the queue was continuously extended and if there was steady inflow of high volume of data, packet drop ratio was insignificant. Conclusions: Thus by the adoption of the proposed work, network throughput rose considerably thereby enabling effective data transfer. So it exhibits high bandwidth utilization, good throughput and processing time.

  15. 一种改进的ARED主动队列管理算法%An Improved ARED Active Queue Management Algorithm

    Institute of Scientific and Technical Information of China (English)

    张卓; 周井泉; 张萌

    2015-01-01

    RED is an active queue management algorithm that avoids network congestion effectively. ARED algorithm is also one of the important active queue management algorithms, an improved RED algorithm, which can determine the degree of network congestion through detecting the average queue length,and regulate the maximum drop probability to achieve the effect of a stable queue length. However,the network is lag and cannot adapt to the network busty traffic well. In order to make average queue length more stable and re-duce packet loss rate,H-ARED algorithm is proposed in this paper,which uses piecewise function to optimize the packet loss probability function of the ARED algorithm and adds a parameter Hth after the maximum threshold maxth of the average queue length. The data will be not all dropped when the average queue length is greater than the maximum threshold maxth . Within the range of the router buffer,it takes full advantage of the router buffer, so that it can better control network congestion, reducing network packet loss probability. Through simulation using NS2 network simulation tool,the results show that H-ARED algorithm improves the stability of the average queue length,reduces packet loss rate and has a stronger robustness in the complex network environment.%RED算法是一种非常有效地避免网络拥塞的主动队列管理算法。 ARED算法也是重要的主动队列管理算法之一,RED的改进算法,通过检测平均队列长度来判定网络拥塞程度,调节最大丢包概率来稳定队列长度,存在网络的滞后性和参数设置敏感问题。为了使该算法平均队列长度更加稳定并且减小丢包率,文中提出H-ARED算法,采用分段函数对ARED算法的丢包概率函数进行优化,在平均队列长度最大阈值maxth之后增加一个参数Hth ,当平均队列长度大于maxth时数据包不会被全部丢弃。该算法充分利用路由器缓冲区的大小,控制队列长度,使之能够更好地控制网

  16. 一种基于动态阈值的主动队列管理算法%A DT-Based Active Queue Management Algorithm

    Institute of Scientific and Technical Information of China (English)

    龙艳

    2011-01-01

    One improved method of active queue management algorithm was presented in this paper.Aiming the shortcoming of parameter setting in BLUE, the paper improved BLUE through introducing into dynamic threshold algorithm.The simulation results demonstrate that the proposed approach can effectively stabilize the queue occupation at a level and mitigate the queue overflow and underflow, and it can improve link utilization.%针对BLUE算法缺少早期拥塞检测机制,导致队列溢出或空闲现象频繁发生的问题,通过引进基于动态阈值算法的控制机制,借鉴RED算法所采用的早期拥塞检测机制,提出了DT-BLUE算法.仿真实验表明本文算法能保持队列长度的稳定性,有效降低队列空闲或溢出现象的发生,提高链路的利用率.

  17. New Active Queue Management Algorithm Based on Delay Jitter%基于时延抖动的主动队列管理算法

    Institute of Scientific and Technical Information of China (English)

    蔡珍珍; 周井泉

    2012-01-01

    With the rapid development of Interne!,resulted in the IP services growth rapidly and diversification. At the same time as the number of users increase dramatically, network traffic exploding, network congestion problems become more serious, so the quality of service (QoS) has become one of the world's research focuses. In order to achieve the relative performance of QoS,congestion control plays an important role, while the active queue management (Active Queue Management, AQM) mechanism is one of important means to achieve congestion control, AQM has become an attention and in-depth study of the hot issues in the field of IP network congestion control. Based on the fairness of the CHOKe, proposed a new delay jitter algorithm. The routers detect network congestion through the delay jitter and the average queue length .uses dynamic sampling hit and adaptive packet loss technology. The simulation experimental results show that the algorithm can protect the response stream effectively and improve the hit probability of non-response flow,improve the fairness of the algorithm.%随着Internet的迅速发展,致使IP业务的快速增长和多样化,用户数量急剧增加,网络流量呈爆炸式增长,网络拥塞问题变得越来越严重,因此服务质量(QoS)成为了当今世界研究热点之一.为了能达到相对的QoS的性能指标,拥塞控制发挥着相当重要的作用,而主动式队列管理(Active Queue Management,AQM)机制又是实现拥塞控制的重要手段之一,AQM成为了IP网络拥塞控制研究领域中备受关注和深入研究的热点问题.文中在增强CHOKe算法的公平性上,提出一种新的基于时延抖动的AQM算法-CZ-CHOKe.路由器通过时延抖动和队列的平均队长检测网络拥塞,同时采用动态采样击中和自适应丢包技术.仿真结果表明,该算法能有效地保护响应流,提高非响应流的击中概率,提高其算法的公平性.

  18. 主动队列管理的PI/PID拥塞控制器的调节%Tuning PI/PID Congestion Controller for Active Queue Management

    Institute of Scientific and Technical Information of China (English)

    郑国庆; 张平健

    2007-01-01

    Active Queue Management strategies are important means for internet congestion control. However, it is hard to configure the controlling parameters to achieve good tradeoff among a set of performance objectives. Much work is devoted to find effective ways to parameter tuning. A simplified PI/PID controller for Active Queue Management was proposed and an empirical formula was utilized to tune the parameter of the controller. Simulation results demonstrate that the new controller shows some advantages over the traditional ones.%主动队列管理是一类重要的互联网拥塞控制策略.然而,要调节控制参数以达到性能目标是比较困难的,目前,许多研究工作致力于寻找简明有效的调节方法.提出了网络拥塞控制中主动队列管理的PI/PID控制器的一个简化模型,给出了控制器参数调节的经验公式.仿真结果表明,新的拥塞控制器简单易行,并具有系统响应时间短、网络流量吞吐率高等优点.

  19. 基于模型算法控制的主动队列管理算法%Active queue management algorithm based on model algorithmic control

    Institute of Scientific and Technical Information of China (English)

    徐琴; 孙金生

    2013-01-01

    Through the analysis of the TCP/AQM system dynamics, a new predictive model is proposed. New active queue management(AQM) algorithm based on model algorithmic control(MACAQM) is proposed. The design details and the principles of choosing parameters are also presented. The results of simulations under different network environments show that MACAQM is effective in controlling the queue length to the desired value. In comparison to other AQM algorithms, such like PI, RaQ and REM, MACAQM has faster response and lower queue fluctuations. In the same time, MACAQM has larger interval with simple implementation, so it uses less resource on the routers.%通过深入分析TCP/AQM系统的动态特性,提出一个新的预测模型。基于该模型,结合模型算法控制(MAC)提出一种新的主动队列管理算法(MACAQM),并给出了MACAQM的详细设计过程和参数选取的原则。大量不同网络环境的仿真实验表明了MACAQM算法的有效性。与PI, RaQ和REM等算法相比较, MACAQM具有收敛速度快、队列抖动小的优点。同时, MACAQM的采样间隔相对较大,算法实现简单,所以计算量较小,占用的路由器资源也较少。

  20. Managing Network Congestion with a Modified Kohonen-based RED Queue

    Directory of Open Access Journals (Sweden)

    Maria Priscilla,

    2010-11-01

    Full Text Available The robustness of today’s Internet depends heavily on the TCP congestion control mechanism. Congestion is a key factor in transmission control protocol (TCP which leads to many researches. Congestion control techniques are extensively used in order to maintain the stability and reliability of the network. One of theimportant issues in the congestion control study is the Queue management technique employed by the network. An exponential increase in network traffic causes increasing packet loss rates. So, the IETF is considering the deployment of active queue management techniques to stem the increasing packet loss rates. Even though the packet loss rates are reduced in the internet by means of active queue management, the prevention of high loss rates is still a major concern for the present techniques. The severity of congestion is indicated by the queue lengths which is the main problem in the present queue management algorithms. Therefore, a fundamentally different active queue management algorithm called Random Early Detection (RED is proposed to overcome the above mentioned problem. BLUE uses packet loss and link idle events to manage congestion. Usingsimulation and controlled experiments, RED is shown to perform significantly better than other techniques both in terms of packet loss rates and buffer size requirements in the network. Then RED approach is combined with Kohonen technique that enables a stable queue length without complex parameters setting and passive measurements. This paper extends the Kohonen RED technique with the modified Kohonen based RED queue technique. It is clearly observed from the experimental results that the proposed approach provides better recognition accuracy with very low training time.

  1. A NovelActive Queue Management Method of Ad Hoc Network%一种新的AdHoc网络主动队列管理方法

    Institute of Scientific and Technical Information of China (English)

    段谟意

    2012-01-01

    针对AdHoc网络拥塞问题提出了一种新的主动队列管理方法该方法首先基于离散时间Erlang消失系统建立了转移概率矩阵,并且推导了平均队长的数学表达式.同时结合节点服务率和业务流到达率给出了系统的丢包策略,最后通过仿真实验深入研究了丢包率与利用率之间的关系,结果表明它们之间成正相关.%In order to mitigate the congestion of Ad Hoc network, a novel active queue management method is proposed. In this method, transition probability matrix is presented base on discrete time Erlang loss system at first, and the mathematic formula of average queue length is derived. Then, the drop strategy is designed with node service rate and traffic arrive rate, and a simulation was conducted to research on the relationships between drop rate and utilization rate. The result shows that drop rate is positive correlation with utilization rate.

  2. An Active Queue Management Algorithm of Variable Structure Control%一种基于可变结构的主动队列管理算法

    Institute of Scientific and Technical Information of China (English)

    丛林尤; 周井泉

    2012-01-01

    Active queue management algorithm (AQM) is a research area in network congestion control. There are many active queue management algorithms such as RED,ARED,SRED,PI,REM have been proposed. In this paper,design an active queue management algorithm of variable structure based on control theory. By analyzing the robustness and performance of control scheme foT the nonlinear TCP/AQM model, show that the proposed design has good performance and robustness with respect to the uncertainties of the round-trip time and the number of active TCP sessions,which are central to the notion of AQM. NS simulations are provided to validate the design and compare its performance to other peer schemes' in different scenarios. Simulation shows that it takes the stability and robustness indices into consideration,proposed design outperforms the other AQM schemes.%主动队列管理算法(AQM)是近年来网络拥塞控制的研究热点之一,已经提出了许多的主动队列管理算法,例如:RED,ARED,SRED,PI,REM等.文中设计一种基于控制理论的可变结构的主动队列管理.通过分析控制机制对于非线性的TCP/AQM模式的鲁棒性和性能,展示了在不确定的RTT( round-trip time)和活跃的TCP连接个数的情况下,有很好的性能和鲁棒性,这正是主动队列管理最重要的理念.运用网络仿真软件NS对设计进行仿真验证,从不同的角度对其性能与现有队列管理算法进行比较.仿真结果显示,从稳定性和鲁棒性等角度,可变结构控制算法显著胜过现有的AQM算法.

  3. Active Queue Management Algorithm:CHOKe Performance Analysis%主动队列管理算法:CHOKe性能分析

    Institute of Scientific and Technical Information of China (English)

    聂敏

    2011-01-01

    CHOKe is a kind of fair active queue management algorithm without state. The re is few research on the features of CHOKe. This paper analyzed the features of CHOKe using ns2 simulation platform. The result shows that CHOKe algorithm can not adapt to the dynamic changes of the flow, and the CHOKe hit probability, the effectiveness are main reason for the equity.%CHOKe是一种无状态的近似公平的主动队列管理算法,有关它性能的研究较少,本文利用ns2仿真平台分析了CHOKe性能。研究表明,CHOKe算法不能适应流量的动态变化,CHOKe击中的概率以及击中的有效性是影响其公平性的主要原因。

  4. Priority-based active queue management algorithm for satellite networks%一种基于优先级的卫星网络AQM算法

    Institute of Scientific and Technical Information of China (English)

    孙力娟; 谢慧婷; 肖甫; 叶晓国; 王汝传

    2011-01-01

    针对卫星网络大带宽、长时延、高误码等特点,结合控制理论,提出了一种基于优先级的卫星网络主动队列管理(active queue management,AQM)算法.首先,借鉴控制理论中比例-积分-微分(propertional-integral-derivative,PID)控制器设计方法计算总的报文丢弃概率;然后,针对IN和OUT两种不同优先级报文定义不同的丢弃概率,以实现不同优先级业务流量的区分服务.仿真实验表明,相对于低优先级流量,高优先级业务在保持高吞吐量的同时具有较低的报文丢失率,且整体队列长度抖动小,从而实现高优先级流量报文的有效保护.%Aimming at the characteristics of high bandwidth, long delay and high bit error ratio in satellite networks, a satellite network active queue management (AQM) algorithm based on prioity, which is integrated with control theory, is proposed. Firistly, based on the designing of the propertional-integral-derivative (PID) controller in control theory, a total probability of dropped messages is defined. Then, to differentiate between IN and OUT flows with different priorities, different probabilities of dropped messages are designed as well. Simulation results show that, compared with the case of flow with low priority, the proposed algorithm can effectively protect high priority flow by means of achieving a higher throughput with smaller jitter and low probability of dropped messages.

  5. RESEARCH ON MATCH FACTOR-BASED ACTIVE QUEUE MANAGEMENT STRATEGY IN WIRELESS MESH NETWORKS%无线 Mesh网络中基于匹配因子的积极队列管理策略研究

    Institute of Scientific and Technical Information of China (English)

    夏汉铸; 刘辉元

    2015-01-01

    针对无线Mesh网络的网络特性,分析现有的队列管理策略,提出一种基于匹配因子的积极队列管理策略MFAQM.MFAQM算法通过网络的实际情况确定匹配因子MF,根据匹配因子来调整队列管理策略中丢包率和ECN标记概率,从而实现动态的积极队列管理. 详细讨论MFAQM算法的实现过程和相关参数的计算方法,通过仿真分析验证了该算法对无线Mesh网络性能的提高.%In light of the network property of wireless Mesh networks ( WMNs ) , we analyse existing queue management strategies and present a match factor-based active queue management strategy MFAQM.The algorithm determines the match factor MF through actual condition of networks, and adjusts packet loss rate and ECN marking probability in queue management strategy based on MF, so as to realise the dynamically active queue management.The paper thoroughly discusses the implementation process of MFAQM algorithm and the computation method for correlated parameters, by simulation we verify the improvement of the algorithm in performance of wireless Mesh net-works.

  6. A robust and high-performance queue management controller for large round trip time networks

    Science.gov (United States)

    Khoshnevisan, Ladan; Salmasi, Farzad R.

    2016-05-01

    Congestion management for transmission control protocol is of utmost importance to prevent packet loss within a network. This necessitates strategies for active queue management. The most applied active queue management strategies have their inherent disadvantages which lead to suboptimal performance and even instability in the case of large round trip time and/or external disturbance. This paper presents an internal model control robust queue management scheme with two degrees of freedom in order to restrict the undesired effects of large and small round trip time and parameter variations in the queue management. Conventional approaches such as proportional integral and random early detection procedures lead to unstable behaviour due to large delay. Moreover, internal model control-Smith scheme suffers from large oscillations due to the large round trip time. On the other hand, other schemes such as internal model control-proportional integral and derivative show excessive sluggish performance for small round trip time values. To overcome these shortcomings, we introduce a system entailing two individual controllers for queue management and disturbance rejection, simultaneously. Simulation results based on Matlab/Simulink and also Network Simulator 2 (NS2) demonstrate the effectiveness of the procedure and verify the analytical approach.

  7. Comparison of TEAR and TFRC throughput for Drop tail and RED Queue Management Techniques

    Directory of Open Access Journals (Sweden)

    Parminderjeet Singh

    2014-12-01

    Full Text Available The comparison of throughput for TEAR (TCP emulation at receivers and TFRC TCP friendly rate control in MANETs is done with varying Active queue Management Techniques. The analysis reveals that for bandwidth constraint links, TEAR and TFRC perform far better than normal traffic propagation through TCP. In case of TEAR, the processing and route congestion algorithm load is shared by the receiver resulting in lesser load at the transmitters. In TFRC the TCP traffic is propagated via an algorithm to curb acknowledgement congestions. The effect of these two techniques is monitored on Droptail and RED, two of the most common Active Queue Management Techniques.

  8. FastQueue:A High Performance Disk Queue Storage Management Mechanism%FastQueue:一种高性能的磁盘队列存储管理机制

    Institute of Scientific and Technical Information of China (English)

    魏青松; 卢显良; 周旭

    2003-01-01

    High reliability is the primary requirement for messaging system. Messaging system always utilizes disk queue to temporarily store message to be delivered. Experiments show that Disk queue I/O is the primary performance bottleneck in the messaging system. In this paper we present a high performance disk queue storage management mechanism-FastQueue. The FastQueue utilizes a large file to serve as disk queue to reduce file manage overhead, in which adjacent messages are stored in adjacent disk block. Several messages are written to disk queue in a one large write by Lazy Gathering Write. Several adjacent messages are read into buffer in a one read by Sequential Grouping Prcfetch. The Lazy Gathering Write and Sequential Grouping Prefetch policies take full advantage of the disk bandwidth. Experiment shows that performance of the FastQueue is more than an order of magnitude higher than that of traditional disk queue.

  9. Study on active queue management algorithm based on twice dropping packets strategy%基于两次丢包策略的主动队列管理算法研究

    Institute of Scientific and Technical Information of China (English)

    张春琴; 谢立春

    2014-01-01

    In order to mitigate the network congestion, a novel active queue management algorithm TDPQW is proposed by twice dropping packets method. In this algorithm, the mathematic formula of actual queue length and waiting time are deducted with M/G/1 queuing model, and the dropping strategy in queue front and in queue random location is presented. A simulation is conducted to research on the algorithm performance between TDPQW and RED, as well as DROP-TAIL. The result shows that it has better adaptability for TDPQW.%针对网络拥塞现象,基于两次丢包方法建立了一种新的主动队列管理算法TDPQW。该算法利用M/G/1排队模型推导了实际队列长度和等待时间的数学表达式,以此提出在队列头部和队中随机位置进行丢包的策略。同时,通过仿真实验对比分析了该算法与RED、DROP-TAIL算法的性能,结果表明TDPQW具有较好的适应性。

  10. The congestion control algorithm based on queue management of each node in mobile ad hoc networks

    Science.gov (United States)

    Wei, Yifei; Chang, Lin; Wang, Yali; Wang, Gaoping

    2016-12-01

    This paper proposes an active queue management mechanism, considering the node's own ability and its importance in the network to set the queue threshold. As the network load increases, local congestion of mobile ad hoc network may lead to network performance degradation, hot node's energy consumption increase even failure. If small energy nodes congested because of forwarding data packets, then when it is used as the source node will cause a lot of packet loss. This paper proposes an active queue management mechanism, considering the node's own ability and its importance in the network to set the queue threshold. Controlling nodes buffer queue in different levels of congestion area probability by adjusting the upper limits and lower limits, thus nodes can adjust responsibility of forwarding data packets according to their own situation. The proposed algorithm will slow down the send rate hop by hop along the data package transmission direction from congestion node to source node so that to prevent further congestion from the source node. The simulation results show that, the algorithm can better play the data forwarding ability of strong nodes, protect the weak nodes, can effectively alleviate the network congestion situation.

  11. 瓶颈网络TCP/主动队列管理模型及仿真%TCP/Active Queue Management Model and Simulation for Bottleneck Networks

    Institute of Scientific and Technical Information of China (English)

    曹振臻; 肖扬; 迟彩霞

    2009-01-01

    提出了一种基于离散时间Markov链的时延闭环反馈TCP/AQM(Active Queue Management)模型,并得到其稳态分布.通过以环路时延为单位,将系统时间分割成长度不同的时隙,分析每个时隙内TCP发送端发送窗口模型和瓶颈路由器队列模型.通过结合相邻时隙的参数,提出了TCP/AQM整体分析模型.该模型可以估计路由器的队列平均长度和丢包率、TCP发送端的平均发送窗口值,因此可以用于分析AQM算法性能以及给新算法的设计提供理论支持.通过在Matlab实施该模型与NS2仿真结果作比较,证实了该模型在模拟时延闭环反馈的TCP/RED系统的有效性.

  12. An Active Queue Management Algorithm Based on Adaptive Global Sliding Mode Control%基于自适应全局滑模控制的主动队列管理算法

    Institute of Scientific and Technical Information of China (English)

    叶成荫

    2011-01-01

    For the problem of congestion control in the Internet, a novel active queue management ( AQM ) algorithm based on the sliding mode control theory is proposed. Considering UDP flow, an active queue management algorithm based on adaptive global sliding mode control is designed. The algorithm guarantees the network system robustness during the whole control process and uses RBF neural netword as adaptive law to eliminate the effect from the disturbance of UDP flow. Simulation results demonstrate that the algorithm enables the queue length to converge to set value quickly,keeps the small queue oscillation, and outperforms the conventional IP control and sliding mode control.%针对TCP网络的拥塞控制问题,采用滑模控制理论提出了一种新的主动队列管理算法.考虑到UDP流干扰的情况,设计了基于自适应全局滑模控制的主动队列管理算法.该算法保证网络系统在整个控制过程中的鲁棒性,并且使用RBF神经网络作为自适应律来消除UDP流干扰对系统的影响.仿真结果表明该算法可以使队列长度快速收敛到设定值,同时维持较小的队列振荡,优于传统的PI控制和滑模控制.

  13. 显示拥塞指示标记的主动队列管理研究%Active queue management with explicit congestion notification marks

    Institute of Scientific and Technical Information of China (English)

    闫巧; 胡晓娟

    2012-01-01

    主动队列管理对于解决网路拥塞具有重要意义.针对PID主动队列管理算法在调节队列长度时有较大的丢包率这一缺点,提出一种显示拥塞指示标记即ECN标记的PID主动队列管理算法.该算法用显示拥塞指示标记取代丢包机制,用于通知源端网络即将发生拥塞,采用PID控制器实现反馈控制,保证系统的稳定性.仿真结果表明,显示拥塞指示标记的主动队列管理算法适用于多变的网络环境,比PID算法具有低丢包率、低延时和高吞吐量的特点.%Active Queue Management(AQM) is very significant for network congestion control. This paper presents a new PID controller for AQM with ECN marks to overcome the shortcomings of PID AQM--high loss rate. In this algorithm, the mechanism ofdropping packet is replaced with ECN marks. It uses the PID controller as feed-backward compensation to ensure the stability of the system. The results of simulation show that the PID controller for AQM with ECN marks can adapt to the changing network environment and has lower loss rate, lower delay and higher throughput than the conventional PID AQM algorithm.

  14. Extended Queue Management Backward Congestion Control Algorithms for Web Transfers in Wireless Environment

    Directory of Open Access Journals (Sweden)

    V.Sinthu Janita Prakash

    2012-10-01

    Full Text Available Wireless links are characterized by high error rates and intermittent connectivity. TCP congestion control has been developed on the assumption that network congestion is the only cause for packet loss. Upon detecting a packet loss, TCP drops its transmit window resulting in an unnecessary reduction of end-to-end throughput which results in suboptimal performance.The sender has to be made aware by some feedback mechanism that some of the losses reported are not due to congestion. The Active Queue Management algorithms (AQM are used to reduce congestion, and in this paper, we have analysed four AQM algorithms, Random Early Deduction (RED, Wireless Explicit Congestion Notification (WECN, Queue Management Backward Congestion Control Algorithm (QMBCCA and its enhanced version Extended Queue Management Backward Congestion Control Algorithm (EQMBCCA. WECN, QMBCCA & EQMBCCA algorithms make use of feedback mechanisms. WECN gives feedback using the CE bit. QMBCCA and EQMBCCA make use of ISQ notifications and also the CE bit whenever the average queue size crosses minimum threshold value. EQMBCCA reduces the reverse ISQ traffic by introducing a configurable intermediate threshold value IntThres. The comparison is made in terms of Delay, HTTP packet loss percentage and fairness for FTP flows in a wireless environment. It is found that the performance of EQMBCCA is almost equal to that of QMBCCA and better than RED and WECN.

  15. Adaptive Queue Management with Restraint on Non-Responsive Flows

    Directory of Open Access Journals (Sweden)

    Lan Li

    2003-12-01

    Full Text Available This paper proposes an adaptive queue management scheme (adaptive RED to improve Random Early Detection (RED on restraining non-responsive flows. Due to a lack of flow control mechanism, non-responsive flows can starve responsive flows for buffer and bandwidth at the gateway. In order to solve the disproportionate resource problem, RED framework is modified in this way: on detecting when the non-responsive flows starve the queue, packet-drop intensity (Max_p in RED can be adaptively adjusted to curb non-responsive flows for resource fair-sharing, such as buffer and bandwidth fair-sharing. Based on detection of traffic behaviors, intentionally restraining nonresponsive flows is to increase the throughput and decrease the drop rate of responsive flows. Our experimental results based on adaptive RED shows that the enhancement of responsive traffic and the better sharing of buffer and bandwidth can be achieved under a variety of traffic scenarios.

  16. The Study of Active Queue Management Algorithm Based on Cellular Genetic Method%基于元胞遗传方法的主动队列管理算法研究

    Institute of Scientific and Technical Information of China (English)

    黄绍川; 郑华

    2013-01-01

    In order to mitigate the network congestion problem, a novel active queue management algorithm New-SCHOKe is proposed by CHOKe. In this algorithm, the dropping policy and dropping rate are defined by sampling hit and queue hit, and the average queue length is depicted by cellular genetic. Then, a simulation was conducted to research on the performance of New-SCHOKe and SCHOKe, as well as CHOKe algorithm with actual data. The results show that New-SCHOKe has better adaptability.%为了解决网络拥塞现象,基于CHOKe方法建立了一种新的主动队列管理算法New-SCHOKe.该方法首先根据采样击中和队列击中定义了丢包策略和丢包概率,并且利用元胞遗传技术刻画了平均队列长度.同时,以实际数据进行仿真实验,对比分析了该算法与SCHOKe和CHOKe之间的性能,结果表明New-SCHOKe具有较好的适应性.

  17. 基于神经元自适应变结构控制的主动队列管理算法%Active queue management algorithm based onneuron adaptive variable structure control

    Institute of Scientific and Technical Information of China (English)

    周川; 王宗欣; 吴益飞; 陈庆伟

    2011-01-01

    Considering the non-linearity of TCP model, uncertainty of Round Trip Time ( RTT) and fluctuation of network load, an Active Queue Management ( AQM) scheme based on Variable Structure Controller ( VSC) using single neuron adaptive learning was proposed. The nonlinear VSC was used to guarantee the swiftness and robustness of queue response at router. However, the jitter of VSC would cause the queue fluctuation and performance degradation. Therefore, a single neuron was introduced to adjust the parameters of the VSC in order to alleviate the effect of jitter and modeling uncertainty. The proposed scheme can reduce the jitter and enhance the robustness for AQM control system greatly. Finally, the simulation results show the effectiveness of the proposed algorithm through NS-2 simulator.%针对网络TCP模型的非线性以及回路延时和负载波动等不确定性因素,提出一种基于神经元自适应变结构控制(VSC)的主动队列管理(AQM)算法.通过非线性变结构控制以保证路由器队列响应的快速性和鲁棒性;同时考虑到滑模控制中存在的抖振会引起队列波动和控制精度降低等问题,引入神经元在线调整控制器参数以减弱抖振,从而减小队列延时和模型不确定性的影响,提高AQM系统的鲁棒性和性能.最后通过NS-2仿真实验验证了算法的有效性.

  18. Discrete-time H-infinity robust active queue management scheme for uncertain TCP flow model%不确定TCP流模型的离散H∞鲁棒主动队列管理算法

    Institute of Scientific and Technical Information of China (English)

    周川; 何俊伟; 陈庆伟

    2013-01-01

    Considering the problem of congestion control for the time-varying and uncertain TCP/IP network, we proposed a novel discrete-time robust active queue management (AQM) scheme based on H-infinity feedback control for the TCP flow model with link capacity disturbance and parameter uncertainties simultaneously. In this method, the bandwidth occupied by short-lived connections is treated as the external disturbances, and the effect of both delay and parameter uncertainties is taken into account for the TCP/AQM system model. By using Lyapunov stability theory and LMI techniques, we propose a discrete-time robust H-infinity AQM controller to guarantee the asymptotic stability and robustness of the queue length response of a router queues. Finally the NS-2 simulation results demonstrate effectiveness of the proposed method.%针对TCP/IP网络存在参数时变和不确定性下的拥塞控制问题,提出一种新的基于H∞状态反馈控制的离散鲁棒主动列队管理算法(AQM).该方法针对不确定TCP流模型,将短期突发流所占据的带宽作为系统的外部干扰,同时考虑时滞和参数不确定性因素,基于Lyapunov稳定性理论和线性矩阵不等式技术,设计了离散鲁棒状态反馈控制器以保证路由器队列响应的稳定性和鲁棒性.最后,通过NS-2仿真验证了本文方法的有效性.

  19. 一种适于Internet拥塞控制的自校正队列管理算法%A Self-Tuning Queue Management Algorithm for Internet Congestion Control

    Institute of Scientific and Technical Information of China (English)

    张敬辕; 谢剑英; 刘立祥

    2002-01-01

    As an effective method for congestion control, Active Queue Management plays an important role in im-proving the Internet QoS. In this paper,we first analyze the properties of RED,then design an effective queue manage-ment algorithm based on gradient descent approach. With the application of this algorithm,routers in IP network ad-just its packet drop probability according to the queue length in the buffer. The main advantage of this algorithm isthat the queue length can keep stable at a low level in a varity of network environments. Simulations show that thisself-tuning queue management algorithm is efficient,stable and outperforms RED queue management algorithms sig-nificantly.

  20. A Self-tuning Fuzzy Queue Management Algorithm for Congestion Control

    Institute of Scientific and Technical Information of China (English)

    Zhang Jingyuan(张敬辕); Xie Jianying

    2004-01-01

    This letter presents an effective self-tuning fuzzy queue management algorithm for congestion control. With the application of the algorithm, routers in IP network regulate its packet drop probability by a self-tuning fuzzy controller. The main advantage of the algorithm is that, with the parameter self-tuning mechanism, queue length can keep stable in a variety of network environments without the difficulty of parameter configuration. Simulations show that the algorithm is efficient, stable and outperforms the popular RED queue management algorithm significantly.

  1. Comparison of Active Queue Management Congestion Control Algorithms Based on NS%基于ns的主动队列管理拥塞控制算法的比较

    Institute of Scientific and Technical Information of China (English)

    赵雪梅; 牛秦洲; 侯辉

    2008-01-01

    主动式队列管理(Active Queue Management, AQM)技术是IETF(The Internet Engineering Task Force)为了解决Internet拥塞控制问题而提出的一种路由器缓存管理技术.本文详细分析了RED算法、BLUE算法以及基于RED改进策略的SRED算法三种算法的优缺点,并在NS2中对它们的性能进行了仿真和比较.仿真结果表明RED和SRED性能都要优于BLUE算法.

  2. PID Active Queue Management Method Based on Artificial Bee Colony and Wavelet Transform%基于人工蜂群和小波变换的PID主动队列管理方法

    Institute of Scientific and Technical Information of China (English)

    鄢树

    2013-01-01

    针对日益严重的网络拥塞问题,基于PID控制器建立了一种新的主动队列管理方法(PID active queue management algorithm based-artificial bee colony and wavelet,PIDAW).该方法首先利用小波技术对到达流量进行变换,并且采用人工蜂群算法来计算小波系数,同时通过重构方式获得实际队列长度,以此优化丢包概率.最后,以实际数据进行仿真实验,深入分析了该方法与PID、RED方法之间的性能,结果表明PIDAW具有较好的适应性.

  3. Infinite Queue Management via Cascade Control for Industrial Routers in Smart Grid IP Networks

    Directory of Open Access Journals (Sweden)

    Ku-Hwan Kim

    2016-01-01

    Full Text Available Smart grid applications experience an extremely wide range of communication delay. Data flows of those applications are normally aggregated at industrial network routers in substations, form infinite (long queues termed bufferbloat issue, and might damage the operation of transmission control protocol. The default queue management scheme, DropTail, in such routers just drops packets if queue is full while the others in literature are mostly based on one-loop feedback control where an optimal point of performance between queue length and drop rate is limited. In this paper, we study the problem of managing a long queue of industrial router at substation under heterogeneous smart grid networks. Specifically, we propose an enqueue-dequeue dropping cascade control using a two-loop design method to control both window size and queue length. Moreover, our proposal can be easily implemented into router firmware with provided discrete expressions. Finally, our simulation results are presented to validate the possible benefits that can be gained from cascade control and compare the existing queue management methods as well.

  4. The Stability Studies of PSO-PID Active Queue Management in Wired Network%有线网络PSO-PID主动队列管理算法稳定性分析

    Institute of Scientific and Technical Information of China (English)

    孙慧玉; 姜文刚

    2014-01-01

    主动队列管理算法的稳定性是实现拥塞控制的基础,针对目前PID-AQM 控制器控制参数大多基于经验、缺乏稳定性分析的问题,提出了粒子群优化PID参数的整定策略,同时运用稳定分析论分析PSO-PID队列管理算法的稳定性。考虑TCP/AQM系统的时滞性,将时延系统利用泰勒展开转化为非时延系统进行稳定性判定。通过NS2仿真,结果表明,PSO-PID算法稳定性明显优于PID算法。%The stability of the active queue management is the basis of the congestion control ,most of the control parameters of the PID-AQM controller based on experience ,lack of stability analysis .In order to solve the problem , particle swarm optimize the PID parameters strategy was proposed ,while use the theory of stability to analysis the stability of the PSO-PID active queue management .Consider the TCP/AQM system delay ,the paper transfers the delay system into non-delay system by using Taylor series expansion .The NS2 simulation results the PSO-PID algorithm shows some advantages over the PID algorithm .

  5. A New Active Queue Management Algorithm Based on Dynamic Matrix Control%基于动态矩阵控制的主动队列管理算法

    Institute of Scientific and Technical Information of China (English)

    徐琴; 孙金生

    2014-01-01

    针对Internet系统,通过对流体流模型的分析,提出了一个新的预测模型。该模型形式简单,参数的计算相对容易,并且能根据当前的网络情况有效的预测拥塞窗口的变化。结合动态矩阵控制(Dynamic Matrix Control ,DMC )理论,提出了一种新的主动队列管理算法---DMCAQM算法,给出了DMCAQM 的详细设计过程,稳定性分析和参数选取原则。大量不同网络环境的仿真实验表明DMCAQM 算法是有效的。与PI、RaQ和REM等算法相比较,DMCAQM 有收敛速度快、队列抖动小的优点。同时,由于DMCAQM 的采样间隔相对较大,而算法实现简单,所以计算量小,占用的路由器资源更少。%Through the analysis of the fluid-based model ,a new predictive model is proposed for Internet system .This model is simple ,and the way of selecting parameters is relatively easy .It′s able to predict the change of congestion window according to the network environment .Based on the theory of Dynamic Matrix Control (DMC) ,a new Active Queue Management (AQM) algo-rithm is proposed ,called DMCAQM .The design details ,the stability analysis and the principles of choosing parameters are also pre-sented .The results of simulations under different network environments demonstrate that DMCAQM is effective in controlling the queue length to the desired value .In comparison to other AQM algorithms ,such as PI ,RaQ and REM ,DMCAQM have faster re-sponse and lower queue fluctuations .In addition ,DMCAQM has larger interval while with simple implementation ,so it use less re-source on the routers .

  6. Research and Simulation of Queue Management Algorithms DropTail and RED%队列管理算法DropTail和RED研究与仿真

    Institute of Scientific and Technical Information of China (English)

    肖权权; 段迅

    2011-01-01

    Queue management functions are responsible for router's queue establishment, maintenance and line up and determine when to accept or discard packets. Active queue management algorithm DropTail is widely used for congestion control in Internet. Random Early Detection (PIED) is recommendedly used by IETF for queue management. The article uses the NS2.network simulator to simulate DropTail and RED queue management algorithm. Through analysis of the simulation data, the obtained RED queue management algorithm is higher than the overall performance of DropTail. This study provides the basis for further research of the RED algorithm.%队列管理主要负责路由器内部队列的建立、维护和排队,以决定何时接收或者丢弃某个包.目前Internet普遍采用的拥塞控制机制是DropTail主动队列管理算法,而随机早期检测(RED,Random Early Detection)是IETF推荐使用的队列管理算法.本文利用NS2网络仿真器在队列监视角度对DropTail与RED进行仿真模拟,比较分析得出RED队列管理算法整体性能高于DropTail,为进一步研究RED算法提供了依据.

  7. Study on PI active queue management based on cellular automaton%基于元胞自动机的PI主动队列管理方法研究

    Institute of Scientific and Technical Information of China (English)

    俞立峰

    2013-01-01

    针对传统的PI(Proportional Integral)算法收敛速度慢等问题,基于瞬时到达速率提出了一种新的PI主动队列管理算法PICA(Proportional Integral Based on Cellular Automaton).首先,该算法结合瞬时队长和瞬时到达速率建立了丢包策略,并利用元胞自动机刻画了数据包的动态特性.同时,通过仿真实验,将该算法与传统的PI算法以及RPI (Rate based Proportional and Integral)算法进行比较,结果发现PICA算法在有效传输数据包、时延和丢包率等方面的性能都较优.%In order to mitigate the slow of convergence rate in traditional Proportional Integral algorithm, a novel active queue management algorithm (Proportional Integral Based on Cellular Automaton, PICA) is proposed based on instantaneous arrival rate. At first, combined with instantaneous queue length and instantaneous arrival rate, the dropping strategy is presented in this algorithm, and the dynamic characteristic of packet is depicted by cellular automaton. Then, a simulation was conducted to study on the algorithm performance between PICA and PI, as well as RPKRate based Proportional and Integral). The result shows that it is better performance in efficient transmission packets, delay and dropping rate for PICA algorithm.

  8. Collaborative Virtual Queue: Fair Management of Congested Departure Operations and Benefit Analysis

    CERN Document Server

    Burgain, Pierrick; Clarke, John-Paul

    2008-01-01

    Due to the stochastic nature of departure operations, working at full capacity makes major US airports very sensitive to uncertainties. Consequently, airport ground operations face critically congested taxiways and long runway queues. In this report, we show how improved management of departure operations from the ready-to-push-back time to the wheels-off time can potentially yield significant benefits to airlines and air traffic services. We develop a Collaborative Virtual Queue to enable better optimization capabilities during congested situations while taking into account the laissez-faire competitive environment. Results are evaluated using a departure system model, validated using current statistics and previous studies. First, the Collaborative Virtual Queue enables keeping aircraft away from runway queues, which increases wheels-off time predictability. Second, holding aircraft enables last-minute intra-airline flight switching. This creates new optimization capabilities for airlines i.e. it gives airl...

  9. Queue Management Practices of Quick ServiceRestaurants (QSR in Lipa City, Philippines

    Directory of Open Access Journals (Sweden)

    Leoven A. Austria

    2015-12-01

    Full Text Available –Problems regarding waiting line in quick service restaurants (QSR has been one of the main concerns of industries and scholars nowadays. It is because people today demand not only for qualityfood but also for speed. Quick service restaurant players explore on the approaches to optimize the efficiency of restaurant management. One important area that defines how well and efficient a fast food restaurant delivers its product and services to customers is its waiting line (queue management practices. The study was conducted at Lipa City, involving five popular quick service restaurants named by the researcher as QSR A, B, C, D, and E. It made used of 363customer respondents proportionally obtained from five restaurants.It intended to assess the extent of implementation of the queue management practices of the restaurants and the level of satisfaction of the customers in such practices in terms of customer arrival, waiting line and service facility. The findings revealed the queuing system used and the waiting line structured utilized by the restaurants. The extent of implementation of the queue management practices in the three areas mentioned of the five QSR’s was presented comparatively. Likewise, the level of customer’s satisfaction on the queue management practices was also determined. Significant difference in the extent of implementation and in the level of customer satisfaction were determined if the respondents were grouped according to restaurant’s profile. Recommendations in the improvement of queue were given based on the findings.

  10. Optimal Control for Bufferbloat Queue Management Using Indirect Method with Parametric Optimization

    Directory of Open Access Journals (Sweden)

    Amr Radwan

    2016-01-01

    Full Text Available Because memory buffers become larger and cheaper, they have been put into network devices to reduce the number of loss packets and improve network performance. However, the consequences of large buffers are long queues at network bottlenecks and throughput saturation, which has been recently noticed in research community as bufferbloat phenomenon. To address such issues, in this article, we design a forward-backward optimal control queue algorithm based on an indirect approach with parametric optimization. The cost function which we want to minimize represents a trade-off between queue length and packet loss rate performance. Through the integration of an indirect approach with parametric optimization, our proposal has advantages of scalability and accuracy compared to direct approaches, while still maintaining good throughput and shorter queue length than several existing queue management algorithms. All numerical analysis, simulation in ns-2, and experiment results are provided to solidify the efficiency of our proposal. In detailed comparisons to other conventional algorithms, the proposed procedure can run much faster than direct collocation methods while maintaining a desired short queue (≈40 packets in simulation and 80 (ms in experiment test.

  11. A Parallel Virtual Queue Structure for Active Queue Management

    Science.gov (United States)

    2003-01-01

    ideal tcp congestion avoidance ftp://ftp.bellcore.com/pub/tjo/tcpwindow.ps. [8] Teunis J. Ott, T. V. Lakshman, and Larry H. Wong. SRED : Stabilized RED. In Proceedings of INFOCOM, volume 3, pages 1346–1355, 1999.

  12. Cluster load balance system based on active queue management%基于主动队列管理的集群计算负载平衡系统

    Institute of Scientific and Technical Information of China (English)

    张书奎

    2007-01-01

    在分析了分组到达率和服务率的关系及主动队列管理AQM(Active Queue Management)的Balanced RED算法的基础上,提出了一个计算连接权重的动态分配算法"基于AQM加权时序动态法"(Weighted Opportunity Dynamic Algorithm based on AQM),它具有对终端用户透明、能自动找出最佳服务器来处理请求的特点,从而实现集群计算服务器的负载平衡.另外据此算法设计并实现了一个支持服务器集群的动态负载平衡原型系统,实验结果表明该算法在负载平衡的效能上有明显的提高.

  13. 基于反步滑模控制的TCP网络的主动队列管理%Active queue management for TCP networks based on backstepping sliding mode control

    Institute of Scientific and Technical Information of China (English)

    叶成荫

    2012-01-01

    For the problem of congestion control in TCP networks,considered the parameter uncertainties of the networks itself and the disturbance of unresponsive flows, an active queue management algorithm is proposed based on the backstepping sliding mode control. Considered the bound of the lumped uncertainty known and not to be small, a backstepping sliding mode controller is designed to compensate the effects of the system uncertainties. The simulation results verify that the proposed algorithm has good robustness and fast system response for complicated changes in TCP networks.%针对TCP网络的拥塞问题,考虑到网络本身存在参数不确定因素和非响应流的干扰,基于反步滑模控制提出了一种主动队列管理算法.在总的不确定的界已知而且不必很小的情况下,设计了一种反步滑模控制器来补偿系统不确定所带来的影响.仿真结果表明,该方法对TCP网络的复杂变化具有较好的鲁棒性和较快的系统响应.

  14. Scheduling and Active Queue Management Algorithm Based on Priority Differentiation%基于优先级区分的调度及主动队列管理算法

    Institute of Scientific and Technical Information of China (English)

    刘春; 董育宁; 彭宇珏; 孔瑞溪

    2014-01-01

    文中研究在UMTS网络的AM模式(Acknowledged Mode)下实现基于优先级区分的调度及主动队列管理.提出了MP-SAQM(Multi-priorities Scheduling and Active Queue Management Algorithm)算法.算法将不同的QoS类别归入不同的优先级队列,根据MPADRR(Multi-priorities Average Deficit Round Robin)调度算法按照优先级高低进行调度,并对不同QoS类别设置均匀的队列缓冲区,保证了调度的公平性.同时使用差异化的RED(Random Early Drop)算法进行主动队列管理,对不同优先级队列执行不同的丢包策略.仿真结果验证了该算法的有效性.

  15. Transient probabilities for queues with applications to hospital waiting list management.

    Science.gov (United States)

    Joy, Mark; Jones, Simon

    2005-08-01

    In this paper we study queuing systems within the NHS. Recently imposed government performance targets lead NHS executives to investigate and instigate alternative management strategies, thereby imposing structural changes on the queues. Under such circumstances, it is most unlikely that such systems are in equilibrium. It is crucial, in our opinion, to recognise this state of affairs in order to make a balanced assessment of the role of queue management in the modern NHS. From a mathematical perspective it should be emphasised that measures of the state of a queue based upon the assumption of statistical equilibrium (a pervasive methodology in the study of queues) are simply wrong in the above scenario. To base strategic decisions around such ideas is therefore highly questionable and it is one of the purposes of this paper to offer alternatives: we present some (recent) research whose results generate performance measures and measures of risk, for example, of waiting-times growing unacceptably large; we emphasise that these results concern the transient behaviour of the queueing model-there is no asssumption of statistical equilibrium. We also demonstrate that our results are computationally tractable.

  16. Design and analysis of active queue management algorithm based on predictive control%预测控制主动队列管理算法的设计与分析

    Institute of Scientific and Technical Information of China (English)

    王萍; 陈虹; 卢晓晖

    2011-01-01

    针对Intemet时滞网络系统,提出了基于模型预测控制的主动队列管理算法MPAQM.首先考虑时滞系统的因果性来定义预测输出,然后根据拥塞控制的要求描述优化问题,求得路由器缓冲区的分组丢失率;另外分析给出保证闭环时滞系统稳定的充分条件,为算法的参数调节提供理论指导,使得队列能快速、稳定地到达期望值.在单瓶颈和多瓶颈网络拓扑中,仿真分析结果显示MPAQM算法能快速收敛于队列长度的期望值,具有较小的分组丢失率.在抗干扰能力、稳定性和顽健性等方面,它明显优于RED、PI和SPI-RED等算法.%Model predictive control as a novel active queue management (AQM) algorithm was proposed for Internet system with large delay, called MPAQM. Considering the causality of time-delay system, the predicted output was defined. Then, the control requirement was converted to the optimal control objective, and the drop probability was obtained by solving the optimal problem. Furthermore, the delay-independent stability condition of closed-loop system was derived, which gave the guidelines how to select the parameters of MPAQM algorithm to assure the stability and fast convergence of the network system. The performances of MPAQM were evaluated through a series of simulations in NS2 under the single/multiple topology. The simulation results show that the queue length with MPAQM algorithm reaches the desired value with minimal tracking error and lower drop probability. MPAQM algorithm outperforms RED, PI and SPI-RED algorithms in terms of disturbance rejection, stability, and robustness.

  17. Passive queue management algorithm based on synchronized queue%基于S排队的被动队列管理算法

    Institute of Scientific and Technical Information of China (English)

    谢立春

    2012-01-01

    为了解决网络拥塞问题,基于“弃头”方式建立了一种新的被动队列管理算法(DFSQ).该算法首先利用S排队推导网络队长的数学表达式,并提出丢包概率和丢包策略.同时,通过仿真实验深入研究了影响网络队长的关键因素,并将DFSQ与随机早期检测算法(RED)、“弃尾”算法进行对比分析,结果表明DFSQ算法性能更优.%In order to mitigate the network congestion problem, a new passive queue management algorithm Drop Front n based on Synchronized Queue (DFSQ) was proposed by Drop Front. In this algorithm, the network queue length was deducted with synchronized queue, and drop packet probability and drop packet strategy were presented. Then, a simulation was conducted to research on the key influencing factors of queue length. The results show that, compared with Random Early Detection (RED) and Drop Tail algorithm, the performance of DFSQ is better.

  18. Managing target of opportunity (ToO) observations in queue mode at Gemini Observatory

    Science.gov (United States)

    Roth, Katherine C.; Carrasco, E. Rodrigo; Miller, Bryan W.; Stephens, Andrew W.; Jørgensen, Inger; Rodgers, Bernadette

    2010-07-01

    Target of opportunity observations (ToO) are an integral part of multi-instrument queue operations at Gemini Observatory. ToOs comprise a significant fraction of the queue (20-25% of the highest ranking band) and with the advent of large survey telescopes (eg. Pan-STARRS, LSST) dedicated to searching for transient events this fraction may reasonably be expected to increase significantly in the coming years. While some important aspects of ToO execution at Gemini Observatory are managed automatically (eg. trigger alerts, data distribution), other areas such as duplications checking, scheduling and relative priority determination still require manual intervention. In order to increase efficiency and improve our commitment to ToOs and queue observing in general, these aspects need to be formalized and incorporated into improved phase 2 checking, automated queue scheduling and on-the-fly nightly plan generation software. We discuss the different flavors of ToOs supported at Gemini Observatory and how each kind is scheduled with respect to existing queue observations. We present ideas for formalizing these practices into a system of dynamical prioritization which automatically self adjusts as new ToO observations are triggered, high priority targets become endangered, and timing windows near expiration.

  19. MULTIPATH VIRTUAL QUEUE MANAGEMENT SYSTEM FOR EFFECTIVE PACKET SCHEDULING IN MPLS NETWORKS

    Directory of Open Access Journals (Sweden)

    V. Ramachandran

    2012-09-01

    Full Text Available With the rapid development of communication and networking technologies VOIP has become an alternate to traditional telephony. These applications prefer timeliness in packet delivery. To perform load balancing, link utilization and to minimize the packet loss rate Multipath virtual Queue Management System for Effective Packet Scheduling in MPLS networks is proposed. The VoIP flows are dispersed into multiple available label switched paths to perform load balancing and link utilization. Virtual queues are maintained in all output ports to avoid queuing delay and HOL blocking. The proposed system ensures the arrival order of all the packets and plays back in the order of transmission. The performance of the proposed Virtual queuing system is compared with single path CSFQ queuing system with no virtual queue and Simulation results are proposed to show theefficiency of the proposed system.

  20. A queueing model of pilot decision making in a multi-task flight management situation

    Science.gov (United States)

    Walden, R. S.; Rouse, W. B.

    1977-01-01

    Allocation of decision making responsibility between pilot and computer is considered and a flight management task, designed for the study of pilot-computer interaction, is discussed. A queueing theory model of pilot decision making in this multi-task, control and monitoring situation is presented. An experimental investigation of pilot decision making and the resulting model parameters are discussed.

  1. Modeling active queue management based on transmission control protocol in Ad Hoc network%基于传输控制协议的无线自组网主动队列管理建模

    Institute of Scientific and Technical Information of China (English)

    陈亮; 张宏

    2011-01-01

    主动队列管理(AQM)通常研究队列控制器的设计.作为被控对象,传输控制协议(TCP)往往利用网络仿真器(NS)的仿真实现,因此有必要研究无线自组网的TCP及AQM特性.基于TCP窗口加性增一乘性减算法及排队原理,推导了TCP窗口及队列的微分方程,再基于比例积分AQM控制,推导了拥塞丢弃概率的微分方程,通过建立联立微分方程组,提出了AdHoc网络TCP/AQM微分模型.对比仿真显示,新模型能较好地估计无线白组网的性能.模型研究也表明,网络跳数,无线丢失和过小的队列成为AQM性能瓶颈,队列信息则有助于TCP区%The active queue management(AQM) is usually concerned with the queue controller design. As a controlled object, the transmission control protocol(TCP) is often realized by the simulation of Network Simulator(NS). Thus, it is necessary to study the characteristics of TCP and AQM in Ad Hoc network. Differential equations for the TCP window- size and queue-length are developed based on the TCP window additive-increase multiplicative-decrease algorithm and the queuing principle. Next, the differential equation of the congestion-loss probability is derived based on the proportional- integral AQM control. Then, the Ad I-Ioc network TCP/AQM differential model is proposed through the simultaneous differential equations. The comparison simulations show that the new model can estimate Ad Hoe network performance. The model research also shows that the number of hops, wireless loss and the very small queue become the bottleneck of the AQM performances. Furthermore, the queue information can help TCP discriminate between congestion loss and wireless loss in Ad Hoc network.

  2. DROP TAIL AND RED QUEUE MANAGEMENT WITH SMALL BUFFERS:STABILITY AND HOPF BIFURCATION

    Directory of Open Access Journals (Sweden)

    Ganesh Patil

    2011-06-01

    Full Text Available There are many factors that are important in the design of queue management schemes for routers in the Internet: for example, queuing delay, link utilization, packet loss, energy consumption and the impact of router buffer size. By considering a fluid model for the congestion avoidance phase of Additive Increase Multiplicative Decrease (AIMD TCP, in a small buffer regime, we argue that stability should also be a desirable feature for network performance. The queue management schemes we study are Drop Tail and Random Early Detection (RED. For Drop Tail, the analytical arguments are based on local stability and bifurcation theory. As the buffer size acts as a bifurcation parameter, variations in it can readily lead to the emergence of limit cycles. We then present NS2 simulations to study the effect of changing buffer size on queue dynamics, utilization, window size and packet loss for three different flow scenarios. The simulations corroborate the analysis which highlights that performance is coupled with the notion of stability. Our work suggests that, in a small buffer regime, a simple Drop Tail queue management serves to enhance stability and appears preferable to the much studied RED scheme.

  3. 无线环境下具有实时约束的主动队列管理机制%Deadline-constrained Active Queue Management Mechanism in Wireless Networks

    Institute of Scientific and Technical Information of China (English)

    裴畅姣; 卢汉成; 洪佩琳

    2013-01-01

    The expired-time packet loss rate is a common parameter to measure the quality of service of transmission of deadline-constrained traffic in wireless networks. However, this parameter can not reflect the influence on the quality of service of video caused by the packets with different levels of importance. In this paper, the definition of the weighted expired-time packet loss rate is first introduced with the consideration of the importance of different kinds of packets, which describes the connection between the packet loss and quality of video more specifically. Based on the definition, an active queue management mechanism is proposed, which can be applied to deadline-constrained transmissions in wireless networks, and this mechanism, considering different levels of importance of video packets, drop packets actively to minimize the weighted expired-time packet loss rate during the service. Simulation results show that compared with the traditional queue management mechanism and real-time video filtering mechanism, the active packet discard mechanism can effectively reduce the weighted expired-time packet loss rate and improve the quality of service of video to about 0.5~1.5 dB Peak Signal to Noise Ratio (PSNR) gain.%  实时流业务的超期丢包率是衡量无线网络传输过程服务质量的常用参数,但是该参数并不能反映出具有不同重要度的数据包对视频质量的影响。该文将实时传输流的数据包重要度与超期丢包率结合,提出加权超期丢包率的概念,更加准确地描述丢包与视频质量的关系,在无线环境下提出基于数据包不同重要度的适用于实时约束流的主动队列管理算法,通过主动丢弃数据包以最小化服务过程中实时流的加权超期丢包率。仿真结果表明,相比于传统的队列管理算法和实时视频流滤波器算法,该超期数据包主动丢弃算法能够有效降低加权超期丢包率,提供更好的服务质量

  4. 基于自适应反步滑模控制的主动队列管理%Active Queue Management Based on Adaptive Backstepping Sliding Mode Control

    Institute of Scientific and Technical Information of China (English)

    叶成荫

    2012-01-01

    针对TCP网络的拥塞控制问题,基于自适应反步滑模控制提出了一种主动队列管理算法.由于系统的不确定在实际工程中很难或根本无法事先获得,设计一个自适应律来实时适应系统不确定的值,从而消除系统不确定所带来的影响.利用此自适应律,提出一个自适应反步滑模控制器,使得系统具有较好的暂态性能和鲁棒性能.仿真结果表明,该方法对TCP网络的复杂变化具有较好的鲁棒性和较快的系统响应.%For the problem of congestion control in TCP networks,an active queue management algorithm is proposed based on the adaptive backstepping sliding mode control. Since the lumped uncertainties of the network systems is difficult to obtain in advance in practical applications, an adaptive law is proposed to compensate the effects of the system uncertainties. Using the proposed adaptive law, an adaptive backstepping sliding mode controller is proposed to make systems possesses the advantages of good transient control and robust performance. Simulation results verifies that the proposed algorithm has good robustness and fast system response for complicated changes in TCP networks.

  5. N次弃头的被动队列管理算法%Passive Queue Management Algorithm Based on Dropping Front N Times

    Institute of Scientific and Technical Information of China (English)

    姜文刚; 孙金生; 王执铨

    2011-01-01

    主动队列管理算法存在参数设置敏感,响应相对滞后于实际网络状况的缺陷,并没有在实际网络上推广使用,因此对目前使用最多的弃尾被动队列管理进行改进,提出N次弃头的被动队列管理算法,在队列满时,从队列头部丢弃N个数据包,N为大于等于2的整数.该算法改善了弃尾队列管理的缺陷,提高了网络传输性能,能有效改善RTT公平性和速度公平性,算法计算量小,最后通过NS2仿真验证该算法的有效性.%Active queue management is sensitive to parameter settings, and the response lags behind the actual network conditions, so it has not promote the use of the actual network. Therefore, in order to improve drop tail passive queue management, which is most widely used,passive queue management algorithm based on dropping front N times is proposed. When the queue is full, dropping packet N times in the front of queue, N is an integer greater than or equal to 2. The algorithm improves the defects of drop tail, and improves the network transmission performance. Passive queue management algorithm based on dropping front N times can effectively improve the RTT fairness and fairness of speed; Computation of this algorithm is small. Finally, NS2 simulation results show the effectiveness of the algorithm.

  6. BOB-RED queue management for IEEE 802.15.4 wireless sensor networks

    Directory of Open Access Journals (Sweden)

    Wu Jean-Lien

    2011-01-01

    Full Text Available Abstract Multimedia services over resource constrained wireless sensor networks (WSNs face a performance bottleneck issue from the gateway node to the sink node. Therefore, the queue management at the gateway node is crucial for diversified messages conveyed from the front nodes to the sink node. In this article, beacon order-based random early detection (BOB-RED queue management is proposed. BOB-RED is a dynamic adaptation scheme based on adjusting beacon interval and superframe duration in the IEEE 802.15.4 MAC superframe accompanied with RED queue management scheme to increase the transmission efficiency of multimedia over WSNs. We focus on the performance improvement upon different traffic loads over WSNs. Evaluation metrics include end-to-end delay, packet delivery ratio, and energy consumption in IEEE 802.15.4 beacon enabled mode. Simulation results show that BOB-RED can effectively decrease end-to-end delay and energy consumption compared to the DropTail scheme.

  7. RED- DTB:A Dual Token Bucket Based Queue Management Algorithm

    Institute of Scientific and Technical Information of China (English)

    Yin Jian-hua; Cao Yang; Ling Jun; Huang Tian-xi

    2003-01-01

    Improving the Quality of Service (QoS) of Internet traffic is wide-ly recognized as a critical issue for the next-generation networks. In this paper,we present a new algorithm for the active queue management, namely RED-DTB. This buffer control technique is used to enforce approximate fairness among a large number of concurrent Internet flows. Like RED (Random Early Detection) algorithm, the RED-DTB mechanism can be deployed to actively re-spond to the gateway congestion, keep the gateway in a healthy state, and pro-tect the fragile flows from being stolen band width by greedy ones. The algo-rithm is based on the so-called Dual Token Bucket (DTB) pattern. That is, onthe one hand, every flow is rate-limited by its own token bucket, to ensure thatit can not consume more than its fair share of bandwidth; On the other hand,to make some compensations to less aggressive flows, such as connections with larger round trip time or smaller sending window, and to gain a relatively high-er system utilization coefficient, all flows, depending on their individual behav-ior, may have a chance to fetch tokens from the public token bucket when theyrun out of their own share of tokens. The algorithm is analyzed and evaluatedby simulations, and is proved to be effective in protecting the gateway bufferand controlling the fair allocation of bandwidth among flows.

  8. RED-DTB: A Dual Token Bucket Based Queue Management Algorithm

    Institute of Scientific and Technical Information of China (English)

    YinJian-hua; CaoYang; LingJun; HuangTian-xi

    2003-01-01

    Improving the Quality of Service (QoS) of Internet traffic is widely recognized as a critical issue for the next-generation networks. In this paper,we present a new algorithm for the active queue management, namely RED-DTB. This buffer control technique is used to enforce approximate fairness among a large number of concurrent Internet flows. Like RED (Random Early Detection) algorithm, the RED-DTB mechanism can be deployed to actively respond to the gateway congestion, keep the gateway in a healthy state, and protect the fragile flows from being stolen bandwidth by greedy ones. The algorithm is based on the so-called Dual Token Bucket (DTB) pattern. That is, on the one hand, every flow is rate-limited by its own token bucket, to ensure that it can not consume more than its fair share of bandwidth; On the other hand,to make some compensations to less aggressive flows, such as connections with larger round trip time or smaller sending window, and to gain a relatively higher system utilization coefficient, all flows, depending on their individual behavior, may have a chance to fetch tokens from the public token bucket when they run out of their own share of tokens. The algorithm is analyzed and evaluated by simulations, and is proved to be effective in protecting the gateway buffer and controlling the fair allocation of bandwidth among flows.

  9. Active Methodologies in a Queueing Systems Course for Telecommunication Engineering Studies

    Science.gov (United States)

    Garcia, J.; Hernandez, A.

    2010-01-01

    This paper presents the results of a one-year experiment in incorporating active methodologies in a Queueing Systems course as part of the Telecommunication Engineering degree at the University of Zaragoza, Spain, during the period of adaptation to the European Higher Education Area. A problem-based learning methodology has been introduced, and…

  10. Active Methodologies in a Queueing Systems Course for Telecommunication Engineering Studies

    Science.gov (United States)

    Garcia, J.; Hernandez, A.

    2010-01-01

    This paper presents the results of a one-year experiment in incorporating active methodologies in a Queueing Systems course as part of the Telecommunication Engineering degree at the University of Zaragoza, Spain, during the period of adaptation to the European Higher Education Area. A problem-based learning methodology has been introduced, and…

  11. 两次随机丢包的被动队列管理算法%Passive Queue Management Algorithm Based on Twice Randomly Dropping Packets

    Institute of Scientific and Technical Information of China (English)

    姜文刚; 孙金生; 王执铨

    2011-01-01

    The active queue management increases the spending of hardware resources and computation amount,and also there exists sensitive parameter settings and the phenomenon of response lagging behind actual network in it,so the active queue management has not been widely used in actual network.Therefore,the drop tail passive queue management was improved,which is most widely used now,and the passive queue management algorithm based on twice randomly dropping packets was proposed.When the queue is full,randomly dropping packets in twice,which will improve the defects of drop tail,and develop the transmission performance of the network;the concept of speed fairness was put forward.This passive queue management algorithm based on twice randomly dropping packets will punish "TCP link" greatly,which occupies more spaces in the queue,and improve the RTT fairness and speed fairness effectively;Computation of this algorithm is small;the NS2 simulation results show the effectiveness of the algorithm.%主动队列管理算法增加了硬件资源和运算量的开销,并且存在参数设置敏感,响应相对滞后于实际网络状况的缺陷,并没有在实际网络上推广使用。因此对目前使用最多的弃尾被动队列管理进行改进,提出了两次随机丢包的被动队列管理算法。在队列满时,两次随机丢弃队列中的数据包,改善弃尾队列管理的缺陷,提高了网络传输性能;提出了速度公平性的概念,两次随机丢包的被动队列管理算法对占据队列较多的TCP链接有更好的惩罚作用,能有效提高RTT公平性和速度公平性;该算法计算量小;NS2仿真表明该算法的有效性。

  12. Active Queue Management Algorithm Based on single neurons-Smith for networks with big time delay%大延时网络中基于单神经元-Smith的AQM算法

    Institute of Scientific and Technical Information of China (English)

    李婷; 苗增强; 周玲; 满高华

    2011-01-01

    本文利用智能控制理论设计了针对大延时网络的单神经元-Smith AQM(Active Queue Management)算法。对算法的设计目标、参数整定规则等问题进行了深入研究,最后的仿真结果验证了该算法在大延时网络主动队列管理中的有效性。%This thesis designs a AQM algorithm based on intelligent control theory,which is single neurons-Smith AQM algorithm for large delay network.The design target and parameter adjusting rule of this algorithm are presented detailed in this thesis.The results

  13. Method, apparatus and system for managing queue operations of a test bench environment

    Science.gov (United States)

    Ostler, Farrell Lynn

    2016-07-19

    Techniques and mechanisms for performing dequeue operations for agents of a test bench environment. In an embodiment, a first group of agents are each allocated a respective ripe reservation and a second set of agents are each allocated a respective unripe reservation. Over time, queue management logic allocates respective reservations to agents and variously changes one or more such reservations from unripe to ripe. In another embodiment, an order of servicing agents allocated unripe reservations is based on relative priorities of the unripe reservations with respect to one another. An order of servicing agents allocated ripe reservations is on a first come, first served basis.

  14. An energy-efficient MAC protocol using dynamic queue management for delay-tolerant mobile sensor networks.

    Science.gov (United States)

    Li, Jie; Li, Qiyue; Qu, Yugui; Zhao, Baohua

    2011-01-01

    Conventional MAC protocols for wireless sensor network perform poorly when faced with a delay-tolerant mobile network environment. Characterized by a highly dynamic and sparse topology, poor network connectivity as well as data delay-tolerance, delay-tolerant mobile sensor networks exacerbate the severe power constraints and memory limitations of nodes. This paper proposes an energy-efficient MAC protocol using dynamic queue management (EQ-MAC) for power saving and data queue management. Via data transfers initiated by the target sink and the use of a dynamic queue management strategy based on priority, EQ-MAC effectively avoids untargeted transfers, increases the chance of successful data transmission, and makes useful data reach the target terminal in a timely manner. Experimental results show that EQ-MAC has high energy efficiency in comparison with a conventional MAC protocol. It also achieves a 46% decrease in packet drop probability, 79% increase in system throughput, and 25% decrease in mean packet delay.

  15. Queue size and delay analysis for a communication system subject to traffic activity mode changes

    Science.gov (United States)

    Zukerman, M.; Rubin, I.

    1986-06-01

    A discrete single-server queueing/communication system in which the arrival distribution is changing stochastically with time is considered. The distribution of the number of messages to arrive within a time slot depends on a traffic activity process of modes. This process of modes is a two-state Markov chain: mode 0 and mode 1, which represent light and heavy traffic conditions, respectively. The transition probabilities of this Markov chain, or mode duration parameters (MDP's) determine the distribution of the duration of time the process stays in each mode. Expressions for the z-transform, expectation, and variance are obtained for the steady-state queue size and delay. A special consideration is given to the effect of the MDPs on the system performance, and the limiting cases (where the MDPs approach zero) are studied.

  16. WQM: An Aggregation-aware Queue Management Scheme for IEEE 802.11n based Networks

    KAUST Repository

    Showail, Ahmad

    2014-08-17

    Choosing the right buffer size in Wi-Fi networks is challenging due to the dynamic nature of the wireless environment. Over buffering or \\'bufferbloat\\' may produce unacceptable end-to-end delays, while static small buffers may limit the performance gains that can be achieved with various 802.11n enhancements, such as frame aggregation. We propose WQM, a queue management scheme customized for wireless networks. WQM adapts the buffer size based on measured link characteristics and network load. Furthermore, it accounts for aggregate length when deciding about the optimal buffer size. We implement WQM on Linux and evaluate it on a wireless testbed. WQM reduces the end-to-end delay by up to 8x compared to Linux default buffer size, and 2x compared to CoDel, the state-of-the-art bufferbloat solution, while achieving comparable network goodput. Further, WQM improves fairness as it limits the ability of a single flow to saturate the buffer.

  17. Review on buffer management schemes for packet queues in wired & wireless network

    Directory of Open Access Journals (Sweden)

    Shaheen C. Pathan,

    2015-08-01

    Full Text Available Mobile AdHoc Network (MANET is a wireless network with a set of mobile nodes that can communicate with each other with no access point and without any fixed infrastructure. But mobile devices usually have limited resources (battery power, memory, CPU which limit their transmission range. Hence, in order to conserve the limited resource, it is highly desirable that transmission should be as efficient as possible. MANET can be implemented in any environment because of its dynamic nature. For routing of information packets queuing is done at the buffer and transferred through intermediate nodes to the destination on priority basis which help to improve the overall network performance. This paper provides a review of various buffer management schemes for packet queues in wired & wireless networks (specialy MANET.

  18. Big queues

    CERN Document Server

    Ganesh, Ayalvadi; Wischik, Damon

    2004-01-01

    Big Queues aims to give a simple and elegant account of how large deviations theory can be applied to queueing problems. Large deviations theory is a collection of powerful results and general techniques for studying rare events, and has been applied to queueing problems in a variety of ways. The strengths of large deviations theory are these: it is powerful enough that one can answer many questions which are hard to answer otherwise, and it is general enough that one can draw broad conclusions without relying on special case calculations.

  19. Queueing for healthcare.

    Science.gov (United States)

    Palvannan, R Kannapiran; Teow, Kiok Liang

    2012-04-01

    Patient queues are prevalent in healthcare and wait time is one measure of access to care. We illustrate Queueing Theory-an analytical tool that has provided many insights to service providers when designing new service systems and managing existing ones. This established theory helps us to quantify the appropriate service capacity to meet the patient demand, balancing system utilization and the patient's wait time. It considers four key factors that affect the patient's wait time: average patient demand, average service rate and the variation in both. We illustrate four basic insights that will be useful for managers and doctors who manage healthcare delivery systems, at hospital or department level. Two examples from local hospitals are shown where we have used queueing models to estimate the service capacity and analyze the impact of capacity configurations, while considering the inherent variation in healthcare.

  20. Stability Analysis of Active Queue Management Algorithm Based on Generalized Predictive Control%基于GPC的主动队列管理算法稳定性分析

    Institute of Scientific and Technical Information of China (English)

    陈玉峰; 殷刚; 邹宽胜

    2012-01-01

    The discrete network model and the expression of Generalized Predictive Control (GPC) controller are educed based upon the fluid-flow model of TCP congestion window. Then the closed loop transfer function of router' s output queue length and referenced queue length are obtained. It is proved that the closed -loop systems is stable no mater how the network parameters changing,if some specific constraints of GPC controller's parameters are satisfied. Finally,the validity is verified by a simulation.%根据主动队列管理算法中TCP拥塞窗口的流体流模型,给出了离散模型和广义预测控制(GPC)算法的表达式;得出了路由器输出队列长度与参考队列长度的闭环传递函数;证明了GPC控制器在满足特定控制参数的条件下,无论网络参数如何变化,闭环系统都是稳定的;并通过仿真验证了其正确性.

  1. Optimal management for infinite capacity N-policy M/G/1 queue with a removable service station

    Science.gov (United States)

    Chang, Y. C.; Pearn, W. L.

    2011-07-01

    In this article, we consider an infinite capacity N-policy M/G/1 queueing system with a single removable server. Poisson arrivals and general distribution service times are assumed. The server is controllable that may be turned on at arrival epochs or off at service completion epochs. We apply a differential technique to study system sensitivity, which examines the effect of different system input parameters on the system. A cost model for infinite capacity queueing system under steady-state condition is developed, to determine the optimal management policy at minimum cost. Analytical results for sensitivity analysis are derived. We also provide extensive numerical computations to illustrate the analytical sensitivity properties obtained. Finally, an application example is presented to demonstrate how the model could be used in real applications to obtain the optimal management policy.

  2. Flow Time Analysis of Load Management Late Arrival Discrete Time Queueing System with Dual Service Rate Using Hypogeometrical Distribution

    Directory of Open Access Journals (Sweden)

    Syed Asif Ali Shah

    2012-01-01

    Full Text Available Flow time analysis is a powerful concept to analyze the flow time of any arriving customer in any system at any instant. A load management mechanism can be employed very effectively in any queueing system by utilizing a system which provides probability of dual service rate. In this paper, we develop and demonstrate the flow and service processes transition diagram to determine the flow time of a customer in a load management late arrival state dependent finite discrete time queueing system with dual service rate where customers are hypogeometrically distributed. We compute the probability mass function of each starting state and total probability mass function. The obtained analytical results are validated with simulation results for varying values of arrival and service probabilities.

  3. Optimal (batch) dispatching in a tandem queue

    NARCIS (Netherlands)

    D. van Leeuwen (Daphne); R. Núñez Queija (Rudesindo (Sindo))

    2016-01-01

    textabstractMotivated by various applications in logistics, road traffic and production management, we investigate two versions of a tandem queueing model in which the service rate of the first queue can be controlled. The objective is to keep the mean number of jobs in the second queue as low as po

  4. An Energy-Efficient MAC Protocol Using Dynamic Queue Management for Delay-Tolerant Mobile Sensor Networks

    Directory of Open Access Journals (Sweden)

    Yugui Qu

    2011-02-01

    Full Text Available Conventional MAC protocols for wireless sensor network perform poorly when faced with a delay-tolerant mobile network environment. Characterized by a highly dynamic and sparse topology, poor network connectivity as well as data delay-tolerance, delay-tolerant mobile sensor networks exacerbate the severe power constraints and memory limitations of nodes. This paper proposes an energy-efficient MAC protocol using dynamic queue management (EQ-MAC for power saving and data queue management. Via data transfers initiated by the target sink and the use of a dynamic queue management strategy based on priority, EQ-MAC effectively avoids untargeted transfers, increases the chance of successful data transmission, and makes useful data reach the target terminal in a timely manner. Experimental results show that EQ-MAC has high energy efficiency in comparison with a conventional MAC protocol. It also achieves a 46% decrease in packet drop probability, 79% increase in system throughput, and 25% decrease in mean packet delay.

  5. New TETRA Trunked Queue Management Method%一种新的TETRA集群队列管理方法

    Institute of Scientific and Technical Information of China (English)

    游晓黔; 喻后强

    2011-01-01

    This paper compares the advantages and disadvantages of additive increase and multiplicative decrease control mechanism and proportional fair schedule on TETRA trunked network, and it finds that the additive increase and multiplicative decrease scheme of TCP can degrade QoS performance of TETRA trunked system. For solving this problem, it puts forward a new TETRA trunked queue management method, and designs a queue management counter based on dynamic starting mechanism to manage queue based on average channel quality. The effectiveness of the method on TETRA trunked network is demonstrated by simulation.%比较陆地集群无线电系统(TETRA)集群网络中加增乘减控制机制和按比公平时序调度的优缺点,指出TCP的加增乘减机制会降低TETRA集群系统的QoS性能.提出一种新的TETRA集群队列管理方法,设计基于动态起点机制的队列管理计数器,基于平均信道质量进行队列管理.仿真实验验证了该方法在TETRA集群网络中的有效性.

  6. Active Queue Management算法研究%Study on Active Queue Management Algorithm

    Institute of Scientific and Technical Information of China (English)

    沈捷; 林锦国; 王莉

    2007-01-01

    主动队列管理算法对于IP网络的性能影响重大,是网络拥塞控制一个主要手段.介绍了目前主要的主动队列管理算法如RED、改进的RED以及P控制器、PI控制器、模糊控制器、鲁棒控制器、内模控制器.通过对这些算法的分析,指出其中的不足之处,并对AQM算法的设计提出了一些思路.

  7. AQM Algorithm with Adaptive Reference Queue Threshold for Communication Networks

    Directory of Open Access Journals (Sweden)

    Liming Chen

    2012-09-01

    Full Text Available Nowadays, congestion in communication networks has been more intractable than ever before due to the explosive growth of network scale and multimedia traffic. Active queue management (AQM algorithms had been proposed to alleviate congestion to improve quality of service (QoS, but existing algorithms often suffer from some flaws in one aspect or another. In this paper, a novel AQM algorithm with adaptive reference queue threshold (ARTAQM is proposed of which the main innovative contributions are recounted as follows. First, traffic is predicted to calculate the packet loss ratio (PLR and the traffic rate based on traffic prediction algorithm. Second, by means of periodical measurements, a weighted PLR is obtained to dynamically adjust packet dropping probability in ARTAQM algorithm. Third, ARTAQM algorithm runs in both coarse and fine granularities. In coarse granularity, the mismatch of the predicted traffic rate and link capacity can adjusts the reference queue length in every period, while in fine granularity, reference queue remains fixed and the  instantaneous queue is adjusted packet by packet in one period. Simulation results indicate that ARTAQM algorithm not only maintains stable queue and fast response speed, but has lower PLR and higher link utilization as well.

  8. Vacation queueing models theory and applications

    CERN Document Server

    Tian, Naishuo

    2006-01-01

    A classical queueing model consists of three parts - arrival process, service process, and queue discipline. However, a vacation queueing model has an additional part - the vacation process which is governed by a vacation policy - that can be characterized by three aspects: 1) vacation start-up rule; 2) vacation termination rule, and 3) vacation duration distribution. Hence, vacation queueing models are an extension of classical queueing theory. Vacation Queueing Models: Theory and Applications discusses systematically and in detail the many variations of vacation policy. By allowing servers to take vacations makes the queueing models more realistic and flexible in studying real-world waiting line systems. Integrated in the book's discussion are a variety of typical vacation model applications that include call centers with multi-task employees, customized manufacturing, telecommunication networks, maintenance activities, etc. Finally, contents are presented in a "theorem and proof" format and it is invaluabl...

  9. Adaptive Filtering Queueing for Improving Fairness

    Directory of Open Access Journals (Sweden)

    Jui-Pin Yang

    2015-06-01

    Full Text Available In this paper, we propose a scalable and efficient Active Queue Management (AQM scheme to provide fair bandwidth sharing when traffic is congested dubbed Adaptive Filtering Queueing (AFQ. First, AFQ identifies the filtering level of an arriving packet by comparing it with a flow label selected at random from the first level to an estimated level in the filtering level table. Based on the accepted traffic estimation and the previous fair filtering level, AFQ updates the fair filtering level. Next, AFQ uses a simple packet-dropping algorithm to determine whether arriving packets are accepted or discarded. To enhance AFQ’s feasibility in high-speed networks, we propose a two-layer mapping mechanism to effectively simplify the packet comparison operations. Simulation results demonstrate that AFQ achieves optimal fairness when compared with Rotating Preference Queues (RPQ, Core-Stateless Fair Queueing (CSFQ, CHOose and Keep for responsive flows, CHOose and Kill for unresponsive flows (CHOKe and First-In First-Out (FIFO schemes under a variety of traffic conditions.

  10. Resources Management in Active Networks

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    In an active network, users can insert customized active codes into active nodes to execute. Thus it needs more resources than those required by conventional networks, and these resources must be effectively monitored and managed. Management policies in existing OSs are too complicated to apply to simple active packets. In this paper, we present new resources management policies that are mainly adoped to manage CPU, storage and transmission bandwidth. Namely, we use SPF algorithm to schedule and process active packets, and import an interval queue method to allocate transmission bandwidth, and use feedback mechanism to control congestion. At the same time, we design some experiments on prototype systems with and without resources management policies respectively. The experiments results show that management policies presented by us can effectively manage resources in active nodes and can improve the performance of active networks.

  11. Preventing messaging queue deadlocks in a DMA environment

    Science.gov (United States)

    Blocksome, Michael A; Chen, Dong; Gooding, Thomas; Heidelberger, Philip; Parker, Jeff

    2014-01-14

    Embodiments of the invention may be used to manage message queues in a parallel computing environment to prevent message queue deadlock. A direct memory access controller of a compute node may determine when a messaging queue is full. In response, the DMA may generate and interrupt. An interrupt handler may stop the DMA and swap all descriptors from the full messaging queue into a larger queue (or enlarge the original queue). The interrupt handler then restarts the DMA. Alternatively, the interrupt handler stops the DMA, allocates a memory block to hold queue data, and then moves descriptors from the full messaging queue into the allocated memory block. The interrupt handler then restarts the DMA. During a normal messaging advance cycle, a messaging manager attempts to inject the descriptors in the memory block into other messaging queues until the descriptors have all been processed.

  12. 弃头和随机结合的被动队列管理%Combination of randomly drop and drop front in passive queue management

    Institute of Scientific and Technical Information of China (English)

    姜文刚; 孙金生; 王执铨

    2011-01-01

    AQM algorithm did not promote the actual use of the network for its many defects.In order to improve the drop tail passive queue management for its wide use, this paper proposed a new algorithm, that was combination of drop front and randomly drop in passive queue management.When the queue was full, dropped a packet from the head of the queue was firstly,afterward,dropped another packet in the queue randomly.NS2 simulation shows that the RTT fairness and speed fairness will be improved efficiently, the defects of the drop tail queue management will be avoided, the transmission performance of the network will be advanced.The computation of this algorithm is small, so it is suitable for using on the Internet.%主动队列管理算法存在诸多缺陷,并没有在实际网络上推广使用.为了对目前使用最多的弃尾被动队列管理进行改进,提出了随机和弃头相结合的被动队列管理算法.在队列满时,先从队列头部丢弃一个数据包,然后再在队列中随机丢弃一个数据包.NS2仿真表明该算法能有效改善RTT和速度公平性,避免弃尾队列管理的缺陷,提高了网络传输性能.该算法计算量小,适合在Internet上使用.

  13. A Research on Some Acitve Queue Management Algorithms%几种主动式队列管理算法的比较研究

    Institute of Scientific and Technical Information of China (English)

    吴春明; 姜明; 朱淼良

    2004-01-01

    主动式队列管理(Active Queue Management,AQM)技术是IETF为了解决Internet拥塞控制问题而提出的一种路由器缓存管理技术.本文对几种主要AQM算法RED、BLUE、ARED和SRED的性能在基于ns-2仿真实验的基础上进行了比较研究.研究的性能包括队列长度、丢包概率、丢包率、连接数对吞吐量的影响及缓冲区大小对链路利用率的影响等.仿真结果表明BLUE、ARED和SRED在这几方面的性能都要优于RED算法.

  14. Managing patients' wait time in specialist out-patient clinic using real-time data from existing queue management and ADT systems.

    Science.gov (United States)

    Ju, John Chen; Gan, Soon Ann; Tan Siew Wee, Justine; Huang Yuchi, Peter; Mei Mei, Chan; Wong Mei Mei, Sharon; Fong, Kam Weng

    2013-01-01

    In major cancer centers, heavy patients load and multiple registration stations could cause significant wait time, and can be result in patient complains. Real-time patient journey data and visual display are useful tools in hospital patient queue management. This paper demonstrates how we capture patient queue data without deploying any tracing devices; and how to convert data into useful patient journey information to understand where interventions are likely to be most effective. During our system development, remarkable effort has been spent on resolving data discrepancy and balancing between accuracy and system performances. A web-based dashboard to display real-time information and a framework for data analysis were also developed to facilitate our clinics' operation. Result shows our system could eliminate more than 95% of data capturing errors and has improved patient wait time data accuracy since it was deployed.

  15. Near-optimal switching strategies for a tandem queue

    NARCIS (Netherlands)

    Leeuwen, D. van; Núñez Queija, R.; Boucherie, R.J.; van Dijk, N.M.

    2015-01-01

    Motivated by various applications in logistics, road traffic and production management, we investigate two versions of a tandem queueing model in which the service rate of the first queue can be controlled. The objective is to keep the mean number of jobs in the second queue as low as possible, with

  16. Multifractal Internet Traffic Model and Active Queue Management

    Science.gov (United States)

    2003-01-01

    there have been some modifications such as Stabilized RED ( SRED ) [93], Flow RED (FRED) [94], Weighted RED [95], Random Early Marking (REM) [38], BLUE...La, “Nonlinear instabilities in TCP-RED,” in Proceedings of INFOCOM, 2002, pp. 249 –258. [93] T.J. Ott, T.V. Lakshman, and L.H. Wong, “ SRED : Stabilized

  17. Architecture and robustness tradeoffs in speed-scaled queues with application to energy management

    Science.gov (United States)

    Dinh, Tuan V.; Andrew, Lachlan L. H.; Nazarathy, Yoni

    2014-08-01

    We consider single-pass, lossless, queueing systems at steady-state subject to Poisson job arrivals at an unknown rate. Service rates are allowed to depend on the number of jobs in the system, up to a fixed maximum, and power consumption is an increasing function of speed. The goal is to control the state dependent service rates such that both energy consumption and delay are kept low. We consider a linear combination of the mean job delay and energy consumption as the performance measure. We examine both the 'architecture' of the system, which we define as a specification of the number of speeds that the system can choose from, and the 'design' of the system, which we define as the actual speeds available. Previous work has illustrated that when the arrival rate is precisely known, there is little benefit in introducing complex (multi-speed) architectures, yet in view of parameter uncertainty, allowing a variable number of speeds improves robustness. We quantify the tradeoffs of architecture specification with respect to robustness, analysing both global robustness and a newly defined measure which we call local robustness.

  18. A course on queueing models

    CERN Document Server

    Jain, Joti Lal; Böhm, Walter

    2006-01-01

    The application of engineering principles in divergent fields such as management science and communications as well as the advancement of several approaches in theory and computation have led to growing interest in queueing models, creating the need for a comprehensive text. Emphasizing Markovian structures and the techniques that occur in different models, A Course on Queueing Models discusses recent developments in the field, different methodological tools - some of which are not available elsewhere - and computational techniques.While most books essentially address the classical methods of

  19. Probability, statistics, and queueing theory

    CERN Document Server

    Allen, Arnold O

    1990-01-01

    This is a textbook on applied probability and statistics with computer science applications for students at the upper undergraduate level. It may also be used as a self study book for the practicing computer science professional. The successful first edition of this book proved extremely useful to students who need to use probability, statistics and queueing theory to solve problems in other fields, such as engineering, physics, operations research, and management science. The book has also been successfully used for courses in queueing theory for operations research students. This second edit

  20. Usage of Message Queueing Technologies in the ATLAS Distributed Data Management System

    Science.gov (United States)

    Calfayan, Philippe; Dongsong, Zang; Garonne, Vincent

    2011-12-01

    The ATLAS Distributed Data Management system is composed of semi-autonomous, heterogeneous, and independently designed subsystems. To achieve successful operation of such a system, the activities of the agents controlling the subsystems have to be coordinated. In addition, external applications can require to synchronize on events relative to data availability. A common way to proceed is to implement polling strategies within the distributed components, which leads to an increase of the load in the overall system. We describe an alternative based on notifications using standard message queuing. The application of this technology in the distributed system has been exercised.

  1. On retrial queueing model with fuzzy parameters

    Science.gov (United States)

    Ke, Jau-Chuan; Huang, Hsin-I.; Lin, Chuen-Horng

    2007-01-01

    This work constructs the membership functions of the system characteristics of a retrial queueing model with fuzzy customer arrival, retrial and service rates. The α-cut approach is used to transform a fuzzy retrial-queue into a family of conventional crisp retrial queues in this context. By means of the membership functions of the system characteristics, a set of parametric non-linear programs is developed to describe the family of crisp retrial queues. A numerical example is solved successfully to illustrate the validity of the proposed approach. Because the system characteristics are expressed and governed by the membership functions, more information is provided for use by management. By extending this model to the fuzzy environment, fuzzy retrial-queue is represented more accurately and analytic results are more useful for system designers and practitioners.

  2. Mathematical Analysis of Queue with Phase Service: An Overview

    Directory of Open Access Journals (Sweden)

    Richa Sharma

    2014-01-01

    Full Text Available We discuss various aspects of phase service queueing models. A large number of models have been developed in the area of queueing theory incorporating the concept of phase service. These phase service queueing models have been investigated for resolving the congestion problems of many day-to-day as well as industrial scenarios. In this survey paper, an attempt has been made to review the work done by the prominent researchers on the phase service queues and their applications in several realistic queueing situations. The methodology used by several researchers for solving various phase service queueing models has also been described. We have classified the related literature based on modeling and methodological concepts. The main objective of present paper is to provide relevant information to the system analysts, managers, and industry people who are interested in using queueing theory to model congestion problems wherein the phase type services are prevalent.

  3. discouraged by queue length

    Directory of Open Access Journals (Sweden)

    P. R. Parthasarathy

    2001-01-01

    Full Text Available The transient solution is obtained analytically using continued fractions for a state-dependent birth-death queue in which potential customers are discouraged by the queue length. This queueing system is then compared with the well-known infinite server queueing system which has the same steady state solution as the model under consideration, whereas their transient solutions are different. A natural measure of speed of convergence of the mean number in the system to its stationarity is also computed.

  4. The effectiveness of throughput sampling for capacity management: A queueing approach

    NARCIS (Netherlands)

    Ellens, W.; Mandjes, M.; Worm, D.T.H.; Berg, J.L. van den

    2014-01-01

    For effective capacity management in access networks, it is essential to have a good insight in the service quality perceived by the users. As users share the service capacity available, one would want to know how the achieved per-user throughput fluctuates over time. In this paper we present a

  5. Resource manager for GRID with global job queue and with planning based on local schedules

    Energy Technology Data Exchange (ETDEWEB)

    Kovalenko, V.N. E-mail: kvn@keldysh.ru; Kovalenko, E.I.; Koryagin, D.A.; Ljubimskii, E.Z.; Orlov, A.V.; Huhlaev, E.V

    2003-04-21

    In this paper we discuss some of the problems of job management in a virtual Grid organization. The consideration mainly concerns the issue of job scheduling and, in particular, one version of the scheduling architecture under development that, we believe, has some advanced properties.

  6. Resource manager for GRID with global job queue and with planning based on local schedules

    Science.gov (United States)

    Kovalenko, V. N.; Kovalenko, E. I.; Koryagin, D. A.; Ljubimskii, E. Z.; Orlov, A. V.; Huhlaev, E. V.

    2003-04-01

    In this paper we discuss some of the problems of job management in a virtual Grid organization. The consideration mainly concerns the issue of job scheduling and, in particular, one version of the scheduling architecture under development that, we believe, has some advanced properties.

  7. Increasing available FIFO space to prevent messaging queue deadlocks in a DMA environment

    Science.gov (United States)

    Blocksome, Michael A [Rochester, MN; Chen, Dong [Croton On Hudson, NY; Gooding, Thomas [Rochester, MN; Heidelberger, Philip [Cortlandt Manor, NY; Parker, Jeff [Rochester, MN

    2012-02-07

    Embodiments of the invention may be used to manage message queues in a parallel computing environment to prevent message queue deadlock. A direct memory access controller of a compute node may determine when a messaging queue is full. In response, the DMA may generate an interrupt. An interrupt handler may stop the DMA and swap all descriptors from the full messaging queue into a larger queue (or enlarge the original queue). The interrupt handler then restarts the DMA. Alternatively, the interrupt handler stops the DMA, allocates a memory block to hold queue data, and then moves descriptors from the full messaging queue into the allocated memory block. The interrupt handler then restarts the DMA. During a normal messaging advance cycle, a messaging manager attempts to inject the descriptors in the memory block into other messaging queues until the descriptors have all been processed.

  8. Fast meldable priority queues

    DEFF Research Database (Denmark)

    Brodal, Gerth Stølting

    1995-01-01

    We present priority queues that support the operations Find-Min, Insert, MakeQueue and Meld in worst case time O(1) and Delete and DeleteMin in worst case time O(log n). They can be implemented on the pointer machine and require linear space. The time bounds are optimal for all implementations wh...

  9. An Optimal Lower Bound for Buffer Management in Multi-Queue Switches

    CERN Document Server

    Bienkowski, Marcin

    2010-01-01

    We consider a competitive analysis of the online packet buffering problem (also known as the unweighted FIFO variant of buffer management). In this scenario, we focus on a single network packet switching device, which has several input ports and one output port. This device forwards unit-size, unit-value packets from its input ports to the output port. The burstiness of the incoming traffic motivates the use of buffers of a certain size, attached to input ports, which can accumulate incoming packets and store them for later transmission. If a buffer cannot accommodate all incoming packets, the excess is lost. The aim of a packet buffering algorithm is --- for an adversarial packet injection pattern --- to choose from which buffers to transmit packets in order to minimize the number of packets lost and thus maximize the throughput. We present a tight lower bound of e/(e-1) ~ 1.582 on the competitive ratio of the throughput maximization, which holds even for randomized algorithms. This improves previously best ...

  10. Fundamentals of queueing theory

    CERN Document Server

    Gross, Donald; Thompson, James M; Harris, Carl M

    2013-01-01

    Praise for the Third Edition ""This is one of the best books available. Its excellent organizational structure allows quick reference to specific models and its clear presentation . . . solidifies the understanding of the concepts being presented.""-IIE Transactions on Operations Engineering Thoroughly revised and expanded to reflect the latest developments in the field, Fundamentals of Queueing Theory, Fourth Edition continues to present the basic statistical principles that are necessary to analyze the probabilistic nature of queues. Rather than pre

  11. Covert Bits Through Queues

    OpenAIRE

    Mukherjee, Pritam; Ulukus, Sennur

    2016-01-01

    We consider covert communication using a queuing timing channel in the presence of a warden. The covert message is encoded using the inter-arrival times of the packets, and the legitimate receiver and the warden observe the inter-departure times of the packets from their respective queues. The transmitter and the legitimate receiver also share a secret key to facilitate covert communication. We propose achievable schemes that obtain non-zero covert rate for both exponential and general queues...

  12. On RAM priority queues

    Energy Technology Data Exchange (ETDEWEB)

    Thorup, M. [Univ. of Coepnhagen (Denmark)

    1996-12-31

    Priority queues are some of the most fundamental data structures. They are used directly for, say, task scheduling in operating systems. Moreover, they are essential to greedy algorithms. We study the complexity of priority queue operations on a RAM with arbitrary word size. We present exponential improvements over previous bounds, and we show tight relations to sorting. Our first result is a RAM priority queue supporting insert and extract-min operations in worst case time O(log log n) where n is the current number of keys in the queue. This is an exponential improvement over the O({radical}log n) bound of Redman and Willard from STOC`90. Our algorithm is simple, and it only uses AC{sup 0} operations, meaning that there is no hidden time dependency on the word size. Plugging this priority queue into Dijkstra`s algorithm gives an 0(mloglogm) algorithm for the single source shortest path problem on a graph with m edges, as compared with the previous O(m {radical} log m) bound based on Redman and Willard`s priority queue.

  13. Queueing analysis of a shared voice-data link

    Science.gov (United States)

    Friedman, D. U.

    1981-11-01

    We consider a link shared by some number of off-hook phone callers and a data queue. The allocation of capacity to voice and data depends on the level of speaker activity (number of talkspurt). A Markov chain model is adopted for this activity, and the resulting data queue performance is analyzed.

  14. Queues, stores, and tableaux

    CERN Document Server

    Draief, Moez; O'Connell, Neil

    2005-01-01

    Consider the single server queue with an infinite buffer and a FIFO discipline, either of type M/M/1 or Geom/Geom/1. Denote by A the arrival process and by s the services. Assume the stability condition to be satisfied. Denote by D the departure process in equilibrium and by r the time spent by the customers at the very back of the queue. We prove that (D,r) has the same law as (A,s) which is an extension of the classical Burke Theorem. In fact, r can be viewed as the departures from a dual storage model. This duality between the two models also appears when studying the transient behavior of a tandem by means of the RSK algorithm: the first and last row of the resulting semi-standard Young tableau are respectively the last instant of departure in the queue and the total number of departures in the store.

  15. Research on NS2-based Simulation of Queue Management Algorithms%基于NS2的队列管理算法研究

    Institute of Scientific and Technical Information of China (English)

    凌云; 韩冬

    2011-01-01

    Some traditional queue management algorithms,such as DropTail,RED,are studied in this paper.According to the experiment results,it is easy to find out the disadvantages of these two algorithms.DropTail easily causes several questions such as lock-outs,full queues and global synchronizations.RED can effectively avoid the system's TCP global synchronizations,and improve the network utilization and the system robustness.But RED may cause high ratios of losing packets and long time-delay of network.Then an improved new algorithm-,ARED,is presented.By adjusting the control parameters of RED,ARED can improves the system robustness of RED and the responses,and acquire more stable and excellent performances in accord with the network's flow.%研究了传统的队列管理DropTail、RED的算法原理,依据实验结果,说明DropTail算法存在死锁、满队列、全局同步等问题;RED算法虽然可有效地避免系统出现TCP流全局同步现象,提高了网络利用率和系统的鲁棒性,但对参数设置过于敏感,可能会造成较高的丢包率和较大的时延。本文提出了一种新的ARED算法,通过将RED的控制参数进行动态调整,进一步提高了RED算法的鲁棒性和响应的快速性,使之更能适应网络流量的变化,获得更加稳定和优异的性能。

  16. Design and Development of the Queue Management System Base on Radiation Therapy Information System%基于放疗信息系统的排队叫号系统设计与实现

    Institute of Scientific and Technical Information of China (English)

    郭凌菱

    2013-01-01

    目的研究基于放疗科信息系统的排队叫号系统,提高对放疗病人的服务质量。方法分析放疗科排队叫号系统的工作流程和功能需求,分别从硬件和软件两方面对系统进行架构设计。结果采用接口模块化以及语音控制和自助终端等重要技术实现放疗科信息系统与排队叫号系统的集成。结论排队叫号系统的运行,提高了医院的整体服务水平和管理水平。%Objective Research a queue management system based on radiation therapy information system to improve the service quality for radiotherapy patients. Methods Analyze the workflow and requirements and design the architecture of the system from two aspects of hardware and software respectively. Results Realize the integration of radiation therapy information system and queue management system by using the technique of interface modular and self-service terminals. Conclusion The operation of the queue management system can improve the overall service and management level of the hospital.

  17. Updatable Queue Protocol Based On TCP For Virtual Reality Environment

    CERN Document Server

    Al-Howaide, Ala'a Z; Salhieh, Ayad M

    2011-01-01

    The variance in number and types of tasks required to be implemented within Distributed Virtual Environments (DVE) highlights the needs for communication protocols can achieve consistency. In addition, these applications have to handle an increasing number of participants and deal with the difficult problem of scalability. Moreover, the real-time requirements of these applications make the scalability problem more difficult to solve. In this paper, we have implemented Updatable Queue Abstraction protocol (UQA) on TCP (TCP-UQA) and compared it with original TCP, UDP, and Updatable Queue Abstraction based on UDP (UDP-UQA) protocols. Results showed that TCP-UQA was the best in queue management.

  18. Waiting for coronary angiography: is there a clinically ordered queue?

    Science.gov (United States)

    Hemingway, H; Crook, A M; Feder, G; Dawson, J R; Timmis, A

    2000-03-18

    Among over 3000 patients undergoing coronary angiography in the absence of a formal queue-management system, we found that a-priori urgency scores were strongly associated with waiting times, prevalence of coronary-artery disease, rate of revascularisation, and mortality. These data challenge the widely held assumption that such waiting lists are not clinically ordered; however, the wide variation in waiting times within urgency categories suggests the need for further improvements in clinical queueing.

  19. 一种模糊自适应虚拟队列管理算法%A Fuzzy-Adaptive Virtual Queue Management Algorithm

    Institute of Scientific and Technical Information of China (English)

    崔亮; 路向中; 党倩; 王健肃

    2009-01-01

    With the dramatic growth of network traffics, AQM is becoming a focus in filed of TCP end - to - end congestion control research. In order to solve the problems of queue congestion, utilize queue's resource effectively and reduce queue's jitter, this text adopts a method of computing packet's drop probability through Fuzzy - Controlling Model to reduce queue's jitter caused by "hard -judging" ; at the same time, the expected queue length is introduced into the algorithm to explicitly control and stabilize the queue length, and improve queue's resource utility. Finally, three different kinds of traffics are simulated using NS2 simulation platform, the results of simulations demonstrate that the proposed algorithm is of a certain feasibility and application value , and can solve the problems of queue's jitter and low queue's resource utility to a certain extent.%随着网络流量的剧增,主动队列管理是近来端到端拥塞控制研究中的一个研究热点.为了解决队列拥塞、高效利用队列资源和减少队列抖动等队列管理问题,采用模糊控制模块计算分组丢弃概率,减少了由于"硬判断"所造成的队列抖动问题;同时在算法中引入期望队列长度来显式控制并稳定队列长度,提高了队列资源利用率.最后通过在NS2平台上仿真三种不同的业务流量对该算法进行实验测试,结果表明,算法在一定程度上解决了PI算法队列抖动大和AVQ算法队列资源使用率低的问题,具有一定的可行性和应用价值.

  20. Lévy-driven queues

    NARCIS (Netherlands)

    K. Dębicki; M. Mandjes

    2012-01-01

    This survey addresses the class of queues with Lévy input, which covers the classical M/G/1 queue and the reflected Brownian motion as special cases. First the stationary behavior is treated, with special attention to the case of the input process having one-sided jumps (i.e., spectrally one-sided L

  1. A Survey on Priority Queues

    DEFF Research Database (Denmark)

    Brodal, Gerth Stølting

    2013-01-01

    Back in 1964 Williams introduced the binary heap as a basic priority queue data structure supporting the operations Insert and ExtractMin in logarithmic time. Since then numerous papers have been published on priority queues. This paper tries to list some of the directions research on priority...

  2. 星载交换机中高性能队列管理器的研究与实现%Research and implementation of a high performance queue management equipment on the satellite onboard switch

    Institute of Scientific and Technical Information of China (English)

    王孟磊; 施扬; 乔庐峰; 禹明刚

    2012-01-01

    针对星载交换机中硬件处理速度和存储器容量受限的情况,设计实现了一个高性能队列管理器.采用虚拟输出排队机制改善输入缓存中存在的队头阻塞问题;使用前向地址指针pre_addr和后向地址指针nxt addr控制信元的写入和读出.通过ModelSim SE行为级时序仿真可知,其能够达到星载交换机的队列时延要求,具有较高的交换性能及稳定性.%This paper implements a high performance queue management equipment due to the limitation of hardware procession speed and memory capacity on the satellite onboard switch. It utilizes virtual output queue(VOQ) to improve the HOL problem of input buffer, and control the writing and reading of a cell by implementing the previous address pointer (pre_addr) and the next address pointer (nxt_addr). The results of ModelSim SE behavioral timing simulation show that it satisfies the need of queue delay of the satellite onboard switch, and has high performance and stability.

  3. Decomposing the queue length distribution of processor-sharing models into queue lengths of permanent customer queues

    NARCIS (Netherlands)

    Cheung, S.-K.; Berg, H. van den; Boucherie, R.J.

    2005-01-01

    We obtain a decomposition result for the steady state queue length distribution in egalitarian processor-sharing (PS) models. In particular, for multi-class egalitarian PS queues, we show that the marginal queue length distribution for each class equals the queue length distribution of an equivalent

  4. A new queueing strategy for the Adversarial Queueing Theory

    CERN Document Server

    Hilker, Michael

    2008-01-01

    In the today's Internet and TCP/IP-networks, the queueing of packets is commonly implemented using the protocol FIFO (First In First Out). Unfortunately, FIFO performs poorly in the Adversarial Queueing Theory. Other queueing strategies are researched in this model and better results are performed by alternative queueing strategies, e.g. LIS (Longest In System). This article introduces a new queueing protocol called interval-strategy that is concerned with the reduction from dynamic to static routing. We discuss the maximum system time for a packet and estimate with up-to-date results how this can be achieved. We figure out the maximum amount of time where a packet can spend in the network (i.e. worst case system time), and argue that the universal instability of the presented interval-strategy can be reached through these results. When a large group of queueing strategies is used for queueing, we prove that the interval-strategy will be universally unstable. Finally, we calculate the maximum time of the stat...

  5. Buffer Management Strategy of Priority Queue Based on Gray Prediction Model%基于灰色预测模型的优先级队列缓存管理策略

    Institute of Scientific and Technical Information of China (English)

    唐定勇; 林正红; 江虹

    2015-01-01

    为解决企业服务总线( ESB)集成平台中的服务队列管理问题,在考虑队列优先级因素的基础上,提出一种优先级消息服务队列缓存管理策略。将不同优先级的业务数据封装为消息服务放入不同队列中,按照消息优先级顺序对其进行服务管理,在下一次业务消息到达前,使用灰色预测模型实时预测优先级队列的缓存分配情况,使得队列缓存分配更合理。实验结果表明,该策略能保障ESB集成平台中高优先级业务和低优先级业务的正常运行,并降低高优先级业务的平均等待时间、平均停留时间及消息队列拥塞的风险。%To solve the service queue management problem in the Enterprise Service Bus( ESB) integration platform, the buffer management strategy of priority message service queue is proposed. This strategy puts the different priorities business data into different queues. The Business is serviced according to the order of priority packets. Before the next packets arrive,the strategy uses gray prediction to make a real-time prediction about the priority queue ’ s buffer size which can be assigned,makes the queue’ s buffer allocation more reasonable. Experimental results show that the proposed strategy not only can guarantee high priority and low priority traffic to run smoothly in ESB integration platform,but also can reduce the average waiting time,the average residence time for high priority traffic and the risk of message queue congestion.

  6. Two-Queue Polling Model with a Timer and a Randomly-Timed Gated Mechanism

    Institute of Scientific and Technical Information of China (English)

    LI Jin Zhi

    2009-01-01

    In this paper, we consider two-queue polling model with a Timer and a RandomlyTimed Gated (RTG) mechanism. At queue Q1, we employ a Timer T(1): whenever the server polls queue Q1 and finds it empty, it activates a Timer. If a customer arrives before the Timer expires, a busy period starts in accordance with exhaustive service discipline. However, if the Timer is shorter than the interarrival time to queue Q1, the server does not wait any more and switches back to queue Q2. At queue Q2, we operate a RTG mechanism T(2), that is, whenever the server reenters queue Q2, an exponential time T(2) is activated. If the server empties the queue before T(2), it immediately leaves for queue Q1. Otherwise, the server completes all the work accumulated up to time T(2) and leaves. Under the assumption of Poisson arrivals, general service and switchover time distributions, we obtain probability generating function (PGF) of the queue lengths at polling instant and mean cycle length and Laplace Stieltjes transform (LST) of the workload.

  7. Queues and risk models with simultaneous arrivals

    NARCIS (Netherlands)

    Badila, E.S.; Boxma, O.J.; Resing, J.A.C.; Winands, E.M.M.

    2014-01-01

    We focus on a particular connection between queueing and risk models in a multidimensional setting. We first consider the joint workload process in a queueing model with parallel queues and simultaneous arrivals at the queues. For the case that the service times are ordered (from largest in the firs

  8. Applied discrete-time queues

    CERN Document Server

    Alfa, Attahiru S

    2016-01-01

    This book introduces the theoretical fundamentals for modeling queues in discrete-time, and the basic procedures for developing queuing models in discrete-time. There is a focus on applications in modern telecommunication systems. It presents how most queueing models in discrete-time can be set up as discrete-time Markov chains. Techniques such as matrix-analytic methods (MAM) that can used to analyze the resulting Markov chains are included. This book covers single node systems, tandem system and queueing networks. It shows how queues with time-varying parameters can be analyzed, and illustrates numerical issues associated with computations for the discrete-time queueing systems. Optimal control of queues is also covered. Applied Discrete-Time Queues targets researchers, advanced-level students and analysts in the field of telecommunication networks. It is suitable as a reference book and can also be used as a secondary text book in computer engineering and computer science. Examples and exercises are includ...

  9. Queueing theory and network applications

    CERN Document Server

    Takahashi, Yutaka; Yue, Wuyi; Nguyen, Viet-Ha

    2016-01-01

    The 16 papers of this proceedings have been selected from the submissions to the 10th  International Conference on Queueing Theory and Network Applications (QTNA2015) held on 17-20 August, 2015 in Ha Noi and Ha Long, Vietnam. All contributions discuss theoretical and practical issues connected with queueing theory and its applications in networks and other related fields. The book brings together researchers, scientists and practitioners from the world and offers an open forum to share the latest important research accomplishments and challenging problems in the area of queueing theory and network applications.

  10. Joining Longer Queues: Information Externalities in Queue Choice

    OpenAIRE

    Senthil Veeraraghavan; Laurens Debo

    2009-01-01

    A classic example that illustrates how observed customer behavior impacts other customers' decisions is the selection of a restaurant whose quality is uncertain. Customers often choose the busier restaurant, inferring that other customers in that restaurant know something that they do not. In an environment with random arrival and service times, customer behavior is reflected in the lengths of the queues that form at the individual servers. Therefore, queue lengths could signal two factors--p...

  11. Bayesian Inference in Queueing Networks

    CERN Document Server

    Sutton, Charles

    2010-01-01

    Modern Web services, such as those at Google, Yahoo!, and Amazon, handle billions of requests per day on clusters of thousands of computers. Because these services operate under strict performance requirements, a statistical understanding of their performance is of great practical interest. Such services are modeled by networks of queues, where one queue models each of the individual computers in the system. A key challenge is that the data is incomplete, because recording detailed information about every request to a heavily used system can require unacceptable overhead. In this paper we develop a Bayesian perspective on queueing models in which the arrival and departure times that are not observed are treated as latent variables. Underlying this viewpoint is the observation that a queueing model defines a deterministic transformation between the data and a set of independent variables called the service times. With this viewpoint in hand, we sample from the posterior distribution over missing data and model...

  12. JobCenter: an open source, cross-platform, and distributed job queue management system optimized for scalability and versatility

    Directory of Open Access Journals (Sweden)

    Jaschob Daniel

    2012-07-01

    Full Text Available Abstract Background Laboratories engaged in computational biology or bioinformatics frequently need to run lengthy, multistep, and user-driven computational jobs. Each job can tie up a computer for a few minutes to several days, and many laboratories lack the expertise or resources to build and maintain a dedicated computer cluster. Results JobCenter is a client–server application and framework for job management and distributed job execution. The client and server components are both written in Java and are cross-platform and relatively easy to install. All communication with the server is client-driven, which allows worker nodes to run anywhere (even behind external firewalls or “in the cloud” and provides inherent load balancing. Adding a worker node to the worker pool is as simple as dropping the JobCenter client files onto any computer and performing basic configuration, which provides tremendous ease-of-use, flexibility, and limitless horizontal scalability. Each worker installation may be independently configured, including the types of jobs it is able to run. Executed jobs may be written in any language and may include multistep workflows. Conclusions JobCenter is a versatile and scalable distributed job management system that allows laboratories to very efficiently distribute all computational work among available resources. JobCenter is freely available at http://code.google.com/p/jobcenter/.

  13. 基于动态共享队列的缓存管理技术%Buffer Management Technology Based on Dynamic Sharing Queue

    Institute of Scientific and Technical Information of China (English)

    祝京; 晏坚; 刘序明

    2010-01-01

    针对星载交换系统设计中高缓存利用率与低实现复杂度之间的矛盾,提出一种基于动态共享队列(Dynamic Sharing Queue,DSQ)的缓存分配与管理机制,可灵活利用存储资源,且结构简单,尤其适合在FPGA器件中实现.通过与其他缓存管理技术方案的对比分析和仿真表明,缓存管理机制用于PQ(Priority Queue)队列调度算法时,在系统重负载与业务强突发的情况下均表现出明显的性能优势.

  14. Queueing networks a fundamental approach

    CERN Document Server

    Dijk, Nico

    2011-01-01

    This handbook aims to highlight fundamental, methodological and computational aspects of networks of queues to provide insights and to unify results that can be applied in a more general manner.  The handbook is organized into five parts: Part 1 considers exact analytical results such as of product form type. Topics include characterization of product forms by physical balance concepts and simple traffic flow equations, classes of service and queue disciplines that allow a product form, a unified description of product forms for discrete time queueing networks, insights for insensitivity, and aggregation and decomposition results that allow subnetworks to be aggregated into single nodes to reduce computational burden. Part 2 looks at monotonicity and comparison results such as for computational simplification by either of two approaches: stochastic monotonicity and ordering results based on the ordering of the proces generators, and comparison results and explicit error bounds based on an underlying Markov r...

  15. Assessment of Active Queue Management algorithms by using NS2 simulator

    Directory of Open Access Journals (Sweden)

    Kamal Preet Kaur

    2014-03-01

    Full Text Available Network security has become very important and foremost issue for the personal computer users, organizations, business and military. With the advent of internet, security has become the major concern. The main objective of this research is to simulate and analyze the effect of queuing algorithms RED and DROPTAIL with CPR on the TCP targeted LDDoS attack flows. LDDoS attack is more vulnerable to the network traffic than the classic DDoS attacks as they are difficult to identify. We use network simulator ns-2 to implement the network and investigate the behaviors of queuing algorithms in the network. The performance metrics of the comparison are average delay and packet drop. CPR based approach is used to detect and filter attacks. The test-bed experiments are conducted to analyze the performance of this approach which is compared to the existing DFT approach.

  16. M/G/∞ tandem queues

    NARCIS (Netherlands)

    Boxma, O.J.

    1984-01-01

    We consider a series of queues with Poisson input. Each queueing system contains an infinite number of service channels. The service times in each channel have a general distribution. For this M/G∞ tandem model we obtain the joint time-dependent distribution of queue length and residual service tim

  17. M/G/∞ tandem queues

    NARCIS (Netherlands)

    Boxma, O.J.

    1984-01-01

    We consider a series of queues with Poisson input. Each queueing system contains an infinite number of service channels. The service times in each channel have a general distribution. For this M/G∞ tandem model we obtain the joint time-dependent distribution of queue length and residual service tim

  18. Mean sojourn time in a parallel queue

    NARCIS (Netherlands)

    B. Kemper

    2009-01-01

    This account considers a parallel queue, which is two-queue network, where any arrival generates a job at both queues. It is noted that earlier work has revealed that this class of models is notoriously hard to analyze. We first evaluate a number of bounds developed in the literature, and observe th

  19. Random queues and risk averse users

    DEFF Research Database (Denmark)

    de Palma, André; Fosgerau, Mogens

    2013-01-01

    We analyze Nash equilibrium in time of use of a congested facility. Users are risk averse with general concave utility. Queues are subject to varying degrees of random sorting, ranging from strict queue priority to a completely random queue. We define the key “no residual queue” property, which...

  20. A two-enqueuer queue

    CERN Document Server

    Eisenstat, David

    2008-01-01

    The question of whether all shared objects with consensus number 2 belong to Common2, the class of objects that can be implemented from two-process consensus and atomic registers, was first posed by Herlihy. In the absence of general results, several researchers have obtained implementations for restricted-concurrency versions of FIFO queue. We present the first Common2 algorithm for a queue with two enqueuers and any number of dequeuers. This algorithm is compatible with the unbounded concurrency model, and its enqueue and dequeue methods require only a constant number of steps.

  1. Prediction of Ready Queue Processing Time in Multiprocessor Environment Using Lottery Scheduling (ULS

    Directory of Open Access Journals (Sweden)

    Amita CHOUDHARY

    2011-01-01

    Full Text Available While in multi-user environment, CPU has to manage lot of requests generated over the same time. Waiting queue of processes generates a problem of scheduling for processors. Designers and hardware architects have suggested system of multiprocessors to overcome the queue length. Lottery scheduling is one such method where processes in waiting queue are selected through a chance manner. This opens a way to use probability models to get estimates of system parameters. This paper is an application where the processing time of jobs in ready queue is predicted using the sampling method under the k-processors environment (k>1.The random selection of one process by each of k processors through without replacement method is a sample data set which helps in the prediction of possible ready queue processing time. Some theorems are established and proved to get desired results in terms of confidence intervals.

  2. a Model for Quantum Queue

    Science.gov (United States)

    Gawron, Piotr; Kurzyk, Dariusz; Puchała, Zbigniew

    2013-05-01

    We consider an extension of discrete time Markov chain queueing model to the quantum domain by use of discrete time quantum Markov chain. We introduce methods for numerical analysis of such models. Using these tools we show that quantum model behaves fundamentally different from the classical one.

  3. Asymptotic inference for waiting times and patiences in queues with abandonment

    DEFF Research Database (Denmark)

    Gorst-Rasmussen, Anders; Hansen, Martin Bøgsted

    2009-01-01

    Motivated by applications in call center management, we propose a framework based on empirical process techniques for inference about waiting time and patience distributions in multiserver queues with abandonment. The framework rigorises heuristics based on survival analysis of independent...

  4. Gateway queue management algorithm based on delay detection mechanism%基于延迟探测机制的网关队列管理算法

    Institute of Scientific and Technical Information of China (English)

    赖峻; 张广驰

    2014-01-01

    提出一种基于延迟探测机制的算法,该算法通过探测分组在瓶颈网关队列中的延迟时间来估计网络的拥塞状况,设置一个探测门限。当分组的排队延迟超过门限时,采用显式拥塞指示(explicit congestion notifica-tion,ECN)机制标记分组以向传输控制协议(transport control protocol,TCP)源端通知拥塞。为了使该算法在网关中更易实现且具有自适应性,算法在每个周期中都根据不同 TCP 流对网关资源的占用情况来评估其权重,然后选取权重最大的若干 TCP 流的测量结果来更新拥塞探测门限,使网关对于突发流量在达到高吞吐量、高链路利用率和稳定的平均队列长度的同时,能更公平地分配资源。通过 ns-2下的仿真,证明算法能达到预期的效果。%An algorithm based on the delay detection mechanism is proposed,which estimates the state of congestion by monitoring the packet queueing delay in the bottleneck gateway and sets a detection threshold. Once the queueing delay of a packet exceeds the threshold,the packet will be marked according to the mecha-nism of explicit congestion notification (ECN)to notify the transport control protocol (TCP)source.In order to be self-adaptive and easier to perform in the gateway,the algorithm evaluates the weight of different TCP flows according to their occupancy of the gateway resources in every cycle and chooses the measurements of several TCP flows whose weights are the heaviest to update the congestion detection threshold.Through the algorithm, the gateway is not only capable of achieving high throughput,high link utilization and stable mean queue length, but also able to allocate resources more fairly for bursty traffic.The simulation result on network simulator ver-sion 2(ns-2)shows that the algorithm can achieve desired performance.

  5. Dynamic server assignment in a two-queue model

    NARCIS (Netherlands)

    Boxma, O.J.; Down, D.G.

    1995-01-01

    We consider a polling model of two $M/G/1$ queues, served by a single server. The service policy for this polling model is of threshold type. Service at queue 1 is exhaustive. Service at queue 2 is exhaustive unless the size of queue 1 reaches some level $T$ during a service at queue 2; in the latte

  6. Cost Comparison of B-1B Non-Mission-Capable Drivers Using Finite Source Queueing with Spares

    Science.gov (United States)

    2012-09-06

    the other internal users (Dewan & Mendelson , 1990). Queueing Much research has been done in the queueing field. Two specific categories of...Dewan, S., & Mendelson , H. (1990). User Delay Costs and Internal Pricing for a Service Facility. Management Science, 36 (12), 1502-1517. Elsayed, E

  7. QUEUEING NETWORKS WITH INSTANTANEOUSSEQUENTIAL TRANSITIONS

    Institute of Scientific and Technical Information of China (English)

    Chao Xiuli

    2001-01-01

    We study queueing networks with instantaneous transitions of sequential batch departures and sequential batch arrivals. Unlike most of the existing models, this network is shown not to have a product form solution. An "extra arrival condition” is introduced under which the network is shown to possess a product form stationary distribution. Furthermore, the product form solution serves as a stochastic upper bound for the original network without the extra arrival process. The results include many queueing network models reported in the literature, e.g. the assembly transfer networks recently introduced by Miyazawa and Taylor, as special cases. We show that the network with the extra arrival process is "structurally reversible” in the sense that its reversed process has the same network structure. Local balances for this network are presented and discussed.

  8. Queue-Dispatch Asynchronous Systems

    CERN Document Server

    Geeraerts, Gilles; Raskin, Jean-François

    2012-01-01

    To make the development of efficient multi-core applications easier, libraries, such as Grand Central Dispatch, have been proposed. When using such a library, the programmer writes so-called blocks, which are chunks of codes, and dispatches them, using synchronous or asynchronous calls, to several types of waiting queues. A scheduler is then responsible for dispatching those blocks on the available cores. Blocks can synchronize via a global memory. In this paper, we propose Queue-Dispatch Asynchronous Systems as a mathematical model that faithfully formalizes the synchronization mechanisms and the behavior of the scheduler in those systems. We study in detail their relationships to classical formalisms such as pushdown systems, Petri nets, fifo systems, and counter systems. Our main technical contributions are precise worst-case complexity results for the Parikh coverability problem for several subclasses of our model.

  9. Stabilization of Branching Queueing Networks

    CERN Document Server

    Brázdil, Tomáš

    2011-01-01

    Queueing networks are gaining attraction for the performance analysis of parallel computer systems. A Jackson network is a set of interconnected servers, where the completion of a job at server i may result in the creation of a new job for server j. We propose to extend Jackson networks by "branching" and by "control" features. Both extensions are new and substantially expand the modelling power of Jackson networks. On the other hand, the extensions raise computational questions, particularly concerning the stability of the networks, i.e, the ergodicity of the underlying Markov chain. We show for our extended model that it is decidable in polynomial time if there exists a controller that achieves stability. Moreover, if such a controller exists, one can efficiently compute a static randomized controller which stabilizes the network in a very strong sense; in particular, all moments of the queue sizes are finite.

  10. A pathwise comparison result for parallel queues

    OpenAIRE

    Moyal, Pascal

    2013-01-01

    We introduce the appropriate framework for pathwise comparison of multiple server queues under general stationary ergodic assumptions. We show in what sense it is better to have more servers for a system under FCFS ('First Come, First Served') or equivalently, more queues in a system of parallel queues under the JSW ('Join the Shortest Workload') allocation policy. This comparison result is based on the recursive representation of Kiefer and Wolfowitz, and on a non-mass conservative generaliz...

  11. MARKOVIAN QUEUES WITH CORRELATED ARRIVAL PROCESSES

    OpenAIRE

    Hunter, Jeffrey J.

    2007-01-01

    In an attempt to examine the effect of dependencies in the arrival process on the steady state queue length process in single server queueing models with exponential service time distribution, four different models for the arrival process, each with marginally distributed exponential inter-arrivals to the queueing system, are considered. Two of these models are based upon the upper and lower bounding joint distribution functions given by the Fréchet bounds for bivariate distributions with spe...

  12. Analysis of queues methods and applications

    CERN Document Server

    Gautam, Natarajan

    2012-01-01

    Introduction Analysis of Queues: Where, What, and How?Systems Analysis: Key ResultsQueueing Fundamentals and Notations Psychology in Queueing Reference Notes Exercises Exponential Interarrival and Service Times: Closed-Form Expressions Solving Balance Equations via Arc CutsSolving Balance Equations Using Generating Functions Solving Balance Equations Using Reversibility Reference Notes ExercisesExponential Interarrival and Service Times: Numerical Techniques and Approximations Multidimensional Birth and Death ChainsMultidimensional Markov Chains Finite-State Markov ChainsReference Notes Exerci

  13. Curing the queue

    NARCIS (Netherlands)

    Zonderland, Maartje Elisabeth

    2012-01-01

    In this dissertation we study several problems related to the management of healthcare and the cure of disease. In each chapter a hospital capacity distribution problem is analyzed using techniques from operations research, also known as mathematical decision theory. The problems considered are insp

  14. FROM BALLOT THEOREMS TO THE THEORY OF QUEUES,

    Science.gov (United States)

    QUEUEING THEORY, DISTRIBUTION THEORY ), (*PROBABILITY, DISTRIBUTION THEORY ), (* DISTRIBUTION THEORY , QUEUEING THEORY), (*STOCHASTIC PROCESSES... DISTRIBUTION THEORY ), SEQUENCES(MATHEMATICS), DIFFERENCE EQUATIONS, INTEGRAL TRANSFORMS, TIME, STATISTICAL FUNCTIONS

  15. Application of queueing models to multiprogrammed computer systems operating in a time-critical environment

    Science.gov (United States)

    Eckhardt, D. E., Jr.

    1979-01-01

    A model of a central processor (CPU) which services background applications in the presence of time critical activity is presented. The CPU is viewed as an M/M/1 queueing system subject to periodic interrupts by deterministic, time critical process. The Laplace transform of the distribution of service times for the background applications is developed. The use of state of the art queueing models for studying the background processing capability of time critical computer systems is discussed and the results of a model validation study which support this application of queueing models are presented.

  16. Two coupled queues with heterogeneous traffic

    NARCIS (Netherlands)

    Borst, S.C.; Boxma, O.J.; Uitert, M.J.G. van

    2001-01-01

    We consider a system with two heterogeneous traffic classes, one having light-tailed characteristics, the other one exhibiting heavy-tailed properties. When both classes are backlogged, the two corresponding queues are each served at a certain nominal rate. However, when one queue empties, the servi

  17. GPS queues with heterogeneous traffic classes

    NARCIS (Netherlands)

    Borst, Sem; Mandjes, Michel; Uitert, van Miranda

    2002-01-01

    We consider a queue fed by a mixture of light-tailed and heavy-tailed traffic. The two traffic classes are served in accordance with the generalized processor sharing (GPS) discipline. GPS-based scheduling algorithms, such as weighted fair queueing (WFQ), have emerged as an important mechanism for a

  18. Priority-queue framework: Programs

    DEFF Research Database (Denmark)

    Katajainen, Jyrki

    2009-01-01

    This is an electronic appendix to the article "Generic-programming framework for benchmarking weak queues and its relatives". The report contains the programs related to our priority-queue framework. Look at the CPH STL reports 2009-3 and 2009-4 to see examples of other component frameworks....

  19. Tandem queue with server slow-down

    NARCIS (Netherlands)

    D.I. Miretskiy; W.R.W. Scheinhardt; M.R.H. Mandjes

    2007-01-01

    We study how rare events happen in the standard two-node tandem Jackson queue and in a generalization, the socalled slow-down network, see [2]. In the latter model the service rate of the first server depends on the number of jobs in the second queue: the first server slows down if the amount of job

  20. Queues and Lévy Fluctuation Theory

    NARCIS (Netherlands)

    Dębicki, K.; Mandjes, M.

    2015-01-01

    The book provides an extensive introduction to queueing models driven by Lévy-processes as well as a systematic account of the literature on Lévy-driven queues. The objective is to make the reader familiar with the wide set of probabilistic techniques that have been developed over the past decades,

  1. Unreliable Retrial Queues in a Random Environment

    Science.gov (United States)

    2007-09-01

    state space decompositions. In 1992, Korotaev and Spivak [57] considered finite-capacity 6The output rate is usually deterministic. 23 queues with...and operating in a random environment. Automation and Remote Control, 37(12), 1828–1835. 158 57. Korotaev, I. A. and Spivak , L. R. (1992). Queueing

  2. Norton's theorem for batch routing queueing networks

    NARCIS (Netherlands)

    Bause, Falko; Boucherie, Richard J.; Buchholz, Peter

    2001-01-01

    This paper shows that the aggregation and decomposition result known as Norton’s theorem for queueing networks can be extended to a general class of batch routing queueing networks with product-form solution that allows for multiple components to simultaneously release and receive (batches of) custo

  3. Stability of Join the Shortest Queue Networks

    CERN Document Server

    Bramson, Maury

    2010-01-01

    Join the shortest queue (JSQ) refers to networks whose incoming jobs are assigned to the shortest queue from among a randomly chosen subset of the queues in the system. After completion of service at the queue, a job leaves the network. We show that, for all non- idling service disciplines and for general interarrival and service time distributions, such networks are stable when they are subcritical. We then obtain uniform bounds on the tails of the marginal distributions of the equilibria for families of such networks; these bounds are employed to show relative compactness of the marginal distributions. We also present a family of subcritical JSQ networks whose workloads in equilibrium are much larger than for the corresponding networks where each incoming job is assigned randomly to a queue. Part of this work generalizes results in Foss and Chernova [12], which applied fluid limits to study networks with the FIFO discipline. Here, we apply an appropriate Lyapunov function.

  4. Application of Vehicle Queue Management Practice in Integration and Optimization of Tobacco Warehousing and Transport Systems%车辆排队管理在烟草仓储运输整合优化中的应用

    Institute of Scientific and Technical Information of China (English)

    黄飞航; 陈之华; 陈树敏

    2014-01-01

    In this paper, we introduced the principle and application of the vehicle queue management practice in the transportation management systems, proposed a highly cost-effective method to optimize the capacity of the warehouses by putting the vehicles to balanced use, and at the end, demonstrated the effectiveness of the practice in increasing the on-time rate of the inbound arrival and loading of third party logistics vehicles in tobacco transportation.%车辆排队管理作为仓储运输整合优化的不可缺少内容,已经成为供应链一体化战略研究的重要内容之一。介绍了在运输管理系统中车辆排队管理的原理及应用。根据车辆预约的到库提货时间以及仓库每小时的额定作业量这两项重要因素,提出了一种高费效比的设计方法以优化安排车辆均衡利用仓库作业能力的目标。在实践中,该功能的应用对提高烟草运输中第三方物流车辆到库装运的准时率起到有效作用。

  5. Markov Skeleton Processes and Applications to Queueing Systems

    Institute of Scientific and Technical Information of China (English)

    Zhen-ting Hou

    2002-01-01

    In this paper, we apply the backward equations of Markov skeleton processes to queueing systems.The transient distribution of the waiting time of a GI/G/1 queueing system, the transient distribution of the length of a GI/G/N queueing system and the transient distribution of the length of queueing networks are obtained.

  6. Multimedia Traffic Queueing Analysis in High-Speed Networks: a Frequency Domain Approach

    Science.gov (United States)

    Hwang, Chia-Lin

    Multimedia traffic in high speed networks possesses correlation and burstiness properties. Classical queueing theory has generally ignored such properties by making renewal assumption on message interarrival time. Developing a new traffic theory for integration of multimedia services on high speed networks becomes absolutely essential. In this dissertation, we explore a new concept of spectral characterization of wide-band input process in high speed networks. It provides us a much richer and heterogeneous input environment, while keeping the complexity of queueing analysis tractable. The correlation nature of multimedia traffic is well captured by the input spectral functions. The queue response to the power spectrum and higher order statistics has been studied. Our study shows that the input power spectrum is the most essential statistic for queueing analysis. Further, the input power in low-frequency band has dominant impact on queueing performance, whereas the high-frequency power to a large extent can be neglected. Understanding of queue response to input spectrum provides us a great deal of knowledge to develop advanced network traffic measure theory, and to introduce effective network resource allocation policies. The interrelationship between the traffic spectral statistics and link capacity allocation in high speed network has been investigated. Finally we developed a sophisticated computational tool, called SMAQ, that can integrate traffic measurement and queueing analysis for stochastic modeling. The SMAQ tool takes a unique frequency-domain approach to combine the techniques of signal processing and performance analysis. Essentially, signal processing techniques are used to obtain the steady -state and second-order statistics of a traffic stream. The focus here is on the construction of a special class of Markov chains that can statistically match with each given traffic stream (or superposition of different traffic streams). The analytical queueing

  7. ANALYSIS OF MULTI-SERVER SINGLE QUEUE

    OpenAIRE

    2011-01-01

    Queuing properties such as expected total service time and its variance and some performance measures like the expected number of phases in the system, expected number of phases in the queue, expected number of customers in the queue, expected waiting time in the queue and in the system as well as the number of customers in the system have been derived for an  M/Ek/s: ( /FCFS) queuing model with k identified stages in series, each with average service time of . Also, numerical illustrati...

  8. ANALYSIS OF MULTI-SERVER SINGLE QUEUE

    Directory of Open Access Journals (Sweden)

    Emmanuel John Ekpenyong

    2011-04-01

    Full Text Available Queuing properties such as expected total service time and its variance and some performance measures like the expected number of phases in the system, expected number of phases in the queue, expected number of customers in the queue, expected waiting time in the queue and in the system as well as the number of customers in the system have been derived for an  M/Ek/s: ( /FCFS queuing model with k identified stages in series, each with average service time of . Also, numerical illustrations have also been used to illustrate the results.

  9. Subexponential tail equivalence of the queue length distributions of BMAP/GI/1 queues with and without retrials

    OpenAIRE

    2013-01-01

    The main contribution of this paper is to prove the subexponential tail equivalence of the stationary queue length distributions in the BMAP/GI/1 queues with and without retrials. We first present a stochastic-decomposition-like result of the stationary queue length in the BMAP/GI/1 retrial queue, which is an extension of the stochastic decomposition of the stationary queue length in the M${}^X$/GI/1 retrial queue. The stochastic-decomposition-like result shows that the stationary queue lengt...

  10. The theory of networks of single server queues and the tandem queue model

    Directory of Open Access Journals (Sweden)

    Pierre Le Gall

    1997-01-01

    Full Text Available We consider the stochastic behavior of networks of single server queues when successive service times of a given customer are highly correlated. The study is conducted in two particular cases: 1 networks in heavy traffic, and 2 networks in which all successive service times have the same value (for a given customer, in order to avoid the possibility of breaking up the busy periods. We then show how the local queueing delay (for an arbitrary customer can be derived through an equivalent tandem queue on the condition that one other local queueing delay is added: the jitter delay due to the independence of partial traffic streams.

  11. Queues and Lévy fluctuation theory

    CERN Document Server

    Dębicki, Krzysztof

    2015-01-01

    The book provides an extensive introduction to queueing models driven by Lévy-processes as well as a systematic account of the literature on Lévy-driven queues. The objective is to make the reader familiar with the wide set of probabilistic techniques that have been developed over the past decades, including transform-based techniques, martingales, rate-conservation arguments, change-of-measure, importance sampling, and large deviations. On the application side, it demonstrates how Lévy traffic models arise when modelling current queueing-type systems (as communication networks) and includes applications to finance. Queues and Lévy Fluctuation Theory will appeal to graduate/postgraduate students and researchers in mathematics, computer science, and electrical engineering. Basic prerequisites are probability theory and stochastic processes.

  12. Discrete time queues with phase dependent arrivals

    Science.gov (United States)

    Daigle, J. N.; Lee, Y.; Magalhaes, M. N.

    1994-02-01

    The queueing behavior of many communication systems is well modeled by a queueing system in which time is slotted, and the number of entities that arrive during a slot is dependent upon the state of a discrete time, discrete state Markov chain. Techniques for analyzing such systems have appeared in the literature from time to time, but distributions have been presented in only rare instances. In this paper, we present the probability generating function (PGF) for joint and marginal buffer occupancy distributions of statistical time division multiplexing systems in this class. We discuss inversion of the PGF using discrete Fourier transforms, and also discuss a simple technique for obtaining moments of the queue length distribution. Numerical results, including queue length distributions for some special cases, are presented.

  13. Investigating Dependences in Packet-queues

    Institute of Scientific and Technical Information of China (English)

    Cao Weihua(曹卫华); Girigi Deogratias; Wu Min

    2004-01-01

    Many packet communication networks carry several classes of traffic,each with its own service characteristics. The packet arrival processes from each source are also often bursty (highly variable),which can contribute to long packet delay. Ssociated dependence among successive service times and between service times and inter arrival times also can be for packet queues involving variable packet lengths. These dependence effects are demonstrated analytically by considering a multi class single server queue with batch Poisson arrival process.

  14. Simulation of queue with cyclic service in signalized intersection system

    Directory of Open Access Journals (Sweden)

    Muhammad Dermawan Mulyodiputro

    2015-03-01

    Full Text Available The simulation was implemented by modeling the queue with cyclic service in the signalized intersection system. The service policies used in this study were exhaustive and gated, the model was the M/M/1 queue, the arrival rate used was Poisson distribution and the services rate used was Exponential distribution. In the gated service policy, the server served only vehicles that came before the green signal appears at an intersection. Considered that there were 2 types of exhaustive policy in the signalized intersection system, namely normal exhaustive (vehicles only served during the green signal was still active, and exhaustive (there was the green signal duration addition at the intersection, when the green signal duration at an intersection finished. The results of this queueing simulation program were to obtain characteristics and performance of the system, i.e. average number of vehicles and waiting time of vehicles in the intersection and in the system, as well as system utilities. Then from these values, it would be known which of the cyclic service policies (normal exhaustive, exhaustive and gated was the most suitable when applied to a signalized intersection system

  15. E-Queue Mobile Application

    Directory of Open Access Journals (Sweden)

    Khong Yeen Lai

    2017-01-01

    Full Text Available Waiting in line is a common experience in daily life, whether for a table at a popular restaurant or for the service at a bank. This experience is not always pleasant for most of people because they always have to wait for a long time to be serviced. The ability to interact with waiting customers is highly desirable because it allows businesses the opportunity to optimize their existing services and offer new services to waiting customers. However, interacting with individuals waiting in a queue has been inefficient and costly because employees must either talk with each waiting customer on an ongoing basis or the business must provide high tech devices that interact with each waiting customer. Agile methodology which will be used to develop this application, it incorporates the SDLC phases starting from the Planning phase up to the Maintenance phase. End of the research, we found that majority of respondents are prefer to use the proposed system compared with current method.

  16. FIFO Queueing Policies for Packets with Heterogeneous Processing

    CERN Document Server

    Kogan, Kirill; Nikolenko, Sergey I; Sirotkin, Alexander V; Tugaryov, Denis

    2012-01-01

    We consider the problem of managing a bounded size First-In-First-Out (FIFO) queue buffer, where each incoming unit-sized packet requires several rounds of processing before it can be transmitted out. Our objective is to maximize the total number of successfully transmitted packets. We consider both push-out (when the policy is permitted to drop already admitted packets) and non-push-out cases. In particular, we provide analytical guarantees for the throughput performance of our algorithms. We further conduct a comprehensive simulation study which experimentally validates the predicted theoretical behaviour.

  17. 餐饮服务排队管理中等候区设置必要性研究%Research on the Necessity of Setting Waiting Room in Restaurant Queue Management

    Institute of Scientific and Technical Information of China (English)

    韩亚娟; 谢会

    2012-01-01

    To improve restaurant service quality and increase revenue, the issue of restaurant queue man-agement is discussed in an integrated perspective of both capacity management and the psychology of wait-ing in line. Two cases are considered: 1) there is no waiting room, leading to loss of customers; and 2) there is a waiting room, but some customers may renege because of the waiting time. With customer per-ception in waiting considered, queuing theory models are developed for both cases. To maximize profit, revenue functions for the models are derived. Then, simulation analysis is done by using Matlab. It shows that there is a strategy of setting waiting room such that maximum profit can be achieved, which indicates that the traditional view of conflict between service quality and cost can be overcome by integrating per-spective from both customers and the company. In addition, the number of dinner tables is negatively re-lated to the reneging parameter, whereas the number of waiting tables is positively related to the reneging parameter.%为了达到同时提高饭店服务质量和收益的双重目的,从顾客等待心理和饭店能力管理相结合的角度研究了饭店排队管理问题,提出了建立顾客等候区的排队管理策略.充分考虑顾客感知等待时间,采用排队论的方法分别建立了在不设置等候区时的损失制排队模型及设置等候区时的带有顾客中途退出的排队模型,并以饭店收益最大化为目标建立两种模型下的收益函数,最后用Matlab编程比较分析了两个模型.结果表明:设置等侯区能够使饭店获得更大的收益;同时,要保证利润最大,餐桌数与顾客中途退出指数成负相关,等候桌数与顾客中途退出指数成正相关,这为进行有效排队管理提供了理论依据.

  18. A Service Ratio-Based Dynamic Fair Queueing Algorithm for Packet Switching Networks

    Institute of Scientific and Technical Information of China (English)

    YIN De-bin; XIE Jian-ying; ZHANG Yan; WU Jian-zhen; SUN Hua-li

    2008-01-01

    A new weighted fair queeetng algodthm is proposed,which uses the novel flow-based service ratio parameters to schedule flows.This solves the main drawback of traditional weighted fair quoneing algorithmsthe packet-based calculation of the weight parameters.In addition,this paper proposes a novel service ratio calculation method and a queue management techaology.The former adjusts the service ratio parameters adaptively based on the dynamics of the packet lengths and then solves the unfairness problem induced by the variable packet length.The latter impgoves the utilization of the server's queue buffeg and reduces the delay jitter throegh restricting the buffer length for each flow.

  19. Stochastic Processes and Queueing Theory used in Cloud Computer Performance Simulations

    Directory of Open Access Journals (Sweden)

    Florin-Catalin ENACHE

    2015-10-01

    Full Text Available The growing character of the cloud business has manifested exponentially in the last 5 years. The capacity managers need to concentrate on a practical way to simulate the random demands a cloud infrastructure could face, even if there are not too many mathematical tools to simulate such demands.This paper presents an introduction into the most important stochastic processes and queueing theory concepts used for modeling computer performance. Moreover, it shows the cases where such concepts are applicable and when not, using clear programming examples on how to simulate a queue, and how to use and validate a simulation, when there are no mathematical concepts to back it up.

  20. Difference and differential equations with applications in queueing theory

    CERN Document Server

    Haghighi, Aliakbar Montazer

    2013-01-01

      A Useful Guide to the Interrelated Areas of Differential Equations, Difference Equations, and Queueing Models Difference and Differential Equations with Applications in Queueing Theory presents the unique connections between the methods and applications of differential equations, difference equations, and Markovian queues. Featuring a comprehensive collection of

  1. The power-series algorithm for Markovian queueing networks

    NARCIS (Netherlands)

    van den Hout, W.B.; Blanc, J.P.C.

    1994-01-01

    A newversion of the Power-Series Algorithm is developed to compute the steady-state distribution of a rich class of Markovian queueing networks. The arrival process is a Multi-queue Markovian Arrival Process, which is a multi-queue generalization of the BMAP. It includes Poisson, fork and round-robi

  2. Note---A Note on Computing Optimal Control Limits for GI/M/1 Queueing Systems

    OpenAIRE

    1987-01-01

    This note corrects an error in van Nunen and Puterman (van Nunen, J. A. E. E., M. L. Puterman. 1983. Computing optimal control limits for GI/M/s queueing systems with controlled arrivals. Management Sci. 29 725--734.) and extends some of their results to the average reward case.

  3. Fluid queues driven by an M / M / 1 / N queue

    Directory of Open Access Journals (Sweden)

    Lenin R. B.

    2000-01-01

    Full Text Available In this paper, we consider fluid queue models with infinite buffer capacity which receives and releases fluid at variable rates in such a way that the net input rate of fluid into the buffer (which is negative when fluid is flowing out of the buffer is uniquely determined by the number of customers in an M / M / 1 / N queue model (that is, the fluid queue is driven by this Markovian queue with constant arrival and service rates. We use some interesting identities of tridiagonal determinants to find analytically the eigenvalues of the underlying tridiagonal matrix and hence the distribution function of the buffer occupancy. For specific cases, we verify the results available in the literature.

  4. Fluid queues driven by an M/M/1/N queue

    Directory of Open Access Journals (Sweden)

    R. B. Lenin

    2000-01-01

    Full Text Available In this paper, we consider fluid queue models with infinite buffer capacity which receives and releases fluid at variable rates in such a way that the net input rate of fluid into the buffer (which is negative when fluid is flowing out of the buffer is uniquely determined by the number of customers in an M/M/1/N queue model (that is, the fluid queue is driven by this Markovian queue with constant arrival and service rates. We use some interesting identities of tridiagonal determinants to find analytically the eigenvalues of the underlying tridiagonal matrix and hence the distribution function of the buffer occupancy. For specific cases, we verify the results available in the literature.

  5. TRANSIENT SOLUTION FOR QUEUE-LENGTH DISTRIBUTION OF Geometry/G/1 QUEUEING MODEL

    Institute of Scientific and Technical Information of China (English)

    Luo Chuanyi; Tang Yinghui; Liu Renbin

    2007-01-01

    In this paper, the Geometry/G/1 queueing model with inter-arrival times generated by a geometric(parameter p) distribution according to a late arrival system with delayed access and service times independently distributed with distribution {gj}, j ≥ 1 is studied. By a simple method (techniques of probability decomposition, renewal process theory) that is different from the techniques used by Hunter(1983), the transient property of the queue with initial state i(i ≥ 0) is discussed. The recursion expression for u -transform of transient queue-length distribution at any time point n+ is obtained, and the recursion expression of the limiting queue length distribution is also obtained.

  6. A User Fair Core-Stateless Queue Management Algorithm%一种对用户公平的核心无状态队列管理算法

    Institute of Scientific and Technical Information of China (English)

    曾振平; 汪秉文; 汤强; 尹安

    2008-01-01

    在对"流"公平的CSFQ(Core-Stateless Fair Queueing)算法基础上进行改进,将算法设计思想由对流速率的公平分配改为对表征用户需求的效用函数的公平分配,从而提出一种对用户公平的核心无状态队列管理算法(Core-Stateless User Fair Queueing,CSUFQ),该算法能近似实现边界及核心路由器上对用户需求的最大最小公平,仿真实验证明了其效果.

  7. Ramp Metering by Limitation of Density and Queue Length

    Science.gov (United States)

    Kamel, Boumediene; Benasser, Amar; Jolly, Daniel

    2009-03-01

    As shown by many works and studies, the control of traffic flow remains the best and the efficient solution of the congestion problems. The ramp metering is a means to reduce congestion effects, it has shown his effectiveness to improve the flow and consequently to reduce the total time spent (TTS) by the vehicles in the network. In Kamel et al. [2008] the concept of flatness-based control was applied to regulate the flow at the mainline section of the road on the traffic flow model LWR. This work was preceded by Abouaïssa et al. [2006]. In this article we have proceeded the same way to set the flat output for a second order model METANET. Unfortunately we were unable to prove that the system is flat and therefore define density as flat output, but we manage to define the control laws in order to respect constraints on density and queue length at the on-ramp. The idea is to express the control variable (the outflow of the on-ramp) according to the output (density or queue length at the on-ramp), then inject it in the system. We use this control method in the ramp metering case. The first aim of the control is to keep the density in the segment where the on-ramp is connected below a density (called the target density YT) for which we have the lowest TTS, and the second aim is to keep the queue length at the on-ramp below a maximum value. In order to evaluate the controller's efficiency and applicability, a comparison is made with traditional ALINEA based controller. We illustrate this approach by comparing the cases 'no control' and 'ramp metering' for a simple network.

  8. Worst-case efficient priority queues

    Energy Technology Data Exchange (ETDEWEB)

    Brodal, G.S. [Aarhus Univ. (Denmark)

    1996-12-31

    An implementation of priority queues is presented that supports the operations MAKEQUEUE, FINDMIN, INSERT, MELD and DECREASEKEY in worst case time O(1) and DFLETEMIN and DELETE in worst case time O(log n). The space requirement is linear. The data structure presented is the first achieving this worst case performance.

  9. Queueing networks : Rare events and fast simulations

    NARCIS (Netherlands)

    Miretskiy, D.I.

    2009-01-01

    This monograph focuses on rare events. Even though they are extremely unlikely, they can still occur and then could have significant consequences. We mainly consider rare events in queueing networks. More precisely, we are interested in the probability of collecting some large number of jobs in the

  10. Funnel Heap - A Cache Oblivious Priority Queue

    DEFF Research Database (Denmark)

    Brodal, Gerth Stølting; Fagerberg, Rolf

    2002-01-01

    model. Arge et al. recently presented the first optimal cache oblivious priority queue, and demonstrated the importance of this result by providing the first cache oblivious algorithms for graph problems. Their structure uses cache oblivious sorting and selection as subroutines. In this paper, we devise...

  11. Open problems in Gaussian fluid queueing theory

    NARCIS (Netherlands)

    Dȩbicki, K.; Mandjes, M.

    2011-01-01

    We present three challenging open problems that originate from the analysis of the asymptotic behavior of Gaussian fluid queueing models. In particular, we address the problem of characterizing the correlation structure of the stationary buffer content process, the speed of convergence to

  12. Designing of vague logic based multilevel feedback queue scheduler

    Directory of Open Access Journals (Sweden)

    Supriya Raheja

    2016-03-01

    Full Text Available Multilevel feedback queue scheduler suffers from major issues of scheduling such as starvation for long tasks, fixed number of queues, and static length of time quantum in each queue. These factors directly affect the performance of the scheduler. At many times impreciseness exists in attributes of tasks which make the performance even worse. In this paper, our intent is to improve the performance by providing a solution to these issues. We design a multilevel feedback queue scheduler using a vague set which we call as VMLFQ scheduler. VMLFQ scheduler intelligently handles the impreciseness and defines the optimum number of queues as well as the optimal size of time quantum for each queue. It also resolves the problem of starvation. This paper simulates and analyzes the performance of VMLFQ scheduler with the other multilevel feedback queue techniques using MatLab.

  13. A comparison of queueing, cluster and distributed computing systems

    Science.gov (United States)

    Kaplan, Joseph A.; Nelson, Michael L.

    1993-01-01

    Using workstation clusters for distributed computing has become popular with the proliferation of inexpensive, powerful workstations. Workstation clusters offer both a cost effective alternative to batch processing and an easy entry into parallel computing. However, a number of workstations on a network does not constitute a cluster. Cluster management software is necessary to harness the collective computing power. A variety of cluster management and queuing systems are compared: Distributed Queueing Systems (DQS), Condor, Load Leveler, Load Balancer, Load Sharing Facility (LSF - formerly Utopia), Distributed Job Manager (DJM), Computing in Distributed Networked Environments (CODINE), and NQS/Exec. The systems differ in their design philosophy and implementation. Based on published reports on the different systems and conversations with the system's developers and vendors, a comparison of the systems are made on the integral issues of clustered computing.

  14. [Active management of labor].

    Science.gov (United States)

    Ruiz Ortiz, E; Villalobos Román, M; Flores Murrieta, G; Sotomayor Alvarado, L

    1991-01-01

    Eighty three primigravidae patients at the end of latency labor, erased cervix, 3 cm dilation, vertex presentation and adequate pelvis, were studied. Two groups were formed: 53 patients in the study group, who received active management of labor, and 30 patients in the control group, treated in the traditional way. In all the patients a graphic recording of labor, was carried out; it included all the events, and as labor advanced, a signoidal curve of cervical dilatation, was registered, as well as the hyperbolic one for presentation descent. The study group received the method in a systematized manner, as follows: 1. Peridular block. 2. Amniotomy. 3. IV oxytocin one hour after amniotomy. 4. FCR monitoring. 5. Detection of dystocia origin. Materno-fetal morbidity was registered in both groups, as well as cesarean section rate, instrumental delivery and its indications, labor duration, and time of stay in labor room. Diminution of above intems and opportune detection of dystocia, were determined. It was concluded that a constructive action plan, starting at hospital admission in most healthy women, allows a normal delivery of brief duration.

  15. Packet Queueing Delay in Resilient Packet Ring Network Nodes

    Institute of Scientific and Technical Information of China (English)

    史国炜; 方红波; 曲建岭; 曾烈光

    2004-01-01

    The packet queueing delay is one of the most important performance measures of a data network and is also a significant factor to be considered in the scheduling buffer design for a network node.This paper presents a traffic queueing model for resilient packet ring (RPR) networks and a method for quantitatively analyzing queueing delays in RPR nodes.The method was used to calculate the average queueing delays of different priority traffic for different transit queue modes.The simulations show that,in the transmit direction,lower priority traffic is delayed more than higher priority traffic,and that Class-A traffic is delayed more in a single-queue ring than in a dual-queue ring.In the transit direction,the secondary transit buffer in the dual-queue ring contributes more to the traffic delay than the primary transit buffer in the single-queue ring,which in turn causes more delay than the primary transit buffer in the dual-queue ring.

  16. Autonomous Hybrid Priority Queueing for Scheduling Residential Energy Demands

    Science.gov (United States)

    Kalimullah, I. Q.; Shamroukh, M.; Sahar, N.; Shetty, S.

    2017-05-01

    The advent of smart grid technologies has opened up opportunities to manage the energy consumption of the users within a residential smart grid system. Demand response management is particularly being employed to reduce the overall load on an electricity network which could in turn reduce outages and electricity costs. The objective of this paper is to develop an intelligible scheduler to optimize the energy available to a micro grid through hybrid queueing algorithm centered around the consumers’ energy demands. This is achieved by shifting certain schedulable load appliances to light load hours. Various factors such as the type of demand, grid load, consumers’ energy usage patterns and preferences are considered while formulating the logical constraints required for the algorithm. The algorithm thus obtained is then implemented in MATLAB workspace to simulate its execution by an Energy Consumption Scheduler (ECS) found within smart meters, which automatically finds the optimal energy consumption schedule tailor made to fit each consumer within the micro grid network.

  17. Priority Queue Based on Multilevel Prefix Tree

    CERN Document Server

    Planeta, David S

    2007-01-01

    Tree structures are very often used data structures. Among ordered types of trees there are many variants whose basic operations such as insert, delete, search, delete-min are characterized by logarithmic time complexity. In the article I am going to present the structure whose time complexity for each of the above operations is $O(\\frac{M}{K} + K)$, where M is the size of data type and K is constant properly matching the size of data type. Properly matched K will make the structure function as a very effective Priority Queue. The structure size linearly depends on the number and size of elements. PTrie is a clever combination of the idea of prefix tree -- Trie, structure of logarithmic time complexity for insert and remove operations, doubly linked list and queues.

  18. Theoretical description of metabolism using queueing theory.

    Science.gov (United States)

    Evstigneev, Vladyslav P; Holyavka, Marina G; Khrapatiy, Sergii V; Evstigneev, Maxim P

    2014-09-01

    A theoretical description of the process of metabolism has been developed on the basis of the Pachinko model (see Nicholson and Wilson in Nat Rev Drug Discov 2:668-676, 2003) and the queueing theory. The suggested approach relies on the probabilistic nature of the metabolic events and the Poisson distribution of the incoming flow of substrate molecules. The main focus of the work is an output flow of metabolites or the effectiveness of metabolism process. Two simplest models have been analyzed: short- and long-living complexes of the source molecules with a metabolizing point (Hole) without queuing. It has been concluded that the approach based on queueing theory enables a very broad range of metabolic events to be described theoretically from a single probabilistic point of view.

  19. Large deviations for tandem queueing systems

    Directory of Open Access Journals (Sweden)

    Roland L. Dobrushin

    1994-01-01

    Full Text Available The crude asymptotics of the large delay probability in a tandem queueing system is considered. The main result states that one of the two channels in the tandem system defines the crude asymptotics. The constant that determines the crude asymptotics is given. The results obtained are based on the large deviation principle for random processes with independent increments on an infinite interval recently established by the authors.

  20. Schedulers with load-store queue awareness

    Science.gov (United States)

    Chen, Tong; Eichenberger, Alexandre E.; Jacob, Arpith C.; Sura, Zehra N.

    2017-01-24

    In one embodiment, a computer-implemented method includes tracking a size of a load-store queue (LSQ) during compile time of a program. The size of the LSQ is time-varying and indicates how many memory access instructions of the program are on the LSQ. The method further includes scheduling, by a computer processor, a plurality of memory access instructions of the program based on the size of the LSQ.

  1. Schedulers with load-store queue awareness

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Tong; Eichenberger, Alexandre E.; Jacob, Arpith C.; Sura, Zehra N.

    2017-01-24

    In one embodiment, a computer-implemented method includes tracking a size of a load-store queue (LSQ) during compile time of a program. The size of the LSQ is time-varying and indicates how many memory access instructions of the program are on the LSQ. The method further includes scheduling, by a computer processor, a plurality of memory access instructions of the program based on the size of the LSQ.

  2. Schedulers with load-store queue awareness

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Tong; Eichenberger, Alexandre E.; Jacob, Arpith C.; Sura, Zehra N.

    2017-02-07

    In one embodiment, a computer-implemented method includes tracking a size of a load-store queue (LSQ) during compile time of a program. The size of the LSQ is time-varying and indicates how many memory access instructions of the program are on the LSQ. The method further includes scheduling, by a computer processor, a plurality of memory access instructions of the program based on the size of the LSQ.

  3. Control of Entry to a Queueing System

    Science.gov (United States)

    1979-11-01

    University of New Mexico . Zacks, S. and Yadin, M. (1970). Analytic characterization of the optimal control of a queueing system. J. Appl. Prob. 7, pp. 617...WILL. BE RH OF SYST!!¶. 29q VI~iSIO!I &A (2501)) , BE (101 ,TDOLD 50) c DIMEISION 0’P AA XW 3 5B vT FS !XNC~rtY IT MY Nf AND N ?OR VINO c TIRESE AP

  4. Cost performance satellite design using queueing theory

    Science.gov (United States)

    Hein, G. F.

    1975-01-01

    The Poisson arrival model was used to determine the effects of limiting the number of channels for a disaster warning satellite. State probabilities and delay probabilities were estimated for several values of the number of channels (C) for arrival and service rates obtained from disaster warnings issued by the National Weather Service. The results predicted by the queueing model were compared with the results of a digital computer simulation.

  5. Influence of queue propagation and dissipation on route travel times

    DEFF Research Database (Denmark)

    Raovic, Nevena

    The representation of queue spillbacks in a congested network plays an important role in transportation network analysis. Dynamic network loading (DNL) models that are able to represent queue spillbacks suggest two approaches to represent traffic flow propagation. One is based on the kinemtic wave...... into account (Bliemer, 2008). Yperman (2007) indicates that there is a significant difference in queue-propagation and queue-dissipation between the LTM and DQM. This results in different route travel times, and can further affect route choice. In this paper, different approaches to represent queue propagation...... and dissipation through the CTM, LTM and DQM are studied. A simple network allows to show how these approaches influence route travel time. Furthermore, the possibility of changing the existing DQM is considered in order to more realistically represent queue propagation and dissipation, which would lead to more...

  6. Control of a heterogeneous two-server exponential queueing system

    Science.gov (United States)

    Larsen, R. L.; Agrawala, A. K.

    1983-01-01

    A dynamic control policy known as 'threshold queueing' is defined for scheduling customers from a Poisson source on a set of two exponential servers with dissimilar service rates. The slower server is invoked in response to instantaneous system loading as measured by the length of the queue of waiting customers. In a threshold queueing policy, a specific queue length is identified as a 'threshold,' beyond which the slower server is invoked. The slower server remains busy until it completes service on a customer and the queue length is less than its invocation threshold. Markov chain analysis is employed to analyze the performance of the threshold queueing policy and to develop optimality criteria. It is shown that probabilistic control is suboptimal to minimize the mean number of customers in the system. An approximation to the optimum policy is analyzed which is computationally simple and suffices for most operational applications.

  7. Scaling of avalanche queues in directed dissipative sandpiles

    Science.gov (United States)

    Tadic; Priezzhev

    2000-09-01

    Using numerical simulations and analytical methods we study a two-dimensional directed sandpile automaton with nonconservative random defects (concentration c) and varying driving rate r. The automaton is driven only at the top row and driving rate is measured by the number of added particles per time step of avalanche evolution. The probability distribution of duration of elementary avalanches at zero driving rate is exactly given by P1(t,c)=t(-3/2) exp[t ln(1-c)]. For driving rates in the interval 0 server queue in the queue theory. We study scaling properties of the busy period and dissipated energy of sequences of noninterrupted activity. In the limit c-->0 and varying linear system size Lqueues are characterized by a multifractal scaling and we determine the corresponding spectral functions. For L>1/c increasing the driving rate somewhat compensates for the energy losses at defects above the line r approximately sqrt[c]. The scaling exponents of the distributions in this region of phase diagram vary approximately linearly with the driving rate. Using properties of recurrent states and the probability theory we determine analytically the exact upper bound of the probability distribution of busy periods. In the case of conservative dynamics c=0 the probability of a continuous flow increases as F(infinity) approximately r(2) for small driving rates.

  8. Invasion percolation on a tree and queueing models.

    Science.gov (United States)

    Gabrielli, A; Caldarelli, G

    2009-04-01

    We study the properties of the Barabási model of queuing [A.-L. Barabási, Nature (London) 435, 207 (2005); J. G. Oliveira and A.-L. Barabási, Nature (London) 437, 1251 (2005)] in the hypothesis that the number of tasks grows with time steadily. Our analytical approach is based on two ingredients. First we map exactly this model into an invasion percolation dynamics on a Cayley tree. Second we use the theory of biased random walks. In this way we obtain the following results: the stationary-state dynamics is a sequence of causally and geometrically connected bursts of execution activities with scale-invariant size distribution. We recover the correct waiting-time distribution PW(tau) approximately tau(-3/2) at the stationary state (as observed in different realistic data). Finally we describe quantitatively the dynamics out of the stationary state quantifying the power-law slow approach to stability both in single dynamical realization and in average. These results can be generalized to the case of a stochastic increase in the queue length in time with limited fluctuations. As a limit case we recover the situation in which the queue length fluctuates around a constant average value.

  9. The ×-BMAP/G/1 Queueing Model: Queue Contents and Delay Analysis

    Directory of Open Access Journals (Sweden)

    Bart Steyaert

    2011-01-01

    Full Text Available We consider a single-server discrete-time queueing system with N sources, where each source is modelled as a correlated Markovian customer arrival process, and the customer service times are generally distributed. We focus on the analysis of the number of customers in the queue, the amount of work in the queue, and the customer delay. For each of these quantities, we will derive an expression for their steady-state probability generating function, and from these results, we derive closed-form expressions for key performance measures such as their mean value, variance, and tail distribution. A lot of emphasis is put on finding closed-form expressions for these quantities that reduce all numerical calculations to an absolute minimum.

  10. 考虑展宽段的路段排队长度检测算法%Road Queue Length Detection Algorithm Considering Stretching Segment

    Institute of Scientific and Technical Information of China (English)

    杨雷; 吕鹏

    2012-01-01

    为了实时估计路段车辆排队长度,利用铺设在路段上的检测器,提出了一种车辆排队估计方法,对车辆排队进行实时跟踪.该方法考虑了一般的道路拓扑结构,路段排队的演化过程分为四个阶段:初始排队阶段、排队蔓延阶段、排队上溯阶段和堵塞路段阶段,不同阶段的排队利用不同的信息,通过不同的模型进行推算,通过实地调查验证,可以高效实时追踪路段排队的演化.%In order to estimate real-time queue length and provide information for traffic management, an algorithm was proposed. This method uses detector lay under road surface to track vehicle queue. General road topology was considered. Queue evolution was divided into four stages: initial queue stage, queue propagation stage, queue spillover stage, and fully congested stage. Different information was used to estimate queue length in different stages. The field test proves the effectiveness of the method.

  11. New Approach to Measuring Traffic Queue at Intersections

    Institute of Scientific and Technical Information of China (English)

    SONG Lei; SHI Zhong-ke

    2008-01-01

    To measure the length of traffic queue, a vehicle motion model at intersections was built, and based on it the effective traffic queue was defined. Color images segmentation and frame differencing technique were used to detect the foreground and the moving vehicles by detecting regions of the images, and then measure the length of effective traffic queue. By processing the image sequence acquired at certain intersection, the results prove that it is able to work out the traffic queue effectively by using the two techniques.

  12. TRANSIENT QUEUE SIZE DISTRIBUTION SOLUTION OF GEOM/G/1 QUEUE WITH FEEDBACK-A RECURSIVE METHOD

    Institute of Scientific and Technical Information of China (English)

    Chuanyi LUO; Yinghui TANG; Cailiang LI

    2009-01-01

    This paper considers the Geom/G/1 queueing model with feedback according to a late arrival system with delayed access (LASDA). Using recursive method, this paper studies the transient property of the queue size from the initial state N(0+) = I. Some new results about the recursive expression of the transient queue size distribution at any epoch n+ and the recursive formulae of the equilibrium distribution are obtained, Furthermore, the recursive formulae of the equilibrium queue size distribution at epoch n-, and n are obtained, too. The important relations between stationary queue size distributions at different epochs are discovered (being different from the relations given in M/G/1 queueing system). The model discussed in this paper can be widely applied in all kinds of communications and computer network.

  13. Environmental management activities

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-07-01

    The Office of Environmental Management (EM) has been delegated the responsibility for the Department of Energy`s (DOE`s) cleanup of the nuclear weapons complex. The nature and magnitude of the waste management and environmental remediation problem requires the identification of technologies and scientific expertise from domestic and foreign sources. Within the United States, operational DOE facilities, as well as the decontamination and decommissioning of inactive facilities, have produced significant amounts of radioactive, hazardous, and mixed wastes. In order to ensure worker safety and the protection of the public, DOE must: (1) assess, remediate, and monitor sites and facilities; (2) store, treat, and dispose of wastes from past and current operations; and (3) develop and implement innovative technologies for environmental restoration and waste management. The EM directive necessitates looking beyond domestic capabilities to technological solutions found outside US borders. Following the collapse of the Soviet regime, formerly restricted elite Soviet scientific expertise became available to the West. EM has established a cooperative technology development program with Russian scientific institutes that meets domestic cleanup objectives by: (1) identifying and accessing Russian EM-related technologies, thereby leveraging investments and providing cost-savings; (2) improving access to technical information, scientific expertise, and technologies applicable to EM needs; and (3) increasing US private sector opportunities in Russian in EM-related areas.

  14. Environmental management activities

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-07-01

    The Office of Environmental Management (EM) has been delegated the responsibility for the Department of Energy`s (DOE`s) cleanup of the nuclear weapons complex. The nature and magnitude of the waste management and environmental remediation problem requires the identification of technologies and scientific expertise from domestic and foreign sources. Within the United States, operational DOE facilities, as well as the decontamination and decommissioning of inactive facilities, have produced significant amounts of radioactive, hazardous, and mixed wastes. In order to ensure worker safety and the protection of the public, DOE must: (1) assess, remediate, and monitor sites and facilities; (2) store, treat, and dispose of wastes from past and current operations; and (3) develop and implement innovative technologies for environmental restoration and waste management. The EM directive necessitates looking beyond domestic capabilities to technological solutions found outside US borders. Following the collapse of the Soviet regime, formerly restricted elite Soviet scientific expertise became available to the West. EM has established a cooperative technology development program with Russian scientific institutes that meets domestic cleanup objectives by: (1) identifying and accessing Russian EM-related technologies, thereby leveraging investments and providing cost-savings; (2) improving access to technical information, scientific expertise, and technologies applicable to EM needs; and (3) increasing US private sector opportunities in Russian in EM-related areas.

  15. The Completion of Non-Steady-State Queue Model on The Queue System in Dr. Yap Eye Hospital Yogyakarta

    Science.gov (United States)

    Helmi Manggala Putri, Arum; Subekti, Retno; Binatari, Nikenasih

    2017-06-01

    Dr Yap Eye Hospital Yogyakarta is one of the most popular reference eye hospitals in Yogyakarta. There are so many patients coming from other cities and many of them are BPJS (Badan Penyelenggara Jaminan Sosial, Social Security Administrative Bodies) patients. Therefore, it causes numerous BPJS patients were in long queue at counter C of the registration section so that it needs to be analysed using queue system. Queue system analysis aims to give queue model overview and determine its effectiveness measure. The data collecting technique used in this research are by interview and observation. After getting the arrival data and the service data of BPJS patients per 5 minutes, the next steps are investigating steady-state condition, examining the Poisson distribution, determining queue models, and counting the effectiveness measure. Based on the result of data observation on Tuesday, February 16th, 2016, it shows that the queue system at counter C has (M/M/1):(GD/∞/∞) queue model. The analysis result in counter C shows that the queue system is a non-steady-state condition. Three ways to cope a non-steady-state problem on queue system are proposed in this research such as bounding the capacity of queue system, adding the servers, and doing Monte Carlo simulation. The queue system in counter C will reach steady-state if the capacity of patients is not more than 52 BPJS patients or adding one more server. By using Monte Carlo simulation, it shows that the effectiveness measure of the average waiting time for BPJS patients in counter C is 36 minutes 65 seconds. In addition, the average queue length of BPJS patients is 11 patients.

  16. Using simulation in out-patient queues: a case study.

    Science.gov (United States)

    Huarng, F; Lee, M H

    1996-01-01

    Overwork and overcrowding in some periods was an important issue for the out-patient department of a local hospital in Chia-Yi in Taiwan. The hospital administrators wanted to manage the patient flow effectively. Describes a study which focused on the utilization of doctors and staff in the out-patient department, the time spent in the hospital by an out-patient, and the length of the out-patient queue. Explains how a computer simulation model was developed to study how changes in the appointment system, staffing policies and service units would affect the observed bottleneck. The results show that the waiting time was greatly reduced and the workload of the doctor was also reduced to a reasonable rate in the overwork and overcrowding periods.

  17. Environmental Management vitrification activities

    Energy Technology Data Exchange (ETDEWEB)

    Krumrine, P.H. [Waste Policy Institute, Gaithersburg, MD (United States)

    1996-05-01

    Both the Mixed Waste and Landfill Stabilization Focus Areas as part of the Office of Technology Development efforts within the Department of Energy`s (DOE) Environmental Management (EM) Division have been developing various vitrification technologies as a treatment approach for the large quantities of transuranic (TRU), TRU mixed and Mixed Low Level Wastes that are stored in either landfills or above ground storage facilities. The technologies being developed include joule heated, plasma torch, plasma arc, induction, microwave, combustion, molten metal, and in situ methods. There are related efforts going into development glass, ceramic, and slag waste form windows of opportunity for the diverse quantities of heterogeneous wastes needing treatment. These studies look at both processing parameters, and long term performance parameters as a function of composition to assure that developed technologies have the right chemistry for success.

  18. Optimal Multi-Server Allocation to Parallel Queues With Independent Random Queue-Server Connectivity

    CERN Document Server

    Al-Zubaidy, Hussein; Viniotis, Yannis

    2011-01-01

    We investigate an optimal scheduling problem in a discrete-time system of L parallel queues that are served by K identical, randomly connected servers. Each queue may be connected to a subset of the K servers during any given time slot. This model has been widely used in studies of emerging 3G/4G wireless systems. We introduce the class of Most Balancing (MB) policies and provide their mathematical characterization. We prove that MB policies are optimal; we de?ne optimality as minimization, in stochastic ordering sense, of a range of cost functions of the queue lengths, including the process of total number of packets in the system. We use stochastic coupling arguments for our proof. We introduce the Least Connected Server First/Longest Connected Queue (LCSF/LCQ) policy as an easy-to-implement approximation of MB policies. We conduct a simulation study to compare the performance of several policies. The simulation results show that: (a) in all cases, LCSF/LCQ approximations to the MB policies outperform the o...

  19. Optimal queue-size scaling in switched networks

    NARCIS (Netherlands)

    Shah, D.; Walton, N.S.; Zhong, Y.J.

    2014-01-01

    We consider a switched (queuing) network in which there are constraints on which queues may be served simultaneously; such networks have been used to effectively model input-queued switches and wireless networks. The scheduling policy for such a network specifies which queues to serve at any point i

  20. On Markovian multi-class, multi-server queueing

    NARCIS (Netherlands)

    Harten, van A.; Sleptchenko, A.

    2003-01-01

    Multi-class multi-server queueing problems are a generalisation of the well-known M/M/k queue to arrival processes with clients of N types that require exponentially distributed service with different average service times. In this paper, we give a procedure to construct exact solutions of the stati

  1. A fixed-size batch service queue with vacations

    Directory of Open Access Journals (Sweden)

    Ho Woo Lee

    1996-01-01

    Full Text Available The paper deals with batch service queues with vacations in which customers arrive according to a Poisson process. Decomposition method is used to derive the queue length distributions both for single and multiple vacation cases. The authors look at other decomposition techniques and discuss some related open problems.

  2. Monotonicity properties for multi-class queueing systems

    NARCIS (Netherlands)

    Verloop, I.M. (Maaike); Ayesta, U.; Borst, S.C.

    2008-01-01

    We study multi-dimensional stochastic processes that arise in queueing models used in the performance evaluation of wired and wireless networks. The evolution of the stochastic process is determined by the scheduling policy used in the associated queueing network. For general arrival and service pro

  3. 2-Layered Architecture of Vague Logic Based Multilevel Queue Scheduler

    Directory of Open Access Journals (Sweden)

    Supriya Raheja

    2014-01-01

    Full Text Available In operating system the decisions which CPU scheduler makes regarding the sequence and length of time the task may run are not easy ones, as the scheduler has only a limited amount of information about the tasks. A good scheduler should be fair, maximizes throughput, and minimizes response time of system. A scheduler with multilevel queue scheduling partitions the ready queue into multiple queues. While assigning priorities, higher level queues always get more priorities over lower level queues. Unfortunately, sometimes lower priority tasks get starved, as the scheduler assures that the lower priority tasks may be scheduled only after the higher priority tasks. While making decisions scheduler is concerned only with one factor, that is, priority, but ignores other factors which may affect the performance of the system. With this concern, we propose a 2-layered architecture of multilevel queue scheduler based on vague set theory (VMLQ. The VMLQ scheduler handles the impreciseness of data as well as improving the starvation problem of lower priority tasks. This work also optimizes the performance metrics and improves the response time of system. The performance is evaluated through simulation using MatLab. Simulation results prove that the VMLQ scheduler performs better than the classical multilevel queue scheduler and fuzzy based multilevel queue scheduler.

  4. Closed Queueing Networks Under Congestion: Nonbottleneck Independence and Bottleneck Convergence

    NARCIS (Netherlands)

    Anselmi, J.; D'Auria, B.; Walton, N.

    2013-01-01

    We analyze the behavior of closed multiclass product-form queueing networks when the number of customers grows to infinity and remains proportionate on each route (or class). First, we focus on the stationary behavior and prove the conjecture that the stationary distribution at nonbottleneck queues

  5. Queues with waiting time dependent service

    DEFF Research Database (Denmark)

    Bekker, R.; Koole, G. M.; Nielsen, Bo Friis

    2011-01-01

    Motivated by service levels in terms of the waiting-time distribution seen, for instance, in call centers, we consider two models for systems with a service discipline that depends on the waiting time. The first model deals with a single server that continuously adapts its service rate based...... on the waiting time of the first customer in line. In the second model, one queue is served by a primary server which is supplemented by a secondary server when the waiting of the first customer in line exceeds a threshold. Using level crossings for the waiting-time process of the first customer in line, we...

  6. Decomposability queueing and computer system applications

    CERN Document Server

    Courtois, P J

    1977-01-01

    Decomposability: Queueing and Computer System Applications presents a set of powerful methods for systems analysis. This 10-chapter text covers the theory of nearly completely decomposable systems upon which specific analytic methods are based.The first chapters deal with some of the basic elements of a theory of nearly completely decomposable stochastic matrices, including the Simon-Ando theorems and the perturbation theory. The succeeding chapters are devoted to the analysis of stochastic queuing networks that appear as a type of key model. These chapters also discuss congestion problems in

  7. Queueing phase transition: theory of translation.

    Science.gov (United States)

    Romano, M Carmen; Thiel, Marco; Stansfield, Ian; Grebogi, Celso

    2009-05-15

    We study the current of particles on a lattice, where to each site a different hopping probability has been associated and the particles can move only in one direction. We show that the queueing of the particles behind a slow site can lead to a first-order phase transition, and derive analytical expressions for the configuration of slow sites for this to happen. We apply this stochastic model to describe the translation of mRNAs. We show that the first-order phase transition, uncovered in this work, is the process responsible for the classification of the proteins having different biological functions.

  8. Queues with Dropping Functions and General Arrival Processes.

    Science.gov (United States)

    Chydzinski, Andrzej; Mrozowski, Pawel

    2016-01-01

    In a queueing system with the dropping function the arriving customer can be denied service (dropped) with the probability that is a function of the queue length at the time of arrival of this customer. The potential applicability of such mechanism is very wide due to the fact that by choosing the shape of this function one can easily manipulate several performance characteristics of the queueing system. In this paper we carry out analysis of the queueing system with the dropping function and a very general model of arrival process--the model which includes batch arrivals and the interarrival time autocorrelation, and allows for fitting the actual shape of the interarrival time distribution and its moments. For such a system we obtain formulas for the distribution of the queue length and the overall customer loss ratio. The analytical results are accompanied with numerical examples computed for several dropping functions.

  9. Career management: an active process.

    Science.gov (United States)

    Mackowiak, J; Eckel, F M

    1985-03-01

    The self-assessment, goal-setting, and career-planning techniques of career management are discussed, and the organization's role in career management is discussed. Career management is a planned process, initiated and carried out by an individual with the assistance of others. Because work and nonwork activities are so interrelated, career and life management planning can maximize a pharmacist's personal success. The career- and life-management process begins with the development of a personal definition of success. A self-assessment must be made of one's values, needs, interests, and activities. The next step of the process involves setting goals and establishing a plan or strategy to achieve them. Establishing a career path requires researching alternate career goals. Career competencies are identified that can increase an employee's chances of success. The employer shares the responsibility for career development through coaching, job structuring, and keeping the employee aware of constraints. Through the integration of the roles of the individual and the organization in the career-management process, employees can optimize their contribution to an organization. Pharmacists can successfully manage their careers by applying the techniques of self-assessment, goal setting, and career planning.

  10. Simple Queueing Model Applied to the City of Portland

    Science.gov (United States)

    Simon, Patrice M.; Esser, Jörg; Nagel, Kai

    We use a simple traffic micro-simulation model based on queueing dynamics as introduced by Gawron [IJMPC, 9(3):393, 1998] in order to simulate traffic in Portland/Oregon. Links have a flow capacity, that is, they do not release more vehicles per second than is possible according to their capacity. This leads to queue built-up if demand exceeds capacity. Links also have a storage capacity, which means that once a link is full, vehicles that want to enter the link need to wait. This leads to queue spill-back through the network. The model is compatible with route-plan-based approaches such as TRANSIMS, where each vehicle attempts to follow its pre-computed path. Yet, both the data requirements and the computational requirements are considerably lower than for the full TRANSIMS microsimulation. Indeed, the model uses standard emme/2 network data, and runs about eight times faster than real time with more than 100 000 vehicles simultaneously in the simulation on a single Pentium-type CPU. We derive the model's fundamental diagrams and explain it. The simulation is used to simulate traffic on the emme/2 network of the Portland (Oregon) metropolitan region (20 000 links). Demand is generated by a simplified home-to-work destination assignment which generates about half a million trips for the morning peak. Route assignment is done by iterative feedback between micro-simulation and router. An iterative solution of the route assignment for the above problem can be achieved within about half a day of computing time on a desktop workstation. We compare results with field data and with results of traditional assignment runs by the Portland Metropolitan Planning Organization. Thus, with a model such as this one, it is possible to use a dynamic, activities-based approach to transportation simulation (such as in TRANSIMS) with affordable data and hardware. This should enable systematic research about the coupling of demand generation, route assignment, and micro

  11. Data Model Approach And Markov Chain Based Analysis Of Multi-Level Queue Scheduling

    Directory of Open Access Journals (Sweden)

    Diwakar Shukla

    2010-01-01

    Full Text Available There are many CPU scheduling algorithms inliterature like FIFO, Round Robin, Shortest-Job-First and so on.The Multilevel-Queue-Scheduling is superior to these due to itsbetter management of a variety of processes. In this paper, aMarkov chain model is used for a general setup of Multilevelqueue-scheduling and the scheduler is assumed to performrandom movement on queue over the quantum of time.Performance of scheduling is examined through a rowdependent data model. It is found that with increasing value of αand d, the chance of system going over the waiting state reduces.At some of the interesting combinations of α and d, it diminishesto zero, thereby, provides us some clue regarding better choice ofqueues over others for high priority jobs. It is found that ifqueue priorities are added in the scheduling intelligently thenbetter performance could be obtained. Data model helpschoosing appropriate preferences.

  12. Performance optimization of queueing systems with perturbation realization

    KAUST Repository

    Xia, Li

    2012-04-01

    After the intensive studies of queueing theory in the past decades, many excellent results in performance analysis have been obtained, and successful examples abound. However, exploring special features of queueing systems directly in performance optimization still seems to be a territory not very well cultivated. Recent progresses of perturbation analysis (PA) and sensitivity-based optimization provide a new perspective of performance optimization of queueing systems. PA utilizes the structural information of queueing systems to efficiently extract the performance sensitivity information from a sample path of system. This paper gives a brief review of PA and performance optimization of queueing systems, focusing on a fundamental concept called perturbation realization factors, which captures the special dynamic feature of a queueing system. With the perturbation realization factors as building blocks, the performance derivative formula and performance difference formula can be obtained. With performance derivatives, gradient-based optimization can be derived, while with performance difference, policy iteration and optimality equations can be derived. These two fundamental formulas provide a foundation for performance optimization of queueing systems from a sensitivity-based point of view. We hope this survey may provide some inspirations on this promising research topic. © 2011 Elsevier B.V. All rights reserved.

  13. DIRAC pilot framework and the DIRAC Workload Management System

    Science.gov (United States)

    Casajus, Adrian; Graciani, Ricardo; Paterson, Stuart; Tsaregorodtsev, Andrei; LHCb DIRAC Team

    2010-04-01

    DIRAC, the LHCb community Grid solution, has pioneered the use of pilot jobs in the Grid. Pilot Jobs provide a homogeneous interface to an heterogeneous set of computing resources. At the same time, Pilot Jobs allow to delay the scheduling decision to the last moment, thus taking into account the precise running conditions at the resource and last moment requests to the system. The DIRAC Workload Management System provides one single scheduling mechanism for jobs with very different profiles. To achieve an overall optimisation, it organizes pending jobs in task queues, both for individual users and production activities. Task queues are created with jobs having similar requirements. Following the VO policy a priority is assigned to each task queue. Pilot submission and subsequent job matching are based on these priorities following a statistical approach.

  14. Probability, statistics and queueing theory, with computer science applications

    CERN Document Server

    Allen, Arnold O

    1978-01-01

    Probability, Statistics, and Queueing Theory: With Computer Science Applications focuses on the use of statistics and queueing theory for the design and analysis of data communication systems, emphasizing how the theorems and theory can be used to solve practical computer science problems. This book is divided into three parts. The first part discusses the basic concept of probability, probability distributions commonly used in applied probability, and important concept of a stochastic process. Part II covers the discipline of queueing theory, while Part III deals with statistical inference. T

  15. A unifying property for distribution-sensitive priority queues

    DEFF Research Database (Denmark)

    Elmasry, Amr Ahmed Abd Elmoneim; Farzan, Arash; Iacono, John

    2011-01-01

    , before) the last access of x and are still in the priority queue at the time when the corresponding operation is performed. Our priority queue then has both the working-set and the queueish properties; and, more strongly, it satisfies these properties in the worst-case sense. We also argue...... that these bounds are the best possible with respect to the considered measures. Moreover, we modify our priority queue to satisfy a new unifying property - the time-finger property - which encapsulates both the working-set and the queueish properties. In addition, we prove that the working-set bound...

  16. Transient analysis of a queue with queue-length dependent MAP and its application to SS7 network

    Directory of Open Access Journals (Sweden)

    Bong Dae Choi

    1999-01-01

    Full Text Available We analyze the transient behavior of a Markovian arrival queue with congestion control based on a double of thresholds, where the arrival process is a queue-length dependent Markovian arrival process. We consider Markov chain embedded at arrival epochs and derive the one-step transition probabilities. From these results, we obtain the mean delay and the loss probability of the nth arrival packet. Before we study this complex model, first we give a transient analysis of an MAP/M/1 queueing system without congestion control at arrival epochs. We apply our result to a signaling system No. 7 network with a congestion control based on thresholds.

  17. Care on demand in nursing homes: a queueing theoretic approach.

    Science.gov (United States)

    van Eeden, Karin; Moeke, Dennis; Bekker, René

    2016-09-01

    Nursing homes face ever-tightening healthcare budgets and are searching for ways to increase the efficiency of their healthcare processes without losing sight of the needs of their residents. Optimizing the allocation of care workers plays a key role in this search as care workers are responsible for the daily care of the residents and account for a significant proportion of the total labor expenses. In practice, the lack of reliable data makes it difficult for nursing home managers to make informed staffing decisions. The focus of this study lies on the 'care on demand' process in a Belgian nursing home. Based on the analysis of real-life 'call button' data, a queueing model is presented which can be used by nursing home managers to determine the number of care workers required to meet a specific service level. Based on numerical experiments an 80/10 service level is proposed for this nursing home, meaning that at least 80 percent of the clients should receive care within 10 minutes after a call button request. To the best of our knowledge, this is the first attempt to develop a quantitative model for the 'care on demand' process in a nursing home.

  18. A single-server queue with random accumulation level

    Directory of Open Access Journals (Sweden)

    Jewgeni H. Dshalalow

    1991-01-01

    The author establishes an ergodicity criterion for both the queueing process with continuous time parameter and the imbedded process. Under this criterion, the author obtains explicit formulas for the stationary distributions of both processes by using semi-regenerative techniques.

  19. Opportunistic Channel Scheduling for Ad Hoc Networks with Queue Stability

    Science.gov (United States)

    Dong, Lei; Wang, Yongchao

    2015-03-01

    In this paper, a distributed opportunistic channel access strategy in ad hoc network is proposed. We consider the multiple sources contend for the transmission opportunity, the winner source decides to transmit or restart contention based on the current channel condition. Owing to real data assumption at all links, the decision still needs to consider the stability of the queues. We formulate the channel opportunistic scheduling as a constrained optimization problem which maximizes the system average throughput with the constraints that the queues of all links are stable. The proposed optimization model is solved by Lyapunov stability in queueing theory. The successive channel access problem is decoupled into single optimal stopping problem at every frame and solved with Lyapunov algorithm. The threshold for every frame is different, and it is derived based on the instantaneous queue information. Finally, computer simulations are conducted to demonstrate the validity of the proposed strategy.

  20. Stack- and Queue-like Dynamics in Recurrent Neural Networks

    OpenAIRE

    Grüning, A

    2006-01-01

    What dynamics do simple recurrent networks (SRNs) develop to represent stack-like and queue-like memories? SRNs have been widely used as models in cognitive science. However, they are interesting in their own right as non-symbolic computing devices from the viewpoints of analogue computing and dynamical systems theory. In this paper, SRNs are trained oil two prototypical formal languages with recursive structures that need stack-like or queue-like memories for processing, respectively. The ev...

  1. THE M/M/c QUEUE WITH PH SYNCHRONOUS VACATIONS

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    In this paper, we give a detailed analysis of the M/M/c queue with Phase Type synchronous vacations. Two models are considered. Firstly, the vacation strategy is a multiple synchronous vacation. Secondly, only a single vacation is taken each time. For model 1, we give the distributions of the stable queue length and the waiting time. Finally,it is shown that model 2 may be analyzed similarly to model 1.

  2. The SM/M/N queueing system with broadcasting service

    Directory of Open Access Journals (Sweden)

    Moon Ho Lee

    2006-01-01

    Full Text Available We consider a multiserver queueing model with the semi-Markovian arrival process and exponential service time distribution. Novel customers admission discipline is under study. The customer, which sees several free servers upon arrival, is served simultaneously by all these servers. Such situation occurs, for example, in modeling wireless communication network with broadcasting. Systems with infinite buffer and with losses are investigated. Stationary distributions of a queue, waiting and sojourn times, and the main performance measures are calculated.

  3. Queue-based random-access algorithms: Fluid limits and stability issues

    Directory of Open Access Journals (Sweden)

    Javad Ghaderi

    2014-09-01

    Full Text Available We use fluid limits to explore the (instability properties of wireless networks with queue-based random-access algorithms. Queue-based random-access schemes are simple and inherently distributed in nature, yet provide the capability to match the optimal throughput performance of centralized scheduling mechanisms in a wide range of scenarios. Unfortunately, the type of activation rules for which throughput optimality has been established, may result in excessive queue lengths and delays. The use of more aggressive/persistent access schemes can improve the delay performance, but does not offer any universal maximum-stability guarantees. In order to gain qualitative insight and investigate the (instability properties of more aggressive/persistent activation rules, we examine fluid limits where the dynamics are scaled in space and time. In some situations, the fluid limits have smooth deterministic features and maximum stability is maintained, while in other scenarios they exihibit random oscillatory characteristics, giving rise to major technical challenges. In the latter regime, more aggressive access schemes continue to provide maximum stability in some networks, but may cause instability in others. In order to prove that, we focus on a particular network example and conduct a detailed analysis of the fluid limit process for the associated Markov chain. Specifically, we develop a novel approach based on stopping time sequences to deal with the switching probabilities governing the sample paths of the fluid limit process. Simulation experiments are conducted to illustrate and validate the analytical results.

  4. 区分服务网络队列调度策略的研究与仿真%RESEARCHING AND SIMULATING DYNAMIC QUEUE SCHEDULING IN DiffServ NETWORK

    Institute of Scientific and Technical Information of China (English)

    关学铭; 刘种

    2011-01-01

    In this paper we make a study on several queue scheduling algorithms in DiflServ network and put forward a dynamic queue scheduling strategy to improve the efficiency of the queue forwarding. Dynamic queue management is achieved by dynamically adjusting the queue weight so as to have the network resources utilisation improved and the QoS in DiffServ network meliorated. The queue scheduling algorithm is simulated by NS2 and experiment results show that the dynamic queue scheduling algorithm can effectively improve the DiffServ network data forwarding efficiency.%针对目前几种DiffServ( Differentiated Service)网络队列调度算法进行研究,提出一种动态队列调度策略来提高队列转发效率.通过动态调整队列权值实现队列的动态管理,从而改进网络资源的利用效率,改善DiffServ网络QoS.利用NS2模拟动态队列调度算法,实验表明动态队列调度算法有效地提高了区分服务网络的队列转发效率.

  5. Ethics in radiology: wait lists queue jumping.

    Science.gov (United States)

    Cunningham, Natalie; Reid, Lynette; MacSwain, Sarah; Clarke, James R

    2013-08-01

    Education in ethics is a requirement for all Royal College residency training programs as laid out in the General Standards of Accreditation for residency programs in Canada. The ethical challenges that face radiologists in clinical practice are often different from those that face other physicians, because the nature of the physician-patient interaction is unlike that of many other specialties. Ethics education for radiologists and radiology residents will benefit from the development of teaching materials and resources that focus on the issues that are specific to the specialty. This article is intended to serve as an educational resource for radiology training programs to facilitate teaching ethics to residents and also as a continuing medical education resource for practicing radiologists. In an environment of limited health care resources, radiologists are frequently asked to expedite imaging studies for patients and, in some respects, act as gatekeepers for specialty care. The issues of wait lists, queue jumping, and balancing the needs of individuals and society are explored from the perspective of a radiologist.

  6. Two Coupled Queues with Vastly Different Arrival Rates: Critical Loading Case

    Directory of Open Access Journals (Sweden)

    Charles Knessl

    2011-01-01

    Full Text Available We consider two coupled queues with a generalized processor sharing service discipline. The second queue has a much smaller Poisson arrival rate than the first queue, while the customer service times are of comparable magnitude. The processor sharing server devotes most of its resources to the first queue, except when it is empty. The fraction of resources devoted to the second queue is small, of the same order as the ratio of the arrival rates. We assume that the primary queue is heavily loaded and that the secondary queue is critically loaded. If we let the small arrival rate to the secondary queue be O(ε, where 0≤ε≪1, then in this asymptotic limit the number of customers in the first queue will be large, of order O(ε-1, while that in the second queue will be somewhat smaller, of order O(ε-1/2. We obtain a two-dimensional diffusion approximation for this model and explicitly solve for the joint steady state probability distribution of the numbers of customers in the two queues. This work complements that in (Morrison, 2010, which the second queue was assumed to be heavily or lightly loaded, leading to mean queue lengths that were O(ε-1 or O(1, respectively.

  7. Upper Bounds on Performance Measures of Heterogeneous // Queues

    Directory of Open Access Journals (Sweden)

    F. S. Q. Alves

    2011-01-01

    Full Text Available In many real-life queueing systems, the servers are often heterogeneous, namely they work at different rates. This paper provides a simple method to compute tight upper bounds on two important performance measures of single-class heterogeneous multi-server Markovian queueing systems, namely the average number in queue and the average waiting time in queue. This method is based on an expansion of the state space that is followed by an approximate reduction of the state space, only considering the most probable states. In most cases tested, we were able to approximate the actual behavior of the system with smaller errors than those obtained from traditional homogeneous multiserver Markovian queues, as shown by GPSS simulations. In addition, we have correlated the quality of the approximation with the degree of heterogeneity of the system, which was evaluated using its Gini index. Finally, we have shown that the bounds are robust and still useful, even considering quite different allocation strategies. A large number of simulation results show the accuracy of the proposed method that is better than that of classical homogeneous multiserver Markovian formulae in many situations.

  8. Asymptotic inference for waiting times and patiences in queues with abandonment

    DEFF Research Database (Denmark)

    Gorst-Rasmussen, Anders; Hansen, Martin Bøgsted

    confidence intervals and statistical tests, including a simple bootstrap two-sample test for comparing patience distributions. The methods are exemplified in a small simulation study, and a real data example is given involving comparison of patience distributions for two customer classes in a call center.......Motivated by applications in call center management, we propose a framework based on empirical process techniques for inference about the waiting time and patience distribution in multiserver queues with abandonment. The framework rigorises heuristics based on survival analysis of independent...

  9. Properties of Multi-Stage M/G/1/K Queues with Series Arrangement

    Directory of Open Access Journals (Sweden)

    Hernández-González Salvador

    2015-07-01

    Full Text Available We propose a modification to the Buzacott & Shantikumar (1993 method to evaluate the properties of M/G/1/K queues with series arrangement. We made several tests and compared with simulation to validate the results. We observed that, with the proposed modification, the method has an acceptable level of exactitude. It can be considered an alternative calculation to other methods in the literature. The fact that this method requires less computational effort, can be useful to practitioners and managers that require tools to analyze the performance of systems in production and services areas.

  10. IMPLEMENTATION OF CENTRAL QUEUE BASED REALTIME SCHEDULER FOR MULTIPLE SOURCE DATA STREAMING

    Directory of Open Access Journals (Sweden)

    V. Kaviha

    2014-01-01

    Full Text Available Real-time data packet sources are required to remain robust against different security threats. This study proposes a real-time secure scheduling strategy for data transmission to enhance the communication throughput and reduce the overheads. The proposed system combines real-time scheduling with security service enhancement, error detection and realtime scheduler based on EDF algorithm using uc/os-II real time operating system, implemented on cortex M3 processor. The scheduling unit uses central queue management model and the security enhancement scheme adopts a blowfish encryption mechanism.

  11. 一种高效的磁盘队列I/O机制%An Efficient Disk Queue I/O Mechanism

    Institute of Scientific and Technical Information of China (English)

    魏青松; 卢显良; 任立勇; 周旭

    2003-01-01

    分析了传统磁盘队列的存储管理开销和读写性能,针对磁盘队列I/O已成为影响消息服务器性能的首要瓶颈,提出了一种高效磁盘队列I/O机制-FlashQ.FlashQ采用物理上连续的磁盘块作为磁盘队列,以紧凑方式组织数据,采用延迟写策略和预先读策略提高读写性能.实验表明,FlashQ的性能比传统磁盘队列好.%The storage management overload and read-write performance of traditional disk queue are analyzed. To solve the problem that disk queue I/O is the primary performance bottleneck in messaging server, an efficient disk queue I/O mechanism called FlashQ is proposed. FlashQ utilizes preassigned continuous disk blocks to act as disk queue and organizes data in compact layout and adopts the Lazy Write and the Ahead Read polices to elevate the performance of read-write. Experiment shows that performance of the FlashQ is much better than that of traditional disk queue.

  12. Simple queueing model applied to the city of Portland

    Energy Technology Data Exchange (ETDEWEB)

    Simon, P.M.; Nagel, K. [Los Alamos National Lab., NM (United States)]|[Santa Fe Inst., NM (United States)

    1998-07-31

    The authors present a simple traffic micro-simulation model that models the effects of capacity cut-off, i.e. the effect of queue built-up when demand is exceeding capacity, and queue spillback, i.e. the effect that queues can spill back across intersections when a congested link is filled up. They derive the model`s fundamental diagrams and explain it. The simulation is used to simulate traffic on the emme/2 network of the Portland (Oregon) metropolitan region (20,000 links). Demand is generated by a simplified home-to-work assignment which generates about half a million trips for the AM peak. Route assignment is done by iterative feedback between micro-simulation and router. Relaxation of the route assignment for the above problem can be achieved within about half a day of computing time on a desktop workstation.

  13. An introduction to queueing theory modeling and analysis in applications

    CERN Document Server

    Bhat, U Narayan

    2015-01-01

    This introductory textbook is designed for a one-semester course on queueing theory that does not require a course on stochastic processes as a prerequisite. By integrating the necessary background on stochastic processes with the analysis of models, the work provides a sound foundational introduction to the modeling and analysis of queueing systems for a wide interdisciplinary audience of students in mathematics, statistics, and applied disciplines such as computer science, operations research, and engineering. This edition includes additional topics in methodology and applications. Key features: • An introductory chapter including a historical account of the growth of queueing theory in more than 100 years. • A modeling-based approach with emphasis on identification of models. • Rigorous treatment of the foundations of basic models commonly used in applications with appropriate references for advanced topics. • Applications in manufacturing and, computer and communication systems. • A chapter on ...

  14. Queues, Stacks, and Transcendentality at the Transition to Chaos

    CERN Document Server

    Moore, Cristopher; Moore, Cristopher; Lakdawala, Porus

    1998-01-01

    We examine the one-humped map at the period-doubling transition to chaos, and ask whether its long-term memory is stack-like (last-in, first-out) or queue-like (first-in, first-out). We show that it can be recognized by a real-time automaton with one queue, or two stacks, and give several new grammatical characterizations of it. We argue that its memory has a queue-like character, since a single stack does not suffice. We also show that its dynamical zeta function, generating function and growth function are transcendental. The same results hold for any period-multiplying cascade. We suggest that transcendentality might be a sign of dynamical phase transitions in other systems as well.

  15. Bulk input queues with quorum and multiple vacations

    Directory of Open Access Journals (Sweden)

    Jewgeni H. Dshalalow

    1996-01-01

    Full Text Available The authors study a single-server queueing system with bulk arrivals and batch service in accordance to the general quorum discipline: a batch taken for service is not less than r and not greater than R(≥r. The server takes vacations each time the queue level falls below r(≥1 in accordance with the multiple vacation discipline. The input to the system is assumed to be a compound Poisson process. The analysis of the system is based on the theory of first excess processes developed by the first author. A preliminary analysis of such processes enabled the authors to obtain all major characteristics for the queueing process in an analytically tractable form. Some examples and applications are given.

  16. Bulk input queues with quorum and multiple vacations

    Directory of Open Access Journals (Sweden)

    Dshalalow Jewgeni H.

    1996-01-01

    Full Text Available The authors study a single-server queueing system with bulk arrivals and batch service in accordance to the general quorum discipline: a batch taken for service is not less than r and not greater than R ( ≥ r . The server takes vacations each time the queue level falls below r ( ≥ 1 in accordance with the multiple vacation discipline. The input to the system is assumed to be a compound Poisson process. The analysis of the system is based on the theory of first excess processes developed by the first author. A preliminary analysis of such processes enabled the authors to obtain all major characteristics for the queueing process in an analytically tractable form. Some examples and applications are given.

  17. Algorithm for queueing networks with multi-rate traffic

    DEFF Research Database (Denmark)

    Iversen, Villy Bæk; Ko, King-Tim

    2011-01-01

    In this paper we present a new algorithm for evaluating queueing networks with multi-rate traffic. The detailed state space of a node is evaluated by explicit formulæ. We consider reversible nodes with multi-rate traffic and find the state probabilities by taking advantage of local balance. Theory...... of queueing networks in general, presumes that we have product form between the nodes. Otherwise, we have the state space explosion. Even so, the detailed state space of each node may become very large because there is no product form between chains inside a node. A prerequisite for product form...... the nodes behave as independent nodes. For closed queueing networks with multiple servers in every node and multi-rate services we may apply multidimensional convolution algorithm to aggregate the nodes so that we end up with two nodes, the aggregated node and a single node, for which we can calculate...

  18. THE M/M/c QUEUE WITH (e,d) SETUP TIME

    Institute of Scientific and Technical Information of China (English)

    Xiuli XU; Naishuo TIAN

    2008-01-01

    The authors present a new queueing model with (e, d) setup time. Using the quasi-birth-and-death process and matrix-geometric method, the authors obtain the stationary distribution of queue length and the LST of waiting time of a customer in the system. Furthermore, the conditional stochastic decomposition results of queue length and waiting time are given.

  19. A Parallel Priority Queue with Constant Time Operations

    DEFF Research Database (Denmark)

    Brodal, Gerth Stølting; Träff, Jesper Larsson; Zaroliagis, Christos D.

    1998-01-01

    We present a parallel priority queue that supports the following operations in constant time:parallel insertionof a sequence of elements ordered according to key,parallel decrease keyfor a sequence of elements ordered according to key,deletion of the minimum key element, anddeletion of an arbitrary...... element. Our data structure is the first to support multi-insertion and multi-decrease key in constant time. The priority queue can be implemented on the EREW PRAM and can perform any sequence ofnoperations inO(n) time andO(mlogn) work,mbeing the total number of keyes inserted and/or updated. A main...

  20. Extreme Values of Queues, Point Processes and Stochastic Networks.

    Science.gov (United States)

    2014-09-26

    AD-A158 619 EXTREMIE YALUES OF QUEUES POINT PROCESSES AND STOCHASTIC i/i NETUORKS(U) GEORGIA INST OF TECH ATLANTA R F SERFOZO 25 JUN 85 SFOSR-TR-85...O If "Extreme Values of Queues, Point Processes VW- and Stochastic Networks" 1 Grant No. AFOSR 84-0367 by Professor Richard F. Serfozo Industrial and...Claaraicajton) Extreme Values of Oueues. Point Processes & Stochastic Networks_ 12. PERSONAL AUTHOR(S) R_ F_ Serfozo 13. TYPE OF REPORT 13b. TIME COVERED 14

  1. Strategic behavior and social outcomes in a bottleneck queue

    DEFF Research Database (Denmark)

    Breinbjerg, Jesper Breinbjerg; Sebald, Alexander Christopher; Østerdal, Lars Peter

    2016-01-01

    the first-in-first-out (FIFO), last-in-first-out (LIFO), and service-in-random-order (SIRO) queue disciplines and compare these predictions to outcomes from a laboratory experiment. In line with our theoretical predictions, we find that people arrive with greater dispersion when participating under the LIFO...... discipline, whereas they tend to arrive immediately under FIFO and SIRO. As a consequence, shorter waiting times are obtained under LIFO as compared to FIFO and SIRO. However, while our theoretical predictions admit higher welfare under LIFO, this is not recovered experimentally as the queue disciplines...

  2. 基于时延的动态优先级调度算法%Delay-Based Dynamic Priority Queue Scheduling

    Institute of Scientific and Technical Information of China (English)

    张登银; 许扬扬; 蒋娟

    2011-01-01

    队列管理是提高网络 QoS 的一种有效方法.在基于时延的调度算法(BDS)基础上将时间片与优先级相结合,提出了一种基于时延的动态优先级调度算法(DDPQS).为了实现该算法,针对进入缓冲区的每个子队列设置一个计数器,以调整的计数器值为基准来动态的改变队列的优先级,从而达到队列调度的效果;又从研究该算法的过程中,发现其局限性,即计数器值对时间片过于敏感的问题,于是进一步采用设置阈值进行区分的方法来优化.优化前后的仿真结果表明,时延和吞吐率性能具有明显改善.%Queue management is an effective method to improve the QoS of network. Investigating queue management based on the delay scheduling (BDS), combining the time chip and priority, advances Delay-based Dynamic Priority Queue Scheduling (DDPQS) algorithm. To achieve the algorithm, sets a counter for every sub-queue entering the buffer. It dynamically adjusts the sub-queue priorities by the value of counters to achieve the effect of queue scheduling. During the research, the limitation was found that the counters are sensitive to the time chip. The paper uses threshold values to optimize the algorithm. The simulation results before and after the optimizations demonstrate that the performance of the delay and the throughput rate has significantly improved.

  3. Study on the Queue-Length Distribution in Geo/G(MWV/1/N Queue with Working Vacations

    Directory of Open Access Journals (Sweden)

    Chuanyi Luo

    2015-01-01

    Full Text Available This paper analyzes a finite buffer size discrete-time Geo/G/1/N queue with multiple working vacations and different input rate. Using supplementary variable technique and embedded Markov chain method, the queue-length distribution solution in the form of formula at arbitrary epoch is obtained. Some performance measures associated with operating cost are also discussed based on the obtained queue-length distribution. Then, several numerical experiments follow to demonstrate the effectiveness of the obtained formulae. Finally, a state-dependent operating cost function is constructed to model an express logistics service center. Regarding the service rate during working vacation as a control variable, the optimization analysis on the cost function is carried out by using parabolic method.

  4. A queueing system with queue length dependent service times, with applications to cell discarding in ATM networks

    Directory of Open Access Journals (Sweden)

    Doo Il Choi

    1999-01-01

    Full Text Available A queueing system (M/G1,G2/1/K is considered in which the service time of a customer entering service depends on whether the queue length, N(t, is above or below a threshold L. The arrival process is Poisson, and the general service times S1 and S2 depend on whether the queue length at the time service is initiated is

  5. Active Risk Management and Banking Stability

    NARCIS (Netherlands)

    Silva Buston, C.F.

    2013-01-01

    Abstract: This paper analyzes the net impact of two opposing effects of active risk management at banks on their stability: higher risk-taking incentives and better isolation of credit supply from varying economic conditions. We present a model where banks actively manage their portfolio risk by buy

  6. Active Risk Management and Banking Stability

    NARCIS (Netherlands)

    Silva Buston, C.F.

    2013-01-01

    Abstract: This paper analyzes the net impact of two opposing effects of active risk management at banks on their stability: higher risk-taking incentives and better isolation of credit supply from varying economic conditions. We present a model where banks actively manage their portfolio risk by

  7. An asymptotic analysis of closed queueing networks with branching populations

    NARCIS (Netherlands)

    Bayer, N.; Coffman, E.G.; Kogan, Y.A.

    1995-01-01

    Closed queueing networks have proven to be valuable tools for system performance analysis. In this paper, we broaden the applications of such networks by incorporating populations of {em branching customers: whenever a customer completes service at some node of the network, it is replaced by N>=0 cu

  8. Queueing and Service Patterns in a University Teaching Hospital FO ...

    African Journals Online (AJOL)

    acer

    algorithms at a service points such as the ones obtainable in the ... determines the measure of performance of waiting lines such as ... the queue based on some order of priority. (Taha, 2007). ..... time get faster later in the day. The reason for.

  9. Arrival first queueing networks with applications in kanban production systems

    NARCIS (Netherlands)

    Boucherie, Richard J.; Chao, Xiuli; Miyazawa, Masakiyo

    2003-01-01

    In this paper, we introduce a new class of queueing networks called arrival first networks. We characterise its transition rates and derive the relationship between arrival rules, linear partial balance equations, and product form stationary distributions. This model is motivated by production syste

  10. Moving toward queue operations at the Large Binocular Telescope Observatory

    Science.gov (United States)

    Edwards, Michelle L.; Summers, Doug; Astier, Joseph; Suarez Sola, Igor; Veillet, Christian; Power, Jennifer; Cardwell, Andrew; Walsh, Shane

    2016-07-01

    The Large Binocular Telescope Observatory (LBTO), a joint scientific venture between the Instituto Nazionale di Astrofisica (INAF), LBT Beteiligungsgesellschaft (LBTB), University of Arizona, Ohio State University (OSU), and the Research Corporation, is one of the newest additions to the world's collection of large optical/infrared ground-based telescopes. With its unique, twin 8.4m mirror design providing a 22.8 meter interferometric baseline and the collecting area of an 11.8m telescope, LBT has a window of opportunity to exploit its singular status as the "first" of the next generation of Extremely Large Telescopes (ELTs). Prompted by urgency to maximize scientific output during this favorable interval, LBTO recently re-evaluated its operations model and developed a new strategy that augments classical observing with queue. Aided by trained observatory staff, queue mode will allow for flexible, multi-instrument observing responsive to site conditions. Our plan is to implement a staged rollout that will provide many of the benefits of queue observing sooner rather than later - with more bells and whistles coming in future stages. In this paper, we outline LBTO's new scientific model, focusing specifically on our "lean" resourcing and development, reuse and adaptation of existing software, challenges presented from our one-of-a-kind binocular operations, and lessons learned. We also outline further stages of development and our ultimate goals for queue.

  11. Waiting time distribution in M/D/1 queueing systems

    DEFF Research Database (Denmark)

    Iversen, Villy Bæk; Staalhagen, Lars

    1999-01-01

    The well-known formula for the waiting time distribution of M/D/1 queueing systems is numerically unsuitable when the load is close to 1.0 and/or the results for a large waiting time are required. An algorithm for any load and waiting time is presented, based on the state probabilities of M/D/1...

  12. Python for Scientific Computing Education: Modeling of Queueing Systems

    Directory of Open Access Journals (Sweden)

    Vladimiras Dolgopolovas

    2014-01-01

    Full Text Available In this paper, we present the methodology for the introduction to scientific computing based on model-centered learning. We propose multiphase queueing systems as a basis for learning objects. We use Python and parallel programming for implementing the models and present the computer code and results of stochastic simulations.

  13. Job Queues, Certification Status, and the Education Labor Market

    Science.gov (United States)

    Evans, Lorraine

    2011-01-01

    This research explores the interaction between training programs and certification status in one education labor market to examine the micro-level interactions that shape the recruitment process. Using job queue theory, it is found that the information available to novice teachers operates to stratify and shape their worksite choices in addition…

  14. The Exactly Solvable Simplest Model for Queue Dynamics

    OpenAIRE

    Y. Sugiyama; Yamada, H.

    1996-01-01

    We present an exactly solvable model for queue dynamics. Our model is very simple but provides the essential property for such dynamics. As an example, the model has the traveling cluster solution as well as the homogeneous flow solution. The model is the limiting case of Optimal Velocity (OV) model, which is proposed for the car following model to induce traffic jam spontaneously.

  15. The asymptotic variance of departures in critically loaded queues

    NARCIS (Netherlands)

    A. Al Hanbali; M.R.H. Mandjes (Michel); Y. Nazarathy (Yoni); W. Whitt

    2010-01-01

    htmlabstractWe consider the asymptotic variance of the departure counting process D(t) of the GI/G/1 queue; D(t) denotes the number of departures up to time t. We focus on the case that the system load rho equals 1, and prove that the asymptotic variance rate satisfies lim_t Var D(t)/t = lambda

  16. Processor-sharing queues and resource sharing in wireless LANs

    NARCIS (Netherlands)

    Cheung, Sing Kwong

    2007-01-01

    In the past few decades, the processor-sharing (PS) model has received considerable attention in the queueing theory community and in the field of performance evaluation of computer and communication systems. The scarce resource is simultaneously shared among all users in these systems. PS models ar

  17. Arrival first queueing networks with applications in kanban production systems

    NARCIS (Netherlands)

    Boucherie, R.J.; Chao, X.; Miyazawa, M.

    2001-01-01

    In this paper we introduce a new class of queueing networks called {\\it arrival first networks}. We characterise its transition rates and derive the relationship between arrival rules, linear partial balance equations, and product form stationary distributions. This model is motivated by production

  18. Scheme for evaluating a local queue warning system.

    NARCIS (Netherlands)

    Botma, H. & Oei, H.L.

    1977-01-01

    A method of evaluating an automatic queue warning system is outlined. The main object of the evaluation is to measure the effect of such a system on traffic behaviour and road safety, although the overall journey time is also examined. The chosen method of research entails before and after studies,

  19. Integrated service resource reservation using queueing networks theory

    DEFF Research Database (Denmark)

    Brewka, Lukasz Jerzy; Iversen, Villy Bæk; Kardaras, Georgios

    2014-01-01

    This study analyses multi-server multi-service queueing networks with service protection. To guarantee each service a certain quality-of-service and at the same time ensure high utilisation of servers, a minimum capacity is reserved each service. In addition, all services share the remaining non...

  20. Job Queues, Certification Status, and the Education Labor Market

    Science.gov (United States)

    Evans, Lorraine

    2011-01-01

    This research explores the interaction between training programs and certification status in one education labor market to examine the micro-level interactions that shape the recruitment process. Using job queue theory, it is found that the information available to novice teachers operates to stratify and shape their worksite choices in addition…

  1. Sojourn time approximations in queueing networks with feedback

    NARCIS (Netherlands)

    Gijsen, B.M.M.; Mei, R.D. van der; Engelberts, P.; Berg, J.L. van den; Wingerden, K.M.C. van

    2006-01-01

    This paper is motivated by the response-time analysis of distributed information systems, where transactions are handled by a sequence of front-end server and back-end server actions. We study sojourn times in an open queueing network with a single Processor Sharing (PS) node and an arbitrary number

  2. Large Deviations without Principle: Join the Shortest Queue

    NARCIS (Netherlands)

    Ridder, Ad; Shwartz, Adam

    2004-01-01

    We develop a methodology for studying "large deviations type" questions. Our approach does not require that the large deviations principle holds, and is thus applicable to a larg class of systems. We study a system of queues with exponential servers, which share an arrival stream. Arrivals are route

  3. Stability analysis of interacting queues in the ALOHA system

    Science.gov (United States)

    Rao, Ramesh

    The author considers the finite-user, infinite-buffer slotted ALOHA system and analytically extends the known bounds for its stability region. The technique used consists of expressing the stability region in terms of certain status probabilities and then solving for the status probabilities by using results from the analysis of dependent queues and that of Markov chains.

  4. Arrival first queueing networks with applications in kanban production systems

    NARCIS (Netherlands)

    Boucherie, Richardus J.; Chao, X.; Miyazawa, M.

    2003-01-01

    In this paper, we introduce a new class of queueing networks called arrival first networks. We characterise its transition rates and derive the relationship between arrival rules, linear partial balance equations, and product form stationary distributions. This model is motivated by production

  5. Arrival first queueing networks with applications in kanban production systems

    NARCIS (Netherlands)

    Boucherie, Richardus J.; Chao, X.; Miyazawa, M.

    2001-01-01

    In this paper we introduce a new class of queueing networks called {\\it arrival first networks}. We characterise its transition rates and derive the relationship between arrival rules, linear partial balance equations, and product form stationary distributions. This model is motivated by production

  6. Worst-case efficient external-memory priority queues

    DEFF Research Database (Denmark)

    Brodal, Gerth Stølting; Katajainen, Jyrki

    1998-01-01

    . In this paper a priority-queue implementation is given which is efficient with respect to the number of block transfers or I/Os performed between the internal and external memories of a computer. Let B and M denote the respective capacity of a block and the internal memory measured in elements. The developed...

  7. Multi-Resource Fair Queueing for Packet Processing

    Science.gov (United States)

    2012-06-19

    Huawei , Intel, MarkLogic, Microsoft, NetApp, Oracle, Quanta, Splunk, VMware and by DARPA (contract #FA8650-11-C-7136). Multi-Resource Fair Queueing for...Google PhD Fellowship, gifts from Amazon Web Services, Google, SAP, Blue Goji, Cisco, Cloud- era, Ericsson, General Electric, Hewlett Packard, Huawei

  8. A novel application of queueing theory on the Caulerpenyne secreted by invasive Caulerpa taxifolia (Vahl C.Agardh (Ulvophyceae, Caulerpales: a preliminary study

    Directory of Open Access Journals (Sweden)

    C. KANDEMIR-CAVAS

    2012-12-01

    Full Text Available Aquarium originated marine green alga Caulerpa taxifolia was introduced into the Mediterranean Sea accidentally in 1984. This invasion has been negatively affecting the sub-littoral ecosystem of the Mediterranean. One of the important reasons for its success in the Mediterranean is its secondary toxic metabolite called caulerpenyne (CPN. Furthermore, CPN has anti-proliferative and apoptotic activities, therefore, CPN can be considered as a potential native source in cancer therapy. For that reason, modeling this metabolite might be of importance. Increase and decrease of the CPN level before reaching the critical level can be expressed by means of a queueing system in which the number of ‘customers' increases and decreases. In fact, production of CPN shows fluctuations for many environmental reasons, which allow us to apply queueing theory. In the present study, the expected time to reach the maximum caulerpenyne level was analyzed and evaluated using queueing theory.

  9. 一种新的主动队列管理自适应PI算法%New Adaptive PI Algorithm for Active Queue Management

    Institute of Scientific and Technical Information of China (English)

    王明文; 朱清新; 卿利

    2007-01-01

    为克服PI算法所存在的响应速度慢,对网络参数变化敏感的缺点,将神经网络理论引入主动队列管理的研究中,提出一种基于单神经元的主动队列管理算法NPI(Neuron based PI).NPI算法将PI控制器看成是二输入的ADALINE神经元,控制器的比例系数和积分系数按照LMS算法进行在线调整,对网络状态的变化有自学习能力,使队列长度能够快速收敛到目标值,并增强了队列的稳定性.仿真试验结果表明NPI算法比PI有更好的性能.

  10. Queue-Aware Dynamic Clustering and Power Allocation for Network MIMO Systems via Distributive Stochastic Learning

    CERN Document Server

    Cui, Ying; Lau, Vincent K N

    2010-01-01

    In this paper, we propose a two-timescale delay-optimal dynamic clustering and power allocation design for downlink network MIMO systems. The dynamic clustering control is adaptive to the global queue state information (GQSI) only and computed at the base station controller (BSC) over a longer time scale. On the other hand, the power allocations of all the BSs in one cluster are adaptive to both intra-cluster channel state information (CCSI) and intra-cluster queue state information (CQSI), and computed at the cluster manager (CM) over a shorter time scale. We show that the two-timescale delay-optimal control can be formulated as an infinite-horizon average cost Constrained Partially Observed Markov Decision Process (CPOMDP). By exploiting the special problem structure, we shall derive an equivalent Bellman equation in terms of Pattern Selection Q-factor to solve the CPOMDP. To address the distributive requirement and the issue of exponential memory requirement and computational complexity, we approximate the...

  11. Structuring medication related activities for information management.

    Science.gov (United States)

    Luukkonen, Irmeli; Mykkänen, Juha; Kivekäs, Eija; Saranto, Kaija

    2014-01-01

    Medication treatment and the related information management are central parts of a patient's health care. As a cross-organizational and cooperative process, medication information management is a complex domain for development activities. We studied medication activities and related information management in a regional project in order to produce a shared broad picture of its processes and to understand the main issues and the needs for improvement. In this paper we provide a summary of the findings in a structured form, based on a six-dimensioned framework for design and analysis of activities and processes.

  12. Organizational Actively Management for Opportunity Hunting

    Directory of Open Access Journals (Sweden)

    Nasser Fegh-hi FARAHMAND

    2012-03-01

    Full Text Available Organizational Actively Management (OAM is the responsibility of every manager. Because, an approach for OAM is becoming more widely accepted is a community-based development approach. In Opportunity Hunting Approach (OHA, OAM is the responsibility of every manager for his/her actions. OAM is using from top to bottom development model. According to the survey of market and customers, after understand customers’ needs, organization then decide how the quality policy and target will develop, from there the actively management system can be developed. The aim of this study in field of organizational actively management and policy of it can provide the specific process required for setting up and monitoring the actively target. As it also is customer-oriented, it aims to improve customer satisfaction. In addition, the actively target should be set up and implemented within every organization department and at each level, in accordance with actively policy. Furthermore, organization should develop the actively management system, in order to conform to general requirements and actively target.

  13. Fuzzy-Based Dynamic Distributed Queue Scheduling for Packet Switched Networks

    Institute of Scientific and Technical Information of China (English)

    Chollette C.Chude-Olisah; Uche A.K.Chude-Okonkwo; Kamalrulnizam A.Balar; Ghazali Sulong

    2013-01-01

    Addressing the problem of queue scheduling for the packet-switched system is a vital aspect of congestion control.In this paper,the fuzzy logic based decision method is adopted for queue scheduling in order to enforce some level of control for traffic of different quality of service requirements using predetermined values.The fuzzy scheduler proposed in this paper takes into account the dynamic nature of the Internet traffic with respect to its time-varying packet arrival process that affects the network states and performance.Three queues are defined,viz low,medium and high priority queues.The choice of prioritizing packets influences how queues are served.The fuzzy scheduler not only utilizes queue priority in the queue scheduling scheme,but also considers packet drop susceptibility and queue limit.Through simulation it is shown that the fuzzy scheduler is more appropriate for the dynamic nature of Internet traffic in a packet-switched system as compared with some existing queue scheduling methods.Results show that the scheduling strategy of the proposed fuzzy scheduler reduces packet drop,provides good link utilization and minimizes queue delay as compared with the priority queuing (PQ),first-in-first-out (FIFO),and weighted fair queuing (WFQ).

  14. Entrainment of a Synthetic Oscillator through Queueing Coupling

    Science.gov (United States)

    Hochendoner, Philip; Mather, William; Butzin, Nicholas; Ogle, Curtis

    2014-03-01

    Many biological systems naturally exhibit (often noisy) oscillatory patterns that are capable of being entrained by external stimuli, though the mechanism of entrainment is typically obscured by the complexity of native networks. A synthetic biology approach, where genetic programs are wired ``by hand,'' has proven useful in this regard. In the present study, we use a synthetic oscillator in Escherichia coli to demonstrate a novel and potentially widespread mechanism for biological entrainment: competition of proteins for degradation by common pathway, i.e. a entrainment by a bottleneck. To faithfully represent the discrete and stochastic nature of this bottleneck, we leverage results from a recent biological queueing theory, where in particular, the queueing theoretic concept of workload is discovered to simplify the analysis. NSF Award 1330180.

  15. Queue-length Variations In A Two-Restaurant Problem

    CERN Document Server

    Chakrabarti, Anindya S

    2008-01-01

    This paper attempts to find out numerically the distribution of the queue-length ratio in the context of a model of preferential attachment. Here we consider two restaurants only and a large number of customers (agents) who come to these restaurants. Each day the same number of agents sequentially arrives and decides which restaurant to enter. If all the agents literally follow the crowd then there is no difference between this model and the famous `P\\'olya's Urn' model. But as agents alter their strategies different kind of dynamics of the model is seen. It is seen from numerical results that the existence of a distribution of the fixed points is quite robust and it is also seen that in some cases the variations in the ratio of the queue-lengths follow a power-law.

  16. Transient Analysis of Hysteresis Queueing Model Using Matrix Geometric Method

    Directory of Open Access Journals (Sweden)

    Wajiha Shah

    2011-10-01

    Full Text Available Various analytical methods have been proposed for the transient analysis of a queueing system in the scalar domain. In this paper, a vector domain based transient analysis is proposed for the hysteresis queueing system with internal thresholds for the efficient and numerically stable analysis. In this system arrival rate of customer is controlled through the internal thresholds and the system is analyzed as a quasi-birth and death process through matrix geometric method with the combination of vector form Runge-Kutta numerical procedure which utilizes the special matrices. An arrival and service process of the system follows a Markovian distribution. We analyze the mean number of customers in the system when the system is in transient state against varying time for a Markovian distribution. The results show that the effect of oscillation/hysteresis depends on the difference between the two internal threshold values.

  17. COOPERATIVE DYNAMICS OF LOYAL CUSTOMERS IN QUEUEING NETWORKS

    Institute of Scientific and Technical Information of China (English)

    Olivier GALLAY; Max-Olivier HONGLER

    2008-01-01

    We consider queueing networks (QN's) with feedback loops roamed by "intelligent" agents, able to select their routing on the basis of their measured waiting times at the QN nodes. This is an idealized model to discuss the dynamics of customers who stay loyal to a service supplier, provided their service time remains below a critical threshold. For these QN's, we show that the traffic flows may exhibit collective patterns typically encountered in multi-agent systems. In simple network topologies, the emergent cooperative behaviors manifest themselves via stable macroscopic temporal oscillations, synchronization of the queue contents and stabilization by noise phenomena. For a wide range of control parameters, the underlying presence of the law of large numbers enables us to use deterministic evolution laws to analytically characterize the cooperative evolution of our multi-agent systems. In particular, we study the case where the servers are sporadically subject to failures altering their ordinary behavior.

  18. Queueing analysis of some buffered random multiple access schemes

    Science.gov (United States)

    Sykas, E. D.; Karvelas, D. E.; Protonotarios, E. N.

    1986-08-01

    A queueing model appropriate for the analysis of multiple-access schemes with finite user buffer capacity is proposed. This model can be applied to several slotted random multiple-access schemes, such as the URN, ALOHA, random TDMA channels, etc. The examined system, in general, can be modeled as a multidimensional Markov chain. The enormous state space for its complete description makes numerical analysis intractable. Nevertheless, symmetry properties of the system can be exploited so that the state will be reduced. In particular, the queue length at one station and the number of busy stations are used to characterize the behavior of the system. In this way, a two-dimensional Markov chain can be constructed and an approximate solution is obtained which is in excellent agreement with simulation results.

  19. Elements of queueing theory palm martingale calculus and stochastic recurrences

    CERN Document Server

    Baccelli, François

    2003-01-01

    The Palm theory and the Loynes theory of stationary systems are the two pillars of the modern approach to queuing. This book, presenting the mathematical foundations of the theory of stationary queuing systems, contains a thorough treatment of both of these. This approach helps to clarify the picture, in that it separates the task of obtaining the key system formulas from that of proving convergence to a stationary state and computing its law. The theory is constantly illustrated by classical results and models: Pollaczek-Khintchin and Tacacs formulas, Jackson and Gordon-Newell networks, multiserver queues, blocking queues, loss systems etc., but it also contains recent and significant examples, where the tools developed turn out to be indispensable. Several other mathematical tools which are useful within this approach are also presented, such as the martingale calculus for point processes, or stochastic ordering for stationary recurrences. This thoroughly revised second edition contains substantial addition...

  20. Diagonal queue medical image steganography with Rabin cryptosystem.

    Science.gov (United States)

    Jain, Mamta; Lenka, Saroj Kumar

    2016-03-01

    The main purpose of this work is to provide a novel and efficient method to the image steganography area of research in the field of biomedical, so that the security can be given to the very precious and confidential sensitive data of the patient and at the same time with the implication of the highly reliable algorithms will explode the high security to the precious brain information from the intruders. The patient information such as patient medical records with personal identification information of patients can be stored in both storage and transmission. This paper describes a novel methodology for hiding medical records like HIV reports, baby girl fetus, and patient's identity information inside their Brain disease medical image files viz. scan image or MRI image using the notion of obscurity with respect to a diagonal queue least significant bit substitution. Data structure queue plays a dynamic role in resource sharing between multiple communication parties and when secret medical data are transferred asynchronously (secret medical data not necessarily received at the same rate they were sent). Rabin cryptosystem is used for secret medical data writing, since it is computationally secure against a chosen-plaintext attack and shows the difficulty of integer factoring. The outcome of the cryptosystem is organized in various blocks and equally distributed sub-blocks. In steganography process, various Brain disease cover images are organized into various blocks of diagonal queues. The secret cipher blocks and sub-blocks are assigned dynamically to selected diagonal queues for embedding. The receiver gets four values of medical data plaintext corresponding to one ciphertext, so only authorized receiver can identify the correct medical data. Performance analysis was conducted using MSE, PSNR, maximum embedding capacity as well as by histogram analysis between various Brain disease stego and cover images.

  1. The queue as a social statement / Maria-Kristiina Soomre

    Index Scriptorium Estoniae

    Soomre, Maria-Kristiina, 1978-

    2010-01-01

    Tallinna Lauluväljakul veebruaris 2010 olnud töötute järjekorrast, kus 5000-st said alternatiivse töö reisisaatjatena 400. Keskerakonna kampaaniatest, mida võib vaadata sotsiaalse kunsti kontekstis. Sügisel 2010 Tallinna Kunstihoone juures korraldatud kunstiprojektist "Art Queue 100x100 EEK", millega sooviti tõmmata tähelepanu kunstiinstitutsioonile. Seoses kunstiga tekkinud järjekordadest, masside valmidusest kampaania korras rünnata kunsti

  2. The asymptotic variance of departures in critically loaded queues

    NARCIS (Netherlands)

    Al Hanbali, Ahmad; Mandjes, M.R.H.; Nazarathy, Y.; Whitt, W.

    2011-01-01

    We consider the asymptotic variance of the departure counting process D(t) of the GI/G/1 queue; D(t) denotes the number of departures up to time t. We focus on the case where the system load ϱ equals 1, and prove that the asymptotic variance rate satisfies limt→∞varD(t) / t = λ(1 - 2 / π)(ca2 +

  3. The queueing model for quantum key distribution network

    Institute of Scientific and Technical Information of China (English)

    Wen Hao; Han Zheng-Fu; Guo Guang-Can; Hong Pei-Lin

    2009-01-01

    This paper develops a QKD (quantum key distribution)-based queueing model to investigate the data delay on QKD link and network, especially that based on trusted relays. It shows the mean packet delay performance of the QKD system. Furthermore, it proposes a key buffering policy which could effectively improve the delay performance in practice. The results will be helpful for quality of service in practical QKD systems.

  4. The queue as a social statement / Maria-Kristiina Soomre

    Index Scriptorium Estoniae

    Soomre, Maria-Kristiina, 1978-

    2010-01-01

    Tallinna Lauluväljakul veebruaris 2010 olnud töötute järjekorrast, kus 5000-st said alternatiivse töö reisisaatjatena 400. Keskerakonna kampaaniatest, mida võib vaadata sotsiaalse kunsti kontekstis. Sügisel 2010 Tallinna Kunstihoone juures korraldatud kunstiprojektist "Art Queue 100x100 EEK", millega sooviti tõmmata tähelepanu kunstiinstitutsioonile. Seoses kunstiga tekkinud järjekordadest, masside valmidusest kampaania korras rünnata kunsti

  5. Management of active Crohn disease.

    Science.gov (United States)

    Cheifetz, Adam S

    2013-05-22

    Treatment of Crohn disease is rapidly evolving, with the induction of novel biologic therapies and newer, often more intensive treatment approaches. Knowing how to treat individual patients in this quickly changing milieu can be a challenge. To review the diagnosis and management of moderate to severe Crohn disease, with a focus on newer treatments and goals of care. MEDLINE was searched from 2000 to 2011. Additional citations were procured from references of select research and review articles. Evidence was graded using the American Heart Association level-of-evidence guidelines. Although mesalamines are still often used to treat Crohn disease, the evidence for their efficacy is lacking. Corticosteroids can be effectively used to induce remission in moderate to severe Crohn disease, but they do not maintain remission. The mainstays of treatment are immunomodulators and biologics, particularly anti-tumor necrosis factor. Immunomodulators and biologics are now the preferred treatment options for Crohn disease.

  6. Offset Optimization Based on Queue Length Constraint for Saturated Arterial Intersections

    Directory of Open Access Journals (Sweden)

    Xianmin Song

    2012-01-01

    Full Text Available Offset optimization is of critical importance to the traffic control system, especially when spillovers appear. In order to avoid vehicle queue spillovers, an arterial offset optimization model was presented in saturated arterial intersections based on minimizing the queue length over the whole duration of the saturated traffic environment. The paper uses the shockwave theory to analyze the queue evolution process of the intersection approach under the saturated traffic environment. Then through establishing and analyzing a function relationship between offset and the maximum queue length per cycle, a mapping model of offset and maximum queue length was established in the saturated condition. The validity and sensitivity of this model were tested by the VISSIM simulation environment. Finally, results showed that when volumes ratios are 0.525–0.6, adjusting offset reasonably under the saturated condition could decrease the queue length and effectively improve the vehicle operating efficiency.

  7. Decay of Tails at Equilibrium for FIFO Join the Shortest Queue Networks

    CERN Document Server

    Bramson, Maury; Prabhakar, Balaji

    2011-01-01

    In join the shortest queue networks, incoming jobs are assigned to the shortest queue from among a randomly chosen subset of D queues, in a system of N queues; after completion of service at its queue, a job leaves the network. We also assume that jobs arrive into the system according to a rate-\\alpha N Poisson process, \\alpha 1. We show under the above ansatz that, as N goes to infinity, the tail of the equilibrium queue size exhibits a wide range of behavior depending on the relationship between \\beta and D. In particular, if \\beta > D/(D-1), the tail is doubly exponential and, if \\beta < D/(D-1), the tail has a power law. When \\beta = D/(D-1), the tail is exponentially distributed.

  8. Virtual queueing techniques for UBR+ service in ATM with fair access and minimum bandwidth guarantee

    Energy Technology Data Exchange (ETDEWEB)

    Siu, K.Y.; Wu, Y.; Ren, W.

    1998-11-01

    The ATM Forum is currently discussing the need for a new best-effort service called UBR+, which is an enhancement to the existing UBR service, to support data traffic. The objective of the UBR+ service is to provide each user with a minimum service rate guarantee and a fair access to any excess available bandwidth. In this paper, the authors present a new efficient scheme for supporting this service. The key advantage of the scheme is that it employs only FIFO queueing (instead of per-VC queueing) and admits simple implementation in ATM switches. The ideas involve a simple scheduling mechanism that is based on per-VC queueing and incorporate the virtual queueing technique that can efficiently emulate per-VC queueing on a shared FIFO queue. Simulation results are presented to show that the schemes can deliver almost ideal performance for supporting the new service requirements of UBR+.

  9. 具有QoS特征宽带IP网络队列调度算法的研究%The Study of Queue Scheduling Algorithm with QoS Character in Broadband IP Network

    Institute of Scientific and Technical Information of China (English)

    刘宴兵; 李秉智

    2003-01-01

    IP Quality of Service (QoS) guarantee is realized by managing and avoiding congestion in network. In thispaper ,the primary queue algorithms are compared in managing congestion. On the basis of these theories, a newLLQ+CBWFQ algorithm is achieved, and the minimum bandwidth is assigned according to priority or request.

  10. Queueing network model for obstetric patient flow in a hospital.

    Science.gov (United States)

    Takagi, Hideaki; Kanai, Yuta; Misue, Kazuo

    2016-03-03

    A queueing network is used to model the flow of patients in a hospital using the observed admission rate of patients and the histogram for the length of stay for patients in each ward. A complete log of orders for every movement of all patients from room to room covering two years was provided to us by the Medical Information Department of the University of Tsukuba Hospital in Japan. We focused on obstetric patients, who are generally hospitalized at random times throughout the year, and we analyzed the patient flow probabilistically. On admission, each obstetric patient is assigned to a bed in one of the two wards: one for normal delivery and the other for high-risk delivery. Then, the patient may be transferred between the two wards before discharge. We confirm Little's law of queueing theory for the patient flow in each ward. Next, we propose a new network model of M/G/ ∞ and M/M/ m queues to represent the flow of these patients, which is used to predict the probability distribution for the number of patients staying in each ward at the nightly census time. Although our model is a very rough and simplistic approximation of the real patient flow, the predicted probability distribution shows good agreement with the observed data. The proposed method can be used for capacity planning of hospital wards to predict future patient load in each ward.

  11. Multilevel Queue-Based Scheduling for Heterogeneous Grid Environment

    Directory of Open Access Journals (Sweden)

    Kumaresh.V.S

    2012-11-01

    Full Text Available Grid computing is the federation of pooling resources so as to solve large-scale problems. Scheduling is the main issue in grid computing and is the process of making scheduling decisions over multiple grid resources. In this paper, we propose a scheduling technique which classifies the subtasks based on the priority assigned by the user. This is mainly applicable in places where the high priority critical subtasks may need to be scheduled prior to other low priority subtasks. We thus segregate the subtasks into three queues based on their priority. Subtasks within each queue are reordered based on two new parameters, viz. complexity factor and realization factor, with computational complexity defined as the time of computation of a process. We evaluate the realization factor as the product of number of operations per cycle per processor and the speed of the processor. The subtasks are assigned high priority when both complexity factor and realization factor are high. Once the processes are classified into three queues we make use of a technique similar to round robin that reduces starvation of low and medium priority subtasks. The effectiveness of Starvation free (SF Scheduling algorithm is evaluated through simulation results.

  12. Queueing induced by bidirectional motor motion near the end of a microtubule

    Science.gov (United States)

    Ashwin, Peter; Lin, Congping; Steinberg, Gero

    2010-11-01

    Recent live observations of motors in long-range microtubule (MT) dependent transport in the fungus Ustilago maydis have reported bidirectional motion of dynein and an accumulation of the motors at the polymerization-active (the plus-end) of the microtubule. Quantitative data derived from in vivo observation of dynein has enabled us to develop an accurate, quantitatively-valid asymmetric simple exclusion process (ASEP) model that describes the coordinated motion of anterograde and retrograde motors sharing a single oriented microtubule. We give approximate expressions for the size and distribution of the accumulation, and discuss queueing properties for motors entering this accumulation. We show for this ASEP model, that the mean accumulation can be modeled as an M/M/∞ queue that is Poisson distributed with mean Farr/pd , where Farr is the flux of motors that arrives at the tip and pd is the rate at which individual motors change direction from anterograde to retrograde motion. Deviations from this can in principle be used to gain information about other processes at work in the accumulation. Furthermore, our work is a significant step toward a mathematical description of the complex interactions of motors in cellular long-range transport of organelles.

  13. A New Vector Markov Process for M/G/1 Queue

    Institute of Scientific and Technical Information of China (English)

    严庆强; 史定华; 郭兴国

    2005-01-01

    In this paper, by considering the stochastic process of the busy period and the idle period, and introducing the unfinished work as a supplementary variable, a new vector Markov process was presented to study the M/G/1 queue again. Through establishing and solving the density evolution equations, the busy-period distribution, and the stationary distributionof waiting time and queue length were obtained. In addition, the stability condition of this queue system was given by means of an imbedded renewal process.

  14. The priority queue as an example of hardware/software codesign

    DEFF Research Database (Denmark)

    Høeg, Flemming; Mellergaard, Niels; Staunstrup, Jørgen

    1994-01-01

    The paper identifies a number of issues that are believed to be important for hardware/software codesign. The issues are illustrated by a small comprehensible example: a priority queue. Based on simulations of a real application, we suggest a combined hardware/software realization of the priority...... queue. A priority queue is a data structure with a simple interface which in many applications is a performance bottleneck...

  15. On the Fluid Approximation for a Multiclass Queue under Non-Preemptive SBP Service Discipline

    Institute of Scientific and Technical Information of China (English)

    Yong Jiang GUO

    2012-01-01

    A multi-class single server queue under non-preemptive static buffer priority (SBP) service discipline is considered in this paper.Using a bounding technique,we obtain the fluid approximation for the queue length and busy time processes.Furthermore,we prove that the convergence rate of the fluid approximation for the queue length and busy time processes is exponential for large N.Additionally,a sufficient condition for stability is obtained.

  16. Sojourn time distributions in a Markovian G-queue with batch arrival and batch removal

    OpenAIRE

    1999-01-01

    We consider a single server Markovian queue with two types of customers; positive and negative, where positive customers arrive in batches and arrivals of negative customers remove positive customers in batches. Only positive customers form a queue and negative customers just reduce the system congestion by removing positive ones upon their arrivals. We derive the LSTs of sojourn time distributions for a single server Markovian queue with positive customers and negative custom...

  17. Flow-level convergence and insensitivity for multi-class queueing networks

    Directory of Open Access Journals (Sweden)

    Neil S. Walton

    2012-01-01

    Full Text Available We consider a multi-class queueing network as a model of packet transfer in a communication network. We define a second stochastic model as a model of document transfer in a communication network where the documents transferred have a general distribution. We prove the weak convergence of the multi-class queueing process to the document transfer process. Our convergence result allows the comparison of general document size distributions, and consequently, we prove general insensitivity results for the limit queueing process. We discuss how this separation of time-scales method of proving insensitivity may be applied to other insensitive queueing systems.

  18. Many-server queues with customer abandonment: Numerical analysis of their diffusion model

    Directory of Open Access Journals (Sweden)

    Shuangchi He

    2013-01-01

    Full Text Available We use a multidimensional diffusion process to approximate the dynamics of aqueue served by many parallel servers. Waiting customers in this queue may abandonthe system without service. To analyze the diffusion model, we develop a numericalalgorithm for computing its stationary distribution. A crucial part of the algorithm ischoosing an appropriate reference density. Using a conjecture on the tailbehavior of the limit queue length process, we propose a systematic approach toconstructing a reference density. With the proposed reference density, thealgorithm is shown to converge quickly in numerical experiments. Theseexperiments demonstrate that the diffusion model is a satisfactory approximation formany-server queues, sometimes for queues with as few as twenty servers.

  19. Stability Analysis of GI/G/c/K Retrial Queue with Constant Retrial Rate

    CERN Document Server

    Avrachenkov, Konstantin

    2010-01-01

    We consider a GI/G/c/K-type retrial queueing system with constant retrial rate. The system consists of a primary queue and an orbit queue. The primary queue has $c$ identical servers and can accommodate the maximal number of $K$ jobs. If a newly arriving job finds the full primary queue, it joins the orbit. The original primary jobs arrive to the system according to a renewal process. The jobs have general i.i.d. service times. A job in front of the orbit queue retries to enter the primary queue after an exponentially distributed time independent of the orbit queue length. Telephone exchange systems, Medium Access Protocols and short TCP transfers are just some applications of the proposed queueing system. For this system we establish minimal sufficient stability conditions. Our model is very general. In addition, to the known particular cases (e.g., M/G/1/1 or M/M/c/c systems), the proposed model covers as particular cases the deterministic service model and the Erlang model with constant retrial rate. The l...

  20. Grouping Based Job Scheduling Algorithm Using Priority Queue and Hybrid Algorithm in Grid Computing

    Directory of Open Access Journals (Sweden)

    Pinky Rosemarry

    2013-01-01

    Full Text Available Grid computing enlarge with computing platform which is collection of heterogeneous computing resources connected by a network across dynamic and geographically dispersed organization to form a distributed high performance computing infrastructure. Grid computing solves the complex computing problems amongst multiple machines. Grid computing solves the large scale computational demands in a high performance computing environment. The main emphasis in the grid computing is given to the resource management and the job scheduler .The goal of the job scheduler is to maximize the resource utilization and minimize the processing time of the jobs. Existing approaches of Grid scheduling doesn’t give much emphasis on the performance of a Grid scheduler in processing time parameter. Schedulers allocate resources to the jobs to be executed using the First come First serve algorithm. In this paper, we have provided an optimize algorithm to queue of the scheduler using various scheduling methods like Shortest Job First, First in First out, Round robin. The job scheduling system is responsible to select best suitable machines in a grid for user jobs. The management and scheduling system generates job schedules for each machine in the grid by taking static restrictions and dynamic parameters of jobs and machinesinto consideration. The main purpose of this paper is to develop an efficient job scheduling algorithm to maximize the resource utilization and minimize processing time of the jobs. Queues can be optimized byusing various scheduling algorithms depending upon the performance criteria to be improved e.g. response time, throughput. The work has been done in MATLAB using the parallel computing toolbox.

  1. Medical ethics and new public management in Sweden.

    Science.gov (United States)

    Hansson, Sven Ove

    2014-07-01

    In order to shorten queues to healthcare, the Swedish government has introduced a yearly "queue billion" that is paid out to the county councils in proportion to how successful they are in reducing queues. However, only the queues for first visits are covered. Evidence has accumulated that queues for return visits have become longer. This affects the chronically and severely ill. Swedish physicians, and the Swedish Medical Association, have strongly criticized the queue billion and have claimed that it conflicts with medical ethics. Instead they demand that their professional judgments on priority setting and medical urgency be respected. This discussion provides an interesting illustration of some of the limitations of new public management and also more generally of the complicated relationships between medical ethics and public policy.

  2. Binomial Schedule for an M/G/1 Type Queueing System with an Unreliable Server under N-Policy

    Directory of Open Access Journals (Sweden)

    Lotfi Tadj

    2014-01-01

    Full Text Available We consider in this paper an M/G/1 type queueing system with the following extensions. First, the server is unreliable and is subject to random breakdowns. Second, the server also implements the well-known N-policy. Third, instead of a Bernoulli vacation schedule, the more general notion of binomial schedule with K vacations is applied. A cost function with two decision variables is developed. A numerical example shows the effect of the system parameters on the optimal management policy.

  3. Approximations for the waiting time distribution in an M/G/c priority queue

    NARCIS (Netherlands)

    Al Hanbali, A.M.; Alvarez, E.M.; Heijden, van der M.C.

    2013-01-01

    We investigate the use of priority mechanisms when assigning service engineers to customers as a tool for service differentiation. To this end, we analyze a non-preemptive M/G/c priority queue with various customer classes. For this queue, we present various accurate and fast methods to estimate the

  4. Exponential and Strong Ergodicity for Markov Processes with an Application to Queues

    Institute of Scientific and Technical Information of China (English)

    Yuanyuan LIU; Zhenting HOU

    2008-01-01

    For an ergodic continuous-time Markov process with a particular state in its space, the authors provide the necessary and sufficient conditions for exponential and strongerg odicity in terms of the moments of the first hitting time on the state. An application to the queue length process of M/G/1 queue with multiple vacations is given.

  5. First in Line Waiting Times as a Tool for Analysing Queueing Systems

    DEFF Research Database (Denmark)

    Koole, G. M.; Nielsen, Bo Friis; Nielsen, Thomas Bang

    2012-01-01

    We introduce a new approach to modelling queueing systems where the priority or the routing of customers depends on the time the first customer has waited in the queue. This past waiting time of the first customer in line, WFIL, is used as the primary variable for our approach. A Markov chain is ...

  6. The challenge of stabilizing control for queueing systems with unobservable server states

    NARCIS (Netherlands)

    Nazarathy, Y.; Taimre, T.; Asanjarani, A.; Kuhn, J.; Patch, B.; Vuorinen, A.

    2016-01-01

    We address the problem of stabilizing control for complex queueing systems where servers follow unobservable Markovian environments. The controller needs to assign servers to queues without full information about the servers' states. A control challenge is to devise a policy that matches servers to

  7. Approximate queueing models for capacitated multi-stage inventory systems under base-stock control

    NARCIS (Netherlands)

    Avsar, Zeynep Müge; Zijm, Willem H.M.

    2014-01-01

    A queueing analysis is presented for base-stock controlled multi-stage production-inventory systems with capacity constraints. The exact queueing model is approximated by replacing some state-dependent conditional probabilities (that are used to express the transition rates) by constants. Two

  8. Analysis of a single server queue interacting with a fluid reservoir

    NARCIS (Netherlands)

    Adan, I.J.B.F.; van Doorn, Erik A.; Resing, J.A.C.; Scheinhardt, Willem R.W.

    1998-01-01

    We consider a single-server queueing system with Poisson arrivals in which the speed of the server depends on whether an associated fluid reservoir is empty or not. Conversely, the rate of change of the content of the reservoir is determined by the state of the queueing system, since the reservoir

  9. Rare-event simulation for tandem queues: A simple and efficient importance sampling scheme

    NARCIS (Netherlands)

    Miretskiy, D.; Scheinhardt, W.; Mandjes, M.

    2009-01-01

    This paper focuses on estimating the rare event of overflow in the downstream queue of a tandem Jackson queue, relying on importance sampling. It is known that in this setting ‘traditional’ state-independent schemes perform poorly. More sophisticated state-dependent schemes yield asymptotic efficien

  10. Rainfall time series synthesis from queue scheduling of rain event fractals over radio links

    Science.gov (United States)

    Alonge, Akintunde A.; Afullo, Thomas J.

    2015-12-01

    Rainfall attenuation over wireless networks stems from random fluctuations in the natural process of arriving rainfall rates over radio links. This arrival process results in discernible rainfall traffic pattern which manifests as naturally scheduled and queue-generated rain spikes. Hence, the phenomenon of rainfall process can be approached as a semi-Markovian queueing process, with event characteristics dependent on queue parameters. However, a constraint to this approach is the knowledge of the physical characteristics of queue-generated rain spikes. Therefore, this paper explores the probability theory and descriptive mathematics of rain spikes in rainfall processes. This investigation presents the synthesis of rainfall queue with rain spikes at subtropical and equatorial locations of Durban (29°52'S, 30°58'E) and Butare (2°36'S, 29°44'E), respectively. The resulting comparative analysis of rainfall distributions, using error analysis at both locations, reveals that queue-generated rainfall compares well with measured rainfall data set. This suggests that the time-varying process of rainfall, though stochastic, can be synthesized via queue scheduling with the application of relevant queue parameters at any location.

  11. Correlations in Output and Overflow Traffic Processes in Simple Queues

    Directory of Open Access Journals (Sweden)

    Don McNickle

    2007-01-01

    Full Text Available We consider some simple Markov and Erlang queues with limited storage space. Although the departure processes from some such systems are known to be Poisson, they actually consist of the superposition of two complex correlated processes, the overflow process and the output process. We measure the cross-correlation between the counting processes for these two processes. It turns out that this can be positive, negative, or even zero (without implying independence. The models suggest some general principles on how big these correlations are, and when they are important. This may suggest when renewal or moment approximations to similar processes will be successful, and when they will not.

  12. Stochastic network optimization with application to communication and queueing systems

    CERN Document Server

    Neely, Michael

    2010-01-01

    This text presents a modern theory of analysis, control, and optimization for dynamic networks. Mathematical techniques of Lyapunov drift and Lyapunov optimization are developed and shown to enable constrained optimization of time averages in general stochastic systems. The focus is on communication and queueing systems, including wireless networks with time-varying channels, mobility, and randomly arriving traffic. A simple drift-plus-penalty framework is used to optimize time averages such as throughput, throughput-utility, power, and distortion. Explicit performance-delay tradeoffs are prov

  13. A note on bias optimality in controlled queueing systems

    OpenAIRE

    2000-01-01

    The use of bias optimality to distinguish among gain optimal policies was recently studied by Haviv and Puterman [1] and extended in Lewis et al. [2]. In [1], upon arrival to an M/M/1 queue, customers offer the gatekeeper a reward R. If accepted, the gatekeeper immediately receives the reward, but is charged a holding cost, c(s), depending on the number of customers in the system. The gatekeeper, whose objective is to `maximize' rewards, must decide whether to admit the cust...

  14. Algorithm for queueing networks with multi-rate traffic

    DEFF Research Database (Denmark)

    Iversen, Villy Bæk; Ko, King-Tim

    2011-01-01

    In this paper we present a new algorithm for evaluating queueing networks with multi-rate traffic. The detailed state space of a node is evaluated by explicit formulæ. We consider reversible nodes with multi-rate traffic and find the state probabilities by taking advantage of local balance. Theory...... is reversibility which implies that the arrival process and departure process are identical processes, for example state-dependent Poisson processes. This property is equivalent to reversibility. Due to product form, an open network with multi-rate traffic is easy to evaluate by convolution algorithms because...

  15. The Robo-AO automated intelligent queue system

    Science.gov (United States)

    Riddle, Reed L.; Hogstrom, Kristina; Papadopoulos, Athanasios; Baranec, Christoph; Law, Nicholas M.

    2014-07-01

    Robo-AO is the first automated laser adaptive optics instrument. In just its second year of scientific operations, it has completed the largest adaptive optics surveys to date, each comprising thousands of targets. Robo-AO uses a fully automated queue scheduling system that selects targets based on criteria entered on a per observing program or per target basis, and includes the ability to coordinate with US Strategic Command automatically to avoid lasing space assets. This enables Robo-AO to select among thousands of targets at a time, and achieve an average observation rate of approximately 20 targets per hour.

  16. The Robo-AO automated intelligent queue system

    CERN Document Server

    Riddle, Reed L; Papadopoulos, Athanasios; Baranec, Christoph; Law, Nicholas M

    2014-01-01

    Robo-AO is the first automated laser adaptive optics instrument. In just its second year of scientific operations, it has completed the largest adaptive optics surveys to date, each comprising thousands of targets. Robo-AO uses a fully automated queue scheduling system that selects targets based on criteria entered on a per observing program or per target basis, and includes the ability to coordinate with US Strategic Command automatically to avoid lasing space assets. This enables Robo-AO to select among thousands of targets at a time, and achieve an average observation rate of approximately 20 targets per hour.

  17. PRIORITIZED QUEUE WITH ROUND ROBIN SCHEDULER FOR BUFFERED CROSSBAR SWITCHES

    Directory of Open Access Journals (Sweden)

    N. Narayanan Prasanth

    2014-03-01

    Full Text Available Research in high speed switching systems is in greater demand as the internet traffic gets rapid increase. Designing an efficient scheduling algorithm with high throughput and low delay is an open challenge. Most of the algorithms achieve 100% throughput in uniform traffics but failed to attain the same performance under non-uniform traffics. Moreover these algorithms are also suffers from starvation leads to extended waiting time of VOQ. In this paper, Prioritized Queue with Round Robin Scheduler (PQRS is proposed for Buffered Crossbar Switches. We proved that our proposed scheduler can achieve 85% throughput under any non-uniform traffic without starvation.

  18. Queueing interpretation of adaptive reconstructive multiparameter τ-opening filters

    Science.gov (United States)

    Chen, Yidong; Dougherty, Edward R.

    1998-04-01

    A multiparameter binary (tau) -opening is a union of parameterized openings in which parameters for each opening are individually defined and a structuring element can be parameterized relative to both size and shape. The reconstructive filter corresponding to an opening is defined by fully passing any grain not eliminated by the opening and deleting all other grains. Adaptive design results from treating the parameter vector of a reconstructive multiparameter (tau) -opening as the state space of a Markov chain. The present paper considers the relationship between Markovian queueing networks and adaptive multiparameter (tau) - openings for the signal-union-noise model.

  19. Scheduling in Parallel Queues with Randomly Varying Connectivity and Switchover Delay

    CERN Document Server

    Celik, Guner D; Modiano, Eytan

    2010-01-01

    We consider a dynamic server control problem for two parallel queues with randomly varying connectivity and server switchover time between the queues. At each time slot the server decides either to stay with the current queue or switch to the other queue based on the current connectivity and the queue length information. The introduction of switchover time is a new modeling component of this problem, which makes the problem much more challenging. We develop a novel approach to characterize the stability region of the system by using state action frequencies, which are stationary solutions to a Markov Decision Process (MDP) formulation of the corresponding saturated system. We characterize the stability region explicitly in terms of the connectivity parameters and develop a frame-based dynamic control (FBDC) policy that is shown to be throughput-optimal. In fact, the FBDC policy provides a new framework for developing throughput-optimal network control policies using state action frequencies. Furthermore, we d...

  20. Cycle-by-Cycle Queue Length Estimation for Signalized Intersections Using Multi-Source Data

    Institute of Scientific and Technical Information of China (English)

    Zhongyu Wang; Qing Cai; Bing Wu; Yinhai Wang; Linbo Li

    2015-01-01

    In order to estimate vehicular queue length at signalized intersections accurately and overcome the shortcomings and restrictions of existing studies especially those based on shockwave theory, a new methodology is presented for estimating vehicular queue length using data from both point detectors and probe vehicles. The methodology applies the shockwave theory to model queue evolution over time and space. Using probe vehicle locations and times as well as point detector measured traffic states, analytical formulations for calculating the maximum and minimum ( residual) queue length are developed. The proposed methodology is verified using ground truth data collected from numerical experiments conducted in Shanghai, China. It is found that the methodology has a mean absolute percentage error of 17�09%, which is reasonably effective in estimating the queue length at traffic signalized intersections. Limitations of the proposed models and algorithms are also discussed in the paper.

  1. Ten Year Review of Queue Scheduling of the Hobby-Eberly Telescope

    CERN Document Server

    Shetrone, Matthew; Fowler, James R; Gaffney, Niall; Laws, Benjamin; Mader, Jeff; Mason, Cloud; Odewahn, Stephen; Roman, Brian; Rostopchin, Sergey; Schneider, Donald P; Umbarger, James; Westfall, Amy

    2007-01-01

    This paper presents a summary of the first 10 years of operating the Hobby-Eberly Telescope (HET) in queue mode. The scheduling can be quite complex but has worked effectively for obtaining the most science possible with this uniquely designed telescope. The queue must handle dozens of separate scientific programs, the involvement of a number of institutions with individual Telescope Allocation Committees as well as engineering and instrument commissioning. We have continuously revised our queue operations as we have learned from experience. The flexibility of the queue and the simultaneous availability of three instruments, along with a staff trained for all aspects of telescope and instrumentation operation, have allowed optimum use to be made of variable weather conditions and have proven to be especially effective at accommodating targets of opportunity and engineering tasks. In this paper we review the methodology of the HET queue along with its strengths and weaknesses.

  2. Analysis of performance measures with single channel fuzzy queues under two class by using ranking method

    Science.gov (United States)

    Mueen, Zeina; Ramli, Razamin; Zaibidi, Nerda Zura

    2016-08-01

    In this paper, we propose a procedure to find different performance measurements under crisp value terms for new single fuzzy queue FM/F(H1,H2)/1 with two classes, where arrival rate and service rates are all fuzzy numbers which are represented by triangular and trapezoidal fuzzy numbers. The basic idea is to obtain exact crisp values from the fuzzy value, which is more realistic in the practical queueing system. This is done by adopting left and right ranking method to remove the fuzziness before computing the performance measurements using conventional queueing theory. The main advantage of this approach is its simplicity in application, giving exact real data around fuzzy values. This approach can also be used in all types of queueing systems by taking two types of symmetrical linear membership functions. Numerical illustration is solved in this article to obtain two groups of crisp values in the queueing system under consideration.

  3. The M/M/1 Queue with Controlled Multiple Working Vacations

    Institute of Scientific and Technical Information of China (English)

    ZHANG Hong-bo; FENG Ping-hua

    2013-01-01

    In this paper,we study an M/M/1 queue with multiple working vacations under following Bernoulli control policy:at the instants of the completion of a service in vacation,the server will interrupt the vacation and enter regular busy period with probabiiity1-p (if there are customers in the queue) or continue the vacation with probability p.For this model,we drive the analytic expression of the stationary queue length and demonstrate stochastic decomposition structures of the stationary queue length and waiting time,also we obtain the additional queue length and the additional delay of this model.The results we got agree with the corresponding results for working vacation model with or without vacation interruption if we set p =0 or p =1,respectively.

  4. Transient Solution to an infinite Server Queue with Varying Arrival and Departure Rate

    Directory of Open Access Journals (Sweden)

    A. A. El-Sherbiny

    2010-01-01

    Full Text Available Problem statement: In many potential application of queueing theory, the transient solution of queueing system is important. Approach: This study presented the transient solution for infinite server queues with Poisson arrivals and exponential service times when the parameters of both distributions are allowed to vary with time. Based on generating functions technique which results in a simple differential equation. Using the properties of Bessel functions in the solution of this differential equation, the solution of an infinite server queues can be given in simple form. Results: The researcher obtained the transient solution an infinite server queues with Poisson arrivals and exponential service times when the parameters of both distributions are allowed to vary with time and prove that some past results are special case from his results. Conclusion: These results indicated that the probabilities can be extracted in a direct way.

  5. New Approach for Finding Basic Performance Measures of Single Server Queue

    Directory of Open Access Journals (Sweden)

    Siew Khew Koh

    2014-01-01

    Full Text Available Consider the single server queue in which the system capacity is infinite and the customers are served on a first come, first served basis. Suppose the probability density function f(t and the cumulative distribution function F(t of the interarrival time are such that the rate f(t/1-F(t tends to a constant as t→∞, and the rate computed from the distribution of the service time tends to another constant. When the queue is in a stationary state, we derive a set of equations for the probabilities of the queue length and the states of the arrival and service processes. Solving the equations, we obtain approximate results for the stationary probabilities which can be used to obtain the stationary queue length distribution and waiting time distribution of a customer who arrives when the queue is in the stationary state.

  6. Convolution Model of a Queueing System with the cFIFO Service Discipline

    Directory of Open Access Journals (Sweden)

    Sławomir Hanczewski

    2016-01-01

    Full Text Available This article presents an approximate convolution model of a multiservice queueing system with the continuous FIFO (cFIFO service discipline. The model makes it possible to service calls sequentially with variable bit rate, determined by unoccupied (free resources of the multiservice server. As compared to the FIFO discipline, the cFIFO queue utilizes the resources of a multiservice server more effectively. The assumption in the model is that the queueing system is offered a mixture of independent multiservice Bernoulli-Poisson-Pascal (BPP call streams. The article also discusses the results of modelling a number of queueing systems to which different, non-Poissonian, call streams are offered. To verify the accuracy of the model, the results of the analytical calculations are compared with the results of simulation experiments for a number of selected queueing systems. The study has confirmed the accuracy of all adopted theoretical assumptions for the proposed analytical model.

  7. THE BULK INPUT M[X]/M/1 QUEUE WITH WORKING VACATIONS

    Institute of Scientific and Technical Information of China (English)

    Xiuli XU; Mingxin LIU; Xiaohua ZHAO

    2009-01-01

    In this paper, we analyze a bulk input M[X]/M/1 queue with multiple working vacations. A quasi upper triangle transition probability matrix of two-dimensional Markov chain in this model is obtained, and with the matrix analysis method, highly complicated probability generating function(PGF) of the stationary queue length is firstly derived, from which we got the stochastic decomposition result for the stationary queue length which indicates the evident relationship with that of the classical M[X]/M/1 queue without vacation. It is important that we find the upper and the lower bounds of the stationary waiting time in the Laplace transform order using the properties of the conditional Erlang distribution. Furthermore, we gain the mean queue length and the upper and the lower bounds of the mean waiting time.

  8. Batch arrival retrial queue with delay time and additional multi-optional repair

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    D. Sumitha

    2016-12-01

    Full Text Available This paper deals with MX/G/1 retrial queue with unreliable server and multi-optional repair. It is assumed that the server is subject to active breakdowns and the repair of the failed server starts after a random amount of time. Restoration of the failed server is done with two phases, first essential and second multi optional. After completion of the repair the server continues the interrupted service and it is not allowed to accept new customers until the interrupted customer leaves the system. The retrial, service, delay and repair times are arbitrarily distributed. The model is analysed using the supplementary variable technique and the probability generating function of system size at random epoch and stochastic decomposition are obtained. Performance measures and reliability indices to predict the behaviour of the system are derived.

  9. MODELING AND SIMULATION OF QUEUE WAITING THROUGH THE CONCEPT OF PETRI NETS

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    Emilija KAMCEVA

    2011-08-01

    Full Text Available Petri Nets-PN are a graphical formalism which is gaining popularity in recent years as a tool in Matlab for the representation of complex logical interactions among physical components or activities in a system. This notes are devoted to introduce the formalism of Petri nets with particular emphasis on the application of the methodology in the area of the performance and reliability modelling and analysis of systems. A technique is presented whereby queueing network models and generalized stochastic Petri nets are combined in such a way as to exploit the best features of both modeling techniques. The resulting hierarchical modeling approach is useful in the solution of complex models of system behavior.

  10. Management of Logistics Activities and Costing Approaches

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    İlker KIYMETLİ ŞEN

    2014-06-01

    Full Text Available In recent years, enterprises are required to reconsider the management of logistics activities as a result of developments such as increasing competition, rapid technological development, and the shortening of product life cycles. As a result of globalization, costs of logistics activities have also increased depending on changes in the quality and quantity of logistics activities. According to research on logistics activities, the physical distribution costs of enterprises may reach up to 30% of sales. For this reason, the management of logistics operations and control of costs caused by these activities is a necessity. The increase in costs negatively impact on the financial performance of enterprises, cash flows, profitability and so value of the shares. The aim of this study was to describe the structure of logistics costs and logistics activities to explain the methods used in costing. For this purpose, many studies in the literature were investigated. The aim of this study was to describe the structure of logistics costs and logistics activities to explain the methods used in costing. For this purpose, many studies in the literature were investigated.

  11. On queue-size scaling for input-queued switches

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    Devavrat Shah

    2016-11-01

    Full Text Available We study the optimal scaling of the expected total queue size in an n×n input-queued switch, as a function of the number of ports n and the load factor ρ, which has been conjectured to be Θ(n/(1−ρ (cf. [15]. In a recent work [16], the validity of this conjecture has been established for the regime where 1−ρ=O(1/n2. In this paper, we make further progress in the direction of this conjecture. We provide a new class of scheduling policies under which the expected total queue size scales as O(n1.5(1−ρ−1log(1/(1−ρ when 1−ρ=O(1/n. This is an improvement over the state of the art; for example, for ρ=1−1/n the best known bound was O(n3, while ours is O(n2.5logn.

  12. Multiserver Queue with Guard Channel for Priority and Retrial Customers

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    Kazuki Kajiwara

    2016-01-01

    Full Text Available This paper considers a retrial queueing model where a group of guard channels is reserved for priority and retrial customers. Priority and normal customers arrive at the system according to two distinct Poisson processes. Priority customers are accepted if there is an idle channel upon arrival while normal customers are accepted if and only if the number of idle channels is larger than the number of guard channels. Blocked customers (priority or normal join a virtual orbit and repeat their attempts in a later time. Customers from the orbit (retrial customers are accepted if there is an idle channel available upon arrival. We formulate the queueing system using a level dependent quasi-birth-and-death (QBD process. We obtain a Taylor series expansion for the nonzero elements of the rate matrices of the level dependent QBD process. Using the expansion results, we obtain an asymptotic upper bound for the joint stationary distribution of the number of busy channels and that of customers in the orbit. Furthermore, we develop an efficient numerical algorithm to calculate the joint stationary distribution.

  13. Queueing-Based Synchronization and Entrainment for Synthetic Gene Oscillators

    Science.gov (United States)

    Mather, William; Butzin, Nicholas; Hochendoner, Philip; Ogle, Curtis

    Synthetic gene oscillators have been a major focus of synthetic biology research since the beginning of the field 15 years ago. They have proven to be useful both for biotechnological applications as well as a testing ground to significantly develop our understanding of the design principles behind synthetic and native gene oscillators. In particular, the principles governing synchronization and entrainment of biological oscillators have been explored using a synthetic biology approach. Our work combines experimental and theoretical approaches to specifically investigate how a bottleneck for protein degradation, which is present in most if not all existing synthetic oscillators, can be leveraged to robustly synchronize and entrain biological oscillators. We use both the terminology and mathematical tools of queueing theory to intuitively explain the role of this bottleneck in both synchronization and entrainment, which extends prior work demonstrating the usefulness of queueing theory in synthetic and native gene circuits. We conclude with an investigation of how synchronization and entrainment may be sensitive to the presence of multiple proteolytic pathways in a cell that couple weakly through crosstalk. This work was supported by NSF Grant #1330180.

  14. Upper Bound for Queue length in Regulated Burst Service Scheduling

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    Mahmood Daneshvar Farzanegan

    2016-01-01

    Full Text Available Quality of Service (QoS provisioning is very important in next computer/communication networks because of increasing multimedia services. Hence, very investigations are performed in this area. Scheduling algorithms effect QoS provisioning. Lately, a scheduling algorithm called Regulated Burst Service Scheduling (RBSS suggested by author in [1] to provide a better service to bursty and delay sensitive services such as video. One of the most significant feature in RBSS is considering burstiness of arrival traffic in scheduling algorithm. In this paper, an upper bound of queue length or buffer size and service curve are calculated by Network Calculus analysis for RBSS. Because in RBSS queue length is a parameter that is considered in scheduling arbitrator, analysis results a differential inequality to obtain service curve. To simplify, arrival traffic is assumed to be linear that is defined in the paper clearly. This paper help to analysis delay in RBSS for different traffic with different specifications. Therefore, QoS provisioning will be evaluated.

  15. Managing CSCL Activity through networking models

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    Luis Casillas

    2014-04-01

    Full Text Available This study aims at managing activity carried out in Computer-Supported Collaborative Learning (CSCL environments. We apply an approach that gathers and manages the knowledge underlying huge data structures, resulting from collaborative interaction among participants and stored as activity logs. Our method comprises a variety of important issues and aspects, such as: deep understanding of collaboration among participants in workgroups, definition of an ontology for providing meaning to isolated data manifestations, discovering of knowledge structures built in huge amounts of data stored in log files, and development of high-semantic indicators to describe diverse primitive collaborative acts, and binding these indicators to formal descriptions defined in the collaboration ontology; besides our method includes gathering collaboration indicators from web forums using natural language processing (NLP techniques.

  16. The Recursive Solution for Geom/G/1(E,SV) Queue with Feedback and Single Server Vacation

    Institute of Scientific and Technical Information of China (English)

    Chuan-yi Luo; Ying-hui Tang

    2011-01-01

    Using recursive method, this paper studies the queue size properties at any epoch n+ in Geom/G/i(E, SV) queueing model with feedback under LASDA (late arrival system with delayed access) setup. Some new results about the recursive expressions of queue size distribution at different epoch (n+, n, n-) are obtained.Furthermore the important relations between stationary queue size distribution at different epochs are discovered.The results are different from the relations given in M/G/1 queueing system. The model discussed in this paper can be widely applied in many kinds of communications and computer network.

  17. Identification of waiting time distribution of M/G/1, Mx/G/1, GIr/M/1 queueing systems

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    A. Ghosal

    1988-01-01

    Full Text Available This paper brings out relations among the moments of various orders of the waiting time of the 1st customer and a randomly selected customer of an arrival group for bulk arrivals queueing models, and as well as moments of the waiting time (in queue for M/G/1 queueing system. A numerical study of these relations has been developed in order to find the (β1,β2 measures of waiting time distribution in a comutable form. On the basis of these measures one can look into the nature of waiting time distribution of bulk arrival queues and the single server M/G/1 queue.

  18. Steps in Designing Queue and Interview Process using Information System: A Case of Re-registration of New Students in Universitas Negeri Makassar

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    Ansari Saleh Ahmar

    2016-06-01

    Full Text Available Universitas Negeri Makassar (UNM have a number of prospective students is quite a lot. Based on data released by the BAPSI UNM (2015 that the data student candidates of UNM who passed the selection with SNMPTN SBMPTN selection as 3,791 people. If the prospective graduate students interviewed are normally it will take a long time and will certainly make students uncomfortable. Therefore it is necessary design an information systems to solving this problem. This research aim to develop an information system to facilitate the process queue. The method used in this research is to use the three stages in the Software Development Life Cycle method namely Initiation Phase, Development/Acquisition Phase, and Implementation Phase. This information system development using PHP and CodeIgniter as a its framework. This design results will be obtained an queues and interviews information system that can be used to manage the queue and interview data. By implementing this system, it potentially reduce time to wait and the process of managing results of interviews can be obtained directly without a process of inputting interview repeat if done manually.

  19. Control of parallel non-observable queues: Asymptotic equivalence and optimality of periodic policies

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    Jonatha Anselmi

    2015-12-01

    Full Text Available We consider a queueing system composed of a dispatcher that routes jobs to a set of non-observable queues working in parallel. In this setting, the fundamental problem is which policy should the dispatcher implement to minimize the stationary mean waiting time of the incoming jobs. We present a structural property that holds in the classic scaling of the system where the network demand (arrival rate of jobs grows proportionally with the number of queues. Assuming that each queue of type r is replicated k times, we consider a set of policies that are periodic with period k∑rpr and such that exactly pr jobs are sent in a period to each queue of type r. When k→∞, our main result shows that all the policies in this set are equivalent, in the sense that they yield the same mean stationary waiting time, and optimal, in the sense that no other policy having the same aggregate arrival rate to all queues of a given type can do better in minimizing the stationary mean waiting time. This property holds in a strong probabilistic sense. Furthermore, the limiting mean waiting time achieved by our policies is a convex function of the arrival rate in each queue, which facilitates the development of a further optimization aimed at solving the fundamental problem above for large systems.

  20. Heavy traffic queue length behavior in a switch under the MaxWeight algorithm

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    Siva Theja Maguluri

    2016-11-01

    Full Text Available We consider a switch operating under the MaxWeight scheduling algorithm, under any traffic pattern such that all the ports are loaded. This system is interesting to study since the queue lengths exhibit a multi-dimensional state-space collapse in the heavy-traffic regime. We use a Lyapunov-type drift technique to characterize the heavy-traffic behavior of the expectation of the sum queue lengths in steady-state, under the assumption that all ports are saturated and all queues receive non-zero traffic. Under these conditions, we show that the heavy-traffic scaled queue length is given by (1−1/2n||σ||2, where σ is the vector of the standard deviations of arrivals to each port in the heavy-traffic limit. In the special case of uniform Bernoulli arrivals, the corresponding formula is given by (n−3/2+1/2n. The result shows that the heavy-traffic scaled queue length has optimal scaling with respect to n, thus settling one version of an open conjecture; in fact, it is shown that the heavy-traffic queue length is at most within a factor of two from the optimal. We then consider certain asymptotic regimes where the load of the system scales simultaneously with the number of ports. We show that the MaxWeight algorithm has optimal queue length scaling behavior provided that the arrival rate approaches capacity sufficiently fast.

  1. Characteristics of rainfall queues for rain attenuation studies over radio links at subtropical and equatorial Africa

    Science.gov (United States)

    Alonge, Akintunde A.; Afullo, Thomas J.

    2014-08-01

    Attenuation due to precipitation remains an important design factor in the future deployment of terrestrial and earth-space communication radio links. Largely, there are concerted efforts to understand the dynamics of precipitation in attenuation occurrence at subtropical, tropical, and equatorial region of Africa. In this deliberate approach, rainfall spikes pertaining to rain cells are conceptualized as distinct rain spike traffic over radio links, by applying queueing theory concepts. The queue distributions at Durban (29°52'S, 30°58'E) and Butare (2°36'S, 29°44'E)—respectively, of subtropical and equatorial climates—are investigated from distrometer measurements. The data sets at both sites are observed over four rain regimes: drizzle, widespread, shower, and thunderstorm. The queue parameters of service time and inter-arrival of rain spikes traffic at both regions are found to be Erlang-k distributed (Ek) and exponentially distributed (M), respectively. It is established that the appearance of rain rates over radio links invariably follows a First Come, First Served (FCFS), multi-server (s), infinite queue, and semi-Markovian process, designated as M/Ek/s/∞/FCFS discipline. Modeled queue parameters at both regions are found to vary significantly over different regimes. However, these queue parameters over the entire data set suggest similar queue patterns at both sites. More importantly, power law relationships describing other queue-related parameters are formulated. The paper concludes by demonstrating an application of queueing theory for rainfall synthesis. The proposed technique will provide an alternative method of estimating rain cell sizes and rain attenuation over satellite and terrestrial links.

  2. Design professional activity analysis in design management

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    Claudia de Souza Libanio

    2013-08-01

    Full Text Available Design use perception, as an essential element for achieving competitive advantage, also suggests the need to manage the design activities in companies. However, a few is discussed about the activity of these design professionals who participate in this process, their roles, functions and competencies, including  their connections to a company and other involved sectors. This article aims to analyze, during the design management processes, the work relations of design professionals connected to organizations both internal and externally, in order to comprehend the structure and intervenient factors on the activity of these professionals, as well as the interactions with their main coworkers. The methodology was exploratory and qualitative, using in-depth interviews with three design professionals. Subsequently, the responses were analyzed allowing the comparison of these obtained data to the theoretical bases researched. Through this case study, it was possible to realize the aspects and the structure of the design professional activity, connected intern and externally to organizations, as well as its relations with the main coworkers.

  3. Carbon sink activity of managed grasslands

    Science.gov (United States)

    Klumpp, Katja; Chabbi, Abad; Gastal, Francois; Senapati, Nimai; Charrier, Xavier; Darsonville, Olivier; Creme, Alexandra

    2017-04-01

    In agriculture, a large proportion of GHG emission saving potential may be achieved by means of soil C sequestration. Recent demonstrations of carbon sink activities however, often questioned the existence of C storing grasslands, as uncertainty surrounding estimates are often larger than the sink itself. Besides climate, key components of the carbon sink activity in grasslands are type and intensity of management practices. Here, we analysed long term data on C flux and soil organic carbon stocks for two long term (>13yrs) national observation sites in France (SOERE-ACBB). These sites comprise a number of grassland fields and managements options (i.e. permanent, sowing, grazing, mowing, and fertilization) offering an opportunity to study carbon offsets (i.e. compensation of CH4 and N2O emissions), climatic-management interactions and trade-offs concerning ecosystem services (e.g. production). Furthermore, for some grassland fields, the carbon sink activity was compared using two methods; repeated soil inventory and estimation of the ecosystem C budget by continuous measurement of CO2 exchange (i.e. eddy covariance) in combination with quantification of other C imports and exports, necessary to estimate net C storage. In general grasslands, were a potential sink of C (i.e. net ecosystem exchange, NEE), where grazed sites had lower NEE compared the cut site. However, when it comes to net C storage (NCS), mowing reduced markedly potential sink leading to very low NCS compared to grazed sites. Including non-CO2 fluxes (CH4 and N2O emission) in the budget, revealed that GHG emissions were offset by C sink activity.

  4. On the M/G/1 queueing system with multiclass customers and fixed feedback

    Institute of Scientific and Technical Information of China (English)

    ZHANG Qi-zhi

    2008-01-01

    The M/G/1 queueing system with multiclass customer arrivals, fixed feedback, and first come first served policy is considered, where different classes of customers have different arrival rates, service-time distributions, and feedback numbers. The joint probability generation function of queue size of each class and the Laplace-Stieltjes transform of the total sojourn time of a customer in each class are presented, which extended the results obtained by Choi B D. The mean queue size of each class and mean total sojourn time of a customer in each class are obtained with this result. The results can be used in computer and communication networks for their performance analysis.

  5. Practical Multiwriter Lock-Free Queues for "Hard Real-Time" Systems without CAS

    CERN Document Server

    Lee, Jeremy

    2007-01-01

    FIFO queues with a single reader and writer can be insufficient for "hard real-time" systems where interrupt handlers require wait-free guarantees when writing to message queues. We present an algorithm which elegantly and practically solves this problem on small processors that are often found in embedded systems. The algorithm does not require special CPU instructions (such as atomic CAS), and therefore is more robust than many existing methods that suffer the ABA problem associated with swing pointers. The algorithm gives "first-in, almost first-out" guarantees under pathological interrupt conditions, which manifests as arbitrary "shoving" among nearly-simultaneous arrivals at the end of the queue.

  6. Sojourn time distributions in a Markovian G-queue with batch arrival and batch removal

    Directory of Open Access Journals (Sweden)

    Yang Woo Shin

    1999-01-01

    Full Text Available We consider a single server Markovian queue with two types of customers; positive and negative, where positive customers arrive in batches and arrivals of negative customers remove positive customers in batches. Only positive customers form a queue and negative customers just reduce the system congestion by removing positive ones upon their arrivals. We derive the LSTs of sojourn time distributions for a single server Markovian queue with positive customers and negative customers by using the first passage time arguments for Markov chains.

  7. Basic components of construction enterprises’ management marketing activities system

    OpenAIRE

    Seleznova Olha Olexandrivna

    2015-01-01

    This article investigated the basic components of construction enterprises’ management marketing activities system. It is developed the model of the construction enterprises’ management marketing activities system. The article explores the essence of the stages of forming the construction enterprises’ management marketing activities system. The article reveals the basic elements of marketing management – mission, goals, strategy. It describes the basic functions of marketing management system...

  8. REGIONALIZATION OF MANAGEMENT PROCESS BY INNOVATIVE ACTIVITY

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    E. V. Sibirskaia

    2014-01-01

    Full Text Available Summary. In current market conditions, the economy and Russia's accession to international trade scholars and experts from various fields of knowledge paying special attention to a huge set of regional problems. The growing role of regional research determines the level of establishing effective mechanisms for the implementation of the economic interests of actors as well as economic development and improving the quality of human life is the priority objectives of federal, regional and local authorities. Today, the Russian economic science faces a global goal - to develop ways and means of transformation of the Russian economy and bring it to a path of sustainable, innovative development, providing new quality of life. Achieving this goal must surely be a central task of the Russian economics and politics, as in the near future and the long term In article authors opened the maintenance of determinants of innovative development of the territory, mediated by strengthening of regionalization of management by innovative activity: condition of resource and innovative potential; the developed forms and nature of interaction between public authorities of regional level, local community and business; applied forms of integration of subjects of managing for realization of their innovative potential due to expansion of opportunities of participation in the perspective directions of scientific and technical, economic and social development; system of the incentives developing favorable conditions for introduction and development of innovative technologies, and also increases in the enterprise activity, formed by the external institutional environment; regional economic policy as instrument of increase of efficiency of innovative activity.

  9. Ultrasound waiting lists: rational queue or extended capacity?

    Science.gov (United States)

    Brasted, Christopher

    2008-06-01

    The features and issues regarding clinical waiting lists in general and general ultrasound waiting lists in particular are reviewed, and operational aspects of providing a general ultrasound service are also discussed. A case study is presented describing a service improvement intervention in a UK NHS hospital's ultrasound department, from which arises requirements for a predictive planning model for an ultrasound waiting list. In the course of this, it becomes apparent that a booking system is a more appropriate way of describing the waiting list than a conventional queue. Distinctive features are identified from the literature and the case study as the basis for a predictive model, and a discrete event simulation model is presented which incorporates the distinctive features.

  10. Channel Coding over Multiple Coherence Blocks with Queueing Constraints

    CERN Document Server

    Qiao, Deli; Velipasalar, Senem

    2010-01-01

    This paper investigates the performance of wireless systems that employ finite-blocklength channel codes for transmission and operate under queueing constraints in the form of limitations on buffer overflow probabilities. A block fading model, in which fading stays constant in each coherence block and change independently between blocks, is considered. It is assumed that channel coding is performed over multiple coherence blocks. An approximate lower bound on the transmission rate is obtained from Feintein's Lemma. This lower bound is considered as the service rate and is incorporated into the effective capacity formulation, which characterizes the maximum constant arrival rate that can be supported under statistical queuing constraints. Performances of variable-rate and fixed-rate transmissions are studied. The optimum error probability for variable rate transmission and the optimum coding rate for fixed rate transmission are shown to be unique. Moreover, the tradeoff between the throughput and the number of...

  11. A-MMLQ Algorithm for Multi-level Queue Scheduling

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    Manupriya Hasija

    2013-07-01

    Full Text Available This being the era of advancement in computing domain, the emphasis is on better resource scheduling. Scheduling is not confined to dealing multiple tasks by a single processor. It’s a dawn with multiprocessing and multitasking. Although multiprocessor systems impose several overheads but still make the concept amazingly interesting. The scheduling field has taken a whirlwind after the notion of multiprocessing. Many of the uniprocessor algorithms do fit well under the multiprocessor systems but, still necessitating a further development aiming solely on multiprocessor scheduling. This paper thus sketches a new idea to modify and extend the well-known multi-level queue scheduling, taking into account the arrival time/ arrival sequence to conceptualize an innovative scheduling algorithm.

  12. Analysis of a multi-server queueing model of ABR

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    R. Núñez-Queija

    1998-01-01

    Full Text Available In this paper we present a queueing model for the performance analysis of Available Bit Rate (ABR traffic in Asynchronous Transfer Mode (ATM networks. We consider a multi-channel service station with two types of customers, denoted by high priority and low priority customers. In principle, high priority customers have preemptive priority over low priority customers, except on a fixed number of channels that are reserved for low priority traffic. The arrivals occur according to two independent Poisson processes, and service times are assumed to be exponentially distributed. Each high priority customer requires a single server, whereas low priority customers are served in processor sharing fashion. We derive the joint distribution of the numbers of customers (of both types in the system in steady state. Numerical results illustrate the effect of high priority traffic on the service performance of low priority traffic.

  13. Asymptotic expansions for large closed and loss queueing networks

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    Kogan Yaakov

    2002-01-01

    Full Text Available Loss and closed queueing network models have long been of interest to telephone and computer engineers and becoming increasingly important as models of data transmission networks. This paper describes a uniform approach that has been developed during the last decade for asymptotic analysis of large capacity networks with product form of the stationary probability distribution. Such a distribution has an explicit form up to the normalization constant, or the partition function. The approach is based on representing the partition function as a contour integral in complex space and evaluating the integral using the saddle point method and theory of residues. This paper provides an introduction to the area and a review of recent work.

  14. Adaptive Epidemic Routing Algorithm Based on Multi Queue in DTN%基于多队列自适应的DTN传染路由算法

    Institute of Scientific and Technical Information of China (English)

    郭航; 王兴伟; 黄敏; 蒋定德

    2012-01-01

    Epidemic routing is one of the basic Simple routing algorithms in the Delay/Disruption Tolerant Networks (DTN). This paper proposes a multi queues adaptive epidemic routing algorithm according to the variable characteristics of DTN and shortcomings of epidemic routing, introduces multi queues into storage managements, adopts the utility function to sort the messages in queue, and uses the different forwarding policy for different queues and network conditions. The proposed routing algorithm can reduce the overhead ratio of networks and communication delay, increase the delivery ratio and offer the simple QoS. The simulation shows that the algorithm is superior to Spray and wait, Maxprop in performance.%传染路由是DTN中一类较简单的基本路由算法.钎对DTN网络环境易变的特点及传染路由的不足提出多队列自适应传染路由,采用多队列方式管理存储空间,利用效用函数对队列内信息进行排序,针对不同队列及网络情况采用相异的转发机制,从而降低网络负载率、提高传输率并降低传输时延,同时可提供简单的QoS.仿真证明本算法优于路由算法Spray and wait和MaxProp.

  15. Fluid Approximation and Its Convergence Rate for GI/G/1 Queue with Vacations

    Institute of Scientific and Technical Information of China (English)

    Yong-jiang Guo

    2011-01-01

    A GI/G/1 queue with vacations is considered in this paper. We develop an approximating technique on max function of independent and identically distributed (i.i.d.) random variables, that is max{ηi, 1 ≤ i ≤ n}.The approximating technique is used to obtain the fluid approximation for the queue length, workload and busy time processes. Furthermore, under uniform topology, if the scaled arrival process and the scaled service process converge to the corresponding fluid processes with an exponential rate, we prove by the approximating technique that the scaled processes characterizing the queue converge to the corresponding fluid limits with the exponential rate only for large N. Here the scaled processes include the queue length process, workload process and busy time process.

  16. A Hybrid Circular Queue Method for Iterative Stencil Computations on GPUs

    Institute of Scientific and Technical Information of China (English)

    Yang Yang; Hui-Min Cui; Xiao-Bing Feng; Jing-Ling Xue

    2012-01-01

    In this paper,we present a hybrid circular queue method that can significantly boost the performance of stencil computations on GPU by carefully balancing usage of registers and shared-memory.Unlike earlier methods that rely on circular queues predominantly implemented using indirectly addressable shared memory,our hybrid method exploits a new reuse pattern spanning across the multiple time steps in stencil computations so that circular queues can be implemented by both shared memory and registers effectively in a balanced manner.We describe a framework that automatically finds the best placement of data in registers and shared memory in order to maximize the performance of stencil computations.Validation using four different types of stencils on three different GPU platforms shows that our hybrid method achieves speedups up to 2.93X over methods that use circular queues implemented with shared-memory only.

  17. Queueing model for an ATM multiplexer with unequal input/output link capacities

    Science.gov (United States)

    Long, Y. H.; Ho, T. K.; Rad, A. B.; Lam, S. P. S.

    1998-10-01

    We present a queuing model for an ATM multiplexer with unequal input/output link capacities in this paper. This model can be used to analyze the buffer behaviors of an ATM multiplexer which multiplexes low speed input links into a high speed output link. For this queuing mode, we assume that the input and output slot times are not equal, this is quite different from most analysis of discrete-time queues for ATM multiplexer/switch. In the queuing analysis, we adopt a correlated arrival process represented by the Discrete-time Batch Markovian Arrival Process. The analysis is based upon M/G/1 type queue technique which enables easy numerical computation. Queue length distributions observed at different epochs and queue length distribution seen by an arbitrary arrival cell when it enters the buffer are given.

  18. Store operation with conditional push of a tag value to a queue

    Energy Technology Data Exchange (ETDEWEB)

    Heidelberger, Philip; Steinmacher-Burow, Burkhard

    2015-07-28

    According to one embodiment, a method for a store operation with a conditional push of a tag value to a queue is provided. The method includes configuring a queue that is accessible by an application, setting a value at an address in a memory device including a memory and a controller, receiving a request for an operation using the value at the address and performing the operation. The method also includes the controller writing a result of the operation to the address, thus changing the value at the address, the controller determining if the result of the operation meets a condition and the controller pushing a tag value to the queue based on the condition being met, where the tag value in the queue indicates to the application that the condition is met.

  19. The Number Served in a Head Of The Line Priority Queue with General Service

    Directory of Open Access Journals (Sweden)

    K.N. Gaur

    1977-04-01

    Full Text Available In this paper, using the supplementary variable method, the head-of-the-line priority queueing system with general service time distributions have been studied to obtain an expression for the Laplace transform of the generating function of the joint probability distribution of the number of priority and non-priority units in the queue at time t, and the number of units served (including non-priority units in time t. In particular cases, explicit solution for the model with exponential service time distributions have been obtained; expression for the joint distribution of the queue length and the number served in time t, for an M/G/1 queue has also been derived.

  20. Reliability analysis of M/G/1 queues with general retrial times and server breakdowns

    Institute of Scientific and Technical Information of China (English)

    WANG Jinting

    2006-01-01

    This paper concerns the reliability issues as well as queueing analysis of M/G/1 retrial queues with general retrial times and server subject to breakdowns and repairs. We assume that the server is unreliable and customers who find the server busy or down are queued in the retrial orbit in accordance with a first-come-first-served discipline. Only the customer at the head of the orbit queue is allowed for access to the server. The necessary and sufficient condition for the system to be stable is given. Using a supplementary variable method, we obtain the Laplace-Stieltjes transform of the reliability function of the server and a steady state solution for both queueing and reliability measures of interest. Some main reliability indexes, such as the availability, failure frequency, and the reliability function of the server, are obtained.

  1. Methods for estimating vehicle queues at a marine terminal: A computational comparison

    Directory of Open Access Journals (Sweden)

    Chen Gang

    2014-09-01

    Full Text Available A long queue of vehicles at the gate of a marine terminal is a common traffic phenomenon in a port-city, which sometimes causes problems in urban traffic. In order to be able to solve this issue, we firstly need accurate models to estimate such a vehicle queue length. In this paper, we compare the existing methods in a case study, and evaluate their advantages and disadvantages. Particularly, we develop a simulation-based regression model, using the micro traffic simulation software PARAMIC. In simulation, it is found that the queue transient process follows a natural logarithm curve. Then, based on these curves, we develop a queue length estimation model. In the numerical experiment, the proposed model exhibits better estimation accuracy than the other existing methods

  2. An algorithmic technique for a class of queueing models with packet switching applications

    Science.gov (United States)

    Morris, R. J. T.

    The need to analyze the performance of a class of hardware packet switches leads to consideration of a queueing model consisting of a single server queue with input given by a function of a Markov chain. An algorithmic technique is developed to obtain the joint stationary distribution of the bivariate Markov chain which describes the system. Both the infinite and finite capacity cases are considered. The technique is used to study several design issues which arise when a packet switch is subjected to independent streams of bursty input traffic. Guidelines are given which aid in estimating the queueing space required to keep traffic losses acceptably small. It is seen that the commonly employed heuristic of dimensioning queueing space using the tail of the infinite capacity distribution can lead to considerable error when compared with exact results.

  3. Mean time for the development of large workloads and large queue lengths in the GI/G/1 queue

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    Charles Knessl

    1996-01-01

    Full Text Available We consider the GI/G/1 queue described by either the workload U(t (unfinished work or the number of customers N(t in the system. We compute the mean time until U(t reaches excess of the level K, and also the mean time until N(t reaches N0. For the M/G/1 and GI/M/1 models, we obtain exact contour integral representations for these mean first passage times. We then compute the mean times asymptotically, as K and N0→∞, by evaluating these contour integrals. For the general GI/G/1 model, we obtain asymptotic results by a singular perturbation analysis of the appropriate backward Kolmogorov equation(s. Numerical comparisons show that the asymptotic formulas are very accurate even for moderate values of K and N0.

  4. Non-stationary analysis of queueing delay behavior in the GI/M/1/N-type queue with server working vacations

    Science.gov (United States)

    Kempa, Wojciech M.

    2015-11-01

    A finite-buffer GI/M/1/N-type queueing model with single working vacations is considered. Every time when the system becomes empty the server initializes an exponentially distributed single working vacation period, during which the processing of jobs is carried out with another (slower) rate. After finishing the vacation period the service process is being continued with normal (higher) speed. The next working vacation period is started at the next moment at which the queue empties and so on. The systems of integral equations for time-dependent queueing delay distributions, conditioned by the initial level of buffer saturation and related to each other, are built for systems beginning the operation in normal and working vacation modes, separately. The solutions for corresponding systems written for Laplace transforms are given explicitly using the linear algebraic approach.

  5. Scheduling queues in the Ethernet switch, considering the waiting time of frames

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    Kizilov Evgeniy

    2016-01-01

    Full Text Available Authors proposes an algorithm to scheduling queues with temporal selection of frames in the Ethernet switches with QoS support, which is based on the waiting time of frames in the queues of different classes. Evaluation of the effectiveness of this algorithm compared to the classical cyclic algorithms by simulation with hierarchical temporal coloured Petri nets using CPN Tools package was conducte.

  6. The Jackson Queueing Network Model Built Using Poisson Measures. Application To A Bank Model

    OpenAIRE

    Ciuiu Daniel

    2014-01-01

    In this paper we will build a bank model using Poisson measures and Jackson queueing networks. We take into account the relationship between the Poisson and the exponential distributions, and we consider for each credit/deposit type a node where shocks are modeled as the compound Poisson processes. The transmissions of the shocks are modeled as moving between nodes in Jackson queueing networks, the external shocks are modeled as external arrivals, and the absorption of shocks as departures fr...

  7. AN M/M/C RETRIAL QUEUEING SYSTEM WITH BERNOULLI VACATIONS

    Institute of Scientific and Technical Information of China (English)

    B. Krishna KUMAR; R. RUKMANI; V. THANGARAJ

    2009-01-01

    In this paper, a steady-state Markovian multi-server retrial queueing system with Bernoulli vacation scheduling service is studied. Using matrix-geometric approach, various interesting and important system performance measures are obtained. Further, the probability descriptors like ideal retrial and vain retrial are provided. Finally, extensive numerical illustrations are presented to indicate the quantifying nature of the approach to obtain solutions to this queueing system.

  8. A Second-order Fluid Queue with Subordinator Input and Markov-modulated Linear Output

    Institute of Scientific and Technical Information of China (English)

    Jin-zhi Li

    2009-01-01

    We consider an infinite capacity second-order fluid queue with subordinator input and Markov-modulated linear release rate. The fluid queue level is described by a generalized Langevin stochastic differ-ential equation (SDE). Applying infinitesimal generator, we obtain the stationary distribution that satisfies an integro-differential equation. We derive the solution of the SDE and study the transient level's convergence in distribution. When the coefficients of the SDE are constants, we deduce the system transient property.

  9. A Simple Proof for the Stability of Global FIFO Queueing Networks

    Institute of Scientific and Technical Information of China (English)

    Jian-kui Yang

    2009-01-01

    We study the stability of multiclass queueing networks under the global FIFO (first in first out) service discipline,which was established by Bramson in 2001.For these networks,the service priority of a customer is determined by his entrance time.Using fluid models,we describe the entrance time of the most senior customer in the networks at time t,which is the key to simplify the proof for the stability of the global FIFO queueing networks.

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

    Science.gov (United States)

    2012-01-01

    quasi-toeplitz markov chains and their application in queueing theory. Queueing Systems: Theory and Applications, 54:245– 259, 2006. [26] V. G. Kulkarni...assume the environment is an ergodic continuous-time Markov chain (CTMC) on a finite state space. We analyze this system using classical matrix...process can be viewed as an asymptotically quasi-Toeplitz Markov chain . Using results from [25], they determine the stability condition and devise an

  11. AVAILABILITY ANALYSIS OF THE QUEUEING SYSTEM GI/PH/1 WITH SERVER BREAKDOWNS

    Institute of Scientific and Technical Information of China (English)

    YUAN Xueming; LI Wei

    2003-01-01

    In the existing literature of Repairable Queueing Systems (RQS), i.e., queueing systems with server breakdowns, it is almost all assumed that interarrival times of successive customers are independent, identically exponentially distributed. In this paper, we deal with more generic system GI/PH/1 with server's exponential uptime and phase-type repair time. With matrix analysis theory, we establish the equilibrium condition and the characteristics of the system, derive the transient and stationary availability behavior of the system.

  12. Classroom Management to Support Active Middle Level Classrooms

    Directory of Open Access Journals (Sweden)

    Bryan Lloyd McCoy

    2012-09-01

    Full Text Available This article presents a discussion of connections between middle level concepts of teaching and learning and managing a classroom through creating opportunities for active and engaged learning. The article argues and concludes that classroom management is more about managing learning than managing behavior and that one effective way to manage student behavior is to create an environment where students continuously engage in active learning (Haydon, Borders, Embury, & Clarke, 2009.

  13. Classroom Management to Support Active Middle Level Classrooms

    Directory of Open Access Journals (Sweden)

    Bryan Lloyd McCoy

    2012-09-01

    Full Text Available

    This article presents a discussion of connections between middle level concepts of teaching and learning and managing a classroom through creating opportunities for active and engaged learning. The article argues and concludes that classroom management is more about managing learning than managing behavior and that one effective way to manage student behavior is to create an environment where students continuously engage in active learning (Haydon, Borders, Embury, & Clarke, 2009.

  14. All-optical queue buffer using optical threshold functions and wavelength converters

    Institute of Scientific and Technical Information of China (English)

    Yuancheng Zhang; Hongming Zhang; Minyu Yao

    2012-01-01

    A modular,cascadable,and self-controlled optical queue buffer is proposed,which can solve the packet contention at a 2 × 1 optical node.Controlled by incoming optical packets,the buffer can realize firstin-first-out queue buffering without the necessity of external control signals.By using optical threshold functions and wavelength converters based on semiconductor optical amplifier,the push and pop operations of packets on queue can both be achieved.In addition,preliminary experiment is carried out.%A modular, cascadable, and self-controlled optical queue buffer is proposed, which can solve the packet contention at a 2 x 1 optical node. Controlled by incoming optical packets, the buffer can realize first-in-first-out queue buffering without the necessity of external control signals. By using optical threshold functions and wavelength converters based on semiconductor optical amplifier, the push and pop operations of packets on queue can both be achieved. In addition, preliminary experiment is carried out.

  15. Ergodicity of the IPP +M=M=c Queue%IPP+M/M/C排队的遍历性

    Institute of Scientific and Technical Information of China (English)

    李晓花; 侯振挺

    2011-01-01

    The IPP + M/M/c queueing system has been extensively used in the modern communication system. The existence and uniqueness of stationary distribution of the queue length L(t) for IPP + M/M/1 queue has been proved in [10]. In this paper, we shall give the su±cient and necessary conditions of l-ergodicity, geometric ergodicity, and prove that they are neither uniformly polynomial ergodicity nor strong ergodicity.

  16. Performance Simulation and Analysis for LTE System Using Human Behavior Queue Model

    Directory of Open Access Journals (Sweden)

    Tony Tsang

    2013-05-01

    Full Text Available Understanding the nature of traffic has been a key concern of the researchers particularly over the last two decades and it has been noticed through extensive high quality studies that traffic found in different kinds of IP/wireless IP networks is human operators . Despite the recent findings of real time human behavior in measured traffic from data networks, much of the current understanding of IP traffic modeling is still based on simplistic probability distributed traffic. Unlike most existing studies that areprimarily based on simplistic probabilistic model and traditional scheduling algorithms, this research presents an analytical performance model for real time human behavior queue systems with intelligent task management traffic input scheduled by anovel and promising scheduling mechanism for 4G -LTE system. Our proposed model is substantiated on human behavior queuing system that considers real time of traffic exhibiting homogeneous tasks characteristics. We analyze the model on the basis of newly proposed scheduling scheme for 4G - LTE system. We present closed form expressions of expected response times for real time traffic classes. We develop a discrete event simulator to understand the behavior of real time of arriving tasks traffic under this newly proposed scheduling mechanism for 4G - LTE system . The results indicate that our proposed scheduling algorithm provides preferential treatment to real -time applications such as voice and video but not to that extent that data applications are starving for bandwidth and outperforms all other scheduling schemes that are available in the market.

  17. A bulk queueing system under N-policy with bilevel service delay discipline and start-up time

    Directory of Open Access Journals (Sweden)

    David C. R. Muh

    1993-01-01

    Full Text Available The author studies the queueing process in a single-server, bulk arrival and batch service queueing system with a compound Poisson input, bilevel service delay discipline, start-up time, and a fixed accumulation level with control operating policy. It is assumed that when the queue length falls below a predefined level r(≥1, the system, with server capacity R, immediately stops service until the queue length reaches or exceeds the second predefined accumulation level N(≥r. Two cases, with N≤R and N≥R, are studied.

  18. On the Discrete-Time GeoX/G/1 Queues under N-Policy with Single and Multiple Vacations

    Directory of Open Access Journals (Sweden)

    Sung J. Kim

    2013-01-01

    Full Text Available We consider the discrete-time GeoX/G/1 queue under N-policy with single and multiple vacations. In this queueing system, the server takes multiple vacations and a single vacation whenever the system becomes empty and begins to serve customers only if the queue length is at least a predetermined threshold value N. Using the well-known property of stochastic decomposition, we derive the stationary queue-length distributions for both vacation models in a simple and unified manner. In addition, we derive their busy as well as idle-period distributions. Some classical vacation models are considered as special cases.

  19. A queueing theory based model for business continuity in hospitals.

    Science.gov (United States)

    Miniati, R; Cecconi, G; Dori, F; Frosini, F; Iadanza, E; Biffi Gentili, G; Niccolini, F; Gusinu, R

    2013-01-01

    Clinical activities can be seen as results of precise and defined events' succession where every single phase is characterized by a waiting time which includes working duration and possible delay. Technology makes part of this process. For a proper business continuity management, planning the minimum number of devices according to the working load only is not enough. A risk analysis on the whole process should be carried out in order to define which interventions and extra purchase have to be made. Markov models and reliability engineering approaches can be used for evaluating the possible interventions and to protect the whole system from technology failures. The following paper reports a case study on the application of the proposed integrated model, including risk analysis approach and queuing theory model, for defining the proper number of device which are essential to guarantee medical activity and comply the business continuity management requirements in hospitals.

  20. The Effectiveness Analysis of Waiting Processes in the Different Branches of a Bank by Queue Model

    Directory of Open Access Journals (Sweden)

    Abdullah ÖZÇİL

    2015-06-01

    Full Text Available Despite the appreciable increase in the number of bank branches every year, nowadays queues for services don’t decrease and even become parts of our daily lives. By minimizing waiting processes the least, increasing customer satisfaction should be one of branch managers’ main goals. A quick and also customer oriented service with high quality is the most important factor for customer loyalty. In this study, Queueing theory, one of Operation Research techniques, is handled and in application, the data are obtained related to waiting in queue of customer in six different branches of two banks operating in Denizli and then they are analyzed by Queueing theory and also calculated the average effectiveness of the system. The study’s data are obtained by six branches of two banks called as A1, A2, A3, B1, B2 and B3. At the end of study it is presented to the company some advices that can bring benefits to the staff and customers. In this study, Queueing theory, one of Operation Research techniques, is handled and in application, the data are obtained related to waiting in queue of customer in three different branches of a bank operating in Denizli and then they are analyzed by Queueing theory and also calculated the average effectiveness of the system. The study’s data are obtained by three branches of the bank called A1, A2 and A3. At last it is presented to the company some advices that can bring more benefits to the staff and clients.

  1. QUEUEING MODELS IN MOBILE AD-HOC NETWORKS

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    S. Baskar

    2014-01-01

    Full Text Available The Mobile Ad-hoc Networks (MANETs has gain an essential part of the attention of researchers and become very well-liked in last few years. MANETs can operate with no fixed communications and can live rapid changes in the network topology. They can be studied officially as graphs in which the set of boundaries varies in time. One of the main methods to determine the presentation of MANETs is simulation. This study proposes Enhanced Probabilistic Adhoc on Demand Distance Vector (EPAODV routing protocol, which solves the broadcast storm problem of Adhoc on Demand Distance Vector (AODV. Our evaluation of MANETs is based on the evaluation of the throughput, end to end delay and packet delivery ratio. We evaluated the end to end delay as it is one of the most important characteristic evaluation metric in computer networks. In our proposed algorithm, using a queueing model M/M/C: ∞/FIFO, we are able to enhance that better results are obtained in the case EPAODV protocol such as increasing throughput, data delivery ratio and then decreasing the end delay compare to the existing protocols.

  2. Probabilistic Analysis of Buffer Starvation in Markovian Queues

    CERN Document Server

    Xu, Yuedong; El-Azouzi, Rachid; Haddad, Majed; Elayoubi, Salaheddine; Jimenez, Tania

    2011-01-01

    Our purpose in this paper is to obtain the exact distribution of the number of buffer starvations within a sequence of $N$ consecutive packet arrivals. The buffer is modeled as an M/M/1 queue, plus the consideration of bursty arrivals characterized by an interrupted Poisson process. When the buffer is empty, the service restarts after a certain amount of packets are prefetched. With this goal, we propose two approaches, one of which is based on Ballot theorem, and the other uses recursive equations. The Ballot theorem approach gives an explicit solution, but at the cost of the high complexity order in certain circumstances. The recursive approach, though not offering an explicit result, needs fewer computations. We further propose a fluid analysis of starvation probability on the file level, given the distribution of file size and the traffic intensity. The starvation probabilities of this paper have many potential applications. We apply them to optimize the quality of experience (QoE) of media streaming serv...

  3. Optimum and equilibrium in a transport problem with queue effects

    CERN Document Server

    Crippa, Gianluca; Pratelli, Aldo

    2008-01-01

    Consider a distribution of citizens in an urban area in which some services (supermarkets, post offices...) are present. Each citizen, in order to use a service, spends an amount of time which is due both to the travel time to the service and to the queue time waiting in the service. The choice of the service to be used is made by every citizen in order to be served more quickly. Two types of problems can be considered: a global optimization of the total time spent by the citizens of the whole city (we define a global optimum and we study it with techniques from optimal mass transportation) and an individual optimization, in which each citizen chooses the service trying to minimize just his own time expense (we define the concept of equilibrium and we study it with techniques from game theory). In this framework we are also able to exhibit two time-dependent strategies (based on the notions of prudence and memory respectively) which converge to the equilibrium.

  4. Preemptive queueing system with randomized push-out mechanism

    Science.gov (United States)

    Muliukha, Vladimir; Ilyashenko, Alexander; Zayats, Oleg; Zaborovsky, Vladimir

    2015-04-01

    In this article considered a queueing theory model with limited buffer size, one service channel, and two incoming flows. In this model one of the flows has a power to preempt other tasks. We call it a high-priority flow. Another one is low-priority. This priority mechanism is realized in a two different ways. The first one is a preemptive priority, which allows high-priority packets to interrupt low-priority packets in service channel and push them out. The second one is a randomized push-out mechanism with probability α, which allows us to choose what type of packets should be pushed out of the system when it is full. In this article we provide an algorithm for computing statistical characteristics of the model for all values of push-out probability α. We have used generating functions method to simplify the system of linear equations. This method allows us to reduce the order of linear equations system from k(k + 1)/2 to (k + 1). As the result we have got two effects in this model. The first one is a linear behavior of loss probabilities in the model with low overload. The second one is a "closing" of a system for low-priority packets with high overload.

  5. Tele-Network Design Based on Queue Competition Algorithm

    Institute of Scientific and Technical Information of China (English)

    Huang Zhang-can; Wan Li-jun; Tang Tao; Chen Zheng-xu

    2003-01-01

    In this paper, we report research on how to design the tele-network. First of all, we defined the reliability of tele-network. According to the definition, we divide the whole reliability into two parts:the reliability of the mini-way and that of the whole system. Then we do algebra unintersection of the mini-way, deriving a function of reliability of tele-network. Also, we got a function of the cost of tele-network after analyzing the cost of arcs and points. Finally, we give a mathematical model to design a tele-network. For the algorithm, we define the distance of a network and adjacent area within certain boundaries . We present a new algorithm Queue Competition Algorithm(QCA)based on the adja cent area . The QCA correlates sequence of fitnesses in their fathergenerations with hunting zone of mutation and the number of individuals generated by mutation, making the stronger fitness in a small zone converge at a local extreme value, but the weaker one takes the advantage of lots of individuals and a big zone to hunt a new local extreme value. In this way, we get the overall extreme value. Numerical simulation shows that we can get the efficient hunting and exact solution by using QCA. The QCA efficient hunting and exact solution.

  6. DESAIN FRAMEWORK MULTIMEDIA QUEUEING SYSTEM BERBASIS ANDROID ANTRIAN PASIEN PUSKESMAS

    Directory of Open Access Journals (Sweden)

    Erika Devi Udayanti

    2015-10-01

    Full Text Available Saat ini antrian di puskesmas masih dilakukan dengan metode konvensional, yaitu dengan menumpuk kartu registrasi. Metode seperti ini memungkinkan kartu menjadi terselip. Selain itu, penumpukan kartu yang tidak benar dapat mengakibatkan urutan menjadi tidak sesuai dengan urutan yang seharusnya. Pasien yang datang lebih ahir dimungkinkan untuk dapat dilayani lebih awal dari pasien yang sudah lama menunggu. Penelitian ini mengusulkan multimedia queueing system berbasis android untuk layanan antrian pasien puskesmas. Sistem ini mencatat antrian di dalam database server, sehingga tidak ada kartu yang terselip ataupun salah tumpuk. Lebih lanjut lagi, penelitian ini akan mengangkat kecanggihan mesin android sebagai input device. Sedangkan untuk output devicenya, menggunakan portable bluetooth printer dan layar LCD. Setiap pasien yang datang dapat mencetak tiket antrian dengan menyentuh tombol pada layar mesin android. Mesin android tersebut kemudian akan mencetak tiket melaui printer portable yang disediakan dan mengirim nomor antrian ke database server. Selain itu, mesin android ini juga memotret wajah pasien yang masuk, dan file foto akan dikirim beserta nomor antrian ke server. Pada saat giliran pasien tiba, layar LCD akan menampilkan nomor antrian pasien beserta fotonya. Metode ini diharapkan mampu menyelesaikan problem kartu registrasi terselip, dan juga membantu pasien yang buta huruf/angka. Kata Kunci: puskesmas, sistem antrian, android

  7. Research on Customer Queueing System and Its Model of Commercial Bank%商业银行客户排队系统及其模型研究

    Institute of Scientific and Technical Information of China (English)

    杨兵; 左垒

    2014-01-01

    For the growing queueing problem of commercial bank,combine commercial bank management,mathematical statistics and oth-er disciplines knowledge based on the queueing theory to research. First,based on the illustration about the general structure of queueing system,describe bank queueing system architecture through a graphic. Second,research random variable distribution,including customer reaching obey Poisson distribution and the exponential distribution of service time obey. Finally,construct bank queueing system model including key quantitative indicators calculation model and objective function model. This study,fundamentally solves the contradiction between customer waiting costs and operating costs of the bank itself,and has an important role for commercial banks to optimize the re-sources allocation,improve service quality and increase customer satisfaction.%针对商业银行日益加剧的排队问题,文中以排队论理论为基础,结合商业银行管理、数理统计等学科知识进行研究。首先,在阐明排队系统一般结构的基础上,通过图形描述了银行排队系统结构;然后,研究随机变量分布,包括客户到达服从的Poisson分布和服务时间服从的指数分布;最后,构造银行排队系统模型,包括主要数量指标计算模型和目标函数模型。文中的研究内容,从根本上解决客户等待成本和银行自身经营成本之间的矛盾,对商业银行优化网点资源配置、提高服务质量、增加顾客满意度等方面具有重要作用。

  8. Network-of-queues approach to B-cell-receptor affinity discrimination

    Science.gov (United States)

    Felizzi, Federico; Comoglio, Federico

    2012-06-01

    The immune system is one of the most complex signal processing machineries in biology. The adaptive immune system, consisting of B and T lymphocytes, is activated in response to a large spectrum of pathogen antigens. B cells recognize and bind the antigen through B-cell receptors (BCRs) and this is fundamental for B-cell activation. However, the system response is dependent on BCR-antigen affinity values that span several orders of magnitude. Moreover, the ability of the BCR to discriminate between affinities at the high end (e.g., 109M-1-1010M-1) challenges the formulation of a mathematical model able to robustly separate these affinity-dependent responses. Queuing theory enables the analysis of many related processes, such as those resulting from the stochasticity of protein binding and unbinding events. Here we define a network of queues, consisting of BCR early signaling states and transition rates related to the propensity of molecular aggregates to form or disassemble. By considering the family of marginal distributions of BCRs in a given signaling state, we report a significant separation (measured as Jensen-Shannon divergence) that arises from a broad spectrum of antigen affinities.

  9. Queue Content Analysis in a 2-Class Discrete-Time Queueing System under the Slot-Bound Priority Service Rule

    Directory of Open Access Journals (Sweden)

    Sofian De Clercq

    2012-01-01

    Full Text Available The paper we present here introduces a new priority mechanism in discrete-time queueing systems. It is a milder form of priority when compared to HoL priority, but it favors customers of one type over the other when compared to regular FCFS. It also provides an answer to the starvation problem that occurs in HoL priority systems. In this new priority mechanism, customers of different priority classes entering the system during the same time slot are served in order of their respective priority class—hence the name slot-bound priority. Customers entering during different slots are served on an FCFS basis. We consider two customer classes (pertaining to two levels of priority such that type-1 customers are served before type-2 customers that enter the system during the same slot. A general independent arrival process and generally distributed service times are assumed. Expressions for the probability generating function (PGF of the system content (number of type- customers, in regime are obtained using a slot-to-slot analysis. The first moments are calculated, as well as an approximation for the probability mass functions associated with the found PGFs. Lastly, some examples allow us some deeper insight into the inner workings of the slot-bound priority mechanism.

  10. Priority Queues with Fractional Service for Tiered Delay QoS

    Directory of Open Access Journals (Sweden)

    Gary Chang

    2015-12-01

    Full Text Available Packet scheduling is key to quality of service (QoS capabilities of broadband wired and wireless networks. In a heterogeneous traffic environment, a comprehensive QoS packet scheduler must strike a balance between flow fairness and access delay. Many advanced packet scheduling solutions have targeted fair bandwidth allocation while protecting delay-constrained traffic by adding priority queue(s on top of a fair bandwidth scheduler. Priority queues are known to cause performance uncertainties and, thus, various modifications have been proposed. In this paper, we present a packet queueing engine dubbed Fractional Service Buffer (FSB, which, when coupled with a configurable flow scheduler, can achieve desired QoS objectives, such as fair throughputs and differentiated delay guarantees. Key performance metrics, such as delay limit and probability of delay limit violation, are derived as a function of key FSB parameters for each delay class in the packet queueing engine using diffusion approximations. OPNET simulations verify these analytical results.

  11. Multiserver queue with semi-Markovian batch arrivals with application to the MPEG frame sequence

    Science.gov (United States)

    Takagi, Hideaki; Wu, De-An

    2002-07-01

    We consider a queueing system consisting of multiple identical servers and a common queue. The service time follows an exponential distribution and the arrival process is governed by a semi-Markov process (SMP). The motivation to study the queueing system with SMP arrivals lies in that it can model the auto-correlated traffic on the high speed network generated by a real time communication, for example, the MPEG-encoded VBR video. Our analysis is based on the theory of piecewise Markov process. We first derive the distributions of the queue size and the waiting time. When the sojourn time of SMP follows an exponential distribution all the unknown constants contained in the generating function of queue size can be determined through the zeros of the denominator for this generating function. Based on the result of the analysis, we propose a model to evaluate the waiting time of MPEG video traffic on an ATM network with multiple channels. Here, the SMP corresponds to the exact MPEG sequence of frames. Finally, a numerical example using a real video data is shown.

  12. A parametric programming solution to the F-policy queue with fuzzy parameters

    Science.gov (United States)

    Yang, Dong-Yuh; Chang, Po-Kai

    2015-03-01

    This paper investigates the F-policy queue using fuzzy parameters, in which the arrival rate, service rate, and start-up rate are all fuzzy numbers. The F-policy deals with the control of arrivals in a queueing system, in which the server requires a start-up time before allowing customers to enter. A crisp F-policy queueing system generalised to a fuzzy environment would be widely applicable; therefore, we apply the α-cuts approach and Zadeh's extension principle to transform fuzzy F-policy queues into a family of crisp F-policy queues. This study presents a mathematical programming approach applicable to the construction of membership functions for the expected number of customers in the system. Furthermore, we propose an efficient solution procedure to compute the membership function of the expected number of customers in the system under different levels of α. Finally, we give an example of the proposed system as applied to a case in the automotive industry to demonstrate its practicality.

  13. Unreliable bulk retrial queues with delayed repairs and modified vacation policy

    Science.gov (United States)

    Jain, Madhu; Bhagat, Amita

    2014-06-01

    The present investigation deals with the bulk arrival M/G/1 retrial queue with impatient customers and modified vacation policy. The incoming customers join the virtual pool of customers called orbit if they find the server being busy, on vacation or in broken down state otherwise the service of the customer at the head of the batch is started by the server. The service is provided in k essential phases to all the customers by the single server which may breakdown while rendering service to the customers. The broken down server is sent to a repair facility wherein the repair is performed in d compulsory phases. As soon as the orbit becomes empty, the server goes for vacation and takes at most J vacations until at least one customer is noticed. The incoming customers are impatient and may renege on seeing a long queue of the customers for the service. The probability generating functions and queue length for the number of customers in the orbit and queue have been obtained using supplementary variable technique. Various system characteristics viz. average number of customers in the queue and the orbit, long run probabilities of the system states, etc. are obtained. Furthermore, numerical simulation has been carried out to study the sensitivity of various parameters on the system performance measures by taking an illustration.

  14. A Study on improvement of comprehensive environmental management system - activation of liberalized environmental management

    Energy Technology Data Exchange (ETDEWEB)

    Chung, Hweu Sung; Kang, Chul Goo [Korea Environment Institute, Seoul (Korea)

    1998-12-01

    As a part of improvement on a comprehensive environmental management system, this study was attempted to find an activating policy for a liberalized environmental management. This study provided an activation plan of reasonable environmental regulation reform and liberalized environmental management through the analysis of foreign examples and domestic situation. Furthermore, it analyzed an institutional mechanism for a smooth operation of liberalized environmental management. 68 refs., 5 figs., 51 tabs.

  15. Optimal Control of the D-Policy M/G/1 Queueing System with Server Breakdowns

    Directory of Open Access Journals (Sweden)

    Kuo-Hsiung Wang

    2008-01-01

    Full Text Available This study deals with a single server in the D-policy M/G/1 queueing system in which the server is turned off at the end of each complete period and is activated again only when the cumulative completion times of the customers in the system exceeds a given level D. While the server is working, he is subject to breakdowns according to a Poisson process. When the server breaks down, he requires repair at a repair facility, where the repair time obeys a general distribution. We have demonstrated that the probability that the server is busy in the steady-state is equal to the traffic intensity. The total expected cost function per customer per unit time is constructed to determine the optimal operating D-policy at a minimum cost. We use the steady-state analytic results and apply an efficient Matlab computer program to calculate the optimal value of D. Based on three different service distributions: exponential, 3-stage Erlang and deterministic, we provide extensive numerical computation for illustration purpose. Sensitivity analysis is also investigated.

  16. Analysis of a state-independent change of measure for the $G|G|1$ tandem queue

    NARCIS (Netherlands)

    Buijsrogge, Anne; de Boer, Pieter-Tjerk; Scheinhardt, Willem R.W.

    2016-01-01

    In 1989, Parekh and Walrand introduced a method to efficiently estimate the probability of a rare event in a single queue or network of queues. The event they consider is that the total number of customers in the system reaches some level $N$ in a busy cycle. Parekh and Walrand introduce a simple ch

  17. Analysis of a state-independent change of measure for the $G|G|1$ tandem queue

    NARCIS (Netherlands)

    Buijsrogge, Anne; de Boer, Pieter-Tjerk; Scheinhardt, Willem R.W.

    2016-01-01

    In (Parekh and Walrand, 1989) a method is introduced to efficiently estimate the probability of a rare event in a single queue or network of queues. The event they consider is that the total number of customers in the system reaches some level N in a busy cycle. Parekh and Walrand introduce a simple

  18. Some reflections on the Renewal-theory paradox in queueing theory

    Directory of Open Access Journals (Sweden)

    Robert B. Cooper

    1998-01-01

    Full Text Available The classical renewal-theory (waiting time, or inspection paradox states that the length of the renewal interval that covers a randomly-selected time epoch tends to be longer than an ordinary renewal interval. This paradox manifests itself in numerous interesting ways in queueing theory, a prime example being the celebrated Pollaczek-Khintchine formula for the mean waiting time in the M/G/1 queue. In this expository paper, we give intuitive arguments that “explain” why the renewal-theory paradox is ubiquitous in queueing theory, and why it sometimes produces anomalous results. In particular, we use these intuitive arguments to explain decomposition in vacation models, and to derive formulas that describe some recently-discovered counterintuitive results for polling models, such as the reduction of waiting times as a consequence of forcing the server to set up even when no work is waiting.

  19. A discrete single server queue with Markovian arrivals and phase type group services

    Directory of Open Access Journals (Sweden)

    Attahiru Sule Alfa

    1995-01-01

    Full Text Available We consider a single-server discrete queueing system in which arrivals occur according to a Markovian arrival process. Service is provided in groups of size no more than M customers. The service times are assumed to follow a discrete phase type distribution, whose representation may depend on the group size. Under a probabilistic service rule, which depends on the number of customers waiting in the queue, this system is studied as a Markov process. This type of queueing system is encountered in the operations of an automatic storage retrieval system. The steady-state probability vector is shown to be of (modified matrix-geometric type. Efficient algorithmic procedures for the computation of the rate matrix, steady-state probability vector, and some important system performance measures are developed. The steady-state waiting time distribution is derived explicitly. Some numerical examples are presented.

  20. ON THE SINGLE SERVER RETRIAL QUEUE WITH PRIORITY SUBSCRIBERS AND SERVER BREAKDOWNS

    Institute of Scientific and Technical Information of China (English)

    Jinting WANG

    2008-01-01

    The author concerned the reliability evaluation as well as queueing analysis of M1, M2/G1, G2/1 retrial queues with two different types of primary customers arriving according to independent poisson flows. In the case of blocking, the first type of customers can be queued whereas the second type of customers must leave the service area but return after some random period of time to try their luck again. The author assumes that the server is unreliable and it has a service-type dependent, exponentially distributed life time as well as a service-type dependent, generally distributed repair time. The necessary and sufficient condition for the system to be stable is investigated. Using a supplementary variable method, the author obtains a steady-state solution for queueing measures, and the transient as well as the steady-state solutions for reliability measures of interest.

  1. Improving Packet Processing Efficiency on Multi-core Architectures with Single Input Queue

    Directory of Open Access Journals (Sweden)

    Peter Orosz

    2012-06-01

    Full Text Available Generic purpose multi-core PC architectures are facing performance challenges of high rate packet reception on gigabit per second and higher speed network interfaces. In order to assign a CPU core to a networking softIRQ, the single input queue design of the low-level packet processing subsystem relies on the kernel's Symmetric Multiprocessing (SMP scheduler, which does not perform load balancing of the softIRQ instances between the CPU cores. In practice, when single receive queue is used all of the softIRQs are assigned to a single CPU core. This typical arrangement could easily drive to CPU resource exhaustion and high packet loss ratio on high bandwidth interfaces. The non-steady state of the system is triggered by the high arrival rate of the packets. This work presents a proposal for improving the packet processing efficiency in single input queue multi-core systems.

  2. MX/G/1 unreliable retrial queue with option of additional service and Bernoulli vacation

    Directory of Open Access Journals (Sweden)

    Charan Jeet Singh

    2016-03-01

    Full Text Available In this paper, retrial queue with unreliable server and bulk arrivals is investigated. The server is capable of providing m-optional services and any one of these available services, may be rendered to the customer after the first essential service if the customer opts for the same. It is assumed that the server may fail while rendering any phase of service and undergoes for the immediate repair. After the completion of the service of a customer, the server may either take a vacation for a random period or may continue to provide the service to the other customers waiting in the queue. The supplementary variables corresponding to service time, repair time and retrial time are incorporated to determine the queue size distribution. To examine the effect of different parameters on the performance measures of the system, the numerical illustration is given which is supported by numerical simulation and sensitivity analysis.

  3. ANALYSIS OF FUZZY QUEUES: PARAMETRIC PROGRAMMING APPROACH BASED ON RANDOMNESS - FUZZINESS CONSISTENCY PRINCIPLE

    Directory of Open Access Journals (Sweden)

    Dhruba Das

    2015-04-01

    Full Text Available In this article, based on Zadeh’s extension principle we have apply the parametric programming approach to construct the membership functions of the performance measures when the interarrival time and the service time are fuzzy numbers based on the Baruah’s Randomness- Fuzziness Consistency Principle. The Randomness-Fuzziness Consistency Principle leads to defining a normal law of fuzziness using two different laws of randomness. In this article, two fuzzy queues FM/M/1 and M/FM/1 has been studied and constructed their membership functions of the system characteristics based on the aforesaid principle. The former represents a queue with fuzzy exponential arrivals and exponential service rate while the latter represents a queue with exponential arrival rate and fuzzy exponential service rate.

  4. A Batch Arrival Retrial Queue with Two Phases of Service and Bernoulli Vacation Schedule

    Institute of Scientific and Technical Information of China (English)

    Gautam Choudhury; Kandarpa Deka

    2013-01-01

    We consider an MX/G/1 queueing system with two phases of heterogeneous service and Bernoulli vacation schedule which operate under a linear retrial policy.In addition,each individual customer is subject to a control admission policy upon the arrival.This model generalizes both the classical M/G/1 retrial queue with arrivals in batches and a two phase batch arrival queue with a single vacation under Bernoulli vacation schedule.We will carry out an extensive stationary analysis of the system,including existence of the stationary regime,embedded Markov chain,steady state distribution of the server state and number of customer in the retrial group,stochastic decomposition and calculation of the first moment.

  5. On the Queueing Behavior of Random Codes over a Gilbert-Elliot Erasure Channel

    CERN Document Server

    Parag, Parimal; Pfister, Henry D; Narayanan, Krishna R

    2010-01-01

    This paper considers the queueing performance of a system that transmits coded data over a time-varying erasure channel. In our model, the queue length and channel state together form a Markov chain that depends on the system parameters. This gives a framework that allows a rigorous analysis of the queue as a function of the code rate. Most prior work in this area either ignores block-length (e.g., fluid models) or assumes error-free communication using finite codes. This work enables one to determine when such assumptions provide good, or bad, approximations of true behavior. Moreover, it offers a new approach to optimize parameters and evaluate performance. This can be valuable for delay-sensitive systems that employ short block lengths.

  6. An agent-based model for queue formation of powered two-wheelers in heterogeneous traffic

    Science.gov (United States)

    Lee, Tzu-Chang; Wong, K. I.

    2016-11-01

    This paper presents an agent-based model (ABM) for simulating the queue formation of powered two-wheelers (PTWs) in heterogeneous traffic at a signalized intersection. The main novelty is that the proposed interaction rule describing the position choice behavior of PTWs when queuing in heterogeneous traffic can capture the stochastic nature of the decision making process. The interaction rule is formulated as a multinomial logit model, which is calibrated by using a microscopic traffic trajectory dataset obtained from video footage. The ABM is validated against the survey data for the vehicular trajectory patterns, queuing patterns, queue lengths, and discharge rates. The results demonstrate that the proposed model is capable of replicating the observed queue formation process for heterogeneous traffic.

  7. STRATEGIC APPROACH TO QUALITY MANAGEMENT ENTERPRISES MARKETING ACTIVITIES

    OpenAIRE

    DATSII NADIIA VASYLIVNA

    2017-01-01

    The conceptual model of quality strategic management of marketing activities includes the following elements: strategic architecture, strategic organization, strategic audit, each is considered in terms of information, functional, methodological, organizational and economic aspects. The implementation of this model will enhance the effectiveness of strategic management of enterprise marketing activities and ensure their long-term competitiveness.Conceptual-categorical apparatus is supplemente...

  8. The CMS workload management system

    Science.gov (United States)

    Cinquilli, M.; Evans, D.; Foulkes, S.; Hufnagel, D.; Mascheroni, M.; Norman, M.; Maxa, Z.; Melo, A.; Metson, S.; Riahi, H.; Ryu, S.; Spiga, D.; Vaandering, E.; Wakefield, S.; Wilkinson, R.

    2012-12-01

    CMS has started the process of rolling out a new workload management system. This system is currently used for reprocessing and Monte Carlo production with tests under way using it for user analysis. It was decided to combine, as much as possible, the production/processing, analysis and T0 codebases so as to reduce duplicated functionality and make best use of limited developer and testing resources. This system now includes central request submission and management (Request Manager); a task queue for parcelling up and distributing work (WorkQueue) and agents which process requests by interfacing with disparate batch and storage resources (WMAgent).

  9. US - Former Soviet Union environmental management activities

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1995-09-01

    The Office of Environmental Management (EM) has been delegated the responsibility for US DOE`s cleanup of nuclear weapons complex. The nature and the magnitude of the waste management and environmental remediation problem requires the identification of technologies and scientific expertise from domestic and foreign sources. This booklet makes comparisons and describes coordinated projects and workshops between the USA and the former Soviet Union.

  10. The Geo/Geo/1+1 Queueing System with Negative Customers

    Directory of Open Access Journals (Sweden)

    Zhanyou Ma

    2013-01-01

    Full Text Available We study a Geo/Geo/1+1 queueing system with geometrical arrivals of both positive and negative customers in which killing strategies considered are removal of customers at the head (RCH and removal of customers at the end (RCE. Using quasi-birth-death (QBD process and matrix-geometric solution method, we obtain the stationary distribution of the queue length, the average waiting time of a new arrival customer, and the probabilities of servers in busy or idle period, respectively. Finally, we analyze the effect of some related parameters on the system performance measures.

  11. Chaotic queue-based genetic algorithm for design of a self-tuning fuzzy logic controller

    Science.gov (United States)

    Saini, Sanju; Saini, J. S.

    2012-11-01

    This paper employs a chaotic queue-based method using logistic equation in a non-canonical genetic algorithm for optimizing the performance of a self-tuning Fuzzy Logic Controller, used for controlling a nonlinear double-coupled system. A comparison has been made with a standard canonical genetic algorithm implemented on the same plant. It has been shown that chaotic queue-method brings an improvement in the performance of the FLC for wide range of set point changes by a more profound initial population spread in the search space.

  12. Calculations of Backscattering Mueller Matrices for Turbid Media with a Sphere Queue Model

    Institute of Scientific and Technical Information of China (English)

    WANG Qing-Hua; LI Zhen-Hua; LAI Jian-Cheng; ZHANG Ying-Ying; HE An-Zhi

    2006-01-01

    A sphere queue model is introduced to calculate Mueller matrices of turbid media. Combined with the single scattering approximation, the backscattering Mueller matrices of turbid media can be computed rapidly by Mie theory. The numerical results agree with the azimuthal dependences of backscattering Mueller matrices' patterns from turbid media, which indicates that the major contribution to the Mueller matrices' patterns comes from the single scattering of the sphere queue, and the multiple scattering considered as a high-order correction does not change the patterns. The numerical analysis reveals that the contrast of Mueller matrices' patterns will decrease with increase of the concentration of media and the distance from the incident point.

  13. The Jackson Queueing Network Model Built Using Poisson Measures. Application To A Bank Model

    Directory of Open Access Journals (Sweden)

    Ciuiu Daniel

    2014-07-01

    Full Text Available In this paper we will build a bank model using Poisson measures and Jackson queueing networks. We take into account the relationship between the Poisson and the exponential distributions, and we consider for each credit/deposit type a node where shocks are modeled as the compound Poisson processes. The transmissions of the shocks are modeled as moving between nodes in Jackson queueing networks, the external shocks are modeled as external arrivals, and the absorption of shocks as departures from the network.

  14. Optimal scaling of average queue sizes in an input-queued switch: an open problem

    OpenAIRE

    Shah, Devavrat; Tsitsiklis, John N.; Zhong, Yuan

    2011-01-01

    We review some known results and state a few versions of an open problem related to the scaling of the total queue size (in steady state) in an n×n input-queued switch, as a function of the port number n and the load factor ρ. Loosely speaking, the question is whether the total number of packets in queue, under either the maximum weight policy or under an optimal policy, scales (ignoring any logarithmic factors) as O(n/(1 − ρ)).

  15. A queueing model for error control of partial buffer sharing in ATM

    Directory of Open Access Journals (Sweden)

    Ahn Boo Yong

    1999-01-01

    Full Text Available We model the error control of the partial buffer sharing of ATM by a queueing system M 1 , M 2 / G / 1 / K + 1 with threshold and instantaneous Bernoulli feedback. We first derive the system equations and develop a recursive method to compute the loss probabilities at an arbitrary time epoch. We then build an approximation scheme to compute the mean waiting time of each class of cells. An algorithm is developed for finding the optimal threshold and queue capacity for a given quality of service.

  16. Efficient simulation of finite horizon problems in queueing and insurance risk

    DEFF Research Database (Denmark)

    Rojas-Nandayapa, Leonardo; Asmussen, Søren

    Let ψ(u, t) be the probability that the workload in an initially empty M/G/1 queue exceeds u at time t < ∞, or, equivalently, the ruin probability in the classical Crámer-Lundberg model. Assuming service times/claim sizes to be subexponential, various Monte Carlo estimators for ψ(u, t) are sugges......Let ψ(u, t) be the probability that the workload in an initially empty M/G/1 queue exceeds u at time t service times/claim sizes to be subexponential, various Monte Carlo estimators for ψ(u, t...

  17. The Application of The Double Queue Asymmetric Gated Service Polling Control Theory in Intelligent Traffic System

    Directory of Open Access Journals (Sweden)

    Zhao Yi Fan

    2016-01-01

    Full Text Available paper presents a new use of double queues asymmetric gated service polling system in the intelligent traffic light control system.Usually there are more vehicles in main road than minor road,so there are more green light time be needed in the main road.From the computer simulation and theory analysis,we can find that the application of double queues asymmetric gated service polling theory in intelligent traffic system can balance intersections load and set suitable passing time for vehicles to assure the roads open.

  18. On Eigenvalues of the Generator of a C0-Semigroup Appearing in Queueing Theory

    Directory of Open Access Journals (Sweden)

    Geni Gupur

    2014-01-01

    Full Text Available We describe the point spectrum of the generator of a C0-semigroup associated with the M/M/1 queueing model that is governed by an infinite system of partial differential equations with integral boundary conditions. Our results imply that the essential growth bound of the C0-semigroup is 0 and, therefore, that the semigroup is not quasi-compact. Moreover, our result also shows that it is impossible that the time-dependent solution of the M/M/1 queueing model exponentially converges to its steady-state solution.

  19. A finite-buffer queue with a single vacation policy: An analytical study with evolutionary positioning

    Directory of Open Access Journals (Sweden)

    Woźniak Marcin

    2014-12-01

    Full Text Available In this paper, application of an evolutionary strategy to positioning a GI/M/1/N-type finite-buffer queueing system with exhaustive service and a single vacation policy is presented. The examined object is modeled by a conditional joint transform of the first busy period, the first idle time and the number of packets completely served during the first busy period. A mathematical model is defined recursively by means of input distributions. In the paper, an analytical study and numerical experiments are presented. A cost optimization problem is solved using an evolutionary strategy for a class of queueing systems described by exponential and Erlang distributions.

  20. A Novel Analytic Technique for the Service Station Reliability in a Discrete-Time Repairable Queue

    Directory of Open Access Journals (Sweden)

    Renbin Liu

    2013-01-01

    Full Text Available This paper presents a decomposition technique for the service station reliability in a discrete-time repairable GeomX/G/1 queueing system, in which the server takes exhaustive service and multiple adaptive delayed vacation discipline. Using such a novel analytic technique, some important reliability indices and reliability relation equations of the service station are derived. Furthermore, the structures of the service station indices are also found. Finally, special cases and numerical examples validate the derived results and show that our analytic technique is applicable to reliability analysis of some complex discrete-time repairable bulk arrival queueing systems.

  1. An M/M/2 Queueing System with Heterogeneous Servers Including One with Working Vacation

    Directory of Open Access Journals (Sweden)

    A. Krishnamoorthy

    2012-01-01

    Full Text Available This paper analyzes an M/M/2 queueing system with two heterogeneous servers, one of which is always available but the other goes on vacation in the absence of customers waiting for service. The vacationing server, however, returns to serve at a low rate as an arrival finds the other server busy. The system is analyzed in the steady state using matrix geometric method. Busy period of the system is analyzed and mean waiting time in the stationary regime computed. Conditional stochastic decomposition of stationary queue length is obtained. An illustrative example is also provided.

  2. Reservicing some customers in M/G/1 queues under three disciplines

    Directory of Open Access Journals (Sweden)

    M. R. Salehi-Rad

    2004-01-01

    Full Text Available Consider an M/G/1 production line in which a production item is failed with some probability and is then repaired. We consider three repair disciplines depending on whether the failed item is repaired immediately or first stockpiled and repaired after all customers in the main queue are served or the stockpile reaches a specified threshold. For each discipline, we find the probability generating function (p.g.f. of the steady-state size of the system at the moment of departure of the customer in the main queue, the mean busy period, and the probability of the idle period.

  3. Single-Producer/Single-Consumer Queues on Shared Cache Multi-Core Systems

    CERN Document Server

    Torquati, Massimo

    2010-01-01

    Using efficient point-to-point communication channels is critical for implementing fine grained parallel program on modern shared cache multi-core architectures. This report discusses in detail several implementations of wait-free Single-Producer/Single-Consumer queue (SPSC), and presents a novel and efficient algorithm for the implementation of an unbounded wait-free SPSC queue (uSPSC). The correctness proof of the new algorithm, and several performance measurements based on simple synthetic benchmark and microbenchmark, are also discussed.

  4. Performance Study of OBS Combined Node via Mixed Loss Delay Queueing Systems

    Directory of Open Access Journals (Sweden)

    Muhammad Faisal Hayat

    2014-01-01

    Full Text Available In this paper, we present a performance study of OBS (Optical Burst Switched combined node via mixed loss delay queueing models. In an OBS network, a node combining both edge and core switching functions multiplex the local traffic with the transit traffic on the output wavelengths channels. To control the channel sharing, strategies are proposed and analyzed in this study by extending the basic mixed loss delay queueing models. The presented models are solved by Markov chain techniques and the results are compared, and where necessary also supported, by the simulations of an OBS node implemented in detail

  5. A closed-form solution for a two-server heterogeneous retrial queue with threshold policy

    Indian Academy of Sciences (India)

    TIEN VAN DO; DENES PAPP; RAM CHAKKA; JINTING WANG; JANOS SZTRIK

    2016-08-01

    In this paper, we reconsider a two-server heterogeneous retrial queue with threshold policy. However, the computation time with the existing method is prohibitively large for certain values of the threshold parameter. Applying the spectral expansion method, we derive a closed-form expression for the eigenvalues and eigenvectors matrix that are needed to determine the steady-state distribution of a quasi-birth-death process describing the queue. As a result, the computation time for the performance measures does not depend on the threshold parameter.

  6. Approximating response time distributions in closed queueing network models of computer performance

    Energy Technology Data Exchange (ETDEWEB)

    Salza, S.; Lavenberg, S.S.

    1981-01-01

    Hierarchical decomposition methods for approximating response time distributions in certain closed queueing network models of computer performance are investigated. The methods investigated apply whenever part of a customer's response time consists of a geometrically distributed number of successive cycles within a subnetwork. The key step involves replacing the subnetwork with parallel exponential servers having queue-size dependent service rates. Results on thinning stochastic point processes are used to justify this replacement when the mean number of cycles is large. Preliminary numerical comparisons of the approximations with simulation results indicate that the approximations are quite accurate even when the mean number of cycles is small. 17 references.

  7. A power-efficient and scalable load-store queue design

    OpenAIRE

    Castro, F.; Chaver Martínez, Daniel Ángel; Piñuel Moreno, Luis; Prieto Matías, Manuel; Huang, M.C.; Tirado Fernández, Francisco

    2005-01-01

    The load-store queue (LQ-SQ) of modem superscalar processors is responsible for keeping the order of memory operations. As the performance gap between processing speed and memory access becomes worse, the capacity requirements for the LQ-SQ increase, and its design becomes a challenge due to its CAM structure. In this paper we propose an efficient load-store queue state filtering mechanism that provides a significant energy reduction (on average 35% in the LSQ and 3.5% in the whole processor)...

  8. Diffusion approximations for multiclass queueing networks under preemptive priority service discipline

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    We prove a heavy traffic limit theorem to justify diffusion approximations for multiclass queueing networks under preemptive priority service discipline and provide effective stochastic dynamical models for the systems. Such queueing networks appear typically in high-speed integrated services packet networks about telecommunication system. In the network, there is a number of packet traffic types. Each type needs a number of job classes (stages) of processing and each type of jobs is assigned the same priority rank at every station where it possibly receives service. Moreover, there is no inter-routing among different traffic types throughout the entire network.

  9. Design of ATM Networks Congestion Controller Based on the Virtual Queue

    Institute of Scientific and Technical Information of China (English)

    LIU Zhi-xin; GUAN Xin-ping; LONG Cheng-nian

    2004-01-01

    The single bottleneck node of ATM networks is considered. The virtual queue mechanism and the method of proportion-integral-differential(PID) control are adopted in the congestion control. The sufficient condition of the considered system's stability is given. The method of determining the PID parameters is given further. To quicken the speed of startup and remove the congestion rapidly, the factors of increase and decrease are set according to the length of queue. The result of simulation shows that the system, given an appropriate group of parameters, can acquire good robustness and dynamic performance, and guarantees the quality of service at the same time.

  10. The M/M/1 queue with inventory, lost sale and general lead times

    DEFF Research Database (Denmark)

    Saffari, Mohammad; Asmussen, Søren; Haji, Rasoul

    We consider an M/M/1 queueing system with inventory under the (r,Q) policy and with lost sales, in which demands occur according to a Poisson process and service times are exponentially distributed. All arriving customers during stockout are lost. We derive the stationary distributions of the joi...... queue length (number of customers in the system) and on-hand inventory when lead times are random variables and can take various distributions. The derived stationary distributions are used to formulate long-run average performance measures and cost functions in some numerical examples....

  11. Energy saving for OpenFlow switch on the NetFPGA platform based on queue engineering.

    Science.gov (United States)

    Vu, Tran Hoang; Luc, Vu Cong; Quan, Nguyen Trung; Thanh, Nguyen Huu; Nam, Pham Ngoc

    2015-01-01

    Data centers play an important role in our daily activities. The increasing demand on data centers in both scale and size has led to huge energy consumption that rises the cost of data centers. Besides, environmental impacts also increase considerably due to a large amount of carbon emissions. In this paper, we present a design aimed at green networking by reducing the power consumption for routers and switches. Firstly, we design the Balance Switch on the NetFPGA platform to save consumed energy based on Queue Engineering. Secondly, we design the test-bed system to precisely measure the consumed energy of our switches. Experimental results show that energy saving of our switches is about 30% - 35% of power consumption according to variation of input traffic compared with normal Openflow Switch. Finally, we describe performance evaluations.

  12. Quarterly Briefing Book on Environmental and Waste Management Activities

    Energy Technology Data Exchange (ETDEWEB)

    Brown, M.C.

    1991-06-01

    The purpose of the Quarterly Briefing Book on Environmental and Waste Management Activities is to provide managers and senior staff at the US Department of Energy-Richland Operations Office and its contractors with timely and concise information on Hanford Site environmental and waste management activities. Each edition updates the information on the topics in the previous edition, deletes those determined not to be of current interest, and adds new topics to keep up to date with changing environmental and waste management requirements and issues. Section A covers current waste management and environmental restoration issues. In Section B are writeups on national or site-wide environmental and waste management topics. Section C has writeups on program- and waste-specific environmental and waste management topics. Section D provides information on waste sites and inventories on the site. 15 figs., 4 tabs.

  13. Planning as a part of human resource management activities

    OpenAIRE

    Kulić, Živko; Milošević, Goran

    2012-01-01

    Human resource management activities are most often grouped, or classified in that they are reduced to some ten basic activities. These activities are considered to be: work analysis; human resource planning; human resource recruitment; human resource selection; employee socialization and orientation; employee training and education; employee performance evaluation; employee rewarding and motivating; employee health and security; career management, and employee degradation and lying off. The ...

  14. Employer Branding; influencing student perception by campus management activities

    OpenAIRE

    Strnad, Martin

    2012-01-01

    The target of this thesis was to define the concept of employer branding and its relation to campus management, the activities companies do in order to attract students and promote themselves as quality employers. The theoretical research captures the marketing essence of branding and further develops it into the employer branding framework. Further research focussed on possible campus management activities. In the practical part the popularity and effectiveness of the activities were tested ...

  15. International Project Management Committee: Overview and Activities

    Science.gov (United States)

    Hoffman, Edward

    2010-01-01

    This slide presentation discusses the purpose and composition of the International Project Management Committee (IMPC). The IMPC was established by members of 15 space agencies, companies and professional organizations. The goal of the committee is to establish a means to share experiences and best practices with space project/program management practitioners at the global level. The space agencies that are involved are: AEB, DLR, ESA, ISRO, JAXA, KARI, and NASA. The industrial and professional organizational members are Comau, COSPAR, PMI, and Thales Alenia Space.

  16. Fast concurrent array-based stacks, queues and deques using fetch-and-increment-bounded, fetch-and-decrement-bounded and store-on-twin synchronization primitives

    Science.gov (United States)

    Chen, Dong; Gara, Alana; Heidelberger, Philip; Kumar, Sameer; Ohmacht, Martin; Steinmacher-Burow, Burkhard; Wisniewski, Robert

    2014-09-16

    Implementation primitives for concurrent array-based stacks, queues, double-ended queues (deques) and wrapped deques are provided. In one aspect, each element of the stack, queue, deque or wrapped deque data structure has its own ticket lock, allowing multiple threads to concurrently use multiple elements of the data structure and thus achieving high performance. In another aspect, new synchronization primitives FetchAndIncrementBounded (Counter, Bound) and FetchAndDecrementBounded (Counter, Bound) are implemented. These primitives can be implemented in hardware and thus promise a very fast throughput for queues, stacks and double-ended queues.

  17. Queueing for coronary surgery during severe supply-demand mismatch in a Canadian referral centre: a case study of implicit rationing.

    Science.gov (United States)

    Naylor, C D; Levinton, C M; Wheeler, S; Hunter, L

    1993-07-01

    Queues for in-patient surgery are commonplace in universal health care systems. Clinicians and hospitals usually manage these waiting lists with informal criteria for determining patient priority--a form of implicit rationing. To understand the workings of implicit rationing by queue, we took advantage of a natural experiment in the Canadian province of Ontario. Unprecedentedly severe supply-demand mismatch led to long waiting lists for coronary surgery [CABS] in Ontario during 1987-88. The crisis was resolved by increased funding and widespread adoption of a multifactorial clinical index for patient priority that was developed by an expert panel in 1989. Thus, we audited randomly chosen charts of patients who underwent coronary angiography at four Toronto hospitals during the crisis period, and calculated urgency scores for each case based on the multifactorial index. From 413 charts, 193 eligible patients were identified who proceeded to CABS. Waiting times did correlate with urgency ratings (r = 0.42, P < 0.0001). However, mean wait from catheterization to CABS varied among hospitals by as much as 8 weeks (P < 0.0001 after controlling for urgency scores). At the hospital with shortest queues, waiting times were twice as long for patients catheterized by cardiologists off-site vs those referred by on-site practitioners (P < 0.0001, after controlling for urgency scores); a similar form of bias was found at a second coronary surgery centre (P = 0.056, after controlling for urgency scores). Over half the patients waited longer than the maximum suggested for their category by the expert panel.(ABSTRACT TRUNCATED AT 250 WORDS)

  18. [Physical activity and management of obese patients].

    Science.gov (United States)

    Oppert, J M; Balarac, N

    2001-09-01

    Physical activity is recognized as an integral part of obesity treatment, in association with other therapeutic means. A major benefit of physical activity is the association with better long-term maintenance of weight loss. Physical activity has also positive psychological effects and increases quality of life. An evaluation of the usual level of physical activity and inactivity is needed for each patient. Physical activity counselling should be individualized and graded, in a perspective of individual progression. In subjects with massive obesity, remobilization based on physiotherapy techniques is the first step. All patients should be given simple advice to decrease sedentary behavior: use the stairs instead of the escalators, limit the time spent seated, etc. In general, current physical activity recommendations for the general population fit well with a majority of obese patients, i.e. a minimum of 30 minutes/day of moderate intensity physical activity (brisk walking or equivalent) on most, and preferably all, days of the week. Physical activities of higher intensities (endurance training programme) can be proposed on an individual basis. The type of physical activity required for long-term weight maintenance, and the question of adherence to physical activity recommendations in obese patients should be further investigated.

  19. Dynamic properties of chasers in a moving queue based on a delayed chasing model

    Science.gov (United States)

    Ning, Guo; Jian-Xun, Ding; Xiang, Ling; Qin, Shi; Reinhart, Kühne

    2016-05-01

    A delayed chasing model is proposed to simulate the chase behavior in the queue, where each member regards the closest one ahead as the target, and the leader is attracted to a target point with slight fluctuation. When the initial distances between neighbors possess an identical low value, the fluctuating target of the leader can cause an amplified disturbance in the queue. After a long period of time, the queue recovers the stable state from the disturbance, forming a straight-line-like pattern again, but distances between neighbors grow. Whether the queue can keep stable or not depends on initial distance, desired velocity, and relaxation time. Furthermore, we carry out convergence analysis to explain the divergence transformation behavior and confirm the convergence conditions, which is in approximate agreement with simulations. Project supported by the National Natural Science Foundation of China (Grant Nos. 71071044, 71001001, 71201041, and 11247291), the Doctoral Program of the Ministry of Education of China (Grant Nos. 20110111120023 and 20120111120022), the Postdoctoral Fund Project of China (Grant No. 2013M530295), the National Basic Research Program of China (Grant No. 2012CB725404), and 1000 Plan for Foreign Talent, China (Grant No. WQ20123400070).

  20. A fast cross-entropy method for estimating buffer overflows in queueing networks

    NARCIS (Netherlands)

    Boer, de P.T.; Kroese, D.P.; Rubinstein, R.Y.

    2004-01-01

    In this paper, we propose a fast adaptive importance sampling method for the efficient simulation of buffer overflow probabilities in queueing networks. The method comprises three stages. First, we estimate the minimum cross-entropy tilting parameter for a small buffer level; next, we use this as a

  1. Fokker-Planck description for the queue dynamics of large tick stocks

    Science.gov (United States)

    Garèche, A.; Disdier, G.; Kockelkoren, J.; Bouchaud, J.-P.

    2013-09-01

    Motivated by empirical data, we develop a statistical description of the queue dynamics for large tick assets based on a two-dimensional Fokker-Planck (diffusion) equation. Our description explicitly includes state dependence, i.e., the fact that the drift and diffusion depend on the volume present on both sides of the spread. “Jump” events, corresponding to sudden changes of the best limit price, must also be included as birth-death terms in the Fokker-Planck equation. All quantities involved in the equation can be calibrated using high-frequency data on the best quotes. One of our central findings is that the dynamical process is approximately scale invariant, i.e., the only relevant variable is the ratio of the current volume in the queue to its average value. While the latter shows intraday seasonalities and strong variability across stocks and time periods, the dynamics of the rescaled volumes is universal. In terms of rescaled volumes, we found that the drift has a complex two-dimensional structure, which is a sum of a gradient contribution and a rotational contribution, both stable across stocks and time. This drift term is entirely responsible for the dynamical correlations between the ask queue and the bid queue.

  2. Production Task Queue Optimization Based on Multi-Attribute Evaluation for Complex Product Assembly Workshop.

    Directory of Open Access Journals (Sweden)

    Lian-Hui Li

    Full Text Available The production task queue has a great significance for manufacturing resource allocation and scheduling decision. Man-made qualitative queue optimization method has a poor effect and makes the application difficult. A production task queue optimization method is proposed based on multi-attribute evaluation. According to the task attributes, the hierarchical multi-attribute model is established and the indicator quantization methods are given. To calculate the objective indicator weight, criteria importance through intercriteria correlation (CRITIC is selected from three usual methods. To calculate the subjective indicator weight, BP neural network is used to determine the judge importance degree, and then the trapezoid fuzzy scale-rough AHP considering the judge importance degree is put forward. The balanced weight, which integrates the objective weight and the subjective weight, is calculated base on multi-weight contribution balance model. The technique for order preference by similarity to an ideal solution (TOPSIS improved by replacing Euclidean distance with relative entropy distance is used to sequence the tasks and optimize the queue by the weighted indicator value. A case study is given to illustrate its correctness and feasibility.

  3. Analysis of Markov-modulated infinite-server queues in the central-limit regime

    NARCIS (Netherlands)

    Blom, J.G.; Turck, K. de; Mandjes, M.R.H.

    2014-01-01

    This paper focuses on an infinite-server queue modulated by an independently evolving finite-state Markovian background process, with transition rate matrix $Q\\equiv(q_{ij})_{i,j=1}^d$. {Both arrival rates and service rates are depending on the state of the background process.} The main contributi

  4. Queueing Delay and Energy Efficiency Analyses of Sleep Based Power Saving Mechanism

    Science.gov (United States)

    Zhu, Fan; Wu, Yiqun; Niu, Zhisheng

    In wireless networks, sleep mode based power saving mechanisms can reduce the energy consumption at the expense of additional packet delay. This letter analyzes its packet queueing delay and wireless terminals' energy efficiency. Based on the analysis, optimal sleep window size can be derived to optimize terminal energy efficiency with delay constraint.

  5. Production Task Queue Optimization Based on Multi-Attribute Evaluation for Complex Product Assembly Workshop.

    Science.gov (United States)

    Li, Lian-Hui; Mo, Rong

    2015-01-01

    The production task queue has a great significance for manufacturing resource allocation and scheduling decision. Man-made qualitative queue optimization method has a poor effect and makes the application difficult. A production task queue optimization method is proposed based on multi-attribute evaluation. According to the task attributes, the hierarchical multi-attribute model is established and the indicator quantization methods are given. To calculate the objective indicator weight, criteria importance through intercriteria correlation (CRITIC) is selected from three usual methods. To calculate the subjective indicator weight, BP neural network is used to determine the judge importance degree, and then the trapezoid fuzzy scale-rough AHP considering the judge importance degree is put forward. The balanced weight, which integrates the objective weight and the subjective weight, is calculated base on multi-weight contribution balance model. The technique for order preference by similarity to an ideal solution (TOPSIS) improved by replacing Euclidean distance with relative entropy distance is used to sequence the tasks and optimize the queue by the weighted indicator value. A case study is given to illustrate its correctness and feasibility.

  6. Analysis of congestion periods of an m/m/∞-queue

    NARCIS (Netherlands)

    Roijers, F.; Mandjes, M.; Berg, J.L. van den

    2007-01-01

    A c-congestion period of an m/m/ ∞-queue is a period during which the number of customers in the system is continuously above level c. Interesting quantities related to a c-congestion period are, besides its duration Dc, the total area Ac above c, and the number of arrived customers Nc. In the liter

  7. Simulating Tail Probabilities in GI/GI.1 Queues and Insurance Risk Processes with Subexponentail Distributions

    NARCIS (Netherlands)

    Boots, Nam Kyoo; Shahabuddin, Perwez

    2001-01-01

    This paper deals with estimating small tail probabilities of thesteady-state waiting time in a GI/GI/1 queue with heavy-tailed (subexponential) service times. The problem of estimating infinite horizon ruin probabilities in insurance risk processes with heavy-tailed claims can be transformed into th

  8. Analysis of congestion periods of an M/M/infinity-queue

    NARCIS (Netherlands)

    Roijers, F.; Mandjes, M.R.H.; van den Berg, H

    2007-01-01

    ABSTRACT A c-congestion period of an m/m/~-queue is a period during which the number of customers in the system is continuously above level c. Interesting quantities related to a c-congestion period are, besides its duration D"c, the total area A"c above c, and the number of arrived customers N"c. I

  9. Improving Adaptive Importance Sampling Simulation of Markovian Queueing Models using Non-parametric Smoothing

    NARCIS (Netherlands)

    Woudt, Edwin; de Boer, Pieter-Tjerk; van Ommeren, Jan C.W.

    2007-01-01

    Previous work on state-dependent adaptive importance sampling techniques for the simulation of rare events in Markovian queueing models used either no smoothing or a parametric smoothing technique, which was known to be non-optimal. In this paper, we introduce the use of kernel smoothing in this con

  10. A new, analysis-based, change of measure for tandem queues

    NARCIS (Netherlands)

    Boer, de Pieter-Tjerk; Scheinhardt, Werner R.W.

    2010-01-01

    In this paper, we introduce a simple analytical approximation for the overflow probability of a two-node tandem queue. From this, we derive a change of measure, which turns out to have good performance in almost the entire parameter space. The form of our new change of measure sheds an interesting n

  11. Simulating Tail Probabilities in GI/GI.1 Queues and Insurance Risk Processes with Subexponentail Distributions

    NARCIS (Netherlands)

    Boots, Nam Kyoo; Shahabuddin, Perwez

    2001-01-01

    This paper deals with estimating small tail probabilities of thesteady-state waiting time in a GI/GI/1 queue with heavy-tailed (subexponential) service times. The problem of estimating infinite horizon ruin probabilities in insurance risk processes with heavy-tailed claims can be transformed into th

  12. Adaptive state-dependent importance sampling simulation of Markovian queueing networks

    NARCIS (Netherlands)

    de Boer, Pieter-Tjerk; Nicola, V.F.

    2002-01-01

    In this paper, a method is presented for the efficient estimation of rare-event (buffer overflow) probabilities in queueing networks using importance sampling. Unlike previously proposed change of measures, the one used here is not static, i.e., it depends on the buffer contents at each of the

  13. Optimal hysteretic control for a BMAP/SM/1/N queue with two operation modes

    Directory of Open Access Journals (Sweden)

    Alexander N. Dudin

    2000-01-01

    Full Text Available We consider BMAP/SM/1 type queueing system with finite buffer of size N. The system has two operation modes, which are characterized by the matrix generating function of BMAP-input, the kernel of the semi-Markovian service process, and utilization cost. An algorithm for determining the optimal hysteresis strategy is presented.

  14. ON THE TRANSIENT DEPARTURE PROCESS OF Mx/G/1 QUEUEING SYSTEM WITH SINGLE SERVER VACATION

    Institute of Scientific and Technical Information of China (English)

    Yinghui TANG

    2007-01-01

    This paper studies the transient departure process of Mx/G/1 queueing system with single server vacation. We present a simple probability decomposition method to derive the expected number of departures occurring in finite time interval from any initial state and the asymptotic expansion of the expected number. Especially, we derive some more practical results for some special cases.

  15. Proposition of delay model for signalized intersections with queueing theory analytical models usage

    Directory of Open Access Journals (Sweden)

    Grzegorz SIERPIŃSKI

    2007-01-01

    Full Text Available Time delay on intersections is a very important transport problem. Thearticle includes a proposition of time delay model. Variance of service times is considered by used average waiting time in queue for queuing system with compressed queuing processes usage as a part of proposed time delays model.

  16. A Busy period analysis for the state dependent M/M/1/K queue

    NARCIS (Netherlands)

    Al Hanbali, Ahmad; Boxma, Onno

    2010-01-01

    In this paper, we study the transient behavior of a state dependent M/M/1/K queue during the busy period. We derive in closed-form the joint transform of the length of the busy period, the number of customers served during the busy period, and the number of losses during the busy period. For two

  17. A Busy period analysis of the level dependent PH/PH/1/K queue

    NARCIS (Netherlands)

    Al Hanbali, Ahmad

    2011-01-01

    In this paper, we study the transient behavior of a level dependent single server queuing system with a waiting room of finite size during the busy period. The focus is on the level dependent PH/PH/1/K queue. We derive in closed form the joint transform of the length of the busy period, the number

  18. Large Deviations Methods and the Join-the-Shortest-Queue Model

    NARCIS (Netherlands)

    Ridder, Ad; Shwartz, Adam

    2005-01-01

    We develop a methodology for studying ''large deviations type'' questions. Our approach does not require that the large deviations principle holds, and is thus applicable to a larg class of systems. We study a system of queues with exponential servers, which share an arrival stream. Arrivals are rou

  19. Fluid limits for overloaded multiclass FIFO single-server queues with general abandonment

    Directory of Open Access Journals (Sweden)

    Amber L. Puha

    2013-01-01

    Full Text Available We consider an overloaded multiclass nonidling first-in-first-outsingle-server queue with abandonment. The interarrival times, servicetimes, and deadline times are sequences of independent and identically,but generally distributed random variables. In prior work, Jennings andReed studied the workload process associated with this queue. Undermild conditions, they establish both a functional law of large numbersand a functional central limit theorem for this process. We build on thatwork here. For this, we consider a more detailed description of thesystem state given by K finite, nonnegative Borel measures on thenonnegative quadrant, one for each job class. For each time and jobclass, the associated measure has a unit atom associated with each jobof that class in the system at the coordinates determined by what arereferred to as the residual virtual sojourn time and residual patiencetime of that job. Under mild conditions, we prove a functional law oflarge numbers for this measure-valued state descriptor. This yieldsapproximations for related processes such as the queue lengths andabandoning queue lengths. An interesting characteristic of theseapproximations is that they depend on the deadline distributions intheir entirety.

  20. Many-server queues with customer abandonment: numerical analysis of their diffusion models

    CERN Document Server

    Dai, J G

    2011-01-01

    We use multidimensional diffusion processes to approximate the dynamics of a queue served by many parallel servers. The queue is served in the first-in-first-out (FIFO) order and the customers waiting in queue may abandon the system without service. Two diffusion models are proposed in this paper. They differ in how the patience time distribution is built into them. The first diffusion model uses the patience time density at zero and the second one uses the entire patience time distribution. To analyze these diffusion models, we develop a numerical algorithm for computing the stationary distribution of such a diffusion process. A crucial part of the algorithm is to choose an appropriate reference density. Using a conjecture on the tail behavior of a limit queue length process, we propose a systematic approach to constructing a reference density. With the proposed reference density, the algorithm is shown to converge quickly in numerical experiments. These experiments also show that the diffusion models are go...