Performance Comparison of Active Queue Management Techniques
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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.
A Robust Algorithm in Active Queue Management
Institute of Scientific and Technical Information of China (English)
无
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.
Comparison of load-based and queue-based active queue management algorithms
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.
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.
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.
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.
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.
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.
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.
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.
A FUZZY-LOGIC CONTROL ALGORITHM FOR ACTIVE QUEUE MANAGEMENT IN IP NETWORKS
Institute of Scientific and Technical Information of China (English)
无
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.
Directory of Open Access Journals (Sweden)
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.
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
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.
Design and analysis of a model predictive controller for active queue management.
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.
A GA-based PID active queue management control design for TCP/IP networks
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.
Multicast Services of QoS-Aware Active Queue Management over IP Multimedia Applications
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.
Improving Internet Quality of Service through Active Queue Management in Routers
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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.
Predictive functional control for active queue management in congested TCP/IP networks.
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.
Optimal Tracking Controller Design for Active Queue Management Routers via LQ-Servo
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.
Directory of Open Access Journals (Sweden)
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.
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.
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.
Fuzzy variable structure algorithms for active queue management with delay compensation
Institute of Scientific and Technical Information of China (English)
无
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.
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.
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.
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.
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.
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.
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.
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.
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.
The WorkQueue project - a task queue for the CMS workload management system
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
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 TCPs 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.
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
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.
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.
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.
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。
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.
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.
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.
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。
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.
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.
A robust and high-performance queue management controller for large round trip time networks
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.
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.
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。
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.
The congestion control algorithm based on queue management of each node in mobile ad hoc networks
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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 .
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.
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.
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 .
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.
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.
Collaborative Virtual Queue: Fair Management of Congested Departure Operations and Benefit Analysis
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...
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.
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.
A Parallel Virtual Queue Structure for Active Queue Management
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.
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.
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.
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.
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.
Transient probabilities for queues with applications to hospital waiting list management.
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.
Managing target of opportunity (ToO) observations in queue mode at Gemini Observatory
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.
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.
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.
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.
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
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.
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.
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.
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.
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.
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.
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
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。
Active Methodologies in a Queueing Systems Course for Telecommunication Engineering Studies
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…
Method, apparatus and system for managing queue operations of a test bench environment
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.
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.
Queue size and delay analysis for a communication system subject to traffic activity mode changes
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.
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.
WQM: An Aggregation-aware Queue Management Scheme for IEEE 802.11n based Networks
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.
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.
Optimal management for infinite capacity N-policy M/G/1 queue with a removable service station
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.
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.
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.
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.
Resources Management in Active Networks
Institute of Scientific and Technical Information of China (English)
无
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.
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.
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.
Vacation queueing models theory and applications
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...
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.
Preventing messaging queue deadlocks in a DMA environment
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.
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.
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.
Multifractal Internet Traffic Model and Active Queue Management
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
Near-optimal switching strategies for a tandem queue
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
Architecture and robustness tradeoffs in speed-scaled queues with application to energy management
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.
Usage of Message Queueing Technologies in the ATLAS Distributed Data Management System
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.
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
Probability, statistics, and queueing theory
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
On retrial queueing model with fuzzy parameters
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.
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.
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.
Resource manager for GRID with global job queue and with planning based on local schedules
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.
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.
Increasing available FIFO space to prevent messaging queue deadlocks in a DMA environment
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.
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...
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...
Fundamentals of queueing theory
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
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.
Queueing analysis of a shared voice-data link
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.
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。
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.
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.
Waiting for coronary angiography: is there a clinically ordered queue?
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.
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.
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.
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...
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
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.
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
A new queueing strategy for the Adversarial Queueing Theory
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...
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.
Queues and risk models with simultaneous arrivals
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
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...
Queueing theory and network applications
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.
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/.
Joining Longer Queues: Information Externalities in Queue Choice
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...
Bayesian Inference in Queueing Networks
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...
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.
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.
Queueing networks a fundamental approach
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...
Mean sojourn time in a parallel queue
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
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
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...
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.
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...
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.
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.
Dynamic server assignment in a two-queue model
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
Cost Comparison of B-1B Non-Mission-Capable Drivers Using Finite Source Queueing with Spares
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
Stabilization of Branching Queueing Networks
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.
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.
Analysis of queues methods and applications
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
MARKOVIAN QUEUES WITH CORRELATED ARRIVAL PROCESSES
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...
A pathwise comparison result for parallel queues
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...
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
FROM BALLOT THEOREMS TO THE THEORY OF QUEUES,
QUEUEING THEORY, DISTRIBUTION THEORY ), (*PROBABILITY, DISTRIBUTION THEORY ), (* DISTRIBUTION THEORY , QUEUEING THEORY), (*STOCHASTIC PROCESSES... DISTRIBUTION THEORY ), SEQUENCES(MATHEMATICS), DIFFERENCE EQUATIONS, INTEGRAL TRANSFORMS, TIME, STATISTICAL FUNCTIONS
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.
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。
Queues and Lévy Fluctuation Theory
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,
Tandem queue with server slow-down
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
Two coupled queues with heterogeneous traffic
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
GPS queues with heterogeneous traffic classes
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
Unreliable Retrial Queues in a Random Environment
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
Norton's theorem for batch routing queueing networks
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
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.
Multimedia Traffic Queueing Analysis in High-Speed Networks: a Frequency Domain Approach
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
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.
ANALYSIS OF MULTI-SERVER SINGLE QUEUE
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...
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...
Discrete time queues with phase dependent arrivals
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.
Queues and Lévy fluctuation theory
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.
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.
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
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.
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.
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.
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.
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.
The power-series algorithm for Markovian queueing networks
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
Difference and differential equations with applications in queueing theory
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
Note---A Note on Computing Optimal Control Limits for GI/M/1 Queueing Systems
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.
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.
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.
Ramp Metering by Limitation of Density and Queue Length
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.
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.
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.
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.
A comparison of queueing, cluster and distributed computing systems
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.
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...
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.
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.
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.
Priority Queue Based on Multilevel Prefix Tree
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.
Control of a heterogeneous two-server exponential queueing system
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.
Control of Entry to a Queueing System
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
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.
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.
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.
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.
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.
Influence of queue propagation and dissipation on route travel times
DEFF Research Database (Denmark)
Raovic, Nevena
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...... 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...... accurate route travel times....
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.
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.
Using simulation in out-patient queues: a case study.
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.
Optimal Multi-Server Allocation to Parallel Queues With Independent Random Queue-Server Connectivity
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...
Monotonicity properties for multi-class queueing systems
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
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.
Optimal queue-size scaling in switched networks
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
On Markovian multi-class, multi-server queueing
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
Closed Queueing Networks Under Congestion: Nonbottleneck Independence and Bottleneck Convergence
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
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...
Decomposability queueing and computer system applications
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
Queueing phase transition: theory of translation.
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.
Queues with Dropping Functions and General Arrival Processes.
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.
Simple Queueing Model Applied to the City of Portland
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
DIRAC pilot framework and the DIRAC Workload Management System
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.
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.
Performance optimization of queueing systems with perturbation realization
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.
Probability, statistics and queueing theory, with computer science applications
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
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.
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.
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.
THE M/M/c QUEUE WITH PH SYNCHRONOUS VACATIONS
Institute of Scientific and Technical Information of China (English)
无
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.
Stack- and Queue-like Dynamics in Recurrent Neural Networks
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...
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.
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.
Active Risk Management and Banking Stability
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
Ethics in radiology: wait lists queue jumping.
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.
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.
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...
IMPLEMENTATION OF CENTRAL QUEUE BASED REALTIME SCHEDULER FOR MULTIPLE SOURCE DATA STREAMING
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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.
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.
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.
Structuring medication related activities for information management.
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.
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.
An introduction to queueing theory modeling and analysis in applications
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 ...
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.
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.
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.
Extreme Values of Queues, Point Processes and Stochastic Networks.
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
Worst-case efficient external-memory priority queues
DEFF Research Database (Denmark)
Brodal, Gerth Stølting; Katajainen, Jyrki
1998-01-01
A priority queue Q is a data structure that maintains a collection of elements, each element having an associated priority drawn from a totally ordered universe, under the operations Insert, which inserts an element into Q, and DeleteMin, which deletes an element with the minimum priority from Q....... 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...
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.
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
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.
The Exactly Solvable Simplest Model for Queue Dynamics
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.
Scheme for evaluating a local queue warning system.
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,
Processor-sharing queues and resource sharing in wireless LANs
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
Large Deviations without Principle: Join the Shortest Queue
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
Moving toward queue operations at the Large Binocular Telescope Observatory
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.
Stability analysis of interacting queues in the ALOHA system
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.
Arrival first queueing networks with applications in kanban production systems
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
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.
Job Queues, Certification Status, and the Education Labor Market
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…
An asymptotic analysis of closed queueing networks with branching populations
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
Arrival first queueing networks with applications in kanban production systems
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
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...
Multi-Resource Fair Queueing for Packet Processing
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
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.
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...
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).
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.
Management of Logistics Activities and Costing Approaches
Directory of Open Access Journals (Sweden)
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.
Transient Analysis of Hysteresis Queueing Model Using Matrix Geometric Method
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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.
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.
Queueing analysis of some buffered random multiple access schemes
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.
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...... application is a parallel implementation of Dijkstra's algorithm for the single-source shortest path problem, which runs inO(n) time andO(mlogn) work on a CREW PRAM on graphs withnvertices andmedges. This is a logarithmic factor improvement in the running time compared with previous approaches....
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.
The queue as a social statement / Maria-Kristiina Soomre
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
Diagonal queue medical image steganography with Rabin cryptosystem.
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.
Queueing induced by bidirectional motor motion near the end of a microtubule
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.
Multilevel Queue-Based Scheduling for Heterogeneous Grid Environment
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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.
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.
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.
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.
Sojourn time distributions in a Markovian G-queue with batch arrival and batch removal
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...
Medical ethics and new public management in Sweden.
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.
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.
Flow-level convergence and insensitivity for multi-class queueing networks
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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.
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.
Grouping Based Job Scheduling Algorithm Using Priority Queue and Hybrid Algorithm in Grid Computing
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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.
Basic components of construction enterprises’ management marketing activities system
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...
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.
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...
The challenge of stabilizing control for queueing systems with unobservable server states
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
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.
Rare-event simulation for tandem queues: A simple and efficient importance sampling scheme
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
Approximations for the waiting time distribution in an M/G/c priority queue
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
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...
The Robo-AO automated intelligent queue system
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.
The Robo-AO automated intelligent queue system
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.
Queueing interpretation of adaptive reconstructive multiparameter τ-opening filters
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.
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.
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.
Stochastic network optimization with application to communication and queueing systems
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
A note on bias optimality in controlled queueing systems
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...
Classroom Management to Support Active Middle Level Classrooms
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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.
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.
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.
Transient Solution to an infinite Server Queue with Varying Arrival and Departure Rate
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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.
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.
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.
Scheduling in Parallel Queues with Randomly Varying Connectivity and Switchover Delay
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...
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.
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.
Ten Year Review of Queue Scheduling of the Hobby-Eberly Telescope
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.
MODELING AND SIMULATION OF QUEUE WAITING THROUGH THE CONCEPT OF PETRI NETS
Directory of Open Access Journals (Sweden)
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.
Batch arrival retrial queue with delay time and additional multi-optional repair
Directory of Open Access Journals (Sweden)
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.
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.
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.
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.
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.
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.
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.
Directory of Open Access Journals (Sweden)
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.
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.
Sojourn time distributions in a Markovian G-queue with batch arrival and batch removal
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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.
Practical Multiwriter Lock-Free Queues for "Hard Real-Time" Systems without CAS
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.
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.
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.
Channel Coding over Multiple Coherence Blocks with Queueing Constraints
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...
Ultrasound waiting lists: rational queue or extended capacity?
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.
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.
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.
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.
The Number Served in a Head Of The Line Priority Queue with General Service
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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.
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.
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.
An algorithmic technique for a class of queueing models with packet switching applications
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.
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.
Queueing model for an ATM multiplexer with unequal input/output link capacities
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.
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.
Mean time for the development of large workloads and large queue lengths in the GI/G/1 queue
Directory of Open Access Journals (Sweden)
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.
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.
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.
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.
The Jackson Queueing Network Model Built Using Poisson Measures. Application To A Bank Model
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...
The Unreliable M/M/1 Retrial Queue in a Random Environment
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
Scheduling queues in the Ethernet switch, considering the waiting time of frames
Directory of Open Access Journals (Sweden)
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.
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.
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.
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.
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.
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.
Planning as a part of human resource management activities
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 ...
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.
A queueing theory based model for business continuity in hospitals.
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.
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.
International Project Management Committee: Overview and Activities
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.
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.
A bulk queueing system under N-policy with bilevel service delay discipline and start-up time
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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.
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。
The Effectiveness Analysis of Waiting Processes in the Different Branches of a Bank by Queue Model
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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.
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.
Preemptive queueing system with randomized push-out mechanism
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.
Optimum and equilibrium in a transport problem with queue effects
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.
Probabilistic Analysis of Buffer Starvation in Markovian Queues
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...
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.
DESAIN FRAMEWORK MULTIMEDIA QUEUEING SYSTEM BERBASIS ANDROID ANTRIAN PASIEN PUSKESMAS
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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
The CMS workload management system
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).
Innovation activity management in scientific and research and development organizations
Directory of Open Access Journals (Sweden)
Jerzy Baruk
2015-09-01
Full Text Available A new trend called “revolution of innovation” is clear visible in the development of the modern economy. Its benefits can be maximized through the rational approach to innovation activity management, knowledge management (treated as a source of innovation and systemic connection between the science with industry and customers in the process of creating value. The content of the publication is thus the concept of systematic approach to innovation activity management, with special emphasis on the commercialization of innovation, and using of knowledge as a source of innovation. Three models of approach to management are proposed: 1 model of rational organization management, 2 model of conceptual structure of innovative activity management, 3 model of integration of knowledge management and innovation management. Management according to the proposed models allows to use resources of various organizations in creating value materialized in innovations in the optimal way, especially in the context of the relatively low impact of universities and research organizations on creating ideas of innovations.
Analysis of information systems for the enterprises marketing activities management
Directory of Open Access Journals (Sweden)
A.O. Natorina
2014-06-01
Full Text Available The article deals with the role of the computer information systems in the enterprise marketing activities strategic management, enterprises marketing management information systems. Tthe stages of the development system and launch of a new product into the market within its life cycle are analyzed, exemplified by fat and oil industry.
Effectiveness of marketing in management marketing activity agricultural companies
KUCHER O.
2012-01-01
Modern approaches to evaluating the effectiveness of marketing activity are investigated. The influence of marketing expenses on actualization volume of output is analyzed. A methodical approach of defining economic efficiency in marketing sales in management business is offered.
Facilities of management magnetoresistive transformer of active power
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Val. S. Vuntesmeri
2009-03-01
Full Text Available Management facilities are considered, spectral composition is certain and the form of коммутируемого signal of magnetoresistive transformer of active power is rotined.
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.
Unreliable bulk retrial queues with delayed repairs and modified vacation policy
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.
Priority Queues with Fractional Service for Tiered Delay QoS
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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.
A parametric programming solution to the F-policy queue with fuzzy parameters
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.
Multiserver queue with semi-Markovian batch arrivals with application to the MPEG frame sequence
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.
Preliminary Tritium Management Design Activities at ORNL
Energy Technology Data Exchange (ETDEWEB)
Harrison, Thomas J. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Felde, David K. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Logsdon, Randall J. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); McFarlane, Joanna [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Qualls, A. L. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
2016-09-01
Interest in salt-cooled and salt-fueled reactors has increased over the last decade (Forsberg et al. 2016). Several private companies and universities in the United States, as well as governments in other countries, are developing salt reactor designs and/or technology. Two primary issues for the development and deployment of many salt reactor concepts are (1) the prevention of tritium generation and (2) the management of tritium to prevent release to the environment (Holcomb 2013). In 2016, the US Department of Energy (DOE) initiated a research project under the Advanced Reactor Technology Program to (1) experimentally assess the feasibility of proposed methods for tritium mitigation and (2) to perform an engineering demonstration of the most promising methods. This document describes results from the first year’s efforts to define, design, and build an experimental apparatus to test potential methods for tritium management. These efforts are focused on producing a final design document as the basis for the apparatus and its scheduled completion consistent with available budget and approvals for facility use.
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.
Managing Brain Extracellular K(+) during Neuronal Activity
DEFF Research Database (Denmark)
Larsen, Brian Roland; Stoica, Anca; MacAulay, Nanna
2016-01-01
During neuronal activity in the brain, extracellular K(+) rises and is subsequently removed to prevent a widespread depolarization. One of the key players in regulating extracellular K(+) is the Na(+)/K(+)-ATPase, although the relative involvement and physiological impact of the different subunit...... isoform compositions of the Na(+)/K(+)-ATPase remain unresolved. The various cell types in the brain serve a certain temporal contribution in the face of network activity; astrocytes respond directly to the immediate release of K(+) from neurons, whereas the neurons themselves become the primary K......(+) absorbers as activity ends. The kinetic characteristics of the catalytic α subunit isoforms of the Na(+)/K(+)-ATPase are, partly, determined by the accessory β subunit with which they combine. The isoform combinations expressed by astrocytes and neurons, respectively, appear to be in line with the kinetic...
KNOWLEDGE MANAGEMENT FOR MAINTENANCE ACTIVITIES IN THE MANUFACTURING SECTOR
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M.A. Mansor
2012-06-01
Full Text Available Maintenance is an indispensable part of the business process and plays an important role in an organisation’s success and survival. The main purpose of maintenance is to ensure equipment functions at its original optimal level. Thus, the knowledge and skills of operators are crucial and in demand. This paper presents a knowledge management of maintenance activities transfer method. Knowledge management is a process that a company cannot avoid, because it is a step in providing the necessary information for business performance measurements. Based on the example of a knowledge management system for a consultant company, we propose a knowledge repository or warehouse for maintenance activities that consists of four elements: best practice, databases, discussion forums and assessment tools. Each element has its own role and contribution towards better maintenance activities. Therefore, knowledge management has a deep relationship with performance evaluation or measurement.
University Knowledge Management Tool for Academic Research Activity Evaluation
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Mihaela OPREA
2011-01-01
Full Text Available The implementation of an efficient university knowledge management system involves the de-velopment of several software tools that assist the decision making process for the three main activities of a university: teaching, research, and management. Artificial intelligence provides a variety of techniques that can be used by such tools: machine learning, data mining, text mining, knowledge based systems, expert systems, case-based reasoning, decision support systems, intelligent agents etc. In this paper it is proposed a generic structure of a university knowledge management system, and it is presented an expert system, ACDI_UPG, developed for academic research activity evaluation, that can be used as a decision support tool by the university knowledge management system for planning future research activities according to the main objectives of the university and of the national / international academic research funding organizations.
Short communication: Biochemically active humic substances in contrasting agricultural managements
Energy Technology Data Exchange (ETDEWEB)
Benitez, E.; Nogales, R.; Doni, S.; Masciandaro, G.; Moreno, B.
2016-11-01
Because their crucial role in several soil biochemical cycles and their fast response to changes in soil management, extracellular enzymes activities are widely used as sensitive indicators of ecological change and soil quality. The aim of this work was to determine the effects of soil management on the stable pool of soil carbon cycling enzymes as indicators of essential functions. For this, extracellular β-glucosidase enzymes bounded by humic acids (C higher than 104 Da) were used to compare four long-term contrasting agricultural managements in a rainfed olive orchard representative of semi-arid Mediterranean habitats. The study was conducted for 30 years by designing a random-block of four treatments (nude vs. covered soils) and four replicates. Maintaining cover crops through fall, winter and early spring provoked a more stable and active pool of extracellular β-glucosidase in soils only if spontaneous vegetation was managed with mechanical methods. When herbicides were used during 30 years, the pattern of the molecular composition and activity of humus β-glucosidase complexes were similar in covered and nude soils, although higher activity was retrieved in the former. Tillage management increased carbon mineralization and the level of humic substances and the activity of β-glucosidase humic-bound were quite lower than in the rest of treatments. Given the ecological role of extracellular soil carbon cycling enzymes, the characterization of humus β-glucosidase complexes could be an adequate indicator of sustainability of agricultural management systems. (Author)
Short communication: Biochemically active humic substances in contrasting agricultural managements
Directory of Open Access Journals (Sweden)
Emilio Benitez
2016-08-01
Full Text Available Because their crucial role in several soil biochemical cycles and their fast response to changes in soil management, extracellular enzymes activities are widely used as sensitive indicators of ecological change and soil quality. The aim of this work was to determine the effects of soil management on the stable pool of soil carbon cycling enzymes as indicators of essential functions. For this, extracellular β-glucosidase enzymes bounded by humic acids (C higher than 104 Da were used to compare four long-term contrasting agricultural managements in a rainfed olive orchard representative of semi-arid Mediterranean habitats. The study was conducted for 30 years by designing a random-block of four treatments (nude vs. covered soils and four replicates. Maintaining cover crops through fall, winter and early spring provoked a more stable and active pool of extracellular β-glucosidase in soils only if spontaneous vegetation was managed with mechanical methods. When herbicides were used during 30 years, the pattern of the molecular composition and activity of humus β-glucosidase complexes were similar in covered and nude soils, although higher activity was retrieved in the former. Tillage management increased carbon mineralization and the level of humic substances and the activity of β-glucosidase humic-bound were quite lower than in the rest of treatments. Given the ecological role of extracellular soil carbon cycling enzymes, the characterization of humus β-glucosidase complexes could be an adequate indicator of sustainability of agricultural management systems.
Young, Joyce A.; Hawes, Jon M.
2013-01-01
This paper describes an application of active learning within two different courses: professional selling and sales management. Students assumed the roles of sales representatives and sales managers for an actual fund-raiser--a golf outing--sponsored by a student chapter of the American Marketing Association. The sales project encompassed an…
An agent-based model for queue formation of powered two-wheelers in heterogeneous traffic
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.
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.
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.
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.
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.
On the Queueing Behavior of Random Codes over a Gilbert-Elliot Erasure Channel
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.
A discrete single server queue with Markovian arrivals and phase type group services
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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.
Some reflections on the Renewal-theory paradox in queueing theory
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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.
The Active Audience? Gurus, Management Ideas and Consumer Variability
Groß, C.; Heusinkveld, H.S.; Clark, T
2015-01-01
This study draws on an active audience perspective to develop a better understanding of mass audiences' attraction towards popular management ideas. It focuses on audience members' own experiences and, in particular, what audience activities actually play a role in shaping mass attraction, and how t
Activity-Based Costing: A Cost Management Tool.
Turk, Frederick J.
1993-01-01
In college and university administration, overhead costs are often charged to programs indiscriminately, whereas the support activities that underlie those costs remain unanalyzed. It is time for institutions to decrease ineffective use of resources. Activity-based management attributes costs more accurately and can improve efficiency. (MSE)
Activity-based costing management in a private practice setting.
Carlomagno, M; Draper, V
1997-01-01
Activity-based costing is a method of calculating cost of a service, focusing on operations. It gives quick and tangible cost information to operations and financial managers. While this method has be used more in the manufacturing area, it is gaining acceptance in the medical practice. This article describes activity-based costing and illustrates how to start utilizing it in a practice.
Energy saving for OpenFlow switch on the NetFPGA platform based on queue engineering.
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.
On Eigenvalues of the Generator of a C0-Semigroup Appearing in Queueing Theory
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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.
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.
A Novel Analytic Technique for the Service Station Reliability in a Discrete-Time Repairable Queue
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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.
An M/M/2 Queueing System with Heterogeneous Servers Including One with Working Vacation
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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.
Reservicing some customers in M/G/1 queues under three disciplines
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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.
Single-Producer/Single-Consumer Queues on Shared Cache Multi-Core Systems
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.
A power-efficient and scalable load-store queue design
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)...
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.
Optimal scaling of average queue sizes in an input-queued switch: an open problem
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)).
The Jackson Queueing Network Model Built Using Poisson Measures. Application To A Bank Model
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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.
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.
A queueing model for error control of partial buffer sharing in ATM
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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.
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.
The Geo/Geo/1+1 Queueing System with Negative Customers
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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.
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...
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.
Institute of Scientific and Technical Information of China (English)
无
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.
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....
Actively Managed Investment Portfolio Dilemmas, ‘Lost Returns Approach’
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Mohamed Elmesseary
2014-10-01
Full Text Available Extending the basic belief on which the investment management business is built upon: Professional managers can beat the market; linking within a practical approach betweenthe academics’ views and practitioners’ opinions regarding the market beating inability and the reasons from behind; paying some more attention to the returns, managers lose due totheir insufficient active strategies; this work analyzes the past performance of the whole stocks that actually traded in the Egyptian market between June, 2007 and June, 2012 in order to measure how fund managers are geniuses by the zero returns they lose. It performs T-test among three types of portfolios, a well-known market index, the funds’ portfolios, and the best actively managed portfolio that can be built and used as a restrict criterion. The findings reveal that adopting the simple thought of naïve investors, away from the portfolio optimization possibilities, do generate the active portfolio, which is economically optimized, as the investors initial resources are not only significantly sufficient for accessing its investments, but can be also recovered with no more than 3 months. And which can significantly out-perform the comparable benchmarks, butunfortunately, the fund managers are not geniuses due to the impressive returns they lose.JEL classification: G1; G2Keywords: Capital markets, mutual funds, performance evaluation, market timing ability, stock picking ability
WAX ActiveLibrary: a tool to manage information overload.
Hanka, R; O'Brien, C; Heathfield, H; Buchan, I E
1999-11-01
WAX Active-Library (Cambridge Centre for Clinical Informatics) is a knowledge management system that seeks to support doctors' decision making through the provision of electronic books containing a wide range of clinical knowledge and locally based information. WAX has been piloted in several regions in the United Kingdom and formally evaluated in 17 GP surgeries based in Cambridgeshire. The evaluation has provided evidence that WAX Active-Library significantly improves GPs' access to relevant information sources and by increasing appropriate patient management and referrals this might also lead to an improvement in clinical outcomes.
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.
Analysis of Markov-modulated infinite-server queues in the central-limit regime
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
Busy period analysis of the level dependent PH/PH/1/K queue
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 o
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.
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.
Large Deviations Methods and the Join-the-Shortest-Queue Model
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
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...
The application of queue theory in cloud computing to reduce the waiting time
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N.N. Bharkad
2014-10-01
Full Text Available Cloud computing is a new technology in computer field to provide on line service to the customers. -Cloud computing has got enormous popularity as it offers dynamic, low-cost computing solutions. To get the service of cloud the user has to be in queue until he is served. Each arriving Cloud computing User (CCU requests Cloud computing Service Provider (CCSP to use the resources, if server is available, the arriving user will seize and hold it for a length of time, which leads to queue length and more waiting time. A new arrival leaves the queue with no service. After service completion the server is made immediately available to others. From the user’s point of view he needs to be served immediately and to prevent waiting the CCSP’s can use infinite servers to reduce waiting time & queue length. The arrival pattern is often Poisson in queuing theory. In this article we analyzed the dynamic behavior of the system with infinite servers by finding various effective measures like response time, average time spend in the system, utilization and throughput.
Stochastic Approximations and Monotonicity of a Single Server Feedback Retrial Queue
2012-01-01
This paper focuses on stochastic comparison of the Markov chains to derive some qualitative approximations for an M/G/1 retrial queue with a Bernoulli feedback. The main objective is to use stochastic ordering techniques to establish various monotonicity results with respect to arrival rates, service time distributions, and retrial parameters.
Stochastic Approximations and Monotonicity of a Single Server Feedback Retrial Queue
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Mohamed Boualem
2012-01-01
Full Text Available This paper focuses on stochastic comparison of the Markov chains to derive some qualitative approximations for an M/G/1 retrial queue with a Bernoulli feedback. The main objective is to use stochastic ordering techniques to establish various monotonicity results with respect to arrival rates, service time distributions, and retrial parameters.
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.
Analysis of congestion periods of an m/m/∞-queue
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
Dynamic properties of chasers in a moving queue based on a delayed chasing model
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).
A new, analysis-based, change of measure for tandem queues
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
Strategic behavior and social outcomes in a bottleneck queue: experimental evidence
DEFF Research Database (Denmark)
Breinbjerg, Jesper Breinbjerg; Sebald, Alexander Christopher; Østerdal, Lars Peter
2016-01-01
We theoretically and experimentally study the differential incentive effects of three well known queue disciplines in a strategic environment in which a bottleneck facility opens and impatient players decide when to arrive. For a class of three-player games, we derive equilibrium arrivals under...
A fast cross-entropy method for estimating buffer overflows in queueing networks
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
Fokker-Planck description for the queue dynamics of large tick stocks
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.
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.
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.
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
Efficient simulation of finite horizon problems in queueing and insurance risk
DEFF Research Database (Denmark)
Rojas-Nandayapa, Leonardo; Asmussen, Søren
2007-01-01
Let ψ(u,t) be the probability that the workload in an initially empty M/G/1 queue exceeds u at time tservice times/claim sizes to be subexponential, various Monte Carlo estimators for ψ(u,t) are suggested...
Proposals for refinements in international nuclear knowledge management activities
Energy Technology Data Exchange (ETDEWEB)
Chung, Bum Jin; Kang, Doo Hyuk; Ko, Sang Hyuk; Kim, Hyung Seok [Cheju National University, Cheju (Korea, Republic of)
2004-07-01
Concerns are raised world-wide on the sustainability of nuclear society due to the aging of nuclear manpower, coming massive retirements of senior workers within the next several years, declination of nuclear education and training, as well as the shortage of nuclear manpower supply. These concerns were reflected in the international activities such as the OECD/NEA report on the nuclear education and training and the IAEA conference on Nuclear Knowledge Management. Many more follow-up activities are currently being formulated and implemented. This paper discusses the nature of the issue, proposes a Four-Season Model of nuclear industry and manpower demand and supply, and raises an issue regarding the possibility of manpower shortage propagation from the advanced countries to the developing countries. The international activities are also reviewed and proposals for further refinements of the nuclear knowledge management activities are made.
System-functional approach in enterprise''s innovation activity management
Olikh, L.; Maslyukivska, А.
2012-01-01
The article is devoted to the problems of forming management system of enterprise innovation activity. The authors pick out the enterprise's innovation subsystem main parts and generalize management functions' realization in the context of its innovation activity management.
Directory of Open Access Journals (Sweden)
Dudu G. Sokhela
2013-07-01
Full Text Available Background: Comprehensive Primary Health Care (PHC, based on the principles of accessibility, availability, affordability, equity and acceptability, was introduced in South Africa to address inequalities in health service provision. Whilst the Fast Queue was instrumental in the promotion of access to health care, a major goal of the PHC approach, facilities were not prepared for the sudden influx of clients. Increased access resulted in long waiting times and queues contributing to dissatisfaction with the service which could lead to missed appointments and non-compliance with established treatment plans.Objectives: Firstly to describe the experiences of clients using the Fast Queue strategy to access routine healthcare services and secondly, to determine how the clients’ experiences led to satisfaction or dissatisfaction with the Fast Queue service.Method: A descriptive qualitative survey using content analysis explored the experiences of the Fast Queue users in a PHC setting. Setting was first identified based on greatest number using the Fast Queue and geographic diversity and then a convenience sample of health care users of the Fast Queue were sampled individually along with one focus group of users who accessed the Queue monthly for medication refills. The same interview guide questions were used for both individual interviews and the one focus group discussion. Five clinics with the highest number of attendees during a three month period and a total of 83 health care users of the Fast Queue were interviewed. The average participant was female, 31 years old, single and unemployed.Results: Two themes with sub-themes emerged: health care user flow and communication, which highlights both satisfaction and dissatisfaction with the fast queue and queue marshals, could assist in directing users to the respective queues, reduce waiting time and keep users satisfied with the use of sign posts where there is a lack of human resources
[Preterm premature rupture of membranes: active or expectant management?].
Kayem, G; Maillard, F
2009-04-01
Preterm premature rupture of membranes (PPROM) occurs in 3% of pregnancies and is responsible for 30% of preterm births. The management is discussed between active and expectant management. French recommendations let open both possibilities. The risks described in the case of PPROM are those of prematurity, maternofetal infection, acute procidence of the umbilical cord and abruptio placentae. Before 32 weeks of gestation (WG) and even 34 WG, a prolongation of one week of gestational age significantly decreases neonatal mortality and morbidity. Therefore, most of the authors choose expectant management in case of PPROM. Between 34 and 37 WG, the risk of rare severe morbidity associated with prematurity has to be balanced with risks of an acute maternofetal infection and of abruptio placentae. Further randomized trials are required to choose a type of management with a sufficient level of evidence.
Contributions for territorial management of risks associated with oil activity
Directory of Open Access Journals (Sweden)
Felipe Pinto Gonçalves
2013-06-01
Full Text Available Whereas that the growing complexity of technical and spatial organization of the oil activity in Espírito Santo state gives new demands for land use management to the local governments, this article addresses the issue of economic and technological risks associated with such activities. Based on the evaluation of legal instruments such as the classification of land uses and the zoning, are discussed the possibilities of insertion the risks in municipal policies for land use planning
Buffer management in wireless full-duplex systems
Bouacida, Nader
2015-10-19
Wireless full-duplex radios can simultaneously transmit and receive using the same frequency. In theory, this can double the throughput. In fact, there is only little work addressing aspects other than throughput gains in full-duplex systems. Over-buffering in today\\'s networks or the so-called “bufferbloat” phenomenon creates excessive end-to-end delays resulting in network performance degradation. Our analysis shows that full-duplex systems may suffer from high latency caused by bloated buffers. In this paper, we address the problem of buffer management in full-duplex networks by using Wireless Queue Management (WQM), which is an active queue management technique for wireless networks. Our solution is based on Relay Full-Duplex MAC (RFD-MAC), an asynchronous media access control protocol designed for relay full-duplexing. We compare the performance of WQM in full-duplex environment to Drop Tail mechanism over various scenarios. Our solution reduces the end-to-end delay by two orders of magnitude while achieving similar throughput in most of the cases.
Management of Hypertension: Adapting New Guidelines for Active Patients.
Tanji, Jeffrey L.; Batt, Mark E.
1995-01-01
Discusses recent guidelines on hypertension from the National Heart, Lung, and Blood Institute and details the latest management protocols for patients with high blood pressure. The article helps physicians interpret the guidelines for treating active patients, highlighting diagnosis, step care revision, pharmacology, and sports participation…
Draft position paper on knowledge management in space activities
Holm, Jeanne; Moura, Denis
2003-01-01
As other fields of industry, space activities are facing the challenge of Knowledge Management and the International Academy of Astronautics decided to settle in 2002 a Study Group to analyse the problem and issue general guidelines. This communication presents the draft position paper of this group in view to be discussed during the 2003 IAF Congress.
The compatibility of general managers' activities and intentions in managing change in the NHS.
Spurgeon, P; Barwell, F
1990-03-01
As Hales (1986) has observed, the problem of much of the managerial research to date has been the reluctance to ask why managers behave in the way they do. The behaviour of general managers in tackling organisational change in the NHS needs to be viewed not only with respect to what is done but also with respect to how personal and organisational objectives are construed. In other words, the implementation of organisational change ultimately rests on how general managers perceive the nature of this change and their role in structuring their own personal and organisational objectives into appropriate activities. Examining the compatibility of managerial activities and the underlying values and intentions which support them is of critical importance in any cognitively-based approach. These intentions provide an important link between perceptions (i.e. how the organisation is construed) and behaviour (i.e. what activities managers choose to perform). Understanding the conceptual frameworks which underpin managerial activities could have profound implications for assessing the performance of general managers.
Multiple time-delays system modeling and control for router management
Ariba, Yassine; Labit, Yann
2009-01-01
This paper investigates the overload problem of a single congested router in TCP (Transmission Control Protocol) networks. To cope with the congestion phenomenon, we design a feedback control based on a multiple time-delays model of the set TCP/AQM (Active Queue Management). Indeed, using robust control tools, especially in the quadratic separation framework, the TCP/AQM model is rewritten as an intercon- nected system and a structured state feedback is constructed to stabilize the network variables. Finally, we illustrate the proposed methodology with a numerical example and simulations using NS-2 simulator.
A spectral approach to compute the mean performance measures of the queue with low-order BMAP input
Directory of Open Access Journals (Sweden)
Ho Woo Lee
2003-01-01
Full Text Available This paper targets engineers and practitioners who want a simple procedure to compute the mean performance measures of the Batch Markovian Arrival process (BMAP/G/1 queueing system when the parameter matrices order is very low. We develop a set of system equations and derive the vector generating function of the queue length. Starting from the generating function, we propose a spectral approach that can be understandable to those who have basic knowledge of M/G/1 queues and eigenvalue algebra.
Directory of Open Access Journals (Sweden)
Dudu G. Sokhela
2013-01-01
Full Text Available Background: Comprehensive Primary Health Care (PHC, based on the principles of accessibility, availability, affordability, equity and acceptability, was introduced in South Africa to address inequalities in health service provision. Whilst the Fast Queue was instrumental in the promotion of access to health care, a major goal of the PHC approach, facilities were not prepared for the sudden influx of clients. Increased access resulted in long waiting times and queues contributing to dissatisfaction with the service which could lead to missed appointments and non-compliance with established treatment plans. Objectives: Firstly to describe the experiences of clients using the Fast Queue strategy to access routine healthcare services and secondly, to determine how the clients’ experiences led to satisfaction or dissatisfaction with the Fast Queue service.Method: A descriptive qualitative survey using content analysis explored the experiences of the Fast Queue users in a PHC setting. Setting was first identified based on greatest number using the Fast Queue and geographic diversity and then a convenience sample of health care users of the Fast Queue were sampled individually along with one focus group of users who accessed the Queue monthly for medication refills. The same interview guide questions were used for both individual interviews and the one focus group discussion. Five clinics with the highest number of attendees during a three month period and a total of 83 health care users of the Fast Queue were interviewed. The average participant was female, 31 years old, single and unemployed.Results: Two themes with sub-themes emerged: health care user flow and communication, which highlights both satisfaction and dissatisfaction with the fast queue and queue marshals, could assist in directing users to the respective queues, reduce waiting time and keep users satisfied with the use of sign posts where there is a lack of human resources
CDC's Emergency Management Program activities - worldwide, 2003-2012.
2013-09-06
In 2003, recognizing the increasing frequency and complexity of disease outbreaks and disasters and a greater risk for terrorism, CDC established the Emergency Operations Center (EOC), bringing together CDC staff members who respond to public health emergencies to enhance communication and coordination. To complement the physical EOC environment, CDC implemented the Incident Management System (IMS), a staffing structure and set of standard operational protocols and services to support and monitor CDC program-led responses to complex public health emergencies. The EOC and IMS are key components of CDC's Emergency Management Program (EMP), which applies emergency management principles to public health practice. To enumerate activities conducted by the EMP during 2003-2012, CDC analyzed data from daily reports and activity logs. The results of this analysis determined that, during 2003-2012, the EMP fully activated the EOC and IMS on 55 occasions to support responses to infectious disease outbreaks, natural disasters, national security events (e.g., conventions, presidential addresses, and international summits), mass gatherings (e.g., large sports and social events), and man-made disasters. On 109 other occasions, the EMP was used to support emergency responses that did not require full EOC activation, and the EMP also conducted 30 exercises and drills. This report provides an overview of those 194 EMP activities.
SECONDARY WASTE MANAGEMENT STRATEGY FOR EARLY LOW ACTIVITY WASTE TREATMENT
Energy Technology Data Exchange (ETDEWEB)
TW, CRAWFORD
2008-07-17
This study evaluates parameters relevant to River Protection Project secondary waste streams generated during Early Low Activity Waste operations and recommends a strategy for secondary waste management that considers groundwater impact, cost, and programmatic risk. The recommended strategy for managing River Protection Project secondary waste is focused on improvements in the Effiuent Treatment Facility. Baseline plans to build a Solidification Treatment Unit adjacent to Effluent Treatment Facility should be enhanced to improve solid waste performance and mitigate corrosion of tanks and piping supporting the Effiuent Treatment Facility evaporator. This approach provides a life-cycle benefit to solid waste performance and reduction of groundwater contaminants.
Management of female handball players' activity applying interactive technologies
Directory of Open Access Journals (Sweden)
Frolova L.S.
2012-04-01
Full Text Available The efficiency of developed methods for the control of female handball players' readiness to competitive activity was determined. The opportunities of team management regarding the specification of playing role, the formation of the starting line of players and the replacement according to game priorities in attack or defense were considered. The availability of the adequate zone of handball players' mobilizing readiness that allows to have a significant influence on individual effectiveness in the conditions of optimal management and to increase the quality of team game was determined.
Route activity tracking and management using available technology
Directory of Open Access Journals (Sweden)
Sam Yousef Khoury
2012-01-01
Full Text Available Small organizations that maintain their own fleet and make their own deliveries are responsible for ensuring their drivers are utilizing the most efficient routes while delivering products to their customers. Furthermore, efficient delivery requires that drivers spend as little time as possible dropping off and picking up products, since these activities are referred to as “non-value added activities,” although they are necessary tasks in the order cycle process. To aid in reducing order cycle times, large organizations that can afford it have employed transportation management systems. Unfortunately, small organizations with limited resources are less likely to adopt transportation management systems, despite the need for such automation. One solution is to use available productivity software to track and manage driver route activity in an effort to improve and maintain driver productivity by reducing non-value time and identifying optimal routes. This paper will outline how office productivity software such as Microsoft® Access can meet the needs of small organizations with limited resources by describing the development and use of a route activity database that employs an easy-to-use multi-user interface. This paper also includes the details of the underlying infrastructure and the user interface.
Sergio Ricardo Mendes Vasconcelos; Silvana Festa Sabes; Alexandre Gonzales
2016-01-01
This paper aimed to evaluate the performance of a specific group of active management equity investments funds relating it to the management fees charged by managers in order to answer the following research problem: open equity funds with active management, that charge higher management fees, are those that provide the best returns for the investor? The objective was to test the hypothesis under which it is evident that the funds that charged the highest rates are those with the best perform...
Directory of Open Access Journals (Sweden)
M.ReniSagaya Raj
2016-03-01
Full Text Available In this paper, we consider a state-dependent queueing system in which the system is subject to random breakdowns. Customer arrive at the system randomly following a Poisson process with state-dependent rates. Service times follows PH distribution and repair times are exponentially distributed. The server may fail to service with probability depending on the number of customer completed since the last repair. The main result of this paper is the matrix-geometric solution of the steady-state queue length from which many performance measurements of this queueing system like the stationary queue length distribution, waiting time distribution and the distribution of regular busy period, system utilization are obtained. Numerical examples are presented for both cases.
ANALYSIS AND COMPUTATIONAL ALGORITHM FOR QUEUES WITH STATE-DEPENDENT VACATIONS I: G/M(n)/1/K
Institute of Scientific and Technical Information of China (English)
Xiuli CHAO; Ayyar RAHMAN
2006-01-01
In this paper we study a queueing system with state-dependent services and state-dependent vacations, or simply G/M(n)/1/K. Since the service rate is state-dependent, this system includes G/M/c and G/M/c/K queues with various types of station vacations as special cases. We provide a recursive algorithm using the supplementary variable technique to numerically compute the stationary queue length distribution of the system. The only input requirement is the Laplace-Stieltjes transform of the interarrival distribution as well as the state-dependent service rate and state-dependent vacation rate. In a subsequent companion paper, we study its dual system M(n)/G/1/K queue with statedependent vacations.
Microgrids in Active Network Management-Part I
DEFF Research Database (Denmark)
Palizban, Omid; Kauhaniemia, Kimmo; Guerrero, Josep M.
2014-01-01
The microgrid concept has been closely investigated and implemented by numerous experts worldwide. The first part of this paper describes the principles of microgrid design, considering the operational concepts and requirements arising from participation in active network management. Over the las......, energy storage systems, and market participation in both island and grid-connection operation. Finally, control techniques and the principles of energy-storage systems are summarized in a comprehensive flowchart.......The microgrid concept has been closely investigated and implemented by numerous experts worldwide. The first part of this paper describes the principles of microgrid design, considering the operational concepts and requirements arising from participation in active network management. Over the last...
Waste Management Policy Framework to Mitigate Terrorist Intrusion Activities
Energy Technology Data Exchange (ETDEWEB)
Redus, Kenneth, S.
2003-02-26
A policy-directed framework is developed to support US Department of Energy (DOE) counterterrorism efforts, specifically terrorist intrusion activities that affect of Environmental Management (EM) programs. The framework is called the Security Effectiveness and Resource Allocation Definition Forecasting and Control System (SERAD-FACS). Use of SERAD-FACS allows trade-offs between resources, technologies, risk, and Research and Development (R&D) efforts to mitigate such intrusion attempts. Core to SERAD-FACS is (1) the understanding the perspectives and time horizons of key decisionmakers and organizations, (2) a determination of site vulnerabilities and accessibilities, and (3) quantifying the measures that describe the risk associated with a compromise of EM assets. The innovative utility of SERAD-FACS is illustrated for three integrated waste management and security strategies. EM program risks, time delays, and security for effectiveness are examined to demonstrate the significant cost and schedule impact terrorist activities can have on cleanup efforts in the DOE complex.
United States-Russia: Environmental management activities, Summer 1998
Energy Technology Data Exchange (ETDEWEB)
NONE
1998-09-01
A Joint Coordinating Committee for Environmental Restoration and Waste Management (JCCEM) was formed between the US and Russia. This report describes the areas of research being studied under JCCEM, namely: Efficient separations; Contaminant transport and site characterization; Mixed wastes; High level waste tank remediation; Transuranic stabilization; Decontamination and decommissioning; and Emergency response. Other sections describe: Administrative framework for cooperation; Scientist exchange; Future actions; Non-JCCEM DOE-Russian activities; and JCCEM publications.
Managing depression through needlecraft creative activities: A qualitative study
2000-01-01
This qualitative study explored the personal meanings of needlecrafts and their role in the self-management of depression. Written and spoken narratives from 39 women were studied. Respondents described themselves as experiencing chronic or episodic depression (e.g. associated with stressful work situations, bereavement or caring for an ill relative). Some had received treatment for depression but most had not. When analysing the therapeutic effects of creative activity, most women describ...
Managing Value-Based Activity Flexibility on Integrated ERP
Institute of Scientific and Technical Information of China (English)
WANG Manling; YANG Deli
2004-01-01
On the background of integrated ERP development, activity-value-flexibility management (AVFM) is defined. By using economic-value-added (EVA) and corporate value creation as the objective of AVFM, custom value deviating rate, capital cost deviating rate, cash-flow-out per purchase deviating rate and cash-flow-in per sell deviating rate are developed to be the key responding variates for A VFM, and they also decide the rational quantity range for A VFM tactics. Method for rational AVFM tactics solution could be got by means of redesigning activity information process on integrated ERP.
业务流程的时延预测多类型队列挖掘方法%Method ofTime Delay Prediction for Multi-class Queue Mining
Institute of Scientific and Technical Information of China (English)
曹芮浩; 方贤文; 王晓悦
2016-01-01
The process mining is one of the core content of business process management .The existing methods are most based on the view of control‐flow .However ,there are some limitations in the existing methods for the execution of the business processes which hold delay .At present ,the method of process mining based on queue view provides quantitative analysis for the process of time delay ,but it is insufficient in multi class queue mining .This paper put forward different delay prediction algorithm according to G/M/s+ M ,D/M/c+ M and M/M/1 three different type of queue system .In addition ,in consideration of the effect of different customer categories in the service process ,predict the time delay based on the delay of the queue length for target‐customer at the instant .At the same time ,the method of optimizing the initial process model is introduced by summarizing the behavior information which mined by the data of delay prediction of the event .Multi‐class queue mining method is proposed in this paper ,which not only can accurately mining the business process with time delay ,but also but also improve the problem of queue mining in the case of multi‐class queue system .At the same time ,the proposed multi class queue mining method can be used in the optimization process model ,and finally through an example to verify the effectiveness of the method .%过程挖掘是业务流程管理的核心内容之一。现有的方法多是基于控制流观点进行过程挖掘的，但是在挖掘存在时延的业务流程时，此方法存在一定的局限性。目前基于队列观点进行过程挖掘的方法，为挖掘存在时延的流程提供了定量分析的技术支持，但是在多类别队列挖掘方面存在不足。笔者针对G／M／s＋M，D／M／c＋M和M／M／1三种不同的队列类型提出不同的时延预测方法，并且将服务流程中不同的顾客类别对时延预测产生的影响考虑在内，对特定顾客进行基于
A SINGLE SERVER RETRIAL QUEUE WITH GENERAL RETRIAL TIMES AND TWO-PHASE SERVICE
Institute of Scientific and Technical Information of China (English)
Jinting WANG; Jianghua LI
2009-01-01
An M/G/1 retrial queue with a first-come-first-served (FCFS) orbit, general retrial time, two-phase service and server breakdown is investigated in this paper. Customers are allowed to balk and renege at particular times. Assume that the customers who find the server busy are queued in the orbit in accordance with an FCFS discipline. All customers demand the first "essential" service, whereas only some of them demand the second "optional" service, and the second service is multi-optional. During the service, the server is subject to breakdown and repair. Assume that the retrial time, the service time, and the repair time of the server are all arbitrarily distributed. By using the supplementary variables method, the authors obtain the steady-state solutions for both queueing and reliability measures of interest.
A finite capacity queue with Markovian arrivals and two servers with group services
Directory of Open Access Journals (Sweden)
S. Chakravarthy
1994-01-01
Full Text Available In this paper we consider a finite capacity queuing system in which arrivals are governed by a Markovian arrival process. The system is attended by two exponential servers, who offer services in groups of varying sizes. The service rates may depend on the number of customers in service. Using Markov theory, we study this finite capacity queuing model in detail by obtaining numerically stable expressions for (a the steady-state queue length densities at arrivals and at arbitrary time points; (b the Laplace-Stieltjes transform of the stationary waiting time distribution of an admitted customer at points of arrivals. The stationary waiting time distribution is shown to be of phase type when the interarrival times are of phase type. Efficient algorithmic procedures for computing the steady-state queue length densities and other system performance measures are discussed. A conjecture on the nature of the mean waiting time is proposed. Some illustrative numerical examples are presented.
On a BMAP/G/1 G-queue with Setup Times andMultiple Vacations
Institute of Scientific and Technical Information of China (English)
Yi PENG; Xiang-qun YANG
2011-01-01
In this paper,we consider a BMAP/G/1 G-queue with setup times and multiple vacations.Arrivals of positive customers and negative customers follow a batch Markovian arrival process (BMAP) and Markovian arrival process (MAP) respectively.The arrival of a negative customer removes all the customers in the system when the server is working.The server leaves for a vacation as soon as the system empties and is allowed to take repeated (multiple) vacations.By using the supplementary variables method and the censoring technique,we obtain the queue length distributions.We also obtain the mean of the busy period based on the renewal theory.
A Discrete-Time Queue with Balking, Reneging, and Working Vacations
Directory of Open Access Journals (Sweden)
Veena Goswami
2014-01-01
Full Text Available This paper presents an analysis of balking and reneging in finite-buffer discrete-time single server queue with single and multiple working vacations. An arriving customer may balk with a probability or renege after joining according to a geometric distribution. The server works with different service rates rather than completely stopping the service during a vacation period. The service times during a busy period, vacation period, and vacation times are assumed to be geometrically distributed. We find the explicit expressions for the stationary state probabilities. Various system performance measures and a cost model to determine the optimal service rates are presented. Moreover, some queueing models presented in the literature are derived as special cases of our model. Finally, the influence of various parameters on the performance characteristics is shown numerically.
The MAP, M/G1,G2/1 queue with preemptive priority
Directory of Open Access Journals (Sweden)
Bong Dae Choi
1997-01-01
Full Text Available We consider the MAP, M/G1,G2/1 queue with preemptive resume priority, where low priority customers arrive to the system according to a Markovian arrival process (MAP and high priority customers according to a Poisson process. The service time density function of low (respectively: high priority customers is g1(x (respectively: g2(x. We use the supplementary variable method with Extended Laplace Transforms to obtain the joint transform of the number of customers in each priority queue, as well as the remaining service time for the customer in service in the steady state. We also derive the probability generating function for the number of customers of low (respectively, high priority in the system just after the service completion epochs for customers of low (respectively, high priority.
Directory of Open Access Journals (Sweden)
Bindu Abraham
2014-05-01
Full Text Available In this paper we analyze DAR(1/D/s Queue with Discrete Mittag-Leffler [DML(α] as marginal distribution. Simulation study of the sample path of the arrival process is conducted. For this queueing system, the stationary distribution of the system size and the waiting time distribution of an arbitrary packet is obtained with the help of matrix analytic methods and Markov regenerative theory. The quantitative effect of the stationary distribution on system size, waiting time and the autocorrelation function as well as the parameters of the input traffic is illustrated empirically. The model is applied to a real data on the passenger arrivals at a subway bus terminal in Santiago de Chile and is established that the model well suits this data.
Second order effect of binary sources on characteristics of queue and loss rate
Sheng, Hong-Dah; Li, San-Qi
1994-02-01
A wideband source in high speed networks is typically represented by a binary random process. In this paper we characterize the second-order properties of each binary source by a multi-state MMPP. A comprehensive numerical study is carried out to identify the individual effect of the source second-order dynamics on the queue length and loss rate. The results can be used to verify the validity of the two-state Markov chain binary source assumption which is commonly made within the framework of input rate control and bandwidth allocation in high speed networks. The concept of input power spectrum is then developed as a unified source characterization for multimedia traffic queueing analyses.
Optimal operating policy for a controllable queueing model with a fuzzy environment
Institute of Scientific and Technical Information of China (English)
Chuen-homg LIN; Jau-chuan KE
2009-01-01
We construct the membership functions of the fuzzy objective values of a controllable queueing model, in which cost elements, arrival rate and service rate are all fuzzy numbers. Based on Zadeh's extension principle, a set of parametric nonlinear programs is developed to find the upper and lower bounds of the minimal average total cost per unit time at the possibility level. The membership functions of the minimal average total cost are further constructed using different values of the possibility level. A numerical example is solved successfully to illustrate the validity of the proposed approach. Because the object value is ex-pressed and governed by the membership functions, the optimization problem in a fuzzy environment for the controllable queueing models is represented more accurately and analytical results are more useful for system designers and practitioners.
Jain, Mamta; Kumar, Anil; Choudhary, Rishabh Charan
2016-09-09
In this article, we have proposed an improved diagonal queue medical image steganography for patient secret medical data transmission using chaotic standard map, linear feedback shift register, and Rabin cryptosystem, for improvement of previous technique (Jain and Lenka in Springer Brain Inform 3:39-51, 2016). The proposed algorithm comprises four stages, generation of pseudo-random sequences (pseudo-random sequences are generated by linear feedback shift register and standard chaotic map), permutation and XORing using pseudo-random sequences, encryption using Rabin cryptosystem, and steganography using the improved diagonal queues. Security analysis has been carried out. Performance analysis is observed using MSE, PSNR, maximum embedding capacity, as well as by histogram analysis between various Brain disease stego and cover images.
Impact of sensing errors on the queueing delay and transmit power in cognitive radio access
Hamza, Doha R.
2011-03-01
We study a multiple-access system with a primary user (PU) and a secondary user (SU) utilizing the same frequency band and communicating with a common receiver. Both users transmit with a fixed transmission rate by employing a channel inversion power control scheme. The SU transmits with a certain probability that depends on the sensing outcome, its queue length and whether it has a new packet arrival. We consider the case of erroneous sensing. The goal of the SU is to find the optimal transmission scheduling policy so as to minimize its queueing delay under constraints on its average transmit power and the maximum tolerable primary outage probability caused by miss-detection. The access probabilities are obtained efficiently using linear programming. © 2011 IEEE.
OPTIMAL CONTROL OF AN M/G/1 RETRIAL QUEUE WITH VACATIONS
Institute of Scientific and Technical Information of China (English)
Arnar AISSANI
2008-01-01
In this note, we consider an M/G/1 retrial queue with server vacations, when retrial times, servicetimes and vacation times are arbitrary distributed. The distribution of the number of customers in the system in stationary regime is obtained in terms of generating function. Next, we give heavy traffic approximation of such distribution. We show that the system size can be decomposed into two random variables, one of which corresponds to the system size of the ordinary M/G/1 FIFO queue without vacation. Such a stochastic decomposition property is useful for the computation of performance measures of interest. Finally, we solve simple problems of optimal control of vacation and retrial policies.
Fast distributed strategic learning for global optima in queueing access games
Tembine, Hamidou
2014-08-24
In this paper we examine combined fully distributed payoff and strategy learning (CODIPAS) in a queue-aware access game over a graph. The classical strategic learning analysis relies on vanishing or small learning rate and uses stochastic approximation tool to derive steady states and invariant sets of the underlying learning process. Here, the stochastic approximation framework does not apply due to non-vanishing learning rate. We propose a direct proof of convergence of the process. Interestingly, the convergence time to one of the global optima is almost surely finite and we explicitly characterize the convergence time. We show that pursuit-based CODIPAS learning is much faster than the classical learning algorithms in games. We extend the methodology to coalitional learning and proves a very fast formation of coalitions for queue-aware access games where the action space is dynamically changing depending on the location of the user over a graph.
Energy Efficiency in the Low-SNR Regime under Queueing Constraints and Channel Uncertainty
Qiao, Deli; Velipasalar, Senem
2009-01-01
Energy efficiency of fixed-rate transmissions is studied in the presence of queueing constraints and channel uncertainty. It is assumed that neither the transmitter nor the receiver has channel side information prior to transmission. The channel coefficients are estimated at the receiver via minimum mean-square-error (MMSE) estimation with the aid of training symbols. It is further assumed that the system operates under statistical queueing constraints in the form of limitations on buffer violation probabilities. The optimal fraction of power allocated to training is identified. Spectral efficiency--bit energy tradeoff is analyzed in the low-power and wideband regimes by employing the effective capacity formulation. In particular, it is shown that the bit energy increases without bound in the low-power regime as the average power vanishes. A similar conclusion is reached in the wideband regime if the number of noninteracting subchannels grow without bound with increasing bandwidth. On the other hand, it is pr...
Analysis of an M/M/c Queueing System with Impatient Customers and Synchronous Vacations
Directory of Open Access Journals (Sweden)
Dequan Yue
2014-01-01
Full Text Available We consider an M/M/c queueing system with impatient customers and a synchronous vacation policy, where customer impatience is due to the servers’ vacation. Whenever a system becomes empty, all the servers take a vacation. If the system is still empty, when the vacation ends, all the servers take another vacation; otherwise, they return to serve the queue. We develop the balance equations for the steady-state probabilities and solve the equations by using the probability generating function method. We obtain explicit expressions of some important performance measures by means of the two indexes. Based on these, we obtain some results about limiting behavior for some performance measures. We derive closed-form expressions of some important performance measures for two special cases. Finally, some numerical results are also presented.
Queue-Aware Distributive Resource Control for Delay-Sensitive Two-Hop MIMO Cooperative Systems
Wang, Rui; Cui, Ying
2010-01-01
In this paper, we consider a queue-aware distributive resource control algorithm for two-hop MIMO cooperative systems. We shall illustrate that relay buffering is an effective way to reduce the intrinsic half-duplex penalty in cooperative systems. The complex interactions of the queues at the source node and the relays are modeled as an average-cost infinite horizon Markov Decision Process (MDP). The traditional approach solving this MDP problem involves centralized control with huge complexity. To obtain a distributive and low complexity solution, we introduce a linear structure which approximates the value function of the associated Bellman equation by the sum of per-node value functions. We derive a distributive two-stage two-winner auction-based control policy which is a function of the local CSI and local QSI only. Furthermore, to estimate the best fit approximation parameter, we propose a distributive online stochastic learning algorithm using stochastic approximation theory. Finally, we establish techn...
2013-08-08
..., Information and Records Management Services, Office of Management. BILLING CODE 4000-01-P ... Agency Information Collection Activities; Submission to the Office of Management and Budget for Review and Approval; Comment Request; Integrated Postsecondary Education Data System (IPEDS) 2013-...
Carbon sink activity and GHG budget of managed European grasslands
Klumpp, Katja; Herfurth, Damien; Soussana, Jean-Francois; Fluxnet Grassland Pi's, European
2013-04-01
In agriculture, a large proportion (89%) of greenhouse gas (GHG) emission saving potential may be achieved by means of soil C sequestration. Recent demonstrations of carbon sink activities of European ecosystemes, however, often questioned the existence of C storing grasslands, as though a net sink of C was observed, uncertainty surrounding this estimate was larger than the sink itself (Janssens et al., 2003, Schulze et al., 2009. Then again, some of these estimates were based on a small number of measurements, and on models. Not surprising, there is still, a paucity of studies demonstrating the existence of grassland systems, where C sequestration would exceed (in CO2 equivalents) methane emissions from the enteric fermentation of ruminants and nitrous oxide emissions from managed soils. Grasslands are heavily relied upon for food and forage production. A key component of the carbon sink activity in grasslands is thus the impact of changes in management practices or effects of past and recent management, such as intensification as well as climate (and -variation). We analysed data (i.e. flux, ecological, management and soil organic carbon) from a network of European grassland flux observation sites (36). These sites covered different types and intensities of management, and offered the opportunity to understand grassland carbon cycling and trade-offs between C sinks and CH4 and N2O emissions. For some sites, the assessment of carbon sink activities were compared using two methods; repeated soil inventory and determination of the ecosystem C budget by continuous measurement of CO2 exchange in combination with quantification of other C imports and exports (net C storage, NCS). In general grassland, were a potential sink of C with 60±12 g C /m2.yr (median; min -456; max 645). Grazed sites had a higher NCS compared to cut sites (median 99 vs 67 g C /m2.yr), while permanent grassland sites tended to have a lower NCS compared to temporary sown grasslands (median 64 vs
Predicting and preventing the future: actively managing multiple sclerosis.
LENUS (Irish Health Repository)
Hutchinson, Michael
2012-02-01
Relapsing-remitting multiple sclerosis (MS) has a highly variable clinical course but a number of demographic, clinical and MRI features can guide the clinician in the assessment of disease activity and likely disability outcome. It is also clear that the inflammatory activity in the first five years of relapsing-remitting MS results in the neurodegenerative changes seen in secondary progressive MS 10-15 years later. While conventional first-line disease modifying therapy has an effect on relapses, about one third of patients have a suboptimal response to treatment. With the advent of highly active second-line therapies with their evident marked suppression of inflammation, the clinician now has the tools to manage the course of relapsing-remitting MS more effectively. The development of treatment optimisation recommendations based on the clinical response to first-line therapies can guide the neurologist in more active management of the early course of relapsing-remitting MS, with the aim of preventing both acute inflammatory axonal injury and the neurodegenerative process which leads to secondary progressive MS.
Fight for your breeding right: hierarchy re-establishment predicts aggression in a social queue
Wong, Marian; Balshine, Sigal
2010-01-01
Social aggression is one of the most conspicuous features of animal societies, yet little is known about the causes of individual variation in aggression within social hierarchies. Recent theory suggests that when individuals form queues for breeding, variation in social aggression by non-breeding group members is related to their probability of inheriting breeding status. However, levels of aggression could also vary as a temporary response to changes in the hierarchy, with individuals becom...
Brouns, G.A.J.F.; van der Wal, J.
2006-01-01
We consider a two-class M-lambda 1,M-lambda 2\\M-mu\\1 preemptive priority queue in which there are two essential, on-line decisions that have to be taken. The first is the decision to either accept or reject new type-1 or type-2 jobs. The second is the decision to abort jobs, i.e., to remove any type
R+WFQ: a novel SLA-supported packet fair queueing algorithm for OLT scheduler
Zou, Junni; Qi, Shijie; Song, Yingxiong; Lin, Rujian
2005-02-01
To implement both fairness and priority scheduling in OLT scheduler, this paper proposes a SLA-supported packet fair queueing algorithm named R+WFQ. It employs WFQ discipline to serve high-priority sessions and Round Robin discipline to transmit low-priority sessions in free moments existed in traditional WFQ. Computer simulation results as well as theoretic analysis show that the proposed algorithm has excellent performance in terms of the implementation complexity, fairness and delay properties.
Delay decomposition at a single server queue with constant service time and multiple inputs
Ziegler, C.; Schilling, D. L.
1978-01-01
Two network consisting of single server queues, each with a constant service time, are considered. The external inputs to each network are assumed to follow some general probability distribution. Several interesting equivalencies that exist between the two networks considered are derived. This leads to the introduction of an important concept in delay decomposition. It is shown that the waiting time experienced by a customer can be decomposed into two basic components called self-delay and interference delay.
Computing the Performance Measures in Queueing Models via the Method of Order Statistics
Directory of Open Access Journals (Sweden)
Yousry H. Abdelkader
2011-01-01
Full Text Available This paper focuses on new measures of performance in single-server Markovian queueing system. These measures depend on the moments of order statistics. The expected value and the variance of the maximum (minimum number of customers in the system as well as the expected value and the variance of the minimum (maximum waiting time are presented. Application to an M/M/1 model is given to illustrate the idea and the applicability of the proposed measures.
Dynamic Performance Optimization for Cloud Computing Using M/M/m Queueing System
Directory of Open Access Journals (Sweden)
Lizheng Guo
2014-01-01
Full Text Available Successful development of cloud computing has attracted more and more people and enterprises to use it. On one hand, using cloud computing reduces the cost; on the other hand, using cloud computing improves the efficiency. As the users are largely concerned about the Quality of Services (QoS, performance optimization of the cloud computing has become critical to its successful application. In order to optimize the performance of multiple requesters and services in cloud computing, by means of queueing theory, we analyze and conduct the equation of each parameter of the services in the data center. Then, through analyzing the performance parameters of the queueing system, we propose the synthesis optimization mode, function, and strategy. Lastly, we set up the simulation based on the synthesis optimization mode; we also compare and analyze the simulation results to the classical optimization methods (short service time first and first in, first out method, which show that the proposed model can optimize the average wait time, average queue length, and the number of customer.
A BATCH ARRIVAL RETRIAL QUEUE WITH STARTING FAILURES, FEEDBACK AND ADMISSION CONTROL
Institute of Scientific and Technical Information of China (English)
Jinting WANG; Peng-Feng ZHOU
2010-01-01
This paper is concerned with the analysis of a feedback M[X]/G/1 retrial queue with starting failures and general retrial times.In a batch,each individual customer is subject to a control admission policy upon arrival.If the server is idle,one of the customers admitted to the system may start its service and the rest joins the retrial group,whereas all the admitted customers go to the retrial group when the server is unavailable upon arrival.An arriving customer(primary or retrial)must turn-on the server,which takes negligible time.If the server is started successfully(with a certain probability),the customer gets service immediately.Otherwise,the repair for the server commences immediately and the customer must leave for the orbit and make a retrial at a later time.It is assumed that the customers who find the server unavailable are queued in the orbit in accordance with an FCFS discipline and only the customer at the head of the queue is allowed for access to the server.The Markov chain underlying the considered queueing system is studied and the necessary and sufficient condition for the system to be stable is presented.Explicit formulae for the stationary distribution and some performance measures of the system in steady-state are obtained.Finally,some numerical examples are presented to illustrate the influence of the parameters on several performance characteristics.
Huang, Xuan-Chao
2010-01-01
One of the main problems in all-optical packet-switched networks is the lack of optical buffers, and one feasible technology for the constructions of optical buffers is to use optical crossbar Switches and fiber Delay Lines (SDL). In this two-part paper, we consider SDL constructions of optical queues with a limited number of recirculations through the optical switches and the fiber delay lines. Such a problem arises from practical feasibility considerations. In Part I, we have proposed a class of greedy constructions for certain types of optical queues, including linear compressors, linear decompressors, and 2-to-1 FIFO multiplexers, and have shown that every optimal construction among our previous constructions of these types of optical queues under the constraint of a limited number of recirculations must be a greedy construction. In Part II, the present paper, we further show that there are at most two optimal constructions and give a simple algorithm to obtain the optimal construction(s). The main idea i...
Nearly periodic behavior in the overloaded G/D/s+GI queue
Directory of Open Access Journals (Sweden)
Ward Whitt
2011-01-01
Full Text Available Under general conditions, the number of customers in a GI/D/s+GI many-server queue at time t converges to a unique stationary distribution as t → ∞. However, simulations show that the sample paths routinely exhibit nearly periodic behavior over long time intervals when the system is overloaded and s is large, provided that the system does not start in steady state. Moreover, the precise periodic behavior observed depends critically on the initial conditions. We provide insight into the transient behavior by studying the deterministic fluid model, which arises as the many-server heavy-traffic limit. The limiting fluid model also has a unique stationary point, but that stationary point is not approached from any other initial state as t → ∞. Instead, the fluid model performance approaches one of its uncountably many periodic steady states, depending on the initial conditions. Simulation experiments confirm that the time-dependent performance of the stochastic queueing model is well approximated by the fluid model. Like the fluid model, the behavior of the queueing system is highly sensitive to the initial conditions over long intervals of time.
Surgery or physical activity in the management of sciatica
DEFF Research Database (Denmark)
Fernandez, Matthew; Ferreira, Manuela L; Refshauge, Kathryn M
2016-01-01
PURPOSE: Previous reviews have compared surgical to non-surgical management of sciatica, but have overlooked the specific comparison between surgery and physical activity-based interventions. METHODS: Systematic review using MEDLINE, CINAHL, Embase and PEDro databases was conducted. Randomised...... controlled trials comparing surgery to physical activity, where patients were experiencing the three most common causes of sciatica-disc herniation, spondylolisthesis and spinal stenosis. Two independent reviewers extracted pain and disability data (converted to a common 0-100 scale) and assessed...... than physical activity for disc herniation: disability [WMD -9.00 (95 % CI -13.73, -4.27)], leg pain [WMD -16.01 (95 % CI -23.00, -9.02)] and back pain [WMD -12.44 (95 % CI -17.76, -7.09)]; for spondylolisthesis: disability [WMD -14.60 (95 % CI -17.12, -12.08)], leg pain [WMD -35.00 (95 % CI -39...
Microgrids in Active Network Management-Part II
DEFF Research Database (Denmark)
Palizban, Omid; Kauhaniemi, Kimmo; Guerrero, Josep M.
2014-01-01
, following planned or unplanned transitions to island mode, microgrids may develop instability. For this reason, the paper addresses the principles behind island-detection methods, black-start operation, fault management, and protection systems, along with a comprehensive review of power quality. Finally......The development of distribution networks for participation in active network management (ANM) and smart grids is introduced using the microgrid concept. In recent years, this issue has been researched and implemented by many experts. The second part of this paper describes those developed...... operational concepts of microgrids that have an impact on their participation in ANM and in the requirements for achieving targets. Power quality is the most challenging task in microgrids, especially when the system switches from normal parallel operation (grid-connection mode) to island operation. Indeed...
Energy management and control of active distribution systems
Shariatzadeh, Farshid
Advancements in the communication, control, computation and information technologies have driven the transition to the next generation active power distribution systems. Novel control techniques and management strategies are required to achieve the efficient, economic and reliable grid. The focus of this work is energy management and control of active distribution systems (ADS) with integrated renewable energy sources (RESs) and demand response (DR). Here, ADS mean automated distribution system with remotely operated controllers and distributed energy resources (DERs). DER as active part of the next generation future distribution system includes: distributed generations (DGs), RESs, energy storage system (ESS), plug-in hybrid electric vehicles (PHEV) and DR. Integration of DR and RESs into ADS is critical to realize the vision of sustainability. The objective of this dissertation is the development of management architecture to control and operate ADS in the presence of DR and RES. One of the most challenging issues for operating ADS is the inherent uncertainty of DR and RES as well as conflicting objective of DER and electric utilities. ADS can consist of different layers such as system layer and building layer and coordination between these layers is essential. In order to address these challenges, multi-layer energy management and control architecture is proposed with robust algorithms in this work. First layer of proposed multi-layer architecture have been implemented at the system layer. Developed AC optimal power flow (AC-OPF) generates fair price for all DR and non-DR loads which is used as a control signal for second layer. Second layer controls DR load at buildings using a developed look-ahead robust controller. Load aggregator collects information from all buildings and send aggregated load to the system optimizer. Due to the different time scale at these two management layers, time coordination scheme is developed. Robust and deterministic controllers
Management plan for Facility Effluent Monitoring Plan activities
Energy Technology Data Exchange (ETDEWEB)
Nickels, J.M.; Pratt, D.R.
1991-08-01
The DOE/RL 89-19, United States Department of Energy-Richland Operations Office Environmental Protection Implementation Plan (1989), requires the Hanford Site to prepare an Environmental Monitoring Plan (EMP) by November 9, 1991. The DOE/EH-0173T, Environmental Regulatory Guide for Radiological Effluent Monitoring and Environmental Surveillance (1991), provides additional guidance and requires implementation of the EMP within 36 months of the effective data of the rule. DOE Order 5400.1, General Environmental Protection Program, requires each US Department of Energy (DOE) site, facility, or activity that uses, generates, releases, or manages significant quantities of hazardous materials to prepare an EMP. This EMP is to identify and discuss two major activities: (1) effluent monitoring and (2) environmental surveillance. At the Hanford Site, the site-wide EMP will consist of the following elements: (1) A conceptual plan addressing effluent monitoring and environmental surveillance; (2) Pacific Northwest Laboratory (PNL) site-wide environmental surveillance program; (3) Westinghouse Hanford Company (Westinghouse Hanford) effluent monitoring program consisting of the near-field operations environmental monitoring activities and abstracts of each Facility Effluent Monitoring Plan (FEMP). This management plan addresses the third of these three elements of the EMP, the FEMPs.
MANAGING ENGINEERING ACTIVITIES FOR THE PLATEAU REMEDIATION CONTRACT - HANFORD
Energy Technology Data Exchange (ETDEWEB)
KRONVALL CM
2011-01-14
In 2008, the primary Hanford clean-up contract transitioned to the CH2MHill Plateau Remediation Company (CHPRC). Prior to transition, Engineering resources assigned to remediation/Decontamination and Decommissioning (D&D) activities were a part of a centralized engineering organization and matrixed to the performing projects. Following transition, these resources were reassigned directly to the performing project, with a loose matrix through a smaller Central Engineering (CE) organization. The smaller (10 FTE) central organization has retained responsibility for the overall technical quality of engineering for the CHPRC, but no longer performs staffing and personnel functions. As the organization has matured, there are lessons learned that can be shared with other organizations going through or contemplating performing a similar change. Benefits that have been seen from the CHPRC CE organization structure include the following: (1) Staff are closely aligned with the 'Project/facility' that they are assigned to support; (2) Engineering priorities are managed to be consistent with the 'Project/facility' priorities; (3) Individual Engineering managers are accountable for identifying staffing needs and the filling of staffing positions; (4) Budget priorities are managed within the local organization structure; (5) Rather than being considered a 'functional' organization, engineering is considered a part of a line, direct funded organization; (6) The central engineering organization is able to provide 'overview' activities and maintain independence from the engineering organizations in the field; and (7) The central engineering organization is able to maintain a stable of specialized experts that are able to provide independent reviews of field projects and day-to-day activities.
Impact of Demand Side Management in Active Distribution Networks
DEFF Research Database (Denmark)
Ponnaganti, Pavani; Bak-Jensen, Birgitte; Pillai, Jayakrishnan Radhakrishna
2017-01-01
Demand Side Management (DSM) is an efficient flexible program which helps distribution network operators to meet the future critical peak demand. It is executed in cases of not only technical issues like voltage sag or swell, transformer burdening, cable congestions, but also to increase the degree...... of visibility in the electricity markets. The aim of this paper is to find the optimal flexible demands that can be shifted to another time in order to operate the active distribution system within secure operating limits. A simple mechanism is proposed for finding the flexibility of the loads where electric...
STAFF ACTIVE AND REFLECTIVE LEARNING (ARL TO ENHANCE STUDENT MANAGEMENT
Directory of Open Access Journals (Sweden)
Tay Sing Leong
2010-11-01
Full Text Available The Staff Active Reflective Learning (ARL is a new scheme designed to enhance student management though regular get-togethers of a group of teaching staff. It provides a platform for staff to share issues related to teaching, and seek solutions. This addresses current and future challenges faced in classroom management. The implementation of the Staff ARL is one of the recent initiatives taken under a new approach to shared learning within the School of Electronic and Info-Comm Technology. It provides a platform for mentors to facilitate in developing fellow staff members through the provision of professional support, helping existing staff to learn and grow professionally. Insights into classroom management techniques are provided for new staff to apply while waiting to attend the formal Pedagogic Certification in Technical Education (a compulsory component for all staff. The Staff ARL fosters good working relationships, as staff can ‘chill out’ and be rewarded through the enrichment of knowledge, sharpening of capabilities, building of confidence, and growth of mutual support. The scheme received good feedback as it resulted in the creation of a range of purposeful learning tools and strategies for thedevelopment of problem solving skills, reflective thinking skills and awareness of upto-date classroom situations.
Introduction to Queueing Theory and Stochastic Teletraffic Models
Zukerman, Moshe
2013-01-01
The aim of this textbook is to provide students with basic knowledge of stochastic models that may apply to telecommunications research areas, such as traffic modelling, resource provisioning and traffic management. These study areas are often collectively called teletraffic. This book assumes prior knowledge of a programming language, mathematics, probability and stochastic processes normally taught in an electrical engineering course. For students who have some but not sufficiently strong b...
CHANGE OF CONTRACTOR FOR THE FACILITIES MANAGEMENT ACTIVITIES AT CERN
2003-01-01
The Facilities Management contract at CERN, under the responsibility of ST Division, Group FM, is in charge of the maintenance and minor works on tertiary installations (i.e. all structures and installations that have no direct relation to the running of the accelerators) for the following trades: - Technical: heating, ventilation, air conditioning, plumbing, electricity, civil engineering (painting, roofing, glazing, blinds, fencing, masonry etc.), cleansing, passenger and goods lifts, automatic and powered doors, kitchen equipment, roads, signs, keys and locks, office furniture, - Services: waste collection, security, green areas, cleaning and sanitary supplies, disinfection, rodent control and insect control. Starting from the 1st June the present contractor will stop some activities that will be taken under its responsibility by the new one, INGEST Facility. Others activities will be moved on the 1st July. Minor perturbation in the service might occur. The contact number will not change and will be opera...
CHANGE OF CONTRACTOR FOR THE FACILITIES MANAGEMENT ACTIVITIES AT CERN
2003-01-01
The Facilities Management contract at CERN, under the responsibility of ST Division, Group FM, is in charge of the maintenance and minor works on tertiary installations (i.e. all structures and installations that have no direct relation to the running of the accelerators) for the following trades: - Technical: heating, ventilation, air conditioning, plumbing, electricity, civil engineering (painting, roofing, glazing, blinds, fencing, masonry etc.), cleansing, passenger and goods lifts, automatic and powered doors, kitchen equipment, roads, signs, keys and locks, office furniture, - Services: waste collection, security, green areas, cleaning and sanitary supplies, disinfection, rodent control and insect control. Starting from the 1st June the present contractor will stop some activities that will be taken under its responsibility by the new one, INGEST Facility. The remaining activities (including cleaning) will be moved on the 1st July. Minor perturbation in the service might occur. The contact number will ...
一类N-策略M/G/1排队系统队长分布%The Queue Length Distribution of Queueing System under N-Policy
Institute of Scientific and Technical Information of China (English)
刘晓燕; 孙玺菁; 刘丹
2013-01-01
In this paper, a new method was developedfor calculating the queue length distribution on one M/G/1 queueing system under N-policy with general startup/closedown. Firstly, the stochastic decomposition property was used to derive the p.g.f. of the queue length distribution. By the Leibniz formula of derivation, the addition⁃al queue length distribution was investigated, and then, the expression of queue length distribution was derived. Finally, an example was given for illustrating the application of the expression.% 引入一种新的分析方法，研究了一类具有启动/关闭时间的N-策略的M/G/1排队系统的队长分布。首先，使用随机分解技术导出了系统的队长分布的概率母函数；再根据Leibniz公式结合随机分解结果直接得到附加队长分布，进一步得到该排队系统队长分布的表达式；最后，举例说明队长分布表达式的分析应用。
Research data management and libraries: relationships, activities, drivers and influences.
Pinfield, Stephen; Cox, Andrew M; Smith, Jen
2014-01-01
The management of research data is now a major challenge for research organisations. Vast quantities of born-digital data are being produced in a wide variety of forms at a rapid rate in universities. This paper analyses the contribution of academic libraries to research data management (RDM) in the wider institutional context. In particular it: examines the roles and relationships involved in RDM, identifies the main components of an RDM programme, evaluates the major drivers for RDM activities, and analyses the key factors influencing the shape of RDM developments. The study is written from the perspective of library professionals, analysing data from 26 semi-structured interviews of library staff from different UK institutions. This is an early qualitative contribution to the topic complementing existing quantitative and case study approaches. Results show that although libraries are playing a significant role in RDM, there is uncertainty and variation in the relationship with other stakeholders such as IT services and research support offices. Current emphases in RDM programmes are on developments of policies and guidelines, with some early work on technology infrastructures and support services. Drivers for developments include storage, security, quality, compliance, preservation, and sharing with libraries associated most closely with the last three. The paper also highlights a 'jurisdictional' driver in which libraries are claiming a role in this space. A wide range of factors, including governance, resourcing and skills, are identified as influencing ongoing developments. From the analysis, a model is constructed designed to capture the main aspects of an institutional RDM programme. This model helps to clarify the different issues involved in RDM, identifying layers of activity, multiple stakeholders and drivers, and a large number of factors influencing the implementation of any initiative. Institutions may usefully benchmark their activities against the
Active microbial soil communities in different agricultural managements
Landi, S.; Pastorelli, R.
2009-04-01
We studied the composition of active eubacterial microflora by RNA extraction from soil (bulk and rhizosphere) under different environmental impact managements, in a hilly basin in Gallura (Sardinia). We contrasted grassy vineyard, in which the soil had been in continuous contact with plant roots for a long period of time, with traditional tilled vineyard. Moreover, we examined permanent grassland, in which plants had been present for some years, with temporary grassland, in which varying plants had been present only during the respective growing seasons. Molecular analysis of total population was carried out by electrophoretic separation by Denaturing Gradient Gel Electrophoresis (DGGE) of amplified cDNA fragments obtained from 16S rRNA. In vineyards UPGMA (Unweighted Pair Group Mathematical Average) analysis made up separate clusters depending on soil management. In spring both clusters showed similarity over 70%, while in autumn the similarity increased, 84% and 90% for grassy and conventional tilled vineyard respectively. Permanent and temporary grassland joined in a single cluster in spring, while in autumn a partial separation was evidenced. The grassy vineyard, permanent and temporary grassland showed higher richness and diversity Shannon-Weiner index values than vineyard with conventional tillage although no significant. In conclusion the expected effect of the rhizosphere was visible: the grass cover influenced positively the diversity of active microbial population.