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.
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.
Anakyzing the performance of Active Queue Management Algorithms
Ahammed, G F Ali; 10.5121/ijcnc.2010.2201
2010-01-01
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 paper we analyzed several active queue management algorithms with respect to their abilities of maintaining high resource utilization, identifying and restricting disproportionate bandwidth usage, and their deployment complexity. We compare the performance of FRED, BLUE, SFB, and CHOKe based on simulation results, using RED and Drop Tail as the evaluation baseline. The characteristics of different algorithms are also discussed and compared. Simulation is done by using Network Simulator(NS2) and the graphs are drawn using X- graph.
Analyzing the Performance of Active Queue Management Algorithms
Ahammed, G F Ali; 10.5121/ijcnc.2010.2201
2010-01-01
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 paper we analyzed several active queue management algorithms with respect to their abilities of maintaining high resource utilization, identifying and restricting disproportionate bandwidth usage, and their deployment complexity. We compare the performance of FRED, BLUE, SFB, and CHOKe based on simulation results, using RED and Drop Tail as the evaluation baseline. The characteristics of different algorithms are also discussed and compared. Simulation is done by using Network Simulator(NS2) and the graphs are drawn using X- graph.
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.
Some Improvements on Active Queue Management Mechanism Based on Adaptive Fuzzy Control
Directory of Open Access Journals (Sweden)
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.
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.
Processor Based Active Queue Management for providing QoS in Multimedia Application
Selvam, N Saravana
2010-01-01
The objective of this paper is to implement the Active Network based Active Queue Management Technique for providing Quality of Service (QoS) using Network Processor(NP) based router to enhance multimedia applications. The performance is evaluated using Intel IXP2400 NP Simulator. The results demonstrate that, Active Network based Active Queue Management has better performance than RED algorithm in case of congestion and is well suited to achieve high speed packet classification to support multimedia applications with minimum delay and Queue loss. Using simulation, we show that the proposed system can provide assurance for prioritized flows with improved network utilization where bandwidth is shared among the flows according to the levels of priority. We first analyze the feasibility and optimality of the load distribution schemes and then present separate solutions for non-delay sensitive streams and delay-sensitive streams. Rigorous simulations and experiments have been carried out to evaluate the performan...
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.
International Nuclear Information System (INIS)
On the basis of variable structure control (VSC), an active queue management (AQM) controller is presented for a class of TCP communication networks. In the TCP/IP networks, the packet drop probability is limited between 0 and 1. Therefore, we modeled TCP/AQM as a rate-based non-linear system with a saturated input. The objective of the VSC-based AQM controller is to achieve the desired queue size and to guarantee the asymptotic stability of the closed-loop TCP non-linear system with saturated input. The performance and effectiveness of the proposed control law are then validated for different network scenarios through numerical simulations in both MATLAB and Network Simulator-2 (NS-2). Both sets of simulation results have confirmed that the proposed scheme outperforms other AQM schemes.
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.
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Vitalio Alfonso Reguera
2010-05-01
Full Text Available This paper presents a comprehensive study about the impact of active queue management (AQM on Voice over Internet Protocol (VoIP quality of service. One of the most representative AQM scheme is analyzed through extensive simulation and its effect on the perceived quality of voice calls is evaluated. Different network scenarios, changing network loads and different scheme control parameters areinvestigated. Network impairments are related to user perception by means of well known algorithmic models, expressing user satisfaction in the MOS scale. The main results obtained show that the use of active queue management schemes like adaptive random early detection (ARED significantly improve the perceived quality of voice calls.
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.
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.
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.
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.
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.
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.
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.
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.
基于内模控制的自适应主动队列管理算法%Adaptive active queue management algorithm based on internal model control
Institute of Scientific and Technical Information of China (English)
林开司; 林开武; 张露
2011-01-01
实际网络具有大时滞性和动态特性.针对大时滞特性,根据内模控制( IMC)和改进的TCP/AQM控制理论模型设计了一种适合于大延时网络环境的主动队列管理算法.而对于网络的动态特性,分析了网络参数的变化给算法带来的影响,并以此对算法参数进行在线修正,得到符合大时滞网络的自适应AQM算法.最后通过NS2仿真实验验证了设计的AQM算法的可靠性.%Real networks are of large delay and dynamics. According to the IMC (Internal Model Control) and improved control theory model with TCP/AQM, an active queue management algorithm suitable for the large delay network environment was designed to cope with the large delays. For the dynamics of the networks, the impact that the change of network parameter brings to the algorithm was analyzed to correct the algorithm parameter online. The adaptive active queue management algorithm suitable for the large delay network was acquired. The reliability of the algorithm has been verified by NS2 simulation.
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.
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.
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.
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.
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.
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 .
基于预测控制的时滞网络主动队列管理%Active queue management of delay network based on model predictive control
Institute of Scientific and Technical Information of China (English)
王萍; 陈虹; 卢晓晖
2011-01-01
针对Internet网络这种典型的延迟系统,基于模型预测控制理论,提出了一种新的主动队列管理算法——MPAQM算法.首先考虑时滞系统的因果性定义预测输出,根据预测模型和状态估计器,预测瓶颈链路队列的未来动态特性；然后将拥塞控制的控制要求转化为优化目标函数,求解优化问题得到丢包率.在单瓶颈和多瓶颈网络拓扑中进行仿真验证,结果显示MPAQM算法能快速平稳地收敛于队列长度的期望值,丢包率小且具有较好的稳定性和鲁棒性.%Based on the theory of model predictive control, a novel Active Queue Management (AQM) algorithm is proposed for typical Internet systems with large delay, called MPAQM. First, the predicted output is defined by considering the causality of time-delay system. Then, according to the predictive model and state estimator, the future dynamic queue length in data buffer is predicted. Finally, the control requirement of congestion is converted to optimal control objective function, and drop probability is obtained by solving the optimal problem. The performances of MPAQM are evaluated through a series of simulations in simulator NS2 with single and multiple-bottleneck network topologies. Simulation results show that the proposed MPAQM algorithm outperforms RED and PI algorithms in terms of stability, disturbance rejection and robustness.
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.
Directory of Open Access Journals (Sweden)
V.SAVITHA
2012-08-01
Full Text Available At present there has been a tremendous growth in the computer networks and wireless networks. Due to the enormous growth of voice, audio, video and data applications over the wireless networks, therequirement of congestion control mechanism is also developing along with the development of wireless network applications. The congestion in the network has drastically affected the Quality of Service (QoSrequirements of the applications. Active Queue Management (AQM is the technique of signaling Transmission Control Protocol (TCP sources from middle routers and its major purpose is to lessen the congestion and also satisfy the QoS requirements. In this paper, Modified Robust Queue Management with Feedback Compensation Technique is proposed that helps to reduce the delay and low loss service. The proposed technique is based on feedback compensation technique and the algorithm used in this Modified RQM is called Modified Proportional Integral based series compensation, and Position feedback compensation (Modified PIP. The performance of Modified RQM with Feedback (MFPIP is evaluated against the existing RQM in terms of packet loss, queue size, unloaded buffer size, End-to-End delay, bandwidth utilization and jitter value. It is revealed from theresults that the Modified RQM with Feedback (MFPIP is more effective in handling the congestion control in Wireless Communication Networks.
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.
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
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.
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.
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.
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…
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。
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.
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.
Ganesh, Ayalvadi; Wischik, Damon
2004-01-01
Big Queues aims to give a simple and elegant account of how large deviations theory can be applied to queueing problems. Large deviations theory is a collection of powerful results and general techniques for studying rare events, and has been applied to queueing problems in a variety of ways. The strengths of large deviations theory are these: it is powerful enough that one can answer many questions which are hard to answer otherwise, and it is general enough that one can draw broad conclusions without relying on special case calculations.
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.
International Nuclear Information System (INIS)
Flow time analysis is a powerful concept to analyze the flow time of any arriving customer in any system at any instant. A load management mechanism can be employed very effectively in any queueing system by utilizing a system which provides probability of dual service rate. In this paper, we develop and demonstrate the flow and service processes transition diagram to determine the flow time of a customer in a load management late arrival state dependent finite discrete time queueing system with dual service rate where customers are hypo geometrically distributed. We compute the probability mass function of each starting state and total probability mass function. The obtained analytical results are validated with simulation results for varying values of arrival and service probabilities. (author)
Palvannan, R Kannapiran; Teow, Kiok Liang
2012-04-01
Patient queues are prevalent in healthcare and wait time is one measure of access to care. We illustrate Queueing Theory-an analytical tool that has provided many insights to service providers when designing new service systems and managing existing ones. This established theory helps us to quantify the appropriate service capacity to meet the patient demand, balancing system utilization and the patient's wait time. It considers four key factors that affect the patient's wait time: average patient demand, average service rate and the variation in both. We illustrate four basic insights that will be useful for managers and doctors who manage healthcare delivery systems, at hospital or department level. Two examples from local hospitals are shown where we have used queueing models to estimate the service capacity and analyze the impact of capacity configurations, while considering the inherent variation in healthcare. PMID:20703697
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.
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...
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.
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.
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.
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.
An Optimal Lower Bound for Buffer Management in Multi-Queue Switches
Bienkowski, Marcin
2010-01-01
In the online packet buffering problem (also known as the unweighted FIFO variant of buffer management), we focus on a single network packet switching device with several input ports and one output port. This device forwards unit-size, unit-value packets from input ports to the output port. Buffers attached to input ports may accumulate incoming packets for later transmission; if they cannot accommodate all incoming packets, their excess is lost. A packet buffering algorithm has to choose fro...
Increasing available FIFO space to prevent messaging queue deadlocks in a DMA environment
Energy Technology Data Exchange (ETDEWEB)
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.
Energy Technology Data Exchange (ETDEWEB)
Heidelberger, Philip; Steinmacher-Burow, Burkhard
2015-01-06
According to one embodiment, a method for implementing an array-based queue in memory of a memory system that includes a controller includes configuring, in the memory, metadata of the array-based queue. The configuring comprises defining, in metadata, an array start location in the memory for the array-based queue, defining, in the metadata, an array size for the array-based queue, defining, in the metadata, a queue top for the array-based queue and defining, in the metadata, a queue bottom for the array-based queue. The method also includes the controller serving a request for an operation on the queue, the request providing the location in the memory of the metadata of the queue.
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...... where Meld takes worst case time o(n). To our knowledge this is the first priority queue implementation that supports Meld in worst case constant time and DeleteMin in logarithmic time....
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
The queue-length in GI/G/s queues
Directory of Open Access Journals (Sweden)
Pierre Le Gall
2000-01-01
Full Text Available The distribution of the queue-length in the stationary symmetrical GI/G/s queue is given with an application to the M/G/s queue, particularly in the case of the combination of several packet traffics, with various constant service times, to dimension the buffer capacity.
Single server queueing networks with varying service times and renewal input
Directory of Open Access Journals (Sweden)
Pierre Le Gall
2000-01-01
Full Text Available Using recent results in tandem queues and queueing networks with renewal input, when successive service times of the same customer are varying (and when the busy periods are frequently not broken up in large networks, the local queueing delay of a single server queueing network is evaluated utilizing new concepts of virtual and actual delays (respectively. It appears that because of an important property, due to the underlying tandem queue effect, the usual queueing standards (related to long queues cannot protect against significant overloads in the buffers due to some possible agglutination phenomenon (related to short queues. Usual network management methods and traffic simulation methods should be revised, and should monitor the partial traffic streams loads (and not only the server load.
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.
Analysis of feedback fluid queues
Scheinhardt, Werner R.W.
2001-01-01
We consider the stationary behaviour of a class of feedback fluid queues. A feedback fluid queue is a natural generalisation of the well-known Markov modulated fluid queue. The essential difference is that the current state of the fluid buffer influences the behaviour of the regulating process. Ther
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。
International Nuclear Information System (INIS)
We introduce the prioritising exclusion process, a stochastic scheduling mechanism for a priority queueing system in which high priority customers gain advantage by overtaking low priority customers. The model is analogous to a totally asymmetric exclusion process with a dynamically varying lattice length. We calculate exact local density profiles for an unbounded queue by deriving domain wall dynamics from the microscopic transition rules. The structure of the unbounded queue carries over to bounded queues where, although no longer exact, we find the domain wall theory is in very good agreement with simulation results. Within this approximation we calculate average waiting times for queueing customers. (paper)
Queueing system with passive servers
Directory of Open Access Journals (Sweden)
Alexander N. Dudin
1996-01-01
Full Text Available In this paper the authors introduce systems in which customers are served by one active server and a group of passive servers. The calculation of response time for such systems is rendered by analyzing a special kind of queueing system in a synchronized random environment. For an embedded Markov chain, sufficient conditions for the existence of a stationary distribution are proved. A formula for the corresponding vector generating function is obtained. It is a matrix analog of the Pollaczek-Khinchin formula and is simultaneously a matrix functional equation. A method for solving this equation is proposed.
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.
Updatable Queue Protocol Based On TCP For Virtual Reality Environment
Al-Howaide, Ala'a Z; Salhieh, Ayad M
2011-01-01
The variance in number and types of tasks required to be implemented within Distributed Virtual Environments (DVE) highlights the needs for communication protocols can achieve consistency. In addition, these applications have to handle an increasing number of participants and deal with the difficult problem of scalability. Moreover, the real-time requirements of these applications make the scalability problem more difficult to solve. In this paper, we have implemented Updatable Queue Abstraction protocol (UQA) on TCP (TCP-UQA) and compared it with original TCP, UDP, and Updatable Queue Abstraction based on UDP (UDP-UQA) protocols. Results showed that TCP-UQA was the best in queue management.
Multiserver queueing networks and the tandem queue model
Directory of Open Access Journals (Sweden)
Pierre Le Gall
1998-01-01
Full Text Available Using a tandem queue model we evaluate the local endogenous (= internal queueing delay in single server and multiserver queueing networks. The new concept of the apparent overall upstream queueing delay(as perceived by the downstream network allows us to analyze the distribution of this local queue by interpolating between the distributions of the tandem queue (generated by a concentration tree and the isolated G/G/squeue. The interpolation coefficients depend on the proportion of premature departures, typically interfering in the upstream stage and leaving the considered path without being offered to the considered local queue. On the other hand, local exogenous arrivals (from outside the network require the introduction of the interference delay concept. Finally, in the case of single server queueing networks, we stress the need to extend the capacities of the buffers, by considering the worst case scenario and by using an equivalent tandem queue model.
Analysis and Optimization of a Multistage Inventory-Queue System
Liming Liu; Xiaoming Liu; David D. Yao
2004-01-01
An important issue in the management of supply chains and manufacturing systems is to control inventory costs at different locations throughout the system while satisfying an end-customer service-level requirement. The challenge involved is to solve a nonlinear constrained optimization problem that captures the key dynamics of a complex production-inventory system. In this paper, we first develop a multistage inventory-queue model and a job-queue decomposition approach that evaluates the perf...
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.
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
Optimal purely functional priority queues
DEFF Research Database (Denmark)
Brodal, Gerth Stølting; Okasaki, Chris
1996-01-01
Brodal's data structure to a purely functional setting. In doing so, we both simplify the data structure and clarify its relationship to the binomial queues of Vuillemin, which support all four operations in O(log n) time. Specifically, we derive our implementation from binomial queues in three steps...
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.
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...
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.
Amita CHOUDHARY; Jain, Anjali; Shukla, Diwakar
2011-01-01
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 applicatio...
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.
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.
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...
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/.
Optimal control of two queues in series
International Nuclear Information System (INIS)
In this paper we give a fairly complete survey of the available results on the control of arrival and service rates for both single queue and networks of queues. We also study two M/M/1 queues in series. At the first queue, the arrival and the service rates are chosen in pair from a finite set whenever the queue lengths at both queues change. Each choice has a switching cost depending on the chosen rates and the queue lengths. At the second queue, the arrival and the service rates are fixed. Our objective is to find a policy for dynamically choosing rates, based on the current rates and queues lengths that minimizes the expected total discounted cost over a finite horizon, numerical results are given. (author). 8 refs, 1 fig
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.
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...
Delay in a tandem queueing model with mobile queues : an analytical approximation
Al Hanbali, A Ahmad; Haan; Boucherie, RJ Richard; Ommeren, van, J.C.
2009-01-01
In this paper, we analyze the end-to-end delay performance of a tandem queueing system with mobile queues. Due to state-space explosion there is no hope for a numerical exact analysis for the joint-queue length distribution. For this reason, we present an analytical approximation that is based on queue length analysis. Through extensive numerical validation, we nd that the queue length approximation exhibits excellent performance for light tra c load.
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.
Anjali Jain; Diwakar Shukla
2013-01-01
The ready queue processing estimation problem appears when many processes remain in the ready queue after the sudden failure. The system manager has to decide immediately how much further time is required to process all the remaining jobs in the ready queue. In lottery scheduling, this prediction is possible with the help of sampling techniques. Ratio method, existing in sampling literature, was previously used by authors to predict the time required for remaining jobs to finish a...
Institute of Scientific and Technical Information of China (English)
王霞; 姜宏岸
2014-01-01
为了解决由于网络环境中多媒体业务需求的快速增加，导致应用对延迟和拥塞概率等性能指标的要求逐渐提高的问题，提出了一种改进的优先级队列的缓存管理机制。详细研究了该机制的实现原理和方法，并使用Petri工具及排队理论对改进的优先级队列进行了建模。通过仿真实验分析了该缓存管理机制在缓存管理过程中的性能指标，证明了该缓存管理机制能有效地提高多媒体通信的性能，满足多媒体通信的服务质量要求。%The rapid increase of multimedia services in the network environment has led to higher requirements for the handling of network latency and high-rate packet loss.We proposed an im-proved priority queue based buffer management mechanism in this paper to cope with this prob-lem.We probed in detail into the principle and implementation method of the mechanism,and es-tablished a model on the improved priority queue by using the Petri net tools and queuing theory. Through simulation analysis,we analyzed the buffer management mechanism performance index in the process of buffer management,proving that the mechanism can effectively improve the per-formance of communication,and meet the requirements of multimedia communication service.
Asymptotic inference for waiting times and patiences in queues with abandonment
DEFF Research Database (Denmark)
Gorst-Rasmussen, Anders; Hansen, Martin Bøgsted
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...
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...
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
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.
DEFF Research Database (Denmark)
Chen, Gang; Govindan, Kannan; Yang, Zhong-Zhen;
2013-01-01
Long truck queue is a common problem at big marine container terminals, where the resources and equipment are usually scheduled to serve ships prior to trucks. To reduce truck queues, some container terminals adopt terminal appointment system (TAS) to manage truck arrivals. This paper addresses t...
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
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
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。
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
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.
MultiQueues: Simpler, Faster, and Better Relaxed Concurrent Priority Queues
Rihani, Hamza; Sanders, Peter; Dementiev, Roman
2014-01-01
Priority queues with parallel access are an attractive data structure for applications like prioritized online scheduling, discrete event simulation, or branch-and-bound. However, a classical priority queue constitutes a severe bottleneck in this context, leading to very small throughput. Hence, there has been significant interest in concurrent priority queues with a somewhat relaxed semantics where deleted elements only need to be close to the minimum. In this paper we present a very simple ...
The theory of networks of single server queues and the tandem queue model
Directory of Open Access Journals (Sweden)
Pierre Le Gall
1997-01-01
Full Text Available We consider the stochastic behavior of networks of single server queues when successive service times of a given customer are highly correlated. The study is conducted in two particular cases: 1 networks in heavy traffic, and 2 networks in which all successive service times have the same value (for a given customer, in order to avoid the possibility of breaking up the busy periods. We then show how the local queueing delay (for an arbitrary customer can be derived through an equivalent tandem queue on the condition that one other local queueing delay is added: the jitter delay due to the independence of partial traffic streams.
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.
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...... an alternative optimal cache oblivious priority queue based only on binary merging. We also show that our structure can be made adaptive to different usage profiles....
International Nuclear Information System (INIS)
One of the missions of the Department of Energy's (DOE) Oak Ridge Office (ORO) has been the management of the Department's uranium materials. This mission has been accomplished through successful integration of ORO's uranium activities with the rest of the DOE complex. Beginning in the 1980's, several of the facilities in that complex have been shut down and are in the decommissioning process. With the end of the Cold War, the shutdown of many other facilities is planned. As a result, inventories of uranium need to be removed from the Department facilities. These inventories include highly enriched uranium (HEU), low enriched uranium (LEU), normal uranium (NU), and depleted uranium (DU). The uranium materials exist in different chemical forms, including metals, oxides, solutions, and gases. Much of the uranium in these inventories is not needed to support national priorities and programs. (author)
Fixed points for multi-class queues
Martin, James B
2010-01-01
Burke's theorem can be seen as a fixed-point result for an exponential single-server queue; when the arrival process is Poisson, the departure process has the same distribution as the arrival process. We consider extensions of this result to multi-type queues, in which different types of customer have different levels of priority. We work with a model of a queueing server which includes discrete-time and continuous-time M/M/1 queues as well as queues with exponential or geometric service batches occurring in discrete time or at points of a Poisson process. The fixed-point results are proved using interchangeability properties for queues in tandem, which have previously been established for one-type M/M/1 systems. Some of the fixed-point results have previously been derived as a consequence of the construction of stationary distributions for multi-type interacting particle systems, and we explain the links between the two frameworks. The fixed points have interesting "clustering" properties for lower-priority ...
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.
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.
A Queue Simulation Tool for a High Performance Scientific Computing Center
Spear, Carrie; McGalliard, James
2007-01-01
The NASA Center for Computational Sciences (NCCS) at the Goddard Space Flight Center provides high performance highly parallel processors, mass storage, and supporting infrastructure to a community of computational Earth and space scientists. Long running (days) and highly parallel (hundreds of CPUs) jobs are common in the workload. NCCS management structures batch queues and allocates resources to optimize system use and prioritize workloads. NCCS technical staff use a locally developed discrete event simulation tool to model the impacts of evolving workloads, potential system upgrades, alternative queue structures and resource allocation policies.
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.
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.
Algorithms for Scheduling Weighted Packets with Deadlines in a Bounded Queue
LI Fei
2008-01-01
Motivated by the Quality-of-Service (QoS) buffer management problem, we consider online scheduling of packets with hard deadlines in a finite capacity queue. At any time, a queue can store at most $b \\in \\mathbb Z^+$ packets. Packets arrive over time. Each packet is associated with a non-negative value and an integer deadline. In each time step, only one packet is allowed to be sent. Our objective is to maximize the total value gained by the packets sent by their deadlines in an online manner...
Directory of Open Access Journals (Sweden)
Peter Wanke
2011-04-01
Full Text Available The ship-berth link is one of the most critical aspects to be managed at port operations. Until now, simulation models have considered the impact of queue priorities, such as size and type of ships, on waiting times. This research differentiates from previous studies not only by considering another variable - the demurrage cost for each type of ship -, but also by considering the possibility of different berth allocation policies. It reports on a simulation study on small Brazilian private container terminal, where different berth allocation policies and queue priorities have been tested. Results and further analyses conducted via MANOVA indicate that the demurrage cost ratio between large and small ships and the critical waiting time in queue, after which demurrage costs are charged, impact on the choice of most adequate combination of policies and priorities. The analysis presented in this paper may help port authorities in determining a more precise figure for total demurrage costs
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
Task Release Control for Decision Making Queues
Srivastava, Vaibhav; Bullo, Francesco; Langbort, Cédric
2010-01-01
We consider the optimal duration allocation in a decision making queue. Decision making tasks arrive at a given rate to a human operator. The correctness of the decision made by human evolves as a sigmoidal function of the duration allocated to the task. Each task in the queue loses its value continuously. We elucidate on this trade-off and determine optimal policies for the human operator. We show the optimal policy requires the human to drop some tasks. We present a receding horizon optimization strategy, and compare it with the greedy policy.
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.
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.
International Nuclear Information System (INIS)
''Management of customized SAT implementation'' was presented and entailed the following topics: NPP training policy; management aspects for the SAT project; project infrastructure; SAT project implementation in the context of QAP/QCP; the assembly and training of the SAT Project Team; communication and translation obstacles; project implementation strategy; initial SAT implementation for selected job positions; key considerations for the SAT project. This presentation was bases on lessons-learned from hands-on practices of SAT projects (with an involvement of international experts), publications on this topic, and recent personal experience of the instructor in this field [a very similar project has been undertaken in Russia with the joint venture of EXITECH International Training Corporation (USA) and Joint-Stock Company, ENIKO MIFI (Russia)
Environmental management activities
International Nuclear Information System (INIS)
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
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.
Emphasis: an active management model
International Nuclear Information System (INIS)
The Institute of Nuclear Materials Management was founded and has grown on the basis of promoting professionalism in the nuclear industry. This paper is concerned with professional management of nuclear material. The paper introduces the reader to Emphasis, an active management model. The management model provides the framework to assist a manager in directing his available resources. Emphasis provides for establishing goals, identifying and selecting objectives, matching objectives to specific personnel, preparing and monitoring action plans, and evaluating results. The model stresses crisis prevention by systematically administering and controlling resources. A critical requirement for implementation of the model is the desire to manage, to be in charge of the situation. The nuclear industry does need managers - people who realize the sensitive nature of the industry, professionals who insist on improved performance
Call packing bounds for overflow queues
N.M. van Dijk; E. van der Sluis
2004-01-01
Finite queueing loss systems are studied with overflow. For these systems there is no simple analytic expression for the loss probability or throughput. This paper aims to prove and promote easily computable bounds as based upon the so-called call packing principle. Under call packing a standard pro
Synchronized reneging in queueing systems with vacations
I. Adan; A. Economou; S. Kapodistria
2008-01-01
In this paper we present a detailed analysis of queueing models with vacations and impatient customers, where the source of impatience is the absence of the server. Instead of the standard assumption that customers perform independent abandonments, we consider situations where customers abandon the
Synchronized reneging in queueing systems with vacations
I. Adan; A. Economou; S. Kapodistria
2009-01-01
In this paper we present a detailed analysis of queueing models with vacations and impatient customers, where the source of impatience is the absence of the server. Instead of the standard assumption that customers perform independent abandonments, we consider situations where customers abandon the
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.
Managing hazardous activities and substances
International Nuclear Information System (INIS)
The primary purpose of this paper is to provide background information on the process, principles and policies being employed in OECD Member Countries for managing hazardous activities (non-nuclear) and products involving chemicals (non-radioactive). In addition, the author highlights certain areas in the risk management process where certain assumptions and conclusions may be of particular relevance to the goal of a review, reconsideration and restatement of the strategy of geological disposal of radioactive wastes. (O.L.)
Career management: an active process.
Mackowiak, J; Eckel, F M
1985-03-01
The self-assessment, goal-setting, and career-planning techniques of career management are discussed, and the organization's role in career management is discussed. Career management is a planned process, initiated and carried out by an individual with the assistance of others. Because work and nonwork activities are so interrelated, career and life management planning can maximize a pharmacist's personal success. The career- and life-management process begins with the development of a personal definition of success. A self-assessment must be made of one's values, needs, interests, and activities. The next step of the process involves setting goals and establishing a plan or strategy to achieve them. Establishing a career path requires researching alternate career goals. Career competencies are identified that can increase an employee's chances of success. The employer shares the responsibility for career development through coaching, job structuring, and keeping the employee aware of constraints. Through the integration of the roles of the individual and the organization in the career-management process, employees can optimize their contribution to an organization. Pharmacists can successfully manage their careers by applying the techniques of self-assessment, goal setting, and career planning. PMID:3985018
MIMO Wireless Communications under Statistical Queueing Constraints
Gursoy, Mustafa Cenk
2009-01-01
The performance of multiple-input multiple-output wireless systems is investigated in the presence of statistical queueing constraints. Queuing constraints are imposed as limitations on buffer violation probabilities. The performance under such constraints is captured through the effective capacity formulation. A detailed analysis of the effective capacity is carried out in the low-power, wideband, and high--signal-to-noise ratio (SNR) regimes. In the low-power analysis, expressions for the first and second derivatives of the effective capacity with respect to SNR at SNR= 0 are obtained under various assumptions on the degree of channel state information at the transmitter. Transmission strategies that are optimal in the sense of achieving the first and second derivatives are identified. It is shown that while the first derivative does not get affected by the presence of queueing constraints, the second derivative gets smaller as the constraints become more stringent. Through the energy efficiency analysis, t...
Cost performance satellite design using queueing theory
Hein, G. F.
1975-01-01
The Poisson arrival model was used to determine the effects of limiting the number of channels for a disaster warning satellite. State probabilities and delay probabilities were estimated for several values of the number of channels (C) for arrival and service rates obtained from disaster warnings issued by the National Weather Service. The results predicted by the queueing model were compared with the results of a digital computer simulation.
Scaling of avalanche queues in directed dissipative sandpiles
Tadic; Priezzhev
2000-09-01
Using numerical simulations and analytical methods we study a two-dimensional directed sandpile automaton with nonconservative random defects (concentration c) and varying driving rate r. The automaton is driven only at the top row and driving rate is measured by the number of added particles per time step of avalanche evolution. The probability distribution of duration of elementary avalanches at zero driving rate is exactly given by P1(t,c)=t(-3/2) exp[t ln(1-c)]. For driving rates in the interval 0 server queue in the queue theory. We study scaling properties of the busy period and dissipated energy of sequences of noninterrupted activity. In the limit c-->0 and varying linear system size Lqueues are characterized by a multifractal scaling and we determine the corresponding spectral functions. For L>1/c increasing the driving rate somewhat compensates for the energy losses at defects above the line r approximately sqrt[c]. The scaling exponents of the distributions in this region of phase diagram vary approximately linearly with the driving rate. Using properties of recurrent states and the probability theory we determine analytically the exact upper bound of the probability distribution of busy periods. In the case of conservative dynamics c=0 the probability of a continuous flow increases as F(infinity) approximately r(2) for small driving rates. PMID:11088824
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.
Staging queues in material handling and transportation systems
Gue, Kevin R.; Kang, Keebom
2001-01-01
Proceedings of the 2001 Winter Simulation Conference B. A. Peters, J. S. Smith, D. J. Medeiros, and M. W. Rohrer, eds. In most physical queueing applications, customers join a queue andmove forward after each service, leaving room for others to join behind them. Some queues found in material handling and transportation systems do not operate like this because the queued entities (pallets or unoccupied cars, for example) are incapable of moving forward autonomously. We ...
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.
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.
Influence of queue propagation and dissipation on route travel times
DEFF Research Database (Denmark)
Raovic, Nevena
into account (Bliemer, 2008). Yperman (2007) indicates that there is a significant difference in queue-propagation and queue-dissipation between the LTM and DQM. This results in different route travel times, and can further affect route choice. In this paper, different approaches to represent queue propagation...... and dissipation through the CTM, LTM and DQM are studied. A simple network allows to show how these approaches influence route travel time. Furthermore, the possibility of changing the existing DQM is considered in order to more realistically represent queue propagation and dissipation, which would lead to more...... accurate route travel times....
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.
Single server queueing networks with varying service times and renewal input
Pierre Le Gall
2000-01-01
Using recent results in tandem queues and queueing networks with renewal input, when successive service times of the same customer are varying (and when the busy periods are frequently not broken up in large networks), the local queueing delay of a single server queueing network is evaluated utilizing new concepts of virtual and actual delays (respectively). It appears that because of an important property, due to the underlying tandem queue effect, the usual queueing stan...
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.
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.
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
A feedback fluid queue with two congestion control thresholds
Malhotra, R.; Mandjes, M.R.H.; Scheinhardt, W.R.W.; Berg, J.L. van den
2009-01-01
Feedback fluid queues play an important role in modeling congestion control mechanisms for packet networks. In this paper we present and analyze a fluid queue with a feedback-based traffic rate adaptation scheme which uses two thresholds. The higher threshold B 1 is used to signal the beginning of c
2-Layered Architecture of Vague Logic Based Multilevel Queue Scheduler
Directory of Open Access Journals (Sweden)
Supriya Raheja
2014-01-01
Full Text Available In operating system the decisions which CPU scheduler makes regarding the sequence and length of time the task may run are not easy ones, as the scheduler has only a limited amount of information about the tasks. A good scheduler should be fair, maximizes throughput, and minimizes response time of system. A scheduler with multilevel queue scheduling partitions the ready queue into multiple queues. While assigning priorities, higher level queues always get more priorities over lower level queues. Unfortunately, sometimes lower priority tasks get starved, as the scheduler assures that the lower priority tasks may be scheduled only after the higher priority tasks. While making decisions scheduler is concerned only with one factor, that is, priority, but ignores other factors which may affect the performance of the system. With this concern, we propose a 2-layered architecture of multilevel queue scheduler based on vague set theory (VMLQ. The VMLQ scheduler handles the impreciseness of data as well as improving the starvation problem of lower priority tasks. This work also optimizes the performance metrics and improves the response time of system. The performance is evaluated through simulation using MatLab. Simulation results prove that the VMLQ scheduler performs better than the classical multilevel queue scheduler and fuzzy based multilevel queue scheduler.
Queueing phase transition: theory of translation
Romano, M. Carmen; Thiel, Marco; Stansfield, Ian; Grebogi, Celso
2009-01-01
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 thi...
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
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...
Asymptotic inference for waiting times and patiences in queues with abandonment
Gorst-Rasmussen, Anders; Hansen, Martin Bøgsted
2008-01-01
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 and identically distributed observations by allowing correlated successive waiting times. Assuming a regenerative structure of the sequence of offered waiting times, we establish asymptotic properties of...
Peter Wanke
2011-01-01
The ship-berth link is one of the most critical aspects to be managed at port operations. Until now, simulation models have considered the impact of queue priorities, such as size and type of ships, on waiting times. This research differentiates from previous studies not only by considering another variable - the demurrage cost for each type of ship -, but also by considering the possibility of different berth allocation policies. It reports on a simulation study on small Brazilian private co...
Directory of Open Access Journals (Sweden)
Anjali Jain
2013-08-01
Full Text Available The ready queue processing estimation problem appears when many processes remain in the ready queue after the sudden failure. The system manager has to decide immediately how much further time is required to process all the remaining jobs in the ready queue. In lottery scheduling, this prediction is possible with the help of sampling techniques. Ratio method, existing in sampling literature, was previously used by authors to predict the time required for remaining jobs to finish after failure, provided that highly correlated source of auxiliary information provides better processing time prediction. This paper proposes two new estimators TA and TB which are compared with previously defined ratio estimator in terms of total processing time. Under large sample approximation the bias and m.s.e of proposed estimators have been obtained in the set up of lottery scheduling. The confidence intervals are calculated for the numerical support to the theoretical findings.
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. PMID:26943171
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.
Transient Solution of the M/M/C1 Queue with Additional C2 Servers for Longer Queues and Balking
Directory of Open Access Journals (Sweden)
R. O. Al-Seedy
2008-01-01
Full Text Available The goal of this research is to discuss the M/M/C1 queue with additional C2 servers for longer queues and balking. By using generating function technique the transient probabilities are derived in terms of the modified Bessel function.
Optimal Stopping of Active Portfolio Management
Kyoung Jin Choi; Hyeng Keun Koo; Do Young Kwak
2004-01-01
We study an investor¡¯s decision to switch from active portfolio management to passive management. This problem is mathematically modelled by a mixture of a consumption-portfolio selection problem and an optimal stopping problem. We assume that the investor has stochastic differential utility with ambiguity aversion and incurs utility loss from active portfolio management that can be avoided by switching to passive management, and show that she manages actively as long as her level of wealth ...
Randomized Scheduling Algorithm for Queueing Networks
Shah, Devavrat
2009-01-01
There has recently been considerable interest in design of low-complexity, myopic, distributed and stable scheduling policies for constrained queueing network models that arise in the context of emerging communication networks. Here, we consider two representative models. One, a model for the collection of wireless nodes communicating through a shared medium, that represents randomly varying number of packets in the queues at the nodes of networks. Two, a buffered circuit switched network model for an optical core of future Internet, to capture the randomness in calls or flows present in the network. The maximum weight scheduling policy proposed by Tassiulas and Ephremide in 1992 leads to a myopic and stable policy for the packet-level wireless network model. But computationally it is very expensive (NP-hard) and centralized. It is not applicable to the buffered circuit switched network due to the requirement of non-premption of the calls in the service. As the main contribution of this paper, we present a st...
Data Model Approach And Markov Chain Based Analysis Of Multi-Level Queue Scheduling
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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.
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.
一种基于排队论的主动队列拥塞控制算法%A New Congestion Control Algorithm for Active Queue Based on Queuing Theory
Institute of Scientific and Technical Information of China (English)
闫英战; 田立伟
2012-01-01
AQM algorithm has many deficiencies, such as a large queuing delay, strong delay jitter, the rate of the data into and out the team not matched, and thus it always leads to data retention, loss and oscillation. Based on this, the M/M/m (n) queuing system thought based on the BLUE algorithm is introduced which is called PBLUE. The algorithm ensures the stability of the queue length according to equilibrium equation under stable state. Meanwhile , it increases the expansion factor and adjusts the router's cache for quickly recovering of the lost data. In the simulation, the improved algorithm reduced the packet loss rate and increased the bandwidth utilization and stabled the queue length.%主动队列(AQM)算法存在诸多的不足,如排队延时大、时延抖动性强、数据进队与出队速率不匹配等,从而导致数据的滞留、丢失和振荡.基于此,在BLUE算法的基础上,引入M/M/m (n)排队系统的思想,提出一种新的算法——PBLUE.该算法根据稳定状态下的平衡方程来保证队列长度的稳定性,增加扩充因子调节路由器的缓存来快速恢复丢失的数据.通过仿真实验,改进的算法降低了丢包率,提高了带宽利用率,并稳定了队列长度.
Optimal Control of a Queue With High-Low Delay Announcements: The Significance of the Queue
Directory of Open Access Journals (Sweden)
Alexandra Koshman-Kaz
2015-02-01
Full Text Available This article deals with strategic control of information in a single-server model. It considers an M/M/1 system with identical customers. There is a single cut-off number, and the level of congestion is said to be low (high if the queue length is less than (at least this value. The firm can dynamically change the admission fee according to the level of congestion. Arriving customers cannot observe the queue length, but they are informed about the current level of congestion and the admission fee. The article deals with finding the profit maximizing admission fee, using analytical and numerical methods. We observe that such a pricing regime can be used to increase the profit and the proportion of the increase relative to the single price unobservable queue is unbounded. We observe that the profit maximizing threshold is usually quite small and therefore raise a question whether there is a significant difference in profit when rather than being informed about the congestion level, customers only join the system when the server is idle. We also investigate this question considering the classical observable model.
Practical memory checkers for stacks, queues and deques
Fischlin, Marc
2005-01-01
A memory checker for a data structure provides a method to check that the output of the data structure operations is consistent with the input even if the data is stored on some insecure medium. In [8] we present a general solution for all data structures that are based on insert(i,v) and delete(j) commands. In particular this includes stacks, queues, deques (double-ended queues) and lists. Here, we describe more time and space efficient solutions for stacks, queues and deques. Each algorithm...
A large deviation principle for join the shortest queue
Puhalskii, Anatolii A.; Vladimirov, Alexander A.
2005-01-01
We consider a join-the-shortest-queue model which is as follows. There are $K$ single FIFO servers and $M$ arrival processes. The customers from a given arrival process can be served only by servers from a certain subset of all servers. The actual destination is the server with the smallest weighted queue length. The arrival processes are assumed to obey a large deviation principle while the service is exponential. A large deviation principle is established for the queue-length process. The a...
Transient analysis of a queue with queue-length dependent MAP and its application to SS7 network
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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.
Simple queueing approach to segregation dynamics in Schelling model
Sobkowicz, Pawel
2007-01-01
A simple queueing approach for segregation of agents in modified one dimensional Schelling segregation model is presented. The goal is to arrive at simple formula for the number of unhappy agents remaining after the segregation.
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.
Opportunistic Channel Scheduling for Ad Hoc Networks with Queue Stability
Dong, Lei; Wang, Yongchao
2015-03-01
In this paper, a distributed opportunistic channel access strategy in ad hoc network is proposed. We consider the multiple sources contend for the transmission opportunity, the winner source decides to transmit or restart contention based on the current channel condition. Owing to real data assumption at all links, the decision still needs to consider the stability of the queues. We formulate the channel opportunistic scheduling as a constrained optimization problem which maximizes the system average throughput with the constraints that the queues of all links are stable. The proposed optimization model is solved by Lyapunov stability in queueing theory. The successive channel access problem is decoupled into single optimal stopping problem at every frame and solved with Lyapunov algorithm. The threshold for every frame is different, and it is derived based on the instantaneous queue information. Finally, computer simulations are conducted to demonstrate the validity of the proposed strategy.
Networks of multi-server queues with parallel processing
Bonald, Thomas; Comte, Céline
2016-01-01
We consider a network of multi-server queues wherein each job can be processed in parallel by any subset of servers within a pre-defined set that depends on its class. Each server is allocated in FCFS order at each queue. Jobs arrive according to Poisson processes, have independent exponential service requirements and are routed independently at random. We prove that, when stable, the network has a product-form stationary distribution. From a practical perspective, we propose an algorithm on ...
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.
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....... The principles are also applicable for other queueing systems...
A message queue based event notification system : football lottery system
Xu, Yunpeng
2010-01-01
The event notification service enables user of getting informed about the occurrence of their events of interest. Message queue technology provides asynchronous message exchange functions between computer processes. This thesis presents a solution of building event notification system using the message queue approach. The events in the experiment are generated during the football match and used for both stateless and stateful processing. The system includes three main applic...
Queue-based random-access algorithms: Fluid limits and stability issues
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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.
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.
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
ACTIVITY BASED COSTING FOR BETTER COST MANAGEMENT
Mohan, K.(Centre for High Energy Physics, Indian Institute of Science, Sir C.V. Raman Road, Bangalore, 560012, India); Babu, George P.
2006-01-01
Implementing change in management, successfully and profitably, is the greatest challenge for modern enterprises. Innovation in strategies, marketing performance, role of competition, change in technology, change in customer needs, management initiatives are all facts of life in the global environment today. Cost management works with its customer to manage change more profitably. Activity-Based Costing (ABC) is a new methodology of product costing which measures the cost of products more acc...
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.
Upper Bounds on Performance Measures of Heterogeneous // Queues
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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.
The Diseconomies of Queue Pooling: An Empirical Investigation of Emergency Department Length of Stay
Song, Hummy; Tucker, Anita Lynn; Murrell, Karen L
2014-01-01
We conduct an empirical investigation of the impact of two different queue management systems on throughput times. Using an Emergency Department’s (ED) patient-level data (N = 231,081) from 2007 to 2010, we find that patients’ lengths of stay (LOS) were longer when physicians were assigned patients under a pooled queuing system, compared to when each physician operated under a dedicated queuing system. The dedicated queuing system resulted in a 10 percent decrease in LOS—a 32-minute reduction...
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.
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.
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 ...
Queue Stability and Probability 1 Convergence via Lyapunov Optimization
Neely, Michael J
2010-01-01
Lyapunov drift and Lyapunov optimization are powerful techniques for optimizing time averages in stochastic queueing networks subject to stability. However, there are various definitions of queue stability in the literature, and the most convenient Lyapunov drift conditions often provide stability and performance bounds only in terms of a time average expectation, rather than a pure time average. We extend the theory to show that for quadratic Lyapunov functions, the basic drift condition implies all major forms of stability. Further, we show that the basic drift-plus-penalty condition implies that the same bounds for queue backlog and penalty expenditure that are known to hold for time average expectations also hold for pure time averages with probability 1. Our analysis combines Lyapunov drift theory with the Kolmogorov law of large numbers for martingale differences with finite variance.
Bulk input queues with quorum and multiple vacations
Directory of Open Access Journals (Sweden)
Dshalalow Jewgeni H.
1996-01-01
Full Text Available The authors study a single-server queueing system with bulk arrivals and batch service in accordance to the general quorum discipline: a batch taken for service is not less than r and not greater than R ( ≥ r . The server takes vacations each time the queue level falls below r ( ≥ 1 in accordance with the multiple vacation discipline. The input to the system is assumed to be a compound Poisson process. The analysis of the system is based on the theory of first excess processes developed by the first author. A preliminary analysis of such processes enabled the authors to obtain all major characteristics for the queueing process in an analytically tractable form. Some examples and applications are given.
Bulk input queues with quorum and multiple vacations
Directory of Open Access Journals (Sweden)
Jewgeni H. Dshalalow
1996-01-01
Full Text Available The authors study a single-server queueing system with bulk arrivals and batch service in accordance to the general quorum discipline: a batch taken for service is not less than r and not greater than R(≥r. The server takes vacations each time the queue level falls below r(≥1 in accordance with the multiple vacation discipline. The input to the system is assumed to be a compound Poisson process. The analysis of the system is based on the theory of first excess processes developed by the first author. A preliminary analysis of such processes enabled the authors to obtain all major characteristics for the queueing process in an analytically tractable form. Some examples and applications are given.
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.
Service Differentiation in Cognitive Radio Networks: A Priority Queueing Model
Azarfar, Arash; Sansò, Brunilde
2012-01-01
The popularity of opportunistic spectrum access (OSA), implemented by cognitive radios (CRs), necessitates that these networks should be able to provide service differentiation for different classes of traffic. One of the classic schemes for such a goal is through priority queueing. As link interruptions in OSA networks are frequent, we discuss in this paper four priority queueing disciplines in the presence of interruptions: preemptive-resume, non-preemptive, exceptional non-preemptive and preemptive in case of occurrence of an interruption. Analytical results, in addition to simulation results to validate their accuracy, are provided.
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.
Improvement of active queue management for VOIP QoS%队列管理算法对VOIP QoS的提高
Institute of Scientific and Technical Information of China (English)
王笑妍
2013-01-01
Voice over IP (VoIP) has become increasingly popular over the IP network, Nevertheless, these real-time traffic may experience less than desirable quality, and the performance is unsatisfactory particularly when the link is congested. This paper presents a method of improving the QoS of real-time audio over IP network infrastructure at low service cost and with no changes to the existing network. A thorough study of RED' s effects on voice over IP is given, concluding that RED is able to control the delay distribution, jitter and effective loss of VoIP.%VoIP日益成为受用户欢迎的IP网络服务,然而,这些IP网络上的VOIP通话质量却并不能得到令人满意的保证,尤其是当网络拥塞的时候.文中提出了一种不涉及改造网络结构,低成本地提高VOIP的通话质量的方法.通过随机早期检测算法的应用,可以有效地降低VOIP通话的延迟、抖动和有效丢包率,从而提高VOIP的通话质量.
Efficient Simulation of Population Overflow in Parallel Queues
Nicola, Victor F.; Zaburnenko, Tatiana S.
2006-01-01
In this paper we propose a state-dependent importance sampling heuristic to estimate the probability of population overﬂow in networks of parallel queues. This heuristic approximates the “optimal” state-dependent change of measure without the need for difﬁcult mathematical analysis or costly optimiz
A Parallel Priority Queue with Constant Time Operations
DEFF Research Database (Denmark)
Brodal, Gerth Stølting; Träff, Jesper Larsson; Zaroliagis, Christos D.
1998-01-01
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...
A note on queues with $M/G/\\infty$ input
Mandjes, Michel
2001-01-01
We consider a fluid queue fed by sessions, arriving according to a Poisson process; a session has a heavy-tailed duration, during which traffic is sent at a constant rate. We scale Poisson input rate $\\Lambda$, buffer space $B$, and link rate $C$ by $n$, such that we get $n\\lambda$, $nb$, and $nc$,
A Cooperative Approach to Queue Allocation of Indivisible Objects
Hamers, H.J.M.; Klijn, F.; Slikker, M.; van Velzen, S.
2004-01-01
We consider the allocation of a finite number of indivisible objects to the same number of agents according to an exogenously given queue.We assume that the agents collaborate in order to achieve an efficient outcome for society.We allow for side-payments and provide a method for obtaining stable ou
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
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,
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.
Python for Scientific Computing Education: Modeling of Queueing Systems
Vladimiras Dolgopolovas; Valentina Dagienė; Saulius Minkevičius; Leonidas Sakalauskas
2014-01-01
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…
Worst-case efficient external-memory priority queues
DEFF Research Database (Denmark)
Brodal, Gerth Stølting; Katajainen, Jyrki
1998-01-01
. In this paper a priority-queue implementation is given which is efficient with respect to the number of block transfers or I/Os performed between the internal and external memories of a computer. Let B and M denote the respective capacity of a block and the internal memory measured in elements. The developed...
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...
Optimal Server Assignment in Multi-Server Queueing Systems with Random Connectivities
Halabian, Hassan; Lung, Chung-Horng
2011-01-01
In this paper, we investigate the problem of assignment of $K$ identical servers to a set of $N$ parallel queues in a time slotted queueing system. The connectivity of each queue to each server is randomly changing with time; each server can serve at most one queue and each queue can be served by at most one server per time slot. Such multi-server queueing systems were widely applied in modeling the scheduling (or resource allocation) problem in wireless networks. It has been previously proven that Maximum Weighted Matching (MWM) is a throughput optimal server assignment policy for such queueing systems. In this paper, first we prove that for a symmetric system with i.i.d. Bernoulli packet arrivals and connectivities, MWM minimizes, in stochastic ordering sense, a broad range of cost functions of the queue lengths including total queue occupancy (or equivalently minimizes the average queueing delay). Then, we extend the model by considering imperfect services where it is assumed that the service of a schedule...
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).
Pricing Analysis in Geo/Geo/1 Queueing System
Directory of Open Access Journals (Sweden)
Yan Ma
2015-01-01
Full Text Available This paper studies the equilibrium behavior of customers and optimal pricing strategies of servers in a Geo/Geo/1 queueing system. Two common pricing mechanisms are considered. The first one is called ex-post payment (EPP scheme where the server collects tolls proportional to queue times, and the second one is called ex-ante payment (EAP scheme where the server charges a flat fee for the total service. The server sets the toll price to maximize its own profit. It is found that, under a customer’s choice equilibrium, the two toll mechanisms are equivalent from the economic point of view. Finally, we present several numerical experiments to investigate the effects of system parameters on the equilibrium customer joining rate and servers’ profits.
The Effect of Queueing Strategy on Network Traffic
International Nuclear Information System (INIS)
In recent years, the transportation system has been faced by increasing challenge in congestion and inefficiency, and research in traffic network has become a significant area of interest. In this paper, we introduce a dynamic-information-based (DIB) queueing strategy into network traffic model under the efficient routing strategy. DIB makes a packet with higher priority to be delivered if there are less packets travelling along its path from the current node to the destination. It is found that, compared with the traditional first-in-first-out (FIFO) queueing strategy, DIB can effectively balance the traffic load of the system via delaying packets to be delivered to congested nodes. Although the network capacity has no obvious changes, some other indexes which reflect transportation efficiency are efficiently improved in the congestion state. Besides, extensive simulation results and discussions are provided to explain the phenomena. The results may provide novel insights for research on traffic systems. (condensed matter: structural, mechanical, and thermal properties)
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.
Transient Analysis of Hysteresis Queueing Model Using Matrix Geometric Method
Directory of Open Access Journals (Sweden)
Wajiha Shah
2011-10-01
Full Text Available Various analytical methods have been proposed for the transient analysis of a queueing system in the scalar domain. In this paper, a vector domain based transient analysis is proposed for the hysteresis queueing system with internal thresholds for the efficient and numerically stable analysis. In this system arrival rate of customer is controlled through the internal thresholds and the system is analyzed as a quasi-birth and death process through matrix geometric method with the combination of vector form Runge-Kutta numerical procedure which utilizes the special matrices. An arrival and service process of the system follows a Markovian distribution. We analyze the mean number of customers in the system when the system is in transient state against varying time for a Markovian distribution. The results show that the effect of oscillation/hysteresis depends on the difference between the two internal threshold values.
Elements of queueing theory palm martingale calculus and stochastic recurrences
Baccelli, François
2003-01-01
The Palm theory and the Loynes theory of stationary systems are the two pillars of the modern approach to queuing. This book, presenting the mathematical foundations of the theory of stationary queuing systems, contains a thorough treatment of both of these. This approach helps to clarify the picture, in that it separates the task of obtaining the key system formulas from that of proving convergence to a stationary state and computing its law. The theory is constantly illustrated by classical results and models: Pollaczek-Khintchin and Tacacs formulas, Jackson and Gordon-Newell networks, multiserver queues, blocking queues, loss systems etc., but it also contains recent and significant examples, where the tools developed turn out to be indispensable. Several other mathematical tools which are useful within this approach are also presented, such as the martingale calculus for point processes, or stochastic ordering for stationary recurrences. This thoroughly revised second edition contains substantial addition...
Entrainment of a Synthetic Oscillator through Queueing Coupling
Hochendoner, Philip; Mather, William; Butzin, Nicholas; Ogle, Curtis
2014-03-01
Many biological systems naturally exhibit (often noisy) oscillatory patterns that are capable of being entrained by external stimuli, though the mechanism of entrainment is typically obscured by the complexity of native networks. A synthetic biology approach, where genetic programs are wired ``by hand,'' has proven useful in this regard. In the present study, we use a synthetic oscillator in Escherichia coli to demonstrate a novel and potentially widespread mechanism for biological entrainment: competition of proteins for degradation by common pathway, i.e. a entrainment by a bottleneck. To faithfully represent the discrete and stochastic nature of this bottleneck, we leverage results from a recent biological queueing theory, where in particular, the queueing theoretic concept of workload is discovered to simplify the analysis. NSF Award 1330180.
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.
A unified approach to fast teller queues and ATM
BECK, B.; Dabrowski, A R; McDonald, D. R.
1999-01-01
This paper examines a problem of importance to the telecommunications industry. In the design of modern ATM switches, it is necessary to use simulation to estimate the probability that a queue within the switch exceeds a given large value. Since these are extremely small probabilities, importance sampling methods must be used. Here we obtain a change of measure for a broad class of models with direct applicability to ATM switches. ¶ We consider a model with A independent ...
Perceptions of waiting time in different service queues
Jones, Peter; Hwang, Jen-Li
2005-01-01
This paper investigates the extent to which there is a gap between customers' perception of waiting time compared with actual waiting times; and whether this gap varies according to service context. It also investigates a new proposition that customers’ perception of time available for the service influences their perception of wait time. A field study collected 455 actual and perceived customer waiting times in a single queue single server system from a retail grocery store, cafeteria, post...
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
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.
Decay of Tails at Equilibrium for FIFO Join the Shortest Queue Networks
Bramson, Maury; Prabhakar, Balaji
2011-01-01
In join the shortest queue networks, incoming jobs are assigned to the shortest queue from among a randomly chosen subset of D queues, in a system of N queues; after completion of service at its queue, a job leaves the network. We also assume that jobs arrive into the system according to a rate-\\alpha N Poisson process, \\alpha 1. We show under the above ansatz that, as N goes to infinity, the tail of the equilibrium queue size exhibits a wide range of behavior depending on the relationship between \\beta and D. In particular, if \\beta > D/(D-1), the tail is doubly exponential and, if \\beta < D/(D-1), the tail has a power law. When \\beta = D/(D-1), the tail is exponentially distributed.
Virtual queueing techniques for UBR+ service in ATM with fair access and minimum bandwidth guarantee
Energy Technology Data Exchange (ETDEWEB)
Siu, K.Y.; Wu, Y.; Ren, W.
1998-11-01
The ATM Forum is currently discussing the need for a new best-effort service called UBR+, which is an enhancement to the existing UBR service, to support data traffic. The objective of the UBR+ service is to provide each user with a minimum service rate guarantee and a fair access to any excess available bandwidth. In this paper, the authors present a new efficient scheme for supporting this service. The key advantage of the scheme is that it employs only FIFO queueing (instead of per-VC queueing) and admits simple implementation in ATM switches. The ideas involve a simple scheduling mechanism that is based on per-VC queueing and incorporate the virtual queueing technique that can efficiently emulate per-VC queueing on a shared FIFO queue. Simulation results are presented to show that the schemes can deliver almost ideal performance for supporting the new service requirements of UBR+.
A Virtual Queue Approach for Online Estimation of Loss Probability Based on MVA Theory
Hu, Guoqiang; Nevin, Anne
2010-01-01
In network quality of service provisioning, premium services generally require to keep a very small loss probability, which is infeasible to measure directly. The proposed virtual queue scheme estimates the small packet loss probability of a real queueing system by measuring queue statistics in a set of separate virtual queues. A novel scaling property between the real queue and the virtual queues is deduced on the basis of the maximum variance asymptotic (MVA) theory. The new scheme retains the high accuracy and wide applicability of the MVA method for aggregated traffic while avoiding the high computational complexity in a direct application of the original MVA analysis in real time. This makes it suitable for online measurement applications such as network performance monitoring and measurement-based admission control.
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.
Critically loaded queueing models that are throughput suboptimal
Atar, Rami; 10.1214/08-AAP551
2009-01-01
This paper introduces and analyzes the notion of throughput suboptimality for many-server queueing systems in heavy traffic. The queueing model under consideration has multiple customer classes, indexed by a finite set $\\mathcal{I}$, and heterogenous, exponential servers. Servers are dynamically chosen to serve customers, and buffers are available for customers waiting to be served. The arrival rates and the number of servers are scaled up in such a way that the processes representing the number of class-$i$ customers in the system, $i\\in\\mathcal{I}$, fluctuate about a static fluid model, that is assumed to be critically loaded in a standard sense. At the same time, the fluid model is assumed to be throughput suboptimal. Roughly, this means that the servers can be allocated so as to achieve a total processing rate that is greater than the total arrival rate. We show that there exists a dynamic control policy for the queueing model that is efficient in the following strong sense: Under this policy, for every f...
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.
The stationary G/G/s queue with non-identical servers
Directory of Open Access Journals (Sweden)
Pierre Le Gall
1998-01-01
Full Text Available We extend a recently developed factorization method to the case of the G/G/s queue with non-identical servers, by presenting three simple properties which lead to a simple numerical calculation method. We compare our results with those determined by classical Markovian (phase methods in the case of the symmetrical M/G/s queue, and for the mean queueing delay we compare with results given by traffic simulation.
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.
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.
The priority queue as an example of hardware/software codesign
DEFF Research Database (Denmark)
Høeg, Flemming; Mellergaard, Niels; Staunstrup, Jørgen
1994-01-01
The paper identifies a number of issues that are believed to be important for hardware/software codesign. The issues are illustrated by a small comprehensible example: a priority queue. Based on simulations of a real application, we suggest a combined hardware/software realization of the priority...... queue. A priority queue is a data structure with a simple interface which in many applications is a performance bottleneck...
On the busy period of discretized GI/GI/infinity queue
International Nuclear Information System (INIS)
The problem of determining the distribution of the busy period, i. e., of the time when at least one customer is served, of the discretized queueing system with infinitely many servers is investigated. Moreover, the idle period and the cycle of a queue are studied. The recurrent formulae are determined and in particular case of a queue with the geometric input the simpler recurrent formulae are given. Those problems arise in the discrete blob length determination in track chambers in high energy physics
FUNCTIONAL ANALYSIS METHOD FOR THE M/G/1 QUEUEING MODEL WITH OPTIONAL SECOND SERVICE
Institute of Scientific and Technical Information of China (English)
艾尼·吾甫尔; 艾合买提·卡斯木
2014-01-01
By studying the spectral properties of the underlying operator corresponding to the M/G/1 queueing model with optional second service we obtain that the time-dependent solution of the model strongly converges to its steady-state solution. We also show that the time-dependent queueing size at the departure point converges to the corresponding steady-state queueing size at the departure point.
Managing CSCL Activity through networking models
Directory of Open Access Journals (Sweden)
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.
Kernel Density Estimation for Interdeparture Time of GI/G/1 Queues
Directory of Open Access Journals (Sweden)
Hsing Luh
2005-01-01
Full Text Available The departure process of a single queue has been studied since the 1960s. Due to its inherent complexity, closed form solutions for the distribution of the departure process are nearly intractable. In this study, kernel type estimators of the density of interdeparture time in a GI/G/1 queue are studied. Uniform strong consistency of the estimators in a GI/G/1 queue and their rates of convergence are obtained. The stochastic processes are shown to satisfy the strong mixing condition with random instants of sampling. With the analysis presented, we provide a novel analytic tool for studying the departure process in a general queueing model.
Flow-level convergence and insensitivity for multi-class queueing networks
Directory of Open Access Journals (Sweden)
Neil S. Walton
2012-01-01
Full Text Available We consider a multi-class queueing network as a model of packet transfer in a communication network. We define a second stochastic model as a model of document transfer in a communication network where the documents transferred have a general distribution. We prove the weak convergence of the multi-class queueing process to the document transfer process. Our convergence result allows the comparison of general document size distributions, and consequently, we prove general insensitivity results for the limit queueing process. We discuss how this separation of time-scales method of proving insensitivity may be applied to other insensitive queueing systems.
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.
Grouping Based Job Scheduling Algorithm Using Priority Queue and Hybrid Algorithm in Grid Computing
Directory of Open Access Journals (Sweden)
Pinky Rosemarry
2013-01-01
Full Text Available Grid computing enlarge with computing platform which is collection of heterogeneous computing resources connected by a network across dynamic and geographically dispersed organization to form a distributed high performance computing infrastructure. Grid computing solves the complex computing problems amongst multiple machines. Grid computing solves the large scale computational demands in a high performance computing environment. The main emphasis in the grid computing is given to the resource management and the job scheduler .The goal of the job scheduler is to maximize the resource utilization and minimize the processing time of the jobs. Existing approaches of Grid scheduling doesn’t give much emphasis on the performance of a Grid scheduler in processing time parameter. Schedulers allocate resources to the jobs to be executed using the First come First serve algorithm. In this paper, we have provided an optimize algorithm to queue of the scheduler using various scheduling methods like Shortest Job First, First in First out, Round robin. The job scheduling system is responsible to select best suitable machines in a grid for user jobs. The management and scheduling system generates job schedules for each machine in the grid by taking static restrictions and dynamic parameters of jobs and machinesinto consideration. The main purpose of this paper is to develop an efficient job scheduling algorithm to maximize the resource utilization and minimize processing time of the jobs. Queues can be optimized byusing various scheduling algorithms depending upon the performance criteria to be improved e.g. response time, throughput. The work has been done in MATLAB using the parallel computing toolbox.
Design professional activity analysis in design management
Directory of Open Access Journals (Sweden)
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.
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.
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.
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...
Design for manufacturability production management activity report
Miyazaki, Norihiko; Sato, T.; Honma, M.; Yoshioka, N.; Hosono, K.; Onodera, T.; Itoh, H.; Suzuki, H.; Uga, T.; Kadota, K.; Iriki, N.
2006-05-01
Design For Manufacturability Production Management (DFM-PM) Subcommittee has been started in succession to Reticle Management Subcommittee (RMS) in Semiconductor Manufacturing Technology Committee for Japan (SMTCJ) from 2005. Our activity focuses on the SoC (System On Chip) Business, and it pursues the improvement of communication in manufacturing technique. The first theme of activity is the investigation and examination of the new trends about production (manufacturer) technology and related information, and proposals of business solution. The second theme is the standardization activity about manufacture technology and the cooperation with related semiconductors' organizations. And the third theme is holding workshop and support for promotion and spread of the standardization technology throughout semiconductor companies. We expand a range of scope from design technology to wafer pattern reliability and we will propose the competition domain, the collaboration area and the standardization technology on DFM. Furthermore, we will be able to make up a SoC business model as the 45nm node technology beyond manufacturing platform in cooperating with the design information and the production information by utilizing EDA technology.
Innovative Knowledge Management At Disney: Human Capital And Queuing Solutions For Services
Rachelle F. Cope; Robert F. Cope III; Anna N. Bass; Holly A. Syrdal
2011-01-01
It is well known that most activities in which a service is provided require customers to wait in a queue during the experience. One thing that is inherent in waiting lines is the universal dislike for the process. In fact, the feelings and opinions developed in waiting lines influence the customer’s perception of the awaited experience. In this paper, Disney is used as a case study for queuing solutions. In particular, we examine their implementation of Knowledge Management (KM) solutions to...
Slowdown in the $M/M/1$ discriminatory processor-sharing queue
Cheung, Sing-Kong; Kim, Bara; Kim, Jeongsim
2008-01-01
We consider a queue with multiple K job classes, Poisson arrivals, and exponentially distributed required service times in which a single processor serves according to the discriminatory processor-sharing (DPS) discipline. For this queue, we obtain the first and second moments of the slowdown, which
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
Rainfall time series synthesis from queue scheduling of rain event fractals over radio links
Alonge, Akintunde A.; Afullo, Thomas J.
2015-12-01
Rainfall attenuation over wireless networks stems from random fluctuations in the natural process of arriving rainfall rates over radio links. This arrival process results in discernible rainfall traffic pattern which manifests as naturally scheduled and queue-generated rain spikes. Hence, the phenomenon of rainfall process can be approached as a semi-Markovian queueing process, with event characteristics dependent on queue parameters. However, a constraint to this approach is the knowledge of the physical characteristics of queue-generated rain spikes. Therefore, this paper explores the probability theory and descriptive mathematics of rain spikes in rainfall processes. This investigation presents the synthesis of rainfall queue with rain spikes at subtropical and equatorial locations of Durban (29°52'S, 30°58'E) and Butare (2°36'S, 29°44'E), respectively. The resulting comparative analysis of rainfall distributions, using error analysis at both locations, reveals that queue-generated rainfall compares well with measured rainfall data set. This suggests that the time-varying process of rainfall, though stochastic, can be synthesized via queue scheduling with the application of relevant queue parameters at any location.
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.
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.
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
Integrated service resource reservation using queueing networks theory
DEFF Research Database (Denmark)
Brewka, Lukasz Jerzy; Iversen, Villy Bæk; Kardaras, Georgios
2014-01-01
This study analyses multi-server multi-service queueing networks with service protection. To guarantee each service a certain quality-of-service and at the same time ensure high utilisation of servers, a minimum capacity is reserved each service. In addition, all services share the remaining non......-reserved capacity and all buffers in such a way that the system becomes reversible. This implies the model has product form between nodes and is insensitive to the packet size distribution. An analytical model and algorithm for performance evaluation are presented....
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...
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.
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.
Transient Solution to an infinite Server Queue with Varying Arrival and Departure Rate
Directory of Open Access Journals (Sweden)
A. A. El-Sherbiny
2010-01-01
Full Text Available Problem statement: In many potential application of queueing theory, the transient solution of queueing system is important. Approach: This study presented the transient solution for infinite server queues with Poisson arrivals and exponential service times when the parameters of both distributions are allowed to vary with time. Based on generating functions technique which results in a simple differential equation. Using the properties of Bessel functions in the solution of this differential equation, the solution of an infinite server queues can be given in simple form. Results: The researcher obtained the transient solution an infinite server queues with Poisson arrivals and exponential service times when the parameters of both distributions are allowed to vary with time and prove that some past results are special case from his results. Conclusion: These results indicated that the probabilities can be extracted in a direct way.
New Approach for Finding Basic Performance Measures of Single Server Queue
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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.
Request queues for interactive clients in a shared file system of a parallel computing system
Bent, John M.; Faibish, Sorin
2015-08-18
Interactive requests are processed from users of log-in nodes. A metadata server node is provided for use in a file system shared by one or more interactive nodes and one or more batch nodes. The interactive nodes comprise interactive clients to execute interactive tasks and the batch nodes execute batch jobs for one or more batch clients. The metadata server node comprises a virtual machine monitor; an interactive client proxy to store metadata requests from the interactive clients in an interactive client queue; a batch client proxy to store metadata requests from the batch clients in a batch client queue; and a metadata server to store the metadata requests from the interactive client queue and the batch client queue in a metadata queue based on an allocation of resources by the virtual machine monitor. The metadata requests can be prioritized, for example, based on one or more of a predefined policy and predefined rules.
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.
MODELING AND SIMULATION OF QUEUE WAITING THROUGH THE CONCEPT OF PETRI NETS
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Emilija KAMCEVA
2011-08-01
Full Text Available Petri Nets-PN are a graphical formalism which is gaining popularity in recent years as a tool in Matlab for the representation of complex logical interactions among physical components or activities in a system. This notes are devoted to introduce the formalism of Petri nets with particular emphasis on the application of the methodology in the area of the performance and reliability modelling and analysis of systems. A technique is presented whereby queueing network models and generalized stochastic Petri nets are combined in such a way as to exploit the best features of both modeling techniques. The resulting hierarchical modeling approach is useful in the solution of complex models of system behavior.
Classroom Management to Support Active Middle Level Classrooms
Bryan Lloyd McCoy
2012-01-01
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, ...
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.
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.
Queueing-Based Synchronization and Entrainment for Synthetic Gene Oscillators
Mather, William; Butzin, Nicholas; Hochendoner, Philip; Ogle, Curtis
Synthetic gene oscillators have been a major focus of synthetic biology research since the beginning of the field 15 years ago. They have proven to be useful both for biotechnological applications as well as a testing ground to significantly develop our understanding of the design principles behind synthetic and native gene oscillators. In particular, the principles governing synchronization and entrainment of biological oscillators have been explored using a synthetic biology approach. Our work combines experimental and theoretical approaches to specifically investigate how a bottleneck for protein degradation, which is present in most if not all existing synthetic oscillators, can be leveraged to robustly synchronize and entrain biological oscillators. We use both the terminology and mathematical tools of queueing theory to intuitively explain the role of this bottleneck in both synchronization and entrainment, which extends prior work demonstrating the usefulness of queueing theory in synthetic and native gene circuits. We conclude with an investigation of how synchronization and entrainment may be sensitive to the presence of multiple proteolytic pathways in a cell that couple weakly through crosstalk. This work was supported by NSF Grant #1330180.
Upper Bound for Queue length in Regulated Burst Service Scheduling
Directory of Open Access Journals (Sweden)
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.
Applications of queueing theory to stochastic models of gene expression
Kulkarni, Rahul
2012-02-01
The intrinsic stochasticity of cellular processes implies that analysis of fluctuations (`noise') is often essential for quantitative modeling of gene expression. Recent single-cell experiments have carried out such analysis to characterize moments and entire probability distributions for quantities of interest, e.g. mRNA and protein levels across a population of cells. Correspondingly, there is a need to develop general analytical tools for modeling and interpretation of data obtained from such single-cell experiments. One such approach involves the mapping between models of stochastic gene expression and systems analyzed in queueing theory. The talk will provide an overview of this approach and discuss how theorems from queueing theory (e.g. Little's Law) can be used to derive exact results for general stochastic models of gene expression. In the limit that gene expression occurs in bursts, analytical results can be obtained which provide insight into the effects of different regulatory mechanisms on the noise in protein steady-state distributions. In particular, the approach can be used to analyze the effect of post-transcriptional regulation by non-coding RNAs leading to new insights and experimentally testable predictions.
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.
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.
Alonge, Akintunde A.; Afullo, Thomas J.
2014-08-01
Attenuation due to precipitation remains an important design factor in the future deployment of terrestrial and earth-space communication radio links. Largely, there are concerted efforts to understand the dynamics of precipitation in attenuation occurrence at subtropical, tropical, and equatorial region of Africa. In this deliberate approach, rainfall spikes pertaining to rain cells are conceptualized as distinct rain spike traffic over radio links, by applying queueing theory concepts. The queue distributions at Durban (29°52'S, 30°58'E) and Butare (2°36'S, 29°44'E)—respectively, of subtropical and equatorial climates—are investigated from distrometer measurements. The data sets at both sites are observed over four rain regimes: drizzle, widespread, shower, and thunderstorm. The queue parameters of service time and inter-arrival of rain spikes traffic at both regions are found to be Erlang-k distributed (Ek) and exponentially distributed (M), respectively. It is established that the appearance of rain rates over radio links invariably follows a First Come, First Served (FCFS), multi-server (s), infinite queue, and semi-Markovian process, designated as M/Ek/s/∞/FCFS discipline. Modeled queue parameters at both regions are found to vary significantly over different regimes. However, these queue parameters over the entire data set suggest similar queue patterns at both sites. More importantly, power law relationships describing other queue-related parameters are formulated. The paper concludes by demonstrating an application of queueing theory for rainfall synthesis. The proposed technique will provide an alternative method of estimating rain cell sizes and rain attenuation over satellite and terrestrial links.
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
Directory of Open Access Journals (Sweden)
Yang Woo Shin
1999-01-01
Full Text Available We consider a single server Markovian queue with two types of customers; positive and negative, where positive customers arrive in batches and arrivals of negative customers remove positive customers in batches. Only positive customers form a queue and negative customers just reduce the system congestion by removing positive ones upon their arrivals. We derive the LSTs of sojourn time distributions for a single server Markovian queue with positive customers and negative customers by using the first passage time arguments for Markov chains.
Estimation of Ready Queue Processing Time Under Systematic Lottery Scheduling Scheme
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Anjali Jain
2010-03-01
Full Text Available This paper presents a scheduling scheme which provides lottery tickets (containing random numbers to each process in the ready queue. The CPU has a unit to draw random numbers, whenever a scheduling decision has to be made, a random number is generated by CPU and the process in ready queue holding that number gets selected to utilize the resource. This paper presents an estimate of total processing time of all processes in the ready queue. A simulation study is incorporated to support the findings.
Film traffic queueing model for the DUMC radiology department
International Nuclear Information System (INIS)
This paper discusses the radiology department traffic model for Duke University Medical Center (DUMC) which simulates the flow of film through the department, and then incorporates the effect of introducing a PACS-type system into present operations. Each Radiology Section is considered separately for queuing of two types of film: old film (from previous exams) and new film (from the present exam). The amount of film in each queue at any time is controlled by controlling hours of operation, service times, delay, and arrival rates. The model also takes into account the use of film in each major radiology area. This gives some idea of the load on a device in that area as well as the amount of storage needed to adequately handle its daily load is local storage at the display device is desired
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.
Analysis of a multi-server queueing model of ABR
Directory of Open Access Journals (Sweden)
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.
Stochastic queueing-theory approach to human dynamics
Walraevens, Joris; Demoor, Thomas; Maertens, Tom; Bruneel, Herwig
2012-02-01
Recently, numerous studies have shown that human dynamics cannot be described accurately by exponential laws. For instance, Barabási [Nature (London)NATUAS0028-083610.1038/nature03459 435, 207 (2005)] demonstrates that waiting times of tasks to be performed by a human are more suitably modeled by power laws. He presumes that these power laws are caused by a priority selection mechanism among the tasks. Priority models are well-developed in queueing theory (e.g., for telecommunication applications), and this paper demonstrates the (quasi-)immediate applicability of such a stochastic priority model to human dynamics. By calculating generating functions and by studying them in their dominant singularity, we prove that nonexponential tails result naturally. Contrary to popular belief, however, these are not necessarily triggered by the priority selection mechanism.
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.
Radio Active Waste Management: Underground Repository Method
International Nuclear Information System (INIS)
Finding a solution for nuclear waste is a key issue, not only for the protection of the environment but also for the future of the nuclear industry. Ten years from now, when the first decisions for the replacement of existing nuclear power plants will have to be made, The general public will require to know the solution for nuclear waste before accepting new nuclear plants. In other words, an acceptable solution for the management of nuclear waste is a prerequisite for a renewal of nuclear power. Most existing wastes are being stored in safe conditions waiting for permanent solution, with some exceptions in the former Eastern Bloc. Temporary surface or shallow storage is a well known technique widely used all over the world. A significant research effort has been made by the author of this paper in the direction of underground repository. The underground repository appears to be a good solution. Trying to transform dangerous long lived radionuclides into less harmful short lived or stable elements is a logical idea. It is indeed possible to incinerate or transmute heavy atoms of long lived elements in fast breeder reactors or even in pressurised or boiling water reactors. There are also new types of reactors which could be used, namely accelerator driven systems. High level and long lived wastes (spent fuel and vitrified waste) contain a mixture of high activity (heat producing) short lived nuclides and low activity long lived alpha emitting nuclides. To avoid any alteration due to temperature of the engineered or geological barrier surrounding the waste underground, it is necessary to store the packages on the surface for several decades (50 years or more) to allow a sufficient temperature decrease before disposing of them underground. In all cases, surface (or shallow) storage is needed as a temporary solution. This paper gives a detailed and comprehensive view of the Deep Geological Repository, providing a pragmatic picture of the means to make this method, a
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.
The Number Served in a Head Of The Line Priority Queue with General Service
Directory of Open Access Journals (Sweden)
K.N. Gaur
1977-04-01
Full Text Available In this paper, using the supplementary variable method, the head-of-the-line priority queueing system with general service time distributions have been studied to obtain an expression for the Laplace transform of the generating function of the joint probability distribution of the number of priority and non-priority units in the queue at time t, and the number of units served (including non-priority units in time t. In particular cases, explicit solution for the model with exponential service time distributions have been obtained; expression for the joint distribution of the queue length and the number served in time t, for an M/G/1 queue has also been derived.
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.
Methods for estimating vehicle queues at a marine terminal: A computational comparison
Directory of Open Access Journals (Sweden)
Chen Gang
2014-09-01
Full Text Available A long queue of vehicles at the gate of a marine terminal is a common traffic phenomenon in a port-city, which sometimes causes problems in urban traffic. In order to be able to solve this issue, we firstly need accurate models to estimate such a vehicle queue length. In this paper, we compare the existing methods in a case study, and evaluate their advantages and disadvantages. Particularly, we develop a simulation-based regression model, using the micro traffic simulation software PARAMIC. In simulation, it is found that the queue transient process follows a natural logarithm curve. Then, based on these curves, we develop a queue length estimation model. In the numerical experiment, the proposed model exhibits better estimation accuracy than the other existing methods
Information Theory vs. Queueing Theory for Resource Allocation in Multiple Access Channels
ParandehGheibi, Ali; Ozdaglar, Asuman; Eryilmaz, Atilla
2008-01-01
We consider the problem of rate allocation in a fading Gaussian multiple-access channel with fixed transmission powers. The goal is to maximize a general concave utility function of the expected achieved rates of the users. There are different approaches to this problem in the literature. From an information theoretic point of view, rates are allocated only by using the channel state information. The queueing theory approach utilizes the global queue-length information for rate allocation to guarantee throughput optimality as well as maximizing a utility function of the rates. In this work, we make a connection between these two approaches by showing that the information theoretic capacity region of a multiple-access channel and its stability region are equivalent. Moreover, our numerical results show that a simple greedy policy which does not use the queue-length information can outperform queue-length based policies in terms of convergence rate and fairness.
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.
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.
Discrete Time Analysis of Multi-Server Queueing Systems in Material Handling and Service
Matzka, Judith M.
2011-01-01
In this doctoral thesis, performance parameters of multi-server queueing systems are estimated under general stochastic assumptions. We present an exact calculation method for the discrete time distribution of the number of customers in the queueing system at the arrival moment of an arbitrary customer. The waiting time distribution and the sojourn time distribution are estimated exactly, as well. For the calculation of the inter departure time distribution, we present an approximation method.
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.
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.
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.
Flow-level convergence and insensitivity for multi-class queueing networks
Neil S. Walton
2012-01-01
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 result...
Random Linear Network Coding for Time-Division Duplexing: Queueing Analysis
Lucani, Daniel E.; Médard, Muriel; Stojanovic, Milica
2009-01-01
We study the performance of random linear network coding for time division duplexing channels with Poisson arrivals. We model the system as a bulk-service queue with variable bulk size. A full characterization for random linear network coding is provided for time division duplexing channels [1] by means of the moment generating function. We present numerical results for the mean number of packets in the queue and consider the effect of the range of allowable bulk sizes. We show that there exi...
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.
Chronic Fatigue Syndrome (CFS): Managing Activities and Exercise
... message, please visit this page: About CDC.gov . Chronic Fatigue Syndrome (CFS) Share Compartir Managing Activities and Exercise ... activities. Top of Page Related Links Disability and Chronic Fatigue Syndrome Print page View page in: Español (Spanish) ...
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.
Active management of food allergy: an emerging concept.
Anagnostou, Katherine; Stiefel, Gary; Brough, Helen; du Toit, George; Lack, Gideon; Fox, Adam T
2015-04-01
IgE-mediated food allergies are common and currently there is no cure. Traditionally, management has relied upon patient education, food avoidance and the provision of an emergency medication plan. Despite this, food allergy can significantly impact on quality of life. Therefore, in recent years, evolving research has explored alternative management strategies. A more active approach to management is being adopted, which includes early introduction of potentially allergenic foods, anticipatory testing, active monitoring, desensitisation to food allergens and active risk management. This review will discuss these areas in turn. PMID:25378378
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.
R and D Activities for NPP Life Management in Korea
International Nuclear Information System (INIS)
Many R and D activities related to PLiM have been carried out and implemented to Korean NPP for the long term operation. Those activities include ageing management study, periodic safety review, steam generator management programme, materials reliability programme, thinned pipe management programme, study on dissimilar metal welds, etc. Based on the R and D activities, long term operation of Kori Unit 1 was successfully started from January 17, 2008 for next 10 years beyond its original design life. In this paper, all the activities and their results of the R and D programmes are briefly introduced. (author)
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. PMID:24109839
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.
Analysis of DAR(1)/D/s Queue with Quasi-Negative Binomial-II as Marginal Distribution
Kanichukattu Korakutty Jose; Bindu Abraham
2011-01-01
In this paper we consider the arrival process of a multiserver queue governed by a discrete autoregressive process of order 1 [DAR(1)] with Quasi-Negative Binomial Distribution-II as the marginal distribution. This discrete time multiserver queueing system with autoregressive arrivals is more suitable for modeling the Asynchronous Transfer Mode(ATM) multiplexer queue with Variable Bit Rate (VBR) coded teleconference traffic. DAR(1) is described by a few parameters and it is easy to match 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.
ANDRA 2009 activity report: managing today to prepare the future
International Nuclear Information System (INIS)
This activity report first presents the four-year contract between the French State and the ANDRA (the French national agency for the management of radioactive wastes), the personnel working for ANDRA. Then, it presents various activities of ANDRA in the field of the management of radioactive materials and pollutions (material and waste survey, security of polluted sites, collecting radioactive wastes and objects, public information), its operational activities (evolution and project of storage sites), its design activities for storage sites for different types of wastes (life and activity). It also describes activities in the fields of international expertise and of protection of industrial concepts
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.
Quarterly Briefing Book on Environmental and Waste Management Activities
International Nuclear Information System (INIS)
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
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
Directory of Open Access Journals (Sweden)
David C. R. Muh
1993-01-01
Full Text Available The author studies the queueing process in a single-server, bulk arrival and batch service queueing system with a compound Poisson input, bilevel service delay discipline, start-up time, and a fixed accumulation level with control operating policy. It is assumed that when the queue length falls below a predefined level r(≥1, the system, with server capacity R, immediately stops service until the queue length reaches or exceeds the second predefined accumulation level N(≥r. Two cases, with N≤R and N≥R, are studied.
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.
Network-of-queues approach to B-cell-receptor affinity discrimination
Felizzi, Federico; Comoglio, Federico
2012-06-01
The immune system is one of the most complex signal processing machineries in biology. The adaptive immune system, consisting of B and T lymphocytes, is activated in response to a large spectrum of pathogen antigens. B cells recognize and bind the antigen through B-cell receptors (BCRs) and this is fundamental for B-cell activation. However, the system response is dependent on BCR-antigen affinity values that span several orders of magnitude. Moreover, the ability of the BCR to discriminate between affinities at the high end (e.g., 109M-1-1010M-1) challenges the formulation of a mathematical model able to robustly separate these affinity-dependent responses. Queuing theory enables the analysis of many related processes, such as those resulting from the stochasticity of protein binding and unbinding events. Here we define a network of queues, consisting of BCR early signaling states and transition rates related to the propensity of molecular aggregates to form or disassemble. By considering the family of marginal distributions of BCRs in a given signaling state, we report a significant separation (measured as Jensen-Shannon divergence) that arises from a broad spectrum of antigen affinities.
DESAIN FRAMEWORK MULTIMEDIA QUEUEING SYSTEM BERBASIS ANDROID ANTRIAN PASIEN PUSKESMAS
Directory of Open Access Journals (Sweden)
Erika Devi Udayanti
2015-10-01
Full Text Available Saat ini antrian di puskesmas masih dilakukan dengan metode konvensional, yaitu dengan menumpuk kartu registrasi. Metode seperti ini memungkinkan kartu menjadi terselip. Selain itu, penumpukan kartu yang tidak benar dapat mengakibatkan urutan menjadi tidak sesuai dengan urutan yang seharusnya. Pasien yang datang lebih ahir dimungkinkan untuk dapat dilayani lebih awal dari pasien yang sudah lama menunggu. Penelitian ini mengusulkan multimedia queueing system berbasis android untuk layanan antrian pasien puskesmas. Sistem ini mencatat antrian di dalam database server, sehingga tidak ada kartu yang terselip ataupun salah tumpuk. Lebih lanjut lagi, penelitian ini akan mengangkat kecanggihan mesin android sebagai input device. Sedangkan untuk output devicenya, menggunakan portable bluetooth printer dan layar LCD. Setiap pasien yang datang dapat mencetak tiket antrian dengan menyentuh tombol pada layar mesin android. Mesin android tersebut kemudian akan mencetak tiket melaui printer portable yang disediakan dan mengirim nomor antrian ke database server. Selain itu, mesin android ini juga memotret wajah pasien yang masuk, dan file foto akan dikirim beserta nomor antrian ke server. Pada saat giliran pasien tiba, layar LCD akan menampilkan nomor antrian pasien beserta fotonya. Metode ini diharapkan mampu menyelesaikan problem kartu registrasi terselip, dan juga membantu pasien yang buta huruf/angka. Kata Kunci: puskesmas, sistem antrian, android
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.
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.
Queueing theoretical analysis of foreign currency exchange rates
Inoue, J; Inoue, Jun-ichi; Sazuka, Naoya
2006-01-01
We propose a useful approach to investigate statistical properties of foreign currency exchange rates. Our approach is based on queueing theory, especially, the so-called renewal-reward theorem. For first passage processes of the Sony bank USD/JPY exchange rate, we evaluate the average waiting time which is defined as the average time for customers to wait until the next rate change from any time point when they want to check the rate, for example, when they login to their computer systems. We find that the assumption of exponential distribution on the first passage process should be rejected and a Weibull distribution seems to be more suitable to explain the stochastic process of the Sony bank rate. Our approach also enables us to evaluate the expected reward for customers, namely, one can predict how long customers wait and how much reward they obtain by the next price change after they login to the computer systems. We check the validity by comparing our prediction with empirical data analysis.
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.
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...
International Nuclear Information System (INIS)
Compliance with the Nuclear Waste Policy Act of 1982 (PL 97-425) will require the transportation of large volumes of spent fuel to a central receiving facility (either a geologic repository or a monitored retrievable storage facility). Decisions on the transport mode and technology will evolve over the next several years, in anticipation of the deployment of a receiving facility in the late 1990s. Regardless of the particular transportation mode or modes and the details of cask technology, the transport system from many diverse sources to a single point will generate an essentially random arrival pattern. This random arrival pattern will lead to the formation of queues at the receiving facility. As is normal in any queueing system, the waiting time distribution caused by this queueing will depend on the receiving facility input processing rate and the characteristics of the traffic. Since this is a cyclic system, there is also a reverse effect in which (for a given size cask fleet) average wait time affects traffic intensity. Both effects must be accounted for to properly represent the system. This paper develops a simple analytic queueing model which accounts for both of these effects simultaneously. Since both effects are determined by receiving facility input rates and cask fleet size and characteristics, two major sets of system design parameters are linked by the queueing process. The model is used with estimated traffic and service parameters to predict the severity of queueing under plausible reference system conditions, and to establish shadow prices for the trade off between larger cask fleets and more efficient receiving facilities. Since many of the parameter values used in this estimation are quite preliminary, these results are presented primarily in the context of demonstrating the utility of the queueing model for future trade off studies
The Effectiveness Analysis of Waiting Processes in the Different Branches of a Bank by Queue Model
Directory of Open Access Journals (Sweden)
Abdullah ÖZÇİL
2015-06-01
Full Text Available Despite the appreciable increase in the number of bank branches every year, nowadays queues for services don’t decrease and even become parts of our daily lives. By minimizing waiting processes the least, increasing customer satisfaction should be one of branch managers’ main goals. A quick and also customer oriented service with high quality is the most important factor for customer loyalty. In this study, Queueing theory, one of Operation Research techniques, is handled and in application, the data are obtained related to waiting in queue of customer in six different branches of two banks operating in Denizli and then they are analyzed by Queueing theory and also calculated the average effectiveness of the system. The study’s data are obtained by six branches of two banks called as A1, A2, A3, B1, B2 and B3. At the end of study it is presented to the company some advices that can bring benefits to the staff and customers. In this study, Queueing theory, one of Operation Research techniques, is handled and in application, the data are obtained related to waiting in queue of customer in three different branches of a bank operating in Denizli and then they are analyzed by Queueing theory and also calculated the average effectiveness of the system. The study’s data are obtained by three branches of the bank called A1, A2 and A3. At last it is presented to the company some advices that can bring more benefits to the staff and clients.
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。
Does active portfolio management create value? An evaluation of fund managers' decisions
Engström, Stefan
2004-01-01
In this paper, I obtain new measures of the value of active portfolio management by forming replicating portfolios. These measures allow for a separate evaluation of fund managers' strategic and tactical decisions. I also obtain new evidence on the value of trading by decomposing it into long-term trading decisions, short-term trading decisions, and trading that is the result of regulatory restrictions. Overall, the evidence supports the value of active portfolio management and that the avera...
SOCIAL ORIENTATION MANAGEMENT OF COMMERCIAL BANKS ACTIVITY
Directory of Open Access Journals (Sweden)
N. G. Shpankovskaya
2010-06-01
Full Text Available The modern theoretical approaches to definition of essence of social activity of enterprises are analyzed. The directions of development of social activity of commercial banks are determined. The expedience of formulation of mission of commercial banks and general requirements it must meet to is grounded.
Multiple objective optimization for active sensor management
Page, Scott F.; Dolia, Alexander N.; Harris, Chris J.; White, Neil M.
2005-03-01
The performance of a multi-sensor data fusion system is inherently constrained by the configuration of the given sensor suite. Intelligent or adaptive control of sensor resources has been shown to offer improved fusion performance in many applications. Common approaches to sensor management select sensor observation tasks that are optimal in terms of a measure of information. However, optimising for information alone is inherently sub-optimal as it does not take account of any other system requirements such as stealth or sensor power conservation. We discuss the issues relating to developing a suite of performance metrics for optimising multi-sensor systems and propose some candidate metrics. In addition it may not always be necessary to maximize information gain, in some cases small increases in information gain may take place at the cost of large sensor resource requirements. Additionally, the problems of sensor tasking and placement are usually treated separately, leading to a lack of coherency between sensor management frameworks. We propose a novel approach based on a high level decentralized information-theoretic sensor management architecture that unifies the processes of sensor tasking and sensor placement into a single framework. Sensors are controlled using a minimax multiple objective optimisation approach in order to address probability of target detection, sensor power consumption, and sensor survivability whilst maintaining a target estimation covariance threshold. We demonstrate the potential of the approach through simulation of a multi-sensor, target tracking scenario and compare the results with a single objective information based approach.
Improvement of enterprise activities based on process management
Łuczak, Ja.
2015-01-01
Process management has been increasingly popular for several years now, yet most frequently it is limited to fragmentary actions, at times even to declarative activity. Few organizations have brought their management systems in conformity with the idea of process management; more frequently some particular actions within the range of process approach may be observed. Specialization allows efficient realizations of tasks; however, it separates individual organizational unities and amount...
Visual Impacts of Forest Management Activities: Findings on Public Preferences
United States Department of Agriculture, Forest Service
1981-01-01
A major concern of forest land managers is the visual impact that activities such as timber harvest, road building, and mining have on the forest landscape. Management of the visual resource is a regular part of planning on National Forests, and many other public and private forest land managers are increasing their efforts to protect and enhance this resource. The Forest Residue and Harvesting Research Program at the Intermountain Station includes studies of the impact of harvest and roadi...
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.
[Approval of predator management activities in North Dakota, 2005
US Fish and Wildlife Service, Department of the Interior — Request from U.S. Fish and Wildlife Service and approval from North Dakota Game & Fish Department for predator management activities outside of the state...
Guide to good practices for line and training manager activities
Energy Technology Data Exchange (ETDEWEB)
NONE
1998-06-01
The purpose of this guide is to provide direction for line and training managers in carrying out their responsibilities for training and qualifying personnel and to verify that existing training activities are effective.
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.
Nonexercise activity thermogenesis in obesity management.
Villablanca, Pedro A; Alegria, Jorge R; Mookadam, Farouk; Holmes, David R; Wright, R Scott; Levine, James A
2015-04-01
Obesity is linked to cardiovascular disease. The global increase in sedentary lifestyle is an important factor contributing to the rising prevalence of the obesity epidemic. Traditionally, counseling has focused on moderate- to vigorous-intensity exercise, with disappointing results. Nonexercise activity thermogenesis (NEAT) is an important component of daily energy expenditure. It represents the common daily activities, such as fidgeting, walking, and standing. These high-effect NEAT movements could result in up to an extra 2000 kcal of expenditure per day beyond the basal metabolic rate, depending on body weight and level of activity. Implementing NEAT during leisure-time and occupational activities could be essential to maintaining a negative energy balance. NEAT can be applied by being upright, ambulating, and redesigning workplace and leisure-time environments to promote NEAT. The benefits of NEAT include not only the extra calories expended but also the reduced occurrence of the metabolic syndrome, cardiovascular events, and all-cause mortality. We believe that to overcome the obesity epidemic and its adverse cardiovascular consequences, NEAT should be part of the current medical recommendations. The content of this review is based on a literature search of PubMed and the Google search engine between January 1, 1960, and October 1, 2014, using the search terms physical activity, obesity, energy expenditure, nonexercise activity thermogenesis, and NEAT. PMID:25841254
CONTEMPORARY MANAGEMENT ASPECTS OF THE COMPANIES WITH INTERNATIONAL ACTIVITY
Sebastian ENE; Mihaela IONECI
2010-01-01
The activity of the national and international companies is determined by the manner in which their management is implemented. Obviously, the management must be structured starting from each company’s particularities in accordance with the economic environment where the respective organization develops its activity. In the contemporary times, the rigorous organization, the planning on a short-term, medium-term and long-term, the human capital quality as well as the control represent elements ...
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).
Management Control of Public and Not-for-Profit Activities
Hofstede, G.
1981-01-01
Traditional approaches to management control usually fail for public and not-for-profit activities. The type of control applicable to such activities depends on four criteria: are objectives unambiguous, outputs measurable, effects of interventions known, and is the activity repetitive? Depending on where activities stand with regard to these criteria, the control applicable corresponds to one of six different types: routine, expert, trial-and-error, intuitive, judgemental, or political contr...
Maintenance in Single-Server Queues: A Game-Theoretic Approach
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Najeeb Al-Matar
2009-01-01
examine a single-server queue with bulk input and secondary work during server's multiple vacations. When the buffer contents become exhausted the server leaves the system to perform some diagnostic service of a minimum of L jobs clustered in packets of random sizes (event A. The server is not supposed to stay longer than T units of time (event B. The server returns to the system when A or B occurs, whichever comes first. On the other hand, he may not break service of a packet in a middle even if A or B occurs. Furthermore, the server waits for batches of customers to arrive if upon his return the queue is still empty. We obtain a compact and explicit form functional for the queueing process in equilibrium.
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.
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 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.
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.
Henrique Teixeira, Eduardo; Patrícia Favacho de Araújo, Aletéia
2015-10-01
Elasticity in computing refers to dynamically adjusting the amount of allocated resources to process a distributed application. In order to achieve this, mechanisms are needed to avoid the phenomenon of the elasticity threshold detection moving constantly up or down. The existing work fails to deliver sequential integrity of asynchronous messages processing and the asymmetries of data distribution to achieve parallel consumption. This paper fills this gaps and proposes a middleware solution to dynamically analyze the flow of message queue, and a mechanism to increase the parallelized consumption based on the output behavior. An architecture for IOD (Increase On Demand) middleware is presented, with support for the increase and decrease of thread's to cope with the growth of message queues, using the technique of limit-based heuristics over a given period of time and grouping messages into sub-queues based on classification criteria.
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.
Professional activity of officers on questions of physical training management
Directory of Open Access Journals (Sweden)
Olkhovyi O.M.
2012-11-01
Full Text Available Certain requirement to the typical tasks of professional activity of officers on questions of guidance, organization and leadthrough of physical training in Military Powers of Ukraine is determined. Constituents, components and structure of model of professional activity of officers on questions of physical preparation management are analysed. The basic factors of guidance and way of their realization are exposed. It is selected that the process of managing of physical training in accordance with principles and management methods and taken to making a decision and their realization is carried out. The technological sequence of creation of components of the system of preparation of officers to implementation of official questions is certain. The model of professional activity of officers on questions of management is created. The selected kinds by which officers carry out the functional duties are guidance.
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 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.
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)
The Geo/Geo/1+1 Queueing System with Negative Customers
Zhanyou Ma; Yalin Guo; Pengcheng Wang; Yumei Hou
2013-01-01
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, ...
The Geo/Geo/1+1 Queueing System with Negative Customers
Directory of Open Access Journals (Sweden)
Zhanyou Ma
2013-01-01
Full Text Available We study a Geo/Geo/1+1 queueing system with geometrical arrivals of both positive and negative customers in which killing strategies considered are removal of customers at the head (RCH and removal of customers at the end (RCE. Using quasi-birth-death (QBD process and matrix-geometric solution method, we obtain the stationary distribution of the queue length, the average waiting time of a new arrival customer, and the probabilities of servers in busy or idle period, respectively. Finally, we analyze the effect of some related parameters on the system performance measures.
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.
Asymptotic Behavior of the Moments of the Maximum Queue Length During a Busy Period
Eschenfeldt, Patrick; Pippenger, Nicholas
2011-01-01
We give a simple derivation of the distribution of the maximum L of the length of the queue during a busy period for the M/M/1 queue with lambda<1 the ratio between arrival rate and service rate. We observe that the asymptotic behavior of the moments of L is related to that of Lambert series for the generating functions for the sums of powers of divisors of positive integers. We show how to obtain asymptotic expansions for these moments with error terms having order as large a power of 1-lambda as desired.
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.
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.
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.
First in Line Waiting Times as a Tool for Analysing Queueing Systems
DEFF Research Database (Denmark)
Koole, G. M.; Nielsen, Bo Friis; Nielsen, Thomas Bang
2012-01-01
We introduce a new approach to modelling queueing systems where the priority or the routing of customers depends on the time the first customer has waited in the queue. This past waiting time of the first customer in line, WFIL, is used as the primary variable for our approach. A Markov chain...... is used for modelling the system where the states represent both the number of free servers and a discrete approximation to WFIL. This approach allows us to obtain waiting time distributions for complex systems, such as the N-design routing scheme widely used, e.g., in call centers and systems...
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.
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.
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.
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.
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…
Passive and active adaptive management: Approaches and an example
Williams, B.K.
2011-01-01
Adaptive management is a framework for resource conservation that promotes iterative learning-based decision making. Yet there remains considerable confusion about what adaptive management entails, and how to actually make resource decisions adaptively. A key but somewhat ambiguous distinction in adaptive management is between active and passive forms of adaptive decision making. The objective of this paper is to illustrate some approaches to active and passive adaptive management with a simple example involving the drawdown of water impoundments on a wildlife refuge. The approaches are illustrated for the drawdown example, and contrasted in terms of objectives, costs, and potential learning rates. Some key challenges to the actual practice of AM are discussed, and tradeoffs between implementation costs and long-term benefits are highlighted. ?? 2010 Elsevier Ltd.
Radwaste management activities in the republic of Korea
International Nuclear Information System (INIS)
Being short of natural resources, the Republic of Korea depends relatively large portion of its power generation upon nuclear energy. For the continuous utilization of nuclear energy, the public should be convinced that the necessary technologies and wherewithals are already available for the guarantee of the safe management of radwastes. The status and national policy of the radwaste management in Korea including R and D activities are covered herein. The ongoing activities of the Korea Advanced Energy Research Institute (KAERI) in the field of radwaste management include the areas of handling, treatment, storage and disposal of various radwastes, safety assessment of radwaste disposal, and the decontamination and decommissioning of nuclear facilities. In compliance with the national radwaste management programme, a centralized repository is expected to be operable by the early 1990's in the Republic. (author)
Actively Managed Investment Portfolio Dilemmas, ‘Lost Returns Approach’
Directory of Open Access Journals (Sweden)
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
IAEA activities in the field of NPP life management
International Nuclear Information System (INIS)
The IAEA has established programmes in the field of Nuclear Plant Lifetime in the Division of Nuclear Power and the Fuel Cycle (NEPF) and also in the Division of Nuclear Safety. In the Division of NEPF the International Working Group on Life Management of Nuclear Power Plants carries out its activities within the IAEA Project A2.03 ''Nuclear Power Plant Life Management''. Activities under this project have produced a wealth of information by organizing specialists meeting, preparing technical publications on related topics and arranging co-ordinated research programmes with good results. The most recent development is a database which has been developed and is being maintained. 4 figs
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. PMID:10662094
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.
Sojourn time asymptotics in Processor Sharing queues with varying service rate
R. Egorova; M.R.H. Mandjes; B. Zwart
2007-01-01
Abstract This paper addresses the sojourn time asymptotics for a GI/GI/⋅ queue operating under the Processor Sharing (PS) discipline with stochastically varying service rate. Our focus is on the logarithmic estimates of the tail of sojourn-time distribution, under the assumption that the job-size di
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
The application of queue theory in cloud computing to reduce the waiting time
Directory of Open Access Journals (Sweden)
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.
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 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.
Many-server queues with customer abandonment: numerical analysis of their diffusion models
Dai, J G
2011-01-01
We use multidimensional diffusion processes to approximate the dynamics of a queue served by many parallel servers. The queue is served in the first-in-first-out (FIFO) order and the customers waiting in queue may abandon the system without service. Two diffusion models are proposed in this paper. They differ in how the patience time distribution is built into them. The first diffusion model uses the patience time density at zero and the second one uses the entire patience time distribution. To analyze these diffusion models, we develop a numerical algorithm for computing the stationary distribution of such a diffusion process. A crucial part of the algorithm is to choose an appropriate reference density. Using a conjecture on the tail behavior of a limit queue length process, we propose a systematic approach to constructing a reference density. With the proposed reference density, the algorithm is shown to converge quickly in numerical experiments. These experiments also show that the diffusion models are go...
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
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 joint...
Computing a constrained control policy for a single-server queueing system
DEFF Research Database (Denmark)
Larsen, Christian
We consider a single-server queueing system designed to serve homogeneous jobs. The jobs arrive to the system after a Poisson process and all processing times are deterministic. There is a set-up cost for starting up production and a holding cost rate is incurred for each job present. Also...
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
Proposition of delay model for signalized intersections with queueing theory analytical models usage
Directory of Open Access Journals (Sweden)
Grzegorz SIERPIŃSKI
2007-01-01
Full Text Available Time delay on intersections is a very important transport problem. Thearticle includes a proposition of time delay model. Variance of service times is considered by used average waiting time in queue for queuing system with compressed queuing processes usage as a part of proposed time delays model.
Analysis And Optimization Of Exponential Queueing Networks By Means Of Parallel Calculations
Pankov, A.; Koluzaeva, E.
2011-01-01
The method of a finding of mean characteristics of an open exponential queueing network (QN) and solution of the problem of coasts optimization in such network by means of parallel calculations is considered. The software for solution of the formulated problems, developed with usage of technology of programming MPI and libraries PETSc is described.
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.
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
A two-station queue with dependent preparation and service times
M. Vlasiou; I.J.B.F. Adan; O.J. Boxma
2009-01-01
We discuss a single-server multi-station alternating queue where the preparation times and the service times are auto- and cross-correlated. We examine two cases. In the first case, preparation and service times depend on a common discrete time Markov chain. In the second case, we assume that the se
Loss asymptotics for the single-server queue with complete rejection
Zwart, A.P.
2015-01-01
Consider the single-server queue in which customers are rejected if their total sojourn time would exceed a certain level K. A basic performance measure of this system is the probability PK that a customer gets rejected in steady state. This paper presents asymptotic expansions for PK as K ... If
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...
Design of a Tree-Queue Model for a Large-Scale System
Park, Byungsung; Yoo, Jaeyeong; Kim, Hagbae
In a large queuing system, the effect of the ratio of the filled data on the queue and waiting time from the head of a queue to the service gate are important factors for process efficiency because they are too large to ignore. However, many research works assumed that the factors can be considered to be negligible according to the queuing theory. Thus, the existing queuing models are not applicable to the design of large-scale systems. Such a system could be used as a product classification center for a home delivery service. In this paper, we propose a tree-queue model for large-scale systems that is more adaptive to efficient processes compared to existing models. We analyze and design a mean waiting time equation related to the ratio of the filled data in the queue. Based on simulations, the proposed model demonstrated improvement in process-efficiency, and it is more suitable to realistic system modeling than other compared models for large-scale systems.
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.
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.
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
Proposals for refinements in international nuclear knowledge management activities
International Nuclear Information System (INIS)
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
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.
COMMUNICATION COMPETENCES TRAINING FOR MANAGERS THROUGH ROLE-PLAY ACTIVITIES
Assist. Răzvan - Alexandru Călin Ph. D Student
2010-01-01
Communication competences are an important indicator of professional success in most areas of activity and a predictor of social success of modern man. This study is a theoretical approach aimed to substantiate a number of good practices based on role-play as an active-participatory communication competences training in general, and for managers in particular. Starting from the definition of „communication” and „competence”, it was decided to operationalize the concept of „communication compe...
Managing Suspicious Activity Reporting Systems at Small Agency Police Departments
Roberts, Bryan A.
2012-01-01
Approved for public release; distribution is unlimited Law enforcement agencies have managed anonymous tip line programs for decades whereby community members can submit suspected criminal activity to their local law enforcement agency. As a result of the increasing threat of terrorism in the United States, suspicious activity reporting programs (SAR) accompany the traditional anonymous tip line. SARs include the reporting of suspicious behavior related to terrorism, as well as other crimi...
Quality Management Activities for Software Architecture and Software Architecture Process
Hämäläinen, Niina
2008-01-01
Architecture processes are considerably new parts of organisations’ processes. These processes have the responsibility to aim at high quality and financially successful architectures. However, the activities which promote this aim are not clearly defined yet. This study reviews literature and practitioners’ experiences on quality management activities that could be suggested to promote the achievement of high quality software architectures and a good quality software a...
2012-06-26
... of the Secretary TRICARE Management Activity Adoption of Department of the Treasury's Administrative Wage Garnishment Procedures AGENCY: TRICARE Management Activity (TMA), DoD. ACTION: Adoption of... Treasury's Financial Management Service (FMS), to use administrative wage garnishment as an additional...
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.
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.
Moodog: Tracking Student Activity in Online Course Management Systems
Zhang, Hangjin; Almeroth, Kevin
2010-01-01
Many universities are currently using Course Management Systems (CMSes) to conduct online learning, for example, by distributing course materials or submitting homework assignments. However, most CMSes do not include comprehensive activity tracking and analysis capabilities. This paper describes a method to track students' online learning…
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...
This is how we manage Sweden's radioactive waste. Activities 1995
International Nuclear Information System (INIS)
SKB operates systems and facilities for the management and final disposal of spent nuclear fuel and other radioactive waste in Sweden. SKB has conducted extensive R, D and D work with regard to constructing a spent fuel encapsulation plant and a deep repository in crystalline bedrock. This annual report treats all the different activities without going into technical details
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.
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. PMID:10104281
Directory of Open Access Journals (Sweden)
Luminita Zait
2009-12-01
Full Text Available The best known definitions provided to the concept of marketing management, in the last decades of the 21st century have in common – the orientation towards the client and the development of successfull relations with the clients, the substantion and operationalization of the mix of marketing, as the basis of the exchange relation, the involvement of all functional areas inside the organisation in managing relations in order to achieve the long term objectives of the organization – but the main issues are related to four basic activities: - analysis, planning, implementing and controlling marketing activities.
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.
Implementation of a Quality Management System in regulatory inspection activities
International Nuclear Information System (INIS)
The Institute for Radioprotection and Dosimetry - IRD -, of the Brazilian National Nuclear Energy Commission, CNEN, started in 2001, the implementation of a quality management system (SGQ), in the inspection, testing and calibration activities. The SGQ was an institutional guideline and is inserted in a larger system of management of the IRD started in 1999, with the adoption of the National Quality Award criteria - PNQ, within the Project for Excellence in Technological Research of Associacao Brasileira das Instituicoes de Pesquisas Tecnologicas - ABIPTI (Brazilian Association of Technological Research institutions). The proposed quality management system and adopted at the IRD was developed and implemented in accordance with the requirements of NBR ISO/IEC 17025 - General requirements for the competence of testing and calibration laboratories, and ISO/IEC 17020 - General criteria for operation of various types of bodies performing inspections. For regulatory inspection activities, the quality system was implemented on three program inspection services of radiological protection led, respectively, by clinics and hospitals that operate radiotherapy services; industries that use nuclear gauges in their control or productive processes and power reactor operators (CNAAA) - just the environmental part. It was formed a pioneering team of inspectors for standardizing the processes, procedures and starting the implementation of the system in the areas. This work describes the implementation process steps, including difficulties, learning and advantages of the adoption of a quality management system in inspection 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.
Implementation of benchmark management in quality assurance audit activities
International Nuclear Information System (INIS)
The concept of Benchmark Management is that the practices of the best competitor are taken as benchmark, to analyze and study the distance between that competitor and the institute, and take efficient actions to catch up and even exceed the competitor. This paper analyzes and rebuilds all the process for quality assurance audit with the concept of Benchmark Management, based on the practices during many years of quality assurance audits, in order to improve the level and effect of quality assurance audit activities. (author)
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.
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.
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.
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.
Management of nuclear PRs activity with optimal conditions
International Nuclear Information System (INIS)
A methodology is proposed to derive optimal conditions for the activity of nuclear public relations (PRs). With the use of data-bases available at present, expressions were derived which connect the budget allocated for the PRs activity with the intensity of stimulus for four types of activity of the advertisement in the press, the exclusive publicity, the pamphlet and the advertisement on television. Optimal conditions for the activity were determined by introducing a model describing a relation between the intensity of stimulus and the extent of the change of public's attitude to nuclear energy, namely the effect of PRs activity, and also by giving the optimal ratio of allocation of the budget among the four types of activity as a function of cost versus effectiveness of each type. Those optimal conditions, being for the ratio of allocation of the budget, the execution time and the intensity of each type of activity at that time, vary depending on the number of household in a target region, the target class of demography, the duration time of activity, and the amount of budget for the activity. It becomes clear from numerical calculation that the optimal conditions and the effect of activity show quite strong non-linearity with respect to the variation of those variables, and that the effect of PRs activity averaged over all public in the target region becomes to be maximum, in Japan, when the activity is executed with the optimal conditions determined for the target class of middle- and advanced-aged women. The management of nuclear PRs activity becomes possible by introducing such a method of fixation of optimal conditions for the activity as described here. (author)
Developing knowledge management systems with an active expert methodology
International Nuclear Information System (INIS)
Knowledge management, understood as the ability to store, distribute and utilize human knowledge in an organization, is the subject of this dissertation. In particular we have studied the design of methods and supporting software for this process. Detailed and systematic description of the design and development processes of three case-study implementations of knowledge management software are provided. The outcome of the projects is explained in terms of an active expert development methodology, which is centered around support for a domain expert to take substantial responsibility for the design and maintenance of a knowledge management system in a given area of application. Based on the experiences from the case studies and the resulting methodology, an environment for automatically supporting knowledge management was designed in the KNOWLEDGE-LINKER research project. The vital part of this architecture is a knowledge acquisition tool, used directly by the experts in creating and maintaining a knowledge base. An elaborated version of the active expert development methodology was then formulated as the result of applying the KNOWLEDGE-LINKER approach in a fourth case study. This version of the methodology is also accounted for and evaluated together within the supporting KNOWLEDGE-LINKER architecture. (au)
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
International Nuclear Information System (INIS)
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
Coordinating Management Activities in Distributed Software Development Projects
Bendeck, Fawsy; Goldmann, Sigrid; Holz, Harald; Kötting, Boris
1999-01-01
Coordinating distributed processes, especially engineering and software design processes, has been a research topic for some time now. Several approaches have been published that aim at coordinating large projects in general, and large software development processes in specific. However, most of these approaches focus on the technical part of the design process and omit management activities like planning and scheduling the project, or monitoring it during execution. In this paper, we focus o...
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.
Implementation of activity based cost management aboard base installations
Stanley, James; Perkins, Nicholas R.; Zander, Laura
2004-01-01
Approved for public release; distribution is unlimited. MBA Professional Report This project is a comparative analysis of the implementation process of Activity Based Cost Management of Marine Corps Logistics Base, (MCLB), Albany, and the implementation procedures used aboard MCB Camp Lejeune. Interviews and data gathering were conducted to identify how the respective Business Performance Offices (BPO), plan, implement, monitor, and measure performance of their process to introduce ABCM...
Briefing book on environmental and waste management activities
International Nuclear Information System (INIS)
The purpose of the Briefing Book is to provide current information on Environmental Restoration and Waste Management Activities at the Hanford Site. Each edition updates the information in the previous edition by deleting those sections determined not to be of current interest and adding new topics to keep up to date with the changing requirements and issues. This edition covers the period from October 15, 1992 through April 15, 1993
Management of female handball players' activity applying interactive technologies
Frolova L.S.; Glazyrin I.D.; Petrenko Y.O.; Rudenko E.; Udod M.
2012-01-01
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 ...
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
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.
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.
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.
Sto godina Teorije redova čekanja / A hundred years of the Queueing Theory
Directory of Open Access Journals (Sweden)
Nebojša V. Nikolić
2009-07-01
Full Text Available U radu je prikazan nastanak i razvoj Teorije redova čekanja, poznate i kao Teorija masovnog opsluživanja. Opisan je i istorijsko-tehnološki kontekst vremena u kojem je došlo do publikovanja prvih radova u oblasti koja će se kasnije razviti u samostalnu naučnu disciplinu. U 2009. godini Teorija redova čekanja navršava čitav vek od svog nastanka. / The paper presents a short review of histrorical development of the Queueing Theory, also known as Theory of Waiting Lines or Theory of Mass Servicing. We described historical and technological conditions at the time when first Queueing Theory papers were published. The motivation for this report comes from fact that the year 2009 is the 100th birthday of this theory.
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...
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.
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.
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.
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.
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.
Queues and care: how medical residents organize their work in a busy clinic.
Finlay, W; Mutran, E J; Zeitler, R R; Randall, C S
1990-09-01
How do medical residents organize their work in settings where queue demands are heavy and resources are limited? Under such conditions, a queue theory would predict the delivery of care that is indifferent to clients' needs or that gets rid of clients as quickly as possible. In an exploratory case study of medical residents in a Veterans Administration outpatient clinic, we found instead that the medical residents' work was characterized by a high level of professional commitment: they provided thorough medical examinations and attempted to expedite patient care in other ways. We attribute the residents' professional ethos to opportunities provided in the VA hospital to learn the craft of routine medicine and to be directly responsible for patient care; such opportunities were not available in other settings. PMID:2133482
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.