排队系统仿真及应用

根据排队论的单窗口和多窗口排队模型,利用MATLAB语言对模型进行仿真.仿真结果表明,多窗口混合制排队模型优于单窗口模型,适合在现代通信网中加以应用.     

基于排队模型的教务管理系统的资源优化分析

介绍了排队论的基本概念,讨论和研究多服务台排队模型的过程和基本原理,通过数学计算得出多服务员排队模型在教务管理系统中重要的运行指标,编程实现系统服务台的优化。     

基于分层排队网络模型的MCU性能预测及优化研究

针对视频会议系统中的多点控制单元(MCU)提出了一个基于分层排队网络模型的性能预测方法．通过对分层排队网络模型进行扩展，建立了多点控制单元的分层排队模型．设计了一个仿真程序对模型进行评价，仿真程序的输入即模型配置文件．该方法可以较快地从多种设计方案或硬件平台中选择满足系统性能设计目标的软件或硬件配置．仿真结果显示，选择双处理器配置和采用多线程技术，多点控制单元的接入容量提高了50％．最后，多点控制单元终端接入实验证明了该方法的有效性。     

预警机引导下的编队协同作战仿真分析

关于预警机指挥编队协同作战提高作战能力问题,结合排队算法,构建了预警机指挥引导编队协同作战的排队模型.将预警机引导的作战编队看作一个整体,分析了作战效能与来袭目标到达时间间隔、编队成员火力转移时间以及预警机引导编队成员数目之间的关系.根据排队模型,并结合预警机的自身特点,对影响因素进行了仿真.仿真结果为提高预警机指挥引导下的编队协同作战效能了提供了方向,并为实际作战提供了重要参考依据.     

排队模型的计算机模拟

排队系统是离散事件系统中最典型的问题。计算机模拟是求解排队系统和分析排队系统性能的非常有效的方法。通过对高速路收费站车辆排队问题的模拟，建立了不同的三类计算机模拟模型。并给出了其中一种单队列、多服务台（并联）的排队模型在高速路收费站车辆调度中的应用。     

关于机场出租车上客区排队管理模型

出租车是机场接驳的主要的交通工具之一，但是机场出租车管理不佳导致接驳效率在极端情况下极低的情况时有发生，对司机和乘客都造成了安全与利益上的冲突。通过数学建模，合理化设置行人上车点，并通过在两条车道上设置不同数量的泊车位置与规定不同的人车放行策略，建立了适合人流量较少机场的错列式排队模型与适合人流量较大机场的交叉式排队模型，提高出租车泊位的运行效率，满足短时间疏散客流的要求，并提高乘客乘车效率。     

高性能路由器输入排队模型的研究与实现

目前基于输入队列技术的路由器研究日益活跃。本文讨论了路由器的交换方式、阻塞问题、调度算法等设计高速路由器的输入排队模型时所要考虑的关键问题,通过对相关的技术进行比较和选择,给出了一个交换式高速路由器中输入排队模型的设计方案。     

门诊动态溢流排队系统感性和理性退出率分析

在现实医疗服务中,面对医生座席数量供不应求的现状,采用传统的双队列独立排队系统很难高效利用医院资源。对此,在不改变医院现有资源的情况下设置系统动态用来合理配比各门诊患者容量,在传统双队列独立排队系统的基础上建立动态溢流门诊排队生灭模型,并考虑患者在感性与理性因素下退出系统的概率,便于更准确地分析系统的真实状态。借助ProModel这一灵活、可靠的离散事件仿真软件,将模型可视化研究,并与传统的门诊排队模型进行对比分析。仿真结果显示,新型排队模型的队列平均长度、患者等待时间等服务指标均优于传统的排队模型。     

IEEE 802.16e节能类型III的性能分析

基于IEEE 802.16e节能类型III的工作原理,考虑用户触发数据的无后效性,建立一个带有多重休假的Geom/G/1排队模型。利用嵌入式马尔可夫链方法推导出该排队系统的稳态指标,相应给出数据帧平均响应时间、能量节省率等性能指标的表达式。构造一个综合考虑能量节省与系统响应时间的成本函数,通过数值例子说明系统性能指标对休眠窗口长度的依赖关系,给出不同负载下休眠窗口长度的最优值。     

提高路由器性能的排队方法

文简单介绍了路由器的体系结构,以及数据交换的路径和方法。并且以ＣＩＳＣＯ公司路由器为例,介绍端口采用的排队模型。针对于阻塞状态,提出了一种可以提高性能的排队模型。     

基于FARIMA模型的网络排队性能分析

利用能够同时反映通信量长程和短程相关性的FARIMA模型，研究了长程相关和短程相关对于FIFO排队系统性能的影响，讨论了在给定系统缓存溢出概率条件下，FARIMA模型为输入时，排队队长分布的渐近解析表达式。研究表明，短程相关性在缓存较小时，对系统队长分布会有影响，但是在自相似存在的情况下，系统的排队长度分布为渐近Weibull分布，与通信量的短程相关性无关。蒙特卡罗仿真分析表明了结果的正确性和有效性。     

Managing Internet routers congested links with a Kohonen-RED queue

The behaviour of the TCP AIMD algorithm is known to cause queue length oscillations when congestion occurs at a router output link. Indeed, due to these queueing variations, end-to-end applications experience large delay jitter. Many studies have proposed efficient active queue management (AQM) mechanisms in order to reduce queue oscillations and stabilize the queue length. These AQM attempt to improve the random early detection (RED) model. Unfortunately, these enhancements do not react in a similar manner for various network conditions and are strongly sensitive to their initial setting parameters. Although this paper proposes a solution to overcome the difficulties of configuring the RED parameters by using a Kohonen neural network model; another goal of this study is to investigate whether cognitive intelligence could be placed in the core network to solve such stability problem. In our context, we use results from the neural network area to demonstrate that our proposal, named Kohonen-RED (KRED), enables a stable queue length without complex parameters setting or passive measurements to obtain a correct configuration.     

On the diffusion approximation to two parallel queues withprocessor sharing

A two-dimensional queuing model is considered in which the server in the second queue helps the server in the first queue during periods when the second queue is empty. The system is analyzed in the heavy traffic limit and explicit approximate solutions are obtained to the resulting diffusion equations using singular perturbation methods. Approximate asymptotic formulas are obtained for the stationary distribution of the number of customers as well as for some first-passage-time problems associated with the busy period. It is shown that these formulas reduce to the asymptotic expansions of the exact solutions, when the latter are available     

基于离散时间排队的ARQ性能分析

基于自动请求重传(ARQ)协议的工作原理,提出基于离散时间带有启动机制的Geom/G/1排队模型。使用嵌入马尔可夫链方法推导出排队系统的稳态队长、等待时间、忙期和忙循环等性能指标的解析表达式,给出ARQ协议中数据帧的平均响应时间、信道利用率、系统吞吐量等性能指标的解析表达式。利用仿真工具Matlab进行计算机仿真,数值例子证明了性能指标解析表达式的正确性。     

Sticky States in Banyan Network Queues and Their Application to Analysis

A finite-buffered banyan network analysis technique designed to model networks at high traffic loads is presented. The technique specially models two states of the network queues: queue empty and queue congested (roughly, zero or one slots free). A congested queue tends to stay congested because packets bound for the queue accumulate in the previous stage. The expected duration of this state is computed using a probabilistic model of a switching module feeding the congested queue. A technique for finding a lower arrival rate to an empty queue is also described. The queues themselves are modeled using independent Markov chains with an additional congested state added. The new analysis technique is novel in its modeling the higher arrival rate to a congested queue and a lower arrival rate to an empty queue. Comparison of queue state distributions obtained with the analysis and simulation shows that an important feature of congestion is modeled.     

天线交换柜系统网络性能的测试评估

在嵌入式天线交换柜系统设计过程中，由于资源有限，不能无限制的增强系统的处理能力，又不能使系统的吞吐率太低，使应用程序无法正常运转，系统性能与资源使用率如何最佳配置是一个问题。本文根据排队论中的开环排队网络模型，将嵌入式天线交换柜系统抽象为一个排队服务系统，而将网络上到达的数据作为顾客，这些顾客的到来是符合一定的概率分布的，这样就可以根据系统要达到的性能推算出系统资源的配置方案，同时也可以确定系统相应的目标参量，根据这个方案来分配系统资源可以达到性能和资源最优组合。     

Queueing systems with random service rate

We consider a queue with the arrival process, the service time process and the service rate process as regenerative processes. We provide conditions for its stability, rates of convergence, finiteness of moments and functional limit theorems. This queue can model a queue serving ABR and UBR traffic in an ATM switch; a multiple access channel with TDMA or CDMA protocol and fading; a queue holding best effort or controlled and guaranteed traffic in a router in the integrated service architecture (ISA) of IP-based Internet and a scheduler in the router of a differentiated service architecture. In the process we also provide results for a queue with a leaky bucket controlled bandwidth scheduler. This result is of independent interest. We extend these results to feed-forward networks of queues. We also obtain the results when the arrival rate to the queue can be feedback controlled based on the congestion information in the queue (as in ABR service in the ATM networks or in the real time applications controlled by RTCP protocol in the Internet).     

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

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.     

主动队列管理算法性能分析通用仿真模型

主动队列管理算法提供因特网中网络拥塞规避和控制机制,是因特网中分组转发设备的重要功能模块。文章提出在网络仿真工具OPNET Modeler下搭建一种通用的网络仿真模型,通过该模型来对不同的主动队列管理算法进行性能评估和分析。通过对RED和LQD算法的仿真,表明了该模型的有效性和通用性。文章也给出了在该模型下实现新的队列管理算法的步骤。该模型为评估不同的主动队列管理算法提供了重要的平台,有助于下一代因特网路由器中缓存队列管理模块的设计。     

控制排队长度的高密度路网信号优化模型

为了提高高密度路网地区的交通管理水平,针对高密度路网特点,提出了一种分布式信号控制模型,用于控制交叉口的排队管理.该模型建立了多目标函数,包括了平均出行延误最小和平均排队占比最小;模型约束包括了排队长度估计、信号控制参数约束.此外,为了避免排队回流现象的产生,还建立了具有高优先级的排队回流约束.仿真结果表明,该模型提高了高密度路网地区的交通通行效率,并有效避免交叉口排队回流现象.