Individual Traffic Characteristics Queueing Systems with Multiple Poisson and Overflow Inputs

A theoretical method for analyzing overflow problems in queueing systems is presented. An interrupted Poisson process (IPP) approximation of overflow traffic is employed. An overflow stream is replaced by an IPP using the three-moment matching method. For a three-input model, to which one Poisson and two IPP streams are offered simultaneously, explicit and iterative formulas are derived to calculate the mean waiting time, overflow probability, and moments of overflow traffic intensity from the system for each of the three input streams. This three-input model is a general one, and can be used for analyzing complex problems such as multistage overflow models and individual traffic characteristics for a model with more than three inputs. By setting the capacity of the waiting room of the three-input model to 0, this method can cover loss systems. For both queueing and loss systems, several numerical examples of typical traffic models are shown. Comparisons are made between theoretical values and experimental values by computer simulations, and it is demonstrated that the accuracy of the method is excellent.     

A Queueing Analysis of Two ARQ Protocols

In every data communication system, a procedure must be provided to allow for the retransmission of data when errors are detected. The receiving node is required to make a (positive/negative) acknowledgment (ACK/NACK) to the sending node. Until an acknowledgment is received, a "copy" of the message must be retained at the sending node. If an ACK is received, the space assigned to the "copy" is released. If either a NACK or no acknowledgment is received in a suitable interval of time, retransmission is required. Different protocols specifying how the nodes recover from a transmission error can be defined. In this paper, we present a queueing analysis of the two ARQ (automatic repeat request) protocols-block and select ARQ-for a (slotted) concentrator network node.     

Queueing Systems with Stochastic Time out

In this paper, formulas are derived for queueing systems where the delayed customers are controlled by a stochastic time out, i.e., the delays are limited by a timeTthat is drawn from a general probability distribution. Formulas are also worked out for the case of a limitation of the time spent in the total system (queue + servers). In order to simplify numerical calculations, an approximate method is worked out and numerical examples are shown.     

两类特殊光学系统的光路计算

本文针对包含圆柱面和圆锥面的光学系统,讨论其光路的解析计算。指出一般迭代逼近方法的弊端,阐述了自动优选最佳像面的程序设计思想,列举了实例。     

信息技术呼唤培养新型人才

在综合探讨信息技术对国民经济以及军事的影响的基础上,提出要设置通讯系统工程系及相应的新专业,以培养新型信息人才。     

Stabilization of Interconnected Discrete Systems with Quantization and Overflow Nonlinearities

In this paper, we address the problem of decentralized feedback control design for a class of linear interconnected discrete-time systems subject to quantization and overflow nonlinearities and unknown-but-bounded couplings. A decentralized quantized state feedback controller is designed at the subsystem level to render the closed-loop system asymptotically stable. When the local output measurements are available, a decentralized output-feedback quantized controller is developed attain similar asymptotic stability and guaranteed performance of the closed-loop quantized system. Several special cases of interest are derived and simulation results are provided.     

Transient Analysis of Markovian Queueing Systems and Its Application to Congestion-Control Modeling

In applied queueing theory, it is often important to deal with transient system behavior. Performance evaluation of congestioncontrol mechanisms in a packet-switching network is an excellent example in which there is frequently a strong need to deal with the intrinsic dynamic character of congestion. In that case, the queueing models have to be analyzed for a transient environment. In this paper, we show that such problems can be treated in a uniform way, when the system of coupled differential equations describing the system-state or flow process is solved numerically. For this, the fourth-order RungeKutta procedure allows a good balance between memory requirements, computing time, and accuracy. To illustrate the explanatory power of this kind of transient queueing analysis, three models will be considered: the common-store queueing system showing the priority deadlock, the foreground-background congestion-control mechanism, and a two-level global congestion-control mechanism.     

A Performance Model for Loss Systems with Crisis Calls

In this paper a mathematical model is developed for the performance of crisis calls. In such a system, a finite number of crisis calls attempt to use a communication link that has been receiving ordinary calls. The performance of the link with respect to the crisis calls is analyzed and studied. A numerical analysis is conducted to determine the behavior of the crisis calls under various scenarios. Some simple upper and lower bounds on the blocking and loss probabilities for crisis calls are given.     

Task-Oriented Queueing: An Analysis Tool for Software Design of Communication Processing Systems

Jobs associated with messages arriving to a communication processing system (CPS) can be described as ordered sets of prioritized tasks, where each task represents the execution of some part of the system's software. The service system of the CPS consists of a collection of queues, one for each distinct priority, serviced by a single server under a preemptive resume discipline. The routing of the job through this collection of queues is defined by a job's priority vector which specifies the priority at which each task in the job is to execute. For example, if a two-task job's priority vector is (3, 2), then the job first joins the priority 3 queue, obtains service for the first task, then joins the priority 2 queue. In a previous paper, the author and a colleague described a method through which average delays in such task-oriented processing systems could be computed for the special case in which all jobs have identical structure. This paper presents a substantially simplified version of the analysis methodology presented previously and extends that work to the case of a finite number of job classes, each job class having a finite number of tasks.     

Simple Derivation of Queueing Formulas for Loop Systems

Some queueing theory formulas for loop systems with random slot seizure previously obtained by the author via a lengthy series of derivations are shown to follow immediately from priority queueing formulas derived by Takács if an appropriate artifice is used to make Takács' results applicable.     

Comments on "Discrete-Time Queueing Systems and Their Networks"

In the paper Bharath-Kumar presented an analysis of a discrete buffered system of infinite capacity, where the length of the packets is drawn from a geometric distribution and the packets leaving the resource have to be retransmitted with some probability. In this correspondence an analysis of the same system is given which applies for a general packet length distribution, and where the length of a packet remains the same each time it is retransmitted, as opposed to Bharath-Kumar's model where the retransmission packet lengths are independently chosen.     

基于FPGA的两种DDS实现

阐述了两种DDS的原理,频率合成方式（DDFS）和直读方式（DDWS）,给出了FPGA实现方式,分析了DDS的几个关键的技术指标,并通过Matlab仿真。频率合成方式是比较常用的DDS产生方式,对它做了详细的原理性介绍和实现说明,重点通过仿真详细对比了两种实现方式在性能指标上的优劣,为后人的选择提供技术参考。     

两种新型泵浦腔结构片状激光放大器性能分析

介绍了两种新型闪光灯泵浦的不同泵浦腔构型片状激光放大器的结构组成,利用行波法对两种放大器的增益性能进行了实验测试,实验结果表明,采用模块化设计的阵列式片状放大器（MSA）比单口径片状放大器（SSA）具有更高的能量转换效率和增益能力。     

两种晶体管饱和输出状态的比较分析

在高校的数字电路课程教学中,通常要对分立NPN晶体管和TTL门电路的低电平输出近饱和、饱和以及退饱和状态进行讲解,其中出现了貌似矛盾的现象.本文给出了两种情况下的比较分析,力图廓清对它们模棱两可的理解,并尝试给出了被动饱和与主动饱和两个新概念,建议了更为合理的饱和深度的定量表达式,以期对相关的教学以及教材编...     

基于两种通信体系的ADSL技术分析

不对称数字用户线ADSL技术作为实现宽带接入的解决方案,现阶段技术上已趋成熟、在应用上得到了很大的发展。本文对两种基于不同网络的ADSL高速接入分别做了技术分析,并对其特点进行了对比。     

Modeling and Simulation of Mixed Queueing and Loss Systems

In this paper, we investigate a multi-rate network in which wide-band calls are allowed to wait if insufficient resources are available at the time of the call arrival. On the link level, an analytical model is presented and simulations have been carried out on the network level. The results indicate that allowing a few wide-band calls to queue can give a significant improvement in performance in terms of network revenue , as well as a means to level out the blocking probabilities of the different traffic classes. This improvement becomes significant when the service discipline of the waiting calls (of different bandwidth requirements) is adaptive in the sense that longer queues get served first. This observation motivates the investigation of the impact of various buffer space assignment and queueing disciplines on network revenue and call blocking probabilities. The study of such mixed delay and queueing networks is motivated by its possible applications to traffic problems in future Broadband Integrated Services Digital Networks as well as in multi-rate cellular radio networks.     

两种高密度声频光盘

激光唱片（ComPactDisc,即CD）问世已近17年了,由于它的优美逼真的音质、完备多样的功能、方便灵活的操作、小巧精致的外形,是以往的密纹唱片（【P,＊P）无法比拟的,因而赢得了人们的喜爱,使密纹唱片很快趋于淘汰。据报道,全世界c累计生产了5亿台CD唱机和约100亿张...     

两种双频微带天线的分析与设计

首先结合软件设计并测试一种双层双频微带天线,然后介绍了一种改进的采用单模馈电的双频微带天线,通过原理分析和最后给出的驻波曲线验证了这种改进的可行性。     

两种用于SOC设计中的PCI Core的研究

PCI Local Bus是广泛使用的一种局部总线规范,也是一种工业标准。在IC设计中选择合适的PCI Core是十分重要的。文章对ALTERA和XILINX公司提供的PCI Core的功能指标、接口和参考设计作了比较,指出了两个公司PCI Core的特点。     

ATM交换中输入输出开窗排队算法的改进

本文为ＡＴＭ交换系统提出了一种改进的输入输出开窗算法，通过在原有输入开窗排队算法中引入因子Ｐｓ，改进算法允许至多Ｐｓ个信元同时到达同一输出口，并利用输入输出缓冲队列来减缓输出碰撞，改进的开窗算法不仅能得到几科与输出排队一亲的最优吞吐和延迟性能，还具有好得多的分组单元丢失性能，尤其适合缓冲容量有限的情形，因而不失为一有效的ＡＴＭ交换系统设计方案，本文讨论了算法及其复杂度分析，给出了计算机仿真的性能结