Simple Approximations for Token Rings

Recently, a conservation law for the waiting times at a token ring has been derived. This conservation law is used here to develop simple approximations to the waiting times at individual queues on a token ring. Although exact algorithms are available, they may require significant computation time. In contrast, the approximation developed here is easily calculated on a pocket calculator, and is more accurate than earlier approximations.     

Minimization of Job Waiting Time Variance on Identical Parallel Machines

We consider the problem of scheduling independent jobs on identical parallel machines so as to minimize the waiting time variance of the jobs (Pm//WTV). We show that the optimal value of(Pm//WTV) is identical to the optimal value of the problem for minimizing the completion time variance of jobs on identical parallel machines(Pm//WTV). We prove that, given the same job set, any feasible schedule of (Pm//WTV) can be transformed into the feasible solution for (Pm//WTV) with the same job set by applying the polynomial algorithms proposed in this paper. Several other important properties of (Pm//WTV) are also proved. Heuristic algorithms are proposed to solve (Pm//WTV) problems. We present the testing results of these heuristic algorithms, which are applied to problems with both small and large job sets.     

关于候时抖动最大值的计算

本文提出了全频域内候时抖动最大值和低频候时抖动最大值的计算方法。这些方法经过严格数学论证，其结论简单，易于使用。文中还举例说明了这些方法的应用。     

Flow Control in Local-Area Networks of Interconnected Token Rings

We investigate flow-control issues in local-area networks consisting of multiple token rings interconnected through bridges. To achieve high throughput, bridges perform only a very simple routing and store-and-forward function, but are not involved in error- or flowcontrol. In case of congestion, bridges discard arriving frames, which will be recovered through an appropriate end-to-end protocol between the communicating stations. The end-to-end protocol considered is the IEEE 802.2 type-2 logical-link-control (LLC) protocol. Extensive simulations show that performance can be severely degraded if, in such a network, the LLC protocol is employed as defined today. Therefore, we suggest an enhancement to this protocol in the form of a dynamic flow-control algorithm. As our results demonstrate, this enhancement guarantees close-to-optimal network performance under both normal traffic load and overload conditions.     

候时抖动抑制方法研究

针对正码速调整、正／零／负码速调整和指针调整等，提出并讨论了相应的可以有效减小候时抖动的方法。     

网通上市,择机而发

中国网通作为国有特大型电信运营企业。近期的重组、改制和上市行动引起了普遍关注。此次中国网通上市既有国企改制和竞争压力的宏观背景，又存在外部融资和内部整合的微观目的。然而网通上市的成功与否，很大程度上取决于公司上市方式和卖点。并且，公司上市时机的选择同样重要。此外。网通公司应尽量降低融资成本，将完善公司治理结构作为上市的最终目标。     

脉冲神经网络的时间计算--世界中心识别原理

本文表明传统的基于脉冲平均点火车（averagefiringrate）的人工神经网的全并行计算是不妥的，因为它不能进行时间操作我们提出一个脉冲神经网（Spikingnetwork），对神经计算引入空间搜索机制搜索能够将空间坐标转化为时间坐标这使得空间相对坐标也转化为时间相对坐标利用延迟的连接，神经网能够非常容易地完成时间相对坐标的计算设计了一个以世界为中心的模型（World-centeredMedel，WCM），它由空间搜索器和特征转移向量存储器组成WCM是单纯的神经网络，它代表了不变识别的神经原理     

A Study on Adaptive Time Token Priority-Based Queuing Scheme

Several famous priority-based queuing schemes operated in a gateway to support differentiated services among internet traffic. Examining packet forwarding operations in these queueing schemes, they only support a priority-based service either in a packet enqueuing process or in a packet dequeuing process. If a queuing scheme can support priority-based services in both packet enqueuing/dequeuing processes; it would enhance differentiated service performance for internet traffic. This study proposes a priority-based queuing scheme with an adaptive time token allotment measure to support a differentiated packet forwarding process for different types of IP traffic both in packet enqueuing/dequeuing processes. Depending on packet sizes and packet forwarding priorities of IP traffic, the proposed queuing scheme assigns fix and adaptive time token thresholds dynamically to logical queuing buffers separately. With assigned time tokens, logical queuing buffers allow arrival IP packets to be enqueued in a differentiated way. Moreover, the proposed queuing scheme uses a transferred WRR dequeuing measure to enhance a differentiated packet forwarding process. The simulation results show that the proposed queuing scheme supports a differentiated packet forwarding process for different types of IP traffic. The differentiated packet forwarding performance supported by the proposed scheme is close to the IETF DiffServ scheme; this result shows that the proposed scheme can support differentiated packet forwarding performance for different types of IP traffic with a lower operation cost.     

指针调整过程中候时抖动的减小

本文主要分析SDH的STM通信网中指针调整引起的候时抖动的频谱,并采用两过程法进行指针调整,减小候时抖动。     

Mean and Variance of Overflow Traffic for Time Dependent Inputs

Telecommunications networks have been designed to maintain predetermined service levels for time-varying traffic loads. This inevitably causes redundant investments, and thus, there are possibilities for further economization by adaptively controlling the systems. In order to establish the optimum strategy of controlling telecommunications networks, it is essential to study time dependent traffic characteristics. This paper analyzes a system in which a time-dependent Poisson input is offered to a finite primary trunk group, and the overflow traffic is carried by an infinite secondary trunk group. Methods for calculating the mean and variance of the overflow traffic (the number of calls existing in the secondary group) are proposed, including an approximate evaluation for which accuracy is examined. Calculated examples are given for various time dependent inputs, and properties of the overflow traffic are discussed. The methods and results presented will be useful for analysis and optimum design of the network systems with time dependent traffic.     

周期查询式门限服务排队系统中信息分组的延迟分析

本文采用嵌入马尔可夫链理论和概率母函数的方法，对在离散时间状态下的周期查询式门限服务排队系统进行了分析，推导出信息分组的平均等待时间公式，改进了文献［３］中的计算结果。     

一种具有超短等待时间的ENVoD

提出了一种具有超短等待时间的NVoD改进方案--ENVoD.它将节目划分为子块,以不同的周期在TS流信道中传送,利用接收机内置的硬盘录像功能对子块进行存储播放,显著改善了NVoD系统的最长等待时间.     

Variance Reduction for Particle Filters of Systems With Time Scale Separation

We present a particle filter construction for a system that exhibits time-scale separation. The separation of time scales allows two simplifications that we exploit: 1) the use of the averaging principle for the dimensional reduction of the dynamics for each particle during the prediction step and 2) the factorization of the transition probability for the Rao–Blackwellization of the update step. The resulting particle filter is faster and has smaller variance than the particle filter based on the original system. The method is tested on a multiscale stochastic differential equation and on a multiscale pure jump diffusion motivated by chemical reactions.      

令牌网络中非对称性问题研究

本文采用嵌入马尔可夫链理论和概率母函数的方法，根据循环查询时间变量的二阶特性，在离散时间状态下对非对称性令牌网络进行了分析，给出了一种报文分组平均等待时间的近似解析式，同时也给出了计算机模拟实验结果。     

Mean Waiting Time Analysis in Finite Storage Queues for Wireless Cellular Networks

In this paper priority is assigned to the handover calls over new call attempts and blocked handover calls are placed in a finite storage queue. Total handover forced termination probability is evaluated and a suitable function for the mean service time at each position in the queue is theoretically estimated. Quality of service is obtained by introducing a threshold in the maximum waiting time of a handover call in the queue. In case the handover call mean service time at each queue position is found to be greater than this threshold, this call will be blocked. Simulation results show that this scheme provides satisfactory results for both types of calls. Spiros Louvros was born in Corfu Island, Hellas in 1971. He received his Bachelor in Physics from the University of Crete, Hellas and his Master of Science in telecommunications from the University of Cranfield, U.K. with a graduate scholarship from the Alexandros Onassis Institution. In 2004 he received his PhD from the University of Patras, Hellas, in mobile communications. He has worked for Siemens as a microwave engineer, for Vodafon-Hellas as a switching engineer and for Cosmote S.A. as section manager in the Operations, Maintenance & Optimization Department. His current occupation is in the Telecommunication Systems & Networks Department, Technical University of Messologi, Hellas, as an Assistant Professor. He holds several papers in international journals and conferences and he has participated in several research projects regarding mobile communications. His area of interest is in mobile networks, telecommunication traffic engineering, wireless ATM and optical communications and is documented by over 30 papers in international literature and conference proceedings. He is member of FITCE and Hellenic Physics Union. Gerasimos Pylarinos – Stamatelatos was born in Kefalonia, Greece in 1966. He receieved the B.E. in Electrical and Computer Systems Engineering from Monash University, Melbourne, Australia in 1992 and the B.E. in Electrical and Computer Systems Engineering from the University of Patras, Greece in 1994. He received the M.Sc. in Data Communications Systems from Brunel University, United Kingdom. He is currently pursuing the PhD degree at the University of Patras Greece. He has worked at Philips Radio Communication Systems, Melbourne, Australia developing hardware for mobile radio communication systems for 2 years. He subsequently worked as project manager in the Research and Development department at Intracom Radio Communication Systems, Greece for 7 years. He is now manager of the Biomedical Engineering department of Kefalonia Hospital, Greece. His research interests lie in the areas of 3G and 4G wireless communications. S. Kotsopoulos was born in Argos-Argolidos (Greece) in the year 1952. He received his B.Sc. in Physics in the year 1975 from the University of Thessaloniki, and in the year 1984 got his Diploma in Electrical and Computer Engineering from the University of Patras. He did his postgraduate studies in the University of Bradford in United Kingdom. And he is an M.Phil and Ph.D. holder since 1978 and 1985 correspondingly. Currently he is member of the academic staff of the Department of Electrical and Computer Engineering of the University of Patras and holds the position of Associate Professor. Since 2004, is the Director of the Wireless Telecommunications Laboratory and develops his professional life teaching and doing research in the scientific area of Telecommunications, with interest in mobile communications, interference, satellite communications, telematics applications, communication services and antennae design. Moreover he is the (co)author of the book titled “mobile telephony”. The research activity is documented by more than 160 publications in scientific journals and proceedings of International Conferences. Associate Professor Kotsopoulos has been the leader of several international and many national research projects. Finally, he is member of the Greek Physicists Society and member of the Technical Chamber of Greece.     

Waiting for the rapture

This special report examines the concept and the reality of the singularity. It introduces the articles that comprise this special issue on the subject.     

Hybrid Broadcasting With Small Buffer Demand and Waiting Time for Video-on-Demand Applications

One way to broadcast a popular video is to partition the video into segments, which are transmitted on several channels currently and periodically. The approach lets multiple users share channels, and thus obtains high bandwidth utilization. Many previous studies such as the recursive frequency-splitting (RFS) and harmonic broadcasting schemes focus on decreasing clients' waiting time. Another issue on reduction of clients' buffer demands is also important, especially for the goal to provide video services using limited-capability client devices such as PDAs and set-top boxes (STBs). Related work includes the skyscraper broadcasting (SkB), client-centric approach (CCA), greedy disk-conserving broadcasting (GDB), and reverse fast broadcasting (RFB) schemes. By combining RFS and RFB, this paper designs a hybrid broadcasting scheme (HyB), which exhibits a good tradeoff between client buffering spaces and waiting time. In comparison with SkB, CCA, GDB, RFB, and RFS, HyB requires smallest buffers, only 25% of video size. For waiting time, the scheme also outperforms all the schemes, except RFS.     

An Efficient Transmission Scheme for Minimizing User Waiting Time in Video-On-Demand Systems

To take the advantage of skewed popularity of videos, efficient video-on-demand (VOD) systems are more likely to deliver the most popular videos through periodic broadcasting and the least popular videos through on-demand multicasting. While videos delivered through multicasting usually share a pool of server channels, broadcasting of each video demands one or more channels dedicated to it. Given a total number of available channels, distributing them for individual broadcasting and the multicasting pool to achieve the optimal average user waiting time is a nonlinear optimization problem. This letter addresses this problem by proposing a hybrid transmission scheme, which uses dynamic programming approach to ensure optimally for any given number of channels and request arrival rate     

Minimizing Packet Waiting Time in a Multibeam Satellite System

In this paper, we examine the problem of time-slot assignment in an SS/TDMA system operating in a packet-switched environment. We seek to assign time slots in order to minimize average packet waiting time and in order to maximize transponder utilization. We show that an assignment which achieves both objectives exists and develop a branch-and-bound algorithm to find it. In addition, we suggest several heuristics which require much less computational effort and give very close to optimal results. We derive theoretical bounds on the performance of these heuristics and perform simulation trials to show that, on average, the heuristics are very much better than their bounds suggest, and are, in fact, extremely close to optimal.     

Dependability of a Complex System with General Waiting Time Distributions

This paper considers the possibility of the inclusion of general waiting time distributions for failed system while examining its behavior with regard to dependability. The probabilities that the system is operable, waiting for repair and under repair are obtained. Some particular cases are also discussed in details. The behavior of the complex system under steady state has also been examined. It may be noted that in the particular case when the simple system is put under repair instantaneously the results correspond to those obtained by Hosford [1].