Performance analysis of circuit-switched networks withstate-dependent routing

A novel nonhierarchical dynamic routing technique called state-dependent routing (SDR) is studied. SDR uses traffic measurements and statistics to produce its call by call routing decisions. The SDR scheme has a two-level, two-time scale structure. The algorithm for evaluating the performance of networks using SDR, is based on analytical models for the fast and slow stages that capture the behavior of the network at the link level and the node-pair level, respectively. Very good results were obtained for both small and large networks, especially in the performance range that is useful for design purposes     

Analysis of rerouting in circuit-switched networks

Dynamic routing has been adopted in circuit-switched networks in many parts of the world. Most of the routing algorithms used are least loaded routing (LLR) based for its simplicity and efficiency. Rerouting is the practice of routing calls on alternate paths back to direct paths or to other less congested alternate paths. It allows the continuous redistribution of network loads for the relief of the congestion on direct paths. In this paper, we present an original analysis of an LLR-based rerouting scheme. Through numerical examples and confirmation by computer simulation, the throughput gain of rerouting is established     

A mutual alternative routing model for circuit-switched networks

Security measures are being applied in the Telecom Eireann trunk telephone network to minimise disruption due to excess traffic or system failure. Dynamic measures, such as network management, will be deployed in the very near future, but in the meantime static measures are being applied. Geographically separate exchanges of the same status are provided at major nodes with traffic shared equally between them on separate transmission links. Rerouting is provided automatically when a system fails, but at a reduced grade of service. The paper presents a model which simulates this concept of mutual alternative routing using the UNIX-based OPNET (Optimised Network Engineering Tools) package     

A taxonomy of rerouting in circuit-switched networks

In circuit-switched networks it is well known that dynamic routing can provide significant throughput gain over fixed routing. Rerouting is the practice of routing calls currently on alternate paths to direct paths or other less congested alternate paths. Previous studies have shown that rerouting can not only increase the throughput of dynamic routing, but also maintain network stability without the need for trunk reservation. This article presents a taxonomy of rerouting in circuit-switched networks showing the various ways rerouting can be designed. In addition, a comparative study on a number of rerouting schemes are performed in a uniformly loaded, fully connected circuit-switched network     

General criterion for decomposition of exact blocking computationin circuit-switched networks

The criterion for the decomposition of the computation of blocking probabilities in circuit-switched networks is given. As the criterion does not depend on the network topology or the traffic distribution, more efficient decomposition can be obtained accordingly     

Comparative evaluations of randomized and dynamic routingstrategies for circuit-switched networks

The performances of two classes of routing algorithms, randomized and deterministic, are evaluated and compared in terms of revenue generated and link failures. The randomized algorithm evaluated is dynamic alternate routing, and for the deterministic algorithm, attempts to carry a call are made in a specific precomputed order. The design of the routing sequences depends upon analytic approximations based on fixed-point equations to evaluate network performance and heuristics for the complicated problem of network revenue maximization. The control mechanism of trunk reservations is shown to play an important role in all cases. The performances of the algorithms were evaluated on a fully connected six-node network, the data for which were extracted from a realistic network. The design tools, time constants of various algorithms, and hybrid algorithms developed using the evaluation results are described     

New queueing strategies employing service interval-based priority for real-time communications in atm networks

In this paper, we propose queueing strategies employing the service interval-based priority (sip) which can provide delay-bounded, and loss-free services, while maximizing bandwidth utilization in the atm network. We also describe a variation of the sip, the residual service interval-based priority (rsip) which can achieve almost full utilization by assigning priorities dynamically on the basis of the residual service interval. We store the realtime cells belonging to different connections in logically separated queues, and for each queue, we set a parameter called service interval, during which only one cell is allowed to be transmitted. The sip server takes and transmits the head-of-line (hol) cell of the queue which has the smallest service interval, while the rsip server selects the queue with the smallest residual service interval. When there is no eligible real-time cell, it transmits non-real-time cell, thus enabling a maximized bandwidth utilization. Employing the above queueing strategies, we analyze the delay characteristics deterministically with the leaky bucket bounded input traffic and then dimension the optimal service interval. In dimensioning the service interval and buffer space of each real-time service queue, we consider burstiness of traffic in conjunction with delay constraints, so that bandwidth utilization can get maximized. In addition, we consider the issues of protection from malicious users, average bandwidth utilization, and coupling between the delay bound and the bandwidth allocation granularity.     

湖南省公用IP网络的优化策略

IP网络的现状及面临的问题目前,湖南电信的IP网络包括省干IP网络和本地IP网络(窄带拨号、宽带IP)两部分,主要采用IP路由技术、以太网交换技术、POS技术、xDSL技术等组建IP网络。省干IP网络主要采用Cisco的GSR系列路由器,利用POS技术,通过双星型结构、主备2.5G/155M链路组建。所有传送链路都由省干DWDM网承载,因此省干IP的扩展能力、增值业务的开放能力都较强,能够满足业务发展的需求。本地IP网络由窄带拨号网络和宽带IP城域网两个部分组成。窄带拨号网络通过PSTN网络的直达中继电路与拨号服务器连接,主要采用7号信令实现…     

Behaviour of circuit-switched multistage networks in presence of memory hot spot

Addresses the important problem of evaluating the performance of tightly coupled multiprocessor systems under memory hot spot traffic by presenting an interference analysis of multistage interconnection networks (MINs) for such systems. It is shown that the tree saturation effect does not occur in nonblocking circuit-switched MINs.<>     

Very-high-speed fibre-optic networks for broadband communications

Single-mode optical fibres have an enormous transmission bandwidth which can support ultra-high-speed digital transmission and networking. The use of electrical signal-processing, however, ultimately limits the network capacity. To eliminate the throughput bottleneck, all-optical processing techniques should be employed in a fibre-optic network. This paper discusses several schemes for implementing optical time division multiple access (OTDMA) networks with the emphasis on optical clock distribution, synchronisation and all-optical detection. The use of a fast-switching bistable laser diode as an all-optical threshold detector and data regenerator is suggested. A dual-wavelength OTDMA technique is investigated, which can be used for digital TV or future HDTV distributions. Moreover, an efficient multiple access scheme, called wavelength division multiple access with optical time division multiplexing (WDMA-OTDM), is proposed for broadband communication services. It is shown that WDMA-OTDM has all the advantages possessed by the individual OTDMA and WDMA schemes but offers improved flexibility and capacity     

Feedback strategies for a class of two-user multiple-accesschannels

Feedback strategies are presented for the class of two-user discrete memoryless multiple-access channels for which one of the inputs to the channel is determined by the second input and the channel output. The strategies achieve any rate point inside the capacity region of these channels     

Cognitive radio networks for green wireless communications: an overview

As power consumption results in greenhouse gas emissions and energy costs for operators, analyzing power consumption in wireless networks and portable devices is of crutial importance. Due to environmental effects resulted from energy generation and exploitation as well as the cost of surging energy, energy-aware wireless systems attract unprecedented attention. Cognitive Radio (CR) is one of the optimal solutions that allows for energy savings on both the networks and devices. Thus, cognitive radio contributes to increase spectral and energy efficiency as well as reduction in power consumption. In addition, energy consumption of the CR technologies as intelligent technology should be considered to realize the green networks objective. In this article, we look into energy efficiency of the cognitive wireless network paradigms. Moreover, energy efficiency analysis and modelling in these systems are specifically focused on achieving green communications objectives. However, CRs by altering all elements of wireless data communications are considered in this paper, and the energy-efficient operation and energy efficiency enabler perspectives of CRs are also analyzed.

     

Optical signal processing for lightwave communications networks

A number of optical signal processing functions that might be potentially important for future lightwave communication networks are described. An optical network with a distribution capacity of 100 HDTV channels is considered along with how such a network can be implemented using the following functional subsystems: frequency converters; transmitter banks; modified (wavelength division multiplexing) WDM demultiplexers; and tunable optical receivers. Discussed are the key network-level issues: the power budget, the channel separation, and the overall rationale for selection of multiplexing techniques. A hardware implementation of the functional subsystems using three basic building blocks-tunable amplifiers/filters, phase locked loops, and comb generators-is discussed     

On location management for personal communications networks

Personal communications services (PCS) support mobile terminals (MTs) which are free to travel within the service coverage area. In order to effectively locate an MT when a called is initiated, location management schemes are used to keep track of the locations of the MTs. The current approach to location management requires each MT to report its location to the network periodically. The location information is then stored in databases. When a call is initiated. The network determines the current location of the called MT through a database lookup and paging procedure. A currently available standard for location management is described. Research results on location management are surveyed in detail     

Using a packet switch for circuit-switched traffic: a queueingsystem with periodic input traffic

Consideration is given to the effects of time-multiplexed stream traffic on the performance of a store-and-forward packet switch. Substantially reducing the amount of buffering in the switch results in only a small probability that an existing circuit will be disrupted during the length of its connection. For example, with a circuit-switched frame of length 1000 and 100% loading, reducing the buffer size from 999 packets to 83 results in only a 10^-6 circuit-disruption probability