OTDM-based optical communications networks at 160 Gbit/s and beyond

The virtually unlimited bandwidth of optical fibers has caused a great increase in data transmission speed over the past decade and, hence, stimulated high-demand multimedia services. Nowadays, opto-electronic conversion is still required at each network node to process the incoming signal. However, when the single channel bit rate increases beyond electronic speed limit, optical time division multiplexing (OTDM) becomes a forced choice, and all-optical processing must be performed to extract the information from the incoming packet. In this paper the state of art, the advantages and drawbacks of the OTDM technology will be discussed in order to highlight its potentialities in different application scenarios for optical communications networks, and its perspectives in different temporal horizons. In detail, a recent experiment of a 160 Gbit/s OTDM system is presented. Furthermore, a photonic node architecture suitable for optical packet switching networks is proposed, and possible solutions for the implementation of all the required subsystems are presented and compared in order to optimize the node performance. In particular innovative schemes for optical add/drop multiplexer, optical logic gates, optical switches, and optical flip-flop are introduced with a particular emphasis on emerging nonlinear materials and enabling technologies.     

Electrical ingress buffering and traffic aggregation for opticalpacket switching and their effect on TCP-level performance in opticalmesh networks

The wide deployment of wavelength-division multiplexing technology and new transmission techniques have resulted in significant increases in the transmission capacity in optical fibers, both in the number of wavelengths and the bandwidth of each wavelength channel. Meanwhile, the fast growth of the Internet demands more data switching capacity in the network in order to deliver high bandwidth to end users. Although the capacity of electronic routers has been increasing consistently in the past, optical switching appears to be a more cost-effective way to switch individual wavelengths. As the bit rate per wavelength channel continues to grow, optical subwavelength switching emerges as a new paradigm capable of dynamically delivering the vast bandwidth WDM offers. This article discusses one of such techniques, namely optical packet switching, and its performance perceived by end users in optical mesh networks. Specifically, our investigation reveals the benefit of using electrical ingress buffering and traffic aggregation to reduce packet-loss rate of optical packet-switched networks. Through simulation experiments, we present an evaluation of the network's TCP-level performance based on the proposed architecture     

A Distributed Experimental Communications System

The packet experimental communications system (packet XCS) is a new experimental voice and data switch. It uses a local-area network (LAN) for digital voice transmission, with local intelligence for switching. The packet XCS also has highly distributed control. The individual sites cooperate to provide user services as well as internal data management. We have learned that several local networks, including CSMA/CD networks, can be made to work well for voice transmission and that highly distributed control is practical in such a system. A system has been constructed which is used as a testbed for distributed voice and data communications experiments. This system is purely for experimentation and does not indicate a direction for future Bell System product offerings.     

Commercial, legal, and international aspects of packet communications

Packet switching technology emerged rapidly in the 1970's as another viable mode of communications switching, along with circuit and message switching. Since packet switching offers economical and versatile data communication capabilities in a multiuser environment, it is particularly well suited for furnishing public data communication network services. Public packet networks are now established or being developed in most industrialized countries, and the introduction of these networks has raised policy issues relating to the structure and regulation of the national networks, and the interconnection of national networks into an international packet switching system. This paper reviews these issues and concludes that public packet switching network services will continue to be regulated in all cases; that competitive packet networks will coexist in the U.S. and in Canada, but that only one national packet network will exist in each of most other countries; that packet networks will aggravate the problem of distinguishing nonregulated data processing services from regulated data communication services; that international interconnection of public packet networks based upon CCITT standanh will occur rapidly over the next several years; and that a unified international packet switching system will eventually emerge similar to today's international telephone and telex systems.     

Security in Wireless Communication

Security is a critical issue in mobile radio applications both forthe users and providers of such systems. Although the same may besaid of all communications systems, mobile application havespecial requirements and vulnerabilities, and are therefore ofspecial concern. Emerging wireless networks share many commoncharacteristics with traditional wire-line networks such as publicswitch telephone/data networks, and hence many security issueswith the wire-line networks also apply to the wirelessenvironment. However the integration of security features intowireless communication must take into account restrictions thatmay apply to their use such as small packet size, low bandwidth,high transmission costs, limited processing and storage resourcesand real time constraints. In this paper security requirements inwireless communications along with security features in 2G and 3Gsystems are described.     

Unified approaches to integrated-service networks–burst and fast packet switching

The increasing demand for communication services, coupled with recent technological advances in communication media and switching techniques, has resulted in a proliferation of new and expanded services. Currently, networks are needed which can transmit voice, data and video services in an application-independent fashion. Unified approaches employ a single switching technique across the entire network bandwidth, thus allowing services to be switched in an application-independent manner. This paper presents a taxonomy of integrated-service networks, including a look at NISDN, while focusing on unified approaches to integrated-service networks. The two most promising unified approaches are burst and fast packet switching. Burst switching is a circuit switching-based approach which allocates channel bandwidth to a connection only during the transmission of ‘bursts’ of information. Fast packet switching is a packet switching-based approach which can be characterized by very high transmission rates on network links and simple, hard-wired protocols which match the rapid channel speed of the network. Both approaches are being proposed as possible implementations for integrated-service networks. We survey these two approaches, and also examine the key performance issues found in fast packet switching. We then present the results of a simulation study of a fast packet switching network.     

The telephone network of the 1960s

In 1960 the transmission technology of the public switched telephone network was ordinary cable pairs, carrier systems on both paired and coaxial cable, and point-to-point microwave radio systems. Voice signals were frequency multiplexed for efficient transmission, but remained in analog form from end to end of a connection. Electromechanical switching systems provided circuit-switched connections, and about half of the customers could directly dial long distance calls. The following decade saw the beginnings of electronic switching and direct distance dialing on a global basis. Meanwhile, applying digital technology to achieve lower costs and better quality for voice transport began in earnest, and the interconnection of data terminals and computer centers became an increasingly important communications need. The initial data communications approach, still used with ever increasing sophistication and speed, was to convert data to speech-like form with data modems. Later, the direct connection of digital data to digital network facilities became the method of choice for building computer communications networks and the backbone of the Internet. It now appears likely that one day all signals, including voice, will be transported by unified high-speed digital networks with a common set of protocols     

Performance evaluation of a protocol for packet radio network in mobile computer communications

The need to provide computer network access to mobile terminals and computer communications in the mobile environment has stimulated and motivated the current developments in this area. Packet radio technology has developed over the past decade in response to the need for real-time, interactive communications among mobile users and shared computer resources. In computer communication systems we have a great need for sharing expensive resources among a collection of high peak-to-average (i.e., bursty) users. Packet radio networks provide an effective way to interconnect fixed and mobile resources. The results of an attempt to study the performance of the mobile packet radio network for computer communications over degraded channels are presented. We develop a model under fading conditions and derive a protocol for evaluating the performance of the mobile packet radio network (MPRNET) in terms of the packet error rate, packet delay, throughput and average number of retransmitted packets per cycle. The analytical results are presented and numerical examples are given to illustrate the behavior of these performance criteria as a function of packet transmission rate, packets transmitted per cycle, packet size, and vehicle speed with the help of appropriate plots.     

The evolving art of packet switching

Rapid developments in computer and information technology continue to expose new requirements for switched data services, e.g. teletext, electronic funds transfer, electronic mail. The features of packet switching make it attractive for many of these new services, and many countries, including the UK, now operate or plan to introduce public packet-switched data networks. But packet switching is a relatively new art, particularly in the realm of public-switched networks, and is itself developing rapidly, driven both by the increasing demand for switched data services and by advances in semiconductor technology. It tends therefore to be the preserve of a relatively small band of specialists. This paper reviews the principles, origins and evolution of packet switching, with particular reference to public-switched networks. The picture emerges of well laid foundations and the prospect of rapid expansion in public packet-switched networks throughout the world. The development of large switches, such as those being developed at BTRL, will play an important part in this.     

分组网络上的视频流传输面临的挑战及对策

视频已成为通信、娱乐中十分重要的媒介，视频流传输在因特网上得到了快速发展及广泛应用。分组网络所呈现出的异构性、时变性等本质属性，使得基于分组网络的视频流传输面临许多挑战。首先，当分组从一个节点传输到另一个节点时，由于其所经历的实际网络路径不同，路由器及通信信道的性能和表示这些分组连接的参数(如带宽、分组丢失概率及分组延迟)也会彼此不同。甚至会出现几个数量级大的差异。此外，上述参数还会随着时间发生变化。本从端主机的角度出发，分析在分组网络视频流传输过程中面临的挑战，并提出相应对策。     

Tree-type photonic switching networks

The enormous bandwidth offered by optical systems makes photonic switching a very attractive solution for broadband communications. Tree-type architectures play an important role in the design of photonic switching networks. The authors present and discuss all known tree-type space-division photonic switching networks architectures in a unified framework, and propose a number of new solutions. The discussed networks can be implemented with guided-wave-based switching elements, or laser diodes and passive splitters and combiners. The following network types are considered: conventional, simplified, and two-active stage networks. Techniques for improving SNR as well as waveguide crossover minimization are presented and discussed     

Evolution of Terrestrial Optical System and Core Network Architecture

Optical systems and technologies have been radically changing the telecommunication networks for past 15 years; today wavelength division multiplexing (WDM) technology, optical amplifiers, and simple optical switching elements like optical add-drop multiplexers (OADMs) are used in the backbone networks of all operators worldwide. Optical systems nowadays provide the basis for cost-effective transmission of large amounts of bandwidth over the Internet, and will enable its future growth and the spreading of new applications and services. This paper summarizes the main trends in optical networking and investigates potential future application areas. Optical system technology has become so pervasive in network design that it needs to be considered in the context of provisioning new applications and services. Therefore, the analysis is not limited to the aspects of physical transmission, but also takes into account recent developments in integrated network design as well as network control and management. The following sections describe the key functionalities of future optical network architectures, and the key findings of the theoretical analysis are supported by the results of a field trial of advanced transmission technology.     

Economic analysis of integrated voice and data networks: A case study

This paper describes the results of a study to evaluate alternative switching strategies for future integrated voice and data networks. Three fundamental problems are addressed: 1) the economics of integrating voice and data applicatiom in a common communications system; 2) the comparison of alternative switching technologies for integrated voice and data networks; 3) the cost-effectiveness of alternative voice digitization rates and strategies. Three broad switching technologies and variations thereof are investigated and compared. The switching technologies are: circuit switching, packet switching, and hybrid (circuit-packet) switching. Each switching technology can accommodate either voice or data applications separately or combined voice and data requirements in an integrated fashion. Results of studies regarding communications systems option are provided and the sensitivity of the results are tested with respect to traffic variations, cost trends of switching and transmission, and network performance variables. The significant variables which affect the results are identified and quantified. The intent of this study is to identify and quantify network technologies which demonstrate long-term low operating costs, This is a necessary effort to provide the basis for determining the most cost-effective evolutionary path for future communication systems. It is recognized that transition problems and associated costs may be other important factors determining the ultimate evolutionary path. However, determining these costs was not an objective of this study. Neverthless, this study provides a framework and a target technology for detailed evolution, planning, and cost analysis.     

MSTP内嵌RPR技术在城域网中的组网应用

由于网络电视(IPTV)、3G业务的开展,网络业务呈现多样化,对业务的可靠承载传送和带宽的高效利用提出了更高的要求,需要通过技术手段加以解决.利用多业务传送节点(MSTP)内嵌弹性分组环(RPR)技术所具有的业务分类传送、快速保护倒换、公平接入机制及高效带宽利用的特点,在城域网组网中实现了快速提供大客户专线业务、IPTV业务的有保障传送和3G接入传输网建设的最优化等应用.该技术已被中兴通讯在城域网组网中进行商用.MSTP内嵌RPR技术适合当前IPTV、3G建网应用,可实现不同类型业务综合应用的高效可靠传送.     

QOS distributed routing protocol for mobile ad-hoc wireless networks using intelligent packet carrying systems

The wireless network should provide high throughput and positive status and this paper suggest a system that supports real-time communications with excellence of service necessities for application based on wireless communications. In addition a hybrid network that interconnects both mobile networks and wireless networks. By inheriting the features of Solid Rocket Booster technology for mobile and wireless networks the race condition, and invalid condition problem has been solved. The number of packets received may vary based on the parameter like mobility, energy, memory, bandwidth, jamming and other parameter. In past years many algorithm has been proposed for increasing the probability of packet delivery but it’s still a challenge. This paper uses an algorithm called intelligent packet carrying systems; it provides a tracking mechanism that tracks nodes in rural places. The effectives and reability has been calculated and the results are obtained using OPNET simulator.     

奥帆赛通信安全保障方案

作为奥运会合作伙伴,中国网通精心打造安全可靠的奥运通信网络,青岛网通运用多种先进的通信技术为奥帆赛提供通信保障工作。本文从传输网络、IP数据网络、交换网络、光缆通信保障和电源系统五个方面详细介绍奥帆基地网络保障方案。     

High-Speed Packet Switching Systems for Multimedia Communications

High-speed packet switching (HPS) systems can Provide flexible, economical, high-quaiity services for integrated voice, video, and data communications. To realize such HPS systems, methods have been developed to bring about high-speed protocol processing as well as a system architecture for facilitating high-throughput switching. Adopting the parallel processing algorithm into protocol processing allows us to achieve high-speed packet protocol processing of about 100 times faster than conventional processing. Furthermore, a fully distributed system architecture in addition to hierarchical interconnection networks can achieve high-capacity packet switching systems. The proposed HPS system is thus capable of accommodating lines of up to 10-50 Mbits/s, of providing high-throughput switching capability of 1 000 000 packets/s, and of having an average delay of less than 2 ms. Furthermore, an evaluation of network delay performances of video conferencing and voice communications indicate that HPS systems are quite suitable for handling such multimedia communications.     

Enhanced VoIP Support in OFDMA-based Packet Radio Networks

As the first OFDMA-based cellular packet radio network, Evolved UTRAN has already been well studied in 3GPP and semi-persistent scheduling was selected as the most relevant packet scheduling scheme for VoIP traffic. With further evolution of Evolved UTRAN to meet the ambitious goal set by IMT-A, the performance of VoIP needs to be enhanced. In this article, we establish a semi-persistent scheduling centered framework for efficient VoIP support in OFDMA-based packet radio network and evaluate different enhancement methods, such as adaptive transmission bandwidth in persistent resource allocation, dynamic packet bundling, and frequency diversity transmission that can be added into this framework. In addition, we investigate practical constraints, e.g. wideband CQI reporting on real network performance as well as possible corrective measures. The whole system design is verified through large-scale network level simulations in which all the details of various VoIP-specific radio resource management algorithms and enhancement mechanisms as well as interactions between them are explicitly modeled. Simulation results indicate that VoIP in Evolved UTRAN can be well supported using this framework and further improved through different enhancement methods. Compared with fixed transmission bandwidth approach, adaptive transmission bandwidth approach can provide additional capacity gain of 11 and 8% respectively in 3GPP Macro Case 1 and Case 3 deployment scenario. In a highly-loaded network, switching from adaptive transmission bandwidth to dynamic packet bundling can accommodate 18 and 15% more users in Case 1 and 3 respectively. The performance degradation due to wideband CQI reporting can be partly compensated with frequency diversity transmission. It is finally concluded that the enhanced performance of VoIP is sufficient to meet the ambitious target set by IMT-A in all four ITU deployment scenarios.     

下一代通信网络中的SIP语音业务

介绍了最新的基于因特网的语音技术。在该方案设计中采用了融合传统电路交换网和IP网的结构思想,不仅将语音的传输放到了IP网上,更为集成将来的业务,诸如网页、电子邮件、多媒体技术等提供了灵活的结构。其初期目的在于替代传统的企业级电话业务。     

Analysis of Group 4 Facsimile Throughput

The CCITT (Consultive Committee for International Telephone and Telegraph) is developing recommendations for a new generation of facsimile equipment which is designed as Group 4. This class of equipment will transmit an ISO A4-sized page overcommunications networks having error control. Most commercial packet switched and circuit data networks have been designed primarily for the communications of short bursty messages (typically 1000-2000 bits/message between computers and data terminals. The length of a G4 message is forecast to be very long-typically 500 000 bits. There is serious concern that data networks may not handle facsimile traffic very efficiently. This paper projects the near term characteristics of data networks and Group 4 facsimile systems, and estimates the efficiency with which Group 4 messages will be transmitted over three types of data networkspacket switching (PSDN), circuit switched (CSDN), and the public switched telephone network (PSTN). Throughput has been measured by the amount of time required to send a single facsimile page of 500 000 coded bits. In all cases the overhead, as a percentage of the basic facsimile transmission time, is in the range of 50-60 percent. For each network there is a different factor is the halts are forced is transmission as a result of the network window. For the CSDN, the process if converting from voice to data mode is the dominating factor. For the PSTN, packet retransmission due to transmission errors is the dominating factor. The paper includes the assumptions and some of the analytical details of the throughput analysis. Conclusions are drawn regarding the relative transmission efficints through the three types of networks.