Building open programmable multimedia networks

Recent advances in distributed systems and transportable software and increasing demand for better quality of service (QoS) control in multiservice networks are driving a reexamination of network software architectures. We established the Comet (Control, Management, and Telemedia) Group at Columbia University's Center for Telecommunications Research to provide comprehensive understanding of network software architecture for the 1990s and beyond. This research focuses on developing new network architectures that support service creation, QoS control, and the joint allocation of computing and communications resources. This provides an opportunity to reconcile the perspectives of the computing and communication communities. Future multiservice (multimedia) networks will carry traffic such as video, audio, and computer data with diverse QoS requirements. Such networks will thus require that we develop ways to manage many physical and logical entities, services, and users     

实施双网覆盖提升移动数据业务品质

本文主要从运营角度,根据移动通信向数据业务方向发展的特点,结合几种通信技术设备对数据业务支持的差异性,从客户发展、建设成本、支持速度、未来升级等方面,利用理论数据和运营经验,通过对比,得出结论,数据专网＋（GSM或3G）双网覆盖,发挥各自长处,会大大提高移动数据业务的品质,促进信息化的大发展,进一步提高工作效率,改善人民生活质量。     

A Digital Satellite Communications System for Corporate Telecommunications

A satellite communications system has been implemented by Citicorp to meet its present and future internal domestic telecommunications requirements. This system is currently being used for voice and data transmission and video teleconferencing between corporate facilities in New York, Los Angeles, San Francisco, and Sioux Falls, SD. Six additional cities will be served by the end of 1984. This system utilizes an 11-m earth station in each city to transmit and receive 60 Mbit/s TDMA signals from a satellite transponder on the Western Union WESTAR V satellite. Various terrestrial microwave, fiber optic, and copper cable facilities interconnect the earth stations to the users of the system. The basic trunk is digital at a T1, or 1.544 Mbit/s rate or multiple thereof, except some local distribution. A network control center provides centralized monitoring and control for all facilities in the system.     

A MEMS-based wireless multisensor module for environmental monitoring

In order to enable further developments in low cost wireless sensor networks (WSNs) for unobtrusive environmental monitoring, increased miniaturisation and integration of hardware is essential. This paper outlines the design concept and preliminary results for a multifunctional micromachined sensor unit, comprising CMOS-compatible temperature, humidity and gas sensors on a single silicon substrate.The sensor is being developed for integration with the highly modular and programmable Tyndall25 mote, where the “plug and play” stackable layers incorporate communications, power supply and on-board data processing capabilities. This will enable the assembly of a miniature sensor network node complete with wireless transmission capability as well as intelligent data mining and storage.     

An access cell selection algorithm for next generation mobile environments

Next generation of mobile communications will be based on a heterogeneous infrastructure comprising different wireless access systems in a complementary manner. This paper proposes a network selection algorithm based on user activity, user preferences, service requirements, and networks conditions which provides users a prospect of being always best connected within an environment of heterogeneous mobile networks. This is achieved by a learning process which allows user to select an access network based in previous connections and a cost function that helps the user to select the best network that adapts to the needs.     

Integration of Voice and Data in the Wideband Packet Satellite Network

The Wideband (packet satellite) network is an experimental 3 Mbit/s communications system developed under sponsorship of the Defense Advanced Research Projects Agency and the Defense Communications Agency. This system is being used to evaluate the use of packet transmission for efficient voice communication, voice conferencing, and integration of voice and data over a satellite channel. Each station in the Wideband network consists of an earth terminal (dedicated 5 m antenna plus associated IF/RF equipment), a burst-modem and codec unit, and a station controller. Station controllers provide interfaces to host computers (including packet speech sources) and manage the allocation of the satellite channel on a TDMA demand-assigned basis. TDMA demand-assignment is implemented using a reservation-based packet-oriented protocol capableof handling traffic at multiple priority levels. The channel protocol provides a reservation-per-message mode of service (datagrams) to support transmission from bursty traffic sources and a reservation-per-call mode of service (streams) to support traffic with more regular arrival statisticS (e.g., vioce). A distributed scheduler running in every station controller eliminates the need for a central control station and minimizes network transit delay for datagram transmission as well as stream creation, modification, and deletion. In this paper we describe the protocols and mechanisms upon which the Wideband packet satellite network is based.     

Subscriber Stations in Service Integrated Optical Broad Band Communications Systems

Subscriber stations in service integrated communications systems can be implemented in many different ways. Within the HHI Broad-Band Communications System two extremely different solutions have been realized: on the one hand, subscriber stations in a conventional star type network with central exchange and analog transmission, and on the other hand, subscriber stations in a digital, loop-structured network employing distributed control. In both cases, the same services (telephone, data, videophone, TV, and stereo broadcasting) are carried to the subscriber via one single optical fiber. This paper describes these different realizations of service integrated subscriber stations in detail. The size of terminal equipment, power consumption, extendability to further subscribers, and services and reliability are the main parameters of an appropriate comparison. An analysis of both realizations, giving emphasis to the switching and multiplexing, and the feasibility of analog optical transmission will be made. Alternative realizations and an estimation concerning subscriber stations for future service integrated broad band communications systems will be presented.     

A Portable Fiber Optic Local Area Network

A portable fiber optic local area network has been implemented for emergency command center communications. This network operates under a carrier sense multiple-access (CSMA) protocol and employs an architecture based on a unique active star node. The node consists of a transmissive optical star coupler and active electro-optical transceivers. Terminal-to-node or node-to-node links may be as long as 1 km. An architecture developed around this node design is capable of modular expansion to accommodate a large number (several hundread) of data subscribers. In addition to data services, this network can support broadcast video and integrated technical control.     

统一通信技术在战术通信网中的应用研究

战术通信的业务可分为会话型、数据型以及协作型三类,当前这三类业务的控制信令与控制方式都截然不同,从而存在一系列问题。未来的战术通信网络向全IP技术体制演进已成为一种必然趋势,而在全IP技术体制下,实现这三类业务的统一通信就成为可能。针对这种情况,提出了一种既能够统一控制这三类业务,又能够适应战术通信网本身的特点并确保各种业务的服务质量,还能够满足未来各种业务的扩展需求的统一通信技术,在此基础上设计了战术统一通信服务端框架,并针对战术通信网络环境的特点分析了一系列关键技术的突破途径。     

SATELLITE-ENHANCED PERSONAL COMMUNICATIONS EXPERIMENTS

Users of future generation wireless information services will have diverse needs for voice, data, and potentially even video communications in a wide variety of circumstances. For users in dense, inner-city areas, low power personal communications services (PCS) technology should be ideal. Vehicular-based users travelling at high speeds will need high-power cellular technology. For users in remote or inaccessible locations, or for applications that are broadcast over a wide geographic area, a satellite technology would be the best choice. Packet data networks provide an excellent solution for users requiring occasional small messages, whereas circuit switched networks provide more economical solutions for larger messages. To provide ubiquitous personal communications service, it is necessary to capitalize on the strength of each wireless technology and network to create one seamless internetwork including both current and future wired and wireless networks. As an initial step in exploring the opportunities afforded by the merging of satellite and terrestrial networks, Bellcore and JPL conducted several experiments. These experiments utilized Bellcore's experimental personal communications system (including several messaging applications with adaptations to wireless networks), NASA's advanced communications technology satellite (ACTS), JPL's ACTS mobile terminal, and various commercial data networks (such as the wireline Internet and the RAM wireless packet data network). Looking at loss of bits, packets and higher layer blocks (over the satellite-terrestrial internetworks with mobile and stationary users under various conditions) our initial results indicate that the communication channel can vary dramatically, even within a single network. We show that these conditions necessitate powerful and adaptive protocols if we are to achieve a seamless internetworking of satellite and terrestrial networks.     

An approach for failure recognition in IP‐based industrial control networks and systems

Industrial control networks (ICNs) and systems support robust communications of devices in process control or manufacturing environments. ICN proprietary protocols are being migrated to Ethernet/IP networks in order to merge various different types of networks into a single common network. ICNs are deployed in mission‐critical operations, which require a maximum level of network stability. Network stability is often described using several categories of network performance quality‐of‐service metrics, such as throughput, delay, and loss measurements. The question arises as to whether these network performance metrics are sufficient to run valuable diagnostics of ICN components and their communications. Any abnormal decision with respect to typical IP traffic behavior does not necessarily coincide with ICN fault cases. A precise and specific diagnostic technique for ICNs is required to remove the uncertainty in detecting problems. However, existing Ethernet/IP diagnosis tools have not been able to fully handle fault symptoms and mainly focus on network diagnostics rather than process or device diagnostics. This paper demonstrates that the absence of advanced fault diagnosis techniques leads to the development of new methodologies that are suitazble for ICN. We describe unique traffic characteristics and categorize the faults of ICN. We also propose a fault diagnosis, prediction, and adaptive decision methodologies, and verify them with real‐world ICN data from the steel‐making company POSCO. Our experience in developing the fault diagnosis system provides a firm guideline to understand the fault management mechanisms in large ICNs. Copyright © 2012 John Wiley & Sons, Ltd.     

中国多媒体通信业务市场展望

多媒体通信发展如火如荼，对未来业务市场的正确估计将对网络的发展和建设具有重要的指导意义。本文提出ＩＰ网络、ＩＰ技术和宽带技术，社会发展影响是多媒体通信业务市场的构成因素，并在此基础上，通过列举详尽的数据，从业务终端，计算机普及率和上网率以及计算机的应用状况（包括商用和家用）等方面，对我国２０００年乃至２０１０年的多媒体通信业务市场进行了展望。     

Securing network availability

We live in a world that relies increasingly on its communications infrastructure. Network availability problems affect customers and their businesses, and can damage trust in the resilience of the network. As such, ensuring that networks are robust, reliable and resistant to external attack is a key part of network design. In this paper we examine some of the vulnerabilities and issues posed by connectionless packet networks and outline potential solutions to these problems. A key theme throughout this discussion is the separation of the data and control planes. Within the PSTN, the control network is physically separate from the data circuits. This, along with tightly controlled and limited network interfaces, makes certain types of attack impossible. Unfortunately, with a connectionless packet network, this type of separation will never be completely possible. Further, the nature of network interworking is changing as we move towards a world of increasing service diversity and dynamic, ad hoc networks.     

Advanced Modelling Techniques for Designing Survivable Telecommunications Networks

Near-future multimedia communications will require high-capacity networks employing optical WDM technology to simultaneously carry increasingly large numbers of broadband users. Fast and efficient restoration of network service after failure will be critical to maintaining customer satisfaction and ensuring business success.This paper discusses state-of-the-art software tools and algorithms developed by BTexact Technologies for automated design of such networks, planning of their restoration/resilience capacity, and calculating corresponding end-to-end service availability.The tools and underlying algorithms/models are largely technology independent, and may therefore be applied to a wide variety of scenarios. In this work, a generic network model representing an inter-city telecommunications network for a large European country is considered as a realistic test case.     

Research activities on next-generation mobile communications and services in Korea

In this article we present a perspective on next-generation mobile communications and services. As a preliminary research work on next-generation mobile communications, we exploit what next-generation mobile services will be (S. Ryu et al., May 2003). We define next-generation mobile services as a hierarchy of services consisting of three different service levels: the service areas, the service functionalities, and the service technologies. We derive these service levels by means of scenario-based analysis. Next we propose conceptual reference network architecture, focusing on the realization of the service technologies. We divide the network into four different parts: a user equipments and access part, a network service provisioning layer part, a network control layer part, and non-mobile network operator service pan, according to characteristics of information and service flows within a network. In this reference network architecture, service elements such as servers, processors, and gateways are placed in each network part to support the derived next-generation mobile services. Finally, we give a brief introduction of research and development activities for next-generation mobile communication systems and services in Korea.     

中国国家金融网络的规划设计和应用

正在试点的中国国家金融网络，是一个基于开放系统结构的，支持国家级金融应用系统的数据通信网络，它有用模块化结构设计，物理网络分主干网和区域子网２层，并将向准网格状网络拓扑演进。网络层以Ｘ．２５协议为基础并引入了帧中继技术。该网的网管系统和灾难恢复措施使网络具有较高的安全性。ＣＮＦＮ将全方位地为我国金融界广大用户提供各类数据通信服务。     

Surviving a disaster [optical communications]

The next-generation optical communications network, not surprisingly at all, will be as optical as it can be. Only optical dense wavelength-division multiplexing can provide the bandwidth elasticity that new emerging communications services demand. This is well understood, and despite an apparent slowdown in the world economy, multibillion-dollar commitments have been made to upgrade existing networks to next-generation DWDM. The next optical network is expected to be massive, yet flexible and ubiquitous. Current DWDM technology supports 160 wavelengths (in the C+L bands) per fiber; at 10 Gb/s this amounts to an astonishing 1.6 Tb/s aggregate bandwidth per fiber. Research has also demonstrated that ultra dense WDM (UDWDM) is possible, and it is a matter of time until 320 wavelengths (and a little later 640) will be multiplexed in a single fiber. As a consequence, we examine what the next optical network should be like, and proactively identify some areas that require special attention. One of the critical areas is service and network survivability not only when a node and/or link fails, but also when a cluster of nodes and/or links fail; that is, avoiding a disaster. Disaster avoidance has also become more important for both natural disasters and geo-political unrest     

CDPD——未来个人通信的重要基石

计算机技术和无线通信技术的发展以及数据通信的市场需求推动了以ＣＤＰＤ为代表的无线数据通信技术的迅速发展。ＣＤＰＤ是以数字分组数据技术为基础，以蜂窝移动通信为组网方式来配置的。它采用ＴＣＰ／ＩＰ为基础的Ｉｎｔｅｒｎｅｔ协议，可视为Ｉｎｔｅｒｎｅｔ的延伸。优异的性能、强大的功能以及开放的系统平台使ＣＤＰＤ可适用多种业务，它将在“金卡”工程，现代化管理、电子商务和信息服务等领域大屏身手。     

An integrated voice and data multiple-access scheme for a land-mobile satellite system

A Land-Mobile Satellite System (LMSS) is a satellite-based communications network which provides voice and data communications to mobile users in a vast geographical area. By placing a "relay tower" at a height of 22300 mi, an LMSS can provide ubiquitous radio communication to vehicles roaming in remote or thinly populated area. LMSS is capable of supporting a variety of services, such as two-way alphanumeric service, paging service, full-duplex voice service, and half-duplex dispatch service. A Network Management Center (NMC) will handle the channel requests, channel assignments, and in general the network control functions. A pool of channels is managed at the NMC to be shared by all mobile users. An integrated demand-assigned multiple-access protocol has been developed for the experimental LMSS. The pool of channels is divided into reservation channels and information channels. The information channels can be assigned by the NMC to be either voice channels or data channels. Each mobile user must send a request through one of the reservation channels to the NMC via the ALOHA random-access scheme. Once the request is received and processed, the NMC will examine the current traffic condition and assign an information channel to the user. NMC will periodically update the partitions between the reservation channels, voice channels, and data channels to optimize system performance. Data channel requests are queued at the NMC while voice channel requests are blocked calls cleared. Various operational scenarios have been investigated. Tradeoffs between the data and voice users for a given delay requirement and a given voice call blocking probability have been studied. In addition, performance impacts of such technological advancements as satellite on-board switching and variable bandwidth assignment are discussed.     

Mobile communications

The principal problem faced by networks with mobile users is how to ensure that the service provider functions keep pace with the continually changing network state resulting from user mobility, without consuming large amounts of network resources in the process. Regardless of whether the users are mobile or stationary, all telecommunications networks must perform basic service provider functions such as controlling access to services, locating users, routing traffic, and accounting and billing for service use. However, in the presence of mobile users, all of these functions must be performed much more often and much more rapidly. Developing low-overhead high-performance service provider solutions has been and will continue to be a key area of research in mobile communications. This special issue on mobile communications comprises five articles, each of which covers a different aspect of mobile communications