Satellites and the isdn

This paper addresses the question of integrating satellites within the ISDN, concentrating on PSTN application. After a brief look at the role satellites have played to date in international telecommunications, and the new environment that ISDN will bring, an examination is made of the work done by CCITT on the transmission aspects of ISDN. This is followed by a look at the main features of digital satellite systems at the present time, including transmission performance as defined by CCIR, and a critical comparison is made with ISDN requirements including an indication of how error performance may need improving. The paper concludes with a discussion of how satellite system operators might respond to the demands of the ISDN.     

Metropolitan area networks and ATM technology

Metropolitan area networks are evolving to fill the gap between local and wide area networks. The standards organization for such networks, IEEE Project 802.6, is defining a standard with unique advantages in scheduling and failure recovery. It is highly compatible with broadband ISDN and ATM switch technology. The resulting combination will be a seamless network embracing both customer buildings within metropolitan areas and world-wide interconnection.     

卫星数据链的发展研究

本文分析了卫星数据链的需求背景,介绍了卫星数据链的概念和特点,论述了国外的卫星数据链发展状况,并针对卫星数据链的关键技术进行了讨论。     

中国气象系统卫星通信专用网

本文对中国气象局正在建设中的中国气象卫星综合应用业务系统作了较全面的描述，重点介绍了卫星通信部分的网络总体结构和布局，并特别提出了亚洲卫星２号Ｋｕ转器覆盖盖边缘区的技术设计原则。     

Paris: An approach to integrated high-speed private networks

This paper describes a design of a high-speed packet switching system for integrated voice, video and data communications. The system makes use of a simplified network architecture in order to achieve the low packet delay and high nodal throughput necessary for the transport of voice and video. A prototype of this system has been implemented and is now being tested under a variety of packet traffic loads. We have demonstrated that this system provides a cost-effective solution for private integrated networks.     

Video and image applications on narrowband and broadband isdn

Two major ISDN applications which will undoubtedly affect world-wide telecommunications in the coming decade are discussed. They are: (1) video transmission and (2) image transmission. Brief reviews of videophone chronicle and the current video coding technologies are presented. The application of videophones using p × 64 (CCITT coding algorithm up to 1·5 Mb/s) and the DCT (discrete cosine transform) algorithm for narrowband ISDN are discussed. Broadcast TV quality DS3-45 MB/s video codecs are also briefly discussed as a probable videophone system in the broadband ISDN era. The explosive growth of facsimile services is reviewed, and the progress of image coding technologies and their standards are covered. The prospects of high resolution image transfer systems with ISDN are addressed.     

不断发展的中国电信新业务

近年来，各种电信新业务在我国蓬勃发展并呈现出广阔的市场前景。本文以翔实的数据全面介绍了数据通信、移动通信、智能网、ＩＳＤＮ等各种新业务的发展现状，今年内和２０００的发展目标。     

Ku-Band satellite data networks using very small aperture terminals—part II: System design

In this part of the paper on Ku-band VSAT networks, the issue of overall system design is considered. After discussing possible system architectures, primary attention is given to the star network configuration in which customer-premise VSATs communicate with a central hub station, co-located with, or terrestrially connected to a host computer. The component elements of a Ku-band star network for interactive data applications are discussed and the critical items from the point-of-view of performance, capacity and cost are identified. An analytical model for the network, which combines delay-throughput characterization of the multi-access inbound and TDM outbound channels with satellite link analysis is described. The analytical model is exercised over a range of typical system component, traffic model and performance objective scenarios to provide a set of general design guidelines. These guidelines are useful for evaluating the trade-offs between key system elements (channel access unit, modem, VSAT antenna and satellite), VSAT traffic message length parameters and the performance objectives (average and peak network response time and availability). The results are used to address the issue of multi-access protocol selection over a range of scenarios typical of 1.2 or 1.8m VSAT-based interactive networks using current commercial Ku-band satellites. The results show that interactive star networks are often limited by satellite power rather than bandwidth, so that the use of simple contention access for VSATs may not imply a significant system capacity penalty.     

Novel algorithm for time division multiple access in broadband ISDN passive optical networks

For shared access to a broadband communication network using the asynchronous transfer mode (ATM) a passive optical network (PON) has previously been proposed. A novel algorithm to evaluate the time division multiple access (TDMA) protocol which controls the traffic from the various subscribers towards the shared access equipment (upstream direction) is proposed. It uses counters to estimate the moment of a data packet arrival at the subscriber side. By this ‘look-ahead’ technique no extra upstream channels are needed to initiate the polling by the subscriber. The algorithm guarantees fair access for all subscribers and minimizes the necessary overhead. Both the maximum access delay and overhead may be readily calculated, and the obtained results were supported by numerical simulation. Applicability in the standard broadband network environment has been proved by hardware design simulation.     

一种基于链路稳定性模型的LEO/MEO双层卫星网星间链路设计方法

卫星网动态拓扑、长变时延等特性及其所处的复杂空间环境带来的通信干扰是影响网络通信稳定的重要因素。综合考虑这些影响因素,提出了一种衡量星间链路稳定性的模型,并基于此模型给出了LEO/MEO双层卫星网的星间链路设计方案。结合具体的星座实例对该方案进行了仿真分析,结果表明通过适当的参数调整该模型可以适应不同的网络性能要求。     

Services and supporting architecture of the ESA OBP system

The ESA on-board processing (OBP) satellite system using on-board regeneration and baseband circuit switching has been designed to provide ISDN connectivity and services to users on a Pan-European basis. It is thus seen at its periphery as a 2 Mb/s primary rate access, hence allowing for the interconnection of equipment and terminals compatible with this standard interface. Among the various possible network architectures that the system could support, the business-oriented closed networks look most promising. It has therefore been retained as a prime design driver for OBP system developments. Optionally, connectivity can be offered in an optimized manner to pure data networks, e.g. for LAN-to-LAN interconnection at rates up to 1 Mb/s. In the paper, communication services and networking capabilities offered by the system are briefly reviewed. The internal characteristics of the satellite system allowing for such capabilities are then reviewed and the corresponding performance outlined. The system is shown to be compatible with critical CCITT performance criteria.     

移动卫星网络中基于最小费用的切换算法

对于移动卫星网络,合理的星地链路切换方案需要在保证最小切换时延的同时,能够最优地使用网络资源。该文通过引入业务的中断概率和费用模型,给出了切换过程中重路由的最优触发条件,提出一种基于最小费用的切换(SMCH)算法。该算法可在保证切换业务通信的连续性和时延等指标不被破坏的基础上,通过适当的触发重路由来降低切换费用。仿真表明该算法在保证切换业务的QoS,降低切换费用以及适应性、灵活性等方面都优于同类切换算法。     

N—ISDN在德国的发展

随着用户对数据和图象通信需求的不断增加，ＩＳＤＮ的优势渐露峥嵘。许多国家的电信运营商开始重视ＩＳＤＮ业务的发展，并采取各种措施来促进ＩＳＤＮ的推广。本文介绍了近年德国电信推广ＩＳＤＮ的措施和经验，供我国有关方面参考借鉴。     

江苏省前期ISDN试验及应用思考

充分利用现有电话网和积极发展在电话网上的数据传输业务，具有十分重要的现实意义。江苏省先后在省内十个城市中进行了前期ＩＳＤＮ试验，利用２Ｂ＋３设备进行数据通信，既满足了用户对数据通信的需求，对于提高企业的竞争力也具深远影响。本文作者介绍了江苏省前期ＩＳＤＮ实验的具体设备，技术及其应用情况，并对今后的工作提出了积极建议。     

卫星数据分发系统中的分组级FEC技术性能分析

本文根据所给出的信道差错模型和里德所罗门删除码(RSE)编码技术,研究了在卫星数据分发系统中采用分组级前向纠错(FEC)技术的文件成功分发概率和吞吐量效率与文件长度、分组长度、接收站点数及RSE码纠错能力之间的关系,所得到的结论对于卫星数据分发系统中的参数选择及性能优化具有指导意义。     

俄罗斯卫星通信技术的发展

作者根据不久前赴俄罗斯考察所获的第一手资料简述了俄罗斯卫星通信技术的发展过程,着重介绍了现在运行的“荧光屏”和“地平线”卫星系统以及正在研制的“快车”卫星。最后,还对俄罗斯卫星通信技术的优缺点进行了分析。     

Satellite handover techniques for LEO networks

Low earth orbit satellite constellations could play an important role in future mobile communication networks due to their characteristics, such as global coverage and low propagation delays. However, because of the non‐stationarity of the satellites, a call may be subjected to handovers, which can be cell or satellite handovers. Quite many techniques have been proposed in the literature dealing with the cell handover issue. In this paper, a satellite handover procedure is proposed, that investigates and exploits the partial satellite diversity (namely, the existing common coverage area between contiguous satellites) in order to provide an efficient handover strategy, based always on a tradeoff of blocking and forced termination probabilities for a fair treatment of new and handover calls. Three different criteria were examined for the selection of a satellite. Each one of them could be applied either to new or handover calls, therefore we investigated nine different service schemes. A simulation tool was implemented in order to compare the different service schemes and simulation results are presented at the end of the paper. Copyright © 2004 John Wiley & Sons, Ltd.     

走向宽带化的VSAT卫星通信

受数据音频视频广播、计算机卫星宽带交互接入和音视频会议等业务的推动,VSAT卫星通信网向宽带业务发展巳成为必然趋势。分别对应以上业务的VSAT卫星通信网也日益趋于融合成一个统一的宽带VSAT通信网。发展宽带VSAT通信网的关键技术涉及到宽带数据广播、宽带多址接入、卫星通信规程、网络综合管理和宽带虚拟子网等。     

LEO卫星接入TDRSS的可行性分析与仿真

该文讨论了使用固定天线和中低发射功率的LEO卫星接入到跟踪与数据中继卫星系统(TDRSS),并通过跟踪与数据中继卫星(TDRS)来实现空-地数据传输的可行性。文中给出了LEO卫星与TDRS进行通信需满足的前提条件,提出了通过计算机仿真来计算LEO卫星与TDRS全天通信时间和通信业务量的一般思路和具体实现方法,为论证具有固定天线的LEO卫星接入TDRSS的可行性提供了依据。