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.     

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.     

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。     

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.     

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。     

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。     

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。     

A survey of free space optical networks

Free Space Optical (FSO) networks, also known as optical wireless networks, have emerged as viable candidates for broadband wireless communications in the near future. The range of the potential application of FSO networks is extensive, from home to satellite. However, FSO networks have not been popularized because of insufficient availability and reliability. Researchers have focused on the problems in the physical layer in order to exploit the properties of wireless optical channels. However, recent technological developments with successful results make it practical to explore the advantages of the high bandwidth. Some researchers have begun to focus on the problems of network and upper layers in FSO networks. In this survey, we classify prospective global FSO networks into three subnetworks and give an account of them. We also present state-of-the-art research and discuss what kinds of challenges exist.     

纤维光学技术在通信卫星中的应用

本文介绍了纤维光学技术在通信卫星中的应用,所论应用领域包括卫星地面终端微波光纤线路、大孔径相控阵天线和卫星通信转发器。     

蓬勃发展的中国公众卫星通信

本文通过详细的统计数字，介绍了我国公众卫星通信发展现状及新的一年规划，剖析了国内其它卫星系统如移动卫星通信，农村卫星通信和ＶＡＳＴ的发展，并对我国２０００年前卫星通信的发展规划和策略进行了探讨。     

Secure data aggregation without persistent cryptographic operations in wireless sensor networks

In-network data aggregation is an essential operation to reduce energy consumption in large-scale wireless sensor networks. With data aggregation, however, raw data items are invisible to the base station and thus the authenticity of the aggregated data is hard to guarantee. A compromised sensor node may forge an aggregation value and mislead the base station into trusting a false reading. Due to the stringent constraints of energy supply and computing capability on sensor nodes, it is challenging to detect a compromised sensor node and keep it from cheating, since expensive cryptographic operations are unsuitable for tiny sensor devices. This paper proposes a secure aggregation tree (SAT) to detect and prevent cheating. Our method is essentially different from other existing solutions in that it does not require any cryptographic operations when all sensor nodes work honestly. The detection of cheating is based on the topological constraints in the aggregation tree. We also propose a weighted voting scheme to determine a misbehaving node and a secure local recovery scheme to avoid using the misbehaving node.     

Performance of LAMS-DLC: A protocol for low altitude satellite networks

LAMS-DLC, a data link control protocol for low altitude satellite networks, was developed to overcome throughput limitations inherent in event-based positive acknowledgment (POS-ACK) automatic repeat request (ARQ) class protocols by relaxing certain reliability constraints, in particular the in-sequence delivery constraint. This relaxation results in a new class of link layer service, that of reliable datagram, and permits a fresh approach to link layer protocol design. In this paper we discuss the motivation for such a protocol, describe one such protocol, LAMS-DLC, and compare throughput efficiency with results obtained from a simulation model. Results suggest that LAMS-DLC provides near optimal throughput efficiencies in the target environment, while using significantly less buffer space than is required for conventional POS-ACK protocols.     

卫星互联网下的VSAT卫星通信

本文介绍了VSAT通信在卫星互联网下的新发展,分析了VSAT系统的互联网接入方式,研究了卫星互联网的技术热点,展望了卫星互联网的发展前景.