Digital Time Division Switching for Military Communications

This paper describes system designs and design techniques applied in the design of a digital time-division switching system for a military communication network. The digital switches are interconnected by bit interleaved digital time-division multiplexed trunk groups. The switching system uses an advanced non-blocking, bit interleaved, digital time-division switch matrix to switch synchronous voice and data communications. The nodes of the model network are timed by high accuracy atomic clocks and use first-in-first-out buffers to compensate for clock frequency differences. The digital switching system uses common channel digital message signaling to communicate signaling and supervision data between connected switching centers. Signaling channels use a comprehensive error control system to provide reliable signaling and maintain signaling throughput in adverse transmission noise environments. The switching system's stored program control provides a telephone switching system which can be applied to many different networks. The flexible stored program control enables the same hardware system to perform switching for networks with different network signaling and/or routing/numbering plans.     

数字移动通信中的抗多径衰落技术

移动信道的主要特征是由移动和多径传播所产生的多径衰落现象。在高速移动通信系统中，必须采用抗多径衰落技术，才能实现有效传输。本文首先概述了移动信道的数学模型及其典型形式，在此基础上，分别讨论了时分多址（ＴＤＭＡ）和码分多址（ＣＤＭＡ）系统的抗多径衰落方法──自适应信道均衡技术及多径分集接收技术，并简述了近年来较为活跃的多用户检测技术和自适应天线分集技术。     

一种改进的插值定时恢复结构

在数字同步接收系统中使用插值法提取定时信号的过程中,由于插值滤波器的频域特性是非理想的,为了减小插值器频域内的失真而引起的插值误差,提出了一种改进型的插值结构。该方法在插值之前对输入的信号进行上采样,分析表明该方法可降低插值滤波器的阶数,减少乘法器的使用,从而大大地减少了运算量,降低了系统的实现成本。     

可生存网络系统的构建方法

在攻击、故障和意外事故存在的情况下，可生存的网络系统仍然具有提供连续、可靠的网络服务的能力．本文提出了构建可生存网络系统的方法，可以增强网络系统最重要的三个特性：抵御、识别和恢复，从而从整体上有效地增强了网络系统的可生存性．这种构建网络系统的方法使得网络系统的可生存性不再依赖于特定的系统组件，相应地保护了网络系统的应用．     

A Digital Approach to Symbol Timing Recovery Systems

An analysis of a symbol timing recovery (STR) technique using digital processing is presented. The ratio of the discrete spectral power at the symbol rate frequency to the nearby continuous spectral power is used as a criterion of STR performance. It is shown that this power ratio equals the quality factor of the narrow bandpass filter and that it does not depend on the value of the delay element. The performance of the STR subsystem is consequently determined by the quality factor of the bandpass filter rather than by the specific delay. In addition to this, some experimental evidence that the additive channel noise has little effect on the power ratio is given. A modified phase-locked loop with anLCprefiiter is proposed to extract the symbol timing clock. This prefilter improves the acquisition and synchronization performance of the PLL. The STR technique presented here has the advantages of lower cost and simpler hardware implementation over other serial STR techniques.     

Timing Synchronization in MF-TDMA Systems for Geostationary Satellites[Topics in Radio Communications]

The most expensive costs in satellite communication are incurred by the space segment. Therefore, effort should be focused on the efficient use of this resource. One aspect is the optimization of the physical layer, to approach the Shannon limit of channel capacity. In IP-based networks, communication between arbitrary terminals can be established, which must hold for IP-based satellite networks as well. A commonly used topology is the star network, where data are routed via the master station, which in case of satellite communications introduces a double hop for terminal-to-terminal connections [1]. A double hop requires twice the bandwidth and twice the response time, which is very unattractive for interactive services. This drawback is avoided with a fully meshed topology, where terminals can communicate directly. Of course, an appropriately designed access system is required in this context. The well-known multi-frequency, time-division multiple access (MF-TDMA) scheme slices the channel capacity along both time and frequency axes. Each fragment (slot) can be used by any station for direct communication [2, 3]. This article describes the method on an abstraction layer, starting with the high-level timing that copes with frame numbers; the low-level timing that maps the frame numbers to time instants of the local time scale; and ends with the time stamp handled in the hardware, where calculation delays and filter flushing affect the received time stamp. Compared to commercial systems, the method described in this article uses differential time stamps, which reduces the effort of the synchronization procedure.     

On the Timing Information Disappearance of Digital Transmission Systems

Probability distribution of a timing-wave envelope level in a regenerative repeater, which transmits a random binary sequence, is analyzed. The result obtained is that the probability of timing information disappearance in a repeated line can be disregarded compared with that of failure of a repeater.     

Design of Power and Area Efficient Digital Down-converters for Broadband Communications Systems

This paper shows that when a digital receiver is designed utilizing two clock scopes, the digital down-converter can be designed to be efficient in terms of area and power consumption. The main design parameter that contributes to make the design efficient is the relationship between the transition band of the designed filter and its sampling frequency.

光纤数字通信中NRZ与RZ码序列的定时时钟提取

在光纤数字通信系统中,NRZ非归零码和RZ归零码是最常见的基带信号。由于两者频谱成分不同,其定时时钟提取方式则不同。本文通过对NRZ、RZ伪随机码序列进行频谱分析,得知当NRZ码变换成码元占空比为1/2的RZ码时,所提取出的定时时钟功率最强。     

美军卫星通信系统的发展及其技术研究

随着信息技术的快速发展,美军为满足未来战争需要不断地规划研发新的通信卫星系统。文中主要讨论了美军卫星通信系统的现状和未来发展,归纳了相关的关键技术,最后总结了目前卫星通信的重要性并指出了今后研究的方向。研究美军在这一领域的新发展和成果,目的是为我国构建空间信息网络奠定必要的基础。     

复杂对抗下军事通信系统的随机延迟分析

随着信息化技术的发展,现代军事指挥越来越依靠综合化、集群化的军事通信系统。在战争局势复杂多变,尤其是敌方干扰严重、战场环境复杂等对抗性强的环境下,如何确保有效军事情报及时地准确地传递给指挥者显得尤为重要。针对战场有效数据产生的随机性和传输过程的不稳定性,提出了一种基于随机网络演算的端到端延迟分析方法。由此获得的端到端延迟上界,不仅为有效信息的传输提供了实时性能保证,而且能充分的利用系统资源。这对于军事通信系统的设计以及传输系统的性能改善有着非常重要的指导意义。     

打造多业务通信平台,服务全世界通信用户——吉来特卫星通信公司高层访谈

吉来特卫星通信公司（Gilat Satelllite Networks Ltd.）是世界领先的卫星通信网络产品及服务提供商。公司成立二十年来,一直站在VSAT技术和服务领域的前沿,致力于卫星新技术的创新和开发,以SkyEdge和SkyEdgeⅡ多业务平台为代表的产品使其享誉全球。在＂2010年中国卫星应用大会＂上,     

Free-Space Optical Communications for Next-generation Military Networks

There is a continuing need for increased capacity for military applications, especially in network-centric operational concepts that promote the use of information as fundamental for gaining superiority on the battlefield. As an example, the access to, and distribution of, sensor data is a major tenet of network-centric warfare and yet radio frequency (RF) links will struggle to provide the needed capacity. Free-space optical communications (FSOC) has the potential to meet these emerging military needs by offering dramatic increases in capacity. However, there are many technical challenges al multiple layers of the communications protocol stack. This article describes these challenges and discusses some mitigation approaches to provide a path to realizing this capability on the battlefield     

中华人民共和国通信行业标准——通信用不间断电源——UPS

7标志、包装、运输、贮存 7．1标志 7．1．1产品表面应有中文标识,包括产品名称、产品型号、产品编号、制造厂名、制造日期、产品主要参数等。     

Integrated Circuits for Broad-Band Communications Systems

Integrated circuits for broad-band communication systems which enable broad-band communication between subscribers require LSI's with a performance concerning speed, complexity, and power dissipation which cannot be fully met by present semiconductor technologies. The requirements for coders and decoders, line transmission circuits, and broad-band switching network elements depend upon the system concept chosen. For one chosen system concept, these requirements are derived. By using a representative model for the development of the demand, characteristic curves for the demand of subscriber-line circuits and for central unit elements are resulting. From these curves the optimum semiconductor technologies, complexities, and design strategies are derived. It can be assumed that the results are rather independent of variations of system concept and introduction models.     

Design and FPGA-Implementation of a High Performance Timing Recovery Loop for Broadband Communications

Timing recovery in communication systems with linear modulations is usually performed with a non-data-aided feedback loop based on a fractional interpolator timing corrector and the Gardner’s timing error detector. The contribution of this paper is twofold. First, some design rules are given to predict the behaviour of the loop if pipeline is used. Second, it is shown that pipelining can be used to reduce power consumption in a timing feedback loop. A timing recovery loop has been implemented in an FPGA device and power consumption measures indicates that by including 16 extra registers in the loop the power consumption decreases a 63% and the synchronizer can process up to 66.5 MSPS.

Automatic Testing and Automatic Test Systems for Communications Systems

Over the past years, a considerable number of electronic test facilities have been converted to automatic test systems (ATE).     

通信对抗系统对抗能力测试方法研究

对通信对抗系统对抗能力测试的原理进行了说明,提出以反应时间和对抗成功率做为通信对抗系统对抗能力的评定指标,指出了已往测试中存在的问题,并提出根据通信误组率来判定对抗是否成功的实现方法,为通信对抗系统对抗能力测试提供了依据.