The Datran system

The Datran system is designed to serve the specific needs of the data communications user. Data communications terminals almost universally employ a digital format; therefore, an early consideration was the use of digital transmission in lieu of the analog transmission employed by most conventional common-carrier systems. The location of the potential users was examined, this having an important bearing on the transmission media selected. Growth expectancy for future years establishes the base upon which to plan the initial system capacity, the hierarchy of system subassemblies for economical modular growth, and phased construction. The employment of digital channel derivation equipment provides a high channel capacity for a given channel bandwidth as compared to analog transmission and permits the use of highly reliable integrated components at a significant reduction in channel end costs. Time-division multiplexing (TDM) switching with a stored program controller provides reliability and flexibility to meet the changing needs of the data communications user and affords significant savings in space, power, and implementation costs of conventional space-division switches.     

Design Technique for Multiplexing Asynchronous Digital Video and Audio Signals

To apply digital transmission to the distribution of television program material it is necessary to encode both sound and picture signals, protect them from the effects of transmission errors and multiplex them into a form suitable for the transmission link that is to be used. Coding, error protection and multiplexing have all received extensive study but their combined application in a system has received little discussion in the literature. This paper shows how a system was designed for a particular experimental application with a specified total bit rate. Particular emphasis is given to the multiplexing arrangements, including the necessary use of justification techniques. The equipment designed has been used in successful field trials of digital transmission by both cable and satellite.     

An Experiment in Integrated Digital Satellite Communications

The experiment we conducted for integrated digital satellite communications is aimed at realizing integrated services digital networks by satellite communication. The experiment was carried out in 1980 using the Japanese experimental communication satellite "CS." This experiment uses 30/20 GHz small earth stations and demand-assignment time-division multiple-access (TDMA) systems. Communications between customer terminals, which contain video conferencing, high-speed facsimile communication, high-speed computer communication, and packet-switching signal transmission, were carried out through the experimental digital satellite link. This paper describes the configuration of the experimental integrated digital satellite communications system and the experimental results of communications between customer terminals.     

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.     

新一代数字集群技术带来的机遇

在信息产业部的部署下,中国铁通在沈阳、长春、重庆等地开展了数字集群商用试验,由中兴通讯在中国铁通辽宁分公司开通的实验局顺利通过了信息产业部通信标准研究所的MTNet测试,数字集群通信有可能迎来发展机遇.文章介绍了数字集群技术的应用、市场需求、特点及发展方向,分析了数字集群系统的现状和市场应用前景,并以数字集群系统GoTa的性能指标为实例说明了数字集群通信持续发展在网络和设备上具有保障.     

A Digital Hybrid Transmission System for 280 Mbits/s and 560 Mbits/s

This paper presents the development of repeaters and line equipment for an experimental digital long-haul transmission system using coaxial cable. A comparison, of different types of digital transmission systems indicates that the digital repeater hybrid system with binary transmission code is the most desirable. This development has resulted in digital pulse reshaping repeaters with very small dimensions, low cost, and good reliability. Both digital repeaters that are without timing and regenerators that include timing have been developed. Their circuitry and the corresponding signal shapes are described. The dc power-feeding system and the fault-location system are also discussed. An experimental field trial with the Deutsche Bundespost was performed over 10-repeater sections of the International Telephone and Telegraph Consultative Committee (CCITT) normal coaxial tube with a section length of 1/2 mi, The experiments confirmed that a long-haul digital transmission system of 560 Mbits/s, and later of 1100 Mbits/s using the described system concept and technology, can be established with relatively low cost and good reliability.     

Digital video coding standards and their role in videocommunications

The efficient digital representation of image and video signals has been subject of considerable research over the past 20 years. With the growing availability of digital transmission links, progress in signal processing, VLSI technology and image compression research, visual communications has become more feasible than ever. Digital video coding technology has developed into a mature field and a diversity of products has been developed-targeted for a wide range of emerging applications, such as video on demand, digital TV/HDTV broadcasting, and multimedia image/video database services. With the increased commercial interest in video communications the need for international image and video coding standards arose. Standardization of video coding algorithms holds the promise of large markets for video communication equipment. Interoperability of implementations from different vendors enables the consumer to access video from a wider range of services and VLSI implementations of coding algorithms conforming to international standards can be manufactured at considerably reduced costs. The purpose of this paper is to provide an overview of today's image and video coding standards and their role in video communications. The different coding algorithms developed for each standard are reviewed and the commonalities between the standards are discussed     

基于XSBI的10Gb/s光纤通信系统的设计(本期优秀论文)

光纤通信凭借其通信容量大、中继距离长、保密性能好、适应能力强等诸多优点在数据通信方面得到了广泛的应用.而单波长10Gb/s的SDH传输平台,代表着当今实用光通信设备的最高水平,文章提出了一种基于XSBI接口协议的10Gb/s光纤通信系统的设计方案,使用FPGA和编解码芯片使以往复杂、高成本的高速光纤通信系统得到了简化.     

面向消息的中间件技术在告警网管中的设计与实现

MDCN作为一个公共信息传输平台,将各个业务系统整合到了一起,在移动通信网络管理中起到了非常重要的作用。当前,如何监控MDCN上的设备正常工作,已经成为研究的热点问题。本文利用面向消息的中间件技术对设备告警的管理平台进行了设计与实现。     

美军JRE应用协议研究

JRE 应用协议是为了克服战术数据链视距传输限制，利用卫星信道、光纤网络等其他媒介来传输战术消息而设计。本文首先介绍了 JRE 应用协议的工作原理和协议参考模型，然后针对应用协议的帧结构初步设计和通用时间基准建立的协议机制展开研究。     

SDH数字微波传输系统原理及应用

SDH数字微波传输系统广泛用于国家级及省级广播电视微波传输干线电路中,它具有传输容量大,远距离传输质量高、抗自然灾害性强等优点,是广播电视节目信号传输的主力设备。在此简明阐述了数字微波传输系统的基本原理,并结合实际详细分析了SDH数字微波传输设备在我站的具体应用,为提高微波传输电路维护水平具有一定意义。     

Implementation of a field programmable gate array for wireless control of a <Emphasis Type="Italic">lab</Emphasis>-<Emphasis Type="Italic">on</Emphasis>-<Emphasis Type="Italic">a</Emphasis>-<Emphasis Type="Italic">robot</Emphasis>

We report the design of a digital system to wirelessly control microchip capillary electrophoresis (CE) equipment and a mobile unit for chemical analysis. The digital system consists of an embedded processor designed for digital control, decoding and applying of wirelessly-transmitted test parameters, data acquisition, and mobility control. The design is implemented on a field programmable gate array (FPGA) and its development board interfaces with four digital-to-analog converters on a newly-designed 3-channel high voltage power supply, electrochemical detector, wireless modems for communications with a base unit, mobile platform motor controllers, GPS sensor, and an air micropump. The FPGA allows for all the interfacing hardware to perform CE and transmission of the data acquired from the interfacing electrochemical detector. The work described herein extends the utilization of microchip capillary electrophoresis to include remotely controlled field applications.     

Analysis and design of a frequency-hopped spread-spectrumtransceiver for wireless personal communications

Personal communications services (PCS) require low-power radio technologies. One such transceiver architecture employing frequency-hopped spread-spectrum techniques is presented. System features such as antenna diversity with equal-gain combining and sequential hop combining are incorporated into the transceiver design to achieve robust wireless digital data transmission over fading channels. A direct-conversion architecture from radio frequency (RF) to baseband reduces the overall power consumption by eliminating intermediate frequency (IF) components. High-rate frequency hopping with frequency-shift keying (FSK) modulation is implemented using a direct digital frequency synthesis technique. A multiplierless correlation FSK detector, suitable for direct-conversion receivers, has been designed for quadrature noncoherent detection. Robust acquisition algorithms based on energy detection and pattern matching and tracking architectures using digital phase-locked loops are also described for system synchronization. The proposed transceiver is well-suited for low-power PCS applications and other portable wireless communications     

FPGA层次化实验教学案例分析

现场可编程门阵列(Field Programmable Gate Array, FPGA)已经从电子设计的外围器件逐渐演变为当今数字系统的核心,在计算机、通信、航天、电子设备等诸多领域有着广泛的应用。通过调研企业对FPGA工程师专业技能的需求,本文提出了层次化的实验教学方法,并以硬件演奏电路作为案例阐述层次化实验教学的实施过程。实践证明层次化实验教学方法可以满足不同水平学生的需求,有助于培养学生的工程应用能力和创新能力,提高学生的就业竞争力。     

一种高数据率DS/FH扩频系统的设计

为适应当前无线通信强抗干扰能力、高数据传输速率的需求,设计并实现了一种适用于直扩/跳频（DS/FH）混合扩频通信系统在高速数据传输状态下的跳频捕获方法,并根据应用需要实现了高数据率下的编码扩频技术和高速直接数字频率合成技术,完成了系统的硬件实现与调试。实际测试表明,系统在一定的扩频增益和3000跳/秒的跳频速率下,传输数据速率大于1 Mb/s,满足工程应用需求。     

Experimental investigations of a new adaptive dual-antenna array for handset applications

This paper presents the design and implementation of a new adaptive dual-antenna array for mitigation of both interference and multipath effects in digital mobile communications at the handset level. This proposed system employs a nonlinear adaptive algorithm in the front end of the receiver to enhance the transmission quality in confined areas. The enhancement is blind since no priori knowledge of spatial signatures or training sequences is required. Furthermore, to obtain a compact antenna array system, a miniaturized shorting postmicrostrip antenna that operates in the 1.9 GHz PCS band is used as a radiating element. Using this microstrip antenna, a new experimental adaptive dual-antenna array prototype was designed and implemented. To examine the expected performance of this approach, experimental measurements were carried out and the measured performances indicate that gain improvement of 7 dB can be achieved by using this approach.     

International Connection of Plesiochronous Networks via TDMA Satellite Link

Digital transmission techniques are expected to spread throughout the fixed-satellite service in the near future. The introduction of digital satellite systems will lead to a new requirement regarding how to connect the satellite link with terrestrial digital networks. This paper presents a satellite/terrestrial digital interface that has been developed to interconnect 2.048 Mbit/s PCM terrestrial and INTELSAT TDMA links which are in the plesiochronous relationship. Major functions of the interface include frame slip control, compensation for path length variation, and rate and format conversions. This paper also describes the design and implementation of the developed equipment, and experimental results for signal impairment due to the frame slips and PCM multiplex standard conversion. The experimental results demonstrate that a large humber of bit errors are induced by frame slips for voiceband data transmission above 4800 bits/s.     

Universal Digital Portable Communications: A System Perspective

In our highly mobile society, the provision of voice and data communications to a person away from his/her wireline telephone has become a major communications frontier. The early penetration of this frontier has been based on very limited portable communications approaches, e.g., cordless telephones, mobile radio telephones, and radio paging. Each of these approaches only partially satisfies portable communications needs. This paper describes an approach to providing universal digital portable communications integrated into telephone networks. A system configuration employing time-division multiple-access radio link architecture and frequency reuse is described. Issues affecting radio link transmission rates and radio system coverage are discussed. Characteristics and parameters of a possible system to supplement the wire (or fiber) loop are indicated.     

Analysis of the data transmission system based on the manipulation with statistical characteristics of a random process

An advanced system of data transmission in digital wideband communications channels based on the manipulation with statistical characteristics of random processes has been proposed and investigated.     

Digital visions: where the superhighway will lead

The author looks forward to the world of interactivity made possible entirely by digital communications, storage and compression. Digital technology has also expanded the capacity of communications networks, supporting an enormous rate of growth in traffic. Compression has immediate transmission cost benefits for satellite broadcasters, since an analogue PAL transponder covering Europe, say, may cost £4 million per year. A compressed 8 Mbit/s digital service (Filmnet), with four digital channels per transponder, quarters the cost per programme service. For a 2 Mbit/s digital service, costs could fall to around £250 000 per year. As the cost of compression equipment falls, many more services can be delivered direct to homes by satellite or cable systems