利用高空无人机实现区域通信的系统设计方法

提出了利用高空无人机实现军用(或应急民用)无线数字移动通信系统的一种设计方法;描述了该通信系统的概念框架、机载通讯设备的组成方式和系统的工作原理;给出了无线链路的分析方法和计算公式,并列出了对上下行链路的计算结果。     

On numerical optimization of communications system design

The limiting factor in the use of computer tools for the design of communications systems is often the amount of human intervention needed, rather than the actual computation time. A technique is presented by which a large proportion of the low-level decision making is delegated to the computer, thereby allowing the designer to concentrate on the engineering aspects and higher-level tradeoffs. The implementation described can be used with existing design programs (e.g., transmission simulators). The possibilities and limitations of the technique are discussed, and several examples of its application are given     

Erlang capacity of ATM-based CDMA satellite system

The capacity and throughput of an ATM-based CDMA system offering flexible access rates on demand are analysed. Extending the existing analysis of traffic capacity of a power-controlled CDMA cellular system, it is shown that offering multiple access rates may result in higher throughput efficiency. An example given of a satellite system shows that the gain in capacity may be some 10%     

On mobile communications smart base-station system design

A design technique for mobile base-station antennas is presented. Beam tilting to avoid intersymbol interference is considered, and the orthogonal method (OM) under constraints on the radiation pattern is applied. The adaptive architecture of the mobile system, in conjunction with the direction of arrival (DoA) and the least mean square algorithms, is explained. A set of useful examples shows the applicability of the whole design.     

Object-oriented specification of a bandwidth management system for ATM-based virtual private networks

This paper describes the specification of a bandwidth management system for ATM-based virtual private networks (vpn). Such a system allows a vpn customer to dynamically modify the bandwidth allocated to vpn connections. The analysis process focuses on the service management information model and interfaces required to provide that service to the customer. The specification work is performed according to a second generation object-oriented development method called Fusion. The vpn service and management architectures as well as the different actors involved are also described in detail.     

An evolvable ATM-based video network design supporting multipleaccess network technologies

This article describes an overall video network architecture with primary focus on the ATM subnetwork. The ATM subnetwork provides efficient switching capability for providing constant bit rate and variable bit rate video communication services. The ATM subnetwork can support multiple access networks like hybrid fiber coax (HFC), asymmetric digital subscriber line (ADSL), and fiber to the curb (FTTC). A broadband network controller is presented as the external controller for the ATM subnetwork which performs the functions of the session/network manager and the ATM-based connection management. The initial deployment of video is likely to be permanent virtual connection (PVC)-based, so a dynamic PVC-based scenario is described. The ATM switch architecture presented here has been optimized to support video applications. An evolution to the switched virtual connection environment and support of multiple services over the ATM subnetwork is also addressed. Traffic management schemes are discussed which provide the negotiated quality of service to the connections     

船载通信天线控制系统的稳定设计

为解决船体姿态的变化对天线视轴的影响问题,采用陀螺检测和前馈补偿的方法.该系统利用3个陀螺检测船摇量在三维空间的分量的方法,生成对天线3个视轴的船摇扰动的附加角速度,加入天线控制系统的速度环输入进行补偿,消除其对天线跟踪的影响.工程使用结果表明,实测隔离度指标达到46.4 dB,跟踪精度达到0.031°,与传统方法相比有效解决了船摇引起的抗扰动问题.     

基于现代通信技术的家庭无线监控系统设计

文章主要介绍了利用现代无线通信技术及视频数据处理技术、控制技术,设计家庭无线监控系统的思路和工作原理.重点介绍了核心器件,如视频数据处理器件DSP(TMS320VC5402)、系统控制器件单片机(AT89C2051)、无线发射收发模块(WE915CTX1).给出了前端(用户家庭)和后端(多媒体手机)设计原理框图,重点介绍发射系统的信息处理过程,器件的选择与关键连接,并对控制系统的软件设计给出了设计流程.     

室内可见光通信中的自适应STBC MIMO-OFDM系统设计

提出基于空时块码（STBC）调制的自适应多输入多输出正交频分复用（MIMO-OFDM）可见光通信（VLC）系统,该系统能够克服MIMO信道相关性并实现可靠通信。同时,引入功率比特分配（PBA）与OFDM相结合,以适应信道传输条件从而有效提高频谱效率。通过搭建一个22的MIMOOFDM VLC演示系统,实现了80 cm距离的传输,实验中测得的误码率始终保持在7%的前向纠错阈值3.810-3之下。实验结果表明,STBC MIMO-OFDM系统对MIMO信道相关性鲁棒,且PBA的应用能够大幅度提高数据速率。     

一种适合中小企业易操作的统一通信系统的研究与设计

通过分析中小企业统一通信应用的需要,结合目前市场上存在的统一通信系统的情况,设计了一套适合面向中小企业的功能简单、价格便宜的统一通信解决方案。     

基于Android的通信安防设计

针对当前Android手机用户通过手机访问网络的需求日益增加的情况。提出了增强基于Android手机网络通信的安全性的目标,研究并采用在Android系统上实现拦截和过滤骚扰电话及短信的关键技术。继而给出一种实现Android系统过滤电话和短信黑白名单的防骚扰的方法。通过测试Android系统手机的实时短信以及来电．达到拦截白名单以外所有电话以及短信,或者拦截黑名单内所有的电话以及短信的效果,从而验证Android通信安防系统的方法性和可实现性。     

A software-defined communications baseband design

Software-defined radios offer a programmable and dynamically reconfigurable method of reusing hardware to implement the physical layer processing of multiple communications systems. An SDR can dynamically change protocols and update communications systems over the air as a service provider allows. In this article we discuss a baseband solution for an SDR system and describe a 2 Mb/s WCDMA design with GSM/GPRS and 802.11b capability that executes all physical layer processing completely in software. We describe the WCDMA communications protocols with a focus on latency reduction and unique implementation techniques. We also describe the underlying technology that enables software execution. Our solution is programmed in C and executed on a multithreaded processor in real time.     

基于IP技术的煤矿通信系统交换单元的设计

本文以煤矿通信系统内部网络为基础,提出一种基于IP网络来实现信息交换,实现数字网和模拟网的统一,达到通信的目的,同时此设计系统升级更为方便灵活,矿井中各处可以根据要求实现较自由的功能扩展。     

System-on-a-chip design for modern communications

In this article, the trends and opportunities in SoC IC design for the networking communication industry is presented. These trends will significantly affect innovation and practice of the microelectronics business in the future. Microchip development and deployment will not be treated as pure components business. In fact, it will become a solution-oriented business that requires knowledge of electronics, software, systems, and soft skills such as business, marketing, psychology for human factors, etc     

Signal design for phase-incoherent communications

The problem of determining optimal signal waveforms for transmission through a phase-incoherent channel is examined under the following conditions: 1) the channel adds white Gaussian noise to the signal, 2) the receiver is synchronized, 3) the receiver is designed to minimize probability of error, 4) all signals have equal energy, 5) all messages are, a priori, equiprobable, and 6) there is no bandwidth restriction on the signal set. This signal design problem is expressed as a variational problem involving a search for the optimal matrix in a specific class of non-negative-definite matrices, or, equivalently, involving a search for the optimal signal correlation set in a collection of admissible signal correlation sets. For all signal-to-noise ratios, the probability of error is shown to have a local extremum in the class of all admissible signal sets at the orthogonal signal set. This extremum is then classified as a local minimum by proving that the second-order variations are, indeed, always positive. The probability of error is then evaluated numerically for the orthogonal signal structure.     

移动通信中的开放性

技术创新的层出不穷,使得关于开放体系和专有体系之间的争论愈演愈烈。历史经验证明,开放体系带来长期的令人瞩目的商业价值。如开放标准通过漫游呼叫和不断增长的短信互通流量,大大提高了运营商的收入。汲取早期的成功经验,移动通信产业正在选择开放?体系,以期在多媒体信息及更先进的第三代移动服务方面取得进一步的成功。移动产业中的有关各方均从开放性中获益:消费者在终端、服务方面有更多选择,成本也更低廉;运营商能够以更低廉的成本快速部署新服务;设备制造商可以从更大的规模效益和由此带来的低成本中获益;应用开发商、供应商和转包…     

Information theory: The copernican system of communications

IT IS ARGUED that Shannon's theory of information is the scientific basis of commumcataons in the same sense that Copernicus' heliocentric theory is the scientific basis of astronomy. Some parallels between Copernicus and Shannon are drawn. It is further argued that the fundamental thesis of information theory is that all communications is essentially digital and that the main theorem of information theory is the separation theorem for source and channel coding. Some observations about the source coding theorem and the channel coding theorem are offered.     

某Ku频段卫星通信系统的设计

为了让两个地面站通过卫星链路进行无线通信,设计了一个Ku频段卫星通信系统 ,数据速率是512 kbit/s～4.096 Mbit/s,速率可调步进1 bit/s。选取了一 种较简洁的Ku频段地面 站设计方案,信道的本振为固定点频,调制解调器的中频范围是950～1 450 MHz。对卫 星通信 链 路功率进行了预算。地面站的组成设备,如调制解调器、低噪声放大器、上变频单元、下变 频单元等均选用成熟的商用货架产品,降低了设计风险和成本。本系统研制周期短,通信稳 定可靠,得到了用户的认可。     

Doubling the capacity of a communications satellite system

Two one-way channels are normally used in digital two-way voice communication. Each channel is in effect-used only one half the time. A recent discovery of ours recognized that any one-way channel within a satellite spot-beam can be accessed by anyone in the footprint of the beam. In a two-way voice call, the two parties alternate (in principle) in their transmissions-when one speaks the other is silent. Therefore, the two can share a single one-way channel and provide continuous use of the channel, their respective transmissions interleaved with one another. This condition is unique to intrabeam communication via satellite (or balloon). In a satellite system, capacity is a valued commodity, where capacity is limited by allocated bandwidth and power available. Under those two constraints of bandwidth and power limitation, the discovery described generates a doubling of capacity. This article addresses this concept and some of the engineering challenges and opportunities arising therefrom     

Privacy and authentication on a portable communications system

Public-key/private-key hybrid key agreements and authentication protocols which maintain privacy of conversation and location information, and deter usage fraud, are presented. These protocols are optimized for low complexity in the portable unit and network infrastructure. The basic cryptographic techniques are described, and some complexity information obtained from these laboratory experiments and from other sources are presented. The three public-key protocols described have differing levels of security and complexity: and the tradeoffs are discussed. Because of the complexity concerns mentioned above, the public-key protocols are compared to a representative private-key approach in the areas of both security and computational complexity