System aspects of cellular radio

The greatest single factor in enhancing spectral efficiency of a network is the mass deployment of microcells. By this simple technique we can repeatedly and efficiently reuse the precious spectrum. The number of users a network can support is fundamentally dependent on the common air interface (CAI) over which users communicate. User capacity is dependent on many factors, but the cardinal ones are the amount of spectrum the regulators allocate, the size of the radio coverage area from a base station (BS), and the amount of interference a particular radio link can tolerate. In this article we are primarily concerned with the system aspects associated with the CAI. We focus on the critical importance of BS siting. Starting with existing large cells, we deliberate on the problems that might arise in siting BSs in three dimensional microcells, in order to consider suitable multiple access methods for future cellular environments     

工作流技术综述

工作流技术是业务流程自动化的核心技术,对于提高企业的生产管理水平和业务处理能力具有重要的意义.本文首先介绍了工作流技术的起源与发展,然后对工作流技术做出综述,主要包括了工作流的定义,工作流参考模型以及工作流管理系统这三个方面.同时概括了当前工作流产品的特点,分析了其所存在的问题.在文章最后探讨了工作流技术的未来研究热点以及发展趋势.     

TeleMIP技术概述

TeleMIP 提供了一种在无线蜂窝网中实现快速、无缝、平滑切换的解决方案。     

Ethernet PON 技术概述

随着Internet的高速发展,用户对网络带宽的需求不断提高,传统的接入网已经成为整个网络中的瓶颈,以新的宽带接入技术取而代之成为目前研究的热点。正是在这种背景下,IEEE于2000年底成立了EFM工作组（Ethernet in the First Mile Study Group）,试图引入一种新的接入技术标准－Ethernet PON（或Ethernet over PON, EPON是利用PON（无源光网络）的拓扑结构实现以太网的接入。目前,该项技术正处在研究讨论阶段,还未形成标准,但由于EPON具有其它接入技术无法比拟的优势,可以预见在不久的将来,它将很可能成为IEEE802.3…     

On the eigenvalue distribution of smart-antenna arrays in wireless communication systems

The recent development of communication theory and smart-antenna techniques such as space-time coding (STC), which exchange efficiency for complexity, has intensified the interest in a general theory of multiple-antenna communication. These techniques use parallel channels to increase the capacity of wireless systems. The parallel channels are formed either in a natural way, due to radiowave propagation (receiving diversity, RD, RAKE), or in an artificial way, due to appropriate pre-processing and coding (transmitting diversity, TD, STC), or in both ways (multiple-input multiple-output, MIMO, systems, STC, BLAST). The demand for ubiquitous, heterogeneous, and sophisticated wireless systems has led to the need for a better understanding of fundamental issues in space-time communication theory, and their implications for the design of reliable, high-bandwidth and high-speed wireless communications. The authors discuss the issue of eigenvalue distribution for antenna arrays. The present article provides an approach that should be useful in simulations, analysis, and design of smart-antenna wireless systems. The results show that this parameter of the spatial channel has an important rcHe to play in analyzing the performance of antenna arrays in wireless systems.     

Economic aspects of configuring cellular networks

This paper addresses economic aspects of configuring cellular networks. Major components of costs and revenues and the major stakeholders are identified and a model is developed to determine the system configuration (e.g. cell size, number of channels, etc.) which will maximize the annual expected net revenues to the system operator. Key properties relating the various parameters of interest are derived. The results of computational experiments are presented and their implications are discussed. The computational results show that the optimal net revenue curves have a saw-tooth structure with two types of teeth; Large ones that come from switching between cellular technologies, and smaller jumps come the discretenes of base stations. The importance of capturing a high fraction of potential users, in early stages of cellular system introduction is investigated. Finally, the cost of competition and its implications for the regulatory agency and the cellular service providers are analyzed. It is shown that by dividing the available frequency spectrum between too many system operators, the overall value of the cellular system is reduced when compared to an approach which uses division of the overall service area into a larger number of service areas, each with only two system operatos. The above results have profound implications on public policies for frequency spectrum allocation.     

An overview of electric vehicle technology

An overview of the present status and future trends in electric vehicle technology is provided. The emphasis is on the impact of rapid development of electric motors, power electronics, microelectronics, and new materials. Comparisons are made among various electric drive systems and battery systems. The market size of electric vehicles in the coming years and the potential electric vehicle impacts are discussed     

An overview of smart power technology

The evolution of smart power technology and the impact of this technology on electronic systems are reviewed. After providing a definition of smart power technology, the author describes the key technological developments in power semiconductor devices, namely power MOSFETs and IGBTs (insulated-gate bipolar transistors). These developments are the foundation upon which smart power technology rests. Smart power technology requires the marriage of power device technology with CMOS logic and bipolar analog circuits. The technical challenges involved in combining power handling capability with on-chip regulation of overcurrent, overvoltage, and overtemperature conditions are described, together with examples of solutions for telecommunications, motor control, and switch mode power supplies     

电子邮件认证技术

主要讨论电子邮件认证技术的相关问题，详细介绍了目前互联网中新出现的几种电子邮件认证技术，如发件人策略框架、发件人身份标识、域密钥以及互联网电子邮件标识技术，通过对这些技术的分析指出电子邮件认证技术面临的主要问题及未来的发展趋势。     

An overview of today's thick-film technology

How thick-film systems are used in all facets of today's electronic industry, starting with their initial application in the computer and defense industries, is described. As the state of the art grew, composition suppliers broadened their lines, developing new higher performance materials to meet changing and more sophisticated packaging requirements. The present technology offers advantages of simple processing, fast and inexpensive tooling systems, economy, quick tumaround time between need and prototype, using wider tolerance active devices, high reliability, and multilevel circuit capabilities. As a result, virtually all sectors of today's electrical and electronics industries are turning to solid-state systems which utilize thick-film hybrid microcircuitry. Consumer and automotive electronic uses are exhibiting the highest rate of new thick-film circuitry adoption at the present time. Industrial usage for high power, measuring and control systems, is also increasing rapidly, and thick-film hybrid circuits are strong candidates to replace electromechanical switching devices. The use of. hybrid microcircuits is forecasted to double or triple current usage on a worldwide basis by 1975. In the future, thick films are expected to play an ever increasing role in the packaging of semicpnductor devices because of their low production cost and high performance advantages.     

无线电定位技术在蜂窝通信系统中的应用及实现

当前，移动用户对基于无线定位技术的新业务的需求不断增加，推动了对无线测距及定位技术的深入研究，向用户提供精确的定位信息已经成为新一代PCS系统的标准业务之一。本文主要介绍几种基于现有蜂窝通信系统的无线定位技术的实现原理，所要解决的主要问题和应用前景。     

Control aspects of intraaortic balloon pumping: an overview

Temporary or permanent, internal or external, in-series or bypass cardiac assist devices are examined with emphasis on intraaortic balloon pumping. Physiological and clinical consequences of the medical assistance are discussed. Major advantages of the devices are to provide adequate perfusion and, secondarily, to unload the heart and to reduce oxygen consumption of the failing myocardium. Major problems with the cardiac assist devices are related to synchronization with the natural heart, or proper timing, and to the determination of suitable control variables. Optimization algorithms based on the selected performance criteria and computer-based automatic controls are instituted to overcome some of these shortcomings. Finally schemes of automatic control of implantable assist devices are discussed     

An overview of optical data storage technology

Optical techniques for data storage have advanced rapidly during the last decade. Optical data storage presents many unique advantages, notably the high storage density and low access time, not attainable by conventional recording techniques. The special features of optical recording, the proposed materials and techniques, the components for optical storage as well as some representative optical bit-by-bit and holographic recording systems are reviewed. It is noted that in spite of the lack of widespread commercial success of the optical recording at the present, some unique devices have been successfully demonstrated. The knowledge accumulated in the development of optical data storage should be useful for many recent Applications such as video recording. It is expected that when the conventional magnetic memory technology reaches its limit, optical storage technology should be a competitive contender for the next generation data storage.     

An overview of the Bluetooth wireless technology

The Bluetooth^TM wireless technology is designed as a short-range connectivity solution for personal, portable, and handheld electronic devices. Since May 1998 the Bluetooth SIG has steered the development of the technology through the development of an open industry specification, including both protocols and application scenarios, and a qualification program designed to assure end-user value for Bluetooth products. This article highlights the Bluetooth wireless technology     

Interference cancellation for cellular systems: a contemporary overview

Cellular networks today are interference-limited and only becomes increasingly so in the future due to the many users that need to share the spectrum to achieve high-rate multimedia communication. Despite the enormous amount of academic and industrial research in the past 20 years on interference-aware receivers and the large performance improvements promised by these multi-user techniques, today's receivers still generally treat interference as background noise. In this article, we enumerate the reasons for this widespread scepticism, and discuss how current and future trends increases the need for and viability of multi-user receivers for both the uplink, where many asynchronous users are simultaneously detected, and the downlink, where users are scheduled and largely orthogonalized; but the mobile handset still needs to cope with a few dominant interfering base stations. New results for interference cancelling receivers that use conventional front-ends are shown to alleviate many of the shortcomings of prior techniques, particularly for the challenging uplink. This article gives an overview of key recent research breakthroughs on interference cancellation and highlights system-level considerations for future multi-user receivers.     

Fiber Bragg grating technology fundamentals and overview

The historical beginnings of photosensitivity and fiber Bragg grating (FBG) technology are recounted. The basic techniques for fiber grating fabrication, their characteristics, and the fundamental properties of fiber gratings are described. The many applications of fiber grating technology are tabulated, and some selected applications are briefly described     

图像中的隐秘术分析技术及其研究概况

简要介绍了信息隐藏技术和隐秘术分析技术，分析了基于数字图像的隐秘术分析技术，并深入讨论了现有的多种隐秘术分析算法和技术现状。     

多路径传输控制协议技术综述

随着互联网的应用发展,用户对带宽的需求日益增大。同时,伴随着宽带接入技术的发展,终端可以同时具有多条网络链接,然而传统传输控制协议(TCP)采取单路通信,因而造成资源浪费。为此,IETF专门提出了多路径TCP(MPTCP)来实现TCP的多路传输,从而提高链路利用率和协议鲁棒性。本文对国内外MPTCP的最新研究成果进行了总结,包括MPTCP的体系结构、路由和拥塞控制等内容,可为国内研究者进一步深入研究提供参考。     

Ubiquitous computing: An overview of technology impacts

Ubiquitous computing is considered as a promising technological path of innovation. Intensive R&D activities and political strategies are addressing the objective to foster marketable technologies and applications. This article explores the state-of-the-art on the way towards the “Internet of things”. Which application fields have already proved their potential for realising the vision and promises related to the new technology? What are the technical, legal and social challenges that have to be addressed – and how can policy-makers contribute? We deal with these questions in the light of recent developments in research and business, illustrating the findings by examples in retail, logistics and health care. The article concludes that further efforts by all stakeholders from businesses, society and politics are necessary to make ubiquitous computing applications economically sustainable and socially compatible in order to tap its full potential.     

Modeling spatial aspects of cellular CDMA/SDMA systems

The probability density functions (PDFs) describing various physical aspects of hybrid cellular code division multiple-access/space-division multiple-access (CDMA/SDMA) networks are derived. All mobile users are considered to be surrounded by a Gaussian bell shape of scattering elements, and a general rule of thumb for the standard deviation of the scattering elements is proposed. Second, in order to describe the distribution of mobile users in the cell, a general PDF describing mobile user distributions is proposed. Using the mentioned distribution a general PDF for the angle-of-arrival (AOA) of signals at the CDMA base station is derived