超宽带无线技术

本文主要介绍了超宽带无线技术（UWB-RT）的基本特点和超宽带无线技术的调制方式，并分析了超宽带无线技术的管制和标准化现状，最后介绍了超宽带无线技术的发展动态．     

超宽带无线技术

本文主要介绍了超宽带无线技术（UWB-RT）的基本特点和超宽带无线技术的调制方式，并分析了超宽带无线技术的管制和标准化现状，最后介绍了超宽带无线技术的发展动态。     

UWB--超宽带无线技术

UWB（Ultra Wideband）——超宽带无线技术是一种使用1GHz以上带宽的最先进的无线通信技术。虽然是无线通信,但其通信速度可以达到几百Mbit/s以上。     

超宽带无线技术简介

“UWB”（Ultra Wideband）是超宽带无线技术的缩写。UWB技术是一种使用1GHz以上带宽的最先进的无线通信技术。虽然是无线通信，但其通信速度可以达到每秒几百兆位以上。     

下一代无线接入网--基于IP的无线接入

下一代无线网络的体系结构标准正在制定中,本文介绍了一种基于IP的网络体系结构,它可以作为不同接入技术的通用接入网。这种基于IP的无线接入网采用Intemet标准和Mobile IP协议支持移动终端的宏移动,当移动终端只做微移动或需实现无线呼叫功能时,就采用HAWAII协议。在网络部署规模日益增长的情形下,基于IP的无线接入在网间互连互通等方面表现出了明显的优势。     

超宽带无线技术——UWB

提到宽带无线技术,人们自然会想到目前三类成熟产品。第一类是提供2Mbit/s速率的产品,如微波一点多址系统;第二类是LMDS(Local Multipoint Distribu-tion System)以及MMDS(Multipoint Microwave Distribu-tion System)系统;第三类是按IEEE、无线ATM论坛和ETSI推出的标准构成的系统,最为人熟知的是IEEE802.11、IEEE 802.11b、IEEE 802.11a和IEEE 802.11g。还有其他技术,诸如宽带移动无线技术(分为地面移动3G和卫星移动3G、U-11(Unlicensed National Informa-tion Infrastrure,俗称5G无线技术)、3.5G技术、无线光通信技术等。而超宽带无线技术却鲜为人知。     

下一代高性能无线局域网技术

HiperLAN/2是一种由ETSI制订的高性能的无线局域网标准，它提供了54Mbit/s的传输速率。本对HiperLAN/2协议体系结构、HiperLAN/2网络应用与特点进行了介绍，并对其与GPRS／UMTS网络的互联进行了论述。     

下一代高性能无线局域网技术

HiperLAN/2是一种由ETSI制订的高性能的无线局域网标准,它提供了54Mbit/s的传输速率。本文对HiperLAN/2协议体系结构、HiperLAN/2网络应用与特点进行了介绍,并对其与GPRS/UMTS网络的互联进行了讨论。     

下一代宽带无线接入技术

在介绍IEEE802．16的发展的基础之上，着重阐述了其协议栈模型、物理层特性和MAC特性，并总结了它的优势所在。相信802．16技术作为下一代理想的宽带无线接入技术，一定能够解决目前仍然存在的技术和应用问题，构建出理想的下一代宽带无线接入网。     

下一代的宽带无线接入技术

近年来，随着用户数据业务量的迅猛发展，以ADSL为代表的有线宽带接入技术发展非常迅速，在宽带接入网市场上占据了主导性的地位。但在缺乏有效的有线接入手段的地域内，无需光纤或双绞线等线缆资源的宽带无线接入技术得到了运营商的青睐，通过架设无线网络，用户同样可以便捷地接入到宽带网络。     

能有效测试下一代宽带设计的新测试方法

Credence的ASL 3000RF为无线器件的特性化测试带来了强有力的新工具，帮助工程师面对下一代无线器件及应用，包括802．11WLAN标准和5G移动通信服务，在技术上和经济上遇到的挑战。调制S参数以新视角来看器件性能，提供了“真实”复杂的调制信号作为测试条件。该分析方法结合有调制信号能力的网络分析技术使得S参数对于目前的宽带通讯系统更为有用。     

无线多媒体接入中的超宽带技术

简要介绍了超宽带(UWB)的概念及发展过程，通过与现有短距离无线接入技术的比较，表明它在无线多媒体接入系统中具有传输速率高、空间容量大等特点，分析了尚需解决的关键技术并展望了应用前景。     

下一代网络技术

随着通信技术的快速发展,人们对网络服务提出了更高的要求,基于分组交换的下一代网络(NGN)技术就是解决这些问题的最佳方案。介绍了下一代网络的概念和特点,分析了下一代网络的体系结构、主要技术、相关协议及发展前景。     

超宽带无线通信技术--UWB

半导体技术与网络技术的不断发展,为无线通信的应用开辟了广阔前景,诸如无线因特网、无线局域网、无线个人区域网等等的广泛应用,潜移默化地改变着人们的工作与生活,与此同时,这些应用的推广与提高又呼唤着新的技术进步.     

超宽波段透射式中继镜头设计北大核心CSCD

瞄准镜、高温炉内窥镜、复印镜头、大倍率变焦系统等光学系统中,通常采用中继系统实现系统的延长、转向和系统出入瞳的匹配等等。本文探索了一种实现超宽带宽中继光学系统的像差矫正要求、玻璃选择方法以及设计结果,完成了超宽波段中继光学系统的设计,Zemax的设计结果表明,在工作波段0.4~1.7μm,物方NA=0.2,视场为10 mm的要求内,系统的MTF接近于衍射极限,轴向色差小于40μm,成像质量较好。     

A new approach to peer-to-peer wireless LANs based on ultra wide band technology

The advent of Ultra Wide Band (UWB) technology offers a unique opportunity to consider a new type of peer-to-peer wireless Local Area Network (LAN) that requires neither access at a peak data rate commensurate with the full bandwidth of the medium nor a conventional medium access protocol. Rather, due to the extraordinarily high bandwidth afforded by UWB, which is typically much greater than the peak bandwidth required by any ad-hoc radio node, one might imagine a network for which pairs of nodes are interconnected by one or more dedicated (non-shared) radio channels created by time, frequency, or code division multiplexing. In this paper, we consider a network containing N ad-hoc nodes and 2N independent radio channels. Starting with (1) an N × N power matrix, where element p _i,j represents the power needed for a successful transmission from node i to node j including the effects of path loss and shadow fading, and (2) a second N × N traffic matrix where element t _i,j represents the exogenous traffic originating from node i and destined for node j, we seek to assign radio channels and multi-hop route the traffic between source-destination pairs such that the resulting connectivity pattern and traffic flow minimize the average transmit energy needed to deliver a packet between an arbitrarily chosen pair of nodes. With no medium access protocol needed, collisions cannot occur and retransmissions become unnecessary. Moreover, the available capacity grows with the number of channels created (or, alternatively, as some common set of channels are re-used on a non-interfering basis via sufficient spatial separation). In this fashion, such a UWB ad-hoc network takes on the characteristics of a multi-hop Wavelength-Division Multiplexed (WDM) network well known from the multihop lightwave network art, although the constraints and dynamics are certainly different. Since the optimum connectivity and flow problem is shown to be NP hard, several heuristics are considered and compared. These heuristics seek, first, to establish a “good” connectivity graph, and then to flow the traffic in an optimum fashion. Our results suggest that application of these techniques may provide a distinct wireless LAN advantage achievable only via UWB radio technology, and several opportunities for future work based on this novel approach to ad-hoc local area radio networks are identified and discussed. Marc Krull received his B.S. degree in electrical engineering from Brown University in 2001 and his M.S. degree in electrical engineering from the University of California, San Diego in 2004. His graduate research focused on the investigation of energy efficient routing protocols for ultrawideband networks. He is currently with Raytheon Companys Intelligence and Information Systems division in Aurora, Colorado, where he is involved in software development for satellite ground systems. Anthony Acampora is a Professor of Electrical and Computer Engineering at the University of California, San Diego, and is involved in numerous research projects addressing various issues at the leading edge of telecommunication networks, including the Internet, ATM, broadband wireless access, network management and dense wavelength division multiplexing. From 1995 through 1999, he was Director of UCSDs Center for Wireless Communications, responsible for an industrially funded research effort which included circuits, signal processing, smart antennas, basic communication theory, wireless telecommunications networks, infrastructure for wireless communications, and software for mobility. Prior to joining the faculty at UCSD in 1995, he was Professor of Electrical Engineering at Columbia University and Director of the Center for Telecommunications Research, a National Science Foundation Engineering Research Center. He joined the faculty at Columbia in 1988 following a 20-year career at AT&T Bell Laboratories, most of which was spent in basic research where his interests included radio and satellite communications, local and metropolitan area networks, packet switching, wireless access systems, and lightwave networks. His most recent position at Bell Labs was Director of the Transmission Technology Laboratory where he was responsible for a wide range of projects, including broadband networks, image communications, and digital signal processing. At Columbia, he was involved in research and education programs concerning broadband networks, wireless access networks, network management, optical networks and multimedia applications. He received his PhD. in Electrical Engineering from the Polytechnic Institute of Brooklyn and is Fellow of the IEEE and a former member of the IEEE Communication Society Board of Governors. Professor Acampora has published over 160 papers, holds 33 patents, and has authored a textbook entitled An Introduction to Broadband Networks: MANs, ATM, B-ISDN, Self Routing Switches, Optical Networks, and Network Control for Voice, Data, Image and HDTV Telecommunications. He sits on numerous telecommunications advisory committees and frequently serves as a consultant to government and industry.     

下一代数据库技术综述

引言 如今是信息的世界，大量的数据需要有地方存放和管理，数据库应用而生。数据库正在从一段相对停滞的时期走出来，那段时期议程是让SQL执行得更好。现在数据库体系结构处于打破平衡的阶段。它们已经成为一种媒介，提供集成的应用软件开发环境，作为因特网上的存储数据节点，能进行数据搜索和自我管理。我们最大的希望是能够很好地处理冲击了个人，组织及人类团体各个方面的信息雪崩效应。     

A novel wide band super transistor based voltage feedback current amplifier

This paper is assigned to the design of voltage feedback current amplifiers (VFCAs). Their operation and interesting characteristics are covered and a novel CMOS VFCA is presented. New ideas based on super transistors (STs) are devised and used to design a high performance VFCA. Benefiting from the interesting properties of STs, the proposed VFCA exhibits high linearity, high output impedance, very low input impedance and wide bandwidth. The proposed circuit is designed using TSMC 0.18 μm CMOS technology parameters and supply voltage of ±0.75 V. Simulation results with HSPICE show low THD of ?60 dB at the output signal, very low impedance of 0.6 Ω and 0.2 Ω at the input and feedback ports respectively and high output impedance of 10 MΩ. Moreover it can provide wide ?3 dB bandwidth of 15.5 MHz. The results prove the high capability of the VFCA in current mode signal processing and encourage strong motivation to develop commercially available VFCAs.     

下一代网络管理技术研究

针对下一代网络的发展特点,介绍了下一代网络管理技术的研究重点主要集中在对混合网元的管理、对多个专业网组成网络的综合管理以及基于新一代OSS的网络管理三个方面,并简要介绍了其基本实现方法。     

A millimeter wave broadband wireless access technology demonstratorfor the next generation Internet network reach extension

We report design and implementation scenarios for a gigabit-capacity and high-data-rate fixed wireless access technology demonstrator. The system is based on a broadband wireless access concept and implementation techniques utilizing millimeter-wave and newly introduced free-space optical wireless high-speed links. The demonstration platform is to provide broadband “last mile” access and networking solutions to Internet users in densely populated areas with homes and businesses (e.g., building-centric and inner city environments) in need of high bandwidth not served by the fiber infrastructure. The investigation focuses on the radio link design, network architecture, system integration, and a compatible interface to the existing ATM fiber and satellite core networks in support of the next-generation Internet (NGI) reach network extension by the wireless technology