最新h科技英语翻译大全

科技英语词汇

科技英语词汇科技在现代社会中起着至关重要的作用，我们可以通过学习科技英语词汇来更好地理解和应用相关的科技知识。

本文将介绍一些常用的科技英语词汇，并分为四个部分进行分类讨论。

一、计算机与互联网技术（Computing and Internet Technologies）1. Algorithm（算法）- A step-by-step procedure for solving a problem.2. Artificial intelligence（人工智能）- The simulation of intelligent behavior in computers.3. Database（数据库）- An organized collection of data stored and accessed electronically.4. Encryption（加密）- The process of converting information intoa secret code to prevent unauthorized access.5. Firewall（防火墙）- A network security system that monitors and controls incoming and outgoing network traffic.6. HTML（超文本标记语言）- The standard language for creating web pages and web applications.7. Network（网络）- A group of interconnected devices that can share resources and communicate with each other.8. Operating system（操作系统）- The software that manages computer hardware and software resources and provides common services for computer programs.9. Software（软件）- The programs and operating information used by a computer.10. Virus（病毒）- A type of malicious software that can replicate itself and infect computer systems.二、通讯技术（Communication Technologies）1. Broadband（宽带）- A high-speed internet connection that can transmit large amounts of data simultaneously.2. Cellular network（移动通信网络）- A wireless network that allows mobile devices to connect to the internet.3. GPS（全球定位系统）- A navigation system that uses satellites to determine the precise location of a device or user.4. Modem（调制解调器）- A device that modulates and demodulates analog signals to enable digital data transmission over telephone or cable lines.5. Satellite（卫星）- An object that orbits around a planet or star and is used for communication or navigation purposes.6. Telecommunication（电信）- The transmission of information over long distances using electronic devices.7. Video conference（视频会议）- A communication session between two or more participants in different locations, conducted through video and audio transmissions.8. VoIP（网络电话）- Voice over Internet Protocol, a technology that allows voice communication over the internet.三、机器和设备（Machines and Devices）1. 3D printer（3D打印机）- A device that creates three-dimensional objects by adding layers of material.2. Drone（无人机）- An unmanned aerial vehicle that can be controlled remotely or autonomously.3. Robot（机器人）- A programmable machine that can perform tasks automatically or with human guidance.4. Sensor（传感器）- A device that detects and responds to physical inputs, such as light, heat, or motion.5. Smartphone（智能手机）- A mobile phone with advanced features and connectivity to the internet.6. Virtual reality（虚拟现实）- A computer-generated simulation that immerses the user in a virtual environment.7. Wearable device（可穿戴设备）- A technology device that can be worn on the body, such as a smartwatch or fitness tracker.8. X-ray machine（X射线机器）- A device that uses electromagnetic radiation to produce images of the internal structure of an object or body.四、能源与环境技术（Energy and Environmental Technologies）1. Biofuel（生物燃料）- Fuel derived from renewable biological sources, such as plant biomass or animal waste.2. Carbon footprint（碳足迹）- The amount of greenhouse gases produced by human activities, measured in units of carbon dioxide (CO2) equivalent.3. Renewable energy（可再生能源）- Energy derived from natural resources that are replenished, such as sunlight, wind, or water.4. Solar panel（太阳能电池板）- A device that converts sunlight into electricity.5. Sustainable（可持续发展的）- Describes practices and technologies that meet the needs of the present without compromising the ability of future generations to meet their own needs.6. Waste management（废物管理）- The collection, transportation, and disposal of waste materials in an environmentally responsible manner.7. Wind turbine（风力发电机）- A device that converts wind energy into electricity.总结：通过学习科技英语词汇，我们可以更好地理解和应用科技知识，与他人进行有效的沟通和交流。

科技英语翻译中译英常

1、直流电是一种总是沿着同一方向流动的电流。

A diret current is a current flowing always in the same direction.2、阿基米德最先发现固体排水的原理．Archimedes first discovered the principle of displacement of water by solid bodies.3、地球绕轴自转，引起昼夜变化．The earth rotates on its own axis, which causes the change from day to night.4、极化产生的异常会远远大于地形引起的异常。

Anomalies due to polarization can be so much larger than those resulting from topography.5、娱乐用水标准的发展是一个棘手的问题。

Development of standards for recreational water is therefore a complicated issue.6、结构材料的选择应使其在外界条件中保持弹性。

Materials to be used for structural purposes are chosen so that they hehave elastically in the environmental conditions.7、柔性转子动平衡一直是现代工业中一项很实用的关键技术。

Flexible rotor balancing is a practical and key technique in modern industry.8、你可以采取手动的方法将此服务添加到本地连接里。

You can manually add the service to the local area connection.9、他们特别强调提高电子设备的质量。

科技英语新词汇

干扰素（Interferon）干细胞（Stem Cells）干燥综合征(Sjogren Syndrome,SS)高技术（High Technology, 简称Hi-tech）高技术战争（high-tech warfare）高温超导电缆（High-TC Superconducting Cable）高温超导体（High-TC Superconductor）公共密钥基础结构(Public Key Infrastructure，PKI)供应链管理(Supply Chain Management)光纤通信（Optical Fiber Communication）国防高技术（defense high technology）国防关键技术（defense critical technology）国防信息基础结构（DII Defence Information Infrastructure）国际空间站（ISS(International Space Station)）()互联网时间（Internet Time）大规模杀伤性武器（Weapons of mass destruction）（陶子）中微子（T au neutrino ）大科学(Big Science)地球模拟器（Earth Simulator）地球资料卫星（earth resources satellite）地震矩规模（moment magnitude scale）电子现金(Electronic Cash)电子支票(Electronic Check)动漫（Comic and Animation）都市农业(Urban Agriculture或Agriculture in City Countryside) 二恶英”(Dioxin)非典型肺炎（Atypical Pneumonias）分布式计算（Distributed Computing）分布式能源（distributed energy sources）分子遗传学（Molecular genetics）疯牛病（Mad Cow Disease）白色农业（white agriculture）办公自动化（OA：Office Automation）半导体材料（semiconductor material）比较医学（Comparative Medicine）并行工程(Concurrent Engineering)博客（Blog/Blogger）超级网站（Super Website）城市垃圾管理的三C原则（Clean Cycle Control）创新决策权（Authority innovation-decisions）磁悬浮列车(Magnetically Levitated Train)3C 融合(3c fusion)3G（3rd Generation）3R技术(3R techniques)4A（Anyone Anytime Anywhere Anything）CG( Computer Graphics )DVD( Digital Versatile Disk，多功能数码光盘)EVD (Enhanced Versatile Disk，增强型多媒体盘片系统)Open AccessSOI材料(Silicon on Insulator Materials)Wi-Fi技术（Wireless Fidelity）阿尔法客车”(AlphaBus)爱普（APIEL：Advanced Placement International English Language）按需计算（On-Demand Computing）ACPR — adjacent-channel power ratio 邻频功率比ADC — analog-to-digital converter 模数转换AGC — automatic gain control 自动增益控制AMPS — advanced mobile phone system 高级移动电话系统ASIC — application-specific integrated circuit 专用集成电路ASK — amplifier shift keying 幅移键控ATM — asynchronous transfer mode 异步传输模式AWGN — additive white gaussian noise 加白高斯噪声BER — bit error rate 误码率BPSK — binary phase shift keying 二相位键控CCRR — co-channel rejection ratio 同频抑制比CDMA — code-division multiple access 码分多址CDPD — cellular digital packet data 蜂窝数字包数据/蜂窝状数字式分组数据交换系统，也指相应的技术或标准CMRR — common-mode rejection ratio 共模抑制比HAPS ----高空平台站HBS ----HARDWARE BENCHMARK SYSTEMHDTV ----高清晰度电视HDTV ----高清晰度电视HEC ----混合纠错HFC ----光纤电缆混合网HFC ----光纤铜轴混合网HGC ----HERCULES GRAPHICS CARD 大力神图形卡HHS ----美国卫生和公众服务部HIS ----医院信息系统HLM ----异类局域网管理HLR ----HOME LACATION REGISTEMHMI ----人机接口HOME PNA ----电话线联网联盟HOME RF ----研究策划家庭网络无线传送规格的业界机构HON ----互联网保健基金会HOPS ----Hast Pioxionity SecoiceHPA ----高功率放大器HPC ----手掌电脑HPCC ----HIGH PERFORMANCE COMPUTING AND COMMUNICATION PROGRAM 高性能计算机与通信规划HPCC ----HIGH PERFORMANCE CONYUTING AND COMMUNICATING 高性能计算与通讯HPCS ----高性能计算机系统HPFS ----高性能文件系统HPSN ----高性能可延展网络HRN ----HARDWARE REVISION NUMBERHSCDS ----高速电路交换数据HSCSD ----HIGH SPEED CINCUIT SWITCHED DATAHSCSD ----高速数据传输HSSG ----HIGH SPEED STUDY GROUNHTTP ----HYPER TEXT TRANSFER PROTOCALHUML ----HYPER TEXT MARKUP LANGUAGE科学技术教育与培训（S&T education and training）科学素养(Scientific Literacy)可视图文（Visual pictures and literature）空间站（space station）空中交通管制（air traffic control— ATC）蓝色农业（blue agriculture）蓝牙技术(Bluetooth)立体农业（stereo farming）量子纠缠（Quantum Entanglement）量子密码术(Quantum cryptography)量子隐形传送(Quantum T eleportation)硫污染（Pollution by Sulfur）绿色GDP（Green GDP）绿色纤维（Lyocell fibre）绿箱政策（GreenBox Policies）密钥加密技术（Key Encryption Technology）敏捷制造（Agile Manufacturing）()纳米材料(nano material)与纳米粒子(nano particle)纳米机器人（Nano Robot）纳米科学技术（NanoST (Nano Science and Technology)）纳卫星（Nano-Satellite）农业产业化（Agriculture Industrialization）欧洲洁净空气”计划（CAFE ( Clean “Air For Europe rogramme”）贫铀弹(Depleted Uranium Bomb)平均无故障工作时间（mean-time-between-failures — MTBF）普适计算（Pervasive Computing）气象卫星（meteorological satellite）千年生态系统评估（Millennium Ecosystem Assessment）清洁生产(Cleaner Production)全球定位系统（Global Positioning System，简称GPS）全球警报与反应网络(Global Out-break Alert and Response Network)燃料电池（Fuel Cell）人工乘客（Artificial Passenger）人类脑计划（Human Brain Project）人文发展指数(HDI)认证中心（Certificate Authority, 简称CA）柔性制造技术（flexible manufacturing technology— FMT）朊毒体（Prion）深空探测(Deep Space Exploration)生命体征(vital signs)生命体征(vital signs)生态预报（ecological forecasting 或ecological）生物安全（Biosafety）生物防治(biological control)生物经济（Bio-economy）生物库”计划（“Biobank”Project ）生物入侵(Biological invasion)生物芯片（Biochip）生物信息学（Bioinformatics）生物质能（Biomass Energy）时间旅行（Time Travel）试验发展（Development）受众分割（Audience segmentation）数字地球（Digital Earth ）数字地球（Digital Earth）数字电视(Digital TV，简称DTV)数字鸿沟(Digital Divide)数字化战场（digitizing the battlefield — DB）数字视频广播（DVB “Digital Video Broadcast”）数字图书馆（DL “Digital Library”）数字显示器（Digital Display）数字现金（Digital Cash）数字音频磁带（DAT “Digital Audio Tape”）数字自然音影技术（DNA “Digital Natural Audio/Video”）双星计划（Double Star Programme）水资源（Water Resources）酸雨（Acid Rain）外科手术式打击（Surgical strike）网格计算（Grid Computing）网络数据库(Network Database)网络综合症（Net Synthesis）危机管理（Crisis Management）微机电系统（Micro Electro-Mechanical Systems，MEMS）微流体技术(Microfluidics Technology)温室效应（Greenhouse Effect）物理农业（Physical Agriculture ）严重急性呼吸道综合症(SARS: Severe Acute Respiratory Syndrome) 阳光政策（Sunshine policy）遥感（Remote Sensing）遥医学（Telemedicine）液晶(Liquid Crystal)液晶（liquid crystal）液晶显示器（Liquid Crystal Display，LCD）一票否决权（veto power）医学遗传学（medical genetics）医院信息系统(Integrated Hospital Information System,IHIS)移动计算（Mobile Computing）移动上网（WAP）遗传筛查（Genetic Screening）应用研究（Application Research）营养免疫( Nutrition Immunology)有机（生化）纳米材料(Organic (Biochemical) Nanomaterial)预发式计算（Proactive Computing）远程呈现（telepresence）远程医学（T elemedicine）载人航天(Manned Space Flight)载人航天（manned spaceflight）摘菊使者（Daisy Cutter）知识管理（Knowledge Management, 简称KM）知识经济（The Knowledge Economy）知识引擎（Kengine）知识与资源管理（KRM：Konwlege & Resource Management）脂质体(Liposome)植物全息现象(Plant Holographic Images)中国强制认证（CCC“China Compulsory Certification”）重组DNA技术（Recombinant DNA Technology）转基因动物（Genetically Modified Animal）转基因食品（Genetically Modified Food）准晶（Quasicrystal）准一维纳米材料（Quasi-one-dimensional Nanometer Material）资源安全（Resource Security）自主计算（Autonomic Computing）综合性安全(Comprehensive Security，或非传统安全)总部经济（Headquarters Economy）组织培养技术（Tissue Culture Technology）西尼罗河病毒（West Nile virus）消费电子（consume electronics）信息材料（information materials）信息技术外包（IT Outsourcing）信息经纪人（Information Broker）信息战（information warfare— IW）休闲农业（Recreational Agriculture）虚拟口腔（DentAART）虚拟人（Visual Human）虚拟人（Visual human）虚拟天文台（Virtual Observatory）虚拟现实技术（Virtual Reality Technology）循环经济（Recycling Economy / Cyclic Economy）太空农业(Space Agriculture)太空行走（Walking in space）太阳风暴（Solar Storm）太阳能(Solar Energy)炭疽(Anthrax)炭疽（anthrax）唐氏综合症（Downs Syndrome）提高战略运算能力计划Accelerated Strategic Computing Initiative，ASCI 体细胞遗传学（somatic genetics）通信卫星（communication satellite。

科技英语课文句子翻译Unit1-10

Sentence TranslationUnit 1Text A1.However, the volume of business done on the Internet is growing rapidly, as people orderbooks and other products to make money transactions.但是，因特网上的交易数量急速增长，人们从网上购书和其他的产品，进行资金交易。

2.They use them to prowl the Internet, looking for ways to break into computers systems runby banks, telephone companies and even government departments.他们用电脑上网，寻找能够进入银行电脑系统、电话公司的电脑系统、甚至是政府的电脑系统的方式。

3.The first indication of a security breach may be when a customer discovers a fraudulentmoney transaction on a credit card account.当顾客发现信用卡的帐号上出现了来历不明的消费时，这可能就是安全受到了破坏的第一个标志。

4.The use of credit cards to buy things on the Internet converts the issue of Internet securityinto one of general security.用信用卡在网上购物使网络安全变成了大众所普遍关注的安全的一种5.Few people think twice about giving a credit card number over the phone and many areequally careless about what happens to the carbon copy when completing a transaction over the counter.很多人会在电话里随意报出自己的信用卡号码，同样地，也有很多人不留意交易完成后放在银行柜台上的副本。

科技类英语词汇

advanced science 尖端科学scientific invention 科学发明exert a far-reaching impact on… 对…产生一种深远的影响double-edged sword 双刃剑earth-shaking changes 翻天覆地的改变pave the way for the future development 为未来的发展铺平道路lay a solid foundation for… 为…打下良好的基础energy crisis 能源危机depletion of resources 能源消耗milestone 里程碑sophisticated equipment 尖端设备technical innovation 科技创新over-commercialized 过渡商业化的a heated discussion 热烈的讨论exhaust gas 废气disastrous 灾难性的compared to/with… 与…相比speedy and comfortable 既快捷又舒适opposite forces 负面影响potential hazards 潜在危险pose a threat to… 对…有一种威胁promote relative industries 促进相关产业发展accelerate 加速…means of transportation 交通方式transportation tools 交通工具social status 社会地位environmentally-friendly resources 环保的能源make people's life easier 使人们生活更方便alternative fuel 可替代燃料sustainable development 可持续性发展scientific exploration 科学探索air travel 航空旅行ridiculous 可笑的absurd 荒唐的substitute 取代overcome difficulties 克服困难make progress 取得进步a sense of national pride 民族自豪感unprecedented 前所未有的soaring 不断上升的give a great push to the economic growth 极大地推动了经济发展see dramatic breakthroughs 取得突破性进展aggravate 使恶化cure-all solution 万能良药portable 便携的innovative 创新的cutting-edge 尖端的cost-effective 性价比高的augment/enhance/boost/ efficiency/productivity 提高生产效率be addicted to/be obsessed with 对···着迷/上瘾technological progress/advances 科技进步be accessible to 容易获得的例句：radio broadcasting is accessible to the audience with no charging fee with the advent of 随着···的到来例句：with the advent of advanced technology 随着高科技的到来pay a heavy price for sth. 为···付出惨痛的代价例句：Human being has paid a heavy price for the its curiosity.人类为了他的好奇心付出了惨痛的代价。

科技英语英汉互译

科技英语英汉互译Technology English Chinese Translation科技技术 - Technology计算机 - Computer软件 - Software硬件 - Hardware电子邮件 - Email互联网 - Internet网页 - Web page网络安全 - Cybersecurity人工智能 - Artificial Intelligence机器学习 - Machine Learning大数据 - Big Data云计算 - Cloud Computing数据挖掘 - Data Mining虚拟现实 - Virtual Reality增强现实 - Augmented Reality物联网 - Internet of Things智能手机 - Smartphone平板电脑 - Tablet移动应用程序 - Mobile Application社交媒体 - Social Media无人驾驶 - Self-driving机器人 - Robot无线通信 - Wireless Communication传感器 - Sensor3D打印 - 3D Printing生物技术 - Biotechnology太阳能 - Solar Energy可再生能源 - Renewable Energy核能 - Nuclear Energy人类基因组学 - Human genomics基因编辑 - Gene Editing基因工程 - Genetic Engineering基因改造食品 - Genetically Modified Food 生物多样性 - BiodiversityDNA - DNARNA - RNA基因 - Gene细胞 - Cell分子 - Molecule原子 - Atom电子 - Electron光子 - Photon电路 - Circuit微处理器 - Microprocessor芯片 - Chip操作系统 - Operating System数据存储 - Data Storage计算机网络 - Computer Network主机 - Host服务器 - Server防火墙 - Firewall软件开发 - Software Development编程 - Programming算法 - Algorithm编码 - CodingDebug - 调试界面 - Interface硅 - Silicon导电 - Conductive线路板 - PCB (Printed Circuit Board)电路图 - Circuit Diagram程序员 - Programmer工程师 - Engineer科学家 - Scientist实验室 - Laboratory项目经理 - Project Manager创业公司 - Startup Company软件工程 - Software Engineering网络安全专家 - Cybersecurity Expert数据科学家 - Data Scientist人机交互 - Human-Computer Interaction 信息技术 - Information Technology半导体 - Semiconductor技术支持 - Technical Support创新 - Innovation。

h开头的科技单词

h开头的科技单词
以下是一些以"H"开头的科技相关的单词：
1.HTML（超文本标记语言）：用于创建网页的标记语言。

2.HTTP（超文本传输协议）：用于传输超文本的协议，是互联网的基础之一。

3.HTTPS（超文本传输安全协议）：通过加密通信传输数据的网络协议，提供安全性。

4.Hadoop：处理大规模数据的分布式存储和处理框架。

5.Hackathon（黑客马拉松）：短期的、集中式的编程活动，旨在解决特定问题。

6.Hack（黑客）：指有技术能力并热衷于探索计算机系统的人。

7.Hardware（硬件）：计算机系统的物理组成部分，如处理器、存储器等。

8.Hibernate：用于在Java应用程序中实现对象关系映射的框架。

9.Heuristic（启发式算法）：基于经验和直觉的问题解决方法。

10.Human-Computer Interaction（人机交互）：研究人类与计算机之间交互的领域。

(完整版)科技英语短语汇总大全

(完整版)科技英语短语汇总大全1. 介绍本文档旨在提供一个完整的科技英语短语汇总，旨在帮助读者扩展他们在科技领域的英语词汇量。

这些短语适用于不同科技领域，包括计算机科学、人工智能、网络安全、通讯技术等。

2. 常见短语2.1 计算机科学- Algorithm - 算法- Artificial intelligence - 人工智能- Machine learning - 机器研究- Data mining - 数据挖掘- Big data - 大数据- Internet of Things (IoT) - 物联网- Virtual reality - 虚拟现实- Augmented reality - 增强现实- User interface - 用户界面2.2 人工智能- Neural network - 神经网络- Deep learning - 深度研究- Natural language processing - 自然语言处理- Reinforcement learning - 强化研究- Speech recognition - 语音识别- Predictive analytics - 预测分析- Expert system - 专家系统- Robotics - 机器人技术- Autonomous vehicles - 自动驾驶车辆2.3 网络安全- Cybersecurity - 网络安全- Encryption - 加密- Firewall - 防火墙- Malware - 恶意软件- Phishing - 钓鱼诈骗- Vulnerability - 漏洞- Intrusion detection - 入侵检测- Password cracking - 密码破解- Security audit - 安全审计- Two-factor authentication - 双因素认证2.4 通讯技术- Network protocol - 网络协议- Bandwidth - 带宽- Latency - 延迟- VoIP (Voice over Internet Protocol) - 互联网电话- Fiber optics - 光纤- Mobile network - 移动网络- Video conferencing - 视频会议- Cellular network - 蜂窝网络3. 结论以上是一个包含常见科技英语短语的完整汇总。

中文直译英文高科技的单词

中文直译英文高科技的单词
中文直译英文高科技的单词是 "high-tech"。

“高科技”的英文单词“high-tech”可以用来形容与高科技相关的各种事物和现象。

以下是一些常见的用法：
描述技术产品：例如，“这部手机是高科技的产品”，“这个机器人很高科技”。

形容技术水平：例如，“这家公司的技术水平非常高”，“这个领域的科技发展非常快”。

描述技术行业：例如，“高科技行业正在迅速发展”，“高科技公司需要不断更新技术”。

形容技术环境：例如，“现在是一个高科技的社会”，“我们的生活离不开高科技”。

需要注意的是，“high-tech”也可以用来形容与高科技相关的各种服务、公司和组织等。

科技英语中英文对照翻译

mobile and cellular radio移动和细胞广播in comparison to the relative stability and modest technical developments which are occurring in long haul wideband microwave communication systems there is rapid development and expanding deployment of new mobile personal communication system. These rang from wide coverage area pagers,for simple data message transmission,which employ common standards and hence achieve contiguous coverage over large geographical areas,such as all the major urban centres and transport routes in Europe,Asia or the continental USA.This chapter discusses the special channel characteristics of mobile systems and examines the typical cellular clusters adopted to achieve continuous communication with the mobile user.It then highlights the important properties of current,and emerging,TDMA and code division multiple access(CDMA), mobile digital cellular communication systems.Private mobile radioTerrestrial mobile radio works best at around 250 MHz as lower frequencies than this suffer from noise and interference while higher frequencies experience multipath propagation from buildings,etc,section 15.2.In practice modest frequency bands are allocated between 60MHz and 2GHz. Private mobile radio(PMR) is the system which is used by taxi companies,county councils,health authorities,ambulance services,fire services,the utility industries,etc,for mobile communications.PMR has three spectral at VHF,one just below the 88 to 108 MHz FM broadcast band and one just above this band with another allocation at approximately 170MHz.There are also two allocations at UHF around 450MHz. all these spectral allocations provide a total of just over 1000 radio channels with the channels placed at 12KHz channel spacings or centre frequency offsets. Within the 12khz wide channal the analogue modulation in PMR typically allows 7khz of bandwidth for the signal transmission.when further allowance is made for the frequency drift in the oscillators of these systems a peak deviation of only 2 to 3 khz is available for the speech traffic. Traffic is normally impressed on these systems by amplitude modulation or frequency modulation and again the receiver is of the ubiquitous superheterodyne design,Figure 1.4. A double conversion receiver with two separate local oscillator stages is usually required to achieve the required gain and rejection of adjacent channel signals.One of the problems with PMR receiver is that they are requiredto detect very small signals,typically—120dBm at the antenna output,corresponding to 0.2 uV,and,after demodulating this signal,produce ann output with perhaps 1W of audio equipment, the first IF is normally at10.7MHz and the second IF is very orten at 455KHz . unfortunately,with just over 1000 available channels for the whole of the UK and between 20000and30000issued licences for these systems,it is inevitable that the average busuness user will have to share the allocated channel with other companies in their same geographical area.There are various modes of operation for mobile radio communications networks, the simplest of which is singal frequency simplex. In simplex communication, traffic is broadcast, or one way. PMR uses half duplex(see later Table 15.3) where, at the end of each transmission period, there is a handover of the single channel to the user previously receiving, in order to permit them to reply over the same channel. This is efficient in that it requires only one frequency allocation for the communication link but it has the disadvantage that all units canhear all transmissions provided they are within rage of the mobile and frequencies are allocated for the transmissions. One frequency is used for the forward or downlink, namely base-to-mobile communications. This permits simultaneous two-way communication and greatly reduces the level of interference, but it halves other’s transmissions, which can lead to contention with two mobiles attempting to initiate a call, at the same time, on the uplink in a busy syetem.Although PMR employs relatively simple techniques with analogue speech transmission there have been many enhancements to these systems over the years . Data transmission is now in widespread use in PMR systems using FSK modulation. Data transmission also allows the possibility of hard copy graphics output and it gives direct access to computer services such as databases, etc. Data prembles can also be used, in a selective calling mode, when initiating a transmission to address a special receiver and thus obtain more privacy within the system.15.4.5 Trunked radio for paramilitary use集群无线电的军事使用Another related TDMA mobile radio standard is the European trunked radio(TETRA)network which has been developed as part of the public safety radio communications service(PSRCS) for use by police, utilities, customs office, etc. TETRA in fact is part of wider international collaborations for paramilitary radio use.In these portable radios there is a need for frequency hopping (FH) to give an antieavesdropping capability and encryption for security of transmission to extend military mobile radio capabilities to paramilitary use, i.e. for police, customs and excise offices, etc. these capabilities are included in the multiband interteam radio for the associated public safety communications office in the USA while Europe has adopted the TETRA standard.TETRA is essentially the digital TDMA replacement of the analogue PMR systems. The TETRA standard has spectrum allocations of 380 to 400 and 410 to 430MHz, with the lower band used for mobile transmissions and the upper band for base station use. TETRA mobile have 1 W output power and the base stations 25 W using error with the data throughput rate varying, to meet the required quality of service. TETRA can accommodate up to four users each with a basic speech or data rate of 7.2kbit/s. with coding and signaling overheads, the final transmission rate for the four-user slot is 36 kbit/s. this equipment is large and more sophisticated than a commercial cell phone, and it sells for a very much higher price becase the production runs are much small. However, its advanced capabilities are essential for achieving paramilitary communications which are secure from eavesdropping.15.5 Code division multiple accessAnalogue communication systems predominantly adopt frequency division multiple access (FDMA), where each subscriber is allocated a narrow frequency slot within the available channel. The alternative TDMA(GSM) technique allocates the entire channel bandwidth to a subscriber but constrains the subscriber but constrains the subscriber to transmit only regular short bursts of wideband signal. Both these accessing techniques are well established for long haulterrestrial, satellite and mobile communications as they offer very good utilization of the available bandwidth.15.5.1The inflexibility of these coordinated accessing techniques has resulted in the development of new systems based on the uncoordinated spread spectrum concept. In these systems the bits of slow speed data traffic from each subscriber are deliberately multiplied by a high chip rate spreading code, forcing the low rate (narrowband data signal) to fill a wide channel bandwidth.15.7.2 3G systemsThe evolution of the third generation (3G)system began when the ITU produce the initial recommendations for a new universal mobile telecommunications system(UMTS)[www.] The 3G mobile radio service provides higher data rate services ,with a maximum data rate in excess of 2Mbit/s, but the achievable bit rate is linked to mobility. Multimedia applications encompass services such as voice, audio/video, graphics, data, Internet access and e-mail. These packet and circuit switched services have to be supported by the radio interface and the network subsystem.Several radio transmission technologies(RTT) were evaluated by the ITU and adopted into the new standard, IMT-2000. the European standardization body for 3G, the ETSI Special Mobile Group, agreed on a radio access scheme for 3G UMTS universal terrestrial radio access(UTRA) as an evolution of GSM. UTRA consists of two modes : frequency division duplex(FDD) where the uplink and downlink are transmitted on different frequencies; and time division duplex(TDD) where the uplink and downlink are time multiplexed onto the same carrier frequency. The agreement assigned the unpaired bands (i.e. for UTRA TDD ). TD-CDMA is a pure CDMA based system. Both modes of UTRA have been harmonised with respect to basic system parameters such as carrier spacing, chip rate and frame length to ensure the interworking of UTRA with GSM.The 3G proposal were predominantly based wideband CDMA(WCDMA) and a mix of FDD and TDD access techniques. WCDMA is favoured for 3G in poor propagation environments with a mix of high modest speed data traffic. It is generally accepted that CDMA is the preferred accesstechnique and, with the increase in the data rate, then the spreading modulation needs to increase to wideband transmission.WCDMA is based on 3.84Mchip/s spreading codes with spreading ratio, i.e. , K values, of 4-256 giving corresponging data ratas of 960-15 kbit/s. the upper FDD uplink band I from 1920-1980 MHz is paired with a 2110-2170 MHz downlink. In addition uplink bands II & III at 1850-1910 MHz and 1710-1785 MHz are also paired, respectively, with 1930-1990 MHz and 1805-1880 MHz allocations. the system is configured on a 10 ms frame with 15 individual slots to facilitate TDD as well as FDD transmissions. TDD is more flexible as time-slots can be dynamically reassigned to uplink and downlink functions, as required for asymmetric transfer of large files or video on demand traffic. 3G WCDMA systems use an adaptive multirate speech coder with encoded rates of 4.75-12.2 kbit/s. receivers commonly use the easily integrated direct conversion design, in place of the superheterodyne design . receiver sensitivities are typically -155dBm.The 3GPP2 standard aims to achieve a wide area mobile wireless packet switched capability with CDMA2000 1×EV DO revision A (sometimes called IS-856A). Here 1×refers to the single carrier 1.25 Mchip/s system. It achieves a 3.1 Mbit/s downlink and a delay sensitive services. The 3GPP standard has gone through many release with R4 in 2001 which introduced packet data services and R6 in 2005 to further increase the available data transmission rate . R6 pioneers the use of high-speed downlink packet access and multimedia broadcast multicast services which offer reduced delays and increased uplink data rates approaching 6 Mbit/s.In parallel with the European activities extensive work on 3G mobile radio was also performed in Japan. The Japanese standardisation body also chose WCDMA, so that the Japanese and European proposals for the FDD mode were already aligned closely. Very similar concepts have also been adopted by the North American standardization body.In order to work towards a global 3G mobile radio standard, the third generation partnership project(3GPP), consisting of members of the standardization bodies in Europe, the USA, Japan, Korea and China, was formed. It has merged the already well harmonized proposals of the regional standardization bodies to work on a common 3G international mobile radio standard, still called UTRA. The 3GPP Project 2(3GPP2), on the other hand, works towards a 3G mobile radio standard based on cdmaOne/IS-95 evolution, originally called CDMA2000.比起相对稳定、适度的技术发展是发生在宽带微波通信系统,有长期快速发展和扩大部署的新的移动个人通讯系统。