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1、2012 届本科毕业设计中英文翻译学生姓名：所在院系：信息工程学院所学专业：信息工程导师姓名：完成时间：2010-05-10Wi-Fi stands for Wireless Fidelity, also known as the 802.11b standard. Its biggest advantage is the high transmission speed can reach 11Mbps, another effective long distance, at the same time compatible with the existing variety of 802.1
2、1DSSS equipment. Along with Intels laptop chipset,Centrino is recognized by more and more people, this technology has become a topic of concern to everyone. However, since the end of 2005, many mobile phone manufacturers, especially the production of smart phones based brand Wi-Fi began to introduce
3、 their own products. In short: Wi-Fi wireless networks .Wi-Fi has been widely used in notebook computers, mobile phones, PDAs, digital cameras and other mobile devices.With Wi-Fi, no cable can be linked into the network. More and more devices installed in the factory, Wi-Fi module, but also more and
4、 more places to offer Wi-Fi signal coverage. In this way, the Wi-Fi formed from research to equipment production, from network access to network services is a huge industrial chain. In 2007, the value of the national the wlan industry, including Wi-Fi industry is expected to exceed 100 million U.S.
5、dollars. For individual users, the popularity of Wi-Fi, it will be a leap forward in user experience.Laptop users will be able to any one with Wi-Fi signal coverage fast accessto the Internet without the need to go looking for network cable, a growing number of airports, hotels, public places, offer
6、 Wi-Fi signal coverage. In a timely manner with a laptop computer to meetings, do not worry do not have enough network cable jack in the conference room. At home, you can even in any corner of the coverage of wireless signals, without having to worry about the alignment of the cable affect the overa
7、ll indoor appearance.Wi-Fi in handheld devices are widely used, and smart phones is part of it. Different from the earlier Bluetooth technology used in mobile phones, Wi-Fi has a greater coverage and higher transmission rates, Wi-Fi phones has become a fashion trend of the mobile communications indu
8、stry.Wi-Fi bands in the world without any telecom operator license free band, WLAN wireless devices provides a worldwide can be used, the cost is extremely low and very high data bandwidth wireless air interface. Users can browse the web quickly in the Wi-Fi coverage area, anytime, anywhere and rece
9、ive phone calls. Other WLAN-based broadband data applications such as streaming media, online games and other functions more user should expect. With Wi-Fi capability, long-distance calls (including international long distance), browse the Web, send and receive e-mail, music downloads, digital photo
10、 transfer, will no longer have to worry about slow and costly problem.Wi-Fi flip range more widely in the country, luxury hotels, luxury residential, airports and coffee shops class area has Wi-Fi interface. When we went to the tourist office, you can use ourhandheld devices in such places and enjoy
11、 surfing the web.A Wi-Fi connection point network members and structure of the site (Station), the network of basic components. The basic service unit (Basic service the Set, BSS). Network basic service unit. The most simple unit can only be composed by the two sites. The site can be dynamic link (a
12、ssociate) to the basic service unit.Distribution System Distribution System (DS). The distribution system used to connect different basic service unit. The media distribution system medium (Medium) logic and the basic service unit is completely separate,even though they physically may be the same me
13、dia, for example, the same radio frequency band.Access point (Acess Point, AP). Access point that the identity of the ordinary sites, and access to the distribution function of the system.Extended Service Unit (Extended Service Set ESS). A combination of the distribution system and basic services un
14、it. This combination is logical, not physical - the basic service unit of matter may be geographically far removed from. Distribution system can also use a variety of techniques.Mark (Portal) is a logical composition. For wireless LAN and wired LAN or other network link.Here are three kinds of media
15、, the site uses wireless media distribution system to use the media, and other LAN and wireless LAN integration together media. Physically, they may overlap each other.The IEEE802.11 only responsible for addressing (Addressing,) on the site uses the wireless medium. Distribution systems and other LA
16、N addressing a range of wireless LAN.The IEEE802.11 no specific definition of the distribution system, but the definition of the distribution system should provide the services (Service). The entire wireless LAN defines nine kinds of service, five kinds of services are part of the task of distributi
17、on systems, respectively, joins (Association), the end connection (Diassociation), distribution (Distribution,), integration (Integration), to re-connect.Four kinds of services are the tasks of the site, respectively, authentication (Authentication), the end of the authentication (Deauthentication),
18、 privacy (Privacy), MAC data transmission (the MSDU delivery).The main technical advantage of the Wi-FiFirst A radio wave coverage, the coverage of radio based on Bluetooth technology is very small radius of only about 50 feet, or about 15 meters. Wi-Fi radius of up to about 300 feet, or about 100 m
19、eters. A new type of by Vivato company recently launched the switches, which products to current Wi-Fi wireless network 300 ft, close to 100 m communication distance expanded to four miles, about 6.5 km.Second Although the quality of wireless communications transmitted by the Wi-Fi technology is not
20、 very good performance of data security than Bluetooth worse, the transmission quality to be improved, but the transfer speed is very fast, you can reach 11Mbps, in line with the needs of personal and social information.Third manufacturers to enter the field is relatively low threshold. Vendors set
21、up hot spots in airports, railway stations, coffee shops, libraries and other personnel intensive, and high-speed line Internet access to these places. Such hot spots to emit radio waves can reach tens of meters to 100 meters away from the radius of the access point, as long as the user will support
22、 wireless LAN notebook or PDA to get the region to high-speed Internet access. Means that manufacturers do not have expensive network cabling access, thus saving a lot of cost.Wi-Fi methods of organizingWi-Fi is a wireless network by the AP (Access Point) and Wireless LAN. Generally set up a wireles
23、s network equipped with a wireless card and the AP, so will be able to wireless mode, with both wired architecture to share network resources, erection cost and complexity of the program is far lower than a traditional wired network. If only a few computers, peer-to-peer network, can also be not to
24、the AP, only require each computer is equipped with a wireless card. AP is generally translated as wireless access point, or bridge. It is mainly as a bridge between traditional wired local area networks and wireless local area network, a PC equipped with a wireless card can be wired local area netw
25、ork or wide area network to share resources through the AP, and its working principle is equivalent to a built-in wireless transmitter HUB or routing, wireless NIC is responsible for receiving the transmitted signal by the AP client premise equipment. With the AP as the wired network Hub in general,
26、 wireless stations can be quickly and easily connected to the network. Especially for the use of broadband, Wi-Fi even more advantages, cable broadband networks (ADSL, residential LAN, etc.) to the home, connecting to an AP, then install a wireless card in the computer. Ordinary families have an AP
27、is enough, even the neighborhood of the users authorization, you do not need to add ports to a shared Internet.Wi-Fi is the complement of high-speed wired access technologiesAt present, the wired access technologies including Ethernet, xDSL, etc. Wi-Fi technology as a complement of high-speed wired
28、access technology, has the advantage of mobility, inexpensive Wi-Fi technology is widely used in the field of need a wireless extension of wired access, such as the temporary venue. Data rate, coverage and reliability of the difference, Wi-Fi technology in broadband applications will be as a complem
29、ent of high-speed wired access technologies. The key technology is no doubt decided to supplement efforts of the Wi-Fi. The OFDM, MIMO (Multiple Input Multiple Output) smart antennas and software radio, etc., are beginning to be applied to wireless local area network in order to enhance the performa
30、nce of Wi-Fi, such as 802.11n plans to use MIMO and OFDM combined, so that the data rate has doubled and redoubled . In addition, the improvement of the antenna and transmission technology makes the wireless LAN transmission distance is greatly increased and can reach a few kilometers.Wi-Fi is the c
31、omplement of cellular mobile communication and 3GSecondary positioning of the Wi-Fi technology the complement of cellular mobilecommunication. Cellular mobile communication can provide a wide coverage, high mobility and the low data transfer rate, it can use the Wi-Fi high-speed data transmission ch
32、aracteristics to compensate for the deficiencies of their own data transfer rate is limited. Wi-Fi not only the use of cellular mobile communication network authentication and billing mechanisms, and characteristics of multi-access switching function can be combined with the wide coverage of cellula
33、r mobile communications network. This can be achieved the integration of Wi-Fi and cellular mobile communications, cellular mobile communications operators icing on the cake, to further expand its business volume. For telecom operators, Wi-Fi technology positioning is the complement of high-speed wi
34、red access technology, will gradually become the complement of cellular mobile communications. Of course, Wi-Fi and cellular mobile communications, there are a small amount of competition. On the one hand, for the Wi-Fi Voice over IP terminal has entered the market, part of the substitution effect o
35、n the cellular mobile communication. On the other hand, with the development of cellular mobile communication technology, Wi-Fi hotspots common application may be replaced by cellular mobile communication system part. But in general, the relationship of coexistence, such as some special occasions, h
36、igh-speed data transfer must be by means of Wi-Fi, aircraft like the Boeing internal wireless LAN using Wi-Fi; while on other occasions can be more economical. like to achieve high-speed trains within the wireless LAN. It has a higher advanced technology, strong business skills and a wide range of a
37、pplications. But the Wi-Fi can play in specific regions and within the important complementary role for 3G, Wi-Fi technology and 3G technology the combination will have broad prospects for development.Wi-Fi 技术Wi-Fi的全称是 Wireless Fidelity,又叫802.11b标准。它的最大优点就是传输速度较高,可以达到11Mbps,另外它的有效距离也很长，同时与已有的各种802.1
38、1DSSS设备兼容。伴随着 Intel 公司提出的笔记本电脑芯片组。 “迅驰”被越来越多的人认可，这一技术也逐渐成 为了大家关注的话题。不过自 2005 年底开始，很多手机厂商，特别是以生产智能手机为主 的品牌便开始将 Wi-Fi 引入自己的产品当中。简而言之 ：Wi-Fi 就是无线网络 Wi-Fi 已经广 泛的应用在了笔记本电脑，手机掌上电脑，数码相机等移动终端上。有了 Wi-Fi 之后，不需要网线即可联入网络。越来越多的设备在出厂前安装了 Wi-Fi 模 块，也有越来越多的场所提供了 Wi-Fi 信号覆盖。这样， Wi-Fi 形成了一个从科研到设备生 产、从网络接入到网络内容服务等一个庞大
39、的产业链。 2007年，全国包括 Wi-Fi 在内的 wlan 行业产业价值有望超亿美元。 对于个人用户来说， Wi-Fi 的普及， 将是用户体验的一次飞跃 。笔记本电脑用户将可以任意一个具备 Wi-Fi信号覆盖的地方快速接入In ternet而不需要再 去寻找网线，越来越多的机场、酒店、公共场所都提供了 Wi-Fi 信号覆盖。及时带笔记本电 脑开会，也不用担心会议室没有足够的网线插口。而在家中，您更可以在任何一个角落都覆 盖无线信号，而不需要担心网线的走线影响整体室内美观。Wi-Fi 在掌上设备上应用越来越广泛，而智能手机就是其中一份子。与早前应用 于手机 上的蓝牙技术不同， Wi-Fi 具
40、有更大的覆盖范围和更高的传输速率，因此 Wi-Fi 手机成为了 目前移动通信业界的时尚潮流。由于 Wi-Fi 的频段在世界范围内是无需任何电信运营执照的免费频段， 因此 WLAN 无线 设备提供了一个世界范围内可以使用的， 费用极其低廉且数据带宽极高的无线空中接口。 用 户可以在 Wi-Fi 覆盖区域内快速浏览网页， 随时随地接听拨打电话。 而其它一些基于 WLAN 的宽带数据应用，如流媒体、网络游戏等功能更是值得用户期待。有了 Wi-Fi 功能我们打长 途电话( 包括国际长途哦 ) ，浏览网页、收发电子邮件、音乐下载、数码照片传递等，再无需 担心速度慢和花费高的问题。现在 Wi-Fi 翻盖范
41、围在国内越来越广泛了，高级宾馆，豪华住宅区，飞机场以及咖啡厅 之类的区域都有 Wi-Fi 接口。当我们去旅游，办公时，就可以在这些场所使用我们的掌上设 备尽情网上冲浪了。一个 Wi-Fi 联接点网络成员和结构站点 (Station) ，网络最基本的组成部分。基本服务单 元(Basic Service Set, BSS)。网络最基本的服务单元。最简单的服务单元可以只由两个站点 组成。站点可以动态的联结(associate到基本服务单元中。分配系统 (Distribution System, DS) 分配系统用于连接不同的基本服务单元。 分配系统使 用的媒介 (Medium) 逻辑上和基本服务单元
42、使用的媒介是截然分开的，尽管它们物理上可能 会是同一个媒介，例如同一个无线频段。接入点 (Acess Point, AP) 接入点即有普通站点的身份，又有接入到分配系统的功能。扩展服务单元 (Extended Service Set, ESS) 由分配系统和基本服务单元组合而成。 这种组 合是逻辑上， 并非物理上的 - 不同的基本服务单元物有可能在地理位置相去甚远。 分配系统 也可以使用各种各样的技术。关口 (Portal) 也是一个逻辑成分。用于将无线局域网和有线局域网或其它网络联系起 来。这儿有 3 种媒介，站点使用的无线的媒介，分配系统使用的媒介，以及和无线局域网集 成一起的其它局域网使
43、用的媒介。物理上它们可能互相重迭 。IEEE802.11只负责在站点使用的无线的媒介上的寻址 (Addressing)。分配系统和其它局域 网的寻址不属无线局域网的范围。I EEE802. 1 1没有具体定义分配系统， 只是定义了分配系统应该提供的服务 (Service) 。整 个无线局域网定义了 9种服务 ，5 种服务属于分配系统的任务，分别为，联接 (Association), 结束联接(Diassociation),分配(Distributen),集成(Integration),再联接(Reassociation)。4种服务属于站点的任务，分别为，鉴权(Authentication),结
44、束鉴权(Deauthentication),隐 私(Privacy), MAC 数据传输(MSDU delivery)。Wi-Fi 的主要技术优势1、 无线电波的覆盖范围广，基于蓝牙技术的电波覆盖范围非常小，半径大约只有50英 尺左右，约合15米。而 Wi-Fi的半径则可达300英尺左右，约合100米。最近由Vivato公 司推出的一款新型交换机，该款产品能够把目前 Wi-Fi 无线网络 300英尺，接近 100米的通 信距离扩大到 4英里，约 6.5公里。2、虽然由 Wi-Fi 技术传输的无线通信质量不是很好，数据安全性能比蓝牙差一些， 传输质量也有待改进，但传输速度非常快，可以达到11Mb
45、ps，符合个人和社会信息化的需求。3、厂商进入该领域的门槛比较低。厂商只要在机场、车站、咖啡店、图书馆等人员较 密集的地方设置“热点” ，并通过高速线路将因特网接入上述场所。这样由于“热点”所发 射出的电波可以达到距接入点半径数十米至 100米的地方，用户只要将支持无线 LAN 的笔 记本电脑或 PDA 拿到该区域内，即可高速接入因特网。也就是说厂商不用耗费资金来进行 网络布线接入，从而节省了大量的成本。Wi-Fi 组建方法Wi-Fi是由AP(Access Point)和无线网卡组成的无线网络。一般架设无线网络的基本配 备就是无线网卡及一台AP，如此便能以无线的模式，配合既有的有线架构来分享网
46、络资源， 架设费用和复杂程序远远低于传统的有线网络。 如果只是几台电脑的对等网， 也可不要 AP， 只需要每台电脑配备无线网卡。 AP 一般翻译为“无线访问节点” ，或“桥接器”。它主要当 作传统的有线局域网络与无线局域网络之间的桥梁，因此任何一台装有无线网卡的PC均可透过 AP 去分享有线局域网络甚至广域网络的资源，其工作原理相当于一个内置无线发射器 的 HUB 或者是路由，而无线网卡则是负责接收由 AP 所发射信号的 CLIENT 端设备。有了 AP 就像一般有线网络的 Hub 一般，无线工作站可以快速且轻易地与网络相连。特别是对于 宽带的使用，Wi-Fi更显优势，有线宽带网络（ADSL、
47、小区LAN等）到户后，连接到一个 AP，然后在电脑中安装一块无线网卡即可。普通的家庭有一个 AP已经足够，甚至用户的邻 里得到授权后，则无需增加端口，也能以共享的方式上网。Wi-Fi 是高速有线接入技术的补充目前，有线接入技术主要包括以太网、 xDSL 等。 Wi-Fi 技术作为高速有线接入技术的补 充，具有为可移动性、价格低廉的优点， Wi-Fi 技术广泛应用于有线接入需无线延伸的领域， 如临时会场等。由于数据速率、覆盖范围和可靠性的差异， Wi-Fi 技术在宽带应用上将作为 高速有线接入技术的补充。而关键技术无疑决定着 Wi-Fi 的补充力度。现在 OFDM、 MIMO （多入多出）、智能
48、天线和软件无线电等，都开始应用到无线局域网中以提升 Wi-Fi 性能， 比如说 802.11n 计划采用 MIMO 与 OFDM 相结合，使数据速率成倍提高。另外，天线及传 输技术的改进使得无线局域网的传输距离大大增加，可以达到几公里。Wi-Fi 是蜂窝移动通信与 3G 的补充Wi-Fi 技术的次要定位 蜂窝移动通信的补充。蜂窝移动通信可以提供广覆盖、高移动性和中低等数据传输速率，它可以利用 Wi-Fi 高速数据传输的特点弥补自己数据传输速率 受限的不足。而 Wi-Fi 不仅可利用蜂窝移动通信网络完善的鉴权与计费机制，而且可结合蜂 窝移动通信网络广覆盖的特点进行多接入切换功能。这样就可实现 W
49、i-Fi 与蜂窝移动通信的 融合，使蜂窝移动通信的运营锦上添花， 进一步扩大其业务量。 对于电信运营商来说， Wi-Fi 技术的定位主要是作为高速有线接入技术的补充， 逐渐也会成为蜂窝移动通信的补充。 当然 Wi-Fi 与蜂窝移动通信也存在少量竞争。一方面，用于 Wi-Fi 的 IP 话音终端已经进入市场， 这对蜂窝移动通信有一部分替代作用。另一方面，随着蜂窝移动通信技术的发展，热点地区 的 Wi-Fi 公共应用也可能被蜂窝移动通信系统部分取代。 但是总的来说， 他们是共存的关系， 比如一些特殊场合的高速数据传输必须借助于 Wi-Fi，象波音公司提出的飞机内部无线局域 网；而在另外一些场合使用 Wi-Fi 可以较为经济，象实现高速列车内部的无线局域网时。它 有较高的技术先进性、较强的业务能力和广泛的应用。但是 Wi-Fi 可以在特定的区域和范围 内发挥对3G的重要补充作用，Wi-Fi技术与3G技术相结合会有广阔的发展前景。