1.1.3 Mobile Users移动用户
Mobile computers, such as notebook computers and personal digital assistants (PDAs), are one of the fastest-growing segments of the computer industry. Many owners of these computers have desktop machines back at the office and want to be connected to their home base even when away from home or en route. Since having a wired connection is impossible in cars and airplanes, there is a lot of interest in wireless networks. In this section we will briefly look at some of the uses of wireless networks.
移动计算机，比如，笔记本电脑和PDAs(personal digital assistants 个人数字助理)，是计算机产业中发展最快的部分之一。大多数这些计算机的所有者在办公室还有桌面电脑，他们希望不在家的时候能连上家里的机器，即使在远离家或在路上的时候也能连上。由于在汽车和飞机上，没有有线连接，这引起很多人对无线网络的兴趣。在这部分中，我们将简单来看看一些无线网络的使用。
Why would anyone want one? A common reason is the portable office. People on the road often want to use their portable electronic equipment to send and receive telephone calls, faxes, and electronic mail, surf the Web, access remote files, and log on to remote machines. And they want to do this from anywhere on land, sea, or air. For example, at computer conferences these days, the organizers often set up a wireless network in the conference area. Anyone with a notebook computer and a wireless modem can just turn the computer on and be connected to the Internet, as though the computer were plugged into a wired network. Similarly, some universities have installed wireless networks on campus so students can sit under the trees and consult the library's card catalog or read their e-mail.
为什么大家需要无线网络呢？一个常见的理由是它能提供移动办公。在路上，人们常常想用他们的移动设备来发送或接收电话、传真和电子邮件、浏览网页、访问远程文件或登录远程机器。同时，他们也想在海、陆、空的任何一个地方做到这一点。例如，在如今的计算机会议上，组织者通常会在会议区域内建立无线网络连接。任何一个有笔记本电脑和无线调制解调器与会者都能打开电脑，连上Internet网，就像连接在有线网上一样。类似地，一些大学也在校园内安装了无线网络，学生坐在树下便能查找图书馆的卡片目录，或者阅读电子邮件。
Wireless networks are of great value to fleets of trucks, taxis, delivery vehicles, and repairpersons for keeping in contact with home. For example, in many cities, taxi drivers are independent businessmen, rather than being employees of a taxi company. In some of these cities, the taxis have a display the driver can see. When a customer calls up, a central dispatcher types in the pickup and destination points. This information is displayed on the drivers' displays and a beep sounds. The first driver to hit a button on the display gets the call.
无线网络对快速运输车队、出租车、快递专车和修理工与他们家里保持联系等方面有很大的意义。例如，在许多城市，出租车的司机是独立的经营者，而不是受雇于某一家出租车公司。在这些城市中，出租车装有一个司机能看到的显示屏。如果有顾客呼叫，中心调度员便输入该顾客的上车地点及目的地。这条信息显示在司机的显示屏上，同时会发出“嘟嘟”的提示音。第一个在显示器上按下按钮的司机便得到这个呼叫。
Wireless networks are also important to the military. If you have to be able to fight a war anywhere on earth on short notice, counting on using the local networking infrastructure is probably not a good idea. It is better to bring your own.
无线网络对军事活动也起着非常重要的作用。如果你必须马上到世界的某个地方参加一场战役，寄希望于使用局域网络设备来进行通信可能并不是一个好主意。最好是带上你自己的一套设备。
Although wireless networking and mobile computing are often related, they are not identical, as Fig. 1-5 shows. Here we see a distinction between fixed wireless and mobile wireless. Even notebook computers are sometimes wired. For example, if a traveler plugs a notebook computer into the telephone jack in a hotel room, he has mobility without a wireless network.
尽管无线网络和移动计算机通常联系在一起，但是他们并不相同，如图1-5所示。这里我们来看看固定无线（fixed wireless）与移动无线（mobile wireless）之间的区别。甚至笔记本电脑有时也通过有限网络来实现移动性。比如，一个外出旅行的人在宾馆房间内把笔记本电脑插入电话线的插孔里，这样即使没有无限网络也可以实现移动工作。
Figure 1-5. Combinations of wireless networks and mobile computing.无线网络与移动计算机之间的组合
On the other hand, some wireless computers are not mobile. An important example is a company that owns an older building lacking network cabling, and which wants to connect its computers. Installing a wireless network may require little more than buying a small box with some electronics, unpacking it, and plugging it in. This solution may be far cheaper than having workmen put in cable ducts to wire the building.
另一方面，一些无线计算机并不是可移动的。在这方面很重要的一个例子是，一个公司在一栋很老的建筑内，该建筑以前没有网络电缆，但现在公司希望把他们的计算机联系起来。安装无线网络只需买一个有电子设备的小盒子、拆开然后插上即可。这种解决方案比请工人铺设电缆管道来给建筑安装线路要便宜得多。
posted on 2006-04-12 12:42
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