The GSM system requires a number of functions to be created for a fully operational mobile system.
The cell coverage area is controlled by a base station which is itself made up of two elements. The first element is the transmission system which communicates out to the mobile and also receives information from it to set up and maintain calls when actually in operation. The base station transceiver （BST） is controlled by the base station controller （BSC）， which communicates with the mobile switching center （MSC） -- the essential link to the local public switched telephone network （PSTN）， and to tile subscriber data which is stored in registers within the system. The subscriber registers allow the GSM system to check a subscriber who requests the use of the network， allow access and then set up the charging function， etc.
The use of digital radio transmission and tile advanced handover algorithms between radio cells in GSM network allows for significantly better frequency usage than in analogue cellular systems， thus increasing the number of subscribers that can be served. Since GSM provides common standard， cellular subscribers will also be able to use their telephones over the entire GSM service area. Roaming is fully automatic between and within all countries covered by GSM system. In addition to international roaming， GSM provides new services， such as high-speed data communication， Facsimile and short message service. The GSM technical specifications are designed to work in concert with other standards， e.g. ISDN. Inter-working between the standards is in this way assured. In the long term perspective cellular systems， using a digital technology will become the universal method of telecommunication.
The third generation mobile communication system currently being developed in Europe is intended to integrate all the different services of second generation systems and cover a much wider range of broadband services （voice， data， video and multimedia） consistent and compatible with technology developments taking place within the fixed telecommunication networks.
【New Words】
interconnection
互相联络
transmission
传送，发射，传播
optical
眼的，视力的，光学的
roam
漫步，闲逛，徜徉
spectrum
光谱，频谱
simultaneous
同时的，同步的
subscriber
订户，捐献者
perspective
远景，前途，透视画法
Exercise
1. Multiple Choices
（1）A ______ contains a central computer named host computer.
A. WAN
B. star network
C. ring work
D. network
（2）An advantage of a ring network is that it needs less ______.
A. cable
B. network
C. computer
D. information
（3）Two common applications of LANs are ______ resource sharing and information resource sharing.
A. computer
B. network
C. software
D. hardware
（4）With Internet Explorer and Internet connection， you can search for and view information on the ______.
A. program
B.Active Desktop
C. World Wide Web
D. phone dialer
（5）To open Internet Explorer， just click Start， point to ______， and then click Internet Explorer.
A. view
B. layout
C. control panel
D. programs
（6）______ and news services provide access to world wide discussions.
A. E-mail
B. Fax
C.electronicbulletinboard
D.electronic-commerce
（7）Videodisc and laser technology provide the ability to ______.
A. cost more
B. create some education files
C. enhance other forms of education
D. store large amounts of data
（8）Comparing with WAN， LAN can provide ______.
A. lower data transmission rates
B. higher data transmission rates
C. the same transmission rates
D. very high transmission rates
（9）Local area network （LAN） is structured within ______.
A. a single building
B. a localized group of buildings
C. a country
D. a campus
（10）A station in control token network wants to access the network， it may _______.
A. possess the token
B. release the token
C. passes the token to another station after transmitting a data frame
D. take the token
2. Translate the following phrases into English or Chinese
（1）视频设备
（2）星形网络
（3）激光技术
（4）电子通信
（5）电子商务
（6）Information technology
（7）full-motion video
（8）hardware resource sharing
（9）point to point
（10）physical layout
3. Fill in each blank with a suitable term according to its official definition.
（1）______， a set of semantic and syntactic rules that determines the behavior of functional units in achieving communication.
（2）______， a functional unit that interconnects two computer networks with different network architectures.
（3）______， a hardware and software device designed to perform a specific function for many users.
（4）______， a point in a system or network at which data can either enter or leave.
（5）______， an approach where often-used formats are stored at terminal control instead of being repeatedly sent down the communication line.
（6）______， a memory unit that can be connected to multiple processors and can contain resources for use by processors running on different processors.
（7）______， in data communication， the connection through the public switched telephone network from a terminal to a service， network or computer.
4. Translate the following sentences into Chinese
（1）If the command exists and you typed it correctly， you might have to change directories or specify the directory where the program file is located.
（2）Lying between machine languages and high level languages are assembly languages， which are directly related to a computer’s machine language.
（3）The three basic categories of equipment that are found in a local network are workstations， servers， and gateways.
（4）The Internet is not the Information Superhighway that was praised in the early 1990s.