英語翻譯
Broadband Telecommunications
The developmental process of modern communications can be said to be an evolution to a more direct and natural form of communications.To illustrate:delivering message via a third person was soon replaced by the mail service,which was subsequently supplemented by the telephone,allowing direct,delay-free conversation between two remote parties.From this perspective,it can easily be predicted that the next evolutionary step following the telephone will be the videophone,which enables a more natural and realistic mode of conversing.Such an evolutionary scenario can also be applied to the field of broadcasting.A purely listening form of broadcasting was inevitably followed by television ,with the added visual dimension,and black-and-white televisions became obsolete with the advent of color televisions.In the same context,ordinary color televisions of today will soon be transformed into high-definition television(HDTV),which can display even more realistic and natural-looking pictures.
Our goal is to provide a broad but detailed description of the technologies fundamental to constructing broadband telecommunication systems.Therefore,the five essential components described in Figure 1,fiber-optic communication technology,synchronous digital transmission,B-ISDN and ATM,high-speed data communication,and broadband video communication services,will form the core contents of the broadband telecommunication system,the background of broadband telecommunications will be reviewed briefly.
The basic technologies underling the communication network will be reviewed first,and then the progress of the telecommunication technologies will be examined in terms of transmission,switching,signaling,packet communication,ISDN,and B-ISDN.Finally,the key technologies essential for the implementation of broadband telecommunication systems will be discussed in reference to optical communication medium,broadband transmission,ATM communication,high-speed data network,and broadband video technologies.
As can be inferred from the examples of videophone and HDTV,the evolution of future communications will be via broadband communication centered around video signals.The associated services make up a diverse set of high-speed and broadband services ranging from video signals.The associated services make up a diverse set of high-speed and broadband services ranging from video services such as videophone,video conferencing,video surveillance,cable television(CATV) distribution,and HDTV distribution to the high-speed data services such as high-resolution image transmission,high-speed data transmission,and color facsimile.