4 - Advances in Communication Networks

Abstract

With the data communication system, facsimile communication system, and videotex communication system, information to be transmitted is digitized. In the telephone network, the voice is an analog signal. When the voice signal is digitized, all of the foregoing kinds of information can be transmitted on digital lines. In this way, any kind of communication service can be provided via a single digital network. This idea is called the integrated services digital network (ISDN), which is described in this chapter. To provide the wide area network service, it is necessary to provide network architectures for a wide area. There are N-ISDN, BISDN, and ATM switching systems for this purpose. Prior to ISDN, each service was provided separately through its own network. With ISDN all services can be transmitted via a single digital network. Using ISDN, the source ID can be shown on the display of the telephone before one answers the call. This gives a choice of whether or not to answer the call. One calls it a destination-oriented communication service. Hence, through the introduction of ISDN, a more human-friendly telephone service is achieved.