INTEGRATION OF BROADBAND SERVICES IN THE ISDN

摘要

The basis for integrating numerous services in an uniform Integrated Services Digital Network (ISDN) is provided by digitizing the telephone network.Information is transferred and switched by way of the 64 kbit/s channels between the user terminals.The network is consequently well suited to integrate telephone,text and data services,and permits the existing copper cable network to continue in its role as transmission medium in the periphery.Integration of video services however,e.g.video telephony,calls for bit rates of 1.5 to 140 Mbit/s,and upgrading of the existing network with broadband transmission media in the long distance,local and subscriber access areas.Fiber optic cables provide the most satisfactory solution here as they offer not only a greater transmission capacity than metal conductors but also advantages in terms of attentuation and electromagnetic influences.On top of this they are also much lighter and smaller.For individual communication using broadband services,the user must have the capability to set up freely selectable broadband connections.The local and trunk exchanges in the ISDN thus require switching facilities for the broadband channels.An ISDN expanded in this way,is referred to as a "Broadband ISDN".