Page 30 - Intelligent Communication Systems

1 4 INTELLIGENT COMMUNICATION SYSTEMS

FIGURE 3.1 Communication network structure,

including LS and TS has been used in Japan in its public telephone network. When
the line is busy, an alternate line is selected and the call is transmitted through an
alternate route. This is called routing.
Recently, it has become increasingly necessary to transmit multimedia infor-
mation in real time via communication lines. To accomplish this, high-speed trans-
mission lines or digital transmission lines have been constructed. The high-speed
and digital transmission networks are called the Information Superhighway. The
high-speed network project has been conducted in the public telephone network.
As shown in Figure 3.1, first the transmission lines between TSs are digitized
by the introduction of optical-fiber links. Second, the links between TS and LS are
digitized. Finally, subscriber lines are digitized with a capacity of 156 Mbps.
Multimedia information can be transmitted via subscriber lines in real time. Through
the introduction of high-speed networks, video signals and motion pictures can
readily be sent to subscribers in real time.

3.2 COMPUTER NETWORK ARCHITECTURE

In this section, computer network structure, computer network architecture, and
the OSI protocol are described.
A computer network is composed of networks and computers. In order to
interconnect different types of computers, a network architecture and protocols are
standardized. For example, the OSI reference model has been established to inter-
connect heterogeneous networks. After development of the OSI model, the TCP/IP
protocol was developed and put into practical use for local area networks.