Page 73 - Intelligent Communication Systems

56 FNTELLIGENT COMMUNICATION SYSTEMS

get information, and exchange e-mail messages. It was a great hit in the mobile
phone market in Japan. By the end of 2000, the number of i-mode phones sold was
about 17 million.
In January 2000, NTT DoCoMo, Japan, began to sell more advanced i-mode
mobile phones in which the Java program environment was installed, in coopera-
tion with Sun Microsystems. Java programs in the server are downloaded to a
mobile phone via Hypertext Transfer Protocol (HTTP). Communication between
a mobile phone and a server is conducted by means of HTTP. There are three appli-
cation programs written in Java: a stand-alone application program that runs only
on a mobile phone, a client-server application program that serves communica-
tion functions between client and server, and an agent-type application program
that starts to run automatically every specified time, communicating with the server
and getting information from it. In the mobile phone, a Secure Sockets Layer has
been installed for security. In the i-mode mobile phone, all kinds of application pro-
grams, such as entertainment programs, can be downloaded from the server and
can be executed. The i-mode mobile phone can provide communication functions,
act as a station for Internet access, and execute a Java program.

7.5.5 Personal Digital Assistants

According to the report of the NPD Group, USA, shipment of personal digital
assistants (PDAs) is increasing rapidly. In 2000, the number shipped reached 3.5
million units in the United States. The PDA can be used in stand-alone mode but
also in communication mode. Palm, Inc., and Handspring, Inc., are frontrunners
in the PDA market. Hewlett-Packard, Compac, Casio, and Sony have entered the
PDA market as well.

7.6 THE INTERNET

The Internet is the network of networks. That is, local area networks are intercon-
nected by telephone lines and/or dedicated lines. The basic component of the
Internet is a local area network. In this section the network components, network
topology, and media access control method of a local area network are described.
Then the Internet and Intranet are described.

7.6.1 Local Area Network
Local area networks are widely used in the intranets in offices, colleges, universi-
ties, and factories. For example, a local area network is constructed in an area
covering 5-6 kilometers in a factory by linking large-scale computers, worksta-
tions, personal computers, file servers, and control processors. All of the comput-
ers and terminals are linked, which makes them more efficient and effective than