Page 70 - Intelligent Communication Systems

54 INTELLIGENT COMMUNICATION SYSTEMS
Fl to F7 are cells, each with a diameter of about 10 km. Cells are laid out in hexag-
onal zones. Each zone has the same frequency structure. In this way, frequencies
are used efficiently and effectively.
The mobile communication system comprises a mobile control station (MCS),
a mobile base station (MBS), and a mobile service station (MSS). The system
structure is shown in Figure 7.3. The MCS handles call control and management
of the current position of the MSS. The MBS monitors the MSS and detects its cur-
rent position. The MSS is a car telephone or a portable phone that issues its iden-
tification number and lets the MBS know its current position. The MCS has a home
memory and stores the current position of the portable phone.
When an MSS is switched on, the identification number (ID) of the MSS is
issued. An MBS that captured the ID sends it to the MCS controlling the MBS.
The MCS stores in its home memory the information about the MSS and the area
of the MBS where the MSS is currently located.

7.5.1 Calling a Portable Phone from a Wired Phone
A wired telephone calls a portable phone. The call is identified as a portable phone
call by the dialed number. The numbering plan for portable phones is as follows:
prefix (3 digits) + carrier ID (3 digits) + subscriber number (5 digits)

(The mobile prefix number in Japan is 090.) The call is transmitted via the gate-
way to the MCS, which checks the MSS current location and transmits the call to
the MBS closest to that location. Then the MBS calls the MSS and the call is con-
nected to the MSS.

7.5.2 Calling a Portable Phone from Another Portable Phone
A portable phone calls another portable phone. The call is identified as a portable
phone call by the dialed number. The call is transmitted to the MCS, which checks
the current location of the MSS and transmits the call to the MBS closest to that
location. Then the MBS calls the MSS and the call is connected to the MSS.

7.5.3 Calling a Wired Phone from a Portable Phone
A portable phone calls a wired phone. An MBS captures the call and identifies it
as a call to a wired phone. The call is sent to the telephone network through the
MCS and gateway. Then the call is connected to the wired phone.

7.5.4 l-Mode Phone
In 1999, NTT DoCoMo, Japan, announced it would sell the i-mode mobile phone
in Japan. It was an epoch-making announcement because the phone could
access the Internet. Using the i-mode phone, a customer can access the Internet,