Multiplex communications – Communication techniques for information carried in plural... – Adaptive
Reexamination Certificate
1997-05-05
2001-09-04
Ton, Dang (Department: 2661)
Multiplex communications
Communication techniques for information carried in plural...
Adaptive
C370S474000
Reexamination Certificate
active
06285684
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention generally relates to mobile communication system, mobile terminals, base stations, mobile switching stations and mobile communication control method, and more particularly to a mobile communication system, a mobile terminal, a base station, a mobile switching station and a mobile communication control method which transfer information using asynchronous transfer mode (ATM) cells.
Various kinds of mobile communication systems are known which connect a mobile terminal such as a car telephone and a portable telephone to a base station via a radio line, and connect the base station and a mobile switching station via a wire line. The utilization efficiency of radio frequencies on the radio line is improved using frequency division or time division multiplexing. In such mobile communication systems, there are demands to further improve the system efficiency.
FIG. 1
is a system block diagram showing an example of a conventional mobile communication system. The mobile communication system shown in
FIG. 1
includes mobile terminals (or stations)
101
1
through
101
k
such as car telephones and portable telephones, base stations
102
1
through
102
m
, a mobile switching station (or center)
103
, a general switched network
104
, a base station controller
105
, and general telephones
106
.
The base stations
102
1
through
102
m
which connect to the mobile switching station, and the mobile terminals
101
1
through
101
k
which are mobile, are connected via radio channels respectively made up of a control channel and a plurality of communication channels. The base stations
102
1
through
102
m
cope with call information from the mobile switching station
103
and call the mobile terminals
101
1
through
101
k
using the control channel. In addition, the mobile terminals
101
1
through
101
k
can call using the control channel. The base stations
102
1
through
102
m
specify the communication channels between the base stations
102
1
through
102
m
and the mobile terminals
101
1
through
101
k
via the control channel. Talk information is transferred between the mobile terminals
101
1
through
101
k
and the base stations
102
1
through
102
m
by use of the specified communication channels.
In addition, a base station control station
105
controls registration of positions where the mobile terminals
101
1
through
101
k
are located, and when the mobile terminals
101
1
through
101
k
are called, controls the base stations
102
1
through
102
m
and the mobile switching station
103
by referring to a home memory (not shown) which registers the position of the mobile terminals
101
1
through
101
k
, so as to call the mobile terminals
101
1
through
101
k
by use of the control channel. The functions of the base station control station
105
may be provided in the mobile switching station
103
.
The base station control station
105
also collects and monitors intensities of received signals during communication between the mobile terminals
101
1
through
101
k
and the base stations
102
1
through
102
m
. For example, if the mobile terminal
101
1
moves during the communication and the received signal intensity of one base station
102
1
decreases and the received signal intensity of another base station
102
2
increases, the base station control station
105
sends an instruction to the mobile switching station
103
to switch from the base station
102
1
having the decreased received signal intensity to the base station
102
2
having the increased received signal intensity. The mobile switching station
103
switches the base stations in response to this instruction, and the switched base station
102
2
instructs the mobile terminal
101
1
to switch to a new communication channel. As a result, the communication channel is switched to the new communication channel, and the communication can be continued while the mobile terminal
101
1
moves.
Conventionally, the radio channels between the base stations
102
1
through
102
m
and the mobile terminals
101
1
through
101
k
employ various multiplexing techniques in order to improve the utilization efficiency of the radio frequencies. Frequency division multiple access (FDMA), time division multiple access (TDMA), time division multiple access/time division duplex (TDMA/TDD) and code division multiple access (CDMA) are examples of such multiplexing techniques. Further, with respect to the data transfer, there is a known technique which transfers the data in packets.
According to the conventional mobile communication system, the mobile terminals
101
1
through
101
k
communicate by occupying the communication channels specified from the base stations
102
1
through
102
m
, and the utilization efficiency of the radio frequencies can be improved by subjecting an audio signal to a band compression coding. However, the audio signal includes a relatively large amount of silent (or unvoiced) intervals, and the communication channels are occupied even during such silent intervals.
In addition, if the mobile stations
101
1
through
101
k
move among service areas of the base stations
102
1
through
102
m
during communication, the base stations
102
1
through
102
m
are switched and the communication channels are switched, thereby requiring a complex control so as not to interrupt the communication. As a result, there was a problem in that the load on the processes of the mobile switching station
103
and the base station control station
105
is extremely large.
SUMMARY OF THE INVENTION
Accordingly, it is a general object of the present invention to provide a novel and useful mobile communication system, a mobile terminal, a base station, a mobile switching station and a mobile communication control method, in which the problem described above is eliminated.
Another and more specific object of the present invention is to provide a mobile communication system, a mobile terminal, a base station, a mobile switching station and a mobile communication control method, which realize an efficient mobile communication using ATM cells.
Still another object of the present invention is to provide a mobile communication system comprising a mobile terminal, a base station, and a mobile switching station, where the mobile terminal, the base station and the mobile switching station are constructed so that communication information and control information are transferred by an asynchronous transfer mode (ATM) cell between the mobile terminal and the base station, between mobile switching station and the base station. According to the mobile communication system of the present invention, it is possible to facilitate common use of the same communication channels by a plurality of mobile terminals by compression coding or the like of the audio information. The switching of the base stations can be carried out in a simple manner by rewriting the base station number in the cell header part of the ATM cell. In addition, the communication between the mobile terminals via the base stations connected to different mobile switching stations can be continued by the ATM cells by rewriting the mobile switching station number in the cell header part of the ATM cell.
A further object of the present invention is to provide a mobile terminal for use in a mobile communication system including mobile terminals, base stations and mobile switching stations, comprising a radio transmitter/receiver part transmitting and receiving an asynchronous transfer mode (ATM) cell, an audio input/output part inputting and outputting audio information, a transmitting cell assembling part assembling the ATM cell from the audio information output from the audio input/output part and control information, and transferring the ATM cell to the radio transmitter/receiver part, a received cell disassembling part disassembling the ATM cell received by the radio transmitter/receiver part to restore audio information, and transferring the restored audio information to the audio input/output part, a
Kameyama Keiji
Morita Eiji
Samejima Noriko
Suzuki Norio
Tomita Kazuhiko
Fujitsu Limited
Helfgott & Karas P.C.
Sam Phirin
Ton Dang
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