Telecommunications – Transmitter and receiver at same station – Radiotelephone equipment detail
Reexamination Certificate
1999-09-03
2001-01-30
Vo, Nguyen (Department: 2745)
Telecommunications
Transmitter and receiver at same station
Radiotelephone equipment detail
C455S426100, C455S432300, C455S456500, C455S067150
Reexamination Certificate
active
06181952
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a mobile communication unit that receives communications services from a cellular communication system if the unit is located within the service area of the cellular communication system and receives communications services from a satellite communication system if the unit is outside the service area. The invention also relates to a mobile communication system utilizing such a mobile communication unit.
2. Description of the Related Art
A dual-mode mobile communication system using dual-mode mobile communication terminals capable of connecting with both a cellular communication system and a satellite communication system has been heretofore available as a mobile communication system for offering wide-coverage mobile communications services to users. Each mobile communication terminal used for such a dual-mode mobile communication system is designed, for example, to detect the reception levels at the systems, to preferentially select a communication system with higher reception power, and to register its location or request connection with the network.
FIG. 11
is a block diagram of the related art mobile communication terminal described in Japanese Unexamined Patent Laid open No. 116949/1997. In
FIG. 11
, a satellite-based mobile station transmitter
55
and a satellite-based mobile station receiver
56
are connected with a satellite-based mobile station antenna
72
via a transmit-receive switch (DUT)
80
. A ground mobile station transmitter
57
and a ground mobile station receiver
58
are connected with a ground mobile station antenna
73
via a transmit-receive switch (DUT)
81
. The outputs of a control signal generator circuit
91
and of a voice encoder circuit
92
are connected with the inputs of the transmitters
55
,
57
, respectively. The outputs of the receivers
56
and
58
are connected with the inputs of a control signal analyzer
93
and of a voice decoder circuit
94
, respectively. The input of the voice encoder circuit
92
and the output of the voice decoder circuit
94
are connected with a handset
96
. The ground mobile station receiver
58
is connected with a reception level detector circuit
95
whose output is connected with a mobile phone controller
90
.
If this mobile communication terminal
30
moves into a location where the reception level of a signal transmitted from a base station of a ground cellular telephone system is in excess of a given level, the location is registered in the base station of the cellular communication system so that the communication mode is switched from the satellite-based communication system to the ground-based communication system. For example, if the reception level detector circuit
95
of the mobile communication terminal
30
detects a reception power exceeding the minimum permissible level of the ground cellular telephone, the mobile communication terminal
30
causes the control signal generator circuit
91
to generate a so-called random access signal (hereinafter referred to as the location registration-requesting signal) for making a request for connection of the ground cellular phone with the network. This location registration-requesting signal is sent to a wireless base station of the ground-based cellular telephone system via the ground mobile station transmitter
57
, the transmit-receive switch
81
, and the ground mobile station antenna
73
.
The mobile communication terminal
30
that is the related art mobile communication unit is constructed as described thus far. The terminal does not make a decision as to whether its present location is within the service area of ground cellular telephone network. The base station of the ground cellular telephone network makes this decision. Even if the reception level detector
95
detects a power exceeding the minimum permissible level for the ground cellular telephone, there is a possibility that the mobile communication terminal
30
is not in the service area of the ground cellular telephone network in practice. Under this condition, if the mode is switched based on the result of the decision made by the reception level detector circuit
95
, and if a location registration-requesting signal is sent to the wireless base station of the ground cellular telephone network, then the base station of the ground cellular telephone network rejects it on the grounds that the requested location does not exist within the service area of the ground cellular telephone network. Therefore, there exists a possibility that request for connection of the ground cellular telephone network cannot be made in spite of the cellular processing in the mobile communication terminal
30
.
Some mobile communication terminals are designed to operate only one of the satellite-based and ground-based systems because of power saving requirement. Because of the structure, the terminal is urged to receive services of one of these two communication systems at a time. If the above-described situation takes place in the mobile communication system of this construction, it is impossible to make a request for connection with either system. In this way, the continuity of the communications services given to the users using these communication systems has presented problems.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide novel mobile communication terminals (mobile communication units) and mobile communication system which permit the mode of operation to be switched between plural communication systems reliably and with greatly reduced power consumption and can offer communications services of improved continuity to users.
A mobile communication unit in accordance with the present invention receives communications services of a cellular communication system if the unit is within the service area of the cellular communication system and receives communications services of a satellite-based communication system if the unit is outside the service area. The mobile communication unit comprises a state monitor for monitoring the services of the satellite-based communication system, a memory in which information about the service area of the cellular communication system is stored, a decision circuit for making a decision as to whether the location of the unit itself is within the service area of the cellular communication system based on the information stored in the memory, if the state monitor detects deterioration of the state of the services of the satellite communication system, and a switching controller. If the result of the decision made by the decision circuit is that the location of the unit itself is outside the cellular service area, the switching controller maintains the services of the satellite communication system. If the location of the unit itself is within the cellular service area, the switching controller switches the reception from the services of the satellite communication system to the services of the cellular communication system. In this way, the services of the satellite communication system is continued until it is confirmed that the present location of the unit itself is within the service area of the cellular communication system. This assures that the connection is switched between the two communication systems. Furthermore, the continuity of the communications services offered to users is assured. In addition, wasteful power consumption produced when the reception is switched can be reduced greatly.
The decision circuit described above makes a decision as to whether the location of the unit itself is within the selected service area. This makes it unnecessary to make decisions regarding every service area stored in the memory. The time taken to make a decision for switching of the reception state can be shortened. The power necessary for the decision processing can be reduced.
The memory described above consists of a storage means that can be detached from the body of the mobile communication unit. This makes it unnecessary to previously load the body
Kincaid Lester G.
Mitsubishi Denki & Kabushiki Kaisha
Rothwell Figg Ernst & Manbeck
Vo Nguyen
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