JP3053402B2 - Mobile communication system - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention scans a signal level of a control channel transmitted from a plurality of ground base stations when a call request is made from a mobile communication device. If the signal level of the control channel is not higher than the predetermined value, or if the signal level of the control channel is higher than the predetermined value, but the terrestrial base station does not specify an available communication channel, the space satellite base station is The present invention relates to a mobile communication system in which a signal level of a control channel from a terrestrial base station is scanned when communication is performed via the satellite base station and no free channel is specified by the space satellite base station. . 2. Description of the Related Art Generally, in a mobile communication system in which an automobile is used as a mobile body and a mobile communication device is mounted on the mobile body,
In order to increase the capacity of the subscriber, a plurality of ground stations are provided at predetermined intervals, and communication is possible while moving the mobile body itself in each zone (communicable area) of each of the ground stations. The so-called small zone method is adopted. A communication system capable of performing such communication is described in a magazine “Journal of the Institute of Electronics and Communication Engineers” published in January 1981 (VOL64, No. 1, pages 7 to 29). . However, it is economically difficult to universally install a large number of ground base stations,
In particular, it is not preferable to provide a ground base station even in an area where there is little car traffic. On the other hand, especially in mountainous areas,
Since the radio waves from each of the ground base stations are blocked and the communication distance of the radio waves is limited, more ground base stations are required. The object of the present invention is to eliminate the need for providing many ground base stations, even in mountainous areas,
An object of the present invention is to provide a mobile communication system capable of performing communication between a mobile communication device and a terrestrial communication network more economically. An object of the present invention is to provide a mobile communication system having a mobile communication device, a terrestrial communication network, and a plurality of terrestrial base stations for wirelessly communicating with the mobile communication device in a small zone. The body communication device can communicate with a space satellite base station that wirelessly communicates in a large zone, scans signal levels of control channels emitted from a plurality of terrestrial base stations, and sets the signal level of the control channel to a predetermined value or more. In this case, if the signal level of the control channel is designated as a vacant channel for communication from a terrestrial base station having a predetermined value or more, control is performed so as to communicate with the terrestrial base station, and from the plurality of terrestrial base stations. If the signal level of the control channel is not more than a predetermined value by scanning the signal level of the emitted control channel, or even if the signal level of the control channel is more than a predetermined value,
If there is no designation of a vacant channel for communication from the ground base station which is equal to or greater than the predetermined value, control is performed so as to communicate via the space satellite base station, and if there is no designation of a vacant channel for communication from the space satellite base station, This is achieved by providing control means for controlling to scan the signal level of the control channel from the terrestrial base station. [0007] The present invention will be described below with reference to FIGS. 1 to 4. First, FIG. 1 shows an outline of a mobile communication system according to an embodiment of the present invention. As shown in the figure, the mobile communication system has a mobile communication device 11 mounted on each mobile that can be moved at any time, for example, each automobile 1, and performs ground communication with each of these automobiles 1. Terrestrial base stations 2a and 2b, and a space satellite base station 3 and a space station base for performing satellite communication with the vehicle 1 when the vehicle 1 moves out of the small zone of each of the terrestrial base stations 2a and 2b. 4a and 4b, and terrestrial communication networks 5a and 5b for connecting each of the automobiles 1 to a communication partner station via one of the terrestrial base stations 2a and 2b or the space satellite base station 3. ing. In the mobile communication system, for example, when each automobile 1 is located in the zone of the ground base station 2a (left position in the figure), the ground base station 2a and the ground communication network 5
When communication is performed with the communication partner station via a, and each of the automobiles 1 is simultaneously located outside the zone of each of the ground base stations 2a and 2b (center position in the figure), each of the automobiles 1 Communication is performed with the communication partner station via the space satellite base station 3, the space station base 4a (or the space station base 4b), and the terrestrial communication network 5a (or the terrestrial communication network 5b). . FIG. 2 shows an example of the configuration of a mobile communication device 11 mounted on each of the automobiles 1. As shown, the mobile communication device 11 includes an antenna 1 for transmitting and receiving radio waves to and from a ground base station and a space satellite base station.
0, an antenna duplexer 20 for sharing the antenna 10 with a transmitter 30 and a receiver 40 to be described later, a frequency synthesizer 50 for generating various frequencies for transmission and reception, and a frequency synthesizer based on a signal received from the antenna 10. Multi-channel receiver 4 for receiving a required radio signal (channel signal) from a high-frequency signal from 50
0, an A / D converter 60 for converting the detection output of the intermediate frequency stage received by the receiver 40 into a digital signal,
A data receiver 70 for identifying and detecting a control signal from the terrestrial base station received by the receiver 40, an A / D converter 60
A microcomputer 90 for selecting and controlling a communication line based on an output signal from the data receiver 70, a telephone 100 for making a telephone call with a communication partner station, and a transmission audio signal from the telephone 100 by a frequency from the frequency synthesizer 50. A multi-channel transmitter 30 for converting to a transmission radio signal, and a data transmission unit 80 for generating a transmission control signal to the transmitter 30 based on transmission control data from the microcomputer 90; Has become. Here, the operation of selecting a communication line in the mobile communication device 11 will be described with reference to FIG. 3. In the mobile communication device 11, radio waves are transmitted from the ground base stations 2a and 2b to the antenna 10 and the antenna duplexer. The control signal and the detection output are transmitted to the microcomputer 90 via the data receiver 70 and the A / D converter 60, respectively. As a result, in the microcomputer 90, as shown in FIG. 3, the ground station control channel levels from the ground base stations 2a and 2b are known based on the detection output from the A / D converter 60. Therefore, if the largest ground station control channel level among the ground station control channel levels is equal to or higher than the communicable level, the ground base station transmitting the control signal having the larger control channel level is selected. It is good to do. Therefore, after that, after receiving the designation of the vacant communication channel for the terrestrial base station from the selected terrestrial base station, the frequency synthesizer 50 places the transmitter 30 and the receiver 40 in the desired radio frequency setting state. For example, wireless communication with the selected terrestrial base station is enabled. On the other hand, if the control channel levels for the ground stations from each of the ground base stations 2a and 2b have not reached the communicable level and communication with either of the ground base stations 2a or 2b is impossible, the microcomputer 90 determines If determined, the radio frequency is set by the frequency synthesizer 50 to each of the transmitter 30 and the receiver 40 via the space satellite base station 3 so that the communication is performed via the space satellite base station 3. In this state, wireless communication with the space satellite base station 3 is enabled by the same method as in the case of the ground base station. At the time of standby, the receiver 40 is always set to a state in which the ground base station control channel can be received by the frequency synthesizer 50. Accordingly, when each of the automobiles 1 moves into the zone 2b with the ground base station with the movement after the end of the telephone call, the microcomputer 90 sets the radio transmission / reception frequency again for the ground base station, Communication with the station is enabled. [0010] Finally, the acquisition of the communication channel by the microcomputer 90 will be described with reference to FIG. 4. First, the signal level of each control channel in the ground station control channel group is detected by scanning. When it is confirmed that the signal level of any of the control channels is equal to or higher than the communicable level, an idle communication channel designation request is transmitted to the corresponding ground base station. As a response to this, when an idle communication channel is designated by the control channel from the ground base station, the communication with the communication partner station is performed via the ground base station with the empty communication channel captured thereafter. Communication is performed. At this time, if none of the control channels is higher than the communicable level or if there is no available communication channel, the signal level of each control channel is detected by scanning in the space station control channel group for the first time. Is what is being done. Hereinafter, in the same manner, when an empty communication channel is designated from the space satellite base station via the control channel, the empty communication channel is captured, and the space communication base station communicates with the communication partner station via the space satellite base station. Communication is being performed. If the user's cost is different between the case where communication is performed via the ground base station and the case where communication is performed via the space satellite base station, the communication via the ground / space satellite base station is performed. The cost display function may be provided in the mobile communication device 11 in addition to the guidance function for the user that the communication is performed. As described above, according to the first aspect, even in a mountainous area, there is no need to provide many terrestrial base stations, so that a mobile communication apparatus and a terrestrial communication network can be provided. There has been obtained a mobile communication system capable of performing communication between them more economically.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing an outline of an embodiment of a mobile communication system according to the present invention. FIG. 2 is an example of a mobile communication device according to the present invention. FIG. 3 is a diagram illustrating a flow for explaining a ground station / satellite station selection method in the mobile communication device. FIG. 4 is a diagram illustrating a ground station communication / Diagram showing assignment of control channel and space station communication / control channel as an example [Description of References] 1 ... Automobile, 2a, 2b ... Ground base station, 3 ... Space satellite base station, 4a, 4b ... Space station base 5a, 5b terrestrial communication network, 10 antenna, 20 antenna duplexer, 30
Multi-channel transmitter, 40 Multi-channel receiver, 50 Frequency synthesizer, 60 A / D converter, 70 Data receiver, 80 Data transmitter, 90
Microcomputer, 100 ... telephone.

Claims (1)

(57) [Claims] A mobile communication system comprising: a mobile communication device, a terrestrial communication network, and a plurality of terrestrial base stations that wirelessly communicate with the mobile communication device in a small zone. It can communicate with a space satellite base station with which it communicates, scans the signal level of a control channel emitted from a plurality of ground base stations, and when the signal level of the control channel is equal to or higher than a predetermined value, When a level of a free channel for communication is received from a terrestrial base station whose level is equal to or higher than a predetermined value, control is performed so as to communicate with the terrestrial base station, and a signal level of a control channel transmitted from the plurality of terrestrial base stations is scanned. And when the signal level of the control channel is not higher than a predetermined value, or even when the signal level of the control channel is higher than a predetermined value, If the station does not specify a free channel for communication, control is performed so as to communicate via the space satellite base station.If no free channel is specified for communication from the space satellite base station, control is performed from the ground base station. A mobile communication system comprising control means for controlling to scan a signal level of a channel.