JPH11331055A - Mobile body communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To quickly avoid blocking during communication between a mobile body and a communication satellite. SOLUTION: In the case of making communication with a communication satellite 11 via an antenna 21, when a blocking takes place, an arithmetic section 25 selects a communication satellite 14 whose azimuth angle differs from that of the communication satellite 11 in place of the communication satellite 11 whose communication is interrupted based on orbit data. Then an antenna control section 24 generates a drive control signal based on an antenna position detected by an antenna position detection section 23 and a position of the communication satellite 14 calculated by the arithmetic section 25 and drives an antenna drive section 22 based on this signal to drive the antenna 21 from the position of the communication satellite 11 to a position of the communication satellite 14 to make communication with the communication satellite 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile communication system, and more particularly to a mobile communication system suitable for performing communication between a communication satellite orbiting the earth along an elliptical orbit and a large-capacity mobile body. The present invention relates to a body communication system.

[0002]

2. Description of the Related Art Conventionally, as a communication system for performing communication between a communication satellite and a mobile body, a geostationary satellite above the equator orbiting around the earth along an elliptical geostationary orbit is used as a communication satellite. A system for performing communication between a satellite and a satellite tracking device mounted on a vehicle is known. As a satellite tracking device used in this type of system, for example, there is a satellite tracking device developed for an SNG mobile relay vehicle owned by Fuji Television (broadcasting technology, published in 1997. 8 Kenrokukan Publishing).

[0003]

In the conventional communication mobile communication system, since a geostationary satellite is used as a communication satellite, even a single geosynchronous satellite requires 24 hours between a terrestrial satellite tracking device and the communication satellite. Medium communication can be performed. However, since the visual elevation angle of the geostationary satellite is fixed at about 45 degrees, if the vehicle equipped with the satellite tracking device moves during communication, the communication satellite may be out of the field of view of the vehicle due to a building or the like. In such a case, a communication radio wave is blocked by a building or the like, and a blocking (shadowing) phenomenon that communication cannot be performed occurs. In particular, in a large city such as Tokyo where high-rise buildings are lined up, once blocking occurs, the blocking may not be avoided.
That is, even if blocking occurs during communication with one geostationary satellite as a communication target, it cannot be switched to another communication satellite. On the other hand, even if a system in which a plurality of geostationary satellites are to be communicated is constructed, the viewing angle of each geostationary satellite is fixed at about 45 degrees. Satellites often fall outside the field of view of the vehicle, and once communication radio waves are interrupted by a building or the like, it is difficult to avoid blocking.

An object of the present invention is to provide a mobile communication system capable of quickly avoiding blocking during communication between a mobile and a communication satellite.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention comprises a plurality of communication satellites orbiting around the earth along an elliptical orbit at a distance from each other, and an antenna installed on a mobile object. A satellite tracking device for capturing and communicating with one communication satellite of the plurality of communication satellites via the communication satellite, and the satellite tracking device switches another communication satellite when communication with one communication satellite is interrupted. This is a mobile communication system configured to capture and resume communication.

[0006] The present invention also provides a communication system comprising: a plurality of communication satellites orbiting around the earth along an elliptical orbit at a distance from each other; and one of the plurality of communication satellites via an antenna installed in a mobile object. A satellite tracking device for capturing and communicating with a satellite, wherein the satellite tracking device is capable of communicating with another communication satellite based on orbit data of each communication satellite when communication with one communication satellite is interrupted. Is selected as a communication target, a selected communication satellite is captured, and communication is resumed to constitute a mobile communication system.

In configuring each of the mobile communication systems, the following elements can be added.

(1) The satellite tracking device selects, as another communicable satellite capable of communication, a communication satellite located at a position having an azimuth opposite to a communication azimuth centered on a reference azimuth with respect to a communication satellite in which communication is interrupted. The direction of the antenna is changed to the position of the communication satellite.

(2) The plurality of communication satellites are arranged in the long elliptical orbit at intervals such that at least one communication satellite always exists at a position having an elevation angle of 70 degrees or more with respect to a moving object in a specific area on the earth. Go get it.

(3) The satellite tracking device includes: an antenna installed on a moving body; antenna driving means for driving the antenna in a designated direction according to a driving command; and antenna position detecting means for detecting a position of the antenna. Communication means for communicating via the antenna with one of a plurality of communication satellites orbiting around the earth along a long elliptical orbit, and communication with the communication satellite by the communication means is interrupted Communication-shutdown detecting means for detecting that a communication has been performed, and a satellite position calculating means for calculating a position of another communication satellite capable of communicating based on the orbit data of each communication satellite in response to a detection output of the communication-shutdown detecting means And a drive command according to the calculated value of the satellite position calculating means and the detection output of the antenna position detecting means when the communication cutoff is detected by the communication cutoff detecting means. Generating and and a drive instruction means for outputting to the antenna drive means.

(4) The satellite tracking device includes: an antenna installed on a moving body; antenna driving means for driving the antenna in a specified direction according to a driving command; and antenna position detecting means for detecting a position of the antenna. Communication means for communicating with one of a plurality of communication satellites orbiting around the earth along a long elliptical orbit through the antenna, and orbit data on the orbit of each of the communication satellites Orbit data storage means for storing data in association with, communication disconnection detection means for detecting that communication with the communication satellite by the communication means has been interrupted, and the detection output in response to the detection output of the communication cutoff detection means. Satellite position calculating means for searching the orbit data using the time of occurrence as a key and calculating the position of another communication satellite with which communication is possible based on the search; Drive command means for generating a drive command in accordance with the calculated value of the satellite position calculation means and the detection output of the antenna position detection means when the communication cutoff is detected by the cutoff detection means, and outputting the drive command to the antenna drive means; Is provided.

(5) The drive command means issues a drive command for maintaining the radio field intensity by the communication of the communication means within a set value range until the communication cutoff is detected by the communication cutoff detection means. It is generated and output to the antenna driving means.

According to the above-mentioned means, since each communication satellite orbits around the earth in a long elliptical orbit at a distance from each other, each communication satellite has a high elevation angle with respect to the mobile object, for example, 70 degrees or more. When two communication satellites are present at a position and are within the field of view of the communication satellite from the mobile object, each communication satellite is located at a reference azimuth, for example, at a position where the azimuths are opposite to each other around the north. . Therefore, when blocking occurs during communication with one of the communication satellites, the blocking can be quickly avoided by selecting a communication satellite located at a position having an opposite azimuth angle.

[0014]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a satellite tracking device according to an embodiment of the present invention, and FIGS. 2 and 3 are diagrams for explaining the orbit of a communication satellite. In FIG. 2 and FIG. 3, the earth 1 is used as a communication satellite used in the mobile communication system.
Around 0, four communication satellites 11, 12, 13, 14 have been launched. Each of the communication satellites 11 to 14
Are launched around an orbit along a long elliptical orbit at a constant distance from each other. When each of the communication satellites 11 to 14 orbits at a constant interval along a long elliptical orbit, when a communication satellite is viewed from a specific region, for example, from Japan, the elevation angle of at least one communication satellite is 24 hours in 24 hours. Viewing angle) can be maintained at a high elevation angle of 70 degrees or more. On the other hand, in the case of the geostationary satellite 15 moving in the geostationary orbit, the elevation angle of the geostationary satellite 15 viewed from Japan is about 45 degrees. Since each of the communication satellites 11 to 14 moves with a plane inclined with respect to the equatorial plane such that the communication satellite comes to the zenith of Japan as an orbital plane, it appears at a high elevation angle. Further, since each of the communication satellites 11 to 14 orbits the orbit planes which intersect at right angles to each other, each of the communication satellites 1 to 14
Azimuth (view azimuth) and elevation (view elevation) for 1-14
Are represented as shown in FIGS. 4 and 5.

In FIG. 4, the communication satellite 11 is at time t1.
In the figure, the trajectory is located at a position of about 120 degrees east with respect to the reference azimuth north, and moves to a position of about minus 100 degrees west at time t10 with the passage of time. At time t1, the communication satellite 14 is located at an azimuth angle different from the azimuth angle of the communication satellite 11, for example, at a position minus 80 degrees west. Further, at time t4, the communication satellite 14 moves -1 to the west.
A trajectory that moves to a position of 00 degrees is drawn.

Referring to the elevation angles of the communication satellites, as shown in FIG. 5, at each time, the elevation angle of at least one or more communication satellites is 70 degrees or more. The elevation angle is 70 degrees, and the elevation angle of the communication satellite 14 is about 83 degrees. And the communication satellite 11
Is maintained at 70 degrees or more from time t1 to time t10, and at time t5, the elevation angle becomes about 88 degrees. Further, looking at the region where the elevation angle is 70 degrees or more, it indicates that two communication satellites are always present in the region where the elevation angle is 70 degrees to 85 degrees.

On the other hand, the satellite tracking device is mounted on a vehicle, such as an ambulance, as a moving body.
Any one of the communication satellites can be captured and communicated. Specifically, the satellite tracking device includes a satellite radio monitor 20, an antenna 21, an antenna driving unit 22, an antenna position detection unit 23, an antenna control unit 24, and a calculation unit 25.

The antenna 21 is configured to transmit and receive radio waves in a high-frequency band such as the Ka band, for example, radio waves in the 30 GHz band, and a satellite radio wave monitor 20 is disposed at a position substantially at the focal point of the antenna 21. The satellite radio wave monitor 20 outputs the radio wave received by the antenna 21 to the antenna control unit 24 and the arithmetic unit 25 as a signal corresponding to the radio wave intensity. The antenna 21 is connected to the antenna driving unit 22 and the direction is adjusted with an accuracy of about ± 1 degree. In order to drive the antenna 21 in a specified direction, the antenna driving unit 22 A motor for driving the antenna 21 to a position of a specified elevation angle and a motor for driving the antenna 21 to a position of a specified azimuth angle are built in according to a drive control signal. That is,
The antenna drive unit 22 is configured as an antenna drive unit that drives the antenna 21 in a specified direction according to a drive control signal (drive command). An antenna 1 detecting unit 23 is connected to the antenna driving unit 22. The antenna position detecting unit 23 detects a driving amount of a driving motor for driving the antenna 21 to a position at a specified elevation angle. The antenna position detecting means is configured to output the detected value to the arithmetic unit 25 as a signal indicating the antenna position.

On the other hand, the arithmetic unit 25 has azimuth data indicating the relationship between the azimuth and time shown in FIG. 4 and elevation data indicating the relationship between the elevation and time of each communication satellite shown in FIG. As a trajectory data storage means for storing the data. The arithmetic unit 25 takes in a signal corresponding to the radio wave intensity from the satellite radio wave monitor 20 and also takes in a signal relating to the antenna position from the antenna position detecting unit 25 to constitute communication means for communicating with any communication satellite, and When communication with the communication satellite is performed by the means, when the radio wave intensity becomes close to, for example, 0, the communication cutoff detecting means for detecting that the communication with the designated communication satellite has been interrupted is configured. Further, when the communication interruption detecting means detects that the communication with the designated communication satellite has been interrupted, the orbit data in the memory is searched using the time when the detection output is generated as a key, and the communication is performed based on the search. A position calculating means for calculating the position of another communication satellite with which communication can be performed in place of the communication satellite which has been interrupted. The data on the position of another communication satellite with which communication is possible is output to the antenna control unit 24 together with the data on the antenna position and data indicating that communication with the designated communication satellite has been interrupted.

Until the communication with the designated communication satellite is interrupted, the antenna control unit 24 maintains the radio wave intensity by the communication with the designated communication satellite within the range of the set value based on the signal from the satellite radio wave monitor 20. For example, a drive control signal is generated as a drive command for generating a drive command for maximizing the radio field intensity, and the generated drive control signal is output to the antenna drive unit 22. Further, when communication with the designated communication satellite is interrupted, the antenna control unit 24 sets the data from the arithmetic unit 24, that is, the data on the antenna position detected by the antenna position detection unit 23, and the position of another communication satellite with which communication is possible. A drive control signal is generated in accordance with the data on the control signal, and the drive control signal is output to the antenna drive unit 22.

Next, the operation of the mobile communication system according to the present invention will be described with reference to FIGS.

A case where an ambulance 30 equipped with the satellite tracking device shown in FIG. 1 travels while communicating with the communication satellite 11 will be described. Here, buildings 31 to 3 are located in the high-rise building area.
7 is present, high-rise building 3 for communication satellite 11
Blocking areas by 1 to 37 are 31a to 37a, and blocking areas of the high-rise buildings 31 to 37 for the communication satellite 14 are 31b to 37b. Then, at time t1, the ambulance 30 becomes a high-rise building 31, 32, 34,
When the satellite tracking device mounted on the ambulance 30 is communicating with the communication satellite 11 when traveling on the roads along 36 and 37, the blocking regions 32a and 34a by the high-rise buildings 32 and 34 remain unchanged. 2 to pass
Times communication will be interrupted. Therefore, in the present embodiment, the satellite tracking device mounted on the ambulance 30 operates at time t.
When the communication satellite 11 enters the blocking area 32a of the high-rise building 32 during communication with the communication satellite 11 and blocking occurs, the arithmetic unit 25 selects the communication satellite 14 as a communicable satellite instead of the communication satellite 11 in the arithmetic unit 25. I have to. That is, at time t1, communication satellite 1
It can be seen from the orbit data shown in FIG. 5 that the communication satellite that can communicate in place of 1 is the communication satellite 14. FIG. 4
It can be understood from the orbit data shown in (1) that the communication satellite 14 is located at an azimuth angle opposite to the azimuth angle of the communication satellite 11 with reference to north (0 degrees). After the communication satellite 14 is selected, the antenna 2 when communicating with the communication satellite 11
The antenna control unit 24 generates a drive control signal in accordance with the data on the position 1 and the data on the position of the communication satellite 14 when the communication satellite 14 is selected, and drives the antenna drive unit 22 according to the drive control signal. In other words, the antenna 21 is driven to change the elevation angle of the antenna 21 with respect to the communication satellite from 70 degrees to about 83 degrees, and is moved from the azimuth angle of the communication satellite 11 (about 120 degrees east) by about 80 degrees.
Drive to change to the azimuth angle west. This angle is performed with an accuracy of about ± 1 degree. And antenna 2
When the vehicle 1 is directed to the position of the communication satellite 14, the ambulance 30 moves out of the blocking areas 31 b and 32 b of the high-rise buildings 31 and 32, and the satellite tracking device mounted on the ambulance 30 communicates with the communication satellite 14 as shown in FIG. Communication can be resumed. Furthermore, the ambulance 30 is a high-rise building 34, 36, 37
When traveling on a nearby road, while communicating with the communication satellite 14, there is no passage through the blocking areas 34b, 36b, 37b by the high-rise buildings 34, 36, 37, so that communication is not interrupted, Communication can be continued in a stable state.

When blocking occurs at times other than the time t1, the blocking phenomenon is selected by selecting a communicable communication satellite instead of a communication satellite whose communication has been interrupted based on the orbit data shown in FIGS. Even if it occurs, blocking can be quickly avoided, and communication can be continued in a stable state.

During communication with the communication satellite 11 during the period from time t4 to time t7, only the communication satellite 11 having an elevation angle of 70 degrees or more is an elevation angle of 80 degrees or more. (Because the communication satellite 11 exists at a position almost at the zenith as viewed from the ambulance), even when the ambulance 30 travels in a high-rise building town, the blocking phenomenon hardly occurs due to the high-rise building, and communication is continued in a stable state. Can be.

In the above embodiment, the case where four communication satellites 11 to 14 are used has been described. However, by increasing the number of communication satellites, two or more communication satellites are always provided in a region where the elevation angle is 70 ° or more. A configuration in which a communication satellite exists may be adopted.

[0027]

As described above, according to the present invention,
As a communication satellite, a plurality of communication satellites orbiting the earth along a long elliptical orbit, and when communication is performed between any communication satellite and the satellite tracking device, communication with the communication satellite When communication is interrupted, another communication satellite is selected and communication is restarted, so that blocking during communication between the mobile unit and the communication satellite can be quickly avoided, and the communication effect due to blocking is minimized. Can be suppressed.

[Brief description of the drawings]

FIG. 1 is a block diagram of a satellite tracking device according to the present invention.

FIG. 2 is a diagram for explaining an orbit of a communication satellite according to the present invention.

FIG. 3 is a diagram for explaining a relationship between a communication satellite and a geostationary satellite according to the present invention.

FIG. 4 is a diagram illustrating a relationship between an azimuth of a communication satellite and time.

FIG. 5 is a diagram showing a relationship between an elevation angle of a communication satellite and time.

FIG. 6 is a diagram for explaining a blocking region of a communication satellite 11 caused by a high-rise building.

FIG. 7 is a diagram for describing a blocking area of a high-rise building for a communication satellite 14;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Earth 11-14 Communication satellite 15 Geostationary satellite 20 Satellite radio wave monitor 21 Antenna 22 Antenna drive part 23 Antenna position detection part 24 Antenna control part 25 Operation part 31-37 High-rise building 31a-37a, 31b-37b Blocking area

Claims (7)

[Claims] A plurality of communication satellites orbiting around the earth along an elliptical orbit at a distance from each other, and one of the plurality of communication satellites is captured via an antenna installed on a mobile body. A mobile communication system comprising: a satellite tracking device that performs communication with another communication satellite, wherein the satellite tracking device captures another communication satellite and resumes communication when communication with one communication satellite is interrupted. 2. A plurality of communication satellites orbiting around the earth along a long elliptical orbit at a distance from each other, and one of the plurality of communication satellites is captured via an antenna installed on a mobile body. A satellite tracking device that communicates with another communication satellite, and when the communication with one communication satellite is interrupted, the satellite tracking device targets another communication satellite that can communicate based on the orbit data of each communication satellite. A mobile communication system which selects, captures the selected communication satellite, and resumes communication. 3. The satellite tracking device selects and selects, as another communicable communication satellite, a communication satellite located at a position at an azimuth opposite to a communication azimuth centered on a reference azimuth with respect to a communication satellite in which communication has been interrupted. 3. The mobile communication system according to claim 2, wherein the direction of the antenna is changed to a position of a communication satellite. 4. The plurality of communication satellites are arranged on the long elliptical orbit at intervals such that at least one communication satellite always exists at a position having an elevation angle of 70 degrees or more with respect to a moving object in a specific area on the earth. The moving device according to claim 1,
4. The mobile communication system according to 2 or 3. 5. The satellite tracking device includes: an antenna installed on a mobile object; an antenna driving unit for driving the antenna in a specified direction according to a driving command; an antenna position detecting unit for detecting a position of the antenna; Communication means for communicating via the antenna with one communication satellite among a plurality of communication satellites orbiting around the earth along a long elliptical orbit and communication with the communication satellite by this communication means has been interrupted A communication cutoff detecting means for detecting that the communication cutoff detecting means; and a satellite position calculating means for calculating a position of another communication satellite capable of communication based on the orbit data of each communication satellite in response to a detection output of the communication cutoff detecting means. And generating a drive command according to the calculated value of the satellite position calculating means and the detection output of the antenna position detecting means when the communication cutoff is detected by the communication cutoff detecting means. 5. The mobile communication system according to claim 1, further comprising: a driving command unit that outputs the signal to the antenna driving unit. 6. The satellite tracking device includes: an antenna installed on a moving object; antenna driving means for driving the antenna in a specified direction according to a driving command; antenna position detecting means for detecting a position of the antenna; A communication means for communicating via the antenna with one of a plurality of communication satellites orbiting the earth along an elliptical orbit at a distance from each other, and orbit data on the orbit of each communication satellite at a time Orbit data storage means for storing in association with
A communication interruption detecting means for detecting that communication with the communication satellite by the communication means has been interrupted; and, in response to a detection output of the communication interruption detecting means, searching for the orbit data by using a time at which the detection output occurs as a key. A satellite position calculating means for calculating the position of another communication satellite with which communication is possible based on the search; and a value calculated by the satellite position calculating means when the communication cutoff is detected by the communication cutoff detecting means. 5. The mobile communication system according to claim 1, further comprising: a drive command unit that generates a drive command according to a detection output of the antenna position detection unit and outputs the drive command to the antenna drive unit. 7. The drive command means generates a drive command for maintaining a radio field intensity by communication of the communication means within a range of a set value until communication interruption is detected by the communication interruption detection means. 7. The mobile communication system according to claim 5, wherein the mobile communication system outputs the data to the antenna driving means.