JP7312147B2 - Base station, program and method for narrowing stay range of mobile terminal - Google Patents

Description

The present invention relates to technology for discovering a mobile terminal using a base station.

A guideline for acquiring location information from a terminal has been published for the purpose of saving lives in the event of a disaster (see, for example, Non-Patent Document 1). Here, base station information based on location registration and GPS (Global Positioning System) information that enables positioning by terminals are used. When the terminal detects radio waves emitted from the base station, it executes an authentication sequence based on position registration with the base station, and transmits position information obtained by GPS positioning to the base station. According to this technology, mobile base stations are used as base stations, and base station functions are installed in flying objects such as drones, helicopters, balloons, and airships.

FIG. 1 is an explanatory diagram showing a mobile base station flying in the air.

According to FIG. 1, a mobile base station 1 moves autonomously while positioning itself by GPS. At this time, the mobile base station 1 flies while emitting radio waves in order to find the mobile terminal 2 . The radio wave range is circular with the radius equal to the radio wave reaching distance.
On the other hand, the mobile terminal 2 is like an existing smart phone or mobile phone owned by the user. The mobile terminal 2 can also measure its own position (latitude and longitude) by GPS.

Conventionally, there is a technique for properly planning an operation plan using a drone, regardless of autonomous navigation or remote control, when finding a person in distress in a mountain (see Patent Document 1, for example). According to this technology, an order data file is referenced to specify the departure point and destination of the drone, and then an air network database for drones is referenced to make an operation plan consisting of a flight route from the departure point to the destination. and manages the dynamics of the drone while receiving state information including the current position that is sequentially transmitted from the drone flying based on the flight plan.

JP 2018-165932 A

Ministry of Internal Affairs and Communications, “Summary on Handling of GPS Location Information in Lifesaving,” Press Release, July 2013, [online], [searched March 19, 2020], Internet <URL: http://www .soumu.go.jp/main_content/000237319.pdf＞

In the case of the GPS positioning described above, the positioning accuracy is high, but the mobile terminal needs to transmit the position information obtained by positioning itself to the base station. At this time, it is necessary to execute an authentication sequence between the mobile terminal and the base station, and there is a constraint that an authentication facility for that purpose is required. In disaster-stricken areas, etc., it is not always possible to provide an environment in which users can use mobile terminals, and it is also assumed that authentication facilities cannot be prepared in advance.
On the other hand, the mobile terminal consumes power to constantly activate GPS and continuously measure its own position. In addition, in disaster areas and remote areas, there are many cases where users cannot operate mobile terminals by themselves. Ultimately, when the battery of a mobile device dies completely, there is no means of discovering the user.
Therefore, trying to find a mobile terminal by GPS positioning poses a problem of authentication equipment on the side of the base station and a problem of power consumption on the side of the mobile terminal.

In general, a mobile terminal waits to receive radio waves emitted from a base station, and upon detecting the radio waves, transmits an access signal to the base station. Using this, there is a technique in which a base station itself moves a directional beam (radio wave) range in order to find a mobile terminal whose staying position is unknown. The base station comprehensively moves the beam range in order to narrow down the wide search area. If the base station is a mobile base station, the mobile base station itself continues to radiate radio waves and flies as if to paint over the wide search area. When the base station receives an access signal response from the mobile terminal, it can be assumed that the mobile terminal exists within its beam range.

However, the wider the range of radio waves emitted by the base station, the wider the position range as a search result. On the other hand, the narrower the radio wave range emitted by the base station, the narrower the position range as a search result can be, but the longer the moving distance of the beam range is for exhaustive search. In the case of a mobile base station, the flying distance of the mobile base station is inevitably long.

Therefore, the present invention provides a base station capable of shortening the overall moving distance in the beam range of the base station when narrowing down the range of stay of the mobile terminal, relying only on the access signal returned from the mobile terminal. The purpose is to provide a program and method.

According to the present invention, in order to discover a mobile terminal, in a base station that emits radio waves,
a first circular radio wave range setting means for setting a first circular radio wave range having a first radius;
Terminal detection means for positioning a detection position when a signal is received from a mobile terminal in the first circular radio wave range;
setting a second circular radio wave range with a second radius shortened from the first radius of the first circular radio wave range until the signal of the mobile terminal cannot be received, centering on the detection position; circular radio wave range setting means;
a third circular radio wave range setting means for setting a third circular radio wave range having a third radius shorter than the second radius;
Beam movement control for searching by moving while radiating a third circular radio wave range along the central circumference of the circular radio wave range where the first circular radio wave range and the second circular radio wave range do not overlap. and means.

According to another embodiment of the base station of the present invention,
A base station is a mobile base station that moves in the air while emitting radio waves.
Preferably, the beam movement control means also controls movement of the mobile base station itself.

According to another embodiment of the base station of the present invention,
It is also preferable that the third circular radio wave range setting means match the diameter of the third circular radio wave range with the predetermined length in the second circular radio wave range setting means.

According to another embodiment of the base station of the present invention,
The second circular radio wave range setting means increases the predetermined length in the second circular radio wave range setting means when a signal is received from the portable terminal within the set second circular radio wave range, and sets the second radius. It is also preferable to set a second circular radio wave range in which is further shortened.

According to another embodiment of the base station of the present invention,
The first circular radio wave range, the second circular radio wave range, and the third circular radio wave range are the movement in the vertical direction (ground altitude), or the radio wave output of the base station (radio wave reachable distance). It is also preferable to set by controlling the

According to another embodiment of the base station of the present invention,
When the third circular radio wave range is less than or equal to the predetermined area, it is also preferable to end the search assuming that the staying position of the mobile terminal is within the first circular radio wave range.

According to another embodiment of the base station of the present invention,
The beam movement control means uses the interval time I between the start times when the mobile terminal detects radio waves radiated from the base station and the diameter R of the circular radio wave range radiated from the base station to determine the direction of travel. It is also preferred to determine the speed of movement v to .

According to the present invention, in order to discover a mobile terminal, in a program that causes a computer installed in a base station that emits radio waves to function,
a first circular radio wave range setting means for setting a first circular radio wave range having a first radius;
Terminal detection means for positioning a detection position when a signal is received from a mobile terminal in the first circular radio wave range;
setting a second circular radio wave range with a second radius shortened from the first radius of the first circular radio wave range until the signal of the mobile terminal cannot be received, centering on the detection position; circular radio wave range setting means;
a third circular radio wave range setting means for setting a third circular radio wave range having a third radius shorter than the second radius;
Beam movement control for searching by moving while radiating a third circular radio wave range along the central circumference of the circular radio wave range where the first circular radio wave range and the second circular radio wave range do not overlap. It is characterized by making a computer function as a means.

According to the present invention, in a beam movement control method for a base station that emits radio waves to discover a mobile terminal,
The base station
a first step of setting a first circular radio range of a first radius;
a second step of positioning the detected position when a signal is received from the mobile terminal in the first circular radio wave range;
setting a second circular radio wave range with a second radius shortened from the first radius of the first circular radio wave range until the signal of the mobile terminal cannot be received, centering on the detection position; a step;
a fourth step of setting a third circular radio range with a third radius that is shorter than the second radius;
A fifth circular radio wave range is radiated and moved along the central circumference of the circular radio wave range where the first circular radio wave range and the second circular radio wave range do not overlap each other. It is characterized by executing steps.

According to the base station, the program and the method of the present invention, when narrowing down the range of stay of the mobile terminal by relying only on the access signal returned from the mobile terminal, the overall moving distance in the beam range of the base station is shortened. can do.

1 is an explanatory diagram showing a mobile base station flying in the air; FIG. 3 is a functional configuration diagram of a base station in the present invention; FIG. 1 is a functional configuration diagram of a mobile base station according to the present invention; FIG. FIG. 4 is an explanatory diagram showing a first circular radio wave range; FIG. 11 is an explanatory diagram showing a second circular radio wave range; FIG. 4 is an explanatory diagram showing superimposition of a first circular radio wave range and a second circular radio wave range; FIG. 11 is an explanatory diagram showing movement of a third circular radio wave range; FIG. 11 is an explanatory diagram showing a third circular radio wave range in which a mobile terminal is detected; FIG. 4 is an explanatory diagram showing the relationship between the traveling speed of the beam range and the detectable range; FIG. 4 is an explanatory diagram showing the advancing speed of the beam range and the detectable range in the present invention;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 2 is a functional configuration diagram of a base station in the present invention.

The base station 1 has a base station function unit 101 that can communicate with the mobile terminal 2 . The base station function unit 101 is described as an LTE (Long Term Evolution) base station based on a wide area wireless communication network, but may be a base station based on, for example, 3G (3rd Generation), 5G (5th Generation) or WiMAX (Worldwide Interoperability for Microwave Access). It may also be a station (eg, an evolved Node B (eNB) in LTE). Of course, it may be a wireless LAN access point based on a short-range wireless communication network or based on Bluetooth (registered trademark).

FIG. 2 shows an embodiment in which the base station function unit 101 of the base station 1 tries to find a mobile terminal 2 whose staying position is unknown while moving a beam range with directivity. The mobile terminal 2 waits to receive radio waves emitted from the base station 1 and transmits an access signal to the base station 1 when detecting the radio waves. In order to receive the access signal from the mobile terminal 2, the base station 1 comprehensively moves the beam range in order to narrow down the wide search area. This makes it possible to narrow down the range of stay of the mobile terminal without depending on a specific carrier.

FIG. 3 is a functional configuration diagram of a mobile base station according to the present invention.

FIG. 3 shows an embodiment in which the base station 1 is a mobile base station 1 that can move autonomously. A mobile base station 1 moves in the air while emitting radio waves in order to find a mobile terminal 2 whose staying position is unknown. The mobile base station 1 of the present invention moves in the air by a hovering search method. For example, when searching for a mountain victim, while hovering over the search area, the range of emitted radio waves is changed to narrow down the range of stay of the victim who has a mobile terminal.
Therefore, compared with the base station 1 in FIG. 2, the mobile base station 1 in FIG. A unit 103 is further mounted.

2 and 3, the base station 1 includes a terminal detection unit 11 that receives an access signal from the mobile terminal 2, and a beam movement control unit 12 that controls autonomous movement (direction, altitude, speed). , a first circular radio wave range setting unit 13 , a second circular radio wave range setting unit 14 , and a third circular radio wave range setting unit 15 . These functional components can be implemented by executing a program that causes a computer installed in the base station to function. In addition, the flow of processing of these functional configuration units can also be understood as a movement control method.
These functional units may be integrally incorporated in the base station 1, or may be instructed from a remote control device capable of wireless communication.

[First circular radio wave range setting unit 13]
The first circular radio wave range setting unit 13 sets a first circular radio wave range with a first radius.

FIG. 4 is an explanatory diagram showing the first circular radio wave range.
According to FIG. 4, the base station 1 is moving in the air while radiating in the first circular radio range. The first circular radio wave range is a radio wave range having a first radius R1 as a radio wave reaching distance. At this time, the mobile terminal 2 staying within the first circular radio wave range can transmit a signal to the base station 1 .

[Terminal detection unit 11]
When the terminal detection unit 11 receives an access signal from the mobile terminal within the first circular radio wave range, the positioning unit 103 measures the detected position. In other words, although it is unknown at which position the mobile terminal 2 exists when viewed from the base station 1, it is certain that the mobile terminal 2 is staying within at least the first circular radio wave range. .

[Second circular radio wave range setting unit 14]
The second circular radio wave range setting unit 14 sets a second circular radio wave range having a second radius R2 shorter than the first radius R1 by a predetermined length, centering on the detection position.
Predetermined length=radius R1 of first circular radio wave range−radius R2 of second circular radio wave range

FIG. 5 is an explanatory diagram showing a second circular radio wave range.
According to FIG. 5, from the first circular radio wave range in which the signal of the mobile terminal 2 is received to the second circular radio wave range in which the signal of the mobile terminal 2 cannot be received, the radius R (radio wave reaching distance) is changed. keep it short.
For example, when the base station 1 receives a signal from the mobile terminal 2 while radiating in a second circular radio wave range having a radius R2 (<radius R1), the predetermined length is further increased to reduce the second radius R2. Make it even shorter.

In order to set the second circular radio wave range from the first circular radio wave range, the base station 1 moves in the vertical direction (ground altitude) or changes the radio wave output (radio wave reachable distance) of the base station. to control. For example, when narrowing the circular radio wave range, the radio wave output of the base station 1 is decreased, or in the case of the mobile base station 1, the ground altitude is decreased. This controls the width of the circular radio wave range toward the ground.

FIG. 6 is an explanatory diagram showing superposition of the first circular radio wave range and the second circular radio wave range.
According to FIG. 6, the portable terminal 2 stays in a radio wave range (ring-shaped radio wave range) where the second circular radio wave range does not overlap with the first circular radio wave range.
Also, according to FIG. 6, a central circumference is drawn at the center of the width of the ring-shaped radio wave range. This center circumference becomes a movement path of the beam range, which will be described later, and becomes a movement path of the mobile base station 1 itself.

[Third circular radio wave range setting unit 15]
The third circular radio wave range setting unit 15 sets a third circular radio wave range with a third radius R3 shorter than the second radius R2.
Area of first circular radio wave range<Area of second circular radio wave range<Area of third circular radio wave range It is preferable to match the diameter D3 of the circular radio wave range with the predetermined length in the second circular radio wave range setting section.
Diameter D3 of the third circular radio wave range
= Radius of first circular radio wave range R1 - Radius of second circular radio wave range R2

FIG. 7 is an explanatory diagram showing movement of the third circular radio wave range.
According to FIG. 7, a third circular radio wave range narrower than the second circular radio wave range is set, and the diameter D3 of the third circular radio wave range is the width of the ring-shaped radio wave range (predetermined length ).

[Beam movement control unit 12]
The beam movement control unit 12 recognizes its own current position by the positioning unit 103 and controls the direction, altitude and speed of the multicopter 102 . At this time, the beam movement control unit 12 radiates in the third circular radio wave range, while controlling the circular radio wave range where the first circular radio wave range and the second circular radio wave range do not overlap (ring-shaped radio wave range). ) along the central circumference.

FIG. 8 is an explanatory diagram showing a third circular radio wave range in which the mobile terminal is detected.
According to FIG. 8, while the base station 1 is traveling while radiating in the third circular radio wave range, it receives an access signal from the mobile terminal 2 at an arbitrary point (detection point). At that time, it is recognized that the mobile terminal 2 is staying within a third circular radio wave range centered on the detected position (latitude and longitude).

If the third circular radio wave range is equal to or smaller than the predetermined area, the search is terminated assuming that the mobile terminal 2 stays within the first circular radio wave range.
(Area of the third circular radio wave range < Narrowing down required area α)
--> The portable terminal 2 stays within the first circular radio wave range and ends.

In the case of FIG. 2, the center of the circular radio wave range (ring-shaped radio wave range) where the first circular radio wave range and the second circular radio wave range do not overlap is controlled by the beam control of the antenna of the base station 1. Moving the third circular radio wave range along the circumference.
On the other hand, in the case of FIG. 3, the movement of the mobile base station 1 itself moves the third circular radio wave range.

FIG. 9 is an explanatory diagram showing the relationship between the advancing speed of the beam range and the detectable range.

FIG. 9(a) shows a case where the advancing speed of the central circumference of the beam range is slow.
FIG. 9(b) shows a case where the traveling speed of the center circumference of the beam range is fast.
In both FIGS. 9A and 9B, it is assumed that the mobile terminal 2 stays on the side of the radio wave range of the base station 1. FIG.
In the case of the mobile base station 1, it is assumed that the altitude is controlled to be constant with respect to the progress of the center circle.

As a wireless operation when the mobile terminal 2 cannot communicate with the base station and is out of service area, the mobile terminal 2 activates the operation of detecting radio waves coming from the base station with intervals in order to reduce battery consumption. Therefore, depending on the position where the portable terminal 2 stays, the beam range may pass within the interval time, and the radio wave in the beam range cannot be detected.

Here, the detectable traveling distance d is calculated as follows.
Detectable travel distance d = interval time I x travel speed v
The detectable traveling distance d is defined to be detectable in the range of radio waves emitted from the base station 1 when the distance toward the traveling side is equal to or greater than the detectable traveling distance d. That is, in the radio wave range of the base station 1, if the distance toward the traveling side is shorter than the detectable traveling distance d, the mobile terminal 2 may not be able to receive the radio waves of the base station 1 at the time of detection.

According to FIG. 9(a), since the traveling speed of the beam range is slow, the detectable traveling distance d becomes relatively short, and the portable terminal staying on the side can also be detected. That is, at the staying position of the mobile terminal on the side, the distance toward the traveling side is equal to or greater than the detectable traveling distance d.
On the other hand, according to FIG. 9B, since the traveling speed of the beam range is fast, the detectable traveling distance d is also relatively long, and there are cases where the portable terminal staying at the side is not detected. This is because the distance toward the advancing side is shorter than the detectable traveling distance d at the staying position of the mobile terminal on the side.

According to FIGS. 9A and 9B, the “detectable travel width” with which the base station 1 can reliably detect the mobile terminal 2 is clearly shown.
According to FIG. 9A, the traveling speed of the beam range is slow, so the detectable traveling distance d is relatively short and the detectable traveling width c is relatively long.
On the other hand, according to FIG. 9B, the traveling speed of the beam range is fast, so the detectable traveling distance d is relatively long and the detectable traveling width c is relatively short.

Based on such a relationship, according to the present invention, the movement speed of the beam range is determined with consideration given to the interval time of the mobile terminal 2 so as to minimize the search time. That is, in the case of the mobile base station 1, an efficient flight speed is determined in order to find a mobile terminal in a wide search area in the shortest possible flight time.

FIG. 10 is an explanatory diagram showing the advancing speed of the beam range and the detectable range in the present invention.
According to FIG. 10, the beam movement control unit 12 described above controls the interval time I between the time when the mobile terminal 2 detects the radio wave emitted from the base station 1 and the circular wave emitted from the base station 1 . The moving speed v in the direction of travel is determined using the diameter D3 of the radio wave range.

According to FIG. 10A, the movement speed v is determined so as to define a square (maximum area) with four vertices in contact with the circumference of the range of radio waves radiated from the base station 1 . However, it is assumed that the base station 1 travels in the air in a predetermined direction and at a predetermined altitude when searching for the mobile terminal 2 .
I: During the startup time when the mobile terminal detects radio waves emitted from the base station
Interval time (s)
R: Diameter (m) of the circular radio range radiated from the base station
v: moving speed in the direction of travel (m/s)
v=R/(√2・I)
By moving at a moving speed v that maximizes (square) the detectable range (square) within the range of radio waves emitted by the base station 1, the range in which the mobile terminal 2 can be found in one flight is also maximized. By repeating it, the overall flight time can also be shortened.

According to FIG. 10(b), the radio wave ranges on both sides with respect to the traveling direction are defined as follows.
Detectable range: Radio wave range inside the progress of the square (decision of detectable progress width c)
Unknown detection range: Radio wave range outside the direction of the square

Further, the detectable advance width c in the detectable range is calculated as follows.
d (=I·v): Detectable travel distance (m) that can travel in interval time I
c: Detectable travel width (m) perpendicular to the travel direction of the beam range
c=√(R ² −d ² )
Here, it is also preferable to match the diameter D3 of the aforementioned third circular radio wave range with the detectable traveling width c.

The search area S per time t in the base station 1 is calculated as follows.
S=√(R ² −d ² )·vt=vt√(R ² −I ² v ² )
Next, when transformed with respect to t, it becomes as follows.
t=S/(v√(R ² −I ² v ² ))
Next, differentiating t with respect to v gives:
∂t/∂v=S(2I ² v ² −R ² )/(v ² (R ² −I ² v ² ) ^3/2 )
Regarding the above equation, when ∂t/∂v=0, t is minimized and can be expressed as follows.
v=R/(√2・I)
By advancing the beam range at this traveling speed v, the flight distance and flight time of the mobile terminal 2 can be minimized.

As described in detail above, according to the base station, program and method of the present invention, when narrowing down the range of stay of a mobile terminal based only on the access signal returned from the mobile terminal, the beam of the base station The overall travel distance in range can be shortened. By autonomously moving the beam range emitted from the base station, the mobile terminal can be found without human intervention. As a result, by shortening the moving distance of the beam range emitted from the base station, the shortening of the time until the mobile terminal is found is realized.

For the various embodiments of the present invention described above, various changes, modifications and omissions within the spirit and scope of the present invention can be easily made by those skilled in the art. The foregoing description is exemplary only and is not intended to be limiting. The invention is to be limited only as limited by the claims and the equivalents thereof.

1 base station, mobile base station 101 base station function unit 102 mobile function unit (multicopter)
103 positioning unit 11 terminal detection unit 12 beam movement control unit 13 first circular radio wave range setting unit 14 second circular radio wave range setting unit 15 third circular radio wave range setting unit 2 mobile terminal

Claims (9)

At a base station that emits radio waves to discover a mobile terminal,
a first circular radio wave range setting means for setting a first circular radio wave range having a first radius;
Terminal detection means for positioning a detection position when a signal is received from a mobile terminal in the first circular radio wave range;
setting a second circular radio wave range with a second radius shortened from the first radius of the first circular radio wave range until the signal of the mobile terminal cannot be received, centering on the detection position; circular radio wave range setting means;
a third circular radio wave range setting means for setting a third circular radio wave range having a third radius shorter than the second radius;
Beam movement control for searching by moving while radiating a third circular radio wave range along the central circumference of the circular radio wave range where the first circular radio wave range and the second circular radio wave range do not overlap. a base station, comprising: A base station is a mobile base station that moves in the air while emitting radio waves.
2. The base station according to claim 1, wherein said beam movement control means controls movement of said mobile base station itself. 3. The base according to claim 1, wherein the third circular radio wave range setting means matches the diameter of the third circular radio wave range with the predetermined length in the second circular radio wave range setting means. station. The second circular radio wave range setting means increases the predetermined length in the second circular radio wave range setting means when a signal is received from the portable terminal within the set second circular radio wave range, and sets the second radius. 4. The base station according to any one of claims 1 to 3, wherein a second circular radio wave range is set by further shortening . The first circular radio wave range, the second circular radio wave range, and the third circular radio wave range are the movement in the vertical direction (ground altitude), or the radio wave output of the base station (radio wave reachable distance). 5. The base station according to any one of claims 1 to 4, wherein the setting is performed by the control of . 6. If the third circular radio wave range is equal to or less than a predetermined area, the search is terminated assuming that the mobile terminal stays in the first circular radio wave range. The base station described in . The beam movement control means uses the interval time I between the start times when the mobile terminal detects radio waves radiated from the base station and the diameter R of the circular radio wave range radiated from the base station to determine the direction of travel. 7. A base station according to any one of claims 1 to 6, characterized in that it determines a moving speed v to . In order to find a mobile terminal, in a program that operates a computer installed in a base station that emits radio waves,
a first circular radio wave range setting means for setting a first circular radio wave range having a first radius;
Terminal detection means for positioning a detection position when a signal is received from a mobile terminal in the first circular radio wave range;
setting a second circular radio wave range with a second radius shortened from the first radius of the first circular radio wave range until the signal of the mobile terminal cannot be received, centering on the detection position; circular radio wave range setting means;
a third circular radio wave range setting means for setting a third circular radio wave range having a third radius shorter than the second radius;
Beam movement control for searching by moving while radiating a third circular radio wave range along the central circumference of the circular radio wave range where the first circular radio wave range and the second circular radio wave range do not overlap. A program characterized by making a computer function as a means. In order to find a mobile terminal, in a beam movement control method for a base station that emits radio waves,
The base station
a first step of setting a first circular radio range of a first radius;
a second step of positioning the detected position when a signal is received from the mobile terminal in the first circular radio wave range;
setting a second circular radio wave range with a second radius shortened from the first radius of the first circular radio wave range until the signal of the mobile terminal cannot be received, centering on the detection position; a step;
a fourth step of setting a third circular radio range with a third radius that is shorter than the second radius;
A fifth circular radio wave range is radiated and moved along the central circumference of the circular radio wave range where the first circular radio wave range and the second circular radio wave range do not overlap each other. A beam movement control method characterized by performing the steps of:

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