JP7334132B2 - Mobile base station, program and method for determining progress speed for mobile terminal search - Google Patents

Description

The present invention relates to technology for discovering a mobile terminal using a mobile 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 mobile base station, it executes an authentication sequence based on location registration with the mobile base station, and transmits location information determined by GPS to the mobile base station. According to this technology, mobile base stations are flying objects such as drones, helicopters, balloons, and airships equipped with base station functions.

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＞

There is a positioning technology using GPS to acquire highly accurate position information, but there is a restriction that an authentication facility is required in order to transmit the position information measured by the mobile terminal to a server or the like. In disaster-stricken areas, it is not always possible for users to use terminals, and it is assumed that authentication facilities cannot be prepared in advance. Therefore, the location information of the mobile terminal may not necessarily be used.
On the other hand, an access signal exchanged between the mobile terminal and the base station can be used to identify the location of the mobile terminal. When radio waves are emitted from the mobile base station and a response from the mobile terminal is received, it can be assumed that the mobile terminal stays within the range of the radio waves.

However, in order to find a mobile terminal whose staying position is unknown, the mobile base station needs to fly exhaustively over a wide search area. The mobile base station continues to radiate radio waves and flies as if to cover the wide search area.
On the other hand, a mobile terminal waits to receive radio waves emitted from a mobile base station, and upon detecting the radio waves, transmits a signal to the mobile base station.

In addition, the wider the range of radio waves emitted by the mobile base station, the wider the position range as a search result. On the other hand, the narrower the radio wave range emitted by the mobile base station, the narrower the position range as a search result can be, but the mobile base station must travel a longer flight distance for exhaustive search.

In addition, the more a mobile terminal constantly waits for a signal from a mobile base station, the more quickly it consumes the power stored in the battery. In particular, 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.

On the other hand, mobile terminals intermittently watch radio waves coming from base stations (detection at intervals) in order to reduce battery consumption even if they are out of range where they cannot receive radio waves from base stations. to initiate an action).
However, the mobile base station is flying regardless of the mobile terminal's interval time (the time interval between the activation points of the sensing operation). Even if the mobile terminal stays within the radio wave range of the mobile base station, if the mobile base station passes by within the interval time, the mobile terminal cannot detect the radio waves emitted by the mobile base station.

In response to this, the inventor of the present application wondered if it would be possible to determine an optimal travel speed that shortens the overall flight distance for searching for mobile terminals for mobile base stations.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a mobile base station, a program, and a method for determining the progress speed for mobile terminal search.

According to the present invention, a mobile base station that travels in the air in a predetermined direction and at a predetermined altitude in order to discover a mobile terminal,
Using the interval time I between the activation points at which the mobile terminal detects radio waves radiated from the mobile base station and the diameter R of the circular radio wave range radiated from the mobile base station, movement in the traveling direction Determine the velocity v as
v=R/(√2・I)
It is characterized by

According to another embodiment of the mobile base station of the present invention,
Using the diameter R of the circular radio wave range radiated from the mobile base station and the detectable traveling distance d (=I·v) in the interval time I, the direction perpendicular to the traveling direction of the mobile base station It is also preferable to calculate the detectable travel width c.

According to another embodiment of the mobile base station of the present invention,
The detectable travel width c is determined as follows: c=√(R ² −d ² )
is also preferred.

According to another embodiment of the mobile base station of the present invention,
When the search area of the mobile terminal is defined in advance,
When a signal is received from a mobile terminal, it is estimated that the mobile terminal is staying in the overlapping range of the radio wave range of the detection point and the search area of the mobile terminal,
When no signal is received from the mobile terminal, it is also preferable to estimate that the mobile terminal is staying in the overlapping range of the outer range of the detectable travel width c and the search area of the mobile terminal.

According to the present invention, a program for determining a moving speed of a mobile base station traveling in a predetermined direction and at a predetermined altitude in order to discover a mobile terminal,
Using the interval time I between the activation points at which the mobile terminal detects radio waves radiated from the mobile base station and the diameter R of the circular radio wave range radiated from the mobile base station, movement in the traveling direction Determine the velocity v as
v=R/(√2・I)
characterized by making the computer function as

According to the present invention, there is provided a moving speed determination method for a mobile base station traveling in a predetermined direction and at a predetermined altitude in order to discover a mobile terminal, comprising:
Using the interval time I between the activation points at which the mobile terminal detects radio waves radiated from the mobile base station and the diameter R of the circular radio wave range radiated from the mobile base station, movement in the traveling direction Determine the velocity v as
v=R/(√2・I)
It is characterized by

According to the mobile base station, program and method of the present invention, it is possible to determine the progress speed for mobile terminal search.

1 is an explanatory diagram showing a mobile base station flying in the air; 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 the relationship between the traveling speed of the mobile base station and the detectable range; FIG. 4 is an explanatory diagram showing the traveling speed and detectable range of a mobile base station in the present invention; FIG. 4 is an explanatory diagram showing a search area of a mobile terminal when a signal from the mobile terminal is detected; FIG. 4 is an explanatory diagram showing a search area of a mobile terminal when no signal is detected from the mobile terminal;

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 mobile base station according to the present invention.

According to FIG. 2, the mobile base station 1 has a base station function 101 capable of communicating with the mobile terminal 2, a multicopter (mobile function) 102 capable of moving by itself, and a GPS function (positioning function) 103 for positioning itself. and

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

The mobile base station 1 also has a terminal detection function 11 that receives signals from the mobile terminal 2, a movement control function 12 that controls autonomous movement (direction, altitude, speed), and a movement control function that is a feature of the present invention. and a speed determination function 13 .
These functional components can be realized by executing a program that causes a computer installed in the mobile base station to function. In addition, the flow of processing of these functional configuration units can also be understood from the movement speed determination method.

The terminal detection function 11 receives a signal from a terminal at an arbitrary point (detection point) while the mobile base station 1 is moving. At that time, it is recognized that the mobile terminal 2 is staying in a circular radio wave range centered on the detected position (latitude and longitude) and having a radio wave reaching distance as a radius. However, at this time, although it is unknown at which position the mobile terminal 2 is present as viewed from the mobile base station 1, it is certain that it is at least within the radio wave range.

The movement control function 12 recognizes its current position by the GPS function 103 and controls the multicopter 102 to move along the flight plan.

The movement speed determination function 13 instructs the movement control function 12 about the movement speed of the mobile base station 1 . The moving speed determination function 13 may be integrally incorporated in the mobile base station 1, or may be instructed from a remote control device capable of wireless communication.

FIG. 3 is an explanatory diagram showing the relationship between the traveling speed of the mobile base station and the detectable range.

FIG. 3(a) shows the case where the mobile base station 1 moves slowly.
FIG. 3(b) shows the case where the mobile base station 1 moves fast.
In both FIGS. 3(a) and 3(b), it is assumed that the mobile terminal 2 stays on the side of the radio wave range of the mobile base station 1. FIG.
It is assumed that the traveling direction and altitude of the mobile base station 1 are controlled to be constant.

As described above, the mobile terminal 2 activates the operation of detecting radio waves coming from the base station at intervals in order to reduce battery consumption as a wireless operation when the mobile terminal 2 cannot communicate with the base station and is out of range. Therefore, depending on the position where the mobile terminal 2 stays, the mobile base station may pass within the interval time, and the radio wave of the mobile base station 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 travel distance d is a range of radio waves emitted from the mobile base station 1 that can be detected when the distance toward the traveling side is greater than or equal to the detectable travel distance d. That is, in the radio wave range of the mobile base station 1, if the distance toward the advancing side is shorter than the detectable traveling distance d, the mobile terminal 2 may not be able to receive the radio waves of the mobile base station 1 at the time of detection.

According to FIG. 3(a), since the moving speed of the mobile base station 1 is slow, the detectable moving distance d becomes relatively short, and the mobile terminal staying on the side is also 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. 3(b), since the traveling speed of the mobile base station 1 is fast, the detectable traveling distance d becomes relatively long, and there are cases where the mobile terminal staying on 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. 3A and 3B, the “detectable travel width” with which the mobile base station 1 can reliably detect the mobile terminal 2 is clearly shown.
According to FIG. 3A, since the traveling speed of the mobile base station 1 is slow, the detectable traveling distance d is relatively short and the detectable traveling width c is relatively long.
On the other hand, according to FIG. 3(b), since the traveling speed of the mobile base station 1 is fast, the detectable traveling distance d is relatively long and the detectable traveling width c is relatively short.

Based on this relationship, according to the present invention, the interval time of the mobile terminal 2 is taken into account to determine the velocity of the flying object so as to minimize the search time. That is, the mobile base station 1 efficiently flies over a wide search area to find the mobile terminal in the shortest possible flight time.

FIG. 4 is an explanatory diagram showing the traveling speed and detectable range of the mobile base station in the present invention.

According to FIG. 4A, the moving 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 emitted from the mobile base station 1 . However, it is assumed that the mobile 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 mobile base station
Interval time (s)
R: Diameter (m) of the circular radio range radiated from the mobile base station
v: moving speed in the direction of travel (m/s)
v=R/(√2・I)
The mobile base station 1 moves at a moving speed v that maximizes the detectable range (square) within the range of radio waves it emits, thereby maximizing the range in which the mobile terminal 2 can be found in one flight. can be repeated, and the overall flight time can also be shortened.

According to FIG. 4B, 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 direction of travel of the mobile base station
c=√(R ² −d ² )

The search area S per time t in the mobile 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 mobile base station 1 at this traveling speed v, the flight distance and flight time of the mobile terminal 2 can be minimized.

FIG. 5 is an explanatory diagram showing the search area of the mobile terminal when a signal from the mobile terminal is detected.
FIG. 6 is an explanatory diagram showing the search area of the mobile terminal when no signal is detected from the mobile terminal.

According to FIGS. 5 and 6, a large “search area” is defined in advance in which the mobile terminal 2 will stay. The search area is, for example, a range of possible distress reported by a local government or a rescue agency when finding a person in distress in a mountain.
At this time, the mobile base station 1 needs to fly exhaustively over the search area while continuing to radiate radio waves.

According to FIG. 5, when the mobile base station 1 receives a signal from the mobile terminal 2, the mobile terminal stays in the overlapping range of the "radio wave range of the detection point" and the "search area of the mobile terminal". presumed to be This overlapping range becomes the next “search area” for the mobile base station 1 .
An: Next determined search area An-1: Previously determined search area Bn: Radio wave range of mobile terminal detection point in mobile base station An = An-1 ∩ Bn

According to FIG. 6, when the mobile base station 1 does not receive a signal from the mobile terminal 2, the mobile terminal stays in the overlapping range of the outer range of the detectable travel width c and the search area of the mobile terminal. presumed to be This overlapping range becomes the next “search area” for the mobile base station 1 .
An: Next determined search area An-1: Previously determined search area Cn: Outer range of detectable progress width c in the progress of the mobile base station An = An-1 ∩ Cn

The mobile base station 1 then autonomously sets a flight route for the determined search area An. For example, it may fly in the center of the search area An, or it may fly from the side.
Thus, by repeating FIGS. 5 and 6 (incrementing n), the mobile base station 1 can determine its own flight route while autonomously narrowing down at least the search area An. . As a result, it leads to shortening of the flight distance in the mobile base station 1 and shortening of the time until the mobile terminal 2 is found.

Finally, the mobile base station 1 terminates the search flight of the mobile terminal 2 when the area |An|
Next determined search area |An|

As described in detail above, according to the mobile base station, program and method of the present invention, it is possible to determine the progress speed for searching for mobile terminals.

In particular, it is possible to estimate the staying position of the mobile terminal only by operating control of the mobile base station without depending on a specific communication carrier. Also, the mobile base station can move autonomously and can find the mobile terminal without human intervention.

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 mobile base station 101 base station function 102 mobile function (multicopter)
103 GPS function 11 Terminal detection function 12 Movement control function 13 Movement speed determination function 2 Portable terminal

Claims (6)

A mobile base station that travels through the air in a predetermined direction and at a predetermined altitude to find a mobile terminal,
Using the interval time I between the activation points at which the mobile terminal detects radio waves radiated from the mobile base station and the diameter R of the circular radio wave range radiated from the mobile base station, movement in the traveling direction Determine the velocity v as follows: v=R/(√2·I)
A mobile base station characterized by: Using the diameter R of the circular radio wave range radiated from the mobile base station and the detectable traveling distance d (=I·v) in the interval time I, the direction perpendicular to the traveling direction of the mobile base station 2. The mobile base station according to claim 1 , wherein the detectable travel width c is calculated. The detectable travel width c is determined as follows: c=√(R ² −d ² )
The mobile base station according to claim 2 , characterized by: When the search area of the mobile terminal is defined in advance,
When a signal is received from a mobile terminal, it is estimated that the mobile terminal is staying in the overlapping range of the radio wave range of the detection point and the search area of the mobile terminal,
Claims characterized in that, when no signal is received from a mobile terminal, it is estimated that the mobile terminal is staying in the overlapping range of the outer range of the detectable travel width c and the search area of the mobile terminal. 4. The mobile base station according to 2 or 3 . A program for determining a moving speed of a mobile base station traveling in a predetermined direction and at a predetermined altitude in order to find a mobile terminal,
Using the interval time I between the activation points at which the mobile terminal detects radio waves radiated from the mobile base station and the diameter R of the circular radio wave range radiated from the mobile base station, movement in the traveling direction Determine the velocity v as follows: v=R/(√2·I)
A program characterized by causing a computer to function as A moving speed determination method for a mobile base station traveling in a predetermined direction and at a predetermined altitude in order to find a mobile terminal, comprising:
Using the interval time I between the activation points at which the mobile terminal detects radio waves radiated from the mobile base station and the diameter R of the circular radio wave range radiated from the mobile base station, movement in the traveling direction Determine the velocity v as follows: v=R/(√2·I)
A movement speed determination method characterized by:

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