Position estimation method for mobile terminal, position estimation device for mobile terminal and position estimation system for mobile terminal

1. A position estimation method for a mobile terminal that estimates a position of a mobile terminal by communicating at least three of communication devices provided in a vehicle with the mobile terminal in a vicinity of the vehicle, the method comprising:

an acquisition step of acquiring distance values and radio wave intensity values between a plurality of the communication devices and the mobile terminal by communicating the communication devices with the mobile terminal;

a communication availability determination step of determining that a corresponding communication device is communicable when the distance value is equal to or less than a first predetermined value and the intensity value is equal to or more than a second predetermined value; and

an estimation step of narrowing down a search range of the mobile terminal based on a distance value from the communication device having the smallest distance value of at least three of communication devices determined to be communicable in the communication availability determination step, and estimating the position of the mobile terminal.

2. The position estimation method for a mobile terminal according to claim 1 , wherein

in the estimation step, the position of the mobile terminal is estimated by providing a plurality of candidate points on a surface of a sphere whose radius is the distance value from the communication device having the smallest distance value.

3. The position estimation method for a mobile terminal according to claim 2 , wherein

in the estimation step, after the position of the mobile terminal is estimated by providing the candidate points on the surface of the sphere at a predetermined angular interval, the position of the mobile terminal is further estimated by providing the candidate points at an angular interval smaller than the predetermined angular interval in a predetermined range near the estimated position of the mobile terminal.

4. The position estimation method for a mobile terminal according to claim 1 , wherein

in the estimation step, an area where the mobile terminal exists is estimated based on a determination result of the communication availability determination step and communication maps that map communicable ranges of the communication devices, and the search range of the mobile terminal is further narrowed down based on the area.

5. The position estimation method for a mobile terminal according to claim 1 , wherein

in the estimation step, the search range of the mobile terminal is narrowed down by using the smallest distance value of the plurality of distance values from the communication device having the smallest distance value.

6. The position estimation method for a mobile terminal according to claim 1 , wherein the distance values are actual distances.

7. The position estimation method for a mobile terminal according to claim 1 , wherein the distance values are measured using time of flight.

8. A position estimation device for a mobile terminal that estimates a position of a mobile terminal by communicating a plurality of communication devices provided in a vehicle with the mobile terminal in a vicinity of the vehicle, the device comprising:

a signal processing unit configured to acquire distance values and radio wave intensity values between the plurality of communication devices and the mobile terminal by communicating the communication devices with the mobile terminal, and determine that a corresponding communication device is communicable when the distance value is equal to or less than a first predetermined value and the intensity value is equal to or more than a second predetermined value; and

an estimation unit configured to narrow down a search range of the mobile terminal based on a distance value from the communication device having the smallest distance value of at least three of communication devices determined to be communicable by the signal processing unit, and estimate the position of the mobile terminal.

9. A position estimation system for a mobile terminal, the system comprising:

a plurality of communication devices provided in a vehicle;

a signal processing unit configured to acquire distance values and radio wave intensity values between the plurality of communication devices and a mobile terminal in a vicinity of the vehicle by communicating the communication devices with the mobile terminal, and determine that a corresponding communication device is communicable when the distance value is equal to or less than a first predetermined value and the intensity value is equal to or more than a second predetermined value; and

an estimation unit configured to narrow down a search range of the mobile terminal based on a distance value from the communication device having the smallest distance value of at least three of communication devices determined to be communicable by the signal processing unit, and estimate the position of the mobile terminal.