Position determination system and position determination method

A position determination method executed by at least one processor to determine a position of a portable device carried by a user of a vehicle, the position determination method comprising:

• acquiring, from each of a plurality of outdoor units, data indicating a reception strength of a signal transmitted from the portable device, the plurality of outdoor units being disposed at respective different positions on an outer surface portion of the vehicle, each of the plurality of outdoor units being configured by a communication device that performs a wireless communication with the portable device;
• acquiring, from at least one indoor unit, data indicating the reception strength of the signal transmitted from the portable device, the at least one indoor unit being configured by a communication device disposed inside a vehicle interior of the vehicle;
• determining whether the portable device is present inside the vehicle interior based on the reception strength observed in each of the plurality of outdoor units and the reception strength observed in the at least one indoor unit;
• acquiring a time of flight (ToF) correlation value as a parameter different from the reception strength, the ToF correlation value directly or indirectly indicating time of flight of a radio wave from at least one of the plurality of outdoor units to the portable device;
• changing a type of the parameter used for position determination corresponding to an area for which the position determination is to be performed;
• and
• determining whether the portable device is present in an outdoor operation area based on the ToF correlation value, the outdoor operation area being defined as an area outside the vehicle interior within a predetermined distance from the vehicle.

A position determination system for a vehicle, the position determination system performing wireless communication with a portable device carried by a user of the vehicle to determine a position of the portable device with respect to the vehicle, the position determination system comprising:

• a plurality of outdoor units each of which is configured by a communication device that allow the wireless communication with the portable device, each of the plurality of outdoor units being installed at a position on an outer surface portion of the vehicle different from one another;
• at least one indoor unit configured by a communication device installed inside a vehicle interior of the vehicle;
• a computer-readable non-transitory storage medium;
• and
• a microcomputer, by executing a program stored in the computer-readable non-transitory storage, configured to:
• control operations of the plurality of outdoor units and the at least one indoor unit;
• determine whether the portable device is present inside the vehicle interior and whether the portable device is present in an outdoor operation area, the outdoor operation area being defined as an area outside the vehicle interior within a predetermined distance from the vehicle;
• acquire a reception strength of a signal from the portable device in each of the communication devices;
• acquire a time of flight (ToF) correlation value as a parameter different from the reception strength, the ToF correlation value directly or indirectly indicating time of flight of a radio wave from at least one of the plurality of outdoor units to the portable device;
• change a type of the parameter used for position determination corresponding to an area for which the position determination is to be performed;
• determine whether the portable device is present inside the vehicle interior based on the reception strength observed in each of the plurality of outdoor units and the reception strength observed in the at least one indoor unit;
• and
• determine whether the portable device is present in the outdoor operation area based on the ToF correlation value.