| 主权项 |
1. An on-board apparatus control system, comprising:
a portable device carried by a user; and an vehicle-mounted device that, by communication with the portable device, make a determination of whether or not the portable device exists in an authorized area, and carries out control of an on-board apparatus in accordance with a result of the determination, the vehicle-mounted device including: a request signal sender that causes a specific transmission antenna mounted on a vehicle to transmit a request signal to the portable device existing in the authorized area around the vehicle; and a determination signal sender that causes another transmission antenna, which is separate from the specific transmission antenna transmitting the request signal, to transmit a determination signal to the portable device existing in an unauthorized area around the vehicle, the determination signal having a high level period where a high level continues for a fixed period and a low level period where a low level continues for a fixed period, the portable device including: a received signal strength measurement unit that measures a received signal strength of the determination signal in the high level period and a received signal strength of the determination signal in the low level period separately; and a response signal sender that, when receiving the request signal, generates a response signal responding to the request signal so as to include received signal strength information representing the received signal strength of the determination signal in the high level period and received signal strength information representing the received signal strength of the determination signal in the low level period, and transmits the response signal to the vehicle-mounted device, the vehicle-mounted device including: a reception determination unit that determines whether or not the response signal has been received; a received strength determination unit that determines, based on the received signal strength information which is included in the response signal and which represents the received signal strength of the determination signal in the high level period, whether or not the received signal strength of the determination signal in the high level period is greater than a specified value; an on-board apparatus control unit that, when the reception determination unit determines that the response signal has been received and the reception strength determination unit determines that the received signal strength of the determination signal in the high level period is greater than the specified value, carries out the control of the on-board apparatus on assumption that the portable device exists in the unauthorized area; a noise level determination unit that determines, based on the received signal strength information representing the received signal strength of the determination signal in the low level period, whether or not a noise level around the vehicle is greater than a specified value; and a transmission level change command unit that, when the noise level determination unit determines that the noise level around the vehicle is greater than the specified value, commands the determination signal sender to transmit the determination signal to the portable device existing in the unauthorized area around the vehicle by increasing a transmission level of the determination signal. |
