RADIO COMMUNICATIONS SYSTEM, COMMUNICATION ANTENNA, ON-VEHICLE DEVICE, IC CARD AND ROADSIDE-VEHICLE COMMUNICATION METHOD

摘要

PROBLEM TO BE SOLVED: To reduce the probability that a roadside machine and an on-vehicle device perform miscommunication outside a communication area, when a communication antenna is mounted onto a ceiling wall or a roof, as in indoor or basement parking lots and drive-throughs in restaurants.

SOLUTION: A communication antenna system is provided which starts to emit transmission radio waves within a communication area to start to communicate with the on-vehicle device, and lowers the transmission power value or stops emitting the transmission radio waves according to the communication termination with the on-vehicle device. The transmission output of the communication antenna system is ≤4 dBm and the reception sensitivity is ≥-55 dBm.

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