Patent ID: 7349669

Claim:
A stationary-station communication system for performing communication with a plurality of on-vehicle units mounted on a plurality of vehicles each passing through a predetermined communication area, each on-vehicle unit operating on one of a plurality of types of protocols for the communication, the communication being directed to predetermined processing, the system comprising: an antenna unit including i) a modem unit configured to selectively perform a plurality of types of modulation/demodulation techniques respectively based on the plurality of types of protocols for the communication with each of the on-vehicle units, and ii) control means configured to allow the modem unit to perform, of the plurality of types of modulation/demodulation techniques, a specified modulation/demodulation technique based on, of the plurality of types of protocols, a protocol selectively specified by a protocol selection signal so that the antenna unit performs the communication with each of the on-vehicle units based on the specified protocol, when each of the plurality of vehicles is within the communication area, and a protocol controller comprising: first producing means for producing the protocol selection signal to cause the modem unit to cycle through the plurality of types of protocols over a predetermined period of time in at least one slot of the communication, such that the communication is performed in turn with a plurality of on-vehicle units, determining means for determining two or more types of protocols employed by two or more of the plurality of on-vehicle units when two or more responses are received from the two or more of the plurality of on-vehicle units in response to the protocol selection signal produced by the first producing means, and second producing means for producing the protocol selection signal to specify use of each of the two or more types of determined protocols in one or more time-division slots following the slot in which the determining means determines the two or more types of protocols, the second producing means producing the protocol selection signal until the predetermined processing for the two or more on-vehicle units that employ the determined two or more protocols are completed, respectively, the protocol selection signal produced by the second producing means enabling the control means of the antenna unit to perform the predetermined processing.