Patent ID: 7479896

Claim:
An electronic toll collection system for conducting toll transactions with vehicles travelling in a roadway, the system comprising: a plurality of directional antennas, each antenna defining a coverage zone within the roadway; and a reader, the reader comprising at least one transceiver for propagating an RF signal through said antennas and receiving RF response signals through said antennas, and a controller for controlling the at least one transceiver to individually excite each antenna with the RF signal in accordance with a time-multiplexed cyclical scanning pattern, wherein the scanning pattern is configured to allocate each antenna an equal length proportion of a cycle of the scanning pattern for conducting RF communications, and wherein the controller includes an adaptive scanning module configured to dynamically modify the scanning pattern to allocate a longer proportion of at least one cycle of the scanning pattern to one of the antennas than is allocated to at least one of the other antennas on the basis of receipt of a response signal by said one of the antennas.