Abstract: Methods of estimating vehicle location in a roadway using an automatic vehicle identification system are described. The methods involve receiving a set of response signals from a vehicle-mounted transponder at points in time and determining a range rate of the transponder relative to the antenna at each point in time; identifying a minima in the magnitude of the range rate; estimating a first position of the transponder at a first time corresponding to the occurrence of the minima; estimating a velocity of the vehicle based upon one or more of the determined range rates; and estimating a second position of the transponder based upon the first position and the velocity.

Abstract: Methods for determining a range rate of a backscatter transponder and readers implementing the methods are described. The reader transmits a continuous wave signal and receives a modulated reflected response signal from the transponder, mixes the modulated reflected response signal with the carrier frequency to produce a downconverted signal, bandpass filters the downconverted signal to pass a bandpass filtered signal containing at least the modulation frequency, applies a non-linear amplitude transfer function to produce a modulation-suppressed signal, and measures the frequency of the modulation-suppressed signal and determines the range rate from the measured frequency.

Abstract: Systems, Methods, and Apparatus for enhanced transponder programming in an open road toll system are disclosed. An example method includes transmitting, in a normal mode, a programming signal from one of the antennas over a first coverage area to instruct the transponder to store data in its memory, the data being contained in the programming signal. The example method further includes determining that the transponder did not store the data in its memory. Based on the determination that the transponder did not store the data in its memory the programming signal is transmitted in an enhanced mode, from one antennas over a second coverage area.

Abstract: Methods for determining a range rate of a backscatter transponder and readers implementing the methods are described. The reader transmits a continuous wave signal and receives a modulated reflected response signal from the transponder, mixes the modulated reflected response signal with the carrier frequency to produce a downconverted signal, bandpass filters the downconverted signal to pass a bandpass filtered signal containing at least the modulation frequency, applies a non-linear amplitude transfer function to produce a modulation-suppressed signal, and measures the frequency of the modulation-suppressed signal and determines the range rate from the measured frequency.

Abstract: Methods of estimating vehicle location in a roadway using an automatic vehicle identification system are described. The methods involve receiving a set of response signals from a vehicle-mounted transponder at points in time and determining a range rate of the transponder relative to the antenna at each point in time; identifying a minima in the magnitude of the range rate; estimating a first position of the transponder at a first time corresponding to the occurrence of the minima; estimating a velocity of the vehicle based upon one or more of the determined range rates; and estimating a second position of the transponder based upon the first position and the velocity.

Abstract: Systems, Methods, and Apparatus for enhanced transponder programming in an open road toll system are disclosed. An example method includes transmitting, in a normal mode, a programming signal from one of the antennas over a first coverage area to instruct the transponder to store data in its memory, the data being contained in the programming signal. The example method further includes determining that the transponder did not store the data in its memory. Based on the determination that the transponder did not store the data in its memory the programming signal is transmitted in an enhanced mode, from one antennas over a second coverage area.

Abstract: A transponder communication system and method for communicating with a transponder in an electronic toll collection system. A roadside reader attempts to program the transponder in a normal mode in which a programming signal is transmitted to a first coverage area. If the programming attempt in the normal mode is unsuccessful, the reader attempts to program the transponder in an enhanced mode in which a programming signal is transmitted to a second coverage area. The coverage area is adjusted after the programming attempt in the normal mode by using an adjacent antenna to the antenna used to transmit in the normal mode or by increasing the power of the programming signal to a level that is greater than the level used to transmit the programming signal in the normal mode.

Abstract: An adaptive communication system and method for use in an electronic toll collection system utilizing transponders located in vehicles travelling on a toll roadway. A transponder memory stores configuration type data that identifies the type of the vehicle carrying the transponder, the transponder or the transponder's mounting. The transponder transmits the configuration type data to the communication system. The communication system includes a memory which contains a database of predetermined communication parameters for various types of configuration types. The communication system looks up the predetermined communication parameters for the configuration type and adjusts variable communication parameters accordingly. Predetermined communication variables may include the transmit power of an antenna, or the receive sensitivity of the antenna or the position of the vehicle in order to maximize the likelihood of a successful communication.

Abstract: A vehicle position determination system for determining the position of a moving vehicle in a multi-lane roadway. Two or more roadway antennas each periodically transmit an identifier that is associated with and unique to the antenna to a transponder located in the moving vehicle. As the moving vehicle passes through the coverage zone of the antennas, the transponder counts the number of times that it receives each unique identifier and reports this information to a roadside controller. Based on this information, the roadside controller can determine a probable location of the moving vehicle. The vehicle location information can be provided to an imaging system to discriminate between transponder and non-transponder equipped vehicles.

Abstract: A system and method for triggering a vehicle inspection in a vehicle inspection bypass system. A handheld device transmits a signal containing the driver information in response to detecting an activation of an actuator on the handheld device. A vehicle mounted transponder detects the signal when the handheld device is in close proximity, and the driver information is stored in the transponder memory. Upon detecting an interrogation signal from a roadside reader, the transponder transmits a signal containing the driver information to the roadside reader. Based on the received driver information, a roadside controller determines whether a vehicle may bypass a vehicle inspection station.

Abstract: A system and method for dynamically selecting a communication protocol in an electronic toll collection system. A reader includes two or more multiprotocol transceivers operating under the control of a processor, each transceiver having a dedicated antenna. The system uses a fixed frame duration. A first communications protocol is used in a first portion of the fixed frame duration. If a response signal is not detected within the first portion, then the system ceases using the first communication protocol and instead uses the second communications protocol for the remainder of the fixed frame duration. The fixed frame duration is shorter than the sum of the durations normally used by the first and second communications protocol to conduct electronic toll transaction communications.

Abstract: A system and method for dynamically selecting a communication protocol in an electronic toll collection system. A first reader communicating under a primary communication protocol is connected to a roadway antenna. If a transponder of the primary protocol is detected within a predetermined duration, then the first reader maintains its access to the roadway antenna so that it may perform an electronic toll transaction with the detected transponder. If a transponder of the primary protocol is not detected within a predetermined duration, then the first reader will switch over access of the antenna to a second reader operating under a secondary protocol so that the second reader may perform an electronic toll transaction with a detected secondary protocol transponder.

Abstract: An electronic toll collection system, reader, method and transponder for communicating occupancy status. The vehicle-mounted transponder includes a selection device that permits a user to select between a normal and high occupancy state. The transponder reports its occupancy status to a reader. If the electronic toll collection system processes a toll transaction and the transponder claims high occupancy status during the toll transaction, the fact that high occupancy status was claimed during the transaction is recorded in memory within the transponder for later enforcement and verification purposes.

Abstract: An electronic toll collection system wherein the reader includes a switching network and a plurality of transceivers operating under the control of a controller. The reader further includes failure detection circuitry for determining whether any of the transceivers have failed based upon the RF outputs of the transceivers. If the controller determines that a transceiver has failed, then it alters the switching pattern such that the switching network excludes the failed transceiver from being connected to the antennas. The reader thereby provides for adaptive RF channel assignment, as the particular transceiver used to excite a particular antenna may be dynamically altered, and the provision of at least two transceivers in the reader ensures transceiver redundancy.

Abstract: A transponder communication system and method for communicating with a transponder in an electronic toll collection system. A roadside reader attempts to program the transponder in a normal mode in which a programming signal is transmitted to a first coverage area. If the programming attempt in the normal mode is unsuccessful, the reader attempts to program the transponder in an enhanced mode in which a programming signal is transmitted to a second coverage area. The coverage area is adjusted after the programming attempt in the normal mode by using an adjacent antenna to the antenna used to transmit in the normal mode or by increasing the power of the programming signal to a level that is greater than the level used to transmit the programming signal in the normal mode.

Abstract: An adaptive communication system and method for use in an electronic toll collection system utilizing transponders located in vehicles travelling on a toll roadway. A transponder memory stores configuration type data that identifies the type of the vehicle carrying the transponder, the transponder or the transponder's mounting. The transponder transmits the configuration type data to the communication system. The communication system includes a memory which contains a database of predetermined communication parameters for various types of configuration types. The communication system looks up the predetermined communication parameters for the configuration type and adjusts variable communication parameters accordingly. Predetermined communication variables may include the transmit power of an antenna, or the receive sensitivity of the antenna or the position of the vehicle in order to maximize the likelihood of a successful communication.

Abstract: An electronic toll collection system, reader, method and transponder for communicating occupancy status. The vehicle-mounted transponder includes a selection device that permits a user to select between a normal and high occupancy state. The transponder reports its occupancy status to a reader. If the electronic toll collection system processes a toll transaction and the transponder claims high occupancy status during the toll transaction, the fact that high occupancy status was claimed during the transaction is recorded in memory within the transponder for later enforcement and verification purposes.

Abstract: An electronic toll collection system wherein the reader includes a switching network and a plurality of transceivers operating under the control of a controller. The reader further includes failure detection circuitry for determining whether any of the transceivers have failed based upon the RF outputs of the transceivers. If the controller determines that a transceiver has failed, then it alters the switching pattern such that the switching network excludes the failed transceiver from being connected to the antennas. The reader thereby provides for adaptive RF channel assignment, as the particular transceiver used to excite a particular antenna may be dynamically altered, and the provision of at least two transceivers in the reader ensures transceiver redundancy.

Abstract: A real-time location system for identifying and locating tagged items. The system may include an identification protocol that tracks in-network transponders and assigns dynamic in-network identification numbers to in-network transponders. The system includes a locator function that employs time-of-arrival analysis. Rather than attempt to synchronize the time base at each reader, the system and process eliminate the need to sync the readers and also eliminate the impact of differential receive delays in the respective readers. Both the transponder and a master reader transmit locate signals, which are measured at slave readers. The system relies on differences in time-of-arrival of the two signals at the respective slave readers to determine the likely location of the transponder.

Abstract: A vehicle position determination system for determining the position of a moving vehicle in a multi-lane roadway. Two or more roadway antennas each periodically transmit an identifier that is associated with and unique to the antenna to a transponder located in the moving vehicle. As the moving vehicle passes through the coverage zone of the antennas, the transponder counts the number of times that it receives each unique identifier and reports this information to a roadside controller. Based on this information, the roadside controller can determine a probable location of the moving vehicle. The vehicle location information can be provided to an imaging system to discriminate between transponder and non-transponder equipped vehicles.