Adaptive channel bandwidth in an electronic toll collection system

• US 7,479,896 B2
• Filed: 09/21/2006
• Issued: 01/20/2009
• Est. Priority Date: 09/21/2005
• Status: Active Grant

• Current Assignee: Mark IV Industries Corporation
• Original Assignee: Mark IV Industries Corporation
• Inventors: Ho, Thua Van, Terrier, Daniel
• Primary Examiner(s): Hofsass; Jeff
• Assistant Examiner(s): McNally; Kerri L
• Application Number:
  US11/534,073
• Publication Number:
  US 20070063872A1
• Time in Patent Office: 852 Days
• Field of Search: 340/928, 340/907, 340/572.1
• US Class Current: 340/928
• CPC Class Codes: G07B 15/06 Arrangements for road pricing or congestion charging of vehicles or vehicle users, e.g. automatic toll systems
• CPC Class Codes: G07B 15/063 using wireless information transmission between the vehicle and a fixed station identification of vehicles G08G

Abstract

A method and system for adaptively allocating bandwidth in an electronic toll collection system. The system includes a reader that adapts the scanning time allocated to specific antennas based upon the traffic conditions. Those antennas that process a higher volume of traffic receive a greater allocation of the scanning time. In some embodiments, the determination as to when to allocate additional time to an antenna may be based upon whether or not a transponder is currently in the coverage zone for the antenna.

Claims

1. 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.

2. The electronic toll collection system claimed in claim 1, wherein each cycle of said scanning pattern includes a timeslot for each of said antennas, and wherein said adaptive scanning module is configured to lengthen the timeslot for said one of the antennas.

3. The electronic toll collection system claimed in claim 2, wherein said adaptive scanning module is configured to lengthen the timeslot for said one of the antennas by stealing a timeslot from one the other antennas within the cycle, such that the duration of the resulting cycle remains constant.

4. The electronic toll collection system claimed in claim 3, wherein said adaptive scanning module is configured to steal said timeslot by identifying a candidate antenna from which to steal said timeslot by determining that said candidate antenna did not receive a response from a transponder within a most recent cycle of said scanning pattern.

5. The electronic toll collection system claimed in claim 4, wherein said adaptive scanning module is configured to further impose a condition that said candidate antenna did not have its timeslot stolen in the most recent cycle of said scanning pattern.

6. The electronic toll collection system claimed in claim 1, wherein said adaptive scanning module is configured to allocate said longer proportion on a condition that at least one of said other antennas did not receive a response from a transponder within a most recent cycle of said scanning pattern.

7. The electronic toll collection system claimed in claim 1, wherein said RF communications comprise communications in accordance with a predefined protocol, wherein said protocol prescribes a read operation, a program operation and a verify operation, and wherein said longer proportion enables said reader to perform said read operation, said program operation and said verify operation in a single timeslot.

8. The electronic toll collection system claimed in claim 1, wherein said RF communications comprise communications in accordance with a predefined protocol, wherein said protocol prescribes a read operation, a program operation and a verify operation, and wherein said equal length proportion is sufficiently long to enable said read operation and said verify operation, and wherein said longer proportion is required to perform said program operation.

9. A method of adaptively modifying channel bandwidth in an electronic toll collection system, the system including a plurality of antennas connected to a reader, the reader including at least one transceiver for conducting RF communications through the antennas, the RF communications including propagating an RF signal and receiving response signals, the method including the steps of:

individually exciting each antenna with the RF signal in accordance with a time-multiplexed cyclical scanning pattern, the scanning pattern allocating each antenna an equal length proportion of a cycle of the scanning pattern for conducting the RF communications;

receiving a response signal from a transponder through one of the antennas; and

allocating a longer proportion of at least one cycle of the scanning pattern to said one of the antennas than is allocated to at least one of the other antennas.

10. The method claimed in claim 9, wherein each cycle of said scanning pattern includes a timeslot for each of said antennas, and wherein said step of allocating comprises lengthening the timeslot for said one of the antennas.

11. The method claimed in claim 10, wherein said step of lengthening comprises stealing a timeslot from one the other antennas within the cycle, such that the duration of the resulting cycle remains constant.

12. The method claimed in claim 11, wherein said step of stealing comprising identifying a candidate antenna from which to steal said timeslot, and wherein said step of identifying comprises determining that said candidate antenna did not receive a response from a transponder within a most recent cycle of said scanning pattern.

13. The method claimed in claim 12, wherein said step of identifying further comprises determining that said candidate antenna did not have its timeslot stolen in the most recent cycle of said scanning pattern.

14. The method claimed in claim 9, wherein said step of allocating includes determining that at least one said other antennas did not receive a response from a transponder within a most recent cycle of said scanning pattern.

15. The method claimed in claim 9, wherein said RF communications comprise communications in accordance with a predefined protocol, wherein said protocol prescribes a read operation, a program operation and a verify operation, and wherein said longer proportion enables said reader to perform said read operation, said program operation and said verify operation in a single timeslot.

16. The method claimed in claim 9, wherein said RF communications comprise communications in accordance with a predefined protocol, wherein said protocol prescribes a read operation, a program operation and a verify operation, and wherein said equal length proportion is sufficiently long to enable said read operation and said verify operation, and wherein said longer proportion is required to perform said program operation.