Methods for interrogating objects to be identified over a communications medium

• US 7,916,001 B2
• Filed: 02/05/2007
• Issued: 03/29/2011
• Est. Priority Date: 03/16/2001
• Status: Active Grant

• Current Assignee: E-Tag Systems Incorporated
• Original Assignee: E-Tag Systems Incorporated
• Inventors: Hulvey, Robert
• Primary Examiner(s): Zimmerman; Brian A
• Assistant Examiner(s): Nguyen; Nam V
• Application Number:
  US11/702,953
• Publication Number:
  US 20070222561A1
• Time in Patent Office: 1,513 Days
• Field of Search: 340/10.31, 340/10.1, 340/10.2, 340/825.02, 340/10.51, 340/825.56, 370/437, 370/458, 370/346, 370/312, 370/445, 370/449, 707/100, 707/101, 711/128, 711/118
• US Class Current: 340/10.31
• CPC Class Codes: G06K 19/0723 the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs
• CPC Class Codes: G06K 7/0008 General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer
• CPC Class Codes: G06K 7/10049 binary tree

Abstract

Systems and methods for efficiently querying and identifying multiple items on a communication channel are disclosed. The invention is well suited to use with radio frequency identification with interrogation devices and systems that identify radio frequency identification transponders. A depth-first tree traversal protocol algorithm, including commands and symbols, is used to more efficiently interrogate a plurality of transponders in a short amount of time.

Claims

1. A method for interrogating objects to be identified over a communication medium, wherein the objects provide predetermined responses indicative of object identification numbers and each include a push counter, the method comprising the steps of:

sending interrogation signals to and receiving responses from the objects over the communication medium, the interrogation signals operating to interrogate a single digit from the objects to be identified;

recording incomplete identification numbers whenever two or more predetermined responses are received from the objects;

retrieving incomplete identification numbers whenever two or more predetermined responses are received from the objects;

sending a signal to the objects to cause the objects to selectively add a number to their respective push counter, wherein the number is determined by each object and is dependent upon one or more previous responses of the object to interrogation signals;

sending a signal to the objects to cause the objects to selectively subtract a number from their respective push counter, wherein the number is determined by each object and is dependent upon one or more previous responses of the object to the interrogation signals; and

recording complete identification numbers as they are determined.

2. The method of claim 1, wherein the objects are identified based on a depth-first tree traversal algorithm.

3. The method of claim 2, wherein a speed for determining the identification numbers is deterministic given a set of objects to have their identification numbers determined.

4. The method of claim 1, wherein, in response to interrogation of a signal digit from the objects, each object provides a response regardless of the value of the digit being interrogated.

5. The method of claim 1, wherein the communication channel comprises a radio channel.

6. The method of claim 5, wherein the objects each include an RFID transponder.

7. The method of claim 6, wherein the counter is included in control circuitry for the RFID transponder.

8. The method of claim 1, wherein the communication channel comprises a wired communication channel.

9. The method of claim 1, wherein values of the counters selectively inhibit objects from responding to interrogation signals.

10. The method of claim 1, wherein the selective inhibit occurs as part of a depth-first tree traversal algorithm.

11. A method for interrogating objects to be identified over a communication medium, wherein the objects provide predetermined responses indicative of object identification numbers and each includes a push counter, the interrogation comprising the steps of:

sending signals to and receiving signals from the objects over the communication medium;

recording and later retrieving incomplete identification numbers whenever two or more predetermined responses are received from the objects;

sending a signal to the objects to cause the objects to selectively add a number to their respective push counter, the number to be determined by each individual object and dependent upon one or more previous responses of the individual object to the interrogation;

sending a signal to the objects to cause the objects to selectively subtract a number from their respective push counter, the number to be determined by each individual object and dependent upon one or more previous responses of the individual object to the interrogation;

recording complete identification numbers as they are determined; and

sending a signal to interrogate a single digit from the objects to be identified.

12. The method of claim 11, wherein the objects are identified based on a depth-first tree traversal algorithm.

13. The method of claim 12, wherein a speed for determining the identification numbers is deterministic given a set of objects to have their identification numbers determined.

14. The method of claim 11, wherein, in response to interrogation of a signal digit from the objects, each object provides a response regardless of the value of the digit being interrogated.

15. The method of claim 11, wherein the communication channel comprises a radio channel.

16. The method of claim 15, wherein the objects each include an RFID transponder.

17. The method of claim 16, wherein the counter is included in control circuitry for the RFID transponder.

18. The method of claim 11, wherein the communication channel comprises a wired communication channel.

19. The method of claim 11, wherein values of the respective counters selectively inhibit objects from responding to interrogation signals.

20. The method of claim 11, wherein the selective inhibit occurs as part of a depth-first tree traversal algorithm.