Efficient protocol for reading RFID tags

• US 20040046644A1
• Filed: 09/05/2002
• Published: 03/11/2004
• Est. Priority Date: 09/05/2002
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Bauhahn, Paul E.
• Granted Patent: US 7,239,229 B2
• Time in Patent Office: Days
• US Class Current: 340/10.42
• 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 7/10019 resolving collision on the communication channels between simultaneously or concurrently interrogated record carriers. collision between the communication channels used by wireless communication devices, where the solution is not particularly adapted for RFIDs or the like, H04W74/08

Abstract

An RFID tag has an N data element tag identifier that uniquely identifies the RFID tag. The RFID tag selects M data elements of the tag identifier, where M<N, and transmits only the selected M data elements to a tag reader so as to identify the RFID tag to the tag reader.

Claims

1. A method of communicating an identifier from an RFID tag to a tag reader, wherein the identifier includes N data elements, and wherein the method comprises:

selecting M data elements of the identifier, wherein M<

N; and

, transmitting only the selected M data elements from the RFID tag to the tag reader so as to identify the RFID tag to the tag reader.

2. The method of claim 1 wherein the selected M data elements are sequential data elements of the identifier.

3. The method of claim 1 wherein the selecting of M data elements of the identifier comprises selecting the M data elements of the identifier based on a start position R1 and an end position R2 defining a limiting range within the identifier.

4. The method of claim 3 further comprising storing the start position R1 and the end position R2 in a memory of the RFID tag.

5. The method of claim 4 wherein the memory comprises at least one register.

6. The method of claim 4 wherein the memory comprises first and second registers, wherein the storing of the start position R1 and end position R2 comprises storing the start position R1 in the first register, and wherein the storing of the start position R1 and the end position R2 comprises storing the end position R2 in the second register.

7. The method of claim 3 further comprising receiving the start position R1 and the end position R2 from the tag reader and storing the start position R1 and the end position R2 in a memory of the RFID tag.

8. The method of claim 3 further comprising receiving the start position R1 and the end position R2 from the tag reader and storing the start position R1 and the end position R2 in corresponding registers of the RFID tag.

9. The method of claim 1 wherein the transmitting of only the selected M data elements from the RFID tag to the tag reader comprises:

determining a time slot based on the selected M data elements; and

,

transmitting the selected M data elements from the RFID tag to the tag reader in the time slot.

10. The method of claim 9 wherein the selecting of M data elements of the identifier comprises:

receiving a start position R1 and an end position R2 from the tag reader;

selecting the M data elements of the identifier based on the received start position R1 and the received end position R2 defining a limiting range within the identifier; and

,

wherein the transmitting of only the selected M data elements from the RFID tag to the tag reader comprises;

transmitting only the data elements within the limited range.

11. The method of claim 1 further comprising:

receiving a silence message from the tag reader; and

,

suppressing the transmitting of the selected M data elements from the RFID tag to the tag reader in response to the silence message.

12. The method of claim 11 wherein the selecting of M data elements of the identifier comprises:

receiving a start position R1 and an end position R2 from the tag reader;

selecting the M data elements of the identifier based on the received start position R1 and the received end position R2 defining a limiting range within the identifier; and

,

wherein the transmitting of only the selected M data elements from the RFID tag to the tag reader comprises;

transmitting only the data elements within the limited range.

13. The method of claim 11 wherein the transmitting of only the selected M data elements from the RFID tag to the tag reader comprises:

determining a time slot based on the selected M data elements; and

,

transmitting the selected M data elements from the RFID tag to the tag reader in the time slot.

14. The method of claim 13 wherein the selecting of M data elements of the identifier comprises:

receiving a start position R1 and an end position R2 from the tag reader;

selecting the M data elements of the identifier based on the received start position R1 and the received end position R2 defining a limiting range within the identifier; and

,

wherein the transmitting of only the selected M data elements from the RFID tag to the tag reader comprises;

transmitting only the data elements within the limited range.

15. A method of identifying an RFID tag comprising:

transmitting a signal from a tag reader to the RFID tag, wherein the RFID tag includes an identifier comprising N data elements;

receiving only M of the N data elements from the RFID tag, wherein M<

N; and

,

identifying the RFID tag from only the M data elements.

16. The method of claim 15 wherein the transmitting of a signal from a tag reader to the RFID tag comprises transmitting a signal that identifies the M data elements to be transmitted by the RFID tag to the tag reader.

17. The method of claim 16 wherein the transmitting of a signal that identifies the M data elements to be transmitted by the RFID tag to the tag reader comprises transmitting a start position R1 and an end position R2 from the tag reader to the RFID tag, and wherein the start position R1 and the end position R2 define the M data elements.

18. The method of claim 17 wherein the signal that identifies the M data elements to be transmitted by the RFID tag to the tag reader comprises an interrogation signal.

19. The method of claim 16 further comprising:

detecting contention between the RFID tag and at least one other RFID tag;

transmitting a signal that identifies K data elements, wherein the K data elements comprises a subset of the M data elements, and wherein K<

M<

N;

receiving only the K data elements of the M data elements of the N data elements from the RFID tag; and

,

identifying the RFID tag from only the K data elements.

20. The method of claim 19 wherein the transmitting of a signal that identifies the K data elements to be transmitted by the RFID tag to the tag reader comprises transmitting a revised start position R1 and a revised end position R2 from the tag reader to the RFID tag, and wherein the revised start position R1 and the revised end position R2 define the K data elements.

21. The method of claim 20 wherein the signal that identifies the K data elements to be transmitted by the RFID tag to the tag reader comprises an interrogation signal.

22. The method of claim 15 wherein the transmitting of a signal from a tag reader to the RFID tag comprises:

determining the value of M based upon responses from the RFID tag and from other RFID tags; and

,

transmitting a signal that identifies the M data elements to be transmitted by the RFID tag to the tag reader.

23. The method of claim 22 wherein the signal that identifies the M data elements to be transmitted by the RFID tag to the tag reader comprises an interrogation signal.

24. The method of claim 22 wherein the transmitting of a signal that identifies the M data elements to be transmitted by the RFID tag to the tag reader comprises transmitting a start position R1 and an end position R2 from the tag reader to the RFID tag, and wherein the start position R1 and the end position R2 define the M data elements.

25. The method of claim 24 wherein the signal that identifies the M data elements to be transmitted by the RFID tag to the tag reader comprises an interrogation signal.

26. The method of claim 22 further comprising:

detecting contention between the RFID tag and at least one other RFID tag;

transmitting a signal that identifies K data elements, wherein the K data elements comprises a subset of the M data elements, and wherein K<

M<

N;

receiving only the K data elements of the M data elements of the N data elements from the RFID tag; and

,

identifying the RFID tag from only the K data elements.

27. The method of claim 26 wherein the transmitting of a signal that identifies the K data elements to be transmitted by the RFID tag to the tag reader comprises transmitting a revised start position R1 and a revised end position R2 from the tag reader to the RFID tag, and wherein the revised start position R1 and the revised end position R2 define the K data elements.

28. The method of claim 27 wherein the signal that identifies the K data elements to be transmitted by the RFID tag to the tag reader comprises an interrogation signal.

29. An RFID tag uniquely identified by an N data element tag identifier comprising:

a transmitter arranged to transmit M data elements so as to identify the RFID tag, wherein the M data elements comprises a subset of the N data element tag identifier, and wherein M<

N;

a receiver arranged to receive a message from a tag reader; and

,

a memory storing the N data element tag identifier and storing a definition of the M data elements.

30. The RFID tag of claim 29 wherein the receiver comprises a direct sequence spread spectrum RF receiver.

31. The RFID tag of claim 29 wherein the transmitter comprises a frequency agile RF transmitter.

32. The RFID tag of claim 29 wherein the receiver comprises a direct sequence spread spectrum RF receiver, and wherein the transmitter comprises a frequency agile RF transmitter.

33. The RFID tag of claim 29 wherein the memory comprises at least one register storing the definition of the M data elements.

34. The RFID tag of claim 29 wherein the definition comprises a start data element position R1 and an end data element position R1, wherein the start data element position R1 defines a start data element location within the N data element tag identifier, and wherein the end data element position R2 defines an end data element location within the N data element tag identifier.

35. The RFID tag of claim 34 wherein a first register stores the start data element position R1, and wherein a second register stores the end data element position R2.

36. The RFID tag of claim 29 wherein the M data elements comprise M sequential data elements of the N data element tag identifier.