Broadcast refresh of RFID tag persistence

• US 9,330,284 B1
• Filed: 10/12/2011
• Issued: 05/03/2016
• Est. Priority Date: 04/18/2011
• Status: Active Grant

• Current Assignee: Impinj, Inc.
• Original Assignee: Impinj, Inc.
• Inventors: Diorio, Christopher J.
• Primary Examiner(s): Backer, Firmin
• Assistant Examiner(s): Tun, Nay
• Application Number:
  US13/271,937
• Time in Patent Office: 1,665 Days
• US Class Current: 1/1
• 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 7/10009 sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves
• CPC Class Codes: G06K 7/10039 interrogator driven, i.e. synchronous
• CPC Class Codes: G06Q 10/087 Inventory or stock management, e.g. order filling, procurement or balancing against orders

Abstract

A reader may broadcast a refresh command to a population or subpopulation of tags and thereby refresh and extend the persistence time of a tag flag, such as an inventoried flag. The characteristics, timing, and other details of this broadcast refresh command may be determined based on the state of a reader, environmental, tag-population, and/or tag-capability conditions and parameters. The refresh command may be a Select command of the Gen2 Specification, in which case parameters of the Select command specify the refresh operation.

Claims

1. An RFID reader configured to communicate with a plurality of RFID tags, the reader comprising:

a transceiver; and

a processor block coupled to the transceiver, the processor block configured to;

transmit a broadcast command including an indicator field, a first command code, and a mask field, wherein;

a first value for the indicator instructs the plurality of RFID tags to execute an operation specified by the first command code and the mask field; and

a second value for the indicator instructs the plurality of RFID tags to ignore the first command code, interpret at least a portion of the mask field as a second command code, and perform a second operation specified by the second command code, wherein;

if the second command code specifies a refresh operation, then the plurality of RFID tags are instructed to perform the refresh operation; and

if the second command code specifies another operation, then the plurality of RFID tags are instructed to perform the other operation using a data field, the data field included in the broadcast command and associated with the second command code.

2. The reader of claim 1, wherein the processor block is configured to transmit the broadcast command based on at least one of a previous refresh parameter, a previous-command parameter, a next-command parameter, a communication-rate parameter, and an impending frequency-hop parameter.

3. The reader of claim 1, wherein the processor block is configured to transmit the broadcast command based on at least one of an RF noise parameter, a signal-to-noise ratio parameter, and a temperature parameter.

4. The reader of claim 1, wherein the processor block is configured to transmit the broadcast command based on at least one of a number of tags in a tag population, a population-flush parameter, and a recurring-tag parameter.

5. The reader of claim 1, wherein the processor block is configured to transmit the broadcast command based on at least one of a flag-persistence parameter and a tag-refresh support parameter.

6. The reader of claim 1, wherein the broadcast command is a “

Select”

command according to the Gen2 Specification.

7. The reader of claim 1, wherein the first command code specifies a command operable to select a subpopulation of the plurality of RFID tags.

8. The reader of claim 1, wherein the refresh operation causes the plurality of RFID tags to refresh their respective one or more inventoried flags.

9. The reader of claim 1, wherein the refresh operation is configured to adjust a flag stored charge.

10. A method for an RFID reader to communicate with a plurality of RFID tags, comprising:

determining a refresh parameter based on at least one of a reader state, an environmental condition, a tag-population parameter, and a tag-capability parameter; and

transmitting a broadcast command based on the refresh parameter and including an indicator field, a first command code, and a mask field, wherein

a first value for the indicator instructs the plurality of RFID tags to execute an operation specified by the first command code and the mask field; and

a second value for the indicator instructs the plurality of RFID tags to ignore the first command code, interpret at least a portion of the mask field as a second command code, and perform a second operation specified by the second command code, wherein;

if the second command code specifies a refresh operation, then the plurality of RFID tags are instructed to perform the refresh operation; and

if the second command code specifies another operation, then the plurality of RFID tags are instructed to perform the other operation using a data field, the data field included in the broadcast command and associated with the second command code.

11. The method of claim 10, wherein the reader state includes at least one of a previous value of the refresh parameter, a previous-command parameter, a next-command parameter, a communication-rate parameter, and an impending frequency-hop parameter.

12. The method of claim 10, wherein the environmental condition includes at least one of an RF noise parameter, a signal-to-noise ratio parameter, and a temperature parameter.

13. The method of claim 10, wherein the tag-population parameter includes at least one of a number of tags in a tag population, a population-flush parameter, and a recurring-tag parameter.

14. The method of claim 10, wherein the tag-capability parameter includes at least one of a flag-persistence parameter and a tag-refresh support parameter.

15. The method of claim 10, wherein the broadcast command is a “

Select”

command according to the Gen2 Specification.

16. The method of claim 10, wherein the first command code specifies a command operable to select a subpopulation of the plurality of RFID tags.

17. The method of claim 10, wherein the refresh operation causes the plurality of RFID tags to refresh their respective one or more inventoried flags.

18. The method of claim 10, wherein the refresh operation adjusts a flag stored charge.

19. A method for an RFID reader to communicate with a plurality of RFID tags, comprising:

determining a subpopulation of the plurality of RFID tags to execute a refresh operation; and

transmitting a broadcast command specifying the subpopulation of tags and including an indicator fi d, a first command code, and a mask field, wherein;

a first value for the indicator instructs the plurality of RFID tags to execute an operation specified by the first command code and the mask field; and

a second value for the indicator instructs the plurality of RFID tags to ignore the first command code, interpret at least a portion of the mask field as a second command code, and perform a second operation specified by the second command code, wherein;

if the second command code specifies a refresh operation, then the plurality of RFID tags are instructed to perform the refresh operation; and

if the second command code specifies another operation, then the plurality of RFID tags are instructed to perform the other operation using a data field, the data field included in the broadcast command and associated with the second command code.

20. The method of claim 19, further comprising:

transmitting the broadcast command based on at least one of a previous refresh parameter, a previous-command parameter, a next-command parameter, a communication-rate parameter, and an impending frequency-hop parameter.