Method and system for optimizing radio frequency identification (RFID) reader operation

• US 20070126555A1
• Filed: 12/06/2005
• Published: 06/07/2007
• Est. Priority Date: 12/06/2005
• Status: Abandoned Application

• Current Assignee: Symbol Technologies, Inc. (Zebra Technologies Corporation)
• Original Assignee: Symbol Technologies, Inc. (Zebra Technologies Corporation)
• Inventors: Bandy, William
• Application Number:
  US11/294,418
• Publication Number:
  US 20070126555A1
• Time in Patent Office: Days
• US Class Current: 340/10.200
• 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 7/10039 interrogator driven, i.e. synchronous

Abstract

Methods and apparatuses are described for optimizing an interrogation of a radio frequency identification (RFID) tag population. An RFID reader sets an initial number of time slots used to interrogate a population of tags. The reader does not previously know the size of the tag population. The reader monitors responses of tags for one or more time slots of an interrogation round to collect statistical data, estimates a number of tags in the population based on the statistical data, and determines a new number of time slots based on the estimated number of tags. The reader adjusts the number of time slots accordingly for a subsequent interrogation round. The reader may repeat this process as needed to converge closer to the actual number of tags in the population, and an acceptable number of time slots, to enhance an efficiency of the process of interrogating the tag population.

Claims

1. A method in a radio frequency identification (RFID) reader to adjust a number of time slots in an inventory round for interrogating a population of tags, comprising:

setting a first number of time slots in a tag inventory round;

monitoring time slots for responses from tags to obtain statistical data based on the responses;

estimating a number of tags in the population based on the statistical data; and

setting a second number of time slots in a round based on the estimated number of tags.

2. The method of claim 1, wherein said monitoring further comprises counting a total number of empty time slots, a total number of contended time slots and a total number of single response time slots for a predetermined number of time slots.

3. The method of claim 1, wherein estimating a number of tags further comprises determining at least one of a probability of an empty time slot, a probability of a contended time slot and a probability of a single response time slot.

4. The method of claim 1, wherein said monitoring is performed for a predetermined number of time slots.

5. The method of claim 1, wherein the second number of time slots is set equal to the estimated number of tags.

6. The method of claim 1, wherein the second number of time slots is set to twice the first number of time slots if the estimated number of tags is greater than the first number of time slots.

7. The method of claim 1, wherein the second number of time slots is set to half the first number of time slots if the estimated number of tags is lesser than the first number of time slots.

8. The method of claim 1, further comprising transmitting a Query command prior to said monitoring.

9. The method of claim 8, wherein said monitoring further comprises transmitting a QueryRep command.

10. The method of claim 8, wherein said setting a second number comprises transmitting a QueryAdjust command.

11. A radio frequency identification (RFID) reader device, comprising:

a RFID controller;

a transceiver coupled to the RFID controller;

at least one RF antenna coupled to the transceiver;

wherein the RF antenna transmits commands received from the RFID controller via the transceiver and receives responses from a population of RFID tags in an environment; and

wherein the RFID controller is configured to set a first number of time slots in a tag inventory round, monitor time slots for tag responses to collect statistical RFID tag response data, estimate a number of tags in the environment based on the statistical RFID tag response data, and set a second number of time slots in a round based on the estimated number of tags.

12. The reader device of claim 11, wherein the RFID controller is configured to monitor a predetermined number of time slots for a total number of empty time slots, a total number of contended time slots and a total number of single response time slots.

13. The reader device of claim 11, wherein the RFID controller determines at least one of a probability of an empty time slot, a probability of a contended time slot, and a probability of a single response time slot.

14. The reader device of claim 11, wherein the tag response data is collected for a predetermined number of tags.

15. The reader device of claim 11, wherein the RFID controller sets the second number of time slots equal to the estimated number of tags.

16. The reader device of claim 11, wherein the RFID controller sets the second number of time slots to twice the first number of time slots if the estimated number of tags is greater than the first number of time slots.

17. The reader device of claim 11, wherein the RFID controller sets the second number of time slots to half the first number of time slots if the estimated number of tags is lesser than the first number of time slots.

18. The reader device of claim 11, wherein the RFID controller generates a Query command transmitted by the at least one RF antenna.

19. The reader device of claim 11, wherein the RFID controller generates a QueryRep command transmitted by the at least one antenna.

20. The reader device of claim 11, wherein the RFID controller generates a QueryAdjust command transmitted by the at least one antenna.