Adaptive radio frequency identification control algorithm

• US 7,561,044 B2
• Filed: 04/04/2006
• Issued: 07/14/2009
• Est. Priority Date: 04/04/2006
• Status: Expired due to Fees

• Current Assignee: Pitney Bowes Incorporated (Böwe Systec AG)
• Original Assignee: Pitney Bowes Incorporated (Böwe Systec AG)
• Inventors: Coffy, Jean-Hiram, Braun, John F., Parkos, Arthur J., Swenson, Michael P.
• Primary Examiner(s): BLOUNT, ERIC
• Application Number:
  US11/397,244
• Publication Number:
  US 20070229260A1
• Time in Patent Office: 1,197 Days
• Field of Search: 3405721-5728, 340/10.1, 340/10.2, 235/375, 235/385
• US Class Current: 340/572.1
• CPC Class Codes: G06Q 20/203 Inventory monitoring
• CPC Class Codes: H04B 5/48 Transceivers
• CPC Class Codes: H04B 5/77 for interrogation
• CPC Class Codes: H04B 7/0606 Random or pseudo-random switching scheme

Abstract

A method for adaptively controlling a Radio Frequency IDentification (RFID) system having a plurality of interrogating antennas and RFID tags. The method comprises the steps of establishing a timeout setting indicative of the time that each interrogating antenna powers a read field during a respective read period and a threshold time period indicative of the time required to transmit energy/exchange data between the RFID tag and the interrogating antenna. A period differential is then calculated which is indicative of the difference between the timeout setting and the time elapsed for the final RFID tag within a respective read field to communicate its RFID tag information. The timeout setting for each interrogating antenna may then be adaptively tuned or varied in accordance with the period differential. To expedite and/or refine the adaptive tuning feature, a variance may also be calculated indicative of the difference between the threshold time period and the period differential. The timeout setting may be decremented when the threshold time period is greater than the period differential and/or variance and incremented when the time period is less than the period differential and/or variance. Such variation of the timeout setting is evaluated with each interrogation cycle of the RFID system.

Claims

1. A method for adaptively controlling a Radio Frequency IDentification (RFID) system having a plurality of interrogating antennas and RFID tags, the interrogating antennas transmitting RF energy within a read field;

the method comprising the steps of;

establishing a timeout setting indicative of the time that each interrogating antenna powers a read field during a respective read period;

calculating a period differential indicative of the difference between the timeout setting and an elapsed time for a final RFID tag within a respective read field to communicate its RFID tag information; and

varying the timeout setting of each interrogating antenna in accordance with the respective period differential.

2. The method according to claim 1 further comprising the steps of:

establishing a threshold time period X indicative of a reporting period to acquire the RF energy and communicate RFID tag information to the respective interrogating antenna;

determining a variance indicative of the difference between the threshold time period X and the period differential, and

varying the timeout setting of each interrogating antenna based upon the magnitude of the variance.

3. The method according to claim 2 wherein the threshold time period X is based on a number of RFID tags anticipated to be located within the respective read field.

4. The method according to claim 2 wherein the threshold time period X is a percentage of the time required for an RFID to exchange information between the RFID tag and an interrogating antenna.

5. The method according to claim 2 wherein the threshold time period X is a percentage equal to at least 150% of the reporting time period.

6. The method according to claim 2 wherein the threshold time period X is a percentage equal to at least 200% of the reporting time period.

7. The method according to claim 2 wherein the step of varying the timeout setting further comprises the step of decrementing the timeout setting by a first value when the period differential exceeds the threshold time period.

8. The method according to claim 7 wherein the first value is about 50% of the variance.

9. The method according to claim 2 wherein the step of varying the timeout setting further comprises the step of incrementing the timeout setting by a second value when the period differential is less than the threshold time period.

10. The method according to claim 9 wherein the second value is about 200% of the variance.

11. The method according to claim 2 wherein the RFID system sequentially interrogates each read field by serially querying the RFID antennas within an interrogation cycle, and further comprising the step of varying the timeout setting of each interrogating antenna by an adaptive tuning value with each interrogation cycle.

12. An RFID system comprising:

a reader including a timeout setting indicative of the time that each interrogating antenna powers a read field during a respective read period;

at least one interrogating antenna in communication with the reader and operative to transmit RF energy within a read field during an interrogation cycle,

a plurality of RFID tags disposed within the read field communicating with the antenna; and

a processor including program code operative to control the reader and calculate a period differential indicative of the difference between the timeout setting and an elapsed time for a final RFID tag within a respective read field to communicate its RFID tag information and

vary the timeout setting of each interrogating antenna in accordance with the respective period differential.

13. The RFID system according to claim 12 wherein the program code includes a threshold time period X indicative of a reporting period to acquire the RF energy and communicate RFID tag information to the respective interrogating antenna, the controller, furthermore, operative to determine a variance indicative of the difference between the threshold time period X and the period differential and vary the timeout setting of each interrogating antenna based upon the magnitude of the variance.

14. The RFID system according to claim 13 wherein the RFID system sequentially interrogates each read field by serially querying the RFID antennas within an interrogation cycle, and further comprising the step of varying the timeout setting of each interrogating antenna by an adaptive tuning value with each interrogation cycle.

15. The RFID system according to claim 13 wherein the threshold time period X is based on a number of RFID tags anticipated to be located within the respective read field.

16. The RFID system according to claim 13 wherein the threshold time period X is a percentage of the time required for an RFID to exchange information between the RFID tag and an interrogating antenna.

17. The RFID system according to claim 13 wherein the processor is operative to decrement the timeout setting by a first value when the period differential exceeds the threshold time period.

18. The RFID system according to claim 17 wherein the first value is about 50% of the variance.

19. The RFID system according to claim 13 wherein the processor is operative to increment the timeout setting by a second value when the period differential is less than the threshold time period.

20. The RFID system according to claim 19 wherein the second value is about 200% of the variance.