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WO-2026096215-A1 - RFID FREQUENCY MANAGEMENT USING PRECISION TIME PROTOCOL

WO2026096215A1WO 2026096215 A1WO2026096215 A1WO 2026096215A1WO-2026096215-A1

Abstract

Certain aspects and features of the present disclosure relate to a method and/or a system that reduces interference in the operation of multiple radio frequency identification (RFID) readers in proximity to each other. The method uses network time resources available to all RFID readers in a group of readers to schedule frequency channel usage. Centralized control signaling is not required. Readers run a channel hop schedule based on system clocks that are universally synchronized using network time resources, and readers can determine how the other readers are sequencing in frequency by independently accessing or determining information about the other RFID readers in the group.

Inventors

  • FREDERICK, THOMAS J.
  • WILLIAMS, OWEN

Assignees

  • CLAIRVOYANT TECNOLOGY, INC.

Dates

Publication Date
20260507
Application Date
20251016
Priority Date
20241028

Claims (20)

  1. 1. A method comprising: accessing, by a radio frequency identification (RFID) reader among a plurality of RFID readers, a precision time protocol (PTP) signal; accessing, by the RFID reader, a channel hop sequence, a specified channel dwell time, and information regarding other RFID readers among the plurality of RFID readers; determining, by the RFID reader, an offset within the channel hop sequence based on the information regarding the other RFID readers; and synchronously transmitting an RFID interrogation signal using the PTP signal and the offset, wherein the RFID interrogation signal varies in frequency according to the channel hop sequence.
  2. 2. The method of claim 1, wherein the information comprises signal strength statistics, the method further comprising: cycling through the channel hop sequence using the RFID reader in listening mode; determining, based on the cycling, the signal strength statistics for each of a plurality of available RFID frequency channels; and calculating the offset using the signal strength statistics.
  3. 3. The method of claim 2, further comprising: tuning the RFID reader in listening mode to a mid-band frequency to access adjacent channels above and below an initial listening channel; and cycling through the channel hop sequence beginning at the mid-band frequency to determine the signal strength statistics.
  4. 4. The method of claim 2 or claim 3, wherein the signal strength statistics comprise a minimum weighted average of sampled co-channel and adjacent channel receive strength values. Page 18 of 24 US2008 32083532 1 Attorney Docket No.: 102832-1520032 RFID Frequency Management using Precision Time Protocol
  5. 5. The method of claim 1, wherein the information comprises a number of readers in the plurality of RFID readers and an assigned reader number for the RFID reader, wherein the method further comprises: computing a current dwell slot number for the RFID reader; computing a synchronous start time for the number of readers using the PTP signal; and determining, using the current dwell slot number and the synchronous start time, a current channel for the RFID reader, the current channel defining the offset within the channel hop sequence.
  6. 6. The method of claim 5, further comprising computing the current dwell slot number using a ceiling function of a current time from the PTP signal and the specified channel dwell time.
  7. 7. The method of claim 5 or claim 6, further comprising: computing a target channel separation for the plurality of RFID readers based on the number of readers and available RFID frequency channels; and computing the synchronous start time based at least in part on the target channel separation.
  8. 8. A radio frequency identification (RFID) reader comprising: a processor; and a non-transitory storage medium associated with the processor, the non-transitory storage medium including instructions executable by the processor to cause the processor to: access a precision time protocol (PTP) signal at a radio frequency identification (RFID) reader among a plurality of RFID readers; access a channel hop sequence, a specified channel dwell time, and information regarding other RFID readers among the plurality of RFID readers; determine an offset within the channel hop sequence based on the information regarding the other RFID readers; and Page 19 of 24 US2008 32083532 1 Attorney Docket No.: 102832-1520032 RFID Frequency Management using Precision Time Protocol synchronously transmit an RFID interrogation signal using the PTP signal and the offset, wherein the RFID interrogation signal varies in frequency according to the channel hop sequence.
  9. 9. The RFID reader of claim 8, wherein the information comprises signal strength statistics, and wherein the instructions are executable to cause the processor to: tune the RFID reader in listening mode to a mid-band frequency to access adjacent channels above and below an initial listening channel; cycle through the channel hop sequence beginning at the mid-band frequency to determine the signal strength statistics. determine, based on the cycling, the signal strength statistics for each of a plurality of available RFID frequency channels; and calculate the offset using the signal strength statistics.
  10. 10. The RFID reader of claim 9, wherein the signal strength statistics comprise a minimum weighted average of sampled co-channel and adjacent channel receive strength values.
  11. 11. The RFID reader according to any of claims 8 through 10, wherein the information comprises a number of readers in the plurality of RFID readers and an assigned reader number for the RFID reader, and wherein the instructions are executable to cause the processor to: compute a current dwell slot number for the RFID reader; compute a synchronous start time for the number of readers using the PTP signal; and determine, using the current dwell slot number and the synchronous start time, a current channel for the RFID reader, the current channel defining the offset within the channel hop sequence.
  12. 12. The RFID reader of claim 11, wherein the instructions are executable to cause the processor to compute the current dwell slot number using a ceiling function of a current time from the PTP signal and the specified channel dwell time. Page 20 of 24 US2008 32083532 1 Attorney Docket No.: 102832-1520032 RFID Frequency Management using Precision Time Protocol
  13. 13. The RFID reader of claim 11 or claim 12, wherein the instructions are executable to cause the processor to: compute a target channel separation for the plurality of RFID readers based on the number of readers and available RFID frequency channels; and compute the synchronous start time based at least in part on the target channel separation.
  14. 14. A system comprising the plurality of RFID readers including the RFID reader according to any of claims 8 through 13, wherein each of the plurality of RFID readers uses a different offset.
  15. 15. A non-transitory computer-readable medium storing executable instructions, which when executed by a processor, cause the processor to perform operations comprising: accessing a precision time protocol (PTP) signal at a radio frequency identification (RFID) reader among a plurality of RFID readers; accessing a channel hop sequence, a specified channel dwell time, and information regarding other RFID readers among the plurality of RFID readers; determining an offset within the channel hop sequence based on the information regarding the other RFID readers; and synchronously transmitting an RFID interrogation signal using the PTP signal and the offset, wherein the RFID interrogation signal varies in frequency according to the channel hop sequence.
  16. 16. The non-transitory computer-readable medium of claim 15, wherein the information comprises signal strength statistics, and wherein the operations further comprise: cycling through the channel hop sequence using the RFID reader in listening mode; determining, based on the cycling, the signal strength statistics for each of a plurality of available RFID frequency channels; and Page 21 of 24 US2008 32083532 1 Attorney Docket No.: 102832-1520032 RFID Frequency Management using Precision Time Protocol calculating the offset using the signal strength statistics.
  17. 17. The non-transitory computer-readable medium of claim 16, wherein the operations further comprise: tuning the RFID reader in listening mode to a mid-band frequency to access adjacent channels above and below an initial listening channel; and cycling through the channel hop sequence beginning at the mid-band frequency to determine the signal strength statistics.
  18. 18. The non-transitory computer-readable medium of claim 17 or claim 16, wherein the signal strength statistics comprise a minimum weighted average of sampled co-channel and adjacent channel receive strength values.
  19. 19. The non-transitory computer-readable medium according to any of claims 15 through 18, wherein the information comprises a number of readers in the plurality of RFID readers and an assigned reader number for the RFID reader, and wherein the operations further comprise: computing a current dwell slot number for the RFID reader; computing a synchronous start time for the number of readers using the PTP signal; and determining, using the current dwell slot number and the synchronous start time, a current channel for the RFID reader, the current channel defining the offset within the channel hop sequence.
  20. 20. The non-transitory computer-readable medium of claim 19, wherein the operations further comprise: computing the current dwell slot number using a ceiling function of a current time from the PTP signal and the specified channel dwell time; computing a target channel separation for the plurality of RFID readers based on the number of readers and available RFID frequency channels; and computing the synchronous start time based at least in part on the target channel separation. Page 22 of 24 US2008 32083532 1 Attorney Docket No.: 102832-1520032 RFID Frequency Management using Precision Time Protocol

Description

Attorney Docket No.: 102832-1520032 RFID FREQUENCY MANAGEMENT USING PRECISION TIME PROTOCOL Cross-Reference to Related Application [0001] This application claims priority to U.S. Provisional Patent Application 63/712,736 filed October 28, 2024, the entire disclosure of which is incorporated herein by reference. Technical Field [0002] The present disclosure relates generally to radio frequency identification (RFID) systems. More particularly, though not exclusively, the present disclosure relates to systems that involve multiple RFID readers operating in proximity within regulatory regions where multiple carrier frequencies can be used. Background [0003] RFID systems include, at least, an RFID reader and an antenna. The antenna is used by the RFID reader to transmit interrogation signals to RFID tags and receive responses from the RFID tags. Passive UHF RFID readers can read low-cost battery -free passive RFID tags at many meters distance without line of sight between the RFID reader and the RFID tag. Passive RFID readers transmit with enough power to energize the tags, so that nearby readers can cause interference with an RFID reader. As with most RF systems, maintaining physical and/or frequency distance between readers can reduce interference, as the receive filtering of the RFID reader in question will typically provide adjacent channel rejection. Summary [0004] Aspects and features of this disclosure include a method of using precision time protocol (PTP) to manage frequencies used over time by RFID readers in a group of readers to minimize interference within the group. The method involves accessing a PTP signal at an RFID reader among a group of RFID readers, and accessing a channel hop sequence, a specified channel dwell time, and information regarding other RFID readers among the group of RFID readers. The method also involves determining an offset within the channel hop sequence based on the information regarding the other RFID readers. The Page 1 of 24 US2008 32083532 1 Attorney Docket No.: 102832-1520032 RFID Frequency Management using Precision Time Protocol method further involves synchronously transmitting an RFID interrogation signal using the PTP signal and the offset, wherein the RFID interrogation signal varies in frequency according to the channel hop sequence. [0005] Aspects and features of this disclosure also include a method of configuring an RFID reader to use PTP to manage frequencies used over time to minimize interference within the group. The method involves determining a number of available RFID frequency channels for a target location of an RFID reader. The method also involves selecting, from candidate channel increments, and based on the number of available RFID frequency channels, a channel increment for the RFID reader and producing a channel hop sequence based at least in part on the number of available RFID channels. The method further involves using a specified channel dwell time for the RFID reader and storing the specified channel dwell time and the channel hop sequence in the RFID reader to configure the RFID reader for synchronous RFID interrogation using a precision time protocol (PTP) signal. [0006] Aspects and features of this disclosure may also include a non-transitory storage medium with instructions to perform the operations of one or more of the methods described. Aspects and features may also include RFID readers and/or processing systems to perform the operations of one or more of the methods described. Brief Description of the Drawings [0007] FIG. 1 is a system block diagram showing an example of provisioning RFID readers according to some aspects of the present disclosure. [0008] FIG. 2A and FIG. 2B illustrate two different views of a frequency vs. time plot showing examples of frequency curves for two RFID readers. FIG. 2A is a view showing the frequency channels being used in a free-running fashion, prior to beginning transmission according to a channel hop sequence, and FIG. 2B shows the frequency channels being used with aspects of the present disclosure once the channel hop sequence is engaged. [0009] FIG. 3 is a diagram illustrating how to arrange readers in two-dimensional space to minimize frequency interference and allow frequency channel reuse according to example embodiments. Page 2 of 24 US2008 32083532 1 Attorney Docket No.: 102832-1520032 RFID Frequency Management using Precision Time Protocol [0010] FIG. 4 is a system block diagram showing an RFID system in which readers according so some aspects of the present disclosure use RF frequency channels to interrogate for RFID tags when system time is synchronized using a network precision time protocol according to example embodiments. [0011] FIG. 5 is a flowchart of a method to determine a channel increment for constructing a pseudorandom channel hop sequence according to example embodiments. [0012] FIG. 6 is a flowchart of a method of configuring an RFID reader for synchronous RFID inter