# US 10,121,031 B2 · Determining a location based on radio frequency identification (RFID) read events

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- Number: US 10,121,031 B2
- Document ID: US10121031B2
- Status: Granted
- Kind: B2
- Application number: 15/634,659
- Filed: 2017-06-27
- Published: 2017-12-21
- Granted: 2018-11-06
- Earliest claimed: 2016-06-17
- Assignees: Amazon Technologies, Inc.
- Applicants: Amazon Technologies, Inc.
- Inventors: Oleg Kantor; Tak Keung Joseph Lui
- Web page: https://patentgrep.com/patent/US10121031B2

## CPC

- G06K 7/10366: {the interrogation device being adapted for miscellaneous applications}
- G01S 1/02: using radio waves (G01S19/00 takes precedence)
- G01S 5/0295: {Proximity-based methods, e.g. position inferred from reception of particular signals}
- G01S 13/878: {Combination of several spaced transmitters or receivers of known location for determining the position of a transponder or a reflector (G01S13/874 takes precedence)}
- G06K 7/10356: {using a plurality of antennas, e.g. configurations including means to resolve interference between the plurality of antennas}
- G01S 13/75: using transponders powered from received waves, e.g. using passive transponders {, or using passive reflectors}
- G01S 2205/01: specially adapted for specific applications
- G06K: GRAPHICAL DATA READING (image or video recognition or understanding G06V); PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
- G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES

## Abstract

Techniques for determining an item location based on multiple RFID parameters from multiple read events are described. In an example, a computer system may access a first read event. A first RFID reader located within a first zone may have generated the first read event at a first time. The first read event may identify an RFID tag and may include first RFID parameters. The computer system may access a second read event. A second RFID reader located within a second zone may have generated the second read event at a second time within a predefined amount of time from the first time. The second read event may identify the RFID tag and include second RFID parameters. The computer system may determine whether the item location falls within the first zone or the second zone based on two or more first RFID parameters and two or more second RFID parameters.

## Claims

### Claim 1

A computer-implemented method comprising:
receiving, by a computer system, a first read event generated by a first radio frequency identification (RFID) reader located within a first zone, the first read event identifying an RFID tag associated with an item and comprising first RFID parameters;
accessing, by the computer system, a map of RFID readers;
determining, by the computer system, a relevance of a second read event relative to the first read event based at least in part on the map, the second read event generated by a second RFID reader located within a second zone, identifying the RFID tag, and comprising second RFID parameters;
determining, by the computer system, two or more of the first RFID parameters from the first read event and two or more of the second RFID parameters from the second read event based at least in part on the relevance of the second read event; and
determining, by the computer system, an association between a location of the item and one of the first zone or the second zone based at least in part on the two or more of the first RFID parameters and the two or more of the second RFID parameters.

### Claim 2 (depends on 1)

The computer-implemented method of claim 1, wherein determining the relevance comprises determining an indication of a potential cross-read between the first RFID reader and the second RFID reader based at least in part on the map.

### Claim 3 (depends on 2)

The computer-implemented method of claim 2, wherein the indication of the potential cross-read is further determined based at least in part on the first RFID parameters and the second RFID parameters comprising the RFID tag associated with the item.

### Claim 4 (depends on 1)

The computer-implemented method of claim 1, wherein the relevance is determined based at least in part on the map indicating that the first RFID reader and the second RFID reader are in locations that are adjacent to each other.

### Claim 5 (depends on 1)

The computer-implemented method of claim 1, wherein the relevance is determined based at least in part on the map indicating an overlap between the first zone of the first RFID reader and the second zone of the second RFID reader.

### Claim 6 (depends on 1)

The computer-implemented method of claim 1, wherein the relevance is determined based at least in part on the map indicating a potential cross-read between the first RFID reader and the second RFID reader and based at least in part on timing information associated with the first read event and the second read event.

### Claim 7 (depends on 6)

The computer-implemented method of claim 6, wherein the timing information indicates that the first read event and the second read event are within a predefined amount of time of each other.

### Claim 8 (depends on 6)

The computer-implemented method of claim 6, wherein the timing information indicates an overlap between read cycles of the first RFID reader and the second RFID reader.

### Claim 9

A non-transitory computer-readable storage medium comprising instructions that, upon execution by a processor of a computer system, configure the computer system to perform operations comprising:
receiving a first read event generated by a first radio frequency identification (RFID) reader located within a first zone, the first read event identifying an RFID tag associated with an item and comprising first RFID parameters;
accessing a map of RFID readers;
determining a relevance of a second read event relative to the first read event based at least in part on the map, the second read event generated by a second RFID reader located within a second zone and comprising second RFID parameters;
determining two or more of the first RFID parameters from the first read event and two or more of the second RFID parameters from the second read event based at least in part on the relevance of the second read event; and
determining an association between a location of the item and one of the first zone or the second zone based at least in part on the two or more of the first RFID parameters and the two or more of the second RFID parameters.

### Claim 10 (depends on 9)

The non-transitory computer-readable storage medium of claim 9, wherein the instructions cause the computer system to determine the association between the location of the item and the one of the first zone or the second zone by acts that comprise determining whether the location of the item falls within the first zone or the second zone based at least in part on a normalization of the two or more of the first RFID parameters according to the two or more of the second RFID parameters.

### Claim 11 (depends on 9)

The non-transitory computer-readable storage medium of claim 9, wherein the instructions cause the computer system to determine the association between the location of the item and the one of the first zone or the second zone by acts that comprise:
generating a first score for the first read event based at least in part on the two or more of the first RFID parameters and the two or more of the second RFID parameters; and
determining whether the location of the item falls within the first zone or the second zone based at least in part on the first score.

### Claim 12 (depends on 11)

The non-transitory computer-readable storage medium of claim 11, wherein the instructions cause the computer system to determine whether the location of the item falls within the first zone or the second zone by acts that comprise comparing the first score generated for the first read event to a second score generated for the second read event.

### Claim 13 (depends on 11)

The non-transitory computer-readable storage medium of claim 11, wherein the instructions cause the computer system to generate the first score by acts that comprise:
for each of the two or more of the first RFID parameters, generating an individual score based at least in part on a respective one of the first RFID parameters and a corresponding one of the second RFID parameters; and
generating the first score based at least in part on the individual scores of the two or more of the first RFID parameters from the first read event.

### Claim 14 (depends on 11)

The non-transitory computer-readable storage medium of claim 11, wherein the instructions cause the computer system to generate the first score by acts that comprise generating, from the first read event and the second read event, a total count of times the RFID tag was read, an average signal strength, and a maximum signal strength.

### Claim 15 (depends on 11)

The non-transitory computer-readable storage medium of claim 11, wherein the instructions cause the computer system to generate the first score by acts that comprise:
dividing a first count of times the RFID tag was read from the first read event by a total count of times the RFID tag was read to generate a normalized count;
dividing a first average signal strength from the first read event by an average signal strength to generate a normalized average signal strength;
dividing a first maximum signal strength from the first read event by a maximum signal strength to generate a normalized maximum signal strength; and
summing the normalized count, the normalized average signal strength, and the normalized maximum signal strength to generate the first score.

### Claim 16 (depends on 15)

The non-transitory computer-readable storage medium of claim 15, wherein the instructions cause the computer system to generate the first score by further acts that comprise:
determining that a difference between the first score and a second score generated for the second read event is within a threshold amount; and
comparing, based at least in part on the difference being within the threshold amount, a last time stamp from the first read event to a last time stamp from the second read event.

### Claim 17

A system comprising:
a first radio frequency identification (RFID) reader located within a first zone;
a second RFID reader located within a second zone;
a processor; and
a non-transitory computer-readable storage medium comprising instructions that, upon execution by the processor, cause the system to:
receive a first read event that is generated by the first RFID reader, identifies an RFID tag associated with an item, and comprises first RFID parameters;
access a map of RFID readers;
determine a relevance of a second read event relative to the first read event based at least in part on the map, the second read event that is generated by the second RFID reader and comprises second RFID parameters;
determine two or more of the first RFID parameters from the first read event and two or more of the second RFID parameters from the second read event based at least in part on the relevance of the second read event; and
determine an association between a location of the item and one of the first zone or the second zone based at least in part on the two or more of the first RFID parameters and the two or more of the second RFID parameters.

### Claim 18 (depends on 17)

The system of claim 17, wherein the map indicates that the first RFID reader is located within the first zone, the second RFID reader is located within the second zone, and the first zone and the second zone are adjacent to each other.

### Claim 19 (depends on 17)

The system of claim 17, wherein the instructions further cause the system to:
determine that the second zone is adjacent to the first zone based at least in part on the map; and
access the second read event based at least in part on the first read event being received and the second zone being adjacent to the first zone.

### Claim 20 (depends on 17)

The system of claim 17, wherein the instructions further cause the system to:
determine that a location overlap between first zone and the second zone exists based at least in part on the map; and
determine that a timing overlap between the first zone and the second zone exists based at least in part on reading cycles of the first RFID reader and the second RFID reader, wherein the relevance of the second read event is determined based at least in part on the location overlap and the timing overlap.