# US 2024/0201306 A1 · Estimating position from reference signals received by coordinating access points

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- Number: US 2024/0201306 A1
- Document ID: US20240201306A1
- Status: Published application
- Kind: A1
- Application number: 18/065,871
- Filed: 2022-12-14
- Published: 2024-06-20
- Earliest claimed: 2022-12-14
- Assignees: Cisco Technology, Inc.
- Applicants: Cisco Technology, Inc.
- Inventors: Domenico Ficara; Pascal Thubert; Jerome Henry; Amine Choukir; Brian Hart
- Web page: https://patentgrep.com/patent/US20240201306A1

## CPC

- G01S 5/0036: {of measured values, i.e. measurement on mobile and position calculation on base station}
- G01S 5/0221: {Receivers}
- G01S 5/0063: {of measured values, i.e. measurement on base station and position calculation on mobile}
- G01S 5/02213: {Receivers arranged in a network for determining the position of a transmitter}
- G01S 5/02216: {Timing or synchronisation of the receivers}
- G01S 5/06: Position of source determined by co-ordinating a plurality of position lines defined by path-difference measurements (G01S5/12 takes precedence)
- G01S 13/765: {with exchange of information between interrogator and responder}
- H04J 3/0661: {using timestamps}
- 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
- H04J: MULTIPLEX COMMUNICATION (transmission in general H04B; peculiar to transmission of digital information H04L5/00; systems for the simultaneous or sequential transmission of more than one television signal H04N7/08; in exchanges H04Q11/00; stereophonic systems H04S)

## Abstract

Disclosed are systems, apparatuses, methods, and computer-readable media for identifying a location of a wireless device. A method for identifying a location of a wireless device includes transmitting a request message to the wireless device for identifying a position of the wireless device; receiving a response message from the wireless device; determining first time information based on a time of flight (ToF) of the request message and the response message, wherein the ToF corresponds to a distance of the wireless device from the AP; receiving a second message from a second AP that includes second time information associated with the request message and the response message; receiving a third message from a third AP that includes third time information associated with the request message and the response message; and transmitting location configuration information to the wireless device for the wireless device to determine a position of the wireless device.

## Claims

### Claim 1

A method of a first access point (AP) for identifying a location of a wireless device, comprising:
transmitting a request message to the wireless device for identifying a position of the wireless device;
receiving a response message from the wireless device;
determining first time information based on a time of flight (ToF) of the request message and the response message, wherein the ToF corresponds to a distance of the wireless device from the AP;
receiving a second message from a second AP that includes second time information associated with the request message and the response message;
receiving a third message from a third AP that includes third time information associated with the request message and the response message; and
transmitting location configuration information to the wireless device for the wireless device to determine the position of the wireless device.

### Claim 2 (depends on 1)

The method of claim 1, further comprising:
subtracting a first predetermined time offset from the second time information based on a distance from the first AP to the second AP; and
subtracting a second predetermined time offset from the third time information based on a distance from the first AP to the third AP.

### Claim 3 (depends on 2)

The method of claim 2, further comprising determining a first distance to the first AP and a second distance to the second AP.

### Claim 4 (depends on 3)

The method of claim 3, wherein the first predetermined time offset corresponds to the first distance, and wherein the second predetermined time corresponds to the second distance.

### Claim 5 (depends on 1)

The method of claim 1, further comprising:
receiving a plurality of beacons transmitted from the second AP; and
identifying a clock drift associated with the second AP based on time information identified in the plurality of beacons.

### Claim 6 (depends on 5)

The method of claim 5, wherein at least some beacons of the plurality of beacons include a timestamp with nanosecond accuracy.

### Claim 7 (depends on 1)

The method of claim 1, wherein at least one of the second message and the third message are received on a backhaul network connection.

### Claim 8 (depends on 1)

The method of claim 1, wherein the first AP, the second AP, and the third AP are synchronized via a timing protocol via a backhaul network connection.

### Claim 9 (depends on 1)

The method of claim 1, wherein the wireless device computes a round trip time from the wireless device to the second AP and a round trip time to the third AP to determine the position.

### Claim 10 (depends on 1)

The method of claim 1, wherein the request message includes a timestamp, and wherein the second AP, the third AP, and the wireless device use the timestamp as a reference clock.

### Claim 11

A first access point (AP) for providing location estimation information, comprising:
a storage configured to store instructions;
a processor configured to execute the instructions and cause the processor to:
transmit a request message to a wireless device for identifying a position of the wireless device;
receive a response message from the wireless device;
determine first time information based on a time of flight (ToF) of the request message and the response message, wherein the ToF corresponds to a distance of the wireless device from the AP;
receive a second message from a second AP that includes second time information associated with the request message and the response message;
receive a third message from a third AP that includes third time information associated with the request message and the response message; and
transmit location configuration information to the wireless device for the wireless device to determine a position of the wireless device.

### Claim 12 (depends on 11)

The first AP of claim 11, wherein the processor is configured to execute the instructions and cause the processor to:
subtract a first predetermined time offset from the second time information based on a distance from the first AP to the second AP; and
subtract a second predetermined time offset from the third time information based on a distance from the first AP to the third AP.

### Claim 13 (depends on 12)

The first AP of claim 12, wherein the processor is configured to execute the instructions and cause the processor to: determine a first distance to the first AP and a second distance to the second AP.

### Claim 14 (depends on 13)

The first AP of claim 13, wherein the first predetermined time offset corresponds to the first distance, and wherein the second predetermined time corresponds to the second distance.

### Claim 15 (depends on 11)

The first AP of claim 11, wherein the processor is configured to execute the instructions and cause the processor to:
receive a plurality of beacons transmitted from the second AP; and
identify a clock drift associated with the second AP based on time information identified in the plurality of beacons.

### Claim 16 (depends on 15)

The AP of claim 15, wherein at least some beacons of the plurality of beacons include a timestamp with nanosecond accuracy.

### Claim 17 (depends on 11)

The first AP of claim 11, wherein at least one of the second message and the third message are received on a backhaul network connection.

### Claim 18 (depends on 11)

The first AP of claim 11, wherein the first AP, the second AP, and the third AP are synchronized via a timing protocol via a backhaul network connection.

### Claim 19 (depends on 11)

The first AP of claim 11, wherein the wireless device computes a round trip time from the wireless device to the second AP and a round trip time to the third AP to determine the position.

### Claim 20 (depends on 11)

The first AP of claim 11, wherein the request message includes a timestamp, and wherein the second AP, the third AP, and the wireless device use the timestamp as a reference clock.