# US 2019/0174332 A1 · Method to estimate and compensate for nlos bias in time difference of arrival estimate

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 2019/0174332 A1
- Document ID: US20190174332A1
- Status: Published application
- Kind: A1
- Application number: 16/266,517
- Filed: 2019-02-04
- Published: 2019-06-06
- Earliest claimed: 2015-09-14
- Assignees: Red Point Positioning Corporation
- Applicants: Red Point Positioning Corporation
- Inventors: Chunjie DUAN; Georgiy PEKHTERYEV; Zhenzhen YE; Yu Zhao
- Web page: https://patentgrep.com/patent/US20190174332A1

## CPC

- H04W 24/02: Arrangements for optimising operational condition
- G01S 1/20: using a comparison of transit time of synchronised signals transmitted from non-directional antennas or antenna systems spaced apart, i.e. path-difference systems
- G01S 5/0081: {Transmission between base stations}
- G01S 5/0226: {Transmitters}
- G01S 5/0273: {using multipath or indirect path propagation signals in position determination}
- G01S 5/06: Position of source determined by co-ordinating a plurality of position lines defined by path-difference measurements (G01S5/12 takes precedence)
- H04W 24/10: Scheduling measurement reports {; Arrangements for measurement reports}
- H04W 64/00: Locating users or terminals {or network equipment} for network management purposes, e.g. mobility management
- H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72)
- 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

Devices, systems, and method for compensating for non-line-of-sight (“NLOS”) bias in time difference of arrival (“TDOA”) estimates between a first anchor and a second anchor in a network having an obstacle in the line-of-sight therebetween are provided. The systems and methods include transmitting a first packet from a first anchor; indirectly receiving the first packet by a second anchor, then transmitting a second packet by the second anchor; indirectly receiving the second packet by the first anchor; and receiving the first packet and the second packet by a mobile node. The true fly-time of the first or second packets between the first anchor and the second anchor and the bias in time of flight of the first or second packets between the first anchor and the second anchor are estimated. The time difference of arrival at the mobile device between a direct path and an indirect path is further estimated and the NLOS bias in the time difference of arrival estimated at the mobile device is corrected.

## Claims

### Claim 1

A method for compensating for non-line-of-sight (“NLOS”) bias in time difference of arrival (“TDOA”) estimate between a first anchor and a second anchor in a network having an obstacle in the line-of-sight therebetween, the method comprising:
transmitting a first packet from a first anchor;
indirectly receiving the first packet by a second anchor, then transmitting a second packet by the second anchor;
indirectly receiving the second packet by the first anchor;
receiving the first packet and the second packet by a mobile node;
estimating the true fly-time of the first or second packets between the first anchor and the second anchor;
estimating the bias in time of flight of the first or second packets between the first anchor and the second anchor;
estimating the time difference of arrival at the mobile device between a direct path and an indirect path;
correcting the NLOS bias in the time difference of arrival estimated at the mobile device.

### Claim 2 (depends on 1)

The method of claim 1, wherein the estimating and correcting is performed by the first and second anchors.

### Claim 3 (depends on 1)

The method of claim 1, wherein the estimating of fly-time is performed by the first anchor.

### Claim 4 (depends on 1)

The method of claim 1, wherein correcting the NLOS bias in the time difference of arrival is performed by the mobile device.

### Claim 5 (depends on 1)

The method of claim 1, wherein the estimated bias is filtered.

### Claim 6 (depends on 1)

The method of claim 1, wherein the true locations of the first anchor and the second anchor are known.

### Claim 7 (depends on 1)

The method of claim 1, wherein the estimated bias is embedded in a packet and transmitted.

### Claim 8 (depends on 1)

The method of claim 1, wherein the bias between the first and second anchors is compensated, according to:
ΔRAB=tAB*c−RAB=ΔtA/2*c−RAB,
where tAB is the time of travel of the first packet from the first anchor to the second anchor, and
wherein RAB is the direct path between the first and second anchors.

### Claim 9 (depends on 1)

The method of claim 1, wherein the estimated bias between anchors is used directly in estimating a corrected distance difference, according to:
ΔRCAB=ΔRMAB−ΔRAB
wherein ΔRMAB is the original distance difference measured at the mobile device.

### Claim 10 (depends on 1)

The method of claim 1, wherein the true fly-time between the first and second anchor is embedded in a first packet and transmitted.

### Claim 11 (depends on 1)

The method of claim 1, wherein the true locations of one or both of the first and second anchors are unknown.

### Claim 12 (depends on 1)

The method of claim 1, wherein the NLOS bias between the first and second anchors is estimated and updated a plurality of times.

### Claim 13 (depends on 1)

The method of claim 1, wherein the NLOS bias between the first and second anchors is estimated during the initial setup of the network.

### Claim 14 (depends on 1)

The method of claim 1 further comprising,
estimating the position of the mobile device in an external computing device.

### Claim 15

A method to compensate for non-line-of-sight (“NLOS”) bias in a time difference of arrival estimate, using an uplink time difference of arrival (“UL-TDOA”) scheme, the method comprising:
transmitting a first packet by a mobile device;
receiving the first packet by at least one first anchor and then transmitting a second packet by the at least one first anchor;
receiving the first packet and the second packet by at least one second anchor in range of the mobile device and at least one first anchor;
estimating the time differences of arrival at the at least one second anchor; and
correcting the time differences of arrival at the at least one second anchor by subtracting the NLOS bias between the at least one first anchor and at least one second anchor.

### Claim 16 (depends on 15)

The method of claim 15 further comprising,
estimating the position of the mobile device using the corrected time differences of arrival.

### Claim 17 (depends on 16)

The method of claim 16, wherein estimating the position of the mobile device is done in an external computing device.

### Claim 18

A method to compensate for the non-line-of-sight (“NLOS”) bias in a beacon synchronized time difference of arrival (“BS-TDOA”) estimate, the method comprising:
transmitting a first packet by a first anchor;
receiving the first packet by a mobile node and then transmitting a second packet by the mobile node;
receiving the first packet and the second packet by at least one second anchor that is within range of the first anchor and the mobile node; and
measuring the time differences of arrival between a direct packet transmission path and an indirect packet transmission path by the at least one second node;
correcting the time differences of arrival with an estimated bias of fly-time between the first anchor and at least one second anchor.

### Claim 19 (depends on 18)

The method of claim 18 further comprising,
estimating the position of the mobile device using the corrected time differences of arrival.

### Claim 20 (depends on 19)

The method of claim 19, wherein estimating the position of the mobile device is done in an external computing device.