# US 9,883,342 B2 · Localization using access point

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- Number: US 9,883,342 B2
- Document ID: US9883342B2
- Status: Granted
- Kind: B2
- Application number: 15/114,875
- Filed: 2014-01-31
- Published: 2017-01-12
- Granted: 2018-01-30
- Earliest claimed: 2014-01-31
- Assignees: Hewlett Packard Enterprise Development LP
- Applicants: Hewlett Packard Enterprise Development LP
- Inventors: Souvik Sen; Jung Gun Lee; Alexander Timothy Mariakakis
- Web page: https://patentgrep.com/patent/US9883342B2

## CPC

- H04W 4/023: {using mutual or relative location information between multiple location based services [LBS] targets or of distance thresholds}
- G01S 5/0264: {at least one of the systems being a non-radio wave positioning system}
- G01S 5/0273: {using multipath or indirect path propagation signals in position determination}
- G01S 5/0294: {Trajectory determination or predictive filtering, e.g. target tracking or Kalman filtering}
- G01S 5/10: Position of receiver fixed by co-ordinating a plurality of position lines defined by path-difference measurements {, e.g. omega or decca systems}(G01S5/12 takes precedence {; beacons and receivers cooperating therewith G01S1/306, G01S1/308})
- H04W 64/00: Locating users or terminals {or network equipment} for network management purposes, e.g. mobility management
- H04W 4/027: {using movement velocity, acceleration information}
- 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

Localizing a location of a mobile device may be performed by obtaining times of flights between the mobile device and an access point at a first and second location. A heading of the mobile device and a distance between the first and second location may be further obtained. The times of flight, heading, and distance may be used to localize the second location.

## Claims

### Claim 1

A method, comprising:
obtaining a first time of flight between a mobile device at a first location and an access point;
obtaining a second time of flight between the mobile device at a second location and the access point;
obtaining a heading of the mobile device;
obtaining a distance between the first location and the second location;
using the first time of flight, the second time of flight, the heading, and the distance to localize the second location; wherein:
at least one of the first time of flight or the second time of flight is obtained using a channel impulse response to estimate a positive bias due to multipath and using the positive bias to calculate the first time of flight or the second time of flight.

### Claim 2 (depends on 1)

The method of claim 1, further comprising obtaining at least one of the first time of flight or the second time of flight by:
obtaining a plurality of channel impulse responses of a corresponding plurality of antennas of the access point, the channel impulse response being one of the plurality of the channel impulse responses;
combining a plurality of largest components of the channel impulse responses to determine the positive bias;
using the positive bias to determine a time of arrival; and
using the time of arrival to determine the first time of flight or the second time of flight.

### Claim 3 (depends on 1)

The method of claim 1, further comprising:
using the first time of flight to estimate a second distance between the first location and the access point;
using the second time of flight to estimate a third distance between the second location and the access point
obtaining a velocity estimate of the mobile device; and
using a Kalman filter applied to the velocity estimate to correct an error in the estimate of the third distance.

### Claim 4 (depends on 1)

The method of claim 1, further comprising obtaining the distance by using the accelerometer data to track a step length of a user of the mobile device as the mobile device travels from the first location to the second location by:
using a step bounce factor and a step frequency to identify a relationship between step frequency and step length for the user;
measuring the user's step frequency as the mobile device travels from the first location to the second location; and
using the relationship and the measured step frequency to track the step length as the mobile device travels from the first location to the second location.

### Claim 5 (depends on 1)

The method of claim 1, further comprising:
obtaining the heading by comparing a measured magnetic field characteristic to a reference magnetic field characteristic to determine if the measured magnetic field characteristic is valid.

### Claim 6

A system, comprising:
a distance calculator to:
use a first time of flight to determine a first distance between an access point and a mobile device at a first location;
use a second time of flight to determine a second distance between the access point and the mobile device at a second location; and
obtain a third distance between the first location and the second location; and
a localizer to use the first, second, and third distances to localize the second location; and
a time of flight calculator to:
obtain a channel impulse response for a channel between the access point and the mobile device;
use the channel impulse response to determine if a time of arrival of a packet from the mobile device to the access point corresponds to a reflected path between the mobile device and the access point; and
if the time of arrival corresponds to a reflected path, use the channel impulse response to obtain a time of arrival correction; and
use the time of arrival and time of arrival correction to calculate the first time of flight or the second time of flight.

### Claim 7 (depends on 6)

The system of claim 6, wherein the distance calculator is to:
use a fourth distance between the access point and the mobile device and a velocity estimate of the mobile device to determine the second distance using a Kalman filter, the fourth distance being determined before the second distance.

### Claim 8 (depends on 6)

The system of claim 6, wherein the time of flight calculator is to:
obtain a plurality of channel impulse responses for a plurality of signal paths between the mobile device and a corresponding plurality of antennas of the access point, the channel impulse response being one of the plurality of channel impulse responses;
estimate the time of arrival by combining a plurality of largest channel impulse response components of the plurality of channel impulse.

### Claim 9 (depends on 6)

The system of claim 6, wherein the time of flight calculator is to:
combine a plurality of times of arrivals from a plurality of transmissions received from the mobile device to calculate a combined time of arrival; and
use the combined time of arrival to calculate the first time of flight or the second time of flight.

### Claim 10 (depends on 6)

The system of claim 6, further comprising:
a step length calculator to:
determine a step length of a user of the mobile device by mapping a step bounce factor of the user to a relationship between step frequency and step length and tracking a step frequency of the user, and
provide a plurality of step lengths obtained while the user moves from the first location to the second location to the distance calculator.

### Claim 11

A non-transitory computer readable medium storing instructions executable by a processor to:
obtain a heading of a mobile device;
obtain a channel impulse response corresponding to an access point;
use the channel impulse response to estimate a positive bias due to multipath;
use the positive bias to calculate a time of flight;
use the time of flight to determine a first distance from the mobile device to the access point when the mobile device is at a first location;
obtain a second distance from the mobile device to the access point when the mobile device is at the second location;
track a step frequency of a user of the mobile device as the user travels from the first location to the second location;
use a relationship between step frequency and step length to determine a third distance between the first location and the second location; and
use the first distance, the second distance, the third distance, and the heading to localize the second location.

### Claim 12 (depends on 11)

The non-transitory computer readable medium of claim 11, wherein the instructions are further executable by the processor to:
obtain a step bounce factor of the user; and
use the step bounce factor to identify the relationship between step frequency and step length.

### Claim 13 (depends on 12)

The non-transitory computer readable medium of claim 12, wherein the instructions are further executable by the processor to:
obtain the step bounce factor by determining the standard deviation of a scalar projection of an acceleration measurement onto a gravitational measurement;
obtain a second step frequency; and
use the second step frequency and the step bounce size to identify the relationship.

### Claim 14 (depends on 11)

The non-transitory computer readable medium of claim 11, wherein the instructions are further executable by the processor to:
obtain a plurality of channel impulse responses of a corresponding plurality of antennas of the access point, the channel impulse response being one of the plurality;
combine a plurality of largest components of the channel impulse responses to determine the positive bias; use the positive bias to determine a time of arrival; and
use the time of arrival to determine the time of flight.