Method and system for wireless LAN-based indoor position location

• US 8,737,279 B1
• Filed: 03/27/2012
• Issued: 05/27/2014
• Est. Priority Date: 12/17/2008
• Status: Active Grant

• Current Assignee: Avaya Incorporated
• Original Assignee: Avaya Incorporated
• Inventors: Aweya, James, Orozco-Barbosa, Luis
• Primary Examiner(s): Ng, Fan
• Application Number:
  US13/431,423
• Time in Patent Office: 791 Days
• Field of Search: 370310-350
• US Class Current: 370/310
• CPC Class Codes: G01S 13/46 Indirect determination of position data
• CPC Class Codes: 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
• CPC Class Codes: G01S 2013/466 by Trilateration, i.e. two antennas or two sensors determine separately the distance to a target, whereby with the knowledge of the baseline length, i.e. the distance between the antennas or sensors, the position data of the target is determined
• CPC Class Codes: G01S 5/14 Determining absolute distances from a plurality of spaced points of known location
• CPC Class Codes: H04J 3/0667 Bidirectional timestamps, e.g. NTP or PTP for compensation of clock drift and for compensation of propagation delays arrangements for monitoring round trip delays in packet switching networks H04L43/0864

Abstract

A method and system for position location of clients in wireless local area networks. (WLANs). The position location technique utilizes time-of-flight (TOF) measurements of signals transmitted from a client to a number of wireless access points (APs) or vice versa to determine distances. Round-trip time (RTT) measurement protocols are used to estimate TOF and distances between the client at an unknown position and the WLAN APs. The method and system improves positioning accuracy by identifying and mitigating non-line-of sight (NLOS) errors such as multipaths. Trilateration algorithms are utilized in combination with median filtering of measurements to accurately estimate the position of the client.

Claims

1. A system for determining a location of a client in a local area network, the local area network including one or more access points in communication with the client, the system comprising:

a ranging subsystem configured to determine estimated distances between the client and each of the one or more access points, each of the one or more access points having a known position; and

a positioning subsystem including a virtual reference station, the positioning subsystem being separate from the client and the one or more access points, the positioning subsystem configured to determine the location of the client utilizing;

the estimated distances between the client and the virtual reference station, and the client and the one or more access points; and

the known position of the virtual reference station and the one or more access points.

2. The system of claim 1, wherein the positioning subsystem includes a location management station in communication with the virtual reference station and the one or more access points over a packet network, the location management station:

receiving, from the virtual reference station and each of the one or more access points, signals representing the estimated distances between;

the client and the virtual reference station; and

the client and the one or more access points; and

determining the location of the client based upon the estimated distances.

3. The system of claim 1, wherein the virtual reference station forwards client location information.

4. The system of claim 1, wherein the ranging subsystem uses time-of-flight measurements to estimate the distance between:

the client and the one or more access points; and

the client and the virtual reference station.

5. The system of claim 1, wherein the positioning subsystem uses a trilateration process to determine the location of the client.

6. The system of claim 5, wherein a number of access points in the local area network is greater than a number of access points needed to perform the trilateration process.

7. The system of claim 5, wherein the virtual reference station does not participate in the trilateration process.

8. The system of claim 1, wherein the positioning subsystem utilizes median filtering of the estimated distance between the client and the one or more access points, and the client and the virtual reference station to determine the position of the client.

9. A system for determining a location of a client in a local area network, the local area network including one or more access points in communication with the client, the system comprising:

a ranging subsystem for determining estimated distances between the client and the one or more access points, each of the one or more access points having a known position; and

a positioning subsystem including a virtual reference station, the positioning subsystem determining the location of the client utilizing;

the estimated distance between the client and the virtual reference station, and the client and the one or more access points; and

the known position of the virtual reference station and the one or more access points,

the positioning subsystem using a trilateration process to determine the location of the client, and the virtual reference station not participating in the trilateration process.

10. A method of determining a location of a client in a local area network, the local area network including a virtual reference station and one or more access points in communication with the client, the virtual reference station and each of the one or more access points having a predetermined position, the method comprising:

receiving, from the virtual reference station and one or more access points, ranging protocol signals used to estimate distances from;

the virtual reference station to the client; and

each access point to the client; and

calculating, by the virtual reference station, the location of the client based on the estimated distances and the positions of each access point, the virtual reference station being separate from the client and the one or more access points.

11. The method of claim 10, further comprising forwarding client location information.

12. The method of claim 10, further comprising using time-of-flight measurements to estimate the distances between the client and the virtual reference station, and the client and the one or more access points.

13. The method of claim 10, further comprising using a trilateration process to calculate the location of the client.

14. The method of claim 13, wherein a number of access points in the local area network is greater than a number of access points needed in the trilateration process.

15. The method of claim 13, wherein the virtual reference station does not participate in the trilateration process.

16. The method of claim 10, further comprising using median filtering of the estimated distances between the client and the virtual reference station, and the client and the one or more access points to calculate the position of the client.

17. A method of determining a location of a client in a local area network, the local area network including a virtual reference station and one or more access points in communication with the client, the virtual reference station and each of the one or more access points having a predetermined position, the method comprising:

receiving, from the virtual reference station and one or more access points, ranging protocol signals used to estimated distances from;

the virtual reference station to the client; and

each access point to the client;

calculating the location of the client based on the estimated distances and the position of each access point; and

using a trilateration process to calculate the location of the client, the virtual reference station not participating in the trilateration process.

18. A location management station for determining a location of a client in a local area network having a virtual reference station and one or more access points, the virtual reference station and each of the one or more access points having a predetermined position, the location management station being separate from the client and the one or more access points, the location management station comprising:

an interface module adapted to receive, from the virtual reference station and the one or more access points, signals representing estimated distances from the virtual reference station to the client and from each access point to the client; and

a processor adapted to calculate the location of the client based on;

the estimated distances from the virtual reference station to the client, and each access point to the client; and

the position of the virtual reference station and each access point.

19. The location management station of claim 18, wherein upon a request from an external entity, the location management station calculates the location of the client and forwards client location information to the requesting external entity.

20. The location management station of claim 18, wherein the processor uses a trilateration process to determine the location of the client.

21. The location management station of claim 20, wherein the virtual reference station does not participate in the trilateration process.

22. The location management station of claim 18, wherein the estimated distances from each access point to the client is determined by a two-way ranging protocol.

23. A location management station for determining a location of a client in a local area network having a virtual reference station and one or more access points, the virtual reference station and each of the one or more access points having a predetermined position, the station comprising:

an interface module adapted to receive, from the virtual reference station and the one or more access points, signals representing estimated distances from the virtual reference station and each access point to the client; and

a processor for calculating the location of the client based on;

the estimated distances from the virtual reference station to the client, and each access point to the client; and

the position of the virtual reference station and each access point,

the processor using a trilateration process to determine the location of the client, the virtual reference station not participating in the trilateration process.