Positioning with wireless local area networks and WLAN-aided global positioning systems

• US 20040162084A1
• Filed: 02/14/2003
• Published: 08/19/2004
• Est. Priority Date: 02/14/2003
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Atheros Communications Incorporated (Qualcomm, Inc.)
• Inventors: Wang, Yi-Hsiu
• Granted Patent: US 7,130,646 B2
• Time in Patent Office: Days
• US Class Current: 455/456.1
• CPC Class Codes: G01S 19/05 providing aiding data
• CPC Class Codes: G01S 19/06 employing an initial estimate of the location of the receiver as aiding data or in generating aiding data
• CPC Class Codes: G01S 19/252 Employing an initial estimate of location in generating assistance data
• CPC Class Codes: G01S 19/28 Satellite selection
• CPC Class Codes: G01S 19/29 carrier including Doppler, related G01S19/246 takes precedence
• CPC Class Codes: G01S 19/48 by combining or switching between position solutions derived from the satellite radio beacon positioning system and position solutions derived from a further system
• CPC Class Codes: G01S 5/12 by co-ordinating position lines of different shape, e.g. hyperbolic, circular, elliptical or radial
• CPC Class Codes: G01S 5/14 Determining absolute distances from a plurality of spaced points of known location
• CPC Class Codes: H04B 7/1851 Systems using a satellite or space-based relay H04B7/18508, H04B7/18521 take precedence; providing specific services H04B7/18523 - H04B7/18576
• CPC Class Codes: H04W 4/02 Services making use of location information
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]
• CPC Class Codes: H04W 88/08 Access point devices

Abstract

Accurate position capability can be quickly provided using a Wireless Local Area Network (WLAN). When associated with a WLAN, a wireless device can quickly determine its relative and/or coordinate position based on information provided by an access point in the WLAN. Before a wireless device disassociates with the access point, the WLAN can periodically provide time, location, and decoded GPS data to the wireless device. In this manner, the wireless device can significantly reduce the time to acquire the necessary GPS satellite data (i.e. on the order of seconds instead of minutes) to determine its coordinate position.

Claims

1. A method of determining a position of a wireless device, the method including:

identifying a first access point having a first known location and a predetermined radio propagation range of r, wherein the position of the wireless device is the first known location with an uncertainty of r.

2. The method of claim 1, further including:

determining a first radio signal strength indicator (RSSI) of the first access point; and

correlating the first RSSI to a first stored distance,

wherein the first stored distance represents a first relative distance from the first access point to the wireless device.

3. The method of claim 2, wherein correlating includes accessing a lookup table that correlates a plurality of RSSI values to their respective stored distances.

4. The method of claim 2, further including:

identifying a second access point and a third access point having a second known location and a third known location, respectively;

determining a second RSSI and a third RSSI of the second access point and the third access point, respectively;

correlating the second RSSI and the third RSSI to a second stored distance and a third stored distance, respectively, wherein the second stored distance represents a second relative distance from the second access point to the wireless device, and wherein the third stored distance represents a third relative distance from the third access point to the wireless device; and

computing a coordinate position of the wireless device using the first, second, and third known positions and the first, second, and third relative distances.

5. The method of claim 4,

wherein the first known position is (x1, y1, z1) and the first relative position is r1,

wherein the second known position is (x2, y2, z2) and the second relative position is r2,

wherein the third known position is (x3, y3, z3) and the third relative position is r3,

wherein the coordinate position of the wireless device is (x0, y0, z0) and

wherein computing the coordinate position includes using a set of equations:

x0=(w1*x1)+(w2*x2)+(w3*x3),y0=(w1*y1)+(w2*y2)+(w3*y3), andz0=(w1*z1)+(w2*z2)+(w3*z3),whereinw1=(1/r1)/(1/r1+1/r2+1/r3),w2=(1/r2)/(1/r1+1/r2+1/r3), andw3=(1/r3)/(1/r1+1/r2+1/r3).

6. The method of claim 1, further including:

determining whether the first access point uses multiple antennas;

if so, then

determining a radio signal strength indicator (RSSI) associated with each of the multiple antennas;

identifying a signal path of the antenna associated with a highest RSSI;

correlating the highest RSSI to a stored distance, wherein the stored distance represents a relative distance from the first access point to the wireless device; and

using angles of the signal path and the relative distance to compute a coordinate position of the wireless device.

7. The method of claim 6, wherein the angles include an angle θ

, which is measured taken from an x-axis to the signal path, and an angle Φ

, which is measured from the signal path to a path connecting the wireless device and the first access point.

8. The method of claim 7, wherein the coordinate position of the wireless device is (x4, y4, z4), wherein the relative position is r4, and wherein using angles of the signal path and the relative position to compute the coordinate position includes using a set of equations:

x4=x5+(r4*cos(Φ

)*cos(θ

)),y4=y5+(r4*cos(Φ

)*sin(74 )), andz4=z5+(r4*sin(Φ

)).

9. A method of determining a position of a device having wireless networking capability, the method including:

identifying a fixed position of an access point accessible by the device; and

computing the position of the device using short radio wave propagation between the access point and the device.

10. The method of claim 9, wherein computing the position includes:

determining a radio signal strength indicator (RSSI) of the access point; and

correlating the RSSI to a stored distance,

wherein the stored distance represents a relative distance from the access point to the device.

11. The method of claim 10, further including:

identifying fixed positions of multiple access points accessible by the device;

determining RSSIs of the multiple access points;

correlating the RSSIs to stored distances, wherein the stored distances represent relative distances from the multiple access points to the device; and

computing a coordinate position of the device using the fixed positions and the relative distances.

12. The method of claim 10, further including:

determining whether the access point uses multiple antennas;

if so, then

determining a radio signal strength indicator (RSSI) associated with each of the multiple antennas;

identifying a signal path of the antenna associated with a highest RSSI;

correlating the highest RSSI to a stored distance, wherein the stored distance represents a relative distance from the access point to the device; and

using angles of the signal path and the relative distance to compute a coordinate position of the device.

13. The method of claim 12, wherein the angles include an angle θ

, which is measured taken from an x-axis to the signal path, and an angle Φ

, which is measured from the signal path to a path connecting the device and the access point.

14. A method of determining a position of a device having wireless networking capability, the method including:

providing information from a wireless local area network (WLAN) to facilitate the determining using a global positioning system (GPS).

15. The method of claim 14, wherein the information from the WLAN includes decoded GPS data, a current time, and a recent position provided one of via and by the WLAN.

16. The method of claim 15, further including:

using the information from the WLAN, computing a first GPS satellite having a highest elevation angle from a set of GPS satellites.

17. The method of claim 16, further including:

searching for the first GPS satellite with multiple correlators.

18. The method of claim 17, wherein searching includes partitioning the multiple correlators into correlator pairs.

19. The method of claim 17, wherein searching includes partitioning the multiple correlators into correlator tracking sets.

20. The method of claim 17, wherein searching includes using a time offset and a frequency offset to find the first GPS satellite.

21. The method of claim 20, further including:

deriving time offsets and frequency offsets for additional GPS satellites using the time offset and the frequency offset that found the first GPS satellite.

22. A method of determining a new common position of a first device and a second device, the first and second devices having wireless networking capability, the method including:

exchanging information between the first device and the second device in an ad hoc communication mode, wherein the shared information includes last positions of the first and second devices and update times associated with the last positions.

23. The method of claim 22, wherein the last positions and the update times are provided by access points previously associated with the first and second devices.

24. The method of claim 23,

wherein the first client has a last position (x11, y11, z11), which was updated t1 seconds ago, and

wherein the second client has a last position (x12, y12, z12), which was updated t2 seconds ago, and further including:

computing the new common position (x, y, z) using a set of equations;

x=w1*x11+w2*x12y=w1*y11+w2*y12z=w1*z11+w2*z12

wherein weighting factors w1 and w2 are defined as;

w1=(1/t1)/(1/t1+1/t2)w2=(1/t2)/(1/t1+1/t2).

25. A wireless local area network (WLAN) system for facilitating providing a global positioning system (GPS) position of a client, the system including:

analog means for associating with the client, the analog means including a frequency synthesizer receiving one of a first signal associated with WLAN baseband operation and a second signal associated with GPS baseband operation;

an analog to digital conversion means; and

digital means for providing the WLAN baseband operation and the GPS baseband operation.

26. The WLAN system of claim 25, further including:

means for providing decoded GPS data to the client preceding disassociation of the client to the WLAN.