System and method for determining the location of a station in a wireless environment

• US 9,055,450 B2
• Filed: 09/23/2011
• Issued: 06/09/2015
• Est. Priority Date: 09/23/2011
• Status: Active Grant

• Current Assignee: Cambium Networks Limited (Cambium Networks Corporation)
• Original Assignee: Xirrus Incorporated
• Inventors: Hand, Alan Jeffrey, Mathews, James Kirk
• Primary Examiner(s): Iqbal, Khawar
• Application Number:
  US13/242,710
• Publication Number:
  US 20130079027A1
• Time in Patent Office: 1,355 Days
• Field of Search: 4554561-4566, 455/67.11, 455/41.2, 455/446, 455522-524, 340/8.1, 340/539.11, 340/539.13
• US Class Current: 1/1
• CPC Class Codes: H04B 17/318 Received signal strength
• CPC Class Codes: H04L 41/142 using statistical or mathematical methods
• CPC Class Codes: H04W 16/24 Cell structures
• CPC Class Codes: H04W 24/00 Supervisory, monitoring or testing arrangements
• CPC Class Codes: H04W 24/08 Testing, supervising or monitoring using real traffic
• CPC Class Codes: H04W 64/003 locating network equipment

Abstract

A system for quantifying the shadow fading observed in a wireless environment having multiple wireless access points is also provided. A distance determination module is in signal communication with the wireless access points. The distance determination module determines a distance between a pair of the wireless access points based on location information that relates to the locations of the wireless access points at the wireless environment. A shadow fading determination module is also in signal communication with the wireless access points. The shadow fading determination module determines a shadow fading factor based on the distance between a pair of the wireless access points and based on RSS information received from one of the wireless access points in the pair of wireless access points.

Claims

1. A computer-implemented method of quantifying shadow fading observed in a wireless environment having a plurality of wireless access points comprising:

receiving location information relating to respective locations of the plurality of wireless access points in the wireless environment;

determining a distance between a pair of wireless access points of the plurality of wireless access points based on the location information; and

determining a shadow fading factor based on the distance between the pair of wireless access points and based on received signal strength (RSS) information received from one of the wireless access points in the pair of wireless access points;

wherein;

the RSS information relates to a signal strength of at least one wireless signal transmitted between the pair of wireless access points; and

the shadow fading factor is determined using a path loss model and an RSS model; and

wherein;

the path loss model is expressed as PL=PL_ref+10 log(Dⁿ)+S, where PL represents the difference between the transmitted signal power and the received signal power;

PL_ref represents a reference path loss in dB between the transmitted signal power and the received signal power when the pair of wireless access points are around one meter apart with no obstructions in between;

D represents the distance in meters between the pair of wireless access points;

n represents a path loss exponent for a wireless environment; and

S represents a shadow fading factor; and

the RSS model is expressed as Rx_pwr=Tx_pwr−

L_Tx+G_Tx−

PL−

L_Rx−

G_Rx, where Rx_pwr is the RSS in dB;

Tx_pwr is the output power of the transmitter;

L_Tx is the sum of all cable and connector losses in dB at the transmitter;

G_Tx is the antenna gain at the transmitter in dBi (decibel isotropic);

PL is the path loss of the wireless signal in dB;

L_Rx is the sum of all cable and connector losses in dB at the receiver; and

G_Rx is the antenna gain at the receiver in dBi.

2. The computer-implemented method of claim 1 further comprising:

selecting a plurality of transceiver pairings from the plurality of wireless access points;

determining a distance between individual wireless access points associated with the transceiver pairings to obtain a plurality of distances;

determining a plurality of shadow fading factors based on the plurality of distances and RSS information respectively associated with the plurality of transceiver pairings; and

determining an average shadow fading factor based on the plurality of shadow fading factors.

3. The computer-implemented method of claim 1 further comprising:

displaying a map of the wireless environment; and

receiving the location information as user input wherein the user input relates to positions on the map and wherein the positions on the map correspond to the respective locations of the plurality of wireless access points at the wireless environment.

4. A system for quantifying the shadow fading observed in a wireless environment having a plurality of wireless access points comprising:

a distance determination module of a network management system in signal communication with the plurality of wireless access points, where the distance determination module determines a distance between a pair of wireless access points in the plurality of wireless access points based on location information that relates to respective locations of the plurality of wireless access points at the wireless environment; and

a shadow fading determination module of the network management system in signal communication with the plurality of wireless access points, where the shadow fading determination module determines a shadow fading factor based on the distance between the pair of wireless access points and based on received signal strength (RSS) information received from one of the wireless access points of the pair of wireless access points;

wherein;

the RSS information relates to a signal strength of at least one wireless signal transmitted between the pair of wireless access points; and

the shadow fading determination module determines the shadow fading factor using a path loss model and an RSS model; and

wherein;

the path loss model is expressed as PL=PL_ref+10 log(Dⁿ)+S, where PL represents the difference between the transmitted signal power and the received signal power;

PL_ref represents a reference path loss in dB between the transmitted signal power and the received signal power when the pair of wireless access points are around one meter apart with no obstructions in between;

D represents the distance in meters between the pair of wireless access points;

n represents a path loss exponent for a wireless environment; and

S represents a shadow fading factor; and

the RSS model is expressed as Rx_pwr=Tx_pwr−

L_Tx+G_Tx−

PL−

L_Rx−

G_Rx, where Rx_pwr is the RSS in dB;

Tx_pwr is the output power of a transmitter of a wireless access point of the pair of wireless access points that transmits the wireless signal;

L_Tx is the sum of all cable and connector losses in dB at the transmitter;

G_Tx is the antenna gain at the transmitter in dBi (decibel isotropic);

PL is the path loss of the wireless signal in dB;

L_Rx is the sum of all cable and connector losses in dB at a receiver of the other wireless access point of the pair of wireless access points; and

G_Rx is the antenna gain at the receiver in dBi.

5. The system of claim 4 wherein:

the distance determination module selects a plurality of transceiver pairings from the plurality of wireless access points;

the distance determination module determines a distance between individual wireless access points associated with the transceiver pairings to obtain a plurality of distances;

the shadow fading determination module determines a plurality of shadow fading factors based on the plurality of distances and RSS information respectively associated with the transceiver pairings; and

the shadow fading determination module determines an average shadow fading factor based on the plurality of shadow fading factors.

6. The system of claim 4 further comprising an interface module that displays a map of the wireless environment and receives the location information as user input wherein the user input relates to positions on the map and wherein the positions on the map correspond to the respective locations of the plurality of wireless access points at the wireless environment.

7. A computer-implemented method of localizing a station in a wireless environment having a plurality of wireless access points comprising:

determining a shadow fading factor for the wireless environment;

determining a plurality of distances between the station and individual wireless access points in the plurality of wireless access points based on the shadow fading factor for the wireless environment and based on received signal strength (RSS) information received from the individual wireless access points;

identifying a sub-region in the wireless environment that the station is located in based on the plurality of distances; and

identifying a location associated with the sub-region that corresponds to an approximate location of the station at the wireless environment;

wherein;

the RSS information relates to signal strengths of at least one wireless signal respectively transmitted between the station and the individual wireless access points, and

individual distances in the plurality of distances are determined using a path loss model and an RSS model; and

wherein;

the path loss model is expressed as PL=PL_ref+10 log(Dⁿ)+S where PL represents the difference between the transmitted signal power and the received signal power;

PL_ref represents a reference path loss in dB between the transmitted signal power and the received signal power when the station and the individual wireless access points are around one meter apart with no obstructions in between;

D represents the distance in meters between the station and the individual wireless access points;

n represents a path loss exponent for a wireless environment; and

S represents a shadow fading factor; and

the RSS model is expressed as Rx_pwr=Tx_pwr−

L_Tx+G_Tx−

PL−

L_Rx−

G_Rx, where Rx_pwr is the RSS in dB;

Tx_pwr is the output power of the station;

L_Tx is the sum of all cable and connector losses in dB at the station;

G_Tx is the antenna gain at the station in dBi (decibel isotropic);

PL is the path loss of the wireless signal in dB;

L_Rx is the sum of all cable and connector losses in dB at the individual wireless access points; and

G_Rx is the antenna gain at the individual wireless access points in dBi.

8. The computer-implemented method of claim 7 wherein:

the group of wireless access points includes at least three wireless access points;

identifying a sub-region in the wireless environment that the station is located in includes;

identifying respective circular regions for the individual wireless access points wherein respective radii of the circular regions respectively correspond to the individual distances in the plurality of distances and wherein centers of the circular regions respectively correspond to locations of the individual wireless access points at the wireless environment; and

identifying an overlapping region corresponding to an intersection of the circular regions; and

identifying a location associated with the sub-region that corresponds to an approximate location of the station in the wireless environment includes;

determining a center of the overlapping region; and

identifying the center of the overlapping region as the location that corresponds to the approximate location of the station at the wireless environment.

9. The computer-implemented method of claim 7 wherein:

the group of wireless access points includes two wireless access points, the wireless access points each having a plurality of transceivers and a magnetometer that determines a spatial orientation of the wireless access point;

the plurality of distances between the station and the individual wireless access points includes distances between the station and individual transceivers in the plurality of transceivers; and

identifying a sub-region in the wireless environment that the station is located in includes;

identifying a plurality of triangular sub-regions of the wireless environment based on respective spatial orientations of the individual transceivers and the respective distances between the station and the individual transceivers; and

determining that one of the triangular sub-regions in the plurality of triangular sub-regions is the sub-region in the wireless environment that the station is located in.

10. The computer-implemented method of claim 9 wherein:

individual triangular sub-regions in the plurality of triangular sub-regions have vertices corresponding to a set of three coordinates in the wireless environment; and

individual coordinates in the set of coordinates correspond to a spatial orientation of one of the transceivers and a distance between the station and the transceiver.

11. The computer-implemented method of claim 9 wherein:

determining that one of the triangular sub-regions in the plurality of triangular sub-regions is the sub-region in the wireless environment that the station is located in includes;

determining respective areas for individual triangular sub-regions in the plurality of triangular sub-regions;

identifying a triangular sub-region in the plurality of triangular sub-regions having the smallest area; and

determining that the triangular sub-region having the smallest area is the triangular sub-region the station is located in.

12. The computer-implemented method of claim 11 wherein identifying a location associated with the sub-region that corresponds to an approximate location of the station in the wireless environment includes:

determining a center of the triangular sub-region the station is located in; and

identifying the center of the triangular sub-region the station is located in as the location that corresponds to the approximate location of the station in the wireless environment.

13. The computer-implemented method of claim 12 wherein the center of the triangular sub-region the station is located in is the circumcenter.

14. The computer-implemented method of claim 9 further comprising determining the respective spatial orientations of the individual transceivers in the individual wireless arrays based on orientation information received from the individual wireless arrays.

15. A system for localizing a station in a wireless environment having a plurality of wireless access points comprising:

a shadow fading determination module of a network management system in signal communication with the plurality of wireless access points that determines a shadow fading factor for the wireless environment;

a distance determination module of a network management system that determines a plurality of distances between the station and individual wireless access points in the plurality of wireless access points based on the shadow fading factor for the wireless environment and based on received signal strength (RSS) information received from individual wireless access points in the plurality of access points; and

a localization module of a network management system that identifies a sub-region in the wireless environment that the station is located in based on the plurality of distances and identifies a location associated with the sub-region that corresponds to an approximate location of the station at the wireless environment;

wherein;

the RSS information relates to signal strengths of at least one wireless signal respectively transmitted between the station and the individual wireless access points, and

individual distances in the plurality of distances are determined using a path loss model and an RSS model; and

wherein;

the path loss model is expressed as PL=PL_ref+10 log(Dⁿ)+S, where PL represents the difference between the transmitted signal power and the received signal power;

PL_ref represents a reference path loss in dB between the transmitted signal power and the received signal power when the station and the individual wireless access points are around one meter apart with no obstructions in between;

D represents the distances in meters between the station and the individual wireless access points;

n represents a path loss exponent for a wireless environment; and

S represents a shadow fading factor; and

the RSS model is expressed as Rx_pwr=Tx_pwr−

L_Tx+G_Tx−

PL−

L_Rx−

G_Rx, where Rx_pwr is the RSS in dB;

Tx_pwr is the output power of the transmitter;

L_Tx is the sum of all cable and connector losses in dB at the station;

G_Tx is the antenna gain at the station in dBi (decibel isotropic);

PL is the path loss of the wireless signal in dB;

L_Rx is the sum of all cable and connector losses in dB at the individual wireless access points and G_Rx is the antenna gain at the individual wireless access points in dBi.

16. The system of claim 15 wherein:

the group of wireless access points includes at least three wireless access points;

the localization module identifies respective circular regions for the individual wireless access points wherein respective radii of the circular regions respectively correspond to the distances between the station and the individual wireless access points and wherein respective centers of the circular regions respectively correspond to locations of the individual wireless access points at the wireless environment;

the localization module identifies an overlapping region corresponding to an intersection of the circular regions;

the localization module determines a center of the overlapping region, and

the localization module identifies the center of the overlapping region as the location that corresponds to the approximate location of the station in the wireless environment.

17. The system of claim 15 wherein:

the group of wireless access points includes two wireless access points, the wireless access points each having a plurality of transceivers and a magnetometer that determines a spatial orientation the wireless access points;

the distance module determines a plurality of distances between the station and individual transceivers in the plurality of transceivers based on the RSS information and the shadow fading factor;

the localization module identifies a plurality of triangular sub-regions of the wireless environment based on respective spatial orientations of the individual transceivers and the respective distances between the station and the individual transceivers; and

the localization module determines that one of the triangular sub-regions in the plurality of triangular sub-regions is the sub-region in the wireless environment that the station is located in.

18. The system of claim 17 wherein:

individual triangular sub-regions in the plurality of triangular sub-regions have vertices corresponding to a set of three coordinates in the wireless environment; and

individual coordinates in the set of coordinates correspond to a spatial orientation of one of the transceivers and a distance between the station and the transceiver.

19. The system of claim 17 wherein the localization module:

determines respective areas for individual triangular sub-regions in the plurality of triangular sub-regions;

identifies a triangular sub-region in the plurality of triangular sub-regions having the smallest area; and

determines that the triangular sub-region having the smallest area is the triangular sub-region the station is located in.

20. The system of claim 19 wherein the localization module:

determines a center of the triangular sub-region the station is located in; and

identifies the center of the triangular sub-region the station is located in as the location that corresponds to the approximate location of the station in the wireless environment.

21. The system of claim 20 wherein the center of the triangular sub-region the station is located in is a circumcenter.

22. The system of claim 17 wherein the localization module determines the respective spatial orientations of individual transceivers in the plurality of transceivers of the individual wireless arrays based on orientation information received from the individual wireless arrays.