Radio frequency coverage map generation in wireless networks

• US 7,983,667 B2
• Filed: 10/05/2006
• Issued: 07/19/2011
• Est. Priority Date: 10/05/2006
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Paranjpe, Milind, Friday, Robert J., Hart, Brian Donald
• Primary Examiner(s): Eng; George
• Assistant Examiner(s): Gao; Jing (Kristen)
• Application Number:
  US11/543,747
• Publication Number:
  US 20080085692A1
• Time in Patent Office: 1,748 Days
• Field of Search: 455/423, 455/456.1
• US Class Current: 455/423
• CPC Class Codes: H04B 17/318 Received signal strength
• CPC Class Codes: H04B 17/3913 Predictive models, e.g. based on neural network models
• CPC Class Codes: H04W 16/20 for indoor coverage or short range network deployment

Abstract

In one embodiment, a method for generating a radio-frequency coverage map. The method includes receiving coverage map data comprising a plurality of locations within a region, and an identification of a location in the plurality of locations corresponding to a radio transceiver, wherein the locations within the region are represented by at least corresponding x- and y-terms of a Cartesian coordinate system. The method further includes receiving calibration data comprising a plurality of observed signal strength values at corresponding ones of the plurality of locations, converting the x- and y-terms of the locations of the coverage map data to corresponding first and second warped coordinate terms of a warped coordinate system, and computing, using linear interpolation and the first and second warped coordinate terms, predicted received signal strength values at one or more locations in the coverage map based on the calibration data.

Claims

1. Logic encoded in one or more storage media for execution and when executed operable to:

receive coverage map data comprising a plurality of locations within a region, and an identification of a location in the plurality of locations corresponding to a radio transceiver, wherein the locations within the region are represented by at least corresponding x- and y-terms of a Cartesian coordinate system;

receive calibration data comprising a plurality of observed signal strength values at corresponding ones of the plurality of locations;

convert the x- and y-terms of the locations of the coverage map data to corresponding first and second warped coordinate terms of a warped coordinate system;

compute, using linear interpolation and the first and second warped coordinate terms, predicted received signal strength values at one or more locations within a convex hull defined by the plurality of locations corresponding to the calibration data in the coverage map based on the calibration data; and

extrapolate, for one or more locations of the coverage map outside of the convex hull, predicted received signal strength values based on a power path loss model and interpolated received signal strength values within the convex hull;

wherein, to extrapolate predicted received signal strength values for locations outside the convex hull, the logic is further operable to;

compute a first received signal strength value at a desired location based on a pathloss model;

determine a convex hull intersection, wherein the convex hull is an area defined by three or more calibration points, wherein the convex hull intersection is the intersection of the convex hull and a line extending between a wireless access point and the desired location;

compute a second received signal strength value at the convex hull intersection based on using the pathloss model;

compute a third received signal strength value at the intersection using interpolation of calibration data; and

compute a predicted received signal strength value based on the first, second, and third received signal strength values.

2. The logic of claim 1 wherein, in the warped coordinate system,

an origin is the location in the region corresponding to the radio transceiver;

D is the distance between the origin and a given location;

θ

is the angle from a fixed line passing through the origin and the given location relative to a reference line; and

for each location in the region, the first warped coordinate term is (log 10 D)cos θ

, and the second warped coordinate term is (log 10 D)sin θ

.

3. The logic of claim 1 wherein a location of the wireless access point is at an origin of the warped coordinate system.

4. The logic of claim 1 wherein the logic is further operable to convert the predicted received signal strength values from a warped coordinate system data to the Cartesian coordinate system data.

5. The logic of claim 1 wherein the logic is further operable to account for walls inside the convex hull, walls partially inside and partially outside the convex hull, and walls outside the convex hull.

6. The logic of claim 1 wherein the warped coordinate system is based on a logarithmic function.

7. A method comprising:

receiving coverage map data comprising a plurality of locations within a region, and an identification of a location in the plurality of locations corresponding to a radio transceiver, and wherein the locations within the region are represented by at least corresponding x- and y-terms of a Cartesian coordinate system;

receiving calibration data comprising a plurality of observed signal strength values at corresponding ones of the plurality of locations;

converting the x- and y-terms of the locations of the coverage map data to corresponding first and second warped coordinate terms of a warped coordinate system; and

computing, using linear interpolation and the first and second warped coordinate terms, predicted received signal strength values at one or more locations within a convex hull defined by the plurality of locations corresponding to the calibration data in the coverage map based on the calibration data; and

extrapolating, for one or more locations of the coverage map outside of the convex hull, predicted received signal strength values based on a power path loss model and interpolated received signal strength values within the convex hull;

wherein extrapolating predicted received signal strength values for locations outside the convex hull comprises;

computing a first received signal strength value at a desired location based on a pathloss model;

determining a convex hull intersection, wherein the convex hull is an area defined by three or more calibration points, wherein the convex hull intersection is the intersection of the convex hull and a line extending between a wireless access point and the desired location;

computing a second received signal strength value at the convex hull intersection based on using the pathloss model;

computing a third received signal strength value at the intersection using interpolation of calibration data; and

computing a predicted received signal strength value based on the first, second, and third received signal strength values.

8. The method of claim 7 wherein, in the warped coordinate system,

an origin is the location in the region corresponding to the radio transceiver;

D is the distance between the origin and a given location;

θ

is the angle from a fixed line passing through the origin and the given location relative to a reference line; and

for each location in the region, the first warped coordinate term is (log 10 D)cos θ

, and the second warped coordinate term is (log 10 D)sin θ

.

9. The method of claim 7 wherein a location of the wireless access point is at an origin of the warped coordinate system.

10. The method of claim 7 further comprising converting the predicted received signal strength values from a warped coordinate system data to the Cartesian coordinate system data.

11. The method of claim 7 further comprising accounting for walls inside the convex hull, walls partially inside and partially outside the convex hull, and walls outside the convex hull.

12. The method of claim 7 wherein the warped coordinate system is based on a logarithmic function.

13. A system comprising:

a coverage map generator node operable to;

receive coverage map data comprising a plurality of locations within a region, and an identification of a location in the plurality of locations corresponding to a radio transceiver, wherein the locations within the region are represented by at least corresponding x- and y-terms of a Cartesian coordinate system;

receive calibration data comprising a plurality of observed signal strength values at corresponding ones of the plurality of locations;

convert the x- and y-terms of the locations of the coverage map data to corresponding first and second warped coordinate terms of a warped coordinate system;

compute, using linear interpolation and the first and second warped coordinate terms, predicted received signal strength values at one or more locations within a convex hull defined by the plurality of locations corresponding to the calibration data in the coverage map based on the calibration data; and

extrapolate, for one or more locations of the coverage map outside of the convex hull, predicted received signal strength values based on a power path loss model and interpolated received signal strength values within the convex hull;

wherein the coverage map generator node, to extrapolate predicted received signal strength values for locations outside the convex hull, is further operable to;

compute a first received signal strength value at a desired location based on a pathloss model;

determine a convex hull intersection, wherein the convex hull is an area defined by three or more calibration points, wherein the convex hull intersection is the intersection of the convex hull and a line extending between a wireless access point and the desired location;

compute a second received signal strength value at the convex hull intersection based on using the pathloss model;

compute a third received signal strength value at the intersection using interpolation of calibration data; and

compute a predicted received signal strength value based on the first, second, and third received signal strength values; and

a wireless access point operable to facilitate collection of the calibration data.

14. The system of claim 13 wherein, in the warped coordinate system,

an origin is the location in the region corresponding to the radio transceiver;

D is the distance between the origin and a given location;

θ

is the angle from a fixed line passing through the origin and the given location relative to a reference line; and

for each location in the region, the first warped coordinate term is (log 10 D)cos θ

, and the second warped coordinate term is (log 10 D)sin θ

.

15. The system of claim 13 wherein a location of the wireless access point is at an origin of the warped coordinate system.

16. The system of claim 13 wherein the coverage map generator node is further operable to convert the predicted received signal strength values from a warped coordinate system data to the Cartesian coordinate system data.

17. The system of claim 13 wherein the coverage map generator node is further operable to account for walls inside the convex hull, walls partially inside and partially outside the convex hull, and walls outside the convex hull.