Locally Adjusted Radio Frequency Coverage Maps in Wireless Networks

• US 20080166973A1
• Filed: 01/04/2007
• Published: 07/10/2008
• Est. Priority Date: 01/04/2007
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Hart, Brian Donald, Douglas, Bretton Lee
• Granted Patent: US 7,904,092 B2
• Time in Patent Office: Days
• US Class Current: 455/67.11
• CPC Class Codes: H04W 16/18 Network planning tools

Abstract

In one embodiment, a method for adjusting a radio-frequency coverage map. The method includes receiving calibration data comprising observed received signal strength values at one or more calibration points corresponding to a radio frequency transmitter, and identifying an applicable coverage map, where the coverage map provides, for the radio frequency transmitter, estimated received signal strength values at one or more locations. The method also includes determining one or more offset values at the one or more calibration points, where an offset value is based on a difference between an observed received signal strength value and an estimated received signal strength value at a given calibration point. The method also includes adjusting one or more estimated received signal strength values at one or more location bins of the coverage map based on a distance from the one or more calibration points and the one or more offset values.

Claims

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

receive calibration data comprising observed received signal strength values at one or more calibration points corresponding to a ratio frequency transmitter;

identify an applicable coverage map, wherein the coverage map provides, for the radio frequency transmitter, estimated received signal strength values at one or more locations;

determine one or more offset values at the one or more calibration points, wherein an offset value is based on a difference between an observed received signal strength value and an estimated received signal strength value at a given calibration point;

define a correction cone for the one or more calibration points based on the respective offset values and a radius parameter, the correction cone defining for one or more location bins a correction to be applied to the RF coverage map based on a distance from the one or more calibration points and the one or more offset values; and

adjust one or more estimated received signal strength values at one or more location bins from the coverage map based on a distance from the one or more calibration points and the one or more offset values.

2. The logic of claim 1 wherein the logic is further operable to superimpose a first correction cone at least partially over a second correction cone on the RF coverage map

3. The logic of claim 1 wherein the logic is further operable to normalize one or more correction conies.

4. The logic of claim 1 wherein an amount that a given estimated received signal strength value is adjusted equals an observed error at a correction cone center.

5. The logic of claim 1 wherein an amount that a given estimated received signal strength value is adjusted decreases linearly from a correction cone center until the estimated received signal strength value tapers to zero at an edge of the correction cone.

6. The logic of claim 1 wherein an amount that a given estimated received signal strength value is adjusted decreases non-linearly from a correction cone center until the estimated received signal strength value tapers to zero at an edge of the correction cone.

7. The logic of claim 1 wherein the logic is further operable to apply corrections defined in a taper matrix, wherein a taper matrix provides taper factors to normalized correction cones.

8. The logic of claim 7, wherein the taper matrix is a 2-dimensional taper matrix.

9. A method comprising:

receiving calibration data comprising observed received signal strength values at one or more calibration points corresponding to a radio frequency transmitter;

identifying an applicable coverage map, wherein the coverage map provides, for the radio frequency transmitter, estimated received signal strength values at one or more locations;

determining one or more offset values at the one or more calibration points, wherein an offset value is based on a difference between an observed received signal strength value and an estimated received signal strength value at a given calibration point;

defining a correction cone for the one or more calibration points based on the respective offset values and a radius parameter, the correction cone defining for one or more location bins a correction to be applied to the RF coverage map based on a distance from the one or more calibration points and the one or more offset values; and

adjusting one or more estimated received signal strength values at one or more location bins of the coverage map based on a distance from the one or more calibration points and the one or more offset values.

10. The method of claim 9 further comprising superimposing one or more correction cones on the RF coverage map.

11. The method of claim 9 further comprising normalizing one or more correction cones.

12. The method of claim 9 wherein an amount that a given estimated received signal strength value is adjusted equals an observed error at a correction cone center.

13. The method of claim 9 wherein an amount that a given estimated received signal strength value is adjusted decreases linearly from a correction cone center until the estimated received signal strength value tapers to zero at an edge of the correction cone.

14. The method of claim 9 wherein an amount that a given estimated received signal strength value is adjusted decreases non-linearly from a correction cone center until the estimated received signal strength value tapers to zero at an edge of the correction cone.

15. The method of claim 9 further comprising applying corrections defined in a taper matrix, wherein a taper matrix provides taper factors to given normalized correction cones.

16. A system comprising:

a wireless network infrastructure node operable to;

receive calibration data comprising observed received signal strength values at one or more calibration points corresponding to a radio frequency transmitter;

identify an applicable coverage map, wherein the coverage map provides, for the radio frequency transmitter, estimated received signal strength values at one or more locations;

determine one or more offset values at the one or more calibration points, wherein an offset value is based on a difference between an observed received signal strength value and an estimated received signal strength value at a given calibration point;

define a correction cone for the one or more calibration points based on the respective offset values and a radius parameters the correction cone defining for one or more location bins a correction to be applied to the RF coverage map based on a distance from the one or more calibration points and the one or more offset values; and

adjust one or more estimated received signal strength values at one or more location bins of the coverage, map based on a distance from the one or more calibration points and the one or more offset values; and

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

17. The system of claim 16 wherein the wireless network infrastructure node is further operable to normalize one or more correction cones.

18. The system of claim 16 wherein the wireless network infrastructure node is further operable to superimpose one or more correction cones on the RF coverage map.

19. The system of claim 16 wherein an amount that a given estimated received signal strength value is adjusted equals an observed error at a correction cone center.

20. The system of claim 16 wherein an amount that a given estimated received signal strength value is adjusted decreases linearly from a correction cone center until the estimated received signal strength value tapers to zero at an edge of the correction cone.