Wireless client position estimating system and method

• US 8,520,647 B2
• Filed: 09/26/2008
• Issued: 08/27/2013
• Est. Priority Date: 09/26/2007
• Status: Active Grant

• Current Assignee: Hewlett Packard Enterprise Development LP (Hewlett-Packard Enterprise Company)
• Original Assignee: Aruba Networks Incorporated (Hewlett-Packard Enterprise Company)
• Inventors: Gray, Gordon P., Burke, Anthony G.
• Primary Examiner(s): Afshar, Kamran
• Assistant Examiner(s): Zewari, Sayed T
• Application Number:
  US12/239,199
• Publication Number:
  US 20090082034A1
• Time in Patent Office: 1,796 Days
• Field of Search: 455/456.1, 455/456.2, 455/456.3, 455/421, 455/440, 370/338
• US Class Current: 370/338
• CPC Class Codes: G01S 5/0244 Accuracy or reliability of position solution or of measurements contributing thereto
• CPC Class Codes: G01S 5/0278 involving statistical or probabilistic considerations G01S5/0252, G01S5/0294 take precedence
• CPC Class Codes: H04W 36/0094 Definition of hand-off measurement parameters
• CPC Class Codes: H04W 4/02 Services making use of location information
• CPC Class Codes: H04W 4/021 Services related to particular areas, e.g. point of interest [POI] services, venue services or geofences
• CPC Class Codes: H04W 4/025 using location based information parameters
• CPC Class Codes: H04W 4/029 Location-based management or tracking services
• CPC Class Codes: H04W 4/33 for indoor environments, e.g. buildings
• CPC Class Codes: H04W 4/90 Services for handling of emergency or hazardous situations, e.g. earthquake and tsunami warning systems [ETWS]
• 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 64/003 locating network equipment
• CPC Class Codes: H04W 76/19 Connection re-establishment

Abstract

The present invention comprises a system and method for determining an estimated position of a wireless mobile client device operating in a communications environment covered by a wireless local area network. The received signal strength of the wireless mobile client device is measured by one or more access points serving devices in the communications environment. In a preferred embodiment, the error between the received signal strength measured by the access points and the expected received signal strength at a plurality of locations in the communications environment is calculated. The location of the device is determined from the error.

Claims

1. A method for determining an estimated position of mobile wireless client device in a communications environment served by a wireless communications network that comprises one or more access points, the method comprising:

identifying a plurality of locations in the communications environment, each of the plurality of locations being a cell on an attenuation grid that uniquely corresponds to one of the one or more access points;

building a model of the communications environment by each of the one or more access points approximating an expected received signal strength for signals output from every cell on the attenuation grid, the approximating of the expected received signal strength is performed using attenuation information including (i) manufacturer and model of an access point of the one or more access points approximating the expected received signal strength and (ii) antenna characteristics of the access point;

measuring a received signal strength at the one or more access points of a signal transmitted from a first mobile wireless client device; and

determining an estimated position of the first mobile wireless client device by calculating an error for each of the plurality of locations forming the attenuation grid, the error being a difference between an expected received signal strength and the received signal strength at each of the plurality of locations so that the first mobile wireless client device is determined to be located at a cell based on the error.

2. The method of claim 1, wherein the determining of the estimated position further comprises selecting a potential location of the first mobile wireless client device based on one of the plurality of locations having a least error.

3. The method of claim 2, further comprising considering the error of locations adjacent to the potential locations to determine the estimated position of the mobile wireless client device.

4. The method of claim 3, wherein the estimated position of the mobile wireless client device is a selected potential location having adjacent locations comprising a least statistical error.

5. The method of claim 1, wherein the attenuation information includes the antenna characteristics being antenna beam width.

6. The method of claim 5, further comprising:

measuring the transmitted signal strength of the first mobile wireless client device under known conditions to assigning an attenuation factor being part of the attenuation information based on the measurement.

7. The method of claim 5, wherein the manufacturer is identified from a media access control layer address of the first mobile wireless client device.

8. The method of claim 1, wherein the building of the model of the communications environment further comprises determining the attenuation information based on an attenuation effect of structural features in the communications environment between a first location of the one or more access points and the second location in the plurality of locations.

9. The method of claim 1, further comprising mapping the plurality of locations on a floor plan represented by the attenuation grid.

10. The method of claim 9, further comprising identifying a known position of the first mobile wireless client device on the floor plan and updating the model based on the received signal strength from the first mobile wireless client device.

11. A system for determining an estimated position of a wireless client device, comprising:

a processor coupled to a memory; and

program code stored on a non-transitory media that, when executed by the processor, generates an executable program in the memory that, when executed by the processor, causes the processor to perform operations comprising;

identifying a plurality of locations in a communications environment, each of the plurality of locations is a cell on an attenuation grid that uniquely corresponds to an access point;

designating a location in the plurality of locations for an access point serving the communications environment;

building a model of the communications environment by each access point associated with the attenuation grid approximating an expected received signal strength for signals output from every cell on the attenuation grid, the approximating of the expected received signal strength is performed using attenuation factors including (i) manufacturer and model of an access point of the one or more access points approximating the expected received signal strength and (ii) antenna characteristics of the access point;

measuring received signal strength at the access point of a signal transmitted from a first mobile wireless client device; and

determining the estimated position of the first mobile wireless client device based on a received signal strength, an identification of transmitted signal strength and the model; and

selecting a predicted location by calculating an error for each cell forming the attenuation grid, each error being a difference between an expected received signal strength for one of the plurality of cells forming the attenuation grid and the received signal strength of the signal transmitted from the first mobile wireless client device so that the first mobile wireless client device is determined to be located at a selected cell of the plurality of cells having a lowest error.

12. The system of claim 11, wherein the executable program further causes the processor to perform an operation comprising:

selecting the predicted location based on a group of cells forming the attenuation grid having the least statistical error.

13. The system of claim 11, wherein the executable program further causes the processor to perform an operation comprising:

identifying a manufacturer of the first mobile wireless client device and determining an assigned attenuation factor from the identification.

14. A method for determining an estimated position of mobile wireless client device in a communications environment served by a wireless communications network, the method comprising:

identifying a plurality of locations in the communications environment, each of the plurality of locations represents a predetermined area on an attenuation grid forming a layout of the communications environment and each cell uniquely corresponds to an access point;

building a model of the communications environment by each access point associated with the attenuation grid approximating an expected received signal strength for signals output from every cell on the attenuation grid, the approximating of the expected received signal strength is performed using attenuation factors including (i) manufacturer and model of an access point of the one or more access points approximating the expected received signal strength and (ii) antenna characteristics of the access point;

measuring a received signal strength at of a signal transmitted from a first mobile wireless client device at access points forming the attenuation grid;

calculating an error between an expected received signal strength and the received signal strength at each location of the plurality of locations; and

selecting a predicted location representing the estimated position of the first mobile wireless client device based on statistical differences in the error where the predicted location is an area on the attenuation grid having a lowest error.