Wireless node location mechanism using antenna pattern diversity to enhance accuracy of location estimates

• US 7,532,896 B2
• Filed: 05/21/2007
• Issued: 05/12/2009
• Est. Priority Date: 02/20/2004
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Systems, Inc.
• Inventors: Friday, Robert J., Dietrich, Paul F.
• Primary Examiner(s): Eisen; Alexander
• Assistant Examiner(s): Addy; Anthony S
• Application Number:
  US11/751,456
• Publication Number:
  US 20070225039A1
• Time in Patent Office: 722 Days
• Field of Search: 455/63.4, 455/404.2, 455/423, 455/432.1, 455/436, 4554561-457, 455/561, 455/562.1, 455/67.11, 455524-525, 342/357.01, 342/357.02, 342/359, 342/450, 342/457, 701/207, 701/213, 701/214, 701/216, 701/208, 343/702, 343/853, 343/882, 343/893
• US Class Current: 455/456.1
• CPC Class Codes: G01S 5/02521 using a radio-map
• CPC Class Codes: G01S 5/14 Determining absolute distances from a plurality of spaced points of known location
• CPC Class Codes: H04B 17/27 for locating or positioning the transmitter
• CPC Class Codes: H04B 17/318 Received signal strength
• CPC Class Codes: H04B 17/391 Modelling the propagation channel
• CPC Class Codes: H04B 7/0805 with single receiver and antenna switching H04B7/0822 takes precedence

Abstract

A wireless node RF Fingerprinting location mechanism that uses multiple antenna patterns to enhance the accuracy of wireless node location in an RF environment. In one implementation, substantially non-overlapping antenna pattern diversity is used to provide a degree of sectorization in computing the estimated location of a wireless node.

Claims

1. In a wireless node location mechanism comprising a plurality of radio transceivers operative to detect the signal strength of signals transmitted by wireless nodes, a method comprising

detecting, at one or more of the plurality of radio transceivers, the signal strength of radio frequency (RF) signals transmitted by a wireless node, wherein at least one of the radio transceivers of the plurality of radio transceivers comprises a plurality of directional antennas, the plurality of directional antennas having substantially non-overlapping patterns relative to each other to achieve sectorization of a region in which the at least one of the radio transceivers is deployed, wherein, for the at least one radio transceiver, peak gains of the plurality of directional antennas are oriented radially and outwardly about an axis and offset relative to each other at an angle substantially equal to 360/N, where N is the number of directional antennas in the plurality of directional antennas;

identifying the directional antennas associated with the detected signal strengths to be used in locating the wireless node;

accessing RF coverage maps corresponding to the plurality of radio transceivers, wherein, as to the at least one radio transceiver comprising a plurality of directional antennas, a unique RF coverage map corresponding to both the radio transceiver and the identified directional antenna is accessed, wherein each of the RF coverage maps is substantially coextensive with antenna patterns of the corresponding antennas of the radio transceivers out to a threshold signal strength level; and

computing the estimated location of the wireless node based on the accessed coverage maps and the signal strengths of the RF signals detected by the infrastructure radios, and wherein computing the estimated location of the wireless node is further based on a determined positional overlap between the accessed RF coverage maps associated with the antennas selected to locate the wireless node.

2. The method of claim 1 wherein the coverage maps each comprise a plurality of location coordinates associated with corresponding signal strength values.

3. The method of claim 2 wherein the coverage maps are heuristically constructed.

4. The method of claim 2 wherein the coverage maps based on a mathematical model.

5. The method of claim 1 wherein the computing the estimated location is isolated to the determined positional overlap between the accessed coverage maps associated with the antennas selected to locate the wireless node.

6. An apparatus facilitating the location of a wireless node in a radio frequency (RF) environment, comprising

a plurality of radio transceivers comprising at least one antenna, the plurality of radio transceivers operative to detect the strength of signals transmitted by wireless nodes and provide the detected signal strengths to a wireless node location model;

wherein at least one of the radio transceivers comprises at least two directional antennas, the at least two directional antennas having substantially non-overlapping patterns relative to each other to achieve sectorization of a region in which the at least one of the radio transceivers is deployed, and is operative to identify the directional antenna associated with the detected signal strength for a given signal, wherein, for the at least one radio transceiver, peak gains of the plurality of directional antennas are oriented radially and outwardly about an axis and offset relative to each other at an angle substantially equal to 360/N, where N is the number of directional antennas in the plurality of directional antennas;

a data store comprising a plurality of RF coverage maps corresponding to the plurality of radio transceivers, wherein each directional antenna of the plurality of directional antennas has a unique RF coverage map associated therewith, wherein each of the RF coverage maps is substantially coextensive with antenna patterns of the corresponding antennas of the radio transceivers out to a threshold signal strength level;

a wireless node location model operative to access the data store and compute the estimated location of a wireless node based on the RF coverage maps corresponding to the antennas identified by one or more of the radio transceivers, a determined positional overlap between the accessed RF coverage maps associated with the antennas selected to locate the wireless node, and the strength of signals transmitted by the wireless node as detected by a plurality of radio transceivers.

7. The apparatus of claim 6 wherein the RF coverage maps include signal strength values for different locations in a physical region.

8. In a wireless network system comprising a plurality of radio transceivers, wherein the peak gains of the antennas are offset relative to each other, a method comprising

detecting, at one of the radio transceivers comprising a plurality of directional antennas, a signal transduced by one of the directional antennas, the plurality of directional antennas having substantially non-overlapping patterns relative to each other to achieve sectorization of a region in which the radio transceiver is deployed, wherein peak gains of the plurality of directional antennas are oriented radially and outwardly about an axis and offset relative to each other at an angle substantially equal to 360/N, where N is the number of directional antennas in the plurality of directional antennas, wherein the signal corresponds to a wireless frame transmitted by a wireless node, the wireless frame including a preamble, and wherein at least some of the plurality of radio transceivers comprise a plurality of directional antennas;

during receipt of the preamble of the frame, selecting one from the plurality of the antennas based on at least one attribute of the respective signals transduced by the antennas;

switching to the selected antenna for receipt of the remainder of the frame;

appending the detected signal strength and an identifier for the selected antenna to the frame; and

transmitting the frame to a wireless node location module;

repeating the detecting, selecting, switching, appending and transmitting steps for a desired number of radio transceivers;

accessing a data store using the appended identifiers for the selected antennas to identify a set of coverage maps, wherein the data store comprises a plurality of coverage maps corresponding to the plurality of radio transceivers, wherein each directional antenna of the plurality of directional antennas has a unique coverage map associated therewith, wherein each of the coverage maps is substantially coextensive with antenna patterns of the corresponding antennas of the radio transceivers out to a threshold signal strength level;

computing the estimated location of the wireless node based on the identified set of coverage maps, a determined positional overlap between the accessed coverage maps associated with the antennas selected to locate the wireless node, and the detected signal strengths.

9. A wireless network system facilitating the location of a wireless node, comprising

a plurality of radio transceivers for communication with a wireless node location module;

wherein the radio transceivers are each operative to

detect the strength of received signals encoding frames transmitted by wireless nodes;

append a signal strength value to frames received from the wireless nodes; and

transmit received frames to a wireless node location module;

wherein at least one of the radio transceivers comprises a plurality of directional antennas, the plurality of directional antennas having substantially non-overlapping patterns relative to each other to achieve sectorization of a region in which the at least one of the radio transceivers is deployed, wherein, for the at least one radio transceiver, peak gains of the plurality of directional antennas are oriented radially and outwardly about an axis and offset relative to each other at an angle substantially equal to 360/N, where N is the number of directional antennas in the plurality of directional antennas, and wherein the at least one of the radio transceivers is further operative to;

select one from the plurality of the directional antennas to receive the frames in received signals;

append an identifier corresponding to the selected antenna to the frames received from the wireless nodes;

a wireless node location module operative to

store signal strength data appended to frames transmitted by the plurality of radio transceivers in association with wireless node identifiers;

access a data store using the appended identifiers for the selected antennas to identify a set of coverage maps, wherein the data store comprises a plurality of coverage maps corresponding to the plurality of radio transceivers, wherein each directional antenna of the plurality of directional antennas has a unique coverage map associated therewith, and wherein each of the coverage maps is substantially coextensive with antenna patterns of the corresponding antennas of the radio transceivers out to a threshold signal strength level; and

compute the estimated location of a wireless node based on the coverage maps associated with the antennas identified by at least one of the radio transceivers, a determined positional overlap between the accessed coverage maps associated with the antennas selected to locate the wireless node, and the signal strength values appended to the frames transmitted by the wireless node as detected by the radio transceivers.

10. The system of claim 9 wherein the frames are 802.11 frames.

11. The system of claim 10 wherein the wireless node identifiers are MAC addresses.

12. In a wireless node location mechanism comprising a plurality of radio transceivers operative to detect the signal strength of signals transmitted by wireless nodes, a method comprising

receiving, from one or more of the plurality of radio transceivers, the detected signal strength of RF signals transmitted by a wireless node wherein at least one of the radio transceivers of the plurality of radio transceivers comprises a plurality of directional antennas, the plurality of directional antennas having substantially non-overlapping patterns relative to each other to achieve sectorization of a region in which the at least one of the radio transceivers is deployed, and wherein, for the at least one radio transceiver, peak gains of the plurality of directional antennas are oriented radially and outwardly about an axis and offset relative to each other at an angle substantially equal to 360/N, where N is the number of directional antennas in the plurality of directional antennas;

accessing a data store to identify a set of coverage maps based on the radio transceivers and the directional antennas used to detect the signal strength of the RF signals, wherein the data store comprises a plurality of coverage maps corresponding to the plurality of radio transceivers, wherein each directional antenna of the plurality of directional antennas has a unique coverage map associated therewith; and

computing the estimated location of the wireless node using at least some of the signal strengths of the RF signals detected by the infrastructure radios, and the identified set of coverage maps, wherein each of the coverage maps is substantially coextensive with antenna patterns of the corresponding antennas of the radio transceivers out to a threshold signal strength level; and

wherein computing the estimated location of the wireless node is isolated to a determined positional overlap between the accessed coverage maps associated with the antennas selected to locate the wireless node.

13. The method of claim 12 wherein the coverage maps each comprise a plurality of location coordinates associated with corresponding signal strength values.

14. The method of claim 13 wherein the coverage maps are heuristically constructed.

15. The method of claim 13 wherein the coverage maps are based on a mathematical model.

16. A wireless node location mechanism operating in association with a wireless network environment comprising a plurality of radio transceivers operative to detect the signal strength of signals transmitted by wireless nodes, comprising:

a wireless node location module operative to

receive, from one or more of the plurality of radio transceivers, the detected signal strength of RF signals transmitted by a wireless node wherein at least one of the radio transceivers of the plurality of radio transceivers comprises a plurality of directional antennas, the plurality of directional antennas having substantially non-overlapping patterns relative to each other to achieve sectorization of a region in which the at least one of the radio transceivers is deployed, and wherein, for the at least one radio transceiver, peak gains of the plurality of directional antennas are oriented radially and outwardly about an axis and offset relative to each other at an angle substantially equal to 360/N, where N is the number of directional antennas in the plurality of directional antennas;

as to the infrastructure radio transceivers comprising a plurality of directional antennas, receive the strength of the RF signals transduced by at least one of the plurality of directional antennas;

access a data store to identify a set of coverage maps based on the radio transceivers and the directional antennas used to detect the signal strength of the RF signals, wherein the data store comprises a plurality of coverage maps corresponding to the plurality of radio transceivers, wherein each directional antenna of the plurality of directional antennas has a unique coverage map associated therewith, wherein each of the coverage maps is substantially coextensive with antenna patterns of the corresponding antennas of the radio transceivers out to a threshold signal strength level; and

compute the estimated location of the wireless node using at least some of the signal strengths of the RF signals detected by the infrastructure radios, a determined positional overlap between the accessed coverage maps associated with the antennas selected to locate the wireless node, and the identified set of coverage maps.