US 7,205,938 B2Granted

Wireless node location mechanism responsive to observed propagation characteristics of wireless network infrastructure signals

AssigneeAirespace, Inc.

InventorsGregg Scott Davi, Paul F. Dietrich, Alexander H. Hills

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Abstract

A wireless node location mechanism that dynamically adapts to changes to a surrounding physical environment that affect the propagation of radio signals. The wireless node location mechanism assesses radio signals from transmitters associated with a wireless node location infrastructure to adjust one or more parameters used to estimate location of a wireless node. In one implementation, path loss exponents are re-computed based on the signals transmitted between infrastructure radio transceivers. These path loss exponents are used, in one implementation, to compute the distance between a wireless node and a given infrastructure radio transceiver and, ultimately, to determine the location of the wireless node based on triangulation. In one implementation, path loss exponents are computed on demand based on the signals observed between infrastructure radios that detect the wireless node whose location is to be estimated.

Claims35

Dependent claims

A method facilitating the location of a wireless node in an RF environment, the RF environment including a plurality of radio transceivers placed in known locations, comprising:

detecting, at the known locations of the plurality of radio transceivers, the strength of RF signals transmitted by the plurality of radio transceivers;
receiving a request to locate a wireless node;
selecting radio transceivers that detect RF signals transmitted by the wireless node;
then, for pairs of the selected radio transceivers:
determining a distance between a first and second radio transceiver, wherein the first and second radio transceivers detected RF signals from each other in the detecting step;
determining an observed path loss between the first and second radio transceivers;
and
computing a path loss exponent based on the determined distance and the observed path loss;
and
then, for each selected radio transceiver, computing an average path loss exponent based on all path loss exponents associated with a respective radio transceiver;
and
estimating the location of the wireless node based on respective estimated distances between the selected radio transceivers and the wireless node, wherein the respective estimated distances are determined according to a path loss model using the average path loss exponents corresponding to a given radio transceiver and the strength of the RF signal transmitted by the wireless node and detected by the given radio transceiver.

9 more elements

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

a plurality of access elements for wireless communication with at least one remote client element and for communication with a central control element;
wherein the access elements are each operative to
establish and maintain, in connection with a central control element, wireless connections with remote client elements;
detect the strength of received signals;
append a signal strength value to frames received from wireless nodes;
and
transmit received frames to a central control element;
at least one central control element for supervising the access elements, wherein the central control element is operative to
manage wireless connections between the access elements and corresponding remote client elements, and
store signal strength data appended to frames transmitted by the plurality of access elements in association with wireless node identifiers;
and
a wireless node location module operative to
receive a request to locate the wireless node;
select access elements that detect RF signals transmitted by the wireless node;
then, for pairs of the selected access elements:
determine a distance between a first and second access element, wherein the first and second access elements detected RF signals from each other;
determine an observed path loss between the first and second radio transceivers;
and
compute a path loss exponent based on the determined distance and the observed path loss;
and
then, for each selected radio transceiver, compute an average path loss exponent based on all path loss exponents associated with a respective radio transceiver;
and
estimate the location of the wireless node based on respective estimated distances between the selected access elements and the wireless node, wherein the respective estimated distances are determined according to a path loss model using the average path loss exponents corresponding to a given access element and the strength of the RF signal transmitted by the wireless node and detected by the given access element.

20 more elements

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

a plurality of access elements for wireless communication with at least one remote client element and for communication with a central control element;
wherein the access elements are each operative to
detect the strength of received signals;
append a signal strength value to frames received from wireless nodes;
and
transmit received frames to a central control element;
at least one central control element for supervising the access elements, wherein the central control element is operative to
store signal strength data appended to frames transmitted by the plurality of access elements in association with wireless node identifiers;
and
a wireless node location module operative to
receive a request to locate a wireless node;
select access elements that detect RF signals transmitted by the wireless node;
then, for pairs of the selected access elements:
determine a distance between first and second access elements, wherein the first and second access elements detected RF signals from each other in the detect step;
determine an observed path loss between the first and second access elements;
and
compute a path loss equivalent based on the determined distance and the observed pathloss;
and
then, for each selected access elements, compute an average path loss exponent based on all path loss exponents associated with a access elements respective radio transceiver;
and
estimate the location of the wireless node based on respective estimated distances between the selected access elements and the wireless node, wherein the respective estimated distances are determined according to a path loss model using the average path loss exponents corresponding to a given access element and the strength of the RF signal transmitted by the wireless node and detected by the given access element.

18 more elements

Dependencies are inferred from the claim text.

Facts

Application: 10/794,842Filed 5 Mar 2004
Published: US 2005/0195109 A18 Sep 2005
Granted: 17 Apr 2007
Term ends: Not estimatedThe source records don’t support an estimate.

Classification5 codes

G01S 5/02527
Creating or updating the radio-map: detecting or resolving anomalies in the radio frequency fingerprints of the radio-map
G01S 5/0226
Details: transmitters
G01S 11/06
Using radio waves: using intensity measurements
G01S 5/14
Using radio waves: determining absolute distances from a plurality of spaced points of known location