Wireless node location mechanism featuring definition of search region to optimize location computation
First Claim
1. A method for estimating a location of a wireless node relative to a plurality of radio receivers operative to detect the strength of RF signals, comprisingcollecting signal strength values, detected at the plurality of radio receivers, corresponding to signals transmitted by a wireless node wherein RF coverage maps, associated with corresponding ones of the radio receivers, each comprise an origin location, and a coverage map region defined by a matrix having elements containing signal strength values for corresponding locations in a physical region out to a threshold signal strength level;
- selecting at least two of the coverage maps of the radio receivers that detected signals transmitted by the wireless node;
defining a search region by determining, based on the origin locations and coverage map regions of the selected coverage maps, an intersection of the RF coverage maps; and
computing, within the defined search region, the estimated location of the wireless node based on the collected signal strength values and the selected RF coverage maps corresponding to the plurality of radio receivers, wherein the computing step comprisescomputing, for each radio receiver, an individual error surface based on the RF coverage map associated with the radio receiver and the signal strength detected by the radio receiver;
aggregating the individual error surfaces to create a total error surface; and
assessing, within the search region, the total error at each location in the total error surface.
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Accused Products
Abstract
A wireless node location mechanism that defines a search region to optimize the computations associated with estimating the location of a given wireless node. According to one implementation, a coverage map associated with each radio receiver that records signal strength data is defined out to a threshold signal strength level. Before computing the estimated location of a given wireless nodes, a search region is defined based on the intersection of the coverage maps associated with each radio receiver that detects the wireless node. Some implementations use information provided by the fact that certain radio receivers did not detect the wireless node to further optimize the location estimate. By defining a search region, which is a generally small area relative to the space encompassed by an entire RF environment, the present invention provides several advantages, such as reducing the processing time and/or power to compute estimated locations for wireless nodes.
198 Citations
26 Claims
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1. A method for estimating a location of a wireless node relative to a plurality of radio receivers operative to detect the strength of RF signals, comprising
collecting signal strength values, detected at the plurality of radio receivers, corresponding to signals transmitted by a wireless node wherein RF coverage maps, associated with corresponding ones of the radio receivers, each comprise an origin location, and a coverage map region defined by a matrix having elements containing signal strength values for corresponding locations in a physical region out to a threshold signal strength level; -
selecting at least two of the coverage maps of the radio receivers that detected signals transmitted by the wireless node; defining a search region by determining, based on the origin locations and coverage map regions of the selected coverage maps, an intersection of the RF coverage maps; and computing, within the defined search region, the estimated location of the wireless node based on the collected signal strength values and the selected RF coverage maps corresponding to the plurality of radio receivers, wherein the computing step comprises computing, for each radio receiver, an individual error surface based on the RF coverage map associated with the radio receiver and the signal strength detected by the radio receiver; aggregating the individual error surfaces to create a total error surface; and assessing, within the search region, the total error at each location in the total error surface. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A method for estimating a location of a wireless node relative to a plurality of radio receivers operative to detect the strength of RF signals, comprising
collecting signal strength values, detected at a plurality of radio receivers, corresponding to signals transmitted by a wireless node wherein RF coverage maps, associated with corresponding ones of the radio receivers, each compromise an origin location, and a coverage map region defined by a matrix having elements containing signal strength values for locations in a physical region out to a threshold signal strength value; -
selecting at least two of the coverage maps of the radio receivers that detected signals transmitted by the wireless node; defining a search region by determining, based on the origin locations and coverage map regions of the selected coverage maps, an intersection of the RF coverage maps; and computing within the search region the estimated location of the wireless node by comparing, for all unique pairs of radio receivers, the differences in the signal strength values detected by the plurality of radio receivers to corresponding differences in the signal strength values in the selected RF coverage maps associated with the plurality of radio receivers, wherein the comparison is weighted as a function of at least one of the signal strength values detected by each unique pair of radio receivers, and wherein the computing step comprises computing, for all unique pairs of radio receivers, the sum of the squares of the difference between the signal strength values detected by a pair of radio receivers less the difference between the signal strength values within the search region in the RF coverage maps associated with the pair of radio receivers; combining the sums to create a differential error surface; and finding within the search region the location corresponding to the minimum of the differential error surface. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22)
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23. In a wireless network environment comprising a plurality of radio receivers deployed within a physical space, a method facilitating location of wireless nodes, the method comprising
defining a location-coordinate model of a physical space, wherein the model includes the locations of a plurality of radio receivers; -
determining coverage maps associated with ones of the radio receivers each comprising an origin location, and a coverage map region defined by a matrix having elements containing signal strength values for corresponding locations in a physical region out to a threshold signal strength level for locations in the physical space proximal to the given radio receiver and wherein each boundary of the coverage maps is rectangular; and storing the coverage maps as individual entities in a database, wherein the individual entities defining a given coverage map each comprise an identifier corresponding to a radio receiver, the location coordinates of a corner of the coverage map, the number of location bins along a first axis, the number of location bins along a second axis, and a matrix of receive signal strength values. - View Dependent Claims (24, 25, 26)
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Specification