Location of wireless nodes using signal strength weighting metric
First Claim
1. A method for estimating the location of a wireless node relative to a plurality of radio receivers operative to detect the strength of RF signals, wherein a RF coverage map, corresponding to each of the radio receivers, characterizes the signal strength values for locations in a physical region, comprisingcollecting signal strength values, detected at a plurality of radio receivers, corresponding to signals transmitted by a wireless node, wherein at least one of the collected signals is transmitted by the wireless node in a first frequency band, and wherein at least one other of the collected signals is transmitted by the wireless node in a second frequency band;
- computing the estimated location of the wireless node based on the collected signal strength values and the RF coverage maps corresponding to the plurality of radio receivers, wherein the contribution of each detected signal strength value to the estimated location is weighted according to a weighting function that varies with the signal strength values detected by the radio receivers, wherein the weighting function weights the signal strength values associated with the first frequency band higher than the signal strength values associated with the second frequency band.
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Abstract
Methods, apparatuses, and systems directed to a wireless node location mechanism that uses a signal strength weighting metric to improve the accuracy of estimating the location of a wireless node based on signals detected among a plurality of radio transceivers. In certain implementations, the wireless node location mechanism further incorporates a differential signal strength metric to reduce the errors caused by variations in wireless node transmit power, errors in signal strength detection, and/or direction-dependent path loss. As opposed to using the absolute signal strength or power of an RF signal transmitted by a wireless node, implementations of the present invention compare the differences between signal strength values detected at various pairs of radio receivers to corresponding differences characterized in a model of the RF environment. One implementation of the invention searches for the locations in the model between each pair of radio receivers where their signal strength is different by an observed amount.
237 Citations
41 Claims
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1. A method for estimating the location of a wireless node relative to a plurality of radio receivers operative to detect the strength of RF signals, wherein a RF coverage map, corresponding to each of the radio receivers, characterizes the signal strength values for locations in a physical region, comprising
collecting signal strength values, detected at a plurality of radio receivers, corresponding to signals transmitted by a wireless node, wherein at least one of the collected signals is transmitted by the wireless node in a first frequency band, and wherein at least one other of the collected signals is transmitted by the wireless node in a second frequency band; computing the estimated location of the wireless node based on the collected signal strength values and the RF coverage maps corresponding to the plurality of radio receivers, wherein the contribution of each detected signal strength value to the estimated location is weighted according to a weighting function that varies with the signal strength values detected by the radio receivers, wherein the weighting function weights the signal strength values associated with the first frequency band higher than the signal strength values associated with the second frequency band. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. An apparatus facilitating the location of a wireless node in a RF environment, comprising
a plurality of radio receivers comprising at least one antenna, the plurality of radio receivers operative to detect the strength of signals transmitted by wireless nodes and provide the detected signal strengths to a wireless node location model; - wherein a RF coverage map, corresponding to each of the radio receivers, characterizes the signal strength values for locations in a physical region wherein at least one of the detected signals is transmitted by the wireless node in a first frequency band, and wherein at least one other of the detected signals is transmitted by the wireless node in a second frequency band, and
a wireless node location module operative to compute the estimated location of the wireless node based on the collected signal strength values and the RF coverage maps corresponding to the plurality of radio receivers, wherein the contribution of each detected signal strength value to the estimated location is weighted according to a weighting function that varies with the signal strength values detected by the radio receivers, wherein the weighting function weights the collected signal strength values associated with the first frequency band higher than the collected signal strength values associated with the second frequency band. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
- wherein a RF coverage map, corresponding to each of the radio receivers, characterizes the signal strength values for locations in a physical region wherein at least one of the detected signals is transmitted by the wireless node in a first frequency band, and wherein at least one other of the detected signals is transmitted by the wireless node in a second frequency band, and
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25. A method for estimating the location of a wireless node relative to a plurality of radio receivers operative to detect the strength of RF signals, wherein a RF coverage map, corresponding to each of the radio receivers, characterizes the signal strength values for locations in a physical region, comprising
collecting signal strength values, detected at a plurality of radio receivers, corresponding to signals transmitted by a wireless node; - and
computing 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 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 in the RF coverage mans associated with the pair of radio receivers; weighting each of the computed sums based on the lower of the two signal strength values detected by the corresponding pair of radio receivers; combining the weighted sums to create a differential error surface; and finding the minimum of the differential error surface. - View Dependent Claims (26, 27, 28, 29, 30, 31)
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32. A wireless node location mechanism operating in association with a wireless network environment comprising a plurality of radio receivers operative to detect the signal strength of signals transmitted by wireless nodes, wherein a RF coverage map, corresponding to each of the radio receivers, includes signal strength values for locations in a physical region, comprising:
a wireless node location module operative to receive, from at least some of the plurality of radio receivers, the detected signal strength of RF signals transmitted by a wireless node; and compute 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 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 compute step comprises compute, 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 in the RF coverage maps associated with the pair of radio receivers; weight each of the computed sums based on the lower of the two signal strength values detected by the corresponding pair of radio receivers; combine the weighted sums to create a differential error surface; and find the minimum of the differential error surface. - View Dependent Claims (33, 34, 35, 36, 37, 38, 39, 40, 41)
Specification