Range-Free Proximity Determination

Abstract

Techniques of range free proximity determination are described. A mobile device can determine an entry into or exit from a proximity fence upon determining that the mobile device is sufficiently close to a signal source. The proximity fence can be a virtual fence defined by the signal source and associated with a service. The mobile device can detect signals from multiple signal sources. The mobile device can determine that, among the signal sources, one or more signal sources are located closest to the mobile device based on a ranking of the signal sources using signal strength. The mobile device can determine a probability indicating a confident level of the ranking. The mobile device can determine that the mobile device entered or exited a proximity fence associated with a highest ranked signal source satisfying a confidence threshold.

What is claimed is: 
     
         1 . A method comprising:
 receiving, by a mobile device, a series of signals from each of a plurality of signal sources;   determining a sorted list of the signal sources based on an estimated signal strength of signals from each of the signal sources, wherein a higher estimated signal strength is associated with a higher ranking in the sorted list;   determining a probability of false sort for each of the signal sources in the sorted list based on a signal strength separation between signals corresponding to the signal source and other received signals, wherein the probability of false sort of a signal source indicates a probability that a rank of the signal source is incorrect, and wherein a greater signal strength separation corresponds to a lower probability of false sort;   determining a sublist of the sorted list based on a probability of false sort, wherein the sublist includes one or more signal sources each of which being associated with a probability of false sort that satisfies a threshold value; and   providing the sublist of signal sources to a subsystem of the mobile device as proximity signal sources for determining a location of the mobile device.   
     
     
         2 . The method of  claim 1 , wherein:
 the signals are radio frequency (RF) signals, and   each signal source is a Bluetooth™ low energy (BLE) device, a near field communication (NFC) device, or a wireless access point in a local area network or a personal area network.   
     
     
         3 . The method of  claim 1 , wherein determining the sorted list comprises:
 calculating the estimated signal strength of signals of each signals based on a cumulative distribution filter being applied to the series of signals corresponding to the signal source over a pre-determined time window; and   determining the sorted list based on the estimated signal strength of signals from each signal source.   
     
     
         4 . The method of  claim 1 , wherein determining the probability of false sort for each of the signal sources comprises determining a cumulative value of a signal strength noise over time for each signal source. 
     
     
         5 . The method of  claim 1 , wherein determining the sublist comprises:
 selecting, from the sorted list, a group of one or more signal sources that includes a highest ranked signal source that is associated with a probability of false sort that satisfies the threshold value; and   designating the selected group as the sublist.   
     
     
         6 . The method of  claim 1 , comprising filtering the sublist based on a detected change of order in the sublist using a recursive filter and a reading from a motion sensor of the mobile device, wherein the mobile device filters out a signal source upon determining a change in rank of the signal source while the reading indicates that the mobile device is stationary. 
     
     
         7 . The method of  claim 1 , wherein determining the sublist is independent of a proximity estimation using a free space signal propagation model. 
     
     
         8 . A non-transitory storage device storing computer instructions operable to cause a mobile device to perform operations comprising:
 receiving, by the mobile device, a series of signals from each of a plurality of signal sources;   determining a sorted list of the signal sources based on an estimated signal strength of signals from each of the signal sources, wherein a higher estimated signal strength is associated with a higher ranking in the sorted list;   determining a probability of false sort for each of the signal sources in the sorted list based on a signal strength separation between signals corresponding to the signal source and other received signals, wherein the probability of false sort of a signal source indicates a probability that a rank of the signal source is incorrect, and wherein a greater signal strength separation corresponds to a lower probability of false sort;   determining a sublist of the sorted list based on a probability of false sort, wherein the sublist includes one or more signal sources each of which being associated with a probability of false sort that satisfies a threshold value; and   providing the sublist of signal sources to a subsystem of the mobile device as proximity signal sources for determining a location of the mobile device.   
     
     
         9 . The non-transitory storage device of  claim 8 , wherein:
 the signals are radio frequency (RF) signals, and   each signal source is a Bluetooth™ low energy (BLE) device, a near field communication (NFC) device, or a wireless access point in a local area network or a personal area network.   
     
     
         10 . The non-transitory storage device of  claim 8 , wherein determining the sorted list comprises:
 calculating the estimated signal strength of signals of each signals based on a cumulative distribution filter being applied to the series of signals corresponding to the signal source over a pre-determined time window; and   determining the sorted list based on the estimated signal strength of signals from each signal source.   
     
     
         11 . The non-transitory storage device of  claim 8 , wherein determining the probability of false sort for each of the signal sources comprises determining a cumulative value of a signal strength noise over time for each signal source. 
     
     
         12 . The non-transitory storage device of  claim 8 , wherein determining the sublist comprises:
 selecting, from the sorted list, a group of one or more signal sources that includes a highest ranked signal source that is associated with a probability of false sort that satisfies the threshold value; and   designating the selected group as the sublist.   
     
     
         13 . The non-transitory storage device of  claim 8 , comprising filtering the sublist based on a detected change of order in the sublist using a recursive filter and a reading from a motion sensor of the mobile device, wherein the mobile device filters out a signal source upon determining a change in rank of the signal source while the reading indicates that the mobile device is stationary. 
     
     
         14 . The non-transitory storage device of  claim 8 , wherein determining the sublist is independent of a proximity estimation using a free space signal propagation model. 
     
     
         15 . A mobile device comprising:
 a processor; and   a non-transitory storage device storing computer instructions operable to cause the mobile device to perform operations comprising:
 receiving, by the mobile device, a series of signals from each of a plurality of signal sources; 
 determining a sorted list of the signal sources based on an estimated signal strength of signals from each of the signal sources, wherein a higher estimated signal strength is associated with a higher ranking in the sorted list; 
 determining a probability of false sort for each of the signal sources in the sorted list based on a signal strength separation between signals corresponding to the signal source and other received signals, wherein the probability of false sort of a signal source indicates a probability that a rank of the signal source is incorrect, and wherein a greater signal strength separation corresponds to a lower probability of false sort; 
 determining a sublist of the sorted list based on a probability of false sort, wherein the sublist includes one or more signal sources each of which being associated with a probability of false sort that satisfies a threshold value; and 
 providing the sublist of signal sources to a subsystem of the mobile device as proximity signal sources for determining a location of the mobile device. 
   
     
     
         16 . The mobile device of  claim 15 , wherein:
 the signals are radio frequency (RF) signals, and   each signal source is a Bluetooth™ low energy (BLE) device, a near field communication (NFC) device, or a wireless access point in a local area network or a personal area network.   
     
     
         17 . The mobile device of  claim 15 , wherein determining the sorted list comprises:
 calculating the estimated signal strength of signals of each signals based on a cumulative distribution filter being applied to the series of signals corresponding to the signal source over a pre-determined time window; and   determining the sorted list based on the estimated signal strength of signals from each signal source.   
     
     
         18 . The mobile device of  claim 15 , wherein determining the probability of false sort for each of the signal sources comprises determining a cumulative value of a signal strength noise over time for each signal source. 
     
     
         19 . The method of  claim 15 , wherein determining the sublist comprises:
 selecting, from the sorted list, a group of one or more signal sources that includes a highest ranked signal source that is associated with a probability of false sort that satisfies the threshold value; and   designating the selected group as the sublist.   
     
     
         20 . The mobile device of  claim 15 , comprising filtering the sublist based on a detected change of order in the sublist using a recursive filter and a reading from a motion sensor of the mobile device, wherein the mobile device filters out a signal source upon determining a change in rank of the signal source while the reading indicates that the mobile device is stationary. 
     
     
         21 . The mobile device of  claim 15 , wherein determining the sublist is independent of a proximity estimation using a free space signal propagation model.