Device-free subject localization methods and systems using wireless signals
Within several applications the ability to localize an individual within an environment is beneficial. However, existing indoor localization approaches depend upon at least one of two assumptions. First, the subject(s) localization is achieved by localizing a wireless device carried by the subject and second, wireless fingerprints are established for the localization via a site survey being performed before a system can actually localize the subject(s). However, in many application scenarios, neither of the above two assumptions are true, namely that the user is not carrying an active wireless device or that the site has been surveyed. Accordingly, embodiments of the invention provide for subject localization by a dynamic calibration of wireless signals between a receiver and a transmitter, where neither the receiver or transmitter are associated with an electronic device carried or worn by the subject.
1. A method for localizing a subject comprising:
receiving wireless signals with a receiver operating according to a first predetermined wireless standard transmitted by a first transmitter operating according to the first predetermined wireless standard;
dynamically calibrating the received wireless signals with a microprocessor; and
establishing a location of a subject with a localization process in execution upon the microprocessor, wherein
the localization process comprises subsequently processing the calibrated received wireless signals;
the first predetermined wireless standard is at least one of a wireless network standard and a wireless data exchange standard;
the localization process of the subject is performed independent of at least one of:
any wireless device associated with the subject;
a wireless device associated with the subject operating upon a second predetermined wireless standard that does not interfere with the first transmitter; and
another wireless device associated with the subject comprising a second transmitter operating according to the first predetermined wireless standard;
dynamically calibrating the received wireless signals comprises:
applying a signal conditioning process to the received wireless signals; and
applying an auto-calibration process to the conditioned received wireless signals;
the signal conditioning process takes wireless channel measurements as input and applying at least one of filtering and normalizing to the wireless channel measurements; and
the auto-calibration process employs direct-link constraints between the first transmitter and the receiver in conjunction with the conditioned received wireless signals.
2. The method according to claim 1 , wherein
the processing is performed without at least one of:
reference to a wireless fingerprint of an environment within which the receiver and transmitter are operating and localization of the subject is sought; and
reference to an initial wireless survey of the environment within which the receiver and transmitter are operating and localization of the subject, wherein the initial wireless survey is performed at installation of the receiver and transmitter.
3. The method of claim 1 , wherein
at least one of:
the dynamic calibration comprises estimating the phase offsets of multiple antennas at the receiver; and
using the calibrated wireless signals to perform subject localization comprises at least one of in-direct-link localization and general localization.
4. The method of claim 3 , wherein
the in-direct-link localization comprises estimating the relative location of the subject in a direct link with respect to the transmitter and the receiver, the direct link being a line-of-sight link between the transmitter and the receiver; and
the general localization estimates the locations of the subject based upon at least one in-direct-link localization result of a plurality of in-direct-link localization results, the at least one in-direct-link localization result of a plurality of in-direct-link localization results being considered a passive fingerprint of the environment.
5. The method of claim 1 , wherein
using the calibrated received wireless signals to perform localization of subject(s) comprises the use of multipath decomposition for every two wireless nodes exchanging wireless signals in order to extend the localization technique to each different wireless path between transmitter and receiver.
6. The method according to claim 1 , wherein
at least one of:
the subject is not directly associated with any electronic devices supporting wireless communications within the wireless network environment within which the subject is; and
the receiver and the first wireless transmitter are not associated with an electronic device associated with the user.
7. The method according to claim 1 , wherein
processing the calibrated wireless signals comprises processing channel state information measurements estimated from the received one or more wireless signals employed for localizing the subject.
8. A device comprising:
a microprocessor; and
non-transitory computer-readable storage medium storing a set of instructions which, when executed by at least one processor, cause the at least one processor to perform steps comprising:
dynamically calibrating received wireless signals with a microprocessor; and
establishing a location of a subject with a localization process in execution upon the microprocessor, wherein
the received wireless signals were received with a receiver operating according to a first predetermined standard and were transmitted by a first transmitter operating according to the first predetermined wireless standard;
the localization process comprises subsequently processing the calibrated received wireless signals;
the first predetermined wireless standard is at least one of a wireless network standard and a wireless data exchange standard;
the localization process of the subject is performed independent of at least one of:
any wireless device associated with the subject; and
a wireless device associated with the subject operating upon a second predetermined wireless standard that does not interfere with the first transmitter; and
another wireless device associated with the subject comprising a second transmitter operating according to the first predetermined wireless standard;
dynamically calibrating the received wireless signals comprises:
applying a signal conditioning process to the received wireless signals; and
applying an auto-calibration process to the conditioned received wireless signals;
the signal conditioning process takes wireless channel measurements as input and applying at least one of filtering and normalizing to the wireless channel measurements; and
the auto-calibration process employs direct-link constraints between the first transmitter and the receiver in conjunction with the conditioned received wireless signals.
9. The device according to claim 8 , wherein
the processing is performed without at least one of:
reference to a wireless fingerprint of an environment within which the receiver and transmitter are operating and localization of the subject is sought; and
reference to an initial wireless survey of the environment within which the receiver and transmitter are operating and localization of the subject, wherein the initial wireless survey is performed at installation of the receiver and transmitter.
10. The device of claim 8 , wherein
at least one of:
the dynamic calibration comprises estimating the phase offsets of multiple antennas at the receiver; and
using the calibrated wireless signals to perform subject localization comprises at least one of in-direct-link localization and general localization.
11. The device of claim 10 , wherein
the in-direct-link localization comprises estimating the relative location of the subject in a direct link with respect to the transmitter and the receiver, the direct link being a line-of-sight link between the transmitter and the receiver; and
the general localization estimates the locations of the subject based upon at least one in-direct-link localization result of a plurality of in-direct-link localization results, the at least one in-direct-link localization result of a plurality of in-direct-link localization results being considered a passive fingerprint of the environment.
12. The device of claim 8 , wherein
using the calibrated received wireless signals to perform localization of subject(s) comprises the use of multipath decomposition for every two wireless nodes exchanging wireless signals in order to extend the localization technique to each different wireless path between transmitter and receiver.
13. The device according to claim 8 , wherein
at least one of:
the subject is not directly associated with any electronic devices supporting wireless communications within the wireless network environment within which the subject is; and
the receiver and the first wireless transmitter are not associated with an electronic device associated with the user.
14. The device according to claim 8 , wherein
processing the calibrated wireless signals comprises processing channel state information measurements estimated from the received one or more wireless signals employed for localizing the subject.
15. A non-transitory computer-readable storage medium storing a set of instructions which, when executed by at least one processor, cause the at least one processor to perform steps comprising:
dynamically calibrating received wireless signals with a microprocessor; and
establishing a location of a subject with a localization process in execution upon the microprocessor, wherein
the received wireless signals were received with a receiver operating according to a first predetermined standard and were transmitted by a first transmitter operating according to the first predetermined wireless standard;
the localization process comprises subsequently processing the calibrated received wireless signals;
the first predetermined wireless standard is at least one of a wireless network standard and a wireless data exchange standard;
the localization process of the subject is performed independent of at least one of:
any wireless device associated with the subject; and
a wireless device associated with the subject operating upon a second predetermined wireless standard that does not interfere with the first transmitter; and
another wireless device associated with the subject comprising a second transmitter operating according to the first predetermined wireless standard;
dynamically calibrating the received wireless signals comprises:
applying a signal conditioning process to the received wireless signals; and
applying an auto-calibration process to the conditioned received wireless signals;
the signal conditioning process takes wireless channel measurements as input and applying at least one of filtering and normalizing to the wireless channel measurements; and
the auto-calibration process employs direct-link constraints between the first transmitter and the receiver in conjunction with the conditioned received wireless signals.
16. The non-transitory computer-readable storage medium according to claim 15 , wherein
the processing is performed without at least one of:
reference to a wireless fingerprint of an environment within which the receiver and transmitter are operating and localization of the subject is sought; and
reference to an initial wireless survey of the environment within which the receiver and transmitter are operating and localization of the subject, wherein the initial wireless survey is performed at installation of the receiver and transmitter.
17. The non-transitory computer-readable storage medium according to claim 15 , wherein
at least one of:
the dynamic calibration comprises estimating the phase offsets of multiple antennas at the receiver; and
using the calibrated wireless signals to perform subject localization comprises at least one of in-direct-link localization and general localization.
18. The non-transitory computer-readable storage medium according to claim 17 , wherein
when the subject localization is the in-direct-link localization it comprises estimating the relative location of the subject in a direct link with respect to the transmitter and the receiver, the direct link being a line-of-sight link between the transmitter and the receiver; and
when the subject localization is the general localization it estimates the locations of the subject based upon at least one in-direct-link localization result of a plurality of in-direct-link localization results, the at least one in-direct-link localization result of a plurality of in-direct-link localization results being considered a passive fingerprint of the environment.
19. The non-transitory computer-readable storage medium according to claim 15 , wherein
using the calibrated received wireless signals to perform localization of subject(s) comprises the use of multipath decomposition for every two wireless nodes exchanging wireless signals in order to extend the localization technique to each different wireless path between transmitter and receiver.
20. The method non-transitory computer-readable storage medium according to claim 15 , wherein
at least one of:
the subject is not directly associated with any electronic devices supporting wireless communications within the wireless network environment within which the subject is; and
the receiver and the first wireless transmitter are not associated with an electronic device associated with the user.
21. The method non-transitory computer-readable storage medium according to claim 15 , wherein
processing the calibrated wireless signals comprises processing channel state information measurements estimated from the received one or more wireless signals employed for localizing the subject.