Indoor Localization Using Commercial Frequency-Modulated Signals

1. A computer system comprising: one or more processing units; and one or more computer storage media storing computer-executable instructions which, when executed by the one or more processing units, cause the one or more processing units to: obtain multiple different signal indicators for a frequency-modulated signal, the multiple different signal indicators characterizing the frequency-modulated signal as received by a mobile device and comprising at least: a detected frequency offset signal indicator that indicates a frequency offset characteristic of the frequency-modulated signal as detected by the mobile device, and another detected signal indicator that indicates another characteristic of the frequency-modulated signal as detected by the mobile device; and compare the detected frequency offset signal indicator and the another detected signal indicator to a database to obtain a current location of the mobile device, the database having prerecorded frequency offset signal indicators that indicate the frequency offset characteristic of the frequency-modulated signal as detected by other mobile devices at various locations and prerecorded other signal indicators that indicate the another characteristic of the frequency-modulated signal as detected by the other mobile devices at the various locations.

2. The computer system of claim 1 , embodied as the mobile device.

3. The computer system of claim 1 , wherein the frequency-modulated signal is a commercial frequency-modulated signal.

4. The computer system of claim 3 , wherein the another detected signal indicator is a received signal strength indicator of the commercial frequency-modulated signal.

5. The computer system of claim 3 , wherein the commercial frequency-modulated signal is transmitted by a radio station at a frequency between 87.8 megahertz and 108 megahertz.

6. The computer system of claim 1 , wherein the frequency-modulated signal is a locally-generated frequency-modulated signal.

7. The computer system of claim 1 , wherein the another detected signal indicator is a multipath indicator of the frequency-modulated signal.

8. The computer system of claim 1 , wherein the computer-executable instructions, when executed by the one or more processing units, cause the one or more processing units to: obtain the multiple different signal indicators for another frequency-modulated signal; include the multiple different signal indicators for the frequency-modulated signal and the another frequency-modulated signal into a location fingerprint of the mobile device; and obtain the current location of the mobile device by comparing the location fingerprint to other fingerprints stored in the database.

9. The computer system of claim 8 , wherein both the frequency-modulated signal and the another frequency-modulated signal are both commercial radio signals.

10. A method for determining a location of a mobile device, the method comprising: obtaining multiple different signal indicators for a frequency-modulated signal, the multiple different signal indicators characterizing the frequency-modulated signal as received by the mobile device and comprising at least: a detected frequency offset signal indicator that indicates a frequency offset characteristic of the frequency-modulated signal as detected by the mobile device, and another detected signal indicator that indicates another characteristic of the frequency-modulated signal as detected by the mobile device; and comparing the detected frequency offset signal indicator and the another detected signal indicator to a database to obtain the location of the mobile device, the database having prerecorded frequency offset signal indicators that indicate the frequency offset characteristic of the frequency-modulated signal as detected by other mobile devices at various locations and prerecorded other signal indicators that indicate the another characteristic of the frequency-modulated signal as detected by the other mobile devices at the various locations.

11. The method of claim 10 performed by the mobile device.

12. The method of claim 10 , wherein the frequency-modulated signal is a commercial frequency-modulated radio signal.

13. The method of claim 12 , wherein the comparing comprises matching a location fingerprint comprising the detected frequency offset signal indicator and the another detected signal indicator to a matching fingerprint stored in the database, wherein the database is located remotely from the mobile device.

14. The method of claim 13 , further comprising: obtaining the prerecorded frequency offset indicators and the prerecorded other signal indicators from the other mobile devices.

15. The method of claim 14 , wherein: the location fingerprint includes a received signal strength indicator that indicates a signal strength characteristic of the frequency-modulated signal that is received by the mobile device, the location fingerprint includes a detected multipath indicator that indicates a multipath characteristic of the frequency-modulated signal that is received by the mobile device, and the comparing comprises comparing the location fingerprint to prerecorded signal strength indicators and prerecorded multipath indicators detected by the other mobile devices at the various locations.

16. The method of claim 14 , wherein: the location fingerprint includes a received signal strength indicator that indicates a signal strength of the frequency-modulated signal that is received by the mobile device, and the comparing comprises comparing the location fingerprint to prerecorded received signal strength indicators detected by the other mobile devices at the various locations.

17. The method of claim 14 , wherein: the location fingerprint includes a detected multipath indicator that indicates a multipath characteristic of the frequency-modulated signal that is received by the mobile device, and the comparing comprises comparing the location fingerprint to prerecorded multipath indicators detected by the other mobile devices at the various locations.

18. A system comprising: a radio signal quality metric module; a fingerprint matching module; and one or more processing units configured to execute the radio signal quality metric module and the fingerprint matching module, wherein the radio signal quality metric module is configured to obtain multiple different signal indicators for a frequency-modulated signal, the multiple different signal indicators characterizing the frequency-modulated signal as received by a mobile device and comprising at least: a detected frequency offset signal indicator that indicates a frequency offset characteristic of the frequency-modulated signal as detected by the mobile device, and another detected signal indicator that indicates another characteristic of the frequency-modulated signal as detected by the mobile device; and wherein the fingerprint matching module is configured to compare the detected frequency offset signal indicator and the another detected signal indicator to a database to obtain a location of the mobile device, the database having prerecorded frequency offset signal indicators that indicate the frequency offset characteristic of the frequency-modulated signal as detected by other mobile devices at various locations and prerecorded other signal indicators that indicate the another characteristic of the frequency-modulated signal as detected by the other mobile devices at the various locations.

19. The system of claim 18 , embodied as the mobile device.

20. The system of claim 19 , further comprising a receiver of the mobile device, wherein the receiver is configured to receive the frequency-modulated signal.