SYSTEMS AND METHODS TO DETERMINE A LOCATION OF A MOBILE DEVICE

1 . A method to determine a location of a mobile device, the method comprising:

storing, in the mobile device, a map of radio frequency signal characteristics in a region identified in the map;

receiving, in a transceiver of the mobile device, radio frequency signals in the region;

determining, by the mobile device, characteristics of the radio frequency signals received in the transceiver;

matching the characteristics of the radio frequency signals with the frequency signal characteristics of the map at a first location in the map;

determining, by an inertial navigation system of the mobile device, a second location based on inertial sensor inputs;

determining, by the mobile device, that a confidence level of the first location as a current location of the mobile device is higher than a confidence level of the second location as the current location of the mobile device; and

initializing the inertial navigation system of the mobile device based at least in part on the first location.

2 . The method of claim 1 , wherein the characteristics of the radio frequency signals received in the transceiver include an identifier of a source that transmits the radio frequency signals.

3 . The method of claim 2 , wherein the characteristics of the radio frequency signals received in the transceiver include a strength level indicator of the radio frequency signals transmitted from the source.

4 . The method of claim 1 , wherein the radio frequency signals received in the transceiver include signals transmitted from a plurality of sources.

5 . The method of claim 4 , wherein the plurality of sources include at least one of:

an access point for a wireless local area network;

a repeater for a wireless local area network;

a wireless router;

a beacon device; and

a bluetooth device.

6 . The method of claim 1 , wherein the initializing of the inertial navigation system of the mobile device based at least in part on the first location includes setting the first location as an initial estimate of the location of the mobile device in dead reckoning position.

7 . The method of claim 1 , further comprising:

computing a third location as the current location of the mobile device based on a weighted average of the first location and the second location.

8 . The method of claim 7 , wherein the first location and the second location are weighted according to the confidence level of the first location as the current location of the mobile device and the confidence level of the second location as the current location of the mobile device respectively in computing the weighted average.

9 . The method of claim 8 , wherein the initializing of the inertial navigation system of the mobile device based at least in part on the first location includes setting the second location as an initial estimate of the location of the mobile device in dead reckoning position.

10 . The method of claim 1 , further comprising:

determining, by the inertial navigation system of the mobile device, a plurality of locations of the mobile device over a period of time based on the inertial sensor inputs, wherein the plurality of locations include the second location, and the radio frequency signals received in the a transceiver are received during the period of time; and

generating, by the mobile device, a local distribution of the characteristics of the radio frequency signals over the plurality of locations by correlating times of the received radio frequency signals in the time period and times of the plurality of locations determined for the time period;

wherein the matching includes matching the local distribution to the frequency signal characteristics of the map in a local area that includes the first location in the map.

11 . The method of claim 1 , wherein the initializing of the inertial navigation system of the mobile device is in response to a determination that the confidence level of the first location as the current location of the mobile device is higher than the confidence level of the second location as the current location of the mobile device.

12 . The method of claim 1 , wherein the initializing of the inertial navigation system of the mobile device is in response to a determination that the confidence level of the first location as the current location of the mobile device is higher than a predetermined threshold.

13 . The method of claim 1 , wherein the initializing of the inertial navigation system of the mobile device is in response to a determination that the confidence level of the first location as the current location of the mobile device is higher than a predetermined threshold and higher than the confidence level of the second current location as the location of the mobile device.

14 . A non-transitory computer storage medium storing instructions which when executed on a mobile device, cause the mobile device to perform a method in determining a location of the mobile device, the method comprising:

storing, in the mobile device, a map of radio frequency signal characteristics in a region identified in the map;

receiving, in a transceiver of the mobile device, radio frequency signals in the region;

determining, by the mobile device, characteristics of the radio frequency signals received in the transceiver;

matching the characteristics of the radio frequency signals with the frequency signal characteristics of the map at a first location in the map;

determining, by an inertial navigation system of the mobile device, a second location based on inertial sensor inputs;

determining, by the mobile device, that a confidence level of the first location as a current location of the mobile device is higher than a confidence level of the second location as the current location of the mobile device; and

initializing the inertial navigation system of the mobile device based at least in part on the first location.

15 . The non-transitory computer storage medium of claim 14 , wherein the inertial sensor inputs are received from motion sensors of the mobile device.

16 . The non-transitory computer storage medium of claim 15 , wherein the motion sensors include accelerometers.

17 . A mobile device, comprising:

a memory storing a map of radio frequency signal characteristics in a region identified in the map;

a transceiver to receive radio frequency signals in the region;

inertial sensors to generate inertial sensor inputs; and

at least one microprocessor executing at least one mobile application to:

determine characteristics of the radio frequency signals received in the transceiver;

match the characteristics of the radio frequency signals with the frequency signal characteristics of the map at a first location in the map;

determine, based on the inertial sensor inputs, a second location based on inputs;

determine that a confidence level of the first location as a current location of the mobile device is higher than a confidence level of the second location as the current location of the mobile device; and

initialize, based at least in part on the first location, dead reckoning operations according to subsequent inputs received from the inertial sensors.

18 . The mobile device of claim 17 , wherein the characteristics of the radio frequency signals received in the transceiver include:

an identifier of a source that transmits the radio frequency signals; and

a signal strength level of the radio frequency signals transmitted from the source.

19 . The mobile device of claim 17 , wherein the inertial sensors include accelerometers and gyroscopes.

20 . The mobile device of claim 17 , wherein the dead reckoning operations according to the subsequent inputs received from the inertial sensors are initialized using the first location in response to a determination that the confidence level of the first location as the current location of the mobile device is higher than both a predetermined threshold and the confidence level of the second location as the current location of the mobile device.