Ad hoc positioning of mobile devices using near ultrasound signals
An approach for providing a lower cost real time location system in less trafficked areas of a building. This approach uses on-board audio capabilities of a mobile device to receive a room response trace resulting from a self-generated acoustic signal. By comparing the room response trace to a modeled room response trace, the location of the mobile device is determined.
1. A method comprising:
modulating an acoustic signal to form a transmitted acoustic signal, the transmitted acoustic signal having a narrow autocorrelation function;
transmitting, by a speaker in a mobile device, the transmitted acoustic signal;
receiving, by a microphone within the mobile device, a received acoustic signal, the received acoustic signal resulting from an interaction by the transmitted acoustic signal with a local acoustic environment in which the mobile device is located;
deconvolving the received acoustic signal with the transmitted acoustic signal to generate a room response trace;
comparing the room response trace to a subset of a plurality of modeled room response traces, at least one of the subset of the plurality of modeled room response traces being calculated based on a model of a building in the local acoustic environment, each of the subset of the plurality of modeled room response traces being previously calculated and stored on one of the mobile device or a central server, wherein the subset of the plurality of modeled room response traces are identified as being likely acoustic environments based on a location history of the mobile device; and
determining a location of the mobile device based on the comparing the room response trace.
2. The method of claim 1 , further comprising:
correcting the room response trace prior to the comparing, the correcting including using spatial transmit characteristics for the speaker and spatial receive characteristics for the microphone.
3. The method of claim 1 , further comprising:
correcting the room response trace prior to the comparing, the correcting including estimating an orientation of the mobile device by using an on-board sensor of the mobile device to determine the orientation with respect to magnetic north or true north.
4. The method of claim 3 , wherein estimating the orientation of the mobile device further includes using the on-board sensor of the mobile device to determine the orientation for a time period during at least one of the transmitting by the speaker or the receiving by the microphone.
5. The method of claim 1 ,
wherein modulating the acoustic signal to form the transmitted acoustic signal includes modulating the acoustic signal using one of phase-shift keying modulation or QAM modulation.
6. The method of claim 1 , wherein transmitting the transmitted acoustic signal includes transmitting the transmitted acoustic signal in a specific time slot associated with the mobile device.
7. The method of claim 1 , wherein the comparing the room response trace to the subset of the plurality of modeled room response traces includes using a positioning algorithm that is a combination of analytic, numerical and machine learning algorithms.
8. The method of claim 1 , wherein the comparing the room response trace to the subset of the plurality of modeled room response traces includes using a positioning algorithm that is aided by sensor data fusion, the sensor data fusion including combined signals from one or more of accelerometers, gyroscopes, magnetometers and pressure sensors.
9. The method of claim 1 , wherein the comparing the room response trace to the subset of the plurality of modeled room response includes limiting search of potential acoustic environments based on location history and data fusion position results.
10. A mobile computing device comprising:
a processing device configured to modulate an acoustic signal to form a transmitted acoustic signal, the transmitted acoustic signal having a narrow autocorrelation function;
a speaker configured to transmit the transmitted acoustic signal;
a microphone configured to receive a received acoustic signal, wherein the received acoustic signal results from an interaction by the transmitted acoustic signal with a local acoustic environment in which the mobile computing device is located; and
the processing device further configured to:
deconvolve the received acoustic signal with the transmitted acoustic signal to generate a room response trace;
compare the room response trace to a subset of a plurality of modeled room response traces, at least one of the subset of the plurality of modeled room response traces being calculated based on a model of a building in the local acoustic environment, each of the subset of the plurality of modeled room response traces being previously calculated and stored on one of the mobile computing device or a central server, wherein the subset of the plurality of modeled room response traces are identified as being likely acoustic environments based on a location history of the mobile computing device; and
determine a location of the mobile computing device based on the comparison of the room response trace.
11. The mobile computing device of claim 10 , wherein the processing device is further configured to:
perform a correction of the room response trace prior to the comparison, wherein the correction includes using spatial transmit characteristics for the speaker and spatial receive characteristics for the microphone.
12. The mobile computing device of claim 10 , wherein the processing device is further configured to:
perform a correction of the room response trace prior to the comparison, wherein the correction includes an estimate of orientation of the mobile computing device by using an on-board sensor of the mobile computing device to determine the orientation with respect to magnetic north or true north.
13. The mobile computing device of claim 10 , wherein the transmitted acoustic signal is a modulated acoustic signal using one of phase-shift keying modulation or QAM modulation.
14. The mobile computing device of claim 10 , wherein the transmitted acoustic signal is transmitted in a specific time slot associated with the mobile computing device.
15. The mobile computing device of claim 10 , wherein the processing device is further configured to compare the room response trace to the subset of the plurality of modeled room response traces by using a positioning algorithm that is a combination of analytic, numerical and machine learning algorithms.
16. The mobile computing device of claim 10 , wherein the processing device is further configured to compare the room response trace to the subset of the plurality of modeled room response traces by using a positioning algorithm that is aided by sensor data fusion, the sensor data fusion including combined signals from one or more of accelerometers, gyroscopes, magnetometers and pressure sensors.
17. A method comprising:
receiving, by a microphone within a first mobile device, a received acoustic signal, the received acoustic signal resulting from an interaction by a transmitted acoustic signal within a local acoustic environment in which the first mobile device is located, wherein the transmitted acoustic signal is transmitted by a second mobile device, the transmitted acoustic signal being a modulated acoustic signal having a narrow autocorrelation function, the modulated acoustic signal being one of a PSK-modulated signal or a QAM-modulated signal;
receiving, by the first mobile device, supplemental information including a strength of the transmitted acoustic signal, an orientation of the second mobile device, one or more spatial characteristics of the second mobile device, timing information associated with the transmitted acoustic signal, and a location history of the first mobile device; and
determining a location of the first mobile device based on the received acoustic signal and the supplemental information.
18. The method of claim 17 , wherein the timing information provides timing data with respect to a common time frame.