Ultrasonic in-building positioning system based on phase difference array with ranging

1. A method for determining position of a mobile electronic device within a building, comprising:

emitting, in the building at least one of an electromagnetic and an optical initiation signal from the mobile electronic device;

identifying the mobile device by detecting the initiation signal at a base station disposed in the building;

transmitting a control signal from the base station to cause emitting an acoustic pulse from the position of the mobile electronic device;

detecting the acoustic pulse at the base station at at least three known spaced apart locations along each of at least two lines extending in different directions;

determining the time differences of arrival of acoustic pulses at each of the detecting locations;

determining a phase difference of the acoustic pulse between each of the detecting locations;

determining a relative position of the device with respect to the base station known position from the time differences of arrival and phase differences; and

at least one of storing or displaying the relative position.

2. The method of claim 1 wherein the at least two lines are orthogonal.

3. The method of claim 1 further comprising determining an absolute position of the device from the relative position.

4. The method of claim 1 wherein a difference between spacing of a first one of the detecting locations and a second one of the detecting locations, and the second one of the detecting locations and a third one of the detecting locations is equal to one-half a wavelength of the acoustic pulse.

5. The method of claim 1 further comprising communicating the relative position between the known position and the mobile device using at least one of a ultrasonic frequency channel, radio frequency channel and/or an infrared channel.

6. The method of claim 1 further comprising emitting an acoustic pulse from the known location, detecting the acoustic pulse from the known location and emitting the acoustic pulse from the mobile device in response to detecting the acoustic pulse from the known location.

7. The method of claim 1 further comprising synchronizing timing devices at the known location with synchronizing devices in the mobile device by transferring timing information over at least one of a radio frequency channel and an infrared channel.

8. The method of claim 1 wherein the phase differences are determined by narrowband phase difference algorithms applied to signals detected at each of the known locations with at least one other signal detected at the known locations.

9. The method of claim 1 wherein the mobile device comprises a smart tag.

10. The method of claim 1 wherein the mobile device comprises a cellular telephone.

11. The method of claim 1 wherein the acoustic pulse comprises a selected number of cycles at a single frequency.

12. The method of claim 1 further comprising:

causing at least a second mobile electronic device to emit at least one of an electromagnetic and optical initiation signal;

detecting the second device initiation signal at the base station;

identifying the second mobile electronic device using the detected second device initiation signal;

after a predetermined time related to transmission time of the acoustic pulse from the first mobile electronic device;

transmitting a control signal from the base station to cause the second mobile electronic device to emit an acoustic signal;

detecting the second device acoustic signal at the base station at the three known spaced apart locations along each of at least two lines extending in different directions;

determining the time differences of arrival of acoustic pulses from the second device acoustic signal at each of the detecting locations;

determining a phase difference of the acoustic pulses from the second device acoustic signal between each of the detecting locations;

determining a relative position of at least the second mobile electronic device with respect to the known position from the time differences of arrival and phase differences; and

at least one of storing or displaying the relative position.