Non-echo ultrasonic doppler for corrected inertial navigation

A method of non-echo ultrasonic Doppler used for corrected inertial navigation of a mobile device, the method comprising the steps of:

• providing a plurality of ultrasonic emitters in known locations within an environment, each emitter configured for transmitting an ultrasonic tone of a same predefined frequency;
• establishing, by a controller of the mobile device, an initial location of the mobile device within the environment and synchronizing, by a backend controller and the controller, clocks of the emitters and the mobile device;
• initiating, by the controller of the mobile device, dead reckoning procedures using sensors within the mobile device;
• receiving, by a microphone circuit of the mobile device, an ultrasonic tone from different emitters in the environment at different times, the particular time that a tone is received indicating a particular emitter in a particular location;
• converting, by an analog-to-digital converter coupled to the microphone circuit of the mobile device, each received ultrasonic tone into a digital waveform;
• determining, by a digital signal processor coupled to the analog-to-digital converter of the mobile device, a peak frequency of each of the digital waveforms;
• subtracting, by the digital signal processor, the peak frequency of each digital waveform from the predefined frequency to determine a Doppler shift for each received ultrasonic tone;
• and
• correcting, by the controller of the mobile device, the dead reckoning of the mobile device using the Doppler shifts of the received tones from the particular emitters at their particular locations.

A mobile device configured to correct inertial navigation using non-echo ultrasonic Doppler, the mobile device comprising:

• a controller operable to establish an initial location of the mobile device within the environment and initiate dead reckoning procedures using sensors within the mobile device;
• a microphone circuit operable to receive an ultrasonic tone of a predefined frequency transmitted from at least one emitter in an environment;
• an analog-to-digital converter coupled to microphone circuit and operable to convert the ultrasonic tone into a digital waveform;
• and
• a digital signal processor coupled to the analog-to-digital converter and operable to determine at least one peak frequency of the digital waveform, and subtract the at least one peak frequency from each predefined frequency to determine at least one Doppler shift, whereupon
• the controller can correct the dead reckoning of the mobile device using the at least one Doppler shift.