Doppler aided inertial navigation
Doppler Aided Inertial Navigation (DAIN) facilitates the determination of position, velocity and direction of mobile devices operating in highly obstructed GPS/GNSS environments. Delivering high precision, high resolution positioning information using signals of opportunity, the present invention measures the Doppler shift of a moving device using a variety of signals combined with inertial accelerometers and environmental sensors to deliver an autonomous positioning and navigation capability that does not require external infrastructure or a priori knowledge of signal sources.
1. A system for determining the speed of a mobile device in a multipath environment, comprising:
a receiver associated with the mobile device configured to intercept at least one radio frequency emission traveling along a plurality of reflected paths from an emitter to the receiver;
a narrowband signal detector configured to employ a spectral compression technique that includes a non-linear operation to transform the at least one intercepted radio frequency emission into Doppler frequency observables;
a signal processor configured to employ Doppler broadening detection to determine the speed of the mobile device based on the Doppler frequency observables.
2. The system of claim 1 , wherein the at least one intercepted radio frequency emission is from a stationary source.
3. The system of claim 1 , wherein the at least one intercepted radio frequency emission is a Wi-Fi, cellular, Bluetooth, satellite radio or digital television signal.
4. The system of claim 1 , wherein the signal processor is configured to transform the reflected radio frequency emission into Doppler frequency observables using Doppler broadening detection by
transforming the radio frequency emission to produce frequency spectral data using a Fourier transformation; and
determining an amplitude distribution within the frequency spectral data of the at least one radio frequency emission, wherein the amplitude distribution is a function of the multipath environment and the Doppler frequency observables.
5. A method for determining the speed of a mobile device in a multipath environment, comprising
intercepting at least one radio frequency emission traveling along a plurality of reflected paths from an emitter to a receiver associated with the mobile device;
processing the at least one radio frequency emission with spectral compression that includes a non-linear operation to produce narrowband radio frequency data comprising Doppler frequency observables; and
applying Doppler broadening detection on the narrowband radio frequency data comprising the Doppler frequency observables to determine the speed of the mobile device.
6. The method of claim 5 , wherein Doppler broadening detection comprises:
transforming the narrowband radio frequency data comprising the Doppler frequency observables to produce frequency spectral data using a Fourier transformation; and
determining an amplitude distribution within the frequency spectral data of the at least one radio frequency emission, wherein the amplitude distribution is a function of the multipath environment and the Doppler frequency observables.
7. The method of claim 6 , repeatedly filtering the amplitude distribution produced by the Fourier transformation with two or more other amplitude distributions to determine a dominant amplitude distribution of frequency spectral data that reduces signal fading and scattering effects.
8. The method of claim 5 , wherein the at least one intercepted radio frequency emission external to the mobile device is from a stationary source.
9. The method of claim 5 , wherein the at least one intercepted radio frequency emission is a Wi-Fi, cellular, Bluetooth, satellite radio or digital television signal.