Data delivery using acoustic transmissions
Systems, methods, and computer program products for delivering information to an individual, group, or device. The information is carried by audio signals beyond the audible frequency range of human hearing, but within the frequency range of an audio system. The information is modulated onto an ultrasonic frequency and embedded into an audio signal transmitted by the audio system. Each individual, group member, or device may have or be coupled to a receiver configured to receive an acoustic signal transmitted by the audio system that includes the modulated ultrasonic frequency. The receiver extracts the information from the modulated ultrasonic frequency and provides the information to the individual, group member, or device.
1. An apparatus comprising a device configured to:
receive an acoustic signal including a communication signal generated by modulating a carrier frequency using a sequence of symbols mapped from a data signal and including a pilot sequence;
extract the communication signal from the acoustic signal;
identify the pilot sequence in the communication signal;
synchronize the sequence of symbols using the pilot sequence; and
recover the data signal by decoding the synchronized sequence of symbols.
2. The apparatus of claim 1 wherein the device is configured to identify the pilot sequence by performing a cross-correlation between one or more known pilot sequences and the communication signal.
3. The apparatus of claim 1 wherein the device is configured to synchronize the sequence of symbols by determining a position of the pilot sequence in the communication signal.
4. The apparatus of claim 1 wherein the device is further configured to estimate an offset in the communication signal using the pilot sequence.
5. The apparatus of claim 4 wherein the offset includes at least one of a frequency shift, a phase shift, and an amplitude shift.
6. The apparatus of claim 5 wherein the device is configured to estimate at least one of the frequency shift and the phase shift by comparing a frequency and a phase of the identified pilot sequence with a known phase and a known frequency of a known pilot sequence.
7. The apparatus of claim 5 wherein the offset includes the frequency shift, and the device uses a recursive algorithm that adjusts a demodulator carrier frequency by the estimated frequency shift, re-synchronizes the communication signal using the pilot sequence, and re-estimates the frequency shift until the frequency shift is below a predetermined frequency error.
8. The apparatus of claim 1 wherein the device is further configured to:
detect a transmit frame comprising one or more symbols of the synchronized sequence of symbols.
9. The apparatus of claim 8 wherein the device is further configured to:
estimate a distortion in the communication signal based on where the detected transmit frame starts and ends.
10. The apparatus of claim 8 wherein the device is further configured to activate an audio circuit in response to detecting the transmit frame.
11. The apparatus of claim 1 wherein the device is further configured to:
process the extracted communication signal through a matched filter.
12. A method comprising:
receiving an acoustic signal including a communication signal generated by modulating a carrier frequency using a sequence of symbols mapped from a data signal and including a pilot sequence;
extracting the communication signal from the acoustic signal;
identifying the pilot sequence in the communication signal;
synchronizing the sequence of symbols using the pilot sequence; and
recovering the data signal by decoding the synchronized sequence of symbols.
13. The method of claim 12 wherein identifying the pilot sequence comprises performing a cross-correlation between one or more known pilot sequences and the communication signal.
14. The method of claim 12 wherein synchronizing the sequence of symbols comprises determining a position of the pilot sequence in the communication signal.
15. The method of claim 12 further comprising:
estimating an offset in the communication signal using the pilot sequence.
16. The method of claim 15 wherein the offset includes at least one of a frequency shift, a phase shift, and an amplitude shift.
17. The method of claim 16 wherein estimating at least one of the frequency shift and the phase shift comprises:
comparing a frequency and a phase of the identified pilot sequence with a known phase and a known frequency of a known pilot sequence.
18. The method of claim 16 wherein the offset includes the frequency shift, and further comprising:
adjusting a demodulator carrier frequency by the estimated frequency shift;
re-synchronizing the communication signal using the pilot sequence;
re-estimating the frequency shift; and
recursively adjusting the demodulator carrier frequency by the estimated frequency shift, re-synchronizing the communication signal using the pilot sequence, and re-estimating the frequency shift until the frequency shift is below a predetermined frequency error.
19. The method of claim 12 further comprising:
detecting a transmit frame comprising one or more symbols of the synchronized sequence of symbols; and
estimating a distortion in the communication signal based on where the detected transmit frame starts and ends.
20. A computer program product comprising:
a non-transitory computer-readable storage medium; and
program code stored on the non-transitory computer-readable storage medium that, when executed by one or more processors, causes the one or more processors to:
receive an acoustic signal including a communication signal generated by modulating a carrier frequency using a sequence of symbols mapped from a data signal and including a pilot sequence;
extract the communication signal from the acoustic signal;
identify the pilot sequence in the communication signal;
synchronize the sequence of symbols using the pilot sequence; and
recover the data signal by decoding the synchronized sequence of symbols.