Acoustic modulation protocol
Exemplary embodiments provide a computer-implemented method for generating a modulated acoustic carrier signal for wireless transmission from a speaker of a transmit device to a microphone of a receive device. Aspects of the exemplary embodiments include converting a message to binary data; modulating one or more selected frequencies for one or more acoustic carrier signals based on the binary data to generate one or more modulated acoustic carrier signals; filtering the one or more modulated acoustic carrier signals to remove any unintended audible harmonics created during modulation, including; equalizing the modulated acoustic carrier signal to pre-compensate for known degradations that will occur further along a signal path; setting a level of the modulated acoustic carrier signal for the intended application; and storing the modulated acoustic carrier signal in a buffer for subsequent output and transmission by the speaker.
1. A computer-implemented method for generating a modulated acoustic carrier signal for wireless transmission from a speaker of a transmit device to a microphone of a receive device, comprising:
converting a message to binary data;
modulating one or more selected frequencies for one or more acoustic carrier signals based on the binary data to generate one or more modulated acoustic carrier signals;
filtering the one or more modulated acoustic carrier signals to remove any unintended audible harmonics created during modulation, including to reduce audibility of the modulated acoustic carrier signal, the filtering further including;
equalizing the modulated acoustic carrier signal to pre-compensate for known degradations that will occur further along a signal path; and
setting a level of the modulated acoustic carrier signal for an intended application;
storing the modulated acoustic carrier signal in a buffer for subsequent output and transmission by the speaker as audio over air for receipt by the microphone of the receive device; and,
in response to the microphone of the receive device receiving the one or more modulated acoustic carrier signals, demodulating the one or more modulated acoustic carrier signals to recover the binary data using an acoustic modulation protocol by:
receiving the one or more modulated acoustic carrier signals as blocks from one or more buffers;
filtering the one or more modulated acoustic carrier signals to eliminate out-of-band signals and improve signal-to-noise ratio;
dynamically adjusting a gain of the one or more modulated acoustic carrier signals to provide a substantially constant power level for the one or more modulated acoustic carrier signals; and
performing a Rasterized Digital Fourier Transform (RFT) that is based on a Goertzel frequency transform in combination with an adjustable Goertzel window length to increase frequency discrimination and to identify frequency components of the one or more modulated acoustic carrier signals.
2. The method of claim 1 wherein the one or more selected frequencies comprise an inaudible frequency greater than 20 kHz.
3. The method of claim 1 wherein the one or more selected frequencies comprises an audible frequency.
4. The method of claim 1 further comprising using a microphone of the transmit device to measure and analyze at least one of ambient noise, audio interference, and the modulated acoustic carrier signal, and in response, performing at least one of setting a speaker level to a higher setting to overcome ambient noise, switching frequencies to minimize the audio interference, and altering equalization of the modulated acoustic carrier signal.
5. The method of claim 1 further comprising constructing multiple (N) modulated acoustic carrier signals that form a parallel data transmission for at least one of: multiplying a base data rate by N, and forming redundant data paths to reduce a chance of bit errors.
6. The method of claim 1 further comprising providing the one or more modulated acoustic carrier signals with a locking segment, a mark segment, and a data segment.
7. The method of claim 6 further comprising providing the data segment with 2 to N words of data followed by at least one of a cyclic redundancy check (CRC) and a checksum.
8. The method of claim 1 further comprising performing the filtering using at least one of a Finite Impulse Response (FIR) filter and an Infinite Impulse Response (IR) filter.
9. The method of claim 1 wherein dynamically adjusting the gain of the one or more modulated acoustic carrier signals further comprises:
detecting a peak level of the one or more modulated acoustic carrier signals, and
adjusting the gain of the one or more modulated acoustic carrier signals so that an adjusted peak of the one or more modulated acoustic signal carriers is less than the detected peak level, and so that a power level of the one or more modulated acoustic carrier signals is normalized to 70% to 90% of the detected peak level.
10. The method of claim 1 further comprising performing sub band level matching to dynamically equalize the one or more modulated acoustic carrier signals to remove mismatched attenuation of one signaling frequency versus another.
11. The method of claim 1 further comprising performing sub bit averaging using a windowing method to reduce bit times into time slices and applying a weighting average to determine a statistical best-fit for a bit during an entire bit period based on the time slices.
12. The method of claim 1 wherein the receiving the one or more modulated acoustic carrier signals as blocks from the one or more buffers further comprises using a decoder state model to lock onto the one or more modulated acoustic carrier signals wherein phases of the state machine match components of the one or more modulated acoustic carrier signals.
13. A system, comprising:
a receive device having a microphone; and
a transmit device having a processor, memory and a speaker, the processor configured to execute an acoustic modulation protocol that is configured to:
convert a message to binary data;
modulate one or more selected frequencies for one or more acoustic carrier signals based on the binary data to generate one or more modulated acoustic carrier signals;
filter the one or more modulated acoustic carrier signals to remove any unintended audible harmonics created during modulation, including to reduce audibility of the modulated acoustic carrier signal, the filtering further including;
equalize the one or more modulated acoustic carrier signals to pre-compensate for known degradations that will occur further along a signal path; and
store the one or more modulated acoustic carrier signals in a buffer for subsequent output and transmission by the speaker as audio over air for receipt by the microphone of the receive device;
wherein in response to the microphone of the receive device receiving the one or more modulated acoustic carrier signals, the receive device executes a demodulation component to recover the binary data using an acoustic modulation protocol that is configured to:
receive data corresponding to the one or more modulated acoustic carrier signals as blocks from one or more buffers;
filter the one or more modulated acoustic carrier signals to eliminate out-of-band signals and improve signal-to-noise ratio;
dynamically adjust a gain of the one or more modulated acoustic carrier signals to provide a substantially constant power level for the one or more modulated acoustic carrier signals; and
perform a Rasterized Digital Fourier Transform (RFT) that is based on a Goertzel frequency transform in combination with an adjustable Goertzel window length to increase frequency discrimination and to identify frequency components of the one or more modulated acoustic carrier signals.
14. The system of claim 13 wherein the one or more selected frequencies comprise an inaudible frequency greater than 20 kHz.
15. The system of claim 13 wherein the one or more selected frequencies comprises an audible frequency.
16. The system of claim 13 wherein the acoustic modulation protocol uses a microphone of the transmit device to measure and analyze ambient noise, audio interference, and the modulated acoustic carrier signal, and in response, performs at least one of setting a speaker level to a higher setting to overcome ambient noise, switching frequencies to minimize the audio interference, and altering equalization of the modulated acoustic carrier signal.
17. The system of claim 13 wherein the acoustic modulation protocol constructs multiple (N) modulated acoustic carrier signals that form a parallel data transmission for at least one of: multiplying a base data rate by N, and forming redundant data paths to reduce a chance of bit errors.
18. The system of claim 13 the acoustic modulation protocol provides the one or more modulated acoustic carrier signals with a locking segment, a mark segment, and a data segment.
19. The system of claim 18 the acoustic modulation protocol provides the data segment with 2 to N words of data followed by at least one of a cyclic redundancy check (CRC) and a checksum.
20. The system of claim 13 the acoustic modulation protocol performs the filtering using at least one of a Finite Impulse Response (FIR) filter and an Infinite Impulse Response (IR) filter.
21. The system of claim 13 wherein the demodulation component is configured to dynamically adjust the gain by:
detecting a peak level of the one or more modulated acoustic carrier signals, and
adjusting the gain of the one or more modulated acoustic carrier signals so that an adjusted peak of the one or more modulated acoustic signal carriers is less than the detected peak level, and so that a power level of the one or more modulated acoustic carrier signals is normalized to 70% to 90% of the detected peak level.
22. The system of claim 13 wherein the demodulation component performs sub band level matching to dynamically equalize the one or more modulated acoustic carrier signals to remove mismatched attenuation of one signaling frequency verses another.
23. The system of claim 13 wherein the demodulation component performs sub bit averaging using a windowing system to reduce bit times into time slices and applying a weighting average to determine a statistical best-fit for a bit during an entire bit period based on the time slices.
24. The system of claim 13 wherein the demodulation component receives the one or more modulated acoustic carrier signals as blocks from the one or more buffers and using a decoder state model to lock onto the one or more modulated acoustic carrier signals, wherein phases of the state machine match components of the one or more modulated acoustic carrier signals.
25. An executable software product stored on a computer-readable medium containing program instructions for generating a modulated acoustic carrier signal for wireless transmission from a speaker of a transmit device to a microphone of a receive device, the program instructions for:
converting a message to binary data;
modulating one or more selected frequencies for one or more acoustic carrier signals based on the binary data to generate one or more modulated acoustic carrier signals;
filtering the one or more modulated acoustic carrier signals to remove any unintended audible harmonics created during modulation, including to reduce audibility of the modulated acoustic carrier signal, the filtering further including, including;
equalizing the modulated acoustic carrier signal to pre-compensate for known degradations that will occur further along a signal path;
setting a level of the modulated acoustic carrier signal for the intended application;
storing the modulated acoustic carrier signal in a buffer for subsequent output and transmission by the speaker as audio over air for receipt by the microphone of the receive device; and,
in response to the microphone of the receive device receiving the one or more modulated acoustic carrier signals, demodulating the one or more modulated acoustic carrier signals to recover the binary data using an acoustic modulation protocol by:
receiving the one or more modulated acoustic carrier signals as blocks from one or more buffers;
filtering the one or more modulated acoustic carrier signals to eliminate out-of-band signals and improve signal-to-noise ratio;
dynamically adjusting a gain of the one or more modulated acoustic carrier signals to provide a substantially constant power level for the one or more modulated acoustic carrier signals; and
performing a Rasterized Digital Fourier Transform (RFT) that is based on a Goertzel frequency transform in combination with an adjustable Goertzel window length to increase frequency discrimination and to identify frequency components of the one or more modulated acoustic carrier signals.