Method and system for digital communication over an acoustic channel

A method of generating and transmitting combined linear frequency modulated signal carrying data, comprising:

• selecting a frequency-domain vector on the basis of a symbol;
• transforming the frequency-domain vector into a kernel vector;
• generating a time-domain vector by copying the kernel vector;
• multiplying the elements of the time-domain vector by a signal with linear frequency modulation;
• and
• transmitting the result of the multiplication to the acoustic channel through the acoustic system.

A method of receiving combined linear frequency modulated signal, comprising:

• detecting of time of arrival and slope of the combined linear frequency modulated signal;
• generating a heterodyne signal with linear frequency modulation;
• multiplying the received combined linear frequency modulated signal by the heterodyne signal with linear frequency modulation;
• splitting frequency band of the result of the multiplication into subbands;
• estimating of an energy parameter for a subband;
• and
• detecting a symbol on the basis of energy parameters, wherein the start of the heterodyne signal with linear frequency modulation is selected on the basis of the detected time of arrival of the combined linear frequency modulated signal, and the slope of the heterodyne signal with linear frequency modulation is a function of the detected slope of the combined linear frequency modulated signal.

A method of detecting of time of arrival and slope of a combined linear frequency modulated signal, comprising:

• delaying a received signal by time corresponding to a length of a kernel vector;
• generating an offset signal with frequency corresponding to a slope hypothesis of the combined linear frequency modulated signal and the length of the kernel vector;
• multiplying the received signal, the delayed received signal and the offset signal;
• integrating the results of the multiplication over time;
• computing an energy parameter of the integration result;
• and
• estimating a time of arrival and slope of the combined linear frequency modulated signal on the basis of the energy parameter.

An acoustic communication system comprising:

• a transmitter;
• and
• a receiver, wherein the receiver comprises:
• an acoustic sensor configured to receive an acoustic signal from the transmitter;
• an alignment delay line;
• a signal detector, wherein the signal detector and the alignment delay line are communicatively coupled to the acoustic sensor;
• a signal generator configured to generate a linear frequency modulated signal, wherein the signal detector is configured to control the signal generator;
• a multiplier communicatively coupled to the signal generator and the alignment delay line;
• a signal buffer communicatively coupled the multiplier and configured to receive and store a resulting signal from the multiplier;
• a Fast Fourier Transform block communicatively coupled to the signal buffer and configured to receive one or more signals from the buffer and transform the one or more signals into one or more frequency domain signals;
• an energy parameter estimator communicatively coupled to the Fast Fourier Transform block, wherein the energy parameter estimator is configured to process the one or more frequency domain signals from the Fast Fourier transform block;
• and
• a symbol detector communicatively coupled to the energy parameter estimator, wherein the symbol detector is configured to identify a received symbol.