Data transmission via wide band acoustic channels
Embodiments of the present invention relate to ultrasound (acoustic) data transmission systems, in particular data transmission over wide-band acoustic channels with frequency-dependant multi-path propagation. More specifically, embodiments of the invention involve increasing the bit rate in the acoustic channel by means of utilization of the entire ultrasound spectrum available for data transmission inside a human body.
1. A method of demodulating acoustic data, comprising:
receiving a wide-band acoustic data signal;
transforming the wide-band acoustic data signal into a plurality of frequency-divided sub-band signals, wherein the plurality of frequency-divided sub-band signals are modulated with a plurality of modulation schemes;
generating a plurality of data streams by demodulating each sub-band signal in the plurality of frequency-divided sub-band signals into a data stream according to a respective frequency band and demodulation scheme, each data stream in the plurality of data streams corresponding to one of the plurality of frequency-divided sub-band signals; and
combining the plurality of data streams into an output data stream.
2. The method of claim 1 , wherein the wide-band acoustic data signal is received over a wide-band acoustic data channel divided into N sub-bands, wherein the first sub-band corresponds to a maximum echo delay and a minimum signal attenuation and the Nth sub-band corresponds to a minimum echo delay and a maximum signal attenuation, such that echo delay decreases and signal attenuation increases as sub-bands increase in frequency from the first sub-band to the Nth sub-band.
3. The method of claim 2 , wherein the plurality of frequency-divided sub-band signals are received over corresponding sub-bands in the wide-band acoustic data channel.
4. The method of claim 1 , wherein generating the plurality of data streams comprises demodulating each sub-band signal according to a demodulation scheme that is different from modulation schemes used for other sub-band signals.
5. The method of claim 1 , wherein the receiving comprises receiving the wide-band acoustic data signal via a combination of wide-band frequency selective transducers and narrow-band frequency selective acoustic transducers.
6. The method of claim 1 , wherein generating a plurality of data streams by demodulating comprises demodulating data in a first sub-band signal and a second sub-band signal based on a first and second number of subcarriers, respectively, the first number of subcarriers being greater than the second number of subcarriers.
7. The method of claim 1 , wherein generating a plurality of data streams by demodulating comprises demodulating a data stream corresponding to a sub-band signal at a lower frequency using more subcarriers than a data stream corresponding to a sub-band signal at a higher frequency.
8. The method of claim 1 , wherein generating a plurality of data streams by demodulating comprises demodulating data using differential quadrature phase-shift keying or quadrature amplitude demodulation.
9. The method of claim 1 , wherein generating a plurality of data streams by demodulating comprises:
demodulating a first sub-band signal using quadrature amplitude demodulation; and
demodulating a second sub-band signal using differential quadrature phase-shift keying demodulation.
10. The method of claim 9 , wherein the first sub-band signal has a first frequency band with a first echo delay and a first signal attenuation and the second sub-band signal has a second frequency band with a second echo delay and a second signal attenuation, the first frequency band being lower than the second frequency band, the first echo delay being greater than the second echo delay, and the first signal attenuation being less than the second signal attenuation.