Modulation device, demodulation device, and acoustic signal transmission method

A modulation device for superposing a data signal on an acoustic signal and transmitting thus obtained signal, the modulation device comprising:

• a selection unit that selects a carrier frequency of the data signal and a PN sequence corresponding to the carrier frequency;
• a modulation unit that modulates the carrier frequency selected by the selection unit with the data signal;
• a generation unit that generates a symbol synchronization signal according to the PN sequence selected by the selection unit;
• and
• a superposition unit that superimposes the symbol synchronization signal generated by the generation unit and the data signal modulated by the modulation unit onto the acoustic signal.

A demodulation device comprising:

• an input unit that receives an acoustic signal superposed with a modulated data signal;
• a calculation unit that calculates correlations between the acoustic signal received by the input unit and a plurality of PN sequences;
• a determination unit that determines the PN sequence having the highest maximum correlation value with the received acoustic signal in the plurality of PN sequences according to a result of calculation by the calculation unit;
• a synchronization processing unit that decides a synchronization point by using the PN sequence determined by the determination unit and synchronizes the modulated data signal superposed on the acoustic signal according to the synchronization point;
• and
• a demodulation unit that demodulates the modulated data signal subjected to the synchronizing by the synchronization processing unit.

An acoustic signal transmission system comprising:

• a modulation device for superposing a data signal on an acoustic signal and transmitting thus obtained signal, the modulation device comprising
• a selection unit that selects a carrier frequency of the data signal and a PN sequence corresponding to the carrier frequency;
• a modulation unit that modulates the carrier frequency selected by the selection unit with the data signal;
• a generation unit that generates a symbol synchronization signal according to the PN sequence selected by the selection unit;
• and
• a superposition unit that superimposes the symbol synchronization signal generated by the generation unit and the data signal modulated by the modulation unit onto the acoustic signal;
• and
• a demodulation device comprising:
• an input unit that receives the acoustic signal superposed with the modulated data signal;
• a calculation unit that calculates correlations between the acoustic signal received by the input unit and a plurality of PN sequences;
• a determination unit that determines the PN sequence having the highest maximum correlation value with the received acoustic signal in the plurality of PN sequences according to a result of calculation by the calculation unit;
• a synchronization processing unit that decides a synchronization point by using the PN sequence determined by the determination unit and synchronizes the modulated data signal superposed on the acoustic signal according to the synchronization point;
• and
• a demodulation unit that demodulates the modulated data signal subjected to the synchronizing by the synchronization processing unit.