Digital signal transmission apparatus and method, digital signal receiving apparatus and method, and digital signal transmission system

A digital signal transmission method for transmitting a digital signal from an apparatus to another apparatus via a coaxial cable connected therebetween, the digital signal transmission method comprising:

• dividing a digital signal to be transmitted into a plurality of signal groups;
• modulating each of the plurality of signal groups obtained in the signal division by using an orthogonal frequency division multiplexing method;
• shifting each of the frequency bands of the plurality of modulation signals obtained in the modulation from a baseband to a mutually different frequency band;
• and
• combining a plurality of modulation signals whose frequency bands are shifted in the frequency shift and transmitting the signals to the coaxial cable.

A digital signal receiving apparatus that receives a digital signal from another apparatus via a coaxial cable connected therebetween, the digital signal receiving apparatus comprising:

• a signal obtaining section configured to obtain, from the coaxial cable, a plurality of modulation signals obtained in such a way that, after a plurality of signal groups obtained by dividing a digital signal are each modulated by an orthogonal frequency division multiplexing method, each of the frequency bands is shifted to a mutually different frequency band;
• a plurality of frequency shifters configured to shift each of the frequency bands of the plurality of modulation signals obtained by the signal obtaining section to a baseband;
• a plurality of demodulators configured to demodulate each of the plurality of modulation signals whose frequency bands are shifted by the plurality of frequency shifters in order to obtain the plurality of signal groups;
• and
• a signal combiner configured to combine the plurality of signal groups obtained by the plurality of demodulators in order to obtain a digital signal to be received.

A digital signal receiving method for receiving a digital signal from an apparatus connected to a coaxial cable, the digital signal receiving method comprising:

• obtaining, from the coaxial cable, a plurality of modulation signals obtained in such a way that, after a plurality of signal groups obtained by dividing a digital signal are each modulated by an orthogonal frequency division multiplexing method, each of the frequency bands is shifted to a mutually different frequency band;
• shifting each of the frequency bands of the plurality of modulation signals obtained in the signal obtainment to a baseband;
• demodulating each of the plurality of modulation signals whose frequency bands are shifted in the frequency shift in order to obtain the plurality of signal groups;
• and
• combining the plurality of signal groups obtained in the modulation in order to obtain a digital signal to be received.

A digital signal transmission system comprising:

• a first device;
• a second device;
• and
• a coaxial cable for connecting between the first device and the second device, a digital signal being transmitted between the first device and the second device via the coaxial cable,
• wherein the first device includes
• a first signal divider configured to divide a first digital signal to be transmitted to the second device into a plurality of signal groups,
• a plurality of first modulators configured to modulate each of the plurality of signal groups obtained from the first signal divider by using an orthogonal frequency division multiplexing method,
• a plurality of first frequency shifters configured to shift the frequency bands of a plurality of modulation signals generated by the plurality of first modulators from a baseband to a plurality of mutually different first frequency bands, and
• a first signal sender configured to combine a plurality of modulation signals whose frequency bands are shifted by the plurality of first frequency shifters and to send the signals to the coaxial cable, and
• wherein the second device includes
• a second signal divider configured to divide a second digital signal to be transmitted to the first device into a plurality of signal groups,
• a plurality of second modulators configured to modulate each of the plurality of signal groups obtained from the second signal divider by using an orthogonal frequency division multiplexing method,
• a second frequency shifter configured to shift each of the frequency bands of the plurality of modulation signals generated by the plurality of second modulators from the baseband to a plurality of second frequency bands that are mutually different from the plurality of first frequency bands, and
• a second signal sender configured to combine the plurality of modulation signals whose frequency bands are shifted by the plurality of second frequency shifters and to send the signals to the coaxial cable.