Transmission device, wireless communication system, and transmission method
A transmission device includes a modulation unit that performs chirp-spread modulation on an input information series to generate a modulation signal; a delay unit that provides, to a plurality of modulation signals obtained by duplicating the modulation signal generated by the modulation unit, delays having lengths different from each other, a difference between the delays being an integral multiple of a reciprocal of a bandwidth of the modulation signal; and a plurality of transmission antennas that transmit the plurality of modulation signals, respectively, to which the delays are provided by the delay unit.
1. A transmission device, comprising:
a modulation unit that performs chirp-spread modulation on an input information series to generate a modulation signal;
a delay unit that provides, to a plurality of modulation signals obtained by duplicating the modulation signal generated by the modulation unit, delays having lengths different from each other, a difference between the delays being an integral multiple of a reciprocal of a bandwidth of the modulation signal; and
a plurality of transmission antennas that transmit the plurality of modulation signals, respectively, to which the delays are provided by the delay unit.
2. The transmission device according to claim 1 ,
wherein the delay unit provides the delays to digital signals representing the plurality of modulation signals.
3. The transmission device according to claim 1 ,
wherein the delay unit provides the delays to analog signals representing the plurality of modulation signals.
4. A wireless communication system, comprising:
a transmission device; and
a reception device,
wherein the transmission device comprises:
a modulation unit that performs chirp-spread modulation on an input information series to generate a modulation signal;
a delay unit that provides, to a plurality of modulation signals obtained by duplicating the modulation signal generated by the modulation unit, delays having lengths different from each other, a difference between the delays being an integral multiple of a reciprocal of a bandwidth of the modulation signal; and
a plurality of transmission antennas that each transmits the plurality of modulation signals to which the delays are provided by the delay unit, and
wherein the reception device comprises:
a reception antenna that receives the plurality of modulation signals transmitted from the plurality of transmission antennas of the transmission device to obtain a reception signal;
a reception unit that performs a frequency conversion and an analog-digital conversion on the reception signal obtained by the reception antenna to generate a digital signal through the conversions; and
a demodulation unit that demodulates the digital signal generated by the reception unit.
5. A transmission method by a transmission device, the method comprising:
a modulation step of performing chirp-spread modulation on an input information series to generate a modulation signal;
a delay step of providing, to a plurality of modulation signals obtained by duplicating the modulation signal generated in the modulation step, delays having lengths different from each other, a difference between the delays being an integral multiple of a reciprocal of a bandwidth of the modulation signal; and
a transmission step of transmitting the plurality of modulation signals, to which the delays are provided in the delay step, from a plurality of transmission antennas, respectively.
6. A transmission device, comprising:
a modulation unit that performs spread modulation on an input information series to generate a modulation signal;
a frequency offset-providing unit that provides, to a plurality of modulation signals obtained by duplicating the modulation signal generated by the modulation unit, frequency offsets different from each other, a difference between the frequency offsets being an integral multiple of a symbol rate; and
a plurality of transmission antennas that transmit the plurality of modulation signals, respectively, to which the frequency offsets are provided by the frequency offset-providing unit.
7. The transmission device according to claim 6 ,
wherein the frequency offset-providing unit comprises:
a local oscillator that generates a carrier signal for each of the plurality of modulation signals;
a frequency converter that performs a frequency conversion on the modulation signals using the carrier signal; and
a band-limiting filter that suppresses a carrier leak and an image leak generated through the frequency conversion.
8. The transmission device according to claim 6 ,
wherein the frequency offset-providing unit comprises:
a local oscillator that generates a first carrier signal and a second carrier signal which have frequencies different from each other for each of the plurality of modulation signals,
a first frequency converter that performs a frequency conversion on the modulation signal using the first carrier signal,
a first band-limiting filter that suppresses a carrier leak and an image leak generated through the frequency conversion by the first frequency converter,
a second frequency converter that performs a frequency conversion on a signal output from the first band-limiting filter by using the second carrier signal, and
a second band-limiting filter that suppresses the carrier leak and the image leak generated through the frequency conversion by the second frequency converter.
9. The transmission device according to claim 6 ,
wherein the frequency offset-providing unit comprises:
a variable-phase shifter that adaptively changes a phase of the modulation signal for each of the plurality of modulation signals, and
a control unit that controls the variable-phase shifter.
10. The transmission device according to claim 9 ,
wherein the frequency offset-providing unit further comprises:
a variable attenuator that attenuates an amplitude of the modulation signal, in which a phase is changed by the variable-phase shifter according to the control of the control unit, for each of the plurality of modulation signals.
11. A wireless communication system, comprising:
a transmission device; and
a reception device,
wherein the transmission device comprises:
a modulation unit that performs spread modulation on an input information series to generate a modulation signal;
a frequency offset-providing unit that provides, to a plurality of modulation signals obtained by duplicating the modulation signal generated by the modulation unit, frequency offsets different from each other, a difference between the frequency offsets being an integral multiple of a symbol rate; and
a plurality of transmission antennas that transmit the plurality of modulation signals, respectively, to which the frequency offsets are provided by the frequency offset-providing unit, and
wherein the reception device comprises:
a reception antenna that receives the plurality of modulation signals transmitted from the plurality of transmission antennas of the transmission device to obtain a reception signal,
a reception unit that performs a frequency conversion and an analog-digital conversion on the reception signal obtained by the reception antenna to generate a digital signal through the conversions, and
a demodulation unit that demodulates the digital signal generated by the reception unit.
12. A transmission method by a transmission device, the method comprising:
a modulation step of performing spread modulation on an input information series to generate a modulation signal;
a frequency offset-providing step of providing, to a plurality of modulation signals obtained by duplicating the modulation signal generated in the modulation step, frequency offsets different from each other, a difference between the frequency offsets being an integral multiple of a symbol rate; and
a transmission step of transmitting the plurality of modulation signals, to which the frequency offsets are provided in the frequency offset-providing step, from a plurality of transmission antennas, respectively.