OAM multiplexing communication system, OAM multiplexing transmission device, OAM multiplexing receiving device, and OAM multiplexing communication method

An OAM multiplexing reception device that receives a signal in an electromagnetic wave orbital angular momentum (OAM) mode subjected to spatial multiplex transmission by using a uniform circular array (UCA) in which a plurality of antenna elements are disposed circularly at an equal interval, the OAM multiplexing reception device comprising:

• a unit receiving the received OAM mode signal to the UCA, demultiplexing the signal into reception streams in OAM modes of each order, and subjecting each of the reception streams to frequency-conversion from a radio frequency (RF) band into a baseband (BB), or subjecting each of the reception streams to frequency-conversion into an intermediate frequency (IF) band and then into the baseband;
• and
• a channel estimation unit converting a signal sequence in each of the reception streams subjected to the frequency-conversion into a digital signal, performing a DFT process with a predetermined length, multiplying a value obtained through the DFT process by a diagonal matrix having, as a diagonal component, an inverse number of a value obtained by performing an FFT process with the length of the DFT process on a channel estimation signal sequence (a basic channel estimation signal sequence) having a predetermined length and a zero correlation, performing an IDFT process with the same length as the length of the DFT process on a result of the multiplication, and using a value obtained by dividing a result of the IDFT process for each predetermined time shift amount as an estimation value of a channel response from all transmission streams to each of the reception streams.

An OAM multiplexing communication method subjecting a signal in an electromagnetic wave orbital angular momentum (OAM) mode to spatial multiplex transmission by using a uniform circular array (UCA) in which a plurality of antenna elements are disposed circularly at an equal interval, the OAM multiplexing communication method comprising:

• causing an OAM multiplexing transmission device to execute
• a step generating each of the transmission streams in a baseband (BB), in which a channel estimation signal sequence is disposed before a transmission target data signal sequence, and a cyclic prefix (CP) having a predetermined length is disposed in the first half of the channel estimation signal sequence, the channel estimation signal sequence is time-shifted with a channel estimation signal sequence (a basic channel estimation signal sequence) having a predetermined length and a zero correlation, by a predetermined shift value for each of the transmission streams,
• a step converting a baseband signal sequence of the generated transmission streams to frequency conversion into radio frequency (RF) band, or converting into intermediate frequency (IF) band and then converting into the RF band, and
• a step converting a plurality of the frequency-converted transmission streams into a plurality of OAM mode signals having different orders, and multiplexing spatially by using the UCA;
• and
• causing an OAM multiplexing reception device to execute
• a step receiving the received OAM mode signal to the UCA, demultiplexing the signal into reception streams in OAM modes of each order, and subjecting each of the reception streams to frequency-conversion from a radio frequency band into a baseband, or subjecting each of the reception streams to frequency-conversion into an intermediate frequency band and then into the baseband, and
• a step converting a signal sequence in each of the reception streams subjected to the frequency-conversion into a digital signal, performing a DFT process with a predetermined length, multiplying a value obtained through the DFT process by a diagonal matrix having, as a diagonal component, an inverse number of a value obtained by performing an FFT process with the length of the DFT process on a channel estimation signal sequence (a basic channel estimation signal sequence) having a predetermined length and a zero correlation, performing an IDFT process with the same length as the length of the DFT process on a result of the multiplication, and performing channel estimation by using a value obtained by dividing a result of the IDFT process for each predetermined time shift amount as an estimation value of a channel response from all transmission streams to each of the reception streams.