Transmission device, reception device, communication system, transmission method and reception method

A transmission device comprising:

• two or more transmission antennas;
• and
• processing circuitry to perform space frequency block coding of a signal stream of a first time length,
• wherein the processing circuitry includes
• first processing circuitry to equally divide the signal stream into sub-streams of second time lengths,
• second processing circuitry to transform the sub-streams respectively into frequency signals by discrete Fourier transform,
• third processing circuitry to generate, for each of the frequency signals, a complex-processed frequency signal that is a signal generated by performing, on the frequency signal, complex conjugate processing and sign inversion processing or a signal generated by performing, on the frequency signal, the complex conjugate processing, give first frequency signals and first complex-processed frequency signals a phase rotation in proportional to a frequency corresponding to a cyclic shift in a time domain, the first frequency signals being one or more frequency signals among the frequency signals and the first complex-processed frequency signals being the complex-processed frequency signals corresponding to the first frequency signals, and generate, for each of the transmission antennas, a frequency arrangement signal corresponding to a transmission signal transmitted by the transmission antenna, by performing, in a frequency domain, mapping of a second frequency signal that is the frequency signal other than the first frequency signals, a second complex-processed frequency signal that is the complex-processed frequency signal corresponding to the second frequency signal, the first frequency signals to which the phase rotation has been given, and the first complex-processed frequency signals to which the phase rotation has been given, and
• fourth processing circuitry to transform the frequency arrangement signals respectively into time signals by inverse discrete Fourier transform, and
• the third processing circuitry generates the frequency arrangement signals in such a manner that components of different frequency signals are mapped at positions adjoining in a frequency domain in the frequency arrangement signals and that each frequency signal in the frequency arrangement signals becomes a comb-shape.

A transmission method in a transmission device that includes two or more transmission antennas and performs space frequency block coding of a signal stream of a first time length, the method comprising:

• equally dividing the signal stream into sub-streams of second time lengths and performing a cyclic shift of one or more sub-streams among the sub-streams in a time length in which a value divided by a primary modulation symbol interval of the sub-streams becomes a non-integer value;
• outputting the sub-streams as they are, as output signals, performing, on the sub-stream, complex signal processing that is time-axis inversion processing, complex conjugate processing and sign inversion processing, or the time-axis inversion processing and complex conjugate processing, and outputting as output signals the sub-streams on which the complex signal processing has been performed;
• generating a repetitive signal, which is a signal of a third time length in which signal arrangement is repeated in a time direction, for each of the output signals and giving a phase rotation to the repetitive signal;
• and
• generating, for each of the transmission antennas, a transmission signal transmitted from the transmission antenna, by multiplexing the repetitive signals to which the phase rotation has been given,
• wherein different phase rotations are given to repetitive signals multiplexed to an identical transmission signal.