Transmission method, transmission device, reception method and reception device

A transmission apparatus comprising:

• a processor;
• and
• a memory coupled to the processor,
• wherein the processor performs:
• generating a first orthogonal frequency division modulated (OFDM) symbol and a second OFDM symbol including first modulated signals s1(k) and second modulated signals s2(k), respectively, k denoting a carrier number, the second modulated signals s2(k) being equal to the first modulated signals s1(k), respectively, the first modulated signals s1(k) including 4-bit data blocks each corresponding to any one of 16 signal points of a first 16 Quadrature Amplitude Modulation (QAM) scheme;
• performing a first phase change on the second modulated signals s2(k) to generate second phase changed signals z2(k), the first phase change multiplying the second modulated signals s2(k) by respective coefficients ejθ(k) where ejθ(k) is a function of k and θ(k) denotes an angle;
• transmitting the first OFDM symbol and the second OFDM symbol through a first antenna and a second antenna, respectively, such that the first modulated signal s1(k) and the second phase changed signal z2(k) are transmitted at a same frequency and a same time for each of the carrier number k;
• generating a third OFDM symbol and a fourth OFDM symbol including third modulated signals s3(k) and fourth modulated signals s4(k), respectively, the fourth modulated signals s4(k) being equal to the third modulated signals s3(k), respectively, the third modulated signals s3(k) including 4-bit data blocks each corresponding to any one of 16 signal points of a second 16QAM scheme, a first arrangement pattern of the 16 signal points of the first 16QAM scheme being different from a second arrangement pattern of the 16 signal points of the second 16QAM scheme;
• performing a second phase change on the fourth modulated signals s4(k) to generate fourth phase changed signals z4(k), the second phase change multiplying the fourth modulated signals s4(k) by respective coefficients eiθ(k);
• and
• transmitting the third OFDM symbol and the fourth OFDM symbol through the first antenna and the second antenna, respectively, such that the third modulated signal s3(k) and the fourth phase changed signal z4(k) are transmitted at a same frequency and a same time for each of the carrier number k,
• wherein an inverse Fourier transform is applied to an OFDM symbol when the OFDM symbol is transmitted, the OFDM symbol being each of the first OFDM symbol, the second OFDM symbol, the third OFDM symbol, and the fourth OFDM symbol.