Transmission method, reception method, transmitter, and receiver

A transmission system comprising:

• circuitry;
• a first antenna;
• a second antenna;
• a third antenna;
• and
• a fourth antenna,
• wherein, in operation, the circuitry:
• generates a first data symbol and a second data symbol from transmission data;
• performs a pre-coding on the first data symbol and the second data symbol to generate a first pre-coded symbol and a second pre-coded symbol;
• performs a first phase changing on the first pre-coded symbol to generate a first transmission signal;
• performs a second phase changing on the second pre-coded symbol to generate a second transmission signal;
• performs a third phase changing on the first pre-coded symbol to generate a third transmission signal;
• performs a fourth phase changing on the second pre-coded symbol to generate a fourth transmission signal;
• and
• transmits the first transmission signal, the second transmission signal, the third transmission signal, and the fourth transmission signal from a first antenna, a second antenna, third antenna, and a fourth antenna, respectively.