Multiple antennas transmit diversity scheme

An apparatus configured to transmit data, the apparatus comprising:

• a modulator configured to modulate data to be transmitted into a plurality of modulated symbols;
• and
• a transmitter configured to transmit the plurality of modulated symbols according to an output matrix by using a space frequency transmission diversity scheme via a plurality of antennas through a plurality of frequency subcarriers,
• wherein a first symbol and a second symbol are transmitted via a first antenna through a first frequency subcarrier and a second frequency subcarrier respectively, a third symbol and a fourth symbol are transmitted via a second antenna through a third frequency subcarrier and a fourth frequency subcarrier respectively, an inverse complex conjugate of the second symbol and a complex conjugate of the first symbol are transmitted via a third antenna through the first frequency subcarrier and the second frequency subcarrier respectively, and an inverse complex conjugate of the fourth symbol and a complex conjugate of the third symbol are transmitted via a fourth antenna through the third frequency subcarrier and the fourth frequency subcarrier respectively, and
• wherein a density of resource elements used for a reference signal transmission on the third antenna and the fourth antenna is lower than a density of resource elements used for the reference signal transmission on the first antenna and the second antenna.