1. A transmission signal generation apparatus comprising:

a mapper configured to generate a transmission signal, including a data frame having preamble information, pilot information,

and data information, using either a first transmission signal generation method of generating a first transmission signal

including a first pilot symbol sequence, a second pilot symbol sequence, and a first preamble multiplied by a factor so that

an average reception power of the first preamble corresponds to an average reception power of the data information received

with the first preamble, and a second transmission signal including a third pilot symbol sequence, a fourth pilot symbol sequence,

and a second preamble multiplied by a factor so that an average reception power of the second preamble corresponds to an average

reception power of data information received with the second preamble or a second transmission signal generation method of

generating a third transmission signal including a fifth pilot symbol sequence, a sixth pilot symbol sequence, and a third

preamble multiplied by a factor so that average reception power of the third preamble corresponds to an average reception

power of data information received with the third preamble; and

an Inverse Fourier transformer configured to:

generate a first OFDM signal by Inverse Fourier transforming the first transmission signal for transmission of the first OFDM

signal from a first antenna, and generate a second OFDM signal by Inverse Fourier transforming the second transmission signal

for transmission of the second OFDM signal from a second antenna in a same frequency and a same transmission period as the

first OFDM signal by the first transmission signal generation method, or generate a third OFDM signal by Inverse Fourier transforming

the third transmission signal for transmission of the third OFDM signal from the first antenna by the second transmission

signal generation method,

wherein:

the Inverse Fourier transformer is configured to arrange:

the first pilot symbol sequence in a first pilot carrier during a first time period;

the second pilot symbol sequence in a second pilot carrier during the first time period;

the third pilot symbol sequence in a third pilot carrier during the first time period; and

the fourth pilot symbol sequence in a fourth pilot carrier during the first time period;

the first pilot carrier and the third pilot carrier are in a same carrier position in the OFDM signal;

the second pilot carrier and the fourth pilot carrier are in a same carrier position in the OFDM signal;

the first pilot symbol sequence is a symbol sequence orthogonal to the third pilot symbol sequence; and

the third pilot symbol sequence is a symbol sequence different from the first pilot symbol sequence and same as the second

pilot symbol sequence.