Patent ID: 7463577

Claim:
An orthogonal frequency division multiplexing (OFDM) communication apparatus comprising: a plurality of antennas; an OFDM signal forming section that forms a plurality of OFDM signals transmitted from the plurality of antennas by executing OFDM processing of a plurality of transmit data; and a selection section that selects whether to insert a known signal or a null signal in a predetermined subcarrier of each OFDM signal in a cycle of predetermined time, wherein: during a first cycle of time, the selection section inserts a known signal in a subcarrier of a first OFDM signal for transmission by a first antenna and inserts a null signal in a corresponding subcarrier of a second OFDM signal for transmission by a second antenna, such that the corresponding subcarriers within the first cycle of time have the same frequency band, during a second cycle of time that does not overlap the first cycle of time, the selection section inserts a null signal in a subcarrier of a third OFDM signal for transmission by the first antenna and inserts a known signal in a corresponding subcarrier of a fourth OFDM signal for transmission by the second antenna, such that the corresponding subcarriers within the second cycle of time have the same frequency band, the subcarrier conveying the known signal within the first OFDM signal has the same frequency band as the subcarrier conveying the null signal in the third OFDM signal, and the subcarrier conveying the null signal in the second OFDM signal has the same frequency band as the subcarrier conveying the known signal in the fourth OFDM signal.