Patent ID: 7099265

Claim:
An OFDM communication system handling OFDM signals composed of a plurality of sub-carriers, the OFDM communication system comprising: a first transmitter-receiver having a first horizontal polarization antenna and a first vertical polarization antenna, first OFDM signals including data signals and pilot signals being transmitted from the first horizontal polarization antenna, second OFDM signals including data signals and pilot signals being transmitted from the first vertical polarization antenna; and a second transmitter-receiver having a second horizontal polarization antenna for receiving the first OFDM signals, a second vertical polarization antenna for receiving the second OFDM signals and a demodulator, the data signals in the first OFDM signals being phase-adjusted using the pilot signals in the first OFDM signals after the first OFDM signals are FFT-processed, the data signals in the second OFDM signals being phase-adjusted using the pilot signals in the second OFDM signals after the second OFDM signals are FFT-processed, both of the phase-adjusted data signals being demodulated by the demodulator, wherein: the pilot signals included in the first OFDM signals and in the second OFDM signals are positioned at sub-carrier positions common to both of the OFDM signals; the first transmitter-receiver further includes a signal level detector for comparing a signal level receiver by the first horizontal polarization antenna with a signal level received by the first vertical polarization antenna for each sub-carrier after signals received by both of the first antennas are FFT-processed and for determining which one of the signal levels is higher than the other, and means for selecting either the first horizontal polarization antenna or the first vertical polarization antenna based on the determination of the signal level detector, so that the data signals for each sub-carrier are transmitted from the selected antenna which is determined to have a higher signal level, wherein: the first OFDM signals transmitted from the first horizontal polarization antenna and the second OFDM signals transmitted from the first vertical polarization antenna are the same signals; the second transmitter-receiver further includes: a signal level detector for detecting which signal level is higher in the signals received by the second horizontal polarization antenna or in the signals received by the second vertical polarization antenna; a selector for selecting signals having a higher signal level for each sub-carrier based on detecting results of the signal level detector; and a sub-carrier synthesizer for synthesizing the selected sub-carriers; and the demodulator demodulates synthesized sub-carriers.