In OFDM (Orthogonal Frequency-Division Multiplexing) communication, input signals are subjected to subcarrier modulation, and the modulated signals are subjected to IFFT (Inverse Fast Fourier Transformation), thereby generating baseband signals. Therefore, if the size of FFT (Fast Fourier Transformation) increases due to the increased number of subcarriers, baseband signals with high peaks are generated, making PAPR (Peak-to-Average Power Ratio) high. The high PAPR requires an amplifier having linearity over a broad range in order to transmit signals without distortion. Therefore, arts to reduce PAPR have been developed.
In an orthogonal frequency division multiplexing communication device disclosed in Unexamined Japanese Patent Application Kokai Publication No. 2006-165781, in order to reduce PAPR, before performing IFFT, the phase of a subcarrier modulation signal is controlled on the basis of an optimal phase calculated by a sequential decision procedure.
The OFDM communication has a problem regarding reducing PAPR. In the orthogonal frequency division multiplexing communication device disclosed in Unexamined Japanese Patent Application Kokai Publication No. 2006-165781, it is required to repeatedly perform calculation processing to find an optimal phase to reduce PAPR and to control a phase for each subcarrier.
USPTO Backgrounds
USPTO Backgrounds