Reducing the effect of the nonlinear distortion in 16-APSK OFDM system by pilot-based automatic phase shift

Abstract

The paper proposed a method to reduce the effect of nonlinear distortion in 16-APSK OFDM system, which is a pilot-based automatic phase shift at the receiver. Transmitted pilot is inserted during the OFDM modulation process in the transmitter. When the pilot passes through the HPA, information about the nonlinear distortion of the HPA will be carried. In the receiver, the phase angle is rotated automatically based on the phase difference between the received pilots and the transmitted pilots, without depending on the HPA amplifier or system parameters. When the OFDM system uses the APS-pilot method, the nonlinear distortion reduction performance is approximately the same as in the OAPS method, the empirical formula to calculate OAPS, as well as the preset of OAPS manually at the receiver, is not needed.