Carrier frequency offset estimation scheme for quasi-constant envelope OFDM satellite system under AWGN channel

摘要

Quasi-Constant Envelope OFDM transmits dual-stream simultaneously to improve the spectral efficiency of Constant Envelope OFDM. It can provide high data rate links and maintain a low PAPR to reduce the distortion caused by the nonlinear power amplifier. Thus, the quasi-constant envelope OFDM is suitable for satellite communication system. However, the carrier frequency offset (CFO) in satellite communication must be estimated and compensated before the demodulation. In this paper a CFO estimation scheme is proposed for quasi-constant envelope OFDM satellite system under additive white Gaussian noise (AWGN) channel. Since the null subcarrier at the transmitter can be considered as the prior information at the receiver, this null subcarrier can be used to estimate the CFO through phase demodulator and inverse discrete Fourier transform (IDFT) module at the receiver. Mathematical analysis reveals that the ideal estimation range of normalized CFO is nearly half of the size of IDFT under AWGN channel. Simulation results show that the proposed scheme performs well at moderate and high signal-to-noise ratio (SNR) conditions.