A Code-Aided Carrier Synchronization Algorithm Based on APPA
一种基于APPA的码辅助载波同步算法

The residual frequency and phase offset will make obvious degradations on the Turbo decoding performance under low SNR conditions, and it must introduce some coded-aided carrier synchronization algorithm for the phase estimation. In this paper, an improved residual carrier frequency offset estimation algorithm based on APPA(A Priori Probability Aided)phase estimation is proposed. It uses the extrinsic information obtained from the turbo decoder to aid an iterative phase estimation process. And the loop filter converts the phase error signal to a control word that is used to bias the numerically controlled oscillator. The simulation results show that the algorithm performs successfully with small frequency offset and phase offset at very low SNR(for example, SNR<-7.8 dB) and its performance is very close to the optimally synchronized system.