Code-Aided Synchronization Algorithm for High-Order QAM

In this paper, an improved timing method is proposed for high-order QAM system. The timing processing block computes the value of weights for each data block and then combines the soft information based on the estimated results. In addition, an improved polarity decision phase detector algorithm is proposed for the carrier recovery, the soft information fed back from the decoder is modulated and then sent to the polarity module for polarity decision. The polarity decision result is fed to the phase detector (PD) module for the phase estimation. Simulation results show that the improved code-aided timing and carrier synchronization system can perform better than the unimproved algorithm at very low SNR.