Performance optimization of high order QAM in presence of phase noise and AWGN:: Application to a decision directed frequency synchronization system

The paper presents an analysis of the impact of Local Oscillators (LO) phase noise on the performance of digital transmission systems. Using an efficient phase noise model, we study degradations induced by phase noise and Additive White Gaussian Noise (AWGN) on a carrier recovery system combined to high order Quadrature Amplitude Modulations (QAM). Simulation results show that an optimum trade-off between AWGN and phase noise robustness for the loop bandwidth can be determined. In order to compare simulated and analytical performance, a new general expression of the bit error probability is developped for square QAM in the presence of phase noise over Gaussian channel. Furthermore, novel decision areas related to Quadrature Amplitude Modulations are determined in order to improve the performance of the carrier recovery algorithm in the presence of phase noise and frequency offset.