Carrier Phase Estimation Based on Error Function Calculation for 16-QAM Systems

A low complexity carrier phase estimation (CPE) for 16-QAM systems is investigated in this letter. First, we propose a single-stage CPE algorithm based on the error function calculation. In this CPE algorithm, we define an error function and use the four error function values corresponding to four test phase angles (-π/4, -π/8, 0, and π/8) to directly calculate the optimal phase angle, which effectively reduces the computational complexity compared with the blind phase search algorithm. Next, we combine the proposed CPE algorithm with an improved V&V algorithm and propose a two-stage CPE algorithm, which has both advantages of good linewidth tolerance and low computational complexity. Through simulations, the effectiveness of the proposed algorithms is demonstrated in a 28-Gbaud 16-QAM coherent optical transmission system.