Low-Complexity Carrier Phase Recovery Based on Constellation Classification for M-ary Offset-QAM Signal

Low-complexity carrier phase recovery (CPR) for M-ary offset quadrature amplitude modulation (OQAM) formats is proposed and numerically verified, based on the technique of constellation classification. Although the OQAM signal has very poor tolerance to the laser linewidth due to the phase noise-induced crosstalk, we find that both even and odd samples of OQAM signal only have conventional constellation rotation with respect to phase noise. Through linear fitting of the classified constellation, carrier phase estimation can be derived from the slope of linear fitting function. Compared with our recently proposed modified blind phase search scheme, the computational complexity (CC) of proposed CPR does not increase much with the OQAM modulation level of M. Taking the CPR of 16-OQAM into account, we show that the CC can be significantly reduced by a factor of 8.47 (or 7.34) in the form of multipliers (or adders) with performance comparable to MBPS (B = 24) under the condition of
$\Delta f \times T_S {\rm = 5} \times 10^{ - 6} $
. In particular, a tolerance of linewidth and symbol duration product of
$8 \times 10^{{\rm - }5} $
, under the condition of CD = 300 ps/nm and DGD = 10 ps, can be secured for 16-OQAM, given 0.7-dB required-OSNR penalty.