Presentation Information
[B-3-04]Time-Domain-Based Carrier Frequency Offset Estimation for Space Optical Communications under Colored Noise
〇Takahiro Suzuki1, Daisaku Ogasahara1, Hidemi Noguchi1, Junichi Abe1, Tomonaga Tanaka1, Kenji Wakafuji1 (1. NEC Corporation)
Keywords:
Space optical communications,Satellite optical communications,Digital coherent communications,Carrier frequency offset estimation,CFO,Doppler shift,Colored noise,Autocorrelation
In digital coherent space optical communications, the estimation and compensation of GHz-level carrier frequency offset (CFO) induced by the Doppler effect are indispensable. A time-domain estimation method utilizing the average phase difference between adjacent samples is attractive for onboard implementation owing to its low computational complexity. However, when the receiver front-end bandwidth is limited, the noise becomes colored, and the resulting noise autocorrelation introduces a bias into estimators based on lag-1 autocorrelation. In this paper, we propose a time-domain CFO estimation method that effectively suppresses estimation bias under colored noise. The proposed method estimates the CFO using autocorrelations at lags selected based on a trade-off between mitigating the effect of noise autocorrelation and preserving signal autocorrelation. Simulation results demonstrate that, compared with the lag-1 autocorrelation method, the proposed method achieves a significant reduction in estimation error over a wide SNR range. The residual CFO falls within the range that can be compensated by subsequent carrier phase recovery, demonstrating the practical effectiveness of the proposed method as a coarse CFO compensation technique for digital coherent space optical communications.