This work introduces a novel symbol time synchronization method for optical fast orthogonal frequency-division multiplexing (FOFDM) systems. The first arrival path of a channel is well known to be related to the best symbol time; however, few approaches exploit this fact. In contrast, the basic idea of this study is to derive an estimate of channel-coefficient power using the periodic property of the discrete cosine transform (DCT) in FOFDM. The proposed method maximizes the effective signal power (ESP), which is defined as the signal power excluding the intersymbol interference (ISI), within the DCT window using the obtained channel-coefficient power. Simulations reveal that the proposed estimator exhibits low complexity and robustness against the presence of chromatic dispersion (CD).
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Wen-Long Chin, "Maximization of Effective Signal Power in DCT Window for Symbol Time Synchronization in Optical Fast OFDM," J. Lightwave Technol. 31, 740-748 (2013)