Non-pilot based synchronization for ACO-OFDM

Abstract

Cyclic-prefix-based synchronization has been used in radio-frequency OFDM for tracking both the timing and frequency offset. The idea behind cyclic-prefix based synchronization is to use the redundancy that is already inherent in the symbol and avoid additional pilots. Asymmetrically-clipped Optical Orthogonal Frequency Division Multiple Access (ACO-OFDM) is a power-efficient form of intensity-modulated/direct-detection (IM/DD) OFDM that avoids the use of a DC-bias. Like OFDM, ACO-OFDM has a cyclic prefix, but it also has additional redundancy in the signal due to the fact that information is transmitted only on the odd carriers. This paper introduces a way to exploit this additional redundancy along with the cyclic-prefix for time-synchronization in ACO-OFDM systems.