Time Synchronization for Spectrally Shaped NC-OFDM by Envelope Fluctuation Detection

The synchronization at the Non-Contiguous Orthogonal Frequency Division Multiplexing (NC-OFDM) based Cognitive Radio (CR) receiver is a challenge. High-power interference from spatially- and spectrally-neighboring wireless systems may disrupt CR synchronization. In the same time, spectrum shaping techniques might be applied in the CR transmitter to reduce interference generated to other wireless systems. In this paper, we show how they can be used for time synchronization. The proposed Envelope Fluctuation Detection (EFD) method uses time- varying mean sample power of the spectrally shaped NC- OFD waveform. The EFD is more robust to narrowband interference than commonly used autocorrelation-based approach.