Pilot Based Synchronization Strategy for a Coherent OFDM Receiver

Receiver synchronization, in terms of time and frequency, is one of the most important tasks designing an OFDM (orthogonal frequency division multiplex) receiver for coherent detection. Any LO (local oscillator) misalignment of the receivers analog front-end against the transmitter carrier frequency leads to ICI (inter carrier interference) and degrades the overall SNR. This paper introduces a frequency synchronization approach for an OFDM receiver based on the broadcast standard DRM (digital radio mondiale). Based on the desired synchronization bandwidth the procedure of synchronization is separated into two steps. First a rough offset is estimated and a pre-correction is accomplished. In a second step the remaining offset is estimated. Both algorithms are implemented before the actual FFT in the OFDM receiver and doesn't depend on any timing or robustness mode information. Both methods are based either on frequency pilots (references) or the information of the guard interval (cyclic prefix).