Modified high-efficiency carrier estimator for OFDM communications with antenna diversity

Orthogonal frequency division multiplexing (OFDM) based wireless communication systems combined with coding and antenna diversity techniques operate at very low signal-to-noise ratio (SNR) levels. Carrier synchronization is critical to the performance of an OFDM system. Tone or sub-carrier orthogonality is lost due to frequency offset error. OFDM carrier frequency offset estimation and subsequent compensation can be performed from the received signal without periodic pilots or preambles. OFDM algebraic structure can be exploited in a blind fashion to estimate carrier offset. However, the performance degrades at low SNR. The algorithm here will allow highly accurate synchronization by exploiting maximum diversity gains to increase effective SNR without reference symbols, pilot carriers or excess cyclic prefix. Furthermore, diversity gains overcome lack of identifiability in the case of channel zeros on the discrete Fourier transform (DFT) grid.