Frequency offset tracking in OFDM based on multicarrier PLL

A novel algorithm for frequency offset tracking in orthogonal frequency-division multiplexing (OFDM) is proposed. The algorithm is based on decision-feedback and assumes differential reception. It makes it possible to track the frequency shift of an OFDM signal transmitted over a frequency dispersive channel. The channel is assumed to be time invariant for each OFDM sub-carrier. The processing is performed in the base band part and does not require any processing in the RF stage. A novel multicarrier phase locked loop (MPLL) for frequency shift tracking is described. The MPLL explores some unique features of the OFDM. A low-complexity real-time algorithm is obtained. It is shown that a receiver based on the suggested algorithm works well even for a relatively low signal to noise ratio (SNR) and its performance closely approaches that of differential detection without a frequency offset. We show that the proposed frequency offset compensation may be used in a tracking mode in OFDM receivers and may be implemented for high frequency (HF) communication, digital audio broadcasting, underwater acoustic communications or digital subscriber lines.