OFDM synchronisation based on the phase rotation of sub-carriers

This paper proposes a method to simultaneously track symbol timing, carrier phase and frequency offset errors for an OFDM (orthogonal frequency division multiplex) communications system. Each of these three offsets rotates the OFDM symbol constellations in a conspicuous way. Their characters are illustrated and it is explained how can the receiver DFT (discrete Fourier transform) outputs be used for estimation. The method presented is based on the rotational impact of offsets-on the individual sub-carriers. The technique employs the joint-ESPRIT (Estimation of Signal Parameters via Rotational Invariance Techniques) algorithm and can be used for data-aided and blind estimation, as well as for the combination of these two. Assuming a prior initial acquisition, it uses the information contained in the phase rotation between the correct and the received sub-symbols after the DFT.