Compensation schemes for phase noise and residual frequency offset in OFDM systems

It is shown in this paper that a random phase noise Wiener process and a fixed but unknown residual (post-FFT) frequency offset, jointly perturbing an OFDM receiver, manifest themselves as a phase-rotation random variable which is common to all subcarriers, provided that their defining values (variance and fixed amount, respectively) are small, in which case the ICI and the per-subcarrier amplitude distortion induced by them are both negligible. Assuming a known arbitrary channel profile, we propose and evaluate by simulations two decision-directed (i.e., non-pilot-based) compensation schemes, one intuitive and the other based on ML theory. The algorithms exhibit robustness despite the lack of pilots, whereas uncompensated performance degrades rapidly.