Decision-directed least-squares phase perturbation compensation in OFDM systems

A low-complexity decision-directed iterative scheme is proposed for the estimation and mitigation of strong phase noise plus frequency offset in OFDM-modulated signals, transmitted over frequency-selective or frequency-flat channels. It is based on a time-domain, windowed least-squares estimation algorithm of the total phase perturbation vector, developed through proper system modeling and optimized so as to minimize the residual inter-carrier interference. An extension of the diagonal-loading technique is also introduced in order to enhance the convergence of the algorithm in high-SNR regimes. The resulting scheme outperforms previously proposed approaches in terms of achievable error rate in the data-detection stage while, in the channel-estimation stage, it attains performance near the Cramer-Rao bound with comparatively smaller computational complexity.