Joint carrier phase and frequency offset tracking in OFDM systems

In this paper, we study an OFDM system subject to carrier phase noise and frequency offset. Contrary to many previous approaches, we assume that the carrier phase and frequency offset are drifting. A scheme for joint estimation of the transmitted sequence and tracking of the carrier phase and frequency offset is prsented. The proposed iterative scheme is based on the ECM algorithm — an extension of the EM algorithm — and it performs the joint estimation in a unified manner by, as it turns out, interconnecting an Extended Kalman Smoother with Yule-Walker type equations.