Iterative Residual Frequency Offset Correction for OFDM Systems

The estimation and tracking of the fractional carrier frequency offset (CFO) is a crucial issue in the implementation of orthogonal frequency division multiplexing (OFDM) systems. In this contribution, we present a novel code-aided fractional CFO estimation algorithm based on the expectation-maximization (EM) algorithm. The proposed algorithm exchanges soft information from the channel decoder, in the form of a posteriori probabilities of the coded symbols, between the demapper, the decoder, and the CFO estimator in an iterative way. The proposed estimation scheme can work with any detector as long as the detector is able to compute the a posteriori probabilities (APPs) of the data symbols.