CFO and Channel Estimation for Frequency Selective MIMO-FBMC/OQAM Systems

This letter estimates carrier frequency offset (CFO) and channel in multiple-input multiple-output (MIMO) filter bank multi-carrier systems based on offset quadrature amplitude modulation. A two-step preamble-based approach is proposed using a novel frame structure. For the first step, we develop a coarse CFO estimator, which does not require channel knowledge, and ensures that fine CFO can be approximated as a constant carrier phase. For the second step, by modeling the carrier phase and channel together as an effective channel, we develop minimum mean square error estimator for effective channel estimation in time domain. Unlike some of the existing estimators, the proposed one does not assume a frequency-flat MIMO channel. We derive the Cramer-Rao lower bound for the proposed estimator, and use it to evaluate the effect of the data interference on the estimation in the second step. We demonstrate the improved performance of the proposed estimator over existing ones.