Frequency Synchronization With Beamforming Network Optimization for Uplink Massive MIMO Systems

In this correspondence, we develop a novel frequency synchronization scheme for multiuser orthogonal frequency division multiplexing (OFDM) uplink with massive uniform linear array (ULA) at base station (BS). With proper user scheduling strategy, the directions of arrival (DOAs) of all users are considered to be disjunct. Our proposed method performs multiuser interference (MUI) cancellation through beamforming network, after which the multiuser OFDM uplink model can be decomposed into a set of parallel single user models. Then, carrier frequency offset (CFO) estimation for each user can be performed individually. The beamforming network is further optimized to minimize the mean square error (MSE) of the CFO estimation. The provided numerical results validate the proposed studies.