High-Mobility OFDM Downlink Transmission with Partly Calibrated Subarray-Based Massive Uniform Linear Array

In this paper, we address the orthogonal frequency division multiplexing (OFDM) downlink transmission in scenarios abundant of scatters when the high- speed rail (HSR), equipped with partly calibrated massive uniform linear array (ULA), is in high- speed motion relative to the base station. A high- resolution beamforming network is designed to separate multiple Doppler frequency offsets (DFOs) in spatial domain into a series of parallel beamforming branches, such that each branch is mainly affected by single dominant DFO, wherein the conventional carrier frequency offset (CFO) compensation and subsequent data detection could be carried out individually. In view of this, a joint- estimation algorithm is proposed to jointly estimate the CFO and equivalent channel of each beamforming branch. Moreover, the calibration- oriented beamforming parameter (COBP) is introduced to mitigate the detrimental effects in presence of inter-subarray uncertainties. Both numerical and theoretical results are provided to corroborate the effectiveness of the proposed method.