Tensor 2-D DOA Estimation for a Cylindrical Conformal Antenna Array in a Massive MIMO System Under Unknown Mutual Coupling

In this paper, a novel 2-D direction of arrival (DOA) estimation approach based on the tensor technique is proposed for a conformal array in a massive multiple-input-multiple-output system under unknown mutual coupling. By placing sensors uniformly on the cylindrical surface, the received signal expression is formulated with the Khatri-Rao product. An unknown mutual coupling auto-suppression method based on the conformal array is investigated. Then, to utilize the multidimensional information of the received data, a third-order tensor is constructed based on the conformal array signal model, and the signal subspace is provided by higher order singular value decomposition. Finally, the DOAs are estimated by conventional subspace-based algorithms. This approach provides improved DOA estimation performance owing to the utilization of the multidimensional information and the covariance tensor method, with lower SNR and fewer snapshots. The simulation results confirm that the proposed method outperforms the conventional method based on the vector model.