Robust DOA Estimation in RIS-Assisted MISO Systems

Reconfigurable Intelligent Surfaces (RIS) are recognized for their ability to actively control signal propagation, presenting a wide array of applications in 5G and the forthcoming 6G networks. In this paper, we design a RIS-assisted multi-input single-output (MISO) model and propose a corresponding direction of arrival (DOA) estimation algorithm. The proposed DOA estimation algorithm leverages the non-convex Ekblom norm to serve as the error criterion, ensuring robustness against impulsive noises, while the smoothed L1 norm is implemented as the regularization constraint to further enhance the performance of the algorithm. Distinct from prior research, the system under consideration operates with a single receive antenna, facilitating DOA estimation through the adjustment of RIS reflection coefficients, thereby markedly reducing system hardware costs. Moreover, we devise an alternating minimization strategy to obtain the optimal solution to the problem. A series of simulation results indicate that the proposed algorithm surpasses existing methods in terms of accuracy and robustness.