Improved Root-MUSIC-Aided Joint AoA and AoD Estimation for Lens Array-Based MIMO Systems

In this paper, we introduce a novel two-step framework for joint angle-of-arrival (AoA) and angle-of-departure (AoD) estimation for lens antenna array (LAA)-based multipleinput and multiple-output (MIMO) systems. This method is based on the properties of the sinc function in the array response of LAAs to reduce the dimensionality of the channel matrix collected through each signal snapshot. After completing the estimation of the AoA or AoD in the first step, the remaining angle can be determined in the next step. For example, for each estimated AoA, the corresponding off-grid AoD is found. Consequently, we eliminate the need for a pairing step as seen in other methods, thereby avoiding pairing errors. Furthermore, since the proposed scheme leverages multiple snapshots, the estimation accuracy at each step can be enhanced. Simulation results indicate that the proposed method achieves the highest performance gain among all studied schemes when the number of antennas and snapshots is sufficiently large.