Real-Time CRLB based Antenna Selection in Planar Antenna Arrays

Estimation of User Terminals' (UTs') Angle of Arrival (AoA) plays a significant role in the next generation of wireless systems. Due to high demands, energy efficiency concerns, and scarcity of available resources, it is pivotal how these resources are used. Installed antennas and their corresponding hardware at the Base Station (BS) are of these resources. In this paper, we address the problem of antenna selection to minimize Cramer-Rao Lower Bound (CRLB) of a planar antenna array when fewer antennas than total available antennas have to be used for a UT. First, the optimal antenna selection strategy to minimize the expected CRLB in a planar antenna array is proposed. Then, using this strategy as a preliminary step, we present a two-step antenna selection method whose goal is to minimize the instantaneous CRLB. Minimizing instantaneous CRLB through antenna selection is a combinatorial optimization problem for which we utilize a greedy algorithm. The optimal start point of the greedy algorithm is presented alongside some methods to reduce the computational complexity of the selection procedure. Numerical results confirm the accuracy of the proposed solutions and highlight the benefits of using antenna selection in the localization phase in a wireless system.