Analysis of CRLB for AoA estimation in Massive MIMO systems

Massive MIMO systems provide high angular resolution in the next generation of wireless systems. This opportunity can be used to estimate the location of user terminals (UTs) accurately. In this paper, we analyze the Cramer-Rao lower bound (CRLB) of planar antenna arrays in Massive MIMO systems for Angle of Arrival (AoA) estimation. With the help of Random Matrix Theory, we prove that for Massive antenna arrays with independent and identically distributed (i.i.d) multipath signals, instantaneous CRLB for AoA estimation converges toward a deterministic value, regardless of channel distribution. In this scenario, CRLB is a function of channel variance instead of instantaneous realizations. Then, antenna selection is studied, and it is shown that using different subsets significantly affects the CRLB of a planar array. Numerical results confirm the convergence of deterministic results and indicate the benefits of antenna selection and the importance of the selection strategy.