A Low-Complexity Beam Selection Algorithm for Two-Dimensional Beamspace Massive MIMO

Abstract

To mitigate the huge investment in radio-frequency devices and associated high power consumption of modern base stations, the beamspace multiple-input multiple-output (B-MIMO) has become a promising solution at an expense of acceptable performance degradation. Facing the increasingly high data throughput demand, two-dimensional (2D) massive B-MIMO systems with beams steering over both elevation and azimuth angles have been developed recently. However, with such a large number of beams available for wireless communication, effective beam selection for multiple users in three-dimensional (3D) space remains technically challenging. In this letter, low-complexity suboptimal beam selection schemes are investigated to overcome this difficulty. By avoiding massive and repetitive matrix-vector product operations in the beam selection procedure through specifically designed linear algebraic calculation strategy, a lower complexity is achieved. Numerical simulations and theoretical analyses demonstrate the proposed methods have around <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$K$ </tex-math></inline-formula> to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$K^{2}$ </tex-math></inline-formula> times speedup compared to state-of-the-art beam selection approaches, where <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$K$ </tex-math></inline-formula> is the number of users.