2D Active Antenna Array Design for mMIMO to Improve Spectral and Energy Efficiency

Abstract

One of the aims of beyond 5G (B5G) wireless communication networks is to increase the data rates, while keeping lower latency and high energy efficiency. To achieve this, massive multiple-input-multiple-output (mMIMO) systems combined with two dimensional (2D) active antenna array (AAA) design are expected to play a key role. The main objective of this paper is to design a 2D-AAA with beamforming both in azimuth and elevation directions in order to improve the spectral efficiency and energy efficiency. Furthermore, we evaluate the impact of the designed 2D-AAA on the signal-to-interference-plus-noise ratio (SINR) performance by considering the 3D channel model given by 3GPP in the Urban Micro scenarios (UMi). For the design of 2D-AAA we consider 64 cross polarized antenna elements that are arranged as an 8-by-8 array, in which, at each column are stacked together pairwise to form sub-arrays. Therefore, transmit/receive (T/R) module, control circuitry and other RF processing unit are dedicated at a sub-array basis, and, due to this fewer components are required. Therefore, the cost of the 2D-AAA design is reduced. However, with the sub-arrays, the performance is degraded in terms of the side lobe level (SLL) when steering the main beam in other directions. In this contribution, we demonstrated that by proper designing of the 2D-AAA with optimal sub-array amplitude and phase tapering, it is possible to reduce the SLL. Moreover, due to the reduction of the SLL, an increase in spectral efficiency and SINR performance can be obtained.