Characteristics of 5.3 GHz MIMO Channels with an Extremely Large Antenna Array in Urban Macro Scenarios

Extremely large antenna array (ELAA) is one of the most promising technologies in 5G-Advanced (5.5G), which is equipped with hundreds or even thousands of antennas at base station (BS), to meet the requirements of higher rate and spectral efficiency. To verify the characteristics of ELAA channel, including spatial non-stationary, near-field spherical wavefront effect and channel hardening, a measurement campaign is performed, which is equipped with 128-element antenna array at BS on 5.3 GHz with 160 MHz bandwidth in a typical urban macro (UMa) scenario. Based on this, the correlation of power angular spectrums (PAS) between sliding windows of antenna array and the standard deviation (STD) of angular spreads (AS) are defined as the metrics to measure the level of variations of ELAA channel along with the antenna array. The correlation goes slightly down while the distance of two subarrays of the BS is larger than 0.6 m and the STD of AS changes in the range from 1° to 8°. The STD of normalized channel gain is also given to measure the channel hardening. Due to the power imbalance along with the antenna array, it decreases non-linearly with the increasing number of antennas. Meanwhile, the comparisons between measurement and simulations by 3GPP TR 3S. 901 and modified COST 2100 are given to show the necessity of the modifications on the current channel model. All of above analyses show that the modified COST 2100 channel model has a better match with the ELAA measurement.

I. Introduction

Massive multiple-input multiple output (MIMO) technology has been commercially deployed successfully owing to its advantages of higher capacity and spectral efficiency. Typically a massive MIMO base station (BS) is equipped with 64 antennas in 5G commercial. To meet the growing demands for immersive experience such as Extended Reality (XR) and holograms as well as the diversified and complex Internet of things (IoT) demands such as machine vision and Vehicle to Everything (V2X), MIMO with hundreds or even thousands of antennas, known as extremely large antenna array (ELAA), is becoming promising in 5G-Advanced (5.5G) [1] [2].