3-D MIMO: How Much Does It Meet Our Expectations Observed From Channel Measurements?

TLDR

Three‑dimensional MIMO with massive antenna arrays is a promising 5G technology, yet most studies rely on simulations and only a few field trials have been conducted. The study aims to determine how well 3‑D MIMO meets expectations across diverse scenarios. Measurements were performed with 56×32 antenna elements at 3.5 GHz and 100 MHz bandwidth in outdoor‑to‑indoor, urban microcell, and urban macrocell deployments, from which elevation and azimuth angles were extracted, channels reconstructed, and capacity and eigenvalue distributions compared. The results show that fully exploiting the elevation domain improves capacity and increases the number of significant eigenvalues, with the largest gains in outdoor‑to‑indoor scenarios, followed by urban microcell and urban macrocell, and that multi‑user capacity depends on scenario, antenna count, and user number.

Abstract

By taking advantage of the elevation domain, three-dimensional (3-D) multiple input and multiple output (MIMO) with massive antenna elements is considered as a promising and practical technique for the fifth Generation mobile communication system. So far, 3-D MIMO is mostly studied by simulation and a few field trials have been launched recently. It still remains unknown how much does the 3-D MIMO meet our expectations in versatile scenarios. In this paper, we answer this based on measurements with 56 × 32 antenna elements at 3.5 GHz with 100-MHz bandwidth in three typical deployment scenarios, including outdoor to indoor (O2I), urban microcell (UMi), and urban macrocell (UMa). Each scenario contains two different site locations and 2-5 test routes under the same configuration. Based on the measured data, both elevation and azimuth angles are extracted and their stochastic behaviors are investigated. Then, we reconstruct two dimensional and 3-D MIMO channels based on the measured data, and compare the capacity and eigenvalues distribution. It is observed that 3-D MIMO channel which fully utilizes the elevation domain does improve capacity and also enhance the contributing eigenvalue number. However, this gain varies from scenario to scenario in reality, O2I is the most beneficial scenario, then followed by UMi and UMa scenarios. More results of multiuser capacity varying with the scenario, antenna number and user number can provide the experimental insights for the efficient utilization of 3-D MIMO in future.