Measurement-based Double-Directional Polarimetric Characterization of Outdoor Massive MIMO Propagation Channels at 3.5GHz

Massive multiple-input multiple-output (MIMO) is a key technology for 5G wireless communications since it can improve network throughput, capacity, spatial efficiency, etc. utilizing large-scale antenna arrays. In this paper, we study the direction of departure (DOD) and direction of arrival (DOA) power spectra and the angular spreads for suburban line-of-sight (LoS) environment. Our study is based on a measurement campaign conducted at a carrier frequency of 3.5GHz, with a bandwidth of 160MHz and ±45◦dual-polarized 4×8 planar and cylindrical antenna arrays at the transmitter and the receiver, respectively. The space-alternating generalized expectation-maximization (SAGE) algorithm is applied to jointly estimate the DOA, DOD, delay and complex amplitude of the propagation channel measured by the massive MIMO system. Results show that the double-directional channel characteristics exhibit dependence with the employed polarization combination. The obtained characterization results are of great value for the analysis of polarization-dependent design and antenna selection strategies for MIMO systems.