3D MIMO Outdoor-to-Indoor Outdoor Indoor Propagation Channel Measurement
Abstract: input multiple-output multiple (3-D D MIMO) systems have received great The 3-D multiple-input interest recently because of the spatial diversity advantage and capability for fullfull dimensional beamforming, making them promising candidates for practical realization of massive MIMO. In this paper, we present a low-cost low cost test equipment (channel sounder) and post-processing post processing algorithms suitable for investigating the 33 D MIMO channels as well as the re results sults from a measurement campaign for obtaining elevation and azimuth characteristics in an outdoor outdoor-to-indoor (O2I) environment. Due to limitations in available antenna switches, our channel sounder consists of a hybrid switched/virtual cylindrical array w with effectively 480 antenna elements at the base station. The virtual setup increased the overall MIMO measurement duration, thereby introducing phase drift errors in the measurements. Using reference antenna measurements, we estimate and correct for the phase hase errors during post-processing. post processing. We provide the elevation and azimuth angular spreads for the measurements done in an urban macro-cellular macro and urban micro-cellular cellular environments, and study their dependence on the user equipment (UE) height. Based on the measurements done with UE placed on different floors, we study the feasibility of separating users in the elevation domain. The measured channel impulse responses are also used to study the channel hardening aspects of the massive MIMO and the optimality o of the maximum ratio combining receiver.