Elevation Power Spectrum Measurement and Interference Analysis of UMa I2O Uplink Channels

Full-dimensional (FD) beamforming extends spatial multiplexing to the elevation domain and increases network capacity significantly. However, the beamforming employing a large number of active antenna elements consumes great power and also causes interference among sectors. The multipath spatial propagation characteristics determines the beamforming performance and should be investigated carefully. This paper presents a field measurement campaign for the indoor-to-outdoor (I2O) uplink channels in a typical urban macro-cellular (UMa) scenario. The elevation power spectra (EPS) were obtained when the user equipment (UE) was on several floors. We have found that the EPS can be well modeled by the modified Laplacian distribution. Furthermore, we evaluate the interference between two UEs on different floors in the elevation multiplexing. Finally, we provide the advice to improve the energy efficiency of FDbeamforming. The obtained channel model can help with the design of the spatial multiplexing and also green communications.