Spatial cross-correlation properties of MmWave massive MIMO channels

To analyze the propagation characteristics of millimeter wave (mmWave) massive multiple-input multiple-output (MIMO) channels, channel measurements in an office environment using a vector network analyzer (VNA) are carried out. Detailed parameter settings of the measurement system and configuration of the large receiver (Rx) antenna array are introduced. Through dividing the Rx array into several sub-arrays, characteristics like spherical wavefront, non-stationarity, and cluster evolution over the array can be found with parameter estimation using the space alternating generalized expectation-maximization (SAGE) algorithm. For signals received by the virtual horizontal planar array, it is shown that the spatial cross-correlation functions (SCCFs) exhibit significant changes along different dimensions of the Rx horizontal planar array. Thus, it is worth taking the relative angle between transmitter (Tx) pointing direction and Rx array location into consideration while carrying out channel measurements. It is also verified that the SCCFs can be influenced by the measurement environment, the coordinates of antenna elements in the large array, as well as the operated frequencies.