Effects of Array Orientations on Degrees of Freedom for 3D LoS Channels in Short-Range Communications

In this letter, we investigate the spatial degrees of freedom (DoF) of line-of-sight (LoS) channels in three-dimensional (3D) space with respect to the array orientations in short-range communications. First, the corresponding response of LoS channels is modeled using the spherical-wave model (SWM). The analytical expression for the spatial DoF of LoS channels with various array orientations is then derived and compared with that obtained in long-range communications. Both the analytical and simulation results show that the array orientations have a significant impact on the spatial DoF of short-range LoS channels.