  Large-scale reconfigurable intelligent surface (RIS) can effectively enhance
the performance of millimeter wave (mmWave) unmanned aerial vehicle (UAV) to
ground communication link with obstructed line-of-sight (LoS) path by
exploiting more reflecting units. However, the non-negligible array dimension
of large-scale RIS and the mobile property of the terminals bring significant
variations in propagation characteristics, making conventional channel models
inapplicable. To address this issue, we propose a dynamic sub-array partition
scheme to divide the large-scale RIS into sub-arrays by exploiting the Rayleigh
distance criterion and the mobile property of the transceivers. Based on the
proposed scheme, a novel non-stationary channel model for large-scale RIS
auxiliary mmWave UAV-to-ground mobile networks is developed, which outperforms
existing models with well balance between model complexity and accuracy.
Numerical results are provided to verify our analysis.
