  The inclusion of material identification in wireless communication system is
an emerging area that offers many opportunities for 6G systems. By using
reflected radio wave to determine the material of reflecting surface, not only
the performance of 6G networks can be improved, but also some exciting
applications can be developed. In this paper, we recap a few prior methods for
material identification, then analyze the impact of thickness of reflecting
surface on reflection coefficient and present a new concept "settling
thickness", which indicates the minimum thickness of reflecting surface to
induce steady reflection coefficient. Finally, we propose a novel material
identification method based on ray-tracing and 3D-map. Compared to some prior
methods that can be implemented in single-bounce-reflection scenario only, we
extend the capability of the method to multiple-bounce-reflection scenarios.
