5G Empowerment: Ushering in a Four-Dimensional Communication Era Across Air, Space, Land, and SeaThroughout the long course of human civilization, the exploration of "reaching the heavens and entering the seas" has never ceased. From the dragon's cloud-riding in the Shan Hai Jing to Sun Wukong's somersault cloud in Journey to the West, the magnificent imaginations in mythology and literature reflect humanity's yearning to transcend the limitations of physical space...