  With the standardization and commercialization completed at an unforeseen
pace for the 5th generation (5G) wireless networks, researchers, engineers and
executives from the academia and industry have turned their attention to new
candidate technologies that can support the next generation wireless networks
enabling more advanced capabilities in sophisticated scenarios. Explicitly, the
6th generation (6G) terrestrial wireless network aims to providing seamless
connectivity not only to users but also to machine type devices for the next
decade and beyond. This paper describes the progresses moving towards 6G, which
is officially termed as "international mobile telecommunications (IMT) for 2030
and beyond" in the International Telecommunication Union Radiocommunication
Sector (ITU-R). Specifically, the usage scenarios, their representative
capabilities, the supporting technologies and spectrum are discussed, and the
future opportunities and challenges are highlighted.
