  Since 5G new radio comes with non-standalone (NSA) and standalone (SA)
versions in 3GPP, research on 6G has been on schedule by academics and
industries. Though 6G is supposed to have much higher capabilities than 5G, yet
there is no clear description about what 6G is. In this article, a
comprehensive discussion of 6G is given based on the review of 5G developments,
covering visions and requirements, technology trends and challenges, aiming at
tackling the challenge of coverage, capacity, the user data rate and movement
speed of mobile communication system. The vision of 6G is to fully support the
development of a Ubiquitous Intelligent Mobile Society with intelligent life
and industries. Finally, the roadmap of the 6G standard is suggested for the
future.
