  As of today, 5G mobile systems have been already widely rolled out, it is the
right time for academia and industry to explore the next generation mobile
communication system beyond 5G. To this end, this paper provides an abstracted
survey for the 6G mobile system. We shed light on the key driving factors for
6G through predicting the growth trend of mobile traffic and mobile service
subscriptions until the year of 2030, envisioning the potential use cases and
applications, as well as deriving the potential use scenarios. Then, a number
of key performance indicators to support the 6G use cases are identified and
their target values are estimated in a quantitatively manner, which is compared
with those of 5G clearly in a visualized way. An investigation of the efforts
spent on 6G research in different countries and institutions until now is
summarized, and a potential roadmap in terms of the definition, specification,
standardization, and spectrum regulation is given. Finally, an introduction to
potential key 6G technologies is provided. The principle, technical advantages,
challenges, and open research issues for each identified technology are
discussed.
