As of today, the fifth generation (5G) mobile communication system has been rolled out in
many countries and the number of 5G subscribers already reaches a very large scale. It is
time for academia and industry to shift their attention towards the next generation. At this
crossroad, an overview of the current state of the art and a vision of future communications
are definitely of interest. This article thus aims to provide a comprehensive survey to draw a
picture of the sixth generation (6G) system in terms of drivers, use cases, usage scenarios …