A Comprehensive View of the Initiatives on the Research of Sixth-Generation Mobile Systems

The Fifth-Generation (5G) mobile communications system is now on its way to being deployed worldwide and the scale of 5G subscribers in some region has reached a very large scale. However, the attention of academia and industry is increasingly shifting towards the next generation technology called Sixth Generation (6G) and many pioneering works are being kicked off by the major players in this filed, placing an important milestone in the history of mobile communications. At this juncture, a view of the current state of the art of 6G research and a vision of future communications are of great interest. This paper thus aims to investigate up-to-date 6G research programs, activities, and main viewpoints of representative countries, institutions and companies worldwide. Then, the key technologies are outlined and a vision on ``What 6G may look like?" is provided. This paper aims to serve as an enlightening guideline for interested researchers to quickly get an overview when kicking off their 6G research.