IEEE Access Special Section Editorial: Ultra-Dense Cellular Networks

To satisfy the significant demand for wireless traffic growth in the near future, ultra-dense cellular networks have been extensively investigated recently in both academia and industry. Many techniques, such as massive MIMO (multiple-in multiple-out) antenna arrays, millimeter wave communication, small cells, and heterogeneous networks, have been proposed for the design of future ultra-dense cellular systems. For example, Massive MIMO technology enables the reduction of antenna transmission power, and millimeter wave channels are suitable for short distance communications in outdoor environments. Motivated by these new technologies, cell coverage has also been correspondingly reduced so as to improve the area spectrum usage. To realize seamless coverage, a large number of small cells will be deployed.