A Study on Cell Configuration for HAPS Mobile Communications

A High-Altitude Platform Station (HAPS), which provides communications services from an altitude of 20 km by using an Unmanned Aerial Vehicle (UAV) such as a balloon, airship, or other aircraft, is attracting much attention as a new mobile communications platform for an ultra-wide coverage area and disaster-resilient networks. A HAPS can provide mobile communications services directly to smartphones, which are commonly used in terrestrial mobile communications networks with Fourth Generation Long Term Evolution (4G LTE), and in the near future, Fifth Generation New Radio (5G NR). To achieve wide coverage and large capacity, it is desirable to introduce a cellular system that uses one- cell frequency reuse much like terrestrial mobile communications. However, a HAPS can provide various numbers of cells ranging from one to more than 100 depending on HAPS and UAV type, which differs from terrestrial base stations that have three to six sectors at most. Additionally, conventional studies on HAPS have paid little attention to cell configuration optimization. In this paper, we propose cell configuration optimization method for a HAPS cellular system with LTE, that can be generally applied regardless of the number of cells. We also clarify the cell configuration with antenna parameters that are suitable for different numbers of cells a HAPS can provide.