Evaluation of diversity gain and system capacity increase in a multiple HAP system

High altitude platform (HAP) system offers establishment of communication links with predominantly line-of-sight (LOS) conditions due to high elevation angles. However, in mobile scenario, the transmitted signal is still subject to blocking due to obstacles between HAP and the user, which increases the probability of link outage. In the light of this, multiple HAP constellations with overlapped coverage areas can be exploited for platform diversity to improve the system reliability and availability or for the increase of the system capacity through the use of highly directional user antennas. In this paper we evaluate a potential diversity gain and capacity increase for a mobile scenario based on a simulation taking into account a digital relief model (DRM) of Slovenia and two main railway tracks, providing results in terms of the timeshare of different visibility events and the CINR values