High Altitude Platform Networks (HAPNs) comprise an emerging communication solution promising to exploit many of the best aspects of terrestrial and satellite-based
systems. Nevertheless, while offering advantageous propagation characteristics, HAP networks are still subject to large fades due to atmospheric precipitation and especially due to rain, for the allocated high frequency bands, necessary though to deliver high data rates. Multi-HAP or orbital HAP diversity is an effective technique to reduce the large fade margins required to assure the specified quality of service (QoS). Received signals from multiple HAPs can be combined at the terminal station with the use of various signal processing techniques. The subject of this paper is to present physical statistical models for
the evaluation of the outage probability of a dual-HAP orbital diversity system using either SC (selection combining) or MRC (maximal ratio combining) techniques. The analytical
probabilistic models are interesting since we have rain attenuation correlated fading channels. Extended numerical results are presented in the final section of the paper comparing
MRC and SC reception techniques. Some significant conclusions are drawn.
