Mobile-to-mobile communications via stratospheric relays: Relay selection and performance analysis

In this work, relay selection policies for a network where a terrestrial source communicates with a terrestrial destination through multiple relay nodes which reside in the stratosphere are presented. More specifically considering realistic three-dimensional (3 - D) non-isotropic scattering channel modelling combined with opportunistic relay selection for various fading conditions. Moreover, the stratospheric nodes are battery-dependent and relay selection aims at power reduction. As Channel State Information (CSI) overhead is introduced by the selection process, proactive and reactive versions are presented based on instantaneous CSI knowledge. In this setting, the selection policies in terms of outage probability, throughput and power reduction are evaluated and comparisons with statistical channels and with a relaying scheme that does not perform power adaptation are provided.