Three-Dimensional Modeling and Simulation of MIMO Mobile-to-Mobile via Stratospheric Relay Fading Channels

As the development of next-generation wireless communication systems envisages the synergetic integration of heterogeneous terrestrial and aerospace networks, high-altitude platforms (HAPs) could play a key role, acting as transparent relay stations in the stratosphere by transferring information from an uplink to a downlink channel. This paper deals with the 3-D modeling of multiple-input-multiple-output (MIMO) mobile-to-mobile via stratospheric relay (MMSR) fading channels in amplify-and-forward (AF) networks. A geometrical two-cylinder reference model is proposed and considers that the scatterers in the vicinity of a source mobile station and a destination mobile station are nonuniformly distributed within two separate cylinders. Both line-of-sight (LoS) and non-LoS (NLoS) propagation conditions are assumed in the transmission links from the source to the destination via the stratospheric relay. Analytical expressions are derived for the 4-D space-time correlation function (STCF), which is also used to evaluate the channel capacity of the entire link using uniform linear arrays (ULAs). Based on the reference model, a sum-of-sinusoids (SoS) statistical simulation model is developed to verify the theoretical results.