Abstract
Non-terrestrial networks, including Unmanned Aerial Vehicles (UAVs),
High Altitude Platform Station (HAPS) and Low Earth Orbiting (LEO)
satellites, are expected to have a pivotal role in the sixth generation
wireless networks. With their inherent features such as flexible
placement, wide footprint, and preferred channel conditions, they can
tackle several challenges in current terrestrial networks. However,
their successful and widespread adoption relies on energy-efficient
on-board communication systems. In this context, the integration of
Reconfigurable Smart Surfaces (RSS) into aerial platforms is envisioned
as a key enabler of energy-efficient and cost-effective deployments of
aerial platforms. Indeed, RSS consist of low-cost reflectors capable of
smartly directing signals in a nearly passive way. We investigate in
this paper the link budget of RSS-assisted communications under the two
discussed RSS reflection paradigms in the literature, namely the
specular and the scattering reflection paradigm types. Specifically, we
analyze the characteristics of RSS-equipped aerial platforms and compare
their communication performance with that of RSS-assisted terrestrial
networks, using standardized channel models. In addition, we derive the
optimal aerial platforms placements under both reflection paradigms. The
obtained results provide important insights for the design of
RSS-assisted communications. For instance, given that a HAPS has a large
RSS surface, it provides superior link budget performance in most
studied scenarios. In contrast, the limited RSS area on UAVs and the
large propagation loss in LEO satellite communications make them
unfavorable candidates for supporting terrestrial users. Finally, the
optimal location of the RSS-equipped platform may depend on the
platform’s altitude, coverage footprint, and type of environment.