On Hybrid Free-Space Optic-Radio Systems as Enablers of 6G Services Over Non-Terrestrial Networks

6G envisions new services such as holographic communications, virtual reality, digital twins, fiber on the sky, augmented reality to name a few of them. These new services will require a large capacity and so, they will be allocated in very high frequency bands, e.g., mmWave, TeraHertz, as well as the optical ones (i.e., fiber and optical wireless). Thus, it is foreseen that 6G will combine free-space optic (FSO) and radio frequency (RF) bands to offer more capacity, resilience to channel impairments and security (e.g. quantum and post-quantum-based security). This paper provides analysis and results on the throughput, and outage probability for the capacity, resilient, and security architectures of hybrid optical-radio systems. For more accuracy, this paper assumes that the optical and radio links have atmospheric impairments–in the optical link, there is a strong turbulence modelled using Gamma-Gamma distribution, whereas in the radio link, there is a fading modelled using Nakagami-m distribution.