Millimeter Wave Backhaul for Stratospheric HAPs: Performance of the Bent-Pipe Architecture

Non-terrestrial networks (NTNs) are envisaged as an integral component of beyond 5G (or 6G) wireless systems. Stratospheric high-altitude platforms (HAPs) provide a promising solution for ubiquitous and high-capacity wireless connectivity. This paper investigates the potential of millimeter wave (mmWave) communication for backhaul (HAP-to-ground) connectivity in a bent-pipe architecture which creates challenging requirements. We develop an analytic framework for backhaul performance evaluation that jointly characterizes availability and capacity aspects, and considers different link attenuation factors. Our evaluation shows the potential of different mmWave spectrum options for backhaul operation and provides important performance insights, particularly in terms of achievable data rates, the impact of rainfall, limits on fronthaul operation, and deployment of ground stations.