Bridging Earth and Space: A Survey on HAPS for Non-Terrestrial Networks

High-altitude platform stations are gaining attention as a bridge between ground-based and satellite networks in the design of sixth-generation wireless systems, according to a survey published on arXiv. The paper outlines how these stratospheric platforms could extend broadband coverage, support massive IoT, and enable low-latency services. The survey, authored by German Svistunov and submitted in October 2025 with a final revision in May 2026, examines the integration of high-altitude platform stations, or HAPS, into the 6G ecosystem [1]. Operating in the stratosphere, HAPS can deliver wide-area coverage and energy-efficient broadband communications with flexible deployment options [2]. The paper reviews architectures for combining terrestrial and non-terrestrial networks and highlights recent field trials [2]. Among the use cases discussed are extending connectivity to underserved regions, supporting dynamic backhauling, enabling massive Internet of Things deployments, and providing reliable low-latency links for autonomous and immersive services [2]. The work also surveys enabling technologies such as channel modeling, AI-driven resource allocation, interference control, mobility management, and energy-efficient communications [2]. HAPS platforms typically rely on free-space optical communication links to exchange data with ground stations or satellites. Free-space optical technology uses light propagating through air or vacuum to transmit data wirelessly over long distances, and it is considered useful where physical fiber connections are impractical due to cost or terrain [3]. This optical layer is one of the technologies that could allow HAPS to serve as backhaul nodes in areas lacking fiber infrastructure. The survey positions HAPS as a foundational component of globally integrated, resilient, and sustainable 6G networks, while also identifying open research challenges that remain to be addressed [2]. The paper does not include direct quotes from the author, and the submission history shows the manuscript evolved through three versions between October 2025 and May 2026 [1].