The technological innovations and the growing urgency to expand the availability of broadband led to the development of high-altitude platform station (HAPS) systems. These easily deployable stations operating in the stratosphere (layer of the Earth's atmosphere starting at 20 kilometres) are high enough to provide service to a large area or to augment the capacity of other broadband service providers.
HAPS is not a new concept and ITU studies of HAPS began around 1996. Nevertheless, HAPS have become more viable due to the evolution of technology through advances in solar panel efficiency, battery energy density, lightweight composite materials, autonomous avionics and antennas.
Recent test deployments delivering broadband Internet access using stations approximately 20 km above ground have demonstrated their ability to provide connectivity to remote or underserved communities.
Nevertheless, HAPS systems face challenges to becoming a commercially available option to drive global broadband delivery, especially in countries with limited infrastructure.
The current ITU-R studies estimate that the total spectrum needs for HAPS systems is in the range from 396 MHz to 2 969 MHz for the ground-to-HAPS platform links and in the range from 324 MHz to 1 505 MHz for the HAPS-platform-to-ground links. These ranges include the spectrum needs to cover specific applications (e.g. disaster relief missions) and for connectivity applications (e.g. commercial broadband).
Three world radiocommunication conferences (WRC-97, WRC-2000 and WRC-12) designated spectrum for HAPS in the frequency bands 47/48 GHz, 2 GHz, 27/31 GHz and 6 GHz respectively.
The ITU-R studies on spectrum needs for HAPS demonstrate that spectrum requirements for broadband HAPS applications may not be fully accommodated within current HAPS identifications. In addition, some of the current HAPS frequency bands have geographical limitations, while common worldwide identifications for HAPS are desirable to improve and harmonize their utilization.
Therefore, ITU Member States agreed at WRC-19 to identify additional radio-frequency bands for HAPS systems.
HAPS trials have been taking place in some countries to demonstrate their ability for providing broadband connectivity, backhaul links and for disaster recovery communications. Global and regionally harmonized designations for HAPS at WRC-19 will facilitate the development of these applications and allow trials to move towards commercial deployments.