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, additional spectrum is being considered to be identified for HAPS systems, taking into account that HAPS will need to ensure the protection of existing and future services, such as mobile and satellite services.
The revision of the regulatory provisions for HAPS may include global or regional designations for HAPS, limitations regarding link directions, and inclusion of technical conditions of operation of HAPS systems for the protection of other services. Further conditions could be imposed on the operation of HAPS, such as mandatory coordination with potentially affected countries and notification of the stations to ITU.