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HAPS – High-altitude platform systems

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Challenges and solutions: building 5G networks for the future

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.

ITU’s contribution

In 1997, the first frequency bands where use for HAPS is permissible were globally designated in the Radio Regulations (RR). Since then, the Radio Regulations have been modified to designate additional frequency bands regionally and in specific countries where HAPS may operate. At that time, determining bands for HAPS considered mainly the concerns about rain fade, i.e. loss of signal power due to the rain, in the upper frequency bands.  These HAPS identifications were established without envisioning that they would need to support today's broadband applications.  

Although the frequency resources for HAPS systems were established in the Radio Regulations a long time ago, they were not used due to the above constraints and immaturity of technical solutions. 

More recently, the technological advances that improved HAPS viability and the pressing need to facilitate access to global broadband applications have led to the review of the current regulatory provisions.

Delegates at WRC-19 agreed that allocations to the fixed service in the frequency bands 31-31.3 GHz, 38-39.5 GHz will be identified for worldwide use by HAPS. They also confirmed the existing worldwide identifications for HAPS in the bands 47.2 – 47.5 GHz and 47.9 – 48.2 GHz are available for worldwide use by administrations wishing to implement high-altitude platform stations.

They agreed to the use of the frequency bands 21.4-22 GHz and  24.25-27.5 GHz by HAPS in the fixed service in Region 2.

They also agreed to limitations regarding link directions, and inclusion of technical conditions of operation of HAPS systems for the protection of other services.

By approving the spectrum for HAPS, the ITU Membership has enabled one more communication platform to connect the unconnected.​

Last update: dec 2019 ​