HAPS – High-altitude platform systems

• Although over half of the global population is already connected to the Internet, greater and more extensive broadband connectivity and telecommunication services are needed in rural and remote communities and areas that are underserved.
• High-altitude platform station (HAPS) systems can be used to provide both fixed broadband connectivity for end-users and transmission links between the mobile and core networks used for backhauling traffic. Both types of HAPS applications would enable wireless broadband deployment, including in remote, mountainous, coastal, and desert areas.
• ​ ITU Radio Regulations (RR) define HAPS as radio stations located on an object at an altitude of 20-50 kilometres and at a specified, nominal, fixed point relative to the Earth.
  
• Demand for access to mobile broadband is growing strongly, necessitating more flexible approaches to expand broadband capacity and coverage. Currently, the World Radiocommunication Conference 2023 (WRC-23) agenda item 1.4 includes studies of the possible new identifications for using HAPS as IMT base stations (HIBS) as part of International Mobile Telecommunications (IMT) networks.
• HAPS can be rapidly deployed for disaster recovery communications, particularly because the use of inter-HAPS links allows the provision of services with minimal ground network infrastructure - for example, for backing up terrestrial networks damaged by disasters.
• Some companies are testing the delivery of broadband access via HAPS using lightweight, solar-powered aircraft and airships at an altitude of 20-25 kilometres operating continually for several months.
• At WRC-23, key discussions regarding HAPS focused on establishing regulatory requirements that would allow HAPS to operate as IMT base stations (HIBS) in bands allocated to the mobile service.
• HAPS technology offers a new platform for providing mobile broadband access with minimal infrastructure using the same frequencies and user devices as IMT mobile networks. HIBS can contribute to bridging the digital divide in remote and rural areas and maintain connectivity during disasters.
• Ensuring that new HIBS do not interfere with existing services and protecting incumbent services like satellite communication, aviation, and weather services is vital.
• New regulatory frameworks and coordination mechanisms are needed to handle potential cross-border interference issues, given that HIBS will operate in near-space environments.
• Global and regionally harmonized designations of frequency bands for HAPS at the WRC-19 are facilitating the development of HAPS services and allow trials to move towards commercial deployments.​
  

Technological innovations and the growing urgency to expand the availability of broadband have helped spur the development of 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 large areas and/or to augment the capacity of other broadband service providers.

HAPS is not a new concept and ITU studies of HAPS began in the mid-1990s. HAPS have recently become more viable due to technological 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. HAPS trials have been taking place in some countries to demonstrate the potential of HAPS for providing broadband connectivity, backhaul links and disaster recovery communications, as well as the move towards commercial deployments. Nevertheless, HAPS systems still face some challenges in becoming a commercially viable option for driving global broadband delivery.

Some recent ITU-R studies estimate that the total spectrum needs in the fixed service for HAPS systems lie 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 needed to cover specific applications (e.g. disaster relief missions) and for connectivity (e.g. commercial broadband).

The first fixed service frequency bands authorized for HAPS were globally designated in the Radio Regulations (RR) in 1997. Since then, the RR have been updated to designate additional fixed service frequency bands regionally, as well as in specific countries where HAPS may operate. Determining the bands suitable for HAPS mainly took into account concerns about rain fade, i.e. loss of signal power due to its attenuation through the rain, in the upper frequency bands.  These early HAPS identifications were established without envisioning that they would need to support today's modern broadband applications.  

Three world radiocommunication conferences (WRC-97, WRC-2000, and WRC-12) designated fixed service spectrum for HAPS in the frequency bands 47/48 GHz, 2 GHz, 27/31 GHz, and 6 GHz respectively. Although the frequency resources for HAPS systems were initially established some time ago, they were not used due to the immaturity of technical solutions. 

Before WRC-19, ITU-R studies had demonstrated that spectrum requirements for broadband HAPS applications may not have been fully accommodated within those bands where use for HAPS had been authorized. In addition, some of the authorized HAPS frequency bands had geographical limitations.  Studies further suggested that worldwide identifications of frequency bands where HAPS could be authorized would be desirable to improve and harmonize their utilization. 

Therefore, at WRC-19, ITU Member States identified additional radio-frequency bands where HAPS systems could operate under specified technical conditions. WRC-19 agreed that the frequency bands 31-31.3 GHz, 38-39.5 GHz be identified as being allowed for use by HAPS worldwide. It was also confirmed the bands 47.2 – 47.5 GHz and 47.9 – 48.2 GHz were available for use worldwide by administrations wishing to implement HAPS. At WRC-19, ITU Member States agreed that the frequency bands 21.4-22 GHz and 24.25-27.5 GHz could be used by HAPS in the fixed service in Region 2. WRC-19 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 use of spectrum for HAPS, the ITU Membership has enabled one more communication platform to connect the unconnected. ​​

Last update: January 2025