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