Introduction:

A High Altitude Platform Station (HAPS) is a wireless network node that operates in the stratosphere at an of altitude around 20 km and is instrumental for providing communication services. Precipitated by technological innovations in the areas of autonomous avionics, array antennas, solar panel efficiency levels, and battery energy densities, and fueled by flourishing industry ecosystems, the HAPS has emerged as an indispensable component of next-generations of wireless networks.

High-altitude platform station (HAPS) systems can potentially be used to provide both fixed broadband connectivity for end users and transmission links between the mobile and core networks for backhauling traffic. Both types of HAPS applications would enable wireless broadband deployment in remote areas, including in mountainous, coastal and desert areas.

In some situations, HAPS may 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.

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.

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An ITU-R “work in progress” report will describe spectrum needs, usage and deployment scenarios, and technical and operational characteristics for the use of high altitude platform stations as IMT base stations (HIBS) for mobile service in certain frequency bands below 2.7 GHz already identified for IMT (International Mobile Telecommunications).  In particular, the report will explain the technical and operational characteristics of HIBS in the bands 694‑960 MHz, 1710-1885 MHz, 1885-1980 MHz, 2010-2025 MHz, 2110-2170 MHz and 2500-2690 MHz to be used in sharing and compatibility studies under WRC-23 agenda item 1.4.

HAPSMobile’s Sunglider can cover 200 km at a distance of 20 km above the Earth in the stratosphere.

Image courtesy of HAPSMobile

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IMT systems have evolved significantly in terms of spectrum identification, network deployment, and radio access technology, with the standardization of IMT-Advanced (4G) and IMT-2020 (5G).

At the same time, recent advances in battery and solar-panel technologies could enable HIBS to provide low latency mobile broadband connectivity to underserved communities, and in rural and remote areas, over a large geographic footprint.

These technological advances could enable HIBS, using the same frequency bands as ground-based IMT base stations, to be used as a part of, and complement terrestrial IMT networks. Existing user equipment (UE), which already supports a variety of frequency bands identified for IMT, could be served by both HIBS and ground-based IMT base stations. HIBS will therefore require new identifications to use certain frequency bands below 2.7 GHz already identified for IMT, considering potential HIBS deployment scenarios and its technical and operational characteristics, while taking into account sharing and compatibility with existing applications and services under WRC-23 Agenda 1.4.

Recognizing this, WRC-19 adopted Resolution 247 to consider “the use of HIBS in the mobile service in certain frequency bands below 2.7 GHz already identified for IMT, on a global or regional level.”

Basic concepts of HIBS applications:

HIBS (high altitude platform station as IMT base station) is defined in No. 1.66A as a “A station located on an object at an altitude of 20 to 50 km and at a specified, nominal, fixed point relative to the Earth.”

It’s important to recognize that HIBS can provide low latency mobile connectivity to unserved areas, including rural and remote areas, over a large footprint ( around 31,500 km²).

HIBS can enhance terrestrial IMT networks with so-called “super macro cells” that complement the existing ground-based deployment methods (e.g. macro cell, micro cell).

HIBS are intended to be used as a part of, and complement to, terrestrial IMT networks, using the same frequency bands as ground-based IMT base stations. In this sense, the UE to be served, whether by HIBS or ground-based IMT base stations, are the same. HIBS applications could provide flexibility and broaden the use of the existing IMT bands to complement coverage and support different use cases, while taking into account sharing and compatibility with existing applications and services.

Such use of spectrum by HIBS would require new identifications for HAPS as IMT base stations are required similar to those in RR no. 5.388A established at WRC-2000. Modifications to the IMT identification under RR No. 5.286AA, 5.317A, 5.341A, 5.341B, 5.341C, 5.346, 5.346A, 5.384A and 5.388 are outside the scope of WRC-23 Agenda Item 1.4.

The amount of spectrum needed in a given deployment scenario would depend on a number of factors and in the following section, examples of spectrum needs for HIBS applications is provided under specific system characteristics and deployment scenarios.

Usage and deployment scenarios:

The aim of HIBS is to provide internet access and services to the UE in remote area cases with quick deployment and less transmission loss.

Some HIBS applications communication usages foreseen are:

– Natural disaster relief missions, where communication for coordination and situation awareness across help and humanitarian aid organizations is needed.

– Fire detection, monitoring and firefighting missions to ensure communication between actors.

– Exploration missions with communication needs between exploration teams and regional home base.

Possible deployment scenarios:

HIBS would be deployed to provide connectivity to areas unserved and/or underserved by ground-based IMT base stations, such as:

– Areas where it is difficult to provide mobile connectivity using ground-based IMT base stations due to economic challenges (e.g. very small population covered, lack of backhaul connectivity and power supply, etc.).

– Areas covered by ground-based IMT base stations, but disruption to power supply and/or backhaul have resulted in a temporary lack of mobile connectivity.

– Unpopulated areas not covered by ground-based IMT base stations.

Mobile connectivity is becoming widespread, connecting objects (IoT: Internet of things, IoE: Internet of everything), as well as people.

Sensor networks which combine different types of sensors and IoT technology based on IMT systems (eMTC: enhanced Machine-Type Communication, NB-IoT: Narrowband IoT) are likely to be widely used in both populated and unpopulated areas. These areas are currently unserved and/or underserved.

Safety and security:

HIBS can help provide ubiquitous mobile coverage in unpopulated areas, thereby allowing users to get mobile connectivity regardless of time, place or circumstances. Thus, users will be able to make an emergency call wherever they are, in the case of a sudden car breakdown, getting lost or another problem.

In the aftermath of a natural disaster, communication networks can be restored quickly by using HIBS to cover these areas.

As they can connect to ordinary mobile phones that people carry all the time, HIBS are well suited for safety and security applications.

Internet of Things:

ICT is now widely used to help maintain and manage public infrastructure, such as roads, pavements, bridges and dams. Using a combination of IMT-based IoT technology and HIBS connectivity, infrastructure in both urban areas and rural/unpopulated areas can be managed on the same sensor network. The same approach can also be used to monitor natural processes, which are difficult for people to get close to, such as an active volcano.

Connected sensor networks can also support large-scale agriculture and livestock farming. The data they collect can be used for automation and the streamlining of processes, and can lead to innovation in this sector.

In this way, HIBS will be able to expand the reach of IoT services to support efficient management and maintenance of both public infrastructure and natural objects, while contributing to the development of the farming industry.

Event services:

HIBS can also be deployed above a venue, such as a stadium, a theme park, a resort, a tourist spot or exhibition place to provide more capacity to accommodate a temporary increase in demand. The rapid deployment of HIBS can augment the terrestrial network infrastructure to satisfy unusually high capacity requirements over short periods of time.

Frequency Bands:

HIBS will need additional and separate identification to use certain frequency bands below 2.7 GHz already identified for IMT taking into account sharing and compatibility with existing applications and services. Modifications to the identifications to IMT (5.286AA, 5.317A, 5.341A, 5.341B, 5.341C, 5.346, 5.346A, 5.384A and 5.388) in the Radio Regulations are outside the scope of WRC-23 Agenda Item 1.4. It may be possible for HIBS to employ the same band plans (see ITU-R Recommendation M.1036) as used by ground based IMT networks.

References:

https://www.itu.int/en/mediacentre/backgrounders/Pages/High-altitude-platform-systems.aspx

https://arxiv.org/pdf/2007.15088.pdf

https://eepower.com/news/hapsmobile-and-apb-collaborate-to-develop-high-energy-density-batteries/#

https://www.engineering.com/story/haps-alliance-is-putting-5g-in-the-stratosphere