Inside 3 Topics for WRC: Earth Stations in Motion, Direct-to-Device, and HAPS

Photo: Via Satellite archive

Following four years of intense technical and regulatory work under the framework of the International Telecommunication Union (ITU), national administrations and non-governmental organizations began meeting this week for the World Radiocommunication Conference (WRC-23) in Dubai.

ITU-R has several institutional objectives. These include ensuring that radiocommunications are operated free of interference, but also promoting efficient use of scarce spectrum resources and addressing technological advancements. This last goal determines not only some of the decisions that are made from a Radio Regulation (RR) point of view but may also determine the shape of the future agenda in the next study cycle, WRC-27.

The decisions made at the WRC will have additional business implications, and this year’s edition is particularly important. The industries involved are experiencing unprecedented levels of growth, investment, and technological innovation, with non-terrestrial networks (NTN) at the core of a paradigm shift related to global communications. This is a look at three topics — earth stations in motion (ESIMs), direct-to-device (D2D), and high altitude platform stations (HAPS) — that are critical to understanding business opportunities and constraints for the satellite industry moving forward.

Earth Stations in Motion

ESIMs have been under discussion since WRC-15, with a focus on how to protect incumbent services on the ground from any interference. The ITU understands that ESIMs are of paramount importance to provide broadband services to moving targets across land, sea, and air, and at higher data speeds than with current mobile satellite service (MSS) systems due to bandwidth limitations.

In previous cycles, the proposed solutions from a regulatory stance led to a series of technical limitations regarding the fixed satellite service (FSS) systems providing connectivity to these ESIMs; notably, the permitted amount of power used through the network. The previous conference decided to identify 1,000 MHz for FSS globally in the highly demanded Ka-band spectrum. In ITU terms, this is reserved bandwidth for a given service typology.

At the time, regulators reached a consensus that the amount of identified spectrum (19.7-20.2 GHz and 29.5-30.0 GHz) provided sufficient protection to other Geosynchronous Orbit (GSO) networks and terrestrial services. However, in 2019, an additional 4,000 MHz in the Ka-band (17.7-19.7 GHz and 27.5-29.5 GHz) was also identified. Now, in 2023, discussions are centered around the potential use of these ESIMs in the Ku-band, while the use of the Ka-band for Non-Geostationary Orbit (NGSO)-powered ESIMs is being considered. In summary, more bandwidth is said to be required for these services moving forward.

One of the topics non-engineering colleagues will hear about ESIMs is Agenda Item 1.15. The final decision reached by the assigned group will have very practical consequences for industry players. If the Ku-band is effectively identified as additional spectrum for ESIMs, many industry players will find the regulatory backing to enter or expand their satellite capacity to service this market. For end users across air, land, and sea, more competition from a number of providers connecting ESIMs would lead to classic innovation and cost reduction benefits. Nevertheless, without dwelling on technical matters, Ka- and Ku-bands are intrinsically different in terms of bandwidth, meaning incumbents in the Ka-band do have a degree of technical advantage.

A related discussion around ESIMs at WRC-23 is Agenda 1.16, which brings the interest of NGSOs to also provide these services in the existing Ka-spectrum. It is a contentious issue and one that some NGSO operators are pushing heavily for because, under current regulations, these systems are not allowed to obtain national authorizations. The final decision on this issue will have major business effects for both types of system operators, either due to lack of access to the growing ESIMs market for some or because many NGSO operators would suddenly be allowed to service it. 

Direct-to-Device 

One of the important roles of each WRC is setting the agenda for the next cycle, guiding industry on what technical studies need to be prioritized during the subsequent four years. Under Agenda Item 10, the conference decides on future agenda items. When this is set, companies get involved in the process by providing the technical parameters required to determine if, after analyzing studies, the ITU should indeed modify Article 5 of the Radio Regulations. This modification provides the reference for countries to update their national frequency allocation tables at the end of the next WRC. Therefore, spectrum is harmonized and technology can be operated globally.

In the middle of the current cycle, satellite connectivity to smartphones, or direct-to-device, (D2D) became a reality, and global interest in expanding and enhancing this application grew in record time. Currently, existing and compliant D2D emergency-type messaging solutions are serviced by MSS operators, albeit with many technical and bandwidth constraints. WRC-23 now has the critical role of deciding whether the 2023-2027 study cycle should prioritize an agenda item that allows MSS operators to further connect smartphone users when they are out of terrestrial coverage. WRC-23 can do so by passing a future agenda item regarding studies for additional bandwidth on the MSS in technically appropriate frequency bands. Current discussions are clearly leading the conference to focus on spectrum below 3 GHz.

If consensus is reached and MSS studies are successfully conducted, the applications powered in the identified spectrum may be varied, inclusive of driving global IoT growth. To move forward, regulators need to account for several factors, including the very nature of D2D and current connectivity constraints. This presents a unique opportunity for mobile network operators (MNOs) and satellite operators to work together for the benefit of the end user, and there is clear consensus on this point. What is not so evident for many is that, due to many technical and business reasons, D2D will only ever be complementary to terrestrial networks, rather than a substitute for them.

There is also a misconception that proposing studies for other services in mobile bands (referred to in ITU as IMT) may somehow prevent MNOs from providing regular services nationally. This is a common misunderstanding, as D2D is only needed in areas where MNOs have limitations to operate, either due to lack of a business case or due to physical limitations to expanding their own network. A decision on these matters would allow the terrestrial-satellite integration to succeed by identifying more MSS spectrum, aiding MNOs and helping to connect more people in more places.

High Altitude Platform Stations as IMT Base Stations (HIBS)

Airborne communications are another component of non-terrestrial networks. High altitude platform stations as IMT base stations (HIBS) are considered a great alternative for supplementing terrestrial connectivity. The concept has been part of discussions since the late 1990s when the first identifications were made in the Radio Regulations. However, public awareness potentially only arrived with the Google Loon project. Learning from experiences of early market deployments of technology pioneers such as Google and Meta, current HIBS projects embrace a positive trajectory grounded in technological advancement and the allocation of more spectrum sources.

HIBS are situated in the stratosphere and provide mobile connectivity in both the uplink and downlink directions for user equipment and terrestrial IMT stations. The real benefit of HIBS is their ability to become part of terrestrial IMT networks while potentially using the same frequency bands as terrestrial IMT base stations. At WRC-23, it is proposed that the IMT mobile stations served by HIBS are the same as those used with terrestrial IMT base stations.

The points of discussion regarding the use of IMT frequencies in high-altitude platforms within non-terrestrial networks have revolved around ensuring the necessary protection to prevent potential interference with other services or applications, such as link concentration systems, public protection and disaster relief (PPDR) applications, digital dispatch systems, and public mobile communications systems with aircraft.

HIBS could be a great connectivity provider for rural or remote areas where conventional base stations are not economically viable. They can also be relocated and rearranged, providing more flexibility in investment and deployment decisions. Moreover, they can be utilized in seasonal or short-term demand increases, such as tourist high seasons or concerts. Finally, they would provide resilience to networks during disasters and network outages.

From a business perspective, HIBS have been difficult to operate until now because of a lack of market incentives, limitations of spectrum sources, and technological challenges such as power consumption, weather conditions, and the need for seamless integration. It seems that further allocations at WRC-23 could be a significant step forward for terrestrial-non-terrestrial integration while 3GPP and industry play their part elsewhere.

HIBS providers could be strong competitors to space-based broadband providers. For instance, MNOs counter broadband competition from the satellite industry in remote areas with bundled offers. Further convergence between the aviation and telecommunication industries is a given and might create new business models and offerings – not only in the operation of HIBS itself but also because HIBS are a connectivity option for drone operations in line of sight and beyond.

Connecting remote areas is a noble task that is not financially incentivized as there is no strong return on investment. As a proven alternative with adequate spectrum and reliable technology, regulators and policymakers can pave the way for HIBS deployments by making use of universal service funds to increase coverage in a wider area with fewer deployments.

WRC-23 will likely have an instrumental role in shaping the future of communication networks and creating a more converged industry while enabling seamless network integrations.

Ivan Suarez is the Space and Spectrum Policy Director for Access Partnership. Gökhan Tok is the Space and Spectrum Senior Policy Manager for Access Partnership.