Ofcom has published a Call for Input (“CFI”) titled “Improving mobile connectivity from the sky and space” seeking views on the potential supply of, and the demand for, direct-to-device (“D2D”) services and mobile-satellite services (“MSS”), and the associated spectrum needs of these services delivered using satellite or high altitude platform systems (“HAPS”). This CFI follows Ofcom’s continued interest in this area to understand the scope and adoption D2D services and prosecute its obligations to manage the efficient use of spectrum resources in the UK in light of current and anticipated spectrum use.

D2D and MSS services

D2D services enable mobile handsets to connect directly to satellites and HAPS. While portable handsets with satellite connectivity have been available on the market for quite some time, next generation D2D services have emerged enabling unmodified mass market mobile handsets to connect to satellites and HAPS for voice, messaging and data services. D2D services promise improved mobile connectivity by extending coverage to areas not currently served (whether sufficiently or at all) by terrestrial networks and providing back up connectivity to existing service areas. Initial use cases of D2D have highlighted emergency services applications enabling assistance to locations previously not possible due to terrestrial network coverage being unavailable.

Mobile satellite services (“MSS”) operate using MSS spectrum allocated by the International Telecommunications Union. Traditionally, the size and cost of delivering and using MSS has meant that MSS spectrum has been used mainly by government or enterprise users requiring dedicated communications in remote locations not adequately covered by terrestrial networks. However, MSS have since evolved to support a broader range of use cases, from enabling the development of the European Aviation Network and emergency services, to providing connectivity for location trackers and IoT devices. Many satellite operators have by now well articulated plans to expand overall capacity for D2D and MSS services, including via collaborations with communications and technology companies supporting an expanded range of connectivity services.

Areas of focus for D2D delivered by satellite or HAPS

This expansion of MSS use, realisation of D2D feasibility, advancing developments internationally, and the fact that both MSS and D2D services require access to scarce spectrum resources, has prompted Ofcom to consider whether it needs to develop “new specific authorisation proposals for this spectrum access”.

In this CFI, Ofcom states that while it is not yet introducing new spectrum authorisations, “the responses to this [CFI] will inform [Ofcom’s] policy thinking on this topic”. Any future policy changes or new authorisations will be subject to Ofcom’s normal consultation process.

In this light, the CFI explores several grounds for potential future spectrum regulatory changes to address D2D use:

1. Potential licensing regime for D2D use. This requires considering the radio transmissions of both the satellite and the user terminal. If D2D services grow at anticipated rates, the number D2D users could soon surpass the number of MSS users in a manner not accounted for by existing spectrum authorisations. Increased D2D use could result in increased interference with existing users (e.g. radio astronomy). More spectrum sharing in MSS bands could increase the risk of interference between D2D services. The increased need to manage MSS spectrum use may require replacing the existing handset licence exemption with a licensing regime.
2. Interference mitigation measures to protect MNO and non-MNO spectrum users. D2D services also risk interference with MNOs operating in terrestrial mobile spectrum bands. As D2D services increase, this may require coordination between D2D operators and MNOs to mitigate interference risks. Exclusion zones may also be needed to avoid harmful interference to other co-channel, adjacent channel and cross-border spectrum use by non-MNOs.
3. WRC-27 spectrum roadmap to support D2D services. The next World Radiocommunications Conference (WRC) will take place in 2027, which will be looking the roadmap for spectrum bands supporting D2D services. Any spectrum regulatory changes to address D2D use introduced by Ofcom would need to be reviewed to reflect any outcomes from WRC-27.
4. Potential licensing regime for HAPS use. HAPS involving airborne base stations utilising mobile spectrum pose a higher interference risk to terrestrial mobile networks due to their propagation characteristics. HAPS operating in MSS spectrum pose even greater interference risks to MSS serving terrestrial applications. Ofcom is therefore considering whether specific spectrum authorisation is required for HAPS use in the UK.

Considering the above, the CFI seeks input from industry on the following:

1. The level of interest in offering D2D services in the UK (delivered by satellite networks or HAPS).
2. The level of potential demand for spectrum to support D2D services.
3. Technological developments to improve spectrum sharing between D2D services and between D2D services and existing spectrum users.
4. Expected demand for MSS spectrum use.
5. How HAPS might be used to deliver D2D services.

What next for D2D services?

The many exciting developments in satellite and HAPS technologies now promises connectivity and performance for unmodified mass market devices that until recently were only possible to be achieved by terrestrial networks or through the use of expensive equipment. This has coincided with the proliferation of non-geostationary orbit satellite constellation networks and the miniaturisation of D2D enabling technologies that can be flown on them.  At the same time consumers have faced stubborn coverage gaps particularly in remote and hard to reach places where terrestrial network operators for economic reasons or otherwise have not built out sufficient coverage.  Tech companies and handset operators too are seeking to leverage their platforms to provide better experiences for their customers, including to provide connectivity in places and in a manner not previously possible with traditional MSS services.

All of these factors are coalescing at once and calling into question whether existing spectrum licensing and allocation rules for MSS and mobile services remain fit for purpose and whether they are appropriate to support and promote the offering and adoption of D2D services whilst protecting other spectrum users from harmful interference.

The CFI is open until 13 September 2024, and can be read in full here.