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Direct-to-Device: The many Routes to the Future

In the second in our series of blogs expanding on issues to be discussed at WRC-23 that impact the satellite industry, we’re focusing on the issue of a satellite signal being sent directly to a cellular handset, often referred to as direct-to-device (D2D). This is not entirely a new phenomenon, as Iridium, Globalstar, and Thuraya have been doing this for years. In Iridium and Globalstar’s case, a specialized handset or terminal is needed and in Thuraya’s case, a specialized sleeve is added to the handset.

Technology outpaces Regulation

What is new, is sending a signal directly to an unmodified handset, or to a modified regular (in size and appearance) handset. In other words, using cellular frequencies from the satellite, or using mobile satellite service (MSS) spectrum. The former requires new satellites with large antennas, in order to transmit in those terrestrial frequencies, and the latter requires adding a chip and integrated modified antenna to the handset in order to receive in MSS frequencies. Both of these approaches have been taken by different early industry players and there are arguments being put forward in favour of both.

Although not everyone agrees with NSR’s assessment that D2D is “the largest opportunity in Satcom’s history,” it is clear, that this is a topic of interest to any organization that is either providing, or intends to provide a D2D service. It is also clear that this is an example of technology outpacing regulations. There are no global or even national regulations for the use of cellular frequencies from space, nor do most cellular licenses include the use of MSS spectrum. As a result, the early players in D2D need to negotiate with the licensing authority in each country that they intend to operate. Earlier this year, in the US, the Federal Communications Commission (FCC) took the initiative to make it easier for satellite operators to collaborate with the mobile network operators (MNOs) in order to use terrestrial spectrum to fill in coverage gaps on land. This initiative forms the basis of the FCC’s ‘Single Network Future’. However, as most other countries have not taken any steps towards licensing, there is no guarantee that such approach will prevail and become the global way forward.

Finding the Way Forward

What is at stake here impacts technology, regulations, and ultimately market growth. Without global consensus and regulations, the market is likely to develop with two competing technology approaches: Cellular vs MSS spectrum. Rather akin to the early days of cellular when the battle was between the Global System for Mobile Communications (GSM) and Code-Division Multiple Access (CDMA). It was discovered then, that the ability to roam is critical, and that ability has to be built into the handset or terminal. As Dr Anton Monk, VP & CTO of Wireless Initiatives, Viasat, stated during a panel at Satellite Innovation last month, “It’s going to require global cooperation amongst spectrum holders.” However, he was not favoring one approach over the other, rather he felt that if the market assessments were accurate, it would need to be a multi-orbit, multi-spectrum solution to provide the needed capacity.

Almost by definition, satellite services are more likely to be regional or global than national. This is particularly true in land masses - other than North America - where a continent is composed of multiple countries. In this situation, spill over and interference to signals in other countries is more likely to occur and more challenging to prevent; particularly if the signal is coming from a LEO satellite that is likely to be crossing multiple countries each hour that it’s over a land mass. This alone presents a rationale for a global consensus. However, before delving into regulations, it's essential to address a prerequisite: spectrum availability.

Whilst the different approaches call for very different business models, the overarching need for the industry is a clear global licensing framework, and so a global frequency allocation will be needed. Something that will only come about once this topic features as an Agenda Item (AI) at a WRC conference. For WRC-23, the topic is covered under AI 10 which specifies topics to be considered for WRC-27. Under AI 10, proposals are made to consider generic and global allocations for satellite D2D and related studies for inclusion in the agenda for WRC-27. This will mean many meetings, working sessions and discussions to try reach consensus on the need for a global allocation, and, if approved, many drafting sessions to formulate a resolution to be included on the agenda at WRC-27.

One of the topics for discussion at WRC-23 is to consider a possible worldwide allocation to the mobile-satellite service for the future development of narrowband mobile-satellite systems in frequency bands within the frequency range 1645.5-1646.5 MHz, 1880-1920 MHz and 2010-2025 MHz under AI 2.13. This would be one way of expanding satellite’s share of the IoT market, but currently has little support presumably due to a current and similar agenda item that reached a deadlock despite four years of discussions.

Applications for D2D services currently include low data rate: texting and emergency messages, with the view to offer in a near future more conventional voice and data communications. Dual-mode devices that connect to both satellite and cellular frequencies have been complex and consequently more expensive, limiting usage and market growth. With a globally harmonised and generic frequency allocation, D2D suddenly becomes a much easier and financially viable proposition.

It is likely to be some time before there is a clear global regulatory path forward for D2D, but as things advance, we will provide updates on this topic.


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