Paul Deedman, Director, Spectrum Regulation at Viasat, a leading satellite company that has just acquired Inmarsat, explains the importance of the upper 6 GHz band in his sector.
1. What’s at stake for the satellite sector at WRC-23?
The potential identification of the upper 6 GHz band for IMT (in ITU Region 1) has some very significant implications … if the ITU sends a message to administrations and industry that the 6 GHz band is suitable for deployment of IMT, that means we have to expect IMT systems to be deployed. That could lead to very significant interference with satellite receivers, which operate throughout the globe in this frequency band.
It is a band that we sometimes refer to as the extended C band. For the Inmarsat network, that’s where we operate our feeder links for our MSS network. We need to be able to operate without interference to be able to provide our maritime, aeronautical, and land MSS services, which are used throughout the globe for safety applications, in particular.
For the satellite industry more generally, the band is used by a variety of satellite applications from VSATS to large gateway applications. It tends to be used for telecommands applications, for control of the satellite functionality, and for the feeder links for radionavigation signals.
Part of the extended C band includes the Appendix 30B allotments, which are there to guarantee to every administration that they have the rights to the geostationary satellite orbit. We think it's very important to protect those.
2. What have you learnt from the studies into the potential coexistence of IMT services and satellite services in the 6 GHz band?
We have been working on those technical studies in the ITU for the last three years and a document has been produced that contains 20 different studies. There are some studies that show interference well above the protection criteria, and you’ve got other studies which predict interference below the criteria.
Why is there quite a big difference in the overall conclusions? The IMT community has made really over-optimistic assumptions, trying to downplay or underestimate the level of interference that would occur in practice … and with the way these processes work, there is very little opportunity to challenge and correct that. They just become a collection of studies and whether they're right or wrong, they are just treated in the same way. So, that makes it difficult for administrations to draw clear conclusions from the studies.
When you consider quite a low density of IMT deployment, covering very small urban and suburban areas only, even then we see that very significant interference will arise. We've seen in other frequency bands where IMT base stations have been deployed there has been interference to satellite receivers. So, we have first-hand experience … and there is no reason to believe it would be any different in the case of the upper 6 GHz band.
3. Is it feasible to relocate satellite services to another band?
Even if it was possible, in practice, clearing the bands would take 20 years, maybe even longer because that is the typical life of a geostationary satellite. Inmarsat launched two geostationary satellites in the last couple of years, both of those operating in the extended C band, and we expect them to operate for at least 15 years … typically, they operate longer.
We use the C band because it's very reliable … and that's really important when providing safety services. It might not be possible to provide that same reliability in different frequency bands. And access to other frequency bands cannot be assured, because all commercial satellite frequency bands are congested. Any system moving to a new frequency band would need to coordinate, not just one location, but would need to coordinate multiple locations for a global constellation. That’s a difficult challenge to achieve.
Regarding Wi-Fi, the CEPT framework has developed power limits for low power indoor and very low power outdoor devices, which means it is possible to have Wi-Fi use in the upper 6 GHz band that is compatible with satellite use.
4. Where do EMEA administrations stand?
We can see quite a spread of different views … there are some who are definitely supporting no change to the Radio Regulations, that think this band is not suitable for IMT. There are some which are supporting IMT, but are also supporting the application of technical constraints on IMT. And then you have got some who are supporting IMT with no constraints at all. And of course, that is the most worrying situation from our perspective.
5. What would an IMT identification in Region 1 mean for Region 2 and Region 3?
Focusing on our use of the 6 GHz band, over time our satellites could suffer interference, so it would impact on the services that we provide in ITU Region 1 countries (EMEA), and quite a number of Region 3 countries (Asia), because a satellite doesn't just cover one region. That’s why we think Region 2 (the Americas) and Region 3 countries should also actively support no change for this agenda item.
6. Does IMT need more spectrum?
No, we are completely certain that this band is not necessary and that there are other solutions available. It's clear that there are ever-increasing demands for terrestrial mobile … But it's also clear that there are other solutions that can be adopted by the mobile industry, particularly the millimeter wave bands that were put in place at WRC-19 for effectively the same purpose – to provide high density local area capacity. Cell densification can also be applied using existing bands, by placing more small cells in the hotspot areas. That is a more efficient way to meet the capacity demands that doesn't require any incumbent spectrum users to be displaced.
The future of the upper 6 GHz band is a combination of the incumbent satellite use and ongoing satellite use, shared with Wi-Fi. That’s a very efficient use of the radio spectrum. It is a solution that meets the demands that administrations have for broadband connectivity.
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