C -band was the first frequency band to be allocated for remote communications when the satellite industry got off the ground over half a century ago. And it is still

used heavily today, particularly in the offshore energy and cruise sectors, where it confers a number of important benefits over other bands in terms of resilience, coverage and capacity.

However, this workhorse frequency is now under threat. Terrestrial mobile operators – the telcos that bring broadband to your smart-phones and tablets – are lobbying hard for the C-band spectrum to be reallocated for new mobile services. If the mobile industry gets its way, it would effectively prevent ships from using C-band in coastal waters and in the long-term could even cast a shadow over the provision of satellite C-band services altogether.

Meeting pointEvery three to four years, global regulators gather at the International Telecommunication Union’s (ITU) World Radiocommunications Conference (WRC) to review, and, if necessary, revise international regulations governing the use of radio spectrum by all technologies including satellite. The next meeting – WRC-15 – will be held in Geneva in November 2015. While that may seem far away, the future of C-band – Agenda item 1.1 – is already viewed as a key battleground.

Patrick van Niftrik, vp spectrum manage-ment and development EMEA for SES sets the scene: “The terrestrial mobile telecom industry is claiming it needs additional spectrum to satisfy the growing demand for mobile data. They started by launching a campaign to try to force satellite service providers to share the C-band. But sharing is not technically viable. Since the beginning of this debate, we have

demonstrated through multiple technical studies that having the two systems operating in the same frequency band is impossible.

The discussion goes back many years. As it prepares for 5G, 6G mobile broadband, the terrestrial telco industry wants to gain rights to all frequencies below 6Ghz – and ideally wants those rights on a global basis.

One outcome of WRC 2007 was the so-called ‘footnote to the table of frequency allocations’, which effectively gave nations the right to use the contested spectrum for mobile applications, whilst retaining some protections of neighbour-

Interference caused by competing services is not a good outcome for anyone Intelsat’s Gonzalo De Dios

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While C-band continues to serve the communication needs of the offshore industry, a battle is underway to safeguard its future

The fighT To save C-band

Words: Kevin Tester

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ing systems, like satcoms. This was popular among European countries where C-band is less widely used. But this piecemeal approach highlights a fundamental misunderstanding among regulators in the global nature of C-band. Each satellite beam offers coverage that is intercontinental. Switching the service on and off for individual nations results in Swiss cheese-style holes that detract from its overall value.

Technical limitationsWhy can’t satellite and terrestrial mobile play nicely with C-band? Terrestrial masts emit high-powered transmissions in every direction. These interfere with the relatively weak signals beamed down from a satellite. The amount of geographical separation it would take for satellite and wireless terrestrial transmissions to both function reliably in C-band makes coexistence impossible.

Despite technological advances on both sides, the practical hurdles of getting satellite and terrestrial mobile to work in harmony cannot be overcome. “Mobile still drowns out satellite on the downlink, whilst satellite still knocks out mobile on the uplink. Interference caused by competing services is not a good outcome for anyone. The best result is rational spectrum allocation decisions that maximise spectrum use,” notes Intelsat’s associate general counsel Gonzalo De Dios.

“It is not even clear that terrestrial mobile networks really need this extra spectrum,” he continues. “For a start, there is already a lot of spectrum reserved for the mobile sector that is currently unused. We also believe that the mobile traffic density assumptions made in the technical studies they have provided to the ITU are unrealistic and therefore may have led to unreliable and misleading data demand forecast.

“The satellite industry is working hard to maximise the utilisation of existing spectrum as well as open up new bands for new services. Specifically in C-band we want to accommo-date innovations on the ESV side that allow

better use of spectrum. Our fear is that due to is a lack of understanding some administrations think C-band is obsolete and only supporting legacy services. But that’s not the case: it is not under-utilised or wasted spectrum.”

Unrealistic forecastsDe Dios questions the spectrum demands being made by the mobile industry: “They are justified largely by expectations of future growth. Warehousing spectrum for predicted growth is not a good strategy until you have extracted the most juice from existing capacity. Moreover, some of their assumptions are dubious and we are seeing new dynamics. For instance, mobile traffic is increasingly being offloaded on to other bands like Wifi, itself a technology which is evolving rapidly at the moment. Such developments would diminish

the appetite for cellular mobile.”Ahead of WRC-15 the satcoms

industry is responding to the threat with its own lobbying activities, spearheaded by the Global VSAT Forum (GVF) and the Satellite Spectrum Initiative

(SSI). Individual operators, like SES, are also undertaking further

technical studies. The goal is to preserve that harmonised

use of spectrum. C-band has certain characteris-tics that cannot be replicated simply by switching to other bands, such as Ku or Ka. For example, it prevails in equatorial regions and other areas with high precipitation, which would degrade the performance of higher frequencies (like Ku and Ka again). Further C-band typically offers ubiquitous reach across entire continents and oceans within a single beam, which coupled with its high availability, make it highly attractive for applications in the offshore business.

Closer approachYet, later in proceedings, members of the WRC will consider provisions aimed at liberalising the use of maritime C-band and Ku-band closer to shore. To minimise the risk of interference with other spectrum users, VSAT antennas

installed on ships (or Earth Stations on Vessels (ESVs) as they known in WRC parlance) are subject to regulations which dictate how close to shore they may be operated.

Last updated in 2003, these are now overdue a review in light of the technological advances made in antenna design that have attenuated disruptive emissions and the fact that VSAT on ships is much more common than before. The gist of the 2003 rules is that within territorial waters (300km) a vessel has to coordinate with shore-based authorities on how satcoms equipment can be used. Like IMO’s rulings, the ITU’s regulations are ratified into law by individual nations. As such, there is considerable variation in the implementation between countries.

Intelsat’s de Dios explains: “This lack of consistency can cause a headaches for ships approaching a new port. As the regulation currently stands it is based on maximum transmit power levels that were typical a decade ago. Power intensities have dropped markedly since then. Taking this into account, you could substantially reduce the distance at which an antenna can be operated without causing interference. Relaxing the regulations would also reduce the burden on shoreside authorities, as they would have fewer ESVs [Ed: ie, vessels] to track in their waters.”

De Dios believes that in the lower ESV power range, operation could become permissible at 60-70km without coordination. Yet, considered together, the two agenda items – 1.1 proposing limits on C-band when mobile is pre-eminent and 1.8 allowing the use of C-band antennas closer to shore – are seemingly at odds.

New normalGoing forward, fending off assaults for spectrum is likely to be a recurring issue for the satellite industry. Spectrum is a scarce commodity, which is in greater demand than ever before following the meteoric rise of mobile broadband. But, says de Dios, the communications ecosystem should be considered as a whole, not application by application. “In many cases satellite and mobile complement each other. Satellite supports mobility as a seller of backhaul, for trains and planes as well as aboard ships. If spectrum is allocated indiscriminately in favour of one application, the ecosystem becomes unbalanced, and the maritime operators will ultimately be the ones that suffer,” he concludes.

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Within territorial waters a vessel has to coordinate with shore-based authorities on how satcoms equipment can be used

300km

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