There is a raging debate in the international and regional spectrum regulatory community on the issue of sharing fixed satellite service C-band downlink spectrum rights with the International Mobile Telecommunication (IMT)-Advanced service. The spectrum is currently being utilized by satellite operators primarily for telecom and TV broadcasting services, whereas the mobile industry wants to access and use the same band for the IMT-Advanced service. IMT-Advanced is a term coined by the International Telecommunications Union (ITU) to define a terrestrial, Internet Protocol-based broadband service for smartphones and other mobile devices.
Questions raised on the hotly debated issue include: Should C-band be shared? Would it cannibalize current spectrum allocation? What are the criteria for C-band sharing and how would it impact users, operators and regulators?
Over the last three years, various study groups at ITU have been discussing the topic of sharing criteria between the incumbent satellite service and IMT-Advanced. The final decision on whether C-band spectrum can be used by IMT-Advanced will be made at the World Radiocommunication Conference (WRC-15) in November. The WRC is held every three to four years and is the highest international treaty-level organization that decides on the international radio regulations governing the allocation and use of frequency spectrum.
Studies conducted by ITU study groups have confirmed that the introduction of IMT-Advanced in C-band will interfere with satellite signals and severely degrade the quality of service. Other studies have shown that the spectrum requirements for IMT-Advanced are overestimated, and the market data provided by the mobile industry are not correct.
As such, the satellite industry and a number of developing countries are rallying against the proposal of IMT-Advanced using the C-band spectrum currently utilized for satellite communications. A key consideration is that developing and underdeveloped countries are dependent on C-band for their critical connectivity requirements, which includes a high reliance on solutions provided by satellite communications.
It is worth noting that the WRC held in 2007 also discussed the use of satellite C-band spectrum by IMT, and even at that time the studies conducted by the ITU study groups confirmed that it is not feasible for IMT-Advanced to share the frequency band with satellite service.
The Significance of C-band
C-band was the first frequency band to be allocated for use by the satellite communications industry for fixed and broadcasting satellite services. C-band frequencies have long been recognized to perform better under adverse weather conditions such as rain and snow in comparison with other satellite frequency ranges such as Ku-band and Ka-band.
Although new frequencies have emerged over the years and are being utilized by the satellite industry, C-band still represents a very significant portion of the total capacity currently supplied by satellites. Today both C- and Ku-bands are nearly reaching congestion levels. In order to meet requirements for reliable and uninterrupted communications for maritime, banking, defense and governments, C-band is often preferred over other higher-frequency bands that are prone to raid fade. C-band also easily meets the stringent reliability requirements of service levels of over 99 percent of satellite operators.
Examples of how C-band is used in satellite communications include:
- Providing connectivity between multiple locations spread around a country.
- Providing direct and backup international connectivity especially in landlocked countries and island communities. In some cases, satellite communications is the only means of connectivity with the outside world.
- Providing communications onboard shipping vessels.
- Providing cellular backhaul services.
- Broadcasting TV signals, including direct-to-home.
While the terrestrial mobile community is looking to use C-band for IMT-Advanced applications, it is also using the same band for backhauling mobile traffic from its own base stations.
C-band is also used by other types of satellite systems such as geostationary mobile satellite systems for their feeder link operations as well as for critical telemetry, tracking and command operations. Mobile satellite systems are increasingly using C-band to support disaster and emergency communications because it is easy to use and deploy. Furthermore, it supports various mobility-based communication requirements for the media, news gathering, maritime, government and defense sectors, among others. Therefore, C-band is the backbone of multimedia messaging service systems, which are the only available means of communication when other channels go down for one reason or another.
To add fuel to the fire, there is an emerging trend among developing countries to launch their own national satellite systems to meet universal service obligation requirements. This trend supports regional and subregional connectivity requirements, which will benefit users who will then have access to a wide selection of low-cost mobile devices. Satellite manufacturers are taking note by innovating and considering the introduction of multibeam satellites in C-band, similar to those in Ka-band, to support higher speeds and throughputs.
As the debate rages on and new trends come to the fore, it is of utmost importance to protect C-band spectrum for use by satellite operators in order to continue providing critical connectivity requirements. It is also pertinent to ensure that C-band technology continues to evolve and grow to meet the future trends in information-communication technologies.
Zahid Zaheer is senior director of GMPCS (Global Mobile Personal Communications by Satellite) affairs for Thuraya.