C-band was the first frequency band allocated for commercial communications satellites with the advent of satellite technology in the 1960s. Even though C-band frequencies were then also used for line-of-sight microwave transmissions on Earth, the C-band could be assigned for use by communications satellites as well since terrestrial fixed point-to-point transmissions could share spectrum with fixed satellite services (“FSS”) stations without a high risk of interference. Commercial satellites operating in C-band use the frequency band from 3400 to 4200 MHz for transmissions from the satellite to an Earth station (the “downlink”), and the frequency band from 5925 to 6725 MHz for transmitting from the Earth station to the satellite (the “uplink”).
Over the past 50 years, the C-band has become the backbone of a wide range of commercial and government communications:
- Virtually every television in the world, including those on the American Forces Radio and Television Service, receives some programming whose signal at one point passed through a C-band satellite.
- The U.S. military uses C-band spectrum for controlling radar, battlefield communications and command and control systems.
- When a rocket launches a satellite, ground controllers use the C-band to maneuver the satellite safely into orbit.
- The C-band is critical to the U.S. and allied militaries for ongoing training that ensures operational readiness.
- The private network linking U.S. embassies around the globe utilizes C-band, as do military forces worldwide for a range of communications.
- A host of other applications such as cellular backhaul, maritime communications, air safety networks, disaster recovery and many others are also provided via C-band.
Because the C-band frequencies represent a rather large continuous block of radio spectrum, they have for many years been coveted by the terrestrially-based wireless telecommunications industry. The International Mobile Telecommunications (“IMT”) community is forecasting a potentially huge increase in spectrum demand for their services over the coming years. While the mobile operators can and should endeavor to use their existing frequencies more efficiently, they are also looking at using additional spectrum, including C-band frequencies.
C-band is by no means an ideal frequency band for mobile services (e.g. insufficient indoor penetration), nonetheless, mobile operators view the C-band as a potential source of additional bandwidth to serve their current and future customers. However, while it is relatively easy for FSS earth stations to share the same frequencies with terrestrial fixed point-to-point services, sharing with mobile/nomadic point-to-area services presents high risk for harmful interference.
In their lobbying efforts for additional spectrum, the well-funded IMT community has the advantage that everyone is familiar with the use of smart phones, while the role and wide-spread use of satellites, to name cellular backhaul as just one example, is far less known and obvious. The mobile wireless industry has begun to use its significant clout to push governments and international regulators to identify parts of the C-band spectrum now used for satellite communication for use by terrestrial wireless devices.
In 2015, the International Telecommunications Union (“ITU”) will hold a World Radiocommunications Conference (“WRC-15”). WRC-15 will consider a proposal by the wireless industry to identify a portion of the C-band for IMT. The wireless industry attempted a similar campaign six years ago, at WRC-07. It won a partial victory then, in that certain countries permitted the identification of a portion of the C-band for wireless communications.
In order to safeguard the C-band spectrum for critical satellite services, the satellite industry has undertaken a number of initiatives in advance of WRC-15. A wide range of satellite trade associations have joined to develop a common global initiative, including but not limited to:
- Global VSAT Forum
- Satellite Industry Association
- Cable & Satellite Broadcast Association of Asia
- European Satellite Operator Association
- Asia-Pacific Satellite Communications Council
Additionally, it is important for the users of satellite communications to help raise awareness about the variety of services they provide in their country and often globally, which rely on satellites and in many cases on C-band. Regulators and decision makers need to hear from satellite communications users in order to be fully cognizant of the multitude and criticality of services provided to governments and citizens via satellite. This will allow regulators to make an informed decision on the C-band leading up to and during the WRC-15.
This article first appeared on IGC’s SATCOM Frontier
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