The C Band Myth
Many of our customers, especially those located in Africa, ask us about the difference between C- and KU band.
Satellite communication systems are subject to international agreements and regualtions. The International Telecommunication Union (ITU) regulates frequency use and defines "bands"
The following bands are commonly used:
- C-band was the first band to be used for satellite communication systems. However, when the band became overloaded (due to the same frequency being used by terrestrial microwave links) satellites were built for the next available frequency band, the Ku-band. Today C-Band also gets disturbed by wirless radio links in particular uncontrolled spreading in Africa. Interferrances can get reduced by cost intensive microwave filters level421 generally recommends each customer who plans to use C-Band.
- Ku-band is typically used for broadcasting and 2-way Internet connections.
The C-band frequency range has one significant problem. It is the frequency region assigned to terrestrial microwave radio communication systems. There are an emerging number of these microwave systems located all over the world and they carry a large volume of commercial communications. Consequently, the VSAT locations needed to be restricted in order to prevent interference with the terrestrial microwave communication systems. As mobile phones get used more and more in countries all over Africa as well, the use of C-Band in future will possibly certainly rather decrease than increase. At the current point of time - C Band nevertheless is widely used. In particular as KU band capacity over some regions is quite limited.
The Ku-band frequency range is allocated to be exclusively used by satellite communication systems, thereby eliminating the problem of interference with microwave systems. Due to higher power levels at new satellites Ku-band allows for significantly smaller earth station antennas and RF units to be installed at the VSAT location.
At the inception of satellite communications in Africa, C-band was the only option. It has been the long held belief that Ku-band could not be deployed in Africa due to the torrential rains associated with the continent. However, with the technology progress in the satellite industry (invention of ACM gain controlled systems), and the fortune that more powerful satellites now exist. This thereby eliminates the impact of heavy showers. Its all a matter of correct design and proper equipment to make Ku band same stable than C Band to rain factor influence.
This allows Level421 to offer up-time guarantees ranging from 99.70% - 99.95% using the Ku-band frequencies. Same we do guaranty for C-Band frequencies.
Which solution to choose depends today from commercial and less from technical factors, as no matter what frequency band used - both technologies supply internet services at acceptable quality.
Commercially it is fact that hardware for C Band is significantly more expensive while the capacity is cheaper. So customers with large bandwith requirements preferrably choose this technology.
KU Band on the other hand operates with small antennas and less expensive equipment, while the capacity price is higher than C Band.
Downlink: 3.7 – 4.2 GHz
Uplink: 5.9 – 6.4 GHz
- Less disturbance from heavy rain fade
- Cheaper Bandwith
- Needs a larger satellite dish (diameters of minimum 2-3m)
- Powerful (=expensive) RF unit
- More expensive hardware
- Possible Interference from microwave links
Downlink: 11.7 – 12.2 GHz
Uplink: 14.0 – 14.5 GHz
- No interference from microwave links and other technologies
- Operates with a smaller satellite dish (diameters from 0.9m) -> cheaper and more easy installation
- Needs less power -> cheaper RF unit
- More expensive capacity
- Sensitive to heavy rain fade (significant attenuation of the signal) / possibly can be managed by appropriate dish size or transmitter power.