In satellite telecommunication, a downlink is the link from a satellite down to one or more ground stations or receivers, and an uplink is the link from a ground station up to a satellite. Some companies sell uplink and downlink services to television stations, corporations, and to other telecommunication carriers. A company can specialize in providing uplinks, downlinks, or both.
The following table shows the main frequency bands used for satellite links.
|C||3,700-4,200 MHz||5,925-6,425 MHz|
|Ku||11.7-12.2 GHz||14.0-14.5 GHz|
|Ka||17.7-21.2 GHz||27.5-31.0 GHz|
The C band is the most frequently used. The Ka and Ku bands are reserved exclusively for satellite communication but are subject to rain attenuation. Some satellites carry transponders for both C and Ku bands.