The downlink [ daʊnlɪŋk ] in a communication system denotes that connection ( English link ) with the direction of data flow that comes from the direction of the telecommunication network in relation to telecommunication networks from the perspective of a terminal. The down link serves the Down load (download), the data transmission from the direction of the (hierarchically higher) telecommunications network (down) to the terminal. The opposite direction is called uplink .
The term derives from the satellite communications from where it via the connection between the so-called downlink frequency satellite describes and earth station where the transmission actually spatially downward ( English downwards takes place). In mobile communications , the downlink refers to the transmission direction from the base station to the mobile device. From the perspective of the phone user, the downlink is the receiving channel .
In radio communication systems with frequency division duplexing (FDD), different frequencies are used for uplink and downlink, and in systems with time division duplex (TDD) different time slots are used (see duplex ).