1) A unidirectional transmission channel from terminal station to central station. 2) In the context of land mobile radiocommunication: the transmission channel from the one or more mobile stations to one base station. 3) In the context of satellite communications: the portion of a communications link used for the transmission of signals from an Earth terminal to a satellite or to any airborne platform.
1) The distance from a transmitter to the point, at which the signal strength begins to fall below the level of minimum usable value for a particular (receiver) antenna and receiver combination or to the point where reception is not possible due to existing interference. 2) The distance from cooperating receiver, at which the (average) received signal power is equal to the effective sensitivity of the receiver.
The radio signal carrying the useful information (desired signal) for wanted user.