10.10 Propagation Delay

One of the problems with real-time communications using satellites is due to the large distance between the earth station and the satellite. The approximate propagation delay equals 275 ms; the two-way propagation delay is double that time (550 ms). Since this propagation delay is so long, echo cancellation is vital to the quality of the communication link especially for voice applications. Video applications, in particular one way broadcasting, generally does not need echo cancellation techniques.