Communications satellites support both "fixed applications" - so-called because the terminals on the ground are in fixed locations, and "mobile applications" where the terminals can be fixed, or in motion such as on a vehicle, a ship or even an airplane.
The worldwide market for fixed satellite services (FSS) is now over $10 billion annually and is significantly larger than the worldwide market for mobile satellite services (MSS). Demand for both FSS and MSS is growing rapidly and the distinction between the two is becoming blurred as each is now serving the other's traditional markets. MSS can use several frequency bands, but has historically relied on L-band and S-band frequencies which facilitate terminal designs. As has happened with FSS, MSS applications are moving to higher frequencies such as Ka-band as capacity demands increase.