It's not quite as bad as the cell phone case, since the exact visibility of users to satellites and ground stations to satellites is completely predictable, sin

It's not quite as bad as the cell phone case, since the exact visibility of users to satellites and ground stations to satellites is completely predictable, since the ground stations don't move, and the satellites move in fairly stable orbits. In the cell phone case, you really have no idea when someone is about to go behind a building or something and have to switch cells. All of the relative dopplers are also known ahead of time, so the transmitter should be able to change frequencies on a preplanned schedule without needing much time for resynchronization.