Down thread there are a lot of numbers thrown about, some slightly wrong or only in miles, so let me summarise them! The values are taken mostly from wikipedia, with some data double checked against [1]
Low Earth Orbit (LEO)
altitude: 160 to 2,000 kilometers (99 to 1,200 miles)
orbital period: ~88 to ~127 minutes
latency: 20 to 40 msecs
Geosynchronous Earth Orbit (GEO)
altitude: 42,164 km (26,199 mi)
orbital period: 1 day (approximately 23 hours 56 minutes and 4 seconds)
So if the orbital period is about an hour and a half to two hours, does that mean that you can expect to hold on to a single satellite's signal for about 40-50 minutes? Longer? I wonder how much power a cell phone will have to use to track a satellite that's moving through the sky - if the tracking will dominate power usage, or sending and receiving the signal will and we won't see much change.
I wonder how this will be different (if at all) from GEO satellites when it's cloudy. Could you presumably find a satellite near the horizon to use to bypass the clouds?
Much less - these satellites are low, so you're not going to have line-of-sight for anything near half the orbital period. Not sure about the precise numbers, but I know Iridium was really challenged by the requirement for clients to roam between satellites on the order of once a minute. As they demonstrated, though, it's a solvable problem.
Low Earth Orbit (LEO)
altitude: 160 to 2,000 kilometers (99 to 1,200 miles)
orbital period: ~88 to ~127 minutes
latency: 20 to 40 msecs
Geosynchronous Earth Orbit (GEO)
altitude: 42,164 km (26,199 mi)
orbital period: 1 day (approximately 23 hours 56 minutes and 4 seconds)
latency: 240 milliseconds
[1] http://iml.jou.ufl.edu/projects/Fall99/Coffey/INDEX.HTM