Why can satellite television service easily play high quality movies/shows, while satellite internet service buffers videos constantly even in low quality?
In: Technology
Satellite TV is broadcast; the satellites “blindly” send TV just once, and everyone watches it at the same time. Easy peasy, but you have fewer choices of what to watch (“500 channels and nothing on”).
Satellite internet is two-way. Unfortunately, the delay between transmission and reception for geostationary satellites is about an eighth of a second each way. So an eighth of a second from you to the satellite, plus an eighth of a second from the satellite to the ground station (where the satellite gets *it’s* internet connection), plus however much time it takes for the normal wired internet connection to complete, plus an eighth second for that data to get uploaded to the satellite, plus another eighth of a second for that data to get back down to you. So you’re at more than half a second for a full back-and-forth data exchange.
This is a problem for internet traffic, because either side sending data needs a reply for confirmation that the data was properly received. The longer the transmission delay, the more difficult it is to send large amounts of data, because any lost or corrupted data will incur a large “penalty” delay as acknowledgements are delayed more than half a second, which means re-transmissions are delayed more than a full second. If everything was working perfectly, internet protocols allow a lot of packets “in-flight” with occasional receipt acknowledgements, but just a single lost or corrupted packet will make the whole thing just grind to a halt for at least a full second. Additionally, whenever a delay like this happens, internet protocols automatically slow themselves down (because there’s no point in trying to stuff 100Mb/s through a 10Mb/s connection).
Plus, you’re sharing limited bandwidth with a bunch of other satellite users. Which, BTW, is why the new Starlink satellite internet is designed to solve this problem by using satellites in Low-Earth Orbit: so they are much closer and have much less delay. (It also uses a *lot* of satellites — instead of just a handful of traditional satellite internet satellites — to allow more bandwidth for more users.)
Edit: fixed delays, thanks koolman2
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