On Mon, 16 Dec 2002, kevin lyda wrote:
> latency seems to be an issue. i've emailed a few users to ask
> about that.
do the basic math. packets have to go up to orbit and back down to
you, which takes time:
if you get your signal from a mesh of low-earth orbit satellites (320
to 800km altitude apparently):
(320*1000/(3*10^8))*2 = .0021
(800*1000/(3*10^8))*2 = .0053
5 milliseconds, not too bad.
However, LEO satellites tend to whizz past. So more likely you'd be
pointing your dish at a geo-stationary satellite, which sit at about
35000km above earths surface. if we ignore lateral displacement (ie
distance ireland is from the spot on earths surface to which sat is
(35000*1000/(3*10^8))*2 = .2333
so you have quarter of second of latency in your internet connection
alone. And that's just in one direction. Ie if the arrangement is
satellite downstream, modem/something else upstream, then above might
However, if you have satellite as both your up and downstream, then
RTT to /just/ your satellite ISP will be .4666s.
So one-way satellite might just be ok (still about 7 times higher
latency on the return path than ISDN). 2-way would definitely suck
for anything interactive.
Paul Jakma paul at clubi.iepaul at jakma.org Key ID: 64A2FF6A
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