Re: Posting picture files
On Mon, May 02, 2016 at 07:08:07PM -0500, John Hasler wrote:
> Ralph Sanchez writes:
> > I guess a lot of those 2.1 million customers probably live in very
> > rural areas where maybe other forms aren't available, or the cost to
> > lay wire would be more then they have. My thinking is, we have GPS
> > that works nearly (ok maybe not) everywhere you'd go and want
> > internet, so why hasn't some billionaire or multi-billion or trillion
> > dollar company decided to provide a wifi type service in the same way?
>
> GPS requires many orders of magnitude less bandwidth than does Internet
> service. There is satellite Internet service and some people in remote
> areas use it. However the present version has serious drawbacks. Elon
> Musk plans to change that.
In particular, GPS is a one way service. Point your receiver at
the sky, let it see several satellite's radio beacons. Each
beacon emits a short pulse train encoding the satellite's
position and a very accurate timestamp. Your receiver does the
math and now knows where it is and what the time is.
The total bandwidth from a satellite is just over 1 megabit per
second. If it had to be shared among various receivers, it would
be completely overwhelmed by demand. But as a broadcast signal,
it is very effective.
-dsr-
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