On 8/14/17 10:24 AM, Magnus Danielson wrote:
Hi Jim,
On 08/14/2017 06:03 PM, jimlux wrote:
And GPS users who care about spoofing tend to use antenna systems that
will reject signals coming from the "wrong" direction. It's pretty
easy to set up 3 antenna separated by 30 cm or so and tell what
direction the signal from each S/V is coming from.
I would expect that as spoofing/jamming becomes more of a problem
(e.g. all those Amazon delivery drones operating in a RF dense
environment) this will become sort of standard practice.
So now your spoofing becomes much more complex, because the sources
have to appear to come from the right place in the sky. (fleets of
UAVs?)
You gain maybe 10 to 20 dB, but not much more.
A real protection scheme needs much more tolerance to handle severe
problems.
I think it is more about are looking for "spoof detection" or "spoof
immunity".. Spoof detection is a easier bar.
There is an overbeliefe in such approaches, rather than trying to look
at the system analysis, since when you loose the GPS signal, what do you
do. I get blank stares all too often when I ask that trick question.
Most successful schemes rely on "side information" of one sort or
another - whether from an IMU or from other sources. Acquisition is
always more vulnerable than track.
I don't do much, if any, of this stuff these days - that was more my
thing in the mid-80s when I would killed to have the cheap processing
power and fast data converters available today.
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