[OLPC Networking] [Server-devel] RSSI value questions

[Ryan Crawford Comeaux]

Just to address a few other issues/questions raised...

If there is only one antenna on a server, then as long as 3 other nodes are
considered relatively stationary, I think their 2D locations can be deduced
from each node's measurements of the other 4. An easy to use interface can
allow the user to orient the generated map with respect to whatever
reference point they like; ideally, the final program would allow for a
floor plan of the building to be displayed underneath the topological
mapping.

With respect to granularity of different measurements, I think inaccurate
measurements can be averaged over time, since some would necessarily be more
accurate than others, allowing for a more accurate map as time passes.

Ben stated that the dynamic gain isn't available in user space.  I'm just
wondering if there's a way to passively determine the gain and if this would
even be helpful in determining location.  Any ideas?  I'm not so experienced
in RF tech that I can come up with how knowing the gain would be useful, but
if it is useful, then I think it'd be easy enough to figure out some sort of
indicator that's relative to the fluctuations in whatever measurements the
gain affects.  Again, let me know if I'm that kid out in left field wearing
his glove on his head and facing away from the bases...

I feel pretty optimistic about the feasibility of this kind of project.
There seem to be a few good measurement techniques to go by, as well
different methods to compute the data.  If the XOs pitch in and tell the
server where they think other nodes and themselves are, relative to each
other, that would provide another set of input to include when averaging out
measurements.

For those of you that would like some light reading on the topic of modeling
this information and computing it, here are a couple of papers that attempt
to do similar things with GSM signals and neural networks:

http://ieeexplore.ieee.org/iel5/9603/30336/01394788.pdf?isnumber=30336&prod=CNF&arnumber=1394788&arSt=+133&ared=+136&arAuthor=Debono%2C+C.J.%3B+Buhagiar%2C+J.K
.
http://ieeexplore.ieee.org/iel5/4222741/4222742/04222782.pdf?arnumber=4222782

- Crawford
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