[Sugar-devel] ESSIDs and BSSIDs, NM and Sugar

[James Cameron]

The instantaneous signal strengths change very quickly, as a result of
micromovements of metallic objects, and the movement of people within
the signal area.

The firmware in the wireless components of the XO can and will make
decisions about which AP to use at a rate which is dependent on the
changing conditions.  The rate at which you can obtain and perceive the
signal strength value is much lower.

If one were to place objects in the near field of one AP's antennas,
reducing the signal strength, then it would be expected and beneficial
for all XOs to swap to the other AP.  Surely this is what you want.

Also, it isn't just signal strength, but also noise level that matters.
The noise level changes dynamically with activity.

On Mon, Aug 10, 2009 at 12:40:15PM -0300, Andr?s Nacelle wrote:
> I wasn?t able to find data witch allow me to say if the throughput was
> affected because of this behavior (I suspect that would be some
> decrease on congested nets), but I don?t like to have in a school half
> of the XO moving from an AP to another all the time. This kind of
> behavior I think would produce dynamical congestion in the net,
> basically because when many XO jumps to the same AP this is not going
> to be able to manage all that much connections and throughput, then
> the XO are going to keep trying and suddenly they will start
> connecting to the other. What I?m afraid of is a mass effect, in witch
> big blocks of XO go from one to another AP sub-employing one of the AP
> and overcharging the other.

These are rational fears, but you need to validate your theory, by
measuring the congestion and load on each AP.

How are you measuring signal strength in your test area?  Is it a
once-off reading using "iwconfig eth0", or do you average several
samples and capture a standard deviation?

-- 
James Cameron
http://quozl.linux.org.au/