Network association algorithm

[Michail Bletsas]

James,

It does work in mesh mode too. 
Keep in mind that in mesh mode, power level modulation works along 
per-link rate adaptation (RREQs are send in 4 different rates and the 
highest successful rate is used for data frames when the path is 
established). In general higher data rates require higher TX power, so the 
trade-off there is between a larger interference radius and the time that 
you keep the medium occupied.

In mesh and ad-hoc modes there is no obvious way to present SNR info (for 
what link?). If you look into the forwarding table you can actually find 
RSSI and rate info for your neighbors.

M.






James Cameron <quozl at us.netrek.org> 
Sent by: quozl at us.netrek.org
05/02/2007 09:04 AM

To
Michail Bletsas <mbletsas at laptop.org>
cc
jg at laptop.org, OLPC Devel <devel at laptop.org>
Subject
Re: Network association algorithm






On Wed, May 02, 2007 at 08:09:32AM -0400, Michail Bletsas wrote:
> The radios already do power control automatically in Infrastructure
> mode,

Agreed, my tests with detuned AM broadcast radios close to the left-hand
antenna show a marked change in cross-band interference products when
a laptop in infrastructure mode is closer to an access point or peer in
ad-hoc.

> we need to confirm that this works in mesh mode too.

I suspect that it does.  I'm interested to know the real answer.

I just did a half hour test in mesh mode, with access point off, using
http://wiki.laptop.org/go/Mesh_Network_Details#Usage and found at least
four distinct levels detected in this way, depending on the distance
between two units, with one unit doing a "ping -f" of the other.  The
thresholds between each level seemed to be logarithmic by distance ...
in that there were more thresholds the closer the units got to each
other.

In http://wiki.laptop.org/go/Wireless_Driver_README there are no obvious
signal to noise measurements for mesh mode.  Each SNR measurement
specifically says it is for infrastructure.

-- 
James Cameron    mailto:quozl at us.netrek.org     http://quozl.netrek.org/