[Commotion-discuss] Battlemesh talk about mesh-wide channel hopping (for DFS, etc)

[Ben West]

Indeed, using a tool that switches a node's radio over to monitor mode
would yield lots of info about free or occupied channels, although this
would have to be 'out of band' since it effectively disables the AP.  I was
curious more about doing periodic noise surveys using both the 'iw wlan0
survey dump' tool, in conjunction with the link ETX values reported by
olsrd, so as to not disable the AP.

The survey dump could at least help identify those neighbor's APs which are
particularly strong (i.e. sources of interference).  The link ETX values,
along with the signal dB values vs. TX retry amounts reported by iw wlan0
station dump, would give some measure of the current channel's quality.



On Tue, May 20, 2014 at 8:43 AM, Grady Johnson
<grady at opentechinstitute.org>wrote:

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> I had some thoughts a while back about using nodes for spectrum
> sensing and came across LinSSID, a Linux-based spectrum analyzer:
> http://sourceforge.net/projects/linssid/
>
> It uses the Linux Wi-Fi drivers to dynamically sense the spectrum
> environment across compatible channels. It's probably too resource
> intense to run on the average node, but could be used on higher
> resource backbone nodes (or client devices) and could feed the data
> into a central server.
>
> Obviously, this would largely tie up the node's radio while it was
> sampling the spectrum, but it wouldn't have to do it continuously,
> only say every hour or even once a day.
>
> On 05/19/2014 05:23 PM, Ben West wrote:
> > Simon Wunderlich gave a talk at this year's Battlemesh about
> > progress in implementing DFS (dynamic frequency selection) in mesh
> > networks, whether through user-space tools or in kernel space.
> >
> >
> http://www.battlemesh.org/BattleMeshV7/Agenda?action=AttachFile&do=view&target=2014-05-17_wbmv7_DFS.pdf
> >
> >  The intended application from Simon's perspective is to permit
> > automated channel hopping for meshes, as required for operating on
> > those 5.8GHz bands shared with radar installations.  Although his
> > talk focused on the EU regulatory environment, the incentives for
> > using these channel in the US would be similar (avoiding otherwise
> > crowded channels).
> >
> > My understanding is that the FCC presently requires unlicensed
> > 5.8GHz radios operating on these channels to be be able to sense
> > the present of radar and hop to another channel, and Ubiquiti stock
> > firmware for their AirMAX products (e.g. Nanostation M5) now does
> > this.  W/r/t running adhoc networks on DFS channels, I'm not sure
> > if the FCC explicitly forbids beaconing, or if radios may sample
> > the band for 30secs before sending out beacons.  The FCC regs may
> > be vague on this detail right now.
> >
> > I'm pointing out this particular talk, however, because the ability
> > for a mesh to reliably channel-hop would also be *very useful* for
> > 2.4GHz meshes.  That band now sees potentially destructive noise
> > from channel-hopping neighbors, i.e. one day your mesh works, the
> > next day it doesn't.  Manually keeping up where a clear channel
> > happens to be becomes increasingly untenable.
> >
> > Any high-level thoughts about mesh-wide noise sensing and channel
> > hopping schemes for a platform like Commotion?
> >
> >
> >
> > _______________________________________________ Commotion-discuss
> > mailing list Commotion-discuss at lists.chambana.net
> > https://lists.chambana.net/mailman/listinfo/commotion-discuss
> >
>
> - --
> Grady Johnson
> Open Technology Institute | New America Foundation
> @geekwrights
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-- 
Ben West
me at benwest.name
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