[Olsr-users] Proposed OLSR plugin to adjust nodes' TX power

[Ben West]

Hi Michel,

This could indeed be an operational mode to incorporate.

Right now, the thinking for "orphan" mode was to power down nodes to a
minimal level, possibly even 0, in the event that the wired node(s) become
unavailable.

>From the standpoint of wanting to reduce a node's detectability to
surveillance, and also to obfuscate any packet's source via multiple hops,
"orphan" mode is intended to address the scenario where a mesh has lost its
wired gateway to outside, and the remaining wireless nodes are very few in
number (and thus easily detectable / locatable).

On Fri, Jun 10, 2011 at 3:31 PM, Micheldegeofroy
<(spam-protected)>wrote:

> Hi all,
>
> IMHO Concerning the scenario where two or more orphan nodes meet they
> should reconfigure as a LAN
>
> Michel
>
> On Jun 10, 2011, at 21:07, Ben West <(spam-protected)> wrote:
>
> Hi Henning and Juliusz,
>
> Thanks for your responses.  Please see my follow-up comments in-line below.
>
> On Sun, Jun 5, 2011 at 2:47 PM, Juliusz Chroboczek < <(spam-protected)>
> (spam-protected)> wrote:
>
>>
>> > primarily low-power / battery-power devices
>>
>> Another advantage is that lowering the tx power, you reduce the amount
>> of interference.  Think of a network where there's a lot of nodes that
>> have access to wired internet, so most often you just want to reach the
>> closest wired node.
>>
>> Besides optimizing for tx power vs. interference (which would be an
> operational goal for normal meshes), another constraint is to reduce the
> node's detectability via minimal tx power.  Remember, the targeted user may
> be a pro-democracy protester in an unfriendly country.  That is, we'd
> anticipate mesh users wanting to only operate their nodes at at some bare
> minimum tx power level to enable the mesh to function, tho necessarily at
> high throughput.
>
> Further along these lines, and to preserve plausible deniability for
> said protesters, it is actually ideal to encourage more hops to the wired
> node(s), which again favors low tx power.  That is, in a star topology (i.e.
> degenerate mesh), any packet passing thru a wireless node can plausibly be
> associated with the node's owner/operator.  In a deeper mesh topology, this
> ability to identify a packet's source becomes more difficult.
>
> > - Gradually turn down TX power until reachability of 2-hop neighbor
>> degrades
>> > below specified LQ
>>
>> Wouldn't it be better to turn down TX power until the reachability of
>> direct neighbours drops just below 1, and then raise it back until it
>> reaches 1?
>>
>> (I assume you're measuging direct reachability here, not ETX.)
>>
>>
> The suggestion to adjust tx power based on 2-hop neighbor LQ was actually a
> suggestion from Jeremy Lakeman from the Serval, as a simple way to push tx
> power down to a bare minimum level while still preserving mesh integrity.
>  Do please note this metric for mesh integrity is still being conceived.
>  Also, I would expect such a mesh to operate with LQ < 1 at all times
> anyway, given the manifold needs to minimize tx power.
>
>
>> > - Battery-powered (or even wire-powered?) node with no visible neighbors
>> > should eventually turn down (or turn off?) its transmitter.
>>
>> What if two such nodes meet?  (Look up -i in the babeld man page.)
>>
>>
> I don't yet have a course of action envisioned if two orphan nodes meet,
> besides no action.  We are still anticipating a mesh with at least one wired
> node.
>
> On Tue, Jun 7, 2011 at 3:15 AM, Henning < <(spam-protected)>
> (spam-protected)> wrote:
>
>> > T ... we discussed a potential OLSR plugin that would gradually turn
>> down a
>> > node's TX power until a minimum specified LQ was reached by one of that
>> > node's 2-hop neighbors.
>>
>> There was a presentation on the Wireless Community Weekend (last weekend)
>> in
>> Berlin about implementing Power Control in mac80211. I will have to see if
>> I
>> find a link for you.
>>
>> Doing power control in the driver allows the mesh to adjust the power
>> separately for each neighbor.
>>
>
> I would certainly be interested in seeing that presentation, also for my
> own mesh use.
>
> For the power plugin as planned, I believe we would need to turn down tx
> power for all neighbors.  A goal is to reduce a node's detectability by
> surveillance (i.e. SpecAn, directional antenna), which won't care which
> neighbor a particular node is talking to.
>
> --
> Ben West
> <(spam-protected)>(spam-protected)
>
>  --
> Olsr-users mailing list
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> https://lists.olsr.org/mailman/listinfo/olsr-users
>
>


-- 
Ben West
(spam-protected)
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