[IAEP] "Mesh" Dreams = OLSR

Andrés Ambrois andresambrois at gmail.com
Tue Aug 24 13:02:28 EDT 2010

On Tuesday, August 24, 2010 11:26:23 am Chris Ball wrote:
> Hi Reuben,
>    > Consider the benefits of using open source software versus our
>    > closed source firmware and partnering with communities like
>    > Freifunk whose network is ~ 800 node, guifi.net is almost 10k
>    > nodes in Barcelona, Athens Wireless is 5k nodes.
> The fact that a custom mesh algorithm would have to run on the CPU --
> prohibiting any kind of idle-suspend -- makes it a non-starter for an
> XO deployment in my eyes.  Did you have any thoughts on this?

We (MontevideoLibre, a free wireless community network) have been using OLSR 
for a while now. And though the topology in a typical OLPC scenario is very 
different, we've talked about assembling an image running OLSRd for a while. 

Anyway, I dont have time for a full response to this thread right now, but I 
had a conversation with smithbone and silbe a while back that may be 
illustrative of the worse-case scenario in terms of power consumption:

<aa>    silbe: I think a working PoC could gather a lot interest from 
<silbe> aa: one thing to consider is the power draw. with libertas_tf, the 
host CPU needs to be powered on. 
<aa>    yes
<aa>    silbe: do you have an idea of what that means in actual numbers?
<aa>    perhaps smithbone has a guesstimate 
<silbe> aa: counter-question: are you thinking of running the protocol while 
the XO is "powered off" (screen off, everything in suspend with wake-on-WLAN) 
or just during regular operation?
<silbe> for the latter case, it might not make much of a difference, 
especially if "automatic power management" (automatic suspend) is disabled.
<smithbone> Running the system is going to cost you in the 5W range. 
<silbe> in the "powered off" case it's going to make a huge difference. I 
don't think it'll be able to run for more than 3h while there's any traffic.
<aa>    silbe: one of the things I want to find out is the convergence time of 
the different options
<silbe> aa: i.e. the time until the network/mesh is stable?
<aa>    yes
<silbe> aa: if you were in europe, you might try getting funding from the EU 
for that ;)
<aa>    silbe: also, BATMAN has a layer 2 kernel module, maybe we could make 
it aware of the PM state?
<silbe> they seem to pay some pretty sums for mesh research
     * aa migrates to Europe
<aa>    :P
<silbe> aa: it should just integrate into the kernel PM QoS framework I 
cuppose, see Documentation/power/pm_qos_interface.txt
<aa>    silbe: will do
<silbe> aa: oh, and some recent mail from me has a link to nice slides 
explaining the PM QoS framework
<aa>    silbe, smithbone: do you guys know if wol would work with libertas_tf?
<aa>    silbe: to sugar-devel?
<silbe> aa: no idea, sorry.
<silbe> aa: I think to devel at l.l.o
<aa>    silbe: found it, thanks!
<smithbone> aa: which gen?
<aa>    smithbone: XO-1
<smithbone> aa: on XO-1 the wakeup is generated by strobing a signal to the 
EC. So libertas_tf would need to support strobing that signal
<aa>    smithbone: thanks a lot, is this documented somewhere?
<aa>    too bad the firmware is closed :(   
<smithbone> aa: no. because none of the systems you are talking about have 
open documentation
<aa>    smithbone: I understand 
<smithbone> aa: But I can certainly tell someone what gpio on the wlan module 
to strobe and for how long.

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