[Commotion-dev] Serval Mesh Helper Device / ISM long-range meshing work

Thu Feb 7 20:36:02 UTC 2013

Hello Dan,

On Fri, Feb 8, 2013 at 6:50 AM, Dan Staples
<danstaples at opentechinstitute.org> wrote:
> Paul, that is very interesting! I am particularly interested in what kind of
> throughput you can get on that frequency.

In principle up to about 128Kbit.  To really achieve that, we need to
rewrite the radio firmware, which needs to happen if we want them to
mesh, anyway. For now we are getting about 30Kbit, which is still
enough to do useful things with Rhizome (MeshMS, software updates,
voice-mail when we finish writing it, and other things).

> Do you attach an external antenna
> to one of the RP-SMA connectors?

It has two antennae connectors for diversity (but not MIMO), and I put
two antennae at 90 degrees on those to give some polarity diversity
and resilience, especially since we intend the thing to end up in
peoples pockets/desks/wherever. We have bought a couple of +6db yagis
as well for some more directional testing.

> As for battery power, I've been experimenting with providing power to a
> Raspberry Pi using a series of D-cell batteries. D-cells have the most
> energy capacity per density/size than any other common consumer battery,
> from my investigation. For the RPi, which uses 5V USB power, drawing
> 500-1000 mA, a couple alkaline D-cells could last 2-3 days. I bet this could
> work for your Mesh Helper as well. All I needed to get that working was a
> simple step-down DC-DC converter, which costs US$2 max. A handful of D-cells
> aren't exactly pocket-sized, but certainly something you could stash in a
> backpack. I'm about to buy a high-current solar cell as well, to try to make
> an always-on solar-powered device.

I spoke with Alex from the Pi foundation at LCA, and he says that it
is possible to get the current on a Pi down to about 50mA in sleep
mode, so some substantial gains over your initial efforts are
possible.

I need to do a blog-post on our battery solution we are using for
these prototypes, as we have ordered some samples from OptimaBattery
in China (who make lots of EV batteries).  The ones we got are a bit
of an overkill, being 10AH 12v LiFePO4 batteries, but at 120WH, they
can run stuff for quite a while.  These are US$66 in sample quantities
(plus about the same in freight!), but should run a mesh helper
prototype for about a week between recharges.

We are trying to get a flexible solar panel intime for KiwiEx, but it
is proving hard with the short lead-time due to Chinese New Year. The
other option is to get one locally for about 3x price.

> Let us know of your progress!

Will do.

Paul.

> Dan
>
>
> On 02/07/2013 09:46 AM, Ben West wrote:
>
> Likewise, Ubiquiti also sells 900MHz versions of their Nanostation and
> Bullet access points.  I understanding these units essentially just have
> 2.4/5.8GHz chipsets that have been translated to a different band, and with
> some consequent penalty in spectral efficiency.
>
> E.g.
> http://www.wirelessnetworkproducts.com/locom900.aspx
>
> I would like to assume OpenWRT and derivatives will run w/o complaint on
> such 900MHz units, but I'm guessing it's not that simple.
>
> On Wed, Feb 6, 2013 at 11:00 PM, Paul Gardner-Stephen
> <paul at servalproject.org> wrote:
>>
>> Hi All,
>>
>> Just a heads up on some stuff we are doing at Serval that I think will
>> be of interest to Commotion deployments more generally.
>>
>> We are now actively working on what we call our "Mesh Helper Device",
>> the prototype of which will consist of a TP-LINK WR703N running
>> Commotion OpenWRT + servald, connected to an RFD900 ISM 915MHz band
>> packet radio and a rechargeable battery.
>>
>> This gives the potential for much greater range than just WiFi, as
>> well as offering some resistance for 2.4GHz jamming in places where
>> that is a problem.
>>
>> The RFD900s with current firmware in urban settings offer 5x to 10x
>> range compared with WiFi.  For example, I could receive a decent
>> signal with one radio sitting on my lounge, and the other radio with
>> me walking around the block, up to about 150m away -- with the signal
>> path obliquely through perhaps 8 or 10 houses, fences, cats, dogs,
>> trees and everything else.
>>
>> With good clear line of sight, and a low noise floor, ranges of 10km
>> or more are possible, with some evidence pointing to the actual limit
>> being around 80km - 120km in very ideal conditions.
>>
>> We have already managed to get Serval Mesh traffic, including some
>> Rhizome transfers (but not yet voice) running over one of these links:
>>
>> servalpaul.blogspot.com.au/2013/02/breaking-wifi-barrier-serval-mesh.html
>>
>> We think a complete Mesh Helper Device, including these really nice
>> radios could be built and sell for <US$200.  It may also be possible
>> to use a cheaper compatible (but slightly lower performance) radio and
>> get the price down to <US$100.
>>
>> The RFD900 firmware only does point-to-point communications, but it is
>> entirely possible to make it do "ad-hoc" point-to-multipoint
>> communications.  Perhaps this is something for us to look at as a
>> follow on after our current work block is complete.
>>
>> We are hoping to have a couple of these with us in New Zealand in a
>> couple of weeks for the KiwiEx field trial. General outline of our
>> thinking for KiwiEx at present is at:
>>
>>
>> http://developer.servalproject.org/dokuwiki/doku.php?id=content:exercises:kiwiex2013
>>
>> If there are other things people would like tested while we are there,
>> let me know, and we will endeavour to cover them.
>>
>> Paul.
>>
>> _______________________________________________
>> Commotion-dev mailing list
>> Commotion-dev at lists.chambana.net
>> https://lists.chambana.net/mailman/listinfo/commotion-dev
>>
>
>
>
> --
> Ben West
> http://gowasabi.net
> ben at gowasabi.net
> 314-246-9434
>
>
> _______________________________________________
> Commotion-dev mailing list
> Commotion-dev at lists.chambana.net
> https://lists.chambana.net/mailman/listinfo/commotion-dev
>
>
> --
> Dan Staples
>
> Open Technology Institute
> https://commotionwireless.net
>
>
> _______________________________________________
> Commotion-dev mailing list
> Commotion-dev at lists.chambana.net
> https://lists.chambana.net/mailman/listinfo/commotion-dev
>