[MLB-WIRELESS] Question to list

[Dan]

> From: owner-melbwireless at wireless.org.au [mailto:owner-
> melbwireless at wireless.org.au] On Behalf Of Miki Shapiro
> One use I have in mind is hook up my CarPC (which will also get an
> antenna) to my home server (VPN) when within reception limits via nodes in
> the area it is in.
> First question is of course can this be done via nodes in close proximity
> to the car?

Yes it could if the nodes in question offer a DHCP service.  Some nodes do,
a lot of nodes don't.  It's up to the node-owner as to what services they
offer.  The network is a collection of individuals more than it is an
organisation, and node setups are mostly not standardised.

> Second question - is there some high-alt node (Dandenong Mtn?) with a
> wide-enough directional cone that I can use when within areas of eastern
> melbourne?

There is - Node GHO on Mt Dandenong has three wireless radios on it -
however the signal strength from any of these radios require you to have a
high-gain directional antenna like a dish, mounted on a high enough mast or
building to get a good line-of-sight.  Your car would need to have a tall
pole sticking out of it with a big, auto-tracking dish on it.

> Third question -  do the nodes know how to route between each other or
> do they only have routing configured to their
> adjacent nodes (and other manually predefined routes)?
> Is any dynamic routing or meshing implementation being used? That's a
> leading question to "will my car be able to access home by hopping" 4
> nodes?

Yes - nodes in Melbourne Wireless use OSPF.  There's a bit written about how
we use it, and some maps of the network in the Melbourne Wireless site.
 
> Final question - anyone have any experience with non-stationary WiFi
> communicating with stationary nodes?

Personally, not much.  In a conventionally routed network like Melbourne
Wireless, mobile nodes can't really "roam" between nodes because their IP
address would have to change from one AP to the next.  Also, Melbourne
Wireless uses different SSIDs on it's APs and 802.11b roaming requires that
the APs have the same SSID.

I have recently taken an interest in Mesh networking and in particular the
OLSR protocol which is being used in a lot of wireless networks around the
world.  Mesh networks do allow roaming over a wide area.  In fact, some
people have gotten mesh networks to work between cars moving at highway
speeds.  I've haven't gotten much further than the thinking about it stage
though.  OLSR and mesh networks in general suffer from non-scalability - but
anecdotal evidence shows that mesh networks of up to 50 nodes are possible
using Linksys WRT54G routers.  If the mesh got any bigger than that you'd
want to think about splitting the mesh into separate meshes and doing more
conventional routing between them.  The most attractive feature of Mesh
networking is the simplicity of configuration.  In Germany some guys have
written a firmware for the Linksys WRT54G and WAP54G called "Freifunk
Firmware" which makes configuring a node amazingly simple (and cheap).  I'm
keeping my eye on the OLSR mailing lists and may experiment with OLSR myself
in the future.

Cheers,

Dan

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