[clug] Wireless network over belconnen

[Alastair]

On Wed, 2004-06-16 at 15:15, Rohan Mitchell wrote:
> Hi all,
> Some friends and myself are planning on setting up a wireless mesh 
> network across belconnen, using 802.11b/g cards with debian, high gain 
> omnidirectional antennas 

I've been trying for the last year to esablish a network around
Tuggeranong. Theres a rudimentary and somewhat unmaintained website at
http://canberra.freenet.in-a.us

These are my findings . . . 

1. Lots of people will say they are interested, but not many will
actually follow through with it.

2. Canberra is unsuited to mesh topologies - theres too much distance
between nodes to use omnidirectional antennas.

3. Stay away from Colinear antennas - they're a pain to make, perform
poorly and are extremely fragile. If you have the time, make a slotted
waveguide, or if time/money is short, a discone. You can make up a
discone in about half an hour and it will perform way better than the
colinear.

4. Carrier licenses are hideously effective (around $10k if I remember
correctly), but what you run over a private VPN is your business :)

5. You don't want any old hardware - most cards I've seen require a PCI
2.1 slot. Pentium 2 or more recent is fine, but I haven't yet come
across a Pentium with a suitable PCI slot (not that I've been looking
particularly hard). I do have a pile of Celeron systems available for
this exact purpose, but they did cost $$, so I'm obliged to ask for $$
in return.

6. We should co-ordinate IP ranges so that the networks can be linked at
some point.


My (new) setups are thus:
If theres power available in the roof space:
FreeBSD gateway with 2 DLink DWL-G520 cards (Atheros based, 108mbps
proprietary mode)
OSPF for routing (Zebra)
a couple of NICs

If theres no power available in the roof, replace the cards with APs or
maybe USB adapters if you can get drivers. You really want to minimize
the distance that you have to run RF, as the cable is lossy and
expensive (whereas CAT5 and USB cables are cheap). If you want to run
power over your cat5 cable (as opposed to power over ethernet, which is
48V), I've designed a small switchmode power supply to step down
anything up to 40V to 5V (check if you really need it first though - the
DWL-1000ap and DWL-900+ap that I've got will accept quite a high input).
I feed +12V from the computer's power supply via cables soldered to the
NIC.

One wireless interface runs as a client on a directional antenna (Golden
Circle is your friend), while the other runs as an access point on the
omnidirectional antenna.

Thats about all I can think of for now - I'm sure I'll come up with more
later.

-- 
Alastair D'Silva		mob: 0423 762 819
Networking Consultant		fax: 0433 141 032
New Millennium Networking	web: http://www.newmillennium.net.au