[d-star] A Portable Mesh Network?

[Doug Reed]

So far, we're trying the Ubiquiti WiFi units for our linking since
they are higher power than WRT54GL. We're also using 5GHz rather than
2.4GHz because of the number of people trying to use the band. There
are three non-overlapping channels on 2.4GHz but more than 12 on 5GHz.

If you pop the new crystal in the WRT54GL or WRT54GS, they will meet
the specs for the hsmm.org units. But in times of emergency you are
going to find they have very limited range and I doubt they will link
very far unless you take the time to setup dishes at high sites like
hsmm.org does.

Before I forget, Dave, you need to do a more detailed check of your
WRT54G and determine exactly which version it is and what version of
the hsmm.org software that you will need. The units Don gave us are
WRT54GL v1.1, the WRT54GS v1 and v1.5, are just as good. Many of the
other WRT54G units, such as v5 and later, are limited in what software
you can install.

But I do like the idea of using the mesh in a portable network for
on-site such as a Red Cross shelter or something like donation
management where they might have hoards of computers scattered around
a half-mile site. That is what we decided to do, mate up one WRT54GL,
hsmm.org style, with every four of the laptops in our emergency "go"
kit.

Another thing I was looking at was Mesh software developed by
Microsoft for use with Win2K and Win XP. It is free for download and I
was able to find all the pieces, although they stopped supporting the
project several years ago. I never quite finished installing it on our
laptops to test with....

Of course if you install Linux on the laptops or other computers, then
the mesh software just becomes a matter of selecting which flavor you
want and going through the install and configure process. I haven't
looked to see if there is mesh software pre-configured in any standard
Linux release. I know it is in routers like the WRT54GL and similar,
but I don't know if anyone had made it part of a standard desktop or
laptop distro. It can be compiled, installed, and configured on any
Linux flavor, it just would be nice to find the work already done....

The other question was can you use the mesh with any standard network.
As far as I know, the answer if no. If you are running mesh, it is
seen as an ad-hoc network and no laptop client can associate with it
since they are usually running in Infrastructure mode..... I least
that is the way I read the articles....

If you are using the WRT54GL or GS with hsmm.org software and the
crystal mod, your WiFi carrier is shifted down below 2.4GHz so it is
out of the Part 15 spectrum and is using that little sliver of Part 97
spectrum from 2390 to 2400MHz. That slot is far enough away from Part
15 channel 1 to reduce the co-user interference, but it is also narrow
enough that you can't run data faster than the 2Mbps that hsmm.org
uses. If you try to go faster, then your bandwidth is wider so you go
outside the Part 97 band *and* you also start interfering with Part 15
channel 1 again....

The lack of multiple channels for hsmm.org and the narrow BW is two of
the reasons that TwinsLAN prefers the 5.7GHz option. 802.11a is only
about 10% as busy (or less) as 802.11bgn and there are Part 97
frequencies that we can use that are above and below the Part 15
channels. Unfortunately I did see an FCC proposal to create some new
data channels in that same spectrum, so we may not have exclusivity
for long....

As for the Saturday work parties, they are scheduled for the third
Saturday of the month. Check the twinslan.net web page for info in the
calendar at the bottom of the page.

73, Doug.