[CQ] Basic questions from a newbie

[Jonathan Lassoff]

2011/5/15 Daniel González Gasull <gasull at gmail.com>:
> Hi.
>
> I've been looking at the Hinternet pages on the Noisebridge wiki, on
> Wikipedia, and some other pages.  I've also browsed same messages in
> the archives of this list.  I still don't get it completely:
>
> - Has Noisebridge set a HSMM tower yet?

Noisebridge has had 802.11s-enabled HSMM radios setup at one time.
I've since taken the dish down from the roof to continue working on
the host computers.

> - If yes, has Noisebridge set up a mesh/ad-hoc subnet to connect to the tower?

I have had two clients going at a time, and speaking mesh-enabling
protocols, but I'd hardly call that a "mesh" :)

> - How can I connect to the Noisebridge tower and/or its mesh/ad-hoc
> subnet?  What gear do I need?  Do I need a ham radio license?

The best way to get started, in my opinion, is to setup a Linux host
with a wireless card that has a driver for the mac80211 system in the
kernel. This implements a full IEEE 802.11 protocol suite in-kernel,
rather than offloading these functions to the card.

mac80211 is great because it allows us to implement other protocols
and 802.11 extensions, entirely in software. The end goal I think we
were seeing with this was being able to use and extend 802.11s, a
standards-based mesh protocol that actually forwards traffic from node
to node.

Probably the easiest way to get started is with a small embedded
computer or laptop that has an Atheros chipset supported by the ath5k
or ath9k drivers. There is a list of PCI IDs (but sadly, not
commercial users) here:

http://linuxwireless.org/en/users/Drivers/ath5k
http://linuxwireless.org/en/users/Drivers/ath9k

> - If I am at the top of a tall building just a few blocks away, can I
> connect to the mesh subnet?  Do I need to be closer?  How close?

This hasn't been tested much. You might be able to reach 2169, and
might not be. The best way for us to find out is to just test it out!
Right now, there's equipment on the roof, but we could stick a small
Ubiquiti AP up there and see if you can hear it from your site.

> - I am encouraged to share the connection with my neighbors, right?

Well, in the context of the "HInternet" idea, not really. That is,
unless your neighbors are licensed amateur radio operators as well.
Because traffic sent by someone unlicensed could trigger a licensed
radio to transmit, they need to be licensed as well, or a licensed
operator needs to be at the control point.

> - Is my understanding right that the mesh/ad-hoc subnet is a regular
> mesh network, like the one you can easily create with you laptop in
> Linux, Windows or Mac?

Yes and no... it's much more. What I and a couple others have been
experimenting with is using 802.11s, which is much more flexible for
an ad-hoc group of smart radios than 802.11 in IBSS (ad-hoc) mode.

With IBSS, all the radios practically need to hear one another. As
more and more radios join, inevitably some subset of them wont be able
to hear some other subset, and they just end up fighting for control
to transmit on the channel.
WIth 802.11s, multiple radios could establish neighborships and
dynamically tune their radios into channels suited for the sets of
neighboring nodes that can hear them, and then forward traffic for
nodes that can't hear that channel.

In this way, we can dynamically add on more radios than an IBSS cell
could support, but there are also practical limits of how many radios
can locate and form neighborships with one another, while still
supporting broadcast traffic across the entire mesh.

At some point, we would either need to find a way to extend 802.11s,
or invent another simple protocol on top of it to figure out how to
dynamically segment the network and establish either fixed wireless or
wire-line trunks between meshes.
That part is still up in the air.

> - Does this route traffic to the regular Internet?

It may, but probably not. There are all kinds of content restrictions
on what can be sent over amateur radio, and it's probably not
practical to filter all internet traffic.
That said, it's certainly possible. There's a single gateway down at
UCSD that announces 44.0.0.0/8 out to the Internet and tunnels to
amateur radio folks around the world.

> - If it does connect to the regular Internet, and if the mesh network
> is a success and a lot of people connect to it, will Noisebridge have
> bandwidth enough to deal with success?

No. :)

> Also, I want to share this idea.  If my understanding is right and
> what is wanted is as many computers forming the mesh subnet as
> possible, I recommend naming the subnet ESSID "Free Public WiFi".
> Why?  Because there's a whole ad-hoc infrastructure waiting to be
> used:
>
> http://www.npr.org/templates/story/story.php?storyId=130451369

It's possible that this could be a good way to link in non-licensed
users into the Hinternet in an emergency, but the goal for this
project (for me at least) was to create a system to connect up
licensed amateur radio operators in an ad-hoc fashion.

Right now, I've stagnated somewhat adapting the current mac80211
Atheros drivers for some of Atheros' WiSOC (Wiress System-on-a-Chip).
These are chips with a little MIPS CPU and wireless card all on one
die.

I've gotten pretty close in that I can detect the silicon revision of
the chips and attach to them, and I have some basic transit and
receive functionality working, but I still need to reverse-engineer
many of the registers for tuning the radio, transmit power, and 802.11
timings.


Let me know if you're interested in setting up a simple, unlicensed
link to 2169 Mission from your place just to test it out. There some
equipment I can get up there for testing.

Cheers,
jof