[OLPC Networking] Some questions about mesh networking (802.11s)

[Javier Cardona]

Hi Stephen,

On Sun, Oct 31, 2010 at 1:19 PM, Stephen Paul Weber
<singpolyma at singpolyma.net> wrote:
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> I am currently working on a project that involves the deployment of an urban
> 802.11s mesh network (at least, the way that we currently envision it).  I
> thought I would write this list as people with OLPC probably have the most
> practical experience with implementing the protocol, especially on
> Linux-based systems.
>
> Is special hardware required to make 802.11s work, similar to how the
> hardware needs to support "master" mode to run as an AP?  I know at least
> driver support will be required, but is it possible to implement driver
> support for any b/g device?

The drivers that are known to work with the pre-802.11s implementation
in the kernel are listed here:
http://www.open80211s.org/trac#DriverStatus

In general, you will need a "thin mac" wireless card (as opposed to a
"full mac" card that implements the 802.11 stack in firmware).  Or you
can use a "fullmac" card with a "thin firmware" (
http://linuxwireless.org/en/users/Drivers/libertastf?highlight=%28libertastf%29
)

> What is the average range of 802.11s?  I would assume it's comparable to
> b/g, but I'm curious if that is the case.

802.11s provides the peering and path selection mechanisms to support
multihop paths over 802.11 links.  The range of a single link will be
determined by the hardware you use (antenna gain, phy, signaling,
etc.)

> Can an 802.11s node simultaneously act as a b/g AP over the same wireless
> hardware, or does the device need two radios for that to be possible?

Not trivial but it can be done:  http://www.youtube.com/watch?v=UUa-DRjj99M

> I've read that Linux-based 802.11s is not compatible with the FreeBSD
> implementation.  Is this still the case?

No, Linux and FreeBSD pre-11s implementations are compatible since
http://www.mail-archive.com/devel@lists.open80211s.org/msg00333.html

> If I run a DHCP server on the mesh network, can that work?

Yes.

> If I can place certain nodes which speak 802.11s around the mesh network
> area, all with wired links to an Internet gateway, will nearby nodes always
> be able to use these nodes to hop onto the Internet without traversing the
> entire mesh?

With careful design, yes.

Cheers,

Javier

-- 
Javier Cardona
cozybit Inc.
http://www.cozybit.com