wlan interface (was: first play with new XO 1.5 machines)

[Albert Cahalan]

On Fri, Oct 23, 2009 at 7:09 AM, Daniel Drake <dsd at laptop.org> wrote:
> 2009/10/23 Albert Cahalan <acahalan at gmail.com>:

>> Thus, properly done, the XO labled "C" might have either of:
>>
>> a. wlan0 to reach A, and wlan1 to reach B (same hardware)
>> b. wlan0, from which wlan0_0 and wlan0_1 are instantiated
>
> It can't do this, unless it has 2 independent clocks in the wifi
> hardware. I do not know of any hardware that does this.
>
> The issue is that A and B are both hosting their own networks, they
> are both beacon masters, spewing beacons based off their own clocks.

How is this any different than the mesh situation?

> C can either talk with A, by finding the beacons, adjusting its own
> clock to match. (at this point, any frames coming from B will be heard
> as noise)
> or it can adjust to B's clock, in order to speak to it (and everyone
> else who's synchronized to B). At this point, frames coming from A are
> just noise.

Which clock? Do you mean one for the individual bits, or one
for packet-level time division?

AFAIK, a clock for individual bits is not something you'd keep.
The preamble should take care of that. A packet-level clock
shouldn't cause the "heard as noise" issue.

If you can't deal with multiple beacon masters spewing beacons
based off their own clocks, then mesh should be impossible.

BTW, this goes beyond ad-hoc and mesh. I might want to serve
as 3 access points and be a client to 7 others. That should work,
subject only to channel and interference troubles. (hardware X can
do 1 channel in each band, hardware Y only does 1 channel total,
and hardware Z can do 2 degraded channels in 1 band)