WLAN: towards a solution for the roaming freeze

[Werner Almesberger]

Andy Green wrote:
> Well it can be avoided OK by not doing it, I am just wondering what it
> leads to if the firmware is broken for some things and we don't have a
> way to update it.

I think this is a question of negotiation :-) It doesn't surprise me
that we ran into such an issue. There was already a similar situation
during early GTA02 prototype development. Back then, the firmware was
updated by physically replacing the modules.

I think the crash issue is about borderline between a mandatory
firmware update and something we can acceptably work around. If this
is good enough to change Atheros' (IMHO silly) position on firmware
upgrades, then we'll have cleared that obstacle when the next problem
happens.

We don't understand the other frequency change issues well enough to
be able to tell whether the firmware is acting properly or not.

> There's no point altruistically researching Atheros
> firmware bugs if it won't pay off for us?

Why do you think it does not pay off for us if we look for solutions
for problems our customers experience because we chose to include
the Atheros module in our product ?

> It sounds like this is fairly uncommon situation, in the case where we
> claim a good association but nothing works,

Quite to the contrary. Please look at
http://people.openmoko.org/werner/wlan-freeze/6ch-DIST.png

If the difference in frequency is one or two channels, you have a
probability of about 10% of experiencing the crash. You have another
10% of communication failure without the crash. And I haven't even
looked for cases where communication is poor but doesn't break down
completely.

Also, this problem was reported as a repeatable real-life observation
by users. It's not just an artefact I create with obscure lab
experiments.

> I guess the user will hit on
> NetworkManager or whatever icon and try to reconnect.  It's what I would
> do anyway.

Yes, I think a way to trigger a manual reset complete with
reconfiguration is a good option to have. However, manual
intervention is often undesirable. E.g., you may roam without
actually noticing, and having your connections hang seemingly
randomly gets annoying very quickly.

- Werner