ubuntu-7.10 and wireless channel search

Derek Broughton news at pointerstop.ca
Thu Nov 1 14:15:16 UTC 2007

Please don't CC me, it's completely unnecessary.

Ed Arnold wrote:

> However, I suppose it's possible that these wireless cards are really
> dumb devices that don't auto tune, and that the host driver software has
> to do the scanning by setting the card's receive frequency and reading
> signal strength for each channel 1-14.  Do you know if that is in fact
> the way the card's interface works?

It isn't.  The wireless card scans (at different rates, depending on the
firmware and the OS, iirc).

You can trigger that yourself:
$ iwlist wlan0 scanning
wlan0     Scan completed :
          Cell 01 - Address: 00:13:10:9F:68:27
                    Protocol:IEEE 802.11g
                    Frequency:2.462 GHz (Channel 11)

which says that it's found one AP in range, and it's on Channel 11.  If your
scan shows no ESSID or Mode other than "Managed", I'd guess that's your
>> But now that you mention it, why on earth do both Network Manager and
>> iwconfig report your channel as a Frequency?  How difficult could it be
>> to map that to the channel set on the router?

And, as shown above, iwlist _does_ map it to a channel.
> Sure, I could change the channel to 11 at the router, then type in
> "iwconfig eth1 channel 11" on the client, but that's not how wireless
> is supposed to operate.

I don't think you can anyway - I believe setting the channel with iwconfig
is only supported for a nic in AP mode.

> Obviously, Windoze XP does this correctly; the 
> question is, why doesn't Ubuntu do the same thing?

Please don't assume that because _you_ have a problem, there's a general
problem in Ubuntu.  Ubuntu _does_ do that, correctly, for almost everybody. 
So, there's some problem with your particular configuration.

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