Realtek 8191SE WiFi on Thinkpad Edge13… again

Once again WiFi on the Edge flakes out. This time it’s a new broadband router furnished by O2. We’ve been upgraded from the O2WirelessBox II to the O2WirelessBox IV. The excitement is almost… non-existant.

Key to this story is the addition of wireless 802.11N which the Realtek card can handle. Except that it can’t with the Linux drivers (and it seems it flakes out on some Win7 setups as well). 

The bad news is that the usual recourse of rolling a new driver from the latest on the Realtek site didn’t work for us, and using iwconfig to force the card not to use N didn’t work either - seems the card doesn’t allow that (the command being: iwconfig wlan0 modulation 11g). 

So I had to disable N on the router which owners of the O2WirelessBox IV will find cannot be done from the GUI. So for this now very niche demographic, here’s what to do:

> telnet o2wirelessbox.lan
Trying 192.168.1.254...
Connected to o2wirelessbox.lan.
Escape character is '^]'.
Username : SuperUser
Password : 
... splash text...
{SuperUser}=>wireless
{SuperUs{SuperUser}[wireless]=>radio
Admin [up] Oper [up] band [2.4GHz] Interop [802.11b/g/n] channel[11]

So from this we see that 802.11N is enabled. To restrict:

{SuperUs{SuperUser}[wireless]=>radio interop = 802.11b/g
{SuperUs{SuperUser}[wireless]=>radio
Admin [up] Oper [up] band [2.4GHz] Interop [802.11b/g] channel[11]

Now disconnect all devices - actually I’d suggest going via the GUI and disabling WiFi, then re-enabling and have all clients re-connect. You should be good to go now. 

One caveat: this setting does not seem to survive a re-boot. There is probably a way to make it persistent but already I’ve lost a little too much time to this one so for now, this blog will be my memory!