I previously posted about this on previous versions of Ubuntu, but despite updating the instructions for 11.10 the instructions are once again obsolete. It seems Intel changes the name of its wifi kernel module every release…
On my Dell E4300 with “Intel Corporation WiFi Link 5100” (as reported by lspci), the module name is now “iwlwifi”. This means the kernel options you add to /etc/modprobe.d should be against this module rather than iwlcore (11.04) or iwlagn (11.10).
So the instructions once again:
$ sudo -i # echo 'options iwlwifi led_mode=1' >> /etc/modprobe.d/wlan.conf # modprobe -r iwlwifi && modprobe iwlwifi
Bear in mind that the second line removes the wifi kernel module temporarily which will disconnect your wifi. It should automatically reconnect, if not reboot.