I recently upgraded my wireless router to 802.11n, as a first step in following in my friend Craig's footsteps. He has an excellent guide to setting up a new wifi router with ipv6.
I figured out what my wireless adapter was called by running
vijayp@ike:~$ lspci | grep -i net
00:19.0 Ethernet controller: Intel Corporation 82577LM Gigabit Network Connection (rev 06)
02:00.0 Network controller: Intel Corporation Centrino Advanced-N 6200 (rev 35)
My lenovo x201 has a Intel Corporation Centrino Advanced-N 6200 wireless controller, but despite upgrading everything, my laptop never seemed to be able to get speeds faster than 54Mb/s. It aggravated me that wireless was so slow! Running
sudo ifconfig wlan0 showed only
IEEE 802.11abg which seemed wrong. I first assumed it was a driver issue (despite these drivers having been integrated into the mainline a while back). I got the latest stable intel drivers (I used compat-wireless-2.6.38-3-ns.tar.bz2 but you should check the site to see if a newer one is there) , then the usual
make && sudo make install, followed by a reboot. (I think you might need to have the kernel headers installed.)
Unfortunately, despite my shiny new drivers, the problem didn't go away. Finally, after much debugging, I realised that for some crazy reason, ubuntu ships with this default modprobe file:
vijayp@ike:~$ cat /etc/modprobe.d/intel-5300-iwlagn-disable11n.conf
options iwlagn 11n_disable=1
Delete this line, then reboot to fix the problem. But BEWARE. Apparently, there is a pretty serious bug in the drivers regarding problems with 802.11n support on intel hardware. One person reports that he has had no problems with the 6200, but another reports issues. Perhaps it's because I updated the drivers, but I have so far seen no problems with n working properly. There are a few notes in the recent latest changelog regarding changes to the lagn driver, including talk of new microcode, but I can't be sure that those changes have solved the issue. The launchpad bugs seems to be unclear.
Also, note that WMM (QoS) is technically required as part of a 802.11n deployment, and you must be running WPA2/AES to get 802.11n speeds.
vijayp@ike:~$ sudo iwconfig wlan0
wlan0 IEEE 802.11abgn ESSID:"TINAFEY"
Mode:Managed Frequency:5.785 GHz Access Point: 30:46:9A:00:E0:05
Bit Rate=108 Mb/s Tx-Power=15 dBm
Retry long limit:7 RTS thr:off Fragment thr:off
Link Quality=53/70 Signal level=-57 dBm
Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0
Tx excessive retries:0 Invalid misc:13 Missed beacon:0