I’ve bumped into issue with Intel Centrino Wireless-N 1030 BGN WiFi adapter under Ubuntu Linux 12.04 LTS. It works extremely slow with some WiFi AP.
How to fix
After some investigation I clarify that you need to switch off 802.11n for Centrino Wireless-B 1030 BGN WiFi adapter, then adapter will work good with all AP. I think that some of AP realize 802.11n protocol in not correct way, And this confuses Centrino WiFi adapter.
Switch off 802.11n
sudo rmmod iwlwifi sudo modprobe iwlwifi 11n_disable=1
Switch on 802.11n
sudo rmmod iwlwifi sudo modprobe iwlwifi 11n_disable=0
Permanently switch off 802.11n
emacs /etc/modprobe.d/iwlwifi-disable11n.conf options iwlwifi 11n_disable=1