Via @mattkirwan, resolved intermittent Internet connection on Thinkpad X200 with Ubuntu 12.04, when laptop and phone work on wifi just fine.

… the problem, the hardware and the linux distribution to which this problem occurs:

  • Fresh install of Ubuntu 12.04 Precise Pangolin
  • Lenovo Thinkpad x200
  • Wireless hardware: Intel Corporation PRO/Wireless 5100 AGN

[….]  A basic google [“wireless slow lenovo ubuntu”] set me on the right tracks, this article on UnixMen.com had me trying out a couple of solutions, unfortunately none of which worked. Reading through the comments led me to this thread, it seemed that Ubuntu 12.04 uses the iwlwifi module NOT the iwlagn module.

Solution described as “Slow Wireless Connection Using Ubuntu 12.04 and a Lenovo Thinkpad x200” | Matt Kirwan | 2012 at http://www.mattkirwan.com/tech/slow-wireless-connection-using-ubuntu-1204-and-a-lenovo-thinkpad-x200/