Slow wireless performance

I had slow wireless performance with Atheros AR928X card in my 2510p notebook with Ubuntu Precise and A-Link RR24AP-N station. I tried all sorts of tweaks with the atk9k kernel driver, but nothing seemed to fix my issues, the wireless speed was dropped to 10-13 Mb/s after a successful connection to the WEP protected wireless network. The solution was to disable the "Aggregation" in the Advanced settings of my router.