I use Intel My WiFi Technology software and an Intel WiFi Link 5100 AGN wireless adapter on my notebook to connect another notebook (which has an Atheros AR9285 wireless adapter). Both adapters are 802.11n-capable, and the network is seen as an 802.11n network on the second notebook, but the link speed is 54 Mbps only. What can be preventing the connection from using higher speeds? Both notebooks run Windows 7 Ultimate. The connection uses WPA2-PSK security and AES-CCMP encryption.
Finally figured it out. The problem was caused by the Atheros AR9285 adapter on the other laptop - its 802.11n capability was locked, and after using the Atheros EEPROM Tool to unlock it, the connection speed increased to 65 Mbps. The AR9285 can run at 150 Mbps on a 40 Mhz channel though, so if anybody knows how to make Intel My WiFi use a wide channel, please reply.
My settings for the adapter are the same as the recommended ones, except for "Throughput Enhancement", which I don't have. However, I don't know how to configure the settings for the router, since I use Intel My WiFi as the router, so I don't have 40 Mhz enabled and can run at 65 Mbps only.