y Asus g551jm have first n 7260 and now ac7260. The have the same problem. Wifi is very very slowwwwww, on other divices its everything ok but on n7260 and ac7260 my internet speed slows from 30Mb to 5Mb..... WHY ??
Please verify you are using WPA2-AES instead of TKIP and try with uAPSD disabled.
http://www.intel.com/support/wireless/wlan/4965agn/sb/cs-025643.htm Intel WiFi Products — Data Rate Will Not Exceed 54 Mbps When WEP or TKIP Encryption is Configured
http://www.intel.com/support/wireless/wlan/sb/CS-034875.htm Intel® Wi-Fi Products — TechNote: Access Point Interoperability Issue with uAPSD
We suggest getting the latest wireless driver from your http://www.intel.com/support/oems.htm system manufacturer's website and verify with them if this wireless adapter was validated to be used with your computer.
You may use wide channel in 5 GHz if available and consider if a firmware update for your router is of help.
I suggest you verifying the internet speed is not being affected by the router security or QoS settings limiting the connectivity to this specific system.
The best way to evaluate throughput is by copying a file to a different wired connected system through the local network.
Did you verify with the system manufacturer if this wireless adapter is validated for your computer model?
This wireless card is installed by default by manufacturer of this notebook ASUS G551JM and this issue was tested on different networks with same results. Also from the start I heave newest drivers and frimework on router