Wifi adapter losing connection

I have Dell 3537 laptop with windows 8.1 and problems with wifi connection. Whenever i try to stream large ammount of data over wifi (full hd video from youtube, movie via dlna server, or just copy bunch of files with total commander from network server to local disk), my wifi connection drops.

This happens always, no matter if laptop is on battery or on external power.. I have cheap chinese external usb wifi adapter and it works without any problem when i plug it in, and also, when i plug network cable, everything works perfect.

Every other device on my network work's perfect...

wifi adapter is dell wireless 1705 802.11/b/g/n with latest drivers...

Is there a way to fix this? I have disabled all power options that could affect wifi adapter.