Dell Lattitude E6440 slow internal WiFi card

I have a problem with Lattitude E6440 . For some reason internal WiFi network card is very slow compared to USB WiFi adapters which I have plugged in.

For an example local network file transfer using built-in is below 2MB/s when USB adapter is above 3MB/s. I have got another card of the eBay and still the same problem.

Any thought on that? Some bloatware is blocking that card or so?