Wi-fi issue

I have following problem. I have home Wi-Fi network. Once I start Windows SB, the speed of downloading is high. With time, however, the speed becomes terrible, and only restarting solves this problem. I've checked the Wi-Fi connection with SB, SP3 and other old laptop.

What can this be?

from Windows Central Forums http://ift.tt/2dutfau
via IFTTT