Having looked around the forum, there are numerous threads on this subject. Sadly I have the same issue.
My new (at xmas) ASUS R510C has the same. Drops out every thre or four minutes.
On the same router (Orange.fr) we have another Laptop running W7 no issues, rock solid. As are 1x iPad, 2x iPhones, my old XP PC and a wi-fi Radio.
Only the 8.1 suffers, so it has to be 8.1 specific.
I hope a 'fix' comes soon, or I will need to explain why I have 'launched' my cimbo pressie through the window, grr!