What kind of router are you using? I've found that range extenders (the ones I've tried anyway...I suppose more recent ones might be better) are finicky and more trouble than they are worth. I upgraded to a better router (in my case a Asus RT-AC3100) and no longer have trouble anywhere in my house. And it sits in one corner of the house, not in the middle. I have a two story house but no basement though...