The first thing to determine is if the problem is with your laptop or your router/access point, which you can do if you have more than one device that can connect to wifi. If the connection goes down for both devices simultaneously, then it's the wifi. If one device goes down and the other stays up, it's the laptop.
I had this happen on routers/access points that had bad software, and fixed it by installing DD-WRT. This was a very long time ago.