What kind of wireless card does your laptop have?
I had similar issues with my HP laptop, back when it was new. I have an Intel wireless card on mine and it would continuously disconnect.
After a couple of newer dirivers were released (and installed) did I get a stable connection.
A couple of thing you could try is to check for newer drivers (as pointed out by gokul36) and also check if there is a power saving feature enabled. If so disable that, it may cause the card to sleep if there is no activity.
Also if it does happen to be an Intel card, it wouldnt hurt to check the Intel site for a driver...