If the distance between the wireless router and the PS3 is greater than your laptop than the problem exists with your PS3's placement itself. Try moving it to a closer distance. If not:
You can plug your PS3 directly into the router using a ethernet cable but that all depends on how far the distance is as well as if you're willing to to have a long wire running to both devices.
If you're willing to spend a little more cash, you can purchase a WiFi booster to get a better signal strength or if you have a cheap-o router you can trash it for a decent quality router.