Ok. Go to System settings on PS3 > Scroll Down to the bottom and go on system information. Write down the I.P address.
Then go to network settings > internet connection settings > custom > wireless > Scan > Select your router (SSID) > Enter WLAN security settings (wep or wpa-psK)
Manual IP address setting > Enter the I.P address which i told you to write down earlier > subnet mask should be 255.255.255.0
Default router and primary DNS should be the same. To find those, on your laptop which is connected to your broadband go to windows and in the search programs and files bar at the bottom type cmd, a black box will pop up, type: ipconfig and press enter, you should see a default gateway address, make a note of it.
back on your ps3, enter that default gateway address in the default router address and in the primary dns address, leave the secondary dns address blank, once that is complete press right on the d-pad > MTU Automatic > Proxy: Do not use > UPnP enabled. Press x to save settings and click test connection
I've just manually tested this myself so i know the steps work, if it doesnt then i'm sorry i couldnt help.