I have never tried this before myself, so it may or may not do the trick...
http://support.wmwifirouter.com/knowledge/KB0806019/
Routes the nets through a hardware access point, which the PS3 should be able to connect to in Infrastructure mode. I know at the very least that a Wii can only connect in Infrastructure mode, not Ad-Hoc - my ventured guess is that the PS3 may have similar limitations (without looking I dont know for sure..)
Hope this helps/works for you.
