Oh I see... sorry... You have two options...
1) Buy a wifi access point and connect PS3 via Wifi... This I think is the best idea because there will only be more and more things using wifi like ipads, kindles, digital picture frames, all types of gadgets... you should get with the times.
2) Buy a
ethernet over powerline (Amazon Link) adapter- there are several models out there, this is just one as an example, I haven't used any personally but they have high ratings. This will allow you to plug an ethernet cable into an outlet on one side of the house, convert the ethernet signal to run over your home's power lines, and then use another adapter to convert the signal back to ethernet more near the PS3.