Ah... I'm afraid you're most like going to be completely out of luck
You
could connect your PS3 to your computer using an
ethernet cable
e.g.
http://www.maplin.co.uk/Module.aspx?ModuleNo=44362
... and set up
Internet Connection Sharing (ICS) on the PC, to share its internet connection with the PS3.
BUT:
You're using mobile broadband (3G / HSDPA)... this really is not suitable for taking the PS3 online. OK, you'd probably get away with using the web browser & Store on the PS3 etc., but I really think it would be too slow for gaming, & have way too high pings for gaming.