ok...ok...I know what your thinking..."sonic rivals isn't an infrastructure a.k.a wi-fi online game so what in the hell have you been smoking dude?

well guess what, theres this thing called Xlink Kai: this application allows you to use your psp with games that use ad-hoc mode to play with others that have the same games as you...like wi-fi...but heres the bad news, you'll need either a lot of equipment like network cards, Ethernet, dsl, blah, blah, blah, or you can use the famous(lol) datel created wi-fi max usb adapter...here is the link and here is the link for the English forums and p.m me if u need any help installing anything!