japanese cell n the u.s.

i actually bought an unlocked japanese cell from ebay, and i live here n brooklyn. all u need is a sim card and a hypersim card. the only thing is u might have signal problems. im having signal probs. with mines and still trying 2 figure out how 2 fix....but when i did hav signal i was able 2 work evrything n the cell, jst some things didnt work here n the u.s. like t.v. mode and gps.