If your iBook is a G3, I think your router would need to be 802.11a or b. It can be other letters, but it needs to support either a or b for it to work with an iBook G3's AirPort Original card. If you have a G4 iBook, it would have an AirPort Extreme Card, so it would use 802.11a/b/g. So your router would need to have either a/b/g.
Hope that helps.