Signing Off His Father's Rights?

My husband has a daughter that he has never seen. Her mother wont even tell her that he is the father when he spoke to her on the phone one time. She is almost four and they don't even have a relationship. His child support payments were calculated from a job he never even had. He has considered signing his rights off.  He feels that he can never establish the relationship he wants with her.  He is wondering how to go about signing his rights off.