Mechanism of relay UE discovery and relay UE selection and reselection for remote UE data transmission with a serving base station via relay UE is proposed. A method operable for relay UE selection and reselection of remote UE is provided. The UE considers additional criteria such as relay load other than purely radio signal quality (e.g., RSRP) criteria. The relay load can serve different purpose for relay UE and remote UE. The relay load can be the criteria for UE to become a relay UE or not. It can be the criteria for a remote UE to select another UE as its relay UE.