A relay of a wireless communication system for handling data forwarding between at least a user equipment (UE) and a base station (BS) is disclosed. The relay includes a UE interfacing unit and a BS interfacing AS unit. The UE interfacing unit is used for communicating with the base station and includes an AS (Access Stratum) unit for performing AS functionalities with the base station based on a first AS protocol. The relay is recognized as a UE by the base station via the first AS protocol. The BS interfacing AS unit wirelessly performs BS AS functionalities with the UEs based on a second AS protocol and exchanging data with the UE interfacing unit.