The disclosure is directed to an extended RA method used by a UE and by a base station and related apparatuses using the same method. In an aspect, the disclosure is directed to an extended RA method used by a UE. The method includes not limited to transmitting a random access preamble (RAP); receiving a random access response (RAR) which responds to the RAP; transmitting an RA request signal which corresponds to the RAR and includes a first small data and a piggyback indicator which indicates whether there is a second small data to be transmitted; and receiving an RA request acknowledgment signal which corresponds to the RA request signal and comprises an uplink grant which indicates a resource for the second small data.