A base station (200) receives a message which is transmitted from a user equipment (100) over an uplink shared channel in a contention based random access procedure, and, if the received message is in compliance with a predetermined format, performs an echo-back process for sending the received message back to the user equipment as identifying data for contention resolution in the contention based random access procedure. If the received message is not in compliance with the predetermined format, the base station (200) does not perform the echo-back process.