A remote UE transmits a first signaling for user registration of the remote UE into an MCPTT server. The MCPTT server detects a relationship of connection between the remote UE that transmitted the first signaling and a relay UE to which the remote UE is connected. Upon receiving voice data from a UE given a floor grant, the MCPTT server determines, as a destination UE of the voice data, only one of the relay UE and the remote UE that have the relationship of connection. The MCPTT server transmits the voice data with use of a unicast bearer for the destination UE. The relay UE transmits, to all of the remote UEs connected to the relay UE, the voice data that is transmitted from the MCPTT server.