Communication method and user equipment

A user equipment used in a mobile communication system for providing a multicast broadcast service (MBS), the user equipment comprising:

• a controller configured to execute:
• in a radio resource control (RRC)_connected state, processing of establishing a multicast radio bearer (MRB) based on an MRB configuration configured from a network;
• processing of receiving, from the network and by using the established multicast MRB, a multicast session corresponding to a first MBS session ID comprised in the MRB configuration;
• processing of receiving, from the network, a multicast configuration, which is information for configuring multicast reception for an RRC_inactive state and comprises a second MBS session ID;
• and
• processing of applying the multicast configuration when a multicast session corresponding to the second MBS session ID is received in the RRC_inactive state in the same cell as a cell in which the multicast session corresponding to the first MBS session ID has been received in the RRC_connected state.

A mobile communication system for providing a multicast broadcast service (MBS), comprising:

• a user equipment configured to:
• establish, in a radio resource control (RRC)_connected state, a multicast radio bearer (MRB) based on an MRB configuration configured from a network;
• receive, from the network and by using the established multicast MRB, a multicast session corresponding to a first MBS session ID comprised in the MRB configuration;
• receive, from the network, a multicast configuration, which is information for configuring multicast reception for an RRC_inactive state and comprises a second MBS session ID;
• and
• apply the multicast configuration when a multicast session corresponding to the second MBS session ID is received in the RRC_inactive state in the same cell as a cell in which the multicast session corresponding to the first MBS session ID has been received in the RRC_connected state.