Mobile communication system

A base station comprising:

• a memory;
• and
• at least one processor coupled to the memory, the at least one processor is configured to:
• transmit configuration information of SC-MTCH (Single Cell Multicast Traffic Channel), a traffic channel for SC-PTM (Single Cell Point-To-Multipoint) transmission, by SC-MCCH (Single Cell Multicast Control Channel), a control channel for the SC-PTM transmission,
• set a first period to a first radio terminal,
• set a second period shorter than the first period to a second radio terminal, as an SC-MCCH change period in which the configuration information of the SC-MTCH can be changed, the first radio terminal configured to transmit and receive a radio signal by using a limited frequency band limited to a bandwidth of a predetermined number of resource blocks, the second radio terminal configured to transmit and receive a radio signal by using a frequency band wider than the limited frequency band,
• receive an MBMS (Multimedia Broadcast Multicast Service) interest indication from the first radio terminal, the first radio terminal being in a connected mode, and
• when the base station starts an MBMS service to the first radio terminal by the SC-PTM transmission, determine whether or not to shift the first radio terminal to an idle mode based on the MBMS interest indication.

A mobile communication method comprising:

• transmitting by a base station, configuration information of SC-MTCH (Single Cell Multicast Traffic Channel), a traffic channel for SC-PTM (Single Cell Point-To-Multipoint) transmission, by SC-MCCH (Single Cell Multicast Control Channel), a control channel for the SC-PTM transmission;
• setting by the base station, a first period to a first radio terminal;
• setting by the base station, a second period shorter than the first period to a second radio terminal, as an SC-MCCH change period in which the configuration information of the SC-MTCH can be changed, the first radio terminal configured to transmit and receive a radio signal by using a limited frequency band limited to a bandwidth of a predetermined number of resource blocks, the second radio terminal configured to transmit and receive a radio signal by using a frequency band wider than the limited frequency band;
• receiving by the base station, an MBMS (Multimedia Broadcast Multicast Service) interest indication from the first radio terminal that is in a connected mode;
• and
• when the base station starts an MBMS service to the first radio terminal by the SC-PTM transmission, determining by the base station whether or not to shift the first radio terminal to an idle mode based on the MBMS interest indication.