A mobile communication system capable of reducing energy consumption of a network node in a local area range. When judging that there is a shift trigger, a local eNB shifts from a normal operation to an energy saving operation. In the energy saving operation, the local eNB stops the operation of transmitting at least a part of downlink transmission signals to be transmitted to a user equipment (UE) and performs the operation of receiving an uplink transmission signal transmitted from the UE. When judging that it has received the uplink transmission signal (RACH) in the energy saving operation, the local eNB shifts to the normal operation.