USER DEVICE, GATEWAY DEVICE, WIRELESS BASE STATION, MOBILE COMMUNICATION SYSTEM, AND MOBILE COMMUNICATION METHOD

摘要

Provided are a user device, a gateway device, a radio base station, a mobile communication system, and a mobile communication method capable of considerably reducing the number of control signals necessary for Small Data Transmission (SDT). A UE 100 transitions from RRC-IDLE state where no communication bearer in the control plane is established and EMM-IDLE state where communication in the user plane is not enabled to RRC-CONNECTED state where a communication bearer in the control plane is established and the EMM-IDLE state. The UE 100 transmits user data inputted into the UE 100, via the communication bearer in the control plane in the RRC-CONNECTED state and the EMM-IDLE state. In addition, the UE 100 transitions from the RRC-CONNECTED state and the EMM-IDLE state to the RRC-IDLE state and the EMM-IDLE state as soon as the transmission of the user data is completed.