User equipment, base station, and connection establishment method

A base station in a mobile communication system that supports a function of performing connection establishment reusing context information retained in each of a terminal and the base station, comprising:

• a transmitting unit that transmits a system information block type 2 (SIB2) including instruction information, to the terminal, indicating whether or not the base station supports a function of a Cellular Internet of Things (CIoT) Evolved Packet System (EPS) optimization scheme,
• wherein the terminal determines whether or not the base station has the function on the basis of the instruction information,
• wherein, when the CIoT EPS optimization scheme is used in the terminal and upon trigger of a procedure using an initial non-access-stratum (NAS) message, a NAS layer of the terminal requests a lower layer of the terminal to resume a suspended connection, and
• wherein when the suspended connection is resumed, a pending initial NAS message different from a service request message is sent.

A connection establishment method performed by a terminal in a mobile communication system that supports a function of performing connection establishment reusing context information retained in each of the terminal and a base station, the connection establishment method comprising:

• a reception step of receiving, from the base station, a system information block type 2 (SIB2) including instruction information indicating whether or not the base station supports a function of a Cellular Internet of Things (CIoT) Evolved Packet System (EPS) optimization scheme;
• and
• a determination step of determining whether or not the base station has the function on the basis of the instruction information received in the reception step;
• wherein, when the CIoT EPS optimization scheme is used in the terminal and upon trigger of a procedure using an initial non-access-stratum (NAS) message, a NAS layer of the terminal requests a lower layer of the terminal to resume a suspended connection, and
• wherein when the suspended connection is resumed, a pending initial NAS message different from a service request message is sent.

A connection establishment method performed by a base station in a mobile communication system that supports a function of performing connection establishment reusing context information retained in each of a terminal and the base station, the connection establishment method comprising:

• a transmission step of transmitting, to the terminal, a system information block type 2 (SIB2) including instruction information indicating whether or not the base station supports a function of a Cellular Internet of Things (CIoT) Evolved Packet System (EPS) optimization scheme,
• wherein the terminal determines whether or not the base station has the function on the basis of the instruction information,
• wherein, when the CIoT EPS optimization scheme is used in the terminal and upon trigger of a procedure using an initial non-access-stratum (NAS) message, a NAS layer of the terminal requests a lower layer of the terminal to resume a suspended connection, and
• wherein when the suspended connection is resumed, a pending NAS message different from a service request message is sent.