Method and apparatus for transmitting/receiving data in mobile communication system

A method for transmitting data by a terminal in a wireless communication system, the method comprising:

• transmitting, to a base station, a first message for requesting an establishment of radio resource control (RRC) connection if a terminal is in idle state and uplink data associated with an evolved packet system (EPS) bearer occurs;
• receiving a second message in response to the first message;
• and
• transmitting a third message comprising an integrity protected non-access stratum (NAS) message, the NAS message including the uplink data associated with the EPS bearer.

A method for receiving data by a network device in a wireless communication system, the method comprising:

• receiving, from a terminal, a first message for requesting an establishment of radio resource control (RRC) connection if the terminal is in idle state and uplink data associated with an EPS bearer occurs;
• transmitting a second message in response to the first message;
• and
• receiving a third message comprising an integrity protected non-access stratum (NAS) message, the NAS message including the uplink data associated with the EPS bearer.

A network device for receiving data in a wireless communication system, the network device comprising:

• a transceiver configured to transmit and receive a signal;
• and
• a controller configured to receive, from a terminal, a first message for requesting establishment of a radio resource control (RRC) connection if the terminal is in evolved packet system (EPS) connection management idle (ECM-IDLE) state and uplink data associated with an EPS bearer occurs, transmit a second message in response to the RRC connection request message, and receive a third complete message comprising a non-access stratum (NAS) message, the NAS message including the uplink data associated with the EPS bearer,
• wherein integrity protection is applied to the NAS message and the uplink data associated with the EPS bearer is ciphered.