Method for handling of data transmission and reception for SeNB related bearer release at a user equipment in a dual connectivity system and device therefor

A User Equipment (UE) for operating in a wireless communication system, the UE comprising:

• a Radio Frequency (RF) module;
• and
• a processor operably coupled with the RF module and configured to:
• receive or transmit, from or to a Master eNB (MeNB), a first message indicating that a SeNB has released or will release a Secondary Cell Group (SCG) bearer or a SCG part of a split bearer configured in the SeNB,
• if the first message includes an identifier of the SCG bearer or an identifier of the split bearer, release a downlink part of the indicated SCG bearer or the indicated SCG part of the split bearer configured in the SeNB, when the first message is received or transmitted,
• receive, from the MeNB, a second message for indicating that a UE has released the SCG bearer or the SCG part of the split bearer configured in the SeNB, and
• if the second message includes the identifier of the SCG bearer or the identifier of the split bearer, release an uplink part of the indicated SCG bearer or the indicated SCG part of the split bearer configured in the SeNB, when the second message is received.