Methods and apparatuses for transmitting and receiving data in wireless communication system

A user equipment (UE) in a wireless communication for performing handover between different radio access technologies, the UE comprising:

• a transceiver;
• a memory;
• and
• at least one processor coupled with the memory and configured to:
• receive a radio resource control (RRC) message;
• identify whether a full configuration indicator is included in the RRC message;
• in case that the full configuration indicator is not included in the RRC message, maintain configuration information of a packet data convergence protocol (PDCP) layer or a service data adaptation protocol (SDAP) layer configured in a source base station (BS);
• and
• based on the identification that the full configuration indicator is not included in the RRC message, use, for a target BS, the maintained configuration information of the PDCP layer or the SDAP layer configured in the source BS.

A source base station (BS) in a wireless communication for performing handover between different radio access technologies, the source BS comprising:

• a transceiver;
• a memory;
• and
• at least one processor coupled with the memory and configured to:
• transmit, to a user equipment (UE), a radio resource control (RRC) message including a full configuration indicator,
• wherein the full configuration indicator is associated with whether the UE maintains or releases configuration information of a packet data convergence protocol (PDCP) layer or a service data adaptation protocol (SDAP) layer configured in the source BS, and
• wherein the full configuration indicator is associated with whether the UE uses, for a target BS, the configuration information of the PDCP layer or the SDAP layer configured in the source BS.