Method and system for handling PDCP operation in wireless communication system

1. A method, performed by a dual connectivity capable user equipment (UE), of handling a packet data convergence protocol (PDCP) operation in a wireless communication system, the method comprising:

receiving a handover message from a first network, wherein the handover message comprises an indicator indicating a packet data convergence protocol (PDCP) version change for a first PDCP layer of the first network;

transmitting the indicator to the first PDCP layer of the UE, wherein the UE is in a connected state with the first network comprising the first PDCP layer and an RLC layer that are established with the UE;

performing re-establishment of the RLC layer based on the indicator;

receiving first PDCP protocol data units (PDUs) from the RLC layer in response to performing the re-establishment of the RLC layer;

processing, based on a first format, the first PDCP PDUs at the first PDCP layer;

performing re-establishment of the first PDCP layer associated with the first network;

transmitting, based on a second format, PDCP service data units (SDUs) to a second network in accordance with a second PDCP layer that is determined by the re-establishment of the first PDCP layer associated with the first network; and

processing, the PDCP SDUs received by the second PDCP layer.

2. The method of claim 1 , wherein the first network is associated with a long term evolution (LTE) network and the second network is associated with a new radio (NR) network.

3. The method of claim 2 , further comprising:

indicating, by the first PDCP layer associated with the first network, to the second PDCP layer associated with the second network to perform a PDCP re-establishment procedure;

performing a robust header compression (ROHC) reset;

deriving security keys, wherein the security keys comprise an integrity key and a ciphering key;

translating LTE PDCP state variables into new radio (NR) PDCP state variables; and

determining re-establishment of the PDCP layer of the UE as re-establishment of a NR PDCP layer.

4. The method of claim 3 , wherein the ROHC reset is performed in case that a drb-continue ROHC parameter is not configured.

5. The method of claim 3 , wherein the integrity key is derived based on a configured NR integrity procedure and the ciphering key is derived based on an NR encryption procedure.

6. The method of claim 3 , wherein the LTE PDCP state variables are translated into the NR PDCP state variables based on one of a continuing sequence number (SN) parameter or a continuing count parameter.

7. The method of claim 1 , wherein transmitting the PDCP SDUs comprises:

identifying the PDCP SDUs to be re-transmitted;

processing a PDCP header of the identified PDCP SDUs based on the second format;

compressing the PDCP header of the identified PDCP SDUs based on a NR PDCP operation;

performing an integrity check of the PDCP PDUs by calculating a message authentication code-integrity (MAC-I) based on a configured NR integrity procedure;

encrypting a PDCP payload of the PDCP PDUs based on a configured NR encryption procedure; and

delivering the encrypted PDCP payload of the PDCP PDUs to an LTE RLC layer for transmission.

8. The method of claim 1 , further comprising:

performing an integrity check of the received PDCP PDUs based on a configured NR integrity procedure;

separating a PDCP header and a PDCP payload of the received PDCP PDUs;

decrypting the PDCP payload based on a configured NR encryption procedure;

decompressing the PDCP header based on an NR operation;

processing the PDCP header based on the second format;

performing a duplicate detection operation by identifying duplicate PDCP SDUs and discarding the identified duplicate PDCP SDUs;

reordering a function on the PDCP SDUs; and

delivering the decrypted PDCP payload to upper layers.

9. An E-UTRA-NR dual connectivity (EN-DC) capable user equipment (UE) for handling a packet data convergence protocol (PDCP) operation in a wireless communication system, the UE comprising:

a memory;

a transceiver; and

at least one processor coupled with the transceiver and configured to:

receive a handover message from a first network, wherein the handover message comprises an indicator indicating a packet data convergence protocol (PDCP) version change for a first PDCP layer of the first network;

transmit the indicator to a the PDCP layer of the UE, wherein the UE is in a connected state with the first network comprising the first PDCP layer and an RLC layer that are established with the UE;

perform re-establishment of the RLC layer based on the indicator;

receive first PDCP protocol data units (PDUs) from the RLC layer in response to performing the re-establishment of the RLC layer;

process, based on a first format, the first PDCP PDUs at the first PDCP layer;

perform re-establishment of the first PDCP layer as associated with the first network;

transmit, based on a second format, PDCP service data units (SDUs) to a second network in accordance with a second PDCP layer that is determined by the re-establishment of the first PDCP layer associated with the first network; and

process, the PDCP SDUs received by the second PDCP layer.

10. The method of claim 2 , further comprising:

performing an integrity check of the received PDCP PDUs based on a configured LTE integrity procedure;

separating a PDCP header and a PDCP payload of the PDCP PDUs;

decrypting the PDCP payload based on a configured LTE encryption procedure;

decompressing the PDCP header based on an LTE operation;

processing the PDCP header based on an LTE format; and

delivering the decrypted PDCP payload to upper layers.