Method and apparatus to optimize conditional PSCell addition and change (CPAC) in wireless communication system

1 . A method performed by a user equipment (UE) supporting a dual connectivity in a wireless communication system, the method comprising:

receiving, from a base station, a radio resource control (RRC) message including configuration information for reporting a successful primary secondary cell (PSCell) change;

performing a random access procedure to a PSCell of a secondary cell group (SCG);

based on the configuration information for reporting the successful PSCell change, storing successful PSCell change information, wherein the successful PSCell change information includes public land mobile network (PLMN) information and includes information indicating whether the successful PSCell change is initiated by a secondary node (SN);

identifying whether the UE has the stored successful PSCell change information and a registered PLMN (RPLMN) is included in the PLMN information stored in the successful PSCell change information;

in case that the UE has the stored successful PSCell change information and the RPLMN is included in the PLMN information stored in the successful PSCell change information, transmitting, to the base station, an RRC complete message including a first indicator indicating an availability of the successful PSCell change information;

receiving, from the base station, a UE information request message including a second indicator indicating the UE to report the successful PSCell change information; and

transmitting, to the base station, a UE information response message including the successful PSCell change information.

2 . The method of claim 1 ,

wherein the configuration information for reporting the successful PSCell change includes at least one of first threshold information for a ratio in percentage between an elapsed timer T304 and a configured value of a timer T304, second threshold information for a ratio in percentage between an elapsed timer T310 and a configured value of a timer T310, or third threshold information for a ratio in percentage between an elapsed timer T312 and a configured value of a timer T312,

wherein the first threshold information is associated with a target PSCell,

wherein the second threshold information is associated with a source PSCell, and

wherein the third threshold information is associated with the source PSCell.

3 . The method of claim 2 , wherein the UE stores the successful PSCell change information,

in case that a ratio between a value of an elapsed time of the timer T304 and the configured value of the timer T304 is greater than the first threshold information, or

in case that a ratio between a value of an elapsed time of the timer T310 and the configured value of the timer T310 is greater than the second threshold information, or

in case that a ratio between a value of an elapsed time of the timer T312 and the configured value of the timer T312 is greater than the third threshold information.

4 . The method of claim 1 ,

wherein the successful PSCell change information includes at least one of first information on a primary cell (PCell) identifier (ID), second information on a source PSCell ID, third information on a target PSCell, fourth information on a measurement result of neighboring cells, fifth information on a time associated with a conditional reconfiguration execution and a reception of the latest conditional reconfiguration, sixth information on a location, or seventh information on a random access (RA).

5 . The method of claim 1 , further comprising:

transmitting, to the base station, UE capability information including a third indicator indicating that the UE supports reporting the successful PSCell change information.

6 . A method performed by a base station supporting a dual connectivity in a wireless communication system, the method comprising:

transmitting, to a user equipment (UE), a radio resource control (RRC) message including configuration information for reporting a successful primary secondary cell (PSCell) change;

receiving, from the UE, an RRC complete message including a first indicator indicating an availability of successful PSCell change information, in case that the successful PSCell change information is stored and a registered public land mobile network (RPLMN) is included in public land mobile network (PLMN) information stored in the successful PSCell change information;

transmitting, to the UE, a UE information request message including a second indicator indicating the UE to report the successful PSCell change information; and

receiving, from the UE, a UE information response message including the successful PSCell change information,

wherein the successful PSCell change information includes PLMN information and includes information indicating whether the successful PSCell change is initiated by a secondary node (SN), and

wherein the configuration information is associated with the successful PSCell change information.

7 . The method of claim 6 ,

wherein the configuration information for reporting the successful PSCell change includes at least one of first threshold information for a ratio in percentage between an elapsed timer T304 and a configured value of a timer T304, second threshold information for a ratio in percentage between an elapsed timer T310 and a configured value of a timer T310, or third threshold information for a ratio in percentage between an elapsed timer T312 and a configured value of a timer T312,

wherein the first threshold information is associated with a target PSCell,

wherein the second threshold information is associated with a source PSCell, and

wherein the third threshold information is associated with the source PSCell.

8 . The method of claim 6 ,

wherein the successful PSCell change information includes at least one of first information on a primary cell (PCell) identifier (ID), second information on a source PSCell ID, third information on a target PSCell, fourth information on a measurement result of neighboring cells, fifth information on a time associated with a conditional reconfiguration execution and a reception of the latest conditional reconfiguration, sixth information on a location, or seventh information on a random access (RA).

9 . The method of claim 6 , further comprising:

receiving, from the UE, UE capability information including a third indicator indicating that the UE supports reporting the successful PSCell change information.

10 . A user equipment (UE) supporting a dual connectivity in a wireless communication system, the UE comprising:

a transceiver; and

a controller coupled with the transceiver, and configured to:

receive, from a base station, a radio resource control (RRC) message including configuration information for reporting a successful primary secondary cell (PSCell) change,

perform a random access procedure to a PSCell of a secondary cell group (SCG),

based on the configuration information for reporting the successful PSCell change, store successful PSCell change information, wherein the successful PSCell change information includes public land mobile network (PLMN) information and includes information indicating whether the successful PSCell change is initiated by a secondary node (SN),

identify whether the UE has the stored successful PSCell change information and a registered PLMN (RPLMN) is included in the PLMN information stored in the successful PSCell change information,

in case that the UE has the stored successful PSCell change information and the RPLMN is included in the PLMN information stored in the successful PSCell change information, transmit, to the base station, an RRC complete message including a first indicator indicating an availability of the successful PSCell change information,

receive, from the base station, a UE information request message including a second indicator indicating the UE to report the successful PSCell change information, and

transmit, to the base station, a UE information response message including the successful PSCell change information.

11 . The UE of claim 10 ,

wherein the configuration information for reporting the successful PSCell change includes at least one of first threshold information for a ratio in percentage between an elapsed timer T304 and a configured value of a timer T304, second threshold information for a ratio in percentage between an elapsed timer T310 and a configured value of a timer T310, or third threshold information for a ratio in percentage between an elapsed timer T312 and configured value of a timer T312,

wherein the first threshold information is associated with a target PSCell,

wherein the second threshold information is associated with a source PSCell, and

wherein the third threshold information is associated with the source PSCell.

12 . The UE of claim 11 , wherein the UE stores the successful PSCell change information,

in case that a ratio between a value of an elapsed time of the timer T304 and the configured value of the timer T304 is greater than the first threshold information; or

in case that a ratio between a value of an elapsed time of the timer T310 and the configured value of the timer T310 is greater than the second threshold information; or

in case that a ratio between a value of an elapsed time of the timer T312 and the configured value of the timer T312 is greater than the third threshold information.

13 . The UE of claim 10 , wherein the successful PSCell change information includes at least one of first information on a primary cell (PCell) identifier (ID), second information on a source PSCell ID, third information on a target PSCell, fourth information on a measurement result of neighboring cells, fifth information on a time associated with a conditional reconfiguration execution and a reception of the latest conditional reconfiguration, sixth information on a location, or seventh information on a random access (RA).

14 . The UE of claim 10 , wherein the controller is further configured to:

transmit, to the base station, UE capability information including a third indicator indicating that the UE supports reporting the successful PSCell change information.

15 . A base station supporting a dual connectivity in a wireless communication system, the base station comprising:

a transceiver; and

a controller coupled with the transceiver, and configured to:

transmit, to a user equipment (UE), a radio resource control (RRC) message including configuration information for reporting a successful primary secondary cell (PSCell) change,

receive, from the UE, an RRC complete message including a first indicator indicating an availability of successful PSCell change information, in case that the successful PSCell change information is stored and a registered public land mobile network (RPLMN) is included in public land mobile network (PLMN) information stored in the successful PSCell change information,

transmit, to the UE, a UE information request message including a second indicator indicating the UE to report the successful PSCell change information, and

receive, from the UE, a UE information response message including the successful PSCell change information,

wherein the successful PSCell change information includes PLMN information and includes information indicating whether the successful PSCell change is initiated by a secondary node (SN), and

wherein the configuration information is associated with the successful PSCell change information.

16 . The base station of claim 15 ,

wherein the configuration information for reporting the successful PSCell change includes at least one of first threshold information for a ratio in percentage between an elapsed timer T304 and a configured value of a timer T304, second threshold information for a ratio in percentage between an elapsed timer T310 and a configured value of a timer T310, or third threshold information for a ratio in percentage between an elapsed timer T312 and a configured value of a timer T312,

wherein the first threshold information is associated with a target PSCell,

wherein the second threshold information is associated with a source PSCell, and

wherein the third threshold information is associated with the source PSCell.

17 . The base station of claim 15 , wherein the successful PSCell change information includes at least one of first information on a primary cell (PCell) identifier (ID), second information on a source PSCell ID, third information on a target PSCell, fourth information on a measurement result of neighboring cells, fifth information on a time associated with a conditional reconfiguration execution and a reception of the latest conditional reconfiguration, sixth information on a location, or seventh information on a random access (RA).

18 . The base station of claim 15 , wherein the controller is further configured to:

receive, from the UE, UE capability information including a third indicator indicating that the UE supports reporting the successful PSCell change information.