METHOD AND APPARATUS FOR CONFIGURING SUBSEQUENT CONDITIONAL PRIMARY SECONDARY CELL ADDITION/CHANGE (S-CPAC)

1 . A method for configuring a subsequent conditional primary secondary cell addition/change (S-CPAC) to a user equipment (UE), the method comprising:

receiving an S-CPAC configuration from a source cell, the S-CPAC configuration comprising a radio resource control (RRC) configuration for a primary secondary cell (PSCell) and a set of conditions for switching to the PSCell;

receiving a secondary key (SK)-counter list associated with the S-CPAC, the SK-counter list comprising one or more SK-counter entries arranged in an order in the SK-counter list;

storing the S-CPAC configuration and the SK-counter list; and

after determining that one or more conditions in the set of conditions are satisfied:

selecting a first SK-counter entry of the SK-counter list,

configuring the UE with the S-CPAC configuration to switch from another PSCell to the PSCell, wherein the first SK-counter entry is applied in configuring the UE with the S-CPAC configuration, and

removing the first SK-counter entry from the SK-counter list.

2 . The method of claim 1 , wherein the source cell comprises one of a primary cell (PCell) of a master node (MN) or the other PSCell of a secondary node (SN).

3 . The method of claim 1 , wherein receiving the SK-counter list comprises:

receiving an information element (IE) comprising the SK-counter list and an identifier (ID) that identifies the SK-counter list.

4 . The method of claim 3 , wherein the S-CPAC configuration and the IE are received in a same radio resource control (RRC) message.

5 . The method of claim 3 , wherein the S-CPAC configuration and the IE are received in separate radio resource control (RRC) messages.

6 . The method of claim 1 , wherein applying the first SK-counter entry in configuring the UE with the S-CPAC configuration comprises:

deriving an SK based on a value of the first SK-counter entry, wherein the UE encodes data transmitted to the PSCell and decodes data received from the PSCell using the SK.

7 . The method of claim 1 , wherein the S-CPAC configuration is a first S-CPAC configuration, the PSCell is a first PSCell, the set of conditions is a first set of conditions, and the SK-counter list is a first SK-counter list, the method further comprising:

receiving a second S-CPAC configuration from the source cell, the second S-CPAC configuration comprising another RRC configuration for a second PSCell and a second set of conditions for switching to the second PSCell;

receiving a second SK-counter list associated with the second S-CPAC, the second SK-counter list comprising one or more SK-counter entries arranged in the order in the second SK-counter list;

storing the second S-CPAC configuration and the second SK-counter list; and

after determining that one or more conditions in the second set of conditions are satisfied:

selecting a first SK-counter entry of the second SK-counter list,

configuring the UE with the second S-CPAC configuration to switch from the first PSCell to the second PSCell, wherein the first SK-counter entry of the second SK-counter list is applied in configuring the UE with the second S-CPAC configuration, and

removing the first SK-counter entry of the second SK-counter list from the second SK-counter list.

8 . The method of claim 7 , wherein the first PSCell and the second PSCell belong to two different secondary nodes (SNs).

9 . The method of claim 7 , further comprising:

determining that one or more conditions in the first set of conditions are satisfied;

selecting a second SK-counter entry of the first SK-counter list, wherein the second SK-counter entry is a next entry, in the order, after the removed first SK-counter entry in the first SK-counter list;

switching from the second PSCell back to the first PSCell, wherein the UE applies the second SK-counter entry of the first SK-counter list when the UE is configured back based on the first S-CPAC configuration; and

removing the second SK-counter entry of the first SK-counter list from the first SK-counter list.

10 . A method for a user equipment (UE) that is capable of being configured with both a conditional primary secondary cell addition/change (CPAC) and a subsequent-CPAC (S-CPAC), the method comprising:

receiving a CPAC configuration and an S-CPAC configuration from a source cell;

storing the CPAC configuration and the S-CPAC configuration in a storage of the UE;

evaluating one or more conditions for configuring the UE with the CPAC configuration or the S-CPAC configuration;

in a case that at least one condition, from the one or more conditions, for configuring the UE with the S-CPAC configuration is met:

configuring the UE with the S-CPAC configuration, and

maintaining the stored S-CPAC configuration and the stored CPAC configuration; and

in a case that at least one other condition, from the one or more conditions, for configuring the UE with the CPAC configuration is met:

configuring the UE with the CPAC configuration,

maintaining the stored S-CPAC configuration in the storage, and

removing the stored CPAC configuration from the storage.

11 . The method of claim 10 , wherein the CPAC configuration and the S-CPAC configuration are associated with a same primary secondary cell (PSCell) of a secondary node (SN).

12 . The method of claim 10 , wherein the CPAC configuration is associated with a first primary secondary cell (PSCell) of a first secondary node (SN) and the S-CPAC configuration is associated with a second PSCell of a second SN.

13 . The method of claim 10 , further comprising:

prior to receiving the CPAC and S-CPAC configurations from the source cell, transmitting a message to the source cell indicating that the UE is capable of being configured with both the CPAC and the S-CPAC at a same time.

14 . The method of claim 10 , wherein the S-CPAC configuration and the CPAC configuration are received in a radio resource control (RRC) message from the source cell.

15 . The method of claim 10 , wherein the S-CPAC configuration and the CPAC configuration are received from the source cell via separate radio resource control (RRC) messages.

16 . The method of claim 10 , wherein the source cell comprises one of a primary cell (PCell) of a master node (MN) or a primary secondary cell (PSCell) of a secondary node (SN).

17 . A user equipment (UE), comprising:

one or more non-transitory computer-readable media storing one or more computer-executable instructions for configuring a subsequent conditional primary secondary cell addition/change (S-CPAC) to the UE; and

at least one processor coupled to the one or more non-transitory computer-readable media, and configured to execute the one or more computer-executable instructions to cause the UE to:

receive an S-CPAC configuration from a source cell, the S-CPAC configuration comprising a radio resource control (RRC) configuration for a primary secondary cell (PSCell) and a set of conditions for switching to the PSCell;

receive a secondary key (SK)-counter list associated with the S-CPAC, the SK-counter list comprising one or more SK-counter entries arranged in an order in the SK-counter list;

store the S-CPAC configuration and the SK-counter list; and

after determining that one or more condition in the set of conditions are satisfied:

select a first SK-counter entry of the SK-counter list,

configure the UE with the S-CPAC configuration to switch from another PSCell to the PSCell, wherein the first SK-counter entry is applied in configuring the UE with the S-CPAC configuration, and

remove the first SK-counter entry from the SK-counter list.

18 . The UE of claim 17 , wherein applying the first SK-counter entry in configuring the UE with the S-CPAC configuration comprises:

deriving an SK based on a value of the first SK-counter entry, wherein the UE encodes data transmitted to the PSCell and decodes data received from the PSCell using the SK.

19 . The UE of claim 17 , wherein:

the S-CPAC configuration is a first S-CPAC configuration, the PSCell is a first PSCell, the set of conditions is a first set of conditions, and the SK-counter list is a first SK-counter list, and

the at least one processor is further configured to execute the one or more computer-executable instructions to cause the UE to:

receive a second S-CPAC configuration from the source cell, the second S-CPAC configuration comprising another RRC configuration for a second PSCell and a second set of conditions for switching to the second PSCell;

receive a second SK-counter list associated with the second S-CPAC, the second SK-counter list comprising one or more SK-counter entries arranged in the order in the second SK-counter list;

store the second S-CPAC configuration and the second SK-counter list; and

after determining that one or more conditions in the second set of conditions are satisfied:

select a first SK-counter entry of the second SK-counter list,

configure the UE with the second S-CPAC configuration to switch from the first PSCell to the second PSCell, wherein the first SK-counter entry of the second SK-counter list is applied in configuring the UE with the second S-CPAC configuration, and

remove the first SK-counter entry of the second SK-counter list from the second SK-counter list.

20 . The UE of claim 19 , wherein the at least one processor is further configured to execute the one or more computer-executable instructions to cause the UE to:

determine that one or more conditions in the first set of conditions are satisfied;

select a second SK-counter entry of the first SK-counter list, wherein the second SK-counter entry is a next entry, in the order, after the removed first SK-counter entry in the first SK-counter list;

switch from the second PSCell back to the first PSCell, wherein the UE applies the second SK-counter entry of the first SK-counter list when the UE is configured back based on the first S-CPAC configuration; and

remove the second SK-counter entry of the first SK-counter list from the first SK-counter list.