Methods and apparatus to activate secondary cell group (SCG) selectively

1 . A method, comprising:

receiving and storing, at user equipment (UE), a radio resource control (RRC) reconfiguration message from a source base station (BS), the RRC reconfiguration message including a first radio resource configuration of a first primary secondary cell (PSCell) in a first target BS, a second radio resource configuration of a second PSCell in a second target BS and conditional PSCell addition (CPA) and conditional PSCell change (CPC) triggering conditions associated with the first and second PSCells, the CPA and CPC triggering conditions corresponding to CPA and CPC steps, respectively;

setting a current triggering condition to be the CPA triggering condition;

evaluating the current triggering condition for the first and second PSCells based on the current triggering condition and determining that the first PSCell satisfies the current triggering condition;

performing the CPA step to add the first PSCell as a current secondary cell group (SCG), applying the first radio resource configuration for the first PSCell, and synchronizing to the first PSCell;

updating the current triggering condition to be the CPC triggering condition, the UE still keeping the first radio resource configuration of the first PSCell, the second radio resource configuration of the second PSCell and the CPA and CPC triggering conditions, without releasing the second radio resource configuration of the second PSCell and the CPA and CPC triggering conditions associated therewith;

evaluating the current triggering condition for the second PSCell based on the current triggering condition and determining that the second PSCell satisfies the current triggering condition; and

performing the CPC step to change the current SCG from the first PSCell to the second PSCell.

2 . The method of claim 1 , further comprising:

releasing the second PSCell; and

updating the current triggering condition to be the CPA triggering condition.

3 . The method of claim 1 , wherein the CPA triggering condition includes an event indicating that the first PSCell becomes better than a threshold.

4 . The method of claim 1 , wherein the CPC triggering condition includes an event indicating that the second PSCell becomes offset better than the first PSCell.

5 . The method of claim 1 , wherein the CPC triggering condition includes an event indicating that the first PSCell is worse than a first threshold and the second PSCell becomes better than a second threshold.

6 . The method of claim 1 , wherein the CPA triggering condition is used before the current SCG is configured with the UE, and the CPC triggering condition is used after the current SCG is configured with the UE.

7 . An apparatus, comprising circuitry configured to perform a method, the method including the following steps of:

receiving and storing a radio resource control (RRC) reconfiguration message from a source base station (BS), the RRC reconfiguration message including a first radio resource configuration of a first primary secondary cell (PSCell) in a first target BS, a second radio resource configuration of a second PSCell in a second target BS and conditional PSCell addition (CPA) and conditional PSCell change (CPC) triggering conditions associated with the first and second PSCells, the CPA and CPC triggering conditions corresponding to CPA and CPC steps, respectively;

setting a current triggering condition to be the CPA triggering condition;

evaluating the current triggering condition for the first and second PSCells based on the current triggering condition and determining that the first PSCell satisfies the current triggering condition;

performing the CPA step to add the first PSCell as a current secondary cell group (SCG), applying the first radio resource configuration for the first PSCell, and synchronizing to the first PSCell;

updating the current triggering condition to be the CPC triggering condition, the circuitry still keeping the first radio resource configuration of the first PSCell, the second radio resource configuration of the second PSCell and the CPA and CPC triggering conditions, without releasing the second radio resource configuration of the second PSCell and the CPA and CPC triggering conditions associated therewith;

evaluating the current triggering condition for the second PSCell based on the current triggering condition and determining that the second PSCell satisfies the current triggering condition; and

performing the CPC step to change the current SCG from the first PSCell to the second PSCell.

8 . The apparatus of claim 7 , wherein the method further comprises:

releasing the second PSCell; and

updating the current triggering condition to be the CPA triggering condition.

9 . The apparatus of claim 7 , wherein the CPA triggering condition includes an event indicating that the first PSCell becomes better than a threshold.

10 . The apparatus of claim 7 , wherein the CPC triggering condition includes an event indicating that the second PSCell becomes offset better than the first PSCell.

11 . The apparatus of claim 7 , wherein the CPC triggering condition includes an event indicating that the first PSCell is worse than a first threshold and the second PSCell becomes better than a second threshold.

12 . The apparatus of claim 7 , wherein the CPA triggering condition is used before the current SCG is configured with the apparatus, and the CPC triggering condition is used after the current SCG is configured with the apparatus.

13 . A non-transitory machine-readable storage medium, storing instructions which, when executed by a processor, causes the processor to execute a method, the method comprising the following steps of:

receiving and storing a radio resource control (RRC) reconfiguration message from a source base station (BS), the RRC reconfiguration message including a first radio resource configuration of a first primary secondary cell (PSCell) in a first target BS, a second radio resource configuration of a second PSCell in a second target BS and conditional PSCell addition (CPA) and conditional PSCell change (CPC) triggering conditions associated with the first and second PSCells, the CPA and CPC triggering conditions corresponding to CPA and CPC steps, respectively;

setting a current triggering condition to be the CPA triggering condition;

evaluating the current triggering condition for the first and second PSCells based on the current triggering condition and determining that the first PSCell satisfies the current triggering condition;

performing the CPA step to add the first PSCell as a current secondary cell group (SCG), applying the first radio resource configuration for the first PSCell, and synchronizing to the first PSCell;

updating the current triggering condition to be the CPC triggering condition, the non-transitory machine-readable storage medium still keeping the first radio resource configuration of the first PSCell, the second radio resource configuration of the second PSCell and the CPA and CPC triggering conditions, without releasing the second radio resource configuration of the second PSCell and the CPA and CPC triggering conditions associated therewith;

evaluating the current triggering condition for the second PSCell based on the current triggering condition and determining that the second PSCell satisfies the current triggering condition; and

performing the CPC step to change the current SCG from the first PSCell to the second PSCell.

14 . The non-transitory machine-readable storage medium of claim 13 , wherein the method further comprises:

releasing the second PSCell; and

updating the current triggering condition to be the CPA triggering condition.

15 . The non-transitory machine-readable storage medium of claim 13 , wherein the CPA triggering condition includes an event indicating that the first PSCell becomes better than a threshold.

16 . The non-transitory machine-readable storage medium of claim 13 , wherein the CPC triggering condition includes an event indicating that the second PSCell becomes offset better than the first PSCell.

17 . The non-transitory machine-readable storage medium of claim 13 , wherein the CPC triggering condition includes an event indicating that the first PSCell is worse than a first threshold and the second PSCell becomes better than a second threshold.

18 . The non-transitory machine-readable storage medium of claim 13 , wherein the CPA triggering condition is used before the current SCG is configured with an apparatus having the non-transitory machine-readable storage medium, and the CPC triggering condition is used after the current SCG is configured with the apparatus.