Methods and apparatus to improve MR-DC SN addition procedure

1. A method of wireless communication at a user equipment (UE), the method comprising:

receiving, from a first base station (BS), a first radio resource control (RRC) reconfiguration message including a conditional primary secondary cell (PSCell) addition command that indicates one or more candidate PSCells of a second BS;

transmitting, to the first BS, an RRC reconfiguration complete message that indicates completion of the conditional PSCell addition command;

determining a candidate target PSCell in the one or more candidate PSCells of the second BS based on the conditional PSCell addition command; and

performing a conditional PSCell addition procedure to add the candidate target PSCell.

2. The method of claim 1 , wherein the conditional PSCell addition command indicates a respective predefined condition for each of the one or more candidate PSCells, and the performing includes performing the conditional PSCell addition procedure to add the candidate target PSCell when a corresponding predefined condition of the candidate target PSCell is satisfied.

3. The method of claim 2 , wherein the conditional PSCell addition command indicates a respective threshold for each of the predefined conditions, and the method further comprises:

receiving, from the first BS, a second RRC reconfiguration message including a configuration that configures the UE to measure qualities of the candidate PSCells of the second BS; and

measuring the qualities of the candidate PSCells, wherein the performing further includes performing the conditional PSCell addition procedure to add the candidate target PSCell when a measured quality of the candidate target PSCell is above a corresponding threshold of the candidate target PSCell.

4. The method of claim 3 , wherein the configuration in the second RRC reconfiguration message is transferred within the first RRC reconfiguration message.

5. The method of claim 1 , further comprising:

transmitting, to the first BS, an RRC message that indicates completion of the conditional PSCell addition procedure.

6. The method of claim 1 , further comprising:

canceling the conditional PSCell addition command when a normal PSCell addition procedure is received from the first BS.

7. The method of claim 1 , wherein the conditional PSCell addition procedure is a random access procedure.

8. An apparatus, comprising processing circuitry configured to:

receive, from a first base station (BS), a first radio resource control (RRC) reconfiguration message including a conditional primary secondary cell (PSCell) addition command that indicates one or more candidate PSCells of a second BS;

transmit, to the first BS, an RRC reconfiguration complete message that indicates completion of the conditional PSCell addition command;

determining a candidate target PSCell in the one or more candidate PSCells of the second BS based on the conditional PSCell addition command; and

perform a conditional PSCell addition procedure to add the candidate target PSCell.

9. The apparatus of claim 8 , wherein the conditional PSCell addition command indicates a respective predefined condition for each of the one or more candidate PSCells, and the processing circuitry is further configured to:

perform the conditional PSCell addition procedure to add the candidate target PSCell when a corresponding predefined condition of the candidate target PSCell is satisfied.

10. The apparatus of claim 9 , wherein the conditional PSCell addition command indicates a respective threshold for each of the predefined conditions, and the processing circuitry is further configured to:

receive, from the first BS, a second RRC reconfiguration message that configures the UE to measure qualities of the candidate PSCells of the second BS;

measure the qualities of the candidate PSCells; and

perform the conditional PSCell addition procedure to add the candidate target PSCell when a measured quality of the candidate target PSCell is above a corresponding threshold of the candidate target PSCell.

11. The apparatus of claim 10 , wherein the second RRC reconfiguration message is transferred within the first configuration message.

12. The apparatus of claim 8 , wherein the processing circuitry is further configured to:

transmit, to the first BS, an RRC message that indicates completion of the conditional PSCell addition procedure.

13. The apparatus of claim 8 , wherein the processing circuitry is further configured to:

cancel the conditional PSCell addition command when a normal PSCell addition procedure is received from the first BS.

14. The apparatus of claim 8 , wherein the conditional PSCell addition procedure is a random access procedure.

15. A method of wireless communication at a first base station (BS), the method comprising:

transmitting, to a user equipment (UE), a first radio resource control (RRC) reconfiguration message including a conditional primary secondary cell (PSCell) addition command that indicates one or more candidate PSCells of a second BS and configures the UE to perform a conditional PSCell addition procedure to add a candidate target PSCell that is one of the one or more candidate PSCells and determined by the UE; and

receiving, from the UE, an RRC reconfiguration complete message that indicates completion of the conditional PSCell addition command.

16. The method of claim 15 , further comprising:

receiving, from the UE, an RRC message that indicates completion of the conditional PSCell addition procedure; and

transmitting, to the second BS, a message forwarding the RRC message.

17. The method of claim 15 , further comprising:

transmitting, to the second BS, an addition request message that indicates the conditional PSCell addition procedure; and

receiving, from the second BS, an addition request acknowledgement (ACK) message.

18. The method of claim 15 , further comprising:

transmitting, to the UE, a second RRC reconfiguration message that configures the UE to measure qualities of the candidate PSCells of the second BS.

19. The method of claim 15 , wherein the conditional PSCell addition command indicates a respective predefined condition for each of the one or more PSCells, and the conditional PSCell addition procedure is performed with the candidate target PSCell when a corresponding predefined condition of the candidate target PSCell is satisfied.

20. The method of claim 15 , wherein the conditional PSCell addition procedure is a random access procedure.