On-demand system information request procedure and error handling

1. A user equipment (UE), comprising:

one or more non-transitory computer-readable media having computer-executable instructions embodied thereon; and

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

transmit a first system information (SI) request message to a base station (BS) on a signaling radio bearer 1 (SRB1) after determining that the UE is in a connected state, the first SI request message indicating at least one requested system information block (SIB);

transmit a second SI request message to the BS on a signaling radio bearer 0 (SRB0) after determining that the UE is not in the connected state, the second SI request message indicating at least one requested SI message; and

perform an error handling procedure after determining that the at least one requested SIB is not received successfully, or after determining that the at least one requested SI message is not received successfully.

2. The UE of claim 1 , wherein the error handling procedure comprises storing SI request failure information.

3. The UE of claim 2 , wherein the at least one processor is further configured to execute the computer-executable instructions to:

transmit the SI request failure information.

4. The UE of claim 2 , wherein the SI request failure information indicates at least one of:

one or more SIBs of the at least one requested SIB;

one or more SI messages of the at least one requested SI message;

a cell identifier (ID) of a cell in which the UE performs an on-demand SI request procedure;

a synchronization signal block (SSB) index for performing the on-demand SI request procedure;

a message type of the on-demand SI request procedure, the message type including an MSG1-based approach and an MSG3-based approach; and

a timestamp for performing the on-demand SI request procedure.

5. The UE of claim 2 , wherein the at least one processor is further configured to execute the computer-executable instructions to:

transmit the SI request failure information to a master node when the UE is in a dual connectivity mode.

6. The UE of claim 1 , wherein, when the UE is not in the connected state, the error handling procedure comprises:

considering a cell in which the UE performs an on-demand SI request procedure as barred; and

performing a cell re-selection procedure.

7. The UE of claim 1 , wherein, when the UE is in the connected state, the error handling procedure comprises activating a prohibit timer.

8. The UE of claim 1 , wherein the at least one processor is further configured to execute the computer-executable instructions to:

activate a prohibit timer after transmitting the first SI request message.

9. The UE of claim 8 , wherein the at least one processor is further configured to execute the computer-executable instructions to:

transmit a third SI request message to the BS on the SRB1 upon an expiration of the prohibit timer.

10. The UE of claim 1 , wherein, when the UE is in a dual connectivity mode, the at least one processor is further configured to execute the computer-executable instructions to:

transmit a third SI request message to a master node when the UE requires SI of a secondary node.

11. A method of performing an on-demand system information (SI) request procedure by a user equipment (UE), the method comprising:

transmitting a first SI request message to a base station (BS) on a signaling radio bearer 1 (SRB1) after determining that the UE is in a connected state, the first SI request message indicating at least one requested system information block (SIB);

transmitting a second SI request message to the BS on a signaling radio bearer 0 (SRB0) after determining that the UE is not in the connected state, the second SI request message indicating at least one requested SI message; and

performing an error handling procedure after determining that the at least one requested SIB is not received successfully, or after determining that the at least one requested SI message is not received successfully.

12. The method of claim 11 , wherein the error handling procedure comprises storing SI request failure information.

13. The method of claim 12 , further comprising:

transmitting the SI request failure information.

14. The method of claim 12 , wherein the SI request failure information indicates at least one of:

one or more SIBs of the at least one requested SIB;

one or more SI messages of the at least one requested SI message;

a cell identifier (ID) of a cell in which the UE performs the on-demand SI request procedure;

a synchronization signal block (SSB) index for performing the on-demand SI request procedure;

a message type of the on-demand SI request procedure, the message type including an MSG1-based approach and an MSG3-based approach; and

a timestamp for performing the on-demand SI request procedure.

15. The method of claim 12 , further comprising:

transmitting the SI request failure information to a master node when the UE is in a dual connectivity mode.

16. The method of claim 11 , wherein, when the UE is not in the connected state, the error handling procedure comprises:

considering a cell in which the UE performs the on-demand SI request procedure as barred; and

performing a cell re-selection procedure.

17. The method of claim 11 , wherein, when the UE is in the connected state, the error handling procedure comprises activating a prohibit timer.

18. The method of claim 11 , further comprising:

activating a prohibit timer after transmitting the first SI request message.

19. The method of claim 18 , further comprising:

transmitting a third SI request message to the BS on the SRB1 upon an expiration of the prohibit timer.

20. The method of claim 11 , wherein, when the UE is in a dual connectivity mode, the method further comprises:

transmitting a third SI request message to a master node when the UE requires SI of a secondary node.