Method for maintaining multi-SIM configuration and user equipment

1. A method for maintaining multi-SIM (Subscriber Identity Module) configuration, adapted to user equipment (UE), comprising:

receiving, by the UE, a first multi-SIM support information from a first cell, wherein the first multi-SIM support information is generated and transmitted from a second cell to the first cell via an inter-node signaling from the second cell to the first cell, and the first cell and the second cell belong to a first network;

transmitting, by the UE, a multi-SIM assistance information message, wherein the multi-SIM assistance information message is determined based on the first multi-SIM support information.

2. The method according to claim 1 , wherein the first multi-SIM support information comprises a release indicator that instructs the UE to release a plurality of first multi-SIM configurations, which are configured by the first cell and stored by the UE before the UE receives the first multi-SIM support information, and the method further comprises:

releasing, by the UE, the plurality of first multi-SIM configurations in response to the release indicator.

3. The method according to claim 1 , wherein the first multi-SIM support information comprises a plurality of second multi-SIM configurations, and the method further comprises:

overwriting, by the UE, a plurality of first multi-SIM configurations with the plurality of second multi-SIM configurations, wherein the plurality of first multi-SIM configurations are configured by the first cell and stored by the UE before the UE receives the first multi-SIM support information.

4. The method according to claim 2 , further comprising:

stopping, by the UE, a running Leave Timer after the UE releases the plurality of first multi-SIM configurations, wherein an initial value of the running Leave Timer is determined based on a first leave WithoutResponseTimer in the plurality of first multi-SIM configurations.

5. The method according to claim 3 , further comprising:

stopping, by the UE, a running Leave Timer after the UE overwrites the plurality of first multi-SIM configurations, wherein an initial value of the running leave timer is determined based on a first leave WithoutResponseTimer in the plurality of first multi-SIM configurations.

6. The method according to claim 2 , wherein the plurality of first multi-SIM configurations comprises a plurality of multi-SIM gap configurations, and the method further comprises:

stopping, by the UE, applying the plurality of multi-SIM gap configurations after the UE releases the plurality of first multi-SIM configurations, wherein the plurality of multi-SIM gap configurations are used for the UE to switch to communicate with a second network during a multi-SIM gap time period decided by the UE based on the plurality of multi-SIM gap configuration.

7. The method according to claim 3 , wherein the plurality of first multi-SIM configurations comprise a plurality of first multi-SIM gap configurations, and the method further comprises:

stopping, by the UE, applying a first multi-SIM gap time period, which is determined by the UE based on the plurality of first multi-SIM gap configurations to communicate with a second network during the first multi-SIM gap time period, after the UE overwrites the plurality of first multi-SIM configurations.

8. The method according to claim 3 , wherein the plurality of second multi-SIM configurations comprises a second leaveWithoutResponseTimer, and the method further comprises:

transmitting, by the UE, a leave indicator to the second cell, wherein the leave indicator informs the second cell that the UE intends to leave the first network; and

starting, by the UE, counting a Leave Timer, wherein an initial value of the Leave Timer is determined based on the second leave WithoutResponseTimer, and

releasing, a radio resource control (RRC) connection with the second cell after the Leave Timer expires.

9. The method according to claim 3 , wherein the plurality of second multi-SIM configurations comprise a plurality of second multi-SIM gap configurations, and the method further comprises:

receiving, by the UE, the plurality of second multi-SIM configurations; and

switching, by the UE, from the first network to communicate with a second network during a second multi-SIM gap time period determined by any combinations of the plurality of second multi-SIM gap configurations, after the UE overwrites the plurality of first multi-SIM configurations.

10. The method according to claim 1 , wherein the first network is a New Radio (NR) cellular network, which is a Public Land Mobile Network (PLMN), Standalone Non-public Network (SNPN), or a Public network integrated Non-Public Network.

11. A user equipment, comprising:

a transceiver; and

a processor, coupled to the transceiver and configured to perform:

controlling the transceiver to receive a first multi-SIM support information from a first cell, wherein the first multi-SIM support information is generated and transmitted from a second cell to the first cell via an inter-node signaling from the second cell to the first cell, and the first cell and the second cell belong to a first network;

controlling the transceiver to transmit a multi-SIM assistance information message, wherein the multi-SIM assistance information message is determined based on the first multi-SIM support information.

12. The UE according to claim 11 , wherein the first multi-SIM support information comprises a release indicator that instructs the UE to release a plurality of first multi-SIM configurations, which are configured by the first cell and stored by the UE before the UE receives the first multi-SIM support information, and the processor further performs:

releasing the plurality of first multi-SIM configurations in response to the release indicator.

13. The UE according to claim 11 , wherein the first multi-SIM support information comprises a plurality of second multi-SIM configurations, and the processor further performs:

overwriting a plurality of first multi-SIM configurations with the plurality of second multi-SIM configurations, wherein the plurality of first multi-SIM configurations are configured by the first cell and stored by the UE before the UE receives the first multi-SIM support information.

14. The UE according to claim 12 , wherein the processor further performs:

stopping a running Leave Timer after the UE releases the plurality of first multi-SIM configurations, wherein an initial value of the running Leave Timer is determined based on a first leaveWithoutResponseTimer in the plurality of first multi-SIM configurations.

15. The UE according to claim 13 , wherein the processor further performs:

stopping a running Leave Timer after the UE overwrites the plurality of first multi-SIM configurations, wherein an initial value of the running Leave timer is determined based on a first leaveWithoutResponseTimer in the plurality of first multi-SIM configurations.

16. The UE according to claim 12 , wherein the plurality of first multi-SIM configurations comprises a plurality of multi-SIM gap configurations, and the processor further performs:

stopping applying the plurality of multi-SIM gap configurations after the UE releases the plurality of first multi-SIM configurations, wherein the plurality of multi-SIM gap configurations are used for the UE to switch to communicate with a second network during a multi-SIM gap time period decided by the UE based on the plurality of multi-SIM gap configuration.

17. The UE according to claim 13 , wherein the plurality of first multi-SIM configurations comprise a plurality of first a multi-SIM gap configurations, and the processor further performs:

stopping applying a first multi-SIM gap time period, which is determined by the UE based on the plurality of first multi-SIM gap configurations to communicate with a second network during the first multi-SIM gap time period, after the UE overwrites the plurality of first multi-SIM configurations.

18. The UE according to claim 13 , wherein the plurality of second multi-SIM configurations comprises a second leaveWithoutResponseTimer, and the processor further performs:

controlling the transceiver to transmit a leave indicator to the second cell, wherein the leave indicator informs the second cell that the UE intends to leave the first network; and

starting counting a Leave Timer, wherein an initial value of the Leave Timer is determined based on the second leave WithoutResponseTimer, and

releasing, a radio resource control (RRC) connection with the second cell after the Leave Timer expires.

19. The UE according to claim 13 , wherein the plurality of second multi-SIM configurations comprise a plurality of second multi-SIM gap configurations, and the processor further performs at least one of following actions:

controlling the transceiver to receive the plurality of second multi-SIM configurations; and

switching from the first network to communicate with a second network during a second multi-SIM gap time period determined by any combinations of the plurality of second multi-SIM gap configurations, after the UE overwrites the plurality of first multi-SIM configurations.

20. The UE according to claim 11 , wherein the first network is a New Radio (NR) cellular network, which is a Public Land Mobile Network (PLMN), Standalone Non-public Network (SNPN), or a Public network integrated Non-Public Network.

21. A communication system, comprising:

a first network node, performing:

receiving an inter-node signaling from a second network node, wherein the inter-node signaling comprises a first multi-SIM support information, and the first network node and the second network node belong to a first network;

transmitting the first multi-SIM support information to user equipment (UE);

UE, coupled with the first network node and performing:

receiving the first multi-SIM support information from the first network node.

22. The communication system according to claim 21 , wherein the UE transmits a multi-SIM assistance information message, wherein the multi-SIM assistance information message is determined based on the first multi-SIM support information.

23. The communication system according to claim 21 , wherein the first network node is a serving base station of the UE.

24. The communication system according to claim 21 , wherein the second network node is a base station and the inter-node signaling is transmitted via an X2 interface or an Xn interface between the first network node and the second network node.

25. The communication system according to claim 21 , wherein the second network node is a core network, wherein the core network comprises an Evolved Packet Core (EPC) or a fifth-generation (5G) core, and the inter-node signaling is transmitted via a backhaul connection between the core network and the first network node.