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EP-4231709-B1 - ENABLING A MULTI-SIM UE IN MULTI-RAT DUAL CONNECTIVITY (MR-DC) OPERATION MODE TO PERFORM FASTER CAMPING ON TERMINATING A SERVICE INITIATED IN ANOTHER RAT

EP4231709B1EP 4231709 B1EP4231709 B1EP 4231709B1EP-4231709-B1

Inventors

  • BETTAPPANAVAR, ARUNAKUMAR
  • GOEL, MEHA
  • MADHURANTAKAM, SHRINATH RAMAMOORTHY
  • RASTOGI, AKSHAY

Dates

Publication Date
20260506
Application Date
20220801

Claims (15)

  1. A method for performing camping in a wireless communication system (200), the method comprising: Registering (501, 701), by a user equipment, UE, (206), with a primary cell (204a) of a first radio access technology, RAT, (202a) providing radio resources to the UE (206) as a master cell group, MCG, on after terminating at least one communication service initiated in a second RAT (202b); and initiating (502, 702), by the UE (206), inter-radio access technology, IRAT, measurement of a secondary cell (204b) before receiving a reconfiguration message about a measurement object of the secondary cell (204b) from the primary cell (204a) in response to the registering (501, 701), the secondary cell (204b) being associated with the primary cell (204a) by providing additional radio resources to the UE (206) as a secondary cell (204b) group, SCG.
  2. The method of claim 1, wherein the UE (206) supports multiple Subscriber Identity Modules, SIMs, and multi-rat dual connectivity, MRDC.
  3. The method of claim 1, wherein the primary cell (204a) is an LTE base station, BS, supporting evolved UMTS terrestrial radio access network, E-UTRAN, - new radio, NR, dual connectivity, DC, ENDC, and the secondary cell (204b) is a NR BS.
  4. The method of claim 1, wherein the primary cell (204a) is a NR BS supporting NR-evolved universal terrestrial radio access, EUTRA-DC, NEDC, and the secondary cell (204b) is an LTE BS.
  5. The method of claim 1, further comprising the UE (206): performing the IRAT measurement of the secondary cell (204b) for a duration to obtain an IRAT measurement report, the duration being based on previous configurations stored in a database; receiving the reconfiguration message from the primary cell (204a), the reconfiguration message being related to measurements of the secondary cell (204b); sending the IRAT measurement report to the primary cell (204a), after the receiving the reconfiguration message; and receiving a configuration from the primary cell (204a).
  6. The method of claim 5, wherein one of, the primary cell (204a) is an LTE BS supporting ENDC, the secondary cell (204b) is an NR BS, and the IRAT measurement is a NR IRAT frequency measurement including an LTE to NR measurement, or the primary cell (204a) is an NR BS supporting NEDC, the secondary cell (204b) is an LTE BS, and the IRAT measurement is an LTE IRAT frequency measurement including an NR to LTE measurement; and the duration of the IRAT measurement is based on at least one of time taken for registering (501, 701, 901) with the primary cell (204a), a radio resource control, RRC, state of peer stacks, a number of NR or LTE frequencies, a number of SIMs or radio access technologies, RATs, supported by the UE (206), a reference signal received power, RSRP, of a previously measured NR or LTE cell, or an offset.
  7. The method of claim 5, wherein one of: the previous configurations are stored in an NR frequency database for performing an NR IRAT frequency measurement, the primary cell (204a) is an LTE BS supporting ENDC, the secondary cell (204b) is an NR BS, and the NR IRAT frequency measurement is performed using a measurement gap configured for at least one of another measurement object, a connected mode discontinuous reception, C-DRX, mode, a DR mode, or another UE (206) capable to measure without the measurement gap; or the previous configurations are stored in an LTE frequency database for performing an LTE IRAT frequency measurement, the primary cell (204a) is an NR BS supporting NEDC, the secondary cell (204b) is an LTE BS, and the LTE IRAT frequency measurement is performed using the measurement gap.
  8. The method of claim 7, further comprising: the UE (206) updating the NR frequency database or the LTE frequency database based on at least one of a previously camped NR or LTE frequency, a cell corresponding to an NR or LTE frequency, a location, or a signal strength of a cell present in the location.
  9. The method of claim 5, wherein one of: the configuration is an NR cell configuration, the primary cell (204a) is an LTE BS supporting ENDC, and the secondary cell (204b) is an NR BS; or the configuration is an LTE cell configuration, the primary cell (204a) is an NR BS supporting NEDC, and the secondary cell (204b) is an LTE BS.
  10. The method of claim 1, further comprising: the UE (206) reserving a radio frequency, RF, grant before receiving the reconfiguration message from the primary cell (204a).
  11. The method of claim 10, wherein the reserving the RF grant includes reserving the RF grant for a duration in response to the registering (501, 701, 901) with the primary cell (204a); the UE (206) receiving the reconfiguration message from the primary cell (204a), after the reserving the RF grant; the UE (206) sending an IRAT measurement report with respect to the secondary cell (204b) to the primary cell (204a); and the UE (206) receiving a configuration from the primary cell (204a).
  12. The method of claim 11, wherein the reserving the RF grant includes: retaining RF resources for at least one SIM among a plurality of SIMs included in the UE (206), the at least one SIM corresponding to the secondary cell (204b); and releasing the RF resources for another SIM among the plurality of SIMs, the other SIM not included among the at least one SIM.
  13. The method of claim 1, wherein camping on the secondary cell (204b) further includes: receiving an indication from the primary cell (204a) about a follow-on radio resource control, RRC, procedure in response to the registering (501, 701, 901) with the primary cell (204a); and reserving an RF grant in response to the receiving the indication.
  14. The method of claim 1, further comprises: the UE (206) camping on the secondary cell (204b) based on a duty cycle of each SIM among a plurality of SIMs included in the UE (206).
  15. The method of claim 14, wherein the camping on the secondary cell (204b) comprises: reserving an RF grant for a duration corresponding to each of the plurality of SIMs of the UE (206) based on the duty cycle.

Description

The following specification particularly describes and ascertains the nature of the inventive concepts and the manner in which they may be performed. TECHNICAL FIELD The present disclosure relates to the field of wireless communication systems and more particularly to enabling multi-Subscriber Identity Module (SIM) User Equipment (UE) to perform faster camping in a wireless communication system. BACKGROUND Wireless communication systems are constantly evolving to provide different kinds of services supported by different Radio Access Technologies (RATs) to different User Equipments (UEs). From a UE point of view, the UE camps on a latest RAT to obtain the better service. Also, from a network deployment point of view, the UE interworks with legacy RATs or fallback to legacy RATs for specific services. In such scenarios, the UE may stay in the legacy RAT for a longer period of time despite the availability of the latest RAT, especially when the UE is a multi-Subscriber Identity Module (SIM) UE or a dual SIM dual standby (DSDS) UE. Consider an example scenario, as depicted in FIG. 1A, wherein the UE initially camps on a cell of a Long-Term Evolution (LTE) network (an example RAT) (hereinafter referred as an LTE cell/Base Station or an eNodeB (eNB)) with an E-UTRAN New Radio - Dual Connectivity (ENDC) configuration (at operation 101-1). Due to Circuit Switched FallBack (CSFB), the UE moves to a 3G/2G network for the specific service (for example: for a voice call) (at operations 102-1, 103-1, and 104-1). Upon an end of the voice call, the UE comes back to the LTE BS (at operations 105-1, and 106-1). The LTE BS configures a New Radio (NR) Inter-RAT (IRAT) measurement object (at operations 107-1 and 108-1). Due to Radio Frequency (RF) grant unavailability in the UE (e.g., the multi-SIM UE), the UE is not able to send a measurement report to the LTE BS within a pre-defined or alternatively, given duration (e.g., the UE may send the measurement report to the LTE BS with a delay) (at operation 109-1). The LTE BS waits for the pre-defined or alternatively, given duration and releases the NR IRAT measurement object for the UE (at operations 110-1 and 111-1). Therefore, the UE stays in the LTE only (the legacy RAT) despite the availability of the NR (the latest RAT) (at operation 112-1). Consider an example scenario, as depicted in FIG. 1B, wherein the UE initially camps on the LTE cell/BS with the ENDC configuration (at operation 101-2). Due to the CSFB, the UE moves to the 3G/2G network for the specific service (for example: for a voice call) (at operations 102-2, 103-2, and 104-2). Upon the end of the voice call, the UE comes back to the LTE BS (at operations 105-2 and 106-2). The LTE BS sends a reconfiguration message with the NR IRAT measurement object to the UE (at operation 107-2). Due to the RF grant unavailability in the UE, the UE does not receive the reconfiguration message from the LTE BS and does not send the measurement report to the LTE BS (at operation 108-2, and 109-2). The LTE BS does not configure a cell of the NR (NR cell) for the UE, as the LTE BS does not receive the measurement report from the UE (at operation 110-2). Therefore, the UE stays in the LTE only (the legacy RAT) despite the availability of the NR (the latest RAT) (at operation 111-2). Consider another example scenario, as depicted in FIG. 1C, wherein the UE initially camps on the LTE cell/BS with the ENDC configuration (at operation 101-3). Due to a Voice over LTE (VoLTE) call (an example of the service provided by the LTE network); the LTE BS releases a NR configuration for the UE (at operations 102-3, 103-3, and 104-3). After the VoLTE call, the LTE BS configures the NR IRAT measurement object for the UE (at operations 105-3, and 106-3). Due to the RF grant unavailability, the UE is not able to send the measurement report to the LTE BS within the pre-defined or alternatively, given duration (e.g., the UE may send the measurement report to the LTE cell with delay) (at operation 107-3). The LTE BS waits for the pre-defined or alternatively, given duration and releases the NR IRAT measurement object for the UE (at operations 108-3 and 109-3). Therefore, the UE stays in the LTE only (the legacy RAT) despite the availability of the NR (the latest RAT) (at operation 110-3). Consider another example scenario, as depicted in FIG. 1D, wherein the UE initially camps on the LTE cell/BS with the ENDC configuration (at operation 101-4). Due to the VoLTE call, the LTE BS releases the NR configuration for the UE (at operations 102-4, 103-4, and 104-4). After the VoLTE call, the LTE BS sends the reconfiguration message with the NR IRAT measurement object to the UE (at operations 105-4, and 106-4). Due to the RF grant unavailability in the UE, the UE does not receive the reconfiguration message from the LTE BS and does not send the measurement report to the LTE BS (at operation 107-4). The LTE BS does not configure the NR cell for the UE, as the LTE