USER EQUIPMENT AND METHOD FOR MAINTAINING UPLINK (UL) SYNCHRONIZATION IN A NON-TERRESTRIAL NETWORK (NTN)

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Patent No.: US None
App. No.: 17/951,878

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Abstract

A method performed by a user equipment (UE) for maintaining uplink (UL) synchronization in a non-terrestrial network (NTN) is provided. The method includes receiving, from a base station (BS), a system information block (SIB) indicating a duration of a timer for the UL synchronization in the NTN; determining whether an epoch time is provided in the SIB; starting or restarting the timer with the duration at a time determined according to whether the epoch time is provided in the SIB; and determining that the UE has lost the UL synchronization upon an expiration of the timer.

Claims (58)

1 . A method performed by a user equipment (UE) for maintaining uplink (UL) synchronization in a non-terrestrial network (NTN), the method comprising:

receiving, from a base station (BS), a system information block (SIB) indicating a duration of a timer for the UL synchronization in the NTN;

determining whether an epoch time is provided in the SIB;

starting or restarting the timer with the duration at a time determined according to whether the epoch time is provided in the SIB; and

determining that the UE has lost the UL synchronization upon an expiration of the timer.

2 . The method of claim 1 , wherein the timer is started or restarted from a subframe indicated by the epoch time in a case that the epoch time is provided in the SIB.

3 . The method of claim 1 , wherein the timer is started or restarted at an end of a system information (SI) window during which the SIB is received in a case that the epoch time is not provided in the SIB.

4 . The method of claim 1 , further comprising:

flushing all hybrid automatic repeat request (HARQ) buffers upon the expiration of the timer.

5 . The method of claim 1 , wherein the UE is not allowed to perform any UL transmission upon the expiration of the timer.

6 . The method of claim 1 , further comprising:

performing, upon the expiration of the timer, at least one of:

notifying a Radio Resource Control (RRC) layer of the UE to release a physical uplink control channel (PUCCH) for at least one serving cell;

notifying the RRC layer of the UE to release a sounding reference signal (SRS) for the at least one serving cell;

clearing any configured downlink assignment and any configured uplink grant;

clearing any physical uplink shared channel (PUSCH) resource for semi-persistent channel state information (CSI) reporting;

treating other running timers associated with the UL synchronization as expired;

maintaining uplink timings of all timing alignment groups (TAGs);

releasing PUCCH-CSI-Resources configured in a CSI-ReportConfig Information Element (IE);

releasing SchedulingRequestResourceConfig instances configured in a PUCCH-Config IE; or

releasing SRS-Resource instances configured in an SRS-Config IE.

7 . The method of claim 1 , wherein the SIB comprises satellite ephemeris information, and the method further comprises:

determining that the satellite ephemeris information is invalid upon the expiration of the timer.

8 . The method of claim 1 , wherein the SIB comprises a plurality of common Timing Advance (TA) parameters, and the method further comprises:

determining that the common TA parameters are invalid upon the expiration of the timer.

9 . The method of claim 1 , further comprising:

triggering a random access (RA) procedure to rebuild the UL synchronization upon the expiration of the timer.

10 . The method of claim 1 , wherein the SIB comprises an NTN-specific SIB.

11 . A user equipment (UE) for maintaining uplink (UL) synchronization in a non-terrestrial network (NTN), the UE comprising:

one or more processors; and

at least one memory coupled to at least one of the one or more processors, wherein the at least one memory stores computer-executable instructions that, when executed by the at least one of the one or more processors, cause the UE to:

receive, from a base station (BS), a system information block (SIB) indicating a duration of a timer for the UL synchronization in the NTN;

determine whether an epoch time is provided in the SIB;

start or restart the timer with the duration at a time determined according to whether the epoch time is provided in the SIB; and

determine that the UE has lost the UL synchronization upon an expiration of the timer.

12 . The UE of claim 11 , wherein the timer is started or restarted from a subframe indicated by the epoch time in a case that the epoch time is provided in the SIB.

13 . The UE of claim 11 , wherein the timer is started or restarted at an end of a system information (SI) window during which the SIB is received in a case that the epoch time is not provided in the SIB.

14 . The UE of claim 11 , wherein the computer-executable instructions, when executed by the at least one of the one or more processors, further cause the UE to:

flush all hybrid automatic repeat request (HARQ) buffers upon the expiration of the timer.

15 . The UE of claim 11 , wherein the UE is not allowed to perform any UL transmission upon the expiration of the timer.

16 . The UE of claim 11 , wherein the computer-executable instructions, when executed by the at least one of the one or more processors, further cause the UE to:

perform, upon the expiration of the timer, at least one of: