ADAPTIVE UPLINK (UL) TIMING ADJUSTMENT FOR BEAM SWITCHING IN FIFTH-GENERATION NEW RADIO (5G NR)
The exemplary embodiments describe devices, systems and methods for adaptive uplink (UL) timing adjustment for beam switching. A user equipment (UE) may perform a beam switch from a first beam to a second beam, determine a timing offset associated with the second beam and apply an uplink (UL) timing adjustment based on the timing offset associated with the second beam. In some embodiments, the timing offset may be determined based on information received after the beam switch. In other embodiments, the timing offset may be determined based on information receive prior to the beam switch.
1 . A method, comprising:
at a user equipment (UE):
performing a beam switch from a first beam to a second beam;
determining a timing offset associated with the second beam; and
applying an uplink (UL) timing adjustment based on the timing offset associated with the second beam.
2 . The method of claim 1 , wherein the UL timing adjustment comprises a multi-step UL timing alignment.
3 . The method of claim 1 , further comprising:
determining whether the timing offset satisfies a predetermined threshold corresponding to a cyclic prefix (CP) length of an UL symbol transmitted within an active UL bandwidth part (BWP).
4 . The method of claim 3 , wherein the CP length is determined based at least on the sub-carrier-spacing (SCS) of the active UL BWP.
5 . The method of claim 3 , further comprising:
when the timing offset satisfies the predetermined threshold, the UL timing adjustment comprises a single-step UL timing adjustment.
6 . The method of claim 3 , further comprising:
when the timing offset does not satisfy the predetermined threshold, the UL timing adjustment comprises a multi-step UL timing adjustment.
7 . The method of claim 6 , wherein the multi-step UL timing adjustment is triggered by a timing adjustment command received from a base station.
8 . The method of claim 1 , wherein determining the timing offset may include estimating a timing offset value based at least on a tracking reference signal (TRS) allocated by a base station to the UE after the UE performs the switch from the first beam to the second beam.
9 . The method of claim 1 , wherein determining the timing offset includes estimating a timing offset value based at least on one of a channel state information reference signal (CSI-RS) or a signal synchronization block (SSB) allocated by a base station to the UE before the UE performs the switch from the first beam to the second beam.
10 . The method of claim 1 , further comprising:
identifying a time gap duration;
wherein the UL timing adjustment comprises a single-step UL timing adjustment, applied within the time gap after the UE performs the switch from the first beam to the second beam, and
wherein there is no UL transmission from the UE to a base station during the identified time gap.
11 . A user equipment (UE), comprising:
a transceiver configured to communicate with a base station; and
a processor configured to perform operations, comprising:
performing a beam switch from a first beam to a second beam;
determining a timing offset associated with the second beam; and
applying an uplink (UL) timing adjustment based at least on the timing offset associated with the second beam
12 . The UE of claim 11 , the operations further comprising:
determining whether the timing offset satisfies a predetermined threshold corresponding to a cyclic prefix (CP) length of an UL symbol transmitted within an active UL bandwidth part (BWP);
when the timing offset satisfies the predetermined threshold, the UL timing adjustment comprises a single-step UL timing adjustment; and
when the timing offset does not satisfy the predetermined threshold, the UL timing adjustment comprises a multi-step UL timing adjustment.
13 . The UE of claim 11 , wherein determining the timing offset includes estimating a timing offset value based at least on a tracking reference signal (TRS) allocated by a base station to the UE after the performs the switch from the first beam to the second beam.
14 . The UE of claim 11 , wherein determining the timing offset includes estimating a timing offset value based at least on one of a channel state information reference signal (CSI-RS) or a signal synchronization block (SSB) allocated by a base station to the UE before the UE performs the switch from the first beam to the second beam.
15 . A method, comprising:
at a user equipment (UE) configured to communicate with a base station:
collecting measurement data for a set of candidate beam pairs;
estimating a timing drift for each candidate beam pair based at least on the measurement data;
selecting one of the candidate beam pairs for use in beam switching;
identifying a time gap; and
applying an uplink (UL) timing adjustment based at least on the timing drift associated with the selected one of the candidate beam pairs.
16 . The method of claim 15 , wherein the measurement data comprises layer 1 (L1) reference signal received power (RSRP) value that is based at least on a channel state information reference signal (CSI-RS) or a signal synchronization block (SSB) allocated by the base station.
17 . The method of claim 15 , wherein the one of the candidate beam pairs is reported to the base station.
18 . The method of claim 15 , wherein the UL timing adjustment is applied within the time gap.
19 . The method of claim 15 , wherein estimating the time drift occurs prior to the UE performing beam switching from a first beam to a second beam.
20 . The method of claim 15 , wherein there is no UL transmission from the UE to a base station during the identified time gap.