User equipment synchronization during handover

Patent metadata

Field	Value
Publication number	US-12593292-B2
Application number	US-202218558253-A
Country	US
Kind code	B2
Filing date	Apr 26, 2022
Priority date	May 6, 2021
Publication date	Mar 31, 2026
Grant date	Mar 31, 2026

Abstract

Improved techniques of handover include the source gNB estimating the accuracy of the timing information that the UE may derive from its local clock during and shortly after the HO procedure and exchange this with the target gNB. Based on this estimate, the target gNB can determine when a timing information update is needed at the UE.

First claim

What is claimed is:

1 . An apparatus, comprising:
at least one processor; and at least one memory including computer program code; the at least one memory and the computer program code configured to cause the apparatus at least to: receive, from a source network node in a network during a handover operation, time synchronization data representing a time synchronization accuracy of a user equipment in the network; receive, from the network, time synchronization accuracy budget data representing a time synchronization accuracy budget; and generate a time synchronization headroom based on the time synchronization accuracy of the user equipment and the time synchronization accuracy budget, the time synchronization headroom indicating a periodicity of a time update transmission to the user equipment; determine an instant of time at which a timing update is to be transmitted to the user equipment, the instant of time being based on the time synchronization data received from the source network node and a time and frequency stability of the user equipment.

2 . The apparatus of claim 1 , wherein the time synchronization data includes timestamp data representing a timestamp of a reference time update transmit time to or reception time at the user equipment; and
the at least one memory and the computer program code configured to further cause the apparatus to generate an unavailability time based on the timestamp.

3 . The apparatus of claim 1 , wherein the at least one memory and the computer program code configured to further cause the apparatus to determine whether the timing update is able to be delivered to the user equipment based on the generated instant of time and a handover delay.

4 . An apparatus, comprising:
at least one processor; and at least one memory including computer program code; the at least one memory and the computer program code configured to cause the apparatus at least to: generate time synchronization data representing an estimate of an accuracy of timing information at a user equipment; receive an indication of a handover to a target network node of a user equipment having a radio resource connection to the apparatus; and transmit the time synchronization data to the target network node; receive accuracy feedback from the target network node, wherein the accuracy feedback dependent at least in part on an instant of time at which a timing update is to be transmitted by the target network node to the user equipment, the instant of time being based on the time synchronization data and a time and frequency stability of the user equipment.

5 . The apparatus of claim 4 , wherein generating the time synchronization data includes appending, to the time synchronization data, timestamp data representing a timestamp of a reference time update transmit time to or reception time at the user equipment.

6 . The apparatus of claim 4 , wherein generating the time synchronization data includes adding, to the time synchronization data, an anticipated error caused by an unavailability of a reference time update at the user equipment.

7 . The apparatus of in claim 6 , wherein the anticipated error is based on a worst-case interruption time.

8 . The apparatus of claim 4 , wherein the at least one memory and the computer program code configured to further cause the apparatus to transmit time synchronization accuracy budget data representing a time synchronization accuracy budget to the target network node over a Xn interface.

9 . The apparatus of claim 4 , wherein the at least one memory and the computer program code configured to further cause the apparatus to generate a time available for the target network node to deliver timing information to the user equipment after the user equipment connects to the target network node.

10 . The apparatus of claim 9 , wherein the at least one memory and the computer program code configured to further cause the apparatus to configure the handover based on the generated time available for the target network node.

11 . The apparatus of claim 4 , wherein generating the estimate of accuracy of timing information of the user equipment is based on a second time synchronization accuracy budget obtained from a network.

12 . An apparatus, comprising:
at least one processor; and at least one memory including computer program code; the at least one memory and the computer program code configured to cause the apparatus at least to: receive, from a source network node, a handover command indicating to the apparatus to switch a source of time synchronization from the source network node to a target network node, the handover command including time synchronization accuracy feedback data representing a time synchronization accuracy feedback generated by the target network node; wherein the time synchronization accuracy feedback dependent at least in part on an instant of time at which a timing update is to be transmitted by the target network node to the apparatus, the instant of time being based on time synchronization data received by the target network node and a time and frequency stability of the apparatus.

13 . The apparatus as in claim 12 , wherein the time synchronization accuracy feedback includes a determination of whether a time synchronization accuracy at the apparatus is within a time synchronization accuracy budget provided by a network to the target network node.

14 . The apparatus as in claim 12 , wherein the handover command represents a conditional handover and the target network node is one of a plurality of candidate target network nodes, and
wherein the time synchronization accuracy feedback is received from each of the plurality of candidate target network nodes and the feedback from each of the candidate target network nodes includes a respective time synchronization accuracy headroom indicating an amount of time synchronization error left in a time synchronization accuracy budget.

15 . The apparatus as in claim 12 , wherein the at least one memory and the computer program code configured to further cause the apparatus to, in response to receiving the handover command, select, as the target network node, a candidate target network node having the largest time synchronization accuracy headroom.

16 . The apparatus as in claim 12 , wherein the time synchronization accuracy feedback includes an allocation of reference time update to enable the apparatus to receive a reference time update prior to having completed a physical random access procedure.

17 . The apparatus as in claim 16 , wherein the at least one memory and the computer program code configured to further cause the apparatus to, in response to receiving the handover command, select a reference time update for reception.

18 . The apparatus as in claim 12 , wherein the time synchronization accuracy feedback includes an estimate of a propagation delay between the apparatus and the target network node.

19 . The apparatus as in claim 17 , wherein the at least one memory and the computer program code configured to further cause the apparatus to, in response to receiving the handover command, apply the estimate of the propagation delay to a time-of-departure budget.

Assignees

• Nokia Technologies Oy

Inventors

• Jacobsen Thomas Haaning
• Kolding Troels Emil
• Andrés Maldonado Pilar
• Abreu Renato Barbosa
• Sivasiva Ganesan Rakash
• Kelley Sean

Classifications

• H04W56/001

  Synchronization between nodes · CPC title

• H04W36/0088

  Scheduling hand-off measurements · CPC title

• H04W36/0072

  of resource information of target access point · CPC title

• H04W36/08

  Reselecting an access point · CPC title

• H04W56/0015 Primary

  one node acting as a reference for the others · CPC title