Handling of timing advance acquisition failure in L1/2 triggered inter-cell mobility

Patent metadata

Field	Value
Publication number	US-12563467-B2
Application number	US-202318296918-A
Country	US
Kind code	B2
Filing date	Apr 6, 2023
Priority date	Apr 6, 2023
Publication date	Feb 24, 2026
Grant date	Feb 24, 2026

Abstract

There is provided a user equipment apparatus that includes at least one processor and memory storing instructions. The instructions, when executed by the at least one processor, cause the user equipment apparatus at least to: establish a connection with a serving cell controlled by a serving network node; perform configuration for L1/L2 triggered mobility (LTM) to a target cell, the target cell controlled by one of: the serving network node or a target network node; prior to receiving a command to switch to the target cell: transmit, towards the target cell, a random access preamble for acquiring timing advance for the target cell; and receive, from the serving network node, an instruction to acquire timing advance for the target cell.

First claim

What is claimed is:

1 . A network node that supports at least one of central unit control plane (CU-CP) functionality or a layer 3 protocol of a radio access network, comprising:
at least one processor; and at least one memory storing instructions which, when executed by the at least one processor, cause the network node at least to:
establish a connection with a user equipment apparatus (UE) via a serving cell supported by a serving network node, the serving network node supports at least one of distributed unit, DU, functionality or a layer 2 protocol of a radio access network;
transmit, towards the UE, a message configured to prepare the UE for L1/L2 triggered mobility (LTM) to a target cell, the target cell controlled by one of: the serving network node or a target network node, the target network node supports at least one of distributed unit, DU, functionality or a layer 2 protocol of a radio access network, and which supports a target cell;
transmit, towards at least one of the serving network node or the target network node, a duration of a timer T;
receive, from the target network node, an indication that the random access preamble transmission has not been received from the UE and that a timing advance (TA) value could not be estimated; and
prior to transmitting a command to switch to the target cell:
cause the serving network node to transmit, toward the UE, an instruction to transmit a random access preamble to the target cell for acquiring timing advance for the target cell; and
cause the serving network node to transmit, toward the UE, an instruction to re-transmit the random access preamble to the target cell for acquiring the timing advance for the target cell, in response to the indication from the target network node.

2 . The network node of claim 1 , wherein the instructions when executed by the at least one processor, further cause the network node at least to:
cause the target network node to transmit the indication to the serving network node when the timer T has expired.

3 . The network node of claim 2 , wherein a duration of the timer T is transmitted towards the target network node during L1/L2 triggered mobility (LTM) preparation.

4 . The network node of claim 2 , wherein a duration of the timer T is transmitted towards the target network node when the serving network node has triggered the UE to send the random access preamble transmission to the target cell.

5 . The network node of claim 4 , wherein the timer T is initiated based on the target network node receiving an indication from the serving network node that the UE has been instructed to perform TA acquisition with respect to a target cell among a set of candidate target cells that is controlled by the target network node.

6 . The network node of claim 5 , wherein the indication includes information about at least one of a time occasion or a contention-free random access (CFRA) resource that the UE has been configured to perform random access (RA).

7 . The network node of claim 2 , wherein the instructions when executed by the at least one processor, further cause the network node at least to:
cause the target network node to stop the timer T when the target network node successfully receives the random access preamble transmission from the UE; and cause the target network node to transmit an estimated TA of the UE towards the serving network node.

8 . The network node of claim 2 , wherein the timer T expires when the target network node fails to receive the random access preamble from the UE within a time duration of timer T.

9 . A serving network node that supports at least one of distributed unit, DU, functionality or a layer 2 protocol of a radio access network, comprising:
at least one processor; and
at least one memory storing instructions which, when executed by the at least one processor, cause the serving network node at least to:
establish a connection with a user equipment apparatus (UE) via a serving cell supported by the serving network node;
determine that L1/L2 triggered mobility (LTM) towards a target cell is configured for the UE, the target cell controlled by one of: the serving network node or a target network node, the target network node supports at least one of distributed unit, DU, functionality or a layer 2 protocol of a radio access network, and which supports a target cell;
prior to transmitting a command to connect to the target cell:
transmit, towards the UE, a first instruction configured to cause the performance of acquiring a timing advance for the target cell;
transmit, towards the target network node, a second instruction configured to cause the performance of monitoring and reporting receipt of a random access preamble from the UE; and
monitor and determine whether a report is received from the target network node within a time window, and whether the report includes an information related to a successful or an unsuccessful acquisition of the timing advance,
in case of a successful acquisition proceed with a first action, and in case of unsuccessful acquisition proceed with a second action, first and second action being different.

10 . The serving network node of claim 9 , wherein the second instruction includes at least one of a timer T duration or a value of the time window.

11 . The serving network node of claim 9 , wherein the at least one of a timer T duration or a value of the time window is received from a network node that supports at least one of central unit control plane (CU-CP) functionality or a layer 3 protocol of a radio access network.

12 . The serving network node of claim 11 , wherein the instructions when executed by the at least one processor, further cause the serving network node at least to:
transmit, towards the UE, a second instruction to acquire timing advance for the target cell, and, towards the target network node.

13 . The serving network node of claim 12 , wherein the second instruction includes at least one of: a RACH occasion different than a RACH occasion of the first instruction, a second random access preamble different than the random access preamble of the first instruction, an instruction to cause the performance of retransmitting the random access preamble of the first instruction, or an instruction that when the second instruction is sent within certain time window after the first instruction further cause the performance by the UE of increasing a power of the random access preamble transmission.

14 . The serving network node of claim 12 , wherein the instructions when executed by the at least one processor, further cause the serving network node at least to:
stop considering the target cell for a potential cell change; monitor receipt of L1 measurement report; determine whether to switch or connect UE towards a second target cell based on L1 measurement report; and transmit, towards the UE, a second instruction to acquire timing advance for the second target cell, based on the determination.

15 . The serving network node of claim 12 , wherein the instructions when executed by the at least one processor, further cause the serving network node at least to:
determine whether a successful acquisition of a timing advance related to a second target cell has been received; and stop considering the target cell for a potential cell change based on the determination.

16 . The serving network node of claim 9 , wherein the instructions when executed by the at least one processor, further cause the serving network node at least to:
receive an L1 measurement report; and determin

Assignees

• Nokia Technologies Oy

Inventors

• Awada Ahmad
• Goyal Sanjay
• Spapis Panagiotis
• Karabulut Umur
• Karimidehkordi Ali
• Gürsu Halit Murat

Classifications

• H04W74/04

  Scheduled access (hybrid access H04W74/02) · CPC title

• H04W36/0069

  in case of dual connectivity, e.g. decoupled uplink/downlink · CPC title

• H04W76/10

  Connection setup · CPC title

• H04W74/0833

  Random access procedures, e.g. with 4-step access · CPC title

• H04W56/0045

  compensating for timing error by altering transmission time · CPC title