KR-20260068013-A - METHOD AND APPARATUS FOR LTM FAILURE RECOVERY IN WIRELESS COMMUNICATION SYSTEM

Abstract

In the operation of a wireless user device, the wireless user device may obtain LTM configuration information based on LTM from a source cell. Subsequently, the wireless user device may perform uplink/downlink pre-synchronization with one or more candidate cells. Subsequently, the wireless user device may perform a first LTM attempt, and if the first LTM attempt fails, the wireless user device may perform a second LTM attempt.

Inventors

• 이원석
• 박동현

Assignees

• 주식회사 아이티엘

Dates

Publication Date

20260513

Application Date

20251106

Priority Date

20241106

Claims (12)

1. In a wireless user device, Wireless transceiver; One or more processors; and A memory that stores instructions for the wireless device when executed by one or more of the above processes, The operation of the above wireless user device is: LTM configuration information is obtained from the source cell based on LTM (L1/L2 layer triggered mobility), and The wireless user device performs uplink/downlink pre-synchronization with the one or more candidate cells, and The above wireless user device performs a first LTM attempt, and A wireless user device that performs a second LTM attempt if the first LTM attempt fails.
2. In Article 1, A wireless user device wherein the above LTM configuration information includes information on one or more candidate cells and event condition information for performing LTM.
3. In Article 2, A wireless user device that acquires a reference signal from one or more candidate cells and performs a measurement, and performs the first LTM attempt if an event condition is satisfied based on the measurement result.
4. In Article 2, A wireless user device that, upon receiving an LTM cell switch command MAC CE (medium access control element), performs the first LTM attempt based on the LTM cell switch command MAC CE.
5. In Article 1, A wireless user device that acquires a timing advance command (TAC) for each of the one or more candidate cells based on uplink/downlink pre-synchronization for the one or more candidate cells.
6. In Article 5, A wireless user device that performs the first LTM attempt by transmitting the RRC reconstruction message to the target cell if the TA of the target cell performing the first LTM is valid based on the TAC for each of the one or more candidate cells.
7. In Article 5, A wireless user device that performs the first LTM attempt by performing a RACH (random access channel) procedure to the target cell if the TA of the target cell performing the first LTM is invalid based on the TAC for each of the one or more candidate cells.
8. In Article 1, A wireless user device in which the above-mentioned first LTM attempt is determined to fail based on timer expiration.
9. In Article 1, A wireless user device that, if the first LTM attempt fails, configures a second LTM attempt on the wireless user device, and performs the second LTM attempt if the cell selected by the wireless user device based on the failure of the first LTM attempt is an LTM candidate cell.
10. In Article 9, If the TA of the LTM candidate cell selected by the wireless user device is valid, the second LTM attempt is performed by transmitting an RRC reconstruction message to the LTM candidate cell, and A wireless user device that performs a RACH procedure to the LTM candidate cell to perform the second LTM attempt if the TA of the LTM candidate cell selected by the wireless user device is invalid.
11. In Article 9, A wireless user device that, when the LTM candidate cell selected by the wireless user device is the same as the cell that performed the first LTM attempt, performs the RACH procedure with the LTM candidate cell to perform the second LTM attempt.
12. In a method of operating a wireless user device, A step of obtaining LTM configuration information based on LTM (L1/L2 layer triggered mobility) from a source cell; The step of the wireless user device performing uplink/downlink pre-synchronization with the one or more candidate cells; The step of the wireless user device performing a first LTM attempt; and A method of operation comprising the step of performing a second LTM attempt if the first LTM attempt fails.

Description

Method and apparatus for LTM failure recovery in wireless communication system The present invention relates to a method and apparatus for recovering from an LTM (L1/L2 layer triggered mobility) failure in a wireless communication system. Specifically, the invention relates to a method and apparatus for recovering when an LTM failure occurs after an LTM operation. The International Telecommunication Union (ITU) is developing the International Mobile Telecommunication (IMT) framework and standards, and recently, discussions for 5th generation (5G) communication are underway through a program called "IMT for 2020 and beyond." In order to meet the requirements presented in "IMT for 2020 and beyond," discussions are underway to support various numerologies for time-frequency resource unit standards in 3GPP (3rd Generation Partnership Project) NR (New Radio) systems, taking into account various scenarios, service requirements, and potential system compatibility. Mobility support measures may be necessary in wireless communication systems, and the following describes measures for this purpose. FIG. 1 is a drawing for illustrating an NR frame structure to which the present disclosure can be applied. FIG. 2 is a diagram showing an NR resource structure to which the present disclosure can be applied. FIG. 3 is a diagram showing cell-level mobility and beam-level mobility applicable to the present disclosure. FIG. 4 is a diagram showing an LTM scenario applicable to the present disclosure. FIG. 5 is a diagram showing signaling and setting information in the LTM preparation stage applicable to the present disclosure. FIG. 6 is a diagram illustrating the signaling and setting procedure for an initial synchronization step applicable to the present disclosure. FIG. 7 is a diagram illustrating a method by which a terminal applicable to the present disclosure performs uplink synchronization. FIG. 8 is a diagram showing signaling for an LTM cell change execution procedure applicable to the present disclosure. FIG. 9 is a drawing showing a cell change MAC CE applicable to the present disclosure. FIG. 10 is a diagram showing the signaling of the LTM cell change completion step applicable to the present disclosure. FIG. 11 is a diagram illustrating an inter-base station handover procedure applicable to the present disclosure. FIG. 12 is a diagram illustrating a procedure for performing an intra-AMF/UPF conditional handover applicable to the present disclosure. FIG. 13 is a diagram showing a cell switch command MAC CE applicable to the present disclosure. FIG. 14 is a diagram showing a candidate cell TCI state activation/deactivation MAC CE applicable to the present disclosure. FIG. 15 is a diagram illustrating an LTM failure handling method applicable to the present disclosure. FIG. 16 is a diagram illustrating a conditional LTM failure recovery procedure applicable to the present disclosure. FIG. 17 is a diagram illustrating a conditional LTM failure recovery procedure applicable to the present disclosure. FIG. 18 is a diagram illustrating a conditional LTM failure recovery procedure applicable to the present disclosure. FIG. 19 is a diagram illustrating a conditional LTM failure recovery procedure applicable to the present disclosure. FIG. 20 is a diagram illustrating a RACH-less based LTM failure handling method in the event of an LTM failure applicable to the present disclosure. FIG. 21 is a diagram illustrating a conditional LTM failure recovery procedure applicable to the present disclosure. FIG. 22 is a flowchart illustrating a RACH-less based LTM retry method following a C-LTM failure applicable to the present disclosure. FIG. 23 is a flowchart illustrating a RACH-less based LTM retry method following LTM failure applicable to the present disclosure. FIG. 24 is a flowchart illustrating a RACH-less based LTM retry method following a C-LTM failure applicable to the present disclosure. FIG. 25 is a flowchart illustrating a RACH-less based LTM retry method following LTM failure applicable to the present disclosure. FIG. 26 is a diagram illustrating the operation method of a wireless user device to which the present disclosure applies. FIG. 27 is a drawing showing a device configuration applicable to the present disclosure. Hereinafter, embodiments of the present disclosure are described in detail with reference to the attached drawings so that those skilled in the art can easily implement them. However, the present disclosure may be embodied in various different forms and is not limited to the embodiments described herein. In describing the embodiments of the present disclosure, if it is determined that a detailed description of known configurations or functions may obscure the essence of the present disclosure, such detailed description is omitted. Furthermore, parts of the drawings unrelated to the description of the present disclosure have been omitted, and similar parts are denoted by similar reference numerals. In the