Apparatus and method for generating conditional LTM execution conditions in disaggregated gnb in wireless communication system

Abstract

The present disclosure relates to a wireless communication system. Specifically, the present disclosure relates to an apparatus and a method for generating conditional L1 / L2-triggered mobility (LTM) execution conditions in a disaggregated next generation node B (gNB) in a wireless communication system.

Description

Device and method for generating a conditional LTM execution condition of a detachable GNB in ​​a wireless communication system

[0001] The present disclosure relates to a wireless communication system. Specifically, the present disclosure relates to an apparatus and method for generating conditional LTM (L1 / L2-triggered Mobility) execution conditions in a disaggregated gNB (Next Generation Node B) in a wireless communication system.

[0002]

[0003] In Release-18, a new type of mobility solution called LTM (L1 / L2-based Mobility) was defined to reduce latency, overhead, and downtime during serving cell changes. To achieve faster serving cell changes, early DL / UL synchronization prior to cell switching and L1 measurement-based handover (triggered by MAC CE) were specified for LTM. In Release-19, a new WI was approved for Phase 4 of NR Mobility Enhancement, one of which is to support conditional LTM within the CU. (A new type of mobility solution called LTM (L1 / L2 Triggered Mobility) was specified in Rel-18 to reduce latency, overhead, and interruption time during serving cell change. In order to achieve faster serving cell change, early DL / UL synchronizations before cell switch, and HO based on L1 measurement (and triggered by MAC CE) were specified for LTM. In Rel-19, a new WI has been approved for NR mobility enhancement phase 4 [1], where one of the objectives is to specify support for Conditional Intra-CU LTM.)

[0004] In Rel-18 LTM, the decision of switching the serving cell for a UE was made exclusively by the network. The UE was configured to report (periodic) L1 measurements of candidate cells, based on which the current serving DU determined which cell the UE should be handed over to and explicitly instructed the UE to execute the cell switch via an L2 Cell Switch Command (CSC) MAC CE.

[0005] While this L1 / L2-based mobility successfully reduced cell switching downtime (particularly thanks to the early DL / UL synchronization mechanism developed alongside it), it also had limitations. Network-based mobility is inherently vulnerable to mobility failure because "cell switching" typically occurs when a terminal is close to the edge of the cell coverage area, where signal strength is weak and the quality of the serving cell has already deteriorated. Under these conditions, the terminal may fail to receive a cell switching command from the current serving cell, or the command may be delayed due to multiple retransmissions, leading to improper handover timing and an increased risk of mobility failure. (While this L1 / L2-based mobility successfully reduced cell switching interruption time (especially with the early DL / UL synchronization mechanisms developed together), it also had limitations: The network-triggered mobility is inherently prone to mobility failures, because "cell switching" normally occurs when the UE is near the edge of the cell's coverage area, where signal strength is weak and the serving cell quality has already deteriorated. In such conditions, the UE may fail to receive the cell switch command from the current serving cell, or the command could be delayed due to multiple retransmissions, leading to poor handover timing and an increased risk of mobility failures.).

[0006] Release-19’s Conditional LTM aims to complement the network-based mobility of existing LTMs by allowing the terminal to initiate a handover. This approach is useful for addressing the instability inherent in all network-based mobility solutions, as it eliminates the need for the network to direct the terminal to switch cells. Instead of issuing an immediate command to switch cells, the network pre-sets an "execute" condition for switching while the current serving cell is still in good condition. The terminal then evaluates this condition and autonomously triggers a handover when it is met, improving the timing and success rate of cell switching. (Conditional LTM in Rel-19 aims to serve as a complementary approach to the existing network-triggered mobility in LTM by embracing the handover initiation from the UE. This approach is useful in addressing the inherent unreliability found in any network-triggered mobility solution, as it can remove the need for the network to instruct the UE to do a cell switch. Instead of issuing an immediate cell switch command, the network pre-configures "execution" conditions for cell switching while the current serving cell is still in good condition.The UE then evaluates these conditions and autonomously triggers the handover itself when they are met, thereby improving the timing and success rate of cell switches.).

[0007] However, the current mechanisms specified by 3GPP for Intra-CU LTM lack support for the Conditional LTM feature, which is particularly evident in disaggregated gNB deployments where the CU and DU are interconnected via the F1 interface. This specification proposes several mechanisms to add "Conditional LTM" on top of the existing Intra-CU LTM feature, ensuring that the two functions can work seamlessly together in such deployments.

[0008]

[0009] To solve the above-mentioned problem, the present disclosure provides an apparatus and method for generating a conditional LTM execution condition of a detachable gNB in ​​a wireless communication system.

[0010] The technical problems to be solved in this disclosure are not limited to those mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art to which this disclosure belongs from the description below.

[0011]

[0012] According to various embodiments of the present disclosure, a method performed by a first node comprises the step of transmitting a first message of a request related to a UE context (user equipment context) to a second node, wherein the first message is related to a request for generating a conditional L1 / L2-Triggered Mobility execution condition, and the first message includes a candidate cell ID related to the first message; and in response to the first message, receiving a second message from the second node that includes configuration information.

[0013] According to various embodiments of the present disclosure, a method performed by a second node comprises the step of receiving a first message of a request related to a UE context (user equipment context) from a first node, wherein the first message is related to a request for generating a conditional L1 / L2-Triggered Mobility execution condition, and the first message includes a candidate cell ID related to the first message; and in response to the first message, the method comprises the step of transmitting a second message to the first node that includes configuration information.

[0014] According to various embodiments of the present disclosure, a first node is provided, comprising: a transceiver; at least one processor; and at least one memory operably connected to the at least one processor and storing instructions for performing operations when executed by the at least one processor, wherein the operations include all steps of a method performed by the first node according to various embodiments of the present disclosure.

[0015] According to various embodiments of the present disclosure, a second node is provided, comprising: a transceiver; at least one processor; and at least one memory operably connected to the at least one processor and storing instructions for performing operations when executed by the at least one processor, wherein the operations include all steps of a method performed by the second node according to various embodiments of the present disclosure.

[0016] According to various embodiments of the present disclosure, a control device for controlling a first node in a wireless communication system comprises at least one processor and at least one memory operably connected to said at least one processor, said at least one memory stores instructions for performing operations based on execution by said at least one processor, said operations include all steps of a method performed by the first node according to various embodiments of the present disclosure.

[0017] According to various embodiments of the present disclosure, a control device for controlling a second node in a wireless communication system comprises at least one processor and at least one memory operably connected to said at least one processor, said at least one memory stores instructions for performing operations based on execution by said at least one processor, said operations include all steps of a method performed by the second node according to various embodiments of the present disclosure.

[0018] According to various embodiments of the present disclosure, one or more non-transitory computer-readable media storing one or more instructions, wherein the one or more instructions perform operations based on execution by one or more processors, and said operations include all steps of a method performed by a first node according to various embodiments of the present disclosure.

[0019] According to various embodiments of the present disclosure, one or more non-transitory computer-readable media storing one or more instructions, wherein the one or more instructions perform operations based on execution by one or more processors, and said operations include all steps of a method performed by a second node according to various embodiments of the present disclosure.

[0020]

[0021] To solve the aforementioned problems, the present disclosure may provide an apparatus and method for generating a conditional LTM execution condition of a detachable gNB in ​​a wireless communication system.

[0022]

[0023] The drawings attached below are intended to aid in understanding the present disclosure and may provide embodiments of the present disclosure together with the detailed description. However, the technical features of the present disclosure are not limited to specific drawings, and the features disclosed in each drawing may be combined with one another to form new embodiments. Reference numerals in each drawing may denote structural elements.

[0024] FIG. 1 is a diagram illustrating an example of physical channels used in a system applicable to the present disclosure and a general signal transmission method using them.

[0025] FIG. 2 is a drawing illustrating an example of a wireless frame structure used in a system applicable to the present disclosure.

[0026] FIG. 3 is a drawing illustrating an example of a slot structure used in a system applicable to the present disclosure.

[0027] FIG. 4 is a drawing illustrating an example of a slot structure of a wireless frame used in a system applicable to the present disclosure.

[0028] FIG. 5 is a diagram illustrating an example of an LTM signaling procedure (Signalling procedure for LTM) in a system applicable to the present disclosure.

[0029] FIG. 6 is a drawing illustrating an example of an Intra-gNB-DU LTM in a system applicable to the present disclosure.

[0030] FIG. 7 is a drawing illustrating an example of an Intra-gNB-DU LTM in a system applicable to the present disclosure.

[0031] FIG. 8 is a drawing illustrating an example of an Inter-gNB-DU LTM in a system applicable to the present disclosure.

[0032] FIG. 9 is a drawing illustrating an example of an Inter-gNB-DU LTM in a system applicable to the present disclosure.

[0033] FIG. 10 is a diagram illustrating an example of a process for supporting the generation and configuration of Conditional LTM execution conditions in a system applicable to the present disclosure.

[0034] FIG. 11 is a diagram illustrating an example of a process for supporting the generation and configuration of Conditional LTM execution conditions in a system applicable to the present disclosure.

[0035] FIG. 12 is a diagram illustrating an example of the operation process of a first node in a system applicable to the present disclosure.

[0036] FIG. 13 is a diagram illustrating an example of the operation process of a second node in a system applicable to the present disclosure.

[0037] FIG. 14 is a drawing illustrating an example of the structure of a first node and a second node in a system applicable to the present disclosure.

[0038]

[0039] In various embodiments of the present disclosure, "A or B" may mean "only A," "only B," or "both A and B." Alternatively, in various embodiments of the present disclosure, "A or B" may be interpreted as "A and / or B." For example, in various embodiments of the present disclosure, "A, B or C" may mean "only A," "only B," "only C," or "any combination of A, B and C."

[0040] In various embodiments of the present disclosure, a slash ( / ) or a comma used may mean "and / or." For example, "A / B" may mean "A and / or B." Accordingly, "A / B" may mean "only A," "only B," or "both A and B." For example, "A, B, C" may mean "A, B or C."

[0041] In various embodiments of the present disclosure, "at least one of A and B" may mean "only A," "only B," or "both A and B." Additionally, in various embodiments of the present disclosure, the expressions "at least one of A or B" or "at least one of A and / or B" may be interpreted as synonymous with "at least one of A and B."

[0042] Additionally, in various embodiments of the present disclosure, “at least one of A, B and C” may mean “only A,” “only B,” “only C,” or “any combination of A, B and C.” Also, “at least one of A, B or C” or “at least one of A, B and / or C” may mean “at least one of A, B and C.”

[0043] Additionally, parentheses used in various embodiments of the present disclosure may mean "for example." Specifically, when indicated as "control information (PDCCH)," "PDCCH" may be proposed as an example of "control information." In other words, the "control information" of various embodiments of the present disclosure is not limited to "PDCCH," and "PDDCH" may be proposed as an example of "control information." Furthermore, even when indicated as "control information (i.e., PDCCH)," "PDCCH" may be proposed as an example of "control information."

[0044] Technical features described individually within one drawing in various embodiments of the present disclosure may be implemented individually or simultaneously.

[0045]

[0046] Common signal transmission methods in 3GPP

[0047] Physical channels and general signal transmission

[0048] FIG. 1 is a diagram illustrating an example of physical channels used in a system applicable to the present disclosure and a general signal transmission method using them. Specifically, FIG. 1 illustrates physical channels used in a 3GPP system and a general signal transmission.

[0049] Figure 1 illustrates physical channels used in a 3GPP system and general signal transmission. In a wireless communication system, a terminal receives information from a base station via a downlink (DL) and transmits information to the base station via an uplink (UL). The information transmitted and received by the base station and the terminal includes data and various control information, and various physical channels exist depending on the type and purpose of the information they transmit and receive.

[0050] When the power is turned on again after being off, or when a terminal newly enters a cell, it performs an initial cell search operation, such as synchronizing with the base station (S11). To do this, the terminal receives PSCH (Primary Synchronization Channel) and SSCH (Secondary Synchronization Channel) from the base station to synchronize with the base station and obtain information such as cell ID (cell identity). In addition, the terminal can obtain cell broadcast information by receiving PBCH (Physical Broadcast Channel) from the base station. Furthermore, during the initial cell search phase, the terminal can check the downlink channel status by receiving DL RS (Downlink Reference Signal).

[0051] After completing the initial cell search, the terminal can obtain more specific system information by receiving the PDCCH (Physical Downlink Control Channel) and the corresponding PDSCH (Physical Downlink Control Channel) (S12).

[0052] Subsequently, the terminal may perform a Random Access Procedure to complete the connection to the base station (S13~S16). Specifically, the terminal transmits a preamble through a PRACH (Physical Random Access Channel) (S13) and receives a RAR (Random Access Response) for the preamble through a PDCCH and a corresponding PDSCH (S14). Subsequently, the terminal transmits a PUSCH (Physical Uplink Shared Channel) using scheduling information within the RAR (S15) and may perform a Conflict Resolution Procedure such as a PDCCH and a corresponding PDSCH (S16).

[0053] A terminal that has performed the procedure described above may subsequently perform PDCCH / PDSCH reception (S17) and PUSCH / PUCCH (Physical Uplink Control Channel) transmission (S18) as a general uplink / downlink signal transmission procedure. The control information transmitted by the terminal to the base station is referred to as UCI (Uplink Control Information). UCI includes HARQ ACK / NACK (Hybrid Automatic Repeat and reQuest Acknowledgement / Negative-ACK), SR (Scheduling Request), CSI (Channel State Information), etc. CSI includes CQI (Channel Quality Indicator), PMI (Precoding Matrix Indicator), RI (Rank Indication), etc. UCI is generally transmitted via PUCCH, but it may be transmitted via PUSCH if control information and data need to be transmitted simultaneously. Additionally, the terminal may transmit UCI non-periodically via PUSCH in response to requests / instructions from the network.

[0054]

[0055] OFDM (Orthogonal Frequency Division Multiplexing) Numerology

[0056] The new RAT system uses the OFDM transmission method or a similar transmission method. The new RAT system may follow OFDM parameters different from those of LTE. Alternatively, the new RAT system may follow the existing LTE / LTE-A numerology but have a larger system bandwidth (e.g., 100 MHz). Or, a single cell may support multiple numerologies. That is, UEs operating with different numerologies can coexist within a single cell.

[0057]

[0058] radio frame structure

[0059] FIG. 2 is a drawing illustrating an example of the structure of a wireless frame used in a system applicable to the present disclosure.

[0060] In NR, uplink and downlink transmissions consist of frames. A radio frame has a length of 10 ms and is defined as two 5 ms half-frames (HF). A half-frame is defined as five 1 ms subframes (SF). A subframe is divided into one or more slots, and the number of slots within a subframe depends on the subcarrier spacing (SCS). Each slot contains 12 or 14 OFDM(A) symbols depending on the cyclic prefix (CP). When a standard CP is used, each slot contains 14 symbols. When an extended CP is used, each slot contains 12 symbols. Here, the symbols may include OFDM symbols (or CP-OFDM symbols) or SC-FDMA symbols (or DFT-s-OFDM symbols).

[0061] Table 1 illustrates how the number of symbols per slot, the number of slots per frame, and the number of slots per subframe vary depending on the SCS when a standard CP is used.

[0062] SCS (15*2^u)N slot symb N frame,u slot N subframe,u slot 15KHz (u=0)1410130KHz (u=1)1420260KHz (u=2)14404120KHz (u=3)14808240KHz (u=4)1416016

[0063] N slot symb is the number of symbols in the slot. N frame,u slotis the number of slots within the frame. N subframe,u slot is the number of slots within the subframe.

[0064]

[0065] Table 2 illustrates how, when extended CP is used, the number of symbols per slot, the number of slots per frame, and the number of slots per subframe vary depending on the SCS.

[0066] SCS (15*2^u)N slot symb N frame,u slot N subframe,u slot 60KHz (u=2)12404

[0067] NR supports multiple numerologies (or subcarrier spacing (SCS)) to support various 5G services. For example, when the SCS is 15 kHz, it supports a wide area in traditional cellular bands; when the SCS is 30 kHz / 60 kHz, it supports dense-urban, lower latency, and wider carrier bandwidth; and when the SCS is 60 kHz or higher, it supports a bandwidth greater than 24.25 GHz to overcome phase noise.

[0068] The NR frequency band can be defined by two types of frequency ranges (FR1, FR2). The numerical values ​​of the frequency ranges may change; for example, the two types of frequency ranges (FR1, FR2) may be as shown in Table 3 below. For convenience of explanation, among the frequency ranges used in the NR system, FR1 may mean "sub 6GHz range" and FR2 may mean "above 6GHz range" and may be referred to as millimeter wave (mmW).

[0069] Frequency Range designationCorresponding frequency rangeSubcarrier SpacingFR1450MHz - 6000MHz15, 30, 60kHzFR224250MHz - 52600MHz60, 120, 240kHz

[0070] As described above, the numerical value of the frequency range of the NR system may change. For example, FR1 may include a band of 410 MHz to 7125 MHz as shown in Table 4 below. That is, FR1 may include a frequency band of 6 GHz (or 5850, 5900, 5925 MHz, etc.) or higher. For example, the frequency band of 6 GHz (or 5850, 5900, 5925 MHz, etc.) or higher included within FR1 may include an unlicensed band. The unlicensed band may be used for various purposes, for example, for communication for vehicles (e.g., autonomous driving).

[0071] Frequency Range designationCorresponding frequency rangeSubcarrier SpacingFR1410MHz - 7125MHz15, 30, 60kHzFR224250MHz - 52600MHz60, 120, 240kHz

[0072] In an NR system, the OFDM(A) numerology (e.g., SCS, CP length, etc.) can be configured differently among multiple cells that are merged into a single terminal. Accordingly, the (absolute time) interval of a time resource (e.g., SF, slot, or TTI) (collectively referred to as TU (Time Unit) for convenience) composed of the same number of symbols can be configured differently among the merged cells.

[0073]

[0074] FIG. 3 is a drawing illustrating an example of a slot structure used in a system applicable to the present disclosure.

[0075] A slot contains multiple symbols in the time domain. For example, in the case of a standard CP, one slot contains 7 symbols, whereas in the case of an extended CP, one slot contains 6 symbols. A carrier contains multiple subcarriers in the frequency domain. A Resource Block (RB) is defined as multiple (e.g., 12) consecutive subcarriers in the frequency domain. A Bandwidth Part (BWP) is defined as multiple consecutive (P)RBs in the frequency domain and can correspond to a single numerology (e.g., SCS, CP length, etc.). A carrier can contain up to N (e.g., 5) BWPs. Data communication is performed through the active BWPs, and only one BWP can be active for a single terminal. In the resource grid, each element is referred to as a Resource Element (RE) and can be mapped to a single complex symbol.

[0076]

[0077] FIG. 4 is a drawing illustrating an example of a slot structure of a wireless frame used in a system applicable to the present disclosure.

[0078] Figure 4 illustrates the slot structure of a frame of an NR system as an exemplary system.

[0079] The frame structure of NR is characterized by a self-contained structure in which a DL control channel, DL or UL data, and a UL control channel can all be included within a single slot unit, as shown in the example of FIG. 4. In this case, DL data scheduling information and UL data scheduling information can be transmitted in the DL control channel, while ACK / NACK information for DL ​​data, CSI information (modulation and coding scheme information, MIMO transmission-related information, etc.), and scheduling requests can be transmitted in the UL control channel. In FIG. 4, a time gap for DL-to-UL or UL-to-DL switching may exist between the control area and the data area. Additionally, some of the DL control, DL data, UL data, and UL control channels may not be configured within a single slot. Alternatively, the order of channels constituting a single slot may vary (for example, DL control, DL data, UL control, UL data, or UL control, UL data, DL control, DL data, etc.).

[0080]

[0081] The present disclosure relates to the generation and configuration of Conditional LTM (L1 / L2-triggered Mobility) execution conditions in a disaggregated gNB.

[0082]

[0083] Technical terms used in this disclosure

[0084] Terms defined in TS 38.300, TS 38.401

[0085] - CU (Centralized Unit): A logical node that controls the operation of one or more DUs, hosting the RRC, SDAP, and PDCP protocols of the gNB or the en-gNB. The CU terminates the F1 interface connected to the DU.

[0086] - DU (Distributed Unit): A logical node hosting the RLC, MAC, and PHY layers of the gNB or en-gNB, and its operation is partly controlled by the CU. One DU supports one or multiple cells, and a single cell is supported by only one DU. The DU terminates the F1 interface connected to the CU.

[0087] - LTM (L1 / L2 Triggered Mobility): A PCell (or PSCell) cell switch procedure that the network triggers via MAC CE based on L1 measurements.

[0088]

[0089] Explanation of background technology

[0090] TS 38.300 v18.2.0

[0091] 9.2.3.5 L1 / L2 Triggered Mobility

[0092] 9.2.3.5.1 General

[0093] LTM is a procedure in which a gNB receives L1 measurement report(s) from a UE, and based on this, the gNB may change the UE serving cell by a cell switch command signaled via a MAC CE. The cell switch command indicates an LTM candidate configuration that the gNB previously prepared and provided to the UE through RRC signaling. Then, the UE switches to the target configuration according to the cell switch command. The LTM procedure can be used to reduce mobility latency as described in Annex G.

[0094] When configured by the network, it is possible to activate the TCI states of one or multiple cells that differ from the current serving cell. For instance, the TCI states of the LTM candidate cells can be activated in advance before any of those cells become the serving cell. This allows the UE to be DL synchronized with those cells, thereby facilitating a faster cell switch to one of those cells when a cell switch is triggered. All activated TCI states, except those received in the cell switch command, are deactivated upon LTM cell switch execution.

[0095] When configured by the network, it is possible to initiate the UL TA acquisition (referred to as Early TA) procedure for one or more cells different from the current serving cell. If a cell has the same NTA as the current serving cell or if NTA=0, the Early TA acquisition procedure is not required. The network may request the UE to perform Early TA acquisition for candidate cells prior to cell switching. The Early TA acquisition procedure is realized either by being triggered by the PDCCH command as specified in Section 9.2.6 or through UE-based TA measurement configured by the RRC. In the former case, the gNB / gNB-DU to which the candidate cell belongs calculates the TA value and transmits it via the gNB-CU to the gNB / gNB-DU to which the serving cell belongs. When the serving cell triggers LTM cell switching, it sends the TA value in the LTM cell switching command MAC CE. In the latter case, the UE performs TA measurement for the candidate cell after being configured by the RRC, but the exact time at which the UE performs the TA measurement depends on the UE implementation. If the cell switching command does not include a valid TA value, the UE applies a self-measured TA value and performs LTM without RACH. The network may also send the TA value to the LTM cell switching command MAC CE without early TA acquisition. (When configured by the network, it is possible to initiate the UL TA acquisition (called early TA) procedure of one or multiple cells that are different from the current serving cells. If the cell has the same NTA as the current serving cells or NTA=0, the early TA acquisition procedure is not required.)The network may request the UE to perform early TA acquisition of a candidate cell before a cell switch. The early TA acquisition procedure is triggered by PDCCH order as specified in clause 9.2.6 or realized through UE-based TA measurement as configured by RRC. In the former case, the gNB / gNB-DU to which the candidate cell belongs calculates the TA value and sends it to the gNB / gNB-DU to which the serving cell belongs via gNB-CU. The serving cell sends the TA value in the LTM cell switch command MAC CE when triggering LTM cell switch. In the latter case, the UE performs TA measurement for the candidate cells after being configured by RRC but the exact time the UE performs TA measurement is up to UE implementation. The UE applies the TA value measured by itself and performs RACH-less LTM upon receiving the cell switch command, if it does not include any valid TA value. The network may also send a TA value in the LTM cell switch command MAC CE without early TA acquisition.).

[0096] Depending on the availability of a valid TA value, the UE performs either a RACH-free LTM or a RACH-based LTM cell switch. If a valid TA value is provided in the cell switch command, the UE applies the TA value as directed by the network. If UE-based TA measurement is configured but a valid TA value is not provided in the cell switch command, the UE applies a valid TA value itself if available. Whenever a valid TA value is available, the UE performs a RACH-free LTM cell switch upon receiving a cell switch command. If a valid TA value is not available, the UE performs a RACH-based LTM cell switch. (Depending on the availability of a valid TA value, the UE performs either a RACH-less LTM or RACH-based LTM cell switch. If the valid TA value is provided in the cell switch command, the UE applies the TA value as instructed by the network. In the case where UE-based TA measurement is configured, but no valid TA value is provided in the cell switch command, the UE applies the valid TA value by itself if available. The UE performs RACH-less LTM cell switch upon receiving the cell switch command whenever a valid TA value is available. If no valid TA value is available, the UE performs RACH-based LTM cell switch.)

[0097] Regardless of whether the UE is configured for UE-based TA measurement for a specific candidate cell, the UE will still follow the PDCCH order, which includes performing a random access procedure toward one or more candidate cells. This also applies to candidate cells for which the UE is capable of deriving TA values ​​itself. Additionally, regardless of whether the UE has already performed a random access procedure toward the candidate cells, the UE will still follow the UE-based measurement configuration if configured by the network.

[0098] For LTM without RACH, the UE connects to the target cell using either a configured grant or a dynamic grant. A configured grant is provided from the LTM candidate configuration, and the UE selects a configured grant opportunity associated with the beam indicated in the cell switch command. When the LTM cell switch to the target cell begins, the UE starts PDCCH monitoring on the target cell for dynamic scheduling. Before the LTM without RACH procedure is completed, the UE must not trigger a random access procedure if there are no valid PUCCH resources for the triggered SR. (For RACH-less LTM, the UE accesses the target cell using either a configured grant or a dynamic grant. The configured grant is provided in the LTM candidate configuration, and the UE selects the configured grant occasion associated with the beam indicated in the cell switch command. Upon initiation of LTM cell switch to the target cell, the UE starts to monitor PDCCH on the target cell for dynamic scheduling. Before RACH-less LTM procedure completion, the UE shall not trigger random access procedure if it does not have a valid PUCCH resource for triggered SRs.)

[0099] The following principles apply to LTM: security keys are retained during LTM cell switching; subsequent LTMs are supported.

[0100] (The following principles apply to LTM: Security keys are maintained upon an LTM cell switch; Subsequent LTM is supported.)

[0101] LTM supports both in-gNB-DU mobility and between gNB-DU mobility within the same gNB-CU. LTM supports both in-frequency and inter-frequency mobility, including mobility to inter-frequency cells other than the current serving cell. LTM is supported only for licensed spectrum. The following scenarios are supported: PCell changes in non-CA and non-DC scenarios; PCell and SCell(s) changes in CA scenarios; duplex scenarios: including PCell and MCG SCell(s) changes and in-SN PSCell and SCG SCell(s) changes without MN intervention. LTM is not supported for simultaneous PCell and PSCell changes. (LTM supports both intra-gNB-DU and inter-gNB-DU mobility within the same gNB-CU. LTM supports both intra-frequency and inter-frequency mobility, including mobility to inter-frequency cell that is not a current serving cell. LTM is supported only for licensed spectrum. The following scenarios are supported: PCell change in non-CA scenario and non-DC scenario; PCell and SCell(s) change in CA scenario; Dual connectivity scenario: including PCell and MCG SCell(s) change and intra-SN PSCell and SCG SCell(s) change without MN involvement for simultaneous PCell and PSCell change is not supported.)

[0102] While the UE has stored LTM candidate configurations, the UE can also execute any L3 handover except for DAPS handover. In the RRC message that the UE applies to any L3 handover (except DAPS), LTM candidate configurations can be added, modified, or released by the target cell.

[0103]

[0104] FIG. 5 is a diagram illustrating an example of an LTM signaling procedure (Signalling procedure for LTM) in a system applicable to the present disclosure.

[0105] Figure 5 corresponds to the LTM signaling procedure in Figure 9.2.3.5.2-1.

[0106] 9.2.3.5.2 C-Plane Handling

[0107] The cell switch command is conveyed to a MAC CE, which contains the information necessary to perform the LTM cell switch.

[0108] The overall procedure for LTM is shown in Figure 9.2.3.5.2-1. Subsequent LTM is performed by repeating the early synchronization, LTM cell switch execution, and LTM cell switch completion steps without releasing other LTM candidate configurations after each LTM cell switch completion. The general procedure over the air interface is applicable to SCG LTM. Further details of SCG LTM can be found in TS 37.340

[0021] .

[0109] The LTM procedure is as follows:

[0110] 1. The UE sends a `MeasurementReport` message to the gNB. The gNB decides to configure LTM and initiates LTM preparation.

[0111] 2. The gNB transmits an `RRCReconfiguration` message to the UE including the LTM candidate configurations.

[0112] 3. The UE stores the LTM candidate configurations and transmits an `RRCReconfigurationComplete` message to the gNB.

[0113] 4.a. The UE performs DL synchronization with the LTM candidate cell(s) before receiving the cell switch command. The UE may activate and deactivate the TCI states of the LTM candidate cell(s), as triggered by the gNB.

[0114] 4.b. Before receiving a cell switch command, the UE may perform UL synchronization with the LTM candidate cell(s) by using a UE-based TA measurement, if configured, or by sending a preamble to the candidate cell as triggered by the gNB. If a UE-based TA measurement is configured, the UE obtains the TA value of the candidate cell(s) through the measurement. The UE performs an early TA acquisition with the candidate cell(s) at the request of the network before receiving a cell switch command, as specified in Section 9.2.6. This is done via a CFRA triggered by a PDCCH command from the source cell, after which the UE sends a preamble to the designated candidate cell. To minimize data interruption in the source cell caused by the CFRA toward the candidate cell(s), the UE does not receive random access responses from the network for the purpose of obtaining the TA value, and the TA value of the candidate cell is indicated in the cell switch command. The UE does not maintain a TA timer for the candidate cell and relies on the network implementation to guarantee TA validity. (The UE may perform UL synchronization with LTM candidate cell(s) before receiving the cell switch command, by using UE-based TA measurement, if configured, and / or by transmitting a preamble towards the candidate cell, as triggered by the gNB. When UE-based TA measurement is configured, UE acquires the TA value(s) of the candidate cell(s) by measurement.UE performs early TA acquisition with the candidate cell(s) as requested by the network before receiving the cell switch command as specified in clause 9.2.6. This is done via CFRA triggered by a PDCCH order from the source cell, following which the UE sends preamble towards the indicated candidate cell. In order to minimize the data interruption of the source cell due to CFRA towards the candidate cell(s), the UE does not receive random access response from the network for the purpose of TA value acquisition and the TA value of the candidate cell is indicated in the cell switch command. The UE does not maintain the TA timer for the candidate cell and relies on network implementation to guarantee the TA validity.).

[0115] 5. The UE performs L1 measurements on the configured LTM candidate cell(s) and transmits L1 measurement reports to the gNB. L1 measurements should be performed while RRC reconfiguration (step 2) is applicable.

[0116] 6. The gNB decides to execute a cell switch to a target cell and transmits an LTM cell switch command MAC CE triggering a cell switch by including a target configuration ID which indicates the index of the candidate configuration of the target cell, a beam indicated with a TCI state or beams indicated with DL and UL TCI states, and a timing advance command for the target cell, if available. The UE switches to the target cell and applies the candidate configuration indicated by the target configuration ID.

[0117] 7. As specified in clause 5.18.35 of TS 38.321[6], if the UE does not have a valid TA of the target cell, the UE performs the random access procedure towards the target cell.

[0118] 8. The UE completes the LTM cell switch procedure by sending the `RRCReconfigurationComplete` message to the target cell. If the UE performed an RA procedure in step 7, the UE considers the LTM cell switch execution to be successfully completed when the random access procedure is successfully completed. For RACH-less LTM, the UE considers the LTM cell switch execution to be successfully completed when it determines that the network has successfully received its first UL data.

[0119] Steps 4 through 8 can be performed multiple times for subsequent LTM cell switch executions using the LTM candidate configuration(s) provided in step 2.

[0120] The procedure over the air interface described in Figure 9.2.3.5.2-1 is applicable to both intra-gNB-DU LTM and inter-gNB-DU LTM. The overall LTM procedures over the F1-C interface are described in TS 38.401[4].

[0121] 9.2.3.5.3 U-Plane Handling

[0122] After receiving an LTM cell switch command MAC CE, the UE performs a MAC reset. Whether the UE performs RLC re-establishment and PDCP data recovery during cell switching is explicitly controlled by the network through RRC signaling.

[0123] 9.2.3.6 RACH-less handover

[0124] - During the intra-gNB HO procedure, RACH-less handover can be configured for a UE. The RACH-less handover procedure applies the following functionality:

[0125] The UE uses the same timing advance value at the target cell as in the source cell, or uses a timing advance value of 0.

[0126] The handover command for the UE may include a beam identifier for the beam to be used by the UE at the target cell. The beam may be determined based on a UE measurement report or left up to the gNB implementation, e.g., using the target cell's knowledge about the beam(s) used by the UE at the co-located source cell.

[0127] The handover command may include a configured UL grant. The UE can fall back to RACH when there is no valid configured uplink grant. Alternatively, a UL grant may be dynamically signaled by the target cell.

[0128] The UE transmits the RRCReconfigurationComplete message using the configured or dynamically signaled UL grant. Successful UL data reception on the target cell terminates the RACH-less handover execution.

[0129]

[0130] FIG. 6 is a drawing illustrating an example of an Intra-gNB-DU LTM in a system applicable to the present disclosure.

[0131] FIG. 7 is a drawing illustrating an example of an Intra-gNB-DU LTM in a system applicable to the present disclosure.

[0132] Figures 6 and 7 correspond to Figure 8.2.1.4-1 (Figure 8.2.1.4-1) Intra-gNB-DU LTM.

[0133] TS 38.401 v18.2.0

[0134] 8.2.1.4 LTM within gNB-DU (Intra-gNB-DU LTM)

[0135] This procedure is used when the UE moves within the same gNB-DU during NR operation for LTM. Figure 8.2.1.4-1 shows the intra-gNB-DU LTM procedure for intra-NR.

[0136] 1. The UE sends a `MeasurementReport` message (L3 measurement result) containing measurements of neighboring cells to the gNB-DU. The gNB-DU sends an `UL RRC MESSAGE TRANSFER` message conveying the received `MeasurementReport` message to the gNB-CU.

[0137] 2. The gNB-CU decides to initiate LTM configuration.

[0138] 3. The gNB-CU sends a `UE CONTEXT MODIFICATION REQUEST` message to the gNB-DU for each candidate cell, containing one candidate cell ID and a CSI resource configuration for the subsequent LTM. The gNB-CU may provide the gNB-DU with a list of LTM configuration ID mappings. The gNB-CU may request a PRACH resource from the gNB-DU. The gNB-CU may request the gNB-DU to provide a lower-tier configuration for the purpose of creating a reference configuration, or may provide the lower-tier reference configuration to the gNB-DU. (The gNB-CU sends a `UE CONTEXT MODIFICATION REQUEST` message to the gNB-DU for each candidate cell, containing one candidate cell ID and the CSI resource configuration for subsequent LTM. The gNB-CU may provide the LTM configuration ID mapping list to the gNB-DU. The gNB-CU may request PRACH resources from the gNB-DU. The gNB-CU may request the gNB-DU to provide the lower layer configuration for the purpose of generating the reference configuration or provide the lower layer reference configuration to the gNB-DU.)

[0139] 4. If the gNB-DU accepts the LTM configuration request, it responds with a `UE CONTEXT MODIFICATION RESPONSE` message including the generated lower-layer RRC configurations for the accepted candidate cell.

[0140] Note 1: Steps 3 and 4 may be initiated multiple times for LTM candidate cell preparation of multiple cells, including the source cell.

[0141] 5. The gNB-CU sends a `UE CONTEXT MODIFICATION REQUEST` message to the gNB-DU, which may include the LTM configuration ID mapping list and / or the updated CSI resource configuration.

[0142] 6. The gNB-DU responds with a `UE CONTEXT MODIFICATION RESPONSE` message which includes an updated lower layer configuration, e.g., containing the updated CSI report configuration of the source cell.

[0143] Note 2: In the case of a subsequent LTM, the CU-initiated UE Context Modification procedure may be invoked per candidate cell to transfer the updated CSI resource configuration to the gNB-DU.

[0144] 7. The gNB-CU sends a `DL RRC MESSAGE TRANSFER` message to the gNB-DU, which includes the generated `RRCReconfiguration` message with the LTM configuration.

[0145] 8. The gNB-DU forwards the received `RRCReconfiguration` message to the UE.

[0146] 9. The UE responds to the gNB-DU with an `RRCReconfigurationComplete` message.

[0147] 10. The gNB-DU forwards the `RRCReconfigurationComplete` message to the gNB-CU via an `UL RRC MESSAGE TRANSFER` message.

[0148] 11. Early synchronization to the candidate cell(s) may be performed as specified in TS 38.300 [2].

[0149] 12. The UE sends the L1 measurement result to the gNB-DU. The gNB-DU decides to execute LTM.

[0150] 13. The gNB-DU sends the Cell Switch Command to the UE.

[0151] 14. The gNB-DU sends the `DU-CU CELL SWITCH NOTIFICATION` message to the gNB-CU to indicate the initiation of the Cell Switch Command to the UE, including the target cell ID.

[0152] 15. The gNB-DU detects the UE access in the target cell as specified in TS 38.300 [2].

[0153] 16. The gNB-DU sends the `ACCESS SUCCESS` message to the gNB-CU with the target cell ID.

[0154] 17. The UE sends an `RRCReconfigurationComplete` message to the gNB-DU.

[0155] 18. The gNB-DU forwards the `RRCReconfigurationComplete` message to the gNB-CU via an `UL RRC MESSAGE TRANSFER` message.

[0156] 19. The gNB-CU may send the `UE CONTEXT MODIFICATION REQUEST` message to the gNB-DU to release the resources of prepared cells.

[0157] 20. The gNB-DU responds with a `UE CONTEXT MODIFICATION RESPONSE` message.

[0158]

[0159] FIG. 8 is a drawing illustrating an example of an Inter-gNB-DU LTM in a system applicable to the present disclosure.

[0160] FIG. 9 is a drawing illustrating an example of an Inter-gNB-DU LTM in a system applicable to the present disclosure.

[0161] Figures 8 and 9 correspond to Figure 8.2.1.5-1 (Figure 8.2.1.5-1) Inter-gNB-DU LTM.

[0162] This procedure is used when the UE moves from one gNB-DU to another gNB-DU within the same gNB-CU during NR operation for LTM. Figure 8.2.1.5-1 shows the inter-gNB-DU LTM procedure for intra-NR.

[0163] 1. The UE sends a `MeasurementReport` message (L3 measurement result) containing measurements of neighboring cells to the source gNB-DU. The source gNB-DU sends an `UL RRC MESSAGE TRANSFER` message conveying the received `MeasurementReport` message to the gNB-CU.

[0164] 2. The gNB-CU decides to initiate LTM configuration.

[0165] 3. The gNB-CU sends a `UE CONTEXT SETUP REQUEST` message to the candidate gNB-DU(s) for each candidate cell, containing one candidate cell ID and a CSI resource configuration for the subsequent LTM. The gNB-CU may provide the candidate gNB-DU(s) with a list of LTM configuration ID mappings. The gNB-CU may request PRACH resources from the candidate gNB-DU(s). The gNB-CU may request the candidate gNB-DU(s) to provide a lower-level configuration for the purpose of creating a reference configuration, or may provide the candidate gNB-DU(s) with a lower-level reference configuration. (The gNB-CU sends a `UE CONTEXT SETUP REQUEST` message to the candidate gNB-DU(s) for each candidate cell, containing one candidate cell ID and the CSI resource configuration for subsequent LTM. The gNB-CU may provide the LTM configuration ID mapping list to the candidate gNB-DU(s). The gNB-CU may request PRACH resources from the candidate gNB-DU(s). The gNB-CU may request the candidate gNB-DU(s) to provide the lower layer configuration for the purpose of generating the reference configuration or provide the lower layer reference configuration to the candidate gNB-DU(s).)

[0166] 4. If the candidate gNB-DU accepts the LTM configuration request, it responds with a `UE CONTEXT SETUP RESPONSE` message including the generated lower-layer RRC configurations for the accepted target candidate cell.

[0167] Note 1: As specified in steps 3 and 4 of 8.2.1.4 Intra-gNB-DU LTM, the CU-initiated UE Context Modification procedure may be initiated for preparing candidate cells in the source gNB-DU.

[0168] 5. The gNB-CU sends a `UE CONTEXT MODIFICATION REQUEST` message to the source gNB-DU, including information related to early synchronization and the LTM configuration ID mapping list for the accepted target candidate cell(s). The gNB-CU may send the updated CSI resource configuration to the source gNB-DU.

[0169] 6. The source gNB-DU responds with a `UE CONTEXT MODIFICATION RESPONSE` message which includes an updated lower layer configuration, e.g., containing the updated CSI report configuration of the source cell.

[0170] 7. The gNB-CU may send a `UE CONTEXT MODIFICATION REQUEST` message to the candidate gNB-DU(s) containing information for a subsequent LTM or for updating the configurations of candidate cells. The gNB-CU may also provide the lower layer part of the reference configuration to the candidate gNB-DU(s).

[0171] 8. The candidate gNB-DU responds with a `UE CONTEXT MODIFICATION RESPONSE` message including the updated lower layer configuration (e.g., the updated CSI report configuration).

[0172] Note 2: Step 7 may also be triggered after step 19 or after step 22 by implementation for subsequent LTM.

[0173] 9. The gNB-CU sends a `DL RRC MESSAGE TRANSFER` message to the source gNB-DU, which includes the generated `RRCReconfiguration` message with the LTM configuration.

[0174] 10. The source gNB-DU forwards the received `RRCReconfiguration` message to the UE.

[0175] 11. The UE responds to the source gNB-DU with an `RRCReconfigurationComplete` message.

[0176] 12. The source gNB-DU forwards the `RRCReconfigurationComplete` message to the gNB-CU via an `UL RRC MESSAGE TRANSFER` message.

[0177] 13. Early synchronization to the candidate cell(s) may be performed as specified in TS 38.300 [2].

[0178] 14. The candidate gNB-DU sends a `DU-CU TA INFORMATION TRANSFER` message to the gNB-CU, which includes the TA value, the associated PRACH resource information, and etc.

[0179] 15. The gNB-CU forwards the TA value and the associated PRACH resource information to the source gNB-DU in the `CU-DU TA INFORMATION TRANSFER` message.

[0180] 16. The UE sends the L1 measurement result to the source gNB-DU.

[0181] 17. The source gNB-DU decides to execute LTM to a target cell.

[0182] 18. The source gNB-DU sends the Cell Switch Command to the UE.

[0183] 19. The source gNB-DU sends the `DU-CU CELL SWITCH NOTIFICATION` message to the gNB-CU to indicate the initiation of the Cell Switch Command to the UE, including the target cell ID, the TCI state ID(s), and the TA values ​​for subsequent LTM.

[0184] 20. The gNB-CU forwards the target cell ID, the TCI state ID(s), and the TA values ​​for subsequent LTM to the target gNB-DU in the `CU-DU CELL SWITCH NOTIFICATION` message.

[0185] 21. The target gNB-DU detects the UE access as specified in TS 38.300 [2].

[0186] 22. The target gNB-DU sends the `ACCESS SUCCESS` message to the gNB-CU with the target cell ID.

[0187] 23. The UE sends an `RRCReconfigurationComplete` message to the target gNB-DU.

[0188] 24. The target gNB-DU forwards the `RRCReconfigurationComplete` message to the gNB-CU via an `UL RRC MESSAGE TRANSFER` message.

[0189] 25. The gNB-CU may send the `UE CONTEXT RELEASE COMMAND` message to the source gNB-DU to release the resources of prepared cells.

[0190] 26. The source gNB-DU responds with a `UE CONTEXT RELEASE COMPLETE` message.

[0191]

[0192] Composition and Method of the Invention

[0193] In the present disclosure, '()' can be interpreted as both excluding the contents inside () and including the contents inside the parentheses.

[0194] In the present disclosure, ' / ' may mean including (and) all of the contents separated by / or including (or) only some of the separated contents.

[0195]

[0196] Problem Description:

[0197] In Release 18, a new type of mobility solution called LTM (L1 / L2 Triggered Mobility) was specified to reduce latency, overhead, and interruption time during serving cell changes. To achieve faster serving cell changes, early DL / UL synchronization before cell switch and handover based on L1 measurement (triggered by MAC CE) were specified for LTM.

[0198] In Rel-19, a new WI has been approved for NR mobility enhancement phase 4 [1], where one of the objectives is to specify support for Conditional Intra-CU LTM:

[0199] Specify support of conditional Intra-CU LTM [RAN2, RAN3, RAN1]

[0200] Specify UE evaluated conditions for triggering LTM

[0201] Aim to support conditional LTM including subsequent LTM

[0202] Limit specifying the conditional LTM to the scenario where the UE is in non-DC

[0203] Checkpoint at RAN#107 to review the objective on whether Intra-CU conditional LTM can be specified to DC scenarios and, if so, to which cases. RAN WG work to not start before this checkpoint.

[0204]

[0205] In Rel-18 LTM, the decision of switching the serving cell for a UE was made exclusively by the network. The UE was configured to report (periodic) L1 measurements of candidate cells, based on which the current serving DU determined which cell the UE should be handed over to and explicitly instructed the UE to execute the cell switch via an L2 Cell Switch Command (CSC) MAC CE.

[0206] While this L1 / L2-based mobility successfully reduced cell switching downtime (particularly thanks to the early DL / UL synchronization mechanism developed alongside it), it also had limitations. Network-based mobility is inherently vulnerable to mobility failure because "cell switching" typically occurs when a terminal is close to the edge of the cell coverage area, where signal strength is weak and the quality of the serving cell has already deteriorated. Under these conditions, the terminal may fail to receive a cell switching command from the current serving cell, or the command may be delayed due to multiple retransmissions, leading to improper handover timing and an increased risk of mobility failure. (While this L1 / L2-based mobility successfully reduced cell switching interruption time (especially with the early DL / UL synchronization mechanisms developed together), it also had limitations: The network-triggered mobility is inherently prone to mobility failures, because "cell switching" normally occurs when the UE is near the edge of the cell's coverage area, where signal strength is weak and the serving cell quality has already deteriorated. In such conditions, the UE may fail to receive the cell switch command from the current serving cell, or the command could be delayed due to multiple retransmissions, leading to poor handover timing and an increased risk of mobility failures.).

[0207] Release-19’s Conditional LTM aims to complement the network-based mobility of existing LTMs by allowing the terminal to initiate a handover. This approach is useful for addressing the inherent instability found in all network-based mobility solutions, as it eliminates the need for the network to direct the terminal to switch cells. Instead of issuing an immediate command to switch cells, the network pre-sets an "execute" condition for switching while the current serving cell is still in good condition. The terminal then evaluates this condition and autonomously triggers a handover when it is met, improving the timing and success rate of cell switching. (Conditional LTM in Rel-19 aims to serve as a complementary approach to the existing network-triggered mobility in LTM by embracing the handover initiation from the UE. This approach is useful in addressing the inherent unreliability found in any network-triggered mobility solution, as it can remove the need for the network to instruct the UE to do a cell switch. Instead of issuing an immediate cell switch command, the network pre-configures "execution" conditions for cell switching while the current serving cell is still in good condition.The UE then evaluates these conditions and autonomously triggers the handover itself when they are met, thereby improving the timing and success rate of cell switches.).

[0208] However, the current mechanisms specified by 3GPP for Intra-CU LTM lack support for the Conditional LTM feature, which is particularly evident in disaggregated gNB deployments where the CU and DU are interconnected via the F1 interface. This specification proposes several mechanisms to add "Conditional LTM" on top of the existing Intra-CU LTM feature, ensuring that the two functions can work seamlessly together in such deployments.

[0209] [1] RP-242356, Revised Work Item: NR Mobility Enhancements Phase 4, Apple, China Telecom ([1] RP-242356, Revised Work Item: NR mobility enhancements Phase 4, Apple, China Telecom)

[0210]

[0211] Detailed Description (DETAILED DESCRIPTION):

[0212] Support for generation and configuration of Conditional LTM execution conditions

[0213] To support "Conditional LTM" and ensure seamless integration of both Conditional and traditional (non-Conditional) LTM features in a disaggregated architecture, the following considerations are addressed in this embodiment:

[0214] Conditional LTM, introduced in Release 19, is a new feature that relies on the UE's capability, which is known only to the CU. However, since LTM was originally developed for faster mobility, relying on L1 resources and measurements managed by DUs, the responsibility for generating the execution conditions for Conditional LTM is expected to lie with the DU. Given this, coordination between the CU and the DU is essential.

[0215] Given the nature of LTM relying on L1 measurements, L1-based execution conditions are more intuitive, but L3 measurement-based execution conditions are also possible. CUs are already allowed to execute LTM cell switching based on L3 measurements, and the concept of L3-based execution conditions is not new, as it has been used in many conditional mobility solutions developed in previous releases. Considering the possibilities of L1-based execution conditions generated by DUs and L3-based conditions generated by CUs in "conditional LTM," close coordination between the CU and each DU(s) is required to generate optimal execution conditions. (While L1-based execution conditions are more intuitive given the nature of LTM's reliance on L1 measurements, L3 measurement-based execution condition is also possible. The CU is already allowed to execute an LTM cell switch based on L3 measurements, and the concept of L3-based execution condition is nothing new, having been used in many Conditional mobility solutions developed in earlier releases. With the potential of L1-based execution conditions generated by DU and L3-based conditions generated by CU in "Conditional LTM", close coordination between the CU and the respective DU(s) is required to generate the optimal execution conditions.)

[0216] This process must also consider the traditional L1 measurement reporting used for network-triggered LTM, ensuring that the UE-triggered execution conditions complement or even replace network-triggered methods where appropriate, thereby enhancing overall handover performance and reducing the risks of delayed or failed cell switches.

[0217] Most importantly, these interactions must be incorporated into the existing Intra-CU LTM preparation steps already specified in Rel-18.

[0218]

[0219] FIG. 10 is a diagram illustrating an example of a process for supporting the generation and configuration of Conditional LTM execution conditions in a system applicable to the present disclosure.

[0220] FIG. 11 is a diagram illustrating an example of a process for supporting the generation and configuration of Conditional LTM execution conditions in a system applicable to the present disclosure.

[0221] The UE is currently being served by the S-DU (source DU), which is under the control of the CU via the F1 interface.

[0222] Step 1: The CU decides to initiate LTM configuration for the UE.

[0223] Step 2: The CU determines which candidate cells to prepare for the LTM for the UE (this may be based on the L3 measurement result reported from the UE, including measurements of neighboring cells).

[0224] The CU also checks whether the UE is capable of Conditional LTM (which could be based on UE capability). Since the Conditional LTM feature requires the ability to handle new or enhanced network configurations, continuously evaluate measurement conditions, and trigger a serving cell switch autonomously when the conditions are met, not all UEs would support this feature.

[0225] Step 3-4: If the candidate cells selected by the CU are under a DU other than the S-DU (e.g., C-DU - candidate DU), the CU sends a `UE CONTEXT SETUP REQUEST` message to the C-DU for each candidate cell, containing the corresponding cell ID and the L1 measurement resource configuration of other candidate cells to be used by the C-DU for generating the Conditional LTM execution conditions.

[0226] The CU may also indicate that the UE is capable of the Conditional LTM feature, or may explicitly request the C-DU to generate the Conditional LTM execution conditions for the UE.

[0227] If the C-DU accepts the request for LTM configuration, it responds with a `UE CONTEXT SETUP RESPONSE` message containing generated lower-layer RRC configurations for the accepted candidate cell, which includes the generated execution conditions for Conditional LTM and / or L1 measurement report configurations for non-Conditional LTM.

[0228] In the response message associated with a specific accepted candidate cell, the C-DU may also provide the CU with information on how the execution conditions for Conditional LTM or L1 measurement report configuration for non-Conditional LTM are prepared for other candidate cells. This allows the CU to recognize which potential target cell is subject to network-triggered mobility, UE-based execution conditions, or both, when the admitted candidate cell associated with the received message becomes the serving cell for the UE.

[0229] Note A1: It is assumed that the L1 measurement resource configurations of candidate cells provided by the CU in Step 3 are used to generate execution conditions for conditional LTMs. However, similar to existing LTM behavior within the CU, they may also be used to generate L1 measurement reporting configurations (for unconditional LTMs). Alternatively, without an explicit request or indication from the UE for support for conditional LTMs, the CU may restrict the use of the provided L1 measurement resource configurations to conditional LTMs only—that is, to generating execution conditions by the DU—and inform the C-DU of this restricted use. Alternatively, the CU may provide separate resource configurations for conditional and unconditional LTMs, respectively. (NOTE A1: The L1 measurement resource configuration of candidate cells provided by the CU in Step 3 is assumed to be used for generating execution conditions for Conditional LTM. But it can also be used for generating the L1 measurement report configuration (for non-Conditional LTM), similar to the legacy intra-CU LTM operations. Or, without explicit request or indication of the UE's support for Conditional LTM, the CU may limit the usage of the provided L1 measurement resource configuration exclusively for Conditional LTM, ie for only generating execution conditions by the DU, and inform such limited usage to the C-DU.Or, CU may provide separate resource configurations for Conditional and non-Conditional LTM, respectively.).

[0230] Note A2: If the CU is unaware of the L1 measurement resource configuration of a candidate cell under the C-DU required for the Conditional LTM decided UE, Step 3-4 may be used by the CU to retrieve such resource configuration from the C-DU for that candidate cell. In this case, the generation and configuration steps of the Conditional LTM execution conditions and / or L1 measurement report configuration can be deferred and performed between the CU and the C-DU, e.g., in Step 8-9.

[0231] Note A3: Conditional LTM execution conditions generated by the DU are associated with specific candidate cells corresponding to messages received from the CU. These conditions are evaluated and executed only when the corresponding candidate cell becomes the UE's serving cell. Execution conditions may consist of one or more L1 measurement-based criteria (e.g., RSRP, RSRQ, SINR, etc.) associated with other candidate cells (i.e., potential target cells), which are generated based on the L1 measurement resource configurations of other cells provided by the CU. This resource configuration represents the physical layer resources specifically allocated by each candidate cell for LTM preparation, and may be applicable to the entire cell (applicable to all UEs) or dedicated to a specific UE. (NOTE A3: The Conditional LTM execution conditions generated by a DU are associated with a specific candidate cell that corresponds to the message received from the CU. These conditions are evaluated and executed only when that candidate cell becomes the serving cell for the UE. The execution conditions may consist of one or more L1 measurement-based criteria (eg RSRP, RSRQ, SINR, etc.) related to other candidate cells (ie potential target cells), which is generated based on the L1 measurement resource configuration of those other cells provided by the C.U.This resource configuration represents the physical layer resources allocated by each candidate cell specifically for LTM preparation, either on a cell-wide basis (that could be applicable for any UEs), or as dedicated resources for a particular UE.).

[0232] Note A4: Even without an explicit request from the CU, a DU that knows that the UE supports conditional LTM may independently determine and generate a conditional LTM execution condition for the UE while approving the candidate cells requested for LTM. Alternatively, when the CU requests the DU to generate an execution condition for a specific candidate cell, it may request that execution conditions be generated for only a subset of other candidate cells. For example, if the CU requests an execution condition from candidate cell A toward other cells B and C, the DU may specify that an execution condition be generated only for cell B, excluding cell C. (NOTE A4: Without explicit request from CU, the DU who learns that the UE is capable of Conditional LTM may decide on its own and generate the Conditional LTM execution conditions for the UE while admitting the requested candidate cell for LTM. Or, when CU requesting the DU to generate execution conditions of a specific candidate cell, it may request to generate the execution conditions limited to only a subset of other candidate cells. For example, if CU requests the execution conditions from a candidate cell A towards other cells B and C, it may specify that the DU should generate the execution conditions only for cell B, while excluding cell C.)

[0233] Note A5: Similar to the existing LTM behavior within the CU, the DU may decide to generate L1 measurement report configurations based on the L1 measurement resource configurations of candidate cells received from the CU. L1 measurement report configurations from candidate cells may be generated for all other candidate cells regardless of the CU's request, or may be generated only for a subset of cells for which the CU did not request the generation of execution conditions for conditional LTM. Consequently, the 4-step response from the approved candidate cells may include only execution conditions (for conditional LTM), only L1 measurement report configurations (for unconditional LTM), or both for each potential target cell. (NOTE A5: A DU may decide to generate the L1 measurement report configuration based on the L1 measurement resource configuration of candidate cells received from the CU, similar to the legacy intra-CU LTM operations. The L1 measurement report configuration from a candidate cell could be generated for any other candidate cell, regardless of a request from the CU, or only for a subset of cells that were not requested by the CU for execution condition generation for Conditional LTM.As a result, the Step 4 response from an admitted candidate cell may include, for each potential target cell, either the execution condition only (for Conditional LTM), the L1 measurement report configuration only (for non-Conditional LTM), or both.).

[0234] Step 5-6: If the candidate cells selected by the CU are under the S-DU, the CU sends a `UE CONTEXT MODIFICATION REQUEST` message to the S-DU for each candidate cell. The process described in Step 3-4 above applies similarly, with the difference being the use of the `UE Context Modification` procedure and the request being made to the S-DU instead of the C-DU.

[0235] Note B: If the current serving cell in S-DU is also one of the candidate cells chosen by the CU, Step 5-6 will apply to the current serving cell as well. On the other hand, even if the current serving cell in S-DU is not among the candidate cells selected by the CU, Step 5-6 will still be executed to enable the S-DU to generate the Conditional LTM execution conditions from the current serving cell toward one or more candidate cells, but the conditions described in the above Note A2 do not apply in this case.

[0236] Step 7: The CU may decide to configure L3 measurement-based conditional LTM execution conditions for the UE. This decision can be made individually for each admitted candidate cell, and may vary depending on the specific target cell to which the L3-based conditional LTM execution conditions are set, taking into account the execution conditions or L1 measurement report configurations generated by the DUs in the earlier steps.

[0237] Step 8-9: If the CU has decided and generated L3 measurement-based execution conditions for a candidate cell prepared by the C-DU, the CU sends a `UE CONTEXT MODIFICATION REQUEST` message to the C-DU for that candidate cell, containing the corresponding cell ID and information about the generated L3-based execution conditions.

[0238] If there have been updates to the candidate cell configuration—such as differences between the candidate cells initially selected by the CU (in Step 2) and those finally admitted / prepared by all the involved DUs (after Step 6), or any changes in the L1 measurement resource configurations for one or more prepared candidate cells—these updates are also included in the message.

[0239] The C-DU takes into account the received information and responds with a `UE CONTEXT MODIFICATION RESPONSE` message including the updated lower layer RRC configurations for the indicated candidate cell, which may further include detailed information about the updated execution conditions (for Conditional LTM) and / or L1 measurement report configuration (for non-Conditional LTM), as described in Step 3-4.

[0240] Note C: For example, if the CU learns that an L1-based conditional LTM execution condition from Cell A to Cell B has not been prepared by the C-DU, but instead an L1 measurement reporting configuration for network-based mobility has been prepared, it may decide to create an L3-based conditional LTM execution condition from Cell A targeting Cell B. In this case, information regarding the L3-based conditional LTM execution condition may be displayed to the C-DU via Step 8, allowing the C-DU to recognize that when the UE is served by Cell A, a UE-based conditional LTM transition to Cell B is possible, and therefore an L2 cell transition command via MAC CE to Cell B may not be essential (i.e., it may rely on the L3-based conditional LTM execution condition configured on the UE). Alternatively, the C-DU may choose to update or remove the corresponding L1 measurement reporting configuration that has already been prepared, thereby relying entirely on the UE-based conditional LTM and not sending an L1 measurement report for the transition from Cell A to Cell B. (NOTE C: For example, the CU may decide to generate the L3-based execution condition from a candidate cell A, targeting a cell switch to a cell B, once it knows that L1-based execution condition from cell A to cell B has not been prepared by the C-DU, but the L1 measurement report configuration has been prepared instead for the network triggered mobility.In this case, the information about the L3-based execution condition may be indicated to the C-DU via Step 8, which allows the C-DU to recognize that, when the UE is served by cell A, a UE-based Conditional LTM switching to cell B is possible and thus an L2 cell switch command via MAC CE for cell B may not be essential (i.e., relying solely on the L3-based execution condition configured for the UE). Or, C-DU may choose to update and remove the corresponding L1 measurement report configuration already prepared, thus relying entirely on the UE-based Conditional LTM, and preventing the UE from sending the L1 measurement reports for the switch from cell A to cell B.).

[0241] Alternatively, the CU, together with the L3 measurement results reported by the UE, may determine that a certain L3-based conditional LTM execution condition can provide better service for the handover than the L1-based conditional LTM execution condition already prepared by the C-DU. In this case, the L3-based conditional LTM execution condition information indicated in Step 8 may explicitly instruct the C-DU to remove the corresponding L1-based conditional LTM execution condition.

[0242] Step 10-11: If the CU has determined and generated L3 measurement-based execution conditions for a candidate cell prepared by the S-DU, the CU sends a `UE CONTEXT MODIFICATION REQUEST` message to the S-DU for that candidate cell. The process described in Step 8-9 above applies similarly, with the difference being that the request is made to the S-DU instead of the C-DU.

[0243] Note D: If the current serving cell located in the S-DU is also one of the admitted candidate cells, Step 10-11 will apply to the current serving cell as well. On the other hand, even if the current serving cell in the S-DU is not among the admitted candidate cells, Step 10-11 will still be executed if the CU has decided and generated L3 measurement-based execution conditions for the current serving cell.

[0244] Step 12: Based on the updated L1 measurement report configurations (for non-Conditional LTM) and / or execution conditions (for Conditional LTM) of the candidate cells, CU may choose to further update the L3-based execution conditions for the UE.

[0245] Note E: If necessary (e.g., to inform a DU that the network-triggered cell switching prepared by the DU is not the only option for a certain candidate cell toward another, etc.), the information about the updated L3-based execution conditions can be communicated to the relevant DUs similarly following Steps 8-9 or 10-11, though it is omitted for brevity.

[0246] Step 13: The CU finalizes the LTM configuration to be applied to the UE, incorporating the execution conditions generated by the CU and / or DUs.

[0247] Steps 14-15: The CU sends a `DL RRC MESSAGE TRANSFER` message to the S-DU, which includes the generated `RRC Reconfiguration` message with the LTM configuration. This is then forwarded to the UE.

[0248] Steps 16-17: The UE responds to the S-DU with an RRC Reconfiguration Complete message, which is forwarded to the CU via an UL RRC MESSAGE TRANSFER message.

[0249] Step 18: The UE starts evaluating the configured execution conditions.

[0250]

[0251] Technical features of various embodiments of the present disclosure

[0252] Advantageous Effects

[0253] The inventions described in this present disclosure aim to enable seamless integration of both Conditional and traditional (non-Conditional) LTMs in a disaggregated gNB architecture. By allowing seamless coordination between a CU and DU(s) to optimize the generation of L1-based or L3-based execution conditions for Conditional LTMs, alongside the existing network-triggered mobility of the non-Conditional LTMs, this enhances overall handover performance in intra-CU LTMs and reduces the risks of delayed or failed cell switches.

[0254]

[0255] Characteristic configurations of various embodiments of the present disclosure

[0256] In a network system supporting the Conditional LTM feature in Intra-CU LTM, it is as follows:

[0257] - The CU may inform the DU of the UE's ability for Conditional LTM.

[0258] - CU may request DU to generate execution conditions for Conditional LTM.

[0259] - DU may generate execution conditions for Conditional LTM, once it becomes aware of the UE's support (based on the CU's indication or request related to Conditional LTM).

[0260] The L1 measurement resource configuration provided for the DU can be used for generating execution conditions (for Conditional LTM), or for generating L1 measurement report configuration (for non-Conditional LTM), or both, for which its usage may be explicitly indicated to the DU.

[0261] The DU may provide to the CU how execution conditions (for Conditional LTM) and L1 measurement report configurations (for non-Conditional LTM) were generated from its candidate cells.

[0262] The CU may generate L3 measurement-based execution conditions for Conditional LTM for some candidate cells and may communicate such information to the associated DU, which may trigger further updates to the LTM configuration.

[0263]

[0264] [Explanation regarding the 1st Node (gNB-CU) claim]

[0265] The embodiments described above will be explained in detail below with reference to FIG. 12 regarding the operation of the first node. The methods described below are distinguished only for the convenience of explanation, and it is understood that, as long as they are not mutually excluded, a part of one method may be substituted with a part of another method or combined with one another and applied.

[0266] FIG. 12 is a diagram illustrating an example of the operation process of a first node in a system applicable to the present disclosure.

[0267] In the embodiment of FIG. 12, the first node may correspond to gNB-CU, and the second node may correspond to gNB-DU.

[0268] In step S1210, the first node sends a first message of a request related to the UE context (user equipment context) to the second node.

[0269] The first message above relates to a request for generating a conditional L1 / L2-Triggered Mobility execution condition.

[0270] The first message above includes a candidate cell ID associated with the first message.

[0271] In step S1220, in response to the first message, the first node receives a second message containing configuration information from the second node.

[0272]

[0273] According to various embodiments of the present disclosure, the first message may be a UE CONTEXT SETUP REQUEST or a UE CONTEXT MODIFICATION REQUEST.

[0274] According to various embodiments of the present disclosure, the first node may be a centralized unit (CU) of gNB, and the second node may be a distributed unit (DU) of gNB.

[0275] According to various embodiments of the present disclosure, the second node may be a source DU (S-DU) serving a terminal (user equipment, UE), or the second node may be a candidate DU (C-DU).

[0276] According to various embodiments of the present disclosure, the first message may include an LTM indicator associated with a conditional LTM (C-LTM) for a terminal (user equipment, UE).

[0277] According to various embodiments of the present disclosure, the conditional LTM execution condition may be a conditional LTM layer 1 execution condition. The first message may further include an L1 measurement resource configuration for generating the conditional LTM execution condition.

[0278] According to various embodiments of the present disclosure, the first message may further include condition information regarding a layer 3-based conditional execution condition generated by the first node. The condition information may enable the second node to skip the transmission of an L2 cell switch command for a candidate cell corresponding to the candidate cell ID.

[0279]

[0280] According to various embodiments of the present disclosure, a first node is provided in a wireless communication system. The first node includes a transceiver and at least one processor, and the at least one processor may be configured to perform a method of operation of the first node according to FIG. 12.

[0281]

[0282] According to various embodiments of the present disclosure, an apparatus for controlling a first node in a wireless communication system is provided. The apparatus comprises at least one processor and at least one memory operably connected to the at least one processor. The at least one memory may be configured to store instructions for performing a method of operation of the first node according to FIG. 12 based on execution by the at least one processor.

[0283]

[0284] According to various embodiments of the present disclosure, one or more non-transitory computer-readable media (CRMs) storing one or more instructions are provided. The one or more instructions perform operations based on execution by one or more processors, and the operations may include a method of operation of a first node according to FIG. 12.

[0285]

[0286] [Explanation regarding the 2nd node (gNB-DU) claim]

[0287] The embodiments described above will be explained in detail below with reference to FIG. 13 regarding the operation of the second node. The methods described below are distinguished only for convenience of explanation, and it is obvious that as long as they are not mutually excluded, a part of one method may be substituted with a part of another method or combined with one another and applied.

[0288] FIG. 13 is a diagram illustrating an example of the operation process of a second node in a system applicable to the present disclosure.

[0289] In the embodiment of FIG. 13, the first node may correspond to gNB-CU, and the second node may correspond to gNB-DU.

[0290] In step S1310, the second node receives a first message of a request related to the UE context (user equipment context) from the first node.

[0291] The first message above relates to a request for generating a conditional L1 / L2-Triggered Mobility execution condition.

[0292] The first message above includes a candidate cell ID associated with the first message.

[0293] In step S1320, in response to the first message, the second node transmits a second message containing configuration information to the first node.

[0294]

[0295] According to various embodiments of the present disclosure, the first message may be a UE CONTEXT SETUP REQUEST or a UE CONTEXT MODIFICATION REQUEST.

[0296] According to various embodiments of the present disclosure, the first node may be a centralized unit (CU) of gNB, and the second node may be a distributed unit (DU) of gNB.

[0297] According to various embodiments of the present disclosure, the second node may be a source DU (S-DU) serving a terminal (user equipment, UE), or the second node may be a candidate DU (C-DU).

[0298] According to various embodiments of the present disclosure, the first message may include an LTM indicator associated with a conditional LTM (C-LTM) for a terminal (user equipment, UE).

[0299] According to various embodiments of the present disclosure, the conditional LTM execution condition may be a conditional LTM layer 1 execution condition. The first message may further include an L1 measurement resource configuration for generating the conditional LTM execution condition.

[0300] According to various embodiments of the present disclosure, the first message may further include condition information regarding a layer 3-based conditional execution condition generated by the first node. The condition information may enable the second node to skip the transmission of an L2 cell switch command for a candidate cell corresponding to the candidate cell ID.

[0301]

[0302] According to various embodiments of the present disclosure, a second node is provided in a wireless communication system. The second node includes a transceiver and at least one processor, and the at least one processor may be configured to perform the operation method of the second node according to FIG. 13.

[0303]

[0304] According to various embodiments of the present disclosure, an apparatus for controlling a second node in a wireless communication system is provided. The apparatus comprises at least one processor and at least one memory operably connected to the at least one processor. The at least one memory may be configured to store instructions for performing a method of operation of the second node according to FIG. 13 based on execution by the at least one processor.

[0305]

[0306] According to various embodiments of the present disclosure, one or more non-transitory computer-readable media (CRMs) storing one or more instructions are provided. The one or more instructions perform operations based on execution by one or more processors, and the operations may include a method of operation of a second node according to FIG. 13.

[0307]

[0308] Wireless devices applicable to the present disclosure

[0309] Hereinafter, examples of wireless devices to which various embodiments of the present disclosure are applied will be described.

[0310] FIG. 14 is a drawing illustrating an example of the structure of a first node and a second node in a system applicable to the present disclosure.

[0311] The first node (1600) may include a processor (1610), an antenna unit (1620), a transceiver (1630), and a memory (1640).

[0312] The processor (1610) performs baseband-related signal processing and may include an upper layer processing unit (1611) and a physical layer processing unit (1615). The upper layer processing unit (1611) may process operations of the MAC layer, RRC layer, or higher upper layers. The physical layer processing unit (1615) may process operations of the PHY layer. For example, if the first node (1600) is a base station device in base station-terminal communication, the physical layer processing unit (1615) may perform uplink reception signal processing, downlink transmission signal processing, etc. For example, if the first node (1600) is a first terminal device in terminal-terminal communication, the physical layer processing unit (1615) may perform downlink reception signal processing, uplink transmission signal processing, sidelink transmission signal processing, etc. In addition to performing baseband-related signal processing, the processor (1610) may also control the overall operation of the first node (1600).

[0313] The antenna section (1620) may include one or more physical antennas, and if it includes multiple antennas, it may support MIMO transmission and reception. The transceiver (1630) may include an RF (Radio Frequency) transmitter and an RF receiver. The memory (1640) may store information processed by the processor (1610) and software, operating systems, applications, etc. related to the operation of the first node (1600), and may include components such as a buffer.

[0314] The processor (1610) of the first node (1600) may be configured to implement the operation of the base station in base station-terminal communication (or the operation of the first terminal device in terminal-terminal communication) in the embodiments described in this disclosure.

[0315]

[0316] The second node (1650) may include a processor (1660), an antenna unit (1670), a transceiver (1680), and a memory (1690).

[0317] The processor (1660) performs baseband-related signal processing and may include an upper layer processing unit (1661) and a physical layer processing unit (1665). The upper layer processing unit (1661) may process operations of the MAC layer, RRC layer, or higher upper layers. The physical layer processing unit (1665) may process operations of the PHY layer. For example, if the second node (1650) is a terminal device in base station-terminal communication, the physical layer processing unit (1665) may perform downlink reception signal processing, uplink transmission signal processing, etc. For example, if the second node (1650) is a second terminal device in terminal-terminal communication, the physical layer processing unit (1665) may perform downlink reception signal processing, uplink transmission signal processing, sidelink reception signal processing, etc. In addition to performing baseband-related signal processing, the processor (1660) may also control the overall operation of the second node (1660).

[0318] The antenna section (1670) may include one or more physical antennas, and if it includes multiple antennas, it may support MIMO transmission and reception. The transceiver (1680) may include an RF transmitter and an RF receiver. The memory (1690) may store information processed by the processor (1660) and software, operating systems, applications, etc. related to the operation of the second node (1650), and may include components such as a buffer.

[0319] The processor (1660) of the second node (1650) may be configured to implement the operation of the terminal in base station-terminal communication (or the operation of the second terminal device in terminal-terminal communication) in the embodiments described in this disclosure.

[0320] In the operation of the first node (1600) and the second node (1650), the details described in the examples of the present disclosure regarding the base station and the terminal (or the first terminal and the second terminal in terminal-to-terminal communication) in base station-to-terminal communication may be applied in the same way, and redundant descriptions are omitted.

[0321]

[0322] Here, the wireless communication technology implemented in the device (1600, 1650) of the present disclosure may include LTE, NR and 6G as well as various other wireless communication technologies.

[0323]

[0324] The claims described in various embodiments of the present disclosure may be combined in various ways. For example, the technical features of the method claims of various embodiments of the present disclosure may be combined to be implemented as a device, and the technical features of the device claims of various embodiments of the present disclosure may be combined to be implemented as a method. Furthermore, the technical features of the method claims and the technical features of the device claims of various embodiments of the present disclosure may be combined to be implemented as a device, and the technical features of the method claims and the technical features of the device claims of various embodiments of the present disclosure may be combined to be implemented as a method.

Claims

1. In a method performed by the first node, The method includes the step of transmitting a first message of a request related to the UE context (user equipment context) to a second node, and The above first message is related to a request for generating a conditional L1 / L2-Triggered Mobility execution condition, and The first message above includes a candidate cell ID associated with the first message; A method comprising the step of receiving a second message containing configuration information from the second node in response to the first message above. method.

2. In Paragraph 1, The first message above is a UE context setup request or a UE context modification request, method.

3. In Paragraph 1, The above-mentioned first node is a CU (centralized unit) of gNB, and The above second node is a DU (distributed unit) of the gNB, method.

4. In Paragraph 3, The second node is an S-DU (source DU) serving a terminal (user equipment, UE), or, The above second node is a C-DU (candidate DU), method.

5. In Paragraph 1, The first message above includes an LTM indicator associated with a conditional LTM (C-LTM) for a terminal (user equipment, UE). method.

6. In Paragraph 1, The above conditional LTM execution condition is an L1-based conditional LTM execution condition (conditional LTM layer 1 execution condition), and The first message further includes an L1 measurement resource configuration for generating the conditional LTM execution condition, method.

7. In Paragraph 1, The first message further includes condition information regarding a layer 3-based conditional execution condition generated by the first node, and The above condition information enables the second node to skip the transmission of an L2 cell switch command for a candidate cell corresponding to the candidate cell ID. method.

8. In a method performed by the second node, The method includes the step of receiving a first message of a request related to the UE context (user equipment context) from a first node, and The above first message is related to a request for generating a conditional L1 / L2-Triggered Mobility execution condition, and The first message above includes a candidate cell ID associated with the first message; A method comprising the step of transmitting a second message containing configuration information to the first node in response to the first message. method.

9. In Paragraph 8, The first message above is a UE context setup request or a UE context modification request, method.

10. In Paragraph 8, The above-mentioned first node is a CU (centralized unit) of gNB, and The above second node is a DU (distributed unit) of the gNB, method.

11. In Paragraph 10, The second node is an S-DU (source DU) serving a terminal (user equipment, UE), or, The above second node is a C-DU (candidate DU), method.

12. In Paragraph 8, The first message above includes an LTM indicator associated with a conditional LTM (C-LTM) for a terminal (user equipment, UE). method.

13. In Paragraph 8, The above conditional LTM execution condition is an L1-based conditional LTM execution condition (conditional LTM layer 1 execution condition), and The first message further includes an L1 measurement resource configuration for generating the conditional LTM execution condition, method.

14. In Paragraph 8, The first message further includes condition information regarding a layer 3-based conditional execution condition generated by the first node, and The above condition information enables the second node to skip the transmission of an L2 cell switch command for a candidate cell corresponding to the candidate cell ID. method.

15. In the first node, Transmitter / Receiver; At least one processor; and It includes at least one memory that is operablely connectable to the at least one processor and stores instructions for performing operations when executed by the at least one processor. The above operations are, Comprising all steps of the method according to any one of claims 1 to 7, Node 1.

16. In the second node, Transmitter / Receiver; At least one processor; and It includes at least one memory that is operablely connectable to the at least one processor and stores instructions for performing operations when executed by the at least one processor. The above operations are, Comprising all steps of the method according to any one of claims 8 through 14, Node 2.

17. In a control device for controlling a first node, At least one processor; and It includes at least one memory operably connected to the above at least one processor, and The above at least one memory stores instructions for performing operations based on execution by the above at least one processor, and The above operations are, Comprising all steps of the method according to any one of claims 1 to 7, controller.

18. In a control device for controlling a second node, At least one processor; and It includes at least one memory operably connected to the above at least one processor, and The above at least one memory stores instructions for performing operations based on execution by the above at least one processor, and The above operations are, Comprising all steps of the method according to any one of claims 8 through 14, controller.

19. In a non-transitory computer-readable medium storing one or more instructions, The above one or more instructions perform operations based on being executed by one or more processors, and The above operations are, Comprising all steps of the method according to any one of claims 1 to 7, Computer-readable media.

20. In a non-transitory computer-readable medium storing one or more instructions, The above one or more instructions perform operations based on being executed by one or more processors, and The above operations are, Comprising all steps of the method according to any one of claims 8 through 14, Computer-readable media.

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