Method and apparatus for LTM with early TA acquisition

Abstract

Aspects of the present disclosure relate to methods and apparatus for a lower layer triggered mobility (LTM) procedure with early timing advance (TA) acquisition. In accordance with an embodiment of the present disclosure, a user equipment (UE) comprises: at least one memory; and at least one processor coupled to the at least one memory and configured to cause the UE to: receive, from a source cell of a first base station (BS), lower layer triggered mobility (LTM) configuration information related to a candidate cell of a second BS, where the first BS is the same as or different from the second BS; receiving, from the source cell, an LTM cell handover command for triggering a cell handover procedure, wherein the LTM cell handover command includes at least one of: identifier (ID) information of the candidate cell; or an early timing advance (TA) value of the candidate cell; and upon receiving the LTM cell handover command, performing the cell handover procedure towards the candidate cell and initiating a supervision timer.

Description

Technical Field

[0001] This disclosure relates to wireless communications, and more specifically, to methods and apparatus for lower-layer triggered mobility (LTM) procedures with early timing advance (TA) acquisition. LTM may also be referred to as L1 / L2 lower-layer triggered mobility or the like. Background Technology

[0002] A wireless communication system may include one or more network communication devices, such as a base station, which can support wireless communication of one or more user communication devices (which may also be referred to as user equipment (UE) or other suitable terms). The wireless communication system can support wireless communication with one or more user communication devices by utilizing the resources of the wireless communication system (e.g., time-domain resources (e.g., symbols, time slots, subframes, frames, or the like) or frequency-domain resources (e.g., subcarriers, carriers, or the like)). Furthermore, the wireless communication system can support wireless communication across various radio access technologies, including third-generation (3G) radio access technology, fourth-generation (4G) radio access technology, fifth-generation (5G) radio access technology, and other suitable radio access technologies beyond 5G (e.g., sixth-generation (6G)). Summary of the Invention

[0003] The article “a” preceding an element is unrestricted and should be understood to refer to “at least one” or “one or more” of those elements. The terms “a,” “at least one,” “one or more,” and “at least one of one or more” are interchangeable. As used herein (included in the claims), the word “or” used in a list of items (e.g., a list of items beginning with phrases such as “at least one of…”, “one or more of…”, or “one or both of…”) indicates an inclusive list, such that (e.g.) a list of at least one of A, B, or C means A or B or C or AB or AC or BC or ABC (i.e., A and B and C). Furthermore, as used herein, the phrase “based on” should not be construed as referring to a closed set of conditions. For example, without departing from the scope of this disclosure, an example step described as “based on condition A” may be based on both condition A and condition B. In other words, as used herein, the phrase “based on” should be interpreted in the same manner as the phrase “at least partially based on.” Furthermore, as used herein (included in the claims), a “group” may comprise one or more elements.

[0004] Some embodiments of this disclosure provide a user equipment (UE). The UE includes: at least one memory; and at least one processor coupled to the at least one memory and configured to cause the UE to: receive lower-layer triggered mobility (LTM) configuration information associated with a candidate cell of a second base station (BS) from a source cell of a first base station (BS), wherein the first BS is the same as or different from the second BS; receive an LTM cell handover command from the source cell for triggering a cell handover procedure, wherein the LTM cell handover command includes at least one of: an identifier (ID) information of the candidate cell; or an early timing advance (TA) value of the candidate cell; and, upon receiving the LTM cell handover command, execute the cell handover procedure toward the candidate cell and start a supervisory timer.

[0005] In some implementations of the UE described herein, the cell handover procedure is: a primary cell (PCell) handover procedure for the primary cell group; or a primary auxiliary cell group (PSCell) handover procedure.

[0006] In some implementations of the UE described herein, if the cell handover procedure is the PCell handover procedure, then the processor is configured to cause the UE to: connect to the cell of the third BS via a reconstruction procedure after the supervisory timer expires; transmit information to the cell of the third BS indicating that a report indicating an LTM cell handover failure is available; receive a request for the report from the third BS; and transmit the report to the third BS.

[0007] In some implementations of the UE described herein, the report includes at least one of the following: the early TA value of the candidate cell; information indicating whether the cell handover procedure is an LTM cell handover based on no random access channel (RACH) or an LTM cell handover based on RACH; information indicating whether the cell handover procedure is a failed LTM cell handover based on no RACH with configured authorization (CG); information indicating whether the cell handover procedure is a failed LTM cell handover based on no RACH without CG; information indicating whether the LTM cell handover failure occurred; the Layer 1 (L1) measurement result of the source cell when the LTM cell handover failure occurred; or the L1 measurement result of the candidate cell when the LTM cell handover failure occurred.

[0008] In some implementations of the UE described herein, the early TA value of the candidate cell is obtained by the source cell via early TA acquisition and received by the UE from the source cell; the early TA value of the candidate cell is set to a fixed value; or the early TA value of the candidate cell is set to be the same as the TA value of the source cell.

[0009] In some implementations of the UE described herein, the processor is configured to transmit to the third BS the total number of LTMs performed toward the same candidate cell in support of subsequent LTMs.

[0010] In some implementations of the UE described herein, the total number includes: the total number of successful completions of the cell handover procedure alone; or both the total number of failed LTM cell handovers and the total number of successful completions of the cell handover procedure.

[0011] In some implementations of the UE described herein, if the cell handover procedure is a PSCell handover procedure, then the processor is configured to cause the UE to: transmit an auxiliary cell group (SCG) failure information message to the primary node (MN) serving the UE after the supervisory timer expires.

[0012] In some implementations of the UE described herein, the SCG failure information message includes at least one of the following: information indicating an LTM cell handover failure; a Layer 1 (L1) measurement result of the source cell when the LTM cell handover failure occurs; an L1 measurement result of the candidate cell when the LTM cell handover failure occurs; information indicating an LTM cell handover failure based on RACH-free; information indicating an LTM cell handover failure based on RACH-free with Configurable Citation (CG); information indicating an LTM cell handover failure based on RACH-free without CG; information indicating an LTM cell handover failure based on RACH; or information indicating the expiration of the surveillance timer.

[0013] In some implementations of the UE described herein, at least one of the L1 measurement results of the source cell or the L1 measurement results of the candidate cell is encapsulated in a container of a Radio Resource Control (RRC) message.

[0014] Some embodiments of this disclosure provide a processor for wireless communication, comprising: at least one controller coupled to at least one memory and configured to: receive lower-layer triggered mobility (LTM) configuration information associated with a candidate cell of a second base station (BS) from a source cell of a first base station (BS), wherein the first BS is the same as or different from the second BS; receive an LTM cell handover command from the source cell for triggering a cell handover procedure, wherein the LTM cell handover command includes at least one of: identifier (ID) information of the candidate cell; or an early timing advance (TA) value of the candidate cell; and, upon receiving the LTM cell handover command, execute the cell handover procedure toward the candidate cell and start a supervisory timer.

[0015] Some embodiments of this disclosure provide a method performed by a user equipment (UE). The method includes: receiving lower-layer triggered mobility (LTM) configuration information associated with a candidate cell of a second BS from a source cell of a first base station (BS), wherein the first BS is the same as or different from the second BS; receiving an LTM cell handover command from the source cell for triggering a cell handover procedure, wherein the LTM cell handover command includes at least one of: an identifier (ID) information of the candidate cell; or an early timing advance (TA) value of the candidate cell; and, upon receiving the LTM cell handover command, executing the cell handover procedure toward the candidate cell and starting a supervisory timer.

[0016] Some embodiments of this disclosure provide a base station (BS). The BS includes: at least one memory; and at least one processor coupled to the at least one memory and configured to cause the BS to: receive a Radio Resource Control (RRC) reconstruction request from a User Equipment (UE) after a failure of a lower-layer triggered mobility (LTM) cell handover procedure; and transmit an RRC reconstruction message to the UE.

[0017] In some implementations of the BS described herein, the LTM cell handover procedure is: a primary cell (PCell) handover procedure for the primary cell group; or a primary auxiliary cell group (PSCell) handover procedure.

[0018] In some implementations of the BS described herein, the processor is configured to cause the BS to: receive from the UE information that a report indicating an LTM cell handover failure is available; transmit a request for the report to the UE; and receive the report from the UE.

[0019] In some implementations of the BS described herein, the processor is configured to transmit the report to the source BS of the source cell.

[0020] In some implementations of the BS described herein, the report includes at least one of the following: an early TA value of the candidate cell; information indicating whether the cell handover procedure is an LTM cell handover based on no random access channel (RACH) or an LTM cell handover based on RACH; information indicating whether the cell handover procedure is a failed LTM cell handover based on no RACH with configured authorization (CG); information indicating whether the cell handover procedure is a failed LTM cell handover based on no RACH without CG; information indicating whether the LTM cell handover failure occurred; a Layer 1 (L1) measurement of the source cell when the LTM cell handover failure occurred; or an L1 measurement of the candidate cell when the LTM cell handover failure occurred.

[0021] In some implementations of the BS described herein, the processor is configured to receive from the UE the total number of LTM executions toward the same candidate cell in the event of subsequent LTM.

[0022] In some implementations of the BS described herein, the total number includes: the total number of successful completions of the cell handover procedure alone; or both the total number of failed LTM cell handovers and the total number of successful completions of the cell handover procedure.

[0023] Some embodiments of this disclosure provide a processor for wireless communication, comprising: at least one controller coupled to at least one memory and configured to: receive a Radio Resource Control (RRC) reconstruction request from a User Equipment (UE) after a failure of a lower-layer triggered Mobility (LTM) cell handover procedure; and transmit an RRC reconstruction message to the UE.

[0024] Some embodiments of this disclosure provide a method performed by a base station (BS). The method includes: receiving a Radio Resource Control (RRC) reconstruction request from a User Equipment (UE) after a failure of a lower-layer triggered mobility (LTM) cell handover procedure; and transmitting an RRC reconstruction message to the UE.

[0025] Some embodiments of this disclosure provide a source base station (BS). The source BS includes: at least one memory; and at least one processor coupled to the at least one memory and configured to cause the source BS to: transmit lower-layer triggered mobility (LTM) configuration information associated with a candidate cell of the UE to a user equipment (UE); and transmit an LTM cell handover command to the UE for triggering a cell handover procedure from the source cell of the source BS to the candidate cell, wherein the LTM cell handover command includes at least one of: an identifier (ID) information of the candidate cell; or an early timing advance (TA) value of the candidate cell.

[0026] In some implementations of the source BS described herein, the processor is configured to receive a report of LTM cell handover failure from a third BS, wherein the report is transmitted by the UE to the third BS.

[0027] In some implementations of the source BS described herein, the report includes at least one of the following: the early TA value of the candidate cell; information indicating whether the cell handover procedure is an LTM cell handover based on no random access channel (RACH) or an LTM cell handover based on RACH; information indicating whether the cell handover procedure has failed for a RACH-based LTM cell handover with configuration authorization (CG); information indicating whether the cell handover procedure is a RACH-based LTM cell handover failure without CG; information indicating whether the LTM cell handover failure occurred; the Layer 1 (L1) measurement result of the source cell when the LTM cell handover failure occurred; or the L1 measurement result of the candidate cell when the LTM cell handover failure occurred.

[0028] In some implementations of the source BS described herein, the processor is configured to receive a secondary cell group (SCG) failure information message from the UE after a supervisory timer expires.

[0029] In some implementations of the source BS described herein, the SCG failure information message includes at least one of the following: information indicating an LTM cell handover failure; a Layer 1 (L1) measurement result of the source cell when the LTM cell handover failure occurs; an L1 measurement result of the candidate cell when the LTM cell handover failure occurs; information indicating an LTM cell handover failure based on RACH-free; information indicating an LTM cell handover failure based on RACH-free with Configurable Citation (CG); information indicating an LTM cell handover failure based on RACH-free without CG; information indicating an LTM cell handover failure based on RACH; or information indicating the expiration of the surveillance timer.

[0030] In some implementations of the source BS described herein, at least one of the L1 measurement results of the source cell or the L1 measurement results of the candidate cell is encapsulated in a container of a Radio Resource Control (RRC) message.

[0031] Some embodiments of this disclosure provide a processor for wireless communication, comprising: at least one controller coupled to at least one memory and configured to: transmit to a user equipment (UE) lower-layer triggered mobility (LTM) configuration information associated with a candidate cell of the UE; and transmit to the UE an LTM cell handover command for triggering a cell handover procedure from a source cell of the source BS to the candidate cell, wherein the LTM cell handover command includes at least one of: identifier (ID) information of the candidate cell; or early timing advance (TA) value of the candidate cell.

[0032] Some embodiments of this disclosure provide a method performed by a source base station (BS). The method includes: transmitting lower-layer triggered mobility (LTM) configuration information associated with a candidate cell of the UE to a user equipment (UE); and transmitting an LTM cell handover command to the UE for triggering a cell handover procedure from the source cell of the source BS to the candidate cell, wherein the LTM cell handover command includes at least one of: an identifier (ID) information of the candidate cell; or an early timing advance (TA) value of the candidate cell.

[0033] Some embodiments of this disclosure provide a distributed unit (DU) for a base station (BS). The DU includes: at least one memory; and at least one processor coupled to the at least one memory and configured to cause the DU to: transmit a physical downlink control channel (PDCCH) command to a user equipment (UE) for triggering an early timing advance (TA) acquisition associated with a candidate cell, wherein the candidate cell is associated with a cell handover procedure; determine whether a failure of the early TA acquisition has occurred; and if it is determined that the failure of the early TA acquisition has occurred, then transmit information indicating the failure of the early TA acquisition to a centralized unit (CU) of the BS.

[0034] In some implementations of the DU described herein, the cell handover procedure is: a primary cell (PCell) handover procedure for the primary cell group; or a primary auxiliary cell group (PSCell) handover procedure.

[0035] In some implementations of the DU described herein, the processor is configured to transmit at least one of the following to the CU of the BS: the UE's identifier (ID) information; or the timer length of a timing advance timer (TAT) associated with the early TA acquisition.

[0036] In some implementations of the DU described herein, in response to the occurrence of the failure, the processor is configured to cause the DU to: trigger an early TA reacquisition associated with the candidate cell; or retransmit the PDCCH command to the UE for triggering the early TA reacquisition associated with the candidate cell.

[0037] In some embodiments of the DU described herein, the processor is configured to transmit to the CU of the BS at least one of the following: information indicating whether an early TA reacquisition caused by the occurrence of the failure is triggered; a total number of early TA acquisitions performed on the candidate cell before the DU receives the early TA value of the candidate cell; or a total number of PDCCH commands for triggering the early TA acquisition associated with the candidate cell before the DU receives the early TA value of the candidate cell.

[0038] Some embodiments of this disclosure provide a processor for wireless communication, comprising: at least one controller coupled to at least one memory and configured to: transmit to a user equipment (UE) a physical downlink control channel (PDCCH) command for triggering an early timing advance (TA) acquisition associated with a candidate cell, wherein the candidate cell is associated with a cell handover procedure; determine whether a failure of the early TA acquisition has occurred; and if it is determined that the failure of the early TA acquisition has occurred, then transmit information indicating the failure of the early TA acquisition to a centralized unit (CU) of the BS.

[0039] Some embodiments of this disclosure provide a method performed by a distributed unit (DU) of a base station (BS). The method includes: transmitting a physical downlink control channel (PDCCH) command to a user equipment (UE) for triggering an early timing advance (TA) acquisition associated with a candidate cell, wherein the candidate cell is associated with a cell handover procedure; determining whether a failure of the early TA acquisition has occurred; and if it is determined that the failure of the early TA acquisition has occurred, then transmitting information indicating the failure of the early TA acquisition to a centralized unit (CU) of the BS.

[0040] Some embodiments of this disclosure provide a first distributed unit (DU) for a first base station (BS). The first DU includes: at least one memory; and at least one processor coupled to the at least one memory and configured such that the first DU: transmits a physical downlink control channel (PDCCH) command for triggering early timing advance (TA) acquisition associated with a candidate cell, wherein the candidate cell is associated with a cell handover procedure of a user equipment (UE); receives an early TA value of the candidate cell from a candidate DU of a second BS associated with the candidate cell, wherein the first BS is the same as or different from the second BS; stores the early TA value of the candidate cell; and determines whether the early TA value of the candidate cell is valid.

[0041] In some embodiments of the first DU described herein, the processor is configured to determine whether the early TA value of the candidate cell is valid based on a timer or a threshold of reference signal received power (RSRP), and wherein the processor is configured to cause the first DU to: determine that the early TA value of the candidate cell is invalid if the timer expires; or determine that the early TA value of the candidate cell is invalid if the RSRP change is greater than the threshold.

[0042] In some implementations of the first DU described herein, if the early TA value of the candidate cell is invalid, the processor is configured to cause the first DU to retransmit the PDCCH command to the UE for triggering the early TA acquisition associated with the candidate cell.

[0043] In some embodiments of the first DU described herein, the processor is configured to send an LTM cell handover command to the UE for triggering a cell handover procedure toward the candidate cell, wherein the LTM cell handover command includes at least one of the following: identifier (ID) information of the candidate cell; or the early TA value of the candidate cell.

[0044] In some embodiments of the first DU described herein, the processor is configured to cause the first DU to: log the time when the LTM cell handover command is transmitted; and transmit the time when the LTM cell handover command is transmitted to the candidate DU associated with the candidate cell.

[0045] In some embodiments of the first DU described herein, the processor is configured to transmit to the CU of the first BS or the second BS one of the following: the time elapsed between receiving the earliest received early TA value of the candidate cell and the time of triggering the cell handover procedure toward the candidate cell; or the time elapsed between receiving the most recently received early TA value of the candidate cell and the time of triggering the cell handover procedure toward the candidate cell.

[0046] In some embodiments of the first DU described herein, the processor is configured to transmit to the CU of the first BS or the second BS at least one of the following: information indicating whether an early TA reacquisition associated with the candidate cell has been triggered, wherein the early TA reacquisition is due to an invalid determination of the received early TA value of the candidate cell; the total number of early TA reacquisitions performed on the candidate cell due to the invalid determination of the early TA value of the candidate cell; a timer length for a time alignment timer (TAT) for determining whether the received early TA value of the candidate cell is valid; or a threshold related to a change in reference signal received power (RSRP) for determining whether the received early TA value of the candidate cell is valid.

[0047] Some embodiments of this disclosure provide a processor for wireless communication, comprising: at least one controller coupled to at least one memory and configured to: transmit a physical downlink control channel (PDCCH) command for triggering early timing advance (TA) acquisition associated with a candidate cell, wherein the candidate cell is associated with a cell handover procedure of a user equipment (UE); receive an early TA value of the candidate cell from a candidate DU of a second BS associated with the candidate cell, wherein the first BS is the same as or different from the second BS; store the early TA value of the candidate cell; and determine whether the early TA value of the candidate cell is valid.

[0048] Some embodiments of this disclosure provide a method performed by a first distributed unit (DU) of a first base station (BS). The method includes: transmitting a physical downlink control channel (PDCCH) command for triggering early timing advance (TA) acquisition associated with a candidate cell, wherein the candidate cell is associated with a cell handover procedure of a user equipment (UE); receiving an early TA value of the candidate cell from a candidate DU of a second BS associated with the candidate cell, wherein the first BS may be the same as or different from the second BS; storing the early TA value of the candidate cell; and determining whether the early TA value of the candidate cell is valid.

[0049] Some embodiments of this disclosure provide a first centralized unit (CU) for a base station (BS). The first CU includes: at least one memory; and at least one processor coupled to the at least one memory and configured to cause the first CU to: transmit a lower-layer triggered mobility (LTM) candidate cell configuration associated with a candidate cell to a user equipment (UE); and transmit random access channel (RACH) resources for early timing advance (TA) acquisition to a source distributed unit (DU) managed by the first CU, wherein the candidate cell is associated with a cell handover procedure from the UE's source cell to the candidate cell.

[0050] In some embodiments of the first CU described herein, the processor is configured to receive information from the DU of the BS managed by the first CU indicating a failure of the early TA acquisition associated with the candidate cell.

[0051] In some implementations of the first CU described herein, the cell handover procedure is: a primary cell (PCell) handover procedure for the primary cell group; or a primary auxiliary cell group (PSCell) handover procedure.

[0052] In some embodiments of the first CU described herein, the processor is configured to receive from the source DU at least one of the following: the UE's identifier (ID) information; or the timer length of a timing advance timer (TAT) associated with the early TA acquisition.

[0053] In some implementations of the first CU described herein, if the candidate cell is associated with the target DU of the BS, then the processor is configured to cause the first CU to transmit at least one of the following to the target DU: the information indicating the failure; the ID information of the UE; or the timer length of the TAT associated with the early TA acquisition.

[0054] In some implementations of the first CU described herein, if the candidate cell is associated with the second CU, then the processor is configured such that the first CU transmits at least one of the following to the second CU: the information indicating the failure; the ID information of the UE; or the timer length of the TAT associated with the early TA acquisition.

[0055] In some embodiments of the first CU described herein, the processor is configured to receive from the source DU first information containing at least one of the following: information indicating whether an early TA reacquisition caused by the occurrence of the failure has been triggered; the total number of times an early TA acquisition procedure is performed on the candidate cell before the source DU receives the early TA value of the candidate cell; or the total number of times a PDCCH command for triggering the early TA acquisition associated with the candidate cell is transmitted before the source DU receives the early TA value of the candidate cell.

[0056] In some embodiments of the first CU described herein, the processor is configured to receive from the source DU second information comprising one of the following: the time elapsed between receiving the earliest received early TA value of the candidate cell and the time at which the cell handover procedure toward the candidate cell is triggered; or the time elapsed between receiving the most recently received early TA value of the candidate cell and the time at which the cell handover procedure toward the candidate cell is triggered.

[0057] In some embodiments of the first CU described herein, the processor is configured to receive from the source DU third information including at least one of the following: information indicating whether an early TA reacquisition associated with the candidate cell has been triggered, wherein the early TA reacquisition is due to an invalid determination of the received early TA value of the candidate cell; the total number of early TA reacquisitions performed on the candidate cell due to the invalid determination of the early TA value of the candidate cell; a timer length for a time alignment timer (TAT) for determining whether the received early TA value of the candidate cell is valid; or a threshold related to a change in reference signal received power (RSRP) for determining whether the received early TA value of the candidate cell is valid.

[0058] In some implementations of the first CU described herein, if the candidate cell is associated with a third CU, then the processor is configured such that the first CU transmits at least one of the following to the third CU: the first information; the second information; or the third information.

[0059] In some implementations of the first CU described herein, the timer length for determining whether the TA value of the candidate cell is valid is generated by the source DU, and wherein if the UE fails to complete the cell handover procedure from the source cell to the candidate cell, the processor is configured to cause the first CU to transmit information to the source DU indicating that the cell handover procedure to the candidate cell has failed.

[0060] Some embodiments of this disclosure provide a processor for wireless communication, comprising: at least one controller coupled to at least one memory and configured to: transmit a lower-layer triggered mobility (LTM) candidate cell configuration associated with a candidate cell to a user equipment (UE); and transmit random access channel (RACH) resources for early timing advance (TA) acquisition to a source distributed unit (DU) managed by a first CU, wherein the candidate cell is associated with a cell handover procedure from the UE's source cell toward the candidate cell.

[0061] Some embodiments of this disclosure provide a method performed by a first centralized unit (CU) of a base station (BS). The method includes: transmitting a lower-layer triggered mobility (LTM) candidate cell configuration associated with a candidate cell to a user equipment (UE); and transmitting random access channel (RACH) resources for early timing advance (TA) acquisition to a source distributed unit (DU) managed by the first CU, wherein the candidate cell is associated with a cell handover procedure from the UE's source cell to the candidate cell.

[0062] Some embodiments of this disclosure provide a target centralized unit (CU) for a first base station (BS). The target CU includes: at least one memory; and at least one processor coupled to the at least one memory and configured such that the target CU: receives from a source CU of a second BS information indicating a failure to acquire an early timing advance (TA) associated with a candidate cell or an invalid early timing advance (TA) value for the candidate cell, wherein the candidate cell is associated with a cell handover procedure from a source cell of a user equipment (UE) toward the candidate cell, and wherein the source cell is associated with the source CU and the candidate cell is associated with the target CU.

[0063] In some implementations of the target CU described herein, the cell handover procedure is: a primary cell (PCell) handover procedure for the primary cell group; or a primary auxiliary cell group (PSCell) handover procedure.

[0064] In some implementations of the target CU described herein, the processor is configured to receive from the source CU at least one of the following: the UE's identifier (ID) information; or the timer length of a timing advance timer (TAT) associated with the early TA acquisition.

[0065] In some implementations of the target CU described herein, the processor is configured to transmit at least one of the following to a target DU managed by the target CU associated with the candidate cell: information indicating the occurrence of the failure; the ID information of the UE; or the timer length of the TAT associated with the early TA acquisition.

[0066] In some embodiments of the target CU described herein, the processor is configured to receive from the source CU first information containing at least one of the following: information indicating whether an early TA reacquisition caused by the occurrence of the failure has been triggered; the total number of early TA acquisitions performed on the candidate cell before the source DU receives the early TA value of the candidate cell; or the total number of PDCCH commands transmitted to trigger the early TA acquisition associated with the candidate cell before the source DU receives the early TA value of the candidate cell.

[0067] In some embodiments of the target CU described herein, the processor is configured to receive from the source CU second information including one of the following: the time elapsed between receiving the earliest received early TA value of the candidate cell and the time at which the cell handover procedure toward the candidate cell is triggered; or the time elapsed between receiving the most recently received early TA value of the candidate cell and the time at which the cell handover procedure toward the candidate cell is triggered.

[0068] In some implementations of the target CU described herein, the processor is configured to receive from the source CU third information including at least one of the following: information indicating whether an early TA reacquisition associated with the candidate cell has been triggered, wherein the early TA reacquisition is due to an invalid determination of the received early TA value of the candidate cell; the total number of early TA reacquisitions performed on the candidate cell due to the invalid determination of the early TA value of the candidate cell; a timer length for a time alignment timer (TAT) used to determine whether the received early TA value of the candidate cell is valid; or a threshold related to a change in reference signal received power (RSRP) used to determine whether the received early TA value of the candidate cell is valid.

[0069] In some implementations of the target CU described herein, the processor is configured to cause the target CU to transmit at least one of the following to a target DU managed by the target CU associated with the candidate cell: the first information; the second information; or the third information.

[0070] Some embodiments of this disclosure provide a processor for wireless communication, comprising: at least one controller coupled to at least one memory and configured such that the processor: receives from a source CU of a BS information indicating a failure of early timing advance (TA) acquisition associated with a candidate cell or an invalid early timing advance (TA) value of the candidate cell, wherein the candidate cell is associated with a cell handover procedure from a source cell of a user equipment (UE) toward the candidate cell, and wherein the source cell is associated with the source CU and the candidate cell is associated with the target CU.

[0071] Some embodiments of this disclosure provide a method performed by a target centralized unit (CU) of a first base station (BS). The method includes receiving from a source CU of a second BS information indicating a failure to acquire an early timing advance (TA) associated with a candidate cell or an invalid early timing advance (TA) value for the candidate cell, wherein the candidate cell is associated with a cell handover procedure from a source cell of a user equipment (UE) toward the candidate cell, and wherein the source cell is associated with the source CU and the candidate cell is associated with the target CU. Attached Figure Description

[0072] Figure 1 Examples of wireless communication systems according to aspects of this disclosure are described.

[0073] Figure 2 An example of a user equipment (UE) 200 according to aspects of this disclosure is described.

[0074] Figure 3 An example of processor 300 according to aspects of this disclosure is described.

[0075] Figure 4 An example of a network equipment (NE) 400 according to aspects of this disclosure is described.

[0076] Figure 5A A schematic diagram illustrating a mobility scenario within a CU and DU according to aspects of this disclosure.

[0077] Figure 5B A schematic diagram illustrating a scenario of mobility between DUs within a CU according to aspects of this disclosure.

[0078] Figure 5C A schematic diagram illustrating a scenario of inter-CU mobility according to aspects of this disclosure.

[0079] Figures 6 to 8 A flowchart illustrating a method related to LTM cell handover procedures according to aspects of this disclosure.

[0080] Figure 9A schematic diagram illustrating the MCG LTM procedure according to aspects of this disclosure.

[0081] Figure 10 A schematic diagram illustrating the SCG LTM procedure according to aspects of this disclosure.

[0082] Figures 11 to 13 A flowchart illustrating a method related to LTM cell handover procedures according to aspects of this disclosure.

[0083] Figure 14 A schematic diagram illustrating the LTM cell handover procedure according to aspects of this disclosure.

[0084] Figure 15 A schematic diagram illustrating the LTM cell handover procedure according to aspects of this disclosure. Detailed Implementation

[0085] Generally, when a UE moves from one cell to another, a serving cell change is required at some point. Traditionally, serving cell changes are accomplished through explicit RRC reconfiguration signaling (e.g., handover (HO) commands) used to trigger synchronization of the target cell based on L3 measurement reports. Compared to beam-level mobility, explicit RRC reconfiguration signaling results in longer latency, greater overhead, and longer downtime. Therefore, in 3GPP, LTM is permitted to change serving cells via L1 / L2 signaling to reduce latency, overhead, and downtime.

[0086] LTM is a procedure in which the BS receives an L1 measurement report from the UE and, based on the report, changes the UE's serving cell via a cell handover command signaled via MACCE. The cell handover command indicates a previously prepared LTM candidate cell configuration provided to the UE via RRC signaling. The UE then hands over to the target cell according to the cell handover command. LTM procedures can be used to reduce mobility latency.

[0087] In some cases, subsequent LTM may be supported. Subsequent LTM means that the UE does not need a subsequent LTM cell handover procedure between candidate cells that has been reconfigured by the network.

[0088] A supervisory timer can be used to detect failures in LTM execution or LTM cell handover procedures. If the LTM supervisory timer expires, the LTM procedure fails, and the UE initiates an RRC connection re-establishment procedure. For example, the conventional T304 timer is used as a supervisory timer to monitor the LTM cell handover procedure.

[0089] "LTM candidate cell" refers to the candidate cell configured for LTM by the UE. Multiple LTM candidate cells can be prepared for the UE, and these LTM candidate cells can belong to the same or different candidate DUs.

[0090] "LTM candidate cell configuration" refers to the configuration associated with an LTM candidate cell. An LTM candidate cell configuration can be a complete LTM candidate cell configuration or a differential configuration relative to an LTM reference configuration. Each LTM candidate cell configuration can be identified by an index, referred to as the LTM candidate cell configuration index, LTM candidate configuration index, or other names. In one instance, the LTM candidate cell configuration index is LTM-CandidateId, which identifies the LTM candidate cell configuration.

[0091] "LTM reference configuration" refers to the configuration provided by the network to the UE that is common to all configured LTM candidate cells. The UE uses the LTM reference configuration to generate a complete LTM candidate cell configuration (i.e., by applying the LTM candidate cell configuration on top of the LTM reference configuration).

[0092] "Complete LTM candidate cell configuration" refers to a configuration containing all the necessary fields required to perform the LTM cell handover procedure. This configuration can be the LTM candidate cell configuration itself or generated by applying the LTM candidate cell configuration on top of the LTM reference configuration.

[0093] MCG LTM is a PCell handover procedure triggered by the Media Access Control (MAC) element (CE) based on L1 measurements. SCG LTM is a PSCell handover procedure triggered by the Media Access Control (MAC) element (CE) based on L1 measurements. Potential application scenarios for LTM include "CU-DU LTM", "CU-DU inter-CU LTM", and "CU-inter-CU LTM", as described below. Figures 5A to 5C It is displayed in the middle.

[0094] (1) Intra-CU and intra-DU mobility: UE moves between different cells within a DU.

[0095] (2) Mobility between DUs within a CU: The UE moves between different cells belonging to different DUs but within the same CU.

[0096] (3) Inter-CU mobility: The UE moves between different cells belonging to different DUs and different CUs.

[0097] Mobility Robustness Optimization (MRO) is designed to detect connection failures caused by premature or late handovers or handovers to the wrong cell. The general procedure is that after an RLF (Reconnection-Based Failure) or handover (HO) failure, the UE can re-establish or configure the connection to access a new cell. Once the UE is in a connected state, it transmits an RLF report and a RACH (Reconnection-Based Response) report to the serving cell. The serving cell then transmits a failure indication containing the RLF report to the last serving cell. Finally, this information is used to optimize mobility. One of the functions of MRO is to detect connection failures caused by premature or late handovers or handovers to the wrong cell.

[0098] Currently, in order to analyze connection failures, the UE can make RLF reports available to the network. The UE stores the latest RLF report, including both LTE and NR RLF reports, until the RLF report is retrieved by the network or stored for 48 hours after a connection failure is detected. For example, the UE only indicates the availability of RLF reports and only provides RLF reports to the network if the current RPLMN is present in the UE's EPLMN list or is the PLMN of the RPLMN at the time the connection failure is detected. In the case of an RLF occurring in an E-UTRA cell, the UE makes LTE RLF reports available to the NG-RAN node and eNB, and in the case of an RLF occurring in an NR cell, the UE makes NR RLF reports available to the gNB. If an LTE RLF report is reported to an NG-RAN node and the last serving node is an E-UTRAN node, the NG-RAN node can transmit the LTE RLF report to the E-UTRAN node by triggering an uplink RAN ​​configuration transfer procedure on the NG, and the E-UTRAN node can take this into account, as defined in 3GPP TS 36.300 [2].

[0099] In 3GPP Rel-17, Successful Handover Reports (SHRs) were introduced for the MRO (Maintenance, Repair, and Operations) of the PCell change procedure. Specifically, the MRO functionality in NR (Normally, Radio Frequency) needs to be enhanced to provide more robust mobility by reporting failure events observed during successful handover. The solution to this problem is to configure the UE to compile a report associated with successful handover, which includes a set of measurements collected during the handover phase—measurements at the time the handover is triggered, at the end of the handover execution, or after the handover execution. The UE can be configured with trigger conditions to compile the SHR, so the report is only triggered when the conditions are met. This restricts UE reporting to relevant situations, such as underlying problems detected by the RLM (Remote Management System) or BFD (Breakpoint Defect) detected at the time of a successful handover event.

[0100] Information related to a successful PCell change can be included in the SHR. The availability of the SHR can be indicated by a handover completion message (e.g., an RRC reconfiguration completion message) transmitted from the UE to the target NG-RAN node via RRC. The target NG-RAN node can retrieve the successful handover report information via the UE information request / response mechanism. Additionally, the target NG-RAN node can then forward the SHR to the source NG-RAN node to indicate any failures experienced during the successful handover event.

[0101] Upon receiving an SHR, the receiving node can analyze whether its mobility configuration needs adjustment. Such adjustments can lead to changes in mobility configuration, such as changes to the RLM configuration or changes to the mobility threshold between the source and destination. Additionally, during a successful handover, the destination NG-RAN node can further optimize dedicated RACH resources based on measurements reported after a successful handover.

[0102] One goal of mobility enhancements in 3GPP Rel-18 is to specify LTM procedures (i.e., PCell or PSCell handover procedures triggered by the MAC CE based on L1 measurements). To improve mobility robustness, the following issues regarding the MRO mechanism for LTM procedures need to be considered, including, for example: what is the MRO mechanism for MCG / SCG LTM failures in intra-CU or inter-CU mobility scenarios; what is the MRO mechanism for failure detection of early TA acquisition in intra-CU or inter-CU mobility scenarios; and / or what is the MRO mechanism for invalid determination of early TA values ​​in intra-CU or inter-CU mobility scenarios. Currently, details regarding this MRO mechanism have not been discussed. Embodiments of this disclosure aim to address the above-mentioned problems.

[0103] Specifically, some embodiments of this application study the MRO mechanism for MCG LTM failure, where LTM is supported for intra-CU or inter-CU mobility scenarios. If MCG LTM failure occurs, the UE is expected to report auxiliary information for network optimization purposes.

[0104] Some embodiments of this application investigate the MRO mechanism for SCG LTM failure in intra-CU or inter-CU mobility scenarios, wherein an SCG failure information message can be triggered once an SCG LTM failure occurs. For example, auxiliary information related to the SCG LTM failure can be included in the SCG failure information message for network optimization purposes.

[0105] Some embodiments of this application study an MRO mechanism for detecting early TA acquisition failures in intra-CU or inter-CU mobility scenarios, wherein the source DU is responsible for detecting early TA acquisition failures; the RACH resources for early TA acquisition can be configured by the target DU; and it is expected that the source DU will report some auxiliary information for network optimization purposes.

[0106] Some embodiments of this disclosure investigate an MRO mechanism for invalid determination of early TA values ​​in intra- or inter-CU mobility scenarios, wherein the source DU is responsible for checking the validity of early TA values ​​associated with candidate cells. If the source DU determines that an early TA value is invalid, then the source DU may issue a PDCCH command for early TA reacquisition.

[0107] Further details of embodiments of this disclosure will be described below in conjunction with the accompanying drawings.

[0108] Figure 1 This describes an example of a wireless communication system 100 according to aspects of this disclosure. The wireless communication system 100 may include one or more NEs 102, one or more UEs 104, and a core network (CN) 106. The wireless communication system 100 may support various radio access technologies. In some embodiments, the wireless communication system 100 may be a 4G network, such as an LTE network or an LTE-A network. In some other embodiments, the wireless communication system 100 may be an NR network, such as a 5G network, a 5G-A network, or a 5G Ultra Wideband (5G-UWB) network. In other embodiments, the wireless communication system 100 may be a combination of 4G and 5G networks or other suitable radio access technologies, including IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), and IEEE 802.20. The wireless communication system 100 may support radio access technologies beyond 5G, such as 6G. In addition, the wireless communication system 100 can support technologies such as Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), or Code Division Multiple Access (CDMA).

[0109] One or more NEs 102 may be distributed throughout a geographic area to form a wireless communication system 100. One or more of the NEs 102 described herein may be, include, or be referred to as a network node, base station, network element, network function, network entity, wireless access network (RAN), NodeB, eNodeB (eNB), next-generation NodeB (gNB), or other suitable terms. NEs 102 and UEs 104 may communicate via a communication link, which may be wireless or wired. For example, NEs 102 and UEs 104 may perform wireless communication (e.g., receiving signaling, transmitting signaling) via a Uu interface.

[0110] NE 102 can provide a geographic coverage area for which NE 102 can support services for one or more UEs 104 within the geographic coverage area. For example, NE 102 and UE 104 can support wireless communication of signals associated with services (e.g., voice, video, packet data, messaging, broadcasting, etc.) using one or more radio access technologies. In some embodiments, NE 102 can be mobile, such as a satellite associated with a non-terrestrial network (NTN). In some embodiments, different geographic coverage areas 112 associated with the same or different radio access technologies can overlap, but different geographic coverage areas can be associated with different NEs 102.

[0111] One or more UEs 104 may be distributed throughout the geographic area of ​​the wireless communication system 100. UE 104 may include or be referred to as a remote unit, mobile device, wireless device, remote device, subscriber device, transmitter device, receiver device, or some other suitable term. In some embodiments, UE 104 may be referred to as a unit, station, terminal, or client, and other instances thereof. Alternatively or additionally, UE 104 may be referred to as an Internet of Things (IoT) device, Internet of Everything (IoE) device, or Machine-Type Communication (MTC) device, and other instances thereof.

[0112] UE 104 may be able to support direct wireless communication with other UE 104 via a communication link. For example, UE 104 may support direct wireless communication with another UE 104 via a device-to-device (D2D) communication link. In some implementations, such as vehicle-to-vehicle (V2V) deployments, vehicle-to-everything (V2X) deployments, or cellular-V2X deployments, the communication link 114 may be referred to as a sidelink. For example, UE 104 may support direct wireless communication with another UE 104 via a PC5 interface.

[0113] NE 102 may support communication with CN 106 or another NE 102, or both. For example, NE 102 may interface with other NE 102 or CN 106 via one or more backhaul links (e.g., S1, N2, N3, or network interfaces). In some implementations, NE 102 may communicate directly with each other. In other implementations, NE 102 may communicate with each other indirectly (e.g., via CN 106). In some implementations, one or more NE 102 may include sub-components, such as access network entities, which may be instances of Access Node Controllers (ANCs). The ANC may communicate with one or more UE 104s via one or more other access network transmitting entities, which may be referred to as radio headends, smart radio headends, or transmit-receive points (TRPs).

[0114] CN 106 can support user authentication, access authorization, tracking, connectivity, and other access, routing, or mobility functions. CN 106 can be an evolved packet core (EPC) or a 5G core (5GC), which may include control plane entities (e.g., Mobility Management Entity (MME), Access and Mobility Management Function (AMF)) that manage access and mobility, and user plane entities (e.g., Serving Gateway (S-GW), Packet Data Network (PDN) Gateway (P-GW), or User Plane Function (UPF)) that route packets or interconnects to external networks. In some implementations, the control plane entities may manage non-access stratum (NAS) functions, such as mobility, authentication, and bearer management (e.g., data bearers, signaling bearers, etc.) of one or more UEs 104 served by one or more NEs 102 associated with CN106.

[0115] CN 106 can communicate with a packet data network (e.g., via S1, N2, N3, or another network interface) through one or more backhaul links. The packet data network may contain an application server. In some implementations, one or more UEs 104 can communicate with the application server. UE 104 can establish a session (e.g., a Protocol Data Unit (PDU) session or the like) with CN 106 via NE 102. CN 106 can use the established session (e.g., an established PDU session) to route traffic (e.g., control information, data, and the like) between UE 104 and the application server. A PDU session may be an instance of a logical connection between UE 104 and CN 106 (e.g., one or more network functions of CN 106).

[0116] In the wireless communication system 100, NE 102 and UE 104 can use the resources of the wireless communication system 100 (e.g., time resources (e.g., symbols, time slots, subframes, frames, or the like) or frequency resources (e.g., subcarriers, carriers)) to perform various operations (e.g., wireless communication). In some embodiments, NE 102 and UE 104 may support different resource structures. For example, NE 102 and UE 104 may support different frame structures. In some embodiments, such as in 4G, NE 102 and UE 104 may support a single frame structure. In some other embodiments, such as in 5G and other suitable radio access technologies, NE 102 and UE 104 may support various frame structures (i.e., multiple frame structures). NE 102 and UE 104 may support various frame structures based on one or more sets of parameters.

[0117] The wireless communication system 100 may support one or more parameter sets, and the parameter sets may include subcarrier spacing and cyclic prefixes. A first parameter set (e.g., μ=0) may be associated with a first subcarrier spacing (e.g., 15 kHz) and a regular cyclic prefix. In some embodiments, the first parameter set (e.g., μ=0) associated with the first subcarrier spacing (e.g., 15 kHz) may utilize one time slot per subframe. A second parameter set (e.g., μ=1) may be associated with a second subcarrier spacing (e.g., 30 kHz) and a regular cyclic prefix. A third parameter set (e.g., μ=2) may be associated with a third subcarrier spacing (e.g., 60 kHz) and a regular cyclic prefix or an extended cyclic prefix. A fourth parameter set (e.g., μ=3) may be associated with a fourth subcarrier spacing (e.g., 120 kHz) and a regular cyclic prefix. A fifth parameter set (e.g., μ=4) may be associated with a fifth subcarrier spacing (e.g., 240 kHz) and a regular cyclic prefix.

[0118] Time intervals for resources (such as communication resources) can be organized according to frames (also known as radio frames). Each frame may have a duration, for example, 10 milliseconds (ms). In some embodiments, each frame may contain multiple subframes. For example, each frame may contain 10 subframes, and each subframe may have a duration, for example, 1 ms. In some embodiments, each frame may have the same duration. In some embodiments, each subframe of a frame may have the same duration.

[0119] Alternatively, the time intervals of resources (e.g., communication resources) can be organized according to time slots. For example, a subframe may contain a certain number (e.g., a set of parameters). The number of time slots in each subframe may also depend on one or more parameter sets supported in the wireless communication system 100. For example, the first, second, third, fourth, and fifth parameter sets (i.e., μ=0, μ=1, μ=2, μ=3, μ=4) associated with corresponding subcarrier intervals of 15 kHz, 30 kHz, 60 kHz, 120 kHz, and 240 kHz can respectively utilize one time slot per subframe, two time slots per subframe, four time slots per subframe, eight time slots per subframe, and 16 time slots per subframe. Each time slot may contain a certain number (e.g., a set of parameters) of symbols (e.g., OFDM symbols). In some embodiments, the number (e.g., quantity) of time slots in a subframe may depend on the parameter set. For a conventional cyclic prefix, a time slot may contain 14 symbols. For an extended cyclic prefix (e.g., applicable to a 60 kHz subcarrier spacing), a time slot may contain 12 symbols. The relationship between the number of symbols per time slot, the number of time slots per subframe, and the number of time slots per frame for the regular and extended cyclic prefixes may depend on the parameter set. It should be understood that references to the first parameter set (e.g., μ=0) associated with the first subcarrier spacing (e.g., 15 kHz) can be used interchangeably between subframes and time slots.

[0120] In the wireless communication system 100, the electromagnetic (EM) spectrum can be divided into various categories, bands, channels, etc., based on frequency or wavelength. For example, the wireless communication system 100 may support one or more operating frequency bands, such as frequency ranges represented as FR1 (410 MHz to 7.125 GHz), FR2 (24.25 GHz to 52.6 GHz), FR3 (7.125 GHz to 24.25 GHz), FR4 (52.6 GHz to 114.25 GHz), FR4a or FR4-1 (52.6 GHz to 71 GHz), and FR5 (114.25 GHz to 300 GHz). In some embodiments, NE 102 and UE 104 may perform wireless communication on one or more of the operating frequency bands. In some embodiments, FR1 may be used by NE 102 and UE 104, as well as other equipment or devices, for cellular communication services (e.g., control information, data). In some implementations, FR2 can be used by NE 102 and UE 104, as well as other equipment or devices, for short-range, high data rate capabilities.

[0121] FR1 can be associated with one or more parameter sets (e.g., at least three parameter sets). For example, FR1 can be associated with: a first parameter set (e.g., μ=0) containing a 15 kHz subcarrier spacing; a second parameter set (e.g., μ=1) containing a 30 kHz subcarrier spacing; and a third parameter set (e.g., μ=2) containing a 60 kHz subcarrier spacing. FR2 can be associated with one or more parameter sets (e.g., at least two parameter sets). For example, FR2 can be associated with: a third parameter set (e.g., μ=2) containing a 60 kHz subcarrier spacing; and a fourth parameter set (e.g., μ=3) containing a 120 kHz subcarrier spacing.

[0122] Figure 2 An example of a UE 200 according to aspects of this disclosure is described. UE 200 may include a processor 202, a memory 204, a controller 206, and a transceiver 208. The processor 202, memory 204, controller 206, or transceiver 208, or various combinations thereof, or various components thereof, may be examples of components for performing the aspects of this disclosure described herein. These components may be coupled via one or more interfaces (e.g., operatively, communicatively, functionally, electronically, or electrically).

[0123] Processor 202, memory 204, controller 206, or transceiver 208, or various combinations or components thereof, may be implemented in hardware (e.g., a circuit system). The hardware may include processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), or other programmable logic devices, or any combination thereof configured or otherwise supporting components for performing the functions described in this disclosure.

[0124] Processor 202 may include intelligent hardware devices (e.g., general-purpose processors, DSPs, CPUs, ASICs, FPGAs, or any combination thereof). In some embodiments, processor 202 may be configured to operate memory 204. In some other embodiments, memory 204 may be integrated into processor 202. Processor 202 may be configured to execute computer-readable instructions stored in memory 204 to cause UE 200 to perform various functions of this disclosure.

[0125] Memory 204 may comprise volatile or non-volatile memory. Memory 204 may store computer-readable, computer-executable code containing instructions that, when executed by processor 202, cause UE 200 to perform the various functions described herein. The code may be stored in a non-transitory computer-readable medium, such as this memory 204 or another type of memory. Computer-readable media includes both non-transitory computer storage media and communication media, including any medium that facilitates the transfer of computer programs from one place to another. Non-transitory storage media may be any available medium accessible by a general-purpose or special-purpose computer.

[0126] In some implementations, processor 202 and memory 204 coupled to processor 202 may be configured to cause UE 200 to perform one or more of the functions described herein (e.g., instructions stored in memory 204 are executed by processor 202). For example, processor 202 may support wireless communication at UE 200 according to the examples disclosed herein. In response to the occurrence of a failure associated with an LTM PCell handover procedure from source cell to target cell of UE 200, UE 200 may be configured to support: means for receiving LTM configuration information related to a candidate cell of a second BS from the source cell of a first BS, wherein the first BS and the second BS may be the same or different; means for receiving an LTM cell handover command from the source cell to trigger a cell handover procedure, wherein the LTM cell handover command includes at least one of candidate cell identifier (ID) information or candidate cell early timing advance (TA) value; and means for executing a cell handover procedure toward the candidate cell and starting a supervisory timer after receiving the LTM cell handover command.

[0127] Controller 206 manages the input and output signals of UE 200. Controller 206 can also manage peripheral devices not integrated into UE 200. In some embodiments, controller 206 may utilize an operating system, such as iOS®, ANDROID®, WINDOWS®, or other operating systems. In some embodiments, controller 206 may be implemented as part of processor 202.

[0128] In some embodiments, UE 200 may include at least one transceiver 208. In other embodiments, UE 200 may have more than one transceiver 208. Transceiver 208 may represent a wireless transceiver. Transceiver 208 may include one or more receiver chains 210, one or more transmitter chains 212, or a combination thereof. The aforementioned components for receiving in processor 202 or for transmitting in processor 202 may be implemented via at least one transceiver 208.

[0129] Receiver chain 210 may be configured to receive signals (e.g., control information, data, packets) via a wireless medium. For example, receiver chain 210 may include one or more antennas for receiving signals over the air or via a wireless medium. Receiver chain 210 may include at least one amplifier (e.g., a low-noise amplifier (LNA)) configured to amplify the received signal. Receiver chain 210 may include at least one demodulator configured to demodulate the received signal by reversing the modulation technique applied during signal transmission and to obtain the transmitted data. Receiver chain 210 may include at least one decoder for decoding and processing the demodulated signal to receive the transmitted data.

[0130] Transmitter chain 212 can be configured to generate and transmit signals (e.g., control information, data, packets). Transmitter chain 212 may include at least one modulator for modulating data onto a carrier signal in preparation for transmission over a wireless medium. The at least one modulator may be configured to support one or more techniques, such as amplitude modulation (AM), frequency modulation (FM), or digital modulation schemes like phase shift keying (PSK) or quadrature amplitude modulation (QAM). Transmitter chain 212 may also include at least one power amplifier configured to amplify the modulated signal to an appropriate power level suitable for transmission over a wireless medium. Transmitter chain 212 may also include one or more antennas for transmitting the amplified signal into the air or a wireless medium.

[0131] Figure 3An example of a processor 300 according to aspects of this disclosure is described. Processor 300 may be an example of a processor configured to perform various operations according to the examples described herein. Processor 300 may include a controller 302 configured to perform various operations according to the examples described herein. Processor 300 may optionally include at least one memory 304, which may be, for example, an L1 / L2 / L3 cache. Additionally or alternatively, processor 300 may optionally include one or more arithmetic logic units (ALUs) 306. One or more of these components may be electronically communicated or otherwise coupled (e.g., operatively, communicatively, functionally, electronically, electrically) via one or more interfaces (e.g., buses).

[0132] Processor 300 may be a processor chipset and includes a protocol stack (e.g., a software stack) executed by the processor chipset to perform various operations (e.g., receive, acquire, retrieve, transmit, output, forward, store, determine, identify, access, write, read) according to the examples described herein. The processor chipset may include one or more cores, one or more caches (e.g., memory local to the processor chipset (e.g., processor 300) or included in the processor chipset) or other memory (e.g., random access memory (RAM), read-only memory (ROM), dynamic RAM (DRAM), synchronous dynamic RAM (SDRAM), static RAM (SRAM), ferroelectric RAM (FeRAM), magnetic RAM (MRAM), resistive RAM (RRAM), flash memory, phase-change memory (PCM), and others).

[0133] Controller 302 can be configured to manage and coordinate various operations of processor 300 (e.g., signaling, receiving, acquiring, retrieving, transmitting, outputting, forwarding, storing, determining, identifying, accessing, writing, and reading) to enable processor 300 to support various operations according to the examples described herein. For example, controller 302 can operate as a control unit of processor 300, generating control signals that manage the operation of various components of processor 300. These control signals include enabling or disabling functional units, selecting data paths, initiating memory access, and coordinating operation timing.

[0134] Controller 302 may be configured to fetch (e.g., fetch, retrieve, receive) instructions from memory 304 and determine subsequent instructions to be executed to enable processor 300 to support various operations according to the examples described herein. Controller 302 may be configured to track the memory addresses of instructions associated with memory 304. Controller 302 may be configured to decode instructions to determine the operations to be performed and the operands involved. For example, controller 302 may be configured to interpret instructions and determine control signals to be output to other components of processor 300 to enable processor 300 to support various operations according to the examples described herein. Alternatively or additionally, controller 302 may be configured to manage data flow within processor 300. Controller 302 may be configured to control data transfers between registers, arithmetic logic unit (ALU), and other functional units of processor 300.

[0135] Memory 304 may include one or more caches (e.g., memory local to or included in processor 300) or other memories, such as RAM, ROM, DRAM, SDRAM, SRAM, MRAM, flash memory, etc. In some embodiments, memory 304 may reside within or on the processor chipset (e.g., locally to processor 300). In some other embodiments, memory 304 may reside outside the processor chipset (e.g., remotely from processor 300).

[0136] Memory 304 may store computer-readable, computer-executable code containing instructions that, when executed by processor 300, cause processor 300 to perform the various functions described herein. The code may be stored in a non-transitory computer-readable medium, such as system memory or another type of memory. Controller 302 and / or processor 300 may be configured to execute the computer-readable instructions stored in memory 304 to cause processor 300 to perform various functions. For example, processor 300 and / or controller 302 may be coupled to or coupled to memory 304, and processor 300, controller 302, and memory 304 may be configured to perform the various functions described herein. In some instances, processor 300 may include multiple processors, and memory 304 may include multiple memories. One or more of the multiple processors may be coupled to one or more of the multiple memories, which may be individually or jointly configured to perform the various functions described herein.

[0137] One or more ALUs 306 may be configured to support various operations according to the examples described herein. In some embodiments, one or more ALUs 306 may reside within or on a processor chipset (e.g., processor 300). In some other embodiments, one or more ALUs 306 may reside outside the processor chipset (e.g., processor 300). One or more ALUs 306 may perform one or more computations on data, such as addition, subtraction, multiplication, and division. For example, one or more ALUs 306 may receive input operands and opcodes, which determine the operation to be performed. One or more ALUs 306 are configured with various logic and arithmetic circuitry, including adders, subtractors, shifters, and logic gates, to process and manipulate data according to the operation. Alternatively, one or more ALU 306s may support logical operations such as AND, OR, XOR, NOR, and NAND, enabling one or more ALU 306s to handle conditional operations, comparisons, and bitwise operations.

[0138] Processor 300 can support wireless communication according to the examples disclosed herein.

[0139] In some implementations, processor 300 may be configured to support the execution of [specific actions / functions]. Figure 6 The described operation includes components. For example, processor 300 may be configured or operable to support: components for receiving LTM configuration information related to a candidate cell of a second BS from a source cell of a first BS, wherein the first BS and the second BS may be the same or different; components for receiving an LTM cell handover command from the source cell for triggering a cell handover procedure, wherein the LTM cell handover command includes at least one of the following: ID information of the candidate cell; or an early TA value of the candidate cell; and components for executing a cell handover procedure toward the candidate cell and starting a monitoring timer after receiving the LTM cell handover command.

[0140] In some implementations, processor 300 may be configured to support the execution of [specific actions / functions]. Figure 7 The components of the described operation. For example, the processor 300 may be configured or operable to support: components for receiving an RRC reconstruction request from the UE after a failure of the LTM cell handover procedure; and components for transmitting an RRC reconstruction message to the UE.

[0141] In some implementations, processor 300 may be configured to support the execution of [specific actions / functions]. Figure 8The described operation is a component. For example, the processor 300 may be configured or operable to support: a component for transmitting LTM configuration information related to a candidate cell of the UE to the UE; and a component for transmitting an LTM cell handover command to the UE for triggering a cell handover procedure from the source cell of the source BS to the candidate cell, wherein the LTM cell handover command includes at least one of the following: the ID information of the candidate cell; or the early TA value of the candidate cell.

[0142] In some implementations, processor 300 may be configured to support the execution of [specific actions / functions]. Figure 11 The components of the described operation. For example, the processor 300 may be configured or operable to support: components for transmitting to the UE a PDCCH command for triggering early TA acquisition associated with a candidate cell, wherein the candidate cell is associated with a cell handover procedure; components for determining whether an early TA acquisition failure has occurred; and components for transmitting information indicating the failure of early TA acquisition to the CU of the BS if it is determined that an early TA acquisition failure has occurred.

[0143] In some implementations, processor 300 may be configured to support the execution of [specific actions / functions]. Figure 12 The components of the described operation. For example, processor 300 may be configured or operable to support: components for transmitting a PDCCH command to trigger early TA acquisition associated with a candidate cell, wherein the candidate cell is associated with a cell handover procedure of the UE; components for receiving the early TA value of the candidate cell from a candidate DU of a second BS associated with the candidate cell, wherein the first BS and the second BS may be the same or different; components for storing the early TA value of the candidate cell; and components for determining whether the early TA value of the candidate cell is valid.

[0144] In some implementations, processor 300 may be configured to support the execution of [specific actions / functions]. Figure 13 The components of the described operation. For example, the processor 300 may be configured or operable to support: components for transmitting to the UE an LTM candidate cell configuration associated with the candidate cell; and components for transmitting to the source DU managed by the first CU RACH resources for early TA acquisition, wherein the candidate cell is associated with a cell handover procedure from the UE's source cell to the candidate cell.

[0145] In some additional embodiments, processor 300 may be configured to support components for performing the operations disclosed herein. Processor 300 may be configured or operable to support: components for receiving information from a source CU of the BS indicating a failure of early TA acquisition associated with a candidate cell or an invalid early TA value of the candidate cell, wherein the candidate cell is associated with a cell handover procedure from the source cell of the UE to the candidate cell, and wherein the source cell is associated with the source CU and the candidate cell is associated with the target CU.

[0146] Those skilled in the art will understand that components in the exemplary processor 300 can be changed; for example, some components in the exemplary processor 300 can be omitted or modified, or new components can be added to the exemplary processor 300, without departing from the spirit and scope of this disclosure. For instance, in some embodiments, the processor 300 may not include an ALU 306.

[0147] Figure 4 An example of NE 400 according to aspects of this disclosure is described. NE 400 may include a processor 402, a memory 404, a controller 406, and a transceiver 408. The processor 402, memory 404, controller 406, or transceiver 408, or various combinations thereof, or various components thereof, may be examples of components for performing the aspects of this disclosure described herein. These components may be coupled via one or more interfaces (e.g., operatively, communicatively, functionally, electronically, electrically).

[0148] Processor 402, memory 404, controller 406, or transceiver 408, or various combinations or components thereof, may be implemented in hardware (e.g., a circuit system). The hardware may include processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), or other programmable logic devices, or any combination thereof configured or otherwise supporting components for performing the functions described in this disclosure.

[0149] Processor 402 may include intelligent hardware devices (e.g., general-purpose processors, DSPs, CPUs, ASICs, FPGAs, or any combination thereof). In some embodiments, processor 402 may be configured to operate memory 404. In some other embodiments, memory 404 may be integrated into processor 402. Processor 402 may be configured to execute computer-readable instructions stored in memory 404 to cause NE 400 to perform various functions of this disclosure.

[0150] Memory 404 may comprise volatile or non-volatile memory. Memory 404 may store computer-readable, computer-executable code containing instructions that, when executed by processor 402, cause NE 400 to perform the various functions described herein. The code may be stored in a non-transitory computer-readable medium, such as this memory 404 or another type of memory. Computer-readable media include both non-transitory computer storage media and communication media, encompassing any medium that facilitates the transfer of computer programs from one place to another. Non-transitory storage media may be any available medium accessible by a general-purpose or special-purpose computer.

[0151] In some implementations, processor 402 and memory 404 coupled to processor 402 may be configured to cause NE 400 to perform one or more of the functions described herein (e.g., instructions stored in memory 404 are executed by processor 402). For example, processor 402 may support wireless communication at NE 400 according to the examples disclosed herein. For example, NE 400 may be configured to support the execution of instructions regarding... Figure 6 The components of the operation described or the operation of the candidate target SN described below.

[0152] In some implementations, the NE 400 may be a BS. The NE 400 may be configured to support: components for receiving an RRC reconstruction request from the UE after an LTM cell handover procedure failure; and components for transmitting an RRC reconstruction message to the UE.

[0153] In some implementations, NE 400 may be a source BS and configured to support: a component for transmitting LTM configuration information related to the candidate cell of the UE to the UE; and a component for transmitting an LTM cell handover command to the UE for triggering a cell handover procedure from the source cell of the source BS to the candidate cell, wherein the LTM cell handover command includes at least one of the following: the ID information of the candidate cell; or the early TA value of the candidate cell.

[0154] In some implementations, NE 400 may be a source DU of the BS and configured to support: a component for transmitting to the UE a PDCCH command for triggering an early TA acquisition associated with a candidate cell, wherein the candidate cell is associated with a cell handover procedure; a component for determining whether an early TA acquisition failure has occurred; and a component for transmitting information indicating the failure of the early TA acquisition to a first CU of the first BS if it is determined that an early TA acquisition failure has occurred.

[0155] In some implementations, NE 400 may be a source DU of a BS and configured to support: means for transmitting a PDCCH command for triggering early TA acquisition associated with a candidate cell, wherein the candidate cell is associated with a cell handover procedure of the UE; means for receiving an early TA value of a candidate cell from a candidate DU of a second BS associated with the candidate cell, wherein the first BS and the second BS may be the same or different; means for storing the early TA value of the candidate cell; and means for determining whether the early TA value of the candidate cell is valid.

[0156] In some implementations, the NE 400 may be a source DU of the BS and configured to support: a component for transmitting to the UE an LTM candidate cell configuration associated with the candidate cell; and a component for transmitting to the source DU managed by the first CU a RACH resource for early TA acquisition, wherein the candidate cell is associated with a cell handover procedure from the UE's source cell to the candidate cell.

[0157] In some additional implementations, NE 400 may be the target CU of the BS and configured to support: a component for receiving information from the source CU of the BS indicating a failure of early TA acquisition associated with a candidate cell or an invalid early TA value of the candidate cell, wherein the candidate cell is associated with a cell handover procedure from the source cell of the UE to the candidate cell, and wherein the source cell is associated with the source CU and the candidate cell is associated with the target CU.

[0158] Controller 406 manages the input and output signals of NE 400. Controller 406 can also manage peripheral devices not integrated into NE 400. In some embodiments, controller 406 may utilize an operating system, such as iOS®, Android®, Windows®, or other operating systems. In some embodiments, controller 406 may be implemented as part of processor 402.

[0159] In some embodiments, NE 400 may include at least one transceiver 408. In other embodiments, NE 400 may have more than one transceiver 408. Transceiver 408 may represent a wireless transceiver. Transceiver 408 may include one or more receiver chains 410, one or more transmitter chains 412, or a combination thereof. The aforementioned receiving or transmitting components in processor 402 may be implemented via at least one transceiver 408.

[0160] Receiver chain 410 may be configured to receive signals (e.g., control information, data, packets) via a wireless medium. For example, receiver chain 410 may include one or more antennas for receiving signals over the air or via a wireless medium. Receiver chain 410 may include at least one amplifier (e.g., a low-noise amplifier (LNA)) configured to amplify the received signal. Receiver chain 410 may include at least one demodulator configured to demodulate the received signal and obtain transmitted data by reversing the modulation technique applied during signal transmission. Receiver chain 410 may include at least one decoder for decoding and processing the demodulated signal to receive the transmitted data.

[0161] Transmitter chain 412 can be configured to generate and transmit signals (e.g., control information, data, packets). Transmitter chain 412 may include at least one modulator for modulating data onto a carrier signal in preparation for transmission over a wireless medium. The at least one modulator may be configured to support one or more techniques, such as amplitude modulation (AM), frequency modulation (FM), or digital modulation schemes like phase shift keying (PSK) or quadrature amplitude modulation (QAM). Transmitter chain 412 may also include at least one power amplifier configured to amplify the modulated signal to an appropriate power level suitable for transmission over a wireless medium. Transmitter chain 412 may also include one or more antennas for transmitting the amplified signal into the air or a wireless medium.

[0162] Those skilled in the art will understand that components in the exemplary NE 400 can be changed; for example, some components in the exemplary NE 400 can be omitted or modified, or new components can be added to the exemplary NE 400, without departing from the spirit and scope of this disclosure. For instance, in some embodiments, the NE 400 may not include the controller 406.

[0163] Figure 5A A schematic diagram illustrating a mobility scenario within a CU and DU according to aspects of this disclosure. Figure 5A The wireless communication system includes a DU, UEs (e.g., UE 101A), and several access nodes (e.g., access node 102A and access node 103A). Access nodes 102A and 103A are controlled by the DU and provide services to UEs in cell #1 and cell #2, respectively. Even Figure 5A There may be only one UE and two access nodes in the system, but those skilled in the art should recognize that any number of UEs and access nodes may be included in a wireless communication system.

[0164] exist Figure 5AIn this scenario, UE 101A is moving from cell #1 to cell #2 and can perform a handover procedure from cell #1 to cell #2, which is a handover procedure performed between different cells within a DU. This scenario can be referred to as intra-CU / intra-DU mobility. This scenario can be simply referred to as intra-DU mobility.

[0165] Figure 5B A schematic diagram illustrating a scenario of mobility between DUs within a CU according to aspects of this disclosure. Figure 5B The wireless communication system includes a CU, UEs (e.g., UE 101B), and several DUs (e.g., DU 1#1 and DU #2). DU #1 and DU #2 are controlled by the CU and provide services to UEs in cell #A and cell #B, respectively. Even Figure 5B There may be only one UE and two DUs in the system, but those skilled in the art should recognize that any number of UEs and DUs may be included in a wireless communication system.

[0166] exist Figure 5B In this scenario, UE 101B is moving from cell #A to cell #B and can perform a handover procedure from cell #A to cell #B. This handover procedure is performed between different cells belonging to different DUs but within the same CU. This scenario can be referred to as intra-CU inter-DU mobility. It can also be simply referred to as inter-DU mobility.

[0167] Figure 5C A schematic diagram illustrating a scenario of inter-CU mobility according to aspects of this disclosure. Figure 5C The wireless communication system includes several CUs (e.g., CU #1 and CU #2), UEs (e.g., UE 101C), and several DUs (e.g., DU #A and DU #B). DU #A is controlled by CU #1 and provides services to UEs in cell #X. DU #B is controlled by CU #2 and provides services to UEs in cell #Y. Even Figure 5C There may be only one UE, two DUs and two CUs, but those skilled in the art should recognize that any number of UEs, DUs and CUs may be included in a wireless communication system.

[0168] exist Figure 5C In this scenario, UE 101C is moving from cell #X to cell #Y and can execute a handover procedure from cell #X to cell #Y. This handover procedure is performed between different cells belonging to different DUs within different CUs. This scenario can be referred to as inter-CU mobility.

[0169] Figure 6A flowchart illustrating a method related to an LTM cell handover procedure according to aspects of this disclosure is provided. The operation of the method can be implemented by a UE, as described herein. In some embodiments, the UE can execute a set of instructions to control functional elements of the UE to perform the described functions. In some embodiments, aspects operating 602, 604, and 606 can be referenced from... Figure 2 , 5A Performed on any of the UEs described in 5C, 9, and 10, namely UE 200, UE 101A, UE 101B, UE 101C, UE 901, or UE 1001. Each of operations 602, 604, and 606 may be performed according to the examples described herein.

[0170] In operation 602, the method may include receiving LTM configuration information related to a candidate cell of another BS (denoted as "BS #2") from the source cell of a BS (represented as "BS #1"). BS #1 may be the same as or different from BS #2. For example, if BS #1 is the same as BS #2, then it is an intra-BS scenario, i.e., an intra-CU mobility scenario. If BS #1 is different from BS #2, then it is an inter-BS scenario, i.e., an inter-CU mobility scenario.

[0171] In operation 604, the method may include receiving an LTM cell handover command from a source cell to trigger a cell handover procedure. The LTM cell handover command includes at least one of the following: (1) ID information of a candidate cell; or (2) an early TA value of a candidate cell.

[0172] In operation 606, the method may include performing a cell handover procedure toward a candidate cell upon receiving an LTM cell handover command and starting a supervisory timer (also referred to as an LTM timer or similar).

[0173] In some implementations, the cell handover procedure is a PCell handover procedure, i.e., an MCG LTM procedure. In other implementations, the cell handover procedure is a PSCell handover procedure, i.e., an SCG LTM procedure.

[0174] In the implementation scheme, if the cell handover procedure is a PCell handover procedure, i.e., an MCG LTM procedure, then the UE can connect to the cell of the additional BS (denoted as "BS #3") via a reconstruction procedure after the supervisory timer (i.e., the LTM timer) expires. The UE can then transmit information to the cell of BS #3 indicating that a report (denoted as "report #1") indicating an LTM cell handover failure is available. The UE can receive a request for report #1 from BS #3 and then transmit report #1 to BS #3.

[0175] In some implementations of the methods described herein, report #1 (i.e., a report of LTM cell handover failure) includes at least one of the following:

[0176] (1) Early TA value of the candidate cell. In some embodiments, the early TA value of the candidate cell is obtained by the source cell via early TA acquisition and received by the UE from the source cell. In some other embodiments, the early TA value of the candidate cell is set to a fixed value. In some additional embodiments, the early TA value of the candidate cell is set to be the same as the TA value of the source cell.

[0177] (2) Information indicating whether the cell handover procedure is an LTM cell handover based on no random access channel (RACH) or an LTM cell handover based on RACH.

[0178] (3) Indicates whether the cell handover procedure is a failure of LTM cell handover without RACH with configured authorization (CG).

[0179] (4) Indicates whether the cell handover procedure is a failure of LTM cell handover without CG and without RACH.

[0180] (5) Information indicating whether an LTM cell handover failure has occurred.

[0181] (6) When an LTM cell handover failure occurs, the L1 measurement results of the source cell can be encapsulated in the container of the RRC message.

[0182] (7) When an LTM cell handover failure occurs, the L1 measurement results of the candidate cell can be encapsulated in the container of the RRC message.

[0183] In some implementations of the methods described herein, the UE may transmit to BS #3 the total number of LTM executions toward the same candidate cell, provided subsequent LTM is supported. In one implementation, the total number includes only the total number of successful cell handover procedures (i.e., how many times the cell handover procedure was successfully completed). In another implementation, the total number includes both the total number of LTM cell handover failures (i.e., how many times LTM cell handover failures occurred) and the total number of successful cell handover procedures. Specific examples are provided in... Figure 9 The embodiments are described below.

[0184] In some implementations of the methods described herein, if the cell handover procedure is a PSCell handover procedure, i.e., an SCG LTM procedure, then the UE may transmit an SCG failure information message to the MN serving the UE after the supervisory timer (i.e., the LTM timer) expires. For example, the SCG failure information message (represented as "Message #1") may contain at least one of the following:

[0185] (1) Information indicating LTM cell handover failure;

[0186] (2) When an LTM cell handover failure occurs, the L1 measurement results of the source cell can be encapsulated in a container of an RRC message;

[0187] (3) When an LTM cell handover failure occurs, the L1 measurement results of the candidate cell can be encapsulated in a container of an RRC message;

[0188] (4) Information indicating a failed handover of an LTM cell without RACH;

[0189] (5) Information indicating a failed handover of an LTM cell with CG and no RACH;

[0190] (6) Information indicating a failed handover of an LTM cell without CG and without RACH;

[0191] (7) Information indicating a failed LTM cell handover based on RACH; or

[0192] (8) Indicates information about the expiration of the monitoring timer. Specific instances in... Figure 10 The embodiments are described below.

[0193] It should be noted that Figure 6 The methods described herein describe possible implementations, and the operations and steps may be rearranged or otherwise exempted or modified, and other implementations are possible without departing from the spirit and scope of this disclosure.

[0194] Figure 7 A flowchart illustrating a method related to an LTM cell handover procedure according to aspects of this disclosure is provided. The operation of the method can be implemented by a network node, as described herein. In some embodiments, the network node can be a BS (e.g., a Base Station). Figure 6 The BS (#3) described in the embodiments is executable with a set of instructions to control the functional elements of the BS to perform the described functions. In some embodiments, aspects of operation 702 and 704 may be referenced. Figure 4 or Figure 9 The described NE 400 or BS 906 are executed. Each of operations 702 and 704 can be executed according to the instance described herein. Specific instances are... Figure 9 The embodiments are described below.

[0195] In operation 702, the method may include receiving an RRC reconstruction request from the UE after an LTM cell handover procedure failure occurs. In operation 704, the operation may include transmitting an RRC reconstruction message to the UE.

[0196] In some implementations, the LTM cell handover procedure is a PCell handover procedure, i.e., the MCG LTM procedure. In other implementations, the cell handover procedure is a PSCell handover procedure, i.e., the SCG LTM procedure.

[0197] In some implementations of the methods described herein, the BS (e.g., BS #3) may receive a report from the UE indicating an LTM cell handover failure (e.g. Figure 6 The report #1 described in the embodiments is available information. The BS can then send a request for the report to the UE and receive the report from the UE. In some embodiments, the BS can transmit the report to the source BS of the source cell (e.g., Figure 6 The BS #1 described in the embodiments is shown. The report may contain information related to... Figure 6 The elements of report #1 described in the embodiments are similar to those of other elements.

[0198] In some implementations of the methods described herein, the BS may receive from the UE the total number of LTM executions toward the same candidate cell, provided subsequent LTM is supported. In one implementation, the total number includes only the total number of successful cell handover procedures. In another implementation, the total number includes both the total number of failed LTM cell handovers and the total number of successful cell handover procedures.

[0199] It should be noted that Figure 7 The methods described herein describe possible implementations, and the operations and steps may be rearranged or otherwise exempted or modified, and other implementations are possible without departing from the spirit and scope of this disclosure.

[0200] Figure 8 A flowchart illustrating a method related to an LTM cell handover procedure according to aspects of this disclosure is provided. The operation of the method can be implemented by a network node, as described herein. In some embodiments, the network node can be the source BS (e.g., Figure 6 The embodiment describes a BS (#1), and can execute a set of instructions to control the functional elements of the source BS to perform the described functions. In some embodiments, aspects of operation 802 and 804 may be referenced. Figure 4 , 9 Or any of the NE 400, BS905, or BS 1005 described in 10. Each of operations 802 and 804 may be performed according to the examples described herein.

[0201] In operation 802, the method may include transmitting LTM configuration information related to the candidate cell of the UE to the UE. In operation 804, the method may include transmitting an LTM cell handover command to the UE for triggering a cell handover procedure from the source cell of the source BS to the candidate cell. The LTM cell handover command may include at least one of the following: (1) the ID information of the candidate cell; or (2) the early TA value of the candidate cell.

[0202] In some implementations of the method described herein, the source BS may receive an LTM cell handover failure report from another BS, wherein the report is transmitted by the UE to this other BS. The report may contain information related to... Figure 6 The elements of report #1 described in the embodiments are similar to those of other elements.

[0203] In some implementations of the method described herein, the source BS may receive an SCG failure information message from the UE after the supervisory timer (i.e., the LTM timer) expires. The SCG failure information message may contain... Figure 6 The elements are similar to those in message #1 described in the embodiments.

[0204] It should be noted that Figure 8 The methods described herein describe possible implementation schemes, and the operations and steps may be rearranged or otherwise exempted or modified, and other implementation schemes are possible without departing from the spirit and scope of this disclosure.

[0205] Figure 9 A schematic diagram illustrating an MCG LTM procedure according to aspects of this disclosure. The details described in all other embodiments of this disclosure are applicable. Figure 9 The embodiments shown in the figure.

[0206] like Figure 9 The diagram shows that the BS 905 features a CU-DU architecture, including CU 904, source DU 902, and candidate DU 903. Figure 9 In the embodiments, the cell handover operation performed by UE 901 can refer to a CU-based mobility scenario where the source cell and the target cell are in the same CU (e.g., CU 904) or to a scenario where the source cell and the target cell are located in different CUs (e.g., CU 904 and CU 905). Figure 9 The scene of inter-CU mobility at another CU (not shown in the text). For example, Figure 9 The flowchart 900 shown is for illustrative purposes only, illustrating cell handover operations in a mobility scenario within a CU, where source DU 902 and candidate DU 903 are managed by the same CU 904 (e.g., BS #1 and BS #2 are the same, such as...). Figure 6(As described in the embodiments). Flowchart 900 can also be applied where source DU 902 and candidate DU 903 are managed by different CUs (e.g., BS #1 and BS #2 are different, such as...). Figure 6 The CU mobility scenario described in the embodiments.

[0207] exist Figure 9 In the exemplary flowchart 900 shown, during operation 911, UE 901 can access the serving BS (e.g., BS 905) and send measurement reports to the serving BS. The serving BS may contain a CU (e.g., gNB-CU) and one or more DUs (e.g., gNB-DU). The serving cell is associated with the CU and DU. An F1 interface exists between the DU and the CU. For example, in the context of the MCG LTM procedure... Figure 9 In this embodiment, BS 905 is an MCG BS (e.g., an MCG gNB). BS 905 includes CU 904, source DU 902, and candidate DU 903. BS 905 may include one or more other candidate DUs ( Figure 9 (Not shown in the text). In some implementations, UE 901 may send measurement reports to CU 904 via source DU 902.

[0208] In operation 912, the source CU 904 of service BS 905 can determine to initiate an inter-cell mobility configuration procedure based on L1 / L2, that is, to make an inter-cell mobility configuration decision based on L1 / L2.

[0209] In Operation 913, under the intra-CU LTM scenario (i.e., intra-CU mobility scenario), the source CU (e.g., source CU 904) can send a request message (e.g., UE CONTEXT SETUP REQUEST) containing the ID information of the candidate cell to a candidate (target) DU (e.g., candidate DU 903) within the same BS. Requests for RACH resources used for early TA acquisition can also be included in the request message sent to the candidate (target) DU. The candidate cell can also be referred to as the candidate (target) cell. Figure 9 As shown, CU904 can send a request message containing the ID information of the candidate cell to candidate DU903 via the F1 interface.

[0210] Alternatively, in inter-CU LTM scenarios (i.e., inter-CU mobility scenarios), the source CU (e.g., source CU 904 of BS 905) (e.g., BS #1) can send a request message (e.g., a handover (HO) request) containing the candidate cell ID information to the candidate (target) CU. Figure 9(Not shown in the image) (e.g., BS #2). Requests for RACH resources used for early TA acquisition can also be included in the request message transmitted to the candidate (target) CU. The candidate (target) CU can then send a request message containing the candidate cell's ID information (e.g., UE CONTEXT SETUP REQUEST) to the candidate (target) DU. Requests for RACH resources used for early TA acquisition can also be included in the request message transmitted to the candidate (target) DU.

[0211] In operation 914, in the case of LTM within the CU, if the candidate (target) DU (e.g., candidate DU 903) decides to accept the request for LTM configuration associated with the candidate cell, then it responds to the CU (e.g., source CU 904) via, for example, UE CONTEXT SETUP RESPONSE, including the accepted RRC configuration of the candidate (target) cell. Figure 9 As shown, if candidate DU 903 decides to accept the request for LTM configuration associated with the candidate cell, then candidate DU 903 can send a response message to CU904 via the F1 interface, which includes the accepted RRC configuration of the candidate (target) cell. The F1 interface response may include at least one of the following:

[0212] (1) RACH resources used for early TA acquisition

[0213] (2) An indication of the early TA value of candidate cells determined by the candidate (target) DU.

[0214] (3) An indication that the early TA value of a candidate cell is equal to a fixed value (e.g., 0), or

[0215] (4) An indication that the early TA value of the candidate cell is equal to the TA value of the source cell.

[0216] Alternatively, in the case of inter-CU LTM, if the candidate (target) DU (e.g., the DU of BS #2) decides to accept the request for LTM configuration associated with the candidate cell, it responds to the target CU (e.g., the CU of BS #2) via the F1 interface, including the accepted RRC configuration of the candidate (target) cell. The F1 interface response may include at least one of the following:

[0217] (1) RACH resources used for early TA acquisition

[0218] (2) An indication of the early TA value of candidate cells determined by the candidate (target) DU.

[0219] (3) An indication that the early TA value of a candidate cell is equal to a fixed value (e.g., 0), or

[0220] (4) An indication that the early TA value of the candidate cell is equal to the TA value of the source cell.

[0221] Next, the candidate (target) CU can transmit a response, such as a handover request confirmation, to the source CU (e.g., source CU 904) via the Xn interface. The Xn interface response may contain elements similar to those in the F1 interface response received from the candidate (target) CU.

[0222] In operation 915, source CU 904 of BS 905 will transmit configurations to source DU 902 of BS 905. In some implementations, CU 904 may transmit configurations to source DU 902, such as RACH resources for early TA acquisition.

[0223] In some implementations, CU 904 may generate an RRC reconfiguration message based on the configuration from candidate cells and transmit the RRC reconfiguration message to UE 901 via source DU 902. For example, the RRC reconfiguration message includes candidate cell configuration for LTM and / or RACH resources for early TA acquisition.

[0224] In operation 916, UE 901 may receive from source DU 902 an RRC reconfiguration message associated with one or more candidate cells for LTM configuration.

[0225] In operation 917, UE 901 may receive from source DU 902 a PDCCH command for triggering TA acquisition for a specific candidate cell (e.g., a candidate cell associated with candidate DU 903).

[0226] In operation 918, UE 901 may transmit a preamble for early TA acquisition to candidate DU 903 after receiving a PDCCH command. In some implementations, if candidate DU 903 can calculate the early TA value of a specific candidate cell based on the received preamble, then candidate DU 903 may transmit the preamble and corresponding RACH timing, beam indication, UE 901's ID, RA-RNTI, candidate cell ID (i.e., target cell ID), candidate cell's TCI status index or similar information, and / or the calculated TA value to source DU 902 via CU 904. In some implementations, candidate DU 903 may store the calculated TA value.

[0227] Regarding the mobility scenario between CUs, in Operation 918, the target CU of the managing candidate (target) DU ( Figure 9(Not shown in the diagram) (e.g., the CU of BS #2) can transmit at least one of the following to the source CU 904 via the F1 interface: the early TA value and corresponding preamble of the candidate cell, the RACH timing, the UE ID, or the target cell ID. Then, the source CU 904 can transmit the received information to the source DU 902.

[0228] In operation 919, source DU 902 receives the early TA value of the candidate cell from source CU 904. In some implementations, source DU 902 is responsible for checking the validity of the early TA value of the candidate cell. For example, source DU 902 starts a timer after receiving the early TA value from candidate DU 903 via the target CU and the source CU (which are the same CU in intra-CU mobility scenarios and different CUs in inter-CU mobility scenarios). Once the timer expires, source DU 902 can issue a PDCCH command for early TA reacquisition. Therefore, if source DU 902 determines that the early TA value is invalid, then source DU 902 can issue a PDCCH command for early TA reacquisition.

[0229] In operation 920, source DU 902 can send an LTM cell handover command for a candidate cell to UE 901 to trigger a cell handover associated with the candidate cell.

[0230] In Operation 921, upon receiving an LTM cell handover command, UE 901 may start a supervisory timer (i.e., an LTM timer) and perform an LTM cell handover toward the candidate cell indicated in the LTM cell handover command. After the supervisory timer expires, UE 901 may consider an LTM cell handover failure to have occurred (which may also be referred to as "LTM failure" or "MCG LTM failure" or similar). UE 901 should initiate an RRC reconstruction procedure after the LTM cell handover failure occurs.

[0231] In Operation 922, after an LTM cell handover failure occurs, UE 901 can reconnect to another BS via RRC rebuild or establishment procedure (i.e., Figure 9 BS 906 (for example) Figure 6 The new cell described in the embodiment is BS #3. UE901 may transmit an indication LTM failure report (e.g., to the serving cell of BS 906) Figure 6 The report #1 described in the embodiments is an available instruction.

[0232] In Operation 923, the serving cell of BS 906 sends a UE Information Request message to UE 901, in which UE 901 is requested to send an LTM failure report.

[0233] In operation 924, UE 901 transmits an LTM failure report related to an LTM cell handover failure to the serving cell, which may be included in a UE information response message. In some implementations, the LTM failure report includes at least one of the following:

[0234] (1) The early TA value of the candidate cell, which may be obtained by the source cell via the early TA and received by the UE from the source cell; or may be set to a fixed value (e.g., 0); or may be set to the same as the TA value of the source cell.

[0235] (2) Information indicating whether the cell handover procedure is based on LTM cell handover without RACH or LTM cell handover based on RACH.

[0236] (3) Indicates whether the cell handover procedure is a failure of LTM cell handover without RACH with CG.

[0237] (4) Indicates whether the cell handover procedure is a failure of LTM cell handover without CG and without RACH.

[0238] (5) Information indicating whether an LTM cell handover failure has occurred.

[0239] (6) When an LTM cell handover failure occurs, the L1 measurement results of the source cell can be encapsulated in the container of the RRC message.

[0240] (7) When an LTM cell handover failure occurs, the L1 measurement results of the candidate cell can be encapsulated in the container of the RRC message.

[0241] In Operation 925 (optional), if a subsequent LTM cell handover procedure between candidate cells that does not require network reconfiguration for UE 901 is performed, then UE 901 may report the total number of LTMs performed toward the same candidate cell in support of subsequent LTMs to the serving BS (e.g., BS #3).

[0242] In one implementation, the total includes the total number of successful cell handover procedures (i.e., how many times the cell handover procedure was successfully completed). In another implementation, the total includes both the total number of LTM cell handover failures (i.e., how many times the LTM cell handover failure occurred) and the total number of successful cell handover procedures.

[0243] Figure 10 A schematic diagram illustrating an SCG LTM procedure according to aspects of this disclosure. The details described in all other embodiments of this disclosure are applicable. Figure 10 The embodiments shown in the figure.

[0244] like Figure 10As shown, BS 1005 features a CU-DU architecture and includes CU 1004, source DU 1002, and candidate DU 1003. Figure 10 In the embodiments, the cell handover operation performed by UE 1001 can refer to an intra-CU mobility scenario where the source cell and the target cell are in the same CU, or an inter-CU mobility scenario where the source cell and the target cell are located in different CUs. For example, Figure 10 The flowchart 1000 shown is for illustrative purposes only, illustrating cell handover operations in a mobility scenario within a CU, where source DU 1002 and candidate DU 1003 are managed by the same CU 1004 (e.g., BS #1 and BS #2 are the same, such as...). Figure 6 (As described in the embodiments). Flowchart 1000 can also be applied where source DU 1002 and candidate DU 1003 are managed by different CUs (e.g., BS #1 and BS #2 are different, such as...). Figure 6 The CU mobility scenario described in the embodiments.

[0245] exist Figure 10 In the exemplary flowchart 1000 shown, during operation 1011, UE 1001 can access the serving BS (e.g., BS 1005) and send measurement reports to the serving BS. The serving BS may contain a CU (e.g., gNB-CU) and one or more DUs (e.g., gNB-DU). The serving cell is associated with the CU and DU. An F1 interface exists between the DU and the CU. For example, in the context of SCG LTM procedures... Figure 10 In this embodiment, BS 1005 is an SCG BS (e.g., an SCG gNB). BS 1005 includes CU 1004, source DU 1002, and candidate DU 1003. BS 1005 may include one or more other candidate DUs ( Figure 10 (Not shown in the text). In some implementations, UE 1001 may send measurement reports to CU 1004 via source DU 1002.

[0246] In operation 1012, the source CU 1004 of SCG BS 1005 can determine to initiate an inter-cell mobility configuration procedure based on L1 / L2, that is, to make an inter-cell mobility configuration decision based on L1 / L2.

[0247] In Operation 1013, under the intra-CU LTM scenario (i.e., intra-CU mobility scenario), the source CU (e.g., source CU 1004) can send a request message (e.g., UE CONTEXT SETUP REQUEST) containing the ID information of the candidate cell to the candidate (target) DU (e.g., candidate DU 1003) within the same BS. Requests for RACH resources used for early TA acquisition can also be included in the request message sent to the candidate (target) DU. The candidate cell can also be referred to as the candidate (target) cell. Figure 10 As shown, CU 1004 can send a request message containing the ID information of the candidate cell to candidate DU 1003 via the F1 interface.

[0248] Alternatively, in inter-CU LTM scenarios (i.e., inter-CU mobility scenarios), the source CU (e.g., source CU1004 of BS 1005) (e.g., BS #1) can send a request message (e.g., a handover (HO) request) containing the candidate cell's ID information to the candidate (target) CU. Figure 10 (Not shown in the image) (e.g., BS #2). Requests for RACH resources used for early TA acquisition can also be included in the request message transmitted to the candidate (target) CU. The candidate (target) CU can then send a request message containing the candidate cell's ID information (e.g., UE CONTEXT SETUP REQUEST) to the candidate (target) DU. Requests for RACH resources used for early TA acquisition can also be included in the request message transmitted to the candidate (target) DU.

[0249] In operation 1014, under the LTM case within the CU, if the candidate (target) DU (e.g., candidate DU 1003) decides to accept the request for LTM configuration associated with the candidate cell, then it responds to the CU (e.g., source CU 1004) via, for example, UE CONTEXT SETUP RESPONSE, including the accepted RRC configuration of the candidate (target) cell. Figure 10 As shown, if candidate DU 1003 decides to accept the request for LTM configuration associated with the candidate cell, then candidate DU 1003 can send a response message to CU 1004 via the F1 interface, which includes the accepted RRC configuration of the candidate (target) cell. The F1 interface response may include at least one of the following:

[0250] (1) RACH resources used for early TA acquisition

[0251] (2) An indication of the early TA value of candidate cells determined by the candidate (target) DU.

[0252] (3) An indication that the early TA value of a candidate cell is equal to a fixed value (e.g., 0), or

[0253] (4) An indication that the early TA value of the candidate cell is equal to the TA value of the source cell.

[0254] Alternatively, in the case of inter-CU LTM, if the candidate (target) DU (e.g., the DU of BS #2) decides to accept the request for LTM configuration associated with the candidate cell, it responds to the target CU (e.g., the CU of BS #2) via the F1 interface, including the accepted RRC configuration of the candidate (target) cell. The F1 interface response may include at least one of the following:

[0255] (1) RACH resources used for early TA acquisition

[0256] (2) An indication of the early TA value of candidate cells determined by the candidate (target) DU.

[0257] (3) An indication that the early TA value of a candidate cell is equal to a fixed value (e.g., 0), or

[0258] (4) An indication that the early TA value of the candidate cell is equal to the TA value of the source cell.

[0259] Next, the candidate (target) CU can transmit a response, such as a handover request confirmation, to the source CU (e.g., source CU 1004) via the Xn interface. The Xn interface response may contain elements similar to those in the F1 interface response received from the candidate (target) CU.

[0260] In operation 1015, source CU 1004 of BS 1005 will transmit configuration to source DU 1002 of BS 1005. In some implementations, CU 1004 may transmit configuration to source DU 1002, such as RACH resources for early TA acquisition.

[0261] In some implementations, CU 1004 may generate an RRC reconfiguration message based on the configuration from the candidate cells and transmit the RRC reconfiguration message to UE 1001 via source DU 1002. For example, the RRC reconfiguration message includes the candidate cell configuration for LTM and / or RACH resources for early TA acquisition.

[0262] In operation 1016, UE 1001 may receive from source DU 1002 an RRC reconfiguration message associated with one or more candidate cells for LTM configuration.

[0263] In operation 1017, UE 1001 may receive a PDCCH command from source DU 1002 to trigger TA acquisition for a specific candidate cell (e.g., a candidate cell associated with candidate DU 1003).

[0264] In operation 1018, UE 1001 may transmit a preamble for early TA acquisition to candidate DU 1003 after receiving a PDCCH command. In some implementations, if candidate DU 1003 can calculate the early TA value of a specific candidate cell based on the received preamble, then candidate DU 1003 may transmit the preamble and corresponding RACH timing, beam indication, UE 1001's ID, RA-RNTI, candidate cell ID (i.e., target cell ID), candidate cell's TCI status index or similar information, and / or the calculated TA value to source DU 1002 via CU 1004. In some implementations, candidate DU 1003 may store the calculated TA value.

[0265] Regarding the mobility scenario between CUs, in operation 1018, the target CU of the management candidate (target) DU is ( Figure 10 (Not shown in the diagram) (e.g., the CU of BS #2) can transmit at least one of the following to the source CU 1004 via the F1 interface: the early TA value and corresponding preamble of the candidate cell, the RACH timing, the UE ID, or the target cell ID. Then, the source CU 1004 can transmit the received information to the source DU 1002.

[0266] In operation 1019, source DU 1002 receives the early TA value of the candidate cell from source CU 1004. In some implementations, source DU 1002 is responsible for checking the validity of the early TA value of the candidate cell. For example, source DU 1002 starts a timer after receiving the early TA value from candidate DU 1003 via the target CU and the source CU (which are the same CU in intra-CU mobility scenarios and different CUs in inter-CU mobility scenarios). Once the timer expires, source DU 1002 can transmit a PDCCH command for early TA reacquisition. Therefore, if source DU 1002 determines that the early TA value is invalid, then source DU 1002 can transmit a PDCCH command for early TA reacquisition.

[0267] In operation 1020, source DU 1002 can send an LTM cell handover command for the candidate cell to UE 1001 to trigger a cell handover associated with the candidate cell.

[0268] In operation 1021, upon receiving an LTM cell handover command, UE 1001 may start an LTM timer (i.e., a supervisory timer) and perform an LTM cell handover to the candidate cell indicated in the LTM cell handover command. After the LTM timer expires, UE 1001 may consider an LTM cell handover failure to have occurred (which may also be referred to as "LTM failure" or "SCG LTM failure" or similar). UE 1001 should initiate an SCG failure information procedure after the LTM cell handover failure occurs. For example, UE 1001 may call the MCG BS (which is serving UE 1001)... Figure 10 (not shown in the text) (i.e., MCG gNB) transmits SCG failure information messages (e.g. Figure 6 The message #1 described in the embodiments. In some embodiments, the following information may be included in the SCG failure information message:

[0269] (1) Information indicating LTM cell handover failure;

[0270] (2) When an LTM cell handover failure occurs, the L1 measurement results of the source cell can be encapsulated in a container of an RRC message;

[0271] (3) When an LTM cell handover failure occurs, the L1 measurement results of the candidate cell can be encapsulated in a container of an RRC message; or

[0272] (4) Failure type of LTM cell handover failure, such as: LTM cell handover failure without RACH, LTM cell handover failure with CG without RACH, LTM cell handover failure without CG without RACH, LTM cell handover failure based on RACH; or expiration of the monitoring timer.

[0273] Figure 11 A flowchart illustrating a method related to an LTM cell handover procedure according to aspects of this disclosure is provided. The operation of the method can be implemented by a network node, as described herein. In some embodiments, the network node can be a source DU of the BS and can execute a set of instructions to control the functional elements of the source DU to perform the described functions. In some embodiments, aspects of operations 1102, 1104, and 1106 can be referenced from... Figure 4 or Figure 14 The described NE 400 or source DU 1402 is executed. Each of operations 1102, 1104, and 1106 can be executed according to the instance described herein. Specific instances are... Figure 14 The embodiments are described below.

[0274] In operation 1102, the method may include transmitting a PDCCH command to the UE to trigger early TA acquisition associated with a candidate cell. The candidate cell is associated with a cell handover procedure. For example, the cell handover procedure may be a PCell handover procedure or a PSCell handover procedure.

[0275] In operation 1104, the method may include determining whether an early TA acquisition failure has occurred. In operation 1106, the method may include, if it is determined that an early TA acquisition failure has occurred, sending a request to the BS's CU (e.g., reference...) Figure 14 The description of the CU 1404) indicates that the early TA acquisition failed.

[0276] In some implementations of the methods described herein, the source DU may transmit to the CU at least one of the following: the UE's ID information; or the timer length of the TAT associated with the early TA acquisition.

[0277] In response to an early TA acquisition failure, in some implementations, the source DU may trigger an early TA reacquisition associated with the candidate cell, or in some other implementations, the DU may retransmit the PDCCH command to the UE to trigger an early TA acquisition associated with the candidate cell.

[0278] In some implementations of the methods described herein, the source DU may transmit at least one of the following to the CU of the BS:

[0279] (1) Indicates whether the early TA reacquisition caused by the failure has been triggered;

[0280] (2) Before the DU receives the early TA value of the candidate cell, perform the total number of early TA acquisitions for the candidate cell; or

[0281] (2) Before the DU receives the early TA value of the candidate cell, transmit the total number of PDCCH commands used to trigger the early TA acquisition associated with the candidate cell.

[0282] It should be noted that Figure 8 The methods described herein describe possible implementations, and the operations and steps may be rearranged or otherwise exempted or modified, and other implementations are possible without departing from the spirit and scope of this disclosure.

[0283] Figure 12A flowchart illustrating a method related to an LTM cell handover procedure according to aspects of this disclosure is provided. The operation of the method can be implemented by a network node, as described herein. In some embodiments, the network node can be a source DU of the BS and can execute a set of instructions to control the functional elements of the source DU to perform the described functions. In some embodiments, aspects operating 1204, 1204, 1206, and 1208 can be referenced from... Figure 4 or Figure 15 The described NE 400 or source DU 1502 is executed. Each of operations 1202 through 1208 can be executed according to the instance described herein. Specific instances are... Figure 15 The embodiments are described below.

[0284] In operation 1202, the method may include a PDCCH command transmitted by a source DU of the BS (denoted as "BS #a") to trigger an early TA acquisition associated with a candidate cell. The candidate cell is associated with the UE's cell handover procedure. For example, the cell handover procedure may be a PCell handover procedure or a PSCell handover procedure.

[0285] In operation 1204, the method may include receiving an early TA value of the candidate cell from a candidate DU of another BS (denoted as "BS #b") associated with the candidate cell. BS #a may be the same as or different from BS #b. For example, if BS #a is the same as BS #b, then it is an intra-BS case, such as an intra-CU mobility scenario. If BS #a is different from BS #b, then it is an inter-BS case, such as an inter-CU mobility scenario.

[0286] In operation 1206, the method may include storing the early TA values ​​of the candidate cells. In operation 1208, the method may include determining whether the early TA values ​​of the candidate cells are valid.

[0287] In some implementations of the methods described herein, the source DU may determine whether the early TA value of a candidate cell is valid based on a timer or a threshold of RSRP change. For example, if the timer expires, the DU may determine that the early TA value of the candidate cell is invalid. If the RSRP change is greater than a threshold, the DU may determine that the early TA value of the candidate cell is invalid. For example, if the early TA value of the candidate cell is invalid, the DU may retransmit the PDCCH command to the UE to trigger the early TA acquisition associated with the candidate cell.

[0288] In some implementations of the method described herein, the source DU may transmit an LTM cell handover command to the UE to trigger a cell handover procedure toward a candidate cell. The LTM cell handover command includes at least one of the following: the candidate cell's ID information; or the candidate cell's early TA value.

[0289] In some implementations of the method described herein, the source DU may log the time when the LTM cell handover command is transmitted and transmit the time when the LTM cell handover command is transmitted to the candidate DU associated with the candidate cell.

[0290] In some implementations of the methods described herein, the source DU may transmit one of the following to the CU (e.g., in the case of intra-BS or inter-BS situations):

[0291] (1) The time elapsed between receiving the early TA value of the first received candidate cell and the time when the cell handover procedure toward the candidate cell is triggered; or

[0292] (2) The time elapsed between receiving the early TA value of the most recently received candidate cell and triggering the cell handover procedure toward the candidate cell.

[0293] In some implementations of the methods described herein, the source DU may transmit at least one of the following to the CU (e.g., in the case of intra-BS or inter-BS):

[0294] (1) Information indicating whether early TA reacquisition associated with a candidate cell has been triggered, wherein early TA reacquisition is due to invalid determination of the early TA value of the received candidate cell;

[0295] (2) The total number of candidate cells whose early TA values ​​were invalidated and thus required to be reacquired again;

[0296] (3) The timer length for determining whether the early TA value of the received candidate cell is valid; or

[0297] (4) A threshold related to RSRP changes used to determine whether the early TA value of the received candidate cell is valid.

[0298] It should be noted that Figure 12 The methods described herein describe possible implementations, and the operations and steps may be rearranged or otherwise exempted or modified, and other implementations are possible without departing from the spirit and scope of this disclosure.

[0299] Figure 13 A flowchart illustrating a method related to an LTM cell handover procedure according to aspects of this disclosure is provided. The operation of the method can be implemented by a network node, as described herein. In some embodiments, the network node can be a source CU of the BS and can execute a set of instructions to control the functional elements of the source CU to perform the described functions. In some embodiments, aspects of operation 1302 and 1304 can be referenced... Figure 4 The described NE 400 is executed. Each of operations 1302 and 1304 can be executed according to the instances described herein.

[0300] In operation 1302, the method may include transmitting an LTM candidate cell configuration associated with a candidate cell to the UE from the CU of the BS (denoted as CU #a).

[0301] In operation 1304, the method may include transmitting RACH resources for early TA acquisition to the source DU managed by CU #a. The candidate cell is associated with a cell handover procedure from the UE's source cell to the candidate cell. For example, the cell handover procedure may be a PCell handover procedure or a PSCell handover procedure.

[0302] In some implementations of the method described herein, CU #a may receive information from the DU of the BS managed by CU #a indicating the failure of an early TA acquisition associated with a candidate cell.

[0303] In some implementations of the method described herein, CU #a may receive at least one of the following from the source DU: the UE's ID information; or the timer length of the TAT associated with the early TA acquisition.

[0304] In some implementations, if a candidate cell is associated with a target DU of the BS (e.g., within the BS), then CU #a can transmit at least one of the following to the target DU:

[0305] (1) Indicates a failure message;

[0306] (2) UE ID information; or

[0307] (3) The timer length of the TAT associated with the early TA acquisition.

[0308] In some other implementations, if a candidate cell is associated with another CU (denoted as CU #b) (e.g., in the case of inter-BS), then CU #a may transfer at least one of the following to CU #b:

[0309] (1) Indicates a failure message;

[0310] (2) UE ID information; or

[0311] (3) The timer length of the TAT associated with the early TA acquisition.

[0312] In some implementations of the method described herein, CU #a may receive at least one of the following information (denoted as information #1) from the source DU:

[0313] (1) Indicates whether the early TA reacquisition caused by the failure has been triggered;

[0314] (2) The total number of times the early TA acquisition procedure is performed on the candidate cell before the source DU receives the early TA value of the candidate cell; or

[0315] (3) Before the source DU receives the early TA value of the candidate cell, transmit the total number of PDCCH commands used to trigger the early TA acquisition associated with the candidate cell.

[0316] In some implementations of the method described herein, CU #a may receive at least one of the following information (denoted as information #2) from the source DU:

[0317] (1) The time elapsed between receiving the early TA value of the first received candidate cell and the time when the cell handover procedure toward the candidate cell is triggered; or

[0318] (2) The time elapsed between receiving the early TA value of the most recently received candidate cell and triggering the cell handover procedure toward the candidate cell.

[0319] In some implementations of the method described herein, CU #a may receive at least one of the following information (denoted as information #3) from the source DU:

[0320] (1) Information indicating whether early TA reacquisition associated with a candidate cell has been triggered, wherein early TA reacquisition is due to invalid determination of the early TA value of the received candidate cell;

[0321] (2) The total number of candidate cells whose early TA values ​​were invalidated and thus required to be reacquired again;

[0322] (3) The timer length for determining whether the early TA value of the received candidate cell is valid; or

[0323] (4) A threshold related to RSRP changes used to determine whether the early TA value of the received candidate cell is valid.

[0324] In some implementations, if a candidate cell is associated with another CU (e.g., the target CU of the management target DU) (e.g., CU#b), then CU#a may transmit at least one of information #1, information #2, or information #3 to the other CU.

[0325] In some implementations of the method described herein, the timer length for determining whether the TA value of a candidate cell is valid is generated by the source DU. If the UE fails to complete the cell handover procedure from the source cell to the candidate cell, then CU #a may transmit a message to the source DU indicating that the cell handover procedure to the candidate cell has failed. Specific examples are... Figure 14 and 15The embodiments are described below.

[0326] It should be noted that Figure 13 The methods described herein describe possible implementations, and the operations and steps may be rearranged or otherwise exempted or modified, and other implementations are possible without departing from the spirit and scope of this disclosure.

[0327] According to other aspects of this disclosure, the operation of methods related to LTM cell handover procedures can be implemented by a target CU of the BS, as described herein. In some embodiments, the target CU may execute a set of instructions to control the functional elements of the target CU to perform the described functions. In some embodiments, the method may involve the target CU of the BS receiving data from a source CU of another BS (e.g., from CU #b to CU #a, as described herein). Figure 13 (As described in the embodiments) Receives information indicating a failure to acquire an early TA associated with a candidate cell or an invalid early TA value for the candidate cell. A candidate cell is associated with a cell handover procedure from the UE's source cell to the candidate cell. The source cell is associated with a source CU (e.g., CU #a). The candidate cell is associated with a target CU (e.g., CU #b).

[0328] In some implementations, the cell handover procedure may be a PCell handover procedure or a PSCell handover procedure.

[0329] In some implementations of the methods described herein, the target CU may receive at least one of the following from the source CU: the UE's ID information; or the timer length of the TAT associated with the early TA acquisition.

[0330] In some implementations of the method described herein, the target CU may transmit at least one of the following to the target DU managed by the target CU associated with the candidate cell: (1) information indicating that a failure has occurred; (2) the UE's ID information; or (3) the timer length of the TAT associated with the early TA acquisition.

[0331] In some implementations of the methods described herein, the target CU may receive at least one of the following from the source CU: Figure 13 Information #1, information #2, or information #3 as described in the embodiments.

[0332] In some implementations of the method described herein, the target CU may transmit at least one of the following to the target DU managed by the target CU associated with the candidate cell: Figure 13 Information #1, information #2, or information #3 as described in the embodiments.

[0333] Figure 14A schematic diagram illustrating an LTM cell handover procedure according to aspects of this disclosure. The details described in all other embodiments of this disclosure are applicable to... Figure 14 The embodiments shown in the figure.

[0334] like Figure 14 The diagram shows that the BS 1405 features a CU-DU architecture, including CU 1404, source DU 1402, and candidate DU 1403. Figure 14 In the embodiments, the cell handover operation performed by UE 1401 can refer to an intra-CU mobility scenario where the source cell and the target cell are in the same CU, or an inter-CU mobility scenario where the source cell and the target cell are located in different CUs. For example, Figure 14 The flowchart 1400 shown is for illustrative purposes only, illustrating cell handover operations in a CU-based mobility scenario where source DU 1402 and candidate DU 1403 are managed by the same CU 1404. Flowchart 1400 can also be applied to inter-CU mobility scenarios where source DU 1402 and candidate DU 1403 are managed by different CUs.

[0335] exist Figure 14 In the exemplary flowchart 1400 shown, during operation 1411, UE 1401 can access the serving BS (e.g., gNB) and send measurement reports to the serving BS (e.g., BS 1405). The serving BS may contain a CU (e.g., gNB-CU) and one or more DUs (e.g., gNB-DU). The serving cell is associated with the CU and DU. An F1 interface exists between the DU and the CU. For example, as Figure 14 As shown, BS 1405 includes CU 1404, source DU 1402, and candidate DU 1403. BS 1405 may include one or more other candidate DUs. Figure 14 (Not shown in the text). In some implementations, UE 1401 may send measurement reports to CU 1404 via source DU 1402.

[0336] In operation 1412, the source CU 1404 of service BS 1405 can determine to initiate an L1 / L2-based inter-cell mobility configuration procedure, that is, to make an L1 / L2-based inter-cell mobility configuration decision.

[0337] In operation 1413, under the intra-CU LTM scenario (i.e., intra-CU mobility scenario), the source CU (e.g., source CU 1404) can send a request message (e.g., UE CONTEXT SETUP REQUEST) containing the ID information of the candidate cell to a candidate (target) DU (e.g., candidate DU 1403) within the same BS. Requests for RACH resources used for early TA acquisition can also be included in the request message sent to the candidate (target) DU. The candidate cell can also be referred to as the candidate (target) cell. Figure 14 As shown, CU 1404 can send a request message containing the ID information of the candidate cell to candidate DU 1403 via the F1 interface.

[0338] Alternatively, in inter-CU LTM scenarios (i.e., inter-CU mobility scenarios), the source CU (e.g., source CU1404 of BS 1405) can send a request message (e.g., a handover (HO) request) containing the ID information of the candidate cell to the candidate (target) CU. Figure 14 (Not shown in the text). Requests for RACH resources used for early TA acquisition can also be included in the request message transmitted to the candidate (target) CU. The candidate (target) CU can then send a request message containing the candidate cell's ID information (e.g., UECONTEXT SETUP REQUEST) to the candidate (target) DU. Requests for RACH resources used for early TA acquisition can also be included in the request message transmitted to the candidate (target) DU.

[0339] In operation 1414, in the case of LTM within the CU, if the candidate (target) DU (e.g., candidate DU 1403) decides to accept the request for LTM configuration associated with the candidate cell, then it responds to the CU (e.g., source CU 1404) via, for example, UE CONTEXT SETUP RESPONSE, including the accepted RRC configuration of the candidate (target) cell. Figure 14 As shown, if candidate DU 1403 decides to accept the request for LTM configuration associated with the candidate cell, then candidate DU 1403 can send a response message to CU 1404 via the F1 interface, which includes the accepted RRC configuration of the candidate (target) cell. The F1 interface response may include at least one of the following:

[0340] (1) RACH resources used for early TA acquisition

[0341] (2) An indication of the early TA value of candidate cells determined by the candidate (target) DU.

[0342] (3) An indication that the early TA value of a candidate cell is equal to a fixed value (e.g., 0), or

[0343] (4) An indication that the early TA value of the candidate cell is equal to the TA value of the source cell.

[0344] Alternatively, in the case of inter-CU LTM, if the candidate (target) DU (e.g., the DU of BS #2) decides to accept the request for LTM configuration associated with the candidate cell, it responds to the target CU via the F1 interface, including the accepted RRC configuration of the candidate (target) cell. The F1 interface response may include at least one of the following:

[0345] (1) RACH resources used for early TA acquisition

[0346] (2) An indication of the early TA value of candidate cells determined by the candidate (target) DU.

[0347] (3) An indication that the early TA value of a candidate cell is equal to a fixed value (e.g., 0), or

[0348] (4) An indication that the early TA value of the candidate cell is equal to the TA value of the source cell.

[0349] Next, the candidate (target) CU can transmit a response, such as a handover request confirmation, to the source CU (e.g., source CU 1404) via the Xn interface. The Xn interface response may contain elements similar to those in the F1 interface response received from the candidate (target) CU.

[0350] In operation 1415, source CU 1404 of BS 1405 will transmit configuration to source DU 1402 of BS 1405. In some embodiments, CU 1404 may transmit configuration to source DU 1402, such as RACH resources for early TA acquisition.

[0351] In some implementations, CU 1404 may generate an RRC reconfiguration message based on the configuration from the candidate cells and transmit the RRC reconfiguration message to UE 1401 via source DU 1402. For example, the RRC reconfiguration message includes the candidate cell configuration for LTM and / or RACH resources for early TA acquisition.

[0352] In operation 1416, UE 1401 may receive from source DU 1402 an RRC reconfiguration message associated with one or more candidate cells for LTM configuration.

[0353] In operation 1417, UE 1401 may receive a PDCCH command from source DU 1402 to trigger TA acquisition for a specific candidate cell (e.g., a candidate cell associated with candidate DU 1403).

[0354] In operation 1418, UE 1401 may transmit a preamble for early TA acquisition to candidate DU 1403 after receiving a PDCCH command.

[0355] In operation 1419, source DU 1402 may start a timer (e.g., TAT) for early TA acquisition after transmitting a PDCCH command. Candidate DU may fail to calculate the early TA value or may not receive the preamble. If source DU 1402 fails to receive the early TA value before the timer expires, source DU 1402 may retransmit a PDCCH command for early TA reacquisition.

[0356] In some implementations, when source DU 1402 transmits a PDCCH command to trigger early TA acquisition, source DU 1402 starts an early TA timer (e.g., TAT). Source DU 1402 stops the timer after receiving the early TA value associated with the transmitted preamble. Once the timer expires, source DU 1402 considers early TA acquisition failure to have occurred. If early TA acquisition failure occurs, source DU 1402 may trigger early TA reacquisition associated with the candidate cell, or source DU 1402 may retransmit the PDCCH command to the UE to trigger early TA acquisition associated with the candidate cell.

[0357] In operation 1420, source DU 1402 may transmit the following information to source CU 1404. In different embodiments, the following two options may exist, namely, option #A or option #B.

[0358] Option #A: Once source DU 1402 determines that an early TA acquisition failure has occurred, source DU 1402 indicates the early TA acquisition failure to source CU 1404. For example, CU 1404 may receive at least one of the following from source DU 1402: early TA acquisition failure; UE ID information; or the timer length of the TAT associated with the early TA acquisition. Then, CU 1404 may perform different operations depending on the circumstances.

[0359] (1) In the case of LTM within CU, CU 1404 will transmit the information indicating that the early TA acquisition received from source DU 1402 failed to be transmitted to candidate (target) DU 1403.

[0360] (2) In the case of LTM between CUs, CU 1404 (i.e., the source gNB / CU) transmits information indicating early TA acquisition failure to the target gNB / CU via the Xn interface. For example, the source CU 1404 (e.g., CU #a) transmits at least one of the following to the target gNB / CU (e.g., CU #b): information indicating failure; UE ID information; or the timer length of the TAT associated with early TA acquisition.

[0361] Option #B: Once source DU 1402 determines that an early TA acquisition failure has occurred, source DU 1402 may transmit the following to CU 1404 (e.g.) Figure 13 At least one of the information #1) described in the embodiments:

[0362] (1) Indicates whether the early TA reacquisition caused by the failure has been triggered;

[0363] (2) Before the DU receives the early TA value of the candidate cell, perform an early TA acquisition of the total number of candidate cells, such as 1, 2, 3, etc.; or

[0364] (3) Before the DU receives the early TA value of the candidate cell, transmit the total number of PDCCH commands used to trigger the early TA acquisition associated with the candidate cell, such as 1, 2, 3, etc.

[0365] Figure 15 A schematic diagram illustrating an LTM cell handover procedure according to aspects of this disclosure. The details described in all other embodiments of this disclosure are applicable to... Figure 15 The embodiments shown in the figure.

[0366] like Figure 15 The diagram shows that the BS 1505 features a CU-DU architecture and includes CU 1504, source DU 1502, and candidate DU 1503. Figure 15 In the embodiments, the cell handover operation performed by UE 1501 can refer to an intra-CU mobility scenario where the source cell and the target cell are in the same CU, or an inter-CU mobility scenario where the source cell and the target cell are located in different CUs. For example, Figure 15 The flowchart 1500 shown is for illustrative purposes only, illustrating cell handover operations in a mobility scenario within a CU, where source DU 1502 and candidate DU 1503 are managed by the same CU 1504 (e.g., BS #a and BS #b are the same, such as...). Figure 12 (As described in the embodiments). Flowchart 1500 can also be applied where source DU 1502 and candidate DU 1503 are managed by different CUs (e.g., BS #a and BS #b are different, such as...). Figure 12The CU mobility scenario described in the embodiments.

[0367] exist Figure 15 In the exemplary flowchart 1500 shown, during operation 1511, UE 1501 can access the serving BS (e.g., BS 1505) and send a measurement report to the serving BS. The serving BS may contain a CU (e.g., gNB-CU) and one or more DUs (e.g., gNB-DU). The serving cell is associated with the CU and DU. There is an F1 interface between the DU and the CU. For example, BS 1505 contains CU 1504, source DU 1502, and candidate DU 1503. BS 1505 may contain one or more other candidate DUs ( Figure 15 (Not shown in the text). In some implementations, UE 1501 may send measurement reports to CU 1504 via source DU 1502.

[0368] In operation 1512, the source CU 1504 of service BS 1505 can determine to initiate an L1 / L2-based inter-cell mobility configuration procedure, that is, to make an L1 / L2-based inter-cell mobility configuration decision.

[0369] In Operation 1513, under the intra-CU LTM scenario (i.e., intra-CU mobility scenario), the source CU (e.g., source CU 1504) can send a request message (e.g., UE CONTEXT SETUP REQUEST) containing the ID information of the candidate cell to the candidate (target) DU (e.g., candidate DU 1503) within the same BS. Requests for RACH resources used for early TA acquisition can also be included in the request message sent to the candidate (target) DU. The candidate cell can also be referred to as the candidate (target) cell. Figure 15 As shown in the diagram, CU 1504 can send a request message containing the ID information of the candidate cell to the candidate DU 1503 via the F1 interface.

[0370] Alternatively, in inter-CU LTM scenarios (i.e., inter-CU mobility scenarios), the source CU (e.g., source CU1504 of BS 1505) (e.g., BS #a) can send a request message (e.g., a handover (HO) request) containing the candidate cell's ID information to the candidate (target) CU. Figure 15(Not shown in the text) (e.g., CU of BS #b). Requests for RACH resources used for early TA acquisition can also be included in the request message transmitted to the candidate (target) CU. The candidate (target) CU can then send a request message containing the candidate cell ID information (e.g., UE CONTEXT SETUP REQUEST) to the candidate (target) DU. Requests for RACH resources used for early TA acquisition can also be included in the request message transmitted to the candidate (target) DU.

[0371] In operation 1514, in the case of LTM within the CU, if the candidate (target) DU (e.g., candidate DU 1503) decides to accept the request for LTM configuration associated with the candidate cell, then it responds to the CU (e.g., source CU 1504) via, for example, UE CONTEXT SETUP RESPONSE, including the accepted RRC configuration of the candidate (target) cell. Figure 15 As shown, if candidate DU 1503 decides to accept the request for LTM configuration associated with the candidate cell, then candidate DU 1503 can send a response message to CU 1504 via the F1 interface, which includes the accepted RRC configuration of the candidate (target) cell. The F1 interface response may include at least one of the following:

[0372] (1) RACH resources used for early TA acquisition

[0373] (2) An indication of the early TA value of candidate cells determined by the candidate (target) DU.

[0374] (3) An indication that the early TA value of a candidate cell is equal to a fixed value (e.g., 0), or

[0375] (4) An indication that the early TA value of the candidate cell is equal to the TA value of the source cell.

[0376] Alternatively, in the case of inter-CU LTM, if the candidate (target) DU (e.g., the DU of BS #a) decides to accept the request for LTM configuration associated with the candidate cell, it responds to the target CU (e.g., the CU of BS #b) via the F1 interface, including the accepted RRC configuration of the candidate (target) cell. The F1 interface response may include at least one of the following:

[0377] (1) RACH resources used for early TA acquisition

[0378] (2) An indication of the early TA value of candidate cells determined by the candidate (target) DU.

[0379] (3) An indication that the early TA value of a candidate cell is equal to a fixed value (e.g., 0), or

[0380] (4) An indication that the early TA value of the candidate cell is equal to the TA value of the source cell.

[0381] Next, the candidate (target) CU can transmit a response, such as a handover request confirmation, to the source CU (e.g., source CU 1504) via the Xn interface. The Xn interface response may contain elements similar to those in the F1 interface response received from the candidate (target) CU.

[0382] In operation 1515, source CU 1504 of BS 1505 will transmit configuration to source DU 1502 of BS 1505. In some implementations, CU 1504 may transmit configuration to source DU 1502, such as RACH resources for early TA acquisition.

[0383] In some implementations, CU 1504 may generate an RRC reconfiguration message based on the configuration from the candidate cells and transmit the RRC reconfiguration message to UE 1501 via source DU 1502. For example, the RRC reconfiguration message includes the candidate cell configuration for LTM and / or RACH resources for early TA acquisition.

[0384] In operation 1516, UE 1501 may receive from source DU 1502 an RRC reconfiguration message associated with one or more candidate cells for LTM configuration.

[0385] In operation 1517, UE 1501 may receive a PDCCH command from source DU 1502 to trigger TA acquisition for a specific candidate cell (e.g., a candidate cell associated with candidate DU 1503).

[0386] In operation 1518, UE 1501 may transmit a preamble for early TA acquisition to candidate DU 1503 after receiving a PDCCH command. In some implementations, if candidate DU 1503 can calculate the early TA value of a specific candidate cell based on the received preamble, then candidate DU 1503 may transmit the preamble and corresponding RACH timing, beam indication, UE 1501's ID, RA-RNTI, candidate cell ID (i.e., target cell ID), candidate cell's TCI status index or similar information, and / or the calculated TA value to source DU 1502 via CU 1504. In some implementations, candidate DU 1503 may store the calculated TA value.

[0387] Regarding the inter-CU mobility scenario, in operation 1518, the target CU for managing candidate DUs ( Figure 15(Not shown) can transmit at least one of the following to the source CU 1504 via the F1 interface: TA value and corresponding preamble, RACH timing, UE ID, or target cell ID. The source CU can then transmit the received information to the source DU 1502.

[0388] In operation 1519, source DU 1502 receives the early TA value of the candidate cell from source CU 1504. In some implementations, source DU 1502 is responsible for checking the validity of the early TA value of the candidate cell. For example, source DU 1502 starts a timer after receiving the early TA value from candidate DU 1503 via the target CU and the source CU (which are the same CU in intra-CU mobility scenarios and different CUs in inter-CU mobility scenarios). Once the timer expires, source DU 1502 can issue a PDCCH command for early TA reacquisition. Therefore, if source DU 1502 determines that the early TA value is invalid, then source DU 1502 can issue a PDCCH command for early TA reacquisition.

[0389] In operation 1520, source DU 1502 may send an LTM cell handover command for the candidate cell to UE 1501 to trigger a cell handover to source CU 1504 associated with the candidate cell.

[0390] In operation 1521, after receiving an LTM cell handover command, UE 1501 may perform an LTM cell handover toward a candidate cell indicated by the LTM cell handover command.

[0391] After operation 1521, the following options may exist in different embodiments, namely, option #1, option #2, or option #3.

[0392] Option #1 (Execute operation 1522A)

[0393] In Operation 1522A, if UE 1501 successfully completes the LTM cell handover to the candidate cell, then source DU 1502 can report the following information to source CU 1504 (e.g. Figure 13 (Information #2 and Information #3 described in the embodiments). Regarding the inter-CU mobility scenario, after the source CU 1504 receives a report from the source DU, the source CU 1504 may transmit a report to the target CU / gNB (e.g., BS#b).

[0394] (1) The time elapsed between receiving the early TA value of the first received candidate cell and the time when the cell handover procedure toward the candidate cell is triggered; or

[0395] (2) The time elapsed between receiving the early TA value of the most recently received candidate cell and triggering the cell handover procedure toward the candidate cell.

[0396] (3) Information indicating whether early TA reacquisition associated with the candidate cell has been triggered, wherein early TA reacquisition is due to invalid determination of the received early TA value of the candidate cell;

[0397] (4) The total number of candidate cells whose early TA values ​​were invalidated and thus required to be reacquired again;

[0398] (5) The timer length for determining whether the early TA value of the received candidate cell is valid; or

[0399] (6) A threshold related to RSRP changes used to determine whether the early TA value of the received candidate cell is valid.

[0400] Option #2 (Execute operation 1522B)

[0401] In Operation 1522B, if the source DU 1502 itself provides the timer length for TAT, and UE 1501 successfully performs LTM cell handover, then the target DU 1503 indicates to the source DU 1502 via the source CU 1504 that the LTM cell handover was successful. If UE 1501 fails to complete the LTM cell handover, for example, if the LTM timer expires, then the source CU 1504 notifies the source DU 1502 of the LTM cell handover failure.

[0402] Option #3 (Execute operation 1522C)

[0403] In Operation 1522C, with the target DU 1503 providing the timer length for the TAT, UE 1501 logs the timestamp of receiving the LTM cell handover command. If UE 1501 fails to perform the LTM cell handover, then UE 1501 reports the timestamp of receiving the LTM cell handover command to the source DU 1502.

[0404] The description herein is provided to enable those skilled in the art to make or use this disclosure. Various modifications to this disclosure will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other variations without departing from the scope of this disclosure. Therefore, this disclosure is not limited to the examples and designs described herein, but should be given the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A user equipment (UE) comprising: At least one memory; and At least one processor coupled to the at least one memory and configured to cause the UE to: Receive lower-layer triggered mobility LTM configuration information related to the candidate cell of the second BS from the source cell of the first base station BS, wherein the first BS may be the same as or different from the second BS; Receive an LTM cell handover command from the source cell to trigger a cell handover procedure, wherein the LTM cell handover command includes at least one of the following: The identifier ID information of the candidate cell; or The early timing advance TA value of the candidate cell; and Upon receiving the LTM cell handover command, the cell handover procedure toward the candidate cell is executed and a monitoring timer is started.

2. The UE according to claim 1, wherein the cell handover procedure is: The primary cell PCell handover procedure for the primary cell group; or It primarily assists in the PSCell handover process for cell groups.

3. The UE of claim 2, wherein if the cell handover procedure is the PCell handover procedure, then the processor is configured to cause the UE to: The cell connects to the third BS via a reconstruction procedure after the monitoring timer expires; The information transmitted to the cell of the third BS indicating that the LTM cell handover failure is available is information; Receive a request for the report from the third BS; and The report is transmitted to the third BS.

4. The UE of claim 3, wherein the report comprises at least one of the following: The early TA value of the candidate cell; Information indicating whether the cell handover procedure is based on LTM cell handover without a random access channel (RACH) or LTM cell handover based on RACH; Information indicating whether the cell handover procedure is a failed LTM cell handover with a configured authorized CG and no RACH; Information indicating whether the cell handover procedure is a failed LTM cell handover without CG and without RACH; Information indicating whether a handover failure of the LTM cell has occurred; The Layer 1 (L1) measurement results of the source cell when the LTM cell handover failure occurs; or The L1 measurement results of the candidate cell when the LTM cell handover failure occurs.

5. The UE according to claim 3, wherein: The early TA value of the candidate cell is obtained by the source cell via early TA acquisition and is received by the UE from the source cell; The early TA value of the candidate cell is set to a fixed value; or The early TA value of the candidate cell is set to be the same as the TA value of the source cell.

6. The UE of claim 3, wherein the processor is configured to transmit to the third BS the total number of LTMs performed toward the same candidate cell in support of subsequent LTMs.

7. The UE of claim 6, wherein the total number comprises: The total number of successful completions of the cell handover procedure only; or Both the total number of LTM cell handover failures and the total number of successful cell handover procedures.

8. The UE of claim 2, wherein if the cell handover procedure is a PSCell handover procedure, then the processor is configured to cause the UE to: After the monitoring timer expires, an auxiliary cell group (SCG) failure message is sent to the primary node MN serving the UE.

9. The UE of claim 8, wherein the SCG failure information message comprises at least one of the following: This indicates an LTM cell handover failure message. The Layer 1 (L1) measurement results of the source cell when the LTM cell handover failure occurs; The L1 measurement results of the candidate cell when the LTM cell handover failure occurs; This indicates a failed handover message for an LTM cell without RACH. This indicates a failed handover of an LTM cell without RACH with a configured authorized CG; This indicates a failed handover of an LTM cell without a CG and without RACH. Information indicating a failed LTM cell handover based on RACH; or Information indicating the expiration of the monitoring timer.

10. The UE according to claim 4 or claim 9, wherein at least one of the L1 measurement result of the source cell or the L1 measurement result of the candidate cell is encapsulated in a container of a Radio Resource Control (RRC) message.

11. A base station (BS), comprising: At least one memory; and At least one processor coupled to the at least one memory and configured to cause the UE to: After a failure to trigger the LTM cell handover procedure at the lower layer, a Radio Resource Control (RRC) reconstruction request is received from the User Equipment (UE); and An RRC reconstruction message is sent to the UE.

12. The BS according to claim 11, wherein the LTM cell handover procedure is: The primary cell PCell handover procedure for the primary cell group; or It primarily assists in the PSCell handover process for cell groups.

13. The BS of claim 11, wherein the processor is configured to cause the BS to: The UE is able to receive a report indicating an LTM cell handover failure. Send a request for the report to the UE; and The report is received from the UE.

14. The BS of claim 13, wherein the processor is configured to transmit the report to the source BS of the source cell.

15. The BS according to claim 13 or claim 14, wherein the report comprises at least one of the following: Early TA value of candidate cells; Information indicating whether the cell handover procedure is based on LTM cell handover without a random access channel (RACH) or LTM cell handover based on RACH; Information indicating whether the cell handover procedure is a failed LTM cell handover with a configured authorized CG and no RACH; Information indicating whether the cell handover procedure is a failed LTM cell handover without CG and without RACH; Information indicating whether a handover failure of the LTM cell has occurred; The Layer 1 (L1) measurement results of the source cell when the LTM cell handover failure occurs; or The L1 measurement results of the candidate cell when the LTM cell handover failure occurs.

16. The BS of claim 11, wherein the processor is configured to receive from the UE the total number of LTM executions toward the same candidate cell in support of subsequent LTMs.

17. The BS of claim 16, wherein the total number comprises: The total number of successful completions of the cell handover procedure only; or Both the total number of LTM cell handover failures and the total number of successful cell handover procedures.

18. A source base station (BS), comprising: At least one memory; and At least one processor coupled to the at least one memory and configured to cause the UE to: Transmit lower-layer triggered mobility (LTM) configuration information related to the candidate cell of the user equipment (UE); and The LTM cell handover command is transmitted to the UE to trigger a cell handover procedure from the source cell of the source BS to the candidate cell, wherein the LTM cell handover command includes at least one of the following: The identifier ID information of the candidate cell; or The early timing advance TA value of the candidate cell.

19. The source BS of claim 18, wherein the processor is configured to receive a report of LTM cell handover failure from a third BS, wherein the report is transmitted by the UE to the third BS.

20. The source BS of claim 19, wherein the report comprises at least one of the following: The early TA value of the candidate cell; Information indicating whether the cell handover procedure is based on LTM cell handover without a random access channel (RACH) or LTM cell handover based on RACH; Information indicating whether the cell handover procedure is a failed LTM cell handover with a configured authorized CG and no RACH; Information indicating whether the cell handover procedure is a failed LTM cell handover without CG and without RACH; Information indicating whether a handover failure of the LTM cell has occurred; The Layer 1 (L1) measurement results of the source cell when the LTM cell handover failure occurs; or The L1 measurement results of the candidate cell when the LTM cell handover failure occurs.

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