Method and apparatus for mobility robustness optimization (MRO) mechanism for l1 / l2 triggered mobility (LTM) procedure

Abstract

Various aspects of the present disclosure relate to methods and apparatuses for mobility robustness optimization (MRO) mechanisms for L1 / L2 triggered mobility (LTM) procedures, such as master cell group (MCG) LTM procedures or secondary cell group (SCG) LTM procedures. According to embodiments of the present disclosure, a user equipment (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 an L1 / L2 triggered mobility (LTM) cell switch command indicating a configuration identifier (ID) related to a candidate cell configured to the UE by a network equipment (NE), determine whether the LTM cell switch command includes an early timing advance (TA) value for the candidate cell, and perform an LTM cell switch toward the candidate cell and start a mobility timer.

Description

Technical Field

[0001] This disclosure relates to wireless communications, and more particularly to methods and apparatus for a mobility robustness optimization (MRO) mechanism for L1 / L2 triggered mobility (LTM) procedures (e.g., primary cell group (MCG) LTM procedures or secondary cell group (SCG) LTM procedures). Background Technology

[0002] A wireless communication system may include one or more network communication devices, such as base stations, which may support wireless communication with one or more user communication devices, also 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 may support wireless communication across a variety of radio access technologies, including third-generation (3G), fourth-generation (4G), fifth-generation (5G), and other suitable radio access technologies other than 5G (e.g., sixth-generation (6G)).

[0003] LTM is a process in which a network device (e.g., a gNB) receives a Layer 1 (L1) measurement report from a UE and changes the UE's serving cell via a cell handover command. LTM can also be named Layer 1 / L2 (L1 / L2) lower-layer triggered mobility or similar. LTM cell handover procedures include LTM primary cell (PCell) handover procedures or LTM primary / secondary cell group (PSCell) handover procedures. An LTM PSCell handover procedure from a source cell (or source PCell) to a target cell (or target PCell) can also be named an MCG LTM procedure. An LTM PSCell handover procedure from a source PSCell to a target PSCell can also be named an SCG LTM procedure. Summary of the Invention

[0004] The article “a” preceding an element is not limited 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, the word “or” included in the claims, as used in the 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 a list of at least one of, for example, 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, an example step described as “based on condition A” may be based on both condition A and condition B without departing from the scope of this disclosure. 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, the term "group" may include one or more elements contained in the claims.

[0005] Some embodiments of this disclosure provide a user equipment (UE) for wireless communication. 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 an L1 / L2 triggered mobility (LTM) cell handover command, the LTM cell handover command indicating a configuration identifier (ID) associated with a candidate cell configured for the UE by a network equipment (NE); determine whether the LTM cell handover command contains an early timing advance (TA) value for the candidate cell; and perform an LTM cell handover toward the candidate cell and initiate a mobility timer.

[0006] In some implementations of the UE described herein, if the LTM cell handover command includes the early TA value of the candidate cell, then in order to perform the LTM cell handover, the processor is configured to cause the UE to: perform an LTM cell handover based on a random access channel (RACH); and start a first timer for the early TA value.

[0007] In some implementations of the UE described herein, the processor is configured to cause the UE to: perform the LTM cell handover via the UE-measured TA if the first timer expires while the mobility timer is running, and if the TA identifier (ID) measured by the UE of the candidate cell is equal to the TA ID measured by the UE of the serving cell; and to start a second timer associated with the TA measured by the UE.

[0008] In some implementations of the UE described herein, the processor is configured such that the UE: if the second timer expires while the mobility timer is running, then performs a RACH-based LTM cell handover, wherein the RACH resources used during the RACH-based LTM cell handover are one of the following: contention-free random access (CFRA) resources indicated by the LTM cell handover command, CFRA resources configured by the Radio Resource Control (RRC) configuration, or contention-based random access (CBRA) resources configured by the RRC configuration.

[0009] In some implementations of the UE described herein, if the first timer expires while the mobility timer is running, the processor is configured to cause the UE to fall back from the RACH-based LTM cell handover to the RACH-based LTM cell handover in response to one of the following: if the TA ID measured by the UE in the candidate cell is not equal to the TA ID measured by the UE in the serving cell; if the TA ID measured by the UE in the candidate cell is not configured; or if the TA ID measured by the UE in the serving cell is not configured.

[0010] In some implementations of the UE described herein, if the LTM cell handover command does not contain the early TA value of the candidate cell, and if the TA identifier (ID) measured by the UE of the candidate cell is equal to the TA ID measured by the UE of the serving cell, then the processor is configured to cause the UE to: perform an LTM cell handover based on the TA measured by the UE; and start a second timer associated with the TA measured by the UE.

[0011] In some implementations of the UE described herein, the processor is configured such that the UE: if the second timer expires while the mobility timer is running, then performs a RACH-based LTM cell handover, wherein the RACH resources used during the RACH-based LTM cell handover are one of the following: contention-free random access (CFRA) resources indicated by the LTM cell handover command, CFRA resources configured by the Radio Resource Control (RRC) configuration, or contention-based random access (CBRA) resources configured by the RRC configuration.

[0012] In some implementations of the UE described herein, if the UE is unable to access the candidate cell when the mobility timer expires, the processor is configured to cause the UE to: reconnect to the first cell via Radio Resource Control (RRC) rebuild or RRC establishment procedure; and transmit information to the first cell indicating that first auxiliary information is available; receive a request for the first auxiliary information from the first cell; and transmit the first auxiliary information to the first cell in association with the failure of the LTM cell handover, wherein the first auxiliary information is included in a UE information response message.

[0013] In some implementations of the UE described herein, if the UE successfully accesses the candidate cell via the LTM cell handover, the processor is configured to cause the UE to: stop the mobility timer; and if a triggering condition for reporting the second assistance information is met, transmit information indicating that the second assistance information is available to the candidate cell; receive a request for the second assistance information from the candidate cell; and transmit the second assistance information associated with the success of the LTM cell handover, wherein the second assistance information is included in a UE information response message.

[0014] In some implementations of the UE described herein, at least one of the first auxiliary information or the second information includes information indicating whether: a RACH-free LTM cell handover is performed via the early TA value included in the LTM cell handover command; whether a first timer for the early TA value included in the LTM cell handover command has expired; whether a backoff has occurred from a RACH-free LTM cell handover via the early TA value included in the LTM cell handover command to a RACH-free LTM cell handover via a TA measured by the UE; and whether a backoff has occurred from a RACH-free LTM cell handover via the early TA value included in the LTM cell handover command to a RACH-based LTM cell handover, wherein the RACH-based LTM cell handover is performed via one of the following: by the LTM cell handover... The following are considered: a contention-free random access (CFRA) indicated by the handover command, a CFRA configured by the RRC, or a contention-based random access (CBRA) configured by the RRC; whether a fallback has occurred from a RACH-free LTM cell handover to the RACH-based LTM cell handover via a TA measured by the UE; whether a second timer associated with the TA measured by the UE has expired; whether the CFRA resource is indicated by the LTM cell handover command; whether a fallback has occurred from the CFRA indicated by the LTM cell handover command to the CFRA configured by the RRC; whether a fallback has occurred from the CFRA indicated by the LTM cell handover command to the CBRA configured by the RRC; whether a fallback has occurred from the CFRA configured by the RRC to the CBRA configured by the RRC; or a combination thereof.

[0015] In some implementations of the UE described herein, at least one of the first auxiliary information or the second auxiliary information includes: if configured with a configured authorization (CG), then the total number of attempts to transmit in the CG during the time period of a first timer of the early TA value; reports related to early TA acquisition; if the CG is configured, then the total number of attempts to transmit in the CG when the UE measures the TA; or a combination thereof.

[0016] In some implementations of the UE described herein, the report related to early TA acquisition includes: the total number of attempts toward the same candidate cell; the total number of LTM cell handover commands received toward the same candidate cell; a preamble index; RACH timing (RO) resources; a time interval between two attempts toward the same candidate cell; an RA purpose, wherein the RA purpose is set to early TA acquisition; or a combination thereof.

[0017] In some implementations of the UE described herein, if a fallback occurs from a RACH-free LTM cell handover to a RACH-based LTM cell handover via the early TA value included in the LTM cell handover command, or if a fallback occurs from a RACH-free LTM cell handover to a RACH-based LTM cell handover via the TA measured by the UE, then the first auxiliary information or the second auxiliary information further includes information related to the preamble field, time domain, or frequency domain of one of the following: the CFRA indicated by the LTM cell handover command; the CFRA configured by the RRC configuration; or the CBRA configured by the RRC configuration.

[0018] In some implementations of the UE described herein, the information associated with the preamble domain, the time domain, or the frequency domain includes: the absolute frequency of point A, indicating the absolute frequency location of the reference resource block; the frequency domain location and bandwidth of the bandwidth portion (BWP), associated with one or more random access resources used by the UE; a subcarrier spacing used in the BWP associated with the one or more random access resources used by the UE; a msg1 frequency start, indicating the offset of the lowest physical random access channel (PRACH) transmission timing in the frequency domain relative to physical resource block (PRB) 0; and a msg1 frequency start for CFRA, indicating the lowest PRACH transmission timing in the frequency domain relative to the PRB for CFRA. 0 offset; msg1 subcarrier spacing, indicating the subcarrier spacing of PRACH; msg1 subcarrier spacing for CFRA, indicating the subcarrier spacing of PRACH for CFRA; msg1 frequency division multiplexing (FDM), indicating the number of PRACH transmission opportunities for frequency division multiplexing (FDM) in a time example; msg1 FDM for CFRA, indicating the number of PRACH transmission opportunities for FDM in a time example of CFRA; a list of information for an RN procedure within one or more RA procedures performed by the UE; the initial preamble for the RA attempt; the total number of preamble transmissions; the total number of preamble transmissions per synchronization signal block (SSB); the total number of preamble transmissions per channel state information reference signal (CSI-RS); or a combination thereof.

[0019] In some implementations of the UE described herein, the second auxiliary information is a successful handover report (SHR) or a successful primary / secondary cell group cell (PSCell) report (SPR).

[0020] Some embodiments of this disclosure provide a processor for wireless communication, the processor including at least one controller coupled to at least one memory and configured to: receive an L1 / L2 triggered mobility (LTM) cell handover command, the LTM cell handover command indicating a configuration identifier (ID) associated with a candidate cell configured to the UE by a network equipment (NE); determine whether the LTM cell handover command contains an early timing advance (TA) value for the candidate cell; and perform an LTM cell handover toward the candidate cell and initiate a mobility timer.

[0021] Some embodiments of this disclosure provide a method performed by a user equipment (UE). The method includes: receiving an L1 / L2 triggered mobility (LTM) cell handover command, the LTM cell handover command indicating a configuration identifier (ID) associated with a candidate cell configured for the UE by a network equipment (NE); determining whether the LTM cell handover command contains an early timing advance (TA) value for the candidate cell; and performing an LTM cell handover toward the candidate cell and initiating a mobility timer.

[0022] Some embodiments of this disclosure provide a network apparatus (NE) for wireless communication. The NE includes: at least one memory; and at least one processor coupled to the at least one memory and configured to cause the NE to: receive from a user equipment (UE) information indicating the availability of auxiliary information associated with failed or successful mobility; transmit a request for the auxiliary information to the UE; and receive from the UE a response containing the auxiliary information associated with L1 / L2 triggered mobility (LTM) cell handover.

[0023] In some implementations of the NE described herein, if the auxiliary information is associated with the failure of the LTM cell handover, then the UE is configured to reconnect to the first cell of the NE via a Radio Resource Control (RRC) rebuild or RRC establishment procedure.

[0024] In some implementations of the NE described herein, if the auxiliary information is associated with the success of the LTM cell handover, then the UE is configured to hand over from the source cell of the NE to a candidate cell via the LTM cell handover.

[0025] In some implementations of the NE described herein, the auxiliary information includes information indicating whether a random access channel-free (RACH) LTM cell handover via an early timing advance (TA) value included in the LTM cell handover command is performed by the UE; whether a first timer for the early TA value included in the LTM cell handover command has expired; whether a fallback has occurred from a RACH-free LTM cell handover via the early TA value included in the LTM cell handover command to a RACH-free LTM cell handover via a TA measured by the UE; and whether a fallback has occurred from a RACH-free LTM cell handover via the early TA value included in the LTM cell handover command to a RACH-based LTM cell handover, wherein the RACH-based LTM cell handover is performed via one of the following: by the LTM cell handover The following are considered: a contention-free random access (CFRA) indicated by the command, a CFRA configured by the RRC, or a contention-based random access (CBRA) configured by the RRC; whether a fallback has occurred from a RACH-free LTM cell handover to the RACH-based LTM cell handover via a TA procedure measured by the UE; whether a second timer associated with the TA measured by the UE has expired; whether the CFRA resource is indicated by the LTM cell handover command; whether a fallback has occurred from the CFRA indicated by the LTM cell handover command to the CFRA configured by the RRC; whether a fallback has occurred from the CFRA indicated by the LTM cell handover command to the CBRA configured by the RRC; whether a fallback has occurred from the CFRA configured by the RRC to the CBRA configured by the RRC; or a combination thereof.

[0026] In some implementations of the NE described herein, the auxiliary information includes: if configured with a Configurable Authorization (CG), then the total number of attempts to transmit in the CG during the time period of a first timer of the early TA value; reports related to early TA acquisition; if the CG is configured, then the total number of attempts to transmit in the CG when the UE measures the TA; or a combination thereof.

[0027] In some implementations of the NE described herein, the report associated with early TA acquisition includes: the total number of attempts toward the same candidate cell; the total number of LTM cell handover commands received toward the same candidate cell; a preamble index; RACH timing (RO) resources; the time interval between two attempts toward the same candidate cell; the RA purpose, wherein the RA purpose is set to early TA acquisition; or a combination thereof.

[0028] In some implementations of the NE described herein, if a fallback occurs from a RACH-free LTM cell handover to a RACH-based LTM cell handover via the early TA value included in the LTM cell handover command, or if a fallback occurs from a RACH-free LTM cell handover to a RACH-based LTM cell handover via the TA measured by the UE, then the auxiliary information further includes information related to the preamble field, time domain, or frequency domain of one of the following: the CFRA indicated by the LTM cell handover command; the CFRA configured by the RRC configuration; or the CBRA configured by the RRC configuration.

[0029] In some implementations of the NE described herein, the information associated with the preamble domain, the time domain, or the frequency domain includes: the absolute frequency of point A, indicating the absolute frequency location of the reference resource block; the frequency domain location and bandwidth of the bandwidth portion (BWP), associated with one or more random access resources used by the UE; a subcarrier spacing used in the BWP associated with the one or more random access resources used by the UE; a msg1 frequency start, indicating the offset of the lowest physical random access channel (PRACH) transmission timing in the frequency domain relative to physical resource block (PRB) 0; and a msg1 frequency start for CFRA, indicating the lowest PRACH transmission timing in the frequency domain relative to the PRB for CFRA. 0 offset; msg1 subcarrier spacing, indicating the subcarrier spacing of PRACH; msg1 subcarrier spacing for CFRA, indicating the subcarrier spacing of PRACH for CFRA; msg1 frequency division multiplexing (FDM), indicating the number of PRACH transmission opportunities for frequency division multiplexing (FDM) in a time example; msg1 FDM for CFRA, indicating the number of PRACH transmission opportunities for FDM in a time example of CFRA; a list of information for an RN procedure within one or more RA procedures performed by the UE; the initial preamble for the RA attempt; the total number of preamble transmissions; the total number of preamble transmissions per synchronization signal block (SSB); the total number of preamble transmissions per channel state information reference signal (CSI-RS); or a combination thereof.

[0030] In some implementations of the NE described herein, if the auxiliary information is associated with the success of the LTM cell handover, then the response is a Successful Handover Report (SHR) or a Successful Primary / Secondary Cell Group (PSCell) Report (SPR).

[0031] Some embodiments of this disclosure provide a processor for wireless communication, the processor including at least one controller coupled to at least one memory and configured to: receive from a user equipment (UE) information indicating that auxiliary information associated with failed mobility or successful mobility is available; transmit a request for the auxiliary information to the UE; and receive from the UE a response containing the auxiliary information associated with L1 / L2 triggered mobility (LTM) cell handover.

[0032] Some embodiments of this disclosure provide a method performed by a network equipment (NE). The method includes: receiving from a user equipment (UE) information indicating that auxiliary information associated with failed mobility or successful mobility is available; transmitting a request for the auxiliary information to the UE; and receiving from the UE a response containing the auxiliary information associated with L1 / L2 triggered mobility (LTM) cell handover.

[0033] Some embodiments of this disclosure provide a serving network equipment (NE) for a user equipment (UE). The serving NE includes: at least one memory; and at least one processor coupled to the at least one memory and configured to: transmit a request to a candidate NE, wherein the request includes a set of IDs associated with at least one of Layer 2 (L2) reset identifiers (IDs) of a plurality of candidate cells of the candidate NE or TA IDs measured by the UE; receive a response from the candidate NE, wherein the response includes one or more IDs of the set of IDs belonging to one or more candidate cells of the candidate NE; and transmit a first message to the UE, wherein the first message includes: L1 / L2 triggered mobility (LTM) configuration information of the one or more candidate cells; and the one or more IDs of the one or more candidate cells, wherein the one or more IDs are applied when the UE switches to the candidate cell.

[0034] In some implementations of the Service NE described herein, if the one or more IDs of the one or more candidate cells are associated with the L2 Reset-Free ID: if the L2 Reset-Free feature is available during handover between two or more candidate cells within the plurality of candidate cells, then the two or more candidate cells are configured with the same ID within the set of IDs; and if the L2 Reset-Free feature is not available during handover between any two candidate cells within the plurality of candidate cells, then each of the one or more candidate cells is configured with a different ID within the set of IDs.

[0035] In some implementations of the Service NE described herein, if the one or more IDs of the one or more candidate cells are related to the TA ID measured by the UE: if the TA measured by the UE is available during handover between two or more candidate cells within the plurality of candidate cells, then the two or more candidate cells are configured with the same ID in the set of IDs; and if the TA measured by the UE is not available during handover between any two candidate cells within the plurality of candidate cells, then each of the one or more candidate cells is configured with a different ID in the set of IDs.

[0036] In some implementations of the Service NE described herein, if the two or more candidate cells are configured with the same ID within the set of IDs, then the one or more IDs are a subset of the set of IDs; and if each of the one or more candidate cells is configured with the different ID within the set of IDs, then the one or more IDs are equal to the set of IDs.

[0037] Some embodiments of this disclosure provide a processor for wireless communication, including at least one controller coupled to at least one memory and configured to: transmit a request to a candidate NE, wherein the request includes a set of IDs associated with at least one of Layer 2 (L2) reset identifiers (IDs) of a plurality of candidate cells of the candidate NE or TA IDs measured by a UE; receive a response from the candidate NE, wherein the response includes one or more IDs of the set of IDs belonging to one or more candidate cells of the candidate NE; and transmit a first message to the UE, wherein the first message includes: L1 / L2 triggered mobility (LTM) configuration information of the one or more candidate cells; and the one or more IDs of the one or more candidate cells, wherein the one or more IDs are applied when the UE switches to the candidate cell.

[0038] Some embodiments of this disclosure provide a method performed by a serving network equipment (NE) of a user equipment (UE). The method includes: transmitting a request to a candidate NE, wherein the request includes a set of IDs associated with at least one of Layer 2 (L2) reset identifiers (IDs) of a plurality of candidate cells of the candidate NE or TA IDs measured by the UE; receiving a response from the candidate NE, wherein the response includes one or more IDs of the set of IDs belonging to one or more candidate cells of the candidate NE; and transmitting a first message to the UE, wherein the first message includes: L1 / L2 triggered mobility (LTM) configuration information of the one or more candidate cells; and the one or more IDs of the one or more candidate cells, wherein the one or more IDs are applied when the UE switches to the candidate cell.

[0039] Some embodiments of this disclosure provide a candidate network equipment (NE). The candidate NE includes: at least one memory; and at least one processor coupled to the at least one memory and configured to cause the candidate NE to: receive a request from a serving NE of a user equipment (UE), wherein the request includes a set of IDs associated with at least one of a plurality of candidate cells of the candidate NE, or a TA ID measured by the UE; and transmit a response to the serving NE, wherein the response includes one or more IDs belonging to one or more candidate cells of the candidate NE, and wherein the one or more IDs are applied when the UE switches to the one or more candidate cells.

[0040] In some implementations of the candidate NE described herein, if the one or more IDs of the one or more candidate cells are associated with the L2-free reset ID, then the processor is configured such that the candidate NE: if the L2-free reset feature is available during handover between two or more candidate cells within the plurality of candidate cells, then the two or more candidate cells are configured with the same ID in the set of IDs; and if the L2-free reset feature is not available during handover between any two candidate cells within the plurality of candidate cells, then each of the one or more candidate cells is configured with a different ID in the set of IDs.

[0041] In some implementations of the candidate NE described herein, if the one or more IDs of the one or more candidate cells are associated with the TA ID measured by the UE, then the processor is configured such that the candidate NE: if the TA measured by the UE is available during handover between two or more candidate cells within the plurality of candidate cells, then the two or more candidate cells are configured with the same ID in the set of IDs; and if the TA measured by the UE is not available during handover between any two candidate cells within the plurality of candidate cells, then each of the one or more candidate cells is configured with a different ID in the set of IDs.

[0042] In some implementations of the candidate NEs described herein, if the two or more candidate cells are configured with the same ID within the set of IDs, then the one or more IDs are a subset of the set of IDs; and if each of the one or more candidate cells is configured with the different ID within the set of IDs, then the one or more IDs are equal to the set of IDs.

[0043] Some embodiments of this disclosure provide a processor for wireless communication, including at least one controller coupled to the at least one memory and configured to: receive a request from a serving NE of a user equipment (UE), wherein the request includes a set of IDs associated with at least one of a Layer 2 (L2) reset identifier (ID) of a plurality of candidate cells of the candidate NE or a TA ID measured by the UE; and transmit a response to the serving NE, wherein the response includes one or more IDs belonging to one or more candidate cells of the candidate NE, and wherein the one or more IDs are applied when the UE switches to the one or more candidate cells.

[0044] Some embodiments of this disclosure provide a method performed by a candidate network equipment (NE). The method includes: receiving a request from a serving NE of a user equipment (UE), wherein the request includes a set of IDs associated with at least one of a Layer 2 (L2) reset identifier (ID) of a plurality of candidate cells of the candidate NE or a TA ID measured by the UE; and transmitting a response to the serving NE, wherein the response includes one or more IDs belonging to the set of IDs of one or more candidate cells of the candidate NE, and wherein the one or more IDs are applied when the UE switches to the one or more candidate cells. Attached Figure Description

[0045] Figure 1 Examples of wireless communication systems according to aspects of this disclosure are described.

[0046] Figure 2 An example of a user equipment (UE) 200 according to aspects of this disclosure is described.

[0047] Figure 3 An example of processor 300 according to aspects of this disclosure is described.

[0048] Figure 4 Examples of network equipment (NE) 400 according to aspects of this disclosure are described.

[0049] Figure 5 and 6 A flowchart illustrating a method related to handover of an MCG or SCG LTM cell according to aspects of this disclosure.

[0050] Figure 7 A schematic diagram illustrating MCG or SCG LTM cell handover according to aspects of this disclosure.

[0051] Figure 8 A schematic diagram illustrating MCG LTM cell handover according to aspects of this disclosure.

[0052] Figure 9Another schematic diagram illustrating MCG or SCG LTM cell handover according to aspects of this disclosure.

[0053] Figure 10 and 11 A flowchart illustrating a method related to handover of an MCG or SCG LTM cell according to aspects of this disclosure.

[0054] Figure 12 A schematic diagram illustrating MCG or SCG LTM cell handover according to aspects of this disclosure. Detailed Implementation

[0055] Generally, when a UE moves from one cell to another, a serving cell change needs to be performed at some point. Traditionally, serving cell changes are accomplished through explicit RRC reconfiguration signaling (e.g., handover (HO) commands) to trigger synchronization of the target cell based on L3 measurement reports. This results in longer latency, greater overhead, and longer downtime compared to beam-level mobility. Therefore, in 3GPP, LTM is approved to change the serving cell via L1 / L2 signaling to reduce latency, overhead, and downtime.

[0056] LTM is a process in which a base station (BS) receives an L1 measurement report from a UE, and based on the report, the BS changes the UE's serving cell by sending a cell handover command (e.g., LTM cell handover command MAC CE or LTM command MAC CE) signaled via a Media Access Control (MAC) control element (CE). The cell handover command indicates the target cell for LTM, for example, an LTM candidate cell configuration previously prepared by the BS and provided to the UE via RRC signaling. The UE then hands over to the target cell according to the cell handover command. The LTM procedure can be used to reduce mobility latency.

[0057] When configured by the network, the Transmit Configuration Indicator (TCI) state of one or more cells that are different from the currently serving cell can be activated. For example, the TCI state of an LTM candidate cell can be activated in advance before any of those cells becomes the serving cell. This allows the UE to DL synchronize with those cells, thereby facilitating a faster cell handover to one of those cells when a handover is triggered.

[0058] When configured by the network, a UL TA acquisition (called an early TA) process can be initiated for one or more cells that are different from the current serving cell. If a cell has the same N as the current serving cell... TA or N TAIf the value is 0, then an early TA acquisition procedure is not required. The network may request the UE to perform early TA acquisition for the candidate cell before cell handover. The early TA acquisition procedure may be triggered by a PDCCH command or implemented via UE-based TA measurement configured by RRC signaling as described below.

[0059] In the early TA acquisition process, implemented via UE-based TA measurement configured by RRC signaling, the UE can perform TA measurement on candidate cells after configuration by RRC signaling, and the exact timing of the UE performing the TA measurement depends on the UE's implementation scheme. The UE can apply the TA value measured by itself and perform LTM without RACH upon receiving a cell handover command. The network can also send the TA value in the LTM cell handover command MAC CE without early TA acquisition.

[0060] Depending on the availability of a valid TA value, the UE performs either LTM without RACH or LTM based on RACH for cell handover. If a TA value is provided in the cell handover command, the UE applies the TA value as instructed by the network. UE-based TA measurements are configured in this configuration, but if no TA value is provided in the cell handover command, the UE applies the TA value itself if available. Simultaneously, the UE performs LTM without RACH for cell handover upon receiving the cell handover command. If no valid TA value is available, the UE performs LTM based on RACH for cell handover.

[0061] For LTM without RACH, the UE uses either Configured Grant (CG) or Dynamic Grant to access the target cell. A CG is provided in the LTM candidate configuration, and the UE selects a Configured Grant timing associated with the beam indicated in the cell handover command. Upon initiating an LTM cell handover to the target cell, the UE begins monitoring the PDCCH on the target cell for dynamic scheduling. If the UE does not have valid PUCCH resources for a triggered SR before the LTM procedure without RACH is completed, the UE should not trigger a random access procedure.

[0062] Generally, 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 48 hours after a connection failure is detected. The UE only indicates the availability of RLF reports and only provides RLF reports to the network if the current RPLMN is a PLMN present in the UE's EPLMN list or is an RPLMN at the time the connection failure is detected. In the case of an RLF 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 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 consider this LTE RLF report as defined in TS 36.300 [2].

[0063] One of the functions of Mobility Robustness Optimization (MRO) is to detect suboptimal successful handover events. The aim is to identify potential conditions during successful normal handovers, successful Dual Active Protocol Stack (DAP) handovers, or successful conditional handovers. To analyze successful handovers, the UE can collect Successful Handover Reports (SHRs) based on the network configuration, and if stored, make the SHRs available to the network, as specified in 3GPP standard document TS 38.331.

[0064] For SHRs collected during intra-NR handover, if the target New Radio (NR) node retrieves the SHR from the UE and the SHR trigger is timer T310 or T312, it can forward the information to the source NR node (i.e., the node that handles the cell reported as the source cell in this SHR) via the ACCESS AND MOBILITY INDICATION message on Xn or via the uplink RAN ​​configuration transmission procedure and downlink RAN ​​configuration transmission procedure on NG. If the NG-RAN node retrieving the SHR from the UE is neither the source nor the target node for the handover, it forwards the information to the node that configured the SHR trigger that caused the SHR to be generated via the ACCESS AND MOBILITY INDICATION message on Xn or via the uplink RAN ​​configuration transmission procedure and downlink RAN ​​configuration transmission procedure on NG. Upon retrieval of the SHR, the receiving node can analyze whether its mobility configuration needs adjustment.

[0065] Currently, 3GPP Release 19 will support MROs for LTM (e.g., including MCG LTM and SCG LTM). Regarding MROs for LTM, the following issues need to be addressed. In some cases, the issues include: if the TA ID measured by the UE in the candidate cell is equal to the TA ID measured by the UE in the serving cell, is a fallback from an early TA triggered by a PDCCH command to a TA measured by the UE supported? And how should a fallback from LTM without RACH to RACH-based LTM be performed? Additionally, issues need to be addressed include: "When should the UE perform a RACH-free LTM via an early TA included in the LTM command?" and "What auxiliary information should be reported to the network for failed or successful LTMs?"

[0066] In some cases, after intra-CU LTM or inter-CU LTM toward the target cell, the target cell's CU and DU can be aware of the TA IDs measured by the UE for all candidate cells and the Layer 2 (L2) reset IDs for all candidate cells. For example, the TA IDs measured by the UE for all candidate cells and the L2 reset IDs for all candidate cells can be transmitted to the target DU via the Xn and F1 interfaces. For example, on the Xn interface, the handover preparation phase can support the reset IDs and / or TA IDs measured by the UE in the inter-BS LTM. In some cases, if a separate L2 reset ID and TA ID measured by the UE are configured for the serving cell for a Layer 3 (L3) handover to a candidate target cell, then the issues to be addressed include how the target BS assigns IDs to the candidate target cells and how the source BS knows the ID assignments of the candidate target cells.

[0067] Currently, details regarding MROs for LTM (e.g., including MCG LTM and SCG LTM) have not been discussed. Embodiments of this disclosure aim to address the aforementioned issues. Some embodiments of this application describe a fallback mechanism from a RACH-free LTM via an early TA from an LTM command to a RACH-free LTM via a TA measured by the UE. In some embodiments of this application, when the UE performs a RACH-free LTM via an early TA, the TAT of the early TA may expire before the LTM is completed (e.g., T304 is running), and the UE may fall back to the UE-based TA and start the corresponding TAT. If the TAT of the UE-based TA expires while timer T304 is running, then the UE may fall back to CFRA from the LTM cell handover command. Furthermore, the UE may fall back to CFRA or CBRA configured by the RRC message. In this case, some RACH information may be reported in both successful and failed LTMs. In these embodiments, in the case of a failed or successful LTM, auxiliary information for self-optimization (SON) purposes may be reported to the network. In some other embodiments of this application, the separate Layer 2 (L2) reset ID of the serving cell and the TAID measured by the UE are configured for L3 handover of the candidate target cell, and the source BS should provide the target BS with information for ID allocation of the candidate target cell.

[0068] In this application, the LTM command may also be named "LTM Cell Handover Command" or similar. The candidate target cell may also be named "Candidate Cell" or "Target Candidate Cell" or similar. The No-Layer 2 (L2) Reset ID may also be named "NoReset ID" or "No Reset ID" or similar. The TA ID measured by the UE may also be named "Early TA ID of UE Measurement," "UE-Based Measurement TA ID," "Early TA ID of UE Measurement," or similar. The TA measured by the UE may also be named "Early TA Procedure of UE Measurement," "Early TA of UE Measurement," "UE-Based Measurement TA," "Early TA of UE Measurement," or similar.

[0069] Further details regarding embodiments of this disclosure will be described below in conjunction with the accompanying drawings.

[0070] Figure 1This section 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 other than 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).

[0071] One or more NEs 102 may be distributed across a geographical 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, radio 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 a wireless or wired connection. For example, NEs 102 and UEs 104 may perform wireless communication (e.g., receive signaling, transmit signaling) via a Uu interface.

[0072] NE 102 can provide a geographic coverage area that supports services for one or more UEs 104 within that 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.) according to one or more radio access technologies. In some embodiments, NE 102 can be mobile, for example, 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.

[0073] One or more UEs 104 may be distributed across a geographical 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, an Internet of Everything (IoE) device, or a Machine Type Communication (MTC) device, and other instances thereof.

[0074] 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, 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.

[0075] NE 102 may support communication with CN 106 or with 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, or network interfaces). In some implementations, NE 102 may communicate directly with each other. In some other implementations, NE 102 may communicate with each other or 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 heads, smart radio heads, or transmit-receive points (TRPs)).

[0076] 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 that manage access and mobility (e.g., a mobility management entity (MME), access and mobility management functions (AMF)), and user plane entities that route packets or interconnect to external networks (e.g., a serving gateway (S-GW), a packet data network (PDN) gateway (P-GW), or a user plane function (UPF)). In some implementations, the control plane entities may manage non-access stratum (NAS) functions of one or more UEs 104 served by one or more NEs 102 associated with CN 106, such as mobility, authentication, and bearer management (e.g., data bearers, signaling bearers, etc.).

[0077] CN 106 can communicate with the packet data network via one or more backhaul links (e.g., via S1, N2, or another network interface). 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).

[0078] 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 parameter sets.

[0079] 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.

[0080] Time intervals for resources (e.g., 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.

[0081] Alternatively or concurrently, 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., quantity) of time slots. 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 may utilize a single 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, respectively. Each time slot may contain a certain number (e.g., quantity) 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 for the regular cyclic prefix and the extended cyclic prefix, the number of time slots per subframe, and the number of time slots per frame 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) may be used interchangeably between subframes and time slots.

[0082] In the wireless communication system 100, the electromagnetic (EM) spectrum can be divided into various categories, frequency 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 range names 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 said 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.

[0083] FR1 may be associated with one or more parameter sets (e.g., at least three parameter sets). For example, FR1 may be associated with a first parameter set containing a 15 kHz subcarrier spacing (e.g., μ=0); a second parameter set containing a 30 kHz subcarrier spacing (e.g., μ=1); and a third parameter set containing a 60 kHz subcarrier spacing (e.g., μ=2). FR2 may be associated with one or more parameter sets (e.g., at least two parameter sets). For example, FR2 may be associated with a third parameter set containing a 60 kHz subcarrier spacing (e.g., μ=2); and a fourth parameter set containing a 120 kHz subcarrier spacing (e.g., μ=3).

[0084] 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 various aspects of this disclosure as described herein. These components may be coupled via one or more interfaces (e.g., operatively, communicatively, functionally, electronically, electrically).

[0085] 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 to or otherwise support elements for performing the functions described in this disclosure.

[0086] Processor 202 may include intelligent hardware devices (e.g., a general-purpose processor, DSP, CPU, ASIC, FPGA, 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.

[0087] 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 memory 204 or another type of memory. Computer-readable medium includes both non-transitory computer storage media and communication media, wherein the communication media includes any media that facilitates the transfer of a computer program from one place to another. Non-transitory storage media may be any available media accessible by a general-purpose or special-purpose computer.

[0088] 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, as per [reference to...] Figure 5 The publicly disclosed example of wireless communication at UE 200.

[0089] For example, processor 202 may support wireless communication at UE 200, and UE 200 may be configured to support: components for receiving an L1 / L2 triggered mobility (LTM) cell handover command, the LTM cell handover command indicating a configuration identifier (ID) associated with a candidate cell configured to the UE by the network equipment (NE); components for determining whether the LTM cell handover command contains an early timing advance (TA) value of the candidate cell; and components for performing an LTM cell handover toward the candidate cell and components for initiating a mobility timer.

[0090] 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.

[0091] 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 components in processor 202 for receiving the above-described components or for transmitting components in processor 202 may be implemented via at least one transceiver 208.

[0092] Receiver chain 210 may be configured to receive signals (e.g., control information, data, packets) via wireless media. For example, receiver chain 210 may include one or more antennas for receiving signals in the air or via wireless media. 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 and obtain transmitted data by reversing the modulation technique applied during signal transmission. Receiver chain 210 may include at least one decoder for decoding the processed demodulated signal to receive transmitted data.

[0093] 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, preparing the signal 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 wireless medium.

[0094] Figure 3 An 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).

[0095] 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 native to the processor chipset (e.g., processor 300) or contained within the processor chipset (e.g., processor 300)) 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).

[0096] 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 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 accesses, and coordinating timing of operations.

[0097] 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.

[0098] Memory 304 may include one or more caches (e.g., memory local to processor 300 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., local to processor 300). In some other embodiments, memory 304 may reside outside the processor chipset (e.g., remote from processor 300).

[0099] 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 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, and the processors and memories may be individually or collectively configured to perform the various functions described herein.

[0100] 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 calculations on data, such as addition, subtraction, multiplication, and division. For example, one or more ALUs 306 may receive input operands and an opcode that determines the operation to be performed. One or more ALUs 306 may be 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, thereby enabling one or more ALU 306s to handle conditional operations, comparisons, and bitwise operations.

[0101] Processor 300 can support wireless communication according to examples disclosed herein.

[0102] In some implementations, processor 300 may be configured to support the execution of tasks such as those related to... Figure 5 The processor 300 is configured or operable to support: components for receiving an L1 / L2 triggered mobility (LTM) cell handover command, the LTM cell handover command indicating a configuration identifier (ID) associated with a candidate cell configured for the UE by the network equipment (NE); components for determining whether the LTM cell handover command contains an early timing advance (TA) value for the candidate cell; components for performing an LTM cell handover toward the candidate cell; and components for initiating a mobility timer.

[0103] In some implementations, processor 300 may be configured to support the execution of tasks such as those related to... Figure 6 The components for the operation of the disclosed NE. The processor 300 may be configured or operable to support: components for receiving from the UE information indicating the availability of auxiliary information associated with failed mobility or successful mobility; components for transmitting a request for the auxiliary information to the UE; and components for receiving from the UE a response containing the auxiliary information associated with LTM cell handover.

[0104] In some implementations, processor 300 may be configured to support the execution of tasks such as those related to... Figure 10 The processor 300 is configured or operable to support: a component for transmitting a request to a candidate NE, wherein the request includes a set of IDs associated with at least one of a plurality of candidate cells of the candidate NE, namely a Layer 2 (L2) reset ID or a TAID measured by the UE; a component for receiving a response from the candidate NE, wherein the response includes one or more IDs belonging to one or more candidate cells of the candidate NE; and a component for transmitting a first message to the UE, wherein the first message includes: LTM configuration information of the one or more candidate cells; and the one or more IDs of the one or more candidate cells, wherein the one or more IDs are applied when the UE switches to the candidate cell.

[0105] In some implementations, processor 300 may be configured to support the execution of tasks such as those related to... Figure 11The processor 300 may be configured or operable to support: a component for receiving a request from a serving NE of a UE, wherein the request includes a set of IDs associated with at least one of a plurality of candidate cells of the candidate NE and a TAID measured by the UE; and a component for transmitting a response to the serving NE, wherein the response includes one or more IDs belonging to one or more candidate cells of the candidate NE, wherein the one or more IDs are applied when the UE switches to one or more candidate cells.

[0106] Those skilled in the art will understand that components in the exemplary processor 300 may be altered without departing from the spirit and scope of this disclosure. For example, some components in the exemplary processor 300 may be omitted or modified, or new components may be added to the exemplary processor 300. For instance, in some embodiments, the processor 300 may not include an ALU 306.

[0107] 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 various aspects of this disclosure as described herein. These components may be coupled via one or more interfaces (e.g., operatively, communicatively, functionally, electronically, electrically).

[0108] 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 to or otherwise support elements for performing the functions described in this disclosure.

[0109] Processor 402 may include intelligent hardware devices (e.g., a general-purpose processor, DSP, CPU, ASIC, FPGA, 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.

[0110] 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 memory 404 or another type of memory. Computer-readable medium includes both non-transitory computer storage media and communication media, wherein the communication media includes any media that facilitates the transfer of a computer program from one place to another. Non-transitory storage media may be any available media accessible by a general-purpose or special-purpose computer.

[0111] 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., processor 402 executing instructions stored in memory 404). For example, processor 402 may support wireless communication at NE 400 according to examples disclosed herein.

[0112] In some implementations, NE 400 can be as follows: Figure 6 The disclosed NE, and NE 400, may be configured to support: means for receiving from the UE information indicating the availability of auxiliary information associated with failed mobility or successful mobility; means for transmitting a request for the auxiliary information to the UE; and means for receiving from the UE a response containing the auxiliary information associated with LTM cell handover.

[0113] In some implementations, NE 400 can be as follows: Figure 10 The publicly disclosed UE's serving NE, and NE 400, can be configured to support: a component for transmitting a request to a candidate NE, wherein the request includes a set of IDs associated with at least one of a plurality of candidate cells of the candidate NE, namely, a Layer 2 (L2) reset ID or a TA ID measured by the UE; a component for receiving a response from the candidate NE, wherein the response includes one or more IDs belonging to one or more candidate cells of the candidate NE; and a component for transmitting a first message to the UE, wherein the first message includes: LTM configuration information of the one or more candidate cells; and the one or more IDs of the one or more candidate cells, wherein the one or more IDs are applied when the UE switches to the candidate cell.

[0114] In some implementations, NE 400 can be as follows: Figure 11The publicly disclosed candidate NE, and NE 400 may be configured to support: a component for receiving a request from a serving NE of the UE, wherein the request includes a set of IDs associated with at least one of a plurality of candidate cells of the candidate NE, a Layer 2 (L2) reset ID or a TA ID measured by the UE; and a component for transmitting a response to the serving NE, wherein the response includes one or more IDs belonging to one or more candidate cells of the candidate NE, wherein the one or more IDs are applied when the UE switches to one or more candidate cells.

[0115] 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.

[0116] 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 means for receiving or transmitting the above-described components in processor 402 may be implemented via at least one transceiver 408.

[0117] Receiver chain 410 may be configured to receive signals (e.g., control information, data, packets) via wireless media. For example, receiver chain 410 may include one or more antennas for receiving signals in the air or via wireless media. 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 the processed demodulated signal to receive transmitted data.

[0118] 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, preparing the signal 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 wireless medium.

[0119] Those skilled in the art will understand that components in the exemplary NE 400 may be changed without departing from the spirit and scope of this disclosure. For example, some components in the exemplary NE 400 may be omitted or modified, or new components may be added to the exemplary NE 400. For example, in some embodiments, the NE 400 may not include the controller 406.

[0120] Figure 5 A flowchart illustrating a method related to handover of an MCG or SCG LTM cell 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 502, 504, and 506 can be provided by reference to... Figure 2 The UE 200 described is executed. Each of operations 502, 504, and 506 can be executed according to the examples described herein. The following is... Figures 7 to 9 Specific examples are described in the embodiments.

[0121] At operation 502, the method may include the UE receiving an LTM cell handover command indicating a configuration identifier (ID) associated with a candidate cell (referred to as candidate cell #1) configured to the UE by the NE. For example, candidate cell #1 was previously provided to the UE by the NE. Candidate cell #1 may also be named an LTM candidate cell or similar.

[0122] At operation 504, the method may include the UE determining whether the LTM cell handover command contains an early TA value for candidate cell #1.

[0123] At operation 506, the method may further include the UE performing an LTM cell handover toward candidate cell #1 and initiating a mobility timer (e.g., T304).

[0124] In some embodiments of the method, if the LTM cell handover command includes an early TA value for candidate cell #1, then in order to perform an LTM cell handover, the UE may execute a timer (denoted as timer #1) based on an LTM cell handover without RACH and starting with the early TA value. For example, timer #1 is a time alignment timer (TAT).

[0125] In some implementations of the method, if timer #1 expires while the mobility timer (e.g., T304) is running, and if the TA ID measured by the UE in candidate cell #1 is equal to the TA ID measured by the UE in the serving cell, then the UE may perform an LTM cell handover via the TA measured by the UE and start a timer associated with the TA measured by the UE (denoted as timer #2).

[0126] In the implementation scheme, if timer #2 expires while the mobility timer (e.g., T304) is running, the UE may perform a RACH-based LTM cell handover. For example, the RACH resources used during this RACH-based LTM cell handover may be one of the following:

[0127] (1) CFRA resources indicated by the LTM cell handover command,

[0128] (2) CFRA resources configured by RRC, or

[0129] (3) CBRA resources configured by RRC. See below. Figure 7 Specific examples are described in #a of the embodiments.

[0130] In some implementations of the method, if timer #1 expires while the mobility timer (e.g., T304) is running, the UE can fall back from RACH-based LTM cell handover to RACH-based LTM cell handover in response to one of the following:

[0131] (1) If the TA ID measured by the UE in candidate cell #1 is not equal to the TA ID measured by the UE in the serving cell;

[0132] (2) If the TA ID of the UE measurement for candidate cell #1 is not configured; or

[0133] (3) If the TA ID for UE measurements of the serving cell is not configured. See below. Figure 7 Specific examples are described in #b of the embodiments.

[0134] In some implementations of the method, if the LTM cell handover command does not contain an early TA value for candidate cell #1, and if the TA ID measured by the UE for candidate cell #1 is equal to the TA ID measured by the UE for the serving cell, then the UE may perform a RACH-based LTM cell handover via the UE-measured TA and initiate a timer (denoted as timer #3) associated with the UE-measured TA. In some implementations, if timer #3 associated with the UE-measured TA expires while a mobility timer (e.g., T304) is running, then the UE may perform a RACH-based LTM cell handover. For example, the RACH resource used during this RACH-based LTM cell handover may be one of the following:

[0135] (1) CFRA resources indicated by the LTM cell handover command,

[0136] (2) CFRA resources configured by RRC, or

[0137] (3) CBRA resources configured by RRC.

[0138] In some implementations of the method, if the UE fails to access candidate cell #1 when the mobility timer (e.g., T304) expires, the UE can reconnect to the cell (denoted as cell #1) via an RRC rebuild or RRC establishment procedure. The UE can then transmit information to cell #1 indicating the availability of auxiliary information (denoted as auxiliary information #1). After receiving a request for auxiliary information #1 from cell #1, the UE can transmit auxiliary information #1 associated with the failure of LTM cell handover to cell #1. For example, auxiliary information #1 can be included in a UE information response message transmitted to cell #1. (The following is an example...) Figure 8 Specific examples are described in the embodiments.

[0139] In some implementations of the method, if the UE successfully accesses candidate cell #1 via LTM cell handover, the UE may stop the mobility timer (e.g., T304), and if the triggering condition for reporting second auxiliary information is met, transmit information indicating the availability of auxiliary information (represented as auxiliary information #2) to candidate cell #1. After receiving a request for auxiliary information #2 from candidate cell #1, the UE may transmit auxiliary information #2 associated with the success of the LTM cell handover. For example, auxiliary information #2 may be included in a UE information response message transmitted to candidate cell #1. In some implementations, auxiliary information #2 may be a successful handover report (SHR). In some other implementations, auxiliary information #2 may be a successful primary / secondary cell group cell (PSCell) report (SPR). The following is in... Figure 9 Specific examples are described in the embodiments.

[0140] In some embodiments of the method, auxiliary information #1 and / or auxiliary information #2 may include information indicating at least one of the following (denoted as information #A):

[0141] (1) Whether to perform LTM cell handover without RACH based on the early TA value included in the LTM cell handover command;

[0142] (2) Whether the timer (e.g., TAT) for the early TA value contained in the LTM cell handover command has expired;

[0143] (3) Whether a fallback has occurred from a RACH-free LTM cell handover based on an early TA value included in the LTM cell handover command to a RACH-free LTM cell handover based on a TA measured by the UE;

[0144] (4) Whether a fallback has occurred from a handover to a RACH-based LTM cell without RACH via an early TA value included in the LTM cell handover command; for example, a RACH-based LTM cell handover via one of the following:

[0145] a) CFRA indicated by the LTM cell handover command (i.e., CFRA from the LTM command),

[0146] b) CFRA configured by RRC (e.g., by RRC messages) (i.e., CFRA configured from RRC), or

[0147] c) CBRA configured by RRC (i.e., CBRA from RRC configuration);

[0148] (5) Whether a fallback has occurred from a RACH-free LTM cell handover to a RACH-based LTM cell handover via the TA measured by the UE;

[0149] (6) Whether the timer (e.g., TAT) associated with the TA measured by the UE has expired;

[0150] (7) Whether CFRA resources are indicated by LTM cell handover commands;

[0151] (8) Whether a rollback has occurred from the CFRA indicated by the LTM cell handover command to the CFRA configured by the RRC configuration;

[0152] (9) Whether a fallback has occurred from the CFRA indicated by the LTM cell handover command to the CBRA configured by the RRC configuration; or

[0153] (10) Whether a rollback occurs from a CFRA configured by RRC to a CBRA configured by RRC.

[0154] In some embodiments of the method, auxiliary information #1 and / or auxiliary information #2 may include at least one of the following (denoted as content #A):

[0155] (1) If configured with Configurable Grant (CG), then it is the total number of attempts to be emitted in the CG during the time period of the timer of the early TA value;

[0156] (2) If CG is configured, then it is the total number of attempts to be transmitted in CG when the TA is measured by the UE; or

[0157] (3) Reports related to early TA acquisition. In some implementations, reports related to early TA acquisition include:

[0158] 1) The total number of attempts toward the same candidate cell;

[0159] 2) The total number of LTM cell handover commands (e.g., PDCCH commands) received toward the same candidate cell;

[0160] 3) Preamble index;

[0161] 4) RACH timing (RO) resources;

[0162] 5) The time interval between two attempts toward the same candidate cell;

[0163] 6) RA objective, wherein the RA objective is set to early TA acquisition;

[0164] 7) or a combination thereof.

[0165] In some implementations of the method, if a fallback occurs from a RACH-free LTM cell handover to a RACH-based LTM cell handover via an early TA value included in the LTM cell handover command, or if a fallback occurs from a RACH-free LTM cell handover to a RACH-based LTM cell handover via a TA measured by the UE, then auxiliary information #1 and / or auxiliary information #2 may further include information related to the preamble domain, time domain, or frequency domain (represented as information #B). Information #B may be associated with one of the following:

[0166] (1) CFRA indicated by LTM cell handover command;

[0167] (2) CFRA configured by RRC; or

[0168] (3) CBRA configured by RRC.

[0169] In some implementations, information #B may include:

[0170] (1) The absolute frequency of point A, which indicates the absolute frequency location of the reference resource block (common RB 0), such as absoluteFrequencyPointA;

[0171] (2) The frequency domain location and bandwidth of the bandwidth portion (BWP), which is associated with one or more random access resources used by the UE, such as locationAndBandwidth;

[0172] (3) Subcarrier spacing, which is used in a BWP associated with one or more random access resources used by the UE, such as subcarrierSpacing;

[0173] (4) msg1 Frequency Start indicates the offset of the lowest Physical Random Access Channel (PRACH) transmission timing in the frequency domain relative to Physical Resource Block (PRB) 0, e.g. msg1-FrequencyStart;

[0174] (5) msg1 frequency start for CFRA, which indicates the offset of the lowest PRACH transmission timing in the frequency domain relative to PRB 0 for CFRA, e.g. msg1-FrequencyStartCFRA.

[0175] (6) msg1 subcarrier spacing, which indicates the subcarrier spacing of PRACH, such as msg1-SubcarrierSpacing;

[0176] (7) msg1 subcarrier spacing for CFRA, which indicates the subcarrier spacing for PRACH used in CFRA, such as msg1-SubcarrierSpacingCFRA;

[0177] (8) msg1 Frequency Division Multiplexing (FDM), which indicates the number of PRACH transmission opportunities for Frequency Division Multiplexing (FDM) in a time example, such as msg1-FDM;

[0178] (9) msg1 FDM for CFRA, which indicates the number of PRACH transmission opportunities of FDM in a time example for CFRA, e.g. msg1-FDMCFRA;

[0179] (10) A list of information about an RN procedure within one or more RA procedures executed by the UE, such as perRAInfoList;

[0180] (11) An initial preamble for the RA attempt, such as a first preamble for the RA attempt;

[0181] (12) The total number of preamble transmissions, for example;

[0182] (13) The total number of preamble transmissions per synchronization signal block (SSB), for example, the number of preamble transmissions;

[0183] (14) The total number of preambles transmitted per Channel State Information Reference Signal (CSI-RS), for example, the number of preambles transmitted per SSB (or per CSI-RS);

[0184] (15) or a combination thereof.

[0185] Figure 6 A flowchart illustrating a method related to handover of an MCG or SCG LTM cell according to aspects of this disclosure is provided. The operation of the method can be implemented by an NE (e.g., a rebuilt gNB, a candidate gNB, or a target gNB) as described herein. The NE can execute a set of instructions to control the functional elements of the NE to perform the described functions. In some embodiments, aspects of the operation of the NE can be described by reference to... Figure 4 The NE 400 is described in the following description. Each of the operations can be performed according to the example described herein. The following is in... Figure 8 and 9 Specific examples are described in the embodiments.

[0186] At operation 602, the method may include the NE receiving from the UE information indicating that auxiliary information associated with failed or successful mobility is available. At operation 604, the method may include the NE transmitting a request for auxiliary information to the UE. At operation 606, the method may include the NE receiving from the UE a response containing auxiliary information associated with LTM cell handover.

[0187] In some embodiments, if the auxiliary information is associated with a failed LTM cell handover, then the UE is configured to reconnect with the NE's cell via an RRC rebuild or RRC establishment procedure (e.g., as described above). Figure 5 The example describes cell #1) reconnection.

[0188] In some other embodiments, if the assistance information is associated with a successful LTM cell handover, the UE is configured to hand over from the source cell of the NE to the candidate cell via the LTM cell handover. In some implementations, if the assistance information is associated with a successful LTM cell handover, the response received in operation 606 may be an SHR or an SPR.

[0189] The auxiliary information received in operation 606 may include, for example, Figure 5 The elements described in the embodiments of auxiliary information #1 or auxiliary information #2 (e.g., information #A, information #B and / or content #A) are the same.

[0190] In some embodiments, if the NE is a rebuilt gNB, then the NE can receive auxiliary information (i.e., auxiliary information #1) associated with the failure of LTM cell handover from the UE. See below... Figure 8 Specific examples are described in the embodiments.

[0191] In some other embodiments, if the NE is a candidate gNB or a target gNB, then the NE may receive auxiliary information (i.e., auxiliary information #2) from the UE associated with the success of the LTM cell handover. See below. Figure 9 Specific examples are described in the embodiments.

[0192] It should be noted that, without departing from the spirit and scope of this disclosure, Figure 5 or Figure 6 The methods described herein describe possible implementation schemes, and the operations and steps may be rearranged or otherwise eliminated or modified, and other implementation schemes are possible.

[0193] Figure 7 A schematic diagram illustrating MCG or SCG LTM cell handover according to aspects of this disclosure. Details described in all other embodiments of this disclosure are applicable. Figure 7 The embodiments shown in the figure.

[0194] In such Figure 7 In the exemplary flowchart shown, during operation 711, UE 701 can access BS 702, i.e., the serving BS (e.g., BS-CU). UE 701 can send measurement reports to the serving BS 702. In some instances, the serving BS 702 can be an MCG or a primary node (MN). In other instances, the serving BS 702 can be an SCG or a secondary node (SN).

[0195] In operation 712, BS 702 can determine to initiate inter-cell mobility configuration preparation based on L1 / L2, i.e., LTM configuration preparation.

[0196] In some embodiments, if BS 702 determines to initiate an intra-BS LTM cell handover, the following operations may occur:

[0197] - BS 702 may be located within a CU-DU architecture and may include a BS-CU and one or more BS-DUs. The BS-CU (i.e., the source BS-CU) may send a request message containing information about the candidate target cell to the candidate BS-DU, such as a UE CONTEXT SETUPREQUEST message. Requests for RACH resources for early TA acquisition may also be included in the request message sent to the candidate BS-DU. If the candidate BS-DU decides to accept the request for LTM configuration associated with the candidate target cell, the candidate BS-DU may respond to the BS-CU, for example via the F1 interface through a UE CONTEXT SETUP RESPONSE response message, containing the accepted RRC configuration of the candidate target cell. This F1 interface response may include one of the following: (1) RACH resources for early TA acquisition; (2) an indication that the TA value of the candidate target cell is equal to 0; or (3) an indication that the TA value of the candidate target cell is equal to the TA value of the source cell.

[0198] - If the service BS 702 is an MCG or MN, then the intra-BS LTM cell handover is an MCG LTM cell handover process configured for PCell change purposes.

[0199] - If the service BS 702 is an SCG or SN, then the intra-BS LTM cell handover is an SCG LTM cell handover process configured for PSCell change purposes.

[0200] In some other embodiments, if BS 702 determines to initiate an inter-BS LTM cell handover, the following operations may occur:

[0201] - BS 702 (i.e., the source BS) may send a request message containing information about the candidate target cell to the candidate BS, such as a handover request message. Requests for RACH resources used for early TA acquisition may also be included in the request message transmitted to the candidate BS. For example, the request may include:

[0202] (1) The instruction request is an instruction for LTM purposes;

[0203] (2) LTM configuration ID list;

[0204] (3) Reference configuration; The Information Element (IE) of “Reference Configuration” may contain a request for a lower-level reference configuration or a generated lower-level reference configuration for LTM preparation.

[0205] (4) CSI resource allocation;

[0206] (5) Provide instructions for RACH resources used in early TA acquisition; and / or

[0207] (6) LTM BS-DU List. The IE of the “LTM BS-DU List” contains the IDs of the source BS-DU and candidate BS-DU.

[0208] - If the “LTM Information Settings” IE included in the UE CONTEXT SETUP REQUEST message contains “CSI Resource Configuration”, then the candidate BS-DU should (if the CU-DU architecture is supported in the candidate BS) use it to generate an LTM CSI report configuration in the “CellGroupConfig” IE for the requested LTM candidate cell. If the candidate BS-DU decides to accept the request for LTM configuration related to the candidate cell, then the candidate BS-DU may respond to the candidate BS-CU, for example via the F1 interface, including the accepted RRC configuration of the candidate target cell. This F1 interface response may include one of the following: (1) RACH resources for early TA acquisition; (2) an indication that the TA value of the candidate target cell is equal to 0; or (3) an indication that the TA value of the candidate target cell is equal to the TA value of the source cell.

[0209] - Next, the candidate BS (e.g., candidate BS-CU, which may also be named "target BS" or "target BS-CU") transmits a response (e.g., a handover request confirmation message) to the source BS 702 (e.g., source BS-CU) via the Xn interface. This Xn interface response may include one of the following: (1) RACH resources for early TA acquisition; (2) an indication that the TA value of the candidate target cell is equal to 0; or (3) an indication that the TA value of the candidate target cell is equal to the TA value of the source cell.

[0210] - If the serving BS 702 is MCG or MN, then the inter-BS LTM cell handover is an MCG LTM cell handover process.

[0211] - If the serving BS 702 is SCG or SN, then the inter-BS LTM cell handover is an SCG LTM cell handover process.

[0212] In operation 713, the serving BS 702 transmits LTM configurations for one or more candidate cells to the UE 701. The LTM configuration may also be named "Candidate Cell Configuration Information for LTM," "Configuration of One or More LTM Candidate Cells," or similar. The LTM configuration may contain one or more RACH resources for RACH-based LTM cell handover. RACH-based LTM cell handover may be CFRA-based LTM cell handover and / or CBRA-based LTM cell handover.

[0213] For example, if a CU-DU architecture is supported, the BS-CU of BS 702 can transmit configuration information, such as RACH resources for early TA acquisition, to the source BS-DU of BS 702. In operation 713, the BS-CU can generate an RRC reconfiguration message based on the configuration from candidate cells and transmit the RRC reconfiguration message to UE 701. The RRC reconfiguration message may contain the configuration of one or more LTM candidate cells and / or one or more RACH resources for early TA acquisition.

[0214] In operation 714, BS 702 sends an LTM command to UE 701 (which may also be named "LTM cell handover command" or similar).

[0215] In some embodiments, UE 701 receives an RRC reconfiguration message associated with one or more LTM candidate cells in operation 713, and the RRC reconfiguration message may contain the value of the TA ID measured by the UE of the serving cell (e.g., ltm-ServingCellUE-MeasuredTA-ID) or the value of the TA ID measured by the UE of the LTM candidate cells (e.g., ltm-UE-MeasuredTA-ID). When UE 701 receives an LTM command toward a candidate cell in operation 714, if the value of the TA ID measured by the UE of the candidate cell is equal to the value of the TA ID measured by the UE of the serving cell, then UE 701 is allowed to perform a RACH-free LTM procedure via the UE-measured TA. Otherwise, if the value of the TA ID measured by the UE of the candidate cell is not equal to the value of the TA ID measured by the UE of the serving cell, then UE 701 may replace the value of the TA ID measured by the UE of the serving cell with the value of the TA ID measured by the UE of the candidate cell. In this application, the TA ID for UE measurements may also be named "Early TA ID for UE Measurements", "UE-based Measurement TA ID", "Early TA ID for UE-based Measurements", or similar. The TA for UE measurements may also be named "Early TA Process for UE Measurements", "Early TA for UE Measurements", "UE-based Measurement TA", "Early TA for UE-based Measurements", or similar.

[0216] In some embodiments, if a CU-DU architecture is supported, then BS 702 (e.g., BS-DU) may transmit a PDCCH command to UE 701 in operation 713 to trigger TA acquisition associated with a specific candidate cell. UE 701 may then transmit a preamble for TA acquisition to BS 702 (e.g., candidate BS-DU) upon receiving the PDCCH command. The candidate BS-DU may calculate the TA value based on the preamble received from UE 701. The source BS-DU of BS 702 may receive the value of an earlier TA from the candidate BS-DU of BS 702, which calculates the TA value via the BS-CU of BS 702.

[0217] In operation 715, different operations may be performed in different embodiments, namely, cases #a, #b and #c as described below.

[0218] Case #a: The LTM command received by UE 701 in operation 714 contains an early TA value obtained from the RACH procedure. In case #a, in operation 715, UE 701 performs LTM without RACH via the early TA from the LTM command and starts a timer (e.g., timer #1) for the early TA. If the timer for the early TA expires while the mobility timer (e.g., T304) is running, then if the TA ID measured by the UE in the candidate cell is equal to the TA ID measured by the UE in the serving cell, UE 701 falls back from the early TA from the LTM command to the TA measured by the UE. UE 701 starts another timer for the TA measured by the UE (e.g., timer #2). If timer #2 expires while the mobility timer (e.g., T304) is running, then UE 701 falls back to RACH-based LTM. In RACH-based LTM, if the CFRA is included in the LTM command, then the CFRA from the LTM command will be processed first. If UE 701 fails again, then UE 701 falls back to the CFRA configured from the RRC. Then, if the CFRA configured from the RRC fails, then UE 701 falls back to the CBRA configured from the RRC.

[0219] Case #b: The LTM command received by UE 701 in operation 714 contains an early TA value obtained from the RACH procedure. In case #b, in operation 715, UE 701 performs LTM based on RACH-free and starts a timer for the early TA via the early TA from the LTM command. If the timer for the early TA expires while the mobility timer (e.g., T304) is running, then if the TA ID measured by the UE in the candidate cell is not equal to the TA ID measured by the UE in the serving cell (or if no TA measured by the UE in the candidate cell or serving cell is configured), UE 701 falls back to RACH-based LTM from the early TA from the LTM command. In RACH-based LTM, if the CFRA is included in the LTM command, then the CFRA from the LTM command is processed first. If the UE fails again, then the UE falls back to the CFRA configured from the RRC. Then, if the CFRA configured from the RRC fails, then UE 701 falls back to the CBRA configured from the RRC.

[0220] Case #c: The LTM command received by UE 701 does not contain an early TA value (i.e., there is no early TA value). In Case #c, in Operation 715, if the TA ID measured by the UE in the candidate cell is equal to the TA ID measured by the UE in the serving cell, then UE 701 performs RACH-based LTM via the UE-measured TA and starts a timer for the UE-measured TA. If the timer for the early TA expires while the mobility timer (e.g., T304) is running, then UE 701 falls back from RACH-based LTM via the UE-measured TA to RACH-based LTM. In RACH-based LTM, if a CFRA is included in the LTM command, then the CFRA from the LTM command will be processed first. If UE 701 fails again, then UE 701 falls back to the CFRA configured by the RRC. Then, if the CFRA configured by the RRC fails, then UE 701 falls back to the CBRA configured by the RRC.

[0221] In operation 716, UE 701 may successfully access an LTM candidate cell, or UE 701 may fail to access an LTM candidate cell if the mobility timer expires.

[0222] Figure 8 This diagram illustrates MCG LTM cell handover according to aspects of this disclosure. Details described in all other embodiments of this disclosure are applicable. Figure 8 The embodiment shown is illustrated. Because failures may occur during MCG LTM cell handover, therefore... Figure 8 The embodiments involve failed MCG LTMs.

[0223] In such Figure 8 In the exemplary flowchart shown, during operation 811, UE 801 can access BS 802, i.e., the serving BS (e.g., BS-CU). UE 801 can send measurement reports to the serving BS 802. In some instances, the serving BS 802 can be an MCG or a master node (MN).

[0224] In operation 812, BS 802 can determine to initiate inter-cell mobility configuration preparation based on L1 / L2, i.e., LTM configuration preparation.

[0225] In some embodiments, if BS 802 determines to initiate an intra-BS LTM cell handover, the following operations may occur:

[0226] - BS 802 may be located within a CU-DU architecture and may include a BS-CU and one or more BS-DUs. The BS-CU (i.e., the source BS-CU) may send a request message containing the ID information of the candidate target cell to the candidate BS-DU, for example, a UE CONTEXT SETUPREQUEST message. Requests for RACH resources for early TA acquisition may also be included in the request message sent to the candidate BS-DU. If the candidate BS-DU decides to accept the request for LTM configuration associated with the candidate target cell, the candidate BS-DU may respond to the BS-CU, for example via the F1 interface through a UE CONTEXT SETUP RESPONSE response message, containing the accepted RRC configuration of the candidate target cell. This F1 interface response may include one of the following: (1) RACH resources for early TA acquisition; (2) an indication that the TA value of the candidate target cell is equal to 0; or (3) an indication that the TA value of the candidate target cell is equal to the TA value of the source cell.

[0227] - If the serving BS 802 is an MCG or MN, then the intra-BS LTM cell handover is an MCG LTM cell handover process configured for PCell change purposes.

[0228] In some other embodiments, if BS 802 determines to initiate an inter-BS LTM cell handover, the following operations may occur:

[0229] - BS 802 (i.e., the source BS) sends a request message containing information about the candidate target cell to the candidate BS, such as a handover request message. Requests for RACH resources used for early TA acquisition can also be included in the request message transmitted to the candidate BS. For example, the request might include:

[0230] (1) The instruction request is an instruction for LTM purposes;

[0231] (2) LTM configuration ID list;

[0232] (3) Reference configuration; The Information Element (IE) of “Reference Configuration” may contain a request for a lower-level reference configuration or a generated lower-level reference configuration for LTM preparation.

[0233] (4) CSI resource allocation;

[0234] (5) Provide instructions for RACH resources used in early TA acquisition; and / or

[0235] (6) LTM BS-DU List. The IE of the “LTM BS-DU List” contains the IDs of the source BS-DU and candidate BS-DU.

[0236] - If the "LTM Information Settings" IE included in the UE CONTEXT SETUP REQUEST message contains "CSI Resource Configuration", then the candidate BS-DU should (if the CU-DU architecture is supported in the candidate BS) use it to generate an LTM CSI report configuration in the "CellGroupConfig" IE for the requested LTM candidate cell. If the candidate BS-DU decides to accept the request for LTM configuration related to the candidate cell, then the candidate BS-DU may respond to the candidate BS-CU, for example via the F1 interface, including the accepted RRC configuration for the candidate target cell. This F1 interface response may include one of the following: (1) RACH resources for early TA acquisition; (2) an indication that the TA value of the candidate target cell is equal to 0; or (3) an indication that the TA value of the candidate target cell is equal to the TA value of the source cell.

[0237] - Next, the candidate BS (e.g., candidate BS-CU, which may also be named "target BS" or "target BS-CU") sends a response, such as a handover request confirmation message, to the source BS (e.g., source BS-CU) via the Xn interface. This Xn interface response may include one of the following: (1) RACH resources for early TA acquisition; (2) an indication that the TA value of the candidate target cell is equal to 0; or (3) an indication that the TA value of the candidate target cell is equal to the TA value of the source cell.

[0238] - If the serving BS 802 is MCG or MN, then the inter-BS LTM cell handover is an MCG LTM cell handover process.

[0239] In operation 813, the serving BS 802 transmits LTM configurations for one or more candidate cells to the UE 801. The LTM configuration may also be named "Candidate Cell Configuration Information for LTM," "Configuration of One or More LTM Candidate Cells," or similar. The LTM configuration may contain one or more RACH resources for RACH-based LTM cell handover. RACH-based LTM cell handover may be CFRA-based LTM cell handover and / or CBRA-based LTM cell handover.

[0240] For example, if a CU-DU architecture is supported, the BS-CU of BS 802 can transmit configuration information, such as RACH resources for early TA acquisition, to the source BS-DU of BS 802. In operation 813, the BS-CU can generate an RRC reconfiguration message based on the configuration from candidate cells and transmit the RRC reconfiguration message to UE 801. The RRC reconfiguration message may contain the configuration of one or more LTM candidate cells and / or one or more RACH resources for early TA acquisition.

[0241] In operation 814, BS 802 sends an LTM command to UE 801 (which may also be named "LTM cell handover command" or similar).

[0242] In some embodiments, UE 801 receives an RRC reconfiguration message associated with one or more LTM candidate cells in operation 813, and the RRC reconfiguration message may contain the value of the TA ID measured by the UE of the serving cell (e.g., ltm-ServingCellUE-MeasuredTA-ID) or the value of the TA ID measured by the UE of the LTM candidate cells (e.g., ltm-UE-MeasuredTA-ID). When UE 801 receives an LTM command toward a candidate cell in operation 814, if the value of the TA ID measured by the UE of the candidate cell is equal to the value of the TA ID measured by the UE of the serving cell, then UE 801 is allowed to perform a RACH-free LTM procedure via the UE-measured TA. Otherwise, if the value of the TA ID measured by the UE of the candidate cell is not equal to the value of the TA ID measured by the UE of the serving cell, then UE 801 may replace the value of the TA ID measured by the UE of the serving cell with the value of the TA ID measured by the UE of the candidate cell. In this application, the TA ID for UE measurements may also be named "Early TA ID for UE Measurements", "UE-based Measurement TA ID", "Early TA ID for UE-based Measurements", or similar. The TA for UE measurements may also be named "Early TA Process for UE Measurements", "Early TA for UE Measurements", "UE-based Measurement TA", "Early TA for UE-based Measurements", or similar.

[0243] In some embodiments, if a CU-DU architecture is supported, then BS 802 (e.g., BS-DU) may transmit a PDCCH command to UE 801 in operation 813 to trigger TA acquisition associated with a specific candidate cell. UE 801 may then transmit a preamble for TA acquisition to BS 802 (e.g., candidate BS-DU) upon receiving the PDCCH command. The candidate BS-DU may calculate the TA value based on the preamble received from UE 801. The source BS-DU of BS 802 may receive the value of an earlier TA from the candidate BS-DU of BS 802, the candidate BS-DU calculating the TA value based on the preamble received via BS-CU of BS 702.

[0244] In operation 815, different operations may be performed in different embodiments, namely, cases #A, #B and #C as described below.

[0245] Case #A: The LTM command received by UE 801 in operation 814 contains an early TA value obtained from the RACH procedure. In Case #A, in operation 815, UE 801 performs LTM based on RACH-free and starts a timer (e.g., timer #1) for the early TA via the early TA from the LTM command. If the timer for the early TA expires while the mobility timer (e.g., T304) is running, then if the TA ID measured by the UE in the candidate cell is equal to the TA ID measured by the UE in the serving cell, UE 801 falls back from the early TA from the LTM command to the TA measured by the UE. UE 801 starts another timer for the TA measured by the UE (e.g., timer #2). If timer #2 expires while the mobility timer (e.g., T304) is running, then UE 801 falls back to RACH-based LTM. In RACH-based LTM, if the CFRA is included in the LTM command, then the CFRA from the LTM command will be processed first. If UE 801 fails again, then UE 801 falls back to the CFRA configured from the RRC. Then, if the CFRA configured from the RRC fails, then UE 801 falls back to the CBRA configured from the RRC.

[0246] Case #B: The LTM command received by UE 801 in operation 814 contains an early TA value obtained from the RACH procedure. In Case #B, in operation 815, UE 801 performs LTM based on RACH without RACH and starts a timer for the early TA via the early TA from the LTM command. If the timer for the early TA expires while the mobility timer (e.g., T304) is running, then if the TA ID measured by the UE in the candidate cell is not equal to the TA ID measured by the UE in the serving cell (or if no TA measured by the UE in the candidate cell or serving cell is configured), UE 801 falls back from the early TA from the LTM command to RACH-based LTM. In RACH-based LTM, if the CFRA is included in the LTM command, then the CFRA from the LTM command is processed first. If UE 801 fails again, then the UE falls back to the CFRA configured from the RRC. Then, if the CFRA configured from the RRC fails, then UE 801 falls back to the CBRA configured from the RRC.

[0247] Case #C: The LTM command received by UE 801 does not contain an early TA value (i.e., there is no early TA value). In Case #C, during operation 815, if the TA ID measured by the UE in the candidate cell is equal to the TA ID measured by the UE in the serving cell, then UE 801 performs RACH-based LTM via the UE-measured TA and starts a timer for the UE-measured TA. If the timer for the early TA expires while the mobility timer (e.g., T304) is running, then UE 801 falls back from RACH-based LTM via the UE-measured TA to RACH-based LTM. In RACH-based LTM, if a CFRA is included in the LTM command, then the CFRA from the LTM command will be processed first. If UE 801 fails again, then UE 801 falls back to the CFRA configured by the RRC. Then, if the CFRA configured by the RRC fails, then UE 801 falls back to the CBRA configured by the RRC.

[0248] In operation 816, if the mobility timer (e.g., T304) expires, then UE 801 cannot access the LTM candidate cell. UE 801 can reconnect to the new cell via RRC rebuild or RRC establishment procedure.

[0249] In operation 817, UE 801 transmits an indication to the serving cell that auxiliary information (e.g., auxiliary information #1) is available. The auxiliary information is associated with a failed LTM cell handover (i.e., LTM failure). The auxiliary information may also be named "LTM Failure Information" or something similar.

[0250] In operation 818, the serving cell belonging to the rebuilt BS (i.e., BS 803) sends a UE information request message to UE 801, requesting UE 801 to report LTM failure information.

[0251] In operation 819, UE 801 transmits auxiliary information related to LTM failure to the serving cell of BS 803. This auxiliary information may be included in the UE information response message. The auxiliary information related to LTM failure may also be included in the radio link failure (RLF) report contained within the UE information response message.

[0252] In some embodiments, the auxiliary information related to LTM failure (e.g., auxiliary information #1) includes at least one of the following:

[0253] (1) Information used to indicate whether to execute RACH-free LTM via an early TA from an LTM command.

[0254] (2) Information used to indicate whether the timer for the early TA included in the LTM cell handover command has expired. For example, auxiliary information related to LTM failure may further include at least one of the following:

[0255] - If a CG is configured, the number of attempts to fire in the CG during the first timer period is included in the auxiliary information.

[0256] - RA Report for Early TA Acquisition: UE 801 may report, for example, the number of attempts toward the same candidate cell, the number of PDCCH commands received toward the same candidate cell, the preamble index and / or RACH timing (RO) resources; the time interval between two attempts toward the same candidate cell; and / or the RA purpose. For example, the RA purpose (e.g., raPurposeIE) may be set to early TA acquisition.

[0257] (3) Information used to indicate whether a fallback has occurred from the early TA from the LTM command to the TA measured by the UE.

[0258] - If CG is configured, then the number of transmission attempts in CG when using TA measured by the UE.

[0259] (4) Information used to indicate whether a rollback has occurred from a non-RACH LTM via an early TA from an LTM command to a RACH-based LTM via one of the following: CFRA from an LTM command, CFRA from an RRC configuration, or CBRA from an RRC configuration.

[0260] (5) Information used to indicate whether a fallback has occurred from a RACH-free LTM measured by the TA via the UE to a RACH-based LTM via one of the following: CFRA from the LTM command, CFRA from the RRC configuration, or CBRA from the RRC configuration.

[0261] - If a rollback to RACH-based LTM occurs, the following information can be reported:

[0262] • For CFRA from LTM commands, information related to the preamble and time-frequency domains can be reported.

[0263] • For CFRA from RRC configuration, information related to the preamble domain and time-frequency domain can be reported.

[0264] • For CBRAs from RRC configurations, information related to the preamble and time-frequency domains can be reported.

[0265] - For example, the above information related to the preamble field and the time-frequency field can be one or more of the following IEs with variable names:

[0266] - The absolute frequency of point A, which indicates the absolute frequency location of the reference resource block (common RB 0), such as absoluteFrequencyPointA;

[0267] - The frequency domain location and bandwidth of the bandwidth portion (BWP), which is associated with one or more random access resources used by the UE, such as locationAndBandwidth;

[0268] - Subcarrier spacing, which is used in a BWP associated with one or more random access resources used by the UE, such as subcarrierSpacing;

[0269] - msg1 FrequencyStart indicates the offset of the lowest Physical Random Access Channel (PRACH) transmission timing in the frequency domain relative to Physical Resource Block (PRB) 0, e.g. msg1-FrequencyStart;

[0270] - msg1 frequency start for CFRA indicates the offset of the lowest PRACH transmission timing in the frequency domain relative to PRB 0 for CFRA, e.g. msg1-FrequencyStartCFRA.

[0271] - msg1 Subcarrier Spacing, which indicates the subcarrier spacing of PRACH, e.g., msg1-SubcarrierSpacing;

[0272] - msg1 subcarrier spacing for CFRA, which indicates the subcarrier spacing for PRACH used in CFRA, e.g. msg1-SubcarrierSpacingCFRA;

[0273] - msg1 Frequency Division Multiplexing (FDM) indicates the number of PRACH transmit opportunities for Frequency Division Multiplexing (FDM) in a time example, e.g., msg1-FDM;

[0274] - msg1 FDM for CFRA, which indicates the number of PRACH transmission opportunities of FDM in a time example for CFRA, e.g. msg1-FDMCFRA;

[0275] - A list of information about an RN procedure within one or more RA procedures executed by the UE, such as perRAInfoList;

[0276] - The initial preamble used for RA attempts, such as the first preamble used for RA attempts;

[0277] - The total number of preamble transmissions, such as the number of preamble transmissions;

[0278] - The total number of preambles transmitted per synchronization signal block (SSB), such as the number of preambles transmitted per SSB;

[0279] - The total number of preambles transmitted per Channel State Information Reference Signal (CSI-RS), such as the number of preambles transmitted per CSI-RS;

[0280] (6) Information used to indicate whether the time alignment timer (TAT) based on the UE has expired.

[0281] (7) Information used to indicate whether CFRA resources are included in LTM cell handover commands.

[0282] (8) Information used to indicate whether a fallback has occurred from a CFRA from an LTM cell handover command to a CFRA from an RRC configuration.

[0283] (9) Information used to indicate whether a fallback has occurred from the CFRA from the LTM cell handover command to the CBRA from the RRC configuration.

[0284] (10) Indicates whether a rollback has occurred from the CFRA configured by the RRC to the CBRA configured by the RRC.

[0285] In operation 820, after receiving a report from UE 801, the rebuilt BS 803 can transmit the received report to the source BS 802.

[0286] Figure 9 Another schematic diagram illustrating MCG or SCG LTM cell handover according to aspects of this disclosure. Details described in all other embodiments of this disclosure are applicable to... Figure 9 The embodiments shown in the figure. Figure 9 The implementation examples involve successful MCG or SCG LTM cell handover.

[0287] In such Figure 9 In the exemplary flowchart shown, during operation 911, UE 901 can access BS 902, i.e., the serving BS (e.g., BS-CU). UE 901 can send measurement reports to the serving BS 902. In some instances, the serving BS 902 can be an MCG or a primary node (MN). In other instances, the serving BS 902 can be an SCG or a secondary node (SN).

[0288] In operation 912, BS 902 can determine to initiate L1 / L2-based inter-cell mobility configuration preparation, i.e., LTM configuration preparation.

[0289] In some embodiments, if BS 902 determines to initiate an intra-BS LTM cell handover, the following operations may occur:

[0290] - BS 902 may be located within a CU-DU architecture and may include a BS-CU and one or more BS-DUs. The BS-CU (i.e., the source BS-CU) may send a request message containing the ID information of the candidate target cell to the candidate BS-DU, for example, a UE CONTEXT SETUPREQUEST message. Requests for RACH resources for early TA acquisition may also be included in the request message sent to the candidate BS-DU. If the candidate BS-DU decides to accept the request for LTM configuration associated with the candidate target cell, the candidate BS-DU may respond to the BS-CU, for example via the F1 interface through a UE CONTEXT SETUP RESPONSE response message, containing the accepted RRC configuration of the candidate target cell. This F1 interface response may include one of the following: (1) RACH resources for early TA acquisition; (2) an indication that the TA value of the candidate target cell is equal to 0; or (3) an indication that the TA value of the candidate target cell is equal to the TA value of the source cell.

[0291] - If the serving BS 902 is an MCG or MN, then the intra-BS LTM cell handover is an MCG LTM cell handover process configured for PCell change purposes.

[0292] - If the service BS 902 is an SCG or SN, then the intra-BS LTM cell handover is an SCG LTM cell handover process configured for PSCell change purposes.

[0293] In some other embodiments, if BS 902 determines to initiate an inter-BS LTM cell handover, the following operations may occur:

[0294] - BS 902 (i.e., the source BS) sends a request message containing information about the candidate target cell to the candidate BS, such as a handover request message. Requests for RACH resources used for early TA acquisition can also be included in the request message transmitted to the candidate BS. For example, the request might include:

[0295] (1) An instruction request is an instruction for LTM purposes;

[0296] (2) LTM configuration ID list;

[0297] (3) Reference configuration; This IE of "reference configuration" contains a request for a lower-level reference configuration or a generated lower-level reference configuration for LTM preparation.

[0298] (4) CSI resource allocation;

[0299] (5) Provide instructions for RACH resources used in early TA acquisition; and / or

[0300] (6) LTM BS-DU List. This IE, “LTM BS-DU List”, contains the IDs of source BS-DUs and candidate BS-DUs.

[0301] - If the "LTM Information Settings" IE included in the UE CONTEXT SETUP REQUEST message contains "CSI Resource Configuration", then the candidate BS-DU should (if the CU-DU architecture is supported in the candidate BS) use it to generate an LTM CSI report configuration in the "CellGroupConfig" IE for the requested LTM candidate cell. If the candidate BS-DU decides to accept the request for LTM configuration related to the candidate cell, then the candidate BS-DU may respond to the candidate BS-CU, for example via the F1 interface, including the accepted RRC configuration for the candidate target cell. This F1 interface response may include one of the following: (1) RACH resources for early TA acquisition; (2) an indication that the TA value of the candidate target cell is equal to 0; or (3) an indication that the TA value of the candidate target cell is equal to the TA value of the source cell.

[0302] - Next, the candidate BS (e.g., candidate BS-CU, which may also be named "target BS" or "target BS-CU") sends a response, such as a handover request confirmation message, to the source BS (e.g., source BS-CU) via the Xn interface. This Xn interface response may include one of the following: (1) RACH resources for early TA acquisition; (2) an indication that the TA value of the candidate target cell is equal to 0; or (3) an indication that the TA value of the candidate target cell is equal to the TA value of the source cell.

[0303] - If the serving BS is MCG or MN, then the LTM cell handover between BSs is MCG LTM.

[0304] - If the serving BS is SCG or SN, then the LTM cell handover between BSs is SCG LTM.

[0305] In Operation 913, the serving BS transmits LTM configurations for one or more candidate cells to UE 901. The LTM configuration may also be named "Candidate Cell Configuration Information for LTM," "Configuration of One or More LTM Candidate Cells," or similar. The LTM configuration may contain one or more RACH resources for RACH-based LTM cell handover. RACH-based LTM cell handover may be CFRA-based LTM cell handover and / or CBRA-based LTM cell handover.

[0306] For example, if a CU-DU architecture is supported, the BS-CU of BS 902 can transmit configuration information, such as RACH resources acquired in the early TA, to the source BS-DU of BS 902. In operation 913, the BS-CU can generate an RRC reconfiguration message based on the configuration from candidate cells and transmit the RRC reconfiguration message to UE 901. The RRC reconfiguration message may contain the configuration of one or more LTM candidate cells and / or one or more RACH resources acquired in the early TA.

[0307] In operation 914, BS 902 sends an LTM command to UE 901 (which may also be named "LTM cell handover command" or similar).

[0308] In some embodiments, UE 901 receives an RRC reconfiguration message associated with one or more LTM candidate cells in operation 913, and the RRC reconfiguration message may contain the value of the TA ID measured by the UE of the serving cell (e.g., ltm-ServingCellUE-MeasuredTA-ID) or the value of the TA ID measured by the UE of the LTM candidate cells (e.g., ltm-UE-MeasuredTA-ID). When UE 901 receives an LTM command toward a candidate cell in operation 914, if the value of the TA ID measured by the UE of the candidate cell is equal to the value of the TA ID measured by the UE of the serving cell, then UE 901 is allowed to perform a RACH-free LTM procedure via the UE-measured TA. Otherwise, if the value of the TA ID measured by the UE of the candidate cell is not equal to the value of the TA ID measured by the UE of the serving cell, then UE 901 may replace the value of the TA ID measured by the UE of the serving cell with the value of the TA ID measured by the UE of the candidate cell. In this application, the TA ID for UE measurements may also be named "Early TA ID for UE Measurements", "UE-based Measurement TA ID", "Early TA ID for UE-based Measurements", or similar. The TA for UE measurements may also be named "Early TA Process for UE Measurements", "Early TA for UE Measurements", "UE-based Measurement TA", "Early TA for UE-based Measurements", or similar.

[0309] In some embodiments, if a CU-DU architecture is supported, then BS 902 (e.g., BS-DU) may transmit a PDCCH command to UE 901 in operation 913 to trigger TA acquisition associated with a specific candidate cell. UE 901 may then transmit a preamble for TA acquisition to BS 902 (e.g., candidate BS-DU) upon receiving the PDCCH command. The candidate BS-DU may calculate the TA value based on the preamble received from UE 901. The source BS-DU of BS 902 may receive the value of an earlier TA from the candidate BS-DU of BS 902, which calculates the TA value via the BS-CU of BS 902.

[0310] In operation 915, different operations can be performed in different embodiments, namely, cases #X, #Y and #Z as described below.

[0311] Case #X: The LTM command received by UE 901 in Operation 914 contains an early TA value obtained from the RACH procedure. In Case #X, in Operation 915, UE 901 performs LTM without RACH via the early TA from the LTM command and starts a timer (e.g., timer #1) for the early TA. If the timer for the early TA expires while the mobility timer (e.g., T304) is running, then if the TA ID measured by the UE in the candidate cell is equal to the TA ID measured by the UE in the serving cell, UE 901 falls back from the early TA from the LTM command to the TA measured by the UE. UE 901 starts another timer for the TA measured by the UE (e.g., timer #2). If timer #2 expires while the mobility timer (e.g., T304) is running, then UE 901 falls back to RACH-based LTM. In RACH-based LTM, if the CFRA is included in the LTM command, then the CFRA from the LTM command is processed first. If UE 901 fails again, then UE 901 falls back to the CFRA configured from the RRC. Then, if the CFRA configured from the RRC fails, then UE 901 falls back to the CBRA configured from the RRC.

[0312] In scenario #X, UE 901 can successfully access the LTM candidate cell (i.e., the target cell) via one of the following: an early TA from an LTM command, a TA measured by the UE, a RACH based on a CFRA from an LTM command, a CFRA reconfigured from an RRC, or a CBRA reconfigured from an RRC. For example, after UE 901 falls back from an early TA from an LTM command to a TA measured by the UE, UE 901 successfully accesses the target cell via the TA measured by the UE.

[0313] Case #Y: The LTM command received by UE 901 in Operation 914 contains an early TA value obtained from the RACH procedure. In Case #Y, in Operation 915, UE 901 performs LTM based on RACH without RACH and starts a timer for the early TA via the early TA from the LTM command. If the timer for the early TA expires while the mobility timer (e.g., T304) is running, then if the TA ID measured by the UE in the candidate cell is not equal to the TA ID measured by the UE in the serving cell (or if no TA measured by the UE in the candidate cell or serving cell is configured), UE 901 falls back from the early TA from the LTM command to RACH-based LTM. In RACH-based LTM, if the CFRA is included in the LTM command, then the CFRA from the LTM command is processed first. If the UE fails again, then the UE falls back to the CFRA configured from the RRC. Then, if the CFRA configured from the RRC fails, then UE 901 falls back to the CBRA configured from the RRC.

[0314] In scenario #Y, UE 901 can successfully access the LTM candidate cell (i.e., the target cell) via one of the following: an early TA from an LTM command, a RACH based on a CFRA from an LTM command, a CFRA reconfigured from an RRC, or a CBRA reconfigured from an RRC. For example, after UE 901 falls back from an early TA from an LTM command to a CFRA configured from an RRC, UE 901 successfully accesses the target cell via a CFRA configured from an RRC.

[0315] Case #Z: The UE receives an LTM cell handover command without an early TA value. In Case #Z, in Operation 915, if the TA ID measured by the UE in the candidate cell is equal to the TA ID measured by the UE in the serving cell, then UE 901 executes LTM without RACH via the UE-measured TA and starts a timer for the UE-measured TA. If the timer for the early TA expires while the mobility timer (e.g., T304) is running, then UE 901 falls back from LTM without RACH via the UE-measured TA to RACH-based LTM. In RACH-based LTM, if a CFRA is included in the LTM command, then the CFRA from the LTM command will be processed first. If UE 901 fails again, then UE 901 falls back to the CFRA configured by the RRC. Then, if the CFRA configured by the RRC fails, then UE 901 falls back to the CBRA configured by the RRC.

[0316] In scenario #Z, UE 901 can successfully access the LTM candidate cell (i.e., the target cell) via one of the following: LTM without RACH via the TA measured by the UE, RACH LTM based on the CFRA from the LTM command, CFRA reconfigured from the RRC, or CBRA reconfigured from the RRC. For example, after UE 901 falls back from the TA measured by the UE to the CFRA configured from the RRC, UE 901 successfully accesses the target cell via the CFRA configured from the RRC.

[0317] In Operation 916, UE 901 can successfully access the LTM candidate cell. Furthermore, UE 901 can stop the mobility timer, for example, T304.

[0318] For example, such as Figure 9 As demonstrated in Operation 916, during an inter-BS LTM cell handover, UE 901 successfully accessed the target BS 903's cell. Figure 9 The handover of LTM cells within the BS is not shown, but similar operations can be performed by UE 901 and BS 902.

[0319] In some embodiments, such as in operation 911, UE 901 may receive a configuration of a threshold for triggering a Successful HO Report (SHR) or a Successful PSCell Report (SPR). If an SHR is triggered based on a successful handover configuration, then the SHR can be used to provide a successful handover report. If an SPR is triggered based on a successful PSCell change or add report configuration, then the SPR can be used to provide a successful PSCell change or add report. For example, the threshold may be a percentage related to the length of timer T310 (e.g., 500 ms), such as 60%. For example, in operation 915 or operation 916, UE 901 may determine whether the elapsed time of timer T310 since UE 901 started timer T310 is greater than 60%. The value is 500 ms (i.e., 300 ms). If this condition for SHR is met, then UE 901 can record the parameters of SHR.

[0320] In Operation 917, UE 901 transmits an indication to the target BS 903 that auxiliary information (e.g., auxiliary information #2) is available. The auxiliary information is associated with a successful LTM cell handover (i.e., successful LTM). The auxiliary information may also be named "Successful LTM Information" or similar.

[0321] In operation 918, the serving cell of target BS 903 sends a UE Information Request message to UE 901, requesting UE 901 to report successful LTM information. The UE Information Request message may contain a request for LTM information reporting.

[0322] In Operation 919, UE 901 transmits auxiliary information related to successful LTM to the serving cell of target BS 903. This auxiliary information may be included in the UE Information Response message. The auxiliary information related to successful LTM may be included in the SHR or SPR contained within the UE Information Response message.

[0323] In some embodiments, the auxiliary information associated with a successful LTM (e.g., auxiliary information #2) includes at least one of the following:

[0324] (1) Information used to indicate whether to execute RACH-free LTM via an early TA from an LTM command.

[0325] (2) Information used to indicate whether the timer for the early TA included in the LTM cell handover command has expired. For example, auxiliary information related to a successful LTM may further include at least one of the following:

[0326] - If a CG is configured, the number of attempts to fire in the CG during the first timer period is included in the auxiliary information.

[0327] - RA Report for Early TA Acquisition: UE 801 may report, for example, the number of attempts toward the same candidate cell, the number of PDCCH commands received toward the same candidate cell, the preamble index and / or RACH timing (RO) resources; the time interval between two attempts toward the same candidate cell; and / or the RA purpose. For example, the RA purpose (e.g., raPurposeIE) may be set to early TA acquisition.

[0328] (3) Information used to indicate whether a fallback has occurred from the early TA from the LTM command to the TA measured by the UE.

[0329] - If CG is configured, then it is the number of transmit attempts in CG when using TA measured by UE.

[0330] (4) Information used to indicate whether a rollback has occurred from a non-RACH LTM via an early TA from an LTM command to a RACH-based LTM via one of the following: CFRA from an LTM command, CFRA from an RRC configuration, or CBRA from an RRC configuration.

[0331] (5) Information used to indicate whether a fallback has occurred from a RACH-free LTM measured by the TA via the UE to a RACH-based LTM via one of the following: CFRA from the LTM command, CFRA from the RRC configuration, or CBRA from the RRC configuration.

[0332] - If a rollback to RACH-based LTM occurs, the following information can be reported:

[0333] • For CFRA from LTM commands, information related to the preamble and time-frequency domains can be reported.

[0334] • For CFRA from RRC configuration, information related to the preamble domain and time-frequency domain can be reported.

[0335] • For CBRAs from RRC configurations, information related to the preamble and time-frequency domains can be reported.

[0336] - For example, the above information related to the preamble field and the time-frequency field can be one or more of the following IEs with variable names:

[0337] - The absolute frequency of point A, which indicates the absolute frequency location of the reference resource block (common RB 0), such as absoluteFrequencyPointA;

[0338] - The frequency domain location and bandwidth of the bandwidth portion (BWP), which is associated with one or more random access resources used by the UE, such as locationAndBandwidth;

[0339] - Subcarrier spacing, which is used in a BWP associated with one or more random access resources used by the UE, such as subcarrierSpacing;

[0340] - msg1 FrequencyStart indicates the offset of the lowest Physical Random Access Channel (PRACH) transmission timing in the frequency domain relative to Physical Resource Block (PRB) 0, e.g. msg1-FrequencyStart;

[0341] - msg1 frequency start for CFRA indicates the offset of the lowest PRACH transmission timing in the frequency domain relative to PRB 0 for CFRA, e.g. msg1-FrequencyStartCFRA.

[0342] - msg1 Subcarrier Spacing, which indicates the subcarrier spacing of PRACH, e.g., msg1-SubcarrierSpacing;

[0343] - msg1 subcarrier spacing for CFRA, which indicates the subcarrier spacing for PRACH used in CFRA, e.g. msg1-SubcarrierSpacingCFRA;

[0344] - msg1 Frequency Division Multiplexing (FDM) indicates the number of PRACH transmit opportunities for Frequency Division Multiplexing (FDM) in a time example, e.g., msg1-FDM;

[0345] - msg1 FDM for CFRA, which indicates the number of PRACH transmission opportunities of FDM in a time example for CFRA, e.g. msg1-FDMCFRA;

[0346] - A list of information about an RN procedure within one or more RA procedures executed by the UE, such as perRAInfoList;

[0347] - The initial preamble used for RA attempts, such as the first preamble used for RA attempts;

[0348] - The total number of preamble transmissions, such as the number of preamble transmissions;

[0349] - The total number of preambles transmitted per synchronization signal block (SSB), such as the number of preambles transmitted per SSB;

[0350] - The total number of preambles transmitted per Channel State Information Reference Signal (CSI-RS), such as the number of preambles transmitted per CSI-RS;

[0351] (6) Information used to indicate whether the time alignment timer (TAT) based on the UE has expired.

[0352] (7) Information used to indicate whether CFRA resources are included in LTM cell handover commands.

[0353] (8) Information used to indicate whether a fallback has occurred from a CFRA from an LTM cell handover command to a CFRA from an RRC configuration.

[0354] (9) Information used to indicate whether a fallback has occurred from the CFRA from the LTM cell handover command to the CBRA from the RRC configuration.

[0355] (10) Indicates whether a rollback has occurred from the CFRA configured by the RRC to the CBRA configured by the RRC.

[0356] In operation 920, after receiving a report from UE 901, target BS 903 may transmit the received report to source BS 902.

[0357] Figure 10A flowchart illustrating a method related to handover of an MCG or SCG LTM cell according to aspects of this disclosure is provided. The operation of the method can be implemented by an NE (e.g., a source / serving gNB) as described herein. The NE can execute a set of instructions to control its functional elements to perform the described functions. In some embodiments, aspects of the NE's operation can be described by reference to... Figure 4 The NE 400 is described in the following description. Each of the operations can be performed according to the example described herein. The following is in... Figure 12 Specific examples are described in the embodiments.

[0358] At operation 1002, the method may include the UE's serving NE transmitting a request (e.g., a handover request for L3 handover) to a candidate NE. The request may include a set of IDs associated with at least one of a "Layer 2 (L2) Reset ID" or a "TA ID measured by the UE" for a plurality of candidate cells of the candidate NE.

[0359] At operation 1004, the method may include receiving a response from a candidate NE by the serving NE. The response may include one or more IDs of the set of IDs belonging to one or more candidate cells of the candidate NE.

[0360] At operation 1006, the method may include transmitting a message from the serving NE to the UE. The message may include:

[0361] (1) LTM configuration information for one or more candidate cells; and

[0362] (2) One or more IDs of one or more candidate cells, wherein one or more IDs are applied when the UE switches to a candidate cell.

[0363] In some implementations of the method, if one or more IDs of one or more candidate cells are associated with an ID without L2 reset:

[0364] (1) If the feature of no L2 reset is available during handover between two or more candidate cells within a plurality of candidate cells, then (e.g., by a candidate NE, such as a candidate gNB) two or more candidate cells are configured with the same ID within the set of IDs. One or more IDs of one or more candidate cells may be a subset of the set of IDs.

[0365] (2) If the feature of no L2 reset cannot be used during handover between any two candidate cells within a plurality of candidate cells, then (e.g., by candidate NE) each of one or more candidate cells is configured with a different ID within the set of IDs. Thus, one or more IDs of one or more candidate cells are equal to the set of IDs.

[0366] In some other embodiments of the method, if one or more IDs of one or more candidate cells are associated with the TA ID measured by the UE:

[0367] (1) If the TA measured by the UE is available during handover between two or more candidate cells within a plurality of candidate cells, then (e.g., by the candidate NE) the two or more candidate cells are configured with the same ID within the set of IDs. One or more IDs of one or more candidate cells may be a subset of the set of IDs.

[0368] (2) If the TA measured by the UE cannot be used during handover between any two candidate cells within a plurality of candidate cells, then (e.g., by the candidate NE) each of the one or more candidate cells is configured with a different ID within the set of IDs. Therefore, one or more IDs of the one or more candidate cells are equal to the set of IDs.

[0369] Figure 11 A flowchart illustrating a method related to handover of an MCG or SCG LTM cell according to aspects of this disclosure is provided. The operation of the method can be implemented by an NE (e.g., a candidate gNB) as described herein. The NE can execute a set of instructions to control the functional elements of the NE to perform the described functions. In some embodiments, aspects of the operation of the NE can be described by reference to... Figure 4 The NE 400 is described in the following description. Each of the operations can be performed according to the example described herein. The following is in... Figure 12 Specific examples are described in the embodiments.

[0370] At operation 1102, the method may include a candidate NE receiving a request from a serving NE of a user equipment (UE). The request may include a set of IDs associated with at least one of a “Layer 2 (L2) Reset ID” or a “TA ID measured by the UE” of a plurality of candidate cells of the candidate NE.

[0371] At operation 1104, the method may include transmitting a response from a candidate NE to a serving NE. The response may include one or more IDs belonging to the set of IDs of one or more candidate cells belonging to the candidate NE. The one or more IDs are applied when the UE switches to one or more candidate cells.

[0372] In some implementations of the method, if one or more IDs of one or more candidate cells are associated with an ID without L2 reset:

[0373] (1) If the feature of no L2 reset is available during handover between two or more candidate cells within a plurality of candidate cells, then the candidate NE may allow two or more candidate cells to be configured with the same ID within the set of IDs. One or more IDs may be a subset of the set of IDs.

[0374] (2) If the feature of no L2 reset cannot be used during handover between any two candidate cells within a plurality of candidate cells, then the candidate NE may configure each of one or more candidate cells with a different ID within the set of IDs. Therefore, one or more IDs are equal to the set of IDs.

[0375] In some other embodiments of the method, if one or more IDs of one or more candidate cells are associated with the TA ID measured by the UE:

[0376] (1) If the TA measured by the UE is available during handover between two or more candidate cells within a plurality of candidate cells, then the candidate NE may enable two or more candidate cells to be configured with the same ID within the set of IDs. One or more IDs may be a subset of the set of IDs.

[0377] (2) If the TA measured by the UE cannot be used during handover between any two candidate cells within a plurality of candidate cells, then the candidate NE may configure each of the one or more candidate cells with a different ID within the set of IDs. Therefore, one or more IDs are equal to the set of IDs.

[0378] It should be noted that, without departing from the spirit and scope of this disclosure, Figure 10 or Figure 11 The methods described herein describe possible implementation schemes, and the operations and steps may be rearranged or otherwise eliminated or modified, and other implementation schemes are possible.

[0379] Figure 12 A schematic diagram illustrating MCG or SCG LTM cell handover according to aspects of this disclosure. Details described in all other embodiments of this disclosure are applicable. Figure 12 The embodiments shown in the figure.

[0380] In such Figure 12 In the exemplary flowchart shown, during operation 121, UE 1201 can access BS 1202, i.e., the serving or source BS. UE 1201 can send measurement reports to BS 1202. In some instances, MCG LTM can be configured in the case of MCG only or DC only. In some other instances, SCG LTM is configured in the case of DC.

[0381] In operation 122, the source BS 1202 (e.g., MCG or MN) may determine to initiate L1 / L2-based inter-cell mobility configuration preparation, i.e., LTM configuration preparation.

[0382] In operation 123, on the MCG LTM, the source BS 1202 (i.e., the source MN) transmits a request message to the candidate BS 1203 (i.e., the target MN). For example, the candidate BS 1203 transmits a handover request for L3 handover. In some embodiments, the source BS 1202 transmits auxiliary information (i.e., one or more IDs) to the candidate BS 1203. For example, the handover request for L3 handover may include a set of IDs associated with the "Layer 2 (L2) Reset ID" and / or the "UE-measured TA ID" of multiple candidate cells of the candidate BS 1203.

[0383] In operation 124, candidate BS 1203 configures LTM candidate cells based on the received assistance information in the request.

[0384] In operation 124, different operations may be performed in different embodiments, namely, as in cases #1, #2 and #3 below.

[0385] Case #1, perform the following operations.

[0386] (1) Source BS 1202 provides candidate BS 1203 with a list (or range) of TA IDs for UE measurements of one or more candidate cells (i.e., a candidate cell list). Candidate BS 1203 then configures the TA IDs for UE measurements of one or more candidate cells. If the TA measured by the UE is available for handover from candidate cell #1 to candidate cell #2, then the same ID can be configured for both candidate cell #1 and candidate cell #2.

[0387] a) In this example, source BS 1202 provides a list of TA IDs measured by the UE to three candidate cells of candidate BS 1203 (e.g., candidate cell #1, candidate cell #2, and candidate cell #3), such as 2, 3, and 5. If the TA measured by the UE can be used between candidate cell #1 and candidate cell #2, then candidate BS 1203 configures the same TA ID measured by the UE (e.g., 2) for both candidate cell #1 and candidate cell #2. If the TA measured by the UE cannot be used between candidate cell #1 and candidate cell #3, then candidate BS 1203 configures another TA ID measured by the UE (e.g., 3) for candidate cell #3.

[0388] Case #2, perform the following operations.

[0389] (1) Source BS 1202 provides a list (or range) of L2-free reset IDs for one or more candidate cells (i.e., a candidate cell list) to candidate BS 1203. Candidate BS 1203 then configures the L2-free reset IDs for one or more candidate cells. If the L2-free reset feature (UE 1201 does not perform RLC reconstruction) is available for handover from one candidate cell to another, then the same L2-free reset ID (e.g., ltm-ServingCellNoResetID) can be configured for both candidate cells.

[0390] a) For example, source BS 1202 provides a list of no-reset IDs (e.g., 2, 3, and 5) to three candidate cells of candidate BS 1203 (e.g., candidate cell #1, candidate cell #2, and candidate cell #3). If the no-L2 reset feature can be used between candidate cell #1 and candidate cell #2 (UE 1201 does not perform RLC reconstruction), then candidate BS 1203 will assign the same no-L2 reset ID (e.g., 2) to both candidate cell #1 and candidate cell #2. If the no-L2 reset TA cannot be used between candidate cell #1 and candidate cell #3, then candidate BS 1203 will assign another no-L2 reset ID (e.g., 3) to candidate cell #3.

[0391] Case #3: Perform all the operations performed in both Case #1 and Case #2. Specifically, perform the following operations in Case #3.

[0392] (1) Source BS 1202 provides a list (or range of TA IDs) of UE measurements for one or more candidate cells (i.e., a candidate cell list) to candidate BS 1203. Candidate BS 1203 then configures the TA IDs of the UE measurements for one or more candidate cells. If the TA measured by the UE is available for handover from candidate cell #1 to candidate cell #2, then the same ID can be configured for both candidate cell #1 and candidate cell #2.

[0393] (2) Source BS 1202 also provides candidate BS 1203 with a list (or range) of L2-free reset IDs for one or more candidate cells (i.e., a candidate cell list). Candidate BS 1203 then configures the L2-free reset IDs for one or more candidate cells. If the L2-free reset feature (UE 1201 does not perform RLC reconstruction) is available for handover from one candidate cell to another, then the same L2-free reset ID (e.g., ltm-ServingCellNoResetID) can be configured for both candidate cells.

[0394] In operation 125, on MCG LTM, candidate BS 1203 (i.e., target MN) transmits a response to source BS 1202 (i.e., source MN). On SCG LTM, target SN transmits a response to source BS 1202 (i.e., source MN). The response may contain one or more IDs (provided by source BS 1202) belonging to one or more candidate cells of candidate NE. For example, candidate BS 1203 may add ID information to the response, such as ltm-ServingCellUE-MeasuredTA-ID or ltm-ServingCellNoResetID.

[0395] In operation 126, source BS 1202 (i.e., source MN) transmits configuration related to a candidate cell (e.g., candidate cell #3) to UE 1201. In some embodiments, source BS 1202 generates an RRC reconfiguration message based on the configuration received from candidate BS 1203 and transmits the RRC reconfiguration message to UE 1201 via source DU. The RRC reconfiguration message may include:

[0396] (1) The ID of the TA measured by the LTM UE, for example, the ltm-UE-MeasuredTA-ID of candidate cell #3; and / or

[0397] (2) IDs without L2 reset, for example, ltm-NoResetID of candidate cell #3.

[0398] In some embodiments, if the TA measured by the UE is available for cell handover from candidate cell #1 to candidate cell #3, then the same ID of the TA measured by the UE should be set to candidate cell #3. For example, if the TA ID measured by the UE in candidate cell #1 is 5, the TA ID measured by the UE in candidate cell #3 should also be set to 5.

[0399] Next, in operation 126, UE 1201 may receive an RRC configuration message associated with a candidate cell (e.g., candidate cell #3) for LTM configuration.

[0400] 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 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) for wireless communication, 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 an L1 / L2 triggered mobility LTM cell handover command, wherein the LTM cell handover command indicates a configuration identifier ID associated with a candidate cell configured to the UE by the network equipment NE; Determine whether the LTM cell handover command includes the early timing advance TA value of the candidate cell; and Perform an LTM cell handover toward the candidate cell and start a mobility timer.

2. The UE of claim 1, wherein if the LTM cell handover command includes the early TA value of the candidate cell, then in order to perform the LTM cell handover, the processor is configured to cause the UE to: Perform LTM cell handover based on RACH without random access channel; and The first timer that starts the early TA value.

3. The UE of claim 2, wherein the processor is configured to cause the UE to: If the first timer expires while the mobility timer is running, and if the TA identifier ID measured by the UE of the candidate cell is equal to the TA ID measured by the UE of the serving cell, then the LTM cell handover is performed via the TA measured by the UE; and Start a second timer associated with the TA measured by the UE.

4. The UE of claim 3, wherein the processor is configured to cause the UE to: If the second timer expires while the mobility timer is running, then a RACH-based LTM cell handover is performed, wherein the RACH resource used during the RACH-based LTM cell handover is one of the following: a contention-free random access CFRA resource indicated by the LTM cell handover command, a CFRA resource configured by the Radio Resource Control (RRC) configuration, or a contention-based random access CBRA resource configured by the RRC configuration.

5. The UE of claim 2, wherein if the first timer expires while the mobility timer is running, the processor is configured to cause the UE to fall back from the RACH-based LTM cell handover to the RACH-based LTM cell handover in response to one of the following: If the TA ID measured by the UE of the candidate cell is not equal to the TA ID measured by the UE of the serving cell; If the TA ID of the UE measurement for the candidate cell is not configured; or If the TA ID of the UE measurement for the serving cell is not configured.

6. The UE of claim 1, wherein if the LTM cell handover command does not include the early TA value of the candidate cell, and if the TA identifier ID measured by the UE of the candidate cell is equal to the TA ID measured by the UE of the serving cell, then the processor is configured to cause the UE to: Perform LTM cell handover based on RACH without random access channel via TA measured by the UE; and Start a second timer associated with the TA measured by the UE.

7. The UE of claim 6, wherein the processor is configured to cause the UE to: If the second timer expires while the mobility timer is running, then a RACH-based LTM cell handover is performed, wherein the RACH resource used during the RACH-based LTM cell handover is one of the following: a contention-free random access CFRA resource indicated by the LTM cell handover command, a CFRA resource configured by the Radio Resource Control (RRC) configuration, or a contention-based random access CBRA resource configured by the RRC configuration.

8. The UE of claim 1, wherein if the UE is unable to access the candidate cell when the mobility timer expires, the processor is configured to cause the UE to: Reconnect to the first cell via Radio Resource Control (RRC) Reconstruction or RRC Establishment process; Transmit information indicating the availability of first auxiliary information to the first cell; Receive a request for the first auxiliary information from the first cell; and The first auxiliary information associated with the failure of the LTM cell handover is transmitted to the first cell, wherein the first auxiliary information is included in the UE information response message.

9. The UE according to claim 1, wherein if the UE successfully accesses the candidate cell via the LTM cell handover, then the processor is configured to cause the UE to: Stop the mobility timer; If the triggering conditions for reporting the second auxiliary information are met, then information indicating that the second auxiliary information is available is transmitted to the candidate cell; Receive a request for the second auxiliary information from the candidate cell; and Transmit the second auxiliary information associated with the successful handover of the LTM cell, wherein the second auxiliary information is included in the UE information response message.

10. The UE according to claim 8 or claim 9, wherein at least one of the first auxiliary information or the second information includes information indicating the following: Whether to perform an LTM cell handover based on RACH-free via the early TA value included in the LTM cell handover command; Whether the first timer of the early TA value included in the LTM cell handover command has expired; Whether a fallback occurs from a RACH-free LTM cell handover to a RACH-free LTM cell handover via the early TA value included in the LTM cell handover command; Whether a fallback occurs from a RACH-based LTM cell handover to a RACH-based LTM cell handover via the early TA value included in the LTM cell handover command, wherein the RACH-based LTM cell handover is via one of: a contention-free random access CFRA indicated by the LTM cell handover command, a CFRA configured by the RRC configuration, or a contention-based random access CBRA configured by the RRC configuration; Whether a fallback occurs from a RACH-free LTM cell handover to the RACH-based LTM cell handover via the TA measured by the UE; Has the second timer associated with the TA measured by the UE expired? Whether the CFRA resource is indicated by the LTM cell handover command; Whether a fallback has occurred from the CFRA indicated by the LTM cell handover command to the CFRA configured by the RRC configuration; Whether a fallback has occurred from the CFRA indicated by the LTM cell handover command to the CBRA configured by the RRC configuration; Whether a rollback occurs from the CFRA configured by the RRC configuration to the CBRA configured by the RRC configuration; Or a combination thereof.

11. The UE according to claim 8 or claim 9, wherein at least one of the first auxiliary information or the second auxiliary information comprises: If a configured authorized CG is configured, then it is the total number of attempts to be emitted in the CG during the time period of the first timer of the early TA value; Reports related to early TA acquisition; If the CG is configured, then it is the total number of attempts to be transmitted in the CG when the TA is measured by the UE. Or a combination thereof.

12. The UE of claim 11, wherein the report related to early TA acquisition comprises: The total number of attempts toward the same candidate cell; The total number of LTM cell handover commands received toward the same candidate cell; Preamble index; RACH timing RO resources; The time interval between two attempts toward the same candidate cell; RA objective, wherein the RA objective is set to early TA acquisition; Or a combination thereof.

13. The UE of claim 10, wherein if a fallback occurs during a handover from a RACH-free LTM cell to the RACH-based LTM cell handover via the early TA value included in the LTM cell handover command, or if a fallback occurs during a handover from a RACH-free LTM cell to the RACH-based LTM cell handover via the TA measured by the UE, then the first auxiliary information or the second auxiliary information further includes information related to a preamble field, time domain, or frequency domain of one of the following: The CFRA indicated by the LTM cell handover command; The CFRA configured by the RRC configuration; or The CBRA is configured by the RRC configuration.

14. The UE of claim 13, wherein the information related to the preamble field, the time domain, or the frequency domain includes: The absolute frequency of point A indicates the absolute frequency position of the reference resource block; The frequency domain location and bandwidth of the bandwidth portion BWP are associated with one or more random access resources used by the UE; Subcarrier spacing, which is used in the BWP associated with the one or more random access resources used by the UE; msg1 frequency start indicates the offset of the lowest physical random access channel (PRACH) transmission timing in the frequency domain relative to physical resource block (PRB 0); The msg1 frequency start for CFRA indicates the offset of the lowest PRACH transmission timing in the frequency domain relative to PRB 0 for CFRA. msg1 subcarrier spacing, which indicates the subcarrier spacing of PRACH; The msg1 subcarrier spacing used for CFRA indicates the subcarrier spacing used for PRACH in CFRA. msg1 Frequency Division Multiplexing (FDM) indicates the number of PRACH transmit opportunities for FDM in a time example; The msg1 FDM used for CFRA indicates the number of PRACH transmission opportunities for the FDM in a time example used for CFRA; A list of information about one RN procedure within one or more RA procedures executed by the UE; Initial preamble for RA attempt; The total number of preamble transmissions; The total number of preambles transmitted per synchronization signal block (SSB); The total number of preambles transmitted for each Channel State Information Reference Signal (CSI-RS); Or a combination thereof.

15. The UE according to claim 9, wherein the second auxiliary information is a successful handover report (SHR) or a successful primary / secondary cell group cell report (PSCell SPR).

16. A network device NE for wireless communication, comprising: At least one memory; and At least one processor, coupled to the at least one memory and configured to enable the NE: Receive information from the user equipment (UE) indicating the availability of auxiliary information associated with failed or successful mobility; Send a request for the auxiliary information to the UE; and The UE receives a response containing the auxiliary information associated with L1 / L2-triggered mobility LTM cell handover.

17. The NE of claim 16, wherein if the auxiliary information is associated with the failure of the LTM cell handover, then the UE is configured to reconnect to the first cell of the NE via a Radio Resource Control (RRC) reconstruction or RRC establishment procedure.

18. The NE of claim 16, wherein if the auxiliary information is associated with the success of the LTM cell handover, then the UE is configured to hand over from the source cell of the NE to a candidate cell via the LTM cell handover.

19. A processor for wireless communication, comprising: At least one controller, coupled to at least one memory and configured to enable the processor to: Receive an L1 / L2 triggered mobility LTM cell handover command, wherein the LTM cell handover command indicates a configuration identifier ID associated with a candidate cell configured to the UE by the network equipment NE; Determine whether the LTM cell handover command includes the early timing advance TA value of the candidate cell; and Perform an LTM cell handover toward the candidate cell and start a mobility timer.

20. A method performed by a user equipment (UE), comprising: Receive an L1 / L2 triggered mobility LTM cell handover command, wherein the LTM cell handover command indicates a configuration identifier ID associated with a candidate cell configured to the UE by the network equipment NE; Determine whether the LTM cell handover command includes the early timing advance TA value of the candidate cell; and Perform an LTM cell handover toward the candidate cell and start a mobility timer.

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