indicate timing advance (TA) values that can be used for subsequent L1 / L2 triggered mobility

Abstract

Embodiments include a UE method configured for LTM in a RAN. Such a method includes performing early UL synchronization with a first LTM candidate cell and a second LTM candidate cell provided by a second RAN node and a third RAN node, respectively. Such a method includes receiving a first command to perform a first LTM cell handover from a source cell to the first LTM candidate cell, and performing the first LTM cell handover based on a first TA value included in the first command and without random access to the first LTM candidate cell during the first LTM cell handover. Such a method includes receiving a second command to perform a second LTM cell handover from the first LTM candidate cell to the second LTM candidate cell, and performing the second LTM cell handover based on a second TA value included in the second command and without random access to the second LTM candidate cell during the second LTM cell handover.

Description

Technical Field

[0001] This disclosure generally relates to wireless networks, and more specifically to techniques for improving the mobility of user equipment (UE) across multiple cells in a radio access network (RAN), such as techniques related to sharing within the RAN a timing advance (TA) value determined for the UE to facilitate subsequent Layer 1 (L1) or Layer 2 (L2) triggered inter-cell mobility (LTM) operation of the UE. Background Technology

[0002] Currently, fifth-generation (5G) cellular systems are being standardized within the Third Generation Partnership Project (3GPP). 5G development aims to achieve maximum flexibility to support many different use cases, including enhanced mobile broadband (eMBB), machine-type communication (MTC), ultra-reliable low-latency communication (URLLC), sidelink device-to-device (D2D) communication, and several other use cases.

[0003] Figure 1 A high-level view of an exemplary 5G network architecture is shown, consisting of a Next-Generation Radio Access Network (NG-RAN, 199) and a 5G core (5GC, 198). The NG-RAN may include one or more gNodeBs (gNBs) connected to the 5GC via one or more NG interfaces, such as gNBs (100, 150) connected via corresponding interfaces 102, 152. More specifically, gNBs may connect to one or more Access and Mobility Management Functions (AMFs) in the 5GC via corresponding NG-C interfaces and to one or more User Plane Functions (UPFs) in the 5GC via corresponding NG-U interfaces. The 5GC may include various other network functions (NFs), such as Session Management Functions (SMFs).

[0004] Although not shown, in some deployments, the 5GC can be replaced by the Evolved Packet Core (EPC, 198), which has traditionally been used with the Long Term Evolution (LTE) Evolved UMTS RAN (E-UTRAN). In such deployments, gNBs (e.g., 100, 150) can connect to one or more Mobility Management Entities (MMEs) in the EPC via the corresponding S1-C interface and to one or more Serving Gateways (SGWs) in the EPC via the corresponding NG-U interface.

[0005] Additionally, gNBs can connect to each other via one or more Xn interfaces (e.g., Xn interface (140) between gNBs (100, 150)). NG-RAN radio technology is commonly referred to as "New Radio" (NR). Regarding the NR interface to the UE, each gNB can support Frequency Division Duplex (FDD), Time Division Duplex (TDD), or a combination thereof. Each gNB can provide service for a geographic coverage area comprising one or more cells, and in some cases, various directional beams can also be used to provide coverage within the respective cells. Generally, a DL "beam" is the coverage area of ​​a reference signal (RS) transmitted by the network that can be measured or monitored by the UE.

[0006] An NG RAN logical node (e.g., gNB 100) comprises a central unit (CU or gNB-CU, e.g., 110) and one or more distributed units (DUs or gNB-DUs, e.g., 120, 130). A CU is a logical node that hosts higher-level protocols and performs various gNB functions (e.g., controlling the operation of the DU). A DU is a distributed logical node that hosts lower-level protocols and may include various subsets of gNB functions depending on the function partitioning options. Each CU and DU may include various circuitry required to perform its respective functions, including processing circuitry, communication interface circuitry (e.g., transceiver), and power supply circuitry.

[0007] gNB-CU communicates via the corresponding F1 logic interface (e.g., Figure 1 Interfaces 122 and 132 shown connect to one or more gNB-DUs. However, each gNB-DU can only connect to one gNB-CU. The gNB-CU and its connected gNB-DUs are visible to other gNBs and 5GCs only as gNBs. In other words, the F1 interface is not visible outside of the gNB-CU.

[0008] Seamless mobility is a key feature of 3GPP Radio Access Technology (RAT). Generally, the RAN (e.g., NG-RAN) configures the UE to perform and report Radio Resource Management (RRM) measurements to aid network control mobility decisions, such as handovers from the serving cell to neighboring cells. Seamless handover ensures that the UE can move between different cell coverage areas without excessively disrupting data transmission.

[0009] As specified in 3GPP document RP-223520, NR Release 18 includes work items on further NR mobility enhancements, including L1 / L2-based inter-cell mobility (also known as L1 / L2 triggered mobility (LTM)) technology. When a UE moves between the coverage areas of two cells, a serving cell change needs to be performed at some point in time. Traditionally, serving cell changes are triggered by Layer 3 (L3, e.g., RRC) measurements and involve RRC signaling for changing the primary cell (PCell) and releasing / adding secondary cells (SCell, e.g., when carrier aggregation is configured).

[0010] Currently, all inter-cell mobility involves a full L1 and L2 reset, resulting in longer latency, increased signaling overhead, and longer outages (compared to intra-cell beam handover). Therefore, the goal of the Release 18 L1 / L2 Mobility Enhancement is to facilitate serving cell changes via L1 / L2 signaling to address these issues and / or difficulties.

[0011] In LTM, the serving RAN node pre-configures a Radio Resource Control (RRC) configuration for each LTM candidate cell for the UE; this is sometimes referred to as the "LTM candidate cell configuration." The UE performs measurements on the configured LTM candidate cells and sends the corresponding measurement reports to the RAN node. Based on this, the RAN node triggers the UE to perform an LTM cell handover procedure to one of the configured LTM candidate cells. The RAN node can trigger the LTM cell handover procedure by sending an LTM cell handover command to the UE.

[0012] Each LTM candidate cell configuration may include a configuration for early uplink (UL) synchronization within the cell. By using the early UL synchronization configuration for an LTM candidate cell, the UE transmits on the random access channel (RACH) in that cell before receiving an LTM cell handover command. This LTM cell handover command may include a timing advance (TA) determined based on the UE's previous RACH transmissions. In this way, the UE can achieve UL synchronization with LTM candidate cells that are different from the UE's current serving cell. Summary of the Invention

[0013] According to 3GPP protocols, a UE can perform multiple LTM cell handover procedures without requiring RAN reconfiguration. For example, after a UE has performed an LTM cell handover from the serving cell to a first target cell (e.g., the first LTM candidate cell), the UE can perform another LTM cell handover to a second target cell (e.g., the second LTM candidate cell) without receiving another RRCReconfiguration message in the first target cell. This second LTM cell handover is often referred to as a "subsequent LTM".

[0014] In the original serving cell, the UE may have already performed early UL synchronization with the second LTM candidate cell. Based on this, the RAN node serving the second LTM candidate cell obtains the UE's TA value in that cell. When the UE performs an LTM cell handover, the UE's TA value in the first target (LTM candidate) cell may be the same as or different from the UE's TA value in the original serving cell. However, the RAN node serving the second LTM candidate cell does not know the UE's TA value in the first target cell, which may cause various problems, difficulties, and / or challenges for subsequent LTM.

[0015] The purpose of this disclosure is to improve early UL synchronization of the UE for LTM, for example, by providing, implementing, and / or facilitating solutions to overcome the exemplary problems summarized above and described in more detail below.

[0016] Examples include UE methods (e.g., procedures) configured for LTM in a radio access network (RAN, such as E-UTRAN, NG-RAN).

[0017] These exemplary methods include: when operating in a source cell provided by a first RAN node, performing early uplink (UL) synchronization with a first LTM candidate cell provided by a second RAN node and a second LTM candidate cell provided by a third RAN node. These exemplary methods also include receiving from the first RAN node a first command for performing a first LTM cell handover from the source cell to the first LTM candidate cell. The command includes or indicates a first TA value used by the UE in the first LTM candidate cell. These exemplary methods also include: performing a first LTM cell handover from the source cell to the first LTM candidate cell based on the first TA value and the fact that random access (RA) to the first LTM candidate cell is not performed during the first LTM cell handover.

[0018] In some embodiments, these exemplary methods further include the following operations:

[0019] - Receive a second command from the second RAN node for performing a handover of the second LTM cell from the first LTM candidate cell to the second LTM candidate cell, wherein the second command includes or indicates a second TA value used by the UE in the second LTM candidate cell; and

[0020] - Based on the second TA value and the fact that the RA is not executed during the second LTM cell handover, perform the second LTM cell handover from the first LTM candidate cell to the second LTM candidate cell.

[0021] In some embodiments, the first TA value is based on the early UL synchronization between the UE and the first LTM candidate cell, and the second TA value is based on the early UL synchronization between the UE and the second LTM candidate cell.

[0022] Other embodiments include exemplary methods (e.g., procedures) of a first RAN node configured to facilitate LTM for a UE in the RAN. In general, these exemplary methods may complement the exemplary methods for a UE summarized above.

[0023] These exemplary methods include sending an instruction to the UE via a source cell provided by a first RAN node to perform corresponding early UL synchronization with a first LTM candidate cell provided by a second RAN node and a second LTM candidate cell provided by a third RAN node. These exemplary methods also include subsequently receiving the following TA value:

[0024] - The first TA value from the second RAN node, used by the UE in the first LTM candidate cell, and

[0025] - The second TA value from the third RAN node, used by the UE in the second LTM candidate cell.

[0026] These exemplary methods also include sending a command to the UE for performing a first LTM cell handover from the source cell to a first LTM candidate cell. The command includes or indicates a first TA value. These exemplary methods also include sending a first message to a second RAN node, the first message including or indicating one or more of the following: a first TA value and a second TA value.

[0027] In some embodiments, the first TA value is based on the early UL synchronization between the UE and the first LTM candidate cell, and the second TA value is based on the early UL synchronization between the UE and the second LTM candidate cell. In some embodiments, the indication includes one or more PDCCH commands.

[0028] In some embodiments, the first message includes a second TA value to facilitate a second LTM cell handover of the UE from a first LTM candidate cell to a second LTM candidate cell, as summarized above regarding the UE embodiments.

[0029] In some embodiments, the first message is an LTM cell handover notification message, which indicates that a first RAN node has initiated an LTM cell handover of the UE to a first LTM candidate cell. In some embodiments, the first message is sent to a second RAN node via a fourth RAN node. In some embodiments of these embodiments, these exemplary methods further include the following operations:

[0030] - Receive from the fourth RAN node the first early UL synchronization configuration and the second early UL synchronization configuration for the corresponding first LTM candidate cell and second LTM candidate cell; and

[0031] - Send the first early UL synchronization configuration and the second early UL synchronization configuration to the UE via the source cell.

[0032] In some variations of these embodiments, the instruction references one or more parameters in a corresponding first early UL synchronization configuration and a second early UL synchronization configuration, and the corresponding early UL synchronization is performed by the UE using the parameters referenced by the instruction.

[0033] Other embodiments include exemplary methods (e.g., procedures) of a second RAN node configured to facilitate LTM for a UE in the RAN. In general, these exemplary methods may complement the exemplary methods for a UE and a first RAN node summarized above.

[0034] These exemplary methods include sending an early UL synchronization configuration of the UE to a first LTM candidate cell provided by a second RAN node to a fourth RAN node. The UE is served by a source cell provided by the first RAN node. These exemplary methods also include: receiving an RA preamble from the UE in the first LTM candidate cell according to the early UL synchronization configuration; and determining a first TA value of the UE in the first LTM candidate cell based on the RA preamble. These exemplary methods also include sending the first TA value to the first RAN node via the fourth RAN node. These exemplary methods also include: receiving a corresponding TA value of the UE in one or more of the following cells: the source cell, the first LTM candidate cell, and a second LTM candidate cell provided by a third RAN node.

[0035] In some embodiments, the first RAN node is the first DU, the second RAN node is the second DU, the third RAN node is the third DU, and the fourth RAN node is the CU associated with the first DU, the second DU, and the third DU. In some embodiments, one or more TA values ​​are received in response to the transmission of the first TA value. In other embodiments, one or more TA values ​​are received in a request from the fourth RAN node to provide the UE with an LTM candidate cell configuration in the first LTM candidate cell. In this case, in response to the request, the early UL synchronization configuration of the UE in the first LTM candidate cell is sent to the fourth RAN node.

[0036] In some embodiments, the first message is received from the first RAN node via the fourth RAN node. In some embodiments, the first message is an LTM cell handover notification message, which indicates that the first RAN node has initiated an LTM cell handover of the UE to the first LTM candidate cell.

[0037] Other embodiments include exemplary methods (e.g., procedures) of a fourth RAN node configured to facilitate LTM for a UE in the RAN. In general, these exemplary methods may complement the exemplary methods for a UE, a first RAN node, and a second RAN node summarized above.

[0038] These exemplary methods include receiving the following for a UE served by a source cell provided by a first RAN node:

[0039] - The first TA value of the UE in the first LTM candidate cell provided by the second RAN node, from the second RAN node; and

[0040] - The second TA value of the UE in the second LTM candidate cell provided by the third RAN node, from the third RAN node.

[0041] These exemplary methods also include sending a first TA value and a second TA value to a first RAN node. These exemplary methods also include sending a first message to a second RAN node, the first message including one or more of the following: the first TA value and the second TA value.

[0042] In some embodiments, these exemplary methods further include the following operations:

[0043] - Receive the corresponding first early UL synchronization configuration and second early UL synchronization configuration for each of the first LTM candidate cells and the second LTM candidate cells from the second RAN node and the third RAN node; and

[0044] - Send the first early UL synchronization configuration and the second early UL synchronization configuration to the UE via the first RAN node.

[0045] The first TA value and the second TA value are based on the UE's early UL synchronization with the first LTM candidate cell and the second LTM candidate cell according to the corresponding first early UL synchronization configuration and second early UL synchronization configuration.

[0046] In some embodiments, these exemplary methods further include receiving a second message from a first RAN node, the second message including or indicating one or more of the following TA values ​​for the UE: a first TA value, a second TA value, and the UE's TA value in the source cell. In some embodiments of these embodiments, the second message received from the first RAN node is an LTM cell handover notification message, which indicates that the first RAN node has initiated an LTM cell handover of the UE to a first LTM candidate cell.

[0047] In some variations of these embodiments, a first message is sent in response to receiving a second message. In some variations of these embodiments, the first message is also an LTM cell handover notification message indicating that a first RAN node has initiated an LTM cell handover of the UE to a first LTM candidate cell. In some variations of these embodiments, the first message sent to the second RAN node also includes or indicates the TA value of the UE in the source cell (i.e., the TA value received in the second message).

[0048] In some embodiments of the above embodiments, the first RAN node is the first DU, the second RAN node is the second DU, the third RAN node is the third DU, and the fourth RAN node is the CU associated with the first DU, the second DU, and the third DU.

[0049] In some embodiments of the above examples, for each of the first LTM candidate cell and the second LTM candidate cell, the associated early UL synchronization configuration includes one or more of the following:

[0050] -RA preamble identifier or index;

[0051] - Identifier of the first RAN node;

[0052] -SSB index;

[0053] -RA configuration identifier;

[0054] -UE identifier; and

[0055] - Identifier of the associated LTM candidate cell.

[0056] Other embodiments include UEs (e.g., wireless devices) and RAN nodes (e.g., base stations, eNBs, gNBs, ng-eNBs, CUs, DUs, etc.) configured to perform operations corresponding to any of the exemplary methods described herein. Other embodiments include a non-transitory computer-readable medium storing program instructions that, when executed by processing circuitry, configure such UEs and RAN nodes to perform operations corresponding to any of the exemplary methods described herein.

[0057] The embodiments described herein, including these, can provide various advantages, benefits, and / or solutions to problems. For example, by sharing the TA value previously determined for LTM candidate cells for the UE, the embodiments can inform the source RAN node of the TA values ​​determined for other LTM candidate cells for the UE during subsequent LTM cell handovers. This allows the source RAN node to explicitly instruct the UE which TA value to use for subsequent LTM in one of these LTM candidate cells. Furthermore, the embodiments can eliminate the need for the RAN to reconfigure the UE after each LTM cell handover to facilitate early TA acquisition and can implement subsequent LTM without requiring the UE to randomly access an LTM candidate cell. Therefore, the embodiments can reduce downtime and handover latency, as well as the risk of connection failures during subsequent LTM.

[0058] These and other objects, features, and advantages of embodiments of the present disclosure will become apparent when reading the following detailed description in conjunction with the accompanying drawings, which are briefly described below. Attached Figure Description

[0059] Figure 1 A high-level view of an exemplary 5G / NR network architecture is shown.

[0060] Figure 2 An exemplary NR user plane (UP) and control plane (CP) protocol stack is shown.

[0061] Figure 3 The logical architecture of the NG-RAN node is shown.

[0062] Figure 4 A signaling diagram of an exemplary LTM cell handover process is shown.

[0063] Figure 5 The signaling diagram for the UE's early timing advance (TA) acquisition process is shown.

[0064] Figures 6A to 6B The various aspects of the LTM within the CU / between the DU of the UE are shown.

[0065] Figure 7 A flowchart illustrating an exemplary method for a UE (e.g., a wireless device) according to various embodiments of the present disclosure is shown.

[0066] Figure 8 A flowchart illustrating an exemplary method for a first RAN node (e.g., base station, eNB, gNB, DU, etc.) according to various embodiments of the present disclosure is shown.

[0067] Figure 9 A flowchart illustrating an exemplary method for a second RAN node (e.g., a base station, eNB, gNB, DU, etc.) according to various embodiments of the present disclosure is shown.

[0068] Figure 10 A flowchart illustrating an exemplary method for a fourth RAN node (e.g., base station, eNB, gNB, CU, etc.) according to various embodiments of the present disclosure is shown.

[0069] Figure 11 Communication systems according to various embodiments of the present disclosure are shown.

[0070] Figure 12 The UEs of various embodiments of this disclosure are shown.

[0071] Figure 13 Network nodes according to various embodiments of this disclosure are shown.

[0072] Figure 14 The present disclosure illustrates virtualized environments that can be virtualized according to some embodiments of the present disclosure. Detailed Implementation

[0073] Some embodiments contemplated herein will now be described more fully with reference to the accompanying drawings. However, other embodiments are included within the scope of the subject matter disclosed herein, and the disclosed subject matter should not be construed as being limited to the embodiments set forth herein; rather, these embodiments are provided as examples to convey the scope of the subject matter to those skilled in the art.

[0074] Generally, unless a different meaning is explicitly defined and / or implied in the context of use, all terms used herein are to be interpreted according to their ordinary meaning to those skilled in the art. Unless otherwise expressly stated or clearly implied from the context of use, all references to “an / element, device, component, apparatus, step, etc.” should be openly interpreted as referring to at least one instance of an element, device, component, apparatus, step, etc. Unless it must be explicitly stated that an operation is described as occurring after or before another operation and / or implicitly implied that an operation must occur after or before another operation, the operation of any methods and / or processes disclosed herein need not be performed in the exact order disclosed. Where appropriate, any feature of any embodiment disclosed herein may be applied to any other disclosed embodiment. Similarly, where appropriate, any advantage of any embodiment described herein may be applied to any other disclosed embodiment.

[0075] In addition, the following terms are used throughout the description given below:

[0076] - Radio Access Node: As used herein, a “radio access node” (or equivalently, a “radio network node,” “radio access network node,” or “RAN node”) can be any node in a radio access network (RAN) used for wirelessly transmitting and / or receiving signals. Some examples of radio access nodes include, but are not limited to, base stations (e.g., gNBs in 3GPP 5G / NR networks or enhanced node Bs or eNBs in 3GPP LTE networks), base station distributed components (e.g., CUs and DUs), high-power or macro base stations, low-power base stations (e.g., micro, pico, femto, or femto base stations), integrated access backhaul (IAB) nodes, transport points (TPs), transport receiver points (TRPs), remote radio units (RRUs or RRHs), and relay nodes.

[0077] - Core Network Nodes: As used in this document, a "core network node" is any type of node in the core network. Some examples of core network nodes include, for example, Mobility Management Entity (MME), Serving Gateway (SGW), PDN Gateway (P-GW), Policy and Charging Rules Function (PCRF), Access and Mobility Management Function (AMF), Session Management Function (SMF), User Plane Function (UPF), Charging Function (CHF), Policy Control Function (PCF), Authentication Server Function (AUSF), Location Management Function (LMF), etc.

[0078] - Wireless Device: As used herein, a “wireless device” (or “WD” for short) is any type of device capable of, configured, positioned, and / or operable to wirelessly communicate with network nodes and / or other wireless devices. Wireless communication may include transmitting and / or receiving wireless signals using electromagnetic waves, radio waves, infrared waves, and / or other types of signals suitable for transmitting information through the air. Unless otherwise stated, the term “wireless device” is used interchangeably herein with the term “user equipment” (“UE” for short), which have different meanings than the term “network node”.

[0079] - Radio Node: As used herein, "radio node" can be "radio access node" (or equivalent term) or "wireless device".

[0080] - Network Node: As used herein, a “network node” is any node that is part of the radio access network (e.g., a radio access node or equivalent term) or the core network (e.g., the core network node discussed above) of a cellular communication network. Functionally, a network node is a device that is capable of, configured to, arranged to, and / or operable to communicate directly or indirectly with wireless devices and / or with other network nodes or devices in the cellular communication network to enable and / or provide radio access to the wireless devices, and / or perform other functions (e.g., management) in the cellular communication network.

[0081] - Node: As used herein, the term "node" (without prefix) can be any type of node capable of operating in or with a wireless network (including RAN and / or core network), including radio access nodes (or equivalent terms), core network nodes, or wireless devices. However, the term "node" may be limited to a particular type (e.g., radio access node, IAB node) based on its specific characteristics in any given context.

[0082] The above definitions are not exclusive. In other words, the various terms used above may be interpreted and / or described elsewhere in this disclosure using the same or similar terms. However, if any other interpretation and / or description conflicts with the above definitions, the above definitions shall prevail.

[0083] Note that the descriptions presented herein focus on 3GPP cellular communication systems, and therefore 3GPP terminology or similar terms are frequently used. However, the concepts disclosed herein are not limited to 3GPP systems and can be applied to any communication system from which it can benefit.

[0084] Figure 2 An exemplary configuration of the NR user plane (UP) and control plane (CP) protocol stack between the UE (210), gNB (220), and AMF (230) is shown. The physical layer (PHY), media access control (MAC), radio link control (RLC), and packet data convergence protocol (PDCP) layers between the UE and gNB are common to both the UP and CP. The PDCP provides encryption / decryption, integrity protection, sequence numbering, reordering, and deduplication detection for both the CP and UP, as well as header compression and retransmission for UP data.

[0085] On the UP side, Internet Protocol (IP) packets arrive at the PDCP as Service Data Units (SDUs), and the PDCP creates Protocol Data Units (PDUs) for transmission to the RLC. The Service Data Adaptation Protocol (SDAP) layer handles Quality of Service (QoS), including mapping between QoS flows and Data Radio Bearers (DRBs) and marking QoS Flow Identifiers (QFIs) in UL and DL packets. The RLC transmits PDCP PDUs to the MAC via the Logical Channel (LCH). The RLC provides error detection / correction, concatenation, segmentation / reassembly, sequence numbering, and reordering for data transmitted to / from the upper layer. The MAC provides mapping between the LCH and PHY transport channels, LCH prioritization, multiplexing into or demultiplexing from transport blocks (TBs), Hybrid ARQ (HARQ) error correction, and dynamic scheduling (in gNBs). The PHY provides transport channel services to the MAC and processes transmissions through the NR radio interface, for example, via modulation, coding, antenna mapping, and beamforming.

[0086] On the CP side, the Non-Access Stratum (NAS) layer between the UE and AMF handles UE / gNB authentication, mobility management, and security control. The RRC resides below the NAS within the UE but terminates at the gNB, not the AMF. The RRC controls communication between the UE and gNB at the radio interface and the UE's mobility between cells in the NG-RAN. The RRC also broadcasts System Information (SI) and performs the establishment, configuration, maintenance, and release of DRBs and Signaling Radio Bearers (SRBs) used by the UE. Additionally, the RRC controls the addition, modification, and release of the UE's Carrier Aggregation (CA) and Dual Connectivity (DC) configurations and performs various security functions such as key management.

[0087] After the UE is powered on, it will be in the RRC_IDLE state until an RRC connection is established with the network, at which point the UE will transition to the RRC_CONNECTED state (e.g., data transmission may occur). The UE returns to RRC_IDLE after the connection with the network is released. In the RRC_IDLE state, the UE's radio is active on Discontinuous Receive (DRX) scheduling configured by the upper layer. During the DRX active period (also known as the "DRX On Duration"), the RRC_IDLE UE receives SI broadcasts in the cell where the UE is camped, performs measurements on neighboring cells to support cell reselection, and monitors the paging channel on the PDCCH to receive paging from the 5GC via the gNB. An NR UE in the RRC_IDLE state is unknown to the gNB serving the cell where the UE is camped. However, the NR RRC includes the RRC_INACTIVE state, which the serving gNB knows (e.g., via the UE context). RRC_INACTIVE has some properties similar to the "suspend" condition used in LTE.

[0088] Figure 3 This illustrates NG-RAN nodes (e.g., gNB or ng-eNB) arranged in a split CU / DU architecture (e.g., Figure 1 The logical architecture of the gNB 100 is as follows. This logical architecture separates the CU into CP and UP functions, referred to as CU-C (or CU-CP) and CU-U (or CU-UP), respectively. Furthermore, each of the NG, Xn, and F1 interfaces is divided into a CP interface (e.g., NG-C) and a UP interface (e.g., NG-U). Additionally, CU-U and CU-C can communicate via an E1 interface. Each DU can connect to only one CU-C, and each CU-U can connect to only one CU-C. However, under the control of the same CU-C, a single DU can connect to multiple CU-Us, or under the control of the same CU-C, a single CU-U can connect to multiple DUs. Note that... Figure 3 The terms "central entity" and "distributed entity" refer to physical network nodes.

[0089] 3GPP Release 10 introduced support for channel bandwidths greater than 20 MHz in LTE networks. To maintain compatibility with UEs from earlier releases (e.g., LTE Release 8), wideband LTE Release 10 carriers are represented as multiple component carriers (CCs), each with the same structure as LTE Release 8 carriers. Release 10 UEs can receive multiple CCs based on carrier aggregation (CA). A CC can also be considered a "cell," allowing a UE in a CA to have one primary cell (PCell) and one or more secondary cells (SCells), collectively referred to as a "cell group." LTE Release 12 introduced Dual Connectivity (DC), whereby a UE can simultaneously connect to both the primary node (MN) providing the primary cell group (MCG) and the secondary node (SN) providing the secondary cell group (SCG).

[0090] Each cell group comprises a MAC entity, a set of logical channels with associated RLC entities, a primary cell (PCell or PSCell), and one or more optional secondary cells (SCells). The term "Special Cell" (or simply "SpCell") refers to the PCell of the MCG or the PSCell of the SCG, depending on whether the UE's MAC entity is associated with the MCG or the SCG. In non-DC operations (e.g., carrier aggregation), SpCell refers to the PCell. The SpCell is always active and supports the UE's Physical UL Control Channel (PUCCH) transmission and contention-based random access.

[0091] NR includes support for CA and DC in version 15 and later. 3GPP TR 38.804 (v14.0.0) describes various exemplary DC scenarios or configurations that MN and SN can apply NR, LTE or both.

[0092] Seamless mobility is a key feature of 3GPP Radio Access Technology (RAT). When a UE moves between the coverage areas of two cells, a serving cell change needs to be performed at some point in time. Currently, serving cell changes are triggered by L3 (e.g., RSRP) measurements and involve RRC signaling for changing PCell and PSCell (e.g., when dual connectivity is configured) and releasing / adding SCell (e.g., when CA is configured).

[0093] Generally, the RAN (e.g., NG-RAN) configures a UE in the RRC_CONNECTED state to perform and report Radio Resource Management (RRM) measurements to assist network control mobility decisions, such as handovers from the serving cell to the target cell (e.g., PCel changes). When the reported measurements meet specific conditions or thresholds, the serving RAN node can send a handover command to the UE indicating the target cell for the handover. In NR, the handover command is an RRCReconfiguration message with a reconfigurationWithSync field. The process used to perform the handover is sometimes referred to as "L3 mobility" because it is controlled by Layer 3 (L3, i.e., the RRC layer), and the messages exchanged are part of L3.

[0094] Upon receiving a request from the UE's serving RAN node, these reconfigurations are prepared in advance by the target RAN node serving the target cell. If both the serving and target RAN nodes are part of the NG-RAN, the request is sent via the Xn interface. The reconfiguration in the handover command takes into account the UE's existing RRC configuration in its current serving cell (also referred to as the "source cell"), which is provided in the inter-node request. In some cases, the reconfiguration can be provided as an "increment" relative to the UE's existing configuration in the source cell, reducing the size of the handover command.

[0095] The reconfiguration provided by the target RAN node contains all the information required for the UE to access the target cell, such as the random access configuration, the new cell radio network temporary identifier (C-RNTI) assigned to the UE in the target cell, and parameters that enable the UE to calculate the security key that can be used when the UE communicates with the target cell (including sending a handover completion message).

[0096] Generally, UE mobility in the RRC_CONNECTED state is network-based because the network has the most information about conditions such as cell load (UE and / or traffic), available node resources (e.g., processing), available frequencies, etc. Seamless handover ensures that the UE can move around within the coverage areas of different cells without excessively interrupting data transmission. However, there will be scenarios where the network cannot hand over the UE to the “correct” neighboring cell in a timely manner (which may cause the UE to declare a Radio Link Failure (RLF) or a Handover Failure (HOF)).

[0097] 3GPP Release 18 includes NR mobility enhancements, known as L1 / L2-based inter-cell mobility or L1 / L2-triggered mobility (LTM). Current L3-based inter-cell mobility procedures involve L1 and L2 resets, resulting in longer latency, increased signaling overhead, and longer outages (compared to intra-cell beam handover). Therefore, Release 18 LTM aims to facilitate serving cell changes via L1 / L2 signaling, which reduces latency, signaling overhead, and outages.

[0098] In LTM, the UE's serving RAN pre-configures an RRC configuration for each LTM candidate cell, sometimes referred to as the "LTM candidate cell configuration." This configuration can be an RRCReconfiguration message or a part thereof, such as one or more IEs / fields / parameters (e.g., CellGroupConfig IE). The UE performs measurements on the configured LTM candidate cells and sends the corresponding measurement report to the RAN. The RAN triggers the UE to perform an LTM cell handover procedure to one of the configured LTM candidate cells. This triggering is accomplished by sending an LTM cell handover command to the UE in lower-layer signaling (e.g., DCI or MAC CE). Based on this command, the UE connects to the associated LTM candidate cell and uses the previously received RRC configuration for that cell.

[0099] Figure 1 The illustrated split CU / DU architecture also supports LTM, including for intra-DU and inter-DU / intra-CU cell changes. In the inter-DU / intra-CU scenario, the candidate cells for LTM are cells served by neighboring DUs of the currently serving UE's PCell (or PSCell, for SCG changes in the DC). In the intra-DU scenario, the candidate cells for LTM are cells served by the same DU as the currently serving UE's PCell (or PSCell, for SCG changes in the DC).

[0100] Figure 4 A signaling diagram of an exemplary LTM cell handover procedure is shown. Although the operations are shown with numerical labels, this is done for illustrative purposes and not to require or imply any particular sequence of operations, unless otherwise explicitly stated below.

[0101] In Operation 1, the UE sends a MeasurementReport message to the gNB. Based on this message, the gNB determines the LTM configuration for the UE and initiates preparation for one or more LTM candidate cells. In Operation 2, the gNB sends an RRCReconfiguration message to the UE, which includes the LTM candidate cell configuration for one or more candidate cells. In Operation 3, the UE stores the received LTM candidate cell configuration and sends an RRCReconfigurationComplete message to the gNB.

[0102] Since the goal of LTM is to reduce UE data transmission interruption time, the UE needs to be ready to communicate with the LTM candidate cell as soon as it receives L1 / L2 signaling for mobility execution from the source cell (or shortly thereafter). For example, the UE must be able to send UL data or scheduling requests (SRs) to the LTM candidate cell and / or monitor the DL control channel (e.g., PDCCH) from the LTM candidate cell. In other words, the UE needs to know which cell it is moving to so that it can apply the corresponding configuration, including the correct timing alignment and / or TCI state of the cell. Similarly, in the case of inter-DU LTM, when the source DU sends L1 / L2 signaling for mobility execution, the target DU needs to be ready to schedule UL and DL transmissions for the UE in the target cell and receive SRs from the UE.

[0103] Therefore, before receiving any LTM cell handover command, the UE performs operations 4a to 4b. In operation 4a, the UE performs early DL synchronization with the configured LTM candidate cell. In operation 4b, if UE-based TA measurement is configured, the UE obtains the TA value of the candidate cell through measurement. Otherwise, in operation 4b, the UE performs early TA acquisition with the candidate cell according to network requests. This is accomplished via contention-free random access (CFRA) triggered by a Physical DL Control Channel (PDCCH) command from the source cell, after which the UE sends an RA preamble to the indicated LTM candidate cell. To minimize data interruption in the source cell due to CFRA to the LTM candidate cell, the UE does not receive an RA response (with TA) from the LTM candidate cell; instead, the TA of the LTM candidate cell is indicated in subsequent LTM cell handover commands. Similarly, the UE does not maintain a TA timer for the LTM candidate cell, but relies on the RAN to guarantee TA validity.

[0104] In operation 5, the UE performs L1 measurements on the configured LTM candidate cells and sends an L1 measurement report to the gNB. The UE performs this L1 measurement as long as the LTM candidate cell configuration received in operation 2 is still applicable.

[0105] In operation 6, the gNB determines to trigger an LTM cell handover for the UE to one of the configured LTM candidate cells (“target cell”) and sends an LTM cell handover command, which is a MAC CE including the identifier (e.g., index) of the corresponding LTM candidate cell configured for the UE in operation 2. The MAC CE may also include the identifier (e.g., TCI status ID) of the beam through which the UE should access the target cell.

[0106] The gNB selects the identified beam based on L1 measurements reported by the UE. These are typically based on beam measurements, such as the L1 reference signal received power (RSRP) of the synchronization signal / PBCH block (SSB). These measurements may not undergo Layer 3 (L3) filtering, and therefore they can change relatively frequently as the UE's radio conditions change. Therefore, determining the optimal beam for the UE in an LTM cell handover command can be challenging for the gNB.

[0107] Upon receiving an LTM cell handover command, the UE monitors the PDCCH on the indicator beam of the target cell. In other words, when performing an LTM cell handover, the UE treats the TCI state / TCI state ID of the indicated beam as "activated". The UE also applies the configuration identified in MACCE.

[0108] In Operation 7, if the UE does not have a valid TA for the target cell, the UE performs the RA procedure to the target cell. If the LTM cell handover command contains the necessary information as specified in Clause 6.1.3 of 3GPP TS 38.321 (v17.7.0), the UE performs CFRA. In Operation 8, the UE completes the LTM cell handover procedure by sending an RRCReconfigurationComplete message to the gNB via the target cell. If the UE has already performed the RA procedure in Operation 7, the UE considers the LTM cell handover execution to be successfully completed when the RA procedure is successfully completed. For LTM without RACH, the UE considers the LTM cell handover execution to be successfully completed when it determines that the gNB has successfully received its first UL data. The UE determines the successful reception of its first UL data by receiving a PDCCH addressed to the UE's C-RNTI in the target cell, which schedules new transmissions following the first UL data. The PDCCH carries a DL assignment or UL authorization that processes the same HARQ procedure as the first UL data.

[0109] To trigger LTM for the UE, the network sends an LTM cell handover command to the UE, which includes an indication of the LTM candidate cell and a beam indication of the LTM candidate cell to which the UE should access. In 5G / NR, the beam indication is provided as a Transport Configuration Indicator (TCI) status identifier (ID) associated with the LTM candidate cell (which can be indicated by the LTM candidate configuration ID). In response, the UE performs an LTM cell handover, accesses the indicated cell / beam, and sends a completion message.

[0110] Figure 5 The signaling diagram of the early TA acquisition process is shown. This early TA acquisition process can be... Figure 4 This is a part of the LTM cell handover process shown. Although the operations are shown with numerical labels, this is for illustrative purposes and not to require or imply any particular sequence of operations, unless otherwise explicitly stated below.

[0111] In Operation 1, the gNB serving cell A provides the TA acquisition configuration to the UE within the RRCReconfiguration message. For example, in the case of the UE performing an LTM cell handover procedure to cell B, the TA acquisition configuration includes the RRC configuration information required to send the random access preamble to cell B, enabling the gNB serving cell B to calculate the TA value to be used by the UE. The TA acquisition configuration may include information about one or more cells from which the UE can perform the TA acquisition procedure. In Operation 2, the UE responds with an RRCReconfigurationComplete message.

[0112] At operation 3, the gNB serving cell A sends a PDCCH command message to the UE to initiate a TA acquisition procedure with cell B. The PDCCH command includes additional information required to send the random access preamble to cell B. In operation 4, the UE sends the random access preamble to cell B according to this configuration, enabling the gNB serving cell B to calculate the TA value available to the UE in cell B, as described above. Note that if the TA is not obtained, the gNB serving cell A can instruct the retransmission of the random access preamble used for TA acquisition.

[0113] In operation 5, the gNB serving cell A provides the TA value of cell B, which is calculated by the gNB serving cell B during the TA acquisition process, for example in the LTM cell handover command (e.g., MAC CE) that initiates the LTM cell handover process from the UE to cell B.

[0114] In summary, LTM candidate cell configuration may include random access (or RACH) configuration. The UE performs an early UL synchronization procedure based on this configuration, and the serving RAN node can send a PDCCH command indicating certain parameters of the RACH configuration of the LTM candidate cell. This triggers the UE to initiate a random access procedure to the LTM candidate cell according to the indicated parameters. For example, the UE selects the SSB of the LTM candidate cell indicated in the PDCCH command, selects PRACH resources based on the selected SSB, and uses the selected PRACH resources to send the preamble. When the RAN node serving the LTM candidate cell (e.g., candidate DU) receives the random access preamble from the UE, it calculates the timing advance (TA) value of the UE in the LTM candidate cell and provides this TA value to the RAN node of the current serving cell (e.g., source DU) providing the UE.

[0115] Figures 6A to 6B The various aspects of LTM within a CU / between DU for the UE (610) are shown. The CU (650) is associated with three DUs: the UE’s initial S-DU (620, i.e., the initial S-DU that provides the UE’s serving cell), candidate DU1 (C-DU1, 630) that provides the first LTM candidate cell, and candidate DU2 (C-DU2, 640) that provides the second LTM candidate cell.

[0116] exist Figure 6A In this process, the CU requests and receives early UL synchronization configurations from S-DU, C-DU1, and C-DU2, and then provides all three early UL synchronization configurations to the S-DU. These early UL synchronization configurations are represented by rectangles filled with different patterns, as shown in the example.

[0117] exist Figure 6B In the process, the S-DU sends a PDCCH command to the UE to trigger early UL synchronization between the UE and the LTM candidate cell served by the C-DU2. The PDCCH command, which indicates certain parameters of the RACH configuration of the LTM candidate cell, was previously... Figure 6A The PDCCH command is sent to the UE. The UE sends a Random Access (RA) preamble according to the PDCCH command, and C-DU2 determines the appropriate TA value for the UE and sends this TA value to the CU, which in turn provides the TA value to the S-DU. Subsequently, the S-DU sends an LTM cell handover command for the LTM candidate cell served by C-DU2 to the UE, including the received TA value. The S-DU sends an LTM cell handover notification to the CU, which forwards the notification to C-DU2. The UE then sends an RRCReconfigurationComplete message to C-DU2.

[0118] like Figure 6BAs shown, after the UE hands over to an LTM candidate cell served by C-DU2 (the new S-DU), only the UE, CU, and the previous S-DU know the early UL synchronization configuration provided by the S-DU, C-DU1, and C-DU2. Therefore, the UE's new S-DU (formerly C-DU2) is unaware of the early UL synchronization configuration provided by the UE's previous S-DU (now "C-DU3") and C-DU1, and thus cannot send PDCCH commands referencing parameters in these configurations to the UE. On the UE side, after the initial LTM cell handover and before initiating early UL synchronization in the LTM candidate cell, the UE will need to receive another RRCReconfiguration message, which includes the early UL synchronization configuration known at the C-DU of the LTM candidate cell.

[0119] As mentioned above Figure 5 and Figure 6B The serving RAN node can provide the TA value to the UE in the LTM cell handover command, enabling the UE to access the LTM candidate cell without performing random access (i.e., because it has already been performed previously). Alternatively, the serving RAN node can instruct the UE that it should use the same TA value in the LTM candidate cell as the TA value used in the current serving cell (from which the LTM cell handover procedure is performed). 3GPP has agreed that when instructing the same TA value, the serving RAN node should explicitly copy the latest TA value it sent to the UE.

[0120] According to 3GPP protocols, a UE can perform multiple LTM cell handover procedures without requiring RAN reconfiguration. For example, after a UE has performed an LTM cell handover from the serving cell to a first target cell (e.g., a first LTM candidate cell), the UE can perform another LTM cell handover to a second target cell (e.g., a previously configured second LTM candidate cell) without receiving another RRCReconfiguration message in the first target cell. This second LTM cell handover can be referred to as a "subsequent LTM" or "subsequent LTM cell handover".

[0121] However, when a UE performs subsequent LTM without being reconfigured, some issues, challenges, and / or difficulties may arise related to the TA value. Consider a scenario where the UE has a serving cell and a first LTM candidate cell and a second LTM candidate cell. When in the serving cell, the UE performs early UL synchronization with the first and second LTM candidate cells. Based on this, the RAN nodes serving these cells obtain the UE's TA values ​​(e.g., TA1 and TA2, respectively). The UE also has a TA value (e.g., TA0) in its serving cell.

[0122] Subsequently, the UE receives an LTM cell handover command to enter the first LTM candidate cell (as the first target cell), along with an indication to use the same TA value (i.e., TA0) as in the source cell when entering the first LTM candidate cell. While in the first target cell, the UE receives another LTM cell handover command to enter the second LTM candidate cell (as the second target cell), along with an indication to use the same TA value as in the source cell (i.e., the first target cell) when entering the second LTM candidate cell. However, the RAN node serving the second LTM candidate (target) cell is unaware of what TA value was indicated to the UE in the handover command to the first LTM candidate (target) cell.

[0123] As an option, the RAN node serving the second LTM candidate cell can cause the RAN node serving the first target cell to initiate a new early UL synchronization with the second LTM candidate cell before subsequent LTM. This is undesirable because it delays LTM cell handover and carries the risk of UE connection failure with the RAN. Alternatively, the RAN node serving the first target cell can indicate to the UE that subsequent LTM needs to be completed via random access to the second LTM candidate cell, which undesirably increases connection interruption time and handover latency.

[0124] Another issue is that a UE can sequentially execute multiple subsequent LTM procedures, meaning it is only within the coverage of each individual cell for a short period. In this case, the corresponding serving RAN node does not have enough time to initiate early UL synchronization between the UE and other LTM candidate cells. Even so, there are scenarios where a TA calculated in one cell can be used in another cell, such as when two cells are co-located or fully synchronized. In this case, it makes sense for the serving cell to forward all calculated / received TA values ​​to the "next" serving cell and / or other candidate cells.

[0125] In the original serving cell, the UE may have already performed early UL synchronization with the second LTM candidate cell. Based on this, the RAN node serving the second LTM candidate cell obtains the UE's TA value in that cell. When the UE performs an LTM cell handover, the UE's TA value in the first target (LTM candidate) cell may be the same as or different from the UE's TA value in the original serving cell. However, the RAN node serving the second LTM candidate cell does not know the UE's TA value in the first target cell, which may cause various problems, difficulties, and / or challenges for subsequent LTM.

[0126] Therefore, embodiments of this disclosure address these problems and / or challenges through flexible and efficient techniques. These techniques allow RAN nodes (e.g., CU, S-DU, C-DU) to share the relevant TA values ​​for LTM candidate cells determined by early UL synchronization for the UE. This enables the source RAN node in subsequent LTM cell handover procedures to explicitly instruct the UE in the LTM cell handover command to use the same TA value as used in the UE's current serving cell (i.e., the LTM source cell). In this context, "explicitly instruct" means that the source RAN node includes in the LTM cell handover command the TA value that the UE should use, which is the same as the TA value used by the UE in the LTM source cell.

[0127] The embodiments of this disclosure can provide various advantages and / or benefits. For example, by sharing the TA value previously determined for the LTM candidate cells for the UE, the embodiments enable the source RAN node for subsequent LTM cell handovers to know the TA values ​​determined for other LTM candidate cells for the UE. This allows the source RAN node to explicitly indicate which TA value the UE uses for subsequent LTM in one of these LTM candidate cells. Furthermore, the embodiments can eliminate the need for the RAN to reconfigure the UE after each LTM cell handover to facilitate early TA acquisition and can enable subsequent LTM without the UE randomly accessing an LTM candidate cell. Therefore, the embodiments can reduce downtime and handover latency during subsequent LTM and the risk of connection failures.

[0128] The embodiments can be summarized as follows. In some embodiments, after triggering an LTM cell handover process for the UE to the first LTM candidate cell (e.g., based on an LTM cell handover command), the UE's S-DU sends the TA value included in the LTM cell handover command to the C-DU serving the first LTM candidate cell. This TA value can be sent directly or via a public CU.

[0129] In other embodiments, after triggering an LTM cell handover procedure for the UE to the first LTM candidate cell (e.g., based on an LTM cell handover command), the UE's S-DU not only sends its TA value included in the LTM cell handover command, but also sends one or more other TA values ​​for other UE LTM candidate cells obtained based on early UL synchronization performed by the UE while being served by the S-DU. The S-DU may send these TA values ​​to the C-DU serving the first LTM candidate cell, and optionally to the C-DU serving other UE LTM candidate cells. These TA values ​​may be sent directly or via a public CU.

[0130] In other embodiments, after the UE triggers an early UL synchronization procedure to an LTM candidate cell served by the C-DU (via the UE's S-DU) and receives the TA value determined by the C-DU, the CU sends the TA value to the C-DUs serving other LTM candidate cells of the UE. In variations of these embodiments, the S-DU requests the CU to send the TA value of the LTM candidate cell (determined by the C-DU and sent to the CU) to the C-DUs serving other LTM candidate cells of the UE.

[0131] In this disclosure, the following terms are used interchangeably: “L1 / L2-based inter-cell mobility,” “L1 / L2 mobility,” “L1 mobility,” “L1-based mobility,” “L1 / L2-centric inter-cell mobility,” “L1 / L2 inter-cell mobility,” “inter-cell beam management,” “inter-DU L1 / L2-based inter-cell mobility,” and “L1 / L2-triggered mobility” (or LTM). These terms refer to scenarios where a UE receives low-layer (i.e., below RRC, such as MAC or PHY) signaling from the network that instructs the UE to change its serving cell (e.g., PCell) from the source cell to the target cell.

[0132] The content of low-layer signaling can be referred to as "LTM cell handover command". Exemplary low-layer signaling includes L1 DL control information (DCI) and L2 MAC control element (CE). Compared with conventional RRC signaling, low-layer signaling reduces processing time and downtime during mobility and can also improve mobility robustness because the network can respond more quickly to changes in the UE's channel conditions.

[0133] The term "LTM candidate cell" refers to a cell configured with LTM for a UE, specifically the cell to which the UE can move during an LTM cell handover in response to receiving an LTM cell handover command. LTM candidate cells may also be referred to herein as "candidate cell," "(LTM) candidate," "mobility candidate," "non-serving cell," "additional cell," "(LTM) target candidate cell," and similar terms. The UE can perform and report measurement (e.g., CSI measurement) results on LTM candidate cells. Based on these measurements, the UE's serving RAN node can make an informed decision about which beam (or TCI state) and / or cell to hand over the UE to. An LTM candidate cell can be a candidate to become a target PCell or PSCell, or an SCell of a cell group (e.g., an MCG SCell). In the case of LTM fast recovery, when a failure is detected and the UE selects an LTM candidate cell, the UE performs an LTM cell handover to the selected LTM candidate cell (e.g., by applying the associated LTM candidate cell configuration) instead of performing an RRC reconstruction.

[0134] For example, if an LTM cell handover command triggers a UE to change to a different cell group configuration of the same type (e.g., another MCG configuration), a change in the serving cell (e.g., PCell) can also lead to a change in the SCell of the same cell group. For instance, an LTM cell handover can include changes to the SpCell (e.g., the PCell of the MCG, the PSCell of the SCG) and changes to the SCell of the same cell group (e.g., adding, modifying, and / or releasing). This can happen when the command triggers a UE to change to a different cell group configuration of the same type (e.g., another SCG configuration).

[0135] Before the UE receives the LTM cell handover command, the network configures one or more "LTM candidate cell configurations" for the UE via the RCReconfiguration message. The terms "(LTM) candidate configuration", "(LTM) candidate target cell configuration" and "(LTM) target candidate (cell) configuration" can be used interchangeably with LTM candidate cell configuration.

[0136] LTM candidate cell configurations can be included in the LTM candidate cell's RRC IE (e.g., CellGroupConfig, SpCellConfig, or SCellConfig and / or embedded RRCReconfiguration messages). The LTM candidate cell configuration includes configuration parameters that the UE needs to operate in the LTM candidate cell when performing an LTM cell handover procedure (e.g., upon receiving an LTM cell handover command). As some more specific examples, an LTM candidate cell configuration may include the PCell configuration of the MCG and one or more SCell configurations, or the PSCell configuration of the SCG and one or more SCell configurations. The exact content and / or structure of the LTM candidate cell configuration's IE and / or embedded messages may be referred to as the "RRC model of the candidate configuration" or more simply as the "RRC model".

[0137] The UE can receive LTM candidate cell configurations in full form or in incremental (or differential) form relative to a reference configuration (which can be transmitted separately by signaling). In the latter case, the actual LTM candidate configuration is a combination of the incremental configuration and the reference configuration.

[0138] Low-layer signaling from the RAN may include an identifier (or index) associated with the LTM candidate cell configuration. This identifier may be sent along with an LTM cell handover command that instructs the UE to perform an LTM cell handover to the associated LTM candidate cell.

[0139] The term "LTM configuration" refers to a data structure used for or relating to UE LTM operation, and may (non-exclusively) include one or more of the following elements:

[0140] -LTM candidate configuration, i.e., LTM candidate configuration of LTM candidate cells;

[0141] - Measurement configurations, such as L1 measurement and reporting configurations for LTM candidate cells;

[0142] - Configurations for early DL synchronization, such as configurations for early TCI state activation;

[0143] - Configurations for early UL synchronization, such as preambles for sending PDCCH commands and configurations for receive timing advance (TA);

[0144] - Configuration used to perform LTM cell handover procedures based on a given LTM candidate cell configuration (e.g., whether to perform RA, RLC reconstruction, MAC reset, PDCP recovery, etc.).

[0145] The term “part of LTM configuration” can refer to a subset of the elements in the list above and / or a subset of the items that include any current element (e.g., a subset of the configuration used for DL ​​pre-synchronization).

[0146] The phrase "LTM cell handover process" refers to the process by which a UE uses LTM to hand over from a source cell to a target cell (i.e., an LTM candidate cell). The LTM cell handover process is also known as "L1 / L2-based inter-cell mobility execution," "LTM execution," "dynamic handover," "LTM handover," "(LTM) cell handover," "(LTM) serving cell change," or "LTM cell change." Similarly, the phrase "handover to LTM candidate cell configuration" means that the UE applies an LTM candidate cell configuration, causing the associated LTM candidate cell to become its new special cell (SpCell, such as a PCell used for LTM in an MCG or a PSCell used for LTM in an SCG) or its new SCell. In other words, an LTM candidate cell can be a candidate for the UE's PCell, PSCell, or SCell.

[0147] Furthermore, LTM cell handover can involve a UE using LTM to hand over (or change) from a source cell group to a target cell group. For example, this can involve changes to the SpCell of a cell group (e.g., the PCell of an MCG, the PSCell of an SCG), changes to the SCell of a cell group (e.g., the addition, modification, and / or release of one or more SCells), and / or the swapping of SpCell and SCell roles between two cells in the same cell group.

[0148] The phrase “early TA acquisition” describes the process performed by the UE and RAN node to determine the timing advance (TA) value of the UE in the LTM candidate cell before the RAN triggers (and the UE performs) the LTM cell handover to the LTM candidate cell. This phrase is used interchangeably with “TA acquisition”, “early UL synchronization”, and “early synchronization” in this document.

[0149] The various features of the above embodiments correspond to Figures 7 to 10 The various operations shown, Figures 7 to 10 Exemplary methods (e.g., procedures) for a UE, a first RAN node, a second RAN node, and a fourth RAN node are illustrated respectively. In other words, various features of the operations described below correspond to the various embodiments described above. Furthermore, they can be used in conjunction with each other. Figures 7 to 10 The exemplary methods shown are intended to provide various benefits, advantages, and / or solutions to the problems described herein. Although Figures 7 to 10 Specific boxes are shown in a particular order, but the operation of this exemplary method may be performed in a different order than shown, and may be combined and / or divided into boxes with functions different from those shown. Optional boxes or operations are indicated by dashed lines.

[0150] Specifically, Figure 7 Exemplary methods (e.g., procedures) for a UE configured for LTM in a RAN according to various embodiments of this disclosure are shown. These exemplary methods can be performed by a UE (e.g., a wireless device), as described elsewhere herein.

[0151] The exemplary method includes the operation of block 730, wherein, when operating in a source cell provided by a first RAN node, the UE performs corresponding early uplink (UL) synchronization with a first LTM candidate cell provided by a second RAN node and a second LTM candidate cell provided by a third RAN node. The exemplary method also includes the operation of block 740, wherein the UE receives from the first RAN node a first command for performing a first LTM cell handover from the source cell to the first LTM candidate cell. This command includes or indicates a timing advance (TA) value used by the UE in the first LTM candidate cell. The exemplary method further includes the operation of block 750, wherein the UE performs the first LTM cell handover from the source cell to the first LTM candidate cell based on the first TA value and the absence of random access (RA) to the first LTM candidate cell during the LTM cell handover.

[0152] In some embodiments, the exemplary method further includes the following operations, which are marked with corresponding box numbers:

[0153] - (760) Receive from the second RAN node a second command for performing a second LTM cell handover from the first LTM candidate cell to the second LTM candidate cell, wherein the second command includes or indicates a second TA value used by the UE in the second LTM candidate cell; and

[0154] - (770) Based on the second TA value and the fact that the RA is not performed to the second LTM candidate cell during the second LTM cell handover, perform the second LTM cell handover from the first LTM candidate cell to the second LTM candidate cell.

[0155] In some embodiments, the first RAN node is the first DU, the second RAN node is the second DU, the third RAN node is the third DU, and the fourth RAN node is the CU associated with the first DU, the second DU, and the third DU. Figures 6A to 6B The arrangements shown are examples of these embodiments.

[0156] In some embodiments, the first TA value is based on the early UL synchronization between the UE and the first LTM candidate cell, and the second TA value is based on the early UL synchronization between the UE and the second LTM candidate cell.

[0157] In some embodiments, the exemplary method further includes the operation of block 720, wherein the UE receives, via the source cell, an indication for performing early UL synchronization with a first LTM candidate cell and a second LTM candidate cell. The corresponding early UL synchronization is performed according to the indication. In some embodiments of these embodiments, the indication includes one or more Physical Downlink Control Channel (PDCCH) commands.

[0158] In some embodiments of these examples, the exemplary method further includes the operation of block 710, wherein the UE receives, via the source cell, corresponding first early UL synchronization configurations and second early UL synchronization configurations of the first LTM candidate cell and the second LTM candidate cell from the fourth RAN node. The corresponding early UL synchronization is performed based on the first early UL synchronization configuration and the second early UL synchronization configuration.

[0159] In some variations of these embodiments, the indication references one or more parameters in a first early UL synchronization configuration and a second early UL synchronization configuration, and the corresponding early UL synchronization is performed using the one or more parameters referenced by the indication. In some further variations, performing early UL synchronization with a first LTM candidate cell in block 730 includes the operation in sub-block 731, wherein the UE uses the RA resources of the first LTM candidate cell to transmit an RA preamble. The RA preamble and / or RA resources are referenced by the indication. For example, the RA resources referenced by the indication may include one or more of the following: time / frequency resources and one or more beams.

[0160] In some embodiments, for each of the first LTM candidate cell and the second LTM candidate cell, the associated early UL synchronization configuration includes one or more of the following:

[0161] -Identifier or index of the random access (RA) preamble;

[0162] - Identifier of the first RAN node;

[0163] - Synchronization signal / PBCH (SSB) index;

[0164] -RA configuration identifier;

[0165] -UE identifier; and

[0166] - The identifier of the associated LTM candidate cell.

[0167] in addition, Figure 8 Exemplary methods (e.g., procedures) of a first RAN node configured to facilitate LTM for a UE according to various embodiments of this disclosure are illustrated. These exemplary methods can be performed by RAN nodes (e.g., base stations, eNBs, gNBs, ng-eNBs, DUs, etc.) as described elsewhere herein.

[0168] The exemplary method includes the operation of block 830, wherein a first RAN node sends to the UE via a source cell provided by the first RAN node for performing corresponding early UL synchronization with a first LTM candidate cell provided by a second RAN node and with a second LTM candidate cell provided by a third RAN node. The exemplary method also includes the operation of block 835, wherein the first RAN node subsequently receives the following timing advance (TA) value:

[0169] - The first TA value from the second RAN node, used by the UE in the first LTM candidate cell, and

[0170] - The second TA value from the third RAN node, used by the UE in the second LTM candidate cell.

[0171] The exemplary method also includes the operation of block 850, wherein the first RAN node sends a command to the UE for performing a first LTM cell handover from the source cell to the first LTM candidate cell. The command includes or indicates a first TA value. The exemplary method also includes the operation of block 860, wherein the first RAN node sends one of the following:

[0172] - A request sent to the fourth RAN node to transmit TA values ​​determined based on early UL synchronization to the second and third RAN nodes; or

[0173] - A first message sent to the second RAN node, which includes or indicates one or more of the following: a first TA value and a second TA value.

[0174] In some embodiments, the exemplary method further includes the operation of block 840, wherein the first RAN node determines the TA value of the UE in the source cell.

[0175] In some embodiments, the first TA value is received from the second RAN node via the fourth RAN node. In some embodiments, the first message is sent to the second RAN node via the fourth RAN node. In some embodiments, the second TA value is received from the third RAN node via the fourth RAN node. In some embodiments, the first RAN node is the first DU, the second RAN node is the second DU, the third RAN node is the third DU, and the fourth RAN node is the CU associated with the first DU, the second DU, and the third DU. Figures 6A to 6B The arrangements shown are examples of these embodiments.

[0176] In some embodiments, the first message includes a second TA value to facilitate a second LTM cell handover of the UE from a first LTM candidate cell to a second LTM candidate cell, as summarized above regarding the UE embodiments.

[0177] In some embodiments, the first TA value is based on the early UL synchronization of the UE with the first LTM candidate cell, and the second TA value is based on the early UL synchronization of the UE with the second LTM candidate cell. In some embodiments, (e.g., in block 830) the indication includes one or more PDCCH commands.

[0178] In some of these embodiments, before sending the command in block 850, the request is sent to the fourth RAN node in block 860, and the request includes one or more of the following: the TA value used by the UE in the source cell (e.g., the TA value determined in block 840), the first TA value, and the second TA value.

[0179] In other embodiments of these examples, in response to sending the command at block 850, a first message is sent to the second RAN node at block 860. In other embodiments of these examples, in response to receiving a first TA value and a second TA value at block 835, a first message is sent to the second RAN node at block 860.

[0180] In some embodiments, in block 860, the first message may also be sent to a third RAN node. In some of these embodiments, the first message sent to the third RAN node may include one or more of the following: a TA value used by the UE in the source cell (e.g., a TA value as determined in block 840), a first TA value, and a second TA value. In some of these embodiments, the first message is sent to the third RAN node via a fourth RAN node.

[0181] In other embodiments, in response to sending the instruction in block 830, the request is sent to the fourth RAN node in block 860.

[0182] In some embodiments, the exemplary method further includes the following operations, which are marked with corresponding box numbers:

[0183] - (810) Receive from the fourth RAN node a first early UL synchronization configuration and a second early UL synchronization configuration for the corresponding first LTM candidate cell and second LTM candidate cell; and

[0184] - (820) Send the first early UL synchronization configuration and the second early UL synchronization configuration to the UE via the source cell.

[0185] In some embodiments of these embodiments, the indication references one or more parameters in a corresponding first early UL synchronization configuration and a second early UL synchronization configuration, and the corresponding early UL synchronization is performed by the UE using the parameters referenced by the indication. In some variations of these embodiments, the one or more parameters referenced by the indication include one or more of the following: random access (RA) preamble; time / frequency domain RA resources; and one or more beams.

[0186] In some embodiments, for each of the first LTM candidate cell and the second LTM candidate cell, the associated early UL synchronization configuration includes one or more of the following:

[0187] -RA preamble identifier or index;

[0188] - Identifier of the first RAN node;

[0189] -SSB index;

[0190] -RA configuration identifier;

[0191] -UE identifier; and

[0192] - The identifier of the associated LTM candidate cell.

[0193] The following is given Figure 8Some further examples of the illustrated embodiments are provided. In one example, in block 860, the first RAN node only transmits the TA values ​​included in the LTM cell handover command in block 850. In another example, the first RAN node transmits one or more TA values ​​not included in the LTM cell handover command. These TA values ​​are TA values ​​received from other LTM candidate cells that are not included in the LTM cell handover command. In yet another example, the first RAN node transmits the TA values ​​included in the LTM cell handover command along with one or more other TA values ​​from other LTM candidate cells.

[0194] In one example, the first RAN node only sends the TA value to the second RAN node indicated in the LTM cell handover command. In another example, the first RAN node sends the TA value to a different RAN node than the one indicated in the LTM cell handover command (i.e., not the second RAN node).

[0195] In one example, after receiving a TA value from an LTM candidate cell, the first RAN node sends all TA values ​​received from all other LTM candidate cells to the same LTM candidate cell. In another example, after receiving a TA value from one LTM candidate cell, the first RAN node sends all TA values ​​received from all other LTM candidate cells that have already sent TA values ​​or are expected to send TA values ​​to the same LTM candidate cell.

[0196] In one example, the first RAN node sends one or more TA values ​​to other RAN nodes that it commands or requests to initiate the UE's early TA acquisition process in the LTM candidate cell. In another example, the first RAN node sends one or more TA values ​​to other RAN nodes besides the RAN node that it commands or requests to initiate the UE's early TA acquisition process.

[0197] In one example, when the first RAN node receives a request to configure LTM candidate cell configuration, it sends one or more TA values. As a more specific example, the first RAN node receives the request to configure LTM candidate cells from a fourth RAN node (e.g., CU), and if the first RAN node has TA values ​​stored from other LTM candidate cells, it provides those TA values ​​along with the LTM candidate cell configuration.

[0198] In one example, the first RAN node sends one or more TA values ​​to a fourth RAN node (e.g., CU), which transparently forwards these TA values ​​to one or more other RAN nodes (e.g., DU) indicated by the first RAN node. In another example, the fourth RAN node reads the received TA values ​​and autonomously determines which RAN nodes should send the TA values ​​to.

[0199] in addition, Figure 9 Exemplary methods (e.g., procedures) of a second RAN node configured to facilitate LTM for a UE according to various embodiments of this disclosure are illustrated. These exemplary methods can be performed by RAN nodes (e.g., base stations, eNBs, gNBs, ng-eNBs, DUs, etc.) as described elsewhere herein.

[0200] The exemplary method includes the operation at block 920, wherein a second RAN node receives an RA preamble from a UE served by a source cell provided by a first RAN node in a first LTM candidate cell provided by the second RAN node. The exemplary method also includes the operations at blocks 930-940, wherein, based on the RA preamble, the second RAN node determines a first TA value used by the UE in the first LTM candidate cell and transmits the first TA value to the first RAN node via a fourth RAN node. The exemplary method further includes the operation at block 950, wherein the second RAN node receives a first message from a second RAN node, the first message including or indicating one or more of the following: the first TA value, and a second TA value used by the UE in a second LTM candidate cell provided by a third RAN node.

[0201] In some embodiments, the exemplary method includes the operation of block 910, wherein the second RAN node sends the UE to the fourth RAN node an early UL synchronization configuration for a first LTM candidate cell provided by the second RAN node. The RA preamble is received based on the early UL synchronization configuration (e.g., in block 920). In some embodiments of these embodiments, the early UL synchronization configuration for the UE in the first LTM candidate cell includes one or more of the following:

[0202] -Identifier or index of the random access (RA) preamble;

[0203] - Identifier of the first RAN node;

[0204] - Synchronization signal / PBCH (SSB) index;

[0205] -RA configuration identifier;

[0206] -UE identifier; and

[0207] - Identifier of the first LTM candidate cell.

[0208] In some embodiments, the first RAN node is the first DU, the second RAN node is the second DU, the third RAN node is the third DU, and the fourth RAN node is the CU associated with the first DU, the second DU, and the third DU. Figures 6A to 6B The arrangements shown are examples of these embodiments.

[0209] In some embodiments, the first message is received in response to the transmission of a first TA value. In other embodiments, the first message is received from a fourth RAN node in a request to provide the UE with an LTM candidate cell configuration in the first LTM candidate cell. In this case, in response to the request, the UE's early UL synchronization configuration in the first LTM candidate cell is sent to the fourth RAN node.

[0210] In some embodiments, the exemplary method further includes the operation of block 960, wherein, after the first TA value is sent in block 940 and no other RA preamble is received from the UE in the first LTM candidate cell, the second RAN node receives from the UE a reconfiguration completion message indicating that the UE has completed the LTM cell handover to the first LTM candidate cell.

[0211] In some embodiments of these examples, the timing alignment of the reconfiguration completion message in the first LTM candidate cell is based on the TA value used by the UE for timing alignment in the source cell. In some variations of these embodiments, the received TA value includes the TA value used by the UE for timing alignment in the source cell.

[0212] In some of these embodiments, the first message is an LTM cell handover notification message, which indicates that the first RAN node has initiated an LTM cell handover of the UE to the first LTM candidate cell.

[0213] In some embodiments of these examples, the received TA value includes a second TA value of the second LTM candidate cell, based on the early UL synchronization between the UE and the second LTM candidate cell. In this case, the exemplary method further includes the operation of block 980, wherein the second RAN node sends a command to the UE to perform a second LTM cell handover from the first LTM candidate cell to the second LTM candidate cell. This command includes the received second TA value. In some variations of these embodiments, the exemplary method further includes the operation of block 970, wherein, based on the received second TA value, the second RAN node avoids initiating early UL synchronization between the UE and the second LTM candidate cell before sending the command in block 980.

[0214] In some embodiments, one or more TA values ​​are received from one of the following nodes: a first RAN node or a fourth RAN node.

[0215] The following is given Figure 9Some further examples of the illustrated embodiments are provided. In one example, when providing LTM candidate cell configuration, the second RAN node also includes one or more TA values ​​associated with the first (source) RAN node and one or more other RAN nodes (e.g., a third RAN node) serving other LTM candidate cells. In another example, the second RAN node receives one or more TA values ​​from the first or third RAN node within a notification (or indication) that an LTM cell handover procedure has been triggered for the UE. In yet another example, the second RAN node receives one or more TA values ​​from the first or third RAN node after TA values ​​have been sent to the first or third RAN node due to an early TA acquisition procedure triggered at the UE.

[0216] In one example, the second RAN node receives the identifier of the associated RAN node for each TA value, so that each TA value is linked to a specific RAN node.

[0217] In one example, communication between the first RAN node and the second RAN node can be via a direct interface between them (e.g., between DUs). In another example, communication between the first RAN node and the second RAN node can be via a fourth RAN node (e.g., a CU), such as via an F1AP interface. In either case, communication can involve existing messages or newly defined messages.

[0218] in addition, Figure 10 Exemplary methods (e.g., procedures) of a fourth RAN node configured to facilitate LTM for a UE according to various embodiments of this disclosure are illustrated. These exemplary methods can be performed by RAN nodes (e.g., base stations, eNBs, gNBs, ng-eNBs, CUs, etc.) as described elsewhere herein.

[0219] This exemplary method includes the operation of block 1030, wherein the fourth RAN node receives the following items for the UE served by the source cell provided by the first RAN node:

[0220] - The first TA value from the second RAN node, used by the UE in the first LTM candidate cell provided by the second RAN node; and

[0221] - The second TA value from the third RAN node, used by the UE in the second LTM candidate cell provided by the third RAN node.

[0222] The exemplary method includes the operation of block 1040, wherein the fourth RAN node sends a first TA value and a second TA value to the first RAN node. The exemplary method also includes the operation of block 1080, wherein the fourth RAN node sends a first message to the second RAN node, the first message including one or more of the following: the first TA value and the second TA value.

[0223] In some embodiments, the first RAN node is the first DU, the second RAN node is the second DU, the third RAN node is the third DU, and the fourth RAN node is the CU associated with the first DU, the second DU, and the third DU. Figures 6A to 6B The arrangements shown are examples of these embodiments.

[0224] In some embodiments, the exemplary method further includes the following operations, which are marked with corresponding box numbers:

[0225] - (1010) Receive the corresponding first early UL synchronization configuration and second early UL synchronization configuration for each of the first LTM candidate cells and the second LTM candidate cells from the second RAN node and the third RAN node; and

[0226] - (1020) Send the first early UL synchronization configuration and the second early UL synchronization configuration to the UE via the first RAN node.

[0227] The first TA value and the second TA value are based on the UE's early UL synchronization with the first LTM candidate cell and the second LTM candidate cell according to the corresponding first early UL synchronization configuration and second early UL synchronization configuration.

[0228] In some embodiments of these examples, for each of the first LTM candidate cell and the second LTM candidate cell, the associated early UL synchronization configuration includes one or more of the following:

[0229] -RA preamble identifier or index;

[0230] - Identifier of the first RAN node;

[0231] -SSB index;

[0232] -RA configuration identifier;

[0233] -UE identifier; and

[0234] - The identifier of the associated LTM candidate cell.

[0235] In some of these embodiments, the first message may be sent in one of the following ways: in response to receiving a second TA value, in response to sending the second TA value to a first RAN node, or based on receiving a first early UL synchronization configuration.

[0236] In some of these embodiments, the first message may also be sent to a third RAN node. In this case, the first message may be sent to the third RAN node in one of the following ways: in response to receiving a first TA value, in response to sending a first TA, or based on receiving a second early UL synchronization configuration.

[0237] In some embodiments, the exemplary method further includes the operation of block 1060, wherein the fourth RAN node receives one of the following from the first RAN node:

[0238] - A request to send one or more TA values ​​of the UE to at least one of the second RAN node and the third RAN node; or

[0239] - The second message includes or indicates one or more of the following TA values ​​for the UE: the first TA value, the second TA value, and the TA value of the UE in the source cell.

[0240] In some embodiments of these examples, the exemplary method further includes operations at blocks 1050 and 1070, wherein the fourth RAN node stores the received first TA value and second TA value, and retrieves the stored first TA value and second TA value based on a request. Each of the retrieved first TA value and second TA value is included in a first message sent to the second RAN node (and optionally to the third RAN node).

[0241] In some embodiments of these embodiments, a request from a first RAN node indicates which of the second and third RAN nodes should receive each of one or more TA values, and a first message is sent to the second and / or third RAN node according to that indication.

[0242] In other embodiments of these examples, the second message received from the first RAN node is an LTM cell handover notification message, which indicates that the first RAN node has initiated an LTM cell handover of the UE to the first LTM candidate cell. In some variations of these embodiments, a first message is sent in response to receiving the second message. In some variations of these embodiments, the first message is also an LTM cell handover notification message, which indicates that the first RAN node has initiated an LTM cell handover of the UE to the first LTM candidate cell. In some variations of these embodiments, the first message sent to the second RAN node also includes or indicates the TA value of the UE in the source cell (i.e., the TA value received in the second message).

[0243] The following is given Figure 10 Some additional examples of the embodiments shown.

[0244] In one example, when the fourth RAN node receives an indication from the first RAN node that an LTM cell handover procedure has been triggered at the UE, along with one or more TA values, the fourth RAN node shares all TA values ​​received from the first RAN node with other RAN nodes (e.g., other DUs). In another example, the fourth RAN node sends the TA values ​​to the RAN node serving the LTM candidate cell for which an LTM cell handover has been triggered at the UE. In yet another example, the fourth RAN node sends the TA values ​​to all other RAN nodes that have provided the LTM candidate cell configuration to be sent to the UE. In yet another example, the fourth RAN node sends the TA values ​​to all other RAN nodes that have provided TA values ​​due to an early TA acquisition procedure at the UE. In yet another example, the fourth RAN node sends the TA values ​​to all other RAN nodes that have provided the configuration for initiating an early DL synchronization procedure at the UE.

[0245] In one example, after receiving an indication from the first RAN node that an early TA acquisition procedure has been triggered at the UE, the fourth RAN node sends one or more TA values. As a more specific example, when the fourth RAN node has received a TA value from the first RAN node from the target network node to which it triggered the early TA acquisition procedure, the fourth RAN node will automatically send the received TA value to one or more other RAN nodes.

[0246] In one example, after the first RAN node triggers an early TA acquisition procedure at the UE, the first RAN node explicitly indicates the receiving RAN node for the TA value. In another example, the receiving RAN node for the TA value is any other RAN node besides the one to which the first RAN node has triggered the early TA acquisition procedure.

[0247] In one example, the fourth RAN node first sends a request to the first, second, and third RAN nodes to provide LTM candidate cell configurations, and then receives the requested LTM candidate cell configurations along with one or more TA values. Subsequently, the fourth RAN node sends all received TA values ​​to each RAN node that provided the LTM candidate cell configurations.

[0248] In another example, when requesting LTM candidate cell configuration, the fourth RAN node may instruct that one or more TA values ​​should also be sent (if available). After receiving these TA values, the fourth RAN node forwards them to other RAN nodes.

[0249] In one example, communication between the fourth RAN node (e.g., CU) and the first, second, and third RAN nodes (e.g., DU) is via the F1AP interface. Existing and / or newly defined F1AP messages can be used for this communication.

[0250] Although various embodiments have been described above in terms of methods, techniques and / or processes, those skilled in the art will readily understand that such methods, techniques and / or processes can be embodied by various combinations of hardware and software in various systems, communication devices, computing devices, control devices, apparatuses, non-transitory computer-readable media, computer program products and the like.

[0251] Figure 11An example of a communication system 1100 according to some embodiments is shown. In this example, the communication system 1100 includes a telecommunications network 1102, which includes an access network 1104 (e.g., a RAN) and a core network 1106, which includes one or more core network nodes 1108. The access network 1104 includes one or more access network nodes, such as network nodes 1110a to 1110b (one or more of which may generally be referred to as network node 1110), or any other similar 3GPP access node or non-3GPP access point. Furthermore, those skilled in the art will understand that network nodes are not necessarily limited to an implementation that is provided by a single vendor and integrates the radio and baseband portions. Therefore, it should be understood that network nodes include decomposed implementations or portions thereof. For example, in some embodiments, the telecommunications network 1102 includes one or more Open RAN (ORAN) network nodes. An ORAN network node is a node in the telecommunications network 1102 that supports the ORAN specification (e.g., the ORAN specification published by the O-RAN Alliance or any similar organization) and can operate independently or together with other nodes to perform one or more functions of any node in the telecommunications network 1102 (including one or more network nodes 1110 and / or core network nodes 1108).

[0252] Examples of ORAN network nodes include Open Radio Units (O-RUs), Open Distributed Units (O-DUs), Open Central Units (O-CUs), including O-CU control planes (O-CU-CPs) or O-CU user planes (O-CU-UPs), managed software or software plug-ins (e.g., near real-time control applications (e.g., xApps) or non-real-time control applications (e.g., rApps)), RAN intelligent controllers (near real-time or non-real-time), or any combination thereof (the adjective "open" indicates support for the ORAN specification). Network nodes can support the specification by, for example, supporting interfaces defined by the ORAN specification (e.g., A1, F1, W1, E1, E2, X2, Xn interfaces), open fronthaul user plane interfaces, or open fronthaul management plane interfaces. Furthermore, ORAN access nodes can be logical nodes within physical nodes. Additionally, ORAN network nodes can be implemented in a virtualized environment (described further below) where one or more network functions are virtualized. For example, a virtualized environment may include an open cloud (O-Cloud) computing platform orchestrated by a service management and orchestration framework via an O-2 interface or equivalent technology defined by the O-RAN Alliance. Network node 1110 facilitates direct or indirect connections for UEs, such as connecting UEs 1112a to 1112d (one or more of which may generally be referred to as UE 1112) to core network 1106 via one or more wireless connections.

[0253] Examples of wireless communication via wireless connection include transmitting and / or receiving wireless signals using electromagnetic waves, radio waves, infrared waves, and / or other types of signals suitable for transmitting information without using wiring, cables, or other conductors. Furthermore, in various embodiments, communication system 1100 may include any number of wired or wireless networks, network nodes, UEs, and / or any other components or systems that can facilitate or participate in the communication of data and / or signals (whether via wired or wireless connections). Communication system 1100 may include any type of communication, telecommunications, data, cellular, radio network, and / or other similar system, and / or interface with any type of communication, telecommunications, data, cellular, radio network, and / or other similar system.

[0254] UE 1112 can be any of a wide variety of communication devices, including wireless devices that are arranged, configured, and / or operable to communicate wirelessly with network node 1110 and other communication devices. Similarly, network node 1110 is arranged, capable, configured, and / or operable to communicate directly or indirectly with UE 1112 and / or with other network nodes or devices in telecommunication network 1102 to achieve and / or provide network access (e.g., wireless network access) and / or to perform other functions in telecommunication network 1102 (e.g., management).

[0255] In the depicted example, core network 1106 connects network node 1110 to one or more hosts (e.g., host 1116). These connections can be direct connections or indirect connections via one or more intermediate networks or devices. In other examples, network nodes can be directly coupled to hosts. Core network 1106 includes one or more core network nodes (e.g., 1108) composed of hardware and software components. The characteristics of these components can be substantially similar to those described with respect to UEs, network nodes, and / or hosts, such that the description is generally applicable to the corresponding components of core network node 1108. Example core network nodes include the functions of a Mobile Switching Center (MSC), Mobility Management Entity (MME), Home Subscriber Server (HSS), Access and Mobility Management Function (AMF), Session Management Function (SMF), Authentication Server Function (AUSF), Subscription Identifier Unhiding Function (SIDF), Unified Data Management (UDM), Secure Edge Protection Agent (SEPP), Network Open Function (NEF), and / or User Plane Function (UPF).

[0256] Host 1116 may be owned or under the control of a service provider other than the operator or provider of access network 1104 and / or telecommunications network 1102, and may be operated by or on behalf of that service provider. Host 1116 may host a variety of applications to provide one or more services. Examples of such applications include real-time and pre-recorded audio / video content, data collection services (e.g., retrieving and compiling data about various environmental conditions detected by multiple UEs), analytics functions, social media, functions for controlling or otherwise interacting with remote devices, functions for alarm and monitoring centers, or any other such functions performed by a server.

[0257] As a whole, Figure 11 The communication system 1100 enables connectivity between the UE, network nodes, and hosts. In this sense, the communication system can be configured to operate according to predefined rules or procedures, such as specific standards, including but not limited to: Global System for Mobile Communications (GSM); Universal Mobile Telecommunications System (UMTS); Long Term Evolution (LTE) and / or other suitable 2G, 3G, 4G, 5G standards, or any applicable future generation standard (e.g., 6G); Wireless Local Area Network (WLAN) standards, such as the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard (WiFi); and / or any other suitable wireless communication standards, such as Global Microwave Access Interoperability (WiMax), Bluetooth, Z-Wave, Near Field Communication (NFC) ZigBee, LiFi, and / or any Low Power Wide Area Network (LPWAN) standards such as LoRa and Sigfox.

[0258] In some examples, telecommunications network 1102 is a cellular network implementing 3GPP standardized features. Therefore, telecommunications network 1102 can support network slicing to provide different logical networks to different devices connected to it. For example, telecommunications network 1102 can provide ultra-reliable low-latency communication (URLLC) services to some UEs while providing enhanced mobile broadband (eMBB) services to other UEs, and / or massive machine-type communication (mMTC) / massive IoT services to yet another UE.

[0259] In some examples, UE 1112 is configured to send and / or receive information without direct human interaction. For example, the UE may be designed to send information to access network 1104 according to a predetermined schedule when triggered by an internal or external event or in response to a request from access network 1104. Additionally, the UE may be configured to operate in single-RAT mode, multi-RAT mode, or multi-standard mode. For example, the UE may operate using any one or a combination of Wi-Fi, NR (New Radio), and LTE, i.e., configured for multi-radio dual connectivity (MR-DC), such as E-UTRAN (Evolved UMTS Terrestrial Radio Access Network) New Radio Dual Connectivity (EN-DC).

[0260] In this example, hub 1114 communicates with access network 1104 to facilitate indirect communication between one or more UEs (e.g., 1112c and / or 1112d) and network nodes (e.g., 1110b). In some examples, hub 1114 may be a controller, router, content source and analyzer, or any other communication device relating to the UE described herein. For example, hub 1114 may be a broadband router that enables the UE to access core network 1106. As another example, hub 1114 may be a controller that sends commands or instructions to one or more actuators in the UE. Commands or instructions may be received from the UE, network node 1110, or via executable code, scripts, procedures, or other instructions in hub 1114. As another example, hub 1114 may be a data collector that acts as a temporary storage device for UE data, and in some embodiments, may perform data analysis or other processing. As another example, hub 1114 may be a content source. For example, for a UE acting as a VR headset, display, speaker, or other media delivery device, hub 1114 can retrieve VR assets, video, audio, or other media or data related to perceived information via network nodes, and then provide them directly to the UE after performing local processing and / or adding additional local content. In yet another example, hub 1114 acts as a proxy server or orchestrator for the UE, particularly if one or more of the UEs are low-power IoT devices.

[0261] Hub 1114 may have a persistent / persistent or intermittent connection to network node 1110b. Hub 1114 may also allow different communication schemes and / or scheduling between hub 1114 and UEs (e.g., UE 1112c and / or UE 1112d) and between hub 1114 and core network 1106. In other examples, hub 1114 is connected to core network 1106 and / or one or more UEs via a wired connection. Furthermore, hub 1114 may be configured to connect to an M2M service provider via access network 1104 and / or to another UE via a direct connection. In some scenarios, a UE may establish a wireless connection with network node 1110 while still being connected via hub 1114 through a wired or wireless connection. In some embodiments, hub 1114 may be a dedicated hub (i.e., a hub whose primary function is to route communication from network node 1110b to UE / to route communication from UE to network node 1110b). In other embodiments, the hub 1114 may be a non-dedicated hub—that is, a device capable of routing communication between the UE and network node 1110b but additionally capable of operating as a communication start point and / or endpoint for certain data channels.

[0262] In some embodiments, UE 1112 can be configured to perform various operations described above (including those in the embodiments described above). Figure 7 The exemplary method shown above) performs operations belonging to the UE. In some embodiments, one or more network nodes 1110 may be configured to perform operations belonging to the UE in the various embodiments described above (including the exemplary method shown above). Figures 8 to 10 The exemplary method shown performs various operations belonging to the RAN node.

[0263] Figure 12 A UE 1200 according to some embodiments is illustrated. Examples of UEs include, but are not limited to, smartphones, mobile phones, cellular phones, Voice over IP (VoIP) phones, wireless local loop phones, desktop computers, personal digital assistants (PDAs), wireless cameras, game consoles or devices, music storage devices, playback devices, wearable terminal devices, wireless endpoints, mobile stations, tablet computers, laptop computers, laptop embedded devices (LEEs), laptop-mounted devices (LMEs), smart devices, wireless client devices (CPEs), vehicle-mounted or vehicle-embedded / integrated wireless devices, etc. Other examples include any UE recognized by 3GPP, including Narrowband Internet of Things (NB-IoT) UEs, Machine Type Communication (MTC) UEs, and / or Enhanced MTC (eMTC) UEs.

[0264] The UE can support device-to-device (D2D) communication, for example, by implementing 3GPP standards for sidelink communication, Dedicated Short-Range Communication (DSRC), vehicle-to-vehicle (V2V), vehicle-to-infrastructure (V2I), or vehicle-to-everything (V2X). In other examples, the UE may not necessarily be a user in the sense of a human user who owns and / or operates the associated device. Alternatively, the UE may represent a device intended to be sold to or operated by a human user but which may not or initially may not be associated with a specific human user (e.g., a smart sprinkler controller). Alternatively, the UE may represent a device not intended to be sold to or operated by an end user but which may be associated with or operated for the benefit of the user (e.g., a smart power meter).

[0265] UE 1200 includes processing circuitry 1202, which is operatively coupled via bus 1204 to input / output interface 1206, power supply 1208, memory 1210, communication interface 1212, and / or any other component or any combination thereof. Some UEs may utilize... Figure 12 The components shown may be all or a subset. The level of integration between components can vary depending on the UE. Furthermore, some UEs may contain multiple instances of components, such as multiple processors, memories, transceivers, transmitters, receivers, etc.

[0266] Processing circuitry 1202 is configured to process instructions and data and can be configured to implement any sequential state machine operable to execute instructions stored in memory 1210 as a machine-readable computer program. Processing circuitry 1202 can be implemented as: one or more hardware-implemented state machines (e.g., implemented with discrete logic, field-programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), etc.); programmable logic together with appropriate firmware; one or more stored computer programs, general-purpose processors (e.g., microprocessors or digital signal processors (DSPs)) together with appropriate software; or any combination of the foregoing. For example, processing circuitry 1202 may include multiple central processing units (CPUs).

[0267] In the example, input / output interface 1206 can be configured to provide one or more interfaces to input devices, output devices, or one or more input and / or output devices. Examples of output devices include speakers, sound cards, video cards, displays, monitors, printers, actuators, transmitters, smart cards, other output devices, or any combination thereof. Input devices can allow users to capture information into UE 1200. Examples of input devices include touch-sensitive or presence-sensitive displays, cameras (e.g., digital cameras, digital camcorders, webcams, etc.), microphones, sensors, mice, trackballs, directional keyboards, touchpads, scroll wheels, smart cards, etc. Presence-sensitive displays may include capacitive or resistive touch sensors to sense input from the user. Sensors may be, for example, accelerometers, gyroscopes, tilt sensors, force sensors, magnetometers, optical sensors, proximity sensors, biometric sensors, etc., or any combination thereof. Output devices can use the same type of interface port as input devices. For example, a Universal Serial Bus (USB) port can be used to provide both input and output devices.

[0268] In some embodiments, power supply 1208 is configured as a battery or battery pack. Other types of power sources may be used, such as external power sources (e.g., power outlets), photovoltaic devices, or batteries. Power supply 1208 may also include power supply circuitry for delivering power from power supply 1208 itself and / or external power sources to various parts of UE 1200 via input circuitry or an interface such as a power cable. The delivery of power may, for example, be used to charge power supply 1208. The power supply circuitry may perform any formatting, conversion, or other modifications on the power from power supply 1208 to suit the power for the various components of UE 1200 to which it supplies power.

[0269] Memory 1210 may be or be configured to include memory such as random access memory (RAM), read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), disk, optical disk, hard disk, removable magnetic tape, flash drive, etc. In one example, memory 1210 includes one or more applications 1214, such as an operating system, web browser application, widget, utility engine, or other application, and corresponding data 1216. Memory 1210 may store any one or a combination of various operating systems used by UE 1200.

[0270] The memory 1210 can be configured to include multiple physical drive units, such as a redundant array of independent disks (RAID), flash memory, a USB flash drive, an external hard drive, a thumb drive, a pen drive, a key drive, a high-density digital multifunction optical disc (HD-DVD) drive, an internal hard drive, a Blu-ray disc drive, a holographic digital data storage (HDDS) disc drive, an external mini dual in-line memory module (DIMM), synchronous dynamic random access memory (SDRAM), external micro DIMM SDRAM, smart card memory (e.g., a tamper-proof module in the form of a universal integrated circuit card (UICC), including one or more subscriber identification modules (SIMs), such as USIM and / or ISIM), other memory, or any combination thereof. The UICC can be, for example, an embedded UICC (eUICC), an integrated UICC (iUICC), or a removable UICC commonly referred to as a "SIM card." The memory 1210 can allow the UE 1200 to access instructions, applications, etc., stored on transient or non-transient storage media to offload or upload data. Articles of art (e.g., articles of art utilizing a communication system) may be tangibly embodied in or in memory 1210, which may be or include a device-readable storage medium.

[0271] Processing circuitry 1202 can be configured to communicate with an access network or other network using communication interface 1212. Communication interface 1212 may include one or more communication subsystems and may include or be communicatively coupled to antenna 1222. Communication interface 1212 may include one or more transceivers for communication (e.g., via one or more remote transceivers capable of wireless communication with another device (e.g., another UE or a network node in the access network). Each transceiver may include a transmitter 1218 and / or a receiver 1220 suitable for providing network communication (e.g., optical, electrical, frequency allocation, etc.). Furthermore, transmitter 1218 and receiver 1220 may be coupled to one or more antennas (e.g., antenna 1222) and may share circuitry, software, or firmware, or alternatively, be implemented separately.

[0272] In the illustrated embodiment, the communication functions of the communication interface 1212 may include cellular communication, Wi-Fi communication, LPWAN communication, data communication, voice communication, multimedia communication, short-range communication such as Bluetooth, near-field communication, location-based communication (e.g., using a Global Positioning System (GPS) to determine location), another type of communication function, or any combination thereof. Communication may be implemented according to one or more communication protocols and / or standards such as IEEE 802.11, Code Division Multiple Access (CDMA), Wideband Code Division Multiple Access (WCDMA), GSM, LTE, New Radio (NR), UMTS, WiMax, Ethernet, Transmission Control Protocol / Internet Protocol (TCP / IP), Synchronous Optical Network (SONET), Asynchronous Transfer Mode (ATM), QUIC, Hypertext Transfer Protocol (HTTP), etc.

[0273] Regardless of the sensor type, the UE can provide the output of data captured by its sensors via its communication interface 1212 through a wireless connection with a network node. Data captured by the UE's sensors can be transmitted via another UE through the same wireless connection. The output can be periodic (e.g., every 15 minutes if it reports the sensed temperature), random (e.g., to balance the load of reports from several sensors), responsive to a triggering event (e.g., sending an alarm when humidity is detected), responsive to a request (e.g., a user-initiated request), or a continuous stream (e.g., real-time video feed of a patient).

[0274] As another example, the UE includes actuators, motors, or switches associated with a communication interface configured to receive wireless input from a network node via a wireless connection. The state of the actuator, motor, or switch can change in response to the received wireless input. For example, the UE may include a motor that adjusts the control surfaces or rotors of a flying drone based on the received input, or adjusts a robotic arm performing a medical procedure based on the received input.

[0275] When the UE is in the form of an Internet of Things (IoT) device, the UE can be a device used in one or more application areas, including but not limited to urban wearable technology, extended industrial applications, and healthcare. Non-limiting examples of such IoT devices include or embedded in the following devices: connected refrigerators or freezers, televisions, connected lighting devices, electricity meters, robotic vacuum cleaners, voice-controlled smart speakers, home security cameras, motion detectors, thermostats, smoke detectors, door and window sensors, flood / humidity sensors, electronic door locks, connected doorbells, air conditioning systems (such as heat pumps), autonomous vehicles, surveillance systems, weather monitoring devices, vehicle parking monitoring devices, electric vehicle charging stations, smartwatches, fitness trackers, head-mounted displays for augmented reality (AR) or virtual reality (VR), wearable devices for haptic or sensory enhancement, sprinklers, animal or item tracking devices, sensors for monitoring plants or animals, industrial robots, unmanned aerial vehicles (UAVs), and any kind of medical device (such as heart rate monitors or remote-controlled surgical robots). In addition to the above... Figure 12 In addition to the other components described in the UE 1200 shown, UEs in the form of IoT devices also include circuitry and / or software depending on the intended application of the IoT device.

[0276] As another specific example, in an IoT scenario, a UE can represent a machine or other device that performs monitoring and / or measurement and sends the results of such monitoring and / or measurement to another UE and / or network node. In this case, the UE can be an M2M device, which can be referred to as an MTC device in the 3GPP context. As a specific example, this UE can implement the 3GPP NB-IoT standard. In other scenarios, a UE can represent a vehicle (e.g., a car, bus, truck, ship, and aircraft) or other device capable of monitoring and / or reporting its operational status or other functions associated with its operation.

[0277] In practice, any number of UEs can be used together for a single use case. For example, the first UE can be a drone or integrated into a drone, and provides the drone's speed information (obtained via a speed sensor) to a second UE, which is a remote controller for operating the drone. When the user makes a change from the remote controller, the first UE can adjust the throttle on the drone (e.g., by controlling the actuators) to increase or decrease the drone's speed. The first UE and / or the second UE can also include more than one of the functions described above. For example, the UE can include sensors and actuators, and handle data communication between both the speed sensor and the actuators.

[0278] In some embodiments, UE 1200 can be configured to operate in the various embodiments described above (including...). Figure 7The operation belonging to the UE is performed in the exemplary method shown.

[0279] Figure 13 A network node 1300 according to some embodiments is shown. Examples of network nodes include, but are not limited to, access points (APs) (e.g., radio access points), base stations (e.g., radio base stations, NodeBs, eNBs, and gNBs), and O-RAN nodes or components of O-RAN nodes (e.g., O-RUs, O-DUs, O-CUs).

[0280] Base stations can be classified based on the coverage they provide (or, in other words, their transmission power levels); therefore, depending on the coverage provided, a base station can be called a femtobase, picobase, microbase, or macrobase. A base station can be a relay node or a relay donor for control relays. Network nodes can also include one or more (or all) portions of a distributed radio base station, such as centralized digital units, distributed units (e.g., in O-RAN access nodes), and / or remote radio units (RRUs), sometimes referred to as remote radio headends (RRHs). These remote radio units can be integrated with antennas to form an antenna-integrated radio, or they can be independent of antenna integration. A portion of a distributed radio base station can also be referred to as a node in a distributed antenna system (DAS).

[0281] Other examples of network nodes include multi-transmitter point (multi-TRP) 5G access nodes, multi-standard radio (MSR) devices (e.g., MSR BS), network controllers (e.g., radio network controllers (RNC) or base station controllers (BSC)), base transceiver stations (BTS), transmitter points, transmitter nodes, multi-cell / multicast coordination entities (MCE), operations and maintenance (O&M) nodes, operations support system (OSS) nodes, self-organizing network (SON) nodes, location nodes (e.g., evolved Serving Mobility Location Center (E-SMLC)) and / or minimized drive test (MDT).

[0282] Network node 1300 includes processing circuitry 1302, memory 1304, communication interface 1306, and power supply 1308. Network node 1300 may consist of multiple physically separate components (e.g., Node B components and RNC components, BTS components and BSC components, etc.), each with its own corresponding components. In some scenarios where network node 1300 includes multiple separate components (e.g., BTS and BSC components), one or more of these separate components may be shared among multiple network nodes. For example, a single RNC can control multiple NodeBs. In such scenarios, each unique “NodeB and RNC pair” may, in some cases, be considered a single, separate network node. In some embodiments, network node 1300 may be configured to support multiple Radio Access Technologies (RATs). In such embodiments, some components may be replicated (e.g., separate memory 1304 exists for different RATs) and some components may be reused (e.g., the same antenna 1310 may be shared by different RATs). Network node 1300 may also include multiple sets of various components shown herein for different wireless technologies (e.g., GSM, WCDMA, LTE, NR, WiFi, Zigbee, Z-wave, LoRaWAN, RFID, or Bluetooth wireless technologies). These wireless technologies may be integrated into the same or different chips or chipsets and other components within network node 1300.

[0283] The processing circuitry 1302 may include one or more of the following: a microprocessor, a controller, a central processing unit, a digital signal processor, an application-specific integrated circuit, a field-programmable gate array, or any other suitable computing device, resource, or combination of hardware, software and / or coding logic, operable to provide network node 1300 functionality, either alone or in combination with other network node 1300 components (e.g., memory 1304).

[0284] In some embodiments, the processing circuitry 1302 includes a system-on-a-chip (SOC). In some embodiments, the processing circuitry 1302 includes one or more of a radio frequency (RF) transceiver circuitry 1312 and a baseband processing circuitry 1314. In some embodiments, the RF transceiver circuitry 1312 and the baseband processing circuitry 1314 may be on separate chips (or chipsets), boards, or units (e.g., radio units and digital units). In alternative embodiments, some or all of the RF transceiver circuitry 1312 and the baseband processing circuitry 1314 may be on the same chip or chipset, board, or unit group.

[0285] Memory 1304 may include any form of volatile or non-volatile computer-readable memory, including but not limited to permanent storage devices, solid-state memory, remotely mounted memory, magnetic media, optical media, random access memory (RAM), read-only memory (ROM), mass storage media (e.g., hard disk), removable storage media (e.g., flash drives, optical discs (CDs), or digital video discs (DVDs)) and / or any other volatile or non-volatile, non-transitory device-readable and / or computer-executable memory device that stores information, data, and / or instructions that can be used by processing circuitry 1302. Memory 1304 may store any suitable instructions, data, or information, including computer programs, software, applications including logic, rules, codes, tables, and / or other instructions that can be executed by processing circuitry 1302 and used by network node 1300 (collectively referred to as computer program 1304a, which may be in the form of a computer program product). Storage device 1304 may be used to store any calculations performed by processing circuitry 1302 and / or any data received via communication interface 1306. In some embodiments, the processing circuitry 1302 and the memory 1304 are integrated together.

[0286] Communication interface 1306 is used for wired or wireless communication of signaling and / or data between network nodes, access networks, and / or UEs. As shown, communication interface 1306 includes a port / terminal 1316 for transmitting and receiving data to and from the network, for example, via a wired connection. Communication interface 1306 also includes radio front-end circuitry 1318, which may be coupled to antenna 1310 or, in some embodiments, is part of antenna 1410. Radio front-end circuitry 1318 includes a filter 1320 and an amplifier 1322. Radio front-end circuitry 1318 may be connected to antenna 1310 and processing circuitry 1302. Radio front-end circuitry 1318 may be configured to modulate the signal transmitted between antenna 1310 and processing circuitry 1302. Radio front-end circuitry 1318 may receive digital data to be transmitted to other network nodes or UEs via a wireless connection. Radio front-end circuitry 1318 may use a combination of filter 1320 and / or amplifier 1322 to convert the digital data into a radio signal with suitable channel and bandwidth parameters. The radio signal may then be transmitted via antenna 1310. Similarly, when receiving data, antenna 1310 can collect radio signals, which are then converted into digital data by radio front-end circuitry 1318. The digital data can then be passed to processing circuitry 1302. In other embodiments, the communication interface may include different components and / or different combinations of components.

[0287] In some alternative embodiments, network node 1300 does not include a separate radio front-end circuitry 1318; instead, processing circuitry 1302 includes radio front-end circuitry and is connected to antenna 1310. Similarly, in some embodiments, all or some of the RF transceiver circuitry 1312 is part of communication interface 1306. In yet another embodiment, communication interface 1306 includes one or more ports or terminals 1316, radio front-end circuitry 1318, and RF transceiver circuitry 1312 as part of a radio unit (not shown), and communication interface 1306 communicates with baseband processing circuitry 1314, which is part of a digital unit (not shown).

[0288] Antenna 1310 may include one or more antennas or antenna arrays configured to transmit and / or receive wireless signals. Antenna 1310 may be coupled to radio front-end circuitry 1318 and may be any type of antenna capable of wirelessly transmitting and receiving data and / or signals. In some embodiments, antenna 1310 is decoupled from network node 1300 and may be connected to network node 1300 via an interface or port.

[0289] Antenna 1310, communication interface 1306, and / or processing circuitry 1302 can be configured to perform any receive operation and / or certain acquire operation as described herein by a network node. Any information, data, and / or signals can be received from the UE, another network node, and / or any other network device. Similarly, antenna 1310, communication interface 1306, and / or processing circuitry 1302 can be configured to perform any transmit operation as described herein by a network node. Any information, data, and / or signals can be transmitted to the UE, another network node, and / or any other network device.

[0290] Power supply 1308 provides power to the various components of network node 1300 in a form suitable for the various components (e.g., at the voltage and current levels required by each respective component). Power supply 1308 may also include or be coupled to power management circuitry to supply power to the components of network node 1300 for performing the functions described herein. For example, network node 1300 may be connected to an external power source (e.g., mains, power outlet) via input circuitry or an interface (e.g., cable), thereby supplying power to the power circuitry of power supply 1308. As another example, power supply 1308 may include a power source in the form of a battery or battery pack, which is connected to or integrated into the power circuitry. The battery can provide backup power if the external power source fails.

[0291] Embodiments of network node 1300 may include more than Figure 13Additional components shown are provided to offer certain aspects of the functionality of the network node, including any of the functionalities described herein and / or any functionality required to support the topics described herein. For example, network node 1300 may include a user interface device to allow information to be input into and output from network node 1300. This allows users to perform diagnostic, maintenance, repair, and other management functions on network node 1300.

[0292] In some embodiments, one or more network nodes 1300 may be configured to perform various embodiments described above (including Figures 8 to 10 The exemplary method shown performs various operations belonging to the RAN node.

[0293] Figure 14 This is a block diagram illustrating a virtualization environment 1400 in which functionality implemented by some embodiments can be virtualized. In this context, virtualization means creating a virtual version of an apparatus or device that may include a virtualized hardware platform, storage devices, and networking resources. As used herein, virtualization can be applied to any device or component thereof described herein, and involves at least a portion of its functionality being implemented as an implementation of one or more virtual components. Some or all of the functionality described herein can be implemented as virtual components executed by one or more virtual machines (VMs) in one or more virtual environments 1400 hosted by one or more hardware nodes (e.g., hardware computing devices operating as network nodes, UEs, core network nodes, or hosts). Furthermore, in embodiments where virtual nodes do not require radio connectivity (e.g., core network nodes or hosts), the nodes can be fully virtualized. In some embodiments, the virtualization environment 1400 includes components defined by the O-RAN Alliance, such as an open cloud environment orchestrated via an O-2 interface by a service management and orchestration framework.

[0294] Application 1402 (which may alternatively be referred to as a software instance, virtual application, network function, virtual node, virtual network function, etc.) runs in virtualization environment 1400 to implement some of the features, functions, and / or benefits of some embodiments disclosed herein. In some embodiments, one or more virtual nodes 1402 may be configured to run in the various embodiments described above (including...) Figures 8 to 10 The exemplary method shown performs various operations belonging to the RAN node.

[0295] Hardware 1404 includes processing circuitry, memory storing software and / or instructions executable by the hardware processing circuitry (collectively referred to as computer program 1404a, which may be in the form of a computer program product), and / or other hardware devices described herein (e.g., network interface, input / output interface, etc.). The software may be executed by the processing circuitry to instantiate one or more virtualization layers 1406 (also referred to as a hypervisor or virtual machine monitor (VMM)), provide VMs 1408a and 1408b (one or more of which may generally be referred to as VM 1408), and / or perform any functions, features, and / or benefits described in relation to some embodiments described herein. Virtualization layer 1406 may present a virtual operating platform to VM 1408, which appears as network hardware.

[0296] VM 1408 includes virtual processing, virtual memory, virtual network or interface, and virtual storage, and can be run by a corresponding virtualization layer 1406. Different embodiments of instances of virtual device 1402 can be implemented on one or more VMs 1408, and these implementations can be made in different ways. In some contexts, hardware virtualization is referred to as Network Functions Virtualization (NFV). NFV can be used to unify many network device types into industry-standard high-capacity server hardware, physical switches, and physical storage, which can reside in data centers and customer residential equipment.

[0297] In the context of NFV, VM 1408 can be a software implementation of a physical machine, whose running program behaves as if it were running on a physical, non-virtualized machine. Each VM 1408, along with the portion of hardware 1404 that executes that VM (whether it is dedicated hardware for that VM and / or hardware shared by that VM with other VMs), forms a separate virtual network element. Still within the context of NFV, the virtual network function is responsible for handling the operation of one or more VMs 1408 on top of hardware 1404 and corresponds to the specific network function of application 1402.

[0298] Hardware 1404 can be implemented in a standalone network node with general or specific components. Hardware 1404 may implement some functions via virtualization. Alternatively, hardware 1404 may be part of a larger hardware cluster (e.g., in a data center or CPE) where many hardware nodes work together and are managed by management and orchestration 1410, which in particular oversees the lifecycle management of application 1402. In some embodiments, hardware 1404 is coupled to one or more radio units, each radio unit including one or more transmitters and one or more receivers that can be coupled to one or more antennas. The radio units may communicate directly with other hardware nodes via one or more suitable network interfaces and may be used in conjunction with virtual components to provide radio capabilities to virtual nodes, such as radio access nodes or base stations. In some embodiments, some signaling may be provided using a control system 1412, which may alternatively be used for communication between hardware nodes and radio units.

[0299] The foregoing merely illustrates the principles of this disclosure. Various modifications and alterations to the described embodiments will be apparent to those skilled in the art in light of the teachings herein. Therefore, it should be understood that those skilled in the art will be able to design numerous systems, arrangements, and processes that, while not expressly shown or described herein, embody the principles of this disclosure and are thus within its spirit and scope. As will be understood by those skilled in the art, various embodiments can be used together and interchangeably.

[0300] As used herein, the terminology may have a conventional meaning in the field of electronic, electrical and / or electronic equipment, and may include, for example, electrical and / or electronic circuits, devices, modules, processors, memories, logic solid-state and / or discrete devices, computer programs or instructions for performing various tasks, processes, calculations, outputs and / or display functions, such as those described herein.

[0301] Any suitable steps, methods, features, functions, or benefits disclosed herein can be performed by one or more functional units or modules of one or more virtual devices. Each virtual device may include multiple such functional units. These functional units may be implemented by processing circuitry, which may include one or more microprocessors or microcontrollers and other digital hardware (which may include digital signal processors (DSPs), application-specific digital logic, etc.). The processing circuitry may be configured to execute program code stored in memory, which may include one or more types of memory, such as read-only memory (ROM), random access memory (RAM), cache memory, flash memory devices, optical storage devices, etc. The program code stored in memory includes program instructions for executing one or more telecommunications and / or data communication protocols and instructions for executing one or more technologies described herein. In some embodiments, the processing circuitry may be used to cause the various functional units to perform corresponding functions according to one or more embodiments of this disclosure.

[0302] As described herein, devices and / or apparatuses may be represented by semiconductor chips, chipsets, or (hardware) modules including such chips or chipsets; however, this does not preclude the possibility that the functionality of a device or apparatus may be implemented as a software module (e.g., including a computer program or computer program product comprising executable software code portions for execution or running on a processor). Furthermore, the functionality of a device or apparatus may be implemented by any combination of hardware and software. A device or apparatus may also be considered as a combination of multiple devices and / or apparatuses, whether they functionally cooperate with each other or are independent of each other. Moreover, devices and apparatuses may be implemented in a distributed manner throughout a system, provided that the functionality of the device or apparatus is preserved. This principle and similar principles are considered to be known to those skilled in the art.

[0303] Unless otherwise defined, all terms used herein, including technical and scientific terms, shall have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. It will be further understood that the terms used herein should be interpreted in accordance with their meaning in the context of this specification and related art, and not in an ideal or overly formal sense, unless so explicitly defined herein.

[0304] Additionally, certain terms used in this disclosure (including the specification and drawings) may be used synonymously in certain instances (e.g., "data" and "information"). Although such terms may be used synonymously herein, there may also be instances where such terms are not intended to be used synonymously.

[0305] Embodiments of the technologies and apparatus described herein also include, but are not limited to, the following examples:

[0306] A1. A method for configuring a user equipment (UE) for triggering inter-cell mobility (LTM) at Layer 1 (L2) / Layer 2 (L2) in a radio access network (RAN), the method comprising:

[0307] When operating in a source cell provided by the first RAN node, perform early uplink (UL) synchronization with the first LTM candidate cell provided by the second RAN node and with the second LTM candidate cell provided by the third RAN node;

[0308] Receive a command from the first RAN node to perform an LTM cell handover from the source cell to the first LTM candidate cell, wherein the command includes or indicates the timing advance (TA) value of the UE in the source cell;

[0309] Based on the TA value and the fact that random access (RA) to the first LTM candidate cell is not performed during LTM cell handover, an LTM cell handover from the source cell to the first LTM candidate cell is performed.

[0310] A2. The method according to embodiment A1, wherein the TA value included in the command is the same as the first TA value determined based on early UL synchronization with the first LTM candidate cell.

[0311] A3. The method according to any one of embodiments A1 to A2 further includes:

[0312] Receives a second command from the second RAN node for performing a handover of a second LTM cell from a first LTM candidate cell to a second LTM candidate cell, wherein the second command includes or indicates a second timing advance (TA) value determined based on early UL synchronization between the UE and the second LTM candidate cell; and

[0313] Based on the second TA value and the fact that the RA is not executed during the second LTM cell handover to the second LTM candidate cell, the second LTM cell handover from the source cell to the first LTM candidate cell is performed.

[0314] A4. The method according to any one of embodiments A1 to A3 further includes receiving, via the source cell, an instruction for performing early UL synchronization with the first LTM candidate cell and the second LTM candidate cell, wherein the early UL synchronization is performed according to the instruction.

[0315] A5. The method according to embodiment A4, wherein the indication includes one or more Physical Downlink Control Channel (PDCCH) commands.

[0316] A6. The method according to any one of embodiments A4 to A5 further includes: receiving, via the source cell, a first early UL synchronization configuration and a second early UL synchronization configuration of the corresponding first LTM candidate cell and the second LTM candidate cell from a fourth RAN node, wherein the early UL synchronization is performed based on the corresponding first early UL synchronization configuration and the second early UL synchronization configuration.

[0317] A7. The method according to embodiment A6, wherein the instruction references one or more parameters in the corresponding first early UL synchronization configuration and second early UL synchronization configuration, and the first early UL synchronization and the second early UL synchronization are performed using the parameters referenced by the instruction.

[0318] A8. The method according to embodiment A7, wherein performing early UL synchronization with the first LTM candidate cell includes: using the random access (RA) resources of the first LTM candidate cell to send an RA preamble, wherein the RA preamble and / or RA resources are referenced by the indication.

[0319] A9. The method according to embodiment A8, wherein the RA resource referenced by the indication includes one or more of the following: time / frequency resources and one or more beams.

[0320] A10. The method according to any one of embodiments A6 to A9, wherein the first RAN node is a first distributed unit (DU), the second RAN node is a second DU, the third RAN node is a third DU, and the fourth RAN node is a centralized unit (CU) associated with the first DU, the second DU, and the third DU.

[0321] A11. The method according to any one of embodiments A1 to A10, wherein, for each of the first LTM candidate cell and the second LTM candidate cell, the associated early UL synchronization configuration includes one or more of the following:

[0322] The identifier or index of the random access (RA) preamble;

[0323] The identifier of the first RAN node;

[0324] Synchronization signal / PBCH (SSB) index;

[0325] RA configuration identifier;

[0326] The UE identifier; and

[0327] The identifier of the associated LTM candidate cell.

[0328] B1. A method for a second radio access network (RAN) node configured to facilitate Layer 1 (L1) / Layer 2 (L2) triggering of inter-cell mobility (LTM) by a user equipment (UE), the method comprising:

[0329] The UE is sent an instruction via the source cell provided by the first RAN node to perform uplink (UL) synchronization with the first LTM candidate cell provided by the second RAN node and with the second LTM candidate cell provided by the third RAN node;

[0330] Determine the timing advance (TA) value of the UE in the source cell;

[0331] Send a command to the UE to perform an LTM cell handover from the source cell to the first LTM candidate cell, wherein the command includes or indicates a TA value determined by the UE in the source cell; and

[0332] Send one of the following:

[0333] Requests to the fourth RAN node, to the second RAN node and the third RAN node, to send TA values ​​determined based on early UL synchronization; or

[0334] A message destined for at least one of the second RAN node and the third RAN node, the message including one or more TA values ​​of the UE.

[0335] B1a. The method according to embodiment B1, wherein the TA value included in the command is the same as the first TA value determined based on the early UL synchronization between the UE and the first LTM candidate cell.

[0336] B2. The method according to any one of embodiments B1 to B1a, wherein the indication includes one or more Physical Downlink Control Channel (PDCCH) commands.

[0337] B3. The method according to any one of embodiments B1 to B2 further includes: receiving, via a fourth RAN node, a corresponding first TA value and a second TA value of the UE in the corresponding first LTM candidate cell and the corresponding second LTM candidate cell from the second RAN node and the third RAN node, wherein the first TA value and the second TA value are based on the corresponding early UL synchronization.

[0338] B3a. The method according to embodiment B3, wherein the request is sent to the fourth RAN node before sending the command, and the request includes one or more of the following: the determined TA value, the first TA value of the UE in the first LTM candidate cell, and the second TA value of the UE in the second LTM candidate cell.

[0339] B4. The method according to embodiment B3, wherein a message sent to at least one of the second RAN node and the third RAN node responds to one of the following operations: receiving a first TA value and a second TA value, or sending the command.

[0340] B5. The method according to any one of embodiments B3 to B4, wherein one or more of the following TA values ​​are included in the message sent to the second RAN node: the TA value included in or indicated by the command, the first TA value of the UE in the first LTM candidate cell, and the second TA value of the UE in the second LTM candidate cell.

[0341] B6. The method according to embodiment B5, wherein the message is sent to the second RAN node via the fourth RAN node.

[0342] B7. The method according to any one of embodiments B3 to B6, wherein one or more of the following TA values ​​are included in the message sent to the third RAN node: the TA value included in or indicated by the command, the first TA value of the UE in the first LTM candidate cell, and the second TA value of the UE in the second LTM candidate cell.

[0343] B8. The method according to embodiment B7, wherein the message is sent to the third RAN node via the fourth RAN node.

[0344] B9. The method according to any one of embodiments B1 to B3, wherein the request sent to the fourth RAN node is in response to sending the instruction.

[0345] B10. The method according to any one of embodiments B1 to B9 further includes:

[0346] Receive the first early UL synchronization configuration and the second early UL synchronization configuration of the corresponding first LTM candidate cell and second LTM candidate cell from the fourth RAN node; and

[0347] The first early UL synchronization configuration and the second early UL synchronization configuration are sent to the UE via the source cell.

[0348] B11. The method according to embodiment B10, wherein the indication references one or more parameters in a corresponding first early UL synchronization configuration and a second early UL synchronization configuration, and the first early UL synchronization and the second early UL synchronization are performed by the UE using the parameters referenced by the indication.

[0349] B12. The method according to embodiment B11, wherein one or more parameters referenced by the indication include one or more of the following: random access (RA) preamble, time / frequency RA resources, and one or more beams.

[0350] B13. The method according to any one of embodiments B1 to B12, wherein the first RAN node is a first distributed unit (DU), the second RAN node is a second DU, the third RAN node is a third DU, and the fourth RAN node is a centralized unit (CU) associated with the first DU, the second DU, and the third DU.

[0351] B14. The method according to any one of embodiments B1 to B13, wherein, for each of the first LTM candidate cell and the second LTM candidate cell, the associated early UL synchronization configuration includes one or more of the following:

[0352] The identifier or index of the random access (RA) preamble;

[0353] The identifier of the first RAN node;

[0354] Synchronization signal / PBCH (SSB) index;

[0355] RA configuration identifier;

[0356] The UE identifier; and

[0357] The identifier of the associated LTM candidate cell.

[0358] C1. A method for a second radio access network (RAN) node configured to facilitate Layer 1 (L1) / Layer 2 (L2) triggering of inter-cell mobility (LTM) by a user equipment (UE), the method comprising:

[0359] Send the early uplink (UL) synchronization configuration of the UE to the first LTM candidate cell provided by the second RAN node to the fourth RAN node, wherein the UE is served by the source cell provided by the first RAN node;

[0360] Based on the early UL synchronization configuration, the random access (RA) preamble is received from the UE in the first LTM candidate cell;

[0361] Based on the RA preamble, the first timing advance (TA) value of the UE in the first LTM candidate cell is determined;

[0362] The first TA value is sent to the first RAN node via the fourth RAN node; and

[0363] Receive the corresponding TA value of the UE in one or more of the following cells: the source cell, the first LTM candidate cell, and the second LTM candidate cell provided by the third RAN node.

[0364] C2. The method according to embodiment C1, wherein one or more TA values ​​are received in response to sending a first TA value.

[0365] C3. The method according to embodiment C1, wherein:

[0366] One or more TA values ​​are received from the fourth RAN node in a request providing the UE with LTM candidate cell configuration in the first LTM candidate cell; and

[0367] The early UL synchronization configuration of the UE in the first LTM candidate cell is sent to the fourth RAN node in response to this request.

[0368] C4. The method according to embodiment C3, wherein the early UL synchronization configuration of the UE in the first LTM candidate cell includes one or more of the following:

[0369] The identifier or index of the random access (RA) preamble;

[0370] The identifier of the first RAN node;

[0371] Synchronization signal / PBCH (SSB) index;

[0372] RA configuration identifier;

[0373] The UE identifier; and

[0374] The identifier of the first LTM candidate cell.

[0375] C5. The method according to any one of embodiments C1 to C4, wherein the received TA value includes a first TA value sent to the first RAN node via the fourth RAN node.

[0376] C6. The method according to embodiment C1 further includes: after sending the first TA value and if no other RA preamble is received from the UE in the first LTM candidate cell, receiving from the UE a reconfiguration completion message indicating that the UE has completed the LTM cell handover to the first LTM candidate cell.

[0377] C7. The method according to embodiment C6, wherein the timing alignment of the reconfiguration completion message in the first LTM candidate cell is based on the TA value used by the UE for timing alignment in the source cell.

[0378] C8. The method according to embodiment C7, wherein the received TA value includes a TA value used by the UE for timing alignment in the source cell.

[0379] C9. The method according to any one of embodiments C6 to C8, wherein one or more TA values ​​are received in or through a notification that an LTM cell handover to the first LTM candidate cell has been initiated.

[0380] C10. The method according to any one of embodiments C6 to C9, wherein:

[0381] Based on the early UL synchronization between the UE and the second LTM candidate cell, the received TA value includes the second TA value of the second LTM candidate cell; and

[0382] The method further includes sending a command to the UE to perform a second LTM cell handover from a first LTM candidate cell to a second LTM candidate cell, wherein the command includes the received second TA value.

[0383] C11. The method according to embodiment C10 further includes: based on the received second TA value, avoiding initiating early UL synchronization between the UE and the second LTM candidate cell before sending the command.

[0384] C12. The method according to any one of embodiments C1 to C11, wherein the one or more TA values ​​are received from one of the following nodes: a first RAN node or a fourth RAN node.

[0385] C13. The method according to any one of embodiments C1 to C12, wherein the first RAN node is a first distributed unit (DU), the second RAN node is a second DU, the third RAN node is a third DU, and the fourth RAN node is a centralized unit (CU) associated with the first DU, the second DU, and the third DU.

[0386] D1. A method for a fourth radio access network (RAN) node configured to facilitate Layer 1 (L1) / Layer 2 (L2) triggering of inter-cell mobility (LTM) by a user equipment (UE), the method comprising:

[0387] For the UE served by the source cell provided by the first RAN node, the following items are received:

[0388] The first timing advance (TA) value of the UE in the first LTM candidate cell provided by the second RAN node; and

[0389] The second TA value of the UE in the second LTM candidate cell provided by the third RAN node, from the third RAN node.

[0390] Send the received first TA value and second TA value to the first RAN node; and

[0391] Send at least one message including one or more TA values ​​of the UE, each message being sent to a second RAN node or a third RAN node.

[0392] D2. The method according to embodiment D1 further includes:

[0393] Receive the corresponding first early UL synchronization configuration and second early UL synchronization configuration for each of the first LTM candidate cells and the second LTM candidate cells from the second RAN node and the third RAN node; and

[0394] The first early UL synchronization configuration and the second early UL synchronization configuration are sent to the UE via the first RAN node.

[0395] The first TA value and the second TA value are based on the early UL synchronization of the UE with the first LTM candidate cell and the second LTM candidate cell according to the corresponding first early UL synchronization configuration and the second early UL synchronization configuration.

[0396] D2a. The method according to embodiment D2, wherein the at least one message includes a first message sent to a second RAN node, wherein the first message includes a second TA value and is sent in one of the following ways: in response to receiving the second TA value, in response to sending the second TA value to a first RAN node, or based on receiving a first early UL synchronization configuration.

[0397] D2b. The method according to any one of embodiments D2 to D2a, wherein the at least one message includes a second message sent to a third RAN node, wherein the second message includes a first TA value and is sent in one of the following ways: in response to receiving the first TA value, in response to sending the first TA, or based on receiving a second early UL synchronization configuration.

[0398] D2c. The method according to any one of embodiments D2 to D2b further includes receiving the TA value of the UE in the source cell from the first RAN node, wherein each of the at least one message further includes the TA value of the UE in the source cell.

[0399] D3. The method according to any one of embodiments D1 to D2 further includes receiving one of the following from the first RAN node:

[0400] A request to send one or more TA values ​​of the UE to at least one of the second RAN node and the third RAN node; or

[0401] A message including one or more TA values ​​of the UE, which should be sent to at least one of the second RAN node and the third RAN node.

[0402] D4. The method according to embodiment D3 further includes: storing the received first TA value and second TA value; and retrieving the stored first TA value and second TA value based on a request, wherein each of the retrieved first TA value and second TA value is included in at least one of the messages sent to the second RAN node and the third RAN node.

[0403] D5. The method according to any one of embodiments D3 to D4, wherein the request from the first RAN node indicates which of the second RAN node and the third RAN node should receive each of one or more TA values, and the message is sent to at least one of the second RAN node and the third RAN node according to the indication.

[0404] D6. According to the method described in embodiment D3, the message received from the first RAN node is an LTM cell handover notification, which indicates that the first RAN node has initiated an LTM cell handover of the UE to the first LTM candidate cell, and the messages sent to the second RAN node and the third RAN node are corresponding LTM cell handover notification messages.

[0405] D7. The method according to embodiment D3, wherein one or more of the following TA values ​​are included in the message received from the first RAN node: the TA value of the UE in the source cell, the first TA value of the UE in the first LTM candidate cell, and the second TA value of the UE in the second LTM candidate cell.

[0406] D8. The method according to embodiment D7, wherein one or more of the following TA values ​​from the message from the first RAN node are included in the message sent to the second RAN node: the TA value of the UE in the source cell, the first TA value of the UE in the first LTM candidate cell, and the second TA value of the UE in the second LTM candidate cell.

[0407] D9. The method according to any one of embodiments D7 to D8, wherein one or more of the following TA values ​​are included in the message sent to the third RAN node: the TA value of the UE in the source cell, the first TA value of the UE in the first LTM candidate cell, and the second TA value of the UE in the second LTM candidate cell.

[0408] D10. The method according to any one of embodiments D7 to D9, wherein the message received from the first RAN node includes an indication of which of the second RAN node and the third RAN node should receive each of the one or more TA values ​​included, and the message is sent to at least one of the second RAN node and the third RAN node according to the indication.

[0409] D11. The method according to any one of embodiments D1 to D10, wherein the first RAN node is a first distributed unit (DU), the second RAN node is a second DU, the third RAN node is a third DU, and the fourth RAN node is a centralized unit (CU) associated with the first DU, the second DU, and the third DU.

[0410] D12. The method according to any one of embodiments D1 to D11, wherein, for each of the first LTM candidate cell, the second LTM candidate cell, and the third LTM candidate cell, the associated early UL synchronization configuration includes one or more of the following:

[0411] The identifier or index of the random access (RA) preamble;

[0412] The identifier of the first RAN node;

[0413] Synchronization signal / PBCH (SSB) index;

[0414] RA configuration identifier;

[0415] The UE identifier; and

[0416] The identifier of the associated LTM candidate cell.

[0417] E1. A user equipment (UE) configured for triggering inter-cell mobility (LTM) at Layer 1 (L2) / Layer 2 (L2) in a radio access network (RAN), the UE comprising:

[0418] The communication interface circuit is configured to communicate with the RAN node; and

[0419] The processing circuit is operatively coupled to the communication interface circuit, wherein the processing circuit and the communication interface circuit are configured to perform operations corresponding to the method described according to any one of embodiments A1 to A11.

[0420] E2. A user equipment (UE) configured for triggering inter-cell mobility (LTM) at Layer 1 (L2) / Layer 2 (L2) in a radio access network (RAN), the UE being further configured to perform an operation corresponding to the method described according to any one of embodiments A1 to A11.

[0421] E3. A non-transitory computer-readable medium storing computer-executable instructions that, when executed by processing circuitry of a user equipment (UE) configured for triggering inter-cell mobility (LTM) in a Layer 1 (L2) / Layer 2 (L2) radio access network (RAN), configure the UE to perform an operation corresponding to the method described according to any one of embodiments A1 to A11.

[0422] E4. A computer program product including computer-executable instructions that, when executed by a processing circuit of a user equipment (UE) configured for triggering inter-cell mobility (LTM) in a Layer 1 (L2) / Layer 2 (L2) radio access network (RAN), configure the UE to perform an operation corresponding to the method described according to any one of embodiments A1 to A11.

[0423] F1. A first radio access network (RAN) node configured to facilitate Layer 1 (L2) / Layer 2 (L2) triggered inter-cell mobility (LTM) by a user equipment (UE), the first RAN node comprising:

[0424] The communication interface circuitry is configured to communicate with the UE and other RAN nodes; and

[0425] The processing circuit is operatively coupled to the communication interface circuit, wherein the processing circuit and the communication interface circuit are configured to perform operations corresponding to the method described according to any one of embodiments B1 to B14.

[0426] F2. A first radio access network (RAN) node configured to facilitate Layer 1 (L2) / Layer 2 (L2) triggering of inter-cell mobility (LTM) by a user equipment (UE), the first RAN node being further configured to perform operations corresponding to the method described according to any one of embodiments B1 to B14.

[0427] F3. A non-transitory computer-readable medium storing computer-executable instructions that, when executed by processing circuitry of a first radio access network (RAN) node configured to facilitate inter-cell mobility (LTM) triggering by a layer 1 (L2) / layer 2 (L2) of a user equipment (UE), configure the first RAN node to perform an operation corresponding to the method described according to any one of embodiments B1 to B14.

[0428] F4. A computer program product including computer-executable instructions that, when executed by processing circuitry of a first radio access network (RAN) node configured to facilitate inter-cell mobility (LTM) triggering by a layer 1 (L2) / layer 2 (L2) of a user equipment (UE), configure the first RAN node to perform an operation corresponding to the method described according to any one of embodiments B1 to B14.

[0429] G1. A second radio access network (RAN) node configured to facilitate Layer 1 (L2) / Layer 2 (L2) triggered inter-cell mobility (LTM) for user equipment (UE), the second RAN node comprising:

[0430] The communication interface circuitry is configured to communicate with the UE and other RAN nodes; and

[0431] The processing circuit is operatively coupled to the communication interface circuit, wherein the processing circuit and the communication interface circuit are configured to perform operations corresponding to the method described according to any one of embodiments C1 to C13.

[0432] G2. A second radio access network (RAN) node configured to facilitate Layer 1 (L2) / Layer 2 (L2) triggering of inter-cell mobility (LTM) by a user equipment (UE), the second RAN node being further configured to perform operations corresponding to the method described according to any one of embodiments C1 to C13.

[0433] G3. A non-transitory computer-readable medium storing computer-executable instructions that, when executed by processing circuitry of a second radio access network (RAN) node configured to facilitate inter-cell mobility (LTM) triggering by a layer 1 (L2) / layer 2 (L2) of a user equipment (UE), configure the second RAN node to perform operations corresponding to the method described according to any one of embodiments C1 to C13.

[0434] G4. A computer program product including computer-executable instructions that, when executed by processing circuitry of a second radio access network (RAN) node configured to facilitate inter-cell mobility (LTM) triggering by a layer 1 (L2) / layer 2 (L2) of a user equipment (UE), configure the second RAN node to perform an operation corresponding to the method described according to any one of embodiments C1 to C13.

[0435] H1. A fourth radio access network (RAN) node configured to facilitate Layer 1 (L2) / Layer 2 (L2) triggered inter-cell mobility (LTM) for user equipment (UE), the fourth RAN node comprising:

[0436] The communication interface circuitry is configured to communicate with the UE and other RAN nodes; and

[0437] The processing circuit is operatively coupled to the communication interface circuit, wherein the processing circuit and the communication interface circuit are configured to perform operations corresponding to the method described according to any one of embodiments D1 to D12.

[0438] H2. A fourth radio access network (RAN) node configured to facilitate Layer 1 (L2) / Layer 2 (L2) triggering of inter-cell mobility (LTM) by a user equipment (UE), the fourth RAN node being further configured to perform operations corresponding to the method described according to any one of embodiments D1 to D12.

[0439] H3. A non-transitory computer-readable medium storing computer-executable instructions that, when executed by processing circuitry of a fourth radio access network (RAN) node configured to facilitate inter-cell mobility (LTM) triggering by a layer 1 (L2) / layer 2 (L2) of a user equipment (UE), configure the fourth RAN node to perform operations corresponding to the method described according to any one of embodiments D1 to D12.

[0440] H4. A computer program product including computer-executable instructions that, when executed by processing circuitry of a fourth radio access network (RAN) node configured to facilitate inter-cell mobility (LTM) triggering by a layer 1 (L2) / layer 2 (L2) of a user equipment (UE), configure the fourth RAN node to perform an operation corresponding to the method described according to any one of embodiments D1 to D12.

Claims

1. A method for a user equipment (UE) configured to trigger inter-cell mobility LTM in a Layer 1 / Layer 2 radio access network (RAN), the method comprising: When operating in the source cell provided by the first RAN node, perform (730) to synchronize the corresponding early uplink UL with the first LTM candidate cell provided by the second RAN node and with the corresponding early uplink UL of the second LTM candidate cell provided by the third RAN node; Receive (740) a first command from the first RAN node for performing a first LTM cell handover from the source cell to the first LTM candidate cell, wherein the first command includes or indicates a first timing advance TA value used by the UE in the first LTM candidate cell; Based on the first TA value and the fact that random access RA to the first LTM candidate cell is not performed during the first LTM cell handover, (750) the first LTM cell handover from the source cell to the first LTM candidate cell is performed; Receive (760) a second command from the second RAN node for performing a second LTM cell handover from the first LTM candidate cell to the second LTM candidate cell, wherein the second command includes or indicates a second TA value used by the UE in the second LTM candidate cell; and Based on the second TA value and the fact that no RA is performed to the second LTM candidate cell during the second LTM cell handover, (770) the second LTM cell handover from the first LTM candidate cell to the second LTM candidate cell is performed.

2. The method according to claim 1, wherein, The first TA value is based on the early UL synchronization of the UE with the first LTM candidate cell, and the second TA value is based on the early UL synchronization of the UE with the second LTM candidate cell.

3. The method according to any one of claims 1 to 2, further comprising: The source cell receives (720) the following instruction: perform early UL synchronization with the first LTM candidate cell and the second LTM candidate cell, wherein the corresponding early UL synchronization is performed according to the instruction.

4. The method according to claim 3, wherein, The indication includes one or more Physical Downlink Control Channel (PDCCH) commands.

5. The method according to any one of claims 3 to 4, further comprising: The source cell receives (710) a first early UL synchronization configuration and a second early UL synchronization configuration for the first LTM candidate cell and the second LTM candidate cell from the fourth RAN node, wherein the corresponding early UL synchronization is performed based on the first early UL synchronization configuration and the second early UL synchronization configuration.

6. The method according to claim 5, wherein, The instruction references one or more parameters in the first early UL synchronization configuration and the second early UL synchronization configuration, and the corresponding early UL synchronization is performed using the one or more parameters referenced by the instruction.

7. The method according to claim 6, wherein, Performing (730) early UL synchronization with the first LTM candidate cell includes: using the RA resources of the first LTM candidate cell to send (731) an RA preamble, wherein the RA preamble and / or the RA resources are referenced by the indication.

8. The method according to claim 7, wherein, The RA resources referenced by the indication include one or more of the following: time / frequency resources, and one or more beams.

9. The method according to any one of claims 5 to 8, wherein, The first RAN node is a first distributed unit (DU); the second RAN node is a second DU; the third RAN node is a third DU; and the fourth RAN node is a centralized unit (CU) associated with the first DU, the second DU, and the third DU.

10. The method according to any one of claims 1 to 9, wherein, For each of the first LTM candidate cell and the second LTM candidate cell, the associated early UL synchronization configuration includes one or more of the following: The identifier or index of the RA preamble; The identifier of the first RAN node; Synchronization signal / PBCH "SSB" index; RA configuration identifier; The identifier of the UE; as well as The identifier of the associated LTM candidate cell.

11. A method for a first radio access network (RAN) node, the first RAN node being configured to facilitate Layer 1 / Layer 2 triggered inter-cell mobility LTM for a user equipment (UE), the method comprising: The UE is sent (830) the following instruction via the source cell provided by the first RAN node: to perform early uplink UL synchronization with the first LTM candidate cell provided by the second RAN node and with the corresponding early uplink UL of the second LTM candidate cell provided by the third RAN node; Then receive the following timing advance TA value (835): The first TA value from the second RAN node, used by the UE in the first LTM candidate cell, and The second TA value from the third RAN node, used by the UE in the second LTM candidate cell; Send a command (850) to the UE to perform a first LTM cell handover from the source cell to the first LTM candidate cell, wherein the command includes or indicates the first TA value; as well as Send a first message (860) to the second RAN node, the first message including or indicating one or more of the following: the first TA value and the second TA value.

12. The method according to claim 11, wherein, The first TA value is based on the early UL synchronization of the UE with the first LTM candidate cell, and the second TA value is based on the early UL synchronization of the UE with the second LTM candidate cell.

13. The method according to any one of claims 11 to 12, wherein, The indication includes one or more Physical Downlink Control Channel (PDCCH) commands.

14. The method according to any one of claims 11 to 13, wherein, One or more of the following apply: In response to sending the command (850), the first message is sent to the second RAN node; and The first message is an LTM cell handover notification message, which indicates that the first RAN node has initiated an LTM cell handover of the UE to the first LTM candidate cell.

15. The method according to any one of claims 11 to 14, wherein, The first message includes the second TA value to facilitate the UE's handover from the first LTM candidate cell to the second LTM candidate cell in the second LTM cell.

16. The method according to any one of claims 11 to 15, wherein, The first message is sent to the second RAN node via the fourth RAN node.

17. The method according to claim 16, wherein, The first RAN node is a first distributed unit (DU); the second RAN node is a second DU; the third RAN node is a third DU; and the fourth RAN node is a centralized unit (CU) associated with the first DU, the second DU, and the third DU.

18. The method according to any one of claims 11 to 17, further comprising: Receive (810) from the fourth RAN node the first early UL synchronization configuration and the second early UL synchronization configuration corresponding to the first LTM candidate cell and the second LTM candidate cell; and (820) First early UL synchronization configuration and second early UL synchronization configuration are sent to the UE via the source cell.

19. The method according to claim 18, wherein, The indication references one or more parameters in the corresponding first early UL synchronization configuration and the second early UL synchronization configuration, and the corresponding early UL synchronization is performed by the UE using the parameters referenced by the indication.

20. The method according to claim 19, wherein, The one or more parameters referenced by the indication include one or more of the following: random access RA preamble; time / frequency RA resources; and one or more beams.

21. The method according to any one of claims 11 to 20, wherein, For each of the first LTM candidate cell and the second LTM candidate cell, the associated early UL synchronization configuration includes one or more of the following: The identifier or index of the random access RA preamble; The identifier of the first RAN node; Synchronization signal / PBCH "SSB" index; RA configuration identifier; The identifier of the UE; as well as The identifier of the associated LTM candidate cell.

22. A method for a second radio access network (RAN) node, the second RAN node being configured to facilitate Layer 1 / Layer 2 triggered inter-cell mobility LTM for a user equipment (UE), the method comprising: In the first LTM candidate cell provided by the second RAN node, the UE served by the source cell provided by the first RAN node receives (920) random access RA preamble; Based on the RA preamble, determine (930) the first timing advance TA value used by the UE in the first LTM candidate cell; The first TA value (940) is sent to the first RAN node via the fourth RAN node; as well as Receive (950) a first message from the first RAN node, the first message including or indicating one or more of the following: the first TA value, and the second TA value used by the UE in a second LTM candidate cell provided by the third RAN node.

23. The method of claim 22, further comprising: Send (910) the early uplink UL synchronization configuration of the UE to the first LTM candidate cell to the fourth RAN node, wherein the RA preamble is received according to the early UL synchronization configuration.

24. The method according to claim 23, wherein, The early UL synchronization configuration of the UE in the first LTM candidate cell includes one or more of the following: The identifier or index of the RA preamble; The identifier of the first RAN node; Synchronization signal / PBCH "SSB" index; RA configuration identifier; The identifier of the UE; and The identifier of the first LTM candidate cell.

25. The method according to any one of claims 22 to 24, wherein, One or more of the following apply: Receive the first message from the first RAN node via the fourth RAN node; and The first message is an LTM cell handover notification message, which indicates that the first RAN node has initiated an LTM cell handover of the UE to the first LTM candidate cell.

26. The method of claim 25, further comprising: After sending (940) the first TA value and if no other RA preamble is received from the UE in the first LTM candidate cell during the LTM cell handover, the UE receives (960) a reconfiguration completion message indicating that the UE has completed the LTM cell handover to the first LTM candidate cell.

27. The method according to claim 26, wherein, One or more of the following apply: The timing alignment of the reconfiguration completion message in the first LTM candidate cell is based on the first TA value; and The first message also includes a TA value used by the UE for timing alignment in the source cell.

28. The method according to any one of claims 22 to 27, wherein, The first TA value is based on the early UL synchronization of the UE with the first LTM candidate cell, and the second TA value is based on the early UL synchronization of the UE with the second LTM candidate cell.

29. The method according to any one of claims 22 to 28, further comprising: Send a command (980) to the UE to perform a second LTM cell handover from the first LTM candidate cell to the second LTM candidate cell, wherein the command includes the received second TA value.

30. The method of claim 29, further comprising: Based on the received second TA value, before sending the command, avoid initiating (970) early UL synchronization between the UE and the second LTM candidate cell.

31. The method according to any one of claims 22 to 30, wherein, The first RAN node is a first distributed unit (DU); the second RAN node is a second DU; the third RAN node is a third DU; and the fourth RAN node is a centralized unit (CU) associated with the first DU, the second DU, and the third DU.

32. A method for a fourth radio access network (RAN) node, the fourth RAN node being configured to facilitate Layer 1 / Layer 2 triggered inter-cell mobility LTM for a user equipment (UE), the method comprising: For the UE served by the source cell provided by the first RAN node, receive (1030) the following: The first timing advance TA value from the second RAN node, used by the UE in the first LTM candidate cell provided by the second RAN node; as well as The second TA value from the third RAN node, used by the UE in the second LTM candidate cell provided by the third RAN node; Send the first TA value and the second TA value (1040) to the first RAN node; as well as Send a first message (1080) to the second RAN node, the first message including or indicating one or more of the following: the first TA value and the second TA value.

33. The method of claim 32, further comprising: Receive corresponding first early UL synchronization configurations and second early UL synchronization configurations for the first LTM candidate cell and the second LTM candidate cell from the second RAN node and the third RAN node; and The first early UL synchronization configuration and the second early UL synchronization configuration are sent to the UE via the first RAN node. The first TA value and the second TA value are based on the early UL synchronization of the UE with the first LTM candidate cell and the second LTM candidate cell according to the corresponding first early UL synchronization configuration and second early UL synchronization configuration.

34. The method according to claim 33, wherein, For each of the first LTM candidate cell and the second LTM candidate cell, the associated early UL synchronization configuration includes one or more of the following: The identifier or index of the random access RA preamble; The identifier of the first RAN node; Synchronization signal / PBCH "SSB" index; RA configuration identifier; The identifier of the UE; as well as The identifier of the associated LTM candidate cell.

35. The method according to any one of claims 32 to 34, further comprising: The UE receives a second message from the first RAN node. The second message includes or indicates one or more of the following TA values: the first TA value, the second TA value, and the TA value of the UE in the source cell.

36. The method according to claim 35, wherein, The second message received from the first RAN node is an LTM cell handover notification message, which indicates that the first RAN node has initiated an LTM cell handover of the UE to the first LTM candidate cell.

37. The method according to any one of claims 35 to 36, wherein, One or more of the following apply: In response to receiving the second message, the first message is sent; and The first message is an LTM cell handover notification message, which indicates that the first RAN node has initiated an LTM cell handover of the UE to the first LTM candidate cell.

38. The method according to any one of claims 35 to 37, wherein, The first message sent to the second RAN node also includes or indicates the TA value of the UE in the source cell.

39. The method according to any one of claims 32 to 38, wherein, The first RAN node is a first distributed unit (DU); the second RAN node is a second DU; the third RAN node is a third DU; and the fourth RAN node is a centralized unit (CU) associated with the first DU, the second DU, and the third DU.

40. A user equipment (UE) (210, 610, 1112, 1200) configured for Layer 1 / Layer 2 triggered inter-cell mobility LTM in a radio access network (RAN) (199, 1104), the UE comprising: The communication interface circuit (1212) is configured to communicate with RAN nodes (110, 120, 130, 220, 620, 630, 640, 650, 1110, 1300, 1402); as well as Processing circuitry (1202) is operatively coupled to the communication interface circuitry, wherein the processing circuitry and the communication interface circuitry are configured as follows: When operating in a source cell provided by the first RAN node, perform corresponding early uplink UL synchronization with the first LTM candidate cell provided by the second RAN node and with the second LTM candidate cell provided by the third RAN node; The first command is received from the first RAN node to perform a first LTM cell handover from the source cell to the first LTM candidate cell, wherein the first command includes or indicates a first timing advance TA value used by the UE in the first LTM candidate cell; Based on the first TA value and the fact that random access RA to the first LTM candidate cell is not performed during the first LTM cell handover, a first LTM cell handover from the source cell to the first LTM candidate cell is performed. Receives a second command from the second RAN node for performing a second LTM cell handover from the first LTM candidate cell to the second LTM candidate cell, wherein the second command includes or indicates a second TA value used by the UE in the second LTM candidate cell; and Based on the second TA value and the fact that no RA is performed to the second LTM candidate cell during the second LTM cell handover, the second LTM cell handover from the first LTM candidate cell to the second LTM candidate cell is performed.

41. The UE according to claim 40, wherein, The processing circuit and the communication interface circuit are further configured to perform operations corresponding to the method according to any one of claims 2 to 10.

42. A user equipment (UE) (210, 610, 1112, 1200) configured for Layer 1 / Layer 2 triggered inter-cell mobility LTM in a radio access network (RAN) (199, 1104), the UE further configured to: When operating in a source cell provided by the first RAN node (120, 130, 220, 620, 1110, 1300, 1402), perform corresponding early uplink UL synchronization with the first LTM candidate cell provided by the second RAN node (120, 130, 220, 630, 1110, 1300, 1402) and with the second LTM candidate cell provided by the third RAN node (120, 130, 220, 640, 1110, 1300, 1402); The first command is received from the first RAN node to perform a first LTM cell handover from the source cell to the first LTM candidate cell, wherein... The first command includes or indicates a first timing advance TA value used by the UE in the first LTM candidate cell; Based on the first TA value and the fact that random access RA is not performed to the first LTM candidate cell during the first LTM cell handover, the first LTM cell handover from the source cell to the first LTM candidate cell is performed; The second command is received from the second RAN node to perform a second LTM cell handover from the first LTM candidate cell to the second LTM candidate cell, wherein the second command includes or indicates a second TA value used by the UE in the second LTM candidate cell; as well as Based on the second TA value and the fact that no RA is performed to the second LTM candidate cell during the second LTM cell handover, the second LTM cell handover from the first LTM candidate cell to the second LTM candidate cell is performed.

43. The UE according to claim 42 is further configured to perform an operation corresponding to the method according to any one of claims 2 to 10.

44. A non-transitory computer-readable medium (1210) storing computer-executable instructions, which, when executed by a processing circuit (1202) of a user equipment (210, 610, 1112, 1200) configured for triggering inter-cell mobility LTM in a Layer 1 / Layer 2 radio access network (199, 1104), configure the UE to perform an operation corresponding to the method according to any one of claims 1 to 10.

45. A computer program product (1214) comprising computer-executable instructions, which, when executed by a processing circuit (1202) of a user equipment (210, 610, 1112, 1200) configured for triggering inter-cell mobility LTM in a Layer 1 / Layer 2 radio access network (199, 1104), configure the UE to perform an operation corresponding to the method according to any one of claims 1 to 10.

46. ​​A first radio access network (RAN) node (120, 130, 220, 620, 1110, 1300, 1402) configured to facilitate Layer 1 / Layer 2 triggered inter-cell mobility LTM for user equipment (UE) (210, 610, 1112, 1200), the first RAN node comprising: The communication interface circuits (1306, 1404) are configured to communicate with the UE and other RAN nodes (110, 220, 630, 640, 650, 1110, 1300, 1402); as well as The processing circuitry (1302, 1404) is operatively coupled to the communication interface circuitry, wherein the processing circuitry and the communication interface circuitry are configured as follows: The UE is instructed via the source cell provided by the first RAN node to perform early uplink UL synchronization with the first LTM candidate cell provided by the second RAN node and with the corresponding early uplink UL of the second LTM candidate cell provided by the third RAN node. Then receive the following timing advance TA value: The first TA value from the second RAN node, used by the UE in the first LTM candidate cell, and The second TA value from the third RAN node, used by the UE in the second LTM candidate cell; Sending a command to the UE to perform a first LTM cell handover from the source cell to the first LTM candidate cell, wherein the command includes or indicates the first TA value; and Send a first message to the second RAN node, the first message including or indicating one or more of the following: the first TA value, and the second TA value.

47. The first RAN node according to claim 46, wherein, The processing circuit and the communication interface circuit are further configured to perform operations corresponding to the method according to any one of claims 12 to 21.

48. A first radio access network (RAN) node (120, 130, 220, 620, 1110, 1300, 1402) is configured to facilitate Layer 1 / Layer 2 triggered inter-cell mobility LTM for user equipment (UE) (210, 610, 1112, 1200), wherein the first RAN node is further configured to: The UE is instructed via the source cell provided by the first RAN node to perform early uplink UL synchronization with the first LTM candidate cell provided by the second RAN node (120, 130, 220, 630, 1110, 1300, 1402) and with the second LTM candidate cell provided by the third RAN node (120, 130, 220, 640, 1110, 1300, 1402). Then receive the following timing advance TA value: The first TA value from the second RAN node, used by the UE in the first LTM candidate cell, and The second TA value from the third RAN node, used by the UE in the second LTM candidate cell; Send a command to the UE to perform a first LTM cell handover from the source cell to the first LTM candidate cell, wherein the command includes or indicates the first TA value; as well as Send a first message to the second RAN node, the first message including or indicating one or more of the following: the first TA value, and the second TA value.

49. The first RAN node according to claim 48 is further configured to perform operations corresponding to the method according to any one of claims 12 to 21.

50. A non-transitory computer-readable medium (1304, 1404) storing computer-executable instructions, which, when executed by processing circuitry (1302, 1404) of a first radio access network RAN ​​node (120, 130, 220, 620, 1110, 1300, 1402) configured to facilitate Layer 1 / Layer 2 triggering of inter-cell mobility LTM for a user equipment (UE) (210, 610, 1112, 1200), configure the first RAN node to perform an operation corresponding to the method according to any one of claims 11 to 21.

51. A computer program product (1304a, 1404a) comprising computer-executable instructions, wherein the computer-executable instructions, when executed by a processing circuit (1302, 1404) of a first radio access network RAN ​​node (120, 130, 220, 620, 1110, 1300, 1402) configured to facilitate inter-cell mobility LTM triggering at Layer 1 / Layer 2 of a user equipment (UE) (210, 610, 1112, 1200), configure the first RAN node to perform an operation corresponding to the method according to any one of claims 11 to 21.

52. A second radio access network (RAN) node (120, 130, 220, 630, 1110, 1300, 1402), configured to facilitate Layer 1 / Layer 2 (210, 610, 1112, 1200) inter-cell mobility LTM for user equipment (UE), the second RAN node comprising: The communication interface circuits (1306, 1404) are configured to communicate with the UE and other RAN nodes (110, 220, 620, 640, 650, 1110, 1300, 1402); as well as The processing circuitry (1302, 1404) is operatively coupled to the communication interface circuitry, wherein the processing circuitry and the communication interface circuitry are configured as follows: In the first LTM candidate cell provided by the second RAN node, the UE served by the source cell provided by the first RAN node (120, 130, 220, 620, 1110, 1300, 1402) receives the random access RA preamble. Based on the RA preamble, determine the first timing advance TA value used by the UE in the first LTM candidate cell; The first TA value is sent to the first RAN node via the fourth RAN node (110, 220, 650, 1110, 1300, 1402); as well as The UE receives a first message from the first RAN node, the first message including or indicating one or more of the following: the first TA value, and a second TA value used by the UE in a second LTM candidate cell provided by a third RAN node (120, 130, 220, 640, 1110, 1300, 1402).

53. The second RAN node according to claim 52, wherein, The processing circuit and the communication interface circuit are further configured to perform operations corresponding to the method according to any one of claims 23 to 31.

54. A second radio access network (RAN) node (120, 130, 220, 630, 1110, 1300, 1402) is configured to facilitate Layer 1 / Layer 2 triggered inter-cell mobility LTM for user equipment (UE) (210, 610, 1112, 1200), wherein the second RAN node is further configured to: In the first LTM candidate cell provided by the second RAN node, the UE served by the source cell provided by the first RAN node (120, 130, 220, 620, 1110, 1300, 1402) receives the random access RA preamble. Based on the RA preamble, determine the first timing advance TA value used by the UE in the first LTM candidate cell; The first TA value is sent to the first RAN node via the fourth RAN node (110, 220, 650, 1110, 1300, 1402); and The UE receives a first message from the first RAN node, the first message including or indicating one or more of the following: the first TA value, and a second TA value used by the UE in a second LTM candidate cell provided by a third RAN node (120, 130, 220, 640, 1110, 1300, 1402).

55. The second RAN node according to claim 54 is further configured to perform operations corresponding to the method according to any one of claims 23 to 31.

56. A non-transitory computer-readable medium (1304, 1404) storing computer-executable instructions, which, when executed by processing circuitry (1302, 1404) of a second radio access network RAN ​​node (120, 130, 220, 630, 1110, 1300, 1402) configured to facilitate inter-cell mobility LTM triggering at Layer 1 / Layer 2 of a user equipment (UE) (210, 610, 1112, 1200), configure the second RAN node to perform operations corresponding to the method according to any one of claims 22 to 31.

57. A computer program product (1304a, 1404a) comprising computer-executable instructions, which, when executed by processing circuitry (1302, 1404) of a second radio access network RAN ​​node (120, 130, 220, 630, 1110, 1300, 1402) configured to facilitate inter-cell mobility LTM triggering at Layer 1 / Layer 2 of a user equipment (UE) (210, 610, 1112, 1200), configure the second RAN node to perform operations corresponding to the method according to any one of claims 22 to 31.

58. A fourth radio access network (RAN) node (110, 220, 650, 1110, 1300, 1402), configured to facilitate Layer 1 / Layer 2 triggered inter-cell mobility LTM for user equipment (UE) (210, 610, 1112, 1200), the fourth RAN node comprising: The communication interface circuits (1306, 1404) are configured to communicate with the UE and other RAN nodes (120, 130, 220, 620, 630, 640, 1110, 1300, 1402); as well as The processing circuitry (1302, 1404) is operatively coupled to the communication interface circuitry, wherein the processing circuitry and the communication interface circuitry are configured as follows: For the UE served by the source cell provided by the first RAN node, the following items are received: The first timing advance TA value from the second RAN node, used by the UE in the first LTM candidate cell provided by the second RAN node; and The second TA value from the third RAN node, used by the UE in the second LTM candidate cell provided by the third RAN node; Send the first TA value and the second TA value to the first RAN node; and Send a first message to the second RAN node, the first message including or indicating one or more of the following: the first TA value, and the second TA value.

59. The fourth RAN node according to claim 58, wherein, The processing circuit and the communication interface circuit are further configured to perform operations corresponding to the method according to any one of claims 33 to 39.

60. A fourth radio access network (RAN) node (110, 220, 650, 1110, 1300, 1402) configured to facilitate Layer 1 / Layer 2 triggered inter-cell mobility LTM for user equipment (UE) (210, 610, 1112, 1200), said fourth RAN node further configured to: For the UE served by the source cell provided by the first RAN node (120, 130, 220, 620, 1110, 1300, 1402), the following items are received: The first timing advance TA value, obtained from the second RAN nodes (120, 130, 220, 630, 1110, 1300, 1402), used by the UE in the first LTM candidate cell provided by the second RAN nodes; as well as The second TA value obtained from the third RAN nodes (120, 130, 220, 640, 1110, 1300, 1402) and used by the UE in the second LTM candidate cell provided by the third RAN nodes; Send the first TA value and the second TA value to the first RAN node; as well as Send a first message to the second RAN node, the first message including or indicating one or more of the following: the first TA value, and the second TA value.

61. The fourth RAN node according to claim 60 is further configured to perform operations corresponding to the method according to any one of claims 33 to 39.

62. A non-transitory computer-readable medium (1304, 1404) storing computer-executable instructions, which, when executed by processing circuitry (1302, 1404) of a fourth radio access network RAN ​​node (110, 220, 650, 1110, 1300, 1402) configured to facilitate Layer 1 / Layer 2 triggering of inter-cell mobility LTM for a user equipment (UE) (210, 610, 1112, 1200), configure the fourth RAN node to perform operations corresponding to the method according to any one of claims 32 to 39.

63. A computer program product (1304a, 1404a) including computer-executable instructions, which, when executed by processing circuitry (1302, 1404) of a fourth radio access network RAN ​​node (110, 220, 650, 1110, 1300, 1402) configured to facilitate Layer 1 / Layer 2 triggering of inter-cell mobility LTM for a user equipment (UE) (210, 610, 1112, 1200), configure the fourth RAN node to perform operations corresponding to the method according to any one of claims 32 to 39.

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