Method and apparatus for supporting inter-cell mobility

Abstract

The embodiment of the invention relates to a method and equipment for supporting inter-cell mobility. In accordance with some embodiments of the present disclosure, a first network node may include a transceiver configured to: transmit a first message related to a Layer 3 (L3) mobility procedure over an F1 interface to a second network node; and receiving a second message from the second network node over the F1 interface in response to the first message, wherein the second message includes at least one of: first information related to the L3 mobility procedure; or second information related to a Layer 1 (L1) or Layer 2 (L2) mobility procedure; and a processor coupled to the transceiver.

Description

Technical Field

[0001] Embodiments of the present application generally relate to wireless communication technology, and more particularly, to a method and apparatus for supporting inter-cell mobility. Background Art

[0002] Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, broadcast, etc. Wireless communication systems may employ multiple access technologies capable of supporting communication with multiple users by sharing available system resources (e.g., time, frequency, and power). Examples of wireless communication systems may include fourth generation (4G) systems (e.g., long term evolution (LTE) systems, LTE-Advanced (LTE-A) systems, or LTE-A Pro systems) and fifth generation (5G) systems (which may also be referred to as new radio (NR) systems).

[0003] Inter-cell mobility may be supported in a wireless communication system. However, detailed procedures and signaling enhancements between network nodes to support inter-cell mobility have not been discussed. Summary of the invention

[0004] The embodiments of the present application at least provide a technical solution for at least inter-cell mobility.

[0005] According to some embodiments of the present application, a first network node may include: a transceiver, which is configured to: transmit a first message related to a layer 3 (L3) mobility procedure to a second network node via an F1 interface; and receive a second message in response to the first message from the second network node via the F1 interface, wherein the second message includes at least one of the following: first information related to the L3 mobility procedure; or second information related to a layer 1 (L1) or layer 2 (L2) mobility procedure; and a processor, which is coupled to the transceiver.

[0006] In some embodiments of the present application, the first message indicates at least one of the following: the first network node's intention to trigger the L3 mobility procedure; the first SpCell that is considered as the source special cell (SpCell) associated with the L3 mobility procedure; the second network node stops triggering any L1 or L2 mobility procedures; or the second network node responds to the second SpCell to which the user equipment (UE) is currently connected. In an embodiment, the SpCell may be a primary cell (PCell) or a primary secondary cell (PSCell).

[0007] In some embodiments of the present application, the second message is a response message including the second information, and the second information indicates at least one of the following: the second SpCell to which the UE is currently connected; or a configuration related to the second SpCell.

[0008] In some embodiments of the present application, the processor is configured to: generate a handover request message including a configuration associated with the UE applied in the first network node; and remove a configuration related to a candidate SpCell or cell group to which the UE is not connected from the configuration associated with the UE included in the handover request message; and wherein the transceiver is further configured to transmit the handover request message to a third network node.

[0009] In some embodiments of the present application, the second message is a failure message, wherein the first information includes an indication that the L3 mobility procedure should be re-initiated, and the second information includes at least one of the following: an indication that the L1 or L2 mobility procedure has been triggered; an indication that the UE is no longer connected to the second network node; or the second SpCell to which the UE is currently connected.

[0010] In some embodiments of the present application, the transceiver is further configured to receive a third message from the second network node, wherein the third message indicates one of the following: the L1 or L2 mobility procedure has been triggered by the second network; and successful execution of the L1 or L2 mobility procedure.

[0011] In some embodiments of the present application, the first message indicates at least one of: an L3 mobility configuration; or a first SpCell that is considered as a source SpCell associated with the L3 mobility procedure.

[0012] In some embodiments of the present application, the processor is further configured to: generate a switching request message including a configuration associated with the UE applied in the first network node; and remove the configuration related to the candidate SpCell or cell group to which the UE is not connected from the configuration associated with the UE included in the switching request message; and the transmitter is further configured to transmit the switching request message to a third network node.

[0013] In some embodiments of the present application, the second message is a failure message including the second information, and the second information includes at least one of the following: an indication that the L1 or L2 mobility procedure has been triggered; an indication that the UE is no longer connected to the second network node; an indication that a timer associated with the L1 or L2 mobility procedure is running; or a second SpCell to which the UE is currently connected.

[0014] In some embodiments of the present application, in response to the second message, the processor is further configured to cancel the L3 mobility program, and the transceiver is further configured to transmit a handover cancellation message to a third network node, wherein the handover cancellation message includes at least one of the following: an indication indicating that the L1 or L2 mobility program has been triggered; an indication indicating that the UE is no longer connected to the second network node; or an indication indicating that a timer associated with the L1 or L2 mobility program is running.

[0015] In some embodiments of the present application, the first message includes an L3 mobility configuration associated with a source SpCell; and the L3 mobility configuration indicates a source SpCell or a cell group associated with the L3 mobility procedure, or includes a configuration related to the source SpCell and an incremental L3 mobility configuration.

[0016] In some embodiments of the present application, the processor is further configured to: generate a handover request message including a configuration associated with the UE applied in the first network node; and remove a configuration related to a candidate SpCell or cell group to which the UE is not connected from the configuration associated with the UE included in the handover request message; and wherein the transmitter is further configured to transmit the handover request message to a third network node.

[0017] In some embodiments of the present application, the second message is a failure message including the second information, and the second information includes at least one of the following: an indication that the L1 or L2 mobility procedure has been triggered; an indication that the UE is no longer connected to the second network node; or the second SpCell to which the UE is currently connected.

[0018] According to some other embodiments of the present application, a second network node may include: a transceiver, which is configured to: receive a first message related to an L3 mobility program from a first network node via an F1 interface; and transmit a second message in response to the first message to the first network node via the F1 interface, wherein the second message includes at least one of the following: first information related to the L3 mobility program; or second information related to an L1 or L2 mobility program; and a processor, which is coupled to the transceiver.

[0019] In some embodiments of the present application, the first message indicates at least one of the following: the intention of the first network node to trigger the L3 mobility procedure; the first SpCell that is regarded as the source SpCell associated with the L3 mobility procedure; the second network node stops triggering any L1 or L2 mobility procedures; or the second network node responds to the second SpCell to which the UE is currently connected.

[0020] In some embodiments of the present application, the processor is further configured to determine whether the UE is connected to the second network node, and in response to determining that the UE is connected to the second network node, the second message is a response message including the second information, and wherein the second information indicates at least one of: the second SpCell to which the UE is currently connected; or a configuration related to the second SpCell.

[0021] In some embodiments of the present application, the processor is further configured to determine whether the UE is connected to the second network node, and in response to determining that the UE is connected to the second network node, the second message is a failure message, the first information includes an indication that the L3 mobility procedure should be re-initiated, and the second information includes at least one of the following: an indication that the L1 or L2 mobility procedure has been triggered; an indication that the UE is no longer connected to the second network node; or the second SpCell to which the UE is currently connected.

[0022] In some embodiments of the present application, the transceiver is further configured to transmit a third message to the first network node, wherein the third message indicates one of: the L1 or L2 mobility procedure has been triggered by the second network; and successful execution of the L1 or L2 mobility procedure.

[0023] In some embodiments of the present application, the first message indicates at least one of: an L3 mobility configuration; or a first SpCell that is considered as a source SpCell associated with the L3 mobility procedure.

[0024] In some embodiments of the present application, the processor is configured to determine whether the L3 mobility configuration is outdated, and in response to determining that the L3 mobility configuration is outdated, the second message is a failure message including the second information, and the second information includes at least one of the following: an indication that the L1 or L2 mobility procedure has been triggered; an indication that the UE is no longer connected to the second network node; an indication that a timer associated with the L1 or L2 mobility procedure is running; or a second SpCell to which the UE is currently connected.

[0025] In some embodiments of the present application, the transceiver is further configured to transmit a third message to the first network node, wherein the third message indicates one of the following: the L1 or L2 mobility procedure has been triggered by the second network; and the successful execution of the L1 or L2 mobility procedure; and in the event that the first message is received before the third message is transmitted to the first network node, the processor is further configured to determine that the L3 mobility configuration is outdated.

[0026] In some embodiments of the present application, if a first SpCell regarded as a source SpCell associated with the L3 mobility procedure is different from a second SpCell to which the UE is currently connected, the processor is further configured to determine that the L3 mobility configuration is outdated.

[0027] In some embodiments of the present application, the processor is further configured to: start a timer after triggering the L1 or L2 mobility procedure; and in response to receiving the first message while the timer is running, determine that the L3 mobility configuration is outdated.

[0028] In some embodiments of the present application, when the second network node attempts to trigger an emergency L1 or L2 mobility procedure or the emergency L1 or L2 mobility procedure has been triggered, the processor is further configured to: determine that the L3 mobility configuration is outdated; or determine that the L3 mobility configuration is outdated in response to the L3 mobility configuration indicating that the UE will switch to a target SpCell different from the target SpCell determined by the second network node.

[0029] In some embodiments of the present application, the first message indicates an L3 mobility configuration associated with a source SpCell; and the L3 mobility configuration indicates a source SpCell or a cell group associated with the L3 mobility procedure, or includes a configuration related to the source SpCell and an incremental L3 mobility configuration.

[0030] In some embodiments of the present application, the processor is further configured to determine whether the UE is connected to the second network node, and in response to determining that the UE is connected to the second network node, the transceiver is further configured to transmit the L3 mobility configuration to the UE.

[0031] In some embodiments of the present application, the processor is further configured to determine whether the UE is connected to the second network node, and in response to determining that the UE is connected to the second network node, the second message is a failure message including the second information, and the second information includes at least one of the following: an indication that the L1 or L2 mobility procedure has been triggered; an indication that the UE is no longer connected to the second network node; or the second SpCell to which the UE is currently connected.

[0032] According to some other embodiments, a UE may include: a transceiver configured to: receive a message related to an L3 mobility procedure from a second network node, wherein the message includes: an L3 mobility configuration associated with a first SpCell as a source SpCell; and a processor coupled to the transceiver and configured to execute the L3 mobility procedure based on the L3 mobility configuration associated with the first SpCell.

[0033] In some embodiments of the present application, the first SpCell indicated in the L3 mobility configuration is different from the second SpCell to which the UE is currently connected, and the processor is further configured to apply the received L3 mobility configuration based on a configuration related to the first SpCell that has been provided to the UE but not yet applied.

[0034] According to some embodiments of the present application, a method performed by a first network node may include: transmitting a first message related to an L3 mobility procedure to a second network node via an F1 interface; and receiving a second message in response to the first message from the second network node via the F1 interface, wherein the second message includes at least one of the following: first information related to the L3 mobility procedure; or second information related to an L1 or L2 mobility procedure.

[0035] According to some other embodiments of the present application, a method performed by a second network node may include: receiving a first message related to an L3 mobility procedure from a first network node via an F1 interface; and transmitting a second message in response to the first message to the first network node via the F1 interface, wherein the second message includes at least one of the following: first information related to the L3 mobility procedure; or second information related to an L1 or L2 mobility procedure.

[0036] According to some other embodiments, a method performed by a UE may include: receiving a message related to an L3 mobility procedure from a second network node, wherein the message includes: an L3 mobility configuration associated with a first SpCell serving as a source SpCell; and performing the L3 mobility procedure based on the L3 mobility configuration associated with the first SpCell. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to describe the manner in which the advantages and features of the present application can be obtained, the description of the present application is presented by reference to specific embodiments of the present application illustrated in the accompanying drawings. These drawings depict only example embodiments of the present application and are therefore not to be considered limiting of its scope.

[0038] Figure 1 is a diagram illustrating an exemplary wireless communication system according to some embodiments of the present application.

[0039] Figure 2 An exemplary inter-gNB switching procedure according to some embodiments of the present application is described.

[0040] Figure 3 An exemplary inter-gNB switching procedure involving gNB-CU-UP change according to some embodiments of the present application is described.

[0041] Figure 4 An exemplary inter-gNB-DU mobility procedure according to some embodiments of the present application is described.

[0042] Figure 5 An exemplary flow chart for triggering L1 / L2 mobility and L3 mobility according to some embodiments of the present application is illustrated.

[0043] Figure 6 An exemplary solution for supporting coexistence of L1 / L2 mobility and L3 mobility according to some embodiments of the present application is described.

[0044] Figure 7 A flow chart illustrating an exemplary method for supporting inter-cell mobility according to some embodiments of the present application.

[0045] Figure 8 An exemplary method for performing an inter-CU L3 mobility procedure according to some embodiments of the present application is described;

[0046] Fig. 9 An exemplary method for performing an intra-CU L3 mobility procedure according to some embodiments of the present application is described;

[0047] Fig.10 An exemplary method for rejecting outdated L3 mobility configuration according to some embodiments of the present application is described.

[0048] Fig.11 An exemplary method for transmitting L3 mobility configuration according to some embodiments of the present application is described.

[0049] Fig.12 An exemplary method for rejecting L3 mobility configuration according to some embodiments of the present application is described.

[0050] Fig.13 A simplified block diagram illustrating an exemplary apparatus for supporting inter-cell mobility according to some embodiments of the present application. DETAILED DESCRIPTION

[0051] The detailed description of the accompanying drawings is intended as a description of the currently preferred embodiments of the present application, rather than being intended to represent the only form in which the present application can be practiced. It should be understood that the same or equivalent functions can be implemented by different embodiments, which are intended to be included in the spirit and scope of the present application.

[0052] Although the operations are depicted in a particular order in the accompanying drawings, those skilled in the art will readily recognize that such operations need not be performed in the particular order or sequential order shown, or that one or more operations may sometimes be skipped among all the illustrated operations to be performed in order to achieve the desired result. In addition, the accompanying drawings may schematically depict one or more example processes in the form of flow charts. However, other operations not depicted may be incorporated into the example processes schematically illustrated. For example, one or more additional operations may be performed before, after, simultaneously with, or between any illustrated operations. In some cases, multitasking and parallel processing may be advantageous.

[0053] Reference will now be made in detail to some embodiments of the present application, examples of which are illustrated in the accompanying drawings. For ease of understanding, embodiments are provided under specific network architectures and new service scenarios (e.g., 3GPP 5G (i.e., New Radio (NR)), 3GPP Long Term Evolution (LTE) Release 8, etc.). It is clear to those skilled in the art that, with the development of network architectures and new service scenarios, the embodiments in the present application are also applicable to similar technical problems; and in addition, the terms listed in the present application may be changed, which should not affect the principles of the present application.

[0054] Figure 1 is a diagram illustrating an exemplary wireless communication system 100 according to some embodiments of the present application.

[0055] like Figure 1 1, the wireless communication system 100 includes at least one BS 101 and at least one UE (eg, UE 102a and UE 102b). Figure 1One BS and two UEs are depicted in FIG. 1 , but it is contemplated that any number of BSs and UEs may be included in the wireless communication system 100 .

[0056] The wireless communication system 100 is compatible with any type of network capable of sending and receiving wireless communication signals. For example, the wireless communication system 100 is compatible with wireless communication networks, cellular telephone networks, networks based on time division multiple access (TDMA), networks based on code division multiple access (CDMA), networks based on orthogonal frequency division multiple access (OFDMA), LTE networks, networks based on 3GPP, 3GPP 5G networks, satellite communication networks, high altitude platform networks, and / or other communication networks.

[0057] BS 101 may also be referred to as an access point, an access terminal, a base station, a macro cell, a radio access network (RAN) node, a next generation (NG) radio access network (RAN) node, a Node B, an enhanced Node B (eNB), a gNB, a home Node B, a relay node or a device, or described using other terms used in the art. BS 101 is typically part of a RAN, which may include a controller communicatively coupled to BS 101.

[0058] According to some embodiments of the present application, UE 102a and UE 102b may include vehicle UE (VUE) and / or power saving UE (also referred to as power sensitive UE). Power saving UE may include vulnerable road users (VRU), public safety UE (PS-UE) and / or commercial side link UE (CS-UE) that are sensitive to power consumption. In an embodiment of the present application, VRU may include pedestrian UE (P-UE), cyclist UE, wheelchair UE or other UE that requires power saving compared to VUE. In an embodiment of the present application, UE 102a may be a power saving UE, and UE 102b may be a VUE. In another embodiment of the present application, both UE 102a and UE 102b may be VUE or power saving UE.

[0059] According to some other embodiments of the present application, UE 102a and UE 102b may include computing devices, such as desktop computers, laptop computers, personal digital assistants (PDAs), tablet computers, smart TVs (e.g., TVs connected to the Internet), set-top boxes, game consoles, security systems (including security cameras), vehicle-mounted computers, network devices (e.g., routers, switches, and modems), or the like.

[0060] According to some other embodiments of the present application, UE 102a and UE 102b may include a portable wireless communication device, a smart phone, a cellular phone, a flip phone, a device with a subscriber identification module, a personal computer, a selective call receiver, or any other device capable of sending and receiving communication signals on a wireless network.

[0061] According to some other embodiments of the present application, UE 102a and UE 102b may include wearable devices, such as smart watches, fitness bands, optical head-mounted displays, or the like.

[0062] In addition, a UE may be referred to as a subscriber unit, a mobile device, a mobile station, a user, a terminal, a mobile terminal, a wireless terminal, a fixed terminal, a subscriber station, a user terminal or a device, or described using other terms used in the art.

[0063] Figure 1 In the embodiment of the present invention, both UE 102a and UE 102b are in the coverage area of ​​BS 101, and can transmit information or data to BS 101 and receive control information or data from BS 101, for example, via LTE or NR Uu interface. In some embodiments of the present application, UE 102a and UE 102b can communicate with each other via a side link.

[0064] In a wireless communication system, a UE may move between different cells. The following embodiments illustrate several handover procedures for supporting the mobility of a UE between different cells.

[0065] Figure 2 An exemplary inter-gNB switching procedure according to some embodiments of the present application is described.

[0066] refer to Figure 2 In step 201, the source gNB may initiate a handover and send a handover request as specified in the 3GPP standard document to the target gNB via the Xn interface.

[0067] In step 202', the target gNB may perform admission control.

[0068] In step 202, the target gNB may provide a new RRC configuration as part of a handover request confirmation and transmit the handover request confirmation to the source gNB.

[0069] In step 203, the source gNB may provide the RRC configuration to the UE by forwarding the RRCReconfiguration message received in the Handover Request Acknowledgement. The RRCReconfiguration message contains at least the cell ID and all information required to access the target cell, so that the UE can access the target cell without reading system information. For some cases, the information required for contention-based and contention-free random access may be included in the RRCReconfiguration message. The information required to access the target cell may include beam-specific information (if present).

[0070] In step 204', the UE may move the RRC connection to the target gNB.

[0071] In step 204, the UE may reply to the target gNB with an RRCReconfigurationComplete message as specified in the 3GPP standard documentation.

[0072] According to some embodiments of the present application, the internal structure of the BS may be divided into a centralized unit (CU) and at least one distributed unit (DU). The CU and at least one DU are connected to each other via an interface F1 as specified in the 3GPP standard document. RRC layer functionality, service data adaptation protocol (SDAP) functionality, and packet data convergence protocol (PDCP) layer functionality are included in the CU. RLC layer functionality, media access control (MAC) layer functionality, and physical (PHY) layer functionality are included in each DU.

[0073] According to some embodiments of the present application, the CU may be divided into a CU control plane (CU-CP) unit and at least one CU user plane (CU-UP) unit. The CU-CP unit and each CU-UP unit may be connected to each other via an interface E1 as specified in the 3GPP standard document. The CU-CP unit and the DU are connected via an interface F1-C as specified in the 3GPP document. Each CU-UP unit and at least one DU are connected via an interface F1-U as specified in the 3GPP standard document.

[0074] In some embodiments of the present application, the source gNB (or source RAN) may transmit HandoverPreparationInformation as specified in the 3GPP standard document to the target gNB. In such embodiments, the message may be used to convey NRRRC information used by the target gNB during handover preparation or for UE context retrieval, such as in the case of recovery or reestablishment, including UE capability information.

[0075] In some other embodiments, the CU may transmit HandoverPreparationInformation to the DU to transfer information between the CU and the DU.

[0076] Figure 3 An exemplary inter-gNB switching procedure involving gNB-CU-UP change according to some embodiments of the present application is described.

[0077] refer to Figure 3 , in step 301, the source gNB-CU-CP may send a handover request message as specified in the 3GPP standard document to the target gNB-CU-CP. In case of conditional handover, the target gNB is considered as a candidate gNB, which is accessed by the UE only when the CHO condition is met.

[0078] In steps 302 to 304, a bearer context establishment procedure may be performed as described in clause 8.9.2 of TS 38.401.

[0079] In step 305, the target gNB-CU-CP may respond to the source gNB-CU-CP with a Handover Request Ack message as specified in the 3GPP standard documents.

[0080] In step 306, an F1 UE context modification procedure may be performed to send a handover command to the UE and instruct to stop data transmission for the UE.

[0081] In steps 307 to 308, a bearer context modification procedure (which is initiated by the gNB-CU-CP) may be performed to enable the gNB-CU-CP to retrieve the PDCP uplink (UL) or downlink (DL) status and exchange data forwarding information for the bearers.

[0082] In step 309, the source gNB-CU-CP may send a sequence number (SN) status transfer message to the target gNB-CU-CP.

[0083] In steps 310 to 311, the bearer context modification procedure may be performed as described in clause 8.9.2 of TS 38.401. If the PDCP state does not need to be preserved (e.g., fully configured), the target gNB-CU-CP does not transfer the PDCP UL / or DL ​​state carried by the SN STATUS TRANSFER message to the target gNB-CU-UP. In case of Dual Active Protocol Stack (DAP) handover or conditional handover, the counting related information carried by the Early STATUS TRANSFER message is provided to the target gNB-CU-UP.

[0084] In step 312, data forwarding from the source gNB-CU-UP to the target gNB-CU-UP may be performed.

[0085] In step 312', in case of conditional handover, when the CHO condition is met, the UE performs RACH. Upon successful access, the target gNB-DU sends an access success message to inform the target gNB-CU-CP which cell the UE has accessed.

[0086] In step 312a, in case of DAPS handover or conditional handover, the target gNB-CU-CP sends a handover success message to the source gNB-CU-CP to notify the UE that it has successfully accessed the target cell.

[0087] In step 312b, in case of DAPS handover or conditional handover, an F1 UE context modification procedure is performed to instruct to stop data transmission for the UE.

[0088] In steps 312c to 312d, in case of DAPS handover or conditional handover, a bearer context modification procedure (initiated by the gNB-CU-CP) is performed to instruct the source gNB-CU-UP to stop packet delivery and also retrieve the PDCP UL / DL status.

[0089] In step 312e, in case of DAPS handover or conditional handover, the source gNB-CU-CP sends an SN status transfer message to the target gNB-CU-CP.

[0090] In steps 312f to 312g, in case of DAPS handover or conditional handover, the bearer context modification procedure is performed to provide the PDCP UL / DL status to the target gNB-CU-UP only when the PDCP status needs to be preserved as described in TS 38.300.

[0091] In steps 313 to 315, a path switching procedure is performed to update the DL transport network layer (TNL) address information of the NG-U towards the core network.

[0092] In step 316, the target gNB-CU-CP may send a UE context release message to the source gNB-CU-CP.

[0093] In steps 317 and 319, a bearer context release procedure is performed.

[0094] In step 318, the F1 UE context release procedure is performed to release the UE context in the source gNB-DU.

[0095] Figure 4 An exemplary inter-gNB-DU mobility procedure according to some embodiments of the present application is described. Figure 4The procedures in can be used for the case when the UE moves from one gNB-DU to another gNB-DU within the same gNB-CU during NR operation.

[0096] refer to Figure 4 In step 400, uplink packets are sent from the UE and forwarded to the gNB-CU via the source gNB-DU. Downlink packets are sent from the gNB-CU and forwarded to the UE via the source gNB-DU.

[0097] In step 401, the UE may send a MeasurementReport message to the source gNB-DU.

[0098] In step 402, the source gNB-DU may send an UL RRC messaging message as specified in the 3GPP standard document to the gNB-CU to convey the received MeasurementReport message.

[0099] In step 402a, the gNB-CU may send a UE Context Modification Request message as specified in the 3GPP standard document to the source gNB-DU to query the latest configuration.

[0100] In step 402b, the source gNB-DU may respond with a UE CONTEXT MODIFICATION RESPONSE message containing complete configuration information as specified in the 3GPP standard documents.

[0101] In step 403, the gNB-CU may send a UE Context Setup Request message as specified in the 3GPP standard document to the target gNB-DU to create a UE context and establish one or more data bearers. The UE Context Setup Request message may include HandoverPreparationInformation as described above.

[0102] In step 404, the target gNB-DU may respond to the gNB-CU with a UE Context Setup Response message as specified in the 3GPP standard documents.

[0103] In step 405, the gNB-CU may send a UE CONTEXT MODIFICATION REQUEST message as specified in the 3GPP standard document to the source gNB-DU, which includes the generated RRCReconfiguration message as specified in the 3GPP standard document and indicates to stop data transmission for the UE. The source gNB-DU also sends a Downlink Data Delivery Status frame to notify the gNB-CU of the downlink data that was not successfully transmitted to the UE.

[0104] In step 406, the source gNB-DU may forward the received RRCReconfiguration message to the UE.

[0105] In step 407, the source gNB-DU may respond to the gNB-CU with a UE Context Modification Response message as specified in the 3GPP standard documents.

[0106] In step 408, a random access procedure may be performed at the target gNB-DU. The target gNB-DU sends a downlink data delivery status frame to inform the gNB-CU. Downlink packets that may include PDCP PDUs that were not successfully transmitted in the source gNB-DU are sent from the gNB-CU to the target gNB-DU.

[0107] In step 409, the UE may respond to the target gNB-DU with an RRCReconfigurationComplete message as specified in the 3GPP standard documentation.

[0108] In step 410, the target gNB-DU may send an UL RRC Messaging message to the gNB-CU to convey the received RRCReconfigurationComplete message. Downlink packets are sent to the UE. In addition, uplink packets are sent from the UE, which are forwarded to the gNB-CU by the target gNB-DU.

[0109] In step 411, the gNB-CU may send a UE Context Release Command message to the source gNB-DU as specified in the 3GPP standard document.

[0110] In step 412, the source gNB-DU may release the UE context and respond to the gNB-CU with a UE context release complete message to the source gNB-DU as specified in the 3GPP standard documents.

[0111] In addition to the above procedures, the intra-gNB-CU and intra-gNB-DU handover procedures can be used for the case where the UE moves from one cell to another within the same gNB-DU, or for the case where an intra-cell handover is performed during NR operation, and is supported by the UE context modification procedure (which is initiated by the gNB-CU) as specified in TS 38.473.

[0112] In some embodiments, when performing an intra-gNB-DU handover (inter-cell or intra-cell), the gNB-CU may provide a new UL General Packet Radio Service (GPRS) Tunneling Protocol (GTP) Tunnel Endpoint Identifier (TEID) to the gNB-DU, and the gNB-DU provides a new DL GTP TEID to the gNB-CU. The gNB-DU may continue to send UL PDCP Protocol Data Units (PDUs) to the gNB-CU using the previous UL GTP TEID until it reestablishes Radio Link Control (RLC), and thereafter begins sending using the new UL GTP TEID. The gNB-CU may continue to send DL PDCP PDUs to the gNB-DU using the previous DL GTP TEID until it performs PDCP reestablishment or PDCP data recovery, and thereafter begins sending using the new DL GTP TEID.

[0113] In 3GPP Release 18, inter-cell L1 or L2 mobility may be supported. L1 or L2 mobility may be triggered by a DU of a BS based on L1 (e.g., physical layer) measurements. In some embodiments, when a DU triggers L1 or L2 mobility, the DU may transmit an L1 or L2 mobility command via a media access control (MAC) control element (CE) or downlink control information (DCI). Therefore, triggering L1 or L2 mobility means that the DU has transmitted an L1 or L2 mobility command to the UE. The successful execution of L1 or L2 mobility means that the UE has successfully switched to a target cell. In some embodiments of the present application, L1 or L2 mobility may also be referred to as an L1 or L2 mobility procedure, L1 / L2 mobility, L1 / L2 mobility procedure, L1 or L2 handover, L1 or L2 handover procedure, L1 / L2 handover, or L1 / L2 handover procedure.

[0114] In some embodiments of the present application, before receiving the L1 or L2 mobility command from the DU, the UE may receive a configuration of multiple candidate SPCells or multiple candidate cell groups for L1 or L2 mobility. In some embodiments of the present application, after performing the L1 or L2 mobility triggered by the DU, the UE does not release the configuration of the multiple candidate SPcells or multiple candidate cell groups. For example, the multiple candidate SpCells may include at least one of the following: one or more primary cells (PCells) or one or more primary secondary cells (PSCells).

[0115] Compared with L1 or L2 mobility, L3 mobility can be triggered by the CU of the BS based on L3 measurement results. After triggering L3 mobility, the CU can generate an L3 mobility configuration (e.g., RRC reconfiguration) for the UE, and transmit an F1 AP message conveying the L3 mobility configuration (e.g., RRC reconfiguration) for the UE to the DU. Then, the DU will transmit an RRC reconfiguration message related to L3 mobility to the UE over the air interface. The RRC reconfiguration may include a full configuration or an incremental configuration associated with L3 mobility. In some embodiments of the present application, L3 mobility may also be referred to as an L3 mobility procedure, an L3 handover, or an L3 handover procedure.

[0116] Assuming that L1 or L2 mobility has been configured or enabled (eg, multiple candidate SPcells or cell groups for L1 or L2 mobility have been configured for both UE and DU), whether the CU can still trigger L3 mobility becomes an issue and needs to be resolved.

[0117] According to some embodiments of the present application, when L1 or L2 mobility is configured or enabled, the CU cannot trigger L3 mobility. In such embodiments, unnecessary restrictions may be defined for network implementation, or the CU may be required to first deconfigure the current L1 or L2 mobility configuration before triggering L3 mobility, which may delay L3 mobility execution and may cause radio link failures.

[0118] According to some embodiments of the present application, when L1 or L2 mobility has been configured or enabled, the CU may trigger L3 mobility. In such an embodiment, there may be a situation where the CU triggers L3 mobility without knowing that the DU has triggered or is about to trigger L1 or L2 mobility. In this case, L1 or L2 mobility and L3 mobility may give different instructions, for example, giving different target SPcells to which the UE will switch.

[0119] Figure 5 An exemplary flow chart for triggering L1 / L2 mobility and L3 mobility according to some embodiments of the present application is illustrated.

[0120] refer to Figure 5 , the UE is initially connected to SpCell#1. In step 501, the DU may attempt to trigger L1 or L2 mobility. Then, in step 502, the DU may transmit an L1 or L2 mobility command to the UE (e.g., via DCI or MAC CE) to trigger intra-DU L1 or L2 mobility from SpCell#1 to SpCell#2.

[0121] In step 503, the CU may attempt to trigger L3 mobility. Step 503 may occur before, after, or simultaneously with step 502.

[0122] Next, in step 504, the CU may transmit a message (e.g., a UE context modification request message containing an RRC reconfiguration related to L3 mobility as specified in the 3GPP standard document) to the DU to trigger L3 mobility from SpCell#1 to SpCell#3. The RRC reconfiguration may include a full configuration or an incremental configuration associated with L3 mobility.

[0123] In step 505, the DU may transmit a message to the CU to notify that L1 or L2 mobility is triggered.

[0124] exist Figure 5 In FIG. 4 , it can be seen that L3 mobility is triggered before the CU is notified of the triggered L1 or L2 mobility. That is, the CU triggers L3 mobility without knowing that the DU has triggered or is about to trigger L1 or L2 mobility, which may cause some problems.

[0125] For example, if the L3 mobility configuration (e.g., RRC reconfiguration) in step 504 is associated with SpCell#1 as the source SpCell, the L3 mobility configuration may be outdated if the UE has switched to SpCell#2 after step 202. The RRC reconfiguration may include a full configuration or an incremental configuration associated with the L3 mobility. In such an example, it is necessary to solve how to avoid transmitting such an outdated L3 mobility configuration to the UE in order to avoid any confusion or complexity on the UE side.

[0126] In another example, if the L3 mobility configuration (e.g., RRC reconfiguration) in step 504 is associated with SpCell#1 as the source SpCell, the L3 mobility configuration will be outdated if the UE has switched to SpCell#2 after step 202. The RRC reconfiguration may include a full configuration or an incremental configuration associated with L3 mobility. However, if the UE does not release the configuration of the candidate SpCell for L1 or L2 mobility, the UE may still apply the L3 mobility configuration based on the stored SpCell#1 configuration. In this example, it is necessary to solve how to transmit such an outdated L3 mobility configuration to the UE and let the UE apply the outdated L3 mobility configuration.

[0127] In view of the above, embodiments of the present application propose solutions for supporting inter-cell mobility. For example, embodiments of the present application propose solutions for detailed procedures and related signaling for at least solving the above problems, thereby supporting the coexistence of inter-cell L1 or L2 mobility and L3 mobility. More details about embodiments of the present application will be described in the following text in conjunction with the accompanying drawings.

[0128] Figure 6An exemplary solution for supporting coexistence of L1 / L2 mobility and L3 mobility according to some embodiments of the present application is described.

[0129] refer to Figure 6 , in the case where the CU cannot trigger L3 mobility when L1 or L2 mobility is already configured or enabled, solution #0 may be used. For example, solution #0 may include requiring the CU to first deconfigure the current L1 or L2 mobility configuration before triggering L3 mobility.

[0130] In the case where the CU can trigger L3 mobility when L1 or L2 mobility is already configured or enabled and the BS cannot transmit an outdated L3 mobility configuration to the UE, two solutions may be used, such as Solution #1 and Solution #2.

[0131] Solution #1 can be summarized as follows: before the CU triggers L3 mobility, the CU coordinates with the DU to confirm the current SpCell and stop possible L1 or L2 mobility triggered by the gNB DU to avoid outdated L3 mobility configuration. The specific operations in Solution #1 can be described in Example 1 below.

[0132] Solution #2 can be summarized as follows: When the DU receives a message containing an L3 mobility configuration triggered by the CU, the DU can determine whether the L3 mobility configuration is valid (or outdated), or whether it conflicts with the L1 or L2 mobility that has been or will be triggered by the gNB DU, and can reject or fail the L3 mobility procedure. The specific operations in Solution #2 can be described in Example 2 below.

[0133] Scheme #3 may be used in the case where the CU may trigger L3 mobility when L1 or L2 mobility is already configured or enabled and the BS may transmit an outdated L3 mobility configuration to the UE.

[0134] Solution #3 can be summarized as follows: L3 mobility configuration (e.g., RRC reconfiguration) may indicate a related source SpCell (e.g., SpCell #1). RRC reconfiguration may include a full configuration or an incremental configuration associated with L3 mobility. After receiving an outdated L3 mobility configuration from the BS, the UE may apply the L3 mobility configuration based on the saved configuration associated with SpCell #1 and perform L3 mobility. Alternatively, the configuration associated with the source SpCell #1 may be provided together with the incremental L3 mobility configuration (e.g., RRC reconfiguration). The specific operations in Solution #3 may be described in Embodiment 3 below.

[0135] Figure 7 A flow chart illustrating an exemplary method for supporting inter-cell mobility according to some embodiments of the present application. Figure 7The method described in the embodiment may be performed by two network nodes (e.g., a first network node and a second network node). In some other embodiments of the present application, the first network node may be a CU of a BS (e.g., a gNB-CU) or other devices with similar functions. The second network node may be a DU of a BS (e.g., a gNB-DU) or other devices with similar functions. Although the method is described at the system level, it should be understood by those skilled in the art that the methods implemented in the two network nodes may be implemented separately and incorporated into other devices with similar functions.

[0136] exist Figure 7 In an embodiment, L1 or L2 mobility has been configured or enabled at the BS (e.g., including both CU and DU) and the UE. In an embodiment, before receiving the L1 or L2 mobility command from the second network node, the configuration of multiple candidate SPcells or multiple candidate cell groups may be provided to the UE. The SpCell may be a PCell or a PSCell. The second network node may trigger the L1 or L2 mobility based on the L1 measurement report from the UE. The L1 or L2 mobility command may be transmitted to the UE via a MAC CE or a DCI. Before knowing that the L1 or L2 mobility occurs, the first network node may trigger the L3 mobility based on the L3 measurement report from the UE.

[0137] refer to Figure 7 In step 701, a first network node (eg, CU) may transmit a first message related to an L3 mobility procedure to a second network node (eg, DU) through an F1 interface. Thus, in step 702, the second network node may receive the first message related to an L3 mobility procedure.

[0138] In step 703, the second network node may transmit a second message in response to the first message to the first network node through the F1 interface. The second message may include at least one of the following: first information related to the L3 mobility procedure; or second information related to the L1 or L2 mobility procedure. Therefore, in step 704, the first network node may receive the second message from the first network node.

[0139] As described above, in different solutions, the specific operations in steps 701 to 704 may be different. The following embodiments may describe the specific operations of different solutions.

[0140] Example 1

[0141] In embodiment 1, the first network node may coordinate with the second network node before triggering the L3 mobility procedure to avoid outdated L3 mobility configuration. In other words, if L1 or L2 mobility has been configured or enabled, when the first network node wants (or attempts) to trigger the L3 mobility procedure based on the L3 measurement report from the UE, the first network node first coordinates with the second network node before actually triggering the L3 mobility procedure to avoid outdated L3 mobility configuration (e.g., RRC reconfiguration). The RRC reconfiguration may include a full configuration or an incremental configuration associated with the L3 mobility procedure.

[0142] Specifically, in Embodiment 1, the first message in step 701 and step 702 may indicate at least one of the following:

[0143] The first network node's intention to trigger an L3 mobility procedure (e.g., represented as content #1);

[0144] The first SpCell that is considered as the source SpCell associated with the L3 mobility procedure (e.g., represented as content #2);

[0145] The second network stops triggering any L1 or L2 mobility procedures (e.g., as represented by content #3); or

[0146] The second network node responds with the SpCell to which the UE is currently connected (eg, represented as content #4).

[0147] In an embodiment, the first message may be a new F1 Application Protocol (AP) message. In another embodiment, the first message may be a UE Context Modification Request message as specified in a 3GPP standard document.

[0148] In an embodiment, the above content in the first message may be indicated by an indicator. For example, the first message may include an indicator indicating at least one of content #1 to #4. In another embodiment, each content may be indicated by a corresponding indicator in the message. For example, the message may include four indicators indicating content #1 to #4, respectively.

[0149] In an embodiment, the first SpCell may be indicated by a physical cell identifier (PCI), a cell global identifier (CGI), or an index for L1 or L2 mobility configuration contained in the first message that may be understood by the second network node.

[0150] After receiving the first message, the second network node may determine whether the UE is still connected to the second network node, because the UE may have switched to another network node (eg, another DU) at that time. Based on the determination, embodiment 1 may further include two embodiments, eg, embodiment 1.1 and embodiment 1.2.

[0151] Example 1.1

[0152] In embodiment 1.1, the second network node may determine that the UE is connected to the second network node, and thus the second message in steps 703 and 704 may be an F1 AP message, such as a response message (e.g., a UE context modification response message as specified in a 3GPP standard document). In such an embodiment, the second message may indicate at least one of the following:

[0153] The second SpCell to which the UE is currently connected; or

[0154] Configuration related to the second SpCell.

[0155] The above content may be the second information related to the L1 or L2 mobility procedure. In an embodiment, the second SpCell may be indicated by a PCI, a CGI or an index for L1 or L2 mobility configuration included in the second message and understandable by the first network node.

[0156] In some instances, when the L1 or L2 mobility procedure has been triggered by the second network node before receiving the second message (e.g., the second network node has transmitted an L1 or L2 mobility command to the UE), the second SpCell indicated by the second message may be the target SpCell indicated by the L1 or L2 mobility command to which the UE is to switch or has switched.

[0157] In some examples, if the second SpCell to which the UE is currently connected is the same as the first SpCell that is considered as the source SpCell associated with the L3 mobility procedure, the response message may not include the second SpCell to which the UE is currently connected and the configuration related to the second SpCell.

[0158] In some examples, after receiving the second message, the second network node may temporarily stop triggering any L1 / L2 mobility.

[0159] In embodiment 1.1, after receiving the second message from the second network node, the first network node may continue to trigger the L3 mobility procedure. In the case where the second SpCell to which the UE is currently connected is the same as the first SpCell regarded as the source SpCell associated with the L3 mobility procedure, the L3 mobility procedure may be associated with the first SpCell as the source SpCell; if the second SpCell is different from the first SpCell, the L3 mobility procedure may be associated with the second SpCell as the source SpCell.

[0160] In an example, the L3 mobility procedure may be an intra-CU L3 mobility procedure. In such an embodiment, the first network node may transmit an L3 mobility configuration (e.g., an RRC reconfiguration as specified in a 3GPP standard document) to the DU. The RRC reconfiguration may include a full configuration or an incremental configuration associated with the L3 mobility procedure. As described above, the L3 mobility configuration may be associated with a first SpCell or a second SpCell as a source SpCell. The L3 mobility configuration may include a configuration for performing the L3 mobility procedure as specified in a 3GPP standard document. The DU may then transmit the L3 mobility configuration to the UE. For example, the first network node may generate an RRC reconfiguration message including the L3 mobility configuration, and transmit the RRC reconfiguration message to the DU in a UE context modification request message. The DU may then transmit the RRC reconfiguration message to the UE. After receiving the RRC reconfiguration message, the UE may perform the L3 mobility procedure based on the L3 mobility configuration.

[0161] In another example, the L3 mobility procedure may be an inter-CU L3 mobility procedure. In such an embodiment, the first network node may generate a handover request message including a configuration associated with the UE applied in the first network node. The first network node may remove the configuration related to the candidate SpCell or cell group to which the UE is not connected from the configuration associated with the UE included in the handover request message. Then, the first network node may transmit the handover request message to a third network node (e.g., another CU to which the UE can be switched). The handover request message may include a configuration related to the SpCell or cell group to which the UE is currently connected. Then, the first network node may receive a handover request confirmation message from the third network node.

[0162] Thereafter, the first network node may transmit an L3 mobility configuration (e.g., an RRC reconfiguration as specified in a 3GPP standard document) to the DU. The RRC reconfiguration may include a full configuration or an incremental configuration associated with the L3 mobility procedure. As described above, the L3 mobility configuration may be associated with the first SpCell or the second SpCell as the source SpCell. Then, the DU may transmit the L3 mobility configuration (e.g., an RRC reconfiguration) to the UE. For example, the first network node may generate an RRC reconfiguration message including the L3 mobility configuration, and transmit the RRC reconfiguration message to the DU in a UE context modification request message. Then, the DU may transmit the RRC reconfiguration message to the UE. After receiving the RRC reconfiguration message, the UE may perform the L3 mobility procedure based on the L3 mobility configuration.

[0163] Example 1.2

[0164] In embodiment 1.2, the second network node may determine that the UE is not connected to the second network node. That is, due to the triggered L1 or L2 mobility, the UE has been handed over to another network node (e.g., another DU). In such an embodiment, the second message may be an F1 AP message, such as a failure message (e.g., a UE context modification failure message as specified in a 3GPP standard document). The second message may include first information related to an L3 mobility procedure and second information related to an L1 or L2 mobility procedure. For example, the second message may include at least one of the following:

[0165] An indication that an L1 or L2 mobility procedure has been triggered (e.g., a cause value);

[0166] an indication (e.g. a cause value) indicating that the UE is no longer connected to the second network node;

[0167] An indication (e.g., a cause value) indicating that the L3 mobility procedure should be re-initiated; or

[0168] The second SpCell to which the UE is currently connected.

[0169] In this example, the first information may include at least one of an indication indicating that the L3 mobility procedure should be re-initiated or a field in the second message indicating that the second message is a failure message. The second information may include at least one of: an indication indicating that the L1 or L2 mobility procedure has been triggered; an indication indicating that the UE is no longer connected to the second network node; and a second SpCell to which the UE is currently connected.

[0170] In an embodiment, the second SpCell may be indicated by a PCI, a CGI, or an index for L1 or L2 mobility configuration contained in the second message that may be understood by the first network node.

[0171] In some embodiments of embodiment 1.2, after receiving the second message, the first network node may repeat the above steps in embodiment 1 to coordinate with another network node (e.g., another DU), where the first network node believes that the UE is connected to the other network node. For example, the first network node may identify the other network node (e.g., the second SpCell to which the UE is currently connected) based on the second message. In another example, the first network node may identify the other network node based on a notification message from the second network node or from another network node. Alternatively or additionally, after receiving the second message, the first network node may stop the "to-be-triggered" L3 mobility procedure.

[0172] The above embodiment describes the transmission of the first message and the second message. Alternatively or additionally, in some cases of embodiment 1, if the second network node triggers the L1 or L2 mobility procedure, the second network node may transmit a third message to the first network node. The third message indicates one of the following:

[0173] the L1 or L2 mobility procedure has been triggered by the second network node (in other words, triggering of the L1 or L2 mobility procedure), which means that the second network node has transmitted a L1 or L2 mobility command to the UE; and

[0174] Successful execution of the L1 or L2 mobility procedure, which means that the UE has successfully handed over to the target SpCell indicated by the L1 or L2 mobility command.

[0175] For example, the third message may be a new F1 AP message, or may be a UE context modification required message as specified in the 3GPP standard document. In an embodiment, the third message may indicate the SpCell (e.g., which may be represented by a PCI, CGI or index for L1 or L2 mobility configuration understood by the first network node) to which the UE is switched (if the third message indicates the triggering of the L1 or L2 mobility procedure) or has been connected (if the third message indicates the successful execution of the L1 or L2 mobility procedure).

[0176] Figure 8 An exemplary method for performing an inter-CU L3 mobility procedure according to some embodiments of the present application is described.

[0177] refer to Figure 8 , in step 801, it is assumed that L1 or L2 mobility has been configured or enabled.

[0178] In step 802, the source DU may attempt to trigger intra-DU L1 or L2 mobility based on the L1 measurement report. In step 803, the source DU may transmit an L1 or L2 mobility command to the UE via DCI or MAC CE, instructing the UE to switch from SpCell#1 to SpCell#2. Steps 802 and 803 are two optional steps and may not occur in other embodiments.

[0179] In step 804, the source CU wishes (or attempts) to trigger an L3 mobility procedure based on the L3 measurement report. In step 805, the source CU may transmit a first message (eg, a UE context modification request message) containing the information described in Embodiment 1 to the source DU.

[0180] In step 806, if L1 or L2 mobility does not occur (i.e., steps 802 and 803 do not occur) or if intra-DU L1 or L2 mobility has occurred (i.e., steps 802 and 803 occur) and the source DU has not informed the source CU, the source DU sends a second message (e.g., UE context modification response message) back to the source CU. The second message may contain information as described in embodiment 1.1 of embodiment 1. In step 807, the source DU may also temporarily stop triggering any L1 or L2 mobility.

[0181] In some embodiments, if steps 802 and 803 occur, then in step 808, the source DU may also transmit a third message as described above to inform the source CU of the triggering of the L1 or L2 mobility procedure or the successful execution of the L1 or L2 mobility procedure. Step 808 is an optional step and may not occur in some other embodiments.

[0182] In step 809, if the source CU wants to trigger the inter-CU L3 mobility procedure, it may transmit a handover request message to the target CU in step 810. In step 811, the target CU may transmit a handover request confirmation to the source CU. In step 812, the source CU may transmit an L3 mobility configuration (e.g., RRC reconfiguration) to the source DU, and then the source DU may transmit the L3 mobility configuration to the UE. The RRC reconfiguration may include a full configuration or an incremental configuration associated with the L3 mobility procedure. After receiving the L3 mobility configuration, the UE may perform the L3 mobility procedure based on the L3 mobility configuration.

[0183] Fig. 9 An exemplary method for performing an intra-CU L3 mobility procedure according to some embodiments of the present application is described.

[0184] refer to Fig. 9 , in step 801, it is assumed that L1 or L2 mobility has been configured or enabled.

[0185] In step 902, the source DU may attempt to trigger inter-DU L1 or L2 mobility based on the L1 measurement report. In step 803, the source DU may transmit an L1 or L2 mobility command to the UE via DCI or MAC CE, instructing the UE to switch from SpCell#1 (belonging to the source DU) to SpCell#2 (belonging to the target DU).

[0186] In step 904, the source CU wishes (or attempts) to trigger an L3 mobility procedure based on the L3 measurement report. In step 905, the source CU may transmit a first message (eg, a UE context modification request message) containing the information described in embodiment 1 to the source DU.

[0187] Since the UE is no longer connected to the source DU, in step 906, the source DU may transmit a second message (eg, a UE context modification failure message) containing the information as described in embodiment 1.2 of embodiment 1 to the source DU.

[0188] In step 907, after the UE receives the L1 or L2 mobility command, the UE may switch to SpCell#2. After successfully performing the L1 or L2 mobility procedure, in step 908, the target DU may inform the source CU of the successful execution of the L1 or L2 mobility procedure.

[0189] Example 2

[0190] In embodiment 2, if L1 or L2 mobility has been configured or enabled, the first network node may trigger an L3 mobility procedure based on an L3 measurement report, and attempt to transmit a possibly "outdated" L3 mobility configuration (e.g., RRC reconfiguration) to the UE via a second network node, the second network node may determine whether the L3 mobility configuration is "outdated", and if so, reject or fail the L3 mobility procedure. The RRC reconfiguration may include a full configuration or an incremental configuration associated with the L3 mobility procedure.

[0191] For example, if the L3 mobility configuration considers the first SpCell as the source SpCell and the UE has switched from the first SpCell to the second SpCell or is about to switch from the first SpCell to the second SpCell due to L1 or L2 mobility, then the L3 mobility configuration generated by the first network node is considered "outdated".

[0192] In some cases of embodiment 2, when the first network node triggers the intra-BS (e.g., intra-CU) L3 mobility procedure, the first network mode may transmit a first message to the second network node. The first message may be a new F1 application protocol (AP) message. In another embodiment, the first message may be a UE context modification request message as specified in a 3GPP standard document. For example, the first message may indicate at least one of the following:

[0193] L3 mobility configuration (e.g., RRC reconfiguration). RRC reconfiguration may include full configuration or incremental configuration associated with L3 mobility procedures; or

[0194] • A first SpCell that is considered as a source SpCell associated with the L3 mobility procedure. For example, the first SpCell may be indicated by a PCI, CGI or an index for L1 or L2 mobility configuration contained in the first message that can be understood by the second network node.

[0195] In some other cases of embodiment 2, when the first network node triggers the inter-CU L3 mobility procedure, the first network node may generate a handover request message including a configuration associated with the UE applied to the first network node. The first network node may remove the configuration related to the candidate SpCell or cell group to which the UE is not connected from the configuration associated with the UE included in the handover request message. Then, the first network node may transmit the handover request message to a third network node (e.g., another CU to which the UE can be handed over). The handover request message may include a configuration related to the first SpCell or cell group to which the UE is currently connected.

[0196] After receiving the handover request confirmation message from the target CU, the first network node may transmit a first message to the second network node. The first message may be a new F1 application protocol (AP) message. In another embodiment, the first message may be a UE context modification request message as specified in the 3GPP standard document. For example, the first message may indicate at least one of the following:

[0197] L3 mobility configuration (e.g., RRC reconfiguration). RRC reconfiguration may include full configuration or incremental configuration associated with L3 mobility procedures; or

[0198] • A first SpCell that is considered as a source SpCell associated with the L3 mobility procedure. For example, the first SpCell may be indicated by a PCI, CGI or an index for L1 or L2 mobility configuration included in the first message that can be understood by the second network node.

[0199] After receiving the first message, the second network node may determine whether the L3 mobility configuration included in the first message is outdated (or invalid). The following embodiments may provide various methods for determining whether the L3 mobility configuration included in the first message is outdated.

[0200] Example 2.1

[0201] In embodiment 2.1, if the second network node triggers the L1 or L2 mobility procedure, the second network node may transmit a third message to the first network node. The third message indicates one of the following:

[0202] the L1 or L2 mobility procedure has been triggered by the second network node (in other words, triggering of the L1 or L2 mobility procedure), which means that the second network node has transmitted a L1 or L2 mobility command to the UE; and

[0203] Successful execution of the L1 or L2 mobility procedure, which means that the UE has successfully handed over to the target SpCell indicated by the L1 or L2 mobility command.

[0204] For example, the third message may be a new F1 AP message, or may be a UE context modification required message as specified in the 3GPP standard document. In an embodiment, the third message may indicate the SpCell (e.g., which may be represented by a PCI, CGI or index for L1 or L2 mobility configuration understood by the first network node) to which the UE is switched (if the third message indicates the triggering of the L1 or L2 mobility procedure) or has been connected (if the third message indicates the successful execution of the L1 or L2 mobility procedure).

[0205] In embodiment 2.1, in case the first message is received before the third message is transmitted to the first network node, the second network node may determine that the L3 mobility configuration is outdated.

[0206] Example 2.2

[0207] In embodiment 2.2, in the case where the first SpCell regarded as the source SpCell associated with the L3 mobility procedure is different from the second SpCell to which the UE is currently connected, the second network node may determine that the L3 mobility configuration is outdated.

[0208] Example 2.3

[0209] In embodiment 2.3, after triggering the L1 or L2 mobility procedure, the second network node may start a timer. For example, the timer may have a value denoted as T mobility In response to receiving the first message while the timer is running, the second network node may determine that the L3 mobility configuration is out of date.

[0210] Example 2.4

[0211] In embodiment 2.4, the second network node may attempt to trigger an emergency L1 or L2 mobility procedure (e.g., a radio link failure would otherwise occur), or the emergency L1 or L2 mobility procedure has been triggered. In this case, the second network node may receive the first message. The second network node may then determine that the L3 mobility configuration is outdated, or may determine that the L3 mobility configuration is outdated in response to the L3 mobility configuration indicating that the UE is to switch to a target SpCell that is different from the target SpCell determined by the second network node in the emergency L1 or L2 mobility procedure.

[0212] Based on the above embodiment, the second network node may determine that the L3 mobility configuration is outdated. Then, the second network node may transmit a second message to the first network node. The second message may be an F1 AP message, for example, a failure message (for example, a UE context modification failure message as specified in a 3GPP standard document). The second message may include first information related to an L3 mobility procedure and second information related to an L1 or L2 mobility procedure. For example, the first information may include a field in the second message indicating that the second message is a failure message. The second information may include at least one of the following:

[0213] An indication that an L1 or L2 mobility procedure has been triggered (e.g., a cause value);

[0214] an indication (e.g. a cause value) indicating that the UE is no longer connected to the second network node;

[0215] an indication (e.g. a cause value) that a timer associated with an L1 or L2 mobility procedure is running; or

[0216] The second SpCell to which the UE is currently connected. For example, the second SpCell may be indicated by a PCI, a CGI or an index for L1 or L2 mobility configuration contained in the second message that can be understood by the first network node.

[0217] In some embodiments, in the case where the L3 mobility procedure triggered by the first network node is an inter-CU L3 mobility procedure, in response to receiving the second message, the first network node may cancel the L3 mobility procedure and transmit a handover cancellation message to the third network node. The handover cancellation message includes at least one of the following:

[0218] An indication that an L1 or L2 mobility procedure has been triggered (e.g., a cause value);

[0219] an indication (e.g. a cause value) indicating that the UE is no longer connected to the second network node; or

[0220] An indication that a timer associated with an L1 or L2 mobility procedure is running (e.g., a cause value)

[0221] Fig.10 An exemplary method for rejecting outdated L3 mobility configuration according to some embodiments of the present application is described.

[0222] refer to Fig.10 , in step 1001, it is assumed that L1 or L2 mobility has been configured or enabled.

[0223] In step 1002, the source CU may attempt to trigger an inter-CU L3 mobility procedure based on an L3 measurement report.

[0224] In step 1003, the source CU may transmit a switching request message including the information described in Embodiment 2 to the target CU. In step 1004, the source CU may receive a switching request confirmation message from the target CU.

[0225] In step 1005, the source DU may attempt to trigger an intra-DU or inter-DU L1 or L2 mobility procedure based on the L1 measurement report. In step 1006, the source DU may transmit an L1 or L2 mobility command to the UE via DCI or MAC CE, instructing the UE to switch from SpCell#1 to SpCell#2.

[0226] Before knowing the L1 or L2 mobility procedure, the source CU may transmit a first message (eg, UE context modification request message) to the source DU in step 1007. The first message may include L3 mobility configuration and the source SpCell, ie, SpCell#1.

[0227] In step 1008, the source DU may determine that the L3 mobility configuration received from step 1007 is outdated. Next, in step 1009, the source DU may transmit a second message (eg, UE context modification failure message) including the information described in Embodiment 2 to the source CU.

[0228] In the case where the inter-CU switching has been prepared in steps 1003 and 1004 , in step 1010 , the source CU may transmit a switching cancel message including the information described in Embodiment 2 to the target CU.

[0229] In some cases, in step 1011 , the source DU may also transmit a third message as described in Embodiment 2.1 to the source CU to indicate the triggering of the L1 or L2 mobility procedure or the successful execution of the L1 or L2 mobility procedure.

[0230] Example 3

[0231] In embodiment 3, "outdated" L3 mobility configurations may still be transmitted to and applied by the UE. The motivation for embodiment 3 is that in some cases, L3 mobility decisions may be made based on long time scale measurements, which may be considered to have higher priority than L1 or L2 mobility and may therefore be applicable to both the UE and the network.

[0232] In Embodiment 3, the UE may not release the configuration related to the candidate SpCell or cell group after performing L1 or L2 mobility. Therefore, when the UE has switched from SpCell#1 to SpCell#2 due to L1 or L2 mobility and then receives an "outdated" L3 mobility configuration that considers SpCell#1 as the source SpCell, the UE will still apply the incremental configuration based on the saved SpCell#1 configuration.

[0233] In some cases of embodiment 3, when the first network node triggers the intra-BS (e.g., intra-CU) L3 mobility procedure, the first network mode may transmit a first message to the second network node. The first message may be a new F1 application protocol (AP) message. In another embodiment, the first message may be a UE context modification request message as specified in the 3GPP standard document.

[0234] The first message may include an L3 mobility configuration associated with the source SpCell. In an example, the L3 mobility configuration associated with the source SpCell may be an L3 mobility configuration (e.g., RRC reconfiguration) indicating the source SpCell (e.g., the source SpCell may be indicated by a PCI, CGI, or an index for L1 or L2 mobility configuration understandable by the UE) or a cell group associated with the L3 mobility procedure. The RRC reconfiguration may include a full configuration or an incremental configuration associated with the L3 mobility procedure. In another example, the L3 mobility configuration associated with the source SpCell may include a configuration associated with the source SpCell and an incremental L3 mobility configuration.

[0235] In some other cases of embodiment 3, when the first network node triggers the inter-CU (e.g., inter-CU) L3 mobility procedure, the first network node may generate a handover request message including a configuration associated with the UE applied to the first network node. The first network node may remove the configuration related to the candidate SpCell or cell group to which the UE is not connected from the configuration associated with the UE included in the handover request message. Then, the first network node may transmit the handover request message to a third network node (e.g., another CU to which the UE can be switched). The handover request message may include a configuration related to the first SpCell or cell group to which the UE is currently connected.

[0236] After receiving the handover request confirmation message from the target CU, the first network node may transmit a first message to the second network node. The first message may be a new F1 application protocol (AP) message. In another embodiment, the first message may be a UE context modification request message as specified in the 3GPP standard document.

[0237] The first message may include an L3 mobility configuration associated with the source SpCell. In an example, the L3 mobility configuration associated with the source SpCell may be an L3 mobility configuration (e.g., RRC reconfiguration) indicating the source SpCell (e.g., the source SpCell may be indicated by a PCI, CGI, or an index for L1 or L2 mobility configuration understandable by the UE) or a cell group associated with the L3 mobility procedure. The RRC reconfiguration may include a full configuration or an incremental configuration associated with the L3 mobility procedure. In another example, the L3 mobility configuration associated with the source SpCell may include a configuration associated with the source SpCell and an incremental L3 mobility configuration.

[0238] After receiving the first message, the second network node may determine whether the UE is still connected to the second network node, because the UE may have switched to another network node (eg, another DU) at that time. Based on the determination, Embodiment 3 may further include two embodiments, eg, Embodiment 3.1 and Embodiment 3.2.

[0239] Example 3.1

[0240] In embodiment 3.1, the second network node may determine that the UE is connected to the second network node. Then, the second network node may transmit a second message to the first network node. The second message may be an F1 AP message, for example, a response message (e.g., a UE context modification response message as specified in a 3GPP standard document). In such an embodiment, the second message may include information related to the L3 mobility procedure.

[0241] In this embodiment, regardless of whether the L3 mobility configuration included in the first message is outdated (i.e., the second network node is not sure whether the L3 mobility configuration included in the first message is outdated), the second network node can transmit the L3 mobility configuration associated with the source SpCell included in the first message to the UE.

[0242] After receiving the L3 mobility configuration associated with the source SpCell, the UE may perform an L3 mobility procedure based on the L3 mobility configuration associated with the source SpCell. In some embodiments, the source SpCell may be the same as the second SpCell to which the UE is currently connected. In some other embodiments, the source SpCell may be different from the second SpCell to which the UE is currently connected. For example, even if the UE is not connected to the source SpCell, the UE may apply the received L3 mobility configuration (e.g., incremental L3 mobility configuration) based on a configuration related to the source SpCell that has been provided to the UE but not yet applied.

[0243] Example 3.2

[0244] In embodiment 3.2, the second network node may determine that the UE is not connected to the second network node. That is, due to the triggered L1 or L2 mobility, the UE has been handed over to another network node (e.g., another DU). In such an embodiment, the second message may be an F1 AP message, for example, a failure message (e.g., a UE context modification failure message as specified in a 3GPP standard document). The second message may include first information related to an L3 mobility procedure and second information related to an L1 or L2 mobility procedure. For example, the first information may include a field in the second message indicating that the second message is a failure message. The second information may include at least one of the following:

[0245] An indication that an L1 or L2 mobility procedure has been triggered (e.g., a cause value);

[0246] an indication (e.g. a cause value) indicating that the UE is no longer connected to the second network node;

[0247] The second SpCell to which the UE is currently connected (eg, the second SpCell may be indicated by a PCI, CGI or index for L1 or L2 mobility configuration contained in the second message that may be understood by the first network node).

[0248] In some embodiments of embodiment 3.2, after receiving the second message, the first network node may repeat the above steps in embodiment 3 to coordinate with another network node (e.g., another DU), where the first network node believes that the UE is connected to the other network node. For example, the first network node may identify the other network node (e.g., the second SpCell to which the UE is currently connected) based on the second message. In another example, the first network node may identify the other network node based on a notification message from the second network node or from another network node. Alternatively or additionally, after receiving the second message, the first network node may stop the "to-be-triggered" L3 mobility procedure.

[0249] Fig.11 An exemplary method for transmitting L3 mobility configuration according to some embodiments of the present application is described.

[0250] refer to Fig.11 , in step 1101, it is assumed that L1 or L2 mobility has been configured or enabled.

[0251] In step 1102, the source CU may attempt to trigger an inter-CU L3 mobility procedure based on the L3 measurement report.

[0252] In step 1103, the source CU may transmit a switching request message including the information described in Embodiment 3 to the target CU. In step 1104, the source CU may receive a switching request confirmation message from the target CU.

[0253] In step 1105, the source DU may attempt to trigger an intra-DU L1 or L2 mobility procedure based on the L1 measurement report. In step 1106, the source DU may transmit an L1 or L2 mobility command to the UE via DCI or MAC CE, instructing the UE to switch from SpCell#1 to SpCell#2.

[0254] After receiving the L1 or L2 mobility command, in step 1107, the UE may perform the L1 or L2 mobility procedure and switch from SpCell#1 to SpCell#2.

[0255] Before knowing the L1 or L2 mobility procedure, the source CU may transmit a first message (eg, UE context modification request message) to the source DU in step 1108. The first message may include L3 mobility configuration associated with SpCell#1 as the source cell, as described in Embodiment 3.

[0256] Next, in step 1109, the source DU may transmit a second message (eg, a UE context modification response message) including information related to the L3 mobility procedure.

[0257] In some cases, in step 1110, the source DU may also transmit a third message to the source CU to indicate the triggering of the L1 or L2 mobility procedure or the successful execution of the L1 or L2 mobility procedure.

[0258] In step 1111, the source DU may transmit the L3 mobility configuration associated with SpCell#1 to the UE via the air interface.

[0259] In step 1112, the UE may perform an L3 mobility procedure based on the L3 mobility configuration associated with SpCell#1. For example, even if the UE is not connected to SpCell#1, the UE may apply the received L3 mobility configuration (e.g., incremental L3 mobility configuration) based on a configuration related to SpCell#1 that has been provided to the UE but not yet applied.

[0260] Fig.12 An exemplary method for rejecting L3 mobility configuration according to some embodiments of the present application is described.

[0261] refer to Fig.12 , in step 1201, it is assumed that L1 or L2 mobility has been configured or enabled.

[0262] In step 1202, the source CU may attempt to trigger an inter-CU L3 mobility procedure based on an L3 measurement report.

[0263] In step 1203, the source CU may transmit a switching request message including the information described in Embodiment 3 to the target CU. In step 1204, the source CU may receive a switching request confirmation message from the target CU.

[0264] In step 1205, the source DU may attempt to trigger an inter-DU L1 or L2 mobility procedure based on the L1 measurement report. In step 1206, the source DU may transmit an L1 or L2 mobility command to the UE via DCI or MAC CE, instructing the UE to switch from SpCell#1 (belonging to the source DU) to SpCell#2 (belonging to the target DU).

[0265] Before knowing the L1 or L2 mobility procedure, the source CU may transmit a first message (eg, UE context modification request message) to the source DU in step 1207. The first message may include L3 mobility configuration associated with SpCell#1 as the source cell, as described in Embodiment 3.

[0266] Since the UE is no longer connected to the source DU, at step 1208, the source DU may transmit a second message (eg, a UE context modification failure message) including the information as described in Embodiment 3.2.

[0267] In step 1209, the UE may perform inter-DU L1 or L2 mobility to switch from SpCell#1 to SpCell#2.

[0268] In step 1210, after successfully performing the L1 or L2 mobility procedure, the target DU may transmit a message regarding the successful performance of the L1 or L2 mobility procedure to the source CU.

[0269] Fig.13 A simplified block diagram illustrating an exemplary device for supporting inter-cell mobility according to some embodiments of the present application. Fig.13 , the device 1300 may include at least one processor 1306 and at least one transceiver 1302 coupled to the processor 1306. In some embodiments, the device 1300 may be a first network node (e.g., a CU of a BS). In some embodiments, the device 1300 may be a second network node (e.g., a DU of a BS). In some embodiments, the device 1300 may be a UE.

[0270] Although in this figure, elements such as at least one transceiver 1302 and processor 1306 are described in the singular, the plural is contemplated unless limitation to the singular is explicitly stated. In some embodiments of the present application, the transceiver 1302 may be divided into two devices, such as a receiving circuit system and a transmitting circuit system. In some embodiments of the present application, the device 1300 may further include an input device, a memory and / or other components.

[0271] In some embodiments of the present application, the device 1300 may be the first network node as described above. The transceiver 1302 and the processor 1306 may interact with each other to perform Figures 2 to 12 The operations of the first network node described in .

[0272] In some embodiments of the present application, the device 1300 may be the second network node as described above. The transceiver 1302 and the processor 1306 may interact with each other to perform Figures 2 to 12 The operations of the second network node described in .

[0273] In some embodiments of the present application, the device 1300 may be a UE as described above. The transceiver 1302 and the processor 1306 may interact with each other to perform Figures 2 to 12 The operations of the UE are described in .

[0274] In some embodiments of the present application, the apparatus 1300 may further include at least one non-transitory computer-readable medium.

[0275] For example, in some embodiments of the present application, the non-transitory computer-readable medium may store thereon computer-executable instructions to enable the processor 1306 to implement the method described above with respect to the first network node. For example, when the computer-executable instructions are executed, the processor 1306 interacts with the transceiver 1302 to perform Figures 2 to 12 The operations of the first network node described in .

[0276] In some embodiments of the present application, the non-transitory computer-readable medium may store thereon computer-executable instructions to enable the processor 1306 to implement the method described above with respect to the second network node. For example, when the computer-executable instructions are executed, the processor 1306 interacts with the transceiver 1302 to perform Figures 2 to 12 The operations of the second network node described in .

[0277] In some embodiments of the present application, the non-transitory computer-readable medium may store computer-executable instructions thereon to enable the processor 1306 to implement the method for the UE as described above. For example, when the computer-executable instructions are executed, the processor 1306 interacts with the transceiver 1302 to perform Figures 2 to 12 The operations of the UE are described in .

[0278] Those skilled in the art will appreciate that the operations or steps of the methods described in conjunction with the aspects disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. The software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. Additionally, in some aspects, the operations or steps of the methods may reside as one or any combination or set of codes and / or instructions on a non-transitory computer-readable medium, which may be incorporated into a computer program product.

[0279] Although the present disclosure has been described with specific embodiments of the present disclosure, it is apparent that many alternatives, modifications and variations may be apparent to those skilled in the art. For example, various components of the embodiments may be interchanged, added or replaced in other embodiments. In addition, all elements of each figure are not necessary for the operation of the disclosed embodiments. For example, a person skilled in the art of the disclosed embodiments will be able to make and use the teachings of the present disclosure by simply adopting the elements of the independent claims. Therefore, the embodiments of the present disclosure as set forth herein are intended to be illustrative, not restrictive. Various changes may be made without departing from the spirit and scope of the present disclosure.

[0280] In this document, the term "includes / including", "comprising" or any other variant thereof is intended to cover non-exclusive inclusion, so that the process, method, article or equipment containing the list of elements not only contains those elements, but also may contain other elements that are not explicitly listed or inherent to this process, method, article or equipment. Elements starting with "one", "one" or the like do not exclude the presence of additional identical elements in the process, method, article or equipment containing the elements without more restrictions. In addition, the term "another" is defined as at least the second or more. The term "having" and the like as used herein are defined as "comprising". For example, the expression of "A and / or B" or "at least one of A and B" may include any and all combinations of words enumerated together with the expression. For example, the expression "A and / or B" or "at least one of A and B" may include A, B or both A and B. The wording "first", "second" or the like is only used to clearly illustrate the embodiments of the present application, and is not used to limit the essence of the present application.

Claims

1. A first network node, comprising: A transceiver configured to: transmitting a first message related to a layer 3 L3 mobility procedure to a second network node via an F1 interface; and receiving, from the second network node via the F1 interface, a second message in response to the first message, wherein the second message includes at least one of: first information related to the L3 mobility procedure; or second information related to a layer 1 L1 or layer 2 L2 mobility procedure; and A processor is coupled to the transceiver.

2. The first network node according to claim 1, wherein the first message indicates at least one of the following: an intention of the first network node to trigger the L3 mobility procedure; The first SpCell is considered as the source special cell SpCell associated with the L3 mobility procedure. The second network stops triggering any L1 or L2 mobility procedures; The second network node responds to a second SpCell to which the user equipment UE is currently connected; or 3. The first network node according to claim 2, wherein the second message is a response message including the second information, and the second information indicates at least one of the following: The second SpCell to which the UE is currently connected; or Configuration associated with the second SpCell.

4. The first network node according to claim 2, wherein the second message is a failure message, the first information includes an indication indicating that the L3 mobility procedure should be re-initiated, and the second information includes at least one of the following: an indication indicating that the L1 or L2 mobility procedure has been triggered; an indication that the UE is no longer connected to the second network node; or The second SpCell to which the UE is currently connected.

5. The first network node of claim 1 , wherein the transceiver is further configured to receive a third message from the second network node, wherein the third message indicates one of: The L1 or L2 mobility procedure has been triggered by the second network; and Successful execution of the L1 or L2 mobility procedure.

6. The first network node of claim 1, wherein the first message indicates at least one of: an L3 mobility configuration; or The first SpCell is considered as the source SpCell associated with the L3 mobility procedure.

7. The first network node according to claim 6, wherein the second message is a failure message including the second information, and the second information includes at least one of the following: an indication that the L1 or L2 mobility procedure has been triggered; an indication that the UE is no longer connected to the second network node; an indication that a timer associated with the L1 or L2 mobility procedure is running; or The second SpCell to which the UE is currently connected.

8. The first network node of claim 7, wherein in response to the second message, the processor is further configured to cancel the L3 mobility procedure, and the transceiver is further configured to transmit a handover cancel message to a third network node, wherein the handover cancel message includes at least one of: an indication that the L1 or L2 mobility procedure has been triggered; an indication that the UE is no longer connected to the second network node; or An indication that a timer associated with the L1 or L2 mobility procedure is running.

9. The first network node of claim 1 , wherein the first message comprises an L3 mobility configuration associated with a source SpCell; and The L3 mobility configuration indicates a source SpCell or a cell group associated with the L3 mobility procedure, or includes a configuration related to the source SpCell and an incremental L3 mobility configuration.

10. The first network node according to any one of claims 3, 6 and 9, The processor is further configured to: generating a handover request message including a configuration associated with the UE to be applied in the first network node; and removing configurations related to candidate SpCells or cell groups to which the UE is not connected from the configurations associated with the UE included in the handover request message; and The transmitter is further configured to transmit the handover request message to a third network node.

11. The first network node according to claim 9, wherein the second message is a failure message including the second information, and the second information includes at least one of the following: an indication that the L1 or L2 mobility procedure has been triggered; an indication that the UE is no longer connected to the second network node; or The second SpCell to which the UE is currently connected.

12. A second network node, comprising: A transceiver configured to: receiving a first message related to a layer 3 L3 mobility procedure from a first network node via an F1 interface; and transmitting a second message in response to the first message to the first network node over the F1 interface, wherein the second message includes at least one of: first information related to the L3 mobility procedure; or second information related to a layer 1 L1 or layer 2 L2 mobility procedure; and A processor is coupled to the transceiver.

13. The second network node according to claim 12, wherein the first message indicates at least one of: an L3 mobility configuration; or The first SpCell is considered as the source SpCell associated with the L3 mobility procedure.

14. A user equipment UE, comprising: A transceiver configured to: receiving a message related to a layer 3 L3 mobility procedure from a second network node, wherein the message comprises: L3 mobility configuration, which is associated with the first SpCell as the source special cell SpCell; a processor coupled to the transceiver and configured to receive, based on the first SpCell associated with the first SpCell; The L3 mobility configuration is used to perform the L3 mobility procedure.

15. The UE of claim 14, wherein the first SpCell indicated in the L3 mobility configuration is different from a second SpCell to which the UE is currently connected, and the processor is further configured to apply the received L3 mobility configuration based on a configuration related to the first SpCell that has been provided to the UE but not yet applied.

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