Method and apparatus for supporting data transfer

Abstract

[0003] Embodiments of the present application relate to a method and apparatus for supporting data forwarding. An exemplary apparatus, for example, a candidate target master node (MN), may include: a processor configured to determine routing optimization information for early data forwarding associated with one or more candidate target secondary nodes (SNs) at least prepared by the MN, where the early data forwarding is for a conditional handover (CHO) to a secondary cell group (SCG) of a user equipment (UE); and a transceiver coupled to the processor, configured to transmit the routing optimization information to a source MN.

Description

[Technical Field]

[0001] Embodiments of the present application generally relate to wireless communication technologies, and more particularly, to methods and apparatus for supporting data transfer, e.g., supporting early data transfer for conditional handover (CHO) of a user equipment (UE) to a secondary cell group (SCG). [Background technology]

[0002] Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, broadcasts, and so on. 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, such as Long Term Evolution (LTE) systems, LTE-Advanced (LTE-A) systems, or LTE-A Pro systems, and fifth-generation (5G) systems, sometimes referred to as New Radio (NR) systems.

[0003] When a UE moves from one cell to another, a serving cell change will be performed at some point. Legacy, the serving cell change is performed by explicit Radio Resource Control (RRC) reconfiguration signaling to trigger target cell synchronization based on Layer 3 (L3) measurement reports, which usually leads to long latency, large overhead, and long interruption time. Therefore, CHO is introduced to improve handover performance, which is defined as a handover performed by a UE when one or more handover execution conditions are met. The UE will start evaluating the execution conditions after receiving the CHO configuration, and will stop evaluating the execution conditions after the handover is performed.

[0004] With respect to an SCG, it is a group of serving cells associated with a secondary node (SN), including a primary secondary cell (PSCell) and possibly one or more secondary cells (SCells). In a multi-radio (MR) dual connectivity (DC) scenario, a UE is to perform a CHO from a source master node (MN) toward a potential target MN, and a conditional PSCell addition (CPA) or conditional PSCell modification (CPC) toward a potential SN. CPA is defined as a PSCell addition performed by the UE when an execution condition is met, and CPC is defined as a PSCell modification performed by the UE when an execution condition is met. In short, such a scenario is called a CHO with an SCG. In a CHO with an SCG, there are multiple potential target MNs, as well as one target SCG (or only one potential target SCG), or multiple potential target SCGs. A potential target MN may also be called or referred to as a target MN, a candidate target MN, a candidate MCG, a candidate target MCG, a target MCG, or a candidate MN. A target SCG or potential target SCG may also be referred to or considered as a candidate target SCG, candidate SCG, candidate target SN, target SN, or candidate SN.

[0005] To reduce latency or interruption of data transfer, early data transfer is introduced for CHO and CPA / CPC, where data transfer is initiated in advance to multiple potential target nodes. When early data transfer is applied, a source node, e.g., a source MN or a source SN, initiates data transfer to the potential target node before the UE performs handover. Because there are multiple candidate target MNs (e.g., up to eight according to the current specification) and each candidate target MN may prepare multiple candidate target SNs (e.g., up to eight according to the current specification) for CHO with an SCG, there are multiple data transfer paths for the same UE. Without data transfer optimization, data would be sent via multiple paths, which would overwhelm network resources in some scenarios.

[0006] In light of the above, the industry desires technology to improve data transfer for SCGs and CHOs. Summary of the Invention [Problem to be solved by the invention]

[0007] An objective of embodiments of the present application is to provide a technical solution for supporting data transfer, for example, a method and an apparatus for supporting data transfer to at least improve early data transfer for CHO with SCG. [Means for solving the problem]

[0008] Some embodiments of the present application provide an MN, for example, a candidate target MN, which includes a processor configured to determine routing optimization information for early data transfer associated with one or more candidate target SNs at least prepared by the MN, where the early data transfer is for CHO with an SCG of the UE, and a transceiver coupled to the processor, configured to transmit the routing optimization information to a source MN.

[0009] In some embodiments of the present application, the transceiver is configured to receive, from a candidate target SN among one or more candidate target SNs, identification information of the candidate target SN, wherein the identification information of the candidate target SN is a globally unique identification information.

[0010] In some embodiments of the present application, the routing optimization information indicates at least one of the following: identification information of one of the one or more candidate target SNs; a random number allocated at one of the candidate target SNs; or an indicator of the same candidate target SN indicating that the data transfer address associated with the early data transfer will map to the same data transfer address of one of the candidate target SNs.

[0011] According to some embodiments of the present application, the routing optimization information further indicates an estimated arrival probability for the UE towards one candidate target SN prepared by the MN.

[0012] According to some embodiments of the present application, the transceiver is configured to receive information indicating that the same data transfer address is shared with the MN by other candidate target MNs, and to cause indicators of the same candidate target SNs to be determined by the MN.

[0013] According to some embodiments of the present application, the early data forwarding associated with the UE is indirect early data forwarding for CHO with one target SCG.

[0014] In some embodiments of the present application, the routing optimization information indicates at least one of the following: an estimated arrival probability for a UE heading to one candidate target SN prepared by the MN among one or more candidate target SNs, or data forwarding address sharing information indicating the number of candidate target MNs using the same data forwarding address of one candidate target SN.

[0015] According to some embodiments of the present application, the early data forwarding associated with the UE is direct early data forwarding for CHO with multiple candidate SCGs.

[0016] In some embodiments of the present application, the routing optimization information indicates at least one of the following: identification information of one or more candidate target SNs; information sharing a data forwarding address indicating the number of candidate target MNs using the same data forwarding address of one candidate target SN; one or more first estimated arrival probabilities, each first estimated arrival probability being for a UE heading towards a corresponding candidate target SN among one or more candidate target SNs prepared by the MN; or one or more second estimated arrival probabilities, each second estimated arrival probability being for a UE heading towards a corresponding candidate target SN among one or more candidate target SNs prepared by another candidate target MN different from the MN.

[0017] According to some embodiments of the present application, a second estimated arrival probability associated with the candidate target SN is received from the candidate target SN via an SN Addition Request Acknowledgement message or an SN Modification Required message.

[0018] According to some embodiments of the present application, a transceiver is configured to transmit, to a candidate target SN, information indicating a first time based on which a second estimated arrival probability associated with the candidate target SN will be provided, and to receive a message indicating the second estimated arrival probability associated with the candidate target SN. In some scenarios, the transceiver is configured to receive, from a source MN, information indicating a second time based on which the second estimated arrival probability associated with the candidate target SN will be provided, where the first time is equal to or less than the second time.

[0019] According to some embodiments of the present application, a transceiver is configured to receive, from a source MN, a destination for data forwarding for an SN terminated bearer, where the destination is an identification of a target SN determined by the source MN.

[0020] According to some embodiments of the present application, the early data transfer associated with the UE is an indirect early data transfer for CHO with multiple candidate SCGs.

[0021] According to some embodiments of the present application, information related to the number of candidate target MNs using the same data transfer address of a candidate target SN is indicated via an SN Addition Request Acknowledgement message or an SN Modification Required message. In some scenarios, a transceiver is configured to send, to a candidate target SN, information indicating a first time based on which the information related to the number of candidate target MNs using the same data transfer address of the candidate target SN will be provided, and to receive information related to the number of candidate target MNs using the same data transfer address of the candidate target SN. In some scenarios, a transceiver is configured to receive, from a source MN, information indicating a second time based on which the information sharing the data transfer address will be provided, the first time being equal to or shorter than the second time. Exemplary information related to the number of candidate target MNs using the same data transfer address of a candidate target SN is indicated by a candidate target SN using, in addition to the MN, the numerical value of, or at least identification information of, other candidate target MNs using the same data transfer address.

[0022] An exemplary first time is a length of time or a point in time. An exemplary second time is also a length of time or a point in time.

[0023] According to some embodiments of the present application, the time length is the time to wait and indicates the maximum allowable waiting time for providing information sharing the data transfer address.

[0024] According to some embodiments of the present application, the time length is a time to wait and indicates a maximum allowable waiting time for providing a second estimated arrival probability associated with the candidate target SN.

[0025] Some other embodiments of the present application provide another MN, e.g., a source MN, including a processor and a transceiver coupled to the processor, the transceiver configured to: send a handover request for a CHO with an SCG of the UE to a candidate target MN among one or more candidate target MNs; and receive, from the candidate target MN, routing optimization information for early data transfer associated with one or more candidate target SNs prepared at least by the candidate target MN, where the early data transfer is for a CHO with the SCG.

[0026] According to some embodiments of the present application, information on routing optimization for early data transfer is received from the candidate target MN via a handover request acknowledgement message or a message subsequent to the handover request acknowledgement message.

[0027] In some embodiments of the present application, the transceiver is configured to transmit to the candidate target MN information indicating a time based on which the information sharing the data forwarding address will be provided.

[0028] According to some embodiments of the present application, the information sharing the data forwarding address is received via the handover request acknowledgement message or a message subsequent to the handover request acknowledgement message.

[0029] In some embodiments of the present application, the transceiver is configured to transmit to the candidate target MN information indicating a time based on which a second estimated arrival probability associated with the corresponding candidate target SN will be provided.

[0030] In some embodiments of the present application, the processor is configured to determine, based on routing optimization information from one or more candidate target MNs, that data will be forwarded to only one of the one or more candidate target MNs.

[0031] According to some embodiments of the present application, when two or more estimated arrival probabilities are received from two or more candidate target MNs, only one candidate target MN is the candidate target MN with the greatest estimated arrival probability. In some scenarios, the processor is configured to perform early data forwarding to only one candidate target MN or indicate only one candidate target MN to the source SN.

[0032] In some embodiments of the present application, the processor is configured to determine, based on routing optimization information from one or more candidate target MNs, that data will be forwarded based on only one data forwarding address.

[0033] According to some embodiments of the present application, if two or more estimated arrival probabilities are received from two or more candidate target MNs, only one data transfer address is the data transfer address with the largest estimated arrival probability. If data transfer addresses are provided by different candidate target MNs with different estimated arrival probabilities, the estimated arrival probability of the data transfer address is the average of the different estimated arrival probabilities.

[0034] According to some embodiments of the present application, when information sharing a data transfer address is received from two or more candidate target MNs, only one data transfer address is the data transfer address used by the greatest number of candidate target MNs.

[0035] According to some embodiments of the present application, the processor is configured to indicate to the source SN only one data transfer address.

[0036] In some embodiments of the present application, the processor is configured to, when the routing optimization information from two or more candidate target MNs includes information about the identification information of one or more candidate target SNs, determine the candidate target MN with the greatest number of candidate target SNs as the only candidate target MN to which the early data will be forwarded.

[0037] According to some embodiments of the present application, the processor is configured to perform early data transfer to only one candidate target MN or indicate only one candidate target MN to the source SN.

[0038] In some embodiments of the present application, the processor is configured to, when routing optimization information from two or more candidate target MNs includes information on one or more first estimated arrival probabilities, determine the candidate target SN with the largest estimated arrival probability as a destination for data forwarding for the SN-terminated bearer, where the largest estimated arrival probability is the largest first estimated arrival probability.

[0039] According to some embodiments of the present application, the processor is configured such that, when the routing optimization information from two or more candidate target MNs includes information about one or more second estimated arrival probabilities associated with the candidate target SNs, the estimated arrival probability of the candidate target SN is the average of the first estimated arrival probability and different second estimated arrival probabilities from different candidate target MNs.

[0040] According to some embodiments of the present application, a transceiver is configured to: transmit to a candidate target MN a destination for data forwarding for an SN terminated bearer, the destination being an identity of the candidate target MN with the highest estimated arrival probability; and a processor is configured to perform early data forwarding to the candidate target MN for the SN terminated bearer and indicate the destination to the candidate target MN or indicate the destination to the source SN.

[0041] Some embodiments of the present application provide an SN, for example, a candidate target SN, which includes a processor and a transceiver coupled to the processor, the transceiver configured to receive, from the candidate target MN, first information related to a CHO with an SCG of the UE, and to transmit, to the candidate target MN, second information related to routing optimization for early data transfer for the CHO with the SCG.

[0042] In some embodiments of the present application, the second information is transmitted via an SN Addition Request Acknowledgement message or an SN Modification Required message.

[0043] In some embodiments of the present application, the second information indicates at least one of the following: identification information of the SN, a random number allocated in the SN, or information indicating that the same data transfer address is shared with the candidate target MN by other candidate target MNs.

[0044] In some embodiments of the present application, the second information indicates information related to the number of candidate target MNs that use the same data transfer address of the SN, in addition to the candidate target MN, using the numerical values ​​of other candidate target MNs that use the same data transfer address of the SN, or at least using their identification information.

[0045] According to some embodiments of the present application, the transceiver is configured to receive, from a candidate target MN, information indicating a time based on which information related to the number of candidate target MNs using the same data transfer address of the SN will be provided, and to determine, based on the indicated time, the information related to the number of candidate target MNs using the same data transfer address.

[0046] In some embodiments of the present application, the second information indicates at least one of the following: identification information of the SN, information related to the number of candidate target MNs using the same data forwarding address of the SN, or one or more second estimated arrival probabilities, each second estimated arrival probability being for a UE heading towards an SN prepared by another candidate target MN different from the candidate target MN.

[0047] According to some embodiments of the present application, the transceiver is configured to receive, from a candidate target MN, information indicating a time based on which information related to the number of candidate target MNs using the same data transfer address of the SN or at least one of one or more second estimated arrival probabilities will be provided, and to report to the candidate target MN, based on the indicated time, the information related to the number of candidate target MNs using the same data transfer address of the SN or at least one of the one or more second estimated arrival probabilities.

[0048] In view of the above, embodiments of the present application provide a method and apparatus for supporting data transfer that can at least optimize early data transfer for CHO with SCG and reduce resource abuse. Thus, the present application can enable and improve implementations of NR.

[0049] To describe how the advantages and features of the present application may be obtained, the present application will be described by reference to specific embodiments thereof, which are illustrated in the accompanying drawings. These drawings depict only exemplary embodiments of the present application and are therefore not to be considered limiting of the scope of the present application. [Brief explanation of the drawings]

[0050] [Figure 1] FIG. 1 illustrates a wireless communication system in accordance with some embodiments of the present application. [Figure 2a] FIG. 1 illustrates an exemplary scenario of indirect early data transfer for a CHO with one target SCG. [Figure 2b] FIG. 1 illustrates an exemplary scenario of indirect early data transfer for a CHO with multiple candidate SCGs. [Figure 2c] FIG. 1 illustrates an exemplary scenario of direct early data transfer for a CHO with one target SCG. [Figure 2d] FIG. 1 illustrates an exemplary scenario of direct early data transfer for a CHO with multiple candidate SCGs. [Figure 3] 1 is a flowchart of an exemplary procedure for supporting data transfer in Scenario 1, according to some embodiments of the present application. [Figure 4] 10 is a flowchart of an exemplary procedure for supporting data transfer in Scenario 2, according to some embodiments of the present application. [Figure 5] 10 is a flowchart of another exemplary procedure for supporting data transfer in Scenario 2, according to some other embodiments of the present application. [Figure 6] 10 is a flowchart of an exemplary procedure for supporting data transfer in Scenario 3, according to some embodiments of the present application. [Figure 7] 10 is a flowchart of another exemplary procedure for supporting data transfer in Scenario 3, according to some other embodiments of the present application. [Figure 8]1 is a block diagram of an apparatus supporting data transfer according to some embodiments of the present application. [Figure 9] FIG. 10 is a block diagram of an apparatus supporting data transfer according to some other embodiments of the present application. DETAILED DESCRIPTION OF THE INVENTION

[0051] The detailed description of the accompanying drawings is intended as an illustration of a preferred embodiment of the present application and does not represent the only form in which the present application may be practiced. It is to be understood that the same or equivalent function may be accomplished by different embodiments that are encompassed within the spirit and scope of the present application.

[0052] Reference will now be made in detail to several embodiments of the present application, examples of which are illustrated in the accompanying drawings. For ease of understanding, the embodiments are provided under specific network architectures and new service scenarios, such as 3GPP 5G and 3GPP LTE. With the development of network architectures and new service scenarios, it is contemplated that all embodiments in the present application are also applicable to similar technical problems. Furthermore, the terms used in the present application may change without affecting the principles of the present application.

[0053] In an NR-DC scenario, a UE with multiple transceivers may be configured to utilize resources provided by two different nodes connected via a non-ideal backhaul, where one node may provide NR access and the other node may provide either Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA) (E-UTRA) or NR access. One node may act as a MN and the other node may act as a SN. The MN and SN are connected via a network interface, e.g., the Xn interface specified in 3GPP standard documents, which connects at least the MN to a core network (CN).

[0054] For example, FIG. 1 illustrates a schematic diagram of a wireless communication system 100 in accordance with some embodiments of the present application.

[0055] As shown in Figure 1, the wireless communication system 100 may be a dual connectivity system 100 that includes at least one UE 101, at least one MN 102, and at least one SN 103. In particular, the dual connectivity system 100 in Figure 1 includes, for purposes of illustration, one illustrated UE 101, one illustrated MN 102, and one illustrated SN 103. Although a particular number of UEs 101, MNs 102, and SNs 103 are shown in Figure 1, it is contemplated that any number of UEs 101, MNs 102, and SNs 103 may be included within the wireless communication system 100.

[0056] 1, the UE 101 may connect to the MN 102 and the SN 103 via an interface, for example, a Uu interface specified in a 3GPP standard document. The MN 102 and the SN 103 may be connected to each other via a network interface, for example, an Xn interface specified in a 3GPP standard document. The MN 102 may be connected to a core network (not shown in FIG. 1) via a network interface, for example, an NG interface specified in a 3GPP standard document. The UE 101 may be configured to utilize resources provided by the MN 102 and the SN 103 to perform data transmission.

[0057] In some embodiments of the present application, the UE 101 may include a computing device such as a desktop computer, a laptop computer, a personal digital assistant (PDA), a tablet computer, a smart television (e.g., a television connected to the Internet), a set-top box, a game console, a security system (including security cameras), a vehicle-mounted computer, a network device (e.g., a router, a switch, and a modem), etc. In some other embodiments of the present application, the UE 101 may include a portable wireless communication device, a smartphone, a cellular telephone, a flip phone, a device with a subscriber identity module, a personal computer, selective call reception circuitry, or any other device capable of sending and receiving communication signals over a wireless network. In some other embodiments of the present application, the UE 101 may include a wearable device such as a smart watch, a fitness band, an optical head-mounted display, etc. Moreover, the UE 101 may be referred to as a subscriber unit, a mobile, 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 may be described using other terms used in the art.

[0058] The MN 102 refers to a Radio Access Network (RAN) node that provides a control plane connection to a core network. In one embodiment of the present application, in an E-UTRA-NR DC (EN-DC) scenario, the MN 102 may be an eNB. In another embodiment of the present application, in a Next Generation E-UTRA-NR DC (NGEN-DC) scenario, the MN 102 may be a Next Generation (ng)-eNB. In yet another embodiment of the present application, in an NR-DC scenario or an NR-E-UTRA DC (NE-DC) scenario, the MN 102 may be a gNB. The MN 102 may also be referred to as a Master NG-RAN (M-NG-RAN) node in some embodiments of the present application.

[0059] An MCG may refer to a group of serving cells associated with the MN 102 and may include a primary cell (PCell) and possibly one or more SCells. The PCell may provide a control plane connection to the UE 101.

[0060] The SN 103 may refer to a radio access network node without a control plane connection to a core network but that provides additional resources to the UE 101. In some embodiments of the present application, in an EN-DC scenario, the SN 103 may be an en-gNB. In some other embodiments of the present application, in an NR-DC scenario, the SN 103 may be an ng-eNB. In yet other embodiments of the present application, in an NR-DC scenario or an NGEN-DC scenario, the SN 103 may be a gNB. The SN 103 may also be referred to as a Secondary NG-RAN (S-NG-RAN) node in some embodiments of the present application.

[0061] An SCG may refer to a group of serving cells associated with an SN and may include a PSCell and possibly one or more SCells. The PCell of the MCG and the PSCell of the SCG may also be referred to as special cells (SpCells).

[0062] In a CHO with an SCG, early data forwarding can be indirect early data forwarding or direct early data forwarding. In the case of indirect early data forwarding, the source MN or source SN forwards data to a candidate target MN, which then forwards the data to the candidate target SN. In the case of direct early data forwarding, the source MN or source SN forwards data directly to the candidate target SN without forwarding by the candidate target MN. Without data forwarding optimization, data would be sent via multiple routes, which could strain network resources and cause other problems.

[0063] For example, in indirect early data forwarding for a CHO with one target SCG, a source node, e.g., a source MN, has a data forwarding address toward a candidate target MN but does not have a data forwarding address toward a candidate target SN. Without data forwarding optimization, a source MN may send data to multiple candidate target MNs, causing the data to be forwarded by multiple candidate target MNs to the same candidate target SN. That is, data is sent via multiple routes, thereby straining network resources. In addition, when increased data from multiple routes is received, the candidate target SN must occasionally remove the increased data, requiring high processing and storage capabilities.

[0064] In direct early data forwarding for a CHO with multiple candidate SCGs, a source node, e.g., a source MN, has a data forwarding address directed to a candidate target SN and sends data directly to the candidate target SN. However, without data forwarding optimization, there are multiple paths for direct early data forwarding, and data is sent via multiple paths.

[0065] In indirect early data forwarding for a CHO with multiple candidate SCGs, a source node, e.g., a source MN, has a data forwarding address toward a candidate target MN but does not have a data forwarding address toward a candidate target SN. Thus, the source MN sends data to the candidate target MN, and the data is forwarded by the candidate target MN to multiple candidate target SNs. Thus, the same candidate target SN may be prepared by multiple candidate target MNs and may receive incremental data via multiple routes. In addition, the same candidate target MN may prepare multiple candidate target SNs, and the same data is forwarded to multiple candidate target SNs.

[0066] 2a-2d show four exemplary scenarios of early data transfer for a CHO with an SCG without data transfer optimization: FIG. 2a shows an exemplary scenario of indirect early data transfer for a CHO with one target SCG; FIG. 2b shows an exemplary scenario of indirect early data transfer for a CHO with multiple candidate SCGs; FIG. 2c shows an exemplary scenario of direct early data transfer for a CHO with one target SCG; and FIG. 2d shows an exemplary scenario of direct early data transfer for a CHO with multiple candidate SCGs. Dashed lines, e.g., S1, S2, etc., represent data transfer paths.

[0067] Referring to FIG. 2a, in an exemplary scenario of indirect early data transfer for a CHO with one target SCG, there is only one candidate target SN (one target SN) and multiple (e.g., m>1) candidate targets MN. The candidate targets SN are prepared by candidate targets MN1, MN2, ..., and MNm. The source MN will forward data to candidate target MN1 via S1, and then candidate target MN1 will forward data to candidate target SN via S5. Similarly, the source MN will forward data to candidate target MN2 via S2, and then candidate target MN2 will forward data to candidate target SN via S7, and so on. The source MN will forward data to candidate target MNm via Sm, and then candidate target MNm will forward data to candidate target SN via S9.

[0068] Referring to FIG. 2b, in an exemplary scenario of indirect early data transfer for a CHO with multiple candidate SCGs, there are multiple (e.g., n>1) candidate targets SN and multiple (e.g., m>1) candidate targets MN. Each candidate target SN may be prepared by one or more candidate targets MN. For example, candidate target SN1 is prepared by candidate target MN1 and candidate target MN2, candidate target SN2 is prepared by candidate target MN1, candidate target MN2, and candidate target MNm, ... candidate target SNn is prepared by candidate target MN2 and candidate target MNm. The source MN will forward data to candidate target MN1 via S1, and then candidate target MN1 will forward data to candidate target SN1 via S4 and to candidate target SN2 via S5. Similarly, source MN will forward data to candidate target MN2 via S2, which in turn will forward data to candidate target SN1 via S6, to candidate target SN2 via S7, and to candidate target SNn via S8, etc. Source MN will forward data to candidate target MNm via Sm, which in turn will forward data to candidate target SN2 via S9, and to candidate target SNn via S10.

[0069] Similar to Figure 2a, in the exemplary scenario of direct early data transfer for CHO with one target SCG shown in Figure 2c, there is only one candidate target SN (1 target SN) and multiple (e.g., m>1) candidate targets MN. The candidate targets SN are prepared by candidate targets MN1, MN2, ..., and MNm. The source MN will transfer data directly to the candidate targets SN via S1.

[0070] Similar to FIG. 2b, in the exemplary scenario of direct early data transfer for a CHO with multiple candidate target SCGs shown in FIG. 2d, there are multiple (e.g., n>1) candidate targets SN and multiple (e.g., m>1) candidate targets MN. Each candidate target SN may be prepared by one or more candidate targets MN. For example, candidate target SN1 is prepared by candidate target MN1 and candidate target MN2, candidate target SN2 is prepared by candidate target MN1, candidate target MN2, and candidate target MNm, ... candidate target SNn is prepared by candidate target MN2 and candidate target MNm. A source MN will forward data directly to candidate target SN1 via S1, directly to candidate target SN2 via S2, and directly to candidate target SNn via Sn.

[0071] 2a, 2b, and 2d, it can be seen that there are multiple data transmission paths for the same UE. Without data transmission optimization, data would be sent via multiple paths, causing the problems described above. If the source node is the source SN instead of the source MN, the same problem would also occur.

[0072] In order to at least solve the above problems in data transfer for CHO with SCG, embodiments of the present application provide technical solutions for supporting data transfer, for example, methods and apparatuses for supporting data transfer, which can at least optimize early data transfer for CHO with SCG and reduce resource overuse in the network.

[0073] For example, some embodiments of the present application provide a method for supporting data transfer that may be performed by a candidate target MN, such as the candidate target MN1 shown in Figures 2a, 2b, and 2d. The method includes determining routing optimization information for early data transfer (or routing optimization information) associated with one or more candidate target SNs at least prepared by the candidate target MN, where the early data transfer is for CHO with the SCG of the UE. The method also includes transmitting the routing optimization information to the source MN, for example, via a handover request acknowledgement (ACK) message or other message.

[0074] Some other embodiments of the present application provide another method for supporting data transfer, which may be performed by a source MN, such as the source MNs shown in Figures 2a, 2b, and 2d. The method includes sending a handover request for CHO with an SCG of the UE to a candidate target MN of one or more candidate target MNs, e.g., via a HANDOVER REQUEST message. The method also includes receiving, from the candidate target MN, e.g., by a HANDOVER REQUEST ACK message or other message, routing optimization information for early data transfer associated with one or more candidate target SNs prepared by the candidate target MN, where the early data transfer is for CHO with an SCG.

[0075] For example, in some scenarios (Scenario 1) where the early data forwarding associated with the UE is an indirect early data forwarding for a CHO with one target SCG as shown in FIG. 2a, the routing optimization information indicates at least one of the following: an identification of one of one or more candidate target SNs; a random number allocated at one candidate target SN; or an indicator of the same candidate target SN indicating that the data forwarding address associated with the early data forwarding will map to the same data forwarding address of one candidate target SN.

[0076] The data forwarding address (also referred to as data forwarding information) may be a downlink (DL) data forwarding address, or an uplink (UL) data forwarding address, or a DL and UL data forwarding address. An exemplary data forwarding address includes transport layer (TNL) information for establishing a data forwarding tunnel toward a target node (MN or SN). The TNL information corresponds to an Internet Protocol (IP) address and a General Packet Radio Service Tunneling Protocol (GTP) Tunnel Endpoint Identifier (TEID). In addition, the data forwarding address is per protocol data unit (PDU) session or DRB level, for example, per PDU level, or per DRB level, or per PDU and DRB level. When the data forwarding address is per DRB level, or per PDU and DRB level, the data forwarding address will include a DRB ID.

[0077] According to some embodiments of the present application, for simplicity, a data transfer address associated with an early data transfer will map to the same data transfer address of a candidate target SN, indicating that the data transfer address associated with an early data transfer will map to the same candidate target SN. According to some embodiments of the present application, for simplicity, a data transfer address associated with an early data transfer will map to the same candidate target SN, indicating that the data will be transferred to the same data transfer address allocated by the candidate target SN.

[0078] Based on the routing optimization information, the source MN will know that data will be forwarded to the same candidate target SN and will select (or determine) one candidate target MN for data forwarding. The candidate target MN may be selected randomly by the source MN or based on configured or predefined rules. For example, the routing optimization information may also indicate an estimated reachability probability for UEs heading to the same candidate target SN prepared by the MN. The candidate target MN may provide an estimated reachability probability of the candidate target SN prepared by the candidate target MN. When a candidate target SN is prepared by multiple candidate target MNs, each candidate target MN will have an estimated reachability probability for the candidate target SN, which may be the same or different. When the source MN knows that data will be forwarded to the same candidate target SN and receives data forwarding addresses from multiple candidate target MNs with different estimated reachability probabilities, the source MN may select the candidate target MN with the largest estimated reachability probability for data forwarding.

[0079] In some other scenarios (Scenario 2), for example, where the early data forwarding associated with the UE is direct early data forwarding for CHO with multiple candidate SCGs as shown in Figure 2d, the routing optimization information indicates at least one of the following: an estimated arrival probability for the UE towards one candidate target SN prepared by the MN among one or more candidate target SNs, or data forwarding address sharing information indicating the number of candidate target MNs using the same data forwarding address of one candidate target SN.

[0080] Based on the routing optimization information received from multiple candidate target MNs, the source MN will select one candidate target SN for data forwarding. In some cases, the source MN may indicate a time based on which information sharing data forwarding addresses will be provided by the candidate target MN or corresponding candidate target SNs to avoid race conflicts. The candidate target MN may also indicate a similar time to the candidate target SNs, independently of or in accordance with instructions from the source MN. For example, if a time is required, the T-SN will wait for the required time to count or determine the number of candidate target MNs using the same data forwarding address.

[0081] For example, in some other scenarios (Scenario 3) where the early data forwarding associated with the UE is indirect early data forwarding for CHO with multiple candidate SCGs as shown in FIG. 2b, the routing optimization information indicates at least one of the following: identification information of one or more candidate target SNs; information indicating the number of candidate target MNs using the same data forwarding address of one candidate target SN, sharing of data forwarding addresses indicating the number of candidate target MNs using the same data forwarding address of one candidate target SN; one or more first estimated arrival probabilities, each first estimated arrival probability for a UE heading toward a corresponding candidate target SN among one or more candidate target SNs prepared by the MN; or one or more second estimated arrival probabilities, each second estimated arrival probability for a UE heading toward a corresponding candidate target SN among one or more candidate target SNs prepared by another candidate target MN different from the MN.

[0082] Based on the routing optimization information received from the multiple candidate target MNs, the source MN determines a candidate target MN as the only candidate target MN to which early data will be forwarded, or determines a candidate target SN as the destination for data forwarding for an SN-terminated bearer. Similarly, to avoid race conflicts, the required time may be based on the information sharing the data forwarding address and / or one or more second estimated arrival probabilities.

[0083] Some other embodiments of the present application provide yet another method for supporting data forwarding, which may be performed by, for example, a candidate target SN. The method includes receiving, from the candidate target MN, first information related to a CHO with an SCG of the UE, for example, via an SN Addition Request message. The method also includes transmitting, to the candidate target MN, second information related to routing optimization for early data forwarding for the CHO with the SCG, for example, via an SN Addition Request ACK message or an SN Modification Required message. Based on the received second information, the candidate target MN can provide routing optimization information for the source MN.

[0084] For example, in some scenarios (Scenario 1) where the early data transfer associated with the UE is an indirect early data transfer for CHO with one target SCG, the second information indicates at least one of the following: identification information of the SN, a random number allocated in the SN, or information indicating that the same data transfer address is shared with the candidate target MN by other candidate target MNs.

[0085] For example, in some other scenarios (Scenario 2) where the early data transfer associated with the UE is a direct early data transfer for CHO with multiple candidate SCGs, the second information indicates information related to the number of candidate target MNs using the same data forwarding address of the SN, using the numerical value of, or at least identification information of, other candidate target MNs using the same data forwarding address of the SN in addition to the candidate target MN. The candidate target MN may determine or derive the number of candidate target MNs using the same data forwarding address based on the second information, or directly use what is indicated in the second information and send information sharing the data forwarding address to the source MN. For example, the second information may directly indicate the number of candidate target MNs using the same data forwarding address, and the candidate target MN will directly indicate the same number sharing the data forwarding address to the source MN. If the candidate target MN receives identification information of other candidate target MNs using the same data transfer address (in some other cases, the second information may indicate the identification information of all candidate target MNs using the same data transfer address), the candidate target MN may determine the number of candidate target MNs using the same data transfer address based on the identification information of the other candidate target MNs (or all candidate target MNs) using the same data transfer address. In some other cases, the candidate target MN may also directly use the identification information of at least other candidate target MNs using the same data transfer address indicated in the second information as information for sharing the data transfer address with the source MN, and the source MN will determine or derive the number of candidate target MNs using the same data transfer address based on the indicated identification information.

[0086] For example, in some other scenarios (Scenario 3) where the early data transfer associated with the UE is an indirect early data transfer for CHO with multiple candidate SCGs, the second information indicates at least one of the following: identification information of the SN, information sharing a data forwarding address using the numerical value or identification information of other candidate target MNs using the same data forwarding address of the SN in addition to the candidate target MN, or one or more second estimated arrival probabilities, each second estimated arrival probability being for a UE heading towards an SN prepared by another candidate target MN different from the candidate target MN.

[0087] More detailed embodiments of the present application are presented below in light of several exemplary data transfer scenarios. Although MN and SN in NR-DC are shown in the exemplary embodiments, those skilled in the art should understand that the presented technical solutions may also be applied to similar RAN nodes and / or similar scenarios and should not be limited to specific devices and scenarios. In addition, different exemplary embodiments are shown to focus on different technical means for clarity, which may be combined in various ways by those skilled in the art under the disclosure and teachings of the present application, although not shown in detail.

[0088] 3 is a flowchart of an exemplary procedure for supporting data transfer in Scenario 1 according to some embodiments of the present application. Although there are multiple candidate target MNs, the operation of only one candidate target MN is shown in detail as an example for simplicity and clarity. Those skilled in the art will be familiar with the disclosure and teachings of the candidate target MN shown in detail, and the corresponding operations in other candidate target MNs may be the same, similar, or different from those of the shown target MN by adopting the same, similar, or different solutions taught by various embodiments of the present application.

[0089] Referring to Figure 3, in step 301a, a source MN (also referred to as "S-MN" for simplicity) initiates a CHO procedure by sending a handover request message or the like to a candidate target MN (also referred to as "T-MN" for simplicity), for example, candidate target MN1 shown in Figure 2a. The handover request message or the like includes the MCG configuration and, if the UE is configured with an SCG, the SCG configuration. The handover request message or the like also includes CHO-related information. The CHO-related information includes the S-MN identity (ID) and the UE ID allocated in the S-MN.

[0090] Similarly, in step 301b, the S-MN may also initiate a CHO handover procedure by sending a handover request message or the like to one or more other candidate target MNs (also referred to as "other T-MNs" for simplicity), for example, T-MN2 or T-MNm shown in FIG. 2a.

[0091] In step 303a, the T-MN sends an SN addition request message or the like, including CHO-related information, to at least the candidate target SNs (also referred to as "T-SNs" for simplicity) prepared by the candidate target MN. In some embodiments of the present application, in addition to the S-MN ID and the UE ID allocated in the S-MN, the CHO-related information may also include an estimated arrival probability for the UE heading to the candidate target SNs prepared by the candidate target MN.

[0092] Other T-MNs may perform equal or similar actions in step 303b.

[0093] The T-SN will reply in step 305a with an SN Add Request Acknowledgement message or the like that includes the data forwarding address allocated by the T-SN, which data forwarding address relates to the PDU session for the DRB configured with the SN terminated bearer option.

[0094] The T-SN may also provide routing optimization related information to the T-MN in the same or similar messages to assist the T-MN in determining routing optimization information.

[0095] In some embodiments of the present application, the T-SN may indicate the identity of the T-SN. An exemplary identity of the T-SN is the globally unique identity of the T-SN. If there are multiple user planes (UPs) for the T-SN, the identity of the T-SN is a combination of the global node identity of the candidate target SN and the UP identity that uniquely identifies the UP at least within the candidate target SN.

[0096] In some other embodiments of the present application, the T-SN may indicate a random number to the T-MN. For example, based on the received S-MN ID and the assigned UE ID in the S-MN, the T-SN will know that SN addition requests from multiple T-MNs are for the same UE. The T-SN may allocate the same data forwarding address for the UE and the same random number for the data forwarding address and then send them to the T-MN.

[0097] In some other embodiments of the present application, after learning that SN addition requests from multiple T-MNs are for the same UE, the T-SN may send information to the T-MN indicating that the same data forwarding address is also shared by other candidate target MNs.

[0098] The T-SN may send to the T-MN in the routing optimization related information at least one of the above, for example, only the T-SN's identification information, or only a random number, or only information indicating that the same data forwarding address is also shared by other candidate target MNs, or any combination thereof.

[0099] If a similar message is received from another T-MN in step 303b, the T-SN will send a similar message back to the other T-MN in step 305b.

[0100] After receiving the SN Addition Request ACK message, the T-MN will send, in step 307a, to the S-MN, a Handover Request Acknowledgement message or the like, including the data forwarding address allocated by the T-MN. The data forwarding address relates to the PDU session for the DRB configured with the SN terminated bearer option.

[0101] The T-MN may also include routing optimization information in the same message or a different message. Based on information received from the T-SN, the routing optimization information includes at least one of a T-SN identification information, a random number allocated in the T-SN, or an indicator of the same candidate target SN. The indicator of the same candidate target SN (also referred to as the same candidate target SN indicator) indicates that the data forwarding address associated with the early data forwarding will map to the same data forwarding address allocated by the candidate target SN (also referred to as "the data forwarding address associated with the early data forwarding will map to the same candidate target SN" for brevity). In some embodiments of the present application, the indicator of the same candidate target SN is generated by the T-MN based on information indicating that the same data forwarding address is shared with the T-MN by other T-MNs. An exemplary indicator of the same candidate target SN is an enumeration type. When the indicator of the same candidate target SN is set to true, it means that data will be forwarded to the same data forwarding address allocated by the T-SN (also referred to as "data will be forwarded to the same T-SN" for brevity).

[0102] In some embodiments of the present application, in addition to at least one of the T-SN identification information, the random number, and the same candidate target SN indicator being indicated to the S-MN, the routing optimization information may further include an estimated arrival probability for the UE heading to the T-SN prepared by the T-MN.

[0103] Other T-MNs may send similar messages to the S-MN in step 307b.

[0104] Based on the routing optimization information, the S-MN will know that data will be forwarded to the same T-SN and will select (or determine) one candidate target MN for the data forwarding. In some cases, the S-MN will perform an early data forwarding to the selected one candidate target MN, e.g., T-MN, in step 309, and the selected one candidate target MN will forward the data to the T-SN in step 311. In some other cases, the S-MN will indicate the selected candidate target MN to the source SN so that the source SN will perform the data forwarding to the selected candidate target MN.

[0105] For example, if the T-SN identification information received from multiple T-MNs is the same, the S-MN will determine that data will be forwarded to the same T-SN. Therefore, the S-MN will forward data to the selected candidate target MN but not to other candidate targets MN. For example, if the T-SN identification information received from candidate targets MN1, MN2, and MNm shown in FIG. 2a is the same, the S-MN will select only one of candidate targets MN1, MN2, and MNm for data forwarding.

[0106] If the random numbers allocated in the T-SN received from multiple T-MNs are the same, the S-MN will determine that the data will be forwarded to the same T-SN. Thus, the S-MN will forward the data to the selected candidate target MN but not to other candidate targets MN. For example, if the random numbers received from candidate targets MN1, MN2, and MNm shown in FIG. 2a are the same, the S-MN will select only one of candidate targets MN1, MN2, and MNm for data forwarding.

[0107] If the S-MN receives the same candidate target SN indicator from multiple T-MNs, the S-MN will determine that data will be forwarded to the same T-SN. Thus, the S-MN will forward data to the selected candidate target MN but not to the other candidate targets MN. For example, if the same candidate target SN indicator is received from candidate target MN1, candidate target MN2, and candidate target MNm shown in FIG. 2a, the S-MN will select only one of candidate target MN1, candidate target MN2, and candidate target MNm for data forwarding.

[0108] When an S-MN determines that data is to be forwarded to the same T-SN and receives estimated arrival probabilities from multiple T-MNs toward the same T-SN, the S-MN selects the candidate target MN with the largest estimated arrival probability for data forwarding. For example, if candidate target MN1 provides an estimated arrival probability of 90%, candidate target MN2 provides an estimated arrival probability of 80%, and candidate target MNm provides an estimated arrival probability of 70%, the S-MN selects candidate target MN1 for data forwarding to the T-SN.

[0109] 4 is a flowchart of an exemplary procedure for supporting data transfer in Scenario 2 according to some embodiments of the present application. Although there are multiple candidate target MNs and multiple candidate target SNs, the operations of only one candidate target MN and at least one candidate target SN prepared by the candidate target MN are shown in detail as an example for simplicity and clarity. Under the disclosure and teachings of the candidate target MNs and candidate target SNs shown in detail, those skilled in the art should be familiar with corresponding operations in other candidate target MNs and candidate target SNs, which may be the same, similar, or different from those of the shown target MN by adopting the same, similar, or different solutions taught by various embodiments of the present application.

[0110] Referring to Figure 4, in step 401a, the S-MN initiates the CHO procedure by sending a handover request message or the like to a T-MN, for example, the candidate target MN1 shown in Figure 2d. The handover request message or the like includes the MCG configuration and, if the UE is configured with an SCG, the SCG configuration. The handover request message or the like also includes CHO-related information. The CHO-related information includes the S-MN ID and the UE ID allocated in the S-MN.

[0111] Similarly, in step 401b, the S-MN may also initiate a CHO handover procedure by sending a handover request message or the like to one or more other T-MNs, for example, candidate target MN2 or candidate target MNm shown in FIG. 2d.

[0112] In step 403a1, the T-MN sends an SN Addition Request message or the like to a candidate target SN (also referred to as "T-SN" for simplicity) including CHO-related information. In some embodiments of the present application, in addition to the S-MN ID and the UE ID allocated in the S-MN, the CHO-related information may also include an estimated arrival probability for the UE heading to the candidate target SN prepared by the T-MN.

[0113] The T-MN may also send the same message to other candidate target SNs (also referred to as "other T-SNs" for simplicity) in step 403a2. The other T-MNs may perform equal or similar operations on the T-SN in step 403b1 and on the other T-SNs in step 403b2.

[0114] The T-SN will reply in step 405a1 with an SN Add Request Acknowledgement message or the like that includes the data forwarding address allocated by the T-SN, which data forwarding address relates to the PDU session for the DRB configured with the SN terminated bearer option.

[0115] The T-SN may also provide routing optimization related information to the T-MN in the same or similar messages to assist the T-MN in determining routing optimization information.

[0116] Since a data forwarding address is allocated for each T-MN by the T-SN, the T-SN can obtain the number of T-MNs that share a data forwarding address. Thus, in some embodiments of the present application, the T-SN may indicate information related to the number of candidate target MNs that use the same data forwarding address of the T-SN, so that the T-MN can determine the information that shares the data forwarding address. The information related to the number of candidate target MNs that use the same data forwarding address of the T-SN may be explicitly indicated using a numerical value, e.g., 3, of other T-MNs that use the same data forwarding address of the T-SN, or may be implicitly indicated using at least identification information thereof.

[0117] In some cases, in step 403a1, the T-MN may indicate a first time based on which information related to the number of candidate target MNs using the same data transfer address of the T-SN will be provided, for example, included in an SN addition request message. An exemplary example of the first time is a time length or a point in time. For example, the time length may be a time for waiting, indicating a maximum allowable waiting time for the T-SN to provide the number of candidate target MNs using the same data transfer address of the T-SN. The T-SN will determine the information related to the number of candidate target MNs using the same data transfer address based solely on counting the number of candidate target MNs using the same data transfer address at the indicated time, for example, the indicated point in time, or solely on counting the number of candidate target MNs using the same data transfer address at or within the first time determined based on the time length.

[0118] In some embodiments of the present application, the T-MN may receive, in step 401a, information indicating a second time based on which the S-MN will provide information sharing the data forwarding address, for example, included in a handover request message. Similarly, the second time is a time length or a point in time. An exemplary time length may be a time for waiting, indicating a maximum allowable waiting time for the T-MN to provide the number of candidate target MNs using the same data forwarding address of the T-MN. The T-MN will ensure that the first time is equal to or shorter than the second time.

[0119] When a first time is indicated, it is assumed that information related to the number of candidate target MNs using the same data forwarding address of the T-SN is obtained based on the first time, and then in step 405a1, the T-SN will return an SN addition request acknowledgment message, etc., so in step 405a1, the T-SN can indicate information related to the number of candidate target MNs using the same data forwarding address of the T-SN, such as in the SN addition request acknowledgment message.

[0120] If the T-SN receives a similar message from another T-MN in step 403b1, the T-SN will reply with a similar message to the other T-MN in step 405a2. If the other T-SN receives a similar message from the T-MN and another T-MN in steps 403a2 and 403b2, the other T-SN will reply with a similar message to the T-MN in step 405b1 and to the other T-MN in step 405b2.

[0121] After receiving the SN Addition Request Acknowledgement message from the T-SN, the T-MN will send, in step 407a, to the S-MN a Handover Request Acknowledgement message or the like, including the data forwarding address allocated by the T-SN. The data forwarding address is associated with the PDU session for the DRB configured with the SN terminated bearer option.

[0122] The T-MN may also include, in the same message or a different message, routing optimization information, based on information received from the T-SN, including at least one of an estimated reachability probability for UEs heading to the T-SN prepared by the T-MN, or information sharing a data forwarding address indicating the number of candidate target MNs using the same data forwarding address of the T-SN.

[0123] Other T-MNs will send similar messages to the S-MN in step 407b.

[0124] Based on the routing optimization information, the S-MN selects (or determines) one data forwarding address (or one candidate target SN) for data forwarding. The source MN performs early data forwarding to the selected one candidate target SN, e.g., T-SN, via the selected data forwarding address, in step 409, or indicates the selected candidate target SN to the source SN so that the source SN performs data forwarding to the selected candidate target SN.

[0125] For example, if an S-MN receives different data transfer addresses from multiple T-MNs with different estimated arrival probabilities, the S-MN will select the data transfer address sent from the T-MN with the largest estimated arrival probability for data transfer. For example, if candidate target MN1 shown in Figure 2d provides data transfer address 1 toward SN1 with an estimated arrival probability of 90%, candidate target MN2 provides data transfer address 2 toward SN2 with an estimated arrival probability of 50%, and candidate target MNm provides data transfer address n toward candidate target SNn with an estimated arrival probability of 80%, the S-MN will select data transfer address 1 for data transfer. Data will be sent directly from the S-MN or source SN to candidate target SN1.

[0126] In some cases, the same T-SN may be prepared by multiple T-MNs, e.g., candidate target SN1 is prepared by candidate target MN1 and candidate target MN2. When an S-MN receives the same data forwarding address with different estimated arrival probabilities from multiple T-MNs, the S-MN may further process the received estimated arrival probabilities associated with the T-SN, e.g., average the received estimated arrival probabilities. For example, for the same data forwarding address, e.g., that of candidate target SN1, candidate target MN1 provides an estimated arrival probability of 80%, while candidate target MN2 provides an estimated arrival probability of 60%, then the S-MN will derive or determine that the estimated arrival probability for the UE heading towards candidate target SN1 is 70%.

[0127] If information sharing data transfer addresses is received from two or more T-MNs, the S-MN may select the data transfer address to be used according to the maximum number of candidate target MNs for the data transfer or according to the maximum number of shared data transfer addresses. For example, candidate target MN1 shown in Figure 2d provides that the number of candidate target MNs sharing data transfer address 1 toward candidate target SN1 is 5, while candidate target MN2 provides that the number of candidate target MNs sharing data transfer address 2 toward candidate target SN2 is 2, and the source MN may select data transfer address 1 for the data transfer.

[0128] When both information about estimated arrival probability and information sharing data forwarding addresses are received from two or more candidate target MNs, the S-MN will select a data forwarding address in various ways based on its own implementation.

[0129] 5 is a flowchart of another exemplary procedure for supporting data transfer in Scenario 2 according to some other embodiments of the present application. Similarly, although there are multiple candidate target MNs and multiple candidate target SNs, the operations of only one candidate target MN and at least one candidate target SN prepared by the candidate target MN are shown in detail as an example for simplicity and clarity. Under the disclosure and teachings of the candidate target MNs and candidate target SNs shown in detail, those skilled in the art should be familiar with corresponding operations in other candidate target MNs and candidate target SNs, which may be the same as, similar to, or different from those of the shown target MN by adopting the same, similar, or different solutions taught by various embodiments of the present application.

[0130] Compared with Fig. 4, Fig. 5 differs in that routing optimization related information is sent to the T-MN in an SN modification required message, etc., rather than in an SN addition request ACK message. Steps 501a to 503b2 are equal to steps 401a to 403b2, and steps 505a1 to 505b2 can also refer to steps 405a1 to 405b2, such that only a legacy SN addition request ACK message is sent, and routing optimization related information is not sent to the T-MN.

[0131] In step 507a, the T-MN may only return a handover request ACK message, or may include routing optimization information in the handover request ACK message indicating an estimated reachability for the UE heading to the T-SN prepared by the T-MN. Step 507b is similar. If the S-MN receives routing optimization information indicating an estimated reachability, it may perform routing optimization based on the received estimated reachability, as indicated above, or wait for further routing optimization information.

[0132] In step 509a1, the T-SN sends a message to the T-MN, for example by an SN modification required message, indicating information related to the number of candidate target MNs using the same data forwarding address of the SN, which information may be the numerical value of other T-MNs using the same data forwarding address of the T-SN, for example 3, or their identification information, or the identification information of all T-MNs using the same data forwarding address of the T-SN, etc. Steps 509a2 to 509b2 are similar.

[0133] In some cases, the T-MN may indicate in step 503a1 a first time based on information related to the number of candidate target MNs using the same data forwarding address of the SN being provided, including, for example, in an SN addition request message. The T-MN will determine the information related to the number of candidate target MNs using the same data forwarding address based on the indicated time. If the T-MN receives in step 501a a second time based on information sharing a data forwarding address being provided from the S-MN, including, for example, in a handover request message, the first time will be equal to or less than the second time.

[0134] After receiving the information related to the number of candidate target MNs using the same data forwarding address indicated by the T-SN, the T-MN is caused to transmit routing optimization information including information sharing the data forwarding address to the S-MN in step 511a, for example, by a message after the handover request ACK message. In some embodiments of the present application, the T-MN may not transmit any routing optimization information to the S-MN in step 507a, and is caused to transmit routing optimization information including at least one of estimated reachability probability for UEs heading to the T-SN prepared by the T-MN or information sharing the data forwarding address to the source MN, as shown in step 407a shown in FIG. 4.

[0135] Other T-MNs will send similar messages to the S-MN in step 511b.

[0136] Similar to Figure 4, based on the routing optimization information, the S-MN will select (or determine) one data forwarding address (or one candidate target SN) for data forwarding. The source MN will perform early data forwarding to the selected one SN, e.g., T-SN via the selected data forwarding address, in step 513, or will indicate the selected candidate target SN to the source SN so that the source SN will perform data forwarding to the selected candidate target SN.

[0137] 6 is a flowchart of an exemplary procedure for supporting data transfer in Scenario 3 according to some embodiments of the present application. Similarly, although there are multiple candidate target MNs and multiple candidate target SNs, the operations of only one candidate target MN and at least one candidate target SN prepared by the candidate target MN are shown in detail as an example for simplicity and clarity. Under the disclosure and teachings of the candidate target MNs and candidate target SNs shown in detail, those skilled in the art should be familiar with corresponding operations in other candidate target MNs and candidate target SNs, which may be the same, similar, or different from those of the shown target MN by adopting the same, similar, or different solutions taught by various embodiments of the present application.

[0138] Referring to Figure 6, in step 601a, the S-MN initiates the CHO procedure by sending a handover request message or the like to a T-MN, for example, the candidate target MN1 shown in Figure 2b. The handover request message or the like includes the MCG configuration and, if the UE is configured with an SCG, the SCG configuration. The handover request message or the like also includes CHO-related information. The CHO-related information includes the S-MN ID and the UE ID allocated in the S-MN.

[0139] Similarly, in step 601b, the S-MN may also initiate a CHO handover procedure by sending a handover request message or the like to one or more other T-MNs, for example, candidate target MN2 or candidate target MNm shown in FIG. 2b.

[0140] In some cases, the S-MN may also indicate to the T-MN a time (second time) based on the routing optimization information to be determined, such as the information sharing the data forwarding address and / or one or more second estimated arrival probabilities. For example, the second time is a length of time to wait and indicates a maximum tolerable waiting time for providing the information sharing the data forwarding address and / or the maximum tolerable waiting time for providing the second estimated arrival probabilities.

[0141] In step 603a1, the T-MN will send an SN addition request message or the like to the T-SN, including CHO-related information. In some embodiments of the present application, in addition to the S-MN ID and the UE ID allocated in the S-MN, the CHO-related information may also include an estimated arrival probability for the UE heading to the target SN prepared by the T-MN.

[0142] In some cases, the T-MN may also indicate to the T-SN a time (first time) based on which routing optimization-related information is to be determined, such as its information related to the number of candidate target MNs using the same data forwarding address of the T-SN and / or one or more second estimated reach probabilities. If the second time is provided by the S-MN, the first time may be shorter than or later than the second time. In some other cases, the S-MN may directly indicate the first time based on which the routing optimization-related information is to be determined.

[0143] The T-MN may also send the same message to other T-SNs in step 603a2, and the other T-MNs may perform equal or similar actions on the T-SN in step 603b1 and on other T-SNs in step 603b2.

[0144] The T-SN will reply in step 605a1 with an SN Add Request Acknowledgement message or the like, which includes the data forwarding address allocated by the T-SN, which data forwarding address relates to the PDU session for the DRB configured with the SN terminated bearer option.

[0145] Similarly, the T-SN may also provide routing optimization related information to the T-MN in the same or similar messages to assist the T-MN in determining routing optimization information.

[0146] For example, similar to Figure 3, in some embodiments of the present application, the T-SN may indicate the identity of the T-SN. An exemplary identity of the T-SN is the globally unique identity of the T-SN.

[0147] 4, in some embodiments of the present application, the T-SN may indicate information related to the number of candidate target MNs using the same data forwarding address either explicitly with a numerical value, e.g., 3, of other T-MNs using the same data forwarding address of the T-SN, or implicitly with at least identification information thereof. When the first time is provided, the T-SN will determine the number of candidate target MNs using the same data forwarding address based on the first time.

[0148] In some cases, a T-SN may indicate to a T-MN estimated arrival probabilities (second estimated arrival probabilities) from other T-MNs. Each second estimated arrival probability is an estimated arrival probability for a UE heading to a T-SN prepared by another candidate target MN. For example, if candidate target SN2 is prepared by candidate target MN2 and candidate target MNm in addition to candidate target MN1, as shown in FIG. 2b, candidate target SN2 will provide candidate target MN1 with second estimated arrival probabilities, including the estimated arrival probability from candidate target MN2 and the estimated arrival probability from candidate target MNm. When the first time is provided, the T-SN will determine the second estimated arrival probabilities from other T-MNs based on the first time.

[0149] 6, when a first time is indicated, it is assumed that information related to the number of candidate target MNs using the same data forwarding address and / or one or more second estimated arrival probabilities is obtained based on the first time, and then the T-SN returns an SN addition request acknowledgement message or the like in step 605a1, whereby the T-SN can indicate the information related to the number of candidate target MNs using the same data forwarding address and / or one or more second estimated arrival probabilities in the SN addition request acknowledgement message or the like in step 605a1.

[0150] The T-SN may transmit to the T-MN at least one of the above routing optimization related information, for example, only the identification information of the T-SN, or only information related to the number of candidate target MNs using the same data forwarding address, or only one or more second estimated arrival probabilities, or any combination thereof.

[0151] If the T-SN receives a similar message from another T-MN in step 603b1, the T-SN will reply with a similar message to the other T-MN in step 605a2. If the other T-SN receives a similar message from the T-MN and the other T-MN in steps 603a2 and 603b2, the other T-SN will reply with a similar message to the T-MN in step 605b1 and to the other T-MN in step 605b2.

[0152] After receiving an SN addition request acknowledgement message or the like from the T-SN, the T-MN will send a handover request acknowledgement message or the like to the S-MN in step 607a, including the data forwarding address allocated by the T-MN. The data forwarding address is associated with a PDU session for the DRB configured with the SN terminated bearer option.

[0153] The T-MN may also include routing optimization information in the same message or a different message. Based on information received from the T-SN, the routing optimization information includes at least identification information of one or more candidate target SNs, for example, by a list of T-SN identification information prepared by the T-MN. The routing optimization information may further include at least one of: data forwarding address sharing information indicating the number of candidate target MNs using the same data forwarding address of one candidate target SN; one or more first estimated arrival probabilities, each first estimated arrival probability for UEs heading to a corresponding candidate target SN among one or more candidate target SNs prepared by the T-MN; or one or more second estimated arrival probabilities, each second estimated arrival probability for UEs heading to a corresponding candidate target SN among one or more candidate target SNs prepared by another candidate target MN different from the T-MN.

[0154] For example, exemplary routing optimization information from T-MN1 is shown in Table 1 below. The exemplary information indicates the identification information of T-SNs prepared by the T-MN, e.g., T-SN1 and T-SN2 prepared by T-MN1. For each T-SN, Table 1 further indicates the estimated arrival probability for UEs heading to the T-SN prepared by the T-MN (first estimated arrival probability) and the estimated arrival probability for UEs heading to T-SNs prepared by other T-MNs (second estimated arrival probability) (or the estimated arrival probability for UEs heading to the T-SN from other T-MNs). Taking T-SN2 as an example, the first estimated arrival probability from T-MN1 and the second estimated arrival probability from T-MN4 are shown.

[0155] [Table 1]

[0156] Other T-MNs will send similar messages to the S-MN in step 607b.

[0157] Based on the routing optimization information, the S-MN performs routing optimization for data forwarding, for example, selects one candidate target MN for data forwarding, and in some cases further determines a destination for data forwarding for the SN terminated bearer, where the destination is the identity of the selected T-SN.

[0158] When an S-MN receives data forwarding addresses from multiple T-MNs along with T-SN identification information, e.g., multiple T-SN identification lists, the S-MN may determine the T-MN for data forwarding based on the received T-SN identification lists. In some embodiments of the present application, the S-MN selects the T-MN with the largest number of shared T-SNs. For example, assume that T-MN1 provides data forwarding addresses of T-SN1, T-SN2, and T-SN3, T-MN2 provides data forwarding addresses of T-SN2, T-SN3, and T-SN4, and T-MN3 provides data forwarding addresses with T-SN3 and T-SN4. Then, the S-MN selects T-MN2 for data forwarding because T-MN2 has the largest number of shared T-SNs. In some other embodiments of the present application, the S-MN may select the T-MN with the largest number of T-SNs as the candidate target MN for data forwarding. More methods may be adopted by the S-MN based on its implementation.

[0159] If the estimated arrival probability (first estimated arrival probability and / or second estimated arrival probability) for a UE heading to a T-SN prepared by the T-MN is included in the routing optimization information, the S-MN may select the T-SN with the largest estimated arrival probability for data forwarding.

[0160] For example, as shown in Figure 2b, if the first estimated arrival probability towards candidate target SN1 is 90% and the first estimated arrival probability towards candidate target SN2 is 70%, the S-MN will select candidate target SN1 as the destination for data transfer. In step 609, destination notification is performed, and the S-MN will notify the selected one T-MN of the destination for data transfer. If the data transfer is to be performed by the source SN, the S-MN will also indicate the destination for data transfer to the source SN.

[0161] If the routing optimization information includes an estimated arrival probability (second estimated arrival probability) toward a T-SN prepared by another T-MN, the S-MN may process the estimated arrival probability associated with the same T-SN, for example, averaging the first estimated arrival probability and the second estimated arrival probability of the T-SN. For example, for candidate target SN1, the estimated arrival probability from candidate target MN1 is 90%, and the estimated arrival probability from candidate target MN2 is 50%, while for candidate target SN2, the estimated arrival probability from candidate target MN1 is 90%, the estimated arrival probability from candidate target MN2 is 80%, and the estimated arrival probability from candidate target MNm is 70%. In this case, the S-MN derives that the estimated arrival probability toward candidate target SN1 is 70%, but the estimated arrival probability toward T-SN2 is 80%, and then the S-MN selects candidate target SN2 as the destination for data transfer.

[0162] The source MN will either perform early data transfer to one selected T-MN or indicate the selected candidate target MN to the source SN so that the source SN will perform data transfer to the selected candidate target MN.

[0163] If the routing optimization information indicates information to share a data forwarding address, the S-MN may select a T-SN in a manner similar to that shown in FIG.

[0164] In addition, if the routing optimization information indicates multiple types of information as shown above, the S-MN will perform routing optimization in different ways based on its implementation.

[0165] After the routing for data forwarding is optimized, the S-MN or source SN will perform data forwarding based on the optimized routing, e.g., forward data only to selected T-MNs and then to the destination.

[0166] 7 is a flowchart of another exemplary procedure for supporting data transfer in Scenario 3 according to some other embodiments of the present application. Similarly, although there are multiple candidate target MNs and multiple candidate target SNs, the operations of only one candidate target MN and at least one candidate target SN prepared by the candidate target MN are shown in detail as an example for simplicity and clarity. Under the disclosure and teachings of the candidate target MNs and candidate target SNs shown in detail, those skilled in the art should be familiar with corresponding operations in other candidate target MNs and candidate target SNs, which may be the same as, similar to, or different from those of the shown target MN by adopting the same, similar, or different solutions taught by various embodiments of the present application.

[0167] Compared with Fig. 6, Fig. 7 differs in that some or all of the routing optimization related information is sent to the T-MN in an SN Modification Required message, rather than an SN Addition Request ACK message. Steps 701a to 703b2 are equal to steps 601a to 603b2, and steps 705a1 to 705b2 can also refer to steps 605a1 to 605b2, and only the legacy SN Addition Request ACK message is sent, and no routing optimization related information, or only part of it, e.g., only T-SN identification information, is sent to the T-MN.

[0168] In step 707a, the T-MN may only return a handover request ACK message, or may include in the handover request ACK message at least routing optimization information indicating the identification information of the T-SNs prepared by the T-MN. The routing optimization information may further include estimated arrival probabilities (first estimated arrival probabilities) for UEs heading to each T-SN prepared by the T-MN. This is similar to step 707b.

[0169] When receiving routing optimization information indicating the identity of the T-SN and possibly a first estimated arrival probability, the S-MN may perform routing optimization based on the received routing optimization information as indicated above or may wait for further routing optimization information.

[0170] In step 709a1, the T-SN transmits, for example, by an SN modification required message, to the T-MN, information related to the number of candidate target MNs using the same data forwarding address, or at least one of one or more second estimated arrival probabilities, as in steps 709a2 to 709b2.

[0171] In some cases, the T-MN may indicate in step 703a1 a first time based on information being provided relating to the number of candidate target MNs using the same data forwarding address of the SN, including, for example, in an SN addition request message. The T-MN will determine the number of candidate target MNs using the same data forwarding address based on the indicated time. If the T-MN receives in step 701a a second time based on information being provided from the S-MN sharing the data forwarding address, including, for example, in a handover request message, the first time will be equal to or less than the second time.

[0172] Similarly, in some cases, the T-MN may indicate a first time based on which one or more second estimated delivery probabilities will be provided in step 703a1, including, for example, in an SN addition request message. The T-MN will determine the one or more second estimated delivery probabilities based on the indicated time. If the T-MN receives a second time based on which one or more second estimated delivery probabilities will be provided from the S-MN in step 701a, including, for example, in a handover request message, the first time will be equal to or less than the second time.

[0173] After receiving routing optimization related information from the T-SN, e.g., indicating information related to the number of candidate target MNs using the same data forwarding address based on the indicated time, or at least one of one or more second estimated reachability probabilities, the T-MN is proceeded to transmit the routing optimization information including the data forwarding address sharing information and / or one or more second estimated reachability probabilities to the S-MN in step 711a, e.g., by a message after the handover request ACK message. In some embodiments of the present application, the T-MN may not transmit any routing optimization information to the S-MN in step 707a, but is proceeded to transmit the routing optimization information including at least one of the identification information of the T-SN prepared by the T-MN, the first estimated reachability probability of the T-SN, the data forwarding address sharing information, or the second estimated reachability probability of the T-SN, as indicated in step 607a.

[0174] Other T-MNs will send similar messages to the S-MN in step 711b.

[0175] Similar to Figure 6, based on the routing optimization information, the S-MN will select (or determine) one candidate target MN for data forwarding or determine the destination for the SN terminated bearer. If a destination is determined, the S-MN will inform the T-MN or indicate the destination to the source SN in step 713 before data forwarding.

[0176] In addition to the method, the embodiments of the present application also propose an apparatus for supporting data transfer. For example, Figure 8 is a block diagram of an apparatus for supporting data transfer according to some embodiments of the present application.

[0177] 8, the apparatus 800 may include at least one non-transitory computer-readable medium 801, at least one receiving circuit 802, at least one transmitting circuit 804, and at least one processor 806 coupled to the non-transitory computer-readable medium 801, the receiving circuit 802, and the transmitting circuit 804. The apparatus 800 may be a RAN node (e.g., MN or SN) configured to perform methods such as those presented above.

[0178] In this figure, elements such as at least one processor 806, transmit circuitry 804, and receive circuitry 802 are described in the singular, but the plural is contemplated unless limitation to the singular is expressly stated. In some embodiments of the present application, the receive circuitry 802 and the transmit circuitry 804 may be combined into a single device such as a transceiver. The processor 806 may be a central processing unit (CPU), a digital signal processing (DSP), a microprocessor, etc. In some embodiments of the present application, the apparatus 800 may further include an input device, a memory, and / or other components.

[0179] In some embodiments of the present application, the non-transitory computer-readable medium 801 may store computer-executable instructions for causing the processor 806 to perform a method relating to a RAN node, e.g., an MN or an SN, as described above. For example, the computer-executable instructions, when executed, cause the processor 806, interacting with the receiving circuitry 802 and the transmitting circuitry 804, to perform steps relating to a RAN node as shown above.

[0180] FIG. 9 shows a block diagram of an apparatus 900 for supporting data transfer according to some other embodiments of the present application.

[0181] 9, an apparatus 900, e.g., an MN or SN, may include at least one processor 902 and at least one transceiver 904. The transceiver 904 may include at least one separate receiving circuit 906 and transmitting circuit 908, or at least one integrated receiving circuit 906 and transmitting circuit 908. The at least one processor 902 may be a CPU, DSP, microprocessor, etc.

[0182] According to some embodiments of the present application, when the apparatus 900 is an MN, for example, a candidate target MN, the processor is configured to determine routing optimization information for early data transfer associated with one or more candidate target SNs at least prepared by the MN, where the early data transfer is for CHO with the SCG of the UE, and the transceiver is coupled to the processor and configured to transmit the routing optimization information to the source MN.

[0183] According to some other embodiments of the present application, when the apparatus 900 is an MN, e.g., a source MN, the processor may be configured to: send a handover request for CHO with an SCG of the UE to a candidate target MN among one or more candidate target MNs; and receive from the candidate target MN information of routing optimization for early data transfer associated with one or more candidate target SNs at least prepared by the candidate target MN, where the early data transfer is for CHO with the SCG.

[0184] According to some other embodiments of the present application, when the apparatus 900 is an SN, for example, a candidate target SN, the processor may be configured to receive, from the candidate target MN, first information related to a CHO with an SCG of the UE, and to send, to the candidate target MN, second information related to routing optimization for early data transfer for the CHO with the SCG.

[0185] The methods according to the embodiments of the present application may also be implemented on a programmed processor. However, the controller, flowcharts, and modules may also be implemented in hardware electronic or logic circuitry such as a general-purpose or special-purpose computer, a programmed microprocessor or microcontroller and peripheral integrated circuit elements, integrated circuits, discrete element circuits, programmable logic devices, etc. In general, any device capable of implementing the flowcharts shown in the figures may be used to implement the processor functions of the present application. For example, one embodiment of the present application provides an apparatus including a processor and a memory. Computer-programmable instructions for implementing the method are stored in the memory, and the processor is configured to execute the computer-programmable instructions for implementing the method. The method may be as described above or another method according to an embodiment of the present application.

[0186] An alternative embodiment preferably implements a method according to an embodiment of the present application in a non-transitory computer-readable storage medium that stores computer-programmable instructions. The instructions are preferably executed by a computer-executable component, preferably incorporated with the network security system. The non-transitory computer-readable storage medium may be stored on any suitable computer-readable medium, such as random access memory (RAM), read-only memory (ROM), flash memory, electrically erasable programmable read-only memory (EEPROM), an optical storage device (compact disc (CD) or digital video disc (DVD)), a hard drive, a floppy drive, or any suitable device. The computer-executable component is preferably a processor, although the instructions may alternatively or additionally be executed by any suitable dedicated hardware device. For example, one embodiment of the present application provides a non-transitory computer-readable storage medium having computer-programmable instructions stored therein. The computer-programmable instructions are configured to implement a method as described above or other methods according to an embodiment of the present application.

[0187] While the present application has been described with particular embodiments thereof, it is apparent that numerous alternatives, modifications, and variations may be apparent to those skilled in the art. For example, various components of the embodiments may be exchanged, added, or substituted in other embodiments. Also, not all elements in each figure are necessary for the operation of the disclosed embodiments. For example, one skilled in the art of the disclosed embodiments will be enabled to make and use the teachings of the present application by simply employing the elements of the independent claims. Accordingly, the embodiments of the present application described herein are intended to be illustrative, not limiting. Various changes may be made without departing from the spirit and scope of the present application. [Explanation of symbols]

[0188] 100 Wireless Communication System, Dual Connectivity System 101UE 102 MN 103SN 800, 900 equipment 801 Non-Transitory Computer-Readable Medium 802, 906 receiving circuit 804, 908 Transmitting circuit 806, 902 processors 904 Transceiver

Claims

1. A master node (MN), 1. A processor, comprising: determining routing optimization information for early data forwarding associated with one or more candidate target secondary nodes (SNs) prepared at least by the MN, wherein the early data forwarding is for a conditional handover (CHO) to a secondary cell group (SCG) of a user equipment (UE); a processor configured to: a transceiver coupled to the processor, sending said routing optimization information to a source MN; a transceiver configured to A master node (MN) is provided with:

2. The routing optimization information includes the following: an identity of one candidate target SN among said one or more candidate target SNs; a random number allocated in said one candidate target SN; or a same candidate target SN indicator indicating that a data transfer address associated with the early data transfer will map to the same data transfer address of the one candidate target SN. The MN of claim 1, wherein the MN exhibits at least one of the following:

3. The MN of claim 2 , wherein the routing optimization information further indicates an estimated arrival probability for the UE toward the one candidate target SN prepared by the MN.

4. The transceiver receiving information indicating that the same data forwarding address is shared with the MN by other candidate target MNs, and causing an indicator of the same candidate target SN to be determined by the MN; The MN of claim 2, configured to:

5. The routing optimization information includes the following: an estimated arrival probability for the UE towards one candidate target SN prepared by the MN among the one or more candidate target SNs; or and information for sharing a data transfer address, indicating the number of candidate target MNs that use the same data transfer address of said one candidate target SN. The MN of claim 1, wherein the MN exhibits at least one of the following:

6. The routing optimization information includes the following: Identification of said one or more candidate target SNs; data transfer address sharing information indicating the number of candidate target MNs using the same data transfer address of one candidate target SN among the one or more candidate target SNs; one or more first estimated arrival probabilities, each first estimated arrival probability being for the UE heading to a corresponding candidate target SN among the one or more candidate target SNs prepared by the MN; or one or more second estimated arrival probabilities, each of which is for the UE heading toward a corresponding candidate target SN among the one or more candidate target SNs prepared by another candidate target MN different from the MN; The MN of claim 1, wherein the MN exhibits at least one of the following:

7. 7. The MN of claim 5 or 6, wherein information relating to the number of candidate target MNs using the same data forwarding address of the one candidate target SN is indicated by the one candidate target SN via an SN addition request acknowledgement message or an SN modification required message.

8. The transceiver transmitting to the one candidate target SN information indicating a first time based on which the information relating to the number of candidate target MNs using the same data forwarding address of the one candidate target SN will be provided; receiving said information relating to said number of candidate target MNs using said same data transfer address of said one candidate target SN; The MN of claim 7, configured to:

9. MN according to claim 7, wherein the information relating to the number of candidate target MNs using the same data transfer address of the one candidate target SN is indicated by the one candidate target SN using the numerical value of other candidate target MNs using the same data transfer address in addition to the MN, or at least their identification information.

10. The transceiver transmitting to the candidate target SN information indicative of a first time based on which a second estimated arrival probability associated with the candidate target SN will be provided; receiving a message indicating the second estimated arrival probability associated with the candidate target SN; The MN of claim 6, configured to perform the following.

11. The transceiver receiving, from the source MN, a destination for data forwarding for an SN terminated bearer, the destination being an identity of a target SN determined by the source MN; The MN of claim 6, configured to perform the following.

12. A master node (MN), a processor; a transceiver coupled to the processor, sending a handover request to a candidate target MN among one or more candidate target MNs for a conditional handover (CHO) with a secondary cell group (SCG) of a user equipment (UE); receiving, from the candidate target MN, routing optimization information for early data transfer associated with one or more candidate target secondary nodes (SNs) at least prepared by the candidate target MN, the early data transfer being for the CHO with the SCG; a transceiver configured to A master node (MN) comprising:

13. A secondary node (SN), a processor; a transceiver coupled to the processor, receiving first information related to a conditional handover (CHO) of a user equipment (UE) to a secondary cell group (SCG) from a candidate target master node (MN); sending, to the candidate target MN, second information related to routing optimization for early data transfer for the CHO with the SCG; a transceiver configured to A secondary node (SN) comprising:

14. The second information is: The identification information of the SN; A random number assigned in the SN, or Information indicating that the same data forwarding address is shared with the candidate target MN by other candidate target MNs.

14. The SN of claim 13, wherein the SN exhibits at least one of the following:

15. The second information is: The identification information of the SN; Information relating to the number of candidate target MNs using the same data forwarding address of said SN; or one or more second estimated arrival probabilities, each second estimated arrival probability being for the UE heading to the SN prepared by another candidate target MN different from the candidate target MN; 14. The SN of claim 13, wherein the SN exhibits at least one of the following:

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