Radio access network node and method thereof

Abstract

In the present invention, a secondary node (SN) (2), in response to reception, in a PSCell of a secondary cell group (SCG) from a User Equipment (UE) (3), of a first signal representing a request for or a display of SCG activation, transmits a second signal indicating SCG activation to the UE (3) in the PSCell. The second signal is transmitted to the UE (3) before the SN (2) transmits, to a master node (MN) (1), an inter-node message indicating SCG activation, or before the SN (2) receives a response to the inter-node message from the MN (1). The foregoing can contribute to, for example, reducing a delay in SCG activation triggered by a UE.

Description

[Technical field]

[0001] The present disclosure relates to wireless communication systems, and more particularly to activation and deactivation of a Secondary Cell Group (SCG) in multi-connectivity (eg, dual connectivity). [Background technology]

[0002] The 3rd Generation Partnership Project (3GPP) is working on Release 17. 3GPP is discussing efficient activation and deactivation mechanisms for Secondary Cell Groups (SCGs). SCG deactivation allows deactivating one SCG that contains the Primary SCG Cell (PSCell).

[0003] It is agreed in this discussion that (re)activation of a deactivated SCG can be triggered (or initiated) by the Master Node (MN) and Secondary Node (SN) in the case of downlink, and by the User Equipment (UE) in the case of uplink (see, for example, non-patent documents 1-3). Regarding UE initiated / triggered / requested SCC reactivation, a first solution has been proposed in which the UE sends an SCG (re)activation request (or indication) to the MN, and a second solution has been proposed in which the UE sends an SCG (re)activation request (or indication) directly to the SN.

[0004] Specifically, in one example of a procedure according to the first solution, the UE sends an SCG (re)activation request (or indication) to the MN, which notifies the SN of the SCG (re)activation and instructs the UE to perform the SCG (re)activation (see Non-Patent Document 1). The (re)activation request (or indication) sent from the UE to the MN may be a Radio Resource Control (RRC) message (see Non-Patent Documents 2 and 3), e.g., a UE Assistance Information (UAI) (see Non-Patent Document 3). Alternatively, the (re)activation request (or indication) may be a Buffer Status Report (BSR) (i.e., a Medium Access Control (MAC) Control Element (CE)) (see Non-Patent Document 2).

[0005] On the other hand, in an example of a procedure according to the second solution, the UE activates the SCG by performing a random access to the SN (i.e., the PSCell) (see Non-Patent Documents 1-3). If the UE maintains a valid uplink timing of the SCG, the UE may skip the random access upon SCG activation and may perform an uplink transmission (see Non-Patent Document 1). For example, the UE may send an SCG activation indication to the SCG (SN) by sending a scheduling request (SR) (i.e., a physical layer message) in the PSCell (see Non-Patent Document 2). [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] vivo, "Signaling aspect of SCG activation and deactivation", R2-2101015, 3GPP TSG-RAN WG2 Meeting #113-e, January 25 - February 5, 2021 [Non-Patent Document 2] Qualcomm Incorporated, "Activation of deactivated SCG", R2-2103895, 3GPP TSG-RAN WG2 Meeting #113bis-e, April 12-20, 2021 [Non-Patent Document 3] Apple Inc, "UE initiation of SCG re-activation request", R2-2105140, 3GPP TSG-RAN WG2 Meeting #113bis-e, April 12-20, 2021 Summary of the Invention [Problem to be solved by the invention]

[0007] The inventors have considered SCG activation and deactivation and found various challenges. One of these challenges relates to how to perform SCG activation initiated (or triggered, requested) by the UE. Specifically, when the SN receives a request or indication for SCG activation (e.g., random access or SR) from the UE, it is not clear how the SN authorizes the UE to activate the SCG. If the SN must perform signaling with the MN before authorizing the UE to activate the SCG, this may prevent the UE from using the SCG in a timely manner.

[0008] Another problem that the inventors have encountered concerns messages exchanged between the MN and the SN regarding SCG activation. In particular, when the SN sends a request or indication of SCG activation to the MN, it may be preferable for the MN to know whether this SCG activation was triggered by the SN or the UE.

[0009] Another problem that the inventors have obtained relates to the second solution of UE initiated SCG activation mentioned above. In one specific example of the second solution, the UE activates the SCG by performing a random access to the SN (i.e., the PSCell). However, if the SN needs to assign a dedicated random access preamble to each of the UEs with a deactivated SCG, this may lead to a shortage of preamble resources for Contention-Free Random Access (CFRA). On the other hand, if the random access for SCG activation is simply contention-based, this may lead to an increase in the delay of SCG activation.

[0010] One of the objectives that the embodiments disclosed in this specification aim to achieve is to provide an apparatus, a method, and a program that contribute to solving at least one of the problems including the problems described above. It should be noted that this objective is only one of the objectives that the embodiments disclosed in this specification aim to achieve. Other objectives or objectives and novel features will be apparent from the description of this specification or the accompanying drawings. [Means for solving the problem]

[0011] A first aspect is directed to a Radio Access Network (RAN) node configured to operate as a secondary node associated with an SCG in dual connectivity for a UE. The RAN node includes at least one memory and at least one processor coupled to the at least one memory. The at least one processor is configured to receive a first signal in a PSCell of the SCG from the UE when the SCG is deactivated, the first signal representing a request or indication of activation of the SCG. In response to receiving the first signal, the at least one processor transmits in the PSCell to the UE a second signal indicating activation of the SCG. The at least one processor is further configured to transmit an inter-node message indicating the activation of the SCG to a master node associated with a Master Cell Group (MCG) of the dual connectivity. The second signal is transmitted to the UE before the secondary node transmits the inter-node message to the master node or before the secondary node receives a response to the inter-node message from the master node.

[0012] A second aspect is directed to a method performed by a RAN node configured to operate as a secondary node associated with an SCG in dual connectivity for a UE, the method including: (a) receiving a first signal in a PSCell of the SCG from the UE when the SCG is deactivated, the first signal indicating a request or indication of activation of the SCG; (b) transmitting a second signal in the PSCell to the UE in response to receiving the first signal, the second signal indicating activation of the SCG; and (c) transmitting an inter-node message indicating activation of the SCG to a master node associated with an MCG of the dual connectivity. The second signal is transmitted to the UE before the secondary node transmits the inter-node message to the master node or before the secondary node receives a response to the inter-node message from the master node.

[0013] A third aspect is directed to a RAN node configured to operate as a secondary node associated with an SCG in dual connectivity for a UE, the RAN node including at least one memory and at least one processor coupled to the at least one memory. The at least one processor is configured to receive a first signal in a PSCell from the UE when the SCG is deactivated, the first signal representing a request or indication of activation of the SCG. In response to receiving the first signal, the at least one processor is configured to transmit an inter-node message indicating activation of the SCG to a master node associated with an MCG of the dual connectivity and receive a response to the inter-node message from the master node. The at least one processor is configured to transmit a second signal in the PSCell to the UE indicating activation of the SCG if the response indicates that the activation of the SCG is accepted.

[0014] A fourth aspect is directed to a method performed by a RAN node configured to operate as a secondary node associated with an SCG in dual connectivity for a UE, the method including: (a) the at least one processor receiving in a PSCell from the UE when the SCG is deactivated a first signal representing a request or indication of activation of the SCG, (b) in response to receiving the first signal, transmitting an inter-node message indicating activation of the SCG to a master node associated with an MCG of the dual connectivity, (c) receiving from the master node a response to the inter-node message, and (d) if the response indicates that the activation of the SCG is accepted, transmitting in the PSCell a second signal to the UE indicating activation of the SCG.

[0015] A fifth aspect is directed to a RAN node configured to operate as a secondary node associated with an SCG in dual connectivity for a UE, the RAN node including at least one memory and at least one processor coupled to the at least one memory. The at least one processor is configured to determine which of a plurality of options is used to activate the SCG, the plurality of options being used to activate the SCG in response to receiving a first signal from the UE in a PSCell of the SCG representing a request or indication of activation of the SCG. The plurality of options include a first option and a second option. The first option is an option in which the secondary node transmits a second signal indicative of activation of the SCG to the UE in the PSCell prior to transmitting an inter-node message indicating activation of the SCG to a master node associated with an MCG of the dual connectivity, while the second option is an option in which the secondary node transmits the second signal to the UE after receiving a response to the inter-node message from the master node.

[0016] A sixth aspect is directed to a method performed by a RAN node configured to operate as a secondary node associated with an SCG in dual connectivity for a UE, the method including determining which of a plurality of options is used to activate the SCG in response to receiving a first signal from the UE in a PSCell of the SCG indicating a request or indication of activation of the SCG. The plurality of options includes a first option and a second option. The first option is an option in which the secondary node transmits a second signal in the PSCell to the UE indicating activation of the SCG prior to transmitting an inter-node message indicating activation of the SCG to a master node associated with an MCG of the dual connectivity, while the second option is an option in which the secondary node transmits the second signal to the UE after receiving a response to the inter-node message from the master node.

[0017] A seventh aspect is directed to a RAN node configured to operate as a master node associated with an MCG in dual connectivity for a UE. The RAN node includes at least one memory and at least one processor coupled to the at least one memory. The at least one processor is configured to determine which of a plurality of options is used to activate an SCG of the dual connectivity. The plurality of options is used to activate the SCG in response to receiving a first signal from the UE via the MCG representing a request or indication of activation of the SCG. The plurality of options includes a first option and a second option. The first option is an option in which the master node transmits a second signal indicating activation of the SCG to the UE via the MCG prior to transmitting an inter-node message indicating activation of the SCG to a secondary node associated with the SCG. Meanwhile, the second option is an option in which the master node transmits the second signal to the UE after receiving a response to the inter-node message from the secondary node.

[0018] An eighth aspect is directed to a method performed by a RAN node configured to operate as a master node associated with an MCG in dual connectivity for a UE, the method including determining which of a plurality of options is used to activate an SCG for the dual connectivity, the plurality of options being used to activate the SCG in response to receiving a first signal from the UE via the MCG indicating a request or indication of activation of the SCG. The plurality of options includes a first option and a second option. The first option is an option in which the master node transmits a second signal indicating activation of the SCG to the UE via the MCG prior to transmitting an inter-node message indicating activation of the SCG to a secondary node associated with the SCG, while the second option is an option in which the master node transmits the second signal to the UE after receiving a response to the inter-node message from the secondary node.

[0019] A ninth aspect is directed to a RAN node configured to operate as a secondary node associated with an SCG in dual connectivity for a UE, the RAN node including at least one memory and at least one processor coupled to the at least one memory. The at least one processor is configured to receive a first signal from the UE at a PSCell of the SCG when the SCG is deactivated, the first signal representing a request or indication of activation of the SCG. In response to receiving the first signal, the at least one processor is configured to transmit an inter-node message representing a request or indication of activation of the SCG to a master node associated with an MCG in the dual connectivity. The inter-node message is the same as a message transmitted from the secondary node to the master node when activation of the SCG is initiated by the secondary node, but includes information indicating SCG activation initiated by the UE.

[0020] A tenth aspect is directed to a method performed by a RAN node configured to operate as a secondary node associated with an SCG in dual connectivity for a UE, the method including: (a) receiving a first signal from the UE at a PSCell of the SCG when the SCG is deactivated, the first signal indicating a request or indication of activation of the SCG, and (b) in response to receiving the first signal, sending an inter-node message indicating the request or indication of activation of the SCG to a master node associated with an MCG of the dual connectivity. The inter-node message is the same as a message sent from the secondary node to the master node when activation of the SCG is initiated by the secondary node, but includes information indicating the SCG activation initiated by the UE.

[0021] An eleventh aspect is directed to a RAN node configured to operate as a master node associated with an MCG in dual connectivity for a UE, the RAN node including at least one memory and at least one processor coupled to the at least one memory. The at least one processor is configured to receive a first signal from the UE via the MCG when an SCG of the dual connectivity is deactivated, the first signal representing a request or indication of activation of the SCG. In response to receiving the first signal, the at least one processor is configured to transmit an inter-node message representing a request or indication of activation of the SCG to a secondary node associated with the SCG. The inter-node message is the same as a message transmitted from the master node to the secondary node when activation of the SCG is initiated by the master node, but includes information indicating SCG activation initiated by the UE.

[0022] A twelfth aspect is directed to a method performed by a RAN node configured to operate as a master node associated with an MCG in dual connectivity for a UE, the method including: (a) receiving a first signal from the UE via the MCG when an SCG of the dual connectivity is deactivated, the first signal being indicative of a request or indication of activation of the SCG; and (b) in response to receiving the first signal, transmitting an inter-node message indicative of a request or indication of activation of the SCG to a secondary node associated with the SCG. The inter-node message is the same as a message transmitted from the master node to the secondary node when activation of the SCG is initiated by the master node, but includes information indicative of the SCG activation initiated by the UE.

[0023] A thirteenth aspect is directed to a RAN node configured to operate as a secondary node associated with an SCG in dual connectivity for a UE. The RAN node includes at least one memory and at least one processor coupled to the at least one memory. The at least one processor is configured to receive a first signal from the UE in a PSCell of the SCG, the first signal indicating a request or indication of activation of the SCG when the SCG is deactivated. The at least one processor is configured to transmit, in response to receiving the first signal, an inter-node message indicating a request or indication of activation of the SCG to a master node associated with an MCG in the dual connectivity. The inter-node message includes information indicating whether a first or second option is used to activate the SCG. The first option is an option in which the secondary node transmits a second signal in the PSCell to the UE indicating activation of the SCG prior to transmitting the inter-node message to the master node. Meanwhile, the second option is an option in which the secondary node transmits the second signal to the UE after receiving a response to the inter-node message from the master node.

[0024] A fourteenth aspect is directed to a method performed by a RAN node configured to operate as a secondary node associated with an SCG in dual connectivity for a UE, the method including: (a) receiving a first signal in a PSCell of the SCG from the UE when the SCG is deactivated, the first signal indicating a request or indication of activation of the SCG; and (b) in response to receiving the first signal, transmitting an inter-node message indicating a request or indication of activation of the SCG to a master node associated with an MCG in the dual connectivity. The inter-node message includes information indicating whether a first or second option is being used to activate the SCG. The first option is an option in which the secondary node transmits a second signal in the PSCell to the UE indicating activation of the SCG prior to transmitting the inter-node message to the master node, while the second option is an option in which the secondary node transmits the second signal to the UE after receiving a response to the inter-node message from the master node.

[0025] A fifteenth aspect is directed to a RAN node configured to operate as a master node associated with an MCG in dual connectivity for a UE. The RAN node includes at least one memory and at least one processor coupled to the at least one memory. The at least one processor is configured to receive a first signal from the UE via the MCG when an SCG of the dual connectivity is deactivated, the first signal indicating a request or indication of activation of the SCG. In response to receiving the first signal, the at least one processor is configured to transmit an inter-node message indicating a request or indication of activation of the SCG to a secondary node associated with the SCG. The inter-node message includes information indicating whether a first or second option is used to activate the SCG. The first option is an option in which the master node transmits a second signal indicating activation of the SCG to the UE via the MCG prior to transmitting the inter-node message to the secondary node. Meanwhile, the second option is an option in which the master node transmits the second signal to the UE after receiving a response to the inter-node message from the secondary node.

[0026] A sixteenth aspect is directed to a method performed by a RAN node configured to operate as a master node associated with an MCG in dual connectivity for a UE, the method including: (a) receiving a first signal from the UE via the MCG when an SCG of the dual connectivity is deactivated, the first signal being indicative of a request or indication of activation of the SCG; and (b) in response to receiving the first signal, transmitting an inter-node message to a secondary node associated with the SCG, the inter-node message being indicative of a request or indication of activation of the SCG. The inter-node message includes information indicating whether a first or second option is being used to activate the SCG. The first option is an option in which the master node transmits a second signal to the UE via the MCG indicating activation of the SCG prior to transmitting the inter-node message to the secondary node, while the second option is an option in which the master node transmits the second signal to the UE after receiving a response to the inter-node message from the secondary node.

[0027] A seventeenth aspect is directed to a RAN node configured to operate as a secondary node associated with an SCG in dual connectivity for a UE, the RAN node including at least one memory and at least one processor coupled to the at least one memory, the at least one processor configured to configure the UE with a random access preamble pool dedicated for SCG activation, the random access preamble pool used by one or more UEs to perform contention based random access to a PSCell of the SCG for SCG activation.

[0028] An eighteenth aspect is directed to a method performed by a RAN node configured to operate as a secondary node associated with an SCG in dual connectivity for a UE, the method including configuring the UE with a random access preamble pool dedicated for SCG activation, the random access preamble pool used by one or more UEs to perform contention based random access to a PSCell of the SCG for SCG activation.

[0029] A nineteenth aspect is directed to a UE configured to support dual connectivity using an MCG associated with a master node and an SCG associated with a secondary node. The UE includes at least one memory and at least one processor coupled to the at least one memory. The at least one processor is configured to receive a configuration of a random access preamble pool dedicated for SCG activation from the secondary node. The at least one processor is configured to select a preamble from the random access preamble pool for contention-based random access to a PSCell of the SCG to activate the SCG.

[0030] A twentieth aspect is directed to a method performed by a UE configured to support dual connectivity with an MCG associated with a master node and an SCG associated with a secondary node, the method including (a) receiving a configuration of a random access preamble pool dedicated for SCG activation from the secondary node, and (b) selecting a preamble from the random access preamble pool for contention based random access to a PSCell of the SCG to activate the SCG.

[0031] A twenty-first aspect is directed to a RAN node configured to operate as a secondary node associated with an SCG in dual connectivity for a UE, the RAN node including at least one memory and at least one processor coupled to the at least one memory, the at least one processor configured to send a random access prioritization configuration to the UE if the SCG is currently deactivated or is to be deactivated, the random access prioritization causing the UE to set one or both of a power ramping factor and a scaling factor for a back-off indicator to values ​​indicated by the random access prioritization configuration if a random access procedure is initiated to activate the SCG and the random access prioritization configuration has been configured for the UE by the secondary node.

[0032] A twenty-second aspect is directed to a method performed by a RAN node configured to operate as a secondary node associated with an SCG in dual connectivity for a UE, the method being configured to send a random access prioritization configuration to the UE if the SCG is currently deactivated or is to be deactivated, the random access prioritization causing the UE to set one or both of a power ramping factor and a scaling factor for a back-off indicator to values ​​indicated by the random access prioritization configuration if a random access procedure is initiated to activate the SCG and the random access prioritization configuration has been configured for the UE by the secondary node.

[0033] A twenty-third aspect is directed to a UE configured to support dual connectivity using an MCG associated with a master node and an SCG associated with a secondary node. The UE includes at least one memory and at least one processor coupled to the at least one memory. The at least one processor is configured to set one or both of a power ramping factor and a scaling factor for a back-off indicator to values ​​indicated by a random access prioritization setting when a random access procedure is initiated to activate the SCG and a random access prioritization setting is configured for the UE by the secondary node. The at least one processor is configured to perform random access to a PSCell of the SCG.

[0034] A twenty-fourth aspect is directed to a method performed by a UE configured to support dual connectivity with an MCG associated with a master node and an SCG associated with a secondary node, the method including: (a) if a random access procedure is initiated to activate the SCG and a random access prioritization configuration is configured for the UE by the secondary node, setting one or both of a power ramping factor and a scaling factor for a back-off indicator to values ​​indicated by the random access prioritization configuration, and (b) performing random access to a PSCell of the SCG.

[0035] A twenty-fifth aspect is directed to a program comprising a set of instructions (software code) for causing a computer to carry out a method according to the second, fourth, sixth, eighth, tenth, twelfth, fourteenth, sixteenth, eighteenth, twentieth, twenty-second, or twenty-fourth aspect when the program is loaded into the computer. Effect of the Invention

[0036] According to the above-mentioned aspects, it is possible to provide an apparatus, a method, and a program that contribute to solving at least one of a number of problems related to SCG activation and deactivation, including the problems described above. [Brief description of the drawings]

[0037] [Figure 1] 1 is a diagram illustrating an example of the configuration of a wireless communication network according to an embodiment. [Diagram 2] FIG. 2 is a diagram illustrating a configuration example of a RAN node according to an embodiment. [Diagram 3] 11 is a flowchart illustrating an example of a process performed by a secondary node according to the embodiment. [Figure 4] FIG. 11 is a sequence diagram showing an example of processing performed by a master node, a secondary node, and a UE according to an embodiment. [Diagram 5] FIG. 11 is a sequence diagram showing an example of processing performed by a master node, a secondary node, and a UE according to an embodiment. [Figure 6] 11 is a flowchart illustrating an example of a process performed by a secondary node according to the embodiment. [Figure 7] FIG. 11 is a sequence diagram showing an example of processing performed by a master node, a secondary node, and a UE according to an embodiment. [Figure 8] 11 is a flowchart illustrating an example of a process performed by a master node and a secondary node according to the embodiment. [Figure 9] FIG. 11 is a sequence diagram illustrating an example of a process performed by a master node and a secondary node according to the embodiment. [Figure 10] FIG. 11 is a sequence diagram showing an example of processing performed by a master node, a secondary node, and a UE according to an embodiment. [Figure 11] FIG. 11 is a sequence diagram showing an example of processing performed by a master node, a secondary node, and a UE according to an embodiment. [Figure 12]FIG. 11 is a sequence diagram illustrating an example of a process performed by a master node and a secondary node according to the embodiment. [Figure 13] FIG. 11 is a sequence diagram showing an example of processing performed by a master node, a secondary node, and a UE according to an embodiment. [Figure 14] FIG. 11 is a sequence diagram showing an example of processing performed by a master node, a secondary node, and a UE according to an embodiment. [Figure 15] FIG. 11 is a sequence diagram illustrating an example of a process performed by a master node and a secondary node according to the embodiment. [Figure 16] FIG. 11 is a sequence diagram showing an example of processing performed by a master node, a secondary node, and a UE according to an embodiment. [Figure 17] FIG. 11 is a sequence diagram showing an example of processing performed by a master node, a secondary node, and a UE according to an embodiment. [Figure 18] FIG. 11 is a sequence diagram illustrating an example of a process performed by a master node and a secondary node according to the embodiment. [Figure 19] FIG. 11 is a sequence diagram showing an example of processing performed by a master node, a secondary node, and a UE according to an embodiment. [Figure 20] FIG. 11 is a sequence diagram showing an example of processing performed by a master node, a secondary node, and a UE according to an embodiment. [Figure 21] FIG. 11 is a sequence diagram illustrating an example of a process performed by a secondary node and a UE according to the embodiment. [Figure 22] FIG. 11 is a sequence diagram illustrating an example of a process performed by a secondary node and a UE according to the embodiment. [Figure 23] FIG. 2 is a block diagram showing a configuration example of a RAN node according to the embodiment. [Figure 24] FIG. 2 is a block diagram showing an example of the configuration of a UE according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0038] In the following, specific embodiments will be described in detail with reference to the drawings. In each drawing, the same or corresponding elements are denoted by the same reference numerals, and duplicated descriptions will be omitted as necessary for clarity of explanation.

[0039] The multiple embodiments described below can be implemented independently or in appropriate combination. These multiple embodiments have different novel features. Therefore, these multiple embodiments contribute to solving different objects or problems and provide different effects.

[0040] The following embodiments are described with a focus on the 3GPP Long Term Evolution (LTE) system and the fifth generation mobile communication system (5G system). However, these embodiments may be applied to other wireless communication systems that support technologies similar to 3GPP multi-connectivity (e.g. Dual Connectivity). In addition, the term LTE used in this specification includes improvements and developments of LTE and LTE-Advanced to enable interworking with the 5G system, unless otherwise specified.

[0041] As used herein, depending on the context, "if" may be interpreted to mean "when," "at or around the time," "after," "upon," "in response to determining," "in accordance with a determination," or "in response to detecting." These expressions may be interpreted to have the same meaning, depending on the context.

[0042] <First embodiment> Fig. 1 illustrates an example of a configuration of a wireless communication network according to a number of embodiments including the present embodiment. In the example of Fig. 1, the wireless communication network includes a RAN node 1, a RAN node 2, and a UE 3. Each element (network function) illustrated in Fig. 1 can be implemented, for example, as a network element on dedicated hardware, as a software instance running on the dedicated hardware, or as a virtualized function instantiated on an application platform.

[0043] The RAN node 1 may be a Central Unit (e.g., eNB-CU or gNB-CU) in a cloud RAN (C-RAN) deployment, or may be a combination of a CU and one or more Distributed Units (e.g., eNB-DUs or gNB-DUs). C-RAN is also referred to as CU / DU split. Furthermore, a CU may include a Control Plane (CP) Unit (e.g., gNB-CU-CP) and one or more User Plane (UP) Units (e.g., gNB-CU-UP). Thus, the RAN node 1 may be a CU-CP or may be a combination of a CU-CP and a CU-UP. Similarly, the RAN node 2 may be a CU or may be a combination of a CU and one or more DUs. The RAN node 2 may be a CU-CP or may be a combination of a CU-CP and a CU-UP.

[0044] Each of the RAN nodes 1 and 2 may be an Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (EUTRAN) node or a Next generation Radio Access Network (NG-RAN) node. The EUTRAN node may be an eNB or an en-gNB. The NG-RAN node may be a gNB or an ng-eNB. The en-gNB is a node that provides NR user plane and control plane protocol terminations towards the UE and acts as a secondary node (SN) in E-UTRA-NR Dual Connectivity (EN-DC). The ng-eNB is a node that provides E-UTRA user plane and control plane protocol terminations towards the UE and is connected to the 5GC via the NG interface. The Radio Access Technology (RAT) of the RAN node 1 may be different from that of the RAN node 2.

[0045] The RAN node 1 and the RAN node 2 communicate with each other via an inter-node interface (i.e., an X2 interface or an Xn interface) 103. The RAN node 1 and the RAN node 2 act as a master node (MN) and a secondary node (SN) of dual connectivity, respectively. Hereinafter, the RAN node 1 may be referred to as an MN1, and the RAN node 2 may be referred to as an SN2. The UE 3 communicates with the MN1 and the SN2 via air interfaces 101 and 102, and performs dual connectivity of a master cell group (MCG) and a secondary cell group (SCG).

[0046] This dual connectivity may be Multi-Radio Dual Connectivity (MR-DC). MR-DC includes E-UTRA-NR Dual Connectivity (EN-DC), NG-RAN E-UTRA-NR Dual Connectivity (NGEN-DC), NR-E-UTRA Dual Connectivity (NE-DC), and NR-NR Dual Connectivity (NR-DC). Accordingly, the MN1 may be any of a master eNB (in EN-DC), a master ng-eNB (in NGEN-DC), and a master gNB (in NR-DC and NE-DC). Similarly, the SN2 may be any of an en-gNB (in EN-DC), a secondary ng-eNB (in NE-DC), and a secondary gNB (in NR-DC and NGEN-DC). In EN-DC, the UE3 is connected to an eNB operating as the MN1 and an en-gNB operating as the SN2. In NGEN-DC, UE3 is connected to an ng-eNB operating as MN1 and to a gNB operating as SN2. In NE-DC, UE3 is connected to a gNB operating as MN1 and to an ng-eNB operating as SN2. In NR-DC, UE3 is connected to one gNB (or gNB-DU) operating as MN1 and to another gNB (or gNB-DU) operating as SN2.

[0047] The MCG is a group of serving cells associated with (or provided by) MN1, and includes an SpCell (i.e., a Primary Cell (PCell)) and, optionally, one or more Secondary Cells (SCells). On the other hand, the SCG is a group of serving cells associated with (or provided by) SN2, and includes a Primary SCG Cell (PSCell) and, optionally, one or more Secondary Cells (SCells). A PSCell is a Special Cell (SpCell) of the SCG, and supports Physical Uplink Control Channel (PUCCH) transmission and contention-based Random Access. Note that in LTE (e.g., LTE-DC and NE-DC), PSCell may be an abbreviation for Primary SCell.

[0048] As used herein, the term "primary SCG cell" and its abbreviation "PSCell" refer to a cell included in a cell group provided by a dual connectivity SN, having an uplink component carrier, and having uplink control channel (e.g. PUCCH) resources configured. Specifically, the term "primary SCG cell" and its abbreviation "PSCell" may refer to a Primary SCG Cell of a cell group provided by an SN supporting 5G NR (e.g. en-gNB in ​​EN-DC, gNB in ​​NGEN-DC, or gNB in ​​NR-DC), or may refer to a Primary SCell of a cell group provided by an SN supporting E-UTRA (e.g. eNB in ​​LTE DC, or ng-eNB in ​​NE-DC).

[0049] One or both of the MN1 and the SN2 may have the configuration shown in Figure 2. Each element (network function) shown in Figure 2 may be implemented, for example, as a network element on dedicated hardware, as a software instance running on the dedicated hardware, or as a virtualized function instantiated on an application platform. One or both of the RAN nodes 1 and 2 may include, but are not limited to, a CU 21 and one or more DUs 22 as shown in Figure 2. The CU 21 and each DU 22 are connected by an interface 201. The UE 3 is connected to at least one DU 22 via at least one air interface 202.

[0050] The CU21 may be a logical node that hosts the Radio Resource Control (RRC), Service Data Adaptation Protocol (SDAP), and Packet Data Convergence Protocol (PDCP) protocols (or the RRC and PDCP protocols) of the gNB. The DU22 may be a logical node that hosts the Radio Link Control (RLC), Medium Access Control (MAC), and Physical (PHY) layers of the gNB. If the CU21 is a gNB-CU and the DUs22 are gNB-DUs, the interface 201 may be an F1 interface. The CU21 may include a CU-CP and a CU-UP.

[0051] In the following, the operations of MN1, SN2, and UE3 regarding the activation of the SCG associated with SN2 will be described. Note that in this embodiment and subsequent embodiments, the activation and deactivation of the SCG may be referred to as the resume and suspend of the SCG, respectively. FIG. 3 illustrates an example of the operation of SN2. In step 301, when the SCG is deactivated, SN2 receives a first signal in a PSCell from UE3, which indicates a request or indication of SCG activation. The first signal informs SN2 that the SCG needs to be activated. For example, if uplink data to be transmitted on the SCG occurs when the SCG is deactivated, UE3 may transmit the first signal. In other words, if uplink data to be transmitted on a Data Radio Bearer (DRB) using SCG resources arrives, UE3 may transmit the first signal. The DRB may be an SCG DRB (SCG bearer) or a split DRB (split bearer). The SCG DRB is a DRB having an RLC bearer only in the SCG associated with the SN2. On the other hand, the split DRB is a DRB having both an RLC bearer in the MCG associated with the MN1 and an RLC bearer in the SCG. The SCG DRB and the split DRB may be bearers terminated by the SN2 (SN terminated) or bearers terminated by the MN1 (MN terminated). The SN terminated bearer is a radio bearer for which a PDCP is arranged in the SN2. The MN terminated bearer is a radio bearer for which a PDCP is arranged in the MN1. Furthermore, the fact that the primary path of the split DRB is set in the SCG may be considered as a condition for the UE3 to transmit the first signal. Alternatively, if the UE3 detects a Radio Link Failure (RLF) of the MCG, the UE3 may transmit the first signal.

[0052] As already explained, the UE 3 may activate the SCG by performing a random access to the SN2 (i.e., the PSCell). If the UE 3 maintains a valid uplink timing of the SCG, the UE 3 may skip the random access upon SCG activation and may perform an uplink transmission. For example, the UE 3 may send an SCG activation indication to the SN2 by transmitting a Scheduling Request (SR) (i.e., an uplink physical layer message) in the PSCell. Thus, the SN2 may receive the first signal of step 301 via the random access to the PSCell or via the uplink physical layer message. In other words, the first signal may be or may be included in a signal or data (e.g., a random access preamble) transmitted from the UE 3 in the random access. Alternatively, the first signal may be or may be included in an SR, an Uplink Control Information (UCI) indicating the SR, or a physical channel (e.g., a Physical Uplink Control Channel (PUCCH) carrying the UCI.

[0053] In step 302, the SN2 transmits a second signal indicating SCG activation to the UE3 in the PSCell in response to receiving the first signal. In step 303, the SN2 transmits an inter-node message (e.g., X2 message, Xn message, or inter-node RRC message) indicating SCG activation to the MN1. Here, the second signal (302) is transmitted to the UE3 before the SN2 transmits the inter-node message (303) to the MN1 or before the SN2 receives a response to the inter-node message (303) from the MN1. In other words, when the SN2 activates the SCG in response to a request from the UE3, the SN2 allows the UE3 to perform SCG activation (or allows uplink transmission on the DRB using the SCG resource) without waiting for confirmation (or acceptance) of the MN1. This can contribute to reducing the delay of the SCG activation. Preferably, the SN2 may send the second signal (302) to the UE3 before sending the inter-node message (303) to the MN1. In other words, when the SN2 activates the SCG in response to a request from the UE3, the SN2 may not need to perform signaling with the MN1 before allowing the UE3 to perform the SCG activation.

[0054] The second signal (302) may indicate the SCG activation to the UE 3 explicitly or implicitly. The SN 2 may transmit the second signal to the UE 3 via a random access procedure or via a downlink physical layer message. The second signal may be or may be included in a signal or data (e.g., a random access response) transmitted from the SN 2 to the UE 3 in the random access procedure. Alternatively, the second signal may be or may be included in an uplink grant, downlink control information (Downlink Control Information (DCI)) indicating the uplink grant, or a physical channel (e.g., a Physical Downlink Control Channel (PDCCH)) carrying the DCI. Additionally or alternatively, the second signal may be or may be included in a downlink signal (e.g., MAC CE, PDCCH) following the random access procedure. Note that the second signal indicating the SCG activation may indicate the acceptance of the SCG activation request.

[0055] The inter-node message (303) may include information indicating that the SCG has already been activated and / or that the activation of the SCG has been indicated to the UE3. The inter-node message (303) may be sent to inform the MN1 of the SCG activation initiated (or triggered, requested) by the UE3. The inter-node message (303) is the same as the message sent from the SN2 to the MN1 when the SCG activation is initiated (or triggered) by the SN2, but may include information indicating, explicitly or implicitly, the UE-initiated (or triggered, requested) SCG activation. By receiving the inter-node message (303) indicating such information, the MN1 can know that the SCG activation has been triggered by the UE3. In other words, the MN1 can identify whether the SCG activation has been triggered by the SN2 or by the UE3. Alternatively, the MN1 can know that the SCG has already been activated based on the request of the UE3.

[0056] 4 shows an example of the operation of MN1, SN2 and UE3. In step 401, the SCG provided by SN2 to UE3 is deactivated. The SCG deactivation in step 401 may be initiated, triggered or requested by any of MN1, SN2 and UE3. By way of example and not limitation, the SCG deactivation in step 401 may be performed according to any of the options described in chapter 2.3.1 of Non-Patent Document 1.

[0057] In step 402, UE3 sends an SCG activation request (or indication) to SN2 in the PSCell. Step 402 corresponds to step 301 in Fig. 3. In step 403, SN2 sends an SCG activation indication (or notification) to UE3 in the PSCell. Step 403 corresponds to step 302 in Fig. 3. In step 404, SN2 sends an inter-node message to MN1 including the SCG activation indication (or notification). The inter-node message may be an SGNB MODIFICATION REQUIRED message, an S-NODE MODIFICATION REQUIRED message or an RRC TRANSFER message containing an inter-node RRC message. Step 404 corresponds to step 303 in Fig. 3. In step 405, MN1 sends an inter-node message to SN2 indicating confirmation (or acceptance) of the SCG activation. The inter-node message may be an SGNB MODIFICATION CONFIRM message, an S-NODE MODIFICATION CONFIRM message, or an RRC TRANSFER message containing an inter-node RRC message. In some implementations, step 405 may be omitted. Alternatively, the transmission of step 403 may occur between step 404 and step 405. In other words, the SN2 may send an SCG activation indication (or notification) to the UE3 after sending (404) an SCG activation indication (or notification) to the MN1 and before receiving (405) a response from the MN1.

[0058] <Second embodiment> The configuration example of the wireless communication network according to this embodiment is similar to the example shown in Figures 1 and 2. In the following, the operations of MN1, SN2, and UE3 regarding the activation of the SCG associated with SN2 will be described.

[0059] 5 shows an example of the operation of MN1, SN2, and UE3. In step 501, the SCG provided by SN2 to UE3 is deactivated. The SCG deactivation in step 501 may be initiated, triggered, or requested by any of MN1, SN2, and UE3.

[0060] In step 502, the UE3 sends an SCG activation request (or indication) to the MN1 via the MCG (e.g. PCell). The SCG activation request (or indication) sent from the UE3 to the MN1 may be an MN RRC message, e.g., UE Assistance Information (UAI). Alternatively, the activation request (or indication) may be a Buffer Status Report (BSR) (i.e., Medium Access Control (MAC) Control Element (CE)). In step 503, the MN1 sends an SCG activation indication (or notification) to the UE3 via the MCG. The SCG activation indication (or notification) of step 503 may be sent to the UE3 via an MN RRC message, a MAC CE, or a DCI.

[0061] In step 504, MN1 sends an inter-node message (e.g. X2 message, Xn message, or inter-node RRC message) including an SCG activation indication (or notification) to SN2. The inter-node message may be an SGNB MODIFICATION REQUEST message, an S-NODE MODIFICATION REQUEST message, or an RRC TRANSFER message including an inter-node RRC message. In step 505, SN2 sends an inter-node message indicating confirmation (or acceptance) of the SCG activation to MN1. The inter-node message may be an SGNB MODIFICATION REQUEST ACKNOWLEDGE message, an S-NODE MODIFICATION REQUEST ACKNOWLEDGE message, or an RRC TRANSFER message including an inter-node RRC message. In some implementations, step 505 may be omitted. Alternatively, the sending of step 503 may be performed between step 504 and step 505. In other words, MN1 may send an SCG activation indication (or notification) to UE3 after sending an SCG activation indication (or notification) to SN2 (504) and before receiving a response from SN2 (505).

[0062] That is, according to the procedure of Fig. 5, when MN1 activates the SCG in response to a request from UE3, MN1 permits SCG activation to UE3 without waiting for confirmation (or consent) from SN2. This can contribute to reducing the delay of SCG activation. Preferably, MN1 may transmit an SCG activation indication (or notification) (503) to UE3 before transmitting an inter-node message (504) to SN2.

[0063] <Third embodiment> The configuration example of the wireless communication network according to this embodiment is similar to the example shown in Figures 1 and 2. In the following, the operations of MN1, SN2, and UE3 regarding the activation of the SCG associated with SN2 will be described.

[0064] FIG. 6 shows an example of the operation of the SN2. Step 601 is similar to step 301 of FIG. 3. Specifically, in step 601, when the SCG is deactivated, the SN2 receives a first signal in the PSCell from the UE3, which indicates a request or indication of SCG activation. The first signal informs the SN2 that the SCG needs to be activated. The SN2 may receive the first signal in step 601 via a random access to the PSCell or via an uplink physical layer message. In other words, the first signal may be or may be included in a signal or data (e.g., random access preamble) transmitted from the UE3 in random access. Alternatively, the first signal may be or may be included in an SR, a UCI indicating the SR, or a physical channel carrying the UCI (e.g., PUCCH).

[0065] In step 602, the SN2 sends an inter-node message (e.g. an X2 message, an Xn message, or an inter-node RRC message) to the MN1 indicating SCG activation. In step 603, the SN2 receives an inter-node message from the MN1 indicating a response to the message of step 302. In step 604, if the response from the MN1 indicates that the SCG activation is accepted, the SN2 sends a second signal in the PSCell to the UE3 indicating the SCG activation.

[0066] According to the procedure of Fig. 6, when the SN2 activates the SCG in response to a request from the UE3, the SN2 allows the UE3 to perform the SCG activation (or allows uplink transmission on the DRB using the SCG resource) after obtaining the confirmation (or consent) of the MN1. This can, for example, allow the MN1 to reject the UE-initiated (or triggered, requested) SCG activation.

[0067] The inter-node message (602) may be sent to inform the MN1 of the SCG activation initiated (or triggered, requested) by the UE3. In other words, the inter-node message (602) may include information indicating, explicitly or implicitly, the UE-initiated (or triggered, requested) SCG activation. The inter-node message (602) is the same as the message sent from the SN2 to the MN1 when the SCG activation is initiated (or triggered) by the SN2, but may include information indicating, explicitly or implicitly, the UE-initiated (or triggered, requested) SCG activation. By receiving the inter-node message (602) indicating such information, the MN1 can know that the SCG activation was triggered by the UE3. In other words, the MN1 can identify whether the SCG activation was triggered by the SN2 or by the UE3.

[0068] The second signal (604) may indicate the SCG activation to the UE3 explicitly or implicitly. The SN2 may transmit the second signal to the UE3 via a random access procedure or via a downlink physical layer message. The second signal may be or may be included in a signal or data (e.g., a random access response) transmitted from the SN2 to the UE3 in the random access procedure. Alternatively, the second signal may be or may be included in an uplink grant, downlink control information (Downlink Control Information (DCI)) indicating the uplink grant, or a physical channel (e.g., a Physical Downlink Control Channel (PDCCH)) carrying the DCI. Additionally or alternatively, the second signal may be or may be included in a downlink signal (e.g., MAC CE, PDCCH) following the random access procedure. Note that the second signal indicating the SCG activation may indicate the acceptance of the SCG activation request.

[0069] Figure 7 shows an example of the operation of MN1, SN2 and UE3. Steps 701 and 702 are similar to steps 401 and 402 in Figure 4. Specifically, in step 701, the SCG provided by SN2 to UE3 is deactivated. The SCG deactivation in step 701 may be initiated, triggered or requested by any of MN1, SN2 and UE3. In step 702, UE3 sends an SCG activation request (or indication) to SN2 in the PSCell. Step 702 corresponds to step 601 in Figure 6.

[0070] In step 703, the SN2 sends an inter-node message including an SCG activation request (or indication) to the MN1. The inter-node message may be an SGNB MODIFICATION REQUIRED message, an S-NODE MODIFICATION REQUIRED message, or an RRC TRANSFER message containing an inter-node RRC message. Step 703 corresponds to step 602 in Fig. 6. In step 704, the MN1 sends an inter-node message indicating confirmation (or acceptance) of the SCG activation to the SN2. The inter-node message may be an SGNB MODIFICATION CONFIRM message, an S-NODE MODIFICATION CONFIRM message, or an RRC TRANSFER message containing an inter-node RRC message. Step 704 corresponds to step 603 in Fig. 6. In step 705, the SN2 sends an SCG activation indication (or notification) to the UE3 in the PSCell. Step 705 corresponds to step 604 in Fig. 6.

[0071] <Fourth embodiment> The configuration example of the wireless communication network according to this embodiment is similar to the example shown in Figures 1 and 2. In the following, the operations of MN1, SN2, and UE3 regarding the activation of the SCG associated with SN2 will be described.

[0072] FIG. 8 shows an example of the operation of the SN2. In step 801, the SN2 determines which of a plurality of options is used for UE-initiated (or triggered, requested) SCG activation. In step 802, the SN2 performs the UE-initiated SCG activation according to the determined option. The plurality of options include a first option and a second option. The first option is an option in which the SN2 transmits a second signal indicating SCG activation in the PSCell to the UE3 after receiving a first signal representing an SCG activation request (or indication) from the UE3 and before transmitting an inter-node message indicating SCG activation to the MN1. Thus, in one example, the first option corresponds to the SCG activation procedure described in the first embodiment with reference to FIG. 3 and FIG. 4. Meanwhile, the second option is an option in which the SN2 transmits a second signal in the PSCell to the UE3 after receiving a response to the inter-node message from the MN1. Thus, in one example, the second option corresponds to the SCG activation procedure described in the third embodiment with reference to Figures 6 and 7.

[0073] The inter-node message sent from SN2 to MN1 during SCG activation may include information indicating which of the first and second options is being used. This allows MN1 to know whether the SCG has already been activated based on the request of UE3. Specifically, if the inter-node message includes information indicating the first option, MN1 can recognize that the SCG has already been activated based on the request of UE3. If not, MN1 can recognize that SCG activation has not yet been permitted by UE3.

[0074] Instead of or in addition to SN2, MN1 may perform the operations shown in Fig. 8. Specifically, MN1 may determine which of a plurality of options is used for UE-initiated (or triggered, requested) SCG activation (step 801). Then, MN1 may perform UE-initiated SCG activation according to the determined option (step 802). In this case, the plurality of options include a first option and a second option. The first option is an option in which MN1 transmits a second signal indicating SCG activation to UE3 via MCG after receiving a first signal representing an SCG activation request (or indication) from UE3 and before transmitting an inter-node message indicating SCG activation to SN2. Thus, in one example, the first option corresponds to the SCG activation procedure described in the second embodiment with reference to Fig. 5. Meanwhile, the second option is an option in which MN1 transmits a second signal to UE3 via MCG after receiving a response to the inter-node message from SN2.

[0075] The inter-node message sent from MN1 to SN2 during SCG activation may include information indicating which of the first and second options is being used. This allows SN2 to know whether the SCG has already been activated based on the request of UE3. Specifically, if the inter-node message includes information indicating the first option, SN2 can recognize that the SCG has already been activated based on the request of UE3. Otherwise, SN2 can recognize that SCG activation has not yet been granted to UE3.

[0076] In some implementations, the SN2 or MN1 may determine whether the first or second option is used based on a priority level or urgency level of the uplink transmission by the UE3. The priority level or urgency level of the uplink transmission by the UE3 may be determined by the SN2 or MN1 before or while the UE3 is deactivated. Alternatively, the priority level or urgency level of the uplink transmission by the UE3 may be determined by the UE3. In this case, the first signal transmitted from the UE3 to the SN2 or MN1 may indicate the priority level or urgency level. If the priority level or urgency level of the uplink transmission by the UE3 exceeds a reference value, the SN2 or MN1 may determine to use the first option to activate the SCG based on the request of the UE3.

[0077] <Fifth embodiment> The configuration example of the wireless communication network according to this embodiment is similar to the example shown in Figures 1 and 2. In the following, the operations of MN1, SN2, and UE3 regarding the activation of the SCG associated with SN2 will be described.

[0078] Figure 9 shows an example of the operation of MN1 and SN2. In step 901, SN2 sends an inter-node message for SCG activation to MN1. The inter-node message includes an indication of whether the SCG activation is initiated by SN2 or UE3. The inter-node message may be an X2 message, an Xn message, or an inter-node RRC message. More specifically, the inter-node message may be an SGNB MODIFICATION REQUIRED message, an S-NODE MODIFICATION REQUIRED message, or an RRC TRANSFER message that contains an inter-node RRC message.

[0079] Specifically, in response to receiving a signal (e.g., a random access preamble, or SR) indicating an SCG activation request or indication from the UE 3 in the PSCell when the SCG is deactivated, the SN2 transmits an inter-node message indicating an SCG activation request or indication to the MN 1 (step 903). In this case, the inter-node message is the same as the message transmitted from the SN2 to the MN 1 upon SN-initiated (or triggered, requested) SCG activation, but includes information indicating, explicitly or implicitly, the UE-initiated (or triggered, requested) SCG activation.

[0080] SN2 also sends an inter-node message representing an SCG activation request or indication to MN1 to activate the SCG upon SN2's request (step 903), except that in this case the inter-node message explicitly or implicitly indicates SN-initiated (or triggered, requested) SCG activation to MN1. In one example, the inter-node message may indicate SN-initiated SCG activation to MN1 by not including an indication of UE-initiated SCG activation.

[0081] FIG. 10 shows an example of operations of MN1, SN2, and UE3 regarding UE-initiated (or triggered, requested) SCG activation. Steps 1001 to 1005 are similar to steps 401 to 405 in FIG. 4. However, the inter-node message in step 1004 is the same as the message sent from SN2 to MN1 at the time of SN-initiated SCG activation, but indicates UE-initiated SCG activation explicitly or implicitly. The inter-node message in step 1004 may be an SGNB MODIFICATION REQUIRED message, an S-NODE MODIFICATION REQUIRED message, or an RRC TRANSFER message including an inter-node RRC message. The inter-node message in step 1005 may be an SGNB MODIFICATION CONFIRM message, an S-NODE MODIFICATION CONFIRM message, or an RRC TRANSFER message including an inter-node RRC message.

[0082] FIG. 11 shows another example of the operations of MN1, SN2, and UE3 regarding UE-initiated (or triggered, requested) SCG activation. Steps 1101 to 1105 are the same as steps 701 to 705 in FIG. 7. However, the inter-node message in step 1103 is the same as the message sent from SN2 to MN1 in the case of SN-initiated SCG activation, but indicates UE-initiated SCG activation explicitly or implicitly. The inter-node message in step 1103 may be an SGNB MODIFICATION REQUIRED message, an S-NODE MODIFICATION REQUIRED message, or an RRC TRANSFER message including an inter-node RRC message. The inter-node message in step 1104 may be an SGNB MODIFICATION CONFIRM message, an S-NODE MODIFICATION CONFIRM message, or an RRC TRANSFER message including an inter-node RRC message.

[0083] The operations of MN1 and SN2 described in this embodiment can enable MN1 to know whether the SCG activation is initiated by SN2 or UE3.

[0084] Sixth embodiment The configuration example of the wireless communication network according to this embodiment is similar to the example shown in Figures 1 and 2. In the following, the operations of MN1, SN2, and UE3 regarding the activation of the SCG associated with SN2 will be described.

[0085] Figure 12 shows an example of the operation of MN1 and SN2. In step 1201, MN1 sends an inter-node message for SCG activation to SN2. The inter-node message includes an indication of whether the SCG activation is initiated by MN1 or UE3. The inter-node message may be an X2 message, an Xn message, or an inter-node RRC message. More specifically, the inter-node message may be an SGNB MODIFICATION REQUEST message, an S-NODE MODIFICATION REQUEST message, or an RRC TRANSFER message that contains an inter-node RRC message.

[0086] Specifically, in response to receiving a signal (e.g., MN RRC message, or MAC CE (e.g., BSR)) indicating an SCG activation request or indication from UE3 via the MCG when the SCG is deactivated, MN1 transmits an inter-node message indicating an SCG activation request or indication to SN2 (step 903). In this case, the inter-node message is the same as the message transmitted from MN1 to SN2 upon MN-initiated (or triggered, requested) SCG activation, but includes information indicating, explicitly or implicitly, UE-initiated (or triggered, requested) SCG activation.

[0087] MN1 also sends an inter-node message representing an SCG activation request or indication to SN2 to activate the SCG upon MN1's request (step 903), except that in this case the inter-node message explicitly or implicitly indicates MN-initiated (or triggered, requested) SCG activation to SN2. In one example, the inter-node message may indicate MN-initiated SCG activation to SN2 by not including an indication of UE-initiated SCG activation.

[0088] FIG. 13 shows an example of operations of MN1, SN2, and UE3 regarding UE-initiated (or triggered, requested) SCG activation. Steps 1301 to 1305 are the same as steps 501 to 505 in FIG. 5. However, the inter-node message in step 1304 is the same as the message sent from MN1 to SN2 at the time of MN-initiated SCG activation, but indicates UE-initiated SCG activation explicitly or implicitly. The inter-node message in step 1303 may be an SGNB MODIFICATION REQUEST message, an S-NODE MODIFICATION REQUEST message, or an RRC TRANSFER message including an inter-node RRC message. The inter-node message in step 1304 may be an SGNB MODIFICATION REQUEST ACKNOWLEDGE message, an S-NODE MODIFICATION REQUEST ACKNOWLEDGE message, or an RRC TRANSFER message including an inter-node RRC message.

[0089] FIG. 14 shows another example of the operations of MN1, SN2 and UE3 regarding UE-initiated (or triggered, requested) SCG activation. Steps 1401 and 1402 are similar to steps 1301 and 1302 of FIG. 13 and steps 501 and 502 of FIG. 5. In step 1403, MN1 sends an inter-node message including an SCG activation indication (or notification) to SN2. The inter-node message is the same as the message sent from MN1 to SN2 upon MN-initiated SCG activation, but indicates UE-initiated SCG activation explicitly or implicitly. The inter-node message may be an SGNB MODIFICATION REQUEST message, an S-NODE MODIFICATION REQUEST message or an RRC TRANSFER message that contains an inter-node RRC message. In step 1404, SN2 sends an inter-node message indicating confirmation (or acceptance) of SCG activation to MN1. The inter-node message may be an SGNB MODIFICATION REQUEST ACKNOWLEDGE message, an S-NODE MODIFICATION REQUEST ACKNOWLEDGE message, or an RRC TRANSFER message containing an inter-node RRC message. In step 1405, the MN1 sends an SCG activation indication (or notification) to the UE3 via the MCG. The SCG activation indication (or notification) of step 1405 may be sent to the UE3 via a MN RRC message, a MAC CE, or a DCI.

[0090] The operations of MN1 and SN2 described in this embodiment can enable SN2 to know whether the SCG activation is initiated by MN1 or UE3.

[0091] Seventh embodiment The configuration example of the wireless communication network according to this embodiment is similar to the example shown in Figures 1 and 2. In the following, the operations of MN1, SN2, and UE3 regarding the activation of the SCG associated with SN2 will be described.

[0092] FIG. 15 shows an example of the operation of MN1 and SN2. In step 1501, SN2 sends an inter-node message for SCG activation to MN1. The inter-node message may be an SGNB MODIFICATION REQUIRED message, an S-NODE MODIFICATION REQUIRED message, or an RRC TRANSFER message containing an inter-node RRC message. The inter-node message includes an indication of which option is used for UE-initiated (or triggered, requested) SCG activation. The multiple options include a first option and a second option. Thus, the inter-node message may include information indicating whether the first or second option is used to activate the SCG.

[0093] It should be noted that the first option is an option in which the SN2 sends a second signal indicating SCG activation to the UE3 in the PSCell after receiving a first signal representing an SCG activation request (or indication) from the UE3 and before sending an inter-node message indicating SCG activation to the MN1. Thus, in one example, the first option corresponds to the SCG activation procedure described in the first embodiment with reference to Figures 3 and 4. Meanwhile, the second option is an option in which the SN2 sends a second signal to the UE3 in the PSCell after receiving a response to the inter-node message from the MN1. Thus, in one example, the second option corresponds to the SCG activation procedure described in the third embodiment with reference to Figures 6 and 7.

[0094] FIG. 16 shows an example of operations of MN1, SN2, and UE3 regarding UE-initiated (or triggered, requested) SCG activation. Steps 1601 to 1605 are similar to steps 401 to 405 in FIG. 4 or steps 1001 to 1005 in FIG. 10. However, the inter-node message in step 1604 explicitly or implicitly indicates that the first option is used for UE-initiated SCG activation. The inter-node message in step 1604 may be an SGNB MODIFICATION REQUIRED message, an S-NODE MODIFICATION REQUIRED message, or an RRC TRANSFER message including an inter-node RRC message. The inter-node message in step 1605 may be an SGNB MODIFICATION CONFIRM message, an S-NODE MODIFICATION CONFIRM message, or an RRC TRANSFER message including an inter-node RRC message.

[0095] FIG. 17 shows another example of the operations of MN1, SN2, and UE3 regarding UE-initiated (or triggered, requested) SCG activation. Steps 1701-1705 are similar to steps 701-705 in FIG. 7 or steps 1101-1105 in FIG. 11. However, the inter-node message in step 1703 explicitly or implicitly indicates that the second option is used for UE-initiated SCG activation. The inter-node message in step 1703 may be an SGNB MODIFICATION REQUIRED message, an S-NODE MODIFICATION REQUIRED message, or an RRC TRANSFER message including an inter-node RRC message. The inter-node message in step 1704 may be an SGNB MODIFICATION CONFIRM message, an S-NODE MODIFICATION CONFIRM message, or an RRC TRANSFER message including an inter-node RRC message.

[0096] The operations of the MN1 and SN2 described in this embodiment can enable the MN1 to know which option is being used for UE-initiated (or triggered, requested) SCG activation.

[0097] <Eighth embodiment> The configuration example of the wireless communication network according to this embodiment is similar to the example shown in Figures 1 and 2. In the following, the operations of MN1, SN2, and UE3 regarding the activation of the SCG associated with SN2 will be described.

[0098] FIG. 18 shows an example of the operation of MN1 and SN2. In step 1801, MN1 sends an inter-node message for SCG activation to SN2. The inter-node message may be an SGNB MODIFICATION REQUEST message, an S-NODE MODIFICATION REQUEST message, or an RRC TRANSFER message containing an inter-node RRC message. The inter-node message includes an indication of which option is used for UE-initiated (or triggered, requested) SCG activation. The multiple options include a first option and a second option. Thus, the inter-node message may include information indicating whether the first or second option is used to activate the SCG.

[0099] It should be noted that the first option is an option in which MN1 transmits a second signal indicating SCG activation to UE3 via MCG after receiving a first signal representing an SCG activation request (or indication) from UE3 and before transmitting an inter-node message indicating SCG activation to SN2. Thus, in one example, the first option corresponds to the SCG activation procedure described in the second embodiment with reference to Fig. 5. Meanwhile, the second option is an option in which MN1 transmits a second signal to UE3 via MCG after receiving a response to the inter-node message from SN2.

[0100] FIG. 19 shows an example of operations of MN1, SN2, and UE3 regarding UE-initiated (or triggered, requested) SCG activation. Steps 1901 to 1905 are similar to steps 501 to 505 in FIG. 5 or steps 1301 to 1305 in FIG. 13. However, the inter-node message in step 1904 explicitly or implicitly indicates that the first option is used for UE-initiated SCG activation. The inter-node message in step 1903 may be an SGNB MODIFICATION REQUEST message, an S-NODE MODIFICATION REQUEST message, or an RRC TRANSFER message including an inter-node RRC message. The inter-node message in step 1904 may be an SGNB MODIFICATION REQUEST ACKNOWLEDGE message, an S-NODE MODIFICATION REQUEST ACKNOWLEDGE message, or an RRC TRANSFER message including an inter-node RRC message.

[0101] FIG. 20 shows another example of the operations of MN1, SN2, and UE3 regarding UE-initiated (or triggered, requested) SCG activation. Steps 2001 to 2005 are similar to steps 1401 to 1405 in FIG. 14. However, the inter-node message in step 2003 explicitly or implicitly indicates that the second option is used for UE-initiated SCG activation. The inter-node message in step 2003 may be an SGNB MODIFICATION REQUEST message, an S-NODE MODIFICATION REQUEST message, or an RRC TRANSFER message including an inter-node RRC message. The inter-node message in step 2004 may be an SGNB MODIFICATION REQUEST ACKNOWLEDGE message, an S-NODE MODIFICATION REQUEST ACKNOWLEDGE message, or an RRC TRANSFER message including an inter-node RRC message.

[0102] The operations of MN1 and SN2 described in this embodiment may enable SN2 to know which option is being used for UE-initiated (or triggered, requested) SCG activation.

[0103] <Ninth embodiment> The configuration example of the wireless communication network according to this embodiment is similar to the example shown in Figure 1 and Figure 2. In the following, the operation of the SN2 and the UE3 regarding the activation of the SCG associated with the SN2 will be described.

[0104] Figure 21 shows an example of the operation of the SN2 and UE3. In step 2101, the SN2 configures the UE3 with a random access preamble pool dedicated for SCG activation. The random access preamble pool dedicated for SCG activation (i.e., used when the UE3 makes a request for SCG activation to the SN2) is used by one or more UEs including the UE3 to perform contention-based random access to the PSCell of the SCG for SCG activation.

[0105] Specifically, in step 2101, the SN2 may transmit an SN RRC Reconfiguration message to the UE3, including a configuration of a preamble pool dedicated to SCG activation. For example, the SN2 may transmit the SN RRC Reconfiguration message to the UE3 before the SCG is deactivated. In this case, the SN2 may transmit the SN RRC Reconfiguration message to the UE3 via a Signaling Radio Bearer (SRB) (e.g., SRB3) of the SCG (e.g., PSCell). Alternatively, the SN2 may transmit the SN RRC Reconfiguration message to the UE3 via an SRB (e.g., SRB1) of the MN1 and the MCG. Alternatively, the SN2 may transmit the SN RRC Reconfiguration message to the UE3 while the SCG is deactivated. In this case, the SN2 may transmit the SN RRC Reconfiguration message to the UE3 via an SRB (e.g., SRB1) of the MN1 and the MCG.

[0106] In step 2102, UE-initiated SCG activation is triggered. For example, SCG activation is triggered by the arrival of uplink data transmitted on a DRB using SCG resources when the SCG is deactivated. The DRB may be an SCG DRB or a split DRB. An SCG DRB is a DRB having an RLC bearer only in the SCG associated with SN2. On the other hand, a split DRB is a DRB having both an RLC bearer in the MCG associated with MN1 and an RLC bearer in the SCG. The SCG DRB and the split DRB may be bearers terminated by SN2 (SN terminated) or MN1 (MN terminated). An SN terminated bearer is a radio bearer for which a PDCP is located in SN2. An MN terminated bearer is a radio bearer for which a PDCP is located in MN1. Alternatively, detection of a Radio Link Failure (RLF) in the MCG by UE3 triggers SCG activation.

[0107] In step 2103, the UE 3 selects a preamble from a preamble pool dedicated for SCG activation. In step 2104, the UE 3 initiates a contention-based random access to the PSCell using the selected preamble to activate the SCG. The random access (or random access preamble) of step 2104 requests the SN2 to activate the SCG. Alternatively, the random access (or random access preamble) of step 2104 indicates to the SN2 that the SCG needs to be activated.

[0108] According to the operation of the SN2 and UE3 described in this embodiment, the SN2 and UE3 use Contention-Based Random Access (CBRA) to activate the SCG. Therefore, in this embodiment, the SN2 and UE3 do not need Contention-Free Random Access (CFRA) to activate the SCG. In other words, the SN2 does not need to allocate a dedicated random access preamble for CFRA to each of the UEs with a deactivated SCG. This can contribute to avoiding a shortage of preamble resources for CFRA. In addition, the UE3 performs CBRA for SCG activation, but uses a preamble pool dedicated to SCG activation. Therefore, it is expected that the probability of collision of preamble transmission can be reduced compared to the case where the preamble pool is also used for purposes other than SCG activation. This can contribute to reducing the delay of SCG activation.

[0109] <Tenth embodiment> The configuration example of the wireless communication network according to this embodiment is similar to the example shown in Figure 1 and Figure 2. In the following, the operation of the SN2 and the UE3 regarding the activation of the SCG associated with the SN2 will be described.

[0110] FIG. 22 shows an example of the operation of SN2 and UE3. In step 2201, SN2 sends random access prioritization configuration to UE3 if the SCG of UE3 is currently deactivated or will be deactivated. Specifically, in step 2201, SN2 may send an SN RRC Reconfiguration message including the random access prioritization configuration to UE3. For example, SN2 may send the SN RRC Reconfiguration message to UE3 before the SCG is deactivated. In this case, SN2 may send the SN RRC Reconfiguration message to UE3 via the SRB (eg, SRB3) of the SCG (eg, PSCell). Alternatively, SN2 may send the SN RRC Reconfiguration message to UE3 via the SRB (eg, SRB1) of MN1 and MCG. Alternatively, SN2 may send the SN RRC Reconfiguration message to UE3 while the SCG is deactivated. In this case, the SN2 may transmit the SN RRC Reconfiguration message to the UE3 via the SRB (eg, SRB1) of the MN1 and the MCG.

[0111] The random access priority setting causes the UE 3 to set one or both of the power ramping factor and the scaling factor for the back-off indicator to values ​​indicated by the random access priority setting if a contention based random access procedure is initiated to activate the SCG and the random access priority setting has been configured for the UE 3 by the SN 2. The power ramping factor indicates the step (power ramping step size) by which the transmission power is ramped up for retransmission after a preamble transmission failure. The back-off indicator is used by the UE 3 to determine the time delay (i.e. backoff window size) when the UE 3 retries random access after a preamble transmission failure. The back-off indicator is indicated by the MAC subheader for the random access response. In case of normal (non-prioritized) random access, the UE 3 sets the scaling factor for the back-off indicator to 1. In contrast, the random access priority setting can indicate that the scaling factor for the back-off indicator is set to a value smaller than 1 (e.g. 0, 0.25, 0.5, or 0.75).

[0112] In step 2202, UE-initiated SCG activation is triggered. For example, SCG activation is triggered by the arrival of uplink data transmitted on a DRB using SCG resources when the SCG is deactivated. The DRB may be an SCG DRB or a split DRB. An SCG DRB is a DRB having an RLC bearer only in the SCG associated with SN2. On the other hand, a split DRB is a DRB having both an RLC bearer in the MCG associated with MN1 and an RLC bearer in the SCG. The SCG DRB and the split DRB may be bearers terminated by SN2 (SN terminated) or MN1 (MN terminated). An SN terminated bearer is a radio bearer for which a PDCP is located in SN2. An MN terminated bearer is a radio bearer for which a PDCP is located in MN1. Alternatively, detection of a Radio Link Failure (RLF) in the MCG by UE3 triggers SCG activation.

[0113] In step 2203, the UE 3 sets one or more Random Access Channel (RACH) parameters to respective values ​​indicated in the random access preference configuration. The one or more RACH parameters include a power ramping factor, or a scaling factor for the backoff indicator, or both. The one or more RACH parameters may include other RACH parameters.

[0114] In step 2204, the UE 3 initiates a contention based random access to the PSCell using the configured RACH parameter(s) to activate the SCG. The random access (or random access preamble) of step 2204 requests the SN 2 to activate the SCG. Alternatively, the random access (or random access preamble) of step 2204 indicates to the SN 2 that the SCG needs to be activated.

[0115] According to the operation of the SN2 and UE3 described in this embodiment, the SN2 and UE3 use the CBRA to activate the SCG. Therefore, in this embodiment, the SN2 and UE3 do not need the CFRA to activate the SCG. In other words, the SN2 does not need to allocate a dedicated random access preamble for the CFRA to each of the UEs with a deactivated SCG. This can contribute to avoiding a shortage of preamble resources for the CFRA. In addition, the UE3 performs the CBRA for SCG activation, which is a prioritized random access. Therefore, even if the UE3 fails to transmit the preamble initially, the probability that the UE3 will succeed in retrying the preamble can be increased. This can contribute to reducing the delay of the SCG activation.

[0116] Next, configuration examples of MN1, SN2, and UE3 according to the above-mentioned embodiments will be described below. FIG. 23 is a block diagram showing a configuration example of MN1 according to the above-mentioned embodiments. The configuration of SN2 may also be similar to the configuration shown in FIG. 23. Referring to FIG. 23, MN1 includes a Radio Frequency transceiver 2301, a network interface 2303, a processor 2304, and a memory 2305. The RF transceiver 2301 performs analog RF signal processing to communicate with UEs including UE3. The RF transceiver 2301 may include multiple transceivers. The RF transceiver 2301 is coupled to an antenna array 2302 and a processor 2304. The RF transceiver 2301 receives modulation symbol data from the processor 2304, generates a transmission RF signal, and provides the transmission RF signal to the antenna array 2302. The RF transceiver 2301 also generates a baseband reception signal based on the reception RF signal received by the antenna array 2302, and provides the baseband reception signal to the processor 2304. The RF transceiver 2301 may include an analog beamformer circuit for beamforming, which may include, for example, multiple phase shifters and multiple power amplifiers.

[0117] The network interface 2303 is used to communicate with network nodes (eg, SN2, and control and forwarding nodes of the core network). The network interface 2303 may include, for example, a network interface card (NIC) that complies with the IEEE 802.3 series.

[0118] The processor 2304 performs digital baseband signal processing (data plane processing) and control plane processing for wireless communication. The processor 2304 may include multiple processors. For example, the processor 2304 may include a modem processor (e.g., Digital Signal Processor (DSP)) performing digital baseband signal processing and a protocol stack processor (e.g., Central Processing Unit (CPU) or Micro Processing Unit (MPU)) performing control plane processing. The processor 2304 may include a digital beamformer module for beamforming. The digital beamformer module may include a Multiple Input Multiple Output (MIMO) encoder and a precoder.

[0119] The memory 2305 is configured by a combination of volatile memory and non-volatile memory. The volatile memory is, for example, Static Random Access Memory (SRAM) or Dynamic RAM (DRAM), or a combination thereof. The non-volatile memory is, for example, Mask Read Only Memory (MROM), Electrically Erasable Programmable ROM (EEPROM), flash memory, or a hard disk drive, or any combination thereof. The memory 2305 may include storage located remotely from the processor 2304. In this case, the processor 2304 may access the memory 2305 via the network interface 2303 or an I / O interface not shown.

[0120] The memory 2305 may store one or more software modules (computer programs) 2306 including instructions and data for performing the processing by MN1 described in the above-mentioned embodiments. In some implementations, the processor 2304 may be configured to read the software modules 2306 from the memory 2305 and execute them to perform the processing by MN1 described in the above-mentioned embodiments.

[0121] In addition, when the MN1 is a CU (eg, eNB-CU or gNB-CU) or a CU-CP, the MN1 does not need to include the RF transceiver 2301 (and the antenna array 2302).

[0122] FIG. 24 is a block diagram showing a configuration example of the UE3. The Radio Frequency (RF) transceiver 2401 performs analog RF signal processing to communicate with the MN1 and the SN2. The RF transceiver 2401 may include multiple transceivers. The analog RF signal processing performed by the RF transceiver 2401 includes frequency up-conversion, frequency down-conversion, and amplification. The RF transceiver 2401 is coupled to the antenna array 2402 and the baseband processor 2403. The RF transceiver 2401 receives modulation symbol data (or OFDM symbol data) from the baseband processor 2403, generates a transmission RF signal, and provides the transmission RF signal to the antenna array 2402. The RF transceiver 2401 also generates a baseband reception signal based on the reception RF signal received by the antenna array 2402, and provides the baseband reception signal to the baseband processor 2403. The RF transceiver 2401 may include an analog beamformer circuit for beamforming. The analog beamformer circuitry includes, for example, multiple phase shifters and multiple power amplifiers.

[0123] The baseband processor 2403 performs digital baseband signal processing (data plane processing) and control plane processing for wireless communication. Digital baseband signal processing includes (a) data compression / decompression, (b) data segmentation / concatenation, (c) generation / decomposition of transmission format (transmission frame), (d) transmission line coding / decoding, (e) modulation (symbol mapping) / demodulation, and (f) generation of OFDM symbol data (baseband OFDM signal) by Inverse Fast Fourier Transform (IFFT). Meanwhile, control plane processing includes communication management of layer 1 (e.g., transmission power control), layer 2 (e.g., radio resource management, and hybrid automatic repeat request (HARQ) processing), and layer 3 (e.g., signaling related to attachment, mobility, and call management).

[0124] For example, the digital baseband signal processing by the baseband processor 2403 may include signal processing of a Service Data Adaptation Protocol (SDAP) layer, a Packet Data Convergence Protocol (PDCP) layer, a Radio Link Control (RLC) layer, a MAC layer, and a PHY layer. Also, the control plane processing by the baseband processor 2403 may include processing of a Non-Access Stratum (NAS) protocol, an RRC protocol, and a MAC CE.

[0125] The baseband processor 2403 may perform MIMO encoding and precoding for beamforming.

[0126] The baseband processor 2403 may include a modem processor (e.g., DSP) that performs digital baseband signal processing and a protocol stack processor (e.g., CPU or MPU) that performs control plane processing. In this case, the protocol stack processor that performs control plane processing may be shared with the application processor 2404 described later.

[0127] The application processor 2404 is also called a CPU, an MPU, a microprocessor, or a processor core. The application processor 2404 may include multiple processors (multiple processor cores). The application processor 2404 executes a system software program (operating system (OS)) and various application programs (e.g., a calling application, a web browser, a mailer, a camera operation application, and a music playback application) read from the memory 2406 or a memory not shown, thereby implementing various functions of the UE3.

[0128] In some implementations, the baseband processor 2403 and the application processor 2404 may be integrated on a single chip, as shown by the dashed line (2405) in Figure 24. In other words, the baseband processor 2403 and the application processor 2404 may be implemented as a single System on Chip (SoC) device 2405. An SoC device may also be called a system Large Scale Integration (LSI) or a chipset.

[0129] The memory 2406 is a volatile memory or a non-volatile memory, or a combination thereof. The memory 2406 may include a plurality of physically independent memory devices. The volatile memory is, for example, an SRAM or a DRAM, or a combination thereof. The non-volatile memory is an MROM, an EEPROM, a flash memory, or a hard disk drive, or any combination thereof. For example, the memory 2406 may include an external memory device accessible from the baseband processor 2403, the application processor 2404, and the SoC 2405. The memory 2406 may include an internal memory device integrated in the baseband processor 2403, the application processor 2404, or the SoC 2405. Furthermore, the memory 2406 may include a memory in a Universal Integrated Circuit Card (UICC).

[0130] The memory 2406 may store one or more software modules (computer programs) 2407 including instructions and data for performing processing by the UE 3 described in the above-mentioned embodiments. In some implementations, the baseband processor 2403 or the application processor 2404 may be configured to read the software module 2407 from the memory 2406 and execute it to perform processing by the UE 3 described in the above-mentioned embodiments using the drawings.

[0131] In addition, the control plane processing and operations performed by UE3 described in the above embodiment can be realized by elements other than the RF transceiver 2401 and the antenna array 2402, i.e., at least one of the baseband processor 2403 and the application processor 2404, and the memory 2406 storing the software module 2407.

[0132] As described with reference to FIG. 23 and FIG. 24, each of the processors included in MN1, SN2, and UE3 according to the above-mentioned embodiments can execute one or more programs including instructions for making a computer execute the algorithms described with reference to the drawings. The programs include instructions (or software codes) for making a computer execute one or more functions described in the embodiments when the programs are loaded into a computer. The programs may be stored in a non-transitory computer-readable medium or a tangible storage medium. By way of example and not limitation, computer-readable media or tangible storage media include random-access memory (RAM), read-only memory (ROM), flash memory, solid-state drive (SSD) or other memory technology, CD-ROM, digital versatile disk (DVD), Blu-ray (registered trademark) disk or other optical disk storage, magnetic cassette, magnetic tape, magnetic disk storage or other magnetic storage device. The programs may be transmitted on a transitory computer-readable medium or communication medium. By way of example and not limitation, the transitory computer-readable medium or communication medium includes electrical, optical, acoustic, or other forms of propagated signals.

[0133] <Other embodiments> In the above-mentioned embodiment, MN1 and SN2 may be configured as CU / DU split in C-RAN deployment. For example, DU may receive SCG activation request from UE3, determine whether to allow SCG activation, and notify CU. Alternatively, DU may notify CU that it has received SCG activation request from UE3, and CU may determine whether to allow SCG activation, and notify CU.

[0134] In one or more of the above-described embodiments, the SN2 (or MN1) receiving the SCG activation request from the UE3 may transmit a second signal indicating SCG activation to the UE3 without waiting for confirmation (or consent) from the MN1 (or SN2). On the other hand, when the MN1 (or SN2) transmits the SCG activation request to the SN2 (or MN1) without receiving (independently of) the SCG activation request from the UE3, it may wait for confirmation (or consent) from the SN2 (or MN1) and transmit the SCG activation instruction to the UE3 after the confirmation (or consent) from the SN2 (or MN1). Alternatively, the MN1 (or SN2) may transmit the SCG activation instruction to the UE3 without waiting for confirmation (or consent) from the SN2 (or MN1) if a predetermined condition is satisfied. The predetermined condition may be that the SN2 (or MN1) has notified the MN1 (or SN2) of the permission (or consent) in advance. Additionally or alternatively, the predetermined condition may be occurrence of downlink data on a bearer using only SCG resources (SCG DRB) or a split bearer (Split DRB) whose primary path is set to the SCG. In the above embodiment, it can also be said that the predetermined condition is receipt of a request for SCG activation from UE3. Thus, when the predetermined condition is met, MN1 (or SN2) may transmit an instruction for SCG activation or a signal indicating SCG activation to UE3 without waiting for confirmation (or acceptance) from SN2 (or MN1).

[0135] In one or more of the above-mentioned embodiments, the SN2 (or MN1) may perform SCG activation in response to a request for SCG activation by the UE3 without waiting for confirmation (or acceptance) of the MN1 (or SN2). In this case, the SN2 (or MN1) may send an uplink grant to the UE3 for actually transmitting uplink data in an indication of SCG activation or a signal indicating SCG activation. The UE3 transmits the uplink data according to the uplink grant. Alternatively, the SN2 (or MN1) may transmit the uplink grant after confirmation (or acceptance) of the MN1 (or SN2). The uplink data may be data in an SCG DRB (SCG bearer).

[0136] In one or more of the above-mentioned embodiments, the UE 3 may perform the SCG activation request (to the SN 2) by performing random access. Here, the random access may be CFRA or CBRA based on a four-step random access procedure (4 Step RACH). Alternatively, the random access may be CFRA or CBRA based on a two-step random access procedure (2 Step RACH). When the UE 3 uses two-step random access (e.g., 2 Step RACH), for example, the data portion of the first message (MsgA) may include a terminal identifier (e.g., C-RNTI) in the SCG of the UE 3 and information indicating that the first message is a request for SCG activation. In this way, the SN 2 can detect which UE is requesting SCG activation by receiving the first message. Additionally or alternatively, the UE 3 may transmit either or both of the amount of uplink data (or buffer amount) to be transmitted and the uplink data in the data portion of the first message. The uplink data may be data in an SCG DRB (SCG bearer).

[0137] In one or more of the above-mentioned embodiments, the UE3 can send an SCG activation request to the SN2 on a random access or uplink control channel (e.g., SR, PUCCH). However, it is also possible that the SCG activation request fails (ends in failure). In this case, the UE3 may send an SCG activation request to the MN1, which may be sent on a random access or uplink control channel. Alternatively, the UE3 may regard the failure of the SCG activation request to the SN2 as an SCG radio link disconnection (SCG RLF) and send SCG failure information to the MN1. On the other hand, it is also possible that the UE3 receives an SCG activation instruction from the SN2 or MN1 before the SCG activation request to the SN2 or MN1 is successfully completed. In this case, the UE3 may abort its own SCG activation request procedure and activate the SCG according to the SCG activation instruction.

[0138] The above-described embodiment is merely an example of the application of the technical idea obtained by the inventor of the present invention. In other words, the technical idea is not limited to the above-described embodiment, and various modifications are possible.

[0139] For example, some or all of the above embodiments may be described as, but are not limited to, the following supplementary notes.

[0140] (Appendix 1) 1. A Radio Access Network (RAN) node configured to operate as a secondary node associated with a Secondary Cell Group (SCG) in dual connectivity for a User Equipment (UE), comprising: At least one memory; at least one processor coupled to the at least one memory; Equipped with The at least one processor: receiving a first signal from the UE at a Primary SCG Cell (PSCell) of the SCG when the SCG is deactivated, the first signal indicating a request or indication of activation of the SCG; In response to receiving the first signal, transmitting a second signal in the PSCell to the UE indicating activation of the SCG; configured to send an inter-node message indicating activation of the SCG to a master node associated with a Master Cell Group (MCG) of the dual connectivity; the second signal is transmitted to the UE before the secondary node transmits the inter-node message to the master node or before the secondary node receives a response to the inter-node message from the master node. RAN node. (Appendix 2) the at least one processor is configured to transmit the second signal to the UE prior to transmitting the inter-node message to the master node. RAN node as described in Appendix 1. (Appendix 3) The inter-node message includes information indicating that the SCG has already been activated or that activation of the SCG has been indicated to the UE; 3. The RAN node according to claim 1 or 2. (Appendix 4) The inter-node message is the same as the message sent from the secondary node to the master node when activation of the SCG is initiated by the secondary node, but includes information indicating SCG activation initiated by the UE. 4. The RAN node according to claim 1 , (Appendix 5) The at least one processor: receiving the first signal via a random access procedure to the PSCell by the UE or via an uplink physical layer message; and configured to transmit the second signal to the UE via the random access procedure or via a downlink physical layer message. 4. The RAN node according to claim 1 , (Appendix 6) the second signal is a random access response and implicitly indicates activation of the SCG; RAN node as described in Supplementary Note 5. (Appendix 7) the second signal is an uplink grant; RAN node as described in Supplementary Note 5. (Appendix 8) the at least one processor is configured to determine which of a plurality of options is to be used to activate the SCG; the plurality of options include a first option in which the secondary node transmits the second signal to the UE prior to transmitting the inter-node message to the master node, and a second option in which the secondary node transmits the second signal to the UE after receiving the response to the inter-node message from the master node. 8. The RAN node according to any one of Supplementary Notes 1 to 7. (Appendix 9) The at least one processor is configured to determine which of the first and second options is used based on a priority level or urgency level of an uplink transmission by the UE. RAN node as described in Supplementary Note 8. (Appendix 10) the first signal indicates the priority level or the urgency level. RAN node as described in Supplementary Note 9. (Appendix 11) the inter-node message includes information indicating which of the first and second options is being used; 11. The RAN node according to any one of Supplementary Notes 8 to 10. (Appendix 12) The at least one processor is configured to configure the UE with a random access preamble pool dedicated for SCG activation; the random access preamble pool is used by one or more UEs to perform contention based random access to the PSCell for SCG activation; 12. The RAN node according to any one of Supplementary Notes 1 to 11. (Appendix 13) The at least one processor is configured to: send a random access prioritization configuration to the UE if the SCG is currently deactivated or will be deactivated; the random access preference setting causes the UE to set one or both of a power ramping factor and a scaling factor for a back-off indicator to values ​​indicated by the random access preference setting if a random access procedure is initiated to activate the SCG and the random access preference setting has been configured for the UE by the secondary node; 12. The RAN node according to any one of Supplementary Notes 1 to 11. (Appendix 14) 1. A method performed by a Radio Access Network (RAN) node configured to operate as a secondary node associated with a Secondary Cell Group (SCG) in dual connectivity for a User Equipment (UE), the method comprising: receiving a first signal from the UE at a Primary SCG Cell (PSCell) of the SCG when the SCG is deactivated, the first signal indicating a request or indication of activation of the SCG; in response to receiving the first signal, transmitting a second signal in the PSCell to the UE indicating activation of the SCG; and sending an inter-node message indicating activation of the SCG to a master node associated with a Master Cell Group (MCG) of the dual connectivity; Equipped with the second signal is transmitted to the UE before the secondary node transmits the inter-node message to the master node or before the secondary node receives a response to the inter-node message from the master node. method. (Appendix 15) 1. A program for causing a computer to perform a method for a Radio Access Network (RAN) node configured to operate as a secondary node associated with a Secondary Cell Group (SCG) in dual connectivity for a User Equipment (UE), the method comprising: receiving a first signal from the UE at a Primary SCG Cell (PSCell) of the SCG when the SCG is deactivated, the first signal indicating a request or indication of activation of the SCG; in response to receiving the first signal, transmitting a second signal in the PSCell to the UE indicating activation of the SCG; and sending an inter-node message indicating activation of the SCG to a master node associated with a Master Cell Group (MCG) of the dual connectivity; Equipped with the second signal is transmitted to the UE before the secondary node transmits the inter-node message to the master node or before the secondary node receives a response to the inter-node message from the master node. program. (Appendix 16) 1. A Radio Access Network (RAN) node configured to operate as a secondary node associated with a Secondary Cell Group (SCG) in dual connectivity for a User Equipment (UE), comprising: At least one memory; at least one processor coupled to the at least one memory; Equipped with The at least one processor: receiving a first signal from the UE at a Primary SCG Cell (PSCell) of the SCG when the SCG is deactivated, the first signal indicating a request or indication of activation of the SCG; In response to receiving the first signal, sending an inter-node message indicating activation of the SCG to a master node associated with a Master Cell Group (MCG) of the dual connectivity; receiving a response to the inter-node message from the master node; if the response indicates that the activation of the SCG is accepted, then transmitting a second signal in the PSCell to the UE indicating the activation of the SCG. RAN node. (Appendix 17) The inter-node message is the same as the message sent from the secondary node to the master node when activation of the SCG is initiated by the secondary node, but includes information indicating SCG activation initiated by the UE. 16. The RAN node according to claim 16. (Appendix 18) the at least one processor is configured to determine which of a plurality of options is to be used to activate the SCG; the plurality of options include a first option in which the secondary node transmits the second signal to the UE prior to transmitting the inter-node message to the master node, and a second option in which the secondary node transmits the second signal to the UE after receiving the response to the inter-node message from the master node. 18. The RAN node of claim 16 or 17. (Appendix 19) the inter-node message includes information indicating which of the first and second options is being used; 17. The RAN node according to claim 18. (Appendix 20) 1. A method performed by a Radio Access Network (RAN) node configured to operate as a secondary node associated with a Secondary Cell Group (SCG) in dual connectivity for a User Equipment (UE), the method comprising: receiving a first signal from the UE at a Primary SCG Cell (PSCell) of the SCG when the SCG is deactivated, the first signal indicating a request or indication of activation of the SCG; responsive to receiving the first signal, transmitting an inter-node message indicating activation of the SCG to a master node associated with a Master Cell Group (MCG) of the dual connectivity; receiving a response to the inter-node message from the master node; and if the response indicates that the activation of the SCG is accepted, sending a second signal in the PSCell to the UE indicating activation of the SCG; A method for providing the above. (Appendix 21) 1. A program for causing a computer to perform a method for a Radio Access Network (RAN) node configured to operate as a secondary node associated with a Secondary Cell Group (SCG) in dual connectivity for a User Equipment (UE), the method comprising: receiving a first signal from the UE at a Primary SCG Cell (PSCell) of the SCG when the SCG is deactivated, the first signal indicating a request or indication of activation of the SCG; responsive to receiving the first signal, transmitting an inter-node message indicating activation of the SCG to a master node associated with a Master Cell Group (MCG) of the dual connectivity; receiving a response to the inter-node message from the master node; and if the response indicates that the activation of the SCG is accepted, sending a second signal in the PSCell to the UE indicating activation of the SCG; A program that includes: (Appendix 22) 1. A Radio Access Network (RAN) node configured to operate as a secondary node associated with a Secondary Cell Group (SCG) in dual connectivity for a User Equipment (UE), comprising: At least one memory; at least one processor coupled to the at least one memory; Equipped with the at least one processor is configured to determine which of a plurality of options is to be used to activate the SCG; the plurality of options are used to activate the SCG in response to receiving a first signal from the UE at a Primary SCG Cell (PSCell) of the SCG indicating a request or indication of activation of the SCG; the plurality of options includes a first option and a second option; The first option is an option in which the secondary node transmits a second signal indicating activation of the SCG to the UE in the PSCell before transmitting an inter-node message indicating activation of the SCG to a master node associated with a Master Cell Group (MCG) of the dual connectivity; The second option is an option in which the secondary node transmits the second signal to the UE after receiving a response to the inter-node message from the master node. RAN node. (Appendix 23) The at least one processor is configured to determine which of the first and second options is used based on a priority level or urgency level of an uplink transmission by the UE. 23. The RAN node according to claim 22. (Appendix 24) the first signal indicates the priority level or the urgency level. 23. The RAN node according to claim 23. (Appendix 25) the inter-node message includes information indicating which of the first and second options is being used; 25. The RAN node according to any one of Supplementary Notes 22 to 24. (Appendix 26) 1. A method performed by a Radio Access Network (RAN) node configured to operate as a secondary node associated with a Secondary Cell Group (SCG) in dual connectivity for a User Equipment (UE), the method comprising: determining which of a plurality of options is to be used to activate the SCG; the plurality of options are used to activate the SCG in response to receiving a first signal from the UE at a Primary SCG Cell (PSCell) of the SCG indicating a request or indication of activation of the SCG; the plurality of options includes a first option and a second option; The first option is an option in which the secondary node transmits a second signal indicating activation of the SCG to the UE in the PSCell before transmitting an inter-node message indicating activation of the SCG to a master node associated with a Master Cell Group (MCG) of the dual connectivity; The second option is an option in which the secondary node transmits the second signal to the UE after receiving a response to the inter-node message from the master node. method. (Appendix 27) 1. A program for causing a computer to perform a method for a Radio Access Network (RAN) node configured to operate as a secondary node associated with a Secondary Cell Group (SCG) in dual connectivity for a User Equipment (UE), the method comprising: The method comprises determining which of a plurality of options is to be used to activate the SCG; the plurality of options are used to activate the SCG in response to receiving a first signal from the UE at a Primary SCG Cell (PSCell) of the SCG indicating a request or indication of activation of the SCG; the plurality of options includes a first option and a second option; The first option is an option in which the secondary node transmits a second signal indicating activation of the SCG to the UE in the PSCell before transmitting an inter-node message indicating activation of the SCG to a master node associated with a Master Cell Group (MCG) of the dual connectivity; The second option is an option in which the secondary node transmits the second signal to the UE after receiving a response to the inter-node message from the master node. program. (Appendix 28) 1. A Radio Access Network (RAN) node configured to operate as a master node associated with a Master Cell Group (MCG) in dual connectivity for a User Equipment (UE), comprising: At least one memory; at least one processor coupled to the at least one memory; Equipped with The at least one processor is configured to determine which of a plurality of options is to be used to activate a Secondary Cell Group (SCG) of the dual connectivity; the plurality of options are used for activating the SCG in response to receiving a first signal from the UE via the MCG indicating a request or indication of activation of the SCG; the plurality of options includes a first option and a second option; The first option is an option in which the master node transmits a second signal indicating activation of the SCG to the UE via the MCG before transmitting an inter-node message indicating activation of the SCG to a secondary node associated with the SCG; The second option is an option in which the master node transmits the second signal to the UE after receiving a response to the inter-node message from the secondary node. RAN node. (Appendix 29) The at least one processor is configured to determine which of the first and second options is used based on a priority level or urgency level of an uplink transmission by the UE. 27. The RAN node according to claim 28. (Appendix 30) the first signal indicates the priority level or the urgency level. 29. The RAN node of claim 29. (Appendix 31) the inter-node message includes information indicating which of the first and second options is being used; 31. The RAN node according to any one of Supplementary Notes 28 to 30. (Appendix 32) 1. A method performed by a Radio Access Network (RAN) node configured to operate as a master node associated with a Master Cell Group (MCG) in dual connectivity for a User Equipment (UE), the method comprising: determining which of a plurality of options is to be used to activate a Secondary Cell Group (SCG) of the dual connectivity; the plurality of options are used for activating the SCG in response to receiving a first signal from the UE via the MCG indicating a request or indication of activation of the SCG; the plurality of options includes a first option and a second option; The first option is an option in which the master node transmits a second signal indicating activation of the SCG to the UE via the MCG before transmitting an inter-node message indicating activation of the SCG to a secondary node associated with the SCG; The second option is an option in which the master node transmits the second signal to the UE after receiving a response to the inter-node message from the secondary node. method. (Appendix 33) 1. A program for causing a computer to perform a method for a Radio Access Network (RAN) node configured to operate as a master node associated with a Master Cell Group (MCG) in dual connectivity for a User Equipment (UE), the method comprising: The method comprises determining which of a plurality of options is to be used to activate a Secondary Cell Group (SCG) of the dual connectivity; the plurality of options are used for activating the SCG in response to receiving a first signal from the UE via the MCG indicating a request or indication of activation of the SCG; the plurality of options includes a first option and a second option; The first option is an option in which the master node transmits a second signal indicating activation of the SCG to the UE via the MCG before transmitting an inter-node message indicating activation of the SCG to a secondary node associated with the SCG; The second option is an option in which the master node transmits the second signal to the UE after receiving a response to the inter-node message from the secondary node. program. (Appendix 34) 1. A Radio Access Network (RAN) node configured to operate as a secondary node associated with a Secondary Cell Group (SCG) in dual connectivity for a User Equipment (UE), comprising: At least one memory; at least one processor coupled to the at least one memory; Equipped with The at least one processor: receiving a first signal from the UE at a Primary SCG Cell (PS Cell) of the SCG indicating a request or indication of activation of the SCG when the SCG is deactivated; configured to, in response to receiving the first signal, send an inter-node message representing a request or indication of activation of the SCG to a master node associated with a Master Cell Group (MCG) of the dual connectivity; The inter-node message is the same as the message sent from the secondary node to the master node when activation of the SCG is initiated by the secondary node, but includes information indicating SCG activation initiated by the UE. RAN node. (Appendix 35) 1. A method performed by a Radio Access Network (RAN) node configured to operate as a secondary node associated with a Secondary Cell Group (SCG) in dual connectivity for a User Equipment (UE), the method comprising: receiving a first signal from the UE at a Primary SCG Cell (PS Cell) of the SCG when the SCG is deactivated, the first signal indicating a request or indication of activation of the SCG; and responsive to receiving the first signal, transmitting an inter-node message representing a request or indication of activation of the SCG to a master node associated with a Master Cell Group (MCG) of the dual connectivity; Equipped with The inter-node message is the same as the message sent from the secondary node to the master node when activation of the SCG is initiated by the secondary node, but includes information indicating SCG activation initiated by the UE. method. (Appendix 36) 1. A program for causing a computer to perform a method for a Radio Access Network (RAN) node configured to operate as a secondary node associated with a Secondary Cell Group (SCG) in dual connectivity for a User Equipment (UE), the method comprising: receiving a first signal from the UE at a Primary SCG Cell (PS Cell) of the SCG when the SCG is deactivated, the first signal indicating a request or indication of activation of the SCG; and responsive to receiving the first signal, transmitting an inter-node message representing a request or indication of activation of the SCG to a master node associated with a Master Cell Group (MCG) of the dual connectivity; Equipped with The inter-node message is the same as the message sent from the secondary node to the master node when activation of the SCG is initiated by the secondary node, but includes information indicating SCG activation initiated by the UE. program. (Appendix 37) 1. A Radio Access Network (RAN) node configured to operate as a master node associated with a Master Cell Group (MCG) in dual connectivity for a User Equipment (UE), comprising: At least one memory; at least one processor coupled to the at least one memory; Equipped with The at least one processor: receiving a first signal from the UE via the MCG indicating a request or indication of activation of a Secondary Cell Group (SCG) of the dual connectivity when the SCG is deactivated; configured to, in response to receiving the first signal, send an inter-node message to a secondary node associated with the SCG representing a request or indication of activation of the SCG; The inter-node message is the same as the message sent from the master node to the secondary node when activation of the SCG is initiated by the master node, but includes information indicating SCG activation initiated by the UE. RAN node. (Appendix 38) 1. A method performed by a Radio Access Network (RAN) node configured to operate as a master node associated with a Master Cell Group (MCG) in dual connectivity for a User Equipment (UE), the method comprising: receiving a first signal from the UE via the MCG indicating a request or indication of activation of a Secondary Cell Group (SCG) of the dual connectivity when the SCG is deactivated; and responsive to receiving the first signal, transmitting an inter-node message to a secondary node associated with the SCG representing a request or indication of activation of the SCG; Equipped with The inter-node message is the same as the message sent from the master node to the secondary node when activation of the SCG is initiated by the master node, but includes information indicating SCG activation initiated by the UE. method. (Appendix 39) 1. A program for causing a computer to perform a method for a Radio Access Network (RAN) node configured to operate as a master node associated with a Master Cell Group (MCG) in dual connectivity for User Equipment (UE), the method comprising: receiving a first signal from the UE via the MCG indicating a request or indication of activation of a Secondary Cell Group (SCG) of the dual connectivity when the SCG is deactivated; and responsive to receiving the first signal, transmitting an inter-node message to a secondary node associated with the SCG representing a request or indication of activation of the SCG; Equipped with The inter-node message is the same as the message sent from the master node to the secondary node when activation of the SCG is initiated by the master node, but includes information indicating SCG activation initiated by the UE. program. (Appendix 40) 1. A Radio Access Network (RAN) node configured to operate as a secondary node associated with a Secondary Cell Group (SCG) in dual connectivity for a User Equipment (UE), comprising: At least one memory; at least one processor coupled to the at least one memory; Equipped with The at least one processor: receiving a first signal from the UE at a Primary SCG Cell (PS Cell) of the SCG indicating a request or indication of activation of the SCG when the SCG is deactivated; configured to, in response to receiving the first signal, send an inter-node message representing a request or indication of activation of the SCG to a master node associated with a Master Cell Group (MCG) of the dual connectivity; the inter-node message includes information indicating whether a first or second option is being used to activate the SCG; The first option is an option in which the secondary node transmits a second signal indicating activation of the SCG to the UE in the PSCell before transmitting the inter-node message to the master node; The second option is an option in which the secondary node transmits the second signal to the UE after receiving a response to the inter-node message from the master node. RAN node. (Appendix 41) 1. A method performed by a Radio Access Network (RAN) node configured to operate as a secondary node associated with a Secondary Cell Group (SCG) in dual connectivity for a User Equipment (UE), the method comprising: receiving a first signal from the UE at a Primary SCG Cell (PS Cell) of the SCG when the SCG is deactivated, the first signal indicating a request or indication of activation of the SCG; and responsive to receiving the first signal, transmitting an inter-node message representing a request or indication of activation of the SCG to a master node associated with a Master Cell Group (MCG) of the dual connectivity; Equipped with the inter-node message includes information indicating whether a first or second option is being used to activate the SCG; The first option is an option in which the secondary node transmits a second signal indicating activation of the SCG to the UE in the PSCell before transmitting the inter-node message to the master node; The second option is an option in which the secondary node transmits the second signal to the UE after receiving a response to the inter-node message from the master node. method. (Appendix 42) 1. A program for causing a computer to perform a method performed by a Radio Access Network (RAN) node configured to operate as a secondary node associated with a Secondary Cell Group (SCG) in dual connectivity for User Equipment (UE), the method comprising: receiving a first signal from the UE at a Primary SCG Cell (PS Cell) of the SCG when the SCG is deactivated, the first signal indicating a request or indication of activation of the SCG; and responsive to receiving the first signal, transmitting an inter-node message representing a request or indication of activation of the SCG to a master node associated with a Master Cell Group (MCG) of the dual connectivity; Equipped with the inter-node message includes information indicating whether a first or second option is being used to activate the SCG; The first option is an option in which the secondary node transmits a second signal indicating activation of the SCG to the UE in the PSCell before transmitting the inter-node message to the master node; The second option is an option in which the secondary node transmits the second signal to the UE after receiving a response to the inter-node message from the master node. program. (Appendix 43) 1. A Radio Access Network (RAN) node configured to operate as a master node associated with a Master Cell Group (MCG) in dual connectivity for a User Equipment (UE), comprising: At least one memory; at least one processor coupled to the at least one memory; Equipped with The at least one processor: receiving a first signal from the UE via the MCG indicating a request or indication of activation of a Secondary Cell Group (SCG) of the dual connectivity when the SCG is deactivated; configured to, in response to receiving the first signal, send an inter-node message to a secondary node associated with the SCG representing a request or indication of activation of the SCG; the inter-node message includes information indicating whether a first or second option is being used to activate the SCG; The first option is an option in which the master node transmits a second signal indicating activation of the SCG to the UE via the MCG before transmitting the inter-node message to the secondary node; The second option is an option in which the master node transmits the second signal to the UE after receiving a response to the inter-node message from the secondary node. RAN node. (Appendix 44) 1. A method performed by a Radio Access Network (RAN) node configured to operate as a master node associated with a Master Cell Group (MCG) in dual connectivity for a User Equipment (UE), the method comprising: receiving a first signal from the UE via the MCG indicating a request or indication of activation of a Secondary Cell Group (SCG) of the dual connectivity when the SCG is deactivated; and responsive to receiving the first signal, transmitting an inter-node message to a secondary node associated with the SCG representing a request or indication of activation of the SCG; Equipped with the inter-node message includes information indicating whether a first or second option is being used to activate the SCG; The first option is an option in which the master node transmits a second signal indicating activation of the SCG to the UE via the MCG before transmitting the inter-node message to the secondary node; The second option is an option in which the master node transmits the second signal to the UE after receiving a response to the inter-node message from the secondary node. method. (Appendix 45) 1. A program for causing a computer to perform a method for a Radio Access Network (RAN) node configured to operate as a master node associated with a Master Cell Group (MCG) in dual connectivity for User Equipment (UE), the method comprising: receiving a first signal from the UE via the MCG indicating a request or indication of activation of a Secondary Cell Group (SCG) of the dual connectivity when the SCG is deactivated; and responsive to receiving the first signal, transmitting an inter-node message to a secondary node associated with the SCG representing a request or indication of activation of the SCG; Equipped with the inter-node message includes information indicating whether a first or second option is being used to activate the SCG; The first option is an option in which the master node transmits a second signal indicating activation of the SCG to the UE via the MCG before transmitting the inter-node message to the secondary node; The second option is an option in which the master node transmits the second signal to the UE after receiving a response to the inter-node message from the secondary node. program. (Appendix 46) 1. A Radio Access Network (RAN) node configured to operate as a secondary node associated with a Secondary Cell Group (SCG) in dual connectivity for a User Equipment (UE), comprising: At least one memory; at least one processor coupled to the at least one memory; Equipped with The at least one processor is configured to configure the UE with a random access preamble pool dedicated for SCG activation; The random access preamble pool is used by one or more UEs to perform contention-based random access to a Primary SCG Cell (PSCell) of the SCG for SCG activation. RAN node. (Appendix 47) 1. A method performed by a Radio Access Network (RAN) node configured to operate as a secondary node associated with a Secondary Cell Group (SCG) in dual connectivity for a User Equipment (UE), the method comprising: Configuring a random access preamble pool dedicated for SCG activation in the UE; The random access preamble pool is used by one or more UEs to perform contention-based random access to a Primary SCG Cell (PSCell) of the SCG for SCG activation. method. (Appendix 48) 1. A program for causing a computer to perform a method for a Radio Access Network (RAN) node configured to operate as a secondary node associated with a Secondary Cell Group (SCG) in dual connectivity for a User Equipment (UE), the method comprising: The method comprises configuring the UE with a random access preamble pool dedicated for SCG activation; The random access preamble pool is used by one or more UEs to perform contention-based random access to a Primary SCG Cell (PSCell) of the SCG for SCG activation. program. (Appendix 49) A User Equipment (UE) configured to support dual connectivity using a Master Cell Group (MCG) associated with a master node and a Secondary Cell Group (SCG) associated with a secondary node, At least one memory; at least one processor coupled to the at least one memory; Equipped with The at least one processor receives from the secondary node a configuration of a random access preamble pool dedicated for SCG activation; and configured to select a preamble from the random access preamble pool for contention-based random access to a Primary SCG Cell (PSCell) of the SCG to activate the SCG. U.E. (Appendix 50) 1. A method performed by a User Equipment (UE) configured to support dual connectivity using a Master Cell Group (MCG) associated with a master node and a Secondary Cell Group (SCG) associated with a secondary node, comprising: receiving from the secondary node a configuration of a random access preamble pool dedicated for SCG activation; and selecting a preamble from the random access preamble pool for contention based random access to a Primary SCG Cell (PSCell) of the SCG to activate the SCG; A method for providing the above. (Appendix 51) 1. A program for causing a computer to perform a method for User Equipment (UE) configured to support dual connectivity using a Master Cell Group (MCG) associated with a master node and a Secondary Cell Group (SCG) associated with a secondary node, the method comprising: receiving from the secondary node a configuration of a random access preamble pool dedicated for SCG activation; and selecting a preamble from the random access preamble pool for contention based random access to a Primary SCG Cell (PSCell) of the SCG to activate the SCG; A program that includes: (Appendix 52) 1. A Radio Access Network (RAN) node configured to operate as a secondary node associated with a Secondary Cell Group (SCG) in dual connectivity for a User Equipment (UE), comprising: At least one memory; at least one processor coupled to the at least one memory; Equipped with The at least one processor is configured to: send a random access prioritization configuration to the UE if the SCG is currently deactivated or will be deactivated; the random access preference setting causes the UE to set one or both of a power ramping factor and a scaling factor for a back-off indicator to values ​​indicated by the random access preference setting if a random access procedure is initiated to activate the SCG and the random access preference setting has been configured for the UE by the secondary node; RAN node. (Appendix 53) 1. A method performed by a Radio Access Network (RAN) node configured to operate as a secondary node associated with a Secondary Cell Group (SCG) in dual connectivity for a User Equipment (UE), the method comprising: If the SCG is currently deactivated or will be deactivated, sending a random access prioritization configuration to the UE; the random access preference setting causes the UE to set one or both of a power ramping factor and a scaling factor for a back-off indicator to values ​​indicated by the random access preference setting if a random access procedure is initiated to activate the SCG and the random access preference setting has been configured for the UE by the secondary node; RAN node. (Appendix 54) 1. A program for causing a computer to perform a method for a Radio Access Network (RAN) node configured to operate as a secondary node associated with a Secondary Cell Group (SCG) in dual connectivity for a User Equipment (UE), the method comprising: If the SCG is currently deactivated or will be deactivated, sending a random access prioritization configuration to the UE; the random access preference setting causes the UE to set one or both of a power ramping factor and a scaling factor for a back-off indicator to values ​​indicated by the random access preference setting if a random access procedure is initiated to activate the SCG and the random access preference setting has been configured for the UE by the secondary node; program. (Appendix 55) A User Equipment (UE) configured to support dual connectivity using a Master Cell Group (MCG) associated with a master node and a Secondary Cell Group (SCG) associated with a secondary node, At least one memory; at least one processor coupled to the at least one memory; Equipped with The at least one processor: If a random access procedure is initiated to activate the SCG and a random access prioritization configuration is configured for the UE by the secondary node, setting one or both of a power ramping factor and a scaling factor for a back-off indicator to a value indicated by the random access prioritization configuration; configured to perform random access to a Primary SCG Cell (PSCell) of the SCG; U.E. (Appendix 56) 1. A method performed by a User Equipment (UE) configured to support dual connectivity using a Master Cell Group (MCG) associated with a master node and a Secondary Cell Group (SCG) associated with a secondary node, comprising: If a random access procedure is initiated to activate the SCG and a random access prioritization configuration is configured for the UE by the secondary node, setting one or both of a power ramping factor and a scaling factor for a back-off indicator to a value indicated by the random access prioritization configuration; and performing random access to a Primary SCG Cell (PSCell) of the SCG; A method for providing the above. (Appendix 57) 1. A program for causing a computer to perform a method for User Equipment (UE) configured to support dual connectivity using a Master Cell Group (MCG) associated with a master node and a Secondary Cell Group (SCG) associated with a secondary node, the method comprising: If a random access procedure is initiated to activate the SCG and a random access prioritization configuration is configured for the UE by the secondary node, setting one or both of a power ramping factor and a scaling factor for a back-off indicator to a value indicated by the random access prioritization configuration; and performing random access to a Primary SCG Cell (PSCell) of the SCG; A program that includes:

[0141] This application claims priority to Japanese Patent Application No. 2021-116353, filed on July 14, 2021, the disclosure of which is incorporated herein in its entirety. [Explanation of symbols]

[0142] 1 Master Node (MN) 2 Secondary Node (SN) 3. User Equipment (UE) 2304 Processor 2305 Memory 2306 Modules 2403 Baseband Processor 2404 Application Processor 2406 Memory 2407 Modules

Claims

1. 1. A Radio Access Network (RAN) node configured to operate as a secondary node associated with a Secondary Cell Group (SCG) in dual connectivity for a User Equipment (UE), comprising: means for receiving, at a Primary SCG Cell (PSCell) of the SCG from the UE when the SCG is deactivated, a first signal representing a request or indication of activation of the SCG; means for transmitting, in the PSCell, a second signal to the UE in response to receiving the first signal, the second signal indicating activation of the SCG; means for transmitting an inter-node message indicating activation of the SCG to a master node associated with a Master Cell Group (MCG) of the dual connectivity; the second signal is transmitted to the UE before the secondary node transmits the inter-node message to the master node or before the secondary node receives a response to the inter-node message from the master node. RAN node.

2. The means for transmitting the second signal is configured to transmit the second signal to the UE prior to transmitting the inter-node message to the master node.

2. The RAN node of claim 1.

3. The inter-node message includes information indicating that the SCG has already been activated or that activation of the SCG has been indicated to the UE; 3. A RAN node according to claim 1 or 2.

4. The inter-node message is the same as the message sent from the secondary node to the master node when activation of the SCG is initiated by the secondary node, but includes information indicating SCG activation initiated by the UE.

3. A RAN node according to claim 1 or 2.

5. The means for receiving the first signal is configured to receive the first signal via a random access procedure to the PSCell by the UE or via an uplink physical layer message; the means for transmitting the second signal is configured to transmit the second signal to the UE via the random access procedure or via a downlink physical layer message.

3. A RAN node according to claim 1 or 2.

6. the second signal is a random access response and implicitly indicates activation of the SCG.

6. The RAN node of claim 5.

7. the second signal is an uplink grant.

6. The RAN node of claim 5.

8. The method according to claim 8, further comprising: means for determining which of a plurality of options is to be used to activate the SCG; the plurality of options include a first option in which the secondary node transmits the second signal to the UE prior to transmitting the inter-node message to the master node, and a second option in which the secondary node transmits the second signal to the UE after receiving the response to the inter-node message from the master node.

3. A RAN node according to claim 1 or 2.

9. 1. A method performed by a Radio Access Network (RAN) node configured to operate as a secondary node associated with a Secondary Cell Group (SCG) in dual connectivity for a User Equipment (UE), the method comprising: receiving a first signal from the UE at a Primary SCG Cell (PSCell) of the SCG when the SCG is deactivated, the first signal indicating a request or indication of activation of the SCG; in response to receiving the first signal, transmitting a second signal in the PSCell to the UE indicating activation of the SCG; and sending an inter-node message to a master node associated with a Master Cell Group (MCG) of the dual connectivity indicating activation of the SCG; Equipped with the second signal is transmitted to the UE before the secondary node transmits the inter-node message to the master node or before the secondary node receives a response to the inter-node message from the master node. method.

10. 1. A program for causing a computer to perform a method for a Radio Access Network (RAN) node configured to operate as a secondary node associated with a Secondary Cell Group (SCG) in dual connectivity for a User Equipment (UE), the method comprising: receiving a first signal from the UE at a Primary SCG Cell (PSCell) of the SCG when the SCG is deactivated, the first signal indicating a request or indication of activation of the SCG; in response to receiving the first signal, transmitting a second signal in the PSCell to the UE indicating activation of the SCG; and sending an inter-node message to a master node associated with a Master Cell Group (MCG) of the dual connectivity indicating activation of the SCG; Equipped with the second signal is transmitted to the UE before the secondary node transmits the inter-node message to the master node or before the secondary node receives a response to the inter-node message from the master node. program.

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