Radio access network node and method therein

Abstract

To enable a radio communication network to provide User Equipment (UE) with a user plane (UP) path including a radio connection of a specific secondary cell of dual connectivity upon request of the UE or an application function.SOLUTION: UE (3) includes, in a Non-Access Stratum (NAS) message requesting for establishment or modification of a protocol data unit (PDU) session, either or both of a first identifier representing a candidate secondary cell (12) of dual connectivity and a second identifier representing a frequency band on which the candidate secondary cell operates. The UE (3) sends the NAS message to a core network (30) via a radio access network (10).SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to wireless communication networks, and more particularly to user plane path control. [Background technology]

[0002] Patent Document 1 discloses handing over a mobile terminal from a macrocell to a specific small cell so that the mobile terminal can use a special service provided only in the small cell. In one example disclosed in Patent Document 1, a mobile terminal is present in a macrocell provided by a radio base station (hereinafter referred to as a macrocell base station) and transmits a service establishment request for establishing a specific service to a core network node via the macrocell base station. The core network node is, for example, a Serving GPRS Support Node (SGSN) or a Mobility Management Entity (MME). In response to receiving the service establishment request from the mobile terminal, the core network node requests the macrocell base station to establish the requested specific service. The macrocell base station manages a table indicating which type of specific service is provided in each of a plurality of small cells. The macrocell base station selects a small cell associated with the requested specific service based on the table, and determines whether or not the mobile terminal can be handed over to the selected small cell. The determination is made based on, for example, whether or not radio waves of a predetermined strength or more are received from the mobile terminal at the macrocell base station. If it is determined that the mobile terminal can be handed over to the selected small cell, the macro cell base station transmits a response indicating failure of service establishment to the core network node, and hands over the mobile station to the selected small cell. After completion of the handover, the radio base station providing the small cell (hereinafter referred to as the small cell base station) notifies the core network node of the completion of the handover. After completion of the handover, the core network node requests the small cell base station to establish a specific service.

[0003] In another example disclosed in Patent Document 1, the above-mentioned table is managed by a core network node (eg, SGSN or MME) rather than by a macrocell base station. Specifically, in response to receiving a service establishment request from a mobile terminal via a macrocell base station, the core network node refers to a table associated with the macrocell base station, selects a small cell associated with the requested specific service, and determines whether or not the mobile terminal can be handed over to the selected small cell. The determination is made, for example, based on whether or not a radio wave of a predetermined strength or more is received from the mobile terminal at the macrocell base station. If it is determined that the mobile terminal can be handed over to the selected small cell, the core network node requests the macrocell base station to execute the handover. In response to the handover execution request from the core network node, the macrocell base station hands over the mobile station from the macrocell to the small cell. After the handover is completed, the small cell base station notifies the core network node of the handover completion. After the handover is completed, the core network node requests the small cell base station to establish the specific service.

[0004] On the other hand, Non-Patent Document 1 (e.g., Section 5.6.7) and Non-Patent Document 2 (e.g., Section 4.3.6) disclose Application Function (AF) influence on traffic routing. AF influence on traffic routing is a control plane solution that enables an AF to provide input to a 5G Core Network (5GC) on how certain traffic should be routed. More specifically, an AF sends requests to a 5GC to influence routing decisions by a Session Management Function (SMF) regarding the traffic (i.e., one or more QoS Flows) of a Protocol Data Unit (PDU) session. For example, AF requests can influence a User Plane Function (UPF) selection by the SMF to route user traffic to a local access to a Data Network (DN) identified by a DN Access Identifier (DNAI). The UPF selection by the SMF involves the insertion of a UL Classifier (ULCL) UPF or a Branching Point (BP) UPF into the User Plane (UP) path of the PDU session. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2014 / 013646 [Non-patent literature]

[0006] [Non-Patent Document 1] 3GPP TS 23.501 V16.3.0 (2019-12) "3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; System Architecture for the 5G System (5GS); Stage 2 (Release 16)", December 2019 [Non-Patent Document 2] 3GPP TS 23.502 V16.3.0 (2019-12) "3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; Procedures for the 5G System (5GS); Stage 2 (Release 16)", December 2019 Summary of the Invention [Problem to be solved by the invention]

[0007] The 5G system supports millimeter wave frequency bands from 4.25 GHz to 52.6 GHz in addition to the sub-6 GHz frequency bands also used in Long Term Evolution (LTE). The sub-6 GHz frequency bands are called Frequency Range 1 (FR1), and the millimeter wave frequency bands are called Frequency Range 2 (FR2). By using the FR2 bands, 5G Next Radio (NR) devices can exchange data over a wider carrier bandwidth and achieve very low scheduling latencies. However, considering the propagation characteristics of millimeter waves, FR2 cells will be local cells or small cells located within FR1 cells.

[0008] The inventors have considered an improvement to enable a wireless terminal (hereinafter referred to as User Equipment (UE)) to promptly start communication in a local cell (e.g., FR2 cell). For example, if a UE can request a network to add a specific cell (e.g., FR2 cell) as a secondary cell (Secondary Cell Group (SCG) cell) of dual connectivity, this may contribute to improving the user experience. Alternatively, if an application server (or a control server linked thereto) can request a wireless communication network (e.g., 5G system) to add a specific cell (e.g., FR2 cell) as an SCG cell of dual connectivity for the UE, this may contribute to improving the user experience.

[0009] Patent Document 1 does not disclose dual connectivity, and does not disclose that a UE requests dual connectivity to a network. On the other hand, the AF influence on traffic routing described in Non-Patent Documents 1 and 2 enables an AF to request a core network to change an UP route. However, Non-Patent Documents 1 and 2 do not disclose a procedure for an AF to request a core network to provide dual connectivity to a UE.

[0010] One of the objectives to be achieved by the embodiments disclosed herein is to provide an apparatus, a method, and a program that contribute to enabling a wireless communication network to provide a UE with an UP path including a radio connection of a specific secondary cell of dual connectivity based on a request from the UE or an application function (AF). It should be noted that this objective is only one of the objectives to be achieved by the embodiments disclosed herein. Other objectives or problems and novel features will be apparent from the description of this specification or the accompanying drawings. [Means for solving the problem]

[0011] In a first aspect, a User Equipment (UE) includes at least one memory and at least one processor coupled to the at least one memory, the at least one processor including one or both of a first identifier representing a candidate secondary cell for dual connectivity and a second identifier representing a frequency band in which the candidate secondary cell operates in a Non-Access Stratum (NAS) message requesting establishment or modification of a protocol data unit (PDU) session, and the at least one processor transmits the NAS message to a core network via a Radio Access Network (RAN).

[0012] In a second aspect, an Application Function (AF) device includes at least one memory and at least one processor coupled to the at least one memory, the at least one processor including in a first message one or both of a first identifier representing a candidate secondary cell for dual connectivity for a User Equipment (UE) and a second identifier representing a frequency band in which the candidate secondary cell operates, and the at least one processor transmits the first message to a core network.

[0013] In a third aspect, a Session Management Function (SMF) apparatus includes at least one memory and at least one processor coupled to the at least one memory, the at least one processor receiving a second message from a Policy Control Function (PCF) based on a request from an Application Function (AF), the at least one processor requesting a Radio Access Network (RAN) via an Access and Mobility management Function (AMF) to set up or modify a user plane path such that user data belonging to a protocol data unit (PDU) session for a User Equipment (UE) is forwarded via the user plane path including a radio connection of a secondary cell of dual connectivity in response to the second message from the PCF.

[0014] In a fourth aspect, a method performed by a User Equipment (UE) includes the following steps: (a) including in a Non-Access Stratum (NAS) message requesting establishment or modification of a protocol data unit (PDU) session one or both of a first identifier representing a candidate secondary cell for dual connectivity and a second identifier representing a frequency band in which the candidate secondary cell operates; and (b) transmitting the NAS message to a core network via a radio access network (RAN);

[0015] In a fifth aspect, a method performed by an Application Function (AF) device includes the steps of: (a) including in a first message one or both of a first identifier representing a candidate secondary cell for dual connectivity for User Equipment (UE) and a second identifier representing a frequency band in which the candidate secondary cell operates; and (b) transmitting the first message to a core network.

[0016] In a sixth aspect, a method performed by a Session Management Function (SMF) device includes the steps of: (a) receiving a second message from a Policy Control Function (PCF) based on a request from an Application Function (AF); and (b) in response to the second message from the PCF, requesting a radio access network (RAN) via an access and mobility management function (AMF) to set up or modify a user plane path such that user data belonging to a protocol data unit (PDU) session for a user equipment (UE) is forwarded via a user plane path including a radio connection of a secondary cell of dual connectivity.

[0017] In a seventh aspect, a program comprises instructions (software code) which, when loaded into a computer, causes the computer to carry out a method according to the fourth, fifth or sixth aspect above. Effect of the Invention

[0018] According to the above-described aspects, an apparatus, a method, and a program can be provided that contribute to enabling a wireless communication network to provide a UE with an UP path including a radio connection of a specific secondary cell of dual connectivity based on a request from the UE or an application function (AF). [Brief description of the drawings]

[0019] [Figure 1] 1 is a diagram illustrating an example of the configuration of a wireless communication network according to an embodiment. [Diagram 2] 10 is a flowchart illustrating an example of an operation of a UE according to an embodiment. [Diagram 3] 10 is a flowchart illustrating an example of an operation of an application function according to the embodiment. [Figure 4] FIG. 11 is a sequence diagram showing an example of signaling according to an embodiment. [Diagram 5] FIG. 11 is a sequence diagram showing an example of signaling according to an embodiment. [Figure 6A] A diagram showing an example of a user plane path before dual connectivity is implemented. [Figure 6B] A diagram showing an example of a user plane path after dual connectivity is initiated. [Figure 6C] A diagram showing an example of a user plane path after dual connectivity is initiated. [Figure 7] FIG. 11 is a sequence diagram showing an example of signaling according to an embodiment. [Figure 8] 10 is a flowchart illustrating an example of an operation of an application function according to the embodiment. [Figure 9] 10 is a flowchart illustrating an example of an operation of an application function according to the embodiment. [Figure 10] FIG. 11 is a sequence diagram showing an example of signaling according to an embodiment. [Figure 11] FIG. 11 is a sequence diagram showing an example of signaling according to an embodiment. [Figure 12]A diagram showing an example of a user plane path after dual connectivity is initiated. [Figure 13] FIG. 2 is a block diagram showing a configuration example of a RAN node according to the embodiment. [Figure 14] FIG. 2 is a block diagram showing an example of the configuration of a UE according to the embodiment. [Figure 15] FIG. 2 is a block diagram showing an example of the configuration of an application function according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] 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.

[0021] 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.

[0022] The following embodiments will be described with a focus on a fifth generation mobile communication system (5G system (5GS)). However, these embodiments may be applied to other wireless communication systems (eg, LTE system).

[0023] <First embodiment> FIG. 1 illustrates an example of the configuration of a wireless communication network (i.e., 5GS) according to some embodiments including the present embodiment. Each of the elements illustrated in FIG. 1 is a network function, and provides an interface defined by the 3rd Generation Partnership Project (3GPP). Each of the elements (network functions) illustrated in FIG. 1 can be implemented, for example, as a network element on dedicated hardware, as a software instance running on dedicated hardware, or as a virtualized function instantiated on an application platform.

[0024] The wireless communication network shown in Fig. 1 may be provided by a Mobile Network Operator (MNO) or may be a Non-Public Network (NPN) provided by a party other than an MNO. When the wireless communication network shown in Fig. 1 is an NPN, it may be an independent network represented as a Stand-alone Non-Public Network (SNPN) or an NPN linked with an MNO network represented as a Public network integrated NPN.

[0025] In the example of FIG. 1, the wireless communication network includes a Radio Access Network (RAN) 10, a 5G Core Network (5GC) 30, and an Application Function (AF) 41. The RAN 10 includes RAN nodes 1 and 2. The 5GC 30 includes an Access and Mobility Management Function (AMF) 31, a Session Management Function (SMF) 32, a User Plane Function (UPF) 33, a Policy Control Function (PCF) 34, and a Network Exposure Function (NEF) 35.

[0026] Each of the RAN nodes 1 and 2 may be a gNB or an ng-eNB. The RAN nodes 1 and 2 may be a Central Unit (eg, gNB-CU) in a cloud RAN (C-RAN) deployment. The RAN node 1 terminates a Control Plane (CP) interface (i.e., N2 interface) with the 5GC 30 and interworks with the AMF 31 in the 5GS 30 over the CP interface. In some implementations, the RAN node 2 may also terminate a CP interface (i.e., N2 interface) with the 5GC 30 and interwork with the AMF 31 over the CP interface. In other implementations, the RAN node 2 may not have a CP interface with any AMF. For example, if the RAN node 2 is responsible for only a secondary node (SN) of Dual Connectivity (DC) in a non-standalone deployment, the RAN node 2 may not have a CP interface with the 5GC 30.

[0027] RAN node 1 provides one or more cells including cell 11, and RAN node 2 provides one or more cells including cell 12. Cell 11 may operate in a different frequency band than cell 12. For example, cell 11 may operate in any sub-6 GHz frequency band in FR1, and cell 12 may operate in any mmWave frequency band in FR2. As shown in FIG. 1, cell 12 in the higher frequency band may be a local cell (small cell) located within cell 11 in the lower frequency band. Cell 11 may completely cover cell 12 or may partially overlap with cell 12.

[0028] The AMF 31 is one of the network functions in the 5GC control plane. The AMF 31 provides the termination of the RAN CP interface (i.e., N2 interface). The AMF 31 terminates a single signaling connection (i.e., N1 Non-Access Stratum (NAS) signalling connection) with the UE 3 and provides registration management, connection management, and mobility management. Additionally, the AMF 31 provides NF services to NF consumers (e.g., other AMFs, SMF 32, and Authentication Server Function (AUSF)) over a service-based interface (i.e., Namf interface). Furthermore, the AMF 31 consumes NF services provided by other NFs (e.g., Unified Data Management (UDM), Network Slice Selection Function (NSSF), and PCF 34).

[0029] The SMF32 is one of the network functions in the 5GC control plane. The SMF32 manages PDU sessions. The SMF32 transmits and receives SM signaling messages (NAS-SM messages) to and from the Non-Access Stratum (NAS) Session Management (SM) layer of the UE3 via the communication service provided by the AMF31. The SMF32 provides NF services to NF consumers (e.g., AMF31, other SMFs) over a service-based interface (i.e., Nsmf interface). The NF services provided by the SMF32 include a PDU session management service (Nsmf_PDUSession). The NF services allow NF consumers (e.g., AMF31) to handle PDU sessions. The SMF32 may be an Intermediate SMF (I-SMF). The I-SMF is inserted between the AMF 31 and the original SMF as necessary when the UPF 33 belongs to a different SMF service area and cannot be controlled by the original SMF.

[0030] The UPF 33 is one of the network functions in the 5GC user plane. The UPF 33 processes and forwards user data. The functionality of the UPF 33 is controlled by the SMF 32. The UPF 33 interconnects with the data network (DN) 50 and acts as an anchor point toward the DN 50 for one or more PDU sessions of the UE 3. The UPF 33 may include multiple UPFs interconnected via an N9 interface. More specifically, the UP path for the PDU session of the UE 3 may include one or more PDU Session Anchor (PSA) UPFs, may include one or more Intermediate UPFs (I-UPFs), and may include one or more Uplink Classifier (UL CL) UPFs (or Branching Point (BP) UPFs).

[0031] The PCF 34 provides various policy controls, including policy control for session management related functions and policy control for access and mobility related functions. For example, the PCF 34 interacts with the AF 41 directly or via the NEF 35 (via the N5 interface) and with the SMF 32 (via the N7 interface) for session management related policy control.

[0032] The NEF35 has a role similar to the Service Capability Exposure Function (SCEF) of the Evolved Packet System (EPS). Specifically, the NEF35 supports the exposure of services and capabilities from 5G systems to applications and network functions inside and outside the operator network.

[0033] A wireless terminal (ie, UE) 3 uses a 5G connectivity service to communicate with a data network (DN) 50. More specifically, the UE 3 is connected to the RAN 10 and communicates with the DN 50 at the application layer via the UPF 33 in the 5G GC 30. Note that the term "application layer" in this specification means all protocol layers above the PDU session (PDU session layer) between the UE 3 and the DN 50 provided by the 5GS. For example, if the PDUs are IP packets, the application layer includes application protocols such as Hypertext Transfer Protocol (HTTP) and File Transfer Protocol (FTP), as well as transport layer protocols between the IP and the application protocols (e.g., User Datagram Protocol (UDP) and Transmission Control Protocol (TCP)).

[0034] The AF 41 interacts with the PCF 34 to request policy control for the PDU session of the UE 3 from the 5GC 30. As described above, the AF 41 interacts with the PCF 34 directly or via the NEF 35. In addition, in the example of FIG. 1, the AF 41 can communicate with an application (UE application) running on a processor of the UE 3 via the DN 50 (e.g., the internet or other IP network) and a PDU session between the DN 50 and the UE 3. The AF 41 may include one or more computers. For example, the AF 41 may include one or more servers (e.g., content distribution server, online game server) that communicate with the UE 3 at the application layer, and a controller (i.e., an AF in the 3GPP definition) that cooperates with the one or more servers and interacts with the 5GC 30 (e.g., PCF 34). Furthermore, the AF 41 may include multiple servers that are distributed. For example, the AF 41 may include one or more edge computing servers located near the RAN 10 in addition to a central server. The edge computing servers and the local UPF that provides steering of user plane traffic for local access to the edge computing servers may be collocated with any RAN node or at a network aggregation site between the RAN 10 and the CN 30.

[0035] For convenience of explanation, only representative NFs are shown in the configuration example of Fig. 1. The wireless communication network according to the present embodiment may include other NFs not shown in Fig. 1.

[0036] FIG. 2 shows an example of the operation of the UE 3 according to the present embodiment. In step 201, the UE 3 generates a NAS message requesting establishment or modification of a PDU session. The NAS message may be a PDU Session Establishment Request message or a PDU Session Modification Request message. At this time, the UE 3 includes in the NAS message one or both of a cell identifier of a candidate secondary cell (SCG cell) for dual connectivity and a frequency band identifier representing a frequency band in which the candidate SCG cell operates. The cell identifier may be a Physical Cell ID (PCI). The frequency band identifier may be NR Absolute Radio Frequency Channel Numbers (NR-ARFCN). In step 202, the UE 3 transmits the generated NAS message to the 5GC 30 via the RAN 10.

[0037] The NAS message causes the 5GC 30 to set up or modify a UP path such that the user data belonging to the PDU session of the UE 3 is forwarded via a UP path including a radio connection (e.g., Data Radio Bearer (DRB)) of a candidate SCG cell specified by the UE 3. In other words, in response to the NAS message from the UE 3, the 5GC 30 and the RAN 10 set up or modify a UP path such that the user data belonging to the PDU session of the UE 3 is forwarded via a UP path including a radio connection (e.g., DRB) of a specific SCG cell of the dual connectivity. The user data belonging to the PDU session of the UE 3 may be one or more Quality of Service (QoS) flows.

[0038] If the request from UE3 is to establish a new PDU session, the UP paths of one or more QoS flows belonging to the newly established PDU session are set up as described above, whereas if the request from UE3 is to modify the new PDU session, the UP paths of one or more QoS flows belonging to the already established PDU session are set up or modified as described above.

[0039] The UP path includes an N3 tunnel between the UPF 33 (specifically, the PSA UPF) in the 5GC 30 and the RAN 10 (specifically, the RAN node 1 or 2), and a radio connection (DRB) between the RAN 10 (specifically, the RAN node 1 or 2) and the UE 3. If multiple UPFs are used for a PDU session, the UP path may further include one or more N9 tunnels between the UPFs. The N3 tunnel and the N9 tunnel may be General Packet Radio Service (GPRS) Tunnelling Protocol for User Plane (GTP-U) tunnels.

[0040] Dual connectivity enables a UE to simultaneously use a Master Cell Group (MCG) provided by a Master Node (MN) (e.g., RAN node 1) and a Secondary Cell Group (SCG) provided by a Secondary Node (SN) (e.g., RAN node 2). An MCG is a group of serving cells associated with (or provided by) a RAN node (e.g., RAN node 1) acting as an MN of a DC, and includes an SpCell (i.e., a Primary Cell (PCell)) and, optionally, one or more Secondary Cells (SCells). On the other hand, an SCG is a group of serving cells associated with (or provided by) a RAN node (e.g., RAN node 2) acting as an SN of a DC, and includes an SCG primary cell and, optionally, one or more Secondary Cells (SCells). The SCG primary cell is the Primary SCG Cell (PSCell) or the Primary Secondary Cell (PSCell). The PSCell is the SCG Special Cell (SpCell).

[0041] The UE 3 may receive the cell identifiers or frequency band identifiers or both of the candidate secondary cells from the AF 41. The UE 3 may receive these from the AF 41 via communication at the application layer. Alternatively, the UE 3 may receive these from the AF 41 via a device trigger message. The device trigger message reaches the UE via the 5GC 30 and the RAN 10 based on a request from the AF 41.

[0042] According to the procedure of FIG. 2, it is possible for 5GC 30 and RAN 10 to provide UE 3 with a UP path including a radio connection of a specific secondary cell (SCG cell) of the DC based on a request from UE 3.

[0043] FIG. 3 shows an example of the operation of the AF41 according to the present embodiment. In step 301, the AF41 detects that the UE3 is located in a predetermined geographical area associated with a candidate SCG cell (eg, FR2 cell, cell 12). The predetermined geographical area may be a larger area than the coverage area of ​​the candidate SCG cell. Alternatively, the predetermined geographical area may be an area through which a user will necessarily pass before arriving at the location of the candidate SCG cell. Therefore, it can be said that the AF41 determines that the UE3 is approaching the candidate SCG cell.

[0044] In some implementations, the AF 41 may receive a report from the UE 3 indicating the current location of the UE 3 via application layer communication, and determine whether the UE 3 is located in a predetermined geographic area based on the report. The UE 3 may, for example, send Global Positioning System (GPS) location information to the AF 41.

[0045] In step 302, in response to the detection of step 301, the AF 41 sends a control message including a cell identifier representing the candidate SCG cell to the UE 3 via application layer communication or a device trigger. As already explained, the AF 41 may send to the UE 3 an identifier of a frequency band in which the candidate SCG cell operates instead of or in addition to the cell identifier representing the candidate SCG cell.

[0046] 2 in response to receiving one or both of the cell identifier and the frequency band identifier of the candidate SCG cell in step 302. This allows, for example, the UE 3 to request the 5GC 30 to prepare for dual connectivity using the candidate SCG cell before the UE 3 actually receives a radio signal from the candidate SCG cell. Such an operation can reduce the delay required for the UE 3 to transmit or receive user data in a candidate SCG cell when the UE 3 is able to receive a radio signal from the candidate SCG cell.

[0047] Note that the UE 3 may receive in advance one or both of the cell identifier and the frequency band identifier of the candidate SCG cell from the AF 41. Furthermore, the UE 3 may receive in advance information indicating the above-mentioned predetermined geographical area from the AF 41. In this case, the UE 3 may determine whether the UE 3 is located in the predetermined geographical area, and may start the operation shown in FIG. 2 if the UE 3 is located in the predetermined geographical area.

[0048] An example of signaling according to this embodiment is shown in Fig. 4. According to the procedure of Fig. 4, in response to a NAS message from the UE 3 requesting the establishment or modification of a PDU session, the 5GC 30 and the RAN 10 set up or modify a UP path such that user data belonging to the PDU session of the UE 3 is forwarded via the UP path including the radio connection of a particular SCG cell of the dual connectivity.

[0049] The procedure shown in Figure 4 is initiated (or triggered) by the UE 3 when the UE 3 is camped on a cell 11 (e.g., FR1 macro cell) provided by the RAN node 1. The UE 3 requests the 5GC 30 to set up or modify a UP path for traffic (i.e., one or more QoS flows) belonging to the UE 3's PDU session to pass through a particular SCG cell 12 (e.g., FR2 local cell) provided by the RAN node 2.

[0050] In step 401, the UE 3 communicates with the AF 41 at the application layer. The UE 3 may receive cell identities (e.g., PCI) of candidate SCG cells from the AF 41. Additionally or alternatively, the UE 3 may receive identifiers (e.g., NR-ARFCN) of frequency bands in which the candidate SCG cells are operating from the AF 41.

[0051] In step 402, the UE 3 sends a PDU Session Establishment Request message to the 5GC 30 to request the establishment of a new PDU session. Alternatively, the UE 3 may send a PDU Session Modification Request message to the 5GC 30 to request the modification of an established PDU session. The NAS-SM message sent in step 402 includes one or both of the cell identifiers and the frequency band identifiers of the candidate SCG cells. Additionally or alternatively, the UE 3 may include a list of identifiers of one or more frequency bands in the NAS-SM message. In this case, the 5GC 30 (e.g., SMF 32 or AMF 31) or the RAN 10 (e.g., RAN node 1) may select one or more specific cells (including cell 12) operating in any of the frequency bands included in the list of frequency band identifiers.

[0052] The NAS-SM message sent in step 402 may include other information elements required for establishing or modifying a PDU session. More specifically, if the NAS-SM message is a PDU Session Establishment Request message, it may include a PDU Session ID, a Requested PDU Session Type, a Requested Session and Service Continuity (SSC) mode, information on the lifetime of the PDU Session, and other information elements. On the other hand, if the NAS-SM message is a PDU Session Modification Request message, it may include a PDU Session ID, Packet Filters, Requested QoS, information on the lifetime of the PDU Session, and other information elements. For example, the information on the lifetime of the PDU Session may be used as information for RAN optimization (e.g., Core Network assistance information for RAN optimization).

[0053] The AMF 31 receives the NAS-SM message in step 402 and forwards it to the SMF 32. In step 403, the SMF 32 interacts with the NFs including the PCF 34 and the UPF 33 to establish a new PDU session for the UE 3 or to modify an established PDU session of the UE 3.

[0054] More specifically, when establishing a new PDU session for UE3, SMF32 may select a PSA UPF for the PDU session and request UPF33 to set up an N3 tunnel to route one or more QoS flows of the PDU session to RAN node 2.

[0055] On the other hand, when modifying an established PDU session, the SMF 32 may decide to insert a UL CL UPF and an additional PSA UPF into the UP path of the established PDU session of the UE 3. In this case, the SMF 32 may provide the UPF 33 with an N9 tunnel configuration and packet detection and forwarding rules for the insertion of the UL CL UPF and the additional PSA UPF.

[0056] In step 404, the 5GC 30 sends an N2 request to the RAN node 1. The N2 request may be a PDU SESSION RESOURCE SETUP REQUEST message or a PDU SESSION RESOURCE MODIFY REQUEST message. The N2 request includes one or both of a cell identifier and a frequency band identifier of the candidate SCG cell 12. The N2 request thereby requests the RAN node 1 to add the candidate SCG cell (here, the cell 12) specified by the UE 3 as an SCG cell of the DC for the UE 3. The N2 request further requests the RAN node 1 to set up or modify a UP path such that user data belonging to a PDU session for the UE 3 is forwarded via a UP path including a radio connection of the SCG cell 12.

[0057] The AMF 31 (or SMF 32) may receive one or both of the Index to RAT / Frequency Selection Priority (RFSP index) and Additional Radio Resource Management (RRM) Policy Index (ARPI) from the UDM. The RFSP index and ARPI are set for each UE, each PDU session, each QoS Flow Identifier (QFI), each Single Network Slice Selection Assistance Information (S-NSSAI), each Data Network (DN), or each Data Network Name (DNN) (each Access Point Name (APN)). The DNN is an identifier indicating the DN, and indicates the DN (e.g., DN50) to which the traffic of the UE 3 should be routed. The S-NSSAI is an identifier of the network slice. For example, the AMF 31 (or SMF 32) may set the RFSP index (and ARPI) corresponding to the S-NSSAI, DN, and APN to which the PDU session belongs in the N2 request. The AMF 31 can receive and manage the RFSP index (and ARPI) set for each UE, each PDU session, each QFI, each S-NSSAI, each DN, or each DNN (per APN) by executing (invoke) Nudm_SDM_Get for UDM. Similarly, the SMF 32 can receive and manage the RFSP index (and ARPI) set for each UE, each PDU session, each QFI, each S-NSSAI, each DN, or each DNN (per APN) by executing (invoke) Nudm_SDM_Get for UDM. The RFSP index is used by the RAN 10 (e.g., RAN node 1) to derive UE-specific cell reselection priorities to control camping in idle mode, for example. Alternatively, the RFSP index is used by the RAN 10 (e.g., RAN node 1) to determine to redirect a UE in a connected mode (active mode) to a different frequency layer or a different RAT.The RAN 10 (e.g., RAN node 1) may select one or more specific cells (including cell 12) operating in any frequency band selected based on the RFSP index as SCG cells of the DC for the UE 3. The ARPI is also used by the RAN 10 (e.g., RAN node 1) to prioritize allocation of RAN resources to UEs.

[0058] More specifically, the SMF 32 sends the N2 SM information and the N1 SM container to the AMF 31. The SMF 32 executes (invokes) Namf_Communication_N1N2MessageTransfer. The N1 SM container encapsulates the NAS-SM message sent to the UE 3. The NAS-SM message is a PDU Session Establishment Accept message in the case of PDU session establishment, and a PDU Session Modification Command message in the case of PDU session modification. Meanwhile, the N2 SM information includes information required for routing of the QoS flow to be added or updated (e.g. PDU Session ID, QoS Flow Identifier(s) (QFI(s)), and QoS Profile(s), CN Tunnel Info). The CN Tunnel Info indicates the N3 (GTP-U) tunnel endpoint of the UPF 33. The N2 SM information may further include any or any combination of PCI, NR-ARFCN, RFSP index, and ARPI of the candidate SCG cell (cell 12) specified by the UE 3. The N2 SM information may explicitly indicate that dual connectivity is required. Alternatively, the SMF 32 may include a cause in the Nsmf_PDUSession_UpdateSMContext Response or Namf_Communication_N1N2MessageTransfer indicating that dual connectivity or handover is required.

[0059] The RAN node 1 receives the N2 request from the AMF 31 and decides to add the cell 12 as an SCG cell of the DC for the UE 3. In step 405, the RAN node 1 may cause the UE 3, which is Radio Resource Control (RRC)_CONNETED, to perform inter-frequency measurement. The RAN node 1 may create a configuration for inter-frequency measurement to enable the UE 3 to measure the frequency band in which the cell 12 operates. More specifically, the RAN node 1 may create a configuration (e.g., measurement gap) required to measure the frequency band in which the cell 12 operates (e.g., FR2 band) taking into account the radio capability of the UE 3 (e.g., the number of Radio Frequency (RF) chains of the UE 3). The RAN node 1 may send an RRC message including the created configuration for inter-frequency measurement to the UE 3. The RRC message may be an RRC Reconfiguration message. Note that if the RAN node 1 has already received the measurement result by the UE 3, the measurement in step 405 may be skipped.

[0060] In step 406, the RAN node 1 performs a Secondary Node (SN) addition procedure to add the cell 12 as an SCG cell. More specifically, the RAN node 1 sends an SN Addition Request message to the RAN node 2. The RAN node 2 sends an SN Addition Request Acknowledge message to the RAN node 1. The SN Addition Request Acknowledge message includes an SN RRC message. Then, the RAN node 1 sends a Master Node (MN) RRC Reconfiguration message to the UE 3. The MN RRC Reconfiguration message includes the SN RRC message received from the RAN node 2 and includes an N1 SM container (PDU Session Establishment Accept or PDU Session Modification Command) received from the AMF 31.

[0061] Thereafter, for the radio bearers of the SCG cell 12, the RAN node 1 (or RAN node 2) updates the UP path with the 5GC (UPF 33) via a PDU Session Path Update procedure. Specifically, in step 407, the RAN node 1 sends an N2 response to the AMF 31. The N2 response may be a PDU SESSION RESOURCE SETUP RESPONSE message or a PDU SESSION RESOURCE MODIFY RESPONSE message. The N2 response includes N2 SM information. The N2 SM information includes AN Tunnel Info, which indicates the N3 (GTP-U) tunnel endpoint of the RAN node 2, which is the SN of the DC. In step 408, the AMF 31 forwards the N2 SM information received from the RAN node 1 to the SMF 32, which updates the UPF 33 based on the N2 SM information. This allows the UE 3 to perform DC using the cell 11 as a Master Cell Group (MCG) cell and the cell 12 as an SCG cell.

[0062] FIG. 5 illustrates another example of signaling according to this embodiment. In step 501, the UE 3 receives a device trigger message from the AF 41. The device trigger message may include one or both of a cell identifier and a frequency band identifier of a candidate SCG cell. Alternatively, the device trigger message may include a request for establishing or modifying a PDU session. Steps 502-508 in FIG. 5 are similar to steps 402-408 in FIG. 4.

[0063] Next, a specific example of UP path change will be described below with reference to Figs. 6A to 6C. In the example shown in Figs. 6A to 6C, cell 11 may operate in the FR1 band (sub-6 GHz) and cell 12 may operate in the FR2 band (e.g., 28 GHz). Fig. 6A shows an UP path before a change in UP path with dual connectivity is performed. The UP path 601 shown in Fig. 6A is used for the transfer of all QoS flows belonging to a PDU session between DN 50A and UE 3. The UP path 601 includes a radio connection (DRB) of cell 11 and an N3 tunnel between RAN node 1 and central UPF 33A. The IP address assigned to UE 3 in the PDU session is "IP1".

[0064] FIG. 6B shows the UP path after a new PDU session is established for UE3 and dual connectivity is started using cell 11 as MCG cell and cell 12 as SCG cell. The UP path 611 shown in FIG. 6B is the same as the UP path 601 in FIG. 6A and is used for forwarding all QoS flows belonging to the PDU session established before DC. Meanwhile, the UP path 612 is used for forwarding all QoS flows belonging to the newly established PDU session between DN 50B and UE3. The UP path 612 includes the radio connection (DRB) of the SCG cell 12 as well as the N3 tunnel between the RAN node 2 and the local UPF 33B. The IP address assigned to UE3 in the new PDU session using the UP path 612 is “IP2”. The local UPF 33B in FIG. 6B can forward the uplink traffic of the QoS flow of the newly established PDU session (IP2) to DN 50B for local access via the UP path 612.

[0065] FIG. 6C also shows the UP path after dual connectivity is started, but in FIG. 6C, the UP path of the PDU session already established before dual connectivity is modified. The local UPF 33B in FIG. 6C operates as a UL CL and an additional PSA. This allows the local UPF 33B to forward uplink traffic of one or more newly added QoS flows to the DN 50B for local access via the UP path 622. Furthermore, the local UPF 33B can forward uplink traffic of one or more QoS flows already configured before DC to the DN 50A via the central UPF 33A via the UP path 621. In the example of FIG. 6C, the DN 50A and the DN 50B are the same DN. Furthermore, the PDU session is split in the local UPF 33B. The local UPF 33B forwards downlink traffic of one or more QoS flows already configured before DC to the RAN node 1 (MN), and forwards downlink traffic of one or more newly added QoS flows to the RAN node 2 (SN).

[0066] FIG. 7 shows an example of signaling for initiating dual connectivity based on a request from UE 3. In step 701, AF 41 communicates with one or more applications 700 (UE applications) running on UE 3. For example, AF 41 may communicate with UE application 700 via an application layer above a PDU session between DN 50 and UE 3. AF 41 may receive a request for a specific service (e.g., large content delivery, online gaming) from UE application 700. AF 41 may receive a current location of UE 3 from UE application 700. UE application 700 may receive one or both of cell identifiers and frequency band identifiers of candidate SCG cells from AF 41.

[0067] In step 702, the UE application 700 requests the NAS layer of the UE 3 to establish a PDU session. The request may include a DNN or an S-NSSAI or a combination of both. The request may include one or both of cell identifiers and frequency band identifiers of candidate SCG cells.

[0068] In step 703, the UE 3 sends an N1 NAS message containing a NAS-SM message to the AMF 31 via the RAN 10 (RAN node 1). The NAS-SM message is a PDU Session Establishment Request message. The NAS-SM message includes one or both of a cell identifier and a frequency band identifier of a candidate SCG cell.

[0069] In step 704, the AMF 31 forwards the NAS-SM message received from the UE 3 to the SMF 32. The AMF 31 may perform a Nsmf_PDUSession_CreateSMContext Request.

[0070] In step 705, the SMF 32 interacts with NFs including the PCF 34 and the UPF 33 to establish a new PDU session for the UE 3. More specifically, the SMF 32 selects a PSA UPF for the PDU session and requests the UPF 33 to set up an N3 tunnel to route one or more QoS flows of the PDU session to the RAN node 2. The SMF 32 generates N2 SM information and an N1 SM container. The N1 SM container encapsulates a PDU Session Establishment Accept message to be sent to the UE 3. Meanwhile, the N2 SM information includes information required for routing the QoS flow to be added or updated (e.g. PDU Session ID, QoS Flow Identifier(s) (QFI(s)), and QoS Profile(s), CN Tunnel Info).

[0071] In step 706, the SMF 32 sends the N2 SM information and the N1 SM container to the AMF 31 for forwarding them to the RAN 10. The SMF 32 may perform Namf_Communication_N1N2MessageTransfer.

[0072] In step 707, the AMF 31 generates an N2 request containing the N2 SM information and the N1 SM container received from the SMF 32, and sends it to the RAN 10 (i.e., RAN Node 1). The N2 request may be a PDU SESSION RESOURCE SETUP REQUEST message.

[0073] The messages of steps 701-704, 706 and 707 may indicate one or both of the cell identifiers and frequency band identifiers of the candidate SCG cells, which are associated with the UE application 700. This allows the RAN 10 to be provided with RAN related information included in the AF request from the AF 41.

[0074] Steps 708 and 709 are similar to steps 405 and 406 in FIG. 2. The RAN node 1 receives the N2 request from the AMF 31 and decides to add the cell 12 as an SCG cell of the DC for the UE 3. In step 708, the RAN node 1 may cause the UE 3, which is Radio Resource Control (RRC)_CONNETED, to perform inter-frequency measurements. If the RAN node 1 has already received the measurement results by the UE 3, the measurement in step 708 may be skipped. In step 709, the RAN node 1 communicates with the RAN node 2 and performs a Secondary Node (SN) addition procedure to add the cell 12 as a secondary cell (SCG cell).

[0075] In step 710, the RAN node 1 sends an MN RRC Reconfiguration message to the UE 3. The MN RRC Reconfiguration message contains the SN RRC message received from the RAN node 2 and contains an N1 SM container (PDU Session Establishment Accept) received from the AMF 31. After this, the UE 3 sends an MN RRC Reconfiguration Complete message to the RAN node 1. The MN RRC Reconfiguration Complete message contains an SN RRC response message for the SN. The RAN node 1 (MN) informs the RAN node 2 (SN) that the reconfiguration procedure of the UE 3 has been successfully completed via the SN Reconfiguration Complete message containing the SN RRC response message.

[0076] In step 711, the RAN node 1 sends an N2 response to the AMF 31. The N2 response may be a PDU SESSION RESOURCE SETUP RESPONSE message. The N2 response includes N2 SM information. The N2 SM information includes AN Tunnel Info, which indicates the N3 (GTP-U) tunnel endpoint of the RAN node 2, which is the SN of the DC.

[0077] In step 712, the AMF 31 forwards the N2 SM information received from the RAN node 1 to the SMF 32, which updates the UPF 33 based on the N2 SM information. The AMF 31 may perform a Nsmf_PDUSession_UpdateSMContext Request.

[0078] <Second embodiment> A configuration example of the wireless communication network according to this embodiment is similar to the example described with reference to Fig. 1. This embodiment provides signaling for starting dual connectivity based on a request from the AF 41.

[0079] FIG. 8 shows an example of the operation of the AF 41 according to this embodiment. In step 801, the AF 41 generates an AF request. The AF request includes one or both of a cell identifier of a candidate SCG cell of a DC for the UE 3 and a frequency band identifier representing a frequency band in which the candidate SCG cell operates. The cell identifier may be a PCI. The frequency band identifier may be an NR-ARFCN.

[0080] The AF request of step 801 may include other information elements. More specifically, the AF request may include an identifier of the UE 3. The identifier of the UE 3 may be a Generic Public Subscription Identifier (GPSI), such as a Mobile Subscriber Integrated Services Digital Network Number (MSISDN) or an external identifier. The AF request may include an identifier of a PDU session (e.g., PDU Session ID). The AF request may include information for identifying one or more QoS flows included in the PDU session (e.g., 5-tuple). The AF request may include a combination of a DNN and an S-NSSAI. The AF request may include a list of one or more DN Access Identifiers (DNAIs). The DNAI(s) represent the access location to the DN.

[0081] In step 802, the AF 41 sends the generated AF request to the PCF 34 directly or via the NEF 35. The AF request requests the 5GC 30 to modify the established PDU session for the UE 3 such that user data belonging to the established PDU session is forwarded via a UP path including a radio connection of the candidate SCG cell. In this embodiment, the AF request causes the 5GC 30 to control the RAN 10 to add the candidate SCG cell as an SCG cell of the DC for the UE 3.

[0082] According to the procedure of FIG. 8, it is possible to enable the 5GC 30 and the RAN 10 to provide the UE 3 with a UP path including a radio connection of a specific SCG cell of the DC based on a request from the AF 41.

[0083] FIG. 9 illustrates another example of the operation of the AF41 according to the present embodiment. In step 901, the AF41 detects that the UE3 is located in a predefined geographical area associated with a candidate SCG cell (eg, FR2 cell, cell 12). The predefined geographical area may be a larger area than the coverage area of ​​the candidate SCG cell. Alternatively, the predefined geographical area may be an area through which a user will necessarily pass before reaching the location of the candidate SCG cell. Therefore, it can be said that the AF41 determines that the UE3 is approaching the candidate SCG cell.

[0084] In some implementations, the AF 41 may receive a report from the UE 3 indicating the current location of the UE 3 through application layer communication, and determine whether the UE 3 is located in a predetermined geographic area based on the report. The UE 3 may, for example, send GPS location information to the AF 41.

[0085] In step 902, in response to the detection in step 901, the AF 41 sends an AF request including one or both of a cell identifier and a frequency band identifier of the candidate SCG cell to the 5GC 30. This allows, for example, the AF 41 to request the 5GC 30 to prepare for dual connectivity using the candidate SCG cell before the UE 3 actually receives a radio signal from the candidate SCG cell. Such an operation can reduce the delay required for the UE 3 to transmit or receive user data in the candidate SCG cell when the UE 3 is able to receive a radio signal from the candidate SCG cell.

[0086] Figure 10 shows an example of signaling according to this embodiment. In the example of Figure 10, data mobility known as SSC mode 2 is performed based on a request from the AF 41. In SSC mode 2, the SMF 32 involves releasing the existing PDU session and establishing a new PDU session to the same DN as the existing PDU session. In establishing the new PDU session, the SMF 32 can select a new PDU Session Anchor (PSA) UPF.

[0087] In step 1001, the AF 41 communicates with the UE 3 at an application layer. The AF 41 may receive a report of the current location of the UE 3 from the UE 3.

[0088] In step 1002, the AF 41 sends an AF request to the 5GC 30. Specifically, the AF 41 sends the AF request to the PCF 34 directly or via the NEF 35. The AF request requests the SMF 32 to reconfigure (reselect) the PSA UPF according to SSC mode 2 to enable routing of user traffic to a local access. The AF request includes any or any combination of cell identifiers (e.g., PCI), frequency band identifiers (e.g., NR-ARFCN), RFSP index, and ARPI of candidate SCG cells of DC for the UE 3. The AF request may further include a DNAI or a Fully Qualified Domain Name (FQDN) to be used by the SMF 32 to select a local UPF. The AF request may include an identifier (e.g., GPSI) of the UE 3, a PDU Session ID, information for identifying a QoS flow (e.g., 5-tuple), and the like.

[0089] The PCF 34 receives the AF request directly or via the NEF 35, makes a policy decision based on the AF request, and determines that updated or new Session Management (SM) policy information needs to be sent to the SMF 32. The updated or new SM policy information may include the PCI or NR-ARFCN sent from the AF 41. The PCF 34 then provides the updated or new SM policy information to the SMF 32. The PCF 34 may issue an Npcf_SMPolicyControl_UpdateNotify request with the updated or new SM policy information.

[0090] In step 1003, the SMF 32 receives updated or generated SM policy information based on the AF request from the PCF 34. The SMF 32 determines that the PSA UPF for an established PDU session of the UE 3 according to SSC mode 2 needs to be changed.

[0091] In step 1004, the SMF 32 initiates a PDU Session Release procedure to release the PDU session associated with the current PSA UPF (e.g., central UPF 33A). The SMF 32 includes in the PDU Session Release Command message sent to the UE 3 the PDU Session ID of the PDU session to be released and a Cause indicating that a PDU Session re-establishment to the same DN is required.

[0092] In step 1005, in response to receiving the PDU Session Release Command message, the UE 3 generates a new PDU Session ID and starts a PDU session establishment procedure. The AMF 31 selects the SMF 32. The SMF 32 selects a new UPF (e.g., local UPF 33B) for the re-established PDU session in SSC mode 2. The subsequent steps in step 1005 are similar to steps 404-408 in FIG. 4 or steps 706-712 in FIG. 7. Step 1005 may be performed before step 1004.

[0093] Figure 11 shows another example of signaling according to this embodiment. In the example of Figure 11, data mobility known as SSC mode 3 is performed based on a request from the AF 41. In SSC mode 3, the SMF 32 establishes a new PDU session to the same DN as the existing PDU session before releasing the existing PDU session, and then releases the existing PDU session. As in SSC mode 2, in establishing a new PDU session, the SMF 32 can select a new PDU Session Anchor (PSA) UPF.

[0094] Steps 1101 to 1103 are similar to steps 1001 to 1003 in Fig. 10. However, in step 1103, the SMF 32 determines that the PSA UPF for the established PDU session of the UE 3 according to SSC mode 3 needs to be changed.

[0095] In step 1104, the SMF 32 sends a PDU Session Modification Command message to the UE 3. The PDU Session Modification Command message includes a PDU Session ID indicating the existing PDU Session to be relocated, and includes a Cause indicating that a PDU Session re-establishment to the same DN is required.

[0096] In step 1105, the UE 3 initiates a PDU session establishment procedure to the same DN in response to the PDU Session Modification Command in step 1104. Specifically, the UE 3 transmits a PDU Session Establishment Request message. The PDU Session Establishment Request message includes a newly generated new PDU Session ID and an Old PDU Session ID indicating an existing PDU session to be relocated. The AMF 31 selects the same SMF 32 serving the Old PDU Session ID and performs a Nsmf_PDUSession_CreateSMContext Request. The AMF 31 includes both the (new) PDU Session ID and the Old PDU Session ID in the Nsmf_PDUSession_CreateSMContext Request. The SMF 32 selects a new UPF (e.g., local UPF 33B) for the new PDU session of SSC mode 3. The steps performed after this in step 1105 are similar to steps 404 to 408 in FIG. 4 or steps 706 to 712 in FIG.

[0097] In step 1106, the UE 3 or the SMF 32 initiates a release procedure for the old PDU Session.

[0098] Figure 12 shows an UP path after the PDU Session Anchor is changed according to SSC mode 2 or SSC mode 3 and dual connectivity is started using cell 11 as the MCG cell and cell 12 as the SCG cell. The UP path 1201 shown in Figure 12 includes the radio connection (DRB) of the SCG cell 12 and the N3 tunnel between the RAN node 2 and the local UPF 33B.

[0099] Next, configuration examples of the RAN node 1, the RAN node 2, the UE 3, the control plane node (eg, SMF 32) in the 5GC 30, and the AF 41 according to the above-mentioned embodiments will be described below. FIG. 13 is a block diagram showing a configuration example of the RAN node 1 according to the above-mentioned embodiments. The RAN node 2 may have a similar configuration to that shown in FIG. 13. Referring to FIG. 13, the RAN node 1 includes a Radio Frequency (RF) transceiver 1301, a network interface 1303, a processor 1304, and a memory 1305. The RF transceiver 1301 performs analog RF signal processing to communicate with UEs. The RF transceiver 1301 may include multiple transceivers. The RF transceiver 1301 is coupled to the antenna array 1302 and the processor 1304. The RF transceiver 1301 receives modulation symbol data from the processor 1304, generates a transmit RF signal, and provides the transmit RF signal to the antenna array 1302. The RF transceiver 1301 also generates a baseband receive signal based on the receive RF signal received by the antenna array 1302 and supplies the baseband receive signal to the processor 1304. The RF transceiver 1301 may include an analog beamformer circuit for beamforming. The analog beamformer circuit includes, for example, multiple phase shifters and multiple power amplifiers.

[0100] The network interface 1303 is used to communicate with network nodes (eg, other RAN nodes, the AMF 31, and the UPF 33). The network interface 1303 may include, for example, a network interface card (NIC) that complies with the IEEE 802.3 series.

[0101] The processor 1304 performs digital baseband signal processing (data plane processing) and control plane processing for wireless communication. The processor 1304 may include multiple processors. For example, the processor 1304 may include a modem processor (e.g., Digital Signal Processor (DSP)) that performs digital baseband signal processing and a protocol stack processor (e.g., Central Processing Unit (CPU) or Micro Processing Unit (MPU)) that performs control plane processing.

[0102] For example, digital baseband signal processing by the processor 1304 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 Medium Access Control (MAC) layer, and a Physical (PHY) layer, and control plane processing by the processor 1304 may include processing of Non-Access Stratum (NAS) messages, RRC messages, MAC CEs, and DCIs.

[0103] The processor 1304 may include a digital beamformer module for beamforming, which may include a Multiple Input Multiple Output (MIMO) encoder and a precoder.

[0104] The memory 1305 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 1305 may include storage located remotely from the processor 1304. In this case, the processor 1304 may access the memory 1305 via the network interface 1303 or an I / O interface not shown.

[0105] The memory 1305 may store one or more software modules (computer programs) 1306 including instructions and data for performing the processes of the RAN node 1 described in the above embodiments. In some implementations, the processor 1304 may be configured to read and execute the software modules 1306 from the memory 1305 to perform the processes of the RAN node 1 described in the above embodiments.

[0106] In addition, when the RAN node 1 is a Central Unit (eg, gNB-CU) in a C-RAN deployment, the RAN node 1 may not include the RF transceiver 1301 (and the antenna array 1302).

[0107] FIG. 14 is a block diagram showing a configuration example of the UE 3. The Radio Frequency (RF) transceiver 1401 performs analog RF signal processing to communicate with NG-RAN nodes. The RF transceiver 1401 may include multiple transceivers. The analog RF signal processing performed by the RF transceiver 1401 includes frequency up-conversion, frequency down-conversion, and amplification. The RF transceiver 1401 is coupled to the antenna array 1402 and the baseband processor 1403. The RF transceiver 1401 receives modulation symbol data (or OFDM symbol data) from the baseband processor 1403, generates a transmission RF signal, and provides the transmission RF signal to the antenna array 1402. The RF transceiver 1401 also generates a baseband reception signal based on the reception RF signal received by the antenna array 1402, and provides the baseband reception signal to the baseband processor 1403. The RF transceiver 1401 may include an analog beamformer circuit for beamforming. The analog beamformer circuitry includes, for example, multiple phase shifters and multiple power amplifiers.

[0108] The baseband processor 1403 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).

[0109] For example, the digital baseband signal processing by the baseband processor 1403 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 Medium Access Control (MAC) layer, and a Physical (PHY) layer. Also, the control plane processing by the baseband processor 1403 may include processing of a Non-Access Stratum (NAS) protocol, a Radio Resource Control (RRC) protocol, and MAC Control Elements (CEs).

[0110] The baseband processor 1403 may perform Multiple Input Multiple Output (MIMO) encoding and precoding for beamforming.

[0111] The baseband processor 1403 may include a modem processor (e.g., Digital Signal Processor (DSP)) that performs digital baseband signal processing and a protocol stack processor (e.g., Central Processing Unit (CPU) or Micro Processing Unit (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 1404 described later.

[0112] The application processor 1404 is also called a CPU, an MPU, a microprocessor, or a processor core. The application processor 1404 may include multiple processors (multiple processor cores). The application processor 1404 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 1406 or a memory not shown, thereby implementing various functions of the UE3.

[0113] In some implementations, the baseband processor 1403 and the application processor 1404 may be integrated on a single chip, as shown by the dashed line (1405) in Figure 14. In other words, the baseband processor 1403 and the application processor 1404 may be implemented as a single System on Chip (SoC) device 1405. An SoC device may also be called a system Large Scale Integration (LSI) or a chipset.

[0114] The memory 1406 is a volatile memory or a non-volatile memory, or a combination thereof. The memory 1406 may include a plurality of physically independent memory devices. The volatile memory is, for example, a Static Random Access Memory (SRAM) or a Dynamic RAM (DRAM), or a combination thereof. The non-volatile memory is a Mask Read Only Memory (MROM), an Electrically Erasable Programmable ROM (EEPROM), a flash memory, or a hard disk drive, or any combination thereof. For example, the memory 1406 may include an external memory device accessible from the baseband processor 1403, the application processor 1404, and the SoC 1405. The memory 1406 may include an internal memory device integrated in the baseband processor 1403, the application processor 1404, or the SoC 1405. Furthermore, the memory 1406 may include a memory in a Universal Integrated Circuit Card (UICC).

[0115] The memory 1406 may store one or more software modules (computer programs) 1407 including instructions and data for performing the processing by the UE 3 described in the above-mentioned embodiments. In some implementations, the baseband processor 1403 or the application processor 1404 may be configured to read the software module 1407 from the memory 1406 and execute it to perform the processing by the UE 3 described in the above-mentioned embodiments using the drawings.

[0116] 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 1401 and the antenna array 1402, i.e., at least one of the baseband processor 1403 and the application processor 1404, and the memory 1406 storing the software module 1407.

[0117] FIG. 15 shows an example of the configuration of the AF 41. The control plane nodes (eg, AMF 31, SMF 32, PCF 34, and NEF 35) in the 5GC 30 may also have a similar configuration as shown in FIG. 15. Referring to FIG. 15, the AF 41 includes a network interface 1501, a processor 1502, and a memory 1503. The network interface 1501 is used, for example, to communicate with the DN 50 and to communicate with network functions (NFs) or nodes in the 5GC. Other NFs or nodes in the 5GC include, for example, UDM, AUSF, SMF, and PCF. The network interface 1501 may include, for example, a network interface card (NIC) conforming to the IEEE 802.3 series.

[0118] The processor 1502 may be, for example, a microprocessor, a Micro Processing Unit (MPU), or a Central Processing Unit (CPU). The processor 1502 may include multiple processors.

[0119] The memory 1503 is composed of a volatile memory and a non-volatile memory. The memory 1503 may include a plurality of physically independent memory devices. The volatile memory is, for example, a static random access memory (SRAM) or a dynamic RAM (DRAM), or a combination thereof. The non-volatile memory is, for example, a mask read only memory (MROM), an electrically erasable programmable ROM (EEPROM), a flash memory, or a hard disk drive, or any combination thereof. The memory 1503 may include a storage located away from the processor 1502. In this case, the processor 1502 may access the memory 1503 via the network interface 1501 or an I / O interface not shown.

[0120] The memory 1503 may store one or more software modules (computer programs) 1504 including instructions and data for performing processing by the AF 41 described in the above-mentioned embodiments. In some implementations, the processor 1502 may be configured to read the software modules 1504 from the memory 1503 and execute them to perform processing by the AF 41 described in the above-mentioned embodiments.

[0121] As described with reference to FIG. 13, FIG. 14, and FIG. 15, each of the processors of the RAN node 1, the RAN node 2, the control plane node (e.g., SMF 32) in the 5GC 30, and the AF 41 according to the above-mentioned embodiment executes one or more programs including instructions for causing a computer to execute the algorithm described with reference to the drawings. The programs can be stored and provided to a computer using various types of non-transitory computer readable media. The non-transitory computer readable media includes various types of tangible storage media. Examples of the non-transitory computer readable media include magnetic storage media (e.g., flexible disks, magnetic tapes, hard disk drives), magneto-optical storage media (e.g., magneto-optical disks), Compact Disc Read Only Memory (CD-ROM), CD-R, CD-R / W, and semiconductor memory (e.g., mask ROM, programmable ROM (PROM), erasable PROM (EPROM), flash ROM, random access memory (RAM)). The program may be provided to the computer by various types of transitory computer readable media. Examples of the transitory computer readable medium include an electric signal, an optical signal, and an electromagnetic wave. The transitory computer readable medium may provide the program to the computer via a wired communication path such as an electric wire and an optical fiber, or via a wireless communication path.

[0122] <Other embodiments> The above-described embodiments may be implemented independently of each other, or the whole or part of the embodiments may be implemented in appropriate combination.

[0123] Furthermore, the above-described embodiment is merely an example of 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. [Explanation of symbols]

[0124] 1 RAN node 2. RAN Node 3. UE 10 RAN 11, 12 Cells 30 5GC 31 AMF 32 SMF 33, 33A, 33B UPF 34 PCF 35 NEF 41AF 50, 50A, 50B DN 1305 Memory 1306 Modules 1403 Baseband Processor 1404 Application Processor 1407 Modules 1503 Memory 1504 Modules

Claims

1. 1. A radio access network node, comprising: A receiver for receiving a RAT / Frequency Selection Priority (RFSP) index from a mobility management node; A determination unit for determining a secondary cell for dual connectivity for a User Equipment (UE) based on the RFSP index; A radio access network node comprising:

2. A method in a radio access network node, comprising: Receives the RAT / Frequency Selection Priority (RFSP) index from the mobility management node, determining a secondary cell for dual connectivity for a User Equipment (UE) based on the RFSP index; method.

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