Radio access network node, radio terminal, core network node and method

Abstract

The present invention relates to a radio access network node, a radio terminal, a core network node and a method. During a handover of a radio terminal (1) from a first network to a second network, a target RAN node (3) is operable to: receive slice information about a network slice included in the second network and to which the radio terminal (1) is to be connected from a core network (5); after receiving the slice information, create radio resource configuration information in the second network to be used by the radio terminal (1) after the handover; and transmit the radio resource configuration information to the radio terminal (1) via the first network. It is possible to facilitate the AS layer or NAS layer of the target RAT to be appropriately configured in the inter-RAT handover.

Description

[0001] This application is a divisional application of an application which entered the Chinese national phase on August 30, 2018, with PCT application number PCT / JP2017 / 018224, international application date May 15, 2017, Chinese application number 201780014285.6, and invention name “Radio Access Network Node, Radio Terminal, Core Network Node and Method Thereof”. Technical Field

[0002] The present disclosure relates to a radio communication system, and in particular, to handover of a radio terminal between different Radio Access Technologies (RATs). Background Art

[0003] The 3rd Generation Partnership Project (3GPP) has begun work on standardization for the fifth generation mobile communication system (5G) (i.e., 3GPP Release 14, in 2016) to make 5G a commercial reality within 2020 (see non-patent document 1). 5G is expected to be achieved by continuous enhancement / evolution of LTE and LTE-Advanced and innovative enhancement / evolution caused by the introduction of new 5G air interfaces (i.e., new radio access technologies (RATs)). The new RAT supports, for example, higher frequency bands than those supported by LTE / LTE-Advanced (e.g., 6 GHz or lower) and their continuous evolution. For example, the new RAT supports centimeter wave bands (10 GHz or higher) and millimeter wave bands (30 GHz or higher).

[0004] In this specification, the fifth generation mobile communication system is also referred to as the next generation (NextGen) system (NG system). The new RAT of the NG system is referred to as the new radio (NR), 5G RAT or NG RAT. The new radio access network (RAN) and the core network for the NG system are respectively referred to as the NextGen RAN (NG RAN) and the NextGen core (NG core). The radio terminal (ie, user equipment (UE)) connected to the NG system is referred to as the NextGen UE (NG UE). The official names of the RAT, UE, radio access network, core network, network entity (or node), protocol layer, etc. of the NG system will be determined in the future as the standardization work progresses.

[0005] Unless otherwise specified, the term "LTE" used in this specification includes enhancements / evolutions of LTE / LTE-Advanced to provide interaction with NG systems. The enhancements / evolutions of LTE and LTE-Advanced that interact with NG systems are also referred to as LTE-Advanced Pro, LTE+, or enhanced LTE (eLTE). Further, unless otherwise specified, terms related to LTE networks and logical entities used in this specification such as "Evolved Packet Core (EPC)", "Mobility Management Entity (MME)", "Serving Gateway (S-GW)", and "Packet Data Network (PDN) Gateway (P-GW)" include enhancements / evolutions thereof to provide interaction with NG systems. Enhanced EPC, enhanced MME, enhanced S-GW, and enhanced P-GW are also referred to as, for example, enhanced EPC (eEPC), enhanced MME (eMME), enhanced S-GW (eS-GW), and enhanced P-GW (eP-GW), respectively.

[0006] In LTE and LTE-Advanced, in order to achieve Quality of Service (QoS) and packet routing, bearers per QoS level and per PDN connection are used in both the RAN (i.e., Evolved Universal Terrestrial RAN) and the core network (i.e., Evolved Packet Core (EPC)). That is, in the bearer-based QoS (or per-bearer QoS) concept, one or more Evolved Packet System (EPS) bearers are configured between the UE and the P-GW in the EPC, and multiple Service Data Flows (SDFs) with the same QoS level are transmitted through one EPS bearer that meets the QoS. The SDF is one or more packet flows that match the SDF template (i.e., packet filter) based on the policy and charging control (PCC) rules. Further, each packet to be sent through the EPS bearer for packet routing contains information for identifying which bearer (i.e., General Packet Radio Service (GPRS) Tunneling Protocol (GTP) tunnel) the packet is associated with.

[0007] In contrast, with respect to the NG system, it has been suggested that although radio bearers may be used in the NG RAN, no bearers are used in the NG core or in the interface between the NG RAN and the NG core (see non-patent document 1). In particular, instead of the EPS bearer, a PDU flow is defined, and one or more SDFs are mapped to one or more PDU flows. The PDU flow between the NG UE and the user plane terminal entity in the NG core (i.e., the entity corresponding to the P-GW in the EPC) corresponds to the EPS bearer in the EPS bearer-based QoS concept. That is, the NG system adopts a flow-based QoS (or per-flow QoS) concept instead of a bearer-based QoS concept. In the flow-based QoS concept, QoS is handled per PDU flow. Note that the association between the UE and the data network is called a "PDU session". The term "PDU session" corresponds to the term "PDN connection" in LTE and LTE-Advanced. Multiple PDU flows can be configured in one PDU session.

[0008] In the present specification, a system such as LTE and LTE-Advanced systems that configure an end-to-end bearer (e.g., EPS bearer) between a UE and an edge node (e.g., P-GW) in a core network and adopt a bearer-based QoS concept is referred to as a "bearer-based system" or a "bearer-based network". In contrast, a system that does not use any bearer in the core network or in the interface between the core network and the RAN and adopts a flow-based QoS concept (such as an NG system) is referred to as a "bearerless system" or a "bearerless network". Similar to the NG system described above, a radio bearer may be used in a RAN in a bearerless network. The term "bearerless" can also be expressed as, for example, no GTP, no (PDN) connection, no tunnel, (IP) flow-based, SDF-based, transport flow-based, or (PDU) session-based. However, in the present specification, the NG system may be used as a bearer-based system and may support both flow-based transmission of user data and bearer-based transmission of user data.

[0009] Further, it has been suggested that the NG system supports network slicing (see non-patent document 1). Network slicing uses network function virtualization (NFV) technology and software defined network (SDN) technology and makes it possible to create multiple virtualized logical functions on a network network. Each virtualized logical network is called a network slice or a network slice instance, includes logical nodes and functions, and is used for specific flows and signaling. The NG RAN or the NG core or both have a slice selection function (SSF). The SSF selects one or more network slices suitable for the NG UE based on information provided by at least one of the NG UE and the NG core.

[0010] Patent document 1 discloses a handover from a bearerless network (e.g., 5G) to a bearer-based network (e.g., LTE) and a handover from a bearer-based network (e.g., LTE) to a bearerless network (e.g., 5G). In the handover from 5G to LTE disclosed in patent document 1, the source control node (i.e., access control server (ACS) / eMME) in the 5G core (or NG core) maps the QoS parameters of the service flow in the bearerless network (i.e., 5G) to the EPS bearer-level QoS in the bearer-based network (i.e., LTE). The 5G QoS parameters of the service flow are, for example, DiffServ code point (DSCP) values. The EPS bearer-level QoS in LTE is, for example, a QoS class identifier (QCI) and an allocation and retention priority (ARP). Mapping the DSCP value to the EPS bearer can be performed in a one-to-one manner or in an n-to-one manner. The source ACS / eMME sends the APN information including information about the EPS bearer-level QoS to the target MME. The target MME establishes a GTP tunnel for the UE based on the received APN information.

[0011] Further, in the handover from LTE to 5G disclosed in patent document 1, the source MME in the LTE core (ie, EPC) sends a forward relocation request containing necessary bearer context information to the target ACS / eMME in the 5G core (NG core). The target ACS / eMME performs mapping of the QCI value received from LTE (ie, the source MME) to 5G QoS parameters (ie, DSCP values) and supplies them to the transmission node (ie, mobility gateway access router (M-GW / AR) or mobility gateway edge router (M-GW / ER)) in the 5G core (or NG core). By doing so, the target ACS / eMME establishes at least one generic routing encapsulation (GRE) tunnel for transmitting the service flow (ie, IP packet) of the UE.

[0012] Citation List

[0013] Patent Literature

[0014] Patent Document 1: International Patent Publication No. WO2015 / 160329

[0015] Non-patent literature

[0016] Non-patent document 1: 3GPP TR 23.799 V0.6.0 (2016-07) "3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; Study on Architecture for Next Generation System (Release 14)", July 2016 Summary of the invention

[0017] Technical issues

[0018] The inventors have studied the handover between the NR system (ie, 5G) and the LTE system and found several problems. For example, Patent Document 1 fails to teach that during the handover process from the LTE system to the NG system, the network slice to which the UE will be connected after the handover is considered for configuring the access stratum (AS) layer or the non-access stratum (NAS) of the target RAT (ie, NG RAT).

[0019] Therefore, one of the objectives to be achieved by the embodiments disclosed herein is to provide an apparatus, method, and program that facilitates proper configuration of the AS layer or NAS layer of the target RAT in a handover from a network that does not support network slicing to a network that supports network slicing. It should be noted that the objectives described above are 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 following description and the accompanying drawings.

[0020] Technical Solution

[0021] In one aspect, a target radio access network (RAN) node associated with a second network includes at least one memory and at least one processor, the at least one processor being coupled to the at least one memory. The at least one processor is configured to: receive slice information about a network slice included in the second network and to which the radio terminal is to be connected from a core network during a handover of a radio terminal from a first network to a second network; upon receiving the slice information, create radio resource configuration information in the second network to be used by the radio terminal after the handover; and transmit the radio resource configuration information to the radio terminal via the first network.

[0022] In one aspect, a source radio access network (RAN) node associated with a first network includes at least one memory and at least one processor, the at least one processor being coupled to the at least one memory. The at least one processor is configured to receive a handover-related message from the second network during a handover of a radio terminal from the first network to the second network, and transmit the handover-related message to the radio terminal. The handover-related message contains at least one of slice information about a network slice included in the second network and to which the radio terminal is to be connected and radio resource configuration information based on the network slice in the second network.

[0023] In one aspect, a radio terminal includes at least one memory and at least one processor, the at least one processor being coupled to the at least one memory. The at least one processor is configured to receive a handover-related message from a radio access network (RAN) node of the first network during a handover from a first network to which the radio terminal is connected to a second network. The handover-related message contains at least one of slice information about a network slice in the second network and radio resource configuration information based on the network slice in the second network.

[0024] In one aspect, the core network 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, during handover of a radio terminal from a first network to a second network, send slice information about a network slice included in the second network and to which the radio terminal is to be connected to, to a target radio access network (RAN) node associated with the second network.

[0025] In one aspect, a method in a target radio access network (RAN) node associated with a second network, comprising:

[0026] During a handover of the radio terminal from the first network to the second network,

[0027] receiving, from the core network, slice information about a network slice included in the second network and to which the radio terminal is to be connected;

[0028] upon receiving the slice information, creating radio resource configuration information in a second network to be used by the radio terminal after handover; and

[0029] The radio resource configuration information is transmitted to the radio terminal through the first network.

[0030] In one aspect, a method in a source radio access network (RAN) node associated with a first network, comprising:

[0031] During a handover of the radio terminal from the first network to the second network,

[0032] receiving a handover-related message from the second network, the handover-related message including at least one of slice information about a network slice included in the second network and to which the radio terminal is to be connected and radio resource configuration information based on the network slice in the second network; and

[0033] Transmit handover related messages to the radio terminals.

[0034] In one aspect, a method in a radio terminal comprises: during handover from a first network to which the radio terminal is connected to a second network, receiving a handover-related message from a radio access network (RAN) node of the first network, the handover-related message including slice information about a network slice in the second network and at least one of radio resource configuration information based on the network slice in the second network.

[0035] In one aspect, a method in a core network node includes: during handover of a radio terminal from a first network to a second network, sending slice information about a network slice included in the second network and to which the radio terminal is to be connected to to a target radio access network (RAN) node associated with the second network.

[0036] In one aspect, a program comprises a set of instructions (software codes) which, when loaded into a computer, causes the computer to perform a method according to the aspects described above.

[0037] Beneficial Effects

[0038] According to the aspects described above, it is possible to provide an apparatus, method, and program that facilitates proper configuration of the AS layer or NAS layer of a target RAT in a handover from a network that does not support network slicing to a network that supports network slicing. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 shows an example configuration of a radio communications network according to some embodiments;

[0040] Figure 2 shows an example configuration of a radio communications network according to some embodiments;

[0041] Figure 3A is a sequence diagram showing an example of an Inter-RAT handover procedure from an LTE system to an NG system according to the first embodiment;

[0042] Figure 3B is a sequence diagram showing this example of an Inter-RAT handover procedure from an LTE system to an NG system according to the first embodiment;

[0043] Figure 4A is a sequence diagram showing another example of the Inter-RAT handover procedure from the LTE system to the NG system according to the first embodiment;

[0044] Figure 4B is a sequence diagram showing this other example of the Inter-RAT handover procedure from the LTE system to the NG system according to the first embodiment;

[0045] Figure 5 is a flowchart illustrating an example of a method performed by a core network according to a first embodiment;

[0046] Figure 6 is a flowchart showing an example of a method performed by a target NR Node B (NR NB) according to the first embodiment;

[0047] Figure 7 is a flow chart showing an example of a method performed by a source LTE eNB according to the first embodiment;

[0048] Figure 8 is a flowchart showing an example of a method performed by a radio terminal according to the first embodiment;

[0049] Fig. 9 is a sequence diagram showing an example of an Inter-RAT handover procedure from an LTE system to an NG system according to the second embodiment;

[0050] Fig.10 is a sequence diagram showing an example of an Inter-RAT handover procedure from an LTE system to an NG system according to the second embodiment;

[0051] Fig.11 is a sequence diagram showing an example of an Inter-RAT handover procedure from an LTE system to an NG system according to the third embodiment;

[0052] Fig.12 is a sequence diagram showing an example of an Inter-RAT handover procedure from an LTE system to an NG system according to the third embodiment;

[0053] Fig.13A is a sequence diagram showing an example of an Inter-RAT handover procedure from an NG system to an LTE system according to the fourth embodiment;

[0054] Fig. 13B is a sequence diagram showing this example of an Inter-RAT handover procedure from an NG system to an LTE system according to the fourth embodiment;

[0055] Fig.14A is a sequence diagram showing another example of the Inter-RAT handover procedure from the NG system to the LTE system according to the fourth embodiment;

[0056] Fig. 14B is a sequence diagram showing this other example of the Inter-RAT handover procedure from the NG system to the LTE system according to the fourth embodiment;

[0057] Fig.15 is a block diagram showing a configuration example of a radio terminal according to some embodiments;

[0058] Fig.16 is a block diagram showing an example of a configuration of a base station according to some embodiments;

[0059] Fig.17 is a block diagram showing an example of a configuration of a base station according to some embodiments;

[0060] Fig.18 is a block diagram illustrating an example of a configuration of a core network node according to some embodiments;

[0061] Fig.19A An example of the format of a Mobility from EUTRA Command message is shown;

[0062] Fig.19B An example of the format of a Mobility from EUTRA Command message is shown;

[0063] Fig. 20 An example of the format of a handover request message is shown;

[0064] Fig.21 An example of the format of a source NR NB to target NR NB transparent container is shown;

[0065] Fig. 22 An example of the format of a source NR NB to target NR NB transparent container is shown;

[0066] Fig.23 An example of the format of a source NR NB to target NR NB transparent container is shown;

[0067] Fig.24 An example of the format of a source NR NB to target NR NB transparent container is shown;

[0068] Fig.25 An example of the format of a (NR) Handover Request message is shown;

[0069] Fig.26 An example of the format of a (NR) Handover Request message is shown;

[0070] Fig. 27 An example of the format of a (NR) Handover Request message is shown;

[0071] Fig.28An example of the format of slice information is shown;

[0072] Fig.29 An example of the format of a session endpoint ID is shown;

[0073] Fig.30 An example of the format of a (NR) Handover Request Reply message is shown;

[0074] Fig.31 An example of the format of a target-to-source transparent container is shown;

[0075] Fig.32 An example of the format of a (NR) Handover Request Reply is shown;

[0076] Fig.33 An example of the format of a (NR) Handover Request Reply is shown;

[0077] Fig.34 An example of the format of a forwarding address is shown;

[0078] Fig.35 shows an example of the format of an S1AP Handover Command message; and

[0079] Fig.36 An example of the format of an NG2AP Handover Command message is shown. DETAILED DESCRIPTION

[0080] Hereinafter, specific embodiments will be described in detail with reference to the accompanying drawings. The same or corresponding elements are denoted by the same symbols throughout the drawings, and repeated explanations are omitted as needed for the sake of clarity.

[0081] Each embodiment in the embodiments described below can be used individually, or two or more of the embodiments can be appropriately combined with each other. These embodiments include novel features that are different from each other. Therefore, these embodiments help to achieve the goal or solve problems that are different from each other and also help to obtain advantages that are different from each other.

[0082] First embodiment

[0083] Figure 1 An example of a configuration of a radio communication network according to some embodiments including this embodiment is shown. Figure 1 In the example shown in , the radio communication network includes a radio terminal (UE) 1, an LTE base station (i.e., eNB) 2, a new radio (NR) base station (i.e., NR Node B (NR NB) 3), an EPC 4, and a NextGen (NG) core 5. UE 1 has the ability to connect to an LTE system including LTE eNB 2 and EPC 4, and based on the ability to connect to a NextGen (NG) system including NR NB 3 and NG core 5.

[0084] exist Figure 1 In the example shown in , the EPC 4 is connected to the NG core 5. In particular, one or more nodes in the EPC 4 are connected to one or more nodes in the NG core 5 via a control plane interface. In some embodiments, the MME in the EPC 4 may be connected to a control node (i.e., a control plane function (CPF) node) via a control plane interface, which is included in the NG core 5 and has at least a portion of the MME function. Further, one or more nodes in the EPC 4 may be connected to one or more data nodes (i.e., a user plane function (UPF) node) in the NG core 5 via a user plane interface. Each data node (i.e., UPF node) may be a node having at least a portion of the S-GW function. That is, the EPC 4 may be enhanced to perform interaction with an NG system including the NG core 5 and may be referred to as an eEPC.

[0085] Similarly, the NR NB 3 may be connected to one or more CPF nodes in the NG core 5 via a control plane interface (e.g., NG2 interface). Further, the NR NB 3 may be connected to one or more UPF nodes in the NG core 5 via a user plane interface (e.g., NG3 interface). Moreover, the UE 1 may be connected to one or more CPF nodes in the NG core 5 via a control plane interface (e.g., NG1 interface). The NG1 interface may be defined as a logical interface for transmitting NAS layer information, and the transmission of the NAS layer information may be performed through the NG2 interface and through a radio interface (e.g., NG Uu) between the NR NB 3 and the UE 1.

[0086] Figure 2 Another configuration example of a radio communication network according to some embodiments including this embodiment is shown. Figure 2In the example shown in , LTE eNB 2 is connected to NG core 5. That is, LTE eNB 2 is connected to MME in NG core 5 or a control node (i.e., CPF node) having at least part of MME functions through a control plane interface (e.g., NG2 interface). Further, LTE eNB 2 is connected to a serving gateway (S-GW) in NG core 5 or a data node (i.e., UPF node) having at least part of S-GW functions through a user plane interface (e.g., NG3 interface). As described above, LTE eNB 2 may be enhanced to be connected to NG core 5 and may be referred to as eLTE eNB. In some embodiments, NG core 5 may establish a virtualized network slice that provides logical EPC nodes and EPC functions. In some embodiments, E-UTRAN including LTE eNB2 may be connected to the same network slice as NG RAN including NR NB 3. Alternatively, E-UTRAN including LTE eNB2 may be connected to different network slices.

[0087] exist Figure 1 and 2 In the example shown in , LTE eNB 2 can be connected to NR NB 3 via a direct inter-base station interface (e.g., X3 interface). The direct inter-base station interface can be used for signaling or user packet transmission or both between LTE eNB 2 and NR NB 3. However, the direct inter-base station interface between LTE eNB 2 and NR NB 3 can be omitted.

[0088] In addition to the NG1, NG2 and NG3 interfaces described above, the NG system may also include other interfaces. Each interface may be referred to as a reference point. NG RAN (i.e., different NR NBs) may be connected to each other via the NX2 interface. A CPF node having one or both of a mobility management function (MMF) and a session management function (SMF) may be connected to a UPF node via a control plane interface (e.g., an NG4 interface). Different UPF nodes may be connected to each other via a user plane interface (e.g., an NG9 interface). CPF nodes having different functions may be connected to each other via a control plane interface. For example, a CPF node having MMF and SMF may be connected to a CPF node having a policy control function (PCF) via a control plane interface (e.g., an NG7 interface). A CPF node having MMF and SMF may be connected to a node having a subscriber data management (SDM) function via a control plane interface (e.g., an NG8 interface). A CPF node may be connected to a node having an application function (AF) via a control plane interface (e.g., an NG5 interface). The UPF node can be connected to an external or local data network (DN) through a user plane interface (e.g., NG6 interface). The SMF may include functions for authenticating users or terminals and authorizing services or network slices. The network nodes described above are individually or collectively referred to as network functions (NFs).

[0089] In some embodiments, the NG system including the NR NB 3 and the NG core 5 supports data transmission based on the flow-based QoS (or per-flow QoS) concept described above. The NG system including the NR NB 3 and the NG core 5 can also be configured to support bearer-based transmission using bearers per QoS level and per PDU session. The bearers in the NG system can be configured between a pair of network functions (NFs), for example, between the NR NB 3 and the user plane function in the NG core 5, or between two user plane functions in the NG core 5. Alternatively, the bearers in the NG system can be configured between the UE 1 and the user plane function in the NG core 5 through the NR NB 3. The bearers in the NG system can be referred to as NG-EPS bearers and the radio access bearers in the NG system can be referred to as NG-RAB. The bearers in the NG system can be used for the transmission of multiple packet flows (i.e., PDU flows).

[0090] The NG-RAB may include a radio bearer configured between the UE 1 (NG UE) and the NR NB 3 and a bearer (e.g., an NG3 bearer) configured between the NR NB 3 and the user plane function in the NG core 5. The NG-EPG bearer may include a core network bearer (e.g., an NG9 bearer) between the NG-RAB and the user plane function configured in the NG core 5 (e.g., between the edge GW and the data network gateway (DNGW)). The edge GW is a gateway to the radio access network and has similar user plane functions to the LTE S-GW. However, in the NG system, unlike the LTE S-GW, the UE 1 may be connected to multiple edge GWs. The DN GW is a gateway to an external network (i.e., a data network) and has similar user plane functions to the LTE P-GW. In the NG system, similar to the LTE P-GW, the UE 1 may be connected to multiple DN GWs.

[0091] More specifically, the NG-EPS bearer may be configured between the UE 1 (i.e., NG UE) and a specific slice user plane control (i.e., a specific slice user plane NF (SUNF)) in the NG core 5. The NG-RAB may be configured between the UE 1 (i.e., NG UE) and a common user plane function (i.e., a common user plane (CUNF)) in the NG core 5. In this case, the CUNF provides the functionality of an edge GW and the SUNF provides the functionality of a DN GW. The CUNF may associate the NG-RAB with a core network bearer (e.g., an NG9 bearer). That is, the NG-EPS bearer may include the NG-RAB between the UE 1 (i.e., NG UE) and the CUNF and a core network bearer (e.g., an NG9 bearer) between the CUNF and the SUNF.

[0092] The NG system supporting bearer-based transmission may also be configured to distinguish between data flows (e.g., PDU flows) in a bearer to perform QoS processing (e.g., discarding of packets) on a per-data flow basis (e.g., on a per-PDU flow basis). For example, NR NB3 may associate a bearer (e.g., NG3 bearer) configured between the NR NB 3 and the user plane function in the NG core 5 with a radio bearer, perform packet forwarding between the bearer (e.g., NG3 bearer) and the radio bearer, and perform QoS processing (e.g., discarding of packets) per data flow (e.g., PDU flow) in the bearer.

[0093] Note that when the (e)LTE eNB 2 is connected to the NG core 5 via the NG2 interface, the radio access bearer corresponding to the LTE EPS radio access bearer (E-RAB) may be defined as an NG EPS radio access bearer (NE-RAB) and the bearer corresponding to the LTE EPS may be defined as an NG EPS bearer (NEPS bearer). The NE-RAB may include a radio bearer configured between the UE 1 and the LTE eNB 2 and a bearer (e.g., an NG3 bearer) configured between the LTE eNB 2 and a user plane function (e.g., an edge GW or a CUNF) in the NG core 5. The NEPS bearer may include a core network bearer (e.g., an NG 9 bearer) between the NE-RAB and a user plane control configured in the NG core 5 (e.g., between the edge GW and the DN GW, or between the CUNF and the SUNF).

[0094] The LTE eNB 2 connected to the NG system may be configured to distinguish between data flows (e.g., PDU flows) in the NE-RAB and perform QoS processing (e.g., discarding of packets) on a per-data flow basis (e.g., on a per-PDU flow basis). For example, the LTE eNB 2 may associate a bearer (e.g., NG3 bearer) configured between the LTE eNB 2 and the user plane function in the NG core 5 with a radio bearer, perform packet forwarding between the bearer (e.g., NG3 bearer) and the radio bearer, and perform QoS processing (e.g., discarding of packets) according to the data flow (e.g., PDU flow) in the bearer.

[0095] This embodiment provides a method for handing over UE 1 from an LTE system that does not support network slicing to an NG system that supports network slicing. Figure 3A and Figure 3B Shows Figure 1 An example of a procedure for handing over UE 1 from the LTE system to the NG system in the configuration example of the radio communication network shown in . Figure 3A shows the handover preparation phase and Figure 3B The handover execution phase is shown.

[0096] exist Figure 3A and Figure 3B In the process shown in , the source base station (ie, LTE eNB 2) starts the handover by sending a handover request message on the interface (or reference point) between the source base station (ie, LTE eNB 2) and the core network (ie, EPC 4). Figure 3A and Figure 3BThe process shown in may be an enhancement / evolution of the "E-UTRAN to UTRAN Iu mode Inter RAT handover" in LTE. Figure 3A and Figure 3B The process shown in may be an enhancement / evolution of “S1 based handover” with respect to MME relocation in LTE.

[0097] In step 301, UE 1 is connected to LTE eNB 2 and is in a connected state (ie, RRC_Connected). UE 1 receives a measurement configuration from LTE eNB 2, performs neighbor cell measurement and inter-radio access technology (inter-RAT) measurement, including measurement of E-UTRAN (LTE) cells and NG-RAN cells according to the received measurement configuration, and sends a measurement report to LTE eNB 2. The measurement configuration is, for example, included in an RRC connection reconfiguration message transmitted from E-UTRAN to UE.

[0098] In step 302, LTE eNB 2 determines to perform an inter-RAT handover on the cell of NR NB 3 and sends a handover request message to the source control node (i.e., source MME) in EPC 4. The handover request message contains an identifier of the target NR NB 3. Further, the handover request message may contain a handover type information element (IE) indicating that it is handing over from LTE to NR. For example, "LTE to NR (LTEtoNR)" is set in the handover type IE. Additionally or alternatively, the handover request message may contain a target NR-NB identifier information element (IE). The handover request message may contain a source to target transparent container IE. The source to target transparent container IE may include RRC layer information (i.e., RRC container) and may also include information about bearers (e.g., E-RAB). The RRC layer information (i.e., RRC container) includes, for example, at least a portion of the radio resource configuration in the serving cell of UE1 managed by LTE eNB 2, which is necessary for the radio resource configuration in NR NB 3.

[0099] In step 303, the source MME in EPC 4 determines that the type of handover is an inter-RAT handover to NR (or NG system) based on the handover type IE or the target NR-NB identifier UE contained in the received handover request message. The MME in EPC 4 selects a target control node in the NG core 5. The target control node is a node having at least part of the functions of the MME in EPC 4. The MME in EPC 4 sends a forward relocation request message to the target control node to start the handover resource allocation process. The forward relocation request message contains a mobility management (MM) context and all PDN connections valid for UE 1 in the source system (i.e., LTE system). Each PDN connection includes a list of associated APNs and EPS bearer contexts. The MM context includes information about the EPS bearer context and security-related information. The forward relocation request message may also include information for identifying one or more service data flows associated with each EPS bearer context (e.g., an SDF template or a service flow template (TFT)).

[0100] In step 304, the target control node in the NG core 5 performs a process for creating a bearerless session. In particular, the target control node determines that the packet transfer node (or gateway) for UE 1 needs to be relocated and then selects the target transfer node (or gateway) in the NG core 5. The target transfer node (or gateway) is a node having at least part of the functionality of the S-GW in the EPC 4. The target control node sends a create session request message to the target transfer node (or gateway). The create session request message may also include information for identifying one or more service data flows associated with each EPS bearer context (e.g., an SDF template or a traffic flow template (TFT)). This information for identifying one or more service data flows is derived from a forward relocation request message, which has been sent from the source MME in the EPC 4 to the target control node in the NG core 5. The target transfer node (or gateway) allocates its local resources and sends a create session response message to the target control node.

[0101] Note that when the NG system supports bearer-based delivery using bearers per QoS class and per PDU session, and when relocation of the delivery node is not required, the target control node in the NG core 5 may perform the bearer modification procedure in step 304 instead of the session creation procedure.

[0102] Further, in step 304, the target control node (e.g., CPF) in the NG core 5 determines (or selects) a network slice to which the UE 1 will be connected after the handover. In one example, the target control node (e.g., CPF) in the NG core 5 may select a network slice for the UE 1 based on the QoS required for the EPS bearer of the SDF of the UE 1. Additionally or alternatively, the forward relocation request message (step 303) sent by the source MME in the EPC 4 may also include network slice assistance information. The network slice assistance information assists the target control node in selecting, configuring or authorizing a network slice. The source MME in the EPC 4 may receive at least a portion of the network slice assistance information from the UE 1 and send it to the target control node in the NG core 5. The target control node in the NG core 5 may perform creation of the selected network slice instance.

[0103] The network slice assistance information may indicate, for example, any one or any combination of the following: the type of UE 1 (e.g., device type or UE category); the purpose of access by UE 1 (e.g., UE usage type); the type of service desired by UE 1 (e.g., requested / preferred service type or multi-dimensional descriptor (MDD)); slice information selected by UE 1 (e.g., selected slice type, selected slice identity (ID) or selected network function (NF) ID); slice information that UE 1 has previously authorized (e.g., authorized slice type, authorized slice ID or authorized NF ID); acceptable latency for UE 1 (e.g., allowed latency or tolerable latency). The service type may indicate, for example, the type of use case, such as broadband communication (e.g., enhanced mobile broadband: eMBB), highly reliable / low latency communication (e.g., highly reliable and low latency communication: URLLC), M2M communication with a large number of connections (e.g., massive machine type communication: mMTC), or similar types thereof. The slice ID may indicate, for example, any one or any combination of the following: slice instance information (e.g., network slice instance (NSI) ID); dedicated network information (e.g., dedicated core network (DCN) ID); and network domain name information (e.g., domain network name (DNN) ID). The NF UD may indicate, for example, an identifier of any one or any combination of the following: a common network function (e.g., a common NF (CNF)); a common control plane function (e.g., a common control plane NF (CCNF)); a common user plane function (e.g., a common user plane NF (CUNF)); and a data gateway (e.g., a data network gateway (DN GW)).

[0104] In step 305, the target control node in the NG core 5 sends an NR handover request message to the target NR NB 3. The NR handover request message contains slice information. The slice information includes, for example, information about at least one of the following: a network slice included in the NG core 5 and to which the UE 1 will be connected (or to which the UE 1 will be connected) after the handover; a network slice included in the NG core 5 and to which the UE 1 is permitted to connect; and a network slice included in the NG core 5 and to which the UE 1 can connect.

[0105] In particular, the slice information may include identification information of a determined (or selected) slice (i.e., network slice: NS), identification information of a network node (NF), or type information of the slice, or any combination thereof. The slice identification information may be, for example, a slice ID, an NSI ID, an MDD, a DCN ID, or a DNN, or any combination thereof. The identification information of the network node may include, for example, an NF ID, a CNF ID, a CCNF ID, a slice-specific control plane NF (SCNF) ID, a CUNF ID, a slice-specific user plane (SUNF) ID, a UPF ID, or a DN GW ID, or any combination thereof. The slice type information may include, for example, a slice type indicating any one or any combination of the following: a service type, a service class, and a use case. Additionally or alternatively, the slice type information may include a tenant ID or a subscription contract (subscription group, e.g., a local UE or a roaming UE) indicating a use case. The slice type information may include an MDD including a slice type and a tenant ID as its elements. Note that the content of the slice information described above may be specified per network slice. Therefore, when UE 1 is to be connected to multiple network slices simultaneously, the slice information may include a set of multiple information items corresponding to the number of network slices to which UE 1 is to be connected.

[0106] The slice information may also include a mobility level or a session level or both. The mobility level may indicate one of the predefined mobility levels (e.g., high mobility, low mobility, and no mobility). For example, high mobility means that the geographical area in which the network slice supports mobility for UE 1 (or permits the mobility of UE 1) is larger than the geographical area of ​​low mobility, and the level of continuity required for the service (or PDU session) during the handover is higher. No mobility means that the network slice supports the mobility of UE 1 (or permits the mobility of UE 1) only in a very limited geographical area. The mobility level may be specified per UE or may be specified per network slice. The session level may indicate one of the predefined session types (e.g., session pre-setting, session post-setting, and no PDU session). For example, in order to maintain a service (or PDU session) during mobility as in the case of an existing handover, the session pre-setting may indicate that a PDU session needs to be established before the UE completes the movement of the target (i.e., cell, beam, etc.). In contrast, the post-session setting may indicate that the PDU session can be established after the UE has moved to the target. The session level may be specified per PDU session. The mobility level and session level may be included in the slice type. In other words, the slice type may contain multiple attributes including the mobility level and session level.

[0107] The slice information may include at least a portion of the network slice assistance information. That is, in step 305, the target control node in the NG Core 5 may include at least a portion of the network slice assistance information, which has been received from the source MME in the EPC4 in the slice information included in the NR Handover Request message and forwarded to the target NR NB 3.

[0108] Further, the NR handover request message in step 305 may include flow information. The flow information relates to at least one session (i.e., PDU session) established in a bearerless network (i.e., NG system) to transmit at least one packet flow (i.e., PDU flow) of UE 1. For each packet flow (i.e., PDU flow) of UE 1, the flow information includes a flow identifier (e.g., PDU flow ID), an address of a transmitting node in the NG core 5 (e.g., a transport layer address), and an uplink (UL) session endpoint identifier (SEID), and also includes flow QoS parameters. The session endpoint identifier (SEID) may be, for example, a tunnel endpoint identifier (TEID) or a network function (node) identifier (NF ID). The TEID may be, for example, a GTP-TEID or a GRE-TEID.

[0109] The flow information may also indicate a mapping between EPS bearers and PDU flows for UE 1. For example, the flow information may indicate one or more SDFs mapped to each EPS bearer of UE 1 and a flow identifier (e.g., PDU flow ID) assigned to each of these one or more SDFs. The flow information may also include priority information (e.g., a priority indicator), flow type information (e.g., a flow type indicator), or a flow level. The priority information may indicate, for example, a relative priority order among multiple flows or an absolute priority order for each flow. The flow type information may indicate, for example, which use case or which service the flow corresponds to. Further, the flow level may indicate, for example, one of the predefined flow types (e.g., lossless, delay tolerant, delay sensitive, and mission critical). The flow information may include the mobility level or session level described above, or both.

[0110] As already described, the NG system including the NR NB 3 and the NG core 5 may be configured to support bearer-based transmission using per QoS class and per PDU session, or may be configured to distinguish between data flows (e.g., PDU flows) in a bearer to perform QoS processing (e.g., discard of packets) on a per data flow basis (e.g., on a per PDU flow basis). For example, the NR NB 3 may associate a bearer (e.g., NG3 bearer) configured between the user plane function in the NR NB 3 and the NG core 5 with a radio bearer, perform packet forwarding between the bearer (e.g., NG3 bearer) and the radio bearer, and perform QoS processing (e.g., discard of packets) per data flow (e.g., PDU flow) in the bearer.

[0111] In this case, the flow information described above may indicate an association between a bearer (e.g., NG-RAB or NG3 bearer) for UE 1 and one or more packet flows (i.e., PDU flows) of UE 1 transmitted through the bearer. In other words, the control node (e.g., CPF) in the NG core 5 may send the flow information to the NR NB 3 to inform the NR NB 3 of the association between the bearer (e.g., NG-RAB or NG3 bearer) for UE 1 and one or more packet flows (i.e., PDU flows) of UE 1 transmitted through the bearer. The NR NB 3 may receive the flow information from the control node in the NG core 5, and then perform QoS processing (e.g., discard of packets) per data flow (e.g., PDU flow) in a bearer (e.g., NG3 bearer) configured between the NR NB 3 and the user plane function in the NG core 5 according to the received flow information.

[0112] The target NR NB 3 can perform admission control based on the NR handover request message containing slice information. For example, the target NR NB 3 can determine whether to accept the bearer or flow on a per-bearer basis or a per-flow basis. Additionally or alternatively, the target NR NB 3 can perform admission control based on the slice information, per network slice to which the UE 1 will be connected. In this process, NR NB 3 can determine whether it can accept each network slice. When there is a network slice that NR NB 3 cannot accept (or does not accept), NR NB 3 can map the network slice to a specific network slice (e.g., a default network slice) or connect the network slice to a specific NF (e.g., CUPF). Alternatively, NR NB 3 may determine that it has failed in accepting the network slice.

[0113] In step 306, upon receiving the NR handover request message containing the slice information, the target NR NB 3 creates a UE context and allocates resources. The target NR NB 3 also creates (or derives from the slice information) radio resource configuration information (e.g., radio parameters) necessary for UE 1 to establish a radio connection (e.g., RRC connection or radio bearer) associated with the NG system supporting network slicing based on the slice information. The radio resource configuration information may include at least one parameter included in the slice information.

[0114] The radio resource configuration information derived from the slice information may include radio (or RAN) parameters per network slice (or per use case). Use cases include, for example, enhanced mobile broadband (eMBB), massive machine type communications (mMTC), and highly reliable low latency communications (URLLC). The radio parameters per network slice (or per use case) may be basic physical channel parameters or basic Layer 2 / Layer 3 (L2 / L3) configurations. The basic physical channel parameters may include, for example, frame / subframe structure, transmission time interval (TTI) length, subcarrier spacing, and physical random access channel (PRACH) resources. PRACH resources may be one or both of preamble indexes and time / frequency resources. The basic L2 / L3 configuration may include, for example, frame / subframe mode and configuration of the L2 protocol sublayer (L2 configuration, for example, PDCP config, RLC config, or MAC config).

[0115] Additionally or alternatively, when signaling the RRC layer to specify (or indicate) radio resource configuration information derived from slice information, at least one of a message structure, an information element (IE) format, a parameter value, and objects to be encoded and decoded according to ASN.1 (Abstract Syntax Notation 1) that defines the information structure may be different for each slice.

[0116] The target NR NB 3 then sends an NR Handover Request Reply message containing a target-to-source transparent container to the target control node. The target-to-source transparent container contains radio resource configuration information (e.g., radio parameters) created by the target NR NB 3. As described later, the target-to-source transparent container is forwarded to the source LTE eNB 2 through the core network (i.e., EPC 4 and NG Core 5).

[0117] Further, in step 306, when creating the UE context and radio resource configuration information, the target NR NB 3 may consider the flow information contained in the NR handover request message. In particular, the target NR NB 3 may create a UE context and a security context including information about a packet flow (i.e., a PDU flow) based on the NR handover request message containing the flow information. Further, the target NR NB 3 may create (or derive from the flow information) radio resource configuration information necessary for UE 1 to establish a radio connection (e.g., an RRC connection or a radio bearer) associated with a bearerless network (i.e., an NG system) based on the flow information. The radio resource configuration information may include at least one parameter included in the flow information. The radio resource configuration information may include system information (e.g., a system information block: SIB) about a cell (or a mobility area or a beam coverage area) of the target NR NB 3, a common radio resource configuration for the UE (e.g., a common resource configuration), or a UE-specific radio resource configuration (e.g., a dedicated resource configuration). The radio resource configuration information may also include information indicating the mapping between bearers (e.g., EPS bearers or data radio bearers (DRBs)) in the cell of the source LTEeNB 2 and flows (e.g., PDU flows) to be established in the cell of the target NR NB 3.

[0118] In step 307, the target control node in the NG Core 5 sends a forward relocation response message containing the target to source transparent container to the source MME in the EPC 4. The forward relocation response message may also include the address and TEID allocated for downlink data forwarding. When indirect downlink forwarding is used, these addresses and TEIDs may be the addresses and TEIDs of the S-GW in the EPC 4. When direct downlink forwarding is used, these addresses and TEIDs may be the addresses and TEIDs of the target NR NB 3.

[0119] In step 308, the source MME sends a handover command message containing a target to source transparent container to the source LTE eNB 2. The handover command message may also contain a list of bearers subject to downlink data forwarding (e.g., a bearer list subject to data forwarding). The "Bearers Subject to Data forwarding list" IE includes, for example, an address and TEID for user service data forwarding, and an identifier of a flow subject to data forwarding (e.g., a PDU flow). The source LTE eNB 2 starts data forwarding for the bearers or flows (e.g., PDU flows) specified by the "Bearers Subject to Data forwarding list" IE.

[0120] In step 309, the source LTE eNB 2 sends a radio resource control (RRC) message containing a handover command message to the UE 1. The handover command message includes a transparent container containing the radio resource configuration information that has been established by the target NR NB 3 in the preparation phase. The RRC message can be, for example, a mobility command message from EUTRA or an RRC connection reconfiguration message.

[0121] In step 310, upon receiving the RRC message containing the handover command message, UE 1 moves to the target RAN (i.e., NG RAN) and performs handover per the radio resource configuration information provided by the handover command message. That is, UE 1 establishes a radio connection with the target NR NB 3 associated with the NG system. In step 311, UE 1 sends a handover confirmation for NR message to the target NR NB 3 after it has successfully synchronized with the target cell. The message in step 311 may be an NR RRC connection reconfiguration complete message.

[0122] In step 312, when UE 1 has successfully accessed the target NR NB 3, the target NR NB 3 notifies the target control node in the NG Core 5 by sending an NR Handover Notification message.

[0123] In step 313, the target control node in the NG core 5 recognizes that the UE 1 has arrived at the target side and notifies it to the source MME in the EPC 4 by sending a forward relocation complete notification message. The source MME sends a forward relocation complete response message to the target control node.

[0124] In step 314, the target control node in the NG core 5 performs a flow modification process and thereby completes the inter-RAT handover process. For example, the target control node may send a modify flow request message per session (i.e., per PDU session) to the transmission node in the NG core 5. The modify flow request message may include a flow identifier (e.g., PDU flow ID) and also include the address of the target NRNB 3 and a downlink (DL) session endpoint identifier (SEID). The session endpoint identifier (SEID) may be, for example, a tunnel endpoint identifier (TEID). The transmission node in the NG core 5 may communicate with the edge node (i.e., eP-GW) in the EPC 4 to notify the edge node (i.e., (e)P-GW) in the EPC 4 of the relocation of the transmission node or the change of the RAT type due to the inter-RAT HO. In particular, the transmission node in the NG core 5 may send a modify bearer request message per session (i.e., per PDN connection) to the edge node in the EPC 4. The edge node in the EPC 4 may send a modify bearer response message to the transmission node in the NG core 5. The transmitting node in the NG core 5 may send a modify flow response message to the target control node.

[0125] In accordance with Figure 3A and 3B After the handover is completed according to the process shown in , the path shown below can be used for data transmission of UE 1. When the NG system including the NR NB 3 and the NG core 5 supports bearer-based transmission in the NG core 5 and the bearer (e.g., Ng-EPS bearer) is used for UE 1 after the handover, both the uplink path and the downlink path may include, for example, a path (e.g., a GTP tunnel or a GRE tunnel) between the source (or old) S / P-GW and the target (or new) user plane control (e.g., CUNF) in the NG core 5. In particular, the S / P-GW can transmit downlink data to the user plane control (e.g., CUNF) in the NG core 5, while the user plane control (e.g., CUNF) in the GN core 5 can transmit uplink data to the S / P-GW.

[0126] In contrast, when a bearer (e.g., an NG-EPS bearer) is not used for UE 1 after handover, the CUNF may relay between the source (or old) S / P-GW and the target (or new) user plane function (e.g., a SUNF with NW slicing functionality). In particular, the S / P-GW may transmit downlink data to a CUNF in the NG core 5 and then the CUNF may transmit the downlink data to another UNF with a flow-by-flow control functionality. Alternatively, data transmission may be performed directly between the S / P-GW and the SUNF without traversing the CUNF. The data transmission path described above after handover may also be used in other handover processes described below.

[0127] Figure 4A and Figure 4B Shows Figure 2 An example of a procedure for handing over UE 1 from the LTE system to the NG system in the configuration example of the radio communication network shown in . Figure 4A shows the handover preparation phase and Figure 4B The handover execution phase is shown.

[0128] and Figure 3A and Figure 3B Similar to the process shown in Figure 4A and Figure 4B In the process shown in FIG. 1 , the source base station (ie, LTE eNB 2) starts handover by sending a handover request message on the interface between the source base station (ie, LTE eNB 2) and the core network (ie, NG core 5). Figure 3A and Figure 3B Similar to the process shown in Figure 4A and Figure 4B The procedure shown in may be an enhancement / evolution of “E-UTRAN to UTRAN Iu mode Inter-RAT handover” in LTE, or may be an enhancement / evolution of “S1 based handover” regarding MME relocation in LTE.

[0129] Figure 4A The process in steps 401 to 402 is the same as Figure 3A The processes in steps 301 to 302 of FIG. 4 are similar. However, in step 402, the LTE eNB 2 sends a handover request message to the NG core 5. As already described, in Figure 2 In the network configuration example shown in , the E-UTRAN including the LTE eNB 2 and the NG RAN including the NR NB 3 may be connected to the same network slice. In this embodiment, the handover of the UE 1 from the LTE eNB to the NR NB 3 is performed by signaling between one or more logical control nodes (i.e., control plane functions) and one or more logical transport nodes (i.e., user plane functions) created within the same network slice. In this embodiment, the handover requirement message in step 402 may be sent to a new or enhanced control node corresponding to the MME.

[0130] Alternatively, the E-UTRAN including the LTE eNB 2 and the NG RAN including the NR NB 3 may be connected to different network slices. In this embodiment, the handover of the UE 1 from the LTE eNB 2 to the NR NB 3 is performed through inter-slice communication between the network slice instance corresponding to the EPC to which the LTE eNB 2 is connected and the network slice instance corresponding to the pure NG core to which the NRNB 3 is connected. In this embodiment, the handover requirement message in step 402 may be sent to the MME in the network slice instance to which the LTE eNB 2 is connected.

[0131] Figure 4A The process in steps 403 to 405 in Figure 3A The processes in steps 303 to 307 are similar. Figure 4A In the process shown in Figure 3A Processes corresponding to those in steps 303 and 307 are executed within the NG core 5.

[0132] Figure 4B The process in steps 406 to 411 in Figure 3B The processes in steps 308 to 314 are similar. Figure 4B In the process shown in Figure 3B Processes corresponding to those in step 313 are executed within the NG core 5.

[0133] Figure 5 is a flow chart illustrating a process 500 as an example of a method performed by a core network. The core network corresponds to Figure 1 EPC 4 and NG Core 5 as shown in, or Figure 2 In step 501, the core network receives a handover request message from the source LTE eNB 2 for starting to hand over the UE 1 from the LTE system to the NG system. Step 501 corresponds to Figure 3A Step 302 in or Figure 4A Step 402 in .

[0134] In step 502, the core network sends a (NR) handover request message containing slice information about a network slice included in the NG core 5 and to which the UE 1 will be connected after the handover to the target NR NB 3. Step 502 corresponds to Figure 3A Step 305 in or Figure 4A Step 404 in .

[0135] In step 503, the core network receives a (NR) handover request reply message containing a target-to-source transparent container from the target NR NB 3. The target-to-source transparent container contains radio resource configuration information (e.g., radio parameters) necessary for UE 1 to establish a radio connection associated with the NG system. Step 503 corresponds to Figure 3A Step 306 in or Figure 4A Step 405 in .

[0136] In step 504, the core network sends a handover command message including a target to source transparent container to the source LTEeNB 2. Step 504 corresponds to Figure 3B Step 308 in or Figure 4B Step 406 in .

[0137] Figure 6 6 is a flow chart showing a process 600 as an example of a method performed by the target NR NB 3. In step 601, the target NR NB 3 receives a (NR) handover request message containing slice information about a network slice included in the NG core 5 and to which the UE 1 will be connected after the handover from the core network (i.e., the NG core 5). Step 601 corresponds to Figure 3A Step 305 in or Figure 4A Step 404 in .

[0138] In step 602, the target NR NB 3 sends a (NR) handover request reply message containing a target-to-source transparent container to the core network. The target-to-source transparent container contains radio resource configuration information (e.g., radio parameters) necessary for UE1 to establish a radio connection associated with the NG system. Step 602 corresponds to Figure 3A Step 306 in or Figure 4A Step 405 in .

[0139] In step 603, the target NR NB 3 establishes a radio connection associated with the NG system for UE 1 based on the radio resource configuration information. Step 603 corresponds to Figure 3B Step 310 in or Figure 4B Step 408 in .

[0140] Figure 7 7 is a flow chart showing a process 700 as an example of a method performed by the source LTE eNB 2. In step 701, the source LTE eNB 2 sends a handover required message to the core network (ie, the EPC 4 or the NG core 5) for starting handover of the UE 1 from the LTE system to the NG system. Step 701 corresponds to Figure 3A Step 302 or Figure 4A Step 402.

[0141] In step 702, the source LTE eNB 2 receives a handover command message from the core network containing a target-to-source transparent container. The target-to-source transparent container contains the radio resource configuration information necessary for UE 1 to establish a radio connection associated with the NG system supporting network slicing. Step 702 corresponds to Figure 3B Step 308 in or Figure 4B Step 406 in .

[0142] In step 703, the source LTE eNB 2 sends a mobility command message (eg, a handover command message) to the UE 1, which includes radio resource configuration information and indicates handover to the bearerless network. Step 703 corresponds to Figure 3B Step 309 in or Figure 4B Step 407 in .

[0143] Figure 8 8 is a flow chart illustrating a process 800 as an example of a method performed by UE 1. In step 801, UE 1 receives a mobility command message (e.g., a handover command message) from a source LTE eNB 2. The mobility command message contains radio resource configuration information necessary for UE 1 to establish a radio connection associated with the NG system. Step 801 corresponds to Figure 3B Step 309 in or Figure 4B Step 407 in .

[0144] In step 802, UE 1 establishes a radio connection with a target NR NB 3 associated with the NG system by using the radio resource configuration information. Step 802 corresponds to Figure 3B Step 310 in or Figure 4B Step 408 in .

[0145] In this embodiment, the network may be configured to enable UE 1 to know in advance whether the handover target cell (i.e., NR cell) supports network slicing. For example, NR NB 3 may broadcast system information (e.g., system information block type x: SIBx, e.g., x=1), which includes network slicing support information that explicitly or implicitly indicates that network slicing is supported in the NR cell (or that connection to an NG core that can provide network slicing is possible). In order to indicate support for network slicing, the explicitly transmitted network slicing support information may also include the type of supported services (e.g., supported service type) or the supported slice type (e.g., supported slice type). In contrast, the explicitly transmitted network slicing support information may include information about different radio resource configurations per network slice. UE 1 may know that network slicing is supported in the cell when detecting that at least a portion of the received radio resource configuration is specified per network slice. The information about the radio resource configuration may include configuration information about physical resources, or system configuration information, or both. The configuration information about physical resources may indicate at least one of the following: code, time, frequency, and RACH preamble sequence (group). The system configuration information may indicate at least one of the following: subcarrier spacing, sampling rate, TTI, and subframe / frame format type. The network slicing support information may be transmitted as NAS layer information or may be transmitted as AS layer information. In the former case, the AS layer (ie, RRC) of UE 1 receives the information and transmits it to the NAS layer.

[0146] The detailed process of handover from the LTE system to the NG system according to the present embodiment is not limited to the specific examples described above. For example, the names of the messages in the handover process are not limited to those shown in the several examples described above. In the several examples described above of the handover process, the order of the messages may be changed and some of them may be omitted. Further, they may include one or more additional messages.

[0147] As understood from the above description, the process of handover from an LTE system that does not support network slicing to an NG system that supports network slicing according to this embodiment includes the following steps. That is, the target NR NB 3 receives slice information about the network slice to which the UE 1 will be connected from the NG core 5. After receiving the slice information, the target NR NB 3 creates radio resource configuration information to be used by the UE 1 in the NG system (i.e., NR NB 3) after the handover, and transmits the created radio resource configuration information to the UE 1 through the LTE system (i.e., LTEeNB 2). In this way, the UE 1 uses the radio resource configuration information created by the target NR NB 3 based on the slice information, thereby appropriately configuring one or both of the AS layer and the NAS layer of the target RAT associated with the NG system that supports network slicing.

[0148] Second embodiment

[0149] This embodiment provides a modified example of the method for handing over UE 1 from the LTE system to the NG system according to the first embodiment. Fig. 9 Shows Figure 1 An example of a procedure for handing over UE 1 from the LTE system to the NG system in the configuration example of the radio communication network shown in . Fig. 9 The handover process shown in Figure 3A and Figure 3B Details and modifications of the handover process shown in . In particular, Fig. 9 The configuration within the NG Core 5 and the selection of network slices performed by the NG Core 5 are shown in a specific manner.

[0150] Fig. 9 The NG core 5 shown in the figure includes a common network function (NF) 51, a network function for network slicing (NF for slice A) 52, a network function for network slice B (NF for slice B) 53 and a home subscriber server (HSS) 54.

[0151] Note that each network element (ie, NF) is a component of a network slice. Each network slice includes the network functions (NFs) necessary to provide the required telecommunication services and network capabilities. Each network element (NF) is a processing function in the network and defines functional behaviors and interfaces.

[0152] Each network element may be implemented as a network element on dedicated hardware, as a software instance running on dedicated hardware, or as a virtualized function instantiated on an appropriate platform.

[0153] Each network slice may be identified by a specific network slice specific instance ID (NSI-ID). Each network function (NF) may be identified by a network function ID (NF ID). When a common control plane network function (common CP NF) exists (or is used), the NSI-ID may be a combination of the common CP NF ID and a slice specific ID (i.e., the NF ID for the selected slice).

[0154] Fig. 9 The public NF 51 shown in FIG. 5 includes a control plane network function (CP NF). The public NF 51 may also include a user plane network function (UP NF). The NF for slice A 52 includes a UP NF and may also include a CP NF. Similarly, the NF for slice B 53 includes a UP NF and may also include a CP NF.

[0155] Fig. 9An example is shown in which a slice selection function (SSF) is located in common with the public NF 51. However, the SSF may be located separately from the public NF 51. In this case, the public NF 51 exchanges messages with the SSf. The SSF selects a network slice to be associated with the UE 1. For example, the SSF may associate the UE 1 with a default network slice. Additionally or alternatively, the SSF may associate the UE 1 with a network slice (or slice type) that has been specified by the UE 1. Further, the SSF may provide a NAS node selection function (NNSF) to select a CP NF (or CP NFID) corresponding to the selected slice. Note that the default network slice may be configured per public land mobile network (PLMN), per RAT, per UE usage type, per service type, or per slice type.

[0156] Allocating one or more packet flows of UE 1 to a network slice may be performed according to one of the three examples described below. In the first example, the NG system including the NR NB 3 and the NG core 5 supports bearer-based delivery using per QoS class and per PDU session. As already explained, the bearers in the NG system may be referred to as NG-EPS bearers and the radio access bearers in the NG system may be referred to as NG-RABs. In the first example, each bearer is allocated to a network slice. In some embodiments, the common NF 51 communicates with a specific slice user plane NF (SUNF) of the network slice selected for UE 1 and establishes a bearer for UE 1 in the SUNF.

[0157] In the second example, similar to the first example, the NG system including the NR NB 3 and the NG core 5 supports bearer-based transmission using per QoS level and per PDU session. The bearers in the NG system can be used for the transmission of multiple packet flows (e.g., PDU flows). In the second example, the NG system is configured to distinguish between data flows (e.g., PDU flows) in the bearer and perform QoS processing (e.g., discarding of packets) on a per data flow basis (e.g., on a per PDU flow basis). In the second example, each packet flow (e.g., PDU flow) of the UE 1 is allocated to a network slice on a per flow basis (e.g., on a per PDU flow basis).

[0158] In the third example, the NG system including the NR NB 3 and the NG core 5 supports flow-based transmission of user data. In the third example, a network slice is configured per PDU session of the UE 1. In other words, a set of packet flows (e.g., PDU flows) included in one PDU session is commonly allocated to the network slice.

[0159] In step 901, UE 1 is connected to LTE eNB 2 and is in a connected state (i.e., RRC_Connected). UE 1 sends network slice assistance information to LTE eNB 2. LTE eNB 2 sends the received network slice assistance information to EPC 4. As already explained, the network slice assistance information may indicate, for example, the type of UE 1, the type of service desired by UE 1, or the acceptable latency of UE 1, or any combination thereof. The network slice assistance information may be NAS information and may be included in a measurement report sent from UE 1 to LTE eNB 2. Note that the transmission of the network slice assistance information performed by UE 1 may be omitted.

[0160] Step 902 corresponds to Figure 3A 303 in step 901. In particular, the source MME of EPC 4 sends a forward redirection request message to the target control node in the NG core 5 (in this example, the public NF 51). The forward redirection request message includes the EPS radio access bearer (E-RAB) QoS information element (IE). The E-RAB QoS IE indicates the QoS of the E-RAB of UE 1 (e.g., QoS class identifier (QCI), allocation and retention priority (ARP)). The forward redirection request message may also include network slice assistance information sent from the NAS layer of UE 1 (step 901).

[0161] In step 903, if necessary, the public NF 51 performs authentication of the UE 1. The authentication includes confirming the slices allowed (or authorized) for the UE 1 (slice authorization). In the slice authorization, the public NF 51 can decide / determine whether the UE 1 is allowed for each slice.

[0162] Fig. 9 Case A (i.e., steps 904 to 906) and case B (i.e., steps 907 and 908) are shown. Either case A or case B is performed. Case A corresponds to a case where at least one network slice is allowed to UE 1 or where at least one network slice is suitable for an ongoing service performed by UE 1 or a service requested by UE 1. In contrast, case B corresponds to a case where no network slice is allowed to UE 1 or where no network slice is suitable for an ongoing (or multiple) service performed by UE 1 or a service requested by UE 1.

[0163] In case A, the public NF 51 selects a slice (step 904). In other words, the public NF 51 selects a network slice to be associated with the UE 1. Fig. 9In the example shown in , the public NF 51 selects slice A for UE 1. The slice selection in step 904 may be performed per ongoing service performed by UE 1 or per service requested by UE 1 (e.g., EPS bearer / E-RAB, IP flow). As already described, the slice selection in step 904 may be performed by an SSF located separately from the public NF 51.

[0164] Step 905 corresponds to Figure 3A 304 in step 304. The public NF 51 communicates with the UP NF (i.e., the NF for slice A 52) of the slice selected for the UE 1 (in this example, slice A) to create a bearer-free session in the selected slice. Note that when the NG system supports bearer-based transmission of user data and when relocation of the transmission node is not required, the public NF 51 can perform a bearer modification procedure instead of a session creation procedure.

[0165] Step 906 corresponds to Figure 3A Step 305 in. In particular, the public NF 51 sends a NR handover request message to the target NR NB 3. The NR handover request message includes information about the network slice selected by the public NF 51 (or SSF) (i.e., a slice information information element (IE)). The slice information IE may contain, for example, an NSI ID indicating the selected network slice, an NF ID indicating the selected network function (NF), or a multi-dimensional descriptor (MDD), or any combination thereof. The MDD can be provided by the UE in the RRC signaling layer and the NAS signaling layer. The MDD represents a tenant ID and a service descriptor / slice type. The service descriptor / slice type indicates a service or use case associated with the UE 1 or with the selected network slice (e.g., eMBB, mMTC, URLLC, or crisis communication (CriC)).

[0166] In case B, the public NF 51 does not perform slice selection. Step 907 corresponds to Figure 3A In step 304 of . In order to create a bearer-free session in a predetermined network slice, the public NF 51 communicates with the UP NF of the slice. The predetermined network slice may be a network slice to which the public NF 51 belongs. Note that when the NG system supports bearer-based transmission of user data and when relocation of the transmission node is not required, the public NF 51 may perform a bearer modification procedure instead of a session creation procedure.

[0167] Step 908 corresponds to Figure 3AStep 305 in. Public NF 51 sends an NR handover request message to the target NR NB 3. The NR handover request message does not include information about the network slice (i.e., the slice information IE). Alternatively, the NR handover request message may include a slice information IE about a predetermined network slice (e.g., a network slice to which public NF 51 belongs).

[0168] Fig.10 yes Figure 2 An example of a procedure for handing over UE 1 from the LTE system to the NG system in the configuration example of the radio communication network shown in . Fig.10 The handover process shown in Figure 4A and Figure 4B Details and modifications of the handover process shown in . In particular, Fig.10 The configuration in the NG Core 5 and the selection of network slices performed by the NG Core 5 are shown in a specific manner.

[0169] In step 1001, UE 1 is connected to LTE eNB 2 and is in a connected state (ie, RRC_Connected). UE 1 sends network slice assistance information to LTE eNB 2. The network slice assistance information may be NAS information and may be included in a measurement report sent from UE 1 to LTE eNB 2. Note that the transmission of the network slice assistance information performed by UE 1 may be omitted.

[0170] Step 1002 corresponds to Figure 4A In step 402 of . In particular, the LTE eNB 2 sends a handover required message to the public NF 51 in the NG core 5. The handover required message includes the E-RAB QoS IE. The handover required message may also include network slice assistance information sent from the NAS layer of the UE 1 (step 1001).

[0171] The process in steps 1003 to 1008 is the same as Fig. 9 The processes in steps 903 to 908 are similar.

[0172] According to the handover process from the LTE system to the NG system according to this embodiment, the NG core 5 can provide the target NR NB 3 with information about the network slice selected by the public NF 51 for the UE 1 (i.e., the slice information IE). Therefore, for example, the target NR NB 3 can use this information about the network slice selected by the public NF 51 for the UE 1 to create or derive information or parameters to be included in the handover command (i.e., transparent container (RRCConnectionReconfiguration)) and to be sent to the UE 1. Further, the information about the network slice selected by the public NF 51 (i.e., the slice information IE) can be sent to the UE 1.

[0173] Third embodiment

[0174] This embodiment provides a modified example of the method for handing over UE 1 from the LTE system to the NG system according to the first embodiment. Fig.11 Shows Figure 1 An example of a procedure for handing over UE 1 from the LTE system to the NG system in the configuration example of the radio communication network shown in . Fig.11 The handover process shown in Figure 3A and Figure 3B Details and modifications of the handover process shown in . In particular, Fig.11 The configuration in the NG Core 5 and the selection of network slices performed by the NG Core 5 are shown in a specific manner.

[0175] Note that in the second embodiment described above Fig. 9 In the process shown in FIG. 9 , the slice selection (in step 904) is performed by the public NF 51 in the handover preparation phase. In contrast, in Fig.11 In the process shown in , the slice selection (in step 1109) is performed by the public NF 51 in the handover completion phase. This difference is mainly described below.

[0176] Step 1101 corresponds to Figure 3A In step 303 of the EPC 4, in particular, the source MME of the EPC 4 sends a forward redirection request message to the target control node (in this example, the public NF 51) in the NG Core 5. The forward redirection request message includes the E-RAB QoS IE.

[0177] Step 1102 corresponds to Figure 3AIn step 304 of . In order to create a bearer-free session in a predetermined network slice, the public NF 51 communicates with the UP NF of the slice. The predetermined network slice may be a network slice to which the public NF 51 belongs. Note that when the NG system supports bearer-based transmission of user data and when relocation of the transmission node is not required, the public NF 51 may perform a bearer modification procedure instead of a session creation procedure.

[0178] Step 1103 corresponds to Figure 3A 305 and 306 in the steps. The public NF 51 sends an NR handover request message to the target NR NB 3. The NR handover request message does not include information about the network slice (i.e., the slice information IE). Alternatively, the NR handover request message may include a slice information IE about a predetermined network slice (e.g., a network slice to which the public NF 51 belongs).

[0179] Step 1104 corresponds to Figure 3A Step 307 in the above. The public NF 51 sends a forward relocation response message to the MME in the EPC 4.

[0180] Step 1105 is the handover execution phase and corresponds to Figure 3B The handover execution phase (step 1105) includes transmitting a handover confirmation message for NR (e.g., an NR RRC connection reconfiguration complete message) from UE 1 to the target NR NB 3 (step 1106). The handover confirmation for NR message may include network slice assistance information. The network slice assistance information may be NAS information or RRC information.

[0181] Step 1106 corresponds to Figure 3B In step 312. In particular, the target NR NB 3 sends an NR handover notification message to the target control node (in this example, the public NF 51) in the NG core 5. The NR handover notification message may include network slice assistance information.

[0182] The process in step 1108 is the same as Fig. 9 The processes are similar to those in step 903 in . That is, if necessary, the public NF 51 performs authentication of the UE 1. The authentication includes confirming the slices allowed (or authorized) for the UE 1 (slice authorization). In the slice authorization, the public NF 51 can decide / determine whether the UE 1 is allowed for each slice.

[0183] Fig.11 Only reference is shown Fig. 9Case A is between Cases A and B described above. Case A corresponds to a case where at least one network slice is allowed to UE 1 or where at least one network slice is suitable for an ongoing service performed by UE 1 or a service requested by UE 1. In step 1109, public NF 51 selects a slice for UE 1. The process in step 1109 is the same as that in step 1109. Fig. 9 The process is similar to that in step 904 in .

[0184] Step 1110 corresponds to Figure 3B 314 in step 1102. That is, the public NF 51 performs the flow modification process. In particular, the public NF 51 changes the transmission node participating in the bearerless session created in step 1102 from the UP NF of the predetermined network slice (e.g., the network slice to which the public NF 51 belongs) to the UP NF of the slice A selected for the UE 1. For example, the public NF 51 may send a create session request message to the UP NF of the slice A selected for the UE 1 (i.e., the NF for slice A 52). In addition, the public NF 51 may transmit a delete session request message to the UPNF of the predetermined network slice (e.g., the network slice to which the public NF 51 belongs).

[0185] Further, in step 1110, the transport node of slice A (i.e., the UP NF of the NF for slice A52) may communicate with the edge node (i.e., the eP-GW) in EPC 4 to notify the edge node (i.e., the (e)P-GW) in EPC 4 of the relocation of the transport node or the change of the RAT type due to the inter-RAT HO. In particular, the transport node of slice A (i.e., the UP NF of the NF for slice A52) may send a per-session (i.e., per-PDN connection) modify bearer request message to the edge node in EPC 4. The edge node in EPC 4 may send a modify bearer response message to the transport node of slice A (i.e., the UP NF of the NF for slice A52).

[0186] In step 1111, the public NF 51 transmits information about the network slice selected for UE 1 (i.e., Slice Information IE) to UE 1. When the NF for slice A 52 has a CP NF, the transmission in step 1111 may be performed by the NF for slice A 52. The Slice Information IE may be NAS information and may be transmitted from the target NR NB 3 to the UE 1 by using an RRC:DL INFORMATION TRANSFER message. Alternatively, the Slice Information IE may be RRC information and may be transmitted from the target NR NB 3 to the UE 1 by using an RRC:RRC CONNECTION RECONFIGURATION message.

[0187] Fig.12 yes Figure 2An example of a procedure for handing over UE 1 from the LTE system to the NG system in the configuration example of the radio communication network shown in . Fig.12 The handover process shown in Figure 4A and Figure 4B The details and modifications of the handover process shown in FIG. 1 and FIG. 2 are shown in more detail. In particular, Fig.12 The configuration in the NG Core 5 and the selection of network slices performed by the NG Core 5 are shown in a specific manner.

[0188] Step 1201 corresponds to Figure 4A In step 402 of . In particular, the LTE eNB 2 sends a handover required message to the common NF 51 in the NG Core 5. The handover required message includes the E-RAB QoS IE.

[0189] Step 1202 corresponds to Figure 4A Step 403 in step 1202. Fig.11 The processes in step 1102 are similar. Step 1203 corresponds to Figure 4A The process in step 1203 is the same as steps 404 and 405. Fig.11 The processes are similar to those in step 1103 in .

[0190] Step 1204 corresponds to Figure 4B The public NF 51 sends a handover command message to the source LTE eNB 2.

[0191] Step 1205 is the handover execution phase and corresponds to Figure 4B The handover execution phase (step 1205) includes transmitting a handover confirmation message for NR (e.g., an NR RRC connection reconfiguration complete message) from UE 1 to the target NR NB 3 (step 1206). The handover confirmation for NR message may include network slice assistance information. The network slice assistance information may be NAS information or RRC information.

[0192] The process in steps 1207 to 1211 is the same as Fig.11 The processes are similar to those in steps 1107 to 1111 in .

[0193] According to the handover process from the LTE system to the NG system according to this embodiment, the NG core 5 can provide the target NR NB 3 with information about the network slice selected by the public NF 51 for the UE 1 (i.e., NSI-ID, MDD or NFID). Therefore, for example, the target NR NB 3 can create or derive information or parameters to be included in the handover command (i.e., transparent container (RRCConnectionReconfiguration)) and to be sent to the UE 1 using this information about the network slice selected by the public NF 51 for the UE 1. Further, information about the network slice selected by the public NF 51 (i.e., slice information IE) can be sent to the UE 1.

[0194] Fourth embodiment

[0195] This embodiment provides a method for handing over UE 1 from an NG system that supports network slicing to an LTE system that does not support network slicing. Fig.13A and Fig. 13B Shows Figure 1 An example of a process for handing over UE1 from the NG system to the LTE system in the configuration example of the radio communication network shown in . Fig.13A shows the handover preparation phase and Fig. 13B The handover execution phase is shown.

[0196] exist Fig.13A and Fig. 13B In the process shown in , the source base station (i.e., NR NB 3) starts the handover by sending a handover request message on the interface (or reference point) between the source base station (i.e., NR NB3) and the core network (i.e., NG Core 5). Fig.13A and Fig. 13B The process shown in may be an enhancement / evolution of the "UTRAN Iu mode to E-UTRAN Inter-RAT handover" in LTE. Fig.13A and Fig. 13B The process shown in may be an enhancement / evolution of “S1 based handover” with respect to MME relocation in LTE.

[0197] In step 1301, UE 1 is connected to NR NB 3 and is in a connected state (e.g., RRC_Connected). UE 1 receives measurement configuration from NR NB 3, performs neighbor cell measurement and inter-RAT measurement (including measurement of NG-RAN cells and E-UTRAN (LTE) cells) per the received measurement configuration, and sends a measurement report to NR NB 3.

[0198] In step 1302, NR NB 3 determines to perform an inter-RAT handover on the cell of LTE eNB 2 and sends a handover request message to the source control node in the NG core 5. The handover request message includes an identifier of the target LTE eNB 2. Further, the handover request message may include a handover type information element (IE) indicating that it is handing over from NR to LTE. For example, "NR to LTE (NRtoLTE)" is set in the handover type IE. Alternatively, the handover request message may include a target LTEeNB identifier information element (IE). The handover request message may include a source to target transparent container IE.

[0199] In step 1303, the source control node in the NG core 5 determines that the type of handover is an inter-RAT handover for the LTE system based on the handover type IE or the target LTE eNB identifier contained in the received handover request message. The source control node in the NG core 5 selects a target MME in the EPC 4. The source control node in the NG core 5 sends a forward relocation request message to the target MME to start handover resource allocation. The forward relocation request message contains a mobility management (MM) context and all PDU sessions that are valid for UE 1 in the source system (i.e., the NG system). Each PDN session includes a list of associated APNs and PDU flow contexts. The MM context includes information about the PDU flow and security-related information. The forward relocation request message also includes information for identifying one or more service data flows associated with each PDU flow context (e.g., an SDF template or a service flow template (TFT)).

[0200] In step 1304, the target MME in the EPC 4 performs a process for creating a bearer-based session. In particular, the target MME determines that the packet transfer node (or gateway) for the UE 1 needs to be relocated and selects a target transfer node (i.e., S-GW) in the EPC 4. The target MME sends a create session request message to the target S-GW. The create session request message may also include information for identifying one or more service data flows associated with each PDU flow context (e.g., SDF template or traffic flow template (TFT)). This information for identifying one or more service data flows is derived from the forward relocation request message, which has been sent from the source control node in the NG core 5 to the target MME in the EPC 4. The target S-GW allocates its local resources and sends a create session response message to the target MME.

[0201] In step 1305 , the target MME in the EPC 4 sends a handover request message to the target LTE eNB 2 .

[0202] In step 1306, upon receiving the handover request message, the target LTE eNB 2 creates a UE context and a security context including information about the EPS bearer and allocates resources. The target LTE eNB 2 then sends a handover request reply message containing a target to source transparent container to the target MME.

[0203] In step 1307, the target MME in the EPC 4 sends a forward relocation response message containing a target to source transparent container to the source control node in the NG core 5. The forward relocation response message may also include the address and TEID allocated for downlink data forwarding. When indirect downlink forwarding is used, these addresses and TEIDs may be the addresses and TEIDs of the transmitting node in the NG core 5. When direct downlink forwarding is used, these addresses and TEIDs may be the addresses and TEIDs of the target LTEeNB 2.

[0204] In step 1308, the source control node sends a handover command message containing a target to source transparent container to the source NRNB 3. The handover command message may also contain a list of flows subject to downlink data forwarding (e.g., a flow list subject to data forwarding). The "Flows Subject to Data forwarding list" IE includes, for example, an address and TEID for user service data forwarding, and an identifier of a flow subject to data forwarding (e.g., a PDU flow). The source NRNB 3 starts data forwarding for the flow (e.g., a PDU flow) specified by the "Flows Subject to Data forwarding list" IE.

[0205] In step 1309, the source NR NB 3 sends an RRC message containing a handover command message to the UE 1. The handover command message includes a transparent container containing the radio resource configuration information that has been established by the target LTE eNB 2 in the preparation phase. The RRC message can be, for example, a mobility command message or an RRC connection reconfiguration message from the NR.

[0206] In step 1310, upon receiving the RRC message containing the handover command message, UE1 moves to the target RAN (i.e., E UTRAN) and performs handover according to the radio resource configuration information provided by the handover command message. That is, UE 1 establishes a radio connection with a target LTE eNB 2 associated with a bearer-based network (i.e., LTE system). In step 1311, UE 1 sends a handover confirmation for EUTRA message to the target LTE eNB 2 after it has successfully synchronized with the target cell. The message in step 1311 may be an RRC connection reconfiguration complete message.

[0207] In step 1312, when UE 1 has successfully accessed target LTE eNB 2, target LTE eNB 2 notifies the target MME in EPC 4 by sending a handover notification message.

[0208] In step 1313, the target MME in the EPC 4 recognizes that the UE 1 has arrived at the target side and notifies it to the source control node in the NG Core 5 by sending a forward relocation complete notification message. The source control node sends a forward relocation complete response message to the target MME.

[0209] In step 1314, the target MME in the EPC 4 performs a bearer modification procedure and thereby completes the inter-RAT handover procedure. For example, the target MME may transmit a per-session (i.e., per-PDN connection) modify bearer request message to the (e)S-GW in the EPC 4. The modify bearer request message may contain a bearer identifier (e.g., EPS bearer ID) and also contain an address and a downlink (DL) TEID of the target LTE eNB2. The (e)S-GW in the EPC 4 may communicate with the edge node in the NG core 5 to inform the edge node in the NG core 5 of the relocation of the transmitting node or the change of the RAT type due to the inter-RAT HO. In particular, the S-GW in the EPC 4 may send a modify flow request message to the edge node in the NG core 5 per bearer-free session (i.e., per PDU session). The edge node in the NG core 5 may send a modify flow response message to the S-GW in the EPC 4. The S-GW in the EPC 4 may send a modify bearer response message to the target MME.

[0210] Fig.14A and Fig. 14B Shows Figure 2 An example of a procedure for handing over UE 1 from the NG system to the LTE system in the configuration example of the radio communication network shown in . Fig.14A shows the handover preparation phase and Fig. 14B The handover execution phase is shown.

[0211] and Fig.13A and Fig. 13B Similar to the process shown in Fig.14A and Fig. 14B In the process shown in FIG. 1 , the source base station (ie, NR NB 3) starts the handover by sending a handover request message on the interface between the source base station (ie, NR NB 3) and the core network (ie, NG core 5). Fig.13A and Fig. 13B Similar to the process shown in Fig.14A and Fig. 14BThe procedure shown in may be an enhancement / evolution of “UTRAN Iu mode to E-UTRAN Inter-RAT handover” in LTE, or may be an enhancement / evolution of “S1 based handover” regarding MME relocation in LTE.

[0212] Fig.14A The process in steps 1401 to 1405 in Fig.13A The processes in steps 1301 to 1307 are similar. Fig.14A In the process shown in Fig.13A Processes corresponding to those in steps 1303 and 1307 are executed within the NG core 5.

[0213] Fig. 14B The process in steps 1406 to 1411 in Fig. 13B The processes in steps 1308 to 1314 are similar. Fig. 14B In the process shown in Fig. 13B Processes corresponding to those in step 1313 are executed within the NG core 5.

[0214] The detailed process of handover from the NG system to the LTE system according to the present embodiment is not limited to the specific examples described above. For example, the names of the messages in the handover process are not limited to those shown in the several examples described above. In the several examples described above of the handover process, the order of the messages may be changed and some of them may be omitted. Further, they may include one or more additional messages.

[0215] The following provides configuration examples of UE 1, LTE eNB 2, NR NB 3 and core network nodes according to the embodiments described above. Fig.15 1501 is a block diagram showing a configuration example of UE 1. LTE transceiver 1501 performs analog RF signal processing related to the PHY layer of LTE RAT to communicate with LTE eNB 2. The analog RF signal processing performed by LTE transceiver 1501 includes frequency up-conversion, frequency down-conversion, and amplification. LTE transceiver 1501 is coupled to antenna 1502 and baseband processor 1505. That is, LTE transceiver 1501 receives modulation symbol data (or OFDM symbol data) from baseband processor 1505, generates a transmission RF signal, and supplies the generated transmission RF signal to antenna 1502. Further, LTE transceiver 1501 generates a baseband reception signal based on the reception RF signal received by antenna 1502, and supplies the generated baseband reception signal to baseband processor 1505.

[0216] The new radio (NR) transceiver 1503 performs analog RF signal processing related to the PHY layer of the NG RAT to communicate with the NRNB 3. The new 5G transceiver 1503 is coupled to an antenna 1504 and a baseband processor 1505.

[0217] The baseband processor 1505 performs digital baseband signal processing (i.e., data plane processing) and control plane processing for radio communication. Digital baseband signal processing includes (a) data compression / decompression, (b) data segmentation / concatenation, (c) composition / decomposition of a transmission format (i.e., a transmission frame), (d) channel coding / decoding, (e) modulation (i.e., symbol mapping) / demodulation, and (f) generation of OFDM symbol data (i.e., baseband OFDM signal) generated by an 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 regarding attachment, mobility, and packet communication).

[0218] In the case of LTE or LTE-Advanced, for example, the digital baseband signal processing performed by the baseband processor 1505 may include signal processing of a packet data convergence protocol (PDCP) layer, a radio link control (RLC) layer, a medium access control (MAC) layer, and a physical (PHY) layer. Further, the control plane processing performed by the baseband processor 1505 may include processing of a non-access stratum (NAS) protocol, an RRC protocol, and a MAC CE.

[0219] The baseband processor 1505 may include a modem processor (e.g., a digital signal processor (DSP)) that performs digital baseband signal processing and a protocol stack processor (e.g., a central processing unit (CPU) or a microprocessing unit (MPU)) that performs control plane processing. In this case, the protocol stack processor that performs control plane processing may be integrated with the application processor 1506 described below.

[0220] The application processor 1506 may also be referred to as a CPU, an MPU, a microprocessor, or a processor core. The application processor 1506 may include a plurality of processors (processor cores). The application processor 1506 loads a system software program (operating system (OS)) and various application programs (e.g., a communication application for collecting metering data or sensing data) from the memory 1508 or from another memory (not shown) and executes these programs, thereby providing various functions of the UE 1.

[0221] In some embodiments, as by Fig.15The dotted line (1507) in the figure indicates that the baseband processor 1505 and the application processor 1506 can be integrated on a single chip. In other words, the baseband processor 1506 and the application processor 1506 can be implemented in a single system on chip (SoC) device 1507. The SoC device can be called a system large-scale integrated circuit (LSI) or a chipset.

[0222] The memory 1508 is a volatile memory, a non-volatile memory, or a combination thereof. The memory 1508 may include a plurality of memory devices that are physically independent of each other. The volatile memory is, for example, a static random access memory (SRAM), 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, a hard disk drive, or any combination thereof. The memory 1508 may include, for example, an external memory device that can be accessed by the baseband processor 1505, the application processor 1506, and the SoC 1507. The memory 1508 may include an internal memory device integrated in the baseband processor 1505, the application processor 1506, or the SoC 1507. Further, the memory 1508 may include a memory in a universal integrated circuit card (UICC).

[0223] The memory 1508 may store one or more software modules (computer programs) 1509, including instructions and data for executing the processing by the UE 1 described in the above embodiments. In some implementations, the baseband processor 1505 or the application processor 1506 may load one or more software modules 1509 from the memory 1508 and execute the loaded software modules, thereby executing the processing of the UE 1 described in the above embodiments.

[0224] Fig.16 is a block diagram showing a configuration example of an LTE eNB 2 according to the embodiment described above. Fig.16 As shown in FIG. 1 , LTE eNB 2 includes an LTE transceiver 1601, a network interface 1603, a processor 1604, and a memory 1605. The LTE transceiver 1601 performs analog RF signal processing to communicate with UEs supporting LTE RAT, including UE 1. The LTE transceiver 1601 may include a plurality of transceivers. The LTE transceiver 1601 is connected to an antenna 1602 and a processor 1604. The LTE transceiver 1601 receives modulation symbol data (or OFDM symbol data) from the processor 1604, generates a transmission RF signal, and supplies the generated transmission RF signal to the antenna 1602. Further, the LTE transceiver 1601 generates a baseband reception signal based on the reception RF signal received by the antenna 1602, and supplies the signal to the processor 1604.

[0225] The network interface 1603 is used to communicate with network nodes, such as the MME and S-GW in the EPC 4. The network interface 1603 may include, for example, a network interface card (NIC) compliant with the IEEE 802.3 series.

[0226] Processor 1604 performs digital baseband signal processing (i.e., data plane processing) and control plane processing for radio communication. In the case of LTE or LTE-Advanced, the digital baseband signal processing performed by processor 1604 may include signal processing of the PDCP layer, RLC layer, MAC layer, and PHY layer. Further, the control plane processing performed by processor 1604 may include processing of the S1 protocol, RRC protocol, and MAC CE.

[0227] The processor 1604 may include a plurality of processors. The processor 1604 may include, for example, a modem processor that performs digital baseband signal processing and a protocol stack processor (eg, a CPU or an MPU) that performs control plane processing.

[0228] The memory 1605 includes a combination of volatile memory and non-volatile memory. The volatile memory is, for example, SRAM, DRAM, or a combination thereof. The non-volatile memory is, for example, MROM, PROM, flash memory, hard disk drive, or a combination thereof. The memory 1605 may include a storage device located separately from the processor 1604. In this case, the processor 1604 may access the memory 1605 through the network interface 1603 or an I / O interface (not shown).

[0229] The memory 1605 may store one or more software modules (computer programs) 1606, including instructions and data for performing processing by the LTE eNB described in the above embodiments. In some implementations, the processor 1604 may load one or more software modules 1606 from the memory 1605 and execute the loaded software modules, thereby performing the processing of the LTE eNB described in the above embodiments.

[0230] Fig.17 is a block diagram showing a configuration example of NR NB 3 according to the embodiment described above. Fig.17As shown in FIG. 1 , NR NB 3 includes a new radio (NR) transceiver 1701, a network interface 1703, a processor 1704, and a memory 1705. The NR transceiver 1701 performs analog RF signal processing to communicate with UEs supporting NG RAT, including UE 1. The NR transceiver 1701 may include a plurality of transceivers. The NR transceiver 1701 is connected to an antenna 1702 and a processor 1704. The NR transceiver 1701 receives modulation symbol data from the processor 1704, generates a transmission RF signal, and supplies the generated transmission RF signal to the antenna 1702. Further, the NR transceiver 1701 generates a baseband reception signal based on the reception RF signal received by the antenna 1702, and supplies the signal to the processor 1704.

[0231] The network interface 1703 is used to communicate with network nodes, such as a control node and a transmission node in the NG core 5. The network interface 1703 may include, for example, a network interface card (NIC) compliant with the IEEE 802.3 series.

[0232] Processor 1704 performs digital baseband signal processing (ie, data plane processing) and control plane processing for radio communication. Processor 1704 may include multiple processors. Processor 1704 may include, for example, a modem processor that performs digital baseband signal processing and a protocol stack processor (eg, CPU or MPU) that performs control plane processing.

[0233] The memory 1705 includes a combination of volatile memory and non-volatile memory. The volatile memory is, for example, SRAM, DRAM, or a combination thereof. The non-volatile memory is, for example, MROM, PROM, flash memory, hard disk drive, or a combination thereof. The memory 1705 may include a storage device located separately from the processor 1704. In this case, the processor 1704 may access the memory 1705 through the network interface 1703 or an I / O interface (not shown).

[0234] The memory 1705 may store one or more software modules (computer programs) 1706, including instructions and data for performing the processing described in the above embodiments by the NR NB 3. In some embodiments, the processor 1704 may load one or more software modules 1706 from the memory 1705 and execute the loaded software modules, thereby performing the processing of the NR NB 3 described in the above embodiments.

[0235] Fig.18 1 is a block diagram showing a configuration example of a core network node 1800 according to the embodiment described above. The core network node 1800 is, for example, an MME in the EPC 4 or a control node in the NG core 5. Fig.18As shown in FIG. 1 , the core network node 1800 includes a network interface 1801, a processor 1802, and a memory 1803. The network interface 1801 is used to communicate with a network node (e.g., a RAN node or other core network node). The network interface 1801 may include, for example, a network interface card (NIC) compliant with the IEEE 802.3 series.

[0236] The processor 1802 may be, for example, a microprocessor, an MPU, or a CPU. The processor 1802 may include a plurality of processors.

[0237] The memory 1803 includes a combination of a volatile memory and a non-volatile memory. The volatile memory is, for example, an SRAM, a DRAM, or a combination thereof. The non-volatile memory is, for example, an MROM, a PROM, a flash memory, a hard disk drive, or a combination thereof. The memory 1803 may include a storage device located separately from the processor 1802. In this case, the processor 1802 may access the memory 1803 through the network interface 1801 or an I / O interface (not shown).

[0238] The memory 1803 may store one or more software modules (computer programs) 1804, including instructions and data for executing processing in the core network node described in the above embodiments (e.g., an MME in the EPC 4 or a control node in the NG core 5). In some implementations, the processor 1802 may load one or more software modules 1804 from the memory 1803 and execute the loaded software modules, thereby performing the processing of the core network node described in the above embodiments.

[0239] As reference Figures 15 to 18As described above, each of the processors included in the UE 1, LTE eNB 2, NR NB 3 and core network nodes in the above embodiments executes one or more programs, which include an instruction set that causes the computer to execute the algorithm described above with reference to the accompanying drawings. These programs can be stored in various types of non-transitory computer-readable media and thus supplied to the computer. Non-transitory computer-readable media include various types of tangible storage media. Examples of non-transitory computer-readable media include magnetic recording media (such as floppy disks, tapes, and hard disk drives), magneto-optical recording media (such as magneto-optical disks), compact disk read-only memories (CD-ROMs), CD-Rs, CD-R / Ws, and semiconductor memories (such as mask ROMs, programmable ROMs (PROMs), erasable PROMs (EPROMs), flash ROMs, and random access memories (RAMs)). These programs can be supplied to the computer using various types of temporary computer-readable media. Examples of temporary computer-readable media include electrical signals, optical signals, and electromagnetic waves. Temporary computer-readable media can be used to supply programs to the computer via wired communication lines (e.g., wires and optical fibers) or wireless communication lines.

[0240] Fifth embodiment

[0241] This embodiment provides specific examples of the RRC messages and control messages (ie, S1 and NG2 messages) between the RAN and the core network described in the above embodiments.

[0242] Fig.19A and 19B An example of the format of a Mobility From EUTRA Command message is shown. In the case of handover from an LTE system to a NG system, the MobilityFromEUTRACommand message includes a purpose set to "handover" and a targetRAT-Type set to "ngutra" corresponding to the NG RAN. Further, the MobilityFromEUTRACommand message includes a targetRAT-MessageContainer. The targetRAT-MessageContainer contains an RRCConnectionReconfigurationNR message created by the target NR NB 3. Moreover, when the targetRAT type is "OTHERRAN" (i.e., "utra", "geran" or "ngutra"), the MobilityFromEUTRACommand message includes nas-SecurityParamFromEUTRA.

[0243] Fig. 20 FIG. 4 shows a handover required message (eg, Figure 3A The handover request message includes a handover type set to "LTE to NR" and a source to target transparent container.

[0244] Fig.21 FIG. 2 shows a handover required message (eg, a message sent from an LTE eNB 2 to a control node (eg, a common control plane NF (CCNF)) over an NG2 interface. Figure 4A The handover request message includes a handover type set to "LTE to NR" and a source to target transparent container. Further, the handover request message includes a CCNF UE NG2AP ID and an eNB UE NG2AP ID. The CCNF UE NG2AP ID is an identifier assigned by a control node (e.g., CCNF) in the NG Core 5 to identify UE 1 on the NG2 interface. The eNB UE NG2AP ID is an identifier assigned by the LTE eNB 2 to identify UE 1 on the NG2 interface.

[0245] Figures 22 to 24 Several examples of the format of the Source NR NB to Target NR NB transparent container contained in the Handover Required message are shown. Fig. 22 In the example shown in , the source NR NB to target NR NB transparent container includes an RRC container and a NextGen (NG)-RAB information list. The RRC container includes an RRC handover preparation information message. The NG-RAB information list indicates a list of radio access bearers (e.g., NG-RABs) to be handed over from the LTE eNB 2 to the NR NB 3. When the NG system including the NR NB 3 and the NG core 5 is configured to support bearer-based delivery using per QoS class and per PDU session, it can be used Fig. 22 As already described, the bearer may be configured between a pair of network functions (NFs), for example between the NRNB 3 and a user plane function in the NG core 5 or between two user plane functions in the NG core 5. The bearer in the NG system may be referred to as an NG-EPS bearer and the radio access bearer in the NG system may be referred to as an NG-RAB.

[0246] Fig.23 The source NR NB to target NR NB transparent container shown in includes as shown in Fig. 22 RRC container and NG-RAB information list in the case of. However, Fig.23The NG-RAB information list shown in includes a flow information list indicating a list of packet flows (e.g., PDU flows) mapped to each NG-RAB. When the NG system including the NR NB 3 and the NG core 5 is configured to support bearer-based transmission using per QoS class and per PDU session and to distinguish between packet flows (e.g., PDU flows) in a bearer to perform QoS processing (e.g., discard of packets) on a per data flow basis (e.g., on a per PDU flow basis), the NG-RAB information list shown in FIG. 5 may be used to perform QoS processing (e.g., discard of packets) on a per data flow basis (e.g., on a per PDU flow basis). Fig.23 The format shown in .

[0247] Fig.24 The source NR NB to target NR NB transparent container shown in FIG may include one or both of a session information list and an NG-RAB information list. When the NG system including the NR NB 3 and the NG core 5 supports both bearer-based transmission and flow-based transmission, the Fig.24 Further, when the NG system including the NR NB 3 and the NG core 5 supports only stream-based transmission, the Fig.24 The format shown in .

[0248] Fig.25 FIG. 4 shows a (NR) Handover Request message (eg, Figure 3A Step 305 and Figure 4A The (NR) handover request message includes CCNF UE NG2AP ID. CCNF UE NG2AP ID is an identifier assigned by the control node (CCNF) in the NG core 5 to identify UE1 on the NG2 interface. Note that CCNF is only an example. That is, the names of other control plane network functions or nodes (e.g., CNF, CPF, SMF, and MMF) can be used instead of CCNF. The (NR) handover request message also includes a security context and NAS security parameters to NG-UTRAN. The security context indicates, for example, a next hop parameter (NH) and a next hop link counter parameter (NCC). In the case of a handover from E-UTRAN to NG RAN (NG-UTRAN), NAS security parameters to NG-UTRAN are included in the (NR) handover request message. The security context and NAS security parameters to NG-UTRAN can be configured per network slice.

[0249] Further, as in Fig.25In the example shown in , the (NR) Handover Request message includes a NG-RAB list to be set up. The NG-RAB list to be set up indicates a list of radio access bearers (e.g., NG-RABs) that should be established in the target NR NB 3. When the NG system including the NR NB 3 and the NG Core 5 is configured to support bearer-based delivery using per QoS class and per PDU session, the NG-RAB list can be used. Fig.25 The format shown in .

[0250] Fig.26 A modified example of a (NR) handover request message is shown. Fig.26 In the example shown in FIG. 1 , the (NR) handover request message includes the following information: Fig.25 NG-RAB list to be set in the case of Fig.26 The NG-RAB list to be set shown in includes a flow information list indicating a list of packet flows (e.g., PDU flows) mapped to each NG-RAB. When the NG system including the NR NB 3 and the NG core 5 is configured to support bearer-based transmission using per QoS class and per PDU session and to distinguish between packet flows (e.g., PDU flows) in the bearer to perform QoS processing (e.g., discard of packets) on a per data flow basis (e.g., on a per PDU flow basis), it can be used Fig.26 The format shown in .

[0251] Fig. 27 Another modified example of a (NR) Handover Request message is shown. Fig. 27 The (NR) handover request message shown in may include one or both of a session list to be set and a NG-RAB list to be set. The session list to be set includes information about one or more sessions of the UE 1 to be handed over. For example, the session list to be set includes per-session slice information. Fig. 27 The slicing information shown in corresponds to the slicing information described in the above embodiment. Further, the session list to be set includes a session endpoint identifier (SEID) per session. When the NG system including the NR NB 3 and the NG core 5 supports both bearer-based transmission and stream-based transmission, it can be used Fig. 27 Further, when the NG system including the NRNB 3 and the NG core 5 supports only stream-based delivery, the Fig. 27 The format shown in .

[0252] Fig.28An example of the format of slice information is shown. As described in detail in the first embodiment, the slice information includes an identifier of the network slice determined (or selected) for UE 1 (i.e., a network slice instance ID) and an identifier of a network function or node associated with the network slice (i.e., a network function ID). The slice information may include type information of the network slice (i.e., a multidimensional descriptor). Further, the slice information may include a mobility level or a session level or both.

[0253] Fig.29 An example of the format of a session endpoint ID is shown. As described in detail in the first embodiment, the session endpoint ID may be a GTP-TEID, a GRE-TEID, or an identifier of a network function or node (NF ID).

[0254] Fig.30 FIG. 4 shows a (NR) Handover Request Reply message (e.g., Figure 3A Step 306 and Figure 4A The (NR) Handover Request Reply message includes a target-to-source transparent container. The target-to-source transparent container includes radio resource configuration information (e.g., radio parameters) created by the target NR NB 3. Fig.31 As shown in , the target to source transparent container may include an RRC container, which contains an RRC NG-UTRA Handover Command message.

[0255] Further, as in Fig.30 In the example shown in , the (NR) Handover Request Reply message includes an accepted NG-RAB list. The accepted NG-RAB list indicates a list of radio access bearers (e.g., NG-RABs) for which resources have been prepared in the target cell. When the NG system including the NR NB 3 and the NG Core 5 is configured to support bearer-based delivery using per QoS class and per PDU session, the Fig.30 The format shown in .

[0256] Fig.32 A modified example of a (NR) Handover Request Reply message is shown. Fig.32 In the example shown in FIG. 1 , the (NR) handover request reply message includes the following information: Fig.30 List of recognized NG-RABs in the case of Fig.32The admitted NG-RAB list shown in includes a flow information list indicating a list of packet flows (e.g., PDU flows) mapped to each NG-RAB. When the NG system including the NR NB 3 and the NG core 5 is configured to support bearer-based transmission using per QoS class and per PDU session and to distinguish between packet flows (e.g., PDU flows) in a bearer to perform QoS processing (e.g., discard of packets) on a per data flow basis (e.g., on a per PDU flow basis), the NG-RAB list may be used. Fig.32 The format shown in .

[0257] Fig.33 Another modified example of a (NR) Handover Request Reply message is shown. Fig.33 The (NR) handover request response message shown in FIG. 1 may include one or both of an acknowledged session list and an acknowledged NG-RAB list. The acknowledged session list includes information about one or more sessions of UE 1 for which resources have been prepared in the target cell. When the NG system including the NR NB 3 and the NG core 5 supports both bearer-based transmission and flow-based transmission, the NG-RAB list may be used. Fig.33 Further, when the NG system including the NR NB 3 and the NG core 5 supports only stream-based transmission, the Fig.33 The format shown in .

[0258] Fig.34 Shows Fig.33 An example of the format of the forwarding address is shown in . The forwarding address includes one or both of information for downlink data forwarding (ie, DL transport layer address and DL session endpoint ID) and information for uplink data forwarding (ie, UL transport layer address and UL session endpoint ID).

[0259] Fig.35 FIG. 4 shows an S1AP Handover Command message (eg, Figure 3B The handover command message includes a list of E-RABs subject to forwarding. The list of E-RABs subject to forwarding indicates the E-RABs subject to data forwarding.

[0260] Further, in the case of a handover from E-UTRAN to "other RAN", in other words, when the Handover Type IE is set to "LTE to NR (or LTE to NGUTRAN (LTEtoNGUTRAN))", "LTE to UTRAN (LTEtoUTRAN)" or "LTE to GERAN (LTEtoGERAN)", the S1AP Handover Command message includes NAS security parameters from E-UTRAN. The NAS security parameters from E-UTRAN include security-related information for inter-RAT handover from E-UTRAN.

[0261] Fig.36 1 shows an NG2AP Handover Command message (eg, CCNF) sent from a control node in the NG Core 5 to the LTE eNB 2 over the NG2 interface. Figure 4B 406 in step 407). The handover command message includes a list of NE-RABs subject to forwarding. The list of NE-RABs subject to forwarding indicates the NextGen E-RABs subject to data forwarding. Note that the NextGen E-RAB (e.g., NE-RAB) is an E-RAB established between the UE and the user plane function (e.g., CUNF) in the NG Core 5 by an eLTE eNB enhanced to support an interface with the NG Core.

[0262] Other embodiments

[0263] Each of the above embodiments may be used alone, or two or more of the embodiments may be appropriately combined with each other.

[0264] The E-URAN and NG RAN described in the above embodiments can be implemented based on the cloud radio access network (C-RAN) concept. C-RAN is also referred to as a centralized RAN. In this case, the processes and operations performed by each of the LTE eNB 2 and NR NB 3 described in the above embodiments can be provided by a digital unit (DU) included in the C-RAN architecture or by a combination of a DU and a radio unit (RU). DU is also referred to as a baseband unit (BBU) or a central unit (CU). RU is also referred to as a remote radio head (RRH), a remote radio equipment (RRE) or a distributed unit (DU). DU and RU can provide the functions of the AS layer provided throughout the RAN, while dividing them into functions provided by the DU and functions provided by the RU. For example, DU and RU can be provided by a configuration in which a portion of the AS layer (e.g., layer 2 / layer 3 or its sublayer, or a portion of the function of the layer) is arranged in the DU and the remaining layers (or the remaining portion of the layer) are arranged in the RU. That is, the processes and operations performed by each of the LTE eNB 2 and NR NB 3 described in the above embodiments can be provided by one or more radio stations (or RAN nodes).

[0265] NR NB 3 may be configured to dynamically change the allocation of the AS layer or its functions to the DU and RU. In other words, NRNB 3 may be configured to dynamically change the split point of the AS layer or its functions between the DU and the RU. For example, NR NB 3 may be configured to dynamically select one of a plurality of different functional splitting options. In this case, in the HO process from LTE to NR in the above embodiment, the NG core 5 may allocate the AS layer or its functions to the DU and RU of NR NB 3 in response to receiving a forward relocation request message or a handover requirement message. Alternatively, NR NB 3 may determine the allocation of the AS layer or its functions to the DU and RU of NR NB 3. The NG core 5 or NR NB 3 may select a functional splitting option to be applied to NR NB 3 from among a plurality of predetermined functional splitting options.

[0266] In the example, the functional split option to be applied to NR NB 3 may be determined (or selected) based on an E-RAB QoS information IE such as QCI or ARP or flow information included in a forward relocation request message or a handover required message. Additionally or alternatively, the functional split option to be applied to NR NB 3 may be determined based on a slice created by the NG core 5 or NR NB 3 or information about the slice (i.e., slice information). Additionally or alternatively, the functional split option to be applied to NR NB 3 may be determined based on network slice assistance information included in NAS information transmitted from UE 1.

[0267] Further, in the above embodiment, the UE identifier may be included in the message transmitted between nodes. The UE identifier is used in the handover process to identify the UE 1 to be handed over.

[0268] More specifically, the UE identity may be a UE identifier used on an interface (e.g., Sn interface or NG2 interface, n is an integer) between the NR NB 3 and a control node corresponding to the MME and included in the NG Core 5. The UE identifier may be expressed as an NR NB UE SnAP ID (NR NB UE Sn Application Protocol Identifier) ​​or an NR NB UE NG2AP ID.

[0269] Alternatively, the UE identifier may be a UE identifier used on an interface (e.g., Xn interface, n is an integer) between the NR NB 3 and the LTE eNB 2. The UE identifier may be expressed as NR NB UE XnAP ID.

[0270] Alternatively, the UE identifier may be a UE identifier used on an interface (e.g., Sm interface, m is an integer) between the MME in the EPC 4 and a control node corresponding to the MME and included in the NG Core 5. The UE identifier may be expressed as eMME UE SmAP ID.

[0271] Alternatively, the UE identifier may be a UE identifier used on an interface (e.g., S1 interface, l is an integer) between the LTE eNB 2 and a control node corresponding to the MME and included in the NG core 5 and allocated by the control node. The UE identifier may be expressed as an eMME UE S1AP ID.

[0272] Further, these UE identifiers may be transmitted between nodes during a handover process. Note that Sn, NG2, Sm, S1, and Xn used to identify the corresponding interfaces are only examples and may be expressed by different symbols.

[0273] Further, the embodiments described above are merely examples of application of the technical ideas obtained by the inventors. These technical ideas are not limited to the embodiments described above and various modifications may be made thereto.

[0274] For example, all or part of the embodiments disclosed above can be described as, but not limited to, the following supplementary explanations.

[0275] (Supplementary Note 1)

[0276] A target radio access network (RAN) node associated with a second network, the target RAN node comprising:

[0277] at least one memory; and

[0278] at least one processor coupled to the at least one memory and configured to, during a handover of a radio terminal from a first network to the second network:

[0279] receiving, from a core network, slice information about a network slice included in the second network and to which the radio terminal is to be connected;

[0280] upon receiving the slice information, creating radio resource configuration information in the second network to be used by the radio terminal after the handover; and

[0281] The radio resource configuration information is transmitted to the radio terminal through the first network.

[0282] (Supplementary Note 2)

[0283] The target RAN node described in Supplementary Note 1, wherein,

[0284] The at least one processor is configured to:

[0285] receiving a handover request message from the core network, the handover request message requesting handover of the radio terminal from the first network to the second network and including the slice information about the network slice included in the second network and to which the radio terminal is to be connected; and

[0286] In response to the handover request message, a handover request response message is transmitted to the core network, wherein the handover request response message includes a target-to-source transparent container, wherein:

[0287] The target-to-source transparent container contains the radio resource configuration information, which is derived from the slice information and is to be forwarded through the core network to a source RAN node associated with the first network.

[0288] (Supplementary Note 3)

[0289] The target RAN node described in Supplementary Note 1 or 2, wherein the slice information includes: (a) identification information of the network slice selected for the radio terminal; (b) type information of the network slice selected for the radio terminal; or (c) identification information of a network node or network function associated with the network slice selected for the radio terminal; or any combination thereof.

[0290] (Supplementary Note 4)

[0291] The target RAN node described in any one of Supplementary Notes 1 to 3, wherein the slice information includes at least one of a mobility level and a session level supported by the network slice selected for the radio terminal.

[0292] (Supplementary Note 5)

[0293] The target RAN node described in any one of Supplementary Notes 1 to 4, wherein the at least one processor is configured to determine whether to accept a bearer or a flow for each bearer or each flow of the radio terminal based on the slice information.

[0294] (Supplementary Note 6)

[0295] The target RAN node described in any one of Supplementary Notes 1 to 5, wherein the at least one processor is configured to determine whether it is possible to accept each network slice based on the slice information.

[0296] (Supplementary Note 7)

[0297] A source radio access network (RAN) node associated with a first network, the source RAN node comprising:

[0298] at least one memory; and

[0299] at least one processor coupled to the at least one memory and configured to, during a handover of a radio terminal from the first network to a second network:

[0300] receiving a handover-related message from the second network, the handover-related message including at least one of slice information about a network slice included in the second network and to which the radio terminal is to be connected and radio resource configuration information based on the network slice in the second network; and

[0301] The handover-related message is transmitted to the radio terminal.

[0302] (Supplementary Note 8)

[0303] The source RAN node described in Supplementary Note 7, wherein the at least one processor is configured to:

[0304] transmitting, to the core network, a handover required message for initiating the handover of the radio terminal from the first network to the second network;

[0305] receiving, from the core network, a handover command message containing a target-to-source transparent container, the target-to-source transparent container containing radio resource configuration information created by a target RAN node associated with the second network, the radio resource configuration information being necessary for the radio terminal to establish a radio connection associated with the network slice included in the second network and to which the radio terminal is to be connected; and

[0306] A mobility command message is transmitted to the radio terminal, the mobility command message including the radio resource configuration information and indicating the handover to the second network.

[0307] (Supplementary Note 9)

[0308] A radio terminal, comprising:

[0309] at least one memory; and

[0310] At least one processor is coupled to the at least one memory and is configured to, during a handover from a first network to which the radio terminal is connected to a second network, receive a handover-related message from a radio access network (RAN) node of the first network, the handover-related message including slice information about a network slice in the second network and at least one of radio resource configuration information based on the network slice in the second network.

[0311] (Supplementary Note 10)

[0312] The radio terminal described in Supplementary Note 8, wherein the at least one processor is configured to:

[0313] receiving, from the RAN node, a mobility command message indicating the handover from the first network to the second network, the mobility command message containing the radio resource configuration information created by a target RAN node associated with the second network, the radio resource configuration information being necessary for the radio terminal to establish the radio connection associated with the network slice included in the second network and to which the radio terminal is to be connected; and

[0314] A radio connection is established with the target RAN node associated with the second network by using the radio resource configuration information.

[0315] (Supplementary Note 11)

[0316] A core network node, comprising:

[0317] at least one memory; and

[0318] At least one processor is coupled to the at least one memory and is configured to, during handover of a radio terminal from a first network to a second network, send slice information about a network slice included in the second network and to which the radio terminal is to be connected to, to a target radio access network (RAN) node associated with the second network.

[0319] (Supplementary Note 12)

[0320] The core network node described in Supplementary Note 11, wherein the at least one processor is configured to:

[0321] receiving a handover required message from a source RAN node associated with the first network for initiating the handover of the radio terminal from the first network to the second network; and

[0322] In response to the handover required message, a handover request message is sent to the target RAN node, the handover request message including the slice information and requesting handover of the radio terminal from the first network to the second network.

[0323] (Supplementary Note 13)

[0324] The core network node described in Supplementary Note 12, wherein the at least one processor is further configured to:

[0325] receiving, from the target RAN node, a handover request reply message comprising a target-to-source transparent container comprising radio resource configuration information derived from the slice information; and

[0326] A handover command message including the target to source transparent container is sent to the source RAN node.

[0327] (Supplementary Note 14)

[0328] The target RAN node described in any one of Supplementary Notes 11 to 13, wherein the slice information includes: (a) identification information of the network slice selected for the radio terminal; (b) type information of the network slice selected for the radio terminal; or (c) identification information of a network node or network function associated with the network slice selected for the radio terminal; or any combination thereof.

[0329] (Supplementary Note 15)

[0330] The target RAN node described in any one of Supplementary Notes 11 to 14, wherein the slice information includes at least one of a mobility level and a session level supported by the network slice selected for the radio terminal.

[0331] (Supplementary Note 16)

[0332] A method in a target radio access network (RAN) node associated with a second network, the method comprising:

[0333] during a handover of the radio terminal from the first network to the second network,

[0334] receiving, from a core network, slice information about a network slice included in the second network and to which the radio terminal is to be connected;

[0335] upon receiving the slice information, creating radio resource configuration information to be used by the radio terminal after the handover in the second network; and

[0336] The radio resource configuration information is transmitted to the radio terminal through the first network.

[0337] (Supplementary Note 17)

[0338] A method in a source radio access network (RAN) node associated with a first network, the method comprising:

[0339] during a handover of the radio terminal from said first network to a second network,

[0340] receiving a handover-related message from the second network, the handover-related message including at least one of slice information about a network slice included in the second network and to which the radio terminal is to be connected and radio resource configuration information based on the network slice in the second network; and

[0341] The handover-related message is transmitted to the radio terminal.

[0342] (Supplementary Note 18)

[0343] A method in a radio terminal, the method comprising:

[0344] During handover from a first network to which the radio terminal is connected to a second network, a handover-related message is received from a radio access network (RAN) node of the first network, the handover-related message including slice information about a network slice in the second network and at least one of radio resource configuration information based on the network slice in the second network.

[0345] (Supplementary Note 19)

[0346] A method in a core network node, the method comprising:

[0347] During handover of a radio terminal from a first network to a second network, slice information about a network slice included in the second network and to which the radio terminal is to be connected is sent to a target radio access network (RAN) node associated with the second network.

[0348] (Supplementary Note 20)

[0349] A program for causing a computer to perform a method in a target radio access network (RAN) node associated with a second network, wherein the method comprises:

[0350] during a handover of the radio terminal from the first network to the second network,

[0351] receiving, from a core network, slice information about a network slice included in the second network and to which the radio terminal is to be connected;

[0352] upon receiving the slice information, creating radio resource configuration information in the second network to be used by the radio terminal after the handover; and

[0353] The radio configuration information is transmitted to the radio terminal through the first network.

[0354] (Supplementary Note 21)

[0355] A program for causing a computer to perform a method in a source radio access network (RAN) node associated with a first network, wherein the method comprises:

[0356] during a handover of the radio terminal from said first network to a second network,

[0357] receiving a handover-related message from the second network, the handover-related message including at least one of slice information about a network slice included in the second network and to which the radio terminal is to be connected and radio resource configuration information based on the network slice in the second network from the second network; and

[0358] The handover-related message is transmitted to the radio terminal.

[0359] (Supplementary Note 22)

[0360] A program for causing a computer to execute a method in a radio terminal, wherein the method comprises:

[0361] During handover from a first network to which the radio terminal is connected to a second network, a handover-related message is received from a radio access network (RAN) node of the first network, the handover-related message including slice information about a network slice in the second network and at least one of radio resource configuration information based on the network slice in the second network.

[0362] (Supplementary Note 23)

[0363] A program for causing a computer to execute a method in a core network node, wherein the method comprises:

[0364] During handover of a radio terminal from a first network to a second network, slice information about a network slice included in the second network and to which the radio terminal is to be connected is sent to a target radio access network (RAN) node associated with the second network.

[0365] This application is based upon and claims the benefit of priority from Japanese patent application No. 2016-158280, filed on August 10, 2016, the disclosure of which is incorporated herein in its entirety by reference.

[0366] Reference numerals list

[0367] 1 User Equipment (UE)

[0368] 2 LTE eNode B (eNB)

[0369] 3 New Radio (NR) Node B (NB)

[0370] 4 Evolved Packet Core (EPC)

[0371] 5 NextGen (NG) Core

[0372] 1505 Baseband Processor

[0373] 1506 Application Processor

[0374] 1508 Memory

[0375] 1604 processor

[0376] 1605 Memory

[0377] 1704 processor

[0378] 1705 Memory

[0379] 1802 processor

[0380] 1803 Memory

Claims

1. A target radio access network (RAN) node, comprising: at least one memory; as well as at least one processor coupled to the at least one memory and configured to, during a handover of a radio terminal from a source eNode B (eNB) connected to a mobility management entity (MME) to a target RAN node connected to the 5G core network node using an interface between the MME and a 5G core network node: receiving a handover request message from the 5G core network node, the handover request message including a PDU session list to be established, wherein the PDU session list includes a PDU session ID corresponding to the PDU session and slice information about a network slice to which the radio terminal is to be connected after the handover, and the slice information indicates a service type; creating radio resource configuration information to be used by the radio terminal after the handover based on the slice information or based on the slice information and flow information of at least one flow within the PDU session; In response to the handover request message, transmitting a handover request response message to the 5G core network node, wherein the handover request response message includes a target-to-source transparent container; as well as The target-to-source transparent container includes radio resource configuration information and is forwarded to the source eNB via the 5G core network node and the MME, and the radio resource configuration information is forwarded by the source eNB to the radio terminal.

2. The target RAN node according to claim 1, wherein: The radio resource configuration information includes at least one radio parameter per slice information.

3. A source eNodeB (eNB), comprising: at least one memory; as well as at least one processor coupled to the at least one memory and configured to, during a handover of a radio terminal from a source eNB connected to a mobility management entity (MME) to a target radio access network (RAN) node connected to the 5G core network node using an interface between the MME and a 5G core network node: transmitting a handover required message to the MME, the handover required message including information indicating handover of the radio terminal from LTE to NR; receiving, from the MME, a handover command message comprising a target to source transparent container, the target to source transparent container comprising radio resource configuration information to be used by the radio terminal to communicate with the target RAN node after the handover, the radio resource configuration information being created by the target RAN node based on slice information and flow information received by the target RAN node from the 5G core network via a handover request message or based on the slice information, the slice information relating to a network slice to which the radio terminal is to connect after the handover, the slice information indicating a service type, and the flow information relating to at least one flow within a PDU session; as well as The radio resource configuration information is transmitted to the radio terminal.

4. A 5G core network node, comprising: at least one memory; as well as at least one processor coupled to the at least one memory and configured to, during a handover of a radio terminal from a source eNode B (eNB) connected to a mobility management entity (MME) to a target RAN node connected to the 5G core network node using an interface between the MME and the 5G core network node: transmitting a handover request message to the target RAN node, the handover request message comprising a PDU session list to be established, wherein the PDU session list comprises a PDU session ID corresponding to the PDU session and slice information about a network slice to which the radio terminal is to be connected after the handover, and the slice information indicates a service type; receiving, in response to the handover request message, a handover request answer message from the target RAN node, the handover request answer message including a target-to-source transparent container; as well as The target-to-source transparent container is forwarded to the source eNB via the MME, wherein the target-to-source transparent container includes radio resource configuration information, which is created by the target RAN node based on the slice information or based on the slice information and flow information of at least one flow within the PDU session, forwarded to the radio terminal by the source eNB, and is to be used by the radio terminal after the handover.

5. The 5G core network node according to claim 4, wherein: The radio resource configuration information includes at least one radio parameter per slice information.

6. A radio terminal comprising: at least one memory; as well as at least one processor coupled to the at least one memory and configured to, during a handover of a radio terminal from a source eNode B (eNB) connected to a mobility management entity (MME) to a target radio access network (RAN) node connected to the 5G core network node using an interface between the MME and a 5G core network node: receiving, from the source eNB, radio resource configuration information to be used by the radio terminal after the handover, the radio resource configuration information being created by the target RAN node based on slice information and flow information received by the target RAN node from the 5G core network node via a handover request message or based on the slice information, the handover request message comprising a PDU session list to be established, wherein the PDU session list comprises PDU session IDs corresponding to PDU sessions and the slice information, the slice information being related to a network slice to which the radio terminal is to be connected after the handover, the slice information indicating a service type, and the flow information being related to at least one flow within the PDU session; as well as The target RAN node is connected using the radio resource configuration information.

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