User Equipment and Methods

Abstract

To make it easy for a wireless terminal in an RRC_INACTIVE state to know the availability of a network slice in a cell to be re-selected or in a cell re-selected.SOLUTION: User Equipment (UE) receives a System Information Block (SIB) or Radio Resource Control (RRC) message from a network containing information for cell re-selection based on a network slice. The information is provided to enable the UE to re-select a cell that supports a particular slice.SELECTED DRAWING: Figure 12

Description

[Technical Field]

[0001] TECHNICAL FIELD The present disclosure relates to wireless communication systems, and more particularly to mobility of wireless terminals. [Background technology]

[0002] The 3rd Generation Partnership Project (3GPP (registered trademark)) began standardization work on the fifth-generation mobile communication system (5G) for deployment after 2020 in 2016 as 3GPP Release 14 (see Non-Patent Document 1). 5G is expected to be realized through a combination of continuous enhancement / evolution of LTE and LTE-Advanced and innovative enhancement / evolution through the introduction of a new 5G air interface (new Radio Access Technology (RAT)). For example, the new RAT will support higher frequency bands than the frequency bands (e.g., 6 GHz or lower) targeted by the continuous evolution of LTE / LTE-Advanced, such as centimeter wave bands above 10 GHz and millimeter wave bands above 30 GHz.

[0003] In this specification, the fifth-generation mobile communication system is also referred to as the 5G System or the Next Generation (NextGen) System (NG System). The new RAT for the 5G System is referred to as the New Radio (NR), 5G RAT, or NG RAT. The new radio access network (RAN) for the 5G System is referred to as the 5G-RAN or NextGen RAN (NG RAN). The new base stations within the 5G-RAN are referred to as the NR NodeB (NR NB) or gNodeB (gNB). The new core network for the 5G System is referred to as the 5G Core Network (5G-CN) or NextGen Core (NG Core). The wireless terminal (User Equipment (UE)) connecting to the 5G System is referred to as the 5G UE, NextGen UE (NG UE), or simply UE. The official names of the RAT, UE, radio access network, core network, network entities (nodes), protocol layers, etc. for the 5G System will be determined in the future as standardization work progresses.

[0004] Additionally, unless otherwise specified, the term "LTE" used herein includes improvements and developments of LTE and LTE-Advanced to enable interworking with 5G systems. Improvements and developments of LTE and LTE-Advanced to enable interworking with 5G systems are also referred to as LTE-Advanced Pro, LTE+, or enhanced LTE (eLTE). Furthermore, terms related to LTE networks or logical entities, such as "Evolved Packet Core (EPC)," "Mobility Management Entity (MME)," "Serving Gateway (S-GW)," and "Packet Data Network (PDN) Gateway (P-GW)," used herein include improvements and developments of these to enable interworking with 5G systems, unless otherwise specified. The improved EPC, MME, S-GW, and P-GW may also be referred to as, for example, enhanced EPC (eEPC), enhanced MME (eMME), enhanced S-GW (eS-GW), and enhanced P-GW (eP-GW).

[0005] In LTE and LTE-Advanced, bearers per QoS class and per PDN connection are used in both the RAN (i.e., Evolved Universal Terrestrial RAN (E-UTRAN)) and the core network (i.e., EPC) for Quality of Service (QoS) and packet routing. In other words, in the Bearer-based QoS (or per-bearer QoS) concept, one or more Evolved Packet System (EPS) bearers are established between the UE and the P-GW in the EPC. Multiple Service Data Flows (SDFs) with the same QoS class are transported through a single EPS bearer that satisfies these QoS requirements. An SDF is one or more packet flows that match SDF templates (i.e., packet filters) based on Policy and Charging Control (PCC) rules. For packet routing, each packet sent through an EPS bearer contains information to identify which bearer (i.e., General Packet Radio Service (GPRS) Tunneling Protocol (GTP) tunnel) the packet is associated with.

[0006] In contrast, in the 5G System, radio bearers may be used in the 5G-RAN, but it is being considered that bearers will not be used in the 5G-CN and in the interface between the 5G-CN and the 5G-RAN (see Non-Patent Document 1). Specifically, PDU flows are defined instead of EPS bearers, and one or more SDFs are mapped to one or more PDU flows. A PDU flow between a 5G UE and a user plane termination entity in the NG Core (i.e., an entity equivalent to a P-GW in the EPC) corresponds to an EPS bearer in the EPS Bearer-based QoS concept. That is, the 5G System adopts the Flow-based QoS (or per-flow QoS) concept instead of the Bearer-based QoS concept. In the Flow-based QoS concept, QoS is handled in units of PDU flows. Therefore, a PDU flow is also called a QoS flow. Note that the association between a 5G UE and a data network is called a PDU session. A PDU session is a term equivalent to a PDN connection in LTE and LTE-Advanced. Multiple PDU flows (or QoS flows) can be configured within one PDU session.

[0007] Furthermore, support for network slicing in the 5G system is also being considered (see Non-Patent Document 1). Network slicing uses Network Function Virtualization (NFV) and software-defined networking (SDN) technologies to enable the creation of multiple virtualized logical networks on a physical network. Each virtualized logical network is called a network slice or network slice instance, and includes logical nodes and functions and is used for specific traffic and signaling. The 5G-RAN, 5G-CN, or both have a Slice Selection Function (SSF). The SSF selects one or more network slices suitable for a 5G UE based on information provided by at least one of the 5G UE and 5G-CN.

[0008] Figure 1 shows the basic architecture of a 5G system. A UE establishes one or more signaling radio bearers (SRBs) and one or more data radio bearers (DRBs) with a gNB. The 5G-CN and gNB establish a control plane interface and a user plane interface for the UE. The control plane interface between the 5G-CN and gNB (i.e., RAN) is called the NG2 interface or NG-c interface and is used to transfer Non-Access Stratum (NAS) information and control information between the 5G-CN and gNB. The user plane interface between the 5G-CN and gNB (i.e., RAN) is called the NG3 interface or NG-u interface and is used to transfer packets of one or more PDU flows (or QoS flows) within a UE PDU session.

[0009] Furthermore, in the 5G system, a new RRC state is introduced in addition to the RRC_CONNECTED state and the RRC_IDLE state (see, for example, Non-Patent Documents 1-5). The new RRC state is called the RRC_INACTIVE state or the RRC_INACTIVE_CONNECTED state.

[0010] The RRC_CONNECTED and RRC_IDLE states of the 5G System have similar characteristics to those of the LTE RRC_CONNECTED and RRC_IDLE states, respectively. When a UE is in the RRC_CONNECTED state, the UE and 5G-RAN maintain the AS context, and the UE's location is known by the 5G-RAN at the cell level. The mobility of a UE in the RRC_CONNECTED state is handled by handover controlled by the 5G-RAN. On the other hand, when a UE is in the RRC_IDLE state, the UE and 5G-RAN release the AS context, the UE's location is unknown by the 5G-RAN, and the UE's location is known by the 5G-CN at the location registration area level. The location registration area corresponds to the Tracking Area (TA) in LTE. The mobility of a UE in the RRC_IDLE state is handled by cell reselection controlled by the UE. Furthermore, the RRC state of the AS layer is associated with the connection management (NG Connection Management (NG CM)) state of the NAS layer. A UE in RRC_CONNECTED state is considered to be in NG-CM-CONNECTED state in the UE and the 5G-CN, while a UE in RRC_IDLE state is considered to be in NG-CM-IDLE state in the UE and the 5G-CN.

[0011] The RRC_INACTIVE state can be said to be an intermediate state between the RRC_CONNETED and RRC_IDLE states. Some characteristics of the RRC_INACTIVE state are similar to those of the RRC_CONNETED state, while some other characteristics of the RRC_INACTIVE state are similar to those of the RRC_IDLE state.

[0012] When a UE is in the RRC_INACTIVE state, the UE and the 5G-RAN maintain at least a portion of the AS context. The AS context maintained by the UE and the 5G-RAN for a UE in the RRC_INACTIVE state includes, for example, radio bearer configuration and AS security context. Furthermore, the 5G-RAN maintains control plane and user plane connections (i.e., the NG2 and NG3 interfaces in Figure 1) with the 5G-CN for a UE in the RRC_INACTIVE state. A UE in the RRC_INACTIVE state is considered to be in the NG-CM-CONNECTED state in the UE and the 5G-CN. That is, the 5G-CN does not distinguish between a UE in the RRC_CONNECTED state and the RRC_INACTIVE state. These characteristics of the RRC_INACTIVE state are similar to those of the RRC_CONNETED state.

[0013] However, the mobility of a UE in RRC_INACTIVE state is similar to that of a UE in RRC_IDLE state, i.e., the mobility of a UE in RRC_INACTIVE state is handled by UE-controlled cell reselection.

[0014] Figure 2 shows the state transitions between the three currently proposed RRC states. A UE can transition between the RRC_CONNECTED state and the RRC_INACTIVE state (steps 201 and 202). The transition between the RRC_CONNECTED state and the RRC_INACTIVE state is expected to reuse the RRC connection suspend and resume procedures defined for LTE in 3GPP Release 13. The AS context stored in the 5G-RAN for a UE in the RRC_INACTIVE state can be transferred between RAN nodes (gNBs). Specifically, when a UE transitions from the RRC_INACTIVE state to the RRC_CONNECTED state, a gNB that receives an RRC message (e.g., an RRC Connection Resume request) from the UE may fetch / retrieve the AS context of the UE from another gNB.

[0015] The location of a UE in RRC_INACTIVE state is known by the 5G-RAN at the level of a newly defined RAN Notification Area (RNA). The RAN Notification Area is also called a RAN-based Notification Area, RAN paging area, or RAN location update area. The RAN Notification Area (RNA) includes one or more cells, is determined by the 5G-RAN, and is configured for the UE by the 5G-RAN. A UE in RRC_INACTIVE state does not need to notify (report) the cell reselection to the 5G-RAN even if it moves between cells within the RAN notification area by cell reselection. A UE in RRC_INACTIVE state requests the 5G-RAN to update the RAN notification area when it reselects a cell outside the RAN notification area.

[0016] 3 shows an example of the mobility of a UE in the RRC_INACTIVE state. Initially, UE 301 is in the RRC_CONNECTED state (321) in cell 351 of gNB 311, and has been assigned dedicated radio resources by gNB 311 to establish dedicated radio bearers 322. gNB 311 determines to transition UE 301 to the RRC_INACTIVE state, configures RAN notification area 340 for UE 301, and transmits an RRC message (e.g., an RRC Suspend message) to UE 301 (323). In response to the instruction from gNB 311, UE 301 transitions from the RRC_CONNECTED state to the RRC_INACTIVE state (324).

[0017] UE 301, which is in the RRC_INACTIVE state, performs a cell reselection procedure and reselects cell 352 of gNB 312 (325). Because cell 352 is included in the RAN notification area 340 configured for UE 301, UE 301 does not report the cell reselection (i.e., update of UE location information) to the 5G-RAN (e.g., cell 352 or gNB 312). UE 301 moves further and reselects cell 353 of gNB 313 (326). Because cell 353 is not included in the RAN notification area 340 configured for UE 301, UE 301 transmits a RAN notification area update request (327) to gNB 313. This request (327) may be transmitted using an RRC message (e.g., an RRC Resume Request message) requesting a transition from RRC_INACTIVE to RRC_CONNECTED. The gNB 313 obtains the AS context of the UE 301 from the gNB 311 and re-establishes the Packet Data Convergence Protocol (PDCP) and Radio Link Control (RLC) for the radio bearers using the obtained AS context. The gNB 313 then transmits an RRC message (e.g., an RRC resume message) to transition the UE 301 to the RRC_CONNECTED state. In response to the instruction from the gNB 311, the UE 301 enters the RRC_CONNECTED state from the RRC_INACTIVE state in the cell 353 (329). The UE 301 can transmit and receive data using dedicated radio bearers 330. [Prior art documents] [Non-patent literature]

[0018] [Non-Patent Document 1] 3GPP TR 23.799 V14.0.0 (2016-12) “3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; Study on Architecture for Next Generation System (Release 14)”, December 2016 Summary of the Invention [Problem to be solved by the invention]

[0019] The present inventors have conducted a study on the mobility of a UE in the RRC_INACTIVE state and found several issues. For example, the mobility of a UE in the RRC_INACTIVE state may require consideration of the network slice. This is because a situation may arise in which a desired network slice is not available in a reselected cell. The UE's desired network slice is, for example, the network slice selected (or configured) for the UE by the network when the UE was in the RRC_CONNECTED state before entering the RRC_INACTIVE state.

[0020] In the example of FIG. 4, the 5G-CN 430 includes Common Network Functions (NFs) 431, network functions for network slice A (NFs for slice A) 432, and network functions for network slice B (NFs for slice B) 433. The Common NFs 431 include a Common Control plane NF (CCNF) and may further include a Common User plane NF (CUNF). The NFs for slice A 432 include a slice-specific User plane NF (SUNF) and may further include a slice-specific Control plane NF (SCNF). Similarly, the NFs for slice B 433 include a SUNF and may further include an SCNF.

[0021] In the example of Figure 4, gNB411 and gNB412 are connected to Common NFs431, NFs for slice A432, and NFs for slice B433. In contrast, gNB413 is connected to Common NFs431 and NFs for slice A432, but is not connected to NFs for slice B433. In other words, network slice B is not available in gNB413's cell 423.

[0022] In the example of FIG. 4, UE 401 is in an RRC_CONNECTED state in cell 421 of gNB 411, and network slice B is configured for UE 401. UE 401 transmits and receives data via network slice B. Subsequently, UE 401 is configured with a RAN notification area 440 by gNB 411, and enters an RRC_INACTIVE state. Further thereafter, UE 401 performs cell reselection (452). However, one issue is how UE 401 in the RRC_INACTIVE state knows whether a desired network slice is available in the target cell, i.e., the cell to be reselected or the reselected cell.

[0023] As an example, it may be preferable for a UE in an RRC_INACTIVE state to be able to determine whether a desired network slice is available in a reselected cell. If it is determined that a desired network slice is available in a reselected cell, the UE in an RRC_INACTIVE state may be able to remain in the RRC_INACTIVE state in the reselected cell without performing any special operations. On the other hand, if it is determined that it is unclear whether a desired network slice is available in a reselected cell, the UE may be able to quickly enter an RRC_CONNECTED state in the reselected cell and request the network to use the network slice. Alternatively, if a UE in an RRC_INACTIVE state determines that a desired network slice is not available in the reselected cell or the reselected cell, it may be able to further reselect another cell.

[0024] Therefore, one of the objectives to be achieved by the embodiments disclosed in this specification is to provide an apparatus, a method, and a program that facilitates a UE in an RRC_INACTIVE state to know the availability of a network slice in a target cell, i.e., a cell to be reselected or a reselected cell. It should be noted that this objective is only one of multiple objectives to be achieved by multiple embodiments disclosed in this specification. Other objectives or problems and novel features will become apparent from the description of this specification or the accompanying drawings. [Means for solving the problem]

[0025] In a first aspect, a base station includes a memory and at least one processor coupled to the memory. The at least one processor is configured to control state transitions of a first radio terminal among a first RRC state, a second RRC state, and a third RRC state. The first RRC state is a state in which the first radio terminal and the RAN maintain an Access Stratum (AS) context, and the location of the first radio terminal is known by the RAN at a cell level. The second RRC state is a state in which the first radio terminal and the RAN maintain at least a portion of the AS context, and the location of the first radio terminal is known by the RAN at a RAN notification area level configured by the RAN. The third RRC state is a state in which the first radio terminal and the RAN release the AS context, and the location of the first radio terminal is unknown by the RAN. The at least one processor is further configured to explicitly or implicitly notify the first radio terminal whether a first network slice configured in the first radio terminal for data communication in at least the first RRC state is available in each cell included in the RAN notification area.

[0026] In a second aspect, a base station includes a memory and at least one processor coupled to the memory, the at least one processor configured to control state transitions of wireless terminals among a first RRC state, a second RRC state, and a third RRC state, and the at least one processor further configured to transmit system information in a first cell of the base station indicating one or more network slices available or unavailable in the first cell.

[0027] In a third aspect, a wireless terminal includes a transceiver and at least one processor, the at least one processor configured to control the transceiver in one or more cells associated with a Radio Access Network (RAN), the at least one processor configured to control state transitions of the wireless terminal among a first RRC state, a second RRC state, and a third RRC state, and the at least one processor further configured to verify whether a first network slice configured in the wireless terminal for data communication in at least the first RRC state is available in a cell reselected by cell reselection in the second RRC state.

[0028] In a fourth aspect, a method in a base station disposed in a radio access network (RAN) includes: (a) controlling state transitions of a first radio terminal among a first RRC state, a second RRC state, and a third RRC state; and (b) explicitly or implicitly notifying the first radio terminal whether a first network slice configured in the first radio terminal for data communication in at least the first RRC state is usable in each cell included in a RAN notification area configured by the RAN.

[0029] In a fifth aspect, a method in a base station disposed in a radio access network (RAN) includes (a) controlling state transitions of a first wireless terminal among a first RRC state, a second RRC state, and a third RRC state, and (b) transmitting system information in a first cell of the base station indicating one or more network slices available or unavailable in the first cell.

[0030] In a sixth aspect, a method in a radio terminal includes: (a) controlling state transitions of the radio terminal among a first RRC state, a second RRC state, and a third RRC state; and (b) checking whether a first network slice configured in the radio terminal for data communication in at least the first RRC state is available in a cell to be reselected by cell reselection in the second RRC state.

[0031] In a seventh aspect, a program includes a group of instructions (software code) that, when loaded into a computer, causes the computer to perform the method according to any one of the fourth to sixth aspects described above. [Effects of the Invention]

[0032] According to the above-described aspects, it is possible to provide an apparatus, a method, and a program that facilitate a UE in an RRC_INACTIVE state to know the availability of a network slice in a target cell, i.e., a cell to be reselected or a reselected cell. [Brief explanation of the drawings]

[0033] [Figure 1] FIG. 1 is a diagram illustrating the basic architecture of a 5G system according to the background art. [Figure 2] FIG. 1 is a diagram illustrating state transitions of three RRC states of a 5G system according to the background art. [Figure 3]FIG. 1 is a diagram illustrating an example of the mobility of a UE in an RRC_INACTIVE state according to the background art. [Figure 4] FIG. 1 is a diagram for explaining one problem regarding the mobility of a UE in an RRC_INACTIVE state that has been identified by the inventor. [Figure 5] FIG. 1 illustrates an example configuration of a wireless communication network according to some embodiments. [Figure 6] A sequence diagram showing an example of information exchange between gNBs according to the first embodiment. [Figure 7] A flowchart showing an example of the operation of a gNB according to the first embodiment. [Figure 8] 5 is a flowchart showing an example of an operation of the UE according to the first embodiment. [Figure 9] 5 is a flowchart showing an example of an operation of the UE according to the first embodiment. [Figure 10] A flowchart showing an example of the operation of a gNB according to the second embodiment. [Figure 11] 10 is a flowchart illustrating an example of an operation of a UE according to the second embodiment. [Figure 12] A sequence diagram showing an example of the operation of a gNB and a UE according to the third embodiment. [Figure 13] A sequence diagram showing an example of the operation of a gNB and a UE according to the third embodiment. [Figure 14] 10 is a flowchart showing an example of an operation of a UE according to the third embodiment. [Figure 15] A block diagram showing an example configuration of a gNB according to some embodiments. [Figure 16] FIG. 1 is a block diagram illustrating an example configuration of a UE according to some embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0034] Hereinafter, specific embodiments will be described in detail with reference to the drawings. In each drawing, the same or corresponding elements are designated by the same reference numerals, and for clarity of explanation, duplicate explanations will be omitted as necessary.

[0035] The multiple embodiments described below can be implemented independently or in appropriate combination. These multiple embodiments have different novel features. Therefore, these multiple embodiments contribute to solving different purposes or problems and to achieving different effects.

[0036] The following embodiments are described primarily for a 5G system that supports network slicing and uses the RRC_INACTIVE state. However, these embodiments may also be applied to other wireless communication systems that support network slicing and use the RRC_INACTIVE state or a similar RRC state.

[0037] First Embodiment 5 shows an example of the configuration of a wireless communication network according to some embodiments, including this embodiment. In the example of FIG. 5, the wireless communication network includes a 5G UE 2, a 5G-RAN 3, and a 5G-CN 4.

[0038] The 5G-CN4 includes Control Plane Network Functions (CP NFs) and User Plane Network Functions (UP NFs), not shown, and provides multiple network slices. The multiple network slices are distinguished by, for example, the services or use cases provided to UEs on each network slice. Use cases include, for example, enhanced Mobile Broadband (eMBB), Ultra Reliable and Low Latency Communication (URLLC), and massive Machine Type Communication (mMTC).

[0039] The 5G-RAN3 includes multiple gNBs, including gNB1A and gNB1B. Each gNB1 (e.g., gNB1A, gNB1B) operates at least one cell 11 (e.g., cell 11A, cell 11B). Each gNB1 is connected to the 5G-CN4 and supports one or more network slices. In other words, one or more network slices are supported or available in each gNB1's cell 11. In some implementations, the 5G-RAN3 assigns a RAN slice and a radio slice associated with a network slice of the 5G-CN4 selected for the UE2 (referred to as a Core Network (CN) slice) to the UE2 to provide end-to-end network slicing to the UE2. Each RAN slice provides storage and processing resources for the infrastructure within the CN-RAN3, including the gNB1. Each radio slice provides radio resources, including time resources, frequency resources, code resources, signal sequence resources, or spatial resources, or any combination thereof.

[0040] The UE 2 uses one or more cells 11 provided by one or more gNBs 1 for uplink and downlink communications. The UE 2 supports multiple RRC states, including an RRC_CONNECTED state, an RRC_INACTIVE state, and an RRC_IDLE state. The 5G-RAN 3 (gNB 1) and the UE 2 control the state transitions of the UE 2 between multiple RRC states, including the RRC_CONNECTED state, the RRC_INACTIVE state, and the RRC_IDLE state.

[0041] For example, when gNB1A transitions UE2 from the RRC_CONNECTED state to the RRC_INACTIVE state, it transmits RAN notification area information to UE2 in an RRC message (e.g., RRC Connection Release, RRC Connection Suspend, or RRC Connection Deactivate) and configures the RAN notification area for UE2. The RAN notification area includes one or more cells provided by one or more gNB1s, and UE2 enters the RRC_INACTIVE state in response to receiving the RRC message from gNB1A. UE2 in the RRC_INACTIVE state moves between cells by UE2-initiated cell reselection and does not need to report cell reselection within the RAN notification area (i.e., update of UE location information) to 5G-RAN3. Meanwhile, in response to reselecting a cell (e.g., cell 11B) outside the configured RAN notification area, UE2 requests the gNB1B of the reselected cell 11B to update the RAN notification area (or notifies gNB1B that it has left the configured RAN notification area). The gNB1B determines a new RAN notification area for UE2 and configures the determined RAN notification area for UE2, i.e., as already explained, the location of UE2 in RRC_INACTIVE state is known to 5G-RAN3 at the RAN notification area level.

[0042] As already explained, a RAN notification area (RNA) includes one or more cells, is determined by the 5G-RAN 3, and is configured by the 5G-RAN 3 to the UE 2. The RAN notification area is also called a RAN-based notification area, a RAN paging area, or a RAN location update area.

[0043] The RAN notification area information may include, for example, at least information indicating which cells are included in the RAN notification area. Furthermore, an identifier (e.g., area number) may be assigned to the RAN notification area. Furthermore, the relationship between the identifier (e.g., RNA ID) of the RAN notification area and the cell(s) included therein may be uniquely determined within a specific area. In this case, the RAN notification area information may include the identifier of the RAN notification area and information on the cells included therein (e.g., cell identifiers).

[0044] The gNB 1A may broadcast RAN notification area information in its own cell 11A. In this case, the RAN notification area information includes multiple RAN notification areas, each of which may be assigned a condition (e.g., category, type), and the UE 2 may select a RAN notification area that corresponds to itself. The condition may be, for example, the slice category or slice type (e.g., Slice / Service Type: SST) of the network slice used (or desired) by the UE 2, the category or type of the terminal, the reception quality of the UE 2 or a coverage level based thereon, the mobility characteristics of the UE 2 (e.g., UE speed, whether or not it is a stationary terminal), or any combination thereof.

[0045] The RAN notification area configured for UE2 may be identical to the location registration area of ​​UE2 (i.e., an area equivalent to a tracking area (TA) in LTE). When an individual RAN notification area (i.e., Slice specific RNA) is configured for each network slice, at least one of the multiple RAN notification areas may be identical to the location registration area (e.g., TA). When the RNA is the same as the TA, an information element (e.g., RanAreaCellList Information Element (IE)) indicating a cell list included in the RNA may be omitted from the RAN notification area information transmitted from gNB1 to UE2 (i.e., Optional IE). Alternatively, the RAN notification area information may include an information element (e.g., TrackingAreaCode IE) indicating a TA identifier instead of the information element indicating the cell list (i.e., Choice). In other words, gNB1 may select either the RanAreaCellList IE or the TrackingAreaCode IE to indicate the RAN notification area.

[0046] In order to include multiple RAN notification areas in the RAN notification area information and transmit it, the gNB1A may receive RAN notification area information (e.g., a combination of a RAN notification area identifier and an identifier of a cell constituting the RAN notification area) from another gNB (e.g., gNB1B) via the inter-gNB interface (Xn). The other gNB may be a gNB that manages cells that belong to a RAN notification area that is different from the RAN notification area to which the gNB1A's cell (e.g., cell 11A) belongs. Similarly, the information on the RAN notification area received from another gNB may be information on a RAN notification area that is different from the RAN notification area to which the gNB1A's cell (e.g., cell 11A) belongs.

[0047] If UE2 uses (or desires to use) multiple network slices, UE2 may select a RAN notification area based on the network slice with the highest priority, or may select a RAN notification area based on the network slice actually being used. Alternatively, UE2 may select a RAN notification area based on the network slice that is included at the top of a list of network slice categories or types included in the RAN notification area information.

[0048] A RAN notification area (default RAN notification area) in which individual information of a network slice (e.g., identifier, category, or type) is not specified may be included in the above-mentioned RAN notification area information. In this case, for example, the default RAN notification area may be a RAN notification area that is valid for UE2 regardless of the network slice, or may be a RAN notification area that is valid for other network slices except for the network slice explicitly notified in the RAN notification area information. Furthermore, when the RAN notification area information includes multiple RAN notification areas, UE2 does not need to send a location information update request to gNB1 as long as the cell after cell reselection is included in at least one of the multiple RAN notification areas.

[0049] Instead of the above-mentioned instruction by the RRC message, the gNB1 may notify the UE2 of the value of a predetermined timer that triggers a transition to the RRC_INACTIVE state, and cause the UE2 to transition to the RRC_INACTIVE state based on the value of the timer and the corresponding timer. For example, the UE2 in the RRC_CONNECTED state may restart the timer (i.e., reset and start the timer again) every time it transmits or receives user data, and transition to the RRC_INACTIVE state when the timer expires.

[0050] The following describes the mobility of UE2 in the RRC_INACTIVE state according to this embodiment. The gNB1 according to this embodiment is configured to explicitly notify UE2 of whether one or more network slices configured (or selected) for UE2 for data communication in at least the RRC_CONNECTED state are available in each cell included in the RAN notification area for UE2. More specifically, in this embodiment, the gNB1 is configured to transmit, to UE2, information (referred to as slice availability information) that explicitly indicates whether one or more network slices configured for UE2 are available in each cell or group of cells included in the RAN notification area. Instead of the slice availability information, the gNB1 may transmit, to UE2, information (referred to as slice support information) that explicitly indicates whether a slice is supported. The slice availability information or slice support information may indicate one or more types (e.g., categories, types) of network slices that are available (supported) in the RAN notification area or one or more cells included in the RAN notification area. Hereinafter, slice availability information will be described as an example, but it goes without saying that slice support information can be used instead.

[0051] In some implementations, the gNB1 may transmit slice availability information to the UE2 when configuring the RAN notification area for the UE2. The slice availability information may be an information element associated with the RAN notification area (e.g., a list of cells). Additionally or alternatively, the gNB1 may transmit the slice availability information to the UE2 within a procedure (e.g., an RRC message) that transitions the UE2 from the RRC_CONNECTED state to the RRC_INACTIVE state.

[0052] FIG. 6 is a flowchart showing an example of the operation of gNB1 (process 600). In step 601, gNB1 generates slice availability information indicating whether the network slice used by UE2 in the RRC_CONNECTED state is available in each cell included in the RAN notification area. In step 602, gNB1 sends the slice availability information to UE2. The gNB1 may send the slice availability information together with the RAN notification area (e.g., a list of cells). In step 603, gNB1 transitions UE2 from the RRC_CONNECTED state to the RRC_INACTIVE state. As described above, gNB1 may also transmit an instruction to transition UE2 to the RRC_INACTIVE state together with the transmission of the slice availability information.

[0053] Each gNB1 needs to know the slice availability (or slice support status) in other gNBs1 or in each cell provided by other gNBs1. In some implementations, a network operator may configure each gNB1 with slice availability in the cells of other gNBs1 via an operation and management (O&M) server. Additionally or alternatively, each gNB1 may communicate with other gNBs1 over the inter-gNB interface (Xn) (e.g., Xn Setup Request / Response messages) to dynamically obtain slice availability in the cells of other gNBs1. Each gNB1 may notify other gNBs1 when slice availability changes (or is updated) (e.g., gNB Configuration Update message). Additionally or alternatively, each gNB1 may communicate with other gNBs1 via the interface (NG2, NG-c) between the gNB1 and the 5G-CN4 to dynamically obtain slice availability in the cells of other gNBs1.

[0054] FIG. 7 is a sequence diagram showing an example of communication between two gNB1s (process 700). In step 701, gNB1A sends information (e.g., Network Slice Availability Information) indicating network slices available in each cell provided by gNB1A to gNB1B. gNB1A may send the information in response to a request from gNB1B. Additionally or alternatively, gNB1A may send an update to gNB1B in response to an update of slice availability in any cell provided by gNB1A. Additionally or alternatively, gNB1A may periodically send slice availability in each cell to gNB1B. In step 702, gNB1B sends information (e.g., Network Slice Availability Information) indicating network slices available in each cell provided by gNB1B to gNB1A. Additionally or alternatively, gNB1A may send information (e.g., Network Slice Availability Information) indicating network slices available in each cell provided by gNB1A to gNB1B via an interface (NG2, NG-c) with the core network (5G-CN4).

[0055] As described above, gNB1A may transmit and receive RAN notification area information (e.g., a combination of a RAN notification area identifier and an identifier of a cell constituting the RAN notification area) to and from gNB1B via the inter-gNB interface (Xn). In this case, the RAN notification area information may indicate the RAN notification area to which the cell 11 of the source gNB1 belongs, or the RAN notification area to which the cell 11 of the destination gNB1 should belong. In other words, when the cell 11A and the cell 11B managed by gNB1A and gNB1B, respectively, belong (or should belong) to different RAN notification areas, each gNB1 may recognize multiple RAN notification areas to be included in the RAN notification area information to be transmitted to UE2 by sharing the RAN notification area information between the gNBs.

[0056] The RAN notification area information communicated between gNBs may be included in information (e.g., Network Slice Availability Information) indicating a network slice available in each cell provided by gNB1A shown in Fig. 7. Conversely, the RAN notification area information communicated between gNBs may include information (e.g., Network Slice Availability Information) indicating a network slice available in each cell provided by gNB1A shown in Fig. 7.

[0057] In some implementations, information indicating the network slices available in each cell provided by gNB1A and gNB1B may be sent from the core network (5G-CN4) to gNB1B and gNB1A. In this case, the 5G-CN needs to know in advance the network slices available (or supported) in each gNB1. For example, the 5G-CN4 may specify to each gNB1 the network slices available (or supported) in each gNB1. Alternatively, the 5G-CN4 may receive a report of the network slices available (or supported) in each gNB1 from each gNB1.

[0058] The UE2 according to this embodiment is configured to check whether one or more network slices configured (or authorized or accepted) for data communication in at least the RRC_CONNECTED state are available (or supported) in a cell reselected (or reselected) by cell reselection in the RRC_INACTIVE state. More specifically, in this embodiment, the UE2 is configured to receive the above-mentioned slice availability information from the gNB1. The slice availability information explicitly indicates whether one or more network slices configured for the UE2 are available in each cell included in the RAN notification area for the UE2.

[0059] FIG. 8 is a flowchart showing an example of the operation of UE2 (process 800). In step 801, UE2 is in the RRC_CONNECTED state and receives the above-mentioned slice availability information from the serving gNB1. In step 802, UE2 transitions from the RRC_CONNECTED state to the RRC_INACTIVE state in response to an instruction from the serving gNB1. In step 803, UE2 performs cell reselection in the RRC_INACTIVE state. UE2 checks whether a desired network slice is available in the reselected (or reselected) cell based on the slice availability information. Here, the desired network slice may be one or more network slices that were configured (or authorized or accepted) for UE2 by the network (i.e., 5G-CN4 or 5G-RAN3, or both) when UE2 was previously in the RRC_CONNECTED state.

[0060] An example of the operation of UE2 after confirming network slice availability will be described below. Figure 9 is a flowchart showing an example of the operation of UE2 (process 900). In step 901, UE2 confirms the network slice availability of a cell that is reselected (or reselected) by cell reselection in the RRC_INACTIVE state. If the desired network slice is available in the reselected cell, UE2 stays in that cell (continues camping on that cell).

[0061] If the desired network slice is not available in the reselected cell, UE2 notifies the gNB1 of the reselected cell of the desired network slice (step 902). The notification may be a request for the desired network slice, such as a request to configure (or provide) the desired network slice for UE2, or a request for movement (e.g., handover, re-direction) to a cell in which the desired network slice is available (or supported). Note that UE2 may notify the gNB1 of the reselected cell of the desired network slice if it cannot confirm that the desired network slice is available in the reselected cell. In other words, UE2 may notify the gNB1 of the reselected cell of the desired network slice if it finds that it is unclear whether the desired network slice is available in the reselected cell.

[0062] In some implementations, the UE2 may transmit the notification of the desired network slice after transitioning to the RRC_CONNECTED state. Alternatively, the UE2 may transmit the notification of the desired network slice in the RRC_INACTIVE state. In other words, the UE2 may transmit the notification without completely transitioning to the RRC_CONNECTED state. In other words, the UE2 may transmit the notification before entering the RRC_CONNECTED state. In one example, the UE2 may transmit the notification within the procedure for transitioning to the RRC_CONNECTED state. Specifically, the UE2 may transmit the notification using an RRC message for transitioning to the RRC_CONNECTED state (e.g., RRC Connection Resume request or RRC Connection Activate). Alternatively, the UE2 may transmit the notification of the desired network slice using a signal (e.g., PRACH preamble, RACH data, UL reference signal, MAC Control Element (CE)) that can be transmitted while remaining in the RRC_INACTIVE state, or an RRC message (e.g., UL Information Transfer, UL Direct Information, or UE Assistance Information). In this case, the signal or message may be transmitted using dedicated radio resources notified (configured) to the UE2 in advance from the gNB1, or may be transmitted using radio resources shared among multiple UE2. In the latter case, for example, the UE2 may transmit the notification of the desired network slice in a grant-free transmission mode that does not require an individual grant for uplink transmission. The RRC message may be sent, for example, in the first step of uplink transmission (e.g., RACH data) in the new random access procedure for NR.The new random access procedure for NR may be a procedure that simplifies the conventional LTE contention-based random access procedure, which consists of four steps, to two steps. Whether UE2 performs two-step or four-step random access may be configured in advance by gNB1. Alternatively, UE2 may perform the random access that is permitted (or supported) in the cell after cell reselection. Whether two-step or four-step random access is permitted (or supported) may be determined based on whether configuration information for the radio resources used for each method is transmitted in the system information.

[0063] The notification of the desired network slice may be, for example, by UE2 explicitly transmitting identification information of the desired network slice (e.g., a unique identifier or temporary identifier of the network slice, a slice category of the network slice, or a slice type (e.g., Slice / Service Type: SST)). For example, the identification information of the desired network slice may be transmitted in Network Slice Selection Assistance Information (NSSAI) included in an RRC message or a MAC Control Element. Additionally or alternatively, the identification information of the desired network slice may be implicitly transmitted using a predetermined signal sequence (e.g., a RACH preamble, an UL reference signal) or predetermined time, frequency, code, or spatial radio resources pre-associated therewith. The gNB1 may broadcast information on association between the identification information of the desired network slice and the signal sequence or radio resources in its own cell or may individually notify the UE2. When broadcast by the gNB1, the UE2 may receive (monitor) the broadcasted association information in the target cell of reselection when reselecting a cell. Furthermore, when multiple network nodes (e.g., Network Slice Instance: NSI) support (provide) the same network slice slice type, the gNB1 or 5G-CN may configure an identifier (e.g., Slice Defferentiator: SD) to distinguish between the multiple network nodes to the UE 2. In this case, the UE 2 may also explicitly or implicitly transmit the identifier in the notification of the desired network slice.

[0064] After receiving an RRC message including the notification or a signal indicating the notification, the gNB1 may place (i.e., transition) UE2 in the RRC_CONNECTED state or may keep UE2 in the RRC_INACTIVE state. In some implementations, the gNB1 may move UE2 to an appropriate cell if the network slice requested by UE2 is not available in the gNB1 or its cell. Specifically, the gNB1 may move UE2 to another cell in which the network slice requested by UE2 is available (or supported). The other cell to which UE2 is moved may be another cell provided by the gNB1 itself, different from the cell in which the gNB1 received notification of the desired network slice from UE2 (i.e., the cell reselected by UE2). Alternatively, the other cell to which UE2 is moved may be a cell of another gNB1. The gNB1 may use a handover procedure or a redirection procedure (e.g., RRC connection release with redirection) to move UE2 to an appropriate cell.

[0065] Note that, when UE2 receives RAN notification area information including multiple RAN notification areas and transmits uplink data in a cell after cell reselection (i.e., there is uplink data to transmit), it may operate as follows. UE2 may determine whether the network slice to which the uplink data belongs (or is associated) is available (or supported) in the cell based on whether the RAN notification area including the cell corresponds to the network slice, or based on whether the RAN notification area corresponding to the network slice includes the cell. For example, UE2 may transmit the uplink data if the RAN notification area corresponding to the network slice to which the uplink data to be transmitted belongs (or is associated) includes the cell after cell reselection. Otherwise (i.e., not included), UE2 may notify gNB1 of the desired network slice.

[0066] As can be understood from the above description, the gNB1 according to this embodiment is configured to transmit slice availability information to the UE2. The slice availability information indicates whether one or more network slices configured (or selected) for data communication in at least the RRC_CONNECTED state for the UE2 are available in each cell included in the RAN notification area for the UE2. The slice availability information thereby enables the UE2 to confirm whether a desired network slice is available in a cell (or a reselected cell) reselected by cell reselection in the RRC_INACTIVE state. Therefore, this embodiment can facilitate the UE2 in the RRC_INACTIVE state to know the availability of a network slice in a reselected cell or a reselected cell.

[0067] <Second embodiment> This embodiment provides a modified example of the mobility of UE2 in the RRC_INACTIVE state. The configuration example of the wireless communication network of this embodiment is the same as that of FIG.

[0068] The gNB1 according to this embodiment is configured to implicitly notify the UE2 of whether one or more network slices configured (or selected, permitted, or authorized) for the UE2 for data communication at least in the RRC_CONNECTED state are usable in each cell included in the RAN notification area for the UE2. More specifically, in this embodiment, the gNB1 is configured to include only one or more cells in which the network slice configured for the UE2 in the RRC_CONNECTED state is usable (or supported) in the RAN notification area for the UE2 in the RRC_INACTIVE state, and to configure the RAN notification area for the UE2. Thus, the RAN notification area implicitly indicates that the network slice configured for the UE2 is usable in each cell included in the RAN notification area.

[0069] 10 is a flowchart showing an example of the operation of gNB1 (process 1000). In step 1001, only one or more cells for which the network slice configured for UE2 in the RRC_CONNECTED state is available are included in the RAN notification area. In step 1002, gNB1 notifies UE2 of the determined RAN notification area. In step 1003, gNB1 transitions UE2 from the RRC_CONNECTED state to the RRC_INACTIVE state.

[0070] FIG. 11 is a flowchart showing an example of the operation of UE2 (process 1100). In step 1101, UE2 is in the RRC_CONNECTED state and receives a RAN notification area configuration from the serving gNB1. The RAN notification area includes only one or more cells for which the network slice configured for UE2 is available. In step 1102, UE2 transitions from the RRC_CONNECTED state to the RRC_INACTIVE state in response to an instruction from the serving gNB1. In step 1103, UE2 performs cell reselection in the RRC_INACTIVE state. UE2 checks whether a desired network slice is available in a reselected cell based on whether the reselected cell is included in the RAN notification area. Here, the desired network slice may be one or more network slices that were configured (or allowed or authorized) for UE2 by the network (i.e., 5G-CN4 or 5G-RAN3, or both) when UE2 was previously in the RRC_CONNECTED state.

[0071] The operations of UE2 and gNB1 after UE2 confirms network slice availability may be similar to the example described in the first embodiment.

[0072] The gNB1 may configure multiple RAN notification areas for the UE2 and may transmit RAN notification area information including the multiple RAN notification areas to the UE2. At least one of the multiple RAN notification areas included in the RAN notification area information may be determined to include only one or more cells for which the network slice configured (or selected, authorized, or approved) for the UE2 is available (or supported). For example, when a first and a second RAN notification area are configured for the UE2, the first RAN notification area may include only one or more cells for which the network slice configured (or selected, authorized, or approved) for the UE2 is available (or supported), and the second RAN notification area may include one or more cells to which the UE2 can move (i.e., cell reselection) without notifying the gNB1. In this case, the second RAN notification area may be configured for the UE2 by default, and the first RAN notification area may be configured for the UE2 as an option. In other words, the gNB1 may always transmit the second RAN notification area to the UE2 as a RAN notification area that applies to the UE2 regardless of the use of a network slice. On the other hand, gNB1 may send the first RAN notification area to UE2 only if UE2 uses a network slice or configures a network slice for UE2.

[0073] Additionally or alternatively, a RAN notification area may be configured for each slice category or slice type of a network slice configured (or selected, permitted, or approved) in UE2. In one example, the correspondence between multiple RAN notification areas and multiple network slices may be determined by the configuration order of multiple RAN notification areas and the configuration order of multiple network slices. That is, the RAN notification area configured first in the configuration order may be associated with the network slice configured first in the configuration order. Alternatively, the correspondence between multiple RAN notification areas and multiple network slices may be determined by the configuration order of multiple RAN notification areas and the ascending order of identifiers of multiple network slices. That is, the RAN notification area configured first in the configuration order may be associated with the network slice with the smallest identifier. Note that if the number of network slices configured in UE2 excluding the above-mentioned default configuration (default RAN notification area) is different from the number of RAN notification areas configured in UE2, UE2 may apply the following handling. If the number of configured network slices is greater than the number of RAN notification areas, UE2 recognizes that the remaining network slices that cannot be associated with the RAN notification areas are not available (or not supported) outside the serving cell (i.e., the cell from which UE2 receives the RAN notification area). Conversely, if the number of configured network slices is less than the number of RAN notification areas, UE2 ignores the remaining RAN notification areas that cannot be associated with the network slices.

[0074] As can be understood from the above description, the gNB1 according to this embodiment determines a RAN notification area including only one or more cells in which one or more network slices configured (or selected) for UE2 are available for data communication at least in the RRC_CONNECTED state, and notifies UE2 of the determined RAN notification area. The RAN notification area thereby enables UE2 to confirm whether a desired network slice is available in a cell (or a reselected cell) that is reselected by cell reselection in the RRC_INACTIVE state. Therefore, this embodiment can facilitate UE2 in the RRC_INACTIVE state to know the availability of a network slice in a reselected cell or a reselected cell.

[0075] <Third embodiment> This embodiment provides a modified example of the mobility of UE2 in the RRC_INACTIVE state. The configuration example of the wireless communication network of this embodiment is the same as that of FIG.

[0076] The gNB1 according to this embodiment is configured to transmit, in each of its cells, system information (SI) indicating one or more network slices that are available (or supported) or unavailable (or unsupported) in the cell. The system information may be included in a broadcast system information block broadcast in each cell. Alternatively, the system information may be included in an on-demand system information block transmitted to a UE2 in response to a request message from the UE2 or in response to a trigger within the network.

[0077] FIG. 12 is a sequence diagram showing an example (process 1200) of the operation of gNB1 and UE2 according to this embodiment. In step 1201, UE2 is in an RRC_INACTIVE state and performs a cell reselection procedure. In step 1202, UE2 receives system information from gNB1 in a reselected cell (or a reselected cell). The system information includes network slice availability information. The network slice availability information indicates one or more network slices that are available or unavailable in the cell. As described above, the network slice availability information may be included in an on-demand system information block.

[0078] If the network slice availability information is a broadcast system information block, UE2 may receive the broadcast system information block in the reselected cell in response to cell reselection and confirm network slice availability in the reselected cell.

[0079] If the network slice availability information is an on-demand system information block, for example, gNB1 broadcasts primary information (e.g., indication of system information on the network slicing, availability of network slicing SI) indicating that system information including the network slice availability information is transmitted in the on-demand system information block. If the primary information is transmitted in system information required for UE2 to access a cell (e.g., essential system information in LTE or minimum system information in NR), UE2 receives the primary information before performing cell reselection. Then, after performing cell reselection (in response thereto), UE2 requests gNB1 to transmit the on-demand system information block. gNB1 transmits the network slice availability information in response to the request from UE2.

[0080] The UE2 may transmit the on-demand system information block transmission request immediately in response to cell reselection. Alternatively, the UE2 may transmit the on-demand system information block transmission request when transitioning to the RRC_CONNECTED state because uplink data to be transmitted has occurred or for other purposes. Additionally or alternatively, the UE2 may transmit the on-demand system information block transmission request while in the RRC_INACTIVE state. Note that if primary information is transmitted in other system information (i.e., system information other than that required for the UE2 to access the cell), the UE2 may receive the primary information after (in response to) performing cell reselection. In some implementations, the UE2 may transmit the on-demand system information block transmission request over a random access channel (RACH) or using dedicated signaling (e.g., RRC signaling or Medium Access Control (MAC) Control Element (CE)).

[0081] FIG. 13 is a sequence diagram showing an example (process 1300) of the operation of gNB1 and UE2 when the network slice availability information is an on-demand system information block. In step 1301, gNB1 transmits a notification of available on-demand system information. The notification of available on-demand system information corresponds to the primary information described above. The notification is necessary for UE2 to access gNB1's cell 11 and is included in system information (e.g., Essential SI, SIB1) broadcast in gNB1's cell 11. Alternatively, the notification of available on-demand system information may be included in another SI other than Essential SI.

[0082] In step 1302, UE2 is in the RRC_INACTIVE state and performs a cell reselection procedure. UE2 checks the "notification of available on-demand system information" included in the system information received in step 1301 and sends a transmission request for on-demand SI including network slice information to gNB1 (step 1304). Note that if the notification of available on-demand system information is included in another SI other than Essential SI, UE2 may receive the other SI (e.g., SIBx) after cell reselection (step 1303). If the notification of available on-demand system information is included in Essential SI (e.g., SIB1), step 1303 is omitted. In step 1305, system information including network slice availability information is received from gNB1.

[0083] 14 is a flowchart showing an example of the operation of UE2 (process 1400). In step 1401, UE2 attempts to receive system information including network slice availability information in the reselected cell in response to cell reselection in the RRC_INACTIVE state. In step 1402, UE2 checks whether a desired network slice is available in the reselected cell based on the received system information. Here, the desired network slice may be one or more network slices that were configured (or allowed or authorized) for UE2 by the network (i.e., 5G-CN4 or 5G-RAN3, or both) when UE2 was previously in the RRC_CONNECTED state.

[0084] The operations of UE2 and gNB1 after UE2 confirms network slice availability may be similar to the example described in the first embodiment.

[0085] As can be understood from the above description, the gNB1 according to this embodiment transmits, in each cell, system information indicating the availability of a network slice for each cell. This enables the UE2 to confirm whether a desired network slice is available in a cell reselected (or a reselected cell) by cell reselection in the RRC_INACTIVE state. Therefore, this embodiment can facilitate the UE2 in the RRC_INACTIVE state to know the availability of a network slice in a reselected cell or a reselected cell.

[0086] <Fourth embodiment> This embodiment provides an operation when downlink user data addressed to UE2 in the RRC_INACTIVE state arrives at the network. The configuration example of the wireless communication network of this embodiment is the same as that of FIG.

[0087] When downlink user data addressed to UE2 in the RRC_INACTIVE state arrives at 5G-CN4, 5G-CN4 forwards the user data to the gNB1 (e.g., gNB1A) to which UE2 was connected when it transitioned to the RRC_INACTIVE state. gNB1A transmits a notification of the arrival of downlink user data (also called RAN-based paging) similar to existing paging messages in its own cell 11A. Furthermore, if the RAN notification area (RNA) configured for UE2 includes the cells of another gNB1 (e.g., gNB1B), it notifies gNB1B of the arrival of downlink user data addressed to UE2 via the inter-gNB interface (Xn) (also called Xn paging). The Xn paging may include information about the RAN notification area (RNA) to which UE2 belongs. gNB1B may then transmit a similar RAN-based paging in its own cell 11B included in the RNA.

[0088] The gNB1A may include information indicating one or more network slices configured (or authorized or accepted) for the UE2 in the Xn paging (i.e., notification that downlink user data for the UE2 has arrived) sent to the gNB1B, thereby enabling the gNB1B to know the network slice that the UE2 is using (or desires).

[0089] gNB1A may include information about the RAN notification area configured (notified) for UE2 in the Xn paging (i.e., notification that downlink user data has arrived for UE2) sent to gNB1B, allowing gNB1B to know the cell to which RAN-based paging should be sent.

[0090] Next, exemplary configurations of gNB1 and UE2 according to the above-described embodiments will be described below. FIG. 15 is a block diagram showing an exemplary configuration of gNB1 according to the above-described embodiments. Referring to FIG. 15, gNB1 includes a radio frequency transceiver 1501, a network interface 1503, a processor 1504, and a memory 1505. The RF transceiver 1501 performs analog RF signal processing for communication with NG UEs, including UE2. The RF transceiver 1501 may include multiple transceivers. The RF transceiver 1501 is coupled to an antenna array 1502 and the processor 1504. The RF transceiver 1501 receives modulation symbol data from the processor 1504, generates a transmit RF signal, and provides the transmit RF signal to the antenna array 1502. The RF transceiver 1501 also generates a baseband receive signal based on the receive RF signal received by the antenna array 1502 and provides the baseband receive signal to the processor 1504. The RF transceiver 1501 may include analog beamformer circuitry for beamforming, which may include, for example, multiple phase shifters and multiple power amplifiers.

[0091] The network interface 1503 is used to communicate with network nodes (e.g., control nodes and forwarding nodes of the 5G-CN4). The network interface 1503 may include, for example, a network interface card (NIC) compliant with the IEEE 802.3 series.

[0092] The processor 1504 performs digital baseband signal processing (data plane processing) and control plane processing for wireless communication. The processor 1504 may include multiple processors. For example, the processor 1504 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 micro processing unit (MPU)) that performs control plane processing. The processor 1504 may include a digital beamformer module for beamforming. The digital beamformer module may include a multiple input multiple output (MIMO) encoder and precoder.

[0093] The memory 1505 is configured by a combination of volatile memory and nonvolatile memory. The volatile memory is, for example, Static Random Access Memory (SRAM), Dynamic RAM (DRAM), or a combination thereof. The nonvolatile memory is, for example, Mask Read Only Memory (MROM), Electrically Erasable Programmable ROM (EEPROM), flash memory, or a hard disk drive, or any combination thereof. The memory 1505 may include storage located remotely from the processor 1504. In this case, the processor 1504 may access the memory 1505 via the network interface 1503 or an I / O interface (not shown).

[0094] The memory 1505 may store one or more software modules (computer programs) 1506 including instructions and data for performing the processing by the gNB1 described in the above-described embodiments. In some implementations, the processor 1504 may be configured to read and execute the software modules 1506 from the memory 1505 to perform the processing by the gNB1 described in the above-described embodiments.

[0095] FIG. 16 is a block diagram showing an example configuration of UE2. A radio frequency (RF) transceiver 1601 performs analog RF signal processing for communication with gNB1. The RF transceiver 1601 may include multiple transceivers. The analog RF signal processing performed by the RF transceiver 1601 includes frequency up-conversion, frequency down-conversion, and amplification. The RF transceiver 1601 is coupled to an antenna array 1602 and a baseband processor 1603. The RF transceiver 1601 receives modulation symbol data (or OFDM symbol data) from the baseband processor 1603, generates a transmit RF signal, and provides the transmit RF signal to the antenna array 1602. The RF transceiver 1601 also generates a baseband receive signal based on the receive RF signal received by the antenna array 1602 and provides the baseband receive signal to the baseband processor 1603. The RF transceiver 1601 may include an analog beamformer circuit for beamforming. The analog beamformer circuitry includes, for example, multiple phase shifters and multiple power amplifiers.

[0096] The baseband processor 1603 performs digital baseband signal processing (data plane processing) and control plane processing for wireless communication. Digital baseband signal processing includes (a) data compression / decompression, (b) data segmentation / concatenation, (c) transmission format (transmission frame) generation / decomposition, (d) transmission path coding / decoding, (e) modulation (symbol mapping) / demodulation, and (f) generation of OFDM symbol data (baseband OFDM signal) using Inverse Fast Fourier Transform (IFFT). Meanwhile, control plane processing includes communication management for Layer 1 (e.g., transmit power control), Layer 2 (e.g., radio resource management and hybrid automatic repeat request (HARQ) processing), and Layer 3 (e.g., signaling related to attachment, mobility, and call management).

[0097] For example, the digital baseband signal processing by the baseband processor 1603 may include signal processing of a Packet Data Convergence Protocol (PDCP) layer, a Radio Link Control (RLC) layer, a MAC layer, and a PHY layer. Also, the control plane processing by the baseband processor 1603 may include processing of a Non-Access Stratum (NAS) protocol, an RRC protocol, and a MAC CE.

[0098] The baseband processor 1603 may perform MIMO encoding and precoding for beamforming.

[0099] The baseband processor 1603 may include a modem processor (e.g., DSP) that performs digital baseband signal processing and a protocol stack processor (e.g., CPU or MPU) that performs control plane processing. In this case, the protocol stack processor that performs control plane processing may be shared with the application processor 1604, which will be described later.

[0100] The application processor 1604 is also referred to as a CPU, MPU, microprocessor, or processor core. The application processor 1604 may include multiple processors (multiple processor cores). The application processor 1604 executes a system software program (operating system (OS)) and various application programs (e.g., a calling application, a web browser, a mailer, a camera operation application, and a music playback application) read from the memory 1606 or a memory not shown, thereby realizing various functions of the UE2.

[0101] In some implementations, the baseband processor 1603 and the application processor 1604 may be integrated on a single chip, as indicated by the dashed line (1605) in Figure 16. In other words, the baseband processor 1603 and the application processor 1604 may be implemented as a single System on Chip (SoC) device 1605. An SoC device may also be called a system Large Scale Integration (LSI) or a chipset.

[0102] The memory 1606 is volatile memory, nonvolatile memory, or a combination thereof. The memory 1606 may include multiple physically independent memory devices. The volatile memory is, for example, SRAM, DRAM, or a combination thereof. The nonvolatile memory is, for example, MROM, EEPROM, flash memory, or a hard disk drive, or any combination thereof. For example, the memory 1606 may include an external memory device accessible from the baseband processor 1603, the application processor 1604, and the SoC 1605. The memory 1606 may also include an internal memory device integrated within the baseband processor 1603, the application processor 1604, or the SoC 1605. Furthermore, the memory 1606 may include memory within a Universal Integrated Circuit Card (UICC).

[0103] The memory 1606 may store one or more software modules (computer programs) 1607 including instructions and data for performing the processing by the UE 2 described in the above embodiments. In some implementations, the baseband processor 1603 or the application processor 1604 may be configured to read and execute the software modules 1607 from the memory 1606 to perform the processing by the UE 2 described in the above embodiments using the drawings.

[0104] As described with reference to FIGS. 15 and 16 , each of the processors included in the gNB1 and UE2 according to the above-described embodiments executes one or more programs including instructions for causing a computer to perform the algorithms described with reference to the drawings. The programs can be stored and provided to a computer using various types of non-transitory computer-readable media. Non-transitory computer-readable media include various types of tangible storage media. Examples of non-transitory computer-readable media include magnetic storage media (e.g., flexible disks, magnetic tapes, hard disk drives), magneto-optical storage media (e.g., magneto-optical disks), Compact Disc Read Only Memory (CD-ROM), CD-R, CD-R / W, and semiconductor memory (e.g., mask ROM, programmable ROM (PROM), erasable PROM (EPROM), flash ROM, random access memory (RAM)). The programs may also be provided to a computer by various types of transitory computer-readable media. Examples of transitory computer-readable media include electrical signals, optical signals, and electromagnetic waves. The temporary computer-readable medium can supply the program to the computer via a wired communication path such as an electric wire or an optical fiber, or via a wireless communication path.

[0105] <Other embodiments> The 5G-RAN 3 described in the above embodiments may be implemented based on the Cloud Radio Access Network (C-RAN) concept. C-RAN is sometimes referred to as Centralized RAN. Therefore, the processing and operations performed by the gNB 1 described in the above embodiments may 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). The DU is also referred to as a Baseband Unit (BBU) or a Central Unit (CU). The RU is also referred to as a Remote Radio Head (RRH), Remote Radio Equipment (RRE), Distributed Unit (DU), or Transmission and Reception Point (TRP or TRxP). In other words, the processing and operations performed by each gNB 1 described in the above embodiments may be provided by any one or more radio stations (or RAN nodes).

[0106] The above-described embodiment has been described with a focus on cell reselection by a UE in the RRC_INACTIVE state. However, network slice availability may be configured not only per cell, but also per PLMN. That is, whether a desired network slice of UE2 is available (or supported) in a visited cell may differ for each PLMN. For example, network slice availability information may be sent to UE2 "per PLMN." If a desired network slice is not available (or not supported) in a selected PLMN of UE2, the UE AS layer may notify the NAS layer. In this case, the AS layer may notify the NAS layer of per-PLMN network slice information (e.g., information on whether a network slice is available or information on available network slices). The NAS layer may then perform PLMN selection taking into account the information received from the AS layer and notify the AS layer of the result (i.e., the newly selected PLMN).

[0107] The above-described embodiments may be applied to other wireless communication systems that support network slicing and use the RRC_INACTIVE state or a similar RRC state, as already mentioned. For example, a case may be considered in which an LTE E-UTRAN (eNB) is connected to a 5G-CN and network slicing is supported in the E-UTRAN cell. Furthermore, a case may be considered in which, like the above-described RRC_INACTIVE state, the UE and the eNB maintain at least a portion of the UE's AS context, and a state, sub-state, or operation mode in which the UE's location is known by the E-UTRAN at the level of a predetermined area established by the E-UTRAN is supported. In this case, the predetermined area may be similar to a RAN notification area or may be the same as a location registration area (e.g., TA) of the core network.

[0108] Furthermore, the above-described embodiments are merely examples of application of the technical ideas obtained by the inventors of the present invention. In other words, the technical ideas are not limited to the above-described embodiments, and various modifications are possible.

[0109] For example, some or all of the above embodiments can be described as, but are not limited to, the following supplementary notes.

[0110] (Appendix 1) A base station disposed in a radio access network (RAN), comprising: Memory and at least one processor coupled to the memory; Equipped with the at least one processor is configured to control state transitions of a first wireless terminal between a first RRC state, a second RRC state, and a third RRC state; the first RRC state is a state in which the first radio terminal and the RAN maintain an Access Stratum (AS) context and the location of the first radio terminal is known by the RAN at a cell level; the second RRC state is a state in which the first radio terminal and the RAN maintain at least a part of the AS context, and the location of the first radio terminal is known by the RAN at the level of a RAN notification area configured by the RAN; the third RRC state is a state in which the first radio terminal and the RAN are releasing the AS context, and the location of the first radio terminal is unknown by the RAN; The at least one processor is further configured to explicitly or implicitly notify the first radio terminal whether a first network slice configured in the first radio terminal for data communication in at least the first RRC state is available in each cell included in the RAN notification area. Base station.

[0111] (Appendix 2) the at least one processor is configured to transmit, to the first wireless terminal, first information that explicitly indicates whether the first network slice is available in each cell included in the RAN notification area; 1. A base station as defined in claim 1.

[0112] (Appendix 3) the at least one processor is configured to transmit the first information to the first wireless terminal when configuring the RAN notification area in the first wireless terminal; 1. A base station as defined in claim 2.

[0113] (Appendix 4) the at least one processor is configured to transmit the first information to the first wireless terminal within a procedure of transitioning the first wireless terminal from the first RRC state to the second RRC state. 4. The base station according to claim 2 or 3.

[0114] (Appendix 5) the at least one processor is configured to include only one or more cells in which the first network slice is available in the RAN notification area for the first wireless terminal, and to configure the RAN notification area for the first wireless terminal; The RAN notification area implicitly indicates that the first network slice is available in each cell included in the RAN notification area. 1. A base station as defined in claim 1.

[0115] (Appendix 6) the at least one processor is configured to receive information from the other base station via an inter-base station interface, the information indicating one or more network slices available or unavailable in each cell of the other base station. 6. The base station according to any one of Supplementary notes 1 to 5.

[0116] (Appendix 7) The at least one processor is configured to receive, during or after a procedure of transitioning a second radio terminal from the second RRC state to the first RRC state, second information from the second radio terminal indicating a second network slice that was previously set in the second radio terminal when the second radio terminal was in the first RRC state. The base station according to any one of Supplementary notes 1 to 6.

[0117] (Appendix 8) the at least one processor is configured to, when the second network slice is not available in the base station or a cell to which the second wireless terminal is connected, transfer the second wireless terminal to another base station or another cell. 8. The base station described in Supplementary Note 7.

[0118] (Appendix 9) the first RRC state is an RRC_CONNECTED state; the second RRC state is an RRC_INACTIVE state; the third RRC state is an RRC_IDLE state; The base station according to any one of Supplementary notes 1 to 8.

[0119] (Appendix 10) The RAN notification area is an area in which the first radio terminal does not need to report the cell reselection to the RAN even if the first radio terminal moves between cells by cell reselection when the first radio terminal is in the second RRC state. The base station according to any one of Supplementary notes 1 to 9.

[0120] (Appendix 11) A base station disposed in a radio access network (RAN), comprising: Memory and at least one processor coupled to the memory; Equipped with the at least one processor is configured to control state transitions of the wireless terminal between a first RRC state, a second RRC state, and a third RRC state; the first RRC state is a state in which the radio terminal and the RAN maintain an Access Stratum (AS) context and the location of the radio terminal is known by the RAN at a cell level; the second RRC state is a state in which the radio terminal and the RAN maintain at least a part of the AS context, and the location of the radio terminal is known by the RAN at the level of a RAN notification area configured by the RAN; the third RRC state is a state in which the radio terminal and the RAN are releasing the AS context, and the location of the radio terminal is not known by the RAN; The at least one processor is further configured to transmit, in a first cell of the base station, system information indicating one or more network slices available or unavailable in the first cell. Base station.

[0121] (Appendix 12) the system information is broadcast system information broadcast in the first cell or on-demand system information transmitted to the wireless terminal in response to a request message from the wireless terminal; 12. The base station of claim 11.

[0122] (Appendix 13) The at least one processor is configured to receive, during or after a procedure of transitioning the radio terminal from the second RRC state to the first RRC state, information from the radio terminal indicating a first network slice that was set in the radio terminal when the radio terminal was previously in the first RRC state. 13. The base station according to claim 11 or 12.

[0123] (Appendix 14) the at least one processor is configured to, when the first network slice is not available in the base station or a cell to which the wireless terminal is connected, transfer the wireless terminal to another base station or another cell. 14. The base station of claim 13.

[0124] (Appendix 15) the first RRC state is an RRC_CONNECTED state; the second RRC state is an RRC_INACTIVE state; the third RRC state is an RRC_IDLE state; The base station according to any one of Supplementary notes 11 to 14.

[0125] (Appendix 16) A wireless terminal, A transceiver; at least one processor configured to control the transceiver in one or more cells associated with a Radio Access Network (RAN); Equipped with the at least one processor is configured to control state transitions of the wireless terminal between a first RRC state, a second RRC state, and a third RRC state; the first RRC state is a state in which the radio terminal and the RAN maintain an Access Stratum (AS) context and the location of the radio terminal is known by the RAN at a cell level; the second RRC state is a state in which the radio terminal and the RAN maintain at least a part of the AS context, and the location of the radio terminal is known by the RAN at the level of a RAN notification area configured by the RAN; the third RRC state is a state in which the radio terminal and the RAN are releasing the AS context, and the location of the radio terminal is not known by the RAN; The at least one processor is further configured to check whether a first network slice configured in the radio terminal for data communication in at least the first RRC state is available in a cell reselected by cell reselection in the second RRC state. Wireless terminal.

[0126] (Appendix 17) the at least one processor is configured to receive, from a base station in the RAN, first information that explicitly indicates whether a first network slice configured in the wireless terminal for data communication in at least the first RRC state is available in each cell included in the RAN notification area; 17. The wireless terminal of claim 16.

[0127] (Appendix 18) the at least one processor is configured to receive the first information during a procedure in which the wireless terminal transitions from the first RRC state to the second RRC state. 18. The wireless terminal of claim 17.

[0128] (Appendix 19) the RAN notification area includes only one or more cells in which the first network slice is available; the at least one processor is configured to receive the RAN notification area configuration from a base station within the RAN; The at least one processor is configured to determine whether the first network slice is available in the reselected cell based on whether the reselected cell is included in the RAN notification area. 17. The wireless terminal of claim 16.

[0129] (Appendix 20) the at least one processor is configured to, in response to cell reselection in the second RRC state, attempt to receive, in the reselected cell, system information indicating one or more network slices available or unavailable in the reselected cell; The at least one processor is configured to determine, based on the system information, whether the first network slice is available in the reselected cell. 17. The wireless terminal of claim 16.

[0130] (Appendix 21) the system information is broadcast system information broadcast in the reselected cell or on-demand system information transmitted to the wireless terminal in response to a request message from the wireless terminal; 21. The wireless terminal of claim 20.

[0131] (Appendix 22) When the at least one processor cannot confirm that the first network slice is available in the reselected cell, the at least one processor is configured to transmit second information indicating the first network slice to a base station of the reselected cell during or after a procedure in which the wireless terminal transitions from the second RRC state to the first RRC state in the reselected cell. 22. A wireless terminal according to any one of Supplementary Notes 16 to 21.

[0132] (Appendix 23) the first RRC state is an RRC_CONNECTED state; the second RRC state is an RRC_INACTIVE state; the third RRC state is an RRC_IDLE state; A wireless terminal according to any one of Supplementary notes 16 to 22.

[0133] (Appendix 24) 1. A method in a base station disposed in a Radio Access Network (RAN), comprising: controlling state transitions of the first wireless terminal between a first RRC state, a second RRC state, and a third RRC state; and notifying the first radio terminal, explicitly or implicitly, of whether a first network slice configured in the first radio terminal for data communication in at least the first RRC state is usable in each cell included in a RAN notification area configured by the RAN; Equipped with the first RRC state is a state in which the first radio terminal and the RAN maintain an Access Stratum (AS) context and the location of the first radio terminal is known by the RAN at a cell level; the second RRC state is a state in which the first radio terminal and the RAN maintain at least a part of the AS context, and the location of the first radio terminal is known by the RAN at the level of the RAN notification area; the third RRC state is a state in which the first radio terminal and the RAN are releasing the AS context, and the location of the first radio terminal is unknown by the RAN; method.

[0134] (Appendix 25) 1. A method in a base station disposed in a Radio Access Network (RAN), comprising: controlling state transitions of the wireless terminal between the first RRC state, the second RRC state, and the third RRC state; and transmitting system information in a first cell of the base station, the system information indicating one or more network slices available or unavailable in the first cell; Equipped with the first RRC state is a state in which the radio terminal and the RAN maintain an Access Stratum (AS) context and the location of the radio terminal is known by the RAN at a cell level; the second RRC state is a state in which the radio terminal and the RAN maintain at least a part of the AS context, and the location of the radio terminal is known by the RAN at the level of a RAN notification area configured by the RAN; the third RRC state is a state in which the radio terminal and the RAN are releasing the AS context, and the location of the radio terminal is not known by the RAN; method.

[0135] (Appendix 26) 1. A method in a wireless terminal, comprising: controlling state transitions of the wireless terminal between a first RRC state, a second RRC state, and a third RRC state; and checking whether a first network slice configured in the radio terminal for data communication in at least the first RRC state is usable in a cell to be reselected by cell reselection in the second RRC state; Equipped with the first RRC state is a state in which the radio terminal and a radio access network (RAN) maintain an access stratum (AS) context and the location of the radio terminal is known by the RAN at a cell level; the second RRC state is a state in which the radio terminal and the RAN maintain at least a part of the AS context, and the location of the radio terminal is known by the RAN at the level of a RAN notification area configured by the RAN; the third RRC state is a state in which the radio terminal and the RAN are releasing the AS context, and the location of the radio terminal is not known by the RAN; method.

[0136] (Appendix 27) A program for causing a computer to perform a method in a base station disposed in a radio access network (RAN), comprising: The method comprises: controlling state transitions of the first wireless terminal between a first RRC state, a second RRC state, and a third RRC state; and notifying the first radio terminal, explicitly or implicitly, of whether a first network slice configured in the first radio terminal for data communication in at least the first RRC state is usable in each cell included in a RAN notification area configured by the RAN; Equipped with the first RRC state is a state in which the first radio terminal and the RAN maintain an Access Stratum (AS) context and the location of the first radio terminal is known by the RAN at a cell level; the second RRC state is a state in which the first radio terminal and the RAN maintain at least a part of the AS context, and the location of the first radio terminal is known by the RAN at the level of the RAN notification area; the third RRC state is a state in which the first radio terminal and the RAN are releasing the AS context, and the location of the first radio terminal is unknown by the RAN; program.

[0137] (Appendix 28) A program for causing a computer to perform a method in a base station disposed in a radio access network (RAN), comprising: The method comprises: controlling state transitions of the wireless terminal between the first RRC state, the second RRC state, and the third RRC state; and transmitting system information in a first cell of the base station, the system information indicating one or more network slices available or unavailable in the first cell; Equipped with the first RRC state is a state in which the radio terminal and a radio access network (RAN) maintain an access stratum (AS) context and the location of the radio terminal is known by the RAN at a cell level; the second RRC state is a state in which the radio terminal and the RAN maintain at least a part of the AS context, and the location of the radio terminal is known by the RAN at the level of a RAN notification area configured by the RAN; the third RRC state is a state in which the radio terminal and the RAN are releasing the AS context, and the location of the radio terminal is not known by the RAN; program.

[0138] (Appendix 29) A program for causing a computer to perform a method in a wireless terminal, comprising: The method comprises: controlling state transitions of the wireless terminal between a first RRC state, a second RRC state, and a third RRC state; and checking whether a first network slice configured in the radio terminal for data communication in at least the first RRC state is usable in a cell to be reselected by cell reselection in the second RRC state; Equipped with the first RRC state is a state in which the radio terminal and a radio access network (RAN) maintain an access stratum (AS) context and the location of the radio terminal is known by the RAN at a cell level; the second RRC state is a state in which the radio terminal and the RAN maintain at least a part of the AS context, and the location of the radio terminal is known by the RAN at the level of a RAN notification area configured by the RAN; the third RRC state is a state in which the radio terminal and the RAN are releasing the AS context, and the location of the radio terminal is not known by the RAN; program.

[0139] This application claims priority based on Japanese Patent Application No. 2017-000800, filed January 5, 2017, the disclosure of which is incorporated herein by reference in its entirety. [Explanation of symbols]

[0140] 1 gNodeB (gNB) 2. User Equipment (UE) 3 5G Radio Access Network (5G-RAN) 4. 5G Core Network (5G-CN) 11 cells 1501 RF Transceiver 1504 processor 1505 memory 1601 RF Transceiver 1603 Baseband Processor 1604 Application Processor 1606 memory

Claims

1. A UE (User Equipment), means for receiving an RRC (Radio Resource Control) message from a network, the RRC message being transmitted to transition the UE from an RRC_CONNECTED state to an RRC_INACTIVE state and including information for cell reselection based on a network slice; the information is cell information specifying one or more cells included in a RAN (Radio Access Network) notification area; The cell information specifies only cells that support a specific network slice and are included in a registration area of ​​the UE; The cell information is provided to enable the UE to reselect a cell that supports the specific network slice. UE.

2. The RRC message is an RRC release message. The UE of claim 1.

3. means for performing the cell reselection in the RRC_INACTIVE state; 3. The UE according to claim 1 or 2.

4. A method for a UE (User Equipment), comprising: receiving an RRC (Radio Resource Control) message from a network, the RRC message being sent to transition the UE from an RRC_CONNECTED state to an RRC_INACTIVE state and including information for cell reselection based on a network slice; the information is cell information specifying one or more cells included in a RAN (Radio Access Network) notification area; The cell information specifies only cells that support a specific network slice and are included in a registration area of ​​the UE; The cell information is provided to enable the UE to reselect a cell that supports the specific network slice. method.

5. The RRC message is an RRC release message. The method of claim 4.

6. performing the cell reselection in the RRC_INACTIVE state; 6. The method according to claim 4 or 5.

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