gNB, user equipment and method thereof

Abstract

The present application provides a gNB, a user equipment and a method thereof. A base station (1) controls a state transition of a wireless terminal (2) between a first RRC state, a second RRC state and a third RRC state. In addition, the base station (1) explicitly or implicitly notifies the wireless terminal (2) whether a network slice configured in the wireless terminal (2) for data communication at least in the first RRC state is available in each cell included in a RAN notification area configured by the RAN (3). Thus, for example, a wireless terminal in a first state (e.g., RRC_INACTIVE state) can be easily aware of the availability of a cell to be reselected or a network slice in a reselected cell.

Description

[0001] (This application is a divisional application of an application filed on November 21, 2017, with application number 201780087884.0, and invention name “Base station, wireless terminal, method thereof, and non-transitory computer-readable medium”.) Technical Field

[0002] The present invention relates to wireless communication systems, and in particular, to mobility of wireless terminals. Background Art

[0003] The 3rd Generation Partnership Project (3GPP) has started standardization of the fifth generation mobile communication system (5G) in 2016 (i.e., 3GPP Release 14) to make 5G a commercial reality in or after 2020 (see Non-Patent Literature 1). 5G is expected to be achieved through continued enhancement / evolution of LTE and Advanced LTE and through innovative enhancement / evolution of the introduction of new 5G air interfaces (i.e., new radio access technologies (RATs)). The new RAT supports, for example, higher frequency bands than those supported by LTE / Advanced LTE and its continued evolution (e.g., below 6 GHz). For example, the new RAT supports centimeter wave bands (above 10 GHz) and millimeter wave bands (above 30 GHz).

[0004] In this specification, the fifth generation mobile communication system is referred to as a 5G system or a next generation (NextGen) system (NG system). The new RAT of the 5G system is referred to as a new air interface (NR), 5G RAT or NG RAT. The new radio access network (RAN) of the 5G system is referred to as 5G-RAN or NextGen RAN (NG RAN). The new base station within the NG-RAN is referred to as an NR node B (NR NB) or gNodeB (gNB). The new core network of the 5G system is referred to as a 5G core network (5G-CN) or NextGen core (NG core). A wireless terminal (ie, user equipment (UE)) that can be connected to the 5G system is referred to as a 5G UE or NextGen UE (NG UE), or simply referred to as a UE. As standardization progresses, the official names of RAT, UE, radio access network, core network, network entity (node) and protocol layer for the 5G system will be determined in the future.

[0005] Unless otherwise specified, the term "LTE" used in this specification includes enhancements / evolutions of LTE and advanced LTE to provide intercommunication with 5G systems. The enhancements / evolutions of LTE and advanced LTE used for intercommunication with 5G systems are referred to as advanced LTE Pro, LTE+, or enhanced LTE (eLTE). In addition, unless otherwise specified, the terms related to LTE networks and logical entities used in this specification (such as "evolved packet core (EPC)", "mobility management entity (MME)", "serving gateway (S-GW)", and "packet data network (PDN) gateway (P-GW)", etc.) include their enhancements / evolutions to provide intercommunication with 5G systems. Enhanced EPC, enhanced MME, enhanced S-GW, and enhanced P-GW are respectively referred to as, for example, enhanced EPC (eEPC), enhanced MME (eMME), enhanced S-GW (eS-GW), and enhanced P-GW (eP-GW).

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

[0007] In contrast, with respect to the 5G system, it is discussed that although a radio bearer can be used in 5G-RAN, the bearer is not used in 5G-CN or in the interface between 5G-CN and NG-RAN (see non-patent document 1). Specifically, a PDU flow is defined instead of an EPS bearer, and one or more SDFs are mapped to one or more PDU flows. The PDU flow between the 5G UE and the user plane terminal entity in the NG core (i.e., the entity corresponding to the P-GW in the EPC) corresponds to the EPS bearer in the EPS bearer-based QoS concept. That is, instead of the bearer-based QoS concept, the 5G system adopts a flow-based QoS (or QoS for each flow) concept. In the flow-based QoS concept, QoS is processed for each PDU flow. Therefore, the PDU flow is also called a QoS flow. The association between the 5G UE and the data network is called a "PDU session". The term "PDU session" corresponds to the term "PDN connection" in LTE and Advanced LTE. Multiple PDU flows (or QoS flows) can be configured in one PDU session.

[0008] In addition, it has been suggested that the 5G system supports network slicing (see non-patent document 1). Network slicing uses network function virtualization (NFV) technology and software defined network (SDN) technology, and makes it possible to create multiple virtualized logical networks on a physical network. Each virtualized logical network is called a network slice or a network slice instance, includes logical nodes and functions, and is used for specific traffic and signaling. 5G-RAN or 5G-CN or both have a slice selection function (SSF). SSF selects one or more network slices suitable for 5G UE based on information provided by at least one of 5G UE and 5G-CN.

[0009] Figure 1 The basic architecture of the 5G system is shown. The UE establishes one or more signaling radio bearers (SRBs) and one or more data radio bearers (DRBs) with the gNB. The 5G-CN and the gNB establish a control plane interface and a user plane interface used by the UE. The control plane interface between the 5G-CN and the gNB (ie, RAN) is called the NG2 interface or the NG-c interface, and is used for the transmission of non-access stratum (NAS) information and for the transmission of control information between the 5G-CN and the gNB. The user plane interface between the 5G-CN and the gNB (ie, RAN) is called the NG3 interface or the NG-u interface, and is used for the transmission of packets of one or more PDU flows (or QoS flows) within the PDU session of the UE.

[0010] In addition, in the 5G system, in addition to the existing RRC_CONNECTED state and RRC_IDLE state, a new RRC state is introduced (for example, see non-patent documents 1 to 5). This new RRC state is called RRC_INACTIVE state or RRC_INACTIVE_CONNECTED state.

[0011] The RRC_CONNECTED state and RRC_IDLE state of the 5G system have the same characteristics as the RRC_CONNECTED state and RRC_IDLE state of LTE, respectively. When the UE is in the RRC_CONNECTED state, the UE and the 5G-RAN maintain the AS context, and the location of the UE is known to the 5G-RAN at the cell level. The mobility of the UE in the RRC_CONNECTED state is handled by switching controlled by the 5G-RAN. On the other hand, when the UE is in the RRC_IDLE state, the UE and the 5G-RAN release the AS context, and the 5G-RAN is unaware of the location of the UE, but the location of the UE is known to the 5G-CN at the location registration area level. The location registration area corresponds to the tracking area (TA) of LTE. The mobility of the UE in the RRC_IDLE state is handled by cell reselection controlled by the UE. In addition, 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 both the UE and 5G-CN. In contrast, a UE in RRC_IDLE state is considered to be in NG-CM-IDLE state in both the UE and 5G-CN.

[0012] It can be said that the RRC_INACTIVE state is an intermediate state between the RRC_CONNETED state and the RRC_IDLE state. Some features of the RRC_INACTIVE state are similar to those of the RRC_CONNETED state, while some other features of the RRC_INACTIVE state are similar to those of the RRC_IDLE state.

[0013] When the 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 the UE in the RRC_INACTIVE state includes, for example, the radio bearer configuration and the AS security context. In addition, the 5G-RAN maintains the control plane connection and the user plane connection (i.e., Figure 1NG2 interface and NG3 interface in RRC_INACTIVE state). A UE in RRC_INACTIVE state is considered to be in NG-CM-CONNECTED state in both the UE and 5G-CN. Therefore, 5G-CN cannot distinguish whether the UE is in RRC_CONNECTED state or RRC_INACTIVE state. These characteristics of the RRC_INACTIVE state are similar to those of the RRC_CONNETED state.

[0014] However, the mobility of a UE in the RRC_INACTIVE state is similar to the mobility of a UE in the RRC_IDLE state. Specifically, the mobility of a UE in the RRC_INACTIVE state is handled by cell reselection controlled by the UE.

[0015] Figure 2 State transitions between the three currently proposed RRC states are shown. The UE can transition from the RRC_CONNECTED state to the RRC_INACTIVE state and vice versa (steps 201 and 202). It is assumed that the transitions between the RRC_CONNECTED state and the RRC_INACTIVE state reuse the Suspend and Resume procedures of the RRC connection defined for LTE in 3GPP Release 13. The AS context stored in the 5G-RAN for the UE in the RRC_INACTIVE state can be transferred between RAN nodes (i.e., gNBs). Specifically, when the UE transitions from the RRC_INACTIVE state to the RRC_CONNECTED state, the gNB that receives an RRC message (e.g., an RRC connection resume request) from the UE can extract or obtain the AS context of the UE from other gNBs.

[0016] The location of a UE in RRC_INACTIVE state is known to 5G-RAN at the level of a newly defined RAN Notification Area (RNA). The RAN Notification Area is also known as a RAN-based Notification Area, a RAN Paging Area or a RAN Location Update Area. The RAN Notification Area (RNA) includes one or more cells, determined by the 5G-RAN, and configured in the UE by the 5G-RAN. Even when a UE in RRC_INACTIVE state moves between cells through cell reselection within the RAN notification area, there is no need to notify (report) the 5G-RAN that the UE has reselected a cell. A UE in RRC_INACTIVE state requests 5G-RAN to update the RAN notification area in response to reselecting a cell outside the RAN notification area.

[0017] Figure 3An example of mobility of a UE in an RRC_INACTIVE state is shown. First, UE 301 is in an RRC_CONNECTED state in a cell 351 of gNB 311 (321), and dedicated radio resources are allocated to UE 301 from gNB 311 and UE 301 establishes a dedicated radio bearer 322. Upon determining to cause UE 301 to enter the RRC_INACTIVE state, gNB 311 configures a RAN notification area 340 to UE 301 and sends an RRC message (e.g., an RRC suspend message) to UE 301 (323). In response to the indication from gNB 311, UE 301 enters an RRC_INACTIVE state from the RRC_CONNECTED state (324).

[0018] UE 301 in the RRC_INACTIVE state performs a cell reselection procedure and accordingly reselects cell 352 of gNB 312 (325). Since cell 352 is included in the RAN notification area 340 configured in UE 301, UE 301 does not report the cell reselection (i.e., update of UE location information) to 5G-RAN (e.g., cell 352 or gNB 312). UE 301 further moves and reselects cell 353 of gNB 313 (326). Cell 353 is not included in the RAN notification area 340 configured in UE 301, so UE 301 sends a request (327) for RAN notification area update to gNB 313. The request (327) may be sent using an RRC message (e.g., an RRC recovery request message) for requesting a transition from RRC_INACTIVE to RRC_CONNECTED. gNB 313 obtains the AS context of UE 301 from gNB 311 and uses the obtained AS context to reestablish the packet data convergence protocol (PDCP) and radio link control (RLC) used for the radio bearer. Then, gNB 313 sends an RRC message (e.g., an RRC recovery message) to put UE 301 into the RRC_CONNECTED state. In response to the indication from gNB 311, UE 301 enters the RRC_CONNECTED state from the RRC_INACTIVE state in cell 353 (329). UE 301 is able to use the dedicated radio bearer 330 to send and receive data.

[0019] Prior art literature

[0020] Non-patent literature

[0021] 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

[0022] Problem that the invention aims to solve

[0023] The inventors have studied the mobility of a UE in the RRC_INACTIVE state and found several problems. For example, the mobility of a UE in the RRC_INACTIVE state may need to consider network slicing. This is because, in some cases, the desired network slice may not be available in the reselected cell. The network slice desired by the UE is, for example, a network slice that has been selected (or configured) by the network for the UE when the UE was in the RRC_CONNECTED state before the UE entered the RRC_INACTIVE state.

[0024] exist Figure 4 In the example shown, 5G-CN 430 includes a public network function (NF) 431, a network function used by network slice A (NF for slice A) 432, and a network function used by network slice B (NF for slice B) 433. The public NF 431 includes a public control plane network function (CCNF) and may also include a public user plane network function (CUNF). The NF 432 for slice A includes a slice-specific user plane network function (SUNF) and may also include a slice-specific control plane NF (SCNF). Similarly, the NF 433 for slice B includes a SUNF and may also include a SCNF.

[0025] exist Figure 4 In the example of , both gNB 411 and gNB 412 are connected to common NF 431, NF 432 for slice A, and NF 433 for slice B. On the other hand, gNB 413 is connected to common NF 431 and NF 432 for slice A, but is not connected to NF 433 for slice B. That is, network slice B is not available in cell 423 of gNB 413.

[0026] exist Figure 4In the example of , first, UE 401 is in RRC_CONNECTED state in cell 421 of gNB 411 and has been configured with network slice B. Thus, UE 401 sends and receives data via network slice B. Afterwards, UE 401 is configured with RAN notification area 440 by gNB 411 and enters RRC_INACTIVE state. In addition, UE 401 performs cell reselection (452). However, one question is how UE 401 in RRC_INACTIVE state can know whether the desired network slice is available in the target cell (i.e., the cell to be reselected or the reselected cell).

[0027] As an example, it may be preferred that a UE in the RRC_INACTIVE state is able to determine whether the desired network slice is available in the reselected cell. If the UE can know that the desired network slice is available in the reselected cell, the UE in the RRC_INACTIVE state may be allowed to maintain the RRC_INACTIVE state in the reselected cell without performing any special operations. On the other hand, if it is unknown whether the desired network slice is available in the reselected cell, the UE may immediately enter the RRC_CONNECTED state in the reselected cell and request the use of the network slice from the network. Optionally, if the UE in the RRC_INACTIVE state may know that the desired network slice is not available in the cell to be reselected or the reselected cell, the UE may further reselect other cells.

[0028] Therefore, one of the purposes to be achieved by the embodiments disclosed herein is to provide a device, method and program, wherein the device, method and program enable a UE in an RRC_INACTIVE state to easily know the availability of network slices in a target cell (i.e., a cell to be reselected or a reselected cell). It should be noted that this purpose is only one of the purposes to be achieved by the embodiments disclosed herein. Other purposes or problems and novel features will become apparent through the following description and drawings.

[0029] Solutions for solving problems

[0030] In a first aspect, a base station comprises: a memory; and at least one processor connected to the memory. The at least one processor is configured to control a state transition 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 wireless terminal and the RAN maintain an access stratum context, i.e., an AS context, and the location of the first wireless terminal is known to the RAN at a cell level. The second RRC state is a state in which the first wireless terminal and the RAN maintain at least a part of the AS context, and the location of the first wireless terminal is known to the RAN at a level of a RAN notification area configured by the RAN. The third RRC state is a state in which the first wireless terminal and the RAN release the AS context, and the location of the first wireless terminal is unknown to the RAN. The at least one processor is further configured to explicitly or implicitly notify the first wireless terminal whether a first network slice configured in the first wireless terminal for data communication at least in the first RRC state is available in each cell included in the RAN notification area.

[0031] In a second aspect, a base station comprises: a memory; and at least one processor connected to the memory. The at least one processor is configured to control a state transition of a first wireless terminal between a first RRC state, a second RRC state, and a third RRC state. The at least one processor is also configured to: send system information in a first cell of the base station for indicating one or more network slices that are available or unavailable in the first cell.

[0032] In a third aspect, a wireless terminal comprises: a transceiver; and at least one processor. The at least one processor is configured to control the transceiver in one or more cells associated with a radio access network (RAN). The at least one processor is configured to control the state transition of the wireless terminal between a first RRC state, a second RRC state, and a third RRC state. The at least one processor is further configured to confirm whether a first network slice configured in the wireless terminal for data communication at least in the first RRC state is available in a cell to be reselected by cell reselection in the second RRC state.

[0033] In a fourth aspect, a method used by a base station, wherein the base station is configured in a radio access network, i.e., RAN, the method comprising: (a) controlling a state transition of a first wireless terminal between a first RRC state, a second RRC state, and a third RRC state; and (b) explicitly or implicitly notifying the first wireless terminal whether a first network slice configured in the first wireless terminal for data communication at least in the first RRC state is available in each cell included in a RAN notification area configured by the RAN.

[0034] In a fifth aspect, a method used by a base station, wherein the base station is configured in a radio access network, i.e., RAN, the method comprising: (a) controlling the state transition of a wireless terminal between a first RRC state, a second RRC state, and a third RRC state; and (b) sending system information in a first cell of the base station for indicating one or more network slices that are available or unavailable in the first cell.

[0035] In a sixth aspect, a method for a wireless terminal, the method comprising: (a) controlling the state transition of the wireless terminal between a first RRC state, a second RRC state, and a third RRC state; and (b) confirming whether a first network slice configured in the wireless terminal for data communication at least in the first RRC state is available in a cell to be reselected through cell reselection in the second RRC state.

[0036] In a seventh aspect, a program comprises instructions (software codes), wherein when the instructions (software codes) are loaded into a computer, the computer is caused to perform the method according to any one of the fourth to sixth aspects described above.

[0037] Effects of the Invention

[0038] According to the above aspects, a device, method and program may be provided, wherein the device, method and program enable a UE in an RRC_INACTIVE state to easily know the availability of network slices in a target cell (i.e., a cell to be reselected or a reselected cell). BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 is a diagram showing a basic architecture of a 5G system according to background technology.

[0040] Figure 2 is a diagram showing state transitions between three RRC states in a 5G system according to the background art.

[0041] Figure 3 is a diagram showing an example of mobility of a UE in an RRC_INACTIVE state according to the background art.

[0042] Figure 4 It is a diagram used to illustrate the problem related to the mobility of UE in RRC_INACTIVE state identified by the present inventors.

[0043] Figure 5 is a diagram showing a structural example of a wireless communication network according to various embodiments.

[0044] Figure 6 is a sequence diagram showing an example of information exchange between gNBs according to the first embodiment.

[0045] Figure 7 is a flowchart showing an example of the operation of a gNB according to the first embodiment.

[0046] Figure 8 is a flowchart showing an example of the operation of the UE according to the first embodiment.

[0047] Fig. 9 is a flowchart showing an example of the operation of the UE according to the first embodiment.

[0048] Fig.10 is a flowchart showing an example of the operation of a gNB according to the second embodiment.

[0049] Fig.11 is a flowchart showing an example of the operation of the UE according to the second embodiment.

[0050] Fig.12 is a sequence diagram showing an example of operations of a gNB and a UE according to the third embodiment.

[0051] Fig.13 is a sequence diagram showing an example of operations of a gNB and a UE according to the third embodiment.

[0052] Fig.14 is a flowchart showing an example of the operation of the UE according to the third embodiment.

[0053] Fig.15 is a block diagram showing a structural example of a gNB according to multiple embodiments.

[0054] Fig.16 is a block diagram showing a structural example of a UE according to various embodiments.

[0055] Description of Reference Numerals

[0056] 1 gNodeB (gNB)

[0057] 2 User Equipment (UE)

[0058] 3 5G Radio Access Network (5G-RAN)

[0059] 4 5G Core Network (5G-CN)

[0060] 11 Community

[0061] 1501 RF Transceiver

[0062] 1504 Processor

[0063] 1505 Memory

[0064] 1601 RF Transceiver

[0065] 1603 Baseband Processor

[0066] 1604 Application Processor

[0067] 1606 Memory DETAILED DESCRIPTION

[0068] The specific embodiments are described in detail below with reference to the accompanying drawings. In the entire drawings, the same reference numerals are used to represent the same or corresponding elements, and for the sake of clarity, repeated descriptions will be omitted as needed.

[0069] Each embodiment described below can be used alone, or two or more of these embodiments can be appropriately combined with each other. These embodiments include novel features that are different from each other. Therefore, these embodiments help to achieve different purposes or solve different problems from each other, and also help to obtain different advantages from each other.

[0070] The following description of the embodiments mainly focuses on a 5G system that supports network slicing and uses the RRC_INACTIVE state. However, these embodiments can be applied to other wireless communication systems that support network slicing and use the RRC_INACTIVE state or similar RRC states.

[0071] First embodiment

[0072] Figure 5 An example of a structure of a wireless communication network according to a plurality of embodiments including this embodiment is shown. Figure 5 In the example, the wireless communication network includes 5G UE 2, 5G-RAN 3 and 5G-CN 4.

[0073] 5G-CN 4 includes a control plane network function (CP NF) and a user plane network function (UP NF) not shown, and provides a plurality of network slices. Network slices are distinguished from each other according to services or use cases provided to UEs on each network slice, for example. Use cases include, for example, enhanced mobile broadband (eMBB), highly reliable and low latency communication (URLLC), and massive machine type communication (mMTC).

[0074] 5G-RAN 3 includes multiple gNBs including gNB 1A and gNB 1B. Each gNB 1 (e.g., gNB 1A and gNB 1B) serves at least one cell 11 (e.g., cell 11A and cell 11B). Each gNB 1 is connected to 5G-CN 4 and supports one or more network slices. In other words, one or more network slices are supported or available in the cell 11 of each gNB 1. In some implementations, in order to provide end-to-end network slicing to UE 2, 5G-RAN 3 allocates RAN slices and radio slices associated with the network slice of 5G-CN 4 selected for UE 2 (referred to as core network (CN) slice) to UE 2. Each RAN slice provides storage and processing resources of the infrastructure within 5G-RAN 3 including gNB 1. Each radio slice provides radio resources including time resources, frequency resources, code resources, signal sequence resources or space resources, or any combination thereof.

[0075] UE 2 uses one or more cells 11 served by one or more gNBs 1 for uplink and downlink communications. UE 2 supports multiple RRC states including RRC_CONNECTED state, RRC_INACTIVE state, and RRC_IDLE state. 5G-RAN 3 (gNB 1) and UE 2 control state transitions of UE 2 between RRC states including RRC_CONNECTED state, RRC_INACTIVE state, and RRC_IDLE state.

[0076] For example, in the case where gNB 1A causes UE 2 to enter RRC_INACTIVE state from RRC_CONNECTED state, gNB 1A sends RAN notification area information to UE 2 via an RRC message (e.g., RRC connection release, RRC connection suspension, or RRC connection deactivation) to configure the RAN notification area in UE 2. The RAN notification area includes one or more cells served by one or more gNB 1. UE 2 enters the RRC_INACTIVE state in response to receiving the RRC message from gNB 1A. UE 2 in the RRC_INACTIVE state moves between cells through cell reselection controlled by UE 2, and there is no need to report the cell reselection within the RAN notification area (i.e., update of UE location information) to 5G-RAN3. In contrast, in response to reselecting a cell outside the configured RAN notification area (e.g., cell 11B), UE 2 requests gNB 1B serving the reselected cell 11B to update the RAN notification area (or to notify gNB 1B that UE 2 has left the configured RAN notification area). The gNB 1B determines a new RAN notification area used by the UE 2 and configures the determined RAN notification area in the UE 2. That is, as described above, the location of the UE 2 in the RRC_INACTIVE state is known to the 5G-RAN 3 at the RAN notification area level.

[0077] As already explained, a RAN Notification Area (RNA) comprises one or more cells, is determined by the 5G-RAN 3, and is configured in the UE 2 by the 5G-RAN 3. A RAN Notification Area is also referred to as a RAN-based Notification Area, a RAN Paging Area or a RAN Location Update Area.

[0078] The RAN notification area information may include, for example, at least information indicating which cell is included in the RAN notification area. In addition, an identifier (e.g., an area number) may be assigned to the RAN notification area. In addition, a relationship between an identifier (e.g., RNA ID) of the RAN notification area and the cells included in the RAN notification area may be uniquely determined within a predetermined area. In this case, the RAN notification area information may include an identifier of the RAN notification area and information related to the included cells (e.g., a cell identifier).

[0079] The gNB 1A may broadcast the RAN notification area information in its own cell 11A. At this time, the RAN notification area information may include information related to a plurality of RAN notification areas, which may be assigned respective conditions (e.g., categories, types), and the UE 2 may select a RAN notification area suitable for the UE 2. The condition is, for example, a slice category or slice type (e.g., slice / service type (SST)) of a network slice used (or desired) by the UE 2, a terminal category or terminal type, a reception quality at the UE 2 or a coverage level based on the reception quality, a mobility characteristic of the UE 2 (e.g., UE speed, whether the UE is a stationary terminal), or any combination thereof.

[0080] The RAN notification area configured in UE 2 may be the same as the location registration area of ​​UE 2 (i.e., an area corresponding to a tracking area (TA) in LTE). In the case where individual RAN notification areas (i.e., slice-specific RNAs) are configured for each network slice, at least one of the RAN notification areas may be the same as the location registration area (e.g., TA). In the case where the RNA is the same as the TA, an information element indicating a cell list included in the RNA (e.g., a RAN area cell list (RanAreaCellList) information element (IE)) may be omitted in the RAN notification area information sent from gNB 1 to UE 2 (i.e., an optional IE). Alternatively, instead of an information element indicating a cell list, the RAN notification area information may include an information element indicating a TA identifier (e.g., a TrackingAreaCode (TrackingAreaCode) IE) (i.e., a Choice). In other words, gNB 1 may select one of the RAN area cell list IE and the tracking area code IE to indicate the RAN notification area.

[0081] In order to transmit RAN notification area information including information related to a plurality of RAN notification areas, gNB 1A may receive RAN notification area information (e.g., a combination of an identifier of a RAN notification area and an identifier of cells constituting the RAN notification area) from other gNBs (e.g., gNB 1B) via an inter-gNB interface (Xn). The other gNBs may manage cells belonging to other RAN notification areas different from the RAN notification area to which the cell of gNB 1A (e.g., cell 11A) belongs. Likewise, the RAN notification area-related information received from the other gNBs may relate to other RAN notification areas different from the RAN notification area to which the cell of gNB 1A (e.g., cell 11A) belongs.

[0082] In the case where UE 2 uses (or expects) multiple network slices, UE 2 may select a RAN notification area based on the network slice with the highest priority or based on the network slice actually being used. Alternatively, UE 2 may select a RAN notification area based on a network slice that is at the top of a list of network slice categories or types contained in the RAN notification area information.

[0083] The above-mentioned RAN notification area information may include a RAN notification area (e.g., a default RAN notification area) for which individual information (e.g., an identifier, a category, or a type) is not explicitly specified. In this case, for example, the default RAN notification area may be used for UE 2 regardless of the network slice, or may be used for a network slice other than the network slice explicitly indicated in the RAN notification area information. In addition, in the case where the RAN notification area information includes a plurality of RAN notification areas, UE 2 may not need to send a request for updating its own location information to gNB 1, as long as the cell after cell reselection is included in at least one of these RAN notification areas.

[0084] Instead of the above-mentioned indication via the RRC message, the gNB 1 may notify the UE 2 of the value of a predetermined timer that triggers the transition to the RRC_INACTIVE state, so that the UE 2 performs the transition to the RRC_INACTIVE state based on the timer value and the corresponding timer. For example, the UE 2 in the RRC_CONNECTED state may restart the timer (i.e., reset the timer and start the timer again) each time it sends or receives user data, and may transition to the RRC_INACTIVE state when the timer expires.

[0085] The mobility of UE 2 in RRC_INACTIVE state according to the present embodiment is described below. According to the present embodiment, the gNB 1 is configured to explicitly notify UE 2 whether one or more network slices configured in UE 2 (or selected for UE 2) for data communication at least in RRC_CONNECTED state are available in each cell included in the RAN notification area used by UE 2. More specifically, in the present embodiment, the gNB 1 is configured to send information (hereinafter referred to as "slice availability information") that explicitly indicates whether one or more network slices configured in UE 2 are available in each cell or each cell group included in the RAN notification area to UE 2. Instead of the slice availability information, the gNB 1 may send information (hereinafter referred to as "slice support information") that explicitly indicates whether the slice is supported to UE 2. The slice availability information or the slice support information may indicate one or more kinds (e.g., categories, types) of network slices available (or supported) in the RAN notification area or one or more cells included in the RAN notification area. In the following, although the slice availability information is described as an example, the slice support information may be used instead.

[0086] In some implementations, gNB 1 may send slice availability information to UE 2 when configuring the RAN notification area in UE 2. The slice availability information may be an information element associated with the RAN notification area (e.g., a list of cells). Additionally or alternatively, gNB 1 may send the slice availability information to UE 2 during a process (e.g., an RRC message) in which gNB 1 causes UE 2 to enter the RRC_INACTIVE state from the RRC_CONNECTED state.

[0087] Figure 6 6 is a flow chart showing a process 600 as an example of the operation of the gNB 1. In step 601, the gNB 1 creates slice availability information for indicating whether a network slice used by the UE 2 in the RRC_CONNECTED state is available in each cell included in the RAN notification area. In step 602, the gNB 1 sends the slice availability information to the UE 2. The gNB 1 may send the slice availability information together with the RAN notification area (e.g., a list of cells). In step 603, the gNB 1 causes the UE 2 to enter the RRC_INACTIVE state from the RRC_CONNECTED state. As described above, the gNB 1 may send an indication to cause the UE 2 to enter the RRC_INACTIVE state together with the slice availability information.

[0088] Each gNB 1 needs to know the slice availability (or slice support status) in other gNBs 1 or in each cell served by other gNBs 1. In some implementations, the network operator may configure the slice availability in the cells of other gNBs 1 in each gNB 1 via an operation and management (O&M) server. Additionally or optionally, each gNB 1 may communicate with other gNBs 1 on an inter-gNB interface (Xn) (e.g., an Xn setting request / response message) to dynamically obtain the slice availability in the cells of other gNBs 1. When the slice availability of each gNB 1 has changed (or updated), it may notify other gNBs 1 of the situation (e.g., a gNB configuration update message). Additionally or optionally, each gNB 1 may communicate with other gNBs 1 via an interface (NG2, NG-c) between gNB 1 and 5G-CN 4 and dynamically obtain the slice availability in the cells of other gNBs 1.

[0089] Figure 7 is a sequence diagram illustrating process 700 as an example of communication between two gNBs 1. In step 701, gNB 1A sends information indicating network slices available in each cell served by gNB 1A (e.g., network slice availability information) to gNB 1B. gNB 1A may send the information in response to a request from gNB 1B. Additionally or alternatively, in response to an update of slice availability in any cell served by gNB 1A, gNB 1A may send the update to gNB 1B. Additionally or alternatively, gNB 1A may periodically send slice availability in each cell to gNB 1B. In step 702, gNB 1B sends information indicating network slices available in each cell served by gNB 1B (e.g., network slice availability information) to gNB 1A. Additionally or optionally, gNB 1A may send information indicating network slices available in each cell served by gNB 1A (e.g., network slice availability information) to gNB 1B via an interface (NG2, NG-c) with the core network (5G-CN 4).

[0090] Note that, as described above, gNB 1A can exchange RAN notification area information (e.g., a combination of an identifier of a RAN notification area and an identifier of cells constituting the RAN notification area) with gNB 1B via the inter-gNB interface (Xn). In this case, the RAN notification area information can indicate the RAN notification area to which the cell 11 of the transmission source gNB 1 belongs, or conversely indicate the RAN notification area to which the cell 11 of the transmission destination gNB 1 should belong. That is, in the case where the cells 11A and 11B managed by gNB 1A and gNB 1B, respectively, belong to (or should belong to) different RAN notification areas, the gNBs 1 can share the RAN notification area information with each other and identify multiple RAN notification areas that should be included in the RAN notification area information to be sent to UE 2.

[0091] The RAN notification area information communicated between gNBs may include the following: Figure 7 In the information of the network slices available in each cell served by the gNB 1A shown (e.g., network slice availability information), the RAN notification area information communicated between gNBs may include information indicating the network slices available in each cell served by the gNB 1A. Figure 7 Information about the network slices available in each cell served by the gNB 1A shown (e.g., network slice availability information).

[0092] In some implementations, information indicating network slices available in each cell served by gNB 1A and corresponding information about gNB 1B may be sent from the core network (5G-CN 4) to gNB 1B and gNB 1A, respectively. In this case, 5G-CN needs to know in advance the network slices available (or supported) in each gNB 1. For example, 5G-CN 4 may specify the network slices available (or supported) in each gNB 1 for each gNB 1. Optionally, 5G-CN 4 may receive a report of the network slices available (or supported) in gNB 1 from each gNB 1.

[0093] According to the present embodiment, the UE 2 is configured to confirm whether one or more network slices configured in the UE 2 (or allowed (authorized) or accepted for the UE 2) for data communication at least in the RRC_CONNECTED state are available in the cell to be reselected (or the reselected cell) by the cell reselection in the RRC_INACTIVE state. More specifically, in the present embodiment, the UE 2 is configured to receive the above-mentioned slice availability information from the gNB 1. The slice availability information explicitly indicates whether one or more network slices configured in the UE 2 are available in each cell included in the RAN notification area used by the UE 2.

[0094] Figure 88 is a flow chart showing a process 800 as an example of the operation of UE 2. In step 801, UE 2 is in the RRC_CONNECTED state and receives the above-mentioned slice availability information from the serving gNB 1. In step 802, UE 2 transitions from the RRC_CONNECTED state to the RRC_INACTIVE state in response to an indication from the serving gNB 1. In step 803, UE 2 in the RRC_INACTIVE state performs cell reselection. UE 2 confirms whether the desired network slice is available in the cell to be reselected (or in the reselected cell) based on the slice availability information. The desired network slice may be one or more network slices that have been configured in UE 2 (or allowed (authorized) or accepted for UE 2) by the network (i.e., 5G-CN 4 or 5G-RAN 3 or both) when UE 2 was previously in the RRC_CONNECTED state.

[0095] The following illustrates an example of the operation of UE 2 after confirming the availability of the network slice. Fig. 9 900 is a flowchart showing an example of a process of the operation of the UE 2. In step 901, the UE 2 confirms the network slice availability in the cell to be reselected (or the reselected cell) by the cell reselection in the RRC_INACTIVE state. If the desired network slice is available in the reselected cell, the UE 2 stays in the cell (continues to reside in the cell).

[0096] If the desired network slice is not available in the reselected cell, UE 2 notifies the gNB 1 serving the reselected cell about the desired network slice (step 902). The notification may be a request for the desired network slice, such as a request for configuring the desired network slice to UE 2 (or providing the desired network slice to UE 2) or a request for moving (e.g., switching, redirecting) to a cell that can utilize (or support) the desired network slice. In the case where UE 2 fails to confirm that the desired network slice is available in the reselected cell, UE 2 may notify the gNB 1 serving the reselected cell of the desired network slice. In other words, in the case where it is unknown whether the desired network slice is available in the reselected cell, UE 2 may notify the gNB 1 serving the reselected cell of the desired network slice.

[0097] In some implementations, UE 2 may send a notification related to a desired network slice after transitioning to the RRC_CONNECTED state. Alternatively, UE 2 may send a notification related to a desired network slice while it is in the RRC_INACTIVE state. In other words, UE 2 may send the notification without fully transitioning to the RRC_CONNECTED state. In addition, in other words, UE 2 may send the notification before entering the RRC_CONNECTED state. In one example, UE 2 may send the notification during a process for transitioning to the RRC_CONNECTED state. Specifically, UE 2 may send the notification using an RRC message (e.g., RRC connection recovery request or RRC connection activation) used for transitioning to the RRC_CONNECTED state. Alternatively, UE 2 may send a notification related to a desired network slice using a signal (e.g., PRACH preamble, RACH data, UL reference signal, MAC control element (CE)) that may be sent while remaining in the RRC_INACTIVE state, or an RRC message (e.g., UL information transmission, UL direct information, or UE assistance information). At this time, the signal or message may be sent using a dedicated radio resource that UE 2 is notified (or configured) in advance, or using a radio resource shared among multiple UEs 2. In the latter case, for example, UE 2 may send a notification related to the desired network slice in a transmission scheme that does not require a separate grant for uplink transmission (i.e., no grant). The RRC message may be sent, for example, in the first uplink transmission (e.g., RACH data) in the new radio access procedure used by NR. The new radio access procedure used by NR may be a process that is a contention-based random access process including a total of two steps, wherein the process is simplified from the original contention-based random access process including a total of four steps in LTE. UE 2 may be pre-configured with two-step random access or four-step random access by gNB 1. Optionally, UE 2 may perform one of the random access procedures allowed (or supported) in the cell after cell reselection. UE 2 may determine whether to allow (or support) two-step random access or four-step random access based on whether configuration information related to the radio resources used by UE 2 is sent in system information.

[0098] The notification related to the desired network slice may be, for example, that UE 2 explicitly sends 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))). The identification information related to the desired network slice may be sent, for example, via network slice selection assistance information (NSSAI) contained in an RRC message or a MAC control element. Additionally or optionally, the identification information related to the desired network slice may be implicitly sent using a pre-associated predetermined signal sequence (e.g., RACH preamble, UL reference signal), or a pre-associated predetermined time, frequency, code, or space radio resource. gNB 1 may broadcast information related to the association between the identification information about the desired network slice and the signal sequence or radio resource in its own cell, or may notify UE 2 of the information separately. In the case where gNB 1 broadcasts information related to the association, UE 2 may receive (or monitor) the information in the reselected target cell after reselection. In addition, in the case where multiple network nodes (e.g., network slice instances (NSIs)) support (or provide) the same slice type, the gNB 1 or 5G-CN may configure an identifier (e.g., a slice distinguisher (SD)) for distinguishing these network nodes in the UE 2. In this case, the UE 2 may also send the identifier explicitly or implicitly via a notification related to the desired network slice.

[0099] After receiving the RRC message including the notification or the signal indicating the notification, the gNB 1 may cause the UE 2 to enter (i.e., may cause the UE 2 to transition to) the RRC_CONNECTED state, or may keep the UE 2 in the RRC_INACTIVE state. In some implementations, in the case where the network slice requested by the UE 2 is not available in the gNB 1 or its cell, the gNB 1 may cause the UE 2 to move to an appropriate cell. Specifically, the gNB 1 may cause the UE 2 to move to other cells that can utilize (or support) the network slice requested by the UE 2. The other cell to which the UE 2 is to move may be other cells served by the same gNB 1 that are different from the cell from which the gNB 1 receives the notification about the desired network slice from the UE 2 (i.e., the cell reselected by the UE 2). Optionally, the other cell to which the UE 2 is to move may be a cell of another gNB 1. The gNB 1 may use a handover procedure or a redirection procedure (e.g., RRC connection release with redirection) to cause the UE 2 to move to an appropriate cell.

[0100] In the case where UE 2 receives RAN notification area information including multiple RAN notification areas and sends uplink data in a cell after cell reselection (i.e., there is uplink data to be sent), UE 2 can operate as follows. UE 2 can determine whether the network slice can be used (or supported) in the cell according to whether the RAN notification area including the cell corresponds to the network slice to which the uplink data belongs (or to which the uplink data is associated), or whether the RAN notification area corresponding to the network slice includes the cell. For example, in the case where the RAN notification area corresponding to the network slice to which the uplink data to be sent belongs (or the network slice associated with the uplink data) includes the cell after cell reselection, UE 2 can send the uplink data. Otherwise, UE 2 can notify the gNB 1 of the desired network slice.

[0101] As can be understood from the above description, the gNB 1 according to this embodiment is configured to send slice availability information to the UE 2. The slice availability information indicates whether one or more network slices configured in the UE 2 (or selected for the UE 2) for data communication at least in the RRC_CONNECTED state are available in each cell included in the RAN notification area used by the UE 2. Therefore, the slice availability information enables the UE 2 to confirm whether the desired network slice is available in the cell to be reselected (or the reselected cell) by the cell reselection in the RRC_INACTIVE state. Therefore, this embodiment can make it easy for the UE 2 in the RRC_INACTIVE state to know the availability of the network slice in the cell to be reselected or the reselected cell.

[0102] Second embodiment

[0103] This embodiment provides a modified example of the mobility of UE 2 in the RRC_INACTIVE state. Figure 5 The structure example is the same as .

[0104] According to the present embodiment, the gNB 1 is configured to implicitly notify the UE 2 whether one or more network slices configured in the UE 2 (or selected, allowed or accepted for the UE 2) for data communication at least in the RRC_CONNECTED state are available in each cell included in the RAN notification area used by the UE 2. More specifically, in the present embodiment, the gNB 1 is configured to include only one or more cells that can utilize (or support) the network slice configured for the UE 2 in the RRC_CONNECTED state in the RAN notification area used by the UE 2 in the RRC_INACTIVE state, and configure the RAN notification area in the UE 2. Thus, the RAN notification area implicitly indicates that the network slice configured in the UE 2 is available in each cell included in the RAN notification area.

[0105] Fig.10 1 is a flow chart showing a process 1000 as an example of the operation of the gNB 1. In step 1001, the gNB 1 includes in the RAN notification area only one or more cells for which the configured network slice in the UE 2 in the RRC_CONNECTED state is available. In step 1002, the gNB 1 notifies the UE 2 of the determined RAN notification area. In step 1003, the gNB 1 causes the UE 2 to enter the RRC_INACTIVE state from the RRC_CONNECTED state.

[0106] Fig.11 1 is a flow chart showing a process 1100 as an example of the operation of UE 2. In step 1101, UE 2 is in the RRC_CONNECTED state and receives the configuration of the RAN notification area from the serving gNB 1. The RAN notification area includes only one or more cells in which the configured network slices in UE 2 are available. In step 1102, UE 2 transitions from the RRC_CONNECTED state to the RRC_INACTIVE state in response to the indication from the serving gNB 1. In step 1103, UE 2 in the RRC_INACTIVE state performs cell reselection. UE 2 confirms whether the desired network slice is available in the cell to be reselected based on whether the cell to be reselected is included in the RAN notification area. Here, the desired network slice may be one or more network slices that have been configured in UE 2 (or allowed or accepted for UE 2) by the network (i.e., 5G-CN 4 or 5G-RAN 3 or both) when UE 2 was previously in the RRC_CONNECTED state.

[0107] The operations of UE 2 and gNB 1 after UE 2 confirms the availability of the network slice may be the same as the operations of the example described in the first embodiment.

[0108] The gNB 1 may configure a plurality of RAN notification areas in the UE 2, and may send RAN notification area information including the plurality of RAN notification areas to the UE 2. At least one of the RAN notification areas included in the RAN notification area information may be determined to include only one or more cells that can utilize (or support) the network slice configured (or selected, allowed, or accepted) for the UE 2. For example, both a first RAN notification area and a second RAN notification area may be configured in the UE 2, and the first RAN notification area may include only one or more cells that can utilize (or support) the network slice configured (or selected, allowed, or accepted) for the UE 2, and the second RAN notification area may include one or more cells to which the UE 2 may move (i.e., perform cell reselection) without notifying the gNB 1. In this case, the second RAN notification area may be configured in the UE 2 as a default configuration, and the first RAN notification area may be configured in the UE 2 as an optional configuration. Specifically, regardless of the use of the network slice, the gNB 1 may always send the second RAN notification area to the UE 2 as the RAN notification area to be applied to the UE 2. In contrast, gNB 1 may send the first RAN notification area to UE 2 only if UE 2 uses network slicing or is configured with network slicing.

[0109] Additionally or optionally, the RAN notification area may be configured for a slice category or slice type of a network slice configured in UE 2 (selected, allowed or accepted by UE 2). In one example, the correspondence between multiple RAN notification areas and multiple network slices may be determined by the configuration order of the multiple RAN notification areas and the configuration order of the multiple network slices. Specifically, a RAN notification area with a first configuration order may be associated with a first network slice with a first configuration order. Optionally, the correspondence between multiple RAN notification areas and multiple network slices may be determined by the configuration order of the multiple RAN notification areas and the ascending order of the identifiers of the multiple network slices. Specifically, a RAN notification area with a first configuration order may be associated with a network slice with a smallest identifier. In the case where the number of network slices configured in UE 2 other than the above-mentioned default configuration (default RAN notification area) is different from the number of RAN notification areas configured in UE 2, UE 2 may apply the following processing. In the case where the number of configured network slices is greater than the number of RAN notification areas, UE 2 recognizes that the remaining network slices that cannot be associated with the RAN notification area are not available (or supported) in any cell other than the serving cell (i.e., the cell in which UE 2 receives the RAN notification area information). On the other hand, in the case where the number of configured network slices is less than the number of RAN notification areas, UE 2 ignores the remaining RAN notification areas that cannot be associated with the network slices.

[0110] As can be understood from the above description, according to the present embodiment, the gNB 1 determines a RAN notification area including only one or more cells available for one or more network slices configured in the UE 2 (or selected for the UE 2) for data communication at least in the RRC_CONNECTED state, and notifies the determined RAN notification area to the UE 2. Therefore, the RAN notification area enables the UE 2 to confirm whether the desired network slice is available in the cell to be reselected (or the reselected cell) by the cell reselection in the RRC_INACTIVE state. Thus, the present embodiment makes it easy for the UE 2 in the RRC_INACTIVE state to know the availability of the network slice in the cell to be reselected or the reselected cell.

[0111] Third embodiment

[0112] This embodiment provides a modified example of the mobility of UE 2 in the RRC_INACTIVE state. Figure 5 The structure example is the same as .

[0113] According to this embodiment, the gNB 1 is configured to send system information (SI) in each cell of the gNB 1 indicating one or more network slices that are available (or supported) or unavailable (or not supported) in the cell. The system information may be included in a broadcast system information block to be broadcast in each cell. Alternatively, the system information may be included in an on-demand system information block to be sent to the UE 2 in response to a request message from the UE 2 or in response to a trigger within the network.

[0114] Fig.12 12 is a sequence diagram showing process 1200 as an example of the operation of gNB 1 and UE 2 according to the present embodiment. In step 1201, UE 2 is in RRC_INACTIVE state and performs a cell reselection procedure. In step 1202, UE 2 receives system information from gNB 1 in a cell to be reselected (or in 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 can be included in an on-demand system information block.

[0115] In the case where the network slice availability information is a broadcast system information block, UE 2 can receive the broadcast system information block in the reselected cell in response to cell reselection, and can confirm the network slice availability in the reselected cell.

[0116] In the case where the network slice availability information is an on-demand system information block, for example, gNB 1 broadcasts the following main information (e.g., an indication of system information related to the network slice, or the availability of the network slice SI), where the main information indicates that the system information indicating the network slice availability information is to be sent as an on-demand system information block. In the case where the main information is sent as system information required for UE 2 to access the cell (e.g., basic system information of LTE or minimum system information of NR), UE 2 receives the main information before performing cell reselection. Then, when performing cell reselection (or in response to performing cell reselection), UE 2 requests gNB 1 to send the on-demand system information block. gNB 1 sends the network slice availability information in response to the request from UE 2.

[0117] UE 2 may immediately send a request to send a system information block on demand in response to cell reselection. Optionally, UE 2 may send a request to send a system information block on demand when it is converted to the RRC_CONNECTED state due to the occurrence of uplink data to be sent or for other purposes. Additionally or optionally, UE 2 may send a request to send a system information block on demand while remaining in the RRC_INACTIVE state. In the case where the main information is sent in other system information (i.e., information other than the system information required for UE 2 to access the cell), UE 2 may receive the main information after (or in response to) performing cell reselection. In some implementations, UE 2 may send a request to send a system information block on demand on a random access channel (RACH) or via dedicated signaling (e.g., RRC signaling or a media access control (MAC) control element (CE)).

[0118] Fig.13 is a sequence diagram showing process 1300 as an example of the operation of gNB 1 and UE 2 in the case where the network slice availability information is an on-demand system information block. In step 1301, gNB 1 sends a notification related to available on-demand system information. The notification related to available on-demand system information corresponds to the main information described above. The notification is required for UE 2 to access cell 11 of gNB 1 and is included in the system information (e.g., basic SI, SIB1) broadcast in cell 11 of gNB 1. Optionally, the notification related to available on-demand system information may be included in other SI that is not basic SI.

[0119] In step 1302, UE 2 is in RRC_INACTIVE state and performs a cell reselection procedure. UE 2 confirms the "notification related to available on-demand system information" included in the system information received in step 1301, and then sends a request for sending on-demand SI including network slice information to gNB 1 (step 1304). Note that in the case where the notification related to available on-demand system information is included in other SI other than basic SI, UE 2 can receive the other SI (e.g., SIBx) after cell reselection (step 1303). In the case where the notification related to available on-demand system information is included in basic SI (e.g., SIB1), step 1303 is omitted. In step 1305, UE 2 receives system information including network slice availability information from gNB 1.

[0120] Fig.1414 is a flowchart showing process 1400 as an example of the operation of UE 2. In step 1401, in response to cell reselection in the RRC_INACTIVE state, UE 2 attempts to receive system information including network slice availability information in the reselected cell. In step 1402, UE 2 confirms whether the 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 have been configured in UE 2 (or allowed or accepted for UE 2) by the network (i.e., 5G-CN 4 or 5G-RAN 3 or both) when UE 2 was previously in the RRC_CONNECTED state.

[0121] The operations of UE 2 and gNB 1 after UE 2 confirms the availability of the network slice may be the same as the operations of the example described in the first embodiment.

[0122] As can be understood from the above description, according to the present embodiment, the gNB 1 transmits system information indicating the availability of a network slice in each cell. Therefore, the system information enables the UE 2 to confirm whether the desired network slice is available in the cell to be reselected (or the reselected cell) by the cell reselection in the RRC_INACTIVE state. Thus, the present embodiment enables the UE 2 in the RRC_INACTIVE state to easily know the availability of the network slice in the cell to be reselected or the reselected cell.

[0123] Fourth embodiment

[0124] This embodiment provides an operation when downlink user data addressed to UE 2 in RRC_INACTIVE state arrives at the network. An example of a structure of a wireless communication network according to this embodiment is similar to Figure 5 The structure example is the same as .

[0125] In the case where downlink user data addressed to UE 2 in the RRC_INACTIVE state arrives at 5G-CN 4, 5G-CN 4 transmits the user data to the gNB 1 (e.g., gNB 1A) to which UE 2 was connected when UE 2 transitioned to the RRC_INACTIVE state. gNB 1A sends a notification of the arrival of downlink user data similar to the existing paging (i.e., paging message) in its own cell 11A, which is referred to as "RAN-based paging". In addition, in the case where the RAN notification area (RNA) configured in UE 2 includes cells of other gNB 1 (e.g., gNB 1B), gNB 1 notifies gNB 1B of the arrival of downlink user data for UE 2 via the inter-gNB interface (Xn), which is referred to as "Xn paging". Xn paging may include information related to the RAN notification area (RNA) to which UE 2 belongs. Then, in the same manner as gNB 1A, gNB 1B may send RAN-based paging in its own cell 11B included in the RNA.

[0126] gNB 1A may include information indicating one or more network slices configured in UE 2 (or allowed or accepted for UE 2) in an Xn paging (i.e., notification of arrival of downlink user data for UE 2) to be sent to gNB 1B. This enables gNB 1B to be aware of the network slices used (or desired) by UE 2.

[0127] gNB 1A may include information about the RAN notification area for which UE 2 has been configured (or has been notified) into the Xn paging (i.e., notification of arrival of downlink user data for UE 2) to be sent to gNB 1B. This enables gNB 1B to be aware of the cell to which the RAN-based paging should be sent.

[0128] The following provides a structural example of gNB 1 and UE 2 according to the above embodiment. Fig.15 1 is a block diagram showing a structural example of the gNB 1 according to the above-mentioned embodiment. Fig.15, gNB 1 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 to communicate with NG UEs including UE 2. The RF transceiver 1501 may include a plurality of transceivers. The RF transceiver 1501 is connected to an antenna array 1502 and a processor 1504. The RF transceiver 1501 receives modulation symbol data from the processor 1504, generates a transmit RF signal, and supplies the transmit RF signal to the antenna array 1502. In addition, the RF transceiver 1501 generates a baseband receive signal based on the receive RF signal received by the antenna array 1502, and supplies the baseband receive signal to the processor 1504. The RF transceiver 1501 may include an analog beamformer circuit for beamforming. The analog beamformer circuit includes, for example, a plurality of phase shifters and a plurality of power amplifiers.

[0129] The network interface 1503 is used to communicate with network nodes, such as control nodes and transmission nodes in the 5G-CN 4. The network interface 1503 may include, for example, a network interface card (NIC) compliant with the IEEE 802.3 series.

[0130] Processor 1504 performs digital baseband signal processing (i.e., data plane processing) and control plane processing for wireless communication. Processor 1504 may include multiple processors. Processor 1504 may include, for example, a modem processor (e.g., a digital signal processor (DSP)) for performing digital baseband signal processing and a protocol stack processor (e.g., a central processing unit (CPU) or a microprocessing unit (MPU)) for performing control plane processing. Processor 1504 may include a digital beamformer module for beamforming. The digital beamformer module may include a multiple-input multiple-output (MIMO) encoder and a precoder.

[0131] The memory 1505 includes a combination of volatile memory and non-volatile memory. The volatile memory is, for example, a static random access memory (SRAM), a dynamic RAM (DRAM), or a combination thereof. The non-volatile memory is, for example, a mask read-only memory (MROM), an electrically erasable programmable ROM (EEPROM), a flash memory, a hard disk drive, or any combination thereof. The memory 1505 may include a memory configured separately 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).

[0132] The memory 1505 may store one or more software modules (computer programs) 1506 including instructions and data for performing the processing using the gNB 1 described in the above embodiments. In some implementations, the processor 1504 may be configured to load the software module 1506 from the memory 1505 and execute the loaded software module, thereby performing the processing of the gNB 1 described in the above embodiments.

[0133] Fig.16 1 is a block diagram showing a structural example of UE 2. A radio frequency (RF) transceiver 1601 performs analog RF signal processing to communicate with gNB 1. The RF transceiver 1601 may include a plurality of transceivers. The analog RF signal processing performed by the RF transceiver 1601 includes up-conversion, down-conversion, and amplification. The RF transceiver 1601 is connected 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 supplies the transmit RF signal to the antenna array 1602. In addition, the RF transceiver 1601 generates a baseband receive signal based on the receive RF signal received by the antenna array 1602, and supplies the baseband receive signal to the baseband processor 1603. The RF transceiver 1601 may include an analog beamformer circuit for beamforming. The analog beamformer circuit includes, for example, a plurality of phase shifters and a plurality of power amplifiers.

[0134] The baseband processor 1603 performs digital baseband signal processing (i.e., data plane processing) and control plane processing for wireless communication. Digital baseband signal processing includes (a) data compression / decompression, (b) data segmentation / concatenation, (c) assembly / decomposition of transmission formats (i.e., transmission frames), (d) channel coding / decoding, (e) modulation (i.e., symbol mapping) / demodulation, and (f) generation of OFDM symbol data (i.e., baseband OFDM signal) using inverse fast Fourier transform (IFFT). On the other hand, control plane processing includes layer 1 communication management (e.g., transmission power control), layer 2 communication management (e.g., radio resource management and hybrid automatic repeat request (HARQ) processing), and layer 3 communication management (e.g., signaling related to attachment, mobility, and call management).

[0135] The digital baseband signal processing performed by the baseband processor 1603 may include, for example, signal processing of a packet data convergence protocol (PDCP) layer, a radio link control (RLC) layer, a MAC layer, and a PHY layer. In addition, the control plane processing performed by the baseband processor 1603 may include processing of a non-access stratum (NAS) protocol, an RRC protocol, and a MAC CE.

[0136] The baseband processor 1603 may perform MIMO encoding and precoding for beamforming.

[0137] The baseband processor 1603 may include a modem processor (e.g., DSP) for performing digital baseband signal processing and a protocol stack processor (e.g., CPU or MPU) for performing control plane processing. In this case, the protocol stack processor for performing control plane processing may be integrated with the application processor 1604 described below.

[0138] The application processor 1604 is also referred to as a CPU, an MPU, a microprocessor, or a processor core. The application processor 1604 may include a plurality of processors (processor cores). The application processor 1604 loads a system software program (operating system (OS)) and various application programs (e.g., a call application, a WEB browser, a mail program, a camera operation application, and a music player application) from the memory 1606 or from other memories (not shown), and executes these programs, thereby providing various functions of the UE 2.

[0139] In some implementations, such as Fig.16 As shown by the dashed line (1605) in FIG. 1 , the baseband processor 1603 and the application processor 1604 may be integrated on a single chip. In other words, the baseband processor 1603 and the application processor 1604 may be implemented on a single system on chip (SoC) device 1605. The SoC device may be referred to as a system large scale integration (LSI) or a chipset.

[0140] The memory 1606 is a volatile memory, a non-volatile memory, or a combination thereof. The memory 1606 may include a plurality of memory devices that are physically independent of each other. The volatile memory is, for example, an SRAM, a DRAM, or a combination thereof. The non-volatile memory is, for example, an MROM, an EEPROM, a flash memory, a hard disk drive, or any combination thereof. The memory 1606 may include, for example, an external memory device accessible from the baseband processor 1603, the application processor 1604, and the SoC 1605. The memory 1606 may include an internal memory device integrated in the baseband processor 1603, the application processor 1604, or the SoC 1605. In addition, the memory 1606 may include a memory in a universal integrated circuit card (UICC).

[0141] The memory 1606 may store one or more software modules (computer programs) 1607 including instructions and data for performing the processing using UE 2 described in the above embodiments. In some implementations, the baseband processor 1603 or the application processor 1604 may load these software modules 1607 from the memory 1606 and execute the loaded software modules, thereby performing the processing of UE 2 described in the above embodiments with reference to the drawings.

[0142] As mentioned above Fig.15 and Fig.16 As described, the processors included in the gNB 1 and UE 2 according to the above-mentioned embodiment execute one or more programs including instructions for causing the computer to perform the algorithm described with reference to the accompanying drawings. Any type of non-transitory computer-readable medium can be used to store these programs and provide these programs to the computer. Non-transitory computer-readable media include any type of tangible storage media. Examples of non-transitory computer-readable media include: magnetic storage media (such as floppy disks, tapes, hard disk drives, etc.), optical magnetic storage media (for example, magneto-optical disks), compact disk read-only memory (CD-ROM), CD-R, CD-R / W, and semiconductor memory (such as mask ROM, programmable ROM (PROM), erasable PROM (EPROM), flash ROM, and random access memory (RAM)). Any type of temporary computer-readable medium can be used to provide these programs to the computer. Examples of temporary computer-readable media include electrical signals, optical signals, and electromagnetic waves. Temporary computer-readable media can provide programs to the computer via wired communication lines (for example, wires and optical fibers) or wireless communication lines.

[0143] Other embodiments

[0144] The 5G-RAN 3 described in the above embodiment can be implemented based on the concept of cloud radio access network (C-RAN). C-RAN is also called centralized RAN. In this case, the processing and operations performed by the gNB1 described in the above embodiment can be provided by a digital unit (DU) included in the C-RAN architecture, or by a combination of a DU and a radio unit (RU). DU is also called a baseband unit (BBU) or a central unit (CU). RU is also called a remote radio head (RRH), a remote radio equipment (RRE), a distributed unit (DU) or a transmit receive point (TRP or TRxP). That is, the processing and operations performed by the gNB 1 described in the above embodiment can be provided by one or more wireless stations (or RAN nodes).

[0145] The above embodiments have been described focusing on cell reselection using a UE in the RRC_INACTIVE state. However, for example, network slice availability may be configured not only for each cell but also for each PLMN. That is, whether the desired network slice of UE 2 is available (or supported) in the camping cell may differ between PLMNs. For example, network slice availability information may be sent to UE 2 for each PLMN. In the event that the desired network slice is not available (or not supported) in the selected PLMN of UE 2, the UE AS layer may notify the NAS layer of the desired network slice. At this time, the AS layer may also notify the NAS layer of information related to the network slice for each PLMN (e.g., information related to whether the network slice is available, or information related to the available network slice). The NAS layer may then perform PLMN selection in consideration of the information received from the AS layer, and may notify the AS layer of the result (i.e., the newly selected PLMN).

[0146] As already explained, the above embodiments can be applied to other wireless communication systems that support network slicing and use the RRC_INACTIVE state or a similar RRC state. For example, a case can be considered where an LTE E-UTRAN (eNB) is connected to a 5G-CN and network slicing is supported in an E-UTRAN cell. In addition, the following case can be assumed: as in the above-mentioned RRC_INACTIVE state, a state (or sub-state, or operating mode) in which the UE and the eNB maintain at least a portion of the AS context of the UE and the location of the UE is known to the E-UTRAN at the level of a predetermined area configured by the E-UTRAN. 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.

[0147] In addition, the above-described embodiments are merely examples of application of the technical ideas obtained by the present inventors. These technical ideas are not limited to the above-described embodiments, and various modifications can be made to these technical ideas.

[0148] For example, all or part of the above-described embodiments may be described as, but not limited to, the following supplementary descriptions.

[0149] (Supplementary Note 1)

[0150] A base station, configured in a radio access network (RAN), the base station comprising: a memory; and at least one processor, connected to the memory and configured to control a state transition of a first wireless terminal between a first RRC state, a second RRC state and a third RRC state, wherein the first RRC state is a state in which the first wireless terminal and the RAN maintain an access stratum context (AS context), and the location of the first wireless terminal is known to the RAN at a cell level, the second RRC state is a state in which the first wireless terminal and the RAN maintain at least a part of the AS context, and the location of the first wireless terminal is known to the RAN at a level of a RAN notification area configured by the RAN, the third RRC state is a state in which the first wireless terminal and the RAN release the AS context, and the location of the first wireless terminal is unknown to the RAN, and the at least one processor is further configured to explicitly or implicitly notify the first wireless terminal whether a first network slice configured in the first wireless terminal for data communication at least in the first RRC state is available in each cell included in the RAN notification area.

[0151] (Supplementary Note 2)

[0152] A base station according to Supplementary Note 1, wherein the at least one processor is configured to send first information for explicitly indicating whether the first network slice is available in each cell included in the RAN notification area to the first wireless terminal.

[0153] (Supplementary Note 3)

[0154] The base station according to Supplementary Note 2, wherein the at least one processor is configured to send the first information to the first wireless terminal when the RAN notification area is configured in the first wireless terminal.

[0155] (Supplementary Note 4)

[0156] The base station according to Supplementary Note 2 or 3, wherein the at least one processor is configured to send the first information to the first wireless terminal during a process for causing the first wireless terminal to enter the second RRC state from the first RRC state.

[0157] (Supplementary Note 5)

[0158] A base station according to Supplementary Note 1, wherein the at least one processor is configured to include only one or more cells available for the first network slice in the RAN notification area used by the first wireless terminal, and configure the RAN notification area in the first wireless terminal, and the RAN notification area implicitly indicates that the first network slice is available in each cell included in the RAN notification area.

[0159] (Supplementary Note 6)

[0160] A base station according to any one of Supplementary Notes 1 to 5, wherein the at least one processor is configured to receive information from other base stations via an inter-base station interface indicating one or more network slices that are available or unavailable in each cell of the other base stations.

[0161] (Supplementary Note 7)

[0162] A base station according to any one of Supplementary Notes 1 to 6, wherein the at least one processor is configured to receive, from the second wireless terminal, second information indicating a second network slice that had been configured in the second wireless terminal when the second wireless terminal was previously in the first RRC state, during or after a process for causing the second wireless terminal to enter the first RRC state from the second RRC state.

[0163] (Supplementary Note 8)

[0164] A base station according to Supplementary Note 7, wherein the at least one processor is configured to move the second wireless terminal to other base stations or other cells when the second network slice is not available in the base station or in the cell to which the second wireless terminal is connected.

[0165] (Supplementary Note 9)

[0166] The base station according to any one of Supplementary Notes 1 to 8, wherein the first RRC state is an RRC_CONNECTED state, the second RRC state is an RRC_INACTIVE state, and the third RRC state is an RRC_IDLE state.

[0167] (Supplementary Note 10)

[0168] The base station according to any one of Supplementary Notes 1 to 9, wherein the RAN notification area is an area in which, when the wireless terminal in the second RRC state moves between cells through cell reselection, the wireless terminal does not need to notify the RAN of the cell reselection.

[0169] (Supplementary Note 11)

[0170] A base station, configured in a radio access network (RAN), the base station comprising: a memory; and at least one processor, connected to the memory and configured to control a state transition of a wireless terminal between a first RRC state, a second RRC state and a third RRC state, wherein the first RRC state is a state in which the wireless terminal and the RAN maintain an access stratum context (AS context), and the location of the wireless terminal is known to the RAN at a cell level, the second RRC state is a state in which the wireless terminal and the RAN maintain at least a part of the AS context, and the location of the wireless terminal is known to the RAN at a level of a RAN notification area configured by the RAN, the third RRC state is a state in which the wireless terminal and the RAN release the AS context, and the location of the wireless terminal is unknown to the RAN, and the at least one processor is further configured to send system information in a first cell of the base station for indicating one or more network slices that are available or unavailable in the first cell.

[0171] (Supplementary Note 12)

[0172] The base station according to Supplementary Note 11, wherein the system information is broadcast system information to be broadcast in the first cell, or on-demand system information to be sent to the wireless terminal in response to a request message from the wireless terminal.

[0173] (Supplementary Note 13)

[0174] A base station according to Supplementary Note 11 or 12, wherein the at least one processor is configured to receive, from the wireless terminal, information indicating a first network slice that had been configured in the wireless terminal when the wireless terminal was previously in the first RRC state, during or after a process for causing the wireless terminal to enter the first RRC state from the second RRC state.

[0175] (Supplementary Note 14)

[0176] A base station according to Supplementary Note 13, wherein the at least one processor is configured to move the wireless terminal to other base stations or other cells when the first network slice is not available in the base station or in the cell to which the wireless terminal is connected.

[0177] (Supplementary Note 15)

[0178] The base station according to any one of Supplementary Notes 11 to 14, wherein the first RRC state is an RRC_CONNECTED state, the second RRC state is an RRC_INACTIVE state, and the third RRC state is an RRC_IDLE state.

[0179] (Supplementary Note 16)

[0180] A wireless terminal comprises: a transceiver; and at least one processor configured to control the transceiver in one or more cells associated with a radio access network (RAN), wherein the at least one processor is configured to control the state transition of the wireless terminal between a first RRC state, a second RRC state, and a third RRC state, the first RRC state being a state in which the wireless terminal and the RAN maintain an access stratum context (AS context), and the location of the wireless terminal is known to the RAN at a cell level, the second RRC state being a state in which the wireless terminal and the RAN maintain at least a part of the AS context, and the location of the wireless terminal is known to the RAN at a level of a RAN notification area configured by the RAN, the third RRC state being a state in which the wireless terminal and the RAN release the AS context, and the location of the wireless terminal is unknown to the RAN, and the at least one processor is further configured to confirm whether a first network slice configured in the wireless terminal for data communication at least in the first RRC state is available in a cell to be reselected through cell reselection in the second RRC state.

[0181] (Supplementary Note 17)

[0182] A wireless terminal according to Supplementary Note 16, wherein the at least one processor is configured to receive first information from a base station within the RAN for explicitly indicating whether the first network slice is available in each cell included in the RAN notification area.

[0183] (Supplementary Note 18)

[0184] The wireless terminal according to Supplementary Note 17, wherein the at least one processor is configured to receive the first information during a process in which the wireless terminal transitions from the first RRC state to the second RRC state.

[0185] (Supplementary Note 19)

[0186] A wireless terminal according to Supplementary Note 16, wherein 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 configuration of the RAN notification area from a base station within the RAN, and the at least one processor is configured to confirm whether the first network slice is available in the cell to be reselected based on whether the cell to be reselected is included in the RAN notification area.

[0187] (Supplementary Note 20)

[0188] A wireless terminal according to Supplementary Note 16, wherein the at least one processor is configured to attempt to receive system information indicating one or more network slices that are available or unavailable in the cell to be reselected in response to cell reselection in the second RRC state, and the at least one processor is configured to confirm whether the first network slice is available in the cell to be reselected based on the system information.

[0189] (Supplementary Note 21)

[0190] The wireless terminal according to supplementary note 20, wherein the system information is broadcast system information to be broadcast in a cell to be reselected, or on-demand system information to be sent to the wireless terminal in response to a request message from the wireless terminal.

[0191] (Supplementary Note 22)

[0192] A wireless terminal according to any one of Supplementary Notes 16 to 21, wherein the at least one processor is configured to send second information indicating the first network slice to a base station of the cell to be reselected during or after a process in which the wireless terminal transitions from the second RRC state to the first RRC state in the cell to be reselected, in response to a failure to confirm whether the first network slice is available in the cell to be reselected.

[0193] (Supplementary Note 23)

[0194] A wireless terminal according to any one of Supplementary Notes 16 to 22, wherein the first RRC state is an RRC_CONNECTED state, the second RRC state is an RRC_INACTIVE state, and the third RRC state is an RRC_IDLE state.

[0195] (Supplementary Note 24)

[0196] A method for a base station, wherein the base station is configured in a radio access network (RAN), the method comprising: controlling a state transition of a first wireless terminal between a first RRC state, a second RRC state, and a third RRC state; and explicitly or implicitly notifying the first wireless terminal whether a first network slice configured in the first wireless terminal for data communication at least in the first RRC state is available in each cell included in a RAN notification area configured by the RAN, wherein the first RRC state is a state in which the first wireless terminal and the RAN maintain an access stratum context (AS context), and the location of the first wireless terminal is known to the RAN at a cell level, the second RRC state is a state in which the first wireless terminal and the RAN maintain at least a part of the AS context, and the location of the first wireless terminal is known to the RAN at a level of the RAN notification area, and the third RRC state is a state in which the first wireless terminal and the RAN release the AS context, and the location of the first wireless terminal is unknown to the RAN.

[0197] (Supplementary Note 25)

[0198] A method for a base station, wherein the base station is configured in a radio access network (RAN), the method comprising: controlling a state transition of a wireless terminal between a first RRC state, a second RRC state, and a third RRC state; and sending system information in a first cell of the base station for indicating one or more network slices that are available or unavailable in the first cell, wherein the first RRC state is a state in which the wireless terminal and the RAN maintain an access layer context (AS context), and the location of the wireless terminal is known to the RAN at a cell level, the second RRC state is a state in which the wireless terminal and the RAN maintain at least a part of the AS context, and the location of the wireless terminal is known to the RAN at a level of a RAN notification area configured by the RAN, and the third RRC state is a state in which the wireless terminal and the RAN release the AS context, and the location of the wireless terminal is unknown to the RAN.

[0199] (Supplementary Note 26)

[0200] A method for a wireless terminal, the method comprising: controlling the state transition of the wireless terminal between a first RRC state, a second RRC state and a third RRC state; and confirming whether a first network slice configured in the wireless terminal for data communication at least in the first RRC state is available in a cell to be reselected through cell reselection in the second RRC state, wherein the first RRC state is a state in which the wireless terminal and a radio access network, i.e., a RAN, maintain an access stratum context, i.e., an AS context, and the location of the wireless terminal is known to the RAN at a cell level, the second RRC state is a state in which the wireless terminal and the RAN maintain at least a part of the AS context, and the location of the wireless terminal is known to the RAN at a level of a RAN notification area configured by the RAN, and the third RRC state is a state in which the wireless terminal and the RAN release the AS context, and the location of the wireless terminal is unknown to the RAN.

[0201] (Supplementary Note 27)

[0202] A non-transitory computer-readable medium storing a program, the program being used to cause a computer to perform a method used by a base station, the base station being configured in a radio access network (RAN), wherein the method comprises: controlling a state transition of a first wireless terminal between a first RRC state, a second RRC state, and a third RRC state; and explicitly or implicitly notifying the first wireless terminal whether a first network slice configured in the first wireless terminal for data communication at least in the first RRC state is available in each cell included in a RAN notification area configured by the RAN, wherein the first RRC state is a state in which the first wireless terminal and the RAN maintain an access stratum context (AS context), and the location of the first wireless terminal is known to the RAN at a cell level, the second RRC state is a state in which the first wireless terminal and the RAN maintain at least a part of the AS context, and the location of the first wireless terminal is known to the RAN at a RAN notification area level, and the third RRC state is a state in which the first wireless terminal and the RAN release the AS context, and the location of the first wireless terminal is unknown to the RAN.

[0203] (Supplementary Note 28)

[0204] A non-transitory computer-readable medium storing a program, the program being used to cause a computer to perform a method used by a base station, the base station being configured in a radio access network (RAN), wherein the method comprises: controlling a state transition of a wireless terminal between a first RRC state, a second RRC state, and a third RRC state; and sending system information in a first cell of the base station for indicating one or more network slices that are available or unavailable in the first cell, wherein the first RRC state is a state in which the wireless terminal and the RAN maintain an access stratum context (AS context), and the location of the wireless terminal is known to the RAN at a cell level, the second RRC state is a state in which the wireless terminal and the RAN maintain at least a part of the AS context, and the location of the wireless terminal is known to the RAN at a level of a RAN notification area configured by the RAN, and the third RRC state is a state in which the wireless terminal and the RAN release the AS context, and the location of the wireless terminal is unknown to the RAN.

[0205] (Supplementary Note 29)

[0206] A non-transitory computer-readable medium storing a program, the program being used to cause a computer to perform a method used by a wireless terminal, wherein the method includes: controlling the state transition of the wireless terminal between a first RRC state, a second RRC state, and a third RRC state; and confirming whether a first network slice configured in the wireless terminal for data communication at least in the first RRC state is available in a cell to be reselected through cell reselection in the second RRC state, wherein the first RRC state is a state in which the wireless terminal and a radio access network, i.e., a RAN, maintain an access stratum context, i.e., an AS context, and the location of the wireless terminal is known to the RAN at a cell level, the second RRC state is a state in which the wireless terminal and the RAN maintain at least a part of the AS context, and the location of the wireless terminal is known to the RAN at a level of a RAN notification area configured by the RAN, and the third RRC state is a state in which the wireless terminal and the RAN release the AS context, and the location of the wireless terminal is unknown to the RAN.

[0207] This application is based upon and claims the benefit of priority from Japanese patent application No. 2017-000800, filed on January 5, 2017, the entire contents of which are incorporated herein by reference.

Claims

1. A gNB, comprising: a controller configured to communicate with a user equipment (UE) in an RRC_CONNECTED state using a network slice, the controller being configured to set cell information, the cell information defining one or more cells belonging to a radio access network notification area (RAN notification area), the cell information indicating only one or more cells supporting the network slice used by the UE in the RRC_CONNECTED state when communicating with the gNB, the cell information being included in information related to the RAN notification area in a radio resource control message (RRC message) to be sent from the gNB to the UE in a case where the UE in the RRC_CONNECTED state transitions to an RRC_INACTIVE state; and A transmitter configured to send the RRC message to the UE in the RRC_CONNECTED state if the gNB decides to transition the UE in the RRC_CONNECTED state to the RRC_INACTIVE state.

2. The gNB according to claim 1, wherein: The information related to the RAN notification area includes an identifier indicating the area notified by the RAN.

3. The gNB according to claim 1 or 2 further includes a receiver configured to receive a message from another gNB via an Xn interface, the message including network slice information indicating at least one network slice supported in at least one cell of the other gNB.

4. The gNB according to claim 3, wherein: The message is sent from the other gNB to notify the gNB of the update of the network slice information.

5. A user equipment (UE), configured to use network slicing, the UE comprising: a receiver configured to receive a radio resource control message (RRC message) from a gNB to transition the UE in the RRC_CONNECTED state to the RRC_INACTIVE state, the RRC message comprising cell information, the cell information defining one or more cells belonging to a RAN notification area, the cell information indicating only one or more cells supporting a network slice used by the UE in the RRC_CONNECTED state when communicating with the gNB, the cell information being included in the information related to the RAN notification area in the RRC message; as well as A controller is configured to cause the UE in the RRC_CONNECTED state to transition to the RRC_INACTIVE state.

6. The UE according to claim 5, wherein: The information related to the RAN notification area includes an identifier indicating the area notified by the RAN.

7. The UE according to claim 5 or 6, wherein: The controller is also configured to decide whether the UE sends a message to another gNB based on whether information of the cell in which the UE decides to reside is included in the cell information.

8. The UE according to claim 7 further includes a transmitter, which is configured to send a message to the other gNB when the information of the cell in which the UE decides to camp is not included in the cell information.

9. The UE according to claim 7 further includes a transmitter, which is configured not to send a message to the other gNB when information of the cell in which the UE decides to camp is included in the cell information.

10. A method for a user equipment (UE), wherein the UE is configured to use network slicing, the method comprising: receiving a radio resource control message (RRC message) from the gNB to transition the UE in the RRC_CONNECTED state to the RRC_INACTIVE state, the RRC message including cell information, the cell information defining one or more cells belonging to a RAN notification area, the cell information indicating only one or more cells supporting a network slice used by the UE in the RRC_CONNECTED state when communicating with the gNB, the cell information being included in the information related to the RAN notification area in the RRC message; and The UE in the RRC_CONNECTED state is transitioned to the RRC_INACTIVE state.

11. The method according to claim 10, wherein: The information related to the RAN notification area includes an identifier indicating the area notified by the RAN.

12. The method according to claim 10 or 11, further comprising: Whether the UE sends a message to another gNB is determined based on whether information of the cell in which the UE decides to reside is included in the cell information.

13. The method according to claim 12, further comprising: In a case where the information of the cell in which the UE decides to reside is not included in the cell information, a message is sent to the other gNB.

14. The method according to claim 12, further comprising: In a case where information about the cell in which the UE decides to reside is included in the cell information, no message is sent to the other gNB.

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