COMMUNICATION CONTROL METHOD, CORE NETWORK NODE, AND USER EQUIPMENT

Abstract

A communication control method according to an aspect of the present invention is for a mobile communication system. This communication control method comprises a step for transmitting, from a core network device to a user device, mobile terminated (MT) slice information indicating a network slice linked to paging.

Description

Communication Control Method

[0001] The present disclosure relates to a communication control method in a mobile communication system.

[0002] Network slicing is defined in the specifications of the Third Generation Partnership Project (3GPP) (registered trademark; the same applies hereinafter), a standardization project for mobile communication systems. Network slicing is a technology that creates network slices, which are virtual networks, by logically dividing a physical network built by a telecommunications carrier.

[0003] A user equipment in a radio resource control (RRC) idle state or an RRC inactive state can perform a cell reselection procedure. 3GPP is considering a network slice-dependent cell reselection procedure called slice specific cell reselection (also called slice aware cell reselection or slice based cell reselection) (see, for example, Non-Patent Document 1). By performing the slice specific cell reselection procedure, the user equipment can, for example, camp on a neighboring cell that supports a desired network slice.

[0004] 3GPP TS 38.300 V17.8.0 (2022-3)

[0005] A communication control method according to one aspect is a communication control method in a mobile communication system, the communication control method including a step of transmitting, by a core network device, MT (Mobile Terminated) slice information representing a network slice associated with paging to a user equipment.

[0006] FIG. 1 is a diagram illustrating an example of the configuration of a mobile communication system according to the first embodiment. FIG. 2 is a diagram illustrating an example of the configuration of a UE (user equipment) according to the first embodiment. FIG. 3 is a diagram illustrating an example of the configuration of a gNB (base station) according to the first embodiment. FIG. 4 is a diagram illustrating an example of the configuration of a protocol stack related to a user plane according to the first embodiment. FIG. 5 is a diagram illustrating an example of the configuration of a protocol stack related to a control plane according to the first embodiment. FIG. 6 is a diagram for explaining an overview of a cell reselection procedure. FIG. 7 is a diagram illustrating a schematic flow of a general cell reselection procedure. FIG. 8 is a diagram illustrating an example of network slicing. FIG. 9 is a diagram illustrating an overview of a slice-specific cell reselection procedure. FIG. 10 is a diagram illustrating an example of slice frequency information. FIG. 11 is a diagram illustrating a basic flow of a slice-specific cell reselection procedure. FIG. 12 is a diagram illustrating an example of an operation according to the first embodiment. FIGS. 13(A) and 13(B) are diagrams illustrating an example of the relationship between slices, slice priority, and frequency priority. FIG. 14 is a diagram illustrating an example of an operation according to the second embodiment. FIG. 15 is a diagram illustrating an example of an operation according to the third embodiment. FIG. 16 is a diagram illustrating an example of an operation according to the fourth embodiment. FIG. 17 is a diagram illustrating an example of operation according to the fifth embodiment.

[0007] The present disclosure aims to enable user equipment to connect to an appropriate cell.

[0008] A mobile communication system according to an embodiment will be described with reference to the drawings. In the description of the drawings, the same or similar parts are denoted by the same or similar reference numerals.

[0009] [First embodiment] (Configuration of mobile communication system) Fig. 1 is a diagram showing the configuration of a mobile communication system according to the first embodiment. The mobile communication system 1 conforms to the 5th Generation System (5GS) of the 3GPP standard. Although the following description will be given using 5GS as an example, the mobile communication system may also be at least partially applied to an LTE (Long Term Evolution) system. The mobile communication system may also be at least partially applied to a 6th Generation (6G) system.

[0010] The mobile communication system 1 includes a user equipment (UE) 100, a 5G radio access network (NG-RAN: Next Generation Radio Access Network) 10, and a 5G core network (5GC: 5G Core Network) 20. Hereinafter, the NG-RAN 10 may be simply referred to as the RAN 10. Furthermore, the 5GC 20 may be simply referred to as the core network (CN) 20.

[0011] The UE 100 is a mobile wireless communication device. The UE 100 may be any device that is used by a user. For example, the UE 100 may be a mobile phone terminal (including a smartphone), a tablet terminal, a notebook PC, a communication module (including a communication card or a chipset), a sensor or a device provided in a sensor, a vehicle or a device provided in a vehicle (Vehicle UE), or an aircraft or a device provided in an aircraft (Aerial UE).

[0012] The NG-RAN 10 includes a base station (called a "gNB" in a 5G system) 200. The gNBs 200 are connected to each other via an Xn interface, which is an interface between base stations. The gNB 200 manages one or more cells. The gNB 200 performs wireless communication with a UE 100 that has established a connection with its own cell. The gNB 200 has a radio resource management (RRM) function, a routing function for user data (hereinafter simply referred to as "data"), a measurement control function for mobility control and scheduling, and the like. The term "cell" is used to indicate the smallest unit of a wireless communication area. The term "cell" is also used to indicate a function or resource for wireless communication with the UE 100. One cell belongs to one carrier frequency (hereinafter simply referred to as "frequency").

[0013] In addition, gNBs can also be connected to the Evolved Packet Core (EPC), which is the core network of LTE. LTE base stations can also be connected to 5GC. LTE base stations and gNBs can also be connected via an inter-base station interface.

[0014] The 5GC20 includes an Access and Mobility Management Function (AMF) and a User Plane Function (UPF) 300. The AMF performs various mobility controls for the UE 100. The AMF manages the mobility of the UE 100 by communicating with the UE 100 using NAS (Non-Access Stratum) signaling. The UPF controls data forwarding. The AMF and the UPF are connected to the gNB 200 via an NG interface, which is an interface between a base station and a core network.

[0015] 2 is a diagram showing the configuration of the UE 100 (user equipment) according to the first embodiment. The UE 100 includes a receiving unit 110, a transmitting unit 120, and a control unit 130. The receiving unit 110 and the transmitting unit 120 constitute a wireless communication unit that performs wireless communication with the gNB 200.

[0016] The receiving unit 110 performs various types of reception under the control of the control unit 130. The receiving unit 110 includes an antenna and a receiver. The receiver converts a radio signal received by the antenna into a baseband signal (received signal) and outputs the baseband signal to the control unit 130.

[0017] The transmitting unit 120 performs various transmissions under the control of the control unit 130. The transmitting unit 120 includes an antenna and a transmitter. The transmitter converts a baseband signal (transmission signal) output by the control unit 130 into a radio signal and transmits it from the antenna.

[0018] The control unit 130 performs various controls and processes in the UE 100. Such processes include processes of each layer described below. The control unit 130 includes at least one processor and at least one memory. The memory stores programs executed by the processor and information used in the processes by the processor. The processor may include a baseband processor and a CPU (Central Processing Unit). The baseband processor performs modulation / demodulation, encoding / decoding, etc. of baseband signals. The CPU executes programs stored in the memory to perform various processes. Note that the control unit 130 may perform each process or operation in the UE 100 in each of the embodiments described below.

[0019] 3 is a diagram showing the configuration of a gNB 200 (base station) according to the first embodiment. The gNB 200 includes a transmitter 210, a receiver 220, a controller 230, and a backhaul communication unit 240. The transmitter 210 and the receiver 220 constitute a wireless communication unit that performs wireless communication with the UE 100. The backhaul communication unit 240 constitutes a network communication unit that communicates with the CN 20.

[0020] The transmitting unit 210 performs various transmissions under the control of the control unit 230. The transmitting unit 210 includes an antenna and a transmitter. The transmitter converts a baseband signal (transmission signal) output by the control unit 230 into a radio signal and transmits it from the antenna.

[0021] The receiving unit 220 performs various types of reception under the control of the control unit 230. The receiving unit 220 includes an antenna and a receiver. The receiver converts a radio signal received by the antenna into a baseband signal (received signal) and outputs the baseband signal to the control unit 230.

[0022] The control unit 230 performs various controls and processes in the gNB 200. Such processes include processes for each layer described below. The control unit 230 includes at least one processor and at least one memory. The memory stores programs executed by the processor and information used in the processes by the processor. The processor may include a baseband processor and a CPU. The baseband processor performs modulation / demodulation, encoding / decoding, etc. of baseband signals. The CPU executes programs stored in the memory to perform various processes. Note that the control unit 230 may perform each process or operation in the gNB 200 in each of the embodiments described below.

[0023] The backhaul communication unit 240 is connected to adjacent base stations via an Xn interface, which is an interface between base stations. The backhaul communication unit 240 is connected to the AMF / UPF 300 via an NG interface, which is an interface between a base station and a core network. Note that the gNB 200 is composed of a CU (Central Unit) and a DU (Distributed Unit) (i.e., functionally divided), and the two units may be connected by an F1 interface, which is a fronthaul interface.

[0024] FIG. 4 is a diagram showing the configuration of a protocol stack of a radio interface of a user plane that handles data.

[0025] The user plane radio interface protocol includes a physical (PHY) layer, a medium access control (MAC) layer, a radio link control (RLC) layer, a packet data convergence protocol (PDCP) layer, and a service data adaptation protocol (SDAP) layer.

[0026] The PHY layer performs encoding / decoding, modulation / demodulation, antenna mapping / demapping, and resource mapping / demapping. Data and control information are transmitted between the PHY layer of UE100 and the PHY layer of gNB200 via a physical channel. The PHY layer of UE100 receives downlink control information (DCI) transmitted from gNB200 on a physical downlink control channel (PDCCH). Specifically, UE100 performs blind decoding of the PDCCH using a radio network temporary identifier (RNTI) and acquires the successfully decoded DCI as DCI addressed to the UE. The DCI transmitted from gNB200 has a CRC parity bit scrambled by the RNTI added.

[0027] The MAC layer performs data priority control, retransmission processing using hybrid ARQ (HARQ), random access procedures, etc. Data and control information are transmitted between the MAC layer of UE100 and the MAC layer of gNB200 via a transport channel. The MAC layer of gNB200 includes a scheduler. The scheduler determines the uplink and downlink transport format (transport block size, modulation and coding scheme (MCS)) and the resource blocks to be allocated to UE100.

[0028] The RLC layer transmits data to the receiving RLC layer using the functions of the MAC layer and PHY layer. Data and control information are transmitted between the RLC layer of the UE 100 and the RLC layer of the gNB 200 via a logical channel.

[0029] The PDCP layer performs header compression / decompression, encryption / decryption, and the like.

[0030] The SDAP layer maps IP flows, which are units for Quality of Service (QoS) control by the core network, to radio bearers, which are units for QoS control by the Access Stratum (AS). Note that if the RAN is connected to the EPC, SDAP may not be required.

[0031] FIG. 5 is a diagram showing the configuration of a protocol stack of a radio interface of a control plane that handles signaling (control signals).

[0032] The protocol stack of the radio interface of the control plane has a Radio Resource Control (RRC) layer and a Non-Access Stratum (NAS) instead of the SDAP layer shown in FIG.

[0033] RRC signaling for various settings is transmitted between the RRC layer of UE100 and the RRC layer of gNB200. The RRC layer controls logical channels, transport channels, and physical channels according to the establishment, re-establishment, and release of radio bearers. When there is a connection (RRC connection) between the RRC of UE100 and the RRC of gNB200, UE100 is in an RRC connected state. When there is no connection (RRC connection) between the RRC of UE100 and the RRC of gNB200, UE100 is in an RRC idle state. When the connection between the RRC of UE100 and the RRC of gNB200 is suspended, UE100 is in an RRC inactive state.

[0034] The NAS, which is located above the RRC layer, performs session management, mobility management, etc. NAS signaling is transmitted between the NAS of the UE 100 and the NAS of the AMF 300. Note that the UE 100 has an application layer and the like in addition to the radio interface protocol. Also, the layer below the NAS is called an Access Stratum (AS).

[0035] (Outline of Cell Reselection Procedure) FIG. 6 is a diagram for explaining an outline of a cell reselection procedure.

[0036] A UE 100 in an RRC idle state or an RRC inactive state performs a cell reselection procedure to transition from a current serving cell (cell #1) to a neighboring cell (any of cells #2 to #4) as it moves. Specifically, the UE 100 identifies a neighboring cell on which it should camp by the cell reselection procedure and reselects the identified neighboring cell. When the frequency (carrier frequency) of the current serving cell and the neighboring cell is the same, this is called intra-frequency, and when the frequency (carrier frequency) of the current serving cell and the neighboring cell is different, this is called inter-frequency. The current serving cell and the neighboring cell may be managed by the same gNB 200. The current serving cell and the neighboring cell may be managed by different gNBs 200.

[0037] FIG. 7 is a diagram illustrating the general flow of a typical (or legacy) cell reselection procedure.

[0038] In step S11, the UE 100 performs frequency prioritization processing based on the priority (also referred to as "absolute priority") for each frequency specified by the gNB 200, for example, by a system information block or an RRC release message. Specifically, the UE 100 manages the frequency priority specified by the gNB 200 for each frequency.

[0039] In step S12, the UE 100 performs a measurement process to measure the radio quality of each of the serving cell and the neighboring cell. The UE 100 measures the received power and received quality of reference signals transmitted by each of the serving cell and the neighboring cell, specifically, CD-SSB (Cell Defining-Synchronization Signal and PBCH block). For example, the UE 100 always measures the radio quality for a frequency having a higher priority than the frequency priority of the current serving cell, and for a frequency having a priority equal to or lower than the frequency priority of the current serving cell, when the radio quality of the current serving cell falls below a predetermined quality, measures the radio quality of the frequency having the same priority or lower priority.

[0040] In step S13, the UE 100 performs a cell reselection process to reselect a cell on which the UE 100 will camp based on the measurement result in step S12. For example, if the frequency priority of a neighboring cell is higher than the priority of the current serving cell and the neighboring cell satisfies a predetermined quality standard (i.e., a minimum required quality standard) for a predetermined period, the UE 100 may perform cell reselection to the neighboring cell. If the frequency priority of the neighboring cell is the same as the priority of the current serving cell, the UE 100 may rank the radio qualities of the neighboring cells and perform cell reselection to a neighboring cell having a higher rank than the rank of the current serving cell for a predetermined period. If the frequency priority of the neighboring cell is lower than the priority of the current serving cell and the radio quality of the current serving cell is lower than a certain threshold and the radio quality of the neighboring cell is higher than another threshold, the UE 100 may perform cell reselection to the neighboring cell.

[0041] (Outline of Network Slicing) Network slicing is a technology for creating multiple virtual networks by virtually dividing a physical network (for example, a network consisting of an NG-RAN 10 and a 5GC 20) constructed by a carrier. Each virtual network is called a network slice. Hereinafter, a network slice may be simply referred to as a "slice."

[0042] Network slicing allows telecommunications operators to create slices according to the service requirements of different service types, such as eMBB (enhanced Mobile Broadband), URLLC (Ultra-Reliable and Low Latency Communications), and mMTC (massive Machine Type Communications), thereby optimizing network resources.

[0043] FIG. 8 is a diagram illustrating an example of network slicing.

[0044] Three slices (slice #1 to slice #3) are configured on a network 50 configured with an NG-RAN 10 and a 5GC 20. Slice #1 is associated with a service type called eMBB, slice #2 is associated with a service type called URLLC, and slice #3 is associated with a service type called mMTC. Note that three or more slices may be configured on the network 50. One service type may be associated with multiple slices.

[0045] Each slice is provided with a slice identifier that identifies the slice. An example of a slice identifier is S-NSSAI (Single Network Slicing Selection Assistance Information). The S-NSSAI includes an 8-bit SST (slice / service type). The S-NSSAI may further include a 24-bit SD (slice differentiator). The SST is information indicating the service type to which the slice is associated. The SD is information for differentiating multiple slices associated with the same service type. Information including multiple S-NSSAIs is called NSSAI (Network Slice Selection Assistance Information).

[0046] Furthermore, one or more slices may be grouped to form a slice group. A slice group is a group including one or more slices, and a slice group identifier is assigned to the slice group. The slice group may be configured by a core network (e.g., the AMF 300) or a radio access network (e.g., the gNB 200). The configured slice group may be notified to the UE 100.

[0047] Hereinafter, the term "network slice (slice)" may refer to an S-NSSAI, which is an identifier of a single slice, or an NSSAI, which is a collection of S-NSSAIs. The term "network slice (slice)" may also refer to a slice group, which is a group of one or more S-NSSAIs or NSSAIs.

[0048] Furthermore, UE100 determines a desired slice that it desires to use. The desired slice may be called an "intended slice." In the first embodiment, UE100 determines a slice priority for each network slice (desired slice). For example, the NAS of UE100 determines the slice priority based on the operation status of an application in UE100 and / or user operation / settings, and notifies the AS of slice priority information indicating the determined slice priority. Note that the NAS of UE100 may receive the slice priority information from AMF300. In this case, the NAS of UE100 may determine the slice priority based on the slice priority information received from AMF300.

[0049] (Overview of Slice-Specific Cell Reselection Procedure) FIG. 9 is a diagram illustrating an overview of a slice-specific cell reselection (also referred to as slice-aware cell reselection or slice-based cell reselection) procedure.

[0050] In the slice-specific cell reselection procedure, the UE 100 performs a cell reselection process based on slice frequency information provided by the network 50. The slice frequency information may be provided to the UE 100 from the gNB 200 by broadcast signaling (e.g., a system information block) or dedicated signaling (e.g., an RRC release message).

[0051] The slice frequency information indicates the correspondence between network slices, frequencies, and frequency priorities. For example, for each slice (or slice group), the slice frequency information indicates the frequency (one or more frequencies) that supports the slice and the frequency priority assigned to each frequency. An example of the slice frequency information is shown in FIG. 10 .

[0052] In the example shown in Fig. 10 , three frequencies F1, F2, and F4 are associated with slice #1 as frequencies supporting slice #1. Of these three frequencies, F1 has a frequency priority of "6," F2 has a frequency priority of "4," and F4 has a frequency priority of "2." In the example of Fig. 10 , the larger the frequency priority number, the higher the priority; however, it may also be the case that the smaller the number, the higher the priority.

[0053] Furthermore, three frequencies F1, F2, and F3 are associated with slice #2 as frequencies supporting slice #2. Of these three frequencies, F1 has a frequency priority of "0," F2 has a frequency priority of "5," and F3 has a frequency priority of "7."

[0054] Furthermore, three frequencies, F1, F3, and F4, are associated with slice #3 as frequencies supporting slice #3. Of these three frequencies, F1 has a frequency priority of "3," F3 has a frequency priority of "7," and F4 has a frequency priority of "2."

[0055] Hereinafter, the frequency priority indicated in the slice frequency information may be referred to as a "slice-specific frequency priority" to distinguish it from the absolute priority in the conventional cell reselection procedure.

[0056] As shown in FIG. 9, the UE 100 may perform a cell reselection process based on slice support information provided by the network 50. The slice support information may be information indicating a correspondence between a cell (e.g., a serving cell and each neighboring cell) and a network slice that the cell does not provide or provides. For example, a cell may temporarily not provide some or all network slices due to congestion or other reasons. That is, even if a slice support frequency has the ability to provide a certain network slice, some cells within the frequency may not provide the network slice. The UE 100 can identify the network slices that each cell does not provide based on the slice support information. Such slice support information may be provided to the UE 100 by broadcast signaling (e.g., a system information block) or dedicated signaling (e.g., an RRC release message) from the gNB 200.

[0057] 11 is a diagram showing a basic flow of a slice-specific cell reselection procedure. Before starting the slice-specific cell reselection procedure, the UE 100 is in an RRC idle state or an RRC inactive state, and has received and stored the above-mentioned slice frequency information. Note that the procedure of "slice-specific cell reselection" is represented as a "slice-specific cell reselection procedure." However, hereinafter, "slice-specific cell reselection" and "slice-specific cell reselection procedure" may be used interchangeably.

[0058] In step S0, the NAS of UE 100 determines slice identifiers of desired slices of UE 100 and slice priorities of each desired slice, and notifies the AS of UE 100 of slice priority information including the determined slice priorities. A "desired slice" is an "intended slice" and includes a slice that is likely to be used, a candidate slice, a desired slice, a slice to be communicated, a requested slice, an allowed slice, or an intended slice. For example, the slice priority of slice #1 is determined to be "3," the slice priority of slice #2 is determined to be "2," and the slice priority of slice #3 is determined to be "1." A larger number for the slice priority indicates a higher priority, but a smaller number may also indicate a higher priority.

[0059] In step S1, the AS of the UE 100 sorts the slices (slice identifiers) notified from the NAS in step S0 in descending order of slice priority. The list of slices sorted in this manner is called a "slice list."

[0060] In step S2, the AS of the UE 100 selects one network slice in descending order of slice priority. The network slice selected in this manner is called a "selected network slice."

[0061] In step S3, the AS of UE100 assigns frequency priorities to each frequency associated with the selected network slice. Specifically, the AS of UE100 identifies a frequency associated with the slice based on slice frequency information, and assigns frequency priorities to the identified frequency. For example, if the selected network slice selected in step S2 is slice #1, the AS of UE100 assigns frequency priority "6" to frequency F1, frequency priority "4" to frequency F2, and frequency priority "2" to frequency F4 based on slice frequency information (e.g., the information of FIG. 10). The AS of UE100 calls the list of frequencies arranged in descending order of frequency priority a "frequency list."

[0062] In step S4, the AS of UE 100 selects one frequency in descending order of frequency priority for the selected network slice selected in step S2, and performs measurement processing on the selected frequency. The frequency selected in this manner is called a "selected frequency." The AS of UE 100 may rank each cell measured within the selected frequency in descending order of radio quality. Among the cells measured within the selected frequency, a cell that satisfies a predetermined quality standard (i.e., a required minimum quality standard) is called a "candidate cell."

[0063] In step S5, the AS of UE100 identifies the highest-ranked cell based on the result of the measurement process in step S4, and determines whether the cell provides the selected network slice based on the slice support information. If it is determined that the highest-ranked cell provides the selected network slice (step S5: YES), in step S5a, the AS of UE100 reselects the highest-ranked cell and camps on the cell.

[0064] On the other hand, if it is determined that the highest-ranked cell does not provide the selected network slice (step S5: NO), in step S6, the AS of UE100 determines whether there are any unmeasured frequencies in the frequency list created in step S3. In other words, the AS of UE100 determines whether there are any frequencies assigned in step S3 other than the selected frequency in the selected network slice. If it is determined that there are any unmeasured frequencies (step S6: YES), the AS of UE100 resumes processing on the frequency with the next highest frequency priority and performs measurement processing with that frequency as the selected frequency (returning to step S4).

[0065] If it is determined that there are no unmeasured frequencies in the frequency list created in step S3 (step S6: NO), in step S7, the AS of UE100 may determine whether or not there are any unselected slices in the slice list created in step S1. In other words, the AS of UE100 may determine whether or not there are any network slices other than the selected network slice in the slice list. If it is determined that there are any unselected slices (step S7: YES), the AS of UE100 resumes processing on the network slice with the next highest slice priority and selects that network slice as the selected network slice (returns processing to step S2). Note that in the basic flow shown in FIG. 11, the processing of step S7 may be omitted.

[0066] If it is determined that there is no unselected slice (step S7: NO), in step S8, the AS of the UE 100 performs a conventional cell reselection process. The conventional cell reselection process may mean the entire general (or legacy) cell reselection procedure shown in Fig. 7. The conventional cell reselection process may mean only the cell reselection process (step S13) shown in Fig. 7. In the latter case, the UE 100 may use the measurement result in step S4 without measuring the radio quality of the cell again.

[0067] (Paging) Next, paging according to the first embodiment will be described.

[0068] Paging is a technique for calling the UE 100 in an RRC idle state or an RRC inactive state from the network. Paging is used, for example, to notify incoming data (such as voice) or emergency information.

[0069] Paging can be categorized into CN-initiated paging and RAN-initiated paging. CN-initiated paging may be referred to as "CN paging." RAN-initiated paging may be referred to as "RAN paging."

[0070] CN paging is performed on a UE 100 in an RRC idle state. For example, a core network device (e.g., AMF 300) of the CN 20 that has received notification of downlink data addressed to the UE 100 generates a Paging message including a Tracking Area Identifier (TAI: Tracking Area Identity) list. The core network device transmits the Paging message to each gNB 200 included in the Tracking Area (TA). In response to receiving the Paging message, each gNB 200 (or each cell) transmits a Paging message including the identifier of the UE 100. As a result, paging messages are transmitted simultaneously from each gNB 200 (or each cell) included in the TA.

[0071] On the other hand, RAN paging is performed on UE100 in an RRC inactive state. For example, a gNB200 that receives downlink data addressed to UE100 transmits a RAN paging message to other gNBs (or other cells) within a RAN-based notification area (RAN-based notification area). Each gNB200 (or each cell) transmits a paging message including an identifier of the UE100. As a result, paging messages are transmitted simultaneously from each gNB200 (or each cell) included in the RNA.

[0072] The UE 100 in the RRC idle state or the RRC inactive state can use discontinuous reception (DRX) to reduce power consumption. The UE 100 monitors the paging channel at one paging occasion (PO) per DRX cycle.

[0073] The UE 100 in the RRC idle state monitors the paging channel by CN paging. In the CN paging, the UE 100 monitors the paging channel using a shorter cycle (DRX cycle) of a default cycle notified in the system information (SIB: System Information Block) and a cycle specific to the UE 100 set in the NAS message.

[0074] Meanwhile, the UE 100 in the RRC inactive state monitors the paging channel by RAN paging. In RAN paging, the UE 100 uses the shortest cycle (DRX cycle) among the default cycle transmitted in the SIB, the UE 100-specific cycle set in the NAS message, and the UE 100-specific cycle set in the RRC message.

[0075] However, there is an overlap between the paging occasions (PO) in CN paging and the paging occasions (PO) in RAN paging, as both are based on the same UE ID.

[0076] When the UE 100 in the RRC idle state or the RRC inactive state receives a paging message using the paging channel, the UE 100 understands that there is an incoming call addressed to the UE 100. Then, the UE 100 executes an RRC connection establishment procedure with the serving cell. This allows the UE 100 to connect to the network, transition to an RRC connected state, and exchange messages (such as RRC messages) with the network.

[0077] (Communication Control Method According to the First Embodiment) Assume a case where a slice is linked to a paging message. In the current 3GPP specifications, UE 100 cannot grasp the slice linked to the paging message. Assume a case where UE 100 executes an RRC connection establishment procedure with a serving cell upon receiving a paging message. In this case, although UE 100 can establish an RRC connection with the serving cell, if the serving cell does not support the slice, UE 100 cannot receive the service corresponding to the slice from the serving cell. In this case, UE 100 will perform handover to a neighboring cell to receive the service of another service. In this way, the serving cell may not necessarily be an appropriate cell for UE 100.

[0078] Therefore, the first embodiment aims to enable the UE 100 to connect to an appropriate cell.

[0079] In the first embodiment, a network slice associated with paging may be referred to as an "MT (Mobile Terminated) slice." The MT slice may be a slice used for paging. Alternatively, the MT slice may be a slice associated with a paging message. Alternatively, the MT slice may be a slice corresponding to paging.

[0080] In the first embodiment, information representing a network slice corresponding to an MT slice may be referred to as "MT slice information." A slice represented by the MT slice information becomes an MT slice. The MT slice information links a slice to an MT slice.

[0081] In the first embodiment, it is assumed that the network knows what kind of slice corresponds to the MT slice. Then, in the first embodiment, a core network device (e.g., AMF 300) included in the CN 20 transmits the MT slice information to the UE 100.

[0082] Specifically, a core network device (e.g., AMF300) transmits MT slice information representing a network slice associated with paging to a user device (e.g., UE100).

[0083] By checking the MT slice information, the UE 100 can grasp the slice associated with the paging. For example, if the UE 100 can grasp whether the serving cell supports the slice, it can perform an RRC connection establishment procedure with the serving cell or a slice-specific cell reselection procedure to connect to a neighboring cell. Thus, the UE 100 can connect to an appropriate cell.

[0084] (Example of Operation According to First Embodiment) Next, an example of operation according to the first embodiment will be described.

[0085] 12 is a diagram showing an example of operation according to the first embodiment. FIG. 12 shows an example of CN paging. It is assumed that the UE 100 has received slice frequency information from the gNB 200 before the processing of FIG. 12 is performed. As described above, the slice frequency information is information indicating the correspondence between the network slice, the frequency, and the frequency priority (for example, FIG. 10).

[0086] As shown in FIG. 12, in step S110, the UE 100 is in an RRC connected (RRC_CONNECTED) state.

[0087] In step S111, AMF300 transmits a NAS message including MT slice information to UE100.

[0088] First, AMF 300 may transmit a NAS message including slice priority information together with MT slice information. Alternatively, AMF 300 may transmit a NAS message including MT slice information in a different NAS message from the NAS message including the slice priority information. The NAS of UE 100 receives the MT slice information and the slice priority information and outputs the MT slice information and the slice priority information to the AS of UE 100. The AS of UE 100 may store the MT slice information and the slice priority information in a memory.

[0089] Second, AMF300 may transmit, to UE100, modification instruction information (e.g., first modification instruction information) instructing to modify the slice priority of the MT slice. AMF300 transmits a NAS message including the modification instruction information to the NAS of UE100. AMF300 may transmit the modification instruction information together with the MT slice information in one NAS message. AMF300 may transmit the modification instruction information in a NAS message separate from the NAS message including the MT slice information. The NAS of UE100 outputs the modification instruction information to the AS of UE100. The AS of UE100 may store the modification instruction information in a memory.

[0090] Third, AMF 300 may transmit a bias value to be added to the slice priority of the MT slice to UE 100. Having received the bias value, UE 100 adds the bias value to the slice priority of the MT slice. The bias value may be included in one NAS message together with the MT slice information and transmitted from AMF 300. Alternatively, the bias value may be included in a NAS message separate from the MT slice information and transmitted from AMF 300. The bias value may be set to any value between "-7" and "+7", for example. The bias value may also be defined in a specification (or the bias value may be hard-coded in UE 100).

[0091] In step S112, the UE 100 transitions to an RRC idle (RRC_IDLE) state.

[0092] In step S113, gNB200 transmits a paging message to UE100. In response to receiving a paging message that is an NG message from AMF300, gNB200 transmits a paging message that is an RRC message.

[0093] In step S114, the UE 100 changes the slice priority of the MT slice based on the MT slice information (step S111). The UE 100 may change the slice priority of the MT slice in accordance with the change instruction information.

[0094] Fig. 13(A) is a diagram showing a correspondence relationship between slices, slice priorities, and frequency priorities. It is assumed that UE 100 acquires the correspondence relationship shown in Fig. 13(A) from slice frequency information. In the example of Fig. 13(A), slice #1 has the highest slice priority and slice #3 has the lowest. Furthermore, with regard to frequency priority, frequency F1 is the highest and frequency F4 is the lowest in slice #1. This shows an example in which the larger the number, the higher the priority, for both slice priority and frequency priority.

[0095] For example, it is assumed that the MT slice information indicates that slice #3 is a slice corresponding to the MT slice. In this case, the UE 100 changes the slice priority of slice #3, which is an MT slice. Specifically, the UE 100 can change the slice priority as follows.

[0096] First, the UE 100 may change the slice priority by changing the slice priority of a slice corresponding to an MT slice so that the slice priority is higher than the slice priority of a slice that is not an MT slice. For example, in the case of FIG. 13(A), the UE 100 may change the slice priority "2" of slice #3 so that the slice priority is higher than the slice priority "5" of slice #2. Alternatively, the UE 100 may change the slice priority "2" of slice #3 to the highest priority (i.e., the intended slice).

[0097] Second, the UE 100 may change the slice priority by changing the slice priority of a slice corresponding to an MT slice to be the same as the slice priority of a slice that is not an MT slice. For example, in the case of Fig. 13(A), the UE 100 may change the slice priority of slice #3 from "2" to "5", which is the same as the slice priority of slice #2.

[0098] Third, UE 100 may change the slice priority by changing the slice priority of a slice corresponding to an MT slice so that the slice priority is lower than the priority of a slice that is not an MT slice. For example, in FIG. 13A , if slice #2 is an MT slice and slice #3 is not an MT slice, UE 100 may change the slice priority of slice #2 by changing the slice priority of slice #2 from “5” to a priority lower than the slice priority of slice #3, “2.”

[0099] Fourth, the UE 100 may change the slice priority by adding a bias value to the slice priority of the MT slice. For example, in the example of Fig. 13(A), the UE 100 adds a bias value (e.g., "7") to the slice priority of slice #3, which is an MT slice, to change the slice priority of slice #3.

[0100] 12 , in step S115, the UE 100 performs a slice-specific cell reselection procedure according to the changed slice priority. Then, the UE 100 performs an RRC connection establishment procedure with respect to the reselected neighbor cell.

[0101] (Another Example of the First Embodiment) In the first embodiment, the UE 100 is described as receiving the MT slice information (step S111) before the paging message (step S113), but this is not limited thereto. For example, the UE 100 may receive the paging message (step S113) and the MT slice information (step S111) at the same time. Even in this case, the UE 100 can change the slice priority of the MT slice based on the MT slice information (step S114), as in the first embodiment.

[0102] Furthermore, in the first embodiment, an example in which an MT slice is linked to a slice has been described, but the present invention is not limited to this. For example, an MO (Mobile Originated) slice may be linked to a slice. The MO slice is, for example, a slice used in a UE 100 in a Mobile Initiated Connection Only (MICO) mode. The UE 100 in the MICO mode can be in an RRC connected state and perform transmission to the network during an extended connected time without performing paging. For example, the MO slice is linked to the transmission. The AMF 300 transmits information indicating the slice corresponding to the MO slice (such information may be referred to as "MO slice information") to the UE 100. Based on the MO slice information, the UE 100 can perform uplink transmission in the MICO mode using the slice linked to the MO slice, giving priority to other slices.

[0103] Furthermore, in the first embodiment, an example in which the UE 100 changes the slice priority has been described, but the present invention is not limited to this. For example, the AMF 300 may change the slice priority. In this case, the AMF 300 transmits slice priority information including the changed slice priority (i.e., the changed slice priority) to the UE 100 without transmitting the MT slice information (or together with the MT slice information). Thereafter, the UE 100 performs the same processing (steps S112 to S115) as in the first embodiment. The change of the slice priority itself may be the same as step S114.

[0104] Furthermore, in the first embodiment, an example of CN paging has been described. For example, in the first embodiment, RAN paging may be performed. In this case, the UE 100 enters an RRC inactive (RRC_INACTIVE) state instead of an RRC idle state (step S112). However, the UE 100 may be in the RRC inactive state before receiving the MT slice information (step S111). When the gNB 200 is triggered to transmit a paging message (for example, when downlink data addressed to the UE 100 is received from the UPF), it transmits a paging message to the UE 100 (step S113).

[0105] Second Embodiment Next, a second embodiment will be described, focusing on the differences from the first embodiment.

[0106] The second embodiment is an example in which a frequency that supports an MT slice is notified. Hereinafter, information indicating a frequency that supports an MT slice may be referred to as "MT slice support frequency information."

[0107] The gNB 200 knows the frequencies that support the MT slices and can transmit MT slice support frequency information to the UE 100. Specifically, first, the base station (e.g., the gNB 200) transmits MT slice support frequency information indicating the frequencies that support the MT slices to the user equipment (e.g., the UE 100).

[0108] This allows, for example, UE 100 to perform a slice-specific cell reselection procedure by selecting a frequency that supports MT slices in preference to other frequencies. UE 100 can then reselect a neighboring cell that supports MT slices from among cells that support the frequency and connect to the cell. Thus, UE 100 can connect to an appropriate cell.

[0109] (Example of Operation According to Second Embodiment) Next, an example of operation according to the second embodiment will be described.

[0110] Fig. 14 is a diagram illustrating an example of operation according to the second embodiment. Fig. 14 illustrates an example of CN paging.

[0111] As shown in FIG. 14, in step S120, UE 100 is in an RRC connected state.

[0112] In step S121, AMF300 transmits MT slice information to UE100, similar to the first embodiment.

[0113] In step S122, the gNB 200 transmits the MT slice support frequency information to the UE 100. The gNB 200 may broadcast a system information block (SIB) including the MT slice support frequency information. The gNB 200 may transmit a dedicated message (e.g., an RRC release message) including the MT slice support frequency information.

[0114] First, the MT slice support frequency information may be transmitted together with the slice frequency information in one RRC message from the gNB 200. Alternatively, the MT slice support frequency information may be transmitted in an RRC message separate from the RRC message including the frequency priority.

[0115] Second, the gNB200 may transmit change instruction information (e.g., second change instruction information) to the UE100 instructing the UE100 to change the frequency priority of the frequency supporting the MT slice. The gNB200 transmits an RRC message (e.g., an SIB or an RRC release message) including the change instruction information. The gNB200 may transmit the change instruction information together with the MT slice support frequency information in one RRC message. The gNB200 may transmit the change instruction information in an RRC message separate from the MT slice support frequency information.

[0116] Third, the gNB200 may transmit to the UE100 a bias value to be added to the frequency priority of the frequency that supports the MT slice. The UE100 that has received the bias value adds the bias value to the frequency priority of the frequency that supports the MT slice. The bias value may be transmitted from the gNB200 in an RRC message together with the MT slice support frequency information. Alternatively, the bias value may be transmitted from the gNB200 in an RRC message separate from the MT slice support frequency information. The frequency bias value may also be set to any value within a range from "-7" to "+7", for example. The bias value may be defined in a specification (or the bias value may be hard-coded in the UE100).

[0117] In step S123, gNB200 transitions to an RRC idle state.

[0118] In step S124, in response to receiving a paging message, which is an NG message, from AMF300, gNB200 sends a paging message to UE100.

[0119] In step S125, the UE 100 changes the slice priority of the MT slice based on the MT slice information, and changes the frequency priority of the frequency supporting the MT slice based on the MT slice support frequency information. The UE 100 may change the frequency priority of the frequency supporting the MT slice according to the change instruction information. Alternatively, the UE 100 may change both the slice priority and the frequency priority according to the change instruction information.

[0120] Fig. 13(B) is a diagram showing the correspondence relationship between slices, slice priorities, and frequency priorities. In the example of Fig. 13(B), slice #1 is an MT slice. It is assumed that UE 100 has acquired the relationship shown in Fig. 13(B) using slice frequency information and MT slice information. UE 100 may change the frequency priority of a frequency supporting an MT slice, for example, as follows.

[0121] First, the UE 100 may change the frequency priority by changing the frequency priority of the frequency supporting the MT slice so that it is higher than the frequency priority of the frequency supporting the slice that is not the MT slice. In the case of FIG. 13(B), the UE 100 may set the frequency priority ("1" and "3") of the frequencies of slice #1 (frequency A and frequency B) higher than the frequency priority ("3") of the frequency of slice #3 (frequency A). Alternatively, the UE 100 may set the frequency priority ("1" and "3") of the frequencies of slice #1 (frequency A and frequency B) higher than the highest priority ("5") of the frequencies of slice #2 (frequency A and frequency C). Alternatively, the UE 100 may set the frequency priority of the frequencies of slice #1 (frequency A and frequency B) to the highest frequency priority.

[0122] Second, the UE 100 may change the frequency priority by changing the frequency priority of a frequency supporting an MT slice to be the same as the frequency priority of a frequency supporting a slice other than an MT slice. In the case of FIG. 13(B), the UE 100 may change the frequency priority of the frequencies (frequency A and frequency B) of slice #1 to be the same as the frequency priority of the frequency (frequency A) of slice #3. In this case, the UE 100 may set the frequency priority for the same frequency (frequency A) in slice #1 and slice #3 to be the same. The UE 100 may set all frequencies (frequency A and frequency B) included in slice #1 to be the same as the frequency (frequency A) of slice #3. Alternatively, the UE 100 may change the frequency priority of the frequencies (frequency A and frequency B) of slice #1 to be the same as the frequency priority of the frequency (frequency A or frequency C) of slice #2. In this case, the UE 100 may also change the frequency priority for the same frequency (frequency A) in slice #1 and slice #2 to be the same. Alternatively, UE100 may change the frequency priority of all frequencies (frequency A and frequency B) included in slice #1 so that they are the same as any of the frequencies (frequency A or frequency B) included in slice #2.

[0123] Third, the UE 100 may change the frequency priority by changing the frequency priority of a frequency supporting an MT slice so that it is lower than the frequency priority of a frequency supporting a slice that is not an MT slice. For example, in FIG. 13(B), if slice #2 is an MT slice and slice #1 is not an MT slice, the UE 100 may change the frequency priority by changing the frequency priority of the frequencies (frequency A and frequency C) included in slice #2 so that it is lower than the frequency priority of the frequencies (frequency A and frequency B) included in slice #1. In this case, the UE 100 may lower the frequency priority of all frequencies (frequency A and frequency C) included in slice #2 lower than the frequency priority of any of the frequencies (frequency A or frequency B) included in slice #1. Alternatively, the UE 100 may lower the frequency priority of all frequencies (frequency A and frequency C) included in slice #2 lower than the frequency priority of the lowest frequency (frequency priority of frequency C) among the frequencies included in slice #1.

[0124] Fourth, the UE 100 may change the frequency priority of the frequency supporting the MT slice by adding a bias value to the frequency priority of the frequency supporting the MT slice.

[0125] The slice priority of the MT slices may be changed in the same manner as in the first embodiment.

[0126] 14 , in step S126, the UE 100 performs a slice-specific cell reselection procedure according to the changed slice priority and the changed frequency priority. After that, the UE 100 performs an RRC connection establishment procedure with respect to the reselected neighbor cell.

[0127] (Another Example of the Second Embodiment) In the second embodiment, an example in which the UE 100 changes the frequency priority has been described, but the present invention is not limited to this. For example, the gNB 200 may change the frequency priority. In this case, the gNB 200 may transmit slice frequency information including the changed frequency priority (i.e., the changed frequency priority) to the UE 100 without transmitting the MT slice support frequency information (or together with the MT slice support frequency information).

[0128] In addition, in the second embodiment, an example of CN paging has been described, but this is not limiting. For example, in the second embodiment, RAN paging may be performed. In this case, the UE 100 enters an RRC inactive (RRC_INACTIVE) state instead of an RRC idle state (step S123). In addition, when the gNB 200 is triggered to transmit a paging message (for example, when downlink data addressed to the UE 100 is received from the UPF), it transmits a paging message to the UE 100 (step S124).

[0129] Third Embodiment Next, a third embodiment will be described, focusing on the differences between the first and second embodiments.

[0130] The third embodiment is an example in which timing of paging occurrence is notified. Specifically, first, a core network device (e.g., AMF 300) transmits timing information indicating timing of paging occurrence to a user equipment (e.g., UE 100).

[0131] This allows, for example, UE100 to know the timing when paging occurs. Therefore, UE100 can predict in advance that a paging message will be transmitted from gNB200 based on the timing of paging occurrence. Then, when UE100 receives a paging message from gNB200, UE100 can prepare in advance to perform a slice-specific cell reselection procedure, such as changing the priority of the MT slice associated with the paging. This allows UE100 to connect to an appropriate cell.

[0132] In the following, paging or receiving a paging message may be simply referred to as "MT (Mobile Terminated)."

[0133] (Example of Operation According to Third Embodiment) Next, an example of operation according to the third embodiment will be described.

[0134] Fig. 15 is a diagram illustrating an example of operation according to the third embodiment. Note that Fig. 15 illustrates an example of CN paging.

[0135] As shown in FIG. 15, in step S130, the UE 100 is in an RRC connected state.

[0136] In step S131, the AMF 300 transmits the MT slice information and the timing information to the UE 100. Specifically, the AMF 300 transmits a NAS message including the MT slice information and the timing information to the UE 100.

[0137] The timing information indicates the timing at which paging occurs. The timing information may indicate the timing at which MT occurs. Alternatively, the timing information may indicate the timing at which a paging message associated with an MT slice is transmitted. MT slice information transmitted together with the timing information indicates an MT slice associated with the paging that is the subject of the timing information.

[0138] The timing information may be represented by the day, date, and / or time at which the MT slice occurs (or the MT occurs). The timing information may also include the location at which the MT slice occurs (or the MT occurs). The location may be represented by a Tracking Area Code (TAC) and / or a Physical Cell Identifier (PCI).

[0139] In step S132, the gNB 200 transmits MT slice support frequency information and timing information to the UE 100. Specifically, the gNB 200 transmits an RRC message (for example, an SIB or an RRC release message) including the MT slice support frequency information and timing information. The timing information may be the same as the timing information transmitted by the AMF 300 (step S131).

[0140] Steps S133 and S134 are the same as steps S112 and S113, respectively, in the first embodiment.

[0141] In step S135, UE100 changes the slice priority of the MT slice based on the MT slice information. At this time, UE100 may transmit to AMF300 a NAS message including information indicating that the slice priority of the MT slice has been changed. Furthermore, UE100 changes the frequency priority of the frequency supporting the MT slice based on the MT slice support frequency information. At this time, UE100 may change the priority based on timing information (step S131 and / or step S132). For example, UE100 may change the priority at the timing indicated in the timing information. Alternatively, UE100 may predict reception of a paging message (step S134) based on the timing information, and change the priority before receiving the paging message.

[0142] In step S136, UE100 performs a slice-specific cell reselection procedure using the changed priority.

[0143] (Another Example of the Third Embodiment) In the third embodiment, an example of CN paging has been described, but the present invention is not limited to this. For example, RAN paging may also be applied to the third embodiment. In this case, in step S133, the RRC idle state may be replaced with the RRC inactive state.

[0144] Fourth Embodiment Next, a fourth embodiment will be described. The fourth embodiment will also be described, focusing on the differences from the first and second embodiments.

[0145] The third embodiment has described an example in which the network notifies the MT slice information and timing information to the UE 100. The fourth embodiment is an example in which the UE 100 notifies the network of the MT slice information and timing information.

[0146] For example, the application layer of UE100 may periodically transmit data. Before entering the RRC idle state, the UE transmits a slice associated with paging (i.e., an MT slice) and the timing of paging to the network. This allows, for example, the network to generate an MT slice at the relevant timing, and the gNB200 to transmit a paging message at the relevant timing. UE100 changes the priority of the MT slice and, when receiving a paging message, performs a slice-specific cell reselection procedure, thereby enabling connection to a neighboring cell that supports the MT slice, as in the first embodiment. Thus, UE100 can connect to an appropriate cell.

[0147] Therefore, in the fourth embodiment, the UE 100 transmits the MT slice information and timing information to the network.

[0148] Specifically, first, a user equipment (e.g., UE100) transmits MT slice information indicating a network slice associated with paging and timing information indicating the timing at which paging occurs to a core network device (e.g., AMF300). Second, the user equipment transmits MT slice support frequency information indicating a frequency that supports the network slice and timing information to a base station (e.g., gNB200).

[0149] (Example of Operation of Fourth Embodiment) Fig. 16 is a diagram showing an example of operation of the fourth embodiment. Fig. 16 also shows an example of CN paging.

[0150] As shown in FIG. 16, in step S140, UE 100 is in an RRC connected state.

[0151] In step S141, the UE 100 transmits MT slice information and timing information to the AMF 300. Specifically, the NAS of the UE 100 transmits a NAS message including the MT slice information and timing information to the AMF 300. The timing information is, for example, the same as that in the third embodiment.

[0152] In step S142, the UE 100 transmits MT slice support frequency information and timing information to the gNB 200. Specifically, the AS of the UE 100 transmits an RRC message including the MT slice support frequency information and timing information to the gNB 200. The timing information is also the same as the timing information transmitted in step S141, for example.

[0153] In step S143, the UE 100 transmits slice priority change request information indicating a request (or request) to change the slice priority of the MT slice to the AMF 300. Specifically, the NAS of the UE 100 transmits a NAS message including the slice priority change request information to the AMF 300.

[0154] In step S144, in response to receiving the slice priority change request information, the AMF 300 transmits slice priority change information indicating that the slice priority of the MT slice is to be changed to the UE 100. Specifically, the AMF 300 transmits a NAS message including the slice priority change information to the NAS of the UE 100. By receiving the slice priority change information, the UE 100 may be able to change the slice priority of the MT slice, as in the first embodiment.

[0155] In step S145, the UE 100 transmits slice frequency priority change request information indicating a request (or request) to change the frequency priority of the frequency supporting the MT slice to the gNB 200. Specifically, the AS of the UE 100 transmits an RRC message including slice frequency priority change request information to the gNB 200.

[0156] In step S146, in response to receiving the slice frequency priority change request information, the gNB 200 transmits slice frequency priority change information indicating a change in the frequency priority of the frequency supporting the MT slice to the UE 100. Specifically, the gNB 200 transmits an RRC message including the slice frequency priority change information to the AS of the UE 100.

[0157] In step S147, the UE 100 changes the priority. The UE 100 may change the slice priority of the MT slice in response to receiving the slice priority change information (step S144). Furthermore, the UE 100 may change the priority of the frequency supporting the MT slice in response to receiving the slice frequency priority change information (step S146).

[0158] Steps S150 and S151 are the same as steps S112 and S113 in the first embodiment.

[0159] In step S152, a slice-specific cell reselection procedure is performed according to the changed slice priority and changed frequency priority.

[0160] (Another Example of the Fourth Embodiment) In the fourth embodiment, an example has been described in which the UE 100 requests the network to change the priority (steps S143 to S146). For example, the UE 100 may change the priority (step S147) without requesting the network to change the priority. In this case, as shown in FIG. 16 , the UE 100 changes the priority (step S147) without performing steps S143 to S146, and then transmits slice priority change information indicating that the slice priority of the MT slice has been changed to the AMF 300 (step S148). The slice priority change information may be transmitted in a NAS message. Then, the UE 100 transmits slice frequency priority change information indicating that the priority of the frequency supporting the MT slice has been changed to the gNB 200 (e.g., a base station) (step S149). The slice frequency priority change information may be transmitted in an RRC message.

[0161] As described above, in the fourth embodiment, the UE 100 requests the network to change the priority (steps S143 to S146), or notifies the network that the priority has been changed (steps S148 and S149). This also meets the 3GPP requirement that the slice priority and frequency priority be controlled by the network.

[0162] In addition, in the fourth embodiment, RAN paging may be applied, similarly to the first embodiment and the like.

[0163] Fifth Embodiment Next, a fifth embodiment will be described, focusing on the differences from the first and second embodiments.

[0164] In the fifth embodiment, an example will be described in which the slice priority after a change in an MT slice and the frequency priority after a change in a frequency supporting an MT slice are restored. Specifically, first, after a user equipment (e.g., UE 100) performs a slice-specific cell reselection procedure, the slice priority after a change in a network slice (e.g., MT slice) is restored to its pre-change state. Second, after a user equipment performs a slice-specific cell reselection procedure, the frequency priority after a change in a frequency supporting a network slice is restored to its pre-change state.

[0165] If UE100 can connect to a neighboring cell that supports MT slices, it may not need to use MT slices thereafter. By restoring the slice priority of the changed MT slice to the slice priority before the change, UE100 can perform a slice-specific cell reselection procedure without prioritizing the MT slice. Therefore, after connecting to a neighboring cell that supports MT slices, UE100 can properly perform the slice-specific cell reselection procedure by restoring the priority to the value before the change. Thus, UE100 can connect to an appropriate cell.

[0166] (Example of Operation According to Fifth Embodiment) Next, an example of operation according to the fifth embodiment will be described.

[0167] Fig. 17 is a diagram illustrating an example of operation according to the fifth embodiment. Fig. 17 illustrates an example of operation that supports both CN paging and RAN paging.

[0168] Steps S160 to S164 are the same as steps S120 to S124 of the second embodiment, respectively.

[0169] In step S165, UE 100 changes the slice priority of the MT slice and the frequency priority of the frequency supporting the MT slice. At this time, UE 100 stores, for example, the slice priority before the change of the MT slice and the frequency priority before the change of the frequency supporting the MT slice in a memory. Then, UE 100 stores the slice priority before the change of the MT slice in a memory, and then changes the respective priorities. UE 100 may store, in a memory, the slice priority before the change of the MT slice and the frequency priority before the change of the frequency supporting the MT slice.

[0170] In step S166, UE100 performs a slice-specific cell reselection procedure according to the changed priority.

[0171] In step S167, the UE 100 resets the changed priority to its original value. The UE 100, for example, changes the changed slice priority to the slice priority before the change stored in the memory, thereby returning the slice priority to its original value. The UE 100 may return the priority of the MT slice to its original value by changing the changed slice priority of the MT slice to the slice priority before the change stored in the memory. Furthermore, the UE 100, for example, returns the frequency priority to its original value by changing the changed frequency priority to the slice priority before the change stored in the memory. The UE 100 may return the frequency priority to its original value by changing the changed frequency priority of the frequency supporting the MT slice to the frequency priority before the change stored in the memory.

[0172] (Another Example of Fifth Embodiment) In the fifth embodiment, an example has been described in which the priority reset (step S167) is performed after the execution of the slice-specific cell reselection procedure (step S166). For example, the priority reset may be performed immediately after the UE 100 executes the slice-specific cell reselection procedure (step S166) and starts an RRC connection establishment procedure to a neighbor cell that supports an MT cell. Alternatively, the priority reset may be performed at any timing after the UE 100 starts the RRC connection establishment procedure.

[0173] Also, in the fifth embodiment, the AMF 300 may transmit a NAS message including information indicating whether or not a priority reset is performed to the UE 100. Also, the gNB 200 may transmit an RRC message including the information indicating whether or not a priority reset is performed to the UE 100.

[0174] Alternatively, the UE 100 may transmit a NAS message including information requesting a reset of the priority to the AMF 300. In this case, the AMF 300 may transmit a NAS message including information indicating that the priority is to be reset in response to receiving the information.

[0175] Alternatively, the NAS of UE100 may notify the AS of UE100 of information requesting a priority reset, and the AS of UE100 may transmit an RRC message including the information to gNB200. In this case, in response to receiving the information, gNB200 transmits an RRC message including information indicating that the priority will be reset to the AS of UE100. Then, the AS of UE100 notifies the NAS of UE100 that the priority reset has been permitted.

[0176] Furthermore, in the fifth embodiment, the resetting of the priority may be defined in the specifications (or may be set by hard coding).

[0177] Furthermore, in the fifth embodiment, the UE 100 may be able to select whether or not to reset the priority order.

[0178] [Other embodiments] A program may be provided that causes a computer to execute each process performed by the UE 100 or the gNB 200. The program may be recorded on a computer-readable medium. Using a computer-readable medium, the program can be installed on a computer. Here, the computer-readable medium on which the program is recorded may be a non-transitory recording medium. The non-transitory recording medium is not particularly limited, and may be, for example, a recording medium such as a CD-ROM or a DVD-ROM. Furthermore, circuits that execute each process performed by the UE 100 or the gNB 200 may be integrated, and at least a portion of the UE 100 or the gNB 200 may be configured as a semiconductor integrated circuit (chip set, SoC: System on a chip).

[0179] As used in this disclosure, the terms "based on" and "depending on" do not mean "based only on" or "depending only on," unless expressly stated otherwise. The term "based on" means both "based only on" and "based at least in part on." Similarly, the term "depending on" means both "depending only on" and "depending at least in part on." Furthermore, the terms "include" and "comprise" do not mean including only the listed items, but may mean including only the listed items or may include additional items in addition to the listed items. Furthermore, the term "or" as used in this disclosure is not intended to mean an exclusive or. Furthermore, any reference to elements using designations such as "first," "second," etc., as used in this disclosure does not generally limit the quantity or order of those elements. These designations may be used herein as a convenient method of distinguishing between two or more elements. Thus, a reference to a first and a second element does not imply that only two elements may be employed therein or that the first element must precede the second element in some way. In this disclosure, where articles are added by translation, such as a, an, and the in English, these articles shall include the plural unless the context clearly indicates otherwise.

[0180] Although one embodiment has been described in detail above with reference to the drawings, the specific configuration is not limited to the above, and various design changes can be made within the scope of the gist. Furthermore, it is also possible to combine all or part of each embodiment, each operation, each process, and each step within the scope of consistent combinations.

[0181] This application claims priority from Japanese Patent Application No. 2022-119418 (filed July 27, 2022), the entire contents of which are incorporated herein by reference.

[0182] (Supplementary Note) (Supplementary Note 1) A communication control method in a mobile communication system, comprising: a step in which a core network device transmits, to a user device, MT (Mobile Terminated) slice information representing a network slice associated with paging.

[0183] (Supplementary Note 2) The communication control method according to Supplementary Note 1 further comprises the steps of: a base station transmitting a paging message to the user equipment; the user equipment changing the slice priority of the network slice based on the MT slice information; and the user equipment performing a slice-specific cell reselection procedure according to the changed slice priority.

[0184] (Supplementary Note 3) The step of transmitting the MT slice information to the user equipment includes a step of the core network device transmitting first change instruction information to the user equipment instructing the core network device to change the slice priority of the network slice. A communication control method as described in Supplementary Note 1 or Supplementary Note 2.

[0185] (Supplementary Note 4) The communication control method according to any one of Supplementary Notes 1 to 3, further comprising a step of a base station transmitting, to the user equipment, MT slice support frequency information indicating a frequency that supports the network slice.

[0186] (Supplementary Note 5) A communication control method according to any one of Supplementary Notes 1 to 4, comprising: a step in which the user equipment changes the frequency priority of a frequency that supports the network slice based on the MT slice support frequency information; and a step in which the user equipment executes a slice-specific cell reselection procedure according to the changed frequency priority.

[0187] (Supplementary Note 6) The communication control method described in any one of Supplementary Notes 1 to 5, wherein the step of transmitting the MT slice support frequency information to the user equipment includes a step of the base station transmitting, to the user equipment, second change instruction information including information instructing the base station to change the frequency priority of the frequency that supports the network slice.

[0188] (Supplementary Note 7) The communication control method according to any one of Supplementary Notes 1 to 6, wherein the step of transmitting the MT slice information to the user equipment includes a step of the core network device transmitting timing information indicating the timing at which the paging occurs to the user equipment.

[0189] (Supplementary Note 8) The communication control method according to any one of Supplementary Notes 1 to 7, wherein the step of transmitting the MT slice support frequency information to the user equipment includes a step of the base station transmitting, to the user equipment, timing information indicating a timing at which the paging occurs.

[0190] (Supplementary Note 9) The communication control method according to any one of Supplementary Notes 1 to 8, further comprising a step in which the user equipment, after performing the slice-specific cell reselection procedure, restores the slice priority after the change of the network slice to its pre-change state.

[0191] (Supplementary Note 10) The communication control method according to any one of Supplementary Notes 1 to 9, further comprising a step in which the user equipment, after performing the slice-specific cell reselection procedure, restores the frequency priority after changing the frequency supporting the network slice to its pre-change state.

[0192] (Supplementary Note 11) A communication control method in a mobile communication system, comprising: a step in which a user equipment transmits, to a core network device, MT slice information representing a network slice associated with paging and timing information representing the timing at which the paging occurs; and a step in which the user equipment transmits, to a base station, MT slice support frequency information representing a frequency that supports the network slice and the timing information.

[0193] 1: Mobile communication system 20: CN 100: UE 110: Receiving unit 120: Transmitting unit 130: Control unit 200: gNB 210: Transmitting unit 220: Receiving unit 230: Control unit 300: AMF

Claims

1. A communication control method in a mobile communication system, comprising: The core network node transmits, to the user equipment, MT (Mobile Terminated) slice information representing a network slice associated with paging. Communications control method. a network node transmitting a paging message to the user equipment; The user equipment changes a slice priority of the network slice based on the MT slice information; and and performing a slice-specific cell reselection procedure by the user equipment according to the changed slice priority. The communication control method according to claim 1.

3. Transmitting the MT slice information to the user equipment includes transmitting, to the user equipment, first change instruction information instructing the core network node to change a slice priority of the network slice. The communication control method according to claim 1.

4. The method further comprises: a network node transmitting MT slice support frequency information to the user equipment, the MT slice support frequency information indicating a frequency at which the network slice is supported. The communication control method according to claim 1.

5. The user equipment changes a frequency priority of the frequency supporting the network slice based on the MT slice support frequency information; and performing a slice-specific cell reselection procedure by the user equipment according to the changed frequency priority order.

5. The communication control method according to claim 4.

6. Transmitting the MT slice support frequency information to the user equipment includes transmitting, to the user equipment, second change instruction information including information instructing the network node to change a frequency priority of the frequency supporting the network slice.

5. The communication control method according to claim 4.

7. Transmitting the MT slice information to the user equipment includes the core network node transmitting timing information indicating a timing at which the paging occurs to the user equipment. The communication control method according to claim 1.

8. Transmitting the MT slice support frequency information to the user equipment includes the network node transmitting timing information to the user equipment, the timing information indicating when the paging occurs.

5. The communication control method according to claim 4.

9. The user equipment may further include returning the slice priority after the change of the network slice to a value before the change after performing the slice-specific cell reselection procedure. The communication control method according to claim 2.

10. The user equipment may further include, after performing the slice-specific cell reselection procedure, restoring the frequency priority after the change of the frequency supporting the network slice to a value before the change. The communication control method according to claim 5.

11. A communication control method in a mobile communication system, comprising: A user equipment transmits, to a core network node, MT slice information indicating a network slice associated with paging and timing information indicating a timing at which the paging occurs; The user equipment transmits MT slice support frequency information indicating a frequency that supports the network slice and the timing information to a network node. Communications control method.

12. A core network node, comprising: A transmitter that transmits MT (Mobile Terminated) slice information representing a network slice associated with paging to a user device. Core network node.

13. A user device, comprising: A transmitter that transmits MT slice information representing a network slice associated with paging and timing information representing a timing at which the paging occurs to a core network node, The transmitting unit transmits MT slice support frequency information indicating a frequency that supports the network slice and the timing information to a radio access network node. User equipment.