Communication control method, core network node, and user device

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

Technical Field

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

Background Art

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

[0003] A user equipment in the radio resource control (RRC) idle state or the RRC inactive state can execute a cell reselection procedure. 3GPP is considering a slice-specific cell reselection procedure that depends on network slices (see, for example, Non-Patent Document 1). By executing the slice-specific cell reselection procedure, the user equipment can, for example, camp on an adjacent cell that supports a desired network slice.

Prior Art Documents

Non-Patent Documents

[0004]

Non-Patent Document 1

Summary of the Invention

[0005] One embodiment of the communication control method is a communication control method in a mobile communication system. The communication control method includes the step of a core network device transmitting MT (Mobile Terminated) slice information, which represents a network slice associated with paging, to a user device. [Brief explanation of the drawing]

[0006] [Figure 1] Figure 1 is a diagram showing an example configuration of a mobile communication system according to the first embodiment. [Figure 2] Figure 2 is a diagram showing an example configuration of a UE (User Equipment) according to the first embodiment. [Figure 3] Figure 3 is a diagram showing an example configuration of a gNB (base station) according to the first embodiment. [Figure 4] Figure 4 is a diagram showing an example of the configuration of a protocol stack related to the user plane according to the first embodiment. [Figure 5] Figure 5 is a diagram showing an example of the configuration of a protocol stack related to the control plane according to the first embodiment. [Figure 6] Figure 6 is a diagram illustrating the overview of the cell reselection procedure. [Figure 7] Figure 7 is a diagram illustrating the general flow of a typical cell reselection procedure. [Figure 8] Figure 8 shows an example of network slicing. [Figure 9] Figure 9 is a diagram illustrating the overview of the slice-specific cell reselection procedure. [Figure 10] Figure 10 shows an example of slice frequency information. [Figure 11] Figure 11 is a diagram illustrating the basic flow of the slice-specific cell reselection procedure. [Figure 12] Figure 12 is a diagram illustrating an example of operation according to the first embodiment. [Figure 13] Figures 13(A) and 13(B) illustrate examples of the relationship between slices, slice priority, and frequency priority. [Figure 14] Figure 14 is a diagram illustrating an example of operation according to the second embodiment. [Figure 15] Figure 15 is a diagram illustrating an example of operation according to the third embodiment. [Figure 16] Figure 16 is a diagram illustrating an example of operation according to the fourth embodiment. [Figure 17] Figure 17 is a diagram illustrating an example of operation according to the fifth embodiment. [Modes for carrying out the invention]

[0007] This disclosure aims to enable user devices to connect to the appropriate cell.

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

[0009] [First Embodiment] (Configuration of mobile communication systems) Figure 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. In the following explanation, 5GS will be used as an example, but the mobile communication system may also have at least a portion of the LTE (Long Term Evolution) system applied to it. The mobile communication system may also have at least a portion of the 6th Generation (6G) system applied to it.

[0010] The mobile communication system 1 comprises User Equipment (UE) 100, a 5G radio access network (NG-RAN) 10, and a 5G core network (5GC) 20. Hereafter, NG-RAN 10 may be simply referred to as RAN 10, and 5GC 20 may be simply referred to as core network (CN) 20.

[0011] UE 100 is a movable wireless communication device. UE 100 can be any device as long as it is used by a user. For example, UE 100 can be a mobile phone terminal (including smartphones), 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), an aircraft or a device provided in an aircraft (Aerial UE).

[0012] NG-RAN 10 includes base stations (referred to as "gNB" in the 5G system) 200. gNBs 200 are interconnected via an Xn interface which is an interface between base stations. gNB 200 manages one or more cells. gNB 200 performs wireless communication with UE 100 that has established a connection with its cell. gNB 200 has functions such as 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, etc. "Cell" is used as a term indicating the minimum unit of a wireless communication area. "Cell" is also used as a term indicating a function or resource for performing wireless communication with UE 100. One cell belongs to one carrier frequency (hereinafter simply referred to as "frequency").

[0013] Note that the gNB can also be connected to an EPC (Evolved Packet Core) which is the core network of LTE. The base station of LTE can also be connected to 5GC. The base station of LTE and the gNB can also be connected via an interface between base stations.

[0014] 5GC20 includes an AMF (Access and Mobility Management Function) and a UPF (User Plane Function) 300. The AMF performs various mobility controls and the like for the UE100. The AMF manages the mobility of the UE100 by communicating with the UE100 using NAS (Non-Access Stratum) signaling. The UPF performs data transfer control. The AMF and the UPF are connected to the gNB200 via the NG interface, which is an interface between the base station and the core network.

[0015] FIG. 2 is a diagram showing the configuration of the UE100 (user device) according to the first embodiment. The UE100 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 gNB200.

[0016] The receiving unit 110 performs various receptions under the control of the control unit 130. The receiving unit 110 includes an antenna and a receiver. The receiver converts the wireless signal received by the antenna into a baseband signal (received signal) and outputs it 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 the baseband signal (transmitted signal) output by the control unit 130 into a wireless signal and transmits it from the antenna.

[0018] The control unit 130 performs various control and processing in the UE 100. Such processing includes processing in each layer described later. 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 processing by the processor. The processor may include a baseband processor and a CPU (Central Processing Unit). The baseband processor performs modulation, demodulation, encoding, and decoding of baseband signals. The CPU executes programs stored in memory and performs various processing. The control unit 130 may perform each processing or operation in the UE 100 in each of the embodiments shown below.

[0019] Figure 3 is a diagram showing the configuration of the gNB200 (base station) according to the first embodiment. The gNB200 comprises a transmitter 210, a receiver 220, a control unit 230, and a backhaul communication unit 240. The transmitter 210 and receiver 220 constitute a wireless communication unit that performs wireless communication with the UE100. The backhaul communication unit 240 constitutes a network communication unit that communicates with the CN20.

[0020] The transmitting unit 210 performs various types of transmissions under the control of the control unit 230. The transmitting unit 210 includes an antenna and a transmitter. The transmitter converts the 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 the radio signal received by the antenna into a baseband signal (received signal) and outputs it to the control unit 230.

[0022] The control unit 230 performs various control and processing in the gNB200. Such processing includes processing in each layer described later. 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 for processing by the processor. The processor may include a baseband processor and a CPU. The baseband processor performs modulation, demodulation, encoding, decoding, etc., of the baseband signal. The CPU executes programs stored in memory and performs various processing. In each of the embodiments shown below, the control unit 230 may perform each processing or operation in the gNB200.

[0023] The backhaul communication unit 240 is connected to an adjacent base station via the Xn interface, which is an inter-base station interface. The backhaul communication unit 240 is connected to the AMF / UPF300 via the NG interface, which is an inter-base station-core network interface. The gNB200 may consist of a CU (Central Unit) and a DU (Distributed Unit) (i.e., functionally separated), and the two units may be connected by the F1 interface, which is a fronthaul interface.

[0024] Figure 4 shows the configuration of the protocol stack for the user plane's wireless interface that handles data.

[0025] The user plane radio interface protocol consists of a physical (PHY) layer, a MAC (Medium Access Control) layer, an RLC (Radio Link Control) layer, a PDCP (Packet Data Convergence Protocol) layer, and an SDAP (Service Data Adaptation Protocol) 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 UE100's PHY layer and the gNB200's PHY layer via a physical channel. The UE100's PHY layer receives downlink control information (DCI) transmitted from the gNB200 over the physical downlink control channel (PDCCH). Specifically, the UE100 performs blind decoding of the PDCCH using a Radio Network Temporary Identifier (RNTI) and acquires the successfully decoded DCI as the DCI addressed to its own UE. The DCI transmitted from the gNB200 has a CRC parity bit added, which is scrambled by the RNTI.

[0027] The MAC layer performs data priority control, retransmission processing using Hybrid ARQ (HARQ), and random access procedures. Data and control information are transmitted between the MAC layer of the UE100 and the MAC layer of the gNB200 via the transport channel. The MAC layer of the gNB200 includes a scheduler. The scheduler determines the transport format for the up and down links (transport block size, modulation and coding scheme (MCS)) and the resource blocks to be allocated to the 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 UE100's RLC layer and the gNB200's RLC layer via a logical channel.

[0029] The PDCP layer performs header compression / decompression, encryption / decryption, etc.

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

[0031] Figure 5 shows the configuration of the protocol stack of the wireless interface of the control plane that handles signaling (control signals).

[0032] The control plane's wireless interface protocol stack includes an RRC (Radio Resource Control) layer and a NAS (Non-Access Stratum) layer, instead of the SDAP layer shown in Figure 4.

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

[0034] The NAS, located above the RRC layer, handles session management and mobility management, among other things. NAS signaling is transmitted between the UE100's NAS and the AMF300's NAS. The UE100 also has application layers in addition to the wireless interface protocol. Layers below the NAS are called AS (Access Stratum).

[0035] (Overview of the cell reselection procedure) Figure 6 is a diagram illustrating the overview of the cell reselection procedure.

[0036] A UE100 in an RRC idle or RRC inactive state performs a cell reselection procedure to move from its current serving cell (cell #1) to an adjacent cell (one of cells #2 through #4) upon movement. Specifically, the UE100 identifies the adjacent cell to which it should camp on using the cell reselection procedure and reselects the identified adjacent cell. When the current serving cell and the adjacent cell have the same frequency (carrier frequency), it is called an intra-frequency, and when the current serving cell and the adjacent cell have different frequencies (carrier frequencies), it is called an inter-frequency. The current serving cell and the adjacent cell may be managed by the same gNB200. The current serving cell and the adjacent cell may be managed by different gNB200s.

[0037] Figure 7 is a schematic diagram illustrating a typical (or legacy) cell reselection procedure.

[0038] In step S11, UE100 performs frequency prioritization based on the frequency-specific priority (also called "absolute priority") specified by gNB200, for example, in a system information block or RRC release message. Specifically, UE100 manages the frequency priority specified by gNB200 for each frequency.

[0039] In step S12, the UE100 performs a measurement process to measure the radio quality for both the serving cell and the adjacent cell. The UE100 measures the received power and received quality of the reference signal transmitted by each of the serving cell and the adjacent cell, specifically the CD-SSB (Cell Defining-Synchronization Signal and PBCH block). For example, the UE100 always measures the radio quality for frequencies with a higher priority than the current serving cell's frequency priority, and for frequencies with the same or lower priority as the current serving cell's frequency priority, it measures the radio quality of frequencies with the same or lower priority if the current serving cell's radio quality falls below a predetermined quality.

[0040] In step S13, UE100 performs a cell reselection process to reselect the cell to which it will camp on, based on the measurement results in step S12. For example, UE100 may reselect a cell to an adjacent cell if the frequency priority of the adjacent cell is higher than the priority of the current serving cell, and the adjacent cell meets a predetermined quality standard (i.e., the minimum required quality standard) for a predetermined period. If the frequency priority of the adjacent cell is the same as the priority of the current serving cell, UE100 may rank the radio quality of the adjacent cell and reselect a cell to an adjacent cell that has a higher rank than the current serving cell for a predetermined period. If the frequency priority of the adjacent cell is lower than the priority of the current serving cell, and the radio quality of the current serving cell remains below a certain threshold, and the radio quality of the adjacent cell remains above another threshold for a predetermined period, UE100 may reselect a cell to that adjacent cell.

[0041] (Overview of network slicing) Network slicing is a technique that creates multiple virtual networks by virtually dividing a physical network built by an operator (for example, a network consisting of NG-RAN10 and 5GC20). Each virtual network is called a network slice. In the following, a network slice may be simply referred to as a "slice."

[0042] Network slicing allows telecommunications carriers to create slices tailored 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] Figure 8 shows an example of network slicing.

[0044] Three slices (slice #1 to slice #3) are configured on network 50, which consists of NG-RAN10 and 5GC20. Slice #1 is associated with the service type eMBB, slice #2 is associated with the service type URLLC, and slice #3 is associated with the service type mMTC. Note that more than three slices may be configured on network 50. A single service type may be associated with multiple slices.

[0045] Each slice is assigned a slice identifier to identify it. An example of a slice identifier is S-NSSAI (Single Network Slicing Selection Assistance Information). S-NSSAI includes an 8-bit SST (slice / service type). S-NSSAI may further include a 24-bit SD (slice differentiator). SST is information indicating the service type to which the slice is associated. SD is information used to differentiate multiple slices associated with the same service type. Information containing multiple S-NSSAIs is called NSSAI (Network Slice Selection Assistance Information).

[0046] Alternatively, one or more slices may be grouped together to form a slice group. A slice group is a group containing one or more slices, and a slice group identifier is assigned to such a slice group. A slice group may be configured by a core network (e.g., AMF300) or by a wireless access network (e.g., gNB200). The configured slice group may be notified to the UE100.

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

[0048] Furthermore, the UE100 determines the desired slice it wishes to use. The desired slice is sometimes called an "intended slice". In the first embodiment, the UE100 determines the slice priority for each network slice (desired slice). For example, the NAS of the UE100 determines the slice priority based on the operating status of applications within the UE100 and / or user operations / settings, and notifies the AS of the slice priority information indicating the determined slice priority. The NAS of the UE100 may also receive the slice priority information from the AMF300. In this case, the NAS of the UE100 may determine the slice priority based on the slice priority information received from the AMF300.

[0049] (Overview of the slice-specific cell reselection procedure) Figure 9 is a diagram illustrating the procedure for slice-specific cell reselection (also known as slice-aware cell reselection or slice-based cell reselection).

[0050] In the slice-specific cell reselection procedure, UE100 performs cell reselection based on slice frequency information provided from network 50. The slice frequency information may be provided to UE100 from gNB200 via broadcast signaling (e.g., system information block) or dedicated signaling (e.g., RRC release message).

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

[0052] In the example shown in Figure 10, three frequencies, F1, F2, and F4, are associated with slice #1 as the frequencies that support 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 in Figure 10, a higher frequency priority number indicates a higher priority, but a lower number could also indicate a higher priority.

[0053] Furthermore, for slice #2, three frequencies, F1, F2, and F3, are associated as frequencies that support 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, for slice #3, three frequencies, F1, F3, and F4, are associated as frequencies that support 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] In the following, to distinguish it from the absolute priority in conventional cell reselection procedures, the frequency priority shown in the slice frequency information may be referred to as "slice intrinsic frequency priority."

[0056] As shown in Figure 9, UE100 may perform cell reselection processing based on slice support information provided from network 50. Slice support information may also be information indicating the correspondence between cells (e.g., serving cells and each adjacent cell) and network slices that the cell does not provide or does provide. For example, a cell may temporarily not provide some or all of the network slices due to congestion or other reasons. That is, even if a slice support frequency has the capability to provide a certain network slice, some cells within that frequency may not provide that network slice. Based on the slice support information, UE100 can identify the network slices that each cell does not provide. Such slice support information may be provided to UE100 from gNB200 via broadcast signaling (e.g., system information block) or dedicated signaling (e.g., RRC release message).

[0057] Figure 11 shows the basic flow of the slice-specific cell reselection procedure. Before starting the slice-specific cell reselection procedure, it is assumed that UE100 is in an RRC idle or RRC inactive state and has received and is holding the slice frequency information described above. The procedure for "slice-specific cell reselection" is referred to as the "slice-specific cell reselection procedure." However, in the following, "slice-specific cell reselection" and "slice-specific cell reselection procedure" may be used interchangeably.

[0058] In step S0, the NAS of UE100 determines the slice identifier of the desired slices of UE100 and the slice priority of each desired slice, and notifies the AS of UE100 of the slice priority information, including the determined slice priorities. "Desired slices" are "Intended slices" and include slices that are likely to be used, candidate slices, desired slices, slices to communicate, requested slices, allowed slices, or intended slices. For example, slice priority of slice #1 is determined to be "3", slice priority of slice #2 is determined to be "2", and slice priority of slice #3 is determined to be "1". A higher number indicates higher priority, although a lower number may also indicate higher priority.

[0059] In step S1, the AS of UE100 sorts the slices (slice identifiers) notified from the NAS in step S0 in order of slice priority. The list of slices sorted in this way is called the "slice list".

[0060] In step S2, the AS of UE100 selects one network slice in order of slice priority. The network slice selected in this way is called the "selected network slice".

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

[0062] In step S4, the AS of UE100 selects one frequency from the selected network slice selected in step S2 in order of frequency priority, and performs measurement processing on the selected frequency. The frequency thus selected is called the "selected frequency". The AS of UE100 may also rank each cell measured within the selected frequency in order of wireless quality. Among the cells measured within the selected frequency, those that meet a predetermined quality standard (i.e., the minimum required quality standard) are called "candidate cells".

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

[0064] On the other hand, if it is determined that the highest-ranked cell does not provide a 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 in the selected network slice other than the selected frequencies that were assigned in step S3. If it is determined that there are unmeasured frequencies (step S6: YES), the AS of UE100 resumes processing targeting the next highest frequency priority and performs measurement processing on 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), then 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 network slices other than the selected network slices in the slice list. If it is determined that there are unselected slices (step S7: YES), the AS of UE100 resumes processing targeting the next highest slice priority network slice and selects that network slice as the selected network slice (returning to step S2). Note that in the basic flow shown in Figure 11, the processing in step S7 may be omitted.

[0066] If it is determined that there are no unselected slices (step S7: NO), in step S8, the AS of UE100 performs the conventional cell reselection process. The conventional cell reselection process may refer to the entire general (or legacy) cell reselection procedure shown in Figure 7. Or, the conventional cell reselection process may refer only to the cell reselection process shown in Figure 7 (step S13). In the latter case, UE100 may reuse the measurement results from step S4 without measuring the wireless quality of the cell again.

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

[0068] Paging is a technique for calling a UE100 that is in an RRC idle or RRC inactive state from the network. Paging is used, for example, for receiving incoming data (such as voice) or for notifying emergency information.

[0069] Regarding paging, there are two types: CN-initiated paging and RAN-initiated paging. CN-initiated paging is sometimes referred to as "CN paging," and RAN-initiated paging is sometimes referred to as "RAN paging."

[0070] CN paging is performed on UE100s that are in an RRC idle state. For example, a core network device (e.g., AMF300) of CN20 that receives notification of downlink data destined for the UE100 generates a PAGING message containing a Tracking Area Identity (TAI) list. The core network device sends the PAGING message to each gNB200 included in the Tracking Area (TA). Each gNB200 (or each cell) sends a Paging message containing the identifier of the UE100 in response to receiving the PAGING message. As a result, paging messages are sent simultaneously from each gNB200 (or each cell) included in the TA.

[0071] On the other hand, RAN paging is performed on UE100s that are in an RRC inactive state. For example, a gNB200 that receives downlink data destined for UE100 sends a RAN paging message to other gNBs (or other cells) within the RAN-based Notification Area (RNA). Each gNB200 (or each cell) sends a paging message containing the identifier of the UE100 in question. As a result, paging messages are sent simultaneously from each gNB200 (or each cell) included in the RNA.

[0072] UE100 units in RRC idle or RRC inactive state can use discontinuous reception (DRX) to reduce power consumption. The UE100 monitors the paging channel once per DRX cycle during a paging opportunity (PO).

[0073] When the UE100 is in an RRC idle state, it monitors the paging channel via CN paging. In CN paging, the UE100 monitors the paging channel using the shorter of the two cycles (DRX cycle) between the default cycle announced in the System Information Block (SIB) and the UE100-specific cycle configured in the NAS message.

[0074] On the other hand, a UE100 in an RRC inactive state monitors the paging channel via RAN paging. In RAN paging, the UE100 uses the shortest cycle (DRX cycle) among the default cycle sent via SIB, the UE100-specific cycle configured in the NAS message, and the UE100-specific cycle configured in the RRC message.

[0075] However, since both paging opportunities (POs) in CN paging and paging opportunities (POs) in RAN paging are based on the same UEID, there is overlap.

[0076] When a UE100 is in an RRC idle or RRC inactive state, it recognizes that it has received a paging message via the paging channel. The UE100 then executes an RRC connection establishment procedure with the serving cell. This allows the UE100 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) Let's assume that a slice is associated with the paging message. Under the current 3GPP specification, UE100 cannot know which slice is associated with the paging message. Let's assume that UE100, upon receiving the paging message, executes the RRC connection establishment procedure to the serving cell. In this case, UE100 can establish an RRC connection to the serving cell, but if the serving cell does not support the slice in question, it cannot receive the service corresponding to that slice from the serving cell. In this case, UE100 will hand over to an adjacent cell to receive other services. Thus, a serving cell may not always be the appropriate cell for UE100.

[0078] Therefore, the objective of the first embodiment is to enable the UE100 to connect to the appropriate cell.

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

[0080] Furthermore, 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 MT slice information becomes an MT slice. Slices are linked to MT slices by MT slice information.

[0081] In the first embodiment, the network is assumed to be able to identify what kind of slice corresponds to the MT slice. In the first embodiment, the core network device included in CN20 (for example, AMF300) transmits the MT slice information to UE100.

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

[0083] The UE100 can identify the slice associated with paging by checking the MT slice information. For example, if the UE100 can determine whether a serving cell supports a particular slice, it can perform an RRC connection establishment procedure on the serving cell or a slice-specific cell reselection procedure to connect to an adjacent cell. Therefore, the UE100 can connect to the appropriate cell.

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

[0085] Figure 12 is a diagram illustrating an example of operation according to the first embodiment. Figure 12 shows an example of CN paging. It is assumed that UE100 receives slice frequency information from gNB200 before the processing shown in Figure 12 takes place. As described above, slice frequency information is information that shows the correspondence between network slices, frequencies, and frequency priorities (for example, Figure 10).

[0086] As shown in Figure 12, in step S110, UE100 is in the RRC_CONNECTED state.

[0087] In step S111, the AMF300 sends a NAS message containing MT slice information to the UE100.

[0088] Firstly, the AMF300 may include slice priority information along with MT slice information in a NAS message and send it. Alternatively, the AMF300 may include MT slice information in a separate NAS message from the one containing slice priority information and send it. The UE100's NAS receives the MT slice information and slice priority information and outputs the MT slice information and slice priority information to the UE100's AS. The UE100's AS may store the MT slice information and slice priority information in memory.

[0089] Secondly, the AMF300 may send change instruction information (e.g., first change instruction information) to the UE100 instructing it to change the slice priority of the MT slices. The AMF300 sends a NAS message containing the change instruction information to the NAS of the UE100. The AMF300 may send the change instruction information together with the MT slice information in a single NAS message. The AMF300 may also send the change instruction information in a separate NAS message from the NAS message containing the MT slice information. The NAS of the UE100 outputs the change instruction information to the AS of the UE100. The AS of the UE100 may store the change instruction information in memory.

[0090] Thirdly, the AMF300 may send a bias value to the UE100 to be added to the slice priority of the MT slice. Upon receiving the bias value, the UE100 adds the bias value to the slice priority of the MT slice. The bias value may be sent from the AMF300 in a single NAS message along with the MT slice information. Alternatively, the bias value may be sent from the AMF300 in a separate NAS message from the MT slice information. The bias value may be set to any value between "-7" and "+7". The bias value may also be specified in the specifications (or the bias value may be hardcoded in the UE100).

[0091] In step S112, UE100 transitions to the RRC idle (RRC_IDLE) state.

[0092] In step S113, gNB200 sends a paging message to UE100. Upon receiving the NG message, which is a paging message, from AMF300, gNB200 sends a RRC message, which is a paging message.

[0093] In step S114, UE100 changes the slice priority of the MT slices based on the MT slice information (step S111). UE100 may also change the slice priority of the MT slices according to the change instruction information.

[0094] Figure 13(A) shows the correspondence between slices, slice priority, and frequency priority. The UE100 is assumed to obtain the correspondence shown in Figure 13(A) based on slice frequency information. In the example in Figure 13(A), slice #1 has the highest slice priority, and slice #3 has the lowest. Similarly, for frequency priority, for slice #1, frequency F1 has the highest priority, and frequency F4 has the lowest. Both slice priority and frequency priority are shown in examples where a higher number indicates higher priority.

[0095] For example, let's assume that the MT slice information indicates that slice #3 is the slice corresponding to an MT slice. In such a case, UE100 changes the slice priority of slice #3, which is an MT slice. Specifically, UE100 can change it as follows:

[0096] Firstly, UE100 may change the slice priority by changing the slice priority of a slice corresponding to an MT slice to a higher priority than the slice priority of a slice that is not an MT slice. For example, in the case of Figure 13(A), UE100 may change the slice priority of slice #3 from "2" to a higher priority than the slice priority of slice #2, which is "5". Alternatively, UE100 may change the slice priority of slice #3 from "2" to the highest priority (i.e., the intended slice).

[0097] Secondly, UE100 may change the slice priority by changing the slice priority of the slice corresponding to the MT slice to the same as the slice priority of the slice that is not an MT slice. For example, in the case of Figure 13(A), UE100 may change the slice priority of slice #3 from "2" to "5", the same as the slice priority of slice #2.

[0098] Thirdly, UE100 may change the slice priority by changing the slice priority of the slice corresponding to the MT slice to a lower priority than the slice that is not an MT slice. For example, in Figure 13(A), if slice #2 is an MT slice and slice #3 is not an MT slice, UE100 may change the slice priority of slice #2 by changing the slice priority of slice #2 to a lower priority than the slice priority of slice #3.

[0099] Fourthly, UE100 may change the slice priority of an MT slice by adding a bias value to its slice priority. For example, in the example in Figure 13(A), UE100 changes the slice priority of slice #3, which is an MT slice, by adding a bias value (e.g., "7") to its slice priority.

[0100] Returning to Figure 12, in step S115, UE100 executes the slice-specific cell reselection procedure according to the modified slice priority. Subsequently, UE100 executes the RRC Connection Establishment procedure for the reselected adjacent cells.

[0101] (Other examples of the first embodiment) In the first embodiment, it was described that the UE100 receives the MT slice information (step S111) before the paging message (step S113), but this is not limited to the first embodiment. For example, the UE100 may receive the paging message (step S113) and the MT slice information (step S111) at the same time. Even in this case, the UE100 can change the slice priority of the MT slices based on the MT slice information, as in the first embodiment (step S114).

[0102] Furthermore, while the first embodiment described an example of associating an MT slice with a slice, the invention is not limited to this. For example, an MO (Mobile Originated) slice may be associated with a slice. An MO slice is, for example, a slice used in a UE100 in Mobile Initiated Connection Only (MICO) mode. In MICO mode, the UE100 can transmit to the network in an RRC connected state for the Extended Connected Time without performing paging. For example, an MO slice may be associated with such a transmission. The AMF300 transmits information representing the slice corresponding to the MO slice (such information may be referred to as "MO slice information") to the UE100. Based on the MO slice information, the UE100 can perform uplink transmission in MICO mode using the slice associated with the MO slice, prioritizing it over other slices.

[0103] Furthermore, while the first embodiment described an example in which UE100 changes the slice priority, the invention is not limited to this. For example, AMF300 may change the slice priority. In this case, AMF300 sends slice priority information, including the changed slice priority (i.e., the changed slice priority), to UE100 without (or together with) the MT slice information. Thereafter, UE100 performs the same processing as in the first embodiment (steps S112 to S115). The change in slice priority itself may be the same as in step S114.

[0104] Furthermore, an example of CN paging was described in the first embodiment. For example, RAN paging may be performed in the first embodiment. In this case, UE100 enters the RRC inactive state (RRC_INACTIVE) instead of the RRC idle state (step S112). However, UE100 may be in the RRC inactive state before receiving MT slice information (step S111). When a trigger for sending a paging message occurs (for example, when downlink data addressed to UE100 is received from UPF), gNB200 sends a paging message to UE100 (step S113).

[0105] [Second Embodiment] Next, a second embodiment will be described. In the second embodiment, the differences from the first embodiment will be the main focus of the description.

[0106] In the second embodiment, an example is provided of notifying the frequencies that support MT slicing. Hereafter, the information representing the frequencies that support MT slicing may be referred to as "MT slice support frequency information".

[0107] The gNB200 knows the frequencies that support MT slicing and can transmit MT slicing support frequency information to the UE100. Specifically, firstly, the base station (e.g., gNB200) transmits MT slicing support frequency information, which represents the frequencies that support MT slicing, to the user equipment (e.g., UE100).

[0108] This allows the UE100, for example, to prioritize frequencies that support MT slices over others and execute a slice-specific cell reselection procedure. The UE100 can then reselect adjacent cells that support MT slices from among the cells that support those frequencies and connect to those cells. Thus, the UE100 can connect to the appropriate cell.

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

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

[0111] As shown in Figure 14, in step S120, UE100 is in the RRC connected state.

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

[0113] In step S122, gNB200 transmits MT slice support frequency information to UE100. gNB200 may also broadcast a system information block (SIB) containing the MT slice support frequency information. gNB200 may also transmit a separate message (e.g., an RRC release message) containing the MT slice support frequency information.

[0114] Firstly, MT slice support frequency information may be transmitted from the gNB200 in a single RRC message along with slice frequency information. Alternatively, MT slice support frequency information may be transmitted in a separate RRC message from the RRC message containing frequency priority.

[0115] Secondly, gNB200 may send change instruction information (e.g., second change instruction information) to UE100 instructing a change in the frequency priority of the frequencies supporting MT slicing. gNB200 sends an RRC message (e.g., an SIB or an RRC release message) containing the change instruction information. gNB200 may send the change instruction information together with the MT slicing support frequency information in a single RRC message. gNB200 may also send the change instruction information in a separate RRC message from the MT slicing support frequency information.

[0116] Thirdly, gNB200 may send a bias value to UE100 to be added to the frequency priority of the frequencies that support MT slicing. Upon receiving the bias value, UE100 adds the bias value to the frequency priority of the frequencies that support MT slicing. The bias value may be sent from gNB200 in a single RRC message together with the MT slicing support frequency information. Alternatively, the bias value may be sent from gNB200 in a separate RRC message from the MT slicing support frequency information. The frequency bias value may also be set to any value within the range of "-7" to "+7". The bias value may be specified in the specifications (or the bias value may be hardcoded in UE100).

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

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

[0119] In step S125, UE100 changes the slice priority of the MT slices based on the MT slice information, and also changes the frequency priority of the frequencies supporting the MT slices based on the MT slice support frequency information. UE100 may change the frequency priority of the frequencies supporting the MT slices according to the change instruction information. Alternatively, UE100 may change both the slice priority and the frequency priority according to the change instruction information.

[0120] Figure 13(B) is a diagram showing the correspondence between slices, slice priority, and frequency priority. In the example in Figure 13(B), slice #1 is the MT slice. The UE100 is assumed to obtain the relationship shown in Figure 13(B) using slice frequency information and MT slice information. The UE100 may change the frequency priority of the frequencies supporting the MT slice, for example, as follows.

[0121] Firstly, UE100 may change the frequency priority by changing the frequency priority of frequencies that support MT slices to be higher than the frequency priority of frequencies that support non-MT slices. In the case of Figure 13(B), UE100 may set the frequency priority ("1" and "3") of slice #1's frequencies (Frequency A and Frequency B) higher than the frequency priority ("3") of slice #3's frequency (Frequency A). Alternatively, UE100 may set the frequency priority ("1" and "3") of slice #1's frequencies (Frequency A and Frequency B) higher than the highest priority ("5") of slice #2's frequencies (Frequency A and Frequency C). Alternatively, UE100 may set the frequency priority of slice #1's frequencies (Frequency A and Frequency B) to the highest frequency priority.

[0122] Secondly, UE100 may change the frequency priority by changing the frequency priority of frequencies that support MT slices to be the same as the frequency priority of frequencies that support non-MT slices. In the case of Figure 13(B), UE100 may change the frequency priority of the frequencies of slice #1 (Frequency A and Frequency B) to be the same as the frequency priority of the frequency of slice #3 (Frequency A). In this case, UE100 may set the frequency priority to be the same for the same frequency (Frequency A) in slice #1 and slice #3. UE100 may set the frequency priority of all frequencies (Frequency A and Frequency B) included in slice #1 to be the same as the frequency of the frequency of slice #3 (Frequency A). Alternatively, UE100 may change the frequency priority of the frequencies of slice #1 (Frequency A and Frequency B) to be the same as the frequency priority of the frequency of slice #2 (Frequency A or Frequency C). In this case as well, UE100 may change the frequency priority to be the same for the same frequency (Frequency A) in slice #1 and slice #2. Alternatively, the UE100 may change the frequency priority of all frequencies (Frequency A and Frequency B) included in slice #1 to be the same as either frequency A or frequency B included in slice #2.

[0123] Thirdly, UE100 may change the frequency priority by changing the frequency priority of frequencies that support MT slices to be lower than the frequency priority of frequencies that support non-MT slices. For example, in Figure 13(B), if slice #2 is an MT slice and slice #1 is not an MT slice, UE100 may change the frequency priority by changing the frequency priority of frequencies included in slice #2 (frequency A and frequency C) to be lower than the frequency priority of frequencies included in slice #1 (frequency A and frequency B). In this case, UE100 may lower the frequency priority of all frequencies included in slice #2 (frequency A and frequency C) to be lower than the frequency priority of any of the frequencies included in slice #1 (frequency A or frequency B). Alternatively, UE100 may lower the frequency priority of all frequencies included in slice #2 (frequency A and frequency C) to be lower than the frequency priority of the lowest frequency included in slice #1 (frequency priority of frequency C).

[0124] Fourthly, the UE100 may change the frequency priority of frequencies that support MT slicing by adding a bias value to the frequency priority of frequencies that support MT slicing.

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

[0126] Returning to Figure 14, in step S126, UE100 executes the slice-specific cell reselection procedure according to the modified slice priority and modified frequency priority. Subsequently, UE100 executes the RRC connection establishment procedure for the reselected adjacent cells.

[0127] (Another example of the second embodiment) The second embodiment describes an example in which UE100 changes the frequency priority, but is not limited to this. For example, gNB200 may change the frequency priority. In this case, gNB200 may send slice frequency information including the changed frequency priority (i.e., the changed frequency priority) to UE100 without sending (or together with) the MT slice support frequency information.

[0128] Furthermore, while the second embodiment describes an example of CN paging, it is not limited to this. For example, RAN paging may be performed in the second embodiment. In this case, UE100 enters the RRC inactive (RRC_INACTIVE) state instead of the RRC idle state (step S123). Also, when a trigger for sending a paging message occurs (for example, when downlink data destined for UE100 is received from UPF), gNB200 sends a paging message to UE100 (step S124).

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

[0130] The third embodiment is an example in which the timing of paging occurrence is notified. Specifically, firstly, the core network device (e.g., AMF300) transmits timing information representing the timing of paging occurrence to the user device (e.g., UE100).

[0131] This allows the UE100, for example, to know when paging will occur. Therefore, the UE100 can anticipate in advance that a paging message will be sent from the gNB200 based on the timing of the paging. When the UE100 receives the paging message from the gNB200, it can then prepare in advance to execute a slice-specific cell reselection procedure, such as changing the priority of the MT slice associated with paging. This enables the UE100 to connect to the appropriate cell.

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

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

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

[0135] As shown in Figure 15, in step S130, UE100 is in the RRC connected state.

[0136] In step S131, the AMF300 sends MT slice information and timing information to the UE100. Specifically, the AMF300 sends a NAS message containing MT slice information and timing information to the UE100.

[0137] The timing information indicates the timing at which paging occurs. This timing information may also indicate the timing at which MT occurs. Alternatively, this timing information may indicate the timing at which a paging message associated with an MT slice is sent. The MT slice information sent along with this timing information represents the MT slice associated with the paging that the timing information pertains to.

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

[0139] In step S132, gNB200 transmits MT slice support frequency information and timing information to UE100. Specifically, gNB200 transmits an RRC message (e.g., SIB or RRC release message) containing MT slice support frequency information and timing information. This timing information may be the same as the timing information transmitted by AMF300 (step S131).

[0140] Steps S133 and S134 are identical to steps S112 and S113 of the first embodiment, respectively.

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

[0142] In step S136, UE100 executes the slice-specific cell reselection procedure using the modified priority order.

[0143] (Another example of the third embodiment) In the third embodiment, an example of CN paging was described, but the embodiment is not limited thereto. 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] In the third embodiment, an example was described in which the network notifies the UE100 of MT slice information and timing information. In the fourth embodiment, an example is described in which the UE100 notifies the network of MT slice information and timing information.

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

[0147] Therefore, in the fourth embodiment, the UE100 transmits MT slice information and timing information to the network.

[0148] Specifically, firstly, the user device (e.g., UE100) transmits MT slice information representing the network slice associated with paging and timing information representing the timing at which paging occurs to the core network device (e.g., AMF300). Secondly, the user device transmits MT slice support frequency information representing the frequencies that support the network slice and timing information to the base station (e.g., gNB200).

[0149] (Example of operation of the fourth embodiment) Figure 16 is a diagram illustrating an example of operation according to the fourth embodiment. Figure 16 also shows an example of CN paging.

[0150] As shown in Figure 16, in step S140, UE100 is in the RRC connected state.

[0151] In step S141, UE100 transmits MT slice information and timing information to AMF300. Specifically, the NAS of UE100 transmits a NAS message containing MT slice information and timing information to AMF300. The timing information is, for example, the same as in the third embodiment.

[0152] In step S142, UE100 transmits MT slice support frequency information and timing information to gNB200. Specifically, the AS of UE100 transmits an RRC message containing MT slice support frequency information and timing information to gNB200. This timing information is, for example, the same as the timing information transmitted in step S141.

[0153] In step S143, UE100 sends slice priority change request information to AMF300, indicating a request (or demand) for a change in the slice priority of the MT slice. Specifically, the NAS of UE100 sends a NAS message containing the slice priority change request information to AMF300.

[0154] In step S144, upon receiving the slice priority change request information, the AMF300 sends slice priority change information to the UE100, indicating that it will change the slice priority of the MT slice. Specifically, the AMF300 sends a NAS message containing the slice priority change information to the NAS of the UE100. Upon receiving the slice priority change information, the UE100 may change the slice priority of the MT slice, similar to the first embodiment.

[0155] In step S145, UE100 sends slice frequency priority change request information to gNB200, indicating a request (or demand) for a change in the frequency priority of the frequencies supporting the MT slice. Specifically, the AS of UE100 sends an RRC message containing the slice frequency priority change request information to gNB200.

[0156] In step S146, upon receiving the slice frequency priority change request information, gNB200 sends slice frequency priority change information to UE100, which represents a change in the frequency priority of the frequencies supporting the MT slice. Specifically, gNB200 sends an RRC message containing the slice frequency priority change information to the AS of UE100.

[0157] In step S147, UE100 changes the priority. UE100 may change the slice priority of the MT slice in response to receiving slice priority change information (step S144). UE100 may also change the priority of the frequencies supporting the MT slice in response to receiving 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, the slice-specific cell reselection procedure is executed according to the modified slice priority and modified frequency priority.

[0160] (Another example of the fourth embodiment) In the fourth embodiment, an example was described in which UE100 requests a change in priority from the network (steps S143 to S146). For example, UE100 may change the priority without requesting a change from the network (step S147). In this case, as shown in Figure 16, UE100 changes the priority without performing steps S143 to S146 (step S147) and then sends slice priority change information to AMF300 indicating that the slice priority of the MT slice has been changed (step S148). Slice priority change information may be sent in a NAS message. Then, UE100 sends slice frequency priority change information to gNB200 (e.g., base station) indicating that the priority of the frequencies supporting the MT slice has been changed (step S149). Slice frequency priority change information may be sent in an RRC message.

[0161] Thus, in the fourth embodiment, the UE100 requests a change in priority from the network (steps S143 to S146), or the UE100 notifies the network that the priority has been changed (steps S148 and S149). This also aligns with 3GPP's requirement to control slice priority and frequency priority through the network.

[0162] In addition, RAN paging may be applied in the fourth embodiment as well, similar to the first embodiment.

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

[0164] In the fifth embodiment, an example is described of restoring the modified slice priority of an MT slice and the modified frequency priority of the frequencies supporting the MT slice. Specifically, firstly, after the user device (e.g., UE100) executes the slice-specific cell reselection procedure, it restores the modified slice priority of the network slice (e.g., an MT slice) to its pre-modification state. Secondly, after the user device executes the slice-specific cell reselection procedure, it restores the modified frequency priority of the frequencies supporting the network slice to its pre-modification state.

[0165] UE100 may not need to use an MT slice after connecting to an adjacent cell that supports an MT slice. By reverting the slice priority of the modified MT slice back to its previous priority, UE100 can execute the slice-specific cell reselection procedure without prioritizing the MT slice. Therefore, after connecting to an adjacent cell that supports an MT slice, UE100 can properly execute the slice-specific cell reselection procedure by reverting the priority back to its previous level. Thus, UE100 can connect to the appropriate cell.

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

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

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

[0169] In step S165, UE100 changes the slice priority of the MT slice and the frequency priority of the frequencies supporting the MT slice. At this time, UE100 saves, for example, the slice priority of the MT slice before the change and the frequency priority of the frequencies supporting the MT slice before the change to memory. Then, UE100 changes each priority after saving to memory. UE100 may also save the slice priority of the MT slice before the change and the frequency priority of the frequencies supporting the MT slice before the change to memory.

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

[0171] In step S167, UE100 resets the modified priority to its original state. UE100 restores the slice priority by, for example, changing the modified slice priority back to the original slice priority stored in memory. UE100 may also restore the priority of MT slices by changing the modified slice priority of MT slices back to the original slice priority stored in memory. Furthermore, UE100 restores the frequency priority by, for example, changing the modified frequency priority back to the original slice priority stored in memory. UE100 may also restore the frequency priority by changing the modified frequency priority of the frequencies supporting MT slices back to the original frequency priority stored in memory.

[0172] (Another example of the fifth embodiment) In the fifth embodiment, an example was 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 UE100 executes the slice-specific cell reselection procedure (step S166) and starts the RRC connection establishment procedure to the adjacent cells supporting the MT cell. Alternatively, the priority reset may be performed at any time after UE100 has started the RRC connection establishment procedure.

[0173] In the fifth embodiment, the AMF300 may send a NAS message to the UE100 containing information indicating whether or not a priority reset will be performed. Alternatively, the gNB200 may send an RRC message to the UE100 containing the same information indicating whether or not a priority reset will be performed.

[0174] Alternatively, the UE100 may send a NAS message to the AMF300 containing information requesting a priority reset. In this case, the AMF300 may send a NAS message indicating that it will reset the priority upon receiving such 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 send an RRC message containing this information to the gNB200. In this case, upon receiving the information, the gNB200 sends an RRC message to the AS of UE100 indicating that it will perform a priority reset. The AS of UE100 then notifies the NAS of UE100 that the priority reset has been authorized.

[0176] Furthermore, in the fifth embodiment, the reset of priority may be specified in the specification (or hardcoded).

[0177] Furthermore, in the fifth embodiment, the UE100 may be configured to allow the user to choose whether or not to reset the priority.

[0178] [Other embodiments] A program may be provided that causes a computer to execute each process performed by the UE100 or gNB200. The program may be recorded on a computer-readable medium. Using a computer-readable medium, it is possible to install the program on a computer. Here, the computer-readable medium on which the program is recorded may be a non-transient recording medium. The non-transient recording medium is not particularly limited, but may be a recording medium such as a CD-ROM or DVD-ROM. Alternatively, the circuits that execute each process performed by the UE100 or gNB200 may be integrated, and at least a part of the UE100 or gNB200 may be configured as a semiconductor integrated circuit (chipset, SoC: System on a chip).

[0179] The terms "based on" and "depending on" used in this disclosure do not mean "based solely on" or "depending solely on" unless otherwise specified. "Based on" means both "based solely on" and "at least partially on." Similarly, "depending on" means both "at least partially on" and "at least partially on." Furthermore, the terms "include" and "comprise" do not mean to include only the listed items, but may include only the listed items or may include additional items in addition to the listed items. Also, the term "or" used in this disclosure is not intended to mean exclusive OR. Moreover, any reference to elements using designations such as "first," "second," etc., used in this disclosure does not generally limit the quantity or order of those elements. These designations may be used herein as a convenient way to distinguish between two or more elements. Therefore, references to the first and second elements do not imply that only two elements may be adopted therein, or that the first element must precede the second element in any way. In this disclosure, where articles are added by translation, such as a, an, and the in English, these articles shall be plural unless it is clearly indicated by the context that they are not.

[0180] Although one embodiment has been described in detail above with reference to the drawings, the specific configuration is not limited to that described above, and various design changes can be made without departing from the gist of the work. Furthermore, it is possible to combine all or part of each embodiment, each operation, each process, and each step, as long as they do not contradict each other.

[0181] This application claims priority to Japanese Patent Application No. 2022-119418 (filed July 27, 2022), and all of its contents are incorporated into the specification of this application.

[0182] (Note) (Note 1) A communication control method in a mobile communication system, The core network device includes the step of transmitting MT (Mobile Terminated) slice information, which represents a network slice associated with paging, to the user device. Communication control method.

[0183] (Note 2) The base station transmits a paging message to the user device, The user device modifies the slice priority of the network slice based on the MT slice information. The user device further includes the step of executing a slice-specific cell reselection procedure according to the changed slice priority. The communication control method described in Appendix 1.

[0184] (Note 3) The step of transmitting the MT slice information to the user device includes the step of transmitting first change instruction information to the user device, which instructs the core network device to change the slice priority of the network slice. The communication control method described in Appendix 1 or Appendix 2.

[0185] (Note 4) The base station further comprises the step of transmitting MT slice support frequency information, which represents the frequencies that support the network slice, to the user device. A communication control method as described in any of Appendix 1 to Appendix 3.

[0186] (Note 5) The user device modifies the frequency priority of the frequencies supporting the network slice based on the MT slice support frequency information, The user device includes the step of performing a slice-specific cell reselection procedure according to the modified frequency priority order. A communication control method as described in any of Appendix 1 to Appendix 4.

[0187] (Note 6) The step of transmitting the MT slice support frequency information to the user device includes the step of transmitting second change instruction information to the user device, which includes information instructing the base station to change the frequency priority of the frequencies supporting the network slice. A communication control method as described in any of Appendix 1 to Appendix 5.

[0188] (Note 7) The step of transmitting the MT slice information to the user device includes the step of the core network device transmitting timing information to the user device that indicates when the paging occurs. A communication control method as described in any of Appendix 1 to Appendix 6.

[0189] (Note 8) The step of transmitting the MT slice support frequency information to the user device includes the step of the base station transmitting timing information to the user device that indicates when the paging occurs. A communication control method as described in any of Appendix 1 to Appendix 7.

[0190] (Note 9) The user device further includes the step of restoring the modified slice priority of the network slice to its pre-modification state after executing the slice-specific cell reselection procedure. A communication control method as described in any of Appendix 1 to Appendix 8.

[0191] (Note 10) The user device further includes the step of restoring the frequency priority after the frequency change that supports the network slice, after executing the slice-specific cell reselection procedure. A communication control method as described in any of Appendix 1 to Appendix 9.

[0192] (Note 11) A communication control method in a mobile communication system, The user device transmits MT slice information representing a network slice associated with paging and timing information representing the timing at which the paging occurs to the core network device. The user device has the step of transmitting MT slice support frequency information, which represents the frequency that supports the network slice, and timing information to a base station. Communication control method. [Explanation of Symbols]

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

Claims

1. A communication control method in a mobile communication system, The user device receives MT (Mobile Terminated) slice information representing the network slice associated with paging from the core network node, The user device receives a paging message from the network node, In response to receiving the pacing message, the user device executes a slice-specific cell reselection procedure based on the MT slice information. Communication control method.

2. The user device changes the slice priority of the network slice based on the MT slice information, The user device further includes executing a slice-specific cell reselection procedure according to the modified slice priority. The communication control method according to claim 1.

3. Transmitting the MT slice information to the user device includes transmitting first modification instruction information to the user device, which instructs the core network node to change the slice priority of the network slice. The communication control method according to claim 1.

4. The network node further comprises transmitting MT slice support frequency information representing the frequencies that support the network slice to the user device. The communication control method according to claim 1.

5. The user device changes the frequency priority of the frequencies supporting the network slice based on the MT slice support frequency information, The user device includes performing a slice-specific cell reselection procedure according to the modified frequency priority order. The communication control method according to claim 4.

6. Transmitting the MT slice support frequency information to the user device includes transmitting to the user device second change instruction information, which includes information instructing the network node to change the frequency priority of the frequencies supporting the network slice. The communication control method according to claim 4.

7. Transmitting the MT slice information to the user device includes the core network node transmitting timing information to the user device that indicates when the paging occurs. The communication control method according to claim 1.

8. Transmitting the MT slice support frequency information to the user device includes the network node transmitting timing information to the user device that indicates when the paging occurs. The communication control method according to claim 4.

9. The user device further includes, after executing the slice-specific cell reselection procedure, restoring the modified slice priority of the network slice to its pre-modification state. The communication control method according to claim 2.

10. The user device further includes, after executing the slice-specific cell reselection procedure, restoring the frequency priority of the network slice after the frequency has been changed. The communication control method according to claim 5.

11. A communication control method in a mobile communication system, The user device transmits MT slice information representing the network slice associated with paging and timing information representing the timing at which the paging occurs to the core network node. The user device transmits MT slice support frequency information, which represents the frequency that supports the network slice, and the timing information to the network node. Communication control method.

12. A user device, A receiving unit that receives MT slice information representing network slices associated with paging from core network nodes and receives paging messages from network nodes, The system includes a control unit that, upon receiving the pacing message, executes a slice-specific cell reselection procedure based on the MT slice information. User device.

13. User device, It has a transmission unit that transmits MT slice information representing a network slice associated with paging and timing information representing the timing at which the paging occurs to the core network node. The transmitting unit transmits MT slice support frequency information, which represents the frequencies that support the network slice, and the timing information to the wireless access network node. User device.

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