Communication control method and user device

Abstract

A communication control method according to one aspect of the present invention is for a mobile communication system. This communication control method includes a step in which a base station reports system information. The communication control method also includes a step in which the base station sends an RRC release message to a user device. Moreover, the communication control method includes a step in which, in a case where there is a difference between first slice information included in the system information and second slice information included in the RRC release message, and / or in a case where there is a difference between first frequency information included in the system information and second frequency information included in the RRC release message, the user device uses prescribed information to execute a slice-specific cell reselection procedure.

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), a standardization project for mobile communication systems. Network slicing is a technology that creates virtual networks, called network slices, 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 V17.2.0 (2022-9)

[0005] A communication control method according to one embodiment includes a user equipment receiving an RRC release message from a network, the user equipment receiving system information from the network to be used in a slice-specific cell reselection procedure, and the user equipment performing the slice-specific cell reselection procedure using only the RRC release message if information indicating a correspondence between a slice group and a frequency is included in the RRC release message.

[0006] A communication control method according to one aspect is a communication control method in a mobile communication system. The communication control method includes a step in which a network device broadcasts system information. The communication control method also includes a step in which the network device transmits an RRC release message to a user equipment. The communication control method further includes a step in which the user equipment performs a slice-specific cell reselection procedure using predetermined information when at least one of first slice information included in the system information and second slice information included in the RRC release message is different and first frequency information included in the system information is different from second frequency information included in the RRC release message.

[0007] 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. FIGS. 12(A) and 12(B) are diagrams illustrating an example of the configuration of an SIB16 according to the first embodiment. FIGS. 13(A) and 13(B) are diagrams illustrating an example of the configuration of an RRC release message according to the first embodiment. FIG. 14 is a diagram illustrating an example of an operation according to the first embodiment. Fig. 15 is a diagram illustrating an example of operation according to the second embodiment. Fig. 16 is a diagram illustrating an example of operation according to the third embodiment. Fig. 17 is a diagram illustrating an example of operation according to the fourth embodiment. Fig. 18 is a diagram illustrating an example of operation according to the fifth embodiment.

[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]

[0010] (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.

[0011] 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.

[0012] 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) and / or 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).

[0013] 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").

[0014] In addition, the gNB200 can be connected to the Evolved Packet Core (EPC), which is the core network of LTE. The LTE base station can also be connected to the 5GC20. The LTE base station and the gNB200 can also be connected via an inter-base station interface.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] FIG. 4 is a diagram showing the configuration of a protocol stack of a radio interface of a user plane that handles data.

[0026] 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.

[0027] 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 successfully decoded DCI as DCI addressed to the UE. The DCI transmitted from gNB200 has a CRC (Cyclic Redundancy Code) parity bit scrambled by the RNTI added.

[0028] The MAC layer performs data priority control, retransmission processing using Hybrid Automatic Repeat reQuest (HARQ), random access procedures, etc. Data and control information are transmitted between the MAC layer of the UE 100 and the MAC layer of the gNB 200 via a transport channel. The MAC layer of the gNB 200 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 the UE 100.

[0029] 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.

[0030] The PDCP layer performs header compression / decompression, encryption / decryption, and the like.

[0031] 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.

[0032] 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).

[0033] 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.

[0034] 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.

[0035] 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).

[0036] (Outline of Cell Reselection Procedure) FIG. 6 is a diagram for explaining an outline of a cell reselection procedure.

[0037] 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.

[0038] FIG. 7 is a diagram illustrating the general flow of a typical (or legacy) cell reselection procedure.

[0039] 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, via an RRC release message. Specifically, the UE 100 manages the frequency priority specified by the gNB 200 for each frequency.

[0040] 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.

[0041] 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.

[0042] (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."

[0043] 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.

[0044] FIG. 8 is a diagram illustrating an example of network slicing.

[0045] 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.

[0046] 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).

[0047] 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.

[0048] 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. A slice group may be represented by an NSSAI. The slice group may also be represented by an NSAG (Network Slice Access Stratum Group).

[0049] 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 receives the slice priority information from AMF300. That is, AMF300 determines the slice priority for each slice. AMF300 transmits slice priority information indicating the slice priority to the NAS of UE100. The NAS of UE100 may determine the slice priority based on the slice priority information received from AMF300.

[0050] (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.

[0051] 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 by dedicated signaling (e.g., an RRC release message) from the gNB 200.

[0052] 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 .

[0053] 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.

[0054] 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."

[0055] 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."

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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."

[0061] 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."

[0062] 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."

[0063] 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."

[0064] 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.

[0065] 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).

[0066] 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.

[0067] 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.

[0068] (Examples of the Configuration of SIB16 and RRC Release Message) Next, examples of the configuration of SIB16 and the configuration of the RRC release message will be described.

[0069] Fig. 12A is a diagram illustrating an example of the configuration of SIB16. Fig. 12B is a diagram illustrating an example of the configuration of "FreqPriorityListSlicing" (X1), which is an information element included in SIB16.

[0070] As shown in (Y1) of FIG. 12(B), SIB16 includes frequency information ("dl-ImplicitCarrierFreq"). The frequency information indicates, for example, frequencies supported in a cell. The frequency information may include a serving frequency. Alternatively, the frequency information may include a frequency defined in SIB4.

[0071] Also, as shown in (Y2), SIB16 includes slice group identification information ("nsag-IdentityInfo") that identifies a slice group. The slice group identification information may be the slice group identifier described above. The information of the network slice (or NSAG information) included in the NSAG (or slice group) itself is transmitted from the AMF 300 to the UE 100 using a NAS message. The slice group identification information represents the identification information of the slice group included in the NSAG information.

[0072] Furthermore, as shown in (Y3) and (Y4), SIB16 includes slice frequency information ("nsag-CellReselectionPriority" and "nsag-CellReselectionSubPriority") for each network slice included in the slice group. This information will be referred to as "slice group frequency information." The slice group frequency information is information that includes the correspondence between network slices, frequencies, and frequency priorities for the number of network slices in the slice group.

[0073] In the following, information including the "slice group identification information" (Y2) and the "slice group frequency information" (Y3 and Y4) will be referred to as "slice group information."

[0074] Furthermore, as shown in (Y5), SIB16 includes slice support information ("sliceAllowedCellList" and "sliceExcludedCellList"). As described above, the slice support information is information that indicates the correspondence between the network slices provided by the cell and the network slices not provided by the cell.

[0075] In this way, SIB16 includes frequency information (Y1), slice group information (Y2, Y3, and Y4), and slice support information (Y5). The slice group information (Y2, Y3, and Y4) includes slice group identification information (Y2) and slice group frequency information (Y3 and Y4). Note that the slice group information (Y2, Y3, and Y4) and slice support information (Y5) included in SIB16 may be collectively referred to as "slice information" (SliceInfo).

[0076] On the other hand, Fig. 13(A) is a diagram showing a configuration example of an RRC release message, and Fig. 13(B) is a diagram showing a configuration example of an information element ("FreqPriorityListDedicatedSlicing") (Z1) included in the RRC release message.

[0077] As shown in (U1) of Fig. 13B, the RRC release message also includes frequency information ("dl-ExplicitCarrierFreq"), which is the same as the frequency information included in SIB16.

[0078] Also, as shown in (U2), the RRC release message also includes slice group identification information ("nsag-IdentityInfo") that identifies the slice group.

[0079] Furthermore, as shown in (U3) and (U4), the RRC release message also includes slice group frequency information ("nsag-CellReselectionPriority" and "nsag-CellReselectionSubPriority"). However, the RRC release message does not include slice support information.

[0080] In this way, the RRC release message also includes frequency information (U1) and slice group information (U2, U3, and U4). The slice group information includes slice group identification information (U2) and slice group frequency information (U3 and U4). Note that the slice group information (U2, U3, and U4) included in the RRC release message may be referred to as "dedicated slice information" (SliceInfoDedicated).

[0081] (Communication Control Method According to First Embodiment) Next, a communication control method according to the first embodiment will be described.

[0082] Currently, 3GPP is discussing the relationship between SIB16 and the RRC release message. Specifically, the following points are being discussed:

[0083] (Proposal 1) Even if slice information (individual slice information) is included in the RRC release message, if SIB16 is not broadcast, UE100 does not perform the slice-specific cell reselection procedure.

[0084] (Proposal 2) If a frequency is present in the information element ("FreqPriorityListDedicatedSlicing") of the received RRC release message and the frequency is not present in the information element ("FreqPriorityListSlicing") of SIB16, the UE cannot use the NSAG (or slice group) related to that frequency.

[0085] (Proposal 3) For NSAGs that exist in the RRC release message but not in SIB16, the UE 100 considers them to be unsupported by frequency.

[0086] However, these proposals are currently on hold.

[0087] As described above, the SIB16 and the RRC release message contain the same information. The same information is slice group information (Y2 to Y4 and U2 to U4) and frequency information (Y1 and U1). The UE 100 uses the slice group information and frequency information to perform a slice-specific cell reselection procedure.

[0088] However, if the slice group information included in SIB16 and the slice group information included in the RRC release message are different, UE100 may not know how to perform a slice-specific cell reselection procedure. For example, if the frequency priority in the slice group information included in SIB16 and the frequency priority in the slice group information included in the RRC release message are different for the same network slice, UE100 does not know how to determine the frequency priority and perform a slice-specific cell reselection procedure.

[0089] Similarly, if the frequency information included in SIB16 and the frequency information included in the RRC release message are different, UE100 may not know whether to use the frequency information included in SIB16 or the frequency information included in the RRC release message to perform the slice-specific cell reselection procedure.

[0090] Therefore, the first embodiment aims to enable UE100 to properly perform a slice-specific cell reselection procedure even when the information contained in SIB16 differs from the information contained in the RRC release message.

[0091] Therefore, in the first embodiment, first, a base station (e.g., gNB200) broadcasts system information (e.g., SIB16). Second, the base station transmits an RRC release message to a user equipment (e.g., UE100). Third, the user equipment performs a slice-specific cell reselection procedure using predetermined information when the first slice information included in the system information and the second slice information included in the RRC release message are different, and / or when the first frequency information included in the system information and the second frequency information included in the RRC release message are different. In the first embodiment, the predetermined information is at least one of the second slice information and the second frequency information.

[0092] As described above, in the first embodiment, when the information included in SIB16 and the information included in the RRC release message are different, UE100 performs the slice-specific cell reselection procedure by using the information included in the RRC release message. Thus, UE100 can appropriately perform the slice-specific cell reselection procedure.

[0093] (Operation Example According to First Embodiment) FIG. 14 is a diagram illustrating an operation example according to the first embodiment.

[0094] 14, in step S10, the gNB 200 broadcasts the SIB 16. However, in the first embodiment, the SIB 16 does not include frequency information and slice group information. The UE 100 receives the SIB 16.

[0095] In step S11, the gNB 200 transmits an RRC release message to the UE 100. However, in the first embodiment, the RRC release message includes frequency information and slice group information. The UE 100 receives an SIB 16 that does not include frequency information and slice group information, and an RRC release message that includes frequency information and slice group information. When the UE 100 receives the RRC release message, it starts counting the T320 timer included in the RRC release message. Thereafter, the UE 100 transitions to an RRC idle state or an RRC inactive state. The UE 100 in the RRC idle state or the RRC inactive state performs the subsequent processing.

[0096] In step S12, the UE 100 detects that the frequency information and the slice group information have not been notified in the SIB16.

[0097] In step S13, it is determined whether the count value of the T320 timer has reached its expiration value (that is, whether the T320 timer has expired).

[0098] If the T320 timer has not expired (No in step S13), in step S14, UE100 performs a slice-specific cell reselection procedure using the frequency information and slice group information included in the RRC release message. UE100 uses the slice group information included in the RRC release message, using the fact that network slices are uniformly supported in the same tracking area (TA) according to the homogeneous rule.

[0099] On the other hand, if T320 has expired (Yes in step S13), the process proceeds to step S15. That is, until the T320 timer expires, the frequency information and slice group information included in the RRC release message are subject to the slice-specific cell reselection procedure (step S14).

[0100] In step S15, the UE 100 determines whether or not the UE 100 has received the SIB 16 including the frequency information and the slice group information.

[0101] If UE100 receives SIB16 (Yes in step S15), in step S16, UE100 performs a slice-specific cell reselection procedure using the frequency information and slice group information included in SIB16.

[0102] On the other hand, in step S15, if UE100 has not received SIB16 (No in step S15), in step S17, UE100 performs a slice-specific cell reselection procedure using the frequency information and slice group information included in the RRC release message (step S11). Even if T320 expires (Yes in step S13), UE100 may perform a slice-specific cell reselection procedure using the frequency information and slice group information included in the RRC release message until receiving SIB16.

[0103] In step S17, since UE100 has not received SIB16, UE100 may not support the slice-specific cell reselection procedure.

[0104] Furthermore, the number of timeouts may be instructed by the gNB 200. When the T320 timer times out, the upper limit number of times to repeatedly start counting the T320 timer may be the number of timeouts. The gNB 200 may set the number of timeouts to the UE 100 using an RRC release message. Furthermore, a new timer other than the T320 timer may be instructed by the gNB 200. The new timer may also be instructed by the RRC release message.

[0105] (Other operation examples according to the first embodiment) In the first embodiment, an example was described in which SIB16 does not include frequency information and slice group information, and the RRC release message includes frequency information and slice group information, but this is not limited to this.

[0106] First, although both SIB16 and the RRC release message include frequency information, there are cases where the frequency information (e.g., first frequency information) included in SIB16 differs from the frequency information (e.g., second frequency information) included in the RRC release message. Even in such a case, as in the first embodiment, the UE 100 may perform a slice-specific cell reselection procedure by using the frequency information included in the RRC release message (steps S14 and S17).

[0107] Second, although slice group information is included in both SIB16 and the RRC release message, there are cases where the slice group information (e.g., first slice group information) included in SIB16 differs from the slice group information (e.g., second slice group information) included in the RRC release message. Even in such a case, as in the first embodiment, the UE 100 may perform a slice-specific cell reselection procedure by using the slice group information included in the RRC release message (steps S14 and S17).

[0108] That is, when the slice group information included in SIB16 is different from the slice group information included in the RRC release message, and / or when the frequency information included in SIB16 is different from the frequency information included in the RRC release message, UE100 performs a slice-specific cell reselection procedure using information included in the RRC release message (at least one of the frequency information and slice group information included in the RRC release message).

[0109] The slice support information may conform to SIB 16. The slice support information may be supported by all cells according to the homogenous principle.

[0110] Second Embodiment Next, a second embodiment will be described, focusing on the differences from the first embodiment.

[0111] The second embodiment is an example in which, when the information included in SIB16 differs from the information included in the RRC release message, the slice-specific cell reselection procedure is performed using the information included in SIB16.

[0112] Specifically, first, a base station (e.g., gNB200) broadcasts system information (e.g., SIB16). Second, the base station transmits an RRC release message to a user equipment (e.g., UE100). Third, the user equipment performs a slice-specific cell reselection procedure using predetermined information when the first slice information included in the system information and the second slice information included in the RRC release message are different, and / or when the first frequency information included in the system information and the second frequency information included in the RRC release message are different. In the second embodiment, the predetermined information is at least one of the first slice information and the first frequency information.

[0113] As described above, in the second embodiment, when the information included in the SIB 16 and the information included in the RRC release message are different, the UE 100 performs the slice-specific cell reselection procedure by using the information included in the SIB 16. Thus, the UE 100 can appropriately perform the cell reselection procedure.

[0114] (Example of Operation According to Second Embodiment) Next, an example of operation according to the second embodiment will be described.

[0115] FIG. 15 is a diagram illustrating an example of operation according to the second embodiment.

[0116] 15, in step S20, the gNB 200 broadcasts the SIB 16. The SIB 16 includes frequency information and slice group information. The UE 100 receives the SIB 16.

[0117] In step S21, the gNB 200 transmits an RRC release message to the UE 100. The RRC release message includes frequency information and slice group information. However, in the second embodiment, some of the frequency information and slice group information included in the RRC release message is not included in the SIB 16. After receiving the RRC release message, the UE 100 transitions to an RRC idle state or an RRC inactive state.

[0118] In step S22, UE100 detects that some of the frequency information and slice groups included in the RRC release message are not included in SIB16.

[0119] In step S23, UE100 performs a slice-specific cell reselection procedure using the frequency information and slice group information included in SIB16 (ignoring the frequency information and slice group information included in the RRC release message).

[0120] In addition, if UE100 does not receive SIB16 in step S20 (or if UE100 receives SIB16 that does not include frequency information and slice group information), UE100 may not support the slice-specific cell reselection procedure.

[0121] (Another Operation Example of Second Embodiment) In the second embodiment, an example has been described in which some of the frequency information and slice groups included in the RRC release message are not included in SIB16, but the present invention is not limited to this.

[0122] First, in addition to the case where part of the frequency information included in the RRC release message is not included in SIB 16, there are also cases where the frequency information (e.g., first frequency information) included in SIB 16 differs from the frequency information (e.g., second frequency information) included in the RRC release message. Even in such a case, as in the second embodiment, UE 100 may perform a slice-specific cell reselection procedure by using the frequency information included in SIB 16 (step S23).

[0123] Second, in addition to the case where some of the slice group information included in the RRC release message is not included in SIB 16, there are also cases where the slice group information (e.g., first slice group information) included in SIB 16 differs from the slice group information (e.g., second slice group information) included in the RRC release message. Even in such a case, as in the second embodiment, UE 100 may execute a slice-specific cell reselection procedure by using the slice group information included in SIB 16 (step S23).

[0124] The slice support information may conform to SIB 16. The slice support information may be supported by all cells according to the homogenous principle.

[0125] Third Embodiment Next, a third embodiment will be described, focusing on the differences from the first embodiment.

[0126] In the third embodiment, an example is described in which, when the information contained in SIB16 and the information contained in the RRC release message are different, an AND condition is taken between the two and a slice-specific cell reselection procedure is executed using the information that is common to both.

[0127] Specifically, first, a base station (e.g., gNB200) broadcasts system information (e.g., SIB16). Second, the base station transmits an RRC release message to a user equipment (e.g., UE100). Third, the user equipment performs a slice-specific cell reselection procedure using predetermined information when the first slice information included in the system information and the second slice information included in the RRC release message are different, and / or when the first frequency information included in the system information and the second frequency information included in the RRC release message are different. In the third embodiment, the predetermined information is at least one of information common to the first slice information and the second slice information and information common to the first frequency information and the second frequency information.

[0128] In this way, when the information included in the SIB16 and the information included in the RRC release message are different, the UE 100 performs the slice-specific cell reselection procedure using the common information. Therefore, the UE 100 can appropriately execute the procedure.

[0129] (Example of Operation According to Third Embodiment) Next, an example of operation according to the third embodiment will be described.

[0130] FIG. 16 is a diagram illustrating an example of operation according to the third embodiment.

[0131] 16, in step S30, the gNB 200 broadcasts the SIB 16. The SIB 16 includes frequency information and slice group information. The UE 100 receives the SIB 16.

[0132] In step S31, the gNB 200 transmits an RRC release message to the UE 100. The RRC release message includes frequency information and slice group information. However, in the third embodiment, as in the second embodiment, some of the frequency information and slice group information included in the RRC release message is not included in the SIB 16. After receiving the RRC release message, the UE 100 transitions to an RRC idle state or an RRC inactive state. Note that the UE 100 starts counting the T320 timer included in the RRC release message when it receives the RRC release message.

[0133] In step S32, UE100 detects that some of the frequency information and slice groups included in the RRC release message are not included in SIB16.

[0134] In step S33, UE 100 performs an AND condition between the frequency information included in SIB16 and the frequency information included in the RRC release message, and executes a slice-specific cell reselection procedure using information common to both. Also, in step S33, UE 100 performs an AND condition between the slice group information included in SIB16 and the slice group information included in the RRC release message, and executes a slice-specific cell reselection procedure using information common to both.

[0135] The slice group information includes frequency priority. When the frequency priority included in SIB16 is different from the frequency priority included in the RRC release message, one of the following methods may be adopted.

[0136] A1) Adopt the one with the higher frequency priority. A2) Adopt the one with the lower frequency priority. A3) Adopt the frequency priority of the RRC release message. A4) Adopt the frequency priority of SIB16. A5) The gNB200 specifies which one to adopt. Note that A5) above will be explained in the fifth embodiment.

[0137] In addition, UE100 may perform a slice-specific cell reselection procedure using common information in SIB16 and the RRC release message until the T320 timer expires, and after the T320 timer expires, perform the procedure using the frequency information and slice group information contained in SIB16.

[0138] Alternatively, if UE100 does not receive SIB16 (or does not receive SIB16 including frequency information and slice group information) even after the T320 timer has expired, UE100 may perform a slice-specific cell reselection procedure using information common to SIB16 and the RRC release message.

[0139] (Another Operation Example of Third Embodiment) In the third embodiment, an example has been described in which some of the frequency information and slice groups included in the RRC release message are not included in SIB16, but the present invention is not limited to this.

[0140] First, in addition to the case where part of the frequency information included in the RRC release message is not included in SIB 16, there are also cases where the frequency information (e.g., first frequency information) included in SIB 16 and the frequency information (e.g., second frequency information) included in the RRC release message are different. Even in such a case, as in the second embodiment, UE 100 may take an AND condition and perform a slice-specific cell reselection procedure using information common to both (step S33).

[0141] Secondly, in addition to the case where some of the slice group information included in the RRC release message is not included in SIB 16, there are also cases where the slice group information (e.g., first slice group information) included in SIB 16 differs from the slice group information (e.g., second slice group information) included in the RRC release message. Even in such a case, as in the third embodiment, UE 100 may execute a slice-specific cell reselection procedure by using information common to both (step S33).

[0142] The slice support information may conform to SIB 16. The slice support information may be supported by all cells according to the homogenous principle.

[0143] Fourth Embodiment Next, a fourth embodiment will be described, focusing on the differences from the first embodiment.

[0144] In the fourth embodiment, an example is described in which, when the information contained in SIB16 and the information contained in the RRC release message are different, an OR condition is taken between the two and a slice-specific cell reselection procedure is performed using both pieces of information.

[0145] Specifically, first, a base station (e.g., gNB200) broadcasts system information (e.g., SIB16). Second, the base station transmits an RRC release message to a user equipment (e.g., UE100). Third, the user equipment performs a slice-specific cell reselection procedure using predetermined information when the first slice information included in the system information and the second slice information included in the RRC release message are different, and / or when the first frequency information included in the system information and the second frequency information included in the RRC release message are different. In the fourth embodiment, the predetermined information is the first slice information, the second slice information, and the first frequency information and the second frequency information.

[0146] In this way, when the information contained in SIB16 differs from the information contained in the RRC release message, UE100 performs the slice-specific cell reselection procedure using both pieces of information, and is therefore able to execute the procedure appropriately.

[0147] (Example of Operation According to Fourth Embodiment) Next, an example of operation according to the fourth embodiment will be described.

[0148] FIG. 17 is a diagram illustrating an example of operation according to the fourth embodiment.

[0149] 17, in step S40, the gNB 200 broadcasts the SIB 16. The SIB 16 includes frequency information and slice group information. The UE 100 receives the SIB 16.

[0150] In step S41, the gNB 200 transmits an RRC release message to the UE 100. The RRC release message includes frequency information and slice group information. However, in the fourth embodiment, as in the second embodiment, some of the frequency information and slice group information included in the RRC release message is not included in the frequency information and slice group included in the SIB 16. After receiving the RRC release message, the UE 100 transitions to an RRC idle state or an RRC inactive state. Note that the UE 100 starts counting the T320 timer included in the RRC release message when it receives the RRC release message.

[0151] In step S42, UE100 detects that some of the frequency information and slice groups included in the RRC release message are not included in SIB16.

[0152] In step S43, UE 100 performs an OR condition between the frequency information included in SIB16 and the frequency information included in the RRC release message, and performs a slice-specific cell reselection procedure using both pieces of information. Also, in step S43, UE 100 performs an OR condition between the slice group information included in SIB16 and the slice group information included in the RRC release message, and performs a slice-specific cell reselection procedure using both pieces of information.

[0153] The slice group information includes frequency priority. When the frequency priority included in SIB16 is different from the frequency priority included in the RRC release message, any of the above-described methods A1) to A5) may be adopted, as in the third embodiment.

[0154] Furthermore, UE100 may perform a slice-specific cell reselection procedure using common information in SIB16 and the RRC release message until the T320 timer expires, and after the T320 timer expires, perform the procedure using the frequency information and slice group information contained in SIB16.

[0155] Alternatively, if UE100 does not receive SIB16 (or does not receive SIB16 including frequency information and slice group information) even after the T320 timer has expired, UE100 may perform a slice-specific cell reselection procedure using both the information in SIB16 and the RRC release message.

[0156] (Another Operation Example of Fourth Embodiment) In the fourth embodiment, an example has been described in which some of the frequency information and slice groups included in the RRC release message are not included in SIB16, but the present invention is not limited to this.

[0157] First, in addition to the case where some of the frequency information included in the RRC release message is not included in SIB 16, there are also cases where the frequency information (e.g., first frequency information) included in SIB 16 differs from the frequency information (e.g., second frequency information) included in the RRC release message. Even in such a case, as in the fourth embodiment, the UE 100 may take an OR condition and perform a slice-specific cell reselection procedure using both pieces of information (step S43).

[0158] Secondly, in addition to the case where some of the slice group information included in the RRC release message is not included in SIB 16, there are also cases where the slice group information (e.g., first slice group information) included in SIB 16 differs from the slice group information (e.g., second slice group information) included in the RRC release message. Even in such a case, as in the fourth embodiment, UE 100 may execute a slice-specific cell reselection procedure by using information common to both (step S43).

[0159] The slice support information may conform to SIB 16. The slice support information may be supported by all cells according to the homogenous principle.

[0160] Fifth Embodiment Next, a fifth embodiment will be described, focusing on the differences from the first embodiment.

[0161] In the fifth embodiment, an example is described in which, when the information contained in SIB16 and the information contained in the RRC release message are different, gNB200 notifies UE100 of instruction information indicating which one to follow.

[0162] Specifically, first, a base station (e.g., gNB200) broadcasts system information (e.g., SIB16). Second, the base station transmits an RRC release message to a user equipment (e.g., UE100). Third, the user equipment performs a slice-specific cell reselection procedure using predetermined information when the first slice information included in the system information and the second slice information included in the RRC release message are different, and / or when the first frequency information included in the system information and the second frequency information included in the RRC release message are different. In the fifth embodiment, the base station further transmits instruction information to the user equipment indicating the predetermined information. Then, the user equipment performs a slice-specific cell reselection procedure according to the instruction information.

[0163] In this way, in the UE 100, when the information included in the SIB 16 and the information included in the RRC release message are different, the slice-specific cell reselection procedure is performed according to the instruction information from the gNB 200. Therefore, in the UE 100, the procedure can be appropriately performed.

[0164] (Example of Operation According to Fifth Embodiment) Next, an example of operation according to the fifth embodiment will be described.

[0165] FIG. 18 is a diagram illustrating an example of operation according to the fifth embodiment.

[0166] As shown in FIG. 18 , in step S50, the gNB 200 broadcasts the SIB 16. The SIB 16 includes frequency information and slice group information. The UE 100 receives the SIB 16. The gNB 200 may broadcast the SIB 16 including the instruction information.

[0167] First, the indication information includes indication information when the frequency information in SIB16 and the RRC release message differ. The indication information includes, for example, the following information:

[0168] B1) According to the frequency information included in the RRC release message B2) According to the frequency information included in SIB16 B3) An AND condition is used B4) An OR condition is used B5) A slice-specific cell reselection procedure is not supported Secondly, the indication information includes indication information when the slice group frequency information differs between SIB16 and the RRC release message. The indication information includes, for example, the following information:

[0169] C1) Adopt the one with the higher priority C2) Adopt the one with the lower priority C3) Adopt the slice group frequency information included in the RRC release message C4) Adopt the slice group frequency information included in SIB16 Third, the indication information includes indication information for slice support information. The indication information includes, for example, the following information:

[0170] D1) Based on the homogeneous rule, the network slice notified in the RRC release message is assumed to be supported by all cells. D2) Whether or not an NSAG present in SIB16 supports network slice depends on the slice allowed cell list ("sliceAllowedCellList") or slice disallowed cell list ("sliceExcludedCellList") included in SIB16.

[0171] In this way, the instruction information is information that indicates what information to use as the specified information when the information contained in SIB16 (at least one of frequency information and slice group information) differs from the information contained in the RRC release message (at least one of frequency information and slice group information).

[0172] In step S51, the gNB 200 transmits an RRC release message to the UE 100. The RRC release message includes frequency information and slice group information. However, in the fifth embodiment, as in the second embodiment, some of the frequency information and slice group information included in the RRC release message is not included in the frequency information and slice group included in SIB16. The gNB 200 may transmit an RRC release message including instruction information. The specific information included in the instruction information may be the same as the instruction information included in SIB16.

[0173] After receiving the RRC release message, the UE 100 transitions to an RRC idle state or an RRC inactive state. Furthermore, the UE 100 starts counting a T320 timer included in the RRC release message, triggered by the reception of the RRC release message.

[0174] In step S52, UE100 detects that some of the frequency information and slice groups included in the RRC release message are not included in SIB16.

[0175] In step S53, UE100 performs a slice-specific cell reselection procedure according to the instruction information included in either SIB16 or the RRC release message.

[0176] In addition, UE100 may perform a slice-specific cell reselection procedure in accordance with the instruction information until the T320 timer expires, and after the T320 timer expires, may perform the procedure using the frequency information and slice group information included in SIB16.

[0177] Alternatively, if UE100 does not receive SIB16 (or does not receive SIB16 including frequency information and slice group information) even after the T320 timer has expired, UE100 may perform a slice-specific cell reselection procedure according to the instruction information.

[0178] (Another Operation Example According to Fifth Embodiment) In the fifth embodiment, an example has been described in which some of the frequency information and slice groups included in the RRC release message are not included in SIB16, but the present invention is not limited to this.

[0179] First, in addition to the case where part of the frequency information included in the RRC release message is not included in SIB 16, there are also cases where the frequency information (e.g., first frequency information) included in SIB 16 differs from the frequency information (e.g., second frequency information) included in the RRC release message. Even in such a case, as in the fourth embodiment, the UE 100 may perform a slice-specific cell reselection procedure according to the instruction information (step S53).

[0180] Secondly, in addition to the case where some of the slice group information included in the RRC release message is not included in SIB 16, there are also cases where the slice group information (e.g., first slice group information) included in SIB 16 differs from the slice group information (e.g., second slice group information) included in the RRC release message. Even in such a case, as in the fifth embodiment, the UE 100 may execute a slice-specific cell reselection procedure according to the instruction information (step S53).

[0181] [Other Embodiments] The gNB 200 may notify the slice support information using an RRC release message. In this case, the difference between SIB16 and the RRC release message can be determined by the methods of the first, second, third, fourth, or fifth embodiments. That is, when the slice support information included in SIB16 differs from the slice support information included in the RRC release message, the UE 100 may use the slice support information included in the RRC release message (first embodiment). The UE 100 may use the slice support information included in SIB16 (second embodiment). The UE 100 may use an AND condition (third embodiment), an OR condition (fourth embodiment), or the gNB 200 may use instruction information (fifth embodiment).

[0182] Furthermore, if slice support information can be notified in an RRC release message, the methods of the first, second, third, fourth, or fifth embodiments can also be applied to slice information including slice support information and slice group information. That is, when the slice information (e.g., first slice information) included in SIB16 differs from the slice information (e.g., second slice information) included in the RRC release message, the UE 100 may use the slice information included in the RRC release message (first embodiment). The UE 100 may use the slice information included in SIB16 (second embodiment). The UE 100 may follow an AND condition (third embodiment), an OR condition (fourth embodiment), or the gNB 200 may instruct by instruction information (fifth embodiment).

[0183] Also, in the first embodiment, an example has been described in which the number of timeouts and the new timer are set from the gNB 300. The example in which the number of timeouts and the new timer are set from the gNB 200 is also applicable to the third embodiment, the fourth embodiment, and the fifth embodiment.

[0184] The above-described operational flows are not limited to being implemented independently, but can also be implemented by combining two or more operational flows. For example, some steps of one operational flow may be added to another operational flow, or some steps of one operational flow may be replaced with some steps of another operational flow. In each flow, it is not necessary to execute all steps, and only some steps may be executed.

[0185] In the above-described embodiments and examples, an example in which the base station is an NR base station (gNB) has been described, but the base station may be an LTE base station (eNB) or a 6G base station. The base station may also be a relay node such as an IAB (Integrated Access and Backhaul) node. The base station may also be a DU of the IAB node. The UE 100 may also be an MT (Mobile Termination) of the IAB node.

[0186] Also, the term "network node" primarily refers to a base station, but may also refer to a device in the core network or part of a base station (CU, DU, or RU).

[0187] 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).

[0188] Furthermore, a program (information processing program) that causes a computer to execute each process or function according to the above-described embodiment may be provided. Alternatively, a program (e.g., a mobile communication program) that causes the mobile communication system 1 to execute each process or function according to the above-described embodiment may be provided. 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-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. Such a recording medium may be memory included in the UE 100 and the gNB 200.

[0189] As used in this disclosure, the terms "based on" and "depending on / in response to" 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." The terms "include," "comprise," and variations thereof 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. Additionally, 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.

[0190] Although the embodiments have 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 without departing from the spirit of the invention. Furthermore, it is also possible to combine the embodiments, operation examples, or processes within a consistent range.

[0191] This application claims priority to U.S. Provisional Application No. 63 / 421,788 (filed November 2, 2022), the entire contents of which are incorporated herein by reference.

[0192] (Appendix 1)

[0193] (Supplementary Note 1) A communication control method in a mobile communication system, comprising: a step in which a network device reports system information; a step in which the network device transmits an RRC release message to a user device; and a step in which the user device executes a slice-specific cell reselection procedure using predetermined information when at least one of the following cases is true: first slice information included in the system information is different from second slice information included in the RRC release message, and first frequency information included in the system information is different from second frequency information included in the RRC release message.

[0194] (Supplementary Note 2) The communication control method according to Supplementary Note 1, wherein the predetermined information is at least one of the second slice information and the second frequency information.

[0195] (Supplementary Note 3) The communication control method described in Supplementary Note 1 or Supplementary Note 2, wherein the executing step includes a step in which the user equipment executes the slice-specific cell reselection procedure using the second slice information and the second frequency information until the user equipment receives the system information, even if a T320 timer expires.

[0196] (Supplementary Note 4) The communication control method according to any one of Supplementary Notes 1 to 3, wherein the predetermined information is at least one of the first slice information and the first frequency information.

[0197] (Appendix 5) A communication control method described in any of Appendices 1 to 4, wherein the specified information is information common to the first slice information and the second slice information, and information common to the first frequency information and the second frequency information.

[0198] (Supplementary Note 6) The communication control method according to any one of Supplementary Notes 1 to 5, wherein the predetermined information is the first slice information, the second slice information, the first frequency information, and the second frequency information.

[0199] (Supplementary Note 7) The communication control method according to any one of Supplementary Notes 1 to 6, further comprising a step in which the network node transmits, to the user equipment, instruction information instructing the predetermined information, and the executing step includes a step in which the user equipment executes the slice-specific cell reselection procedure according to the instruction information.

[0200] (Addendum 2) Introduction In RAN2#119e shown below, the behavior when there is a difference in information for slice-specific cell reselection between SIB16 and dedicated signaling was discussed, but a conclusion was postponed. 5: P1, P2, and P3 of R2-2208519 have been postponed. Is it possible to discuss whether gNB implementations always provide dedicated slice information only for frequencies / NSAGs in SIB16? If not, what should be the applicable UE behavior? R2-2208519 Proposal 1: Even if dedicated slice information is available, if SIB16 is not broadcast, the UE will not perform slice-based cell reselection. Proposal 2: If a frequency is present in the received FreqPriorityListDedicatedSlicing and not present in FreqPriorityListSlicing in SIB16, the UE shall consider that none of the (prioritized) NSAGs can be used on this frequency. Proposal 3: If an nsag-id in FreqPriorityListDedicatedSlicing is not present in FreqPriorityListSlicing in SIB16, the UE shall consider that this (prioritized) NSAG is not supported on the frequency.

[0201] This appendix discusses the behavior when there is a difference in information for slice-specific cell reselection between SIB16 and dedicated signaling (hereinafter RRC release) and the impact on the specifications.

[0202] Discussion Differences between SIB16 and RRC Release IEs Information elements for slice-specific cell reselection in TS38.331 are extracted as shown in Figures 12 and 13.

[0203] The above IEs that can be used / not used between SIB16 and RRC release can be summarized as follows:

[0204] Between SIB16 and RRC release, an IE for slice-specific cell reselection is available.

[0205] The sliceCellList is available in SIB16 but is not available in RRC release according to Table 1.

[0206] Observation 1: The difference between the availability of SIB16 and RRC release is sliceCellListNR, i.e., there is SIB16 but there is no RRC release.

[0207] Other information elements between SIB16 and RRC release, nsag-CellResectionPriority and nsag-CellResectionSubPriority, have already been defined as follows:

[0208] 5.2.4: Cell reselection evaluation process 5.2.4.1: Reselection priority If a field with cellReselectionPriority or nsag-CellReselectionPriority is provided in dedicated signaling, the UE shall ignore the fields with cellReselectionPriority and nsag-CellReselectionPriority provided in the system information.

[0209] Between SIB16 and RRC release, the DL carrier frequency may have different values ​​and nsag-IdentityInfo has the same value, but these IEs are still considered subject to the nsag-CellReselectionPriority as follows: Example 1

[0210] Example 2

[0211]

[0212] Of course, if there is a difference between SIB16 and RRC release, the UE shall use the nsag-CellReselectionPriority and nsag-CellReselectionSubPriority set in RRC release as they are. Therefore, the following observations and suggestions are presented.

[0213] Observation 1: For DL ​​carrier frequency, nsag-IdenityInfo, nsag-CellResectionPriority, and nsag-CellResectionSubPriority, if the values ​​differ between SIB16 and RRC release, the UE should use those values ​​configured in RRC release.

[0214] Therefore, all we need to do is discuss the operation of sliceCellListNR.

[0215] Initially, the principle of homogeneous deployment of slices may be applicable. In Rel-17, RAN2 is aligned with the principle of homogeneity based on the following agreement: However, based on TR38.832, it may not be possible to support slices even if the homogeneous principle is applied.

[0216] Agreement (RAN2#113-bis-e) 1: RAN2 agrees with SA2's assumption that slice support within a TA will be homogeneous in Rel-17 (i.e., all cells in a TA support the same slice availability). If SA2 decides to support heterogeneous deployments, RAN2 may reconsider this. TS38.832 Issue 4: If the serving cell cannot support the requested slice, the serving cell may need to perform a handover to a cell that supports the requested slice or release the RRC connection.

[0217] Therefore, it may not be reasonable for all slices configured in RRC release to be supported, and it is difficult to consider all slices configured in RRC release as unconditionally supported in all cells.

[0218] If sliceCellListNR is present in SIB16, the value of this IE is universal when the UE is configured with slice information in RRC release. Therefore, if SliceCellListNR is not available in RRC release, the UE must check SIB16.

[0219] It is also possible that SIB16 is not broadcast (SIB1 does not have scheduling information for SIB16). In this case, the slice is considered to be supported in all cells. If the slice is partially supported by the cell or not supported by all cells, the gNB only needs to broadcast SIB16, or the gNB does not need to include the slice information in the RRC release (i.e., the UE is considered to be such a gNB implementation).

[0220] Proposal 2: If slice information is set in RRC release, the UE should consider sliceCellListNR to be implicitly the same as SIB16, regardless of whether SIB16 is broadcast or not.

[0221] Regarding the impact on the specification, if SIB16 is broadcast, the current specification is sufficient even without the wording in TS38.304 such as "The UE shall ignore fields with sliceCellListNR provided in the system information." If SIB16 is not broadcast, the behavior is the same as when receiving SIB16 without sliceCellListNR.

[0222] Finally, this appendix discusses the behavior when the values ​​of IEs (i.e., DL carrier frequency, nsag-IdentityInfo, NSAG Cell reselection priority, sliceCellListNR) differ between SIB16 and RRC release. However, since no particular problems are found, there is no need to change the current specifications.

[0223] Proposal 3: For situations where the information for slice-specific cell reselection differs between SIB16 and dedicated signaling, there is no need to change the specifications.

[0224] Whether RRC release only has frequency / NSAG slice information from SIB16. The possibility of a difference in slice-specific cell reselection information between SIB16 and RRC release should be consistent with legacy behavior where information may differ between SIB16 and RRC release. Furthermore, no issues have been observed with this difference.

[0225] Therefore, the principle of the relationship between SIB16 of slice-specific cell reselection information and RRC release should also be independent.

[0226] Proposal 4: The relationship between slice-specific cell reselection information SIB16 and RRC release should be independent, i.e., the information provided in RRC release may differ from the information provided in SIB16.

Claims

1. The user equipment receives an RRC release message from the network, The user equipment receives system information used in a slice-specific cell reselection procedure from the network, When information indicating the correspondence between a slice group and a frequency is included in the RRC release message, among the system information and the RRC release message, only the RRC release message is used to execute the slice-specific cell reselection procedure. A communication control method.

2. The user equipment receives an RRC release message from the network, The user equipment receives system information used in a slice-specific cell reselection procedure from the network, When the first frequency information included in the RRC release message is different from the second frequency information included in the system information, among the first frequency information and the second frequency information, only the first frequency information is used to execute the slice-specific cell reselection procedure. A communication control method.

3. A communication control method in a mobile communication system, The network device notifies system information, The network device transmits an RRC release message to the user equipment, When at least one of the case where the first slice information included in the system information is different from the second slice information included in the RRC release message and the case where the first frequency information included in the system information is different from the second frequency information included in the RRC release message occurs, a slice-specific cell reselection procedure is executed using predetermined information. A communication control method.

4. The predetermined information is at least one of the second slice information and the second frequency information The communication control method according to Claim 3.

5. The execution includes that even when the T320 timer expires, the user equipment executes the slice-specific cell reselection procedure using at least one of the second slice information and the second frequency information. The communication control method according to Claim 4.

6. The predetermined information is at least one of the first slice information and the first frequency information The communication control method according to Claim 3.

7. The predetermined information is information common to the first slice information and the second slice information, and information common to the first frequency information and the second frequency information. The communication control method according to claim 3.

8. The predetermined information is the first slice information and the second slice information, and the first frequency information and the second frequency information. The communication control method according to claim 3.

9. The network device includes transmitting, to the user device, instruction information for instructing the predetermined information. The executing includes the user device executing the slice-specific cell reselection procedure according to the instruction information. The communication control method according to claim 3.

10. A receiving unit that receives, from the network, an RRC release message and system information used in a slice-specific cell reselection procedure; When information indicating a correspondence relationship between a slice group and a frequency is included in the RRC release message, a control unit that executes the slice-specific cell reselection procedure using only the RRC release message among the system information and the RRC release message. User device.