Cell reselection method, user equipment, system, program and chipset

Abstract

This cell reselection method to be used by a user device includes: a step for performing slice-based cell reselection in accordance with the user device receiving, from a network node, slice-specific cell reselection information indicating the cell reselection priority per slice group and per frequency; and a step for determining, on the basis of whether the slice-based cell reselection obtained by applying the slice-specific cell reselection information is being performed, the applicability of highest priority processing in which a frequency or a cell providing a prescribed function different from the slice-based cell reselection is deemed to be the highest priority of cell reselection.

Description

Cell reselection method

[0001] The present disclosure relates to a cell reselection method for use in a mobile communication system.

[0002] The 3GPP (3rd Generation Partnership Project) defines technical specifications for the function of slice-based cell reselection compatible with network slices (see, for example, Non-Patent Document 1).

[0003] 3GPP Technical Specification: TS 38.304 V17.1.0

[0004] A cell reselection method according to a first aspect is a cell reselection method used in a user equipment, and includes the steps of: performing slice-based cell reselection in response to the user equipment receiving slice-specific cell reselection information indicating cell reselection priority for each slice group and each frequency from a network node; and determining whether to apply a highest priority process that considers a frequency or cell that provides a predetermined function different from the slice-based cell reselection as having the highest priority for cell reselection, based on whether the slice-based cell reselection is being performed using the slice-specific cell reselection information.

[0005] A cell reselection method according to a second aspect is a cell reselection method used in a user equipment, and includes the steps of: performing slice-based cell reselection applying slice-specific cell reselection information indicating cell reselection priority for each slice group and each frequency, in response to the user equipment receiving the slice-specific cell reselection information from a network node; and acquiring from the network node or a NAS (Non-Access Stratum) setting information for setting whether or not to apply highest priority processing, in which a frequency or cell that provides a predetermined function different from the slice-based cell reselection is considered to have the highest priority for cell reselection.

[0006] A cell reselection method according to a third aspect is a cell reselection method used in a user equipment, and includes the steps of: transmitting preference information to a network indicating the user equipment's preference as to whether slice-based cell reselection or a predetermined function different from the slice-based cell reselection should be prioritized in cell reselection; and controlling the slice-based cell reselection and a highest priority process in which a frequency or a cell that provides the predetermined function is considered to have the highest priority for cell reselection, depending on configuration information received from the network based on the preference information.

[0007] A cell reselection method according to a fourth aspect is a cell reselection method used in a user equipment, and includes the steps of: acquiring priority slice group information indicating a priority slice group from a non-access stratum (NAS); checking whether information indicating a predetermined function different from the slice-based cell reselection is included in any of the slice groups indicated by the priority slice group information; and, in response to the information indicating the predetermined function being included in any of the slice groups, regarding the slice group including the information indicating the predetermined function or the frequency providing the predetermined function as having the highest priority in cell reselection.

[0008] A cell reselection method according to a fifth aspect is a cell reselection method used in a user equipment, and includes the steps of: acquiring priority slice group information indicating a priority slice group from a NAS (Non-Access Stratum); executing a predetermined function different from the slice-based cell reselection; receiving slice-specific cell reselection information indicating a cell reselection priority for each slice group and each frequency from a network node; and regarding a frequency that provides the predetermined function as the highest priority in cell reselection, among the frequencies for which the cell reselection priority is set in the slice-specific cell reselection information for the highest priority slice group indicated by the priority slice group information.

[0009] 1 is a diagram showing the configuration of a mobile communication system according to an embodiment. FIG. 2 is a diagram showing the configuration of a UE (user equipment) according to an embodiment. FIG. 3 is a diagram showing the configuration of a gNB (base station) according to an embodiment. FIG. 4 is a diagram showing the configuration of a protocol stack of a radio interface of a user plane that handles data. 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). FIG. 6 is a diagram for explaining a general cell reselection procedure. FIG. 7 is a diagram showing a schematic flow of a general cell reselection procedure. FIG. 8 is a diagram showing an example of network slicing. FIG. 9 is a diagram for explaining an overview of slice-based cell reselection. FIG. 10 is a diagram showing an example of slice-specific cell reselection information. FIG. 11 is a diagram showing an example of operation of a UE according to a first operation pattern. FIG. 12 is a diagram showing an example of operation of a mobile communication system according to a second operation pattern. FIG. 13 is a diagram showing an example of operation of a mobile communication system according to a third operation pattern. FIG. 14 is a diagram showing an example of operation of a UE according to a fourth operation pattern. FIG. 15 is a diagram showing an example of operation of a UE according to a fifth operation pattern.

[0010] 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.

[0011] (1) System Configuration First, the configuration of a mobile communication system 1 according to an embodiment will be described. FIG. 1 is a diagram showing the configuration of the mobile communication system 1 according to an embodiment. The mobile communication system 1 conforms to the 5th Generation System (5GS) of the 3GPP standard. In the following description, 5GS will be used as an example, but the mobile communication system may also be at least partially based on an LTE (Long Term Evolution) system. The mobile communication system may also be at least partially based on a 6th Generation (6G) system.

[0012] 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. The RAN 10 and the CN 20 constitute the network of the mobile communication system 1.

[0013] 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).

[0014] The NG-RAN 10 includes a base station (referred to as "gNB" in the 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 the 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, etc. 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").

[0015] In addition, gNBs can also be connected to the Evolved Packet Core (EPC), which is the core network of LTE. LTE base stations can also be connected to 5GC. LTE base stations and gNBs can also be connected via an inter-base station interface.

[0016] The 5GC20 includes an AMF (Access and Mobility Management Function) and a UPF (User Plane Function) 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.

[0017] 2 is a diagram showing the configuration of a UE 100 (user equipment) according to an 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.

[0018] 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.

[0019] 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.

[0020] The control unit 130 performs various controls and processes in the UE 100. Such processes include processes of each layer described below. The operations of the UE 100 described above and below may be operations under the control of the control unit 230. 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 processing by the processor. The processor may include a baseband processor and a CPU (Central Processing Unit). The baseband processor performs modulation / demodulation and encoding / decoding of baseband signals. The CPU executes programs stored in the memory to perform various processes.

[0021] 3 is a diagram showing the configuration of a gNB 200 (base station) according to an 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.

[0022] 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.

[0023] 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.

[0024] The control unit 230 performs various controls and processes in the gNB 200. Such processes include processes for each layer described below. The operations of the gNB 200 described above and below may be operations under the control of the control unit 230. 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 processing by the processor. The processor may include a baseband processor and a CPU. The baseband processor performs modulation / demodulation and encoding / decoding of baseband signals. The CPU executes programs stored in the memory to perform various processes.

[0025] 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.

[0026] FIG. 4 is a diagram showing the configuration of a protocol stack of a radio interface of a user plane that handles data.

[0027] 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.

[0028] The PHY layer performs encoding / decoding, modulation / demodulation, antenna mapping / demapping, and resource mapping / demapping. Data and control information are transmitted between the PHY layer of UE100 and the PHY layer of gNB200 via a physical channel. The PHY layer of UE100 receives downlink control information (DCI) transmitted from gNB200 on a physical downlink control channel (PDCCH). Specifically, UE100 performs blind decoding of the PDCCH using a radio network temporary identifier (RNTI) and acquires the successfully decoded DCI as DCI addressed to the UE. The DCI transmitted from gNB200 has a CRC parity bit scrambled by the RNTI added.

[0029] 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.

[0030] 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.

[0031] The PDCP layer performs header compression / decompression, encryption / decryption, and the like.

[0032] 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.

[0033] 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).

[0034] The protocol stack of the radio interface of the control plane has an RRC (Radio Resource Control) layer and an NAS (Non-Access Stratum) layer instead of the SDAP layer shown in FIG.

[0035] 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.

[0036] The NAS layer (also simply referred to as "NAS") located above the RRC layer performs session management, mobility management, etc. NAS signaling is transmitted between the NAS layer of the UE 100 and the NAS layer of the AMF 300A. Note that the UE 100 has an application layer and the like in addition to the radio interface protocol. Also, a layer lower than the NAS layer is referred to as the AS layer (also simply referred to as "AS").

[0037] (2) Slice-Based Cell Reselection Next, slice-based cell reselection according to the embodiment will be described.

[0038] (2.1) General Cell Reselection Procedure Figure 6 is a diagram for explaining a general cell reselection procedure. UE100 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, UE100 identifies a neighboring cell on which it should camp by the cell reselection procedure and reselects the identified neighboring cell. When the current serving cell and the neighboring cell have the same frequency (carrier frequency), this is called intra-frequency, and when the current serving cell and the neighboring cell have different frequencies (carrier frequencies), this is called inter-frequency. The current serving cell and the neighboring cell may be managed by the same gNB200. The current serving cell and the neighboring cell may be managed by different gNB200.

[0039] FIG. 7 shows a schematic flow diagram of a typical cell reselection procedure.

[0040] In step S10, UE100 performs frequency prioritization processing based on a priority (also referred to as "absolute priority" or "cell reselection priority") for each frequency specified by gNB200, for example, by a system information block (SIB) or an RRC release message. Specifically, UE100 manages the frequency priority specified by gNB200 for each frequency.

[0041] In step S20, 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.

[0042] In step S30, 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 S20. 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.

[0043] (2.2) 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."

[0044] Network slicing enables carriers 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.

[0045] FIG. 8 is a diagram illustrating an example of network slicing.

[0046] 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.

[0047] 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).

[0048] Alternatively, 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. Such a slice group is called a Network Slice AS Group (NSAG).

[0049] (2.3) Overview of Slice-Based Cell Reselection FIG. 9 is a diagram for explaining an overview of slice-based cell reselection.

[0050] The gNB 200 transmits slice-specific cell reselection information to the UE 100 (AS) in an SIB16 and / or an RRC Release message specified by RRC. The slice-specific cell reselection information can include a reselection priority for each frequency and each NSAG, and a list of cells in which the slice of the NSAG is supported or not supported. In the UE 100, the NAS provides the AS with preferred NSAG information (also referred to as "preferred slice group information") including the NSAG and its priority (priority to be considered during cell reselection).

[0051] If UE100 supports slice-based cell reselection and slice-specific cell reselection information is provided to UE100 (AS) from gNB200, UE100 uses the slice-specific cell reselection information. In UE100, if slice-specific cell reselection information is not provided from gNB200 for any NSAG that the AS has acquired from the NAS and is not taken into account during cell reselection, UE100 uses general cell reselection information that is not slice-specific.

[0052] The slice-specific cell reselection information includes information indicating a correspondence relationship between an NSAG, a frequency, and a cell reselection priority. For example, the slice-specific cell reselection information indicates, for each NSAG, a frequency (one or more frequencies) that supports the NSAG and a cell reselection priority (also referred to as a "slice-specific cell reselection priority") assigned to each frequency. An example of the slice-specific cell reselection information is shown in Figure 10. The number indicated by "#" in Figure 10 may be an identifier of the NSAG.

[0053] In the example shown in Fig. 10, three frequencies F1, F2, and F4 are associated with NSAG #1 as frequencies supporting NSAG #1. Of these three frequencies, the slice-specific cell reselection priority of F1 is "6," the slice-specific cell reselection priority of F2 is "4," and the slice-specific cell reselection priority of F4 is "2." In the example of Fig. 10, the slice-specific cell reselection priority is any one of 0 to 7, and the larger the number, the higher the priority.

[0054] Furthermore, three frequencies F1, F2, and F3 are associated with NSAG #2 as frequencies supporting NSAG #2. Of these three frequencies, the slice-specific cell reselection priority of F1 is "0", the slice-specific cell reselection priority of F2 is "5", and the slice-specific cell reselection priority of F3 is "7".

[0055] Furthermore, three frequencies, F1, F3, and F4, are associated with NSAG #3 as frequencies supporting NSAG #3. Of these three frequencies, the slice-specific cell reselection priority of F1 is "3," the slice-specific cell reselection priority of F3 is "7," and the slice-specific cell reselection priority of F4 is "2."

[0056] (3) Highest Priority Processing in Cell Reselection Next, the highest priority processing in cell reselection according to the embodiment will be described.

[0057] The UE 100 performs a highest priority process in which a frequency or a cell that provides a predetermined function different from slice-based cell reselection is considered to have the highest priority for cell reselection. The highest priority may be a priority higher than 0 to 7, which are cell reselection priorities (also referred to as "network-configured priorities") that can be configured for the UE 100 by the network.

[0058] For example, the predetermined functions to which the highest priority process is applied include Multicast / Broadcast Services (MBS), sidelink communication, and a High Speed ​​Dedicated Network (HSDN). In the embodiment, the UE 100 supports at least one feature among the MBS, sidelink communication, and HSDN. Note that the sidelink communication may include sidelink discovery.

[0059] A UE 100 in an RRC idle state or an RRC inactive state that supports MBS applies the normal cell reselection rules with the following modifications. Specifically, a UE 100 that is receiving or interested in receiving MBS broadcast services via PTM (Point-to-Multipoint) is permitted to set a frequency that provides these MBS broadcast services as the highest priority (higher than the priority of other network settings) when it can receive these MBS broadcast services only by camping on the frequency. If an MBS broadcast service that the UE 100 is interested in becomes unavailable (after the session ends) or if the UE 100 is no longer interested in receiving the broadcast service, the UE 100 will no longer prioritize the frequency. Furthermore, a UE 100 that is receiving or interested in receiving MBS broadcast services via PTM is permitted to set a frequency on which it cannot receive these MBS broadcast services as the lowest priority (lower than the priority of other network settings).

[0060] A UE 100 that supports sidelink communication and is interested in V2X services may consider whether NR and / or V2X sidelink communication is supported by the cell when performing cell reselection in an RRC idle or RRC inactive state. The UE 100 may consider the following carrier frequencies as the highest priority (higher than the priorities of other network configurations): - frequencies that provide both NR and V2X sidelink communication configurations when configured to perform both, - frequencies that provide NR sidelink communication configurations when configured to perform only NR sidelink communication, and - frequencies that provide V2X sidelink communication configurations when configured to perform only V2X sidelink communication.

[0061] A UE 100 that supports HSDN and is in a high-speed moving state in an RRC idle state or an RRC inactive state always regards an HSDN cell as the highest priority (higher than the priorities of other network settings). Also, a UE 100 that is not in a high-speed moving state always regards an HSDN cell as the lowest priority (lower than the priorities of other network settings).

[0062] (4) Operation According to the Embodiment As described above, in slice-based cell reselection, preferred slice group information (NSAG priority) is set in the AS of the UE 100 from the NAS (from another perspective, the AMF 300A), and slice-specific cell reselection priority is set from the gNB 200. The AS of the UE 100 performs slice-based cell reselection by applying the slice-specific cell reselection priority corresponding to the preferred NSAG as the cell reselection priority.

[0063] On the other hand, for each function (each service) of the sidelink, HSDN, and MBS, the UE 100 can perform a highest priority process in which the frequency providing the function (each service) is considered to be the highest priority depending on various conditions. Such a highest priority process may conflict with the cell reselection priority determined by slice-based cell reselection. For example, if the UE 100 considers the MBS frequency to be the highest priority, the UE 100 will perform cell reselection using a cell reselection priority that is different from the slice-specific cell reselection priority.

[0064] Hereinafter, first to fifth operation patterns according to the embodiment will be described. The UE 100 is assumed to be in an RRC idle state or an RRC inactive state except when communicating dedicated signaling (e.g., an RRC Release message, an RRC Reconfiguration message) with the network. Of the first to fifth operation patterns, any one of the operation patterns may be implemented alone, or two or more operation patterns may be implemented in combination.

[0065] (4.1) First Operation Pattern In the first operation pattern according to the embodiment, the UE 100 (AS) performs slice-based cell reselection in response to receiving slice-specific cell reselection information indicating cell reselection priority for each NSAG and each frequency from the gNB 200. The UE 100 (AS) determines whether to apply the highest priority process in which a frequency or cell providing a predetermined function (e.g., a sidelink, HSDN, or MBS) is considered to have the highest priority for cell reselection, based on whether slice-based cell reselection is being performed to which the slice-specific cell reselection information is applied.

[0066] Specifically, UE100 (AS) is not permitted to consider any frequency as the highest priority when applying the slice-specific cell reselection priority included in the slice-specific cell reselection information provided by gNB200. In other words, when UE100 (AS) applies the slice-specific cell reselection priority included in the slice-specific cell reselection information provided by gNB200, the highest priority processing is disabled (i.e., prohibited).

[0067] The UE100 (AS) acquires priority NSAG information indicating a priority NSAG from the NAS. Even if the UE100 (AS) acquires priority NSAG information from the NAS, if the UE100 (AS) has not received slice-specific cell reselection information (slice-specific cell reselection priority) from the gNB200, it may determine that the highest priority process can be applied (i.e., enabled) and apply the highest priority process. If the UE100 (AS) has not received slice-specific cell reselection information (slice-specific cell reselection priority) from the gNB200, the UE100 (AS) cannot perform slice-based cell reselection. Therefore, even if priority NSAG information is set in the AS from the NAS, if the UE100 (AS) has not received slice-specific cell reselection information (slice-specific cell reselection priority) from the gNB200, the highest priority process can be applied. This makes it easier for the UE100 to use the desired function through the highest priority process. Furthermore, if the UE100 (AS) has not acquired priority NSAG information from the NAS, even if slice-specific cell reselection information (slice-specific cell reselection priority) is received from the gNB200, it may determine that the highest priority processing can be applied (i.e., enabled), and apply the highest priority processing. If priority NSAG information is not acquired from the NAS, the UE100 (AS) cannot perform slice-based cell reselection. Therefore, if priority NSAG information is not set in the AS from the NAS, even if the UE100 (AS) receives slice-specific cell reselection information (slice-specific cell reselection priority) from the gNB200, the highest priority processing can be applied.

[0068] The enabling / disabling of the highest priority processing related to this operation pattern may apply to all functions of sidelink, HSDN, and MBS (i.e., common enabling / disabling), or may be done separately for each function (i.e., enabling / disabling for each function).

[0069] FIG. 11 is a diagram illustrating an example of the operation of the UE 100 according to the first operation pattern.

[0070] In step S101, the UE 100 (AS) is set with an NSAG priority from the NAS (AMF 300A). The UE 100 may be set with a slice-specific cell reselection priority from the gNB 200. The UE 100 (AS) acquires the NSAG priority from the NAS (AMF 300A) and the slice-specific cell reselection priority from the gNB 200, thereby becoming capable of executing slice-based cell reselection.

[0071] In step S102, the UE 100 (AS) enters a state in which the highest priority process by a predetermined function is possible. For example, the UE 100 (AS) enters one of the following states: Sidelink (V2X sidelink / NR sidelink): Sidelink communication is set or the UE 100 (AS) is interested in sidelink communication, HSDN: The UE 100's movement speed is in a high-speed movement state, or MBS: The UE 100 is interested in receiving an MBS session.

[0072] That is, in step S102, the UE 100 is in a state where it may regard a specific frequency or a specific cell as having the highest priority.

[0073] In step S103, the UE 100 (AS) checks whether the slice-specific cell reselection priority specified in the slice-based cell reselection is applied to the current cell reselection priority. That is, the UE 100 (AS) checks whether slice-based cell reselection (cell reselection associated with slice-based cell reselection) is being performed. Alternatively, the UE 100 (AS) may check whether it has preferred NSAG information (that is, whether preferred NSAG information is set to the UE 100 (NAS) from the AMF 300A).

[0074] If the result of step S103 is YES, in step S104, the UE 100 (AS) does not regard the specific frequency or the specific cell in step S102 as the highest priority, and performs cell reselection by applying (adopting) the slice-specific cell reselection priority in slice-based cell reselection. That is, the UE 100 (AS) does not perform the highest priority processing by the predetermined function.

[0075] On the other hand, if the result of step S103 is NO, in step S105, the UE 100 (AS) adopts the highest priority process and performs cell reselection by regarding the specific frequency or the specific cell in step S102 as the highest priority. That is, the UE 100 (AS) performs the highest priority process using a predetermined function.

[0076] In this operation pattern, it may be considered whether a predetermined cell whose radio quality meets a predetermined criterion supports a prioritized NSAG. The predetermined cell may be a cell (serving cell) on which the UE 100 is camped and / or a candidate cell (for example, a cell with the highest rank (highest ranked cell)). The UE 100 (AS) may determine that the highest priority processing is applicable in accordance with the fact that a predetermined cell whose radio quality meets a predetermined criterion does not support a prioritized NSAG. That is, if the highest ranked cell (which may be the currently camped cell) does not support the desired slice (NSAG with a high priority by the NAS), the UE 100 (AS) may consider the frequency or cell that provides the predetermined function as the highest priority. In this case, the UE 100 (AS) may perform frequency prioritization processing (priority handling) again.

[0077] (4.2) Second operation pattern In the second operation pattern of the embodiment, gNB200 can set to UE100 whether or not to allow highest priority processing using a specified function (i.e., whether or not to prioritize highest priority processing using a specified function over slice-specific cell reselection priority).

[0078] In this operation pattern, the UE100 (AS) performs slice-based cell reselection applying the slice-specific cell reselection information in response to receiving slice-specific cell reselection information indicating cell reselection priority (slice-specific cell reselection priority) for each NSAG and each frequency from the gNB200. The UE100 (AS) acquires from the gNB200 or NAS (from another perspective, the AMF300A) setting information for setting whether or not to apply the highest priority process in which a frequency or cell that provides a predetermined function different from the slice-based cell reselection is considered to have the highest priority for cell reselection. This allows the UE100 (AS) to appropriately perform slice-based cell reselection and / or highest priority processing under the management of the network.

[0079] The predetermined function includes a plurality of functions (for example, a side link, an HSDN, and an MBS). The configuration information may be information that sets whether or not to apply the highest priority process for each function. That is, the gNB 200 (or the AMF 300A) may set (notify) the UE 100 whether or not to allow the highest priority process for each MBS / HSDN / side link.

[0080] The configuration information may be information for setting which of slice-based cell reselection and highest priority processing is to be prioritized in cell reselection. The configuration information may be information for setting priorities in cell reselection for slice-based cell reselection and each of a plurality of functions (e.g., sidelink, HSDN, and MBS) included in the predetermined function.

[0081] FIG. 12 is a diagram showing an example of operation of the mobile communication system 1 according to the second operation pattern.

[0082] In step S201, the gNB 200 transmits to the UE 100 (AS) configuration information indicating whether or not to permit processing that regards the cell reselection priority as the highest priority. The UE 100 (AS) receives the configuration information. Here, the gNB 200 may transmit the configuration information in an SIB, an RRC Release message, an RRC Reconfiguration message, or a newly defined message.

[0083] Alternatively, in step S201, the AMF 300A may transmit, to the UE 100 (NAS), configuration information indicating whether or not to permit processing in which the cell reselection priority is regarded as the highest priority, by NAS signaling. In the UE 100, the NAS may notify the AS of the configuration information.

[0084] The setting information includes at least one of the following information (a1) to (c1).

[0085] (a1) Information indicating whether to allow highest priority processing: The information may be information indicating whether to allow application of the highest priority (i.e., highest priority processing by a predetermined function) to the cell reselection priority. The information may be information indicating whether to prioritize the slice-specific cell reselection priority over the highest priority processing. The information may be information indicating whether to allow application of the highest priority when the slice-specific cell reselection priority (or the NSAG priority by the NAS) is set.

[0086] (b1) Information indicating whether or not to allow highest priority processing for each function: This information may be, for example, information that sets whether or not to allow highest priority processing for each MBS / HSDN / V2X sidelink / NR sidelink.

[0087] (c1) Information indicating priority (priority order) for each function: This information may be information that sets a priority order for each of MBS / HSDN / V2X sidelink / NR sidelink / slice-based cell reselection. Here, slice-based cell reselection may further be a priority order for each NSAG. For example, the information may indicate that NSAG #1 has a higher priority than MBS, but NSAG #2 has a lower priority than MBS. Slice-based cell reselection may further be a priority order for each slice. For example, the information may indicate that NSSAI #1 has a higher priority than MBS, but NSSAI #2 has a lower priority than MBS. Note that, for the NSAG to which the NSSAI belongs, the concept of priority in the NSAG one level above the NSAG may be applied (reused).

[0088] The information may be information that sets whether to prioritize each of MBS / HSDN / V2X sidelink / NR sidelink for slice-based cell reselection, or information that sets whether to prioritize slice-based cell reselection over other functions.

[0089] In step S202, the UE 100 (AS) performs cell reselection control based on the setting information received in step S201.

[0090] For example, when UE100 (AS) sets the priority of MBS higher than slice-based cell reselection and regards the MBS frequency as the highest priority, the highest priority is regarded as a higher priority than the cell reselection priority (0 to 7) in slice-based cell reselection.

[0091] Furthermore, for example, when the priority of the V2X sidelink is set lower than that of slice-based cell reselection, when the UE 100 (AS) regards the V2X sidelink frequency as the highest priority, the highest priority is regarded as a priority lower than the cell reselection priority (0 to 7) in slice-based cell reselection.

[0092] Furthermore, for example, if the cell reselection priority for slice-based cell reselection of a frequency is 5, the highest priority for a V2X sidelink frequency is considered to be 4.

[0093] (4.3) Third Operation Pattern In the second operation pattern described above, it is assumed that the gNB200 and / or the AMF300A are aware in advance of the functions (user preferences) that the UE100 wants to prioritize. However, it is also assumed that such an assumption does not hold. There is a concern that both the gNB200 and the AMF300A do not know which is better in terms of user experience, for example, whether it is better to prioritize NSAG (i.e., a function that uses slices such as URLLC) or MBS. Therefore, there is a possibility that the gNB200 and / or the AMF300A may make inappropriate settings for the UE100, which may cause problems such as the user being unable to access the functions that they really want to prioritize.

[0094] In this operation pattern, the UE 100 transmits preference information indicating the UE 100's preference for which of slice-based cell reselection and a predetermined function (highest priority processing) to prioritize in cell reselection to the network (gNB 200 or AMF 300A). The UE 100 (AS) controls the slice-based cell reselection and the highest priority processing according to the configuration information received from the network based on the preference information. Note that this operation pattern may be an operation performed prior to the operation of the second operation pattern described above. The preference information may be information indicating a priority preference in cell reselection for slice-based cell reselection and each of a plurality of functions (e.g., MBS / HSDN / V2X sidelink / NR sidelink).

[0095] FIG. 13 is a diagram showing an example of operation of the mobile communication system 1 according to the third operation pattern.

[0096] In step S301, the UE 100 (AS) in the RRC connected state transmits preference information indicating a preference for the priority of the function to the gNB 200. The UE 100 (AS) may transmit the preference information by including it in an RRC message, for example, a UE AS Assistance Information message, an MBS Interest Indication message, or a newly defined message. Alternatively, in step S301, the UE 100 (NAS) may transmit the preference information to the AMF 300A by NAS signaling.

[0097] The preference information includes at least one of the following information (a2) to (c2):

[0098] (a) Information indicating priority for each function: This information may be, for example, priority for each of MBS / HSDN / V2X sidelink / NR sidelink / slice-based cell reselection. Note that slice-based cell reselection may be regarded as a slice-based cell reselection function, or as a function assigned to each slice configured in slice-based cell reselection.

[0099] Slice-based cell reselection may further be performed for each NSAG. For example, information may be provided that NSAG #1 has a higher priority than MBS, but NSAG #2 has a lower priority than MBS. Alternatively, information may be provided that NSAG #1 may perform the highest priority process, but NSAG #2 does not allow the highest priority process.

[0100] Slice-based cell reselection may further be performed for each slice. For example, information may be provided that NSSAI #1 has a higher priority than MBS, but NSSAI #2 has a lower priority than MBS. For the NSAG to which the NSSAI belongs, the concept of priority in the NSAG one level above the NSAG may be applied (reused).

[0101] For example, when a slice for V2X (= a slice whose slice type is V2X) is set to be prioritized, a process may be performed in which a frequency that provides a V2X function is considered to have the highest priority (may be considered to be permitted). Additionally, when MBS and / or HSDN, etc. are defined as slice types, a frequency that provides a function designated by the slice type may similarly be considered to have the highest priority. In other words, a frequency that provides an associated function may be permitted to be considered to have the highest priority depending on the slice type and the priority of each slice.

[0102] (b2) Information indicating whether or not to perform highest priority processing for each function: This information may be, for example, information indicating a preference as to whether or not to perform highest priority processing for each of MBS / HSDN / V2X sidelink / NR sidelink.

[0103] (c2) Information indicating priority (priority order) for each function: The information may be information indicating priority order preference for each of MBS / HSDN / V2X sidelink / NR sidelink / slice-based cell reselection.

[0104] In the UE 100, priority information for each function may be notified to the AS from an upper layer (application or NAS).

[0105] The priority information for each function may be notified from the AMF 300A to the UE 100 (NAS). In the UE 100, the priority information notified from the NAS to the AS may be notified from the AS to the gNB 200.

[0106] The gNB 200 that received the preference information in step S301 may store the preference information as a UE context. The gNB 200 may transmit a response (setting) to the UE 100 indicating whether or not to permit the preference information. For example, when permission is set in an RRC Reconfiguration message or an RRC Release message, the UE 100 (AS) may transition to an RRC idle state or an RRC inactive state, and then perform a cell reselection priority determination process according to the permission information.

[0107] In step S302, the gNB 200 may perform cell reselection-related settings for the UE 100 (AS) based on the preference information received in step S301. For example, the gNB 200 may set cell reselection priority in slice-based cell reselection in an RRC Release message.

[0108] (4.4) Fourth Operation Pattern In this operation pattern, slice-based cell reselection allows UE 100 to prioritize functions of interest (e.g., V2X sidelink communication or MBS). The SST in the NSAG / S-NSSAI notified from the NAS to the AS in UE 100 includes standard-defined and operator-defined service type information. If the service indicated by the SST corresponds to a function that UE 100 (AS) desires to consider as the highest priority, UE 100 (AS) considers the cell reselection priority of the frequency providing the service to be the highest priority, or considers the NSAG priority of the NSAG to be the highest priority. This allows slice-based cell reselection and highest priority processing to be compatible.

[0109] That is, in this operation pattern, UE100 (AS) acquires priority NSAG information indicating a priority NSAG from the NAS. UE100 (AS) checks whether information indicating a predetermined function (specifically, a function in which UE100 is interested) is included in any of the NSAGs indicated by the priority NSAG information from the NAS. Then, UE100 (AS) determines that the information indicating the predetermined function is included in any of the NSAGs, and considers the NSAG including the information indicating the predetermined function or the frequency providing the predetermined function to be the highest priority in cell reselection.

[0110] FIG. 14 is a diagram illustrating an example of an operation of the UE 100 according to the fourth operation pattern.

[0111] In step S401, UE100 (AS) acquires preferred NSAG information from NAS. UE100 (AS) also receives slice-specific cell reselection information from gNB200.

[0112] In step S402, UE 100 (AS) checks the S-NSSAI in each NSAG included in the priority NSAG information acquired in step S401, and determines the service content from the SST in the S-NSSAI.

[0113] In step S403, the UE 100 (AS) identifies a particular function of interest to it (e.g., MBS or V2X sidelink communication).

[0114] In step S404, the UE 100 (AS) checks whether the specific function identified in step S403 matches any of the service contents identified in step S402.

[0115] If the result of step S404 is YES, in step S405, the UE 100 (AS) may regard the NSAG priority of the NSAG having the matching service content as the highest priority. In this case, the UE 100 (AS) may apply the cell reselection priority of the slice-based cell reselection corresponding to the NSAG to each frequency, and perform cell reselection.

[0116] Alternatively, in step S405, for an NSAG with the highest NSAG priority, if the SST (service content) of the S-NSSAI in the NSAG matches a specific function identified in step S403, UE100 (AS) may perform cell reselection by considering the frequency that provides the specific function as the highest priority based on the slice-specific cell reselection information.

[0117] On the other hand, if the answer is NO in step S404, in step S406, UE100 (AS) may perform normal slice-based cell reselection as specified in the current technical specifications.

[0118] (4.5) Fifth Operation Pattern In this operation pattern, UE100 (AS) identifies the frequency for which cell reselection priority is set in the slice-specific cell reselection information received from gNB200 for the highest priority NSAG indicated by the priority NSAG information acquired from NAS. Then, UE100 (AS) considers the frequency that provides a predetermined function of interest to itself among the identified frequencies as the highest priority in cell reselection. This makes it possible to achieve both slice-based cell reselection and highest priority processing.

[0119] FIG. 15 is a diagram illustrating an example of an operation of the UE 100 according to the fifth operation pattern.

[0120] In step S501, UE 100 (AS) acquires preferred NSAG information from NAS.

[0121] In step S502, the UE 100 (AS) identifies a particular function of interest to it (e.g., MBS or V2X sidelink communication).

[0122] In step S503, UE100 (AS) receives slice-specific cell reselection information from gNB200, for example, via SIB16.

[0123] In step S504, UE100 (AS) checks the frequency to which cell reselection priority is set based on slice-specific cell reselection information for the highest priority NSAG indicated by the priority NSAG information acquired from the NAS.

[0124] In step S505, the UE 100 (AS) checks whether the frequency confirmed in step S504 matches the frequency that provides the specific function identified in step S502. If the result of step S505 is YES, in step S506, the UE 100 (AS) determines that the cell reselection priority of the frequency is the highest priority.

[0125] On the other hand, if the result of step S505 is NO, in step S507, the UE 100 (AS) may perform normal slice-based cell reselection as defined in the current technical specifications. Here, the UE 100 (AS) determines not to apply the highest priority process and applies the cell reselection priority in slice-based cell reselection to each frequency.

[0126] (5) Other Embodiments In the embodiment, an example of processing with the highest priority is shown, but it may also be applied to processing with the lowest priority. The above-described operational flows are not limited to being implemented separately and independently, but may 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.

[0127] 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.

[0128] 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).

[0129] 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).

[0130] 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.

[0131] The above describes the embodiments in detail with reference to the drawings, but the specific configuration is not limited to that described above, and various design changes can be made within the scope that does not deviate from the gist of the invention.

[0132] This application claims priority to U.S. Provisional Application No. 63 / 411,245 (filed September 29, 2022), the entire contents of which are incorporated herein by reference.

[0133] (6) Supplementary Notes The following are additional notes regarding the features of the above-described embodiment.

[0134] (Supplementary Note 1) A cell reselection method used in a user equipment, comprising: a step of performing slice-based cell reselection in response to the user equipment receiving slice-specific cell reselection information indicating cell reselection priority for each slice group and each frequency from a network node; and a step of determining whether to apply a highest priority process that considers a frequency or cell that provides a predetermined function different from that of the slice-based cell reselection as having the highest priority for cell reselection, based on whether the slice-based cell reselection is being performed using the slice-specific cell reselection information.

[0135] (Supplementary Note 2) The cell reselection method according to Supplementary Note 1, further comprising the step of acquiring priority slice group information indicating a priority slice group from a NAS (Non-Access Stratum), wherein the determining step includes the step of determining that the highest priority processing is applicable when the slice-specific cell reselection information has not been received from the network node even if the priority slice group information has been acquired from the NAS.

[0136] (Supplementary Note 3) The cell reselection method according to Supplementary Note 1 or 2, further comprising: determining that the highest priority process is applicable in response to a predetermined cell whose radio quality satisfies a predetermined criterion not supporting the prioritized slice group.

[0137] (Supplementary Note 4) A cell reselection method used in a user equipment, comprising: a step of performing slice-based cell reselection applying slice-specific cell reselection information indicating cell reselection priority for each slice group and each frequency, in response to the user equipment receiving the slice-specific cell reselection information from a network node; and a step of acquiring, from the network node or a NAS (Non-Access Stratum), setting information for setting whether to apply highest priority processing, in which a frequency or a cell that provides a predetermined function different from the slice-based cell reselection is considered to have the highest priority for cell reselection.

[0138] (Supplementary Note 5) The cell reselection method according to Supplementary Note 4, wherein the predetermined function includes a plurality of functions, and the setting information is information that sets whether or not the highest priority process is applicable for each of the functions.

[0139] (Supplementary Note 6) The cell reselection method according to Supplementary Note 4, wherein the setting information is information for setting which of the slice-based cell reselection and the highest priority process is to be prioritized in cell reselection.

[0140] (Supplementary Note 7) The cell reselection method described in Supplementary Note 4, wherein the predetermined function includes a plurality of functions, and the setting information is information that sets priorities in cell reselection for the slice-based cell reselection and each of the plurality of functions included in the predetermined function.

[0141] (Supplementary Note 8) A cell reselection method used in a user equipment, comprising: a step of transmitting preference information to a network indicating a preference of the user equipment as to which of slice-based cell reselection and a predetermined function different from the slice-based cell reselection should be prioritized in cell reselection; and a step of controlling the slice-based cell reselection and a highest priority process that considers a frequency or a cell that provides the predetermined function as the highest priority for cell reselection in accordance with configuration information received from the network based on the preference information.

[0142] (Supplementary Note 9) The cell reselection method according to Supplementary Note 8, wherein the predetermined function includes a plurality of functions, and the preference information is information indicating a priority preference in cell reselection for the slice-based cell reselection and each of the plurality of functions.

[0143] (Supplementary Note 10) A cell reselection method for use in a user equipment, comprising: a step of acquiring priority slice group information indicating a priority slice group from a non-access stratum (NAS); a step of checking whether information indicating a predetermined function different from the slice-based cell reselection is included in any of the slice groups indicated by the priority slice group information; and a step of regarding the slice group including the information indicating the predetermined function or a frequency providing the predetermined function as having the highest priority in cell reselection, in response to the information indicating the predetermined function being included in any of the slice groups.

[0144] (Supplementary Note 11) A cell reselection method for use in a user equipment, comprising: a step of acquiring priority slice group information indicating a priority slice group from a NAS (Non-Access Stratum); a step of executing a predetermined function different from the slice-based cell reselection; a step of receiving slice-specific cell reselection information indicating cell reselection priority for each slice group and each frequency from a network node; and a step of regarding a frequency that provides the predetermined function as the highest priority in cell reselection, among frequencies for which the cell reselection priority is set in the slice-specific cell reselection information for the highest priority slice group indicated by the priority slice group information.

[0145] (Supplementary Note 12) The cell reselection method according to any one of Supplementary Notes 1 to 11, wherein the predetermined function includes at least one of MBS (Multicast / Broadcast Services), a V2X sidelink, an NR sidelink, and HSDN (High Speed ​​Dedicated Network).

[0146] (7) Supplementary Notes The following are supplementary notes regarding the above-described embodiment. Introduction In RAN2#119e, further consideration is required as to whether / how to handle cell reselection priority from the viewpoints of the "highest priority rule of MBS or HSDN" and the "slice-specific cell reselection priority."

[0147] (1) Between MBS and slice-specific cell reselection Further study is needed to determine whether the frequency priority determination procedure of MBS is affected by the priority of slice-based reselection. (2) Between HSDN and slice-specific cell reselection 19: Postpone the coexistence of HSDN and slice-specific cell reselection (not clear how it will work in this release).

[0148] This appendix discusses the coexistence of cell reselection between the highest priority rule and slice-specific cell reselection priorities.

[0149] Discussion The highest priority rules of TS 38.304 are summarized below:

[0150] Observation 1: In the current specification, HSDN cells are given the highest priority, and V2X sidelink / NR sidelink / MBS frequencies are given the highest priority.

[0151] Observation 2: According to the current specification, highest priority means higher than any other priority (ie, 0-7) set in the network.

[0152] HSDN is specified to support specific network policies, such as arranging HSDN cells along high-speed railways so that a UE moving at high speed will prioritize an HSDN cell during cell reselection.

[0153] On the other hand, the V2X sidelink, NR sidelink, and MBS frequency are supported for user selection. For example, if a user is interested in MBS service, the UE will prioritize the MBS frequency of interest.

[0154] Observation 3: The selection of HSDN cell is determined by network policy, while the selection of V2X sidelink / NR sidelink / MBS frequency is determined by user preference.

[0155] For slice-specific cell reselection, the NSAG priority is set by the AMF and the NSAG frequency priority is set from the gNB, so it is considered to support network policies.

[0156] Observation 4: Cell reselection priority per slice is determined by network policy.

[0157] It is difficult for the network to keep track of the latest user preferences, especially when the UE is idle / inactive, and so it is considered necessary to prioritize user preferences over network policies. For example, if a user is interested in receiving MBS services, the UE needs to camp on a cell / frequency that provides MBS services. Guiding such a UE to a cell / frequency, for example by slice-specific cell reselection, is difficult given that user preferences change from time to time. Therefore, RAN2 needs to ensure that user preferences always take precedence over network policies, as is the case currently.

[0158] Observation 5: It may be difficult for the network to know the latest user preferences, especially when the UE is in idle / inactive state.

[0159] Proposal 1: RAN2 should ensure that user priorities take precedence over current network policies, i.e., no changes are needed to the highest priority rules for V2X and MBS.

[0160] On the other hand, with regard to the prioritization within the network policy, i.e., between HSDN and slice-specific cell reselection, it is entirely up to the network how the UE behaves. In some deployments, it may be better to prioritize HSDN over slice-specific cell reselection, while in other deployments it may be the other way around. So, as a compromise, the network may indicate to the UE which feature should take priority, i.e., whether slice-specific cell reselection should be prioritized or the highest priority of HSDN.

[0161] Observation 6: Prioritization within network policies is up to the network and operation to prioritize slice-specific cell reselection priorities over HSDN highest priorities or vice versa.

[0162] Proposal 2: The gNB indicates to the UE whether to prioritize slice-specific cell reselection priorities or the highest priority HSDN cell.

[0163] 1: Mobile communication system 10: RAN 20: CN 100: UE (user equipment) 110: Receiving unit 120: Transmitting unit 130: Control unit 200: gNB (base station) 210: Transmitting unit 220: Receiving unit 230: Control unit 240: Backhaul communication unit

Claims

1. A cell reselection method for use in a user device, comprising: performing slice-based cell reselection in response to the user device receiving slice-specific cell reselection information indicating cell reselection priorities for each slice group and each frequency from a base station; when a predetermined function different from the slice-based cell reselection is set or there is an interest in executing the predetermined function, performing a process of regarding the frequency providing the predetermined function as the highest priority for cell reselection without considering the cell reselection priority indicated by the slice-specific cell reselection information. A cell reselection method.

2. The user device further performs a process of regarding the frequency providing an HSDN (High Speed Dedicated Network) as the highest priority for cell reselection with a higher priority than the process of regarding a certain frequency as the highest priority for cell reselection. The cell reselection method according to Claim 1.

3. The predetermined function includes at least one of MBS (Multicast / Broadcast Services), NR sidelink, and V2X sidelink. The cell reselection method according to Claim 2.

4. A user device, comprising: a receiving unit that receives slice-specific cell reselection information indicating cell reselection priorities for each slice group and each frequency from a base station; and a control unit that performs slice-based cell reselection in response to the reception of the slice-specific cell reselection information; when a predetermined function different from the slice-based cell reselection is set or there is an interest in executing the predetermined function, the control unit performs a process of regarding the frequency providing the predetermined function as the highest priority for cell reselection without considering the cell reselection priority indicated by the slice-specific cell reselection information. A user device.

5. A system including a user device and a base station, wherein the user device comprises a receiving unit that receives slice-specific cell reselection information indicating cell reselection priorities for each slice group and each frequency from the base station; and a control unit that performs slice-based cell reselection in response to the reception of the slice-specific cell reselection information. When the user device has a predetermined function different from the slice-based cell reselection or is interested in the execution of the predetermined function, the control unit performs a process of regarding the frequency that provides the predetermined function as the highest priority for cell reselection without considering the cell reselection priority indicated by the slice-specific cell reselection information. The base station includes a transmission unit that transmits the slice-specific cell reselection information to the user device. System.

6. A program for a user device, which causes the user device to perform a process of receiving slice-specific cell reselection information indicating a cell reselection priority for each slice group and each frequency from a base station, perform a process of performing slice-based cell reselection in response to the reception of the slice-specific cell reselection information, and when the user device has a predetermined function different from the slice-based cell reselection or is interested in the execution of the predetermined function, perform a process of regarding the frequency that provides the predetermined function as the highest priority for cell reselection without considering the cell reselection priority indicated by the slice-specific cell reselection information. Program.

7. A chipset for a user device, which performs a process of receiving slice-specific cell reselection information indicating a cell reselection priority for each slice group and each frequency from a base station, performs a process of performing slice-based cell reselection in response to the reception of the slice-specific cell reselection information, and when the user device has a predetermined function different from the slice-based cell reselection or is interested in the execution of the predetermined function, performs a process of regarding the frequency that provides the predetermined function as the highest priority for cell reselection without considering the cell reselection priority indicated by the slice-specific cell reselection information. Chipset.