Communication Control Method

Abstract

This communication control method includes: transmitting, to a first base station belonging to a non-public cellular network, a message for executing, by a user device connected to the first base station, connection switching from the non-public cellular network to a public cellular network; and controlling by the first base station the connection switching on the basis of the message received from the user device.

Description

[Technical Field]

[0001] The present invention relates to a communication control method for use in a cellular communication system. [Background technology]

[0002] Non-Patent Document 1 describes a technology for configuring a small-scale non-public cellular network (NPN) available to specific subscribers in a fifth-generation (5G) cellular communication system. Such a non-public cellular network is sometimes called a private network, and is expected to be used for self-operated wireless communication in a factory, for example. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] 3GPP Technical Report TR23.734 V16.1.0, “Study on enhancement of 5G System (5GS) for vertical and Local Area Network (LAN) services”, March 2019 Summary of the Invention

[0004] A communication control method according to a first aspect includes a first base station managing a first cell belonging to a first cellular network transmitting network information about a second cellular network associated with the first cell to a user device in the first cell. The network information includes information indicating whether or not there is network cooperation or an inter-base station interface between the first base station and a second base station managing a second cell belonging to the second cellular network. The first cellular network is one of a public cellular network and a non-public cellular network, and the second cellular network is the other of the public cellular network and the non-public cellular network.

[0005] A communication control method according to a second aspect includes a user device connected to a first base station belonging to a non-public cellular network transmitting a message to the first base station for the user device to switch its connection from the non-public cellular network to a public cellular network, and the first base station performing control for the connection switch based on the message received from the user device.

[0006] A communication control method according to a third aspect includes: a base station managing a cell shared by a first cellular network and a second cellular network; and a user device transmitting, to the base station, information for specifying either the first cellular network or the second cellular network as a destination network for the user device. The first cellular network is one of three cellular networks: a public cellular network, a standalone non-public cellular network, and a non-standalone non-public cellular network. The second cellular network is one of two cellular networks remaining after excluding the one cellular network from the three cellular networks.

[0007] A communication control method according to a fourth aspect includes a base station managing a cell shared by a first cellular network and a second cellular network, and a user equipment connected to the base station performing a network switching process from the first cellular network to the second cellular network without changing the cell. The first cellular network is one of three cellular networks: a public cellular network, a standalone non-public cellular network, and a non-standalone non-public cellular network. The second cellular network is one of two cellular networks remaining after excluding the one cellular network from the three cellular networks.

[0008] A communication control method according to a fifth aspect includes a base station broadcasting system information including a network identifier assigned to a non-public cellular network and a service type identifier indicating a type of service provided by the non-public cellular network, and a user device selecting, based on the system information, the non-public cellular network that provides a predetermined type of service as a network to which the user device is to connect. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a diagram illustrating a configuration of a cellular communication system according to an embodiment. [Figure 2] FIG. 1 is a diagram illustrating a configuration of a UE (user equipment) according to an embodiment. [Figure 3] A diagram showing the configuration of a gNB (base station) according to one embodiment. [Figure 4] FIG. 10 is a diagram showing the configuration of a protocol stack of a radio interface of a user plane that handles data. [Figure 5] FIG. 1 is a diagram showing the configuration of a protocol stack of a radio interface of a control plane that handles signaling (control signals). [Figure 6] FIG. 1 illustrates a non-public cellular network, SNPN, and PNI-NPN, according to one embodiment. [Figure 7] FIG. 10 is a diagram showing NPN information stored in a SIM according to an embodiment. [Figure 8] FIG. 1 illustrates an example of the operation of a UE associated with a SIM according to an embodiment. [Figure 9] FIG. 10 is a diagram illustrating the operation of a UE according to one embodiment. [Figure 10] FIG. 2 illustrates the operation of a cellular communication system according to one embodiment. [Figure 11] FIG. 10 illustrates operations related to an RRC inactive state according to one embodiment. [Figure 12] FIG. 2 illustrates the operation of a cellular communication system according to one embodiment. [Figure 13]FIG. 2 illustrates the operation of a cellular communication system according to one embodiment. [Figure 14] FIG. 10 illustrates a network switching process according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] In a situation where public cellular networks and non-public cellular networks coexist, it is desirable to realize a technology that enables user devices to appropriately use non-public cellular networks.

[0011] Therefore, an object of the present disclosure is to enable user devices to appropriately use non-public cellular networks.

[0012] A cellular 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.

[0013] (cellular communication system) First, a configuration of a cellular communication system according to an embodiment will be described. The cellular communication system according to an embodiment is a 5G system of 3GPP (3rd Generation Partnership Project), but LTE may be applied at least in part to the cellular communication system.

[0014] FIG. 1 is a diagram showing a configuration of a cellular communication system according to an embodiment.

[0015] As shown in FIG. 1, the cellular communication system includes a user equipment (UE) 100, a 5G radio access network (NG-RAN) 10, and a 5G core network (5GC) 20.

[0016] The UE 100 is a mobile device. The UE 100 may be any device used by a user. For example, the UE 100 may be a mobile phone terminal (including a smartphone), a tablet terminal, a laptop 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), and / or an aircraft or a device provided in an aircraft (Aerial UE).

[0017] The NG-RAN 10 includes a base station (called a "gNB" in a 5G system) 200. The gNB 200 is sometimes called an NG-RAN node. 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"), and / or a measurement control function for mobility control and scheduling. 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 that performs wireless communication with a UE 100. One cell belongs to one carrier frequency.

[0018] The gNB may be connected to an Evolved Packet Core (EPC), which is an LTE core network, or the LTE base station may be connected to a 5GC. Also, the LTE base station and the gNB may be connected via an inter-base station interface.

[0019] 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 information about the area in which the UE 100 is located by communicating with the UE 100 using NAS (Non-Access Stratum) signaling. The UPF controls data forwarding. The AMF and UPF are connected to the gNB 200 via an NG interface, which is an interface between a base station and a core network.

[0020] FIG. 2 is a diagram showing a configuration of UE 100 (user equipment).

[0021] As shown in FIG. 2, the UE 100 includes a receiving unit 110, a transmitting unit 120, a control unit 130, and a SIM (Subscriber Identification Module) interface 140.

[0022] 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.

[0023] 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.

[0024] The control unit 130 performs various controls in the UE 100. The control unit 130 includes at least one processor and at least one memory electrically connected to the processor. The memory stores programs executed by the processor and information used in processing by the processor. The processor may include a baseband processor and a CPU (Central Processing Unit). The baseband processor performs modulation / demodulation and encoding / decoding of baseband signals. The CPU executes programs stored in the memory to perform various processes.

[0025] The SIM interface 140 is connected to the SIM 150. The SIM 150 may be called a UIM (User Identity Module) or a UICC (Universal Integrated Circuit Card).

[0026] SIM 150 stores information for identifying the subscriber, carrier identification information for identifying the carrier, and information about available services subscribed to by the subscriber. SIM 150 also stores information necessary for receiving services. Examples of information necessary for receiving services include information for registering location information and / or information about telephone numbers.

[0027] The SIM interface 140 may be configured to be able to load and remove the SIM 150. Alternatively, the SIM 150 may be an embedded eSIM (Embedded SIM). When the SIM interface 140 receives a command to read or write information from the control unit 130, it reads information stored in the SIM 150 and writes the information to the SIM 150.

[0028] Figure 3 is a diagram showing the configuration of gNB200 (base station).

[0029] As shown in FIG. 3, the gNB 200 has a transmitter 210, a receiver 220, a controller 230, and a backhaul communication unit 240.

[0030] The transmission unit 210 performs various transmissions under the control of the control unit 230. The transmission 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.

[0031] 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.

[0032] The control unit 230 performs various controls in the gNB 200. The control unit 230 includes at least one processor and at least one memory electrically connected to the processor. The memory stores programs executed by the processor and information used in processing by the processor. The processor may include a baseband processor and a CPU. The baseband processor performs modulation / demodulation and encoding / decoding of baseband signals. The CPU executes programs stored in the memory to perform various processes.

[0033] The backhaul communication unit 240 is connected to neighboring base stations via an inter-base station interface. The backhaul communication unit 240 is connected to the AMF / UPF 300 via a base station-core network interface. Note that the gNB may be configured (i.e., functionally divided) with a CU (Central Unit) and a DU (Distributed Unit), and both units may be connected via an F1 interface.

[0034] FIG. 4 is a diagram showing the configuration of a protocol stack of a radio interface of a user plane that handles data.

[0035] As shown in Figure 4, 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.

[0036] 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 the UE 100 and the PHY layer of the gNB 200 via a physical channel.

[0037] The MAC layer performs data priority control, retransmission processing using Hybrid ARQ (HARQ), random access procedures, etc. Data and control information are transmitted between the MAC layer of UE 100 and the MAC layer of gNB 200 via a transport channel. The MAC layer of 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 UE 100.

[0038] The RLC layer transmits data to the RLC layer on the receiving side 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 logical channels.

[0039] The PDCP layer performs header compression / decompression and encryption / decryption.

[0040] The SDAP layer maps IP flows, which are the units for QoS control by the core network, to radio bearers, which are the units for QoS control by the AS (Access Stratum). Note that if the RAN is connected to the EPC, SDAP is not necessary.

[0041] 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).

[0042] As shown in FIG. 5, the protocol stack of the radio interface of the control plane has a Radio Resource Control (RRC) layer and a Non-Access Stratum (NAS) layer instead of the SDAP layer shown in FIG.

[0043] 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 in accordance with 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 RRC connection is suspended, UE100 is in an RRC inactive state.

[0044] The NAS layer, which is positioned 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 300.

[0045] The UE 100 has an application layer and the like in addition to the radio interface protocol.

[0046] (non-public cellular network) Next, a non-public cellular network (NPN) according to one embodiment will be described. An NPN is a small-scale cellular network available to specific subscribers. An NPN is used for private wireless communication in a factory, for example. An NPN is also called a private network.

[0047] A typical cellular network, a Public Land Mobile Network (PLMN), is operated by a telecommunications carrier. For example, a license is issued to a telecommunications carrier operating a PLMN on a nationwide basis.

[0048] On the other hand, NPNs can be flexibly constructed and used by various entities according to the needs of each region or industry. NPNs using 5G cellular communication systems are sometimes called local 5G. For example, ordinary companies, organizations, or individuals can receive frequency allocations and operate their own NPNs. NPNs may be licensed only for local areas, such as within the facilities of ordinary companies.

[0049] There are two types of NPNs: standalone NPNs and non-standalone NPNs. Standalone NPNs are called SNPNs (Standalone NPNs), and non-standalone NPNs are called PNI-NPNs (Public Network Integrated NPNs). In the following, when there is no need to distinguish between SNPNs and PNI-NPNs, they will simply be referred to as NPNs.

[0050] FIG. 6 is a diagram illustrating an SNPN and a PNI-NPN according to one embodiment.

[0051] As shown in Figure 6, the SNPN is independent of the PLMN and does not depend on the network functions of the PLMN, whereas the PNI-NPN is configured as part of the PLMN and is capable of network cooperation with the PLMN.

[0052] The PLMN and NPN may each have an NG-RAN 10 and a 5GC 20. One or more frequencies (frequency bands, carrier frequencies) are assigned to one NPN. One frequency may also be assigned to multiple geographically separated NPNs. By dividing the geographic areas of NPNs that use one frequency, the same frequency can be shared by multiple NPNs.

[0053] In the case of an SNPN, an NPN ID is assigned to the NPN as a network identifier for identifying the NPN. The NPN cell (gNB200) broadcasts the NPN ID of the NPN to which it belongs (or the NPN it provides service to or the NPN to which it authorizes access). In addition, a special PLMN ID may be assigned to the NPN to identify it as an NPN, and the NPN cell (gNB200) may broadcast this special PLMN ID.

[0054] In the case of a PNI-NPN, a CAG (Closed Access Group) ID is assigned to the NPN as a network identifier for identifying the NPN. The NPN cell (gNB 200) broadcasts the CAG ID of the NPN to which it belongs (or the NPN to which it provides service or the NPN to which it authorizes access). The CAG ID is also an identifier for a group consisting of a specific subset of subscriber users of the PLMN who are allowed to access the NPN. However, an NPN ID may be assigned to the NPN instead of a CAG ID, or both an NPN ID and a CAG ID may be assigned to the NPN.

[0055] (An example of NPN information stored in a SIM card) Next, a description will be given of an example of NPN information stored in the SIM 150. In one embodiment, information related to the NPN is stored in the SIM 150. The information related to the NPN is stored in the SIM 150 in advance when the SIM 150 is provided.

[0056] FIG. 7 is a diagram showing NPN information stored in the SIM 150 according to an embodiment.

[0057] 7, SIM 150 stores a network identifier (NPN ID or CAG ID) that identifies an NPN that is permitted to be accessed by UE 100, and frequency information that indicates the frequency (frequency band, carrier frequency) of this NPN. An NPN that is permitted to be accessed by UE 100 is an NPN to which UE 100 subscribes and which UE 100 has authority to access.

[0058] The UE 100 performs a search process for the NPN, specifically, a cell search, based on the network identifier and frequency information stored in the SIM. For example, the UE 100 searches for a cell that belongs to the frequency indicated by the frequency information stored in the SIM and broadcasts the same network identifier as the network identifier stored in the SIM. This allows the UE 100 to efficiently detect an NPN cell to which access is permitted.

[0059] SIM 150 may store a plurality of sets of network identifiers and frequency information. In this case, an access priority may be set for each network identifier. FIG. 7 shows an example in which two sets of network identifiers and frequency information are stored in SIM 150. A priority of "1" is set for network identifier "ID#1", and a priority of "2" is set for network identifier "ID#2". Note that the priority does not have to be stored in SIM 150 as explicit information. For example, the priority may be set according to the sort order of network identifiers. UE 100 selects one of the plurality of sets (plurality of network identifiers) based on the set access priority.

[0060] SIM 150 may store valid area information associated with frequency information. The valid area information may be information indicating a geographical location where NPN service is permitted in the corresponding frequency. For example, the valid area information may be latitude, longitude, and / or altitude, or may be a cell ID, a RAN area ID, and / or a tracking area ID of a PLMN base station. One or more pieces of valid area information are associated with one NPN ID or frequency information. UE 100 may identify the network identifier and frequency information of an NPN that is valid for its own location based on the valid area information, and use the identified information in the search process.

[0061] FIG. 8 is a diagram illustrating an example of the operation of the UE 100 associated with the SIM 150 according to an embodiment.

[0062] 8, in step S11, an upper layer entity of UE 100 reads out NPN information from SIM 150. The upper layer entity refers to an entity in a layer higher than the RRC layer of UE 100. The upper layer entity notifies the read-out NPN information to an AS entity of UE 100. The AS entity refers to an entity in a layer lower than the RRC layer of UE 100.

[0063] If multiple sets of network identifiers and frequency information are stored in SIM 150, the upper layer entity may select one of the multiple sets (multiple network identifiers) based on the set access priority and notify the AS entity of the selected set.

[0064] When the AS entity of UE 100 is notified of NPN information (e.g., a set of network identifier and frequency information) from an upper layer entity of UE 100, the AS entity of UE 100 may determine that access to the cell of the NPN indicated by this network identifier is permitted.

[0065] In step S12, the AS entity of the UE 100 performs a search process for the NPN based on the NPN information notified from the upper layer entity of the UE 100.

[0066] Specifically, in the cell selection operation, if frequency information is provided by a higher layer entity, the AS entity searches preferentially on the frequency indicated by this frequency information to detect an NPN ID (or CAG ID). The AS entity may notify the higher layer entity of the detected NPN ID (or CAG ID). If NPN ID (or CAG ID) information is provided by the higher layer entity, the AS entity may notify the higher layer entity of only those of the detected NPN IDs (or CAG IDs) that match the information provided by the higher layer entity. Based on the information notified by the AS entity, the higher layer entity can know which networks are accessible. Alternatively, the higher layer entity may make the final decision on whether to allow or deny access.

[0067] Furthermore, when UE 100 performs cell reselection in an RRC idle state or an RRC inactive state, the AS entity of UE 100 increases the priority of the frequency (NPN frequency) indicated by the frequency information included in the NPN information notified from the upper layer entity, based on the frequency information included in this frequency information. For example, after UE 100 selects an NPN cell by the above-mentioned cell selection operation, UE 100 may increase the priority of the frequency to which the currently selected NPN (the NPN to which the currently selected cell belongs and / or the NPN currently camped) belongs. The AS entity may set the priority of the frequency (NPN frequency) indicated by this frequency information to the highest priority. Note that cell selection or cell reselection refers to selecting or reselecting a cell to be a serving cell of UE 100.

[0068] This allows the AS entity of UE100 to measure the radio quality of the frequency of the NPN to which access is permitted during cell reselection, even if the frequency of the current serving cell is different from the frequency of the NPN to which access is permitted, and to reselect a neighboring cell belonging to the frequency of this NPN as the serving cell of UE100.

[0069] (Actions to transfer UE from PLMN to NPN) Next, the operation for transferring the UE 100 from a PLMN to an NPN will be described.

[0070] In one embodiment, a gNB 200 belonging to a PLMN broadcasts a System Information Block (SIB) including NPN information, which is network information related to an NPN. Specifically, the gNB 200 managing a PLMN cell broadcasts NPN information related to an NPN associated with the PLMN cell to UEs 100 within the cell. If the allocated frequencies of the PLMN and the NPN are different, the gNB 200 managing the PLMN cell may broadcast the NPN information as neighbor frequency information.

[0071] This NPN information includes at least one of a network identifier that identifies the NPN, frequency information that indicates the frequency of the NPN (frequency band, carrier frequency), and a cell identifier of the NPN cell. The cell identifier may be a base station ID (gNB ID). The frequency information may include information that indicates an initial BWP (Bandwidth Part) to be used for initial access. The BWP refers to a portion of the frequency band of the cell. The information broadcast from the gNB 200 may include a beam ID or SSB information (a synchronization signal and broadcast channel block consisting of a synchronization signal and a physical broadcast channel).

[0072] For example, in the case of an SNPN, a gNB 200 managing a PLMN cell broadcasts NPN information about NPNs (SNPNs) that are geographically close to this cell. In the case of a PNI-NPN, a gNB 200 managing a PLMN cell broadcasts NPN information about NPNs (PNI-NPNs) that belong to the same PLMN as itself.

[0073] UE100 receives NPN information broadcast from gNB200 belonging to PLMN and performs a search process for NPNs based on the received NPN information. For example, UE100 searches for cells that belong to the frequency indicated by the frequency information included in the received NPN information and broadcast the same network identifier as the network identifier included in the received NPN information. UE100 located in a cell of gNB200 belonging to PLMN may exclude NPNs whose NPN information is not broadcast from this gNB200 from the search process.

[0074] FIG. 9 is a diagram showing an operation of the UE 100 according to one embodiment.

[0075] 9, in step S21, the gNB 200 managing the PLMN cell broadcasts a SIB including NPN information about the NPN associated with this cell to the UE 100 in this cell. The UE 100 receives the NPN information from the gNB 200.

[0076] In step S22, UE100 performs a search process for an NPN corresponding to the NPN information received from gNB200, based on the NPN information received from this NPN information. For example, UE100 searches for a cell that belongs to the frequency indicated by the frequency information included in the received NPN information and broadcasts the same network identifier as the network identifier included in the received NPN information. UE100 may exclude from the search process NPNs whose NPN information is not broadcast from this gNB200.

[0077] Here, UE 100 may perform a search process only on an NPN whose network identifier is stored in SIM 150, that is, an NPN to which access from UE 100 is permitted. In other words, only when a network identifier broadcast from gNB 200 belonging to a PLMN matches a network identifier stored in SIM 150, UE 100 may perform a search process on an NPN indicated by this network identifier.

[0078] In the following, the description will be given on the assumption that the UE 100 has detected the NPN cell to be searched for through a search process.

[0079] When the UE 100 is in the RRC connected state, in step S23, the UE 100 transmits to the gNB 200 a notification including information (at least one of a network identifier, frequency information, and a cell identifier) regarding the NPN that the UE 100 requests to access. Specifically, when the frequencies of the PLMN and the NPN are different, the gNB 200 needs to configure the UE 100 with inter-frequency measurement in order to perform quality measurement for the frequency of the NPN. For this reason, the UE 100 notifies the gNB 200 of a request to access this NPN, and requests the gNB 200 to configure the inter-frequency measurement. The UE 100 performs the inter-frequency measurement based on the configuration from the gNB 200 and transmits a measurement report including the measurement result to the gNB 200. The gNB 200 decides to hand over the UE 100 to a cell of the NPN based on this measurement report.

[0080] In step S24, UE100 receives a handover instruction from gNB200 that has decided to perform handover, and performs handover to the NPN cell.

[0081] On the other hand, when the UE 100 is in the RRC idle state or the RRC inactive state, the process of step S23 is not performed, and in step S24, the UE 100 may set the priority of the frequency (NPN frequency) indicated by the frequency information included in the NPN information received from the gNB 200 to the highest priority based on the frequency information. This allows the UE 100 to perform cell reselection to the NPN cell.

[0082] In the case of an SNPN, the gNB 200 belonging to the PLMN cannot hand over the UE 100 in the RRC connected state to a cell of the NPN (SNPN). Therefore, if the NPN information received from the gNB 200 does not include the NPN that the UE 100 wants to access, and if the UE 100 detects this NPN through a search process, the UE 100 may request the gNB 200 to release the connection. When the connection is released in response to this request, the UE 100 that has transitioned to the RRC idle state or the RRC inactive state sets the priority of the frequency of the detected NPN to the highest priority, and can perform cell reselection to the cell of this NPN.

[0083] Alternatively, UE100 may notify gNB200 belonging to the PLMN that it has detected a desired NPN cell (or NPN frequency), and gNB200 may decide to perform redirection to the NPN cell (or NPN frequency) and instruct UE100 to do so.

[0084] Although the operation for moving UE 100 from PLMN to NPN has been described, the above operation may also be applied when moving UE 100 from NPN to PLMN. In this case, the direction of movement is reversed, so in the above description, "gNB belonging to PLMN" should be read as "gNB belonging to NPN", "gNB belonging to NPN" should be read as "gNB belonging to PLMN", and "NPN information" should be read as "PLMN information". In this case, gNB 200 belonging to NPN broadcasts PLMN information of adjacent frequencies, for example.

[0085] In one embodiment, the gNB 200a belonging to the PLMN may transmit NPN information to the UE 100, which further includes information indicating whether or not there is an inter-base station interface between the gNB 200b and the gNB 200a belonging to the NPN. The inter-base station interface is, for example, an Xn interface, but may also be an X2 interface. This makes it possible to determine whether or not a connection re-establishment (specifically, RRC re-establishment) with the gNB 200a is possible when a radio link failure (RLF) occurs between the gNB 200a belonging to the PLMN and the UE 100.

[0086] FIG. 10 is a diagram showing the operation of the cellular communication system 1 according to one embodiment.

[0087] In the example shown in Fig. 10, UE 100, which has an RRC connection with gNB 200a belonging to a PLMN, detects an RLF with gNB 200a. After detecting the RLF with gNB 200a, UE 100 can continue communication if it successfully re-establishes RRC with gNB 200a. Here, in order for UE 100 to smoothly re-establish RRC with gNB 200a, there is an inter-base station interface (Xn interface) between gNB 200a and gNB 200b, and gNB 200b needs to obtain context information of UE 100 from gNB 200a.

[0088] However, if the NPN to which gNB200b belongs is an SNPN, there is no network coordination between gNB200a and gNB200b, and gNB200b cannot obtain context information of UE100 from gNB200a. Also, even if the NPN to which gNB200b belongs is a PNI-NPN, there may be a case where there is no inter-base station interface between gNB200a and gNB200b.

[0089] For this reason, gNB200a broadcasts NPN information including information indicating whether or not there is an inter-base station interface with gNB200b. When UE100 detects an RLF, if there is an inter-base station interface between gNB200a and gNB200b, it determines that smooth RRC re-establishment with gNB200b is possible. In this case, UE100 preferentially selects gNB200b as a candidate for RRC re-establishment and transmits an RRC re-establishment request message. On the other hand, when UE100 detects an RLF and there is no inter-base station interface between gNB200a and gNB200b, it may determine that smooth RRC re-establishment with gNB200b is not possible and may lower the priority of gNB200b as a candidate for RRC re-establishment. Furthermore, when UE100 selects gNB200b that does not have an inter-base station interface, UE100 may transmit an RRC setup request message to gNB200b.

[0090] Although PLMN to NPN transfers have been described herein, such operations may also be applied to NPN to PLMN operations.

[0091] (RRC inactive state operations) Next, operations relating to the RRC inactive state according to one embodiment will be described, focusing on differences from the operations described above. Fig. 11 is a diagram showing operations relating to the RRC inactive state according to one embodiment.

[0092] As shown in Fig. 11, the gNB 200a belonging to the PLMN transmits an RRC Release message including an RRC inactive state configuration (SuspendConfig) to the UE 100 in order to transition the UE 100 to the RRC inactive state. The SuspendConfig includes RNA (RAN Notification Area) information. The RNA is an area in which the UE 100 can perform UE-based mobility (e.g., cell reselection operation) while remaining in the RRC inactive state, and is indicated, for example, by a list of cells corresponding to the area. The gNB 200a belonging to the PLMN notifies the UE 100 of NPN information (e.g., NPN ID, CAG ID) using the RNA information included in the RRC Release message.

[0093] This allows RNA to be extended to NPN cells, allowing the UE to move from PLMN to NPN while remaining in RRC inactive state.

[0094] In addition, the RNA information may indicate priority information of each PLMN / NPN and / or each cell. For example, when the priority of the NPN is set higher than that of the PLMN, the UE 100 prioritizes a cell belonging to the NPN in a cell reselection operation.

[0095] For example, the UE 100 evaluates cell reselection by adding an offset value to radio measurement values of cells belonging to the NPN. Alternatively, the UE 100 measures only cells (or frequencies) belonging to the NPN, and if a suitable cell for the cell (or frequency) cannot be detected, measures cells (or frequencies) belonging to the PLMN.

[0096] (Actions for transferring UE from NPN to PLMN) Next, the operation for transferring the UE 100 from the NPN to the PLMN will be described, focusing mainly on the differences from the above-described operation.

[0097] FIG. 12 is a diagram showing the operation of the cellular communication system 1 according to one embodiment.

[0098] 12, when UE 100 in an RRC connected state connected to gNB 200b belonging to an NPN desires to switch its connection network to a PLMN, UE 100 transmits a message to gNB 200b to cause UE 100 to switch its connection network from NPN to PLMN. UE 100 may determine the need for switching its connection network from NPN to PLMN based on a user operation to select a PLMN or a user operation to deselect an NPN.

[0099] Note that, when UE 100 is connected to a PLMN, UE 100 may determine not to transmit the message. For example, even if NPN is deselected by a user operation, when UE 100 is connected to a PLMN, UE 100 determines that there is no need to switch the connection network and does not transmit the message. This makes it possible to save power and radio resources required for message transmission.

[0100] Alternatively, UE 100 may transmit the message even when connected to a PLMN. For example, UE 100 transmits the message if it has previously transmitted information (preference) indicating a desire to connect to an NPN to gNB 200a belonging to a PLMN. This enables gNB 200a belonging to a PLMN to perform control such as changing measurement settings for gNB 200b belonging to an NPN and suppressing handover.

[0101] The message may be an RRC message (e.g., a UE Assistance Information message). The message may include information indicating that the network identifier of the NPN (NPN ID or CAG ID) is not specified. Such information may be a NULL value (or a zero value) set as the NPN ID or CAG ID.

[0102] Based on a message received from UE 100, gNB 200b performs control (i.e., mobility control) for switching the connection from gNB 200b belonging to the NPN to gNB 200a belonging to the PLMN.

[0103] For example, if gNB200b is a PNI-NPN and there is network cooperation between gNB200a, which is the handover target of UE100, and gNB200b, gNB200b performs control to hand over UE100 to gNB200a. Here, if the frequencies of the PLMN and NPN are different, gNB200b configures inter-frequency measurement in UE100 to measure the quality of the PLMN frequency. UE100 performs inter-frequency measurement based on the configuration from gNB200b and transmits a measurement report including the measurement results to gNB200b. Based on this measurement report, gNB200b hands over UE100 to the cell of gNB200a (PLMN cell).

[0104] On the other hand, if gNB200b is an SNPN and there is no network coordination between gNB200a and gNB200b, which are the handover targets of UE100, gNB200b may release the RRC connection between UE100 and gNB200b to enable UE100 to connect to gNB200a. In this case, UE100 establishes an RRC connection with gNB200a after the RRC connection between UE100 and gNB200b is released.

[0105] Alternatively, the UE 100 may determine whether or not there is network cooperation between the gNB 200a (PLMN) and the gNB 200b (NPN) that are the handover targets, and determine the content of the message depending on whether or not there is network cooperation. For example, when there is network cooperation, the UE 100 transmits to the gNB 200b a message including a handover request requesting handover of the UE 100 from the gNB 200b to the gNB 200a. On the other hand, when there is no network cooperation, the UE 100 transmits to the gNB 200b a message including a disconnection request requesting disconnection of the connection between the gNB 200b and the UE 100.

[0106] Here, the UE 100 may determine whether or not there is network cooperation between the gNB 200a and the gNB 200b based on a notification from the gNB 200b. For example, the gNB 200b broadcasts system information including information indicating whether or not there is network cooperation. information may include a network identifier (e.g., PLMN ID), a gNB identifier, and / or a cell identifier for the gNB200a.

[0107] The AS entity of UE 100 may determine whether there is network cooperation between gNB 200a and gNB 200b based on a notification from a higher layer entity of UE 100. For example, if a network identifier (e.g., PLMN ID), a gNB identifier, and / or a cell identifier of gNB 200a (PLMN) that supports network cooperation is configured by user configuration, the higher layer entity obtains information about this configuration and notifies the AS entity of the obtained information.

[0108] (Operation when sharing a single cell) Next, the operation when multiple cellular networks share a single cell will be described.

[0109] FIG. 13 is a diagram showing the operation of the cellular communication system 1 according to one embodiment.

[0110] 13, gNB200 manages a cell shared by the first cellular network and the second cellular network (hereinafter referred to as a "shared cell"). gNB200 can be considered as a shared gNB shared by 5GC20a belonging to the first cellular network and 5GC20b belonging to the second cellular network, that is, a gNB belonging to both the first cellular network and the second cellular network.

[0111] For example, if a shared cell is shared by an SNPN and a PNI-NPN, the gNB200 broadcasts both the network identifier of the SNPN (e.g., NPN ID) and the network identifier of the PNI-NPN (e.g., CAG ID) in the shared cell.

[0112] Here, the first cellular network is one of three cellular networks: PLMN, SNPN, and PNI-NPN. The second cellular network is one of two cellular networks excluding the one cellular network from the three cellular networks. For example, the first cellular network may be an SNPN, and the second cellular network may be a PNI-NPN or a PLMN.

[0113] In such an operating environment, when UE100 connects to gNB200, if gNB200 does not know which cellular network UE100 wants to connect to, it will not be able to connect UE100 to the desired cellular network.

[0114] For this reason, when connecting to the gNB 200, the UE 100 transmits information (hereinafter referred to as "network selection information") for designating either the first cellular network or the second cellular network as the network to which the UE 100 is to be connected to the gNB 200. This allows the gNB 200 to know which cellular network the UE 100 wishes to connect to based on the network selection information, and makes it easier to connect the UE 100 to the desired cellular network.

[0115] The network selection information may be a network identifier of an NPN (NPN ID or CAG ID). Alternatively, the network selection information may be a network type identifier indicating one of three network types: PLMN, SNPN, and PNI-NPN. This allows the gNB 200 to know which cellular network the UE 100 wants to connect to, based on the network selection information, even if the first cellular network is an SNPN and the second cellular network is a PNI-NPN.

[0116] Assuming a case where the first cellular network is a PLMN and the second cellular network is an NPN (SNPN or PNI-NPN), the UE 100 may transmit a flag indicating either the PLMN or the NPN as the network selection information. For example, if the UE 100 desires to connect to an NPN, the UE 100 transmits a 1-bit flag indicating the NPN as the network selection information. On the other hand, if the UE 100 desires to connect to a PLMN, the UE 100 does not transmit the flag as the network selection information. This allows the gNB 200 to know which cellular network the UE 100 desires to connect to. Such a flag can be regarded as one form of a network type identifier.

[0117] In a case where a third cellular network exists in addition to the first cellular network and the second cellular network, and it is assumed that there may be multiple cellular networks to which UE 100 wishes to connect, the flag may be transmitted in the form of a list. Each entry in the list may be associated with each entry in an information list of network identifiers (PLMN ID or NPN ID (or CAG ID)) that are being broadcast. Alternatively, in a case where a third cellular network exists in addition to the first cellular network and the second cellular network, and it is assumed that there is only one cellular network to which UE 100 wishes to connect, the entry number in the information list of network identifiers may be notified as the network to which UE 100 wishes to connect. For example, if UE 100 wishes to connect to the NPN with entry number 2, UE 100 notifies "2" as the network to which UE 100 wishes to connect.

[0118] The UE 100 in the RRC idle state may transmit the network selection information to the gNB 200 during a random access procedure for establishing an RRC connection. The UE 100 in the RRC inactive state may transmit the network selection information to the gNB 200 during a random access procedure for restoring the RRC connection. Alternatively, the UE 100 may transmit the network selection information to the gNB 200 after transitioning to the RRC connected state.

[0119] During the random access procedure, the UE 100 transmits a random access preamble (Msg1) and an RRC message (Msg3, Msg5) to the gNB 200. The UE 100 transmits network selection information to the gNB 200 in any of Msg1, Msg3, and Msg5.

[0120] When transmitting network selection information using Msg1, PRACH (Physical Random Access Channel) resources are divided for each network type identifier, and UE 100 selects a PRACH resource corresponding to its desired network type identifier and transmits Msg1 to gNB 200 using the selected PRACH resource. gNB 200 converts the PRACH resource selected by UE 100 into a network type identifier and can determine which cellular network UE 100 wishes to connect to. On the other hand, when transmitting network selection information using Msg3 or Msg5, UE 100 transmits an RRC message including network selection information such as a network type identifier to gNB 200.

[0121] When the gNB200 identifies the cellular network to which the UE100 wishes to connect based on the network selection information, the gNB200 establishes a network connection (routing path) to the cellular network to which the UE100 wishes to connect. After the connection of the UE100 is completed, the gNB200 may retain the network selection information as part of the context information of the UE100. Then, when controlling handover of the UE100, the gNB200 may select a cellular network to be a handover target based on the retained network selection information.

[0122] Next, a network switching process, which is a process for switching the network to which UE 100 is connected in the operating environment shown in FIG. 13, will be described.

[0123] In the operating environment shown in Fig. 13, the UE 100 connected to the first cellular network (5GC 20a) via the gNB 200 performs a network switching process from the first cellular network to the second cellular network without changing the shared cell that is the current serving cell. In other words, the UE 100 performs a network switching process from the first cellular network to the second cellular network without going through a handover procedure (including a random access procedure).

[0124] 14 is a diagram illustrating a network switching process according to an embodiment. In FIG. 14, an example is shown in which the first cellular network is an SNPN and the second cellular network is a PNI-NPN. Before step S31, the UE 100 is in a state in which connection to the SNPN is completed.

[0125] As shown in FIG. 14, in step S31, UE100 notifies gNB200 of the cellular network to which it wishes to switch, and requests network switching (Preference Indication).

[0126] In step S32, the gNB200 notifies the 5GC20a of the cellular network to which the UE100 wishes to switch (RAN-sharing Handover Required).

[0127] 5GC20a requests 5GC20b, which is the cellular network to which UE100 is to be switched, to change the network to which UE100 is connected, and after the processing within 5GC20b is completed, receives a positive response from 5GC20b. This completes preparations for switching the routing path between gNB200 and 5GC20a to the routing path between gNB200 and 5GC20b.

[0128] In step S33, 5GC20a transmits an acknowledgment corresponding to the RAN-sharing Handover Required received in step S32 to gNB200 (RAN-sharing Handover Ack).

[0129] In step S34, the gNB 200 transmits a notification to the UE 100 indicating that a network switch will be performed (NW switch indication). The UE 100 recognizes that a network switch has been performed while maintaining the radio connection. The NW switch indication may be an RRC message. The AS entity of the UE 100 may notify an upper layer entity of the UE 100 of the network switch.

[0130] In step S35, the gNB200 notifies the 5GC20b of switching to the routing path between the gNB200 and the 5GC20b (Handover Notify). Thereafter, switching to the routing path between the gNB200 and the 5GC20b is performed.

[0131] (Other embodiments) Although the above-described embodiments do not specifically mention network slices, the network may be logically divided into multiple slices. 5G assumes that a variety of user devices will connect to the cellular network, and it is necessary to support a variety of services with different requirements, such as high speed, large capacity, high reliability, and / or low latency. For this reason, 5GC may be theoretically divided into multiple slices according to different services (service requirements).

[0132] Here, each slice is assigned an identifier called S-NSSAI (Single-Network Slice Selection Assistance Information). Each slice is also associated with one service type (SST). The service types specified in the standard are eMBB (high speed, large capacity), mIoT (multiple connections, low power consumption, low cost), and URLLC (low latency, high reliability), but service types not specified in the standard can also be used.

[0133] When a non-public cellular network is constructed for the purpose of providing a specific service, the types of services (SST) provided by the non-public cellular network may be limited. On the other hand, a public cellular network may provide general-purpose services, but may not provide specialized services tailored to the individual needs of a region or industry. Note that "services provided by a cellular communication network" can also be thought of as "functions supported by a cellular communication network."

[0134] In the above-described embodiment, the gNB200 may broadcast system information including a network identifier (NPN ID or CAG ID) assigned to the NPN and a service type identifier indicating the type of service provided by the NPN. As the service type identifier, for example, an SST or an S-NSSAI may be used. In other words, the gNB200 broadcasts the supported service type (network slice information) for each network identifier of the NPN. The gNB200 may broadcast the network identifier of the NPN for each network slice.

[0135] Based on such system information, the UE 100 selects an NPN that provides a predetermined type of service (for example, a service desired by the UE 100) as a network to be connected to (serving network) for the UE itself. Such system information may be a type of the NPN information described above. In this case, the NPN information may include a network identifier that identifies the NPN, frequency information indicating the frequency of the NPN and / or a cell identifier of the cell of the NPN, and a service type identifier of the NPN.

[0136] For example, the UE 100 in the RRC idle state or the RRC connected state preferentially selects a cell of an NPN that provides a service desired by the UE 100 in cell reselection. Such cell reselection control may be realized by setting the frequency of the NPN as the frequency with the highest priority for cell reselection.

[0137] Although the above-described embodiment does not specifically mention conditional handover, a conditional handover may be configured for the UE 100. A conditional handover is a handover in which a condition for executing the handover is attached, and the UE 100 executes the handover when the condition is met. When a conditional handover is configured, there may be multiple target gNB candidates. Furthermore, the target gNB candidates may be not only gNBs belonging to PLMNs but also gNBs belonging to NPNs. In this case, the gNB 200 may notify the UE 100 of the priority of each target gNB candidate and / or each target network (PLMN / NPN) during handover configuration for the conditional handover. The UE 100 may perform measurements or selection (e.g., ranking) with priority given to the target gNB / network based on the priority configuration.

[0138] 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 the 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.

[0139] In addition, circuits that execute each process performed by UE100 or gNB200 may be integrated, and at least a part of UE100 or gNB200 may be configured as a semiconductor integrated circuit (chipset, SoC).

[0140] The above describes one embodiment 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.

[0141] This application claims priority from Japanese Patent Application No. 2020-030893 (filed February 26, 2020), the entire contents of which are incorporated herein by reference.

Claims

1. A base station broadcasts system information including a cell identifier assigned to a cell belonging to a non-public cellular network and network slice identification information identifying a network slice supported by the cell; and the user equipment preferentially selecting, based on the system information, the cell that supports a predetermined network slice as a serving cell for the user equipment. Communication control method.

2. A user device, a receiving unit that receives system information from a base station, the system information including a cell identifier assigned to a cell belonging to a non-public cellular network and network slice identification information that identifies a network slice supported by the cell; a control unit that preferentially selects the cell that supports a predetermined network slice as a serving cell for the user equipment based on the system information. User equipment.

3. a processor for controlling a user device, A process of receiving system information from a base station, the system information including a cell identifier assigned to a cell belonging to a non-public cellular network and network slice identification information identifying a network slice supported by the cell; and performing a process of preferentially selecting the cell that supports a predetermined network slice as a serving cell for the user equipment based on the system information. Processor.

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