Base station, communication terminal, control method, and program

Abstract

To reduce the possibility that a terminal intended to be connected to a public radio communication network designed for congestion detection, is erroneously connected to a network not designed for congestion detection.SOLUTION: A base station is disclosed, which carries out communication conforming to the 3GPP standard, and which has transmission means that transmits a downlink control plane message, wherein the downlink control plane message includes congestion detection capability information related to the ability of the base station to detect network congestion. A communication terminal is disclosed, which carries out communication conforming to the 3GPP standard, and which has reception means that receives the downlink control plane message from the base station, wherein the downlink control plane message includes congestion detection capability information related to the ability of the base station to detect network congestion.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present disclosure relates to a base station, a communication terminal, a control method, and a program. [Background technology]

[0002] BACKGROUND ART A technique is known for detecting congestion in an IP (Internet Protocol) data communication device by notifying congestion capability information of the communication device using an ECN (Explicit Congestion Notification) field (Patent Document 1).

[0003] In addition, in a public wireless communication network system, when a terminal connects to the network, a wireless connection is established by a control message on the C (Control) plane. After the wireless connection is established, communication of user data such as IP data becomes possible via the U (User) plane (Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2008-507204 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-227815 Summary of the Invention [Problem to be solved by the invention]

[0005] Previously, public wireless networks were unable to notify terminals that they supported ECN, which meant that terminals wishing to connect to a public wireless network that supported congestion detection could mistakenly connect to a network that did not support congestion detection.

[0006] The present invention has been made in consideration of at least one of the above-mentioned problems, and an object of the present invention is to provide a mechanism that can reduce the possibility that a terminal that wants to connect to a public wireless communication network that supports congestion detection will mistakenly connect to a public wireless communication network that does not support congestion detection. [Means for solving the problem]

[0007] A base station according to one aspect of the present invention is a base station that performs communication in accordance with the 3GPP standard, a transmitting means for transmitting a downlink control plane message; The downlink control plane message is characterized in that it includes congestion detection capability information relating to the congestion detection capability of the local station's network. [Effects of the Invention]

[0008] According to one aspect of the present invention, it is possible to reduce the possibility that a terminal that wants to connect to a public wireless communication network that supports congestion detection will mistakenly connect to a network that does not support congestion detection. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a system diagram of a public wireless communication network according to a first embodiment. [Figure 2] 3 is a diagram illustrating a configuration example of a hardware block related to wireless communication of a base station according to the first embodiment. [Figure 3] 3 is a configuration example of software function blocks of a base station according to the first embodiment. [Figure 4] 2 is an example of a hardware configuration of a terminal according to the first embodiment. [Figure 5] 3 is a diagram illustrating an example of a configuration of software function blocks of a terminal according to the first embodiment. [Figure 6] 10 is a flowchart of a process in a base station according to the first embodiment. [Figure 7]10 is a diagram illustrating an example of a format when ECN support information is included in a notification signal according to the first embodiment. [Figure 8] 10 is a flowchart of an RRC layer connection process in a terminal according to the first embodiment. [Figure 9] 10 is a flowchart of a process in a base station according to the second embodiment. [Figure 10] 10 is a diagram illustrating an example of a format when ECN support information is included in RRC Setup in the second embodiment. [Figure 11] 10 is a flowchart of an RRC Setup process in a terminal according to the second embodiment. [Figure 12] 10 is a diagram illustrating an example of a format when ECN compatibility information is included in RRCReconfiguration according to the second embodiment. [Figure 13] 10 is a diagram illustrating an example of a format when ECN correspondence information is included in an RRCResume according to the second embodiment. [Figure 14] 13 is a diagram illustrating an example of a format when ECN compatibility information is included in a NAS message according to the third embodiment. [Figure 15] 13 is a flowchart of a NAS layer connection process in a terminal according to the third embodiment. [Figure 16] 13 is an example of a table including ECN correspondence information in an SST according to the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] [First embodiment] Hereinafter, the communication device according to the present embodiment will be described in detail with reference to the drawings.

[0011] FIG. 1 is a system diagram of a public wireless communication network according to this embodiment. Reference numeral 10 denotes a core network. Reference numeral 20 denotes a base station. Reference numeral 30 denotes a terminal. Note that the base station 20 is typically a fixed base station. Note that the base station 20 may use Integrated Access and Backhaul (IAB) technology, which integrates an access line and a backhaul line. In this case, the base station 20 may be an IAB donor or an IAB node. The IAB node may also be a mobile IAB node called mIAB or Mobile BaseStation Relay (MBSR). mIAB is an abbreviation for mobileIAB. The terminal 30 functions as UE (User Equipment) capable of transmitting and receiving signals conforming to the 3GPP standard.

[0012] 2 is a block diagram showing an example of a hardware block 201 related to wireless communication in the base station 20 according to this embodiment. Reference numeral 202 denotes a control unit that controls the entire device by executing a control program stored in a storage unit 203.

[0013] Reference numeral 203 denotes a storage unit that stores a control program executed by the control unit 202 and various information such as the contents of ECN support information in the C-plane and connected terminal information. The various operations described below are performed by the control unit 202 executing the control program stored in the storage unit 203. Reference numeral 204 denotes a wireless communication unit for performing cellular network communication such as LTE (Long Term Evolution) and 5G NR (5th Generation New Radio) that conform to the 3GPP standard. Reference numeral 205 denotes an antenna control unit that controls an antenna for wireless communication performed by the wireless communication unit 204. However, this embodiment can also be applied to cellular network communication other than LTE and 5G (for example, 5G Advanced, 6G, etc.). When this embodiment is applied to 6G, the base station may be a 6gNB / 6GNB.

[0014] 3 is a block diagram showing an example of the configuration of software function blocks of base station 20. Reference numeral 301 denotes the entire software function block.

[0015] Reference numeral 302 denotes a signal transmission unit, 303 denotes a signal reception unit, and these units perform cellular network communication such as LTE and 5G compliant with the 3GPP (3rd Generation Partnership Project) standard with the terminal device. Reference numeral 304 denotes a data storage unit, which stores and holds the software itself.

[0016] A connection control unit 305 performs processing related to the connection and disconnection of the terminal to the cellular network, such as RRC (Radio Resource Control) message communication, between the terminal 30 and the core network 10. The connection control unit 305 also performs processing related to NAS (Non Access Stratum) connection between the terminal 30 and the core network 10.

[0017] An ECN correspondence information generation unit 306 generates ECN correspondence information, which will be described later, and notifies the signal transmission unit 302 of the generated ECN correspondence information.

[0018] FIG. 4 is a block diagram showing an example of the hardware configuration of the terminal 30 according to this embodiment.

[0019] Reference numeral 401 denotes a control unit that controls the entire device by executing a control program stored in a storage unit 402 .

[0020] Reference numeral 402 denotes a storage unit that stores a control program executed by the control unit 401 and various information such as communication parameters and photographed data. The control unit 401 executes the control program stored in the storage unit 402 to perform various operations described below.

[0021] 403 is a wireless communication unit for performing cellular network communication such as LTE, 5G, and 6G that conforms to the 3GPP standard.

[0022] An output unit 404 has a function of outputting visually perceptible information such as an LCD or LED, or a function of outputting sound such as a speaker. An input unit 405 is used by the user to perform various inputs or to acquire sensor information.

[0023] 5 is a block diagram showing an example of the configuration of software function blocks of the terminal 30. Reference numeral 501 denotes the entire software function block.

[0024] Reference numeral 502 denotes a signal transmission unit, 503 denotes a signal reception unit, and these units perform cellular network communication such as LTE, 5G, and 6G compliant with the 3GPP standard with the other device. Reference numeral 504 denotes a data storage unit, which stores and holds the software itself and information such as authentication information.

[0025] A connection control unit 505 performs processing related to connection and disconnection with a cellular network. In this embodiment, the connection control unit 505 has a function of determining a public wireless communication network to connect to based on ECN compatibility information.

[0026] A display control unit 506 controls the screen to be displayed on the output unit 404. This allows various notifications to be sent.

[0027] An ECN compatibility information detection unit 507 detects (acquires) whether the public wireless communication network supports the transmission of ECN compatibility information.

[0028] In this embodiment, the ECN support information is information indicating that the public wireless communication network to which the terminal is connected supports ECN (Explicit Congestion Notification). Specifically, the public wireless communication network has congestion detection capability, and the ECN support information indicates the following when congestion occurs: That is, the ECN support information is information indicating that the public wireless communication network has the capability to notify the terminal or application server of congestion using ECN (i.e., whether the public wireless communication network performs congestion detection and notification). The ECN support information may also be referred to as ECN Capable Transport information. The ECN support information is an example of congestion detection capability information related to congestion detection capability. Note that ECN is a technology defined in RFC8311 for notifying that congestion has occurred in a communication network. When congestion occurs in a communication network, a bit in the ECN field in the IP header is set to "1". This allows an IP communication device receiving the IP header to recognize that congestion has occurred in the communication network.

[0029] FIG. 6 is a diagram showing a flowchart of a process executed in the base station 20 of this embodiment to determine whether or not to include ECN compatibility information in an SIB (System Information Block) of a broadcast signal.

[0030] In this embodiment, this processing is performed by the control unit 202 reading and executing a computer program stored in the storage unit 203 when the base station 20 is started up or periodically.

[0031] After the process starts, it is determined whether or not an ECN non-compliance instruction has been received from the core network 10 (S601).

[0032] If the answer to step S601 is Yes, the ECN compatibility information is not included in the notification signal (SIB) (S602).

[0033] If step S601 is No, it is determined whether or not an ECN support instruction has been received from the core network 10 (S603).

[0034] If the answer to step S603 is Yes, ECN compatibility information is included in the notification signal (S604).

[0035] If step S603 is No, the ECN compatibility information is not included in the notification signal (S605).

[0036] Here, the format when ECN compatibility information is included in the broadcast signal is as shown in FIG.

[0037] As described above, the base station 20 determines, based on an instruction from the core network 10, whether or not to include ECN compatibility information in the broadcast signal that the base station 20 itself transmits.

[0038] FIG. 8 is a diagram showing a flowchart of the RRC layer connection process performed in the terminal 30 of this embodiment.

[0039] In this embodiment, this processing is performed by the control unit 401 reading and executing a computer program stored in the storage unit 402 when the terminal 30 is started up or when the airplane mode is changed from ON to OFF.

[0040] After the process starts, it is determined whether or not a notification signal has been received from a base station of the default destination network of the terminal 30 (S801).

[0041] If the answer at step S801 is No, the peripheral base stations other than the base station of the default destination network are scanned, and the counter i is initialized to i=1 (S802).

[0042] If the answer to step S801 is Yes, it is determined whether the received notification signal contains ECN compatibility information (S803).

[0043] If step S803 is No, the peripheral base stations other than the base station of the default destination network are scanned, and the counter i is initialized to i=1 (S802).

[0044] If step S803 is YES, the RRC connection process proceeds (S804). Specifically, an RRC Setup Request is transmitted.

[0045] In step S805 following step S802, the beacon of the i-th base station is received.

[0046] In step S806 following step S805, it is determined whether the notification signal received in step S805 includes ECN compatibility information.

[0047] If step S806 is YES, the RRC connection process is performed with the i-th base station (S810). Specifically, an RRC Setup Request is transmitted.

[0048] If step S806 is No, it is determined whether all the base stations around the terminal 30 are found to be ECN incompatible (S807).

[0049] If step S807 is No, the counter i is incremented by 1 (S808).

[0050] If step S807 is YES, the user is notified that all the surrounding base stations are ECN incompatible (S809).

[0051] As a result, the terminal 30 can connect to a base station that includes ECN compatibility information in the notification signal, and can notify the user if there is no base station that includes ECN compatibility information in the notification signal.

[0052] In the example shown in Figure 8, if the broadcast signal from a base station contains ECN compatibility information, the RRC connection process is automatically performed for that base station, but the RRC connection process may also be performed if other additional conditions are met.

[0053] [Second embodiment] The system diagram of the public wireless communication network in this embodiment is the same as that in Fig. 1 in the first embodiment. The hardware block configuration and software function block configuration related to wireless communication of the base station 20 in this embodiment are the same as those in Figs. 2 and 3 in the first embodiment. The hardware configuration and software function block configuration of the terminal 30 in this embodiment are the same as those in Figs. 4 and 5 in the first embodiment.

[0054] FIG. 9 is a diagram showing a flowchart of a process performed in the base station 20 of this embodiment to determine whether or not to include ECN compatibility information in an RRC Setup message.

[0055] In this embodiment, this processing is performed by the control unit 202 reading and executing a computer program stored in the storage unit 203 when the base station 20 is started up, after one RRC Setup sequence is completed, or periodically.

[0056] After the process starts, it is determined whether or not an ECN non-compliance instruction has been received from the core network 10 (S901).

[0057] If step S901 is Yes, the process waits until an RRC Setup Request is received from the terminal (S902), and when this is received, an RRC Setup message not including ECN support information is transmitted (S903).

[0058] If step S901 is No, the process waits until an RRC Setup Request is received from the terminal (S904), and when this is received, an RRC Setup message including ECN support information is transmitted (S905).

[0059] Here, the format when ECN support information is included in the RRC Setup message is as shown in FIG.

[0060] As described above, the base station 20 determines, based on an instruction from the core network 10, whether or not to include ECN compatibility information in the RRCSetup message that the base station 20 itself sends.

[0061] FIG. 11 is a diagram showing a flowchart of the RRC Setup process performed in the terminal 30 of this embodiment.

[0062] In this embodiment, this processing is performed by the control unit 401 reading and executing a computer program stored in the storage unit 402 when the terminal 30 is started up or when the airplane mode is changed from ON to OFF.

[0063] First, a counter i is initialized to i=1 (S1101).

[0064] In step S1102 following step S1101, an RRC Setup Request is sent to the i-th base station.

[0065] In step S1103 following step S1102, the process waits until a downlink RRC message is received, and if a downlink RRC message is received, it is determined whether the received downlink RRC message is RRC Setup (S1104).

[0066] If step S1104 is No, the RRC connection process is interrupted (S1105). Specifically, RRCSetupComplete is not transmitted to the i-th base station.

[0067] If the answer to step S1104 is Yes, it is determined whether ECN compatibility information is included in the RRCSetup (S1106).

[0068] If step S1106 is No, the RRC connection process is interrupted (S1105). Specifically, RRCSetupComplete is not transmitted to the i-th base station.

[0069] If step S1106 is YES, the RRC connection process is continued (S1107). Specifically, an RRCSetupComplete is transmitted to the i-th base station.

[0070] In step S1108 following step S1105, it is determined whether or not all of the base stations in the vicinity of the terminal 30 are found to be ECN incompatible (S1108).

[0071] If the answer to step S1108 is Yes, the mobile station connects to the base station of the default destination network (S1109).

[0072] If step S1108 is No, the counter i is incremented by 1 (S1110), and the process returns to step S1102.

[0073] As a result, the terminal 30 can connect to a base station that includes ECN compatibility information in the RRC Setup message. Also, if there is no base station that includes ECN compatibility information in the RRC Setup message, the terminal 30 can connect to a base station of a default destination network that is included in SIM (Subscriber Identity Module) information.

[0074] In this embodiment, the ECN compatibility information is included in the RRC Setup message transmitted by the base station 20. However, as shown in FIG. 12, the ECN compatibility information may be included in the RRC Reconfiguration message. In this case, for example, when a handover instruction is received, it is possible to determine whether the handover destination base station is ECN-capable. Alternatively, as shown in FIG. 13, the ECN compatibility information may be included in the RRC Resume message. In this case, when the terminal 30 returns from the RRC inactive state and connects to a different destination base station different from the one used before the return, it is possible to determine whether the different base station is ECN-capable. Furthermore, in this embodiment, whether to include the ECN compatibility information in the RRC Setup message transmitted by the base station 20 itself is determined based on an instruction from the core network 10. However, whether to include the ECN compatibility information may be configured in advance in the base station 20, rather than being instructed by the core network 10. For example, the base station 20 may store, in a memory or the like, information that is configured by a maintenance management device or the like and defines whether to include the ECN compatibility information in a broadcast signal transmitted by the base station 20 itself. The base station 20 may refer to the information to determine for itself whether or not to include ECN compatibility information in a broadcast signal or an RRC message.

[0075] [Third embodiment] The system diagram of the public wireless communication network in this embodiment is the same as that in Fig. 1 in the first embodiment. The hardware block configuration and software function block configuration related to wireless communication of the base station 20 in this embodiment are the same as those in Figs. 2 and 3 in the first embodiment. The hardware configuration and software function block configuration of the terminal 30 in this embodiment are the same as those in Figs. 4 and 5 in the first embodiment.

[0076] In this embodiment, the core network 10 includes ECN support information in an NAS message sent to the terminal 30 via the base station 20. In this embodiment, a Registration Accept is assumed as the NAS message, but other messages may be used. Here, the format when ECN support information is included in the NAS message is as shown in FIG. 14. This is an extension of the existing 5GS network feature support information element. If the value of octet6 and bit4 in FIG. 14 is 1, it indicates that ECN is supported.

[0077] FIG. 15 is a diagram showing a flowchart of the NAS layer connection process performed in the terminal 30 of this embodiment.

[0078] In this embodiment, this processing is performed by the control unit 401 reading and executing a computer program stored in the storage unit 402 when the terminal 30 transmits a Registration Request message.

[0079] First, in step S1501, the process waits until a Registration Accept message is received. If the message is received, the process determines whether a specific application (hereinafter abbreviated as "app") is currently running on the terminal 30 (S1502). The specific application may be, for example, an application that requires L4S (Low Latency, Low Loss, Scalable Throughput). An application that requires L4S is, for example, an XR (Extended Reality) application.

[0080] If S1502 is No, the connection process of the NAS layer proceeds (S1503). As a result, if the terminal 30 is not running a specific application, it is possible to proceed with the connection process of the NAS layer regardless of the presence or absence of ECN compatibility information. Note that, in a modified example, if S1502 is No, a connection attempt may be made preferentially to an ECN-incompatible network.

[0081] If S1502 is Yes, it is determined whether or not the received Registration Accept message contains ECN compatibility information, that is, whether or not octet 6 and bit 4 in FIG. 14 are 1 (S1504).

[0082] If S1504 is Yes, the connection process for the NAS layer is carried out (S1505).

[0083] If S1504 is No, the user is notified that the device is not ECN compatible (S1506).

[0084] As a result, the terminal 30 can connect to an ECN-compatible network. Furthermore, if no specific application is running, the terminal 30 can connect to a network regardless of whether the network supports ECN.

[0085] In this embodiment, support for ECN is indicated in the 5GS network feature support information element, but this is not limiting. Support for ECN may also be notified using S-NSSAI, which indicates the type of network slice supported by the core network. S-NSSAI is an abbreviation for Network Slice Selection Assistance Information. For example, as shown in FIG. 16, when the value of the SST (Slice Service Type) value included in S-NSSAI is 7, support for ECN may be newly indicated. Also, when the value of the SST value already defined in the same figure is 6, support for ECN may be indicated.

[0086] [Other embodiments] In this embodiment, a recording medium storing software program code for implementing the above-described functions may be supplied to a system or device, and the computer (CPU, MPU) of the system or device may read and execute the program code stored on the recording medium. Note that CPU is an abbreviation for Central Processing Unit, and MPU is an abbreviation for Micro Processing Unit. In this case, the program code itself read from the storage medium implements the functions of the above-described embodiment, and the storage medium storing the program code constitutes this embodiment. The functions can also be implemented by a circuit (e.g., an ASIC or FPGA) that implements one or more functions. Note that ASIC is an abbreviation for Application Specific Integrated Circuit. FPGA is an abbreviation for Field Programmable Gate Array. Furthermore, some or all of the various processes described in the above flowcharts can be implemented by a hardware circuit cooperating with a processor such as a CPU or MPU.

[0087] Examples of storage media that can be used to supply the program code include flexible disks, hard disks, optical disks, magneto-optical disks, CD (Compact Disc)-ROMs, CD-Rs, magnetic tapes, non-volatile memory cards, etc. Also usable are ROMs (Read Only Memory), DVDs (Digital Versatile Discs), HDDs (Hard Disk Drives), SSDs (Solid State Drives), etc.

[0088] In addition, the above-mentioned functions may be realized not only by the computer executing the read program code, but also by the operating system (OS) running on the computer performing some or all of the actual processing based on the instructions of the program code. OS is an abbreviation for Operating System.

[0089] Furthermore, the program code read from the storage medium may be written to a memory provided on a function expansion board inserted into a computer or a function expansion unit connected to the computer, and a CPU provided on the function expansion board or function expansion unit may then perform some or all of the actual processing based on the instructions of the program code to realize the above-mentioned functions.

[0090] Although each embodiment has been described in detail above, it is not limited to a specific embodiment, and various modifications and changes are possible within the scope of the claims. It is also possible to combine all or a plurality of components of the above-described embodiments.

[0091] For example, in the above-described embodiment, ECN support information is used as congestion detection capability information regarding the congestion detection capability of the network, but this is not limited to this.Instead of the ECN support information, information indicating a binary value indicating whether or not a function for notifying the occurrence of congestion using ECN is supported may be used as the congestion detection capability information.

[0092] In addition, the following supplementary notes are disclosed regarding the above-described embodiment.

[0093] [Appendix 1] A base station that performs communication in accordance with the 3GPP standard, a transmitting means for transmitting a downlink control plane message; A base station, characterized in that the downlink control plane message includes congestion detection capability information regarding congestion detection capability of the base station's network. [Appendix 2] The base station according to claim 1, wherein the congestion detection capability information is information indicating that the base station is compatible with a function for notifying that congestion has occurred using ECN (Explicit Congestion Notification). [Appendix 3] The base station according to Supplementary Note 1 or 2, characterized in that the congestion detection capability information is included in at least one of an RRC layer message, a base station notification signal, and a NAS (Non Access Stratum) layer message, an NAS layer information element, a 5GS network feature support information element, an S-NSSAI (Network Slice Selection Assistance Information), and a Slice Service Type. [Appendix 4] The base station according to Supplementary Note 3, wherein the RRC layer message includes an RRC message. [Appendix 5] 5. The base station according to claim 4, wherein the RRC message is an RRC Setup message, an RRC Reconfiguration message, or an RRC Resume message. [Appendix 6] 4. The base station according to claim 3, wherein the broadcast signal of the base station includes a System Information Block. [Appendix 7] The base station described in Supplementary Note 3, characterized in that the congestion detection capability information is included in a message of the RRC layer and the NAS layer. [Appendix 8] A communication terminal that performs communication in accordance with the 3GPP standard, a receiving means for receiving a downlink control plane message from a base station; A communication terminal, wherein the downlink control plane message includes congestion detection capability information regarding a congestion detection capability of the network of the base station. [Appendix 9] 9. The communication terminal according to claim 8, further comprising a decision means for deciding whether or not to connect to the base station's network based on the congestion detection capability information. [Appendix 10] The communication terminal according to Supplementary Note 9, wherein the determining means executes a connection to a network in which the congestion detection capability information is included in the downlink control plane message. [Appendix 11] The communication terminal according to claim 9 or 10, wherein the determination means attempts to connect preferentially to a network in which the congestion detection capability information is included in the downlink control plane message over a network in which the congestion detection capability information is not included in the downlink control plane message. [Appendix 12] The communication terminal according to any one of appendices 9 to 11, characterized in that, when the communication terminal is executing a predetermined communication application, the determination means attempts to connect to a network whose downlink control plane message includes the congestion detection capability information in preference to a network whose downlink control plane message does not include the congestion detection capability information. [Appendix 13] The communication terminal according to any one of appendices 9 to 12, characterized in that the determination means, when the communication terminal is not running a specified communication application, performs a connection to a network in which the congestion detection capability information is not included in the downlink control plane message. [Appendix 14] The communication terminal according to any one of appendices 8 to 13, characterized in that the congestion detection capability information is information indicating that the communication terminal is compatible with a function for notifying that congestion has occurred using ECN (Explicit Congestion Notification). [Appendix 15] The communication terminal according to any one of appendices 8 to 14, characterized in that the congestion detection capability information is included in at least one of an RRC layer message, a base station notification signal, and a NAS (Non Access Stratum) layer message, an NAS layer information element, a 5GS network feature support information element, an S-NSSAI (Network Slice Selection Assistance Information), and a Slice Service Type. [Appendix 16] A communication terminal according to any one of appendices 8 to 15, further comprising a notification means for notifying a user if there is no surrounding network in which the congestion detection capability information is included in the downlink control plane message. [Appendix 17] A control method for controlling communication of a base station that performs communication conforming to the 3GPP standard, transmitting a downlink control plane message; A control method, characterized in that the downlink control plane message includes congestion detection capability information regarding congestion detection capability of the local station's network. [Appendix 18] causing a computer of a base station that performs communication in accordance with the 3GPP standard to execute a process for transmitting a downlink control plane message; The program, characterized in that the downlink control plane message includes congestion detection capability information regarding congestion detection capability of the local station's network. [Appendix 19] A control method for controlling communication of a communication terminal that performs communication conforming to the 3GPP standard, receiving a downlink control plane message from a base station; A control method, characterized in that the downlink control plane message includes congestion detection capability information regarding congestion detection capability of the network of the base station. [Appendix 20] A computer in a communication terminal that communicates in accordance with the 3GPP standard Execute a process to receive a downlink control plane message from a base station; The program, wherein the downlink control plane message includes congestion detection capability information regarding congestion detection capability of the network of the base station. [Explanation of symbols]

[0094] 10 Core Network 20 base station 30 terminals (communication terminals) 505 Connection control unit (determining means)

Claims

1. A base station that performs communication in accordance with the 3GPP standard, a transmitting means for transmitting a downlink control plane message; A base station, characterized in that the downlink control plane message includes congestion detection capability information regarding congestion detection capability of the base station's network.

2. 2. The base station according to claim 1, wherein the congestion detection capability information is information indicating that the base station is compatible with a function of notifying the occurrence of congestion using an ECN (Explicit Congestion Notification).

3. The congestion detection capability information is included in at least one of an RRC layer message, a base station notification signal, and a NAS (Non Access Stratum) layer message, a NAS layer information element, a 5GS network feature support information element, an S-NSSAI (Network Slice Selection Assistance Information), and a Slice Service Type. The base station according to claim 1, characterized in that it is included in at least one of the following:

4. The base station according to claim 3 , wherein the RRC layer message includes an RRC message.

5. The base station according to claim 4 , wherein the RRC message is an RRC Setup message, an RRC Reconfiguration message, or an RRC Resume message.

6. The base station according to claim 3 , wherein the broadcast signal of the base station includes a System Information Block.

7. The base station according to claim 3 , wherein the congestion detection capability information is included in a message of the RRC layer and the NAS layer.

8. A communication terminal that performs communication in accordance with the 3GPP standard, a receiving means for receiving a downlink control plane message from a base station; A communication terminal, wherein the downlink control plane message includes congestion detection capability information regarding a congestion detection capability of the network of the base station.

9. 9. The communication terminal according to claim 8, further comprising a decision unit that decides whether or not to connect to the network of said base station based on said congestion detection capability information.

10. 10. The communication terminal according to claim 9, wherein the determining means executes a connection to a network whose downlink control plane message includes the congestion detection capability information.

11. 10. The communication terminal according to claim 9, wherein the determining means attempts to connect to a network in which the congestion detection capability information is included in the downlink control plane message with priority over a network in which the congestion detection capability information is not included in the downlink control plane message.

12. 12. The communication terminal according to claim 11, wherein, when the communication terminal is executing a predetermined communication application, the determination means attempts to connect to a network whose downlink control plane message includes the congestion detection capability information in preference to a network whose downlink control plane message does not include the congestion detection capability information.

13. 10. The communication terminal according to claim 9, wherein the determining means, when the communication terminal is not executing a predetermined communication application, performs a connection to a network in which the congestion detection capability information is not included in the downlink control plane message.

14. 9. The communication terminal according to claim 8, wherein the congestion detection capability information is information indicating that the communication terminal is compatible with a function of notifying the occurrence of congestion using ECN (Explicit Congestion Notification).

15. The congestion detection capability information is an RRC layer message, a base station notification signal, and a NAS (Non Access Stratum) layer message, a NAS layer information element, a 5GS network feature support information element, an S-NSSAI (Network Slice Selection Assistance Information), or a Slice Service Type. The communication terminal according to claim 8, characterized in that it is included in at least one of the following.

16. 9. The communication terminal according to claim 8, further comprising a notification means for notifying a user, when there is no surrounding network in which the congestion detection capability information is included in the downlink control plane message.

17. A control method for controlling communication of a base station that performs communication conforming to the 3GPP standard, comprising: transmitting a downlink control plane message; A control method, characterized in that the downlink control plane message includes congestion detection capability information regarding congestion detection capability of the local station's network.

18. causing a computer of a base station that performs communication conforming to the 3GPP standard to execute a process of transmitting a downlink control plane message; The program, characterized in that the downlink control plane message includes congestion detection capability information regarding congestion detection capability of the local station's network.

19. A control method for controlling communication of a communication terminal that performs communication conforming to the 3GPP standard, comprising: receiving a downlink control plane message from a base station; A control method, characterized in that the downlink control plane message includes congestion detection capability information regarding congestion detection capability of the network of the base station.

20. A computer of a communication terminal that performs communication in accordance with the 3GPP standard, Execute a process to receive a downlink control plane message from a base station; The program, wherein the downlink control plane message includes congestion detection capability information regarding congestion detection capability of the network of the base station.

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