Access network node, communication system and computer program

Abstract

To perform stable congestion control for an access network (AN) node during an overload state of an access and mobility management function, and achieve computing a proper value of signal regulation probability at the AN node.SOLUTION: An AN node comprises: a storage unit that stores the number of signals of wireless-communication-connection establishing requests from a terminal device for each connection establishing reason including a first reason to be a communication restriction target during congestion, and a second reason not to be a communication restriction target during congestion; a transmission unit that transmits the stored number of signals to a second control device, the second control device being provided apart from the first control device instructing the AN node to initiate the congestion control, the second control device judging necessary of the congestion control and generating an overload control instruction according to the judgment result; a reception unit that receives the overload control instruction from the second control device in response to the transmission of the number of signals; a congestion control unit that performs the congestion control for wireless communication based on the received overload control instruction.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an access network node, a communication system and a computer program. [Background technology]

[0002] Technical specifications for a fifth-generation mobile communication system (5G system) are described in Non-Patent Documents 1 and 2, etc. The technical specifications for the 5G system (5G specifications) stipulate that when an Access and Mobility management Function (AMF) falls into an overload state, the AMF executes NAS (Non-Access-Stratum) level congestion control, and if an Access Network (AN) node supports overload control, the AMF suppresses the load generated by the AN node (see Non-Patent Document 1, 5.19.5 "AMF Control Of Overload").

[0003] More specifically, the AMF sends an "NGAP OVERLOAD START" message to all or some AN ​​nodes to notify the AN nodes that its own AMF is in an overload state. The AN node that receives the "NGAP OVERLOAD START" message recognizes that the AMF that sent the "NGAP OVERLOAD START" message is in an overload state, and regulates traffic by rejecting signals that meet specific conditions among signals addressed to the AMF that sent the "NGAP OVERLOAD START" message. The AMF can include a signal regulation probability in the "NGAP OVERLOAD START" message. The AN node can use the regulation probability included in the "NGAP OVERLOAD START" message as the signal regulation probability for congestion control. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] 3GPP, “TS 23.501”, v17.2.0 [Non-patent document 2] 3GPP, “TS 38.413”, v16.8.0 [Non-patent document 3] 3GPP, “TS 23.288”, v17.5.0 Summary of the Invention [Problem to be solved by the invention]

[0005] In the conventional 5G specifications described above, if the AMF suddenly becomes overloaded due to a sudden increase in traffic, the AMF may fail to send the "NGAP OVERLOAD START" message, which could prevent the AN node from accurately starting congestion control.

[0006] Furthermore, when an AMF falls into an overload state, even if the AMF is able to send an "NGAP OVERLOAD START" message, it is difficult for the AMF to calculate an appropriate value for the signal barring probability. This is because it is difficult for an AMF in an overload state to obtain the information necessary for calculating the signal barring probability. The information necessary for calculating the signal barring probability is, for example, the number of signals per unit time transmitted from an AN node to the AMF. Since an AMF in an overload state cannot measure the number of signals per unit time, it is difficult for the AMF to calculate an appropriate value for the signal barring probability.

[0007] The present invention has been made in consideration of these circumstances, and its purpose is to enable AN nodes to stably perform congestion control when the AMF falls into an overload state, and to calculate an appropriate value for the signal restriction probability at the AN node. [Means for solving the problem]

[0008] (1) One aspect of the present invention is an access network node (AN node) in a mobile communication system, the access network node including a storage unit that stores the number of signals of a wireless communication connection establishment request from a terminal device for each connection establishment reason, the storage unit including a first reason that is subject to communication restriction during congestion and a second reason that is not subject to communication restriction during congestion, and a first control unit that is provided separately from a first control unit that instructs the AN node to start congestion control, and determines the necessity of congestion control and performs a process based on the determination result. The instruction includes a target value of the communication restriction probability calculated based on the number of signals that are not based on the connection establishment reason. a transmitting unit that transmits an overload control instruction to a second control device that generates the overload control instruction; and a receiving unit that receives the overload control instruction returned from the second control device in response to transmitting the number of signals. a restriction probability calculation unit that calculates a communication restriction probability based on the target value included in the received overload control instruction and the stored number of signals for each of the connection establishment reasons; the received overload control instruction The communication restriction probability calculated based on the target value included in and a congestion control unit that performs congestion control of wireless communication based on the above. ( 2 ) In one aspect of the present invention, in the above-mentioned access network node, the communication restriction probability is calculated as a restriction probability for the number of signals for the first reason for which communication restriction should be performed in order to achieve the target value. ( 3 ) One aspect of the present invention is that in the above-mentioned access network node, the number of signals transmitted by the transmitting unit includes information indicating the reason for connection establishment, and the overload control instruction includes a communication restriction probability for the number of signals of the first reason, and the overload control unit performs congestion control of wireless communication based on the communication restriction probability included in the received overload control instruction. ( 4) One aspect of the present invention is a communication system including an access network node (AN node) in a mobile communication system, and a second control device provided separately from a first control device that instructs the AN node to start congestion control, wherein the AN node includes a storage unit that stores the number of signals of a wireless communication connection establishment request from a terminal device for each connection establishment reason, the storage unit storing the number of signals of a wireless communication connection establishment request from a terminal device for each connection establishment reason, the first reason being a first reason that the communication is subject to communication restriction during congestion, and a second reason being a second reason that the communication is not subject to communication restriction during congestion, and a storage unit that stores the number of signals of a wireless communication connection establishment request from a terminal device for each connection establishment reason, the storage unit being provided separately from the first control device that instructs the AN node to start congestion control, and that determines the necessity of congestion control and performs a process based on the determination result. The instruction includes a target value of the communication restriction probability calculated based on the number of signals that are not based on the connection establishment reason. a transmitting unit that transmits an overload control instruction to a second control device that generates the overload control instruction; and a receiving unit that receives the overload control instruction returned from the second control device in response to transmitting the number of signals. a restriction probability calculation unit that calculates a communication restriction probability based on the target value included in the received overload control instruction and the stored number of signals for each of the connection establishment reasons; the received overload control instruction The communication restriction probability calculated based on the target value included in and a congestion control unit that performs congestion control of wireless communication based on the number of signals transmitted by the AN node, wherein the second control device comprises a second receiving unit that receives the number of signals transmitted by the AN node, a control instruction generating unit that generates the overload control instruction based on the received number of signals, and a second transmitting unit that transmits the generated overload control instruction to the AN node. ( 5 One aspect of the present invention is a method for determining whether a communication is necessary or not by a first control device that is provided separately from a first control device that instructs the AN node to start congestion control, and a method for determining whether a communication is necessary or not by ... The instruction includes a target value of the communication restriction probability calculated based on the number of signals that are not based on the connection establishment reason. a transmitting step of transmitting an overload control instruction to a second control device that generates the overload control instruction; and a receiving step of receiving the overload control instruction returned from the second control device in response to transmitting the number of signals. a restriction probability calculation step of calculating a communication restriction probability based on the target value included in the received overload control instruction and the stored number of signals for each of the connection establishment reasons; the received overload control instruction The communication restriction probability calculated based on the target value included in Based on this, a congestion control system is implemented to control congestion in wireless communication. Gosuand a computer program for executing the steps. [Effects of the Invention]

[0009] According to the present invention, it is possible to stably perform congestion control at an AN node when an AMF falls into an overload state, and to calculate an appropriate value for the signal restriction probability at the AN node. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram illustrating an example of the configuration of a control system according to an embodiment. [Figure 2] FIG. 10 is a diagram illustrating an outline of a control procedure at the start of congestion control according to the present embodiment. [Figure 3] FIG. 1 is a diagram illustrating an example of a device configuration of a control system according to an embodiment of the present invention. [Figure 4] FIG. 1 is a diagram showing an overview of a restriction probability procedure according to the present embodiment. [Figure 5] FIG. 1 is a diagram illustrating an example of a congestion control initiation procedure using AMF in the prior art. [Figure 6] FIG. 10 is a diagram illustrating an example of the ratio of the total signal traffic volume to the signal traffic volume subject to regulation. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1 is a diagram illustrating an example of the configuration of a control system 1 according to an embodiment. In FIG. 1, the control system 1 controls an AN node group 10 (AN node 11) and an AMF group 20 (AMF 21) of a 5G system.

[0012] As an example, the control system 1 includes an orchestrator 3, a RAN (Radio Access Network) controller 5, and a core controller 7. The RAN controller 5 performs control related to the AMF 21. The core controller 7 performs control related to the AMF 21. The orchestrator 3 manages and controls the RAN controller 5 and the core controller 7.

[0013] The operation of the control system 1 according to this embodiment will be described below.

[0014] [Overview of congestion control procedures] An outline of the control procedure at the start of congestion control in the control system 1 shown in Fig. 1 will be described with reference to Fig. 2. Fig. 2 is a diagram showing an outline of the control procedure at the start of congestion control according to this embodiment.

[0015] (Step S1) The RAN controller 5 (RAN Con.) collects information necessary for congestion control from the AN node 11. The core controller 7 (Core Con.) collects information necessary for congestion control from the AMF 21.

[0016] Examples of information required for congestion control include resource utilization rates (utilization rates of CPUs (Central Processing Units), memories, storage disks, NICs (Network Interface Cards), etc.), traffic capacity, traffic volume for each signal type, signal delay, etc. Of these examples of information required for congestion control, information to be collected is set in advance in the RAN controller 5 and the core controller 7, respectively.

[0017] The information required for congestion control can be collected from logs and statistical information held within each of the AMF 21 and the AN node, or the information required for congestion control can be collected from information generated from information held in the infrastructure (e.g., virtualization infrastructure) of each of the AMF 21 and the AN node.

[0018] For example, if the AMF 21 and the AN node 11 are constructed as CNFs (Cloud-native Network Functions) on a virtualization platform, a monitoring tool compatible with the virtualization platform can be used to collect information about the CNFs, such as resource usage rates, generated from information stored in the virtualization platform. Furthermore, the traffic capacity of the CNF itself, calculated from the amount of resources allocated to the CNFs on the virtualization platform, can be collected. Furthermore, information specific to the CNFs, such as the traffic volume for each signal type and signal delays, can be collected from logs and statistical information stored within the CNFs.

[0019] (Step S2) The RAN controller 5 transmits the information necessary for congestion control collected from the AN node 11 to the orchestrator 3. The core controller 7 transmits the information necessary for congestion control collected from the AMF 21 to the orchestrator 3. The information necessary for congestion control may be transmitted to the orchestrator 3 periodically or when a specific event occurs.

[0020] The specific event is, for example, the core controller 7 detecting an abnormality in the information necessary for congestion control collected from the AMF. The orchestrator 3, which has received the information necessary for congestion control from the core controller 7 in which this abnormality has been detected, may inquire about the information necessary for congestion control from the RAN controller 5, and may receive from the RAN controller 5 the information necessary for congestion control collected from the AN node 11.

[0021] (Step S3) The orchestrator 3 determines the necessity of congestion control in the AN node 11 based on the information required for congestion control received from the RAN controller 5 and the core controller 7, respectively.

[0022] An example of a method for determining the necessity of congestion control in the AN node 11 is shown below. If the total traffic volume of signals destined for AMF at AN node 11 exceeds the traffic capacity of AMF 21, it is determined that congestion control is necessary at AN node 11; on the other hand, if the total traffic volume does not exceed the traffic capacity of AMF 21, it is determined that congestion control is not necessary at AN node 11.

[0023] If it is determined that congestion control is necessary in the AN node 11, the process proceeds to step S4. On the other hand, if it is determined that congestion control is not necessary in the AN node 11, the processing of FIG. 2 ends.

[0024] (Step S4) The orchestrator 3 determines parameters to be used for congestion control in the AN node 11 based on the information required for congestion control received from the RAN controller 5 and the core controller 7, respectively. The parameters may include parameters determined by the AMF 21 in N2 overload control. The parameters determined by the AMF 21 in N2 overload control include, for example, the type of signal to be restricted, the probability of restricting the signal, a list of Network Slice Selection Assistance Information (NSSAI) to be subject to congestion control, and the probability of restricting the signal for each NSSAI.

[0025] The orchestrator 3 can obtain the traffic volume (number of signals) per unit time for each signal type in the AN node 11 using the RAN controller 5. The orchestrator 3 can also obtain the traffic capacity of the AMF 21 using the core controller 7. This allows the orchestrator 3 to calculate, for example, a value x that satisfies the following equation (1) as the target value for the signal restriction probability.

[0026]

number

[0027] C is the traffic capacity (number of signals that can be processed per unit time) of the AMF 21. D is the total number of signals per unit time that are transmitted from the AN node 11 to the AMF 21 when congestion control is not performed in the AN node 11. In addition, the orchestrator 3 determines the AN node 11 that performs congestion control and the AMF 21 that is the target of congestion control (the AMF 21 that is the destination of the signal that the AN node 11 restricts by congestion control).

[0028] (Step S5) The orchestrator 3 transmits a congestion control instruction message to the RAN controller 5. The congestion control instruction message includes information such as the AN node 11 that performs the congestion control, the AMF 21 that is the target of the congestion control, and parameters used for the congestion control in the AN node 11.

[0029] More specifically, the congestion control instruction message includes the target value of the signal restriction probability calculated as described above. In the following description, the congestion control instruction message is also referred to as an overload control instruction.

[0030] (Step S6) Upon receiving the congestion control instruction message from the orchestrator 3, the RAN controller 5 transmits a congestion control start message instructing the AN node 11 that performs the congestion control indicated in the instruction message to start congestion control. The congestion control start message includes information such as the AMF 21 that is the target of congestion control and parameters used for congestion control in the AN node 11.

[0031] (Step S7) When the AN node 11 receives the congestion control start message from the RAN controller 5, it sets the AMF 21 that is the target of congestion control indicated in the congestion control start message as the target of congestion control, and starts congestion control using the parameters used for congestion control included in the congestion control start message. This congestion control is the same operation as the congestion control executed by an AN node that receives an "NGAP OVERLOAD START" message specified in the 5G specifications from the AMF 21 that is the target of congestion control.

[0032] The above is an explanation of the outline of the operation procedure at the start stage of congestion control in the control system 1 according to this embodiment.

[0033] The AN node 11 may receive messages related to congestion control from both the RAN controller 5 and the AMF 21. Specifically, the AN node 11 may receive a congestion control start message or a congestion control end message from the RAN controller 5, while receiving an “NGAP OVERLOAD START” message from the AMF 21.

[0034] The AN node 11 prioritizes either the message regarding congestion control received from the RAN controller 5 or the message regarding congestion control received from the AMF 21.

[0035] For example, an on / off control of the RAN controller priority flag may be provided for the AN node 11. In this on / off control, the AN node 11 turns on the RAN controller priority flag when it receives a congestion control start message from the RAN controller 5, and turns off the RAN controller priority flag when it receives a congestion control end message from the RAN controller 5. When the RAN controller priority flag is on, the AN node 11 follows the message regarding congestion control received from the RAN controller 5.

[0036] For example, the AN node 11 may be set in advance to follow the message regarding congestion control received from the RAN controller 5 when the content of the message regarding congestion control received from the RAN controller 5 differs from the content of the message regarding congestion control received from the AMF 21. As a result, the AN node 11 follows the message regarding congestion control received from the RAN controller 5 when the content of the message regarding congestion control received from the RAN controller 5 differs from the content of the message regarding congestion control received from the AMF 21.

[0037] For example, the AN node 11 may be set in advance to follow the last received message regarding congestion control, so that the AN node 11 always follows the last received message regarding congestion control.

[0038] Furthermore, the AN node 11 may change the restriction probability for a signal that is the target of congestion control depending on the priority of the signal.

[0039] [Example of calculation procedure for signal regulation probability] Fig. 3 is a diagram showing an example of the device configuration of a control system 1 according to this embodiment. The control system 1 shown in Fig. 3 includes an AMF 21 (first control device) and a second control device 50. The AMF 21 and the second control device 50 are connected via a communication line. The AMF 21 and the second control device 50 are connected to the AN node 11 via a communication line. The second control device 50 is a control device corresponding to the RAN controller 5, the core controller 7, and the orchestrator 3 shown in Fig. 1 described above.

[0040] The second control device 50 is a control device provided separately from the AMF 21 (first control device) that instructs an access network node (AN node) 11 in a 5G system (mobile communication system) to start congestion control. The second control device 50 includes an information collection unit 51, a determination unit 52, a parameter determination unit 53, a transmission unit 54, and a resource extension control unit 55.

[0041] The information collection unit 51 collects predetermined information for congestion control in the AN node 11 from the AN node 11 and the AMF 21. The predetermined information for congestion control includes information on the number of signals stored in the AN node 11. The information collection unit 51 functions as a second receiving unit that receives the number of signals stored by the AN node. The determination unit 52 determines the necessity of congestion control in the AN node 11 based on the information collected by the information collection unit 51. The determination unit 52 functions as a control instruction generation unit that generates a congestion control start message (i.e., an overload control instruction) based on the number of signals received by the information collection unit 51. When the determination unit 52 determines that congestion control is necessary in the AN node 11, the transmission unit 54 transmits a congestion control start message instructing the AN node 11 to start congestion control. The transmission unit 54 functions as a second transmission unit that transmits the generated congestion control start message (i.e., an overload control instruction) to the AN node 11.

[0042] The parameter determination unit 53 determines parameters to be used for congestion control in the AN node 11 based on the information collected by the information collection unit 51. When the determination unit 52 determines that congestion control is necessary in the AN node 11, the transmission unit 54 transmits a message to the AN node 11 notifying the AN node 11 of the parameters determined by the parameter determination unit 53.

[0043] When the determining unit 52 determines that congestion control is not necessary in the AN node 11, the transmitting unit 54 transmits a congestion control end message to the AN node 11 instructing the AN node 11 to end the congestion control. Note that when the determining unit 52 determines that congestion control is not necessary in the AN node 11, there may be cases where the AN node 11 is not in a congested state to begin with and congestion control has not yet been initiated. In this case, the transmitting unit 54 does not need to transmit a congestion control end message.

[0044] The resource extension control unit 55 performs control to extend the resources available to the AMF 21 based on the information collected by the information collection unit 51. The determination unit 52 determines the necessity of congestion control in the AN node 11 based on the information collected by the information collection unit 51 after the resources available to the AMF 21 have been extended by the control of the resource extension control unit 55.

[0045] The AN node 11 is an access network node (AN node) in a 5G system (mobile communication system). The AN node 11 includes a receiving unit 111, a congestion control unit 112, a storage unit 113, a transmitting unit 114, and a restriction probability calculation unit 115.

[0046] FIG. 4 is a diagram showing an outline of the restriction probability procedure according to this embodiment. (Step S11) A terminal device (e.g., UE 40) transmits an RRC connection establishment request to the AN node 11. The RRC connection establishment request transmitted by the terminal device includes a connection establishment reason. The connection establishment reason is information indicating the type of communication to be established. The connection establishment reason includes, for example, a first reason that is subject to communication restriction during congestion (e.g., a general call other than an emergency call) and a second reason that is not subject to communication restriction during congestion (e.g., an emergency call).

[0047] (Step S12) The storage unit 113 stores the number of signals of wireless communication connection establishment requests from the terminal device for each connection establishment reason, which includes a first reason that is subject to communication restriction during congestion and a second reason that is not subject to communication restriction during congestion. That is, the number of signals for each reason for connection establishment is stored as past history information (e.g., statistical information) in storage unit 113. By referring to the number of signals for each reason for connection establishment stored in storage unit 113, it is possible to calculate the ratio of the amount of signal traffic that is subject to communication restrictions and the ratio of the amount of signal traffic that is not subject to communication restrictions to the total amount of signal traffic.

[0048] (Step S13) The transmitter 114 transmits the number of signals stored in the memory 113 to the second control device 50 (for example, any one of the RAN controller 5, the core controller 7, and the orchestrator 3). Here, the second control device 50 is provided separately from the first control device (for example, the AMF 21) that instructs the AN node 11 to start congestion control, and is a device that determines the necessity of congestion control and generates an overload control instruction based on the determination result.

[0049] Here, the transmitting unit 114 transmits the number of signals stored in the storage unit 113 to the second control device 50 by one of the following methods. (1) The transmitting unit 114 transmits the number of signals not depending on the reason for connection establishment (for example, the total number of signals) as the number of signals stored in the storage unit 113 to the second control device 50. In this case, the second control device 50 does not calculate the proportion of signal traffic volume that is subject to communication restriction or the proportion of signal traffic volume that is not subject to communication restriction. In this case, the second control device 50 calculates the signal restriction probability (i.e., the target value of the restriction probability) with respect to the total signal traffic volume. (2) The transmitting unit 114 transmits the number of signals for each connection establishment reason (for example, the number of signals subject to communication restriction and the number of signals not subject to communication restriction) as the number of signals stored in the memory unit 113 to the second control device 50. In this case, the second control device 50 can calculate the ratio of the amount of signal traffic subject to communication restriction and the ratio of the amount of signal traffic not subject to communication restriction to the total amount of signal traffic. In this case, the second control device 50 calculates the probability of signal restriction for the amount of signal traffic subject to communication restriction.

[0050] The following describes the above-mentioned method (1), ie, the case where the transmitting unit 114 transmits the number of signals (for example, the total number of signals) regardless of the reason for establishing connection to the second control device 50, as an example.

[0051] (Step S14) The second control device 50 determines whether or not congestion control is required. If the second control device 50 determines that congestion control is required (S14; YES), the process proceeds to step S15. If the second control device 50 determines that congestion control is not required (S14; NO), the second control device 50 transmits a congestion control end message (or does not start congestion control) and ends the process. (Step S15) The second control device 50 calculates the signal restriction probability (that is, the target value of the restriction probability) for the total signal traffic volume. (Step S16 ) The second control device 50 generates an overload control instruction including the calculated target value of the restriction probability, and transmits the generated overload control instruction to the AN node 11 . The overload control instruction may include the type of signal to be restricted. In this case, the second control device 50 generates an overload control instruction including the calculated target value of restriction probability and the type of signal to be restricted, and transmits the generated overload control instruction to the AN node 11.

[0052] (Step S17) The receiving unit 111 can receive messages related to congestion control (e.g., overload control instructions) from both the AMF 21 (first control device) that instructs the AN node 11 to start congestion control, and the second control device 50 that is provided separately from the AMF 21.

[0053] The overload control instruction received by the receiver 111 from the second control device 50 includes the restriction probability of the signal with respect to the total signal traffic volume (that is, the target value of the restriction probability). That is, the receiving unit 111 receives the overload control instruction returned from the second control device in response to transmitting the number of signals.

[0054] As described above, the overload control instruction received by the receiver 111 includes the signal restriction probability (i.e., the target value of the restriction probability) relative to the total signal traffic volume. In other words, the overload control instruction received by the receiver 111 includes the target value of the communication restriction probability calculated based on the number of signals regardless of the reason for connection establishment. The restriction probability calculation unit 115 calculates a communication restriction probability based on the target value included in the overload control instruction received by the receiving unit 111 and the number of signals for each connection establishment reason stored in the storage unit 113. As described above, the overload control instruction may include the type of signal to be restricted. In this case, the restriction probability calculation unit 115 calculates the communication restriction probability based on the target value and the type of signal to be restricted included in the overload control instruction received by the receiving unit 111, and the number of signals for each connection establishment reason stored in the storage unit 113.

[0055] In one example of this embodiment, the connection establishment reasons stored in the storage unit 113 include a first reason that is subject to communication restriction during congestion (e.g., a general call other than an emergency call) and a second reason that is not subject to communication restriction during congestion (e.g., an emergency call). The first reason is a connection establishment reason for which communication restriction should be performed in order to achieve a target value of the restriction probability. The second reason is a connection establishment reason that is not subject to communication restriction regardless of the target value of the restriction probability. The restriction probability calculation unit 115 calculates the restriction probability for the number of signals for the first reason (that is, the number of signals for which communication restriction should be performed to achieve the target value) out of the first reason and the second reason. In other words, the communication restriction probability is calculated as the restriction probability for the number of signals that is the first reason for communication restriction in order to achieve the target value.

[0056] (Step S18) Based on the overload control instruction received by the receiving unit 111, the congestion control unit 112 performs congestion control of wireless communication.

[0057] In one example of this embodiment, the congestion control unit 112 performs congestion control of wireless communication based on the communication restriction probability calculated based on the communication restriction probability calculated by the restriction probability calculation unit 115 (i.e., the target value included in the overload control instruction received from the second control device 50).

[0058] The congestion control unit 112 may be configured to prioritize either the message regarding congestion control received from the AMF 21 or the message regarding congestion control received from the second control device 50. For example, the congestion control unit 112 may prioritize the message regarding congestion control received from the second control device 50 over the message regarding congestion control received from the AMF 21, and change the restriction probability for the signal.

[0059] In addition, the method (2) described above can also be used, i.e., the transmitting unit 114 can transmit the number of signals for each reason for connection establishment (for example, the number of signals that are subject to communication restrictions and the number of signals that are not subject to communication restrictions) to the second control device 50. In this case, the number of signals transmitted by the transmitting unit 114 includes information indicating the reason for connection establishment. The second control device 50 calculates the probability of signal restriction for the amount of signal traffic that is subject to communication restriction. This restriction probability includes the probability of communication restriction for the number of signals for the first reason. The second control device 50 transmits an overload control instruction to the AN node 11, including the probability of communication restriction for the number of signals for the first reason. In this case, the congestion control unit 112 of the AN node 11 performs congestion control of wireless communication based on the communication restriction probability included in the received overload control instruction (that is, the communication restriction probability for the number of signals of the first reason).

[0060] [Comparison with conventional technology] FIG. 5 is a diagram showing an example of a congestion control initiation procedure by the AMF 21 in the prior art. As described above, when the AMF 21 falls into an overload state, the AMF 21 performs NAS-level congestion control or N2 overload control. In the NAS-level congestion control, the AMF 21 rejects a NAS message that has arrived at the AMF 21 from the UE 40. At this time, a back-off timer may be included in the rejection message. The UE 40 that has received the back-off timer cannot transmit a new NAS message until the back-off timer expires, except in some cases. In N2 overload control, the AMF21 sends an "NGAP OVERLOAD START" to all or some AN ​​nodes to notify them that it is in an overload state. An AN node that receives the "NGAP OVERLOAD START" recognizes that the AMF21 that sent the "NGAP OVERLOAD START" is in an overload state and restricts traffic by rejecting RRC connection establishment requests that meet certain conditions. The AMF21 can include conditions for determining which signals are subject to restriction (RRC Establishment Cause or NSSAI list) and the probability of signal restriction in the "NGAP OVERLOAD START," and the AN node can use this value for congestion control. The 5G mobile core defines the Network Data Analytics Function (NWDAF) as a function for collecting and analyzing data within the network. The NWDAF collects the number of registered UEs (40) per slice and resource information for each NF, and other NFs can obtain current system information values ​​and predicted future system information values ​​from the NWDAF.

[0061] In N2 overload control using the "NGAP OVERLOAD START" message, the AMF 21 must notify the AN node of the signal restriction probability. However, if the AMF 21 falls into a congested state due to bursty signal traffic, it is difficult for the AMF 21 to observe all signal traffic and specify an appropriate restriction probability. Therefore, a method can be considered in which an external device such as an NWDAF (e.g., the second control device 50) observes the signal traffic volume instead of the AMF 21 in a congested state. However, since N2 overload control does not apply to RRC connection establishment requests with high priority, such as emergency calls, in order to calculate an appropriate restriction probability, it is necessary to know the amount of signal traffic that is subject to restriction out of the total signal traffic volume.

[0062] FIG. 6 is a diagram showing an example of the ratio of the total signal traffic volume to the signal traffic volume subject to regulation. An example of signal traffic volume is: A: General (regulated) signal traffic volume (RRC connection establishment requests) is 100 requests / sec B: Emergency (non-restricted) signal traffic volume (RRC connection establishment requests) is 100 requests / sec The total number of requests is 200 requests / sec, and the processing performance of AMF21 is 150 requests / sec. In this case, in order to prevent congestion in the AMF 21, it is desired to reduce the signal traffic from 200 requests / sec to 150 requests / sec at the AN node 11. In other words, in order to prevent congestion in the AMF 21, it is desired to reduce the signal traffic volume at the AN node 11 by 25% of the total signal traffic volume. Here, if the ratio of general (restricted) signal traffic volume to the total signal traffic volume is unknown on the external device (for example, the second control device 50) side, the restriction probability will be calculated as 25%.

[0063] Therefore, the AN node 11 of this embodiment receives the restriction probability transmitted from the second control device 50 as the restriction probability for the total signal traffic volume (i.e., the target value of the restriction probability). The AN node 11 calculates the ratio of the general (restricted) signal traffic volume to the total signal traffic volume based on the number of signals of wireless communication connection establishment requests from terminal devices (e.g., UE 40) for each connection establishment reason stored in the storage unit 113. The AN node 11 calculates the restriction probability for the general (restricted) signal traffic volume based on the calculated ratio of the general (restricted) signal traffic volume to the total signal traffic volume and the target value of the restriction probability received from the second control device 50 (for example, using equation (2)).

[0064]

number

[0065] In equation (2), the restriction probability to be calculated is x, and the number of RRC connection establishment request signals to be restricted is S R , the number of signals of RRC connection establishment requests not subject to restrictions is S NR , the target total traffic is Tt, and the target reduction rate is Tx. R , S NR is the number of signals per AN node 11, and the number of transmission signals of the AN node group 10 connected to the AMF 21 that is the target of congestion control is Σ(S R ), Σ(S NR ) where Tt is a known value determined from the processing performance specifications of the AMF21. Tx is a value indicating the percentage reduction desired for all signals. For simplicity, the traffic load on the AMF21 in the subsequent signal processing is assumed to be constant when one RRC connection establishment request signal is not restricted, but the number of signals may be multiplied by a coefficient suited to the subsequent signal processing flow.

[0066] In the above example, the AN node 11 calculates that the proportion of general (restricted) signal traffic volume to the total signal traffic volume is 50%. Because the target value of the restriction probability received from the second control device 50 is 25%, the AN node 11 calculates the restriction probability for general (restricted) signal traffic volume to be 50% based on the received target value (25%) and the calculated proportion of general (restricted) signal traffic volume (50%).

[0067] Another example of a method for calculating the restriction probability is to tally up the total number of signals in the AN node group 10 and calculate a unified restriction probability x for the entire AN node group 10. In this case, the restriction probability x can be calculated by solving the following equation (3). However, if the calculation result is x<0, it is considered as x=0, and if x>1, it is considered as x=1.

[0068]

number

[0069] This is a method for finding the restriction probability x of each AN node 11 so as to achieve the target reduction rate. At this time, the restriction probability x can be calculated by solving the following equation (4). However, if the calculation result is x<0, it is considered as x=0, and if x>1, it is considered as x=1.

[0070]

number

[0071] In this case, the second control device 50 may transmit information about the target reduction rate to the AN nodes 11, and each AN node 11 may calculate the restriction probability x based on the above formula.

[0072] S used in the calculation of these restriction probabilities x R and S NR For the value of (2), the number of future signals predicted from the statistical value may be used instead of the actually collected statistical value. In addition, to prevent a situation in which an unrestricted RRC connection establishment request signal cannot be processed due to an unexpected increase in traffic, a constant or dynamic value may be added to the obtained value of the restriction probability x. For example, the uncertainty of the prediction may be calculated based on the degree of discrepancy between the future number of signals predicted from statistical values ​​and the actual number of signals, and a dynamic value according to the uncertainty may be added to the restriction probability x.

[0073] According to this embodiment, by providing a second control device 50 (RAN controller 5, core controller 7 and orchestrator 3), it is possible to obtain the effect of enabling stable congestion control to be performed on the AN node 11 when the AMF 21 falls into an overload state.

[0074] In addition, congestion control can be performed by using the target value of the restriction probability calculated by the second control device 50 (RAN controller 5, core controller 7, and orchestrator 3) as the restriction probability for general (restricted) signal traffic volume (i.e., a more appropriate restriction probability based on the reason for connection establishment).

[0075] [Variations] In the above example, a case has been described in which the AN node 11 includes the restriction probability calculation unit 115. That is, in the above example, the second control device 50 transmits the restriction probability for all signal traffic volume (i.e., the target value of the restriction probability) to the AN node 11, and the restriction probability calculation unit 115 of the AN node 11 calculates the restriction probability based on this target value of the restriction probability, but the present invention is not limited to this.

[0076] In this modification, the second control device 50 includes a restriction probability calculation unit 115. In this configuration, the AN node 11 transmits information for calculating the ratio of general (restricted) signal traffic volume to the total signal traffic volume to the second control device 50. The second control device 50 calculates the restriction probability for general (restricted) signal traffic volume based on the information for calculating the ratio of general (restricted) signal traffic volume to the total signal traffic volume. The second control device 50 transmits the calculated restriction probability to the AN node 11. The control system 1 configured in this modified example also makes it possible to perform congestion control using a restriction probability for general (restricted) signal traffic volume (that is, a more appropriate restriction probability based on the reason for connection establishment).

[0077] [Summary of the embodiment] According to this embodiment, by providing the second control device 50 (RAN controller 5, core controller 7 and orchestrator 3), it is possible to stably perform congestion control on the AN node 11 when the AMF 21 falls into an overload state, and it is also possible to calculate an appropriate value for the signal restriction probability at the AN node 11.

[0078] This will enable improvements in the overall service quality of mobile communication systems, such as 5G systems, and will contribute to Goal 9 of the United Nations-led Sustainable Development Goals (SDGs), which is to "Build resilient infrastructure, promote sustainable industrialization and foster innovation."

[0079] Although an embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and design changes and the like are also included within the scope that does not deviate from the gist of the present invention.

[0080] In addition, a computer program for realizing the functions of each of the above-described devices may be recorded on a computer-readable recording medium, and the program recorded on the recording medium may be read and executed by a computer system. Note that the "computer system" here may also include hardware such as an OS and peripheral devices. In addition, "computer-readable recording medium" refers to writable non-volatile memory such as a flexible disk, optical magnetic disk, ROM, or flash memory, portable media such as a DVD (Digital Versatile Disc), or a storage device such as a hard disk built into a computer system.

[0081] Furthermore, the term "computer-readable recording medium" also includes those that retain a program for a certain period of time, such as volatile memory (e.g., DRAM (Dynamic Random Access Memory)) within a computer system that serves as a server or client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. The program may be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by transmission waves in the transmission medium. Here, the "transmission medium" that transmits the program refers to a medium that has the function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line. The program may also be for realizing part of the above-mentioned functions. Furthermore, the above-mentioned functions may be realized in combination with a program already recorded in the computer system, that is, a so-called differential file (differential program). [Explanation of symbols]

[0082] 1...control system, 3...orchestrator, 5...RAN controller, 7...core controller, 10...AN node group, 11...AN node, 20...AMF group, 21...AMF, 50...second control device, 51...information collection unit, 52...determination unit, 53...parameter determination unit, 54...transmission unit, 55...resource extension control unit, 111...reception unit, 112...congestion control unit, 113...storage unit, 114...transmission unit, 115...restriction probability calculation unit

Claims

1. An access network node (AN node) in a mobile communication system, comprising: a storage unit that stores the number of signals of wireless communication connection establishment requests from the terminal device for each connection establishment reason including a first reason that is subject to communication restriction during congestion and a second reason that is not subject to communication restriction during congestion; a transmitter that transmits the stored number of signals to a second control device that is provided separately from a first control device that instructs the AN node to start congestion control, determines the necessity of congestion control, and generates an overload control instruction based on the determination result, the instruction including a target value of a communication restriction probability calculated based on the number of signals that is not based on the connection establishment reason; a receiving unit that receives the overload control instruction returned from the second control device in response to transmitting the number of signals; a restriction probability calculation unit that calculates a communication restriction probability based on the target value included in the received overload control instruction and the stored number of signals for each of the connection establishment reasons; a congestion control unit that performs congestion control of wireless communication based on the communication restriction probability calculated based on the target value included in the received overload control instruction; An access network node comprising:

2. The communication restriction probability is calculated as a restriction probability for the number of signals for the first reason for which communication restriction should be performed in order to achieve the target value.

10. An access network node according to claim 1.

3. the number of signals transmitted by the transmitting unit includes information indicating the reason for establishing the connection; The overload control instruction includes a probability of communication restriction for the number of signals of the first reason, The congestion control unit performs congestion control of wireless communication based on the communication restriction probability included in the received overload control instruction.

10. An access network node according to claim 1.

4. A communication system including an access network node (AN node) in a mobile communication system, and a second control device provided separately from a first control device that instructs the AN node to start congestion control, The AN node: a storage unit that stores the number of signals of wireless communication connection establishment requests from the terminal device for each connection establishment reason including a first reason that is subject to communication restriction during congestion and a second reason that is not subject to communication restriction during congestion; a transmitter that transmits the stored number of signals to a second control device that is provided separately from a first control device that instructs the AN node to start congestion control, determines the necessity of congestion control, and generates an overload control instruction based on the determination result, the instruction including a target value of a communication restriction probability calculated based on the number of signals that is not based on the connection establishment reason; a receiving unit that receives the overload control instruction returned from the second control device in response to transmitting the number of signals; a restriction probability calculation unit that calculates a communication restriction probability based on the target value included in the received overload control instruction and the stored number of signals for each of the connection establishment reasons; a congestion control unit that performs congestion control of wireless communication based on the communication restriction probability calculated based on the target value included in the received overload control instruction; Equipped with The second control device is a second receiving unit that receives the number of signals transmitted by the AN node; a control instruction generation unit that generates the overload control instruction based on the number of received signals; a second transmitting unit configured to transmit the generated overload control instruction to the AN node; A communication system comprising:

5. A computer of an access network node (AN node) in a mobile communication system, a storage step of storing the number of signals of wireless communication connection establishment requests from the terminal device for each connection establishment reason including a first reason that is subject to communication restriction during congestion and a second reason that is not subject to communication restriction during congestion; a transmitting step of transmitting the stored number of signals to a second control device that is provided separately from a first control device that instructs the AN node to start congestion control, determines the necessity of congestion control, and generates an overload control instruction based on the determination result, the instruction including a target value of a communication restriction probability calculated based on the number of signals that is not due to the connection establishment reason; a receiving step of receiving the overload control instruction returned from the second control device in response to transmitting the number of signals; a restriction probability calculation step of calculating a communication restriction probability based on the target value included in the received overload control instruction and the stored number of signals for each of the connection establishment reasons; a congestion control step of performing congestion control of wireless communication based on the communication restriction probability calculated based on the target value included in the received overload control instruction; A computer program for executing

Images