Electronic device and method for selecting network function in communication system

Abstract

Provided in embodiments is a management device for selecting a network function (NF). The management device may comprise: a memory configured to store instructions; at least one transceiver; and at least one processor. When executed by the at least one processor, the instructions can cause the management device to perform an NF selection procedure by: transmitting a request message to each of a plurality of NFs connected to the management device; receiving at least one response message from at least one of the plurality of NFs after transmitting the request message to each NF; obtaining connection state information of each NF on the basis of the request message transmitted to each NF and the at least one response message from the at least one NF; detecting a fault NF from among the plurality of NFs on the basis of the connection state information of each NF; and setting a restriction on a new call connection by using the fault NF.

Description

Electronic device and method for selecting network functions in a communication system

[0001] The present disclosure relates to a communication system. More specifically, the present disclosure relates to an electronic device and method for selecting a network function (NF) in a communication system.

[0002] To support a communication system, a base station can be connected to a core network. The 5G core network is provided based on a service-based architecture (SBA) centered on network function (NF) services. Each NF can be selected by another NF or registered with an NRF. For example, an NF registers the services it supports with a network repository function (NRF), which can then be used by other NFs for NF instance and service discovery.

[0003] The above information may be provided as background art to aid in understanding the present disclosure. No claim or determination is made as to whether any of the above is applicable as prior art related to the present disclosure.

[0004] In embodiments, a management device for network function (NF) selection is provided. The management device may include a memory configured to store instructions, at least one transceiver, and at least one processor. The instructions, when executed by the at least one processor, may cause the management device to transmit a request message to each NF of a plurality of NFs connected to the management device, receive at least one response message from at least one NF among the plurality of NFs after transmitting the request message to each NF, obtain connection state information of each NF based on the request message transmitted to each NF and the at least one response message from the at least one NF, detect a fault NF among the plurality of NFs based on the connection state information of each NF, and set a restriction on a new call connection using the fault NF, thereby performing an NF selection procedure.

[0005] In embodiments, a method performed by a management device for selecting a network function (NF) is provided. The method may include transmitting a request message to each NF of a plurality of NFs connected to the management device. The method may include receiving, after receiving the request message from each NF, at least one response message from at least one NF among the plurality of NFs. The method may include obtaining connection state information of each NF based on the request message transmitted to each NF and the at least one response message from the at least one NF. The method may include detecting a fault NF among the plurality of NFs based on the connection state information of each NF. The method may include performing an NF selection procedure by setting a restriction on a new call connection using the fault NF.

[0006] In embodiments, a non-transitory computer-readable storage medium is provided. The non-transitory computer-readable storage medium may include a memory configured to store instructions. The instructions, when executed by a processor, may cause a management device to transmit a request message to each NF of a plurality of NFs connected to the management device, receive at least one response message from at least one NF among the plurality of NFs after transmitting the request message to each NF, obtain connection state information of each NF based on the request message transmitted to each NF and the at least one response message from the at least one NF, detect a fault NF among the plurality of NFs based on the connection state information of each NF, and set a restriction on a new call connection using the fault NF, thereby performing an NF selection procedure.

[0007] Figure 1a illustrates an example of a communication system.

[0008] Figure 1b illustrates an example of a core network.

[0009] Figure 2 shows an example of NF (network function) selection.

[0010] Figure 3 shows an example of components of a management device for NF selection.

[0011] Figure 4 shows an example of signaling of a management device and NF for obtaining connection status information.

[0012] Figure 5a shows an example of data set collection.

[0013] Figure 5b shows an example of a learning model for quality metrics.

[0014] Figure 6 shows the operation flow of a management device for performing an NF selection procedure based on defective NF detection.

[0015] Figures 7a to 7d show examples of NF selection.

[0016] Figure 8 shows an example of quality indicators for selecting a policy control function (PCF).

[0017] The terms used in this disclosure are used only to describe specific embodiments and may not be intended to limit the scope of other embodiments. The singular expression may include plural expressions unless the context clearly indicates otherwise. Terms used herein, including technical or scientific terms, may have the same meaning as commonly understood by those of ordinary skill in the art described in this disclosure. Terms defined in general dictionaries among the terms used in this disclosure may be interpreted as having the same or similar meaning in the context of the relevant technology, and shall not be interpreted in an idealized or overly formal sense unless explicitly defined in this disclosure. In some cases, even if a term is defined in this disclosure, it cannot be interpreted to exclude embodiments of the present disclosure.

[0018] The various embodiments of the present disclosure described below illustrate a hardware-based approach as an example. However, since the various embodiments of the present disclosure include techniques utilizing both hardware and software, the various embodiments of the present disclosure do not exclude a software-based approach.

[0019] In the following description, terms referring to signals (e.g., signal, information, message, signaling, data), terms referring to data types (e.g., list, set, subset), terms for operational states (e.g., step, operation, procedure), terms referring to data (e.g., packet, user stream, information, bit, symbol, codeword), terms referring to resources (e.g., symbol, slot, subframe, radio frame, subcarrier, resource element (RE), resource block (RB), bandwidth part (BWP), occasion), terms referring to channels, terms referring to network entities, terms referring to components of devices, etc. are examples for convenience of description. Therefore, the present disclosure is not limited to the terms described below, and other terms having equivalent technical meanings may be used.

[0020] In the following description, terms referring to signals (e.g., signal, information, message, signaling), terms referring to resources (e.g., symbol, slot, subframe, radio frame, subcarrier, resource element (RE), resource block (RB), bandwidth part (BWP), occasion), terms for operational states (e.g., step, operation, procedure), terms referring to data (e.g., packet, user stream, information, bit, symbol, codeword), terms referring to channels, terms referring to network entities, terms referring to components of devices, etc. are examples for convenience of description. Therefore, the present disclosure is not limited to the terms described below, and other terms having equivalent technical meanings may be used.

[0021] In the present disclosure, expressions such as “more than” or “less than” may be used to determine whether a specific condition is satisfied or fulfilled, but this is merely a description for expressing an example and does not exclude descriptions such as “more than” or “less than.” A condition described as “more than” may be replaced with “more than,” a condition described as “less than” may be replaced with “less than,” and a condition described as “more than and less than” may be replaced with “more than and less than.” In addition, hereinafter, “A” to “B” mean at least one of elements from A (including A) to B (including B). hereinafter, “C” and / or “D” mean at least one of “C” or “D,” that is, including {“C,” “D,” “C” and “D”}.

[0022] Although the present disclosure describes various embodiments using terms used in some communication standards (e.g., 3rd Generation Partnership Project (3GPP), European Telecommunications Standards Institute (ETSI), extensible radio access network (xRAN), open-radio access network (O-RAN), etc.), these are merely examples for explanation. The various embodiments of the present disclosure can be easily modified and applied to other communication systems.

[0023] Figure 1a illustrates an example of a communication system (100).

[0024] Referring to FIG. 1A, a communication system (100) may include a terminal (110). The terminal (110) is a device used by a user and communicates with a base station (120) via a wireless channel. The link from the base station (120) to the terminal (110) is referred to as a downlink (DL), and the link from the terminal (110) to the base station (120) is referred to as an uplink (UL). In addition, although not shown in FIG. 1A, the terminal (110) and another terminal may communicate with each other via a wireless channel. In this case, the link between the terminal (110) and another terminal (device-to-device link, D2D) is referred to as a sidelink, and the sidelink may be used interchangeably with the PC5 interface. In some other embodiments, the terminal (110) may be operated without the intervention of a user. According to one embodiment, the terminal (110) is a device that performs machine type communication (MTC) and may not be carried by a user. Furthermore, according to one embodiment, the terminal (110) may be a narrowband (NB)-internet of things (IoT) device. The terminal (110) may be referred to as a 'user equipment (UE)', a 'customer premises equipment (CPE)', a 'mobile station', a 'subscriber station', a 'remote terminal', a 'wireless terminal', an electronic device', a 'user device', or other terms having equivalent technical meanings thereto. Hereinafter, in describing the mobility of the terminal of the present disclosure, the terminal (110) is referred to as a UE, but it is to be understood that other terms may be used depending on the communication environment or embodiment.

[0025] The base station (120) is a network infrastructure that provides wireless access to the terminal (110). The base station (120) has coverage defined based on the distance over which a signal can be transmitted. In terms of providing an access network (AN) other than a base station, the base station (120) may be referred to as a 'RAN node', a 'network node', or an 'access point (AP)', or in terms of a supported radio access technology (RAT), it may be referred to as an 'eNodeB (eNB)', a '5G node (5th generation node)', a 'next generation nodeB (gNB)', a 'wireless point', a 'transmission / reception point (TRP)', or other terms having an equivalent technical meaning thereto.

[0026] Although a single network entity is illustrated in FIG. 1A, embodiments of the present disclosure are not limited thereto. For example, the base station (120) may be implemented in a distributed deployment according to a central unit (CU) (505) configured to perform functions of upper layers (e.g., PDCP, RRC) of the access network and a distributed unit (DU) configured to perform functions of lower layers (e.g., RLC, MAC, PHY). For example, to reduce installation costs and increase the available cell coverage, the base station (120) may be implemented with geographically distributed DUs and RUs.

[0027] The core network (133) may be configured to connect the base station (120) to a data network. The core network (133) may include various network entities for managing mobility, session management, policy management, and / or data network connections, and each network entity may represent a node defining a specific network function. For example, the core network (133) may be referred to as an evolved packet core (EPC) (or evolved packet system (EPS)) as a set of network entities for an LTE access network. For example, the core network (133) may be referred to as a 5GC (5 th generation core)(or 5GS(5 th As an example of a core network (133), 5GC is described in detail through Fig. 1b.

[0028] Figure 1b illustrates an example of a core network (e.g., core network (133)).

[0029] Referring to FIG. 1B, the UE exemplifies the terminal (110) of FIG. 1A, and the RAN Node exemplifies the base station (120) of FIG. 1B. Network entities of the core network (133) may include various network functions (NFs). The terminal (110) and the base station (120) may communicate with the NFs of the core network. For example, the core network (133) may include an access and mobility management function (AMF) (130), a session management function (SMF) (140), a user plane function (UPF) (150), a policy and charging function (PCF) (170), and a unified data management (UDM) (180).

[0030] AMF (130) provides a function for access and mobility management per UE (e.g., terminal (110)), and one UE can basically be connected to one AMF.Specifically, the AMF (130) provides signaling between CN (e.g., core network (133)) nodes for mobility between 3GPP access networks, termination of a radio access network (RAN) control plane (CP) interface (i.e., N2 interface), termination of NAS signaling (N1), non-access stratum (NAS) signaling security (NAS ciphering and integrity protection), access stratum (AS) security control, registration management (registration area management), connection management, idle mode UE reachability (including control and performance of paging retransmission), mobility management control (subscription and policy), intra-system mobility and inter-system mobility support, support of network slicing, SMF selection, lawful intercept (for AMF events and interfaces to the LI system), and communication between the UE and the SMF (e.g., It can support functions such as providing transmission of session management (SM) messages between SMFs (140), transparent proxy for SM message routing, access authentication, access authorization including roaming permission check, providing transmission of short message service (SMS) messages between UEs and short message service function (SMSF), security anchor function (SAF) and / or security context management (SCM). Some or all of the functions of AMF (130) can be supported within a single instance of one AMF.Depending on the example, the AMF (130) may select an NF from among multiple NFs. For example, the AMF (130) may perform SMF selection or PCF (policy charging function) selection.

[0031] SMF (140) can provide session management functions. If a UE (e.g., terminal (110)) has multiple sessions, each session can be managed by a different SMF. Specifically, the SMF (140) may support functions such as session management (e.g., session establishment, modification, and termination, including tunnel maintenance between the UPF (150) and the AN node (e.g., base station (120)), UE IP address allocation and management (optionally including authentication), selection and control of UP functions, traffic steering setup to route traffic from the UPF to the appropriate destination, termination of the interface to policy control functions, enforcement of the control portion of policies and quality of service (QoS), lawful intercept (for SM events and interfaces to the LI system), termination of the SM portion of NAS messages, downlink data notification, initiator of AN specific SM information (delivered to the AN node via N2 via AMF), determination of the SSC mode of the session (e.g., SSC mode 2, SSC mode 3), roaming functions, etc. According to embodiments, UPF selection may be performed by the SMF (140). Some or all of the functions of the SMF (140) may be supported within a single instance of one SMF. According to embodiments, the SMF (140) may select an NF from among multiple NFs. For example, the SMF (140) may perform UPF selection or PCF selection.

[0032] UPF (150) can transmit a downlink PDU received from DN (155) to terminal (110) via base station (120), or transmit an uplink PDU received from terminal (110) via base station (120) to DN (155). Specifically, the UPF (150) may support functions such as an anchor point for intra / inter RAT mobility, an external PDU session point for interconnection to a data network, a user plane portion of packet routing and forwarding, packet inspection and policy rule enforcement, an uplink classifier to support lawful intercept, traffic usage reporting, routing of traffic flows to the data network, a branching point to support multi-homed PDU sessions, QoS handling for the user plane (e.g., packet filtering, gating, uplink / downlink rate enforcement), uplink traffic validation (service data flow (SDF) mapping between SDFs and QoS flows), transport level packet marking in uplink and downlink, downlink packet buffering and downlink data notification triggering. Some or all of the functions of UPF (150) may be supported within a single instance of a UPF.

[0033] DN (155) represents an Internet network for connecting to an external communication network. For example, DN (155) may be an operator service, Internet access, or a third party (3 rdparty) service, etc. DN (155) transmits a downlink protocol data unit (PDU) to UPF (150) or receives a PDU transmitted from a terminal (110) from UPF (150).

[0034] PCF (170) can receive information about packet flow from an application server and provide a function to determine policies such as mobility management and session management. Specifically, PCF (170) supports functions such as supporting a unified policy framework for controlling network operations, providing policy rules so that CP functions (e.g., AMF (130), SMF (140), etc.) can enforce the policy rules, and implementing a front end for accessing related subscription information for policy determination within a user data repository (UDR).

[0035] UDM (180) stores user subscription data, policy data, etc. UDM (180) may include two parts: an application front end (FE) and a user data store (UDR).

[0036] The core network (133) may include various NFs in addition to the network entities / network functions described above. For example, the core network (133) may include a network slice selection function (NSSF) (191), a network exposure function (NEF) (192), a network repository function (NRF) (193), a network slice-specific authentication and authorization (NSSAAF) (194), an authentication server function (AUSF) (195), an application function (AF) (196), a service communication proxy (SCP) (197), and a network slice admission control function (NSACF) (198).

[0037] NSSF (191) may support the function of selecting a set of network slice instances that provide services to the terminal (110). NSSF (191) may determine allowed NSSAI (network slice selection assistance information) and, if needed, determine a mapping to a subscribed S (single)-NSSAI. NSSF (191) may determine a configured NSSAI and, if needed, determine a mapping to a subscribed S-NSSAI. NSSF (191) may determine a set of AMFs used to serve the UE, or, based on the configuration, by querying the NRF for a list of AMFs. NSSF (191) may provide support for network slice restrictions and network slice instance restrictions based on NWDAF analysis.

[0038] The NEF (192) may provide a means to securely expose services and capabilities provided by 3GPP NFs, for example, for third parties, internal exposure / re-exposure, application functions, and edge computing. The NEF (192) receives information from other NFs or based on capabilities exposed to other NFs. The NEF (192) may store the received information as structured data using a standardized interface to a data storage network function. The stored information may be re-exposed by the NEF (192) to other NFs and AFs (e.g., AF (196)) and used for other purposes, such as analysis.

[0039] NRF (193) can support service discovery functionality. NRF (193) can receive NF discovery requests from NF instances and provide information about discovered NF instances to the NF instances. In addition, NRF (193) maintains available NF instances and the services they support. NF discovery and selection can be performed independently by a specific NF or with reference to NRF (193).

[0040] NSSAAF(194) can support authentication and authorization functions per network slice.

[0041] AUSF (195) stores data for authentication of UE (e.g. terminal (110)).

[0042] The AF (196) can interact with the 3GPP core network to provide services (e.g., support functions such as application influence on traffic routing, network capability exposure access, and interaction with the policy framework for policy control).

[0043] The SCP (197) can perform functions such as indirect communication, delegated discovery, message forwarding and routing to target NF / NF services, message forwarding and routing to next hop SCPs, communication security (e.g., authorizing NF service consumers to access NF service producer APIs), load balancing, monitoring, and overload control. The SCP (197) can be deployed in a distributed manner. For example, there can be two or more SCPs in a communication path between NF services. Messages can be routed through SCPs. For example, to enable the message routing (i.e., next SCP hop discovery), the SCP (197) can register a profile with the NRF (e.g., the NRF (193)). For another example, the SCP (197) can use a local configuration. Some or all of the functions of the SCP (197) can be supported within a single instance of an AMF.

[0044] NSACF (198) can monitor and control the number of registered UEs per network slice for a network slice to which network slice admission control is applied.

[0045] In the 3GPP system, the conceptual links connecting NFs within a 5G system are defined as reference points or interfaces. The following illustrates reference points included in the 5G system architecture depicted in Figure 1.

[0046] - N1: Reference point or interface between terminal (110) and AMF (130)

[0047] - N2: Reference point or interface between base station (120) and AMF (130)

[0048] - N3: Reference point or interface between base station (120) and UPF (150)

[0049] - N4: Reference point or interface between SMF (140) and UPF (150)

[0050] - N5: Reference point or interface between PCF (170) and AF (196)

[0051] - N6: Reference point or interface between UPF (150) and DN (155)

[0052] - N7: Reference point or interface between SMF (140) and PCF (170)

[0053] - N8: Reference point or interface between UDM (180) and AMF (130)

[0054] - N9: Reference point or interface between two core UPFs (e.g. UPF(150))

[0055] - N10: Reference point or interface between UDM (180) and SMF (140)

[0056] - N11: Reference point or interface between AMF (130) and SMF (140)

[0057] - N12: Reference point or interface between AMF (130) and AUSF (195)

[0058] - N13: Reference point or interface between UDM (180) and AUSF (195)

[0059] - N14: Reference point or interface between two AMFs (e.g. AMF(130))

[0060] - N15: For non-roaming scenarios, a reference point between the PCF (170) and the AMF (130), and for roaming scenarios, a reference point or interface between the PCF (170) and the AMF (130) within the visited network.

[0061] Fig. 2 illustrates an example of NF (network function) selection. The NF selection refers to identifying an NF among multiple NFs. The types of the multiple NFs are one of the NFs exemplified through Fig. 1b (e.g., AMF (130), SMF (140), UPF (150), PCF (170), NEF (192), etc.).

[0062] Referring to FIG. 2, the management device (201) can perform NF selection according to embodiments of the present disclosure. For example, the management device (201) can select an NF from among a plurality of NFs (e.g., NF (230-1), NF (230-2), ..., NF (230-N)). The management device (201) can activate a call connection using the NF or use services provided by the NF (hereinafter, NF service). An NF can expose one or more NF services. An NF service represents one type of capability exposed by an NF (e.g., an NF service producer) to another NF (e.g., an NF service consumer) via a service based interface (SBI). Hereinafter, in the present disclosure, the management device (201) is understood as an NF consumer in terms of being a subject that performs NF selection, and the NF selected by the management device (201) can be understood as an NF producer.

[0063] The management device (201) may be a different NF from the NF being selected or a network entity associated with a specific NF. In one embodiment, the management device (201) may be an entity operating as the AMF (130) or a separate device connected to the AMF (130). For example, the NF (230) may be an SMF (140). The management device (201) may select a specific SMF from among a plurality of SMFs as or for the AMF (130). For example, the NF (230) may be a PCF (170). The management device (201) may select a specific PCF from among a plurality of PCFs as or for the AMF (130). For example, the NF (230) may be a CHF (charging function). The management device (201) can select a specific CHF from among a plurality of CHFs as or for the AMF (130).

[0064] In one embodiment, the management device (201) may be an entity operating as the SMF (140) or a separate device connected to the SMF (140). For example, the NF (230) may be a UPF (150). The management device (201) may select a specific UPF from among a plurality of UPFs as or for the SMF (140). For example, the NF (230) may be a PCF (170). The management device (201) may select a specific PCF from among a plurality of PCFs as or for the SMF (140). For example, the NF (230) may be a CHF. The management device (201) may select a specific CHF from among a plurality of CHFs as or for the SMF (140).

[0065] In one embodiment, the management device (201) may be an entity that operates as the PCF (170) or a separate device connected to the PCF (170). For example, the NF (230) may be a CHF. The management device (201) may select a specific CHF from among a plurality of CHFs as or for the PCF (170).

[0066] In one embodiment, the management device (201) may be a separate device connected to the base station (120). For example, the NF (230) may be an AMF (130). The management device (201) may select a specific AMF from among a plurality of AMFs for the base station (120).

[0067] In core networks (e.g., core network (133), EPC, 5GC), NF selection for services can be utilized for load balancing and fault management. Typically, NFs can form groups, and each NF within the group can serve as a backup NF for another NF. For example, if the connection to a specific NF is lost, the NF consumer can continue to receive service through another NF within the group. As technology advances, the types of NFs within the core network (e.g., core network (133)) are increasing in number and decreasing in size, making network management through NF selection more complex. Previously, a backup NF was selected only in extreme cases, such as when the connection to a specific NF was lost. Therefore, it was difficult to exclude an NF with degraded quality while maintaining connectivity from selection or to take preemptive action before communication became unavailable. Manual control by the operator is required to exclude a problematic NF or adjust the selection ratio. However, monitoring and manually controlling a large number of NFs is practically difficult. Therefore, technologies for automatic fault control are required, utilizing network data collected from each NF. To address the above-described issues, this disclosure describes technologies for preemptively detecting NFs predicted to have faults through network data statistics and limiting call inflow to those NFs.

[0068] According to embodiments of the present disclosure, a management device (201) can evaluate the service quality of an NF linked to the management device (201) and perform fault control of the NF based on the analyzed network data statistics. In order to evaluate the service quality of the NF connected to the management device (201), the management device (201) can transmit a request message to each NF. The management device (201) can receive a response message from at least one NF. The response message can indicate acceptance or rejection. Additionally, the management device (201) may not receive any response from the NF (i.e., no response). The management device (201) can obtain information on the connection status of the NF based on the result according to the request message. The management device (201) can obtain information on the service quality of the NF based on the information on the connection status. The management device (201) can detect an NF (hereinafter, a fault NF) that is predicted to have a fault based on the service quality of each NF. The management device (201) can detect (or identify, determine) a fault NF among a plurality of NFs (e.g., NF (230-1), NF (230-2), ..., NF (230-N)). The management device (201) can restrict the inflow of new calls to the fault NF or reset the distribution ratio so that the call distribution ratio to the fault NF is lowered.

[0069] FIG. 3 shows an example of components of a management device for NF selection (e.g., management device (201)). The management device (201) may be a communication device that operates as another NF connected to the NF (230) that is the selection target, a separate device connected to the other NF, and / or a separate device connected to a base station (e.g., base station (120)). Terms such as '... unit', '... device', etc. used hereinafter mean a unit that processes at least one function or operation, and this may be implemented by hardware or software, or a combination of hardware and software.

[0070] Referring to FIG. 3, the electronic device may include a transceiver (310), a memory (320), and a processor (330).

[0071] The transceiver (310) provides an interface for communicating with other devices within a network. That is, the transceiver (310) converts a bit string transmitted from an electronic device to another electronic device into a physical signal, and converts a physical signal received from another electronic device into a bit string. That is, the transceiver (310) can transmit or receive signals. Accordingly, the transceiver (310) may be referred to as a modem, a communication unit, a transmit unit, a receive unit, or a transmit / receive unit. In this case, the transceiver (310) enables the electronic device to communicate with other electronic devices or systems via a backhaul connection (e.g., a wired backhaul or wireless backhaul) or via a network. The transceiver (310) may include one or more transceivers.

[0072] The transceiver (310) may perform functions for transmitting and receiving signals in a wired communication environment. The transceiver (310) may include a wired interface for controlling direct connection between devices via a transmission medium (e.g., copper wire, optical fiber). For example, the transceiver (310) may support an N2 interface. The transceiver (310) may transmit electrical signals to a node of a base station (e.g., gNB, gNB-CU, gNB-CU-CP) via copper wire, or may perform conversion between electrical signals and optical signals. The management device (210) may be connected to one or more base stations (e.g., base station (120)) via the transceiver (310). In addition, the transceiver (310) may also perform functions for transmitting and receiving signals in a wireless communication environment. For example, the transceiver (310) may support an N1 interface. The management device (201) can support NAS signaling through the transceiver (310). The management device (201) can transmit NAS messages to the terminal (110) through the transceiver (310).

[0073] The memory (320) stores data such as basic programs, application programs, and setting information for the operation of the management device (201). The memory (320) may be composed of volatile memory, non-volatile memory, or a combination of volatile memory and non-volatile memory. In addition, the memory (320) provides stored data upon request from the processor (330). The memory (320) may be referred to as a storage unit.

[0074] The processor (330) controls the overall operations of the management device (201). For example, the processor (330) transmits and receives signals via the transceiver (310). Additionally, the processor (330) writes and reads data to and from the memory (320). The processor (330) may be referred to as a control unit. For this purpose, the processor (330) may be composed of multiple processors or may include at least one sub-processor. According to various embodiments, the processor (330) may control the management device (201) to perform operations according to various embodiments described in the present disclosure.

[0075] In the present disclosure, NF is a logical element for supporting a specific network service and can be implemented as software as well as separate hardware. For example, when transmitting or receiving a message with NF, the management device (201) may call and execute a command corresponding to the message transmission, rather than directly transmitting the message to a physical entity. The management device (201) may be implemented as software including one or more commands. For example, the management device (201) may call and execute at least one command among one or more commands stored from a storage medium. This enables the device to operate to perform at least one function according to the at least one command called. The one or more commands may include code generated by a compiler or code executable by an interpreter. For network virtualization, the operations of the management device (201) according to embodiments may be implemented in the form of a storage medium (e.g., memory).

[0076] FIG. 4 illustrates an example of signaling between a management device (e.g., management device (201)) and an NF (e.g., NF (230)) for obtaining connection status information. NF (230) exemplifies one NF among NF (230-1), NF (230-2), ..., NF (230-N)) of FIG. 2. Hereinafter, the operations of NF (230) can be understood as operations of a device configured to perform NF (230).

[0077] Referring to FIG. 4, in operation (401), the management device (201) may transmit a request message to the NF (230). The request message may be used to request the NF (230) to provide an NF service. The request message may be used to confirm the connection status of the NF (230). The connection status may indicate a communication status related to a call connection using the NF (230).

[0078] In operation (403), the management device (201) may receive a response message from the NF (230). The NF (230) may generate the response message in response to a request from the management device (201), which is a service consumer. The NF (230) may transmit the response message to the management device (201) within a specified time (e.g., the length of a timer) from the time at which the request message is transmitted. Feedback for the request message may be divided into three types. The feedback may be acceptance of the request message, rejection of the request message, or no response. If the management device (201) does not receive any response to the request message from the NF (230) within the specified time, the management device (201) may determine that the NF (230) is in a no-response state.

[0079] Although signaling through direct communication between the management device (201) and the NF (230) is illustrated in FIG. 4, embodiments of the present disclosure are not limited thereto. For example, the management device (201) and the NF (230) may perform indirect communication using an SCP (e.g., SCP (197)). In the indirect communication, an NF service consumer may communicate with an NF service producer through the SCP (197). The NF service consumer may directly perform discovery of a target NF service producer, or delegate discovery of the target NF service producer to the SCP (197). For example, the management device (201) may transmit a request message to the NF (230) through the SCP (197). The management device (201) may transmit a response message (e.g., an acceptance message, a rejection message) from the NF (230) to the NF (230) through the SCP (197).

[0080] The management device (201) can determine various types of quality attribute information to evaluate the connection status of the NF (230). The management device (201) can collect data for determining the connection status of the NF (230) through request message(s) and / or response message(s). According to one embodiment, the management device (201) can obtain connection failure data as the connection status of the NF (230). For example, if a rejection message is received in response to a request message, the management device (201) can determine that the request message has failed. The management device (201) can obtain the connection failure data based on the frequency of reception of rejection messages. For example, the management device (201) can periodically transmit the request message to the NF (230) for a specified period of time. The management device (201) can count the number of rejection messages received from the NF (230). The management device (201) may record the number of rejection messages or the ratio of the number of rejection messages to the number of request messages. For another example, the management device (201) may transmit request messages to the NF (230) a specified number of times. The management device (201) may count the number of rejection messages received from the NF (230). The management device (201) may record the number of rejection messages or the ratio of the number of rejection messages to the specified number of times. As the number of rejection messages increases, the connection failure data may indicate that the connection status of the NF (230) (e.g., a call connection using the NF (230)) is unstable.

[0081] In one embodiment, the management device (201) may apply weights to derived data (e.g., number of rejections, ratio of rejection messages to request messages) when determining the degree of a connection status. For example, a rejection message may include cause information to inform the management device (201) of the cause of the rejection. The management device (201) may collect cause information of the received rejection message. The management device (201) may determine a weight based on the cause information of the rejection message and apply the determined weight to connection failure data. For example, the management device (201) may determine a weight value corresponding to the type of the cause information. The management device (201) may determine a weight value within a specified range (e.g., 0 to 5) depending on the type of the cause information. For example, a weight value to be applied when the type of the cause information is related to call processing (e.g., overload) may be greater than a weight value to be applied when the type of the cause information is not related to call processing (e.g., identification error, authentication error). For example, if the type of the cause information is related to the communication quality of NF (230), the weight value to be applied may be greater than the weight value to be applied if the type of the cause information is not related to the communication quality of NF (230).

[0082] In one embodiment, the management device (201) may obtain timeout data as a connection status of the NF (230). For example, if a response message is not received for a specified period of time (e.g., the length of a timer) in response to a request message, the management device (201) may determine that the NF (230) is unresponsive. The management device (201) may obtain the timeout data based on the frequency with which unresponsiveness occurs, i.e., the frequency with which timeouts occur. For example, the management device (201) may periodically transmit a request message to the NF (230) for a specified period of time. The management device (201) may count the number of instances in which a response does not arrive from the NF (230). The management device (201) may record the number of instances or record the ratio of unresponsiveness to the number of request messages. As another example, the management device (201) may transmit request messages to the NF (230) a specified number of times. The management device (201) can count the number of rejection messages received from the NF (230). The management device (201) can count the number of instances in which a response does not arrive from the NF (230). The management device (201) can record the number of instances or record the ratio of non-response to the number of request messages. A higher number of non-response instances may indicate that the timeout data indicates that the connection status of the NF (230) (e.g., a call connection using the NF (230)) is unstable.

[0083] In one embodiment, the management device (201) may apply weights to derived data (e.g., number of non-responses, non-response rate) when determining the severity of a connection condition. Even in the case of a timeout, weights may be applied, similar to the cause information of the rejection message described above. Since a timeout may indicate a more critical connection condition than the weight, the management device (201) may apply a higher weight to timeout data than to connection failure data.

[0084] According to one embodiment, the management device (201) can obtain round trip time (RTT) data as the connection status of the NF (230). For example, the management device (201) can measure the time taken from the time a request message is transmitted to the time a response message corresponding to the request message is received. For example, the response message may be an acceptance message. Measurement of the RTT may be performed only if the request is accepted. For another example, the response message may include an acceptance message and a rejection message. Measurement of the RTT may be performed even if the request is not accepted. The management device (201) can obtain the RTT data whenever it is linked with the NF. For example, the management device (201) can periodically transmit a request message to the NF (230) for a specified period of time. The management device (201) can measure the RTT based on the response message received from the NF (230) and record data including the measured RTT. For example, the management device (201) can transmit request messages to the NF (230) based on a specified number of times. The management device (201) can measure the RTT based on a response message received from the NF (230) and record data including the measured RTT.

[0085] NF TypeATTEMPTSUCCESSTIMEOUTFAILC_RATIOAVG_RTTPCF532060.001423PCF540180.003241CHF531180.001623

[0086] 'NF Type' indicates the type of NF (230). For example, AMF (130) as a management device (201) can measure the connection status of PCF (170) for selection of PCF (170). 'ATTEMPT' indicates the number of attempts, 'SUCCESS' indicates the number of successes, 'TIMEOUT' indicates the number of timeouts (e.g., no response within a specified time), 'FAIL' indicates the number of failures, 'C_RATIO' indicates the success rate, and 'AVG_RTT' indicates the average RTT value (e.g., unit: ms).

[0087] In this disclosure, techniques for fault control of NFs based on network data analytics are described. A management device (201) can measure the quality of connection states of NFs to be selected as connection failure data, timeout data, and RTT data. The management device (201) can store the measured results as data. The management device (201) can perform machine learning based on the data. Through the machine learning, the management device (201) can detect in advance NFs that are predicted to have problems (e.g., quality degradation is expected) (e.g., faulty NFs). If a quality indicator of a quality attribute of an NF (e.g., connection failure data, timeout data, or RTT data) exceeds a threshold of the quality attribute, the management device (201) can limit the rate of new calls flowing into the NF. The management device (201) can automatically detect the qualities of NFs and limit new calls to NFs that have problems, thereby improving the quality of the entire network and reducing operating costs.

[0088] Figure 5a illustrates an example of data set collection. The data set can be used for learning (e.g., machine learning) of NF (e.g., NF (230)).

[0089] Referring to FIG. 5A, a graph (500) represents a first data set (511) including connection failure data, a second data set (512) including timeout data, and a third data set (513) including RTT data. The management device (201) can classify the collected connection status information data by quality attributes (e.g., connection failure data, timeout data, RTT data) and arrange the classified data by specific time interval units. The first data set (511) can be collected based on connection failure data for indicating the reception frequency of rejection messages received in response to transmission of request messages. The second data set (512) can be collected based on timeout data for indicating the occurrence frequency of timeouts for request messages. The third data set (513) can be collected based on RTT data between the NF (230) and the management device (201).

[0090] The management device (201) can perform learning based on the first data set (511), the second data set (512), and the third data set (513). For example, the management device (201) can use the first data set (511), the second data set (512), and the third data set (513) as inputs of a state model. The management device (201) can collect data during a period to be predicted (hereinafter, “prediction period”) and use the collected data as labels for learning. As a result of the learning, the management device (201) can determine a predicted quality index during the prediction period. Based on the predicted quality index, the management device (201) can determine whether to set a restriction on a new call connection using the corresponding NF. For example, if the predicted quality index is greater than or equal to a threshold, the management device (201) can determine that there is a problem with the connection status for the NF. If the expected quality indicator is greater than or equal to the threshold, the management device (201) may set a restriction on new call connections using the NF. If the expected quality indicator is less than the threshold, the management device (201) may not set a separate restriction on new call connections using the NF.

[0091] Figure 5b illustrates an example learning model for quality metrics. The learning model can be configured for artificial intelligence (AI) learning. For example, the learning described below can operate based on data collected over a certain period of time, starting from the most recent data.

[0092] Referring to Figure 5b, the management device (201) can perform machine learning based on the collected data sets. Various models can be used as the machine learning model. For example, a transformer, which is advantageous for learning time-series data, can be used. The transformer can utilize a self-attention mechanism.

[0093] The first input data (561) may include a source sequence. For example, the source sequence may be a data set (e.g., a first data set (511), a second data set (512), and a third data set (513)) for each item of connection status information (e.g., connection failure data, timeout data, RTT data). As input embedding and first positional encoding (562) are applied to the source sequence, the input of the encoder (563) may be determined. The second input data (571) may include a sequence (hereinafter, referred to as a shifting sequence) obtained by shifting a previous output sequence to the right. As input embedding and second positional encoding (572) are applied to the shifting sequence, the input of the decoder (573) may be determined. The encoder (563) may generate an output through an attention block and a feed-forward block. The output of the encoder (563) can be input to the attention block of the decoder (573). The decoder (573) can generate output through a masked attention block ('masked multi-head attention'), an attention block, and a feed-forward block. The output of the decoder (573) can be sequentially input to a linear layer (581) and a softmax layer (583). The linear layer (581) can be a fully connected (FC) layer. The linear layer (581) can convert the output of the decoder (573) into a logit vector. The softmax layer (583) can apply a sortedmax function to the logit vector. The softmax function can make the range of all element values ​​of the logit vector to be 0 or more and 1 or less, and make the sum of all element values ​​be 1. The output data (591) can include an output sequence. The above output sequence can be used again for the second input data (571).For example, the output sequence may represent an expected quality indicator (e.g., connection failure data, timeout data, RTT data) for a specific interval. For example, the value of the expected quality indicator for the specific interval may be determined based on an element with a high probability value in the output sequence.

[0094] Although a transformer model utilizing attention is exemplified in FIG. 5, embodiments of the present disclosure are not limited thereto. The model for learning may include other types of models in addition to the transformer illustrated in FIG. 5. For example, the model may include a recurrent neural network (RNN) family model. For example, RNN family models such as long short-term memory (LSTM) or gated recurrent units (GRU) may be used. Of course, other AI models, not just RNNs, may also be used.

[0095] FIG. 6 illustrates an operation flow of a management device (e.g., management device (201)) for performing an NF selection procedure based on defective NF detection.

[0096] In operation (601), the management device (201) can transmit a request message to each NF (e.g., NF (230-1), NF (230-2), ..., NF (230-N)). The management device (201) can identify a plurality of NFs connected to the management device (201). According to one embodiment, the management device (201) can identify the plurality of NFs based on at least one of a packet data unit (PDU) session, a data network name, single-network slice selection assistance information (S-NSSAI) for identifying a network slice, and location information of a terminal. The plurality of NFs can form an NF group. According to one embodiment, an NF of the NF group can be used as a backup NF when a service connection using another NF is disconnected. The management device (201) can transmit the request message to each NF of the plurality of NFs. The above request message can be used to check the connection status of each NF.

[0097] In operation (603), the management device (201) may receive at least one response message from at least one NF. The response type of the NF may vary. For example, an NF that has received a request message may transmit a response message indicating acceptance or rejection of the request message to the management device (201). An NF that has not received a request message may have difficulty responding. Even if an NF receives a request message, the NF may not be able to transmit a response message to the management device (201) due to overload or unstable call connection. The management device (201) may record response data for each NF to which a request message has been transmitted. For example, the response data may include success, failure, or a timeout (e.g., no response for a certain period of time). The number of request messages transmitted to one NF may be understood as the number of attempts. The management device (201) may collect response data for each NF.

[0098] In operation (605), the management device (201) can detect a defective NF based on the connection status information of each NF. The management device (201) can obtain the connection status information of each NF based on the request messages transmitted to the NFs and at least one response message received from the at least one NF. For example, for each NF, the management device (201) can obtain the connection status information of the corresponding NF based on the response data for the request message. For example, the management device (201) can obtain connection failure data (e.g., failure rate (e.g., ratio of rejection messages to the number of transmission attempts), number of failures (e.g., number of rejection messages)) based on the number of times request messages are transmitted to the NF (e.g., number of transmission attempts) and the number of rejection messages received. For example, the management device (201) can obtain timeout data (e.g., number of timeouts, timeout ratio) based on the number of times it transmits request messages to the NF (e.g., number of transmission attempts) and the number of timeouts. For example, the management device (201) can obtain RTT data based on the difference between the time at which it transmits a request message to the NF and the time at which it receives a response message (e.g., an acceptance message, or a response message including an acceptance message and a rejection message). The RTT data can be calculated based on measured RTT values ​​for each request message. For example, the RTT data can include an average value, a median value, a maximum value (peak value), and / or other representative values ​​of the measured RTT values.

[0099] The management device (201) can classify the connection status information of the NF by quality attribute. Hereinafter, the description of the NF can be commonly applied to each NF of the plurality of NFs of the operation (601). The management device (201) can classify the connection status information by quality attribute (e.g., connection failure data, timeout data, RTT data) and arrange the classified quality attributes by specific time interval unit. According to one embodiment, based on the arrangement, the management device (201) can obtain a first data set (e.g., first data set (511)). The management device (201) can perform learning based on the first data set. As a result of the learning, the management device (201) can obtain an expected first quality index. The first quality index can indicate the probability or frequency of a rejection message arriving when a request message is sent to the NF in a specific interval. The higher the first quality index, the higher the probability that the connection to the NF will fail. According to one embodiment, based on the above arrangement, the management device (201) can obtain a second data set (e.g., the second data set (512)). The management device (201) can perform learning based on the second data set. As a result of the learning, the management device (201) can obtain an expected second quality indicator. The second quality indicator can indicate a probability or frequency of a timeout occurring when a request message is sent to the NF in a specific section. A higher second quality indicator indicates a higher probability of a connection to the NF failing due to a timeout. According to one embodiment, based on the above arrangement, the management device (201) can obtain a third data set (e.g., the third data set (513)). The management device (201) can perform learning based on the third data set. As a result of the learning, the management device (201) can obtain an expected third quality indicator.The third quality indicator represents the difference between the time a request message is sent to the NF and the time a response message is received within a specific interval. A higher third quality indicator indicates a higher connection delay, which may increase the likelihood of a connection delay to the NF.

[0100] The management device (201) can detect a defective NF based on the quality indicator. The management device (201) can determine a quality indicator for each NF in the NF group. The management device (201) can monitor the quality indicator for each NF, and based on the result of the monitoring, can detect an NF (i.e., a defective NF) predicted to have a defect among a plurality of NFs in the NF group. According to one embodiment, the management device (201) can compare the quality indicator with a threshold value. If the quality indicator exceeds the threshold value, the management device (201) can determine the NF as a defective NF. If the quality indicator is less than or equal to the threshold value, the management device (201) can determine that the NF is normal.

[0101] The management device (201) can determine a quality index for each quality attribute and perform a comparison using a threshold for each quality attribute. For example, the management device (201) can determine a first quality index related to the frequency of rejection messages. The management device (201) can compare the first quality index with a first threshold set for the frequency of rejection messages. For example, the management device (201) can determine a second quality index related to the frequency of occurrence of timeouts. The management device (201) can compare the second quality index with a second threshold set for the frequency of occurrence of timeouts. For example, the management device (201) can determine a third quality index related to RTT. The management device (201) can compare the third quality index with a third threshold set for the RTT.

[0102] The management device (201) can determine whether a defective NF is detected based on the result of the above comparison. For example, if a result exceeding a set threshold value is obtained for any one of the quality attributes, the management device (201) can determine the NF as a defective NF. For another example, if the number of quality attributes having results exceeding the set threshold value among the quality attributes is greater than or equal to a specified number (e.g., 2), the management device (201) can determine the NF as a defective NF. For another example, if a result exceeding a threshold value is obtained for all of the quality attributes, the management device (201) can determine the NF as a defective NF.

[0103] Although the above-described examples describe learning for each quality attribute and outputting quality indicators (e.g., a first quality indicator, a second quality indicator, and a third quality indicator) as a result of the learning, embodiments of the present disclosure are not limited thereto. For example, at least two of the above-described quality indicators may be merged during the learning process. In another example, at least one of the above-described quality indicators may be classified and divided into detailed quality indicators during the learning process.

[0104] In operation (607), the management device (201) may perform an NF selection procedure by setting a restriction on a new call connection using a defective NF. The management device (201) may set a restriction on a new call connection using a defective NF. According to one embodiment, the management device (201) may lower a distribution ratio of a new call connection using the defective NF. The management device (201) may perform the NF selection procedure based on distribution ratio information. The distribution ratio information may indicate a ratio set for distributing NFs in an NF group of the management device (201). For example, the management device (201) may distribute NFs in the NF group at a fixed ratio based on the capacity of each NF in the NF group. The management device (201) may adjust the previously set distribution ratio information based on identifying a defective NF. For example, an NF group may include four NFs. The distribution ratio of the NF group may be 1:1:1:1. The management device (201) can lower the distribution ratio to the defective NF, so that the distribution ratio can be 1:1:1 / 3:1. The value corresponding to the defective NF can be lowered from '1' to '1 / 3'. The distribution ratio of the new call connection using the defective NF can be lowered from 25% to 10%. The management device (201) can lower the distribution ratio of the new call connection using the defective NF, so that relatively fewer new calls are distributed to the defective NF than to other NFs in the NF group.

[0105] According to one embodiment, the management device (201) may reject a request for a new call connection using the defective NF. Through the rejection, the management device (201) may reduce the frequency of new call connections using the defective NF. The management device (201) may determine rejection rate information. For example, the management device (201) may determine rejection rate information for the defective NF. For example, if the rejection rate information is 70%, the management device (201) may reject 70% of call connection requests using the defective NF. Meanwhile, even if the management device rejects a call connection using the defective NF, the access network (e.g., the terminal (110), the base station (120)) may request a new call again, which may increase signaling. To reduce overhead due to the increase in signaling, according to one embodiment, the management device (201) may set a backoff timer for the terminal (110). The management device (201) can transmit information about the backoff timer to the terminal (110). For example, when the management device (201) operates as an AMF (130), the management device (201) can transmit information about the backoff timer to the terminal (110) through NAS signaling. The backoff timer can be used to prevent reconnection of the terminal (110) for the length of the backoff timer. If the length of the backoff timer is set to the same value for all terminals, access signals may be concentrated at the time of expiration of the backoff timer. As a non-limiting example, in order to distribute the access signals, the management device (201) can set the length of the backoff timer differently for each terminal. For example, the management device (201) can set the length of the backoff timer of the terminal by adding a random offset (e.g., an offset value randomly determined for each terminal) to a common timer value.

[0106] The management device (201) can perform an NF selection procedure after setting a limit on a defective NF. The management device (201) can identify an NF among a plurality of NFs of the NF group. For example, the management device (201) can perform an NF selection procedure for the plurality of NFs according to a distribution ratio adjusted to lower the distribution ratio of the defective NF. For example, the management device (201) can perform an NF selection procedure for the remaining NFs excluding the defective NF among the plurality of NFs.

[0107] In FIG. 6, operations are described in which NF selection is performed by comparing a quality indicator and a threshold value to identify a defective NF and limiting a call connection to the defective NF. Although FIG. 6 describes an example in which a threshold value is set for each quality attribute, embodiments of the present disclosure are not limited thereto. A plurality of threshold values ​​may be set for each quality attribute. The plurality of threshold values ​​indicate the level of each quality indicator, and the management device (201) may perform different actions according to the level. The management device (201) may configure three threshold values ​​for defect detection for each quality attribute. The three threshold values ​​may include a lower threshold value (or minor threshold value), a reference threshold value (or major threshold value), and an upper threshold value (or critical threshold value).

[0108] According to one embodiment, the management device (201) may obtain a first quality indicator related to connection failure data (e.g., failure rate). The management device (201) may check a lower threshold (e.g., 'FAIL_MINOR_LIMIT'), a reference threshold (e.g., 'FAIL_MAJOR_LIMIT'), and an upper threshold (e.g., 'FAIL_CRITICAL_LIMIT') for the first quality indicator. Each threshold may indicate a limit on the ratio of the number of rejections to the total number of attempts (e.g., FAIL_RATIO, the ratio of the number of rejection messages to the number of request messages). The management device (201) may check information on the minimum number of attempts for each threshold. If the minimum number of attempts is small, even a small number of failures may drastically worsen the overall failure rate. Therefore, in order to compare the threshold for the failure rate with the first quality indicator while ensuring a certain level of the number of attempts, a limit on the minimum number of attempts corresponding to each threshold may be set. For example, threshold values ​​for the first quality indicator can be configured as shown in the table below.

[0109] LEVELMIN_COUNTFAIL_RATIOFAIL_MINOR_LIMIT300010%FAIL_MAJOR_LIMIT500030%FAIL_CRITICAL_LIMIT1000050%

[0110] According to one embodiment, the management device (201) can obtain a second quality indicator related to timeout data (e.g., timeout ratio). The management device (201) can check a lower threshold (e.g., 'TO_MINOR_LIMIT'), a reference threshold (e.g., 'TO_MAJOR_LIMIT'), and an upper threshold (e.g., 'TO_CRITICAL_LIMIT') for the second quality indicator. Each threshold can indicate a limit on the ratio of the number of timeouts to the total number of attempts (e.g., TOUT_RATIO, the ratio of the number of timeouts to the number of request messages). The management device (201) can check information on the minimum number of attempts for each threshold. If the minimum number of attempts is small, even a small number of timeouts can drastically worsen the overall timeout ratio. Therefore, in order to compare the threshold for the timeout ratio with the second quality indicator while ensuring a certain level of attempt number, a limit on the minimum number of attempts corresponding to each threshold can be set. For example, threshold values ​​for the second quality indicator can be configured as shown in the table below.

[0111] LEVELMIN_COUNTTOUT_RATIOTO_MINOR_LIMIT300010%TO_MAJOR_LIMIT500030%TO_CRITICAL_LIMIT1000050%

[0112] According to one embodiment, the management device (201) can obtain a third quality indicator (e.g., average RTT, maximum RTT) related to RTT data. The management device (201) can check a lower threshold (e.g., 'RTT_MINOR_LIMIT'), a reference threshold (e.g., 'RTT_MAJOR_LIMIT'), and an upper threshold (e.g., 'RTT_CRITICAL_LIMIT') for the third quality indicator. Each threshold can represent a limit on the average time of RTTs, which is the difference between the time of transmitting a request message and the time of receiving a response message. For example, the thresholds for the third quality indicator can be configured as shown in the table below.

[0113] LEVELMEAN_TIMERTT_MINOR_LIMIT3000 msecRTT_MAJOR_LIMIT4000 msecRTT_CRITICAL_LIMIT5000 msec

[0114] For each quality attribute, since multiple thresholds are set, the management device (201) can determine the connection status of a specific NF as one of multiple levels. For example, the multiple levels can include a first level for a case where a quality indicator (e.g., a first quality indicator, a second quality indicator, a third quality indicator) is less than or equal to a lower threshold, a second level for a case where the quality indicator is greater than the lower threshold and less than or equal to a reference threshold, a third level for a case where the quality indicator is greater than the reference threshold and less than or equal to an upper threshold, and a fourth level for a case where the quality indicator is greater than the upper threshold.

[0115] The management device (201) may perform actions on the NF according to the level of the connection status of the NF. For example, if the connection status of the NF is the first level, the management device (201) may determine that the connection status of the NF is normal. For example, if the connection status of the NF is the second level, the third level, or the fourth level, the management device (201) may determine the NF as a faulty NF. The action on the faulty NF may include adjusting distribution ratio information. If the faulty NF has the connection status of the second level, the management device (201) may adjust distribution ratio information (e.g., MINOR_CAPA_REDUCE) of the faulty NF having the connection status of the second level. For example, the management device (201) may reduce the items of the faulty NF by 10% from a preset distribution ratio. As the items of the faulty NF decrease, the distribution ratio may be recalculated. For example, an NF group may include two PCFs (e.g., a first PCF and a second PCF). If a ratio set for the first PCF and the second PCF is 1:1 and the first PCF is defective, the management device (201) may reduce the items of the first PCF by 10%. The distribution ratio for the two PCFs may be recalculated to 0.9:1. In the same manner, if the defective NF has a connection state of the third level, the management device (201) may adjust the distribution ratio information (e.g., MAJOR_CAPA_REDUCE) of the defective NF having the connection state of the third level. As an example, the management device (201) may reduce the items of the defective NF by 30% at a preset distribution ratio. If the above-mentioned defective NF has a connection state of the fourth level, the management device (201) can adjust the ratio information (e.g., CRITICAL_CAPA_REDUCE) of the above-mentioned defective NF.For example, the management device (201) can reduce the number of items of the defective NF by 50% at a preset distribution ratio.

[0116] Meanwhile, as a measure for the defective NF, in addition to adjusting the distribution ratio information, the setting of rejection ratio information may be included. The management device (201) may reject new call requests using the defective NF according to the rejection ratio information. For example, if the defective NF has the connection state of the second level, the management device (201) may set the rejection ratio information (e.g., MINOR_REJ_REDUCE) of the defective NF having the connection state of the second level. As an example, the management device (201) may set the rejection ratio information of the defective NF to 10%. For example, if the defective NF has the connection state of the third level, the management device (201) may set the rejection ratio information (e.g., MAJOR_REJ_REDUCE) of the defective NF having the connection state of the third level. As an example, the management device (201) may set the rejection ratio information of the defective NF to 30%. For example, if the defective NF has a connection state of the fourth level, the management device (201) may set the rejection rate information (e.g., CRITICAL_REJ_REDUCE) of the defective NF having the connection state of the fourth level. As an example, the management device (201) may set the rejection rate information of the defective NF to 50%.

[0117] For example, the table below may be referenced for the above distribution ratio information and the above rejection ratio information.

[0118] LEVELRATIOMINOR_CAPA_REDUCE10%MAJOR_CAPA_REDUCE30%CRITICAL_CAPA_REDUCE50%MINOR_REJ_REDUCE10%MAJOR_REJ_REDUCE30%CRITICAL_REJ_REDUCE50%

[0119] As a measure for the above-mentioned faulty NF, adjusting the distribution ratio information or adjusting the rejection ratio information may be performed dependently rather than independently. Since rejecting distribution is a more certain measure to block the possibility of connection to the faulty NF than limiting distribution, the management device (201) may set the rejection ratio instead of limiting the distribution ratio when a quality indicator above a certain level (e.g., level 4) is confirmed. For example, if the faulty NF has a connection status corresponding to level 3, the management device (201) may only perform an adjustment to lower the distribution ratio to the faulty NF. Thereafter, if the faulty NF has a connection status of level 4, the management device (201) may set the rejection ratio information of the faulty NF. A connection status corresponding to level 4 may indicate that the current status of the faulty NF is deteriorating. The management device (201) may reject the new call connection so that no new call connection is created for the faulty NF for a certain period of time.

[0120] In another non-limiting embodiment, the management device (201) may determine that the connection status of the NF is normal when the connection status of the NF is the first level or the second level. The management device (201) may determine the NF as a faulty NF when the connection status of the NF is the third level or the fourth level. The second level is a pre-fault stage, and the management device (201) may change the monitoring settings instead of restricting the connection of the NF. For example, the management device (201) may increase the frequency of monitoring the connection status of the NF when the connection status of the NF is the second level. For example, since the connection status of the NF may deteriorate, the management device (201) may set a short cycle for collecting connection status information (e.g., connection failure data, timeout data, RTT data) for the NF. For example, the management device (201) can set a short cycle for performing an operation of determining a quality indicator predicted for a specific section based on collected data and an operation of comparing the quality indicator with a threshold value.

[0121] Figures 7a to 7d illustrate examples of NF selection. The NF selection may have various aspects depending on the type of management device (201) that is the subject of the NF selection and the types of NFs that are the target of the NF selection.

[0122] Referring to FIG. 7A, the management device (201) may operate as an AMF (130) or may be linked with an AMF (130). The management device (201) may perform SMF selection. For example, the management device (201) may select an SMF. The management device (201) may identify an SMF to be operated for the AMF (130) among a plurality of SMFs connected to the SMF (140). The management device (201) may identify an SMF, which is a network entity for managing user traffic during a PDU (protocol data unit) session establishment, based on a data network name and a location (e.g., the location of the terminal (110)), for the AMF (130). For example, the management device (201) can collect data on the connection status of each SMF (e.g., SMF (140-1), SMF (140-2), ..., SMF (140-n)) at a specified time (e.g., 5 minutes) and determine the predicted connection status (hereinafter, predicted connection status) of each SMF. The management device (201) can detect an SMF (hereinafter, a defective SMF) in which a defect is predicted to occur based on the connection status of each SMF. The management device (201) can identify another SMF instead of the defective SMF as a session management service to be linked with the AMF (130).

[0123] Referring to FIG. 7b, the management device (201) may operate as an AMF (130) or may be linked with an AMF (130). The management device (201) may perform PCF selection. For example, the management device (201) may select a PCF. The management device (201) may identify a PCF to be operated for the AMF (130) among a plurality of PCFs connected to the SMF (140). For example, the management device (201) may collect data on the connection status of each PCF (e.g., PCF (170-1), PCF (170-2), ..., PCF (170-n)) at a specified time (e.g., 5 minutes) and determine a predicted connection status (hereinafter, predicted connection status) in each PCF. The management device (201) may detect a PCF in which a defect is predicted to occur (hereinafter, a defective PCF) based on the connection status of each PCF. The management device (201) can identify another PCF instead of the defective PCF as a service for policies or billing to be operated in the AMF (130).

[0124] Referring to FIG. 7c, the management device (201) may operate as an SMF (140) or may be linked with an SMF (140). The management device (201) may perform PCF selection. For example, the management device (201) may select a PCF as the SMF (140). The management device (201) may identify a PCF to be operated for the SMF (140) among a plurality of PCFs connected to the SMF (140). For example, the management device (201) may collect data on the connection status of each PCF (e.g., PCF (170-1), PCF (170-2), ..., PCF (170-n)) at a specified time (e.g., 5 minutes) and determine a predicted connection status (hereinafter, predicted connection status) in each PCF. The management device (201) can detect a PCF (hereinafter, “defective PCF”) that is expected to have a defect based on the predicted connection status of each PCF. The management device (201) can identify another PCF instead of the defective PCF as a service for policies or billing to be operated in the SMF (140).

[0125] Referring to FIG. 7d, the management device (201) may be a device connected to the base station (120) (e.g., the RAN node of FIG. 1b). The management device (201) may perform AMF selection through the base station (120). For example, the management device (201) may select an AMF to assist the base station (120). The management device (201) may identify an AMF to be operated for the base station (120) among a plurality of AMFs connected to the base station (120). For example, the management device (201) may collect data on the connection status of each AMF (e.g., AMF (130-1), AMF (130-2), ..., AMF (130-n)) at a specified time (e.g., 5 minutes) and determine a predicted connection status (hereinafter, predicted connection status) in each AMF. The management device (201) can detect an AMF (hereinafter, “defective AMF”) that is expected to have a defect based on the predicted connection status of each AMF. As a mobility and access management service for the base station (120), the management device (201) can identify another AMF instead of the defective AMF.

[0126] Although the type of the management device (201) that is the subject of the NF selection and the types of NFs that are the targets of the NF selection are exemplified in FIGS. 7A to 7D , the embodiments of the present disclosure are not limited thereto. In addition to the examples illustrated through FIGS. 7A to 7D , the description of the NF selection according to the embodiments of the present disclosure can be applied to other combinations. For example, the management device (201) may operate as an AMF (130), an SMF (140), or a PCF (170), and the NF selection may include a CHF (charging function) selection. As another example, the management device (201) may operate as an SMF (140), and the NF selection may include a UPF selection.

[0127] Figure 8 illustrates an example of quality indicators for selecting a policy control function (PCF). The PCF selection can be performed by an AMF (e.g., AMF (130)) or an SMF (e.g., SMF (140)).

[0128] Referring to FIG. 8, a graph (800) represents quality indicators for each PCF. The management device (201) may be an NF operating as an AMF (130) or an SMF (140). The management device (201) may be connected to two PCFs. For example, the management device (201) may be connected to a first PCF (871) and a second PCF (872). The management device (201) may obtain a first quality indicator (881a) for the first PCF (871) (e.g., probability of a rejection message for a request message), a second quality indicator (882a) for the first PCF (871) (e.g., probability of a timeout for a request message), and a third quality indicator (883a) for the first PCF (871) (e.g., average RTT). The management device (201) can obtain a first quality indicator (881b) for the second PCF (872) (e.g., probability of a rejection message for a request message), a second quality indicator (882b) for the second PCF (872) (e.g., probability of a timeout for a request message), and a third quality indicator (883b) for the second PCF (872) (e.g., average RTT).

[0129] The horizontal axis of the graph (800) represents the quality indicators for each PCF, and the vertical axis of the graph (800) represents the relative ratio of the quality indicators for each threshold (e.g., lower threshold (850), reference threshold (840), upper threshold (830)). The management device (201) can determine that the first quality indicator (881a) exceeds the reference threshold (840) and is less than or equal to the reference threshold (840). For example, the management device (201) can determine that the connection status associated with the first quality indicator (881a) is the third level. The management device (201) can determine that the second quality indicator (882a) exceeds the lower threshold (850) and is less than or equal to the reference threshold (840). For example, the management device (201) can determine that the connection status associated with the second quality indicator (881b) is the second level. In one embodiment, if multiple quality indicators exceeding a threshold are detected, the management device (201) may determine an action method for the corresponding NF based on a higher level. For example, the management device (201) may perform an action according to the third level corresponding to the first quality indicator (881a). For example, the management device (201) may lower the item of the first PCF (871) by 30% in the distribution ratio for new calls. For example, the management device (201) may determine the rejection rate of the first PCF (871) to 30% for a request for a new call connection using the first PCF (371).

[0130] In FIG. 8, an example of performing actions on a defective NF based on a higher level in a situation where the connection status of the NF is checked through multiple quality indicators is described, but embodiments of the present disclosure are not limited thereto. According to one embodiment, the management device (201) may apply a weight to each quality indicator and use a weighted sum of the quality indicators. The management device (201) may also determine the level of the corresponding NF by comparing the weighted sum with each threshold value (e.g., a lower threshold value (850), a reference threshold value (840), an upper threshold value (830)). As a non-limiting example, the weight in the weighted sum may be applied in the same manner as the weight used in the data collection step (e.g., a weight using cause information, a weight set higher for a timeout than a rejection message).

[0131] NF selection according to embodiments of the present disclosure can be performed by detecting a defective NF and restricting new connections to the defective NF, instead of a round-robin method that distributes at a fixed ratio according to the capabilities set for each NF. By monitoring the quality of each NF and managing the degree of quality degradation by leveling it, a decline in service quality can be prevented in advance. Since a connection request rejection, timeout, and / or RTT are quality attributes related to the connection delay or overload of the corresponding NF, the management device (201) can detect and predict the expected connection delay and / or overload. By automatically detecting an NF predicted to have a defect and restricting connections to the NF before an actual problem occurs in the connected NF, a failure situation can be easily resolved without manual operator intervention. In addition, as private networks increase and the structure of the core network becomes more sophisticated, automated network management can achieve improved accuracy and reduced operating costs.

[0132] The effects that can be obtained from the present disclosure are not limited to the effects mentioned above, and other effects that are not mentioned can be clearly understood by a person having ordinary skill in the art to which the present disclosure belongs from the description below.

[0133] In embodiments, a management device for network function (NF) selection is provided. The management device may include a memory configured to store instructions, at least one transceiver, and at least one processor. The instructions, when executed by the at least one processor, may cause the management device to transmit a request message to each NF of a plurality of NFs connected to the management device, receive at least one response message from at least one NF among the plurality of NFs after transmitting the request message to each NF, obtain connection state information of each NF based on the request message transmitted to each NF and the at least one response message from the at least one NF, detect a fault NF among the plurality of NFs based on the connection state information of each NF, and set a restriction on a new call connection using the fault NF, thereby performing an NF selection procedure.

[0134] According to one embodiment, the instructions, when executed by the at least one processor, may cause the management device to determine whether a quality metric of the connection state information of each NF exceeds a reference threshold value to perform the NF selection procedure, and based on the determination, determine an NF among the plurality of NFs having a quality metric exceeding the reference threshold value as the defective NF.

[0135] According to one embodiment, the instructions, when executed by the at least one processor, may cause the management device to obtain distribution ratio information, in which a distribution ratio to the defective NF is lowered from default distribution ratio information for the plurality of NFs, when a quality indicator of the defective NF exceeds the reference threshold and is lower than or equal to the upper threshold, and to perform the NF selection procedure based on the distribution ratio information.

[0136] According to one embodiment, the instructions, when executed by the at least one processor, may cause the management device to perform the NF selection procedure, to set rejection rate information for the defective NF if a quality indicator of the defective NF exceeds the upper threshold value, and to reject a call connection request using the defective NF based on the rejection rate information for the defective NF.

[0137] In one embodiment, the instructions, when executed by the at least one processor, may cause the management device to determine to reject a call connection request using the faulty NF and, based on the determination, to transmit information about a backoff timer to the terminal that provided the call connection request. The backoff timer may be used to prevent a call connection request while the backoff timer is running.

[0138] According to one embodiment, the connection status information may include at least one of a first data set regarding the frequency of reception of rejection messages received in response to transmission of request messages to the corresponding NF, a second data set regarding the frequency of occurrence of timeouts for the request messages, and a third data set regarding a round trip time (RTT) between the corresponding NF and the management device.

[0139] In one embodiment, the instructions, when executed by the at least one processor, may cause the management device to collect, for each NF among the plurality of NFs, data on a frequency of reception of the rejection messages at a designated period of time in order to obtain the first data set. The instructions, when executed by the at least one processor, may cause the management device to collect, for each NF among the plurality of NFs, data on a frequency of occurrence of timeouts of the request messages at a designated period of time in order to obtain the second data set. The instructions, when executed by the at least one processor, may cause the management device to collect, for each NF among the plurality of NFs, data on an RTT between the NF and the management device at a designated period of time in order to obtain the third data set.

[0140] According to one embodiment, the instructions, when executed by the at least one processor, may cause the management device to perform machine learning based on at least one of the first data set, the second data set, or the third data set to detect the defective NF, determine a quality indicator of each NF of the plurality of NFs based on a result of the machine learning, and determine, based on the quality indicator of each NF, an NF having a quality indicator exceeding a specified threshold as the defective NF.

[0141] According to one embodiment, the instructions, when executed by the at least one processor, may cause the management device to obtain connection status information of each NF, obtain cause information included in each of the rejection messages, and determine data corresponding to a reception frequency of the rejection messages by applying a weight determined according to a type of the cause information. The weight when the type of the cause information is related to call processing may be set higher than the weight when the type of the cause information is not related to call processing.

[0142] According to one embodiment, the instructions, when executed by the at least one processor, may cause the management device to determine a first data set corresponding to a frequency of reception of the rejection messages based on a first weight to obtain connection state information of each NF, and to determine a second data set corresponding to a frequency of occurrence of the timeout based on a second weight that is higher than the first weight.

[0143] According to one embodiment, the instructions, when executed by the at least one processor, may cause the management device to determine the plurality of NFs based on at least one of a packet data unit (PDU) session, a data network name, single-network slice selection assistance information (S-NSSAI) for identifying a network slice, and location information of the terminal.

[0144] In one embodiment, the management device may be associated with an access and mobility management function (AMF). The plurality of NFs may include session management functions (SMFs) or policy control functions (PCFs).

[0145] In one embodiment, the management device may be associated with a network node providing an access network. The plurality of NFs may include access and mobility management functions (AMFs).

[0146] According to one embodiment, the management device may be associated with an access and mobility management function (AMF), a session management function (SMF), a short message service function (SMSF), or a policy control function (PCF). The plurality of NFs may include charging functions (CHFs).

[0147] In embodiments, a method performed by a management device for selecting a network function (NF) is provided. The method may include transmitting a request message to each NF of a plurality of NFs connected to the management device. The method may include receiving, after receiving the request message from each NF, at least one response message from at least one NF among the plurality of NFs. The method may include obtaining connection state information of each NF based on the request message transmitted to each NF and the at least one response message from the at least one NF. The method may include detecting a fault NF among the plurality of NFs based on the connection state information of each NF. The method may include performing an NF selection procedure by setting a restriction on a new call connection using the fault NF.

[0148] In one embodiment, performing the NF selection procedure may include determining whether a quality metric of the connection status information of each NF exceeds a reference threshold. Performing the NF selection procedure may include determining, based on the determination, an NF among the plurality of NFs that has a quality metric exceeding the reference threshold as the defective NF.

[0149] In one embodiment, performing the NF selection procedure may include obtaining distribution ratio information set such that a distribution ratio toward the defective NF is lowered for the plurality of NFs when a quality indicator of the defective NF exceeds the reference threshold and is lower than or equal to an upper threshold. Performing the NF selection procedure may include performing the NF selection procedure based on the distribution ratio information.

[0150] In one embodiment, performing the NF selection procedure may include setting rejection rate information for the defective NF if a quality indicator of the defective NF exceeds the upper threshold. Performing the NF selection procedure may include performing the NF selection procedure so as to reject a call connection request using the defective NF based on the rejection rate information for the defective NF.

[0151] In one embodiment, the method may include determining whether to reject a call connection request using the defective NF. Based on the determination, the method may include transmitting information about a backoff timer to the terminal of the call connection request. The backoff timer may be used to prevent a call connection request while the backoff timer is running.

[0152] According to one embodiment, the connection status information may include at least one of a first data set regarding the frequency of reception of rejection messages received in response to transmission of request messages to the corresponding NF, a second data set regarding the frequency of occurrence of timeouts for the request messages, and a third data set regarding a round trip time (RTT) between the corresponding NF and the management device.

[0153] In embodiments, a non-transitory computer-readable storage medium is provided. The non-transitory computer-readable storage medium may include a memory configured to store instructions. The instructions, when executed by a processor, may cause a management device to transmit a request message to each NF of a plurality of NFs connected to the management device, receive at least one response message from at least one NF among the plurality of NFs after transmitting the request message to each NF, obtain connection state information of each NF based on the request message transmitted to each NF and the at least one response message from the at least one NF, detect a fault NF among the plurality of NFs based on the connection state information of each NF, and set a restriction on a new call connection using the fault NF, thereby performing an NF selection procedure.

[0154] For one or more embodiments, at least one of the components described in one or more of the preceding drawings may be configured to perform one or more operations, techniques, processes, and / or methods as described herein. For example, a processor (e.g., a baseband processor) described herein with respect to one or more of the preceding drawings may be configured to operate according to one or more examples described herein. For another example, circuitry associated with a user equipment (UE), a base station, a network element, and the like, as described above with respect to one or more of the preceding drawings, may be configured to operate according to one or more examples described herein.

[0155] Any of the embodiments described above may be combined with any other embodiment (or combination of embodiments) unless explicitly stated otherwise. The foregoing description of one or more implementations provides examples and descriptions, but is not intended to be exhaustive or limit the scope of the embodiments to the precise forms disclosed. Modifications and variations are possible in light of the above teachings or may be learned from practicing various embodiments.

[0156] The methods according to the embodiments described in the claims or specification of the present disclosure may be implemented in the form of hardware, software, or a combination of hardware and software.

[0157] When implemented in software, a computer-readable storage medium storing one or more programs (software modules) may be provided. The one or more programs stored in the computer-readable storage medium are configured to be executed by one or more processors in an electronic device. The one or more programs include instructions that cause the electronic device to execute methods according to embodiments described in the claims or specification of the present disclosure. The one or more programs may be provided as a computer program product. The computer program product may be traded between a seller and a buyer as a commodity. The computer program product may be distributed in the form of a machine-readable storage medium (e.g., compact disc read only memory (CD-ROM)), or may be distributed online (e.g., downloaded or uploaded) via an application store (e.g., Play Store™) or directly between two user devices (e.g., smart phones). In the case of online distribution, at least a portion of the computer program product may be temporarily stored or temporarily created in a device-readable storage medium, such as the memory of a manufacturer's server, an application store's server, or an intermediary server.

[0158] These programs (software modules, software) may be stored in random access memory, non-volatile memory including flash memory, read only memory (ROM), electrically erasable programmable read only memory (EEPROM), magnetic disc storage devices, compact disc-ROM (CD-ROM), digital versatile discs (DVDs) or other forms of optical storage devices, magnetic cassettes, or may be stored in memories formed by a combination of some or all of these. In addition, each configuration memory may include multiple copies.

[0159] Additionally, the program may be stored on an attachable storage device that is accessible via a communication network, such as the Internet, an intranet, a local area network (LAN), a wide area network (WAN), a storage area network (SAN), or a combination thereof. Such a storage device may be connected to a device implementing an embodiment of the present disclosure via an external port. Additionally, a separate storage device on the communication network may be connected to a device implementing an embodiment of the present disclosure.

[0160] In the specific embodiments of the present disclosure described above, components included in the disclosure are expressed singularly or plurally, depending on the specific embodiment presented. However, the singular or plural expressions are selected to suit the presented situation for convenience of explanation, and the present disclosure is not limited to singular or plural components. Components expressed in plural may be composed of singular elements, or components expressed in singular may be composed of plural elements.

[0161] According to embodiments, one or more of the components or operations of the aforementioned components may be omitted, or one or more other components or operations may be added. Alternatively or additionally, a plurality of components (e.g., modules or programs) may be integrated into a single component. In such a case, the integrated component may perform one or more functions of each of the plurality of components identically or similarly to those performed by the corresponding component among the plurality of components prior to the integration. According to embodiments, the operations performed by a module, program, or other component may be executed sequentially, in parallel, iteratively, or heuristically, or one or more of the operations may be executed in a different order, omitted, or one or more other operations may be added.

[0162] Meanwhile, although the detailed description of the present disclosure has described specific embodiments, it is obvious that various modifications are possible within the scope of the present disclosure.

Claims

1. In a management device for selecting NF (network function), Memory configured to store instructions; at least one transceiver; and comprising at least one processor, The above instructions, when executed by the at least one processor, cause the management device to: Transmit a request message to each NF of the plurality of NFs connected to the above management device, After transmitting the request message to each NF, at least one response message is received from at least one NF among the plurality of NFs, Based on the request message transmitted to each NF and the at least one response message from the at least one NF, connection status information of each NF is obtained, Based on the above connection status information of each NF, a fault NF is detected among the plurality of NFs, By setting a restriction on new call connections using the above defect NF, causing the NF selection procedure to be performed, Management device.

2. In claim 1, The above instructions, when executed by the at least one processor, cause the management device to perform the NF selection procedure. Determine whether the quality metric of the above connection status information of each NF exceeds the reference threshold, Based on the above decision, causing an NF among the plurality of NFs to be determined as the defective NF having a quality metric exceeding the reference threshold value. Management device.

3. In claim 2, The above instructions, when executed by the at least one processor, cause the management device to perform the NF selection procedure: If the quality indicator of the above defective NF exceeds the above reference threshold and is below the upper threshold, information on the distribution ratio in which the distribution ratio to the above defective NF is lowered is obtained from the default distribution ratio information for the plurality of NFs, Based on the above distribution ratio information, causing the NF selection procedure to be performed, Management device.

4. In claim 3, The above instructions, when executed by the at least one processor, cause the management device to perform the NF selection procedure: If the quality indicator of the above defective NF exceeds the upper threshold, set the rejection rate information for the above defective NF, Based on the rejection rate information for the above fault NF, causing the NF selection procedure to be performed to reject a call connection request using the above fault NF. Management device.

5. In claim 4, the instructions, when executed by the at least one processor, cause the management device to: Decide on the rejection of a call connection request using the above defect NF, Based on the above decision, cause the terminal providing the request for the above call connection to transmit information about the backoff timer, The above backoff timer is used to prevent a call connection request while the above backoff timer is running. Management device.

6. In claim 1, The connection status information includes at least one of a first data set regarding the frequency of reception of rejection messages received in response to transmission of request messages to the corresponding NF, a second data set regarding the frequency of occurrence of timeouts for the request messages, and a third data set regarding a round trip time (RTT) between the corresponding NF and the management device. Management device.

7. In claim 6, The above instructions, when executed by the at least one processor, cause the management device to obtain the connection status information of each NF: In order to obtain the first data set, data on the reception frequency of the rejection messages is collected for each NF among the plurality of NFs at a specified period of time, In order to obtain the second data set, for each NF among the plurality of NFs, data on the frequency of occurrence of timeouts of the request messages for each specified period are collected, In order to obtain the third data set, for each NF among the plurality of NFs, data on RTT between the corresponding NF and the management device is collected at a specified period of time. Management device.

8. In claim 6, The above instructions, when executed by the at least one processor, cause the management device to detect the fault NF: Performing machine learning based on at least one of the first data set, the second data set, or the third data set, Based on the results of the above machine learning, the quality indicator of each NF of the plurality of NFs is determined, Based on the above quality indicators of each NF, causing an NF having a quality indicator exceeding a specified threshold to be determined as a defective NF. Management device.

9. In claim 6, the instructions, when executed by the at least one processor, cause the management device to obtain connection status information of each NF: Obtain cause information included in each of the above rejection messages, By applying a weight determined according to the type of the above cause information, data corresponding to the reception frequency of the above rejection messages is determined, The weight of the case in which the type of the above cause information is related to call processing is set higher than the weight of the case in which the type of the above cause information is not related to call processing. Management device.

10. In claim 6, the instructions, when executed by the at least one processor, cause the management device to obtain connection status information of each NF: Determine the first data set corresponding to the reception frequency of the rejection messages based on the first weight, causing a second data set corresponding to the frequency of occurrence of the timeout to be determined based on a second weight higher than the first weight; Management device.

11. In claim 1, The above instructions, when executed by the at least one processor, cause the management device to: Causing the plurality of NFs to be determined based on at least one of a PDU (packet data unit) session, a data network name, a single-network slice selection assistance information (S-NSSAI) for identifying a network slice, and location information of a terminal. Management device.

12. In claim 1, The above management device is associated with the AMF (access and mobility management function), The above plurality of NFs include session management functions (SMFs) or policy control functions (PCFs). Management device.

13. In claim 1, The above management device is associated with a network node providing an access network, The above plurality of NFs include AMFs (access and mobility management functions). Management device.

14. In claim 1, The above management device is associated with an access and mobility management function (AMF), a session management function (SMF), a short message service function (SMSF), or a policy control function (PCF). The above plurality of NFs include CHFs (charging functions). Management device.

15. In a method performed by a management device for selecting NF (network function), Transmitting a request message to each NF of the plurality of NFs connected to the above management device, After receiving the request message from each of the above NFs, receiving at least one response message from at least one NF among the plurality of NFs; Obtaining connection status information of each NF based on the request message transmitted to each NF and the at least one response message from the at least one NF, Based on the above connection status information of each NF, detecting a fault NF among the plurality of NFs, By setting a restriction on new call connections using the above defect NF, including performing an NF selection procedure, method.

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