Access and Mobility Management Function AMF and Its Method in a Communication System

Abstract

The present disclosure relates to an access and mobility management function AMF and its method in a communication system. The method may include: receiving, from a first session management function SMF, a first message including information indicating a request to transfer a session management SM context to a second SMF; selecting the second SMF based on the first message; sending, to the second SMF, a second message for requesting the second SMF to receive the SM context from the first SMF; starting a timer when sending the second message; and receiving, from the second SMF, a third message as a response to the second message, wherein the method further includes: before receiving the third message, receiving, from a terminal, a service request for a protocol data unit PDU session associated with the SM context; and delaying the processing of the service request with the second SMF until the third message is received.

Description

[0001] This application is a divisional application of the patent application for invention with the application date of May 12, 2020, application number 202080017957.0, and invention title "Method and apparatus for flexibly supporting services in a wireless communication system". Technical Field

[0002] This disclosure relates to a technique for managing an identifier of a terminal and its status information (context) in a mobile communication system. Background Art

[0003] To meet the demand for wireless data services that has increased due to the deployment of 4G communication systems, efforts have been made to develop improved 5G or pre-5G communication systems. Therefore, 5G or pre-5G communication systems are also referred to as "super 4G networks" or "post-LTE systems".

[0004] The 5G communication system is considered to be implemented in a higher frequency (mmWave) band (e.g., 60 GHz band) in order to achieve higher data rates. To reduce the propagation loss of radio waves and increase the transmission distance, beamforming, massive multiple-input multiple-output (MIMO), full-dimensional MIMO (FD-MIMO), array antennas, analog beamforming, and large-scale antenna technologies have been discussed in the 5G communication system.

[0005] In addition, in the 5G communication system, development for system network improvement is in progress based on advanced small cells, cloud radio access network (RAN), ultra-dense networks, device-to-device (D2D) communication, wireless backhaul, mobile networks, cooperative communication, coordinated multipoint (CoMP), receiver interference cancellation, and so on.

[0006] In the 5G system, hybrid FSK and QAM modulation (FQAM) and sliding window superimposed coding (SWSC) as advanced coding modulation (ACM), filter bank multicarrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA) as advanced access technologies have been developed.

[0007] Compared with conventional 4G systems, the 5G system is considered to support more diverse services. For example, the most representative services may include ultra-wideband mobile communication services (enhanced mobile broadband (eMBB)), ultra-high reliability / low latency communication services (ultra-reliable and low-latency communication (URLLC)), massive device-to-device communication services (massive machine type communication (mMTC)), and next-generation broadcast services (evolved multimedia broadcast / multicast service (eMBMS)). A system that provides URLLC services may be referred to as a URLLC system, and a system that provides eMBB services may be referred to as an eMBB system. The terms "service" and "system" may be used interchangeably.

[0008] Among these services, the URLLC service, which is a new service considered in the 5G system compared to the existing 4G system, needs to meet extremely high reliability (e.g., a packet error rate of about 10-5) and low latency (e.g., about 0.5 msec) conditions compared to other services. To meet these stringent conditions required therefor, the URLLC service may need to apply a shorter transmission time interval (TTI) compared to the eMBB service, and various operation schemes adopting it are now under consideration.

[0009] The Internet, which is a human-centered connectivity network where humans generate and consume information, is now evolving into the Internet of Things (IoT), where distributed entities such as items exchange and process information without human intervention. The Internet of Everything (IoE) has emerged, which is a combination of IoT technology and big data processing technology through connection to a cloud server. As technical elements such as "sensing technology", "wired / wireless communication and network infrastructure", "service interface technology", and "security technology" have been required for IoT implementations, recently, sensor networks, machine-to-machine (M2M) communication, machine type communication (MTC), etc. have been studied.

[0010] Such an IoT environment can provide intelligent Internet technology services, which create new value for human life by collecting and analyzing the generated data among the connected items. Through the convergence and combination between existing information technology (IT) and various industrial applications, IoT can be applied to various fields, including smart homes, smart buildings, smart cities, smart cars or connected cars, smart grids, healthcare, smart appliances, and advanced medical services.

[0011] Accordingly, various attempts have been made to apply the 5G communication system to the IoT network. For example, technologies such as sensor networks, machine type communication (MTC), and machine-to-machine (M2M) communication can be implemented through beamforming, MIMO, and array antennas. The application of cloud radio access network (RAN) as the above-described big data processing technology can also be considered an example of the convergence of 5G technology and IoT technology.

[0012] The above information is presented only as background information to assist in the understanding of the present disclosure. No determination has been made, nor any assertion made, as to whether any of the above is suitable as prior art with respect to the present disclosure. Summary of the Invention

[0013] Technical Problem

[0014] An embodiment proposes a structure in which data processed by a network function (NF) is separated and stored to increase communication efficiency and improve customer service quality in a 5G system. In addition, the embodiment proposes an identifier (ID) processing method to solve the ID conflict problem between NFs, which may occur when the above structure is introduced.

[0015] The technical subjects explored in this disclosure may not be limited to the above-mentioned technical subjects, and those skilled in the art to which this disclosure pertains can clearly understand other technical subjects not mentioned through the following description.

[0016] Solution

[0017] According to an aspect of the present disclosure, a method performed by an access and mobility management function (AMF) entity in a wireless communication system is provided. The method includes: receiving, from a first session management function (SMF) entity, a first message for transferring a session management (SM) context to a second SMF entity; sending, to the second SMF entity, a second message for requesting the second SMF entity to receive the SM context from the first SMF entity; starting a timer when sending the second message; and receiving, before the timer expires, a third message as a response to the second message from the second SMF entity.

[0018] In one embodiment, the method further includes: determining that the SM context transfer process fails in the case where the timer expires before receiving the third message.

[0019] In one embodiment, the first message includes information about an indication for transferring the SM context.

[0020] In one embodiment, the method further includes: receiving, from a terminal, a service request message before receiving the third message; and delaying a transaction related to the SM context until the third message is received.

[0021] In one embodiment, the method further includes: receiving, from another AMF entity, a user equipment (UE) context transfer request message before receiving the third message; and delaying a transaction related to the SM context until the third message is received.

[0022] In one embodiment, the first message includes an Nsmf_PDUSession_SMContextStatusNotify message, the second message includes an Nsmf_PDUSession_CreateSMContext request message, and the third message includes an Nsmf_PDUSession_CreateSMContext response message.

[0023] In one embodiment, sending the second message further includes: selecting a second SMF entity based on the first message.

[0024] The present disclosure also provides an access and mobility management function (AMF) in a wireless communication system. The AMF entity includes a transceiver; and a controller configured to: receive, via the transceiver, a first message from a first session management function (SMF) entity for delivering a session management (SM) context to a second SMF entity; send, via the transceiver, a second message to the second SMF entity for requesting the second SMF entity to receive the SM context from the first SMF entity; start a timer when sending the second message; and receive, via the transceiver, a third message as a response to the second message from the second SMF entity before the timer expires.

[0025] The present disclosure also provides a method performed by an access and mobility management function AMF in a communication system, the method including: receiving a first message from a first session management function SMF including information indicating a request to transfer a session management SM context to a second SMF; sending a second message to the second SMF for requesting the second SMF to receive the SM context from the first SMF; starting a timer when sending the second message; and receiving, before the timer expires, a third message as a response to the second message from the second SMF, wherein the method further includes: receiving, before receiving the third message, a service request from a terminal for a protocol data unit PDU session associated with the SM context; and delaying processing of the service request with the second SMF until receiving the third message.

[0026] The present disclosure also provides an access and mobility management function AMF in a communication system, the AMF including: a transceiver; and a controller coupled to the transceiver and configured to: receive a first message from a first session management function SMF including information indicating a request to transfer a session management SM context to a second SMF, send a second message to the second SMF for requesting the second SMF to receive the SM context from the first SMF, start a timer when sending the second message, and receive, before the timer expires, a third message as a response to the second message from the second SMF, wherein the controller is further configured to: receive, before receiving the third message, a service request from a terminal for a protocol data unit PDU session associated with the SM context; and delay processing of the service request with the second SMF until receiving the third message.

[0027] Advantages of the Invention

[0028] In the case of the application embodiment, throughput can be freely distributed by sharing the context of the terminal among NFs, and customer services can be supported without sacrificing quality by enabling the services provided by a malfunctioning NF to be taken over by another NF. In addition, in the case of the application embodiment, the IDs used by the NFs sharing the context with each other can be determined and managed according to the system capacity / performance and customer service characteristics, thereby preventing service errors or deterioration of customer service quality caused by ID conflicts.

[0029] The effects obtainable from the present disclosure may not be limited to the above effects, and through the following description, other effects not mentioned can be clearly understood by those skilled in the art to which the present disclosure pertains. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] To more fully understand the present disclosure and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, in which like reference numerals represent like parts:

[0031] Figure 1 A diagram illustrating the structure of an SBA-based 5G system according to an embodiment;

[0032] Figure 2 A diagram illustrating the separation structure of an NF and a context according to an embodiment;

[0033] Figure 3 A diagram illustrating an example of the operation of a 5G system including a terminal, a base station, and a core according to an embodiment;

[0034] Figure 4 A diagram illustrating another example of the operation of a 5G system (terminal, base station, and NF) according to an embodiment;

[0035] Figure 5 A diagram illustrating an example of effectively managing a temporary identifier even in a structure where the 5G system is dynamically changed according to an embodiment;

[0036] Figure 6 A diagram illustrating a method of dividing a pool of identifiers shared by a set of NFs into chunk units and assigning, managing, and collecting them in units of chunks, rather than requesting and assigning a temporary identifier each time a transaction is processed, according to another embodiment;

[0037] Figure 7 A diagram illustrating a process in which a specific NF returns an ID with an assigned usage terminated according to an embodiment;

[0038] Figure 8 A diagram illustrating a method of selecting a target NF considering the capacity of an NF receiving a context when providing a service by exchanging contexts between a context memory and NFs according to an embodiment;

[0039] Figure 9 A diagram showing a method for managing a context in an NF according to an embodiment;

[0040] Figure 10 A diagram showing a method for preventing failures and overloads caused by context transfer and changes in an NF according to an embodiment;

[0041] Figure 11 A diagram showing the detailed operation of an AMF according to an embodiment;

[0042] Figure 12 A diagram showing the detailed operation of an AMF according to an embodiment;

[0043] Figure 13 A diagram showing the configuration of a terminal according to the present disclosure; and

[0044] Figure 14 A diagram showing the configuration of a network entity according to the present disclosure. Detailed Description of the Invention

[0045] Prior to the following detailed description, it may be advantageous to set forth definitions of certain words used throughout this patent document: The terms "comprises" and "comprising," and derivatives thereof, mean inclusion without limitation; the term "or" is inclusive, meaning and / or; the phrases "associated with" and "associated therewith," and derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or be connected with, couple to or be coupled with, communicate with, cooperate with, interleave, juxtapose, be proximate to, be bound to or be bound with, have, be characterized as, and the like; and the term "controller" means any device, system, or portion thereof that controls at least one operation, such a device may be implemented in hardware, firmware, software, or some combination of at least two thereof. It should be noted that the functions associated with any particular controller, whether local or remote, may be centralized or distributed.

[0046] In addition, the various functions described below can be implemented or supported by one or more computer programs, each of the one or more computer programs being formed of computer-readable program code and embodied in a computer-readable medium. The terms "application" and "program" refer to one or more computer programs, software components, sets of instructions, procedures, functions, objects, classes, instances, related data, or portions thereof that are suitable for implementation in appropriate computer-readable program code. The phrase "computer-readable program code" includes any type of computer code, including source code, object code, and executable code. The phrase "computer-readable medium" includes any type of medium that can be accessed by a computer, such as read-only memory (ROM), random access memory (RAM), hard disk drive, compact disc (CD), digital versatile disc (DVD), or any other type of memory. "Non-transitory" computer-readable media exclude wired, wireless, optical, or other communication links that convey transient electrical or other signals. Non-transitory computer-readable media include media in which data can be stored permanently and media such as rewritable compact discs or erasable memory devices in which data can be stored and later rewritten.

[0047] Throughout this patent document, definitions of certain words are provided. Those of ordinary skill in the art should understand that in many, if not most, instances, such definitions apply to the prior and future use of the words being defined.

[0048] As discussed below Figures 1 to 14 and the various embodiments used to describe the principles of the present disclosure in this patent document are for illustration only and should in no way be construed as limiting the scope of the present disclosure. Those skilled in the art will understand that the principles of the present disclosure can be implemented in any suitably arranged system or device.

[0049] In the following, the operating principles of the present disclosure will be described in detail in conjunction with the accompanying drawings. In the following description of the present disclosure, when a detailed description of a known function or configuration incorporated herein may make the subject matter of the present disclosure rather unclear, the detailed description thereof will be omitted. The terms to be described below are terms defined in consideration of the functions in the present disclosure and may vary according to the user, the user's intention, or custom. Therefore, the definitions of the terms should be made based on the content throughout the specification.

[0050] In the following description, for convenience, terms for identifying access nodes, terms for referring to network entities, terms for referring to messages, terms for referring to interfaces between network entities, terms for referring to various identification information, etc. are used illustratively. Therefore, the present disclosure is not limited to the terms used below, and other terms referring to entities having equivalent technical meanings can be used.

[0051] In the following description, for convenience of description, the present disclosure uses the terms and names defined in the 3rd Generation Partnership Project Long Term Evolution (3GPP LTE) standard. However, the present disclosure is not limited to these terms and names, and can be applied to systems conforming to other standards in the same manner.

[0052] Meanwhile, when describing embodiments, a functional node / NF having the function of separating, storing, and retrieving UE information (UE context) processed / managed by an NF will be referred to as a "context memory", which has criteria including an unstructured data storage function (UDSF) as an NF for storing / sharing unstructured data and a context transfer storage function (CTSF) as an NF for storing / sending contexts.

[0053] Meanwhile, in the present disclosure, the term "service" will be used to refer to an "NF service" in which a specific communication device (or NF) processes a request of another communication device (or NF), and "customer service" will be used separately to specifically indicate a service provided to an end user.

[0054] New system architectures and protocols are needed to support various services of 5G, and then 3GPP decided to introduce a new technology called "service-based architecture (SBA)".

[0055] Figure 1 FIG. illustrates the structure of a 5G system based on SBA according to an embodiment.

[0056] Reference Figure 1 , the access and mobility management function (AMF) 120 is a network function (NF) that manages the access and mobility of the UE 110 in a wireless network. The session management function (SMF) 130 is an NF that manages the session for the UE 110, and the session information includes QoS information, charging information, and information about packet processing. The user plane function (UPF) 125 is an NF that processes user plane traffic and is controlled by the SMF 130. Although not shown in Figure 1 , the 5G system may include a UDSF, and the UDSF is an NF that stores unstructured data. Any type of data can be stored or retrieved upon request of an NF.

[0057] Figure 2 FIG. illustrates the separation structure of an NF and a context according to an embodiment.

[0058] Reference Figure 2, in an embodiment, the data (UE context) in the NF is separated from the NF and stored in a separate context memory, and a set of NFs that can share and use it is called an "NF set". Depending on the implementation environment, a specific NF may be operated / managed in the form of an NF instance, and the subject matter of the present disclosure can be applied to an environment that manages and operates either an NF or an NF instance. Additionally, instead of implementing / realizing in units of NFs, in the case of operating in units of NF services, an NF service can replace an NF. Therefore, the term "NF" in the present disclosure can cover NF instances, NF services, and NF service instances. If multiple NF sets coexist, different identifiers or names can be assigned to the corresponding NF sets for distinction therebetween, and even if the NFs in the NF set operate by sharing contexts with each other, different identifiers / names can be assigned to the corresponding NFs for their management / operation.

[0059] Figure 3 The figure shows an example of the operation of a 5G system including a terminal, a base station, and a core according to an embodiment.

[0060] Reference Figure 3 , step 301 can be performed when the requester 382 that makes a request for a service to any NF 383 included in the NF set is a radio access network (RAN) (base station), and a radio resource control (RRC) connection is established between the UE 381 and the RAN 382 to use radio resources to transmit and receive signaling / data.

[0061] In step 305, the requester 382 makes a request for a specific NF service to the NF 383. If the requester is the RAN 382, the target NF 383 can be the AMF. In this case, the requester 382 can specify the recipient 383 of the request and send it. If a request is sent to the NF set without specifying a specific NF, any NF in the NF set can receive the request.

[0062] In step 309, the receiving NF 383 performs an operation according to the NF service request. The receiving NF 383 identifies whether the requested NF service requires the UE context that is pre-cached in the NF set - that is, in the NF or the context memory 384. If the information is pre-cached in the NF, the cached information can be directly used, so that steps 313 to 321 can be omitted.

[0063] If a UE context in the context memory 384 is needed, in step 313, the NF 383 makes a request to the context memory 384 to retrieve the context. In this case, if the context memory 384 is a UDSF, "Nudsf_UnstructuredDataManagement_Query service(request)" can be used for the context retrieval request, and the request message can include a data identifier for identifying the data to be retrieved. If the NF 383 perceives the correct data identifier, the identifier capable of identifying the data can include its corresponding value. Otherwise, the identifier can include an identifier of a specific UE. The identifier of a specific UE (subscriber) includes a subscription permanent ID (SUPI) (IMSI or NAI type) or a unique temporary identifier in a specific NF set {pre-assigned as one of a 5G - globally unique temporary identifier (GUTI), Internet Protocol (IP) address, tunnel endpoint ID (TEID), flow ID, application / service identifier, charging ID, etc.}.

[0064] In step 317, the context memory 384 searches for the data to be retrieved according to the request of the NF 383, and in step 321, sends a response thereto to the NF 383. If the request is valid, that is, if the context memory 384 can retrieve a valid context using the identifier included in the request message, the response message sent in step 321 includes the corresponding context. In this process, the context memory 384 can consider the identifier (data identifier or UE / subscriber identifier) included in the request and the type of the NF 383 making the request (such as the type of AMF, SMF, etc.) to check the validity of the request of the NF 383 and find the context to be retrieved. In the case where the context memory 384 is a UDSF, the response corresponds to the response of the "Nudsf_UnstructuredDataManagement_Query" service. If the request in step 313 is made using the identifier of a UE (subscriber) instead of a specific data identifier, and if a specific data identifier is pre-assigned to the context memory 384, the response sent in step 321 includes the data identifier. In addition, when receiving the response, the NF 383 can store the data identifier, and when making a request to the context memory 384 in the future, can use the corresponding data identifier. Based on this, the time spent by the context memory 384 searching for the stored context using the UE (subscriber) identifier can be reduced or the load on the context memory 384 for doing so can be decreased.

[0065] In step 325, the corresponding context is used to process the procedure / transaction requested in step 305. In an embodiment, the procedure / transaction includes processing operations in a specific NF, and also includes operations of sending / receiving messages and requesting services by interacting with another NF according to it.

[0066] In the case where it is requested in the context memory 384 to update the UE context or store a new UE context, in step 329, the NF 383 makes a request for storing / updating the context to the context memory 384, and the request includes the identifier of the new context and data or the identifier of the context and data to be updated. If the context memory 384 is a UDSF, the corresponding operations can be performed using the services "Nudsf_UnstructuredDataManagement_Create(storage)" and "Nudsf_UnstructuredDataManagement_Update(update)". In the case of an update, if the NF 383 explicitly knows or receives the data identifier, the NF 383 can use the corresponding data identifier to update the UE context. In addition, in the case of "create", the NF 383 can send the UE (subscriber) identifier and context to be stored to the context memory 384.

[0067] In step 333, the context memory 384 can store the context sent from the NF 383, and if it is necessary to create (generate) a new data identifier (in the case of using the UE or subscriber identifier in step 329), the context memory 384 can create a new data identifier, and can send it to the NF 383 through a response in step 337.

[0068] In step 341, the NF 383 and other nodes 381 and 382 process the remaining procedure / transaction. If a new temporary ID (one or more of 5G-GUTI, TEID, and IP address) for the UE (subscriber) is assigned through the corresponding procedure / transaction, the ID is sent to the UE 381, and the UE 381 stores it for subsequent procedures.

[0069] The above embodiments have described the method of grouping multiple NFs into an NF set and separating / sharing contexts. When processing the connection provided to a user through a 5G system, various types of temporary identifiers are assigned. Although the embodiments are described based on the following temporary identifiers, the subject matter of the present disclosure can be applied to the case of assigning / managing any type of temporary identifier used in a communication system.

[0070] - 5G-GUTI: This is a globally unique temporary identifier and includes the Globally Unique AMF Identifier (GUAMI) of the AMF serving the UE and the MME Temporary Mobile Subscriber Identity (M-TMSI) assigned to the UE. In an AMF set, the M-TMSI must be assigned uniquely to each UE.

[0071] - TEID: This is the endpoint ID for differentiating GTP (General Packet Radio Service (GPRS) Tunneling Protocol) tunnels used to send packets between communication devices (between a base station and an NF or between NFs), especially the UPF, and needs to be assigned uniquely within the IP used by the NF.

[0072] - UE IP address: This is the IP address assigned to the UE when the UE communicates using IP and must be assigned uniquely to each UE within an IP domain.

[0073] - Flow ID: This is an identifier assigned to identify and control a specific traffic flow.

[0074] - Application ID: This is an identifier assigned to identify a specific service application.

[0075] - Analytics ID: This is an identifier assigned to collect / analyze information about the NW and can be used in the Network Data Analytics Function (NWDAF).

[0076] - Background data delivery reference ID: This is an identifier used to send data to the UE in the background.

[0077] - Charging Data Record (CDR) ID: This is an identifier used to control specific charging information.

[0078] If an NF assigns a temporary identifier to a specific UE (subscriber), uniqueness must be ensured according to a certain condition, and if uniqueness is not satisfied, an error occurs, resulting in degraded quality of service or the need for error recovery processing. Different from a system where all resources within one of the NFs are consumed, in the structure described in the above embodiments, the NFs in the NF set share the context, and the NF providing services to a single UE (subscriber) can be changed at any time within the same set. In such a system, since the entire pool of temporary identifiers is also shared by the NFs, there may be a problem that two NFs assign the same temporary identifier to two UEs (subscribers) simultaneously.

[0079] Figure 4 The figure shows a diagram illustrating another example of the operation of a 5G system (UE, base station, and NF) according to an embodiment.

[0080] Reference Figure 4, reference numeral 401 represents an interaction node that can request / trigger NF services in a specific NF, and can be a UE, a RAN (base station), or another NF.

[0081] Reference numeral 402 represents an NF for providing communication functions, and includes NFs defined in 3GPP standards and network devices similar thereto. If a specific NF is implemented / operated in the form of an instance, the NF can be replaced by an NF instance. In the case of operation in units of NF services rather than implementation / realization in units of NFs, the NF can be replaced by an NF service.

[0082] The configuration server (conf.server) 403 is a server that provides functions for managing / configuring communication devices (RAN, NF, etc.), and is usually referred to as an "element management system (EMS)" or an "operation and maintenance (OAM) system". The virtualized network function manager (VNFM) / orchestrator 404 is a system for configuring / managing NFs in a virtualized system. In the present disclosure, embodiments will be described under the assumption that the two systems are separate, but the two systems can be integrated into one, and in this case, the exchange of messages between the two systems can be omitted, or the exchange of messages between the two systems can be processed through an internal process.

[0083] In step 431, the NF 402 is initially installed or configured.

[0084] In step 434, the VNFM / orchestrator 404 notifies the configuration server 403 of the size of the NF (usually corresponding to the maximum capacity) (such as values such as the number of subscribers or sessions that can be processed in parallel, values indicating relative capacity, etc.) and the size of the NF set (the number of NFs included in the NF set, the maximum capacity of the entire set, etc.).

[0085] In step 437, the configuration server 403 can divide the entire pool of temporary identifiers shared by the NF set according to the received size of the NF / NF set, thereby determining the available identifiers for each NF, and can send the information assigned to each NF 402. The available identifier information can be sent to the NF 402 according to its type, and the configuration server 403 can send the starting value of the temporary identifier, the total number in the form, or the range of the temporary identifier (indicating the value from start to end), or a list of all assigned identifiers to the NF 402. When managing temporary identifiers, considering changes in future NW configurations (size of NFs, size of the set, etc.), the configuration server 403 can reserve some segments and use the remaining segments for initial assignment.

[0086] In step 441, the NF 402 stores a pool of temporary identifiers to be used by the NF 402 based on the received information.

[0087] In step 445, the UE (or RAN or another NF) 401 makes a request to the NF 402 for a specific NF service, and if a temporary identifier needs to be assigned to each UE (subscriber), in step 449, the NF 402 can assign an identifier from the stored pool. In step 453, the NF 402 can respond to the UE (or RAN or another NF) 401.

[0088] In the case where multiple NFs are included in an NF set, the above embodiments can be utilized. If the number of NFs in the NF set is dynamically changed (if the scaling size changes due to a failure or load), or if the size of each NF changes, it is difficult to change the identifier pool to conform to the situation.

[0089] Figure 5 The figure shows an example of effectively managing temporary identifiers even in a structure where the 5G system is dynamically changed according to an embodiment.

[0090] Reference Figure 5 , reference numeral 501 represents an interaction node that can request / trigger an NF service in a specific NF, and can be a UE, a RAN (base station), or another NF.

[0091] Reference numeral 502 represents an NF for providing a communication function, and includes NFs defined in 3GPP standards and network devices similar thereto. If a specific NF is implemented / operated in the form of an instance, the NF can be replaced by an NF instance. In the case of an operation in units of NF services rather than an implementation / realization in units of NFs, the NF can be replaced by an NF service.

[0092] The ID management server 503 is a server that provides a function of managing the identifier pool of all NFs. The ID management server 503 can be configured as a separate function (NF), or can be configured as a specific function provided by the context server when integrated with the context server described in the above embodiments.

[0093] Step 531 means that the interaction node (UE / RAN / NF) 501 and the NF 502 are in a state where they can exchange information with each other and perform interaction operations.

[0094] In step 535, the UE or the interaction NF 501 makes a request to the NF 502 for an NF service. In the process of processing the service through a request from the UE, a request from the RAN, or an internal operation of the NF and a request from another NF, a request for the NF service by the interaction NF 501 can be made.

[0095] In step 539, the NF 502 processes the received transaction and determines whether a new context needs to be created or whether a temporary identifier needs to be assigned.

[0096] In step 544, the NF 502 may send a request to the ID management server 503 for ID assignment or context creation / updating. In this case, the NF 502 may make a request to the ID management server 503 for a temporary identifier assigned to the UE (subscriber). The request message may include information about the type of temporary identifier to be used. The type information may include one or more of the identifiers described above, such as M-TMSI, 5G-GUTI, GTP TEID, and IP address. Additionally, when assigning a temporary identifier, the NF 602 may make an explicit request to the ID management server 503 as to whether randomization is to be applied. If the ID management server 503 supports the services of the UDSF, the services described in the above embodiments in Figure 2 may be used to process the request / response.

[0097] In step 549, if a request for context processing is received, the ID management server 503 stores / updates the context and assigns the requested temporary identifier. If the requested temporary identifier needs to be randomized (e.g., in the case of 5G-GUTI or M-TMSI), or if separate randomization is explicitly requested, the ID management server 503 applies randomization when assigning the temporary identifier.

[0098] In step 554, the ID management server 503 sends the assigned temporary identifier to the NF 502 and, in the case of receiving a request for context processing, sends a response to the context processing.

[0099] In step 559, the NF 502 uses the assigned temporary identifier to process the remaining procedures / transactions.

[0100] In step 564, the assigned temporary identifier is sent to the interaction node (UE / base station or interacting NF) 501, and the interaction node 501 that receives the temporary identifier stores it for subsequent processes.

[0101] Figure 6 A diagram showing a method of dividing a pool of identifiers shared by a set of NFs into chunk units and assigning, managing, and collecting them in units of chunks, rather than requesting and assigning a temporary identifier each time a transaction is processed, according to another embodiment.

[0102] Since the signaling for identifier management between NFs can be reduced, and since conflicts can be prevented while each NF can freely assign identifiers within a chunk, the assignment method in units of chunks (chunks) is effective.

[0103] Reference Figure 6 , reference numeral 601 represents an interaction node that can request / trigger NF services in a specific NF, and can be a UE, a RAN (base station), or another NF.

[0104] Reference numeral 602 represents an NF for providing communication functions, and includes NFs defined in 3GPP standards and network equipment similar thereto. If a specific NF is implemented / operated in the form of an instance, the NF can be replaced by an NF instance. In the case of operation in units of NF services rather than implementation / realization in units of NFs, the NF can be replaced by an NF service.

[0105] The ID management server 603 is a server that provides the function of managing the identifier pool of all NFs. The ID management server 603 can be configured as a separate function (NF), or can be configured as a specific function provided by the context server when integrated with the context server described in the above embodiments. The ID management server 603 can be configured for each specific NF set, or the ID management server 603 can be configured to support multiple NF sets.

[0106] Step 630 means that the interaction node (UE / RAN / NF) 601 and the NF 602 are in a state where they can exchange information with each other and perform interaction operations.

[0107] In step 635, the UE or the interaction NF 601 makes a request for an NF service to the NF 602. In the process of processing the service in response to a request from the UE, a request from the RAN, or an internal operation of an NF and a request from another NF, the request for the NF service by the interaction NF 601 can be made.

[0108] In step 640, the NF 602 processes the received transaction and determines whether a temporary identifier needs to be assigned. Step 635 is not necessarily before step 640, and if the assignment of the ID pool is required in the initial processing for processing the service request or in the overall operation scenario, the NF 602 can start from step 640.

[0109] In step 645, the NF 602 may send a request for ID assignment to the ID management server 603. In this case, the NF 602 may make a request to the ID management server 603 for chunk assignment of a temporary identifier to be assigned to a UE (subscriber). The request message may include information about the type of the temporary identifier to be used and the chunk size (i.e., the number of IDs to be assigned). The type information may include one or more of the identifiers described above, such as M-TMSI, 5G-GUTI, GTP TEID, and IP address. In the case where the ID management server 603 is configured to support multiple NF sets simultaneously, the NF 602 may use the request message to notify the ID management server 603 of the name or information of the NF set to which the NF 602 belongs. Additionally, when assigning a temporary identifier, the NF 602 may make an explicit request to the ID management server 603 as to whether to apply randomization. If the ID management server 603 supports the service of the UDSF, the request / response may be processed using the service described in the above embodiments in Figure 2 and the assignment of ID chunks may be implemented by creating an operation for a specific scenario. Alternatively, a separate service for making an explicit request for ID assignment to the UDSF may be used.

[0110] In step 650, the ID management server 603 assigns the requested temporary identifier. If the requested temporary identifier requires randomization (e.g., in the case of 5G-GUTI or M-TMSI), or if separate randomization is explicitly requested, the ID management server 603 applies randomization when assigning the temporary identifier. The ID management server 603 may accept the requested chunks of full size and thus assign the temporary identifier, or may assign smaller chunks. The information about the chunks includes the identifiers of the chunks that will be used for management (return, etc.) in the future in units of chunks.

[0111] In step 655, the ID management server 603 may send the assigned temporary identifier chunks to the NF 602. The ID management server 603 may further send information about success or failure and information about the chunk size to the NF 602.

[0112] In step 660, the NF 602 uses the assigned temporary identifier to process the remaining procedures / transactions.

[0113] In step 665, the assigned temporary identifier is sent to the interaction node (UE / base station or interacting NF) 601, and the interaction node 601 that receives the temporary identifier stores it for subsequent processes.

[0114] Meanwhile, in another embodiment, the operation of assigning / managing IDs in units of chunks may include: the operation of exchanging information about chunks in advance between the NF 602 and the ID management server 603 and only sending the identifiers (or indices) of the chunks in actual operations such as assignment / return, etc., and specifying and sending information about the identifiers included in the chunks (the starting value of the identifiers, the number of identifiers, the range of identifiers, etc.) when performing chunk assignment as described in the above embodiments.

[0115] Figure 7 The figure shows a diagram of a process in which a specific NF returns an assigned ID whose usage has been terminated, according to an embodiment.

[0116] Reference Figure 7 , reference numeral 701 denotes an interaction node that can request / trigger an NF service in a specific NF, and can be a UE, a RAN (base station), or another NF.

[0117] Reference numeral 702 denotes an NF for providing a communication function, and includes NFs defined in 3GPP standards and network devices similar thereto. If a specific NF is implemented / operated in the form of an instance, the NF may be replaced by an NF instance. In the case of implementation / realization in units of NF services rather than in units of NFs, the NF may be replaced by an NF service.

[0118] The ID management server 703 is a server that provides a function of managing an identifier pool for all NFs. The ID management server 703 may be configured as a separate function (NF), or may be configured as a detailed function provided by the context server when integrated with the context server described in the above embodiments. The ID management server 703 may be configured for each specific NF set, or the ID management server 603 may be configured to support multiple NF sets.

[0119] Step 730 means that the interaction node (UE / RAN / NF) 701 and the NF 702 are in a state where they can exchange information with each other and perform interaction operations.

[0120] In step 735, the UE or the interaction NF 701 makes a request for an NF service to NF 702. The request for the NF service by the interaction NF 701 can be made during the process of handling a service in response to a request from the UE, a request from the RAN, or an internal operation of an NF and a request from another NF. In this case, the requested service is characterized in that the use of a specific temporary identifier is terminated, and the use of identifiers such as M-TMSI (or 5G-GUTI) during deregistration processing, GTP TEID, and IP address during session release processing, etc. can also be terminated. According to an embodiment / configuration, instead of being executed immediately, the use of the temporary identifier and the deletion of the context can be executed after the elapse of a predetermined time.

[0121] In step 740, NF 702 processes the received transaction and determines whether a temporary identifier needs to be returned. Step 735 is not necessarily before step 740, and if an ID needs to be returned when a timer expires or in the overall operation scenario, NF 702 can start from step 740.

[0122] In step 745, NF 702 can send a request for returning an ID to the ID management server 703. In this case, NF 702 can make a request to the ID management server 703 for a chunk return of the temporary identifier to be assigned to the UE (subscriber). The request message can include the chunk identifier of the temporary identifier to be used. If the management of the ID is performed simultaneously with the management of the context, the return of the temporary identifier assigned to a specific UE (subscriber) can be performed simultaneously with the deletion of the context for the specific UE (subscriber). If the ID management server 703 supports the service of UDSF, the service described in the above embodiments in Figure 2 can be used to handle the request / response, and the assignment of the ID chunk can be implemented by the operation of deleting a specific context. Alternatively, a separate service for making an explicit request for an ID to the UDSF can be used.

[0123] In step 750, the ID management server 703 switches to a state where the requested temporary identifier is no longer used, and in step 755, the ID management server 703 sends a response to the return to NF 702. If the ID is returned by the processing of the context, the ID management server 703 can send a response to the deletion of the context.

[0124] In step 760, NF 702 processes the remaining process / transaction.

[0125] In step 765, a notification of the deletion of the temporary identifier is sent to the node (UE / base station or interaction NF) 701 through the processed process.

[0126] Figure 8 The figure shows a method of selecting a target NF considering the capacity of an NF that receives a context when providing a service by exchanging contexts between a context memory or NFs according to an embodiment.

[0127] Reference Figure 8 , the context memory 801 represents a function of storing / transmitting data (UE context) created / managed by an NF to provide a communication service, and includes CTSF, UDSF, etc. The Network Repository Function (NRF) / Service Communication Proxy (SCP) 802 is an NF that assists in discovery, selection, and message routing for providing a service between NFs using connection information and status information between NFs.

[0128] In step 810, the context memory 801 may start a new service or may change its state.

[0129] In step 820, the context memory 801 may newly register its own information (NF profile) in the NRF / SCP 802, or may update its own information (when the state / configuration is changed). In this case, the profile of the context memory 801 may include at least one of the maximum capacity that can be provided by the context memory, the current load condition, the throughput indicating the number of contexts that can be processed (sent / received) during a unit time, the size of a context that can be stored by one transaction, etc. When the profile of the context memory 801 represents the maximum capacity, load condition, throughput, and size, relative values calculated based on the maximum value may be used to represent the profile. Alternatively, the maximum capacity, load condition, throughput, and size may be represented as absolute values. For example, the maximum capacity may be represented as a combination of a specific context type (e.g., SM context) and the maximum number of acceptable contexts, and the number of contexts that can be processed at one time may be represented as a combination of a specific context type and the maximum number of contexts. For the operation in step 820, the context memory 801 may send a message such as "NRRegister request (NR registration request)" or "NFUpdate request (NF update request)" etc. to the NRF / SCP 802.

[0130] In step 830, the NRF / SCP 802 may store the capacity, status information, etc. (NF profile) received from the context memory 801.

[0131] In step 840, if the information stored in NF 803 is insufficient, another NF (SMF, AMF, etc.) 803 may send a discovery / selection request for the context memory to the NRF / SCP 802 to make a request for storing and sending the context. Even if the explicit target to be discovered is the context memory (CTSF or UDSF), the discovery / selection request may include information stating that the NF service to be requested is the storage of the context (context creation, update, or push) or its transmission (context delivery). The request in step 840 may be a "NFDiscovery request message".

[0132] In step 850, the NRF / SCP 802 may select the context memory (or a set of candidates) 801 according to the request, and in step 860, may send a response thereto to the NF 803 that made the request. In this case, the response may include the necessary information (a combination of the identifier of the context memory, access address, maximum capacity, current load status, throughput, simultaneous transmission ability, etc.) among the NF profiles of the context memory 801 received and stored in step 820, and the configuration and meaning of the detailed information may be the same as those described above in step 820. The response sent in step 860 may be a "NFDiscovery response message".

[0133] In step 870, the NF 803 may store the information received in step 860, and if it receives a response that can specify a context memory, the NF 803 may select the corresponding context memory. In addition, if it receives candidates for multiple context memories that will be the target, the NF 803 may select one of the candidates. In this case, when performing the selection, the NF 803 may select the context memory 801 that can effectively provide the service in consideration of the information received in step 860 (maximum capacity, load status, etc.). Even when the NF 803 requests a context-related service from the selected context memory 801, the information received in step 860 may be considered. In particular, when the context memory 801 provides a limited transmission volume, the NF 803 may create a request so as not to exceed the transmission volume, and may create a request such that the size of the context included in the request (the number of contexts, the size of the context, etc.) does not exceed the limit.

[0134] In step 880, the NF 803 sends a service request to the context memory 801. Thereafter, the NF 803 receives a response as a result of the processing from the context memory 801, and may trigger another process, the detailed description of which will be omitted in the embodiments. In step 880, the NF 803 may send a CTSF service request message for the service request to the context memory 801.

[0135] Figure 9 The figure shows a diagram of a method for managing a context in an NF according to an embodiment.

[0136] Reference Figure 9 , in step 910, NFs 903 and 904 and the context memory NF 901 may perform registration, discovery, and selection processes to request / receive mutual service provision.

[0137] In step 920, NF#1 (903) may determine that an NF change operation is required.

[0138] In step 930, NF#1 (903) sends the context to the context memory (CTSF / UDSF) 901 and sends a service request for changing the NF. The service used in this case may be a service context push request, and the request message may include at least one of an identifier (context ID) capable of identifying the target context for context transfer and NF change, the type of the context, the identifier of the target UE (subscriber), and the identifier of the target PDU session (if the context type is an SM context). If the operation of the request to be sent to the context memory 901 includes changing the NF and storing the context, the request message may additionally include the identifier of the NF to be changed. In this case, in order to select the NF to be changed, if a backup NF is preconfigured, NF#1 (903) may select one of the backup NFs. Otherwise, NF#1 (903) may select an NF from the same NF set. If there is no need to change the NF, steps 960 and subsequent steps may not be executed.

[0139] In step 940, the context memory 901 stores the context according to the request, and in step 950, sends a response thereto to NF#1 (903). If a request for changing the NF is further requested in step 930, after receiving the result of changing the NF, a response in step 950 to the service request received in step 930 may be sent (step 980). The response in step 950 may be a service context push response.

[0140] In the case where the context memory 901 receives a service request including a change to the NF in step 930, in step 960, the context memory 901 sends the context to the target NF (NF#2) 904 to be changed. The service used in this case may be a service context push request, and the request message may include at least one of an identifier (context ID) capable of identifying the target context for context transfer and the change to the NF, the type of the context, the identifier of the target UE (subscriber), and the identifier of the target PDU session (if the context type is an SM context). Additionally, the request message may include information indicating whether the context push service request is intended for the context memory or whether the context push service request includes a change to the NF.

[0141] NF#2 (904) may store the received context in step 970 and may send a response as a result to the context memory 901 in step 980. In this case, the response message in step 980 may be a service context push response. Then, in step 990, NF#2 (904) performs other processes / transactions based on the reception of the context and the change to the NF. The order of steps 970, 980, and 990 may be changed with respect to each other.

[0142] Table 1 below shows the type and structure of the context when the NF used for sending and receiving the context in the embodiment is the AMF.

[0143] [Table 1]

[0144]

[0145] As shown in Table 1, the AM context refers to the context created / managed by the AMF and represents data shared between AMFs, directly sent and received for changing the AMF, or sent through the context memory (CTSF). The data key for managing and browsing the AM context and indicating a specific AM context represents the identifier of the subscriber (SUPI).

[0146] Figure 10 The figure shows a diagram of a method for preventing failures and overloads caused by context transfer and NF changes according to an embodiment.

[0147] Refer to Figure 10 , in step 1010, the NF 1001 may perform a process of discovering / selecting another NF 1002.

[0148] In step 1020, NF#1 (1001) determines that a context transfer to another NF (NF#2) 1002 is required or that the NF needs to change accordingly, and in step 1030, NF#1 (1001) makes a request for a context push service to the target NF (NF#2) 1002. The message requesting the context push service may include at least one of an identifier (context ID) capable of identifying the target context for context transfer and the change of the NF, the type of the context, the identifier of the target UE (subscriber), and the identifier of the target PDU session (if the context type is an SM context). Additionally, the request message for the context push service may include whether the context push service request is intended for the context memory or whether the context push service request includes information for changing the NF. The request message may be a service context push request.

[0149] In step 1040, NF#2 (1002) may store the received context and, if an NF change is required, may perform other processes / transactions according to the NF change.

[0150] In step 1050, NF#2 (1002) sends the result of the service request to NF#1 (1001), and the response message may include information about the current load status of the NF and information and results for processing the context. More specifically, the response message may include at least one of the maximum capacity that can be provided by NF#2 (1002), the current load status, the throughput indicating the number of contexts that can be processed (sent / received) during a unit time period, and the size of the context that can be stored in a single transaction. The response message may be a service context push response. Additionally, NF#1 (1001) receiving the response may store the information included in the response and may consider this information when selecting a target or requesting the processing of a context in the case of a future need for context transfer or NF change.

[0151] Figure 11 The figure shows the detailed operation of the AMF according to an embodiment. In this embodiment, it is assumed that a pre-operation for triggering the sending of the context of a UE to another SMF is performed by a specific SMF.

[0152] Refer to Figure 11 , in step 1110, the AMF receives from the SMF (referred to as the "old SMF") a message indicating the necessity to send the context and session of a specific UE to another SMF. This message may be "Nsmf_PDUSession_SMContextStatusNotify", and in order to receive the message, the AMF may perform a subscription to the old SMF in advance to receive notifications of changes in the status.

[0153] In step 1120, the AMF can use the information contained in the request message from the SMF to select a target SMF (referred to as the "new SMF"). Additionally, the AMF can send a request to the new SMF to receive the context and session for the target UE from the old SMF. The message used in this case can be the "Nsmf_PDUSession_CreateSMContextrequest".

[0154] In step 1130, the AMF can optionally start a timer for determining whether the session-related context transfer of the SMF and its processing are successful.

[0155] If the timer is set in step 1130 and no response is received from the new SMF until the set timer expires, then in step 1140, the AMF can determine that the context processing procedure requested from the new SMF has failed. Alternatively, if the AMF explicitly receives a message from the new SMF indicating that the context processing procedure has failed, the AMF can recognize that the procedure has failed. Alternatively, the AMF can recognize whether the procedure is successful through an implementation within the AMF or by a method of receiving information from other NFs or OAM.

[0156] If it is determined that the context processing requested from the new SMF has failed, the AMF can determine that the corresponding session has been released and can perform the process of releasing the PDU session in step 1150. Alternatively, the AMF can notify the old SMF that the context processing has failed, so that the old SMF can perform subsequent processes.

[0157] Figure 12 The figure shows the detailed operations of the AMF according to an embodiment. In this embodiment, it is assumed that a specific SMF triggers a pre-operation for sending the context of a UE to another SMF.

[0158] Reference Figure 12 , in step 1210, the AMF receives from an SMF (referred to as the "old SMF") a message indicating the necessity to send a message about the context and session of a specific UE to another SMF. This message can be the "Nsmf_PDUSession_SMContextStatusNotify", and in order to receive the message, the AMF can perform a subscription to the old SMF in advance to receive notifications of status changes.

[0159] In step 1220, the AMF may use the information included in the request message from the SMF to select a target SMF (referred to as the "new SMF"). Additionally, the AMF sends a request to the new SMF for receiving context and session information about the target UE from the old SMF. The message used in this process may be the "Nsmf_PDUSession_CreateSMContext request". Thereafter, the AMF may optionally start a timer for determining whether the session-related context transfer of the SMF and its processing are successful.

[0160] In step 1230, before receiving a message indicating the completion of the context processing for the request to the new SMF in step 1220, the AMF may receive a separate request regarding the corresponding UE (e.g., a context transfer request received from another AMF during a service request or a registration process, etc.). Generally, this may be a request resulting from the mobility of the UE, or it may be a request caused by the emergence of a service for the UE in the idle state (transmission of a call or data).

[0161] In step 1240, when processing the request received in step 1230, the AMF determines whether the target UE and session include the currently changed SMF. More specifically, if the operation to be performed on the UE is a service request, the AMF determines whether the currently changed SMF belongs to the SMF that provides services for the PDU session to be processed for the UE. If the operation to be performed on the UE is a context transfer request made by another AMF, the AMF determines whether the currently changed SMF belongs to the SMF that manages the session of the UE. If the relevant SMF includes the currently changed SMF, the process continues to step 1250. Otherwise, the process continues to step 1260.

[0162] In step 1250, the AMF delays the processing of the request received in step 1230 until it receives a message from the new SMF indicating that the context creation process is completed. That is, the AMF stores the request received in step 1230 and waits. In this step, if the AMF receives a message from the new SMF notifying that the context creation process is completed, the AMF updates the UE context (including the address of the SMF) according to it and proceeds to step 1260. If the AMF sets a timer in step 1220 and if the AMF does not receive a response from the new SMF until the set timer expires, the AMF may determine that the context processing process requested from the new SMF has failed. Alternatively, if the AMF explicitly receives a message from the new SMF indicating that the context processing process has failed, the AMF may recognize that the process has failed. Alternatively, the AMF may recognize whether the process is successful through an implementation within the AMF or a method of receiving information from other NFs or OAM. If it is determined that the context processing requested from the new SMF has failed, the AMF may determine that the corresponding session has been released and may process the request received in step 1230. Alternatively, the AMF may notify the old SMF that the context processing has failed, so that the old SMF can perform subsequent processes.

[0163] Figure 13 The figure shows a diagram of the configuration of a terminal according to the present disclosure.

[0164] Reference Figure 13 , according to an embodiment, the terminal may include a transceiver 1320 and a controller 1310 that controls the overall operation of the terminal. In addition, the transceiver 1320 may include a transmitter 1321 and a receiver 1323.

[0165] The transceiver 1320 may send signals to other network entities and receive signals from other network entities.

[0166] The controller 1310 may perform control so that the terminal performs any one of the operations described in the above embodiments. At the same time, the controller 1310 and the transceiver 1320 are not necessarily implemented as separate modules and may be implemented as a single component in the form of a single chip. In addition, the controller 1310 and the transceiver 1320 may be electrically connected. In addition, for example, the controller 1310 may be a circuit, a dedicated circuit, or at least one processor. In addition, the operation of the terminal may be implemented by providing a memory device that stores the corresponding program code to any component inside the terminal.

[0167] Figure 14 The figure shows a diagram of the configuration of a network entity according to the present disclosure.

[0168] The network entity of the present disclosure includes network functions according to the embodiments of the system.

[0169] Reference Figure 14 According to an embodiment, a network entity may include a transceiver 1420 and a controller 1410 that controls the overall operation of the network entity. Additionally, the transceiver 1420 may include a transmitter 1421 and a receiver 1423.

[0170] The transceiver 1420 may send signals to other network entities and receive signals from other network entities.

[0171] The controller 1410 may perform control such that the network entity performs any one of the operations described in the above embodiments. At the same time, the controller 1410 and the transceiver 1420 are not necessarily implemented as separate modules and may be implemented as a single component in the form of a single chip. In addition, the controller 1410 and the transceiver 1420 may be electrically connected. Further, for example, the controller 1410 may be a circuit, an application-specific circuit, or at least one processor. Additionally, the operation of the network entity may be implemented by providing a memory device storing corresponding program code to any component inside the network entity.

[0172] The network entity may be any one of a base station (RAN), AMF, SMF, UPF, NF, NEF, NRF, CF, NSSF, UDM, AF, AUSF, SCP, UDSF, context memory, OAM, EMS, configuration server, and ID management server.

[0173] It should be noted that Figures 1 to 14 the configuration diagrams illustrated in, the diagrams illustrating examples of methods for transmitting control / data signals, and the diagrams illustrating examples of operation procedures are not intended to limit the scope of the present disclosure. That is, Figures 1 to 14 the components, entities, or operation steps described in should not be construed as essential elements for the implementation of the present disclosure, and the present disclosure can be implemented using only some of the elements without compromising the subject matter of the present disclosure.

[0174] The above-described operations of the base station or the terminal device can be implemented by providing a memory device storing corresponding program code to any component inside the base station or the terminal device. That is, the controller of the base station or the terminal device can use a processor or a central processing unit (CPU) to read and execute the program code stored in the memory device, thereby performing the above-described operations.

[0175] The various components and modules of an entity, base station, or terminal can be operated using, for example, a hardware circuit such as a complementary metal oxide semiconductor-based logic circuit, firmware, and a combination of hardware circuits such as software and / or hardware and firmware and / or software embedded in a machine-readable medium. For example, various electronic structures and methods can be implemented using transistors, logic gates, and electronic circuits such as custom semiconductors and the like.

[0176] Although the present disclosure has been described with respect to various embodiments, various changes and modifications can be suggested to those skilled in the art. The present disclosure is intended to embrace such changes and modifications that fall within the scope of the appended claims.

Claims

1. A method performed by an Access and Mobility Management Function (AMF) in a communication system, the method comprising: Receiving, from a first Session Management Function (SMF), a first message comprising information indicating a request to transfer a Session Management (SM) context to a second SMF; Selecting the second SMF based on the first message; Sending, to the second SMF, a second message for requesting the second SMF to receive the SM context from the first SMF; Starting a timer when sending the second message; And Receiving, from the second SMF, a third message as a response to the second message, Wherein, the method further comprises: Before receiving the third message, receiving, from a terminal, a service request for a Protocol Data Unit (PDU) session associated with the SM context; and Delaying the processing of the service request with the second SMF until the third message is received, and Wherein, the third message indicates that the context creation process is completed.

2. The method according to claim 1, further comprising: Determining that the SM context transfer process fails if the timer expires before the third message is received.

3. The method according to claim 1, further comprising: Before receiving the third message, receiving, due to terminal mobility, a User Equipment (UE) context transfer request from another AMF; And Delaying the processing of the UE context transfer request with the second SMF until the third message is received.

4. The method according to claim 1, Among them, The first message comprises an Nsmf_PDUSession_SMContextStatusNotify message, the second message comprises an Nsmf_PDUSession_CreateSMContext request message, and the third message comprises an Nsmf_PDUSession_CreateSMContext response message.

5. An Access and Mobility Management Function (AMF) in a communication system, the AMF comprising: A transceiver; And A controller, coupled to the transceiver and configured to: Receive, from a first Session Management Function (SMF), a first message comprising information indicating a request to transfer a Session Management (SM) context to a second SMF, Select the second SMF based on the first message; Send, to the second SMF, a second message for requesting the second SMF to receive the SM context from the first SMF, Start a timer when sending the second message, and Receive, from the second SMF, a third message as a response to the second message, Wherein, the controller is further configured to: Before receiving the third message, receive, from a terminal, a service request for a Protocol Data Unit (PDU) session associated with the SM context; and Delaying the processing of the service request with the second SMF until the third message is received, and Wherein, the third message indicates that the context creation process is completed.

6. The AMF according to claim 5, wherein, The controller is further configured to: Determine that the SM context transfer process fails if the timer expires before the third message is received.

7. The AMF according to claim 5, wherein, The controller is further configured to: Before receiving the third message, receive, due to terminal mobility, a User Equipment (UE) context transfer request from another AMF; and Delay the processing of the UE context transfer request with the second SMF until the third message is received.

8. The AMF according to claim 5, Among them, The first message includes an Nsmf_PDUSession_SMContextStatusNotify message, the second message includes an Nsmf_PDUSession_CreateSMContext request message, and the third message includes an Nsmf_PDUSession_CreateSMContext response message.

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