Access and mobility management function AMF in communication system and method thereof

Abstract

The present disclosure relates to an access and mobility management function AMF in a communication system and a method thereof. The method may include: receiving a first message including information indicating that a session management SM context needs to be transferred to a second SMF from a first session management function SMF; sending a second message to the second SMF for requesting the second SMF to receive the SM context from the first SMF; when sending the second message, starting a timer; and receiving a third message from the second SMF as a response to the second message before the timer expires, wherein the method further includes: before receiving the third message, receiving a user equipment UE context transfer request from another AMF due to terminal mobility; and delaying the processing of the UE context transfer request until the third message is received.

Description

[0001] This application is a divisional application of an invention patent application with an application date of May 12, 2020, application number 202080017957.0, and invention name “Method and device for flexibly supporting services in a wireless communication system”. Technical Field

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

[0003] In order 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 quasi-5G communication systems. Therefore, 5G or quasi-5G communication systems are also referred to as "super 4G networks" or "post-LTE systems."

[0004] 5G communication systems are considered to be implemented in higher frequency (mmWave) bands (e.g., 60 GHz bands) to achieve higher data rates. In order 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 massive antenna technologies are discussed in 5G communication systems.

[0005] In addition, in the 5G communication system, development of system network improvements is underway based on advanced small cells, cloud radio access networks (RAN), ultra-dense networks, device-to-device (D2D) communications, wireless backhaul, mobile networks, collaborative communications, coordinated multi-point (CoMP), receiving-end interference cancellation, etc.

[0006] In 5G systems, hybrid FSK and QAM modulation (FQAM) and sliding window superposition coding (SWSC) as advanced coded modulation (ACM), filter bank multi-carrier (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, 5G systems are considered to support more various 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. In order to meet these strict conditions required for this, 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-centric connectivity network where humans generate and consume information, has now evolved into the Internet of Things (IoT), where distributed entities such as objects 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 with 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 implementation, sensor networks, machine-to-machine (M2M) communications, machine type communications (MTC), etc. have been recently studied.

[0010] Such an IoT environment can provide intelligent Internet technology services that create new value for human life by collecting and analyzing the data generated among connected objects. 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, health care, smart appliances, and advanced medical services.

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

[0012] The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with respect to the present disclosure. Summary of the invention

[0013] Technical issues

[0014] The 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 discussed in the present disclosure may not be limited to the above-mentioned technical subjects, and other technical subjects that are not mentioned may be clearly understood by those skilled in the art to which the present disclosure belongs through the following description.

[0016] Solution

[0017] According to aspects 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 a first message from a first session management function (SMF) entity to transfer a session management (SM) context to a second SMF entity; sending a second message to the second SMF entity for requesting the second SMF entity to receive the SM context from the first SMF entity; when sending the second message, starting a timer; and receiving a third message from the second SMF entity as a response to the second message before the timer expires.

[0018] In one embodiment, the method further comprises: determining that the SM context transfer process has failed if the timer expires before receiving the third message.

[0019] In one embodiment, the first message includes information regarding an indication of the delivery SM context.

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

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

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

[0023] In one embodiment, sending the second message further comprises: 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 a first message for delivering a session management (SM) context to a second SMF entity from a first session management function (SMF) entity via the transceiver; send a second message for requesting the second SMF entity to receive the SM context from the first SMF entity via the transceiver to the second SMF entity; start a timer when sending the second message; and receive a third message as a response to the second message from the second SMF entity via the transceiver 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 comprising: receiving a first message from a first session management function SMF indicating a request to transfer information of 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; when sending the second message, starting a timer; and receiving a third message from the second SMF as a response to the second message before the timer expires, wherein the method further comprises: before receiving the third message, receiving a user equipment UE context transfer request from another AMF due to terminal mobility; and delaying processing of the UE context transfer request with the second SMF until the third message is received.

[0026] The present disclosure also provides 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 a first message indicating a request to transfer information of a session management (SM) context to a second SMF from a first session management function (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 a third message from the second SMF as a response to the second message before the timer expires, wherein the controller is further configured to: receive a user equipment (UE) context transfer request from another AMF due to terminal mobility before receiving the third message; and delay processing of the UE context transfer request with the second SMF until the third message is received.

[0027] Advantageous Effects of the Invention

[0028] In the case of applying the embodiment, the throughput can be freely distributed by sharing the context of the terminal between NFs and customer service can be supported without sacrificing quality by enabling the service provided by the erroneous NF to be taken over by another NF. In addition, in the case of applying the embodiment, the IDs used by the NFs that share 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 degradation of customer service quality caused by ID conflicts.

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

[0030] For a more complete understanding of 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 a 5G system based on SBA according to an embodiment;

[0032] Figure 2 A diagram illustrating a separation structure of NFs and contexts according to an embodiment;

[0033] Figure 3 A diagram illustrating an example of 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 of a 5G system in which a dynamic change occurs according to an embodiment;

[0036] Figure 6 A diagram illustrating a method for dividing a pool of identifiers shared by a set of NFs into chunk units and assigning, managing, and collecting in chunk units, 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 whose use is terminated according to an embodiment;

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

[0039] Fig. 9 A diagram illustrating a method of managing context in a NF according to an embodiment;

[0040] Fig.10 A diagram illustrating a method for preventing failure and overload due to context transfer and change of NF according to an embodiment;

[0041] Fig.11 FIG. 1 illustrates detailed operation of the AMF according to an embodiment;

[0042] Fig.12 FIG. 1 illustrates detailed operation of the AMF according to an embodiment;

[0043] Fig.13 A diagram illustrating a configuration of a terminal according to the present disclosure; and

[0044] Fig.14 The figure shows a diagram of a configuration of a network entity according to the present disclosure. DETAILED DESCRIPTION

[0045] Before proceeding to the following detailed description, it may be helpful to set forth definitions of certain words used throughout this patent document: the terms "include" and "comprising" and their derivatives mean inclusion without limitation; the term "or" is inclusive, meaning and / or; the words "associated with" and "associated therewith" and their derivatives may mean including, included, interconnected with, containing, contained within, connected to or connected with, coupled to or coupled with, communicating with, cooperating with, intertwined, juxtaposed, proximate to, bound to or bound with, having, having the property of, and the like; and the term "controller" means any device, system, or portion thereof that controls at least one operation, such device may be implemented in hardware, firmware, or software, or some combination of at least two thereof. It should be noted that the functionality associated with any particular controller, whether local or remote, may be centralized or distributed.

[0046] In addition, various functions as described below can be implemented or supported by one or more computer programs, each of which is formed by a computer-readable program code and is embodied in a computer-readable medium. The terms "application" and "program" refer to one or more computer programs, software components, instruction sets, procedures, functions, objects, categories, instances, related data, or parts thereof suitable for implementation in a suitable computer-readable program code. The phrase "computer-readable program code" includes any type of computer coding, 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 a read-only memory (ROM), a random access memory (RAM), a hard drive, a compact disk (CD), a digital video disk (DVD), or any other type of memory. "Non-transitory" computer-readable media excludes wired, wireless, optical, or other communication links that convey instantaneous electrical signals or other signals. Non-transitory computer-readable media include media in which data can be permanently stored and media in which data can be stored and later rewritten, such as rewritable optical disks or erasable memory devices.

[0047] Definitions for certain terms are provided throughout this patent document, those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior, as well as future uses of such defined terms.

[0048] The following discussion Figures 1 to 14 The various embodiments used to describe the principles of the present disclosure in this patent document are intended to be illustrative only and should not be construed in any way to limit the scope of the present disclosure. Those skilled in the art will appreciate that the principles of the present disclosure can be implemented in any appropriately arranged system or device.

[0049] Hereinafter, the operating principle 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 quite unclear, a detailed description thereof will be omitted. The terms to be described below are defined terms considering the functions in the present disclosure, and may vary depending on the user, the user's intention, or custom. Therefore, the definition of the terms should be made based on the content throughout the specification.

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

[0051] In the following description, for the convenience of description, the present disclosure uses 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 systems conforming to other standards can be applied in the same manner.

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

[0053] Meanwhile, in the present disclosure, the term “service” will be used to refer to “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 the service provided to the end user.

[0054] New system structures 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 The figure shows a diagram of the structure of an SBA-based 5G system according to an embodiment.

[0056] refer to 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 the 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 services and is controlled by the SMF 130. Although not described in Figure 1 Although not shown in FIG, the 5G system may include UDSF, and UDSF is a NF that stores unstructured data. Any type of data may be stored or retrieved at the request of NF.

[0057] Figure 2 A diagram illustrating a separation structure of NFs and contexts according to an embodiment.

[0058] refer to Figure 2In an embodiment, data (UE context) in NF is separated from NF and stored in a separate context memory, and a set of NFs that can share and use it is referred to as 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 may be applied to an environment that manages and operates any one of the NF and the NF instance. In addition, instead of implementing / realizing with NF as a unit, in the case of operating with NF service as a unit, the NF may be replaced by the NF service. Therefore, the term "NF" in the present disclosure may cover NF instances, NF services, and NF service instances. If multiple NF sets coexist, different identifiers or names may be assigned to the corresponding NF sets in order to distinguish between them, and even if the NFs in the NF set operate by sharing contexts with each other, different identifiers / names may 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] refer to 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 send and receive signaling / data.

[0061] In step 305, the requester 382 makes a request to the NF 383 for a specific NF service. If the requester is the RAN 382, ​​the target NF 383 may be the AMF. In this case, the requester 382 may specify the recipient 383 of the request and send it. If the request is sent to the NF set without specifying a specific NF, any NF in the NF set may 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 a UE context pre-cached in the NF set, i.e., in the NF or 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 the UE context cached 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 may include a data identifier for identifying the data to be retrieved. If the NF 383 detects the correct data identifier, the identifier capable of identifying the data may include a value corresponding thereto. Otherwise, the identifier may 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), an Internet Protocol (IP) address, a tunnel endpoint ID (TEID), a flow ID, an application / service identifier, a charging ID, etc.}.

[0064] In step 317, the context storage 384 searches for the data to be retrieved according to the request of the NF 383, and sends a response thereto to the NF 383 in step 321. If the request is valid, that is, if the context storage 384 is able to 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 storage 384 may 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.) in order to check the validity of the request of the NF 383 and find the context to be retrieved. In the case where the context storage 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 the UE (subscriber) instead of using a specific data identifier, and if the specific data identifier is pre-assigned to the context storage 384, the response sent in step 321 includes the data identifier. In addition, upon receiving the response, NF 383 may store the data identifier and may use the corresponding data identifier when making a request to context storage 384 in the future. According to this, the time taken for context storage 384 to search for stored contexts using a UE (subscriber) identifier or the load on context storage 384 for doing so may be reduced.

[0065] In step 325, the process / transaction requested in step 305 is processed using the corresponding context. In an embodiment, the process / transaction includes a processing operation in a specific NF and also includes sending / receiving messages and an operation of requesting a service by interacting with another NF according thereto.

[0066] In the case where the UE context needs to be updated or a new UE context needs to be stored in the context storage 384 by request, in step 329, NF 383 makes a request for storing / updating the context to the context storage 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 storage 384 is a UDSF, the services "Nudsf_UnstructuredDataManagement_Create(storage)" and "Nudsf_UnstructuredDataManagement_Update(update)" can be used to perform the corresponding operations. In the case of updating, if NF 383 explicitly knows or receives the data identifier, NF 383 can use the corresponding data identifier to perform updating the UE context. In addition, in the case of "creating", NF 383 can send the UE (subscriber) identifier and the context to be stored to the context storage 384.

[0067] In step 333, the context memory 384 may store the context sent from NF 383, and if a new data identifier needs to be created (generated) (in the case where a UE or subscriber identifier is used in step 329), the context memory 384 may create a new data identifier and may send it to NF 383 via a response in step 337.

[0068] In step 341, NF 383 and other nodes 381 and 382 process the remaining procedures / transactions. 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 UE 381, and UE 381 stores it for use in subsequent procedures.

[0069] The above embodiments have described a method of grouping multiple NFs into NF sets and separating / sharing contexts. When performing a process of providing a connection 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 identifier GUAMI of the AMF serving the UE and the MME Temporary Mobile Subscriber Identity (M-TMSI) assigned to the UE. In one AMF set, each UE must be uniquely assigned an M-TMSI.

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

[0072] -UE IP address: This is an IP address assigned to the UE when the UE uses IP communication, and must be uniquely assigned to each UE within one 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] - Analysis ID: This is an identifier assigned to collect / analyze information about the NW and can be used in the N / W Data Analysis 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 the NF assigns a temporary identifier to a specific UE (subscriber), uniqueness must be ensured according to a certain condition, and if the uniqueness is not met, an error occurs, so the service quality is degraded or error recovery processing is required. Unlike a system in which all resources inside one NF are consumed, in the structure described in the above embodiment, the NFs in the NF set share the context, and the NF that provides services to a single UE (subscriber) can be changed at any time in the same set. In such a system, because the entire pool of temporary identifiers is also shared by the NFs, there may be a problem in that two NFs assign one temporary identifier to two UEs (subscribers) at the same time.

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

[0080] refer to Figure 4, reference numeral 401 denotes 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 denotes a NF for providing a communication function, and includes NFs defined in the 3GPP standard 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 an operation in units of NF services rather than implementation / realization in units of NFs, the NF may be replaced by an NF service.

[0082] Configuration server (conf.server) 403 is a server that provides a function of managing / configuring communication equipment (RAN, NF, etc.), and is generally referred to as an "element management system (EMS)" or an "operation and maintenance (OAM) system". Virtualized network function manager (VNFM) / orchestrator 404 is a system that configures / manages 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 may be integrated into one, and in this case, the exchange of messages between the two systems may be omitted, or the exchange of messages between the two systems may be processed by an internal process.

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

[0084] In step 434, VNFM / Orchestrator 404 informs Configuration Server 403 of the size of the NF (usually corresponding to the maximum capacity) (a value such as the number of subscribers or sessions that can be processed in parallel, a value 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 may divide the entire pool of temporary identifiers shared by the NF set according to the size of the received NF / NF set, thereby determining the available identifiers to be used for each NF, and may send information assigned to each NF 402. Available identifier information may be sent to the NF 402 according to its type, and the configuration server 403 may send the NF 402 a starting value of the temporary identifier, a total number of forms or a range of temporary identifiers (indicating the start to end values), or a list of all assigned identifiers. When managing temporary identifiers, the configuration server 403 may reserve some segments in consideration of future changes in NW configuration (the size of NFs, the size of sets, etc.), and may use the remaining segments to perform initial assignments.

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

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

[0088] The above embodiment can be utilized in the case where multiple NFs are included in an NF set. If the number of NFs in an NF set is changed dynamically (if the scaled size changes due to failure or load), or if the size of each NF changes, it is difficult to change the pool of identifiers to match the situation.

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

[0090] refer to Figure 5 , reference numeral 501 denotes 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.

[0091] Reference numeral 502 denotes a NF for providing a communication function, and includes NFs defined in the 3GPP standard 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 an operation in units of NF services rather than implementation / realization in units of NFs, the NF may 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 may be configured as a separate function (NF), or may be configured as a specific function provided by a context server when integrated with the context server described in the above embodiment.

[0093] Step 531 means that the interworking node (UE / RAN / NF) 501 and the NF 502 are in a state capable of exchanging information with each other and performing an interworking operation.

[0094] In step 535, the UE or the inter-NF 501 makes a request for the NF service to the NF 502. The request for the NF service by the inter-NF 501 may be made in the process of processing the service by the request of the UE, the request of the RAN, or the internal operation of the NF and the request of another NF.

[0095] In step 539, 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, NF 502 may send a request to the ID management server 503 for assigning an ID or creating / updating a context. In this case, 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. In addition, when assigning a temporary identifier, NF 602 may make an explicit request to the ID management server 503 whether to apply randomization. If the ID management server 503 supports the services of UDSF, the UDSF in the UDSF may be used. Figure 2 The services described in the above embodiments handle request / response.

[0097] In step 549, if a request to process a context is received, the ID management server 503 stores / updates the context and 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 a 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 transmits the assigned temporary identifier to the NF 502, and, in the case of receiving a request to process a context, transmits a response to the context processing.

[0099] In step 559, 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 interactive node (UE / base station or interactive NF) 501, and the interactive node 501 receiving the temporary identifier stores it for use in subsequent processes.

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

[0102] The assignment method in chunk units is effective because signaling for management of identifiers between NFs can be reduced and because collision can be prevented while each NF freely assigns an identifier within a chunk.

[0103] refer to Figure 6 , reference numeral 601 denotes 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 denotes a NF for providing a communication function, and includes NFs defined in the 3GPP standard and network equipment 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 an operation in units of NF services rather than implementation / realization in units of NFs, the NF may 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 embodiment. 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 interworking node (UE / RAN / NF) 601 and the NF 602 are in a state capable of exchanging information with each other and performing interworking operations.

[0107] In step 635, the UE or the inter-NF 601 makes a request for the NF service to the NF 602. The request for the NF service by the inter-NF 601 may be made in the process of processing the service at the request of the UE, the request of the RAN, or the internal operation of the NF and the request of another NF.

[0108] In step 640, 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 NF 602 may start from step 640 if assignment of an ID pool is required in the initial process for processing a service request or in an overall operation scenario.

[0109] In step 645, NF 602 may send a request for ID assignment to the ID management server 603. In this case, NF 602 may make a request to the ID management server 603 for block assignment of temporary identifiers to be assigned to the UE (subscriber). The request message may include information about the type of temporary identifier to be used and the block 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, NF 602 may use a request message to notify the ID management server 603 of the name or information of the NF set to which NF 602 belongs. In addition, when assigning a temporary identifier, NF 602 may make an explicit request to the ID management server 603 whether to apply randomization. If the ID management server 603 supports the services of UDSF, the randomization request in Figure 2 The service described in the above embodiments in the UDSF handles the request / response, and the assignment of the ID chunks can be implemented by creating an operation for a specific context. Alternatively, a separate service for making an explicit request for ID assignment to the UDSF can 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 a 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 full size of the requested chunk and thus assign the temporary identifier, or may assign a smaller chunk. The information about the chunk includes an identifier of the chunk that will be used for management (return, etc.) in units of chunks in the future.

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

[0112] In step 660, 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 interactive node (UE / base station or interactive NF) 601, and the interactive node 601 receiving the temporary identifier stores it for use in subsequent processes.

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

[0115] Figure 7 The diagram illustrates a process in which a specific NF returns an assigned ID whose use is terminated according to an embodiment.

[0116] refer to Figure 7 , reference numeral 701 denotes 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.

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

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

[0119] Step 730 means that the interworking node (UE / RAN / NF) 701 and the NF 702 are in a state capable of exchanging information with each other and performing interworking operations.

[0120] In step 735, the UE or the interworking NF 701 makes a request to the NF 702 for the NF service. The request of the interworking NF 701 for the NF service may be made in the process of processing the service at the request of the UE, the request of the RAN, or the internal operation of the NF and the request of 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 the deregistration process, GTP TEID and IP address during the session release process, etc. may also be terminated. Depending on the embodiment / configuration, the use of the temporary identifier and the deletion of the context may be performed after the lapse of a predetermined time instead of immediately.

[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 NF 702 may start from step 740 if an ID needs to be returned upon expiration of a timer or in an overall operating situation.

[0122] In step 745, NF 702 may send a request for returning the ID to the ID management server 703. In this case, NF 702 may make a request to the ID management server 703 for the chunk return of temporary identifiers to be assigned to the UE (subscriber). The request message may 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 the specific UE (subscriber) may 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 UDSF may be used. Figure 2 The service described in the above embodiments in the UDSF handles the request / response, and the assignment of the ID chunks can be implemented by deleting the operation of the 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 the NF 702. If the ID is returned by processing the context, the ID management server 703 may send a response to the deletion of the context.

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

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

[0126] Figure 8 A diagram illustrating a method of selecting a target NF in consideration of a capacity of a NF receiving a context when providing a service by exchanging contexts in a context storage or between NFs according to an embodiment.

[0127] refer to Figure 8 , the context storage 801 represents a function of storing / transmitting data (UE context) created / managed by NF in order to provide communication services, 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, and is used to provide services between NFs using connection information and state information between NFs.

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

[0129] In step 820, the context memory 801 may newly register its own information (NF profile) in the NRF / SCP802, 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, and the throughput representing the number of contexts that can be processed (sent / received) during a unit time, the size of the context that can be stored by one transaction, etc. In the case where the profile of the context memory 801 represents the maximum capacity, load condition, throughput, and size, the profile may be represented using a relative value calculated based on the maximum value. 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 storage 801 may send a message such as “NRRegister request” or “NFUpdate request” or the like to the NRF / SCP 802 .

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

[0131] In step 840, if the information stored by NF 803 is not sufficient, another NF (SMF, AMF, etc.) 803 may send a discovery / selection request of a context store to NRF / SCP 802 in order to make a request to store and send contexts. Even if the explicit target to be discovered is the context store (CTSF or UDSF), the discovery / selection request may include information stating that the NF service to be requested is storage of contexts (context creation, update or push) or transmission thereof (context transfer). The request in step 840 may be an "NFDiscovery request message".

[0132] In step 850, the NRF / SCP 802 may select a context memory (or a set of candidates) 801 according to the request, and in step 860, a response thereto may be sent to the NF 803 that made the request. In this case, the response may include necessary information (a combination of an identifier, access address, maximum capacity, current load condition, throughput, simultaneous transmission capability, etc. of the context memory) 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 an "NFDiscovery response message".

[0133] In step 870, NF 803 may store the information received in step 860, and if a response capable of specifying a context memory is received, NF 803 may select the corresponding context memory. In addition, if candidates of a plurality of context memories to be the target are received, NF 803 may select one of the candidates. In this case, when performing the selection, NF 803 may select a context memory 801 capable of effectively providing a service in consideration of the information received in step 860 (maximum capacity, load condition, etc.). Even if NF 803 requests a context-related service to the selected context memory 801, the information received in step 860 may be considered. In particular, when context memory 801 provides a limited transmission amount, NF 803 may create a request so as not to exceed the transmission amount, and may create a request so 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, NF 803 sends a service request to context storage 801. Thereafter, NF 803 receives a response as a result of the processing from context storage 801 and may trigger another process, the detailed description of which will be omitted in the embodiment. In step 880, NF 803 may send a CTSF service request message for the service request to context storage 801.

[0135] Fig. 9 A diagram illustrating a method of managing context in a NF according to an embodiment.

[0136] refer to Fig. 9 In step 910, NFs 903 and 904 and context storage 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 a NF change operation is required.

[0138] In step 930, NF#1 (903) sends a context to the context storage (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 delivery and NF change, the type of context, an identifier of the target UE (subscriber), and an 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 storage 901 includes changing the NF and storing the context, the request message may additionally include an identifier of the NF to be changed. In this case, in order to select the NF to be changed, if a backup NF is pre-configured, NF#1 (903) may select one of the backup NFs. Otherwise, NF#1 (903) may select a NF from the same NF set. If the NF does not need to be changed, step 960 and its subsequent steps may not be performed.

[0139] In step 940, the context storage 901 stores the context according to the request, and in step 950, sends a response thereto to NF#1 (903). If a request to change 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 storage 901 receives the service request including the change of NF in step 930, the context storage 901 sends the context to the target NF (NF#2) 904 to be changed in step 960. 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 delivery and change of NF, the type of context, an identifier of the target UE (subscriber), and an identifier of the target PDU session (if the context type is an SM context). In addition, the request message may include information indicating whether the context push service request is intended for the context storage or whether the context push service request includes the change of NF.

[0141] NF#2 (904) may store the received context in step 970, and may send a response as a result thereof to the context storage 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 according to the reception of the context and the change of the NF. The order of steps 970, 980, and 990 may be changed with respect to each other.

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

[0143] [Table 1]

[0144]

[0145] As shown in Table 1, AM context refers to a context created / managed by AMF and represents data shared between AMFs, directly sent and received for changing AMF, or sent through a context storage (CTSF). The data key used to manage and browse AM contexts and indicate a specific AM context represents a subscriber's identifier (SUPI).

[0146] Fig.10 A diagram illustrating a method for preventing failure and overload due to context transfer and change of NFs according to an embodiment.

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

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

[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 condition of the NF and information for processing the context as well as the result. More specifically, the response message may include the maximum capacity that can be provided by NF#2 (1002), the current load condition, and at least one of a throughput indicating the number of contexts that can be processed (sent / received) during a unit time and the size of the context that can be stored through a single transaction. The response message may be a service context push response. In addition, NF#1 (1001) receiving the response may store the information included in the response, and in the event that context transfer or a change of NF is required in the future, the information may be considered when selecting a target or requesting processing of a context.

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

[0152] refer to Fig.11 In step 1110, the AMF receives a message from an SMF (referred to as the "old SMF") indicating that it is necessary to send a context and session about a specific UE to another SMF. The 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 in order to receive notifications of changes in status.

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

[0154] In step 1130, the AMF may optionally start a timer for determining whether the session-related context transmission and its processing by the SMF is successful.

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

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

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

[0158] refer to Fig.12 In step 1210, the AMF receives a message from an SMF (referred to as the "old SMF") indicating that it is necessary to send a context and session about a specific UE to another SMF. The 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 in order to receive notifications of changes in status.

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

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

[0161] In step 1240, while processing the request received in step 1230, the AMF determines whether the target UE and the session include the currently changed SMF. More specifically, if the operation to be processed for the UE is a service request, the AMF determines whether the currently changed SMF belongs to the SMF that provides services to the PDU session so as to be processed for the UE. If the operation to be processed for 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 SMFs include 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 a message indicating that the context creation process is completed is received from the new SMF. That is, the AMF stores the request received in step 1230 and waits. In this step, if the AMF receives a message notifying the completion of the context creation process from the new SMF, 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 to the new SMF has failed. Alternatively, if the AMF explicitly receives a message indicating that the context processing process has failed from the new SMF, the AMF may recognize that the process has failed. Alternatively, the AMF may recognize whether the process is successful by an implementation method within the AMF or a method of receiving information from other NFs or OAMs. If it is determined that the context processing requested to 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 may perform subsequent processes.

[0163] Fig.13 A diagram illustrating a configuration of a terminal according to the present disclosure.

[0164] refer to Fig.13 , the terminal according to the embodiment may include a transceiver 1320 and a controller 1310 controlling 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 and receive signals from other network entities.

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

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

[0168] The network entity of the present disclosure includes a network function according to an embodiment of the system.

[0169] refer to Fig.14 , the network entity according to the embodiment may include a transceiver 1420 and a controller 1410 that controls the overall operation of the network entity. In addition, the transceiver 1420 may include a transmitter 1421 and a receiver 1423.

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

[0171] The controller 1410 may perform control so that the network entity performs any one of the operations described in the above embodiments. Meanwhile, 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. In addition, for example, the controller 1410 may be a circuit, a dedicated circuit, or at least one processor. In addition, the operation of the network entity may be implemented by providing a memory device storing a corresponding program code to any component inside the network entity.

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

[0173] It should be noted that Figures 1 to 14 The configuration diagrams illustrated in the figure, the diagrams illustrating examples of methods of sending control / data signals, and the diagrams illustrating examples of operation processes are not intended to limit the scope of the present disclosure. That is, Figures 1 to 14 The components, entities, or operational steps described in the description 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 impairing the subject matter of the present disclosure.

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

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

[0176] Although the present disclosure has been described in terms of various embodiments, various changes and modifications may be suggested to one skilled in the art. The present disclosure is intended to encompass such changes and modifications as 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 including information indicating that a session management (SM) context needs to be transferred 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; When sending the second message, start the timer; as well as receiving a third message as a response to the second message from the second SMF before the timer expires, Wherein, the method further comprises: Prior to receiving the third message, receiving a user equipment UE context transfer request from another AMF due to terminal mobility; and Processing of the UE context transfer request is delayed until the third message is received.

2. The method according to claim 1, further comprising: In case the timer expires before the third message is received, it is determined that the SM context transfer process has failed.

3. The method according to claim 1, in, The third message indicates that the context creation process is completed.

4. The method according to claim 2, further comprising: Before receiving the third message, receiving from the terminal a service request for a protocol data unit (PDU) session associated with the SM context; as well as The processing of the service request with the second SMF is delayed until the third message is received.

5. The method according to claim 1, in, The first message includes a Nsmf_PDUSession_SMContextStatusNotify message, the second message includes a Nsmf_PDUSession_CreateSMContext request message, and the third message includes a Nsmf_PDUSession_CreateSMContext response message.

6. The method according to claim 1, wherein: Sending the second message further includes: A second SMF is selected based on the first message.

7. An access and mobility management function AMF in a communication system, the AMF comprising: Transceiver; as well as A controller is coupled to the transceiver and is configured to: receiving, from a first session management function SMF, a first message including information indicating that a session management SMF context needs to be transferred 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, When sending the second message, start the timer, and before the timer expires, receiving a third message from the second SMF as a response to the second message, The controller is further configured as follows: Prior to receiving the third message, receiving a user equipment UE context transfer request from another AMF due to terminal mobility; and Processing of the UE context transfer request is delayed until the third message is received.

8. The AMF according to claim 7, wherein: The controller is further configured as: In case the timer expires before the third message is received, it is determined that the SM context transfer process has failed.

9. The AMF according to claim 7, in, The third message indicates that the context creation process is completed.

10. The AMF according to claim 8, wherein: The controller is further configured as: Prior to receiving the third message, receiving from the terminal a service request for a protocol data unit (PDU) session associated with the SM context; and The processing of the service request with the second SMF is delayed until the third message is received.

11. The AMF according to claim 7, in, The first message includes a Nsmf_PDUSession_SMContextStatusNotify message, the second message includes a Nsmf_PDUSession_CreateSMContext request message, and the third message includes a Nsmf_PDUSession_CreateSMContext response message.

12. The AMF according to claim 7, wherein: The controller is further configured as: A second SMF is selected based on the first message.

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