Method and apparatus for supporting establishment of PDU sessions on network slices in communication network

Abstract

The present invention relates to a 5G or 6G communication system for supporting a higher data transmission rate. There is provided a method for supporting a session management function (SMF) of a communication network when establishing a protocol data unit (PDU) session on a network slice, the method comprising the steps of: receiving, from an access and mobility management function (AMF), a PDU session request message including a first network slice identifier and an additional network slice identifier, the additional network slice identifier is replaced by the first network slice identifier; selecting a policy control function (PCF) for the first network slice identifier; sending a policy creation request message including the first network slice identifier and the additional network slice identifier to the selected PCF; and receiving, from the PCF, a message in response to the policy creation request message.

Description

Technical Field

[0001] The present disclosure relates to a method and apparatus for supporting a PDU session for establishing a network slice in a communication network. More specifically, the present disclosure relates to a method and device for determining a session policy when a network slice change occurs. Background Art

[0002] The 5G mobile communication technology defines a wide frequency band, enabling high transmission rates and new services, which can be achieved not only in the "sub-6 GHz" band such as 3.5 GHz, but also in the "above-6 GHz" band called mmWave including 28 GHz and 39 GHz. In addition, the 6G mobile communication technology (referred to as the super 5G system) has been considered to be implemented in the terahertz band (e.g., 95 GHz to 3 THz band) in order to achieve a transmission rate fifty times faster than that of the 5G mobile communication technology and an ultra-low latency of one-tenth of that of the 5G mobile communication technology.

[0003] At the beginning of the development of the 5G mobile communication technology, in order to support services and meet the performance requirements related to enhanced mobile broadband (eMBB), ultra-reliable low-latency communication (URLLC), and massive machine-type communication (mMTC), there has been continuous standardization regarding beamforming and massive MIMO for reducing radio wave path loss and increasing the radio wave transmission distance in mmWave, supporting a parameter set for dynamic operation for effectively utilizing mmWave resources and time slot formats (e.g., operating multiple subcarrier spacings), an initial access technology for supporting multi-beam transmission and broadband, the definition and operation of BWP (bandwidth part), new channel coding methods such as LDPC (low-density parity-check) codes for large data transmission and polar codes for highly reliable transmission of control information, L2 preprocessing, and network slicing for providing a dedicated network dedicated to a specific service.

[0004] Currently, in view of the services to be supported by the 5G mobile communication technology, there has been continuous discussion on the improvement and performance enhancement of the initial 5G mobile communication technology, and there has been physical layer standardization of technologies such as V2X (vehicle-to-everything) for assisting autonomous vehicle driving determination based on information about the position and status of the vehicle sent by the vehicle and for enhancing user convenience, NR-U (new radio unlicensed) for system operation aiming to comply with various regulatory requirements in the unlicensed band, NR UE power saving, non-terrestrial network (NTN) as UE-satellite direct communication for providing coverage in areas where communication with the terrestrial network is unavailable, and positioning.

[0005] In addition, there is continuous standardization of air interface architectures / protocols for technologies such as industrial Internet of Things (IIoT) for supporting new services through interconnection and integration with other industries, integrated access and backhaul (IAB) for providing nodes for network service area expansion by supporting wireless backhaul links and access links in an integrated manner, mobility enhancements including conditional handover and dual active protocol stack (DAPS) handover, and two-step random access (two-step RACH for NR) for simplifying the random access process. There is also continuous standardization of system architectures / services for 5G baseline architectures (e.g., service-based architectures or service-based interfaces), for combining network function virtualization (NFV) and software-defined networking (SDN) technologies, and for mobile edge computing (MEC) for receiving services based on UE location.

[0006] As the 5G mobile communication system is commercialized, the exponentially growing connected devices will be connected to the communication network, and accordingly, enhanced functions and performance of the 5G mobile communication system and integrated operation of the connected devices are expected to be necessary. For this purpose, new research related to extended reality (XR) is arranged to effectively support augmented reality (AR), virtual reality (VR), mixed reality (MR), etc., and to improve 5G performance and reduce complexity by leveraging artificial intelligence (AI) and machine learning (ML), AI service support, metaverse service support, and drone communication.

[0007] Furthermore, such development of the 5G mobile communication system will become the basis for not only developing new waveforms for providing coverage in the terahertz band for 6G mobile communication technology, multi-antenna transmission technologies such as full-dimensional MIMO (FD-MIMO), array antennas and massive antennas, metamaterial-based lenses and antennas for improving the coverage of terahertz band signals, high-dimensional spatial multiplexing technologies using orbital angular momentum (OAM), high-dimensional spatial multiplexing technologies of reconfigurable intelligent surfaces (RIS), full-duplex technologies for improving the frequency efficiency of 6G mobile communication technology and enhancing the system network, AI-based communication technologies for realizing system optimization from the design stage using satellites and AI (artificial intelligence) and internalizing end-to-end AI support functions, but also next-generation distributed computing technologies for realizing services with a complexity exceeding the limitations of UE operation capabilities by leveraging ultra-high-performance communication and computing resources. Summary of the Invention

[0008] Technical Problem

[0009] In the case of establishing a new PDU session to replace an existing PDU session (i.e., the PDU session to be changed) that needs to be replaced, the existing PDU session for data transmission and the like is replaced with the new PDU session. When determining the policy for the new PDU session, the session-related policy or remaining data permission determined for the existing PDU session (i.e., the PDU session in the network slice where the problem has occurred) can be considered. The present disclosure proposes a method and device for supporting the establishment of a PDU session for a new network slice.

[0010] Technical solution

[0011] The present disclosure proposes a method that allows considering the session-related policy and the remaining data permission determined for the existing PDU session when determining the policy for a new PDU session that replaces the existing PDU session for network slice change.

[0012] The present disclosure proposes a method for supporting the establishment of a protocol data unit (PDU) session for a network slice by a session management function (SMF) in a communication network. The method includes receiving, from an access and mobility management function (AMF), a PDU session request message including a first network slice identifier and an additional network slice identifier, where the additional network slice identifier is an identifier of a network slice replaced by the first network slice identifier, selecting a policy control function (PCF) for the first network slice identifier, sending a policy creation request message including the first network slice identifier and the additional network slice identifier to the selected PCF, and receiving a response message to the policy creation request message from the PCF.

[0013] The present disclosure proposes a method for supporting the establishment of a protocol data unit (PDU) session for a network slice by a policy control function (PCF) in a communication network. The method includes: receiving, from a session management function (SMF), a policy creation request message including a first network slice identifier and an additional network slice identifier, where the additional network slice identifier is an identifier of a network slice replaced by the first network slice identifier, sending an identification message requesting PCF information corresponding to the additional network slice identifier to a binding support function (BSF) or a unified data repository (UDR), receiving a first response message to the identification message, and sending a second response message to the policy creation request message to the SMF based on the first response message.

[0014] The present disclosure provides a session management function (SMF) entity for supporting a protocol data unit (PDU) session for establishing a network slice in a communication network. The entity includes: a transceiver configured to receive a PDU session request message including a first network slice identifier and an additional network slice identifier from an access and mobility management function (AMF), where the additional network slice identifier is an identifier of a network slice replaced by the first network slice identifier, and a processor configured to select a policy control function (PCF) for the first network slice identifier. The processor is configured to control the transceiver to send a policy creation request message including the first network slice identifier and the additional network slice identifier to the selected PCF, and receive a response message to the policy creation request message from the PCF.

[0015] The present disclosure provides a policy control function (PCF) entity for supporting a protocol data unit (PDU) session for establishing a network slice in a communication network. The entity includes a transceiver and a processor. The processor is configured to receive, via the transceiver, a policy creation request message including a first network slice identifier and an additional network slice identifier from a session management function (SMF), where the additional network slice identifier is an identifier of a network slice replaced by the first network slice identifier, send an identification message requesting PCF information corresponding to the additional network slice identifier to a binding support function (BSF) or a unified data repository (UDR), receive a first response message to the identification message, and send a second response message to the policy creation request message to the SMF based on the first response message.

[0016] Beneficial effects

[0017] It is possible to select a policy control function (PCF) selected for an existing PDU session to determine the policy for a new PDU session that replaces the existing PDU session for network slice change, so that the session-related policy determined for the existing PDU session can be used. As a result, the overhead of performing new session-related policy decisions can be reduced, and the problem of inability to guarantee service continuity due to policy changes can be avoided.

[0018] In addition, during the process of establishing a new PDU session to change an existing network slice (old S-NSSAI) to a new network slice, information about the existing network slice and the new network slice (alternate S-NSSAI) replacing the existing network slice is reported to the PCF, such that when the PCF performs data usage update for the new PDU session or policy determination considering the remaining data usage, the PCF is allowed to update the network slice identifier (S-NSSAI) and the remaining data usage stored for the data network name (DNN) of the existing PDU session, and consider the S-NSSAI and the remaining data usage of the DNN for the existing PDU session. Therefore, incorrect remaining data usage management or incorrect policy determination for the new PDU session can be avoided. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Shows entities and reference points included in a 5G system architecture.

[0020] Figure 2 Shows a method for selecting the same PCF based on a binding support function (BSF) or UDR and a method for determining a policy according to the present disclosure.

[0021] Figure 3 Shows a method for selecting the same PCF based on a UDM and a method for determining a policy according to the present disclosure.

[0022] Figure 4 Shows a method for supporting a PDU session for establishing a network slice by an SMF in a communication network according to the present disclosure.

[0023] Figure 5 Shows a method for supporting a PDU session for establishing a network slice by a PCF in a communication network according to the present disclosure.

[0024] Figure 6 Shows a device configuration of a network entity according to the present disclosure.

[0025] Figure 7 Shows a device configuration of a UE according to the present disclosure. DETAILED DESCRIPTION

[0026] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings.

[0027] When describing the present disclosure, descriptions related to technical content that is well known in the art and not directly associated with the present disclosure will be omitted. The omission of such unnecessary descriptions aims to prevent obscuring the main idea of the present disclosure and to more clearly convey the main idea. The terms to be described below are terms defined in consideration of the functions in the present disclosure, and may vary depending on the user, the user's intention, or habits. Therefore, the definitions of the terms should be based on the content throughout the specification.

[0028] In the drawings, some elements may be exaggerated, omitted, or shown schematically. Also, the size of each element does not exactly reflect the actual size. In each of the drawings, the same or equivalent elements are labeled with the same reference numerals.

[0029] In the following description, a base station is an entity that allocates resources to terminals, and can be at least one of a gNode B, eNode B, Node B (or xNode B (where x is a letter including one of g and e)), a radio access unit, a base station controller, a satellite, an airborne device, and a node on the network. A user equipment (UE) may include a mobile station (MS) capable of performing communication functions, a vehicle, a satellite, an airborne device, a cellular phone, a smart phone, a computer, or a multimedia system. In the present disclosure, a "downlink (DL)" refers to a radio link through which a base station sends signals to a terminal, and an "uplink (UL)" refers to a radio link through which a terminal sends signals to a base station. Additionally, there may be a "side link (SL)", which refers to a radio link through which a UE sends signals to another UE.

[0030] As used in the embodiments of the present disclosure, the term "unit" refers to a software element or a hardware element, such as a field programmable gate array (FPGA) or an application specific integrated circuit (ASIC), and a "unit" can perform certain functions. However, the meaning of "unit" is not always limited to software or hardware. A "unit" can be configured to be stored in an addressable storage medium or executed by one or more processors. Thus, a "unit" includes, for example, software elements, object-oriented software elements, class elements or task elements, processes, functions, attributes, procedures, subroutines, program code segments, drivers, firmware, microcode, circuits, data, databases, data structures, tables, arrays, and parameters. The elements and functions provided by a "unit" can be combined into a smaller number of elements or "units", or divided into a larger number of elements or "units". Furthermore, the elements and "units" can be implemented as one or more CPUs within a reproduction device or a secure multimedia card. Additionally, a "unit" in the embodiments can include one or more processors.

[0031] In addition, in the following description, the LTE, LTE-A, or 5G system may be described by way of example, but the embodiments of the present disclosure may also be applied to other communication systems with a similar technical background or channel type. For example, 5G-Advance, NR-Advance, or the 6th generation (6G) mobile communication technology developed beyond 5G mobile communication technology (or New Radio (NR)) may be included therein, and in the following description, "5G" may be a concept covering existing LTE, LTE-A, or other similar services. Additionally, based on the determination of those skilled in the art, the present disclosure may be applied to other communication systems with some modifications without significantly departing from the scope of the present disclosure.

[0032] The 5G mobile communication network includes 5G user equipment (UE), 5G radio access network (RAN), and 5G core network. The 5G core network includes at least one network function (NF), such as the access and mobility management function (AMF) that provides the mobility management function of the UE, the session management function (SMF) that provides the session management function, the user plane function (UPF) that performs the data transmission role, the policy control function (PCF) that provides the policy control function, the unified data management (UDM) that provides the data management function, such as for subscriber data and policy control data, and the unified data repository (UDR) that stores data of various network functions such as UDM.

[0033] In the 5G system, network slicing refers to the technology or structure that realizes several virtualized independent logical networks in one physical network. The network operator configures a virtual end-to-end network called a network slice and provides services to meet the specified requirements of services / applications. The network slice is identified by an identifier called the single network slice selection assistance information (S-NSSAI), and the network operator provides the network slice to the UE to receive services.

[0034] Specifically, in the 5G system, when the UE registers in the network, the UE sends the identifier information of the network slice to be requested (i.e., the requested S-NSSAI) to the AMF, and the AMF provides the UE with information about the network slices available to the UE (the allowed NSSAI) by considering the requested S-NSSAI and the subscriber information. Even if the UE does not provide the AMF with information about the network slice requested by the UE, the AMF may still provide the UE with the allowed NSSAI. In this case, the allowed NSSAI may include information about the default configured slice (the default configured NSSAI) and information about the slice (one or more) configured as the default in the subscribed slices (one or more) included in the UE subscriber information (i.e., the default subscribed S-NSSAI).

[0035] When the allowed NSSAI may not include slices (e.g., when the default-configured NSSAI and the default-subscribed S-NSSAI do not exist or are not available), the AMF may send a network registration rejection message including a cause code to the UE, and the cause code indicates the rejection of registration due to the lack of available slices.

[0036] Meanwhile, when the AMF wants to include a pre-defined slice in the UE's allowed NSSAI, it may perform an admission control (Network Slice Admission Control (NSAC)) process and an authentication (Network Slice Specific Authentication and Authorization (NSSAA)) process for the corresponding network slice.

[0037] In the NSAC process, it can be determined whether to allow a network slice based on the number of UEs currently registered in a specific slice and the maximum number of registered UEs allowed in the corresponding slice (i.e., whether the network slice is included in the allowed NSSAI). Specifically, the Network Slice Admission Control Function (NSACF) monitors the number of registered UEs and the number of established Protocol Data Unit (PDU) sessions of each network slice subject to NSAC, and can perform control to ensure that the number of registered UEs and the number of established PDU sessions of each network slice are respectively less than the maximum number of registered UEs and the maximum number of PDU sessions. At this time, when a new UE is registered in the network slice of NSAC, or when an existing registered UE is deregistered, the AMF may send an update request message notifying it to the NSACF. When a new PDU session is established or an existing PDU session is released in the network slice subject to NSAC, the SMF may send an update request message notifying it to the NSACF. When the NSACF receives a message notifying the registration of a new UE or the establishment of a new PDU session in the network slice, it can determine whether to allow the corresponding network slice based on the maximum number of UEs and the maximum number of PDU sessions, and then include the determination of whether to allow the network slice in each response message.

[0038] Meanwhile, in order to send / receive data to / from a specific data network (DN) through an allowed network slice (allowed NSSAI), the UE may select one of the allowed network slices, request to establish a Packet Data Unit (PDU) session to a specific Data Network Name (DNN) in the corresponding slice, and send / receive data through the established PDU session. The PDU session may include one or more traffic flows, and the traffic flow may include a type of Guaranteed Bit Rate Quality of Service flow (GBR QoS flow) or a non-GBR QoS flow.

[0039] There may be a situation where one or all of the protocol data unit (PDU) sessions included in a predetermined network slice should be moved to another network slice. Such situations include examples where congestion occurs between various 5G network entities belonging to the network slice or where the use of a specific slice should be temporarily or permanently suspended for operational reasons (e.g., device replacement, upgrade, etc.), or examples where the performance of the network slice transmitting the application service deteriorates and thus the service needs to be moved to another network.

[0040] In such a case, the network slice of the PDU session that needs to be changed should be changed to an alternative network slice. In the case where a new PDU session is established to replace the PDU session that needs to be changed (i.e., the existing PDU session), the new PDU session replaces the PDU session for data transmission, etc., through the existing PDU session. When determining the policy for the new PDU session, the session-related policy or remaining data permission determined for the existing PDU session (i.e., the PDU session existing in the network slice where the problem has occurred) can be considered. The present disclosure proposes a method and device for supporting the determination of the policy for the new PDU session.

[0041] Figure 1 The entities and reference points included in the 5G system architecture are shown.

[0042] In 3GPP, the conceptual link connecting the NFs in the 5G system is defined as a reference point. Hereinafter, examples of the reference points included in the 5G system architecture described below are provided. Figure 1 Examples of the reference points included in the 5G system architecture described below are provided.

[0043] - N1: The reference point between the UE 110 and the AMF 150

[0044] - N2: The reference point between the (R) AN 120 and the AMF 150

[0045] - N3: The reference point between the (R) AN 120 and the UPF 170

[0046] - N4: The reference point between the SMF 160 and the UPF 170

[0047] - N5: The reference point between the PCF 190 and the application function (AF) 130

[0048] - N6: The reference point between the UPF 180 and the DN 140

[0049] - N7: The reference point between the SMF 160 and the PCF 180

[0050] - N8: The reference point between the UDM 153 and the AMF 150

[0051] -N9: Reference point between two core UPFs 170

[0052] -N10: Reference point between UDM 153 and SMF 160

[0053] -N11: Reference point between AMF 150 and SMF 160

[0054] -N12: Reference point between AMF 150 and the Authentication Server Function (AUSF) 151

[0055] -N13: Reference point between UDM 153 and AUSF 151

[0056] -N14: Reference point between two AMFs 150

[0057] -N15: Reference point between PCF 180 and AMF 150 for non-roaming scenarios, and reference point between PCF 180 and AMF 150 in the visited network for roaming scenarios

[0058] Figure 2 A method of selecting the same PCF and determining a policy based on a Binding Support Function (BSF) or UDR is shown.

[0059] In operation 200, the UE 110 may perform a registration process. Here, the AMF 150 may receive the subscription information of the UE110 from the UDM 153, and the subscription information may include "UE context in SMF data". The UE context in SMF data may include at least one of S-NSSAI, DNN, and an identifier of the Session Management (SM) PCF (i.e., PCF ID) of the identifier of the PDU session that has been established (i.e., PDU session ID). Even after the registration process, when the UE context in SMF data changes (e.g., when the PCF ID is generated or changed), the UDM 153 may also notify the AMF 150 of the UE context in SMF data. The UE 110 may perform a PDU session establishment process after the registration process.

[0060] During the PDU session establishment process, the AMF 150 may select an SMF (i.e., SMF1 161) based on the S-NSSAI (e.g., old S-NSSAI) and DNN received from the UE 110, and send a Session Management Context Create message to the SMF1 161.

[0061] The SMF 161 can select a PCF for the corresponding PDU session. During the PDU session establishment process, when receiving a PCF ID from the AMF 150, the SMF 161 can select the PCF corresponding to the received PCF ID and send an SM policy creation request message to the selected PCF.

[0062] When the PCF serves a new PDU session (i.e., when the PCF is selected), the PCF can transmit the PDU session information served by the PCF itself (i.e., the subscription permanent identifier (SUPI), PDU session ID, DNN, S-NSSAI, and the identifier information of the PCF itself (i.e., the PCF ID)) to the binding support function (BSF) 260 and store the PDU session information therein. Here, the PCF can include the PCF ID and one or more pieces of information among the SUPI, PDU session ID, DNN, and S-NSSAI in the message sent to the BSF 260.

[0063] Alternatively, if the BSF does not exist in the network, when the PCF serves a new PDU session (i.e., when the PCF is selected), the PCF can transmit the PDU session information to be served by the PCF itself (i.e., the SUPI, PDU session ID, DNN, S-NSSAI, and the identifier information of the PCF itself (i.e., the PCF ID)) to the UDR 250 and store the PDU session information therein. Here, the PCF can include the PCF ID and one or more pieces of information among the SUPI, PDU session ID, DNN, and S-NSSAI in the message sent to the UDR 250.

[0064] In operation 201, the AMF 150 can determine, based on local configuration or information received from other NFs, to change the PDU session to be established for an existing network slice (e.g., the old S-NSSAI) to a new network slice (i.e., the alternative S-NSSAI), and can include, in the message sent to the UE 110, information indicating that the alternative S-NSSAI is the network slice identifier replacing the old S-NSSAI, and the allowed network slice information including the alternative S-NSSAI (i.e., the allowed NSSAI).

[0065] In addition, for each PDU session established for the old S-NSSAI, the AMF 150 can send a message to the SMF 161 indicating that the network slice of the corresponding PDU session should be changed via the alternative S-NSSAI. When determining not to maintain the PDU session, the SMF 161 can send, based on the information received from the AMF 150, information to the UE 110 indicating to send a new PDU session establishment request including the alternative S-NSSAI and the DNN (i.e., the DNN of the existing PDU session).

[0066] Alternatively, when determining to maintain the PDU session, the SMF 161 may send information indicating to change the S-NSSAI of the existing PDU session to an alternative S-NSSAI to the UE 110, and send an SM policy association modification message to the PCF 180. The SM policy association modification message may include the S-NSSAI and the alternative S-NSSAI. In this case, operation 209 may be performed after the SMF 161 has sent the SM policy association modification message to the PCF 180 in operation 201.

[0067] Based on the information received from the SMF 161 in operation 201, the UE 110 may send a NAS message for a PDU session establishment request to the AMF 150 through the RAN 120 in operation 202.

[0068] The NAS message may include at least one of the following information:

[0069] - S-NSSAI: The alternative S-NSSAI information received from the SMF 161 in operation 201

[0070] - Additional S-NSSAI: Network slice identifier information (i.e., the old S-NSSAI) replaced by the S-NSSAI (i.e., the alternative S-NSSAI)

[0071] - Old PDU session ID: The PDU session ID included in the information received from the SMF 161 in operation 201, and this is the information capable of identifying the PDU session established in the old S-NSSAI.

[0072] - DNN: Name information of the data network (DN)

[0073] - PDU session ID: The PDU session identifier established by the UE 110

[0074] - Request type: The type of the PDU session establishment request

[0075] - N1 SM container: Information sent to the SMF, and the PDU session establishment request message may be included therein.

[0076] The NAS message may include the PDU session ID, the requested PDU session type, the requested session and service continuity (SSC) mode, 5GSM capabilities, etc.

[0077] Based on the S-NSSAI (i.e., the alternative S-NSSAI) and the DNN included in the information received in operation 202, the AMF 150 may select the SMF 162 in operation 203.

[0078] The AMF 150 may know the previous S-NSSAI information (i.e., the old S-NSSAI) that has been replaced by the S-NSSAI (i.e., the alternative S-NSSAI) included in the information received in operation 202.

[0079] Specifically, in the case where the AMF 150 has sent information in operation 201 to the UE 110 indicating that the alternative S-NSSAI is a network slice identifier that replaces the old S-NSSAI and has received from the UE 110 in operation 202 the same S-NSSAI as the alternative S-NSSAI that replaces the old S-NSSAI and has been sent to the UE 110 in operation 201, the AMF 150 may know that the old S-NSSAI corresponds to a network slice that has been replaced by another network slice.

[0080] Alternatively, when the message sent by the UE 110 in operation 202 includes an additional S-NSSAI or an old PDU session ID, the AMF 150 may identify the old S-NSSAI based on the message. When the message sent by the UE 110 in operation 202 includes an old PDU session ID, the AMF may determine the S-NSSAI for the old PDU session ID as the old S-NSSAI.

[0081] The AMF 150 may include at least one of the following information in the message 203 sent to the SMF 162:

[0082] - SUPI: UE identifier information

[0083] - DNN: The DNN included in the message received in operation 202. When the AMF 150 receives a new DNN from the access and mobility management (AM) PCF, the corresponding DNN may be included.

[0084] - S-NSSAI: The S-NSSAI included in the message received in operation 202.

[0085] - Additional S-NSSAI: When the AMF 150 determines that the S-NSSAI included in the information received in operation 202 is a network slice identifier that replaces the old S-NSSAI, the AMF 150 may include in the message sent to the SMF 162 the additional S-NSSAI (i.e., the network slice identifier information replaced by the S-NSSAI) and the S-NSSAI received in operation 202 (i.e., the alternative S-NSSAI).

[0086] - PDU session ID: The PDU session ID included in the message received in operation 202

[0087] - Old PDU Session ID: The old PDU session ID included in the message received in operation 202

[0088] - AMF ID: AMF identifier

[0089] - Request type, N1 SM container (PDU session establishment request): The request type and N1 SM container included in the message already received in operation 202

[0090] - PCF ID, same PCF selection indication: When the AMF 150 determines, based on the information already received in operation 202 (e.g., additional S-NSSAI), that the S-NSSAI included in the message received in operation 202 is a network slice identifier that replaces the old S-NSSAI, the AMF 150 can identify whether the UE context in the SMF data already received from the UDM 153 in operation 200 contains the old PDU session ID, the additional S-NSSAI, and the PCF ID corresponding to the DNN, which are included in the message received in operation 202. In the case where the UE context in the SMF data already received from the UDM 153 in operation 200 contains the old PDU session ID, the additional S-NSSAI, and the PCF ID corresponding to the DNN received in operation 202, the AMF 150 can include one or more of the corresponding PCF ID and the same PCF selection indication in the message 203 sent to the SMF162. The same PCF selection indication can be included as information indicating the selection of the PCF corresponding to the PCF ID.

[0091] When the message received in operation 203 includes an additional S-NSSAI and an S-NSSAI, or includes an old PDU session ID, in operation 204a, the SMF 162 can identify, based on this, the identifier information of the network slice replaced by the S-NSSAI included in the message received in operation 203 (i.e., the old S-NSSAI).

[0092] The SMF 162 can perform PCF selection. When the PCF ID is received in operation 203, the SMF 162 selects the PCF corresponding to the PCF ID. Otherwise, the SMF 162 can select a PCF by considering the SUPI, DNN, or S-NSSAI.

[0093] In operation 204b, the SMF 162 can send a message requesting SM policy creation to the selected PCF 180. This message can contain one or more of the following information:

[0094] - SUP: UE identifier information

[0095] -DNN: The DNN received in operation 203

[0096] -PDU Session ID: The PDU session ID received in operation 203

[0097] -Old PDU Session ID: The old PDU session ID received in operation 203

[0098] -S-NSSAI: The S-NSSAI received in operation 203

[0099] -Additional S-NSSAI: This indicates the identifier information of the network slice replaced by the S-NSSAI, and can be the additional S-NSSAI received in operation 203.

[0100] When the BSF is available, in operation 205a, the PCF 180 can send a message (e.g., a discovery request message) to the BSF 260, which is used to identify whether there is a pre-selected PCF for the SUPI, DNN, and additional S-NSSAI included in the message already received in operation 204b, or a pre-selected PCF for the SUPI, DNN, additional S-NSSAI, and old PDU session ID. The message sent by the PCF 180 to the BSF 260 can include one or more of the SUPI, DNN, additional S-NSSAI, and old PDU session ID, and each piece of information included in the message can be the same as the information already received in operation 204b.

[0101] When the address of the PCF corresponding to the information received in operation 205a is stored in the BSF 260, in operation 205b, the BSF 260 can include the PCF instance ID or PCF set ID and the address of the corresponding PCF (PCF address) in the response message sent to the PCF 180.

[0102] When the address of the PCF corresponding to the information already received in operation 205a is not stored in the BSF 260, the BSF may not include the PCF address in the response message 205b sent to the PCF 180.

[0103] When the message received by the PCF 180 from the BSF 260 in operation 205b includes the PCF address information, operations 207 to 209 can be omitted, and operation 210 can be executed.

[0104] When the message received by the PCF 180 from the BSF 260 in operation 205b does not include the PCF address information, operation 207 can be executed.

[0105] When the BSF is not available, in operation 206a, the PCF 180 may send a message to the UDR 250 for identifying whether there is a pre-selected PCF for the SUPI, DNN, and additional S-NSSAI (which are included in the message already received in operation 204b) or for the SUPI, DNN, additional S-NSSAI, and old PDU session ID. The message sent by the PCF 180 to the UDR 250 may include one or more of the SUPI, DNN, additional S-NSSAI, and old PDU session ID, and each piece of information included in the message may be the same as the information already received in operation 204b.

[0106] When the PCF information corresponding to the information already received in operation 206a is not stored in the UDR 250, the UDR 250 may not include the PCF address in the response message sent to the PCF 180 in operation 206b.

[0107] When the PCF address is included in the message received by the PCF 180 from the UDR 250 in operation 206b, operations 207 to 209 may be omitted, and operation 210 may be executed.

[0108] When the PCF address is not included in the message received by the PCF 180 from the UDR 250 in operation 206b, operation 207 may be executed.

[0109] In operation 207, the PCF 180 may request from the UDR 250 the additional S-NSSAI and DNN already received in operation 204b and / or the policy information for the S-NSSAI and DNN. That is, the PCF 180 may request the policy information of the existing network slice or the new network slice, or may request both.

[0110] The message 207 sent by the PCF 180 to the UDR 250 may include the SUPI, DNN, S-NSSAI, and / or the SUPI, DNN, and additional S-NSSAI.

[0111] In operation 208, the UDR 250 may include in the response message sent to the PCF 180 at least one of the data usage monitoring related information and the remaining allowable data usage related information of the SUPI, DNN, and S-NSSAI (or the SUPI, DNN, and additional S-NSSAI) included in the information already received in operation 207.

[0112] In operation 209, the PCF 180 may determine the policies of the PDU session (e.g., policy and charging control (PCC) rules, etc.). Here, the PCF 180 may utilize the policy information determined for the additional S-NSSAI and DNN or for the additional S-NSSAI, DNN, and old PDU session ID based on the information received in operation 204b.

[0113] When the PCF 180 receives an SM policy association creation message from the SMF 161, if the S-NSSAI (e.g., alternative S-NSSAI) and the additional S-NSSAI (e.g., old S-NSSAI) are included in the SM policy association creation message, the PCF 180 may associate the SM policy with the S-NSSAI (e.g., alternative S-NSSAI) included in the received message, and additionally associate the SM policy with the additional S-NSSAI (e.g., old S-NSSAI) included in the received message. For example, when receiving an SM policy association creation message, the PCF 180 may generate an SM policy association ID, then store the default S-NSSAI of the ID as the S-NSSAI received from the SMF 161 (e.g., alternative S-NSSAI), and store the additional S-NSSAI of the ID as the additional S-NSSAI (e.g., old S-NSSAI).

[0114] Alternatively, when the SM policy association modification message received from the SMF in operation 201 includes the SM policy association ID, S-NSSAI (e.g., alternative S-NSSAI), and additional S-NSSAI (e.g., old S-NSSAI), the PCF 180 may associate the SM policy stored for the SM policy association ID included in the received message with the S-NSSAI (e.g., alternative S-NSSAI) included in the received message, and additionally associate the stored SM policy with the additional S-NSSAI (e.g., old S-NSSAI) included in the received message. For example, when receiving an SM policy association update message, the PCF 180 may store the default S-NSSAI of the SM policy association ID included in the received message as the S-NSSAI received from the SMF (e.g., alternative S-NSSAI), and store the additional S-NSSAI of the corresponding ID as the additional S-NSSAI (e.g., old S-NSSAI).

[0115] The PCF 180 also stores the additional S-NSSAI (e.g., old S-NSSAI) for the SM policy (or PDU session) through the above process, and thus when receiving a request message including the old S-NSSAI, the PCF 180 may process the corresponding SM policy (or PDU session).

[0116] Although not shown, when the PCF 180 receives an SM policy creation message including an S-NSSAI (e.g., an alternative S-NSSAI) and an additional S-NSSAI (e.g., an old S-NSSAI), the PCF 180 may send a registration message for the PDU session (e.g., an Nbsf_Management_Register message) to the BSF 260.

[0117] The registration message for the PDU session may include at least one of the following pieces of information:

[0118] - SUP: The internal identifier information of the UE

[0119] - UE Address: The address information of the UE

[0120] - General Public Subscription Identifier (GPSI): The external identifier information of the UE (e.g., a phone number)

[0121] - PCF Address: The address of the PCF

[0122] - S-NSSAI: It may include the S-NSSAI included in the message received from the SMF (e.g., an alternative S-NSSAI).

[0123] - Additional S-NSSAI: It may include the additional S-NSSAI included in the message received from the SMF (e.g., an old S-NSSAI).

[0124] - Data Network Name (DNN): It may include the identifier information of the data network (e.g., it may be in the form of a domain name).

[0125] Alternatively, although not shown, when the PCF 180 receives an SM policy association modification message including an S-NSSAI (e.g., an alternative S-NSSAI) and an additional S-NSSAI (e.g., an old S-NSSAI), the PCF 180 may send an update message for the PDU session (e.g., an Nbsf_Management_Update message) to the BSF 260.

[0126] The update message for the PDU session may include one or more of the following pieces of information:

[0127] - SUP: The internal identifier information of the UE

[0128] - UE Address: The address information of the UE

[0129] - GPSI: The external identifier information of the UE (e.g., a phone number)

[0130] - PCF Address: The address of the PCF

[0131] -S-NSSAI: It may include the S-NSSAI (e.g., alternative S-NSSAI) included in the message received from the SMF.

[0132] -Additional S-NSSAI: It may include the additional S-NSSAI (e.g., old S-NSSAI) included in the message received from the SMF.

[0133] -Data Network Name (DNN): It may include the identifier information of the data network (e.g., it may be in the form of a domain name).

[0134] Although not shown, when the BSF 260 receives an Nbsf_Management_Register or Nbsf_Management_Update message from the PCF 180, the BSF 260 may store the PCF address included in the corresponding message as the PCF address of the SUPI, UE address, GSPI, and S-NSSAI (e.g., alternative S-NSSAI) included in the message received from the PCF 180 and the additional S-NSSAI (e.g., old S-NSSAI). By additionally storing the additional S-NSSAI (e.g., old S-NSSAI) in the PCF address information of the serving PDU session through the above process, the BSF 260 may include the stored PCF address information in the response message and send it when receiving a PCF discovery request message including the old S-NSSAI (i.e., when receiving a PCF address request message including the previous S-NSSAI of the PDU session).

[0135] The PCF 180 may also determine the monitoring-related policy for the PDU session. Here, the PCF 180 may use the information received in operation 208 to determine the monitoring-related policy.

[0136] In the case where the PCF information (i.e., PCF address, PCF instance ID, or PCF set ID) is included in the information already received from the BSF 260 in operation 205b or the information already received from the UDR 250 in operation 206b, the PCF 180 may include information indicating redirection and the corresponding PCF information in the message sent to the SMF 162 in operation 210.

[0137] When the information received in operation 210 includes the PCF information to be redirected, the SMF 162 may select the corresponding PCF and execute the process again from operation 204b.

[0138] When the PCF 180 has determined the policy for the PDU session in operation 209, the PCF 180 may include the determined policy, i.e., PCC rules, monitoring-related policy information, policy control request (PCR) trigger information, etc., in the message 210 sent to the SMF 162.

[0139] In operation 211, the remaining PDU session establishment process may be performed. Examples of the remaining processes may include user plane (UP) resource configuration, resource configuration result notification, or data communication through the configured UP resources.

[0140] Figure 3 A method for selecting the same PCF based on the UDM and a method for determining the policy are shown.

[0141] In operation 300, the UE 110 may perform a registration process. Here, the AMF 150 may receive subscription information for the UE 110 from the UDM 153, and the subscription information may include PCF selection assistance information (Selection Assistance Info) and "UE context in SMF data". The PCF selection assistance information includes a combination of DNN and S-NSSAI, and for each included combination, it may include information indicating that the PCF for the AM policy of the UE (i.e., AM PCF) should be selected to be the same as the PCF for the SM policy of the PDU session. The UE context in SMF data may include the SUPI (i.e., UE identifier), S-NSSAI, DNN, and the identifier of the SM PCF (i.e., PCF ID) relative to the identifier of the already established PDU session (i.e., PDU session ID). Even after the registration process, when the UE context in SMF data changes (e.g., when the PCF ID is generated or changed), the UDM 153 may notify the AMF 150 of the UE context in the SMF data.

[0142] The UE 110 may perform a PDU session establishment process after the registration process.

[0143] During the PDU session establishment process, the AMF 150 may select an SMF (i.e., SMF1 161) based on the S-NSSAI (e.g., old S-NSSAI) and DNN received from the UE, and send a SM context creation message to the SMF1 161.

[0144] The SMF1 161 may select a PCF for the corresponding PDU session. During the PDU session establishment process, when receiving a PCF ID from the AMF 150, the SMF1 161 may select the PCF corresponding to the corresponding PCF ID and send a SM policy creation request message to the selected PCF.

[0145] The SMF 161 can store the PCF ID, PDU session ID, DNN, and S-NSSAI determined for the SUPI in the UE context in the SMF data of the UDM 153. For example, when the SMF 161 supports the network slice change function, the SMF 161 can store the PCF ID determined for the SUPI, PDU session ID, DNN, and S-NSSAI in the UE context in the SMF data of the UDM 153.

[0146] At this time, the SMF 161 can include one or more pieces of information such as the SUPI, PDU session ID, DNN, and S-NSSAI, PCF ID (or PCF address), PCF instance ID, or PCF set ID in the message sent to the UDM 153. The UDM 153 can store the PCF ID (or PCF address), PDU session ID, DNN, and S-NSSAI of the SUPI in the UE context in the SMF data based on the information included in the message received from the SMF 161. The UDM 153 can store the UE context in the SMF data in the UDR 250. For example, when the UE context in the SMF data of the UDM 153 changes, the UDM 153 can reflect the change in the UE context in the SMF data stored in the UDR 250.

[0147] In operation 301, the AMF 150 can determine, based on local configuration or information received from other NFs, to change the PDU session established for an existing network slice (e.g., old S-NSSAI) to a new network slice (i.e., alternative S-NSSAI), and can include in the message sent to the UE 110 information indicating that the alternative S-NSSAI is a network slice identifier that replaces the old S-NSSAI, and the allowed network slice information (i.e., allowed NSSAI) containing the alternative S-NSSAI.

[0148] In addition, for each PDU session established for the old S-NSSAI, the AMF 150 can send a message to the SMF indicating that the network slice of the corresponding PDU session should be changed to the alternative S-NSSAI. The SMF 161 can send, based on the information received from the AMF 150, information to the UE 110 indicating to send a new PDU session establishment request containing the alternative S-NSSAI and DNN (i.e., the DNN of the existing PDU session).

[0149] Based on the information already received from the SMF 161 in operation 301, the UE 110 can send, in operation 302, a NAS message for the PDU session establishment request to the AMF 150 via the RAN 120.

[0150] The NAS message may include at least one of the following information:

[0151] - S-NSSAI: The alternative S-NSSAI information received from the SMF 161 in operation 301

[0152] - Additional S-NSSAI: The network slice identifier information (i.e., the old S-NSSAI) replaced by the S-NSSAI (i.e., the alternative S-NSSAI)

[0153] - Old PDU session ID: The PDU session ID included in the information received from the SMF 161 in operation 301, and this is the information capable of identifying the PDU session established in the old S-NSSAI.

[0154] - DNN: The name information of the data network (DN)

[0155] - PDU session ID: The PDU session identifier generated by the UE 110

[0156] - Request type: The type of the PDU session establishment request

[0157] - N1 SM container: The information sent to the SMF, and the PDU session establishment request message may be included therein.

[0158] The NAS message may include the PDU session ID, the requested PDU session type, the requested SSC mode, 5GSM capabilities, etc.

[0159] Based on the S-NSSAI (i.e., the alternative S-NSSAI) and the DNN included in the information already received in operation 302, the AMF150 may select the SMF 162 in operation 303.

[0160] The AMF 150 may know the previous S-NSSAI information (i.e., the old S-NSSAI) replaced by the S-NSSAI (i.e., the alternative S-NSSAI) already included in the information received in operation 302.

[0161] Specifically, in the case where the AMF 150 has sent the information indicating that the alternative S-NSSAI is the network slice identifier replacing the old S-NSSAI to the UE 110 in operation 301 and has received from the UE 110 in operation 302 the same S-NSSAI as the alternative S-NSSAI that replaces the old S-NSSAI and has been sent to the UE 110 in operation 301, the AMF 150 may know that the old S-NSSAI corresponds to the network slice that has been replaced by another network slice.

[0162] Alternatively, when the message sent by the UE 110 in operation 302 includes an additional S-NSSAI or an old PDU session ID, the AMF 150 may identify the old S-NSSAI based on this message. When the message sent by the UE 110 in operation 302 includes an old PDU session ID, the AMF may determine the S-NSSAI for the old PDU session ID as the old S-NSSAI.

[0163] The AMF 150 may include at least one of the following information in the message sent to the SMF 162:

[0164] - SUP: UE identifier information

[0165] - DNN: The DNN included in the message already received in operation 302. When the AMF 150 receives a new DNN from the AM PCF, the corresponding DNN may be included.

[0166] - S-NSSAI: The S-NSSAI included in the message already received in operation 302.

[0167] - Additional S-NSSAI: When the AMF 150 determines that the S-NSSAI included in the information already received in operation 302 is a network slice identifier that replaces the old S-NSSAI, the AMF 150 may include the additional S-NSSAI (i.e., the network slice identifier information replaced by the S-NSSAI) and the S-NSSAI received in operation 302 (i.e., the alternative S-NSSAI) in the message sent to the SMF 162.

[0168] - PDU session ID: The PDU session ID included in the message received in operation 302

[0169] - Old PDU session ID: The old PDU session ID included in the message received in operation 302

[0170] - AMF ID: AMF identifier

[0171] - Request type, N1 SM container (PDU session establishment request): The request type and N1 SM container included in the message already received in operation 302

[0172] - PCF ID, Same PCF Selection Indication: In the case where the PCF selection assistance information received from the UDM 153 in operation 300 includes the S-NSSAI and DNN corresponding to the additional S-NSSAI and DNN received in operation 302, the AMF 150 may include one or more of the PCF ID and the same PCF selection indication in the message that can be sent to the SMF in operation 303. The PCF ID included in the message may be the identifier (PCF ID) corresponding to the PCF selected as the AM PCF in operation 300, or the PCF ID included in the UE context in the SMF data received from the UDM 153 in operation 300.

[0173] When the message received in operation 303 includes the additional S-NSSAI and S-NSSAI or includes the old PDU session ID, the SMF 162 may identify the identifier information (i.e., the old S-NSSAI) of the network slice replaced by the S-NSSAI included in the message received in operation 304a based on this.

[0174] The SMF 162 may perform PCF selection. When the PCF ID is received in operation 303, the SMF 162 selects the PCF corresponding to the PCF ID. Otherwise, the SMF 162 may select the PCF by considering the SUPI, DNN, or S-NSSAI.

[0175] Operation 304b. The SMF may send a message requesting SM policy creation to the selected PCF 180. The message may contain one or more of the following information:

[0176] - SUPI: UE identifier information

[0177] - DNN: The DNN received in operation 303

[0178] - PDU session ID: The PDU session ID received in operation 303

[0179] - Old PDU session ID: The old PDU session ID received in operation 303

[0180] - S-NSSAI: The S-NSSAI received in operation 303

[0181] - Additional S-NSSAI: This indicates the identifier information of the network slice replaced by the S-NSSAI and may be the additional S-NSSAI received in operation 303.

[0182] In operation 305, the PCF 180 may send a message to the UDR 250 for identifying whether there is a pre-selected PCF for the SUPI, DNN, and additional S-NSSAI, a pre-selected PCF for the SUPI, DNN, and additional S-NSSAI, or a pre-selected PCF for the SUPI, DNN, additional S-NSSAI, and old PDU session ID (e.g., identifying whether there is a corresponding UE context in the SMF data). The message 305 sent by the PCF 180 to the UDR 250 may include one or more of the following pieces of information.

[0183] - Data set: indicating the data set information subscribed by the UE

[0184] - Data subset: the data subset representing the UE context in the SMF data

[0185] - Data key: the SUPI received in operation 304b

[0186] - Data sub-key: the DNN, additional S-NSSAI, and old PDU session ID received in operation 304b

[0187] When the PCF information corresponding to the information received in operation 305 (i.e., the PCF ID (or PCF address), PCF instance ID, or PCF set ID) is not stored in the UDR 250, the UDR 250 may not include the PCF information in the response message sent to the PCF 180 in operation 306.

[0188] When the PCF information is included in the message that has been received by the PCF from the UDR 250 in operation 306, operations 307 to 309 may be omitted, and operation 310 may be performed.

[0189] When the PCF information is not included in the message that the PCF receives from the UDR 250 in operation 306, operation 307 may be performed.

[0190] In operation 307, the PCF 180 may request from the UDR 250 at least one of the additional S-NSSAI and DNN received in operation 304b and / or the policy information for the S-NSSAI and DNN. That is, the PCF 180 may request the policy information of the existing network slice or the policy information of the new network slice, or may request both.

[0191] The message 307 sent to the UDR 250 may include the SUPI, DNN, S-NSSAI, and / or the SUPI, DNN, and additional S-NSSAI.

[0192] In operation 308, the UDR 250 may include, in a response message sent to the PCF 180, at least one of data usage monitoring related information and remaining allowable data usage related information of the SUPI, DNN, and S-NSSAI (or SUPI, DNN, and additional S-NSSAI) included in the information received in operation 307.

[0193] In operation 309, the PCF 180 may determine a policy for the PDU session (e.g., PCC rules, etc.). Here, the PCF 180 may use the policy information determined for the additional S-NSSAI and DNN or for the additional S-NSSAI, DNN, and old PDU session ID based on the information received in operation 304b.

[0194] The PCF 180 may also determine a monitoring related policy for the PDU session. Here, the PCF 180 may use the information already received in operation 308 to determine the monitoring related policy.

[0195] In the case where the PCF information (i.e., PCF address, PCF instance ID, or PCF set ID) is included in the information received from the UDR 250 in operation 306, the PCF 180 may include, in a message sent to the SMF 162 in operation 310, information indicating redirection and the corresponding PCF information.

[0196] When the information already received in operation 310 includes the PCF information to be redirected, the SMF 162 may select the corresponding PCF and execute the process again from operation 304b.

[0197] When the PCF 180 has determined a policy for the PDU session in operation 309, the PCF 180 may include the determined policy, i.e., PCC rules, monitoring related policy information, PCR trigger information, etc., in a message 310 sent to the SMF 162.

[0198] In operation 311, the remaining PDU session establishment process may be performed. Examples of the remaining processes may include user plane (UP) resource configuration, resource configuration result notification, or data communication through the configured UP resources.

[0199] Figure 4 A method for supporting a PDU session for establishing a network slice by an SMF in a communication network according to the present disclosure is shown.

[0200] The SMF may receive a PDU session request message including a first network slice identifier and an additional network slice identifier from the AMF (operations 400, 203, and 303). The additional network slice identifier (S-NSSAI) may be an identifier of a network slice replaced by the first network slice identifier (S-NSSAI). In addition to the network slice identifier, the PDU session request message may further include at least one of SUPI, DNN, PDU session ID, old PDU session ID, AMF ID, request type, N1 SM container, PCF ID, and same PCF selection indication. Optionally, the SMF may send the PCF ID for the first network slice identifier to the BSF or UDR and store the PCF ID in the BSF or UDR (operation 200). Optionally, the SMF may send the PCF ID for the first network slice identifier to the UDM and store the PCF ID in the UE context in the SMF data of the UDM (operation 300).

[0201] The SMF may select a policy control function (PCF) for the first network slice identifier (operations 402, 204a, and 304a). When the PDU session request message includes a PCF ID, the SMF may select the PCF corresponding to the PCF ID, and when the PDU session request message does not include a PCF ID, the SMF may select a PCF based on the first network slice identifier. In addition to the first network slice identifier, the SMF may also select a PCF based on SUP and DNN.

[0202] The SMF may send a policy creation request message including the first network slice identifier and the additional network slice identifier to the selected PCF (operations 404, 204b, and 304b).

[0203] The SMF may receive a response message regarding the policy creation request message from the PCF (operations 406, 210, and 310).

[0204] The SMF may support the PDU session creation process for the first network slice identifier by using the response message to respond to the PDU session request message. In particular, since the policy information included in the response message is the policy information related to the existing PDU session obtained based on the additional network slice identifier, the overhead of newly executing session-related policies can be reduced, and the problem of inability to guarantee service continuity due to policy changes can be avoided.

[0205] Figure 5 A method for supporting a PDU session for establishing a network slice by a PCF in a communication network according to the present disclosure is shown.

[0206] The PCF can receive a policy creation request message including a first network slice identifier and an additional network slice identifier from the SMF (operations 500, 204b, and 304b). The additional network slice identifier (S-NSSAI) can be an identifier of a network slice replaced by the first network slice identifier (S-NSSAI). The policy creation request message can further include at least one of SUPI, DNN, PDU session ID, and old PDU session ID in addition to the network slice identifier.

[0207] The PCF can send an identification message requesting PCF information corresponding to the additional network slice identifier to the BSF or UDR (operations 502, 205a, 206a, and 305). The identification message sent by the PCF to the UDR can be a message requesting UE context in the SMF data corresponding to the additional network slice identifier (operation 305).

[0208] The PCF can receive a first response message regarding the identification message (operations 504, 205b, 206b, and 306).

[0209] When the received first response message does not include PCF information, the PCF can send a message requesting at least one of policy information for the first network slice identifier or policy information for the additional network slice identifier to the UDR (operations 207 and 307). The PCF can receive a response message including at least one of policy information for the first network slice identifier or policy information for the additional network slice identifier (operations 208 and 308).

[0210] The PCF can send a second response message regarding the policy creation request message to the SMF based on the first response message (operations 506, 210, and 310). When the received first response message includes PCF information, the second response message can include information indicating redirection to the PCF corresponding to the PCF information.

[0211] The PCF can support the PDU session creation process for the first network slice identifier by sending a second response message to the SMF in response to the policy creation request message. In particular, since the policy information included in the second response message is policy information related to an existing PDU session obtained based on the additional network slice identifier, the overhead of newly executing session-related policies can be reduced, and the problem of inability to guarantee service continuity due to policy changes can be avoided.

[0212] Figure 6 The device configuration of a network entity according to the present disclosure is shown.

[0213] Figure 6The network entity device shown in [the relevant figure] can be a device of an entity in the core network shown in the present disclosure (such as an SMF, PCF, UDR, UDM, BSF, AMF, etc.).

[0214] The network entity 600 may include a transceiver 605 that sends signals to and receives signals from other network entities or UEs, and a controller 610 that controls all operations of the network entity 600. In the present disclosure, all methods performed by entities such as the PCF, SMF, UDR, and UDM can be understood to be performed under the control of the controller 610.

[0215] The controller 610 and the transceiver 605 do not necessarily need to be implemented as separate devices, and of course can be implemented as a single component in the form of a single chip.

[0216] The controller 610 can be implemented as a single processor within the network entity 600.

[0217] Figure 7 The device configuration of a UE according to the present disclosure is shown.

[0218] Figure 7 The UE 700 illustrated in [the relevant figure] can be a UE device illustrated in the present disclosure.

[0219] The UE 700 may include a transceiver 705 that sends signals to and receives signals from other UEs or network entities, and a controller 710 that controls all operations of the UE 700. All operations or methods in the UE described above in the present disclosure can be understood to be performed under the control of the controller 710.

[0220] The controller 710 and the transceiver 705 do not necessarily need to be implemented as separate devices, and of course can be implemented as a single component in the form of a single chip.

[0221] The controller 710 can be implemented as a single processor within the UE 700.

[0222] It should be noted that Figures 1 to 7 The system configuration diagrams, method diagrams, and signal flowcharts shown in [the relevant figure] are not intended to limit the scope of protection of the present disclosure. That is, Figures 1 to 7 All constituent units or operation steps shown in [the relevant figure] should not be construed as essential elements for implementing the present disclosure, and even when only some elements are included, the present disclosure can be implemented without compromising its true nature.

[0223] The methods disclosed in the claims and / or the methods according to the embodiments described in the specification of the present disclosure can be implemented by hardware, software, or a combination of hardware and software.

[0224] When the method is implemented by software, a computer-readable storage medium for storing one or more programs (software modules) can be provided. One or more programs stored in the computer-readable storage medium can be configured to be executed by one or more processors within the electronic device. At least one program includes instructions that cause the electronic device to execute a method according to various embodiments of the present disclosure as defined by the appended claims and / or disclosed herein.

[0225] These programs (software modules or software) can be stored in non-volatile memories, including random access memory and flash memory, read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), magnetic disk storage devices, compact disc-ROM (CD-ROM), digital versatile disc (DVD), or other types of optical storage devices, or magnetic tape cartridges. Alternatively, any combination of some or all of them can form a memory in which the programs are stored. In addition, multiple such memories can be included in the electronic device.

[0226] In addition, the programs can be stored in an attachable storage device that can access the electronic device through a communication network such as the Internet, intranet, local area network (LAN), wide area LAN (WLAN), and storage area network (SAN), or a combination thereof. Such a storage device can access the electronic device via an external port. In addition, a separate storage device on the communication network can access the portable electronic device.

[0227] In the above detailed embodiments of the present disclosure, according to the presented detailed embodiments, the elements included in the present disclosure are represented in singular or plural. However, for ease of description, the singular form or plural form is appropriately selected for the presented situation, and the present disclosure is not limited by the elements expressed in singular or plural. Therefore, elements expressed in plural can also include a single element, or elements expressed in singular can also include multiple elements.

[0228] Although specific embodiments have been described in the detailed description of the present disclosure, it is obvious that various modifications and changes can be made without departing from the scope of the present disclosure. Therefore, the scope of the present disclosure should not be limited to the embodiments described herein, but should be defined by the appended claims and their equivalents.

Claims

1. A method for supporting a protocol data unit (PDU) session for establishing a network slice by a session management function (SMF) in a communication network, the method comprising: Receiving a PDU session request message from an access and mobility management function (AMF), the PDU session request message including a first network slice identifier and an additional network slice identifier, wherein the additional network slice identifier is an identifier of a network slice replaced by the first network slice identifier; Selecting a policy control function (PCF) for the first network slice identifier; Sending a policy creation request message including the first network slice identifier and the additional network slice identifier to the selected PCF; and Receiving a response message to the policy creation request message from the PCF.

2. The method according to claim 1, further comprising: Sending a PCF ID for the first network slice identifier to a binding support function (BSF) or a unified data repository (UDR) to store the PCF ID.

3. The method according to claim 1, further comprising: Sending a PCF ID for the first network slice identifier to a unified data management (UDM) and storing the PCF ID in a UE context in the SMF data of the UDM.

4. The method according to claim 1, wherein Selecting the PCF for the first network slice identifier includes: In the case where the PDU session request message includes a PCF ID, selecting a PCF corresponding to the PCF ID; or In the case where the PDU session request message does not include a PCF ID, selecting a PCF based on the first network slice identifier.

5. The method according to claim 4, wherein, The PDU session request message further includes a subscription permanent identifier (SUPI) and a data network name (DNN), wherein selecting the PCF based on the first network slice identifier includes: selecting the PCF based on the first network slice identifier, the SUPI, and the DNN.

6. A method for supporting a protocol data unit (PDU) session for establishing a network slice by a policy control function (PCF) in a communication network, the method comprising: Receiving a policy creation request message including a first network slice identifier and an additional network slice identifier from a session management function (SMF), wherein the additional network slice identifier is an identifier of a network slice replaced by the first network slice identifier; Sending an identification message requesting PCF information corresponding to the additional network slice identifier to a binding support function (BSF) or a unified data repository (UDR); Receiving a first response message to the identification message; and Based on the first response message, sending a second response message to the SMF for the policy creation request message.

7. The method according to claim 6, In the case where the received first response message includes the PCF information, the second response message includes information indicating redirection to a PCF corresponding to the PCF information.

8. The method according to claim 6, further comprising: In the case that the received first response message does not include the PCF information, send a message to the UDR requesting at least one of the policy information for the first network slice identifier or the policy information for the additional network slice identifier; and Receive a response message including at least one of the policy information for the first network slice identifier or the policy information for the additional network slice identifier.

9. The method according to claim 6, wherein The identification message sent to the UDR to request the PCF information corresponding to the additional network slice identifier includes: Send an identification message to the UDR to request the UE context in the SMF data corresponding to the additional network slice identifier.

10. A session management function (SMF) entity for supporting a protocol data unit (PDU) session for establishing a network slice in a communication network, the SMF entity includes: A transceiver configured to receive a PDU session request message from an access and mobility management function (AMF), the PDU session request message including a first network slice identifier and an additional network slice identifier, where the additional network slice identifier is the identifier of a network slice replaced by the first network slice identifier; and A processor configured to select a policy control function (PCF) for the first network slice identifier, wherein the processor is configured to control the transceiver to: Send a policy creation request message including the first network slice identifier and the additional network slice identifier to the selected PCF; and Receive a response message to the policy creation request message from the PCF.

11. The SMF entity according to claim 10, wherein, The processor is configured to control the transceiver to send the PCF ID for the first network slice identifier to a binding support function (BSF) or a unified data repository (UDR).

12. The SMF entity according to claim 10, wherein, The processor is configured to: send the PCF ID for the first network slice identifier to a unified data management (UDM) through the transceiver and store the PCF ID in the UE context in the SMF data of the UDM.

13. The SMF entity according to claim 10, wherein, The processor is configured to: In the case that the PDU session request message includes a PCF ID, select the PCF corresponding to the PCF ID; or In the case that the PDU session request message does not include a PCF ID, select a PCF based on the first network slice identifier.

14. The SMF entity according to claim 13, wherein, The PDU session request message further includes a subscription permanent identifier (SUPI) and a data network name (DNN), and wherein the processor is configured to select the PCF based on the first network slice identifier, the SUPI, and the DNN.

15. A policy control function (PCF) entity for supporting a protocol data unit (PDU) session for establishing a network slice in a communication network, the PCF entity includes: A transceiver; and A processor, the processor is configured to, through the transceiver, Receive a policy creation request message including a first network slice identifier and an additional network slice identifier from a Session Management Function (SMF), where the additional network slice identifier is the identifier of a network slice replaced by the first network slice identifier; Send an identification message requesting PCF information corresponding to the additional network slice identifier to a Binding Support Function (BSF) or a Unified Data Repository (UDR), Receive a first response message to the identification message, and Based on the first response message, send a second response message to the SMF for the policy creation request message.

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