Alternative Network Slice Support Method and Apparatus in a Wireless Communication System

Abstract

The present disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate. In a wireless communication system according to an embodiment of the present disclosure, a method for solving a problem in which a PDU session creation is rejected by an NSAC using an alternative S-NSSAI is presented.

Description

Technical Field

[0001] The present disclosure relates to an alternative network slice support method and apparatus in a wireless communication system.

Background Art

[0002] The 5G mobile communication technology defines a wide frequency band to enable fast transmission speeds and new services. It is feasible not only in the frequency band below 6 GHz (Sub 6 GHz) such as 3.5 gigahertz (3.5 GHz), but also in the extremely high frequency band (Above 6 GHz) called millimeter wave (mmWave) such as 28 GHz and 39 GHz. Also, in the 6G mobile communication technology called the system after 5G communication (Beyond 5G), in order to achieve a transmission speed 50 times faster and an ultra-low latency reduced to one-tenth compared to the 5G mobile communication technology, implementation in the terahertz (THz) band (for example, the band from 95 GHz to 3 THz) is being considered.

[0003] In the early stage of 5G mobile communication technology, aiming at service support and performance requirement satisfaction for enhanced Mobile BroadBand (eMBB), Ultra-Reliable Low-Latency Communications (URLLC), and massive Machine-Type Communications (mMTC), beamforming and massive multiple-input multiple-output (Massive MIMO) for mitigating radio path loss and increasing radio transmission distance in the millimeter wave band, various numerology supports (such as operation of multiple subcarrier spacings) and dynamic operation for slot format for efficient utilization of millimeter wave frequency resources, initial connection technology for supporting multi-beam transmission and wideband, definition and operation of Band-Width Part (BWP), new channel coding methods such as Low Density Parity Check (LDPC) code for large-capacity data transmission and Polar Code for reliable transmission of control information, L2 pre-processing, network slicing for providing dedicated networks specialized for specific services, etc. have been standardized.

[0004] Currently, discussions are underway for the improvement and enhancement of the initial 5G mobile communication technology in consideration of the services that 5G mobile communication technology aims to support. This includes Vehicle-to-Everything (V2X) to assist in the driving judgment of autonomous vehicles based on the position and status information transmitted by vehicles and to increase user convenience, New Radio Unlicensed (NR-U) for system operations that comply with various regulatory requirements in the unlicensed band, UE Power Saving for NR terminal low power consumption technology, Non-Terrestrial Network (NTN) for terminal-satellite direct communication to ensure coverage in areas where communication with the terrestrial network is impossible, and physical layer standardization for technologies such as Positioning is in progress.

[0005] In addition, standardization in the wireless interface architecture / protocol field for technologies such as intelligent factories (IIoT: Industrial Internet of Things) for new service support using linkages and integrations with other industries, IAB (Integrated Access and Backhaul) that provides nodes for network service area expansion by integrating wireless backhaul links and access links, mobility enhancement technologies including conditional handover and DAPS (Dual Active Protocol Stack) handover, and two-step random access (2-step RACH for NR) that simplifies the random access procedure is also underway. Standardization in the system architecture / service field for 5G baseline architectures for the integration of network function virtualization (NFV) and software-defined networking (SDN) technologies (e.g., SBA: Service-based Architecture, SBI: Service-based Interface), mobile edge computing (MEC) that receives service provision based on the location of the terminal, etc. is also underway.

[0006] When such a 5G mobile communication system is commercialized, connected devices, which are on an explosive growth trend, should be connected to the communication network. Along with this, it is expected that there will be a need to enhance the functions and performance of the 5G mobile communication system and to integrally operate the connected devices. For this purpose, new research is planned to be conducted on 5G performance improvement and complexity reduction, AI service support, metabus service support, drone communication, etc. by utilizing extended reality (XR) that efficiently supports augmented reality (AR), virtual reality (VR), mixed reality (MR), etc., artificial intelligence (AI), and machine learning (ML).

[0007] In addition, the development of such a 5G mobile communication system is not only for new waveforms for coverage guarantee in the terahertz band of 6G mobile communication technology, full dimensional MIMO (FD-MIMO), array antennas, multiple antenna transmission technologies such as large scale antennas, metamaterial-based lenses and antennas to improve the coverage of terahertz band signals, high-dimensional spatial multiplexing technologies using orbital angular momentum (OAM), and reconfigurable intelligent surface (RIS) technology, but also for full duplex technology for improving the frequency efficiency and system network of 6G mobile communication technology, satellite, AI (artificial intelligence) utilized from the design stage, AI-based communication technology that internalizes end-to-end AI support functions to achieve system optimization, and next-generation distributed computer technology that realizes services with complexity beyond the limits of terminal computing capabilities by utilizing ultra-high performance communication and computing sources. This will form the basis for the development of such technologies. Summary of the Invention

Problems to be Solved by the Invention

[0008] In the PDU (protocol data unit) session generation procedure, the acceptance control for the maximum number of PDU sessions per network slice (that is, the network slice acceptance control (NSAC) for the maximum number of PDU sessions) may cause the rejection of PDU session generation. In particular, if the generation of PDU sessions by a specific slice (for example, S-NSSAI) subject to NSAC concentrates within a certain period of time and reaches the maximum number of established PDU sessions for the corresponding slice, many requests for generating PDU sessions to the corresponding slice may be rejected by NSAC. Therefore, a method for alleviating the rejection of PDU session generation requests by NSAC is required.

[0009] The technical problems to be achieved by the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those having ordinary knowledge in the technical field to which the present invention pertains from the following description.

Means for Solving the Problems

[0010] According to one aspect of this disclosure, a method performed by an AMF (access and mobility management function) of a communication system is provided. The method includes receiving, from a terminal, a first message for a request to establish a PDU (protocol data unit) session associated with a first network slice; identifying whether the first network slice is available; selecting, when the first network slice is not available, a second network slice that is an alternative to the first network slice; and transmitting a second message for the establishment of the PDU session to an SMF (session management function) associated with the second network slice.

[0011] In one aspect, the method further includes selecting the SMF based on the second network slice.

[0012] In one aspect, the first message includes an S-NSSAI (single-network slice selection assistance information) of the first network slice.

[0013] In one aspect, the method further includes receiving, from a UDM (unified data management), information on at least one network slice and information on at least one alternative network slice associated with each of the at least one network slice.

[0014] In one aspect, the step of identifying whether the first network slice is available includes receiving, from the SMF, a third message including information indicating whether the first network slice is available; and identifying whether the first network slice is available based on the information.

[0015] In one aspect, the third message further includes information on the second network slice which is an alternative network slice to the first network slice.

[0016] In one aspect, when the number of established PDU sessions is the same as the maximum number of PDU sessions for the first network slice, or when the number of registered terminals is the same as the maximum number of possible terminals for the first network slice, the first network slice is not available.

[0017] This disclosure also provides an AMF (access and mobility management function) of a communication system. The AMF includes a transceiver; and a control unit coupled to the transceiver, receiving from a terminal a first message for a request for establishment of a PDU (protocol data unit) session associated with a first network slice, identifying whether the first network slice is available, selecting a second network slice which is an alternative to the first network slice when the network slice is not available, and transmitting a second message for the establishment of the PDU session to an SMF (session management function) associated with the second network slice.

Advantages of the Invention

[0018] According to an embodiment of the present invention, in a 5G system, by using an alternative network slice technology, a situation where a request for generating a PDU (protocol data unit) session is rejected by network slice admission control (NSAC) can be alleviated or prevented. The alternative network slice technology may be utilized as follows:

[0019] 1) If the initially requested network slice is unavailable, the network administrator can create a session through an alternative slice. This has the advantage of improving the availability of the network slice.

[0020] 2) When sessions concentrate on a specific network slice, the network administrator can achieve a load balancing effect between network slices by making an alternative slice available for a new session request that requests the corresponding network slice.

[0021] 3) For a session creation request that should not be rejected due to the reason of the unavailability of the network slice (for example, an emergency call service, a national security / regulation-related service, when a session established in an environment not supported by NSAC moves to an environment supported by NSAC, etc.), the network administrator can prevent the corresponding session creation request from being rejected by providing an alternative slice.

[0022] The effects obtained from the present invention are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those of ordinary skill in the technical field to which the present disclosure pertains from the following description.

Brief Description of the Drawings

[0023] In the drawings, the same or similar reference numerals can be used for the same or similar components.

[0024]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Mode for Carrying Out the Invention

[0025] Before describing the following detailed description, it is intended to explain the definitions of specific words and phrases used throughout this patent specification. The terms "comprising" and "consisting of" and their derivatives are meant to mean including without limitation. The term "or" is inclusive and means and / or. The phrases "associated with" and "related to" and their derivatives can mean including, included, interconnected, consisting of, composed of, connected, coupled, transmitted, capable of being transmitted, cooperating with, interrupting, juxtaposing, adjacent to, coupled to, coupled with, having the attributes of, or having. The term "controller" means all devices, systems or parts thereof that control at least one operation, and such devices can be implemented by hardware, firmware, software, or a combination of at least two of these. It should be noted that the functions associated with a particular controller can be centralized or decentralized locally or remotely.

[0026] Furthermore, the various functions described below may be embodied or supported by one or more computer programs, each function being constituted by computer-readable program code and embodied in a computer-readable medium. The terms "application" and "program" mean one or more computer programs, software components, instruction sets, procedures, functions, entities, classes, instances, related data, or portions thereof applied to be embodied by appropriate computer-readable program code. The phrase "computer-readable program code" includes any type of computer code including source code, object code, and executable code. The phrase "computer-readable medium" includes any type of medium accessible by a computer, such as read-only memory (ROM), random access memory (RAM), hard disk drive, compact disc (CD), video disc (DVD), or any other type of memory. The "non-transitory" computer-readable medium excludes wired, wireless, optical, or other communication links that transmit transient electrical or other signals. The non-transitory computer-readable medium includes media in which data can be permanently stored, such as rewritable optical discs or erasable memory devices, and media in which data is stored and can be overwritten later.

[0027] Definitions for specific words and phrases are provided throughout this patent document and, although not in most cases, in many cases it will be apparent to those skilled in the art that such definitions apply not only to the previous use of the defined words and phrases but also to their future use.

[0028] The FIGS. 1-6 described below, and the various examples used herein to explain the principles of the present invention, are merely illustrative and should not be construed as limiting the scope of the present invention in any way. Those skilled in the art will appreciate that the principles of the present disclosure may be embodied in any appropriately arranged system or device.

[0029] Hereinafter, with reference to the accompanying drawings, the operating principle of the present invention will be described in detail. In the following description of the present invention, when it is determined that a specific description of a related known function or configuration may obscure the gist of the present invention, the detailed description thereof will be omitted. Note that the terms described below are terms defined in consideration of the functions in the present invention, and they may vary depending on the intention or convention of the user or operator. Therefore, the definition should be given based on the content throughout this specification.

[0030] Hereinafter, when explaining the present invention, if it is determined that a specific description of a related known function or configuration may obscure the gist of the present invention, the detailed description thereof shall be omitted. Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0031] Terms used in the following description for identifying connection nodes, terms indicating network entities, terms indicating messages, terms indicating interfaces between network entities, terms indicating various identification information, etc. are exemplified for convenience of explanation. Therefore, the present invention is not limited to the terms described below, and other terms indicating objects having equivalent technical meanings may be used.

[0032] The 5G mobile communication network is composed of 5G UE (user equipment, such as terminal), 5G RAN (radio access network, such as base station, gNB (5g nodeB), eNB (evolved node B)), and 5G core network. The 5G core network includes AMF (access and mobility management function) that provides the mobility management function of UE, SMF (session management function) that provides the session management function, UPF (user plane function) that plays a role in data transmission, PCF (policy control function) that provides the policy control function, UDM (unified data management) that provides data management functions such as subscriber data and policy control data, and UDR (unified data repository) that stores data of various network functions (such as network function) like UDM.

[0033] In a 5G system, the network slicing technology represents the technology and structure that enable multiple independent logical networks virtualized on one physical network. Network operators can provide services by configuring a virtual end-to-end network called a network slice to meet the specialized requirements of services / applications. At this time, network slices may be distinguished by an identifier called S-NSSAI (single-network slice selection assistance information). The network transmits information about the set of slices allowed for the terminal (e.g., allowed NSSAI(s)) during the terminal registration procedure (e.g., UE registration procedure), and the terminal can send and receive application data through a PDU (protocol data unit) session generated through one of these S-NSSAIs (i.e., network slices).

[0034] On the other hand, in a 5G system, there is a network slice admission control (NSAC) function that ensures that the number of registered terminals per network slice and the number of established PDU sessions per network slice (e.g., the number of registered UEs per network slice and the number of established PDU sessions per network slice, respectively) do not exceed the defined maximum values.

[0035] For the acceptance control of the maximum number of registered UEs (terminals) per network slice, whenever the AMF needs to change (add or delete an S-NSSAI) the set of S-NSSAIs allowed for a UE (allowed NSSAI), it can request the NSACF (NSAC function) to update (request an increase or decrease) the number of registered UEs for the corresponding slice. If the NSACF receives an increase update request from the AMF for an S-NSSAI that has reached the pre-set maximum number of registered UEs per network slice, it can provide the AMF with information that the corresponding S-NSSAI has reached the maximum number of registered UEs. Upon receiving the corresponding information, the AMF can exclude the corresponding S-NSSAI from the set of allowed S-NSSAIs.

[0036] For the acceptance control of the maximum number of PDU sessions per network slice, when the SMF performs a PDU session creation or release procedure for an S-NSSAI, it can request the NSACF (NSAC function) to update (request an increase or decrease) the number of established PDU sessions for the corresponding S-NSSAI. If the NSACF receives an increase update request from the SMF for an S-NSSAI that has reached the pre-set maximum number of established PDU sessions per network slice, it can provide the SMF with information that the corresponding S-NSSAI has reached the maximum number of established PDU sessions. Upon receiving the corresponding information, the SMF does not need to perform PDU session creation using the corresponding S-NSSAI. On the other hand, NSAC target information may be set for each S-NSSAI for the AMF and the SMF, and the AMF and the SMF can perform NSAC procedures only for S-NSSAIs that are NSAC targets.

[0037] FIG. 1 shows how the AMF receives alternative S-NSSAI information in the registration procedure when the alternative S-NSSAI (alternative S-NSSAI) information according to an embodiment of the present invention is defined and provided in the access and mobility (AM) subscription data of the UDM.

[0038] Referring to FIG. 1, the terminal (UE) 101 can send a message to the base station (RAN, gNB, base station) 102 for the UE registration procedure (step 110). At this time, the message for the UE registration procedure may be an AN message (AN parameter, registration request). Here, the AN message represents a message between the terminal 101 and the base station 102. At this time, the registration request message may include at least one of information such as a UE identifier (for example, SUCI (subscription concealed identifier), 5G-GUTI (5G-globally unique temporary identity), or PEI (permanent equipment identifier)), a requested NSSAI (requested NSSAI), and a UE MM (mobility management) core network capability.

[0039] Then, the RAN 102 can select the AMF 103 based on the information in the AN message received from the UE 101 (step 120).

[0040] The RAN 102 can transmit an N2 message (the N2 parameter may include at least one of the registration requests) to the AMF 103 (step 130). The N2 parameter may include a selected PLMN ID (selected PLMN ID), UE location information, a UE context request (UE context request), and the like.

[0041] When determining that UE authentication is required, AMF 103 can select AUSF (authentication server function) 104 based on at least one of the UE identifiers (e.g., SUCI or SUPI (subscription permanent identifier)) (step 140).

[0042] Then, the authentication procedure for UE 101 may be performed through the selected AUSF 104 (step 145). Also, if there is no NAS (non-access stratum) security context for UE 101, a procedure for obtaining it may be performed.

[0043] When AMF 103 needs subscription information for UE 101, it can select UDM 105 based on the SUPI, and UDM 105 can select a UDR (not shown) in which the subscription information for UE 101 is stored (step 150).

[0044] AMF 103 can request the AM subscription information for UE 101 from UDM 105 using a Nudm_SDM_Get request message (which may include at least one of SUPI, AM subscription data (access and mobility subscription data), etc.) (step 160).

[0045] At this time, the Nudm_SDM_Get request message may include information for requesting alternative slice information (e.g., alternative S-NSSAI(s)) in the following cases: determination based on the local configuration of AMF 103, when the ongoing UE registration procedure is a registration due to a move from EPS to 5GS, etc.

[0046] UDM105 can send subscription information including subscribed S-NSSAI(s), alternative slice information (e.g., alternative S-NSSAI(s) for each S-NSSAI in subscribed S-NSSAI(s)), etc. to AMF103 in the Nudm_SDM_Get response message (step 165). At this time, the alternative S-NSSAI information may be defined in the AM subscription data of the Nudm_SDM_Get response message and transmitted to AMF103.

[0047] UDM105 can include alternative S-NSSAI(s) in the Nudm_SDM_Get response message in the following cases: determination based on the local configuration of UDM105, when AMF103 requests alternative S-NSSAI(s), etc.

[0048] At this time, according to an embodiment, UDM105 can obtain the information to be sent to AMF103 from UDR and send it to AMF103.

[0049] AMF103 can calculate the allowed NSSAI considering the subscribed S-NSSAI(s) and store the allowed NSSAI in the UE context (step 170).

[0050] Also, among the S-NSSAIs within the allowed NSSAI, for the S-NSSAI that is subject to NSAC, the AMF 103 can store the per-S-NSSAI alternative S-NSSAI(s) in the UE context. When the AMF 103 attempts to utilize an alternative slice in a situation where NSAC is rejected or a slice is unavailable for other reasons (e.g., a slice congestion situation occurs), the AMF 103 can store the alternative slice (per-S-NSSAI alternative S-NSSAI(s)) in the UE context for the subscribed S-NSSAI(s) or the allowed NSSAI. The AMF 103 can utilize the stored per-S-NSSAI alternative S-NSSAI(s) to determine the slice (i.e., the target slice) to be used in place of the unavailable slice, and can move the PDU session to the target slice upon a PDU session creation / modification request or a handover request to the unavailable slice.

[0051] Then, the remaining registration procedures of the UE 101 may be performed (step 180).

[0052] In the embodiment shown in FIG. 1, the terminal 101 receives the set of slices allowed by the registration procedure (UE registration procedure), and then selects the corresponding slice within the set for each PDU session to be generated, and generates the PDU session by the PDU session generation procedure. When an alternative slice (e.g., an alternative S-NSSAI) is provided by the registration procedure as shown in FIG. 1, there is an advantage of low signaling load because signaling for providing the alternative slice for each PDU session generation procedure is not required.

[0053] FIG. 2 shows a method in which the AMF reselects the S-NSSAI for the PDU session using the alternative S-NSSAI information in the PDU session establishment procedure when the alternative S-NSSAI information according to an embodiment of the present invention is defined and provided in the AM subscription data of the UDM.

[0054] Referring to FIG. 2, in the UE registration procedure, the AMF 203 can store, in the UE context of the AMF, the allowed NSSAI and the alternative S-NSSAI(s) information for each S-NSSAI that is an NSAC target within the allowed NSSAI (step 210). This may be done according to the embodiment described above in connection with FIG. 1.

[0055] The terminal (UE) 201 can send a request message to the AMF 203 (through the base station 202) for the PDU session establishment procedure (step 215). And this message may be a PDU session establishment request message, and the PDU session establishment request message may be included in a NAS (non-access stratum) message and sent to the AMF 203. The NAS message means a message between the terminal 201 and the AMF 203. According to an embodiment, the NAS message may include at least one of an S-NSSAI, a DNN (data network name), a PDU session ID (PDU session ID), etc.

[0056] When the S-NSSAI included in the message received from the UE 201 at step 250 is not currently available, the AMF 203 does not have to select the SMF 205. In this case, steps 230, 240, and 250 are omitted, and the procedure may be performed starting from step 260. The AMF 203 can select the SMF 205 based on at least one of a DNN, an S-NSSAI, etc. (step 220).

[0057] Then, the AMF 203 can send an Nsmf_PDUSession_CreateSMContext request to the selected SMF 205. According to an embodiment, the Nsmf_PDUSession_CreateSMContext request message may include at least one of an S-NSSAI, a DNN, a PDU session ID, a PDU session establishment request message, etc. (step 230).

[0058] When the S-NSSAI included in the message received from the AMF 203 is subject to NSAC (network slice admission control), the SMF 205 can send an Nnsacf_NSAC_NumOfPDUsUpdate request (the request message may include at least one of an S-NSSAI, a UE ID, a PDU session ID, an update flag = INCREASE, etc.) message to the NSACF (NSAC function) 206 (step 240).

[0059] When the update flag value of the received message is INCREASE and the number of PDU sessions established for the S-NSSAI included in the received message has already reached the maximum number of PDU sessions established for the S-NSSAI, the NSACF 206 can send a value indicating that the maximum number of PDU sessions has already been reached to the SMF 205 included in the result value (step 245). At this time, the message may be an Nnsacf_NSAC_NumOfPDUsUpdate response message.

[0060] The SMF 205 can send an Nsmf_PDUSession_CreateSMContext response message to the AMF 203 (step 250). At this time, the cause of the message may include information indicating that the creation of the SM context (session management context) has failed due to reaching the maximum number of established PDU sessions for the S-NSSAI.

[0061] If the cause value of the message from the SMF 205 contains information indicating that the creation of the SM context has failed due to reaching the maximum number of established PDU sessions for the S-NSSAI, or if the AMF 203 determines at step 220 that the S-NSSAI included in the message from the UE 201 is unavailable, then the AMF 203 can select one of the S-NSSAI(s) included in the permitted NSSAI among the alternative S-NSSAI(s) for the failed or unavailable S-NSSAI and attempt to generate the PDU session again (step 260).

[0062] The alternative S-NSSAI(s) may be stored in the AMF 203 in the following forms: stored in the AMF local configuration, stored in the UE context of the AMF 203, etc.

[0063] The AMF 203 can select a new SMF again based on the newly selected S-NSSAI (step 270). In the figure, it is shown that the same SMF as the SMF selected at step 220 is selected at step 270, but the SMF selected at step 220 and the SMF selected at step 270 may be the same or different from each other.

[0064] The AMF 203 can send an Nsmf_PDUSession_CreateSMContext request message to the newly selected SMF (step 280). For the sake of convenience of explanation, Figure 2 shows multiple SMFs as one SMF. The SMF newly selected by the AMF 203 at step 270 may be different from the SMF selected by the AMF 203 at step 220.

[0065] Then, the remaining PDU session establishment procedure may be performed (step 290).

[0066] In the embodiment illustrated in FIG. 2, in a situation where an alternative slice (e.g., alternative-SNSSAI) is provided in advance through a registration procedure (e.g., by the same method as illustrated in FIG. 1), it is shown that the alternative slice is utilized for the PDU session, and since signaling for providing an alternative slice for each PDU session establishment procedure is not required, there is an advantage of a low signaling load.

[0067] FIG. 3 shows a method in which, when alternative S-NSSAI information according to an embodiment of the present invention is defined and provided in the SM subscription data (session management (SM) subscription data) of the UDM, the AMF reselects the S-NSSAI for the PDU session using the alternative S-NSSAI information in the PDU session establishment procedure.

[0068] Referring to FIG. 3, the UE 301 can transmit a PDU session establishment request message (step 310) included in a NAS message to the AMF 303 (via the base station 302) for the PDU session establishment procedure. The NAS message means a message between the terminal 301 and the AMF 303. The NAS message may include at least one of an S-NSSAI, a DNN, a PDU session ID, etc.

[0069] The AMF 303 can select the SMF 305 based on at least one of a DNN, an S-NSSAI, etc. (step 320).

[0070] AMF303 can send an Nsmf_PDUSession_CreateSMContext request (which may include at least one of S-NSSAI, DNN, PDU session ID, PDU session establishment request message, etc.) to SMF305 (step 330).

[0071] When the S-NSSAI included in the message received from AMF303 is subject to NSAC, SMF305 can send an Nnsacf_NSAC_NumOfPDUsUpdate request (which may include at least one of S-NSSAI, UE ID, PDU session ID, update flag = INCREASE, etc.) message to NSACF306 (step 340).

[0072] If the update flag value of the received message is INCREASE and the number of established PDU sessions has reached the maximum number of established PDU sessions for the S-NSSAI in the received message's S-NSSAI, NSACF306 can include information indicating that the maximum number of established PDU sessions for the S-NSSAI has already been reached and is unavailable in the result value and send it to SMF305 (step 345). At this time, the message may be an Nnsacf_NSAC_NumOfPDUsUpdate response message.

[0073] The SMF305 can send a Nudm_SDM_Get request (which may include at least one of the SUPI, DNN, S-NSSAI, SM subscription data, etc.) to the UDM308 to request the SM subscription data of the UE301 (step 350). At this time, the Nudm_SDM_Get request message may include information for requesting alternative S-NSSAI(s) in the following cases: determination based on the local configuration of the SMF305, when the ongoing UE registration procedure is a registration due to a move from the first system (e.g., EPS) to the second system (e.g., 5GS), when the response message at step 345 includes information that the S-NSSAI is unavailable, etc.

[0074] The UDM308 can send subscription information including alternative NSSAI(s) for the S-NSSAI included in the message received from the SMF305 to the SMF305 in the Nudm_SDM_Get response message (step 355). The UDM308 can include alternative S-NSSAI(s) in the following cases: determination based on the local configuration of the UDM308, when the SMF305 requests alternative S-NSSAI(s), etc.

[0075] At this time, according to an embodiment, the UDM308 can obtain the information to be sent to the SMF305 from the UDR (not shown) and send it to the AMF303.

[0076] The SMF305 can send a Nsmf_PDUSession_CreateSMContext response message to the AMF303 (step 360). At this time, the cause of the message may include information indicating that the SM context generation failed due to reaching the maximum number of established PDU sessions for the S-NSSAI, and alternative S-NSSAI(s), etc.

[0077] AMF303 can indicate in the Cause value of the message from SMF305 information indicating that the SM context generation has failed due to reaching the maximum number of established PDU sessions for the S-NSSAI, and if alternative S-NSSAI(s) are included, one of the S-NSSAI(s) included in the allowed NSSAI among the alternative S-NSSAI(s) for the failed S-NSSAI can be selected to retry PDU session generation (step 370).

[0078] AMF303 can select a new SMF again based on the newly selected S-NSSAI (step 380).

[0079] AMF303 can send an Nsmf_PDUSession_CreateSMContext request message to the newly selected SMF305 (step 390). For the sake of convenience of explanation, FIG. 3 shows multiple SMFs as one SMF. The SMF newly selected by AMF303 at step 380 may be a different SMF from the SMF selected by AMF303 at step 320.

[0080] Then, the remaining PDU session generation procedures may be performed (step 395).

[0081] In the embodiment illustrated in FIG. 3, since the alternative slice is provided through UDM308 that provides subscriber information for the session in the PDU session procedure, there is an advantage that the alternative slice can be provided based on information related to the subscriber's segmented session.

[0082] FIG. 4 shows a method in which the AMF reselects the S-NSSAI for the PDU session using the alternative S-NSSAI information in the PDU session establishment procedure when the alternative S-NSSAI information according to an embodiment of the present invention is defined and provided by the NSACF.

[0083] Referring to FIG. 4, the UE 401 can send a PDU session establishment request message included in an NAS message to the AMF 403 (via the base station 402) for the PDU session establishment procedure (step 410). The NAS message means a message between the terminal 401 and the AMF 403. The NAS message may include at least one of an S-NSSAI, a DNN, a PDU session ID, etc.

[0084] The AMF 403 can select the SMF 405 based on at least one of a DNN, an S-NSSAI, etc. (step 420).

[0085] The AMF 403 can send a Nsmf_PDUSession_CreateSMContext request (which may include at least one of an S-NSSAI, a DNN, a PDU session ID, a PDU session establishment request message, etc.) to the selected SMF 405 (step 430).

[0086] When the S-NSSAI included in the message received from the AMF 403 is an NSAC target, the SMF 405 can send a Nnsacf_NSAC_NumOfPDUsUpdate request (which may include at least one of an S-NSSAI, a UE ID, a PDU session ID, an update flag = INCREASE, etc.) message to the NSACF 406 (step 440).

[0087] At this time, the Nnsacf_NSAC_NumOfPDUsUpdate request message may include information for requesting alternative S-NSSAI(s) in the following cases: determination based on the local configuration of the SMF 405, when the ongoing UE registration procedure is a registration due to a movement from a first system (e.g., EPS) to a second system (e.g., 5GS), etc.

[0088] When the update flag value of the received message is INCREASE in NSACF406 and the number of PDU sessions established has already reached the maximum number of established PDU sessions for the S-NSSAI in the Nnsacf_NSAC_NumOfPDUsUpdate request message, NSACF406 can send a value indicating that the maximum number of established PDU sessions has already been reached to SMF405 in the result value (step 445). Also, NSACF406 may include alternative S-NSSAI(s) in the following cases: when the S-NSSAI included in the message from SMF405 is unusable, determined by the local configuration of NSACF406, when alternative S-NSSAI(s) are requested from SMF405, etc.

[0089] NSACF406 may include in the alternative S-NSSAI(s) of the message sent to SMF405 the S-NSSAI(s) among the alternative S-NSSAI(s) for the corresponding S-NSSAI stored that have not reached the maximum number of established PDU sessions, or the S-NSSAI(s) not subject to NSAC.

[0090] SMF405 sends an Nsmf_PDUSession_CreateSMContext response message to AMF403 (step 450). At this time, the cause of the message may include information indicating that the SM context generation has failed due to reaching the maximum number of established PDU sessions for the S-NSSAI, and the alternative S-NSSAI(s) received at step 445.

[0091] If the cause value of the message from SMF405 includes information indicating that the SM context generation has failed due to reaching the maximum number of established PDU sessions for the S-NSSAI and alternative S-NSSAI(s), AMF403 can select one of the S-NSSAI(s) included in the permitted NSSAI among the alternative S-NSSAI(s) for the failed S-NSSAI and attempt to generate a PDU session again (step 460).

[0092] AMF403 can select the SMF again based on the newly selected S-NSSAI (step 470).

[0093] AMF403 can send an Nsmf_PDUSession_CreateSMContext request message to the newly selected SMF405 (step 480). For the sake of convenience of explanation, FIG. 4 shows multiple SMFs as one SMF. The SMF newly selected by AMF403 at step 470 may be different from the SMF selected by AMF403 at step 420.

[0094] Then, the remaining PDU session generation procedures may be performed (step 490).

[0095] In the embodiment illustrated in FIG. 4, since the NSACF406 that knows the load information for the network slice provides an alternative slice (for example, an alternative SNSSAI) for the PDU session, there is an advantage that alternative slice determination / provision considering the load on the network slice is possible. For example, NSACF406 can provide SMF405 with an alternative slice where the number of allowable PDU sessions remaining is sufficiently large.

[0096] FIG. 5 is a diagram showing the configuration of a terminal according to an embodiment of the present invention.

[0097] Referring to FIG. 5, a terminal according to an embodiment of the present invention may include a transceiver unit 520 and a control unit 510 that controls the overall operation of the terminal. And the transceiver unit 520 may include a transmitter unit 525 and a receiver unit 523.

[0098] The transceiver unit 520 can transmit and receive signals with other network entities.

[0099] The control unit 510 can control the terminal to perform the operation of any one of the above-described embodiments. On the other hand, the control unit 510 and the transceiver unit 520 do not necessarily have to be embodied as separate modules, and of course, they may be embodied as a single component in the form of a single chip. And the control unit 510 and the transceiver unit 520 may be electrically connected. And, for example, the control unit 510 may be a circuit, an application-specific circuit, or at least one processor. Also, the operation of the terminal may be realized by providing a memory device storing the corresponding program code in any component within the terminal.

[0100] FIG. 6 is a diagram showing the configuration of a network entity according to an embodiment of the present invention.

[0101] The network entity of the present invention is a concept including network functions by system implementation.

[0102] Referring to FIG. 6, a network entity according to an embodiment of the present invention may include a control unit 610 that controls the overall operation of the transceiver unit 620 and the network entity. And the transceiver unit 620 may include a transmitter unit 625 and a receiver unit 623.

[0103] The transceiver unit 620 can transmit and receive signals with other network entities.

[0104] The control unit 610 can control the network entity to perform any one of the operations of the above-described embodiments. On the other hand, the control unit 610 and the transceiver unit 620 are not necessarily embodied as separate modules, and of course, may be embodied as one component in the form of a single chip. And the control unit 610 and the transceiver unit 620 may be electrically connected. And, for example, the control unit 610 may be a circuit, an application-specific circuit, or at least one processor. Also, the operation of the network entity may be realized by providing a memory device storing the corresponding program code in any component within the network entity.

[0105] The network entity may be any one of a base station (RAN), AMF, SMF, UPF, PCF, NSACF, UDM, UDR.

[0106] It should be noted that the configuration diagrams, the exemplary diagrams of the control / data signal transmission method, the exemplary diagrams of the operation procedures, and the configuration diagrams illustrated in FIGS. 1 to 6 above are not intended to limit the scope of the rights of the present disclosure. That is, all the components, entities, or operation stages described in FIGS. 1 to 6 above should not be construed as essential components for the implementation of the disclosure, and it may be implemented within the scope that does not harm the essence of the disclosure even if only some components are included.

[0107] The operations of the above-described network entity and terminal may be realized by providing a memory device storing the corresponding program code in any component within the network entity or the terminal device. That is, the control unit of the network entity or the terminal device can execute the above-described operations by reading and executing the program code stored in the memory device by a processor or a CPU (Central Processing Unit).

[0108] The various components of the network entities, base stations or terminal devices described in this specification, such as modules, may operate using a hardware circuit, for example, a complementary metal oxide semiconductor-based logic circuit, firmware, software and / or a combination of hardware and firmware and / or software inserted into a machine-readable medium. As an example, various electrical structures and methods may be implemented using transistors, logic gates, and electrical circuits such as application-specific semiconductors.

[0109] On the other hand, although specific embodiments have been described in the detailed description of the present disclosure, it is needless to say that various modifications are possible without departing from the scope of the present disclosure. Therefore, the scope of the present disclosure should not be defined by being limited to the described embodiments, but should be defined by the appended claims and those equivalent to the claims.

[0110] According to an embodiment of the present invention, in a 5G system, by using alternative network slicing technology, it is possible to alleviate or prevent a situation where a PDU (protocol data unit) session generation request is rejected by network slice admission control (NSAC). The alternative network slicing technology may be utilized as follows.

[0111] As an example, when the initially requested network slice is unavailable, the network administrator can generate a session through an alternative slice. This has the advantage of improving the availability of the network slice.

[0112] As another example, when sessions are concentrated in a specific network slice, the network administrator can obtain a load distribution effect among network slices by making an alternative slice available for a new session request that requests the corresponding network slice.

[0113] As yet another example, for a session generation request that should not be rejected due to reasons for a network slice being unavailable (for example, in the case where a session established in an environment not supported by NSAC moves to an environment supported by NSAC for an emergency call service, a national security / regulation-related service, etc.), the network administrator can prevent the corresponding session generation request from being rejected by providing an alternative slice.

[0114] The effects obtained from the present invention are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those of ordinary skill in the technical field to which this disclosure pertains from the following description.

[0115] As described above, the present invention has been explained by various examples, but those of ordinary skill in this technical field may propose various modifications and variations. The present disclosure is intended to include changes and modifications that fall within the scope of the appended claims.

Description of Reference Numerals

[0116] 101 Terminal (UE) 102 Base Station (RAN, gNB, base station) 103 AMF 104 AUSF 105 UDM 201 Terminal (UE) 202 Base Station 203 AMF 205 SMF 206 NSACF 301 Terminal 302 Base Station 303 AMF 305 SMF 306 NSACF 308 UDM 401 UE 401 Terminal 402 Base Station 403 AMF 405 SMF 406 NSACF 510 Control Unit 520 Transceiver Unit 523 Receiver 525 Transmitter 610 Control Unit 620 Transceiver Unit 623 Receiver 625 Transmitter

Claims

1. A method performed by an AMF (access and mobility management function) of a communication system, comprising: receiving, from a terminal, a first message for a request to establish a PDU (protocol data unit) session including network slice information; selecting alternative network slice information that is an alternative to the network slice information; selecting an SMF (session management function) based on the alternative network slice information; transmitting, to the SMF selected based on the alternative network slice information, a second message for establishing the PDU session, the second message including the alternative network slice information.

2. The method according to claim 1, wherein the alternative network slice information is selected from at least one allowed network slice information.

3. In the first message, the network slice information includes S-NSSAI (single-network slice selection assistance information) of the network slice, The method according to claim 1, wherein the alternative network slice information included in the second message includes S-NSSAI of an alternative network slice.

4. The method according to claim 1, further comprising receiving, from a UDM (unified data management), at least one network slice information and at least one alternative network slice information associated with each of the at least one network slice information.

5. The step of selecting the alternative network slice information includes: identifying whether a network slice is available; selecting, when the network slice is not available, the alternative network slice information that is an alternative to the network slice information.

6. The step of identifying whether the network slice is available includes: Receiving, from an SMF, a third message including information indicating whether the network slice is available; Identifying whether the network slice is available based on the information indicating whether the network slice is available; and The method according to claim 5, wherein the third message further includes the alternative network slice information that is an alternative to the network slice information.

7. The first message further includes at least one of a requested DNN (data network name), a PDU session identifier, or a PDU session establishment request message. The method according to claim 3, wherein the second message further includes at least one of the requested DNN, the PDU session identifier, or the PDU session establishment request message.

8. The method according to claim 5, wherein the network slice is not available when the number of established PDU sessions is the same as the maximum number of PDU sessions for the network slice, or when the number of registered terminals is the same as the maximum number of possible terminals for the network slice.

9. An AMF (access and mobility management function) of a communication system, comprising: A transceiver; Connected to the transceiver, Receiving, from a terminal, a first message for a request to establish a PDU (protocol data unit) session including network slice information; Selecting alternative network slice information that is an alternative to the network slice information; Selecting an SMF (session management function) based on the alternative network slice information; and A control unit that includes the alternative network slice information and transmits a second message for establishing the PDU session to the SMF selected based on the alternative network slice information.

10. The AMF according to claim 9, wherein the alternative network slice information is selected from at least one allowed network slice information.

11. In the first message, the network slice information includes the S-NSSAI (single-network slice selection assistance information) of the network slice, The AMF according to claim 9, wherein the alternative network slice information included in the second message includes the S-NSSAI of the alternative network slice.

12. The control unit, The AMF according to claim 9, wherein the control unit receives at least one network slice information and at least one alternative network slice information associated with each of the at least one network slice information from a UDM (unified data management).

13. The control unit, Identifies whether a network slice is available, The AMF according to claim 9, wherein when the network slice is not available, the control unit selects the alternative network slice information that is an alternative to the network slice information.

14. The control unit, Receives a third message including information indicating whether the network slice is available from an SMF, Identifies whether the network slice is available based on the information indicating whether the network slice is available, The AMF according to claim 13, wherein the third message further includes the alternative network slice information that is an alternative to the network slice information.

15. The first message further includes at least one of a requested DNN (data network name), a PDU session identifier, or a PDU session establishment request message, The AMF according to claim 11, wherein the second message further includes at least one of the requested DNN, the PDU session identifier, or the PDU session establishment request message.

16. The AMF according to claim 13, wherein the network slice is not available when the number of established PDU sessions is the same as the maximum number of PDU sessions for the network slice, or when the number of registered terminals is the same as the maximum number of possible terminals for the network slice.

17. A method performed by a terminal of a wireless communication system, comprising: sending a message for a request to establish a PDU (protocol data unit) session including network slice information to an AMF (access and mobility management function); establishing an SMF (session management function) and a PDU session based on alternative network slice information that is an alternative to the network slice information; wherein the SMF is selected based on the alternative network slice information selected by an AMF (access and mobility management function).

18. The method according to claim 17, wherein in the message, the network slice information includes S-NSSAI (single-network slice selection assistance information) of the network slice.

19. The method according to claim 17, wherein at least one network slice information and at least one alternative network slice information associated with each of the at least one network slice information are stored in a UDM (unified data management).

20. The method according to claim 18, wherein the message further includes at least one of a requested DNN (data network name), a PDU session identifier, or a PDU session establishment request message.

21. The method according to claim 17, wherein when the number of established PDU sessions is the same as the maximum number of PDU sessions for a network slice, or when the number of registered terminals is the same as the maximum number of possible terminals for the network slice, the network slice information is replaced with the alternative network slice information.

22. A terminal of a wireless communication system, comprising: a transceiver; coupled to the transceiver, Send a message for the establishment request of a PDU (protocol data unit) session containing network slice information to the AMF (access and mobility management function). Based on alternative network slice information that is an alternative to the network slice information, it includes a control unit that establishes an SMF (session management function) and a PDU session. The terminal is characterized in that the SMF is selected based on the alternative network slice information selected by the AMF (access and mobility management function).

23. The terminal according to claim 22, wherein in the message, the network slice information includes the S-NSSAI (single-network slice selection assistance information) of the network slice.

24. The terminal according to claim 22, wherein at least one network slice information and at least one alternative network slice information associated with each of the at least one network slice information are stored in the UDM (unified data management).

25. The terminal according to claim 23, wherein the message further includes at least one of the requested DNN (data network name), PDU session identifier, or PDU session establishment request message.

26. The terminal according to claim 22, wherein when the number of established PDU sessions is the same as the maximum number of PDU sessions for the network slice, or when the number of registered terminals is the same as the maximum number of possible terminals for the network slice, the network slice information is replaced by the alternative network slice information.

Images