Method and device for session setup and handover

Abstract

A method and device for session setup and handover in a wireless communication system are provided, the method comprising: receiving a message from a second node, the message comprising single network slice selection assistance information (S-NSSAI) for a protocol data unit (PDU) session; and allocating session resources for the PDU session based on the message received from the second node, where if the S-NSSAI for the PDU session is supported by the first node, the session resources for the PDU session comprise resources associated with the S-NSSAI for the PDU session, and if the S-NSSAI for the PDU session is not supported by the first node or resources associated with the S-NSSAI are unavailable or overloaded, the session resources for the PDU session comprise other resources available for the PDU session.

Description

Technical Field

[0001] The present disclosure relates to methods and devices for session setup and handover in a wireless communication system.

Background Art

[0002] Since the deployment of 4G communication systems, efforts have been made to develop improved 5G or pre-5G communication systems to meet the increasing demand for wireless data communication services. Therefore, the 5G or pre-5G communication system is also referred to as "Beyond 4G Network" or "Post LTE System".

[0003] Wireless communication is one of the most successful innovations in modern history. Recently, the number of subscribers to wireless communication services has exceeded 5 billion and continues to grow rapidly. As the popularity of smartphones and other mobile data devices (such as tablet computers, notebook computers, netbooks, e-book readers, machine-type devices, etc.) among consumers and enterprises increases, the demand for wireless data traffic is increasing rapidly. To cope with the rapid increase in mobile data traffic and support new applications and deployments, it is very important to improve the efficiency and coverage of wireless interfaces.

[0004] The present disclosure provides an improved session setup method, a session handover method, and their devices targeted at the problem of service interruption due to session handover failure or session setup failure in the process of session setup when a user equipment (UE) moves or hands over between different base stations.

[0005] Such information is provided only as background information to assist in the understanding of the present disclosure. No determination has been made, and no judgment has been made, as to which of the above information is applicable to the present disclosure as prior art. SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0006] The present disclosure provides methods and apparatus for session setup and session handover in a wireless communication system. MEANS FOR SOLVING THE PROBLEMS

[0007] According to one aspect of the present application, methods and apparatus for session setup and handover in a wireless communication system are provided. The method includes an operation in which a first node receives a message from a second node, the message including single network slice selection assistance information (S-NSSAI) of a protocol data unit (PDU) session; and an operation in which the first node allocates resources of the PDU session based on the message received from the second node, where, when the first node supports the S-NSSAI of the PDU session, the first node allocates resources of the S-NSSAI of the PDU session for the PDU session, but when the first node does not support the S-NSSAI, or when the resources of the S-NSSAI are unavailable or overloaded, the first node allocates other available resources for the PDU session.

[0008] According to another aspect of the present application, in a wireless communication system, a transceiver configured to receive or transmit signals; and a message is received from a second node, the message including single network slice selection assistance information (S-NSSAI) of a PDU session; and at least one processor configured to allocate resources to the PDU session based on the message received from the second node is provided, wherein when the base station supports the S-NSSAI of the PDU session, the base station allocates the resources of the S-NSSAI of the PDU session to the PDU session, but when the base station does not support the S-NSSAI, or when the resources of the S-NSSAI are unavailable or overloaded, the base station allocates other available resources to the PDU session.

[0009] According to another aspect of the present application, in a wireless communication system, a transceiver configured to receive or transmit signals; and a message is received from a second node, the message including a single network slice selection assistance information (S-NSSAI) assigned at the initial stage of a PDU session; and at least one processor configured to allocate resources for the PDU session based at least in part on the message received from the second node is provided, where when a core network node supports the S-NSSAI of the PDU session, the core network node allocates the network slice resources of the S-NSSAI of the PDU session to the PDU session, but when the core network node does not support the S-NSSAI, or when the network slice resources of the S-NSSAI are unavailable or overloaded, the core network node allocates other available network slice resources for the PDU session.

Advantages of the Invention

[0010] The present disclosure provides an improved method and device for session setup and session handover. Thereby, problems such as service interruption due to session handover failure when a user equipment (UE) moves or hands over between different base stations, and problems of session setup failure in the session setup process can be avoided or mitigated. At the same time, during the movement and handover of the UE, or during session setup, the network can always preferentially configure an ongoing session with optimal resources. If the optimal resources are unavailable, the best can be done to provide services to the UE.

Brief Description of the Drawings

[0011]

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DETAILED DESCRIPTION OF THE INVENTION

[0012] The following description is provided to assist in a complete understanding of various embodiments of the present disclosure as defined by the claims and their equivalents, with reference to the accompanying drawings. Although various specific details are included for the purpose of assistance, these details are to be regarded only as examples. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications can be made to the various embodiments described herein without departing from the scope of the present disclosure. Further, descriptions of known functions and configurations may be omitted for clarity and conciseness.

[0013] The terms and expressions used in the following description and claims are not limited to bibliographical meanings and are used only by the inventors to enable a clear and consistent understanding of the present disclosure. Accordingly, it should be apparent to those skilled in the art that the following description of the various embodiments of the present disclosure is provided for illustrative purposes only and is not intended to limit the present disclosure as defined by the appended claims and their equivalents.

[0014] Terms such as "first," "second," etc. can be used to describe various components, but the components are not limited by these terms. These terms are used only to distinguish one component from another.

[0015] The terms used in the present disclosure are used only to describe exemplary embodiments and are not intended to limit the scope of the present disclosure. The singular form includes the plural form as well, unless the context is inconsistent. In the present disclosure, the terms "including" and "comprising" indicate the presence of the features, amounts, steps, operations, components, elements, or combinations thereof described in the present disclosure, but do not exclude the presence or possibility of addition of one or more other features, amounts, steps, operations, components, elements, or combinations thereof.

[0016] In this case, it can be understood that each block of the process flowchart and the combinations of the flowchart can be implemented by computer program instructions. Since these computer program instructions can be installed in a processor of a general-purpose computer, a dedicated computer, or other programmable data processing devices, these instructions executed by the processor of the computer or other programmable data processing devices create means for implementing the functions described in the blocks of the flowchart. These computer program instructions can also be stored in a computer-usable or computer-readable memory of the computer or other programmable data processing devices for implementing functions in a specific scheme. Therefore, the computer program instructions stored in the computer-usable or computer-readable memory can generate a product including instruction means for executing the functions described in the blocks of the flowchart. Since the computer program instructions can also be installed in the computer or other programmable data processing devices, in the computer or other programmable data processing devices, instructions for executing a series of operation steps can also provide steps for implementing the functions described in the blocks of the flowchart to create a computer-executable process for executing the computer or other programmable data processing devices.

[0017] Furthermore, each module, fragment, or part of the code represented by a block includes one or more executable instructions for performing a specific logical function. Additionally, it should be noted that in some alternative embodiments, the functions provided in the blocks may occur regardless of the order. For example, two blocks displayed consecutively may actually be executed simultaneously in some cases, or depending on the corresponding functions, they may be executed in the reverse order.

[0018] The exemplary embodiments described herein are not meant to be limiting. The matters defined in the detailed description, such as specific structures and elements, are merely specific details provided to assist those skilled in the art in fully understanding this disclosure. The aspects of the present disclosure generally described herein and illustrated in the figures can be arranged, substituted, combined, separated, and designed in various different configurations, all of which are contemplated herein. Further, unless otherwise specified in the context, the functions shown in each figure can be used in combination with each other. Therefore, it should be understood that the drawings should generally be regarded as composite parts of one or more general embodiments, but not all of the illustrated features are necessary for each embodiment.

[0019] Depending on the context, the expression "configured" used in various embodiments of the present disclosure can be interchangeably used with, for example, "adapted to", "capable of", "designed to", "adapted to", "enabled", or "able to" from the perspective of hardware or software. Alternatively, in some cases, the expression "a device configured to" may mean that the device is "able to" together with other devices or components. For example, the expression "a processor is adjusted (or configured) to execute A, B, and C" may mean a dedicated processor that only executes the corresponding operations (e.g., an embedded processor), or a general-purpose processor (e.g., a central processing unit (CPU) or an application processor (AP)) that can execute the corresponding operations by executing one or more software programs stored in a memory device.

[0020] It should be noted that there are three types of S-NSSAI related to the present disclosure. One is the S-NSSAI of the PDU session. The S-NSSAI of the PDU session is the S-NSSAI associated with the PDU session identifier included in the N2 SM information transmitted from the core network to the base station during the process of PDU session setup in the current 3GPP specification 23.502, or the S-NSSAI of the PDU session is the S-NSSAI associated with the PDU session identifier transmitted from the UE to the core network during the process of PDU session setup in the current 3GPP specification 23.502. The second is the S-NSSAI that can be configured for the PDU session when the above-mentioned S-NSSAI of the PDU session is not supported, overloaded, or unavailable, which is hereinafter referred to as the supported S-NSSAI. The third is the S-NSSAI actually configured for the PDU session by the base station according to the supported slice information, resource conditions, and / or slice policy information, which is hereinafter referred to as the configured S-NSSAI.

[0021] Modern mobile communication tends to provide users with multimedia services with high-speed transmission, as shown in FIG. 1, which is the system architecture diagram of the System Architecture Evolution (SAE).

[0022] The user equipment (UE) 101 is a terminal device for receiving data. The evolved universal terrestrial radio access network (E-UTRAN) 102 is a radio access network including a macro base station (eNodeB / NodeB) that provides an interface for the UE to access the wireless network. The mobility management entity (MME) 103 is responsible for managing the mobility context, session context, and security information of the UE. The serving gateway (SGW) 104 mainly provides user plane functions, and the MME 103 and the SGW 104 can be within the same physical entity. The packet data network gateway (PGW) 105 is responsible for charging, lawful interception, etc., and can be within the same physical entity as the SGW 104. The policy and charging rules function entity (PCRF) 106 provides quality of service (QoS) policies and charging rules. The general packet radio service support node (SGSN) 108 is a network node device that provides routing for data transmission in the universal mobile telecommunications system (UMTS). The home subscriber server (HSS) 109 is the home subsystem of the UE and is responsible for protecting user information including the current location of the user equipment, the address of the serving node, user security information, and the packet data context of the user equipment.

[0023] The system architecture diagram of the next-generation network or the 5th generation 5G network is shown in Figure 2.

[0024] User Equipment (UE) 201 is a terminal device for receiving data. The next-generation radio access network (NG-RAN) 202 is a radio access network that includes base stations (gNBs or eNBs connected to the 5G Core network (5GC), also called ng-gNBs) that provide an interface for the UE to access the wireless network. The access control and mobility management functional entity (AMF) 203 is responsible for managing the mobility context and security information of the UE. The user plane function entity (UPF) 204 mainly provides user plane functions. The session management function entity (SMF) 205 is responsible for session management. For example, the data network (DN) 206 includes operator services, Internet access, and third-party services.

[0025] This disclosure provides improved methods and devices for session setup and handover.

[0026] An exemplary method for session setup and handover according to this disclosure is shown in Figure 3. Specific descriptions of steps not related to this disclosure are omitted. This method includes the following steps.

[0027] In step 301, the first node receives a message requesting the setup of a PDU session from the second node. This message includes a single network slice selection assistance information (S-NSSAI) of the PDU session to be configured and network slice policy information. If the first node does not support the S-NSSAI, or if the resources of the S-NSSAI are unavailable or overloaded, considering the network slice policy information, the first node allocates resources to the PDU session. The network slice policy information can be a supported S-NSSAI, and the supported S-NSSAI can be one or more S-NSSAIs. For each PDU session, the supported S-NSSAI can be one or more S-NSSAIs. If there are multiple supported S-NSSAIs, the priorities of the multiple supported S-NSSAIs may be different. For example, the S-NSSAI arranged in the front may have a higher priority than the S-NSSAI arranged in the back. When allocating resources, the first node preferentially processes the resources of the supported S-NSSAI with a higher priority.

[0028] The first node can be a base station or a core network node. The second node can be a core network node or a base station. The core network node can be an SMF or an AMF. As an example, a message received by the first node from the second node can be sent from a core network node as the second node to a base station as the first node, from a first base station as the second node to a second base station as the first node (e.g., from a source base station to a target base station), from a first core network as the second node to a second core network node as the first node (e.g., from a source core network to a target core network node), or from a base station as the first node to a core network node as the second node. Depending on the specific implementation of the first node and the second node, the message can be, for example, an initial UE context setup request message (when the first node is a base station and the second node is a core network node), a PDU session resource setup request message (when the first node is a base station and the second node is a core network node), a handover request message (when the first node is a target base station and the second node is a core network node, or when the first node is a target base station and the second node is a source base station), a handover required message (when the first node is a source core network node and the second node is a source base station), a path switch request acknowledgement message (when the first node is a target base station and the second node is a core network node), or a create UE context request message (when the first node is a target core network node and the second node is a source core network node), etc. The above enumeration is merely an example and not a limitation.

[0029] The network slice policy information can be determined considering the network slice selection policy (NSSP), the UE subscription information, the quality of service (QoS) information of the traffic, the S-NSSAI supported by the AMF, and / or the S-NSSAI supported by the SMF, etc. The entity that determines the network slice policy information can be a core network node.

[0030] In step 302, the first node receives a message for session setup request. The first node stores the received PDU session information, such as the S-NSSAI of the PDU session and the network slice policy information.

[0031] When the first node allocates resources to the PDU session for which the setup is requested, or when it is necessary to reallocate resources when the slice is overloaded, the first node considers the S-NSSAI in the message. If the first node or the cell of the first node does not support the S-NSSAI, or if the slice resources of the S-NSSAI are overloaded or unavailable, the first node allocates resources to the PDU session considering the network slice policy information. For example, the first node considers allocating resources of the supported S-NSSAI. If the message received by the first node contains multiple supported S-NSSAIs, the first node gives priority to the slice resources of the S-NSSAI with a higher priority.

[0032] This method may further include the following steps.

[0033] The first node transmits the actually configured S-NSSAI for the PDU session to the core network. According to the actually configured S-NSSAI for the UE, the core network can reselect the session management function entity and / or the user plane function entity of the PDU session for the UE. For example, the base station transmits the actually configured S-NSSAI for the PDU session to the AMF, and the AMF reselects the SMF and / or UPF for the UE's PDU session. Alternatively, the base station transmits the actually configured S-NSSAI for the PDU session to the SMF, and the SMF reselects the UPF for the UE's PDU session. This step is applicable when the first node is a base station.

[0034] When this method is used for handover, the second base station (target base station) does not support the S-NSSAI of the PDU session, and according to the network slice policy information, another network slice resource is configured for the PDU session. As described in step 301, when the second base station as the source base station triggers the handover of the UE to the third base station, the handover request message includes the S-NSSAI of the PDU session and the network slice policy information. If the third base station supports the S-NSSAI, the third base station configures the PDU session on the S-NSSAI resource for the PDU session. By this method, the optimal resources can always be configured for the UE's PDU session.

[0035] When this method is only used for handover, as described in step 301, when the source base station triggers the handover of the UE to the target base station, the message is a handover request message including the S-NSSAI of the PDU session and network slice policy information; when the resources actually configured by the source base station for the PDU session are the resources of the configured S-NSSAI of the selected PDU session based on the network slice policy information, the handover request message can include the configured S-NSSAI. When the target base station supports the S-NSSAI of the PDU session, the PDU session is configured with the resources of the S-NSSAI for the PDU session. When the target base station does not support the S-NSSAI of the PDU session, or the S-NSSAI of the PDU session is overloaded or unavailable, other network slice resources are configured for the PDU session according to the network slice policy information. By this method, the optimal resources can always be configured for the PDU session of the UE. At this point, the description of the exemplary PDU session setup method and the exemplary handover method of the present disclosure is completed. This method can avoid or mitigate the problem of service interruption due to the failure of session handover when the UE moves or hands over between different base stations, or the problem of session setup failure in the process of session setup. At the same time, during the process of UE movement and handover, or session setup, the network can always preferentially allocate the ongoing session to the optimal resources. If the optimal resources are not available, the best efforts can be made to provide services to the UE. Also, after multiple handovers, it can be confirmed that the optimal resources are always configured for the PDU session of the UE.

[0036] An embodiment of the method for session setup and handover of the present disclosure is shown in FIG. 4. Specific descriptions of steps not related to the present disclosure are omitted. The following steps are included.

[0037] In step 401, the UE initiates a non-access stratum (NAS) PDU session setup request message to the AMF. This message includes a PDU session identifier, one or more S-NSSAIs, a UE and core network interface (N1) session management (SM) container. The S-NSSAI exists in the NSSAI permitted for the current access type.

[0038] In step 402, the AMF generates network slice policy information. The AMF may determine the network slice policy information for each PDU session according to the network slice policy (NSSP), the UE's subscription information, the UE's permitted NSSAI, the S-NSSAI supported by the base station serving the UE, and / or the AMF, and / or the SMF, etc. The network slice policy information is a supported S-NSSAI, and the supported S-NSSAI can be one or more. For each PDU session, the supported S-NSSAI can be one or more. If there are multiple supported S-NSSAIs, the multiple supported S-NSSAIs can have different priorities. For example, the S-NSSAI arranged in the front may have a higher priority than the S-NSSAI arranged in the back.

[0039] When the AMF selects an SMF, if it is necessary to inquire about the network slice selection function (NSSF) and the network repository function (NRF), the network slice policy information can be transmitted in the network slice selection acquisition process between the AMF and the NSSF and the network function discovery request process between the AMF and the NSSF so that a more suitable SMF can be selected. When multiple SMFs support the S-NSSAI of the requested PDU session, the SMF that supports the most supported S-NSSAI with the network slice policy information is selected from among the multiple SMFs.

[0040] The AMF stores the S-NSSAI of the PDU session and the network slice policy information.

[0041] In step 403, the AMF sends a session management context creation request message to the selected SMF, which can convey the network slice policy information of each PDU session requested by the SMF. If the SMF does not support the S-NSSAI with the network slice policy, the SMF updates the network slice policy information so that all the S-NSSAIs of the network slice policy are supported by the SMF.

[0042] In step 404, the SMF sends a message for creating a session management context response to the AMF, including the updated network slice policy information of each PDU session managed by the SMF. The AMF stores the updated network slice policy information.

[0043] In step 405, the AMF initiates an initial context setup request message or a PDU session resource setup request message to the base station, and this message conveys the S-NSSAI and network slice policy information necessary to set up the PDU session.

[0044] It should be noted that there are three types of S-NSSAI related to this disclosure. One is the S-NSSAI of the PDU session. The S-NSSAI of the PDU session is the S-NSSAI associated with the PDU session identifier included in the N2SM information transmitted from the core network to the base station during the PDU session setup process in the current 3GPP specification 23.502, or the S-NSSAI of the PDU session is the S-NSSAI associated with the PDU session identifier transmitted from the UE to the core network during the PDU session setup process in the current 3GPP specification 23.502. The second is the S-NSSAI that can be configured for the PDU session when the S-NSSAI of the PDU session is not supported or not useful, hereinafter referred to as the supported S-NSSAI. The third is the S-NSSAI actually configured for the PDU session by the base station according to the supported slice information, resource conditions, and / or slice policy information, hereinafter referred to as the configured S-NSSAI.

[0045] In the case of a PDU session that requires setup, the base station preferentially configures the resources of the S-NSSAI of the PDU session for the PDU session for which setup is requested. If the base station does not support the S-NSSAI of the PDU session, or if the slice resources of the S-NSSAI of the PDU session are overloaded or unavailable, the base station can select an S-NSSAI that provides services to the PDU session according to the network slice policy information, and the base station can select a higher-priority S-NSSAI from those supported by the base station with the network slice policy information. The S-NSSAI selected by the base station from the network slice policy information is the configured S-NSSAI, which is a conditional information element and exists only when the network slice resources corresponding to the S-NSSAI of the PDU session are not supported, overloaded, or unavailable. When the network slice policy information is the supported S-NSSAI, the base station selects the configured S-NSSAI from the supported S-NSSAI.

[0046] The base station stores the S-NSSAI, the configured S-NSSAI, and the network slice policy information in all PDU sessions.

[0047] In step 406, the base station sends a radio resource control (RRC) reconfiguration message to the UE. This message includes a NAS message for the completion of the PDU session setup that transmits the S-NSSAI and the configured S-NSSAI of each PDU session. When the configured S-NSSAI is displayed, it means that the network slice resources used in the corresponding PDU session are not the slice resources corresponding to the S-NSSAI of the PDU session, but the slice resources corresponding to the supported S-NSSAI.

[0048] Upon receiving a message, the UE stores information on the S-NSSAI and the configured S-NSSAI for all PDU sessions.

[0049] In step 407, the base station transmits an initial context setup response message or a PDU session resource setup response message to the AMF, and this message can convey the configured S-NSSAI of the PDU session.

[0050] In step 408, when the configured S-NSSAI is conveyed in the message, the configured S-NSSAI may be conveyed in an update session management context request transmitted from the AMF to the SMF.

[0051] In step 409, the SMF can reselect a UPF for the PDU session according to the configured S-NSSAI and execute a UPF selection process.

[0052] At this point, the description of the embodiments of the exemplary PDU session setup method and the exemplary handover method of the present disclosure is completed. This method can avoid or mitigate the problem of service interruption due to session handover failure when the UE moves or hands over between different base stations. At the same time, during the movement and handover of the UE, the network can always preferentially configure the ongoing sessions to the optimal resources. If the optimal resources are not available, it can do its best to provide services to the UE. Also, after multiple handovers, it can be confirmed that the optimal resources are always configured for the PDU session of the UE.

[0053] Another embodiment of the session setup and handover method of the present disclosure is shown in FIG. 5. Specific descriptions of steps not related to the present disclosure are omitted. This method includes the following steps.

[0054] In step 501, the UE starts an NAS PDU session setup request message to the AMF, which includes a PDU session identifier, one or more S-NSSAIs, and an N1 session management (SM) container. The S-NSSAI exists in the NSSAI permitted for the current access type.

[0055] In step 502, when the AMF needs to query the NSSF and the NRF when selecting an SMF, the NSSP can be executed so that a more appropriate SMF is selected in the network slice selection acquisition process between the AMF and the NSSF and in the network function discovery request process between the AMF and the NRF.

[0056] The AMF starts a session management context creation request message to the SMF, which can convey the NSSP, the UE's subscription information, QoS information, the permitted NSSAI, and / or the S-NSSAI supported by the network node providing services to the UE, etc. The network nodes include core network entities and base stations.

[0057] In step 503, the SMF can determine the network slice policy information for each PDU session according to the NSSP, the UE's subscription information, QoS information, the permitted NSSAI, and / or the S-NSSAI supported by the network entity providing services to the UE, etc. The network slice policy information can be a supported S-NSSAI, and there can be one or more supported S-NSSAIs. For each PDU session, there can be one or more supported S-NSSAIs. When there are multiple supported S-NSSAIs, the priorities of the multiple supported S-NSSAIs may be different. For example, the S-NSSAI arranged in the front may have a higher priority than the S-NSSAI arranged in the back.

[0058] The SMF stores the S-NSSAI of the PDU session and the network slice policy information.

[0059] In step 504, the SMF sends a message for creating a session management context response, which includes the S-NSSAI and network slice policy information of each PDU session managed by the SMF, to the AMF. The AMF stores the network slice policy information.

[0060] In step 505, the AMF initiates an initial context setup request message or a PDU session resource setup request message to the base station, and this message conveys the S-NSSAI and network slice policy information necessary to set up the PDU session.

[0061] In the case of a PDU session that needs to be set up, the base station preferentially configures the resources of the S-NSSAI of the PDU session for the PDU session for which the setup is requested. If the base station does not support the S-NSSAI of the PDU session, or if the slice resources of the S-NSSAI of the PDU session are overloaded or unavailable, the base station can select the S-NSSAI that serves the PDU session according to the network slice policy information, and the base station can select the S-NSSAI with a higher priority from those supported by the base station with the network slice policy information. The S-NSSAI selected by the base station from the network slice policy information is called the configured S-NSSAI, which is a conditional information element and exists only when the network slice resources corresponding to the S-NSSAI of the PDU session are not supported, overloaded, or unavailable. When the network slice policy information is the supported S-NSSAI, the base station selects the configured S-NSSAI from the supported S-NSSAI.

[0062] The base station stores the S-NSSAI, the composed S-NSSAI, and the network slice policy information in all PDU sessions.

[0063] In step 506, the base station sends an RRC reconfiguration message to the UE. This message includes the NAS message for the completion of PDU session setup, which transmits the S-NSSAI and the composed S-NSSAI of each PDU session. When the composed S-NSSAI is indicated, it means that the network slice resources used in the corresponding PDU session are the slice resources corresponding to the serving S-NSSAI, rather than the slice resources of the S-NSSAI of the PDU session.

[0064] Upon receiving the message, the UE stores the information of the S-NSSAI and the composed S-NSSAI of all PDU sessions.

[0065] In step 507, the base station sends an initial context setup response message or a PDU session resource setup response message to the AMF, and this message can transmit the composed S-NSSAI of the PDU session. In step 508, when the composed S-NSSAI is transmitted in the message, the composed S-NSSAI may be transmitted in the update session management context request sent from the AMF to the SMF. In step 509, the SMF can reselect the UPF for the PDU session according to the composed S-NSSAI and execute the UPF selection process. Also, when the SMF does not receive the information of the composed S-NSSAI in the message, the SMF recognizes that the corresponding PDU session is using the slice resources of the S-NSSAI of the PDU session.

[0066] At this point, the description of another embodiment of the exemplary PDU session setup method and the exemplary handover method of the present disclosure is completed. This method can avoid or mitigate the problem of service interruption due to session handover failure when the UE moves or hands over between different base stations. At the same time, during the movement and handover of the UE, the network can always preferentially configure the ongoing sessions to the optimal resources. If the optimal resources are not available, the best effort can be made to provide services to the UE. Also, after multiple handovers, it can be confirmed that the optimal resources are always configured for the PDU session of the UE.

[0067] Another embodiment of the session setup and handover method of the present disclosure is shown in FIG. 6. Specific descriptions of steps not related to the present disclosure are omitted. This method includes the following steps.

[0068] In step 601, the source base station transmits a handover request message to the target base station, and this message includes the S-NSSAI, the configured S-NSSAI, and / or network slice policy information for each PDU session for which setup is requested. The configured S-NSSAI is a conditional information element and is only displayed when the slice resource actually used by the PDU session at the source base station is the resource corresponding to the serving S-NSSAI. The target base station preferentially configures the resources of the S-NSSAI of the PDU session for the PDU session for which setup is requested. If the target base station does not support the S-NSSAI of the PDU session, or if the slice resources of the S-NSSAI are overloaded or unavailable, the target base station can select the slice resources serving the PDU session according to the network slice policy information. If the network slice policy information includes a plurality of supported S-NSSAIs and / or priority information of the supported S-NSSAIs, the target base station selects the resources of the S-NSSAI with the highest priority. For example, the target base station can select the S-NSSAI with the highest priority supported by the target base station in the network slice policy information. When the selection is successful, the newly selected S-NSSAI is indicated by the configured S-NSSAI.

[0069] If the target base station receives the configured S-NSSAI and supports the S-NSSAI of the PDU session, the target base station reselects the slice resources of the S-NSSAI of the PDU session for the PDU session so that the PDU session always uses the optimal slice resources supported by the network. When the selection is successful, the target base station deletes the information of the configured S-NSSAI in the PDU session context.

[0070] The target base station stores the network slice information actually configured for the PDU session.

[0071] In step 602, the target base station sends a handover request confirmation message to the source base station. This message contains a target to a source transparent container. When the network slice resource serving the PDU session is the slice resource of the configured S-NSSAI, information regarding the S-NSSAI configured for the PDU session is transmitted in the message.

[0072] In step 603, after the handover is completed, when the slice resource of the PDU session is the resource of the configured S-NSSAI, the source base station sends a handover execution command to the UE via an RRC reconfiguration message that transmits the configured S-NSSAI of the PDU session. The UE stores the information of the configured S-NSSAI of all PDU sessions. Also, when the UE does not receive the information of the S-NSSAI configured in the message, the UE recognizes that the corresponding PDU session is using the slice resource of the S-NSSAI of the PDU session.

[0073] The UE sends an RRC reconfiguration complete message to the target base station to indicate that the handover is completed.

[0074] In step 604, the target base station starts a path switch request to the AMF that transmits the S-NSSAI configured for the PDU session.

[0075] In step 605, the AMF sends the S-NSSAI configured for the PDU session to the SMF via an update session management context request message. When the SMF does not receive the information of the configured S-NSSAI in the message, the SMF recognizes that the corresponding PDU session is using the slice resource of the S-NSSAI of the PDU session.

[0076] In step 607, the slice resources actually used by the PDU session can be changed, for example, from the slice resources of the S-NSSAI of the PDU session to the resources of the configured S-NSSAI, or from the resources of the configured S-NSSAI to the slice resources of the S-NSSAI of the PDU session. According to the changed S-NSSAI information, the SMF may reselect the UPF of the PDU session and execute the UPF selection process.

[0077] At this point, the description of yet another embodiment of the exemplary PDU session setup method and the exemplary handover method of the present disclosure is completed. This method can avoid or mitigate the problem of service interruption due to session handover failure when the UE moves or hands over between different base stations. At the same time, during the movement and handover of the UE, the network can always preferentially configure the ongoing sessions to the optimal resources. If the optimal resources are not available, the best efforts can be made to provide services to the UE. Also, after multiple handovers, it can be confirmed that the optimal resources are always configured for the PDU session of the UE.

[0078] Yet another embodiment of the session setup and handover method of the present disclosure is shown in FIG. 7. The specific description of the steps not related to the present disclosure is omitted. This method includes the following steps.

[0079] In step 701, the source base station initiates a handover request message to the source AMF. This message conveys the S-NSSAI, the configured S-NSSAI, and / or the network slice policy information to each requested PDU session. The configured S-NSSAI is a conditional information element that is only displayed when the slice resources actually used by the PDU session at the source base station are the resources corresponding to the serving S-NSSAI.

[0080] In step 702, the source AMF sends a UE context creation request message to the target AMF, and this message includes a handover required transfer container from the source base station. The message includes an SM N2 information list, a PDU session identification list, and UE context information. The UE context information includes a PDU session identification list, SMF information corresponding to the PDU session, an S-NSSAI for the PDU session, and a configured S-NSSAI for the PDU session.

[0081] In step 703, the target AMF sends an update session management context request message to the SMF, and the message includes an S-NSSAI, a configured S-NSSAI and / or network slice policy information for each PDU session that is required to be set up during the handover process, and an S-NSSAI supported by the target AMF and the target base station.

[0082] For a PDU session for which setup is requested, the SMF preferentially configures the resources of the S-NSSAI of the PDU session. If the target network does not support the S-NSSAI of the PDU session, or if the slice resources of the S-NSSAI are overloaded or unavailable, the SMF may select the slice resources serving the PDU session according to the network slice policy information. If the network slice policy information includes multiple supported S-NSSAIs and / or priority information of the supported S-NSSAIs, the SMF selects the resources of the S-NSSAI with the highest priority. For example, the SMF can select the S-NSSAI with the highest priority supported by the target network in the network slice policy information. When the selection is successful, the newly selected S-NSSAI is indicated by the configured S-NSSAI. The target network includes a target base station and a target core network.

[0083] If the SMF receives the configured S-NSSAI, but the target network supports the S-NSSAI of the PDU session, the SMF reselects the slice resources of the S-NSSAI of the PDU session for the PDU session to ensure that the PDU session always uses the optimal slice resources supported by the network. When the selection is successful, the SMF deletes the information of the configured S-NSSAI in the PDU session context.

[0084] The SMF stores the network slice information actually configured for the PDU session.

[0085] The SMF can reconstruct the network slice policy information. When the SMF reconstructs the network slice policy information of a PDU session, if the S-NSSAI of the PDU session is not supported, the SMF selects the S-NSSAI configured for the PDU session according to the updated network slice policy information.

[0086] In step 704, since the slice resources actually used by the PDU session may change. For example, the slice resources actually used by the PDU session may change from the resources of the S-NSSAI of the PDU session to the resources of the configured S-NSSAI, or from the resources of the configured S-NSSAI to the resources of the S-NSSAI of the PDU session. Therefore, the SMF may reselect the UPF of the PDU session according to the changed S-NSSAI information and execute the UPF selection process.

[0087] In step 705, the SMF sends an Update Session Management Context Response message to the target AMF, and the message conveys the updated S-NSSAI, configured S-NSSAI, and / or network slice policy information of each PDU session.

[0088] In step 706, the target AMF sends a Handover Request message to the target base station, and this message conveys the S-NSSAI, configured S-NSSAI, and / or network slice policy information of each PDU session for which setup is requested. The configured S-NSSAI is a conditional information element, which is only displayed when the slice resources actually used by the PDU session at the source base station are the resources corresponding to the supported S-NSSAI.

[0089] The target base station preferentially configures the resources of the S-NSSAI of the PDU session for the PDU session for which setup is requested. If the target base station does not support the S-NSSAI of the PDU session, or if the slice resources of the S-NSSAI are overloaded or unavailable, the target base station can select the slice resources serving the PDU session according to the network slice policy information. If the network slice policy information includes a plurality of supported S-NSSAIs and / or priority information of the supported S-NSSAIs, the target base station selects the resources of the S-NSSAI with the highest priority. For example, the target base station can select the S-NSSAI with the highest priority supported by the target base station in the network slice policy information. When the selection is successful, the newly selected S-NSSAI is indicated by the configured S-NSSAI.

[0090] If the target base station receives the configured S-NSSAI and supports the S-NSSAI of the PDU session, the target base station reselects the slice resources of the S-NSSAI of the PDU session for the PDU session to ensure that the PDU session always uses the optimal slice resources supported by the network. When the selection is successful, the target base station deletes the information of the configured S-NSSAI in the PDU session context.

[0091] The target base station stores the network slice information actually configured for the PDU session.

[0092] In step 707, the target base station sends a handover request confirmation message to the target AMF. When the network slice resources serving the PDU session are the network slice resources of the configured S-NSSAI, the message conveys the information of the configured S-NSSAI of the PDU session.

[0093] In step 708, the AMF sends the configured S-NSSAI of the PDU session to the SMF via an Update Session Management Context Request message. If the SMF does not receive the information of the configured S-NSSAI in the message, the SMF recognizes that the corresponding PDU session is using the slice resources of the S-NSSAI of the PDU session.

[0094] In step 709, since the slice resources actually used by the PDU session may change, for example, the slice resources actually used by the PDU session may change from the resources of the S-NSSAI of the PDU session to the resources of the configured S-NSSAI, or from the resources of the configured S-NSSAI to the resources of the S-NSSAI of the PDU session, the SMF can reselect the UPF for the PDU session according to the changed S-NSSAI information and execute the UPF selection process.

[0095] In step 710, the SMF sends an Update Session Management Context Response message to the target AMF.

[0096] If the actually configured network slice resources for the PDU session are the resources of the configured S-NSSAI, the AMF can notify the source AMF of this via a Create UE Context Response message (step 711), the source AMF can notify the source base station of this via a Handover Command message (step 712), and then the source base station can notify the UE of this via an RRC Reconfiguration message (step 713), where all the messages transmit the configured S-NSSAI, which is successfully set up after the handover, to the PDU session.

[0097] The UE stores the information of the configured S-NSSAI of all PDU sessions.

[0098] Also, when the UE does not receive the information of the configured S-NSSAI in a message, the UE recognizes that the corresponding PDU session is using the slice resources of the S-NSSAI of the PDU session.

[0099] At this point, the description of yet another embodiment of the exemplary PDU session setup method and the exemplary handover method of the present disclosure is completed. This method can avoid or mitigate the problem of service interruption due to session handover failure when the UE moves or hands over between different base stations. At the same time, during the movement and handover of the UE, the network can always preferentially configure the ongoing session to the optimal resources. If the optimal resources are not available, the best can be done to provide services to the UE. Also, after multiple handovers, it can be guaranteed that the optimal resources are always configured for the PDU session of the UE.

[0100] Another exemplary method for session setup and handover according to the present disclosure is shown in FIG. 8. Specific descriptions of steps not related to the present disclosure are omitted. This method includes the following steps.

[0101] In step 801, the UE transmits a message requesting PDU session setup to the first node. This message includes a single network slice selection assistance information (S-NSSAI) for the PDU session and also includes network slice policy information. If the network does not support the S-NSSAI of the PDU session, or if the S-NSSAI of the PDU session is overloaded or unavailable, the network allocates resources to the PDU session considering the network slice policy information. The network slice policy information can be a supported S-NSSAI, and there can be one or more supported S-NSSAIs. For each PDU session, there can be one or more supported S-NSSAIs. If there are multiple supported S-NSSAIs, their priorities may be different. For example, the S-NSSAI placed in the front may have a higher priority than the S-NSSAI placed in the back. When allocating resources, the network prioritizes the resources of the supported S-NSSAI with a higher priority.

[0102] The UE determines the network slice policy information according to the UE's subscription information, service type, S-NSSAI supported by the UE, etc.

[0103] The first node can be a core network node or a base station. The second node can be a base station or a core network node. The core network node may be an SMF or an AMF.

[0104] In step 802, the first node transmits a message requesting setup of the PDU session to the second node.

[0105] The detailed description of step 301 is also applicable to this method and will not be repeated here. The first node (for example, a core network node) can send the network slice policy information received from the UE to the second node, or the first node can determine the network slice policy information in consideration of the network slice policy information, network slice selection policy (NSSP), subscription information of the UE, quality of service (QoS) information of the service, and S-NSSAI supported by the AMF, and / or S-NSSAI supported by the SMF received from the UE.

[0106] Step 803 is the same as step 302 and will not be described repeatedly here.

[0107] This method may further include the following steps.

[0108] The second node sends the S-NSSAI actually configured for the PDU session to the core network. According to the S-NSSAI actually configured for the UE, the core network can reselect the session management function entity and / or user plane function entity of the PDU session for the UE. For example, the base station sends the S-NSSAI actually configured for the PDU session to the AMF, and the AMF reselects the SMF and / or UPF for the UE's PDU session. Alternatively, the base station sends the S-NSSAI actually configured for the PDU session to the SMF, and the SMF reselects the UPF for the UE's PDU session.

[0109] It should be noted that step 801 is not required when this method is used for handover.

[0110] When this method is used for handover, the second base station (target base station) does not support the S-NSSAI of the PDU session, and according to the network slice policy information, resources of another network slice are configured for the PDU session. As described in step 802, when the second base station triggers a handover of the UE to the third base station, the handover request message includes the S-NSSAI of the PDU session and the network slice policy information. If the third base station supports the S-NSSAI of the PDU session, the third base station configures the PDU session with the resources of the S-NSSAI. By this method, the optimal resources can always be configured for the UE's PDU session.

[0111] When this method is only used for handover, when the source base station triggers a handover of the UE to the target base station, the message as described in step 802 is a handover request message, which includes the S-NSSAI of the PDU session and the network slice policy information; if the resources actually configured by the source base station for the PDU session are the resources of the configured S-NSSAI of the selected PDU session based on the network slice policy information, the handover request message may include the configured S-NSSAI. If the target base station supports the S-NSSAI of the PDU session, the PDU session is configured with the resources of the S-NSSAI of the PDU session. If the target base station does not support the S-NSSAI of the PDU session, or the S-NSSAI of the PDU session is overloaded or unavailable, other network slice resources are configured for the PDU session according to the network slice policy information. By this method, the optimal resources can always be configured for the UE's PDU session.

[0112] At this point, the description of another exemplary PDU session setup method and an exemplary handover method of the present disclosure is completed. This method can avoid or mitigate the problem of service interruption due to session handover failure when the UE moves or hands over between different base stations. At the same time, during the movement and handover of the UE, the network can always preferentially configure the ongoing sessions to the optimal resources. If the optimal resources are not available, the best efforts can be made to provide services to the UE. Also, after multiple handovers, it can be confirmed that the optimal resources are always configured for the PDU session of the UE. Embodiments of the session setup and handover methods of the present disclosure are shown in FIG. 9. Specific descriptions of steps not related to the present disclosure are omitted. The following steps are included.

[0113] In step 901, the UE determines network slice policy information according to the NSSP, the UE's subscription information, the service type, and / or the permitted NSSAI of the UE, etc. The network slice policy information may be a supported S-NSSAI, and the supported S-NSSAI may be one or more. For each PDU session, the supported S-NSSAI may be one or more. If there are multiple supported S-NSSAIs, the priorities of the multiple supported S-NSSAIs may be different. For example, the S-NSSAI arranged in the front may have a higher priority than the S-NSSAI arranged in the back.

[0114] In step 902, the UE initiates a PDU session setup request message to the AMF, and this message includes a PDU session identifier, one or more S-NSSAIs, network slice policy information, and an N1 session management (SM) container. The S-NSSAI exists in the permitted NSSAI of the current access type.

[0115] In step 903, the AMF can update the network slice policy information according to the base station that provides services to the UE and / or the S-NSSAI status and local configuration supported by the AMF and / or the SMF. For example, the supported S-NSSAI information therein can be updated so that the S-NSSAI in the network slice policy information is guaranteed to be supported by the AMF and the base station.

[0116] When the AMF needs to query the NSSF and the NRF when selecting the SMF, the network slice policy information can be transmitted in the network slice selection acquisition process between the AMF and the NSSF and in the network function discovery request process between the AMF and the NRF so that a more appropriate SMF can be selected. When multiple SMFs support the S-NSSAI of the requested PDU session, the SMF that supports the most supported S-NSSAI in the network slice policy information is selected from among the multiple SMFs.

[0117] The AMF stores the S-NSSAI of the PDU session and the network slice policy information.

[0118] In step 904, the AMF sends a session management context creation request message to the selected SMF, which can transmit the network slice policy information of each PDU session requested by the SMF. If the SMF does not support the S-NSSAI in the network slice policy, the SMF updates the network slice policy information so that all the S-NSSAIs in the network slice policy information are supported by the SMF.

[0119] In step 905, the SMF sends a message for creating a session management context response containing the updated network slice policy information of each PDU session managed by the SMF to the AMF. The AMF stores the updated network slice policy information.

[0120] In step 906, the AMF initiates an initial context setup request message or a PDU session resource setup request message to the base station, and this message conveys the network slice policy information and S-NSSAI required to set up the PDU session.

[0121] In the case of a PDU session that requires setup, the base station preferentially configures the resources of the S-NSSAI of the PDU session for the PDU session for which setup is requested. If the base station does not support the S-NSSAI of the PDU session, or if the slice resources of the S-NSSAI of the PDU session are overloaded or unavailable, the base station can select the S-NSSAI that serves the PDU session according to the network slice policy information, and the base station can select the S-NSSAI with a higher priority from those supported by the base station with the network slice policy information. The S-NSSAI selected by the base station from the network slice policy information is the configured S-NSSAI, which is a conditional information element and exists only when the network slice resources corresponding to the S-NSSAI of the PDU session are not supported, overloaded, or unavailable. When the network slice policy information is the supported S-NSSAI, the base station selects the configured S-NSSAI from the supported S-NSSAI. The base station stores the S-NSSAI of all PDU sessions, the configured S-NSSAI, and the network slice policy information.

[0122] In step 907, the base station transmits an RRC reconfiguration message to the UE. This message includes an NAS message indicating the completion of PDU session setup, and conveys the S-NSSAI configured with the S-NSSAI of each PDU session. When the configured S-NSSAI is displayed, it means that the network slice resources used by the corresponding PDU session are not the slice resources of the S-NSSAI of the PDU session, but the slice resources corresponding to the serving S-NSSAI.

[0123] Upon receiving the message, the UE stores the information of the S-NSSAI and the configured S-NSSAI for all PDU sessions.

[0124] In step 908, the base station transmits an initial context setup response message or a PDU session resource setup response message to the AMF, and this message can convey the configured S-NSSAI of the PDU session. In step 909, when the configured S-NSSAI is conveyed in the message, the configured S-NSSAI can be conveyed in an update session management context request transmitted from the AMF to the SMF. In step 910, the SMF can reselect a UPF for the PDU session according to the configured S-NSSAI and execute a UPF selection process.

[0125] At this point, the description of the exemplary PDU session setup method and the exemplary handover method of the present disclosure is completed. This method can avoid or mitigate the problem of service interruption due to session handover failure when the UE moves or hands over between different base stations. At the same time, during the movement and handover of the UE, the network can always preferentially configure the ongoing sessions to the optimal resources. If the optimal resources are not available, the best efforts can be made to provide services to the UE. Also, after multiple handovers, it can be confirmed that the optimal resources are always configured for the PDU session of the UE.

[0126] Another embodiment of the method for session setup and handover of the present disclosure is shown in FIG. 10. Specific descriptions of steps not related to the present disclosure are omitted. The following steps are included.

[0127] In step 1001, the UE starts a PDU session setup request message to the AMF, and this message includes a PDU session identifier, one or more S-NSSAIs, network slice policy information, and an N1 session management (SM) container. The S-NSSAI exists in the permitted NSSAI of the current access type.

[0128] The UE determines the network slice policy information according to the NSSP, the UE's subscription information, the service type, and / or the UE's permitted NSSAI, etc. The network slice policy information may be a supported S-NSSAI, and the supported S-NSSAI may be one or more. For each PDU session, the supported S-NSSAI may be one or more. When there are multiple supported S-NSSAIs, the priorities of the multiple supported S-NSSAIs may be different. For example, the S-NSSAI arranged in the front may have a higher priority than the S-NSSAI arranged in the back.

[0129] In step 1002, the AMF starts a session management context creation request message to the SMF, and this message can transmit the NSSP, the UE's subscription information, the permitted NSSAI, and / or the S-NSSAI supported by the network that provides services to the UE, etc. The network is composed of a core network and a base station.

[0130] In step 1003, the SMF updates the network slice policy information for each requested PDU session according to the NSSP, UE subscription information, QoS information, permitted NSSAI, S-NSSAI supported by the network node providing services to the UE, and / or local configuration, etc., to confirm that the S-NSSAI of the network slice policy information is supported by the network. The SMF stores the S-NSSAI of the PDU session and the network slice policy information.

[0131] In step 1004, the SMF sends a message for creating a session management context response, which includes the S-NSSAI of each PDU session managed by the SMF and the network slice policy information, to the AMF. The network slice information is the network slice policy information received from the UE or updated by the SMF. The AMF stores the received network slice policy information.

[0132] In step 1005, the AMF initiates an initial context setup request message or a PDU session resource setup request message to the base station, and this message conveys the network slice policy information and S-NSSAI required to set up the PDU session.

[0133] In the case of a PDU session that requires setup, the base station preferentially configures the resources of the S-NSSAI of the PDU session for which the setup is requested. If the base station does not support the S-NSSAI of the PDU session, or if the slice resources of the S-NSSAI of the PDU session are overloaded or unavailable, the base station can select the S-NSSAI that serves the PDU session according to the network slice policy information, and the base station can select a higher-priority S-NSSAI from those supported by the base station in the network slice policy information. The S-NSSAI selected by the base station from the network slice policy information is the configured S-NSSAI, which is a conditional information element and exists only when the network slice resources corresponding to the S-NSSAI of the PDU session are not supported, overloaded, or unavailable. When the network slice policy information is the supported S-NSSAI, the base station selects the configured S-NSSAI from the supported S-NSSAI.

[0134] The base station stores the S-NSSAI of all PDU sessions, the configured S-NSSAI, and the network slice policy information.

[0135] In step 1006, the base station sends an RRC reconfiguration message to the UE. This message includes a NAS message for PDU session setup completion that conveys the S-NSSAI of each PDU session, the configured S-NSSAI, and the network slice policy information. When the configured S-NSSAI is displayed, it means that the network slice resources used by the corresponding PDU session are not the slice resources of the S-NSSAI of the PDU session but the slice resources corresponding to the supported S-NSSAI.

[0136] Upon receiving a message, the UE stores information on the S-NSSAI of all PDU sessions and the configured S-NSSAI.

[0137] In step 1007, the base station transmits an initial context setup response message or a PDU session resource setup response message to the AMF, and this message can convey the configured S-NSSAI of the PDU session. If the configured S-NSSAI is conveyed in the message (in step 1008), the configured S-NSSAI is conveyed in an updated session management context request transmitted from the AMF to the SMF. In step 1009, the SMF can reselect the UPF for the PDU session according to the configured S-NSSAI and execute the UPF selection process.

[0138] At this point, the description of another embodiment of the exemplary PDU session setup method and the exemplary handover method of the present disclosure is completed. This method can avoid or mitigate the problem of service interruption due to session handover failure when the UE moves or hands over between different base stations. At the same time, during the movement and handover of the UE, the network can always preferentially configure the ongoing sessions to the optimal resources. If the optimal resources are not available, the best efforts can be made to provide services to the UE. Also, after multiple handovers, it can be confirmed that the optimal resources are always configured for the PDU session of the UE.

[0139] Another exemplary method for session setup and handover according to the present disclosure is shown in FIG. 11. The specific description of steps not related to the present disclosure is omitted. This method includes the following steps.

[0140] In step 1101, the first node receives a message for requesting PDU session setup from the second node. This message includes the S-NSSAI of the PDU session to be configured.

[0141] The first node can be a base station or a core network node. The second node can be a core network node or a base station. The core network node can be an SMF or an AMF. As an example, a message received by the first node from the second node can be sent from a core network node as the second node to a base station as the first node, from a first base station as the second node to a second base station as the first node (e.g., from a source base station to a target base station), from a first core network node as the second node to a second core network node as the first node (e.g., from a source core network node to a target core network node), or from a base station as the first node to a core network node as the second node. According to a specific implementation of the first node and the second node, the message can be, for example, an initial UE context setup request message (when the first node is a base station and the second node is a core network node), a PDU session resource setup request message (when the first node is a base station and the second node is a core network node), a handover request message (when the first node is a target base station and the second node is a core network node or when the first node is a target base station and the second node is a source base station), a handover required message (when the first node is a source core network node and the second node is a source base station), a path switch request confirmation message (when the first node is a target base station and the second node is a core network node), or the creation of a UE context request message (when the first node is a target core network node and the second node is a source core network node), etc. The above examples are merely examples and not limitations.

[0142] When this method is used for handover, the message for requesting the setup of a PDU session also includes the S-NSSAI actually configured for the PDU session.

[0143] In step 1102, the first node receives a message for a session setup request. The first node stores the received PDU session information including the S-NSSAI of the PDU session.

[0144] When the first node allocates resources to the PDU session for which the setup is requested, it considers the S-NSSAI in the message. If the first node or the cell of the first node does not support the S-NSSAI, the first node configures other network slice resources useful for the PDU session. The first node selects appropriate network slice resources according to, for example, the QoS parameters of the QoS flow in the PDU session, the network slice supported by the base station and / or AMF and / or SMF that provides services to the UE, and / or the configuration of network operation and maintenance (O&M).

[0145] The method may further include the following steps.

[0146] The first node sends the S-NSSAI actually configured for the PDU session to the core network. According to the S-NSSAI actually configured for the UE, the core network can reselect the session management function entity and / or user plane function entity of the PDU session for the UE. For example, the base station sends the S-NSSAI actually configured for the PDU session to the AMF, and the AMF reselects the SMF and / or UPF for the PDU session of the UE. Alternatively, the base station sends the S-NSSAI actually configured for the PDU session to the SMF, and the SMF reselects the UPF for the PDU session of the UE.

[0147] When this method is used for handover, the second base station (target base station) does not support the S-NSSAI of the PDU session, and resources of another network slice are configured for the PDU session. As described in step 1101, when the second base station triggers the handover of the UE to the third base station, the message includes the S-NSSAI of the PDU session and the S-NSSAI actually configured for the PDU session. When the third base station supports the S-NSSAI of the PDU session, the third base station configures the PDU session on the resources of the S-NSSAI of the PDU session. By this method, it is guaranteed that the optimal resources for the PDU session of the UE are always configured.

[0148] When this method is only used for handover, when the source base station triggers the handover of the UE to the target base station, the message described in step 1101 is a handover request message, which can include the S-NSSAI of the PDU session; if the resources actually configured by the source base station for the PDU session are the resources of the S-NSSAI configured for the PDU session, the handover request message may include the configured S-NSSAI. When the target base station supports the S-NSSAI of the PDU session, the PDU session is configured with the resources of the S-NSSAI of the PDU session. When the target base station does not support the S-NSSAI of the PDU session, or the S-NSSAI of the PDU session is overloaded or unavailable, the target base station selects other network slice resources for the PDU session. By this method, the optimal resources for the UE's PDU session can always be configured. At this point, the description of another exemplary PDU session setup method and exemplary handover method of the present disclosure is completed. This method can avoid or mitigate the problem of service interruption due to the failure of session handover when the UE moves or hands over between different base stations. At the same time, during the movement and handover of the UE, the network can always preferentially configure the ongoing session to the optimal resources. If the optimal resources are unavailable, the best efforts can be made to provide services to the UE. Also, after multiple handovers, it can be confirmed that the optimal resources are always configured for the UE's PDU session.

[0149] Embodiments of the session setup and handover methods of the present disclosure are shown in FIG. 12. Specific descriptions of steps not related to the present disclosure are omitted. The following steps are included.

[0150] In step 1201, the AMF initiates an initial context setup request message or a PDU session resource setup request message to the base station, and this message conveys the S-NSSAI of the PDU session to be set up and the QoS parameters of the QoS flows for which the PDU session needs to be set up.

[0151] It should be noted that there are two types of S-NSSAIs related to this disclosure. One is the S-NSSAI of the PDU session. The S-NSSAI of the PDU session is the S-NSSAI associated with the PDU session identifier included in the N2 SM information transmitted from the core network to the base station during the PDU session setup process in the current 3GPP specification 23.502, or the S-NSSAI of the PDU session is the S-NSSAI associated with the PDU session identifier transmitted from the UE to the core network during the PDU session setup process in the current 3GPP specification 23.502. The second is the S-NSSAI actually configured by the base station for the PDU session according to the supported slice information, resource conditions, and / or network operation and maintenance (O&M) configurations, etc., hereinafter referred to as the configured S-NSSAI.

[0152] In the case of a PDU session that requires setup, the base station preferentially configures the resources of the S-NSSAI of the PDU session for the PDU session for which setup is requested. If the base station does not support the S-NSSAI of the PDU session, or if the slice resources of the S-NSSAI of the PDU session are overloaded or unavailable, the base station can select the S-NSSAI that serves the PDU session. The base station selects the S-NSSAI that serves the PDU session according to the QoS parameters of the QoS flow in the PDU session, the S-NSSAI supported by the base station and / or AMF and / or SMF that provides services to the UE, and / or the configuration of network operation and maintenance (O&M). The selected S-NSSAI is the configured S-NSSAI, and the configured S-NSSAI is a conditional information element and is used only when the slice resources configured for the PDU session are the slice resources of the configured S-NSSAI rather than the slice resources of the S-NSSAI of the PDU session.

[0153] The base station stores the information of the S-NSSAI of all PDU sessions and the configured S-NSSAI.

[0154] In step 1202, the base station sends an RRC reconfiguration message to the UE. This message includes the NAS message for the completion of the PDU session setup, which conveys the S-NSSAI of each PDU session and the configured S-NSSAI. When the configured S-NSSAI is displayed, it means that the network slice resources used by the PDU session are not the slice resources corresponding to the S-NSSAI of the PDU session but the slice resources corresponding to the configured S-NSSAI.

[0155] Upon receiving the message, the UE stores the information of the configured S-NSSAI and the S-NSSAI of all PDU sessions.

[0156] In step 1203, the base station transmits an initial context setup response message or a PDU session resource setup response message to the AMF, and this message can convey the configured S-NSSAI of the PDU session. If the configured S-NSSAI is conveyed in the message, the configured S-NSSAI can be conveyed in an update session management context request transmitted from the AMF to the SMF (in step 1204), and the SMF can reselect the UPF for the PDU session according to the configured S-NSSAI and execute the UPF selection process (step 1205). If the SMF does not receive the information of the configured S-NSSAI in the message, the SMF recognizes that the corresponding PDU session is using the slice resources of the PDU session's S-NSSAI.

[0157] At this point, the description of the exemplary PDU session setup method and the exemplary handover method embodiments of the present disclosure is completed. This method can avoid or mitigate the problem of service interruption due to session handover failure when the UE moves or hands over between different base stations. At the same time, during the movement and handover of the UE, the network can always preferentially configure the ongoing session to the optimal resources. If the optimal resources are not available, the best efforts can be made to provide services to the UE. Also, after multiple handovers, it can be confirmed that the optimal resources are always configured for the UE's PDU session.

[0158] Another embodiment of the session setup and handover method of the present disclosure is shown in FIG. 13. Specific descriptions of steps not related to the present disclosure are omitted. The following steps are included.

[0159] In step 1301, the source base station transmits a handover request message to the target base station, where the message conveys the S-NSSAI of each PDU session requested, the configured S-NSSAI, and the QoS parameters of the QoS flow. The configured S-NSSAI is a conditional information element and is used only when the slice resources actually used by the PDU session at the source base station are not the slice resources corresponding to the S-NSSAI of the PDU session but the slice resources corresponding to the configured S-NSSAI.

[0160] The target base station preferentially configures the resources of the S-NSSAI of the PDU session for the PDU session for which setup is requested. If the target base station does not support the S-NSSAI of the PDU session, or if the slice resources of the S-NSSAI are overloaded or unavailable, the target base station selects the network slice resources of an appropriate S-NSSAI. The target base station can select the network slice resources of an appropriate S-NSSAI according to the QoS parameters of the QoS flow of the PDU session, the S-NSSAI supported by the target base station and the target AMF, and / or the configuration of network operation and maintenance (O&M). When the selection is successful, the newly selected S-NSSAI is indicated by the configured S-NSSAI.

[0161] When the target base station receives the configured S-NSSAI but supports the S-NSSAI of the PDU session, the target base station reselects the slice resources of the S-NSSAI of the PDU session for the PDU session, ensuring that the PDU session always uses the optimal slice resources supported by the network. When the selection is successful, the target base station deletes the information of the configured S-NSSAI in the PDU session context.

[0162] The target base station stores the network slice information actually configured for the PDU session.

[0163] In step 1302, the target sends a handover request confirmation message. The message contains the target to the source transmission container.

[0164] In step 1303, after the handover is completed, if the slice resources of the PDU session are the resources of the configured S-NSSAI, the source base station transmits a handover execution command to the UE via an RRC reconfiguration message that conveys the configured S-NSSAI of the PDU session. The UE stores the information of the configured S-NSSAI for all PDU sessions. Also, if the UE does not receive the information of the configured S-NSSAI in the message, the UE recognizes that the corresponding PDU session is using the slice resources of the S-NSSAI of the PDU session.

[0165] In step 1304, the UE sends an RRC reconfiguration complete message to the target base station to indicate that the handover is completed.

[0166] In step 1305, the target base station initiates a path switch request to the AMF and conveys the configured S-NSSAI of the PDU session.

[0167] In step 1306, the AMF sends the configured S-NSSAI of the PDU session to the SMF via an update session management context request message. If the SMF does not receive the information of the configured S-NSSAI in the message, the SMF recognizes that the corresponding PDU session is using the slice resources of the S-NSSAI of the PDU session.

[0168] The slice resources actually used by a PDU session may be changed. For example, the slice resources actually used by a PDU session may be changed from the resources of the S-NSSAI of the PDU session to the resources of the configured S-NSSAI, or from the resources of the configured S-NSSAI to the resources of the S-NSSAI of the PDU session. In step 1307, the SMF can reselect a UPF for the PDU session and execute a UPF selection process according to the changed S-NSSAI information.

[0169] At this point, the description of another embodiment of the exemplary PDU session setup method and the exemplary handover method of the present disclosure is completed. This method can avoid or mitigate the problem of service interruption due to session handover failure when the UE moves or hands over between different base stations. At the same time, during the movement and handover of the UE, the network can always preferentially configure the ongoing sessions to the optimal resources. If the optimal resources are not available, the best efforts can be made to provide services to the UE. Also, after multiple handovers, it can be confirmed that the optimal resources are always configured for the PDU session of the UE.

[0170] Yet another embodiment of the session setup and handover method of the present disclosure is shown in FIG. 14. Specific descriptions of steps not related to the present disclosure are omitted. The following steps are included.

[0171] In step 1401, the source base station initiates a handover request message to the source AMF. This message conveys the S-NSSAI of each PDU session, the configured S-NSSAI, and the QoS parameters of the QoS flow, etc. The configured S-NSSAI is a conditional information element and is only displayed when the slice resources actually used by the PDU session at the source base station are not the resources corresponding to the S-NSSAI of the PDU session but the resources corresponding to the configured S-NSSAI.

[0172] In step 1402, the source AMF sends a UE context creation request message to the target AMF, and this message includes a handover required transfer container from the source base station. The message includes an SM N2 information list, a PDU session identification list, and UE context information. The UE context information includes a PDU session identification list, SMF information corresponding to the PDU session, an S-NSSAI for the PDU session, and a configured S-NSSAI for the PDU session.

[0173] In step 1403, the target AMF sends an update session management context request message to the SMF, which includes the S-NSSAI, configured S-NSSAI and / or QoS parameters of the QoS flow of each PDU session requested to be set up during handover, and the S-NSSAI supported by the target network. The target network includes a target core network and a target base station.

[0174] The SMF preferentially configures the resources of the S-NSSAI of the PDU session for the PDU session for which setup is requested. If the target network does not support the S-NSSAI of the PDU session, or if the slice resources of the S-NSSAI are overloaded or unavailable, the SMF can reselect the network slice resources of an appropriate S-NSSAI according to the QoS parameters of the QoS flow of the PDU session, the base station providing services to the UE and / or the network slice supported by the AMF and / or SMF, and / or the configuration of network operation and maintenance (O&M). If the selection is successful, the newly selected S-NSSAI is indicated by the configured S-NSSAI. The target network is the target core network and the target core base station.

[0175] When the SMF receives the configured S-NSSAI, but the target network supports the S-NSSAI of the PDU session, the SMF reselects the slice resources of the S-NSSAI of the PDU session for the PDU session, ensuring that the PDU session always uses the optimal slice resources supported by the network. If the selection is successful, the SMF deletes the information of the configured S-NSSAI in the PDU session context.

[0176] The SMF stores the network slice information actually configured for the PDU session.

[0177] In step 1404, since the slice resources actually used by the PDU session may change, for example, the slice resources actually used by the PDU session change from the resources of the S-NSSAI of the PDU session to the resources of the configured S-NSSAI, or from the resources of the configured S-NSSAI to the resources of the S-NSSAI, the SMF can reselect the UPF for the PDU session according to the changed S-NSSAI information and execute the UPF selection process.

[0178] In step 1405, the SMF sends an Update Session Management Context Response message to the target AMF, and this message conveys the updated S-NSSAI and the configured S-NSSAI of each PDU session.

[0179] In step 1406, the target AMF sends a Handover Request message to the target base station, and this message conveys the S-NSSAI, the configured S-NSSAI, and the QoS parameters of each PDU session for which the setup is requested. The configured S-NSSAI is a conditional information element, which is only displayed when the slice resources actually used by the PDU session at the source base station are the resources corresponding to the configured S-NSSAI.

[0180] The target base station preferentially configures the resources of the S-NSSAI of the PDU session for the PDU session for which setup is requested. If the target base station does not support the S-NSSAI of the PDU session, or if the slice resources of the S-NSSAI are overloaded or unavailable, the target base station may select appropriate network slice resources of the S-NSSAI according to the QoS parameters of the QoS flow in the PDU session, the S-NSSAI supported by the target base station and the target AMF, and / or the configuration of network operation and maintenance (O&M), etc. When the selection is successful, the newly selected S-NSSAI is indicated by the configured S-NSSAI.

[0181] If the target base station receives the configured S-NSSAI but supports the S-NSSAI of the PDU session, the target base station reselects the slice resources of the S-NSSAI of the PDU session for the PDU session, ensuring that the PDU session always uses the optimal slice resources supported by the network. When the selection is successful, the target base station deletes the information of the configured S-NSSAI in the PDU session context.

[0182] The target base station stores the network slice information actually configured for the PDU session.

[0183] In step 1407, the target base station sends a handover request confirmation message to the target AMF. If the network slice resources serving the PDU session are the slice resources of the configured S-NSSAI, this message conveys the information of the configured S-NSSAI of the PDU session.

[0184] In step 1408, the AMF sends the configured S-NSSAI of the PDU session to the SMF via an update session management context request message. If the SMF does not receive the information of the configured S-NSSAI in the message, the SMF recognizes that the corresponding PDU session is using the slice resources of the PDU session's S-NSSAI. In step 1409, since the slice resources actually used by the PDU session can be changed, for example, the slice resources actually used by the PDU session may be changed from the resources of the PDU session's S-NSSAI to the resources of the configured S-NSSAI, or from the resources of the configured S-NSSAI to the resources of the PDU session's S-NSSAI. Therefore, the SMF can reselect the UPF for the PDU session and execute the UPF selection process according to the changed S-NSSAI information.

[0185] In step 1410, the SMF sends update session management context response information to the target AMF.

[0186] In step 1411, if the network slice resources actually configured for the PDU session are the resources of the configured S-NSSAI, the target AMF can notify the source AMF of this via a UE context creation response message, and the source AMF can notify the source base station via a handover command message (step 1412). Next, the source base station notifies the UE via an RRC reconfiguration message (step 1413). All the messages transmit the configured S-NSSAI to the PDU session that has been successfully set up after the handover.

[0187] The UE stores the information of the configured S-NSSAI of all PDU sessions.

[0188] Also, when the UE does not receive the information of the configured S-NSSAI in a message, the UE recognizes that the corresponding PDU session is using the slice resources of the S-NSSAI of the PDU session.

[0189] At this point, the description of yet another embodiment of the exemplary PDU session setup method and the exemplary handover method of the present disclosure is completed. This method can avoid or mitigate the problem of service interruption due to session handover failure when the UE moves or hands over between different base stations. At the same time, during the movement and handover of the UE, the network can always preferentially configure the ongoing sessions to the optimal resources. If the optimal resources are not available, it can do its best to provide services to the UE. Also, after multiple handovers, it can be guaranteed that the optimal resources are always configured for the PDU session of the UE.

[0190] FIG. 15 shows another exemplary method for PDU session setup and handover according to an embodiment of the present disclosure. The following steps are included.

[0191] In step 1501, the first entity transmits one or more slice information of each frequency or frequency band it supports to the second entity. The first entity can also transmit one or more slice information of the cell it provides to the second entity. The first entity can also transmit one or more slice information of each frequency or frequency band of the cell it serves to the second entity.

[0192] The first entity can be a base station or a base station distribution unit (gNB-DU).

[0193] The slice information can be an S-NSSAI.

[0194] The first entity can send information to the second entity via an Xn setup request, an X2 setup request, a base station configuration update request, or an F1 setup request message.

[0195] According to the received network slice information, since the second entity knows the network slice supported by the cell or the frequency or frequency band of the first entity, for example, whether to hand over the UE to the first entity, or configure the first entity as an auxiliary base station to provide services to the UE, or configure the UE to a cell on the first entity, it can determine whether to allocate resources for the UE to the first entity.

[0196] In step 1502, the second entity sends a response message to the first entity.

[0197] The second entity can send slice information of one or more of each frequency or frequency band it supports to the first entity via the response message. The second entity can also send slice information of one or more of the cells it serves to the first entity. The second entity can also send slice information of one or more of each frequency or frequency band of the cells it serves to the first entity.

[0198] The second entity can be another base station or a base station central unit (gNB-CU).

[0199] The slice information can be an S-NSSAI.

[0200] The response message can be an Xn setup response, an X2 setup response, a base station configuration update confirmation response, or an F1 setup response message.

[0201] According to the received network slice information, since the first entity knows the network slice supported by the cell or the frequency or frequency band of the second entity, for example, it can determine whether to allocate resources for the UE to the second entity by handing over the UE to the second entity or configuring the second entity as an auxiliary base station that provides services to the UE.

[0202] At this point, the description of another exemplary method for PDU session setup and handover according to the present disclosure is completed. Since this method can know the network slice supported by each frequency or frequency band or each cell of the adjacent base station or gNB-DU, it can better configure appropriate resources for the UE, avoid resource configuration or handover failures, and avoid or mitigate the problem of service interruption due to session handover failure when the UE moves or hands over between different base stations. At the same time, during the movement and handover of the UE, the network can always preferentially configure the ongoing session to the optimal resources.

[0203] At this point, the description of the PDU session setup method and handover method of the present disclosure is completed. This method can avoid or mitigate the problem of service interruption due to session handover failure when the UE moves or hands over between different base stations. At the same time, during the movement and handover of the UE, the network can always preferentially configure the ongoing session to the optimal resources. If the optimal resources are not available, it can do its best to provide services to the UE. Also, after multiple handovers, it can be guaranteed that the optimal resources are always configured for the UE's PDU session.

[0204] According to various embodiments, the first node may include a transmitter, a controller, a receiver, and a storage device. Here, the transmitter and the receiver can be implemented as a transceiver. The controller controls the overall operation of the first node. More specifically, the controller controls the first node to execute various operations as described with reference to FIGS. 1 to 15, the description of which is omitted. The transmitter transmits various signals, various messages, etc. to another entity, for example, the second node, under the control of the controller. The various signals, various messages, etc. transmitted by the transmitter are described in FIGS. 1 to 15, and the description is omitted here. The receiver receives various signals, various messages, etc. from another entity, for example, the second node, under the control of the controller. The various signals, various messages, etc. received by the receiver are described in FIGS. 1 to 15, and the description is omitted here. The storage device stores programs and various data necessary for the operation of the first node. The storage device stores various signals, various messages, etc. received by the receiver. The transmitter, the controller, the receiver, and the storage device are described as separate processors, but it should be understood that this is only for convenience of description. In other words, two or more of the transmitter, the controller, the receiver, and the storage device may be incorporated into a single processor.

[0205] According to various embodiments, the second node may include a transmitter, a controller, a receiver, and a storage device. Here, the transmitter and the receiver can be implemented as a transceiver. The controller controls the overall operation of the second node. More specifically, the controller controls the second node to execute various operations as described with reference to FIGS. 1 to 15, and the description thereof is omitted. The transmitter transmits various signals, various messages, etc. to another entity, for example, the first node under the control of the controller. Various signals, various messages, etc. transmitted by the transmitter are described in FIGS. 1 to 15, and the description thereof is omitted here. The receiver receives various signals, various messages, etc. from another entity, for example, the first node under the control of the controller. Various signals, various messages, etc. received by the receiver are described in FIGS. 1 to 15, and the description thereof is omitted here. The storage device stores programs and various data necessary for the operation of the second node. The storage device stores various signals, various messages, etc. received by the receiver. The transmitter, the controller, the receiver, and the storage device are described as separate processors, but it should be understood that this is only for the convenience of description. In other words, two or more of the transmitter, the controller, the receiver, and the storage device may be incorporated into a single processor.

[0206] According to various embodiments, the UE may include a transmitter, a controller, a receiver, and a storage device. Here, the transmitter and the receiver can be implemented as a transceiver. The controller controls the overall operation of the UE. More specifically, the controller controls the UE to execute various operations as described with reference to FIGS. 1 to 15, and the description thereof is omitted here. The transmitter transmits various signals, various messages, etc. to another entity, e.g., the BS, under the control of the controller. The various signals, various messages, etc. transmitted by the transmitter are described in FIGS. 1 to 15, and the description thereof is omitted here. The receiver receives various signals, various messages, etc. from another entity, e.g., the BS, under the control of the controller. The various signals, various messages, etc. received by the receiver are described in FIGS. 1 to 15, and the description thereof is omitted here. The storage device stores programs and various data necessary for the operation of the UE. The storage device stores various signals, various messages, etc. received by the receiver. The transmitter, the controller, the receiver, and the storage device are described as separate processors, but this should be understood to be for convenience of description only. In other words, two or more of the transmitter, the controller, the receiver, and the storage device can be incorporated into a single processor.

[0207] According to various embodiments, the BS may include a transmitter, a controller, a receiver, and a storage device. Here, the transmitter and the receiver can be implemented as a transceiver. The controller controls the overall operation of the BS. More specifically, the controller controls the BS to execute various operations as described with reference to FIGS. 1 to 15, and the description thereof is omitted here. The transmitter transmits various signals, various messages, etc. to another entity, for example, a UE under the control of the controller. The various signals, various messages, etc. transmitted by the transmitter are described in FIGS. 1 to 15, and the description thereof is omitted here. The receiver receives various signals, various messages, etc. from another entity, for example, a UE under the control of the controller. The various signals, various messages, etc. received by the receiver are described in FIGS. 1 to 15, and the description thereof is omitted here. The storage device stores programs and various data necessary for the operation of the BS. The storage device stores various signals, various messages, etc. received by the receiver. Although the transmitter, the controller, the receiver, and the storage device are described as separate processors, this should be understood to be for convenience of explanation only. In other words, two or more of the transmitter, the controller, the receiver, and the storage device may be incorporated into a single processor.

[0208] According to one aspect of the present disclosure, a method and an apparatus for session setup and handover in a wireless communication system are provided. The method includes an operation of receiving, by a first node, a message from a second node, the message including a single network slice selection assistance information S-NSSAI of a PDU session, and an operation of allocating, by the first node, resources for the PDU session based on the message received from the second node, where, when the first node supports the S-NSSAI of the PDU session, it allocates resources of the S-NSSAI of the PDU session for the PDU session, but when the first node does not support the S-NSSAI, or when the resources of the S-NSSAI are unavailable or overloaded, the first node allocates other resources useful for the PDU session.

[0209] According to another aspect of the present disclosure, in a wireless communication system, a base station includes: a transceiver configured to receive or transmit signals; and at least one processor configured to receive a message from a second node, the message including a single network slice selection assistance information (S-NSSAI) of a PDU session, and allocate resources for the PDU session based on the message received from the second node, where, when the base station supports the S-NSSAI of the PDU session, it allocates resources of the S-NSSAI of the PDU session for the PDU session, but when the base station does not support the S-NSSAI, or when the resources of the S-NSSAI are unavailable or overloaded, the base station allocates other resources useful for the PDU session.

[0210] According to another aspect of the present disclosure, a core network in a wireless communication system includes: a transceiver configured to receive or transmit signals; and at least one processor configured to receive a message from a second node, the message including a single network slice selection assistance information (S-NSSAI) assigned at the initial stage of a PDU session, and allocate resources for the PDU session based at least in part on the message received from the second node, wherein when the core network node supports the S-NSSAI of the PDU session, the core network node allocates network slice resources of the S-NSSAI of the PDU session for the PDU session, while when the core network node does not support the S-NSSAI, or when the network slice resources of the S-NSSAI are unavailable or overloaded, the core network node allocates other network slice resources useful for the PDU session.

[0211] In one embodiment, the message received by the first node from the second node includes at least one of an initial UE context setup request message received by the base station from the core network node, a PDU session resource setup request message received by the base station from the core network node, a handover request message received by the target base station from the core network node, a path switch request confirmation message received by the target base station from the core network node, a handover request message received by the target base station from the source base station, a handover request message received by the source core network node from the source base station, and a UE context creation request message received by the target core network node from the source core network node.

[0212] In one embodiment, the first node further allocates other network slice resources useful for the PDU session based on the QoS parameters of the QoS flow in the PDU session, the network slice resources supported by the base station providing services to the UE, and / or the configuration of network operation and maintenance O&M.

[0213] In one embodiment, the first node is a base station or a core network node, and the second node is a core network node or a base station.

[0214] In one embodiment, the core network node includes a session management function entity SMF or an access control and mobility management function entity AMF.

[0215] In one embodiment, the message received by the first node from the second node includes network slice policy information, and the first node allocates other resources useful for the PDU session based on the network slice policy information. In one embodiment, the network slice policy information includes one or more supported S-NSSAIs.

[0216] In one embodiment, the network slice policy information includes a plurality of supported S-NSSAIs with different priorities, and the first node gives priority to the resources of the supported S-NSSAI with a higher priority when allocating resources.

[0217] In one embodiment, the network slice policy information is generated or updated by the AMF or the SMF.

[0218] In one embodiment, the network slice policy information is based on the network slice policy information received from the user equipment UE.

[0219] In one embodiment, the network slice policy information is generated or updated based on a network slice selection policy NSSP, UE subscription information, service quality of service Qos information of the service, and an S-NSSAI supported by a base station that provides the service to the UE.

[0220] In one embodiment, the actually configured S-NSSAI corresponding to the other useful resources is transmitted to a core network node.

[0221] In one embodiment, an SMF and / or a user plane function entity UPF for a PDU session of a UE is reselected according to the actually configured S-NSSAI.

[0222] In one embodiment, when multiple SMFs support the S-NSSAI of the PDU session, the SMF that supports the most supported S-NSSAI in the network slice policy information is selected from among the multiple SMFs.

[0223] In one embodiment, when an SMF does not support a supported S-NSSAI in the received network slice policy information, the network slice policy information is updated to ensure that all S-NSSAIs in the network slice policy information are supported by the SMF.

[0224] In one embodiment, when this method is used for handover, the actually configured S-NSSAI corresponding to the other useful resources is included in a message received from a second node to a first node.

[0225] In one embodiment, when this method is used for handover, if a first node supports the S-NSSAI of the PDU session, it selects the resources of the S-NSSAI of the PDU session for the PDU session and deletes the actually configured S-NSSAI in the PDU session context.

[0226] The methods described in the claims and / or the specification according to various embodiments can be implemented by hardware, software, or a combination of hardware and software.

[0227] When this method is implemented by software, a computer-readable storage medium for storing one or more programs (software modules) may be provided. One or more programs stored in the computer-readable storage medium may be configured to be executed by one or more processors within an electronic device. At least one program may include instructions to cause the electronic device to execute the methods according to various embodiments of the present disclosure as defined by the appended claims and / or disclosed herein.

[0228] The program (software module or software) can be stored in non-volatile memory including random access memory (RAM) and flash memory, read-only memory (ROM), electrically erasable programmable ROM (EEPROM), magnetic disk storage devices, compact disk-ROM (CD-ROM), digital versatile disk (DVD), or other types of optical storage devices or magnetic tape cassettes. Alternatively, any combination of some or all of them can form a memory-stored program. Further, a plurality of such memories may be included in the electronic device.

[0229] Furthermore, the program can be stored in a connectable storage device that can access an electronic device via a communication network such as the Internet, an intranet, a local area network (LAN), a wide area LAN (WLAN), a storage area network (SAN), or a combination thereof. Such a storage device can access the electronic device that executes various embodiments of the present disclosure via an external port. Further, another storage device on the communication network can access the portable electronic device.

[0230] In the various embodiments described above of the present disclosure, according to the specific embodiments presented, the components included in the present disclosure are represented in singular or plural forms. However, the singular or plural form is selected for the convenience of explanation suitable for the presented situation, and the various embodiments of the present disclosure are not limited to its single element or plural elements. Further, the plural elements represented in the description may be composed of a single element, or the single element in the description may be composed of plural elements.

[0231] The present disclosure has been shown and described with reference to various embodiments of the present disclosure. However, it will be understood by those skilled in the art that various changes in form and detail can be made without departing from the spirit and scope of the present disclosure, which are defined by the appended claims and their equivalents.

Description of Reference Numerals

[0232] 101 User Equipment 102 General-Purpose Terrestrial Radio Access Network 103 Mobility Management Entity 104 Serving Gateway 105 Packet Data Network Gateway 106 Charging Rule Function Entity 108 General-Purpose Packet Radio Service Support Node 109 Home Subscriber Server

Claims

1. A method performed by a first base station in a wireless communication system, the method comprising: Receiving, from a second base station, a message for a handover request including at least one first single network slice selection assistance information (S-NSSAI) associated with a protocol data unit (PDU) session and at least one second S-NSSAI regarding resource reselection for the PDU session; and When resources associated with the at least one first S-NSSAI are overloaded, allocating resources for the PDU session based on the at least one second S-NSSAI.

2. Further comprising transmitting, in response to the message for the handover request, an acknowledgment message for the handover request to the second base station, The acknowledgment message for the handover request includes information related to at least one other S-NSSAI associated with the PDU session, the method according to claim 1.

3. The method according to claim 2, further comprising transmitting a message including information associated with the at least one other S-NSSAI to an access control and mobility management function (AMF).

4. The resources for the PDU session are allocated based on at least one of the quality of service (QoS) parameters of the QoS flows in the PDU session, the network slice resources supported by a serving base station providing services to a user equipment (UE), or the configuration of network operation and maintenance, the method according to claim 1.

5. The at least one second S-NSSAI includes a plurality of assisting S-NSSAIs having different priorities, Resources associated with an assisting S-NSSAI of a specific priority among the plurality of assisting S-NSSAIs are prioritized, the method according to claim 1. **Claim 6**: The method according to claim 1, wherein the network slice policy information is generated or updated by an access control and mobility management function (AMF) entity or a session management function (SMF) entity. **Claim 7** In a first base station in a wireless communication system, the first base station comprises: a transceiver; and a controller connected to the transceiver, the controller being configured to: receive, via the transceiver, from a second base station, a message for a handover request including at least one first single network slice selection assistance information (S-NSSAI) associated with a protocol data unit (PDU) session and at least one second S-NSSAI regarding resource reselection for the PDU session; the first base station configured to allocate resources for the PDU session based on the at least one second S-NSSAI when resources associated with the at least one first S-NSSAI are overloaded. **Claim 8** The controller is further configured to: transmit, via the transceiver, an acknowledgment message for the handover request to the second base station in response to the message for the handover request, wherein the acknowledgment message for the handover request includes information associated with at least one other S-NSSAI associated with the PDU session, the first base station according to claim 7. **Claim 9** The controller is further configured to: transmit, via the transceiver, a message including information associated with the at least one other S-NSSAI to an access control and mobility management function (AMF), the first base station according to claim 8. **Claim 10** The resources for the PDU session are allocated based on at least one of the quality of service (QoS) parameters of the QoS flow in the PDU session, the network slice resources supported by the base station providing services to the user equipment (UE), or the configuration of network operation and maintenance. The first base station according to claim 7.

11. The at least one second S-NSSAI includes a plurality of supporting S-NSSAIs having different priorities. For the first base station according to claim 7, the resources related to the supporting S-NSSAI with a specific priority among the plurality of supporting S-NSSAIs are prioritized.

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