Method and apparatus for populating alternative PGW-C / SMF information

Abstract

The embodiment of the invention provides a method and device for filling alternative PGW-C / SMF information. Operations performed by an Access and Mobility Management Function (AMF) in a first telecommunications system may include receiving alternative Packet Data Network Gateway Control Plane / Session Management Function (PGW-C / SMF) information from a first PGW-C / SMF or a second SMF. The method may also include transmitting the alternative PGW-C / SMF information to a Mobility Management Entity (MME) in the second telecommunication system.

Description

Technical Field

[0001] Non-limiting and exemplary embodiments of the present disclosure generally relate to the field of communication technology, and in particular to a method and apparatus for populating alternative packet data network (PDN) gateway (PGW) control plane (PGW-C) / party session management function (SMF) information. background

[0002] This section introduces aspects that may help to better understand the present disclosure. Therefore, the statements in this section should be read in this light and should not be understood as an admission of what is or is not prior art.

[0003] In communication networks, such as New Radio (NR) or Long Term Evolution (LTE) defined by the 3rd Generation Partnership Project (3GPP), session-resilient network functions (NFs) are introduced, which group equivalent control plane NFs into NF sets. For example, several PGW control plane (PGW-C) / SMF instances can be grouped into a PGW-C / SMF set. NFs in a NF set can be interchangeable because they share the same context data. In the event of failure, load balancing, load rebalancing, etc., the NF can be replaced by an alternative NF in the same NF set. SMF can play the role of anchor SMF, intermediate SMF (I-SMF), access SMF (V-SMF) or home SMF (H-SMF) for different protocol data unit (PDU) session contexts.

[0004] In Release 17 of 3GPP, it introduced support for combined PGW-C / SMF sets to recover PDN connections or PDU sessions affected (affected by combined PGW-C / SMF failure) by (alternatively re)selecting an alternative (combined) PGW-C / SMF belonging to the same NF set, so that the PDN connection (provided by the PDN connection) to the packet data network (e.g. for application services) can be maintained. Summary of the invention

[0005] This section is intended to introduce some selected concepts in a simplified form that are further described below in the detailed description. This section is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to limit the scope of the claimed subject matter.

[0006] As specified in 3GPP TS 23.007 V17.4.1, the disclosure of which is incorporated herein by reference in its entirety, alternative PGW-C / SMF information (i.e., PGW Change Information IE (Information Element)) is provided only to the Mobile Management Entity (MME) or when the User Equipment (UE) resides in the fourth generation (4G) network, the PGW-C / SMF may send a PGW-C / SMF message to the Evolved Packet Data Gateway (ePDG). In addition, during PDN connection establishment (see Section 31.2A of 3GPP TS 23.007 V17.4.1), such alternative PGW-C / SMF information may also be populated from the source MME to the target MME during mobility (see Section 31.5 of 3GPP TS 23.007 V17.4.1 below).

[0007] However, when the UE moves from 5GS to EPS (e.g., 3gpp access or non-3gpp access), when the MME or ePDG attempts to contact the combined PGW-C / SMF, if the PGW-C / SMF is not accessible, even if the combined PGW-C / SMF set is deployed, the PDN connection cannot be moved to EPS due to the lack of alternative PGW information by the MME or ePDG, and the PDN connection that should not be interrupted is interrupted.

[0008] The problem becomes more serious when it is a home-routed PDU session involving a V-SMF or a PDU session with an intermediate SMF, without the involvement of the PGW-C / SMF during the preparation phase of the 5G to 4G mobility process.

[0009] The MME / SGSN (Serving GPRS (General Packet Radio Service) Support Node) / AMFUE Evolved Packet System (EPS) PDN connection contained in the Forward Relocation Request message and Context Response message (to be sent from the AMF to the MME during mobility from 5G to 4G) is prepared by the V / I-SMF (for home-routed PDU sessions involving the V-SMF, or PDU sessions with an intermediate SMF).

[0010] When the anchor SMF is reselected, the corresponding information in the EPSPDN connection context information will most likely be updated. For example, the Internet Protocol (IP) address of the S8-cF-TEID (full TEID (qualified terminal endpoint identifier)) may include the IP of the new anchor SMF. The pgwNodeName of different SMFs is likely to be different.

[0011] Currently, the new anchor SMF cannot notify the V-SMF / I-SMF of the updated EPS PDN connection context. If the fifth generation system (5GS) to EPS mobility occurs, the AMF will retrieve the context from the I-SMF / V-SMF based on the old information. Using the old information, the PDU session cannot be moved to EPS because the MME / SGW (Serving Gateway) will find the wrong PGW-C / SMF in EPS.

[0012] To overcome or alleviate at least one of the above problems or other problems, a solution for populating alternative PGW-C / SMF information is needed.

[0013] In a first aspect of the present disclosure, a method is provided which is performed by an access and mobility management function (AMF) in a first telecommunication system. The method may include receiving a control plane / session management function (PGW-C / SMF) information of an alternative packet data network gateway from a first PGW-C / SMF or a second SMF. The method may further include sending the alternative PGW-C / SMF information to a second mobility management entity (MME) in a second telecommunication system.

[0014] In one embodiment, receiving alternative PGW-C / SMF information that is an alternative to the PGW-C / SMF information from the first PGW-C / SMF or the second SMF may include sending a protocol data unit (PDU) session context request to the first PGW-C / SMF or the second SMF, and receiving a PDU session context response including the alternative PGW-C / SMF information from the first PGW-C / SMF or the second SMF.

[0015] In one embodiment, sending the alternative PGW-C / SMF information to the MME may include receiving a context request from the MME and sending a context response including the alternative PGW-C / SMF information to the MME.

[0016] In one embodiment, the first PGW-C / SMF may be a home PGW-C / SMF or an anchor PGW-C / SMF and / or the second SMF may be a visited SMF or an intermediate SMF.

[0017] In one embodiment, the candidate PGW-C / SMF information may include information of at least one PGW-C / SMF so that the candidate PGW-C / SMF can be selected.

[0018] In one embodiment, the alternative PGW-C / SMF information may be alternatively used by the AMF or MME or Evolved Packet Data Gateway (ePDG) to select an alternative PGW-C / SMF.

[0019] In one embodiment, the first PGW-C / SMF and the alternative PGW-C / SMF may be functionally equivalent and interchangeable, and share the same context.

[0020] In a second aspect of the present disclosure, a method performed by a first PGW-C / SMF is provided. The method may include establishing a PDU session for a user equipment (UE). The method may also include sending alternative PGW-C / SMF information to a second SMF for anchoring the PDU session of the first SMF+PGW-C or access and mobility management function (AMF). If the first PGW-C / SMF fails, an alternative PGW-C / SMF will be selected based on the alternative PGW-C / SMF information.

[0021] In one embodiment, sending the alternative PGW-C / SMF information to the second SMF may include receiving a protocol data unit (PDU) session creation request from the second SMF. The method may also include sending a PDU session creation response containing the alternative PGW-C / SMF information to the second SMF.

[0022] In one embodiment, the alternative PGW-C / SMF information may be included in the PDU session creation data of the PDU session creation response.

[0023] In one embodiment, the first PGW-C / SMF may be a home PGW-C / SMF or an anchor PGW-C / SMF and / or the second SMF may be a visited SMF or an intermediate SMF.

[0024] In one embodiment, sending the alternative PGW-C / SMF information to the second SMF may include receiving a PDU session update request from the second SMF and sending a PDU session update response including the alternative PGW-C / SMF information to the second SMF.

[0025] In one embodiment, the alternative PGW-C / SMF information may be included in the home SMF update data of the PDU session update response.

[0026] In one embodiment, the first PGW-C / SMF may be a home PGW-C / SMF or an anchor PGW-C / SMF and / or the second SMF may be a new visited SMF or a new intermediate SMF.

[0027] In one embodiment, sending the alternative PGW-C / SMF information to the second SMF may include sending a PDU session update request including the alternative PGW-C / SMF information to the second SMF and receiving a PDU session update response from the second SMF.

[0028] In one embodiment, the alternative PGW-C / SMF information may be included in the access SMF update data of the PDU session update request.

[0029] In one embodiment, the first PGW-C / SMF may be a home PGW-C / SMF or an anchor PGW-C / SMF and / or the second SMF may be a visited SMF or an intermediate SMF.

[0030] In one embodiment, sending the alternative PGW-C / SMF information to the AMF may include receiving a PDU session context request from the AMF and sending a PDU session context response including the alternative PGW-C / SMF information to the AMF.

[0031] In one embodiment, the candidate PGW-C / SMF information may include information of at least one PGW-C / SMF so that the candidate PGW-C / SMF may be selected.

[0032] In one embodiment, the alternative PGW-C / SMF information may be used by an AMF or a mobility management entity (MME) or an evolved packet data gateway (ePDG) to select an alternative PGW-C / SMF.

[0033] In one embodiment, the first PGW-C / SMF and the alternative PGW-C / SMF may be functionally equivalent and interchangeable, and share the same context.

[0034] In a third aspect of the present disclosure, a method performed by a mobile management entity (MME) is provided. The method may include sending a context request to an access and mobility management function (AMF). The method may also include receiving a context response from the AMF including first session management function (SMF) information and alternative packet data network gateway (PGW) control plane (PGW-C) / SMF information.

[0035] In one embodiment, the method may further include determining that the first PGW-C / SMF has failed. The method may further include selecting an alternative PGW-C / SMF based on the alternative PGW-C / SMF information. The method may further include sending a create session request to the alternative PGW-C / SMF.

[0036] In one embodiment, the first PGW-C / SMF may be a home PGW-C / SMF or an anchor PGW-C / SMF.

[0037] In one embodiment, the first PGW-C / SMF and the alternative PGW-C / SMF may be functionally equivalent and interchangeable, and share the same context.

[0038] In one embodiment, the candidate PGW-C / SMF information may include information of at least one PGW-C / SMF, so that the candidate PGW-C / SMF may be selected.

[0039] In a fourth aspect of the present disclosure, an access and mobility management function (AMF) is provided. The AMF includes a processor and a memory coupled to the processor. The memory contains instructions executable by the processor. The AMF is operated to receive a first second control plane / session management function (PGW-C / SMF) information of an alternative packet data network gateway from a first PGW-C / SMF or a second SMF. The AMF is further operated to send the alternative PGW-C / SMF information to a second mobile management entity (MME) in a second telecommunications system.

[0040] In a fifth aspect of the present disclosure, a first PGW-C / SMF is provided. The first PGW-C / SMF includes a processor and a memory coupled to the processor. The memory contains instructions executed by the processor. The first PGW-C / SMF is operated to establish a PDU session for a user equipment (UE). The first PGW-C / SMF is also operated to send alternative PGW-C / SMF information to a second SMF, which is used to anchor the PDU session of the first SMF+PGW-C or access and mobility management function (AMF). If the first PGW-C / SMF fails, an alternative PGW-C / SMF will be selected based on the alternative PGW-C / SMF information.

[0041] In a sixth aspect of the present disclosure, a mobile management entity (MME) is provided. The MME includes a processor and a memory coupled to the processor. The memory contains instructions executable by the processor. The MME may send a context request to an access and mobility management function (AMF). The MME may also be operable to receive a context response from the AMF, the context response including first PGW-C / SMF information and information from an alternative packet data network gateway (PGW) control plane (PGW-C) / SMF.

[0042] In a seventh aspect of the present disclosure, a first PGW-C / SMF is provided. The first PGW-C / SMF may include an establishment module configured to establish a PDU session for a user equipment (UE). The first PGW-C / SMF may also include a sending module configured to send alternative PGW-C / SMF information to a second SMF for anchoring the PDU session at the first SMF+PGW-C or access and mobility management function (AMF). If the first PGW-C / SMF fails, an alternative PGW-C / SMF will be selected based on the alternative PGW-C / SMF information.

[0043] In an eighth aspect of the present disclosure, an AMF in a first telecommunication system is provided. The AMF may include a receiving module configured to receive alternative packet data network gateway control plane / session management function (PGW-C / SMF) information from a first PGW-C / SMF or a second SMF. The AMF may include a sending module configured to send the alternative PGW-C / SMF information to a mobility management entity (MME) in a second telecommunication system.

[0044] In a ninth aspect of the present disclosure, an MME based on an embodiment of the present disclosure is provided. As shown in the figure, the MME may include a first sending module configured to send a context request to an access and mobility management function (AMF). The MME may also include a receiving module configured to receive a context response including first PGW-C / SMF information and alternative packet data network gateway (PGW) control plane (PGW-C) / SMF information from the AMF.

[0045] In one embodiment, the MME may further include a determination module configured to determine that the first SMF fails.

[0046] In one embodiment, the MME may further include a selection module configured to select an alternative PGW-C / SMF according to the alternative PGW-C / SMF information.

[0047] In one embodiment, the MME may further include a second sending module configured to send a create session request to the alternative PGW-C / SMF.

[0048] In another aspect of the present disclosure, a computer program product is provided, comprising instructions, which, when executed by at least one processor, cause the at least one processor to perform the method according to any one of the first to third aspects.

[0049] In another aspect of the present disclosure, a computer-readable storage medium is provided, which stores instructions, and when the instructions are executed by at least one processor, the at least one processor executes the method according to any one of the first to third aspects.

[0050] The embodiments of this document may provide many advantages, and the following is a non-exhaustive list of examples. In some embodiments of this document, even if the service combination PGW-C / SMF fails (as long as it belongs to the combined PGW-C / SMF set), it can be ensured that the PDU session can be successfully moved from 5G to 4G mobility. In some embodiments of the present invention, it can enable the MME or ePDG or AMF to select an alternative PGW-C / SMF based on the alternative PGW-C / SMF information. The embodiments of this document are not limited to the above-mentioned features and advantages. Those skilled in the art will recognize additional features and advantages after reading the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] The above and other aspects, features and advantages of various embodiments of the present disclosure will become more apparent through the following detailed description in conjunction with the accompanying drawings, in which the same reference numerals or letters are used to represent the same or equivalent elements. The accompanying drawings are shown to facilitate a better understanding of the embodiments of the present disclosure and are not necessarily drawn to scale, wherein:

[0052] Figure 1a A flow chart showing the switching process from 5GS to EPS when supporting N26 is shown;

[0053] Figure 1b A flow chart showing 5GS to EPS idle mode mobility for the N26 interface is shown;

[0054] Figure 1c A handover flow chart from 5GS to EPC / ePDG is shown;

[0055] Figure 1d A flow chart showing a switch from 3GPP access to untrusted non-3GPP IP access via GTP on S2b;

[0056] Figure 1e A flow chart showing a switch from 3GPP access to an untrusted non-3GPP IP via PMIPv6 on S2b;

[0057] Figure 1f A flow chart showing PDN connection establishment;

[0058] Figure 2a The roaming architecture for interworking between 5GS and EPC / E-UTRAN is schematically shown;

[0059] Figure 2b The schematic diagram shows the home routing roaming architecture for interworking between 5GS and EPC / E-UTRAN;

[0060] Figure 2c The schematic diagram shows the home routing roaming architecture for intercommunication between ePDG / EPC and 5GS;

[0061] Figure 3a A flowchart of a method according to an embodiment of the present disclosure is shown;

[0062] Figure 3b A flowchart of a method according to another embodiment of the present disclosure is shown;

[0063] Figure 3c A flowchart of a method according to another embodiment of the present disclosure is shown;

[0064] Figure 3dA flowchart of a method according to another embodiment of the present disclosure is shown;

[0065] Figure 3e A flowchart of a method according to another embodiment of the present disclosure is shown;

[0066] Figure 3f A flowchart of a method according to another embodiment of the present disclosure is shown;

[0067] Figure 3g A flow chart of SMF registration according to an embodiment of the present disclosure is shown;

[0068] Figure 3h A flowchart of a method according to another embodiment of the present disclosure is shown;

[0069] Figure 4a A flowchart of a method according to another embodiment of the present disclosure is shown;

[0070] Figure 4b A flowchart of a method according to another embodiment of the present disclosure is shown;

[0071] Figure 4c A flowchart of a method according to another embodiment of the present disclosure is shown;

[0072] Figure 4d A flowchart of a method according to another embodiment of the present disclosure is shown;

[0073] Figure 4e A flowchart of a method according to another embodiment of the present disclosure is shown;

[0074] Figure 5a A flowchart of a method according to another embodiment of the present disclosure is shown;

[0075] Figure 5b A flowchart of a method according to another embodiment of the present disclosure is shown;

[0076] Figure 5c A flowchart of a method according to another embodiment of the present disclosure is shown;

[0077] Figure 5d A flowchart of a method according to another embodiment of the present disclosure is shown;

[0078] Figure 6a A flowchart of a method according to another embodiment of the present disclosure is shown;

[0079] Figure 6b A flowchart of a method according to another embodiment of the present disclosure is shown;

[0080] Figure 7a A flowchart of a method according to another embodiment of the present disclosure is shown;

[0081] Figure 7b A flowchart of a method according to another embodiment of the present disclosure is shown;

[0082] Figure 8a A flowchart of a method according to another embodiment of the present disclosure is shown;

[0083] Figure 8b A flowchart of a method according to another embodiment of the present disclosure is shown;

[0084] Fig. 9 A flowchart showing how to add PGW change information in various signaling messages according to another embodiment of the present disclosure;

[0085] Fig.10 is a block diagram illustrating an apparatus suitable for practicing some embodiments of the present disclosure;

[0086] Fig.11a is a block diagram of a first SMF according to an embodiment of the present disclosure;

[0087] Fig.11b is a block diagram illustrating a first PGW-C / SMF according to an embodiment of the present disclosure;

[0088] Fig.12 is a block diagram illustrating a second SMF according to an embodiment of the present disclosure;

[0089] Fig.13a is a block diagram of an AMF according to an embodiment of the present disclosure;

[0090] Fig.13b is a block diagram of an AMF in a first telecommunication system according to an embodiment of the present disclosure;

[0091] Fig.14 is a block diagram of an MME according to an embodiment of the present disclosure;

[0092] Fig.15 is a block diagram of a UDM according to an embodiment of the present disclosure; and

[0093] Fig.16 is a block diagram of an ePDG according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0094] Embodiments of the present disclosure are described in detail with reference to the accompanying drawings. It should be understood that these embodiments are discussed only to enable those skilled in the art to better understand and implement the present disclosure, rather than to imply any limitation on the scope of the present disclosure. References to features, advantages or similar language in this specification do not mean that all features and advantages that the present disclosure can achieve should or exist in any single embodiment of the present disclosure. On the contrary, the language referring to features and advantages should be understood to mean that specific features, advantages or characteristics described in relation to the embodiments are included in at least one embodiment of the present disclosure. In addition, the features, advantages and characteristics described in the present disclosure may be combined in one or more embodiments in any suitable manner. Those skilled in the relevant art will recognize that the present disclosure may be implemented without one or more specific features or advantages of a specific embodiment. In other cases, additional features and advantages may be recognized in certain embodiments, and these additional features and advantages may not be present in all embodiments of the present disclosure.

[0095] The term "network" as used herein refers to a network that complies with any appropriate communication standard, such as New Radio (NR), Long Term Evolution (LTE), LTE-Advanced (LTE-A), Wideband Code Division Multiple Access (WCDMA), High Speed ​​Packet Access (HSPA), Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Orthogonal Frequency Division Multiple Access (OFDMA), Single Carrier Frequency Division Multiple Access (SC-FDMA) and other wireless networks. A CDMA network can implement radio technologies such as Universal Terrestrial Radio Access (UTRA). UTRA includes other variants of WCDMA and CDMA. A TDMA network can implement radio technologies such as Global System for Mobile Communications (GSM). An OFDMA network can implement radio technologies such as Evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE802.11 (Wi-Fi), IEEE802.16 (WiMAX), IEEE802.20, Flash-OFDMA, Ad-hoc networks, wireless sensor networks, etc. In the following description, the terms "network" and "system" can be used interchangeably. In addition, communication between two devices in the network can be performed according to any suitable communication protocol, including but not limited to communication protocols defined by a standards organization (e.g., 3GPP). For example, the communication protocol may include first generation (1G), 2G, 3G, 4G, 4.5G, 5G communication protocols and / or any other protocol currently known or developed in the future.

[0096] The term "network device" or "network node" or "network function" refers to any suitable network function (NF) that can be implemented in a network element (physical or virtual) of a communication network. For example, a network function can be implemented as a network element on dedicated hardware, a software instance running on dedicated hardware, or a virtualized function instantiated on an appropriate platform (e.g., on a cloud infrastructure). For example, a 5G system (5GS) may include multiple NFs, such as AMF (Access and Mobility Management Function), SMF (Session Management Function), AUSF (Authentication Service Function), UDM (Unified Data Management), PCF (Policy Control Function), AF (Application Function), NEF (Network Exposure Function), UPF (User Plane Function) and NRF (Network Repository Function), RAN (Radio Access Network), SCP (Service Communication Agent), NWDAF (Network Data Analysis Function), NSSF (Network Slice Selection Function), NSSAAF (Network Slice Specific Authentication and Authorization Function), etc. For example, a 4G system (e.g., LTE) may include an MME (mobility management entity), an HSS (home subscriber server), a policy and charging rules function (PCRF), a packet data network gateway (PGW), a PGW control plane (PGW-C), a PGW user plane (PGW-U), a serving gateway (SGW), a SGW control plane (SGW-C), an E-UTRAN (evolved universal terrestrial radio access network) node B (eNB), etc. In other embodiments, the network function may include different types of NFs, for example, depending on the specific network.

[0097] The term "terminal device" refers to any terminal device that can access a communication network and receive services therefrom. As an example and not a limitation, a terminal device refers to a mobile terminal, a user equipment (UE) or other suitable device. A UE may be, for example, a user station (SS), a portable user station, a mobile station (MS) or an access terminal (AT). Terminal devices may include, but are not limited to, portable computers, image acquisition terminal devices such as digital cameras, game terminal devices, music storage and playback devices, mobile phones, cellular phones, smart phones, voice over IP (VoIP) phones, wireless local loop phones, tablet computers, wearable devices, personal digital assistants (PDAs), portable computers, desktop computers, wearable terminal devices, vehicle-mounted wireless terminal devices, wireless endpoints, mobile stations, notebook embedded devices (LEEs), notebook mounted devices (LMEs), USB adapters, smart devices, wireless client equipment (CPEs), etc. In the following description, the terms "terminal device", "terminal", "user equipment" and "UE" may be used interchangeably. As an example, a terminal device may represent a UE configured for communication according to one or more communication standards (e.g., LTE standards or NR standards of 3GPP) promulgated by 3GPP (Third Generation Partnership Project). As used herein, a "user equipment" or "UE" may not necessarily have a "user", i.e., a human user who owns and / or operates the associated device. In some embodiments, a terminal device may be configured to send and / or receive information without direct human interaction. For example, a terminal device may be designed to send information to a network on a predetermined schedule, when triggered by an internal or external event, or in response to a request from a communication network. Conversely, a UE may represent a device that is intended to be sold to or operated by a human user, but may not be initially associated with a specific human user.

[0098] As another example, in an Internet of Things (IoT) scenario, a terminal device may represent a machine or other device that performs monitoring and / or measurement and transmits the results of such monitoring and / or measurement to another terminal device and / or network device. In this case, the terminal device may be a machine-to-machine (M2M) device, which may be referred to as a machine type communication (MTC) device in the 3GPP context. As a specific example, the terminal device may be a UE that implements the 3GPP Narrowband Internet of Things (NB-IoT) standard. Specific examples of such machines or devices are sensors, metering devices (e.g., power meters), industrial machinery, or household or personal appliances, such as refrigerators, televisions, personal wearable devices (e.g., watches, etc.). In other scenarios, a terminal device may represent a vehicle or other device that is capable of monitoring and / or reporting its operating status or other functions related to its operation.

[0099] References in the specification to "one embodiment," "an embodiment," "an example embodiment," etc. indicate that the embodiment may include certain features, structures, or characteristics, but not every embodiment necessarily includes the certain features, structures, or characteristics. Furthermore, these phrases do not necessarily refer to the same embodiment. Furthermore, when a certain feature, structure, or characteristic is described in conjunction with an embodiment, it should be recognized that those skilled in the art may affect such feature, structure, or characteristic in conjunction with other embodiments, whether or not explicitly described.

[0100] It should be understood that although the terms "first", "second", etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. For example, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element without departing from the scope of the exemplary embodiments. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed terms.

[0101] As used herein, the phrase "at least one of A and B" or "at least one of A or B" should be understood as "only A, only B, or both A and B". The phrase "A and / or B" should be understood as "only A, only B, or both A and B".

[0102] The terms used herein are only used to describe specific embodiments and are not intended to limit the example embodiments. The singular forms "a", "an", and "the" used herein are also intended to include the plural forms, unless the context clearly indicates otherwise. It should be further understood that the terms "include", "comprise", "have", "include" and / or "comprising" used herein specify the presence of the features, elements and / or components, etc., but do not exclude the presence or addition of one or more other features, elements, components and / or combinations thereof.

[0103] It should be noted that the terms used in this article are only for the convenience of describing and distinguishing nodes, devices or networks, etc. As technology develops, other terms with similar / same meanings may also be used.

[0104] In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0105] Clause 31 of 3GPP TS 23.007 V17.4.1 describes the restoration of PDN connections after PGW-C / SMF changes, as shown below.

[0106] The process specified in clause 31 of 3GPP TS 23.007 V17.4.1 can recover PDN connections affected by PGW-C / SMF failure or reduction operations with or without restarting the PGW-C / SMF in the EPC (Evolved Packet Core), thereby maintaining the UE's connection to the PDN and corresponding services with minimal service interruption and minimal network signaling (e.g., no signaling with the UE).

[0107] The procedures specified in 3GPP TS 23.007 V17.4.1 section 31 are optional to support MME, ePDG supporting S2b over GTPv2, SGW and PGW-C / SMF.

[0108] The process specified in clause 31 of 3GPP TS 23.007 V17.4.1 applies to a combined PGW-C / SMF deployed in a PGW-C / SMF set (i.e., a set of PGW-C / SMF instances that are functionally equivalent and interchangeable and share the same context, see clause 5.21.3 of 3GPP TS 23.501 V17.2.0, the disclosure of which is incorporated herein by reference in its entirety).

[0109] In the event that a PGW-C / SMF is no longer available (e.g., the PGW-C / SMF fails but is not restarted, a scale-down operation causes the PGW-C / SMF to be de-instantiated from the PGW-C / SMF set) or the PGW-C / SMF of the PDN connection needs to be changed, other PGW-C / SMFs from the same PGW-C / SMF set may take over control of the PDN connections served by the no longer available PGW-C / SMF. When a PGW-C / SMF fails due to restart, the restarted PGW-C / SMF shall continue to support the same PDN connections as much as possible. When a PGW-C / SMF in a PGW-C / SMF set fails (whether restarted or not), the recovery (restart counter) shall not exceed S5 / S8 (assuming that the PDN connection context in the PGW-C / SMF set is still available).

[0110] The restoration of the PDN connection can be triggered by the MME (for example, when the SGW detects and reports the failure of the PGW-C to the MME), by the ePDG supporting S2b over GTPv2, or by the PGW-C / SMF (for example, a reduction operation performed by another network function such as the PCF or PGW-C / SMF reselection).

[0111] The procedure specified in clause 31 of 3GPP TS 23.007 V17.4.1 supports the restoration of home-routed PDN connections, provided that the VPLMN (visited PLMN (Public Land Mobile Network)) and HPLMN (home PLMN) support this process. If the VPLMN or HPLMN does not support this process, the existing behavior applies, for example, the MME and SGW clear all PDN connections of the PGW-C / SMF when a PGW-C / SMF failure or restart is detected, and the MME can request the UE to release and reactivate certain PDN connections (for example, IMS (IP Multimedia Subsystem) PDN connections).

[0112] Mobility from 5G to 4G (including 3GPP access and non-3GPP access) is supported, as described in Section 4.11 of 3GPP TS 23.502 V17.2.1 below, the disclosure of which is incorporated herein by reference in its entirety.

[0113] 5GS to EPS switching using N26 interface

[0114] Figure 1a The switching flow chart from 5GS to EPS when supporting N26 is shown, which is the same as Figure 4.11.1.2.1-1 of 3GPP TS23.502 V17.2.1.

[0115] In case of handover to a shared EPS network, the source NG-RAN (Next Generation RAN) determines the PLMN to be used in the target network as specified in 3GPP TS 23.501 V17.2.0. The source NG-RAN shall indicate the selected PLMN ID (identifier) ​​to be used in the target network to the AMF as part of the TAI (Tracking Area Identity) sent in the HO (Handover) Required Message.

[0116] If handover is from a shared NG-RAN, the AMF may provide an indication to the MME that the 5GS PLMN is the preferred PLMN when the UE later changes to a 5GS shared network.

[0117] During the handover procedure, as specified in 3GPP TS 23.502 V17.2.1 clause 4.9.1.3.1, the source AMF shall reject any SMF+PGW-C initiated N2 request received since the start of the handover procedure and shall include an indication that the request has been temporarily rejected due to the ongoing handover procedure.

[0118] Upon receiving a rejection of the N2 request initiated by SMF+PGW-C, indicating that the request is temporarily rejected due to the ongoing switching process, the behavior of SMF+PGW-C shall be in accordance with the manner specified in 3GPPTS23.401V17.3.0, the disclosure of which is incorporated herein by reference in its entirety.

[0119] In steps 2a-2c, the AMF determines the handover type as handover to E-UTRAN according to the "Target eNB Identifier" IE. The AMF selects the MME according to Section 4.3.8.3 of 3GPP TS 23.401 V17.3.0.

[0120] For a PDU Session, the AMF determines whether to retrieve the context including the mapped UE EPS PDN connection from the V-SMF (in case of HR (Home Routing) roaming) or SMF+PGW-C (in case of non-roaming or LBO (Local Breakout) roaming) as follows:

[0121] If the AMF determines that one or more EBIs (EPS Bearer Identifiers) can be transmitted, the AMF sends a Nsmf_PDUSession_ContextRequest to the V-SMF or SMF+PGW-C and includes any EBI values ​​that cannot be transmitted in the message.

[0122] If the target MME does not support 15 EPS bearers, the AMF determines the EBI values ​​that cannot be transmitted, i.e. the AMF determines that EBI values ​​in the range 1-4 are not transmitted to the EPS, and if there are still more than 8 EBI values ​​associated with the PDU session, the AMF determines the EBI values ​​that cannot be transmitted to the EPS based on the S-NSSAI and ARP specified in 3GPP TS 23.501 V17.2.0 clause 5.17.2.2.1.

[0123] - The AMF does not retrieve the context of PDU sessions that cannot be transferred to the EPS due to no allocated EBI, or the allocated EBI being non-transferable, or both.

[0124] The remaining steps are described in clause 4.11.1.2.1 of 3GPP TS 23.502 V17.2.1 and will not be repeated here.

[0125] 5GS to EPS Idle Mode Mobility Using N26 Interface

[0126] The 5GS to EPS idle mode mobility flow chart using the N26 interface is the same as Figure 4.11.1.3.2-1 of 3GPP TS 23.502 V17.2.1.

[0127] In case of network sharing, the UE selects the target PLMN ID according to 3GPP TS 23.501 V17.2.0 clause 5.18.3.

[0128] 3GPP TS 23.502 V17.2.1 clause 4.11.1.3.2 covers the idle mode mobility case from 5GC (5G Core) to EPC. When the UE moves from NG-RAN / 5GS to E-UTRA / EPS coverage area, it performs the Tracking Area Update procedure in E-UTRA (Evolved Universal Terrestrial Radio Access) / EPS.

[0129] The procedure specified in clause 4.11.1.3.2 of 3GPP TS 23.502 V17.2.1 involves the tracking area update to the EPC and the setup of the default EPS bearer and dedicated bearer in the EPC in steps 1-11 and reactivation as needed.

[0130] In step 5a, the AMF verifies the integrity of the TAU Request message:

[0131] For a PDU Session, the AMF determines whether to retrieve the context including the mapped UE EPS Connection from the V-SMF (in case of HR roaming) or from the SMF+PGW-C (in case of non-roaming or LBO roaming) as follows:

[0132] - If the AMF determines that one or more EBIs can be transmitted, the AMF sends a Nsmf_PDUSession_ContextRequest to the V-SMF or SMF+PGW-C and includes any EBI values ​​that cannot be transmitted in the message.

[0133] - If the target MME does not support 15 EPS bearers, the AMF determines the EBI values ​​that cannot be transferred, i.e. the AMF determines that EBI values ​​in the range 1-4 are not transferred to the EPS, and if there are still more than 8 EBI values ​​associated with the PDU session, the AMF determines the EBI values ​​that cannot be transferred to the EPS based on the S-NSSAI and ARP specified in 3GPP TS 23.501 V17.2.0 clause 5.17.2.2.1.

[0134] - The AMF shall not retrieve the context for PDU sessions that cannot be transferred to the EPS due to no EBI being allocated, or the allocated EBI being non-transferable, or both.

[0135] In non-roaming or LBO roaming, the AMF retrieves the context containing the mapped EPS bearer context.

[0136] -AMF provides the target MME capabilities in the request to the PGWC+SMF in Nsmf_PDUSession_ContextRequest to allow the SMF+PGW-C to determine whether an EPS bearer context of Ethernet PDN type or non-IP PDN type is contained.

[0137] - If the AMF includes a list of EBIs to be transferred in the Nsmf_PDUSession_ContextRequest and if the EBI value of the QoS flow associated with the default QoS rule is included in that list, the SMF+PGW-C shall not return the PDN connection context (which means that the whole PDU Session will not be transferred to EPS), otherwise if the EBI value of the QoS flow associated with the default QoS rule is not included in the list of EBIs to be transferred, the V-SMF or SMF+PGW-C shall not provide the EPS bearer context mapped from the QoS flow associated with that list.

[0138] - When AMF sends Nsmf_PDUSession_ContextRequest to V-SMF or SMF+PGW-C, AMF indicates whether the target MME supports user plane integrity protection with EPS.

[0139] The above steps are performed for all SMF+PGW-Cs corresponding to the PDU sessions of the UE associated with 3GPP access and allocated with EBI.

[0140] Nsmf_PDUSession_ContextRequest requests V-SMF to provide SMF context.

[0141] Note 1: AMF learns through local configuration whether the MME supports 15 EPS bearers, whether it supports EPS user plane integrity protection, Ethernet PDN type and / or non-IP PDN type.

[0142] The remaining steps have been described in clause 4.11.1.3.2 of 3GPP TS 23.502 V17.2.1 and will not be repeated here.

[0143] Handover from 5GS to EPC / ePDG

[0144] The switching flow chart from 5GS to EPC / ePDG is the same as Figure 4.11.4.2-1 of 3GPPTS23.502V17.2.1.

[0145] In step 2: the UE initiates the handover procedure as described in section 8.6.2.1 of 3GPPTS 23.402 V17.0.0, except for step 11 of reference figure 8.2.3-1 of 3GPPTS 23.402 V17.0.0, which corresponds to the release of resources in the source system.

[0146] The remaining steps have been described in clause 4.11.4.2 of 3GPP TS 23.502 V17.2.1 and will not be repeated here.

[0147] The flowchart for switching from 3GPP access to untrusted non-3GPP IP access, using GTP on S2b, is the same as Figure 8.6.2.1-1 of 3GPP TS 23.402 V17.0.0.

[0148] The procedure of clause 8.2.3 of 3GPP TS 23.402 V17.0.0, before step A, steps 2 to 4.

[0149] The remaining steps have been described in Clause 8.6.2.1 of 3GPP TS 23.402 V17.0.0 and will not be repeated here.

[0150] The flowchart of switching from 3GPP access to untrusted non-3GPP IP access and using PMIPv6 on S2b is the same as Figure 8.2.3-1 of 3GPP TS 23.402 V17.0.0.

[0151] In step 4: UE initiates IKEv2 tunnel establishment procedure. The ePDG IP address with which the UE needs to form an IPsec tunnel is discovered as described in 3GPP TS 23.402 V17.0.0 clause 4.5.4. After the UE is authenticated, the UE is also authorized to access the APN (Access Point Name). As part of the access authentication, the 3GPP AAA (Authentication, Authorization and Accounting) server sends the PDN GW identity to the ePDG.

[0152] The remaining steps have been described in Clause 8.2.3 of 3GPP TS 23.402 V17.0.0 and will not be repeated here.

[0153] According to 3GPPTS23.007V17.4.1, the alternative PGW-C / SMF information (i.e., PGWChangeInfoIE (information element)) is only provided to the mobile management entity (MME) or when the user equipment (UE) resides in the fourth generation (4G) network, the PGW-C / SMF will send the evolved packet data gateway (ePDG) to the PGW-C / SMF. For example, during the establishment of the PDN connection (see 3GPPTS23.007V17.4.1, Section 31.2A), such alternative PGW-C / SMF information can also be filled from the source MME to the target MME during the mobility process (see Section 31.5 of 3GPPTS23.007V17.4.1 below).

[0154] Figure 1f It shows a flow chart of PDN connection establishment, which is the same as Figure 31.2A-1 of 3GPP TS 23.007 V17.4.1.

[0155] The PDN connection shall be established as defined in clause 7.2.4. 3GPP TS 23.402 V17.0.0 adds the following content.

[0156] Step 1: During PDN connection establishment or when a PDU session is moved from 5GS to EPC / ePDG, the ePDG can signal that it supports this procedure by including a PGW Setup Support Indication in the Create Session Request.

[0157] In step 2: If the Create Session Request indicates support for this procedure, the PGW-C / SMF may return a PGW Change Information IE in the Create Session Response. The PGW Change Information IE shall contain the PGW Set FQDN or the Alternative PGW-C / SMF FQDN or the IP address of the PGW / SMF in the set; receipt of this information indicates to the ePDG that the PGW-C / SMF supports this procedure for PDN connectivity, and that if the PGW-C / SMF is no longer accessible, the PGW Set FQDN or the Alternative PGW FQDN or IP address may be used to find an alternative PGW-C / SMF instance.

[0158] Likewise, the PDU session should be moved from 5GS to EPC / ePDG as defined in 3GPP TS 23.502 V17.2.1 clause 4.11.4 with the following additions:

[0159] - the ePDG may indicate that it supports this procedure during handover from 5GS to EPC / ePDG by including a PGW Setup Support Indication in the Create Session Request (see clause 4.11.4.2 of 3GPP TS 23.502 V17.2.1); and

[0160] -If the Create Session Request received by the PGW-C / SMF indicates support for this procedure, the PGW-C / SMF may return a PGW Change Information IE (with the same content as described above) in the Create Session Response to provide the ePDG with the same indication as described above.

[0161] Clause 31.5 of 3GPP TS 23.007 V17.4.1 describes inter-MME mobility. During inter-MME mobility, the source MME shall transmit PGW change information to the target MME (if available).

[0162] However, when the UE moves from 5GS to EPS (3gpp access or non-3gpp access), when the MME or ePDG tries to contact the combined PGW-C / SMF, if the PGW-C / SMF is not accessible, even if the combined PGW-C / SMF group is deployed, the PDN connection cannot be moved to EPS due to the lack of alternative PGW information by the MME or ePDG, and the PDN connection will be interrupted, which should not happen.

[0163] The problem becomes more serious when it comes to home-routed PDU sessions of V-SMF or PDU sessions involving intermediate SMFs, where PGW-C / SMF is not involved in the preparation phase of the 5G to 4G mobility process.

[0164] The MME / SGSN (Serving GPRS (General Packet Radio Service) Support Node) / AMF UEEPS PDN connection (which will be sent from AMF to MME during mobility from 5G to 4G) is prepared by the V / I-SMF (for home-routed PDU sessions involving V-SMF, or PDU sessions with intermediate SMFs).

[0165] The following table is extracted from 3GPP TS 29.274 V17.5.0, the disclosure of which is incorporated herein by reference in its entirety. Table 7.3.1-2: MME / SGSN / AMFUEEPSPDN connections in forward relocation request Table 7.3.1-8: PGW change information with forward relocation request Table 7.3.6-2: MME / SGSN / AMFUEEPSPDN connections in context response Table 7.3.6-6: PGW change information and context response

[0166] The data type SmContextRetrievedData is specified as 3GPPTS29.502V17.4.0 and is the message body of the Nsmf_PDUSession_ContextResponse message. See also 4.11.1.2.2 and 4.11.1.3.2 of 3GPPTS29.502V17.4.0, steps 2a and 5a respectively.

[0167] The following table is extracted from 3GPP TS 29.502 V17.4.0. Table 6.1.6.2.27-1: Definition of SmContextRetrievedData type Table 6.1.6.3.2-1: Simple data types Table 6.1.6.2.31-1: Definition of EpsPdnCnxInfo type

[0168] The corresponding information in the Evolved Packet System (EPS) PDN Connection Context Information is likely to be updated, for example, the Internet Protocol (IP) address of the S8-cF-TEID (Fully Qualified Terminal Endpoint Identifier) ​​will contain the IP of the new anchor SMF. The pgwNodeName of different SMFs is likely to be different.

[0169] Currently, the new anchor SMF cannot notify the V-SMF / I-SMF of the updated EPS PDN connection context. If 5GS (fifth generation system) to EPS mobility occurs, the AMF will retrieve the context from the I-SMF / V-SMF based on the old information. With the old information, the PDU session cannot be moved to EPS because the MME / SGW (serving gateway) will find the wrong PGW-C / SMF in EPS.

[0170] To overcome or alleviate at least one of the above problems or other problems, a solution for populating alternative PGW-C / SMF information is needed.

[0171] Although the subject matter described herein can be implemented in any suitable type of system using any suitable components, the embodiments disclosed herein are directed to systems that conform to Figure 2a-2c The communication system is described with reference to the exemplary system architecture shown in FIG. Figure 2a-2cThe system architecture of the present invention only depicts some exemplary elements. In fact, the communication system may also include any additional elements suitable for supporting communication between terminal devices or between a wireless device and another communication device (such as a fixed-line phone, a service provider, or any other network node or terminal device). The communication system may provide communication and various types of services to one or more terminal devices to facilitate the terminal devices to access and / or use services provided by or through the communication system.

[0172] Figure 2a The roaming architecture for intercommunication between 5GS and EPC / E-UTRAN is schematically shown. Figure 2a The architecture is the same as Figure 4.3.1-1 described in 3GPP TS 23.501 V17.2.0. Figure 2a The system architecture may include some exemplary NFs, such as HSS+UDM, PCF, SMF+PGW-C, UPF+PGW-U, SGW, MME, AMF, E-UTRAN, NG-RAN, UE, etc.

[0173] Figure 2a Some reference points are also shown, such as N10, N7, N4, S5-C, S5-U, N15, N11, S6a, N8, S11, N26, S1-U, N1, N2, N3, S1-MME, etc. These reference points can be implemented, for example, through corresponding interfaces, as well as by specifying some service consumers and providers and the interactions between them, to execute specific system processes.

[0174] Figure 2a The various NFs shown may be responsible for functions such as session management, mobility management, authentication, security, and policy management. Figure 2a The NF shown has been described in 3GPP TS 23.501 V17.2.0 and 3GPP TS 23.401 V17.3.0 and will not be repeated here.

[0175] Figure 2b The home routing roaming architecture for interworking between 5GS and EPC / E-UTRAN is schematically shown. Figure 2b The architecture is the same as Figure 4.3.2-2 described in 3GPP TS 23.501 V17.2.0. Figure 2b The system architecture may include some exemplary NFs, such as HSS+UDM, h-PCF (home PCF), SMF+PGW-C, UPF+PGW-U, SGW, v-PCF (visit PCF), v-SMF (visit SMF), UPF, MME, AMF, E-UTRAN, NG-RAN, UE, etc.

[0176] Figure 2bSome reference points are also shown, such as N10, N24, N7, N16, N9, N4, S6a, N8, S5-C, S5-U, N15, N11, S11, N26, S1-U, N1, N2, N3, S1-MME, etc. These reference points can be implemented, for example, through corresponding interfaces, as well as specifying some service consumers and providers and the interactions between them, to execute specific system processes.

[0177] Figure 2b The various NFs shown may be responsible for functions such as session management, mobility management, authentication, security, and policy management. Figure 2b The NF shown has been described in 3GPP TS 23.501 V17.2.0 and 3GPP TS 23.401 V17.3.0 and will not be repeated here.

[0178] Figure 2c The home routing roaming architecture for interworking between ePDG / EPC and 5GS is schematically shown. Figure 2c The architecture is the same as Figure 4.3.4.2-2 described in 3GPP TS 23.501 V17.2.0. Figure 2c The system architecture may include some exemplary NFs, such as HSS+UDM, h-PCF, SMF+PGW-C, UPF+PGW-U, 3GPP AAA server, 3GPP AAA proxy, v-PCF, v-SMF, UPF, ePDG, AMF, NG-RAN, UE, etc.

[0179] Figure 2c Some reference points are also shown, such as SWx, N10, N7, N4, S6b, N8, N24, S2b-C, S2b-U, N16, N9, N11, N15, SWd, SWm, N1, N2, N3, etc. For example, these reference points can be implemented through corresponding interfaces by specifying some service consumers and providers and the interactions between them to perform specific system processes.

[0180] Figure 2c The various NFs shown may be responsible for functions such as session management, mobility management, authentication, security, and policy management. Figure 2c The NF shown has been described in 3GPP TS 23.501 V17.2.0, 3GPP TS 23.402 V17.0.0 and 3GPP TS 23.401 V17.3.0, and will not be repeated here.

[0181] Figure 3aA flowchart of a method according to an embodiment of the present disclosure is shown, and the method can be performed by a device implemented in a first session management function (SMF) or implemented as a first session management function (SMF) or communicatively coupled to a first SMF. Therefore, the device can provide a device or module for completing each part of the method 300 and a device or module for completing other processes with other components.

[0182] At 302, the first SMF may send alternative packet data network gateway (PGW) control plane (PGW-C) / SMF information to a second SMF or access and mobility management function (AMF) or unified data management (UDM).

[0183] The term "PGW-C / SMF" may refer to the combined PGW-C and SMF.

[0184] The second SMF can be any suitable SMF that needs PGW-C / SMF information. For example, the first SMF can be an old SMF, and the second SMF can be a new SMF. The first SMF can be a home PGW-C / SMF or an anchor PGW-C / SMF, and the second SMF can be a new access SMF or a new intermediate SMF.

[0185] The alternative PGW-C / SMF information may include any appropriate information related to the alternative PGW-C / SMF. For example, the alternative PGW-C / SMF may include the address of the alternative PGW-C / SMF or other information that enables a network node (e.g., AMF, MME, ePDG, etc.) to find / or select the alternative PGW-C / SMF.

[0186] In one embodiment, the alternative PGW-C / SMF information includes at least one of the following: a PGW-set fully qualified domain name (FQDN), an alternative PGW-C / SMF Internet Protocol address, or an alternative PGW-C / SMF FQDN. For example, the alternative PGW-C / SMF information may be the same as the PGW Change Info IE described in 3GPP TS 29.274 V17.5.0.

[0187] The first SMF may send PGW-C / SMF information to the second SMF or AMF or UDM. This can be implemented in various ways, and the present disclosure is not limited to this. For example, the first SMF may send PGW-C / SMF information to the second SMF or AMF or UDM in response to the second SMF or AMF or UDM. Alternatively, the first SMF may actively send PGW-C / SMF information to the second SMF or AMF or UDM. In addition, when the PGW-C / SMF information changes, the first SMF may actively send PGW-C / SMF information to the second SMF or AMF or unified data management.

[0188] The first SMF may send the PGW-C / SMF information to the second SMF or AMF or UDM in an existing message or a new message.

[0189] In one embodiment, the first SMF and the alternative PGW-C / SMF are functionally equivalent and interchangeable and share the same context. For example, the first SMF and the alternative PGW-C / SMF are deployed in a PGW-C / SMF set.

[0190] In one embodiment, the alternative PGW-C / SMF information can be used by the AMF or mobile management using a mobile terminal equipment (MME) or an evolved packet data gateway (ePDG) to select an alternative PGW-C / SMF. For example, when the AMF or MME or ePDG determines or detects that the first SMF fails, the alternative PGW-C / SMF can be selected based on the alternative PGW-C / SMF information. For another example, when the AMF or MME or ePDG determines to select an alternative PGW-C / SMF due to other reasons such as load balancing and load rebalancing, the alternative PGW-C / SMF can be selected based on the alternative PGW-C / SMF information.

[0191] Figure 3b A flowchart of a method according to another embodiment of the present disclosure is shown, and the method can be performed by a device implemented in a first SMF or implemented as a first SMF or communicatively coupled with a first SMF. Therefore, the device can provide a device or module for completing various parts of the method 310 and a device or module for completing other processes in combination with other components. For some parts that have been described in the above embodiments, their description is omitted here for the sake of brevity.

[0192] The first SMF may receive a protocol data unit (PDU) session creation request from the second SMF at 312. The PDU session creation request may be used to create a new PDU session in the first SMF (e.g., H-SMF or SMF), or to create an association with an existing PDN connection in the home SMF+PGW-C.

[0193] In one embodiment, the first SMF is a home PGW-C / SMF or an anchor PGW-C / SMF, and the second SMF is a visiting SMF or an intermediate SMF.

[0194] In one embodiment, the PDU session creation request may be a Nsmf_PDUSession_Create request, as described in 3GPP TS 23.502 V17.2.1. For example, the PDU session creation request may be a Nsmf_PDUSession_Create request, as described in step 6 of Figure 4.3.2.2.2-1 of 3GPP TS 23.502 V17.2.1.

[0195] At 314, the first SMF may send a PDU Session Create Response containing the alternative PGW-C / SMF information to the second SMF.

[0196] In one embodiment, the PDU session creation response may be a Nsmf_PDUSession_Create Response as described in 3GPP TS 23.502 V17.2.1, except that it also includes alternative PGW-C / SMF information. For example, the PDU session creation response may be a Nsmf_PDUSession_Create Response as described in step 13 of Figure 4.3.2.2.2-1 of 3GPP TS 23.502 V17.2.1, except that it also includes alternative PGW-C / SMF information.

[0197] In one embodiment, the alternative PGW-C / SMF information is included in the PDU session creation data of the PDU session creation response.

[0198] For example, Table 6.1.6.2.10-1 of 3GPP TS 29.502 V17.4.0 may add the following underlined content. Table 6.1.6.2.10-1: Definition of PduSessionCreatedData type

[0199] Figure 3c A flow chart of a method according to another embodiment of the present invention is shown, which can be performed by a device implemented in a first SMF or implemented as a first SMF or communicatively coupled with a first SMF. Therefore, the device can provide a device or module for completing various parts of the method 320 and a device or module for completing other processes in combination with other components. For some parts that have been described in the above embodiments, their description is omitted here for the sake of brevity.

[0200] At 322, the first SMF may receive a PDU session update request from the second SMF. The PDU session update request may be used to update an established PDU session.

[0201] In one embodiment, the first SMF is a home PGW-C / SMF or an anchor PGW-C / SMF, and the second SMF is a new visited SMF or a new intermediate SMF.

[0202] In one embodiment, the PDU session update request may be a Nsmf_PDUSession_Update Request, as described in 3GPP TS 23.502 V17.2.1. For example, the PDU session update request may be Nsmf_PDUSession_UpdateRequest as described in step 1a or 1e of Figure 4.3.3.3-1 of 3GPP TS 23.502 V17.2.1.

[0203] At block 324, the first SMF may send a PDU session update response containing the alternative PGW-C / SMF information to the second SMF.

[0204] In one embodiment, the PDU session update response may be a Nsmf_PDUSession_Update response as described in 3GPP TS 23.502 V17.2.1, except that it also includes alternative PGW-C / SMF information. For example, the PDU session update response may be a Nsmf_PDUSession_Update response as described in step 1a or 1e of Figure 4.3.3.3-1 of 3GPP TS 23.502 V17.2.1, except that it also includes alternative PGW-C / SMF information.

[0205] In one embodiment, the alternative PGW-C / SMF information is included in the home SMF update data of the PDU session update response.

[0206] For example, Table 6.1.6.2.12-1 of 3GPP TS 29.502 V17.4.0 may add the following underlined content. Table 6.1.6.2.12-1: Definition of Hsmf type update data

[0207] Figure 3dA flow chart of a method according to another embodiment of the present invention is shown, and the method can be performed by a device implemented in a first SMF or implemented as a first SMF or communicatively coupled with a first SMF. Therefore, the device can provide a device or module for completing various parts of the method 330 and a device or module for completing other processes in combination with other components. For some parts that have been described in the above embodiments, their description is omitted here for the sake of brevity.

[0208] At block 332, the first SMF may send a PDU session update request including the candidate PGW-C / SMF information to the second SMF. The PDU session update request may be used to update an established PDU session.

[0209] In one embodiment, the first SMF is a home PGW-C / SMF or an anchor PGW-C / SMF, and the second SMF is a visiting SMF or an intermediate SMF.

[0210] In one embodiment, the PDU session update request may be a Nsmf_PDUSession_Update Request as described in 3GPP TS 23.502 V17.2.1, but it also includes alternative PGW-C / SMF information. For example, the PDU session update request may be a Nsmf_PDUSession_UpdateRequest as described in step 3 of Figure 4.3.3.3-1 of 3GPP TS 23.502 V17.2.1, except that it also includes alternative PGW-C / SMF information, it also includes alternative PGW-C / SMF information.

[0211] At 334, the first SMF may receive a PDU session update response from the second SMF.

[0212] In one embodiment, the PDU session update response may be a Nsmf_PDUSession_Update response as described in 3GPP TS 23.502 V17.2.1. For example, the PDU session update response may be a Nsmf_PDUSession_Update response as described in step 15 of Figure 4.3.3.3-1 of 3GPP TS 23.502 V17.2.1.

[0213] In one embodiment, the alternative PGW-C / SMF information is included in the access SMF update data of the PDU session update request.

[0214] For example, Table 6.1.6.2.15-1 of 3GPP TS 29.502 V17.4.0 may add the following underlined content. Table 6.1.6.2.15-1: Definition of VsmfUpdateData type

[0215] According to various embodiments, for a home-routed PDU session or a PDU session involving an I-SMF, the first SMF (e.g., a combined PGW-C / SMF) is required to always provide the V / I-SMF with "PGW Change Information" (as a string in the format of "bytes", as defined in the OpenAPI specification (OpenAPIInitiative, "OpenAPI Specification Version 3.0.0", https: / / spec.openapis.org / oas / v3.0.0), i.e., base64 encoded characters, encoding the "PGW Change Information" IE specified in Table 7.3.1-8 or Table 7.3.6-6 of 3GPP TS 29.274 V17.5.0 for the N26 interface. (For more information, see Clause 2)), for example, in PduSessionCreatedData (e.g., for PDU session establishment), HsmfUpdatedData (e.g., for V / I-SMF change procedure), and VsmfUpdateData (e.g., when the combined PGW-C / SMF wishes to change the "PGW Change Information").

[0216] In one embodiment, when the second SMF (e.g. V / I-SMF) receives the "PGW Change Information", it shall store it and include it in the SmContextRetrievedData as described in clause 6.1.6.2.27 of 3GPP TS 29.502 V17.4.0 during the 5G to 4G mobility procedure.

[0217] Figure 3e A flow chart of a method according to another embodiment of the present disclosure is shown, and the method can be performed by a device implemented in a first SMF or implemented as a first SMF or communicatively coupled with a first SMF. Therefore, the device can provide a device or module for completing various parts of method 340 and a device or module for completing other processes in combination with other components. For some parts that have been described in the above embodiments, their description is omitted here for the sake of brevity.

[0218] At block 342, the first SMF may receive a PDU session context request from the AMF. The PDU session context request may be used by the AMF to request an SM (session management) context.

[0219] In one embodiment, the first SMF may be a home PGW-C / SMF or an anchor PGW-C / SMF or a visited SMF or an I-SMF.

[0220] In one embodiment, the PDU session context request may be Nsmf_PDUSession_ContextRequest as described in 3GPP TS 23.502 V17.2.1. For example, the PDU session context request may be Nsmf_PDUSession_ContextRequest as described in step 2a of Figure 4.11.1.2.1-1 of 3GPP TS 23.502 V17.2.1. In another example, the PDU session context request may be Nsmf_PDUSession_ContextRequest as described in step 5a of Figure 4.11.1.3.2-1 of 3GPP TS 23.502 V17.2.1.

[0221] At block 344, the first SMF may send a PDU session context response containing the alternative PGW-C / SMF information to the AMF.

[0222] In one embodiment, the PDU session context response may be a Nsmf_PDUSession_ContextRe response as described in 3GPP TS 23.502 V17.2.1, but it also includes alternative PGW-C / SMF information. For example, the PDU session context response may be a Nsmf_PDUSession_ContextRe response as described in step 2c of Figure 4.11.1.2.1-1 of 3GPP TS 23.502 V17.2.1, except that it also includes alternative PGW-C / SMF information. In another example, the PDU session context response may be a Nsmf_PDUSession_ContextRe response as described in step 5c of Figure 4.11.1.3.2-1 of 3GPP TS 23.502 V17.2.1, except that it also includes alternative PGW-C / SMF information.

[0223] In one embodiment, when a SmContext Retrieval Request is received from an AMF where the UE is moving from 5G to 4G, it requires that the first SMF (e.g. combined PGW-C / SMF) should include the "PGW Change Information" as part of the EpSPdnCnxContainer in the SmContextRetrievedData as described in clause 6.1.6.2.27 of 3GPP TS 29.502 V17.4.0.

[0224] Figure 3fA flowchart of a method according to another embodiment of the present disclosure is shown, and the method can be performed by a device implemented in a first SMF or implemented as a first SMF or communicatively coupled with a first SMF. Therefore, the device can provide a device or module for completing various parts of the method 350 and a device or module for completing other processes in combination with other components. For some parts that have been described in the above embodiments, their description is omitted here for the sake of brevity.

[0225] At block 352, the first SMF may send a registration request including the first SMF information and the alternative PGW-C / SMF information to the UDM. For example, the registration request may be used to register the service NF of the session on the UDM.

[0226] In one embodiment, the registration request may be Nudm_UECM_Registration Request as described in 3GPP TS 23.502 V17.2.1. For example, the registration request may be Nudm_UECM_Registration Request as described in step 12c of Figure 4.3.2.2.2-1 of 3GPP TS 23.502 V17.2.1.

[0227] At block 354, the first SMF may receive a registration response from the UDM.

[0228] In one embodiment, the registration response may be a Nudm_UECM_Registration response as described in 3GPP TS 23.502 V17.2.1. For example, the registration response may be a Nudm_UECM_Registration reply as described in step 12c of Figure 4.3.2.2.2-1 of 3GPP TS 23.502 V17.2.1.

[0229] In one embodiment, when the combined PGW-C / SMF registers the PDU session and sends a Nudm_UECM_Registration request (data type is SmfRegistration specified in 3GPPTS29.503V17.6.0), the first SMF (e.g., the combined PGW-C / SMF) includes the "PGW change information" in the SmfRegistration for UDM, which will enable the network node (e.g., ePDG) to retrieve the "PGW change information" from the UDM / HSS / AAA, which can be used for reselection (if necessary) when the UE moves from 5G to non-3gpp access in 4G.

[0230] Figure 3g A flow chart of SMF registration according to an embodiment of the present disclosure is shown.

[0231] In step 1, the SMF sends a PUT request to the resource ... / {ueId} / registrations / smf-registrations / {pduSessionId} to create the SMF registration present in the message body. The PUT request includes the first SMF information and the alternative PGW-C / SMF information.

[0232] If the SMF belongs to an SMF set, the request message shall contain the NF set ID of the SMF set.

[0233] If EPS interworking is supported, the PCFID selected for the PDU Session should be included in the UDM when the SMF+PGW-C registers in the UDM.

[0234] In step 2a, the UDM responds with a "201 Created" whose message body contains a representation of the SMF registration that was created.

[0235] In step 2b, if the single resource exists, then on success, the UDM will update the resource by replacing it with the received resource information and respond with a "200 OK" with the message body containing a representation of the updated single SmfRegistration resource.

[0236] If the new SMF is not in the SMF set or is not in the same SMF set as the old SMF, the UDM shall call the Unregister Notification Service operation to the old SMF using the callback URI provided by the old SMF.

[0237] In step 2c, if the operation cannot be authorized due to the following reasons: the UE does not have the required subscription data, access barring or roaming restrictions, an HTTP (Hypertext Transfer Protocol) status code "403Forbidden" should be returned with additional error information in the response body (in the "ProblemDetails" element). Subscription information associated with a specific DNN (if any) should take precedence over subscription information associated with a WildcardDNN.

[0238] Upon failure, an appropriate HTTP status code indicating the error should be returned, along with appropriate additional error information in the PUT response body.

[0239] In one embodiment, the alternative PGW-C / SMF information is included in the SMF registration data of the registration request.

[0240] In one embodiment, Table 6.2.6.2.4-1 of 3GPP TS 29.503 V17.6.0 may add the following underlined content. Table 6.2.6.2.4-1: Definition of SmfRegistration type

[0241] Figure 3h A flowchart of a method according to another embodiment of the present disclosure is shown, which can be performed by a device implemented in the first PGW-C / SMF or implemented as the first PGW-C / SMF or communicatively coupled with the first PGW-C / SMF. Therefore, the device can provide a device or module for completing various parts of the method 360 and a device or module for completing other processes in combination with other components. For some parts that have been described in the above embodiments, their description is omitted here for the sake of brevity.

[0242] At 362, the first PGW-C / SMF may establish a PDU session for a user equipment (UE).

[0243] At 364, the first PGW-C / SMF may send the alternative PGW-C / SMF information to a second SMF anchored on the PDU session of the first SMF+PGW-C or Access and Mobility Management Function (AMF).

[0244] In one embodiment, if the first PGW-C / SMF fails, an alternative PGW-C / SMF will be selected based on the alternative PGW-C / SMF information.

[0245] In one embodiment, sending the alternative PGW-C / SMF information to the second SMF may include receiving a protocol data unit (PDU) session creation request from the second SMF. The method may also include sending a PDU session creation response containing the alternative PGW-C / SMF information to the second SMF.

[0246] In one embodiment, the alternative PGW-C / SMF information may be included in the PDU session creation data of the PDU session creation response.

[0247] In one embodiment, the first PGW-C / SMF may be a home PGW-C / SMF or an anchor PGW-C / SMF and / or the second SMF may be a visited SMF or an intermediate SMF.

[0248] In one embodiment, sending the alternative PGW-C / SMF information to the second SMF may include receiving a PDU session update request from the second SMF and sending a PDU session update response including the alternative PGW-C / SMF information to the second SMF.

[0249] In one embodiment, the alternative PGW-C / SMF information may be included in the home SMF update data of the PDU session update response.

[0250] In one embodiment, the first PGW-C / SMF may be a home PGW-C / SMF or an anchor PGW-C / SMF and / or the second SMF may be a new visited SMF or a new intermediate SMF.

[0251] In one embodiment, sending the alternative PGW-C / SMF information to the second SMF may include sending a PDU session update request including the alternative PGW-C / SMF information to the second SMF and receiving a PDU session update response from the second SMF.

[0252] In one embodiment, the alternative PGW-C / SMF information may be included in the access SMF update data of the PDU session update request.

[0253] In one embodiment, the first PGW-C / SMF may be a home PGW-C / SMF or an anchor PGW-C / SMF and / or the second SMF may be a visited SMF or an intermediate SMF.

[0254] In one embodiment, sending the alternative PGW-C / SMF information to the AMF may include receiving a PDU session context request from the AMF and sending a PDU session context response including the alternative PGW-C / SMF information to the AMF.

[0255] In one embodiment, the candidate PGW-C / SMF information may include information of at least one PGW-C / SMF so that the candidate PGW-C / SMF may be selected.

[0256] In one embodiment, the alternative PGW-C / SMF information may be used by the AMF or mobility management using a mobile terminal equipment (MME) or an evolved packet data gateway (ePDG) to select an alternative PGW-C / SMF.

[0257] In one embodiment, the first PGW-C / SMF and the alternative PGW-C / SMF may be functionally equivalent and interchangeable, and share the same context.

[0258] Figure 4a A flowchart of a method according to another embodiment of the present disclosure is shown, which can be performed by a device implemented in or at or as a second SMF, or a device communicatively coupled to the second SMF. Second SMF. In this way, the device can provide a device or module for completing various parts of method 400, and a device or module for completing other processes in combination with other components. For the parts that have been described in the above embodiments, they will not be repeated here.

[0259] At 402, the second SMF may receive alternative packet data network gateway (PGW) control plane (PGW-C) / SMF information from the first SMF.

[0260] For example, in the above embodiment, the first SMF can send the alternative PGW-C / SMF information to the second SMF, and then the second SMF can receive the alternative PGW-C / SMF information. After the second SMF receives the alternative PGW-C / SMF information, it can save the alternative PGW-C / SMF information.

[0261] At 404, the second SMF may send the alternative PGW-C / SMF information to the Access and Mobility Management Function (AMF).

[0262] There are many ways for the second SMF to send the alternative PGW-C / SMF information to the AMF, and the present invention does not limit this. For example, the second SMF can respond to the request of the AMF and send the alternative PGW-C / SMF information to the AMF; or, the second SMF can actively send the alternative PGW-C / SMF information to the AMF; in addition, when the PGW-C / SMF information changes, the second SMF can send the alternative PGW-C / SMF information to the AMF.

[0263] The second SMF can send the alternative PGW-C / SMF information to the AMF through an existing message or a new message.

[0264] In one embodiment, the alternative PGW-C / SMF information includes at least one of the following: a PGW-set fully qualified domain name (FQDN), an alternative PGW-C / SMF Internet Protocol address, or an alternative PGW-C / SMF FQDN.

[0265] In one embodiment, the alternative PGW-C / SMF information is used by the AMF or mobility management to select the alternative PGW-C / SMF using a mobile terminal equipment (MME) or an evolved packet data gateway (ePDG).

[0266] In one embodiment, the first session management function (SMF) and the alternative PGW-C / SMF are functionally equivalent and interchangeable, and share the same context.

[0267] Figure 4bA flowchart of a method according to another embodiment of the present disclosure is shown, which can be performed by a device implemented in or at or as a second SMF, or a device communicatively coupled to the second SMF. Second SMF. In this way, the device can provide a device or module for completing various parts of method 410, and a device or module for completing other processes in combination with other components. For the parts that have been described in the above embodiments, they will not be repeated here.

[0268] At 412, the second SMF may send a PDU session creation request to the first SMF.

[0269] At 414, the second SMF may receive a PDU session creation response including the alternative PGW-C / SMF information from the first SMF.

[0270] In one embodiment, the alternative PGW-C / SMF information is included in the PDU session creation data of the PDU session creation response.

[0271] In one embodiment, the first SMF is a home PGW-C / SMF or an anchor PGW-C / SMF, and the second SMF is a visiting SMF or an intermediate SMF.

[0272] Figure 4c A flowchart of a method according to another embodiment of the present disclosure is shown, which can be performed by a device implemented in or at or as a second SMF, or a device communicatively coupled to the second SMF. Second SMF. In this way, the device can provide a device or module for completing various parts of method 420, and a device or module for completing other processes in combination with other components. For the parts that have been described in the above embodiments, they will not be repeated here.

[0273] At 422, the second SMF may send a PDU session update request to the first SMF.

[0274] At 424, the second SMF may receive a PDU Session Update Response including the alternative PGW-C / SMF information from the first SMF.

[0275] In one embodiment, the alternative PGW-C / SMF information is included in the home SMF update data of the PDU session update response.

[0276] In one embodiment, the first SMF is a home PGW-C / SMF or an anchor PGW-C / SMF, and the second SMF is a new visited SMF or a new intermediate SMF.

[0277] Figure 4dA flowchart of a method according to another embodiment of the present disclosure is shown, which can be performed by a device implemented in or at or as a second SMF, or a device communicatively coupled to the second SMF. Second SMF. In this way, the device can provide a device or module for completing various parts of method 430, and a device or module for completing other processes in combination with other components. For the parts that have been described in the above embodiments, they will not be repeated here.

[0278] At 432, the second SMF may receive a PDU session update request including the alternative PGW-C / SMF information from the first SMF.

[0279] At 434, the second SMF may send a PDU Session Update Response to the first SMF.

[0280] In one embodiment, the alternative PGW-C / SMF information is included in the access SMF update data of the PDU session update request.

[0281] In one embodiment, the first SMF is a home PGW-C / SMF or an anchor PGW-C / SMF, and the second SMF is a visiting SMF or an intermediate SMF.

[0282] Figure 4e A flow chart of a method according to another embodiment of the present disclosure is shown, which can be performed by a device implemented in or at or as a second SMF, or communicatively coupled to the second SMF. In this way, the device can provide a device or module for completing various parts of method 440, and a device or module for completing other processes in combination with other components. For the parts that have been described in the above embodiments, they will not be repeated here.

[0283] At 442, the second SMF may receive a PDU session context request from the AMF.

[0284] At 444, the second SMF may send a PDU session context response containing alternative PGW-C / SMF information to the AMF.

[0285] Figure 5a A flow chart of a method according to another embodiment of the present disclosure is shown, which can be performed by an apparatus in or as or as implemented by AMF or coupled with AMF communication. In this way, the apparatus can provide an apparatus or module for completing various parts of method 500, and an apparatus or module for completing other processes in combination with other components. For the parts that have been described in the above embodiments, they will not be repeated here.

[0286] At 502, the AMF may receive alternative packet data network gateway (PGW) control plane (PGW-C) / SMF information from a first session management function (SMF) or a second SMF.

[0287] For example, in the above embodiment, the first SMF or the second SMF can send the alternative PGW-C / SMF information to the AMF, and then the AMF can receive the alternative PGW-C / SMF information from the first SMF or the second SMF.

[0288] In one embodiment, the first SMF is a home PGW-C / SMF or an anchor PGW-C / SMF, and the second SMF is a visiting SMF or an intermediate SMF.

[0289] In one embodiment, the alternative PGW-C / SMF information includes at least one of the following: a PGW-set fully qualified domain name (FQDN), an alternative PGW-C / SMF Internet Protocol address, or an alternative PGW-C / SMF FQDN.

[0290] In one embodiment, the alternative PGW-C / SMF information is used by the AMF or mobility management to select the alternative PGW-C / SMF using a mobile terminal equipment (MME) or an evolved packet data gateway (ePDG).

[0291] In one embodiment, the first session management function (SMF) and the alternative PGW-C / SMF are functionally equivalent and interchangeable, and share the same context.

[0292] At 504, the AMF may send the alternative PGW-C / SMF information to the mobility management entity (MME).

[0293] There are many ways for AMF to send the candidate PGW-C / SMF information to MME, which is not limited by the present invention. For example, AMF can respond to a request from MME and send the candidate PGW-C / SMF information to MME. Alternatively, AMF can respond to a request from MME and actively send the candidate PGW-C / SMF information to MME.

[0294] The AMF may send the alternative PGW-C / SMF information to the MME through an existing message or a new message.

[0295] Figure 5b A flow chart of a method according to another embodiment of the present disclosure is shown, which can be performed by an apparatus in or as or as implemented by AMF or coupled with AMF communication. In this way, the apparatus can provide an apparatus or module for completing various parts of method 510, and an apparatus or module for completing other processes in combination with other components. For the parts that have been described in the above embodiments, they will not be repeated here.

[0296] At 512, the AMF may send a PDU session context request to the first SMF or the second SMF.

[0297] At 514, the AMF may receive a PDU session context response containing alternative PGW-C / SMF information from the first SMF or the second SMF.

[0298] Figure 5c A flow chart of a method according to another embodiment of the present disclosure is shown, which can be performed by an apparatus in or as or as implemented by AMF or coupled with AMF communication. In this way, the apparatus can provide an apparatus or module for completing various parts of method 520, and an apparatus or module for completing other processes in combination with other components. For the parts already described in the above embodiments, they will not be repeated here.

[0299] At 522, the AMF may receive a context request from the MME.

[0300] In one embodiment, the context request may be the context request described in step 4 of Figure 4.11.1.3.2-1 of 3GPP TS 23.502 V17.2.1.

[0301] At 524, the AMF may send a context response containing alternative PGW-C / SMF information to the MME.

[0302] In one embodiment, the context request may be a context response as described in step 6 of Figure 4.11.1.3.2-1 of 3GPP TS 23.502 V17.2.1, except that it also includes alternative PGW-C / SMF information.

[0303] Figure 5d A flow chart of a method according to another embodiment of the present disclosure is shown, and the method can be performed by an apparatus in or as an implementation of the AMF in the first telecommunication system or is communicatively coupled with the AMF in the first telecommunication system. In this way, the apparatus can provide an apparatus or module for completing various parts of the method 530, and an apparatus or module for completing other processes in combination with other components. For the parts that have been described in the above embodiments, they will not be repeated here.

[0304] At 532, the AMF may receive control plane / session management function (PGW-C / SMF) information of an alternative packet data network gateway from the first PGW-C / SMF or the second SMF.

[0305] At block 534, the AMF may send the alternative PGW-C / SMF information to a mobility management entity (MME) in the mobility management second telecommunication system.

[0306] In one embodiment, accepting alternative PGW-C / SMF information from the first PGW-C / SMF or the second SMF may include sending a protocol data unit (PDU) session context request to the first PGW-C / SMF or the second SMF, and receiving a PDU session context response including alternative PGW-C / SMF information from the first PGW-C / SMF or the second SMF.

[0307] In one embodiment, sending the alternative PGW-C / SMF information to the MME may include receiving a context request from the MME and sending a context response including the alternative PGW-C / SMF information to the MME.

[0308] In one embodiment, the first PGW-C / SMF may be a home PGW-C / SMF or an anchor PGW-C / SMF and / or the second SMF may be a visited SMF or an intermediate SMF.

[0309] In one embodiment, the candidate PGW-C / SMF information may include information of at least one PGW-C / SMF so that the candidate PGW-C / SMF may be selected.

[0310] In one embodiment, the AMF or MME or evolved packet data gateway (ePDG) may use the alternative PGW-C / SMF information to select an alternative PGW-C / SMF.

[0311] In one embodiment, the first PGW-C / SMF and the alternative PGW-C / SMF may be functionally equivalent and interchangeable, and share the same context.

[0312] Figure 6a A flow chart of a method according to another embodiment of the present disclosure is shown, which can be performed by an apparatus in or as or as implemented by an MME or communicatively coupled to an MME. In this way, the apparatus can provide an apparatus or module for completing various parts of method 600, and an apparatus or module for completing other processes in combination with other components. For the parts that have been described in the above embodiments, they are not repeated here for the sake of brevity.

[0313] At 602, the MME may send a context request to an access and mobility management function (AMF).

[0314] At 604, the MME may receive a context response including the first PGW-C / SMF information and the alternative PGW-C / SMF information from the AMF.

[0315] In one embodiment, the MME may receive a context response from the AMF, the context response including first session management function (SMF) information and alternative packet data network gateway (PGW) control plane (PGW-C) / SMF information.

[0316] In one embodiment, the first PGW-C / SMF is a home PGW-C / SMF or an anchor PGW-C / SMF.

[0317] In one embodiment, the first PGW-C / SMF and the alternative PGW-C / SMF are functionally equivalent and interchangeable, and share the same context.

[0318] In one embodiment, the candidate PGW-C / SMF information includes information of at least one PGW-C / SMF so that the candidate PGW-C / SMF can be selected.

[0319] In one embodiment, the alternative PGW-C / SMF information includes at least one of the following: a PGW-set fully qualified domain name (FQDN), an alternative PGW-C / SMF Internet Protocol address, or an alternative PGW-C / SMF FQDN.

[0320] Figure 6b A flow chart of a method according to another embodiment of the present disclosure is shown, and the method can be performed by an apparatus in or as an implementation of an MME or communicatively coupled to an MME. In this way, the apparatus can provide an apparatus or module for completing various parts of method 610, and an apparatus or module for completing other processes in combination with other components. For the parts that have been described in the above embodiments, they will not be repeated here for the sake of brevity.

[0321] At 612, the MME may determine that the first PGW-C / SMF has failed. In an embodiment, the MME may determine that the first SMF has failed. There are multiple ways in which the MME may determine that the first SMF has failed. For example, the MME may send a message to the first SMF. If the MME cannot receive a response from the first AMF, the MME may determine that the first SMF has failed. The MME may determine that the first SMF has failed based on a heartbeat message. Another network node (e.g., an SGW) may report that the first SMF has failed, and then the MME may determine that the first SMF has failed.

[0322] At 614, the MME may select an alternative PGW-C / SMF based on the alternative PGW-C / SMF information. For example, when the alternative PGW-C / SMF includes a PGW-C / SMF Internet Protocol address, the PGW-C / SMF may be selected.

[0323] At 616, the MME may send a create session request to the alternative PGW-C / SMF.

[0324] In one embodiment, the create session request may be the same as the create session request as specified in 3GPP TS 23.401 V17.3.0.

[0325] Figure 7a A flowchart of a method according to another embodiment of the present disclosure is shown, which can be performed by a device in or as an implementation of the UDM or communicatively coupled to the UDM. In this way, the device can provide a device or module for completing various parts of the method 700, and a device or module for completing other processes in combination with other components. For the parts that have been described in the above embodiments, they will not be repeated here.

[0326] At 702, the UDM may receive a registration request including first session management function (SMF) information and alternative packet data network gateway (PGW) control plane (PGW-C) / SMF information from a first session management function (SMF).

[0327] At 704, the UDM may store the first SMF information and the alternative PGW-C / SMF information.

[0328] At 706, the UDM may send a registration response to the first SMF.

[0329] In one embodiment, the alternative PGW-C / SMF information includes at least one of the following: a PGW-set fully qualified domain name (FQDN), an alternative PGW-C / SMF Internet Protocol address, or an alternative PGW-C / SMF FQDN.

[0330] In one embodiment, the alternative PGW-C / SMF information is used by an access and mobility management function (AMF) or a mobility management mobile terminal equipment (MME) or an evolved packet data gateway (ePDG) to select an alternative PGW-C / SMF.

[0331] In one embodiment, the first SMF and the alternative PGW-C / SMF are functionally equivalent and interchangeable, and share the same context.

[0332] In one embodiment, the first SMF is a home PGW-C / SMF or an anchor PGW-C / SMF.

[0333] In one embodiment, the first SMF information and the alternative PGW-C / SMF information are included in the SMF registration data of the registration request.

[0334] Figure 7bA flowchart of a method according to another embodiment of the present disclosure is shown, which can be performed by a device in or as an implementation of the UDM or communicatively coupled to the UDM. In this way, the device can provide a device or module for completing various parts of the method 710, and a device or module for completing other processes in combination with other components. For the parts that have been described in the above embodiments, they will not be repeated here for the sake of brevity.

[0335] At 712, the UDM may receive a request from a network node to retrieve an address of a first session management function (SMF) and alternate PGW-C / SMF information.

[0336] The network node may be any suitable network node, such as AMF, SMF, MME, ePDG, etc. In an embodiment, the network node is an evolved packet data gateway (ePDG).

[0337] At 714, the UDM may send a response including the first SMF information and the alternative PGW-C / SMF information to the network node.

[0338] For example, in step 4 of Figure 8.2.3-1 of 3GPP TS 23.402 V17.0.0, as part of access authentication, the first SMF information and the candidate PGW-C / SMF information are sent by the 3GPP AAA server to the ePDG. The 3GPP AAA server can retrieve the first SMF information and the candidate PGW-C / SMF information from the UDM.

[0339] Figure 8a A flow chart of a method according to another embodiment of the present disclosure is shown, which can be performed by an apparatus in or as an implementation of an ePDG or communicatively coupled to an ePDG. In this way, the apparatus can provide an apparatus or module for completing various parts of method 800, and an apparatus or module for completing other processes in combination with other components. For the parts that have been described in the above embodiments, they are not repeated here for the sake of brevity.

[0340] At 802, the ePDG may send a request to a unified data management (UDM) to retrieve first session management function (SMF) information and alternative packet data network gateway (PGW) control plane (PGW-C) / SMF information. For example, the ePDG may send the request to a 3GPP AAA server, and the 3GPP AAA server may send the request to the UDM.

[0341] At 804, the ePDG may receive a response including the first SMF information and the alternative PGW-C / SMF information from the UDM. For example, the ePDG may receive a response from a 3GPP AAA server, and the 3GPP AAA server may receive a response from the UDM.

[0342] In one embodiment, the first SMF is a home PGW-C / SMF or an anchor PGW-C / SMF.

[0343] In one embodiment, the first SMF and the alternative PGW-C / SMF are functionally equivalent and interchangeable, and share the same context.

[0344] In one embodiment, the alternative PGW-C / SMF information includes at least one of the following: a PGW-set fully qualified domain name (FQDN), an alternative PGW-C / SMF Internet Protocol address, or an alternative PGW-C / SMF FQDN.

[0345] Figure 8b A flow chart of a method according to another embodiment of the present disclosure is shown, which can be performed by an apparatus in or as an implementation of an ePDG or communicatively coupled to an ePDG. In this way, the apparatus can provide an apparatus or module for completing various parts of method 810, and an apparatus or module for completing other processes in combination with other components. For the parts that have been described in the above embodiments, they will not be repeated here for the sake of brevity.

[0346] At 812, the ePDG may determine that the first SMF has failed. There are many ways in which the ePDG may determine that the first SMF has failed. For example, the ePDG may send a message to the first SMF. If the ePDG cannot receive a response from the first AMF, the ePDG may determine that the first SMF has failed. The ePDG may determine that the first SMF has failed based on a heartbeat message. Another network node may report that the first SMF has failed, and then the ePDG may determine that the first SMF has failed.

[0347] At 814, the ePDG may select an alternative PGW-C / SMF based on the alternative PGW-C / SMF information. For example, when the alternative PGW-C / SMF includes a PGW-C / SMF Internet Protocol address, the PGW-C / SMF may be selected.

[0348] At 816, the ePDG may send a create session request to the alternative PGW-C / SMF.

[0349] In one embodiment, the create session request may be executed in the same manner as the create session request in accordance with the manner specified in 3GPP TS 23.402 V17.0.0.

[0350] Fig. 9 A flowchart showing how to add PGW change information in various signaling messages according to another embodiment of the present disclosure.

[0351] Steps 1-7 are used to establish a PDU session for a HomeRoutedPDU session or a PDU session with I-SMF. The UE then moves from 5G to 4G, and steps 8-15 are used for the UE to move from 5G to EPS. Steps 8a to 8d apply to the UE moving from 5G to ePDG.

[0352] In step 1, the UE sends a PDU session establishment request to the AMF.

[0353] In step 2, AMF sends a Nsmf_PDUSession_CreateSMContext request to V / I-SMF.

[0354] In step 3.AMF receives the Nsmf_PDUSession_CreateSMContext response from V / I-SMF.

[0355] Step 4. V / I-SMF sends a Nsmf_PDUSession_Create request (PduSessionCreateData) to (H-)SMF / PGW1.

[0356] Step 5. (H-)SMF / PGW1 sends a Nudm_UECM registration request (SmsfRegistration) containing "pgwChangeInfo" to UDM, and UDM confirms the request.

[0357] In step 6, (H-)SMF / PGW1 sends a Nsmf_PDUSession_Create response (PduSessionCreatedData) including "pgwChangeInfo" to V / I-SMF.

[0358] Step 7. V / I-SMF sends Namf_Communication_N1N2MessageTransfer to transfer the N1 / N2 message, establishes PDU session resources in NG-RAN, and provides the UE with a non-access state (NAS) PDU session establishment accept message. The PDU session is established.

[0359] In step 8, after receiving the TAU (Tracking Area Update) from the UE, the MME sends a GTPv2 message: Context Request to the AMF to retrieve the UE context.

[0360] In step 9.AMF sends Nsmf_PDUSession_ContextRequest (SmContextRetrieveData) to V / I-SMF.

[0361] Step 10. V / I-SMF sends Nsmf_PDUSession_ContextResponse (SmContextRetrievedData) including ueEpsPdnConnection to AMF, where V / I-SMF should include the previously received "pgwChangeInfo".

[0362] In step 11, the AMF sends a GTPv2:ContextResponse to the MME, which contains the PGWChangeInfo.

[0363] In step 12, the MME sends a GTPv2:ContextAck (acknowledgement) to the AMF.

[0364] In step 13, the MME sends a GTPv2: create session request message to the combined PGW-C / SMF1 through the SGW (omitted in the figure), but the combined PGW-C / SMF1 is unreachable.

[0365] In step 14: SGW will report that combined PGW-C / SMF1 is unreachable. MME uses "PGWChangeInfo" to select an alternative PGW-C / SMF, such as PGW-C / SMF2. MME sends a GTPv2: CreateSessionRequest message (omitted in the figure) to combined PGW-C / SMF2 through SGW (which will send a modify bearer request to combined PGW-C / SMF2), and PGW-C / SMF2 accepts the request.

[0366] Step 15: The MME sends a TAU accept message to the UE.

[0367] In step 8a., if the UE accesses the network through non-3gpp access, such as WLAN (Wireless Local Area Network), and the UE sends a handover request to the ePDG, the ePDG will retrieve the PGW address and PGW change information from AAA / HSS / UDM.

[0368] In step 8b: the ePDG sends a GTPv2: Create Session Request message to the combined PGW-C / SMF1. However, the combined PGW-C / SMF1 is not accessible.

[0369] In step 8c: ePDG uses the "PGW Change Information" to select an alternative PGW-C / SMF, such as PGW-C / SMF2. ePDG sends a GTPv2: Create Session Request message to the combined PGW-C / SMF2, and the request is accepted by PGW-C / SMF2.

[0370] Step 8d. ePDG sends "Handover Accepted" to the UE.

[0371] Some messages may be identical to corresponding messages described in 3GPP specifications, such as 3GPP TS 23.401 V17.3.0, 3GPP TS 23.502 V17.2.1, or 3GPP TS 23.402 V17.0.0. Fig. 9 Some messages in can be enhanced to include "PGW change information". In addition, when the MME or ePDG determines that the combined PGW-C / SMF is unreachable, the MME or ePDG can use the "PGW change information" to select an alternative PGW-C / SMF. The MME or ePDG then sends a GTPv2: Create Session Request message to the alternative PGW-C / SMF. In this way, it can be ensured that the PDU session can be successfully moved from 5G to 4G mobile even if the service combined PGW-C / SMF fails (as long as it belongs to the combined PGW-C / SMF set).

[0372] Fig.10 1000 is a block diagram showing an apparatus suitable for implementing some embodiments of the present disclosure. For example, a first single-mode optical fiber, a first PGW-C / SMF, a second SMF, an AMF, a UDM, a MME or an ePDG. The above embodiments can be implemented as the apparatus 1000 or implemented by the apparatus 1000.

[0373] The device 1000 includes at least one processor 1021, such as a digital processor (DP), and at least one memory (MEM) 1022 coupled to the processor 1021. The device 1000 may also include a transmitter TX and a receiver RX1023 coupled to the processor 1021. The MEM 1022 stores a program (PROG) 1024. The PROG 1024 may include instructions that, when executed on the associated processor 1021, enable the device 1000 to operate according to the embodiments of the present disclosure. The combination of at least one processor 1021 and at least one MEM 1022 may form a processing device 1025 suitable for implementing various embodiments of the present disclosure.

[0374] Various embodiments of the present disclosure may be implemented by one or more computer programs executable by the processor 1021 , software, firmware, hardware, or a combination thereof.

[0375] MEM 1022 may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory, and removable memory (as non-limiting examples).

[0376] Processor 1021 may be of any type suitable to the local technical environment, and may include one or more of a general purpose computer, a special purpose computer, a microprocessor, a digital signal processor (DSP), and a processor based on a multi-core processor architecture, as non-limiting examples.

[0377] In an embodiment of the first SMF or at the first SMF, the memory 1022 contains instructions executable by the processor 1021 so that the first PGW-C / SMF operates according to any method related to the first SMF as described above.

[0378] In an embodiment at the PGW-C / SMF or at the first PGW-C / SMF, the memory 1022 contains instructions executable by the processor 1021 so that the first PGW-C / SMF operates according to any method related to the first PGW-C / SMF as described above.

[0379] In an embodiment of the second SMF or at the second SMF, the memory 1022 contains instructions executable by the processor 1021, whereby the second SMF operates according to any of the methods described above in relation to the second SMF.

[0380] In an embodiment implemented at or by the AMF, the memory 1022 contains instructions executable by the processor 1021, whereby the AMF operates according to any method related to the AMF as described above.

[0381] In an embodiment of a UDM or at a UDM, the memory 1022 contains instructions executable by the processor 1021, whereby the UDMF operates according to any of the methods described above in relation to the UDM.

[0382] In an embodiment at the MME, the memory 1022 contains instructions executable by the processor 1021 so that the MME operates according to any of the methods related to the MME as described above.

[0383] In embodiments where the ePDG or the ePDG is implemented therein, the memory 1022 contains instructions executable by the processor 1021 , whereby the ePDG operates according to any of the methods described above in relation to the ePDG.

[0384] Fig.11a A block diagram of the first SMF provided in an embodiment of the present invention, as shown in the figure, the first SMF 1100 includes a sending module 1101, which is used to send alternative packet data network gateway (PGW) control plane (PGW-C) / SMF information to a second SMF or access and mobility management function (AMF) or unified data management (UDM).

[0385] Fig.11b1 is a block diagram showing a first PGW-C / SMF according to an embodiment of the present disclosure. As shown in the figure, the first PGW-C / SMF 1150 may include an establishment module 1151, which is configured to establish a PDU session for a user equipment (UE). The first PGW-C / SMF 1150 may also include a sending module 1152 for sending an alternative PGW-C / SMF information to a second SMF for anchoring a PDU session at the first SMF+PGW-C or an access and mobility management function (AMF). If the first PGW-C / SMF fails, an alternative PGW-C / SMF will be selected based on the alternative PGW-C / SMF information.

[0386] Fig.12 1 is a block diagram showing a second SMF according to an embodiment of the present disclosure. As shown in the figure, the second SMF 1200 includes a receiving module 1201 configured to receive alternative packet data network gateway (PGW) control plane (PGW-C) / SMF information from the first SMF. The second SMF 1200 includes a sending module 1202 for sending the alternative PGW-C / SMF information to an access and mobility management function (AMF).

[0387] Fig.13a 1 is a block diagram showing an AMF according to an embodiment of the present disclosure. As shown in the figure, AMF 1300 includes a receiving module 1301, which is configured to receive alternative packet data network gateway (PGW) control plane (PGW-C) / SMF information from a first session management function (SMF) or a second SMF. AMF 1300 includes a sending module 1302 for sending alternative PGW-C / SMF information of a mobility management entity (MME).

[0388] Fig.13b 1 is a block diagram showing an AMF in a first telecommunication system according to an embodiment of the present disclosure. As shown in the figure, AMF 1350 may include a receiving module 1351, which is configured to receive control plane / session management function (PGW-C / SMF) information of an alternative packet data network gateway from a first PGW-C / SMF or a second SMF. AMF 1350 may include a sending module 1352 for sending the alternative PGW-C / SMF information to a mobile management entity (MME) in a second telecommunication system.

[0389] Fig.141 is a block diagram of an MME according to an embodiment of the present disclosure. As shown in the figure, MME 1400 may include a first sending module 1401 for sending a context request to an access and mobility management function (AMF). MME 1400 may also include a receiving module 1402 for receiving a context response including first PGW-C / SMF information and alternative packet data network gateway (PGW) control plane (PGW-C) / SMF information from AMF.

[0390] In one embodiment, the MME 1400 includes a determining module 1403, configured to determine that a failure occurs in the first SMF.

[0391] In one embodiment, the MME 1400 includes a selection module 1404, configured to select an alternative PGW-C / SMF according to the alternative PGW-C / SMF information.

[0392] In one embodiment, the MME 1400 includes a second sending module 1405, configured to send a create session request to the candidate PGW-C / SMF.

[0393] Fig.15 1 is a block diagram showing a UDM according to an embodiment of the present disclosure. As shown in the figure, UDM 1500 includes a first receiving module 1501, which is configured to receive a registration request including first session management function (SMF) information and alternative packet data network gateway (PGW) control plane (PGW-C) / SMF information from a first session management function (SMF). UDM 1500 includes a storage module 1502, which is used to store the first SMF information and the alternative PGW-C / SMF information. This unified data management 1500 includes: a second sending module 1503, which is used to send a registration response to the first SMF.

[0394] In one embodiment, the UDM 1500 includes a second receiving module 1504 for receiving a request from a network node to retrieve an address of a first session management function (SMF) and candidate PGW-C / SMF information.

[0395] In one embodiment, the UDM 1500 includes a second sending module 1505, configured to send a response including the first SMF information and the candidate PGW-C / SMF information to the network node.

[0396] Fig.161 is a block diagram showing an ePDG according to an embodiment of the present disclosure. As shown in the figure, the ePDG 1600 includes a first sending module 1601, which is used to send a request to a unified data management (UDM) to obtain first session management function (SMF) information and alternative packet data network gateway (PGW) control plane (PGW-C) / SMF information. The data protection guide 1600 includes a receiving module 1602, which is used to receive a response including the first SMF information and the alternative PGW-C / SMF information from the UDM.

[0397] In one embodiment, the ePDG 1600 includes a determination module 1603 for determining that a failure occurs in the first SMF.

[0398] In one embodiment, the ePDG 1600 includes a selection module 1604, configured to select an alternative PGW-C / SMF according to the alternative PGW-C / SMF information.

[0399] In one embodiment, the ePDG 1600 includes a second sending module 1605, configured to send a create session request to the alternative PGW-C / SMF.

[0400] The embodiments of this document may provide many advantages, and the following is a non-exhaustive list of examples. In some embodiments of this document, even if the service combination PGW-C / SMF fails (as long as it belongs to the combined PGW-C / SMF set), it can be ensured that the PDU session can be successfully moved from 5G to 4G mobility. In some embodiments of the present invention, it can enable the MME or ePDG or AMF to select an alternative PGW-C / SMF based on the alternative PGW-C / SMF information. The embodiments of this document are not limited to the above-mentioned features and advantages. Those skilled in the art will recognize additional features and advantages after reading the following detailed description.

[0401] The term "unit" or "module" may have the conventional meaning in the field of electronics, electrical devices and / or electronic devices, and may include, for example, electrical and / or electronic circuits, devices, modules, processors, memories, logical solid-state and / or discrete devices, computer programs or instructions for performing corresponding tasks, processes, calculations, output and / or display functions, etc., such as those described in this document.

[0402] Through the functional unit, the first SMF, the second SMF, the AMF, the first PGW-C / SMF, the UDM, the MME or the ePDG may not need a fixed processor or memory, and any computing resources and storage resources may be obtained from the first SMF, the first PGW-C / SMF, the second SMF, the AMF, the UDM, the MME or the ePDG in the communication system. The introduction of virtualization technology and network computing technology can improve the utilization efficiency of network resources and the flexibility of the network.

[0403] According to one aspect of the present disclosure, there is provided a computer program product, which is tangibly stored on a computer-readable storage medium and includes instructions, which when executed on at least one processor, cause the at least one processor to perform any of the methods described above.

[0404] According to one aspect of the present disclosure, a computer-readable storage medium is provided, which stores instructions. When the instructions are executed by at least one processor, the at least one processor executes any of the methods described above.

[0405] In addition, the present invention may also provide a carrier containing the above-mentioned computer program, wherein the carrier is one of an electronic signal, an optical signal, a radio signal or a computer-readable storage medium. The computer-readable storage medium may be, for example, an optical disc or an electronic storage device, such as a RAM (random access memory), a ROM (read-only memory), a flash memory, a magnetic tape, a CD-ROM, a DVD, a Blu-ray disc, etc.

[0406] The techniques described herein can be implemented by various means, so that the device for implementing one or more functions of the corresponding device described in the embodiment includes not only the prior art means, but also means for implementing one or more functions of the corresponding device described in the embodiment, and it may include a separate means for each separate function, or it may be configured as a means for performing two or more functions. For example, these techniques can be implemented in hardware (one or more devices), firmware (one or more devices), software (one or more modules), or a combination thereof. For firmware or software, it can be implemented by a module (e.g., a program, a function, etc.) that performs the functions described herein.

[0407] Exemplary embodiments of the present invention have been described above with reference to the block diagrams and flow charts of the methods and apparatus. It should be understood that each block in the block diagrams and flow charts and the combination of blocks in the block diagrams and flow charts, respectively, can be implemented by various means including computer program instructions. These computer program instructions can be loaded onto a general-purpose computer, a special-purpose computer, or other programmable data processing device to produce a machine, so that the instructions executed on the computer or other programmable data processing device create means for implementing the functions specified in the flow chart blocks.

[0408] In addition, although the operations are shown in a particular order, it should not be understood that these operations are required to be performed in the particular order or sequence shown, or that all of the operations shown must be performed to achieve the desired result. In some cases, multitasking and parallel processing may be advantageous. Similarly, although the above discussion includes several specific implementation details, they should not be interpreted as limitations on the scope of the subject matter described herein, but rather as descriptions of the features of specific embodiments. Certain features described in the context of separate embodiments may also be implemented in combination in a single embodiment. On the contrary, the various features described in the context of a single embodiment may also be implemented in multiple embodiments individually or in any suitable sub-combination.

[0409] Although this specification contains many specific implementation details, these details should not be interpreted as limitations on any implementation or the scope of what may be claimed, but rather as descriptions of features of specific embodiments of specific implementations. Certain features described in this specification in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment may also be implemented separately or in any suitable sub-combination in multiple embodiments. In addition, although features may be described as working in certain combinations or even initially claimed, in some cases one or more features in the claimed combination may be deleted from the combination, and the claimed combination may be directed to a sub-combination or a variation of a sub-combination.

[0410] It is obvious to those skilled in the art that, with the advancement of technology, the concept of the present invention can be implemented in various ways. The above embodiments are only used to describe the present invention, not to limit the present invention, and those skilled in the art will appreciate that various modifications and changes can be made without departing from the spirit and scope of the present invention. These modifications and changes are considered to belong to the scope of the present invention and the appended claims. The scope of protection of the present invention is defined by the appended claims.

Claims

1. A method (530) performed by an access and mobility management function, AMF, in a first telecommunication system, comprising: receiving (532) candidate PGW-C / SMF information from the first packet data network gateway control plane / session management function PGW-C / SMF or the second SMF; as well as The alternative PGW-C / SMF information is sent (534) to a mobility management entity MME in the second telecommunication system.

2. The method according to claim 1, wherein receiving the alternative PGW-C / SMF information from the first PGW-C or the second SMF comprises: Sending a protocol data unit, PDU, session context request to the first PGW-C / SMF or the second SMF; as well as Receive a PDU session context response including the alternative PGW-C / SMF information from the first PGW-C / SMF or the second SMF.

3. The method according to any one of claims 1 to 2, wherein: Sending the candidate PGW-C / SMF information to the MME includes: receiving a context request from the MME; and Send a context response including the alternative PGW-C / SMF information to the MME.

4. The method of any one of claims 1 to 3, wherein the first PGW-C / SMF is a home PGW-C / SMF or an anchor PGW-C / SMF and / or the second SMF is a visited SMF or an intermediate SMF.

5. The method according to any one of claims 1 to 4, wherein the candidate PGW-C / SMF information includes information of at least one PGW-C / SMF so that the candidate PGW-C / SMF can be selected.

6. The method according to any one of claims 1 to 5, wherein the alternative PGW-C / SMF information is used by the AMF or the MME or the evolved packet data gateway ePDG to select the alternative PGW-C / SMF.

7. The method according to any one of claims 1 to 6, wherein the first PGW-C / SMF and the alternative PGW-C / SMF are functionally equivalent and interchangeable and share the same context.

8. A method (360) performed by a first PGW-C / SMF, comprising: Establishing (362) a PDU session for the user equipment UE; as well as sending (364) alternative PGW-C / SMF information to the second SMF for anchoring said PDU session at the first SMF+PGW-C or access and mobility management function AMF, Among them, when the first PGW-C / SMF has failed, an alternative PGW-C / SMF will be selected according to the alternative PGW-C / SMF information.

9. The method according to claim 8, wherein: Sending the candidate PGW-C / SMF information to the second SMF includes: receiving a protocol data unit (PDU) session creation request from the second SMF; and Send a PDU session creation response including the alternative PGW-C / SMF information to the second SMF.

10. The method according to claim 9, wherein the candidate PGW-C / SMF information is included in PDU session creation data of the PDU session creation response.

11. The method according to claim 9, wherein the first PGW-C / SMF is a home PGW-C / SMF or an anchor PGW-C / SMF and / or the second SMF is a visited SMF or an intermediate SMF.

12. The method according to claim 8, wherein: Sending the candidate PGW-C / SMF information to the second SMF includes: receiving a PDU session update request from the second SMF; and Send a PDU session update response including the alternative PGW-C / SMF information to the second SMF.

13. The method according to claim 12, wherein the alternative PGW-C / SMF information is included in the home SMF update data of the PDU session update response.

14. The method according to claim 12 or 13, wherein: The first PGW-C / SMF is a home PGW-C / SMF or an anchor PGW-C / SMF and / or the second SMF is a new access SMF or a new intermediate SMF.

15. The method according to claim 8, wherein: Sending the candidate PGW-C / SMF information to the second SMF includes: Sending a PDU session update request including the candidate PGW-C / SMF information to the second SMF; and Receive a PDU session update response from the second SMF.

16. The method according to claim 15, wherein: The alternative PGW-C / SMF information is included in the access SMF update data of the PDU session update request.

17. The method according to claim 15 or 16, wherein: The first PGW-C / SMF is a home PGW-C / SMF or an anchor PGW-C / SMF and / or the second SMF is a visited SMF or an intermediate SMF.

18. The method according to any one of claims 8 to 17, wherein: Sending the alternative PGW-C / SMF information to the AMF includes: receiving a PDU session context request from the AMF; and Send a PDU session context response containing the alternative PGW-C / SMF information to the AMF.

19. The method according to any one of claims 8 to 18, wherein the candidate PGW-C / SMF information includes information of at least one PGW-C / SMF so that the candidate PGW-C / SMF can be selected.

20. The method according to any one of claims 8-19, wherein the alternative PGW-C / SMF information is used by AMF or mobility management entity, MME, or evolved packet data gateway, ePDG, to select the alternative PGW-C / SMF.

21. The method according to any one of claims 8 to 20, wherein the first PGW-C / SMF and the alternative PGW-C / SMF are functionally equivalent and interchangeable and share the same context.

22. A method (600) performed by a mobility management entity (MME), comprising: sending (602) a context request to an access and mobility management function, AMF; as well as A context response including first PGW-C / SMF information and alternative PGW-C / SMF information is received (604) from the AMF.

23. The method according to claim 22, further comprising: Determining (612) that the first PGW-C / SMF fails; Selecting (614) an alternative PGW-C / SMF according to the alternative PGW-C / SMF information; as well as A create session request is sent (616) to the alternative PGW-C / SMF.

24. The method according to claim 22 or 23, wherein: The first PGW-C / SMF is a home PGW-C / SMF or an anchor PGW-C / SMF.

25. The method according to any one of claims 22-24, wherein the first PGW-C / SMF and the alternative PGW-C / SMF are functionally equivalent and interchangeable and share the same context.

26. The method according to any one of claims 22 to 25, wherein the candidate PGW-C / SMF information includes information of at least one PGW-C / SMF, so that the candidate PGW-C / SMF can be selected.

27. An access and mobility management function (AMF) (1000) in a first telecommunication system, comprising: Processor(1021); as well as A memory (1022) coupled to the processor (1021), the memory (1022) containing instructions executable by the processor (1021) so that the AMF (1000) is operable to: Receiving candidate PGW-C / SMF information from the first packet data network gateway control plane / session management function PGW-C / SFM or the second SMF; and The candidate PGW-C / SMF information is sent to a mobility management entity MME in the second telecommunication system.

28. The AMF of claim 27, wherein the AMF is further operable to perform the method of any one of claims 2 to 7.

29. A first PGW-C / SMF, comprising: Processor(1021); as well as A memory (1022) coupled to the processor (1021), the memory (1022) containing instructions executable by the processor (1021), whereby the first PGW-C / SMF (1000) is operable to: establishing a PDU session for a user equipment UE; and sending (364) alternative PGW-C / SMF information to the second SMF for anchoring said PDU session at the first SMF+PGW-C or access and mobility management function AMF, Among them, when the first PGW-C / SMF has failed, an alternative PGW-C / SMF will be selected according to the alternative PGW-C / SMF information.

30. The first PGW-C / SMF according to claim 29, wherein: The first PGW-C / SMF is further operable to perform the method as claimed in any one of claims 9 to 21.

31. A mobility management entity, MME (1000), comprising: Processor(1021); as well as A memory (1022) coupled to the processor (1021), the memory (1022) containing instructions executable by the processor (1021) so that the MME (1000) is operated to: Sending a context request to an access and mobility management function (AMF); and Receive a context response from the AMF including the first PGW-C / SMF information and the alternative packet data network gateway control plane / session management function PGW-C / SFM information.

32. The MME according to claim 31, wherein: The MME is further operable to perform the method of any one of claims 23 to 26.

33. A computer-readable storage medium storing instructions, which, when executed by at least one processor, cause the at least one processor to perform the method according to any one of claims 1 to 26.

34. A computer program product comprising instructions which, when executed by at least one processor, cause the at least one processor to perform the method according to any one of claims 1 to 26.

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