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

Abstract

An embodiment of the present disclosure provides a method and apparatus for configuring alternative PGW-C / SMF information. The method performed by an Access and Mobility Management Function (AMF) of a first telecommunications system may include receiving alternative packet data network gateway control plane / session management function (PGW-C / SMF) information from the first PGW-C / SMF or a second SMF. The method may further include sending the alternative PGW-C / SMF information to a Mobility Management Entity (MME) of the second telecommunications system.

Description

[Technical field]

[0001] Non-limiting and exemplary embodiments of the present disclosure relate generally to the technical field of communications, and more particularly, to a method and apparatus for configuring alternative Packet Data Network (PDN) Gateway (PGW) Control Plane (PGW-C) / Session Management Function (SMF) information. [Background technology]

[0002] This section introduces aspects of the disclosure to make it easier to understand, and therefore, the statements in this section are to be read in this light and are not to be understood as admissions about what is in the prior art or what is not in the prior art.

[0003] Communication networks such as New Radio (NR) and Long Term Evolution (LTE) defined by the 3rd Generation Partnership Project (3GPP®) introduce network function (NF) set-based session resilience where equivalent control plane NFs can be grouped into an NF set. For example, multiple PGW control plane (PGW-C) / SMF instances can be grouped into one PGW-C / SMF set. NFs in an NF set are interchangeable since they share the same context data. An NF can be replaced with an alternative NF in the same NF set in case of scenarios such as failure, load balancing, and load rebalancing. An SMF can act as an anchor SMF, intermediate SMF (I-SMF), visited SMF (V-SMF), or home SMF (H-SMF) role for different protocol data unit (PDU) session contexts.

[0004] 3GPP Release 17 introduced support for composite PGW-C / SMF sets, allowing to restore PDN connections or PDU sessions affected (by a composite PGW-C / SMF failure) by (re)selecting an alternative (composite) PGW-C / SMF associated with the same NF set. Summary of the Invention

[0005] This Summary is provided to introduce some concepts in a simplified form that are described later in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

[0006] As specified by 3GPP TS 23.007 V17.4.1, the entire disclosure of which is incorporated herein by reference, the alternative PGW-C / SMF information (i.e., PGWChangeInfoIE (Information Element)) is provided by the PGW-C / SMF to the Mobility Management Entity (MME) or the Evolved Packet Data Gateway (ePDG) only if the User Equipment (UE) is camped on a fourth generation (4G) network. Furthermore, during PDN connection establishment (see clause 31.2A of 3GPP TS 23.007 V17.4.1), such alternative PGW-C / SMF information can also be configured from the source MME to the target MME during mobility procedures (see clause 31.5 below of 3GPP TS 23.007 V17.4.1).

[0007] However, if the UE moves from 5GS to EPS (e.g. 3gpp access or non-3gpp access), when the MME or ePDG tries to contact the composite PGW-C / SMF, if the PGW-C / SMF is not reachable even though a composite PGW-C / SMF set is deployed, the MME or ePDG cannot move the PDN connection to the EPS due to lack of alternative PGW information, and the PDN connection should not be disconnected.

[0008] This problem is exacerbated in the case of home routing PDU sessions involving the V-SMF and PDU sessions with intermediate SMFs where the PGW-C / SMF was not involved in the preparation of 5G to 4G mobility procedures.

[0009] The Evolved Packet System (EPS) PDN connection of the UE in the MME / SGSN (Serving General Packet Radio Service (GPRS) Support Node) / AMF is included in the ForwardRelocationRequest message and the ContextResponse message (sent from the AMF to the MME during 5G to 4G mobility) and is prepared by the V / I-SMF (in case of a HomeRoutedPDU session involving the V-SMF or a PDU session involving an intermediate SMF).

[0010] When an anchor SMF is reselected, the corresponding information in the PDN connection context information of the EPS is likely to be updated. For example, the Internet Protocol (IP) address of the F-TEID (Full TEID (Qualified Terminal Endpoint Identifier)) in S8-c may contain the IP of the new anchor SMF. The pgwNodeName of the different SMFs is likely to be different.

[0011] Currently, there is no way for the new anchor SMF to inform the V-SMF / I-SMF of the updated PDN connection context of the EPS. When mobility occurs from 5GS (5th generation system) to EPS, the AMF gets the context from the I-SMF / V-SMF based on the old information. With the old information, the MME / SGW (Serving Gateway) finds the wrong PGW-C / SMF in the EPS, so the PDU session cannot be moved to the EPS.

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

[0013] In a first aspect of the present disclosure, a method is provided that is performed by an Access and Mobility Management Function (AMF) of a first telecommunications system. The method may include receiving alternative Packet Data Network Gateway Control Plane / Session Management Function (PGW-C / SMF) information from the first PGW-C / SMF or a second SMF. The method may further include transmitting the alternative PGW-C / SMF information to a Mobility Management Entity (MME) of the second telecommunications system.

[0014] In one embodiment, receiving alternative PGW-C / SMF information from a first PGW-C / SMF or a 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 from the first PGW-C / SMF or the second SMF, the PDU session context response including the alternative PGW-C / SMF information.

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

[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 alternative PGW-C / SMF information may include information of at least one PGW-C / SMF such that an alternative PGW-C / SMF may be selected.

[0018] In one embodiment, the alternative PGW-C / SMF information may be used by the AMF or the MME or an 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, may be interchangeable and share the same context.

[0020] In a second aspect of the present disclosure, a method is provided that is performed by a first PGW-C / SMF. The method may include establishing a PDU session for a user equipment (UE). The method may further include transmitting alternative PGW-C / SMF information to a second SMF for the PDU session anchored to the first SMF+PGW-C or an Access and Mobility Management Function (AMF). An alternative PGW-C / SMF is selected based on the alternative PGW-C / SMF information when the first PGW-C / SMF fails.

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

[0022] In one embodiment, the alternative PGW-C / SMF information may be included in 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 alternative PGW-C / SMF information to a second SMF may include receiving a PDU session update request from the second SMF and sending a PDU session update response to the second SMF including the alternative PGW-C / SMF information.

[0025] In one embodiment, the alternative PGW-C / SMF information may be included in 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 visiting SMF or a new intermediate SMF.

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

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

[0032] In one embodiment, the alternative PGW-C / SMF information may be used by the 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, may be interchangeable and share the same context.

[0034] In a third aspect of the present disclosure, a method is provided that is performed by a mobility management entity (MME). The method may include sending a context request to an access and mobility management function (AMF). The method may include receiving a context response from the AMF that includes 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 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, may be interchangeable and share the same context.

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

[0039] In a fourth aspect of the present disclosure, an Access and Mobility Management Function (AMF) of a first telecommunications system is provided. The AMF includes a processor and a memory coupled to the processor. The memory includes instructions executable by the processor. The AMF is operable to receive alternative Packet Data Network Gateway Control Plane / Session Management Function (PGW-C / SMF) information from the first PGW-C / SMF or a second SMF. The AMF is further operable to send the alternative PGW-C / SMF information to a Mobility Management Entity (MME) of 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 includes instructions executable by the processor. The first PGW-C / SMF is operable to establish a PDU session for a user equipment (UE). The first PGW-C / SMF is further operable to send alternative PGW-C / SMF information to a second SMF for the PDU session anchored to the first SMF+PGW-C or an Access and Mobility Management Function (AMF). An alternative PGW-C / SMF is selected based on the alternative PGW-C / SMF information when the first PGW-C / SMF fails.

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

[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 further include a transmission module configured to transmit alternative PGW-C / SMF information to a second SMF for the PDU session anchored to the first SMF+PGW-C or an Access and Mobility Management Function (AMF). The alternative PGW-C / SMF is selected based on the alternative PGW-C / SMF information when the first PGW-C / SMF fails.

[0043] In an eighth aspect of the present disclosure, an AMF of a first telecommunications 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 the first PGW-C / SMF or a second SMF. The AMF may further include a transmitting module configured to transmit the alternative PGW-C / SMF information to a mobility management entity (MME) of the second telecommunications system.

[0044] In a ninth aspect of the present disclosure, an MME is provided. The MME may include a sending module configured to send a context request to an Access and Mobility Management Function (AMF). The MME may further include a receiving module configured to receive a context response from the AMF, the context response including first PGW-C / SMF information and alternative packet data network gateway (PGW) control plane (PGW-C) / SMF information.

[0045] In one embodiment, the MME may further include a determining module configured to determine that the first PGW-C / SMF is faulty.

[0046] In one embodiment, the MME may further include a selection module configured to select an alternative PGW-C / SMF based on 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, there is provided a computer program product comprising instructions which, when executed by at least one processor, cause the at least one processor to perform a 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 having stored thereon instructions that, when executed by at least one processor, cause the at least one processor to perform a method according to any one of the first to third aspects.

[0050] The embodiments herein may provide many advantages, a non-exhaustive list of examples of which follows below. Some embodiments herein may ensure that a PDU session can be successfully transitioned from 5G mobility to 4G mobility even if a serving composite PGW-C / SMF fails (as far as it is related to a composite PGW-C / SMF set). Some embodiments herein may enable an MME or ePDG or AMF to select an alternative PGW-C / SMF based on alternative PGW-C / SMF information. The embodiments herein are not limited to the above-mentioned features and advantages. Those skilled in the art will recognize additional features and advantages upon 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 fully apparent from the following detailed description, taken by way of example only with reference to the accompanying drawings, in which: The drawings are illustrated to facilitate an understanding of embodiments of the present disclosure and are not necessarily drawn to scale:

[0052] [Figure 1a]A flowchart of the handover procedure from 5GS to EPS when N26 is supported is shown.

[0053] [Figure 1b] 1 shows a flowchart for idle mode mobility from 5GS to EPS using the N26 interface.

[0054] [Figure 1c] A flowchart of handover from 5GS to EPC / ePDG is shown.

[0055] [Figure 1d] 1 shows a flowchart of handover from 3GPP access using GTP over S2b to untrusted non-3GPP IP access.

[0056] [Figure 1e] 1 shows a flowchart of handover from 3GPP access using PMIPv6 over S2b to untrusted non-3GPP IP access.

[0057] [Figure 1f] 1 shows a flowchart of PDN connection establishment.

[0058] [Figure 2a] 1 illustrates a schematic of a non-roaming architecture for interworking between 5GS and EPC / E-UTRAN.

[0059] [Figure 2b] 1 illustrates a schematic of a home route roaming architecture for interworking between 5GS and EPC / E-UTRAN.

[0060] [Figure 2c] 1 illustrates a schematic of a home route roaming architecture for interworking between ePDG / EPC and 5GS.

[0061] [Figure 3a] 1 shows a flowchart of a method according to one embodiment of the present disclosure.

[0062] [Figure 3b] 4 shows a flowchart of a method according to another embodiment of the present disclosure.

[0063] [Figure 3c] 4 shows a flowchart of a method according to another embodiment of the present disclosure.

[0064] [Figure 3d] 4 shows a flowchart of a method according to another embodiment of the present disclosure.

[0065] [Figure 3e] 4 shows a flowchart of a method according to another embodiment of the present disclosure.

[0066] [Figure 3f] 4 shows a flowchart of a method according to another embodiment of the present disclosure.

[0067] [Figure 3g] 1 illustrates a flowchart of SMF registration according to one embodiment of the present disclosure.

[0068] [Figure 3h] 4 shows a flowchart of a method according to another embodiment of the present disclosure.

[0069] [Figure 4a] 4 shows a flowchart of a method according to another embodiment of the present disclosure.

[0070] [Figure 4b] 4 shows a flowchart of a method according to another embodiment of the present disclosure.

[0071] [Figure 4c] 4 shows a flowchart of a method according to another embodiment of the present disclosure.

[0072] [Figure 4d] 4 shows a flowchart of a method according to another embodiment of the present disclosure.

[0073] [Figure 4e] 4 shows a flowchart of a method according to another embodiment of the present disclosure.

[0074] [Figure 5a] 4 shows a flowchart of a method according to another embodiment of the present disclosure.

[0075] [Figure 5b] 4 shows a flowchart of a method according to another embodiment of the present disclosure.

[0076] [Figure 5c] 4 shows a flowchart of a method according to another embodiment of the present disclosure.

[0077] [Figure 5d] 4 shows a flowchart of a method according to another embodiment of the present disclosure.

[0078] [Figure 6a] 4 shows a flowchart of a method according to another embodiment of the present disclosure.

[0079] [Figure 6b] 4 shows a flowchart of a method according to another embodiment of the present disclosure.

[0080] [Figure 7a] 4 shows a flowchart of a method according to another embodiment of the present disclosure.

[0081] [Figure 7b] 4 shows a flowchart of a method according to another embodiment of the present disclosure.

[0082] [Figure 8a] 4 shows a flowchart of a method according to another embodiment of the present disclosure.

[0083] [Figure 8b] 4 shows a flowchart of a method according to another embodiment of the present disclosure.

[0084] [Figure 9] 13 shows a flowchart illustrating a method for adding PGWChangeInfo to various signaling messages according to another embodiment of the present disclosure.

[0085] [Figure 10] FIG. 1 is a block diagram illustrating an apparatus suitable for implementing some embodiments of the present disclosure.

[0086] [Figure 11a] FIG. 2 is a block diagram illustrating a first SMF according to one embodiment of the present disclosure.

[0087] [Figure 11b] FIG. 2 is a block diagram illustrating a first PGW-C / SMF according to an embodiment of the present disclosure.

[0088] [Figure 12] FIG. 2 is a block diagram illustrating a second SMF according to an embodiment of the present disclosure.

[0089] [Figure 13a] FIG. 2 is a block diagram illustrating an AMF according to one embodiment of the present disclosure.

[0090] [Figure 13b] A block diagram showing an AMF in a first telecommunications system according to one embodiment of the present disclosure.

[0091] [Figure 14] FIG. 2 is a block diagram illustrating an MME according to one embodiment of the present disclosure.

[0092] [Figure 15] FIG. 2 is a block diagram illustrating a UDM according to one embodiment of the present disclosure.

[0093] [Figure 16] FIG. 2 is a block diagram illustrating an ePDG according to one embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0094] The embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. It should be understood that these embodiments are discussed solely for the purpose of enabling those skilled in the art to better understand and thus practice the present disclosure, and are not intended to imply any limitations on the scope of the present disclosure. Throughout this specification, references to features, advantages, or similar language do not imply that all of the features and advantages that may be realized by the present disclosure should be in any single embodiment of the present disclosure, or are in any single embodiment of the present disclosure. Rather, language referring to features and advantages is understood to mean that the particular features, advantages, or characteristics described in connection with an embodiment are included in at least one embodiment of the present disclosure. Furthermore, the described features, advantages, and characteristics of the present disclosure may be combined in any suitable manner in one or more embodiments. A person skilled in the relevant art will recognize that the present disclosure may be practiced without one or more specific features or advantages of a particular embodiment. In other instances, additional features and advantages that may not be present in all embodiments of the present disclosure may be recognized in a particular embodiment.

[0095] As used herein, the term "network" refers to a network conforming to any suitable communications 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 may implement a radio technology such as Universal Terrestrial Radio Access (UTRA). UTRA includes WCDMA and other variants of CDMA. A TDMA network may implement a radio technology such as Global System for Mobile Communications (GSM). An OFDMA network may implement a radio technology such as Evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDMA, ad-hoc networks, wireless sensor networks, etc. In the following description, the terms "network" and "system" may be used interchangeably. Furthermore, communication between two devices in a network may be performed according to any suitable communication protocol, including, but not limited to, communication protocols defined by a standards organization such as 3GPP. For example, the communication protocol may include first generation (1G), 2G, 3G, 4G, 4.5G, 5G communication protocols, and / or other protocols 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 may be implemented as a network element on dedicated hardware, as a software instance running on dedicated hardware, or as a virtualized function instantiated on a suitable platform (e.g., cloud infrastructure). For example, a 5G system (5GS) is composed of 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 Proxy), NWDAF (Network Data Analysis Function), NSSF (Network Slice Selection Function), NSSAAF (Network Slice Specific Authentication and Authorization Function), etc. For example, a 4G system (such as LTE) may include an MME (Mobile 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), an SGW Control Plane (SGW-C), an E-UTRAN (Evolved Universal Terrestrial Radio Access Network) Node B (eNB), etc. In other embodiments, the network functions may be composed of different types of NFs depending on, for example, the particular network.

[0097] The term "terminal device" refers to any end device capable of accessing and receiving services from a communications network. By way of example and not limitation, a terminal device may refer to a mobile terminal, a user equipment (UE), or other suitable device. A UE may be, for example, a subscriber station (SS), a mobile subscriber station, a mobile station (MS), or an access terminal (AT). Terminal devices include, but are not limited to, portable computers, image capture terminal devices such as digital cameras, gaming terminal devices, music storage and playback appliances, mobile phones, cellular phones, smartphones, voice over IP (VoIP) phones, wireless local loop phones, tablets, wearable devices, personal digital assistants (PDAs), portable computers, desktop computers, wearable terminal devices, in-vehicle wireless terminal devices, wireless endpoints, mobile stations, laptop embedded equipment (LEE), laptop mounted equipment (LME), USB dongles, smart devices, wireless customer premises equipment (CPE), 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 to communicate according to one or more communications standards promulgated by 3GPP (3rd Generation Partnership Project), such as the LTE or NR standards of 3GPP. As used herein, "user equipment" or "UE" does not necessarily have a "user" in the sense of a human user who owns and / or operates the associated equipment. In some embodiments, a terminal device may be configured to transmit and / or receive information without direct human interaction. For example, a terminal device may be designed to transmit information to a network on a predetermined schedule, when triggered by an internal or external event, or in response to a request from the communication network. Instead, a UE may represent a device that is intended for sale to or operation by a human user, but may not be initially associated with a particular human user.

[0098] As yet another example, in an Internet of Things (IoT) scenario, a terminal device may represent a machine or other device that performs monitoring and / or measurements and transmits results of such monitoring and / or measurements to another terminal device and / or network equipment. In this case, the terminal device may be a machine-to-machine (M2M) device, which may be referred to in the 3GPP context as a machine-type communication (MTC) device. As a particular 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 include sensors, metering devices such as power meters, industrial machines, or household or personal appliances (such as personal wearables such as refrigerators, televisions, and watches). In other scenarios, the terminal device may represent a vehicle or other equipment that can monitor and / or report its operating state or other functions related to its operation.

[0099] References herein to "an embodiment," "one embodiment," "exemplary embodiment," and the like indicate that the described embodiment may include a particular feature, structure, or characteristic, but not all embodiments need to include the particular feature, structure, or characteristic. Moreover, such phrases do not necessarily refer to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one of ordinary skill in the art to affect such feature, structure, or characteristic in connection with other embodiments, whether or not expressly described.

[0100] In this specification, terms such as "first" and "second" may be used to describe various elements, but it should be understood that these elements should not be limited by these terms. These terms are merely used to distinguish one element from another element. For example, a first element can be referred to as a second element, and similarly, a second element can be referred to as a first element, without departing from the scope of the exemplary embodiments. As used herein, the term "and / or" 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 to mean "A only, B only, or both A and B." The phrase "A and / or B" should be understood to mean "A only, B only, or both A and B."

[0102] The terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the exemplary embodiments. As used herein, the singular forms "a", "an", and "the" are intended to include the plural forms unless the context clearly indicates otherwise. It will be further understood that as used herein, the terms "comprises", "comprising", "has", "having", "includes", and / or "including" specify the presence of stated 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] Please note that these terms used in this document are only used to briefly describe and distinguish between nodes, devices, networks, etc. As technology evolves, other terms with similar meanings may also be used.

[0104] In the following description and claims, unless otherwise defined, 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 TS23.007 V17.4.1 describes the recovery of PDN connection after PGW-C / SMF change as follows:

[0106] The procedures specified in clause 31 of 3GPP TS23.007 V17.4.1 allow the EPC (Evolved Packet Core) to restore PDN connections affected by a PGW-C / SMF failure with or without restart or scale-in operations, thereby maintaining the UE's connection to the PDN and corresponding services with minimal service interruption and minimal signaling in the network (e.g. no signaling with the UE).

[0107] The procedures specified in Clause 31 of 3GPP TS23.007 V17.4.1 are optional for the MME, ePDG supporting S2b over GTPv2, SGW, and PGW-C / SMF.

[0108] The procedures specified in clause 31 of 3GPP TS 23.007 V17.4.1 apply to a combo PGW-C / SMF located 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 scenarios where a PGW-C / SMF becomes unavailable (e.g. PGW-C / SMF failure without restart, PGW-C / SMF de-instantiated from a PGW-C / SMF set due to a scale-in operation) or where the PGW-C / SMF of a PDN connection needs to be changed, another PGW-C / SMF of the same PGW-C / SMF set may take over control of the PDN connection provided by the unavailable PGW-C / SMF. If a PGW-C / SMF fails due to restart, the restarted PGW-C / SMF should continue to support the same PDN connection if possible. If a PGW-C / SMF of a PGW-C / SMF set fails with or without restart, recovery (restart counter) MUST NOT be incremented over S5 / S8 (assuming the PDN connection context is still available in the PGW-C / SMF set).

[0110] The restoration of the PDN connection may be triggered by the MME (e.g. when the SGW detects a PGW-C failure and reports it to the MME), or by an ePDG supporting S2b over GTPv2, or by the PGW-C / SMF (e.g. a scale-in operation or reselection of the PGW-C / SMF by another network function such as a PCF).

[0111] The procedure specified in clause 31 of 3GPP TS 23.007 V17.4.1 supports restoration of home routed PDN connections if the VPLMN (Visiting PLMN (Public Land Mobile Network)) and HPLMN (Home PLMN) support this procedure. If the VPLMN or HPLMN does not support this procedure, the existing behavior applies. For example, when the MME and SGW detect a failure or restart of the PGW-C / SMF, they may clear all PDN connections of the PGW-C / SMF and the MME may request the UE to release and reactivate some PDN connections (e.g. PDN connections of the IMS (IP Multimedia Subsystem)).

[0112] 5G to 4G mobility (including 3GPP and non-3GPP access) is supported as specified in 3GPP TS23.502 V17.2.1 clause 4.11 below.

[0113] Handover from 5GS to EPS using N26 interface

[0114] Figure 1a shows the flowchart of the handover procedure from 5GS to EPS when N26 is supported, 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) decides which PLMN to use in the target network as specified in 3GPP TS23.501 V17.2.0. The source NG-RAN must indicate to the AMF the selected PLMN ID (identifier) ​​to be used in the target network as part of the Tracking Area Identity (TAI) sent in the HO (Handover) Required message.

[0116] In case of handover 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 is later changed to a 5GS shared network.

[0117] As specified in clause 4.9.1.3.1 of 3GPP TS 23.502 V17.2.1, during the handover procedure the source AMF shall reject any SMF+PGW-C initiated N2 requests received since the handover procedure has started and shall include an indication that the request is temporarily rejected because the handover procedure is in progress.

[0118] Upon receiving a rejection for an N2 request(s) initiated by the SMF+PGW-C indicating that the request is temporarily rejected due to an ongoing handover procedure, the SMF+PGW-C shall act as specified in 3GPP TS23.401 V17.3.0.

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

[0120] For a PDU session, the AMF decides whether to obtain the context containing the EPSPDN connection of the mapped UE from the V-SMF (in case of HR (Home Routed) roaming) or from the SMF+PGW-C (in case of non-roaming or LBO (Local Break Out) roaming) as follows:

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

[0122] -The EBI values ​​that cannot be forwarded are determined by the AMF if the target MME does not support 15 EPS bearers. That is, if the AMF decides not to forward EBI values ​​in the range 1-4 to EPS and there are still 8 or more EBI values ​​related to the PDU session, the AMF determines the EBI values ​​not to forward to EPS based on S-NSSAI and ARP as specified in clause 5.17.2.2.1 of 3GPP TS 23.501 V17.2.0.

[0123] - The AMF does not obtain the context of a PDU session that cannot be transferred to the EPS because there is no assigned EBI, or the assigned EBI is not transferable, or a combination of the two.

[0124] Other procedures are described in 3GPP TS23.502 V17.2.1, section 4.11.1.2.1, but will not be described here for the sake of brevity.

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

[0126] Figure 1b shows the flowchart of idle mode mobility from 5GS to EPS using the N26 interface, which is the same as Figure 4.11.1.3.2-1 of 3GPP TS23.502 V17.2.1.

[0127] In case of network sharing, the UE selects the target PLMN ID according to clause 5.18.3 of 3GPP TS23.501 V17.2.0.

[0128] Clause 4.11.1.3.2 of 3GPP TS23.502 V17.2.1 covers the case of idle mode mobility from 5GC (5G Core) to EPC. When the UE moves from NG-RAN / 5GS to the coverage area of ​​E-UTRA / EPS, it performs a tracking area update procedure in E-UTRA (Evolved Universal Terrestrial Radio Access) / EPS.

[0129] The procedure specified in 3GPP TS 23.502 V17.2.1 clause 4.11.1.3.2 involves a tracking area update to the EPC, setting up default EPS bearers and dedicated bearers in the EPC in steps 1 to 11, and reactivating them if necessary.

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

[0131] For a PDU session, the AMF decides whether to obtain the context including the EPS connection of the mapped UE 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 it can forward one or more EBIs, it sends an Nsmf_PDUSession_ContextRequest to the V-SMF or SMF+PGW-C and includes in the message any EBI values ​​that cannot be forwarded.

[0133] -The EBI values ​​that cannot be transferred are determined by the AMF if the target MME does not support 15 EPS bearers. That is, if the AMF decides not to transfer EBI values ​​in the range 1 to 4 to EPS and there are still 8 or more EBI values ​​related to the PDU session, the AMF determines the EBI values ​​not to transfer to EPS based on S-NSSAI and ARP as specified in 3GPP TS23.501 V17.2.05.17.2.2.1.

[0134] - The AMF does not obtain the context of a PDU session that cannot be transferred to the EPS because there is no assigned EBI, or the assigned EBI is not transferable, or a combination of the two.

[0135] In non-roaming or LBO roaming, the AMF searches for a context that includes the mapped EPS bearer context.

[0136] -The AMF provides the target MME capabilities to the PGW-C+SMF in the Nsmf_PDUSession_ContextRequest, allowing the SMF+PGW-C to determine whether to include an EPS bearer context of Ethernet PDN type or non-IP PDN type.

[0137] -If the AMF includes a not forwarded EBI list in the Nsmf_PDUSession_ContextRequest and 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 entire PDU session shall not be forwarded to EPS), otherwise, if the EBI value of the QoS flow associated with the default QoS rule is not included in the not forwarded EBI list, 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 the AMF sends an Nsmf_PDUSession_ContextRequest to the V-SMF or SMF+PGW-C, the AMF indicates whether the target MME supports user plane integrity protection with EPS.

[0139] The above procedure is performed for all SMF+PGW-Cs associated with a 3GPP access and corresponding to PDU sessions of UEs to which an EBI is assigned.

[0140] In home route roaming, the AMF requests the V-SMF to provide the SMF context using Nsmf_PDUSession_ContextRequest.

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

[0142] Other procedures are described in 3GPP TS23.502 V17.2.1, section 4.11.1.3.2, but will not be described here for the sake of brevity.

[0143] Handover from 5GS to EPC / ePDG

[0144] Figure 1c shows the flowchart of handover from 5GS to EPC / ePDG, which is the same as Figure 4.11.4.2-1 of 3GPP TS23.502 V17.2.1.

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

[0146] Other procedures are described in section 4.11.4.2 of 3GPP TS23.502 V17.2.1, but the description thereof will be omitted here for the sake of brevity.

[0147] FIG. 1d is a flowchart of handover from 3GPP access using GTP in S2b to untrusted non-3GPP IP access, which is the same as FIG. 8.6.2.1-1 in 3GPP TS23.402 V17.0.0.

[0148] Step A, the procedure of subclass 8.2.3 of 3GPP TS23.402 V17.0.0 prior to steps 2 to 4.

[0149] Other procedures are described in section 8.6.2.1 of 3GPP TS23.402 V17.0.0, but the description thereof will be omitted here for the sake of brevity.

[0150] FIG. 1e shows a flowchart of handover from 3GPP access to untrusted non-3GPP IP access via PMIPv6 in S2b, which is the same as FIG. 8.2.3-1 in 3GPP TS23.402 V17.0.0.

[0151] In step 4, the IKEv2 tunnel establishment procedure is initiated by the UE. The ePDG IP address to which the UE needs to form an IPsec tunnel is discovered as specified in 3GPP TS23.402 V17.0.0, clause 4.5.4. After the UE is authenticated, it is also allowed to access the APN (Access Point Name). As part of the access authentication, the PDN GW ID is sent from the 3GPP AAA (Authentication, Authorization, Accounting) server to the ePDG.

[0152] Other procedures are described in section 8.2.3 of 3GPP TS23.402 V17.0.0, but will not be described here for the sake of brevity.

[0153] As specified in 3GPP TS 23.007 V17.4.1, the alternative PGW-C / SMF information (i.e., PGWChangeInfoIE (information element)) is provided by the PGW-C / SMF to the mobility management entity (MME) or evolved packet data gateway (ePDG) only if the user equipment (UE) is camped on a fourth generation (4G) network. For example, during PDN connection establishment (see clause 31.2A of 3GPP TS 23.007 V17.4.1), such alternative PGW-C / SMF information may be set from the source MME to the target MME during the mobility procedure (see clause 31.5 below of 3GPP TS 23.007 V17.4.1).

[0154] FIG. 1f shows a flowchart of PDN connection establishment, which is the same as FIG. 31.2A-1 of 3GPP TS23.007 V17.4.1.

[0155] The PDN connection is established as defined in 3GPP TS 23.402 V17.0.0, clause 7.2.4, with the following additions:

[0156] In step 1, during PDN connection establishment or when a PDU session is moved from 5GS to EPC / ePDG, the ePDG may signal in the CreateSessionRequest that it supports this procedure by including PGWSetSupportIndication.

[0157] In step 2, if the CreateSessionRequest indicates support for this procedure, the PGW-C / SMF may return a PGWChangeInfoIE in the CreateSessionResponse. The PGWChangeInfoIE shall contain the PGW Set FQDN of a PGW / SMF in the set or the FQDN or IP address of an alternative PGW-C / SMF. Receipt of this information indicates to the ePDG that this procedure is supported by the PGW-C / SMF for PDN connectivity and that in case the PGW-C / SMF becomes unreachable, an alternative PGW-C / SMF instance can be found using the PGW Set FQDN or the FQDN or IP address of the alternative PGW.

[0158] Similarly, the PDU session shall move from 5GS to EPC / ePDG as defined in 3GPP TS23.502 V17.2.1 clause 4.11.4, with the following additions:

[0159] -The ePDG can signal its support for this procedure by including PGWSetSupportIndication in the CreateSessionRequest during handover from 5GS to EPC / ePDG (see section 4.11.4.2 of 3GPP TS23.502 V17.2.1).

[0160] -If the CreateSessionRequest received by the PGW-C / SMF indicates support for this procedure, the PGW-C / SMF may return a PGWChangeInfoIE (same content as above) in the CreateSessionResponse and provide the same indication as above to the ePDG.

[0161] Section 31.5 of 3GPP TS23.007 V17.4.1 describes inter-MME mobility. During inter-MME mobility, the source MME forwards PGWChangeInfo to the target MME if the target MME is available.

[0162] However, when the UE moves from 5GS to EPS (3gpp access or non-3gpp access), if the MME or ePDG tries to contact the composite PGW-C / SMF and the PGW-C / SMF cannot be reached even though a composite PGW-C / SMF set is deployed, the PDN connection cannot be moved to EPS because the MME or ePDG does not have the alternative PGW information, and the PDN connection is disconnected.

[0163] This problem is exacerbated in the case of HomeRoutedPDU sessions involving a V-SMF, or PDU sessions with intermediate SMFs where the PGW-C / SMF was not involved in the preparation of the 5G to 4G mobility procedure.

[0164] The EPS PDN connection of the UE in the MME / SGSN (Serving General Packet Radio Service (GPRS) Support Node) / AMF is included in the ForwardRelocationRequest message and the ContextResponse message (sent from the AMF to the MME during 5G to 4G mobility) and is prepared by the V / I-SMF (for a HomeRoutedPDU session involving the V-SMF or for a PDU session involving an intermediate SMF).

[0165] The following table is excerpted from 3GPP TS29.274 V17.5.0, the disclosure of which is incorporated herein by reference in its entirety.

[0166] Table 7.3.1-2: UE EPSPDN connection of MME / SGSN / AMF in ForwardRelocationRequest TIFF2025515580000002.tif30153

[0167] Table 7.3.1-8: PGWChangeInfo with ForwardRelocationRequest TIFF2025515580000003.tif41153

[0168] Table 7.3.6-2: UE EPSPDN connection of MME / SGSN / AMF in ContextResponse TIFF2025515580000004.tif27153

[0169] Table 7.3.6-6: PGWChangeInfo with ContextResponse TIFF2025515580000005.tif41153

[0170] The data type SmContextRetrievedData specified in 3GPP TS29.502 V17.4.0 is the message body of the Nsmf_PDUSession_ContextResponse message, see also steps 2a and 5a of 4.11.1.2.2 and 4.11.1.3.2 of 3GPP TS29.502 V17.4.0.

[0171] The following table is excerpted from 3GPP TS29.502 V17.4.0.

[0172] Table 6.1.6.2.27-1: SmContextRetrievedData Type Definition TIFF2025515580000006.tif29153

[0173] Table 6.1.6.3.2-1: Simple Data Types TIFF2025515580000007.tif13153

[0174] Table 6.1.6.2.31-1: EpsPdnCnxInfo type definition TIFF2025515580000008.tif28153

[0175] When an anchor SMF is reselected, 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 Fully Qualified Terminal Endpoint Identifier (F-TEID) of S8-c will include the IP of the new anchor SMF. The pgwNodeName of different SMFs is likely to be different.

[0176] Currently, there is no way for the new anchor SMF to inform the V-SMF / I-SMF of the updated PDN connection context of the EPS. When mobility occurs from 5GS (5th generation system) to EPS, the AMF gets the context from the I-SMF / V-SMF based on the old information. With the old information, the MME / SGW (Serving Gateway) finds the wrong PGW-C / SMF in the EPS, so the PDU session cannot be moved to the EPS.

[0177] To overcome or mitigate at least one of the above problems and other problems, a solution is needed for configuring alternative PGW-C / SMF information.

[0178] Although the subject matter described herein may be implemented in any suitable type of system using any suitable components, the embodiments disclosed herein are described in the context of a communication system conforming to the exemplary system architecture illustrated in Figures 2a-2c. For simplicity, the system architecture of Figures 2a-2c depicts only some exemplary elements. In practice, the communication system may further include any additional elements suitable for supporting communication between terminal devices, or between a wireless device and another communication device (such as a landline, a service provider, or any other network node or terminal device). The communication system may provide communications and various types of services to one or more terminal devices and facilitate the terminal devices' access to and / or use of services provided by or via the communication system.

[0179] Figure 2a illustrates a schematic diagram of a non-roaming architecture for interworking between 5GS and EPC / E-UTRAN. The architecture in Figure 2a is the same as Figure 4.3.1-1 described in 3GPP TS23.501 V17.2.0. The system architecture in Figure 2a may include several exemplary NFs, such as HSS+UDM, PCF, SMF+PGW-C, UPF+PGW-U, SGW, MME, AMF, E-UTRAN, NG-RAN, and UE.

[0180] Also shown in Figure 2a are reference points such as N10, N7, N4, S5-C, S5-U, N15, N11, S6a, N8, S11, N26, S1-U, N1, N2, N3, S1-MME, etc. For example, these reference points may be realized by specifying several service consumers and providers and their interactions to perform certain system procedures via corresponding interfaces.

[0181] The various NFs shown in Figure 2a may be responsible for functions such as session management, mobility management, authentication, security, policy management, etc. NFs such as those shown in Figure 2a are described in 3GPP TS 23.501 V17.2.0 and 3GPP TS 23.401 V17.3.0, but the description of which is omitted here for brevity.

[0182] Figure 2b shows a schematic diagram of a home route roaming architecture for interworking between 5GS and EPC / E-UTRAN. The architecture of Figure 2b is the same as Figure 4.3.2-2 described in 3GPP TS23.501 V17.2.0. The system architecture of Figure 2b may include several exemplary NFs, such as HSS+UDM, h-PCF (Home PCF), SMF+PGW-C, UPF+PGW-U, SGW, v-PCF (Visiting PCF), v-SMF (Visiting SMF), UPF, MME, AMF, E-UTRAN, NG-RAN, and UE.

[0183] Also shown in Figure 2b are reference points 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 may be realized, for example, by specifying several service consumers and providers and their interactions to perform certain system procedures via corresponding interfaces.

[0184] The various NFs shown in Figure 2b may be responsible for functions such as session management, mobility management, authentication, security, policy management, etc. NFs such as those shown in Figure 2b are described in 3GPP TS 23.501 V17.2.0 and 3GPP TS 23.401 V17.3.0, but the description thereof is omitted here for the sake of brevity.

[0185] Figure 2c shows a schematic diagram of a home route roaming architecture for interworking between ePDG / EPC and 5GS. The architecture in Figure 2c is the same as Figure 4.3.4.2-2 described in 3GPP TS23.501 V17.2.0. The system architecture in Figure 2c may include several 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, and UE.

[0186] Also shown in Fig. 2c are reference points 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 may be realized by specifying several service consumers and providers and their interactions to perform certain system procedures through the corresponding interfaces.

[0187] The various NFs shown in Figure 2c may be responsible for functions such as session management, mobility management, authentication, security, policy management, etc. NFs such as those shown in Figure 2c are described in 3GPP TS 23.501 V17.2.0, 3GPP TS 23.402 V17.0.0, and 3GPP TS 23.401 V17.3.0, but are not described here for brevity.

[0188] 3a illustrates a flowchart of a method according to one embodiment of the present disclosure, which may be performed by an apparatus within or at a first session management function (SMF) or communicatively coupled to the first SMF. In this manner, the apparatus may provide means or modules for accomplishing various portions of the method 300, as well as means or modules for accomplishing other processes in conjunction with other components.

[0189] In block 302, the first SMF may send alternative packet data network gateway (PGW) control plane (PGW-C) / SMF information to a second SMF or an access and mobility management function (AMF) or a unified data management (UDM).

[0190] The term "PGW-C / SMF" may refer to a combination of a PGW-C and an SMF.

[0191] The second SMF may be any suitable SMF that requires PGW-C / SMF information. For example, the first SMF is an old SMF and the second SMF is a new SMF. The first SMF may be a home PGW-C / SMF or an anchor PGW-C / SMF, and the second SMF may be a new visiting SMF or a new intermediate SMF.

[0192] The alternative PGW-C / SMF information may consist of any suitable information related to the alternative PGW-C / SMF, for example, the alternative PGW-C / SMF may consist of an address of the alternative PGW-C / SMF or other information that enables a network node (AMF, MME, ePDG, etc.) to find / select the alternative PGW-C / SMF.

[0193] In one embodiment, the alternate PGW-C / SMF information includes at least one of a PGW Set Fully Qualified Domain Name (FQDN), an Internet Protocol address of the alternate PGW-C / SMF, or an FQDN of the alternate PGW-C / SMF. For example, the alternate PGW-C / SMF information may be the same as the PGWChangeInfoIE described in 3GPP TS29.274 V17.5.0.

[0194] The first SMF may send PGW-C / SMF information to the second SMF or AMF or UDM in various ways, and the present disclosure does not limit it. For example, the first SMF may send PGW-C / SMF information to the second SMF or AMF or UDM in response to a request from 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. Furthermore, if the PGW-C / SMF information is changed, the first SMF may actively send PGW-C / SMF information to the second SMF or AMF or UDM.

[0195] 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.

[0196] In one embodiment, the first SMF and the alternative PGW-C / SMF are functionally equivalent, interchangeable, and share the same context, e.g., the first SMF and the alternative PGW-C / SMF are arranged in a PGW-C / SMF set.

[0197] 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. For example, if the AMF or MME or ePDG determines or detects that the first SMF is down, the AMF or MME or ePDG may select an alternative PGW-C / SMF based on the alternative PGW-C / SMF information. As another example, if the AMF or MME or ePDG decides to select an alternative PGW-C / SMF due to other reasons such as load balancing, load rebalancing, etc., the AMF or MME or ePDG may select an alternative PGW-C / SMF based on the alternative PGW-C / SMF information.

[0198] 3b shows a flowchart of a method according to another embodiment of the present disclosure, which may be implemented in, implemented as, or performed by an apparatus communicatively coupled to the first SMF. In this manner, the apparatus may provide means or modules for accomplishing various parts of the method 310, as well as means or modules for accomplishing other processes in cooperation with other components. Some parts described in the above embodiments are omitted here for brevity.

[0199] In block 312, the first SMF may receive a create protocol data unit (PDU) session request from the second SMF. The create PDU session request may be used to create a new PDU session in the first SMF (such as the H-SMF or SMF) or to create an association with an existing PDN connection in the Home SMF+PGW-C.

[0200] In one embodiment, the first SMF is a home PGW-C / SMF or an anchor PGW-C / SMF, and the second SMF is a visited SMF or an intermediate SMF.

[0201] In one embodiment, the PDU session creation request may be an Nsmf_PDUSession_CreateRequest as described in 3GPP TS23.502 V17.2.1. For example, the PDU session creation request may be an Nsmf_PDUSession_CreateRequest as described in step 6 of Figure 4.3.2.2-1 of 3GPP TS23.502 V17.2.1.

[0202] In block 314, the first SMF may send a PDU session creation response including the alternative PGW-C / SMF information to the second SMF.

[0203] In an embodiment, the PDU session creation response may be a Nsmf_PDUSession_Create response as described in 3GPP TS23.502 V17.2.1, except that the response further includes the 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 FIG. 4.3.2.2-1 of 3GPP TS23.502 V17.2.1, except that the response further includes the alternative PGW-C / SMF information.

[0204] In one embodiment, the alternative PGW-C / SMF information includes PDU session creation data of the PDU session creation response.

[0205] For example, Table 6.1.6.2.10-1 of 3GPP TS29.502 V17.4.0 may add the following underlined content:

[0206] Table 6.1.6.2.10-1: PduSessionCreatedData type definition TIFF2025515580000009.tif42153

[0207] 3c shows a flowchart of a method according to another embodiment of the present disclosure, which may be performed by an apparatus within or at or communicatively coupled to the first SMF. In this manner, the apparatus may provide means or modules for accomplishing various parts of the method 320, as well as means or modules for accomplishing other processes in cooperation with other components. Some parts described in the above embodiments are omitted here for brevity.

[0208] In block 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.

[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 new visiting SMF or a new intermediate SMF.

[0210] In one embodiment, the PDU session update request may be an Nsmf_PDUSession_UpdateRequest as described in 3GPP TS23.502 V17.2.1. For example, the PDU session update request may be an Nsmf_PDUSession_UpdateRequest as described in step 1a or 1e of Figure 4.3.3-1 of 3GPP TS23.502 V17.2.1.

[0211] In block 324, the first SMF may send a PDU session update response including the alternative PGW-C / SMF information to the second SMF.

[0212] In one embodiment, the PDU session update response may be a Nsmf_PDUSession_Update response as described in 3GPP TS23.502 V17.2.1, except that the response further includes the 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 4.3.3-1 of 3GPP TS23.502 V17.2.1, except that the response further includes the alternative PGW-C / SMF information.

[0213] In one embodiment, the alternative PGW-C / SMF information includes home SMF update data in a PDU session update response.

[0214] For example, Table 6.1.6.2.12-1 of 3GPP TS29.502 V17.4.0 may add the following underlined content:

[0215] Table 6.1.6.2.12-1: HsmfUpdatedData type definition TIFF2025515580000010.tif58153

[0216] 3d shows a flowchart of a method according to another embodiment of the present disclosure, which may be implemented in, implemented as, or performed by an apparatus communicatively coupled to the first SMF. In this manner, the apparatus may provide means or modules for accomplishing various parts of the method 330, as well as means or modules for accomplishing other processes in cooperation with other components. Some parts described in the above embodiments are omitted here for brevity.

[0217] In block 332, the first SMF may send a PDU session update request including the alternative PGW-C / SMF information to the second SMF. The PDU session update request may be used to update an established PDU session.

[0218] In one embodiment, the first SMF is a home PGW-C / SMF or an anchor PGW-C / SMF, and the second SMF is a visited SMF or an intermediate SMF.

[0219] In one embodiment, the PDU session update request may be a Nsmf_PDUSession_UpdateRequest as described in 3GPP TS23.502 V17.2.1, except that the PDU session update request further includes the 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 4.3.3-1 of 3GPP TS23.502 V17.2.1, except that the PDU session update request further includes the alternative PGW-C / SMF information.

[0220] In block 334, the first SMF may receive a PDU session update response from the second SMF.

[0221] In one embodiment, the PDU session update response may be a Nsmf_PDUSession_Update response as described in 3GPP TS23.502 V17.2.1. For example, the PDU session update response may be a Nsmf_PDUSession_Update response as described in step 15 of Figure 4.3.3-1 of 3GPP TS23.502 V17.2.1.

[0222] In one embodiment, the alternative PGW-C / SMF information includes visited SMF update data of the PDU session update request.

[0223] For example, Table 6.1.6.2.15-1 of 3GPP TS29.502 V17.4.0 may add the following underlined content:

[0224] Table 6.1.6.2.15-1: VsmfUpdateData type definition TIFF2025515580000011.tif59153

[0225] According to various embodiments, for a home-routed PDU session or a PDU session involving an I-SMF, the first SMF, such as the composite PGW-C / SMF, always provides the “PGWChangeInfo” (a string in “byte” format as defined in the OpenAPI specification (OpenAPI Initiative, “OpenAPI Specification version 3.0.0”, https: / / spec.openapis.org / oas / v3.0.0), i.e. the base64 encoded character of the “PGWChangeInfo” IE specified in Table 7.3.1-8 or Table 7.3.6-6 of 3GPP TS29.274 V17.5.0 for the N26 interface) to the V / I-SMF (e.g. in PduSessionCreatedData (e.g. for a PDU session establishment), HsmfUpdatedData (e.g. for a V / I-SMF change procedure), and VsmfUpdateData (e.g. when the composite PGW-C / SMF wants to change the “PGWChangeInfo”)).

[0226] In one embodiment, when a second SMF, such as a V / I-SMF, receives the “PGWChangeInfo”, it must store it and include it in SmContextRetrievedData during a 5G to 4G mobility procedure, as described in clause 6.1.6.2.27 of 3GPP TS29.502 V17.4.0.

[0227] 3e shows a flowchart of a method according to another embodiment of the present disclosure, which may be implemented in, implemented as, or performed by an apparatus communicatively coupled to the first SMF. In this manner, the apparatus may provide means or modules for accomplishing various parts of the method 340, as well as means or modules for accomplishing other processes in cooperation with other components. Some parts described in the above embodiments are omitted here for brevity.

[0228] In 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 a session management (SM) context.

[0229] In one embodiment, the first SMF is a Home PGW-C / SMF or an Anchor PGW-C / SMF or a Visited SMF or an I-SMF.

[0230] In one embodiment, the PDU session context request may be an Nsmf_PDUSession_ContextRequest as described in 3GPP TS23.502 V17.2.1. For example, the PDU session context request may be an Nsmf_PDUSession_ContextRequest as described in step 2a of Figure 4.11.1.2.1-1 of 3GPP TS23.502 V17.2.1. In another example, the PDU session context request may be an Nsmf_PDUSession_ContextRequest as described in step 5a of Figure 4.11.1.3.2-1 of 3GPP TS23.502 V17.2.1.

[0231] In block 344, the first SMF may send a PDU session context response including the alternative PGW-C / SMF information to the AMF.

[0232] In one embodiment, the PDU session context response may be a Nsmf_PDUSession_ContextReponse as described in 3GPP TS23.502 V17.2.1, except that it further includes the alternative PGW-C / SMF information. For example, the PDU session context response may be a Nsmf_PDUSession_ContextReponse as described in step 2c of Figure 4.11.1.2.1-1 of 3GPP TS23.502 V17.2.1, except that it further includes the alternative PGW-C / SMF information. In another example, the PDU session context response may be a Nsmf_PDUSession_ContextReponse as described in step 5c of Figure 4.11.1.3.2-1 of 3GPP TS23.502 V17.2.1, except that it further includes the alternative PGW-C / SMF information.

[0233] In an embodiment, when a UE receives an SmContextRetrieveRequest from an AMF that is transitioning from 5G to 4G, the first SMF, such as a combined PGW-C / SMF, must include "PGWChangeInfo" as part of the EpSPdnCnxContainer that it includes in the SmContextRetrievedData, as described in clause 6.1.6.2.27 of 3GPP TS29.502 V17.4.0.

[0234] 3f shows a flowchart of a method according to another embodiment of the present disclosure, which may be implemented in, implemented as, or performed by an apparatus communicatively coupled to the first SMF. In this manner, the apparatus may provide means or modules for accomplishing various parts of the method 350, as well as means or modules for accomplishing other processes in cooperation with other components. Some parts described in the above embodiments are omitted here for brevity.

[0235] In block 352, the first SMF may send a registration request to the UDM including the first SMF information and the alternative PGW-C / SMF information. For example, the registration request may be used to register a serving NF for the session with the UDM.

[0236] In one embodiment, the registration request may be a Nudm_UECM_RegistrationRequest as described in 3GPP TS23.502 V17.2.1. For example, the registration request may be a Nudm_UECM_RegistrationRequest as described in step 12c of FIG. 4.3.2.2-1 of 3GPP TS23.502 V17.2.1.

[0237] In block 354, the first SMF receives a registration response from the UDM.

[0238] In one embodiment, the registration response may be a Nudm_UECM_RegistrationResponse as described in 3GPP TS23.502 V17.2.1. For example, the registration response may be a Nudm_UECM_RegistrationResponse as described in step 12c of Figure 4.3.2.2-1 of 3GPP TS23.502 V17.2.1.

[0239] In an embodiment, the first SMF, such as the combined PGW-C / SMF, includes "PGWChangeInfo" in the SmfRegistration to UDM when the combined PGW-C / SMF registers a PDU session and sends a Nudm_UECM_Registration request (data type SmfRegistration as specified in 3GPP TS29.503 V17.6.0). This allows a network node, such as an ePDG, to obtain the "PGWChangeInfo" from the UDM / HSS / AAA and use it for reselection, if necessary, when the UE transitions from 5G to 4G non-3gpp access.

[0240] FIG. 3g illustrates a flowchart of SMF registration according to one embodiment of the present disclosure.

[0241] In step 1, the SMF creates an SMF registration by sending a PUT request to resource ... / {ueId} / registrations / smf-registrations / {pduSessionId}, present in the message body. The PUT request includes the first SMF information and the alternative PGW-C / SMF information.

[0242] If the SMF belongs to an SMF set, the NF set ID of the SMF set is included in the request message.

[0243] If EPS interworking is supported, when the SMF+PGW-C registers to the UDM, it MUST include in the UDM the ID of the PCF selected for the PDU session.

[0244] In step 2a, the UDM responds with "201 Created" with a message body containing a representation of the created SMF registration.

[0245] In step 2b, if the individual resource exists, on success, the UDM updates the resource by replacing it with the received resource information and responds with "200 OK" with a message body containing a representation of the updated individual SmfRegistration resource.

[0246] If the new SMF is not in the SMF set or is not in the same SMF set as the old SMF, the UDM MUST invoke the unsubscribe-notification service operation on the old SMF using the callback URI provided by the old SMF.

[0247] In step 2c, if the operation cannot be authorized due to the UE not having the required subscription data, access denial, or roaming restrictions, then the HTTP (HyperText Transport Protocol) status code "403 Forbidden" should be returned with additional error information in the response body (in the "ProblemDetails" element). Subscription information associated with a specific DNN (if any) shall take precedence over subscription information associated with a wildcard DNN.

[0248] On failure, an appropriate HTTP status code MUST be returned to indicate the error, and any additional error information MUST be returned in the PUT response body.

[0249] In one embodiment, the alternative PGW-C / SMF information is included in the SMF registration data of the registration request.

[0250] In one embodiment, Table 6.2.6.2.4-1 of 3GPP TS29.503 V17.6.0 may add the following underlined content:

[0251] Table 6.2.6.2.4-1: SmfRegistration type definition TIFF2025515580000012.tif77153

[0252] 3h shows a flowchart of a method according to another embodiment of the present disclosure, which may be performed by an apparatus implemented in, implemented as, or communicatively coupled to the first PGW-C / SMF. In this manner, the apparatus may provide means or modules for accomplishing various parts of the method 360, as well as means or modules for accomplishing other processes in cooperation with other components. Some parts described in the above embodiments are omitted here for brevity.

[0253] In block 362, the first PGW-C / SMF may establish a PDU session for a user equipment (UE).

[0254] In block 364, the first PGW-C / SMF may send alternative PGW-C / SMF information to a second SMF for PDU sessions anchored to the first SMF+PGW-C or an access and mobility management function (AMF).

[0255] In an embodiment, if the first PGW-C / SMF fails, an alternative PGW-C / SMF is selected based on the alternative PGW-C / SMF information.

[0256] In one embodiment, sending the alternative PGW-C / SMF information to the second SMF may include receiving a create protocol data unit (PDU) session request from the second SMF. The method may further include sending a create PDU session response to the second SMF that includes the alternative PGW-C / SMF information.

[0257] In one embodiment, the alternative PGW-C / SMF information is included in the create PDU session data of the create PDU session response.

[0258] In one embodiment, the first PGW-C / SMF is a home PGW-C / SMF or an anchor PGW-C / SMF, and / or the second SMF is a visiting SMF or an intermediate SMF.

[0259] 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 to the second SMF including the alternative PGW-C / SMF information.

[0260] In one embodiment, the alternative PGW-C / SMF information may include home SMF update data in a PDU session update response.

[0261] In one embodiment, 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 visiting SMF or a new intermediate SMF.

[0262] 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.

[0263] In one embodiment, the alternative PGW-C / SMF information may include visited SMF update data of a PDU session update request.

[0264] In one embodiment, the first PGW-C / SMF is a home PGW-C / SMF or an anchor PGW-C / SMF, and / or the second SMF is a visiting SMF or an intermediate SMF.

[0265] 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 to the AMF including the alternative PGW-C / SMF information.

[0266] In one embodiment, the alternative PGW-C / SMF information may include information of at least one PGW-C / SMF such that an alternative PGW-C / SMF can be selected.

[0267] 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.

[0268] In one embodiment, the first PGW-C / SMF and the alternative PGW-C / SMF are functionally equivalent and interchangeable and may share the same context.

[0269] 4a shows a flowchart of a method according to another embodiment of the present disclosure, which may be performed by an apparatus implemented in, implemented in, implemented as, or communicatively coupled to the second SMF. In this manner, the apparatus may provide means or modules for accomplishing various parts of the method 400, as well as means or modules for accomplishing other processes in cooperation with other components. Some parts described in the above embodiments are omitted here for brevity.

[0270] At block 402, the second SMF may receive alternative packet data network gateway (PGW) control plane (PGW-C) / SMF information from the first SMF.

[0271] For example, in the above embodiment, the first SMF may send the alternative PGW-C / SMF information to the second SMF, and then the second SMF may receive the alternative PGW-C / SMF information. After receiving the alternative PGW-C / SMF information, the second SMF may store the alternative PGW-C / SMF information.

[0272] At block 404, the second SMF may send the alternative PGW-C / SMF information to an access and mobility management function (AMF).

[0273] The second SMF may send the alternative PGW-C / SMF information to the AMF in various ways, and the present disclosure does not limit it. For example, the second SMF may send the alternative PGW-C / SMF information to the AMF in response to a request from the AMF. Alternatively, the second SMF may proactively send the alternative PGW-C / SMF information to the AMF. Furthermore, if the PGW-C / SMF information is changed, the second SMF may send the alternative PGW-C / SMF information to the AMF.

[0274] The second SMF may send the alternative PGW-C / SMF information to the AMF in an existing message or a new message.

[0275] In one embodiment, the alternative PGW-C / SMF information includes at least one of a PGW set fully qualified domain name (FQDN), an Internet Protocol address of the alternative PGW-C / SMF, or an FQDN of the alternative PGW-C / SMF.

[0276] In one embodiment, the alternative PGW-C / SMF information is used by an AMF or a mobility management entity (MME) or an evolved packet data gateway (ePDG) to select an alternative PGW-C / SMF.

[0277] In one embodiment, the first Session Management Function (SMF) and the alternative PGW-C / SMF are functionally equivalent, interchangeable, and share the same context.

[0278] 4b shows a flowchart of a method according to another embodiment of the present disclosure, which may be performed by an apparatus implemented in, implemented in, implemented as, or communicatively coupled to the second SMF. In this manner, the apparatus may provide means or modules for accomplishing various parts of the method 410, as well as means or modules for accomplishing other processes in cooperation with other components. Some parts described in the above embodiments are omitted here for brevity.

[0279] In block 412, the second SMF may send a PDU session creation request to the first SMF.

[0280] In block 414, the second SMF may receive a PDU session creation response from the first SMF including the alternative PGW-C / SMF information.

[0281] In one embodiment, the alternative PGW-C / SMF information includes PDU session creation data of the PDU session creation response.

[0282] In one embodiment, the first SMF is a home PGW-C / SMF or an anchor PGW-C / SMF, and the second SMF is a visited SMF or an intermediate SMF.

[0283] 4c shows a flowchart of a method according to another embodiment of the present disclosure, which may be performed by an apparatus implemented in, implemented in, implemented as, or communicatively coupled to the second SMF. In this manner, the apparatus may provide means or modules for accomplishing various parts of the method 420, as well as means or modules for accomplishing other processes in cooperation with other components. Some parts described in the above embodiments are omitted here for brevity.

[0284] In block 422, the second SMF may send a PDU session update request to the first SMF.

[0285] In block 424, the second SMF may receive a PDU session update response from the first SMF including the alternative PGW-C / SMF information.

[0286] In one embodiment, the alternative PGW-C / SMF information includes home SMF update data in a PDU session update response.

[0287] 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 visiting SMF or a new intermediate SMF.

[0288] 4d shows a flowchart of a method according to another embodiment of the present disclosure, which may be performed by an apparatus implemented in, implemented in, implemented as, or communicatively coupled to the second SMF. In this manner, the apparatus may provide means or modules for accomplishing various parts of the method 430, as well as means or modules for accomplishing other processes in cooperation with other components. Some parts described in the above embodiments are omitted here for brevity.

[0289] In block 432, the second SMF may receive a PDU session update request including the alternative PGW-C / SMF information from the first SMF.

[0290] In block 434, the second SMF sends a PDU session update response to the first SMF.

[0291] In one embodiment, the alternative PGW-C / SMF information includes visited SMF update data of the PDU session update request.

[0292] In one embodiment, the first SMF is a home PGW-C / SMF or an anchor PGW-C / SMF, and the second SMF is a visited SMF or an intermediate SMF.

[0293] 4e shows a flowchart of a method according to another embodiment of the present disclosure, which may be performed by an apparatus implemented in, implemented in, implemented as, or communicatively coupled to the second SMF. In this manner, the apparatus may provide means or modules for accomplishing various parts of the method 440, as well as means or modules for accomplishing other processes in cooperation with other components. Some parts described in the above embodiments are omitted here for brevity.

[0294] In block 442, the second SMF may receive a PDU session context request from the AMF.

[0295] In block 444, the second SMF may send a PDU session context response to the AMF including the alternative PGW-C / SMF information.

[0296] 5a shows a flowchart of a method according to another embodiment of the present disclosure, which may be performed by an apparatus implemented in, implemented in, implemented as, or communicatively coupled to the AMF. In this manner, the apparatus may provide means or modules for accomplishing various parts of the method 500, as well as means or modules for accomplishing other processes in cooperation with other components. Some parts described in the above embodiments are omitted here for brevity.

[0297] In block 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.

[0298] For example, in the above embodiments, the first SMF or the second SMF may send alternative PGW-C / SMF information to the AMF, and then the AMF may receive the alternative PGW-C / SMF information from the first SMF or the second SMF.

[0299] In one embodiment, the first SMF is a home PGW-C / SMF or an anchor PGW-C / SMF, and the second SMF is a visited SMF or an intermediate SMF.

[0300] In one embodiment, the alternative PGW-C / SMF information includes at least one of a PGW set fully qualified domain name (FQDN), an Internet Protocol address of the alternative PGW-C / SMF, or an FQDN of the alternative PGW-C / SMF.

[0301] In one embodiment, the alternative PGW-C / SMF information is used by an AMF or a mobility management entity (MME) or an evolved packet data gateway (ePDG) to select an alternative PGW-C / SMF.

[0302] In one embodiment, the first Session Management Function (SMF) and the alternative PGW-C / SMF are functionally equivalent, interchangeable, and share the same context.

[0303] At block 504, the AMF may send the alternative PGW-C / SMF information to a mobility management entity (MME).

[0304] The AMF may transmit the alternative PGW-C / SMF information to the MME in various ways, and the present disclosure does not limit thereto. For example, the AMF may transmit the alternative PGW-C / SMF information to the MME in response to a request from the MME. Alternatively, the AMF may proactively transmit the alternative PGW-C / SMF information to the MME in response to a request from the MME.

[0305] The AMF may send the alternative PGW-C / SMF information to the MME in an existing message or a new message.

[0306] 5b shows a flowchart of a method according to another embodiment of the present disclosure, which may be performed by an apparatus implemented in, implemented in, implemented as, or communicatively coupled to the AMF. In this manner, the apparatus may provide means or modules for accomplishing various parts of the method 510, as well as means or modules for accomplishing other processes in cooperation with other components. Some parts described in the above embodiments are omitted here for brevity.

[0307] In block 512, the AMF may send a PDU session context request to the first SMF or the second SMF.

[0308] In block 514, the AMF may receive a PDU session context response from the first SMF or the second SMF, the PDU session context response including the alternative PGW-C / SMF information.

[0309] 5c shows a flowchart of a method according to another embodiment of the present disclosure, which may be implemented in, implemented in, implemented as, or performed by an apparatus communicatively coupled to the AMF. In this manner, the apparatus may provide means or modules for accomplishing various parts of the method 520, as well as means or modules for accomplishing other processes in cooperation with other components. Some parts described in the above embodiments are omitted here for brevity.

[0310] At block 522, the AMF may receive a context request from the MME.

[0311] In one embodiment, the context request may be a context request described in step 4 of Figure 4.11.1.3.2-1 of 3GPP TS23.502 V17.2.1.

[0312] At block 524, the AMF may send a context response including the alternative PGW-C / SMF information to the MME.

[0313] In one embodiment, the context request may be the context response described in step 6 of Figure 4.11.1.3.2-1 of 3GPP TS23.502 V17.2.1, except that it further includes the alternative PGW-C / SMF information.

[0314] 5d shows a flowchart of a method according to another embodiment of the present disclosure, which may be performed by an apparatus implemented as an AMF in a first telecommunications system, or an AMF communicatively coupled to an AMF in a first telecommunications system. In this manner, the apparatus may provide means or modules for accomplishing various parts of the method 530, as well as means or modules for accomplishing other processes in cooperation with other components. Some parts described in the above embodiments are omitted here for brevity.

[0315] In block 532, the AMF may receive alternative packet data network gateway control plane / session management function (PGW-C / SMF) information from the first PGW-C / SMF or the second SMF.

[0316] In block 534, the AMF may send the alternative PGW-C / SMF information to a mobility management entity (MME) of the second telecommunications system.

[0317] In one embodiment, receiving the 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 from the first PGW-C / SMF or the second SMF that includes the alternative PGW-C / SMF information.

[0318] 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 to the MME that includes the alternative PGW-C / SMF information.

[0319] In one embodiment, the first PGW-C / SMF is a home PGW-C / SMF or an anchor PGW-C / SMF, and / or the second SMF is a visiting SMF or an intermediate SMF.

[0320] In one embodiment, the alternative PGW-C / SMF information may include information of at least one PGW-C / SMF such that an alternative PGW-C / SMF can be selected.

[0321] In one embodiment, the alternative PGW-C / SMF information may be used by the AMF or MME or an evolved packet data gateway (ePDG) to select an alternative PGW-C / SMF.

[0322] In one embodiment, the first PGW-C / SMF and the alternative PGW-C / SMF are functionally equivalent and interchangeable and may share the same context.

[0323] 6A illustrates a flowchart of a method according to another embodiment of the present disclosure, which may be performed by an apparatus implemented in, implemented in, implemented as, or communicatively coupled to an MME. In this manner, the apparatus may provide means or modules for accomplishing various parts of the method 600, as well as means or modules for accomplishing other processes in cooperation with other components. Some parts described in the above embodiments are omitted here for brevity.

[0324] At block 602, the MME may send a context request to an access and mobility management function (AMF).

[0325] At block 604, the MME may receive a context response from the AMF including the first PGW-C / SMF information and the alternative PGW-C / SMF information.

[0326] 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.

[0327] In one embodiment, the first PGW-C / SMF is a home PGW-C / SMF or an anchor PGW-C / SMF.

[0328] In one embodiment, the first PGW-C / SMF and the alternative PGW-C / SMF are functionally equivalent, interchangeable and share the same context.

[0329] In one embodiment, the alternative PGW-C / SMF information includes information of at least one PGW-C / SMF such that an alternative PGW-C / SMF can be selected.

[0330] In one embodiment, the alternative PGW-C / SMF information includes at least one of a PGW set fully qualified domain name (FQDN), an Internet Protocol address of the alternative PGW-C / SMF, or an FQDN of the alternative PGW-C / SMF.

[0331] 6B illustrates a flowchart of a method according to another embodiment of the present disclosure, which may be performed by an apparatus implemented in, implemented in, implemented as, or communicatively coupled to an MME. In this manner, the apparatus may provide means or modules for accomplishing various parts of the method 610, as well as means or modules for accomplishing other processes in cooperation with other components. Some parts described in the above embodiments are omitted here for brevity.

[0332] In block 612, the MME may determine that the first PGW-C / SMF has failed. In one embodiment, the MME may determine that the first SMF has failed. The MME may determine that the first SMF has failed in various ways. For example, the MME may send a message to the first SMF. If the MME cannot receive a response from the first SMF, 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, such as an SGW, may report that the first SMF has failed, and the MME may subsequently determine that the first SMF has failed.

[0333] In block 614, the MME may select an alternative PGW-C / SMF based on the alternative PGW-C / SMF information. For example, the MME may select the alternative PGW-C / SMF if the alternative PGW-C / SMF includes a PGW-C / SMF Internet Protocol address.

[0334] At block 616, the MME may send a create session request to the alternative PGW-C / SMF.

[0335] In one embodiment, the create session request is the same as the create session request specified in 3GPP TS23.401 V17.3.0.

[0336] 7a shows a flowchart of a method according to another embodiment of the present disclosure, which may be performed by an apparatus within or at the UDM or communicatively coupled to the UDM. In this manner, the apparatus may provide means or modules for accomplishing various parts of the method 700, as well as means or modules for accomplishing other processes in cooperation with other components. Some parts described in the above embodiments are omitted here for brevity.

[0337] At block 702, the UDM may receive a registration request from a first session management function (SMF), the registration request including the first session management function (SMF) information and an alternative packet data network gateway (PGW) control plane (PGW-C) / SMF information.

[0338] At block 704, the UDM may store the first SMF information and the alternative PGW-C / SMF information.

[0339] At block 706, the UDM may send a registration response to the first SMF.

[0340] In one embodiment, the alternative PGW-C / SMF information includes at least one of a PGW set fully qualified domain name (FQDN), an Internet Protocol address of the alternative PGW-C / SMF, or an FQDN of the alternative PGW-C / SMF.

[0341] In one embodiment, the alternative PGW-C / SMF information is used by an Access and Mobility Management Function (AMF) or a Mobility Management Entity (MME) or an Evolved Packet Data Gateway (ePDG) to select an alternative PGW-C / SMF.

[0342] In one embodiment, the first SMF and the alternative PGW-C / SMF are functionally equivalent, interchangeable, and share the same context.

[0343] In one embodiment, the first SMF is a home PGW-C / SMF or an anchor PGW-C / SMF.

[0344] 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.

[0345] 7b shows a flowchart of a method according to another embodiment of the present disclosure, which may be performed by an apparatus implemented in, at, or as a UDM or communicatively coupled to the UDM. In this manner, the apparatus may provide means or modules for accomplishing various parts of the method 710, as well as means or modules for accomplishing other processes in cooperation with other components. Some parts described in the above embodiments are omitted here for brevity.

[0346] At block 712, the UDM may receive a request from the network node to obtain the address of a first session management function (SMF) and the alternative PGW-C / SMF information.

[0347] The network node may be any suitable network node, such as an AMF, an SMF, an MME, an ePDG, etc. In one embodiment, the network node is an evolved packet data gateway (ePDG).

[0348] At block 714, the UDM may send a response including the first SMF information and the alternative PGW-C / SMF information to the network node.

[0349] For example, in step 4 of Figure 8.2.3-1 of 3GPP TS23.402 V17.0.0, the first SMF information and the alternative PGW-C / SMF information are sent from the 3GPP AAA server to the ePDG as part of the access authentication. The 3GPP AAA server may obtain the first SMF information and the alternative PGW-C / SMF information from the UDM.

[0350] 8A shows a flowchart of a method according to another embodiment of the present disclosure, which may be implemented in an ePDG or executed by an apparatus implemented in an ePDG or communicatively coupled to an ePDG. In this manner, the apparatus may provide means or modules for accomplishing various parts of the method 800, as well as means or modules for accomplishing other processes in cooperation with other components. Some parts described in the above embodiments are omitted here for brevity.

[0351] In block 802, the ePDG may 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. 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.

[0352] In block 804, the ePDG may receive a response from the UDM including the first SMF information and the alternative PGW-C / SMF information. For example, the ePDG may receive a response from a 3GPP AAA server, which may receive the response from the UDM.

[0353] In one embodiment, the first SMF is a home PGW-C / SMF or an anchor PGW-C / SMF.

[0354] In one embodiment, the first SMF and the alternative PGW-C / SMF are functionally equivalent, interchangeable, and share the same context.

[0355] In one embodiment, the alternative PGW-C / SMF information includes at least one of a PGW set fully qualified domain name (FQDN), an Internet Protocol address of the alternative PGW-C / SMF, or an FQDN of the alternative PGW-C / SMF.

[0356] 8b shows a flowchart of a method according to another embodiment of the present disclosure, which may be performed by an apparatus within or at the ePDG or communicatively coupled to the ePDG. In this manner, the apparatus may provide means or modules for accomplishing various parts of the method 810, as well as means or modules for accomplishing other processes in cooperation with other components. Some parts described in the above embodiments are omitted here for brevity.

[0357] In block 812, the ePDG may determine that the first SMF has failed. The ePDG may determine that the first SMF has failed in various ways. 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.

[0358] In block 814, the ePDG may select an alternative PGW-C / SMF based on the alternative PGW-C / SMF information. For example, if the alternative PGW-C / SMF includes a PGW-C / SMF Internet Protocol address, the ePDG may select this PGW-C / SMF.

[0359] At block 816, the ePDG may send a create session request to the alternative PGW-C / SMF.

[0360] In one embodiment, the create session request may be the same as the create session request specified in 3GPP TS23.402 V17.0.0.

[0361] FIG. 9 is a flow chart illustrating a method for adding PGWChangeInfo to various signaling messages according to another embodiment of the present disclosure.

[0362] Steps 1 to 7 are for establishing a home routing PDU session or a PDU session with the I-SMF. After that, the UE moves from 5G to 4G, and steps 8 to 15 are for the UE to move from 5G to EPS. Steps 8a to 8d are for the UE to move from 5G to ePDG.

[0363] In step 1, the UE sends a PDU session establishment request to the AMF.

[0364] In step 2, the AMF sends Nsmf_PDUSession_CreateSMContextRequest to V / I-SMF.

[0365] In step 3, the AMF receives an Nsmf_PDUSession_CreateSMContext response from the V / I-SMF.

[0366] In step 4, the V / I-SMF sends an Nsmf_PDUSession_Create Request (PduSessionCreateData) to the (H-)SMF / PGW1.

[0367] In step 5, (H-)SMF / PGW1 sends a Nudm_UECM registration request (SmsfRegistration) containing “pgwChangeInfo” to UDM, which acknowledges it.

[0368] In step 6, the (H-)SMF / PGW1 sends a Nsmf_PDUSession_CreateResponse(PduSessionCreatedData) including “pgwChangeInfo” to the V / I-SMF.

[0369] In step 7, the V / I-SMF sends a Namf_Communication_N1N2MessageTransfer to deliver the N1 / N2 message, establishes PDU session resources in the NG-RAN, and provides a Non-Access-Statum (NAS) PDU Session Establishment message Accept message to the UE, which establishes the PDU session.

[0370] In step 8, upon receiving a Tracking Area Update (TAU) from the UE, the MME sends a GTPv2 message: Context Request to the AMF to obtain the UE's context.

[0371] In step 9, the AMF sends Nsmf_PDUSession_ContextRequest(SmContextRetrieveData) to the V / I-SMF.

[0372] In step 10, the V / I-SMF sends an Nsmf_PDUSession_ContextResponse(SmContextRetrievedData) including ueEpsPdnConnection to the AMF, where the V / I-SMF must include the previously received “pgwChangeInfo”.

[0373] In step 11, the AMF sends a GTPv2:ContextResponse to the MME, which includes the PGWChangeInfo.

[0374] Step 12: The MME sends a GTPv2: ContextAck (acknowledgement) to the AMF.

[0375] Step 13: The MME sends a GTPv2:CreateSessionRequest message toward the composite PGW-C / SMF1 via the SGW (omitted in the figure), but the composite PGW-C / SMF1 cannot be reached.

[0376] Step 14: The SGW reports that the composite PGW-C / SMF1 is unreachable. The MME uses the "PGWChangeInfo" to select an alternative PGW-C / SMF (e.g., PGW-C / SMF2). The MME sends a GTPv2:CreateSessionRequest message via the SGW towards the composite PGW-C / SMF2 (which sends a ModifyBearerRequest) (not shown in the diagram), which accepts the request.

[0377] Step 15: The MME sends a TAU to the UE.

[0378] Step 8a: If the UE accesses the network via a non-3gpp access (e.g. WLAN (Wireless Local Area Network)) and the UE sends a handover request to the ePDG, the ePDG obtains not only the PGW address but also the PGWChangeInfo from the AAA / HSS / UDM.

[0379] Step 8b: The ePDG sends a GTPv2:CreateSessionRequest message towards the composite PGW-C / SMF1. However, the composite PGW-C / SMF1 is not reachable.

[0380] Step 8c: The ePDG uses the “PGWChangeInfo” to select an alternative PGW-C / SMF (e.g., PGW-C / SMF2). The ePDG sends a GTPv2:CreateSessionRequest message towards the composite PGW-C / SMF2, which accepts the request.

[0381] Step 8d: The ePDG sends “Handover is accepted” to the UE.

[0382] Some messages in FIG. 9 may be the same as the corresponding messages described in 3GPP specifications such as 3GPP TS23.401 V17.3.0, 3GPP TS23.502 V17.2.1, or 3GPP TS23.402 V17.0.0. Some messages in FIG. 9 may be extended to constitute "PGWChangeInfo". Furthermore, if the MME or ePDG determines that the combined PGW-C / SMF is unreachable, the MME or ePDG may use "PGWChangeInfo" to select an alternative PGW-C / SMF. Then, the MME or ePDG sends a GTPv2:CreateSessionRequest message toward the alternative PGW-C / SMF. In this way, it can be ensured that the PDU session can be successfully transitioned from 5G mobility to 4G mobility even if the serving combined PGW-C / SMF fails (as far as the combined PGW-C / SMF set is concerned).

[0383] 10 is a block diagram illustrating an apparatus suitable for implementing some embodiments of the present disclosure. For example, any one of the first SMF, the first PGW-C / SMF, the second SMF, the AMF, the UDM, the MME, or the ePDG described above may be implemented as or via the apparatus 1000.

[0384] The apparatus 1000 comprises at least one processor 1021, such as a digital processor (DP), and at least one memory (MEM) 1022 coupled to the processor 1021. The apparatus 1000 may further comprise a transmitter TX and a receiver RX 1023 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 apparatus 1000 to operate according to an embodiment of the present disclosure. The combination of the at least one processor 1021 and the at least one MEM 1022 may form a processing means 1025 adapted to perform various embodiments of the present disclosure.

[0385] Various embodiments of the present disclosure may be implemented by computer programs executable by one or more of the processor(s) 1021, software, firmware, hardware, or combinations thereof.

[0386] MEM1022 may be of any type suitable for the local technology environment and may be implemented using any suitable data storage technology, such as, by way of non-limiting example, semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed and removable memory.

[0387] The processor 1021 may be of any type suitable for the local technology environment and may include, by way of non-limiting examples, 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.

[0388] In an embodiment in which the apparatus is implemented as or in a first SMF, the memory 1022 includes instructions executable by the processor 1021 to cause the first PGW-C / SMF to operate according to any of the methods associated with the first SMF described above.

[0389] In an embodiment in which the apparatus is implemented as or in the first PGW-C / SMF, the memory 1022 includes instructions executable by the processor 1021 to cause the first PGW-C / SMF to operate according to any of the methods associated with the first PGW-C / SMF described above.

[0390] In an embodiment in which the apparatus is implemented as or in a second SMF, memory 1022 includes instructions executable by processor 1021, thereby causing the second SMF to operate according to any of the methods associated with the second SMF described above.

[0391] In embodiments in which the apparatus is implemented as or in an AMF, the memory 1022 includes instructions executable by the processor 1021 to cause the AMF to operate according to any of the methods associated with the AMF described above.

[0392] In embodiments in which the apparatus is implemented as or in a UDM, the memory 1022 includes instructions executable by the processor 1021 to cause the UDM F to operate according to any of the methods associated with the UDMs described above.

[0393] In embodiments in which the apparatus is implemented as or in an MME, the memory 1022 includes instructions executable by the processor 1021 to cause the MME to operate in accordance with any of the MME-related methods described above.

[0394] In embodiments in which the apparatus is implemented as or in an ePDG, the memory 1022 includes instructions executable by the processor 1021 to cause the ePDG to operate according to any of the methods associated with the ePDG described above.

[0395] 11a is a block diagram illustrating a first SMF according to an embodiment of the present disclosure. As shown, the first SMF 1100 includes a sending module 1101 configured to send alternative packet data network gateway (PGW) control plane (PGW-C) / SMF information to a second SMF or an access and mobility management function (AMF) or a unified data management (UDM).

[0396] 11b is a block diagram illustrating a first PGW-C / SMF according to one embodiment of the present disclosure. As shown, the first PGW-C / SMF 1150 may include an establishing module 1151 configured to establish a PDU session for a user equipment (UE). The first PGW-C / SMF 1150 may further include a sending module 1152 configured to send alternative PGW-C / SMF information to a second SMF for a PDU session anchored to the first SMF+PGW-C or an access and mobility management function (AMF). The alternative PGW-C / SMF is selected based on the alternative PGW-C / SMF information when the first PGW-C / SMF fails.

[0397] 12 is a block diagram illustrating a second SMF according to an embodiment of the present disclosure. As shown, the second SMF 1200 comprises 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 comprises a transmitting module 1202 configured to transmit the alternative PGW-C / SMF information to an access and mobility management function (AMF).

[0398] 13a is a block diagram illustrating an AMF according to an embodiment of the present disclosure. As shown, the AMF 1300 comprises a receiving module 1301 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. The AMF 1300 comprises a transmitting module 1302 configured to transmit the alternative PGW-C / SMF information to a mobility management entity (MME).

[0399] 13b is a block diagram illustrating an AMF in a first telecommunication system according to one embodiment of the present disclosure. As shown, the AMF 1350 may include a receiving module 1351 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 1350 may include a transmitting module 1352 configured to transmit the alternative PGW-C / SMF information to a mobility management entity (MME) of the second telecommunication system.

[0400] 14 is a block diagram illustrating an MME according to an embodiment of the present disclosure. As shown, the MME 1400 may include a first sending module 1401 configured to send a context request to an access and mobility management function (AMF). The MME 1400 may further include a receiving module 1402 configured to receive a context response from the AMF, the context response including the first PGW-C / SMF information and an alternative packet data network gateway (PGW) control plane (PGW-C) / SMF information.

[0401] In one embodiment, the MME 1400 comprises a determining module 1403 configured to determine that the first SMF has failed.

[0402] In one embodiment, the MME 1400 comprises a selection module 1404 configured to select an alternative PGW-C / SMF based on the alternative PGW-C / SMF information.

[0403] In one embodiment, the MME 1400 comprises a second sending module 1405 configured to send a create session request to the alternative PGW-C / SMF.

[0404] 15 is a block diagram illustrating a UDM according to one embodiment of the present disclosure. As shown, the UDM 1500 comprises a first receiving module 1501 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). The UDM 1500 comprises a storage module 1502 configured to store the first SMF information and the alternative PGW-C / SMF information. The UDM 1500 comprises a second sending module 1503 configured to send a registration response to the first SMF.

[0405] In one embodiment, the UDM 1500 comprises a second receiving module 1504 configured to receive a request to obtain an address of a first session management function (SMF) and alternative PGW-C / SMF information from a network node.

[0406] In one embodiment, the UDM 1500 comprises a second sending module 1505 configured to send a response including the first SMF information and the alternative PGW-C / SMF information to the network node.

[0407] 16 is a block diagram illustrating an ePDG according to one embodiment of the present disclosure. As shown, the ePDG 1600 comprises a first sending module 1601 configured 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 ePDG 1600 comprises a receiving module 1602 configured to receive a response from the UDM including the first SMF information and the alternative PGW-C / SMF information.

[0408] In one embodiment, the ePDG 1600 comprises a determination module 1603 configured to determine that the first SMF has failed.

[0409] In one embodiment, the ePDG 1600 comprises a selection module 1604 configured to select an alternative PGW-C / SMF based on the alternative PGW-C / SMF information.

[0410] In one embodiment, the ePDG 1600 comprises a second sending module 1605 configured to send a create session request to an alternative PGW-C / SMF.

[0411] The embodiments herein may provide many advantages, a non-exhaustive list of examples of which follows below. Some embodiments herein may ensure that a PDU session can be successfully transitioned from 5G mobility to 4G mobility even if a serving composite PGW-C / SMF fails (as far as it is related to a composite PGW-C / SMF set). Some embodiments herein may enable an MME or ePDG or AMF to select an alternative PGW-C / SMF based on alternative PGW-C / SMF information. The embodiments herein are not limited to the above-mentioned features and advantages. Those skilled in the art will recognize additional features and advantages upon reading the following detailed description.

[0412] The term unit or module has its conventional meaning in the field of electronics, electrical equipment 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 respective tasks, procedures, computations, output and / or display functions, etc., as described herein.

[0413] The functional unit may allow the first SMF, the second SMF, the AMF, the first PGW-C / SMF, the UDM, the MME, or the ePDG to allocate any computing and storage resources 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 without requiring a fixed processor or memory. The introduction of virtualization technology and network computing technology may improve the utilization efficiency of network resources and the flexibility of the network.

[0414] According to one aspect of the present disclosure, there is provided a computer program product comprising instructions tangibly stored on a computer-readable storage medium and that, when executed on at least one processor, cause the at least one processor to perform any of the methods described above.

[0415] According to one aspect of the present disclosure, there is provided a computer readable storage medium having stored thereon instructions that, when executed by at least one processor, cause the at least one processor to perform any of the methods described above.

[0416] Furthermore, the present disclosure may provide a carrier containing such a computer program, the carrier being one of an electrical signal, an optical signal, a radio signal, or a computer-readable storage medium. The computer-readable storage medium may be, for example, an optical compact 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, or the like.

[0417] The techniques described herein may be implemented by various means, such that an apparatus implementing one or more functions of the corresponding apparatus described in the embodiments may be composed of means for implementing one or more functions of the corresponding apparatus described in the embodiments as well as means of the prior art, and may be composed of separate means for each separate function, or means configured to perform two or more functions. For example, these techniques may be implemented in hardware (one or more devices), firmware (one or more devices), software (one or more modules), or a combination thereof. In the case of firmware or software, the implementation may be through modules (e.g., procedures, functions, etc.) that perform the functions described herein.

[0418] Exemplary embodiments herein have been described above with reference to block diagrams and flowchart illustrations of methods and apparatus. It will be understood that each block of the block diagrams and flowchart illustrations, and combinations of blocks in the block diagrams and flowchart illustrations, respectively, can be implemented by various means including computer program instructions. These computer program instructions may be loaded into a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine such that the instructions, executing on the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart block or block.

[0419] Furthermore, although operations are depicted in a particular order, this should not be understood as requiring such operations to be performed in the particular order shown, or sequentially, or to perform all of the operations depicted, in order to achieve desired results. In certain circumstances, multitasking and parallel processing may be advantageous. Similarly, although some specific implementation details are included in the above discussion, these should not be construed as limitations on the scope of the subject matter described herein, but rather as descriptions of features that may be specific to particular embodiments. Certain features that are described in the context of separate embodiments may be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable subcombination.

[0420] Although many specific implementation details are described herein, these should not be construed as limitations on the scope of any implementation or what may be claimed, but rather as descriptions of features that may be specific to a particular embodiment of a particular implementation. Certain features described herein in the context of separate embodiments may be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable subcombination. Furthermore, although features may be described above as acting in a particular combination, and may even be initially claimed as such, one or more features from a claimed combination may in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or a variation of the subcombination.

[0421] It will be 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-mentioned embodiments are given to illustrate the present disclosure, not to limit it, and it should be understood that those skilled in the art can resort to modifications and variations without departing from the spirit and scope of the present disclosure, as they can easily understand. Such modifications and variations are considered to be within the scope of the present disclosure and the appended claims. The scope of protection of the present disclosure is defined by the appended claims.

Claims

1. A method (530) performed by an Access and Mobility Management Function (AMF) of a first telecommunication system, comprising: receiving alternative packet data network gateway control plane / session management function (PGW-C / SMF) information from the first PGW-C / SMF or the second SMF (532); Sending (534) the alternative PGW-C / SMF information to a Mobility Management Entity (MME) of a second telecommunication system; A method comprising:

2. Receiving alternative PGW-C / SMF information from the first PGW-C / SMF or the second SMF includes: sending a protocol data unit (PDU) session context request to the first PGW-C / SMF or the second SMF; receiving a PDU session context response from the first PGW-C / SMF or the second SMF, the PDU session context response including the alternative PGW-C / SMF information; Includes The method of claim 1.

3. Sending the alternative PGW-C / SMF information to an MME, receiving a context request from the MME; sending a context response to the MME including the alternative PGW-C / SMF information; Includes The method according to claim 1 or 2.

4. The first PGW-C / SMF is a home PGW-C / SMF or an anchor PGW-C / SMF, and / or the second SMF is a visiting SMF or an intermediate SMF.

4. The method according to claim 1 .

5. The alternative PGW-C / SMF information includes information of at least one PGW-C / SMF such that an alternative PGW-C / SMF can be selected.

5. The method according to any one of claims 1 to 4.

6. The alternative PGW-C / SMF information is used by the AMF or the MME or an evolved packet data gateway (ePDG) to select an alternative PGW-C / SMF.

6. The method according to any one of claims 1 to 5.

7. The first PGW-C / SMF and the alternative PGW-C / SMF are functionally equivalent, interchangeable, and share the same context.

7. The method according to any one of claims 1 to 6.

8. A method (360) performed by a first PGW-C / SMF, comprising: Establishing (362) a PDU session for a user equipment (UE); Sending alternative PGW-C / SMF information to a second SMF for the PDU session anchored to the first SMF+PGW-C or an Access and Mobility Management Function (AMF) (364); Including, An alternative PGW-C / SMF is selected based on the alternative PGW-C / SMF information when the first PGW-C / SMF fails. method.

9. Sending the alternative PGW-C / SMF information to the second SMF includes: receiving a protocol data unit (PDU) session create request from the second SMF; sending a Create PDU Session response to the second SMF, the Create PDU Session response including the alternative PGW-C / SMF information; Includes The method according to claim 8.

10. The alternative PGW-C / SMF information is included in the PDU session creation data of the PDU session creation response.

10. The method of claim 9.

11. The first PGW-C / SMF is a home PGW-C / SMF or an anchor PGW-C / SMF, and / or the second SMF is a visiting SMF or an intermediate SMF.

11. The method according to claim 9 or 10.

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

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

14. 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 visiting SMF or a new intermediate SMF.

14. The method according to claim 12 or 13.

15. Sending the alternative PGW-C / SMF information to the second SMF includes: sending a PDU Session Update Request to the second SMF including the alternative PGW-C / SMF information; receiving a PDU session update response from the second SMF; Includes The method according to claim 8.

16. The alternative PGW-C / SMF information is included in the visited SMF update data of the PDU session update request. The method of claim 15.

17. The first PGW-C / SMF is a home PGW-C / SMF or an anchor PGW-C / SMF, and / or the second SMF is a visiting SMF or an intermediate SMF.

17. The method according to claim 15 or 16.

18. Sending the alternative PGW-C / SMF information to the AMF includes: Receiving a PDU session context request from the AMF; sending a PDU session context response to the AMF, the PDU session context response including the alternative PGW-C / SMF information; Includes 18. The method according to any one of claims 8 to 17.

19. The alternative PGW-C / SMF information includes information of at least one PGW-C / SMF such that an alternative PGW-C / SMF can be selected.

19. The method according to any one of claims 8 to 18.

20. The alternative PGW-C / SMF information is used by the AMF or a mobility management entity (MME) or an evolved packet data gateway (ePDG) to select an alternative PGW-C / SMF.

20. The method according to any one of claims 8 to 19.

21. The first PGW-C / SMF and the alternative PGW-C / SMF are functionally equivalent, interchangeable, and share the same context.

21. The method according to any one of claims 8 to 20.

22. A method (600) performed by a mobility management entity (MME), comprising: Sending a context request to an Access and Mobility Management Function (AMF) (602); receiving a context response from the AMF (604), the context response including a first PGW-C / SMF information and an alternative PGW-C / SMF information; A method comprising:

23. Determining (612) that the first PGW-C / SMF is faulty; selecting an alternative PGW-C / SMF based on the alternative PGW-C / SMF information (614); Sending a create session request to the alternative PGW-C / SMF (616); and Also includes 23. The method of claim 22.

24. The first PGW-C / SMF is a home PGW-C / SMF or an anchor PGW-C / SMF.

24. The method of claim 22 or 23.

25. The first PGW-C / SMF and the alternative PGW-C / SMF are functionally equivalent, interchangeable, and share the same context.

25. The method according to any one of claims 22 to 24.

26. The alternative PGW-C / SMF information includes information of at least one PGW-C / SMF such that an alternative PGW-C / SMF can be selected.

26. The method according to any one of claims 22 to 25.

27. An Access and Mobility Management Function (AMF) (1000) of a first telecommunication system, comprising: A processor (1021); a memory (1022) coupled to the processor (1021), the memory (1022) including instructions executable by the processor (1021), such that the AMF (1000) receiving alternative packet data network gateway control plane / session management function (PGW-C / SMF) information from the first PGW-C / SMF or the second SMF; Sending the alternative PGW-C / SMF information to a mobility management entity (MME) of a second telecommunication system. The memory (1022), AMF is equipped with.

28. The AMF is further operable to perform a method according to any one of claims 2 to 7.

28. The AMF of claim 27.

29. A first PGW-C / SMF, A processor (1021); a memory (1022) coupled to said processor (1021), said memory (1022) including instructions executable by said processor (1021), whereby said first PGW-C / SMF (1000) Establishing a PDU session for a user equipment (UE), Sending alternative PGW-C / SMF information to a second SMF for the PDU session anchored to the first SMF+PGW-C or an Access and Mobility Management Function (AMF). The memory (1022), Equipped with An alternative PGW-C / SMF is selected based on the alternative PGW-C / SMF information when the first PGW-C / SMF fails. First PGW-C / SMF.

30. The first PGW-C / SMF is further operable to perform a method according to any one of claims 9 to 21. The first PGW-C / SMF of claim 29.

31. A mobility management entity (MME) (1000), A processor (1021); a memory (1022) coupled to the processor (1021), the memory (1022) including instructions executable by the processor (1021), such that the MME (1000) Sending a context request to an Access and Mobility Management Function (AMF); Receive a context response from the AMF, the context response including the first PGW-C / SMF information and the alternative PGW-C / SMF information. The memory (1022), An MME comprising:

32. The MME is further operable to perform the method according to any one of claims 23 to 26.

32. The MME of claim 31.

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

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

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