Method and apparatus for service management

Abstract

Various embodiments of the present disclosure provide methods and apparatuses for service management. A method performed by a session management function includes receiving, from an access and mobility management function, a first message including fallback information for a terminal device. The fallback information includes a fallback type. The method further includes determining, based on the fallback information, whether data buffering for the terminal device is needed. The method further includes, in response to determining that the data buffering for the terminal device is needed, sending, to a user plane function, a second message including a buffering indication, wherein the buffering indication indicates the user plane function to buffer data for the terminal device.

Description

Technical Field

[0001] This disclosure generally relates to communication networks, and more specifically, to methods and apparatus for service management. Background Technology

[0002] This section introduces several aspects that can help in a better understanding of this disclosure. Therefore, the statements in this section should be read in this light and should not be construed as an admission of what is in or not in the prior art.

[0003] Communication service providers and network operators have always faced challenges such as delivering value and convenience to consumers by providing compelling network services and performance. With the rapid development of network and communication technologies, wireless communication networks such as LTE / 4G and NR / 5G networks promise high service capacity and end-user data rates with lower latency. To meet the diverse requirements for new services across various industries, the 3rd Generation Partnership Project (3GPP) is developing a variety of network function services for various communication networks.

[0004] The Internet Protocol (IP) Multimedia Subsystem (IMS) is specified in 3GPP TS 23.228 V16.6.0 (the disclosure of which is incorporated herein by reference in its entirety). The IP Multimedia Core Network (IM CN) ​​subsystem enables operators to provide multimedia services to their subscribers. The IM CN subsystem enables the convergence and access to voice, video, messaging, data, and network-based technologies for both wireless and wired users. A complete solution to support IP multimedia applications may include terminals, an IP Connectivity Access Network (IP CAN), and specific functional elements of the IM CN subsystem as described in 3GPP TS 23.228 V16.6.0. Examples of IP-connected access networks include: GPRS (General Packet Radio Service) core networks with GERAN (GSM (Global System for Mobile Communications) EDGE (GSM Evolution Enhanced Data Rate) radio access networks) and / or UTRAN (General Terrestrial Radio Access Network) radio access networks; EPC (Evolved Packet Core) core networks and E-UTRAN (Evolved UTRAN) radio access networks; and 5GS (5G Systems) access networks.

[0005] Section 5.16.3.10 of 3GPP TS 23.501 V16.7.0 (the contents of which are incorporated herein by reference in their entirety) describes IMS voice services in 5GS (5G systems) via EPS (Evolved Packet System) fallback or RAT (Radio Access Technology) fallback.

[0006] To support various deployment scenarios for obtaining IMS voice services, the UE and NG-RAN can support mechanisms for directing or redirecting the UE from the NG-RAN (Next Generation Radio Access Network) to E-UTRA (Evolved Universal Terrestrial Radio Access Network) (RAT back-off) connected to the 5GC (5G Core Network) or directing or redirecting the UE to EPS (Evolved Universal Terrestrial Radio Access Network) (System Back-off) connected to the EPC (Evolved Packet Core).

[0007] The following principles apply to IMS voice services: - The Serving AMF (Access and Mobility Management Function) instructs the UE (User Equipment) during the registration process to support IMS voice sessions via PS (Packet Switching). - If a request to establish a QoS (Quality of Service) stream for IMS voice arrives at NG-RAN, NG-RAN responds by indicating that the establishment request is rejected, and NG-RAN can trigger one of the following procedures based on UE capabilities, N26 availability, network configuration, and radio conditions: - Redirect to EPS; -The process of switching to EPS; - Redirect to E-UTRA connected to 5GC; or - Switch to E-UTRA connected to 5GC.

[0008] According to 3GPP TS 38.413 V16.4.0 (the entire contents of which are incorporated herein by reference), NG-RAN sends the same reason "Trigger IMS Voice EPS Fallback or RAT Fallback" for any of the reasons mentioned above. For example, upon receiving a PDU Session Resource Modification Request message for establishing a QoS flow for IMS Voice, if the NG-RAN node does not support IMS Voice, the NG-RAN node should initiate an EPS fallback or RAT fallback procedure for IMS Voice as specified in 3GPP TS 23.501 V16.7.0, and report the failure to establish the QoS flow using the reason value "Trigger IMS Voice EPS Fallback or RAT Fallback" in the PDU Session Resource Modification Response Transmission IE (Information Element) or the PDU Session Resource Modification Failure Transmission IE.

[0009] Figure 1 This demonstrates the EPS backoff for IMS voice, which is consistent with 3GPP TS 23.502V16.7.1. Figure 4 The same applies to .13.6.1-1, the contents of which are incorporated herein by reference in their entirety. For matters already described in clause 4.13.6.1 of 3GPP TS 23.502 V16.7.1... Figure 1Some steps are omitted here for the sake of brevity.

[0010] In step 4, NG-RAN responds to the PDU session modification response message received in step 2 with an indication that mobility is in progress due to backoff for IMS voice via AMF to SMF+PGW-C (Packet Data Network Gateway Control Plane Function) (or, in the case of home route roaming, via V-SMF (Visitor SMF) to H-SMF (Home SMF)+P-GW-C), indicating rejection of the PDU (Protocol Data Unit) session modification received in step 2 for establishing a QoS flow for IMS voice. SMF+PGW-C maintains PCC (Policy and Charging Control) rules associated with the QoS flow and reports the EPS backoff event to the PCF if the PCF (Policy Control Function) has already subscribed to the event.

[0011] In step 5, considering UE capabilities, the NG-RAN initiates a handover (see Clause 4.11.1.2.1 of 3GPP TS 23.502V16.7.1), or initiates an AN release to the EPS via inter-system redirection (see Clauses 4.2.6 and 4.11.1.3.2). As specified in Clauses 4.11.1.2.1 or 4.11.1.3 of 3GPP TS 23.502V16.7.1, if the PCF is subscribed, the SMF+PGW-C reports a change in RAT type. When the UE is connected to the EPS, proceed to step 6a or step 6b.

[0012] Figure 2 The RAT backoff for IMS voice is shown, which is consistent with 3GPP TS 23.502V16.7.1. Figure 4 The same applies to .13.6.2-1, the contents of which are incorporated herein by reference in their entirety. For those already described in clause 4.13.6.2 of 3GPP TS 23.502 V16.7.1... Figure 2 Some steps are omitted here for the sake of brevity.

[0013] In step 4, the source NG-RAN responds with a PDU session response message via AMF toward SMF (or, in the case of roaming, toward V-SMF) indicating that a move is in progress due to a fallback for IMS voice, to indicate rejection of the PDU session modification received in step 2 for establishing a QoS flow for IMS voice. The SMF maintains PCC rules associated with the QoS flow.

[0014] In step 5, the source NG-RAN initiates an Xn-based inter-NG-RAN handover (see Section 4.9.1.2 of 3GPP TS 23.502 V16.7.1) or an N2-based inter-NG-RAN handover (see Section 4.9.1.3 of 3GPP TS 23.502 V16.7.1), or redirects to an E-UTRA connected to the 5GC (see Section 4.2.6 of 3GPP TS 23.502 V16.7.1). If the PCF has subscribed, the SMF reports the change in RAT type.

[0015] Figure 3 This illustrates the AN (Access Network) release process, which is consistent with 3GPP TS 23.502V16.7.1. Figure 4 The same applies to section 2.6-1, the contents of which are incorporated herein by reference in their entirety. For items already described in section 4.2.6 of 3GPP TS 23.502 V16.7.1... Figure 3 Some steps are omitted here for the sake of brevity.

[0016] In step 6a, the SMF (Session Management Function) can send an N4 session modification request (AN or N3 UPF tunnel information to be deleted, buffer on / off) to the UPF (User Plane Function).

[0017] For PDU sessions that do not utilize the control plane CIoT (Cellular IoT) 5GS optimization, the SMF initiates the N4 session modification procedure to indicate the need to delete tunnel information for terminating N3 AN or UPF. Buffer on / off indicates whether the UPF should buffer incoming DL (downlink) PDUs.

[0018] If the SMF has received an indication from the AMF that the downlink data UE is unreachable for a PDU session optimized using the control plane CIoT 5GS, the SMF can initiate the N4 session modification procedure to activate the buffer in the UPF.

[0019] If multiple UPFs are used in a PDU session, and the SMF determines to release the UPF terminating N3, then step 6a is performed toward the UPF terminating N9 (e.g., PSA (PDU session anchor)) towards the current N3 UPF. The SMF then releases the N4 session toward the N3 UPF (N4 release is not shown on the call flow). Summary of the Invention

[0020] The present invention is provided in a simplified form to introduce a chosen concept, which will be further described in the following detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to limit the scope of the claimed subject matter.

[0021] For example Figure 3 The existing UPF buffering solution shown has a short packet loss window.

[0022] Figure 4 An example of a packet loss window in an existing UPF buffering solution used for EPS backoff via redirection is shown. SIP (Session Initiation Protocol) DL (Downlink) signaling loss may result in SIP signaling retransmission. For example... Figure 4 The messages shown are the same as or similar to the corresponding messages described in various 3GPP specifications, such as 3GPP TS 23.502V16.7.1, 3GPP TS23.501V16.7.1 and 3GPP TS 38.413V16.4.0, etc.

[0023] In step 1, the AMF can send a PDU session resource modification request (5QI (5G QoS identifier) ​​= voice) to the (R)AN. NGAP stands for Next Generation Application Protocol.

[0024] Upon receiving a PDU session resource modification request, the RAN can decide to trigger an EPS-FB (back-off) with RwR (Release with Redirection) and select a target frequency (blind-based or measurement-based).

[0025] In step 2, (R)AN can send a PDU session resource modification response to AMF (failure, with the reason for IMS voice fallback).

[0026] In step 3, (R)AN can send an AN (Access Network) connection release request to the UE. The UE can send a UE lower-layer acknowledgment to (R)AN.

[0027] In step 4, the AMF can send an Nsmf_PDUSession_UpdateSMContext(failed, with the reason for IMS voice rollback) request to the SMF.

[0028] In step 5, (R)AN can send an N2 UE context release request to AMF.

[0029] In step 6, the AMF can send an N2 UE context release command to the (R)AN.

[0030] In step 7, (R)AN can send N2 UE context release complete to AMF.

[0031] In step 8, the AMF can send Nsmf_PDUSession_UpdateSMContext to the SMF.

[0032] In step 9, the SMF can send an N4 session modification request (buffer open) to the UPF. Upon receiving the N4 session modification request (buffer open), the UPF buffering begins.

[0033] In step 10, (R)AN can send an N4 session modification response to SMF.

[0034] In step 11, the SMF can send an Nsmf_PDUSession_UpdateSMContext response to the AMF.

[0035] like Figure 4 The delay values ​​shown are estimates, not measurements. If a DL SIP message is sent from the P-CSCF (Proxy Call Service Call Control Function (P-CSCF)) when the packet loss window occurs, the DL SIP message is lost. This triggers a SIP TCP (Transmission Control Protocol) or UDP (User Datagram Protocol) retransmission, which may result in additional CST (Call Setup Time) delay.

[0036] Figure 5 An example of a long retransmission causing call setup delay is shown. Figure 5 The message shown is the same as or similar to the corresponding message described in various SIPs such as Request for Comment (RFC) 3261. Figure 5 As shown, the delayed UPF buffer may cause TCP retransmission, i.e., message 27 is lost. For SIP over TCP, the first TCP retransmission may be delayed by about 3 seconds (after message 28 is sent in EPS after QCI (QoS Class Identifier) ​​-5 is set).

[0037] For example, the TCP RTT (Round-Trip Time) based on TCP segments can be dynamically calculated according to the standard https: / / tools.ietf.org / html / rfc6298. Unfortunately, when the terminated UE is in a connected state, the paging process may be delayed by less than 1.2 seconds, for example, with four TCP segments (one for options and three for invites). Therefore, the RTO increases. This long RTO may cause the first TCP retransmission to be delayed by about 3 seconds (after sending message 28 in EPS after QCI-5 setting).

[0038] Furthermore, for fallbacks via handovers supported by direct / indirect forwarding tunnels, such as Figure 3 The early buffering shown in step 6a may delay call setup because data such as SIP signaling can still be transmitted to the UE without early buffering.

[0039] To overcome or mitigate at least one of the above-mentioned or other problems, embodiments of this disclosure propose an improved service management solution that can optimize service processing, such as avoiding signaling or data loss and / or reducing call setup time.

[0040] According to a first aspect of this disclosure, a method performed by a session management function is provided. The method includes receiving a first message from an access and mobility management function including fallback information for a terminal device. The fallback information includes a fallback type. The method further includes determining, based on the fallback information, whether data buffering for the terminal device is required. The method further includes, in response to determining that data buffering for the terminal device is required, sending a second message including a buffering indication to a user plane function. The buffering indication instructs the user plane function to buffer data for the terminal device.

[0041] In one embodiment, the fallback type includes at least one of the following: redirection; or switching.

[0042] In one embodiment, determining whether data buffering for the terminal device is needed based on fallback information includes: when the fallback type is redirection, determining that data buffering for the terminal device is needed.

[0043] In one embodiment, determining whether data buffering for the terminal device is needed based on rollback information includes: when the rollback type is switching, determining that data buffering for the terminal device is not needed.

[0044] In one embodiment, redirection includes at least one of the following: redirection from a second network to a first network; or redirection to a first network connected to a core network of the second network.

[0045] In one embodiment, the switching includes at least one of the following: switching from a second network to a first network; or switching to a first network connected to a core network of the second network.

[0046] In one embodiment, the first network includes an evolved packet system (EPS), and the second network includes a fifth-generation system.

[0047] In one embodiment, a fallback includes at least one of the following: an evolved packet system (EPS) fallback or a radio access technology (RAT) fallback.

[0048] In one embodiment, the fallback is related to the Internet Protocol Multimedia Subsystem (IMS) service.

[0049] In one embodiment, the session management function includes a packet data network gateway control plane function (PGW-C) combined with the session management function (SMF).

[0050] In one embodiment, the first message includes an Nsmf_PDUSession_UpdateSMContext request message, which has either an N2 PDU session resource modification response transmission or a PDU session resource modification failure transmission.

[0051] In one embodiment, the second message includes an N4 session modification request message.

[0052] In one embodiment, a second message is sent during or before the network access release process.

[0053] In one embodiment, when a buffer indication is sent prior to the access network release process, the buffer indication has a higher priority than a buffer indication sent during the access network release process.

[0054] According to a second aspect of this disclosure, a method performed by an access and mobility management function is provided. The method includes receiving a third message from a radio access network entity including fallback information for a terminal device. The fallback information includes a fallback type. The method also includes sending a first message including the fallback information for the terminal device to a session management function.

[0055] In one embodiment, the third message includes a Protocol Data Unit (PDU) session resource modification response message.

[0056] According to a third aspect of this disclosure, a method performed by a radio access network entity is provided. The method includes determining whether to trigger a fallback for a terminal device. The method further includes sending a third message including fallback information for the terminal device to an access and mobility management function. The fallback information includes a fallback type.

[0057] According to a fourth aspect of this disclosure, a session management function is provided. The session management function includes one or more processors and one or more memories storing computer program code. The one or more memories and the computer program code, together with the one or more processors, are configured to cause the session management function to receive, at least from an access and mobility management function, a first message including fallback information for a terminal device. The fallback information includes a fallback type. The session management function is further configured to determine, based on the fallback information, whether data buffering for the terminal device is required. The session management function is further configured to, in response to determining that data buffering for the terminal device is required, send a second message including a buffering indication to a user plane function. The buffering indication instructs the user plane function to buffer data for the terminal device.

[0058] According to a fifth aspect of this disclosure, an access and mobility management function is provided. The access and mobility management function includes one or more processors and one or more memories storing computer program code. The one or more memories and the computer program code, together with the one or more processors, are configured to cause the access and mobility management function to receive, at least from a radio access network entity, a third message including fallback information for a terminal device. The fallback information includes a fallback type. The access and mobility management function is also caused to send a first message including fallback information for the terminal device to a session management function.

[0059] According to a sixth aspect of this disclosure, a radio access network entity is provided. The radio access network entity includes one or more processors and one or more memories storing computer program code. The one or more memories and the computer program code, together with the one or more processors, are configured to cause the radio access network entity to at least determine that a fallback for a terminal device is triggered. The radio access network entity is also caused to send a third message to an access and mobility management function including fallback information for the terminal device. The fallback information includes a fallback type.

[0060] According to a seventh aspect of this disclosure, a session management function is provided. The session management function includes a receiving module, a determining module, and a sending module. The receiving module can be configured to receive a first message including fallback information for a terminal device from an access and mobility management function. The fallback information includes a fallback type. The determining module can be configured to determine, based on the fallback information, whether data buffering for the terminal device is required. The sending module can be configured to, in response to determining that data buffering for the terminal device is required, send a second message including a buffering indication to a user plane function. The buffering indication instructs the user plane function to buffer data for the terminal device.

[0061] According to an eighth aspect of this disclosure, an access and mobility management function is provided. The access and mobility management function includes a receiving module and a transmitting module. The receiving module can be configured to receive a third message including fallback information for a terminal device from a radio access network entity. The fallback information includes a fallback type. The transmitting module can be configured to send a first message including fallback information for the terminal device to a session management function.

[0062] According to a ninth aspect of this disclosure, a radio access network entity is provided. The radio access network entity includes a determining module and a transmitting module. The determining module can be configured to determine whether to trigger a fallback for a terminal device. The transmitting module can be configured to send a third message including fallback information for the terminal device to an access and mobility management function. The fallback information includes a fallback type.

[0063] According to a tenth aspect of this disclosure, a computer program product including instructions is provided, 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, second, and third aspects.

[0064] According to the eleventh aspect of this disclosure, a computer-readable storage medium is provided that stores 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, second, and third aspects.

[0065] The embodiments described herein offer numerous advantages, and the following is a non-exhaustive list of examples of these advantages. In some embodiments herein, the proposed solutions can address signaling (e.g., SIP signaling) or data loss issues during fallbacks (e.g., EPS fallbacks or RAT fallbacks). In some embodiments herein, the proposed solutions can reduce call setup time for fallbacks via redirection. In some embodiments herein, the proposed solutions can avoid signaling (e.g., SIP signaling) or data retransmissions. In some embodiments herein, the proposed solutions can improve system (e.g., P-CSCF) performance. The embodiments described herein are not limited to the features and advantages described above. Additional features and advantages will be recognized by those skilled in the art upon reading the following detailed description. Attached Figure Description

[0066] From the following detailed description with reference to the accompanying drawings, by way of example, the above and other aspects, features, and benefits of various embodiments of the present disclosure will become more fully apparent, in which similar reference numerals or letters are used to refer to similar or equivalent elements. The drawings are shown to facilitate a better understanding of the embodiments of the present disclosure and are not necessarily drawn to scale, wherein:

[0067] Figure 1 The EPS fallback for IMS voice is shown;

[0068] Figure 2 The RAT fallback for IMS voice is shown;

[0069] Figure 3 The AN (Access Network) release process is shown;

[0070] Figure 4 An example of a packet loss window in an existing UPF buffering solution for EPS rollback via redirection is shown;

[0071] Figure 5 An example of a long retransmission that causes call setup delay is shown;

[0072] Figure 6An advanced architecture in a fifth-generation network according to an embodiment of this disclosure is schematically illustrated;

[0073] Figure 7 The system architecture in a 4G network according to an embodiment of the present disclosure is illustrated schematically;

[0074] Figure 8 A flowchart of a method according to an embodiment of this disclosure is shown;

[0075] Figure 9 A flowchart of a method according to another embodiment of this disclosure is shown;

[0076] Figure 10 A flowchart of a method according to another embodiment of this disclosure is shown;

[0077] Figure 11 This is a flowchart illustrating EPS fallback for IMS voice according to an embodiment of the present disclosure;

[0078] Figure 12 This is a flowchart illustrating the RAT rollback process in 5GC for IMS voice according to an embodiment of the present disclosure;

[0079] Figure 13 This is a flowchart illustrating the UPF buffering method according to an embodiment of the present disclosure;

[0080] Figure 14 This is a block diagram illustrating an apparatus suitable for practicing some embodiments of the present disclosure;

[0081] Figure 15 This is a block diagram illustrating a session management function according to an embodiment of the present disclosure;

[0082] Figure 16 This is a block diagram illustrating access and mobility management functions according to embodiments of the present disclosure; and

[0083] Figure 17 This is a block diagram illustrating a radio access network entity according to an embodiment of the present disclosure. Detailed Implementation

[0084] Embodiments of this disclosure are described in detail with reference to the accompanying drawings. It should be understood that these embodiments are discussed only for the purpose of enabling those skilled in the art to better understand and thus implement this disclosure, and not to suggest any limitation on the scope of this disclosure. References to features, advantages, or similar language throughout this specification do not imply that all features and advantages achievable with this disclosure should be included in or in any single embodiment of this disclosure. Rather, references to features and advantages should be understood as meaning that a particular feature, advantage, or characteristic described in connection with an embodiment is included in at least one embodiment of this disclosure. Furthermore, in one or more embodiments, the features, advantages, and characteristics described in this disclosure may be combined in any suitable manner. Those skilled in the art will recognize that this disclosure can be practiced without one or more particular features or advantages in a particular embodiment. In other instances, additional features and advantages may be recognized in some embodiments, and these additional features and advantages may not be present in all embodiments of this disclosure.

[0085] As used herein, the term "network" refers to a network that conforms to any suitable communication standard, such as New Radio (NR), Long Term Evolution (LTE), LTE Advanced, 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. CDMA networks can implement radio technologies such as Universal Terrestrial Radio Access (UTRA). UTRA includes other variants of WCDMA and CDMA. TDMA networks can implement radio technologies such as Global System for Mobile Communications (GSM). OFDMA networks can implement radio technologies 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" are used interchangeably. Furthermore, communication between two devices in a network can be performed according to any suitable communication protocol, including but not limited to those defined by standards organizations such as 3GPP. For example, communication protocols may include first-generation (1G), 2G, 3G, 4G, 4.5G, 5G communication protocols and / or any other currently known or future-developed protocols.

[0086] The term "network function (NF)" refers to any appropriate network function (NF) that can be implemented in a (physical or virtual) network entity within a communication network. For example, a network function can 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., on cloud infrastructure). For instance, a 5G system (5GS) can include multiple NFs such as AMF (Access and Mobility Function), SMF (Session Management Function), AUSF (Authentication Service Function), UDM (Unified Data Management), PCF (Policy Control Function), AF (Application Function), NEF (Network Open Function), UPF (User Plane Function), and NRF (Network Repository Function), RAN (Radio Access Network), SCP (Serving Communication Agent), NWDAF (Network Data Analysis Function), NSSF (Network Slice Selection Function), NSSAAF (Network Slice Specific Authentication and Authorization Function), etc. For example, a 4G system (e.g., LTE) may include multiple network functions (NFs), such as the MME (Mobility Management Entity), HSS (Home Subscriber Server), Policy and Charging Rules Function (PCRF), Packet Data Network Gateway (PGW), PGW Control Plane (PGW-C or P-GW-C), Serving Gateway (SGW), SGW Control Plane, E-UTRAN Node B (eNB), etc. In other embodiments, depending on the specific network, network functions may include different types of NFs.

[0087] The term "terminal device" refers to any end device that can access a communication network and receive services from it. By way of example and not limitation, a terminal device refers to a mobile terminal, user equipment (UE), or other suitable device. A UE can be, for example, a subscriber station (SS), portable subscriber station, mobile station (MS), or access terminal (AT). Terminal devices can include, but are not limited to, portable computers, image capture terminal devices such as digital cameras, gaming terminal devices, music storage and playback devices, mobile phones, cellular phones, smartphones, Voice over IP (VoIP) phones, wireless local loop phones, tablet computers, wearable devices, personal digital assistants (PDAs), portable computers, desktop computers, wearable terminal devices, in-vehicle wireless terminal devices, wireless endpoints, mobile stations, laptop embedded devices (LEE), laptop installed devices (LME), USB dongles, smart devices, wireless premises equipment (CPE), etc. In the following description, the terms "terminal device," "terminal," "user equipment," and "UE" are used interchangeably. As an example, a terminal device can represent a UE configured to communicate according to one or more communication standards published by 3GPP (3rd Generation Partnership Project), such as 3GPP's LTE or NR standards. As used herein, in relation to a human user who owns and / or operates the relevant device, A “User Equipment” or “UE” may not necessarily have a “user”. In some embodiments, a terminal device may be configured to send and / or receive information without direct human interaction. For example, when triggered by an internal or external event, or in response to a request from a communication network, a terminal device may be designed to send information to the network according to a predetermined schedule. Alternatively, a UE may represent a device intended for sale to a human user or operated by a human user but which may not initially be associated with a particular human user.

[0088] As another example, in the Internet of Things (IoT) scenario, a terminal device can represent a machine or other device that performs monitoring and / or measurement, and transmits the results of such monitoring and / or measurement to another terminal device and / or network device. In this case, the terminal device can be a machine-to-machine (M2M) device, which in the 3GPP context can be referred to as a machine-type communication (MTC) device. As a specific example, a terminal device can be a UE that implements the 3GPP Narrowband Internet of Things (NB-IoT) standard. Specific examples of such machines or devices are sensors, metering devices (e.g., electricity meters, industrial machinery) or household or personal appliances (e.g., refrigerators, televisions), personal wearable devices (e.g., watches), etc. In other scenarios, a terminal device can represent a vehicle or other device capable of monitoring and / or reporting its operational status or other functions related to its operation.

[0089] References to "an embodiment," "embodiment," "exemplary embodiment," etc., in the specification indicate that the described embodiment may include specific features, structures, or characteristics, but not every embodiment necessarily includes such specific features, structures, or characteristics. Furthermore, these phrases do not necessarily refer to the same embodiment. Additionally, when a specific feature, structure, or characteristic is described in connection with an embodiment, whether or not it is explicitly described, it is believed that such features, structures, or characteristics affecting other embodiments are within the knowledge of those skilled in the art.

[0090] It should be understood that while the terms “first” and “second” may be used herein to describe various elements, these elements should not be limited by these terms. These terms are used only to distinguish one element from another. For example, without departing from the scope of the exemplary embodiments, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element. As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed terms.

[0091] As used herein, the phrases “at least one of A and B” and “at least one of A or B” should be understood as meaning “A only, B only, or both A and B”. The phrase “A and / or B” should be understood as “A only, B only, or both A and B”.

[0092] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments. Unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “the” as used herein are also intended to include the plural forms. It will be further understood that, when used herein, the terms “comprising,” “including,” “having,” “owning,” “containing,” and / or “covering” specify the presence of the stated features, elements, and / or components, but do not exclude the presence or addition of one or more other features, elements, components, and / or combinations thereof.

[0093] Note that the terms used in this article are for ease of description and to distinguish between nodes, devices, or networks, etc. As technology evolves, other terms with similar / identical meanings may also be used.

[0094] 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 pertains.

[0095] Although the topics described herein can be implemented in any suitable type of system using any appropriate components, regarding conformity Figure 6-7 The exemplary system architecture shown herein is used to describe the embodiments disclosed herein. For simplicity, Figure 6-7 The system architecture described herein only depicts a few exemplary components. In practice, the communication system may further include any additional components suitable for supporting communication between terminal devices or between a wireless device and another communication device (such as a landline telephone, service provider, or any other network node or terminal device). The communication system may provide communication and various types of services to one or more terminal devices to facilitate the terminal devices' access to the communication system and / or use of services provided by or via the communication system.

[0096] Figure 6 An advanced architecture in a fifth-generation network according to an embodiment of this disclosure is illustrated schematically. For example, the fifth-generation network may be 5GS. Figure 6 The architecture is consistent with that described in 3GPP TS 23.501V16.7.0. Figure 4 Similar to .2.3-1, its public content is incorporated into this article in its entirety by reference. Figure 6 The system architecture may include some exemplary components, such as AUSF, AMF, DN (Data Network), NEF, NRF, NSSF, PCF, SMF, UDM, UPF, AF, UE, (R)AN, SCP (Service Communication Agent), NSSAAF (Network Slice Specific Authentication and Authorization Function), etc.

[0097] According to an exemplary embodiment, such as Figure 6 As shown, the UE can establish a signaling connection with the AMF via reference point N1. This signaling connection enables NAS (Non-Access Stratum) signaling exchange between the UE and the core network, including a signaling connection between the UE and the (R)AN, and an N2 connection between the (R)AN and the AMF for the UE. The (R)AN can communicate with the UPF via reference point N3. The UE can establish a Protocol Data Unit (PDU) session to the DN (Data Network, such as an operator's network or the Internet) via the UPF via reference point N6.

[0098] like Figure 6 As further shown, the exemplary system architecture also includes service-based interfaces such as Nnrf, Nnef, Nausf, Nudm, Npcf, Namf, and Nsmf exhibited by NFs such as NRF, NEF, AUSF, UDM, PCF, AMF, and SMF. Furthermore, Figure 6 Reference points, such as N1, N2, N3, N4, N6, and N9, are also shown, which can support interaction between NF services within an NF. These reference points can be implemented, for example, by using the interfaces of the corresponding NF services and specifying NF service consumers and providers, as well as their interactions, to execute specific system procedures.

[0099] Figure 6 The various NFs shown can be responsible for functions such as session management, mobility management, authentication, and security. AUSF, AMF, DN, NEF, NRF, NSSF, PCF, SMF, UDM, UPF, AF, UE, (R)AN, and SCP can include functions as defined, for example, in Clause 6.2 of 3GPP TS 23.501 V16.7.0.

[0100] Figure 7 The diagram schematically illustrates a system architecture in a 4G network according to an embodiment of this disclosure, which is consistent with 3GPP TS23.682V16.8.0. Figure 4 Similar to .2-1a, the public content of which is incorporated herein by reference in its entirety. Figure 7The system architecture may include exemplary components such as Service Capability Server (SCS), Application Server (AS), SCEF (Service Capability Open Function), HSS, UE, RAN (Radio Access Network), SGSN (Serving GPRS (General Packet Radio Service) Support Node), MME, MSC (Mobile Switching Center), S-GW (Serving Gateway), GGSN / P-GW (Gateway GPRS Support Node / PDN (Packet Data Network) Gateway), MTC-IWF (Machine Type Interoperability Function), CDF / CGF (Charging Data Function / Charging Gateway Function), MTC-AAA (Machine Type Authentication, Authorization, and Accounting), SMS-SC / GMSC / IWMSC (Short Message Service Service Center / Gateway MSC / Interoperability MSC), and IP-SM-GW (Internet Protocol Short Message Gateway). Figure 7 The network elements and interfaces shown may be the same as the corresponding network elements and interfaces described in 3GPP TS 23.682 V16.8.0.

[0101] Figure 8 A flowchart of a method according to an embodiment of this disclosure is shown, which can be performed by means implemented in a session management function, or by means implemented as a session management function, or by means communicatively coupled to a session management function. Therefore, the means can provide components or modules for implementing various parts of method 800, as well as components or modules for implementing other processes in conjunction with other components. The session management function can be any suitable entity or node capable of implementing a session management function. For example, the session management function can be a PGW combined with an SMF (PGW+SMF) or a PGW-C combined with an SMF (PGW-C+SMF).

[0102] In box 802, the session management function receives a first message from the access and mobility management function, including fallback information for the terminal device. The fallback information includes the fallback type. The access and mobility management function can be any suitable network entity that can support access and mobility management functions. For example, the access and mobility management function can be an AMF (Access and Mobility Management Function).

[0103] A fallback may be triggered for various reasons, such as UE capabilities, an indication from the AMF that “redirection of EPS fallback for voice is possible”, network configuration (e.g., N26 availability configuration), radio conditions, load balancing, service requirements, etc.

[0104] Rollback can be associated with various services. In one embodiment, rollback is associated with Internet Protocol Multimedia Subsystem (IMS) services such as IMS voice service.

[0105] The first message can be any suitable message that can be transmitted between the session management function and the access and mobility management function. For example, the message can be an Nsmf_PDUSession_UpdateSMContext request with an N2 PDU session resource modification response transmission or a PDU session resource modification response transmission as described in 3GPP TS 23.502V16.7.0.

[0106] A fallback can be any suitable fallback. In one embodiment, a fallback can include at least one of an evolved packet system (EPS) fallback or a radio access technology (RAT) fallback.

[0107] Rollback information may include information related to the rollback. In one embodiment, rollback information may include a rollback type. The rollback type may indicate a specific rollback procedure triggered by the RAN.

[0108] In one embodiment, the fallback type may include at least one of redirection or switching.

[0109] In one embodiment, redirection may include at least one of the following: redirection from a second network to a first network; or redirection to a first network connected to a core network of the second network.

[0110] In one embodiment, the switching may include at least one of the following: switching from a second network to a first network; or switching to a first network that is connected to a core network of the second network.

[0111] The first network can be any suitable network. The second network can be any suitable network. In one embodiment, the first network may include an evolved packet system (EPS). In one embodiment, the second network may include a fifth-generation system (5GS).

[0112] In one embodiment, the fallback type may indicate at least one process triggered by the RAN: - redirection to EPS; -The process of switching to EPS; - Redirect to E-UTRA connected to 5GC; or - Switch to E-UTRA connected to 5GC.

[0113] In box 804, the session management function can determine whether data buffering for the end device is needed based on fallback information. For example, the session management function can determine whether data buffering for the end device is needed based on the fallback type. This data can be any suitable data, such as signaling data or user data. In one embodiment, the data can be SIP signaling.

[0114] In one embodiment, when the fallback type is a redirect, the session management function can determine that data buffering is required for the end device. For example, when the fallback type is a redirect to EPS, the session management function can determine that data buffering is required for the end device. When the fallback type is a redirect to an E-UTRA connected to 5GC, the session management function can determine that data buffering is required for the end device.

[0115] In one embodiment, when the fallback type is a handover, the session management function can determine that data buffering for the end device is not required. For example, when the fallback type is a handover to EPS, the session management function can determine that data buffering for the end device is not required. When the fallback type is a handover to an E-UTRA connection to 5GC, the session management function can determine that data buffering for the end device is not required.

[0116] For example, in 5GS, if NG-RAN performs a redirection to EPS or to an E-UTRA connected to 5GC, it means the UE will be forced into an idle state, and the fallback type can include redirection (e.g., redirection to EPS or redirection to an E-UTRA connected to 5GC). The session management function can then determine if data buffering for the end device is required. In the case of a handover procedure performed by NG-RAN (e.g., a handover to EPS or a handover to an E-UTRA connected to 5GC), the session management function can then determine if data buffering for the end device is not required.

[0117] In box 806, in response to determining that data buffering for the terminal device is required, the session management function sends a second message including a buffering indication to a user plane function (e.g., UPF). The buffering indication instructs the user plane function to buffer data for the terminal device.

[0118] The second message can be any suitable message that can be transmitted between the session management function and the user plane function. In one embodiment, the second message may include an N4 session modification request message as described in 3GPP TS 23.502V16.7.0.

[0119] The second message can be sent at any suitable time. In one embodiment, the second message can be sent during or before the network access release process. For example, it can be sent... Figure 3 The second message is sent at step 6a. It can be done at this point. Figure 2 The second message is sent at step 4. It can be done at step 4. Figure 1 The second message is sent at step 4.

[0120] In one embodiment, after determining that data buffering for the terminal device is required based on rollback information, a second message is sent immediately.

[0121] In one embodiment, when a buffer indication is sent prior to the access network release procedure, it has a higher priority than a buffer indication sent during the access network release procedure. For example, in Figure 3 In step 6a, the SMF can send an N4 session modification request (AN or N3 UPF tunnel information to be deleted, buffer on / off) to the UPF. The buffer indication sent before the access network release process has a higher priority than... Figure 3 Step 6a in the process sends the buffer opening / closing with higher priority.

[0122] Figure 9 A flowchart of a method according to another embodiment of this disclosure is shown, which can be performed by means implemented in an access and mobility management function, or by means implemented as an access and mobility management function, or by means communicatively coupled to an access and mobility management function. Therefore, the means can provide components or modules for implementing various parts of method 900, as well as components or modules for combining with other components to implement other processes. The access and mobility management function can be any suitable entity or node capable of implementing an access and mobility management function. For example, the access and mobility management function can be an AMF. For some parts already described in the above embodiments, their description is omitted here for brevity.

[0123] In box 902, the Access and Mobility Management function receives a third message from the radio access network entity, including fallback information for the terminal equipment. The fallback information includes the fallback type. The radio access network can be any suitable network entity capable of supporting the radio access function. For example, the radio access network can be NG-RAN. The fallback type has already been described above. The third message can be any suitable message that can be transmitted between the radio access network and the Access and Mobility Management function. For example, the third message can include a Protocol Data Unit (PDU) session resource modification response message as described in 3GPP TS 23.502 V16.7.0.

[0124] In box 904, the Access and Mobility Management function sends a first message to the Session Management function, including fallback information for the terminal device. The first message has been described in the above embodiments. In one embodiment, the Session Management function may be PGW-C+SMF.

[0125] Figure 10A flowchart of a method according to another embodiment of this disclosure is shown, which can be performed by means implemented in a radio access network, or by means implemented as a radio access network, or by means communicatively coupled to a radio access network. Therefore, the means can provide components or modules for implementing various parts of method 1000, as well as components or modules for combining with other components to implement other processes. The radio access network can be any suitable entity or node capable of implementing radio access functionality. For example, the radio access network can be NG-RAN. For the sake of brevity, descriptions of some parts already described in the above embodiments are omitted here.

[0126] In box 1002, the radio access network determines to trigger a backoff for the terminal device. The radio access network may determine to trigger a backoff for the terminal device for various reasons. For example, the NG-RAN may be configured to support EPS backoff for IMS voice and, taking into account UE capabilities, an indication from the AMF that "redirection for EPS backoff for voice is possible," network configuration (e.g., N26 availability configuration), and radio conditions, determine to trigger a backoff to EPS.

[0127] In box 1004, the radio access network sends a third message to the access and mobility management functions, including fallback information for the terminal equipment. The fallback information includes the fallback type. The third message has been described above.

[0128] Figure 11 This is a flowchart of EPS rollback for IMS voice according to an embodiment of the present disclosure.

[0129] When a 5G system serves a UE, the UE has one or more ongoing PDU sessions, each PDU session including one or more QoS flows. The serving PLMN (Public Land Mobile Network) AMF has already sent an indication to the UE during the registration process supporting IMS voice sessions via PS (see section 5.16.3.10 in 3GPP TS 23.501 V16.7.0), and the UE has already registered in IMS. If N26 is not supported, the serving PLMN AMF sends an indication to the UE during the registration process supporting interoperability without N26 (see section 5.17.2.3.1 in 3GPP TS 23.501 V16.7.0).

[0130] In step 1, the UE is camped on the NG-RAN in 5GS, and an MO (Mobile Initiated) or MT (Mobile Termination) IMS voice session has been initiated.

[0131] In step 2, the network-initiated PDU session modification for establishing the QoS flow for voice arrives at the NG-RAN (see N2 PDU session request in Clause 4.3.3 of 3GPP TS 23.502 V16.7.0).

[0132] In step 3, the NG-RAN is configured to support EPS backoff for IMS voice and, taking into account UE capabilities, an indication from the AMF that "redirection for EPS backoff for voice is possible" (received as part of initial context settings, handover resource allocation, or path handover request confirmation as defined in 3GPP TS 38.413 V16.4.0), network configuration (e.g., N26 availability configuration), and radio conditions, determines whether to trigger a backoff to EPS. If the NG-RAN decides not to trigger a backoff to EPS, the process stops here, and the following steps are not performed.

[0133] NG-RAN can initiate UE measurement report requests from the UE, including E-UTRAN as the target.

[0134] Note 1: If the AMF has indicated that "redirection for EPS backoff for voice is not possible", then EPS backoff for IMS voice will not be performed in step 5. If the NG-RAN has not yet received an indication of "redirection for EPS backoff for voice", the decision on whether to perform EPS backoff for IMS voice is based on network configuration (e.g., based on N26 availability and other standards).

[0135] In step 4, NG-RAN uses mobile traffic via AMF to SMF+PGW-C (or via V-SMF to H-SMF+P-GW-C in the case of home route roaming) with backoff for IMS voice. (i.e., switching or having heavy) Targeted AN release) The system responds to the ongoing indication of a PDU session modification response message to indicate rejection of the PDU session modification received in step 2 for establishing a QoS flow for IMS voice. The SMF+PGW-C maintains the PCC rules associated with the QoS flow and reports the EPS fallback event to the PCF if the PCF has already subscribed to the event. If NG-RAN indicates, for example, with If a fallback for IMS voice with AN release is in progress, involving redirection (such as inter-system redirection), then an SMF request is made. UPF buffers downlink packets.

[0136] In step 5, considering UE capabilities, the NG-RAN initiates a handover (see section 4.11.1.2.1 of 3GPP TS 23.502 V16.7.0) or initiates an AN release via inter-system redirection to the EPS (see sections 4.2.6 and 4.11.1.3.2 of 3GPP TS 23.502 V16.7.0). If the PCF is subscribed, as specified in sections 4.11.1.2.1 or 4.11.1.3.2.6 of 3GPP TS 23.502 V16.7.0, the SMF+PGW-C reports a change in RAT type. When the UE is connected to the EPS, proceed with 6a or 6b.

[0137] In step 6a, in the case of a 5GS to EPS handover, refer to section 4.11.1.2.1 of 3GPP TS 23.502 V16.7.0, and in the case of an inter-system redirection to EPS with an N26 interface, refer to section 4.11.1.3.2 of 3GPP TS 23.502 V16.7.0. In either case, the UE initiates a TAU (Tracking Area Update) procedure, and in the case of an inter-system redirection to EPS, the UE includes an activity flag in the request; or

[0138] In step 6b. In the case of inter-system redirection to EPS without N26 interface, see section 4.11.2.2 of 3GPP TS23.502 V16.7.0. As described in section 5.3.2.1 of 3GPP TS 23.401 V16.9.0, if the UE supports the request type flag "Switch" for PDN connection request during the attach procedure and has received an indication to support no N26 interoperability, the UE initiates an attach with a PDN connection request of request type "Switch".

[0139] In the case of inter-system redirection for emergency services, the UE uses an emergency indication in the RRC message as specified in Clause 6.2.2 of 3GPP TS 36.331 V16.3.0, and the E-UTRAN provides the emergency indication to the MME during the tracking area update or attach procedure. For the handover procedure, see Clause 4.11.1.2.1, Step 1 of 3GPP TS 23.502 V16.7.0.

[0140] In step 7, after the completion of the move to EPS or as part of the 5GS to EPS handover process, as specified in clause 4.11.1.2.1 of 3GPP TS 23.502 V16.7.0, the SMF+PGW-C re-initiates the establishment of a dedicated bearer for the PCC rules maintained in step 4, including a dedicated bearer for IMS voice, and maps 5G QoS parameters to EPC QoS parameters. If SMF+PGW-C has already requested UPF buffering of downlink packets in step 4, then SMF+PCW-C will Instructs UPF+PGW-U to send buffered downlink packets. If PCF is subscribed, SMF+PGW-C reports information about successful resource allocation and network access.

[0141] As specified in 3GPP TS 23.228 V16.6.0, the IMS signaling associated with the establishment of an IMS voice call continues after step 1.

[0142] At least for the duration of a voice call in EPS, E-UTRAN is configured not to trigger any handover to 5GS.

[0143] Except for the underlined content. Figure 11 The steps are the same as those described in Clause 4.13.6.1 of 3GPP TS 23.502 V16.7.0.

[0144] Figure 12 This is a flowchart of the RAT rollback process in 5GC for IMS voice according to an embodiment of the present disclosure.

[0145] When the 5GC serves the UE, the UE has one or more ongoing PDU sessions, each session including one or more QoS flows. See section 5.16.3.10 in 3GPP TS 23.501 V16.7.0, the serving PLMN AMF has already sent an indication to the UE during the registration process to support IMS voice sessions via PS, and the UE has already registered in IMS.

[0146] In step 1, the UE is camped on the source NG-RAN in 5GS, and an MO or MT IMS voice session has been initiated.

[0147] In step 2, the network-initiated PDU session modification for establishing the QoS flow for IMS voice arrives at the source NG-RAN (see N2PDU session request in section 4.3.3 of 3GPP TS 23.502 V16.7.0).

[0148] In step 3, if the source NG-RAN is configured to support RAT backoff for IMS voice, the source NG-RAN decides to trigger RAT backoff, taking into account UE capabilities, network configuration, and radio conditions.

[0149] The source NG-RAN can initiate a measurement report request from the UE, including the target NG-RAN.

[0150] In step 4, the source NG-RAN moves via the AMF towards the SMF (or, in the case of roaming, towards the V-SMF) with a backoff due to IMS voice ( That is, switching or AN release with redirection. The system responds to the ongoing PDU session response message to indicate rejection of the PDU session modification received in step 2 for establishing a QoS stream for IMS voice. The SMF maintains the PCC rules associated with the QoS stream. If NG-RAN indicates, for example, that there is a redirection (such as...) If a backoff for IMS voice with AN release (inter-system redirection) is in progress, then the SMF requests the UPF buffered downlink. Road grouping .

[0151] In step 5, the source NG-RAN initiates an Xn-based inter-NG-RAN handover (see Section 4.9.1.2 of 3GPP TS 23.502 V16.7.0) or an N2-based inter-NG-RAN handover (see Section 4.9.1.3 of 3GPP TS 23.502 V16.7.0), or redirects to an E-UTRA connected to the 5GC (see Section 4.2.6 of 3GPP TS 23.502 V16.7.0). If the PCF has subscribed, the SMF reports the change in RAT type.

[0152] In step 6, after completing the NG-RAN (RAT) handover or redirection to the E-UTRA connected to the 5GC, the SMF re-initiates the PDU session modification to establish a QoS flow for IMS voice. If SMF+PGW-C has already been requested in step 4 If the UPF buffers downlink packets, the SMF+PCW-C will instruct the UPF+PGW-U to send the buffered downlink packets. If the PCF is subscribed, the SMF will report information about successful resource allocation and network access.

[0153] As specified in 3GPP TS 23.228 V16.6.0, the IMS signaling associated with the establishment of an IMS voice call continues after step 1.

[0154] At least for the duration of an IMS voice call, the target NG-RAN is configured not to trigger an inter-NG-RAN handover back to the source NG-RAN.

[0155] Except for the underlined content. Figure 12 The steps are the same as those described in Clause 4.13.6.2 of 3GPP TS 23.502 V16.7.0.

[0156] In one embodiment, when NG-RAN rejects QoS flow establishment for a voice call, NG-RAN should additionally include a fallback type. The fallback type indicates redirection or handover. Upon receiving a QoS flow establishment rejection, if the fallback type is redirection, the PGW-C+SMF requests the UPF to immediately buffer the DL payload.

[0157] Figure 13 This is a flowchart illustrating the UPF buffering method according to an embodiment of the present disclosure. Figure 13 Some messages are the same as the corresponding messages described in 3GPP TS 23.502 V16.7.0 and SIP, and their descriptions are omitted here for brevity. AAR / AAA indicates authentication and authorization request / authentication and authorization response.

[0158] In step 6, due to EPS backoff, NG-RAN rejects the establishment QoS flow for IMS voice. NG-RAN indicates the EPS backoff type: handover or AN release with redirection. NG-RAN sends these to PGW_C_SMF via AMF.

[0159] In step 7, the SMF receives the EPS rollback and the EPS rollback type.

[0160] In step 8, if the NG-RAN indicates, for example, that a backoff for IMS voice with AN release is in progress, such as with redirection (e.g., inter-system redirection), the SMF requests the UPF to buffer downlink packets.

[0161] In step 20, after the PDN connection is established in EPS, PGW-C_SMF requests UPF to stop buffering.

[0162] In one embodiment, according to clause 4.13.6.1 of 3GPP TS 23.502V16.7.0, the NG-RAN can be modified as follows: the NG-RAN sends a backoff type to the SMF, and the SMF triggers the UPF buffer upon receiving a backoff type such as "AN release with redirection".

[0163] In one embodiment, according to clause 4.13.6.2 of 3GPP TS 23.502V16.7.0, NG-RAN can be modified as follows: NG-RAN sends a backoff type to SMF, and SMF triggers UPF buffer upon receiving a backoff type such as "AN release with redirection".

[0164] In one embodiment, 3GPP TS 38.413V16.4.0 can provide a fallback type in the PDU session resource modification response transmission IE or in the PDU session resource modification failure transmission IE (reason value).

[0165] TS 38.413: Provide EPS fallback type (reason value) in the PDU session resource modification response transmission IE or in the PDU session resource modification failure transmission IE.

[0166] The embodiments described herein offer numerous advantages, and the following is a non-exhaustive list of examples of these advantages. In some embodiments herein, the proposed solutions can address signaling (e.g., SIP signaling) or data loss issues during fallbacks (e.g., EPS fallbacks or RAT fallbacks). In some embodiments herein, the proposed solutions can reduce call setup time for fallbacks via redirection. In some embodiments herein, the proposed solutions can avoid signaling (e.g., SIP signaling) or data retransmissions. In some embodiments herein, the proposed solutions can improve system (e.g., P-CSCF) performance. The embodiments described herein are not limited to the features and advantages described above. Additional features and advantages will be recognized by those skilled in the art upon reading the following detailed description.

[0167] Figure 8-13 The various boxes shown can be considered as method steps, and / or as operations generated by computer program code, and / or as multiple coupled logic circuit elements constructed to perform related functions. The schematic flowcharts described above are generally presented as logic flowcharts. Therefore, the depicted sequence and labeled steps indicate specific embodiments of the presented method. Other steps and methods that are functionally, logically, or effectively equivalent to one or more steps or portions thereof of the illustrated method are conceivable. Furthermore, the order in which a particular method occurs may or may not strictly adhere to the order of the corresponding steps shown.

[0168] Figure 14 This is a block diagram of an apparatus suitable for practicing certain embodiments of the present disclosure. For example, any of the above-described session management functions, access and mobility management functions, and radio access network entities can be implemented as or through apparatus 1400.

[0169] Device 1400 includes at least one processor 1421, such as a digital processor (DP), and at least one memory (MEM) 1422 coupled to the processor 1421. Device 1400 may also include a transmitter TX and a receiver RX 1423 coupled to the processor 1421. MEM 1422 stores a program (PROG) 1424. PROG 1424 may include instructions that, when executed on the associated processor 1421, enable device 1400 to operate according to embodiments of the present disclosure. Combinations of at least one processor 1421 and at least one MEM 1422 can form a processing device 1425 suitable for implementing various embodiments of the present disclosure.

[0170] Various embodiments of this disclosure can be implemented by a computer program that can be executed by one or more of a processor 1421, software, firmware, hardware, or a combination thereof.

[0171] MEM 1422 can be of any type suitable for the local technical environment and can be implemented using any suitable data storage technology, such as, by way of non-limiting example, semiconductor-based storage devices, magnetic storage devices and systems, optical storage devices and systems, fixed memory and removable memory.

[0172] The processor 1421 may be of any type suitable for the local technical environment and may include one or more of the following: as non-limiting examples, general-purpose computers, special-purpose computers, microprocessors, digital signal processors (DSPs), and processors based on multi-core processor architectures.

[0173] In embodiments where the device is implemented as a session management function or implemented at the session management function, the memory 1422 stores instructions executable by the processor 1421, so that the session management function operates according to any method associated with the session management function described above.

[0174] In embodiments where the device is implemented as an access and mobility management function or implemented at the access and mobility management function, the memory 1422 stores instructions executable by the processor 1421, so that the access and mobility management function operates according to any method associated with the access and mobility management function described above.

[0175] In embodiments where the device is implemented as a radio access network entity or at a radio access network entity, the memory 1422 stores instructions executable by the processor 1421, thereby allowing the radio access network entity to operate in any manner associated with the radio access network entity as described above.

[0176] Figure 15 This is a block diagram illustrating a session management function according to an embodiment of the present disclosure. As shown, the session management function 1500 includes a receiving module 1501, a determining module 1502, and a sending module 1503. The receiving module 1501 can be configured to receive a first message including fallback information for a terminal device from an access and mobility management function. The fallback information includes a fallback type. The determining module 1502 can be configured to determine, based on the fallback information, whether data buffering for the terminal device is required. The sending module 1503 can be configured to, in response to determining that data buffering for the terminal device is required, send a second message including a buffering indication to a user plane function. The buffering indication instructs the user plane function to buffer data for the terminal device.

[0177] Figure 16This is a block diagram illustrating an access and mobility management function according to an embodiment of the present disclosure. As shown, the access and mobility management function 1600 includes a receiving module 1601 and a sending module 1602. The receiving module 1601 can be configured to receive a third message including fallback information for a terminal device from a radio access network entity. The fallback information includes a fallback type. The sending module 1602 can be configured to send a first message including fallback information for a terminal device to a session management function.

[0178] Figure 17 This is a block diagram illustrating a radio access network entity according to an embodiment of the present disclosure. As shown, the radio access network entity 1700 includes a determining module 1701 and a transmitting module 1702. The determining module 1701 can be configured to determine whether to trigger a fallback for a terminal device. The transmitting module 1702 can be configured to send a third message including fallback information for the terminal device to the access and mobility management function. The fallback information includes a fallback type.

[0179] The term “unit” or “module” may have a conventional meaning in the fields of electronics, electrical equipment and / or electronic equipment, and may include, for example, electrical and / or electronic circuits, devices, modules, processors, memories, logic solid-state and / or discrete devices, computer programs or instructions for performing corresponding tasks, processes, calculations, output and / or display functions, etc. (such as those described herein).

[0180] Using functional units, the aforementioned session management functions, access and mobility management functions, and radio access network entities do not require fixed processors or memory; any computing and storage resources can be allocated from these functions. The introduction of virtualization and network computing technologies can improve the efficiency of network resource utilization and network flexibility.

[0181] According to one aspect of this disclosure, a computer program product tangibly stored on a computer-readable storage medium and including instructions is provided, which, when executed on at least one processor, cause the at least one processor to perform any of the methods described above.

[0182] According to one aspect of this disclosure, a computer-readable storage medium is provided that stores instructions which, when executed by at least one processor, cause the at least one processor to perform any of the methods described above.

[0183] Furthermore, this disclosure may also provide a carrier containing the aforementioned computer program, which may be one of electronic signals, optical signals, radio signals, or a computer-readable storage medium. The computer-readable storage medium may be, for example, an optical disc or electronic storage device, such as RAM (random access memory), ROM (read-only memory), flash memory, magnetic tape, CD-ROM, DVD, Blu-ray disc, etc.

[0184] The techniques described herein can be implemented in various ways, such that the means for implementing one or more functions of the corresponding apparatus described in the embodiments includes not only prior art components, but also components for implementing one or more functions of the corresponding apparatus described together with the embodiments, and it may include separate components for each individual function or components that can be configured to perform two or more functions. For example, these techniques can be implemented in hardware (one or more devices), firmware (one or more devices), software (one or more modules), or a combination thereof. For firmware or software, implementation can be accomplished by modules (e.g., processes, functions, etc.) that perform the functions described herein.

[0185] Exemplary embodiments of this document have been described above with reference to block diagrams and flowcharts illustrating methods and apparatus. It will be understood that each block in the block diagrams and flowcharts, as well as combinations of blocks in the block diagrams and flowcharts, can be implemented by various components including computer program instructions. These computer program instructions can be loaded onto a general-purpose computer, a special-purpose computer, or other programmable data processing equipment to produce a machine, such that the instructions, which execute on the computer or other programmable data processing equipment, create components for implementing the functions specified in the flowchart blocks or blocks.

[0186] Furthermore, although the operations are depicted in a specific order, this should not be construed as requiring that these operations be performed in the specific order shown or sequentially, or requiring that all illustrated operations be performed to achieve the desired result. In some cases, multitasking and parallel processing may be advantageous. Similarly, while several specific implementation details are included in the foregoing discussion, these should not be construed as limiting the scope of the subject matter described herein, but rather as descriptions of features that may be specific to particular embodiments. Certain features described in the context of a single embodiment may also be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment may also be implemented individually or in any suitable sub-combination in multiple embodiments.

[0187] While this specification contains numerous specific implementation details, these should not be construed as limiting the scope of any implementation or the scope that may be claimed, but rather as descriptions of features specific to particular embodiments that may be specific to a particular implementation. Certain features described in the context of individual embodiments may also be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment may also be implemented individually or in any suitable sub-combination in multiple embodiments. Furthermore, while the foregoing features may be described as functioning in certain combinations, or even initially claimed in this way, in certain circumstances one or more features from the claimed combination may be removed from the combination, which may be for sub-combinations or variations thereof.

[0188] It will be apparent to those skilled in the art that the inventive concept can be implemented in various ways as technology advances. The above embodiments are given for description purposes only and not for limitation of this disclosure. It should be understood that, as will be readily apparent to those skilled in the art, modifications and variations can be made without departing from the spirit and scope of this disclosure. Such modifications and variations are considered to be within the scope of this disclosure and the appended claims. The scope of protection of this disclosure is defined by the appended claims.

Claims

1. A method (800) performed by a session management function, comprising: Receive (802) a first message from the access and mobility management function including fallback information for the terminal device, wherein the fallback information includes a fallback type; Based on the rollback information, it is determined (804) whether data buffering for the terminal device is needed, wherein when the rollback type is redirection, data buffering for the terminal device is determined to be needed; and In response to determining that the data buffering for the terminal device is required, a second message including a buffering indication is sent to the user plane function (806), wherein the buffering indication instructs the user plane function to buffer the data for the terminal device.

2. The method according to claim 1, wherein, The rollback type includes at least one of the following: Redirect; or Switch.

3. The method according to claim 1, wherein, Based on the rollback information, determining whether the data buffer for the terminal device is needed includes: When the fallback type is a switch, it is determined that the data buffer for the terminal device is not required.

4. The method according to claim 1, wherein, The redirection includes at least one of the following: Redirect from the second network to the first network; or Redirecting to the first network, which is connected to the core network of the second network.

5. The method according to claim 2, wherein, The switching includes at least one of the following: Switch from the second network to the first network; or Switch to the first network that is connected to the core network of the second network.

6. The method according to claim 4 or 5, wherein, The first network includes an evolved packet system (EPS), and the second network includes a fifth-generation system.

7. The method according to any one of claims 1-5, wherein, The fallback includes at least one of the following: Evolved Packet System (EPS) fallback, or Radio Access Technology (RAT) fallback.

8. The method according to any one of claims 1-5, wherein, The rollback is related to the Internet Protocol Multimedia Subsystem (IMS) service.

9. The method according to any one of claims 1-5, wherein, The session management function includes the Packet Data Network Gateway Control Plane Function PGW-C, which is integrated with the Session Management Function (SMF).

10. The method according to any one of claims 1-5, wherein, The first message includes an Nsmf_PDUSession_UpdateSMContext request message that either transmits an N2 PDU session resource modification response or a PDU session resource modification failed to transmit.

11. The method according to any one of claims 1-5, wherein, The second message includes the N4 session modification request message.

12. The method according to any one of claims 1-5, wherein, The second message is sent during or before the network access release process.

13. The method according to claim 12, wherein, When the buffer indication is sent before the access network release process, the buffer indication has a higher priority than the buffer indication sent during the access network release process.

14. A method (900) performed by an access and mobility management function, comprising: Receive (902) a third message from the radio access network entity including fallback information for the terminal device, wherein the fallback information includes a fallback type; and Send (904) a first message to the session management function including the rollback information for the terminal device. Whether or not data buffering is needed for the terminal device is determined based on the rollback information. Specifically, when the fallback type is redirection, the data buffer for the terminal device is determined to be necessary.

15. The method according to claim 14, wherein, The rollback type includes at least one of the following: Redirect; or Switch.

16. The method of claim 14, wherein, The redirection includes at least one of the following: Redirect from the second network to the first network; or Redirecting to the first network, which is connected to the core network of the second network.

17. The method according to claim 15, wherein, The switching includes at least one of the following: Switch from the second network to the first network; or Switch to the first network that is connected to the core network of the second network.

18. The method according to claim 16 or 17, wherein, The first network includes an evolved packet system (EPS), and the second network includes a fifth-generation system.

19. The method according to any one of claims 14-17, wherein, The fallback includes at least one of the following: Evolved Packet System (EPS) fallback, or Radio Access Technology (RAT) fallback.

20. The method according to any one of claims 14-17, wherein, The rollback is related to the Internet Protocol Multimedia Subsystem (IMS) service.

21. The method according to any one of claims 14-17, wherein, The session management function includes the Packet Data Network Gateway Control Plane Function PGW-C, which is integrated with the Session Management Function (SMF).

22. The method according to any one of claims 14-17, wherein, The first message includes an Nsmf_PDUSession_UpdateSMContext request message that either transmits an N2 PDU session resource modification response or a PDU session resource modification failed to transmit.

23. The method according to any one of claims 14-17, wherein, The third message includes a Protocol Data Unit (PDU) session resource modification response message.

24. A method (1000) performed by a radio access network entity, comprising: Confirmation (1002) triggers a fallback for the terminal device; as well as Sending (1004) a third message to the access and mobility management function including fallback information for the terminal device, wherein the fallback information includes a fallback type. Whether or not data buffering is needed for the terminal device is determined based on the rollback information. Specifically, when the fallback type is redirection, the data buffer for the terminal device is determined to be necessary.

25. The method according to claim 24, wherein, The rollback type includes at least one of the following: Redirect; or Switch.

26. The method according to claim 25, wherein, The redirection includes at least one of the following: Redirect from the second network to the first network; or Redirecting to the first network, which is connected to the core network of the second network.

27. The method according to claim 25, wherein, The switching includes at least one of the following: Switch from the second network to the first network; or Switch to the first network that is connected to the core network of the second network.

28. The method according to claim 26 or 27, wherein, The first network includes an evolved packet system (EPS), and the second network includes a fifth-generation system.

29. The method according to any one of claims 24-27, wherein, The fallback includes at least one of the following: Evolved Packet System (EPS) fallback, or Radio Access Technology (RAT) fallback.

30. The method according to any one of claims 24-27, wherein, The rollback is related to the Internet Protocol Multimedia Subsystem (IMS) service.

31. The method according to any one of claims 24-27, wherein, The third message includes a Protocol Data Unit (PDU) session resource modification response message.

32. A session management function (1400), comprising: One or more processors (1421); as well as One or more memories (1422) for storing computer program code. The one or more memories (1422) and the computer program code, together with the one or more processors (1421), are configured such that the session management function (1400) at least: Receive a first message from the access and mobility management function including fallback information for the terminal device, wherein the fallback information includes a fallback type; Based on the rollback information, it is determined whether data buffering for the terminal device is needed, wherein when the rollback type is redirection, data buffering for the terminal device is determined to be needed; and In response to determining that the data buffering for the terminal device is required, a second message including a buffering indication is sent to the user plane function, wherein the buffering indication instructs the user plane function to buffer the data for the terminal device.

33. The session management function according to claim 32, wherein, The session management function can also be operated to perform the method of any one of claims 2 to 13.

34. An access and mobility management function (1400), comprising: One or more processors (1421); as well as One or more memories (1422) for storing computer program code. The one or more memories (1422) and the computer program code, together with the one or more processors (1421), are configured such that the access and mobility management function (1400) at least: Receive a third message from a radio access network entity, including fallback information for a terminal device, wherein the fallback information includes a fallback type; and Send a first message to the session management function, including the rollback information for the terminal device. Whether or not data buffering is needed for the terminal device is determined based on the rollback information. Specifically, when the fallback type is redirection, the data buffer for the terminal device is determined to be necessary.

35. The access and mobility management function according to claim 34, wherein, The access and mobility management function can also be operated to perform the method of any one of claims 15 to 23.

36. A radio access network entity (1400), comprising: One or more processors (1421); as well as One or more memories (1422) for storing computer program code. The one or more memories (1422) and the computer program code, together with the one or more processors (1421), are configured such that the radio access network entity (1400) at least: Determine whether to trigger a fallback for the terminal device; and A third message including fallback information for the terminal device is sent to the access and mobility management function, wherein the fallback information includes a fallback type. Whether or not data buffering is needed for the terminal device is determined based on the rollback information. Specifically, when the fallback type is redirection, the data buffer for the terminal device is determined to be necessary.

37. The radio access network entity according to claim 36, wherein, The radio access network entity can also be operated to perform the method according to any one of claims 25 to 31.

38. A computer-readable storage medium storing instructions that, when executed by at least one processor, cause the at least one processor to perform the method according to any one of claims 1 to 31.

39. A computer program product comprising instructions that, when executed by at least one processor, cause the at least one processor to perform the method according to any one of claims 1 to 31.

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