Method and device for session management

Abstract

The embodiment of the invention provides a session management method and device. A method performed by a first session management function (SMF) includes marking that a state of at least one quality of service (QoS) flow is to be synchronized with a terminal device. The at least one QoS flow is managed by the first SMF and the second SMF.

Description

Technical Field

[0001] Non-limiting and exemplary embodiments of the present disclosure generally relate to the field of communication technology, and particularly to methods and apparatus for session management. Background Art

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

[0003] In some networks, various sessions may exist, such as protocol data unit (PDU) sessions. For example, a user equipment (UE) may initiate a PDU session establishment procedure. The UE may initiate a PDU session handover between a 3GPP (3rd Generation Partnership Project) network and a non-3GPP network. The UE may initiate a PDU session handover from an Evolved Packet System (EPS) to a Fifth Generation System (5GS). The network may trigger a PDU session establishment procedure.

[0004] The PDU Session Modification procedure may be used when one or more of the Quality of Service (QoS) parameters exchanged between a User Equipment (UE) and a network are modified.

[0005] The conditions for when to use the PDU Session Modification procedure for QoS change and the QoS parameters exchanged between the UE and the network are defined in clause 5.7 of 3GPP TS 23.501 V17.5.0, the disclosure of which is incorporated herein by reference in its entirety.

[0006] Figure 1a A flow chart of UE or network requested PDU session modification (for non-roaming and roaming with local breakout) is shown, which is the same as Figure 4.3.3.2-1 of 3GPP TS 23.502 V17.5.0, the disclosure of which is incorporated herein by reference in its entirety.

[0007] For non-roaming and roaming with local breakout, if the N1 PDU Session Modification Command message for deleting one or more QoS flows fails to reach the UE due to no paging response, the SMF marks the QoS flow to be removed, and later at the next UP (User Plane) activation, the SMF performs the PDU Session Modification procedure to remove the one or more QoS flows.

[0008] The following description of steps 1d and 11 is a copy of steps 1d and 11 in clause 4.3.3.2 of 3GPP TS 23.502 V17.5.0.

[0009] In step 1d. (SMF Requested Modification) the Session Management Function (SMF) may decide to modify the PDU Session. This procedure may also be triggered based on locally configured policies or from the (R)AN (Radio Access Network) (see 3GPP TS 23.502 V17.5.0, clauses 4.2.6 and 4.9.1). This procedure may also be triggered if the UP connection is activated (as described in the Service Request procedure) and the SMF has marked the status of one or more QoS (Quality of Service) flows for deletion in the 5GC (Fifth Generation Core Network), but has not yet synchronized with the UE.

[0010] In step 11, AMF (Access and Mobility Management Function) forwards the N1 SM (Session Management) container (PDU Session Modification Command Acknowledgement) and user location information received from AN (Access Network) to SMF via Nsmf_PDUSession_UpdateSMContext service operation. SMF replies with Nsmf_PDUSession_UpdateSMContext response.

[0011] If the modification initiated by the SMF is to delete QoS flows that do not contain QoS flows associated with the default QoS rules (for example, triggered by PCF (Policy Control Function)), and the SMF does not receive a response from the UE, the SMF marks the status of these QoS flows to be synchronized with the UE.

[0012] Figure 1a The other steps are described in Section 4.3.3.2 of 3GPP TS 23.502 V17.5.0. For the sake of brevity, the description of these steps is omitted here.

[0013] Figure 1b A flow chart of UE or network requested PDU session modification (home routing roaming) is shown, which is the same as Figure 4.3.3.3-1 of 3GPP TS 23.502 V17.5.0, the disclosure of which is incorporated herein by reference in its entirety.

[0014] The description of the following steps 1d and 14-15 is a copy of steps 1d and 11 in clause 4.3.3.2 of 3GPP TS 23.502 V17.5.0.

[0015] In step 1d. (HPLMN request) this step is the same as Figure 1a Same as step 1d.

[0016] In steps 13-14. These steps are the same as Figure 1a Steps 11a-11b are the same as above, but are performed in the visited PLMN (Public Land Mobile Network).

[0017] In step 15, the V-SMF responds to the H-SMF with an Nsmf_PDUSession_Update response that carries information such as the Protocol Configuration Option (PCO) and the Secondary RAT (Radio Access Technology) usage data provided by the UE in the SM PDU Session Modification Command Ack message from the UE to the V-SMF. The H-SMF shall modify the PDU session context.

[0018] If the V-SMF has rejected one or more QFIs (step 3) or the (R)AN has Figure 1a If one or more QFIs are rejected in step 6 of UE, the H-SMF is responsible for updating the QoS rules and QoS flow level QoS parameters later (if required for one or more QoS flows associated with one or more QoS rules in the UE).

[0019] Figure 1b The other steps are described in Section 4.3.3.3 of 3GPP TS 23.502 V17.5.0. For the sake of brevity, the description of these steps is omitted here. Summary of the Invention

[0020] This summary is intended to introduce some concepts in a simplified form that are further described below 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 limit the scope of the claimed subject matter.

[0021] according to Figure 1a-Figure 1b , Figure 1b Step 1d in the Figure 1a The same steps as in , i.e., the H-SMF is expected to perform a PDU Session Modification to delete one or more QoS Flows whose state will be synchronized with the UE. However, how the H-SMF knows when to perform step 1d is unclear. To address this issue, there are two options.

[0022] Option 1: V-SMF notifies H-SMF of UP activation.

[0023] Option 2: When the UP connection is activated, the V-SMF notifies the H-SMF of one or more QoS flows whose status will be synchronized with the UE.

[0024] Figure 1b Steps 13-14 in the Figure 1a It is not clear whether the V-SMF and H-SMF should mark the status of these QoS flows to be synchronized with the UE.

[0025] It is not defined how the I-SMF (Intermediate SMF or I_SMF) / V-SMF (Visited SMF or V_SMF) should handle when the H-SMF (Home SMF or H_SMF) / A-SMF (Anchor SMF) triggers a QoS flow modification (e.g., QoS flow deletion) and the UE is unreachable. It is also not defined how the I-SMF / V-SMF should handle when a QoS flow modification (e.g., release) is required during AN release using the I-SMF / V-SMF and the UE is unreachable. In these scenarios, the PDU Session Modification procedure may fail. The function of synchronizing the status of one or more QoS flows between the UE and the 5GC does not work in cases where the V / I-SMF is involved.

[0026] To overcome or alleviate at least one of the above problems or other problems, embodiments of the present disclosure propose an improved solution for session management.

[0027] In an embodiment, when the PDU Session Modification Command message for QoS flow deletion cannot reach the UE (for example, due to no paging response), both the V-SMF / I-SMF and the H-SMF / A-SMF mark the status of one or more QoS flows as deleted in the 5GC, but not yet synchronized with the UE. At the next UP activation, if the V-SMF / I-SMF has marked the status of one or more QoS flows as deleted in the 5GC, but has not yet synchronized with the UE, the V-SMF / I-SMF sends an indication to the H-SMF / A-SMF to synchronize the status of one or more QoS flows with the UE.

[0028] In a first aspect of the present disclosure, a method performed by a first session management function (SMF) is provided. The method includes marking the state of at least one quality of service (QoS) flow to be synchronized with a terminal device. The at least one QoS flow is managed by the first SMF and a second SMF.

[0029] In an embodiment, at least one QoS flow is not associated with a default QoS rule.

[0030] In an embodiment, the status of the at least one QoS flow comprises deletion of the at least one QoS flow.

[0031] In an embodiment, the method further comprises obtaining, from the second SMF during the first SMF insertion process, information that the state of at least one QoS flow will be synchronized with the terminal device and / or information for the first SMF to send an N1 message to the terminal device to synchronize the state of at least one QoS flow with the terminal device.

[0032] In an embodiment, the method further includes obtaining, from the old first SMF during the first SMF change process, information that the state of at least one QoS flow will be synchronized with the terminal device and / or information for the first SMF to send an N1 message to the terminal device to synchronize the state of at least one QoS flow with the terminal device.

[0033] In an embodiment, the method further includes, during the first SMF change process, sending information to the new first SMF that the status of at least one QoS flow will be synchronized with the terminal device and / or information for the new SMF to send an N1 message to the terminal device to synchronize the status of at least one QoS flow with the terminal device.

[0034] In an embodiment, the method further includes receiving a protocol data unit (PDU) session update request including a PDU session modification command for at least one QoS flow from a second SMF. The method further includes determining that the terminal device is unreachable. The method further includes sending a PDU session update response to the second SMF, the PDU session update response including information that a state of the at least one QoS flow is to be synchronized with the terminal device or not to be synchronized with the terminal device.

[0035] In an embodiment, the method further includes determining a PDU session modification command for the at least one QoS flow. The method further includes determining that the terminal device is unreachable. The method further includes sending a PDU session update request to the second SMF, the PDU session update request including information that the state of the at least one QoS flow is to be synchronized with the terminal device or not to be synchronized with the terminal device.

[0036] In an embodiment, the at least one QoS flow comprises at least one guaranteed bit rate (GBR) QoS flow.

[0037] In an embodiment, a PDU session modification command for at least one QoS flow is determined during an access network release procedure.

[0038] In an embodiment, the method further includes receiving a PDU session update request from a second SMF, the PDU session update request including a PDU session modification command for at least one QoS flow and information for the first SMF to send an N1 message to the terminal device to synchronize the state of the at least one QoS flow with the terminal device. The method further includes determining that the terminal device is unreachable. The method further includes sending information that the terminal device is unreachable to the second SMF. The method further includes executing the PDU session modification command for at least one QoS flow. The method further includes, when the terminal device is reachable, complying with the N1 message based on the information for the first SMF to send the N1 message to the terminal device to synchronize the state of the at least one QoS flow with the terminal device. The method further includes sending the N1 message to the terminal device. The method further includes sending information that the state of the at least one QoS flow has been synchronized with the terminal device to the second SMF.

[0039] In an embodiment, the PDU Session Modification Command comprises deletion of at least one QoS flow.

[0040] In an embodiment, the method further includes determining that the terminal device is reachable. The method further includes sending a PDU session update request to the second SMF when there is a flag that the state of at least one QoS flow is to be synchronized with the terminal device, the PDU session update including information instructing the second SMF to synchronize the state of the at least one QoS flow with the terminal device.

[0041] In an embodiment, the method further comprises deleting a flag indicating that the state of the at least one QoS flow will be synchronized with the terminal device when the state of the at least one QoS flow has been synchronized with the terminal device.

[0042] In an embodiment, the first SMF includes at least one of the following: an intermediate SMF or a visited SMF.

[0043] In an embodiment, the second SMF comprises at least one of the following: an SMF or a home SMF.

[0044] In a second aspect of the present disclosure, a method performed by a second SMF is provided. The method includes marking a state of at least one Quality of Service (QoS) flow to be synchronized with a terminal device. The at least one QoS flow is managed by a first SMF and a second SMF.

[0045] In an embodiment, the at least one QoS flow is not associated with a default QoS rule.

[0046] In an embodiment, the status of the at least one QoS flow includes deletion of the at least one QoS flow.

[0047] In an embodiment, the method further includes sending information to the first SMF during the first SMF insertion process that the status of at least one QoS flow will be synchronized with the terminal device and / or information for the first SMF to send an N1 message to the terminal device to synchronize the status of at least one QoS flow with the terminal device.

[0048] In an embodiment, the method further comprises sending a protocol data unit (PDU) session update request including a PDU session modification command for at least one QoS flow to the first SMF. The method further comprises receiving a PDU session update response including information indicating that the state of the at least one QoS flow is to be synchronized with the terminal device or not to be synchronized with the terminal device from the first SMF.

[0049] In an embodiment, the method further comprises receiving, from the first SMF, a PDU session update request including information instructing the second SMF to synchronize the state of at least one QoS flow with the terminal device. The method further comprises sending, to the first SMF, a PDU session update request including a PDU session modification command for the at least one QoS flow.

[0050] In an embodiment, the method further includes sending a PDU session update request to the first SMF, the PDU session update request including a PDU session modification command for at least one QoS flow and information for the first SMF to send an N1 message to the terminal device to synchronize the state of the at least one QoS flow with the terminal device. The method further includes receiving information from the first SMF that the terminal device is unreachable. The method further includes executing the PDU session modification command for the at least one QoS flow. The method further includes receiving information that the state of the at least one QoS flow has been synchronized with the terminal device when the terminal device is reachable.

[0051] In an embodiment, the method further comprises sending an event open subscription request for a reachability event of the terminal device to an access and mobility management function (AMF). The method further comprises receiving the reachability event of the terminal device from the AMF. The method further comprises sending a PDU session update request including a PDU session modification command for at least one QoS flow to the first SMF when there is a flag that the state of at least one QoS flow is to be synchronized with the terminal device.

[0052] In an embodiment, the PDU Session Modification Command comprises deletion of at least one QoS flow.

[0053] In an embodiment, the method further comprises deleting a flag indicating that the state of the at least one QoS flow will be synchronized with the terminal device when the state of the at least one QoS flow has been synchronized with the terminal device.

[0054] In an embodiment, the method further comprises receiving, from the first SMF, a PDU session update request comprising information that a state of at least one QoS flow is to be synchronized with the terminal device or not to be synchronized with the terminal device.

[0055] In an embodiment, the at least one QoS flow comprises at least one guaranteed bit rate (GBR) QoS flow.

[0056] In an embodiment, the first SMF includes at least one of the following: an intermediate SMF or a visited SMF.

[0057] In an embodiment, the second SMF comprises at least one of: an SMF or a home SMF.

[0058] In a third aspect of the present disclosure, a first SMF is provided. The first SMF includes a processor and a memory coupled to the processor. The memory stores instructions executable by the processor. The first SMF is operable to mark the status of at least one Quality of Service (QoS) flow to be synchronized with a terminal device. The at least one QoS flow is managed by the first SMF and a second SMF.

[0059] In a fourth aspect of the present disclosure, a second SMF is provided. The second SMF includes a processor and a memory coupled to the processor. The memory stores instructions executable by the processor. The second SMF is operable to mark the status of at least one Quality of Service (QoS) flow to be synchronized with a terminal device. The at least one QoS flow is managed by the first SMF and the second SMF.

[0060] In a fifth aspect of the present disclosure, a first SMF is provided. The first SMF includes a marking module configured to mark a state of at least one Quality of Service (QoS) flow to be synchronized with a terminal device. The at least one QoS flow is managed by the first SMF and a second SMF.

[0061] In an embodiment, the first SMF further includes a first obtaining module, which is configured to obtain, from the second SMF during the first SMF insertion process, information that the status of the at least one QoS flow will be synchronized with the terminal device and / or information for the first SMF to send an N1 message to the terminal device to synchronize the status of the at least one QoS flow with the terminal device.

[0062] In an embodiment, the first SMF further includes a second obtaining module, which is configured to obtain, from the old first SMF during the first SMF change process, information that the status of at least one QoS flow will be synchronized with the terminal device and / or information for the first SMF to send an N1 message to the terminal device to synchronize the status of at least one QoS flow with the terminal device.

[0063] In an embodiment, the first SMF further includes a first sending module, which is configured to send information to the new first SMF during the first SMF change process that the status of at least one QoS flow will be synchronized with the terminal device and / or information for the new SMF to send an N1 message to the terminal device to synchronize the status of at least one QoS flow with the terminal device.

[0064] In an embodiment, the first SMF further comprises a first receiving module configured to receive a protocol data unit (PDU) session update request comprising a PDU session modification command for at least one QoS flow from the second SMF.

[0065] In an embodiment, the first SMF further comprises a first determination module configured to determine that the terminal device is unreachable.

[0066] In an embodiment, the first SMF further includes a second sending module configured to send a PDU session update response including information that the state of at least one QoS flow will be synchronized with the terminal device or not synchronized with the terminal device to the second SMF.

[0067] In an embodiment, the first SMF further comprises a second determination module configured to determine a PDU session modification command for at least one QoS flow.

[0068] In an embodiment, the first SMF further comprises a third determination module configured to determine that the terminal device is unreachable.

[0069] In an embodiment, the first SMF further includes a third sending module configured to send a PDU session update request including information that the state of at least one QoS flow will be synchronized with the terminal device or not synchronized with the terminal device to the second SMF.

[0070] In an embodiment, the first SMF further includes a second receiving module, which is configured to receive a PDU session update request from the second SMF, the PDU session update request including a PDU session modification command for at least one QoS flow and information for the first SMF to send an N1 message to the terminal device to synchronize the status of the at least one QoS flow with the terminal device.

[0071] In an embodiment, the first SMF further comprises a fourth determination module configured to determine that the terminal device is unreachable.

[0072] In an embodiment, the first SMF further includes a fourth sending module, which is configured to send information that the terminal device is unreachable to the second SMF.

[0073] In an embodiment, the first SMF further comprises an execution module configured to execute the PDU session modification command for at least one QoS flow.

[0074] In an embodiment, the first SMF further comprises a compliance module configured to comply with an N1 message based on information for the first SMF to send an N1 message to the terminal device to synchronize the state of at least one QoS flow with the terminal device when the terminal device is reachable.

[0075] In an embodiment, the first SMF further includes a fifth sending module configured to send an N1 message to the terminal device.

[0076] In an embodiment, the first SMF further includes a sixth sending module, which is configured to send information to the second SMF that the status of at least one QoS flow has been synchronized with the terminal device.

[0077] In an embodiment, the first SMF further comprises a fifth determination module configured to determine that the terminal device is reachable.

[0078] In an embodiment, the first SMF further includes a seventh sending module, which is configured to send a PDU session update request to the second SMF when there is a mark that the status of at least one QoS flow will be synchronized with the terminal device, and the PDU session update request includes information instructing the second SMF to synchronize the status of at least one QoS flow with the terminal device.

[0079] In an embodiment, the first SMF further includes a deletion module configured to delete a mark that the state of at least one QoS flow will be synchronized with the terminal device when the state of at least one QoS flow has been synchronized with the terminal device.

[0080] In a sixth aspect of the present disclosure, a second SMF is provided. The second SMF includes a marking module configured to mark the state of at least one Quality of Service (QoS) flow to be synchronized with a terminal device. The at least one QoS flow is managed by the first SMF and the second SMF.

[0081] In an embodiment, the second SMF further includes a first sending module, which is configured to send information to the first SMF that the status of at least one QoS flow will be synchronized with the terminal device during the first SMF insertion process and / or information for the first SMF to send an N1 message to the terminal device to synchronize the status of at least one QoS flow with the terminal device.

[0082] In an embodiment, the second SMF further includes a second sending module configured to send a protocol data unit (PDU) session update request including a PDU session modification command for at least one QoS flow to the first SMF.

[0083] In an embodiment, the second SMF further includes a first receiving module configured to receive a PDU session update response including information that a state of at least one QoS flow will be synchronized with the terminal device or not synchronized with the terminal device from the first SMF.

[0084] In an embodiment, the second SMF further comprises a second receiving module configured to receive, from the first SMF, a PDU session update request comprising information instructing the second SMF to synchronize the state of at least one QoS flow with the terminal device.

[0085] In an embodiment, the second SMF further includes a second sending module configured to send a PDU session update request including a PDU session modification command for at least one QoS flow to the first SMF.

[0086] In an embodiment, the second SMF further includes a third sending module, which is configured to send a PDU session update request to the first SMF, the PDU session update request including a PDU session modification command for at least one QoS flow and information for the first SMF to send an N1 message to the terminal device to synchronize the status of at least one QoS flow with the terminal device.

[0087] In an embodiment, the second SMF further includes a third receiving module configured to receive information that the terminal device is unreachable from the first SMF.

[0088] In an embodiment, the second SMF further comprises an execution module configured to execute the PDU session modification command for at least one QoS flow.

[0089] In an embodiment, the second SMF further includes a fourth receiving module configured to receive information that the state of at least one QoS flow has been synchronized with the terminal device when the terminal device is reachable.

[0090] In an embodiment, the second SMF further includes a fourth sending module, which is configured to send an event open subscription request for reachability events of the terminal device to the Access and Mobility Management Function (AMF).

[0091] In an embodiment, the second SMF further includes a fifth receiving module, which is configured to receive a reachability event of the terminal device from the AMF.

[0092] In an embodiment, the second SMF further includes a fifth sending module, which is configured to send a PDU session update request including a PDU session modification command for the at least one QoS flow to the first SMF when there is a mark that the state of the at least one QoS flow will be synchronized with the terminal device.

[0093] In an embodiment, the second SMF further includes a deletion module configured to delete a mark indicating that the state of the at least one QoS flow will be synchronized with the terminal device when the state of the at least one QoS flow has been synchronized with the terminal device.

[0094] In an embodiment, the second SMF further includes a sixth receiving module, which is configured to receive a PDU session update request from the first SMF, the PDU session update request including information that the state of at least one QoS flow will be synchronized with the terminal device or not synchronized with the terminal device.

[0095] In another aspect of the present disclosure, a computer program product is provided comprising instructions, which, when executed by at least one processor, cause the at least one processor to perform the method according to any one of the first aspect or the second aspect.

[0096] In another aspect of the present disclosure, a computer-readable storage medium storing instructions is provided. When the instructions are executed by at least one processor, the instructions cause the at least one processor to perform the method according to any one of the first aspect or the second aspect.

[0097] The embodiments herein may provide many advantages, the following being a non-exhaustive list of examples of advantages. In some embodiments herein, when at least one QoS flow is managed by a first SMF and a second SMF, the state of at least one QoS flow may be synchronized with a terminal device. In some embodiments herein, when deletion is triggered, the V-SMF / I-SMF may handle use cases where QoS flow deletion is not synchronized with the UE. The embodiments herein are not limited to the features and advantages described above. Those skilled in the art will recognize additional features and advantages after reading the detailed description below. BRIEF DESCRIPTION OF THE DRAWINGS

[0098] The above and other aspects, features and benefits of various embodiments of the present disclosure will become more fully apparent from the following detailed description taken in conjunction with the accompanying drawings, by way of example, in which like reference numerals or letters are used to designate like or equivalent elements. The accompanying drawings are illustrated to facilitate a better understanding of the embodiments of the present disclosure and are not necessarily drawn to scale, wherein:

[0099] Figure 1a Flowchart showing UE or network requested PDU session modification (for non-roaming and roaming with local breakout);

[0100] Figure 1b Flowchart showing PDU session modification requested by UE or network (home routing roaming);

[0101] Figure 2aSchematically illustrates a 5G system roaming architecture in a home routing scenario using reference point representation according to an embodiment of the present disclosure;

[0102] Figure 2b Schematically illustrates a non-roaming architecture without uplink classifier (UL-CL) / branching point (BP) with I-SMF inserted into a PDU session in reference point representation according to an embodiment of the present disclosure;

[0103] Figure 3a A flowchart of a method according to an embodiment of the present disclosure is shown;

[0104] Figure 3b A flowchart showing a method according to another embodiment of the present disclosure is shown;

[0105] Figure 3c A flowchart showing a method according to another embodiment of the present disclosure is shown;

[0106] Figure 3d A flowchart showing a method according to another embodiment of the present disclosure is shown;

[0107] Figure 3e A flowchart showing a method according to another embodiment of the present disclosure is shown;

[0108] Figure 3f A flowchart showing a method according to another embodiment of the present disclosure is shown;

[0109] Figure 3g A flowchart showing a method according to another embodiment of the present disclosure is shown;

[0110] Figure 3h A flowchart showing a method according to another embodiment of the present disclosure is shown;

[0111] Figure 4a A flowchart showing a method according to another embodiment of the present disclosure is shown;

[0112] Figure 4b A flowchart showing a method according to another embodiment of the present disclosure is shown;

[0113] Figure 4c A flowchart showing a method according to another embodiment of the present disclosure is shown;

[0114] Figure 4d A flowchart showing a method according to another embodiment of the present disclosure is shown;

[0115] Figure 4e A flowchart showing a method according to another embodiment of the present disclosure is shown;

[0116] Figure 4fA flowchart showing a method according to another embodiment of the present disclosure is shown;

[0117] Figure 4g A flowchart showing a method according to another embodiment of the present disclosure is shown;

[0118] Figure 4h A flowchart showing a method according to another embodiment of the present disclosure is shown;

[0119] Figure 5 A flowchart of a PDU session modification process requested by a UE or a network (home routing roaming scenario) according to an embodiment of the present disclosure is shown;

[0120] Figure 6 1. A flowchart illustrating a UE-triggered service request procedure with I-SMF insertion / change / removal according to an embodiment of the present disclosure is shown;

[0121] Figure 7a A flowchart of a network-requested PDU session modification process according to an embodiment of the present disclosure is shown;

[0122] Figure 7b shows a flow chart of a V-SMF / I-SMF insertion process according to an embodiment of the present disclosure;

[0123] Figure 7c 1. A flowchart illustrating a V-SMF / I-SMF change process according to an embodiment of the present disclosure;

[0124] Figure 7d A flowchart of a PDU session modification process according to another embodiment of the present disclosure is shown;

[0125] Figure 8a shows a block diagram of an apparatus suitable for practicing some embodiments of the present disclosure;

[0126] Figure 8b A block diagram illustrating a first SMF according to an embodiment of the present disclosure; and

[0127] Figure 9 A block diagram of a second SMF according to an embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0128] Embodiments of the present disclosure are described in detail with reference to the accompanying drawings. It should be understood that these embodiments are discussed only for the purpose of enabling those skilled in the art to better understand and therefore implement the present disclosure, and that no limitation on the scope of the present disclosure is suggested. References to features, advantages or similar language throughout the specification do not mean that all features and advantages that can be implemented with the present disclosure should be in or in any single embodiment of the present disclosure. On the contrary, language referring to features and advantages should be understood to mean that specific features, advantages or characteristics described in conjunction with the embodiments are included in at least one embodiment of the present disclosure. In addition, in one or more embodiments, the features, advantages and characteristics described in the present disclosure may be combined in any suitable manner. Those skilled in the relevant art will recognize that the present disclosure may be practiced without one or more of the specific features or advantages of a particular embodiment. In other cases, additional features and advantages may be recognized in certain embodiments, while the additional features and advantages may not be present in all embodiments of the present disclosure.

[0129] As used herein, the term "network" refers to a network that complies with any suitable communication standard, such as New Radio (NR), Long Term Evolution (LTE), Advanced LTE, Wideband Code Division Multiple Access (WCDMA), High Speed Packet Access (HSPA), Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Orthogonal Frequency Division Multiple Access (OFDMA), Single Carrier Frequency Division Multiple Access (SC-FDMA), and other wireless networks. A CDMA network can implement a radio technology such as Universal Terrestrial Radio Access (UTRA). UTRA includes WCDMA and other variants of CDMA. A TDMA network can implement a radio technology such as Global System for Mobile Communications (GSM). An OFDMA network can 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" can 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 standards organizations such as 3GPP. For example, the communication protocol may include first generation (1G), 2G, 3G, 4G, 4.5G, 5G communication protocols, and / or any other protocol currently known or developed in the future.

[0130] The term "network device" or "network node" refers to any suitable network function (NF) that can be implemented in a (physical or virtual) network entity of 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 an appropriate platform (e.g., on a cloud infrastructure). For example, a 5G system (5GS) may include multiple NFs, such as access and mobility management function (AMF), session management function (SMF), authentication service function (AUSF), unified data management (UDM), policy control function (PCF), application function (AF), network exposure function (NEF), user plane function (UPF) and network repository function (NRF), radio access network (RAN), service communication agent (SCP), network data analysis function (NWDAF), network slice selection function (NSSF), network slice specific authentication and authorization function (NSSAAF), etc. For example, a 4G system (e.g., LTE (Long Term Evolution)) may include a Mobility Management Entity (MME), a Home Subscriber Server (HSS), a PCRF (Policy and Charging Rules Function), a Packet Data Network Gateway (PGW), a PGW Control Plane (PGW-C), a Serving Gateway (SGW), an SGW Control Plane (SGW-C), an E-UTRAN Node B (eNB), etc. In other embodiments, for example, depending on a specific network, the network functions may include different types of NFs.

[0131] The term "terminal device" refers to any terminal device that can access a communication network and receive services therefrom. By way of example and not limitation, a terminal device refers to a mobile terminal, user equipment (UE), or other suitable device. A UE may be, for example, a subscriber station (SS), a portable subscriber station, a mobile station (MS), or an access terminal (AT). Terminal devices may 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 (LEEs), laptop mounted devices (LMEs), 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 for communicating in accordance with one or more communication standards promulgated by 3GPP (3rd Generation Partnership Project), such as 3GPP's LTE standard or NR standard. As used herein, a "user equipment" or "UE" may not necessarily have a "user" in terms of a human user who owns and / or operates the associated device. In some embodiments, a terminal device may be configured to send and / or receive information without direct human interaction. For example, 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 that is intended to be sold to or operated by a human user but may not initially be associated with a specific human user.

[0132] As another example, in an Internet of Things (IoT) scenario, a terminal device may represent a machine or other device that performs monitoring and / or measurement, and sends the results of such monitoring and / or measurement to another terminal device and / or network device. In this case, the terminal device may be a machine-to-machine (M2M) device, which may be referred to as a machine type communication (MTC) device in the 3GPP context. As a specific example, the terminal device may be a UE that implements the 3GPP Narrowband Internet of Things (NB-IoT) standard. Specific examples of such machines or devices are sensors, metering devices (such as electricity meters), industrial machinery, or household or personal appliances, such as refrigerators, televisions, personal wearable devices (such as watches), etc. In other scenarios, the terminal device may represent a vehicle or other device that is capable of monitoring and / or reporting its operating status or other functions related to its operation.

[0133] References in the specification to "one embodiment," "an embodiment," "an exemplary embodiment," etc. indicate that the described embodiment may include a particular feature, structure, or characteristic, but not every embodiment necessarily includes the particular feature, structure, or characteristic. Furthermore, these phrases do not necessarily refer to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in conjunction with an embodiment, it is intended that it is within the knowledge of those skilled in the art to affect that feature, structure, or characteristic in conjunction with other embodiments, whether or not explicitly described.

[0134] It should be understood that although the terms "first" and "second" etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, without departing from the scope of the example 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.

[0135] 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 "only A, only B, or both A and B." The phrase "A and / or B" should be understood to mean "only A, only B, or both A and B."

[0136] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the example embodiments. Unless the context clearly indicates otherwise, as used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well. It will be further understood that when used herein, the terms "include," "comprising," "having," "having," "containing," and / or "covering" specify the presence of stated features, elements, and / or components, etc., but do not preclude the presence or addition of one or more other features, elements, components, and / or combinations thereof.

[0137] Note that these terms are used herein only for convenience of description and to distinguish between nodes, devices, or networks, etc. As technology develops, other terms with similar / identical meanings may also be used.

[0138] In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0139] Although the subject matter described herein can be implemented in any suitable type of system using any suitable components, the embodiments disclosed herein are directed to systems that conform to Figure 2a-2b For simplicity, the communication system is described based on the exemplary system architecture shown in FIG. Figure 2a-2bThe system architecture depicts only some exemplary elements. In practice, the communication system may further include any additional elements suitable for supporting communications between terminal devices or between a wireless device and another communication device (e.g., a landline phone, 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 to facilitate access and / or use of services provided by or via the communication system by the terminal devices.

[0140] Figure 2a The 5G system roaming architecture in the case of a home routing scenario using reference point representation according to an embodiment of the present disclosure is schematically illustrated. Figure 2a The architecture of is the same as Figures 4.2.4-6 as described in 3GPP TS 23.501 V17.5.0, the disclosure of which is incorporated herein by reference in its entirety. Figure 2a The system architecture shown may include some exemplary elements, such as AUSF, AMF, data network, visited NSSF (V-NSSF), home NSSF (H-NSSF), visited PCF (V-PCF), visited SMF (V-SMF), home SMF (H-SMF), UDM, UPF, AF, UE, (R)AN, NSSAAF (network slice specific authentication and authorization function), etc.

[0141] According to an exemplary embodiment, Figure 2a As shown in Figure 1, the UE can establish a signaling connection with the AMF via reference point N1. This signaling connection enables NAS (Non-Access Stratum) signaling exchanges between the UE and the core network, including a signaling connection between the UE and the (R)AN and an N2 connection for the UE between the (R)AN and the AMF. The (R)AN can communicate with the UPF via reference point N3. The UE can establish a protocol data unit (PDU) session to a data network (e.g., an operator's network or the Internet) through the UPF via reference point N6.

[0142] The N38 reference point may be between V-SMFs in the same VPLMN, or may be between V-SMFs in different VPLMNs (to enable inter-PLMN mobility).

[0143] For the above roaming scenarios, each PLMN implements proxy functionality to ensure interconnection security and hide the topology on the inter-PLMN interface.

[0144] like Figure 2aAs further shown in FIG, it also shows some reference points, such as N1, N2, N3, N4, N6, N9, N11, N38, N16, N7, N5, N22, N15, N8, N24, N10, N58, N12, N31, N59, N13, etc., which can support the interaction between NF services in NF. For example, these reference points can be implemented through corresponding NF service-based interfaces and by specifying some NF service consumers and providers and their interactions in order to perform specific system processes.

[0145] Figure 2a The various NFs shown in FIG may be responsible for functions such as session management, mobility management, authentication, security, etc. Figure 2a The various NFs shown in FIG may include functionality as defined in, for example, clause 6.2 of 3GPP TS 23.501 V17.5.0.

[0146] Figure 2b A non-roaming architecture without uplink classifier (UL-CL) / branching point (BP) with I-SMF inserted into a PDU session in reference point representation according to an embodiment of the present disclosure is schematically illustrated. Figure 2b The architecture is as described in 3GPP TS 23.501 V17.5.0 Figure 5 .34.2.2-1, the disclosure of which is incorporated herein by reference in its entirety. Figure 2b The system architecture may include some exemplary elements, such as AUSF, AMF, DN, NSSF, PCF, I-SMF, SMF, UDM, UPF, AF, UE, (R)AN, CHF (charging function), etc.

[0147] According to an exemplary embodiment, the UE may establish a signaling connection with the AMF via reference point N1, such as Figure 2b This signaling connection enables NAS signaling exchanges 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 PDU session to a data network (e.g., an operator's network or the Internet) through the UPF via reference point N6.

[0148] N16a is the interface between SMF and I-SMF.

[0149] N38 is the interface between I-SMF.

[0150] like Figure 2bAs further shown in FIG, it also shows some reference points, such as N1, N2, N3, N4, N6, N9, N11, N14, N16a, N7, N5, N15, N38, N22, N12, N13, N8, N10, N40, N13, etc. These reference points can support the interaction between NF services in NF. For example, these reference points can be implemented through corresponding NF service-based interfaces and by specifying some NF service consumers and providers and their interactions to perform specific system processes.

[0151] Figure 2b The various NFs shown in FIG may be responsible for functions such as session management, mobility management, authentication, security, etc. Figure 2b The various NFs shown in may include functionality as defined, for example, in clause 6.2 of 3GPP TS 23.501 V17.5.0.

[0152] Figure 3a A flowchart of a method according to an embodiment of the present disclosure is shown, which can be performed by an apparatus implemented in a first session management function (SMF), or an apparatus implemented at the first SMF, or an apparatus implemented as the first SMF, or an apparatus communicatively coupled to the first SMF. Therefore, the apparatus can provide components or modules for implementing various parts of method 300, as well as components or modules for implementing other processes in combination with other components.

[0153] At block 302, a first SMF may mark a state of at least one quality of service (QoS) flow to be synchronized with a terminal device. The at least one QoS flow is managed by the first SMF and a second SMF.

[0154] In other embodiments, the mark indicating that the state of at least one QoS flow will be synchronized with the terminal device may be any other suitable mark that enables the first SMF and the second SMF to know that the state of at least one QoS flow will be synchronized with the terminal device, or that the state of at least one QoS flow has not yet been synchronized with the terminal device. For example, the first SMF may mark that the state of at least one QoS flow has not yet been synchronized with the terminal device. The first SMF may mark an N1 pending state, which indicates that the QoS flow deletion is not synchronized with the terminal device due to user plane inactivity.

[0155] The first SMF may be any suitable network device, node, entity or function capable of supporting session management functions. In an embodiment, the first SMF may be an SMF as described in 3GPP TS 23.501 V17.5.0.

[0156] The second SMF may be any suitable network device, node, entity or function capable of supporting session management functions. In an embodiment, the second SMF may be an SMF as described in 3GPP TS 23.501 V17.5.0.

[0157] In an embodiment, the first SMF may include at least one of the following: an intermediate SMF (I-SMF) or a visited SMF. For example, the I-SMF may be an SMF inserted to support a PDU session because one or more UPFs belong to different SMF service areas and the UE is located in an area that cannot be controlled by the original SMF. For example, the V-SMF may be an SMF inserted to support a PDU session because one or more UPFs belong to a visited network and the UE is located in a visited network that cannot be controlled by the home SMF.

[0158] In an embodiment, the second SMF may include at least one of the following: an SMF, a home SMF (H-SMF), or an anchor SMF. For example, the H-SMF may be an SMF located in the home network.

[0159] For example, the first SMF may be an I-SMF, and the second SMF may be an SMF or an anchor SMF. The first SMF may be a V-SMF, and the second SMF may be an H-SMF.

[0160] The at least one QoS flow can be any suitable QoS flow. A QoS flow can be the finest granularity for QoS forwarding processing in the network. All services mapped to the same QoS flow receive the same forwarding processing (e.g., scheduling policy, queue management policy, rate shaping policy, RLC (Radio Link Control) configuration, etc.). Providing different QoS forwarding processing requires separate QoS flows. In an embodiment, at least one QoS flow is not associated with a default QoS rule.

[0161] The state of the at least one QoS flow may be any suitable state, such as modified or deleted. In an embodiment, the state of the at least one QoS flow comprises deletion of the at least one QoS flow.

[0162] The information that the status of at least one QoS flow will be synchronized with the terminal device can be obtained in a variety of ways. For example, the first SMF can receive this information from the second SMF or the old first SMF, or determine this information on its own. For example, during the PDU session modification process, the second SMF can determine to delete at least one QoS flow, and then it can send a PDU session update request including a command to delete at least one QoS flow to the first SMF. The first SMF can determine this information when the terminal device is unreachable. Alternatively, the first SMF can determine to modify (e.g., delete) at least one QoS flow, and the first SMF can determine this information when the terminal device is unreachable. Alternatively, the first SMF can receive this information from the second SMF during the first SMF insertion process, or receive this information from the old first SMF during the first SMF change process.

[0163] Figure 3b A flowchart of a method according to another embodiment of the present disclosure is shown, which can be performed by an apparatus implemented in a first session management function (SMF), or an apparatus implemented at a first SMF, or an apparatus implemented as a first SMF, or an apparatus communicatively coupled to a first SMF. Therefore, the apparatus can provide components or modules for implementing various parts of method 310, as well as components or modules for implementing other processes in combination with other components. For the sake of brevity, descriptions of some parts already described in the above embodiments are omitted here.

[0164] In box 312, during the first SMF insertion process, the first SMF can obtain information from the second SMF that the status of at least one QoS flow will be synchronized with the terminal device, and / or information for the first SMF to send an N1 message to the terminal device to synchronize the status of at least one QoS flow with the terminal device.

[0165] For example, when the terminal device is located outside the SMF service area, or the current SMF cannot serve the target DNAI (DN Access Identifier) for service routing of local access DN, I-SMF is inserted between SMF and AMF.

[0166] In the case of roaming for a home-routed PDU session, the following scenarios may occur:

[0167] -The terminal equipment moves out of the V-SMF service area in the serving PLMN;

[0168] - The terminal device moves to another (serving) VPLMN;

[0169] - The terminal device moves between the HPLMN (Home PLMN) and the VPLMN.

[0170] In the above case, the procedure for I-SMF in clause 4.23.2-16 of 3GPP TS 23.502 V17.5.0 is applicable to V-SMF insertion / change / removal by replacing I-SMF with V-SMF and replacing SMF with H-SMF.

[0171] For an established PDU session, if the UE is not in the SMF service area, the I-SMF is inserted. In this case, when the UE moves from the HPLMN to the VPLMN, the V-SMF is inserted and the I-SMF is removed. For movement from the VPLMN to the HPLMN, the I-SMF is inserted and the V-SMF is removed. In this case, the procedure applies, i.e., for movement from the HPLMN to the VPLMN, by replacing the target or new I-SMF with the V-SMF, and for movement from the VPLMN to the HPLMN, by replacing the source or old I-SMF with the V-SMF.

[0172] For example, the AMF may select an SMF that provides services for a PDU session. If the service area of the selected SMF does not control user plane functions that can provide services for the UE location, the AMF selects an I-SMF. After the PDU session is established, if the selected SMF cannot provide services for the target DNAI requested by the Policy and Charging Control (PCC) rules, the SMF may issue a PDU session SM (Session Management) context status notification to provide the target DNAI information to the AMF. The AMF then selects an I-SMF that provides services for the target DNAI. For home routing roaming situations, the AMF may select a V-SMF and reselect a V-SMF.

[0173] In an embodiment, the first SMF insertion procedure may be the same as or similar to the UE-triggered service request procedure with I-SMF insertion procedure described in clause 4.23.4.3 of 3GPP TS 23.502 V17.5.0.

[0174] For example, the second SMF may mark that the state of at least one Quality of Service (QoS) flow will be synchronized with the terminal device. Then, during the first SMF insertion process, the second SMF may send information to the first SMF that the state of at least one QoS flow will be synchronized with the terminal device, and / or information for the first SMF to send an N1 message to the terminal device to synchronize the state of at least one QoS flow with the terminal device.

[0175] In an embodiment, the N1 message may be the same as the corresponding message described in 3GPP TS 23.502 V17.5.0.

[0176] This information may be obtained in any suitable message (e.g., a new message or an existing message). For example, during the SMF insertion process, the first SMF may send an Nsmf_PDUSession_Context request as described in 3GPP TS 23.502 V17.5.0 to the second SMF. The first SMF may then receive an Nsmf_PDUSession_Context response as described in 3GPP TS 23.502 V17.5.0 from the second SMF, the response including information that the state of at least one QoS flow is to be synchronized with the terminal device and / or information for the first SMF to send an N1 message to the terminal device to synchronize the state of at least one QoS flow with the terminal device.

[0177] Figure 3c A flowchart of a method according to another embodiment of the present disclosure is shown, which can be performed by an apparatus implemented in a first session management function (SMF), or an apparatus implemented at a first SMF, or an apparatus implemented as a first SMF, or an apparatus communicatively coupled to a first SMF. Therefore, the apparatus can provide components or modules for implementing various parts of method 320, as well as components or modules for implementing other processes in combination with other components. For the sake of brevity, descriptions of some parts already described in the above embodiments are omitted here.

[0178] At step 322, optionally, during the first SMF change process, the first SMF may obtain from the old first SMF information that the state of at least one QoS flow will be synchronized with the terminal device, and / or information for the first SMF to send an N1 message to the terminal device to synchronize the state of at least one QoS flow with the terminal device.

[0179] For example, when a terminal device moves from an old I-SMF service area to a new I-SMF service area, the I-SMF is changed (ie, I-SMF changes).

[0180] In an embodiment, the first SMF change procedure may be the same as the UE-triggered service request procedure with I-SMF change as described in clause 4.23.4.3 of 3GPP TS 23.502 V17.5.0.

[0181] In an embodiment, after obtaining information that the state of at least one QoS flow will be synchronized with the terminal device, the first SMF may mark that the state of at least one QoS flow will be synchronized with the terminal device.

[0182] In an embodiment, when the terminal device is reachable and the state of at least one QoS flow is marked to be synchronized with the terminal device, the first SMF can use the information to comply with the N1 message and send an N1 message to the terminal device to synchronize the state of at least one QoS flow with the terminal device.

[0183] In an embodiment, when the terminal device is reachable and the state of at least one QoS flow is marked to be synchronized with the terminal device, the first SMF may send a PDU session update request to the second SMF, which PDU session update request includes information instructing the second SMF to synchronize the state of at least one QoS flow with the terminal device.

[0184] This information may be obtained in any suitable message (e.g., a new message or an existing message). For example, during an SMF change process, a first SMF, which is a new I-SMF, may send an Nsmf_PDUSession_Context request to a second SMF, which is an old first SMF. The first SMF may then receive an Nsmf_PDUSession_Context response from the second SMF, which includes information that the state of at least one QoS flow will be synchronized with the terminal device and / or information for the first SMF to send an N1 message to the terminal device to synchronize the state of at least one QoS flow with the terminal device.

[0185] At box 324, optionally, during the first SMF change process, the first SMF may send information to the new first SMF that the status of at least one QoS flow will be synchronized with the terminal device, and / or information for the new SMF to send an N1 message to the terminal device to synchronize the status of at least one QoS flow with the terminal device.

[0186] For example, when a terminal device moves from an old I-SMF service area to a new I-SMF service area, the I-SMF changes (ie, the I-SMF changes).

[0187] In an embodiment, the first SMF change procedure may be the same as the UE-triggered service request procedure with I-SMF change as described in clause 4.23.4.3 of 3GPP TS 23.502 V17.5.0.

[0188] In an embodiment, after obtaining information that the state of at least one QoS flow will be synchronized with the terminal device, the new first SMF may mark that the state of at least one QoS flow will be synchronized with the terminal device.

[0189] In an embodiment, when the terminal device is reachable and the state of at least one QoS flow is marked to be synchronized with the terminal device, the new first SMF can use the information to comply with the N1 message and send an N1 message to the terminal device to synchronize the state of at least one QoS flow with the terminal device.

[0190] In an embodiment, when the terminal device is reachable and the state of at least one QoS flow is marked to be synchronized with the terminal device, the new first SMF may send a PDU session update request to the second SMF, which includes information instructing the second SMF to synchronize the state of at least one QoS flow with the terminal device.

[0191] This information may be sent in any suitable message (e.g., a new message or an existing message). For example, during an SMF change process, the new first SMF may send an Nsmf_PDUSession_Context request to the first SMF that was the old first SMF. The first SMF may then send an Nsmf_PDUSession_Context response to the new first SMF, the response including information that the state of at least one QoS flow will be synchronized with the terminal device and / or information for the first SMF to send an N1 message to the terminal device to synchronize the state of at least one QoS flow with the terminal device.

[0192] Figure 3d A flowchart of a method according to another embodiment of the present disclosure is shown, which can be performed by an apparatus implemented in a first session management function (SMF), or an apparatus implemented at a first SMF, or an apparatus implemented as a first SMF, or an apparatus communicatively coupled to a first SMF. Therefore, the apparatus can provide components or modules for implementing various parts of method 330, as well as components or modules for implementing other processes in combination with other components. For some parts already described in the above embodiments, their description is omitted here for the sake of brevity.

[0193] At block 332, the first SMF may receive a protocol data unit (PDU) session update request from the second SMF, the request including a PDU session modification command for at least one QoS flow.

[0194] The PDU session modification command may be any suitable PDU session modification command, such as deletion or modification of at least one QoS flow.

[0195] For example, the PDU session update request may be an Nsmf_PDUSession_Update request as described in clause 4.3.3.3 of 3GPP TS 23.502 V17.5.0.

[0196] For example, during a UE or network requested PDU session modification procedure (home routing roaming scenario) as described in clause 4.3.3.3 of 3GPP TS 23.502 V17.5.0, a first SMF (e.g., I-SMF / V-SMF) may receive an Nsmf_PDUSession_Update request from a second SMF (e.g., SMF / H-SMF).

[0197] At block 334, the first SMF may determine that the terminal device is unreachable. The first SMF may determine that the terminal device is unreachable in a number of ways. For example, the first SMF may receive a notification that the terminal device has not responded. The first SMF (V-SMF / I-SMF) may subscribe to an event for "UE reachability status change" to receive the current reachability status of a UE or a group of UEs in the AMF, and to receive reports of updated reachability status for the UE or any UE in the group when the AMF knows that the reachability status of the UE has changed between reachable, unreachable, and regulatory-only.

[0198] Then, the first SMF may mark that a state of at least one Quality of Service (QoS) flow is to be synchronized with the terminal device. The at least one QoS flow is managed by the first SMF and the second SMF.

[0199] At block 336, the first SMF may send a PDU session update response to the second SMF, the response including information that the state of the at least one QoS flow is to be synchronized with the terminal device or not synchronized with the terminal device.

[0200] For example, during a UE or network requested PDU session modification procedure (home routing roaming scenario) as described in clause 4.3.3.3 of 3GPP TS 23.502 V17.5.0, a first SMF (e.g., V-SMF or I-SMF) may receive a protocol data unit (PDU) session update request including a PDU session modification command for at least one QoS flow from a second SMF (e.g., H-SMF or SMF). The first SMF may determine that the terminal device is unreachable. The first SMF may send a PDU session update response to the second SMF, the response including information that the state of at least one QoS flow will be synchronized with the terminal device or not synchronized with the terminal device.

[0201] Figure 3eA flowchart of a method according to another embodiment of the present disclosure is shown, which can be performed by an apparatus implemented in a first session management function (SMF), or an apparatus implemented at a first SMF, or an apparatus implemented as a first SMF, or an apparatus communicatively coupled to a first SMF. Therefore, the apparatus can provide components or modules for implementing various parts of method 340, as well as components or modules for implementing other processes in combination with other components. For the sake of brevity, descriptions of some parts already described in the above embodiments are omitted here.

[0202] At block 342, the first SMF may determine a PDU session modification command for at least one QoS flow.

[0203] The PDU session modification command may be any suitable PDU session modification command, such as deletion or modification of at least one QoS flow.

[0204] In an embodiment, the at least one QoS flow comprises at least one guaranteed bit rate (GBR) QoS flow or a GBR-dedicated QoS flow.

[0205] In an embodiment, the PDU session modification command for at least one QoS flow is determined during an access network release procedure. For example, the access network release procedure may be an AN release procedure involving an I-SMF as described in clause 4.23.8 of 3GPP TS 23.502 V17.5.0.

[0206] For example, when the first SMF (e.g. V-SMF / I-SMF) finds that the GBR dedicated QoS flow should be released during the AN (Access Network) release process, but the UE is unreachable according to the ngApCause (Next Generation Application Protocol (NGAP) reason) in the AN release. The first SMF (e.g. V-SMF / I-SMF) sends an N1 pending status to the second SMF (e.g. A-SMF / H-SMF), which indicates that the current terminal device is unreachable. Then, the A-SMF / H-SMF marks the QoS flow as deleted, but waits for the N1 QoS flow deletion message to the UE.

[0207] At block 344, the first SMF may determine that the terminal device is unreachable.

[0208] The first SMF may determine that the terminal device is unreachable in a variety of ways. For example, the first SMF may receive a notification that the terminal device has not responded. The first SMF (V-SMF / I-SMF) may subscribe to an event for "UE reachability status change" to receive the current reachability status of a UE or a group of UEs in the AMF, and receive a report on the updated reachability status of the UE or any UE in the group when the AMF knows that the reachability status of the UE has changed between reachable, unreachable, and only supervised.

[0209] Then, the first SMF may mark that a state of at least one Quality of Service (QoS) flow is to be synchronized with the terminal device. The at least one QoS flow is managed by the first SMF and the second SMF.

[0210] At block 346, the first SMF may send a PDU session update request to the second SMF, the request including information that the state of at least one QoS flow is to be synchronized with the terminal device or not synchronized with the terminal device.

[0211] Figure 3f A flowchart of a method according to another embodiment of the present disclosure is shown, which can be performed by an apparatus implemented in a first session management function (SMF), or an apparatus implemented at a first SMF, or an apparatus implemented as a first SMF, or an apparatus communicatively coupled to a first SMF. Therefore, the apparatus can provide components or modules for implementing various parts of method 350, as well as components or modules for implementing other processes in combination with other components. For the sake of brevity, descriptions of some parts already described in the above embodiments are omitted here.

[0212] At box 352, the first SMF can receive a PDU session update request from the second SMF, which includes a PDU session modification command for at least one QoS flow and information for the first SMF to send an N1 message to the terminal device to synchronize at least one QoS flow state with the terminal device.

[0213] The PDU session modification command may be any suitable PDU session modification command, such as deletion or modification of at least one QoS flow.

[0214] For example, the PDU session update request may be an Nsmf_PDUSession_Update request as described in clause 4.3.3.3 of 3GPP TS 23.502 V17.5.0.

[0215] For example, during a UE or network requested PDU session modification procedure (home routing roaming scenario) as described in clause 4.3.3.3 of 3GPP TS 23.502 V17.5.0, a first SMF (e.g., I-SMF / V-SMF) may receive an Nsmf_PDUSession_Update request from a second SMF (e.g., SMF / H-SMF).

[0216] At block 354, the first SMF may determine that the terminal device is unreachable.

[0217] The first SMF can determine that the terminal device is unreachable in a variety of ways. For example, the first SMF receives a notification that the terminal device has not responded. The first SMF (V-SMF / I-SMF) can subscribe to the event for "UE reachability status change" to receive the current reachability status of a UE or a group of UEs in the AMF, and receive a report on the updated reachability status of the UE or any UE in the group when the AMF knows that the UE's reachability status changes between reachable, unreachable, and only supervised.

[0218] At block 356, the first SMF may send information to the second SMF that the terminal device is unreachable.

[0219] At block 358, the first SMF may execute the PDU session modification command for the at least one QoS flow.

[0220] At block 360 , when the terminal device is reachable, the first SMF may comply with the N1 message based on information for the first SMF to send the N1 message to the terminal device to synchronize the state of the at least one QoS flow with the terminal device.

[0221] At block 362, the first SMF may send an N1 message to the terminal device.

[0222] At block 364, the first SMF may send information to the second SMF that the state of at least one QoS flow has been synchronized with the terminal device.

[0223] For example, the second SMF (e.g., H-SMF / A-SMF) can send a QoS flow deletion command to the first SMF (e.g., V-SMF / I-SMF) in the N16 interface, which has QoS flow information and n1smInfoToUE (as described in 3GPP TS29.502V18.0.0). When the first SMF (e.g., V-SMF / I-SMF) finds that the UE is unreachable, the first SMF (e.g., V-SMF / I-SMF) will still trigger the QoS flow release and send the UE unreachable status to the second SMF (e.g., H-SMF / A-SMF). Both the second SMF (e.g., H-SMF / A-SMF) and the first SMF (e.g., V-SMF / I-SMF) can delete this QoS flow. The N1 message marking the QoS flow deletion by both the second SMF (e.g., H-SMF / A-SMF) and the first SMF (e.g., V-SMF / I-SMF) is not sent to the UE.

[0224] After the UE is reachable again using the service request, the first SMF (e.g. V-SMF / I-SMF) will compose an N1 message based on the stored N1 message information and send the N1 pending status to the second SMF (e.g. H-SMF / A-SMF, i.e. anchor SMF). The N1 pending status indicates that the N1 message has been sent to the UE. Therefore, both the second SMF (e.g. H-SMF / A-SMF) and the first SMF (e.g. V-SMF / I-SMF) delete this mark.

[0225] During the insertion of the new first SMF (e.g. V-SMF / I-SMF), the second SMF (e.g. H-SMF / A-SMF) can send this N1 pending state and all information for V-SMF / I-SMF to send NAS messages to the UE in the SMContext as described in 3GPP TS 23.502 V17.5.0.

[0226] During the change of the new first SMF (e.g. V-SMF / I-SMF), the old first SMF (e.g. V-SMF / I-SMF) can send this N1 pending state and all information for the new first SMF (e.g. V-SMF / I-SMF) to send NAS messages to the UE in the SMContext.

[0227] In some embodiments, the PDU session modification command includes deletion of at least one QoS flow.

[0228] Figure 3gA flowchart of a method according to another embodiment of the present disclosure is shown, which can be performed by an apparatus implemented in a first session management function (SMF), or an apparatus implemented at a first SMF, or an apparatus implemented as a first SMF, or an apparatus communicatively coupled to a first SMF. Therefore, the apparatus can provide components or modules for implementing various parts of method 370, as well as components or modules for implementing other processes in combination with other components. For some parts already described in the above embodiments, their description is omitted here for the sake of brevity.

[0229] At block 372, the first SMF may determine that the terminal device is reachable.

[0230] For example, the first SMF (e.g., V-SMF / I-SMF) may discover during the service request process that the terminal device is reachable. The first SMF (e.g., V-SMF / I-SMF) may subscribe to the event for "UE reachability status change" to receive the current reachability status of a UE or a group of UEs in the AMF, and when the AMF knows that the reachability status of the UE changes between reachable, unreachable, and only supervised, receive a report on the updated reachability status of the UE or any UE in the group.

[0231] At box 374, when there is a flag that the state of at least one QoS flow is to be synchronized with the terminal device, the first SMF can send a PDU session update request to the second SMF, which includes information instructing the second SMF to synchronize the state of at least one QoS flow with the terminal device.

[0232] For example, during a service request process, the first SMF may send a PDU session update request to the second SMF, the request including information instructing the second SMF to synchronize the status of at least one QoS flow with the terminal device.

[0233] Figure 3h A flowchart of a method according to another embodiment of the present disclosure is shown, which can be performed by an apparatus implemented in a first session management function (SMF), or an apparatus implemented at a first SMF, or an apparatus implemented as a first SMF, or an apparatus communicatively coupled to a first SMF. Therefore, the apparatus can provide components or modules for implementing various parts of method 380, as well as components or modules for implementing other processes in combination with other components. For some parts already described in the above embodiments, their description is omitted here for the sake of brevity.

[0234] At block 382, when the state of the at least one QoS flow has been synchronized with the terminal device, the first SMF may delete a marking that the state of the at least one QoS flow will be synchronized with the terminal device.

[0235] For example, when the first SMF has synchronized the state of at least one QoS flow with the terminal device, the first SMF may delete a mark that the state of at least one QoS flow will be synchronized with the terminal device.

[0236] Figure 4a A flowchart of a method according to another embodiment of the present disclosure is shown. The method can be performed by an apparatus implemented in a second SMF, or an apparatus implemented at a second SMF, or an apparatus implemented as a second SMF, or an apparatus communicatively coupled to a second SMF. Therefore, the apparatus can provide components or modules for implementing various parts of method 400, as well as components or modules for implementing other processes in combination with other components. For the sake of brevity, descriptions of some parts already described in the above embodiments are omitted here.

[0237] At block 402, a second SMF may mark a state of at least one quality of service (QoS) flow to be synchronized with a terminal device. The at least one QoS flow is managed by a first SMF and a second SMF.

[0238] In other embodiments, the mark that the state of at least one QoS flow will be synchronized with the terminal device can be any other suitable mark that enables the first SMF and the second SMF to know that the state of at least one QoS flow will be synchronized with the terminal device, or that the state of at least one QoS flow has not yet been synchronized with the terminal device. For example, the second SMF can mark that the state of at least one QoS flow has not yet been synchronized with the terminal device. The second SMF can mark the N1 pending state, which indicates that the QoS flow deletion is not synchronized with the terminal device due to user plane inactivity.

[0239] In an embodiment, the first SMF may include at least one of an intermediate SMF (I-SMF) or a visited SMF.

[0240] In an embodiment, the second SMF may include at least one of an SMF, a home SMF (H-SMF), or an anchor SMF.

[0241] In an embodiment, at least one QoS flow is not associated with a default QoS rule.

[0242] In an embodiment, the status of the at least one QoS flow comprises deletion of the at least one QoS flow.

[0243] The information that the status of at least one QoS flow will be synchronized with the terminal device can be obtained in a variety of ways. For example, the second SMF can receive the information from the first SMF, or determine the information on its own. For example, during the PDU session modification process, the second SMF can determine to delete at least one QoS flow, and then it can send a PDU session update request including a command to delete at least one QoS flow to the first SMF. When the terminal device is unreachable, the first SMF can determine the information and send it to the second SMF. Alternatively, the second SMF can determine to modify (e.g., delete) at least one QoS flow, and the second SMF can determine the information when the terminal device is unreachable.

[0244] Figure 4b A flowchart of a method according to another embodiment of the present disclosure is shown. The method can be performed by an apparatus implemented in a second SMF, or an apparatus implemented at a second SMF, or an apparatus implemented as a second SMF, or an apparatus communicatively coupled to a second SMF. Therefore, the apparatus can provide components or modules for implementing various parts of method 410, as well as components or modules for implementing other processes in combination with other components. For the sake of brevity, descriptions of some parts already described in the above embodiments are omitted here.

[0245] In step 412, during the first SMF insertion process, the second SMF may send to the first SMF information that the state of at least one QoS flow will be synchronized with the terminal device and / or information for the first SMF to send an N1 message to the terminal device to synchronize the state of at least one QoS flow with the terminal device.

[0246] Figure 4c A flowchart of a method according to another embodiment of the present disclosure is shown. The method can be performed by an apparatus implemented in a second SMF, or an apparatus implemented at a second SMF, or an apparatus implemented as a second SMF, or an apparatus communicatively coupled to a second SMF. Therefore, the apparatus can provide components or modules for implementing various parts of method 420, as well as components or modules for implementing other processes in combination with other components. For the sake of brevity, descriptions of some parts already described in the above embodiments are omitted here.

[0247] At block 422, the second SMF may send a protocol data unit (PDU) session update request including a PDU session modification command for at least one QoS flow to the first SMF.

[0248] At block 424, the second SMF may receive a PDU session update response from the first SMF, the response including information that a state of at least one QoS flow is to be synchronized with the terminal device or not synchronized with the terminal device.

[0249] In an embodiment, the second SMF may mark that a state of at least one Quality of Service (QoS) flow is to be synchronized with the terminal device. The at least one QoS flow is managed by the first SMF and the second SMF.

[0250] Figure 4d A flowchart of a method according to another embodiment of the present disclosure is shown. The method can be performed by an apparatus implemented in a second SMF, or an apparatus implemented at a second SMF, or an apparatus implemented as a second SMF, or an apparatus communicatively coupled to a second SMF. Therefore, the apparatus can provide components or modules for implementing various parts of method 430, as well as components or modules for implementing other processes in combination with other components. For the sake of brevity, descriptions of some parts already described in the above embodiments are omitted here.

[0251] At block 432, the second SMF may receive a PDU session update request from the first SMF, the request including information instructing the second SMF to synchronize a state of at least one QoS flow with the terminal device.

[0252] At block 434, the second SMF may send a PDU session update request including a PDU session modification command for at least one QoS flow to the first SMF.

[0253] Figure 4e A flowchart of a method according to another embodiment of the present disclosure is shown. The method can be performed by an apparatus implemented in a second SMF, or an apparatus implemented at a second SMF, or an apparatus implemented as a second SMF, or an apparatus communicatively coupled to a second SMF. Therefore, the apparatus can provide components or modules for implementing various parts of method 440, as well as components or modules for implementing other processes in combination with other components. For the sake of brevity, descriptions of some parts already described in the above embodiments are omitted here.

[0254] At box 442, the second SMF may send a PDU session update request to the first SMF, which includes a PDU session modification command for at least one QoS flow and information for the first SMF to send an N1 message to the terminal device to synchronize the status of the at least one QoS flow with the terminal device.

[0255] At block 444, the second SMF may receive information from the first SMF that the terminal device is unreachable.

[0256] In an embodiment, the second SMF may mark that a state of at least one Quality of Service (QoS) flow is to be synchronized with the terminal device. The at least one QoS flow is managed by the first SMF and the second SMF.

[0257] At block 446, the second SMF may execute the PDU session modification command for the at least one QoS flow.

[0258] At block 448, when the terminal device is reachable, the second SMF may receive information that the state of at least one QoS flow has been synchronized with the terminal device.

[0259] Figure 4f A flowchart of a method according to another embodiment of the present disclosure is shown. The method can be performed by an apparatus implemented in a second SMF, or an apparatus implemented at a second SMF, or an apparatus implemented as a second SMF, or an apparatus communicatively coupled to a second SMF. Therefore, the apparatus can provide components or modules for implementing various parts of method 450, as well as components or modules for implementing other processes in combination with other components. For the sake of brevity, descriptions of some parts already described in the above embodiments are omitted here.

[0260] At block 452, the second SMF may send an event open subscription request for reachability events of the terminal device to an access and mobility management function (AMF).

[0261] At block 454, the second SMF may receive a reachability event for the terminal device from the AMF.

[0262] At block 456, when there is a flag that the state of at least one QoS flow is to be synchronized with the terminal device, the second SMF may send a PDU session update request including a PDU session modification command for the at least one QoS flow to the first SMF.

[0263] In some embodiments, the PDU session modification command includes deletion of at least one QoS flow.

[0264] Figure 4g A flowchart of a method according to another embodiment of the present disclosure is shown. The method can be performed by an apparatus implemented in a second SMF, or an apparatus implemented at a second SMF, or an apparatus implemented as a second SMF, or an apparatus communicatively coupled to a second SMF. Therefore, the apparatus can provide components or modules for implementing various parts of method 460, as well as components or modules for implementing other processes in combination with other components. For the sake of brevity, descriptions of some parts already described in the above embodiments are omitted here.

[0265] In step 462, when the state of at least one QoS flow has been synchronized with the terminal device, the second SMF may delete a mark that the state of at least one QoS flow will be synchronized with the terminal device.

[0266] For example, when the second SMF has synchronized the status of at least one QoS flow with the terminal device, or receives an indication that the status of at least one QoS flow has been synchronized with the terminal device, the second SMF can delete the mark that the status of at least one QoS flow will be synchronized with the terminal device.

[0267] Figure 4h A flowchart of a method according to another embodiment of the present disclosure is shown. The method can be performed by an apparatus implemented in a second SMF, or an apparatus implemented at a second SMF, or an apparatus implemented as a second SMF, or an apparatus communicatively coupled to a second SMF. Therefore, the apparatus can provide components or modules for implementing various parts of method 470, as well as components or modules for implementing other processes in combination with other components. For the sake of brevity, descriptions of some parts already described in the above embodiments are omitted here.

[0268] At block 472, the second SMF may receive a PDU session update request from the first SMF, the request including information that a state of at least one QoS flow is to be synchronized with the terminal device or not synchronized with the terminal device.

[0269] In an embodiment, the second SMF may mark that a state of at least one Quality of Service (QoS) flow is to be synchronized with the terminal device. The at least one QoS flow is managed by the first SMF and the second SMF.

[0270] In an embodiment, the at least one QoS flow comprises at least one guaranteed bit rate (GBR) QoS flow.

[0271] Figure 5 A flowchart of a PDU session modification process requested by a UE or a network (home routing roaming scenario) according to an embodiment of the present disclosure is shown.

[0272] Section 4.3.3.3 of 3GPP TS 23.502 V17.5.0 may be modified to the following underlined content.

[0273] 1. The process is triggered by one of the following events:

[0274] 1a. (UE or serving network requested) Same as step 1a of clause 4.3.3.2 of 3GPP TS 23.502 V17.5.0, with the following additions:

[0275] -V-SMF checks whether it can accept the request from the UE;

[0276] - The V-SMF invokes the Nsmf_PDUSession_Update request (SM context ID, UE request for PDU session modification or QoS modification request from the VPLMN, UE location information, time zone, current access type, PCO, [requested persistent PDU session]) service operation to notify the H-SMF to update the PDU session. The H-SMF responds to the request immediately. If the AMF notifies the V-SMF that the access type of the PDU session can be changed, as described in the UE-triggered service request procedure in clause 4.2.3.2 of 3GPP TS 23.502 V17.5.0, the V-SMF shall also indicate that the access type can be changed.

[0277] If the PS Data Off status has been changed, the PS Data Off status shall be included in the PCO (Protocol Configuration Option) in the PDU Session Modification Request message.

[0278] When PCF is deployed, if the PS data off event trigger is provided, the SMF shall further report the PS data off status to the PCF. Additional behaviors of SMF and PCF for 3GPP PS data off are defined in 3GPP TS 23.503.

[0279] 1b. (HPLMN Request) This step is the same as step 1b in clause 4.3.3.2 of 3GPP TS 23.502 V17.5.0. If the H-SMF receives an indication that the access type of the PDU session can be changed, the H-SMF shall indicate the target access type to the PCF in the access type information of the Npcf_SMPolicyControl_Update request.

[0280] 1c. (HPLMN requested) This step is the same as step 1c in clause 4.3.3.2 of 3GPP TS 23.502 V17.5.0.

[0281] 1d. (HPLMN request) This step is the same as step 1d in section 4.3.3.2 of 3GPP TS 23.502 V17.5.0. But there are the following differences :

[0282] When the modification procedure is triggered to synchronize the status of one or more QoS flows with the UE, the H-SMF sends a The modification is initiated upon receiving an indication from the V-SMF to synchronize the status of one or more QoS flows with the UE while the UP connection is active.

[0283] NOTE x: How the H-SMF receives an indication in a service request when a UP connection is activated to synchronize one or more For QoS flow status, please refer to the following revised clauses 4.23.4.2 and 4.23.4.3 of 3GPP TS 23.502 V17.5.0.

[0284] 1e. Same as step 1e of clause 4.3.3.2 of 3GPP TS 23.502 V17.5.0, with the following additions:

[0285] -AMF calls Nsmf_PDUSession_UpdateSMContext(SM context ID, N2 SM information) and sends it to V-SMF;

[0286] - The V-SMF invokes the Nsmf_PDUSession_Update request (SM context ID, ULI, AN type, QoS flow to be released) service operation to notify the H-SMF to update the PDU session. The H-SMF responds to the request immediately. For the AN-initiated notification control in step 1e of clause 4.3.3.2 of 3GPP TS 23.502 V17.5.0, the V-SMF also includes the QoS flow notification information as specified in clause 5.7 of 3GPP TS 23.501 V17.5.0.

[0287] NOTE 1: The SM Context ID is different between AMF and V-SMF and between V-SMF and H-SMF. The SM Context ID has local meaning per SMF instance.

[0288] 2. This step is the same as step 2 in clause 4.3.3.2 of 3GPP TS 23.502 V17.5.0, but the SMF is the H-SMF.

[0289] 3. The H-SMF (requested by the UE or serving network or requested by the HPLMN) invokes the Nsmf_PDUSession_Update request (SM context ID, QoS profile, [alternative one or more QoS profiles], session AMBR, information required to construct the SM PDU session modification command message towards the UE, which contains one or more QoS rules and QoS flow level QoS parameters (if required for one or more QoS flows associated with the one or more QoS rules) and QoS rule operation and QoS flow level QoS parameter operation) service operation to the V-SMF.

[0290] Based on operator policies and roaming agreements, the V-SMF may decide to fully accept or reject the QoS information provided by the H-SMF. The V-SMF shall also be able to accept a subset of QoS flows requested to be created or modified within a single H-SMF request, i.e. the V-SMF may accept certain QoS flows and reject others in the same response to the H-SMF.

[0291] 3a-3b (HPLMN requested) If one or more new QoS flows are to be created, these steps are performed. The SMF updates the UPF with the UL packet detection rules for the new QoS flows.

[0292] NOTE 2: This allows UL packets with the QFI of a new QoS flow to be transmitted.

[0293] If the H-SMF provides a permanent online PDU session authorization indication to indicate that the PDU session will be changed to a permanent online PDU session, the V-SMF decides whether to accept or reject the request from the H-SMF based on local policy.

[0294] 4a-4b. These steps are the same as steps 3a-3b in clause 4.3.3.2 of 3GPP TS 23.502 V17.5.0, but are controlled from the V-SMF. The V-SMF uses the information received in step 3 to generate any N1 and / or N2 signaling to be sent towards the UE and / or (R)AN.

[0295] 5-7. These steps are the same as steps 4-6 in clause 4.3.3.2 of 3GPP TS 23.502 V17.5.0.

[0296] 8. This step is the same as step 7a in clause 4.3.3.2 of 3GPP TS 23.502 V17.5.0, except that the SMF is a V-SMF.

[0297] If the N2 SM information indicates that the modification has failed and the V-SMF rejects the PDU session modification as described in step 7 of clause 4.3.3.2 of 3GPP TS 23.502 V17.5.0, step 9 is skipped.

[0298] Steps 9a-9b are the same as steps 8a-8b in clause 4.3.3.2 of 3GPP TS 23.502 V17.5.0, but are performed in the visited PLMN.

[0299] 10. This step is the same as step 7b in clause 4.3.3.2 of 3GPP TS 23.502 V17.5.0, except that the SMF is a V-SMF.

[0300] 11-12. These steps are the same as steps 8-9 in clause 4.3.3.2 of 3GPP TS 23.502 V17.5.0.

[0301] 13-14. These steps are the same as steps 11a-11b in clause 4.3.3.2 of 3GPP TS 23.502 V17.5.0, but are performed in the visited PLMN.

[0302] 15. The V-SMF responds to the H-SMF with an Nsmf_PDUSession_Update response carrying information such as the PCO and secondary RAT usage data provided by the UE in the SM PDU Session Modification Command Ack message from the UE to the V-SMF. The H-SMF shall modify the PDU session context.

[0303] If the V-SMF has rejected one or more QFIs (step 3), or the (R)AN has rejected one or more QFIs in step 6 of Figure 4.3.3.2-1 of 3GPP TS 23.502 V17.5.0, the H-SMF is responsible for later updating the QoS rules and QoS flow level QoS parameters (if required for one or more QoS flows associated with one or more QoS rules in the UE).

[0304] If the modification initiated by the H-SMF is to delete a QoS flow that does not contain a QoS flow associated with the default QoS rule (e.g. If the UE receives no response from the V-SMF, the V-SMF marks the QoS flows as The status is The UE synchronizes and sends a list of one or more such QoS flows to the H-SMF.

[0305] 16-17. These steps are the same as steps 12-13 in clause 4.3.3.2 of 3GPP TS 23.502 V17.5.0, except that the SMF is an H-SMF.

[0306] In an embodiment, Section 4.23.4.2 of 3GPP TS 23.502 V17.5.0 may be modified to the following underlined content.

[0307] 4.23.4.2 UE-triggered service request, no I-SMF change / removal

[0308] The procedure in this clause is used when both the I-SMF and the SMF are available for a PDU session and no I-SMF change or removal is required during the service request process. Compared to the procedure in clause 4.2.3.2 of 3GPP TS 23.502 V17.5.0, the SMF is replaced by the I-SMF and one or more of the affected intermediate UPFs is a UPF controlled by the I-SMF. The differences are captured as follows:

[0309] - Steps 6a-6b, when inserting the I-SMF, these steps are not required since the CN tunnel information for the UPF (PSA) allocated to N9 is available at the I-SMF.

[0310] -Step 7a, if a new intermediate UPF is selected, the I-SMF invokes the Nsmf_PDUSession_Update request (DN tunnel information of the new intermediate UPF). If this information changes and needs to be notified to the SMF, the I-SMF may also include UE location information, time zone, RAT type, access type, and operation type set to "UP active". If the DL tunnel information of the new intermediate UPF is received, the SMF provides the DL tunnel information of the new intermediate UPF received from the I-SMF to the UPF (PSA).

[0311] -Step 10, this step is not applicable, since in this scenario, I-UPF is always required.

[0312] - In step 16, if the I-SMF needs to update the SMF with the following information, such as a change in UE location information, a change in time zone, a change in RAT type, and / or a change in access type, the I-SMF invokes an Nsmf_PDUSession_Update request to send the user location information, time zone, RAT type, and / or access type to the SMF. If the I-SMF invokes an Nsmf_PDUSession_Update request with an operation type of "UP activated" in step 7a, the I-SMF also includes an operation type set to "UP activated".

[0313] If the I-SMF has marked the status of one or more QoS flows to be synchronized with the UE, the I-SMF calls Nsmf_ PDUSession_Update request, which contains an indication for synchronizing the status of one or more QoS flows with the UE .

[0314] If dynamic PCC is deployed and one or more policy control request triggering conditions have been met (e.g., change of access type, change of UE location), the SMF performs the SMF-initiated SM policy modification procedure as defined in clause 4.16.5.1 of 3GPP TS 23.502 V17.5.0 and may obtain an updated policy.

[0315] - Steps 18a-18b, these steps do not apply, since in this scenario, I-UPF is always required.

[0316] - Step 21a, this step does not apply, since in this scenario, I-UPF is always required.

[0317] In an embodiment, Section 4.23.4.3 of 3GPP TS 23.502 V17.5.0 may be modified to the following underlined content.

[0318] 4.23.4.3 UE-triggered service request with I-SMF insertion / change / removal

[0319] The procedures in this clause are used when an I-SMF is to be inserted, changed or removed as part of a UE-triggered service request. It includes the following cases:

[0320] -The UE moves from the SMF service area to a new I-SMF service area and inserts a new I-SMF (i.e., I-SMF insertion); or

[0321] - The UE moves from the old I-SMF service area to the new I-SMF service area and the I-SMF is changed (i.e. I-SMF change); or

[0322] -The UE moves from the old I-SMF service area to the SMF service area, and the old I-SMF is removed (i.e., I-SMF removal).

[0323] If the service request is triggered by the network due to downlink data and a new I-UPF is selected, a forwarding tunnel is established between the old I-UPF (if the old I-UPF is different from the PSA) and the new I-UPF to forward the buffered data.

[0324] For home routed roaming, the I-SMF (old and new) and I-UPF (old and new) are located in the visited PLMN, while the SMF and UPF (PSA) are located in the home PLMN. In this HR roaming case, only the case where the I-SMF changes (for PDU sessions, there is always a V-SMF) applies.

[0325] Figure 6 A flow chart of a UE-triggered service request procedure with I-SMF insertion / change / removal according to an embodiment of the present disclosure is shown.

[0326] 1. Same as steps 1-3 defined in clause 4.2.3.2 of 3GPP TS 23.502 V17.5.0.

[0327] 2.AMF determines whether a new I-SMF needs to be selected based on the UE location and the service area of the SMF. If a new I-SMF needs to be selected, the AMF selects the new I-SMF as described in Section 4.23.2 of 3GPP TS 23.502V17.5.0.

[0328] Case: I-SMF insertion or I-SMF change. In the case of I-SMF removal, skip steps 3-9.

[0329] 3. If the AMF has selected a new I-SMF, the AMF sends a Nsmf_PDUSession_CreateSMContext request (PDU session ID, SM context ID, UE location information, access type, RAT type and operation type) to the new I-SMF. In the case of I-SMF change, the SM context ID points to the old I-SMF, or in the case of I-SMF insertion, the SM context ID points to the SMF.

[0330] The AMF sets the operation type to "UP Activation" to indicate the establishment of N3 tunnel user plane resources for one or more PDU sessions. The AMF determines the access type and RAT type based on the global RAN node ID associated with the N2 interface.

[0331] If the UE time zone has changed compared to the last reported UE time zone, the AMF shall include the UE Time Zone IE in this message.

[0332] 4a. The new I-SMF retrieves the SM context from the old I-SMF (in the case of an I-SMF change) or SMF (in the case of an I-SMF insertion) by calling Nsmf_PDUSession_Context request (SM context type, SM context ID). The new I-SMF uses the SM context ID received from the AMF for this service operation. The recipient of the Nsmf_PDUSession_Context request uses the SM context ID to determine the target PDU session. The SM context type indicates that the requested information is all SM contexts, i.e., the PDN connection context and the 5G SM context.

[0333] 4b. The old I-SMF (in case of I-SMF change) or SMF (in case of I-SMF insertion) responds with the SM context of the indicated PDU Session.

[0334] If extended buffering is applied in the old SMF or old I-UPF and the extended buffering timer is still running, or the service request is triggered by downlink data, the old I-SMF or SMF includes a forwarding indication in the response to indicate that a forwarding tunnel is required for sending the buffered downlink packets. For I-SMF insertion, if the I-UPF controlled by the SMF is available for this PDU session, the SMF includes a forwarding indication.

[0335] 5. The new I-SMF selects a new I-UPF: Based on the received SM context (e.g. S-NSSAI and UE location information), the new I-SMF selects a new I-UPF as described in clause 6.3.3 of 3GPP TS 23.501 V17.5.0.

[0336] 6. The new I-SMF initiates N4 session establishment to the new I-UPF. The new I-UPF provides the tunnel endpoint to the new I-SMF.

[0337] If a forwarding indication is received, the new I-SMF also requests the new I-UPF to allocate a tunnel endpoint to receive the buffered DL data from the old I-UPF and to indicate the end marker reception on the tunnel via a usage report. In this case, the new I-UPF starts buffering one or more downlink packets received from the UPF (PSA).

[0338] 7a. If a tunnel endpoint for buffered DL data is allocated, then in case of I-SMF change, the new I-SMF calls Nsmf_PDUSession_UpdateSMContext request (tunnel endpoint for buffered DL data) to the old I-SMF in order to establish the forwarding tunnel. The new I-SMF uses the SM context ID received from the AMF for this service operation.

[0339] 7b. In the case of I-SMF change, the old I-SMF initiates N4 session modification to the old I-UPF to send the tunnel endpoint for buffered DL data to the old I-UPF. After this step, the old I-UPF starts sending buffered DL data to the new I-UPF.

[0340] If the old I-UPF receives an end marker packet and there is no associated tunnel to forward these packets, the old I-UPF discards the received end marker packet and does not send any data notification to the SMF.

[0341] 7c. In case of I-SMF change, the old I-SMF responds to the new I-SMF using Nsmf_PDUSession_UpdateSMContext response.

[0342] 8a. In case of I-SMF change, the new I-SMF calls Nsmf_PDUSession_Update request to SMF (SM context ID, new I-UPF DL tunnel information, SM context ID at I-SMF, access type, RAT type, new I-SMF supported DNAI list, operation type). The new I-SMF uses the SM context ID at SMF received from the old I-SMF for this service operation.

[0343] In case of I-SMF insertion, the new I-SMF calls Nsmf_PDUSession_Create request to SMF (new I-UPF DL tunnel information, new I-UPF tunnel endpoint for buffered DL data, SM context ID at I-SMF, access type, RAT type, new I-SMF supported DNAI list, operation type).

[0344] The SM Context ID at the I-SMF will be used by the SMF for further PDU Session operations, for example, notifying the new I-SMF of the PDU Session release. If the SM Context ID at the I-SMF exists (i.e. in the case of a change of the I-SMF), the SMF shall replace the SM Context ID at the I-SMF.

[0345] The new I-UPF tunnel endpoint for buffered DL data is used to establish a forwarding tunnel (from the old I-UPF controlled by the SMF to the new I-UPF controlled by the new I-SMF).

[0346] If the old I-UPF receives an end marker packet and there is no associated tunnel to forward these packets, the old I-UPF discards the received end marker packet and does not send any data notification to the SMF.

[0347] The Operation Type is set to "UP Activate" to indicate that user plane resources for the PDU session will be established.

[0348] 8b.SMF initiates N4 session modification to PDU session anchor UPF. During this step:

[0349] -SMF provides new I-UPF DL tunnel information.

[0350] - If the PSA UPF needs to use different CN tunnel information, that is, the CN tunnel information at the PSA for N3 and N9 is different, the CN tunnel information for the PDU Session Anchor UPF is allocated.

[0351] - For I-SMF insertion, if a new I-UPF tunnel endpoint for buffered DL data is received, the SMF triggers the transmission of the buffered DL data towards the new I-UPF tunnel endpoint for buffered DL data.

[0352] If the DL tunnel information has changed, the SMF instructs the UPF (PSA) to send one or more "end marker" packets for each N9 tunnel to the old I-UPF immediately after switching the path to the new I-UPF. From now on, the PDU Session Anchor UPF begins sending DL data to the new I-UPF as indicated in the new I-UPF DL tunnel information. The UPF (PSA) sends one or more "end marker" packets for each N9 tunnel to the old I-UPF immediately after switching the path to the new I-UPF. If the new I-SMF indicates in step 6, the new I-UPF reports to the SMF upon receiving the "end marker". The new SMF initiates the N4 Session Modification procedure to instruct the new I-UPF to send one or more DL packets received from the UPF (PSA).

[0353] 8c. The SMF responds to the new I-SMF with an Nsmf_PDUSession_Update response (one or more DNAIs of interest for this PDU session in case of I-SMF change) or an Nsmf_PDUSession_Create response (one or more DNAIs of interest for this PDU session, tunnel information at the UPF (PSA) for UL data (if it was allocated in step 8b) in case of I-SMF insertion).

[0354] In case I-SMF is inserted and the PDU Session corresponds to LADN, the SMF shall release the PDU Session after the service request procedure is completed.

[0355] In case of I-SMF insertion, the SMF shall start a timer to release resources, i.e., resources used for the indirect data forwarding tunnel.

[0356] In case the I-SMF is inserted and receives the CN tunnel information at the PSA for N9 in response, the I-SMF provides the CN tunnel information at the PSA for N9 to the I-UPF via the N4 session modification request.

[0357] 9. The new I-SMF sends Nsmf_PDUSession_CreateSMContext response (N2 SM information (PDU session ID, one or more QFIs, one or more QoS profiles, CN N3 tunnel information, S-NSSAI, user plane security enforcement, UE integrity protection maximum data rate), N1 SM container, cause) to the AMF. The CN N3 tunnel information is the UL tunnel information of the new I-UPF.

[0358] If any EPS bearer IDs have been allocated for the PDU session, the new I-SMF also includes the mapping between one or more EPS bearer IDs and one or more QFIs in the N2 SM information to be sent to the NG-RAN.

[0359] The new I-SMF starts a timer to release resources, ie, resources used for the indirect data forwarding tunnel.

[0360] Case: I-SMF removal: For I-SMF insertion or I-SMF change cases, skip steps 10 to 16.

[0361] 10. If the UE has moved from the service area of the old I-SMF to the service area of the SMF, the AMF sends a Nsmf_PDUSession_CreateSMContext request (SUPI, PDU session ID, AMF ID, SM context ID at I-SMF, UE location information, access type, RAT type) to the SMF.

[0362] If the UE time zone has changed compared to the last reported UE time zone, the AMF shall include the UE Time Zone IE in this message.

[0363] The AMF sets the operation type to "UP Activation" to indicate the establishment of user plane resources for one or more PDU sessions. The AMF determines the access type and RAT type based on the definition in clause 4.2.3.2 of 3GPP TS 23.502 V17.5.0.

[0364] 11a. The SMF retrieves the SM context from the I-SMF by calling Nsmf_PDUSession_Context request (SM context type). The SMF uses the SM context ID received from the AMF for this service operation. The SM context type indicates that the requested SM context is the full context, i.e., the PDN connection context and the 5G SM context.

[0365] 11b. The old I-SMF responds with the SM context of the indicated PDU session. If extended buffering is applied in the old SMF or the old I-UPF and the extended buffering timer is still running, or the service request is triggered by downlink data (i.e., the old I-SMF receives a downlink data notification from the old I-UPF), the old I-SMF includes a forwarding indication in the response to indicate that a forwarding tunnel is required for sending the buffered downlink packets from the old I-UPF to the new I-UPF or PSA (if no new I-UPF is selected).

[0366] 12. SMF may select a new I-UPF: If the SMF determines that the service area of the PSA does not cover the UE location, the SMF selects a new I-UPF based on the S-NSSAI and the UE location information, as described in clause 6.3.3 of 3GPP TS 23.501 V17.5.0.

[0367] 13. If the SMF selects a new I-UPF, the SMF initiates N4 session establishment with the new I-UPF. The new I-UPF provides the SMF with a tunnel endpoint. If a forwarding indication is received, the SMF requests the new I-UPF to allocate a tunnel endpoint for forwarding data and indicates the end marker received on the tunnel. In this case, the new I-UPF begins buffering one or more downlink packets received from the UPF (PSA).

[0368] If a new I-UPF is not selected, i.e., the PSA is able to serve the UE location, the SMF initiates an N4 session modification to the PSA to assign the PSA's UL N3 tunnel endpoint information. The PSA provides the SMF with the UL N3 tunnel endpoint. If a forwarding indication is received, the SMF requests the PSA to assign a tunnel endpoint for the buffered DL data from the old I-UPF and instructs the PSA to report the end marker to the SMF using reporting rules. In this case, the UPF (PSA) begins buffering the DL data it may receive simultaneously from the N6 interface. After switching the path to the (R)AN, the UPF (PSA) immediately sends one or more "end marker" packets for each N9 tunnel to the old I-UPF according to the indication from the SMF. If indicated by the SMF, the UPF (PSA) reports to the SMF when the "end marker" packet is received. The SMF then initiates an N4 session modification procedure to instruct the UPF (PSA) to send the DL data received from the N6 interface.

[0369] 14a. If a tunnel endpoint for buffered DL data is allocated, the SMF calls Nsmf_PDUSession_UpdateSMContext request (tunnel endpoint for buffered DL data) to the old I-SMF to establish the forwarding tunnel. The SMF uses the SM context ID received from the AMF for this service operation.

[0370] 14b. The old I-SMF initiates an N4 session modification to the old I-UPF and sends the tunnel endpoint for the buffered DL data to the old I-UPF. After this step, the old I-UPF starts sending the buffered DL data to the new I-UPF, or to the PSA if the new I-UPF is not selected.

[0371] If the old I-UPF receives an end marker packet and there is no associated tunnel to forward these packets, the old I-UPF discards the received end marker packet and does not send any data notification to the SMF.

[0372] 14c. The old I-SMF responds to the SMF with a Nsmf_PDUSession_UpdateSMContext response.

[0373] 15. If the SMF selects a new I-UPF, the SMF initiates an N4 Session Modification to the PDU Session Anchor UPF, providing the new I-UPF DL tunnel information. The PSA begins sending DL data to the new I-UPF as indicated in the new I-UPF DL tunnel information. If a forwarding indication is received, the SMF instructs the PDU Session Anchor UPF to send one or more "end marker" packets. After switching the path to the new I-UPF, the UPF (PSA) immediately sends one or more "end marker" packets for each N9 tunnel to the old I-UPF based on the indication from the SMF. If instructed by the SMF in step 13, the new I-UPF reports to the SMF when the "end marker" packets are received. The SMF initiates the N4 Session Modification procedure to instruct the new I-UPF to send one or more DL packets received from the UPF (PSA).

[0374] 16.SMF sends Nsmf_PDUSession_CreateSMContext response (N2 SM information (PDU session ID, one or more QFIs, one or more QoS profiles, CN N3 tunnel information, S-NSSAI), N1 SM container, cause) to AMF. CN N3 tunnel information is the UL tunnel information of the new I-UPF.

[0375] If any EPS bearer IDs have been allocated for the PDU session, the SMF also includes the mapping between one or more EPS bearer IDs and one or more QFIs in the N2 SM information to be sent to the NG-RAN.

[0376] The SMF starts a timer to release resources, namely, resources used for the indirect data forwarding tunnel.

[0377] 17. These steps are identical to steps 12 to 14 in clause 4.2.3.2 of 3GPP TS 23.502 V17.5.0. After step 16, uplink data is transferred from the (R)AN to the PSA via the new I-UPF (if present). If the procedure in clause 4.2.3 of 3GPP TS 23.502 V17.5.0 is triggered along with this procedure, this step may be performed along with the corresponding steps in clause 4.2.3 of 3GPP TS 23.502 V17.5.0.

[0378] 17a. If step 9 or step 16 is a successful response, then in the case of I-SMF removal or change, the AMF sends an Nsmf_PDUSession_ReleaseSMContext request (I-SMF only indication) to the old I-SMF for the release of resources in the old I-SMF. The I-SMF only indication indicates that the old I-SMF does not call resource release in the SMF.

[0379] The old I-SMF starts a timer to release resources, ie, resources used for the indirect data forwarding tunnel.

[0380] 17b. The old I-SMF responds to the AMF with Nsmf_PDUSession_ReleaseSMContext response.

[0381] Case: I-SMF Insertion or I-SMF Change: For the I-SMF removal case, skip steps 18 to 21.

[0382] 18.AMF sends Nsmf_PDUSession_UpdateSMContext request (N2 SM information, RAT type, access type) to the new I-SMF.

[0383] If the AMF receives N2 SM information(s) in step 17, the AMF shall forward the N2SM information to the relevant new I-SMF based on the PDU session ID.

[0384] 19. The new I-SMF updates the new I-UPF with the AN tunnel information and a list of one or more accepted QFIs. Downlink data is now forwarded from the new I-UPF to the UE.

[0385] 20a. The new I-SMF calls the Nsmf_PDUSession_Update request (RAT type, access type, operation type) to the SMF. The SMF updates the associated access of the PDU session.

[0386] The Operation Type is set to "UP Activated" to indicate that user plane resources for the PDU session have been established.

[0387] If the I-SMF has marked the status of one or more QoS flows to be synchronized with the UE, the I-SMF also contains the Synchronizes the status of one or more QoS flows. .

[0388] 20b. If dynamic PCC is deployed, the SMF may initiate notification of the new location information to the PCF (if subscribed) by executing the SMF-initiated SM Policy Modification procedure (as defined in clause 4.16.5.1 of 3GPP TS 23.502 V17.5.0). The PCF may provide updated policies. If one or more PCC rules are updated, the SMF may initiate an N4 Session Modification procedure to the UPF (PSA) based on the one or more updated PCC rules.

[0389] 20c.SMF responds with a Nsmf_PDUSession_Update response.

[0390] 21. The new I-SMF sends an Nsmf_PDUSession_UpdateSMContext response to the AMF.

[0391] Case: I-SMF removal: For I-SMF insertion or I-SMF change cases, skip steps 22 to 25.

[0392] 22.AMF sends Nsmf_PDUSession_UpdateSMContext request (N2 SM information, RAT type, access type) to SMF. AMF determines the access type and RAT type based on the global RAN node ID associated with the N2 interface.

[0393] If the AMF receives N2 SM information(s) in step 17, the AMF shall forward the N2SM information to the relevant new I-SMF based on the PDU session ID.

[0394] 23. If dynamic PCC is deployed, the SMF may notify the PCF of the new location information by executing the SMF-initiated SM policy modification procedure as defined in clause 4.16.5.1 of 3GPP TS 23.502 V17.5.0. The PCF may provide updated policies.

[0395] 24. If the SMF selects a new I-UPF, the SMF updates the new I-UPF using the AN tunnel information and a list of one or more accepted QFIs, otherwise the SMF updates the PSA using the AN tunnel information and a list of one or more accepted QFIs.

[0396] 25.SMF sends Nsmf_PDUSession_UpdateSMContext response to AMF.

[0397] 26a. In case of I-SMF insertion or I-SMF change, after the timer set in step 9 expires and the indirect data forwarding tunnel was previously established, the new I-SMF sends an N4 session modification request to the new I-UPF to release resources used for the forwarding tunnel.

[0398] In the case of I-SMF removal, after the timer set in step 16 expires and the indirect data forwarding tunnel was previously established, the SMF sends an N4 session modification request to the new I-UPF or PSA to release the resources used for the forwarding tunnel.

[0399] 26b. In the event of I-SMF removal or change, after the timer set in step 17a expires, and if an indirect data forwarding tunnel was previously established, the old I-SMF sends an N4 Session Release Request to the old I-UPF to release resources for the PDU session. The old I-SMF releases the SM context used for the PDU session. If the old I-UPF acts as the UL CL and is not co-located with the local PSA, the old I-SMF also sends an N4 Session Release Request to the local PSA to release resources for the PDU session.

[0400] In case of I-SMF insertion, after the timer set in step 8c expires and the indirect data forwarding tunnel was established before, the SMF sends an N4 session release request to the old I-UPF to release the resources used for the PDU session.

[0401] Figure 7a A flowchart of a network-requested PDU session modification process according to an embodiment of the present disclosure is shown.

[0402] Step 1. PCF sends Npcf_SMPolicyControl_UpdateNotify request to PGW_C_SMF (Packet Data Network Gateway Control Plane (PGW_C) integrated with SMF).

[0403] Step 2. PGW_C_SMF sends Npcf_SMPolicyControl_UpdateNotify response to PCF.

[0404] Step 3. PGW_C_SMF sends an Nsmf_PDUSession_Update request (qosFlowsRelRequestList, n1SmInfoToUe) to I_SMF.

[0405] Step 4. I_SMF sends Namf_Communication_N1N2 transmission request (N1: PDU session modification command) to AMF.

[0406] Step 5.AMF sends Namf_Communication_N1N2 Transport Response 202 with “ATTEMPTING_TO_REACH_UE” to I_SMF.

[0407] Step 6.AMF sends a paging request to NG_RAN.

[0408] Step 7.AMF sends Namf_CommunicationN1N2TransferFailure notification to I_SMF (504UE no response).

[0409] Step 8. The I_SMF sends an Nsmf_PDUSession_Update response (including an indication of the out-of-sync status with the UE) to the PGW_C_SMF.

[0410] The I-SMF / V-SMF needs to mark the UE as unsynchronized for QoS flow deletion (non-default QoS flow). The N1 pending state is used to notify the A-SMF / H-SMF that the UE is unreachable.

[0411] The I-SMF / V-SMF sends a status indication to the A-SMF / H-SMF that the QoS flow deletion is out of sync with the UE due to UP inactivity.

[0412] Step 9. NG_RAN sends a service request (user location) to AMF.

[0413] Step 10.AMF sends a Nsmf_PDUSession_UpdateSMContext request (upCnxState=ACTIVATING) to I_SMF and receives a Nsmf_PDUSession_UpdateSMContext response from I_SMF.

[0414] Step 11.AMF sends an N2 request to the NG_RAN and receives an N2 response from the NG_RAN.

[0415] Step 12.AMF sends a Nsmf_PDUSession_UpdateSMContext request (n2SmInfo=PDU_RES_SETUP_RESP) to I_SMF.

[0416] Step 13. The I_SMF sends an N4 PFCP (Packet Forwarding Control Protocol) Session Modification Request to the I_UPF to update all DL (Downlink) FARs (Forwarding Action Rules) and receives a response from the I_UPF.

[0417] Step 14. I_SMF sends Nsmf_PDUSession_UpdateSMContext response (upCnxState=ACTIVATED) to AMF.

[0418] Step 15. The I_SMF sends an Nsmf_PDUSession_Update request (indication of the state of synchronization with the UE) to the PGW_C_SMF.

[0419] When I-SMF / V-SMF finds that the UE is reachable and there is a mark that the QoS flow status is not synchronized with A-SMF / H-SMF, I-SMF / V-SMF sends the synchronization status (N1 pending status) to A-SMF / H-SMF.

[0420] Step 16. PGW_C_SMF sends an Nsmf_PDUSessionUpdate response to I_SMF.

[0421] Step 17. PGW_C_SMF sends an Nsmf_PDUSessionUpdate request (qosFlowsRelRequestList, n1SmInfoToUe) to I_SMF.

[0422] Step 18. I_SMF sends a Namf_CommunicationN1N2Transfer request to AMF.

[0423] Step 19. I_SMF sends Nsmf_PDUSessionUpdate response to PGW_C_SMF.

[0424] Figure 7a Some of the messages in FIG7 may be the same as corresponding messages described in various 3GPP specifications (eg, 3GPP TS 23.502 V17.5.0). According to an embodiment of the present disclosure, some of the messages in FIG7 (eg, steps 8 and 15) are enhanced.

[0425] Figure 7b A flowchart of a V-SMF / I-SMF insertion process according to an embodiment of the present disclosure is shown.

[0426] Step 1. Perform steps 1 to 16 of the registration procedure described in clause 4.2.2.2 of 3GPP TS 23.502 V17.5.0.

[0427] Step 2. The new AMF decides to insert into the I-SMF.

[0428] Step 3. New_AMF sends Nsmf_PDUSession_CreateSMContext request to I_SMF.

[0429] Step 4. I_SMF sends Nsmf_PDUSession_Context request to SMF.

[0430] Step 5. SMF sends an Nsmf_PDUSession_Context response (SmContext: indication of N1 pending status) to I_SMF.

[0431] For example, the A-SMF / H-SMF may send this N1 pending status to the new V-SMF / I-SMF so that the new V-SMF / I-SMF knows to send the UE synchronization status to the A-SMF / H-SMF when the UE is reachable.

[0432] Step 6. PFCP session establishment is performed between I_SMF and I_UPF.

[0433] Step 7. I_SMF sends an Nsmf_PDUSession_Create request to SMF.

[0434] Step 8. PFCP session modification is performed between SMF and UPF.

[0435] Step 9. SMF sends Nsmf_PDUSession_Create response to I_SMF.

[0436] Step 10. PFCP session modification is performed between I_SMF and I_UPF.

[0437] Step 11. I_SMF sends Nsmf_PDUSession_CreateSMContext response to new_AMF.

[0438] Step 12. The UE triggers a service request and UP is activated. The I-SMF / V-SMF sends the status of synchronization with the UE to the A-SMF / H-SMF, so the A-SMF / H-SMF triggers QoS flow deletion to the UE.

[0439] Figure 7b Some of the messages may be identical to corresponding messages described in various 3GPP specifications (e.g., 3GPP TS 23.502 V17.5.0). According to an embodiment of the present disclosure, Figure 7b Some messages (such as steps 5 and 12) are enhanced.

[0440] Figure 7c A flowchart of a V-SMF / I-SMF change process according to an embodiment of the present disclosure is shown.

[0441] Step 1. The new AMF decides to change the I-SMF.

[0442] Step 2. New_AMF sends Nsmf_PDUSession_CreateSMContext request (SmContextCreate:upCnxState, smContextRef) to I_SMF2.

[0443] Step 3. I_SMF2 sends an Nsmf_PDUSession_Context request (SmContetextRetrieveData:smContextType) to I_SMF.

[0444] Step 4. I_SMF sends an Nsmf_PDUSession_Context response (SmContextRetrievedData: indication of N1 pending status) to I_SMF2.

[0445] For example, the old V-SMF / I-SMF sends the N1 pending state to the new V-SMF / I-SMF.

[0446] Step 5. PFCP session establishment is performed between I_SMF2 and I_UPF2 (if upCnxState is ACTIVATING, N9 tunnel and N3 tunnel are allocated).

[0447] Step 6. I_SMF2 sends an Nsmf_PDUSession_Update request to SMF.

[0448] Step 7. PFCP session modification is performed between SMF and PSA (DL is set to I-UPF2 N9 tunnel).

[0449] Step 8. SMF sends Nsmf_PDUSession_Update response to I_SMF2.

[0450] Step 9. I_SMF2 sends Nsmf_PDUSession_CreateSMContext response to new_AMF.

[0451] Step 10. Old_AMF sends Nsmf_PDUSession_ReleaseSMContext request to I_SMF (I-SMF only indicator).

[0452] Step 11. The UE triggers a service request and UP is activated. The I-SMF / V-SMF sends the status of synchronization with the UE to the A-SMF / H-SMF. As a result, the A-SMF / H-SMF triggers QoS flow deletion to the UE.

[0453] Figure 7c Some of the messages may be identical to corresponding messages described in various 3GPP specifications (e.g., 3GPP TS 23.502 V17.5.0). According to an embodiment of the present disclosure, Figure 7c Some messages (such as steps 4 and 11) are enhanced.

[0454] Figure 7d A flowchart of a PDU session modification process according to another embodiment of the present disclosure is shown.

[0455] Step 1. AN releases the GBR QoS flow, but the ngApCause is not "User Inactivity" and "Redirection".

[0456] Step 2. I_SMF sends a Nsmf_PDUSession_Update request (HsmfUpdateData(NW_REQ_PDU_SES_MOD)) to SMF.

[0457] For example, the I-SMF decides to release this GBR QoS flow and sends a "QoS flow will be released" message to the A-SMF. New indication: N1 pending state.

[0458] Step 3. SMF sends Nsmf_PDUSession_Update response (204 No Content) to I_SMF.

[0459] A-SMF releases the QoS flow without N16 interaction, so both A-SMF and I-SMF retain this QoS flow, but send PCC rule inactive to PCF and remove PDR to UPF.

[0460] Step 4. Npcf_PolicyControl_Update is executed between SMF and PCF (PCC rules are inactive).

[0461] Step 5. SMF sends PFCP session modification (remove DL (downlink) PDR (packet detection rule)) to UPF.

[0462] Step 6. UE triggers service request.

[0463] Step 7. I_SMF sends an Nsmf_PDUSession_Update request to SMF (indicating the state of synchronization with the UE).

[0464] Step 8. SMF sends an Nsmf_PDUSession_Update response to I_SMF (204).

[0465] Step 9. SMF sends an Nsmf_PDUSession_Update request (VsmfUpdateData) to I_SMF.

[0466] Step 10. Namf_communication_N1N2messagetransfer (N1: PDU session modification command) is executed between AMF and I_SMF.

[0467] Step 11.AMF sends NGAP request to NG_RAN.

[0468] Step 12. NAS between UE and NG_RAN.

[0469] Step 13. NG_RAN sends NGAP response to AMF.

[0470] Step 14.AMF sends Nsmf_PDUSession_UpdateSMContext request to I_SMF (N1 PDU session modification completed).

[0471] Step 15. Perform PFCP session modification between I_SMF and I_UPF (remove UL / DLPDR for dedicated QoS flows).

[0472] Step 16. I_SMF sends Nsmf_PDUSession_UpdateSMContext response to AMF.

[0473] Step 17. I_SMF sends Nsmf_PDUSession_Update response (VsmfUpdatedData) to SMF.

[0474] Step 18. Perform PFCP session modification between SMF and UPF (remove UL PDR for dedicated QoS flow).

[0475] Figure 7d Some of the messages may be identical to corresponding messages described in various 3GPP specifications (e.g., 3GPP TS 23.502 V17.5.0). According to an embodiment of the present disclosure, Figure 7d Some messages (such as steps 2 and 7) are enhanced.

[0476] In an embodiment, during a PDU session modification procedure with the V-SMF / I-SMF, if the PDU session modification is to delete at least one QoS flow that does not include a QoS flow associated with a default QoS rule, but the UE is unreachable, the V-SMF / I-SMF sends a status indicating that the at least one QoS flow release cannot be synchronized with the UE to the H-SMF / A-SMF. The H-SMF / A-SMF marks that the at least one QoS flow is not synchronized with the UE.

[0477] In an embodiment, during the AN release procedure, if the V-SMF / I-SMF decides to release at least one GBR QoS flow but the UE is unreachable, the V-SMF / I-SMF sends a status indicating that the release of the at least one GBR QoS flow cannot be synchronized with the UE to the H-SMF / A-SMF. The H-SMF / A-SMF marks that the at least one GBR QoS flow is not synchronized with the UE.

[0478] In an embodiment, during the service request procedure V-SMF / I-SMF process, if the V-SMF / I-SMF has marked that the status of one or more QoS flows will be synchronized with the UE, the V-SMF / I-SMF sends an Nsmf_PDUSession_Update request to the H-SMF / A-SMF, which includes an indication for synchronizing the status of one or more QoS flows with the UE.

[0479] In an embodiment, during V-SMF / I-SMF insertion / change, the new V-SMF / I-SMF can obtain the synchronization status from the SMContext from the H-SMF / A-SMF or the old V-SMF / I-SMF. After the UE is reachable, the new V-SMF / I-SMF can send the synchronization status to the H-SMF / A-SMF.

[0480] The embodiments herein may provide many advantages, the following being a non-exhaustive list of examples of advantages. In some embodiments herein, when at least one QoS flow is managed by a first SMF and a second SMF, the state of at least one QoS flow may be synchronized with a terminal device. In some embodiments herein, when deletion is triggered, the V-SMF / I-SMF may handle use cases where QoS flow deletion is not synchronized with the UE. The embodiments herein are not limited to the features and advantages described above. Those skilled in the art will recognize additional features and advantages after reading the detailed description below.

[0481] Figure 8a 800 is a block diagram illustrating an apparatus suitable for practicing some embodiments of the present disclosure. For example, any of the first SMF or the second SMF described above can be implemented as the apparatus 800 or implemented by the apparatus 800.

[0482] The apparatus 800 includes at least one processor 821, such as a digital processor (DP), and at least one memory (MEM) 822 coupled to the processor 821. The apparatus 800 may further include a transmitter TX and a receiver RX 823 coupled to the processor 821. The MEM 822 stores a program (PROG) 824. The PROG 824 may include instructions that, when executed on the associated processor 821, enable the apparatus 800 to operate in accordance with embodiments of the present disclosure. The combination of the at least one processor 821 and the at least one MEM 822 may form a processing device 825 suitable for implementing various embodiments of the present disclosure.

[0483] Various embodiments of the present disclosure may be implemented by a computer program that may be executed by one or more of the processor 821 , software, firmware, hardware, or a combination thereof.

[0484] The MEM 822 may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology such as semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory, as non-limiting examples.

[0485] Processor 821 may be of any type suitable to the local technical environment, and may include one or more of a general purpose computer, a special purpose computer, a microprocessor, a digital signal processor (DSP), and a processor based on a multi-core processor architecture, as non-limiting examples.

[0486] In embodiments where the apparatus is implemented as or at a first SMF, the memory 822 stores instructions executable by the processor 821 , whereby the first SMF operates according to any of the methods described above in relation to the first SMF.

[0487] In embodiments where the apparatus is implemented as or at a second SMF, the memory 822 stores instructions executable by the processor 821 , whereby the second SMF operates according to any of the methods described above in relation to the second SMF.

[0488] Figure 8b 8 is a block diagram illustrating a first SMF according to an embodiment of the present disclosure. As shown in the figure, the first SMF 830 includes a marking module 831, which is configured to mark the status of at least one Quality of Service (QoS) flow to be synchronized with the terminal device. The at least one QoS flow is managed by the first SMF and the second SMF.

[0489] In an embodiment, the first SMF 830 further includes a first obtaining module 832, which is configured to obtain, from the second SMF during the first SMF insertion process, information that the status of at least one QoS flow will be synchronized with the terminal device and / or information for the first SMF to send an N1 message to the terminal device to synchronize the status of at least one QoS flow with the terminal device.

[0490] In an embodiment, the first SMF 830 further includes a second obtaining module 833, which is configured to obtain, from the old first SMF during the first SMF change process, information that the status of at least one QoS flow will be synchronized with the terminal device and / or information for the first SMF to send an N1 message to the terminal device to synchronize the status of at least one QoS flow with the terminal device.

[0491] In an embodiment, the first SMF 830 further includes a first sending module 834, which is configured to send information to the new first SMF during the first SMF change process that the status of at least one QoS flow will be synchronized with the terminal device and / or information for the new SMF to send an N1 message to the terminal device to synchronize the status of at least one QoS flow with the terminal device.

[0492] In an embodiment, the first SMF 830 further includes a first receiving module 835 configured to receive a protocol data unit (PDU) session update request including a PDU session modification command for at least one QoS flow from the second SMF.

[0493] In an embodiment, the first SMF 830 further comprises a first determination module 836 configured to determine that the terminal device is unreachable.

[0494] In an embodiment, the first SMF 830 further includes a second sending module 837, which is configured to send a PDU session update response including information that the state of at least one QoS flow will be synchronized with the terminal device or not synchronized with the terminal device to the second SMF.

[0495] In an embodiment, the first SMF 830 further comprises a second determination module 838 configured to determine a PDU session modification command for at least one QoS flow.

[0496] In an embodiment, the first SMF 830 further includes a third determination module 839 configured to determine that the terminal device is unreachable.

[0497] In an embodiment, the first SMF 830 further includes a third sending module 840 configured to send a PDU session update request including information that the state of at least one QoS flow will be synchronized with the terminal device or not synchronized with the terminal device to the second SMF.

[0498] In an embodiment, the first SMF 830 further includes a second receiving module 841, which is configured to receive a PDU session update request from the second SMF, the request including a PDU session modification command for at least one QoS flow and information for the first SMF to send an N1 message to the terminal device to synchronize the status of the at least one QoS flow with the terminal device.

[0499] In an embodiment, the first SMF 830 further includes a fourth determination module 842 configured to determine that the terminal device is unreachable.

[0500] In an embodiment, the first SMF 830 further includes a fourth sending module 843, which is configured to send information that the terminal device is unreachable to the second SMF.

[0501] In an embodiment, the first SMF 830 further includes an execution module 844 configured to execute the PDU session modification command for at least one QoS flow.

[0502] In an embodiment, the first SMF 830 further includes a compliance module 845 configured to comply with an N1 message based on information for the first SMF to send an N1 message to the terminal device to synchronize the state of at least one QoS flow with the terminal device when the terminal device is reachable.

[0503] In an embodiment, the first SMF 830 further includes a fifth sending module 846 configured to send an N1 message to the terminal device.

[0504] In an embodiment, the first SMF 830 further includes a seventh sending module 847, which is configured to send information to the second SMF that the status of the at least one QoS flow has been synchronized with the terminal device.

[0505] In an embodiment, the first SMF 830 further comprises a fifth determination module 848 configured to determine that the terminal device is reachable.

[0506] In an embodiment, the first SMF 830 further includes a seventh sending module 849, which is configured to send a PDU session update request to the second SMF including information instructing the second SMF to synchronize the status of at least one QoS flow with the terminal device when there is a mark that the status of the at least one QoS flow will be synchronized with the terminal device.

[0507] In an embodiment, the first SMF 830 further includes a deletion module 850 configured to delete a mark indicating that the state of at least one QoS flow will be synchronized with the terminal device when the state of the at least one QoS flow has been synchronized with the terminal device.

[0508] Figure 9 A block diagram of a second SMF according to an embodiment of the present disclosure is shown. As shown, the second SMF 900 includes a marking module 901, which is configured to mark the status of at least one Quality of Service (QoS) flow to be synchronized with the terminal device. The at least one QoS flow is managed by the first SMF and the second SMF.

[0509] In an embodiment, the second SMF 900 further includes a first sending module 902, which is configured to send information to the first SMF during the first SMF insertion process that the status of at least one QoS flow will be synchronized with the terminal device and / or information for the first SMF to send an N1 message to the terminal device to synchronize the status of at least one QoS flow with the terminal device.

[0510] In an embodiment, the second SMF 900 further includes a second sending module 903 configured to send a protocol data unit (PDU) session update request including a PDU session modification command for at least one QoS flow to the first SMF.

[0511] In an embodiment, the second SMF 900 further includes a first receiving module 904, which is configured to receive a PDU session update response from the first SMF, the response including information indicating whether the state of at least one QoS flow will be synchronized with the terminal device or not.

[0512] In an embodiment, the second SMF 900 further includes a second receiving module 905, which is configured to receive a PDU session update request from the first SMF, the request including information instructing the second SMF to synchronize the state of at least one QoS flow with the terminal device.

[0513] In an embodiment, the second SMF 900 further includes a second sending module 906, which is configured to send a PDU session update request to the first SMF, the request including a PDU session modification command for at least one QoS flow.

[0514] In an embodiment, the second SMF 900 further includes a third sending module 907, which is configured to send a PDU session update request to the first SMF, the request including a PDU session modification command for the at least one QoS flow and information for the first SMF to send an N1 message to the terminal device to synchronize the status of the at least one QoS flow with the terminal device.

[0515] In an embodiment, the second SMF 900 further includes a third receiving module 908, which is configured to receive information that the terminal device is unreachable from the first SMF.

[0516] In an embodiment, the second SMF 900 further comprises an execution module 909 configured to execute the PDU session modification command for at least one QoS flow.

[0517] In an embodiment, the second SMF 900 further includes a fourth receiving module 910, which is configured to receive information that the state of at least one QoS flow has been synchronized with the terminal device when the terminal device is reachable.

[0518] In an embodiment, the second SMF 900 further includes a fourth sending module 911, which is configured to send an event open subscription request for reachability events of the terminal device to the access and mobility management function (AMF).

[0519] In an embodiment, the second SMF 900 further includes a fifth receiving module 912, which is configured to receive a reachability event of the terminal device from the AMF.

[0520] In an embodiment, the second SMF 900 further includes a fifth sending module 913, which is configured to send a PDU session update request including a PDU session modification command for the at least one QoS flow to the first SMF when there is a mark that the state of the at least one QoS flow will be synchronized with the terminal device.

[0521] In an embodiment, the second SMF 900 further includes a deletion module 914, which is configured to delete a mark indicating that the state of the at least one QoS flow will be synchronized with the terminal device when the state of the at least one QoS flow has been synchronized with the terminal device.

[0522] In an embodiment, the second SMF 900 further includes a sixth receiving module 915, which is configured to receive a PDU session update request from the first SMF, the request including information that the state of at least one QoS flow will be synchronized with the terminal device or not synchronized with the terminal device.

[0523] The term unit or module may have a conventional meaning in the field of electronics, electrical devices 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, and the like, such as those described herein.

[0524] By using functional units, the first or second SMF can eliminate the need for fixed processors or memory, and can deploy arbitrary computing and storage resources from the first or second SMF in the communication system. The introduction of virtualization and network computing technologies can improve the efficiency of network resource utilization and network flexibility.

[0525] According to one aspect of the present disclosure, a computer program product is provided, which is tangibly stored on a computer-readable storage medium and includes instructions. When the instructions are executed on at least one processor, the instructions cause the at least one processor to perform any of the above methods.

[0526] According to one aspect of the present disclosure, a computer-readable storage medium is provided, which stores instructions. When the instructions are executed on at least one processor, the instructions enable the at least one processor to perform any of the above methods.

[0527] In addition, the present disclosure may also provide a carrier containing the above-mentioned computer program, wherein the carrier is an electronic signal, an optical signal, a radio signal, or a computer-readable storage medium. The computer-readable storage medium may be, for example, an optical disc or an electronic storage device such as RAM (random access memory), ROM (read-only memory), flash memory, magnetic tape, CD-ROM, DVD, Blu-ray disc, etc.

[0528] The techniques described herein can be implemented in various ways such that a device that implements one or more functions of the corresponding device described using the embodiments includes not only prior art components, but also components for implementing one or more functions of the corresponding device described using the embodiments, and it can include separate components for each separate function, or 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.

[0529] Exemplary embodiments of the present invention have been described above with reference to block diagrams and flow charts of methods and apparatus. It will be understood that each block of the block diagrams and flow charts, and combinations of blocks in the block diagrams and flow charts, respectively, can be implemented by various components comprising computer program instructions. These computer program instructions can be loaded onto a general-purpose computer, a special-purpose computer, or other programmable data processing device to produce a machine, such that the instructions executed on the computer or other programmable data processing device create components for implementing the functions specified in the flow chart block or blocks.

[0530] In addition, although operations are depicted in a particular order, this should not be understood as requiring that the operations be performed in the particular order shown or in sequence, or that all illustrated operations be performed to achieve the desired result. In some cases, multitasking and parallel processing may be advantageous. Similarly, although the above discussion contains several specific implementation details, these should not be interpreted as limitations on the scope of the subject matter described herein, but rather as descriptions of features that may be specific to a particular embodiment. Certain features described in the context of a separate embodiment may also be implemented in combination in a single embodiment. Conversely, the various features described in the context of a single embodiment may also be implemented in multiple embodiments individually or in any suitable subcombination.

[0531] While this specification contains many specific implementation details, these should not be interpreted as limitations on the scope of any implementation or the scope of 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 in this specification in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment may also be implemented separately in multiple embodiments or in any suitable subcombination. Furthermore, while the features described above may be described as working in certain combinations and even initially claimed as such, one or more features from the claimed combination may be deleted from the combination in some cases, and the claimed combination may be directed to subcombinations or variations of subcombinations.

[0532] It will be apparent to those skilled in the art that, as technology advances, the present invention can be implemented in various ways. The above embodiments are provided to illustrate, not to limit, the present disclosure, and it should be understood that modifications and variations can be made without departing from the spirit and scope of the present disclosure, as readily understood by those skilled in the art. 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 (300) performed by a first session management function (SMF), comprising: The state of at least one quality of service (QoS) flow is marked (302) to be synchronized with a terminal device, wherein the at least one QoS flow is managed by the first SMF and the second SMF.

2. The method according to claim 1, wherein The at least one QoS flow is not associated with a default QoS rule.

3. The method according to claim 1 or 2, wherein: The status of the at least one QoS flow includes deletion of the at least one QoS flow.

4. The method according to any one of claims 1 to 3, further comprising: During the first SMF insertion process, information that the state of the at least one QoS flow will be synchronized with the terminal device is obtained (312) from the second SMF and / or information for the first SMF to send an N1 message to the terminal device to synchronize the state of the at least one QoS flow with the terminal device.

5. The method according to any one of claims 1 to 4, further comprising: obtaining (322) from the old first SMF during the first SMF change procedure information that the state of the at least one QoS flow is to be synchronized with the terminal device and / or information for the first SMF to send an N1 message to the terminal device to synchronize the state of the at least one QoS flow with the terminal device; and / or During the first SMF change process, information is sent (324) to the new first SMF that the state of the at least one QoS flow will be synchronized with the terminal device and / or information for the new SMF to send an N1 message to the terminal device to synchronize the state of the at least one QoS flow with the terminal device.

6. The method according to any one of claims 1 to 5, further comprising: receiving (332) a protocol data unit (PDU) session update request from the second SMF, the PDU session update request including a PDU session modification command for the at least one QoS flow; determining (334) that the terminal device is unreachable; as well as A PDU session update response is sent (336) to the second SMF, the PDU session update response including information that the state of the at least one QoS flow is to be synchronized with the terminal device or not.

7. The method according to any one of claims 1 to 6, further comprising: determining (342) a PDU session modification command for the at least one QoS flow; determining (344) that the terminal device is unreachable; as well as A PDU session update request is sent (346) to the second SMF, the PDU session update request including information that the state of the at least one QoS flow is to be synchronized with the terminal device or not.

8. The method according to claim 7, wherein: The at least one QoS flow includes at least one Guaranteed Bit Rate (GBR) QoS flow.

9. The method according to claim 7 or 8, wherein The PDU session modification command for the at least one QoS flow is determined during an access network release procedure.

10. The method according to any one of claims 1 to 9, further comprising: receiving (352) a PDU session update request from the second SMF, the PDU session update request including a PDU session modification command for the at least one QoS flow and information for the first SMF to send an N1 message to the terminal device to synchronize the state of the at least one QoS flow with the terminal device; determining (354) that the terminal device is unreachable; Sending (356) information to the second SMF that the terminal device is unreachable; executing (358) the PDU session modification command for the at least one QoS flow; when the terminal device is reachable, based on the information for the first SMF to send an N1 message to the terminal device to synchronize the state of the at least one QoS flow with the terminal device, complying (360) with the N1 message; sending (362) the N1 message to the terminal device; as well as Information that the state of the at least one QoS flow has been synchronized with the terminal device is sent (364) to the second SMF.

11. The method according to any one of claims 6 to 10, wherein: The PDU session modification command includes deletion of the at least one QoS flow.

12. The method according to any one of claims 1 to 11, further comprising: determining (372) that the terminal device is reachable; as well as When there is a flag indicating that the state of the at least one QoS flow is to be synchronized with the terminal device, a PDU session update request is sent (374) to the second SMF, the PDU session update request including information instructing the second SMF to synchronize the state of the at least one QoS flow with the terminal device.

13. The method according to any one of claims 1 to 12, further comprising: When the state of the at least one QoS flow has been synchronized with the terminal device, a flag indicating that the state of the at least one QoS flow will be synchronized with the terminal device is deleted (382).

14. The method according to any one of claims 1 to 13, wherein The first SMF includes at least one of the following: Intermediate SMF, or Visit SMF.

15. The method according to any one of claims 1 to 14, wherein The second SMF includes at least one of the following: SMF, or Belongs to SMF.

16. A method (400) performed by a second session management function (SMF), comprising: A state of at least one quality of service (QoS) flow is marked (402) to be synchronized with a terminal device, wherein the at least one QoS flow is managed by a first SMF and a second SMF.

17. The method according to claim 16, wherein The at least one QoS flow is not associated with a default QoS rule.

18. The method according to claim 16 or 17, wherein The status of the at least one QoS flow includes deletion of the at least one QoS flow.

19. The method according to any one of claims 16 to 18, further comprising: During the first SMF insertion process, information is sent (412) to the first SMF that the state of the at least one QoS flow will be synchronized with the terminal device and / or information for the first SMF to send an N1 message to the terminal device to synchronize the state of the at least one QoS flow with the terminal device.

20. The method according to any one of claims 16 to 19, further comprising: sending (422) a protocol data unit (PDU) session update request to the first SMF, the PDU session update request including a PDU session modification command for the at least one QoS flow; as well as A PDU session update response is received (424) from the first SMF, the PDU session update response including information that the state of the at least one QoS flow is to be synchronized with the terminal device or not.

21. The method according to any one of claims 16 to 20, further comprising: receiving (432) from the first SMF a PDU session update request including information instructing the second SMF to synchronize the state of the at least one QoS flow with the terminal device; as well as A PDU session update request including a PDU session modification command for the at least one QoS flow is sent (434) to the first SMF.

22. The method according to any one of claims 16 to 21, further comprising: sending (442) a PDU session update request to the first SMF, the PDU session update request including a PDU session modification command for the at least one QoS flow and information for the first SMF to send an N1 message to the terminal device to synchronize the state of the at least one QoS flow with the terminal device; receiving (444) information from the first SMF that the terminal device is unreachable; executing (446) the PDU session modification command for the at least one QoS flow; as well as When the terminal device is reachable, information is received (448) that the state of the at least one QoS flow has been synchronized with the terminal device.

23. The method according to any one of claims 16 to 22, further comprising: Sending (452) an event open subscription request for reachability events of the terminal device to an access and mobility management function AMF; as well as receiving (454) the reachability event of the terminal device from the AMF; as well as When there is a flag that the state of the at least one QoS flow is to be synchronized with the terminal device, a PDU session update request including a PDU session modification command for the at least one QoS flow is sent (456) to the first SMF.

24. The method according to any one of claims 20 to 23, wherein The PDU session modification command includes deletion of the at least one QoS flow.

25. The method according to any one of claims 16 to 24, further comprising: When the state of the at least one QoS flow has been synchronized with the terminal device, a flag indicating that the state of the at least one QoS flow will be synchronized with the terminal device is deleted (462).

26. The method according to any one of claims 16 to 25, further comprising: A PDU session update request is received (472) from the first SMF, the PDU session update request including information that the state of the at least one QoS flow is to be synchronized with the terminal device or not.

27. The method according to claim 26, wherein The at least one QoS flow includes at least one guaranteed bit rate (GBR) QoS flow.

28. The method according to any one of claims 16 to 27, wherein The first SMF includes at least one of the following: Intermediate SMF, or Visit SMF.

29. The method according to any one of claims 16 to 28, wherein The second SMF includes at least one of the following: SMF, or Belongs to SMF.

30. A first SMF (800), comprising: Processor (821); as well as a memory (822) coupled to the processor (821), the memory (822) storing instructions executable by the processor (821), whereby the first SMF (800) is operable to: The state of marking at least one quality of service (QoS) flow is to be synchronized with the terminal device, wherein the at least one QoS flow is managed by the first SMF and the second SMF.

31. The first SMF according to claim 30, wherein The first SMF is further operable to perform a method according to any one of claims 2 to 15.

32. A second SMF (800), comprising: Processor (821); as well as a memory (822) coupled to the processor (821), the memory (822) storing instructions executable by the processor (821), whereby the second SMF (800) is operable to: A state of marking at least one quality of service QoS flow is to be synchronized with the terminal device, wherein the at least one QoS flow is managed by the first SMF and the second SMF.

33. The second SMF according to claim 32, wherein The second SMF is further operable to perform the method of any one of claims 17 to 29.

34. A computer-readable storage medium storing instructions, which, when executed by at least one processor, cause the at least one processor to perform the method according to any one of claims 1 to 29.

35. A computer program product comprising instructions which, when executed by at least one processor, cause the at least one processor to perform the method according to any one of claims 1 to 29.

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