Suppression of N1N2 message transmissions for failure notifications

Abstract

Embodiments herein relate to suppressing N1N2 message transmissions for failure notifications. In some embodiments, a method (700) performed by a first network function (101) implementing an access and mobility management function (AMF) is presented. The method (700) may comprise the step of paging (S701) a user equipment (UE) (106). The method (700) may also include transmitting (S702) a failure notification message to a second network function (102, 302) of the consumer implementing the network function in response to the paging failure, the message containing a first parameter indicating a later retry time. During the later retry time, transmission of messages from the second network function (102, 302) to the first network function (101) may be suppressed. By the described embodiments, by defining a later retry timer in the failure notification, unnecessary signal exchange between the network function service consumer and the AMF prior to timeout of the later retry timer may be reduced.

Description

Cross-reference to related applications

[0001] This application claims priority to PCT Application Serial No. PCT / CN2022 / 128466, filed on Oct. 30, 2022, entitled "SUPPRESS N1N2 MESSAGE TRANSFER FOR FAILURE NOTIFICATION", the entire content of which is incorporated herein by reference. Technical Field

[0002] Embodiments herein generally relate to the field of mobile communications. More specifically, embodiments herein relate to suppressing N1N2 message transfer for failure notification. Background Art

[0003] Figure 1 is a schematic block diagram showing an example architecture 100 of a 5G network architecture in a non-roaming scenario. In a 5G network, the network-triggered service request procedure is used when the network initiates signaling to a user equipment (UE). Figure 2 is a schematic signaling diagram showing messages in an example network-triggered service request procedure. As Figure 2 shown, a session management function (SMF) 102 may transfer N1 and / or N2 messages to an access and mobility management function (AMF) 101, for example when there is downlink data to be sent. Summary of the Invention

[0004] Note that the current network-triggered service request procedure may cause wasted unnecessary resources due to some unnecessary N1N2 message transfers.

[0005] Embodiments herein propose methods, network functions, computer-readable media, and computer program products for suppressing N1N2 message transfer for failure notification.

[0006] In some embodiments, a method performed by a first network function implementing an AMF is proposed. The method may include the step of paging a UE. The method may further include the steps of: in response to a paging failure, transmitting a failure notification message to a second network function implementing a network function consumer, the message including a first parameter indicating a retry-after time. During the retry-after time, message transfer from the second network function to the first network function may be suppressed.

[0007] In one embodiment, the failure notification message may be an N1N2 message transfer failure notification message.

[0008] In one embodiment, the second network function may implement a Session Management Function (SMF), a Short Message Service Function (SMSF), a Location Management Function (LMF), a Policy Control Function (PCF), a Gateway Mobile Location Center (GMLC), a Network Exposure Function (NEF), or a Unified Data Management (UDM).

[0009] In one embodiment, the failure notification message may further include a second parameter indicating the cause of the failure.

[0010] In one embodiment, the cause of the failure may be that the UE is not reachable or there is an ongoing procedure.

[0011] In one embodiment, the ongoing procedure may be an ongoing registration procedure or an ongoing handover procedure.

[0012] In one embodiment, the N1N2 message transmission request message may be suppressed during the post-retry time.

[0013] In some embodiments, a method performed by a second network function implementing a network function consumer is provided. The method may include the steps of: receiving, from a first network function implementing an Access and Mobility Management Function (AMF), a failure notification message that includes a first parameter indicating a post-retry time. The failure notification message may be transmitted in response to a paging failure from the first network function to the UE. In one embodiment, the method may further include the steps of: starting a post-retry timer to suppress message transmission from the second network function to the first network function during the post-retry time.

[0014] In one embodiment, the failure notification message may be an N1N2 message transmission failure notification message.

[0015] In one embodiment, the second network function may implement an SMF, an SMSF, an LMF, a PCF, a GMLC, a NEF, or a UDM.

[0016] In one embodiment, the failure notification message may further include a second parameter indicating the cause of the failure.

[0017] In one embodiment, the cause of the failure may be that the UE is not reachable or there is an ongoing procedure.

[0018] In one embodiment, the ongoing procedure may be an ongoing registration procedure or an ongoing handover procedure.

[0019] In one embodiment, the N1N2 message transmission request message may be suppressed during the post-retry time.

[0020] In one embodiment, the method may further include the steps of: receiving a data transmission request from a third network function implementing a User Plane Function (UPF). In one embodiment, the method may further include the steps of: caching the data transmission request during a subsequent retry time period; and disposing of the data transmission request after the subsequent retry time.

[0021] In one embodiment, the method may further include the steps of: receiving a data transmission request from a third network function implementing a UPF. In one embodiment, the method may further include the steps of: stopping transmitting a message to a first network function; and notifying the third network function to discard the buffer.

[0022] In one embodiment, the data transmission request may be a Downlink Data Notification (DDN) request.

[0023] In one embodiment, the method may further include the steps of: receiving a control plane request from a fourth network function implementing a Policy Control Function (PCF). In one embodiment, the method may further include the steps of: caching the control plane request during a subsequent retry time period; and disposing of the control plane request after the subsequent retry time.

[0024] In one embodiment, the method may further include the steps of: receiving a control plane request from a fourth network function implementing a PCF. In one embodiment, the method may further include the steps of: stopping disposing of the control plane request; and sending an execution failure message to the fourth network function.

[0025] In one embodiment, the execution failure message may further include at least one of a third parameter indicating a failure code and a fourth parameter indicating a rule status.

[0026] In one embodiment, the control plane request may be a Session Management Policy Control Update Notification Request or a Session Management Policy Control Update Response.

[0027] In one embodiment, the session management policy may be a Policy and Charging Control (PCC) rule.

[0028] In some embodiments, a network function is provided. In one embodiment, the network function may include at least one processor; and a non-transitory computer-readable medium coupled to the at least one processor. The non-transitory computer-readable medium may store instructions executable by the at least one processor, whereby the at least one processor may be configured to perform any of the above methods. In one embodiment, the network function may be configured as a first network function or a second network function.

[0029] In some embodiments, a computer-readable medium including computer-readable code is provided, which when run on a device, may cause the device to perform any of the above methods.

[0030] In some embodiments, a computer program product including computer-readable code is provided. When the computer-readable code runs on a device, it enables the device to execute any of the above methods.

[0031] With the embodiments, by defining a retry timer after an N1N2 transmission failure notification, unnecessary signal exchanges between the NF service consumer and the AMF can be reduced before the timeout of the retry timer. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The drawings incorporated herein and constituting a part of the specification illustrate various embodiments of the present disclosure and, together with the specification, further serve to explain the principles of the present disclosure and enable those skilled in the relevant art to make and use the embodiments disclosed herein. In the drawings, like reference numerals indicate the same or functionally similar elements, and in which: Figure 1 is a schematic block diagram showing an example architecture of a 5G network architecture in a non-roaming scenario; Figure 2 is a schematic signaling diagram showing messages in an example network-triggered service request process; Figure 3 is a schematic signaling diagram showing messages in an example N1N2 transmission failure notification process; Figure 4 is a schematic signaling diagram showing messages in an example message throttling sequence flow; Figure 5 is a schematic signaling diagram showing messages in an example process for suppressing N1N2 message transmission in response to a failure notification according to embodiments herein; Figure 6 is a schematic signaling diagram showing messages in another example process for suppressing N1N2 message transmission in response to a failure notification according to embodiments herein; Figure 7 is a schematic flowchart showing an example method in a first network function according to embodiments herein; Figure 8 is a schematic flowchart showing an example method in a second network function according to embodiments herein; Figure 9 is a schematic block diagram showing an example first network function according to embodiments herein; Figure 10 is a schematic block diagram showing an example second network function according to embodiments herein; and Figure 11 is a schematic block diagram showing an example computer-implemented device according to embodiments herein. DETAILED DESCRIPTION

[0033] Embodiments herein will be described in detail below with reference to the accompanying drawings, in which embodiments are shown. However, these embodiments herein may be implemented in many different forms and should not be construed as limited to the embodiments described herein. Elements in the drawings are not necessarily drawn to scale relative to each other.

[0034] Reference to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrase "in an embodiment" throughout the specification do not necessarily all refer to the same embodiment.

[0035] As used herein, the term "A, B, or C" means "A" or "B" or "C"; the term "A, B, and C" means "A" and "B" and "C"; the term "A, B, and / or C" means "A", "B", "C", "A and B", "A and C", "B and C", or "A, B, and C".

[0036] Embodiments may be implemented in the exemplary architecture 100 as shown in Figure 1 .

[0037] In one embodiment, the exemplary architecture 100 may be configured in an over-the-top (OTT) scenario. The OTT connection may be transparent in the sense that the participating communication devices through which the OTT connection passes are not aware of the routing of the uplink and downlink communications. For example, the base station may not or need not be informed of the past routing of the incoming downlink communications, where data originating from network functions in the core network (such as AMF 101, SMF 102, PCF 103, application function (AF) 104, or UPF 105) is to be forwarded (e.g., switched) to the connected UE 106. Similarly, the base station need not know the future routing of the outgoing uplink communications originating from the UE towards network functions in the core network (such as AMF 101, SMF 102, PCF 103, AF 104, or UPF 105).

[0038] It should also be understood that network functions (such as Figure 1 AMF 101, SMF 102, PCF 103, AF 104, or UPF 105 in Network-triggered service request

[0039] Referring to clause 4.2.3.3 of 3GPP TS23.502, the network-triggered service request procedure can be used when the network initiates signaling to UE 106 (e.g., N1 signaling to the UE, mobile-terminated short message service (SMS), activation of the user plane connection of the (one or more) packet data unit (PDU) sessions for delivering mobile-terminated user data). Note that this procedure can also be triggered by the SMSF, PCF, LMF, gateway mobile location center (GMLC), network exposure function (NEF), or unified data management (UDM). In this case, Figure 2 the SMF 102 in

[0040] can be replaced by the corresponding network function (NF). If UE 106 is in the connection management (CM) IDLE state or CM-CONNECTED state in 3GPP access, the network can initiate the network-triggered service request procedure. If UE 106 is in the CM-IDLE state and asynchronous type communication is not activated, the network can send a paging request to the (R)AN / UE (RAN: Radio Access Network). This paging request can trigger the UE-triggered service request procedure in UE 106. If asynchronous type communication is activated, the network can store the received message and forward the message to the (R)AN and / or UE 106 when UE 106 enters the CM-CONNECTED state (i.e., synchronize the context with the (R)AN and / or UE).

[0041] Figure 2 The network-triggered service request procedure in

[0042] mainly includes the following messages or steps:

[0043] Step 3a. [Conditional], SMF 102 to AMF 101: Namf_Communication_N1N2MessageTransfer (subscription permanent identifier (SUPI), PDU session ID, N1 session management (SM) container (SM message), N2 session management information ((one or more) QoS flow identifiers, (one or more) QoS profiles, core network N3 tunnel information, single network slice selection assistance information (S-NSSAI)), area of validity of N2 SM information, address resolution protocol (ARP), paging policy indicator, 5G QoS identifier (5QI), N1N2TransferFailure notification target address, extended buffering support), or NF to AMF 101: Namf_Communication_N1N2MessageTransfer (SUPI, N1 message).

[0044] If the UE 106 is in the CM-IDLE state at the AMF 101 and the AMF 101 is able to page the UE 106, the AMF 101 may immediately send a Namf_Communication_N1N2MessageTransfer response to the SMF 102 to indicate to the SMF 102 that the AMF 101 is attempting to contact the UE 106, and once the UE 106 is reachable, the AMF 101 may ignore the N2 SM information provided in step 3a, and the SMF 102 may be requested to provide the N2 SM information again.

[0045] While waiting for a response from the UE 106 to a previous paging request, if the AMF 101 receives a Namf_Communication_N1N2MessageTransfer request message with the same or lower priority compared to the previous message that triggered the paging, or if the AMF 101 has determined based on local policy not to trigger another paging request for the UE 106, the AMF 101 may reject the Namf_Communication_N1N2MessageTransfer request message.

[0046] If the UE 106 is in the CM-CONNECTED state at the AMF 101, the AMF 101 may immediately send a Namf_Communication_N1N2MessageTransfer response to the SMF 102 to indicate that the N1 / N2 message has been sent.

[0047] If the UE 106 is in the CM-IDLE state and the AMF 101 determines that the UE 106 is not reachable for paging, the AMF 101 shall send a Namf_Communication_N1N2MessageTransfer response to the NF from which the AMF 101 received the request message in step 3a to indicate that the UE 106 is not reachable; or the AMF 101 may perform asynchronous type communication and store the UE context based on the received message, and the AMF 101 shall send a Namf_Communication_N1N2MessageTransfer response to indicate that asynchronous type communication is invoked. If asynchronous type communication is invoked, when the UE 106 is reachable (e.g., when the UE 106 enters the CM-CONNECTED state), the AMF 101 may initiate communication with the UE 106 and the (R)AN.

[0048] After receiving the Namf_Communication_N1N2MessageTransfer response (with an indication that its request has been temporarily rejected), SMF 102 shall start a locally configured protection timer and wait for any message from AMF 101. After receiving a message from AMF 101, SMF 102 shall re-invoke Namf_Communication_N1N2MessageTransfer (with N2 SM information and / or N1 SM information) to the AMF 101 from which it received the message. Otherwise, SMF 102 may take step 3c when the protection timer expires. If SMF 102 determines that the control plane cache is applicable, SMF 102 shall request UPF 105 to start forwarding downlink data PDUs to SMF 102.

[0049] Step 5. [Conditional], AMF 101 to SMF 102: Namf_Communication_N1N2Transfer failure notification.

[0050] AMF 101 may monitor the paging process via a timer. If AMF 101 does not receive a response from UE 106 to the paging request message, AMF 101 may apply further paging according to any applicable paging strategy described in step 4b.

[0051] If UE 106 does not respond to the paging, AMF 101 may notify SMF 102 by sending a Namf_Communications_N1N2MessageTransfer failure notification to the notification target address provided to SMF 102 in step 3a, unless AMF101 knows about an ongoing MM process that prevents UE 106 from responding, i.e., AMF 101 received an N14 context request message indicating that UE 106 is performing a registration process with another AMF. N1N2 transfer failure notification

[0052] Figure 3 Figure 15 is a signaling diagram showing the messages in an example N1N2 transfer failure notification procedure. AMF 101 may use this notification to inform the NF service consumer 302 that initiated the previous Namf_Communication_N1N2MessageTransfer that AMF 101 failed to deliver the N1 and / or N2 messages. The HTTP POST method may be used for the notification callback URI provided by the NF service consumer 302, as specified in clause 5.2.2.3.1.2 of 3GPP TS29.518.

[0053] Figure 3The N1N2 transmission failure notification may include the following messages or steps:

[0054] Step 1. If the NF service consumer 302 has provided a notification URI (see clause 5.2.2.3.1.2 of 3GPP TS 29.518), when the AMF 101 determines the following situations, the AMF 101 shall send a POST request to the NF service consumer 302 on this notification URI: - The paging or NAS notification has failed; - The indicated non-3GPP PDU session is not allowed to move to 3GPP access; - The UE 106 has rejected the paging, as defined in clause 5.38.4 of 3GPP TS 23.501; - The delivery of the N1 message has failed, for example, when the UE 106 is in RRC inactive and the NG-RAN paging is not successful, or when the Xn or N2 handover is triggered at the NG-RAN.

[0055] The AMF 101 shall include in the POST request body the N1N2MessageTransfer request resource URI (if any) previously returned in the N1N2MessageTransfer response (see clause 5.2.2.3.1.2 of 3GPP TS 29.518), otherwise it shall include a virtual URI (see clause 6.1.6.2.30 of 3GPP TS 29.518). The AMF 101 shall also include in the POST request body the N1 / N2 message transfer reason information and set the value as specified in clause 6.1.5.6.3.1 of 3GPP TS 29.518.

[0056] The NF service consumer 302 shall delete any stored representation of the N1N2MessageTransfer request resource URI after receiving this notification.

[0057] Step 2. The NF service consumer 302 shall send a response with a "204 No Content" status code.

[0058] After failure or redirection, one of the HTTP status codes together with the response body (listed in Table 6.1.5.6.3.1-2 of 3GPP TS 29.518) shall be returned. N1N2 Transmission Failure Notification

[0059] Notification standard methods (such as POST) may send an N1 / N2 message transmission failure notification to the NF service consumer 302 (e.g., the SMF 102).

[0060] This method shall support the request data structure specified in Table 6.1.5.6.3.1-1 of 3GPP TS 29.518 (see Table 1 below), as well as the response data structure and response codes specified in Table 6.1.5.6.3.1-3 of 3GPP TS 29.518.

[0061] Table 1: Data Structures Supported in the POST Request Body Message Sequence Flow When the UE is Unreachable

[0062] Based on the network-triggered service request procedure specified in 3GPP TS 23.502 and the N1N2 transmission failure notification procedure specified in 3GPP TS 29.518 as mentioned above, the following sequence flow describes the current sequence flow.

[0063] Figure 4 It is a signaling diagram showing the messages in the example message throttling sequence flow. Figure 4 The message throttling sequence flow in [reference] may include the following messages or steps:

[0064] Step 1. When the UPF 105 receives the downlink data of the PDU session and there is no AN tunnel information stored for this PDU session in the UPF 105, based on the indication from the SMF 102, the UPF 105 may cache the downlink data and send a Downlink Data Notification (DDN) to the SMF 102.

[0065] Step 2. The SMF 102 may determine the AMF 101 and call Namf_Communication_N1N2MessageTransfer to the AMF 101, including the PDU session ID of the PDU session.

[0066] Step 3. If the UE 106 is in the CM-IDLE state at the AMF 101 and the AMF 101 is able to page the UE 106, the AMF 101 may immediately send a Namf_Communication_N1N2MessageTransfer response to the SMF 102 to indicate to the SMF 102 that the AMF 101 is attempting to contact the UE 106.

[0067] Step 4. The AMF 101 may send a paging message to one or more NG-RAN nodes via 3GPP access.

[0068] Step 5. The NG-RAN sends a paging message to the UE 106.

[0069] Step 6. If UE 106 does not respond to the paging, AMF 101 may notify SMF 102 by sending a Namf_Communications_N1N2MessageTransfer failure notification to the notification target address provided by SMF 102 in Step 2.

[0070] Step 7. SMF 102 may notify UPF 105 to discard the buffer.

[0071] Step 8. UPF 105 may send the DDN to SMF 102.

[0072] Step 9. SMF 102 may determine AMF 101 and invoke Namf_Communication_N1N2MessageTransfer to AMF 101. If UE 106 is currently not reachable (e.g., because UE 106 is in a Mobile-Initiated-Only Connection (MICO) mode, UE 106 uses Extended Idle Mode Discontinuous Reception (DRX), or UE 106 is registered only on non-3GPP access and its state is CM-IDLE), AMF 101 may respond with the status code "504 Gateway Timeout". If AMF101 requests the NF service consumer 302 to stop sending N1 / N2 messages before the timeout in the POST response body, AMF 101 will set the application error to "UE_NOT_REACHABLE" and may include a "retryAfter" (i.e., retry after) timer.

[0073] Step 10. If AMF requests the NF service consumer 302 to stop sending N1 / N2 messages before the timeout, SMF102 may start a retry-after timer.

[0074] Step 11. SMF 102 may notify UPF 105 to discard the buffer.

[0075] Step 12. While the retry-after timer is running, SMF 102 may receive a session management (SM) policy control update notification request from PCF 103. SMF 102 may confirm the notification.

[0076] There are two alternatives for new NF requests related to N1N2MessageTransfer:

[0077] Step 13. Alternative 1: SMF 102 may cache the request and process the request after the retry-after timer expires.

[0078] Step 14. Alternative 2: The SMF 102 may send N1N2MessageTransfer (if it has a higher priority), and the SMF 102 may handle the response accordingly.

[0079] Step 15. The SMF 102 may wait for the expiration of the subsequent retry timer.

[0080] Note that in the following scenario, there may be unnecessary signaling. When the NF service consumer 302 initiates a Namf_Communications_N1N2MessageTransfer request to the AMF 101, if paging is issued when the UE 106 is in the CM-IDLE state and reachable for 3GPP access, the AMF 101 may respond with a status code "202 Accepted", and its response body carries the cause "ATTEMPTING_TO_REACH_UE". However, during the paging process, if there is an ongoing registration process, or if there is an ongoing Xn or N2 handover process, and if the UE is currently unreachable, the AMF 101 may send an N1N2Transfer failure notification to the NF service consumer 302.

[0081] In this scenario, the AMF 101 may respond with a failure cause and an optional timer, which indicates when the ongoing process will be completed or when the UE 106 can be reached. Then, the NF service consumer 302 may stop sending the Namf_Communications_N1N2MessageTransfer request and retry the cached request or send a new request after the expiration of the timer.

[0082] However, according to the current 3GPP specification, the AMF 101 does not provide an estimate in the N1N2Transfer failure notification regarding how long it will take before the AMF 101 considers the (one or more) ongoing processes as completed, or how long it will isolate the UE 106 to reduce paging and save RAN resources (because the UE 106 is unreachable or for other unspecified reasons).

[0083] Since there is no mechanism in the Namf_Communications_N1N2MessageTransfer failure notification to inform the NF service consumer 302 to stop sending N1 / N2 messages, the NF service consumer 302 can initiate the Namf_Communication_N1N2MessageTransfer operation for the same UE (even if it receives a Namf_Communications_N1N2MessageTransfer failure notification from the AMF 101), as shown in steps 8 to 11 of Figure 4 After the AMF 101 receives a new Namf_Communication_N1N2MessageTransfer request, the AMF 101 can determine the current state of the AMF 101 and respond with a 4xx or 5xx, the message body of which contains the N1N2MessageTransferError structure, including: - The "ProblemDetails" structure, with the "reason" attribute set to one of the application errors; - The "N1N2MsgTxfrErrDetail" structure, with a "retryAfter" timer for requesting the NF service consumer to stop sending N1 / N2 messages before the timeout.

[0084] Based on the "retryAfter" timer in the response message body of the 4xx or 5xx, the NF service consumer 302 can suppress subsequent processes (such as steps 12 to 14 of Figure 4 ). However, this may be too late, that is, the suppression can occur earlier (such as steps 8 to 11 of Figure 4 ), so that the network can avoid wasting unnecessary resources, the signaling will be simplified, and new error situations can be avoided.

[0085] In addition, it should be noted that the reasons for the N1 / N2 message transfer failure do not cover the case where the UE is not reachable for paging.

[0086] In view of the above deficiencies, the embodiments of this article propose a new information element (IE), namely "retryAfter" (or retry after), which can be defined in the N1N2MsgTxfrFailureNotification to inform the NF service consumer 302 to stop sending new N1N2MessageTransfer requests before the retry after timer times out.

[0087] The NF service consumer 302 (e.g., SMF 102) can suppress subsequent procedures based on the "retryAfter" IE. The NF service consumer 302 shall not send Namf_Communications_N1N2MessageTransfer before the retry timer expires. As a result, unnecessary signaling exchanges between the NF service consumer 302 and the AMF 101 before the retry timer expires can be reduced, and thus paging from the AMF 101 can be reduced, and RAN resources can be saved at an earlier stage.

[0088] In addition, an optional new cause value "UE_NOT_REACHABLE" can be defined in the cause IE to notify the NF service consumer 302 that the N1N2MessageTransfer has failed due to the UE being unreachable.

[0089] Figure 5 is a signaling diagram that shows messages in an example procedure for suppressing N1N2 message transmission for failure notification according to an embodiment herein. Figure 5 Describes an improved message suppression sequence flow (due to UE unreachability).

[0090] The N1N2 message can refer to N1 signaling and / or N2 signaling, which are respectively sent on the N1 interface and the N2 interface as Figure 1 shown.

[0091] In one embodiment, Figure 5 the procedure for suppressing N1N2 message transmission for failure notification in

[0092] Step 1. When the UPF 105 receives downlink data of a PDU session and there is no AN tunnel information stored in the UPF 105 for this PDU session, based on an indication from the SMF 102, the UPF 105 can cache the downlink data and send a Downlink Data Notification (DDN) to the SMF 102.

[0093] Step 2. The SMF 102 can determine the AMF 101 and invoke Namf_Communication_N1N2MessageTransfer to the AMF 101, which contains the PDU session ID of the PDU session.

[0094] Step 3. If UE 106 is in the CM-IDLE state at AMF 101 and AMF 101 is able to page UE 106, then AMF 101 may immediately send a Namf_Communication_N1N2MessageTransfer response to SMF 102 to indicate to SMF 102 that AMF 101 is attempting to contact UE 106.

[0095] Step 4. AMF 101 may send a paging message to the (one or more) NG-RAN nodes via 3GPP access.

[0096] Step 6. The NG-RAN sends a paging message to UE 106.

[0097] Step 6. If UE 106 does not respond to the paging (i.e., there is a failure in paging UE 106), then AMF 101 may notify SMF 102 by sending a Namf_Communications_N1N2MessageTransfer failure notification to the notification target address provided by SMF 102 in Step 2; the response body message may include a "retryAfter" (i.e., retry after) timer to request the NF service consumer 302 (such as SMF 102) to stop sending N1 / N2 messages before the timeout of the timer. The response body message may include the failure reason, i.e., "UE does not respond to paging".

[0098] In one example, the "retryAfter" timer may be added to the Namf_Communications_N1N2MessageTransfer failure notification from AMF 101 to throttle subsequent messages for a certain period of time for the NF consumer service 302.

[0099] That is to say, AMF 101 may provide a retry-after timer value to the NF service consumer 302 so that the NF service consumer 302 will retry the request after the expiration of the timer. When providing the retry-after timer, the NF service consumer 302 shall not initiate downlink message transfer before the expiration of the timer.

[0100] In one example, the N1N2MessageTransfer failure notification may include the data structure in Table 2. Table 2: Data Structures Supported by the POST Request Body

[0101] In one example, the N1N2MessageTransfer failure notification may be configured as in Table 3. Table 3: Definition of MsgTxfrFailureNotification of type N1N2

[0102] In addition, the failure reason can be enhanced. In one example, the common application errors defined in 3GPP TS29.500 (which can also be used for the amf_Communication service) can be enhanced. Table 4 shows the enhanced application errors. Table 4: Application Errors

[0103] Step 7. SMF 102 may start the subsequent retry timer received in Step 6.

[0104] Step 8. SMF 102 may notify UPF 105 to discard the buffer.

[0105] During the running of the subsequent retry timer, SMF 102 may also receive a new downlink data notification.

[0106] Step 9. UPF 105 may send a downlink data notification (DDN) to SMF 102.

[0107] Step 10. As an alternative, SMF 102 may cache the request and dispose of it after the subsequent retry timer expires.

[0108] Step 11. As an alternative, SMF 102 may detect that the subsequent retry timer is running, and SMF 102 may stop (i.e., suppress) sending Namf_Communication_N1N2MessageTransfer to AMF 101 and notify UPF 105 to discard the buffer.

[0109] SMF 102 may receive a control plane (CP) request during the running of the subsequent retry timer.

[0110] Step 12. During the running of the subsequent retry timer, SMF 102 may receive an SM policy control update notification request from PCF 103. SMF 102 may confirm the notification.

[0111] There are two alternatives for new NF requests related to N1N2MessageTransfer.

[0112] Step 13. As an alternative, the SMF 102 may cache the request and dispose of the request after the expiry of the subsequent retry timer.

[0113] Step 14. As another alternative, the SMF 102 may stop (i.e., suppress) the disposal of the SM policy control update request and send the implementation failure request to the PCF 103.

[0114] Step 15. The SMF 102 may wait for the expiry of the subsequent retry timer.

[0115] Figure 6 is a signaling diagram that shows messages in another example process for suppressing N1N2 message transmission for a failure notification according to an embodiment herein. Figure 6 Describes an improved message suppression sequence flow (due to a temporary rejection of an ongoing process).

[0116] In one embodiment, Figure 6 the process for suppressing N1N2 message transmission for a failure notification may include the following messages or steps:

[0117] Step 1. The process may be triggered by the PCF 103.

[0118] Step 1a. (PCF-initiated SM policy association modification) The PCF 103 may perform a PCF-initiated SM policy association modification process to notify the SMF 102 about the policy modification. This may be triggered, for example, by a policy decision or upon request from the AF 104.

[0119] Step 1b. The SMF 102 may confirm the SM policy association modification request.

[0120] Step 2. The SMF 102 may initiate a UPF session establishment or modification process for one or more new or modified quality of service (QoS) flows.

[0121] Step 2a. The SMF 102 may update the UPF 105 with one or more N4 rules associated with the one or more new or modified QoS flows.

[0122] Step 2b. One or more UPFs 105 may respond to the SMF 102.

[0123] Step 3. If the UE 106 is in the CM-IDLE state at the AMF 101 and the AMF 101 is able to page the UE 106, the AMF may immediately send a Namf_Communication_N1N2MessageTransfer response to the SMF 102 to indicate to the SMF 102 that the AMF 101 is attempting to contact the UE 106.

[0124] Step 4. For the modification requested by the SMF, the SMF 102 may invoke Namf_Communication_N1N2MessageTransfer([N2 SM information] (PDU session ID, (one or more) QFIs, (one or more) QoS profiles, [(one or more) alternative QoS profiles], session-AMBR, [CN tunnel information], QoS monitoring indication, QoS monitoring reporting frequency, [(one or more) TSCAIs]), N1 SM container (PDU session modification command (PDU session ID, (one or more) QoS rules, QoS flow level QoS parameters (if required for the (one or more) QoS flows associated with the (one or more) QoS rules), QoS rule operation and QoS flow level QoS parameter operation, session-AMBR))).

[0125] Step 5. The AMF 101 may send a paging message to the (one or more) NG-RAN nodes via 3GPP access.

[0126] Step 6. The NG-RAN may send a paging message to the UE 106.

[0127] Step 7. If the AMF 101 has initiated paging to contact the UE 106, but there is an ongoing registration process (i.e., there is a failure in paging the UE 106), the AMF 101 may notify the SMF 102 by sending a Namf_Communications_N1N2MessageTransfer failure notification to the notification target address provided to the SMF in Step 2; the response body message may include a subsequent retry timer to request the NF service consumer 302 to stop sending N1 / N2 messages before the timer expires. In addition, the response body message may include the failure reason, i.e., there is an ongoing registration process. Table 2-4 may apply to this message.

[0128] Step 14. The SMF 102 may start the subsequent retry timer.

[0129] Step 9. The SMF 102 may send an Npcf_SMPolicyControl_Update request (Step 9a) to report the enforcement failure of the (one or more) PCC rules. The PCF 103 may respond with an Npcf_SMPolicyControl_Update with a 200 OK status code (Step 9b).

[0130] Step 10. If one or more N4 rules are set or modified in Step 2, the SMF 102 may send a UPF session release or modification procedure to roll back the new or modified QoS flow(s).

[0131] When the subsequent retry timer runs, the SMF 102 may receive a new request.

[0132] Step 11. When the subsequent retry timer runs, the SMF 102 may receive a SM policy control update notification request from the PCF 103. The SMF 102 may confirm the notification.

[0133] There are two alternatives for new NF requests related to N1N2MessageTransfer.

[0134] Step 12. As an alternative, the SMF 102 may cache the request and process the request after the subsequent retry timer expires.

[0135] As another alternative, the SMF 102 may stop (i.e., suppress) processing the SM policy control update request and send an implementation failure request to the PCF 103.

[0136] Step 13. The SMF 102 may wait for the subsequent retry timer to expire.

[0137] With the embodiments described above, the NF service consumer 302 may know what the problem is and when it can retry or send an N1N2MessageTransfer request to the AMF 101 (in the N1N2Transfer failure notification).

[0138] With the embodiments described above, by defining a subsequent retry timer in the N1N2 transfer failure notification, unnecessary signal exchanges between the NF service consumer 302 and the AMF 101 before the timeout of the subsequent retry timer can be reduced.

[0139] Furthermore, with the embodiments described above, the signaling can be simplified and the same error situations can be avoided.

[0140] Furthermore, with the embodiments described above, paging from the AMF 101 can be reduced and RAN resources can be saved at an earlier stage.

[0141] Figure 7 is a schematic flowchart showing an example method 700 in a first network function (such as the AMF 101) according to embodiments herein.

[0142] Method 700 may start at step S701, where the first network function (such as the AMF 101) may page the UE.

[0143] Then, method 700 may proceed to step S702, where a first network function (such as AMF 101) may transmit a failure notification message to a second network function (such as SMF 102) that implements a network function consumer in response to a paging failure. The failure notification message may include a first parameter indicating a subsequent retry time. During the subsequent retry time, message transmission from the second network function to the first network function may be suppressed.

[0144] In one embodiment, the failure notification message may be an N1N2 message transmission failure notification message.

[0145] In one embodiment, the second network function may implement SMF, SMSF, LMF, PCF, GMLC, NEF, or UDM.

[0146] In one embodiment, the failure notification message may further include a second parameter indicating the cause of the failure.

[0147] In one embodiment, the cause of the failure may be that the UE is not reachable or there is an ongoing process.

[0148] In one embodiment, the ongoing process may be an ongoing registration process or an ongoing handover process.

[0149] In one embodiment, N1N2 message transmission request messages may be suppressed during the subsequent retry time.

[0150] In one embodiment, the second network function may suppress or not suppress new N1N2 message transmission request messages according to the priority of the new N1N2 message transmission request message. For example, if the new N1N2 message transmission request message has a higher priority than the N1N2 message transmission request message that triggered the subsequent retry time, the second network function may transmit N1 and / or N2 messages.

[0151] The above steps are only examples, and the first network function (such as AMF 101) may perform any of the actions described Figures 2 - 6 to suppress N1N2 message transmission for a failure notification.

[0152] Figure 8 is a schematic flowchart showing an example method 800 in a second network function (such as SMF 102) according to an embodiment herein.

[0153] Method 800 may begin at step S801, where a second network function (such as SMF 102) may receive a failure notification message from a first network function (such as AMF 101) that includes a first parameter indicating a subsequent retry time. The failure notification message may be transmitted in response to a paging failure from the first network function to a UE (such as UE 106).

[0154] In one embodiment, the failure notification message may be an N1N2 message transmission failure notification message.

[0155] In one embodiment, the second network function may implement SMF, SMSF, LMF, PCF, GMLC, NEF, or UDM.

[0156] In one embodiment, the failure notification message may further include a second parameter indicating the cause of the failure.

[0157] In one embodiment, the cause of the failure may be that the UE is not reachable or there is an ongoing process.

[0158] In one embodiment, the ongoing process may be an ongoing registration process or an ongoing handover process.

[0159] Then, method 800 may continue to step S802, where the second network function (such as SMF 102) may start a post-retry timer to suppress the transmission of messages from the second network function to the first network function during the post-retry time.

[0160] In one embodiment, the N1N2 message transmission request message may be suppressed during the post-retry time.

[0161] In one embodiment, the second network function may suppress or not suppress a new N1N2 message transmission request message according to the priority of the new N1N2 message transmission request message. For example, if the new N1N2 message transmission request message has a higher priority than the N1N2 message transmission request message that triggered the post-retry time, the second network function may transmit N1 and / or N2 messages.

[0162] Then, method 800 may continue to step S803, where the second network function (such as SMF 102) may receive a data transmission request from a third network function (such as UPF 105). In one embodiment, the data transmission request may be a downlink data notification (DDN) request.

[0163] Alternatively, in step S803, the second network function (such as SMF 102) may receive a control plane request from a fourth network function (such as PCF 103).

[0164] In one embodiment, the control plane request may be a session management policy control update notification request or a session management policy control update response. In one embodiment, the session management policy may be a PCC rule.

[0165] Then, method 800 may continue to step S804, where a second network function (such as SMF 102) may cache a data transmission request during a subsequent retry time; and dispose of the data transmission request after the subsequent retry time.

[0166] Alternatively, in step S804, a second network function (such as SMF 102) may cache a control plane request during a subsequent retry time; and dispose of the control plane request after the subsequent retry time.

[0167] Then, method 800 may continue to step S805, where a second network function (such as SMF 102) may stop transmitting messages to a first network function; and notify a third network function to discard a buffer.

[0168] Alternatively, in step S805, a second network function (such as SMF 102) may stop disposing of control plane requests; and transmit an execution failure message to a fourth network function.

[0169] In one embodiment, the execution failure message may further include at least one of a third parameter indicating a failure code and a fourth parameter indicating a rule state.

[0170] The above steps are only examples, and a second network function (such as SMF 102) may perform any operation described with respect to Figures 2 - 6 to suppress N1N2 message transmission for a failure notification.

[0171] Figure 9 is a schematic block diagram showing an example first network function 900 (such as AMF 101) according to an embodiment herein.

[0172] In one embodiment, the first network function 900 may include at least one processor 901; and a non-transitory computer-readable medium 902 coupled to the at least one processor 901. The non-transitory computer-readable medium 902 may store instructions executable by the at least one processor 901, whereby the at least one processor 901 may be configured to perform steps in an example method 700 as shown in a Figure 7 schematic flowchart; details of which are omitted herein.

[0173] Note that the first network function 900 may be implemented as hardware, software, firmware, and any combination thereof. For example, the first network function 900 may include multiple units, circuits, modules, or the like, where each may be used to perform one or more steps of the example method 700, or one or more steps related to AMF 101.

[0174] It should be understood that the first network function 900 can be implemented as a network element on dedicated hardware, a software instance running on dedicated hardware, or a virtualized function instantiated on a suitable platform (e.g., on a cloud infrastructure).

[0175] Figure 10 is a schematic block diagram showing an example second network function 1000 (such as SMF 102 or NF consumer 302) according to an embodiment herein.

[0176] In one embodiment, the second network function 1000 may include at least one processor 1001; and a non-transitory computer-readable medium 1002 coupled to the at least one processor 1001. The non-transitory computer-readable medium 1002 may store instructions executable by the at least one processor 1001, whereby the at least one processor 1001 may be configured to execute steps in an example method 800 as shown in Figure 8 the schematic flowchart shown; the details of which are omitted herein.

[0177] Note that the second network function 1000 can be implemented as hardware, software, firmware, and any combination thereof. For example, the second network function 1000 may include multiple units, circuits, modules, or the like, each of which can be used to execute one or more steps of the example method 800, or one or more steps related to SMF 102 or NF consumer 302.

[0178] It should be understood that the second network function 1000 can be implemented as a network element on dedicated hardware, a software instance running on dedicated hardware, or a virtualized function instantiated on a suitable platform (e.g., on a cloud infrastructure).

[0179] Figure 11 is a schematic block diagram showing an example computer-implemented device 1100 according to an embodiment herein. In one embodiment, the device 1100 may be configured as any one of the above devices: such as AMF 101, SMF 102, NF consumer 302, the first network function 900, or the second network function 1000.

[0180] In one embodiment, the device 1100 may include, but is not limited to, at least one processor, such as a central processing unit (CPU) 1101, a computer-readable medium 1102, and a memory 1103. The memory 1103 may include volatile memory (e.g., random access memory RAM) and / or non-volatile memory (e.g., a hard disk or flash memory). In one embodiment, the computer-readable medium 1102 may be configured to store a computer program and / or instructions, which when executed by the processor 1101, cause the processor 1101 to execute any of the above methods.

[0181] In one embodiment, a computer-readable medium 1102 (such as a non-transitory computer-readable medium) may be stored in a memory 1103. In another embodiment, a computer program may be stored in a remote location, such as a computer program product 1104 (which may also be implemented as a computer-readable medium), and may be accessed by a processor 1101 via, for example, a carrier 1105.

[0182] The computer-readable medium 1102 and / or the computer program product 1104 may be distributed and / or stored on a removable computer-readable medium, such as a disk, CD (compact disc), DVD (digital video disc), flash memory, or a similar removable storage medium (such as a compact flash, SD (secure digital), memory stick, mini SD card, MMC multimedia card, smart media), HD-DVD (high definition DVD), or Blu-ray DVD, a USB (universal serial bus)-based removable storage medium, a tape medium, an optical storage medium, a magneto-optical medium, a magnetic bubble memory, or may be distributed as a propagated signal via a network (such as Ethernet, ATM, ISDN, PSTN, X.25, the Internet, a local area network (LAN), or a similar network capable of transmitting data packets to an infrastructure node).

[0183] Furthermore, the following modifications are proposed to modify the current 3GPP technical specification 3GPP TS29.518 V17.7.0.

[0184] Title: Retry after N1N2 Message Transmission Failure

[0185] Reason for change:

[0186] As specified in TS29.518, when an NF service consumer initiates an N1 / N2 message transmission service operation, the AMF may respond with an error status code and, at the same time, provide a retry-after timer to avoid the NF consumer from frequently retrying the N1 / N2 message and to avoid unnecessary load on the AMF and negative KPIs caused by the failure response. For example, if the UE is in 3GPP access and there is an ongoing paging process with a higher priority or the same priority as specified in the TS.

[0187] In fact, the AMF may provide a retry-after timer in other scenarios. For example, if there is an ongoing registration process, or when the AMF has just paged the UE but the UE has not responded, the AMF may request the NF consumer to postpone sending subsequent N1 / N2 messages to the UE for a certain period.

[0188] In addition, if paging is sent when the UE is in the CM-IDLE state and reachable for 3GPP access, the AMF responds with response code 202 (with the cause "ATTEMPTING_TO_REACH_UE"). If the UE does not respond, the AMF sends an N1N2 transfer failure notification to the NF service consumer. In such a notification, the AMF may request the NF consumer to postpone sending subsequent N1 / N2 messages to the UE for a certain period of time.

[0189] Summary of changes: 1 / Define a new IE retryAfter in N1N2MsgTxfrFailureNotification to allow the AMF to notify the NF service consumer to refrain from sending N1 / N2 for a certain period of time. 2 / Update the service operation and resource definition to indicate that the AMF can provide a timer for the NF consumer to refrain from sending further N1 / N2 messages to the UE. 3 / Define a new application for UEs that do not respond. 4 / Update the OpenAPI accordingly.

[0190] Consequences of non-approval: When the AMF has identified that an N1 / N2 message cannot be transmitted at that time, the NF service consumer still sends an N1N2MessageTransfer request to the AMF, which results in unnecessary network traffic and waste of RAN resources.

[0191] Proposed changes:

[0192] ***Change 1*** (Underlining indicates content to be added to the 3GPP technical specification)

[0193] 5.2.2.3.1.2 Detailed behavior of the AMF

[0194] When the NF service consumer requests to send N1 and / or N2 information and the UE is in the CM-IDLE state for the access type associated with the N1 and / or N2 information (hereinafter referred to as "associated access type" in this article), the requirements specified in Article 5.2.2.3.1.1 shall apply with the following modifications:

[0195] Note: The N1 and / or N2 session management information is related to the access type of the target PDU session of a single access PDU session or the target access received in the request for the MA PDU session; the N2 (NRPPa) information related to LCS is related to 3GPP access in this release of the specification.

[0196] When applicable, the 4xx and 5xx response cases shall also apply to UEs in the CM-CONNECTED state.

[0197] 2xx Response Situation:

[0198] Situation A: When the UE is in the CM-IDLE state in 3GPP access and the associated access type is 3GPP access: a) The same as step 2a of Figure 5 .2.2.3.1.1-1. If the "skipInd" attribute in the request body is set to "true", the AMF shall respond with a status code of "200 OK", and its response body shall carry the reason "N1_MSG_NOT_TRANSFERRED". b) The same as step 2a of Figure 5 .2.2.3.1.1-1. If asynchronous type communication is invoked and the UE is not paged as a result, the AMF shall respond with a status code of "202 Accepted", update the UE context and store the N1 and / or N2 information, and initiate communication with the UE and / or 5G-AN when the UE becomes reachable. In this case, the AMF shall provide the URI of the resource in the AMF in the "Location" header of the response, which contains information about the stored N1 / N2 messages. The AMF shall also provide a response body containing the reason "WAITING_FOR_ASYNCHRONOUS_TRANSFER", which indicates the current status of the N1 / N2 message transfer; c) The same as step 2a of Figure 5 .2.2.3.1.1-1. If a paging is issued when the UE is in the CM-IDLE state and reachable for 3GPP access, the AMF shall respond with a status code of "202 Accepted", and its response body shall carry the reason "ATTEMPTING_TO_REACH_UE", as specified in subclauses 4.2.3.3 and 5.2.2.2.7 of 3GPP TS23.502 [3].

[0199] Situation B: When the UE is CM-IDLE in non-3GPP access but CM-CONNECTED in 3GPP access and the associated access type is non-3GPP access: a) The same as step 2a of Figure 5 .2.2.3.1.1-1. If the NF service consumer (i.e., the SMF) requests to send only the N1NAS SM message without any associated N2 SM information, and the current access type associated with the PDU session is non-3GPP access and the UE is CM-CONNECTED in 3GPP access, the AMF shall respond with a status code of "200 OK" (with the reason "N1_N2_TRANSFER_INITIATED") and initiate the N1 NAS SM message transfer via 3GPP access. b) is the same as step 2a of Figure 5 .2.2.3.1.1-1. If the UE issues a NAS notification procedure while in CM-CONNECTED in 3GPP access, the AMF shall respond with a status code "202 Accepted", and its response body shall carry the cause "ATTEMPTING_TO_REACH_UE", as specified in subclause 4.2.3.3 and step 4c of subclause 5.2.2.2.7 in 3GPP TS 23.502 [3].

[0200] Case C: When the UE is in CM-IDLE state under both non-3GPP access and 3GPP access, and the associated access type is non-3GPP access: All items specified in Case A are applicable. If the NF service consumer receives a POST response body with the cause "ATTEMPTING_TO_REACH_UE", it shall not send any further signaling to the UE, unless it has higher-priority signaling. In such cases, the response shall include a "Location" header that contains the URI of the resource created in the AMF that stores the state of N1 / N2 message transmission, such as "... / n1-n2-messages / {n1N2MessageId}". The AMF shall: - Store N1 and / or N2 information related to 3GPP access, and when the UE responds with a service request, use the stored N1 and / or N2 information to initiate communication with the UE and / or 5G-AN; - If N2 information is not received and the AMF initiates paging to the UE, store the N1 NAS SM information related to non-3GPP access. Subsequently, when the UE responds with a service request, the AMF shall use the stored N1 information to initiate communication with the UE via 3GPP access; - Notify the SMF that invoked the service operation that when the UE responds with a "list of allowed PDU sessions" and the indicated non-3GPP PDU session of the N2 (and N1, if received) information is included in the list, the access type of the PDU session can be changed from non-3GPP access to 3GPP access, as specified in subclause 5.2.2.3.2.1 of 3GPP TS 29.502

[16] ; or - When the AMF determines that paging or NAS notification has failed, or when the UE responds with a "list of allowed PDU sessions" and the indicated non-3GPP PDU session of the N2 (and N1, if received) information is not included in the list, notify the NF that invoked the service operation (as specified in subclause 5.2.2.3.2) if a notification URI is provided.

[0201] 4xx response situation: - Similar to step 2b of 2.2.3.1.1-1, in the following cases, the AMF shall respond with a status code of "409 Conflict": Figure 5 .2.2.3.1.1-1, in the following cases, the AMF shall respond with a status code of "409 Conflict": - If the UE is in 3GPP access and there is already an ongoing paging procedure with a higher or equal priority, the AMF shall set the application error to "HIGHER_PRIORITY_REQUEST_ONGOING" in the "reason" attribute of the ProblemDetails structure in the POST response body. The AMF may provide a retry timer value to the NF service consumer so that the NF service consumer can retry the request after the timer expires. When providing the retry timer, the NF service consumer shall not initiate downlink messaging before the timer expires. The AMF may also provide the ARP value of the QoS flow that triggered the highest priority ongoing paging currently, so that the NF service consumer (e.g., SMF) knows whether any subsequent triggers for initiating downlink messaging of QoS flows with the same or lower priority have occurred. - If there is an ongoing registration procedure (see clause 4.2.3.3 of 3GPP TS23.502 [3]), the AMF shall set the application error to "TEMPORARY_REJECT_REGISTRATION_ONGOING" in the "reason" attribute of the ProblemDetails structure in the POST response body; The AMF may provide a retry timer value to the NF service consumer so that the NF service consumer can retry the request after the timer expires. When the retry timer is provided, the NF service consumer shall not initiate a downlink message transfer before the timer expires. When the retry timer is provided, the NF service consumer shall not initiate a downlink message transfer before the timer expires. Respond with the status code "504 Gateway Timeout". The AMF shall set the application error to "UE_NOT_RESPONDING" in the POST response body. The AMF may provide a retryAfter timer value to the NF service consumer so that the NF service consumer can throttle the sending of further downlink requests before the timer expires. When the retry timer is provided, the NF service consumer shall not initiate a downlink message transfer before the timer expires. - If this is a request to transmit an N2 PDU session resource modification request or an N2 PDU session resource release command to the 5G-AN, and if the UE is in the CM-IDLE state at the AMF of the access network type associated with the PDU session (see clauses 4.3.3 and 4.3.4 of 3GPP TS23.502 [3] and clause 5.3.2.1 of 3GPP TS23.527

[33] ), the AMF shall set the application error "UE_IN_CM_IDLE_STATE" in the "reason" attribute of the ProblemDetails structure in the POST response body. - If there is an ongoing Xn or N2 handover procedure (see clauses 4.9.1.2.1 and 4.9.1.3.1 of 3GPP TS23.502 [3]), the AMF shall set the application error to "TEMPORARY_REJECT_HANDOVER_ONGOING" in the "cause" attribute of the ProblemDetails structure in the POST response body (if the AMF rejects the request due to an ongoing handover). - If the RAT type is NB-IoT and the UE already has 2 PDU sessions with active user plane resources, the AMF shall set the application error to "MAX_ACTIVE_SESSIONS_EXCEEDED" in the POST response body. - If the paging restriction information restricts the N1N2MessageTransfer request from causing paging (see clause 4.2.3.3 of 3GPP TS23.502 [3]), the AMF shall set the application error to "REJECTION_DUE_TO_PAGING_RESTRICTION" in the "cause" attribute of the ProblemDetails structure in the POST response body. - Same as Figure 5 .2.2.3.1.1-1 step 2b, if the UE is in a non-allowed area and the service request is not a regulatory prioritized service, the AMF shall respond with status code "403 Forbidden". The AMF shall set the application error to "UE_IN_NON_ALLOWED_AREA" in the POST response body. - The NF service consumer (i.e., SMF) receiving this application error may suppress subsequent messages to the AMF (e.g., N1N2MessageTransfer) for non-regulatory prioritized services. In this case, the NF service consumer (i.e., SMF) shall subscribe to the reachability report event for "UE reachability status change" from the AMF in order to receive notification from the AMF when the UE becomes reachable again. - Same as Figure 5 .2.2.3.1.1-1 step 2b, if the NF service consumer (e.g., LMF) requests to send an N1 LPP message to the UE and the UE has indicated during the registration process that it does not support LPP in N1 mode (see clauses 5.5.1.2.2 and 5.5.1.3.2 of 3GPP TS24.501

[11] ), the AMF shall respond with status code "403 Forbidden". The AMF shall set the application error to "UE_WITHOUT_N1_LPP_SUPPORT" in the POST response body. - Same as Figure 5.2.2.3.1.1 - 1's step 2b is the same. If the request body contains the nfId IE indicating an SMF instance different from the stored SMF instance of the SM context hosting the PDU session, the AMF shall respond with the status code "403 Forbidden". The AMF shall set the application error to "INVALID_SM_CONTEXT" in the POST response body. During a procedure with SM context relocation (e.g., during a UE mobility procedure with I - SMF insertion / change / removal), the AMF shall allow N1N2MessageTransfer from both the old and new SMF instances holding the SM context. The NF service consumer (i.e., the SMF) receiving this application error shall remove the SM context of the PDU session and release the PDU session resources (if available) in the (H -)SMF. The SMF shall not send an SMContextStatusNotification to the AMF for the release of this PDU session.

[0202] 5xx response cases: - Same as Figure 5 .2.2.3.1.1 - 1's step 2b is the same. If the UE is currently not reachable (e.g., because the UE is in MICO mode, the UE uses extended idle mode DRX, or the UE is only registered on non - 3GPP access and its status is CM - IDLE), the AMF shall respond with the status code "504 Gateway Timeout". The AMF shall set the application error to "UE_NOT_REACHABLE" in the POST response body. If the extended caching support indication is received in the request, when the message is rejected due to the UE being in MICO mode or the UE using extended idle mode DRX, the AMF shall include the estimated maximum waiting time in the response body. - Figure 5 .2.2.3.1.1 - Step 2b of 1, if the UE does not respond temporarily (e.g., does not respond to paging), the AMF may Respond with the status code "504 Gateway Timeout". The AMF shall set the application error to "UE_NOT_RESPONDING" in the POST response body. The AMF may provide a retryAfter timer value to the NF service consumer so that the NF service consumer can throttle the sending of further downlink requests before the timer expires. When the retry timer is provided, the NF service consumer shall not initiate a downlink message transfer before the timer expires. The AMF may also include a "retryAfter" IE in the POST request body so that the NF consumer can throttle the sending of further downlink requests before the timer expires, for example, to reduce unnecessary paging of non - responsive UEs for a certain period of time to save RAN resources. When the retry timer is provided, the NF service consumer shall not initiate a downlink message transfer before the timer expires. When the retry timer is provided, the NF service consumer shall not initiate a downlink message transfer before the timer expires.

[0203] ***Second Change*** (Underlined text indicates content to be added to the 3GPP technical specification)

[0204] 5.2.2.3.2 N1N2 Transmission Failure Notification

[0205] The AMF uses this notification to inform the NF service consumer that initiated the previous Namf_Communication_N1N2MessageTransfer that the AMF failed to deliver the N1 and / or N2 message. The HTTP POST method shall be used on the notification callback URI provided by the NF service consumer, as specified in clause 5.2.2.3.1.2.

[0206] Figure 5 .2.2.3.2 - 1 Notification of N1N2 Transmission Failure for UE - related Signaling

[0207] 1. If the NF service consumer has provided a notification URI (see clause 5.2.2.3.1.2), the AMF shall send a POST request to the NF service consumer on that notification URI when the AMF determines the following situations: - Paging or NAS notification has failed; - The indicated non - 3GPP PDU session is not allowed to move to 3GPP access; - The UE has rejected paging (as defined in clause 5.38.4 of 3GPP TS 23.501 [2]); - N1 message delivery has failed, for example, if the UE is in RRC Inactive and NG - RAN paging has not been successful, or if an Xn or N2 handover is being triggered in the NG - RAN. The AMF shall include in the POST request body the N1N2MessageTransfer request resource URI (if any) previously returned in the N1N2MessageTransfer response (see clause 5.2.2.3.1.2), otherwise include a virtual URI (see clause 6.1.6.2.30). The AMF shall also include N1 / N2 message transfer reason information in the POST request body and set the value as specified in clause 6.1.5.6.3.1. After receiving this notification, the NF service consumer shall delete any stored representation of the N1N2MessageTransfer request resource URI. The AMF may also include a "retryAfter" IE in the POST request body so that the NF consumer can throttle the sending of further downlink requests before the timer expires, for example, to reduce unnecessary paging of non - responsive UEs for a certain period of time to save RAN resources. The AMF may also include a "retryAfter" IE in the POST request body so that the NF consumer can throttle the sending of further downlink requests before the timer expires, for example, to reduce unnecessary paging of non - responsive UEs for a certain period of time to save RAN resources. to save RAN resources.

[0208] 2. The NF service consumer shall send a response with a "204 No Content" status code. When there is a failure or redirection, one of the HTTP status codes together with the response body (listed in Table 6.1.5.6.3.1 - 2) shall be returned.

[0209] ***Change 3*** (Underlining indicates content to be added to the 3GPP technical specification)

[0210] 6.1.5.6.3.1 POST This method sends a notification of N1 / N2 message transfer failure to the NF service consumer (e.g., SMF). This method shall support the request data structure specified in Table 6.1.5.6.3.1 - 1 and the response data structure and response codes specified in Table 6.1.5.6.3.1 - 3. Table 6.1.5.6.3.1-1: Data Structures Supported in the POST Request Body Table 6.1.5.6.3.1-2: Data Structures Supported in the POST Response Body Table 6.1.5.6.3.1-3: Headers Supported for the 307 Response Code on this Resource Table 6.1.5.6.3.1-4: Headers Supported for the 308 Response Code on this Resource

[0211] ***Change 4*** (Underlining indicates content to be added to the 3GPP Technical Specification)

[0212] 6.1.6.2.30 Type: N1N2MsgTxfrFailureNotification Table 6.1.6.2.30-1: Definition of Type N1N2MsgTxfrFailureNotification

[0213] ***Change 5*** (Underlining indicates content to be added to the 3GPP Technical Specification)

[0214] 6.1.7.3 Application Errors

[0215] The common application errors defined in Table 5.2.7.2-1 of 3GPP TS29.500[4] can also be used for the Namf_Communication service. The following application errors listed in Table 6.1.7.3-1 are specific to the Namf_Communication service. Table 6.1.7.3-1: Application Errors

[0216] ***Change 6*** (Underlining indicates content to be added to the 3GPP Technical Specification)

[0217] A.2 Namf_Communication API openapi: 3.0.0 **********************Skip text for clarity************************ N1N2MsgTxfrFailureNotification: Description: Data in the N1 / N2 message transfer failure notification request Type: Object Attributes: Cause: $ref:'# / components / schemas / N1N2MessageTransferCause' n1n2MsgDataUri: $ref:'TS29571_CommonData.yaml# / components / schemas / Uri' retryAfter: $ref: 'TS29571_CommonData.yaml# / components / schemas / Uinteger' Required: - Cause - n1n2MsgDataUri **********************Skip text for clarity************************

[0218] ***End of change***

[0219] This document describes example embodiments with reference to block diagrams and / or flowcharts of computer-implemented methods, apparatus (systems and / or devices), and / or non-transitory computer program products. It is to be understood that the blocks in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, can be implemented by computer program instructions executed by one or more computer circuits. These computer program instructions can be provided to the processor circuits of general-purpose computer circuits, special-purpose computer circuits, and / or other programmable data processing circuits to produce a machine such that the instructions executed via the processor of the computer and / or other programmable data processing devices transform and control transistors, values stored in memory locations, and other hardware components in such circuits to implement the functions / actions specified in one or more of the blocks or multiple blocks, and thereby create means (functionalities) and / or structures for implementing the functions / actions specified in the block diagrams and / or (one or more) flowchart blocks. Figure One The functions / actions specified in the one or more blocks or multiple blocks, and thereby create means (functionalities) and / or structures for implementing the functions / actions specified in the block diagrams and / or (one or more) flowchart blocks.

[0220] These computer program instructions can also be stored in a tangible computer-readable medium that can direct a computer or other programmable data processing device to operate in a particular manner, such that the instructions stored in the computer-readable medium produce an article of manufacture including the instructions that implement the functionality / acts specified in the block diagrams and / or flowchart Figure One boxes or boxes. Thus, embodiments of the inventive concept can be implemented in hardware and / or in software (including firmware, resident software, microcode, etc.) running on a processor (such as a digital signal processor), which can be collectively referred to as "circuitry", "module", or variants thereof.

[0221] It should also be noted that in certain alternative implementations, the functions / acts shown in the boxes may be performed in a different order than shown in the flowchart. For example, two consecutive boxes shown may actually be performed substantially simultaneously, or the boxes may sometimes be performed in the reverse order, depending on the functionality / acts involved. Additionally, the functionality of a given box of the flowchart and / or block diagram may be split into multiple boxes, and / or the functionality of two or more boxes of the flowchart and / or block diagram may be at least partially integrated. Finally, other boxes may be added / inserted between the boxes shown, and / or boxes / operations may be omitted, without departing from the scope of the inventive concept. Further, although some of the figures include arrows on communication paths to indicate the primary communication direction, it is to be understood that communication can occur in the direction opposite to that drawn.

[0222] Numerous variations and modifications can be made to the embodiments without materially departing from the principles of the inventive concept. All such variations and modifications are intended to be included within the scope of the inventive concept. Thus, the subject matter disclosed above is to be considered illustrative and not restrictive, and the examples of the embodiments appended are intended to cover all such modifications, enhancements, and other embodiments that fall within the spirit and scope of the inventive concept. Accordingly, to the maximum extent permitted by law, the scope of the inventive concept is to be determined by the broadest permissible interpretation of this disclosure (including the examples of the embodiments below and their equivalents), and should not be limited or restricted by the foregoing detailed description.

[0223] Abbreviations 3GPP Third Generation Partnership Project 5G Fifth Generation Mobile Communication Technology AF Application Function AMF Access and Mobility Management Function DDN Downlink Data Notification HTTP Hypertext Transfer Protocol LMF Location Management Function NF Network Function OTT Over-the-top PCC Policy and Charging Control PCF Policy Control Function PDU Packet Data Unit RAN Radio Access Network SMF Session Management Function SMSF Short Message Service Function UDM Unified Data Management UE User Equipment UPF User Plane Function URI Uniform Resource Identifier.

Claims

1. A method (700) performed by a first network function (101) implementing an Access and Mobility Management Function (AMF), comprising: - Paging (S701) a User Equipment (UE) (106); And - In response to a failure in the paging, transmitting (S702) a failure notification message to a second network function (102, 302) implementing a network function consumer, the failure notification message including a first parameter indicating a time for a subsequent retry, wherein during the time for the subsequent retry, transmission of messages from the second network function (102, 302) to the first network function (101) is suppressed.

2. The method (700) according to claim 1, wherein, The failure notification message further includes a second parameter indicating a cause of the failure; and wherein the cause of the failure is that the UE (106) is not reachable or there is an ongoing process.

3. The method (700) according to claim 1 or 2, wherein, During the time for the subsequent retry, N1N2 message transmission request messages are suppressed; or wherein the ongoing process is an ongoing registration process or an ongoing handover process.

4. The method (700) according to any one of claims 1 to 3, Among them, The failure notification message is an N1N2 message transmission failure notification message; or wherein the second network function (302) implements a Session Management Function (SMF), a Short Message Service Function (SMSF), a Location Management Function (LMF), a Policy Control Function (PCF), a Gateway Mobile Location Center (GMLC), a Network Exposure Function (NEF), or a Unified Data Management (UDM).

5. A method (800) performed by a second network function (102, 302) implementing a network function consumer, comprising: - Receiving (S801) a failure notification message from a first network function (101) implementing an Access and Mobility Management Function (AMF), the failure notification message including a first parameter indicating a time for a subsequent retry, wherein the failure notification message is transmitted in response to a paging failure from the first network function (101) to a User Equipment (UE) (106); and - Starting (S802) a subsequent retry timer to suppress transmission of messages from the second network function (102, 302) to the first network function (101) during the time for the subsequent retry.

6. The method (800) according to claim 5, wherein, The failure notification message further includes a second parameter indicating a cause of the failure; and wherein the cause of the failure is that the UE (106) is not reachable or there is an ongoing process.

7. The method (800) according to claim 5 or 6, wherein, During the time for the subsequent retry, N1N2 message transmission request messages are suppressed; or wherein the ongoing process is an ongoing registration process or an ongoing handover process.

8. The method (800) according to any one of claims 5 to 7, Among them, The failure notification message is an N1N2 message transmission failure notification message; or Among them, the second network function (302) implements a session management function (SMF), a short message service function (SMSF), a location management function (LMF), a policy control function (PCF), a gateway mobile location center (GMLC), a network exposure function (NEF), or a unified data management (UDM).

9. The method (800) according to any one of claims 5 to 8 further comprises: - receiving (S803) a data transmission request from a third network function (105) implementing a user plane function (UPF); - caching (S804) the data transmission request during the post-retry time period; and - disposing of (S804) the data transmission request after the post-retry time.

10. The method (800) according to any one of claims 5 to 8 further comprises: - receiving (S803) a data transmission request from a third network function (105) implementing a user plane function (UPF); - stopping (S805) transmitting a message to the first network function; and - notifying (S805) the third network function to discard the buffer.

11. The method (800) according to claim 9 or 10, wherein, The data transmission request is a downlink data notification (DDN) request.

12. The method (800) according to any one of claims 5 to 8 further comprises: - receiving (S803) a control plane request from a fourth network function implementing a policy control function (PCF); - caching (S804) the control plane request during the post-retry time period; and - disposing of (S804) the control plane request after the post-retry time.

13. The method (800) according to any one of claims 5 to 8 further comprises: - receiving (S803) a control plane request from a fourth network function implementing a policy control function (PCF); - stopping (S805) disposing of the control plane request; and - transmitting (S805) an execution failure message to the fourth network function.

14. The method (800) according to claim 13, wherein, The execution failure message further comprises at least one of a third parameter indicating a failure code and a fourth parameter indicating a rule state.

15. The method (800) according to claim 13 or 14, wherein, The control plane request is a session management policy control update notification request or a session management policy control update response.

16. The method (800) according to claim 15, wherein, The session management policy is a policy and charging control (PCC) rule.

17. A first network function (101, 900) implementing an access and mobility management function (AMF), comprising: - at least one processor (901); and - a non-transitory computer-readable medium (902) coupled to the at least one processor (901), the non-transitory computer-readable medium (902) containing instructions executable by the at least one processor (901), whereby the at least one processor (901) is configured to execute the method (700) according to any one of claims 1-4.

18. A second network function (102, 302, 1000) implementing a network function consumer, comprising: - at least one processor (1001); and - A non-transitory computer-readable medium (1002) coupled to the at least one processor (1001), the non-transitory computer-readable medium (1002) containing instructions executable by the at least one processor (1001), whereby the at least one processor (1001) is configured to perform the method (800) according to any one of claims 5-16.

19. A computer-readable medium (902, 1002, 1102) comprising computer-readable code that, when run on a device (101, 102, 302, 900, 1000, 1100), causes the device (101, 102, 302, 900, 1000, 1100) to perform the method (700, 800) according to any one of claims 1 to 16.

20. A computer program product (1104) comprising computer-readable code that, when run on a device (101, 102, 302, 900, 1000, 1100), causes the device (101, 102, 302, 900, 1000, 1100) to perform the method (700, 800) according to any one of claims 1-16.

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