A data transmission method, apparatus, device, and storage medium

Abstract

The application provides a data transmission method and device, equipment and a storage medium, which are applied to an access and mobility management function (AMF), and include the following steps: receiving downlink data directly issued by a network exposure function (NEF); when it is determined that a current state of a UE is unreachable, it is determined whether the AMF is allowed to cache the downlink data according to a caching instruction of the NEF; and when it is determined that the AMF is allowed to cache the downlink data, the downlink data is cached, so that the related signaling of the core network is reduced, and the time delay of sending Internet of Things data to the UE is reduced.

Description

Technical Field

[0001] This application relates to the field of core network technology, and in particular to a data transmission method, apparatus, device and storage medium. Background Technology

[0002] Narrow Band Internet of Things (NB-IoT) offers advantages such as wide coverage, massive connectivity, and high speed. IoT applications utilize Non-IP Data Delivery (NIDD) application programming interfaces (APIs) to transmit data via NAS signaling in the core network and NB-IoT network, enabling simple, low-power, and secure message sending and receiving for IoT devices.

[0003] 3GPP has proposed a Network Exposure Function (NEF) anchored Mobile Terminated (MT) data transmission method. The specific process is as follows: The Application Function (AF) sends downlink data to the NEF. Then, the NEF needs to wait for feedback from the Access Management Function (AMF) to determine how to process the downlink data. For example, when the User Equipment (UE) is in an unreachable state, the AMF reports the UE's unreachability to the NEF. Based on the AMF's feedback, the NEF caches the downlink data and waits for the AMF to detect that the UE has recovered to a reachable state before notifying the NEF again. Only then can the NEF send the downlink data to the UE. The existing data transmission method caches downlink data in the NEF. The NEF cannot directly detect changes in the UE's connection status in the first instance and needs to rely on the feedback from the AMF to determine the processing method of the downlink data. Therefore, it will increase the core network signaling and the latency of sending IoT data to the UE will be longer. Summary of the Invention

[0004] This application provides a data transmission method, apparatus, device, and storage medium for reducing core network signaling and lowering the latency of sending IoT data to the UE.

[0005] In a first aspect, this application provides a data transmission method applied to the Access and Mobility Management Function (AMF), comprising:

[0006] Receive downlink data directly from the Network Open Function (NEF);

[0007] When the current state of the UE is determined to be unreachable, the system determines whether the AMF is allowed to cache the downlink data based on the cache indication of the NEF.

[0008] If it is confirmed that caching of the downlink data is allowed, the downlink data will be cached.

[0009] In one or more possible embodiments, caching the downlink data includes:

[0010] Based on the energy-saving mode configured in the UE, determine the waiting time corresponding to when the UE is currently unreachable;

[0011] The downlink data received within the specified waiting time is cached.

[0012] In one or more possible embodiments, determining the waiting time corresponding to caching the downlink data includes:

[0013] When the power saving mode configured for the UE is determined to be the mobile terminal-only connection-initiated mode, the waiting time is determined based on the next periodic registration update time of the UE or the data reporting time of the UE.

[0014] When the power saving mode configured for the UE is determined to be extended idle mode, the waiting time is determined based on the start time of the next paging time window.

[0015] In one or more possible embodiments, it also includes:

[0016] If it is confirmed that caching of the downlink data is not allowed, the downlink data will be discarded.

[0017] Send a notification to SMF that downlink data transmission failed.

[0018] In one or more possible embodiments, caching the downlink data includes:

[0019] Determine if the AMF supports additional data storage;

[0020] If additional data storage is supported, the downlink data will be cached.

[0021] Otherwise, the downlink data is discarded, and a downlink data transmission failure notification is sent to the SMF.

[0022] In one or more possible embodiments, it also includes:

[0023] When the current state of the UE is determined to be reachable, the UE is paged;

[0024] If a paging response is received from the UE, the downlink data is sent to the UE;

[0025] Otherwise, the downlink data is discarded, and a downlink data transmission failure notification is sent to the SMF.

[0026] In one or more possible embodiments, after sending the downlink data to the UE, the method further includes:

[0027] Receive the data confirmation response sent by the UE.

[0028] In one or more possible embodiments, the notification of data transmission failure carries the reason for the data transmission failure.

[0029] In one or more possible embodiments, the reason for the data transmission failure includes any of the following:

[0030] The AMF does not support extended buffering;

[0031] No instruction to allow AMF caching was received;

[0032] No paging response was received from the UE.

[0033] In one or more possible embodiments, the caching indication is a new indication added to the interface protocol or a reused extended buffering support indication already present in the interface protocol.

[0034] Secondly, this application provides a data transmission method applied to a terminal UE, comprising:

[0035] Receive a paging from the Access and Mobility Management Function (AMF) and send a paging response to the AMF;

[0036] The system receives downlink data sent by the AMF; wherein the downlink data is sent directly to the AMF by the Network Open Function (NEF), and is data that is allowed to be cached in the AMF according to the caching indication from the NEF when the AMF determines that the UE is in an unreachable state.

[0037] In one or more possible embodiments, after receiving the downlink data sent by the AMF, the method further includes:

[0038] Send a data confirmation response to the AMF.

[0039] Thirdly, this application also provides a data transmission method applied to the Network Open Function (NEF), comprising:

[0040] Receive downlink data from application function AF;

[0041] Obtain pre-configured caching policy parameters, and determine a caching indication based on the values ​​of the caching policy parameters; wherein, the caching indication is used to confirm whether the Access and Mobility Management Function (AMF) is allowed to cache the downlink data;

[0042] The downlink data and the cache indication are sent to the AMF.

[0043] In one or more possible embodiments, the caching indication is a new indication added to the interface protocol or a reused extended buffering support indication already present in the interface protocol.

[0044] Fourthly, this application provides a data transmission apparatus for use in the Access and Mobility Management Function (AMF), comprising:

[0045] The NEF downlink data receiving module is used to receive downlink data directly sent by the Network Open Function (NEF).

[0046] The status determination module is used to determine whether the AMF is allowed to cache the downlink data based on the cache indication of the NEF when the current status of the UE is unreachable.

[0047] The data caching module is used to cache the downlink data when it is confirmed that caching of the downlink data is allowed.

[0048] Fifthly, this application provides a data transmission apparatus applied to a terminal UE, comprising:

[0049] The paging response determination module is used to receive a paging from the Access and Mobility Management Function (AMF) and send a paging response to the AMF.

[0050] The AMF downlink data receiving module is used to receive downlink data sent by the AMF; wherein the downlink data is directly sent to the AMF by the Network Open Function (NEF), and is data that is allowed to be cached in the AMF according to the caching indication from the NEF when the AMF determines that the UE is in an unreachable state.

[0051] Sixthly, this application provides a data transmission apparatus applied to the Network Open Function (NEF), comprising:

[0052] The AF downlink data receiving module is used to receive downlink data from the application function AF.

[0053] A cache indication determination module is used to obtain pre-configured cache policy parameters and determine a cache indication based on the value of the cache policy parameters; wherein, the cache indication is used to confirm whether the Access and Mobility Management Function (AMF) is allowed to cache the downlink data;

[0054] A data transmission module is used to send the downlink data and the cache indication to the AMF.

[0055] In a seventh aspect, this application provides an electronic device, the electronic device comprising:

[0056] At least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor to enable the at least one processor to perform any of the methods in the first aspect.

[0057] Eighthly, this application provides a computer storage medium storing a computer program for causing a computer to perform any of the methods described in the first aspect.

[0058] According to the data transmission method, apparatus, device and storage medium provided in this application, the relevant signaling of the core network is reduced and the latency of sending IoT data to the UE is reduced. Attached Figure Description

[0059] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application, and do not constitute an undue limitation of this application.

[0060] Figure 1 This is a flowchart of a conventional data transmission process according to an embodiment;

[0061] Figure 2 This is a data transmission flowchart for an Access and Mobility Management Function (AMF) according to an embodiment.

[0062] Figure 3 This is a data transmission flowchart applied to a terminal UE according to an embodiment;

[0063] Figure 4 This is a data transmission flowchart for the Network Open Function (NEF) according to an embodiment.

[0064] Figure 5 This is an interactive flowchart provided according to an embodiment;

[0065] Figure 6This is a schematic diagram of a data transmission apparatus applied to an Access and Mobility Management Function (AMF) according to an embodiment;

[0066] Figure 7 This is a schematic diagram of a data transmission device applied to a terminal UE according to an embodiment;

[0067] Figure 8 This is a schematic diagram of a data transmission apparatus applied to the Network Open Function (NEF) according to an embodiment;

[0068] Figure 9 This is a schematic diagram of an electronic device according to an embodiment;

[0069] Figure 10 This is a schematic diagram of a computer-readable storage medium provided according to an embodiment. Detailed Implementation

[0070] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0071] It should be noted that the terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this disclosure are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this disclosure described herein can be implemented in orders other than those illustrated or described herein. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this disclosure. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this disclosure as detailed in the appended claims.

[0072] Furthermore, in the description of the embodiments of this application, unless otherwise stated, " / " means "or". For example, A / B can mean A or B. The "and / or" in the text is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist simultaneously, and B exists alone. In addition, in the description of the embodiments of this application, "multiple" means two or more.

[0073] For ease of understanding, the terms used in the embodiments of this invention are explained below:

[0074] AF (Application Function) is a network function entity that provides application services. Simply put, it's a third-party service provider's or operator's own business platform, such as a streaming media server, online game server, IoT application platform, or video conferencing server. AF securely accesses network capabilities and information through NEF (Network Function).

[0075] NEF (Network Exposure Function) is a key innovative function in the 5G core network. It acts as a "secure gateway" between the internal network and external applications, securely and controllably exposing the internal capabilities of the 5G network (such as QoS management, location services, connection status monitoring, etc.) to the external AF.

[0076] SMF (Session Management Function) is one of the core network elements of the 5G core network control plane, responsible for managing the entire lifecycle of user data sessions.

[0077] AMF (Access Management Function) is another core network element in the 5G core network control plane and serves as the first point of contact for the UE to access the network. It is primarily responsible for connectivity, mobility, and authentication management; user authentication and access control; tracking the UE's location (at the registration area level); handling mobility events such as handover; and processing non-access stratum signaling between the UE and the core network—a direct dialogue between the UE and the core network. It also manages the UE's connection state (e.g., idle state, connected state).

[0078] UE (User Equipment) is the terminal device used by a user to access the mobile network. It is the starting and ending point of the entire mobile communication network. Examples include smartphones, tablets, laptops (via cellular network cards), and IoT devices (such as smart water meters and vehicle communication modules).

[0079] MICO mode (Mobile Initiated Communication Only): In MICO mode, the UE does not listen for any network paging in order to save power. The network cannot actively contact it; it only knows that the UE is reachable when the UE actively "wakes up" (e.g., by sending uplink data or performing periodic registration).

[0080] Extended Idle Mode Discontinuous Reception (DRX): In extended idle mode, the UE is configured with a very long paging listening period (e.g., several minutes to several hours), and only opens the receiver to listen for network paging within a very short "listening window" in each period, remaining in sleep mode the rest of the time.

[0081] The 3GPP has proposed a Network Exposure Function (NEF) anchored Mobile Terminated (MT) data transmission method, the specific process of which is as follows: Figure 1 As shown, it includes:

[0082] If the AF has already activated the NIDD service (Non-IP Data Delivery) for a given UE, and has downlink unstructured data to send to the UE, then the AF sends an Nnef_NIDD_Delivery Request message to the NEF (i.e., a standard service request message between the NEF and SMF used to trigger the downlink non-IP data delivery process); the above Nnef_NIDD_Delivery Request contains the following: GPSI, TLTRI, unstructured data, and ReliableData Service Configuration, all of which are derived from the 3GPP 5G core network standard;

[0083] GPSI (Generic Public Subscription Identifier) ​​is a public identifier used by the External Application Server (AF) to identify a 5G subscriber (UE), similar to a "username" or "device ID". It is assigned by the operator and is visible to applications (such as MSISDN mobile phone number, External Identifier). In the NIDD request, the AF uses GPSI to tell the NEF / SMF which user this data should be sent to.

[0084] Unstructured data refers to the raw binary data content to be sent to the UE. It is not encapsulated according to the IP protocol and is usually very short (e.g., tens of bytes). It is suitable for sensor commands, configuration parameters, etc.

[0085] Reliable Data Service Configuration is an optional parameter used to configure the Reliable Data Service. It is a boolean parameter that indicates whether reliable data service authentication is enabled.

[0086] Step 101a: AF sends an Nnef_NIDD_Delivery Request to NEF;

[0087] Step 101b: The AMF indicates to the NEF that the UE has become reachable, and the NEF resumes transmitting the cached unstructured data to the UE.

[0088] Step 102: NEF determines the 5GS QoS flow context based on the DNN and user identity associated with the NIDD configuration;

[0089] In one or more possible embodiments, if a NEF 5GS QoS flow context corresponding to the GPSI contained in the message sent in step 101a is found, NEF will check whether the AF is authorized to send data and whether it has exceeded its quota or rate. If a NEF 5GS QoS flow context corresponding to the GPSI contained in the message sent in step 101a is not found, or if any one of the authorization check, the quota check, or the rate check fails, a data transmission failure notification is returned; if all checks are successful, step 103 is executed.

[0090] Step 103: NEF uses Nsmf_NIDD_Delivery Request to forward unstructured data to SMF.

[0091] In one or more possible embodiments, Nsmf_NIDD_Delivery Request is a non-IP data delivery request for the session management function. Unstructured data is forwarded to SMF via Nsmf_NIDD_Delivery Request. If NEF has indicated support for Extended Buffering in Nnef_SMContext_Create Response (a standard service response message used by NEF and SMF to establish NIDD session management association) during the establishment of the SMF-NEF connection, then NEF retains a copy of the data, that is, NEF will cache the delivered unstructured data.

[0092] Step 104: In roaming situations, HSMF will send Nsmf_PDUSession_TransferMTData to VSMF, which contains downlink unstructured data.

[0093] In one or more possible embodiments, Nsmf_PDUSession_TransferMTData refers to the session management function PDU session mobility termination data transmission request; it is also worth noting that downlink unstructureddata, downlink data, unstructured data, downlink non-IP data, and non-IP data in this application are all the same data; HSMF is Home Session Management Function, which refers to the session management function located in the user equipment's home network; VSMF is Visited Session Management Function, which refers to the session management function located in the roaming network currently visited by the user equipment.

[0094] Step 105: Use the Namf_Communication_N1N2MessageTransfer service to forward downlink data and PDU session ID to AMF;

[0095] In one or more possible embodiments, VSMF determines whether to apply Extended Buffering based on local policies and whether NEF indicates support for Extended Buffering in the Nnef_SMContext_Create Response during SMF-NEF connection establishment. Local policies are a set of service rules and decision logic pre-configured by the network operator within the session management function, which can determine whether to enable extended buffering for downlink data based on conditions such as service type, user level, and network load. If Extended Buffering is used, it means that (VSMF) includes an Extended Buffering support indication in Namf_Communication_N1N2Message Transfer. At the same time, VSMF applies header compression based on local policies. If applied, the header is compressed to reduce signaling overhead.

[0096] Step 106: If the AMF determines that the UE is unreachable from the SMF, the AMF rejects the request from the SMF.

[0097] In one or more possible embodiments, UE unreachable by SMF means that when the UE is in MICO mode or configured in Extended Idle Mode (DRX), the terminal does not listen to the network's paging signals, making it impossible for the network to actively establish a connection with the terminal through paging. If the SMF has not subscribed to UE reachability events, the AMF can carry an indication in the rejection request message that the SMF does not need to trigger a Namf_Communication_N1N2MessageTransfer request to the AMF. This indication is used to inform the SMF that it is not necessary to try to send downlink data for the terminal to the AMF before the current UE recovers its reachability state, thereby reducing unnecessary signaling interactions in the core network. Furthermore, the AMF will store an indication in its local context that the task of 'notifying the SMF that the terminal is unreachable' has been completed for this specific UE, thereby optimizing network behavior and avoiding signaling redundancy and logical conflicts.

[0098] In one or more possible embodiments, if the SMF includes an Extended Buffering support indication request, the AMF carries the estimated maximum wait time in the message rejecting the request, so that the SMF can determine the Extended Buffering time and send the determined Extended Buffering time to the NEF; for example, if the UE is in MICO mode, the AMF determines the estimated maximum wait time based on the next expected periodic registration timer update expiration or by implementation. Specifically, if the terminal is configured to perform periodic registration every 24 hours and has just completed registration, the estimated maximum wait time can be set to approximately 24 hours. This means that the network expects the terminal to actively contact the network and regain reachability within 24 hours at the latest due to the timer expiring. If the UE is configured in Extended Idle Mode DRX, the AMF will determine the Estimated Maximum Wait time based on the start of the next Paging Time Window (a short time window used by the UE to listen for paging in Extended Idle Mode DRX). Specifically, if the terminal's DRX period is configured to be 2 hours, it is currently in a sleep period, and the next listening window will start in 50 minutes, then the estimated maximum waiting time can be set to 50 minutes. This means that the network expects the terminal to become reachable through paging when it enters the listening window after 50 minutes.

[0099] Step 107: In the roaming case, VSMF sends an Nsmf_PDUSession_TransferMTData(Result Indication) response to HSMF;

[0100] In one or more possible embodiments, the Nsmf_PDUSession_TransferMTData(ResultIndication) response is a result indication of the session management function PDU session move termination data transmission service, indicating that the message is a response to the processing result of the preceding request; at the same time, if the VSMF receives the Estimated Maximum Waittime from the AMF and applies Extended Buffering, the VSMF will also pass the Estimated Maximum Waittime to the HSMF.

[0101] Step 108: HSMF receives an indication of downlink data transmission failure and sends it to NEF;

[0102] In one or more possible embodiments, if the HSMF has received the Estimated Maximum Wait time and the NEF has applied Extended Buffering, the HSMF will include the Extended Buffering time in the downlink data transmission failure indication; the Extended Buffering time is determined by the HSMF and should generally be greater than or equal to the Estimated Maximum Wait time. Within the Extended Buffering time, the NEF stores the downlink data to be transmitted, and if subsequent downlink data is received, the NEF will not send any additional Nsmf_NIDD_DeliveryRequest messages.

[0103] Step 109: When the UE is determined to be reachable, the AMF pages the UE and receives the NAS message sent by the UE after receiving the paging message;

[0104] In one or more possible embodiments, a NAS message (Non-Access Stratum Message) refers to a service request sent by a UE in response to a network paging.

[0105] Step 1010: The AMF should initiate the UE configuration update process to allocate a new 5G-GUTI;

[0106] In one or more possible embodiments, 5G-GUTI (5G Globally Unique Temporary Identifier) ​​is equivalent to a temporary ID number assigned to the UE by the network. Its purpose is to replace the user's permanent identity in the air interface and some signaling interactions, so as to prevent the user's permanent identity from being tracked and eavesdropped on, and to protect the user's privacy and security.

[0107] Step 1011: If the UE does not respond to the paging, the AMF sends a failure notification to the VSMF;

[0108] Step 1012: In the case of roaming, if VSMF receives a failure notification from AMF, VSMF sends an Nsmf_PDUSession_TransferMTData(Result Indication) response to HSMF.

[0109] Step 1013: If the HSMF receives a failure notification, the SMF indicates to the NEF that the requested Nsmf_NIDD_Delivery has failed.

[0110] In one or more possible implementations, if Extended Buffering is applied, NEF will clear the data copy;

[0111] Step 1014: The AMF sends MT data to the UE via downlink transmission messages;

[0112] In one or more possible embodiments, if the Reliable Data Service header indicates that a request for acknowledgment is required, the UE should respond with an acknowledgement to the received DL data to acknowledge receipt of the downlink data.

[0113] Step 1015: AMF notifies VSMF that the data has been forwarded;

[0114] Step 1016: In roaming mode, VSMF sends an Nsmf_PDUSession_TransferMTData(Result Indication) response to HSMF, indicating that the data has been forwarded;

[0115] Step 1017: HSMF indicates to NEF that the data has been forwarded.

[0116] In one or more possible implementations, if Extended Buffering is applied by NEF, NEF will clear the cached downlink data;

[0117] Step 1018: NEF sends an Nnef_NIDD_Delivery Response to AF.

[0118] In one or more possible embodiments, Nnef_NIDD_Delivery Response refers to a Reliable Data Service acknowledgment indication, used to indicate whether acknowledgment information for downlink data reception has been received from the UE; if Reliable Data Service is requested, then after the UE determines that downlink data has been received, it confirms that an Nnef_NIDD_Delivery Response carrying the UE's acknowledgment information is sent to the AF, or if no acknowledgment is received, it sends an Nnef_NIDD_Delivery Response carrying the UE's unacknowledgment information to the AF.

[0119] According to the existing technical process, when data is cached in the NEF, the NEF cannot directly perceive the changes in the UE's connection status in the first instance and needs to rely on the feedback information from the AMF. This results in an increase in core network-related signaling and a longer delay in sending IoT data to the UE. This application discloses a data transmission method that caches downlink data in the AMF, which can reduce core network-related signaling and reduce the delay in sending IoT data to the UE.

[0120] In view of the above-mentioned problems in the prior art, this application provides a data transmission method applied to the Access and Mobility Management Function (AMF), specifically as follows: Figure 2 As shown, it includes:

[0121] Step 201: Receive downlink data directly sent by the Network Open Function (NEF);

[0122] In one or more possible embodiments, regardless of the current connection state of the user equipment (UE), the Network Open Function (NEF) will not perform any caching operations after completing authentication and policy checks. Instead, it will forward downlink data to the AMF, which will then perform operations on the downlink data.

[0123] Step 202: When it is determined that the current state of the UE is unreachable, confirm whether the AMF is allowed to cache the downlink data according to the cache indication of the NEF;

[0124] In one or more possible embodiments, the NEF's caching indication confirms whether the AMF is allowed to cache the downlink data, meaning whether the SMF instructs the AMF to Extended Buffering in Nnef_SMContext_CreateResponse during the SMF-NEF connection establishment to determine whether the AMF needs to perform Extended Buffering of IoT messages.

[0125] Step 203: If it is confirmed that caching of the downlink data is allowed, then the downlink data is cached.

[0126] In one or more possible embodiments, when the NEF's cache indication confirms that the AMF is allowed to cache the downlink data, the AMF caches the downlink data; and when the NEF's cache indication confirms that the AMF is not allowed to cache the downlink data, the AMF discards the downlink data and sends a downlink data transmission failure notification to the SMF after discarding it. The downlink data transmission failure notification may also carry the reason for the downlink data transmission failure. For example, if the UE's current state is determined to be unreachable and the NEF's cache indication confirms that the AMF is not allowed to cache the downlink data, the reason for the downlink data transmission failure is sent as "the NEF's cache indication confirms that the AMF is not allowed to cache the downlink data".

[0127] In one or more possible embodiments, caching the downlink data includes: determining the waiting time corresponding to when the current state of the UE is unreachable according to the power-saving mode configured by the UE; caching the downlink data received within the waiting time; determining the waiting time corresponding to caching the downlink data includes: when the power-saving mode configured by the UE is a mobile terminal-only connection-initiated mode, determining the waiting time according to the next periodic registration update time of the UE or the data reporting time of the UE; when the power-saving mode configured by the UE is an extended idle mode, determining the waiting time according to the start time of the next paging time window;

[0128] Specifically, when the AMF determines that the UE is in an unreachable state and decides to execute data caching, it needs to predict the time point at which the UE may become reachable again. The AMF determines the power-saving mode currently activated by the UE (e.g., mobile terminal-initiated connection mode or extended idle mode) and calculates the waiting time based on the inherent working mechanism of the power-saving mode. For example, if it is determined that the UE is in mobile terminal-initiated connection mode, the AMF will calculate the next active time based on the relevant timer information recorded or obtained from the terminal's last communication, and then determine the waiting time based on the next active time. In mobile terminal-initiated connection mode, the AMF determines the waiting time mainly based on two key time anchors: the next periodic registration update time. Or a pre-determined data reporting time; for example, a water sensor used for remote meter reading is programmed to periodically register and update its data with the network every 24 hours to maintain state synchronization. If the AMF completed the last registration for the water sensor at 8:00 AM today, then when the downlink data arrives at 10:00 AM and the UE (water sensor) is found to be unreachable, the AMF will calculate the interval from the current time (10:00 AM) to the next estimated registration time (8:00 AM the next day), thus determining the waiting time to be approximately 22 hours. As another example, an environmental monitoring terminal is programmed to report data every 6 hours. If the last report was at 2:00 AM, then when the downlink data is received at 5:00 AM, the AMF will predict the next uplink time. The estimated time is 8:00 AM, thus setting a waiting period of approximately 3 hours. Within this time window, all downlink data arriving at the AMF for this UE (not limited to the first data packet triggering this buffering, but also including subsequent data packets belonging to the same service flow or application session) will be stored in a buffer for unified caching. The AMF will continuously monitor the UE's status. Once it detects that the UE has entered the connected state by actively initiating signaling within the window period, it will immediately stop waiting and send all cached data, ensuring that data is efficiently delivered at the time when the terminal is most likely to appear, while avoiding invalid network paging attempts during unpredictable periods. For UEs configured in extended idle mode, the reachability window is determined by the network... The configured paging cycle determines the waiting time in extended idle mode. The AMF determines the waiting time based on the start time of the next paging time window. For example, a smart agriculture sensor is configured in extended idle mode with a discontinuous reception cycle of 163.84 seconds (approximately 2.73 minutes). It listens for paging within a short window at the beginning of each cycle. Assuming the current time is the 100th second, and the next paging cycle window begins at the 163.84th second, when the AMF receives downlink data at this moment (the 100th second) and determines that the UE is unreachable (currently in a non-listening period), it calculates the time difference from the current time to the start of the next paging window (the 163.84th second), which is approximately 63.84 seconds.With an 84-second set wait time, AMF will wait until the paging window opens before initiating a paging attempt, rather than immediately making an invalid paging attempt, thereby maximizing energy efficiency and ensuring a high paging success rate.

[0129] In one or more possible embodiments, caching the downlink data includes: determining whether the AMF supports additional data storage; if it supports additional data storage, caching the downlink data; otherwise, discarding the downlink data and sending a downlink data transmission failure notification to the SMF. Specifically, the AMF determines whether it currently supports additional data storage based on its own hardware resources, software version, or operator-pre-configured policies. If the AMF supports additional data storage, it caches the downlink data; if it does not support it, the AMF will not attempt to cache the data but will discard the data packet and send a downlink data transmission failure notification with a clear reason to the SMF to precisely indicate the root cause of the failure. For example, the AMF does not support extended buffering (does not support additional data storage), thereby informing the SMF and upstream network elements (NEF, AF) that the downlink data transmission failed due to the AMF's capability, rather than a network or terminal problem.

[0130] In one or more possible embodiments, when the current state of the UE is determined to be reachable, the UE is paged; if a paging response is received from the UE, the downlink data is sent to the UE; otherwise, the downlink data is discarded, and a downlink data transmission failure notification is sent to the SMF. Specifically, in this embodiment, the reachable state refers to the UE being within a valid paging time window at the current moment within a configured discontinuous reception period. Within the valid paging time window, the UE's receiver is periodically woken up and actively listens for paging sent by the network. Therefore, when the AMF queries the context and determines that the UE is in this state, it means that the network is initiating a paging at this moment, and the UE has a very high probability of successfully receiving and responding. The AMF then initiates the paging process within this valid window. If the UE responds, it indicates that it is ready to establish a connection, and the AMF can immediately send downlink data; if there is no response, the AMF determines that this paging attempt has failed, directly discards the downlink data, and sends a downlink data transmission failure notification to the SMF, notifying the SMF that this downlink data transmission failed due to "no paging response".

[0131] In one or more possible embodiments, the data transmission failure notification carries the reason for the data transmission failure; the reason for the data transmission failure includes any of the following: the AMF does not support extended buffering; no instruction to allow AMF caching was received; no paging response was received from the UE; specifically, the reason for the data transmission failure is directly related to the operation performed by the AMF in a specific scenario, and can be clearly identified in the data transmission failure notification by a standardized cause value, so that the receiving SMF and upstream network elements can perform accurate follow-up processing; if the failure reason is "the AMF does not support extended buffering", the corresponding triggering scenario is: after the AMF confirms that downlink data needs to be cached, it immediately performs a capability check based on its own hardware resources, software version or operator pre-configuration policy. If it determines that it does not support additional storage of IoT data (i.e., it does not have extended buffering function), the AMF will not attempt to cache, but will directly discard the downlink data; subsequently, the AMF notifies the SMF of the failure by sending a data transmission failure notification Namf_Communication_N1N2MessageTransferFailureNotification, and includes the failure information in the notification. The specific reason value "DROP_AMF_UNSUPPORT_EXTENDED_BUFFERING" clearly indicates that the failure is due to limitations in the AMF node's own capabilities, rather than network or terminal issues. Upon receiving this reason value, the SMF can understand the nature of the failure and report it accordingly to the NEF. If the failure reason is "no indication allowed for AMF caching received," the corresponding trigger scenario is as follows: After determining that the UE's current state is unreachable, the AMF parses the Namf_Communication_N1N2MessageTransfer message from the SMF to find a caching indication sent by the NEF. If the AMF finds that the message does not contain any explicit indication requiring or allowing data caching (e.g., not containing "AMF"), it will attempt to resolve the issue. If the AMF receives an "Extended Buffering Required" instruction or its equivalent, it will discard the downlink data directly according to the protocol rules. Then, the AMF sends a failure notification to the SMF, carrying the reason value "DROP_UE_NOT_REACHABLE" to explicitly indicate to the SMF that the data has been discarded because the terminal is unreachable and the network layer has not authorized the AMF to perform caching, thus avoiding invalid caching attempts without network authorization. If the failure reason is "no paging response received from the UE," the corresponding triggering scenario is: the AMF determines that the UE is currently reachable (e.g., within the paging time window) and immediately initiates a network paging process. If, after a preset paging attempt, the AMF still does not receive any response message from the UE, the AMF determines that the downlink data delivery attempt has failed.The AMF will then discard the downlink data to be transmitted and send a data transmission failure notification to the SMF; it can also use a preset reason value to indicate "paging no response," which indicates that the failure occurred during the terminal access phase and the network was unable to establish a connection with the terminal to deliver data.

[0132] In one or more possible embodiments, the method further includes: receiving a data acknowledgment response sent by the UE; specifically, the data acknowledgment response is triggered only when the AF explicitly requests reliable data service acknowledgment through the Reliable DataService Configuration parameter in the Nnef_NIDD_Delivery Request message. After the UE successfully receives and processes the downlink data, it will generate an application layer acknowledgment message. The acknowledgment message is transmitted to the AMF through uplink NAS signaling and finally returned to the AF through the SMF and NEF paths, thereby completing an end-to-end reliable data transmission transaction. If no acknowledgment request is configured, this response process is omitted.

[0133] This application moves the downlink data buffer point from the network open function to the access and mobility management function, enabling it to perform intelligent scheduling directly based on the real-time status of the terminal, effectively reducing data transmission latency and significantly reducing redundant signaling interactions within the core network.

[0134] This application also provides a data transmission method applied to a terminal UE, specifically as follows: Figure 3 As shown, it includes:

[0135] Step 301: Receive a paging from the Access and Mobility Management Function (AMF) and send a paging response to the AMF;

[0136] Step 302: Receive downlink data sent by the AMF; wherein the downlink data is sent directly to the AMF by the Network Open Function (NEF), and is data that is allowed to be cached in the AMF according to the caching indication from the NEF when the AMF determines that the UE is in an unreachable state.

[0137] This application also provides a data transmission method applied to the Network Open Function (NEF), specifically as follows: Figure 4 As shown, it includes:

[0138] Step 401: Receive downlink data from application function AF;

[0139] Step 402: Obtain the pre-configured caching policy parameters, and determine the caching indication based on the value of the caching policy parameters; wherein, the caching indication is used to confirm whether the Access and Mobility Management Function (AMF) is allowed to cache the downlink data;

[0140] Step 403: Send the downlink data and the cache indication to the AMF.

[0141] In one or more possible embodiments, a pre-configured caching policy parameter is obtained, and a caching indication is determined based on the value of the caching policy parameter. Specifically, when the value of the caching policy parameter is determined to be a first value, a first caching indication is generated; wherein, the first caching indication is used to indicate that the AMF is not allowed to cache the downlink data; when the value of the caching policy parameter is determined to be a second value, a second caching indication is generated; wherein, the second caching indication is used to indicate that the AMF is allowed to cache the downlink data; for example, the first value is "1" and the second value is "0". Then, the NEF generates a corresponding caching indication based on different values ​​and sends the caching indication to the AMF. When the AMF receives downlink data containing the second caching indication (i.e., the allowed caching indication), if it determines that the UE is currently in an unreachable state, it initiates a data caching process according to the second caching indication; conversely, if it receives downlink data containing the first caching indication (i.e., the disallowed caching indication), even if the UE is in an unreachable state, the AMF will not attempt to cache, but will discard the downlink data according to predetermined rules. Alternatively, when the cache policy parameter is determined to be a first value, a cache indication is generated and then sent to the AMF. Upon receiving the cache indication, the AMF indicates that it can cache the downlink data. When the cache policy parameter is determined to be a second value, it indicates that the AMF is not allowed to cache the downlink data. In this case, the NEF can determine not to generate a cache indication based on the second value and will not send a cache indication to the AMF. For the AMF, if it does not receive a cache indication, it confirms that caching the downlink data is not allowed and can directly discard the downlink data.

[0142] The complete multi-terminal interaction process of downlink data caching and delivery is as follows: Figure 5 As shown, this includes Application Function (AF), Network Open Function (NEF), Home Session Management Function (HSMF), Visited Session Management Function (VSMF), Access and Mobility Management Function (AMF), and User Equipment (UE). The specific steps are as follows:

[0143] 1. AF sends an Nnef_NIDD_Delivery Request to NEF;

[0144] 2. NEF determines the 5GS QoS flow context based on the DNN and user identity associated with the NIDD configuration;

[0145] 3. NEF uses Nsmf_NIDD_Delivery Request to forward unstructured data to SMF;

[0146] 4. In roaming situations, HSMF will send Nsmf_PDUSession_TransferMTData to VSMF, which contains downlink unstructured data;

[0147] 5. VSMF includes the AMF ExtendedBuffering Required instruction in Namf_Communication_N1N2Message Transfer;

[0148] In one or more possible embodiments, during the SMF-NEF connection establishment process, the VSMF determines whether the NEF needs to perform Extended Buffering of IoT messages by instructing the AMF to Extended Buffering in the Nnef_SMContext_Create Response, and forwards the data and PDU session ID to the AMF using the Namf_Communication_N1N2MessageTransfer service operation. If AMF Extended Buffering is used, the VSMF includes an AMF Extended Buffering Required indication in the Namf_Communication_N1N2Message Transfer, indicating that the AMF is allowed to buffer the downlink data. Simultaneously, the VSMF determines whether compression is necessary based on its local policy; if header compression is applied, the header is compressed.

[0149] 6. When the AMF determines that the UE is unreachable from the SMF, if the SMF includes an AMF Extended Buffering Required indication and the AMF supports additional storage of IoT data, then the AMF will cache the corresponding data within the Estimated Maximum Wait time.

[0150] In one or more possible embodiments, if the AMF determines that the UE is unreachable from the SMF, and if the SMF includes an AMFExtended Buffering Required indication and the AMF supports additional storage of IoT data, then the AMF caches the corresponding data within the EstimatedMaximum Wait time, during which time no paging is initiated for the UE; UE unreachable from the SMF means that the UE is in MICO mode or configured in Extended Idle Mode DRX, and the terminal does not listen for paging signals from the network, making it impossible for the network to actively establish a connection with the terminal through paging; if the UE is in MICO mode, the AMF registers a timer update to expire according to the next expected period or determines the Estimated Maximum Wait time through implementation; if the UE is configured in Extended Idle Mode DRX, the AMF will determine the EstimatedMaximum Wait time according to the start of the next PagingTime Window, and the specific determination method is the same as the prior art, which will not be repeated here. During this period, subsequent MT data for the UE is also cached.

[0151] In one or more possible embodiments, when the Estimated Maximum Wait time expires, indicating that the UE is reachable, if the AMF determines that the UE has entered the connected state (e.g., in MICO mode, the UE initiates a periodic registration update to the network), the AMF sends the cached data to the UE; if the AMF determines that the UE is in the idle state (e.g., the UE is configured in Extended Idle Mode DRX), the AMF pages the UE.

[0152] In one or more possible embodiments, if the AMF determines that the UE is unreachable from the SMF, and if the SMF includes an AMFExtended Buffering Required indication, but the AMF does not support additional storage of IoT data, then the AMF directly discards the data and sends a downlink data transmission failure notification to the SMF, carrying the reason for the downlink data transmission failure as the AMF does not support additional storage of IoT data. Specifically, the process is as follows: the N1N2 message transfer failure notification Namf_Communication_N1N2MessageTransferFailureNotification (i.e., the downlink data transmission failure notification) of the Access and Mobility Management Function carries the reason value "DROP_AMF_UNSUPPORT_EXTENDED_BUFFERING", indicating that in the case of the UE being unreachable from the SMF, the AMF discards the IoT data packet because it does not support additional storage of IoT data; if the AMF determines that the UE is unreachable from the SMF, and the SMF does not include AMF Extended Buffering... If the Required indication is received, the AMF will directly discard the data and send a downlink data transmission failure notification to the SMF, stating that the downlink data transmission failure is due to the AMF not being allowed to buffer the downlink data. Specifically, the Namf_Communication_N1N2MessageTransferFailureNotification will include the reason value "DROP_UE_NOT_REACHABLE", indicating that the AMF discards the IoT data packet when the UE is unreachable from the SMF and the network has not indicated that the AMF needs to store IoT data additionally. It is worth noting that the aforementioned AMF Extended Buffering is an indication that can be either a new indication added to the interface protocol or a reuse of the Extended Buffering in the existing interface protocol. Similarly, the aforementioned AMFExtended Buffering Required is an indication that can be either a new indication added to the interface protocol or a reuse of the Extended Buffering support in the existing interface protocol.

[0153] 7. Once the UE is confirmed to be reachable, the AMF pages the UE. After receiving the paging message, the UE sends a NAS message to the AMF.

[0154] 8. The AMF should initiate the UE configuration update process to allocate the new 5G-GUTI;

[0155] 9. If the UE does not respond to the paging, the AMF sends a downlink data transmission failure notification to the VSMF and executes step 10; if the UE responds to the paging, the AMF sends the buffered data to the UE and executes step 12.

[0156] 10. In roaming situations, if VSMF receives a notification of downlink data transmission failure from AMF, VSMF sends an Nsmf_PDUSession_TransferMTData(Result Indication) response to HSMF.

[0157] In one or more possible embodiments, the Nsmf_PDUSession_TransferMTData(Result Indication) response here indicates that the downlink data transmission failed;

[0158] 11. If the HSMF receives a notification of downlink data transmission failure, the SMF indicates to the NEF that the requested Nsmf_NIDD_Delivery has failed;

[0159] 12. The AMF sends MT data to the UE via downlink transmission messages;

[0160] 13. AMF notifies VSMF that the data has been forwarded;

[0161] 14. In roaming situations, VSMF sends an Nsmf_PDUSession_TransferMTData (ResultIndication) response to HSMF to indicate that the data has been forwarded;

[0162] 15. HSMF indicates to NEF that the data has been forwarded;

[0163] 16. NEF sends an Nnef_NIDD_Delivery Response to AF;

[0164] Corresponding to the aforementioned data transmission method, this invention also proposes a data transmission device applied to the Access and Mobility Management Function (AMF), specifically as follows: Figure 6 As shown, it includes:

[0165] The NEF downlink data receiving module 601 is used to receive downlink data directly sent by the Network Open Function (NEF).

[0166] The status determination module 602 is used to determine whether the AMF is allowed to cache the downlink data based on the cache indication of the NEF when the current status of the UE is unreachable.

[0167] The data caching module 603 is used to cache the downlink data when it is confirmed that caching of the downlink data is allowed.

[0168] This invention also proposes a data transmission device for use in a terminal UE, specifically as follows: Figure 7 As shown, it includes:

[0169] The paging response determination module 701 is used to receive a paging from the Access and Mobility Management Function (AMF) and send a paging response to the AMF.

[0170] AMF downlink data receiving module 702 is used to receive downlink data sent by the AMF; wherein the downlink data is directly sent to the AMF by the Network Open Function (NEF), and is data that is allowed to be cached in the AMF according to the cache indication from the NEF when the AMF determines that the UE is in an unreachable state.

[0171] This invention also proposes a data transmission device for use in the Network Open Function (NEF), specifically as follows: Figure 8 As shown, it includes:

[0172] The AF downlink data receiving module 801 is used to receive downlink data from the application function AF.

[0173] The cache indication determination module 802 is used to obtain pre-configured cache policy parameters and determine a cache indication based on the value of the cache policy parameters; wherein, the cache indication is used to confirm whether the Access and Mobility Management Function (AMF) is allowed to cache the downlink data;

[0174] The data transmission module 803 is used to send the downlink data and the cache indication to the AMF.

[0175] Since the device embodiments of the present invention correspond to the method embodiments described above, details not disclosed in the device embodiments can be referred to in the method embodiments described above, and will not be repeated in the present invention.

[0176] This application also provides an electronic device, including at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to perform the above-described data transmission method.

[0177] like Figure 9 As shown, the device includes a processor 901, a memory 902, a communication interface 903, and a bus 904. The processor 901, memory 902, and communication interface 903 are interconnected via the bus 904.

[0178] Processor 901 is configured to read instructions from memory 902 and execute them, so that at least one processor can execute the data transmission method provided in the above embodiments.

[0179] The memory 902 is used to store various instructions and programs for the data transmission method provided in the above embodiments.

[0180] The 904 bus can be a Peripheral Component Interconnect (PCI) bus or an Extended Industry Standard Architecture (EISA) bus, etc. Buses can be categorized as address buses, data buses, control buses, etc. For ease of representation, Figure 9 The bus is represented by a single thick line, but this does not mean that there is only one bus or one type of bus.

[0181] Processor 901 can be a central processing unit (CPU), a network processor (NP), a graphics processing unit (GPU), or any combination of CPU, NP, and GPU. It can also be a hardware chip. The aforementioned hardware chip can be an application-specific integrated circuit (ASIC), a programmable logic device (PLD), or a combination thereof. The aforementioned PLD can be a complex programmable logic device (CPLD), a field-programmable gate array (FPGA), a generic array logic (GAL), or any combination thereof.

[0182] In addition, this application also provides a computer-readable storage medium, such as Figure 10 As shown, the computer storage medium stores a computer program that is used to cause the computer to perform any of the methods described in the above embodiments.

[0183] The memory may include a readable medium in the form of volatile memory, such as random access memory (RAM) 1001 and / or cache memory 1002, and may further include read-only memory (ROM) 1003.

[0184] The memory may also include a program / utility 1005 having a set (at least one) program module 1004, such program module 1004 including but not limited to: an operating system, one or more application programs, other program modules, and program data, each or some combination of these examples may include an implementation of a network environment.

[0185] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0186] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to this application. It should be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0187] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0188] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0189] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A data transmission method, characterized in that, The Access and Mobility Management Functions (AMF) applied to include: Receive downlink data and buffering indications directly issued by the Network Open Function (NEF); the buffering indications are determined by the NEF according to the values ​​of pre-configured buffering policy parameters; the buffering indications are newly added indications in the interface protocol or reused extended buffering support indications in the interface protocol. When the current state of the UE is determined to be unreachable, the system confirms whether the AMF is allowed to cache the downlink data based on the cache indication. If it is confirmed that caching of the downlink data is allowed, the downlink data will be cached.

2. The method according to claim 1, characterized in that, Cache the downlink data, including: Based on the energy-saving mode configured in the UE, determine the waiting time corresponding to when the UE is currently unreachable; The downlink data received within the specified waiting time is cached.

3. The method according to claim 2, characterized in that, The waiting time corresponding to determining the current state of the UE as unreachable includes: When the power saving mode configured for the UE is determined to be the mobile terminal-only connection-initiated mode, the waiting time is determined based on the next periodic registration update time of the UE or the data reporting time of the UE. When the power saving mode configured for the UE is determined to be extended idle mode, the waiting time is determined based on the start time of the next paging time window.

4. The method according to claim 1, characterized in that, Also includes: If it is confirmed that caching of the downlink data is not allowed, the downlink data will be discarded. Send a notification to SMF that downlink data transmission failed.

5. The method according to claim 1, characterized in that, The step of caching the downlink data includes: Determine if the AMF supports additional data storage; If additional data storage is supported, the downlink data will be cached. Otherwise, the downlink data is discarded, and a downlink data transmission failure notification is sent to the SMF.

6. The method according to claim 1, characterized in that, Also includes: When the current state of the UE is determined to be reachable, the UE is paged; If a paging response is received from the UE, the downlink data is sent to the UE; Otherwise, the downlink data is discarded, and a downlink data transmission failure notification is sent to the SMF.

7. The method according to claim 6, characterized in that, After sending the downlink data to the UE, the method further includes: Receive the data confirmation response sent by the UE.

8. The method according to any one of claims 4-6, characterized in that, The notification of data transmission failure includes the reason for the failure.

9. The method according to claim 8, characterized in that, The reason for the data transmission failure includes any of the following: The AMF does not support extended buffering; No instruction to allow AMF caching was received; No paging response was received from the UE.

10. A data transmission method, characterized in that, Applied to terminal UE, including: Receive a paging from the Access and Mobility Management Function (AMF) and send a paging response to the AMF; The system receives downlink data sent by the AMF; wherein the downlink data is directly sent to the AMF by the Network Open Function (NEF), and is data that is allowed to be cached in the AMF according to a caching indication when the AMF determines that the UE is in an unreachable state; the downlink data is directly sent to the AMF by the NEF; the caching indication is determined by the NEF according to the value of a pre-configured caching policy parameter; the caching indication is a newly added indication in the interface protocol or a reused extended buffering support indication in the interface protocol.

11. The method according to claim 10, characterized in that, After receiving the downlink data sent by the AMF, the method further includes: Send a data confirmation response to the AMF.

12. A data transmission method, characterized in that, Applied to Network Openness Functions (NEF), including: Receive downlink data from application function AF; Obtain pre-configured caching policy parameters, and determine a caching indication based on the values ​​of the caching policy parameters; wherein, the caching indication is a newly added indication in the interface protocol or a reused extended buffering support indication in the interface protocol; the caching indication is used to confirm whether the Access and Mobility Management Function (AMF) is allowed to cache the downlink data; The downlink data and the cache indication are sent to the AMF.

13. A data transmission device, characterized in that, The Access and Mobility Management Functions (AMF) applied to include: The NEF downlink data receiving module is used to receive downlink data and buffering indications directly issued by the Network Open Function (NEF). The buffering indications are determined by the NEF according to the values ​​of pre-configured buffering policy parameters. The buffering indications are either newly added indications in the interface protocol or reused extended buffering support indications in the interface protocol. The status determination module is used to determine whether the AMF is allowed to cache the downlink data based on the cache indication when the current status of the UE is unreachable. The data caching module is used to cache the downlink data when it is confirmed that caching of the downlink data is allowed.

14. A data transmission device, characterized in that, Applied to terminal UE, including: The paging response determination module is used to receive a paging from the Access and Mobility Management Function (AMF) and send a paging response to the AMF. The AMF downlink data receiving module is used to receive downlink data sent by the AMF; wherein, the downlink data is directly sent to the AMF by the Network Open Function (NEF), and is data that is allowed to be cached in the AMF according to the caching indication when the AMF determines that the UE is in an unreachable state; the downlink data is directly sent to the AMF by the NEF; the caching indication is determined by the NEF according to the value of a pre-configured caching policy parameter; the caching indication is a newly added indication in the interface protocol or a reused Extended Buffering Support indication in the interface protocol.

15. A data transmission device, characterized in that, Applied to Network Openness Functions (NEF), including: The AF downlink data receiving module is used to receive downlink data from the application function AF. A cache indication determination module is used to obtain pre-configured cache policy parameters and determine a cache indication based on the value of the cache policy parameters; wherein, the cache indication is a newly added indication in the interface protocol or a reused extended buffering support indication in the interface protocol; the cache indication is used to confirm whether the Access and Mobility Management Function (AMF) is allowed to cache the downlink data; A data transmission module is used to send the downlink data and the cache indication to the AMF.

16. An electronic device, characterized in that, The electronic device includes: At least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor to enable the at least one processor to perform the method as described in any one of claims 1-9.

17. A computer storage medium, characterized in that, The computer storage medium stores a computer program that enables the computer to perform the method as described in any one of claims 1-9.

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