Data transmission method, system and apparatus, and communication device and storage medium

Abstract

The present application relates to a data transmission method, system and apparatus, and a communication device and a storage medium. The method comprises: if a feed link is available, receiving downlink data sent by a terrestrial device, and caching the downlink data, wherein when the downlink data has arrived and the feed link is unavailable, the terrestrial device caches the downlink data; and if a service link is available, forwarding the downlink data to a terminal.

Description

Data transmission method, system, device, communication device and storage medium

[0001] Related applications

[0002] The present application claims priority to the Chinese patent application No. 202411094437.6, filed on August 9, 2024, entitled “Data transmission method, system, device, communication device and storage medium”, the contents of which are hereby incorporated by reference in its entirety. TECHNICAL FIELD

[0003] The present application relates to the technical field of wireless communication, in particular to a data transmission method, system, device, communication device and storage medium. BACKGROUND

[0004] With the development of 3GPP standardization process, Non-Terrestrial Network (NTN) is proposed in related discussions, which deploys base stations on satellites to make the base stations communicate with ground proxy gateways and terminals respectively, thereby expanding the network coverage.

[0005] In NTN, the communication link between the satellite and the terminal is the service link, and the communication link between the satellite and the proxy gateway is the feeder link. However, due to factors such as geographical location and system control, the satellite may not be able to cover the proxy gateway and the terminal at the same time, resulting in the service link and the feeder link being unable to coexist, and making it difficult to achieve reliable transmission of uplink data and downlink data. SUMMARY

[0006] The embodiments of the present application provide a data transmission method, system, device, communication device, storage medium and computer program product, which can realize reliable transmission of data in NTN.

[0007] In a first aspect, the present application provides a data transmission method applied to a satellite device, the method comprising:

[0008] if the feeder link is available, receiving downlink data sent by a ground device, and buffering the downlink data; the ground device buffers the downlink data when the downlink data arrives and the feeder link is unavailable;

[0009] if the service link is available, forwarding the downlink data to a terminal.

[0010] In a second aspect, the present application provides a data transmission method applied to a ground device, the method comprising:

[0011] if the downlink data arrives and the feeder link is unavailable, buffering the downlink data;

[0012] If the feeder link is available, the downlink data is sent to the satellite device; the satellite device buffers the downlink data and forwards the downlink data to the terminal when the service link is available.

[0013] The application provides a data transmission method in a third aspect, applied to a terminal, and the method comprises:

[0014] If the service link is available, the downlink data sent by the satellite device is received; the ground device buffers the downlink data when the downlink data arrives and the feeder link is unavailable, and sends the downlink data to the satellite device when the feeder link is available, and the satellite device buffers the downlink data.

[0015] The application provides a data transmission system in a fourth aspect, which comprises a ground device, a satellite device and a terminal;

[0016] The ground device is used for buffering the downlink data when the downlink data arrives and the feeder link is unavailable, and sending the downlink data to the satellite device when the feeder link is available;

[0017] The satellite device is used for buffering the downlink data and forwarding the downlink data to the terminal when the service link is available;

[0018] The terminal is used for receiving the downlink data.

[0019] The application provides a data transmission device in a fifth aspect, applied to a satellite device, and the device comprises:

[0020] A storage module is used for receiving the downlink data sent by the ground device and buffering the downlink data if the feeder link is available; the ground device buffers the downlink data when the downlink data arrives and the feeder link is unavailable;

[0021] A forwarding module is used for forwarding the downlink data to the terminal if the service link is available.

[0022] The application provides a communication device in a sixth aspect, which comprises a receiver and a transmitter;

[0023] The receiver is used for receiving the downlink data sent by the ground device and buffering the downlink data if the feeder link is available; the ground device buffers the downlink data when the downlink data arrives and the feeder link is unavailable;

[0024] The transmitter is used for forwarding the downlink data to the terminal if the service link is available.

[0025] The application provides a computer readable storage medium in a seventh aspect, and a computer program is stored on the computer readable storage medium. The computer program is executed by a processor to enable the processor to implement the data transmission method provided by the embodiments of the application. The method comprises the following steps:

[0026] If the feeder link is available, the downlink data transmitted by the ground device is received, and the downlink data is buffered. The ground device buffers the downlink data when the downlink data arrives and the feeder link is unavailable.

[0027] If the service link is available, the downlink data is forwarded to the terminal.

[0028] The application provides a computer program product in an eighth aspect, and the computer program product comprises a computer program. The computer program is executed by a processor to enable the processor to implement the data transmission method provided by the embodiments of the application. The method comprises the following steps:

[0029] If the feeder link is available, the downlink data transmitted by the ground device is received, and the downlink data is buffered. The ground device buffers the downlink data when the downlink data arrives and the feeder link is unavailable.

[0030] If the service link is available, the downlink data is forwarded to the terminal.

[0031] The data transmission method, system, device, communication device, storage medium and computer program product described above can buffer the downlink data in the satellite device when the feeder link is available and the service link is unavailable. When the service link changes from unavailable to available, the satellite device transmits the buffered downlink data to the terminal. Similarly, the uplink data can be buffered in the satellite device when the service link is available and the feeder link is unavailable. When the feeder link changes from unavailable to available, the satellite device transmits the buffered uplink data to the terminal. Thus, the reliable transmission of uplink data and downlink data is realized. BRIEF DESCRIPTION OF DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the application or the related art, the drawings needed to be used in the description of the embodiments of the application or the related art will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the application. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0033] FIG. 1 is a schematic diagram of an application scenario of a data transmission method in an embodiment of the application.

[0034] FIG. 2 is a flow diagram of a data transmission method according to an embodiment of the present application.

[0035] FIG. 3 is a schematic diagram of a network element in a non-terrestrial network according to an embodiment of the present application.

[0036] FIG. 4 is a signaling interaction flow diagram of an IP downlink data transmission process according to an embodiment of the present application.

[0037] FIG. 5 is a signaling interaction flow diagram of an IP downlink data transmission process using control plane optimized transmission according to an embodiment of the present application.

[0038] FIG. 6 is a signaling interaction flow diagram of a non-IP downlink data transmission process according to an embodiment of the present application.

[0039] FIG. 7 is a flow diagram of a data transmission method according to an embodiment of the present application.

[0040] FIG. 8 is a signaling interaction flow diagram of an IP uplink data transmission process according to an embodiment of the present application.

[0041] FIG. 9 is a signaling interaction flow diagram of an IP uplink data transmission process using control plane optimized transmission according to an embodiment of the present application.

[0042] FIG. 10 is a signaling interaction flow diagram of a non-IP uplink data transmission process according to an embodiment of the present application.

[0043] FIG. 11 is a block diagram of a communication device according to an embodiment of the present application. DETAILED DESCRIPTION

[0044] To make the objectives, technical solutions, and superiorities of the present application clearer, the present application will be described in further detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are merely intended to explain the present application, and are not intended to limit the present application.

[0045] FIG. 1 is a schematic diagram of an application scenario of a data transmission method according to an embodiment of the present application. As shown in FIG. 1, the scenario includes a satellite device 102, a ground device 104, and a terminal 106. The satellite device 102 and the ground device 104 perform data transmission through a network, and the transmission link is a feeder link. The satellite device 102 and the terminal 106 perform data transmission through a network, and the transmission link is a service link.

[0046] The satellite device 102 can be, but is not limited to, a base transceiver station (BTS) deployed on a satellite, a core network element, and the like. The ground device 104 can be, but is not limited to, a proxy gateway, a gateway station, and the like deployed on land or sea.

[0047] The terminal 106 can be a wireless terminal, which can refer to a device that provides voice and / or other data connectivity to a user, or a hand-held device having a wireless connection capability, or other processing device connected to a wireless modem. The wireless terminal can communicate with one or more core networks via a Radio Access Network (RAN), and can be a mobile terminal, such as a mobile telephone (or "cell" phone) or a computer with a mobile termination that can be portable, pocket, hand-held, computer-embedded, or car-mounted, which exchanges language and / or data with a radio access network. The wireless terminal can also be referred to as a system, a subscriber unit, a subscriber station, a mobile station, a mobile, a remote station, a remote terminal, an access terminal, a user terminal, a user agent, a user device, or user equipment, without limitation.

[0048] The technical solutions of the present application and how the technical solutions solve the above technical problems will be described in detail below with specific embodiments. The following specific embodiments can be combined with each other, and the same or similar concepts or processes can not be described again in some embodiments. The embodiments of the present application will be described below with reference to the drawings.

[0049] In one embodiment, as shown in FIG. 2, a data transmission method is provided, which is applied to the satellite device 102 in FIG. 1 as an example, and includes the following steps S210 to S220.

[0050] Step S210: If the feeder link is available, receive the downlink data sent by the ground device, and buffer the downlink data; the ground device buffers the downlink data when the downlink data arrives and the feeder link is unavailable;

[0051] Step S220: If the service link is available, forward the downlink data to the terminal.

[0052] In a specific implementation, when the ground device has downlink data arriving but the feeder link is unavailable, the ground device can buffer the downlink data. When the feeder link changes from unavailable to available, the ground device can send the buffered downlink data to the satellite device through the feeder link, and the satellite device receives the downlink data sent by the ground device. If the service link is unavailable at this time, the satellite device can buffer the downlink data, and when the service link changes from unavailable to available, the satellite device sends the buffered downlink data to the terminal through the service link, and the terminal receives the downlink data sent by the satellite device.

[0053] For example, when the satellite runs to cover the ground device, the feeder link is available, and if the service link is unavailable at this time, the satellite device can buffer the downlink data received by the feeder link. When the satellite runs to cover the terminal, the service link changes from unavailable to available, and at this time the satellite device can send the buffered downlink data to the terminal through the service link.

[0054] The above data transmission method can buffer the downlink data in the satellite device when the feeder link is available and the service link is unavailable, and when the service link changes from unavailable to available, the satellite device sends the buffered downlink data to the terminal, so as to realize reliable transmission of the downlink data through storage and forwarding.

[0055] FIG. 3 provides a schematic diagram of network elements in a non-ground network. According to FIG. 3, the satellite device can be provided with a proxy on-board, a service capability exposure function (SCEF) network element, a mobile management entity (MME) network element, a serving gateway (S-GW) network element, a packet data network gateway (P-GW) network element, and an evolved node B (eNodeB) network element. The ground device can be provided with a proxy on-ground. It should be noted that the proxy network element of the satellite device in the following embodiments refers to the proxy on-board.

[0056] In one embodiment, an initial attach or track area update (TAU) or context synchronization procedure is provided, specifically including the following steps S301-S307.

[0057] Step S301: The terminal sends an attach request or a TAU request to the on-board MME network element.

[0058] Step S302: The on-board MME network element interacts with the on-board Home Subscriber Server (HSS) network element to obtain terminal subscription information and determine a list of satellite IDs available to the terminal for data transmission.

[0059] Step S303: The network side sends an attach accept or TAU accept message to the terminal, carrying a list of satellite IDs available to the terminal, and the terminal can perform data transmission or attach or tracking area update procedures by accessing the satellites indicated in the list of satellite IDs.

[0060] Step S304: The terminal saves the list of satellite IDs available for data transmission.

[0061] Step S305: When the feeder link is available, the on-board network element synchronizes the terminal context information with the ground agent network element (proxy gateway).

[0062] Step S306: When the ground agent network element interacts with other satellites indicated in the list of satellite IDs, the context information of the terminal is synchronized or updated with the other satellites.

[0063] Step S307: The mobility management (MM) context includes at least one of the following: terminal mobility state, list of satellite IDs available to the terminal for transmission, store-and-forward connection (indicating that the PDN connection is a delay-tolerant connection supported in store-and-forward mode, and that the P-GW and S-GW support the retention process and support data segmentation transmission, and the S-GW supports data buffering), uplink data buffering expiration time (when the extended buffered uplink data involves the terminal accessing the satellite network in store-and-forward mode, this time indicates the S-GW buffering expiration time), and downlink data buffering expiration time (this information unit is multiplexed in the context or newly added, indicating that when the extended buffered downlink data involves the terminal accessing the satellite network in store-and-forward mode, this time indicates the S-GW buffering expiration time).

[0064] The following embodiments can be applied in the IP downlink data transmission scenario, but are not limited thereto.

[0065] In one embodiment, when the downlink data arrives and the feeder link is unavailable, the ground equipment determines whether the terminal is reachable according to the terminal context; if the terminal is reachable, a first buffering time is determined, the downlink data is buffered, and / or a timer is started according to the first buffering time; if the terminal is not reachable, at least one of the following steps is performed: buffering the downlink data, starting a timer according to a default buffering time, or marking the downlink data as unreachable.

[0066] The first cache time can be either the time that downlink data is cached in the ground equipment or the downlink data cache expiration time.

[0067] In practice, if downlink data arrives at ground equipment but there is no available satellite coverage and the power supply link is unavailable, the ground equipment, after performing necessary authentication and policy control, can determine the mobility status of the terminal corresponding to the downlink data based on the terminal context. The mobility status reflects whether the terminal is reachable. If the terminal is reachable, one or more serving satellites can be determined from the list of satellite IDs monitored by the terminal based on ephemeris and / or the terminal's location. The first buffer time of the downlink data can be estimated based on the serving satellites, and then the downlink data can be buffered, or the downlink data can be buffered and a timer can be started based on the first buffer time. Otherwise, if the terminal is unreachable, the downlink data can be buffered, or the downlink data can be buffered and a timer can be started based on the default buffer time, or the downlink data can be buffered, a timer can be started based on the default buffer time, and the downlink data can be marked as unreachable. Terminal unreachability can specifically mean that the terminal is temporarily unable to respond to paging, such as due to being in power-saving mode or switching from store-and-forward mode to normal mode.

[0068] This embodiment allows downlink data to be cached on ground equipment when there is downlink data arriving but no available satellite coverage, thus ensuring reliable transmission of downlink data.

[0069] In one embodiment, the satellite equipment may include an MME network element, an S-GW network element, a P-GW network element, and a proxy network element. Step S210 may specifically include: if the feeder link is available, the proxy network element receives downlink data, sends the downlink data to the S-GW network element via the P-GW network element, and the S-GW network element sends a downlink data notification to the MME network element; the MME network element determines a second buffer time and / or the estimated delivery time of the downlink data, and returns a downlink data notification ACK to the S-GW network element, wherein the downlink data notification ACK carries at least one of the second buffer time, the estimated delivery time of the downlink data, and a store-and-forward indication; the S-GW network element performs at least one of the following: buffering the downlink data; starting a timer according to the second buffer time; and sending a downlink data buffering success notification and / or the estimated delivery time of the downlink data to the ground equipment via the P-GW network element and the proxy network element.

[0070] Among these, downlink data notification can be a notification indicating that downlink data has arrived. Downlink data notification ACK can be an ACK (acknowledgment) message confirming the delivery of downlink data notification. Second buffer time can be the time that downlink data is buffered in the satellite equipment, or it can be the downlink data buffer expiration time. Store-and-forward indication can be a message instructing store-and-forward. Downlink data estimated delivery time can be the estimated time that downlink data will arrive at the terminal. Downlink data buffering success notification can be an acknowledgment message confirming successful downlink data buffering.

[0071] In a specific implementation, before receiving the downlink data sent by the ground device, the ground device can interact with the satellite device to perform synchronization or update context (including terminal state, security information, key-related information, etc.), synchronize the remaining cache capacity on the satellite, and the like. When the satellite runs to cover the ground device, the feeder link is available, the on-board proxy network element receives the downlink data, and the downlink data is sent to the S-GW network element via the P-GW network element. The S-GW network element can send a downlink data notification to the MME network element to indicate that the downlink data has arrived. The MME network element determines a second cache time and / or a time when the downlink data is expected to arrive at the terminal according to the terminal location and satellite ephemeris information, and returns a downlink data notification ACK to the S-GW network element, wherein the second cache time can be stored in the context, and the downlink data notification ACK can carry, but is not limited to, storage and forwarding indication, second cache time, downlink data expected arrival time, and the like. After that, the S-GW network element can cache the downlink data, or cache the downlink data and start a timer according to the second cache time, or cache the downlink data, start a timer according to the second cache time, and send a downlink data caching success notification, a time when the downlink data is expected to arrive at the terminal, and the like to the ground proxy network element via the P-GW network element and the on-board proxy network element. If the cache timer expires, the S-GW network element can also send a downlink data notification to the MME network element again.

[0072] Through the embodiment, the downlink data can be cached in the satellite device when the satellite covers the ground device, and the reliable transmission of the downlink data is ensured.

[0073] In one embodiment, the satellite device can further include an eNodeB network element. The step S220 can specifically include: if the service link is available, the S-GW network element sends the downlink data to the terminal via the eNodeB network element; and the S-GW network element deletes the cached downlink data when receiving a downlink data sending success notification, and / or sends the downlink data sending success notification to the proxy network element via the P-GW network element.

[0074] The downlink data sending success notification can be an acknowledgement message that the downlink data is successfully sent to the terminal.

[0075] In a specific implementation, when the satellite runs to cover the terminal, the satellite device can page the terminal, establish a connection with the terminal, make the service link unavailable become available, and after the MME network element updates the bearer with the S-GW network element, the S-GW network element sends the downlink data to the terminal through the eNodeB network element. The S-GW network element can also receive the downlink data sending success notification returned by the MME network element. When the downlink data sending success notification is received, the S-GW network element can delete the buffered downlink data, or delete the buffered downlink data and send the downlink data sending success notification to the proxy network element through the P-GW network element. When the downlink data sending success notification is received, the proxy network element marks the downlink data sending success.

[0076] Through the embodiment, the buffered downlink data on the satellite device can be sent to the terminal when the satellite covers the terminal, and the reliable transmission of the downlink data is ensured.

[0077] In one embodiment, after step S220, the method can further include: if the feeder link is available, the proxy network element forwards the downlink data sending success notification to the ground device; and the ground device deletes the buffered downlink data when the downlink data sending success notification is received.

[0078] In a specific implementation, when the satellite runs to cover the terminal, the satellite device can page the terminal, establish a connection with the terminal, make the service link unavailable become available, and after the MME network element updates the bearer with the S-GW network element, the S-GW network element sends the downlink data to the terminal through the eNodeB network element. The S-GW network element can also receive the downlink data sending success notification returned by the MME network element. When the downlink data sending success notification is received, the S-GW network element can delete the buffered downlink data, or delete the buffered downlink data and send the downlink data sending success notification to the proxy network element through the P-GW network element. When the downlink data sending success notification is received, the proxy network element marks the downlink data sending success.

[0079] Through the embodiment, the buffered downlink data on the satellite device can be sent to the terminal when the satellite covers the terminal, and the reliable transmission of the downlink data is ensured.

[0080] FIG. 4 provides a signaling interaction flow diagram of an IP downlink data transmission process. Referring to FIG. 4, the IP downlink data transmission can include the following four stages.

[0081] The first stage: the downlink data arrives, and the feeder link is unavailable. Specifically, the first stage includes steps S401 to S402.

[0082] Step S401: The downlink data arrives at the ground proxy network element.

[0083] Step S402: After the ground proxy network element performs necessary authentication and policy control, the ground proxy network element judges the mobility state of the target terminal according to the target terminal context, and if the terminal is reachable, the ground proxy network element determines a suitable service satellite, estimates the time for which the downlink data needs to be buffered, buffers the data, and starts a timer; if the terminal is not reachable, the ground proxy network element marks the downlink data as not reachable, buffers the data, and starts a default buffering timer, and optionally, based on operator configuration, performs extended buffering, and when the mobility state of the terminal changes from not reachable to reachable, the subsequent steps are performed again; the terminal not being reachable can specifically mean that the terminal temporarily cannot respond to paging, for example, because it is in power saving mode, or is switched from store-and-forward mode to normal mode, and the like.

[0084] The second stage: the feeder link is available, and the service link is not available. Specifically, the second stage includes the following steps S403 to S409.

[0085] Step S403: When the ground proxy network element determines that the feeder link is available, the ground proxy network element and the on-board network element perform information interaction, and the interaction content includes: context synchronization or update, and on-board storage space margin confirmation.

[0086] Step S404: The ground proxy network element sends the downlink data to the on-board proxy network element, and the on-board proxy network element sends the downlink data to the on-board S-GW network element via the on-board P-GW.

[0087] Step S405: The S-GW network element sends a downlink data notification (Downlink Data Notification) to the MME network element, notifying that downlink data has arrived.

[0088] Step S406: The MME network element calculates the time (Downlink Buffering Duration time, i.e., the second buffering time) for which the downlink data needs to be buffered at the S-GW network element according to the target terminal location and satellite ephemeris information, and stores a new value of the downlink data buffering time in the MM context according to the second buffering time.

[0089] Step S407: The MME network element sends a downlink data notification ACK (Downlink Data Notification ACK) to the S-GW network element, which carries information such as store-and-forward indication and / or second buffering time.

[0090] Step S408: The S-GW network element caches the downlink data and starts a timer; the S-GW network element receives the store-and-forward indication in the downlink data notification ACK message, stores a new value for the downlink data cache expiration time based on the second cache time, and does not send additional downlink data notifications before the expiration of this time; if the S-GW network element receives an indication that it is temporarily rejected in the downlink data notification ACK message, the S-GW can start a locally configured protection timer and cache all downlink data packets received for the given terminal and wait for the modify bearer request message.

[0091] Step S409: If the timer expires, the S-GW network element can send the downlink data notification to the MME network element again.

[0092] The third stage: the service link is available, and the feeder link is unavailable. Specifically, the third stage includes the following steps S410-S415.

[0093] Step S410: When the satellite covers the location of the target terminal, the MME network element initiates paging to the target terminal, and the target terminal performs the connection establishment / resumption / reestablishment process.

[0094] Step S411: The MME network element and the S-GW network element update the bearer.

[0095] Step S412: The S-GW network element sends the downlink data to the target terminal through the eNodeB network element.

[0096] Step S413: The eNodeB network element sends a non-access stratum (NAS) transfer notification to the MME network element.

[0097] Step S414: The MME network element sends a downlink data sending success notification to the S-GW network element, the S-GW network element deletes the downlink data corresponding to the terminal, and stops the timer.

[0098] Step S415: The S-GW network element sends the downlink data sending success notification to the on-board proxy network element through the P-GW network element, and the on-board proxy network element marks the downlink data sending success.

[0099] The fourth stage: the feeder link is available again, and the service link is unavailable. Specifically, the fourth stage includes the following step S416.

[0100] Step S416: When the feeder link is available again, the on-board proxy network element forwards the downlink data sending success notification to the ground proxy network element, the ground proxy network element deletes the downlink data, and stops the timer.

[0101] The following embodiments can be applied in the IP downlink data transmission control plane optimization scenario, but are not limited thereto.

[0102] In one embodiment, the step S220 can specifically include: if the service link is available, the MME network element receives the downlink data sent by the S-GW network element, encrypts and integrity protects the downlink data to obtain processed downlink data, and sends the processed downlink data to the terminal; the S-GW network element deletes the buffered downlink data upon receiving the downlink data sending success notification, and / or sends the downlink data sending success notification to the proxy network element via the P-GW network element.

[0103] In the specific implementation, when the satellite runs to cover the terminal, the satellite device can page the terminal, and establish a connection with the terminal to make the service link change from unavailable to available. After the MME network element and the S-GW network element update the bearer, the S-GW network element sends the downlink data to the MME network element. After the MME network element encrypts and integrity protects the downlink data, the MME network element sends the downlink data to the terminal via the eNodeB network element. The S-GW network element can also receive the downlink data sending success notification returned by the MME network element. When the S-GW network element receives the downlink data sending success notification, the S-GW network element can delete the buffered downlink data, or delete the buffered downlink data and send the downlink data sending success notification to the proxy network element via the P-GW network element. The proxy network element marks the downlink data sending success upon receiving the downlink data sending success notification.

[0104] Through the embodiment, the control plane downlink data buffered on the satellite device can be encrypted and integrity protected when the satellite covers the terminal, and sent to the terminal, so as to ensure data security.

[0105] FIG. 5 provides a signaling interaction flow chart of an IP downlink data transmission process using control plane optimization. Referring to FIG. 5, the control plane IP downlink data transmission can specifically include the following four stages.

[0106] The first stage: the downlink data arrives, and the feeder link is unavailable. Specifically, the first stage includes the following steps S501 to S502.

[0107] Step S501: The downlink data arrives at the ground proxy network element.

[0108] Step S502: After the ground proxy network element performs necessary authentication and policy control, the target terminal context is used to determine the mobility state of the downlink data target terminal. If the terminal is reachable, one or more suitable service satellites are determined, the satellite ID of the service satellite is in the satellite ID list listened to by the target terminal, the time for which the downlink data needs to be cached is estimated, the data is cached, and a timer is started. If the terminal is not reachable, the downlink data is marked as not reachable, the data is cached, a default caching timer is started, and optionally, the extended caching is performed based on the operator configuration. When the mobility state of the terminal changes from not reachable to reachable, the subsequent steps are performed. The terminal not being reachable can be that the terminal temporarily cannot respond to paging, for example, due to being in power saving mode, or switching from store-and-forward mode to normal mode, etc. Step S502: After the ground proxy network element performs necessary authentication and policy control, the target terminal context is used to determine the mobility state of the downlink data target terminal. If the terminal is reachable, one or more suitable service satellites are determined, the satellite ID of the service satellite is in the satellite ID list listened to by the target terminal, the time for which the downlink data needs to be cached is estimated, the data is cached, and a timer is started. If the terminal is not reachable, the downlink data is marked as not reachable, the data is cached, a default caching timer is started, and optionally, the extended caching is performed based on the operator configuration. When the mobility state of the terminal changes from not reachable to reachable, the subsequent steps are performed. The terminal not being reachable can be that the terminal temporarily cannot respond to paging, for example, due to being in power saving mode, or switching from store-and-forward mode to normal mode, etc.

[0109]

[0110] Step S503: When the ground proxy network element determines that the feeder link is available, the ground proxy network element and the on-board network element perform information interaction, and the interaction content includes: context synchronization / update, on-board storage space margin confirmation.

[0111] Step S504: The ground proxy network element sends the downlink data to the on-board proxy network element, and the on-board proxy network element sends the downlink data to the on-board S-GW network element through the on-board P-GW network element.

[0112] Step S505: The S-GW network element sends a downlink data notification (Downlink Data Notification) to the MME network element, notifying that downlink data has arrived.

[0113] Step S506: The MME network element calculates the time (Downlink Buffering Duration time, i.e., the second caching time) for which the downlink data needs to be cached at the S-GW network element according to the target terminal position and satellite ephemeris information. The MME network element stores a new value of the downlink data caching expiration time in the MM context for the terminal according to the DL Buffering Duration Time.

[0114] Step S507: The MME network element sends a downlink data notification ACK (Downlink Data Notification ACK) to the S-GW network element, carrying information such as store-and-forward indication and / or second caching time.

[0115] ​Step S508: The S-GW network element caches the downlink data and starts a timer: The S-GW network element receives the store-and-forward indication in the downlink data notification ACK message, stores a new value for the downlink data cache expiration time based on the second cache time, and does not send additional downlink data notifications before this time expires. If the S-GW network element receives an indication that it is temporarily rejected in the downlink data notification ACK message, the S-GW can start a locally configured protection timer and cache all downlink data packets received for the given terminal and wait for the modify bearer request message.

[0116] Step S509: If the timer expires, the S-GW network element can send the downlink data notification to the MME network element again.

[0117] The third stage: the service link is available and the feeder link is unavailable. Specifically, the third stage includes the following steps S510-S515.

[0118] Step S510: When the satellite covers the location where the target terminal is located, the MME network element initiates paging to the target terminal, and the target terminal performs the connection establishment / resumption / reestablishment process.

[0119] Step S511: The MME network element and the S-GW network element update the bearer.

[0120] Step S512: The S-GW network element sends the downlink data to the MME network element, and the MME network element sends the downlink data to the terminal after performing data encryption and integrity protection on the downlink data.

[0121] Step S513: The eNodeB network element sends the NAS transport notification to the MME network element.

[0122] Step S514: The MME network element sends the downlink data sending success notification to the S-GW network element, the S-GW network element deletes the downlink data corresponding to the terminal, and stops the timer.

[0123] Step S515: The S-GW network element sends the downlink data sending success notification to the on-board proxy network element via the P-GW network element, and the on-board proxy network element marks the downlink data sending success.

[0124] The fourth stage: the feeder link is available again and the service link is unavailable. Specifically, the fourth stage includes the following step S516.

[0125] Step S516: When the feeder link is available again, the on-board proxy network element forwards the downlink data sending success notification to the ground proxy network element, the ground proxy network element deletes the downlink data, and stops the timer.

[0126] The following embodiments can be applied in non-IP downlink data transmission scenarios, but are not limited thereto.

[0127] In one embodiment, the satellite device comprises the MME network element, the SCEF network element and the proxy network element. The step S210 can specifically comprise: if the feeder link is available, the proxy network element receives the downlink data, sends the downlink data to the SCEF network element, and the SCEF network element sends the downlink data notification to the MME network element; the MME network element determines the second cache time and / or the downlink data estimated arrival time, and returns the downlink data notification ACK to the SCEF network element; the downlink data notification ACK carries at least one of the second cache time, the downlink data estimated arrival time and the store-and-forward instruction; and the SCEF network element performs at least one of the following: caches the downlink data; starts a timer according to the second cache time; and sends the downlink data cache success notification and / or the downlink data estimated arrival time to the ground device via the proxy network element.

[0128] In a specific implementation, when the satellite runs to cover the ground device, the feeder link is available, the on-board proxy network element receives the downlink data, sends the downlink data to the SCEF network element, and the SCEF network element can send the downlink data notification to the MME network element to indicate that the downlink data arrives, the MME network element determines the second cache time and / or the downlink data estimated arrival time at the terminal according to the terminal location and the satellite ephemeris information, and returns the downlink data notification ACK to the SCEF network element, wherein the second cache time can be saved in the context, and the downlink data notification ACK can carry but is not limited to the store-and-forward instruction, the second cache time, the downlink data estimated arrival time and other information. Then, the SCEF network element can cache the downlink data, or cache the downlink data and start a timer according to the second cache time, or cache the downlink data, start a timer according to the second cache time, and send the downlink data cache success notification, the downlink data estimated arrival time at the terminal and other information to the ground proxy network element via the on-board proxy network element.

[0129] Through the embodiments, the non-IP downlink data can be cached in the satellite device when the satellite covers the ground device, and the reliable transmission of the non-IP downlink data is ensured.

[0130] In one embodiment, the satellite device further comprises the eNodeB network element. The step S220 can specifically comprise: if the service link is available, the SCEF network element sends the downlink data to the terminal via the MME network element and the eNodeB network element; the SCEF network element deletes the cached downlink data when receiving the downlink data sending success notification, and / or sends the downlink data sending success notification to the proxy network element; the proxy network element forwards the downlink data sending success notification to the ground device if the feeder link is available; and the ground device deletes the cached downlink data when receiving the downlink data sending success notification.

[0131] In a specific implementation, when the satellite runs to cover the terminal, the service link can change from unavailable to available, the SCEF network element can send the downlink data to the terminal via the MME network element and the eNodeB network element, the SCEF network element can also receive the downlink data sending success notification returned by the MME network element, when receiving the downlink data sending success notification, the SCEF network element can delete the buffered downlink data, or delete the buffered downlink data and send the downlink data sending success notification to the proxy network element, when receiving the downlink data sending success notification, the proxy network element marks the downlink data sending success, when the satellite runs to cover the ground equipment again, the feeder link changes from unavailable to available, at this time, the proxy network element can send the downlink data sending success notification to the ground equipment, when receiving the downlink data sending success notification, the ground equipment deletes the buffered downlink data, or deletes the buffered downlink data and stops the timer.

[0132] Through the embodiment, the non-IP downlink data buffered on the satellite equipment can be sent to the terminal when the satellite covers the terminal, the reliable transmission of the downlink data is ensured, and when the satellite covers the ground equipment again, the ground equipment is informed to clear the cache, thereby saving the data storage space.

[0133] FIG. 6 provides a signaling interaction flow chart of a non-IP downlink data transmission process. Referring to FIG. 6, the non-IP downlink data transmission can specifically include the following steps S601 to S619.

[0134] Step S601: The SCS / AS sends a downlink data request to the ground proxy network element through a non-IP data delivery (NIDD) submission request message.

[0135] Step S602: After the ground proxy network element performs necessary authentication and policy control, the data is buffered, and a timer is started, the ground proxy network element can also determine the mobility state of the target terminal according to the context, if the terminal is reachable (the reachable state is specifically that the target terminal can be paged according to the context information when the service satellite runs to the area where the target terminal is located), the appropriate service satellite is determined according to the target terminal location information and the terminal listening satellite ID list (the estimated waiting time required for the SCS / AS to receive the downlink data confirmation message), if the terminal is not reachable, the context is marked, and when the terminal mobility state changes, the following steps are performed; the terminal not reachable can be that the terminal temporarily cannot respond to the paging, for example, due to being in power saving mode, or switching from store-and-forward mode to normal mode, etc.

[0136] Step S603: When the satellite feeder link of the satellite ID determined by the ground proxy network element is available.

[0137] Step S604: The ground proxy network element forwards the downlink data to the on-board SCEF network element.

[0138] Step S605: The SCEF network element sends the NIDD submit request to the MME network element.

[0139] Step S606: The MME network element calculates the time for which the downlink data needs to be buffered at the on-board network element SCEF according to the satellite ephemeris and the target terminal location.

[0140] Step S607: The NIDD submit response is sent to the SCEF network element, carrying the store-and-forward instruction and the buffering time information.

[0141] Step S608: The SCEF network element buffers the downlink data and starts a timer; if the timer expires, the NIDD submit request is sent again to the MME network element.

[0142] Step S609: The satellite covers the target terminal, and the MME network element pages the target terminal via the eNodeB network element.

[0143] Step S610: Connection establishment (specifically, the RRC connection establishment / resume / reestablishment procedure).

[0144] Step S611: The MME network element sends the NIDD submit indication to the SCEF network element.

[0145] Step S612: The SCEF network element sends the NIDD submit request to the MME network element, carrying the downlink data.

[0146] Step S613: The MME network element performs NIDD delivery via the eNodeB network element.

[0147] Step S614: The MME network element sends the NIDD submit response to the SCEF network element, which can carry the downlink data transmission success indication.

[0148] Step S615: The SCEF network element clears the downlink data and stops the timer.

[0149] Step S616: The SCEF network element sends the downlink data transmission success notification to the proxy network element.

[0150] Step S617: The proxy network element marks the data as successfully transmitted.

[0151] Step S618: The satellite covers the ground proxy network element again, and the on-board proxy network element forwards the downlink data transmission success notification to the ground proxy network element.

[0152] Step S619: The ground proxy network element clears the downlink data, stops the timer, and sends the NIDD submit response to the SCS / AS, carrying the downlink data arrival indication.

[0153] In one embodiment, as shown in FIG. 7, the above data transmission method further comprises the following steps S310-S320.

[0154] Step S310: If the service link is available, the uplink data transmitted by the terminal is received and buffered.

[0155] Step S320: If the feeder link is available, the uplink data is forwarded to the ground device.

[0156] In a specific implementation, when the terminal has uplink data transmission and the service link is available, the terminal can transmit the uplink data to the satellite device through the service link. If the feeder link is unavailable at this time, the satellite device can buffer the uplink data. When the feeder link changes from unavailable to available, the satellite device can transmit the buffered uplink data to the ground device through the feeder link.

[0157] For example, when the satellite runs to cover the terminal, the service link is available, and the terminal can transmit the uplink data to the satellite device. If the feeder link is unavailable at this time, the satellite device can buffer the received uplink data. When the satellite runs to cover the ground device, the feeder link changes from unavailable to available. At this time, the satellite device can transmit the buffered uplink data to the ground device.

[0158] In this embodiment, by buffering the uplink data transmitted by the terminal if the service link is available, and forwarding the uplink data to the ground device if the feeder link is available, the uplink data can be buffered in the satellite device when the feeder link is unavailable and the service link is available. When the feeder link changes from unavailable to available, the satellite device transmits the buffered uplink data to the ground device, thereby realizing reliable transmission of the uplink data through storage and forwarding.

[0159] The following embodiments can be applied in, but not limited to, IP uplink data transmission scenarios.

[0160] In one embodiment, the satellite device comprises an MME network element, an S-GW network element, a P-GW network element, and a proxy network element. The above data transmission method further comprises: the MME network element determines at least one of the third buffering time, the uplink data estimated arrival time, and the downlink data estimated arrival time; the MME network element sends first information to the S-GW network element, wherein the first information comprises at least one of the storage and forwarding indication, the uplink data buffering response indication, and the third buffering time; and the MME network element sends second information to the terminal, wherein the second information comprises the uplink data estimated arrival time and / or the downlink data estimated arrival time.

[0161] The third buffer time can be either the time the uplink data is buffered in the satellite equipment or the uplink data buffer expiration time. The estimated uplink data delivery time can be the estimated time the uplink data will reach the ground equipment. The estimated downlink data delivery time can be the estimated time the downlink data will reach the terminal. The first information can be the information sent by the MME network element to the S-GW network element. The second information can be the information sent by the MME network element to the terminal. The uplink data buffer response indication can be an acknowledgment message for the uplink data buffer.

[0162] In practical implementation, when a satellite reaches the coverage terminal and the service link is available, the MME network element can estimate the third buffer time and the estimated delivery time of uplink data based on satellite ephemeris and other information. If it indicates that downlink data will arrive after uplink data transmission, the MME network element can also estimate the possible arrival time of the downlink data, i.e., the estimated delivery time of the downlink data. Afterwards, the MME network element can send first information carrying store-and-forward instructions, uplink data buffer response instructions, and the third buffer time to the P-GW network element via the S-GW network element, so that the P-GW network element and the proxy network element can establish / modify the channel. The MME network element can also send second information carrying the estimated delivery time of uplink data and the estimated delivery time of downlink data to the terminal.

[0163] This embodiment enables the MME network element to perform an initial attach process when there is uplink data to be transmitted and satellite coverage is available, ensuring reliable transmission of uplink data.

[0164] In one embodiment, step S310 may specifically include: if the service link is available, the proxy network element receives uplink data forwarded by the S-GW network element and the P-GW network element; the proxy network element performs at least one of the following: caching uplink data, starting a timer according to a third caching time, and returning an uplink data caching success notification to the terminal.

[0165] Among them, the uplink data caching success notification can be a confirmation message returned by the on-board agent network element after successfully caching uplink data.

[0166] In practice, when the satellite reaches the coverage terminal, the service link is available. The MME network element can send uplink data to the on-board agent network element through the S-GW network element and P-GW network element. The on-board agent network element caches the received uplink data, or caches the uplink data and starts a timer according to the third cache time, or caches the uplink data, starts a timer according to the third cache time, and returns an uplink data caching success notification to the terminal.

[0167] This embodiment allows uplink data to be cached on satellite equipment when the satellite covers the terminal, ensuring reliable transmission of uplink data.

[0168] In one embodiment, the step S320 can specifically include: sending the uplink data to the ground device by the proxy network element if the feeder link is available, and / or deleting the buffered uplink data upon receiving the uplink data sending success notification.

[0169] In a specific implementation, when the satellite runs to cover the ground device, the feeder link changes from unavailable to available, the on-board proxy network element can send the buffered uplink data to the ground device, and can also delete the buffered uplink data and stop the timer upon receiving the uplink data sending success notification returned by the ground device.

[0170] Through the embodiment, the uplink data can be forwarded to the ground device when the satellite covers the ground device, and the reliable transmission of the uplink data is ensured.

[0171] FIG. 8 provides a signaling interaction flow chart of an IP uplink data transmission process. Referring to FIG. 8, the IP uplink data transmission can specifically include the following three stages.

[0172] The first stage: the service link is available, the feeder link is unavailable, and the terminal has uplink data demand. The uplink data demand can be real-time uplink demand from an application / user, or non-real-time uplink demand prepared for sending by the terminal judging that downlink data will arrive soon. Specifically, the first stage can include the following steps S801 to S810.

[0173] Step S801: the terminal initiates a service request carrying a store-and-forward identifier.

[0174] Step S802: the eNodeB network element forwards the service request carrying the store-and-forward identifier; the service request can be an attachment request, a re-attachment request, or a TAU request.

[0175] Step S803: the MME network element calculates the uplink data buffering time according to satellite ephemeris information, initiates a create session request to the S-GW network element carrying the store-and-forward identifier, the uplink data buffering response indication, the uplink data buffering expiration time (the third buffering time), etc.; the S-GW network element initiates a create session request to the P-GW network element carrying the store-and-forward identifier, the uplink data buffering response indication, the uplink data buffering expiration time (the third buffering time), etc.; and the P-GW network element initiates a channel establishment request to the proxy network element, which is used to establish a channel between the P-GW and the proxy network element, carrying the store-and-forward identifier, the uplink data buffering response indication, the uplink data buffering expiration time (the third buffering time), etc.

[0176] Step S804: the proxy network element performs a channel establishment response, the P-GW network element performs a create session response, and the S-GW network element performs a create session response.

[0177] Step S805: The MME network element initiates an initial context setup request to the eNodeB network element, carrying the store-and-forward identifier.

[0178] Step S806: Radio bearer establishment.

[0179] Step S807: The terminal sends uplink data to the on-board proxy network element via the S-GW network element and the P-GW network element; optionally, an indication that downlink data needs to be received is sent to the MME network element.

[0180] Step S808: The on-board proxy network element caches the uplink data, starts a timer, and if the terminal needs uplink data cache ACK (the parameter is carried when the session request is created, and the parameter value is enable), sends the uplink data cache ACK to the terminal via the on-board P-GW network element, the on-board S-GW network element, and the on-board eNodeB.

[0181] Step S809: If the terminal indicates that there will be downlink data / response after the uplink data, the MME network element estimates the possible arrival time of the downlink data, and sends second information to the terminal, the second information including the possible arrival time of the downlink data.

[0182] Step S810: The terminal starts a timer.

[0183] The second stage, the feeder link is available, and the service link is unavailable. Specifically, the second stage can include the following steps S811 to S814.

[0184] Step S811: After the feeder link is established, the on-board proxy network element forwards the uplink data to the ground proxy network element.

[0185] Step S812: The ground proxy network element forwards the uplink data to the SCS / AS.

[0186] Step S813: The ground proxy network element sends downlink data to the on-board proxy network element, which can be an ACK / response of the uplink data, or downlink data requested by the uplink data.

[0187] Step S814: The on-board proxy network element deletes the uplink data and stops the timer.

[0188] The third stage, the service link is available, and the feeder link is unavailable. Specifically, the third stage can include the following step S815.

[0189] Step S815: The timer expires, the terminal listens to the paging, and is ready to receive the downlink data; or the timer expires, and the terminal initiates a service request.

[0190] The following embodiments can be applied in, but not limited to, the IP uplink data transmission control plane optimization scenario.

[0191] In one embodiment, the step S310 can specifically include: if the service link is available, the MME network element receives the uplink data sent by the terminal, performs integrity check and decryption on the uplink data, obtains the processed uplink data, and sends the processed uplink data to the proxy network element; and the proxy network element performs at least one of the following: buffering the processed uplink data, starting a timer according to the third buffering time, and sending the uplink data buffering success notification to the terminal via the MME network element.

[0192] In a specific implementation, when the satellite covers the terminal, the service link is available, and after the MME network element performs integrity check and decryption on the received uplink data, the MME network element sends the uplink data to the on-board proxy network element via the S-GW network element and the P-GW network element. The on-board proxy network element buffers the uplink data after integrity check and decryption (processed uplink data), or buffers the uplink data after integrity check and decryption and starts a timer according to the third buffering time, or buffers the uplink data after integrity check and decryption, starts a timer according to the third buffering time, and returns the uplink data buffering success notification to the terminal.

[0193] Through the embodiment, the control plane uplink data can be buffered in the satellite equipment when the satellite covers the terminal, and the reliable transmission of the control plane uplink data is ensured.

[0194] FIG. 9 provides a signaling interaction flowchart of a control plane IP uplink data transmission process. Referring to FIG. 9, the control plane IP uplink data transmission can specifically include the following three stages.

[0195] The first stage: the service link is available, and the feeder link is unavailable. Specifically, the first stage can include the following steps S900 to S910.

[0196] Step S900: the terminal is in an ECM idle state.

[0197] Step S901a: the terminal initiates an RRC connection establishment request or an RRC early data request, carrying uplink data.

[0198] Step S901b: the terminal context is searched.

[0199] Step S902: the eNodeB network element sends the uplink data to the MME network element.

[0200] Step S903: the MME network element checks the data integrity and decrypts the data.

[0201] Step S904: the MME network element estimates the time for which the uplink data needs to be buffered, initiates a modify bearer request to the S-GW network element, and carries a store-and-forward instruction and / or an uplink data buffering expiration time.

[0202] Step S905: The S-GW network element sends a modify bearer response to the MME network element.

[0203] Step S906: The MME network element sends the uplink data to the on-board proxy network element via the S-GW network element and the P-GW network element.

[0204] Step S907: The on-board proxy network element caches the data, starts a timer, and sends an uplink data cache ACK to the MME network element.

[0205] Step S908: If the NAS message indicates that there is downlink data transmission after the uplink data transmission, the MME network element estimates the possible arrival time of the downlink data.

[0206] Step S909: The MME network element sends a message to the terminal, the content of which includes at least one of the following: uplink data cache ACK, possible arrival time of downlink data.

[0207] Step S910: The terminal starts a timer.

[0208] The second stage is that the feeder link is available and the service link is unavailable. Specifically, the second stage can include the following steps S911 to S915.

[0209] Step S911: The feeder link is established.

[0210] Step S912: The on-board proxy network element sends the uplink data to the ground proxy network element.

[0211] Step S913: The ground proxy network element sends the uplink data to the SCS / AS.

[0212] Step S914: The ground proxy sends an uplink data arrival notification to the on-board proxy network element; the ground proxy network element sends the downlink data to the on-board proxy network element.

[0213] Step S915: The on-board proxy network element deletes the uplink data and deletes the timer.

[0214] The third stage is that the service link is available and the feeder link is unavailable. Specifically, the third stage can include the following step S916.

[0215] Step S916: The timer expires, the terminal listens to the paging, and is ready to receive the downlink data; or the timer expires, and the terminal initiates a service request actively.

[0216] The following embodiments can be applied in a non-IP uplink data transmission scenario, but are not limited thereto.

[0217] In an embodiment, the satellite device comprises an MME network element, an SCEF network element and a proxy network element; the data transmission method further comprises: the MME network element determining at least one of the third cache time, the uplink data expected arrival time and the downlink data expected arrival time; the MME network element sending third information to the SCEF network element; the third information comprises at least one of the store-and-forward instruction, the uplink data cache response instruction and the third cache time; the MME network element sending fourth information to the terminal; the fourth information comprises the uplink data expected arrival time and / or the downlink data expected arrival time.

[0218] The third information can be information sent by the MME network element to the SCEF network element. The fourth information can be information sent by the MME network element to the terminal.

[0219] In a specific implementation, when the satellite runs to cover the terminal, the service link is available, the MME network element can estimate the third cache time and the uplink data expected arrival time according to satellite ephemeris and other information, and if it is indicated that there is downlink data after the uplink data transmission, the MME network element can also estimate the time when the downlink data is likely to arrive, i.e. the downlink data expected arrival time. Then, the MME network element can send third information carrying the store-and-forward instruction, the uplink data cache response instruction, the third cache time, etc. to the SCEF network element, and the MME network element can also send fourth information carrying the uplink data expected arrival time, the downlink data expected arrival time, etc. to the terminal.

[0220] Through this embodiment, the MME network element can perform the initial attachment process when there is non-IP uplink data to be transmitted and the satellite covers, to ensure reliable transmission of non-IP uplink data.

[0221] In an embodiment, the step S310 can specifically comprise: if the service link is available, the proxy network element receiving the uplink data forwarded by the MME network element and the SCEF network element; the proxy network element performing at least one of the following: caching the uplink data, starting a timer according to the third cache time, and returning an uplink data cache success notification to the terminal.

[0222] In a specific implementation, when the satellite runs to cover the terminal, the service link is available, the MME network element can send the uplink data to the on-board proxy network element through the SCEF network element, the on-board proxy network element caches the received uplink data, or caches the uplink data and starts a timer according to the third cache time, or caches the uplink data, starts a timer according to the third cache time, and returns an uplink data cache success notification to the terminal.

[0223] Through this embodiment, the non-IP uplink data can be cached in the satellite device when the satellite covers the terminal, to ensure reliable transmission of non-IP uplink data.

[0224] Figure 10 provides a signaling interaction flow chart of a non-IP uplink data transmission process. Referring to Figure 10, the non-IP uplink data transmission can specifically include the following two stages.

[0225] The first stage: the service link is available, and the feeder link is unavailable. Specifically, the first stage can include the following steps S1001 to S1008.

[0226] Step S1001: The terminal initiates uplink non-IP data transmission.

[0227] Step S1002: The MME network element estimates the time for which the uplink data needs to be buffered.

[0228] Step S1003: The MME network element sends an NIDD submission request to the SCEF network element, carrying a store-and-forward indication, uplink data, and / or uplink data buffering ACK, and / or uplink data buffering expiration time; the on-board network element SCEF sends a channel establishment request to the on-board proxy network element, carrying a store-and-forward indication, and / or uplink data buffering ACK, and / or uplink data buffering expiration time; the on-board SCEF network element sends uplink data to the on-board proxy network element.

[0229] Step S1004: The on-board proxy network element buffers the uplink data and starts a timer.

[0230] Step S1005: The on-board proxy network element sends a channel establishment response to the on-board SCEF network element; if the terminal needs an uplink data buffering confirmation ACK (the indication is carried in the NIDD submission request and the channel establishment request), the on-board proxy network element sends an uplink data buffering confirmation ACK to the on-board SCEF network element; the on-board SCEF network element sends an NIDD submission response to the on-board MME network element, carrying an uplink data buffering confirmation ACK, indicating that the SCEF network element successfully buffers the uplink data.

[0231] Step S1006: If the terminal indicates that there is downlink data after the uplink data transmission (such as uplink ACK / response), estimate the expected arrival time of the downlink data.

[0232] Step S1007: The MME network element performs NIDD delivery to the terminal, carrying an uplink data buffering confirmation, and / or the expected arrival time of the downlink data.

[0233] Step S1008: The terminal starts a timer according to the received expected arrival time of the downlink data.

[0234] The second stage: the feeder link is available, and the service link is unavailable. Specifically, the second stage can include the following steps S1009 to S1015.

[0235] Step S1009: The feeder link is available.

[0236] Step S1010: The on-board proxy network element sends uplink data to the ground proxy network element.

[0237] Step S1011: The ground proxy network element sends a MO NIDD indication to the SCS / AS, carrying the uplink data.

[0238] Step S1012: The ground proxy network element receives a MO NIDD ACK, indicating that the SCS / AS successfully receives the uplink data.

[0239] Step S1013: The ground proxy network element sends an uplink data arrival ACK to the on-board proxy network element, and optionally forwards the MO NIDD ACK to the on-board proxy network element; if there is downlink data, the ground proxy network element sends the downlink data to the on-board proxy network element.

[0240] Step S1014: The on-board proxy network element deletes the uplink data and stops the timer.

[0241] Step S1015: The timer expires, the terminal listens to the paging and prepares to receive the downlink data, or the timer expires and the terminal initiates a service request.

[0242] In an embodiment, the following content can be added in the context, but not limited to:

[0243] Storage forwarding identifier: indicates that the terminal runs in the storage forwarding mode, supports maintaining the PDN connection and supports data segment transmission due to the different availability of the service link and the feeder link;

[0244] Uplink data cache ACK: indicates whether the terminal needs an uplink data cache response, and takes the value of enabled or disabled;

[0245] Uplink data cache expiration time: indicates the time that needs to be cached in the on-board proxy network element due to the storage forwarding operation, which can be configured by the operator or given by the MME;

[0246] Suggested cache uplink data packet number: the suggested cache uplink data packet number, which can be given by the terminal subscription information or the MME, and is an optional item;

[0247] Downlink data cache expiration time: indicates the time that needs to be cached in the S-GW due to the storage forwarding operation or the temporary unavailability of the terminal, which can be configured by the operator or given by the MME, and can reuse the existing IE;

[0248] Suggested cache downlink data packet number: the suggested cache downlink data packet number, which can be given by the terminal subscription information or the MME, and is an optional item;

[0249] Terminal monitorable satellite ID list: indicates the monitorable satellite ID of the terminal.

[0250] In one embodiment, the ground agent network element has MME anchor function, and / or S-GW anchor function, and / or P-GW anchor function, and / or SCEF anchor function, and / or HSS anchor function, and the uplink data (Mobile Original, MO for short) and downlink data (Mobile Terminated, MT for short) transmission process is as follows:

[0251] The terminal initiates a service request, and the network carries a satellite ID list that the terminal can listen to in the attachment / TAU acceptance.

[0252] The uplink data transmission can specifically include the following steps S1111 to S1117.

[0253] Step S1111: When creating a session request / modifying a bearer request, the following at least one content is carried: a store-and-forward identifier, a satellite ID list that the terminal can listen to, an uplink data cache ACK, a recommended number of cached uplink data packets, a recommended number of cached downlink data packets, an uplink data cache expiration time, and a downlink data cache expiration time.

[0254] Step S1112: When the terminal initiates a service request due to MO data, the satellite network element MME can estimate the time for which the data needs to be cached on the satellite, store a new value for the uplink data cache expiration time in the context, initiate a modification of the bearer request, and carry the uplink data cache expiration time.

[0255] Step S1113: The satellite network element caches the data and starts a timer. If the timer expires, the data is deleted.

[0256] Step S1114: If the terminal needs an uplink data cache ACK, the satellite agent network element sends the uplink data cache ACK to the terminal via the P-GW, S-GW, and eNodeB. If control plane optimization is used, the ACK is sent by the satellite agent network element to the MME via the P-GW and S-GW, and then sent by the MME to the terminal via the eNodeB. If it is non-IP data, the ACK is sent by the satellite agent network element to the MME via the SCEF, and then sent by the MME to the terminal via the eNodeB.

[0257] Step S1115: If the terminal indicates that there is a need to receive downlink data after the uplink data arrives, the satellite network element MME estimates the downlink data arrival time and sends the estimated downlink data arrival time to the terminal via the eNodeB.

[0258] Step S1116: After the terminal receives the downlink data estimated arrival time, a timer is started, and before the timer expires, no paging is listened to.

[0259] Step S1117: The feeder link is available, the on-board agent sends the data to the ground agent network element, after the data is delivered, the data is deleted, and the timer is stopped.

[0260] The downlink data transmission can specifically include the following steps S1121 to S1129.

[0261] Step S1121: The downlink data arrives, the ground agent network element judges whether the terminal is reachable according to the mobility state of the terminal in the context, if the terminal is reachable, selects a suitable service satellite in the satellite list that can be monitored, calculates the caching time of the downlink data at the ground agent network element (the time should be slightly greater than the time when the downlink data delivery response arrives); caches the data and starts the timer; if the terminal is temporarily unreachable, caches the data based on the operator configuration and marks, and when the terminal mobility state changes (from unreachable to reachable), the subsequent steps are executed.

[0262] Step S1122: When the feeder link is available, the ground agent network element interacts with the on-board network element to perform at least one of the following operations:

[0263] Synchronize or update the context information;

[0264] Whether the number of downlink data packets suggested to be cached by the satellite is greater than or equal to the downlink data to be transmitted.

[0265] Step S1123: If the satellite can meet the requirement of transmitting the downlink data, the downlink data is sent to the on-board agent network element.

[0266] Step S1124: If it is IP data, the on-board agent network element sends the downlink data to the on-board S-GW network element through the on-board P-GW network element, and the on-board network element S-GW sends a downlink data arrival notification to the on-board network element MME; if it is non-IP data, the on-board agent network element sends the downlink data to the on-board SCEF network element, and the on-board SCEF network element sends a NIDD submission request to the on-board MME.

[0267] Step S1125: The on-board network element MME estimates the caching time of the downlink data on the satellite, stores a new value for the downlink data caching expiration time, if it is IP data, carries the estimated downlink data caching time in the downlink data arrival notification ACK and sends it to the S-GW; if it is non-IP data, carries the estimated downlink data caching time in the NIDD submission response and sends it to the SCEF.

[0268] Step S1126: The S-GW / SCEF caches the data and starts the timer, and when the timer times out, the downlink data is deleted.

[0269] Step S1127: The satellite covers the area where the target terminal is located, pages the terminal, and the terminal initiates / resumes the service request process.

[0270] Step S1128: If the data is IP data, the S-GW sends the downlink data to the target terminal via the eNodeB, the eNodeB sends a NAS message delivery notification to the MME, the MME forwards the downlink data delivery notification to the S-GW, the S-GW deletes the data and stops the timer; if the data is IP data using control plane optimization transmission, the S-GW sends the downlink data to the target terminal via the MME and the eNodeB, the eNodeB sends a NAS message delivery notification to the MME, the MME forwards the downlink data delivery notification to the S-GW, the S-GW deletes the data and stops the timer; if the data is non-IP data, the SCEF sends the downlink data to the target terminal via the MME and the eNodeB, the MME sends a NIDD delivery response to the SCEF, indicating that the downlink data is sent successfully, the SCEF deletes the data and stops the timer. The S-GW / SCEF sends a downlink data sending success indication to the on-board proxy, and the on-board proxy marks the data.

[0271] Step S1129: If the feeder link is available, the on-board proxy network element sends a downlink data delivery notification to the ground proxy network element, and the ground proxy network element deletes the data and stops the timer.

[0272] It should be understood that although each step in the flowcharts of FIGS. 1 to 10 is shown in sequence according to the direction of the arrow, these steps are not necessarily executed in sequence according to the direction of the arrow. Unless otherwise explicitly stated herein, there is no strict sequence limitation for the execution of these steps, and these steps can be executed in other sequences. Moreover, at least a part of the steps in FIGS. 1 to 10 can include multiple steps or multiple stages, which are not necessarily executed at the same time, but can be executed at different times, and the execution sequence of these steps or stages is not necessarily sequential, but can be executed in rotation or alternation with at least a part of other steps or steps or stages in other steps.

[0273] In one embodiment, a data transmission method is provided, applied to a ground device, comprising: if downlink data arrives and the feeder link is unavailable, buffering the downlink data; if the feeder link is available, sending the downlink data to a satellite device; the satellite device buffers the downlink data and forwards the downlink data to a terminal when the service link is available.

[0274] In a specific implementation, when the ground device has downlink data arriving but the feeder link is unavailable, the ground device can buffer the downlink data, when the feeder link changes from unavailable to available, the ground device can send the buffered downlink data to the satellite device through the feeder link, the satellite device receives the downlink data sent by the ground device, if the service link is unavailable at this time, the satellite device can buffer the downlink data, when the service link changes from unavailable to available, the satellite device sends the buffered downlink data to the terminal through the service link, and the terminal receives the downlink data sent by the satellite device. Since the specific processing process of the ground device has been described in detail in the foregoing embodiments, details are not described herein.

[0275] Through the embodiment, when the feeder link is available and the service link is unavailable, the downlink data can be buffered in the satellite device, when the service link changes from unavailable to available, the satellite device sends the buffered downlink data to the terminal, thereby realizing reliable transmission of the downlink data through store-and-forward.

[0276] In one embodiment, a data transmission method is provided, applied to a terminal, including: if the service link is available, receiving downlink data sent by a satellite device; and a ground device buffering downlink data when the downlink data arrives and the feeder link is unavailable, and sending the downlink data to the satellite device when the feeder link is available.

[0277] In a specific implementation, when the ground device has downlink data arriving but the feeder link is unavailable, the ground device can buffer the downlink data, when the feeder link changes from unavailable to available, the ground device can send the buffered downlink data to the satellite device through the feeder link, the satellite device receives the downlink data sent by the ground device, if the service link is unavailable at this time, the satellite device can buffer the downlink data, when the service link changes from unavailable to available, the satellite device sends the buffered downlink data to the terminal through the service link, and the terminal receives the downlink data sent by the satellite device. Since the specific processing process of the ground device has been described in detail in the foregoing embodiments, details are not described herein.

[0278] Through the embodiment, when the feeder link is available and the service link is unavailable, the downlink data can be buffered in the satellite device, when the service link changes from unavailable to available, the satellite device sends the buffered downlink data to the terminal, thereby realizing reliable transmission of the downlink data through store-and-forward.

[0279] In one embodiment, a data transmission system is provided, including a ground device, a satellite device and a terminal; the ground device is configured to buffer downlink data when the downlink data arrives and the feeder link is unavailable, and send the downlink data to the satellite device when the feeder link is available; the satellite device is configured to buffer the downlink data and forward the downlink data to the terminal when the service link is available; and the terminal is configured to receive the downlink data.

[0280] In a specific implementation, when the ground device has downlink data arriving but the feeder link is unavailable, the ground device can cache the downlink data, and when the feeder link changes from unavailable to available, the ground device can send the cached downlink data to the satellite device through the feeder link. The satellite device receives the downlink data sent by the ground device, and if the service link is unavailable at this time, the satellite device can cache the downlink data. When the service link changes from unavailable to available, the satellite device sends the cached downlink data to the terminal through the service link. The terminal receives the downlink data sent by the satellite device. Since the specific processing procedures of the ground device, the satellite device, and the terminal have been described in detail in the foregoing embodiments, they will not be described here.

[0281] Through the embodiment, when the feeder link is available and the service link is unavailable, the downlink data can be cached in the satellite device. When the service link changes from unavailable to available, the satellite device sends the cached downlink data to the terminal, thereby realizing reliable transmission of the downlink data through store-and-forward.

[0282] In one embodiment, a data transmission apparatus is provided, applied to a satellite device, comprising a storage block and forwarding module, wherein:

[0283] The storage module is configured to receive downlink data sent by a ground device and cache the downlink data if a feeder link is available. The ground device caches the downlink data when the downlink data arrives and the feeder link is unavailable.

[0284] The forwarding module is configured to forward the downlink data to a terminal if a service link is available.

[0285] In one embodiment, when the downlink data arrives and the feeder link is unavailable, the ground device determines whether the terminal is reachable according to a terminal context. If the terminal is reachable, a first caching time is determined, the downlink data is cached, and / or a timer is started according to the first caching time. If the terminal is not reachable, at least one of the following is performed: caching the downlink data, starting a timer according to a default caching time, and marking the downlink data as unreachable.

[0286] In one embodiment, the storage module is further configured to, if the feeder link is available, receive, by the proxy network element, the downlink data, send, by the P-GW network element, the downlink data to the S-GW network element, send, by the S-GW network element, a downlink data notification to the MME network element, determine, by the MME network element, a second buffering time and / or a downlink data estimated arrival time, and return, by the MME network element, a downlink data notification ACK to the S-GW network element, wherein the downlink data notification ACK carries at least one of the second buffering time, the downlink data estimated arrival time, and a store-and-forward indication, and perform, by the S-GW network element, at least one of buffering the downlink data, starting a timer according to the second buffering time, and sending, by the P-GW network element and the proxy network element, a downlink data buffering success notification and / or the downlink data estimated arrival time to the ground device.

[0287] In one embodiment, the forwarding module is further configured to, if the service link is available, send, by the S-GW network element, the downlink data to the terminal via the eNodeB network element, delete, by the S-GW network element, the buffered downlink data upon receiving a downlink data sending success notification, and / or send, by the S-GW network element, the downlink data sending success notification to the proxy network element via the P-GW network element.

[0288] In one embodiment, the data transmission apparatus further comprises a buffering clearing module configured to, if the feeder link is available, forward, by the proxy network element, the downlink data sending success notification to the ground device, and delete, by the ground device, the buffered downlink data upon receiving the downlink data sending success notification.

[0289] In one embodiment, the forwarding module is further configured to, if the service link is available, receive, by the MME network element, the downlink data sent by the S-GW network element, encrypt and integrity protect the downlink data to obtain processed downlink data, and send the processed downlink data to the terminal, delete, by the S-GW network element, the buffered downlink data upon receiving a downlink data sending success notification, and / or send, by the S-GW network element, the downlink data sending success notification to the proxy network element via the P-GW network element.

[0290] In one embodiment, the storage module is further configured to, if the feeder link is available, receive the downlink data by the proxy network element, send the downlink data to the SCEF network element, and send a downlink data notification by the SCEF network element to the MME network element; determine a second cache time and / or a downlink data expected arrival time by the MME network element, and return a downlink data notification ACK to the SCEF network element; the downlink data notification ACK carries at least one of the second cache time, the downlink data expected arrival time, and a store-and-forward indication; and perform at least one of the following by the SCEF network element: cache the downlink data; start a timer according to the second cache time; and send a downlink data cache success notification and / or the downlink data expected arrival time to the ground device via the proxy network element.

[0291] In one embodiment, the forwarding module is further configured to, if the service link is available, send the downlink data to the terminal by the SCEF network element via the MME network element and the eNodeB network element; delete the cached downlink data by the SCEF network element upon receiving a downlink data sending success notification, and / or send the downlink data sending success notification to the proxy network element; forward the downlink data sending success notification to the ground device by the proxy network element if the feeder link is available; and delete the cached downlink data by the ground device upon receiving the downlink data sending success notification.

[0292] In one embodiment, the data transmission device further comprises:

[0293] an uplink storage module configured to, if the service link is available, receive uplink data sent by the terminal and cache the uplink data;

[0294] an uplink forwarding module configured to, if the feeder link is available, forward the uplink data to the ground device.

[0295] In one embodiment, the uplink storage module is further configured to determine at least one of a third cache time, an uplink data expected arrival time, and a downlink data expected arrival time by the MME network element; send first information to the S-GW network element by the MME network element; the first information comprises at least one of a store-and-forward indication, an uplink data cache response indication, and the third cache time; send second information to the terminal by the MME network element; the second information comprises the uplink data expected arrival time and / or the downlink data expected arrival time.

[0296] In one embodiment, the uplink storage module is further configured to, if the service link is available, receive, by the proxy network element, the uplink data forwarded via the S-GW network element and the P-GW network element; and perform, by the proxy network element, at least one of the following: buffering the uplink data, starting a timer according to the third buffering time, and returning an uplink data buffering success notification to the terminal.

[0297] In one embodiment, the uplink forwarding module is further configured to, if the feeder link is available, send, by the proxy network element, the uplink data to the ground equipment, and / or, upon receiving an uplink data sending success notification, delete the buffered uplink data.

[0298] In one embodiment, the uplink storage module is further configured to, if the service link is available, receive, by the MME network element, the uplink data sent by the terminal, perform integrity check and decryption on the uplink data to obtain processed uplink data, and send the processed uplink data to the proxy network element; and perform, by the proxy network element, at least one of the following: buffering the processed uplink data, starting a timer according to the third buffering time, and sending an uplink data buffering success notification to the terminal via the MME network element.

[0299] In one embodiment, the uplink storage module is further configured to determine, by the MME network element, at least one of the following: a third buffering time, an uplink data expected arrival time, and a downlink data expected arrival time; send, by the MME network element, third information to the SCEF network element, wherein the third information comprises at least one of the following: a storage forwarding indication, an uplink data buffering response indication, and the third buffering time; and send, by the MME network element, fourth information to the terminal, wherein the fourth information comprises the uplink data expected arrival time and / or the downlink data expected arrival time.

[0300] In one embodiment, the uplink storage module is further configured to, if the service link is available, receive, by the proxy network element, the uplink data forwarded via the MME network element and the SCEF network element; and perform, by the proxy network element, at least one of the following: buffering the uplink data, starting a timer according to the third buffering time, and returning an uplink data buffering success notification to the terminal.

[0301] In one embodiment, another data transmission apparatus is provided, comprising:

[0302] a ground storage module configured to, if the downlink data arrives and the feeder link is unavailable, buffer the downlink data;

[0303] a ground forwarding module configured to, if the feeder link is available, send the downlink data to a satellite device; and the satellite device buffers the downlink data and forwards the downlink data to a terminal when a service link is available.

[0304] In one embodiment, another data transmission apparatus is provided, comprising:

[0305] The terminal receiving module is configured to receive downlink data sent by the satellite device if the service link is available; and the ground device is configured to buffer the downlink data when the downlink data arrives and the feeder link is unavailable, and send the downlink data to the satellite device for buffering when the feeder link is available.

[0306] The specific limitation of the data transmission apparatus can refer to the limitation of the data transmission method as described above, which will not be repeated here. Each module in the data transmission apparatus described above can be realized by software, hardware and a combination thereof in whole or in part. The above-mentioned modules can be embedded in or independent of the processor in the computer device in hardware form, or can be stored in the memory in the computer device in software form, so as to call and execute the operations corresponding to the above-mentioned modules by the processor.

[0307] FIG. 11 is a structural schematic diagram of a communication device provided by an embodiment of the present application. The communication device can include a receiver 31, a memory 32, a processor 33, at least one communication bus 34 and a transmitter 35. The communication bus 34 is used to realize the communication connection between elements. The memory 32 can contain a high-speed RAM memory, and can also include a non-volatile storage NVM, such as at least one disk memory. The memory 32 can store various programs for completing various processing functions and implementing the method steps of the embodiment. In the embodiment, the transmitter 35 can be a radio frequency processing module or a baseband processing module in an access network device, and the receiver 31 can also be a radio frequency processing module or a baseband processing module in an access network device. The transmitter 35 and the receiver 31 can be integrated together to realize a transceiver. The transmitter 35 and the receiver 31 can be coupled to the processor 33, and can realize the receiving or transmitting action under the indication or control action of the processor 33.

[0308] In an embodiment, the receiver is configured to receive downlink data sent by the ground device if the feeder link is available, and buffer the downlink data; the ground device is configured to buffer the downlink data when the downlink data arrives and the feeder link is unavailable; and the transmitter is configured to forward the downlink data to the terminal if the service link is available.

[0309] In one embodiment, the ground equipment determines whether the terminal is reachable according to a terminal context when the downlink data arrives and the feeder link is unavailable; if the terminal is reachable, determines a first buffering time, buffers the downlink data, and / or starts a timer according to the first buffering time; if the terminal is not reachable, performs at least one of buffering the downlink data, starting a timer according to a default buffering time, and marking the downlink data as unreachable.

[0310] In one embodiment, the receiver is further configured to, if the feeder link is available, receive, by the proxy network element, the downlink data, send the downlink data to the S-GW network element via the P-GW network element, and send, by the S-GW network element, a downlink data notification to the MME network element; determine, by the MME network element, a second buffering time and / or a downlink data expected arrival time, and return a downlink data notification ACK to the S-GW network element; the downlink data notification ACK carries at least one of the second buffering time, the downlink data expected arrival time, and a store-and-forward indication; and perform, by the S-GW network element, at least one of buffering the downlink data, starting a timer according to the second buffering time, and sending, via the P-GW network element and the proxy network element, a downlink data buffering success notification and / or the downlink data expected arrival time to the ground equipment.

[0311] In one embodiment, the transmitter is further configured to, if the service link is available, send, by the S-GW network element, the downlink data to the terminal via the eNodeB network element; delete, by the S-GW network element, the buffered downlink data upon receiving a downlink data sending success notification, and / or send, by the S-GW network element, the downlink data sending success notification to the proxy network element via the P-GW network element.

[0312] In one embodiment, the transmitter is further configured to, if the feeder link is available, forward, by the proxy network element, the downlink data sending success notification to the ground equipment; and delete, by the ground equipment, the buffered downlink data upon receiving the downlink data sending success notification.

[0313] In one embodiment, the transmitter is further configured to, if the service link is available, receive, by the MME network element, the downlink data sent by the S-GW network element, encrypt and integrity protect the downlink data to obtain processed downlink data, and send the processed downlink data to the terminal; delete, by the S-GW network element, the buffered downlink data upon receiving a downlink data sending success notification, and / or send, by the S-GW network element, the downlink data sending success notification to the proxy network element via the P-GW network element.

[0314] In one embodiment, the receiver is further configured to, if the service link is available, receive the uplink data sent by the terminal, and cache the uplink data; and the transmitter is further configured to, if the feeding link is available, forward the uplink data to the ground device.

[0315] In one embodiment, the transmitter is further configured to, if the service link is available, send the downlink data to the terminal via the MME network element and the eNodeB network element; and the SCEF network element is further configured to, upon receiving a downlink data sending success notification, delete the cached downlink data, and / or send the downlink data sending success notification to the proxy network element; and the proxy network element is further configured to, if the feeding link is available, forward the downlink data sending success notification to the ground device; and the ground device is further configured to, upon receiving the downlink data sending success notification, delete the cached downlink data.

[0316] In one embodiment, the receiver is further configured to, if the service link is available, receive the uplink data sent by the terminal, and cache the uplink data; and the transmitter is further configured to, if the feeding link is available, forward the uplink data to the ground device.

[0317] In one embodiment, the receiver is further configured to, the MME network element determines at least one of a third cache time, an uplink data expected arrival time, and a downlink data expected arrival time; the MME network element sends first information to the S-GW network element; the first information includes at least one of a store-and-forward instruction, an uplink data cache response instruction, and the third cache time; the MME network element sends second information to the terminal; the second information includes the uplink data expected arrival time and / or the downlink data expected arrival time.

[0318] In one embodiment, the receiver is further configured to, if the service link is available, receive the uplink data sent by the terminal, and cache the uplink data; and the transmitter is further configured to, if the feeding link is available, forward the uplink data to the ground device.

[0319] In an embodiment, the transmitter is further configured to, if the feeder link is available, send, by the proxy network element, the uplink data to the ground equipment, and / or delete the buffered uplink data upon receiving a successful uplink data sending notification.

[0320] In an embodiment, the receiver is further configured to, if the service link is available, receive, by the MME network element, the uplink data sent by the terminal, perform integrity check and decryption on the uplink data to obtain processed uplink data, and send the processed uplink data to the proxy network element; and the proxy network element is configured to perform at least one of buffering the processed uplink data, starting a timer according to the third buffering time, and sending an uplink data buffering success notification to the terminal via the MME network element.

[0321] In an embodiment, the receiver is further configured to determine, by the MME network element, at least one of a third buffering time, an uplink data expected arrival time, and a downlink data expected arrival time; send third information to the SCEF network element, wherein the third information comprises at least one of a store-and-forward indication, an uplink data buffering response indication, and the third buffering time; and send fourth information to the terminal, wherein the fourth information comprises the uplink data expected arrival time and / or the downlink data expected arrival time.

[0322] In an embodiment, the receiver is further configured to, if the service link is available, receive, by the proxy network element, the uplink data forwarded via the MME network element and the SCEF network element; and perform at least one of buffering the uplink data, starting a timer according to the third buffering time, and returning an uplink data buffering success notification to the terminal.

[0323] In an embodiment, a computer readable storage medium is provided, which stores a computer program. The computer program is executed by a processor to implement the steps in the above method embodiments.

[0324] In an embodiment, a computer program product is provided, which comprises a computer program. The computer program is executed by a processor to implement the steps in the above method embodiments.

[0325] It should be noted that the user information (including but not limited to user equipment information, user personal information, etc.) and data (including but not limited to data for analysis, stored data, displayed data, etc.) involved in the present application are all information and data authorized by the user or authorized by all parties, and the collection, use and processing of related data need to comply with relevant regulations.

[0326] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a non-volatile computer readable storage medium, and when executed, can include the processes of the above-mentioned embodiment methods. Any reference to memory, storage, database or other medium used in the embodiments provided in the present application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory or optical memory. Volatile memory can include random access memory (RAM) or external cache memory. As an illustration but not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM).

[0327] The technical features of the above embodiments can be combined in any way. In order to make the description simple, all possible combinations of the technical features in the above embodiments are not described, but as long as the combinations of the technical features do not exist, they should be considered as the scope of the present application.

[0328] The above embodiments only express several implementation manners of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent. It should be pointed out that for those skilled in the art, without departing from the concept of the present application, some modifications and improvements can be made, which are all within the scope of the present application. Therefore, the scope of the patent of the present application should be subject to the appended claims.

Claims

1. A data transmission method applied to a satellite device, the method comprising: receiving downlink data sent by a ground device and buffering the downlink data if a feeder link is available; buffering the downlink data if the downlink data arrives and the feeder link is unavailable; forwarding the downlink data to a terminal if a service link is available. 2.The method of claim 1, wherein the ground device determines whether the terminal is reachable according to a terminal context if the downlink data arrives and the feeder link is unavailable; if the terminal is reachable, determines a first buffering time, buffers the downlink data, and / or starts a timer according to the first buffering time; if the terminal is not reachable, at least one of the following is performed: buffering the downlink data, starting a timer according to a default buffering time, or marking the downlink data as unreachable. 3.The method of claim 1, wherein the satellite device comprises a MME network element, a S-GW network element, a P-GW network element, and a proxy network element; receiving downlink data sent by a ground device and buffering the downlink data if the feeder link is available, comprises: if the feeder link is available, the proxy network element receives the downlink data, sends the downlink data to the S-GW network element via the P-GW network element, and the S-GW network element sends a downlink data notification to the MME network element; the MME network element determines a second buffering time and / or a downlink data expected arrival time, and returns a downlink data notification ACK to the S-GW network element; the downlink data notification ACK carries at least one of the second buffering time, the downlink data expected arrival time, and a store-and-forward instruction; the S-GW network element performs at least one of the following: buffering the downlink data; starting a timer according to the second buffering time; sending a downlink data buffering success notification and / or the downlink data expected arrival time to the ground device via the P-GW network element and the proxy network element. 4.The method of claim 3, wherein the satellite device further comprises an eNodeB network element; forwarding the downlink data to a terminal if the service link is available, comprises: if the service link is available, the S-GW network element sends the downlink data to the terminal via the eNodeB network element; the S-GW network element deletes the buffered downlink data upon receiving a downlink data sending success notification, and / or sends the downlink data sending success notification to the proxy network element via the P-GW network element. 5.The method of claim 4, wherein after forwarding the downlink data to a terminal if the service link is available, the method further comprises: if the feeder link is available, the proxy network element forwards the downlink data sending success notification to the ground device; the ground device deletes the buffered downlink data upon receiving the downlink data sending success notification. 6.The method of claim 3, wherein forwarding the downlink data to a terminal if the service link is available, comprises: If the service link is available, the MME network element receives downlink data sent by the S-GW network element, performs encryption and integrity protection processing on the downlink data to obtain processed downlink data, and sends the processed downlink data to the terminal; If the service link is available, the S-GW network element receives uplink data sent by the terminal, and buffers the uplink data.

7. The method of claim 1, wherein the satellite device comprises an MME network element, an SCEF network element, and a proxy network element; if the feeder link is available, receiving downlink data sent by a ground device and buffering the downlink data, comprising: If the feeder link is available, the proxy network element receives the downlink data and sends the downlink data to the SCEF network element, which sends a downlink data notification to the MME network element; The MME network element determines a second buffering time and / or a downlink data expected arrival time, and returns a downlink data notification ACK to the SCEF network element; the downlink data notification ACK carries at least one of the second buffering time, the downlink data expected arrival time, and a store-and-forward indication; The SCEF network element performs at least one of: buffering the downlink data; starting a timer according to the second buffering time; sending a downlink data buffering success notification and / or the downlink data expected arrival time to the ground device via the proxy network element.

8. The method of claim 7, wherein the satellite device further comprises an eNodeB network element; if the service link is available, forwarding the downlink data to a terminal, comprising: If the service link is available, the SCEF network element sends the downlink data to the terminal via the MME network element and the eNodeB network element; The SCEF network element deletes the buffered downlink data upon receiving a downlink data sending success notification, and / or sends the downlink data sending success notification to the proxy network element; If the feeder link is available, the proxy network element forwards the downlink data sending success notification to the ground device; the ground device deletes the buffered downlink data upon receiving the downlink data sending success notification.

9. The method of claim 1, further comprising: If the service link is available, receiving uplink data sent by the terminal and buffering the uplink data; If the feeder link is available, forwarding the uplink data to the ground device.

10. The method of claim 9, wherein the satellite device comprises an MME network element, an S-GW network element, a P-GW network element, and a proxy network element; the method further comprises: The MME network element determines at least one of a third buffering time, an uplink data expected arrival time, and a downlink data expected arrival time; The MME network element sends first information to the S-GW network element, wherein the first information comprises at least one of a store-and-forward indication, an uplink data buffering response indication, and the third buffering time; The MME network element sends first information to the S-GW network element, wherein the first information comprises at least one of a store-and-forward indication, an uplink data buffering response indication, and the third buffering time; The MME network element sends second information to the terminal, wherein the second information comprises the uplink data expected arrival time and / or the downlink data expected arrival time.

11. The method of claim 10, wherein if the service link is available, receiving the uplink data sent by the terminal and buffering the uplink data comprises: if the service link is available, the proxy network element receives the uplink data forwarded by the S-GW network element and the P-GW network element; the proxy network element performs at least one of buffering the uplink data, starting a timer according to the third buffering time, and returning an uplink data buffering success notification to the terminal.

12. The method of claim 9, wherein if the feeder link is available, forwarding the uplink data to the ground equipment comprises: if the feeder link is available, the proxy network element sends the uplink data to the ground equipment, and / or, upon receiving an uplink data sending success notification, deleting the buffered uplink data.

13. The method of claim 10, wherein if the service link is available, receiving the uplink data sent by the terminal and buffering the uplink data comprises: if the service link is available, the MME network element receives the uplink data sent by the terminal, performs integrity check and decryption on the uplink data to obtain processed uplink data, and sends the processed uplink data to the proxy network element; the proxy network element performs at least one of buffering the processed uplink data, starting a timer according to the third buffering time, and sending an uplink data buffering success notification to the terminal via the MME network element.

14. The method of claim 12, wherein the satellite equipment comprises an MME network element, an SCEF network element, and a proxy network element; the method further comprises: the MME network element determines at least one of a third buffering time, an uplink data expected arrival time, and a downlink data expected arrival time; the MME network element sends third information to the SCEF network element, wherein the third information comprises at least one of a store-and-forward indication, an uplink data buffering response indication, and the third buffering time; the MME network element sends fourth information to the terminal, wherein the fourth information comprises the uplink data expected arrival time and / or the downlink data expected arrival time.

15. The method of claim 14, wherein if the service link is available, receiving the uplink data sent by the terminal and buffering the uplink data comprises: if the service link is available, the proxy network element receives the uplink data forwarded by the MME network element and the SCEF network element; the proxy network element performs at least one of buffering the uplink data, starting a timer according to the third buffering time, and returning an uplink data buffering success notification to the terminal.

16. A data transmission method applied to a ground equipment, the method comprising: if downlink data arrives and a feeder link is unavailable, buffering the downlink data; If the feeder link is available, the downlink data is sent to the satellite device; the satellite device caches the downlink data and forwards the downlink data to the terminal when the service link is available.

17. A data transmission method applied to a terminal, the method comprising: If the service link is available, receiving downlink data sent by a satellite device; If the feeder link is available, the downlink data is sent to the satellite device; the satellite device caches the downlink data and forwards the downlink data to the terminal when the service link is available.

18. A data transmission system comprising a ground device, a satellite device and a terminal; wherein If the feeder link is available, the downlink data is sent to the satellite device; the satellite device caches the downlink data and forwards the downlink data to the terminal when the service link is available. The terminal is configured to receive the downlink data.

19. A data transmission apparatus applied to a satellite device, the apparatus comprising: a storage module configured to, if the feeder link is available, receive downlink data sent by a ground device and cache the downlink data; the ground device is configured to cache the downlink data when the downlink data arrives and the feeder link is unavailable; a forwarding module configured to, if the service link is available, forward the downlink data to a terminal. a receiver and a transmitter; 20. A communication device comprising: wherein the receiver is configured to, if the feeder link is available, receive downlink data sent by a ground device and cache the downlink data; the ground device is configured to cache the downlink data when the downlink data arrives and the feeder link is unavailable; the transmitter is configured to, if the service link is available, forward the downlink data to a terminal.

21. A computer readable storage medium having stored thereon a computer program, wherein the computer program, when executed by a processor, causes the processor to implement the steps of the method of any one of claims 1 to 17.

22. A computer program product comprising a computer program, wherein the computer program, when executed by a processor, causes the processor to implement the steps of the method of any one of claims 1 to 17. ​

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