Store-and-forward communication method

Abstract

Disclosed in the present invention is a store-and-forward communication method. The method is used in a satellite, wherein the satellite is communicatively connected to at least one UE and a terrestrial network so as to complete data transmission, and a second timer and a second maximum timing duration are set in the satellite. The method comprises: when the satellite is connected to the UE, sending downlink data to the UE / receiving uplink data from the UE when the second timer has not exceeded the second maximum timing duration; and when the satellite is connected to the terrestrial network, sending uplink data to the terrestrial network / receiving downlink data from the terrestrial network. According to the present invention, the second timer is associated with a first timer, and the satellite keeps connection with the UE in the range of the second maximum timing duration, so that data transmission can be directly carried out, thereby effectively improving the data transmission efficiency between the satellite and the UE.

Description

Store-and-forward communication method Technical Field

[0001] The present invention relates to wireless communication technology, and in particular to a store-and-forward communication method. Background Art

[0002] Please refer to Figures 1A and 1B. Figure 1A illustrates the workflow of a conventional NTN system in normal mode. In normal mode, a satellite-accessed UE exchanges signaling and data services with a terrestrial network. This requires that both the service link and feeder link between the satellite-accessed UE and the remote terrestrial network be active simultaneously. Therefore, when the UE interacts with the satellite via the service link, a continuous end-to-end connection path exists between the UE, the satellite, and the terrestrial network.

[0003] Figure 1B illustrates the workflow of a conventional NTN system in S&F mode. The S&F mode is a store-and-forward mode, meaning that the end-to-end exchange of signaling / data traffic is now handled as a combination of two non-simultaneous steps (steps A and B in Figure 1B). In step A, the satellite is not simultaneously connected to the terrestrial network, and signaling / data is exchanged between the UE and the satellite. This means that the satellite can operate a service link without an active feeder link connection. In step B, the satellite is connected to the terrestrial network, enabling communication between the satellite and the terrestrial network. This means that the satellite can operate a feeder link without an active service link connection. Thus, the satellite moves from being connected to the UE in step A to being connected to the terrestrial network in step B.

[0004] Compared to traditional LTE NB IoT and IoT NTN, there is now a need to utilize the S&F mode to support delay-tolerant services. However, the current design of the LTE S1 / Uu interface protocol and 5G-related content does not take this requirement into account. Therefore, it is necessary to consider how to enhance the existing network and UE side to support data transmission in the S&F mode for delay-tolerant services.

[0005] Changes in network nodes, such as changes in the satellite serving the UE or the gateway connecting to the ground, can cause changes in the interface. Therefore, enhancing the interface to support link switching in S&F mode is a challenge that needs to be addressed.

[0006] In general, during data transmission in the S&F mode of the NTN system, during the initial connection phase (step A), when the satellite connects to the UE, the UE enters the connected state. While in the connected state, the UE performs radio link monitoring (RLM). The satellite continues to move until it eventually loses connection with the UE. During the RLM process, the UE detects a radio link failure (RLF). Since security is not yet activated, the UE enters the idle state. The satellite then continues to move, entering step B. At this point, the satellite can send and receive information with external networks (such as ground stations). The satellite then continues to move, returning to step A. When the satellite needs to send information to the UE again, it cannot do so because the UE has already entered the idle state.

[0007] Summary of the Invention

[0008] In view of this, it is necessary to provide a store-and-forward communication method, which aims to solve the data transmission in the S&F mode that can support delay-tolerant service in the NTN system.

[0009] The present invention provides a store-and-forward communication method for use in a satellite, wherein the satellite is communicatively connected to at least one UE and a ground network to complete data transmission, a second timer and a second maximum timing time are set in the satellite, and the method comprises: when the satellite is connected to the UE, sending downlink data to the UE / receiving uplink data from the UE when the second timer does not exceed the second maximum timing time; and when the satellite is connected to the ground network, sending uplink data to the ground network / receiving downlink data from the ground network.

[0010] The present invention also provides a store-and-forward communication method for use in a UE, wherein the UE is connected to a satellite and a ground network for communication to complete data transmission, a second timer and a second maximum timing time are set in the satellite, and the method includes: when the UE is connected to the satellite, sending a first message carrying uplink data to the satellite / receiving a second message carrying downlink data.

[0011] The first message is at least one of the following:

[0012] RRCEarlyDataRequest message; and

[0013] PURConfigurationRequest message.

[0014] The second message is at least one of the following:

[0015] Paging message;

[0016] RRCEarlyDataComplete message; and

[0017] RRCConnectionRelease message.

[0018] After the UE is disconnected from the satellite, the UE enters any of the following states:

[0019] Maintain RRC connection state;

[0020] Entering the RRC idle state; and

[0021] Enter the RRC IOT idle state.

[0022] The present invention also provides a store-and-forward communication method for use in a terrestrial network, wherein the terrestrial network is connected to a satellite and a UE for communication to complete data transmission. The method comprises: the terrestrial network receives a third message carrying uplink data from the satellite / the terrestrial network sends a fourth message carrying downlink data to the terrestrial network, wherein the third message is a NAS message / initial UE message, and the fourth message is a paging message.

[0023] After the ground network is disconnected from the satellite, it enters at least one of the following states:

[0024] Maintain ECM / CM connection status; and

[0025] Enter ECM / CM suspend state.

[0026] The present invention reflects the connection status of the air interface by setting a second timer on the satellite side, further quickly determines whether to directly send downlink data or receive uplink data when connected to the UE, and improves the efficiency of storage and forwarding.

[0027] The present invention also provides a store-and-forward communication method for use in a user equipment (UE), wherein the UE is connected to a satellite and a terrestrial network for data transmission. The method comprises: when the UE is connected to the satellite, sending a first message carrying uplink data to the satellite and receiving a second message carrying downlink data. The present invention significantly improves the data transmission efficiency of UEs in an NTN system.

[0028] A store-and-forward communication method for use in a terrestrial network, wherein the terrestrial network is communicatively connected to a satellite and a user equipment (UE) to perform data transmission. The method comprises: the terrestrial network receiving a third message carrying uplink data from the satellite and sending a fourth message carrying downlink data to the satellite. The third message is a NAS message or an initial UE message, and the fourth message is a paging message. This invention significantly improves the data transmission efficiency of the terrestrial network of an NTN system.

[0029] The present invention also provides a store-and-forward communication method, which is used in a satellite, wherein the satellite is communicatively connected to a terrestrial network and a user equipment (UE) to perform data transmission. The method comprises: receiving a fifth message carrying uplink data from the UE when the satellite is connected to the UE; and receiving a sixth message carrying downlink data from the terrestrial network when the satellite is connected to the terrestrial network. The present invention significantly improves the data storage and forwarding efficiency of satellites in an NTN system.

[0030] In order to solve the problem of feeder link switching, the present invention also provides a store-and-forward communication method for use in a satellite, wherein the satellite is communicatively connected with at least one UE and a terrestrial network to complete data transmission, wherein the method comprises:

[0031] When the satellite is connected to the UE, the satellite decides to suspend the RRC connection with the UE. The satellite performs an RRC connection suspension operation on the UE, wherein the UE stores an AS context and suspends SRBs / DRBs, and the UE enters an IOT idle (suspended) state. When the satellite is connected to the terrestrial network, the satellite notifies the terrestrial network that the UE maintains the RRC connection state. The satellite performs an ECM / CM connection suspension operation on the terrestrial network, wherein the satellite and the terrestrial network store information related to resuming the RRC connection, and the terrestrial network enters an ECM / CM suspended state.

[0032] The present invention also provides a store-and-forward communication method for use in a satellite, wherein the satellite is communicatively connected to at least one UE and a terrestrial network to complete data transmission. The method comprises: when the satellite is connected to the UE, the satellite determines to maintain an RRC connection with the UE, the satellite performs an RRC connection maintenance operation for the UE, wherein the UE suspends RLM / RLF and starts an AS / NAS timer. When the satellite is connected to the terrestrial network, the satellite notifies the terrestrial network of the UE's RRC connection maintenance status; the satellite performs an ECM / CM connection suspension operation for the terrestrial network, wherein the satellite and the terrestrial network store information related to resuming the RRC connection, and the terrestrial network enters an ECM / CM suspension state.

[0033] The present invention also provides a store-and-forward communication method for use in a satellite, wherein the satellite is communicatively connected to at least one UE and a terrestrial network to complete data transmission. The method comprises: when the satellite is connected to the UE, the satellite / the UE releases the RRC connection and performs an RRC connection release operation, wherein the UE enters an RRC connection idle state; when the satellite releases the RRC connection, the satellite triggers an RRC release procedure and sends an RRC connection release message to the UE; wherein the condition for the UE to release the RRC connection is any one of the following: the UE has completed data transmission, a first timer in the UE has expired, the UE detects RLF, and the UE independently decides to enter RRC idle. When the satellite is connected to the terrestrial network, the satellite notifies the terrestrial network to enter an RRC suspend state; the satellite performs the RRC suspend operation performed by the terrestrial network, and stores information related to resuming the RRC connection.

[0034] The present invention obtains the connection status of the UE when the satellite is connected to the UE, promptly notifies the ground network of the connection status of the UE after disconnection, and synchronously adjusts the connection status with the ground network, thereby achieving flexible switching of the service link and the feeder link. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without inventive efforts. Among them:

[0036] FIG1A shows the working process of the NTN system in the normal mode in the prior art;

[0037] FIG1B shows the working process of the NTN system in the S&F mode in the prior art;

[0038] FIG2 is a diagram of an NTN system according to an embodiment of the present invention;

[0039] 3 is a flow chart of a store-and-forward communication method according to a first embodiment of the present invention;

[0040] 4 is a flow chart of a store-and-forward communication method according to a second embodiment of the present invention;

[0041] 5 is a flow chart of a store-and-forward communication method according to a third embodiment of the present invention;

[0042] FIG6 is an embodiment of a NAS message or initial UE message setting;

[0043] FIG7 is an example of specific message content of a UE;

[0044] 8 is a flow chart of a store-and-forward communication method according to a fourth embodiment of the present invention;

[0045] 9 is a flowchart of a store-and-forward communication method according to a fifth embodiment of the present invention;

[0046] 10 is a flowchart of a store-and-forward communication method according to a sixth embodiment of the present invention;

[0047] 11 is a flow chart of a store-and-forward communication method according to a seventh embodiment of the present invention;

[0048] 12 is a flow chart of a store-and-forward communication method according to an eighth embodiment of the present invention;

[0049] 13A is a flowchart of a store-and-forward communication method according to a ninth embodiment of the present invention;

[0050] 13B is a detailed flow chart of a store-and-forward communication method according to a ninth embodiment of the present invention;

[0051] 14 is a flowchart of a store-and-forward communication method according to a tenth embodiment of the present invention;

[0052] 15A is a flow chart of a store-and-forward communication method according to an eleventh embodiment of the present invention;

[0053] FIG15B is a detailed flow chart of the store-and-forward communication method in the eleventh embodiment of the present invention.

[0054] 16A is a flow chart of a store-and-forward communication method according to a twelfth embodiment of the present invention;

[0055] 16B is a detailed flow chart of a store-and-forward communication method according to a twelfth embodiment of the present invention;

[0056] FIG17 is a flow chart showing an initial connection of an NTN system according to an embodiment of the present invention;

[0057] FIG18 is a module diagram of a satellite according to one embodiment of the present invention;

[0058] FIG19 is a module diagram of a UE in one embodiment of the present invention;

[0059] FIG20 is a module diagram of a ground network in one embodiment of the present invention. DETAILED DESCRIPTION

[0060] The embodiments of the present disclosure describe in detail the technical matters, process steps, implementation objectives and effects with reference to the accompanying drawings, as described below. Specifically, the terms in the embodiments of the present disclosure are only used for the purpose of describing specific embodiments, rather than limiting the present disclosure.

[0061] Please refer to FIG2 , which shows an NTN system according to an embodiment of the present invention. The NTN system may include a satellite 10 , a UE 20 , and a terrestrial network 30 .

[0062] In this embodiment, a first timer and a first maximum timing time are set in the UE 20 . The UE 20 sends the first maximum timing time and an RRC request message to the satellite and starts the first timer.

[0063] In the satellite 10 a second timer is provided, and a second maximum timer duration is provided.

[0064] When the satellite 10 is connected to the UE 20 , the satellite 10 is configured to send uplink data to the UE 20 or receive downlink data from the UE 20 when the second timer does not exceed the second maximum timing time.

[0065] The satellite 10 configures a first timer and a first maximum timing time for the UE 20 / the UE 20 sets the first timer and the first maximum timing time, for example, redefines the first maximum timing time for the existing T300 timer, such as 30 seconds or 60 seconds.

[0066] If UE20 sets the first timer and the first maximum timing time, it needs to send the first timer and the first maximum timing time to satellite 10, and satellite 10 needs to set the second timer and the second maximum timing time according to the first timer and the first maximum timing time.

[0067] In this embodiment, the second timer is associated with the first timer, and the second maximum timing time is associated with / the same as the first timing time.

[0068] In this embodiment, the first maximum timing time is set to one or more fixed values, or the first maximum timing time is associated with the interval period of the satellite 10.

[0069] When the satellite 10 is connected to the ground network 30 , it is used to send uplink data to the ground network / receive downlink data from the ground network 30 .

[0070] In this embodiment, the state of UE 20 may be a fixed state, or the state may change during the process of connecting with the satellite.

[0071] For example, UE20 is in the IOT idle state throughout the entire process, where the IOT idle state is the RRC connection state when UE20 suspends resources related to the RRC connection (in subsequent implementations, the IOT idle state is the same as the definition here). When this solution is improved based on the 4G MO-EDT scenario using the EDT-CP solution, UE20 is in the idle state throughout the entire process.

[0072] When the UE 20 is connected to the satellite 10 , the state changes include: if the UE 20 has data to send or receive, the RRC state of the UE 20 needs to be changed from the idle state or the IOT idle state to the RRC connected state.

[0073] When the terrestrial network 30 is connected to the satellite 10, the state changes include: if the terrestrial network needs to receive data from the satellite 10 or send data, the ECM / CM state of the terrestrial network needs to change from the ECM / CM disconnected state to the ECM / CM connected state.

[0074] In this embodiment, if the terrestrial network is LTE, the connection status of the terrestrial network includes: ECM connection / suspend state; if the terrestrial network is 5G, the connection status of the terrestrial network includes: CM connection / suspend state.

[0075] Satellite 10 can provide communication coverage for communication devices in the geographical area it covers, and can communicate with terminal devices (including: UE 20, ground network 30, etc.) located in the coverage area. Optionally, satellite 10 can be a space station, and satellite 10 or space station carries such as: base stations, core networks, mobile switching centers, relay stations, access points, vehicle-mounted devices, wearable devices, hubs, switches, bridges, routers, network-side devices in 4G / 5G / 6G networks, etc. UE 20 includes, but is not limited to, a device configured to receive / send communication signals via a wired connection, such as a Public Switched Telephone Network (PSTN), a Digital Subscriber Line (DSL), a digital cable, a direct cable connection; and / or another data connection / network; and / or via a wireless interface, such as a cellular network, a Wireless Local Area Network (WLAN), a digital television network such as a DVB-H network, a satellite network, an AM-FM broadcast transmitter; and / or another user equipment; and / or an Internet of Things (IoT) device. A UE 20 configured to communicate via a wireless interface may be referred to as a "wireless communication terminal," "wireless terminal," or "mobile terminal." Examples of mobile terminals include, but are not limited to, satellite or cellular telephones; Personal Communications System (PCS) terminals that can combine cellular radiotelephones with data processing, fax, and data communication capabilities; PDAs that can include radiotelephones, pagers, Internet / Intranet access, web browsers, notepads, calendars, and / or Global Positioning System (GPS) receivers; and conventional laptop and / or palmtop receivers or other electronic devices that include radiotelephone transceivers. User equipment can be referred to as an access terminal, subscriber unit, subscriber station, mobile station, mobile station, remote station, remote user equipment, mobile device, wireless communication device, or user agent. An access terminal can be a cellular phone, cordless phone, Session Initiation Protocol (SIP) phone, Wireless Local Loop (WLL) station, Personal Digital Assistant (PDA), a handheld device with wireless communication capabilities, a computing device or other processing device connected to a wireless modem, an in-vehicle device, a wearable device, a user device in a network or a user device in a future evolved PLMN, etc., such as a mobile phone, a laptop computer, etc.The ground network 30 is a network composed of network equipment located on the ground, which can be a 4G, 5G, 6G, or future network. The ground network 30 includes at least one of the following: a core network, a switch, a gateway, a server, a base station, etc.

[0076] In this invention, when the NTN system transmits data in S&F mode, uplink / downlink data is transmitted as part of other messages to improve data transmission efficiency. Alternatively, a second timer and a second maximum timer are set on the satellite side, and the first timer and first maximum timer are configured for the UE via the satellite. Alternatively, the UE can set the first timer and first maximum timer, and the second timer is linked to the first timer. The satellite maintains a connection with the UE within the second maximum timer range, allowing direct data transmission. This effectively ensures the UE's connection status and improves data transmission efficiency. The connection status between the UE and the satellite, as well as the connection status between the satellite and the terrestrial network, can also be set to ensure the orderly operation of delay-tolerant services.

[0077] Please refer to FIG. 3 , which is a flow chart of a store-and-forward communication method according to a first embodiment of the present invention. In this embodiment, the method is applied to a satellite 10, wherein the satellite 10 is in communication with at least one UE 20 and a terrestrial network 30 to complete data transmission. A second timer and a second maximum timer duration are set in the satellite 10. The method includes:

[0078] In step S200 , when the satellite 10 is connected to the UE 20 , downlink data is sent to the UE 20 and uplink data is received from the UE 20 when the second timer does not exceed a second maximum time.

[0079] In step S202 , when the satellite 10 is connected to the terrestrial network 30 , uplink data is sent to the terrestrial network 30 and downlink data is received from the terrestrial network 30 .

[0080] In other embodiments of the present invention, step S204 is further included. If the ground network 30 receives uplink data / sends downlink data, the satellite 10 executes the interface resource release process of the ground network 30, and the ground network 30 releases the bearer.

[0081] In this embodiment, the satellite 10 configures a first timer and a first maximum timing time for the UE 20 / the UE 20 sets the first timer and the first maximum timing time, for example, redefines the first maximum timing time for the existing T300 timer, such as 30 seconds or 60 seconds.

[0082] If UE20 sets the first timer and the first maximum timing time, it needs to send the first timer and the first maximum timing time to satellite 10, and satellite 10 needs to set the second timer and the second maximum timing time according to the first timer and the first maximum timing time.

[0083] In this embodiment, the second timer is associated with the first timer, and the second maximum timing time is associated with / the same as the first timing time.

[0084] In this embodiment, the first maximum timing time is set to one or more fixed values, or the first maximum timing time is associated with the interval period of the satellite 10.

[0085] In the embodiment of the present invention, the second timer is associated with the first timer, and the satellite maintains connection with the UE within the second maximum timing range, and data transmission can be performed directly, effectively improving the data transmission efficiency between the satellite and the UE.

[0086] Please refer to FIG. 4 , which is a flow chart of a store-and-forward communication method according to a second embodiment of the present invention.

[0087] When UE20 is connected to satellite 10, satellite 10 receives the RRC request message sent by UE20.

[0088] In this embodiment, the RRC request message is an RRC EarlyDataRequst message.

[0089] In this embodiment, when the satellite 10 is connected to the UE 20 , in step S210 , the satellite 10 directly sends an RRC completion message carrying downlink data to the UE 20 within the second maximum timing time range of the second timer.

[0090] In this embodiment, the RRC completion message is an RRC EarlyDataComplete message.

[0091] In step S211 , the satellite 10 sends a paging message to the UE 20 when the second timer exceeds a second maximum time.

[0092] In step S212 , the satellite 10 receives the RRC EarlyDataRequest message sent by the UE 20 .

[0093] In step S213, the satellite 10 determines whether the RRC completion message includes uplink data.

[0094] If the RRC request message does not include uplink data, then in step S214 , the satellite sends an RRC completion message to the UE 20 .

[0095] If the RRC request message carries uplink data, the satellite stores the uplink data. If the second timer exceeds the second maximum timing time, the satellite 10 sends a paging message in step S215.

[0096] Optionally, regardless of whether the second timer exceeds the second maximum timing time, after receiving the RRC request message, when the satellite 10 is connected to the ground network, it is necessary to send the stored uplink data to the ground network and receive downlink data from the ground network in step S202, and store the downlink data.

[0097] When the satellite 10 stores downlink data that needs to be sent, in step S216 , the satellite 10 sends an RRC completion message carrying the downlink data to the UE 20 .

[0098] If the second timer does not exceed the second maximum time, the satellite 10 directly sends an RRC completion message carrying the downlink data to the UE 20 when the satellite 10 has downlink data stored therein that needs to be sent.

[0099] In this embodiment, the first timer is started when the UE sends an RRC request message.

[0100] In this embodiment, the second timer is started when an RRC request is received.

[0101] In other embodiments of the present invention, the RRC request message is an RRCConnectionResumeRequest message, and the RRC completion message is an RRCConnectionRelease message.

[0102] This embodiment may be an improvement of the 4G mobile station initiated early data transmission (MO-EDT) scenario using the early data transmission control plane (EDT-CP) solution or the MO-EDT scenario using the early data transmission user plane (EDT-UP) solution, wherein when this solution is improved based on the MO-EDT scenario using the EDT-UP solution, UE20 is in the IOT idle state throughout the entire process, wherein the IOT idle state is the RRC connection state of UE20 when UE20 suspends the relevant resources connected to the RRC (in subsequent embodiments, the TOT idle state is the same as the definition here). In other embodiments of the present invention, such as in LTE, the IoT idle state is a type of idle state, and in 5G NR, the IoT idle state is an idle state or an inactive state. When this solution is improved based on the 4G MO-EDT scenario using the EDT-CP solution, UE20 is in an idle state throughout the entire process.

[0103] In this embodiment, the satellite carries uplink data / downlink data in the RRC completion message, thereby improving the communication efficiency of the NTN system.

[0104] Please refer to FIG5 , which is a flow chart of a store-and-forward communication method according to a third embodiment of the present invention.

[0105] In this embodiment, the satellite 10 is connected to a plurality of UEs, that is, UEs 1 to n are all under the coverage of the satellite 10 .

[0106] In step S2001, when the satellite 10 receives RRC request messages (such as RRC EarlyData Request messages) from multiple UEs, it integrates the RRC request messages from the multiple UEs into one NAS message or initial UE message.

[0107] It can be understood that the RRC request message includes the S-TMSI (temporary UE identification number) of each UE, which are marked as msg1-1 to msg1-n respectively.

[0108] Furthermore, there are various forms of NAS (Non-Access Stratum) messages or initial UE messages.

[0109] One method is to carry all the information of each UE under each UE ID, and then list the information of n UEs in sequence.

[0110] Another method is to extract the common part of each UE and send it only once, while the UE-specific information is carried under the information of each UE.

[0111] Please refer to FIG. 6 and FIG. 7 . FIG. 6 shows an implementation of a NAS message or initial UE message setting; FIG. 7 shows an example of specific message content of a UE.

[0112] When the satellite 10 is connected to the terrestrial network 30 , in step S2004 , the satellite 10 sends a NAS message or an initial UE message and indication information to the terrestrial network 30 .

[0113] In step S2006, the satellite 10 receives the data response information, wherein the ground network 30 obtains the downlink data requirements required by multiple UEs / uplink data sent by multiple UEs based on the indication information and the NAS message, and integrates the downlink data required by the multiple UEs into a data response message and sends it to the satellite 10.

[0114] In step S2008, the satellite 10 decomposes the data response message into multiple sub-data response messages and directly sends them to multiple UEs when the second timer does not exceed the second maximum timing time, or when the second timer exceeds the second maximum timing time, the satellite sends a paging message to the multiple UEs and then sends the sub-data response messages.

[0115] In this embodiment, the satellite 10 combines multiple RRC request messages into a NAS message or an initial UE message and sends it to the ground network. The ground network disassembles the NAS message or the initial UE message, obtains the downlink data requirements required by multiple UEs / uplink data sent by multiple UEs, and sends a data response message to the satellite, thereby improving the efficiency of the delay-tolerant service.

[0116] Please refer to FIG. 8 , which is a flow chart of a store-and-forward communication method according to a fourth embodiment of the present invention.

[0117] When the satellite 10 is connected to the ground network 30 , in step S222 , the satellite 10 receives a paging message from the ground network 30 .

[0118] In step S224, the satellite 10 determines whether the paging message carries downlink data.

[0119] If the paging message does not carry downlink data, then in step S225, the satellite 10 receives downlink data from the ground network 30. The satellite 10 stores the downlink data.

[0120] If the paging message carries downlink data, the satellite 10 stores the downlink data.

[0121] When the satellite 10 is connected to the UE 20 , in step S226 , the satellite 10 sends a paging message to establish an RRC connection with the UE 20 when the second timer exceeds the second maximum timer time. The satellite 10 sends downlink data to the UE 20 .

[0122] In step S228, the satellite directly sends downlink data to the UE when the second timer does not exceed a second maximum timing time.

[0123] The technical solution of this embodiment can also be an improvement based on the 4G early data transmission control plane (EDT-CP) solution for the mobile terminal early data transmission (MT-EDT) scenario, in which UE20 is in an idle state throughout the process.

[0124] The solution in this embodiment uses paging information to carry downlink data, which reduces the number of data transmission times and improves efficiency.

[0125] Please refer to FIG. 9 , which is a flow chart of a store-and-forward communication method according to a fifth embodiment of the present invention.

[0126] In step S230, when the satellite 10 is connected to the UE 20, the satellite 10 receives a PUR request message carrying data size information from the UE 20 and determines whether to allocate a PUR to the UE and the number of PURs to be allocated.

[0127] In step S232, the satellite 10 sends an RRC completion message to the UE, wherein the RRC completion message is an RRCConnectionRelease message. The RRCConnectionRelease message includes PUR configuration information, a PUR timer, and a third maximum timer, and the UE 20 performs configuration according to the RRCConnectionRelease message.

[0128] In step S234, if the PUR timer exceeds the third maximum time, it indicates that the UE 20 fails to configure the PUR, and the satellite 10 resends the paging message.

[0129] If the PUR timer is within the third maximum timing time range, in the PUR user plane (UP) solution, it is necessary to proceed to step S236, and the satellite 10 sends maximum timing advance (TA) related information and an RRCConnectionRelease message carrying downlink data to the UE20.

[0130] If the PUR timer is within the third maximum timing time range, in the PUR user plane (CP) solution, it is necessary to proceed to step S238, and the satellite 10 sends an RRC EarlyDataComplete message carrying TA related information and downlink data to the UE 20.

[0131] This embodiment can be an improvement on the PUR solution based on 4G. This embodiment uses the PUR timer and the RRCConnectionRelease message / RRC EarlyDataComplete message to carry downlink data, thereby improving the efficiency of the delay tolerance service of the NTN system.

[0132] Please refer to FIG. 10 , which is a flow chart of a store-and-forward communication method according to a sixth embodiment of the present invention.

[0133] The method in this embodiment is used in UE 20, wherein the UE 20 is connected to the satellite 10 and the ground network to complete data transmission. The method includes:

[0134] When the UE 20 is connected to the satellite 10 , in step S110 , the UE 20 sends a first message carrying uplink data to the satellite 10 .

[0135] In step S120 , UE 20 receives a second message carrying downlink data from satellite 10 .

[0136] In this embodiment, the first message is at least one of the following:

[0137] RRCConnectionResumeRequest message

[0138] RRCEarlyDataRequest message; and

[0139] PURConfigurationRequest message.

[0140] In this embodiment, the second message is at least one of the following:

[0141] Paging message;

[0142] RRCEarlyDataComplete message; and

[0143] RRCConnectionRelease message.

[0144] In this embodiment, the UE 20 sets a first timer and a first maximum timing time; or

[0145] Receive timer configuration information from the satellite 10, and configure the first timer and the first maximum timing time according to the timer configuration information, wherein the first timer is associated with the second timer.

[0146] In this embodiment, the satellite 10 configures a first timer and a first maximum timer duration for the UE 20. The satellite 10 sets a second timer and a second maximum timer duration according to the first timer and the first maximum timer duration of the UE 20.

[0147] In another embodiment of the present invention, the UE 20 sets the first timer and the first maximum timer duration. The satellite 10 receives the first timer and the first maximum timer duration sent by the UE 20 and sets a second timer to the second maximum timer duration.

[0148] In this embodiment, the second timer is associated with the first timer, and the second maximum timing time is associated with or equal to the first maximum timing time.

[0149] In this embodiment, the first maximum timing time is set to one or more fixed values, or the first maximum timing time is associated with the interval period of the satellite.

[0150] In this embodiment, when the UE is connected to / disconnected from the satellite, the UE enters any one of the following states:

[0151] Maintain RRC connection state;

[0152] Entering the RRC idle state; and

[0153] Enter the RRC IOT idle state.

[0154] In other embodiments of the present invention, UE 20 initially performs RACH access to satellite 10 and sends a service request to satellite 10. Satellite 10 stores NAS PDUs associated with UE 20. If UE 20 is not configured with SRBs and DRBs and the UE AS context is not set, satellite 10 may choose to release the RRC connection with UE 20. Of course, UE 20 may also choose to enter the idle state on its own.

[0155] When satellite 10 covers UE 20 again, satellite 10 initiates a paging message to establish an RRC connection. After the connection, UE 20 will remain in the RRCL connected state or enter the IOT idle state.

[0156] For example, if satellite 10 decides to suspend the RRC connection, it sends an RRCConnectionRelease message to UE 20. The RRCConnectionRelease message includes a new release cause or a new identity. UE 20 stores the AS context, suspends the SRB and DRB, and enters the IOT idle state.

[0157] In this embodiment, the specific contents of the connection and data transmission between the UE 20 and the satellite 10 are the same as those in the aforementioned first to fifth embodiments and the subsequent ninth to twelfth embodiments.

[0158] In this embodiment, no matter what state the UE 20 is in or will be in, it is necessary to inform the satellite 10 in a timely manner.

[0159] Please refer to FIG. 11 , which is a flow chart of a store-and-forward communication method in an eighth embodiment.

[0160] The method in this embodiment is used in a terrestrial network 30, wherein the terrestrial network 30 is in communication with a satellite 10 and a UE 20 to complete data transmission. The method includes:

[0161] At S110 ′, the ground network 30 receives a third message carrying uplink data from the satellite 10 .

[0162] In this embodiment, the third message is a NAS message / initial UE message.

[0163] In S120 ′, the terrestrial network 30 sends a fourth message carrying downlink data to the satellite 10 .

[0164] In this embodiment, the fourth message is a paging message.

[0165] In this embodiment, after the ground network 30 is disconnected from the satellite 10, it enters at least one of the following states:

[0166] Maintain ECM / CM connection status; and

[0167] Enter ECM / CM suspend state.

[0168] In this embodiment, if the terrestrial network is LTE, the connection status of the terrestrial network includes: ECM connection / suspend state; if the terrestrial network is 5G, the connection status of the terrestrial network includes: CM connection / suspend state.

[0169] In this embodiment, the connection between the terrestrial network 30 and the satellite 10 and the specific contents of the data transmission are the same as those in the aforementioned first to fifth embodiments and the subsequent ninth to twelfth embodiments.

[0170] In this embodiment, no matter what state the ground network 30 is in or will be in, the satellite 10 needs to be informed in a timely manner.

[0171] Please refer to FIG. 12 , which is a flow chart of a store-and-forward communication method in a ninth embodiment.

[0172] The method in this embodiment is used in a satellite 10, wherein the satellite 10 is in communication with a ground network 30 and a UE to complete data transmission. The method includes:

[0173] In step S130, the satellite 10 receives a fifth message carrying uplink data from the UE 20 when connected to the UE 20. Furthermore, in step S140, the satellite 10 receives a sixth message carrying downlink data from the terrestrial network 30 when connected to the terrestrial network 30. The present invention significantly improves the data storage and forwarding efficiency of satellites in the NTN system.

[0174] In this embodiment, the fifth message is any one of the following:

[0175] RRCEarlyDataRequest message; and

[0176] PURConfigurationRequest message.

[0177] In this embodiment, the sixth information is at least one of the following:

[0178] Paging message;

[0179] RRCEarlyDataComplete message; and

[0180] RRCConnectionRelease message.

[0181] In this embodiment, the satellite 10 configures a first timer and a first maximum timer duration for the UE 20. The satellite 10 sets a second timer and a second maximum timer duration according to the first timer and the first maximum timer duration of the UE 20.

[0182] In another embodiment of the present invention, the UE 20 sets the first timer and the first maximum timer duration. The satellite 10 receives the first timer and the first maximum timer duration sent by the UE 20 and sets a second timer to the second maximum timer duration.

[0183] In this embodiment, the second timer is associated with the first timer, and the second maximum timer duration is associated with the first maximum timer duration.

[0184] In this embodiment, the first maximum timing time is set to one or more fixed values, or the first maximum timing time is associated with the interval period of the satellite.

[0185] In this embodiment, the connection and data transmission between the satellite 10 and the UE 20 and the terrestrial network 30 are the same as those in the aforementioned first to fifth embodiments and the subsequent ninth to twelfth embodiments.

[0186] Please refer to FIG. 13A , which is a flow chart of a store-and-forward communication method in a tenth embodiment.

[0187] The method in this embodiment is used in a satellite 10, wherein the satellite 10 is in communication with at least one UE 20 and a ground network 30 to complete data transmission, wherein the method includes:

[0188] When the satellite is connected to the UE, the satellite decides to suspend the RRC connection with the UE. In step S300, the satellite performs an RRC connection suspension operation for the UE. In this embodiment, the UE 20 stores the AS context and suspends the SRB / DRB, and the UE enters the IOT idle state.

[0189] Please refer to FIG. 13B , which is a detailed flowchart of the store-and-forward communication method in the ninth embodiment of the present invention.

[0190] In this embodiment, when the satellite is connected to the terrestrial network, in step S302, the satellite 10 notifies the terrestrial network 30 that the RRC connection of the UE 20 enters the IOT idle state, and performs the ECM / CM connection suspension operation of the terrestrial network 30.

[0191] In this embodiment, the ground network 30 and the satellite 10 store information related to resuming the CM / CM connection, and the ground network 30 enters a suspended state. In other embodiments of the present invention, the suspended state shown is an ECM / CM suspended state.

[0192] When the satellite is connected to the terrestrial network, in step S310, the satellite 10 receives downlink data from the terrestrial network 30. The satellite 10 stores the received downlink data.

[0193] In step S311, the satellite 10 performs an ECM / CM connection recovery process with the terrestrial network 30, and the terrestrial network enters a connected state. In other embodiments of the present invention, the connection state shown is an ECM / CM connection state.

[0194] When the satellite is connected to the UE, in step S311 , the satellite 10 sends a paging message to the UE 20 .

[0195] In step S312 , the satellite 10 performs an RRC connection recovery procedure with the UE 20 .

[0196] In this embodiment, the UE 20 recovers the suspended SRB / DRB and re-establishes the connection access stratum (AS) security, and the UE 20 enters the RRC connected state.

[0197] In step S314 , the satellite transmits the stored downlink data to UE 20 , and UE 20 receives the downlink data.

[0198] When the satellite 10 is connected to the UE 20 and the UE 20 needs to send uplink data, in step S315 , the satellite 10 performs an RRC connection recovery process of the UE.

[0199] In this embodiment, the UE 20 recovers the suspended SRB / DRB and re-establishes AS security, and the UE 20 enters the RRC connected state.

[0200] In step S316, the satellite 10 receives the uplink data sent by the UE 20. The satellite 10 stores the received uplink data.

[0201] In step S317, when the satellite 10 is connected to the terrestrial network 30, the satellite 10 notifies the terrestrial network 30 of the restored RRC connection with the UE 20, and restores the ECM / CM connection with the terrestrial network, and the terrestrial network enters the ECM / CM connection state.

[0202] In step S318 , the satellite 10 sends uplink data to the terrestrial network 30 .

[0203] In this embodiment, the step of "the satellite 10 performs the RRC connection suspension operation of the UE20" includes: receiving an RRC message sent by the UE20, wherein the RRC message is an RRC connection release message, including a "release cause" and a "resume identity".

[0204] In this embodiment, the step of "performing the ECM / CM connection suspension operation of the ground network" includes:

[0205] The satellite 10 sends an S1-AP message to the terrestrial network, wherein the S1-AP message is a UE text suspension request, the satellite and the terrestrial network 30 store data related to the S1-AP message, UE text, and bearer text, and the terrestrial network 30 releases the bearer related to the UE 20 and enters an ECM / CM idle state; and

[0206] The satellite 10 receives a UE text hang-up response from the terrestrial network 30 .

[0207] Please refer to FIG. 14 , which is a flow chart of the store-and-forward communication method in the eleventh embodiment.

[0208] In this embodiment, when the satellite is connected to the UE, the satellite decides to suspend the RRC connection with the UE, and enters step S300 to perform the RRC connection suspension operation with the UE.

[0209] When the satellite 10 is connected to the ground network 30, in step S304, the satellite 10 informs the ground network 30 that the RRC connection of the UE20 enters the IOT idle state, wherein the ground network maintains the ECM / CM connection state and sends a UE text suspension response to the satellite.

[0210] Therefore, when the satellite 10 is connected to the terrestrial network 30, in step S320, the satellite 10 receives downlink data sent by the terrestrial network 30 and then receives a paging message sent by the terrestrial network. The satellite 10 stores the received downlink data.

[0211] When the satellite 10 and the UE 20 are connected, in step S322, the satellite 10 sends a paging message to the UE 20.

[0212] In step S323, the satellite 10 performs the RRC connection recovery process of the UE 20, wherein the UE 20 recovers the suspended SRB / DRB and re-establishes AS security, and the UE 20 enters the RRC connected state;

[0213] In step S324 , the satellite sends downlink data to the UE 20 .

[0214] When UE 20 has uplink data to send, in step S326 , the satellite 10 receives and stores the uplink data sent by UE 20 .

[0215] When the satellite 10 is connected to the terrestrial network 30, in step S327, the satellite 10 informs the terrestrial network 30 that the RRC connection of the UE 20 has been restored, and sends uplink data to the terrestrial network 30. At this time, the terrestrial network always maintains the ECM / CM connection state.

[0216] In this embodiment, satellite 10 promptly notifies terrestrial network 30 of UE 20's IOT idle state and controls terrestrial network 30's state to either ECM / CM connected or ECM / CM suspended. The satellite 10 can synchronously adjust the connection state with the terrestrial network to achieve flexible switching between the service link and the feeder link.

[0217] Please refer to FIG. 15A , which is a flow chart of a store-and-forward communication method in a twelfth embodiment.

[0218] The method in this embodiment is used in a satellite 10 , wherein the satellite 10 is in communication with at least one UE 20 and a ground network 30 to complete data transmission.

[0219] When the satellite is connected to the UE, the satellite decides to maintain the RRC connection with the UE. In step S306, the satellite 10 performs an operation to maintain the RRC connection for the UE 20. In this embodiment, the UE 20 suspends RLM / RLF and starts the AS / NAS timer. The AS / NAS timer is specifically introduced for the S&F mode (store-and-forward mode) to indicate that the NTN system has entered S&F mode.

[0220] In this embodiment, the satellite 10 sends RRC connection maintenance indication information to the UE 20, wherein the RRC connection maintenance indication information is transmitted via RRC, MAC CE or DCI.

[0221] Please refer to FIG. 15B , which is a detailed flowchart of the store-and-forward communication method in the eleventh embodiment of the present invention.

[0222] In this embodiment, when the satellite is connected to the terrestrial network, in step S307 , the satellite 10 notifies the terrestrial network 30 that the UE 30 maintains the RRC connection state, and the satellite 10 performs an ECM / CM connection suspension operation of the terrestrial network 30 .

[0223] In this embodiment, the step of "the satellite performing the ECM / CM connection suspension operation of the ground network" includes:

[0224] The satellite sends an S1-AP message to the terrestrial network, wherein the S1-AP message is a UE text suspension request; the satellite and the terrestrial network store data related to the S1-AP message, UE text and bearer text, and enter an ECM / CM idle state; and the satellite receives a UE text suspension response from the terrestrial network.

[0225] In other embodiments of the present invention, the step of "the satellite executing the ECM / CM connection suspension operation of the terrestrial network" further includes: the terrestrial network 30 releasing the bearer related to the UE20.

[0226] In this embodiment, the satellite 10 and the ground network 30 store information related to resuming the RRC connection, and the ground network 30 enters an ECM / CM suspension state.

[0227] When the satellite is connected to the ground network, the ground network 30 needs to send uplink data. In step S330, the satellite 10 receives the downlink data sent by the ground network and stores the uplink data sent by the ground network 30.

[0228] In step S331, the satellite 10 performs an ECM / CM connection recovery operation of the ground network 30. The ground network 30 enters an ECM / CM connection state.

[0229] When the satellite 10 is connected to the UE 20 , in step S332 , the satellite 10 sends the stored downlink data to the UE 20 .

[0230] When the satellite 10 is connected to the UE 20, and the UE 20 has uplink data to send, in step S333, the satellite 10 receives the uplink data sent by the UE 20. The satellite 10 stores the received uplink data.

[0231] When the satellite 10 is connected to the terrestrial network 30, in step S334, the satellite 10 performs an ECM / CM connection recovery operation of the terrestrial network 30, and the terrestrial network 40 enters an ECM / CM connection state; and

[0232] In step S335 , the satellite 10 sends uplink data to the terrestrial network 30 .

[0233] Please refer to FIG. 16A , which is a flow chart of a store-and-forward communication method in a twelfth embodiment.

[0234] The method in this embodiment is used in a satellite 10, wherein the satellite 10 is connected to at least one UE 20 and a ground network communication 30 to complete data transmission, wherein the method includes:

[0235] When the satellite is connected to the UE, in step S308, the satellite 10 / the UE 20 releases the RRC connection and performs an operation of releasing the UE's RRC connection.

[0236] In this embodiment, the state of the RRC connection of the UE20 after releasing the RRC connection is the RRC idle state.

[0237] In this embodiment, when the satellite 10 releases the RRC connection, the satellite 10 triggers an RRC release procedure and sends an RRC connection release message to the UE 20 .

[0238] In this embodiment, the RRC connection release message includes: a release reason, a store-and-forward (S&F) / no feeder link indication, and a next scheduled time.

[0239] In this embodiment, the condition for UE 20 to release the RRC connection is any one of the following:

[0240] The UE 20 has completed data transmission;

[0241] The first timer in the UE20 times out;

[0242] The UE 20 detects RLF; and

[0243] The UE 20 decides on its own when to enter RRC idle.

[0244] Please refer to FIG. 16B , which is a detailed flowchart of the store-and-forward communication method in the twelfth embodiment of the present invention.

[0245] In this embodiment, when the satellite 10 is connected to the terrestrial network 30, in step S309, the satellite 10 notifies the terrestrial network 30 to enter the ECM / CM suspension state, and the satellite 10 executes the ECM / CM suspension operation on the terrestrial network 30. The satellite 10 and the terrestrial network 30 store information related to resuming the ECM / CM connection.

[0246] When the satellite 10 is connected to the ground network 30, the ground network 30 needs to send uplink data. Then, in step S340, the satellite 10 receives the downlink data and the paging message sent by the ground network.

[0247] In step S341, the satellite 10 executes the ECM / CM connection recovery process of the terrestrial network 30, and the terrestrial network 30 enters the ECM / CM connection state.

[0248] In step S342, when the satellite 10 is connected to the UE 20, it sends a paging message to the UE 20, and the satellite 10 performs the RRC connection establishment process of the UE 20. The UE 20 enters the RRC connected state. In other embodiments of the present invention, the UE may also initiate a random access (RACH) to enter the RRC connected state.

[0249] In step S343 , the satellite 10 sends downlink data to the UE 20 / the satellite 10 receives uplink data from the UE 20 .

[0250] When the satellite 10 is connected to the terrestrial network 40, in step S345, the satellite notifies the terrestrial network of the RRC connection status of the UE and performs an ECM / CM connection recovery process with the terrestrial network, wherein the terrestrial network enters an ECM / CM connection state.

[0251] In step S346 , the satellite 10 transmits the stored uplink data, wherein the ground network 30 receives the uplink data transmitted from the satellite.

[0252] It is understood that in other embodiments of the present invention, the satellite 10 needs to promptly learn the connection status 10 of the UE and the connection status of the ground network 30, and the satellite can also determine the connection status 10 of the UE and the connection status of the ground network 30. Regardless of whether the ground network 30 or the UE 20 decides to enter a certain state on its own or is notified by the satellite to enter a certain state, it is necessary to inform the satellite and the other party in the NTN system so that the connection status between the UE and the ground network can be adjusted, thereby achieving flexible switching between the service link and the feeder link.

[0253] Please refer to Figure 17, which illustrates the initial connection process for an NTN system according to one embodiment of the present invention. In this embodiment, the NTN system includes a satellite 10, at least one UE 20, and a terrestrial network 30. When satellite 10 connects to UE 20, a service request must be initiated if the UE 20 wishes to interact with satellite 10 for either uplink or downlink services. This service request is initiated after the UE completes the RACH (Random Access Channel) and enters the connected state. This process corresponds to step 1 in Figure 17. In step 1, UE 20 sends a delay-tolerant indication to satellite 10.

[0254] In this embodiment, the UE sends a service request message to the satellite via an RRC Connection Setup Complete message, which includes a delay tolerance indicator.

[0255] In other embodiments of the present invention, if it is a Multicast / Broadcast service, the UE does not need to make a service request, and the delay tolerance indication comes from the terrestrial network (from the user plane node of the core network node to the control plane node (P-GW / S-GW)), and step 1 is not required. The delay tolerance indication is carried in the service request sent by the terrestrial network.

[0256] In step 2, after receiving the delay tolerance indication, the satellite 10 sends a service request carrying the delay tolerance indication to the ground network 30, which is used to inform the ground network 30 whether the service is a delay-tolerant service.

[0257] In other embodiments of the present invention, the satellite 10 may also send the delay tolerance indication to the ground network 30 using, for example, an initial UE message.

[0258] In step 3, the ground network 30 configures the start time, duration, session length and data size of the delay tolerant service, and informs the satellite 10 of the start time, duration, session length and data size.

[0259] In other embodiments of the present invention, after receiving the relevant information of the session, the satellite 10 performs S&F-related configuration operations on the session to form configuration information, and sends it to the UE 20 and the ground network 30. The configuration information specifically includes:

[0260] The specific data size of each session (for example, the data size of the session is very large, and the capacity on the satellite 10 is limited, so the data needs to be sent in several batches);

[0261] The start time of each session transmission to the air interface;

[0262] Each session is time stored on the satellite 10 .

[0263] UE 20 determines its RRC connection state based on the configuration information. If the start time of the delay-tolerant service is still very late, UE 20 may first enter the idle state or IOT idle state. If the start time of the delay-tolerant service is approaching soon, UE 20 may remain in the connected state.

[0264] If the UE has previously entered the idle state, the RRC connection establishment process needs to be performed; if the UE has previously entered the IOT idle state, the RRC connection recovery process needs to be performed. If the UE remains in the connected state, this step is not required.

[0265] UE 20 / ground network 30 sends and receives uplink / downlink data according to the received configuration information about the session.

[0266] In this embodiment, the initial state of UE20 is any one of the following three states: IOT idle state, idle state and RRC connected state.

[0267] When there is downlink data to be sent, the ground network 30 initiates Paging. When new data arrives at the uplink buffer of the UE 20, the UE 20 triggers a service request.

[0268] Specifically, when UE 20 is initially in the IOT idle state, has uplink data to send in its buffer, and is within coverage of satellite 10, it initiates a random access call (RACH) to establish an RRC connection with satellite 10. The RACH message includes Msgs 1 through 4. Msg 3, which carries the service request message to satellite 10 via the RRC Connection Resume Request message, includes a delay-tolerant service indication.

[0269] After receiving the service request message, satellite 10 initiates an RRC Connection Resume to UE 20, informing UE 20 to begin the RRC connection recovery process. UE 20 then restores SRB / DRB, reestablishes AS security, and enters the RRC connected state.

[0270] The UE then replies with an RRC Connection Resume Complete message to inform the satellite that the interface between the satellite 10 and the ground network can also perform a recovery process accordingly.

[0271] When the satellite 10 is away from the UE 20 20 , it may be determined by the UE 20 / satellite which of the three states the UE is in.

[0272] Next: If the UE 20 enters the RRC idle state, this step performs the RRC connection establishment process. If the UE enters the IOT idle state, this step performs the RRC connection resume process. If the UE maintains the RRC connection, this step is omitted.

[0273] When the satellite 10 covers the ground network 30, the satellite 10 sends a delay tolerant service indication message to the ground network, which may use a UE text recovery request message (other messages or newly defined messages may also be used here).

[0274] Optionally, the ground network 30 may choose whether to release interface (eg, S1 interface) resources.

[0275] The ground network 30 configures and instructs the session, and may use a UE text response message (other messages or newly defined messages may also be used here).

[0276] Specifically, they may include:

[0277] The start time of the session;

[0278] How long the session will last; and

[0279] The size of the session data.

[0280] After receiving the session-related information from the ground network, the satellite 10 will perform S&F-related configuration operations on the session. Specifically,

[0281] The specific data size of each session;

[0282] The start time of each session transmission to the air interface;

[0283] How long each session will be stored on the satellite 10.

[0284] Next, the satellite 10 sends a service request to the ground network 30 to know the data transmission of the ground network 30 .

[0285] The satellite 10 transmits the configuration information to the UE 20 .

[0286] UE20 replies with an RRC Connection reconfigure complete message to the satellite to indicate receipt of the configuration information.

[0287] In another embodiment of the present invention, if the initial state of UE20 is idle and there is uplink data to be sent in the buffer of UE20, the steps are basically the same as when the initial state of UE is idle, except that:

[0288] a: After UE20 initiates random access (RACH), UE20 sends a service request message to satellite 10 via an RRC Connection Setup Complete message, which includes a delayed service indication.

[0289] b: The satellite 10 sends the delayed service indication to the ground network using a message such as the initial UE message.

[0290] c: The ground network 30 may use the initial UE text setup request message when configuring and instructing for a session.

[0291] d: The satellite 10 sends configuration information to the ground network 30 via an initial UE text setup complete message.

[0292] In other embodiments of the present invention, if the initial state of UE20 is the RRC connection state, the main difference between the process when the initial state of UE20 is the idle state or the IOT idle state is that: when there is a business need to be initiated, UE20 can directly initiate the service request process.

[0293] The NTN system of this embodiment ensures normal operation of the delay service in the S&F mode by transmitting delay-tolerant related information to the ground network and the satellite, and the ground network also knows how to configure for different service types.

[0294] Please refer to FIG. 17 , which is a module diagram of a satellite 10 according to an embodiment of the present invention.

[0295] In this embodiment, the satellite 10 includes a memory 102 and a processor 104. The memory 102 is used to store a computer program for the method executed in the network device 10 in the embodiment of the present application, wherein the memory 102 can be a memory. In this embodiment, the processor 104 is configured to call and execute the computer program stored in the memory 102.

[0296] Please refer to FIG. 18 , which is a module diagram of UE 20 in one embodiment of the present invention.

[0297] In this embodiment, the UE 20 includes a memory 202 and a processor 204. The memory 202 is used to store a computer program of the method executed in the UE 20 in the embodiment of the present application, wherein the memory 202 can be a memory. In this embodiment, the processor 204 is configured to call and execute the computer program stored in the memory 204.

[0298] Please refer to FIG. 19 , which is a module diagram of the ground network 30 in one embodiment of the present invention.

[0299] In this embodiment, the ground network 30 includes a memory 302 and a processor 304. The memory 302 is used to store a computer program for the method executed in the ground network 30 in the embodiment of the present application, wherein the memory 302 can be a memory. In this embodiment, the processor 304 is configured to call and execute the computer program stored in the memory 304.

[0300] The embodiments of the satellite, UE and terrestrial network provided in the above implementation manner may include all the technical features of any of the above method embodiments. The expansion and explanation content of the specification are basically the same as those of the embodiments of the above method, and will not be repeated here.

[0301] An embodiment of the present invention further provides a computer program product, which includes computer program code. When the computer program code runs on a computer, the computer executes the methods in the various possible implementation modes described above.

[0302] An embodiment of the present invention also provides a chip, including a memory and a processor, wherein the memory is used to store computer programs, and the processor is used to call and run the computer programs from the memory, so that a device equipped with the chip executes the methods in various possible implementations as described above.

[0303] The above description is only an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the contents of the description and drawings of the present invention, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A store-and-forward communication method for use in a satellite, wherein: The satellite is communicatively connected with at least one UE and a terrestrial network to complete data transmission, a second timer and a second maximum timer duration are set in the satellite, and the method includes: When the satellite is connected to the UE, sending downlink data to the UE / receiving uplink data from the UE when the second timer does not exceed the second maximum timing time; and When the satellite is connected to the terrestrial network, uplink data is sent to the terrestrial network and downlink data is received from the terrestrial network.

2. The method according to claim 1, wherein Also includes: If the ground network receives uplink data / sends downlink data, the satellite executes the ground network interface resource release process, and the ground network releases the bearer.

3. The method according to claim 1, wherein “Sending downlink data to the UE” includes: The satellite sends a radio resource control protocol (RRC) completion message carrying downlink data to the UE within the second maximum timing time range of the second timer, wherein the RRC completion message includes an RRC EarlyData Complete message.

4. The method according to claim 3, wherein: Also includes: The satellite sends a paging message to the UE when the second timer exceeds a second maximum timing time; Receive an RRC request message sent by the UE.

5. The method according to claim 4, wherein: Also includes: Determining whether the RRC request message contains uplink data; If the RRC request message does not carry uplink data, the satellite sends an RRC completion message to the UE; If the RRC request message carries uplink data, the satellite sends a paging message; Send an RRC completion message carrying downlink data to the UE.

6. The method according to claim 1 or 4, wherein: The method further comprises: The satellite configures a first timer and a first maximum timing time for the UE / the UE sets the first timer and the first maximum timing time, and the second timer is associated with the first timer.

7. The method according to claim 6, wherein: The first timer is started when the UE sends the RRC request message, the first maximum timing time is set to one or more fixed values, or the first maximum timing time is associated with the interval period of the satellite.

8. The method of claim 4, wherein: The second timer is started when the RRC request message is received.

9. The method of claim 1, wherein: Also includes: Upon receiving RRC request messages from multiple UEs, aggregating the RRC request messages from the multiple UEs into a single NAS (non-access stratum) message, and sending the NAS message and indication information to the terrestrial network, wherein the terrestrial network obtains downlink data requirements required by the multiple UEs / uplink data sent by the multiple UEs based on the indication information and the NAS message, and aggregating the downlink data required by the multiple UEs into a single data response message, and sending the response message to the satellite; and Receive the data response message and disassemble it into multiple sub-data response messages, send them to multiple UEs when the second timer does not exceed the second maximum timing time, or when the second timer exceeds the second maximum timing time, send a paging message to multiple UEs, and then send the sub-data response message.

10. The method of claim 1, wherein: “Receiving downlink data from the terrestrial network” includes: When the satellite is connected to the ground network, the satellite receives a paging message from the ground network and determines whether the paging message carries downlink data; If the paging message does not carry downlink data, the satellite sends a paging message to establish an RRC connection with the UE, and the satellite receives downlink data from the ground network; The satellite sends downlink data to the UE when the second timer does not exceed a second maximum timing time.

11. The method according to claim 10, wherein: Also includes: If the paging message carries downlink data, the satellite stores the downlink data and sends the downlink data to the UE when the second timer does not exceed a second maximum timing time.

12. The method according to claim 10 or 11, wherein: Also includes: The satellite re-establishes an RRC connection with the UE when the second timer exceeds a second maximum timing time, and then sends downlink data to the UE.

13. The method of claim 1, wherein: The step of "sending downlink data when the second timer does not exceed the second maximum timing time when the satellite is connected to the UE" includes: When the satellite is connected to the UE, the satellite sends an RRC completion message carrying downlink data to the UE within a second maximum timing time range of the second timer, wherein the RRC completion message also includes an RRCConnectionRelease message.

14. The method of claim 13, wherein: Also includes: When the satellite is connected to the ground network, the satellite receives a paging message from the ground network and determines whether the paging message carries downlink data; If the paging message does not carry downlink data, the satellite receives downlink data from the ground network; When the second timer exceeds a maximum timing time, the satellite sends a paging message to establish an RRC connection with the UE; and The satellite sends downlink data to the UE when the second timer does not exceed a second maximum timing time.

15. The method of claim 14, wherein: Also includes: If the paging message carries downlink data, the satellite stores the downlink data and sends the downlink data to the UE when the second timer does not exceed a second maximum timing time.

16. The method of claim 1, wherein: The step of "receiving uplink data from the UE" includes: When the satellite is connected to the UE, receiving an RRC request message carrying data size information sent by the UE, and determining whether to allocate a PUR to the UE and the number of allocated PURs, wherein the RRC request message includes a preset uplink resource (PUR) request message; Send an RRC completion message to the UE, wherein the PUR request message is a PURConfigurationRequest message, the RRC completion message includes PUR configuration information, a PUR timer, and a third maximum timing time, and the UE performs configuration according to the RRC completion message.

17. The method of claim 16, wherein: Also includes: If the PUR timer exceeds the third maximum time, the UE fails to configure the PUR, and the satellite resends the paging message.

18. The method of claim 16, wherein: Also included: the RRC completion message is a RRC EarlyData Complete message; If the PUR timer is within the third maximum timing time range, the satellite sends information related to the maximum timing advance (TA) and an RRC EarlyDataComplete message carrying downlink data to the UE.

19. The method of claim 17, wherein: Also includes: The RRC completion message is an RRCConnectionRelease message; If the PUR timer is within the third maximum timing time range, the satellite sends an RRCConnectionRelease message carrying TA related information and downlink data to the UE.

20. A store-and-forward communication method, used in a UE, wherein: The UE is communicatively connected to a satellite and a terrestrial network to complete data transmission, and the method includes: When the UE is connected to the satellite, it sends a first message carrying uplink data to the satellite and receives a second message carrying downlink data.

21. The method of claim 20, wherein: The first message is at least one of the following: RRCEarlyDataRequest message; and PURConfigurationRequest message; The second message is at least one of the following: Paging message; RRCEarlyDataComplete message; and RRCConnectionRelease message.

22. The method of claim 20, wherein: Also includes: After the UE is connected to / disconnected from the satellite, the UE enters any of the following states: Maintain RRC connection state; Entering the RRC idle state; and Entering the RRC IOT idle state, wherein the RRC IOT idle state is the RRC connection state when the UE suspends resources related to the RRC connection.

23. A store-and-forward communication method for use in a terrestrial network, wherein: The terrestrial network is communicatively connected to the satellite and the UE to complete data transmission, and the method includes: The ground network receives a third message carrying uplink data from the satellite / the ground network sends a fourth message carrying downlink data to the satellite, wherein the third message is a NAS message / initial UE message, and the fourth message is a paging message.

24. The method of claim 23, wherein: Also includes: After the ground network is connected to / disconnected from the satellite, it enters at least one of the following states: Maintaining Terrestrial Wireless Network Connection Management (ECM) / Connection Management (CM) connection status; and Enter ECM / CM suspend state.

25. A store-and-forward communication method for use in a satellite, wherein: The satellite is communicatively connected with a terrestrial network and a UE to complete data transmission, and the method includes: receiving, by the satellite, a fifth message carrying uplink data from the UE when connected to the UE; and When the satellite is connected to the ground network, it receives a sixth message carrying downlink data from the ground network.

26. The method of claim 25, wherein: The fifth message is at least one of the following: RRCEarlyDataRequest message; and PURConfigurationRequest message; The sixth message is at least one of the following: Paging message; RRCEarlyDataComplete message; and RRCConnectionRelease message.

27. A store-and-forward communication method for use in a satellite, wherein the satellite is communicatively coupled to at least one UE and a terrestrial network to perform data transmission, wherein: The method comprises: When the satellite is connected to the UE, the satellite decides to suspend the RRC connection with the UE, and the satellite performs an RRC connection suspension operation of the UE.

28. The method of claim 27, wherein: Also includes: When the satellite is connected to the terrestrial network, the satellite notifies the terrestrial network that the RRC connection of the UE enters the IOT idle state, and performs an ECM / CM connection suspension operation of the terrestrial network, wherein the satellite stores information related to resuming the ECM / CM connection.

29. The method of claim 28, wherein Also includes: When the satellite is connected to the ground network, the satellite receives downlink data from the ground network; as well as The satellite performs an ECM / CM connection recovery procedure with the terrestrial network.

30. The method of claim 28, wherein Also includes: When the satellite is connected to the UE, the satellite sends a paging message to the UE; The satellite performs an RRC connection recovery procedure with the UE.

31. The method of claim 28, wherein Also includes: When the satellite is connected to the UE and the UE needs to send uplink data, the satellite executes an RRC connection recovery process of the UE; The satellite receives uplink data sent by the UE.

32. The method of claim 31, wherein Also includes: When the satellite is connected to the terrestrial network, the satellite notifies the terrestrial network of a restored RRC connection with the UE and restores an ECM / CM connection with the terrestrial network, and the terrestrial network enters an ECM / CM connected state; The satellite sends uplink data to the ground network.

33. The method of claim 27, wherein: The step of "the satellite executing the RRC connection suspension operation of the UE" includes: receiving an RRC message sent by the UE, wherein the RRC message is an RRC connection release message including a "release cause" and a "resume identity".

34. The method of claim 28, wherein The step of "executing the ECM / CM connection suspension operation of the ground network" includes: The satellite sends an S1 access point (S1-AP) message to the terrestrial network, wherein the S1-AP message is a UE text suspension request, and the satellite stores data related to the S1-AP message, UE text, and bearer text; and The satellite receives a UE text hang-up response from the terrestrial network.

35. The method of claim 27, wherein: Also includes: When the satellite is connected to the terrestrial network, the satellite notifies the terrestrial network that the RRC connection of the UE enters the IOT idle state, wherein the terrestrial network maintains the ECM / CM connection state and sends a UE text suspension response to the satellite.

36. The method of claim 35, wherein: Also includes: When the satellite is connected to the ground network, the satellite receives downlink data sent by the ground network and then receives a paging message sent by the ground network; When the satellite is connected to the UE, the satellite sends a paging message to the UE and executes an RRC connection recovery procedure of the UE; The satellite sends downlink data to the UE.

37. A store-and-forward communication method for use in a satellite, wherein the satellite is communicatively coupled to at least one UE and a terrestrial network to perform data transmission, wherein: The method comprises: When the satellite is connected to the UE, the satellite decides to maintain the RRC connection with the UE, and the satellite performs an operation of maintaining the RRC connection of the UE.

38. The method of claim 37, wherein: Also includes: When the satellite is connected to the terrestrial network, the satellite notifies the terrestrial network that the UE maintains an RRC connected state; The satellite performs an ECM / CM connection suspension operation of the terrestrial network, wherein the satellite stores information related to resuming the RRC connection.

39. The method of claim 38, wherein Also includes: When the satellite is connected to the ground network, the satellite receives downlink data sent by the ground network; as well as The satellite performs an RRC connection recovery operation of the terrestrial network.

40. The method of claim 39, wherein Also includes: When the satellite is connected to the UE, the satellite sends downlink data to the UE.

41. The method of claim 39, wherein: Also includes: When the satellite is connected to the UE, the satellite receives uplink data sent by the UE; When the satellite is connected to the terrestrial network, the satellite performs an ECM / CM connection recovery operation of the terrestrial network; and The satellite sends uplink data to the ground network.

42. The method of claim 37, wherein: Also includes: The satellite sends RRC connection maintenance indication information to the UE, wherein the RRC connection maintenance indication information is transmitted via RRC, MAC CE or DCI.

43. The method of claim 39, wherein: The step of "the satellite executing the ECM / CM connection suspension operation of the ground network" includes: The satellite sends an S1-AP message to the terrestrial network, wherein the S1-AP message is a UE text suspension request, the satellite stores data related to the S1-AP message, UE text, and bearer text, and enters an ECM / CM idle state; and The satellite receives a UE text hang-up response from the terrestrial network.

44. A store-and-forward communication method for use in a satellite, wherein the satellite is communicatively coupled to at least one UE and a terrestrial network to perform data transmission, wherein: The method comprises: When the satellite is connected to the UE, the satellite releases the RRC connection / receives a request from the UE to release the RRC connection, and performs an RRC connection release operation. When the satellite releases the RRC connection, the satellite triggers an RRC release process and sends an RRC connection release message to the UE.

45. The method of claim 44, wherein: Also includes: When the satellite is connected to the ground network, the satellite notifies the ground network to enter an ECM / CM suspension state; The satellite executes the RRC suspension operation of the ground network and stores information related to resuming the RRC connection.

46. ​​The method of claim 45, wherein Also includes: When the satellite is connected to the terrestrial network, the satellite receives downlink data sent by the terrestrial network, wherein the terrestrial network sends a paging message to the satellite, and the satellite executes an ECM / CM connection recovery process of the terrestrial network; and When the satellite is connected to the UE, the satellite sends a paging message to the UE, and the satellite executes an RRC connection establishment process of the UE; The satellite sends downlink data to the UE / the satellite receives uplink data from the UE.

47. The method of claim 46, wherein Also includes: When the satellite is connected to the terrestrial network, the satellite informs the terrestrial network of the RRC connection status of the UE and performs an ECM / CM connection recovery process with the terrestrial network.

48. The method of claim 44, wherein The RRC connection release message includes: a release reason, a store-and-forward (S&F) / no feeder link indication, and a next scheduled time.

Images