Communication method and device

Abstract

Disclosed are a communication method and device, the method comprising: determining whether first context information stored in a first network device of a plurality of network devices is updated, the first context information being context information of a terminal device, the first network device being located on a first satellite, the first satellite being a satellite covering the terminal device; and establishing a connection with a second network device in the event that the first context information is updated, the second network device being located on the first satellite. The terminal device only needs to judge whether the first context information stored in the first network device on the first satellite is updated or not, and does not need to wait for updating of the context information stored in the multiple network devices, so that the terminal device can communicate with the network as early as possible, the service interruption time is shortened, and the data transmission efficiency is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of communication, and in particular to a communication method and device. BACKGROUND

[0002] In a non-terrestrial network (NTN) system, a communication link between a satellite and a terminal is referred to as a service link (SL), a communication link between the satellite and a gateway station of a ground network is referred to as a feeder link (FL), and a communication link between the satellite and another satellite is referred to as an inter-satellite link (ISL). Generally, when a terminal accesses a network through an NTN, the terminal-satellite-ground network communication can be implemented by using the above communication links.

[0003] Since a gateway station is not deployed in some areas, the feeder link is not always available. In order to successfully transmit data, when the feeder link is available, the ground network can send the context information of the terminal to the satellite; when the feeder link is unavailable but the service link is available, the satellite can establish a connection with the terminal by using the context information stored in the satellite. When the context information of the terminal is updated, the ground network also sends the updated context information to the satellite, so that the satellite updates the context information stored in the satellite.

[0004] Currently, when the context information of the terminal is updated, in order to ensure successful access of the terminal, the terminal communicates with the satellite again after the context information of the terminal stored in the satellite is updated. The more satellites serving the terminal, the longer the time required for updating the context information by each satellite, which may result in a longer service interruption time and a lower data transmission efficiency. SUMMARY

[0005] Embodiments of the present application provide a communication method and device for improving the efficiency of data transmission.

[0006] In the first aspect, an embodiment of the present application provides a communication method, which can be executed by a terminal device. The terminal device is, for example, a terminal device, or other device including the function of the terminal device, or a chip system (or chip) or other functional module capable of realizing the function of the terminal device, which is, for example, arranged in the terminal device. The method comprises: determining whether first context information stored by a first network device in a plurality of network devices is updated, wherein the first context information is context information of the terminal device, and the first network device is located on a first satellite, and the first satellite is a satellite covering the terminal device; and establishing a connection with a second network device in a case where the first context information is updated, wherein the second network device is located on the first satellite.

[0007] In the embodiments of the present application, the terminal device establishes a connection with the second network device on the first satellite in a case where the first context information stored by the first network device on the first satellite is updated, which can improve the probability of successful connection of the terminal device. In addition, the terminal device only needs to determine whether the first context information stored by the first network device on the first satellite is updated, and does not need to wait for the context information stored by all the network devices to be updated, so that the terminal device can communicate with the network as soon as possible, reduce the time of service interruption, and improve the data transmission efficiency.

[0008] In a possible implementation, the determining whether the first context information stored by the first network device in the plurality of network devices is updated comprises: determining whether the first context information is updated according to an update time corresponding to part or all of the network devices, wherein the update time corresponding to the first network device is used to indicate a time when the first context information is updated; or determining whether a first identifier is same as a second identifier, wherein if the first identifier is same as the second identifier, it indicates that the first context information is updated, otherwise it indicates that the first context information is not updated, the first identifier is an identifier of the first context information, and the second identifier is an identifier of the context information of the terminal device stored by the terminal device.

[0009] In this embodiment, multiple manners are provided for the terminal device to determine whether the first context information is updated. For example, whether the first context information is updated is determined according to a time when the first context information is updated, the terminal device only needs to determine according to the time, without the aid of other indications of the network device, signaling overhead can be saved, and this determination manner can also be understood as a direct determination manner. For another example, whether the first context information is updated is determined according to whether an identifier of the first context information and an identifier of the second context information are same, the determination is realized through the identifier, and the implementation is relatively simple, and if the identifier occupies a smaller number of bits, the implementation is simpler, and this determination manner can also be understood as an indirect determination manner.

[0010] In a possible implementation, whether the first context information is updated is determined according to the update time corresponding to part or all of the network devices, including: whether the first context information is updated is determined according to the update time corresponding to the first network device; or, whether the first context information is updated is determined according to the update time corresponding to a third network device of the network devices, where the update time corresponding to the third network device is later than the update time corresponding to the remaining network devices of the network devices.

[0011] In this embodiment, multiple manners are provided for the terminal device to determine whether the first context information is updated according to a time when the first context information is updated. For example, the terminal device can determine whether the first context information is updated according to the update time corresponding to the first network device, and the terminal device needs to determine whether the first context information stored by the first network device is updated, and the determination is performed according to the update time corresponding to the first network device, which is beneficial to improve the accuracy of the determination result. For another example, the terminal device can determine a latest update time corresponding to the network devices, and when the time arrives, it can be considered that the network devices are all updated, and therefore the first network device should also be updated, and the determination is performed through the latest update time, which can ensure the reliability of the determination result. For example, even if the terminal device cannot determine the update time corresponding to the first network device, but can determine the latest update time, the terminal device can also determine, thereby improving the determination efficiency.

[0012] In a possible implementation, the method further includes: receiving first information; or, determining the first information according to coverage information of a satellite on which part or all of the network devices are located and position information of a fourth network device on the ground, where the fourth network device is same as the context information of the terminal device stored by each network device of the network devices; and the first information is used to indicate the update time corresponding to part or all of the network devices.

[0013] In this embodiment, the terminal device can determine the first information in multiple ways. For example, the other device can send the first information to the terminal device after determining the first information, without the terminal device determining the first information by itself, so as to simplify the implementation of the terminal device and reduce the power consumption of the terminal device. The terminal device can determine the first information by itself, without the first information being sent to the terminal device by the other device, so as to save signaling overhead.

[0014] In a possible implementation, the method further includes: receiving a first paging message, wherein the first paging message includes the first identifier. In this embodiment, a way for the terminal device to determine the identifier of the first context information is provided. Since the first satellite is a satellite currently covering the terminal device, the terminal device can be currently served by the first satellite, and thus the first paging message can come from the first satellite, for example, from a first network device on the first satellite. Therefore, the first identifier can represent whether the first context information stored by the first network device is updated, so that the terminal device obtains a more accurate first identifier, thereby improving the accuracy of the judgment of the terminal device according to the identifier. In addition, the terminal device can determine the identifier of the first context information in other ways, which are not limited herein.

[0015] In a possible implementation, the method further includes: not establishing a connection with the second network device in a case where the first context information is not updated. In this embodiment, if the first context information stored by the first network device is not updated, the terminal device can not establish a connection with the second network device, thereby improving the probability of successful connection establishment. Optionally, the first network device is a core network device, and the second network device is an access network device.

[0016] In a possible implementation, the method further includes: entering a sleep state. The first satellite is a satellite currently serving the terminal device, but the terminal device determines that the first context information is not updated. It can be considered that the terminal device determines that the first satellite currently cannot provide services for the terminal device, and thus the terminal device can enter a sleep state, thereby reducing the power consumption of the terminal device.

[0017] In a possible implementation, before determining whether the first context information stored by the first network device of the multiple network devices is updated, the method further includes: receiving first indication information, wherein the first indication information is used to indicate that the first context information starts to be updated; or the context information of the terminal device stored by the terminal device is updated.

[0018] In the embodiments of the present application, the "update occurs" can mean that the update process has started but has not ended, or can mean that the update has ended. The "start updating" can mean that the update process has started, can have ended, or can not have ended. The terminal device can determine whether the first context information has updated according to the trigger of the first indication information from other devices, without the terminal device triggering by itself, thereby simplifying the implementation of the terminal device. Alternatively, the terminal device can determine whether the first context information has updated when it is determined that the context information stored by the terminal device has updated, without other devices sending information indication, thereby reducing signaling overhead.

[0019] In a second aspect, the embodiments of the present application further provide a communication method, which can be executed by a network device, for example, a first network device or a fourth network device. The first network device is located on a first satellite or is the first satellite. The fourth network device is located on the ground. The network device is, for example, a network equipment, or other equipment including the function of the network equipment, or a chip system (or a chip) or other functional module, which can implement the function of the network equipment, and is, for example, arranged in the network equipment. The method comprises: sending first information, wherein the first information is used to indicate the update time corresponding to part or all of a plurality of network devices, the plurality of network devices include the first network device, the first network device is located on the first satellite, the first satellite is a satellite covering a terminal device, and the update time corresponding to the first network device is used to indicate the time when the first context information stored by the first network device is updated, the first context information being the context information of the terminal device.

[0020] In the embodiments of the present application, the plurality of network devices are network devices on the satellites of a plurality of service terminal devices for storing the context information of the terminal devices, that is, the first information can indicate the time when the context information of the terminal device stored by part or all of the satellites of the service terminal devices is updated. The first network device on the first satellite or the fourth network device on the ground can send the first information to other devices, for example, the terminal device, after determining the first information. Since the terminal device does not need to determine the first information by itself, the implementation of the terminal device is simplified, and the power consumption of the terminal device is reduced.

[0021] In a possible implementation, the method further comprises: receiving the first information; or the first information is determined according to second information, coverage information of the satellite where part or all of the plurality of network devices are located, and position information of the fourth network device on the ground, wherein the second information is used to determine part of the plurality of network devices, and the fourth network device has the same context information of the terminal device as each of the plurality of network devices.

[0022] In this embodiment, the first network device on the first satellite or the fourth network device on the ground can determine the first information in multiple ways. For example, the other device can send the first information to the first network device or the fourth network device after determining the first information, without the first network device or the fourth network device determining the first information by itself, which simplifies the implementation of the first network device or the fourth network device and reduces the power consumption of the first network device or the fourth network device. The first network device or the fourth network device can determine the first information by itself, without the other device sending the first information to the first network device or the fourth network device, which can save the signaling overhead. Moreover, since the second information can be used to determine part of the network devices, the first information can only indicate the time when the context information of the terminal device stored by part of the network devices is updated, thereby reducing the overhead of the first information.

[0023] In a possible implementation, before receiving the first information, the method further includes: sending third information, where the third information is used to indicate second information, location information of the terminal device, and location information of a fourth network device on the ground, the second information is used to determine part of the network devices, and the fourth network device has the same context information of the terminal device as each of the network devices.

[0024] In this embodiment, the fourth network device on the ground can send the third information to the other device, so that the other device can determine the first information according to the third information and coverage information of the satellite where part or all of the network devices are located. Since the fourth network device on the ground does not need to buffer the coverage information of the satellite where part or all of the network devices are located, the power consumption of the fourth network device on the ground is reduced.

[0025] In a possible implementation, the second information is used to indicate a service type of the terminal device and / or a communication mode of the terminal device.

[0026] In this embodiment, multiple ways of determining part of the network devices according to the second information are provided. For example, the second information can be used to indicate the service type of the terminal device, and according to the second information, it can be determined how many satellites are needed to provide services for the terminal device, and then the network device on the satellite for storing the context information of the terminal device is determined, thereby reducing the waste of satellite resources. For another example, the second information can be used to indicate the communication mode of the terminal device, and according to the second information, it can be determined which satellite coverage time is most suitable for the frequency of the terminal device transmitting data, and then the network device on the satellite for storing the context information of the terminal device is determined, thereby improving the probability of successful data transmission. It can be seen that the way of determining part of the network devices according to the second information is flexible.

[0027] In a possible implementation, the plurality of network devices includes a third network device, and the update time corresponding to the third network device is later than the update time corresponding to the remaining network devices in the plurality of network devices.

[0028] In this implementation, the plurality of network devices are network devices on a plurality of service terminal devices for storing context information of the terminal devices, and when the first information indicates that the context information of the terminal devices stored by part of the plurality of network devices is updated at a time, the first information can include the latest time among the times at which the context information of the terminal devices stored by all the network devices in the plurality of network devices is updated. If the current time is later than the latest time, the terminal device can determine that the context information of the terminal devices stored by all the network devices is updated, so that the terminal device can use the satellite on which all the network devices are located, instead of using only the satellite on which the part of the network devices are located according to the first information, thereby improving the utilization rate of satellite resources.

[0029] In a third aspect, an embodiment of the present application further provides a communication device. The communication device can be the terminal device in the first aspect. The communication device has the functions of the terminal device. The communication device is, for example, a terminal device, or another device including the functions of the terminal device, or a chip system (or a chip) or another functional module, which can implement the functions of the terminal device. The chip system or the functional module is, for example, arranged in the terminal device. In an optional implementation, the communication device includes a baseband device and a radio frequency device. In another optional implementation, the communication device includes a processing unit (also referred to as a processing module) and a transceiver unit (also referred to as a transceiver module). The transceiver unit can implement a sending function and a receiving function. When the transceiver unit implements the sending function, it can be referred to as a sending unit (also referred to as a sending module). When the transceiver unit implements the receiving function, it can be referred to as a receiving unit (also referred to as a receiving module). The sending unit and the receiving unit can be the same functional module, which is referred to as a transceiver unit and can implement the sending function and the receiving function. Alternatively, the sending unit and the receiving unit can be different functional modules, and the transceiver unit is a general term for these functional modules.

[0030] In an optional implementation, the processing unit is configured to determine whether first context information stored by a first network device in the plurality of network devices is updated, the first context information being context information of a terminal device, and the first network device being located on a first satellite, the first satellite being a satellite covering the terminal device. In the case where the first context information is updated, the processing unit is configured to establish a connection with a second network device, the second network device being located on the first satellite.

[0031] In a fourth aspect, an embodiment of the present application provides a communication apparatus. The communication apparatus can be the first network apparatus or the fourth network apparatus of the second aspect. The communication apparatus has the functions of the first network apparatus or the fourth network apparatus. The communication apparatus is, for example, a network device, or another device including the functions of the network device, or a chip system (or chip) or another functional module that can implement the functions of the network device, which is, for example, arranged in the network device. In an optional implementation, the communication apparatus includes a baseband apparatus and a radio frequency apparatus. In another optional implementation, the communication apparatus includes a processing unit (also referred to as a processing module) and a transceiver unit (also referred to as a transceiver module). The transceiver unit can implement the sending function and the receiving function. When the transceiver unit implements the sending function, it can be referred to as a sending unit (also referred to as a sending module). When the transceiver unit implements the receiving function, it can be referred to as a receiving unit (also referred to as a receiving module). The sending unit and the receiving unit can be the same functional module, which is referred to as a transceiver unit and can implement the sending function and the receiving function. Alternatively, the sending unit and the receiving unit can be different functional modules, and the transceiver unit refers to these functional modules in general.

[0032] In an optional implementation, the transceiver unit is configured to send the first information, where the first information is used to indicate the update time corresponding to part or all of the plurality of network apparatuses, the plurality of network apparatuses include the first network apparatus, the first network apparatus is located on the first satellite, the first satellite is a satellite covering the terminal apparatus, and the update time corresponding to the first network apparatus is used to indicate the time when the first context information stored by the first network apparatus is updated, the first context information being the context information of the terminal apparatus.

[0033] In a fifth aspect, a communication apparatus is provided. The communication apparatus can be the terminal apparatus of the first aspect. The communication apparatus has the functions of the terminal apparatus. The communication apparatus is, for example, a terminal device, or another device including the functions of the terminal device, or a chip system (or chip) or another functional module that can implement the functions of the terminal device, which is, for example, arranged in the terminal device. The communication apparatus includes a processor configured to perform the functions of the terminal apparatus of the first aspect. Optionally, the communication apparatus further includes a memory. The memory is configured to store a computer program, and the processor is coupled to the memory. When the processor reads the computer program or instructions, the communication apparatus performs the method performed by the terminal apparatus in the above aspects.

[0034] In a sixth aspect, a communication apparatus is provided, which can be the first network apparatus or the fourth network apparatus in the second aspect. The communication apparatus has the functions of the first network apparatus or the fourth network apparatus. The communication apparatus is, for example, a network device, or another device with network device functions, or a chip system (or chip) or another functional module that can implement the functions of the network device, for example, in the network device. The communication apparatus includes a processor configured to perform the functions of the network apparatus in the second aspect. Optionally, the communication apparatus further includes a memory. The memory is configured to store a computer program, and the processor is coupled to the memory. When the processor reads the computer program or instructions, the communication apparatus performs the method performed by the network apparatus in the aspects.

[0035] In a seventh aspect, a communication system is provided, including a network apparatus, for example, the first network apparatus or the fourth network apparatus in the aspects. The network apparatus is configured to perform the method performed by the first network apparatus or the fourth network apparatus in the second aspect. For example, the network apparatus can be implemented by the communication apparatus in the fourth aspect or the sixth aspect.

[0036] Optionally, the communication system further includes a terminal apparatus. The terminal apparatus is configured to perform the method performed by the terminal apparatus in the first aspect. For example, the terminal apparatus can be implemented by the communication apparatus in the third aspect or the fifth aspect.

[0037] In an eighth aspect, a computer readable storage medium is provided, configured to store a computer program or instructions, which, when executed, cause the method performed by the terminal apparatus or the first network apparatus or the fourth network apparatus in the aspects to be implemented.

[0038] In a ninth aspect, a computer program product including instructions is provided, which, when executed on a computer, causes the method in the aspects to be implemented.

[0039] In a tenth aspect, a chip system is provided, including a processor and an interface. The processor is configured to call and execute instructions from the interface, so that the chip system implements the method in the aspects. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 A structural schematic diagram of an NTN system provided by an embodiment of the present application;

[0041] Figure 2 A structural schematic diagram of an access network device provided by an embodiment of the present application;

[0042] Figure 3 A structural schematic diagram of a communication system provided by an embodiment of the present application is shown in FIG. 1.

[0043] Figure 4 A structural schematic diagram of another communication system provided by an embodiment of the present application is shown in FIG. 2.

[0044] Figure 5 A flowchart of a communication method provided by an embodiment of the present application is shown in FIG. 3.

[0045] Figure 6 A flowchart of another communication method provided by an embodiment of the present application is shown in FIG. 4.

[0046] Figure 7 A flowchart of another communication method provided by an embodiment of the present application is shown in FIG. 5.

[0047] Figure 8 A flowchart of another communication method provided by an embodiment of the present application is shown in FIG. 6.

[0048] Figure 9 A flowchart of another communication method provided by an embodiment of the present application is shown in FIG. 7.

[0049] Figure 10 A flowchart of another communication method provided by an embodiment of the present application is shown in FIG. 8.

[0050] Figure 11 A schematic diagram of a communication device provided by an embodiment of the present application is shown in FIG. 9.

[0051] Figure 12 A schematic diagram of another communication device provided by an embodiment of the present application is shown in FIG. 10. DETAILED DESCRIPTION

[0052] In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the embodiments of the present application will be further described in detail below with reference to the drawings.

[0053] The communication method provided by the embodiments of the present application can be applied to a non-terrestrial network (NTN) system. The NTN system can utilize NTN devices such as unmanned aerial vehicles, high altitude platform stations (HAPS), satellites, etc. to form a network and provide services such as data transmission and voice communication for terminal devices. In addition, the NTN system can also include other NTN devices, which are not limited by the present application.

[0054] The NTN system can also support various mobile communication systems, such as a new radio (NR) system, a long term evolution (LTE) system, or other communication systems in the future, without limitation.

[0055] Taking a satellite as an example of an NTN device in an NTN system, according to the altitude of the satellite, that is, the orbital altitude of the satellite, the satellite can be divided into a geostationary earth orbit (GEO) satellite, a medium earth orbit (MEO) satellite, and a low-earth orbit (LEO) satellite. The GEO is a synchronous earth satellite orbit, and a satellite operating in this orbit is stationary relative to the ground. The orbital altitude of the GEO is generally 35786 kilometers (km). The LEO and the MEO are collectively referred to as a non-geostationary orbit (NGSO), and a satellite operating in such an orbit moves at a high speed relative to the ground. The orbital altitude of the LEO is generally 160-2000 km, and the orbital altitude of the MEO is generally 2000-35786 km. For the NGSO, according to whether the beam of the satellite moves with the satellite, the NGSO can be further divided into an earth moving cell and an earth fixed cell or a quasi-Earth fixed cell. For the earth moving cell, the cell is moving relative to the ground, and the pointing direction of the beam of the satellite follows the satellite. For the earth fixed cell, the cell is fixed relative to the ground within a certain time, and the satellite antenna can use its beamforming capability to point the beam to a certain area fixed on the ground within a certain time.

[0056] In the NTN system, the working mode of the NTN device can include: a transparent mode and a regenerative mode. According to the working mode of the NTN device, the architecture of the NTN system can be divided into two categories: one is a transparent architecture, in which the NTN device can be a relay or an amplifier, and can perform radio frequency filtering, amplification, etc., to regenerate the physical layer signal. The NTN device can be responsible for layer 1 (L1) relay for physical layer forwarding, and the higher layer is invisible. The other is a regenerative architecture, in which the NTN device has the processing function of the access network device, and optionally, the NTN device has the processing function of part of the core network device. For example, taking a satellite as an NTN device in the NTN system, the satellite in the regenerative working mode can be divided into a regenerative satellite without an inter-satellite link (ISL), i.e., there is no ISL between satellites; or a regenerative satellite with an ISL, i.e., there is an interface for direct data interaction between satellites, wherein the ISL is an Xn interface; or a regenerative satellite with the distributed unit (DU) processing function of the access network device, in which case the satellite acts as a DU.

[0057] For example, Figure 1 An NTN system diagram to which the embodiments of the present application are applicable is shown, which can be a regenerative architecture. Figure 1 In the system shown, the access network device can be arranged on the satellite, or the satellite has part or all of the functions of the access network device. The satellite can provide wireless access services for terminal devices, and can communicate with the core network (CN) through the NTN gateway, and then connect to the data network (DN) through the core network. In addition, part or all of the core network devices in the core network can also be arranged on the satellite, or the satellite can have the functions of part or all of the core network devices in the core network. Among them, Figure 1 An example of a regenerative satellite architecture without an ISL is shown.

[0058] Figure 1 Only one satellite and one NTN gateway are shown, and in actual use, an architecture including multiple satellites and / or multiple NTN gateways can be deployed as needed. Among them, each satellite can provide services to one or more terminal devices, each NTN gateway can correspond to one or more satellites, and each satellite can correspond to one or more NTN gateways, which are not limited in detail in the embodiments of the present application.

[0059] The device related to the embodiments of the present application includes a terminal device and a network device, for example, including an access network device and / or a core network device.

[0060] wherein:

[0061] The terminal device is also called user equipment (UE), mobile station (MS), mobile terminal (MT), etc., and refers to a device that provides voice and / or data connectivity to a user. For example, the terminal device can be a handheld device having wireless connection function, a vehicle-mounted device, etc. Currently, some examples of the terminal device can be: mobile phone, tablet computer, notebook computer, palm computer, mobile internet device (MID), wearable device, virtual reality (VR) device, augmented reality (AR) device, wireless terminal in industrial control, wireless terminal in self driving, wireless terminal in remote medical surgery, wireless terminal in smart grid, wireless terminal in transportation safety, wireless terminal in smart city, wireless terminal in smart home, cellular internet of things (CIoT) device, etc.

[0062] Access network equipment can refer to radio access network (RAN) nodes (or devices) that connect terminal devices to a wireless network, such as base stations. Examples of RAN nodes include: evolved Node B (gNB), transmission reception point (TRP), evolved Node B (eNB), radio network controller (RNC), Node B (NB), base station controller (BSC), base transceiver station (BTS), home base station (e.g., home evolved Node B, or home Node B, HNB), baseband unit (BBU), or wireless fidelity (Wi-Fi) access point (AP), etc.

[0063] Additionally, in one network architecture, access network equipment may include centralized unit (CU) nodes, distributed unit (DU) nodes, or a combination of CU and DU nodes. This includes RAN equipment with both CU and DU nodes, which separates the protocol layer of the gNB in ​​the NR system. Some protocol layer functions are centrally controlled by the CU, while the remaining partial or complete protocol layer functions are distributed across the DUs, which are then centrally controlled by the CU. Figure 2As shown. Furthermore, the CU can be divided into a control plane (CU-CP) and a user plane (CU-UP). The CU-CP is responsible for control plane functions, mainly including radio resource control (RRC) and the corresponding packet data convergence protocol (PDCP) (i.e., PDCP-C). PDCP-C is mainly responsible for control plane data encryption / decryption, integrity protection, and data transmission. The CU-UP is responsible for user plane functions, mainly including the service data adaptation protocol (SDAP) and the corresponding PDCP (i.e., PDCP-U). SDAP is mainly responsible for processing core network data and mapping flows to bearers. PDCP-U is mainly responsible for data plane encryption / decryption, integrity protection, header compression, sequence number maintenance, and data transmission. The CU-CP and CU-UP are connected via the E1 interface. The CU-CP represents the gNB connecting to the core network via the NG interface and to the DU via the F1 interface control plane (i.e., F1-C). The CU-UP connects to the DU via the F1 interface user plane (i.e., F1-U). Alternatively, the PDCP-C could also be located within the CU-UP.

[0064] It is understood that CU (including CU-CP or CU-UP) or DU may have different names in different systems, but those skilled in the art will understand their meaning. For example, in an open radio access network (O-RAN) system, CU can also be called O-CU (open CU), DU can also be called O-DU, CU-CP can also be called O-CU-CP, and CU-UP can also be called O-CU-UP. For ease of description, this application uses CU, CU-CP, CU-UP, and DU as examples.

[0065] Core network equipment corresponds to different devices in different systems. For example, such as... Figure 3As shown, the 4th generation (4G) mobile communication system can be divided into two parts: terminal equipment and operator network. The operator network includes a radio access network (such as the evolved Universal Mobile Telecommunications System Terrestrial Radio Access Network, E-UTRAN) and a core network. The core network includes user plane network elements and control plane network elements. User plane network elements include the serving gateway (SGW) and packet data network gateway (PGW), etc. The control plane network elements include the mobility management entity (MME).

[0066] like Figure 4As shown, the 5th generation (5G) mobile communication system can be divided into three parts: terminal equipment, data network, and operator network. The operator network includes a radio access network and a core network. The core network includes user plane network elements and control plane network elements. The user plane network elements of the core network include user plane functions (UPFs). The control plane network elements of the core network include the authentication server function (AUSF), access and mobility management function (AMF), session management function (SMF), network slicing selection function (NSSF), network exposure function (NEF), network repository function (NRF), policy control function (PCF), unified data management (UDM), application function (AF), network slice-specific authentication and authorization function (NSSAAF), service communication proxy (SCP), network slice admission control function (NSACF), and edge application server discovery function (EASDF), etc.

[0067] Optionally, some or all core network devices can adopt a separate architecture. For example, in NTN, some functions of a core network device can be located on a satellite (e.g., the satellite has some of the functions of the core network device, or some functional modules of the core network device are located on the satellite), while the remaining functions are located on the ground. This can be understood as the functions of the core network device on the ground and the functions of the core network device on the satellite not being considered two independent parts, but rather jointly constituting the core network device. These two parts correspond to each other and jointly implement the functions of the core network device.

[0068] For example, in a 4G system, this core network equipment is, for instance, an MME. The MME can adopt a split architecture; for example, some of the MME's functions can be located on a satellite (e.g., the satellite has some of the MME's functions, or some functional modules of the MME are located on the satellite), while the remaining functions are located on the ground. It can be understood that the ground-based MME (called the ground-based MME (MME-Ground)) and the satellite-based MME (called the airborne MME (MME-Onboard)) are not considered two independent devices, but rather together constitute a single MME. MME-Ground and MME-Onboard are corresponding entities that jointly implement the MME's functions.

[0069] For example, in a 5G system, this core network equipment is, for instance, the AMF (Airborne Frame). The AMF can adopt a separate architecture; for example, some functions of the AMF can be located on a satellite (e.g., the satellite has some of the AMF's functions, or some functional modules of the AMF are located on the satellite), while the remaining functions are located on the ground. It can be understood that the ground-based AMF (called terrestrial AMF (AMF-Ground)) and the satellite-based AMF (called airborne AMF (AMF-Onboard)) are not considered two independent devices, but rather together constitute a single AMF. AMF-Ground and AMF-Onboard are corresponding devices that jointly implement the functions of the AMF.

[0070] In other communication systems, the core network equipment can be any corresponding core network equipment, without any specific restrictions.

[0071] In this application embodiment, the communication device used to implement the functions of a terminal device, access network device, or core network device can be the terminal device, access network device, or core network device itself, or it can be a device capable of supporting the terminal device, access network device, or core network device to implement that function, such as a chip system. This device can be installed in the terminal device, access network device, or core network device. In the technical solutions provided in this application embodiment, the terminal device is used as an example of the device used to implement the functions of the terminal device, the access network device is used as an example of the device used to implement the functions of the access network device, and the core network device is used as an example of the device used to implement the functions of the core network device.

[0072] The communication system applicable to the embodiments of this application has been briefly introduced above. The relevant technical solutions involved in the embodiments of this application are described below.

[0073] In an NTN system, the communication link between a satellite and a terminal device is called a service link (SL), the communication link between a satellite and a gateway station in the ground network is called a feeder link (FL), and the communication link between satellites is called an inter-satellite link (ISL). Typically, when a terminal device accesses the network through NTN, it can utilize these communication links to achieve end-to-end connectivity between the terminal device, satellite, and ground network. For example, the connection could be: terminal device - service link - satellite 1 - inter-satellite link - satellite 2 - feeder link - ground network.

[0074] Some communication links between terminal equipment, satellite, and terrestrial networks may become unavailable. For example, in areas without gateway stations deployed with terrestrial networks, when a satellite covers terminal equipment in that area (i.e., the service link is available), it cannot connect to the terrestrial network providing services to users in that area via the feeder link (i.e., the feeder link is unavailable). Conversely, when a satellite covers a gateway station with a terrestrial network outside that area (i.e., the feeder link is available), it cannot cover users in that area (i.e., the service link is unavailable). As another example, in areas with gateway stations deployed with terrestrial networks, when a satellite covers both terminal equipment and the terrestrial network gateway station in that area, both the service link and the feeder link are initially available. However, a failure at the terrestrial network gateway station could render the feeder link unavailable, or a failure of the terminal equipment could render the service link unavailable.

[0075] In scenarios where the feeder link is unavailable, to successfully transmit data, the terrestrial network can send the context information of the terminal device to the satellite when the feeder link is available. When the feeder link is unavailable but the service link is available, the satellite can establish a connection with the terminal device using the context information stored on the satellite. However, many factors can cause the context information of the terminal device to change, such as a change in the terminal device's location. If the context information stored on the satellite is not updated in a timely manner, the context information stored on the terminal device and the context information stored on the satellite will be inconsistent, leading to the terminal device's failure to access the network. Therefore, how to successfully transmit data between the terminal device and the satellite when the terminal device's context information changes is a problem that needs to be solved.

[0076] For example, terminal devices can interact with the network to perform attach, registration, or tracking area update (TAU) procedures, creating or updating their context information. Once the terminal device's context information is created or updated, the ground-based core network equipment generates a corresponding accept message (e.g., attach accept message, registration accept message, TAU accept message). This accept message carries an activation timer, the length of which is greater than or equal to the time required for the ground-based core network equipment to synchronize the latest terminal device context information to the satellite serving the terminal device. When the feed link to the satellite serving the terminal device is available, the ground-based core network equipment can synchronize the latest terminal device context information to that satellite. After receiving the accept message, the terminal device enters the registered state until the activation timer expires.

[0077] It is evident that each time the context information of a terminal device is created or updated, the terminal device needs to wait for the core network equipment on the ground to synchronize the context information of the terminal device to the satellite serving the terminal device before it can transmit data through that satellite. Currently, a terminal device can have multiple satellites serving it at different times. The more satellites serving the terminal device, the longer it takes for the core network equipment on the ground to synchronize the context information of the terminal device to each satellite. This results in the terminal device starting to receive services from each satellite later, potentially leading to longer service interruptions and lower data transmission efficiency.

[0078] Therefore, embodiments of this application provide a communication method that can improve the efficiency of data transmission.

[0079] In the embodiments of this application, "when," "if," and "if" all refer to the device taking corresponding actions under certain objective circumstances, and are not time-limited, nor do they require the device to perform a judgment action, nor do they imply any other limitations. Unless otherwise specified, "if" and "if" can be substituted, and "when" and "in the case of" can be substituted. "When" and "if" / "if" can be substituted.

[0080] In the embodiments of this application, the terms "exemplary" or "for example" are used to indicate that something is an example, illustration, or description. Any embodiment or design that is described as "exemplary" or "for example" in this application should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of the terms "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0081] In this document, "used for indication" can include both direct and indirect indication. For example, when descriptive information I is used to indicate information J, it can mean that information I directly indicates information J or indirectly indicates information J, but it does not necessarily mean that information I carries information J.

[0082] Let information J, indicated by information I, be called the information to be indicated. In practice, there are many ways to indicate the information to be indicated, such as, but not limited to, directly indicating the information to be indicated, such as the information itself or its index. It can also be indirectly indicated by indicating other information, where there is a relationship between the other information and the information to be indicated. It can also indicate only a part of the information to be indicated, while the other parts are known or pre-agreed upon. For example, the indication of specific information can be achieved by using a pre-agreed (e.g., protocol-defined) order of various pieces of information, thereby reducing indication overhead to some extent. Simultaneously, common parts of various pieces of information can be identified and indicated uniformly to reduce the indication overhead caused by individually indicating the same information.

[0083] Furthermore, the specific instruction method can also be any existing instruction method, such as, but not limited to, the above-mentioned instruction methods and their various combinations. As described above, for example, when multiple pieces of information of the same type need to be indicated, the instruction methods for different pieces of information may differ. In specific implementation, the required instruction method can be selected according to specific needs. This application embodiment does not limit the selected instruction method. Therefore, the instruction methods involved in this application embodiment should be understood to cover various methods that enable the party to be instructed to obtain the information to be indicated.

[0084] In the embodiments of this application, "send" and "receive" indicate the direction of signal transmission. For example, "send information to XX" can be understood as the destination of the information being XX, which may include direct transmission via the air interface or indirect transmission via the air interface by other units or modules. "Receive information from YY" can be understood as the source of the information being YY, which may include direct reception from YY via the air interface or indirect reception from YY via the air interface by other units or modules. "Send" can also be understood as the "output" of the chip interface, and "receive" can also be understood as the "input" of the chip interface.

[0085] Information may undergo necessary processing, such as encoding and modulation, between the source and destination ends, but the destination end can understand the valid information from the source end. Similar statements in the embodiments of this application can be understood in a similar way, and will not be repeated here.

[0086] In this application embodiment, the number of nouns, unless otherwise specified, refers to "singular nouns or plural nouns," that is, "one or more." "At least one" means one or more, and "more than one" means two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists alone, A and B exist simultaneously, or B exists alone, where A and B can be singular or plural. The character " / " can indicate that the related objects before and after are in an "or" relationship. For example, A / B means: A or B. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one of a, b, or c means: a, b, c, a and b, a and c, b and c, or a and b and c, where a, b, and c can be single or multiple.

[0087] In this application, the ordinal numbers such as "first" and "second" are used to distinguish multiple objects, and are not used to limit the size, content, order, timing, priority, or importance of the multiple objects. For example, "first information" and "second information" refer to two different pieces of information, and do not indicate a difference in priority or importance between the two pieces of information. For a technical feature, the technical features within that technical feature are distinguished by "A," "B," "C," and "D," and there is no sequential or hierarchical order among the technical features described by "A," "B," "C," and "D." For example, in this document, method A and method B are only used to distinguish different content, and do not limit the sequential or hierarchical order, priority, or importance between method A and method B.

[0088] The solution provided by the embodiments of this application will be described in detail below with reference to the accompanying drawings. In the following description, the communication method provided by the embodiments of this application is applied to... Figures 1-4 The communication system shown is an example. The communication system and application scenarios described in the embodiments of this application are for the purpose of more clearly illustrating the technical solutions of the embodiments of this application, and do not constitute a limitation on the technical solutions provided in the embodiments of this application. As those skilled in the art will know, with the evolution of communication systems and the emergence of new application scenarios, the technical solutions provided in the embodiments of this application are also applicable to similar technical problems.

[0089] The following describes the communication method provided in this application, using an embodiment executed by a terminal device and a network device (access network device and / or core network device) as an example. The steps executed by the terminal device can be implemented by the terminal device itself or by components within the terminal device (such as chips, processing units, or processor modules). The terminal device can be... Figures 1-4 The terminal device shown, or it could be Figures 1-4The steps performed by a network device can be implemented by the network device itself or by components within the network device (such as chips, processing units, or processor modules). A network device can be... Figures 1-4 The core network equipment shown, or it could be Figures 1-4 The chip (system) in the network device. When this communication method is implemented by components in the terminal device and the network device, the receiving and transmitting steps can be understood as the component communicating with other components, such as communication between the baseband chip and the radio frequency circuit. In the embodiments of this application, the processing performed by a single execution subject can also be divided into multiple execution subjects, which can be logically and / or physically separated. For example, the processing performed by the access network device can be divided into execution by at least one of CU, DU, and RU.

[0090] See Figure 5 , Figure 5 This is a flowchart illustrating a communication method provided in an embodiment of this application. Figure 5 As shown, the communication method includes the following steps.

[0091] S501. The terminal device determines whether the first context information stored in the first network device among multiple network devices has been updated, wherein the first context information is the context information of the terminal device, the first network device is located on the first satellite, and the first satellite is a satellite covering the terminal device.

[0092] S502, In the event that the first context information is updated, the terminal device establishes a connection with the second network device, wherein the second network device is located on the first satellite.

[0093] In this embodiment, the multiple satellites can be satellites covering the terminal device at different times, and the first satellite among the multiple satellites can be the satellite covering the terminal device at the current time. The multiple network devices are network devices on the multiple satellites used to store the context information of the terminal device. The multiple network devices can be core network devices on the multiple satellites, and the first network device among the multiple network devices can be the first core network device on the first satellite among the multiple satellites. Optionally, the multiple network devices can also be access network devices on the multiple satellites, and the first network device among the multiple network devices can be the first access network device on the first satellite among the multiple satellites.

[0094] The second network device on the first satellite is the first access network device on the first satellite. That is to say, when the first network device on the first satellite is the first core network device on the first satellite, the first network device and the second network device are different network devices; when the first network device on the first satellite is the first access network device on the first satellite, the first network device and the second network device are the same network device.

[0095] For ease of explanation, this application embodiment uses the multiple network devices as the core network devices on the multiple satellites, that is, the first network device on the first satellite is the first core network device on the first satellite, and the second network device on the first satellite is the first access network device on the first satellite.

[0096] "An update has occurred" can mean that the update process has started but not yet ended, or it can mean that the update process has ended. "Establishing a connection" can mean establishing a radio resource control connection; or it can mean establishing a radio bearer, such as a data radio bearer (DRB), where the DRB is a radio bearer for transmitting user data; or it can mean sending a service request message to request the establishment of a radio bearer with the terminal device. This application embodiment does not limit this. For ease of explanation, this application embodiment uses "an update has occurred" as an example and "establishing a connection" as an example of establishing a radio bearer.

[0097] In other words, the terminal device can establish a connection with the second network device on the first satellite after the context information of the terminal device stored on the satellite covering the terminal device has been updated at the current moment, thereby increasing the probability of successful connection establishment and thus successfully transmitting data. Furthermore, since the terminal device only needs to determine whether the context information of the terminal device stored on the satellite covering the terminal device has been updated at the current moment, it does not need to wait for the context information of the terminal devices stored on all satellites that can cover the terminal device to be updated, thus improving the efficiency of data transmission.

[0098] In one possible implementation, if the first context information is not updated, the terminal device may not establish a connection with the second network device on the first satellite to increase the probability of successful connection establishment. Furthermore, to reduce the power consumption of the terminal device, it may enter a sleep state. Entering a sleep state can be understood as the terminal device listening for system messages from the first satellite but not listening for paging messages from the first satellite; or it can be understood as the terminal device disabling access layer functions, meaning it neither listens for system messages nor paging messages from the first satellite.

[0099] In one possible implementation, before determining whether the first context information stored by the first network device among the plurality of network devices has been updated, the terminal device may receive first indication information. The first indication information is used to indicate that the first context information has begun updating. "Beginning updating" may mean that the update process has started, may have ended, or may not have ended yet. Alternatively, the terminal device may determine that the context information of the terminal device stored by the terminal device (e.g., referred to as second context information) has been updated.

[0100] In other words, after the terminal device determines that the first context information has started updating or the second context information has been updated, in order to avoid the terminal device failing to establish a connection with the second network device on the first satellite due to a difference between the first and second context information, it determines whether the first context information stored by the first network device on the first satellite has been updated, i.e., whether the first context information and the second context information are the same. Specifically, if the first context information has been updated, it is determined that the first context information and the second context information are the same; otherwise, it is determined that the first context information and the second context information are different.

[0101] In practice, the terminal device can determine whether the first context information stored by the first network device among the multiple network devices has been updated through several methods. These methods are described below.

[0102] In Method A, the terminal device can determine whether the first context information has been updated based on the first information.

[0103] The first information can also be referred to as satellite availability information or constellation availability information; however, the name of the first information is not limited in this embodiment. The first information can indicate the update time corresponding to some or all of the multiple network devices. That is, the first information can indicate the update time corresponding to at least one of the multiple network devices. The update time corresponding to one of the multiple network devices can be used to indicate the time when the context information of the terminal device stored in that network device is updated; therefore, the update time corresponding to the first network device among the multiple network devices is used to indicate the time when the first context information is updated.

[0104] The update time can be a single moment, i.e., the update time is the update instant. For example, if the update time corresponding to the first network device is moment 1, then the first context information is updated at moment 1. Alternatively, the update time can be a duration, i.e., the update time is the update duration. For example, if the update time corresponding to the first network device is duration 1, then the first context information is updated at the end of duration 1. The unit of update time can be microseconds (µs), milliseconds (ms), seconds (s), minutes, hours (h), etc. For example, moment 1 is 10:30:30 AM, and duration 1 is 8 hours. Alternatively, the unit of update time can also be a frame, subframe, or time slot, etc. For example, moment 1 is time slot 1, and duration 1 is 50 time slots. This application embodiment does not limit this.

[0105] In one possible implementation, the first information can directly indicate the update time of some or all of the network devices among the plurality of network devices; or, the first information can indirectly indicate the update time of some or all of the network devices among the plurality of network devices.

[0106] For example, when the first information indicates the update time #1 corresponding to the core network device #1 on satellite #1, the first information can directly indicate the identifier (ID) of satellite #1; or it can indirectly indicate the identifier of the access network device #1 on satellite #1. The first information can directly indicate the update time #1; or it can indirectly indicate the index of the update time #1. This application embodiment does not limit this.

[0107] When the first information indicates update time #1, it can use 7 bits to indicate 128 consecutive numbers as the value of update time #1. The unit of update time #1 can be indicated by other bits, such as 0 indicating minutes and 1 indicating hours, or the default unit of the protocol. When the first information indicates the index of update time #1, it can indicate the index of update time #1 as shown in Table 1.

[0108] Table 1

[0109] Index Update time #1 (h) 0 0h 1 10h 2 20h

[0110] For example, when the first information indicates the update time #1 corresponding to the core network device #1 on satellite #1, the update time #2 corresponding to the core network device #2 on satellite #2, the update time #3 corresponding to the core network device #3 on satellite #3, and the update time #4 corresponding to the core network device #4 on satellite #4, the first information can be as shown in Table 2.

[0111] Table 2

[0112]

[0113]

[0114] In one possible implementation, some or all of the network devices among the plurality of network devices may include a first network device. That is, the first information may indicate the update time corresponding to the first network device. Therefore, the terminal device can directly determine whether the first context information has been updated based on the update time corresponding to the first network device. Specifically, if the current time is later than the update time corresponding to the first network device or the end time of the update duration corresponding to the first network device, it is determined that the first context information has been updated; otherwise, it is determined that the first context information has not been updated.

[0115] For example, there are six satellites covering the terminal devices at different times: Satellite #1, Satellite #2, Satellite #3, Satellite #4, Satellite #5, and Satellite #6. The update time #1 for core network device #1 on Satellite #1 is time 1; the update time #2 for core network device #2 on Satellite #2 is time 2; the update time #3 for core network device #3 on Satellite #3 is time 3; the update time #4 for core network device #4 on Satellite #4 is time 4; the update time #5 for core network device #5 on Satellite #5 is time 5; and the update time #6 for core network device #6 on Satellite #6 is time 6. Time 1 is earlier than time 2, time 2 is earlier than time 3, time 3 is earlier than time 4, time 4 is earlier than time 5, and time 5 is earlier than time 6.

[0116] The first information can indicate the update time #1 corresponding to the core network device #1 on satellite #1. That is, the update time corresponding to some or all of the multiple network devices indicated by the first information can include the update time corresponding to the first network device. If the current time is later than time 1, the terminal device can determine that the context information of the terminal device stored in the core network device #1 on satellite #1 has been updated.

[0117] Alternatively, some or all of the network devices among the plurality of network devices may include a third network device. The update time corresponding to the third network device is later than the update time corresponding to the remaining network devices among the plurality of network devices. This can be understood as the update time corresponding to the third network device being later than the update time corresponding to the remaining network devices among the plurality of network devices, or the update duration corresponding to the third network device being later than the end time of the update duration corresponding to the remaining network devices among the plurality of network devices.

[0118] For example, the update time #1 for core network device #1 on satellite #1 is time 1; the update time #2 for core network device #2 on satellite #2 is time 2; the update time #3 for core network device #3 on satellite #3 is time 3; the update time #4 for core network device #4 on satellite #4 is time 4; the update time #5 for core network device #5 on satellite #5 is time 5; and the update time #6 for core network device #6 on satellite #6 is time 6. Since time 1 is earlier than time 2, time 2 is earlier than time 3, time 3 is earlier than time 4, time 4 is earlier than time 5, and time 5 is earlier than time 6, then core network device #6 on satellite #6 is the third network device.

[0119] In other words, the first information can indicate the update time corresponding to the third network device, that is, the latest update time among the update times of each of the multiple network devices. Therefore, the terminal device can indirectly determine whether the first context information has been updated based on the update time corresponding to the third network device. Specifically, if the current time is later than the update time corresponding to the third network device or the end time of the update duration corresponding to the third network device, it is determined that the context information stored by each of the multiple network devices has been updated, and thus it is determined that the first context information has been updated.

[0120] For example, the first information could indicate the update time #1 corresponding to core network device #1 on satellite #1, the update time #2 corresponding to core network device #2 on satellite #2, the update time #3 corresponding to core network device #3 on satellite #3, and the update time #6 corresponding to core network device #6 on satellite #6. That is, the update times corresponding to some or all of the multiple network devices indicated by the first information could include the latest update time among the update times corresponding to each of the multiple network devices, i.e., the update time corresponding to the third network device. If the current time is later than time 6, the terminal device can determine that the context information of the terminal device stored in core network devices #1 on satellite #1, #2 on satellite #2, #3 on satellite #3, #4 on satellite #4, #5 on satellite #5, and #6 on satellite #6 has been updated.

[0121] In one possible implementation, upon update of the first context information, the terminal device can set the state of the first satellite relative to the terminal device to a first state (or active state). This first state indicates that the terminal device can listen for messages from the first satellite and can send messages to the first satellite.

[0122] If the first context information is not updated, the terminal device can set the state of the first satellite relative to the terminal device to a second state (or an inactive state). The second state indicates that the terminal device can listen to system messages from the first satellite, but cannot listen to paging messages from the first satellite, nor can it send messages to the first satellite; alternatively, the second state can also indicate that the terminal device disables access layer functions, meaning the terminal device cannot listen to system messages or paging messages from the first satellite, nor can it send messages to the first satellite.

[0123] It is understandable that the state of the first satellite relative to the terminal device is not the state of the first satellite as perceived by the first satellite, that is, not the actual state of the first satellite, but the state of the first satellite as perceived by the terminal device.

[0124] In one possible implementation, the first information may be generated by the network and sent to the terminal device, or it may be generated by the terminal device itself. This application does not limit this implementation. These will be described separately below.

[0125] In scenario one, the terminal device can receive the first information. That is, the first information is generated and sent to the terminal device by the network (e.g., a fourth network device on the ground, a fifth network device on the ground, or a first network device on a first satellite).

[0126] Among them, the fourth and fifth ground-based network devices are both core network devices. The fourth ground-based network device is not an independent core network device, while the fifth ground-based network device is an independent core network device.

[0127] For example, the first network device on the first satellite and the fourth network device on the ground are not independent core network devices. They are two parts of a core network device. The first network device on the first satellite and the fourth network device on the ground are corresponding and together form a complete core network device. In other words, the first network device on the first satellite + the fourth network device on the ground = the complete core network device.

[0128] Each network device on the multiple network devices and the fourth network device on the ground are not independent core network devices; each network device on the multiple network devices plus the fourth network device on the ground equals the complete core network device. Therefore, the fourth network device on the ground stores the same context information of the terminal devices as each network device on the multiple network devices. In other words, when the context information of the terminal devices stored on the fourth network device on the ground is updated, it needs to be synchronized to each network device on the multiple network devices.

[0129] Taking a 4G mobile communication system as an example, the first network device on the first satellite can be an MME network element, and the fourth network device on the ground can also be an MME network element. The total number of MME network elements on the ground plus the number of MME network elements on the first satellite equals the complete MME network element. The fifth network device on the ground can be a UE reachability estimator (URE) network element.

[0130] For example, consider the case where the first piece of information comes from a fourth network device on the ground. Figure 6 This is a flowchart illustrating another communication method provided in an embodiment of this application. Figure 6 As shown, before executing S501, the embodiments of this application may also perform the following steps.

[0131] Step a1: The fourth network device on the ground determines that the context information of the terminal device stored on the fourth network device on the ground has been updated.

[0132] For example, there are five satellites covering the terminal devices at different times: satellite #1, satellite #2, satellite #3, satellite #4, and satellite #5. Satellite #1 houses access network equipment #1 and core network equipment #1; satellite #2 houses access network equipment #2 and core network equipment #2; satellite #3 houses access network equipment #3 and core network equipment #3; satellite #4 houses access network equipment #4 and core network equipment #4; and satellite #5 houses access network equipment #5 and core network equipment #5. There is one ground-based core network device capable of serving the terminal devices: core network device #6. There are three gateway stations connected to the ground-based core network device #6: gateway station #1, gateway station #2, and gateway station #3. Satellites #1, #2, #3, #4, and #5 can connect to the ground-based core network device #6 through any one of these gateway stations.

[0133] After the terminal device, core network equipment #1 on satellite #1, core network equipment #2 on satellite #2, core network equipment #3 on satellite #3, core network equipment #4 on satellite #4, core network equipment #5 on satellite #5, and ground-based core network equipment #6 all store the terminal device's context information #1, the terminal device triggers the TAU procedure. When the communication link between satellite #1 and the terminal device is available, it sends a TAU request message to satellite #1. When the communication link between satellite #1 and ground-based core network equipment #6 is available, satellite #1 transmits a TAU request message to ground-based core network equipment #6. After receiving the TAU request message, ground-based core network equipment #6 determines that the terminal device's context information stored by the fourth network device on the ground has been updated.

[0134] Step a2: The fourth network device on the ground determines the first information based on the second information, the coverage information of the satellite where some or all of the network devices are located, and the location information of the fourth network device on the ground.

[0135] The second information can be used to identify a portion of the network devices among the plurality of network devices. Optionally, the second information can be used to indicate the service type and / or communication mode of the terminal device. For example, the service type of the terminal device can indicate whether the terminal device's service is a latency-sensitive service, a latency-insensitive service, etc. The communication mode of the terminal device can indicate the communication duration, cycle time, planned communication time, etc. The communication duration refers to the duration of a single communication session in a periodic communication, such as 5 minutes. The cycle time refers to the interval between periodic communications, such as 1 hour. The planned communication time refers to the time zone and weekday in which the terminal device can communicate, such as 13:00-20:00 on Monday. The names of the second information are not limited in the embodiments of this application.

[0136] The coverage information of the satellites on which some or all of the network devices are located refers to ephemeris information or information on the mapping relationship between satellite coverage area and time.

[0137] Specifically, the fourth network device on the ground can determine the update time corresponding to the network device on each satellite covering the terminal device at different times based on the coverage information of each satellite covering the terminal device at different times, the location information of the fourth network device on the ground, and the location information of some or all of the gateway stations corresponding to the fourth network device on the ground. It can also determine the first information based on the update time and the second information corresponding to the network device on each satellite covering the terminal device at different times.

[0138] For example, the ground-based core network device #6 can determine the availability of the communication link between satellite #1 and the ground-based core network device #6 based on the coverage information of satellites #1, #2, #3, #4, and #5, the location information of the ground-based core network device #6, and the location information of gateway stations #1, #2, and #3. It can also determine that the communication link between satellite #2 and the ground-based core network device #6 will be available after 2 hours, after 4 hours, after 6 hours, after 6 hours, and after 8 hours, after 8 hours.

[0139] Taking the update time of the terminal device context information stored by the core network equipment on each satellite as equal to the available communication link time between each satellite and the ground core network equipment #6 as an example, the ground core network equipment #6 can determine that the update time #1 corresponding to the core network equipment #1 on satellite #1 is 0h, the update time #2 corresponding to the core network equipment #2 on satellite #2 is 2h, the update time #3 corresponding to the core network equipment #3 on satellite #3 is 4h, the update time #4 corresponding to the core network equipment #4 on satellite #4 is 6h, and the update time #3 corresponding to the core network equipment #5 on satellite #5 is 8h.

[0140] Taking a terminal device with a latency-insensitive service type as an example, the ground-based core network device #6 can determine that the terminal device requires three satellites to provide services to meet its minimum latency requirements. Assuming the terminal device's communication mode indication period is 1 hour, the ground-based core network device #6 can determine, based on the coverage information of satellites #1, #2, #3, #4, and #5, and the terminal device's location information, that the communication link between satellite #1 and the terminal device is currently available; the communication link between satellite #2 and the terminal device will be available after 1 hour; the communication link between satellite #3 and the terminal device will be available after 2 hours; the communication link between satellite #4 and the terminal device will be available after 3 hours; and the communication link between satellite #5 and the terminal device will be available after 4 hours. Furthermore, the ground-based core network device #6 can determine that the time when satellites #1, #2, and #3 cover the terminal device best matches the frequency of the terminal device's data transmission.

[0141] Therefore, to reduce the overhead of the first information, the ground-based core network equipment #6 can select satellites #1, #2, and #3 from among the satellites #1, #2, #3, #4, and #5 serving the terminal equipment for use by the terminal equipment. In other words, the ground-based core network equipment #6 can determine the update times corresponding to the core network equipment on some or all of the satellites covering the terminal equipment at different times, as indicated by the first information. This includes update time #1 for core network equipment #1 on satellite #1, update time #2 for core network equipment #3 on satellite #2, and update time #3 for core network equipment #3 on satellite #3.

[0142] In addition, since the latest update time among the update times corresponding to each satellite is the update time #5 corresponding to satellite #5, in order to prevent the terminal equipment from only using satellites #1, #2, and #3 and not using satellites #4 and #5, the core network equipment #6 on the ground can determine that the update time corresponding to the core network equipment on some or all of the satellites covering the terminal equipment at different times indicated by the first information also includes the update time #5 corresponding to satellite #5.

[0143] Step a3: When the fourth network device on the ground is within the coverage area of ​​the first satellite, the fourth network device on the ground sends first information to the first network device on the first satellite, and correspondingly, the first network device on the first satellite receives the first information from the fourth network device on the ground.

[0144] For example, the core network device #6 on the ground determines, based on the location information of the terminal device and the coverage information of each satellite covering the terminal device at different times, to send a TAU acceptance message to the terminal device via satellite #1. The TAU acceptance message includes first information.

[0145] When the communication link between satellite #1 and the ground-based core network device #6 is available, the ground-based core network device #6 sends the latest terminal device context information and TAU acceptance message to the core network device #1 on satellite #1. Correspondingly, the core network device #1 on satellite #1 receives the latest terminal device context information and TAU acceptance message from the ground-based core network device #6.

[0146] When communication links between satellites #2, #3, #4, and #5 and the ground-based core network equipment #6 are available, the ground-based core network equipment #6 sends the latest terminal device context information to core network equipment #2 on satellite #2, core network equipment #3 on satellite #3, core network equipment #4 on satellite #4, and core network equipment #5 on satellite #5, respectively. Correspondingly, core network equipment #2 on satellite #2, core network equipment #3 on satellite #3, core network equipment #4 on satellite #4, and core network equipment #5 on satellite #5 receive the latest terminal device context information from the ground-based core network equipment #6.

[0147] Step a4: When the terminal device is within the coverage area of ​​the first satellite, the first network device on the first satellite sends the first information to the terminal device through the second network device on the first satellite. Correspondingly, the terminal device receives the first information from the first network device on the first satellite through the second network device on the first satellite.

[0148] For example, when the communication link between satellite #1 and the terminal device is available, core network device #1 on satellite #1 sends a TAU acceptance message to the terminal device through access network device #1 on satellite #1. Correspondingly, the terminal device receives the TAU acceptance message from core network device #1 on satellite #1 through access network device #1 on satellite #1. The TAU acceptance message includes first information.

[0149] For example, consider a scenario where the first piece of information is generated by a fifth network device on the ground. Figure 7This is a flowchart illustrating another communication method provided in an embodiment of this application. Figure 7 As shown, before executing S501, the embodiments of this application may also perform the following steps.

[0150] Step b1: The fourth network device on the ground determines that the context information of the terminal device stored on the fourth network device on the ground has been updated.

[0151] Step b1 can be referred to step a1 above, and will not be repeated here.

[0152] Step b2: The fourth network device on the ground sends the third information to the fifth network device on the ground, and correspondingly, the fifth network device on the ground receives the third information from the fourth network device on the ground.

[0153] The third information is used to indicate the location information of the second information, the terminal device, and the fourth network device on the ground. The name of the third information is not limited in this embodiment.

[0154] Optionally, the third information can also be used to indicate the location information of some or all of the gateway stations corresponding to the fourth network device on the ground.

[0155] Optionally, the third information can also be used to indicate network devices on some or all of the satellites covering the terminal device at different times. The satellites indicated by the third information covering the terminal device at different times may be the same as those indicated by the first information. The satellites indicated by the third information covering the terminal device at different times may be pre-configured, or they may be selected by a fourth terrestrial network device from the satellites covering the terminal device at different times and provided to the terminal device, for example, based on the terminal device's service type and / or communication mode.

[0156] The second piece of information can be found in step a2 above, and will not be repeated here.

[0157] In specific implementation, the third information can directly indicate the location information of the terminal device, the location information of the fourth network device on the ground, and the location information of some or all of the gateway stations corresponding to the fourth network device on the ground; or it can indirectly indicate the identifier of the terminal device, the identifier of the fourth network device on the ground, and the identifier of some or all of the gateway stations corresponding to the fourth network device on the ground. This application embodiment does not limit this.

[0158] The third piece of information can directly indicate the identifiers of some or all of the satellites covering the terminal device at different times; or it can indirectly indicate the identifiers of the access network devices on some or all of the satellites covering the terminal device at different times. This application does not limit this aspect.

[0159] For example, the ground-based core network device #6 sends information to the ground-based core network device #7. This information includes the service type and / or communication mode of the terminal device, the location information of the terminal device, the location information of the ground-based core network device #6, the location information of gateway stations #1, #2 and #3 connected to the ground-based core network device #6, the identifier of satellite #1, and the identifier of satellite #2.

[0160] Step b3: The fifth network device on the ground determines the first information based on the third information and the coverage information of the satellites where some or all of the network devices are located.

[0161] Specifically, the fifth network device on the ground can determine each satellite covering the terminal device at different times based on the terminal device's location information. Based on the coverage information of each satellite covering the terminal device at different times, the location information of the fourth network device on the ground, and the location information of some or all of the gateway stations corresponding to the fourth network device on the ground, it can determine the update time corresponding to the network device on each satellite covering the terminal device at different times. Based on the update time corresponding to the network device on each satellite covering the terminal device at different times and the second information, it can determine the first information. See step a2 above for details, which will not be repeated here.

[0162] Step b4: The fifth network device on the ground sends the first information to the fourth network device on the ground, and correspondingly, the fourth network device on the ground receives the first information from the fifth network device on the ground.

[0163] For example, the core network device #7 on the ground sends response message 1 to the core network device #6 on the ground. Response message 1 includes first information.

[0164] Step b5: When the fourth network device on the ground is within the coverage area of ​​the first satellite, the fourth network device on the ground sends first information to the first network device on the first satellite, and correspondingly, the first network device on the first satellite receives the first information from the fourth network device on the ground.

[0165] Step b5 can be referred to step a3 above, and will not be repeated here.

[0166] Step b6: When the terminal device is within the coverage area of ​​the first satellite, the first network device on the first satellite sends the first information to the terminal device through the second network device on the first satellite. Correspondingly, the terminal device receives the first information from the first network device on the first satellite through the second network device on the first satellite.

[0167] Step b6 can be referred to step a4 above, and will not be repeated here.

[0168] For example, consider a scenario where the first information is generated and sent to a terminal device by a first network device on a first satellite. Figure 8 This is a flowchart illustrating another communication method provided in an embodiment of this application. Figure 8 As shown, before executing S501, the embodiments of this application may also perform the following steps.

[0169] Step c1: The first network device on the first satellite determines that the context information of the terminal device stored in the first network device on the first satellite has been updated.

[0170] For example, the terminal device, core network device #1 on satellite #1, core network device #2 on satellite #2, core network device #3 on satellite #3, core network device #4 on satellite #4, core network device #5 on satellite #5, and ground-based core network device #6 all store the terminal device's context information #1. The terminal device triggers the TAU procedure. When the communication link between satellite #1 and the terminal device is available, it sends a TAU request message to satellite #1. When the communication link between satellite #1 and ground-based core network device #6 is available, satellite #1 transmits the TAU request message to ground-based core network device #6.

[0171] After receiving the TAU request message, the ground-based core network device #6 determines that the context information of the terminal device stored in its storage has been updated. Based on the terminal device's location information and the coverage information of each satellite covering the terminal device at different times, it determines to send a TAU acceptance message to the terminal device via satellite #1. When the communication link between satellite #1 and the ground-based core network device #6 is available, the ground-based core network device #6 sends the latest terminal device context information and the TAU acceptance message to the core network device #1 on satellite #1. When the communication links between satellites #2, #3, #4, and #5 and the ground-based core network device #6 are available, the ground-based core network device #6 sends the latest terminal device context information to the core network devices #2 on satellite #2, #3 on satellite #3, #4 on satellite #4, and #5 on satellite #5, respectively.

[0172] After receiving the TAU request message and the latest context information of the terminal device, the core network device #1 on satellite #1 determines that the context information of the terminal device stored by the core network device #1 on satellite #1 has been updated.

[0173] Step c2: The first network device on the first satellite determines the first information based on the second information, the coverage information of the satellite where some or all of the network devices are located, and the location information of the fourth network device on the ground.

[0174] Step c2 can be referred to as step a2 above, and will not be repeated here.

[0175] Step c3: When the terminal device is within the coverage area of ​​the first satellite, the first network device on the first satellite sends the first information to the terminal device through the second network device on the first satellite. Correspondingly, the terminal device receives the first information from the first network device on the first satellite through the second network device on the first satellite.

[0176] Step c3 can be referred to step a4 above, and will not be repeated here.

[0177] In scenario two, the terminal device can determine the first information based on the coverage information of the satellites where some or all of the network devices are located and the location information of the fourth network device on the ground.

[0178] Specifically, the terminal device can determine the update time corresponding to the network device on each satellite covering the terminal device at different times based on the coverage information of each satellite covering the terminal device at different times, the location information of the fourth network device on the ground, and the location information of some or all of the gateway stations corresponding to the fourth network device on the ground, and determine the first information based on the update time corresponding to the network device on each satellite covering the terminal device at different times.

[0179] For details, please refer to step a2 above, which will not be repeated here.

[0180] In method B, the terminal device can determine whether the first identifier and the second identifier are the same. If the first identifier and the second identifier are the same, it means that the first context information has been updated; otherwise, it means that the first context information has not been updated. The first identifier is the identifier of the first context information, and the second identifier is the identifier of the terminal device's context information (e.g., referred to as the second context information) stored by the terminal device.

[0181] The first identifier can also be called the first context sequence number (CSN), and the second identifier can also be called the second context sequence number. In this embodiment of the application, the names of the first identifier and the second identifier are not limited.

[0182] In one possible implementation, the first identifier may be sent to the terminal device by a first network device on the first satellite. For example, the first network device on the first satellite may send a first paging message to the terminal device via a second network device on the first satellite. Correspondingly, the terminal device may receive the first paging message from the first network device on the first satellite via the second network device on the first satellite. The first paging message includes the first identifier. The second identifier may be stored locally on the terminal device.

[0183] In one possible implementation, the terminal device may also send the second identifier to the first network device on the first satellite. For example, the terminal device can send a first request message to the first network device on the first satellite via the second network device on the first satellite. Correspondingly, the first network device on the first satellite can receive the first request message from the terminal device via the second network device on the first satellite. The first request message includes the second identifier and is used to request the establishment of a connection with the terminal device. The first network device on the first satellite can determine whether the first identifier and the second identifier are the same. If the first identifier and the second identifier are the same, it indicates that the second context information has been updated; otherwise, it indicates that the second context information has not been updated.

[0184] For example, consider two satellites that cover terminal devices at different times, namely the first satellite and the second satellite. Figure 9 This is a flowchart illustrating another communication method provided in an embodiment of this application. Figure 9 As shown, the terminal device can interact with the network (e.g., the first and second network devices on the first satellite, the sixth and seventh network devices on the second satellite, and the fourth network device on the ground) to execute the attach procedure (steps d1-d5) and the TAU procedure (steps d6-d11) to create or update the terminal device's context information. The first network device on the first satellite, the sixth network device on the second satellite, and the fourth network device on the ground are all core network devices, while the second network device on the first satellite and the seventh network device on the second satellite are access network devices. None of the first network device on the first satellite, the sixth network device on the second satellite, and the fourth network device on the ground are independent core network devices.

[0185] Taking a 4G mobile communication system as an example, the first network device on the first satellite, the sixth network device on the second satellite, and the fourth network device on the ground can all be MME network elements. Among them, the MME network element on the ground + the MME network element on the first satellite = a complete MME network element; the MME network element on the ground + the MME network element on the second satellite = a complete MME network element.

[0186] Step d1: When the terminal device is within the coverage area of ​​the first satellite, the first network device on the first satellite sends an attach accept message to the terminal device through the second network device on the first satellite. Correspondingly, the terminal device receives the attach accept message from the first network device on the first satellite through the second network device on the first satellite.

[0187] The attached receiving message includes CSN#1 assigned to the terminal device by the first network device on the first satellite.

[0188] Step d2: When the terminal device is within the coverage area of ​​the first satellite, the terminal device sends an attach complete message to the first network device on the first satellite through the second network device on the first satellite. Correspondingly, the first network device on the first satellite receives the attach complete message from the terminal device through the second network device on the first satellite.

[0189] Step d3: The terminal device creates and stores the context information of the terminal device. The first network device on the first satellite creates and stores the context information of the terminal device.

[0190] The identifier of the terminal device's context information (i.e., the second context information) stored in the terminal device is CSN#1, and the identifier of the terminal device's context information (i.e., the first context information) stored in the first network device on the first satellite is CSN#1.

[0191] Step d4: When the fourth network device on the ground is within the coverage area of ​​the first satellite, the first network device on the first satellite sends the latest context information and CSN#1 of the terminal device to the fourth network device on the ground. Correspondingly, the fourth network device on the ground receives the latest context information and CSN#1 of the terminal device from the first network device on the first satellite.

[0192] Step d5: When the fourth network device on the ground is within the coverage area of ​​the second satellite, the fourth network device on the ground sends the latest context information and CSN#1 of the terminal device to the sixth network device on the second satellite. Correspondingly, the sixth network device on the second satellite receives the latest context information and CSN#1 of the terminal device from the fourth network device on the ground.

[0193] Step d6: When the terminal device is within the coverage area of ​​the first satellite, the terminal device sends a TAU request message to the first network device on the first satellite through the second network device on the first satellite. Correspondingly, the first network device on the first satellite receives the TAU request message from the terminal device through the second network device on the first satellite.

[0194] Step d7: When the fourth network device on the ground is within the coverage area of ​​the first satellite, the first network device on the first satellite sends a TAU request message to the fourth network device on the ground, and the fourth network device on the ground receives the TAU request message from the first network device on the first satellite.

[0195] Step d8: The fourth network device on the ground determines that the context information of the terminal device stored on the fourth network device on the ground has been updated, and assigns CSN#2 to the terminal device.

[0196] In other words, the identifier of the terminal device's context information stored by the fourth network device on the ground is updated from CSN#1 to CSN#2.

[0197] Step d9: When the fourth network device on the ground is within the coverage area of ​​the first satellite, the fourth network device on the ground sends the latest terminal device context information and TAU acceptance message to the first network device on the first satellite. Correspondingly, the first network device on the first satellite receives the latest terminal device context information and TAU acceptance message from the fourth network device on the ground.

[0198] The message received by the TAU includes CSN#2 assigned to the terminal device by the fourth network device on the ground.

[0199] In other words, the identifier of the first context information is updated from CSN#1 to CSN#2.

[0200] Step d10: When the terminal device is within the coverage area of ​​the first satellite, the first network device on the first satellite sends a TAU acceptance message to the terminal device through the second network device on the first satellite. Correspondingly, the terminal device receives the TAU acceptance message from the first network device on the first satellite through the second network device on the first satellite.

[0201] In other words, the identifier of the second context information is updated from CSN#1 to CSN#2.

[0202] Step d11: When the fourth network device on the ground is within the coverage area of ​​the second satellite, the fourth network device on the ground sends the latest context information and CSN#2 of the terminal device to the sixth network device on the second satellite. Correspondingly, the sixth network device on the second satellite receives the latest context information and CSN#2 of the terminal device from the fourth network device on the ground.

[0203] In other words, the identifier of the terminal device's context information stored by the sixth network device on the second satellite was updated from CSN#1 to CSN#2.

[0204] For example,Figure 10 This is a flowchart illustrating another communication method provided in an embodiment of this application. Figure 10 As shown, the terminal device can interact with the network (e.g., the first and second network devices on the first satellite, the fourth network device on the ground, and the eighth network device on the ground) to execute downlink data transmission procedures (steps e1-e5-2) and uplink data transmission procedures (steps e6-e9-2). The first network device on the first satellite, the fourth network device on the ground, and the eighth network device on the ground are all core network devices. The first network device on the first satellite and the fourth network device on the ground are not independent core network devices. The eighth network device on the ground is an independent core network device.

[0205] Step e1: The eighth network device on the ground sends downlink data to the second network device on the first satellite, and correspondingly, the second network device on the first satellite receives downlink data from the eighth network device on the ground.

[0206] Step e2: When the terminal device is within the coverage area of ​​the first satellite, the first network device on the first satellite sends a first paging message to the second network device on the first satellite, and correspondingly, the second network device on the first satellite receives the first paging message from the first network device on the first satellite.

[0207] The first paging message is used to paging terminal equipment. The first paging message includes a first identifier.

[0208] Step e3: When the terminal device is within the coverage area of ​​the first satellite, the second network device on the first satellite sends a second paging message to the terminal device, and the terminal device receives the second paging message from the second network device on the first satellite.

[0209] The second paging message is used to paging terminal equipment. The second paging message includes a first identifier.

[0210] Step e4: The terminal device determines whether the first identifier and the second identifier are the same.

[0211] Step e5-1: If the identifier of the first context information is the same as the identifier of the second context information, and the terminal device is within the coverage area of ​​the first satellite, the terminal device establishes a connection with the first satellite.

[0212] Step e6-1: The second network device on the first satellite sends downlink data to the terminal device, and correspondingly, the terminal device receives downlink data from the second network device on the first satellite.

[0213] Step e5-2: If the identifier of the first context information is different from the identifier of the second context information, and the terminal device is within the coverage area of ​​the first satellite, the terminal device sends the second instruction information to the first network device on the first satellite through the second network device on the first satellite.

[0214] The second indication information is used to indicate that the reason why the terminal device refuses to respond to the paging of the first network device on the first satellite is that the first context information is invalid.

[0215] Step e6-2: When the fourth network device on the ground is within the coverage area of ​​the first satellite, the first network device on the first satellite obtains the latest context information of the terminal device from the fourth network device on the ground.

[0216] Step e7: When the terminal device is within the coverage area of ​​the first satellite, the terminal device sends a first request message to the first network device on the first satellite through the second network device on the first satellite. Correspondingly, the first network device on the first satellite receives the first request message from the terminal device through the second network device on the first satellite.

[0217] The first request message includes a second identifier. The first request message can be used to request the establishment of a connection with a terminal device; for example, the first request message can be a service request message.

[0218] Step e8: The first network device on the first satellite determines whether the identifier of the first context information is the same as the identifier of the second context information.

[0219] Step e9-1: If the identifier of the first context information is the same as the identifier of the second context information, and the terminal device is within the coverage area of ​​the first satellite, the first satellite establishes a connection with the terminal device.

[0220] Step e10-1: The terminal device sends uplink data to the second network device on the first satellite, and correspondingly, the second network device on the first satellite receives the uplink data from the terminal device.

[0221] Step e9-2: If the identifier of the first context information is different from the identifier of the second context information, and the terminal device is within the coverage area of ​​the first satellite, the first network device on the first satellite sends the third instruction information to the terminal device through the second network device on the first satellite.

[0222] The third indication information is used to indicate that the reason why the first network device on the first satellite refuses to respond to the terminal device's request is that the first context information is invalid.

[0223] Step e10-2: When the fourth network device on the ground is within the coverage area of ​​the first satellite, the first network device on the first satellite obtains the latest context information of the terminal device from the fourth network device on the ground.

[0224] It is understood that the above embodiments of this application can be implemented individually or in combination with each other, and the embodiments of this application are not limited.

[0225] The methods provided by the embodiments of this application have been described above with reference to the accompanying drawings. The apparatus provided by the embodiments of this application will be described below with reference to the accompanying drawings.

[0226] Based on the same technical concept, embodiments of this application provide a communication device, which includes a module / unit / means for executing the method performed by the device in the above-described method embodiments. This module / unit / means can be implemented in software, or in hardware, or implemented by hardware executing corresponding software.

[0227] For example, see Figure 11 This is a schematic diagram of a communication device 1100, which includes a transceiver module 1101 and a processing module 1102.

[0228] When the device 1100 is a terminal device, the functions of each module of the device 1100 are as follows:

[0229] Processing module 1102 is used to determine whether the first context information stored by the first network device among a plurality of network devices has been updated, wherein the first context information is the context information of the terminal device, the first network device is located on a first satellite, and the first satellite is a satellite covering the terminal device;

[0230] Processing module 1102 is configured to establish a connection with a second network device when the first context information is updated, wherein the second network device is located on the first satellite;

[0231] Alternatively, when the device 1100 is a first network device on a first satellite or a fourth network device on the ground, the functions of each module of the device 1100 are as follows:

[0232] The transceiver module 1101 is used to send first information, wherein the first information is used to indicate the update time corresponding to some or all of a plurality of network devices, the plurality of network devices including a first network device, the first network device being located on a first satellite, the first satellite being a satellite covering the terminal device, and the update time corresponding to the first network device being used to indicate the time when the first context information stored by the first network device is updated, the first context information being the context information of the terminal device.

[0233] In practical implementation, the above-mentioned device 1100 can have various product forms. Several possible product forms are introduced below.

[0234] See Figure 12 The diagram shows another communication device. The communication device 1200 includes a processor 1201 and an interface circuit 1202. The interface circuit 1202 is used to receive signals from other communication devices outside the communication device and transmit them to the processor 1201, or to send signals from the processor 1201 to other communication devices outside the communication device. The processor 1201 is used to implement the methods executed by the access network device, terminal device or core network device in the above method embodiments through logic circuits or execution instructions.

[0235] The processor 1201 and the interface circuit 1202 are coupled to each other. It is understood that the interface circuit 1202 can be a transceiver or an input / output interface. Optionally, the communication device 1200 may also include a memory 1203 for storing instructions executed by the processor 1201, or storing input data required by the processor 1201 to execute instructions, or storing data generated after the processor 1201 executes instructions.

[0236] It should be understood that the processor mentioned in the embodiments of this application can be implemented in hardware or software. When implemented in hardware, the processor can be a logic circuit, integrated circuit, etc. When implemented in software, the processor can be a general-purpose processor, implemented by reading software code stored in memory.

[0237] For example, the processor can be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor can be a microprocessor or any conventional processor.

[0238] It should be understood that the memory mentioned in the embodiments of this application can be volatile memory or non-volatile memory, or may include both volatile and non-volatile memory. The non-volatile memory can be read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), or flash memory. The volatile memory can be random access memory (RAM), which is used as an external cache. By way of example, but not limitation, many forms of RAM are available, such as static random access memory (SRAM), dynamic random access memory (DRAM), synchronous dynamic random access memory (SDRAM), double data rate synchronous dynamic random access memory (DDR SDRAM), enhanced synchronous dynamic random access memory (ESDRAM), synchronous linked dynamic random access memory (SLDRAM), and direct rambus RAM (DR RAM).

[0239] It is understandable that when the processor is a general-purpose processor, DSP, ASIC, FPGA, or other programmable logic device, discrete gate or transistor logic device, or discrete hardware component, the memory (storage module) can be integrated into the processor.

[0240] It should be noted that the memories described herein are intended to include, but are not limited to, these and any other suitable types of memories.

[0241] Based on the same technical concept, embodiments of this application also provide a computer-readable storage medium storing a computer program or instructions, which, when executed by a processor, causes the methods executed by the terminal device, access network device, or core network device in the above method embodiments to be implemented.

[0242] Based on the same technical concept, this application also provides a computer program product, which includes a computer program or instructions. When the computer program or instructions are executed by a processor, the methods executed by the terminal device, access network device or core network device in the above method embodiments are implemented.

[0243] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0244] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to this application. It should be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0245] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0246] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

Claims

1. A communication method characterized by comprising: The method comprises: determining whether first context information stored by a first network device of a plurality of network devices is updated, wherein the first context information is context information of a terminal device, and the first network device is located on a first satellite, and the first satellite is a satellite covering the terminal device; in a case where the first context information is updated, establishing a connection with a second network device, wherein the second network device is located on the first satellite.

2. The method of claim 1, wherein, The method further comprises: determining whether the first context information is updated according to an update time corresponding to part or all of the plurality of network devices, wherein the update time corresponding to the first network device is used to indicate a time at which the first context information is updated; or determining whether a first identifier and a second identifier are the same, wherein if the first identifier and the second identifier are the same, it indicates that the first context information is updated, otherwise it indicates that the first context information is not updated, the first identifier is an identifier of the first context information, and the second identifier is an identifier of context information of the terminal device stored by the terminal device.

3. The method of claim 2, wherein, The method further comprises: determining whether the first context information is updated according to the update time corresponding to the first network device; or determining whether the first context information is updated according to an update time corresponding to a third network device of the plurality of network devices, wherein the update time corresponding to the third network device is later than update times corresponding to remaining network devices of the plurality of network devices.

4. The method according to claim 2 or 3, characterized in that, The method further comprises: receiving first information; or determining the first information according to coverage information of a satellite on which part or all of the plurality of network devices are located and position information of a fourth network device on the ground, wherein the fourth network device is the same as the context information of the terminal device stored by each network device of the plurality of network devices; wherein the first information is used to indicate the update time corresponding to part or all of the plurality of network devices.

5. The method of claim 2, wherein, The method further comprises: receiving a first paging message, wherein the first paging message comprises the first identifier.

6. The method according to any one of claims 1 to 5, characterized in that, The method further comprises: in a case where the first context information is not updated, not establishing the connection with the second network device.

7. The method of claim 6, wherein, The method further comprises: entering a sleep state.

8. The method according to any of claims 1 to 7, characterized in that Before determining whether the first context information stored by the first network device of the plurality of network devices is updated, the method further comprises: receiving first indication information, wherein the first indication information is used to indicate that the first context information starts to be updated; or the context information of the terminal device stored by the terminal device is updated.

9. A communication method characterized by comprising: The method comprises: sending first information, wherein the first information is used to indicate update time corresponding to part or all of a plurality of network devices, the plurality of network devices including a first network device, the first network device being located on a first satellite, the first satellite being a satellite covering a terminal device, the update time corresponding to the first network device being used to indicate time when first context information stored by the first network device is updated, the first context information being context information of the terminal device.

10. The method of claim 9, wherein, The method further comprises: receiving the first information; or The first information is determined according to second information, coverage information of a satellite on which part or all of the plurality of network devices are located, and position information of a fourth network device on the ground, wherein the second information is used to determine part of the plurality of network devices, and the fourth network device has the same context information of the terminal device as each of the plurality of network devices.

11. The method of claim 10, wherein, Before receiving the first information, the method further comprises: sending third information, wherein the third information is used to indicate second information, position information of the terminal device, and position information of a fourth network device on the ground, the second information being used to determine part of the plurality of network devices, and the fourth network device having the same context information of the terminal device as each of the plurality of network devices.

12. The method according to claim 10 or 11, characterized in that, The second information is used to indicate service type of the terminal device and / or communication mode of the terminal device.

13. The method according to any of claims 9-12, characterized by, Part of the plurality of network devices includes a third network device, wherein the update time corresponding to the third network device is later than the update time corresponding to the remaining network devices of the plurality of network devices.

14. A communications device, characterized by The communication device comprises a module for performing the method of any one of claims 1-8, or a module for performing the method of any one of claims 9-13.

15. A communications device, characterized by The communication device comprises a processor configured to perform the method of any one of claims 1-8, or perform the method of any one of claims 9-13.

16. A computer-readable storage medium, characterized in that, The computer readable storage medium is configured to store a computer program, when the computer program is run on a computer, causing the method of any one of claims 1-8 to be performed, or causing the method of any one of claims 9-13 to be performed.

17. A computer program product, characterised in that, The computer program product comprises a computer program, when the computer program is run on a computer, causing the method of any one of claims 1-8 to be performed, or causing the method of any one of claims 9-13 to be performed.

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