Communication method and apparatus

Abstract

Disclosed in the present application are a communication method and apparatus. The method comprises: determining whether first context information stored in a first network apparatus among a plurality of network apparatuses has been updated, wherein the first context information is context information of a terminal apparatus, the first network apparatus is located on a first satellite, and the first satellite is a satellite covering the terminal apparatus; and when the first context information has been updated, establishing a connection with a second network apparatus, wherein the second network apparatus is located on the first satellite. Since a terminal apparatus only needs to determine whether first context information stored in a first network apparatus on a first satellite has been updated, and does not need to wait for all pieces of context information stored in a plurality of network apparatuses to be updated, the terminal apparatus can communicate with a network as early as possible, thereby reducing service interruption time and improving data transmission efficiency.

Description

Communication method and apparatus

[0001] Cross-reference to Related Applications

[0002] This application claims priority to the Chinese Patent Application No. 202410875400.0, filed on June 28, 2024, and entitled "A Communication Method and Apparatus", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0003] The present application relates to the field of communication technology, and in particular, to a communication method and apparatus. BACKGROUND

[0004] 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 a satellite and a gateway station of a ground network is referred to as a feeder link (FL), and a communication link between a 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.

[0005] 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 not available 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.

[0006] 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 lower data transmission efficiency. SUMMARY

[0007] Embodiments of the present application provide a communication method and apparatus for improving the efficiency of data transmission.

[0008] In a first aspect, embodiments of this application provide a communication method that can be executed by a terminal device. The terminal device is, for example, a terminal equipment, or other device including terminal equipment functions, or a chip system (or chip) or other functional module capable of implementing the functions of the terminal equipment, and the chip system or functional module is, for example, disposed within the terminal equipment. The method includes: determining whether first context information stored by a first network device among a plurality of network devices has been updated, wherein the first context information is 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; and, if the first context information has been updated, establishing a connection with a second network device, wherein the second network device is located on the first satellite.

[0009] In this embodiment, since the terminal device establishes a connection with the second network device on the first satellite only after determining that the first context information stored by the first network device on the first satellite has been updated, the probability of successful connection for the terminal device can be increased. Furthermore, since the terminal device only needs to determine whether the first context information stored by the first network device on the first satellite has been updated, without waiting for the context information stored by multiple network devices to be updated, the terminal device can communicate with the network as early as possible, reducing service interruption time and improving data transmission efficiency.

[0010] In one possible implementation, determining whether the first context information stored in the first network device among a plurality of network devices has been updated includes: determining whether the first context information has been updated based on the update time corresponding to some or all of the network devices among the plurality of network devices, wherein the update time corresponding to the first network device is used to indicate the time when the first context information was 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 has been updated, otherwise it indicates that the first context information has not been updated, wherein the first identifier is the identifier of the first context information, and the second identifier is the identifier of the context information of the terminal device stored in the terminal device.

[0011] In this embodiment, multiple manners are provided for the terminal device to determine whether the first context information is updated. For example, the terminal device determines whether the first context information is updated according to a time when the first context information is updated, which is a direct determination manner. For another example, the terminal device determines whether the first context information is updated according to whether an identifier of the first context information is same as an identifier of the second context information, which is an indirect determination manner.

[0012] In a possible implementation, the method further includes: determining whether the first context information is updated according to an update time corresponding to each of the plurality of network devices, including: determining whether the first context information is updated according to an 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, where 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.

[0013] 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 determines whether the first context information is updated according to an update time corresponding to the first network device, which is to determine whether the first context information stored by the first network device is updated, and the determination according to the update time corresponding to the first network device is beneficial to improve accuracy of the determination result. For another example, the terminal device determines a latest update time corresponding to the plurality of network devices, and when the time arrives, it is considered that the plurality of network devices are all updated, and thus the first network device is also updated, which is to determine according to the latest update time and is beneficial to improve 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 still determine, which is beneficial to improve determination efficiency.

[0014] 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 each of the plurality of network devices is located and position information of a fourth network device on the ground, where the fourth network device is same as context information of the terminal device stored by each of the plurality of network devices; and the first information is used to indicate the update time corresponding to each of the plurality of network devices.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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. In addition, 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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, which reduces 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, which improves 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] In a fourth aspect, an embodiment of the present application further provides a communication apparatus. The communication apparatus 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 other device including the function of the network device, or a chip system (or chip) or other functional module capable of implementing the function 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 is a general term for these functional modules.

[0034] 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.

[0035] In a fifth aspect, a communication apparatus is provided. The communication apparatus can be the terminal apparatus in the first aspect. The communication apparatus has the functions of the terminal apparatus. The communication apparatus 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 implementing the function 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 in 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.

[0036] In a sixth aspect, a communication apparatus is provided. The communication apparatus can be the first network device or the fourth network device in the second aspect. The communication apparatus has the functions of the first network device or the fourth network device. The communication apparatus can be, 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, which can be arranged in the network device. The communication apparatus includes a processor configured to perform the functions of the network device 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 device in the aspects.

[0037] In a seventh aspect, a communication system is provided. The communication system includes a network device, which can be the first network device or the fourth network device in the aspects. The network device is configured to perform the method performed by the first network device or the fourth network device in the second aspect. For example, the network device can be implemented by the communication apparatus in the fourth aspect or the sixth aspect.

[0038] Optionally, the communication system further includes a terminal device. The terminal device is configured to perform the method performed by the terminal device in the first aspect. For example, the terminal device can be implemented by the communication apparatus in the third aspect or the fifth aspect.

[0039] In an eighth aspect, a computer readable storage medium is provided. The computer readable storage medium is configured to store a computer program or instructions. When the computer program or instructions are executed, the method performed by the terminal device or the first network device or the fourth network device in the aspects is implemented.

[0040] In a ninth aspect, a computer program product is provided. The computer program product includes instructions. When the computer program or instructions are executed on a computer, the method in the aspects is implemented.

[0041] In a tenth aspect, a chip system is provided. The chip system includes 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

[0042] FIG. 1 is a structural schematic diagram of an NTN system provided by an embodiment of the present application;

[0043] FIG. 2 is a structural schematic diagram of an access network device provided by an embodiment of the present application;

[0044] FIG. 3 is a structural schematic diagram of a communication system provided by an embodiment of the present application;

[0045] FIG. 4 is a structural schematic diagram of another communication system provided by an embodiment of the present application;

[0046] FIG. 5 is a flow schematic diagram of a communication method provided by an embodiment of the present application;

[0047] FIG. 6 is a flow schematic diagram of another communication method provided by an embodiment of the present application;

[0048] FIG. 7 is a flow schematic diagram of another communication method provided by an embodiment of the present application;

[0049] FIG. 8 is a flow schematic diagram of another communication method provided by an embodiment of the present application;

[0050] FIG. 9 is a flow schematic diagram of another communication method provided by an embodiment of the present application;

[0051] FIG. 10 is a flow schematic diagram of another communication method provided by an embodiment of the present application;

[0052] FIG. 11 is a schematic diagram of a communication apparatus provided by an embodiment of the present application;

[0053] FIG. 12 is a schematic diagram of another communication apparatus provided by an embodiment of the present application. DETAILED DESCRIPTION

[0054] In order to make the purpose, 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.

[0055] 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 use 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.

[0056] 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, etc. The specific communication system is not limited herein.

[0057] Taking a satellite as an example of an NTN device in an NTN system, according to the altitude of the satellite, i.e., 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 running on 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 running on 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 movement of 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.

[0058] In an NTN system, the working mode of an 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 a physical layer signal. The NTN device can be responsible for layer 1 (L1) relay for physical layer forwarding, and higher layers are invisible. The other is a regenerative architecture, in which the NTN device has the processing function of an 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 an 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, where the ISL is an Xn interface; or a regenerative satellite with the distributed unit (DU) processing function of an access network device, in which case the satellite acts as a DU.

[0059] For example, FIG. 1 shows a schematic diagram of an NTN system to which embodiments of the present application are applicable, and the NTN system can be a regenerative architecture. In the system shown in FIG. 1, an access network device can be disposed on a satellite, or the satellite has part or all of the functions of an access network device. The satellite can provide wireless access services for terminal devices, and can communicate with a core network (CN) through an NTN gateway, and then can be connected to a data network (DN) through the core network. In addition, part or all of the core network devices in the core network can also be disposed on the satellite, or the satellite can have the functions of part or all of the core network devices in the core network. FIG. 1 exemplarily shows a regenerative satellite architecture without an ISL.

[0060] FIG. 1 only shows one satellite and one NTN gateway, and in actual use, an architecture including multiple satellites and / or multiple NTN gateways can be deployed as needed. 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 embodiments of the present application.

[0061] The device related in embodiments of the present application includes a terminal device and a network device, and the network device includes an access network device and / or a core network device. Wherein:

[0062] A terminal device, also referred to as a user equipment (UE), a mobile station (MS), a mobile terminal (MT), etc., refers to a device that provides voice and / or data connectivity to a user. For example, a terminal device can be a handheld device having wireless connection capability, a car-mounted device, etc. Currently, some examples of the terminal device can be: a mobile phone, a tablet computer, a notebook computer, a palm computer, a mobile internet device (MID), a wearable device, a virtual reality (VR) device, an augmented reality (AR) device, a wireless terminal in industrial control, a wireless terminal in self driving, a wireless terminal in remote medical surgery, a wireless terminal in smart grid, a wireless terminal in transportation safety, a wireless terminal in smart city, a wireless terminal in smart home, a cellular internet of things (CIoT) device, etc.

[0063] An access network device can refer to a radio access network (RAN) node (or device) that accesses a terminal device to a wireless network, e.g., a base station. Some examples of the RAN node can be: a continue evolution Node B (gNB), a transmission reception point (TRP), an evolved Node B (eNB), a radio network controller (RNC), a Node B (NB), a base station controller (BSC), a base transceiver station (BTS), a home base station (e.g., home evolved NodeB, or home NodeB, HNB), a base band unit (BBU), or a wireless fidelity (Wifi) access point (AP), etc.

[0064] In addition, in one network structure, the access network device can include a centralized unit (CU) node, or a distributed unit (DU) node, or both. The RAN device including both the CU node and the DU node splits the protocol layers of the gNB in the NR system, with some of the protocol layers' functions being centrally controlled at the CU, and the rest or all of the protocol layers' functions being distributed in the DU, with the CU centrally controlling the DU, as shown in FIG. 2. Further, the CU can be further divided into a control plane (CU-CP) and a user plane (CU-UP). The CU-CP is responsible for the control plane functions, mainly including the radio resource control (RRC) and the control plane corresponding packet data convergence protocol (PDCP) (i.e., PDCP-C). The PDCP-C is mainly responsible for the encryption and decryption of the control plane data, integrity protection, data transmission, etc. The CU-UP is responsible for the user plane functions, mainly including the service data adaptation protocol (SDAP) and the user plane corresponding PDCP (i.e., PDCP-U). The SDAP is mainly responsible for processing the data of the core network and mapping the flow to the bearer. The PDCP-U is mainly responsible for the encryption and decryption of the data plane, integrity protection, header compression, sequence number maintenance, data transmission, etc. The CU-CP and the CU-UP are connected through an E1 interface. The CU-CP represents the gNB to connect to the core network through an NG interface, and to connect to the DU through an F1 interface for the control plane (i.e., F1-C). The CU-UP is connected to the DU through an F1 interface for the user plane (i.e., F1-U). Of course, there is also a possible implementation that the PDCP-C is also in the CU-UP.

[0065] It can be understood that the CU (including the CU-CP or the CU-UP) or the DU can also have different names in different systems, but those skilled in the art can understand their meanings. For example, in an open radio access network (O-RAN) system, the CU can also be referred to as an O-CU (open CU), the DU can also be referred to as an O-DU, the CU-CP can also be referred to as an O-CU-CP, and the CU-UP can also be referred to as an O-CU-UP. For the convenience of description, the CU, the CU-CP, the CU-UP, and the DU are taken as examples for description in this application.

[0066] The core network device corresponds to different devices in different systems. For example, as shown in FIG. 3, a 4th generation (4G) mobile communication system can include two parts, which are a terminal device part and an operator network part respectively. Among them, the operator network includes a radio access network (such as an evolved universal mobile telecommunications system terrestrial radio access network (E-UTRAN)) and a core network. The core network includes a user plane network element and a control plane network element. The user plane network element of the core network includes a serving gateway (SGW) and a packet data network gateway (PGW), etc. The control plane network element of the core network includes a mobility management entity (MME).

[0067] As shown in FIG. 4, the 5th generation (5G) mobile communication system can include three parts, which are terminal device part, data network part and operator network part respectively. Among them, 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 (UPF). The control plane network elements of the core network include authentication server function (AUSF) network elements, access and mobility management functions (AMF), session management functions (SMF), network slicing selection functions (NSSF), network exposure functions (NEF), network repository functions (NRF), policy control functions (PCF), unified data management (UDM), application functions (AF), network slice-specific authentication and authorization functions (NSSAAF), service communication proxies (SCP), network slice admission control functions (NSACF), edge application server discovery functions (EASDF), etc.

[0068] Optionally, part or all of the core network devices can adopt a split architecture. For example, in an NTN, part of the functions of a certain core network device can be arranged on a satellite (for example, the satellite has part of the functions of the core network device, or part of the function modules of the core network device are located on the satellite), and the remaining functions are arranged on the ground. It can be understood that the functions of the core network device on the ground and the functions of the core network device on the satellite can not be regarded as two independent parts, but together constitute the core network device, and the two parts are corresponding and jointly implement the functions of the core network device.

[0069] For example, in a 4G system, the core network device is, for example, an MME. The MME can adopt a split architecture, for example, part of the functions of the MME can be arranged on a satellite (for example, the satellite has part of the functions of the MME, or part of the function modules of the MME are located on the satellite), and the remaining functions are arranged on the ground. It can be understood that the MME on the ground (referred to as ground MME (MME-Ground)) and the MME on the satellite (referred to as onboard MME (MME-Onboard)) can not be regarded as two independent devices, but together constitute an MME, and the MME-Ground and the MME-Onboard correspond to each other and jointly implement the functions of the MME.

[0070] For example, in a 5G system, the core network device is, for example, an AMF. The AMF can adopt a split architecture, for example, part of the functions of the AMF can be arranged on a satellite (for example, the satellite has part of the functions of the AMF, or part of the function modules of the AMF are located on the satellite), and the remaining functions are arranged on the ground. It can be understood that the AMF on the ground (referred to as ground AMF (AMF-Ground)) and the AMF on the satellite (referred to as onboard AMF (AMF-Onboard)) can not be regarded as two independent devices, but together constitute an AMF, and the AMF-Ground and the AMF-Onboard correspond to each other and jointly implement the functions of the AMF.

[0071] In other communication systems, the core network device can be a corresponding core network device, which is not limited in particular.

[0072] In the embodiments of the present application, the communication device for implementing the functions of the terminal device, the access network device or the core network device can be the terminal device, the access network device or the core network device itself, or a device capable of supporting the terminal device, the access network device or the core network device to implement the functions, such as a chip system, which can be installed in the terminal device, the access network device or the core network device. In the technical solutions provided in the embodiments of the present application, the device for implementing the functions of the terminal device is taken as an example, the device for implementing the functions of the access network device is taken as an example, and the device for implementing the functions of the core network device is taken as an example to describe the technical solutions provided in the embodiments of the present application.

[0073] As briefly introduced above, the communication system to which the embodiments of the present application are applicable is introduced, and the related technical solutions involved in the embodiments of the present application are introduced below.

[0074] In an NTN system, a communication link between a satellite and a terminal device is referred to as a service link (SL), a communication link between a satellite and a gateway station of a ground network is referred to as a feeder link (FL), and a communication link between a satellite and another satellite is referred to as an inter-satellite link (ISL). Generally, when a terminal device accesses a network through an NTN, the terminal device can utilize the above communication links to achieve end-to-end connectivity between the terminal device, the satellite, and the ground network, for example, terminal device - service link - satellite 1 - inter-satellite link - satellite 2 - feeder link - ground network.

[0075] Part of the communication links between the terminal device, the satellite, and the ground network can be unavailable. For example, for a region without a deployed gateway station of a ground network, when the satellite covers the terminal devices in the region (i.e., the service link is available), the ground network that serves the users in the region cannot be connected through the feeder link (i.e., the feeder link is unavailable), and when the satellite covers the gateway station of the ground network outside the region (i.e., the feeder link is available), the users in the region cannot be covered (i.e., the service link is unavailable). For another example, for a region with a deployed gateway station of a ground network, when the satellite covers the terminal devices in the region and the gateway station of the ground network, both the service link and the feeder link are available, but when the gateway station of the ground network fails, the feeder link becomes unavailable, or when the terminal device fails, the service link becomes unavailable.

[0076] In the scenario where the feeder link is unavailable, in order to successfully transmit data, the ground network can send the context information of the terminal device to the satellite when the feeder link is available, and the satellite can establish a connection with the terminal device using the stored context information when the feeder link is unavailable but the service link is available. However, there are many factors that can cause the context information of the terminal device to change, such as a change in the location of the terminal device. If the context information stored on the satellite is not updated in time, the context information stored on the terminal device and the context information stored on the satellite are inconsistent, resulting in a failure of the terminal device to access the network. Therefore, when the context information of the terminal device changes, how to successfully transmit data between the terminal device and the satellite is a problem to be solved.

[0077] For example, the terminal device can interact with the network to perform an attach, registration or tracking area update (TAU) procedure, to create or update context information of the terminal device. After the context information of the terminal device is created or updated, the core network device on the ground generates a corresponding accept message (for example, an attach accept message, a registration accept message, a TAU accept message), in which an activation timer is carried, and the length of the activation timer is greater than or equal to the time required by the core network device on the ground to synchronize the latest context information of the terminal device to the satellite serving the terminal device. Wherein, when the feeder link of the satellite serving the terminal device is available, the core network device on the ground can synchronize the latest context information of the terminal device to the satellite. After the terminal device receives the accept message, until the activation timer expires, the terminal device enters a registered state.

[0078] It can be seen that each time the context information of the terminal device is created or updated, the terminal device needs to wait until the core network device on the ground synchronizes the context information of the terminal device to the satellite serving the terminal device, and then the terminal device can perform data transmission through the satellite. At present, the terminal device can have multiple satellites serving the terminal device at different times, and the more satellites serving the terminal device, the longer the time required by the core network device on the ground to synchronize the context information of the terminal device to each satellite, resulting in the later the terminal device starts to accept the service of each satellite, which can cause a longer service interruption time and lower data transmission efficiency.

[0079] In view of this, the embodiment of the present application provides a communication method, which can improve the efficiency of data transmission.

[0080] In the embodiments of the present application, "when", "if" and "whether" all refer to the objective situation that the device will make corresponding processing, and are not limited in time, and do not require the device to have a judgment action when implemented, nor mean that there are other limitations. Unless otherwise specified, "if" and "whether" can be replaced, and "when" and "in the case of" can be replaced. "When" and "if" / "whether" can be replaced.

[0081] In the embodiments of the present application, the words such as "exemplary" or "for example" are used to mean by way of example, illustration or description. Any embodiment or design scheme described as "exemplary" or "for example" in the present application should not be interpreted as more preferred or more advantageous than other embodiments or design schemes. Rather, the words such as "exemplary" or "for example" are intended to present the relevant concept in a specific manner.

[0082] In this document, "for indicating" can include for directly indicating and for indirectly indicating. For example, when describing that information I is for indicating information J, it can include that the information I directly indicates the information J or indirectly indicates the information J, and does not mean that the information J must be carried in the information I.

[0083] The information J indicated by the information I is referred to as to-be-indicated information. In a specific implementation process, there are many ways to indicate the to-be-indicated information, for example, but not limited to, the to-be-indicated information can be directly indicated, such as the to-be-indicated information itself or an index of the to-be-indicated information. The to-be-indicated information can also be indirectly indicated by indicating other information, where the other information and the to-be-indicated information have an association relationship. The to-be-indicated information can also be only indicated in part, and other parts of the to-be-indicated information are known or agreed in advance. For example, the indication of a specific information can also be achieved by means of the arrangement order of various information agreed in advance (for example, a protocol stipulates), thereby reducing the indication overhead to a certain extent. At the same time, a common part of each information can be identified and uniformly indicated, so as to reduce the indication overhead caused by separately indicating the same information.

[0084] In addition, the specific indication manner can also be various existing indication manners, for example, but not limited to, the above-mentioned indication manners and various combinations thereof. As described above, for example, when multiple information of the same type needs to be indicated, the indication manners of different information can be different. In a specific implementation process, the required indication manner can be selected according to specific needs, and the selected indication manner is not limited in the embodiments of the application. In this way, the indication manner involved in the embodiments of the application should be understood as covering various methods that can enable the to-be-indicated party to know the to-be-indicated information.

[0085] In the embodiments of the application, "sending" and "receiving" represent the direction of signal transmission. For example, "sending information to XX" can be understood as that the destination of the information is XX, which can include directly sending through the air interface, and also includes indirectly sending through the air interface by other units or modules. "Receiving information from YY" can be understood as that the source of the information is YY, which can include directly receiving from YY through the air interface, and also includes indirectly receiving from YY through the air interface from other units or modules. "Sending" can also be understood as "output" of a chip interface, and "receiving" can also be understood as "input" of a chip interface.

[0086] The information can be processed as necessary between the source and the destination of the information transmission, such as encoding, modulation, etc., but the destination can understand the effective information from the source. Similar expressions in the embodiments of the application can be similarly understood, and will not be described in detail.

[0087] In the embodiments of the present application, the number of nouns, unless otherwise specified, represents "a singular noun or a plural noun", that is, "one or more". "At least one" refers to one or more, and "multiple" refers to two or more. "And / or" describes the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B can represent the following cases: A exists alone, A and B exist together, and B exists alone, where A and B can be singular or plural. The character " / " can represent that the associated objects before and after are in an "or" relationship. For example, A / B represents A or B. "At least one of the following" or similar expressions means any combination of these items, including any combination of single item or multiple items. For example, at least one of a, b, or c represents 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.

[0088] The ordinal numbers "first", "second", and the like mentioned in the embodiments of the present application are used to distinguish a plurality of objects, and are not used to limit the size, content, order, time sequence, priority, or importance of the plurality of objects. For example, the first information and the second information refer to two different information, and do not mean that the priority or importance of the two information is different. For a technical feature, technical features in the technical feature are distinguished by "A", "B", "C", and "D". There is no order or size order between the technical features described by "A", "B", "C", and "D". For example, the method A and the method B in the present application are only used to distinguish different contents, and do not limit the order or size order, priority or importance between the method A and the method B.

[0089] The scheme provided by the embodiments of the present 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 the present application is applied to the communication system shown in FIGS. 1-4. The communication system and application scenarios described in the embodiments of the present application are used to more clearly illustrate the technical solutions of the embodiments of the present application, and do not constitute a limitation on the technical solutions provided by the embodiments of the present application. Those skilled in the art can know that with the evolution of the communication system and the appearance of new application scenarios, the technical solutions provided by the embodiments of the present application are also applicable to similar technical problems.

[0090] The following introduces the communication method provided by the embodiments of the present application by taking an example of the communication method being executed by a terminal device and a network device (an access network device and / or a core network device). The steps executed by the terminal device can be implemented by the terminal device itself or by a component (such as a chip, a processing unit, or a processor, etc.) in the terminal device. The terminal device can be the terminal device shown in FIGS. 1-4, or can also be a chip (system) in the terminal device in FIGS. 1-4. The steps executed by the network device can be implemented by the network device itself or by a component (such as a chip, a processing unit, or a processor, etc.) in the network device. The network device can be the core network device shown in FIGS. 1-4, or can also be a chip (system) in the network device in FIGS. 1-4. When the communication method is implemented by the components in the terminal device and the network device, the receiving and sending steps therein can be understood as the communication between the components and other components, for example, the communication between a baseband chip and a radio frequency circuit, etc. The processing executed by a single execution subject in the embodiments of the present application can also be divided into processing executed by multiple execution subjects, which can be logically and / or physically separated. For example, the processing executed by the access network device can be divided into processing executed by at least one of a CU, a DU, and a RU.

[0091] Referring to FIG. 5, FIG. 5 is a flowchart of a communication method provided by an embodiment of the present application. As shown in FIG. 5, the flow of the communication method includes the following steps.

[0092] S501, the terminal device determines whether first context information stored by a first network device of multiple network devices is updated, wherein the first context information is 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.

[0093] S502, in a case where the first context information is updated, the terminal device establishes a connection with a second network device, wherein the second network device is located on the first satellite.

[0094] In the embodiments of the present application, the multiple satellites can be satellites covering the terminal device at different time instants, and the first satellite of the multiple satellites can be a satellite covering the terminal device at a current time instant. The multiple network devices are network devices on the multiple satellites for storing 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 of the multiple network devices can be a first core network device on the first satellite of the multiple satellites. Alternatively, the multiple network devices can also be access network devices on the multiple satellites, and the first network device of the multiple network devices can be a first access network device on the first satellite of the multiple satellites.

[0095] The second network device on the first satellite is the first access network device on the first satellite. That is, 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.

[0096] For ease of illustration, the embodiments of the present application take 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.

[0097] The "update occurs" can mean that the updating process has started but not ended, or can mean that the updating process has ended. The "connection is established" can mean that a radio resource control connection is established; or can also mean that a radio bearer, for example, a data radio bearer (DRB), is established, the DRB refers to a radio bearer of user data, which is used to transmit user data; or can also mean that a service request message is sent, the service request message is used to request to establish a radio bearer with the terminal device. The embodiments of the present application do not limit this. For ease of illustration, the embodiments of the present application take the update as meaning that the updating process has ended, and the connection is established as meaning that the radio bearer is established.

[0098] That is, 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 at the current moment is updated, so as to improve the probability of successful connection establishment, thereby successfully transmitting data. Moreover, since the terminal device only needs to judge whether the context information of the terminal device stored on the satellite covering the terminal device at the current moment is updated, it is not necessary to wait for the context information of the terminal device stored on all satellites capable of covering the terminal device to be updated, thereby improving the efficiency of data transmission.

[0099] In a possible implementation, in the case that the first context information is not updated, in order to improve the probability of successful connection establishment, the terminal device can not establish a connection with the second network device on the first satellite. Further, in order to reduce the power consumption of the terminal device, the terminal device can enter a sleep state. Wherein, the terminal device entering the sleep state can be understood as that the terminal device monitors the system message from the first satellite but does not monitor the paging message from the first satellite; or can also be understood as that the terminal device closes the access layer function, that is, the terminal device does not monitor the system message from the first satellite, nor monitors the paging message from the first satellite.

[0100] In a possible implementation, before determining whether the first context information stored by the first network device of the plurality of network devices is updated, the terminal device can receive first indication information. The first indication information is used to indicate that the first context information starts to be updated. The "starts to be updated" can mean that the updating process has started, can have ended, or can not have ended. Alternatively, the terminal device can determine that the context information of the terminal device stored by the terminal device (for example, referred to as second context information) is updated.

[0101] That is, after the terminal device determines that the first context information starts to be updated or the second context information is updated, in order to avoid the first context information and the second context information being different, causing the terminal device to fail to successfully establish a connection with the second network device of the first satellite, the terminal device determines whether the first context information stored by the first network device on the first satellite is updated, that is, whether the first context information is same as the second context information. If the first context information is updated, it is determined that the first context information is same as the second context information, otherwise it is determined that the first context information is different from the second context information.

[0102] In the implementation process, the terminal device can determine whether the first context information stored by the first network device of the plurality of network devices is updated in the following multiple ways. The following will be introduced.

[0103] Method A: The terminal device can determine whether the first context information is updated according to first information.

[0104] The first information can also be referred to as satellite available information or constellation available information, and the name of the first information is not limited in the embodiments of the present application. The first information can indicate the update time corresponding to part or all of the plurality of network devices. That is, the first information can indicate the update time corresponding to at least one network device of the plurality of network devices. The update time corresponding to one network device of the plurality of network devices can be used to indicate the time when the context information of the terminal device stored by the one network device is updated, and the update time corresponding to the first network device of the plurality of network devices is used to indicate the time when the first context information is updated.

[0105] The update time can be a time point, that is, the update time is an update time point, for example, the update time corresponding to the first network device is time point 1, and the first context information is updated at the time point 1; or the update time can also be a time length, that is, the update time is an update time length, for example, the update time corresponding to the first network device is time length 1, and the first context information is updated at the end of the time length 1. The unit of the update time can be microsecond (us), millisecond (ms), second (s), minute, hour (h), and the like, for example, the time point 1 is 10:30:30 am, and the time length 1 is 8 hours; or the unit of the update time can also be frame, subframe, or time slot, for example, the time point 1 is time slot 1, and the time length 1 is 50 time slots. The embodiments of the present application do not limit this.

[0106] In a possible implementation, the first information can directly indicate the update time corresponding to part or all of the plurality of network devices; or the first information can also indirectly indicate the update time corresponding to part or all of the plurality of network devices.

[0107] For example, when the first information indicates the update time 1 corresponding to the core network device 1 on the satellite 1, the first information can directly indicate the identifier (ID) of the satellite 1; or can indirectly indicate the identifier of the access network device 1 on the satellite 1. The first information can directly indicate the update time 1; or can indirectly indicate the index of the update time 1. The embodiments of the present application do not limit this.

[0108] When the first information indicates the update time 1, the first information can indicate 128 consecutive numbers as the numerical value of the update time 1 through 7 bits, and the unit of the update time 1 can be indicated through another bit, for example, 0 indicates minute, 1 indicates hour, or the protocol default unit. When the first information indicates the index of the update time 1, the first information can indicate the index of the update time 1 as shown in Table 1.

[0109] Table 1

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

[0111] Table 2

[0112] In a possible implementation, part or all of the plurality of network devices can include the first network device, that is, the first information can indicate the update time corresponding to the first network device, and thus the terminal device can directly determine whether the first context information is updated according to the update time corresponding to the first network device. If the current time is later than the update time corresponding to the first network device or the end time of the update time corresponding to the first network device, it is determined that the first context information is updated, otherwise it is determined that the first context information is not updated.

[0113] For example, there are 6 satellites covering the terminal device at different time instants, which are satellite #1, satellite #2, satellite #3, satellite #4, satellite #5, and satellite #6. Among them, the update time #1 corresponding to the core network device #1 on the satellite #1 is time instant 1, the update time #2 corresponding to the core network device #2 on the satellite #2 is time instant 2, the update time #3 corresponding to the core network device #3 on the satellite #3 is time instant 3, the update time #4 corresponding to the core network device #4 on the satellite #4 is time instant 4, the update time #5 corresponding to the core network device #5 on the satellite #5 is time instant 5, and the update time #6 corresponding to the core network device #6 on the satellite #6 is time instant 6. Time instant 1 is earlier than time instant 2, time instant 2 is earlier than time instant 3, time instant 3 is earlier than time instant 4, time instant 4 is earlier than time instant 5, and time instant 5 is earlier than time instant 6.

[0114] The first information can indicate the update time #1 corresponding to the core network device #1 on the satellite #1, that is, the update time corresponding to part or all of the plurality of 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 instant 1, the terminal device can determine that the context information of the terminal device stored by the core network device #1 on the satellite #1 is updated.

[0115] Alternatively, part or all of the plurality of network devices can include the third network device. Among them, 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. It can be understood that 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, or the time of the update time corresponding to the third network device is later than the end time of the update time corresponding to the remaining network devices in the plurality of network devices.

[0116] For example, the update time #1 corresponding to the core network device #1 on the satellite #1 is time 1, the update time #2 corresponding to the core network device #2 on the satellite #2 is time 2, the update time #3 corresponding to the core network device #3 on the satellite #3 is time 3, the update time #4 corresponding to the core network device #4 on the satellite #4 is time 4, the update time #5 corresponding to the core network device #5 on the satellite #5 is time 5, and the update time #6 corresponding to the core network device #6 on the 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. Therefore, the core network device #6 on the satellite #6 is the third network device.

[0117] That is, the first information can indicate the update time corresponding to the third network device, that is, the latest update time in the update time corresponding to each network device in the plurality of network devices. Therefore, the terminal device can indirectly determine whether the first context information is updated according to the update time corresponding to the third network device. If the current time is later than the update time corresponding to the third network device or the end time of the update time corresponding to the third network device, it is determined that the context information stored by each network device in the plurality of network devices is updated, and it is further determined that the first context information is updated.

[0118] For example, the first information can indicate the update time #1 corresponding to the core network device #1 on the satellite #1, the update time #2 corresponding to the core network device #2 on the satellite #2, the update time #3 corresponding to the core network device #3 on the satellite #3, and the update time #6 corresponding to the core network device #6 on the satellite #6. That is, the update time corresponding to part or all of the plurality of network devices indicated by the first information can include the latest update time in the update time corresponding to each network device in the plurality of network devices, that is, 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 by the core network device #1 on the satellite #1, the core network device #2 on the satellite #2, the core network device #3 on the satellite #3, the core network device #4 on the satellite #4, the core network device #5 on the satellite #5, and the core network device #6 on the satellite #6 is updated.

[0119] In a possible implementation, in the case that the first context information is updated, the terminal device can set the state of the first satellite relative to the terminal device to a first state (or referred to as an active state). The first state is used to indicate that the terminal device can monitor the message from the first satellite and can send the message to the first satellite.

[0120] In a case where 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 referred to as an inactive state). The second state is used to indicate that the terminal device can monitor system messages from the first satellite, but cannot monitor paging messages from the first satellite, and cannot send messages to the first satellite; or the second state can also be used to indicate that the terminal device turns off the access layer function, that is, the terminal device cannot monitor system messages from the first satellite, cannot monitor paging messages from the first satellite, and cannot send messages to the first satellite.

[0121] It can be understood that the state of the first satellite relative to the terminal device is not the state of the first satellite as believed by the first satellite, that is, not the actual state of the first satellite, but the state of the first satellite as believed by the terminal device.

[0122] In a possible implementation, the first information can be generated by the network and sent to the terminal device, or can also be generated by the terminal device. The embodiments of the present application do not limit this. The following will be introduced respectively.

[0123] Case one, the terminal device can receive the first information. That is, the first information is generated by the network (for example, a fourth network device on the ground, a fifth network device on the ground, or a first network device on the first satellite) and sent to the terminal device.

[0124] The fourth network device on the ground and the fifth network device on the ground are both core network devices. The fourth network device on the ground is not an independent core network device, and the fifth network device on the ground is an independent core network device.

[0125] For example, the first network device on the first satellite and the fourth network device on the ground are both not independent core network devices, they are a core network device split into two parts, and the first network device on the first satellite and the fourth network device on the ground are corresponding and jointly constitute a complete core network device, that is, the first network device on the first satellite + the fourth network device on the ground = complete core network device.

[0126] Each network device of the plurality of network devices and the fourth network device on the ground are not independent core network devices, and each network device of the plurality of network devices + the fourth network device on the ground = complete core network device. Therefore, the fourth network device on the ground stores the same context information of the terminal device as each network device of the plurality of network devices. That is, when the context information of the terminal device stored by the fourth network device on the ground is updated, it needs to be synchronized to each network device of the plurality of network devices.

[0127] Taking the 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, wherein the MME network element on the ground + the MME network element on the first satellite = a complete MME network element. The fifth network device on the ground can be a UE reachability estimator (URE) network element.

[0128] For example, taking the first information as an example which is stored by the fourth network device on the ground. FIG. 6 is a flowchart of another communication method provided by an embodiment of the present application. As shown in FIG. 6, before step S501 is performed, the embodiment of the present application can further perform the following steps.

[0129] Step a1, the fourth network device on the ground determines that the context information of the terminal device stored by the fourth network device on the ground is updated.

[0130] For example, there are 5 satellites covering the terminal device at different time, which are satellite #1, satellite #2, satellite #3, satellite #4 and satellite #5. The access network device #1 and the core network device #1 are deployed on the satellite #1, the access network device #2 and the core network device #2 are deployed on the satellite #2, the access network device #3 and the core network device #3 are deployed on the satellite #3, the access network device #4 and the core network device #4 are deployed on the satellite #4, and the access network device #5 and the core network device #5 are deployed on the satellite #5. There is 1 core network device on the ground which can serve the terminal device, which is the core network device #6. There are 3 gateway stations connected with the core network device #6 on the ground, which are gateway station #1, gateway station #2 and gateway station #3. Among them, the satellite #1, the satellite #2, the satellite #3, the satellite #4 and the satellite #5 can be connected with the core network device #6 on the ground through any one of the gateway station #1, the gateway station #2 and the gateway station #3.

[0131] The terminal device, the core network device #1 on the satellite #1, the core network device #2 on the satellite #2, the core network device #3 on the satellite #3, the core network device #4 on the satellite #4, the core network device #5 on the satellite #5 and the core network device #6 on the ground all store the context information #1 of the terminal device. The terminal device triggers the TAU process, and when the communication link between the satellite #1 and the terminal device is available, sends a TAU request message to the satellite #1. When the communication link between the satellite #1 and the core network device #6 on the ground is available, the satellite #1 delivers the TAU request message to the core network device #6 on the ground. After the core network device #6 on the ground receives the TAU request message, it is determined that the context information of the terminal device stored by the fourth network device on the ground is updated.

[0132] The fourth network device on the ground determines the first information according to the second information, coverage information of the satellite on which the part or all of the network devices are located, and position information of the fourth network device on the ground.

[0133] The second information can be used to determine the part of the network devices. Optionally, the second information can be used to indicate a service type of the terminal device and / or a communication mode of the terminal device. For example, the service type of the terminal device can indicate that the service of the terminal device is a time delay sensitive service, a time delay non-sensitive service, etc. The communication mode of the terminal device can indicate a communication duration of the terminal device, a periodic time, a planned communication time, etc. The communication duration refers to a duration of a single communication of the periodic communication, for example, 5 minutes. The periodic time refers to an interval time of the periodic communication, for example, 1 hour. The planned communication time refers to a time zone and a day of the week in which the terminal device can be used for communication, for example, 13:00-20:00 on Monday. The embodiments of the present application do not limit the name of the second information.

[0134] The coverage information of the satellite on which the part or all of the network devices are located refers to ephemeris information or mapping relationship information of a satellite coverage area and time.

[0135] Specifically, the fourth network device on the ground can determine an update time of the network device on each satellite covering the terminal device at different time according to the coverage information of each satellite covering the terminal device at different time, the position information of the fourth network device on the ground, and the position information of the part or all of the gateway stations corresponding to the fourth network device on the ground, and determine the first information according to the update time of the network device on each satellite covering the terminal device at different time and the second information.

[0136] For example, the core network device #6 on the ground can determine that the communication link between satellite #1 and the core network device #6 on the ground is available at present, the communication link between satellite #2 and the core network device #6 on the ground is available after 2 hours, the communication link between satellite #3 and the core network device #6 on the ground is available after 4 hours, the communication link between satellite #4 and the core network device #6 on the ground is available after 6 hours, and the communication link between satellite #5 and the core network device #6 on the ground is available after 8 hours according to the coverage information of satellite #1, satellite #2, satellite #3, satellite #4, and satellite #5, the position information of the core network device #6 on the ground, and the position information of gateway station #1, gateway station #2, and gateway station #3.

[0137] For example, the updating time of the context information of the terminal device stored by the core network device on each satellite is equal to the available time of the communication link between each satellite and the core network device 6 on the ground. The core network device 6 on the ground can determine that the updating time 1 corresponding to the core network device 1 on satellite 1 is 0h, the updating time 2 corresponding to the core network device 2 on satellite 2 is 2h, the updating time 3 corresponding to the core network device 3 on satellite 3 is 4h, the updating time 4 corresponding to the core network device 4 on satellite 4 is 6h, and the updating time 3 corresponding to the core network device 5 on satellite 5 is 8h.

[0138] For example, the service type of the terminal device is a time delay non-sensitive type. The core network device 6 on the ground can determine that 3 satellites are needed to provide services for the terminal device to meet the minimum time delay requirement of the terminal device. For example, the communication mode indication period of the terminal device is 1h. The core network device 6 on the ground can determine that the communication link between satellite 1 and the terminal device is available at present, the communication link between satellite 2 and the terminal device is available after 1h, the communication link between satellite 3 and the terminal device is available after 2h, the communication link between satellite 4 and the terminal device is available after 3h, and the communication link between satellite 5 and the terminal device is available after 4h according to the coverage information of satellite 1, satellite 2, satellite 3, satellite 4 and satellite 5 and the location information of the terminal device. Further, the core network device 6 on the ground can determine that the time when satellite 1, satellite 2 and satellite 3 cover the terminal device is most suitable for the frequency of the terminal device transmitting data.

[0139] Therefore, in order to reduce the overhead of the first information, the core network device 6 on the ground can select satellite 1, satellite 2 and satellite 3 from satellite 1, satellite 2, satellite 3, satellite 4 and satellite 5 serving the terminal device to provide services for the terminal device. That is, the core network device 6 on the ground can determine that the updating time corresponding to the core network device on part or all of the satellites covering the terminal device at different times indicated by the first information includes the updating time 1 corresponding to the core network device 1 on satellite 1, the updating time 2 corresponding to the core network device 3 on satellite 2 and the updating time 3 corresponding to the core network device 3 on satellite 3.

[0140] In addition, since the latest updating time in the updating time corresponding to each satellite is the updating time 5 corresponding to satellite 5, in order to avoid the terminal device always using only satellite 1, satellite 2 and satellite 3 and not using satellite 4 and satellite 5, the core network device 6 on the ground can determine that the updating time corresponding to the core network device on part or all of the satellites covering the terminal device at different times indicated by the first information also includes the updating time 5 corresponding to satellite 5.

[0141] Step a3, in case the fourth network equipment on the ground is located in the coverage of the first satellite, the fourth network equipment on the ground sends the first information to the first network equipment on the first satellite, and correspondingly, the first network equipment on the first satellite receives the first information from the fourth network equipment on the ground.

[0142] For example, the core network equipment #6 on the ground determines to select to send the TAU accept message to the terminal device through the satellite #1 according to the location information of the terminal device and the coverage information of each satellite covering the terminal device at different time. The TAU accept message includes the first information.

[0143] When the communication link between the satellite #1 and the core network equipment #6 on the ground is available, the core network equipment #6 on the ground sends the latest context information of the terminal device and the TAU accept message to the core network equipment #1 on the satellite #1. Correspondingly, the core network equipment #1 on the satellite #1 receives the latest context information of the terminal device and the TAU accept message from the core network equipment #6 on the ground.

[0144] When the communication link between the satellite #2, the satellite #3, the satellite #4, the satellite #5 and the core network equipment #6 on the ground is available, the core network equipment #6 on the ground sends the latest context information of the terminal device to the core network equipment #2 on the satellite #2, the core network equipment #3 on the satellite #3, the core network equipment #4 on the satellite #4 and the core network equipment #5 on the satellite #5 respectively. Correspondingly, the core network equipment #2 on the satellite #2, the core network equipment #3 on the satellite #3, the core network equipment #4 on the satellite #4 and the core network equipment #5 on the satellite #5 receive the latest context information of the terminal device from the core network equipment #6 on the ground.

[0145] Step a4, in case the terminal device is located in the coverage of the first satellite, the first network equipment on the first satellite sends the first information to the terminal device through the second network equipment on the first satellite, and correspondingly, the terminal device receives the first information from the first network equipment on the first satellite through the second network equipment on the first satellite.

[0146] For example, when the communication link between the satellite #1 and the terminal device is available, the core network equipment #1 on the satellite #1 sends the TAU accept message to the terminal device through the access network equipment #1 on the satellite #1. Correspondingly, the terminal device receives the TAU accept message from the core network equipment #1 on the satellite #1 through the access network equipment #1 on the satellite #1. The TAU accept message includes the first information.

[0147] For example, the first information is generated by the fifth network device on the ground. FIG. 7 is a flow diagram of another communication method provided by the embodiments of the present application. As shown in FIG. 7, before performing S501, the embodiments of the present application can further perform the following steps.

[0148] In step b1, the fourth network device on the ground determines that the context information of the terminal device stored by the fourth network device on the ground is updated.

[0149] The step b1 can refer to the above step a1, and details are not described herein.

[0150] In step b2, the fourth network device on the ground sends 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.

[0151] The third information is used to indicate the second information, the location information of the terminal device and the location information of the fourth network device on the ground. The embodiments of the present application do not limit the name of the third information.

[0152] Optionally, the third information can also be used to indicate the location information of part or all of the gateway stations corresponding to the fourth network device on the ground.

[0153] Optionally, the third information can also be used to indicate part or all of the network devices on the satellites covering the terminal device at different time instants. The part or all of the satellites covering the terminal device at different time instants indicated by the third information can be the same as or different from the part or all of the satellites covering the terminal device at different time instants indicated by the first information. The part or all of the satellites covering the terminal device at different time instants indicated by the third information can be preconfigured, or can be selected by the fourth network device on the ground from the satellites covering the terminal device at different time instants and provided for the terminal device, for example, according to the service type of the terminal device and / or the communication mode of the terminal device.

[0154] The second information can refer to the above step a2, and details are not described herein.

[0155] In the implementation process, 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 part or all of the gateway stations corresponding to the fourth network device on the ground; or can indirectly indicate the identifier of the terminal device, the identifier of the fourth network device on the ground and the identifier of part or all of the gateway stations corresponding to the fourth network device on the ground. The embodiments of the present application do not limit this.

[0156] The third information can directly indicate the identities of the satellites that cover the terminal device at different time instants, or indirectly indicate the identities of the network devices on the satellites that cover the terminal device at different time instants. The embodiments of the present application do not limit this.

[0157] For example, the core network device #6 on the ground sends information to the core network device #7 on the ground, where the information includes the service type and / or the communication mode of the terminal device, the location information of the terminal device, the location information of the core network device #6 on the ground, the location information of the gateway station #1, the gateway station #2 and the gateway station #3 connected to the core network device #6 on the ground, the identity of the satellite #1, and the identity of the satellite #2.

[0158] Step b3, the fifth network device on the ground determines the first information according to the third information and the coverage information of the satellites on which the part or all of the network devices are located.

[0159] Specifically, the fifth network device on the ground can determine each satellite that covers the terminal device at different time instants according to the location information of the terminal device, determine the update time of the network device on each satellite that covers the terminal device at different time instants according to the coverage information of each satellite that covers the terminal device at different time instants, the location information of the fourth network device on the ground, and the location information of the part or all of the gateway stations corresponding to the fourth network device on the ground, and determine the first information according to the update time of the network device on each satellite that covers the terminal device at different time instants and the second information. For details, refer to the above step a2, which will not be repeated here.

[0160] 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.

[0161] For example, the core network device #7 on the ground sends a response message 1 to the core network device #6 on the ground, where the response message 1 includes the first information.

[0162] Step b5, in the case that the fourth network device on the ground is located in the coverage range of the first satellite, the fourth network device on the ground sends the 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.

[0163] This step b5 can refer to the above step a3, which will not be repeated here.

[0164] Step b6, in case the terminal device is located in the coverage 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, and 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.

[0165] The step b6 can refer to the step a4 described above, and will not be described here again.

[0166] For example, the first information is generated by the first network device on the first satellite and sent to the terminal device. FIG. 8 is a flowchart of another communication method provided by the embodiments of the present application. As shown in FIG. 8, before performing S501, the embodiments of the present application can further perform the following steps.

[0167] Step c1, the first network device on the first satellite determines that the context information of the terminal device stored by the first network device on the first satellite is updated.

[0168] For example, after the terminal device, the core network device #1 on the satellite #1, the core network device #2 on the satellite #2, the core network device #3 on the satellite #3, the core network device #4 on the satellite #4, the core network device #5 on the satellite #5 and the core network device #6 on the ground all store the context information #1 of the terminal device, the terminal device triggers the TAU process, and sends a TAU request message to the satellite #1 when the communication link between the satellite #1 and the terminal device is available. The satellite #1 delivers the TAU request message to the core network device #6 on the ground when the communication link between the satellite #1 and the core network device #6 on the ground is available.

[0169] After the core network device #6 on the ground receives the TAU request message, it is determined that the context information of the terminal device stored by the core network device #6 on the ground is updated. According to the location information of the terminal device and the coverage information of each satellite covering the terminal device at different times, it is determined to send a TAU accept message to the terminal device through the satellite #1. The core network device #6 on the ground sends the latest context information of the terminal device and the TAU accept message to the core network device #1 on the satellite #1 when the communication link between the satellite #1 and the core network device #6 on the ground is available. The core network device #6 on the ground sends the latest context information of the terminal device to the core network device #2 on the satellite #2, the core network device #3 on the satellite #3, the core network device #4 on the satellite #4 and the core network device #5 on the satellite #5 respectively when the communication links between the satellite #2, the satellite #3, the satellite #4 and the satellite #5 and the core network device #6 on the ground are available.

[0170] The core network device 1 on the satellite 1 receives the TAU request message and the latest context information of the terminal device, and determines that the context information of the terminal device stored by the core network device 1 on the satellite 1 is updated.

[0171] In step c2, the first network device on the first satellite determines the first information according to the second information, coverage information of satellites where the part or all of the network devices are located, and location information of the fourth network device on the ground.

[0172] The step c2 can refer to the above step a2, and details are not described herein.

[0173] In step c3, 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 when the terminal device is located in the coverage of the first satellite, and 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.

[0174] The step c3 can refer to the above step a4, and details are not described herein.

[0175] In case two, the terminal device can determine the first information according to the coverage information of satellites where the part or all of the network devices are located and the location information of the fourth network device on the ground.

[0176] Specifically, the terminal device can determine the update time of the network device on each satellite covering the terminal device at different time according to the coverage information of each satellite covering the terminal device at different time, the location information of the fourth network device on the ground, and the location information of the part or all of the gateway stations corresponding to the fourth network device on the ground, and determine the first information according to the update time of the network device on each satellite covering the terminal device at different time.

[0177] The step c2 can refer to the above step a2, and details are not described herein.

[0178] In mode B, the terminal device can determine whether the first identifier and the second identifier are the same, where 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 the context information of the terminal device stored by the terminal device (for example, referred to as second context information).

[0179] The first identifier can also be referred to as a first context sequence number (CSN), and the second identifier can also be referred to as a second context sequence number, and the name of the first identifier and the second identifier is not limited in the embodiments of the present application.

[0180] In a possible implementation, the first identifier can be sent by the first network device on the first satellite to the terminal device. For example, the first network device on the first satellite can send a first paging message to the terminal device through the second network device on the first satellite, and the terminal device can receive the first paging message from the first network device on the first satellite through the second network device on the first satellite. The first paging message includes the first identifier. The second identifier can be stored locally by the terminal device.

[0181] In a possible implementation, the terminal device can further 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 through the second network device on the first satellite, and the first network device on the first satellite can receive the first request message from the terminal device through the second network device on the first satellite. The first request message includes the second identifier, and the first request message is used to request to establish 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 is updated, otherwise it indicates that the second context information is not updated.

[0182] For example, there are two satellites covering the terminal device at different times, which are the first satellite and the second satellite. FIG. 9 is a flowchart of another communication method provided by an embodiment of the present application. As shown in FIG. 9, the terminal device can interact with the network (for example, the first network device and the second network device on the first satellite, the sixth network device and the seventh network device on the second satellite, and the fourth network device on the ground) to perform an attach process (steps d1-d5) and a TAU process (steps d6-d11), and create or update the context information of the terminal device. 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, and the second network device on the first satellite and the seventh network device on the second satellite are access network devices. 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 not independent core network devices.

[0183] Taking the 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. 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.

[0184] Step d1, in the case that the terminal device is located in the coverage 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, and 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.

[0185] The attach accept message includes a CSN#1 allocated by the first network device on the first satellite for the terminal device.

[0186] Step d2, in the case that the terminal device is located in the coverage 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, and 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.

[0187] Step d3, the terminal device creates and stores the context information of the terminal device, and the first network device on the first satellite creates and stores the context information of the terminal device.

[0188] The terminal device stores the context information (i.e. second context information) of the terminal device with an identifier of CSN#1, and the first network device on the first satellite stores the context information (i.e. first context information) of the terminal device with an identifier of CSN#1.

[0189] Step d4, in the case that the fourth network device on the ground is located in the coverage of the first satellite, the first network device on the first satellite sends the latest context information of the terminal device and the CSN#1 to the fourth network device on the ground, and correspondingly, the fourth network device on the ground receives the latest context information of the terminal device and the CSN#1 from the first network device on the first satellite.

[0190] Step d5, in the case that the fourth network device on the ground is located in the coverage of the second satellite, the fourth network device on the ground sends the latest context information of the terminal device and the CSN#1 to the sixth network device on the second satellite, and correspondingly, the sixth network device on the second satellite receives the latest context information of the terminal device and the CSN#1 from the fourth network device on the ground.

[0191] Step d6, in the case that the terminal device is located in the coverage 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, and 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.

[0192] Step d7, in the case that the fourth network equipment on the ground is located in the coverage of the first satellite, the first network equipment on the first satellite sends a TAU request message to the fourth network equipment on the ground, and correspondingly, the fourth network equipment on the ground receives the TAU request message from the first network equipment on the first satellite.

[0193] Step d8, the fourth network equipment on the ground determines that the context information of the terminal equipment stored by the fourth network equipment on the ground is updated, and allocates CSN#2 for the terminal equipment.

[0194] That is, the identification of the context information of the terminal equipment stored by the fourth network equipment on the ground is updated from CSN#1 to CSN#2.

[0195] Step d9, in the case that the fourth network equipment on the ground is located in the coverage of the first satellite, the fourth network equipment on the ground sends the latest context information of the terminal equipment and a TAU accept message to the first network equipment on the first satellite, and correspondingly, the first network equipment on the first satellite receives the latest context information of the terminal equipment and the TAU accept message from the fourth network equipment on the ground.

[0196] Wherein, the TAU accept message includes the CSN#2 allocated by the fourth network equipment on the ground for the terminal equipment.

[0197] That is, the identification of the first context information is updated from CSN#1 to CSN#2.

[0198] Step d10, in the case that the terminal equipment is located in the coverage of the first satellite, the first network equipment on the first satellite sends a TAU accept message to the terminal equipment through the second network equipment on the first satellite, and correspondingly, the terminal equipment receives the TAU accept message from the first network equipment on the first satellite through the second network equipment on the first satellite.

[0199] That is, the identification of the second context information is updated from CSN#1 to CSN#2.

[0200] Step d11, in the case that the fourth network equipment on the ground is located in the coverage of the second satellite, the fourth network equipment on the ground sends the latest context information of the terminal equipment and CSN#2 to the sixth network equipment on the second satellite, and correspondingly, the sixth network equipment on the second satellite receives the latest context information of the terminal equipment and CSN#2 from the fourth network equipment on the ground.

[0201] That is, the identification of the context information of the terminal equipment stored by the sixth network equipment on the second satellite is updated from CSN#1 to CSN#2.

[0202] For another example, FIG. 10 is a flow diagram of another method of communication provided by the embodiments of the present application. As shown in FIG. 10, the terminal device can interact with the network (for example, the first network device and the second network device on the first satellite, the fourth network device on the ground, and the eighth network device on the ground) to perform a downlink data transmission process (step e1-step e5-2) and an uplink data transmission process (step e6-step e9-2). Among them, 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.

[0203] 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 the downlink data from the eighth network device on the ground.

[0204] Step e2, in the case that the terminal device is located in the coverage 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.

[0205] Among them, the first paging message is used to page the terminal device. The first paging message includes the first identifier.

[0206] Step e3, in the case that the terminal device is located in the coverage of the first satellite, the second network device on the first satellite sends a second paging message to the terminal device, and correspondingly, the terminal device receives the second paging message from the second network device on the first satellite.

[0207] Among them, the second paging message is used to page the terminal device. The second paging message includes the first identifier.

[0208] Step e4, the terminal device determines whether the first identifier is the same as the second identifier.

[0209] Step e5-1, in the case that the first identifier is the same as the second identifier and the terminal device is located in the coverage of the first satellite, the terminal device establishes a connection with the first satellite.

[0210] Step e6-1, the second network device on the first satellite sends downlink data to the terminal device, and correspondingly, the terminal device receives the downlink data from the second network device on the first satellite.

[0211] Step e5-2, in the case that the first identity is different from the second identity and the terminal device is located in the coverage of the first satellite, the terminal device sends second indication information to the first network device on the first satellite through the second network device on the first satellite.

[0212] 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.

[0213] Step e6-2, in the case that the fourth network device on the ground is located in the coverage of the first satellite, the first network device on the first satellite acquires the latest context information of the terminal device from the fourth network device on the ground.

[0214] Step e7, in the case that the terminal device is located in the coverage 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, and 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.

[0215] The first request message includes the second identity. The first request message can be used to request to establish a connection with the terminal device, for example, the first request message can be a service request message.

[0216] Step e8, the first network device on the first satellite determines whether the first identity is the same as the second identity.

[0217] Step e9-1, in the case that the first identity is the same as the second identity and the terminal device is located in the coverage of the first satellite, the first satellite establishes a connection with the terminal device.

[0218] 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.

[0219] Step e9-2, in the case that the first identity is different from the second identity and the terminal device is located in the coverage of the first satellite, the first network device on the first satellite sends third indication information to the terminal device through the second network device on the first satellite.

[0220] 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 request of the terminal device is that the first context information is invalid.

[0221] Step e10-2, in the case that the fourth network device on the ground is located in the coverage of the first satellite, the first network device on the first satellite acquires the latest context information of the terminal device from the fourth network device on the ground.

[0222] It can be understood that the above-mentioned embodiments of the present application can be implemented independently or in combination, and the embodiments of the present application are not limited.

[0223] The above describes the method provided by the embodiments of the present application with reference to the accompanying drawings. The following describes the device provided by the embodiments of the present application with reference to the accompanying drawings.

[0224] Based on the same technical concept, the embodiments of the present application provide a communication device, which includes a module / unit / means for performing the method performed by the device in the above-mentioned method embodiments. The module / unit / means can be implemented by software or by hardware, or by implementing corresponding software by hardware.

[0225] For example, referring to FIG. 11, a schematic diagram of a communication device 1100 is shown, which includes a transceiver module 1101 and a processing module 1102.

[0226] When the device 1100 is a terminal device, the functions of the modules of the device 1100 are as follows:

[0227] The processing module 1102 is configured to determine 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 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.

[0228] The processing module 1102 is configured to establish 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.

[0229] Alternatively, when the device 1100 is a first network device on the first satellite or a fourth network device on the ground, the functions of the modules of the device 1100 are as follows:

[0230] The transceiver module 1101 is configured to send first information, wherein the first information is used to indicate update times corresponding to part or all of a plurality of network devices, the plurality of network devices include a first network device, the first network device is located on a 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 a time when first context information stored by the first network device is updated, and the first context information is context information of the terminal device.

[0231] In a specific implementation, the device 1100 described above can have various product forms, and the following introduces several possible product forms.

[0232] Referring to FIG. 12, there is a schematic diagram of another communication device 1200, which includes a processor 1201 and an interface circuit 1202 for receiving signals from other communication devices and transmitting signals to other communication devices, and the processor 1201 is configured to implement the methods described in the foregoing method embodiments through a logic circuit or by executing instructions in the storage medium. The processor 1201 and the interface circuit 1202 are coupled to each other. It can be understood that the interface circuit 1202 can be a transceiver or an input / output interface. Optionally, the communication device 1200 can further include a memory 1203 for storing instructions executed by the processor 1201 or storing input data required by the processor 1201 for executing instructions or storing data generated by the processor 1201 after executing instructions.

[0233] The processor 1201 and the interface circuit 1202 are coupled to each other. It can be understood that the interface circuit 1202 can be a transceiver or an input / output interface. Optionally, the communication device 1200 can further include a memory 1203 for storing instructions executed by the processor 1201 or storing input data required by the processor 1201 for executing instructions or storing data generated by the processor 1201 after executing instructions.

[0234] It should be understood that the processor mentioned in the embodiments of the present application can be implemented by hardware or software. When implemented by hardware, the processor can be a logic circuit, an integrated circuit, etc. When implemented by software, the processor can be a general-purpose processor which reads software codes stored in a memory to implement the methods.

[0235] For example, the processor can be a central processing unit (CPU), and can also be other general-purpose processors, digital signal processors (DSP), application specific integrated circuits (ASIC), field programmable gate arrays (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or the processor can also be any conventional processor.

[0236] It should be appreciated that the memory mentioned in the embodiments of the present application can be a volatile memory or a non-volatile memory, or can include both volatile and non-volatile memories. Among them, the non-volatile memory can be a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically EPROM (EEPROM) or a flash memory. The volatile memory can be a random access memory (RAM) 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 SDRAM (ESDRAM), synchlink DRAM (SLDRAM) and direct rambus RAM (DR RAM).

[0237] It can be understood that when the processor is a general processor, a DSP, an ASIC, a FPGA or other programmable logic device, a discrete gate or transistor logic device, a discrete hardware component, the memory (storage module) can be integrated in the processor.

[0238] It should be noted that the memory described herein is intended to include, but not limited to, these and any other suitable types of memory.

[0239] Based on the same technical concept, the embodiments of the present application also provide a computer readable storage medium, which stores a computer program or instructions, and when the computer program or instructions are executed by a processor, the method executed by the terminal device, the access network device or the core network device in the above method embodiment is realized.

[0240] Based on the same technical concept, the embodiments of the present application also provide a computer program product, which contains a computer program or instructions, and when the computer program or instructions are executed by a processor, the method executed by the terminal device, the access network device or the core network device in the above method embodiment is realized.

[0241] Those skilled in the art will appreciate that embodiments of the present application can be readily used as a method, a system or a computer program product. Accordingly, the present application can take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application can take the form of a computer program product on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROMs, optical storage devices, etc.) embodying computer readable program code.

[0242] The present application is described in reference to the flow diagrams and / or block diagrams of the methods, apparatus (systems) and computer program products according to this application. It will be understood that each block of the flow diagrams and / or block diagrams, and combinations of blocks in the flow diagrams 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, create means for implementing the functions specified in the flow diagrams and / or block diagrams block or blocks.

[0243] These computer program instructions can also be stored in a computer- readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instructions which implement the function specified in the flow diagrams and / or block diagrams block or blocks.

[0244] The computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flow diagrams and / or block diagrams block or blocks.

Claims

1. A communication method, characterized in that, include: Determine whether the first context information stored in 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 the first satellite, and the first satellite is a satellite covering the terminal device; If the first context information is updated, a connection is established with a second network device, wherein the second network device is located on the first satellite.

2. The method according to claim 1, characterized in that, Determining whether the first context information stored by the first network device among a plurality of network devices has been updated includes: Based on the update times corresponding to some or all of the plurality of network devices, it is determined whether the first context information has been updated, wherein the update time corresponding to the first network device is used to indicate the time when the first context information was updated; or... 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 context information of the terminal device stored in the terminal device.

3. The method according to claim 2, characterized in that, Determining whether the first context information has been updated based on the update time of some or all of the network devices among the plurality of network devices includes: Based on the update time corresponding to the first network device, determine whether the first context information has been updated; or, Based on the update time corresponding to the third network device among the plurality of network devices, it is determined whether the first context information has been updated, wherein 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.

4. The method according to claim 2 or 3, characterized in that, The method further includes: Receive the first message; or, First information is determined 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, wherein the fourth network device is the same as the context information of the terminal device stored in each of the multiple network devices. The first information is used to indicate the update time of some or all of the network devices among the plurality of network devices.

5. The method according to claim 2, characterized in that, The method further includes: Receive a first paging message, wherein the first paging message includes the first identifier.

6. The method according to any one of claims 1-5, characterized in that, The method further includes: If the first context information is not updated, a connection is not established with the second network device.

7. The method according to claim 6, characterized in that, The method further includes: Enter hibernation mode.

8. The method according to any one of claims 1-7, characterized in that, Before determining whether the first context information stored in the first network device among a plurality of network devices has been updated, the method further includes: Receive first indication information, wherein the first indication information is used to instruct the first context information to begin updating; or... The context information of the terminal device stored in the terminal device is updated.

9. A communication method, characterized in that, include: 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, 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.

10. The method according to claim 9, characterized in that, The method further includes: Receive the first information; or, The first information is determined based on the second information, the coverage information of the satellites where some or all of the plurality of network devices are located, and the location information of the fourth network device on the ground. The second information is used to identify some of the plurality of network devices, and the fourth network device has the same context information of the terminal device stored in each of the plurality of network devices.

11. The method according to claim 10, characterized in that, Before receiving the first information, the method further includes: Send a third message, wherein the third message is used to indicate the second message, the location information of the terminal device, and the location information of the fourth network device on the ground, the second message is used to identify some of the network devices among the plurality of network devices, and the fourth network device has the same context information of the terminal device stored in 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 the service type of the terminal device and / or the communication mode of the terminal device.

13. The method according to any one of claims 9-12, characterized in that, Some of the network devices in the plurality of network devices include a third network device, wherein the update time of the third network device is later than the update time of the remaining network devices in the plurality of network devices.

14. A communication device, characterized in that, The communication device includes a module for performing the method as described in any one of claims 1 to 8, or a module for performing the method as described in any one of claims 9 to 13.

15. A communication device, characterized in that, The communication device includes a processor, which is configured to perform the method as described in any one of claims 1 to 8, or the method as described in any one of claims 9 to 13.

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

17. A computer program product, characterized in that, The computer program product includes a computer program that, when run on a computer, causes the method as described in any one of claims 1 to 8 to be performed, or causes the method as described in any one of claims 9 to 13 to be performed.

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