Satellite base station switching method and device and computer readable storage medium

Abstract

The invention relates to the field of satellite communication, and provides a satellite base station switching method and device and a computer readable storage medium, which can support SDT of terminal equipment in an RRC inactive state in NTN, effectively reduce the power consumption of the terminal equipment and improve the transmission efficiency. Under the condition that a source satellite currently serving a first cell needs to be switched to a target satellite, the source satellite sends first information (such as security information, context information and cell configuration information) related to the first cell to the target satellite, and after the target satellite receives the first information, related configuration is carried out in the target satellite. Therefore, as the context information of the terminal equipment in the RRC inactive state is stored and configured in the target satellite, in the process that the target satellite serves the first cell, the terminal equipment in the RRC inactive state can send the uplink small data, and the target satellite can quickly receive the uplink small data.

Description

Technical Field

[0001] The present application relates to the field of satellite communications, and more specifically, to a method, device, and computer-readable storage medium for switching satellite base stations in the field of satellite communications. Background Art

[0002] In terrestrial network (TN) communication, the terminal device supports small data transmission (SDT) in the radio resource control (RRC-INACTIVE) state, that is, the terminal device does not need to enter the RRC connected state (RRC_CONNECTED) in the RRC inactive state to send small data to the TN communication network device (such as gNB), thereby improving the transmission efficiency of small data and effectively reducing the power consumption of the terminal device.

[0003] In non-terrestrial network (NTN) communications such as satellite communications, the long transmission distance will lead to high power consumption of terminal devices. Therefore, the power consumption of terminal devices is an important indicator of NTN communications. Based on this, related technologies propose to support SDT of terminal devices in RRC inactive state in NTN communications to effectively reduce the power consumption of terminal devices. There is currently no clear technical solution for how to achieve the above technical requirements. Summary of the invention

[0004] The present application provides a satellite base station switching method, device and computer-readable storage medium, which can support SDT of terminal equipment in RRC inactive state in NTN, effectively reduce the power consumption of terminal equipment and improve transmission efficiency.

[0005] In a first aspect, a method for switching a satellite base station is provided, which is applied to a target satellite of a satellite system, wherein the satellite system includes multiple low earth orbit (LEO) satellites, the multiple LEO satellites include a source satellite and a target satellite, the source satellite is a satellite currently serving a first cell, and the target satellite is a satellite that is switched from the source satellite to serve the first cell, the method comprising: receiving first information sent by the source satellite, the first information comprising security information, context information and cell configuration information of the first cell, the context information comprising context information of a terminal device in a radio resource control (RRC) inactive state in the first cell; performing configuration on the target satellite according to the first information; and receiving small uplink data sent by a terminal device in an RRC inactive state in the first cell during the process of the target satellite serving the first cell.

[0006] The method for switching a satellite base station provided in an embodiment of the present application is that when the source satellite currently serving the first cell needs to be switched to the target satellite, the source satellite sends the first information related to the first cell to the target satellite, the first information including security information, context information, and cell configuration information of the first cell, wherein the context information includes the context information of the terminal device in the RRC inactive state in the first cell; after receiving the first information, the target satellite performs configuration on the target satellite. In this way, when the terminal device in the RRC inactive state needs to send small uplink data during the process of the target satellite serving the first cell, the terminal device can send small uplink data in the RRC inactive state (without entering the RRC connected state). Since the context information of the terminal device in the RRC inactive state has been saved and configured in the target satellite, the target satellite does not need to request context information from the source satellite at this time. The target satellite can directly successfully receive small uplink data based on the saved and configured context information, thereby avoiding as much as possible the problem of increased power consumption of the terminal device, decreased transmission efficiency, and large signaling overhead caused by the process of the target satellite requesting context information from the source satellite. In other words, the embodiment of the present application enables a terminal device in an RRC inactive state to quickly transmit small uplink data without entering a connected state, which not only reduces signaling overhead, but more importantly, effectively improves the efficiency of data transmission and reduces the power consumption of the terminal device. In NTN, the advantages of low power consumption and good transmission efficiency of the terminal device performing SDT in an RRC inactive state are fully utilized, so that NTN communication such as satellite communication can friendly support the SDT of the terminal device in an RRC inactive state. In addition, the source satellite sends security information to the target satellite, which can make the target satellite and the terminal device in the first cell have the same understanding of the encryption and decryption of data and signaling, and can encrypt and decrypt data and signaling through security information, ensuring the security of the data and signaling transmission process and the correct decryption of data and signaling as much as possible, and avoiding the problem of high signaling overhead caused by the need for the target satellite to re-negotiate security information with the terminal device in the first cell, which can further reduce signaling interaction.

[0007] In some embodiments, the security information includes a security key of the control plane and a security key of the user plane.

[0008] The security key of the control plane is used to encrypt and decrypt high-level signaling (such as RRC signaling), and the security key of the user plane is used to encrypt and decrypt user data.

[0009] The security keys of the control plane include the encryption key of the control plane and the integrity protection key of the control plane.

[0010] In one example (such as LTE), the security key of the user plane includes an encryption key of the user plane. In another example (such as NR), the security key of the user plane includes an encryption key of the user plane and an integrity protection key of the user plane.

[0011] In some embodiments, in the step of receiving the first information sent by the source satellite, where the first information includes security information, the security information is encrypted by a public key encryption algorithm by the receiving source satellite.

[0012] The satellite base station switching method provided in the embodiment of the present application encrypts security information through a public key encryption algorithm and sends the encrypted security information, which can prevent the security information from being stolen or tampered with during the transmission process, and can ensure the security of the content carried in the security information as much as possible, thereby ensuring the security of data or signaling transmission as much as possible.

[0013] In some embodiments, before the above-mentioned receiving of the first information sent by the source satellite, the method also includes: receiving a satellite data synchronization request sent by the source satellite, the satellite data synchronization request is used to indicate that the source satellite is about to send data; in response to the satellite data synchronization request, sending satellite data synchronization confirmation information to the source satellite, the satellite data synchronization confirmation information is used to indicate that the target satellite confirms receiving the data to be sent by the source satellite.

[0014] In the method for satellite base station switching provided in an embodiment of the present application, the target satellite can confirm that the source satellite is about to send data (such as the first information) based on the satellite data synchronization request sent by the source satellite, so that the target satellite can determine whether it can receive the data to be sent by the source satellite based on the actual situation: if the target satellite can receive the data to be sent by the source satellite, it sends satellite data synchronization confirmation information to the source satellite to inform itself that it can receive the data to be sent by the source satellite. In this way, the source satellite and the target satellite have the same understanding of the event that both parties are about to transmit data, which can avoid some unnecessary problems. For example, if the target satellite is currently unable to receive the data to be sent due to actual conditions (such as no resources, poor signal quality, etc.), but the source satellite has sent the first information, it will result in a waste of signaling.

[0015] In some embodiments, after receiving the first information sent by the source satellite and before receiving uplink small data sent by a terminal device in an RRC inactive state in the first cell during the process of the target satellite serving the first cell, the method also includes: receiving satellite data synchronization completion information sent by the source satellite.

[0016] In this way, the target satellite does not need to continue to wait for (or monitor) the data sent by the source satellite, so that subsequent steps can be executed, which can save the satellite's power consumption.

[0017] In some embodiments, in the process of the above-mentioned target satellite serving the first cell, in the step of receiving small uplink data sent by a terminal device in an RRC inactive state in the first cell, in the process of the target satellite serving the first cell, a third message of a random access process sent by a terminal device in an RRC inactive state is received, and the third message includes small uplink data.

[0018] The method for satellite base station switching provided in the embodiment of the present application is that a terminal device in an RRC inactive state in the NTN sends uplink small data to a satellite (such as a target satellite) through a third message (i.e., message 3) of the random access process, which can not only effectively reduce the power consumption of the terminal device and improve the transmission efficiency, but also, compared with other methods such as transmitting small data by pre-configuring wireless resources, since there is no need to pre-configure resources in advance, the problem of unreasonable resource allocation can be avoided, and the advantages of flexible and reasonable use of resources in the random access process can be fully utilized, and the changes to the existing standards are small, and the existing standards can be friendly adapted.

[0019] In some embodiments, the method further includes: in response to the third message, sending a fourth message (i.e., message 4) of a random access process to the terminal device, the fourth message including RRC release information carrying a suspension indication, and the suspension indication is used to indicate that the terminal device is in an RRC inactive state.

[0020] In some embodiments, the third message also includes an RRC recovery request.

[0021] In some embodiments, multiple LEO satellites cover cells in a manner similar to that of earth staring cells.

[0022] In a second aspect, a method for switching a satellite base station is provided, which is applied to a source satellite of a satellite system, wherein the satellite system includes multiple low earth orbit (LEO) satellites, and the multiple LEO satellites include a source satellite and a target satellite, wherein the source satellite is a satellite currently serving a first cell, and the target satellite is a satellite that is switched from the source satellite to serve the first cell, and the method includes: determining that the satellite serving the first cell needs to be switched from the source satellite to the target satellite; sending first information to the target satellite, the first information including security information, context information and cell configuration information of the first cell, the context information including context information of a terminal device in an inactive state of radio resource control (RRC) in the first cell; and stopping serving the first cell.

[0023] The method for switching a satellite base station provided by an embodiment of the present application is that when the source satellite currently serving the first cell needs to be switched to the target satellite, the source satellite sends the first information related to the first cell to the target satellite, the first information includes security information, context information, and cell configuration information of the first cell, wherein the context information includes the context information of the terminal device in the RRC inactive state in the first cell, so that after receiving the first information, the target satellite can be configured on the target satellite, and has the same security information, the first cell, and the context of the terminal device in the RRC inactive state as the source satellite. In this way, in the process of the target satellite serving the first cell, when the terminal device in the RRC inactive state needs to send small uplink data, the terminal device can send small uplink data in the RRC inactive state (without entering the RRC connected state), because the context information of the terminal device in the RRC inactive state has been saved and configured in the target satellite, at this time, the target satellite does not need to request context information from the source satellite, and the target satellite can directly receive the small uplink data based on the saved and configured context information, thereby avoiding as much as possible the problem of increased power consumption of the terminal device, decreased transmission efficiency, and large signaling overhead caused by the process of the target satellite requesting context information from the source satellite. In other words, the embodiment of the present application enables a terminal device in an RRC inactive state to quickly transmit small uplink data without entering a connected state, which not only reduces signaling overhead, but more importantly, effectively improves the efficiency of data transmission and reduces the power consumption of the terminal device. In NTN, the advantages of low power consumption and good transmission efficiency of the terminal device performing SDT in an RRC inactive state are fully utilized, so that NTN communication such as satellite communication can friendly support the SDT of the terminal device in an RRC inactive state. In addition, the source satellite sends security information to the target satellite, which can make the target satellite and the terminal device in the first cell have the same understanding of the encryption and decryption of data and signaling, and can encrypt and decrypt data and signaling through security information, ensuring the security of the data and signaling transmission process and the correct decryption of data and signaling as much as possible, and avoiding the problem of high signaling overhead caused by the need for the target satellite to re-negotiate security information with the terminal device in the first cell, which can further reduce signaling interaction.

[0024] In some embodiments, the security information includes a security key of the control plane and a security key of the user plane.

[0025] In some embodiments, in the above step of sending the first information to the target satellite, wherein the first information includes security information, the security information encrypted by the source satellite using a public key encryption algorithm is sent to the target satellite.

[0026] In some embodiments, before the above-mentioned stopping of service to the first cell, the method also includes: receiving a first message of a random access process sent by a terminal device in an RRC inactive state in the first cell; in response to the first message (ie, message 1), sending a second message of the random access process to the terminal device (ie, message 2), and the second message does not include scheduling information for uplink resources indicating a third message (ie, message 3).

[0027] The method for satellite base station switching provided by the embodiment of the present application, a timer is configured in the terminal device, and the duration of the timer is determined based on the duration of the satellite switching process. In the satellite switching process for a cell (such as the first cell), if the terminal device in the RRC inactive state in the cell has a demand for sending uplink small data, the terminal device sends a first message (i.e., message 1) of the random access process to initiate random access, and the source satellite sends a second message (i.e., message 2) to the terminal device that does not include (or carry) scheduling information for uplink resources indicating the third message (i.e., message 3). It can be understood that the source satellite sends a message 2 that does not include (or carry) scheduling information to the terminal device, which means that the source satellite and the target satellite are likely to be in the satellite switching process, and the source satellite does not want the terminal device to interact with itself during the satellite switching process to affect the transmission of data. In this way, after the terminal device receives the message 2 that does not include (or carry) scheduling information, it can be determined that the source satellite does not currently want or support the transmission of small data, so that the terminal device can be temporarily not required to continue to perform the random access process to transmit small data. In this way, not only can the signaling overhead be reduced, but also the power consumption of the terminal equipment can be further saved. In addition, after the satellite switching is completed (timer times out), small uplink data can be transmitted in time through the random access process, thereby improving the overall performance of satellite communications.

[0028] In some embodiments, the first message is a random access request including a preamble, and the second message is a random access response.

[0029] After it is determined that the satellite serving the first cell needs to be switched from the source satellite to the target satellite, and before the first information is sent to the target satellite, in some embodiments, a satellite data synchronization request is sent to the target satellite, the satellite data synchronization request is used to indicate that the source satellite is about to send data; and satellite data synchronization confirmation information sent by the target satellite in response to the satellite data synchronization request is received, the satellite data synchronization confirmation information is used to indicate that the target satellite confirms receipt of the data to be sent by the source satellite.

[0030] In some embodiments, after sending the first information to the target satellite, the method further includes: sending satellite data synchronization completion information to the target satellite.

[0031] In the above step of determining that the satellite serving the first cell needs to be switched from the source satellite to the target satellite, in some embodiments, it is determined that the satellite serving the first cell needs to be switched from the source satellite to the target satellite based on ephemeris information.

[0032] In some embodiments, multiple LEO satellites cover cells in a manner similar to that of earth staring cells.

[0033] In a third aspect, a method for switching a satellite base station is provided, which is applied to a terminal device in an inactive state of radio resource control (RRC), wherein the terminal device is used to communicate with a satellite in a satellite system, wherein the satellite system includes multiple LEO satellites, wherein the multiple LEO satellites include a source satellite and a target satellite, wherein the source satellite is a satellite currently serving a first cell, and the target satellite is a satellite to which the source satellite is switched to serve the first cell, wherein the terminal device is located in the first cell, and wherein the method includes: sending a first message (i.e., message 1) of an nth random access process, wherein n is an integer greater than or equal to 1; receiving a second message (i.e., message 2) sent by the source satellite in response to the first message of the nth random access process, wherein the second message of the nth random access process does not include scheduling information of uplink resources for indicating a third message (i.e., message 3); starting a timer after receiving the second message of the nth random access process; after the timer times out, sending the first message of the n+1th random access process; and receiving a second message sent by the target satellite in response to the first message of the n+1th random access process.

[0034] In the method for satellite base station switching provided by an embodiment of the present application, a timer is configured in the terminal device, and the duration of the timer is determined based on the duration of the satellite switching process. In the satellite switching process for a cell (such as the first cell), if a terminal device in an RRC inactive state in the cell has a need to send small uplink data, the terminal device sends a message 1 of a random access process to initiate a random access, and the source satellite sends a message 2 to the terminal device that does not include (or does not carry) scheduling information for uplink resources indicating message 3. After the terminal device receives the message 2 that does not include (or does not carry) scheduling information, the timer is started, and the terminal device no longer continues to perform the random access process to transmit small uplink data within the duration of the timer. It can be understood that the source satellite sends a message 2 that does not include (or does not carry) scheduling information to the terminal device, which means that the source satellite and the target satellite are likely to be in the satellite switching process. The source satellite does not want the terminal device to interact with itself during the satellite switching process to affect the transmission of data. Therefore, after the terminal device receives the message 2 that does not include (or does not carry) scheduling information, it starts the timer and no longer performs the random access process to transmit uplink small data within the timer duration. In this way, not only can the signaling overhead be reduced, but also the power consumption of the terminal device can be further saved. After the timer times out, the terminal device attempts to perform the random access process again to send uplink small data. Therefore, in the above embodiment, in the satellite switching process, by not including (or not carrying) scheduling information message 2 and the setting of the timer, not only can the signaling overhead be reduced, but also the power consumption of the terminal device can be further saved, and, after the satellite switching is completed (timer times out), the random access process is tried again to transmit uplink small data, which improves the performance of satellite communication as a whole.

[0035] In some embodiments, the second message (i.e., message 2) of the n+1th random access process includes scheduling information for indicating uplink resources of the third message (i.e., message 3); and the method also includes: sending the third message (i.e., message 3) of the n+1th random access process according to the uplink resources indicated by the scheduling information in the second message (i.e., message 2) of the n+1th random access process, and the third message of the n+1th random access process includes uplink small data.

[0036] The method for satellite base station switching provided in the embodiment of the present application is that after the timer expires, if there are no special circumstances, the satellite switching has been completed. At this time, the terminal device in the RRC inactive state can communicate with the target satellite. Therefore, after the terminal device attempts to execute the random access process to send message 1 again, the target satellite feeds back a normal message 2, that is, message 2 including the scheduling information of message 3. In this way, the terminal device can carry small uplink data in message 3 to realize the transmission of small data.

[0037] In some embodiments, the method also includes: receiving a fourth message (i.e., message 4) sent by the target satellite in response to the third message (i.e., message 3) of the n+1th random access process, the fourth message including RRC release information carrying a suspension indication, and the suspension indication is used to indicate that the terminal device is in an RRC inactive state.

[0038] In some embodiments, the first message is a random access request including a preamble, and the second message is a random access response.

[0039] In a fourth aspect, the method is applied to a terminal device in an inactive state of a radio resource control (RRC), the terminal device being used to communicate with a satellite in a satellite system, the satellite system comprising a plurality of LEO satellites, the plurality of LEO satellites comprising a source satellite and a target satellite, the source satellite being a satellite currently serving a first cell, the target satellite being a satellite to which the source satellite is switched to serve the first cell, the terminal device being located in the first cell, and the method comprising: sending a first message (i.e., message 1) of an nth random access process; after sending the first message of the nth random access process, starting a timer; if a second message (i.e., message 2) sent by the source satellite in response to the first message of the nth random access process is not received within the duration of the timer, after the timer times out, sending the first message of the n+1th random access process; after sending the first message of the n+1th random access process, starting the timer again; receiving a second message sent by the target satellite in response to the first message of the n+1th random access process within the duration of the timer that is started again, the second message of the n+1th random access process comprising scheduling information for uplink resources indicating a third message (i.e., message 3).

[0040] In the method for switching a satellite base station provided in an embodiment of the present application, a timer is configured in the terminal device, and the duration of the timer is determined based on the duration of the satellite switching process. In the satellite switching process for a cell (such as a first cell), if a terminal device in an RRC inactive state in the cell has a need to send small uplink data, the terminal device sends message 1 of the random access process to initiate the random access process, and the terminal device starts the timer after sending message 1 of the random access process. If message 2 is not received within the duration of the timer, the terminal device no longer continues to perform the random access process to transmit small uplink data within the duration of the timer, and when the timer times out, the terminal device attempts to perform the random access process again to send small uplink data. It can be understood that the source satellite did not send message 2 to the terminal device within the duration of the timer, which means that the source satellite and the target satellite are most likely in the process of satellite switching. The source satellite does not want the terminal device to interact with itself during the satellite switching process to affect the transmission of data. Therefore, if the terminal device does not receive message 2 within the duration of the timer, it will no longer perform a random access process to transmit small uplink data within the duration of the timer. In this way, not only can the signaling overhead be reduced, but also the power consumption of the terminal device can be further saved. After the timer times out, the terminal device tries to perform a random access process again to send small uplink data, which improves the performance of satellite communication as a whole.

[0041] In addition, since the terminal device starts the timer after sending message 1, it does not need to monitor and receive message 2, thus further saving the power consumption of the terminal device and reducing the signaling overhead.

[0042] In some embodiments, the method also includes: sending a third message (i.e., message 3) of the n+1th random access process according to the uplink resources indicated by the scheduling information in the second message (i.e., message 2) of the n+1th random access process, and the third message of the n+1th random access process includes uplink small data.

[0043] The method for satellite base station switching provided in the embodiment of the present application is that after the timer expires, if there are no special circumstances, the satellite switching has been completed. At this time, the terminal device in the RRC inactive state can communicate with the target satellite. Therefore, the terminal device tries to execute the random access process again to send message 1 and then starts the timer again. During the duration of the timer that is started again, the message 2 sent by the target satellite will be received. In this way, the terminal device can carry small uplink data in message 3 to realize the transmission of small data.

[0044] In some embodiments, the method further includes: receiving a fourth message sent by the target satellite in response to a third message of the n+1th random access process, the fourth message including RRC release information carrying a suspension indication, and the suspension indication is used to indicate that the terminal device is in an RRC inactive state.

[0045] In some embodiments, the first message is a random access request including a preamble, and the second message is a random access response.

[0046] In a fifth aspect, a method for switching a satellite base station is provided, which is applied to a communication system including a terminal device and a satellite system in a radio resource control (RRC) inactive state, wherein the satellite system includes multiple low earth orbit (LEO) satellites, and the multiple LEO satellites include a source satellite and a target satellite, wherein the source satellite is a satellite currently serving a first cell, and the target satellite is a satellite that is switched from the source satellite to serve the first cell, and the terminal device in the RRC inactive state is located in the first cell, and the method includes: the source satellite determines that the satellite serving the first cell needs to be switched from the source satellite to the target satellite; the source satellite sends first information to the target satellite, the first information includes security information, context information and cell configuration information of the first cell, and the context information includes context information of the terminal device in the RRC inactive state in the first cell; the target satellite is configured on the target satellite according to the first information; and during the process of the target satellite serving the first cell, the target satellite receives small uplink data sent by the terminal device in the RRC inactive state.

[0047] In some embodiments, in the process of the above-mentioned target satellite serving the first cell, in the step of the target satellite receiving small uplink data sent by a terminal device in an RRC inactive state, in the process of the target satellite serving the first cell, the target satellite receives a third message of the random access process sent by a terminal device in an RRC inactive state, and the third message includes small uplink data.

[0048] In some embodiments, before the source satellite stops serving the first cell, the method further includes: a terminal device in an RRC inactive state sends a first message of the nth random access process, where n is an integer greater than or equal to 1; in response to the first message of the nth random access process, the source satellite sends a second message of the nth random access process to the terminal device, and the second message of the nth random access process does not include scheduling information for uplink resources indicating a third message; after receiving the second message of the nth random access process, the terminal device starts a timer; after the timer expires, the terminal device sends the first message of the n+1th random access process; in the process of the target satellite serving the first cell, in response to the n+1th random access process The target satellite sends a first message of the n+1th random access process to the terminal device, the second message of the n+1th random access process includes scheduling information for uplink resources indicating a third message; the terminal device sends a third message of the n+1th random access process according to the uplink resources indicated by the scheduling information of the n+1th random access process, the third message of the n+1th random access process includes uplink small data; and, in the process of the target satellite serving the first cell, the target satellite receives the third message sent by the terminal device in the RRC inactive state, including: in the process of the target satellite serving the first cell, the target satellite receives the third message of the n+1th random access process sent by the terminal device.

[0049] In some embodiments, before the above-mentioned source satellite stops serving the first cell, the method also includes: a terminal device in an RRC inactive state sends a first message of the nth random access process, where n is an integer greater than or equal to 1; after sending the first message of the nth random access process, the terminal device starts a timer; if the second message sent by the source satellite in response to the first message of the nth random access process is not received within the duration of the timer, after the timer expires, the terminal device sends the first message of the n+1th random access process; after sending the first message of the n+1th random access process, the terminal device starts the timer again; in the process of the target satellite serving the first cell, in response to the first message of the n+1th random access process, the target satellite sends the n+1th random access process to the terminal device. The second message of the access process, the second message of the n+1th random access process includes scheduling information for indicating uplink resources of the third message; when the second message of the n+1th random access process sent by the target satellite is received within the duration of the timer that is restarted, the terminal device sends the third message of the n+1th random access process according to the uplink resources indicated by the scheduling information in the second message of the n+1th random access process, and the third message of the n+1th random access process includes uplink small data; and, in the process of the target satellite serving the first cell, the target satellite receives the third message sent by the terminal device in the RRC inactive state, including: in the process of the target satellite serving the first cell, the target satellite receives the third message of the n+1th random access process sent by the terminal device.

[0050] In a sixth aspect, a device for switching a satellite base station is provided, the device being used to execute the method provided in any one of the first to fourth aspects. Specifically, the device may include a module for executing any possible implementation of any one of the first to fourth aspects.

[0051] In a seventh aspect, a device for switching a satellite base station is provided, comprising a processor. The processor is coupled to a memory and can be used to execute instructions in the memory to implement the method in any possible implementation of any one of the first to fourth aspects. Optionally, the device further comprises a memory. Optionally, the device further comprises a communication interface, and the processor is coupled to the communication interface.

[0052] In an eighth aspect, a communication system is provided for executing the method performed by the source satellite, the target satellite and the terminal device in the fifth aspect.

[0053] In a ninth aspect, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a device, the device implements the method in any possible implementation manner of any aspect from the first to the fourth aspects above.

[0054] In a tenth aspect, a computer program product comprising instructions is provided, wherein when the instructions are executed by a computer, the device implements a method in any possible implementation of any one of the first to fourth aspects above.

[0055] In the eleventh aspect, a chip is provided, comprising: an input interface, an output interface, a processor and a memory, wherein the input interface, the output interface, the processor and the memory are connected via an internal connection path, and the processor is used to execute the code in the memory. When the code is executed, the processor is used to execute the method in any possible implementation of any one of the first to fourth aspects above. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 It is a schematic structural diagram of a communication system of a ground network provided in an embodiment of the present application.

[0057] Figure 2 It is a schematic flowchart of the process of SDT based on 4-step RA provided in an embodiment of the present application.

[0058] Figure 3 It is a schematic flowchart of the process of UE context relocation small data transmission provided in an embodiment of the present application.

[0059] Figure 4 Schematic diagram of a satellite system provided in an embodiment of the present application.

[0060] Figure 5 It is a schematic diagram of covering a cell using an earth gazing cell coverage method provided in an embodiment of the present application.

[0061] Figure 6 It is a schematic flowchart of a method 600 for switching a satellite base station provided in an embodiment of the present application.

[0062] Figure 7 It is a schematic flowchart of a satellite base station switching method 700 provided in an embodiment of the present application.

[0063] Figure 8 It is a schematic flowchart of a method 800 for switching a satellite base station provided in an embodiment of the present application.

[0064] Fig. 9 It is a schematic flowchart of a method 900 for switching a satellite base station provided in an embodiment of the present application.

[0065] Fig.10 It is a schematic block diagram of a satellite base station switching device 1000 provided in an embodiment of the present application.

[0066] Fig.11It is a schematic structural diagram of a satellite base station switching device 1100 provided in an embodiment of the present application. DETAILED DESCRIPTION

[0067] The technical solution in this application will be described below in conjunction with the accompanying drawings.

[0068] Figure 1 It is a schematic structural diagram of a communication system of a ground network provided in an embodiment of the present application.

[0069] The ground network, i.e., TN, can be an existing or future mobile communication network. For example, TN can be a long term evolution (LTE) network, an advanced long term evolution (LTE-A) network, a new radio (NR) network or other fifth generation communication (5th-generation, 5G) network, an evolution network of NR / 5G, a hybrid network of LTE and 5G, a next generation mobile communication network (for example, a sixth generation (6th-generation, 6G) mobile communication network), etc. The TN in the embodiment of the present application can support uplink communication and downlink communication, and can also support device to device (D2D) communication, machine to machine (M2M) communication, machine type communication (MTC), vehicle to vehicle (V2V) communication, and vehicle to everything (V2X) communication, etc.

[0070] refer to Figure 1 The communication system of the ground network includes a network device 110, at least one terminal device (such as Figure 1 The terminal devices 121 and 122 shown in the figure and the core network 130, wherein the terminal devices can be mobile or fixed. The terminal devices can be connected to the network device 110 wirelessly. The network device 110 is connected to the core network 130 wirelessly or by wire. The core network device and the network device 110 in the core network 130 can be independent and different physical devices, or they can be the same physical device that integrates the logical functions of the core network device and the logical functions of the network device. Each network device can provide communication coverage for a specific geographical area, and can communicate with terminal devices located in the coverage area (cell).

[0071] It should be understood that Figure 1The communication system of the ground network is shown exemplarily, but this should not constitute any limitation to the present application. Exemplarily, the communication system may include a larger number of network devices or terminal devices, and each network device may include other number of terminal devices within its coverage area, which is not limited in the present application embodiment.

[0072] The terminal device of the embodiment of the present application is a device with wireless transceiver function, which can be deployed on land, including indoors or outdoors, handheld, wearable or vehicle-mounted; it can also be deployed on the water surface (such as ships, etc.); it can also be deployed in the air (such as airplanes, balloons and satellites, etc.). The terminal device can be a mobile phone, a tablet computer (Pad), a computer with wireless transceiver function, a virtual reality (VR) terminal device, an augmented reality (AR) terminal device, a wireless terminal in industrial control, a vehicle-mounted terminal device, a wireless terminal in self-driving, a wireless terminal in remote medical, 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 wearable terminal device, etc. The embodiment of the present application does not limit the application scenario. A terminal may also sometimes be referred to as a terminal device, user equipment (UE), access terminal equipment, vehicle-mounted terminal, industrial control terminal, UE unit, UE station, mobile station, mobile station, remote station, remote terminal equipment, mobile device, UE terminal equipment, terminal equipment, wireless communication equipment, UE agent or UE device, etc. The terminal device may also be fixed or mobile.

[0073] The network device in the embodiment of the present application can be a device for communicating with a terminal device, and is any device with a wireless transceiver function. The network device includes, but is not limited to: an evolved base station (NodeB or eNB or e-NodeB, evolved Node B) in long term evolution (LTE), a base station (gNodeB or gNB) or a transceiver point (transmission receiving point / transmission reception point, TRP) in the fifth generation (5G), new radio (NR) or the future sixth generation (6G), an access node in a WiFi system, a wireless relay node, a wireless backhaul node, etc. The base station can be: a macro base station, a micro base station, a micro-micro base station, a small station, a relay station, or a balloon station, etc. The network device can also be a wireless controller, a CU, and / or a DU in a cloud radio access network (CRAN) scenario. The network device can also be a server, a wearable device, or a vehicle-mounted device, etc. In an embodiment where the network device is a base station, the multiple network devices may be base stations of the same type or of different types; the base station may communicate with the terminal device or through a relay station; the terminal device may communicate with multiple base stations of different technologies, for example, the terminal device may communicate with a base station that supports an LTE network or a base station that supports a 5G network, and may also support dual connections with base stations of an LTE network and base stations of a 5G network.

[0074] Currently, the protocol defines three RRC states of terminal devices: RRC connected (RRC_CONNECTED) state, RRC idle (RRC-IDLE) state and RRC inactive (RRC-INACTIVE) state.

[0075] The RRC idle state refers to the state of the terminal device when the terminal device resides in the cell but does not perform random access. The terminal device usually enters the RRC idle state after being powered on or after RRC is released. In the RRC idle state, there is no RRC connection between the terminal device and the network device (such as the resident network device), the network device does not store the context of the terminal device, and no connection is established between the network device and the core network for the terminal device. If the terminal device needs to enter the RRC connected state from the RRC idle state, it is necessary to initiate the RRC connection establishment process.

[0076] The RRC connection state may refer to the state in which the terminal device is in after completing the random access process but before performing RRC release. An RRC connection exists between the terminal device and a network device (e.g., an access network device). In the RRC connection state, the terminal device may transmit data with the network device, such as downlink data transmission and / or uplink data transmission. Alternatively, the terminal device may also transmit terminal device-specific data channels and / or control channels with the network device to transmit specific information or unicast information of the terminal device. In the RRC connection state, both the network device and the core network will save the context information of the terminal device. It should be understood that the context information of terminal devices stored in network equipment and core network is different. The context information of terminal devices stored in network equipment is related to the access stratum (AS). The AS layer mainly includes RRC (Radio Resource Control) and radio access network application part (RAN AP) layer and the protocol layers below it; the context information of terminal devices stored in the core network is related to the nonaccess stratum (NAS). The NAS layer is deployed above the AS layer and is mainly responsible for core network-level functions such as mobility management, session management, and security control.

[0077] The RRC inactive state is a newly defined state in 5G or NR, which is a state between the connected state and the idle state. By introducing the RRC inactive state, it is possible to reduce air interface signaling, quickly restore wireless connections, and quickly transmit data. The terminal device has previously entered the RRC connected state, and then released the RRC connection with the network device. In addition, the connection established between the network device and the core network for the terminal device has not been released, that is, in the RRC inactive state, the terminal device disconnects from the network device and retains the connection with the core network. In the RRC inactive state, although the terminal device disconnects from the network device, the network device saves the context information of the terminal device to reduce air interface signaling, quickly restore wireless connections, and quickly transmit data. The core network continues to save the context information of the terminal device.

[0078] In the communication of the ground network, the terminal device supports SDT in the RRC-INACTIVE state, that is, the terminal device can send small data to the network equipment (such as gNB) of the ground network without entering the RRC connected state in the RRC-INACTIVE state, thereby improving the transmission efficiency of small data and effectively reducing the power consumption of the terminal device.

[0079] The 3rd generation partnership project (3GPP) defined two methods for SDT in R15, R16 and R17, namely SDT based on random access (RA) process (abbreviated as RA-SDT) and SDT based on pre-configured wireless resources.

[0080] In SDT based on preconfigured wireless resources, wireless resources are allocated periodically based on an estimate of the traffic demand of the terminal device. This uplink scheduling method is called a configured grant (CG). Therefore, SDT based on preconfigured wireless resources can also be referred to as CG-SDT. Using CG-SDT will not cause message conflicts with other terminal devices because wireless resources are dedicated to each terminal device. When the terminal device leaves the connected state, the network device sends a resource allocation signal to the terminal device.

[0081] RA SDT includes SDT based on two-step random access (2-step RA) and SDT based on four-step random access (4-step RA). It should be noted that the standard RA process itself does not transmit small data. Adjusting or optimizing the standard RA process to meet the needs of small data transmission is called RA SDT. The following introduces the processes of SDT based on 4-step RA and SDT based on 2-step RA respectively.

[0082] Figure 2 It is a schematic flowchart of the process of SDT based on 4-step RA provided in an embodiment of the present application.

[0083] The terminal device is in an RRC inactive state and there is small uplink data to be sent, so the terminal device initiates random access to the network device.

[0084] In step S210, the terminal device sends a message 1 (message 1, Msg1) in the random access process to the network device to start the random access process. Msg 1 includes a preamble.

[0085] Message 1 may also be referred to as a random access request, and includes a preamble, which may also be referred to as a random access preamble. In a non-contention-based random access process, the preamble is configured by the network device. In a contention-based random access process, the preamble is selected by the terminal device from a preamble pool broadcast by the network device through a system information block (SIB).

[0086] In implementation, the terminal device may send a preamble on a random access channel (RACH) resource.

[0087] In step S220, in response to Msg2, the network device sends message 2 (message 2, Msg2) to the terminal device. Msg2 can be carried in a physical downlink control channel (physical downlink control channel, PDCCH).

[0088] Msg2 can also be called a random access response (RAR), which includes scheduling information for uplink resources indicating message 3 (Msg3) and timing advance (TA) instructions required for uplink synchronization. As an example and not a limitation, RAR can also include more information. For example, RAR can also include a backoff indicator (BI), which can be used to indicate the backoff time for retransmitting Msg1. For another example, RAR can also include a random access preamble identifier (RAPID) to indicate the network device's response to the received preamble index. For another example, RAR can also include a temporary cell-radio network temporary identifier (C-RNTI). For a terminal device that initially accesses, the terminal device can use the temporary C-RNTI to decode the PDCCH of Msg4.

[0089] In step S230, in response to Msg2, the terminal device sends Msg 3 to the network device. Msg 3 includes an RRC resume request (RRC resume request) and small uplink data.

[0090] The terminal device can send Msg 3 on the uplink resource indicated by the scheduling information of Msg 2 in the network device. The network device receives Msg 3 and also receives the uplink small data.

[0091] In step S240, the network device sends Msg4 to the terminal device, where Msg 4 includes RRC release information, and the RRC release information carries a suspend indication, i.e., Msg 4 includes RRC release with suspend indication information. The RRC release information is used to indicate the release of the connection between the terminal device and the network device. The suspend indication is used to indicate that the terminal device should not completely enter the RRC idle state after releasing the RRC connection, but should enter the RRC inactive state.

[0092] It should be understood that after the network device receives Msg3, although the RRC recovery request in Msg3 is used to request the restoration of the connection, after the network device receives the uplink small data, in the absence of other special instructions or special circumstances, the network device can believe that the purpose of Msg3 is actually for the transmission of small data, and there is no need to restore the terminal device to the connection state. Therefore, the network device sends the RRC release information carrying the suspension indication to the terminal device through Msg4. In this way, after receiving Msg4, the terminal device still remains in the RRC inactive state.

[0093] It should also be understood that in the RA process without SDT, the Msg 3 sent by the terminal device includes an RRC resume request (RRC resume request) but does not include uplink small data. After the network device processes based on the RRC recovery request, the Msg 4 sent to the terminal device includes RRC recovery information. The RRC recovery information includes configuration information for restoring the connection. The terminal device restores the RRC connection with the network device based on the configuration information for data transmission.

[0094] In the process of SDT based on 2-step RA, the terminal device sends message A (Msg A) to the network device, and Msg A includes the above-mentioned Msg 1 and Msg 3 as well as small uplink data, so that small data can be transmitted quickly. In response to Msg A, the network device sends message B (Msg B) to the terminal device, and message B includes the above-mentioned Msg 4 and the information in Msg 2 except the scheduling information of Msg 3.

[0095] In the terrestrial network, when the terminal device is in the RRC inactive state, the network device will save the context of the terminal device to quickly restore the connection or quickly transmit data. In order to quickly initiate random access to transmit small data, it is necessary to try to ensure that the network device that the terminal device currently initiates random access is the last network device that serves the terminal device, where the last network device that serves the terminal device means the last network device that communicated with the terminal device when the terminal device was in the RRC connected state. Figure 2 As shown, the last network device serving the terminal device is the same as the network device from which the terminal device initiates random access. In this way, random access can be quickly initiated to transmit small uplink data.

[0096] However, if the network device (referred to as the current network device) to which the terminal device initiates random access is not the last network device serving the terminal device, then the current network device to which the terminal device initiates random access needs to request the context information of the terminal device from the last network device. This process can be referred to as UE context relocation, and the SDT performed based on this process can be referred to as UE context relocation small data transmission (SDT with UE context relocation).

[0097] The following takes the SDT based on 4-step RA as an example to introduce the process of transmitting the above UE context relocation small data.

[0098] Figure 3 It is a schematic flowchart of the process of UE context relocation small data transmission provided in an embodiment of the present application.

[0099] The terminal device is in an RRC inactive state and has small uplink data to be sent, so the terminal device initiates random access to the current network device. In the following, the current network device is the network device to which the terminal device initiates random access, the last network device is the last network device that serves the terminal device, and the access and mobility management function (AMF) network element and the user plane function (UPF) network element are network elements of the core network.

[0100] In step S301, the terminal device sends Msg1 in the random access process to the current network device to start the random access process, wherein Msg 1 includes a preamble.

[0101] In step S302, in response to Msg1, the current network device sends Msg2 to the terminal device.

[0102] In step S310, in response to Msg2, the terminal device sends Msg3 to the current network device, where Msg 3 includes an RRC recovery request and small uplink data.

[0103] In step S320, the current network device sends a RETRIEVE UE CONTEXT REQUEST to the last network device to request context information of the terminal device.

[0104] The current network device uses an inactive network temporary identifier (I-RNTI) to identify the last network device serving the terminal device, and sends a request to obtain a UE context to the last network device through the Xn-AP, and the last network device retrieves the UE context according to the request to obtain a UE context. The request to obtain a UE context is for SDT and can also provide SDT auxiliary information (such as a single data packet, multiple data packets).

[0105] In step S330, the last network device sends a UE context acquisition request response to the current network device. The UE context acquisition request response includes the context information of the terminal device.

[0106] In step S340, the current network device determines to continue SDT in the RRC inactive state.

[0107] In step S351, the current network device sends the uplink small data received from the terminal device to the UPF network element of the core network.

[0108] Optionally, in step S352, in order to prevent the downlink user data buffered in the last network device from being lost, the current network device sends an Xn-U address indication (ADDRESS INDICATION) message to the last network device to provide a forwarding address.

[0109] In step S361, the current network device sends a path switching request to the last network device.

[0110] In step S362, the last network device sends a path switching request confirmation message to the current network device.

[0111] In this way, through steps S361 and S362, the new generation access protocol (NG-AP) path switching process is completed to establish a connection for NG UE signaling related to AMF.

[0112] Optionally, in step S354, after the path switching, if the current network device has an uplink (UL) non-access stratum (NAS) protocol data unit (PDU), the current network device sends the UL NAS PDU to the AMF.

[0113] Then, subsequent small data (uplink small data and / or downlink small data) is transmitted between the terminal device and the core network through the current network device.

[0114] In step S370, the current network device determines to stop performing SDT in the RRC inactive state.

[0115] In step S380, the current network device sends Msg4 to the terminal device. Msg 4 includes RRC release information. The RRC release information carries a suspension indication, which is used to instruct the terminal device not to completely enter the RRC idle state after releasing the RRC connection, but to enter the RRC inactive state.

[0116] In step S390, the current network device sends a UE CONTEXT RELEASE message to the last network device to instruct the last network device to remove the context of the terminal device.

[0117] The process of SDT based on 2-step RA is similar to the process of SDT based on 4-step RA. The terminal device sends message A, which includes the above-mentioned Msg1, Msg3 and uplink small data. After receiving message A, the current network device executes step S320 and subsequent steps. Finally, the current network device sends message B to the terminal device. Message B includes the information in the above-mentioned Msg 2 except the scheduling information and Msg 4.

[0118] It can be seen from the UE context relocation process described above that if the current network device that the terminal device initiates random access is not the last network device serving the terminal device, the UE context relocation process performed by the current network device will not only generate a large amount of signaling interaction overhead, but more importantly, the increased processing time causes the terminal device to wait for a longer time and increases the power consumption of the terminal device.

[0119] With the development of technology, non-terrestrial networks, namely NTNs, have been introduced. NTNs may include satellite communication networks, high-altitude platform systems or unmanned aircraft systems (UAS), etc., and have the characteristics of long distance, fast movement, wide coverage, and high reliability. However, the transmission distance of NTN communications, such as satellite communications, is relatively long, which will lead to large power consumption of terminal devices. Therefore, the power consumption of terminal devices is an important indicator of NTN communications. Based on this, the relevant technology proposes to support SDT of terminal devices in the RRC non-activated state in NTN communications to effectively reduce the power consumption of terminal devices. However, if the SDT of terminal devices in the RRC non-activated state is applied to NTN communications, there will be some problems.

[0120] For NTN communication, the network equipment in NTN communication (such as satellite base stations in satellite communication) moves very fast, resulting in frequent changes in the network equipment serving the terminal equipment, or in other words, frequent changes in the service cell of the terminal equipment. Therefore, frequent changes in the service cell of the terminal equipment (or the network equipment serving the terminal equipment) will be the mainstream scenario of NTN communication, which is particularly obvious in the low earth orbit (LEO) satellite of satellite communication. In this way, in most cases, when the terminal equipment in the RRC inactive state initiates random access, the network equipment serving the terminal equipment has a high probability of having changed, and the process of UE context relocation needs to be triggered. This process not only affects the efficiency of data transmission, but also increases the power consumption of the terminal equipment. In this way, it is contrary to the original intention of the terminal equipment to perform SDT in the RRC inactive state (improving the transmission efficiency of small data and effectively reducing the power consumption of the terminal equipment). Not only can the data transmission efficiency and power consumption not be improved, but the data transmission efficiency and power consumption will be reduced, and the advantages of SDT of the terminal equipment in the RRC inactive state cannot be reflected.

[0121] It should be noted that the above-mentioned service cells are logical cells, which are formed by the area covered by the network equipment. For areas at the same physical location, different network equipment provides different service cells.

[0122] Based on this, an embodiment of the present application provides a method for switching a satellite base station, which is applied to a satellite system including multiple LEO satellites. When the source satellite currently serving the first cell needs to be switched to the target satellite, the source satellite sends the first information related to the first cell to the target satellite, the first information includes security information, context information, and cell configuration information of the first cell, and the context information includes the context information of the terminal device in the RRC inactive state in the first cell; after the target satellite receives the first information, it performs relevant configuration on the target satellite according to the first information. In this way, the first information related to the first cell is saved and configured in the target satellite serving the first cell. When the terminal device in the RRC inactive state sends small uplink data during the process of the target satellite serving the first cell, since the context information of the terminal device in the RRC inactive state has been saved and configured in the target satellite, the target satellite does not need to request context information from the source satellite at this time, and the target satellite can directly successfully receive the small uplink data based on the saved and configured context information, thereby avoiding the problem of increased power consumption of the terminal device, decreased transmission efficiency, and large signaling overhead caused by the process of the target satellite requesting context information from the source satellite as much as possible. In other words, the above technical solution effectively improves the efficiency of data transmission and reduces the power consumption of terminal devices, and gives full play to the advantages of low power consumption and good transmission efficiency of SDT of terminal devices in the RRC inactive state, so that NTN communications such as satellite communications can well support SDT of terminal devices in the RRC inactive state.

[0123] In addition, the source satellite sends security information to the target satellite, so that the target satellite and the terminal equipment in the first cell have a consistent understanding of the encryption and decryption of data and signaling, and can encrypt and decrypt data and signaling through security information, thereby ensuring the security of the data and signaling transmission process and the correct decryption of data and signaling as much as possible, and avoiding the problem of high signaling overhead caused by the need for the target satellite to re-negotiate security information with the terminal equipment in the first cell, which can further reduce signaling interaction.

[0124] It should be noted that the satellite described in the embodiment of the present application integrates at least part of the functions of network equipment such as base stations in TN communications (such as control plane functions and user plane functions). Therefore, the satellite in the embodiment of the present application can also be called a satellite base station, and the two descriptions are interchangeable.

[0125] It should be understood that the NTN in the embodiments of the present application may be a 4G-based NTN, a NR-based NTN, an Internet of Things (IoT)-based NTN, a narrowband Internet of Things (NB-IoT)-based NTN, or an NTN based on other current technologies or other technologies that may appear in the future.

[0126] Figure 4 Schematic diagram of a satellite system provided by an embodiment of the present application. Figure 4 , the satellite system includes multiple satellites, and the multiple satellites are LEO satellites. As an example, four satellites are illustrated in the figure, namely, satellite 410a, satellite 410b, satellite 410c and satellite 410d. Each satellite covers a physical cell, and the cells covered by each satellite may overlap (not shown in the figure) or not overlap. In the process of satellite covering the cell, the satellite serves each terminal device in the cell, and the terminal device in the cell covered by each satellite can communicate with the satellite. For example, satellite 410a can communicate with terminal device 420a in the cell it serves, satellite 410b can communicate with terminal device 420b in the cell it serves, satellite 410c can communicate with terminal device 420c in the cell it serves, and satellite 410d can communicate with terminal device 420d in the cell it serves.

[0127] LEO satellites are 500-2000 km from the ground, with relatively low transmission delay and power consumption. Due to the low satellite orbit, LEO satellites have short signal propagation delay and low link loss, which can reduce the requirements for satellites and user terminals. At the same time, due to the fast movement speed of LEO satellites, for a single user, the time from the satellite rising from the horizon to falling below the horizon again is relatively short, so switching between satellites is frequent.

[0128] In some embodiments, the embodiments of the present application can be applied to a satellite system that covers cells based on the coverage method of earth gazing cells (earth fixed cells), that is, the satellites (LEO satellites) in the satellite system all cover cells in the coverage method of earth gazing cells. In this coverage method, there are multiple cells at fixed positions, and the coverage range of the cells does not move with the movement of the satellites. A satellite covers a cell in a fixed period of time (generally a few minutes). After the service time of the currently served cell ends, the satellite will switch to the next fixed cell. In practical applications, in the coverage method of earth gazing cells, a satellite can cover tens of kilometers or hundreds of kilometers, and the coverage area is relatively large. For example, there can be tens of thousands of LEO satellites covering the earth.

[0129] Figure 5It is a schematic diagram of covering a cell using an earth gazing cell coverage method provided in an embodiment of the present application. Figure 5 Figure (a) shows the schematic diagram of the satellite starting to cover the cell and ending to cover the cell. Figure 5 Figures (b) and (c) in the figure are schematic diagrams showing that the same cell is covered by different satellites in different time periods.

[0130] refer to Figure 5 As shown in (a) of FIG. 1 , satellite 510a starts to cover cell 520 at a fixed position at time T0, and thus, satellite 510a starts to serve cell 520 at time T0. Satellite 510a can adjust the angle of the antenna during movement to continuously cover and serve cell 520 within a certain period of time. When satellite 510a moves to position 2 at time T1 along the direction of movement, satellite 510a stops providing service for cell 520, and satellite 510a will cover and serve the next fixed cell (not shown in the figure). Among them, time T0 is the start service time of satellite 510a serving cell 520, and time T1 is the end service time of satellite 510a serving cell 520.

[0131] refer to Figure 5 In (b) of FIG. 1 , satellite 510a starts to cover and serve the cell 520 at a fixed position at time T0, and satellite 520a serves other cells at fixed positions (not shown in the figure). Satellite 510a and satellite 510b move along the direction of movement, and adjust the angle of the antenna during the movement to continuously cover and serve the cells at fixed positions within a certain period of time. At time T1, satellite 510a stops providing services for cell 520, and satellite 510a will cover and serve the next cell at a fixed position (not shown in the figure). At this time, satellite 510b has not yet covered cell 520. Satellite 510a and satellite 510b continue to move along the direction of movement, and at time T2, satellite 510b starts to cover and serve cell 520. In this scenario, time T0 is the start service time of satellite 510a, time T1 is the end service time of satellite 510a, and time T2 is the start service time of satellite 510b. In this scenario, the coverage of the same cell between two adjacent satellites is discontinuous, and during the movement, area 520 cannot be covered and served in a short period between time T1 and time T2.

[0132] refer to Figure 5In (c) of FIG. 5 , satellite 510a starts to cover and serve a cell 520 at a fixed location at time T0, and satellite 520a serves other cells at fixed locations (not shown in the figure). At time T1, satellite 510a stops serving cell 520, and satellite 510b starts serving cell 520. In this scenario, time T0 is the start service time of satellite 510a, and time T1 is the end service time of satellite 510a, which is also the start service time of satellite 510b. In this scenario, the coverage of the same cell between two adjacent satellites is continuous.

[0133] In a satellite system, data and / or signaling may be transmitted between satellites (eg, between satellite 510a and satellite 510b) via an inter-satellite link (ISL).

[0134] Figure 6 It is a schematic flowchart of a method 600 for switching a satellite base station provided in an embodiment of the present application.

[0135] Method 600 is applied to a satellite system including multiple LEO satellites, where the multiple LEO satellites include a source satellite and a target satellite. The source satellite and the target satellite are adjacent, the source satellite is a satellite currently serving a cell (referred to as the first cell) at a fixed location, and the target satellite is a satellite that will serve the first cell next. Figure 5 , the source satellite may be satellite 510a, the target satellite may be satellite 510b, and the first cell may be cell 520.

[0136] The first cell includes at least one terminal device (one or more terminal devices) in an RRC inactive state. Each terminal device in the RRC inactive state has previously entered an RRC connected state, and then is in the RRC inactive state after releasing the RRC connection with the satellite.

[0137] For ease of description, a terminal device in an RRC inactive state in a first cell (referred to as a first terminal device) is taken as an example to describe method 600 from the perspective of interaction between the first terminal device, the source satellite, and the target satellite. It should be understood that the execution subject of the above method 600 may also be a processor or chip in the first terminal device, a processor or chip in the source satellite, or a processor or chip in the target satellite, and the embodiment of the present application does not make any limitation.

[0138] In step S610, the source satellite determines that the satellite serving the first cell needs to be switched from the source satellite to the target satellite.

[0139] In other words, the source satellite determines that the target satellite is to serve the first cell served by the source satellite.

[0140] The source satellite can not only determine that the satellite serving the first cell needs to be switched, but also determine that the switched satellite is the target satellite. In other words, the source satellite can not only determine that it will stop serving the first cell, but also determine that the next satellite that will serve the first cell is the target satellite.

[0141] It should be understood that when the source satellite determines that the satellite serving the first cell needs to be switched from the source satellite to the target satellite, the source satellite is still in the state of serving the first cell, but the source satellite may have moved to the edge area of ​​the first cell and will stop serving the first cell.

[0142] In some embodiments, the source satellite may determine, based on the ephemeris information, that the satellite serving the first cell needs to be switched from the source satellite to the target satellite.

[0143] The ephemeris information provides accurate information about the position and speed of each satellite in the mobile orbit, which is a function of time and can calculate the position and speed of each satellite in the orbit at a specific time point. Therefore, the source satellite can determine that the satellite serving the first cell needs to be switched based on the ephemeris information, and can determine that the switched satellite is the target satellite.

[0144] In one example, the source satellite can determine the end service time of the source satellite serving the first cell and the position of the source satellite on the mobile orbit at the end service time based on the ephemeris information. It can be understood that the position is the position where the source satellite stops serving the first cell. Therefore, the source satellite can determine that the satellite serving the first cell needs to be switched based on the end service time and / or the position.

[0145] In one example, the source satellite may determine that the next satellite serving the first cell is the target satellite based on the ephemeris information. In other examples, the source satellite may also determine that the next satellite serving the first cell is the target satellite based on the ephemeris information and other information, for example, the other information may be ISL measurement information between satellites.

[0146] In step S620, the source satellite sends first information to the target satellite, where the first information includes security information, context information, and cell configuration information of the first cell. Correspondingly, the target satellite receives the first information.

[0147] In this step, the source satellite transmits first information via an ISL between the source satellite and the target satellite.

[0148] It should be understood that the first information is information related to the first cell and is used for communication between the target satellite and the terminal device in the first cell.

[0149] In some embodiments, the security information includes a security key of a control plane (CP) and a security key of a user plane (UP), wherein the security key of the control plane is used to encrypt and decrypt high-layer signaling (such as RRC signaling), and the security key of the user plane is used to encrypt and decrypt user data.

[0150] The security keys of the control plane include the encryption key of the control plane and the integrity protection key of the control plane. The encryption key of the control plane is used to protect the security of the signaling and prevent unauthorized personnel from accessing or stealing sensitive information. The signaling is encrypted by the encryption key of the control plane. Even if the signaling is intercepted during transmission or storage, a third party without the corresponding decryption key cannot read the content of the original signaling, thereby ensuring the confidentiality of the signaling. The integrity protection key of the control plane is a key used to protect the integrity of the signaling message. During the signaling transmission process, the signaling message may be subject to attacks such as tampering or forgery, resulting in the signaling being unable to be correctly parsed or executed at the receiving end. The integrity protection key of the control plane uses specific algorithms and mechanisms to perform integrity verification on the signaling message to ensure that the signaling has not been tampered with or forged during transmission, thereby protecting the legitimate rights and interests of both parties in communication.

[0151] Regarding the security key of the user plane, in one example (such as LTE), the security key of the user plane includes the encryption key of the user plane. In another example (such as NR), the security key of the user plane includes the encryption key of the user plane and the integrity protection key of the user plane. The encryption key of the user plane is used to protect the security of user data and prevent unauthorized personnel from accessing or stealing sensitive information. The integrity protection key of the user plane is a key used to protect the integrity of user data. For a specific description of the encryption key and integrity protection key of the user plane, please refer to the above description of the encryption key and integrity protection key of the control plane, which will not be repeated.

[0152] In other embodiments, the security information includes not only the security key of the control plane and the security key of the user plane, but also includes the selection of the encryption algorithm and integrity protection algorithm of the control plane and the user plane.

[0153] It should be understood that in order to ensure the security of transmission, the signaling and data transmitted in the air interface need to be encrypted, and the sender and the receiver need to have the same understanding of encryption and decryption in order to perform subsequent signaling and data interaction. Therefore, the source satellite sends security information to the target satellite, which can make the target satellite and the terminal equipment in the first cell have the same understanding of encryption and decryption of data and signaling, so as to correctly decrypt the data (such as uplink small data) and signaling sent by the terminal equipment in the first cell; and, the target satellite does not need to renegotiate the content of the security information (such as security keys) with the terminal equipment in the first cell, which can further reduce signaling interaction.

[0154] Since security information is related to security, it is also necessary to ensure the security of the content carried in the security information as much as possible.

[0155] Based on this, in some embodiments, the security information is information encrypted by the source satellite using a public key encryption algorithm, so that the source satellite sends the security information encrypted by the source satellite using the public key encryption algorithm to the target satellite. Correspondingly, after receiving the security information encrypted by the public key encryption algorithm, the target satellite can use a private key encryption algorithm matching the public key encryption algorithm to decrypt the encrypted security information.

[0156] Exemplarily, the public key encryption algorithm can be an asymmetric encryption algorithm, such as the RSA algorithm, the national secret SM2 algorithm, or any other asymmetric encryption algorithm. For the specific description of the non-asymmetric encryption algorithm, please refer to the description of the relevant technology, which will not be repeated here.

[0157] The context information includes context information of each terminal device (including the first terminal device) in the RRC inactive state in the first cell, and the context information of the terminal device in the RRC inactive state represents necessary information maintained between the network and the terminal device, so as to facilitate rapid recovery of the connection state or rapid data transmission. After the target satellite obtains the context information, the target satellite does not need to request the context information from the source satellite, so that it can quickly transmit data or restore the connection state with the terminal device in the RRC inactive state of the first cell.

[0158] It should be understood that the context information of the terminal device in the RRC inactive state in the context information stored in the source satellite mainly stores the relevant information of the terminal device in the RRC inactive state at the AS layer, and the relevant information of the terminal device at the NAS layer is stored in the core network.

[0159] For a terminal device in an RRC inactive state, the context information of the terminal device may include, but is not limited to, the following: identification information of the terminal device, network information, and other relevant information that can be used to restore the connection or to transmit data.

[0160] The identification information of the terminal device is used to identify the terminal device. Exemplarily, the identification information of the terminal device can be used to indicate at least one of the following identifications: 1. International mobile subscriber identity (MSI), used to uniquely identify a user; 2. Globally unique temporary identifier (GUTI), used to protect user privacy in an inactive state; 3. Temporary mobile subscriber identity (SAE temporary mobile subscriber identity, S-TMSI), used to quickly identify the terminal device; 4. Inactive radio network temporary identifier (I-RNTI), used to uniquely identify the identifier of the terminal device in an inactive state. Network information includes registration area information and service cell information. Among them, the registration area information includes tracking area (TA) or location area (LA) information, which is used to locate the terminal device. The service cell information is used to indicate the identifier of the last service cell for fast reconnection. Relevant information may include, for example, capability information, location information, etc. Capability information is used to indicate the capabilities of the terminal device, such as supported frequency bands, modulation modes, carrier aggregation capabilities, etc. The location information may include the last known geographic location or cell information for positioning and service recovery.

[0161] The cell configuration information is used to configure the first cell, and is used to configure various parameters and resources of the first cell. Exemplarily, the cell configuration information includes a physical cell identifier (PCI) of the first cell. The first cell can be distinguished by the PCI of the first cell. It should be understood that different cells correspond to different PCIs. Exemplarily, the cell configuration information may also include various parameters such as frequency parameters (such as carrier frequency) of the first cell, antenna parameters (such as antenna direction, tilt, gain), channel configuration parameters, power control parameters, neighboring cell parameters, etc.

[0162] It should be understood that each piece of information in the first information of the above example is only for illustrative purposes, and the source satellite can also send more information to facilitate the communication between the target satellite and the terminal device in the first cell. For example, if the first cell also includes a terminal device in an RRC connected state, the context information of the first information can also include the context information of the terminal device in the RRC connected state. In this way, the target base station saves the context information of the terminal device in the RRC connected state, and the target base station can directly communicate with the terminal device in the RRC connected state when serving the first cell. Of course, the context information may not include the context information of the terminal device in the RRC connected state. When the target satellite serves the first cell, these terminal devices can re-initiate the random access process to enter the RRC connected state.

[0163] It should also be understood that each information in the above first information can be sent to the target satellite by the source satellite at one time or in batches, and no limitation is made here. For example, the source satellite first sends the cell configuration information and context information, and then sends the security information.

[0164] In step S630, the target satellite is configured on the target satellite according to the first information.

[0165] Specifically, the target satellite configures the content of security information, such as configuring security keys of the control plane and security keys of the user plane, configures the first cell according to the cell configuration information, and configures the context of each terminal device (including the first terminal device) in the RRC inactive state in the first cell according to the context information.

[0166] It should be understood that configuring the content of security information (such as security keys of the control plane and security keys of the user plane) in the target satellite can also be understood as activating the security information in the target satellite. After the configuration is completed on the target satellite, the content of the security information can be used. Configuring the first cell in the target satellite can be understood as establishing or activating the first cell in the target satellite. After the configuration is completed, the target satellite can communicate in the first cell. Configuring the context of the terminal device in the first cell in the target satellite, which is in the RRC inactive state, can also be understood as establishing or activating the terminal device context. After the configuration is completed, the target satellite can communicate with the terminal device in the RRC inactive state.

[0167] It should be understood that since the security information is the security information encrypted by the source satellite using a public key encryption algorithm, the target satellite decrypts the security information using a private key encryption algorithm that matches the public key encryption algorithm of the source satellite to obtain the decrypted security information. After decrypting the security information, the content of the security information is configured in the target satellite.

[0168] After the target satellite is configured, the target satellite and the source satellite are configured with the same cell (first cell), the same security key, and the same terminal device context. In this way, after the target satellite moves to a position covering the first cell, the target satellite can communicate with the terminal device in the first cell based on the above configuration.

[0169] In step S640, the target satellite starts serving the first cell.

[0170] During the satellite movement, the target satellite adjusts the antenna direction so that the target satellite begins to cover the first cell, and thus, the target satellite begins to serve the first cell. In the process of serving the first cell, the target satellite covers the first cell based on the coverage mode of the earth gaze cell, and the target satellite communicates with the terminal device in the first cell based on the configuration of step S630.

[0171] In step S650, the source satellite stops serving the first cell.

[0172] During the satellite movement, the source satellite adjusts the antenna direction so that the source satellite no longer covers the first cell, and thus the source satellite stops serving the first cell. After the source satellite stops serving the first cell, it moves to the next cell, and covers and serves the next cell based on the coverage mode of the earth gaze cell.

[0173] It should be noted that the present application embodiment does not impose any restrictions on the order of step S640 and step S650, which should be determined according to the actual situation of satellite movement. In one example, step S650 can be executed before step S640, that is, the source satellite stops serving the first cell first, and the target satellite starts serving the first cell. This example can correspond to the above Figure 5 In the scenario of discontinuous coverage of the same cell between two adjacent satellites as shown in (b), the end service time of the source satellite (such as time T1) is earlier than the start service time of the target satellite (such as time T2). During the moving process, the first cell cannot be served during the period between when the source satellite stops serving the first cell and when the target satellite starts serving the first cell. In another example, step S650 and step S640 can be performed simultaneously, that is, the source satellite stops serving the first cell while the target satellite starts serving the first cell. This example can correspond to the above Figure 5In the scenario shown in FIG. (c) of FIG. 1 , the coverage of the same cell between two adjacent satellites is continuous, and the end service time of the source satellite (such as time T1) is also the start service time of the target satellite. In another example, step S650 may be performed after step S640, that is, the target satellite first starts to serve the first cell, and the source satellite then stops serving the first cell. In the example, the coverage of the same cell between the two adjacent satellites is continuous, and there is a situation where the two adjacent satellites have repeated coverage of the same cell. For example, the first cell is covered and served by both the source satellite and the target satellite during the period between the start service time of the target satellite and the end service time of the source satellite.

[0174] In addition, the order of step S650 and step S630 may not be limited, and may be determined according to the actual situation of satellite movement. For example, step S650 may be performed after step S630, or step S650 may be performed before step S630 and after step S620, as long as the source satellite stops serving the first cell after sending the first message to the target satellite.

[0175] In the above process, the terminal device does not participate in the satellite switching process. That is to say, for the terminal device in the first cell, the terminal device will not perceive the satellite switching process, which also reduces the signaling overhead generated by the interaction between the terminal device and the satellite to a certain extent.

[0176] Subsequently, the first terminal device in the RRC inactive state generates small uplink data to be sent.

[0177] In step S660, the first terminal device in the RRC inactive state sends small uplink data.

[0178] Correspondingly, the target satellite receives the uplink small data.

[0179] Since the satellite serving the first cell has been switched from the source satellite to the target satellite, the first terminal device in the RRC inactive state sends small uplink data, which is actually the process of initiating SDT to the target satellite. For the target satellite, since the context of the first terminal device in the RRC inactive state in the first cell has been saved and configured in the target satellite, the target satellite does not need to request context information from the source satellite at this time. The target satellite can directly successfully receive the small uplink data sent by the first terminal device in the RRC inactive state based on the saved context information. In this way, the first terminal device in the RRC inactive state and the satellite can quickly transmit small data and effectively save the power consumption of the first terminal device. In this way, the advantages of low power consumption and good transmission efficiency of small data transmission (SDT) of the terminal device in the RRC inactive state are fully utilized in the NTN, so that NTN communication such as satellite communication can well support the SDT of the terminal device in the RRC inactive state.

[0180] As mentioned above, the signaling or data transmitted between the terminal device and the satellite are all encrypted. The uplink small data is the data of the user plane. The uplink small data sent by the source satellite is encrypted using the security key of the user plane. Therefore, after the target satellite receives the uplink small data, it needs to use the security key of the user plane to decrypt the uplink small data and obtain the decrypted uplink small data. Then, the target satellite can send the decrypted uplink small data to the core network for further processing.

[0181] In NTN, there are multiple ways for a first terminal device in an RRC inactive state to send small uplink data.

[0182] In some embodiments, the first terminal device in the RRC inactive state can send uplink small data based on the pre-configured wireless resources. The wireless resources are regularly allocated based on the estimated traffic demand of the terminal device, and the wireless resources are dedicated to each terminal device. In addition, after the satellite switching for the first cell, the target satellite will re-preconfigure wireless resources for each terminal device of the first cell.

[0183] In other embodiments, the first terminal device in the RRC inactive state may send small uplink data based on a random access (RA) process.

[0184] In one example, a first terminal device in an RRC inactive state may send small uplink data based on a 4-step RA.

[0185] Specifically, the first terminal device sends a first message of the random access process (abbreviated as message 1, Msg1), and message 1 includes a preamble; in response to message 1, the target satellite sends a second message of the random access process (abbreviated as message 2, Msg2), and message 2 can also be called a random access response (RAR), and the random access response includes scheduling information for uplink resources indicating a third message (abbreviated as message 3) and a timing advance (TA) instruction required for uplink synchronization; in response to message 2, the first terminal device sends a message 3 (Msg3) of the random access process, and message 3 includes uplink small data. In addition, message 3 also includes an RRC recovery request. If the target satellite determines that it is not necessary to restore the first terminal device to a connected state, in response to message 3, the target satellite sends a fourth message of the random access process to the first terminal device (abbreviated as message 4, Msg4), and message 4 includes RRC release information carrying a suspension indication, and the suspension indication is used to indicate that the first terminal device is in an RRC inactive state. After receiving message 4, the first terminal device can determine that the uplink small data has been sent and it continues to be in an RRC inactive state.

[0186] It should be understood that although the RRC recovery request in message 3 is used to request the restoration of the connection, after the target satellite receives message 3 including uplink small data, in the absence of other special instructions or special circumstances, the target satellite may consider that message 3 is actually used for the transmission of small data, and does not need to restore the first terminal device to the connection state. Therefore, the target satellite sends an RRC release message carrying a suspension indication to the first terminal device through message 4. In this way, after receiving message 4, the first terminal device still remains in the RRC inactive state.

[0187] In another example, the first terminal device may send small uplink data based on 2-step RA.

[0188] Specifically, the first terminal device sends a message A of the random access process, and the message A includes the message 1 and the above-mentioned message 3 (Msg3), and the message 3 includes uplink small data. In addition, the message 3 also includes an RRC recovery request. In response to the message A, the target satellite sends a message B of the random access process to the first terminal device, and the message B includes the above-mentioned message 4 (Msg4), and the message 4 includes RRC release information carrying a suspension indication, and the suspension indication is used to indicate that the first terminal device is in an RRC inactive state.

[0189] In the above embodiment, the terminal device in the RRC inactive state in the NTN sends uplink small data to the satellite through the random access process, which can not only effectively reduce the power consumption of the terminal device and improve the transmission efficiency, but also, compared with other methods of transmitting small data, such as by pre-configuring wireless resources, since there is no need to pre-configure resources in advance, the problem of unreasonable resource allocation can be avoided, and the advantages of flexible and reasonable use of resources in the random access process can be fully utilized, and the changes to the existing standards are small, and the existing standards can be adapted in a friendly manner.

[0190] It should be noted that the embodiments of the present application are applicable to the scenario where the cell (physical cell, such as the first cell) where the terminal device in the RRC inactive state is located remains unchanged. It can be understood that if the cell where the terminal device is located changes, the terminal device cannot maintain the RRC inactive state, but needs to be restored to the RRC connected state to perform the cell switching process. In fact, due to the fast movement speed of the satellite, the switching time is approximately between 2s-10s (including 2s and 10s), and the range of a cell is between tens of kilometers and hundreds of kilometers. The probability of the terminal device moving from one cell to another within the switching time of the satellite is small. Therefore, the embodiments of the present application can be applied to most scenarios of NTN.

[0191] The method for switching a satellite base station provided in an embodiment of the present application is that when the source satellite currently serving the first cell needs to be switched to the target satellite, the source satellite sends the first information related to the first cell to the target satellite, the first information including security information, context information, and cell configuration information of the first cell, wherein the context information includes the context information of the terminal device in the RRC inactive state in the first cell; after receiving the first information, the target satellite performs configuration on the target satellite. In this way, when the terminal device in the RRC inactive state (such as the first terminal device) needs to send small uplink data during the process of the target satellite serving the first cell, the terminal device can send small uplink data in the RRC inactive state (without entering the RRC connection state). Since the context information of the terminal device in the RRC inactive state has been saved and configured in the target satellite, the target satellite does not need to request context information from the source satellite at this time. The target satellite can directly successfully receive the small uplink data based on the saved and configured context information, thereby avoiding as much as possible the problem of increased power consumption of the terminal device, decreased transmission efficiency, and large signaling overhead caused by the process of the target satellite requesting context information from the source satellite. In other words, the embodiment of the present application enables a terminal device in an RRC inactive state to quickly transmit small uplink data without entering a connected state, which not only reduces signaling overhead, but more importantly, effectively improves the efficiency of data transmission and reduces the power consumption of the terminal device. In NTN, the advantages of low power consumption and good transmission efficiency of the terminal device performing SDT in an RRC inactive state are fully utilized, so that NTN communication such as satellite communication can friendly support the SDT of the terminal device in an RRC inactive state. In addition, the source satellite sends security information to the target satellite, which can make the target satellite and the terminal device in the first cell have the same understanding of the encryption and decryption of data and signaling, and can encrypt and decrypt data and signaling through security information, ensuring the security of the data and signaling transmission process and the correct decryption of data and signaling as much as possible, and avoiding the problem of high signaling overhead caused by the need for the target satellite to re-negotiate security information with the terminal device in the first cell, which can further reduce signaling interaction.

[0192] In the present application, in some embodiments, before the source satellite sends the first information (such as step S620), the source satellite and the target satellite may also interact through signaling to determine that the target satellite can receive the data to be subsequently sent by the source satellite.

[0193] In an example, when a satellite serving a first cell needs to be switched from a source satellite to a target satellite, the source satellite sends a satellite data synchronization request to the target satellite, where the satellite data synchronization request is used to indicate that the source satellite is about to send data. The target satellite receives the satellite data synchronization request, and in response to the satellite data synchronization request, the target satellite sends satellite data synchronization confirmation information to the source satellite, where the satellite data synchronization confirmation information is used to indicate that the target satellite confirms receiving the data to be sent by the source satellite.

[0194] Exemplarily, the satellite data synchronization request may include an identifier of a source satellite (such as an ID), an identifier of a target satellite, a size of data to be sent, and the like.

[0195] Exemplarily, the satellite data synchronization confirmation information may include an identifier of a source satellite, an identifier of a target satellite, and an acknowledgment (ACK).

[0196] In the above embodiment, the target satellite can know that the source satellite is going to send data (such as the first information) based on the satellite data synchronization request sent by the source satellite, so that the target satellite can determine whether it can receive the data to be sent by the source satellite according to the actual situation: if the target satellite can receive the data to be sent by the source satellite, it sends satellite data synchronization confirmation information to the source satellite to inform itself that it can receive the data to be sent by the source satellite. In this way, the source satellite and the target satellite have the same understanding of the event that both parties are going to transmit data, which can avoid some unnecessary problems. For example, if the target satellite is currently unable to receive the data to be sent due to the actual situation (such as no resources, poor signal quality, etc.), but the source satellite sends the first information, it will result in a waste of signaling.

[0197] In some embodiments, after the source satellite sends the first information (such as step S620), the source satellite sends satellite data synchronization completion information to the target satellite to indicate that the data has been sent. After the target satellite receives the satellite data synchronization completion information, it can be sure that the source satellite has sent the data. In this way, the target satellite does not need to continue to wait (or monitor) the data sent by the source satellite, so that the subsequent steps can be performed, which can save the power consumption of the satellite.

[0198] The following, combined Figure 7 , combined with specific examples, the method for switching satellite base stations in an embodiment of the present application is described in detail.

[0199] Figure 7700 is a schematic flow chart of a method 700 for switching a satellite base station provided in an embodiment of the present application. The explanations of the first terminal device, the source satellite, the target satellite, and the first cell are the same as those of method 600 and are not repeated here. The difference from method 600 is that method 700, as an example, adds a process in which the terminal device releases resources in an RRC inactive state after establishing an RRC connection, adds a process of interactive signaling between the source satellite and the target satellite, and sends small uplink data through a random access process as a specific scenario.

[0200] In step S710, an RRC connection is established between the first terminal device and the source satellite.

[0201] In the process of the source satellite serving the first cell, the first terminal device initiates a random access process to enter the RRC connection state. Specifically, the first terminal device sends message 1 (Msg1), which includes a preamble to start the random access process; after receiving the preamble in message 1, the source satellite sends message 2 to the first terminal device, which can also be called a random access response (RAR), and RAR includes the TA instruction required for the first terminal device to perform uplink synchronization, the scheduling information of the uplink resource (UL grant) used to indicate message 3 (Msg3), and other information; the first terminal device uses the uplink resources provided in the scheduling information of RAR to send an RRC connection setup request to request to establish an RRC connection; in response to message 3, the source satellite sends message 4 (Msg4), which includes an RRC connection setup complete message to confirm that the first terminal device has successfully accessed the network. If contention-based random access is used, message 4 will also include a contention resolution ID to resolve possible preamble conflicts.

[0202] In step S720, the first terminal device is in an RRC connected state, and performs network registration, uplink data, and downlink data interaction with the source satellite.

[0203] In step S730, the source satellite sends an RRC release message carrying a suspension indication to the first terminal device to instruct the first terminal device to enter an RRC inactive state.

[0204] The first terminal device releases the connection with the source satellite and enters an RRC inactive state with low power consumption and standby, but the source satellite saves the context information of the first terminal device.

[0205] It should be understood that, for the source satellite, the source satellite will save the context information of all terminal devices (such as at least one terminal device) in the first cell that are in an RRC inactive state, including the first terminal device.

[0206] It should be understood that the above steps S710 to S730 are only schematic descriptions of establishing an RRC connection between the first terminal device and the source satellite. In fact, the first terminal device is not necessarily an RRC connection established with the source satellite, but may be an RRC connection established with any satellite that served the first cell before the source satellite. Moreover, the first terminal device enters the RRC inactive state from the RRC connected state, which is not necessarily a state change that occurs during the process of the source satellite serving the first cell, but may be a state change that occurs during the process of any satellite that served the first cell before the source satellite. The RRC inactive state after the state change continues until the source satellite serves the first cell and the target satellite serves the first cell.

[0207] In step S740, the source satellite determines that the satellite serving the first cell needs to be switched from the source satellite to the target satellite.

[0208] For the specific description of this step, please refer to the above description of step S610, which will not be repeated here.

[0209] In step S751, the source satellite sends a satellite data synchronization request to the target satellite to indicate that the source satellite is about to send data.

[0210] In step S752, in response to the satellite data synchronization request, the target satellite sends satellite data synchronization confirmation information to the source satellite to instruct the target satellite to confirm receiving the data to be sent by the source satellite.

[0211] In step S761, the source satellite sends first information to the target satellite, where the first information includes security information, context information, and cell configuration information of the first cell.

[0212] For the specific description of this step, please refer to the above description of step S620, which will not be repeated here.

[0213] In step S762, the source satellite sends satellite data synchronization completion information to the target satellite to indicate that the data has been sent.

[0214] In step S770, the target satellite is configured on the target satellite according to the first information.

[0215] After the target satellite is configured, the target satellite and the source satellite are configured with the same cell (first cell), the same content in the security information (such as security keys), and the same context of the terminal device. In this way, after the target satellite moves to a position covering the first cell, the target satellite can communicate with the terminal device in the first cell based on the above configuration.

[0216] For the specific description of this step, please refer to the above description of step S630, which will not be repeated here.

[0217] In step S781, the target satellite starts serving the first cell.

[0218] In step S782, the source satellite stops serving the first cell.

[0219] For the specific description of step S781 and step S782, please refer to the above description of step S640 and step S650, which will not be repeated here.

[0220] In addition, in the above process, step S751, step S752 and step S762 are optional steps.

[0221] Subsequently, the first terminal device in the RRC inactive state generates small uplink data to be sent.

[0222] In step S781, the first terminal device sends a message 1 (Msg1). Correspondingly, the target satellite receives the message 1. The message 1 includes a preamble to start a random access process.

[0223] Since the satellite serving the first cell has been switched from the source satellite to the target satellite, the message 1 sent by the first terminal device is actually the message 1 sent to the target satellite, and the target satellite receives the message 1.

[0224] In step S792, in response to message 1, the target satellite sends message 2 (Msg2). Correspondingly, the first terminal device receives message 2.

[0225] Message 2 is a random access response (RAR), which includes scheduling information for indicating uplink resources of message 3. Exemplarily, the random access response also includes information such as a timing advance (TA) instruction required for uplink synchronization.

[0226] In step S793, in response to message 2, the first terminal device sends message 3 (Msg3). Correspondingly, the target satellite receives message 3.

[0227] Message 3 includes small uplink data and an RRC recovery request.

[0228] After receiving the small uplink data in message 3, the target satellite uses the security key of the user plane to decrypt the small uplink data and obtain the decrypted small uplink data. Then, the target satellite can send the decrypted small uplink data to the core network for further processing.

[0229] In step S794, in response to message 3, the target satellite sends message 4 (Msg4). Correspondingly, the first terminal device receives message 4.

[0230] Message 4 includes RRC release information carrying a suspension indication, and the suspension indication is used to indicate that the first terminal device is in an RRC inactive state.

[0231] After receiving message 4, the first terminal device can determine that the uplink small data has been sent and it continues to be in the RRC inactive state.

[0232] It should be understood that the order of the steps in the above method 700 does not mean the order of execution. The order of execution of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of the present application. For example, step S782 can be executed before or after step S781, or step S782 and step S781 can be executed at the same time. For another example, step S782 can be executed after step S770, or before step S770 and after step S762, as long as the source satellite stops serving the first cell after sending the first information.

[0233] In the above method 600 and method 700, embodiments of the scenario in which the terminal device initiates small data after the satellite switching is completed are illustrated.

[0234] During the satellite switching process, if the terminal device in the RRC inactive state initiates uplink small data, since the source satellite and the target satellite are switching, and the satellite switching speed is very fast, for example, the satellite switching time is about 2s-10s (including 2s and 10s), there will be many problems for the source satellite to receive the uplink small data during this process. For example, the source satellite may not wait for the uplink small data carried in the message 3 sent by the terminal device to no longer serve the previously served cell (such as the first cell), and the target satellite may not have served the cell yet. In this way, the terminal device not only fails to successfully send the uplink small data, but also increases the signaling overhead and wastes power consumption. For another example, during the satellite switching process, the communication quality between the terminal device and the satellite will deteriorate, resulting in unstable transmission between the satellite and the terminal device, affecting the transmission efficiency of the uplink small data.

[0235] Based on this, the present application embodiment proposes two methods to solve the above problem, which are recorded as method 1 and method 2. Figure 8 and Fig. 9 Based on Method 1 and Method 2, an implementation example of a scenario in which a terminal device initiates small data during satellite switching is introduced in detail.

[0236] Figure 8 800 is a schematic flow chart of a satellite base station switching method provided by an embodiment of the present application. In method 800, during the switching between the source satellite and the target satellite, a first terminal device in an RRC inactive state has a need to send small data, and thus initiates a random access process to send small data.

[0237] In method 800, the specific description of steps S810 to S852 can refer to the relevant description of steps S740 to S782 in method 700, which will not be repeated here. Among them, step S821, step S822 and step S832 are optional steps.

[0238] In the embodiments of the present application, the satellite switching process for the first cell is interpreted differently in different situations.

[0239] Case 1

[0240] The source satellite determines that the satellite serving the first cell needs to be switched from the source satellite to the target satellite, which means that the source satellite is about to end its service to the first cell and the target satellite is about to serve the first cell, which also means that satellite switching is about to begin. Therefore, when the source satellite determines that the satellite serving the first cell needs to be switched from the source satellite to the target satellite (i.e., step S810), it can be considered that the satellite switching process has begun, and the step in which the source satellite determines that the satellite serving the first cell needs to be switched from the source satellite to the target satellite (i.e., step S810) is taken as the starting step of the satellite switching process. The target satellite starts serving the first cell (i.e., step S851) means that the satellite switching is completed. Therefore, the step in which the target satellite starts serving the first cell (i.e., step S851) can be taken as the ending step of the satellite switching process. Figure 8 The process is shown in the dashed box.

[0241] Case 2

[0242] In this case, after the source satellite determines that the satellite serving the first cell needs to be switched from the source satellite to the target satellite, the signaling interaction between the source satellite and the target satellite means the start of the satellite switching process. Therefore, the starting step of the satellite switching process may be the step of the source satellite sending information to the target satellite (such as the first information, the satellite data synchronization request, etc.), and the ending step of the satellite switching process is the step of the target satellite starting to serve the first cell (i.e., step S851). In the embodiment where the source satellite needs to send a satellite data synchronization request to the target satellite (i.e., step S821), the starting step of the satellite switching process may be the step of the source satellite sending a satellite data synchronization request (i.e., step S821), and in the embodiment where the source satellite does not need to send a satellite data synchronization request to the target satellite (i.e., step S821), the starting step of the satellite switching process may be the step of the source satellite sending the first information (i.e., step S831).

[0243] It can be understood that the duration of the satellite switching process in case 1 (referred to as satellite switching duration) is longer than the satellite switching duration in case 2.

[0244] In the following, for the convenience of description, the satellite switching process described in the above case 1 (such as Figure 8The description will be continued by taking the process shown in the dotted box in FIG. 1 as an example.

[0245] During the switching process between the source satellite and the target satellite, the first terminal device in the RRC inactive state has a need to send small data, and thus initiates a random access process to send the small data. It should be understood that the steps of interaction between the source satellite and the first terminal device in the satellite switching process described below (such as steps S861 and S862) are steps performed before the source satellite stops serving the first cell.

[0246] Method 1

[0247] In step S861, the first terminal device in the RRC inactive state sends a message 1 (Msg1). The message 1 includes a preamble to start a random access process. Correspondingly, the source satellite receives the message 1.

[0248] Since the source satellite has not stopped serving the first cell and the target satellite has not started serving the first cell, the message 1 sent by the first terminal device is actually the message 1 sent to the source satellite, and the source satellite receives the message 1.

[0249] In step S862, in response to message 1, the source satellite sends message 2 (Msg2), and correspondingly, the first terminal device receives message 2.

[0250] Message 2 does not include (or does not carry) scheduling information for indicating uplink resources of message 3 (Msg3).

[0251] Message 2 is a random access response (RAR). In implementation, the field configured for scheduling information in the random access response is 0, which is an empty indication, that is, the scheduling for message 3 in the random access response is an empty indication.

[0252] In this way, after receiving message 2, the first terminal device determines that the source satellite does not schedule message 3, which means that the source satellite and the target satellite are most likely in the satellite switching process, and the source satellite does not want the first terminal device to send data or information to itself. Therefore, the first terminal device executes step S863.

[0253] In step S863, the first terminal device starts a timer.

[0254] The duration of the timer is based on the duration of the satellite switching. For example, the duration of the timer is greater than or equal to the duration of the satellite switching. In one example, the duration of the timer is greater than or equal to 2 seconds and less than or equal to 10 seconds. In other examples, the duration of the timer can also be a duration in another range, which is not limited here, and is determined by the duration spent in the satellite switching process in the actual scenario.

[0255] During the timer, the first terminal device no longer performs a random access process to transmit uplink small data, that is, during the timer, the first terminal device no longer attempts to transmit small data (SDT). In this way, not only can the signaling overhead be reduced, but also the power consumption of the terminal device can be further saved.

[0256] When the timer times out, the first terminal device can try to perform the random access process again to transmit small data. It can be understood that the duration of the timer is based on the satellite switching duration. When the timer times out, if there are no special circumstances, it means that the satellite switching has been completed. At this time, the first terminal device in the RRC inactive state can communicate with the target satellite to transmit uplink small data. In this way, uplink small data can be transmitted normally.

[0257] In step S871, when the timer times out, the first terminal device sends message 1. Correspondingly, the target satellite receives message 1.

[0258] Since the satellite serving the first cell has been switched from the source satellite to the target satellite, the source satellite has stopped serving the first cell, and the target satellite has been serving the first cell, the message 1 sent by the first terminal device is actually the message 1 sent to the target satellite.

[0259] In step S872, since the satellite switching has been completed, in response to message 1, the target satellite sends message 2. Correspondingly, the first terminal device receives message 2.

[0260] Message 2 of this step includes scheduling information for indicating uplink resources of message 3.

[0261] In step S873, in response to message 2, the first terminal device sends message 3, which includes an RRC recovery request and uplink small data. Correspondingly, the target satellite receives message 3.

[0262] In this step, the first terminal device receives message 2 including scheduling information, and sends message 3 on the uplink resources indicated by the scheduling information. After receiving the uplink small data in message 3, the target satellite uses the security key of the user plane to decrypt the uplink small data and obtain the decrypted uplink small data. Then, the target satellite can send the decrypted uplink small data to the core network for further processing.

[0263] In step S874, in response to message 3, the target satellite sends message 4. Correspondingly, the first terminal device receives message 4.

[0264] Message 4 includes RRC release information carrying a suspension indication. In this way, the first terminal device continues to be in an RRC inactive state.

[0265] For the specific description of steps S871 to S874, please refer to the relevant description of steps S791 to S794 in method 700, which will not be repeated here.

[0266] In a specific example, the random access process initiated by the first terminal device in step S861 can be defined as the nth random access process initiated by the first terminal device, and the random access process initiated by the first terminal device in step S871 can be defined as the n+1th random access process. The messages (such as message 1 and message 2) interacted between the first terminal device and the satellite (such as the source satellite) in the nth random access process are defined as messages in the nth random access process, and the messages (such as message 1, message 2, message 3 and message 4) interacted between the first terminal device and the satellite (such as the target satellite) in the n+1th random access process are defined as messages in the n+1th random access process. Wherein, n is an integer greater than or equal to 1.

[0267] When n is greater than 1, it means that the first terminal device has also initiated a random access process before. It should be understood that the random access process initiated by the first terminal device before can be a random access process initiated by the first terminal device in any state.

[0268] In the above embodiment, a timer is configured in the terminal device, and the duration of the timer is determined based on the duration of the satellite switching process. In the satellite switching process for a cell (such as the first cell), if a terminal device (such as the first terminal device) in an RRC inactive state in the cell has a need to send small uplink data, the terminal device sends a message 1 of a random access process to initiate a random access, and the source satellite sends a message 2 to the terminal device that does not include (or does not carry) scheduling information for uplink resources indicating message 3. After the terminal device receives the message 2 that does not include (or does not carry) scheduling information, the timer is started, and the terminal device no longer continues to perform the random access process to transmit small uplink data within the duration of the timer. It can be understood that the source satellite sends a message 2 that does not include (or does not carry) scheduling information to the terminal device, which means that the source satellite and the target satellite are likely to be in the process of satellite switching. The source satellite does not want the terminal device to interact with itself during the satellite switching process to affect the transmission of data. Therefore, after the terminal device receives the message 2 that does not include (or does not carry) scheduling information, it starts the timer and no longer performs the random access process to transmit uplink small data within the timer duration. In this way, not only can the signaling overhead be reduced, but also the power consumption of the terminal device can be further saved. After the timer times out, if there are no special circumstances, the satellite switching has been completed. At this time, the terminal device in the RRC inactive state can communicate with the target satellite. Therefore, the terminal device tries to perform the random access process again to send uplink small data. In this way, if there are no special circumstances, the uplink small data can be successfully transmitted between the terminal device and the target satellite. Therefore, in the above embodiment, during the satellite switching process, by not including (or not carrying) the message 2 of the scheduling information and the setting of the timer, not only the signaling overhead can be reduced, but also the power consumption of the terminal device can be further saved. Moreover, after the satellite switching is completed (timer times out), small uplink data can be transmitted in time through the random access process, thereby improving the performance of satellite communication as a whole.

[0269] Fig. 9 : is a schematic flow chart of a method 900 for satellite base station switching provided by an embodiment of the present application. The difference between method 900 and method 800 is that the terminal device in the RRC inactive state directly starts the timer after sending message 1, instead of waiting until message 2 is received before starting the timer. If message 2 sent by the source satellite is not received within the timer, the random access process will not be continued within the timer. After the timer times out, the random access process is re-initiated to transmit small data. The following focuses on the differences between method 900 and method 800.

[0270] In method 900, the specific description of steps S910 to S952 can refer to the relevant description of steps S740 to S782 in method 700, which will not be repeated here. Among them, steps S921, S922 and S932 are optional steps.

[0271] During the switching process between the source satellite and the target satellite, the first terminal device in the RRC inactive state has a need to send small data, and thus initiates a random access process to send the small data. It should be understood that the steps of interaction between the source satellite and the first terminal device in the satellite switching process described below (such as step S961) are steps performed before the source satellite stops serving the first cell.

[0272] Method 2

[0273] In step S961, the first terminal device sends a message 1 (Msg1), which includes a preamble code, to start a random access process. Correspondingly, the source satellite receives the message 1.

[0274] Since the source satellite has not stopped serving the first cell and the target satellite has not started serving the first cell, the message 1 sent by the first terminal device is actually the message 1 sent to the source satellite, and the source satellite receives the message 1.

[0275] In step S962, the first terminal device starts a timer.

[0276] In the case where the first terminal device does not receive message 2 sent by the source satellite within the duration of the timer (recorded as case A), the first terminal device no longer performs a random access process to transmit small uplink data within the duration of the timer, or in other words, the first terminal device no longer attempts to transmit small data within the duration of the timer. It should be understood that in case A, it means that the source base station and the target satellite are likely to be in the process of satellite switching, and the source satellite does not want the first terminal device to send data or information to itself. In this way, not only can the signaling overhead be reduced, but also the power consumption of the terminal device can be further saved.

[0277] Combined with situation A, further, the first terminal device does not receive message 2 sent by the source satellite within the duration of the timer, and after the timer expires, the first terminal device can try to perform the random access process again to transmit small data. It can be understood that after the timer expires, if there is no special situation, the satellite switching has been completed. At this time, the first terminal device in the RRC inactive state can communicate with the target satellite to transmit uplink small data. In this way, the uplink small data can be transmitted normally.

[0278] In the case where the first terminal device receives message 2 sent by the source satellite within the duration of the timer (recorded as case B), message 2 includes scheduling information for indicating the uplink resources of message 3, and the first terminal device sends message 3 based on the scheduling information, and message 3 includes uplink small data, thereby completing the transmission of small data. It can be understood that in case B, the source satellite can send message 2 including scheduling information within the duration of the timer, which means that the source satellite does not perform the satellite switching process, and therefore, the first terminal device can normally perform the random access process to send uplink small data.

[0279] In method 900, after the first terminal device starts the timer, the first terminal device does not receive the message 2 sent by the source satellite within the duration of the timer. Therefore, the first terminal device no longer performs the random access process to transmit uplink small data within the duration of the timer. After the timer expires, the first terminal device executes step S971 and tries to perform the random access process again.

[0280] In step S971, when the timer times out, the first terminal device sends message 1. Correspondingly, the target satellite receives message 2.

[0281] Since the satellite serving the first cell has been switched from the source satellite to the target satellite, the source satellite has stopped serving the first cell, and the target satellite has been serving the first cell, the message 1 sent by the first terminal device is actually the message 1 sent to the target satellite.

[0282] In step S972, the first terminal device starts a timer.

[0283] In step S973, since the satellite has been switched, the target satellite sends message 2 in response to message 1. Correspondingly, the first terminal device receives message 2.

[0284] Message 2 includes scheduling information for indicating uplink resources of message 3.

[0285] For the first terminal device, the first terminal device receives message 2 including scheduling information within the duration of the timer, and therefore continues to perform the random access process.

[0286] In step S974, in response to message 2, the first terminal device sends message 3, which includes an RRC recovery request and uplink small data. Correspondingly, the target satellite receives message 3.

[0287] In this step, the first terminal device receives message 2 including scheduling information, and sends message 3 on the uplink resources indicated by the scheduling information. After receiving the uplink small data in message 3, the target satellite uses the security key of the user plane to decrypt the uplink small data and obtain the decrypted uplink small data. Then, the target satellite can send the decrypted uplink small data to the core network for further processing.

[0288] In step S975 , in response to message 3 , the target satellite sends message 4 , and correspondingly, the first terminal device receives message 4 .

[0289] Message 4 includes RRC release information carrying a suspension indication, so that the first terminal device continues to be in an RRC inactive state.

[0290] For the specific description of step S971 and step S973 to step S975, please refer to the relevant description of step S791 to step S794 in method 700, which will not be repeated here.

[0291] In a specific example, the random access process initiated by the first terminal device in step S961 can be defined as the nth random access process initiated by the first terminal device, and the random access process initiated by the first terminal device in step S971 can be defined as the n+1th random access process. Each message (such as message 1) interacted between the first terminal device and the satellite (such as the source satellite) in the nth random access process is defined as a message in the nth random access process, and each message (such as message 1, message 2, message 3 and message 4) interacted between the first terminal device and the satellite (such as the target satellite) in the n+1 random access process is defined as a message in the n+1th random access process.

[0292] In the above embodiment, a timer is configured in the terminal device, and the duration of the timer is determined based on the duration of the satellite switching process. In the satellite switching process for a cell (such as the first cell), if a terminal device (such as the first terminal device) in an RRC inactive state in the cell has a need to send small uplink data, the terminal device sends message 1 of the random access process to initiate the random access process, and the terminal device starts the timer after sending message 1 of the random access process. If message 2 is not received within the duration of the timer, the terminal device will no longer continue to perform the random access process to transmit small uplink data within the duration of the timer, and if the timer times out, the terminal device will try to perform the random access process again to send small uplink data, so that after the timer times out, if there are no special circumstances, the satellite switching has been completed, and at this time, the terminal device in the RRC inactive state can communicate with the target satellite to transmit small uplink data. It can be understood that the source satellite did not send message 2 to the terminal device within the duration of the timer, which means that the source satellite and the target satellite are most likely in the process of satellite switching. The source satellite does not want the terminal device to interact with itself during the satellite switching process to affect the data transmission. Therefore, if the terminal device does not receive message 2 within the duration of the timer, it will no longer perform the random access process to transmit small uplink data within the duration of the timer. In this way, not only the signaling overhead can be reduced, but also the power consumption of the terminal device can be further saved. In addition, after the satellite switching is completed (timer times out), the uplink small data can be transmitted in time through the random access process, thereby improving the overall performance of satellite communication.

[0293] In addition, when message 2 is received within the timer duration, it means that the source satellite has most likely not performed the satellite switching process. Therefore, the first terminal device can send message 3 carrying uplink small data based on the scheduling information of message 2 to send the uplink small data normally.

[0294] In addition, compared to method 800, in method 900, since the terminal device starts the timer after sending message 1, it does not need to monitor and receive message 2, thus further saving power consumption of the terminal device and reducing signaling overhead.

[0295] It needs to be explained again that the size of the serial numbers of the steps in the above method embodiments does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0296] Combined with the above Figures 1 to 9 , describes in detail the method for switching a satellite base station according to an embodiment of the present application, and will now be combined with Figure 10 to Figure 11 , a device for satellite base station switching according to an embodiment of the present application is described in detail.

[0297] Fig.10The device 1000 for switching a satellite base station provided in an embodiment of the present application is shown. The device 1000 may be the target satellite, source satellite or first terminal device mentioned above, or may be a chip in the target satellite, source satellite or first terminal device. The device 1000 includes: a transceiver unit 1010 and a processing unit 1020.

[0298] In a possible implementation, the apparatus 1000 is used to execute each process and step corresponding to the target satellite in the above method.

[0299] The transceiver unit 1010 is used to: receive first information sent by a source satellite, the first information including security information, context information and cell configuration information of a first cell, the context information including context information of a terminal device in an RRC inactive state in the first cell;

[0300] The processing unit 1020 is used to: perform configuration on the target satellite according to the first information;

[0301] The transceiver unit 1010 is further used to: receive small uplink data sent by a terminal device in an RRC inactive state in the first cell during the process of the target satellite serving the first cell.

[0302] For the specific description of the processes and steps executed by the above-mentioned device 1000, reference can be made to the relevant description of the processes and steps executed by the target satellite above, and no further details will be given.

[0303] In another possible implementation, the apparatus 1000 is used to execute each process and step corresponding to the source satellite in the above method.

[0304] The processing unit 1020 is used to: determine that the satellite serving the first cell needs to be switched from a source satellite to a target satellite;

[0305] The transceiver unit 1010 is used to: send first information to the target satellite, the first information including security information, context information and cell configuration information of the first cell, the context information including context information of a terminal device in an RRC inactive state in the first cell;

[0306] The processing unit 1020 is used to: stop serving the first cell.

[0307] For the specific description of the processes and steps executed by the above-mentioned device 1000, please refer to the relevant description of the processes and steps executed by the source satellite above, which will not be repeated here.

[0308] In another possible implementation, the apparatus 1000 is used to execute each process and step corresponding to the first terminal device in the above method.

[0309] The transceiver unit 1010 is used to: send a first message (i.e., message 1) of an nth random access process, where n is an integer greater than or equal to 1; receive a second message (i.e., message 2) sent by a source satellite in response to the first message of the nth random access process, where the second message of the nth random access process does not include scheduling information for indicating uplink resources of a third message (i.e., message 3);

[0310] The processing unit 1020 is configured to: after receiving the second message of the nth random access process, start a timer;

[0311] The transceiver unit 1010 is further configured to: after the timer expires, send a first message of the (n+1)th random access process;

[0312] The transceiver unit 1010 is further configured to receive a second message sent by the target satellite in response to the first message of the (n+1)th random access process.

[0313] For the specific description of the processes and steps executed by the above-mentioned device 1000, please refer to the relevant description of the processes and steps executed by the first terminal device in the above method 800, which will not be repeated here.

[0314] In another possible implementation, the apparatus 1000 is used to execute each process and step corresponding to the first terminal device in the above method.

[0315] The transceiver unit 1010 is used to: send a first message (i.e., message 1) of the nth random access process;

[0316] The processing unit 1020 is configured to: start a timer after sending a first message of the nth random access process;

[0317] The transceiver unit 1010 is further configured to: if the second message sent by the source satellite in response to the first message of the nth random access process is not received within the duration of the timer, send the first message of the n+1th random access process after the timer times out;

[0318] The processing unit 1020 is further configured to: after sending the first message of the (n+1)th random access process, start the timer again;

[0319] The transceiver unit 1010 is also used to: receive a second message sent by the target satellite in response to the first message of the n+1th random access process within the duration of the timer that is restarted again, and the second message of the n+1th random access process includes scheduling information for indicating uplink resources of the third message (i.e., message 3).

[0320] For the specific description of the processes and steps executed by the above-mentioned device 1000, please refer to the relevant description of the processes and steps executed by the first terminal device in the above method 900, which will not be repeated here.

[0321] It should be understood that the device 1000 here is embodied in the form of a functional unit. The term "unit" here may refer to an application specific integrated circuit (ASIC), an electronic circuit, a processor (such as a shared processor, a dedicated processor or a group processor, etc.) and a memory for executing one or more software or firmware programs, a merged logic circuit and / or other suitable components that support the described functions. In an optional example, those skilled in the art can understand that the device 1000 can be specifically a terminal device, a source satellite or a target satellite in the above-mentioned embodiment, and the device 1000 can be used to execute the various processes and / or steps corresponding to the terminal device, the source satellite or the target satellite in the above-mentioned method embodiment. To avoid repetition, it will not be repeated here.

[0322] The apparatus 1000 of each of the above schemes has the function of implementing the corresponding steps executed by the terminal device, source satellite or target satellite in the above method; the function can be implemented by hardware, or by hardware executing the corresponding software. The hardware or software includes one or more modules corresponding to the above functions; for example, the sending unit can be replaced by a transmitter, the receiving unit can be replaced by a receiver, and other units, such as the determination unit, can be replaced by a processor, respectively performing the sending and receiving operations and related processing operations in each method embodiment.

[0323] Fig.11 The schematic structural diagram of the satellite base station switching device 1100 provided in an embodiment of the present application is shown. The device 1100 includes a processor 1110, a transceiver 1120 and a memory 1130. The processor 1110, the transceiver 1120 and the memory 1130 communicate with each other through an internal connection path, the memory 1130 is used to store instructions, and the processor 1110 is used to execute the instructions stored in the memory 1130 to control the transceiver 1120 to send and / or receive signals.

[0324] In a possible implementation, the apparatus 1100 is used to execute each process and step corresponding to the target satellite in the above method.

[0325] The transceiver 1120 is used to: receive first information sent by a source satellite, where the first information includes security information, context information, and cell configuration information of a first cell, where the context information includes context information of a terminal device in an RRC inactive state in the first cell;

[0326] The processor 1110 is configured to: perform configuration on the target satellite according to the first information;

[0327] The transceiver 1120 is further used to: receive small uplink data sent by a terminal device in an RRC inactive state in the first cell when the target satellite serves the first cell.

[0328] For the specific description of the processes and steps executed by the above-mentioned device 1100, reference can be made to the relevant description of the processes and steps executed by the target satellite above, and no further details will be given.

[0329] In another possible implementation, the apparatus 1100 is used to execute each process and step corresponding to the source satellite in the above method.

[0330] The processor 1110 is configured to: determine that a satellite serving a first cell needs to be switched from a source satellite to a target satellite;

[0331] The transceiver 1120 is used to: send first information to the target satellite, where the first information includes security information, context information, and cell configuration information of the first cell, where the context information includes context information of a terminal device in an RRC inactive state in the first cell;

[0332] The processor 1110 is further configured to: stop serving the first cell.

[0333] For the specific description of the processes and steps executed by the above-mentioned device 1100, reference can be made to the relevant description of the processes and steps executed by the above source satellite, which will not be repeated here.

[0334] In another possible implementation, the apparatus 1100 is used to execute each process and step corresponding to the first terminal device in the above method.

[0335] The transceiver 1120 is configured to: send a first message (i.e., message 1) of an nth random access process, where n is an integer greater than or equal to 1; receive a second message (i.e., message 2) sent by a source satellite in response to the first message of the nth random access process, where the second message of the nth random access process does not include scheduling information for indicating uplink resources of a third message (i.e., message 3);

[0336] The processor 1110 is configured to: after receiving a second message of the nth random access process, start a timer;

[0337] The transceiver 1120 is further configured to: after the timer expires, send a first message of the (n+1)th random access process;

[0338] The transceiver 1120 is further configured to receive a second message sent by the target satellite in response to the first message of the (n+1)th random access process.

[0339] For the specific description of the processes and steps executed by the above-mentioned device 1100, please refer to the relevant description of the processes and steps executed by the first terminal device in the above method 800, which will not be repeated here.

[0340] In another possible implementation, the apparatus 1100 is used to execute each process and step corresponding to the first terminal device in the above method.

[0341] The transceiver 1120 is used to: send a first message (i.e., message 1) of the nth random access process;

[0342] The processor 1110 is configured to: start a timer after sending a first message of an nth random access process;

[0343] The transceiver 1120 is further configured to: if the second message sent by the source satellite in response to the first message of the nth random access process is not received within the duration of the timer, send the first message of the n+1th random access process after the timer times out;

[0344] The processor 1110 is further configured to: after sending the first message of the (n+1)th random access process, restart the timer;

[0345] The transceiver 1120 is also used to: receive a second message sent by the target satellite in response to the first message of the n+1th random access process within the duration of the timer that is restarted again, and the second message of the n+1th random access process includes scheduling information for indicating uplink resources of the third message (i.e., message 3).

[0346] For the specific description of the processes and steps executed by the above-mentioned device 1100, please refer to the relevant description of the processes and steps executed by the first terminal device in the above method 900, which will not be repeated here.

[0347] It should be understood that the device 1100 can be specifically a terminal device, a source satellite or a target satellite in the above-mentioned embodiment, and can be used to execute the various steps and / or processes corresponding to the terminal device, the source satellite or the target satellite in the above-mentioned method embodiment. Optionally, the memory 1130 may include a read-only memory and a random access memory, and provide instructions and data to the processor. A portion of the memory may also include a non-volatile random access memory. For example, the memory may also store information about the device type. The processor 1110 may be used to execute instructions stored in the memory, and when the processor 1110 executes instructions stored in the memory, the processor 1110 is used to execute the various steps and / or processes of the above-mentioned method embodiment corresponding to the satellite, the source satellite or the target satellite.

[0348] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0349] In the several embodiments provided in the present application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the embodiments of the terminal device described above are only schematic. For example, the division of the modules is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interfaces, devices or units, which can be electrical, mechanical or other forms.

[0350] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0351] In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit.

[0352] It should be understood that in the various embodiments of the present application, the size of the serial number of each process does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0353] In addition, the term "and / or" in this article is only a description of the association relationship of the associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0354] If the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application can be essentially or partly embodied in the form of a software product that contributes to the prior art. The computer software product is stored in a storage medium and includes several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the methods described in the various embodiments of the present application. The aforementioned storage media include: various media that can store program codes, such as USB flash drives, mobile hard disks, read-only memories (ROM), random access memories (RAM), magnetic disks or optical disks.

[0355] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims. In short, the above is only a preferred embodiment of the technical solution of the present application, and is not used to limit the protection scope of the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A method for switching a satellite base station, characterized in that: In a target satellite of a satellite system, the satellite system includes a plurality of low earth orbit (LEO) satellites, the plurality of LEO satellites include a source satellite and the target satellite, the source satellite is a satellite currently serving a first cell, and the target satellite is a satellite switched from the source satellite to serve the first cell, the method includes: receiving first information sent by the source satellite, the first information including security information, context information and cell configuration information of the first cell, the context information including context information of a terminal device in a radio resource control (RRC) inactive state in the first cell; Performing configuration on the target satellite according to the first information; In the process of the target satellite serving the first cell, small uplink data sent by the terminal device in the RRC inactive state in the first cell is received.

2. The method according to claim 1, characterized in that The security information includes a security key of the control plane and a security key of the user plane.

3. The method according to claim 2, characterized in that The receiving first information sent by the source satellite, wherein the first information includes security information, comprises: Receive the security information encrypted by the source satellite using a public key encryption algorithm.

4. The method according to any one of claims 1 to 3, characterized in that Before receiving the first information sent by the source satellite, the method further includes: receiving a satellite data synchronization request sent by the source satellite, wherein the satellite data synchronization request is used to indicate that the source satellite is about to send data; In response to the satellite data synchronization request, satellite data synchronization confirmation information is sent to the source satellite, where the satellite data synchronization confirmation information is used to instruct the target satellite to confirm receiving the data to be sent by the source satellite.

5. The method according to any one of claims 1 to 4, characterized in that After receiving the first information sent by the source satellite and before receiving the uplink small data sent by the terminal device in the RRC inactive state in the first cell while the target satellite is serving the first cell, the method further includes: Receive satellite data synchronization completion information sent by the source satellite.

6. The method according to any one of claims 1 to 5, characterized in that The receiving, during the process in which the target satellite serves the first cell, small uplink data sent by the terminal device in the RRC inactive state in the first cell, includes: In the process of the target satellite serving the first cell, a third message of a random access process sent by the terminal device in an RRC inactive state is received, and the third message includes the uplink small data.

7. The method according to claim 6, characterized in that The method further comprises: In response to the third message, a fourth message of the random access process is sent to the terminal device, the fourth message including RRC release information carrying a suspension indication, and the suspension indication is used to indicate that the terminal device is in an RRC inactive state.

8. The method according to claim 6 or 7, characterized in that: The third message also includes an RRC recovery request.

9. The method according to any one of claims 1 to 8, characterized in that The multiple LEO satellites cover the cells based on the coverage manner of the earth gazing cells.

10. A method for switching a satellite base station, characterized in that: In a source satellite of a satellite system, the satellite system includes a plurality of low earth orbit (LEO) satellites, the plurality of LEO satellites include the source satellite and a target satellite, the source satellite is a satellite currently serving a first cell, and the target satellite is a satellite switched from the source satellite to serve the first cell, the method includes: Determining that a satellite serving the first cell needs to be switched from the source satellite to the target satellite; Sending first information to the target satellite, the first information including security information, context information, and cell configuration information of the first cell, the context information including context information of a terminal device in a radio resource control (RRC) inactive state in the first cell; Stop serving the first cell.

11. The method according to claim 10, characterized in that The security information includes a security key of the control plane and a security key of the user plane.

12. The method according to claim 11, characterized in that The sending of first information to the target satellite, wherein the first information includes safety information, comprises: The security information encrypted by the source satellite using a public key encryption algorithm is sent to the target satellite.

13. The method according to any one of claims 10 to 12, characterized in that Before stopping serving the first cell, the method further includes: Receiving a first message of a random access process sent by the terminal device in an RRC inactive state in the first cell; In response to the first message, a second message of the random access process is sent to the terminal device, and the second message does not include scheduling information for indicating uplink resources of the third message.

14. The method according to claim 13, characterized in that The first message is a random access request including a preamble, and the second message is a random access response.

15. The method according to any one of claims 10 to 14, characterized in that After determining that the satellite serving the first cell needs to be switched from the source satellite to the target satellite and before sending the first information to the target satellite, the method further includes: Sending a satellite data synchronization request to the target satellite, wherein the satellite data synchronization request is used to indicate that the source satellite is about to send data; Satellite data synchronization confirmation information is received from the target satellite in response to the satellite data synchronization request, where the satellite data synchronization confirmation information is used to indicate that the target satellite confirms receiving the data to be sent by the source satellite.

16. The method according to any one of claims 10 to 15, characterized in that After sending the first information to the target satellite, the method further includes: Send satellite data synchronization completion information to the target satellite.

17. The method according to any one of claims 10 to 16, characterized in that The determining that the satellite serving the first cell needs to be switched from the source satellite to the target satellite includes: According to the ephemeris information, it is determined that the satellite serving the first cell needs to be switched from the source satellite to the target satellite.

18. The method according to any one of claims 10 to 17, characterized in that The multiple LEO satellites cover the cells based on the coverage manner of the earth gazing cells.

19. A method for switching a satellite base station, characterized in that: Applied to a terminal device in an RRC inactive state, the terminal device is used to communicate with a satellite in a satellite system, the satellite system includes multiple LEO satellites, the multiple LEO satellites include a source satellite and a target satellite, the source satellite is a satellite currently serving a first cell, the target satellite is a satellite switched from the source satellite to serve the first cell, the terminal device is located in the first cell, and the method includes: Sending a first message of an nth random access process, where n is an integer greater than or equal to 1; receiving a second message sent by the source satellite in response to the first message of the nth random access process, wherein the second message of the nth random access process does not include scheduling information for indicating uplink resources of a third message; After receiving the second message of the nth random access process, starting a timer; After the timer times out, sending a first message of the (n+1)th random access process; A second message sent by the target satellite in response to the first message of the (n+1)th random access process is received.

20. The method according to claim 19, characterized in that The second message of the (n+1)th random access process includes scheduling information for indicating uplink resources of the third message; And, the method further comprises: According to the uplink resources indicated by the scheduling information in the second message of the n+1th random access process, a third message of the n+1th random access process is sent, and the third message of the n+1th random access process includes uplink small data.

21. The method according to claim 20, characterized in that The method further comprises: Receive a fourth message sent by the target satellite in response to the third message of the n+1th random access process, wherein the fourth message includes RRC release information carrying a suspension indication, and the suspension indication is used to indicate that the terminal device is in an RRC inactive state.

22. The method according to any one of claims 19 to 21, characterized in that The first message is a random access request including a preamble, and the second message is a random access response.

23. A method for switching a satellite base station, characterized in that: Applied to a terminal device in an RRC inactive state, the terminal device is used to communicate with a satellite in a satellite system, the satellite system includes multiple LEO satellites, the multiple LEO satellites include a source satellite and a target satellite, the source satellite is a satellite currently serving a first cell, the target satellite is a satellite switched from the source satellite to serve the first cell, the terminal device is located in the first cell, and the method includes: Sending a first message of an nth random access process, where n is an integer greater than or equal to 1; After sending the first message of the nth random access process, starting a timer; In the case where the second message sent by the source satellite in response to the first message of the nth random access process is not received within the duration of the timer, after the timer times out, the first message of the (n+1)th random access process is sent; After sending the first message of the (n+1)th random access process, starting the timer again; A second message sent by the target satellite in response to the first message of the n+1th random access process is received within the duration of the timer that is restarted again, wherein the second message of the n+1th random access process includes scheduling information for indicating uplink resources of a third message.

24. The method according to claim 23, characterized in that The method further comprises: According to the uplink resources indicated by the scheduling information in the second message of the n+1th random access process, a third message of the n+1th random access process is sent, and the third message of the n+1th random access process includes uplink small data.

25. The method according to claim 24, characterized in that The method also includes: receiving a fourth message sent by the target satellite in response to the third message of the n+1th random access process, the fourth message including RRC release information carrying a suspension indication, and the suspension indication is used to indicate that the terminal device is in an RRC inactive state.

26. The method according to any one of claims 23 to 25, characterized in that The first message is a random access request including a preamble, and the second message is a random access response.

27. A method for switching a satellite base station, characterized in that: Applied to a communication system including a terminal device and a satellite system in a radio resource control (RRC) inactive state, the satellite system including a plurality of low earth orbit (LEO) satellites, the plurality of LEO satellites including a source satellite and a target satellite, the source satellite being a satellite currently serving a first cell, the target satellite being a satellite to which the source satellite is switched and which will serve the first cell, the terminal device in the RRC inactive state being located in the first cell, the method comprising: The source satellite determines that the satellite serving the first cell needs to be switched from the source satellite to the target satellite; The source satellite sends first information to the target satellite, where the first information includes security information, context information, and cell configuration information of the first cell, and the context information includes context information of the terminal device in an RRC inactive state in the first cell; The target satellite is configured on the target satellite according to the first information; When the target satellite serves the first cell, the target satellite receives small uplink data sent by the terminal device in an RRC inactive state.

28. The method according to claim 27, characterized in that The receiving, by the target satellite, uplink small data sent by the terminal device in an RRC inactive state during the process of the target satellite serving the first cell includes: During the process of the target satellite serving the first cell, the target satellite receives a third message of a random access process sent by the terminal device in an RRC inactive state, wherein the third message includes the uplink small data.

29. The method according to claim 28, characterized in that Before the source satellite stops serving the first cell, the method further includes: The terminal device in the RRC inactive state sends a first message of the nth random access process, where n is an integer greater than or equal to 1; In response to the first message of the nth random access process, the source satellite sends a second message of the nth random access process to the terminal device, wherein the second message of the nth random access process does not include scheduling information for indicating uplink resources of a third message; After receiving the second message of the nth random access process, the terminal device starts a timer; After the timer times out, the terminal device sends a first message of the (n+1)th random access process; In the process of the target satellite serving the first cell, in response to the first message of the n+1th random access process, the target satellite sends a second message of the n+1th random access process to the terminal device, wherein the second message of the n+1th random access process includes scheduling information for indicating uplink resources of a third message; The terminal device sends a third message of the n+1th random access process according to the uplink resource indicated by the scheduling information of the n+1th random access process, wherein the third message of the n+1th random access process includes the uplink small data; and the target satellite receives, during the process in which the target satellite serves the first cell, the third message sent by the terminal device in an RRC inactive state, comprising: During the process of the target satellite serving the first cell, the target satellite receives a third message of the (n+1)th random access process sent by the terminal device.

30. The method according to claim 28, characterized in that Before the source satellite stops serving the first cell, the method further includes: The terminal device in the RRC inactive state sends a first message of the nth random access process, where n is an integer greater than or equal to 1; After sending the first message of the nth random access process, the terminal device starts a timer; In the case where the second message sent by the source satellite in response to the first message of the nth random access process is not received within the duration of the timer, after the timer times out, the terminal device sends the first message of the (n+1)th random access process; After sending the first message of the (n+1)th random access process, the terminal device starts the timer again; In the process of the target satellite serving the first cell, in response to the first message of the n+1th random access process, the target satellite sends a second message of the n+1th random access process to the terminal device, wherein the second message of the n+1th random access process includes scheduling information for indicating uplink resources of a third message; In the case where the second message of the n+1th random access process sent by the target satellite is received within the duration of the timer that is started again, the terminal device sends a third message of the n+1th random access process according to the uplink resources indicated by the scheduling information in the second message of the n+1th random access process, wherein the third message of the n+1th random access process includes the uplink small data; and The receiving, by the target satellite, a third message sent by the terminal device in an RRC inactive state during the process in which the target satellite serves the first cell includes: During the process of the target satellite serving the first cell, the target satellite receives a third message of the (n+1)th random access process sent by the terminal device.

31. A device for switching a satellite base station, characterized in that: include: Memory, for storing computer instructions; A processor, configured to call computer instructions stored in the memory to execute a method according to any one of claims 1 to 9, or any one of claims 10 to 18, or any one of claims 19 to 22, or any one of claims 23 to 26.

32. A computer-readable storage medium, characterized in that: Used to store computer instructions, the computer instructions are used to implement the method of any one of claims 1 to 9, or any one of claims 10 to 18, or any one of claims 19 to 22, or any one of claims 23 to 26.

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