WO2020164492A1 - 切换方法及装置 - Google Patents

切换方法及装置 Download PDF

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Publication number
WO2020164492A1
WO2020164492A1 PCT/CN2020/074778 CN2020074778W WO2020164492A1 WO 2020164492 A1 WO2020164492 A1 WO 2020164492A1 CN 2020074778 W CN2020074778 W CN 2020074778W WO 2020164492 A1 WO2020164492 A1 WO 2020164492A1
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WO
WIPO (PCT)
Prior art keywords
base station
air base
network device
air
request message
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Application number
PCT/CN2020/074778
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English (en)
French (fr)
Inventor
刘琼
晋英豪
谭巍
赖宁格菲利普
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华为技术有限公司
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Publication of WO2020164492A1 publication Critical patent/WO2020164492A1/zh

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/0005—Control or signalling for completing the hand-off
    • H04W36/0011—Control or signalling for completing the hand-off for data sessions of end-to-end connection
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/14—Relay systems
    • H04B7/15—Active relay systems
    • H04B7/185—Space-based or airborne stations; Stations for satellite systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/14—Relay systems
    • H04B7/15—Active relay systems
    • H04B7/185—Space-based or airborne stations; Stations for satellite systems
    • H04B7/1851—Systems using a satellite or space-based relay
    • H04B7/18517—Transmission equipment in earth stations
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/0005—Control or signalling for completing the hand-off
    • H04W36/0083—Determination of parameters used for hand-off, e.g. generation or modification of neighbour cell lists
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W48/00—Access restriction; Network selection; Access point selection
    • H04W48/16—Discovering, processing access restriction or access information
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W48/00—Access restriction; Network selection; Access point selection
    • H04W48/18—Selecting a network or a communication service

Definitions

  • This application relates to the field of communication technology, and in particular to a handover method and device.
  • NTN non-terrestrial networks
  • the NTN solution is to use air base stations to provide users with communication services.
  • the air base station refers to the base station carried on air platforms such as airplanes, hot air balloons, satellites, airships, and drones.
  • the 5G communication network adopts the NTN solution, which can provide network coverage in the inaccessible oceans, deserts, deep mountains, and polar regions to meet the ubiquitous business needs of users.
  • the present application provides a handover method and device, which are used to solve the problem of how an aerial base station switches networks during movement.
  • a handover method including: an air base station sends a first request message to a target network device, where the first request message is used to request the establishment of an interface between the air base station and the target network device.
  • the air base station receives a first response message from the target network device, and the first response message is used to respond to the first request message.
  • the air base station triggers the target network device to establish an interface with the air base station by sending the first request message to realize the network handover of the air base station.
  • the first request message includes at least one of air platform type, mobile type, and air platform information.
  • the air platform information includes at least one of orbit information, capability information, and altitude information.
  • the target network device performs targeted management of the air base station according to the air platform type, movement type, orbit information, capability information, or altitude information carried in the first request message to ensure that the air base station is switched from the source network device After reaching the target network equipment, the base station in the air can communicate with the ground normally.
  • the type of aerial platform is used to indicate the type of aerial platform carrying the aerial base station.
  • the aerial platform type includes: geostationary earth orbit (GEO) satellite, low earth orbit (LEO) satellite, medium Earth orbit (medium earth orbit, MEO) satellites, and high altitude platform (HAPS). Because different types of aerial platforms have different heights and transmission delays, as well as different networking forms. Therefore, the target network device can perform targeted quality of service (QoS) management and other operations on the air base station according to the type of the air platform carrying the air base station.
  • QoS quality of service
  • the movement type is used to indicate whether the base station in the air is in motion. It can be understood that, for terminal location management and paging, terminal handover processing, and other procedures, the processing procedure of a base station in a moving state is different from that of a stationary base station.
  • the core network needs to perform more management on base stations in motion. For example, the core network performs access and mobility management function (AMF) dynamic connection management for base stations in motion. Therefore, the target network device knows whether the base station in the air is in motion according to the movement type, so that the target network device can manage the base station in the air more effectively.
  • AMF access and mobility management function
  • the orbit information is used for the ground station to determine the overhead time of the base station in the air. Therefore, the target network device can determine the time for maintaining communication between the air base station and the target network device according to the overhead time of the air base station at the target ground station.
  • the capability information is used to determine the coverage of the base station in the air, and the capability information may include tilt angle, transmit power, etc. Therefore, the target network device can perform more effective tracking area code (TAC) management and user paging processing on the air base station according to the coverage of the air base station.
  • TAC tracking area code
  • the height information is used to indicate the height of the aerial platform from the ground.
  • the height information can be used to determine the coverage of the aerial base station, the transmission delay between the aerial base station and the ground station, the operating speed of the aerial platform, or the operating trajectory of the aerial platform. Therefore, the target network device can perform QoS management on the air base station according to the transmission delay between the air base station and the ground station. Alternatively, the target network device can determine the ephemeris corresponding to the air base station according to the operating trajectory of the air platform.
  • the air base station sending the first request message to the target network device includes: the air base station sends the first request message to the target network device through the target ground station.
  • the air base station sending the first request message to the target network device includes: the air base station sends the first request message to the target network device at a first preset time, and the first preset time is determined according to the ephemeris; Alternatively, the first preset time is determined according to the movement trajectory of the air base station; or, the first preset time is determined according to the overhead time of the air base station at the target ground station; or, the first preset time is determined according to the first timer. It is understandable that the air base station sends the first request message at the first preset time, which can simplify the handover process and reduce the complexity.
  • the method before the air base station sends the first request message to the target network device, the method further includes: the air base station receives a first instruction message from the source network device, the first instruction message is used to instruct the establishment of the air base station The interface with the target network device. Based on this design, whether the air base station performs network handover is determined by the source network device, which is beneficial to the management of the air base station by the network side.
  • the method before the air base station sends the first request message to the target network device, the method further includes: the air base station receives a transmission link establishment indication message, where the transmission link establishment success indication message is used to indicate the air base station The transmission link with the target ground station has been established. It can be understood that when the air base station receives the transmission link establishment instruction message, it indicates that the air base station and the target network device have normal communication conditions. Therefore, the air base station sends the first request message to the target network device to establish an interface between the air base station and the target network device, thereby ensuring normal communication between the air base station and the ground.
  • the air base station sends the first request message to the target network device, including: if the signal strength of the wireless signal between the target ground station and the air base station meets a preset condition, the air base station sends the target ground station to the target The network device sends the first request message. It is understandable that the signal strength of the wireless signal between the target ground station and the air base station meets the preset condition, which can ensure the communication quality between the air base station and the target network device. Therefore, after an interface is established between the air base station and the target network device, the air base station and the target network device can communicate normally.
  • the preset condition includes one of the following situations: (1) The signal strength of the wireless signal between the target ground station and the air base station is greater than or equal to the first preset value; (2) the target ground station and the air base station The signal strength of the wireless signal between the base stations is greater than the signal strength of the wireless signal between the source ground station and the air base station.
  • the method further includes: the air base station sends a second request message to the source network device, where the second request message is used to request to release the interface between the source network device and the air base station. Based on this design, the air base station sends a second request message to release the interface between the source network device and the air base station, which is beneficial to saving interface resources on the network side.
  • the second request message includes at least one of the following parameters: information of the air base station, release type, and reconstruction period.
  • the re-establishment period is used to indicate the time for the source network device to re-establish the interface with the air base station;
  • the shown release types include: the first type, the second type and the third type; the first type is used to indicate the deletion of the context information of the air base station;
  • the second type is used to indicate the context information of deactivating the air base station;
  • the third type is used to indicate the context information of deactivating the air base station, and the context information of the air base station is activated at the time indicated by the reconstruction period.
  • the release type is the second type or the third type
  • the context information of the air base station is not deleted. Therefore, when the air base station next establishes an interface with the source network device, there is no need to exchange the context information of the air base station between the air base station and the source network device. In this way, it is beneficial to reduce signaling overhead and improve the efficiency of establishing an interface between the air base station and the source network device.
  • the source network device activates the context information of the air base station at the time indicated by the reconstruction period, so as to realize the establishment of an interface between the air base station and the source network device.
  • the air base station does not need to send signaling to trigger the source network device to establish an interface with the air base station, which is beneficial to reduce signaling overhead.
  • the air base station sending the second request message to the source network device includes: the air base station sends the second request message to the source network device through the source ground station.
  • the aerial base station sending the second request message to the source network device includes: the aerial base station sends the second request message to the source network device at a second preset time, and the second preset time is determined according to the ephemeris; Or, the second preset time is determined according to the movement trajectory of the air base station; or, the second preset time is determined according to the overhead time of the air base station at the source ground station; or, the second preset time is determined according to a second timer.
  • the air base station before the air base station sends the second request message to the source network device, it further includes: the air base station receives a second instruction message sent from the source network device, and the second instruction message is used to instruct to release the air base station and The interface between source network devices. Based on this design, whether the air base station releases the interface with the source network device is determined by the source network device, which is conducive to the management of the air base station on the network side.
  • the method before the air base station sends the second request message to the source network device, the method further includes: the air base station receives a transmission link pre-deletion indication message.
  • the transmission link pre-deletion indication message is used to indicate that the transmission link between the air base station and the source ground station is to be deleted. It can be understood that when the air base station receives the transmission link pre-deletion indication message, the transmission link between the air base station and the source ground station is to be deleted, indicating that the air base station and the source ground station will not be able to communicate normally, and the air The base station and the source network device will soon fail to communicate normally. Therefore, the air base station sends a second request message to the source network device to implement network handover.
  • the air base station sends the second request message to the source network device, including: if the signal strength of the wireless signal between the source ground station and the air base station is less than the second preset value, the air base station passes the source ground station Send a second request message to the source network device. It is understandable that the signal strength of the wireless signal between the source ground station and the air base station is less than the second preset value, indicating that the communication quality between the air base station and the source ground station is poor. In other words, the air base station and the source network The communication quality between devices is poor. Therefore, in this case, the air base station sends a second request message to the source network device to release the interface between the source network device and the air base station to implement network switching.
  • the method further includes: the air base station sends a third request message to the target network device, and the third request message is used to request to activate the context information of the air base station.
  • the air base station does not need to exchange the context information of the air base station with the target network device, which is beneficial to saving signaling overhead.
  • the method further includes: the air base station separately determines the signal strength of the wireless signal between the n ground stations and the air base station, and n is an integer greater than 1. In this way, in the handover process, the air base station can determine whether to perform a network handover according to the signal strength of the wireless signal between the n ground stations and the air base station.
  • the method further includes: the air base station updates the ephemeris to ensure the accuracy of the ephemeris.
  • a handover method including: a target network device receives a first request message from an air base station, where the first request message is used to request the establishment of an interface between the air base station and the target network device.
  • the target network device sends a first response message to the air base station, where the first response message is used to respond to the first request message.
  • the target network device receives the first request message sent by the air base station to establish an interface with the air base station to realize the network handover of the air base station.
  • the first request message includes at least one of air platform type, movement type, and air platform information
  • the air platform information includes at least one of orbit information, capability information, and altitude information.
  • the target network device performs targeted management of the air base station according to the air platform type, movement type, orbit information, capability information, or altitude information carried in the first request message to ensure that the air base station is switched from the source network device After reaching the target network equipment, the base station in the air can communicate with the ground normally.
  • the aerial platform type is used to indicate the aerial platform type carrying the aerial base station, the aerial platform type includes: GEO satellite, LEO satellite, MEO satellite, and HAPS. It is understandable that different types of aerial platforms have different heights and transmission delays, as well as different networking forms. Therefore, the target network device can perform targeted QoS management and other operations on the air base station according to the type of the air platform carrying the air base station.
  • the movement type is used to indicate whether the base station in the air is in motion. It is understandable that, with regard to processes such as terminal location management, paging, and terminal handover processing, the processing process of a base station in a moving state is different from that of a stationary base station.
  • the core network needs to perform more management on base stations that are in motion. For example, the core network performs AMF dynamic connection management on base stations that are in motion. Therefore, the target network device knows whether the base station in the air is in motion according to the movement type, so that the target network device can manage the base station in the air more effectively.
  • the orbit information is used for the ground station to determine the overhead time of the base station in the air. Therefore, the target network device can determine the time for maintaining communication between the air base station and the target network device according to the overhead time of the air base station at the target ground station.
  • the capability information is used to determine the coverage of the base station in the air, and the capability information may include tilt angle, transmit power, etc. Therefore, the target network device can perform more effective TAC management and user paging processing on the air base station according to the coverage of the air base station.
  • the height information is used to indicate the height of the aerial platform from the ground.
  • the height information can be used to determine the coverage of the aerial base station, the transmission delay between the aerial base station and the ground station, the operating speed of the aerial platform, or the operating trajectory of the aerial platform. Therefore, the target network device can perform QoS management on the air base station according to the transmission delay between the air base station and the ground station. Alternatively, the target network device can determine the ephemeris corresponding to the air base station according to the operating trajectory of the air platform.
  • the target network device receives the first request message and establishes an interface with the air base station.
  • the target network device can provide better services for the air base station after establishing an interface with the air base station according to the information carried in the first request message, so as to ensure normal communication between the air base station and the ground.
  • the target network device receiving the first request message from the air base station includes: the target network device receives the first request message from the air base station through the target ground station.
  • the method further includes: the target network device receives a third request message sent from the air base station, the third request message is used to request to activate the context information of the air base station; the target network device sends the third request message to the air base station Response message, the third response message is used to respond to the third request message.
  • the target network device receives a third request message sent from the air base station, the third request message is used to request to activate the context information of the air base station; the target network device sends the third request message to the air base station Response message, the third response message is used to respond to the third request message.
  • the target network device receiving the third request message sent from the air base station includes: the target network device receives the third request message sent from the air base station through the target ground station.
  • a handover method including: a source network device receives a second request message from an over-the-air base station, the second request message is used to request to release an interface between the source network device and the over-the-air base station; The base station sends a second response message, and the second response message is used to respond to the second request message. It is understandable that the source network device receives the second request message from the air base station and releases the interface between the source network device and the air base station, which is beneficial to save the interface resources on the network side and realize the network handover of the air base station.
  • the second request message includes at least one of the following parameters: information of the air base station, release type, and reconstruction period.
  • the re-establishment period is used to indicate the time for the source network device to re-establish the interface with the air base station;
  • the indicated release types include: the first type, the second type and the third type.
  • the first type is used to indicate the deletion of the context information of the air base station;
  • the second type is used to indicate the context information of the air base station to be deactivated;
  • the third type is used to indicate the context information of the air base station to be deactivated, and is activated at the time indicated by the reconstruction period Context information of the air base station.
  • the release type is the second type or the third type
  • the context information of the air base station is not deleted. Therefore, when the air base station next establishes an interface with the source network device, there is no need to exchange the context information of the air base station between the air base station and the source network device. In this way, it is beneficial to reduce signaling overhead and improve the efficiency of establishing an interface between the air base station and the source network device.
  • the source network device activates the context information of the air base station at the time indicated by the reconstruction period, so as to realize the establishment of an interface between the air base station and the source network device. In this way, the air base station does not need to send signaling again to trigger the source network device to establish an interface with the air base station, which helps reduce signaling overhead.
  • the method before the source network device receives the second request message from the air base station, the method further includes: the source network device sends a second instruction message to the air base station, and the second instruction message is used to instruct to release the air base station The interface with the source network device.
  • the source network device sends the second indication message to the air base station, including: if the signal strength of the wireless signal between the source ground station and the air base station is less than the second preset value, the source network device passes the source ground The station sends a second indication message to the air base station. It is understandable that the signal strength of the wireless signal between the source ground station and the air base station is less than the second preset value, indicating that the communication quality between the air base station and the source ground station is poor. In other words, the air base station and the source network The communication quality between devices is poor.
  • the source network device sends a second indication message to the air base station through the source ground station to trigger the air base station to execute the process of releasing the interface between the air base station and the source network device, so that the air base station realizes network connectivity Handover to ensure normal communication between the base station in the air and the ground.
  • the method further includes: the source network device sends a first instruction message to the air base station, where the first instruction message is used to instruct to establish an interface between the air base station and the target network device. It is understandable that the source network device sends the first indication message to trigger the air base station to execute the process of establishing an interface between the air base station and the target network device, so that the air base station can switch from the source network device to the target network device, thereby ensuring Normal communication between air base stations and the ground.
  • the source network device sends the first indication message to the air base station, including: if the signal strength of the wireless signal between the target ground station and the air base station meets a preset condition, the source network device sends The air base station sends the first indication message.
  • the preset condition includes one of the following situations: (1) The signal strength of the wireless signal between the target ground station and the air base station is greater than or equal to the first preset value; (2) the target ground station and the air base station The signal strength of the wireless signal between the base stations is greater than the signal strength of the wireless signal between the source ground station and the air base station.
  • an air base station including: a sending module, a receiving module, and a processing module.
  • the air base station is used to execute the handover method described in the first aspect.
  • an air base station including: a processor and a memory, the processor is configured to read instructions in the memory, and implement the handover method as described in the first aspect above according to the instructions.
  • a computer-readable storage medium stores instructions that, when run on a communication device, enable the communication device to execute the switching method described in the first aspect.
  • a computer program product containing instructions which when running on a communication device, enables the communication device to execute the handover method described in the first aspect.
  • a chip in an eighth aspect, includes a processing module and a communication interface.
  • the communication interface is used to receive input signals and provide them to the processing module, and/or output signals generated by the processing module; the processing module is used to execute The handover method described in the first aspect above.
  • the processing module may execute code instructions to execute the switching method described in the first aspect.
  • the code instruction can come from the internal memory of the chip or the external memory of the chip.
  • the processing module may be a processor, microprocessor, or integrated circuit integrated on the chip.
  • the communication interface can be an input/output circuit or transceiver pins on the chip.
  • the technical effects brought about by any one of the four aspects to the eighth aspect can refer to the beneficial effects of the corresponding method provided above and the technical effects brought about by the design method, which will not be repeated here.
  • a target network device including: a receiving module and a sending module. Wherein, the target network device is used to execute the handover method described in the second aspect.
  • a target network device including: a processor and a memory, where the processor is used to read instructions in the memory and implement the switching method according to the second aspect according to the instructions.
  • a computer-readable storage medium stores instructions that, when run on a communication device, enable the communication device to execute the switching method described in the second aspect.
  • a computer program product containing instructions which when running on a communication device, enables the communication device to execute the switching method described in the second aspect.
  • a chip in a thirteenth aspect, includes a processing module and a communication interface.
  • the communication interface is used to receive an input signal and provide it to the processing module, and/or to output a signal generated by the processing module; the processing module is used to Perform the handover method described in the second aspect above.
  • the processing module may execute code instructions to execute the switching method described in the second aspect.
  • the code instruction can come from the internal memory of the chip or the external memory of the chip.
  • the processing module may be a processor, microprocessor, or integrated circuit integrated on the chip.
  • the communication interface can be an input/output circuit or transceiver pins on the chip.
  • the technical effects brought by any of the ninth aspect to the thirteenth aspect can refer to the beneficial effects of the corresponding method provided above and the technical effects brought about by the design method. Repeat.
  • a source network device including: a receiving module, a processing module, and a sending module. Wherein, the source network device is used to execute the handover method described in the third aspect.
  • a source network device including: a processor and a memory, where the processor is used to read instructions in the memory and implement the switching method according to the third aspect according to the instructions.
  • a computer-readable storage medium stores instructions that, when run on a communication device, enable the communication device to execute the switching method described in the third aspect.
  • a computer program product containing instructions which when running on a communication device, enables the communication device to execute the switching method described in the third aspect.
  • a chip in an eighteenth aspect, includes a processing module and a communication interface.
  • the communication interface is used to receive input signals and provide them to the processing module, and/or to output signals generated by the processing module; the processing module is used to Perform the handover method described in the third aspect.
  • the processing module may execute code instructions to execute the switching method described in the third aspect.
  • the code instruction can come from the internal memory of the chip or the external memory of the chip.
  • the processing module may be a processor, microprocessor, or integrated circuit integrated on the chip.
  • the communication interface can be an input/output circuit or transceiver pins on the chip.
  • a communication system including: an air base station, a target network device, and a source network device.
  • the air base station is used to perform the handover method described in the first aspect
  • the target network device is used to perform the handover method described in the second aspect
  • the source network device is used to perform the handover method described in the third aspect.
  • FIG. 1 is a schematic diagram of the architecture of a communication system provided by an embodiment of the application
  • FIG. 2 is a schematic diagram of a centralized node (centralized unit, CU)-distributed unit (DU) architecture provided by an embodiment of the application;
  • FIG. 3 is a schematic diagram 1 of an NTN architecture provided by an embodiment of this application.
  • FIG. 4 is a second schematic diagram of an NTN architecture provided by an embodiment of this application.
  • FIG. 5 is a third schematic diagram of an NTN architecture provided by an embodiment of this application.
  • FIG. 6 is a schematic diagram of overhead of an aerial base station provided by an embodiment of this application.
  • FIG. 7 is a schematic diagram of movement of an aerial base station provided by an embodiment of the application.
  • FIG. 8 is a schematic diagram of the movement of an aerial base station provided by an embodiment of this application.
  • FIG. 9 is a first flowchart of a handover method provided by an embodiment of this application.
  • FIG. 10 is a second flowchart of a handover method provided by an embodiment of this application.
  • FIG. 11 is a third flowchart of a handover method provided by an embodiment of this application.
  • FIG. 12 is a fourth flowchart of a handover method provided by an embodiment of this application.
  • FIG. 13 is a fifth flowchart of a handover method provided by an embodiment of this application.
  • FIG. 14 is a sixth flowchart of a handover method provided by an embodiment of this application.
  • FIG. 15 is a seventh flowchart of a handover method provided by an embodiment of this application.
  • FIG. 16 is a flowchart eight of a handover method provided by an embodiment of this application.
  • FIG. 17 is a ninth flowchart of a handover method provided by an embodiment of this application.
  • FIG. 18 is a schematic structural diagram of an aerial base station provided by an embodiment of this application.
  • FIG. 19 is a schematic structural diagram of a target network device provided by an embodiment of this application.
  • 20 is a schematic structural diagram of a source network device provided by an embodiment of this application.
  • FIG. 21 is a schematic structural diagram of a communication device provided by an embodiment of this application.
  • FIG. 1 is a schematic diagram of the architecture of a communication system provided by an embodiment of this application. As shown in Figure 1, the communication system includes terminals, access network equipment and core networks.
  • the terminal is used to provide users with voice and/or data connectivity services.
  • the terminal may have different names, such as user equipment (UE), access terminal, terminal unit, terminal station, mobile station, mobile station, remote station, remote terminal, mobile equipment, wireless communication equipment, terminal agent Or terminal devices, etc.
  • the terminal may be various handheld devices, vehicle-mounted devices, wearable devices, and computers with communication functions, which are not limited in the embodiment of the present application.
  • the handheld device may be a smart phone or a virtual reality (VR) device.
  • the vehicle-mounted device may be a vehicle-mounted navigation system.
  • the wearable device may be a smart bracelet.
  • the computer can be a personal digital assistant (PDA) computer, a tablet computer, and a laptop computer.
  • PDA personal digital assistant
  • the access network device can be an access point for wireless communication or wired communication, such as a base station or base station controller, an access point or wifi controller for wireless fidelity (wireless-fidelity, wifi), or an access for fixed network access Wait.
  • the base station may include various types of base stations, such as micro base stations (also referred to as small stations), macro base stations, relay stations, access points, etc., which are not specifically limited in the embodiment of the present application.
  • the base station may be a base station (BTS) in the global system for mobile communication (GSM), code division multiple access (CDMA), and broadband
  • BTS base station
  • GSM global system for mobile communication
  • CDMA code division multiple access
  • WCDMA wideband code division multiple access
  • eNB or e-NodeB evolutional node B
  • LTE long term evolution
  • eNB Internet of Things
  • NB-IoT narrowband-internet of things
  • PLMN public land mobile network
  • the core network includes various core network devices, such as AMF, user plane function (UPF), session management function (SMF), and so on.
  • AMF user plane function
  • UPF user plane function
  • SMF session management function
  • AMF is a core network entity and is mainly responsible for the mobility management processing part, such as: access control, mobility management, attach and detach, and SMF selection functions.
  • the AMF provides services for the session in the terminal, it provides storage resources of the control plane for the session to store the session identifier, the SMF identifier associated with the session identifier, and so on.
  • SMF is mainly used for session management, terminal Internet protocol (IP) address allocation and management, selection of end points that can manage user plane functions, policy control, or charging function interfaces, and downlink data notifications.
  • IP Internet protocol
  • UPF can be used for packet routing and forwarding, or QoS processing of user plane data.
  • User data can be connected to the data network (DN) through this network element.
  • DN data network
  • AMF Access Management Function
  • SMF Session Management Function
  • UPF User Plane Function
  • the core network device may be implemented by one device, or jointly implemented by multiple devices, or may be a functional module in one device, which is not specifically limited in the embodiment of the present application.
  • the above-mentioned functional modules may be network elements in hardware devices, software functional modules running on dedicated hardware, or virtualized functional modules instantiated on a platform (for example, a cloud platform).
  • FIG. 2 it is a schematic diagram of a CU-DU architecture provided by an embodiment of this application.
  • the gNB is composed of a CU and at least one DU.
  • part of the functions of the gNB are deployed on the CU, and another part of the functions of the gNB are deployed on the DU.
  • Multiple DUs can share the same CU to save costs.
  • CU and DU are divided into functions according to the protocol stack.
  • CU deploys the radio resource control (Radio Resource Control, RRC) layer in the protocol stack, the packet data convergence protocol (PDCP) layer, and the service data adaptation protocol (service data adaptation protocol, SDAP) layer;
  • DU is deployed with a radio link control (RLC) layer in the protocol stack, a media access control (MAC) layer, and a physical layer (PHY).
  • RRC Radio Resource Control
  • PDCP packet data convergence protocol
  • SDAP service data adaptation protocol
  • DU is deployed with a radio link control
  • RLC radio link control
  • MAC media access control
  • PHY physical layer
  • the CU has the processing capabilities of RRC, PDCP and SDAP.
  • DU has processing capabilities of RLC, MAC and PHY.
  • the aforementioned interfaces are all logical interfaces.
  • the above-mentioned interfaces may also have other names, which are not limited in the embodiment of the present application.
  • the aerial platform as a satellite as an example to introduce the architecture of NTN. It is understandable that when the aerial platform is other equipment (such as a hot air balloon), the same applies to the following NTN architecture. It is understandable that the aerial platform is used to carry the aerial base station, and the aerial base station can be a complete base station or a part of the base station (for example, DU).
  • FIG. 3 it is a schematic diagram of an NTN architecture provided by an embodiment of this application.
  • the satellite does not carry a payload, and the satellite is equivalent to an analog radio frequency repeater, which is used to achieve signal frequency conversion and amplification.
  • the terminal and the satellite communicate through an interface (for example, a UU interface).
  • the satellite and the ground station communicate through an interface (such as a UU interface).
  • the ground station and the satellite form a remote radio unit (RRU).
  • RRU remote radio unit
  • base stations are deployed on the ground. Satellites, ground stations and base stations form a radio access network (Radio Access Network).
  • the base station communicates with the core network (Core Network, CN) through an interface (for example, an NG interface).
  • the CN communicates with a data network (Data Network, DN) through an interface (for example, an N6 interface).
  • Core Network Core Network
  • CN data network
  • DN data network
  • the ground station may be an NTN gateway (gateway, GW), and the NTN gateway is a transport network layer (TNL) node for implementing transparent transmission of data or signaling.
  • NTN gateway gateway, GW
  • TNL transport network layer
  • FIG. 4 it is a schematic diagram of another NTN architecture provided by an embodiment of this application.
  • the payload carried by the satellite is the base station.
  • the terminal and the satellite communicate through an interface (such as a UU interface).
  • the satellite and the ground station communicate through an interface (such as a wireless interface (Satellite Radio interface, SRI)).
  • the base station on the satellite communicates with the CN through an interface (such as an NG interface).
  • the CN and DN communicate through an interface (for example, the N6 interface).
  • FIG. 5 it is a schematic diagram of another NTN architecture provided by an embodiment of this application.
  • the DU is carried on the satellite (that is, the payload carried by the satellite is DU), and the CU is deployed on the ground.
  • a remote radio unit is formed between the satellite and the ground station, and the satellite, the ground station and the CU on the ground form a wireless access network.
  • the satellite and the terminal communicate through an interface (such as a UU interface).
  • the satellite and the ground station communicate through an interface (such as SRI), and the SRI is used to transmit the F1 interface protocol.
  • the DU and CU on the satellite communicate through an interface (for example, an F1 interface).
  • CU and CN communicate through an interface (such as an NG interface).
  • the CN and DN communicate through an interface (for example, the N6 interface).
  • the aerial platform is not limited to being in the air, but can also be on the ground.
  • the aerial platform may be a ground mobile platform.
  • the base station in the air is not limited to the air, but can also be on the ground.
  • the ground station can be replaced with a fixed location receiving node (for example, a donor base station).
  • the technical solutions provided in the embodiments of the present application are also applicable to an architecture composed of a ground mobile platform and a fixed location receiving node.
  • A/B can mean A or B.
  • the "and/or” in this article is only an association relationship describing the associated objects, which means that there can be three relationships, for example, A and/or B, which can mean: A alone exists, A and B exist at the same time, and B exists alone These three situations.
  • “at least one” means one or more
  • “plurality” means two or more. The words “first” and “second” do not limit the quantity and order of execution, and the words “first” and “second” do not limit the difference.
  • over-the-top refers to a state in which an aerial base station passes over the ground station and can communicate with the ground station.
  • the ground station when the air base station is over the top, the ground station is within the communication coverage of the air base station, and the ground station can maintain communication with the air base station.
  • the ground station is not within the communication coverage of the aerial base station, and the ground station cannot communicate with the aerial base station.
  • the over-the-top time is the period of time during which the air base station passes over the ground station and can communicate with the ground station.
  • the over-the-top time may also be referred to as the over-the-top time period, which is not limited in the embodiment of the present application.
  • the source ground station and the target ground station are two different ground stations.
  • the source ground station is the ground station that maintains communication with the air base station before handover
  • the target ground station is the ground station that maintains communication with the air base station after the handover.
  • the source network device is the network device corresponding to the source ground station.
  • the target network device is the network device corresponding to the target ground station.
  • the air base station is the base station
  • the network equipment is the core network equipment (for example, AMF).
  • the base station in the air is the DU and the network equipment is the CU.
  • the ephemeris is used to record the orbit information and position information of the aerial platform carrying the aerial base station.
  • the ephemeris stored by the air base station is specifically used to record the overhead time of the air platform carrying the air base station at multiple ground stations, the orbit period of the air platform, and the like.
  • Table 1 shows the ephemeris stored by the base station in the air. It can be seen from Table 1 that the specified period of the aerial platform is 79200 seconds.
  • the overhead time of the aerial platform is 11:13-15:13 on January 9, 2019; for the European station, the overhead time of the aerial platform is 14:50 on January 9, 2019- 18:13;
  • the overhead time of the aerial platform is 17:50-20:13 on January 9, 2019.
  • the next overhead time of the aerial platform can be determined based on the current overhead time and the orbital period of the aerial platform. For example, for the China station, the next time for the aerial platform to pass the top is January 10, 2019 9:13-13:13; for the European station, the next time for the aerial platform to pass the top is January, 2019 12:50-16:13 on the 10th; for the U.S. station, the next overhead time of the aerial platform is 15:50-18:13 on January 10, 2019.
  • the ephemeris stored in the ground station is specifically used to record the overhead time of multiple aerial platforms passing the ground station and the orbital periods of the multiple aerial platforms.
  • Table 2 shows the ephemeris stored by the ground station.
  • the overhead time of satellite #1 is 11:13-15:13, January 9, 2019, and the orbital period is 79200 seconds
  • the overhead time of satellite #2 is 14: January 9, 2019 50-18:13, the orbital period is 79200 seconds
  • the overhead time of satellite #3 is 17:50-20:13 on January 9, 2019, and the orbital period is 79200 seconds. It is understandable that the ground station can determine the next overhead time of the aerial platform according to the specified period of the aerial platform and the current overhead time of the aerial platform.
  • next topping time of satellite #1 is 9:13-13:13, January 10, 2019; the next topping time of satellite #2 is 12:10, January 10, 2019 50-16:13; Satellite #3's next top time is 15:50-18:13 on January 10, 2019.
  • the network device may store the ephemeris stored by the ground station corresponding to the network device.
  • the network device may be responsible for updating the ephemeris stored in its corresponding ground station.
  • the aerial base station moves with the non-GEO satellite.
  • the base station in the air cannot maintain communication with the same ground station.
  • the air base station communicates with ground station #1; after moving, the air base station communicates with ground station #2. This involves how the air base station performs network handover.
  • the industry has not yet proposed a corresponding solution.
  • a handover method provided in an embodiment of this application includes the following steps:
  • the air base station sends a first request message to the target network device.
  • the first request message is used to request the air base station to establish an interface with a target network device.
  • the first request message includes at least one of the following parameters: air platform type, movement type, and air platform information.
  • air platform information can also be referred to as satellite information.
  • the air platform type is used to indicate the type of the air platform carrying the air base station.
  • the types of aerial platforms include: GEO satellites, LEO satellites, MEO satellites, and HAPS.
  • the movement type is used to indicate whether the base station in the air is in motion.
  • the mobile type is used to indicate whether the base station in the air is moving or stationary.
  • the movement type can be represented by 1 bit, "0" indicates that the air base station is in a moving state, and "1" indicates that the air base station is in a stationary state.
  • the air platform information includes at least one of the following parameters: orbit information, capability information, and altitude information.
  • the orbit information is used for the ground station to determine the overhead time of the base station in the air.
  • the capability information is used to determine the coverage of the base station in the air, and the capability information may include tilt angle, transmit power, etc.
  • the height information is used to indicate the height of the aerial platform from the ground. The height information can be used to determine the coverage of the aerial base station, the transmission delay between the aerial base station and the ground station, the operating speed of the aerial platform, or the operating trajectory of the aerial platform.
  • the air base station is the base station
  • the target network device is the target core network device.
  • the target core network device may be a target AMF, and the embodiment of the present application is not limited thereto.
  • the first request message is recorded as the first request message A, and the first request message A is used to request the air base station to establish an interface with the target core network device, such as an NG interface.
  • the first request message A may be called an NG interface setup request (NG Setup Request), or other names, and the embodiment of the present application is not limited thereto.
  • the first request message A also includes any one of the following parameters: global radio access network node identifier, radio access network node name, tracking area (TA) list, and discontinuous reception (Discontinuous Reception) , DRX) cycle.
  • the tracking area list is used to indicate the tracking areas supported by the air base station.
  • the tracking area list includes: at least one tracking area information, and the tracking area information includes: TAC and at least one public land mobile network (PLMN) identifier.
  • PLMN public land mobile network
  • the maximum number of PLMN identities contained in one tracking area information may be greater than 12, for example, the maximum number of PLMN identities contained in one tracking area information is 64, which is suitable for the coverage of base stations in the air. Regional transnational and cross-regional scenarios.
  • the air base station is the DU and the target network device is the target CU.
  • the first request message is recorded as the first request message B, and the first request message B is used to request the air base station to establish an interface with the target CU, such as an F1 interface.
  • the first request message B may also be called F1 interface request (F1 setup request), or other names.
  • the embodiments of the present application are not limited to this.
  • the first request message B may also include any one of the following parameters: DU ID, DU name, serving cell list, and DU RRC version.
  • the serving cell list is used to indicate the cells supported by the DU (that is, the air base station).
  • the serving cell list includes at least one serving cell information.
  • the serving cell information may include the identity of the serving cell.
  • the air base station sends the first request message to the target network device through the target ground station. That is, the air base station sends the first request message to the target ground station; after that, the target ground station sends the first request message to the target network device.
  • the target network device sends a first response message to the air base station.
  • the first response message is used to respond to the first request message. Specifically, the first response message is used to indicate whether the interface between the air base station and the target network device is successfully established.
  • the first response message when used to indicate that the establishment of an interface between the air base station and the target network device fails, the first response message includes cause information, and the cause information is used to indicate the air The reason for the failure to establish the interface between the base station and the target network device.
  • the first response message used to respond to the first request message A may be recorded as the first response message A.
  • the first response message A is used to indicate whether the interface (for example, the NG interface) between the air base station and the target core network device is successfully established.
  • the first response message A may be called an NG interface setup response message (NG setup response), or other names, which are not limited in this embodiment of the application.
  • the first response message used to respond to the first request message B may be recorded as the first response message B.
  • the first response message B is used to indicate whether the interface (for example, the F1 interface) between the air base station and the target CU is successfully established.
  • the first response message B may be referred to as an F1 interface setup response message (F1 setup response), or another name, which is not limited in this embodiment of the application.
  • the target network device sends the first response message to the air base station through the target ground station. That is, the target network device sends a first response message to the target ground station; after that, the target ground station sends the first response message to the air base station.
  • the target network device, the target ground station, or the air base station may update the ephemeris.
  • the air base station records or updates the time at which the air base station sends the first request message to the target network device through the target ground station in the ephemeris as a reference time for the air base station to establish an interface with the target network device next time.
  • the target network device or target ground station records or updates the time when the first request message is received in the ephemeris.
  • the air base station sends a second request message to the source network device.
  • the second request message is used to request the release of the interface between the air base station and the source network device.
  • the second request message includes at least one of the following parameters: information of the air base station, release type, and reconstruction period.
  • the re-establishment period is used to indicate the time for the source network device to re-establish an interface with the air base station.
  • the release types include: the first type, the second type, and the third type.
  • the first type is used to indicate to delete the context information of the air base station.
  • the second type is used to indicate the context information of deactivating the air base station.
  • the third type is used to indicate to deactivate the context information of the air base station, and activate the context information of the air base station at the time indicated by the reconstruction period.
  • the air base station deletes the information of the source network device.
  • the release type is the second type or the third type, the air base station saves the information of the source network device.
  • the information of the source network device includes the name of the source network device, the identification of the source network device, and so on.
  • the source network device deactivates the context information of the air base station, the source network device saves the context information of the air base station.
  • the context information of the air base station includes: global radio access network node identification, radio access network node name, tracking area list, and DRX cycle. If the NTN adopts the architecture shown in Figure 5, the context information of the air base station includes: DU ID, DU name, serving cell list, and DU RRC version.
  • the second request message can be recorded as a second request message A, which is used to request the release of the NG interface between the air base station and the source core network device.
  • the second request message A may also be called an NG interface release request (NG Release Request), or another name, which is not limited in this embodiment of the application.
  • the information of the air base station includes at least one of the following: a global radio access network node identifier and a radio access network node name.
  • the air base station is the DU
  • the source network device is the source CU.
  • the second request message may be recorded as the second request message B, which is used to request the release of the interface between the air base station and the source CU, such as the F1 interface.
  • the second request message may also be called an F1 interface release request (F1 Release Request), or another name, which is not limited in the embodiment of the application.
  • the information of the air base station includes at least one of the following: DU ID and DU name.
  • S904 The source network device sends a second response message to the air base station.
  • the second response message is used to respond to the second request message. Specifically, the second response message is used to indicate whether the interface between the air base station and the source network device is successfully released.
  • the second response message may also include reason information, and the reason information is used to indicate all The reason why the interface between the air base station and the source network device fails to be released.
  • the second response message used to respond to the second request message A may be recorded as the second response message A.
  • the second response message A is used to indicate whether the interface between the air base station and the source core network device is successfully released.
  • the second response message A may be called an NG interface release response message (NG Release response), or another name, which is not limited in the embodiment of the present application.
  • the second response message used to respond to the second request message B may be recorded as the second response message B.
  • the second response message B is used to indicate whether the interface between the air base station and the source CU is successfully released.
  • the second response message B may be called an F1 interface release response message (F1 Release response), or another name, which is not limited in this embodiment of the application.
  • the source network device sends the second response message to the air base station through the source ground station. That is, the source network device sends a second response message to the source ground station; after that, the source ground station sends the second response message to the air base station.
  • the source network device, the source ground station, or the air base station may update the ephemeris.
  • the air base station records or updates the time at which the air base station sends the second request message to the source network device through the source ground station in the ephemeris as a reference time for the air base station to release the interface with the source network device next time.
  • the source network device or the source ground station records or updates the time when the second request message is received in the ephemeris.
  • the embodiment of the present application does not limit the execution sequence of steps S901-S902 and steps S903-S904. That is to say, the technical solution of the present application may first perform steps S901-S902, and then perform steps S903-S904; or, perform steps S903-S904 first, and then perform steps S901-S902; or, perform steps S901-S902 at the same time, And steps S903-S904.
  • steps S901-S902 can be replaced with steps S905-S906. It is understandable that the context information of the air base station pre-stored by the target network device may come from the previous process of establishing an interface between the air base station and the target network device.
  • the air base station sends a third request message to the target network device.
  • the third request message is used to request activation of an interface between the air base station and the target network device.
  • the third request message is used to request activation of the context information of the air base station.
  • the third request information can be recorded as the third request message A.
  • the third request message A is used to request to activate the interface between the air base station and the target core network device, such as the NG interface.
  • the third request message A may also be called an NG interface activation request (NG Resume Request), or another name, which is not limited in this embodiment of the application.
  • the third request message A includes information of an air base station, and the information of the air base station includes: a global radio access network node identifier and a radio access network node name.
  • the third request message can be recorded as the third request message B.
  • the third request message B is used to request to activate the interface between the air base station and the target CU, such as the F1 interface.
  • the third request message B may also be called an F1 interface activation request (F1 Resume Request), or another name, which is not limited in this embodiment of the application.
  • the third request message B includes the information of the air base station, and the information of the air base station includes: DU ID and DU name.
  • the signaling overhead caused by the third request message is smaller than that of the first request message.
  • the air base station sends the third request message to the target network device through the target ground station. That is, the air base station sends the third request message to the target ground station; after that, the target ground station sends the third request message to the target network device.
  • the target network device sends a third response message to the air base station.
  • the third response message is used to respond to the third request message. Specifically, the third response message is used to indicate whether the context information of the air base station is successfully activated.
  • the third response message when used to indicate that the context information activation of the air base station fails, the third response message includes cause information, and the reason information is used to indicate that the context information activation of the air base station fails. the reason.
  • the third response message used to respond to the third request message A may be recorded as the third response message A.
  • the third response message A is used to indicate whether the target core network device successfully activates the context information of the air base station.
  • the third response message A may be called an NG interface activation response message (NG Resume response), or another name, which is not limited in this embodiment of the application.
  • the third response message used to respond to the third request message B may be recorded as the third response message B.
  • the third response message B is used to indicate whether the target CU successfully activates the context information of the air base station.
  • the third response message B may be referred to as an F1 interface activation response message (F1 Resume response), or another name, which is not limited in the embodiment of the present application.
  • the target network device sends a third response message to the air base station through the target ground station. That is, the target network device sends a third response message to the target ground station; after that, the target ground station sends the first response message to the air base station.
  • the target network device, the target ground station, or the air base station may update the ephemeris.
  • the air base station records or updates the time when the air base station sends the third request message to the target network device through the target ground station in the ephemeris, as a reference time for the air base station to establish an interface with the target network device next time.
  • the target network device or the target ground station records or updates the time when the third request message is received in the ephemeris.
  • the embodiment of this application does not limit the execution order of steps S903-S904 and steps S905-S906. That is to say, the technical solution of this application can first perform steps S903-S904, and then perform steps S905-S906; or, perform steps S905-S906 first, and then perform steps S903-S904; or, perform steps S903-S904 at the same time, And steps S905-S906.
  • a handover method provided by an embodiment of this application includes the following steps:
  • the air base station respectively determines the signal strength of the wireless signal between the n ground stations and the air base station.
  • n ground stations include the source ground station, and n is an integer greater than 1.
  • the wireless signal may refer to an SRI signal or a signal to be measured.
  • the signal to be measured is a synchronization signal or a reference signal.
  • the synchronization signal may refer to a primary synchronization signal (primary synchronization signal, PSS), or a secondary synchronization signal (secondary synchronization signal, SSS), etc.
  • the reference signal may refer to a sounding reference signal (SRS), or a channel state information reference signal (CSI-RS), etc. The embodiment of the application does not specifically limit this.
  • the signal strength of the wireless signal includes any of the following parameters: reference signal receiving power (reference signal receiving power, RSRP), signal noise ratio (signal noise ratio, SNR), or signal to interference plus noise ratio ( signal to interference plus noise ratio, SINR).
  • reference signal receiving power reference signal receiving power
  • SNR signal noise ratio
  • SINR signal to interference plus noise ratio
  • step S1001 may be implemented in any one of the following manners 1 to 3. It should be noted that method one is applicable to scenarios where the wireless signal is an SRI signal, and methods two and three are applicable to scenarios where the wireless signal is a signal under test.
  • each of the n ground stations has established an SRI with the air base station.
  • Method 2 The air base station sends the signal to be measured.
  • Each of the n ground stations receives the signal to be measured and determines measurement report information, which is used to indicate the signal strength of the signal to be measured received by the ground station. After that, each of the n ground stations sends measurement report information to the air base station.
  • other ground stations among the n ground stations except the source ground station send measurement report information to the source ground station; the source ground station sends n measurement report information to the air base station.
  • the air base station receives n measurement report information, and the n measurement report information corresponds to the n ground stations one-to-one; thus, the air base station can respectively determine the signals to be measured between the n ground stations and the air base station. Signal strength.
  • the signal to be measured includes the information of the air base station, such as the identity of the air base station.
  • the air base station sends the signal to be measured at a preset time.
  • the ground station receives the signal to be measured at a preset time.
  • the preset time can be determined according to the ephemeris. In this way, the base station in the air only needs to send the signal to be tested within a certain period of time to save power consumption.
  • the ground station needs to detect and receive the signal to be tested within a certain period of time to save power consumption.
  • Each of the n ground stations sends the signal to be measured separately.
  • the air base station receives the signal to be measured sent by n ground stations and determines n measurement report information.
  • the n measurement report information corresponds to the n ground stations one to one.
  • the measurement report information is used to indicate the signal to be measured received by the air base station. Signal strength.
  • the signal to be measured includes information about the ground station, such as the identity of the ground station and the identity of the core network to which the ground station belongs.
  • the ground station sends the signal to be measured at a preset time.
  • the air base station receives the signal to be measured at a preset time.
  • the preset time can be determined according to the ephemeris. In this way, the ground station only needs to send the signal to be measured within a part of the time to save power consumption.
  • the air base station only needs to detect and receive the signal to be tested within a part of the time to save power consumption.
  • the air base station makes a handover decision.
  • the air base station can make a handover decision based on the signal strength of the wireless signal between the n ground stations and the air base station to determine whether there are other ground stations in the n ground stations except the source ground station. Target ground station.
  • the signal strength of the wireless signal between the target ground station and the air base station meets a preset condition.
  • the preset conditions include one of the following situations:
  • the signal strength of the wireless signal between the target ground station and the air base station is greater than or equal to a first preset value
  • the signal strength of the wireless signal between the target ground station and the air base station is greater than the signal strength of the wireless signal between the source ground station and the air base station.
  • the air base station determines whether there are any ground stations meeting preset conditions among the n ground stations other than the source ground station based on the signal strength of the wireless signals between the n ground stations and the air base station. Ground station. If there are ground stations meeting the preset conditions among the n ground stations other than the source ground station, the ground station meeting the preset conditions is the target ground station. If there is no ground station meeting the preset conditions among the n ground stations except the source ground station, the air base station determines that there is no target ground station.
  • the signal strength of the wireless signal is SNR as an example
  • the ground station #2 is the source ground station
  • the signal strength of the wireless signal between the ground station #1 and the base station in the air is 25dB
  • the ground station #2 is connected to the air station.
  • the signal strength of the wireless signal between the base stations is 30dB
  • the signal strength of the wireless signal between the ground station #3 and the base station in the air is 45dB.
  • the preset condition is: the signal strength of the wireless signal between the target ground station and the aerial base station is greater than or equal to the first preset value, and the first preset value is 40 dB
  • ground station #3 is the target ground station.
  • the preset condition is: the signal strength of the wireless signal between the target ground station and the air base station is greater than the signal strength of the wireless signal between the source ground station and the air base station, then ground station #3 is the target ground station.
  • the air base station can select one from the multiple ground stations that meet the preset conditions.
  • the ground station serves as the target ground station.
  • the ground station with the highest wireless signal strength is used as the target ground station.
  • each ground station has a preset priority.
  • the air base station selects the ground station with the highest priority from the multiple ground stations that meet the preset conditions as the target ground station .
  • ground station #1, ground station #3, and ground station #4 all meet the preset conditions, and suppose that the wireless signal between ground station #1 and the base station in the air The signal strength of is 45dB, the signal strength of the wireless signal between ground station #3 and the air base station is 50dB, and the signal strength of the wireless signal between ground station #4 and the air base station is 55dB. If the ground station with the highest wireless signal strength is used as the target ground station, then ground station #4 is the target ground station.
  • the air base station determines that there is no target ground station among the n ground stations except the source ground station, the air base station maintains the interface with the source network device; if the air base station determines n If there is a target ground station in a ground station other than the source ground station, the air base station establishes an interface with the target network device.
  • the target network device determines that there is a target ground station in n ground stations other than the source ground station, if the target network device does not store the context information of the air base station in advance, the following steps S1003a-S1004a are executed; If the target network device pre-stores the context information of the air base station, the following steps S1003b-S1004b are executed.
  • the air base station may determine whether the target network device has pre-stored the context information of the air base station by determining whether it is the first time to establish an interface with the target network device. Specifically, when the air base station determines to establish an interface with the target network device for the first time, the air base station can determine that the target network device does not pre-store the context information of the air base station. When the air base station determines that it is not the first time to establish an interface with the target network device, the air base station can determine that the target network device stores the context information of the air base station in advance.
  • the air base station may determine whether it is the first time to establish an interface with the target network device according to whether the information of the target network device is stored. Specifically, if the air base station stores the information of the target network device, the air base station determines that it is not the first time to establish an interface with the target network device; if the air base station does not store the information of the target network device, the air base station determines that it is the first The network device establishes an interface.
  • the air base station stores in advance the number of times the air base station establishes an interface with the network device. In this way, the air base station can determine whether the air base station has established an interface with the target network device for the first time by querying the number of times the air base station has established an interface with the target network device.
  • S1003a-S1004a are the same as steps S901-S902, and the specific description can refer to the embodiment shown in FIG. 9, which will not be repeated here.
  • S1003b-S1004b are the same as steps S905-S906.
  • steps S905-S906 please refer to the embodiment shown in FIG. 9, which will not be repeated here.
  • the air base station determines whether to release the interface between the air base station and the source network device.
  • the air base station determines whether to release the interface between the air base station and the source network device according to the signal strength of the wireless signal between the source ground station and the air base station.
  • the air base station determines to release the interface between the air base station and the source network device, and the air base station executes the following step S1006 .
  • S1006-S1007 are the same as steps S903-S904.
  • steps S903-S904 please refer to the embodiment shown in FIG. 9, which will not be repeated here.
  • the air base station determines whether a network handover is required according to the signal strength of the wireless signals between n ground stations and the air base station, so as to ensure the normal communication between the air base station and the ground during the movement.
  • a handover method provided in an embodiment of this application includes the following steps:
  • the source network device respectively determines the signal strength of the wireless signal between the n ground stations and the air base station.
  • n ground stations include the source ground station, and n is an integer greater than 1.
  • the wireless signal may refer to an SRI signal or a signal to be measured.
  • the signal to be measured is a synchronization signal or a reference signal.
  • the synchronization signal may refer to PSS or SSS.
  • the reference signal may refer to SRS or CSI-RS. The embodiment of the application does not specifically limit this.
  • the signal strength of the wireless signal includes any one of the following parameters: RSRP, SNR, or SINR.
  • step S1101 can be implemented in the following manner one or two. It should be noted that method one is applicable to the scenario where the wireless signal is an SRI signal. Method 2 is suitable for scenarios where the wireless signal is the signal to be tested.
  • Each of the n ground stations measures the signal strength of the SRI signal between the ground station and the air base station, and sends the measurement result to the source network device. In this way, the source network device can determine the signal strength of the SRI signal between the n ground stations and the air base station.
  • Method 2 The air base station sends the signal to be measured.
  • Each of the n ground stations receives the signal to be measured and determines measurement report information, which is used to indicate the signal strength of the signal to be measured received by the ground station. After that, each of the n ground stations sends measurement report information to the source network device. In this way, the source network device receives n measurement report information, and the n measurement report information corresponds to the n ground stations one-to-one; thus, the air base station can respectively determine the to-be-tested between the n ground stations and the air base station. The signal strength of the signal.
  • the source network device makes a handover decision.
  • the source network device determines whether there is a target ground station among the n ground stations other than the source ground station according to the signal strength of the wireless signals between the n ground stations and the air base station.
  • the signal strength of the wireless signal between the target ground station and the air base station meets a preset condition.
  • the preset conditions include one of the following situations:
  • the signal strength of the wireless signal between the target ground station and the air base station is greater than or equal to a first preset value
  • the signal strength of the wireless signal between the target ground station and the air base station is greater than the signal strength of the wireless signal between the source ground station and the air base station.
  • the source network device determines whether there are any other ground stations in the n ground stations other than the source ground station that meet the preset conditions according to the signal strength of the wireless signals between the n ground stations and the air base station Ground station. If there are ground stations meeting the preset conditions among the n ground stations other than the source ground station, the ground station meeting the preset conditions is the target ground station. If there is no ground station meeting the preset condition among the n ground stations except the source ground station, the source network device determines that there is no target ground station.
  • the source network device can select one of the multiple ground stations that meet the preset conditions.
  • the ground station serves as the target ground station.
  • each ground station is preset with a priority.
  • the source network device selects the ground station with the highest priority from the multiple ground stations that meet the preset conditions as the target ground. station.
  • the source network device determines that there is no target ground station among the n ground stations except the source ground station, the source network device maintains the interface with the air base station; if the source network device It is determined that there is a target ground station in the n ground stations other than the source ground station, the source network device executes the following step S1103 to ensure normal communication between the air base station and the ground.
  • the source network device sends a first indication message to the air base station.
  • the first indication message is used to indicate the establishment of an interface between the air base station and the target network device.
  • the first indication message includes: information of the target ground station.
  • the information of the target ground station may include: the name of the target ground station, the identification of the target ground station, and so on.
  • the source network device sends the first indication message to the air base station through the source ground station. That is, the source network device sends the first indication message to the source ground station; after that, the source ground station sends the first indication message to the air base station.
  • the air base station determines whether it is the first time to establish an interface with the target network device. If the air base station establishes an interface with the target network device for the first time, the following steps S1104a-S1105a are executed. If the air base station is not establishing an interface with the target network device for the first time, the following steps S1104b-S1105b are executed.
  • S1104a-S1105a are the same as steps S901-S902.
  • steps S901-S902 please refer to the embodiment shown in FIG. 9, which will not be repeated here.
  • S1104b-S1105b are the same as steps S905-S906.
  • steps S905-S906 please refer to the embodiment shown in FIG. 9 and will not be repeated here.
  • S1106 The source network device determines whether to release the interface between the air base station and the source network device.
  • the source network device determines whether to release the interface between the air base station and the source network device according to the signal strength of the wireless signal between the source ground station and the air base station.
  • the source network device determines to release the interface with the air base station, that is, the source network device executes the following step S1107.
  • the source network device sends a second indication message to the air base station.
  • the second indication message is used to instruct to release the interface between the air base station and the source network device.
  • the source network device sends the second indication message to the air base station through the source ground station. That is, the source network device sends the second instruction message to the source ground station; after that, the source ground station sends the second instruction message to the air base station.
  • S1108-S1109 are the same as steps S903-S904.
  • steps S903-S904 please refer to the embodiment shown in FIG. 9, which will not be repeated here.
  • the source network equipment determines whether the air base station performs network handover according to the signal strength of the wireless signal between n ground stations and the air base station, so as to ensure the normal communication between the air base station and the ground during the movement. .
  • a handover method provided in an embodiment of this application includes the following steps:
  • the air base station sends a first request message to the target network device at a first preset time.
  • the first preset time is determined according to the overhead time of the aerial base station at the target ground station. For example, assuming that the overhead time of the aerial base station at the target ground station is 13:00-13:30, the first preset time may be 13:00, or the first preset time may be 13:05.
  • the overhead time of the air base station at the target ground station may be pre-configured in the air base station, or may be determined by the air base station according to the ephemeris or the movement trajectory of the air base station.
  • the ephemeris is used to record the position information and orbit information of the aerial platform carrying the aerial base station.
  • the first preset time may be determined according to the ephemeris; or, the first preset time may be determined according to the movement trajectory of the base station in the air.
  • the first preset time may also be determined according to a first timer, and the first timer may be pre-configured.
  • the air base station sends the first request message to the target network device through the target ground station at the first preset time. That is, the air base station sends the first request message to the target ground station at the first preset time; after that, the target ground station sends the first request message to the target network device.
  • the target network device sends a first response message to the air base station.
  • steps S1201a-S1202a please refer to steps S901-S902, which will not be repeated here.
  • S1201a-S1202a can be replaced with S1201b-S120b.
  • the air base station sends a third request message to the target network device at the first preset time.
  • step S1201a For the detailed description of the first preset time, refer to step S1201a, which will not be repeated here.
  • the air base station sends the third request message to the target network device through the target ground station at the first preset time. That is, the air base station sends the third request message to the target ground station at the first preset time; after that, the target ground station sends the third request message to the target network device.
  • the target network device sends a third response message to the air base station.
  • steps S1201b-S1202b please refer to steps S905-S906, which will not be repeated here.
  • the air base station sends a second request message to the source network device at a second preset time.
  • the second preset time is determined according to the overhead time of the air base station at the source ground station. For example, assuming that the overhead time of the aerial base station at the source ground station is 12:00-12:30, the second preset time may be 12:30, or the second preset time may be 12:25.
  • the overhead time of the air base station at the source ground station may be pre-configured in the air base station, or it may be determined by the air base station according to the ephemeris or the movement trajectory of the air base station.
  • the ephemeris is used to record the position information and orbit information of the base station in the air.
  • the second preset time may be determined according to the ephemeris; or, the second preset time may be determined according to the movement trajectory of the base station in the air.
  • the second preset time may also be determined according to a second timer, and the second timer is pre-configured.
  • the air base station sends the second request message to the source network device through the source ground station at the second preset time. That is, the air base station sends the second request message to the source ground station at the second preset time; after that, the source ground station sends the second request message to the source network device.
  • the source network device sends a second response message to the air base station.
  • steps S1203-S1204 please refer to steps S903-S904, which will not be repeated here.
  • the air base station triggers a corresponding handover procedure at a preset time to ensure normal communication with the ground.
  • a handover method provided by an embodiment of this application includes:
  • the air base station receives a transmission link establishment instruction message.
  • the transmission link establishment indication message is used to indicate that the transmission link between the air base station and the target ground station has been established.
  • the transmission link establishment instruction message comes from the transmission layer protocol stack of the air base station.
  • the air base station establishes an interface with the target network device for the first time, the following steps S1302a-S1303a are executed; if the air base station establishes an interface with the target network device for the first time, the following steps S1302b-S1303b are executed.
  • S1302a-S1303a are the same as steps S901-S902.
  • steps S901-S902 please refer to the embodiment shown in FIG. 9 and will not be repeated here.
  • S1302b-S1303b are the same as steps S905-S906.
  • steps S905-S906 please refer to the embodiment shown in FIG. 9, which will not be repeated here.
  • the air base station receives the transmission link pre-deletion indication message.
  • the transmission link pre-deletion indication message is used to indicate that the transmission link between the air base station and the source ground station is to be deleted.
  • the transmission link pre-deletion indication message comes from the transmission layer protocol stack of the air base station.
  • S1305-S1306 are the same as steps S903-S904.
  • steps S903-S904 please refer to the embodiment shown in FIG. 9, which will not be repeated here.
  • a handover method provided by an embodiment of this application is applicable to the NTN architecture shown in FIG. 4.
  • the method includes:
  • the air base station determines whether to transfer the connected terminal.
  • the air base station detects whether the signal strength of the wireless signal between the target ground station and the air base station is greater than the signal strength of the wireless signal between the source ground station and the air base station. When the signal strength of the wireless signal between the target ground station and the air base station is not greater than the signal strength of the wireless signal between the source ground station and the air base station, the air base station determines not to transfer the connected terminal. When the signal strength of the wireless signal between the target ground station and the air base station is greater than the signal strength of the wireless signal between the source ground station and the air base station, the air base station determines the terminal that moves to the connected state.
  • the air base station detects whether the signal strength of the wireless signal between the source ground station and the air base station is less than a preset value. When the signal strength of the wireless signal between the source ground station and the air base station is less than the preset value, the air base station determines the terminal to be transferred to the connected state. When the signal strength of the wireless signal between the source ground station and the air base station is greater than or equal to the preset value, the air base station determines not to transfer the connected terminal.
  • the air base station detects whether the signal strength of the wireless signal between the source ground station and the air base station is less than a preset value, and whether the signal strength of the wireless signal between the target ground station and the air base station is greater than that between the source ground station and the air base station The signal strength of the wireless signal. If the signal strength of the wireless signal between the source ground station and the air base station is less than the preset value, and the signal strength of the wireless signal between the target ground station and the air base station is greater than the signal strength of the wireless signal between the source ground station and the air base station , The base station in the air determines the terminal to be transferred to the connected state.
  • the air base station determines not to transfer the connected terminal.
  • the air base station when the air base station determines the terminal to be transferred to the connected state, the air base station performs the following step S1402.
  • the air base station triggers the terminal in the connected state to migrate from the source core network device to the target core network device.
  • the migration process of the terminal in the connected state can refer to the prior art, which will not be repeated here.
  • the air base station sends an indication message to the terminal in the connected state, and the indication message is used to instruct the terminal in the connected state to migrate from the source core network device to the target core network device.
  • the connected terminal migrates from the source core network device to the target core network device, it specifically refers to the migration of the context information of the connected terminal from the source core network device to the target core network device.
  • steps S1401-S1402 are performed after the air base station establishes an interface with the target core network device.
  • a handover method provided by an embodiment of this application is applicable to the NTN architecture shown in FIG. 4.
  • the method includes:
  • the source core network device determines whether to migrate a connected terminal.
  • the source core network device detects whether the signal strength of the wireless signal between the target ground station and the air base station is greater than the signal strength of the wireless signal between the source ground station and the air base station. When the signal strength of the wireless signal between the target ground station and the air base station is not greater than the signal strength of the wireless signal between the source ground station and the air base station, the source core network device determines not to transfer the connected terminal. When the signal strength of the wireless signal between the target ground station and the air base station is greater than the signal strength of the wireless signal between the source ground station and the air base station, the source core network device determines the terminal to be transferred to the connected state.
  • the air base station detects whether the signal strength of the wireless signal between the source ground station and the air base station is less than a preset value.
  • the source core network device determines the terminal to be transferred to the connected state.
  • the source core network device determines not to transfer the connected terminal.
  • the source core network equipment detects whether the signal strength of the wireless signal between the source ground station and the air base station is less than a preset value, and whether the signal strength of the wireless signal between the target ground station and the air base station is greater than the source ground station and the air base station The signal strength of the wireless signal between. If the signal strength of the wireless signal between the source ground station and the air base station is less than the preset value, and the signal strength of the wireless signal between the target ground station and the air base station is greater than the signal strength of the wireless signal between the source ground station and the air base station , The source core network device determines the terminal to which the connection state is migrated.
  • the source core network device determines not to migrate the connected terminal.
  • the source core network device executes the following step S1502.
  • the source core network device triggers the terminal in the connected state to migrate from the source core network device to the target core network device.
  • the migration process of the terminal in the connected state can refer to the prior art, which will not be repeated here.
  • the connected terminal migrates from the source core network device to the target core network device, it specifically refers to the migration of the context information of the connected terminal from the source core network device to the target core network device.
  • steps S1501-S1502 are performed after the air base station establishes an interface with the target core network device.
  • a handover method provided by an embodiment of this application is applied to the NTN architecture shown in FIG. 5.
  • the method includes:
  • S1601-S1603 are similar to steps S1005-S1007.
  • steps S1005-S1007 For detailed description, please refer to the embodiment shown in FIG. 10, which will not be repeated here.
  • the air base station initiates an RRC connection release request (RRC connect release) to the terminal.
  • RRC connect release RRC connection release request
  • the air base station receives the RRC connection release response (RRC connect release response) sent by the terminal.
  • steps S1604-S1605 are optional execution steps.
  • S1606a-S1607a are similar to S901-S902, and for specific description, please refer to the embodiment shown in FIG. 9, which will not be repeated here.
  • S1606b-S1607b are similar to steps S905-S906, and for specific description, please refer to the embodiment shown in FIG. 9, which will not be repeated here.
  • the air base station first releases the interface between the air base station and the source CU; then, the air base station establishes an interface with the target CU to ensure that the air base station can complete the network handover Process.
  • the air base station After the air base station establishes an interface with the target CU, the air base station establishes a new cell in order to provide services to the terminal.
  • a handover method provided by an embodiment of this application is applied to the NTN architecture shown in FIG. 5.
  • the method includes:
  • step S1701 is similar to step S1002.
  • step S1002 For detailed description, please refer to the embodiment shown in FIG. 10, which will not be repeated here.
  • the air base station generates a logical DU.
  • the DU that currently establishes an interface with the source CU for ease of description, hereinafter referred to as the original DU
  • the logical DU for ease of description, hereinafter referred to as the original DU
  • the logical DU has the same cell information as the original DU, and the logical DU has the same UE context information as the original DU.
  • the difference between the logical DU and the original DU is: the DU name of the logical DU is different from the DU name of the original DU; or, the DU ID of the logical DU is different from the DU ID of the original DU.
  • step S1703-S1704 are similar to steps S1003a-S1004a, and the specific description can refer to the embodiment shown in FIG. 10, which will not be repeated here.
  • the difference between step S1703 and step S1003a is that the first request message in step S1003a is used to request the establishment of an interface between the air base station and the target network device.
  • the first request message in step S1703 is used to establish an interface between the logical DU and the target network device.
  • S1705-S1707 are similar to steps S1005-S1007.
  • the second request message in S1006 is used to request to release the interface between the air base station and the source network device; the second request message in S1706 is used to request to release the interface between the original DU and the source network device.
  • the air base station after releasing the interface between the original DU and the source network device, deletes the information of the original DU.
  • the air base station when one DU cannot be connected to two DUs at the same time, the air base station generates a logical DU and establishes an interface with the target CU through the logical DU, so that the air base station can complete the network handover. Moreover, since the logical DU has the same UE context information as the original DU, after the air base station completes the network handover, it is ensured that the air base station can provide corresponding services to the terminal.
  • the embodiment shown in FIG. 10 and the embodiment shown in FIG. 11 are based on the signal strength of the wireless signal between the air base station and the ground station to determine whether the air base station performs network handover.
  • the embodiment shown in FIG. 12 triggers an air base station to perform a network handover based on a preset time.
  • the advantages of the embodiment shown in FIG. 10 and the embodiment shown in FIG. 11 are that it can ensure that the air base station has a better communication quality between the air base station and the target ground station after network handover.
  • the advantage of the embodiment shown in FIG. 12 is that the handover process is relatively simple and the complexity is reduced.
  • the interface between the air base station and the source network device can be released first, and then the interface between the air base station and the target network device can be established; or the air base station and the target network device can be established first.
  • first establishing the interface between the air base station and the target network equipment, and then establishing the interface between the air base station and the source network equipment has the following advantages: ensuring that the air base station can always provide services to the terminal and avoiding the terminal being in different states ( For example, between the idle state and the connected state) switch back and forth to avoid the phenomenon of dropped calls in the terminal.
  • the embodiment shown in FIG. 14 is determined by the air base station whether to migrate the terminal from the source network device to the target network device;
  • the source network device determines whether to migrate the terminal from the source network device to the target network device.
  • the difference between the embodiment shown in FIG. 16 and the embodiment shown in FIG. 17 is that, under the restriction that one DU can only be connected to one CU, the embodiment shown in FIG. 16 has lower complexity and is easy to implement; The embodiment shown in FIG. 17 can ensure that the terminal will not drop calls during the handover process and ensure the communication quality of the user.
  • each network element such as an air base station, a source network device, or a target network device
  • each network element includes hardware structures and/or software modules corresponding to each function in order to realize the above functions.
  • the present application can be implemented in the form of hardware or a combination of hardware and computer software. Whether a certain function is executed by hardware or computer software-driven hardware depends on the specific application and design constraint conditions of the technical solution. Professionals and technicians can use different methods for each specific application to implement the described functions, but such implementation should not be considered beyond the scope of this application.
  • each functional module can be divided corresponding to each function, or two or more functions can be integrated into one processing module.
  • the above-mentioned integrated modules can be implemented in the form of hardware or software functional modules. It should be noted that the division of modules in the embodiments of the present application is illustrative, and is only a logical function division, and there may be other division methods in actual implementation. The following is an example of dividing each function module corresponding to each function:
  • FIG. 18 it is a schematic structural diagram of an aerial base station provided by an embodiment of this application.
  • the air base station includes a sending module 1801, a processing module 1802, and a receiving module 1803.
  • the sending module 1801 is configured to send a first request message to the target network device, where the first request message is used to request the establishment of an interface between the air base station and the target network device.
  • the receiving module 1803 is configured to receive a first response message from the target network device, where the first response message is used to respond to the first request message.
  • the first request message includes at least one of air platform type, mobile type, and air platform information; wherein, the air platform type is used to indicate the type of the air platform carrying the air base station; the mobile type is used to indicate Whether the air base station is in motion; the air platform information includes at least one of orbit information, capability information, and altitude information.
  • the sending module 1801 is configured to send the first request message to the target network device, including: sending the first request message to the target network device through the target ground station.
  • the sending module 1801 is configured to send the first request message to the target network device, including: sending the first request message to the target network device at a first preset time, and the first preset time is based on the ephemeris Determine; or, the first preset time is determined according to the movement trajectory of the air base station; or, the first preset time is determined according to the overhead time of the air base station at the target ground station; or, the first preset time is determined according to the first timer .
  • the receiving module 1803 is further configured to receive a first instruction message from the source network device, and the first instruction message is used to instruct to establish an interface between the air base station and the target network device.
  • the receiving module 1803 is further configured to receive a transmission link establishment indication message, where the transmission link establishment success indication message is used to indicate that the transmission link between the air base station and the target ground station has been established.
  • the sending module 1801 is used to send the first request message to the target network device, including: if the signal strength of the wireless signal between the target ground station and the air base station meets a preset condition, the target ground station sends The target network device sends the first request message.
  • the preset condition includes one of the following situations: (1) The signal strength of the wireless signal between the target ground station and the air base station is greater than or equal to the first preset value; (2) the target ground station and the air base station The signal strength of the wireless signal between the base stations is greater than the signal strength of the wireless signal between the source ground station and the air base station.
  • the sending module 1801 is also used to send a second request message to the source network device, and the second request message is used to request to release the interface between the source network device and the air base station.
  • the second request message includes at least one of the following parameters: information of the air base station, release type, and re-establishment period; wherein the re-establishment period is used to indicate the time for the source network device to re-establish the interface with the air base station ;
  • the release types shown include: the first type, the second type and the third type; the first type is used to indicate the deletion of the context information of the air base station; the second type is used to indicate the deactivation of the context information of the air base station; the third type is used To indicate to deactivate the context information of the air base station, and activate the context information of the air base station at the time indicated by the reconstruction period.
  • the sending module 1801 is also used to send the second request message to the source network device, including: sending the second request message to the source network device through the source ground station.
  • the sending module 1801 is further configured to send a second request message to the source network device, including: sending a second request message to the source network device at a second preset time, and the second preset time is based on the ephemeris Table is determined; or, the second preset time is determined according to the movement trajectory of the air base station; or, the second preset time is determined according to the overhead time of the air base station at the source ground station; or, the second preset time is determined according to the second timer determine.
  • the receiving module 1803 is further configured to receive a second instruction message sent from the source network device, and the second instruction message is used to instruct to release the interface between the air base station and the source network device.
  • the receiving module 1803 is also used to receive the transmission link pre-deletion indication message.
  • the transmission link pre-deletion indication message is used to indicate that the transmission link between the air base station and the source ground station is to be deleted.
  • the sending module 1801 is also used to send a second request message to the source network device, including: if the signal strength of the wireless signal between the source ground station and the air base station is less than the second preset value, pass The source ground station sends a second request message to the source network device.
  • the sending module 1801 is also used to send a third request message to the target network device, and the third request message is used to request to activate the context information of the air base station.
  • the processing module 1802 is used to determine the signal strength of the wireless signal between n ground stations and air base stations, and n is an integer greater than 1.
  • the processing module 1802 is used to update the ephemeris.
  • FIG. 19 it is a schematic structural diagram of a target network device provided by an embodiment of this application.
  • the target network device includes: a receiving module 1901 and a sending module 1902.
  • the receiving module 1901 is used to receive a first request message from an air base station.
  • the first request message is used to request the establishment of an interface between the air base station and the target network device.
  • the first request message includes air platform type, mobile type, and air platform At least one of the information; where the air platform type is used to indicate the type of the air platform carrying the air base station; the movement type is used to indicate whether the air base station is in motion; the air platform information includes orbit information, capability information, and altitude information. At least one.
  • the sending module 1902 is configured to send a first response message to the air base station, where the first response message is used to respond to the first request message.
  • the receiving module 1901 is configured to receive the first request message from the air base station, including: receiving the first request message from the air base station through the target ground station.
  • the receiving module 1901 is also used to receive a third request message sent from an air base station, and the third request message is used to request to activate the context information of the air base station.
  • the sending module 1902 is further configured to send a third response message to the air base station, and the third response message is used to respond to the third request message.
  • the receiving module 1901 is further configured to receive the third request message sent from the air base station, including: receiving the third request message sent from the air base station through the target ground station.
  • the source network device includes: a receiving module 2001, a processing module 2002, and a sending module 2003.
  • the receiving module 2001 is configured to receive a second request message from an air base station, and the second request message is used to request to release the interface between the source network device and the air base station.
  • the sending module 2003 is configured to send a second response message to the air base station, and the second response message is used to respond to the second request message.
  • the second request message includes at least one of the following parameters: information of the air base station, release type, and re-establishment period; wherein the re-establishment period is used to indicate the time for the source network device to re-establish the interface with the air base station ;
  • the release types shown include: the first type, the second type and the third type; the first type is used to indicate the deletion of the context information of the air base station; the second type is used to indicate the deactivation of the context information of the air base station; the third type is used To indicate to deactivate the context information of the air base station, and activate the context information of the air base station at the time indicated by the reconstruction period.
  • the sending module 2003 is also used to send a second indication message to the air base station, and the second indication message is used to instruct to release the interface between the air base station and the source network device.
  • the sending module 2003 is also used to send a second indication message to the air base station, including: if the signal strength of the wireless signal between the source ground station and the air base station is less than the second preset value, pass the source The ground station sends a second indication message to the air base station.
  • the sending module 2003 is also used to send a first indication message to the air base station, where the first indication message is used to instruct to establish an interface between the air base station and the target network device.
  • the sending module 2003 is also used to send the first indication message to the air base station, including: if the signal strength of the wireless signal between the target ground station and the air base station meets a preset condition, pass the source ground station Send the first indication message to the air base station.
  • the preset condition includes one of the following situations: (1) The signal strength of the wireless signal between the target ground station and the air base station is greater than or equal to the first preset value; (2) the target ground station and the air base station The signal strength of the wireless signal between the base stations is greater than the signal strength of the wireless signal between the source ground station and the air base station.
  • the above-mentioned embodiments of the present application provide an aerial base station, a target network device, and a source network device that can be collectively referred to as a communication device.
  • the communication device can be implemented in various product forms.
  • the communication device can be configured as a general processing system;
  • the communication device may be implemented by a general bus architecture; for another example, the communication device may be implemented by an application specific integrated circuit (ASIC).
  • ASIC application specific integrated circuit
  • FIG. 21 is a schematic diagram of possible product forms of the communication device according to an embodiment of the present application.
  • the communication device described in the embodiment of the present application may be a communication device, and the communication device includes a processor 2101 and a transceiver 2102.
  • the communication device further includes a storage medium 2103.
  • the processor 2101 is configured to execute the switching method shown in FIG. 9 to FIG. 17.
  • the transceiver 2102 is controlled by the processor 2101 and is used to perform the switching methods shown in FIG. 9 to FIG. 17.
  • the communication device described in the embodiment of the present application may also be implemented by a general-purpose processor, that is, implemented by a commonly called chip.
  • the general-purpose processor includes: a processing circuit 2101 and a transceiver pin 2102.
  • the general-purpose processor may further include a storage medium 2103.
  • the processing circuit 2101 is used to execute the switching methods shown in FIG. 9 to FIG. 17.
  • the transceiver pin 2102 is controlled by the processing circuit 2101 and is used to perform the switching method shown in FIG. 9 to FIG. 17.
  • the communication device described in the embodiments of the present application can also be implemented using the following circuits or devices: one or more field programmable gate arrays (FPGA), programmable logic A programmable logic device (PLD), a controller, a state machine, gate logic, discrete hardware components, any other suitable circuits, or any combination of circuits capable of performing various functions described throughout this application.
  • FPGA field programmable gate arrays
  • PLD programmable logic A programmable logic device
  • controller a state machine
  • gate logic discrete hardware components
  • any other suitable circuits any combination of circuits capable of performing various functions described throughout this application.
  • An embodiment of the present application also provides a computer-readable storage medium that stores instructions.
  • the instructions When the instructions are executed on a communication device, the communication device can execute the switching method shown in Figs. 9-17.
  • the embodiment of the present application provides a computer program product containing instructions.
  • the computer program product runs on a communication device, the communication device can execute the switching method shown in FIG. 9 to FIG. 17.

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Abstract

本申请提供一种切换方法及装置，涉及通信技术领域，用于使空中基站在移动过程中实现网络的切换。该方法包括：空中基站向目标网络设备发送第一请求消息，该第一请求消息用于请求建立空中基站与目标网络设备之间的接口，第一请求消息包括空中平台类型、移动类型、空中平台信息中的至少一种；其中，空中平台类型用于指示搭载空中基站的空中平台的类型；移动类型用于指示空中基站是否处于运动状态；空中平台信息包括轨道信息、能力信息以及高度信息中的至少一种；空中基站接收目标网络设备发送的第一响应消息，该第一响应消息用于响应第一请求消息。

Description

切换方法及装置
本申请要求于2019年2月15日提交国家知识产权局、申请号为201910118113.4、申请名称为“切换方法及装置”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及通信技术领域，尤其涉及切换方法及装置。
背景技术
为了构成天地一体化网络，5G移动通信技术提出了非陆地网络(non-terrestrial networks，NTN)方案。NTN方案在于利用空中基站向用户提供通信服务。其中，空中基站是指搭载在飞机、热气球、卫星、飞艇、无人机等空中平台上的基站。5G通信网络采用NTN方案，能够在人迹罕至的大洋、沙漠、深山、极地等区域提供网络覆盖，以满足用户无处不在的业务需求。
当前，在空中基站围绕地球移动的过程中，由于空中基站的位置相对于地面的位置发生变化，因此空中基站需要进行网络的切换，以保证与地面的正常通信。但是，空中基站在移动过程中如何切换网络，业界尚未提供相应的解决方案。
发明内容
本申请提供一种切换方法及装置，用于解决空中基站在移动过程中如何切换网络的问题。
第一方面，提供一种切换方法，包括：空中基站向目标网络设备发送第一请求消息，第一请求消息用于请求建立空中基站与目标网络设备之间的接口。空中基站接收来自目标网络设备的第一响应消息，第一响应消息用于响应第一请求消息。基于该技术方案，空中基站通过发送第一请求消息，触发目标网络设备建立与空中基站的接口，实现空中基站的网络切换。
一种可能的设计中，第一请求消息包括空中平台类型、移动类型、空中平台信息中的至少一种。空中平台信息包括轨道信息、能力信息以及高度信息中的至少一种。这样一来，目标网络设备根据第一请求消息所携带的空中平台类型、移动类型、轨道信息、能力信息、或者高度信息，对空中基站进行针对性的管理，以保证空中基站从源网络设备切换到目标网络设备后，空中基站能够与地面正常通信。
可以理解的是，空中平台类型用于指示搭载空中基站的空中平台的类型，空中平台类型包括：地球静止轨道(geostationary earth orbit，GEO)卫星，低地球轨道(low earth orbiting，LEO)卫星，中地球轨道(medium earth orbit，MEO)卫星、以及高空平台(high altitude platform station，HAPS)。由于不同类型的空中平台有不同的高度和传输时延，以及不同的组网形式。因此，目标网络设备根据搭载空中基站的空中平台的类型，可以对空中基站进行针对性的服务质量(quality of service，QoS)管理等操作。
移动类型用于指示空中基站是否处于运动状态。可以理解的是，对于终端位置管 理和寻呼、终端的切换处理等流程来说，处于运动状态的基站的处理流程与处于静止状态的基站的处理流程是不相同的。另外，核心网对于处于运动状态的基站需要进行更多的管理，例如核心网对处于运动状态的基站进行接入与移动管理功能网元(access and mobility management function，AMF)动态连接管理。因此，目标网络设备根据移动类型，获知空中基站是否处于运动状态，从而目标网络设备可以对空中基站进行更有效的管理。
轨道信息用于使地面站确定空中基站的过顶时间。从而，目标网络设备可以根据空中基站在目标地面站的过顶时间，确定空中基站与目标网络设备之间保持通信的时间。
能力信息用于确定空中基站的覆盖范围，能力信息可以包括倾向角度、发射功率等。从而，目标网络设备可以根据空中基站的覆盖范围，对空中基站进行更有效的跟踪区代码(tracking area code，TAC)管理以及用户寻呼处理。
高度信息用于指示空中平台距离地面的高度，高度信息可以用于确定空中基站的覆盖范围、空中基站与地面站之间的传输时延、空中平台的运行速度、或者空中平台的运行轨迹等。从而，目标网络设备根据空中基站与地面站之间的传输时延，可以对空中基站进行QoS管理。或者，目标网络设备根据空中平台的运行轨迹，可以确定空中基站对应的星历表。
一种可能的设计中，空中基站向目标网络设备发送第一请求消息，包括：空中基站通过目标地面站向目标网络设备发送第一请求消息。
一种可能的设计中，空中基站向目标网络设备发送第一请求消息，包括：空中基站在第一预设时间向目标网络设备发送第一请求消息，第一预设时间根据星历表确定；或者，第一预设时间根据空中基站的运动轨迹确定；或者，第一预设时间根据空中基站在目标地面站的过顶时间确定；或者，第一预设时间根据第一定时器确定。可以理解的是，空中基站在第一预设时间发送第一请求消息，可以简化切换的流程，减少复杂度。
一种可能的设计中，在空中基站向目标网络设备发送第一请求消息之前，该方法还包括：空中基站接收来自于源网络设备的第一指示消息，第一指示消息用于指示建立空中基站与目标网络设备之间的接口。基于该设计，空中基站是否进行网络切换由源网络设备确定，这有利于网络侧对空中基站的管理。
一种可能的设计中，在空中基站向目标网络设备发送第一请求消息之前，该方法还包括：空中基站接收传输链路建立指示消息，所述传输链路建立成功指示消息用于指示空中基站与目标地面站之间的传输链路已建立。可以理解的是，当空中基站接收传输链路建立指示消息时，说明空中基站与目标网络设备之间具备正常通信的条件。因此，空中基站向目标网络设备发送第一请求消息，以建立空中基站与目标网络设备之间的接口，从而保证空中基站与地面的正常通信。
一种可能的设计中，空中基站向目标网络设备发送第一请求消息，包括：若目标地面站与空中基站之间的无线信号的信号强度符合预设条件，则空中基站通过目标地面站向目标网络设备发送第一请求消息。可以理解的是，目标地面站与空中基站之间的无线信号的信号强度符合预设条件，能够保证空中基站与目标网络设备之间的通信 质量。从而，空中基站与目标网络设备之间建立接口之后，空中基站与目标网络设备之间能够正常通信。
一种可能的设计中，预设条件包括以下情形之一：(1)目标地面站与空中基站之间的无线信号的信号强度大于或等于第一预设值；(2)目标地面站与空中基站之间的无线信号的信号强度大于源地面站与空中基站之间的无线信号的信号强度。
一种可能的设计中，该方法还包括：空中基站向源网络设备发送第二请求消息，第二请求消息用于请求释放源网络设备与空中基站之间的接口。基于该设计，空中基站通过发送第二请求消息，以释放源网络设备和空中基站之间的接口，有利于节省网络侧的接口资源。
一种可能的设计中，第二请求消息包括以下参数中的至少一项：空中基站的信息、释放类型、以及重建周期。其中，重建周期用于指示源网络设备与空中基站重新建立接口的时间；所示释放类型包括：第一类型、第二类型和第三类型；第一类型用于指示删除空中基站的上下文信息；第二类型用于指示去激活空中基站的上下文信息；第三类型用于指示去激活空中基站的上下文信息，并在重建周期所指示的时间激活空中基站的上下文信息。
需要说明的是，当释放类型为第二类型或者第三类型时，由于源网络设备仅是去激活空中基站的上下文信息，并未删除空中基站的上下文信息。因此，在空中基站下一次与源网络设备建立接口时，空中基站和源网络设备之间无需交互空中基站的上下文信息。这样一来，有利于减少信令的开销，提高空中基站与源网络设备之间建立接口的效率。
另外，当释放类型为第三类型时，源网络设备在重建周期所指示的时间激活空中基站的上下文信息，从而实现建立空中基站与源网络设备之间的接口。这样一来，空中基站无需再发送信令以触发源网络设备建立与空中基站的接口，有利于减少信令开销。
一种可能的设计中，空中基站向源网络设备发送第二请求消息，包括：空中基站通过源地面站向源网络设备发送第二请求消息。
一种可能的设计中，空中基站向源网络设备发送第二请求消息，包括：空中基站在第二预设时间向源网络设备发送第二请求消息，第二预设时间根据星历表确定；或者，第二预设时间根据空中基站的运动轨迹确定；或者，第二预设时间根据空中基站在源地面站的过顶时间确定；或者，第二预设时间根据第二定时器确定。
一种可能的设计中，在空中基站向源网络设备发送第二请求消息之前，还包括：空中基站接收来自于源网络设备发送的第二指示消息，第二指示消息用于指示释放空中基站和源网络设备之间的接口。基于该设计，空中基站是否释放与源网络设备的接口由源网络设备确定，这有利于网络侧对空中基站的管理。
一种可能的设计中，在空中基站向源网络设备发送第二请求消息之前，该方法还包括：空中基站接收传输链路预删除指示消息。其中，传输链路预删除指示消息用于指示空中基站与源地面站之间的传输链路待删除。可以理解的是，当空中基站接收到传输链路预删除指示消息时，空中基站与源地面站之间的传输链路待删除，说明空中基站与源地面站之间即将不能正常通信，从而空中基站与源网络设备之间即将不能正 常通信。因此，空中基站向源网络设备发送第二请求消息，以实现网络的切换。
一种可能的设计中，空中基站向源网络设备发送第二请求消息，包括：若源地面站与空中基站之间的无线信号的信号强度小于第二预设值，则空中基站通过源地面站向源网络设备发送第二请求消息。可以理解的是，源地面站与空中基站之间的无线信号的信号强度小于第二预设值，说明空中基站与源地面站之间的通信质量较差，换句话说，空中基站与源网络设备之间的通信质量较差。因此，在这种情况下，空中基站向源网络设备发送第二请求消息，以释放源网络设备和空中基站之间的接口，实现网络的切换。
一种可能的设计中，该方法还包括：空中基站向目标网络设备发送第三请求消息，第三请求消息用于请求激活空中基站的上下文信息。这样一来，空中基站无需与目标网络设备交互空中基站的上下文信息，有利于节省信令开销。
一种可能的设计中，该方法还包括：空中基站分别确定n个地面站与空中基站之间的无线信号的信号强度，n为大于1的整数。这样一来，在切换流程中，空中基站能够根据n个地面站与空中基站之间的无线信号的信号强度，确定是否该进行网络切换。
一种可能的设计中，该方法还包括：空中基站更新星历表，以保证星历表的准确性。
第二方面，提供一种切换方法，包括：目标网络设备接收来自于空中基站的第一请求消息，第一请求消息用于请求建立空中基站与目标网络设备之间的接口。目标网络设备向空中基站发送第一响应消息，第一响应消息用于响应第一请求消息。基于上述技术方案，目标网络设备接收空中基站发送的第一请求消息，以建立与空中基站的接口，实现空中基站的网络切换。
一种可能的设计中，第一请求消息包括空中平台类型、移动类型、空中平台信息中的至少一种，空中平台信息包括轨道信息、能力信息以及高度信息中的至少一种。这样一来，目标网络设备根据第一请求消息所携带的空中平台类型、移动类型、轨道信息、能力信息、或者高度信息，对空中基站进行针对性的管理，以保证空中基站从源网络设备切换到目标网络设备后，空中基站能够与地面正常通信。
空中平台类型用于指示搭载空中基站的空中平台的类型，空中平台类型包括：GEO卫星、LEO卫星、MEO卫星、以及HAPS。可以理解的是，由于不同类型的空中平台有不同的高度和传输时延，以及不同的组网形式。因此，目标网络设备根据搭载空中基站的空中平台的类型，可以对空中基站进行针对性的QoS管理等操作。
移动类型用于指示空中基站是否处于运动状态。可以理解的是，对于终端位置管理和寻呼、终端的切换处理等流程来说，处于运动状态的基站的处理流程与处于静止状态的基站的处理流程是不相同的。另外，核心网对于处于运动状态的基站需要进行更多的管理，例如核心网对处于运动状态的基站进行AMF动态连接管理。因此，目标网络设备根据移动类型，获知空中基站是否处于运动状态，从而目标网络设备可以对空中基站进行更有效的管理。
轨道信息用于使地面站确定空中基站的过顶时间。从而，目标网络设备可以根据空中基站在目标地面站的过顶时间，确定空中基站与目标网络设备之间保持通信的时 间。
能力信息用于确定空中基站的覆盖范围，能力信息可以包括倾向角度、发射功率等。从而，目标网络设备可以根据空中基站的覆盖范围，对空中基站进行更有效的TAC管理以及用户寻呼处理。
高度信息用于指示空中平台距离地面的高度，高度信息可以用于确定空中基站的覆盖范围、空中基站与地面站之间的传输时延、空中平台的运行速度、或者空中平台的运行轨迹等。从而，目标网络设备根据空中基站与地面站之间的传输时延，可以对空中基站进行QoS管理。或者，目标网络设备根据空中平台的运行轨迹，可以确定空中基站对应的星历表。
基于上述技术方案，目标网络设备接收第一请求消息，建立与空中基站的接口。并且，目标网络设备根据第一请求消息所携带的信息，能够在与空中基站建立接口之后，为空中基站提供更好地服务，以保证空中基站与地面的正常通信。
一种可能的设计中，目标网络设备接收来自于空中基站的第一请求消息，包括：目标网络设备通过目标地面站接收来自于空中基站的第一请求消息。
一种可能的设计中，该方法还包括：目标网络设备接收来自于空中基站发送的第三请求消息，第三请求消息用于请求激活空中基站的上下文信息；目标网络设备向空中基站发送第三响应消息，第三响应消息用于响应第三请求消息。这样一来，在目标网络设备预先存储目标网络设备和空中基站无需交互上下文信息，有利于节省信令开销。
一种可能的设计中，目标网络设备接收来自于空中基站发送的第三请求消息，包括：目标网络设备通过目标地面站接收来自于空中基站发送的第三请求消息。
第三方面，提供一种切换方法，包括：源网络设备接收来自于空中基站的第二请求消息，第二请求消息用于请求释放源网络设备与空中基站之间的接口；源网络设备向空中基站发送第二响应消息，第二响应消息用于响应第二请求消息。可以理解的是，源网络设备接收来自于空中基站的第二请求消息，释放源网络设备与空中基站之间的接口，有利于节省网络侧的接口资源，同时实现空中基站的网络切换。
一种可能的设计中，第二请求消息包括以下参数中的至少一项：空中基站的信息、释放类型、以及重建周期。其中，重建周期用于指示源网络设备与空中基站重新建立接口的时间；所示释放类型包括：第一类型、第二类型和第三类型。第一类型用于指示删除空中基站的上下文信息；第二类型用于指示去激活空中基站的上下文信息；第三类型用于指示去激活空中基站的上下文信息，并在重建周期所指示的时间激活空中基站的上下文信息。
需要说明的是，当释放类型为第二类型或者第三类型时，由于源网络设备仅是去激活空中基站的上下文信息，并未删除空中基站的上下文信息。因此，在空中基站下一次与源网络设备建立接口时，空中基站和源网络设备之间无需交互空中基站的上下文信息。这样一来，有利于减少信令的开销，提高空中基站与源网络设备之间建立接口的效率。
另外，当释放类型为第三类型时，源网络设备在重建周期所指示的时间激活空中基站的上下文信息，从而实现建立空中基站与源网络设备之间的接口。这样一来，空 中基站无需再次发送信令以触发源网络设备建立与空中基站的接口，有利于减少信令开销。
一种可能的设计中，在源网络设备接收来自于空中基站的第二请求消息之前，该方法还包括：源网络设备向空中基站发送第二指示消息，第二指示消息用于指示释放空中基站与源网络设备之间的接口。
一种可能的设计中，源网络设备向空中基站发送第二指示消息，包括：若源地面站与空中基站之间的无线信号的信号强度小于第二预设值，则源网络设备通过源地面站向空中基站发送第二指示消息。可以理解的是，源地面站与空中基站之间的无线信号的信号强度小于第二预设值，说明空中基站与源地面站之间的通信质量较差，换句话说，空中基站与源网络设备之间的通信质量较差。因此，在这种情况下，源网络设备通过源地面站向空中基站发送第二指示消息，以触发空中基站执行释放空中基站与源网络设备之间的接口的流程，以使得空中基站实现网络的切换，保证空中基站与地面的正常通信。
一种可能的设计中，该方法还包括：源网络设备向空中基站发送第一指示消息，第一指示消息用于指示建立空中基站与目标网络设备之间的接口。可以理解的是，源网络设备通过发送第一指示消息，以触发空中基站执行建立空中基站与目标网络设备之间的接口的流程，使得空中基站可以从源网络设备切换到目标网络设备，从而保证空中基站与地面的正常通信。
一种可能的设计中，源网络设备向空中基站发送第一指示消息，包括：若目标地面站与空中基站之间的无线信号的信号强度符合预设条件，则源网络设备通过源地面站向空中基站发送第一指示消息。
一种可能的设计中，预设条件包括以下情形之一：(1)目标地面站与空中基站之间的无线信号的信号强度大于或等于第一预设值；(2)目标地面站与空中基站之间的无线信号的信号强度大于源地面站与空中基站之间的无线信号的信号强度。
第四方面，提供一种空中基站，包括：发送模块、接收模块和处理模块。所述空中基站用于执行第一方面所述的切换方法。
第五方面，提供一种空中基站，包括：处理器和存储器，处理器用于读取存储器中的指令，并根据所述指令实现如上述第一方面所述的切换方法。
第六方面，提供一种计算机可读存储介质，该计算机可读存储介质中存储有指令，当其在通信装置上运行时，使得通信装置可以执行上述第一方面所述的切换方法。
第七方面，提供一种包含指令的计算机程序产品，当其在通信装置上运行时，使得通信装置可以执行上述第一方面所述的切换方法。
第八方面，提供一种芯片，该芯片包括处理模块和通信接口，通信接口用于接收输入的信号并提供给处理模块，和/或用于将处理模块生成的信号输出；处理模块用于执行上述第一方面所述的切换方法。在一实施方式中，处理模块可以运行代码指令以执行第一方面所述的切换方法。该代码指令可以来自芯片内部的存储器，也可以来自芯片外部的存储器。可选的，处理模块可以为该芯片上集成的处理器或者微处理器或者集成电路。通信接口可以为芯片上的输入输出电路或者收发管脚。
其中，四方面至第八方面中任一种设计方式所带来的技术效果可参见上文所提供 的对应的方法中的有益效果同设计方式所带来的技术效果，此处不再赘述。
第九方面，提供一种目标网络设备，包括：接收模块和发送模块。其中，目标网络设备用于执行第二方面所述的切换方法。
第十方面，提供一种目标网络设备，包括：处理器和存储器，处理器用于读取存储器中的指令，并根据所述指令实现如上述第二方面所述的切换方法。
第十一方面，提供一种计算机可读存储介质，该计算机可读存储介质中存储有指令，当其在通信装置上运行时，使得通信装置可以执行上述第二方面所述的切换方法。
第十二方面，提供一种包含指令的计算机程序产品，当其在通信装置上运行时，使得通信装置可以执行上述第二方面所述的切换方法。
第十三方面，提供一种芯片，该芯片包括处理模块和通信接口，通信接口用于接收输入的信号并提供给处理模块，和/或用于将处理模块生成的信号输出；处理模块用于执行上述第二方面所述的切换方法。在一实施方式中，处理模块可以运行代码指令以执行第二方面所述的切换方法。该代码指令可以来自芯片内部的存储器，也可以来自芯片外部的存储器。可选的，处理模块可以为该芯片上集成的处理器或者微处理器或者集成电路。通信接口可以为芯片上的输入输出电路或者收发管脚。
其中，第九方面至第十三方面中任一种设计方式所带来的技术效果可参见上文所提供的对应的方法中的有益效果同设计方式所带来的技术效果，此处不再赘述。
第十四方面，提供一种源网络设备，包括：接收模块、处理模块、以及发送模块。其中，源网络设备用于执行第三方面所述的切换方法。
第十五方面，提供一种源网络设备，包括：处理器和存储器，处理器用于读取存储器中的指令，并根据所述指令实现如上述第三方面所述的切换方法。
第十六方面，提供一种计算机可读存储介质，该计算机可读存储介质中存储有指令，当其在通信装置上运行时，使得通信装置可以执行上述第三方面所述的切换方法。
第十七方面，提供一种包含指令的计算机程序产品，当其在通信装置上运行时，使得通信装置可以执行上述第三方面所述的切换方法。
第十八方面，提供一种芯片，该芯片包括处理模块和通信接口，通信接口用于接收输入的信号并提供给处理模块，和/或用于将处理模块生成的信号输出；处理模块用于执行上述第三方面所述的切换方法。在一实施方式中，处理模块可以运行代码指令以执行第三方面所述的切换方法。该代码指令可以来自芯片内部的存储器，也可以来自芯片外部的存储器。可选的，处理模块可以为该芯片上集成的处理器或者微处理器或者集成电路。通信接口可以为芯片上的输入输出电路或者收发管脚。
其中，第十四方面至第十八方面中任一种设计方式所带来的技术效果可参见上文所提供的对应的方法中的有益效果同设计方式所带来的技术效果，此处不再赘述。
第十九方面，提供一种通信系统，包括：空中基站、目标网络设备、以及源网络设备。其中，空中基站用于执行第一方面所述的切换方法，目标网络设备用于执行第二方面所述的切换方法，源网络设备用于执行第三方面所述的切换方法。
附图说明
图1为本申请实施例提供的一种通信系统的架构示意图；
图2为本申请实施例提供的一种集中式节点(centralized unit，CU)-分布式节点 (distributed unit，DU)的架构示意图；
图3为本申请实施例提供的一种NTN的架构示意图一；
图4为本申请实施例提供的一种NTN的架构示意图二；
图5为本申请实施例提供的一种NTN的架构示意图三；
图6为本申请实施例提供的一种空中基站的过顶示意图；
图7为本申请实施例提供的一种空中基站的移动示意图；
图8为本申请实施例提供的一种空中基站的移动示意图；
图9为本申请实施例提供的一种切换方法的流程图一；
图10为本申请实施例提供的一种切换方法的流程图二；
图11为本申请实施例提供的一种切换方法的流程图三；
图12为本申请实施例提供的一种切换方法的流程图四；
图13为本申请实施例提供的一种切换方法的流程图五；
图14为本申请实施例提供的一种切换方法的流程图六；
图15为本申请实施例提供的一种切换方法的流程图七；
图16为本申请实施例提供的一种切换方法的流程图八；
图17为本申请实施例提供的一种切换方法的流程图九；
图18为本申请实施例提供的一种空中基站的结构示意图；
图19为本申请实施例提供的一种目标网络设备的结构示意图；
图20为本申请实施例提供的一种源网络设备的结构示意图；
图21为本申请实施例提供的一种通信装置的结构示意图。
具体实施方式
图1为本申请实施例提供的一种通信系统的架构示意图。如图1所示，通信系统包括终端、接入网设备和核心网。
其中，终端用于向用户提供语音和/或数据连通性服务。所述终端可以有不同的名称，例如用户设备(user equipment，UE)、接入终端、终端单元、终端站、移动站、移动台、远方站、远程终端、移动设备、无线通信设备、终端代理或终端装置等。可选的，所述终端可以为各种具有通信功能的手持设备、车载设备、可穿戴设备、计算机，本申请实施例对此不作任何限定。例如，手持设备可以是智能手机、虚拟现实(virtual reality，VR)设备。车载设备可以是车载导航系统。可穿戴设备可以是智能手环。计算机可以是个人数字助理(personal digital assistant，PDA)电脑、平板型电脑以及膝上型电脑(laptop computer)。
接入网设备可以是无线通信或者有线通信的接入点，例如基站或基站控制器，无线保真(wireless-fidelity，wifi)的接入点或者wifi控制器，或者固网接入的接入点等。其中，所述基站可以包括各种类型的基站，例如：微基站(也称为小站)，宏基站，中继站，接入点等，本申请实施例对此不作具体限定。在本申请实施例中，所述基站可以是全球移动通信系统(global system for mobile communication，GSM)，码分多址(code division multiple access，CDMA)中的基站(base transceiver station，BTS)，宽带码分多址(wideband code division multiple access，WCDMA)中的基站(node B)，长期演进(long term evolution，LTE)中的演进型基站(evolutional node B，eNB或 e-NodeB)，物联网(internet of things，IoT)或者窄带物联网(narrow band-internet of things，NB-IoT)中的eNB，未来5G移动通信网络或者未来演进的公共陆地移动网络(public land mobile network，PLMN)中的基站，本申请实施例对此不作任何限制。
核心网包括各种核心网设备，例如AMF、用户面功能网元(user plane function，UPF)、会话管理功能网元(session management function，SMF)等。
AMF属于核心网实体，主要负责移动性管理处理部分，例如：接入控制、移动性管理、附着与去附着以及SMF选择等功能。AMF为终端中的会话提供服务的情况下，为该会话提供控制面的存储资源，以存储会话标识、与会话标识关联的SMF标识等。
SMF主要用于会话管理、终端的互联网协议(internet protocol，IP)地址分配和管理、选择可管理用户平面功能、策略控制、或收费功能接口的终结点以及下行数据通知等。
UPF可用于分组路由和转发、或用户面数据的QoS处理等。用户数据可通过该网元接入到数据网络(data network，DN)。
上述AMF、SMF以及UPF仅是一个名称，对设备本身不构成限定。可以理解的是，在5G网络以及未来其它的网络中，AMF、SMF以及UPF也可以是其他的名称，本申请实施例对此不作具体限定。例如，UPF还可以被称为UPF网元或者UPF实体，在此进行统一说明，以下不再赘述。
可选的，核心网设备可以由一个设备实现，也可以由多个设备共同实现，还可以是一个设备内的一个功能模块，本申请实施例对此不作具体限定。可以理解的是，上述功能模块既可以是硬件设备中的网络元件，也可以是在专用硬件上运行的软件功能模块，或者是平台(例如，云平台)上实例化的虚拟化功能模块。
如图2所示，为本申请实施例提供的一种CU-DU的架构示意图。以接入网设备为gNB为例，在采用CU-DU的架构下，gNB由CU和至少一个DU构成。这种情况下，gNB的部分功能部署在CU上，gNB的另一部分功能部署在DU上。多个DU可以共用同一个CU，以节省成本。CU和DU是按照协议栈进行功能切分。作为一种实现方式，CU部署有协议栈中的无线资源控制(radio Resource Control，RRC)层，分组数据汇聚协议(packet data convergence protocol，PDCP)层，以及业务数据适应协议(service data adaptation protocol，SDAP)层；DU部署有协议栈中的无线链路控制(radio link control，RLC)层，媒体介入控制(media access control，MAC)层，以及物理层(physical layer，PHY)。从而，CU具有RRC、PDCP和SDAP的处理能力。DU具有RLC、MAC和PHY的处理能力。可以理解的是，上述功能的切分仅为一个示例，不构成对CU和DU的限定。也就是说，CU和DU之间还可以有其他功能切分的方式，本申请实施例在此不予赘述。
CU与DU之间存在接口，本文称之为F1接口。CU与5G核心网(5G Core，5GC)之间存在接口，本文称之为Ng接口。两个CU之间存在接口，本文称之为Xn接口。
可以理解的是，上述接口(例如Ng接口、F1接口等)均为逻辑接口。在5G网络以及未来其他的网络中，上述接口还可以具有其他名称，本申请实施例对此不作限定。
下面以空中平台为卫星为例，介绍NTN的架构。可以理解的是，当空中平台为其 他设备(例如热气球)时，同样适用于下述NTN的架构。可以理解的是，空中平台用于搭载空中基站，空中基站可以是一个完整的基站，也可以是基站的一部分(例如DU)。
如图3所示，为本申请实施例提供的一种NTN的架构示意图。在图3中，卫星不携带载荷，卫星相当于模拟射频中继器，用于实现信号的频率转换和放大。终端和卫星之间通过接口(例如，UU接口)通信。卫星和地面站之间通过接口(例如UU接口)通信。地面站和卫星组成一个射频拉远单元(remote radio unit，RRU)。另外，地面上还部署了基站。卫星、地面站和基站组成无线接入网络(Radio Access Network)。基站与核心网(Core Network，CN)之间通过接口(例如NG接口)通信。CN与数据网络(Data Network，DN)之间通过接口(例如N6接口)通信。
需要说明的是，地面站可以为NTN网关(gateway，GW)，NTN网关是一个传输网络层(transport Network layer，TNL)的节点，用于实现数据或者信令的透传。
如图4所示，为本申请实施例提供的另一种NTN的架构示意图。在图4中，卫星携带的载荷为基站。终端和卫星之间通过接口(例如UU接口)通信。卫星和地面站之间通过接口(例如无线接口(Satellite Radio interface，SRI))通信。卫星上的基站和CN之间通过接口(例如NG接口)通信。CN与DN之间通过接口(例如N6接口)通信。
如图5所示，为本申请实施例提供的另一种NTN的架构示意图。在图5中，当基站采用CU-DU的架构时，DU被携带在卫星上(也即卫星携带的载荷为DU)，CU被部署在地面上。卫星和地面站之间组成射频拉远单元，卫星、地面站以及地面上的CU构成无线接入网络。卫星和终端之间通过接口(例如UU接口)通信。卫星和地面站之间通过接口(例如SRI)通信，SRI用于传输F1接口协议。卫星上的DU和CU之间通过接口(例如F1接口)通信。CU和CN之间通过接口(例如NG接口)通信。CN与DN之间通过接口(例如N6接口)通信。
可以理解的是，本专利申请中，空中平台不限定在空中，还可以是在地面。例如空中平台可以为地面移动平台。空中基站也不限定在空中，还可以是地面上。例如，由地面移动平台搭载的基站。地面站可以替换为位置固定的接收节点(例如宿主(donor)基站)。在这种情况下，本申请实施例所提供的技术方案同样适用于地面移动平台和位置固定的接收节点所构成的架构下。
本申请实施例描述的网络架构以及业务场景是为了更加清楚的说明本申请实施例的技术方案，并不构成对于本申请实施例提供的技术方案的限定，本领域普通技术人员可知，随着网络架构的演变和新业务场景的出现，本申请实施例提供的技术方案对于类似的技术问题，同样适用。
在本申请的描述中，除非另有说明，“/”表示“或”的意思，例如，A/B可以表示A或B。本文中的“和/或”仅仅是一种描述关联对象的关联关系，表示可以存在三种关系，例如，A和/或B，可以表示：单独存在A，同时存在A和B，单独存在B这三种情况。此外，“至少一个”是指一个或多个，“多个”是指两个或两个以上。“第一”、“第二”等字样并不对数量和执行次序进行限定，并且“第一”、“第二”等字样也并不限定一定不同。
需要说明的是，本申请中，“示例性的”或者“例如”等词用于表示作例子、例 证或说明。本申请中被描述为“示例性的”或者“例如”的任何实施例或设计方案不应被解释为比其他实施例或设计方案更优选或更具优势。确切而言，使用“示例性的”或者“例如”等词旨在以具体方式呈现相关概念。
为了便于描述，以下对本申请实施例所涉及的术语进行简单介绍。
(1)过顶时间
如图6所示，过顶是指空中基站经过地面站的上空，能够与地面站进行通信的状态。对于地面站来说，空中基站过顶时，地面站处于空中基站的通信覆盖范围内，地面站可以与空中基站保持通信。在空中基站过顶后，地面站不处于空中基站的通信覆盖范围内，地面站不能与空中基站进行通信。
过顶时间即为空中基站经过地面站的上空，能够与地面站进行通信的一段时间。过顶时间也可以称为过顶时间段，本申请实施例对此不作限定。
(2)源地面站、目标地面站、源网络设备、目标网络设备
源地面站与目标地面站是不同的两个地面站。对于空中基站来说，源地面站即为在切换前与空中基站保持通信的地面站；目标地面站即为在切换后与空中基站保持通信的地面站。
源网络设备即为与源地面站对应的网络设备。目标网络设备即为与目标地面站对应的网络设备。在NTN采用图4所示的架构下，空中基站为基站，网络设备为核心网设备(例如AMF)。在NTN采用图5所示的架构下，空中基站为DU，网络设备为CU。
(3)星历表
星历表用于记录搭载空中基站的空中平台的轨道信息、位置信息等。
可选的，空中基站所存储的星历表具体用于记录搭载所述空中基站的空中平台在多个地面站的过顶时间、该空中平台的轨道周期等。示例性，表1示出空中基站所存储的星历表。由表1可知，空中平台的规定周期为79200秒。对于中国站来说，空中平台的过顶时间为2019年1月9日11:13-15:13；对于欧洲站来说，空中平台的过顶时间为2019年1月9日14:50-18:13；对于美国站来说，该空中平台的过顶时间为2019年1月9日17:50-20:13。可以理解的是，对于每个地面站来说，空中平台的下一次的过顶时间可以根据当前的过顶时间结合空中平台的轨道周期来确定。例如，对于中国站来说，空中平台的下一次过顶时间为2019年1月10日9:13-13:13；对于欧洲站来说，空中平台的下一次过顶时间为2019年1月10日12:50-16:13；对于美国站来说，空中平台的下一次过顶时间为2019年1月10日15:50-18:13。
表1
Figure PCTCN2020074778-appb-000001
Figure PCTCN2020074778-appb-000002
可选的，地面站所存储的星历表具体用于记录多个空中平台经过该地面站的过顶时间以及多个空中平台的轨道周期。示例性的，表2示出地面站所存储的星历表。对于地面站来说，卫星#1的过顶时间为2019年1月9日11:13-15:13，轨道周期为79200秒；卫星#2的过顶时间为2019年1月9日14:50-18:13，轨道周期为79200秒；卫星#3的过顶时间为2019年1月9日17:50-20:13，轨道周期为79200秒。可以理解的，地面站可以根据空中平台的规定周期结合空中平台的当前过顶时间，确定空中平台的下一次过顶时间。例如，对于地面站来说，卫星#1的下一次过顶时间为2019年1月10日9:13-13:13；卫星#2的下一次过顶时间为2019年1月10日12:50-16:13；卫星#3的下一次过顶时间为2019年1月10日15:50-18:13。
表2
Figure PCTCN2020074778-appb-000003
在本申请实施例中，网络设备可以储存该网络设备对应的地面站所存储的星历表。并且，网络设备可以负责更新其对应的地面站所存储的星历表。
下面对本申请实施例所解决的技术问题进行简单分析。
以空中基站搭载在非GEO卫星上为例，空中基站跟随非GEO卫星移动。在移动的过程中，由于非GEO卫星相对于地面并不是静止的，但是地面站的位置相对于地面是固定的，因此空中基站不能保持与同一个地面站的通信。如图7和图8所示，在移动前，空中基站与地面站#1进行通信；在移动后，空中基站与地面站#2进行通信。这就涉及到空中基站如何进行网络切换的问题。目前，业界尚未提出相应的解决方案。
下面结合本申请所提供的附图，对本申请实施例中的技术方案进行描述。
如图9所示，为本申请实施例提供的一种切换方法，该方法包括以下步骤：
S901、空中基站向目标网络设备发送第一请求消息。
其中，所述第一请求消息用于请求所述空中基站与目标网络设备建立接口。
可选的，所述第一请求消息包括以下参数中的至少一项：空中平台类型、移动类型以及空中平台信息。需要说明的是，当空中平台为卫星时，空中平台信息也可以称为卫星信息。
其中，空中平台类型用于指示搭载所述空中基站的空中平台的类型。空中平台类型包括：GEO卫星、LEO卫星、MEO卫星、以及HAPS。
移动类型用于指示空中基站是否处于运动状态。换句话说，移动类型用于指示空中基站是运动的，还是静止的。示例性的，移动类型可以以1个比特来表示，“0”表示空中基站处于运动状态，“1”表示空中基站处于静止状态。
空中平台信息包括以下参数中的至少一项：轨道信息、能力信息、以及高度信息。其中，轨道信息用于使地面站确定空中基站的过顶时间。能力信息用于确定空中基站的覆盖范围，能力信息可以包括倾向角度、发射功率等。高度信息用于指示空中平台距离地面的高度，高度信息可以用于确定空中基站的覆盖范围、空中基站与地面站之间的传输时延、空中平台的运行速度、或者空中平台的运行轨迹等。
若NTN采用图4所示的架构，则空中基站为基站，目标网络设备为目标核心网设备。可选的，所述目标核心网设备可以为目标AMF，本申请实施例不限于此。这种情况下，第一请求消息记为第一请求消息A，第一请求消息A用于请求空中基站与目标核心网设备建立接口，例如NG接口。可选的，第一请求消息A可以称为NG接口建立请求(NG Setup Request)，或者其他名称，本申请实施例不限于此。
可选的，第一请求消息A还包括以下参数中的任意一项：全球无线接入网节点标识、无线接入网节点名称、跟踪区(tracking area，TA)列表、非连续接收(Discontinuous Reception，DRX)周期。其中，跟踪区列表用于指示空中基站支持的跟踪区。跟踪区列表包括：至少一个跟踪区信息，跟踪区信息包括：TAC以及至少一个公共陆地移动网络(public land mobile network，PLMN)标识。
另外，在本申请实施例中，一个跟踪区信息所包含的PLMN标识的最大数目可以大于12个，例如一个跟踪区信息所包含的PLMN标识的最大数目为64个，以适用于空中基站的覆盖区域跨国、跨区域的场景。
若NTN采用图5所示的架构，则空中基站为DU，目标网络设备为目标CU。这种情况下，第一请求消息记为第一请求消息B，第一请求消息B用于请求空中基站与目标CU建立接口，例如F1接口。可以理解的是，第一请求消息B还可以称为F1接口请求(F1 setup request)，或者其他名称。本申请实施例不限于此。
可选的，第一请求消息B还可包括以下参数中的任意一项：DU ID、DU名称、服务小区列表、以及DU RRC版本。其中，服务小区列表用于指示DU(也即空中基站)所支持的小区。服务小区列表包括至少一个服务小区信息。服务小区信息可以包括服务小区的标识。
作为一种实现方式，空中基站通过目标地面站向目标网络设备发送第一请求消息。也就是说，空中基站向目标地面站发送第一请求消息；之后，目标地面站向目标网络设备发送第一请求消息。
S902、目标网络设备向空中基站发送第一响应消息。
其中，第一响应消息用于响应第一请求消息。具体的，第一响应消息用于指示所述空中基站与所述目标网络设备之间的接口是否建立成功。
可选的，当第一响应消息用于指示所述空中基站与所述目标网络设备之间的接口建立失败时，所述第一响应消息包括原因信息，所述原因信息用于指示所述空中基站与所述目标网络设备之间的接口建立失败的原因。
在本申请实施例中，用于响应第一请求消息A的第一响应消息可以记为第一响应消息A。第一响应消息A用于指示所述空中基站与所述目标核心网设备之间的接口(例如NG接口)是否建立成功。第一响应消息A可以称为NG接口建立响应消息(NG setup response)，或者其他名称，本申请实施例对此不作限制。
在本申请实施例中，用于响应第一请求消息B的第一响应消息可以记为第一响应消息B。第一响应消息B用于指示所述空中基站与所述目标CU之间的接口(例如F1接口)是否建立成功。第一响应消息B可以称为F1接口建立响应消息(F1 setup response)，或者其他名称，本申请实施例对此不作限制。
作为一种实现方式，目标网络设备通过目标地面站向空中基站发送第一响应消息。也就是说，目标网络设备向目标地面站发送第一响应消息；之后，目标地面站将该第一响应消息发送给空中基站。
可选的，在第一响应消息指示空中基站与目标网络设备成功建立接口的情况下，目标网络设备、目标地面站、或者空中基站可以更新星历表。对于空中基站来说，空中基站在星历表中记录或者更新空中基站通过目标地面站向目标网络设备发送第一请求消息的时间，以作为空中基站下一次与目标网络设备建立接口的参考时间。对于目标网络设备或者目标地面站来说，目标网络设备或者目标地面站在星历表中记录或者更新接收到第一请求消息的时间。
S903、空中基站向源网络设备发送第二请求消息。
其中，所述第二请求消息用于请求释放所述空中基站与所述源网络设备之间的接口。
在本申请实施例中，所述第二请求消息包括以下参数中的至少一项：空中基站的信息、释放类型、以及重建周期。其中，重建周期用于指示所述源网络设备与所述空中基站重新建立接口的时间。释放类型包括：第一类型、第二类型、以及第三类型。第一类型用于指示删除所述空中基站的上下文信息。第二类型用于指示去激活所述空中基站的上下文信息。第三类型用于指示去激活所述空中基站的上下文信息，并在所述重建周期所指示的时间激活所述空中基站的上下文信息。
另外，需要说明的是，当释放类型为第一类型时，空中基站删除源网络设备的信息。当释放类型为第二类型或第三类型时，空中基站保存源网络设备的信息。可选的，源网络设备的信息包括源网络设备的名称、源网络设备的标识等。
可以理解的是，在源网络设备去激活空中基站的上下文信息之后，源网络设备保存空中基站的上下文信息。
在本申请实施例，若NTN采用图4所示的架构，空中基站的上下文信息包括：全球无线接入网节点标识、无线接入网节点名称、跟踪区列表和DRX周期。若NTN采用图5所示的架构，空中基站的上下文信息包括：DU ID、DU名称、服务小区列表、以及DU RRC版本。
若NTN采用图4所示的架构，则第二请求消息可以记为第二请求消息A，第二请求消息A用于请求释放所述空中基站与所述源核心网设备之间的NG接口。可选的，第二请求消息A还可以称为NG接口释放请求(NG Release Request)，或者其他名称，本申请实施例对此不作限定。
可选的，对于第二请求消息A来说，空中基站的信息包括以下至少一种：全球无线接入网节点标识和无线接入网节点名称。
若NTN采用图5所示的架构，则空中基站为DU，源网络设备为源CU。在这种情况下，第二请求消息可以记为第二请求消息B，第二请求消息B用于请求释放所述 空中基站与所述源CU之间的接口，例如F1接口。可选的，第二请求消息还可以称为F1接口释放请求(F1 Release Request)，或者其他名称，本申请实施例对此不作限定。
可选的，对于第二请求消息B来说，空中基站的信息包括以下至少一种：DU ID和DU名称。
S904、源网络设备向空中基站发送第二响应消息。
其中，所述第二响应消息用于响应第二请求消息。具体的，第二响应消息用于指示所述空中基站与所述源网络设备之间的接口是否释放成功。
可选的，若第二响应消息用于指示所述空中基站与所述源网络设备之间的接口释放失败，则所述第二响应消息还可以包括原因信息，所述原因信息用于指示所述空中基站与所述源网络设备之间的接口释放失败的原因。
在本申请实施例中，用于响应第二请求消息A的第二响应消息可以记为第二响应消息A。第二响应消息A用于指示所述空中基站与所述源核心网设备之间的接口是否释放成功。第二响应消息A可以称为NG接口释放响应消息(NG Release response)，或者其他名称，本申请实施例对此不作限定。
在本申请实施例中，用于响应第二请求消息B的第二响应消息可以记为第二响应消息B。第二响应消息B用于指示所述空中基站与所述源CU之间的接口是否释放成功。第二响应消息B可以称为F1接口释放响应消息(F1 Release response)，或者其他名称，本申请实施例对此不作限定。
作为一种实现方式，源网络设备通过源地面站向空中基站发送第二响应消息。也就是说，源网络设备向源地面站发送第二响应消息；之后，源地面站将该第二响应消息发送给空中基站。
可选的，在第二响应消息指示空中基站与源网络设备成功释放接口的情况下，源网络设备、源地面站、或者空中基站可以更新星历表。对于空中基站来说，空中基站在星历表中记录或者更新空中基站通过源地面站向源网络设备发送第二请求消息的时间，以作为空中基站下一次与源网络设备释放接口的参考时间。对于源网络设备或者源地面站来说，源网络设备或者源地面站在星历表中记录或者更新接收到第二请求消息的时间。
需要说明的是，本申请实施例不限定步骤S901-S902与步骤S903-S904的执行顺序。也就是说，本申请的技术方案可以先执行步骤S901-S902，再执行步骤S903-S904；或者，先执行步骤S903-S904，再执行步骤S901-S902；又或者，同时执行步骤S901-S902，和步骤S903-S904。
可选的，若目标网络设备预先存储有空中基站的上下文信息，则步骤S901-S902可替换为步骤S905-S906。可以理解的是，目标网络设备预先存储的空中基站的上下文信息可以来自于前一次空中基站与目标网络设备建立接口的流程中。
S905、空中基站向目标网络设备发送第三请求消息。
其中，所述第三请求消息用于请求激活所述空中基站与所述目标网络设备之间的接口。或者说，所述第三请求消息用于请求激活所述空中基站的上下文信息。
若NTN采用图4所示的架构，则所述第三请求信息可以记为第三请求消息A。其中，第三请求消息A用于请求激活空中基站与目标核心网设备之间的接口，例如NG 接口。可选的，第三请求消息A还可以称为NG接口激活请求(NG Resume Request)，或者其他名称，本申请实施例对此不作限定。
可选的，第三请求消息A包括空中基站的信息，所述空中基站的信息包括：全球无线接入网节点标识和无线接入网节点名称。
若NTN采用图5所示的架构，则所述第三请求消息可以记为第三请求消息B。其中，第三请求消息B用于请求激活空中基站与目标CU之间的接口，例如F1接口。可选的，第三请求消息B还可以称为F1接口激活请求(F1 Resume Request)，或者其他名称，本申请实施例对此不作限定。
可选的，第三请求消息B包括空中基站的信息，所述空中基站的信息包括：DU ID和DU名称。
可以理解的是，由于第三请求消息携带的信息少于第一请求消息携带的信息，因此相比于第一请求消息，第三请求消息所带来的信令开销较小。
作为一种实现方式，空中基站通过目标地面站向目标网络设备发送第三请求消息。也就是说，空中基站向目标地面站发送第三请求消息；之后，目标地面站将该第三请求消息发送给目标网络设备。
S906、目标网络设备向空中基站发送第三响应消息。
其中，第三响应消息用于响应第三请求消息。具体的，第三响应消息用于指示所述空中基站的上下文信息是否激活成功。
可选的，当第三响应消息用于指示所述空中基站的上下文信息激活失败时，所述第三响应消息包括原因信息，所述原因信息用于指示所述空中基站的上下文信息激活失败的原因。
在本申请实施例中，用于响应第三请求消息A的第三响应消息可以记为第三响应消息A。第三响应消息A用于指示所述目标核心网设备是否成功激活所述空中基站的上下文信息。可选的，第三响应消息A可以称为NG接口激活响应消息(NG Resume response)，或者其他名称，本申请实施例对此不作限定。
在本申请实施例中，用于响应第三请求消息B的第三响应消息可以记为第三响应消息B。第三响应消息B用于指示所述目标CU是否成功激活所述空中基站的上下文信息。可选的，第三响应消息B可以称为F1接口激活响应消息(F1 Resume response)，或者其他与名称，本申请实施例对此不作限定。
作为一种实现方式，目标网络设备通过目标地面站向空中基站发送第三响应消息。也就是说，目标网络设备向目标地面站发送第三响应消息；之后，目标地面站将该第一响应消息发送给空中基站。
可选的，在第三响应消息指示目标网络设备成功激活空中基站的上下文信息的情况下，目标网络设备、目标地面站、或者空中基站可以更新星历表。对于空中基站来说，空中基站在星历表中记录或者更新空中基站通过目标地面站向目标网络设备发送第三请求消息的时间，以作为空中基站下一次与目标网络设备建立接口的参考时间。对于目标网络设备或者目标地面站来说，目标网络设备或者目标地面站在星历表中记录或者更新接收到第三请求消息的时间。
需要说明的是，本申请实施例不限定步骤S903-S904与步骤S905-S906的执行顺 序。也就是说，本申请的技术方案可以先执行步骤S903-S904，再执行步骤S905-S906；或者，先执行步骤S905-S906，再执行步骤S903-S904；又或者，同时执行步骤S903-S904，和步骤S905-S906。
为了使得上述实施例更加的清楚，以下结合具体应用场景对上述实施例的实现流程进行示例性说明。
示例一、
如图10所示，为本申请实施例提供的一种切换方法，该方法包括以下步骤：
S1001、空中基站分别确定n个地面站与空中基站之间的无线信号的信号强度。
其中，所述n个地面站包括源地面站，n为大于1的整数。
需要说明的是，无线信号可以是指SRI的信号或者待测信号。待测信号为同步信号或者参考信号。其中，同步信号可以是指主同步信号(primary synchronization signal，PSS)，或者辅同步信号(secondary synchronization signal，SSS)等。参考信号可以是指探测参考信号(sounding reference signal，SRS)，或者信道状态信息参考信号(channel state information reference siganl，CSI-RS)等。本申请实施例对此不作具体限定。
示例性的，无线信号的信号强度包括以下参数中的任意一项：参考信号接收功率(reference signal receiving power，RSRP)、信噪比(signal noise ratio，SNR)、或者信号与干扰加噪声比(signal to interference plus noise ratio，SINR)。
可选的，步骤S1001可以采用以下方式一至方式三中的任意一种来实现。需要说明的是，方式一适用于无线信号为SRI的信号的场景，方式二和方式三适用于无线信号为待测信号的场景。
方式一、对于n个地面站中的每一个地面站，空中基站测量地面站的SRI的信号，确定地面站与空中基站之间SRI的信号的信号强度。
可以理解的是，所述n个地面站中的每一个地面站均与所述空中基站建立了SRI。
方式二、空中基站发送待测信号。n个地面站中的每一个地面站接收待测信号，并确定测量报告信息，该测量报告信息用于指示地面站接收到的待测信号的信号强度。之后，n个地面站中的每一个地面站向空中基站发送测量报告信息。或者，n个地面站中除源地面站之外的其他地面站将测量报告信息发送给源地面站；源地面站将n个测量报告信息发送给空中基站。这样一来，空中基站接收到n个测量报告信息，n个测量报告信息与n个地面站一一对应；从而，空中基站能够分别确定n个地面站与所述空中基站之间的待测信号的信号强度。
可选的，待测信号包括空中基站的信息，例如空中基站的标识。
可选的，空中基站在预设时间发送待测信号。相应的，地面站在预设时间接收待测信号。其中，预设时间可以根据星历表确定。这样一来，空中基站仅需在部分时间内发送待测信号，以节省电量消耗。相应的，地面站也即需在部分时间内检测并接收待测信号，以节省电量消耗。
方式三、n个地面站中的每一个地面站分别发送待测信号。空中基站接收到n个地面站发送的待测信号，确定n个测量报告信息，n个测量报告信息与n个地面站一一对应，测量报告信息用于指示空中基站接收到的待测信号的信号强度。
可选的，待测信号包括地面站的信息，例如地面站的标识、地面站所属的核心网的标识。
可选的，地面站在预设时间发送待测信号。相应的，空中基站在预设时间接收待测信号。其中，预设时间可以根据星历表确定。这样一来，地面站仅需在部分时间内发送待测信号，以节省电量消耗。相应的，空中基站仅需要在部分时间内检测并接收待测信号，以节省电量消耗。
S1002、空中基站进行切换判决。
作为一种实现方式，空中基站可以根据n个地面站与所述空中基站之间的无线信号的信号强度，进行切换判决，确定n个地面站除源地面站之外的其他地面站中是否存在目标地面站。
其中，目标地面站与所述空中基站之间的无线信号的信号强度符合预设条件。
示例性的，预设条件包括以下情形之一：
(1)目标地面站与所述空中基站之间的无线信号的信号强度大于或等于第一预设值；
(2)目标地面站与所述空中基站之间的无线信号的信号强度大于源地面站与所述空中基站之间的无线信号的信号强度。
以上是对预设条件的示例，本申请实施例不限于此。
作为一种实现方式，空中基站根据n个地面站与所述空中基站之间的无线信号的信号强度，确定n个地面站除源地面站之外的其他地面站中是否存在符合预设条件的地面站。若n个地面站除源地面站之外的其他地面站中存在符合预设条件的地面站，则该符合预设条件的地面站即为目标地面站。若n个地面站除源地面站之外的其他地面站中不存在符合预设条件的地面站，则空中基站确定不存在目标地面站。
举例来说，以无线信号的信号强度为SNR为例，假设地面站#2为源地面站，并且地面站#1与空中基站之间的无线信号的信号强度为25dB，地面站#2与空中基站之间的无线信号的信号强度为30dB，地面站#3与空中基站之间的无线信号的信号强度为45dB。若预设条件为：目标地面站与所述空中基站之间的无线信号的信号强度大于或等于第一预设值，第一预设值为40dB，则地面站#3为目标地面站。若预设条件为：目标地面站与所述空中基站之间的无线信号的信号强度大于源地面站与所述空中基站之间的无线信号的信号强度，则地面站#3为目标地面站。
可以理解的是，若n个地面站除源地面站之外的其他地面站中存在多个符合预设条件的地面站，则空中基站可以从这多个符合预设条件的地面站中选择一个地面站作为目标地面站。例如，在多个符合预设条件的地面站中，以无线信号的信号强度最高的地面站作为目标地面站。又例如，每一个地面站预先设置了优先级，当存在多个符合预设条件的地面站时，空中基站从多个符合预设条件的地面站中选择优先级最高的地面站作为目标地面站。
举例来说，以无线信号的信号强度为SNR为例，地面站#1、地面站#3、地面站#4均符合预设条件，并且，假设地面站#1与空中基站之间的无线信号的信号强度为45dB，地面站#3与空中基站之间的无线信号的信号强度为50dB，地面站#4与空中基站之间的无线信号的信号强度为55dB。若以无线信号的信号强度最高的地面站作为目标地面 站，则地面站#4为，目标地面站。
在本申请实施例中，若空中基站确定n个地面站除源地面站之外的其他地面站中不存在目标地面站，则空中基站保持与源网络设备之间的接口；若空中基站确定n个地面站除源地面站之外的其他地面站中存在目标地面站，则空中基站建立与目标网络设备之间的接口。
具体的，当空中基站确定n个地面站除源地面站之外的其他地面站中存在目标地面站时，若目标网络设备未预先存储空中基站的上下文信息，则执行下述步骤S1003a-S1004a；若目标网络设备预先存储空中基站的上下文信息，则执行下述步骤S1003b-S1004b。
可选的，空中基站可通过确定是否是第一次与目标网络设备建立接口，来判断目标网络设备是否预先存储了空中基站的上下文信息。具体的，当空中基站确定第一次与目标网络设备建立接口，则空中基站能够确定目标网络设备未预先存储空中基站的上下文信息。当空中基站确定不是第一次与目标网络设备建立接口，则空中基站能够确定目标网络设备预先存储空中基站的上下文信息。
示例性的，空中基站可以根据是否存储了目标网络设备的信息，确定是否是第一次与目标网络设备建立接口。具体的，若空中基站存储了目标网络设备的信息，则空中基站确定不是第一次与目标网络设备建立接口；若空中基站未存储目标网络设备的信息，则空中基站确定是第一次与目标网络设备建立接口。
示例性的，空中基站预先存储了空中基站与网络设备建立接口的次数。这样一来，空中基站可以通过查询空中基站与目标网络设备建立接口的次数，确定空中基站是否是第一次与目标网络设备建立接口。
S1003a-S1004a、与步骤S901-S902相同，具体描述可参考图9所示的实施例，在此不再赘述。
S1003b-S1004b、与步骤S905-S906相同，具体描述可参考图9所示的实施例，在此不再赘述。
S1005、空中基站确定是否释放所述空中基站与所述源网络设备之间的接口。
作为一种实现方式，空中基站根据源地面站与空中基站之间的无线信号的信号强度确定是否释放所述空中基站与所述源网络设备之间的接口。
具体的，若源地面站与空中基站之间的无线信号的信号强度大于等于第二预设值，则空中基站保持与所述源网络设备之间的接口。若源地面站与空中基站之间的无线信号的信号强度小于第二预设值，则空中基站确定释放所述空中基站与所述源网络设备之间的接口，从而空中基站执行下述步骤S1006。
S1006-S1007、与步骤S903-S904相同，具体描述可参考图9所示的实施例，在此不再赘述。
基于图10所示的技术方案，空中基站根据n个地面站与空中基站之间的无线信号的信号强度，确定是否需要进行网络切换，从而保证空中基站在移动过程中与地面的正常通信。
示例二、
如图11所示，为本申请实施例提供的一种切换方法，该方法包括以下步骤：
S1101、源网络设备分别确定n个地面站与空中基站之间的无线信号的信号强度。
其中，所述n个地面站包括源地面站，n为大于1的整数。
需要说明的是，无线信号可以是指SRI的信号或者待测信号。待测信号为同步信号或者参考信号。其中，同步信号可以是指PSS，或者SSS等。参考信号可以是指SRS，或者CSI-RS等。本申请实施例对此不作具体限定。
示例性的，无线信号的信号强度包括以下参数中的任意一项：RSRP、SNR、或者SINR。
可选的，步骤S1101可以采用以下方式一或方式二来实现。需要说明的是，方式一适用于无线信号为SRI的信号的场景。方式二适用于无线信号为待测信号的场景。
方式一、n个地面站中的每一个地面站测量地面站与空中基站之间的SRI的信号的信号强度，并将测量结果发送给源网络设备。这样一来，源网络设备能够确定n个地面站与空中基站之间的SRI的信号的信号强度。
方式二、空中基站发送待测信号。n个地面站中的每一个地面站接收待测信号，并确定测量报告信息，该测量报告信息用于指示地面站接收到的待测信号的信号强度。之后，n个地面站中的每一个地面站向源网络设备发送测量报告信息。这样一来，源网络设备接收到n个测量报告信息，n个测量报告信息与n个地面站一一对应；从而，空中基站能够分别确定n个地面站与所述空中基站之间的待测信号的信号强度。
S1102、源网络设备进行切换判决。
作为一种实现方式，源网络设备根据n个地面站与空中基站之间的无线信号的信号强度，确定n个地面站除源地面站之外的其他地面站中是否存在目标地面站。
其中，目标地面站与所述空中基站之间的无线信号的信号强度符合预设条件。
示例性的，预设条件包括以下情形之一：
(1)目标地面站与所述空中基站之间的无线信号的信号强度大于或等于第一预设值；
(2)目标地面站与所述空中基站之间的无线信号的信号强度大于源地面站与所述空中基站之间的无线信号的信号强度。
以上是对预设条件的示例，本申请实施例不限于此。
作为一种实现方式，源网络设备根据n个地面站与所述空中基站之间的无线信号的信号强度，确定n个地面站除源地面站之外的其他地面站中是否存在符合预设条件的地面站。若n个地面站除源地面站之外的其他地面站中存在符合预设条件的地面站，则该符合预设条件的地面站即为目标地面站。若n个地面站除源地面站之外的其他地面站中不存在符合预设条件的地面站，则源网络设备确定不存在目标地面站。
可以理解的是，n个地面站除源地面站之外的其他地面站中存在多个符合预设条件的地面站，则源网络设备可以从这多个符合预设条件的地面站中选择一个地面站作为目标地面站。又例如，每一个地面站预先设置了优先级，当存在多个符合预设条件的地面站时，源网络设备从多个符合预设条件的地面站中选择优先级最高的地面站作为目标地面站。
在本申请实施例中，若源网络设备确定n个地面站除源地面站之外的其他地面站中不存在目标地面站，则源网络设备保持与空中基站之间的接口；若源网络设备确定 n个地面站除源地面站之外的其他地面站中存在目标地面站，则源网络设备执行以下步骤S1103，以保证空中基站与地面之间的正常通信。
S1103、源网络设备向空中基站发送第一指示消息。
其中，第一指示消息用于指示建立空中基站与目标网络设备之间的接口。
可选的，第一指示消息包括：目标地面站的信息。目标地面站的信息可以包括：目标地面站的名称、目标地面站的标识等。
作为一种实现方式，源网络设备通过源地面站向空中基站发送第一指示消息。也就是说，源网络设备向源地面站发送第一指示消息；之后，源地面站将该第一指示消息发送给空中基站。
在本申请实施例中，在空中基站接收到第一指示消息之后，空中基站判断是否是第一次与目标网络设备建立接口。若空中基站是第一次与目标网络设备建立接口，则执行下述步骤S1104a-S1105a。若空中基站不是第一次与目标网络设备建立接口，则执行下述步骤S1104b-S1105b。
S1104a-S1105a、与步骤S901-S902相同，具体描述可参考图9所示的实施例，在此不再赘述。
S1104b-S1105b、与步骤S905-S906相同，具体描述可参考图9所示的实施例，在此不再赘述。
S1106、源网络设备确定是否释放空中基站与源网络设备之间的接口。
作为一种实现方式，源网络设备根据源地面站与空中基站之间的无线信号的信号强度，确定是否释放空中基站与源网络设备之间的接口。
具体的，若源地面站与空中基站之间的无线信号的信号强度大于等于第二预设值，则源网络设备保持与空中基站之间的接口。若源地面站与空中基站之间的无线信号的信号强度小于第二预设值，则源网络设备确定释放与空中基站之间的接口，也即源网络设备执行下述步骤S1107。
S1107、源网络设备向空中基站发送第二指示消息。
其中，第二指示消息用于指示释放空中基站与源网络设备之间的接口。
作为一种实现方式，源网络设备通过源地面站向空中基站发送第二指示消息。也就是说，源网络设备向源地面站发送第二指示消息；之后，源地面站将该第二指示消息发送给空中基站。
S1108-S1109、与步骤S903-S904相同，具体描述可参考图9所示的实施例，在此不再赘述。
基于图11所示的技术方案，源网络设备根据n个地面站与空中基站之间的无线信号的信号强度，确定空中基站是否进行网络切换，从而保证空中基站在移动过程中与地面的正常通信。
示例三
如图12所示，为本申请实施例提供的一种切换方法，该方法包括以下步骤：
S1201a、空中基站在第一预设时间向目标网络设备发送第一请求消息。
其中，第一预设时间根据所述空中基站在所述目标地面站的过顶时间确定。举例来说，假设空中基站在所述目标地面站的过顶时间为13:00-13:30，则第一预设时间可 以为13:00，或者第一预设时间可以为13:05。
需要说明的是，所述空中基站在所述目标地面站的过顶时间可以预先配置在空中基站中，也可以由空中基站根据星历表或者空中基站的运动轨迹来确定。其中，星历表用于记录搭载空中基站的空中平台的位置信息、轨道信息等。换句话说，第一预设时间可以根据星历表确定；或者，第一预设时间可以根据空中基站的运动轨迹确定。
可选的，第一预设时间也可以根据第一定时器确定，第一定时器可以是预先配置的。
作为一种实现方式，空中基站在第一预设时间通过目标地面站向目标网络设备发送第一请求消息。也就是说，空中基站在第一预设时间向目标地面站发送第一请求消息；之后，目标地面站将该第一请求消息发送给目标网络设备。
S1202a、目标网络设备向空中基站发送第一响应消息。
其中，步骤S1201a-S1202a的详细描述可参考步骤S901-S902，在此不再赘述。
可选的，在空中基站不是第一次与目标网络设备建立接口的情况下，S1201a-S1202a可以替换为S1201b-S120b。
S1201b、空中基站在第一预设时间向目标网络设备发送第三请求消息。
其中，第一预设时间的详细描述可参考步骤S1201a，在此不再赘述。
作为一种实现方式，空中基站在第一预设时间通过目标地面站向目标网络设备发送第三请求消息。也就是说，空中基站在第一预设时间向目标地面站发送第三请求消息；之后，目标地面站将该第三请求消息发送给目标网络设备。
S1202b、目标网络设备向空中基站发送第三响应消息。
其中，步骤S1201b-S1202b的详细描述可参考步骤S905-S906，在此不再赘述。
S1203、空中基站在第二预设时间向源网络设备发送第二请求消息。
其中，第二预设时间根据所述空中基站在所述源地面站的过顶时间确定。举例来说，假设空中基站在所述源地面站的过顶时间为12:00-12:30，则第二预设时间可以为12:30，或者第二预设时间可以为12:25。
需要说明的是，所述空中基站在所述源地面站的过顶时间可以预先配置在空中基站中，也可以由空中基站根据星历表或者空中基站的运动轨迹来确定。其中，星历表用于记录空中基站的位置信息以及轨道信息。换句话说，第二预设时间可以根据星历表确定；或者，第二预设时间可以根据空中基站的运动轨迹确定。
可选的，第二预设时间也可以根据第二定时器确定，第二定时器是预先配置的。
作为一种实现方式，空中基站在第二预设时间通过源地面站向源网络设备发送第二请求消息。也就是说，空中基站在第二预设时间向源地面站发送第二请求消息；之后，源地面站将该第二请求消息发送给源网络设备。
S1204、源网络设备向空中基站发送第二响应消息。
其中，步骤S1203-S1204的详细描述可参考步骤S903-S904，在此不再赘述。
基于图12所示的技术方案，空中基站在预设时间触发相应的切换流程，以保证与地面的正常通信。
示例四
如图13所示，为本申请实施例提供的一种切换方法，该方法包括：
S1301、空中基站接收传输链路建立指示消息。
其中，传输链路建立指示消息用于指示空中基站与目标地面站之间的传输链路已建立。
可选的，所述传输链路建立指示消息来自于空中基站的传输层协议栈。
可选的，若空中基站是第一次与目标网络设备建立接口，则执行下述步骤S1302a-S1303a；若空中基站不是第一次与目标网络设备建立接口，则执行下述步骤S1302b-S1303b。
S1302a-S1303a、与步骤S901-S902相同，详细描述可参考图9所示的实施例，在此不再赘述。
S1302b-S1303b、与步骤S905-S906相同，详细描述可参考图9所示的实施例，在此不再赘述。
S1304、空中基站接收传输链路预删除指示消息。
其中，所述传输链路预删除指示消息用于指示空中基站与源地面站之间的传输链路待删除。
可选的，所述传输链路预删除指示消息来自于空中基站的传输层协议栈。
S1305-S1306、与步骤S903-S904相同，详细描述可参考图9所示的实施例，在此不再赘述。
示例五
如图14所示，为本申请实施例提供的一种切换方法，适用于图4所示的NTN架构。该方法包括：
S1401、空中基站确定是否迁移连接态的终端。
作为一种实现方式，空中基站检测目标地面站与空中基站之间的无线信号的信号强度是否大于源地面站与空中基站之间的无线信号的信号强度。当目标地面站与空中基站之间的无线信号的信号强度不大于源地面站与空中基站之间的无线信号的信号强度，空中基站确定不迁移连接态的终端。当目标地面站与空中基站之间的无线信号的信号强度大于源地面站与空中基站之间的无线信号的信号强度，空中基站确定迁移连接态的终端。
作为另一种实现方式，空中基站检测源地面站与空中基站之间的无线信号的信号强度是否小于预设值。当源地面站与空中基站之间的无线信号的信号强度小于预设值时，空中基站确定迁移连接态的终端。当源地面站与空中基站之间的无线信号的信号强度大于或等于预设值时，空中基站确定不迁移连接态的终端。
上述两种实现方式可以相互结合使用。例如，空中基站检测源地面站与空中基站之间的无线信号的信号强度是否小于预设值，以及目标地面站与空中基站之间的无线信号的信号强度是否大于源地面站与空中基站之间的无线信号的信号强度。若源地面站与空中基站之间的无线信号的信号强度小于预设值，并且目标地面站与空中基站之间的无线信号的信号强度大于源地面站与空中基站之间的无线信号的信号强度，空中基站确定迁移连接态的终端。若源地面站与空中基站之间的无线信号的信号强度大于等于预设值，或者目标地面站与空中基站之间的无线信号的信号强度小于等于源地面站与空中基站之间的无线信号的信号强度，则空中基站确定不迁移连接态的终端。
在本申请实施例中，当空中基站确定迁移连接态的终端时，空中基站执行下述步骤S1402。
S1402、空中基站触发连接态的终端从源核心网设备迁移到目标核心网设备。
其中，连接态的终端的迁移流程可参考现有技术，在此不再赘述。
例如，空中基站向连接态的终端发送指示消息，该指示消息用于指示连接态的终端从源核心网设备迁移到目标核心网设备。
可以理解的是，当连接态的终端从源核心网设备迁移到目标核心网设备具体是指，连接态终端的上下文信息从源核心网设备迁移到目标核心网设备。
可选的，步骤S1401-S1402在空中基站与目标核心网设备建立接口之后执行。
基于图14所示的技术方案，在空中基站在切换网络之后，保证空中基站向终端正常提供服务。
示例六
如图15所示，为本申请实施例提供的一种切换方法，适用于图4所示的NTN架构。该方法包括：
S1501、源核心网设备确定是否迁移连接态的终端。
作为一种实现方式，源核心网设备检测目标地面站与空中基站之间的无线信号的信号强度是否大于源地面站与空中基站之间的无线信号的信号强度。当目标地面站与空中基站之间的无线信号的信号强度不大于源地面站与空中基站之间的无线信号的信号强度，源核心网设备确定不迁移连接态的终端。当目标地面站与空中基站之间的无线信号的信号强度大于源地面站与空中基站之间的无线信号的信号强度，源核心网设备确定迁移连接态的终端。
作为另一种实现方式，空中基站检测源地面站与空中基站之间的无线信号的信号强度是否小于预设值。当源地面站与空中基站之间的无线信号的信号强度小于预设值时，源核心网设备确定迁移连接态的终端。当源地面站与空中基站之间的无线信号的信号强度大于或等于预设值时，源核心网设备确定不迁移连接态的终端。
上述两种实现方式可以相互结合使用。例如，源核心网设备检测源地面站与空中基站之间的无线信号的信号强度是否小于预设值，以及目标地面站与空中基站之间的无线信号的信号强度是否大于源地面站与空中基站之间的无线信号的信号强度。若源地面站与空中基站之间的无线信号的信号强度小于预设值，并且目标地面站与空中基站之间的无线信号的信号强度大于源地面站与空中基站之间的无线信号的信号强度，源核心网设备确定迁移连接态的终端。若源地面站与空中基站之间的无线信号的信号强度大于等于预设值，或者目标地面站与空中基站之间的无线信号的信号强度小于等于源地面站与空中基站之间的无线信号的信号强度，则源核心网设备确定不迁移连接态的终端。
在本申请实施例中，当源核心网设备确定迁移连接态的终端时，源核心网设备执行下述步骤S1502。
S1502、源核心网设备触发连接态的终端从源核心网设备迁移到目标核心网设备。
其中，连接态的终端的迁移流程可参考现有技术，在此不再赘述。
可以理解的是，当连接态的终端从源核心网设备迁移到目标核心网设备具体是指， 连接态终端的上下文信息从源核心网设备迁移到目标核心网设备。
可选的，步骤S1501-S1502在空中基站与目标核心网设备建立接口之后执行。
基于图15所示的技术方案，在空中基站在切换网络之后，保证空中基站向终端正常提供服务。
示例七
如图16所示，为本申请实施例提供的一种切换方法，应用于图5所示的NTN架构。该方法包括：
S1601-S1603、与步骤S1005-S1007相似，详细描述可参考图10所示的实施例，在此不再赘述。
S1604、空中基站向终端发起RRC连接释放请求(RRC connect release)。
S1605、空中基站接收终端发送的RRC连接释放响应(RRC connect release response)。
其中，步骤S1604-S1605是可选的执行步骤。
S1606a-S1607a、与S901-S902相似，具体描述可参考图9所示的实施例，在此不再赘述。
S1606b-S1607b、与步骤S905-S906相似，具体描述可参考图9所示的实施例，在此不再赘述。
可以理解的是，在一个DU不能同时连接两个CU的场景下，空中基站先释放空中基站与源CU的接口；之后，空中基站再与目标CU建立接口，以保证空中基站能够完成网络切换的流程。
在空中基站与目标CU建立接口之后，空中基站建立新的小区，以便于向终端提供服务。
基于图16所示的技术方案，在NTN采用图5所示的架构下，保证空中基站能够完成网络切换。
示例八
如图17所示，为本申请实施例提供的一种切换方法，应用于图5所示的NTN架构。该方法包括：
S1701、与步骤S1002相似，详细描述可参考图10所示的实施例，在此不再赘述。
S1702、空中基站生成逻辑DU。
在这种情况下，空中基站存在两个DU：当前与源CU建立接口的DU(为便于描述，下文称为原DU)、以及逻辑DU。
其中，逻辑DU具有与原DU相同的小区信息，并且逻辑DU具有与原DU相同的UE上下文信息。逻辑DU与原DU的区别在于：逻辑DU的DU名称不同于原DU的DU名称；或者，逻辑DU的DU ID不同于原DU的DU ID。
S1703-S1704、与步骤S1003a-S1004a相似，具体描述可参考图10所示的实施例，在此不再赘述。其中，步骤S1703与步骤S1003a的区别在于，步骤S1003a中第一请求消息用于请求建立空中基站与目标网络设备之间的接口。步骤S1703中第一请求消息用于建立逻辑DU与目标网络设备之间的接口。
S1705-S1707、与步骤S1005-S1007相似，详细描述可参考图10所示的实施例， 在此不再赘述。其中，区别在于，S1006中第二请求消息用于请求释放空中基站与源网络设备之间的接口；S1706中第二请求消息用于请求释放原DU与源网络设备之间的接口。
可选的，在释放了原DU与源网络设备之间的接口之后，空中基站删除原DU的信息。
基于图17所示的技术方案，在一个DU不能同时连接两个DU的情况下，空中基站通过生成逻辑DU，并以逻辑DU与目标CU建立接口，从而使得空中基站能够完成网络切换。并且，由于逻辑DU具有与原DU相同的UE上下文信息，从而在空中基站完成网络切换之后，保证空中基站能够向终端提供相应的服务。
为了便于本领域技术人员理解，以下对上述实施例进行分析。
(1)在上述实施例中，图10所示的实施例和图11所示的实施例是基于空中基站与地面站之间的无线信号的信号强度来确定空中基站是否进行网络切换。图12所示的实施例是基于预设时间来触发空中基站进行网络切换。
需要说明的是，图10所示的实施例和图11所示的实施例的优点在于：能够保证空中基站在进行网络切换后，空中基站与目标地面站之间具有较好的通信质量。图12所示的实施例的优点在于，切换流程较为简单，降低了复杂度。
(2)图10所示的实施例和图11所示的实施例的区别在于，图10所示的实施例由空中基站来进行切换判决，图11所示的实施例由源网络设备进行切换判决。
(3)在图10-图12所示实施例中，可以先释放空中基站与源网络设备之间的接口，再建立空中基站与目标网络设备之间的接口；也可以先建立空中基站与目标网络设备之间的接口，再释放空中基站与源网络设备之间的接口。
其中，先建立空中基站与目标网络设备之间的接口，再建立空中基站与源网络设备之间的接口，具有以下优点：保证空中基站能够一直向终端提供服务，避免终端在不同的状态间(例如空闲态和连接态之间)来回切换，避免终端出现掉话的现象。
(4)图14所示的实施例与图15所示的实施例的区别在于，图14所示的实施例由空中基站来确定是否将终端从源网络设备迁移到目标网络设备；图15所示的实施例由源网络设备确定是否将终端从源网络设备迁移到目标网络设备。
(5)图16所示的实施例与图17所示实施例的区别在于，在一个DU只能连接一个CU的限制条件下，图16所示的实施例的复杂度较低，易于实现；图17所示的实施例能够保证在切换过程中终端不会掉话，保证用户的通信质量。
上述主要从每一个网元之间交互的角度对本申请实施例提供的方案进行了介绍。可以理解的是，每一个网元，例如空中基站、源网络设备或者目标网络设备，为了实现上述功能，其包含了执行每一个功能相应的硬件结构和/或软件模块。本领域技术人员应该很容易意识到，结合本文中所公开的实施例描述的各示例的单元及算法步骤，本申请能够以硬件或硬件和计算机软件的结合形式来实现。某个功能究竟以硬件还是计算机软件驱动硬件的方式来执行，取决于技术方案的特定应用和设计约束条件。专业技术人员可以对每个特定的应用来使用不同方法来实现所描述的功能，但是这种实现不应认为超出本申请的范围。
本申请实施例可以根据上述方法示例对网元进行功能模块的划分，例如，可以对 应每一个功能划分每一个功能模块，也可以将两个或两个以上的功能集成在一个处理模块中。上述集成的模块既可以采用硬件的形式实现，也可以采用软件功能模块的形式实现。需要说明的是，本申请实施例中对模块的划分是示意性的，仅仅为一种逻辑功能划分，实际实现时可以有另外的划分方式。下面以采用对应每一个功能划分每一个功能模块为例进行说明：
如图18所示，为本申请实施例提供的一种空中基站的结构示意图。空中基站包括发送模块1801、处理模块1802、以及接收模块1803。
发送模块1801，用于向目标网络设备发送第一请求消息，第一请求消息用于请求建立空中基站与目标网络设备之间的接口。接收模块1803，用于接收来自目标网络设备的第一响应消息，第一响应消息用于响应第一请求消息。
一种可能的设计中，第一请求消息包括空中平台类型、移动类型、空中平台信息中的至少一种；其中，空中平台类型用于指示搭载空中基站的空中平台的类型；移动类型用于指示空中基站是否处于运动状态；空中平台信息包括轨道信息、能力信息以及高度信息中的至少一种。
一种可能的设计中，发送模块1801，用于向目标网络设备发送第一请求消息，包括：通过目标地面站向目标网络设备发送第一请求消息。
一种可能的设计中，发送模块1801，用于向目标网络设备发送第一请求消息，包括：在第一预设时间向目标网络设备发送第一请求消息，第一预设时间根据星历表确定；或者，第一预设时间根据空中基站的运动轨迹确定；或者，第一预设时间根据空中基站在目标地面站的过顶时间确定；或者，第一预设时间根据第一定时器确定。
一种可能的设计中，接收模块1803，还用于接收来自于源网络设备的第一指示消息，第一指示消息用于指示建立空中基站与目标网络设备之间的接口。
一种可能的设计中，接收模块1803，还用于接收传输链路建立指示消息，所述传输链路建立成功指示消息用于指示空中基站与目标地面站之间的传输链路已建立。
一种可能的设计中，发送模块1801，用于向目标网络设备发送第一请求消息，包括：若目标地面站与空中基站之间的无线信号的信号强度符合预设条件，通过目标地面站向目标网络设备发送第一请求消息。
一种可能的设计中，预设条件包括以下情形之一：(1)目标地面站与空中基站之间的无线信号的信号强度大于或等于第一预设值；(2)目标地面站与空中基站之间的无线信号的信号强度大于源地面站与空中基站之间的无线信号的信号强度。
一种可能的设计中，发送模块1801，还用于向源网络设备发送第二请求消息，第二请求消息用于请求释放源网络设备与空中基站之间的接口。
一种可能的设计中，第二请求消息包括以下参数中的至少一项：空中基站的信息、释放类型、以及重建周期；其中，重建周期用于指示源网络设备与空中基站重新建立接口的时间；所示释放类型包括：第一类型、第二类型和第三类型；第一类型用于指示删除空中基站的上下文信息；第二类型用于指示去激活空中基站的上下文信息；第三类型用于指示去激活空中基站的上下文信息，并在重建周期所指示的时间激活空中基站的上下文信息。
一种可能的设计中，发送模块1801，还用于向源网络设备发送第二请求消息，包 括：通过源地面站向源网络设备发送第二请求消息。
一种可能的设计中，发送模块1801，还用于向源网络设备发送第二请求消息，包括：在第二预设时间向源网络设备发送第二请求消息，第二预设时间根据星历表确定；或者，第二预设时间根据空中基站的运动轨迹确定；或者，第二预设时间根据空中基站在源地面站的过顶时间确定；或者，第二预设时间根据第二定时器确定。
一种可能的设计中，接收模块1803，还用于接收来自于源网络设备发送的第二指示消息，第二指示消息用于指示释放空中基站和源网络设备之间的接口。
一种可能的设计中，接收模块1803，还用于接收传输链路预删除指示消息。其中，传输链路预删除指示消息用于指示空中基站与源地面站之间的传输链路待删除。
一种可能的设计中，发送模块1801，还用于向源网络设备发送第二请求消息，包括：若源地面站与空中基站之间的无线信号的信号强度小于第二预设值，则通过源地面站向源网络设备发送第二请求消息。
一种可能的设计中，发送模块1801，还用于向目标网络设备发送第三请求消息，第三请求消息用于请求激活空中基站的上下文信息。
一种可能的设计中，处理模块1802，用于分别确定n个地面站与空中基站之间的无线信号的信号强度，n为大于1的整数。
一种可能的设计中，处理模块1802，用于更新星历表。
如图19所示，为本申请实施例提供的一种目标网络设备的结构示意图。目标网络设备包括：接收模块1901、以及发送模块1902。
接收模块1901，用于接收来自于空中基站的第一请求消息，第一请求消息用于请求建立空中基站与目标网络设备之间的接口，第一请求消息包括空中平台类型、移动类型、空中平台信息中的至少一种；其中，空中平台类型用于指示搭载空中基站的空中平台的类型；移动类型用于指示空中基站是否处于运动状态；空中平台信息包括轨道信息、能力信息以及高度信息中的至少一种。发送模块1902，用于向空中基站发送第一响应消息，第一响应消息用于响应第一请求消息。
一种可能的设计中，接收模块1901，用于接收来自于空中基站的第一请求消息，包括：通过目标地面站接收来自于空中基站的第一请求消息。
一种可能的设计中，接收模块1901，还用于接收来自于空中基站发送的第三请求消息，第三请求消息用于请求激活空中基站的上下文信息。发送模块1902，还用于向空中基站发送第三响应消息，第三响应消息用于响应第三请求消息。
一种可能的设计中，接收模块1901，还用于接收来自于空中基站发送的第三请求消息，包括：通过目标地面站接收来自于空中基站发送的第三请求消息。
如图20所示，为本申请实施例提供的一种源网络设备的结构示意图。源网络设备包括：接收模块2001、处理模块2002和发送模块2003。
接收模块2001，用于接收来自于空中基站的第二请求消息，第二请求消息用于请求释放源网络设备与空中基站之间的接口。发送模块2003，用于向空中基站发送第二响应消息，第二响应消息用于响应第二请求消息。
一种可能的设计中，第二请求消息包括以下参数中的至少一项：空中基站的信息、释放类型、以及重建周期；其中，重建周期用于指示源网络设备与空中基站重新建立 接口的时间；所示释放类型包括：第一类型、第二类型和第三类型；第一类型用于指示删除空中基站的上下文信息；第二类型用于指示去激活空中基站的上下文信息；第三类型用于指示去激活空中基站的上下文信息，并在重建周期所指示的时间激活空中基站的上下文信息。
一种可能的设计中，发送模块2003，还用于向空中基站发送第二指示消息，第二指示消息用于指示释放空中基站与源网络设备之间的接口。
一种可能的设计中，发送模块2003，还用于向空中基站发送第二指示消息，包括：若源地面站与空中基站之间的无线信号的信号强度小于第二预设值，则通过源地面站向空中基站发送第二指示消息。
一种可能的设计中，发送模块2003，还用于向空中基站发送第一指示消息，第一指示消息用于指示建立空中基站与目标网络设备之间的接口。
一种可能的设计中，发送模块2003，还用于向空中基站发送第一指示消息，包括：若目标地面站与空中基站之间的无线信号的信号强度符合预设条件，则通过源地面站向空中基站发送第一指示消息。
一种可能的设计中，预设条件包括以下情形之一：(1)目标地面站与空中基站之间的无线信号的信号强度大于或等于第一预设值；(2)目标地面站与空中基站之间的无线信号的信号强度大于源地面站与空中基站之间的无线信号的信号强度。
上述本申请实施例提供空中基站、目标网络设备、以及源网络设备可以统称为通信装置，通信装置可以有多种产品形态来实现，例如，所述通信装置可配置成通用处理系统；又例如，所述通信装置可以由一般性的总线体系结构来实现；又例如，所述通信装置可以由专用集成电路(application specific integrated circuit，ASIC)来实现等。下面提供本申请实施例所述的通信装置可能的几种产品形态，应当理解的是，以下的产品形态仅为举例，不对本申请实施例所述的通信装置的可能的产品形态进行限定。
图21是本申请实施例所述的通信装置可能的产品形态的示意图。
作为一种可能的产品形态，本申请实施例所述的通信装置可以为通信设备，所述通信设备包括处理器2101和收发器2102。可选的，所述通信设备还包括存储介质2103。其中，所述处理器2101用于执行图9至图17所示的切换方法。所述收发器2102，接受处理器2101的控制，用于执行图9至图17所示的切换方法。
作为另一种可能的产品形态，本申请实施例所述的通信装置也可以由通用处理器来实现，也即俗称的芯片来实现。该通用处理器包括：处理电路2101和收发管脚2102。可选的，该通用处理器还可以包括存储介质2103。其中，处理电路2101用于执行图9至图17所示的切换方法。所述收发管脚2102，接受处理电路2101的控制，用于执行图9至图17所示的切换方法。
作为另一种可能的产品形态，本申请实施例所述的通信装置也可以使用下述电路或者器件来实现：一个或多个现场可编程门阵列(field programmable gate array，FPGA)、可编程逻辑器件(programmable logic device，PLD)、控制器、状态机、门逻辑、分立硬件部件、任何其他适合的电路、或者能够执行本申请通篇所描述的各种功能的电路的任意组合。
本申请实施例还提供一种计算机可读存储介质，该计算机可读存储介质存储有指 令，当指令在通信装置上运行时，使得通信装置可以执行图9至图17所示的切换方法。
本申请实施例提供一种包含指令的计算机程序产品，当计算机程序产品在通信装置上运行时，该通信装置可以执行图9至图17所示的切换方法。
尽管在此结合各实施例对本申请进行了描述，然而，在实施所要求保护的本申请过程中，本领域技术人员通过查看所述附图、公开内容、以及所附权利要求书，可理解并实现所述公开实施例的其他变化。在权利要求中，“包括”(comprising)一词不排除其他组成部分或步骤，“一”或“一个”不排除多个的情况。单个处理器或其他单元可以实现权利要求中列举的若干项功能。相互不同的从属权利要求中记载了某些措施，但这并不表示这些措施不能组合起来产生良好的效果。
尽管结合具体特征及其实施例对本申请进行了描述，显而易见的，在不脱离本申请的精神和范围的情况下，可对其进行各种修改和组合。相应地，本说明书和附图仅仅是所附权利要求所界定的本申请的示例性说明，且视为已覆盖本申请范围内的任意和所有修改、变化、组合或等同物。显然，本领域的技术人员可以对本申请进行各种改动和变型而不脱离本申请的精神和范围。这样，倘若本申请的这些修改和变型属于本申请权利要求及其等同技术的范围之内，则本申请也意图包含这些改动和变型在内。

Claims (35)

  1. 一种切换方法，其特征在于，所述方法包括：
    空中基站向目标网络设备发送第一请求消息，所述第一请求消息用于请求建立所述空中基站与所述目标网络设备之间的接口，所述第一请求消息包括空中平台类型、移动类型、空中平台信息中的至少一种；其中，所述空中平台类型用于指示搭载所述空中基站的空中平台的类型；所述移动类型用于指示所述空中基站是否处于运动状态；所述空中平台信息包括轨道信息、能力信息以及高度信息中的至少一种；
    所述空中基站接收来自所述目标网络设备的第一响应消息，所述第一响应消息用于响应所述第一请求消息。
  2. 根据权利要求1所述的切换方法，其特征在于，所述空中基站向目标网络设备发送第一请求消息，包括：
    所述空中基站通过目标地面站向所述目标网络设备发送所述第一请求消息。
  3. 根据权利要求1或2所述的切换方法，其特征在于，所述空中基站向目标网络设备发送第一请求消息，包括：
    所述空中基站在第一预设时间向所述目标网络设备发送所述第一请求消息，所述第一预设时间根据星历表确定；或者，所述第一预设时间根据所述空中基站的运动轨迹确定；或者，所述第一预设时间根据所述空中基站在所述目标地面站的过顶时间确定；或者，所述第一预设时间根据第一定时器确定。
  4. 根据权利要求1或2所述的切换方法，其特征在于，在所述空中基站向目标网络设备发送第一请求消息之前，还包括：
    所述空中基站接收来自于源网络设备的第一指示消息，所述第一指示消息用于指示建立所述空中基站与所述目标网络设备之间的接口。
  5. 根据权利要求2所述的切换方法，其特征在于，所述空中基站向目标网络设备发送第一请求消息，包括：
    若所述目标地面站与所述空中基站之间的无线信号的信号强度符合预设条件，则所述空中基站通过所述目标地面站向所述目标网络设备发送所述第一请求消息。
  6. 根据权利要求5所述的切换方法，其特征在于，所述预设条件包括以下情形之一：
    所述目标地面站与所述空中基站之间的无线信号的信号强度大于或等于第一预设值；
    所述目标地面站与所述空中基站之间的无线信号的信号强度大于源地面站与所述空中基站之间的无线信号的信号强度。
  7. 根据权利要求1至6任一项所述的切换方法，其特征在于，所述方法还包括：
    所述空中基站向源网络设备发送第二请求消息，所述第二请求消息用于请求释放所述源网络设备与所述空中基站之间的接口。
  8. 根据权利要求7所述的切换方法，其特征在于，所述第二请求消息包括以下参数中的至少一项：空中基站的信息、释放类型、以及重建周期；其中，所述重建周期用于指示所述源网络设备与所述空中基站重新建立接口的时间；所示释放类型包括：第一类型、第二类型和第三类型；所述第一类型用于指示删除所述空中基站的上下文 信息；所述第二类型用于指示去激活所述空中基站的上下文信息；所述第三类型用于指示去激活所述空中基站的上下文信息，并在所述重建周期所指示的时间激活所述空中基站的上下文信息。
  9. 根据权利要求7或8所述的切换方法，其特征在于，所述空中基站向源网络设备发送第二请求消息，包括：
    所述空中基站通过源地面站向所述源网络设备发送所述第二请求消息。
  10. 根据权利要求7至9任一项所述的切换方法，其特征在于，所述空中基站向源网络设备发送第二请求消息，包括：
    所述空中基站在第二预设时间向所述源网络设备发送所述第二请求消息，所述第二预设时间根据星历表确定；或者，所述第二预设时间根据所述空中基站的运动轨迹确定；或者，所述第二预设时间根据所述空中基站在所述源地面站的过顶时间确定；或者，所述第二预设时间根据第二定时器确定。
  11. 根据权利要求7至9任一项所述的切换方法，其特征在于，在所述空中基站向源网络设备发送第二请求消息之前，还包括：
    所述空中基站接收来自于所述源网络设备发送的第二指示消息，所述第二指示消息用于指示释放所述空中基站和所述源网络设备之间的接口。
  12. 根据权利要求9所述的切换方法，其特征在于，所述空中基站向源网络设备发送第二请求消息，包括：
    若所述源地面站与所述空中基站之间的无线信号的信号强度小于第二预设值，则所述空中基站通过源地面站向所述源网络设备发送所述第二请求消息。
  13. 根据权利要求1至12任一项所述的切换方法，其特征在于，所述方法还包括：
    所述空中基站向所述目标网络设备发送第三请求消息，所述第三请求消息用于请求激活所述空中基站的上下文信息。
  14. 一种切换方法，其特征在于，所述方法包括：
    目标网络设备接收来自于空中基站的第一请求消息，所述第一请求消息用于请求建立所述空中基站与所述目标网络设备之间的接口，所述第一请求消息包括空中平台类型、移动类型、空中平台信息中的至少一种；其中，所述空中平台类型用于指示搭载所述空中基站的空中平台的类型；所述移动类型用于指示所述空中基站是否处于运动状态；所述空中平台信息包括轨道信息、能力信息以及高度信息中的至少一种；
    所述目标网络设备向所述空中基站发送第一响应消息，所述第一响应消息用于响应所述第一请求消息。
  15. 根据权利要求14所述的切换方法，其特征在于，所述方法还包括：
    所述目标网络设备接收来自于所述空中基站发送的第三请求消息，所述第三请求消息用于请求激活所述空中基站的上下文信息；
    所述目标网络设备向所述空中基站发送第三响应消息，所述第三响应消息用于响应所述第三请求消息。
  16. 一种切换方法，其特征在于，所述方法包括：
    源网络设备接收来自于空中基站的第二请求消息，所述第二请求消息用于请求释放所述源网络设备与所述空中基站之间的接口；
    所述源网络设备向所述空中基站发送第二响应消息，所述第二响应消息用于响应所述第二请求消息。
  17. 根据权利要求16所述的切换方法，其特征在于，所述第二请求消息包括以下参数中的至少一项：空中基站的信息、释放类型、以及重建周期；其中，所述重建周期用于指示所述源网络设备与所述空中基站重新建立接口的时间；所示释放类型包括：第一类型、第二类型和第三类型；所述第一类型用于指示删除所述空中基站的上下文信息；所述第二类型用于指示去激活所述空中基站的上下文信息；所述第三类型用于指示去激活所述空中基站的上下文信息，并在所述重建周期所指示的时间激活所述空中基站的上下文信息。
  18. 一种空中基站，其特征在于，包括：
    发送模块，用于向目标网络设备发送第一请求消息，所述第一请求消息用于请求建立所述空中基站与所述目标网络设备之间的接口，所述第一请求消息包括空中平台类型、移动类型、空中平台信息中的至少一种；其中，所述空中平台类型用于指示搭载所述空中基站的空中平台的类型；所述移动类型用于指示所述空中基站是否处于运动状态；所述空中平台信息包括轨道信息、能力信息以及高度信息中的至少一种；
    接收模块，用于接收来自所述目标网络设备的第一响应消息，所述第一响应消息用于响应所述第一请求消息。
  19. 根据权利要求18所述的空中基站，其特征在于，所述发送模块，用于向目标网络设备发送第一请求消息，包括：
    通过目标地面站向所述目标网络设备发送所述第一请求消息。
  20. 根据权利要求18或19所述的空中基站，其特征在于，所述发送模块，用于向目标网络设备发送第一请求消息，包括：
    在第一预设时间向所述目标网络设备发送所述第一请求消息，所述第一预设时间根据星历表确定；或者，所述第一预设时间根据所述空中基站的运动轨迹确定；或者，所述第一预设时间根据所述空中基站在所述目标地面站的过顶时间确定；或者，所述第一预设时间根据第一定时器确定。
  21. 根据权利要求18或19所述的空中基站，其特征在于，
    所述接收模块，还用于接收来自于源网络设备的第一指示消息，所述第一指示消息用于指示建立所述空中基站与所述目标网络设备之间的接口。
  22. 根据权利要求18或19所述的空中基站，其特征在于，所述发送模块，用于向目标网络设备发送第一请求消息，包括：
    若所述目标地面站与所述空中基站之间的无线信号的信号强度符合预设条件，通过所述目标地面站向所述目标网络设备发送所述第一请求消息。
  23. 根据权利要求22所述的空中基站，其特征在于，所述预设条件包括以下情形之一：
    所述目标地面站与所述空中基站之间的无线信号的信号强度大于或等于第一预设值；
    所述目标地面站与所述空中基站之间的无线信号的信号强度大于源地面站与所述空中基站之间的无线信号的信号强度。
  24. 根据权利要求18至23任一项所述的空中基站，其特征在于，
    所述发送模块，还用于向源网络设备发送第二请求消息，所述第二请求消息用于请求释放所述源网络设备与所述空中基站之间的接口。
  25. 根据权利要求24所述的空中基站，其特征在于，所述第二请求消息包括以下参数中的至少一项：空中基站的信息、释放类型、以及重建周期；其中，所述重建周期用于指示所述源网络设备与所述空中基站重新建立接口的时间；所示释放类型包括：第一类型、第二类型和第三类型；所述第一类型用于指示删除所述空中基站的上下文信息；所述第二类型用于指示去激活所述空中基站的上下文信息；所述第三类型用于指示去激活所述空中基站的上下文信息，并在所述重建周期所指示的时间激活所述空中基站的上下文信息。
  26. 根据权利要求24或25所述的空中基站，其特征在于，所述发送模块，还用于向源网络设备发送第二请求消息，包括：
    通过源地面站向所述源网络设备发送所述第二请求消息。
  27. 根据权利要求24至26任一项所述的空中基站，其特征在于，所述发送模块，还用于向源网络设备发送第二请求消息，包括：
    在第二预设时间向所述源网络设备发送所述第二请求消息，所述第二预设时间根据星历表确定；或者，所述第二预设时间根据所述空中基站的运动轨迹确定；或者，所述第二预设时间根据所述空中基站在所述源地面站的过顶时间确定；或者，所述第二预设时间根据第二定时器确定。
  28. 根据权利要求24至26任一项所述的空中基站，其特征在于，
    所述接收模块，还用于接收来自于所述源网络设备发送的第二指示消息，所述第二指示消息用于指示释放所述空中基站和所述源网络设备之间的接口。
  29. 根据权利要求26所述的空中基站，其特征在于，所述发送模块，还用于向源网络设备发送第二请求消息，包括：
    若所述源地面站与所述空中基站之间的无线信号的信号强度小于第二预设值，则通过源地面站向所述源网络设备发送所述第二请求消息。
  30. 根据权利要求18至29任一项所述的空中基站，其特征在于，
    所述发送模块，还用于向所述目标网络设备发送第三请求消息，所述第三请求消息用于请求激活所述空中基站的上下文信息。
  31. 一种目标网络设备，其特征在于，包括：
    接收模块，用于接收来自于空中基站的第一请求消息，所述第一请求消息用于请求建立所述空中基站与所述目标网络设备之间的接口，所述第一请求消息包括空中平台类型、移动类型、空中平台信息中的至少一种；其中，所述空中平台类型用于指示搭载所述空中基站的空中平台的类型；所述移动类型用于指示所述空中基站是否处于运动状态；所述空中平台信息包括轨道信息、能力信息以及高度信息中的至少一种；
    发送模块，用于向所述空中基站发送第一响应消息，所述第一响应消息用于响应所述第一请求消息。
  32. 根据权利要求31所述的目标网络设备，其特征在于，
    所述接收模块，还用于接收来自于所述空中基站发送的第三请求消息，所述第三 请求消息用于请求激活所述空中基站的上下文信息；
    所述发送模块，还用于向所述空中基站发送第三响应消息，所述第三响应消息用于响应所述第三请求消息。
  33. 一种源网络设备，其特征在于，包括：
    接收模块，用于接收来自于空中基站的第二请求消息，所述第二请求消息用于请求释放所述源网络设备与所述空中基站之间的接口；
    发送模块，用于向所述空中基站发送第二响应消息，所述第二响应消息用于响应所述第二请求消息。
  34. 根据权利要求33所述的源网络设备，其特征在于，所述第二请求消息包括以下参数中的至少一项：空中基站的信息、释放类型、以及重建周期；其中，所述重建周期用于指示所述源网络设备与所述空中基站重新建立接口的时间；所示释放类型包括：第一类型、第二类型和第三类型；所述第一类型用于指示删除所述空中基站的上下文信息；所述第二类型用于指示去激活所述空中基站的上下文信息；所述第三类型用于指示去激活所述空中基站的上下文信息，并在所述重建周期所指示的时间激活所述空中基站的上下文信息。
  35. 一种计算机可读存储介质，其特征在于，所述计算机可读存储介质存储有指令，当所述指令被处理器执行时使得处理器执行如权利要求1至17任一项所述的切换方法。
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