Cell handover method, apparatus and system

Abstract

Disclosed are a cell handover method, an apparatus and a system, relating to the technical field of communications, and used for solving the problem of during cell handover, when a terminal has disconnected data transmission with a source base station, data interruption or even terminal call drop caused by a too long handover duration when performing synchronous measurement on synchronous resources of all target neighbor cells to implement cell handover. The method comprises: a source base station acquires a handover time and / or a target synchronization resource, and notifies a terminal of the handover time and / or the target synchronization resource, so that, on the basis of the handover time and / or the target synchronization resource, the terminal starts to perform synchronous measurement on the target synchronization resource when the handover time arrives, thereby implementing cell synchronization and accessing a target cell to complete inter-cell handover. The solution of the present application can be widely applied to the technical field of communications and fields such as artificial intelligence, the Internet of Vehicles, and smart home networking.

Description

A cell switching method, device and system

[0001] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office on August 10, 2023, with application number 202311006089.8 and application name “A cell switching method, device and system”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The embodiments of the present application relate to the field of communication technology, and in particular to a cell switching method, device, and system. Background Art

[0003] Non-terrestrial networks (NTN) include satellite communication systems, high altitude platform systems (HAPS), and air-to-ground networks. To date, the focus of discussions on NTN within the 3rd Generation Partnership Project (3GPP) has been on satellite communication networks. The integration of satellite communication networks and terrestrial fifth-generation (5G) mobile communication technology networks can provide ubiquitous coverage without being restricted by topography, connecting multiple dimensions of air, space, land, and sea to form an integrated ubiquitous access network, enabling on-demand access in all scenarios. Satellite communication equipment (or satellites) is in high-speed motion compared to terminals, so the cells providing services to connected terminals can also change in a short period of time. To ensure service continuity for connected terminals, satellite communication networks frequently trigger terminals to switch cells.

[0004] In the NTN scenario, considering the high-speed movement of satellite communication equipment, the process of cell handover by the terminal may include: after receiving the radio resource control (RRC) configuration message sent by the source satellite base station, the terminal disconnects the data transmission with the source satellite base station, resynchronizes with the target satellite base station through cell synchronization, and then accesses the cell to achieve cell handover.

[0005] However, satellite communication equipment sends system messages containing synchronization information (such as synchronization signal block (SSB)) in the form of beam scanning, where the beam that sends system messages containing synchronization information can be called an SSB beam. Currently, it takes a long time for the terminal to measure all neighboring SSB beams to complete cell synchronization and then realize cell switching. The long cell synchronization time leads to a long cell switching time, resulting in long-term data transmission interruption and may even cause the terminal to drop calls.

[0006] Summary of the Invention

[0007] The embodiments of the present application provide a cell handover method, apparatus, and system to address the problem that during a cell handover in an NTN scenario, after a terminal disconnects data transmission with a source base station and performs synchronous measurements on the synchronization resources of all target neighboring cells to implement cell handover, the handover time is too long, resulting in data interruption or even terminal call drop.

[0008] To achieve the above objectives, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present application provides a cell handover method, which can be executed by a terminal and a functional module or chip within the terminal. Taking the terminal as an example, the method includes: the terminal receiving first information indicating a handover time and / or a target synchronization resource for the terminal to perform a cell handover, and switching from a first cell to a second cell based on the first information. The terminal may be in a connected state.

[0010] Based on the method described in the first aspect, the terminal in the connected state can perform the switching time and / or target synchronization resource of the cell switching according to the received indication terminal, disconnect the data transmission with the first cell when the switching time arrives, receive the target synchronization resource, and perform synchronization measurement on the target synchronization resource. The first cell mentioned above can be understood as the source cell, and the second cell can be understood as the target cell that the terminal is about to access. The above-mentioned switching process gives the terminal in the connected state a specific switching time and a specific target synchronization resource. The terminal performs synchronization measurement on the target synchronization resource when the switching time arrives according to the first information indication, avoids disconnecting the data connection in advance to perform synchronization resource measurement and cell switching process, reduces data interruption delay, and / or, measures on the specified target synchronization resource, and improves the efficiency of synchronization measurement and cell switching through purposeful synchronization measurement.

[0011] In one possible design, the first information indicates a switching time and a target synchronization resource for a terminal to perform cell switching, and the terminal performs cell switching based on the first information. The process of the terminal performing cell switching based on the first information includes: when the switching time arrives, the terminal performs synchronization measurement on the target synchronization resource; and then, based on the synchronization measurement result, the terminal switches from the first cell to the second cell.

[0012] The above-mentioned handover process allows the terminal in the connected state to always maintain data transmission with the first cell before the handover time arrives, and then disconnect the data transmission with the first cell when the handover time arrives, thereby reducing the data interruption time during the handover process and further reducing the impact of the handover data interruption time on the service rate. At the same time, the terminal only needs to perform synchronization measurement on the target synchronization resource, that is, the terminal only needs to measure the reference signal received power (RSRP) of the target synchronization resource and switch from the first cell to the second cell based on the synchronization measurement result. At this time, the terminal only needs to perform synchronization measurement on the target synchronization resource, which narrows the scope of the terminal's synchronization measurement and further reduces the terminal's measurement overhead and measurement energy consumption.

[0013] In one possible design, the first information received by the terminal is carried in an RRC configuration message sent to the terminal by the first cell. Based on this possible design, the first information can be sent through the RRC configuration information specified in the standard, saving signaling overhead.

[0014] In one possible design, the terminal maintains a communication connection and / or data transmission with the first cell before a handover time arrives, and disconnects the communication connection and / or data transmission with the first cell when the handover time arrives. This possible design prevents a connected terminal from immediately disconnecting the communication connection and / or data transmission with the first cell upon receiving a handover command, thereby shortening the duration of data interruption.

[0015] In one possible design, the target synchronization resource can be a beam, a carrier, or a bandwidth part BWP. Specifically, when the wireless access network equipment needs to achieve regional coverage through beam scanning, such as 5G equipment, satellite base station equipment, etc., the target synchronization resource can be a beam. When the wireless access network equipment can achieve regional coverage through base station coverage, such as 4G equipment, etc., the target synchronization resource can be a carrier or a bandwidth part BWP. In this way, different target synchronization resources can be used to carry the second cell synchronization information, and this solution can be flexibly and diversely applied to different scenarios, thereby improving the utilization rate of the solution.

[0016] In one possible design, the switching time of the terminal switching cells is determined based on the time when the target synchronization resource arrives at the terminal, wherein the target synchronization resource can be determined based on at least one of the following information: the terminal's location information, the satellite ephemeris information of the second access network device, and the beam scanning rule of the cell of the second access network device, wherein the second access network device corresponds to the second cell. On the one hand, based on this possible design, when the terminal is in a scenario where frequent switching needs to be triggered, the terminal's mobility status information and the mobility status information of the second cell are taken into consideration to determine the target synchronization resource, thereby improving the accuracy of synchronization resource determination and avoiding unnecessary switching. At the same time, the specific beam information that can cover the terminal in the second cell can be determined in advance, reducing signaling interaction overhead. On the other hand, the switching time of the terminal switching cells is determined based on the time when the target synchronization resource arrives at the terminal, thereby reducing the time of terminal switching interruption. Therefore, the above possible design reduces the energy consumption of the terminal during the switching process and improves the service rate of the terminal.

[0017] In one possible design, the first cell corresponds to the first satellite base station, and the second cell corresponds to the second satellite base station; or, the first cell corresponds to the first ground station, and the second cell corresponds to the second ground station. The first cell can send first information to the terminal in the connected state through RRC configuration information to indicate the switching time and / or target synchronization resource of the terminal switching from the first cell to the second cell. The first cell mentioned above can be understood as the source cell in the terminal switching process, and the second cell can be understood as the target cell in the terminal switching process. Based on this possible design, the cell can correspond to different access network devices, and the solution can be flexibly and diversely applied to different scenarios to improve the utilization rate of the solution.

[0018] In one possible design, the target synchronization resource is part of the synchronization resources corresponding to the neighboring cells of the first cell. Based on this possible design, part of the synchronization resources in the neighboring cells can be determined as target synchronization resources. For example, one or more synchronization resources in the neighboring cells can be determined as target synchronization resources. Compared with measuring on all synchronization resources, this design can reduce the number of synchronization resources measured by the terminal, reduce the power consumption caused by the terminal measuring the synchronization resources, and improve the efficiency of synchronization resources (or neighboring cell measurement).

[0019] In the second aspect, the present application provides a cell switching method, which can be executed by a first access network device, and the method includes: the first access network device obtains the switching time and / or target synchronization resources of the terminal for cell switching, and sends a first information to the terminal for indicating the switching time and / or target synchronization resources of the terminal.

[0020] Based on the method described in the second aspect, the first access network device sends the obtained switching time and / or target synchronization resource for the terminal to perform cell switching to the terminal through the first information carried in the RRC configuration message. The first information is used to instruct the terminal to perform synchronization measurement on the target synchronization resource when the switching time arrives, so as to avoid the first access network device from stopping providing data services to the terminal in advance and reducing the terminal data interruption delay; at the same time, the first information instructs the terminal to perform synchronization measurement on the specified target synchronization resource, so as to avoid the terminal blindly measuring all synchronization resources of the neighboring area and reducing the energy consumption of the terminal in measuring synchronization resources. The first access network device can directly or indirectly obtain the switching time and / or target synchronization resource for the terminal to perform cell switching. In the case where the first access network device directly obtains the switching time and / or target synchronization resource for the terminal to perform cell switching, the switching time and / or target synchronization resource for the terminal to perform cell switching is determined by the first access network device; in the case where the first access network device indirectly obtains the switching time and / or target synchronization resource for the terminal to perform cell switching, the switching time and / or target synchronization resource for the terminal to perform cell switching is determined by the second access network device. Compared with the case where the first access network device directly obtains the switching time and / or target synchronization resources for the terminal to switch cells, the case where the first access network device indirectly obtains the switching time and / or target synchronization resources for the terminal to switch cells reduces the signaling interaction between the first access network device and the second access network device and the computing overhead of the second access network device.

[0021] In one possible design, the first access network device sends the first information to the terminal via an RRC configuration message. Based on this possible design, the first information can be sent to the terminal via the RRC configuration information specified in the standard, saving signaling overhead and ensuring that the terminal can receive the first information sent by the first access network device.

[0022] In one possible design, the first access network device maintains the communication connection and / or data transmission between the first cell and the terminal before the handover time arrives, and disconnects the communication connection and / or data transmission between the first cell and the terminal when the handover time arrives. The first cell is the cell assigned by the first access network device to provide wireless communication services to the terminal in a connected state. This possible design avoids the first access network device immediately ceasing to provide communication connection and / or data transmission to the terminal after sending a handover command to the terminal, thereby shortening the duration of terminal data interruption.

[0023] In one possible design, the first access network device can determine the specific type of the target synchronization resource, wherein the target synchronization resource can carry the synchronization information of the second cell. The target synchronization resource can be a beam, or a carrier, or a bandwidth part BWP. Specifically, when the first access network device needs to achieve regional coverage through beam scanning, such as 5G equipment, satellite base station equipment, etc., the target synchronization resource can be a beam. When the first access network device can achieve regional coverage through base station coverage, such as 4G equipment, etc., the target synchronization resource can be a carrier or a bandwidth part BWP. In this way, different target synchronization resources are used to carry the synchronization information of the second cell for different scenarios, and the solution can be flexibly and diversely applied to various scenarios to improve the utilization rate of the solution.

[0024] In one possible design, the terminal switching time obtained by the first access network device is determined based on the time when the target synchronization resource arrives at the terminal, where the target synchronization resource can be determined based on at least one of the following information: the terminal's location information, the satellite ephemeris information of the second access network device, and the beam scanning rules of the cell of the second access network device. Based on this possible design, the target synchronization resource obtained by the first access network device is determined based on the terminal's mobile state information, the mobile state information of the second access network device, and the beam characteristics of the cell of the second access network device, thereby improving the reliability of the target synchronization resource. When the target synchronization resource arrives, the terminal performs a cell switch, avoiding unnecessary switching.

[0025] In one possible design, the target synchronization resource can be determined by the first access network device, or by the second access network device. When the target synchronization resource is determined by the first access network device, the first access network device can determine that part of the SSB beam of the second access network device can scan the terminal at a certain moment based on the location information reported by the terminal, the satellite ephemeris information of the second access network device, and the beam scanning rules of the cell of the second access network device. When the target synchronization resource is determined by the second access network device, the second access network device can determine that part of its own SSB beam can scan the terminal at a certain moment based on the location information of the terminal reported by the first access network device, the satellite ephemeris information of the second access network device, and the beam scanning rules of the cell of the second access network device. As mentioned above, the SSB beam scanning to the terminal means that the location information of the terminal is within the ground coverage range of the beam. Based on this possible design, the target synchronization resource can be determined on demand. In different scenarios, different access network devices can be selected to determine the target synchronization resource, which improves the flexibility of the solution.

[0026] In one possible design, when the switching time between the target synchronization resource and the terminal is determined by the second access network device, the first access network device receives second information sent from the second access network device, where the second information includes the switching time of the terminal and / or information about the target synchronization resource of the second cell. For example, when the first access network device is a source satellite base station, the second access network is a target satellite base station, and the target synchronization resource is an SSB beam, the source satellite base station receives the switching time between the target synchronization resource and the terminal determined by the target satellite base station. Based on the above possible design, the first access network device only needs to forward the second information sent by the second access network device to the terminal, without the need for a calculation process.

[0027] In one possible design, the first access network device corresponds to a first satellite base station, and the second access network device corresponds to a second satellite base station; alternatively, the first access network device corresponds to a first ground station, and the second access network device corresponds to a second ground station. In the above, the first access network device can be understood as the source access network device, and the second access network device can be understood as the target access network device. Based on this possible design, cells can correspond to different access network devices, allowing the solution to be flexibly and diversely applied to different scenarios, thereby improving its utilization.

[0028] In one possible design, the target synchronization resource is part of the synchronization resources corresponding to the neighboring cell of the first cell, where the first cell is the cell where the terminal is currently located. Based on this possible design, part of the synchronization resources in the neighboring cell can be determined as the target synchronization resources, for example, one or more synchronization resources in the neighboring cell can be determined as the target synchronization resource. The terminal only needs to perform synchronization measurement on the target synchronization resource and no longer needs to measure all synchronization resources. This design can reduce the number of synchronization resources measured by the terminal, reduce the power consumption caused by the terminal measuring the synchronization resources, and improve the efficiency of the synchronization resource (or called neighboring cell measurement).

[0029] In a third aspect, a communication device is provided for implementing the various methods described above. The communication device may be the terminal described in the first aspect, or a device comprising the terminal, or a device included in the terminal, such as a chip; the communication device includes modules, units, or means corresponding to implementing the methods described above. The modules, units, or means may be implemented in hardware, software, or by hardware executing corresponding software implementations. The hardware or software includes one or more modules or units corresponding to the functions described above.

[0030] In some possible designs, the communication device may include a processing module and a transceiver module. The transceiver module, which may also be referred to as a transceiver unit, is configured to implement the sending and / or receiving functions described in the first aspect and any possible implementation thereof. The transceiver module may be comprised of a transceiver circuit, a transceiver, a transceiver, or a communication interface. The processing module may be configured to implement the processing functions described in the first aspect and any possible implementation thereof.

[0031] In some possible designs, the transceiver module includes a sending module and a receiving module, which are respectively used to implement the sending and receiving functions in the above-mentioned first aspect and any possible implementation methods thereof.

[0032] Among them, the communication device provided in the third aspect is used to execute the above-mentioned first aspect or any possible implementation method of the first aspect. The specific details can be found in the above-mentioned first aspect or any possible implementation method of the first aspect, and will not be repeated here.

[0033] In a fourth aspect, a communication device is provided for implementing the various methods described above. The communication device includes a processor and a memory; the memory is configured to store computer instructions. When the processor executes the instructions, the communication device performs the method described in the first aspect. The communication device may be the terminal described in the first or second aspect, or a device including the terminal, or a device included in the terminal, such as a chip.

[0034] In some possible designs, the communication device may include: a processor and a communication interface; the communication interface is configured to communicate with a module external to the communication device; and the processor is configured to execute a computer program or instruction to cause the communication device to perform the method described in the first aspect. The communication device may be the terminal described in the first or second aspect, or a device including the terminal, or a device included in the terminal, such as a chip.

[0035] In a fifth aspect, a communication device is provided for implementing the various methods described above. The communication device may be the first access network device described in the second aspect, such as a satellite base station; or a device comprising the first access network device; or a device included in the first access network device, such as a chip. The communication device includes modules, units, or means corresponding to the methods described above. The modules, units, or means may be implemented in hardware, software, or by hardware executing corresponding software implementations. The hardware or software includes one or more modules or units corresponding to the functions described above.

[0036] In some possible designs, the communication device may include a processing module and a transceiver module. The transceiver module, which may also be referred to as a transceiver unit, is configured to implement the sending and / or receiving functions described in the second aspect and any possible implementation thereof. The transceiver module may be comprised of a transceiver circuit, a transceiver, a transceiver, or a communication interface. The processing module may be configured to implement the processing functions described in the second aspect and any possible implementation thereof.

[0037] In some possible designs, the transceiver module includes a sending module and a receiving module, which are respectively used to implement the sending and receiving functions in the above-mentioned second aspect and any possible implementation methods thereof.

[0038] Among them, the communication device provided in the fifth aspect is used to execute the above-mentioned second aspect or any possible implementation method of the second aspect. The specific details can be found in the above-mentioned second aspect or any possible implementation method of the second aspect, and will not be repeated here.

[0039] In a sixth aspect, a communication device is provided for implementing the various methods described above. The communication device includes a processor and a memory; the memory is configured to store computer instructions. When the processor executes the instructions, the communication device performs the method described in the second aspect. The communication device may be the first access network device described in the second aspect, such as a satellite base station; or a device including the first access network device; or a device included in the access network device, such as a chip.

[0040] In some possible designs, the communication device may include: a processor and a communication interface; the communication interface is configured to communicate with a module external to the communication device; and the processor is configured to execute a computer program or instruction to cause the communication device to perform the method described in the second aspect. The communication device may be the access network device described in the second aspect, or a device including the access network device, or a device included in the access network device, such as a chip.

[0041] In a seventh aspect, the present application provides a communication system, which includes the communication device provided in the third aspect and the communication device provided in the fourth aspect and a second access network device.

[0042] In an eighth aspect, the present application provides a computer-readable storage medium storing computer instructions. When the computer instructions are executed on a computer, the computer executes the cell switching method in the first aspect or any possible design of the first aspect, or the computer executes the cell switching method in the second aspect or any possible design of the second aspect.

[0043] In the ninth aspect, the present application provides a computer program product, which includes computer instructions. When the computer instructions are run on a computer, the computer executes the cell switching method in the first aspect or any possible design of the first aspect, or the computer executes the cell switching method in the second aspect or any possible design of the second aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 is a diagram of the NTN communication system architecture;

[0045] Figure 2 is a schematic diagram of the cell switching process in the existing NTN scenario;

[0046] FIG3a is a schematic diagram of a communication system provided by the present application;

[0047] FIG3b is a schematic diagram of a cell switching process provided by the present application;

[0048] FIG4 is a schematic diagram of a cell switching provided by the present application;

[0049] FIG5 is a schematic diagram of a cell switching provided by the present application;

[0050] FIG6 is a schematic diagram of a cell switching provided by the present application;

[0051] FIG7 is a schematic diagram of the structure of a terminal and a network device provided by the present application;

[0052] FIG8 is a schematic diagram of a cell switching process provided by the present application;

[0053] FIG9 is a schematic diagram of a cell switching process provided by the present application;

[0054] FIG10 is a schematic structural diagram of a communication device provided by the present application;

[0055] FIG11 is a schematic structural diagram of a communication device provided in this application. DETAILED DESCRIPTION

[0056] Before introducing the embodiments of the present application, some technical terms involved in the embodiments of the present application are explained. It should be noted that the following explanations are intended to make the embodiments of the present application easier to understand and should not be regarded as limiting the scope of protection claimed by the embodiments of the present application.

[0057] Non-terrestrial networks (NTN) achieve 5G communications through satellite or drone platforms, providing ubiquitous coverage capabilities for terminals without being restricted by terrain. In particular, in places where ground network equipment cannot be popularized, such as in extreme areas such as deserts, oceans, and high altitudes, NTN can be used to complete network coverage and improve coverage. NTN does not consider high elliptical orbit (HEO) satellite systems, but only targets low earth orbit (LEO) / medium earth orbit (MEO) / geostationary earth orbit (GEO) / unmanned aircraft system (UAS) scenarios. Table 1 shows the height of different NTN platforms from the ground, the earth orbit information they are in, and the coverage information of the corresponding beams.

[0058] Table 1

[0059] The NTN communication system architecture is shown in Figure 1. It comprises the space segment, the ground segment, and the user end. The space segment primarily refers to the constellation of multiple satellite base stations in space, as well as the inter-satellite links (ISLs) between them. The ground segment primarily consists of earth stations (also known as gateways), as well as auxiliary components such as service control, monitoring management, and time injection. Transmission equipment, core network equipment, and other network equipment in the terrestrial network can also be considered part of the ground segment. The user segment refers to the terminals that access the satellite base stations. It primarily includes antennas (often called "dishes"), signal processing equipment that provides network access (such as routers), and terminals (such as mobile phones and computers) that access the network. As shown in Figure 1, different satellite base stations are connected via optional inter-satellite links (ISLs). These can be wireless or optical interfaces and can be defined by GPP or non-3GPP standards. The service link between the terminal and the satellite base station is implemented using the New Radio (NR) technology. The feeder link between the satellite base station and the gateway is implemented via a 3GPP or non-3GPP radio interface. Furthermore, a satellite base station (or UAS platform) typically generates multiple beams over a given service area within its coverage area, achieving cell coverage and providing network services to terminals. The coverage of a satellite base station (or UAS platform) depends on the onboard antenna pattern and its minimum elevation angle. The beam's coverage shape is typically elliptical.

[0060] NTN communication systems have two typical architectural modes: transparent transmission mode and regenerative mode. In transparent transmission mode, the satellite (or UAS platform) payload can perform frequency conversion and RF amplification in the uplink and downlink directions. In this mode, the satellite acts as an analog RF repeater. In regenerative mode, the satellite (or UAS platform) payload reprocesses the signals received from the earth terminal. In this mode, the satellite performs the same functions as a ground base station, demodulating / decoding, switching or routing, and encoding / modulating data. In this mode, the satellite performs all or part of the functions of a base station. The satellite payload mentioned above refers to the instruments and equipment installed on the satellite that directly realize certain functions of the satellite, such as cameras used on remote sensing satellites and communication transponders and antennas used on communication satellites.

[0061] Cell handover refers to the situation where, when a terminal is in a connected state and maintains data transmission services, it moves from one cell to another, or due to reasons such as wireless transmission service load adjustment, activation operation maintenance, equipment failure, etc., the original service cell (source cell) can no longer provide services to the terminal. In order to not interrupt the data transmission service and service quality, the wireless bearer system will find the most suitable cell (target cell) or network to continue to provide uninterrupted services to the terminal, thus realizing mobility management with seamless coverage of the wireless network. Cell handover can be divided into the following situations: (1) Handover between cells within a base station; specifically, the terminal switches between the source cell and the target cell, where the source cell and the target cell belong to the coverage of the same base station, in other words, the source cell and the target cell correspond to the same base station. (2) Cell handover between base stations; specifically, the terminal switches between the source cell and the target cell, where the source cell and the target cell belong to the coverage of different base stations under the same core network; or, the source cell and the target cell belong to the coverage of different base stations under different core networks.

[0062] The overall process of cell handover includes the following steps 1-4:

[0063] Step 1. Trigger measurement: After the terminal completes cell access or handover successfully, the base station will immediately send measurement control information to the terminal through the RRC connection configuration message. In addition, if the measurement configuration information is updated, the base station will also send the updated measurement control information through the RRC connection configuration message. The most important part of the measurement control information is the measurement object, measurement configuration, measurement event, etc. Among them, the content of the measurement configuration includes information such as measurement report ID, trigger type, reporting interval, number of reports, and the maximum number of measurement reporting cells. The trigger type can be divided into periodic and event types. The periodic trigger type refers to the terminal performing measurements regularly and reporting measurement reports periodically. The event trigger type refers to the terminal performing measurements regularly and reporting measurement reports to the base station only when certain conditions are met. This condition that needs to be met is called an "event". Common measurement events based on radio resource management (RRM) for handover are shown in Table 2 below.

[0064] Table 2

[0065] Among them, the cell quality can be measured by measuring the reference signal received power (RSRP), reference signal receiving quality (RSRQ) or signal to interference plus noise ratio (SINR) of the cell; Ms represents the measurement result of the serving cell; Mn represents the measurement result of the neighboring cell; TimeToTrig represents the duration for which the event entry condition is continuously met, that is, the time hysteresis; Off represents the bias hysteresis of the measurement result; Hys represents the amplitude hysteresis of the measurement result; Ofs represents the frequency offset of the serving cell; Ofn represents the bias of the neighboring cell; Ocs represents the specific bias CIO of the serving cell; Ocn represents the cell-specific bias CIO of the neighboring cell in the system; Thresh is the threshold value configured for the corresponding event.

[0066] Step 2: Execute measurement: According to the relevant configuration of measurement control, the terminal monitors the wireless channel and reports the measurement report to the source base station when the measurement report conditions (A1-A6, B1 and B2) are met.

[0067] Step 3: Handover decision: The source base station selects a target base station for the terminal to hand over to based on the measurement report reported by the terminal, and selects a corresponding handover strategy (such as handover and redirection).

[0068] Step 4: Handover Execution: The source base station requests and allocates resources to the target base station. The source base station then sends a handover command to the terminal and stops sending downlink data to the terminal. The handover command message carries the resource information allocated by the target base station to the terminal. Following the handover command, the terminal disconnects from the source base station, performs uplink and downlink synchronization with the target base station, initiates initial access to the target base station, and connects to the target cell, completing the cell handover.

[0069] As can be seen from the above, there is a time difference between the time the terminal performs measurement and the time the terminal accesses the target cell. In the NTN scenario, the satellite base station (or UAS platform) is moving at high speed. During the period between the terminal performing measurement and the time the terminal accesses the target cell, the SSB beam covering the terminal's area has changed. Therefore, after receiving the handover command, the terminal needs to perform RSRP measurement and downlink synchronization of the neighboring SSB beam with the target satellite base station before accessing the cell. In the existing NTN scenario, the cell handover process is shown in Figure 2. The specific steps are as follows:

[0070] S201: The source satellite base station sends a measurement event to the terminal, and the terminal receives the measurement event.

[0071] The source satellite base station sends a measurement event for handover to the terminal. The measurement event for handover may be an RRM measurement-based measurement event. Specific information about the RRM measurement-based measurement event is shown in Table 2. The source satellite base station sends the measurement event to the terminal only if the terminal has connected to the source satellite base station and entered the RRC connected state.

[0072] S202: The terminal performs measurement based on the measurement event to obtain a measurement report, and the terminal reports the measurement report. The source satellite base station receives the measurement report.

[0073] The terminal may determine whether a threshold for reporting a measurement event is met, and if so, report the measurement report to the source satellite base station.

[0074] S203: Switching decision.

[0075] The source satellite base station determines the target satellite base station to which the terminal switches based on the measurement report reported by the terminal.

[0076] S204: Handover preparation.

[0077] The source satellite base station applies for and allocates resources to the target satellite base station; the target satellite base station determines whether to allow the terminal's resource access. If the target satellite base station allows the terminal's resource access, the target satellite base station allocates air interface resources and service bearer resources to the terminal.

[0078] S205: The source satellite base station sends a handover command to the terminal, instructing the terminal to handover from the source satellite base station to the target satellite base station.

[0079] The handover command may be carried in an RRC configuration message.

[0080] S206: The terminal accesses the target cell based on the handover command.

[0081] The terminal disconnects from the source base station according to the switching command, performs RSRP measurement of the neighboring SSB beam and completes downlink synchronization, then initiates initial access to the target satellite base station, accesses the target cell, and completes the cell switching.

[0082] Beam sweeping refers to the transmission or reception of beams in a pre-defined manner within a specific period or time period to cover a specific spatial area. For example, beam sweeping is required when a terminal begins initial access (synchronizing with the system and receiving minimal system information broadcasts). The base station transmits a beam in a specific direction at a specific time, then changes direction in the next time frame, and so on, ultimately achieving cell coverage through continuous beam changes. Initial access refers to the process by which a terminal initially finds a cell upon entering the system coverage area.

[0083] To ensure that the terminal can complete downlink synchronization (or initial access), the base station periodically sends SSBs and system messages through beam scanning. The beam that sends SSBs and system messages can be called an SSB beam. The terminal performs a cell search, measures the RSRP of the SSB beam, and completes initial access based on the cell search results. Then, based on the obtained system message, the terminal sends an uplink physical random access channel (PRACH). The synchronization signal block consists of three parts: the primary synchronization signal (PSS), the secondary synchronization signal (SSS), and the physical broadcast channel (PBCH). The terminal performs a cell search to obtain the PSS and SSS, thereby achieving time and frequency synchronization and obtaining the physical layer cell identity (PCI).

[0084] As can be seen above, measuring SSB beams is the first step for a terminal to access a target cell. However, in NTN scenarios, a satellite base station (or UAS platform) includes many SSB beams. Therefore, after receiving a handover command and disconnecting data transmission from the source satellite base station, the terminal needs a long time to measure the RSRP of all neighboring SSB beams and complete downlink synchronization. This results in a long interruption of terminal data transmission and may even cause the terminal to drop calls. Furthermore, the long-term RSRP measurement of neighboring SSB beams by the terminal also increases the terminal's power consumption.

[0085] In order to solve the problem of long-term interruption of data transmission by the terminal during the switching process, the present application provides a cell switching method, which includes: a first access network device (or a source access network device) obtains the switching time and / or target synchronization resource for the terminal to switch the cell, and sends a first information indicating the switching time and / or target synchronization resource of the terminal to the terminal. The terminal receives the first information and switches from the first cell to the second cell according to the switching time and / or target synchronization resource.

[0086] In this way, a specific switching time and a specific target synchronization resource can be given to a terminal in a connected state during a cell switching process. This allows the terminal to perform synchronization measurement on the target synchronization resource when the switching time arrives according to the first information instruction, avoiding premature disconnection of the data connection to perform synchronization resource measurement and cell switching process, reducing data interruption delay, and / or, measuring on the specified target synchronization resource, thereby improving synchronization measurement and cell switching efficiency through purposeful synchronization measurement.

[0087] The cell switching method provided in the embodiment of the present application is described below with reference to the accompanying drawings.

[0088] The technical solutions of the embodiments of the present application can be used in various communication systems, which may be a third generation partnership project (3GPP) communication system, such as a long term evolution (LTE) system, or a fifth generation (5G) mobile communication system, a new radio (NR) system, a new radio vehicle to everything (NR V2X) system, and may also be applied to a system of LTE and 5G hybrid networking, or a device-to-device (D2D) communication system, a machine-to-machine (M2M) communication system, an Internet of Things (IoT), and other next-generation communication systems, and may also be a non-3GPP communication system without limitation.

[0089] The technical solutions of the embodiments of the present application can be applied to various communication scenarios, for example, one or more of the following communication scenarios: enhanced mobile broadband (eMBB), ultra-reliable low latency communication (URLLC), machine type communication (MTC), massive machine type communications (mMTC), D2D, V2X, and IoT communication scenarios.

[0090] The technical solutions of the embodiments of the present application can also be applied to long-distance communication scenarios, such as satellite communication scenarios where the distance between the terminal device and the network device is constantly changing, or other long-distance communication scenarios, without limitation.

[0091] Referring to Figure 3a, a communication system is provided for an embodiment of the present application, which includes at least one access network device (such as a first access network device and a second access network device), and a terminal connected to the network device. Optionally, different access network devices can communicate with each other. The access network device in Figure 3a can be a satellite base station deployed in the air. Each access network device can cover one or more cells, and the terminal can move within the cell covered by the access network device or between cells to receive network services provided by the access network device.

[0092] Taking the interaction between the first access network device and the second access network device and the terminal shown in Figure 3a as an example, in an embodiment of the present application, the cell switching process is shown in Figure 3b and may include: S301: The first access network device determines the cell switching of the terminal. S302: The first access network device obtains the switching time and / or target synchronization resource, and sends first information indicating the switching time and / or target synchronization resource to the terminal. S303: The terminal receives the first information and switches from the first cell to the second cell based on the first information.

[0093] For example, the first access network device sends a measurement event to a terminal in a connected state, and the terminal reports a report that satisfies the measurement event and its own location information to the first access network device. The first access network device makes a switching decision based on the measurement event report and the terminal location information reported by the terminal, and selects the target access network device to which the terminal will switch. The target access network device may be the first access network device or the second access network device. When the target access network device is the first access network device, the cell switching performed by the terminal belongs to the cell switching within the base station. When the target access network device is the second access network device, the cell switching performed by the terminal belongs to the cell switching between base stations, and the first access network device and the second access network device may belong to the same core network device or to different core network devices. When the first access network device has determined the target access network device to which the terminal will switch, the first access network device performs signaling interaction with the target access network device, so that the target access network device allocates available resources to the terminal.

[0094] Subsequently, the terminal receives the first information. The first information is carried in the RRC configuration message sent by the first access network device to the terminal, and is used to indicate the switching time and / or target synchronization resource for the terminal to switch cells. When the terminal receives the first information sent by the first access network device, the terminal maintains the communication connection and / or data transmission with the first cell before the switching time carried in the first information arrives. When the switching time arrives, the terminal disconnects the communication connection and / or data transmission with the first cell, performs synchronization measurement on the target synchronization resource, and switches from the first cell to the second cell based on the synchronization measurement result. The first cell is the coverage area of ​​the communication service provided by the first access network device to the terminal at the current time, and the second cell is the coverage area of ​​the communication service provided by the target access network device to the terminal when the switching time arrives.

[0095] As mentioned above, the switching time is determined based on the time when the target synchronization resource reaches the terminal; the target synchronization resource is determined based on at least one of the following information: the terminal's location information, the satellite ephemeris information of the target access network device, and the beam scanning rule of the cell of the target access network device, and the target synchronization resource is a portion of the synchronization resources corresponding to the neighboring cells of the first cell. The target access network device is the access network device to which the second cell belongs, and the target synchronization resource is a beam, which can be determined by the first access network device or the target access network device.

[0096] Specifically, the detailed process of the cell handover shown in FIG3b may refer to the embodiments corresponding to FIG8 or FIG9 below.

[0097] The terminal involved in the present application may be a terminal device (terminal equipment) or a user equipment (UE) or a mobile station (MS) or a mobile terminal (MT), etc. Specifically, the terminal may be a mobile phone, a tablet computer or a computer with wireless transceiver function, or a virtual reality (VR) terminal, an augmented reality (AR) terminal, a wireless terminal in industrial control, a wireless terminal in unmanned driving, a wireless terminal in telemedicine, a wireless terminal in a smart grid, a wireless terminal in a smart city, a smart home, a vehicle-mounted terminal, etc. In the embodiment of the present application, the device for realizing the function of the terminal may be a terminal, or a device that can support the terminal to realize the function, such as a chip system (such as a processing system composed of a chip or multiple chips) or a modem. The following describes the cell switching method provided in the embodiment of the present application by taking the device for realizing the function of the terminal as an example.

[0098] The access network device involved in this application is a device in a radio access network (RAN) that connects a terminal to a wireless network. The RAN can be connected to a core network (for example, it can be an LTE core network or a 5G core network, etc.). The access network device can be a satellite base station (or flying platform) in an NTN scenario, an evolutionary Node B (eNB or eNodeB) in LTE, or a base station in a 5G network or a future evolved public land mobile network (PLMN), a broadband network gateway (BNG), an aggregation switch or a non-3GPP access device; or the access network device in the embodiment of this application can also be a wireless controller in a cloud radio access network (CRAN); or a transmission and reception point (TRP), or a device including a TRP, etc., which is not specifically limited in this embodiment of the application. Optionally, the base station in the embodiment of the present application can include various forms of base stations, such as: a macro base station, a micro base station (also called a small station), a relay station, an access point, etc., which is not specifically limited in this embodiment of the present application.

[0099] In some embodiments, the access network device in the embodiments of the present application can be carried or deployed on an aircraft platform, such as a low-altitude aircraft platform, a high-altitude aircraft platform, or a satellite. When the network device is carried on the aircraft platform, the access network device moves synchronously with the aircraft platform.

[0100] As an example, in an NTN scenario, a terminal switches from a first cell to a second cell, and the first cell and the second cell belong to the same satellite base station. For example, the terminal switches from cell 3 to cell 1, as shown in FIG4 .

[0101] As an example, in an NTN scenario, a terminal switches from a first cell to a second cell, and the first cell belongs to satellite base station 1, and the second cell belongs to satellite base station 2, but satellite base station 1 and satellite base station 2 belong to the same core network. For example, a terminal switches from cell 1 to cell 2, and satellite base station 1 and satellite base station 2 belong to the same core network device, as shown in Figure 5.

[0102] As an example, in an NTN scenario, a terminal switches from a first cell to a second cell, where the first cell belongs to satellite base station 1 and the second cell belongs to satellite base station 2. Furthermore, satellite base station 1 and satellite base station 2 belong to different core networks. For example, a terminal switches from cell 1 to cell 2, where satellite base station 1 belongs to core network device 1 and satellite base station 2 belongs to core network device 2, as shown in Figure 6.

[0103] As mentioned in the above example, satellite base station 1 and satellite base station 2 may optionally operate in a transparent load mode or a regenerative load mode, and an available inter-satellite link may optionally exist between satellite base station 1 and satellite base station 2.

[0104] In some embodiments, the access network device and the terminal may also be referred to as a communication device, which may be a general device or a dedicated device, and the embodiments of the present application do not specifically limit this.

[0105] As shown in FIG7 , it is a schematic diagram of the structure of the access network device 20 and the terminal 30 provided in an embodiment of the present application.

[0106] The terminal 30 includes at least one processor (in FIG. 7 , the exemplary embodiment includes a processor 301 for example) and at least one transceiver (in FIG. 7 , the exemplary embodiment includes a transceiver 303 for example). Furthermore, the terminal 30 may also include at least one memory (in FIG. 7 , the exemplary embodiment includes a memory 302 for example), at least one output device (in FIG. 7 , the exemplary embodiment includes an output device 304 for example), and at least one input device (in FIG. 7 , the exemplary embodiment includes an input device 305 for example).

[0107] The processor 301, the memory 302 and the transceiver 303 are connected via a communication line. The communication line may include a path for transmitting information between the above components.

[0108] The processor 301 may be a general-purpose central processing unit (CPU), a microprocessor, an application-specific integrated circuit (ASIC), or one or more integrated circuits for controlling the execution of the program of the present application. In a specific implementation, as an embodiment, the processor 301 may also include multiple CPUs, and the processor 301 may be a single-core (single-CPU) processor or a multi-core (multi-CPU) processor. The processor here may refer to one or more devices, circuits, or processing cores for processing data (such as computer program instructions).

[0109] The memory 302 may be a device having a storage function. For example, it may be a read-only memory (ROM) or other types of static storage devices that can store static information and instructions, a random access memory (RAM) or other types of dynamic storage devices that can store information and instructions, or an electrically erasable programmable read-only memory (EEPROM), a compact disc read-only memory (CD-ROM) or other optical disc storage, optical disc storage (including compact discs, laser discs, optical discs, digital versatile discs, Blu-ray discs, etc.), a magnetic disk storage medium or other magnetic storage device, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and can be accessed by a computer, but is not limited thereto. The memory 302 may exist independently and be connected to the processor 301 via a communication line. The memory 302 may also be integrated with the processor 301.

[0110] The memory 302 is used to store computer-executable instructions for executing the solution of the present application, and the execution is controlled by the processor 301. Specifically, the processor 301 is used to execute the computer-executable instructions stored in the memory 302, thereby implementing the method described in the embodiment of the present application.

[0111] Alternatively, in the present application, the processor 301 may also perform processing-related functions in the signal sending and receiving method provided in the present application, and the transceiver 303 may be responsible for communicating with other devices or communication networks. The embodiments of the present application do not specifically limit this.

[0112] The computer-executable instructions involved in this application may also be referred to as application code or computer program code, which is not specifically limited in the embodiments of this application.

[0113] The transceiver 303 can be any transceiver-like device for communicating with other devices or communication networks, such as Ethernet, radio access networks (RAN), or wireless local area networks (WLAN). The transceiver 303 includes a transmitter (Tx) and a receiver (Rx).

[0114] Output device 304 communicates with processor 301 and can display information in a variety of ways. For example, output device 304 can be a liquid crystal display (LCD), a light emitting diode (LED) display device, a cathode ray tube (CRT) display device, or a projector.

[0115] The input device 305 communicates with the processor 301 and can accept user input in various ways. For example, the input device 305 can be a mouse, keyboard, touch screen device, or sensor device.

[0116] The access network device 20 includes at least one processor (in FIG. 7 , the example is illustrated by including a processor 201) and at least one transceiver (in FIG. 7 , the example is illustrated by including a transceiver 203). Furthermore, the access network device 20 may also include at least one memory (in FIG. 7 , the example is illustrated by including a memory 202) and at least one network interface (in FIG. 7 , the example is illustrated by including a network interface 204). The processor 201, the memory 202, the transceiver 203 and the network interface 204 are connected via a communication line. The network interface 204 is used to connect to the core network device through a link (for example, an S1 interface), or to connect to the network interface of other network devices through a wired or wireless link (for example, an X2 interface) (not shown in FIG. 7). This embodiment of the present application does not specifically limit this. In addition, the relevant description of the processor 201, the memory 202 and the transceiver 203 can refer to the description of the processor 301, the memory 302 and the transceiver 303 in the terminal 30, and will not be repeated here.

[0117] It should be understood that the structure shown in FIG7 does not constitute a specific limitation on the terminal 30 and the access network device 20. For example, in other embodiments of the present application, the terminal 30 and the access network device 20 may include more or fewer components than shown, or may combine or separate certain components, or arrange the components differently. The components shown in the figure may be implemented in hardware, software, or a combination of software and hardware.

[0118] The cell handover method provided in the embodiments of the present application will be described below in conjunction with the accompanying drawings, using the communication system (or NTN system) shown in FIG. 3a or any one of FIG. 4 to FIG. 6 as an example. For ease of description, in the following embodiments, the first access network device is referred to as a source satellite base station, the second access network device is referred to as a target satellite base station, and the source and target satellite base stations have the structure of the access network device 20 shown in FIG. 7 . In the following embodiments, the terminal has the structure of the terminal 30 shown in FIG. 7 .

[0119] It is understood that in the embodiments of the present application, the terminal and / or access network device may perform some or all of the steps in the embodiments of the present application. These steps or operations are merely examples, and the embodiments of the present application may also perform other operations or variations of various operations. In addition, the various steps may be performed in a different order than those presented in the embodiments of the present application, and it is possible that not all of the operations in the embodiments of the present application need to be performed.

[0120] It is understandable that the interaction mechanism between the access network device and the terminal in each embodiment of the present application can be appropriately modified to apply to the interaction between the CU or DU and the terminal. It should be noted that the message names between the various devices or the names of the parameters in the messages in the following embodiments of the present application are only examples. Other names may also be used in specific implementations, and the embodiments of the present application do not specifically limit this.

[0121] As shown in FIG8 , a cell switching method provided in an embodiment of the present application includes the following steps:

[0122] S800: The source satellite base station sends a measurement event to the terminal, and the terminal receives the measurement event.

[0123] S801: The terminal reports a measurement event report and location information of the terminal based on a measurement event.

[0124] Among them, the terminal can be a terminal in the communication system shown in Figure 3a, and the terminal should have any one or more of the global navigation satellite systems (GNSS). The global satellite navigation system mentioned above refers to all satellite navigation systems, including the United States' global positioning system (GPS), Russia's global navigation satellite system (Glonass), Europe's Galileo satellite navigation system (Galileo), and China's Beidou satellite navigation system. The global satellite navigation system can provide continuous and accurate location information and time to terminals located anywhere in the world or military terminals in near-Earth space. Specifically, the location information of the terminal can be the three-dimensional spatial location information of the terminal or the latitude and longitude information of the terminal's location. It should be understood that before S800, the terminal has been connected to the source satellite base station and is in a radio resource control connection state (or called a connection state).

[0125] The source satellite base station may be the first access network device in the communication system shown in FIG3a . In this case, the source satellite base station has established an RRC connection with the terminal and can deliver measurement events to the terminal via RRC signaling. Accordingly, the terminal reports a measurement event report and the terminal's location information to the source satellite base station via RRC signaling.

[0126] Specifically, the source satellite base station sends a measurement event message for handover to the terminal via radio resource control (RRC) signaling. The measurement event message includes the object that the terminal needs to measure, a cell list, a reporting method, event parameters, a measurement identifier, etc. The measurement event can be at least one of the following: a time-based measurement event, a location-based measurement event, or an RRM-based measurement event. Based on the measurement event message, the terminal can determine the neighboring cells in the cell list that meet the measurement event and generate a measurement event report for the neighboring cell information that meets the measurement event. Furthermore, the terminal reports the generated measurement event report and the terminal location information provided by the global satellite navigation system configured by the terminal to the source satellite base station via radio resource control (RRC) signaling.

[0127] One possible design is that the measurement event used for switching is a location-based measurement event. The source satellite base station will first send a location measurement event to the terminal through radio resource control RRC signaling, and carry a location measurement threshold. The terminal receives and determines the neighboring cells that meet the location measurement event in the cell list based on the location measurement event, and generates a measurement event report for the neighboring cell information that meets the distance measurement position and reports it to the source satellite base station. The source satellite base station continues to send RRM-based measurement events to the terminal through radio resource control RRC signaling. The terminal receives and determines the neighboring cells that meet the RRM-based measurement event in the cell list based on the RRM-based measurement event, and generates a measurement event report for the neighboring cell information that meets the RRM-based measurement event and reports the terminal location information provided by the global satellite navigation system configured by the terminal to the source satellite base station. Among them, the RRM-based measurement event can be any measurement event for cell switching in Table 2,

[0128] For example, the source satellite base station first sends a location measurement event D1 to the terminal. When the location distance between the terminal and the serving cell is greater than a specific threshold, and the location distance threshold between the terminal and the neighboring cell is less than a specific threshold, after a certain period of time, the RRM-based measurement event A4 is triggered. That is, the source satellite base station sends the RRM-based A4 measurement event to the terminal. The terminal reports the neighboring cell information that the neighboring cell level exceeds the RRM-based A4 event threshold and the latitude and longitude information provided by the global satellite navigation system (for example, GPS system) configured on the terminal to the source satellite base station.

[0129] S802: The source satellite base station makes a handover decision based on the measurement event report reported by the terminal and the location information of the terminal, completes handover preparation with the target satellite base station, and reports the location information of the terminal to the target satellite base station.

[0130] The source satellite base station and terminal should have the same configuration and characteristics as the source satellite base station and terminal mentioned above. The measurement event report and terminal location information are consistent with the above description and are not further described here. The target satellite base station is determined by the source satellite base station based on the measurement report information reported by the terminal and the terminal's location information, combined with the decision policy configured by the source satellite base station.

[0131] The target satellite base station and the source satellite base station may be the same or different.

[0132] When the target satellite base station and the source satellite base station are the same, the terminal performs cell handover within the same satellite base station. This means that the source cell (first cell) providing communication services to the terminal at time t1 and the target cell (second cell) providing communication services to the terminal, selected by the terminal by measuring the SSB beams of the neighboring cells after the handover time arrives, belong to the same satellite base station. The above cell handover process occurs within the same satellite base station and does not involve information exchange between base stations. It is simply resource allocation between two cells within a satellite base station, and does not require application to the core network for a change in the data transmission path.

[0133] When the target satellite base station and the source satellite base station are different, the terminal performs a cell handover between different satellite base stations. This means that the source cell (first cell) providing communication services to the terminal at time t1 and the target cell (second cell) providing communication services to the terminal, selected by the terminal by measuring the SSB beams of the neighboring cells after the handover time, belong to different satellite base stations. An optional intersatellite link exists between the target satellite base station and the source satellite base station. When an intersatellite link is available between the target satellite base station and the source satellite base station, the satellite base stations can communicate directly via the intersatellite link.

[0134] The source satellite base station makes a handover decision based on the terminal's measurement event report and location information, combined with its own decision strategy, and determines the target satellite base station. Simultaneously, the source satellite base station reports the acquired terminal location information to the target satellite base station. The source satellite base station's decision strategy is configurable by the source satellite base station.

[0135] One possible design is that the decision strategy of the source satellite base station can be that the source satellite base station determines the target satellite base station based on the movement trend of the satellite base station belonging to the neighboring area in the measurement event report reported by the terminal and the movement trend of the terminal, and the signal quality of the neighboring area in the measurement event report reported by the terminal, where the neighboring area signal quality can be measured by the RSRP, RSRQ or SINR of the neighboring area.

[0136] Handover preparation between the source and target satellite base stations involves the source base station applying for and allocating resources from the target base station on behalf of the terminal. The target base station then determines whether to grant the terminal access. If so, it allocates air interface resources and service bearer resources to the terminal. If handover preparation between the source and target satellite base stations occurs across core network devices, interaction with the core network is also required.

[0137] One possible design is that the source satellite base station and the target satellite base station belong to the same satellite base station. In this case, the handover preparation does not involve information exchange between base stations, but only involves resource configuration between two cells within a base station. There is no need to apply to the core network for a change in the data transmission path. For example, the source satellite base station determines that the target cell and the source cell to be handed over are the same satellite base station based on the PCI carried in the measurement report and initiates the intra-site handover process. The target cell makes an admission decision based on the context of the source cell. The centralized unit (CU) of the source satellite base station sends a terminal context establishment request to the distributed unit (DU) of the source satellite base station, and applies for new terminal-available resources for the target cell from the distributed unit side of the source satellite base station. If the distributed unit of the source satellite base station successfully allocates resources, it replies with a terminal context establishment response message to the centralized unit of the source satellite base station. The centralized unit of the source satellite base station is used to process non-real-time protocols and services; the distributed unit of the source satellite base station is used to process physical layer protocols and real-time services.

[0138] In one possible design, the source and target satellite base stations are different satellite base stations under the same core network equipment, and an inter-satellite link is available between the source and target satellite base stations. The source satellite base station sends a handover request to the base station of the target cell (the target satellite base station) via the inter-satellite link. If the target cell allows the terminal to access, the target cell allocates resources to the terminal, such as access to the air interface and transmission resources.

[0139] One possible design is that the source satellite base station and the target satellite base station belong to different satellite base stations under the same core network equipment, and there is no inter-satellite link between the source satellite base station and the target satellite base station or the inter-satellite link between the base stations is unavailable, then all signaling interactions and data forwarding between the source satellite base station and the target satellite base station need to be forwarded through the core network.

[0140] One possible design is that the source satellite base station and the target satellite base station belong to different satellite base stations under different core network devices, then all signaling interactions and data forwarding between the source satellite base station and the target satellite base station need to be forwarded through the core network.

[0141] S803. The target satellite base station determines the SSB beam of the target neighboring area covering the terminal and the time when the terminal can measure the SSB beam (i.e., the switching time of the terminal) based on the location information of the terminal, the satellite ephemeris information of the target satellite base station, and the beam scanning rules of the cell of the target satellite base station, and sends second information to the source satellite base station. The second information indicates the SSB beam of the target neighboring area covering the terminal and the switching time of the terminal.

[0142] The target satellite base station is determined by the source satellite base station based on the measurement event report and the terminal's location information reported by the terminal, combined with the source satellite base station's own decision strategy. The target satellite base station's satellite ephemeris information includes information such as the target satellite's row number, satellite number, orbital intersection angle, orbital eccentricity, and mean motion. The mathematical relationship between the six orbital parameters of Kepler's law is used to determine the time, coordinates, orientation, velocity, and other parameters of the target satellite (flying object) with extremely high accuracy. The beam scanning rules of the target satellite base station's cell include information such as the number of SSB beams contained in the target satellite base station's cell, the cell's scanning period, the cell's SSB beam scanning time, and the cell's SSB beam characteristics (for example, the angle value corresponding to the 3dB beamwidth of the SSB beam). These rules can indicate the time, range, and coverage duration of the ground area covered by the target satellite base station's cell's SSB beam.

[0143] The terminal's location information can be used to indicate the terminal's current location. Specifically, the terminal's current location can be represented by longitude and latitude, or by three-dimensional spatial coordinates. In this application, the terminal's location information can be obtained by the terminal itself and reported to the target satellite base station via the source satellite base station. For example, the terminal can obtain the terminal's current location information via its own GNSS system.

[0144] Among them, the beam scanning rules can be information such as the number of SSB beams, the beam scanning period, the scanning time of the SSB beam, the characteristics of the SSB beam (for example, the angle value corresponding to the 3dB width of the SSB beam), etc., which can indicate the time, range and coverage duration of the satellite base station cell and the SSB beam of the satellite base station cell covering the ground area.

[0145] In the present application, the satellite ephemeris information of the target satellite base station and the beam scanning rules of the cell of the target satellite base station can be provided by a platform that controls the target satellite base station on the ground, for example, a core network device to which the target satellite base station belongs. The platform that controls the target satellite base station on the ground is configured with the satellite ephemeris information of the target satellite base station and the beam scanning rules of the cell of the target satellite base station. When a satellite base station or a terminal needs to use the satellite ephemeris information of the target satellite base station and the beam scanning rules of the cell of the target satellite base station, it can apply to the platform that controls the target satellite base station on the ground to call the specific satellite ephemeris information of the target satellite base station and the beam scanning rules of the cell of the target satellite base station.

[0146] The target satellite base station determines the SSB beam of the terminal covered by the target neighboring area and the switching time of the terminal based on the location information of the terminal reported by the source satellite base station, its own satellite ephemeris information called to the ground control platform of the target satellite base station, and the beam scanning rules of its own cell. Specifically, the target satellite base station can apply to the ground control platform to call its own satellite ephemeris information and the beam scanning rules of its own cell. When the target satellite base station receives its own satellite ephemeris information and the beam scanning rules of its own cell, the target satellite base station can determine the time, range and coverage duration of the target satellite base station's cell and the SSB beam of the target satellite base station's cell covering the ground area through information such as the number of SSB beams contained in the target satellite base station's cell, the scanning period of the cell, the scanning time of the SSB beam of the cell, and the characteristics of the SSB beam of the cell (for example, the angle value corresponding to the 3dB width of the SSB beam). The target satellite base station uses the above-determined target satellite base station cell and the time, range and coverage duration of the SSB beam of the target satellite base station cell covering the ground area and the location information of the terminal reported by the source satellite base station to determine the SSB beam number of the terminal scanned by the target satellite base station and the time when the SSB beam scanned the terminal.

[0147] For example, the terminal location information reported by the source satellite base station is the longitude and latitude location information, which are 108°96′39.70″ east longitude and 34°21′84.30″ north latitude respectively. The target satellite base station contains a total of 10 cells, numbered from cell 0 to cell 9, and the SSB beam scanning rules contained in each cell may be the same or different. One possible situation is that the SSB beam scanning rules contained in each cell are the same, that is, each cell contains 10 SSB beams, and the beams in each cell are numbered SSB_0 to SSB_9. The scanning time of each SSB beam is 1ms, the 3dB width of each SSB beam is 3°, and the scanning period of each cell is 10ms. Therefore, the ground coverage range of each cell of the target satellite base station and the ground coverage range of each SSB beam of the target satellite base station's cell can be obtained using the aforementioned beam scanning rules of the target satellite base station's cell. Assume that the target satellite base station determines through calculation that the SSB_1 beam of cell 0 covers the ground range of 107°-110° east longitude and 33°-36° north latitude. Therefore, it can be confirmed that the SSB_1 beam of cell 0 of the target satellite base station can scan the terminal reported by the source satellite base station.

[0148] In the above example, the above process has determined that the SSB_1 beam of cell 0 of the target satellite base station can scan the terminal reported by the source satellite base station. The beam scanning rules of the target satellite base station's cell are also known, namely, the number of SSB beams contained in the target satellite base station's cell, the cell's scanning period, and the cell's SSB beam scanning time. Specifically, the scanning period of cell 0 is 10ms, which is equal to the number of SSB beams contained in cell 0 of the target satellite base station multiplied by the SSB beam scanning time of cell 0. Therefore, the time when the SSB_1 beam of cell 0 of the target satellite base station scans the terminal reported by the source satellite base station can also be determined. The time when the SSB_1 beam of cell 0 of the target satellite base station scans the terminal reported by the source satellite base station is the terminal's handover time.

[0149] For example, the current time is 0 days, 0 hours, 0 minutes, 0 seconds, and 0 milliseconds. The beam number of cell 0 of the current target satellite base station is SSB_0. The SSB beam scanning time of cell 0 is 1 ms. Cell 0 contains a total of 10 SSB beams, and the SSB beams of cell 0 are scanned in the order of SSB_0-SSB_9 with a scanning period of 10 ms. The beam scanned by the target satellite base station to the terminal is SSB_1 of cell 0. The terminal's switching time is 0 days, 0 hours, 0 minutes, 0 seconds, and 1 millisecond. Therefore, the terminal will receive the SSB beam signal of cell 0 of the target satellite base station with beam number SSB_1 at 0 days, 0 hours, 0 minutes, and 0 seconds, and 1 millisecond.

[0150] After the above process, the target satellite base station has determined that the target neighboring cell covers the SSB beam of the terminal reported by the source satellite base station and the terminal switching time. Then, the target satellite base station transmits the determined target neighboring cell covering the SSB beam of the terminal reported by the source satellite base station and the terminal switching time to the source satellite base station through radio resource control signaling.

[0151] S804. The source satellite base station receives the second information sent by the target satellite base station, and sends the first information indicating the SSB beam of the terminal and the switching time of the terminal to the terminal.

[0152] The source satellite base station receives a second message sent by the target satellite base station. The second information includes the target neighboring area covered by the target satellite base station, the SSB beam of the terminal reported by the source satellite base station, and the switching time of the terminal, and sends the first information to the terminal. The first information is used to indicate the SSB beam and switching time of the terminal. Because the terminal has not yet accessed the target satellite base station at this time, the terminal still maintains a communication connection and / or data transmission with the source satellite base station. The target satellite base station needs to transmit the determined target neighboring area covering the SSB beam of the terminal reported by the source satellite base station and the switching time of the terminal to the terminal through the source satellite base station, so as to facilitate the terminal's subsequent access to the target satellite base station.

[0153] S805. The terminal receives the switching time of the terminal and the SSB beam of the target neighboring cell covering the terminal sent by the source satellite base station, and when the switching time arrives, disconnects the communication connection and / or data transmission with the source satellite base station and accesses the target cell.

[0154] Among them, before the switching time arrives, the terminal maintains the communication connection and / or data transmission with the source satellite base station; when the switching time arrives, the terminal disconnects the communication connection and / or data transmission with the source satellite base station, performs RSRP measurement of the SSB beam of the target neighboring area covering the terminal and completes downlink synchronization, and then initiates initial access to the target satellite base station, accesses the target cell, and completes the cell switching.

[0155] When the switching time arrives, the terminal measures the RSRP of the SSB beam of the target neighboring area covering the terminal sent by the source satellite base station. This is not only the first step to access the target cell, but also can verify from the side that the target neighboring area determined by the target satellite base station covers the SSB beam of the terminal and the switching time of the terminal, to prevent the information determined by the target satellite base station from being inaccurate. For example, the switching trigger event of the terminal is A4, and the neighboring area threshold value of A4 is N. When the switching time arrives, the terminal measures the RSRP of the estimated SSB beam. At this time, the RSRP measurement value of the beam should still be greater than the neighboring area threshold value N, ensuring that the signal quality of the target cell is higher than that of the source cell (first cell). The source cell can also be called the first cell, which is the cell for which the source satellite base station provides communication connection and / or data transmission for the terminal at the current moment.

[0156] Based on the handover method shown in Figure 8, when the first access network device is a first satellite base station (source satellite base station), the second access network device is a second satellite base station (target satellite base station), and the target synchronization resource (SSB beam of the target neighboring area covering the terminal) and the handover time of the terminal are determined by the second satellite base station based on the terminal's location information, its own satellite ephemeris information, and its own cell beam scanning rule, the target synchronization resource and the terminal's handover time are transmitted to the first satellite base station (source satellite base station). Then, the first satellite base station sends a first message to the terminal through the radio resource control RRC. The terminal receives the first message and executes the handover process according to the first message instruction. Among them, the target synchronization resource is the SSB beam of the target neighboring area covering the terminal determined by the target satellite base station. The target synchronization resource is also part of the synchronization resources corresponding to the neighboring cells of the first cell. The first cell is the cell in which the first satellite base station currently provides communication connection and / or data transmission for the terminal. Before the handover time arrives, the terminal maintains the communication connection and / or data transmission with the source satellite base station. When the handover time arrives, the terminal disconnects the communication connection and / or data transmission with the source satellite base station, measures the RSRP of the target synchronization resource, completes downlink synchronization, and then initiates initial access to the target satellite base station and accesses the target cell to complete the cell handover. The target cell is the cell to which the SSB beam of the target satellite base station provides communication connection and / or data transmission for the terminal when the handover time arrives.

[0157] Based on the switching method shown in Figure 8, the terminal will not immediately disconnect the data transmission with the first cell after receiving the switching command. The terminal will disconnect the data transmission with the first cell until the switching time arrives, and the first cell stops uplink and downlink scheduling with the terminal, shortening the data interruption time during the switching process; at the same time, the terminal can only measure the RSRP of the SSB beam of the target neighboring area covering the terminal sent by the source satellite base station and complete downlink synchronization, which can not only further shorten the data interruption time during the switching process and reduce the impact of data interruption on the service during the switching process, but also reduce the energy consumption of the terminal for measuring the RSRP of the SSB beam of the neighboring area.

[0158] In the above process, the switching time received by the terminal and the SSB beam of the target neighboring cell covering the terminal are determined by the target satellite base station. Another possible design is that the switching time of the terminal and the SSB beam of the target neighboring cell covering the terminal are determined by the source satellite base station. As shown in Figure 9, a cell switching method provided in an embodiment of the present application includes the following steps:

[0159] S900: The source satellite base station sends a measurement event to the terminal, and the terminal receives the measurement event.

[0160] S901: The terminal reports a measurement event report and its own location information based on a measurement event.

[0161] S902: The source satellite base station makes a handover decision based on the measurement event report reported by the terminal and the location information of the terminal.

[0162] Specifically, the source satellite base station and terminal mentioned in steps S900, S901, and S902 should have the same configuration and characteristics as the source satellite base station and terminal mentioned in steps S800, S801, and S802; and the measurement events, measurement event reports, terminal location information, and the source satellite base station's switching decision process based on the measurement event reports reported by the terminal and the terminal's location information mentioned in steps S900, S901, and S902 are consistent with the description in steps S800, S801, and S802, and will not be repeated here.

[0163] S903: The source satellite base station and the target satellite base station complete handover preparation.

[0164] Specifically, the purpose and process of the source satellite base station and the target satellite base station performing handover preparation in step S903 are consistent with the description of the source satellite base station and the target satellite base station performing handover preparation in step S802, and will not be repeated here.

[0165] S904. The source satellite base station determines the SSB beam of the target neighboring area covering the terminal and the time when the terminal can measure the SSB beam based on the terminal's location information, the satellite ephemeris information of the target satellite base station and the beam scanning rule of the cell of the target satellite base station, and transmits the SSB beam of the target neighboring area covering the terminal and the time when the terminal can measure the SSB beam determined by the source satellite base station to the terminal.

[0166] Specifically, the terminal location information, target satellite base station, satellite ephemeris information of the target satellite base station, and beam scanning rules of the cell of the target satellite base station mentioned in step S904 have the same configuration and characteristics as the terminal location information, target satellite base station, satellite ephemeris information of the target satellite base station, and beam scanning rules of the cell of the target satellite base station mentioned in step S803. The usage process and acquisition process are consistent with those described in step S803 and will not be repeated here.

[0167] It should be noted that the premise for the source satellite base station to determine the SSB beam of the target neighboring cell covering the terminal and the time when the terminal can measure the target beam is that the source base station already knows the satellite ephemeris information of the target satellite base station and the beam scanning rules of the cell of the target satellite base station.

[0168] The timing for the source satellite base station to obtain the satellite ephemeris information of the target satellite base station and the beam scanning rules of the target satellite base station's cell is optional. One possible scenario is that the source satellite base station requests the ground control platform to which the target satellite base station belongs to obtain the satellite ephemeris information of the target satellite base station and the beam scanning rules of the target satellite base station's cell when preparing for the above-mentioned handover. Another possible scenario is that the source satellite base station has already pre-paid the relevant configuration information of the target satellite base station. For example, when the source satellite base station and the target satellite base station configure neighboring cells with each other, the source satellite base station has already obtained the satellite ephemeris information of the target satellite base station and the beam scanning rules of the target satellite base station's cell.

[0169] The source satellite base station determines the SSB beam of the terminal covered by the target neighboring cell and the switching time of the terminal based on the location information of the terminal, the satellite ephemeris information of the target satellite base station and the beam scanning rule of the cell of the target satellite base station. Specifically, the source satellite base station can apply to the platform of the ground control target satellite base station to call the satellite ephemeris information of the target satellite base station and the beam scanning rule of the cell of the target satellite base station. When the source satellite base station receives the satellite ephemeris information of the target satellite base station and the beam scanning rule of the cell of the target satellite base station sent by the platform of the ground control target satellite base station, the source satellite base station can determine the time, range and coverage duration of the ground area covered by the SSB beam of the cell of the target satellite base station and the cell of the target satellite base station through the number of SSB beams contained in the cell of the target satellite base station, the scanning period of the cell, the characteristics of the SSB beam of the cell, and the scanning time of the SSB beam of the cell. The source satellite base station uses the time, range, coverage duration of the ground area covered by the cell of the target satellite base station and the SSB beam of the cell of the target satellite base station determined above and the location information of the terminal to determine the SSB beam number scanned by the target satellite base station to the terminal and the time when the SSB beam scanned to the terminal.

[0170] For example, the terminal location information is the longitude and latitude location information, which are 106°57′9″ east longitude and 29°56′23″ north latitude respectively. The source satellite base station learns through the ground control platform of the target satellite base station (for example, the core network equipment) that the target satellite base station contains a total of 10 cells, numbered from cell 0 to cell 9. Assuming that the SSB beam scanning rules of each cell are the same, each cell contains 10 SSB beams, and the beams in each cell are numbered SSB_0 to SSB_9. The scanning time of each SSB beam is 2ms, the 3dB width of each SSB beam is 3°, and the scanning period of each cell is 20ms. Therefore, the ground coverage range of each cell of the target satellite base station and the ground coverage range of each SSB beam of the cell of the target satellite base station can be obtained using the beam scanning rules of the cell of the aforementioned target satellite base station. Assume that the source satellite base station determines through calculation that the ground coverage range of the SSB_2 beam of cell 1 is 105°-108° east longitude and 28°-31° north latitude. Therefore, the source satellite base station can confirm that the SSB_2 beam of cell 1 of the target satellite base station can scan the terminal.

[0171] In the above example, the source satellite base station has determined through the above process that the SSB_2 beam of cell 1 of the target satellite base station can scan the terminal. The source satellite base station also knows the beam scanning rules of the target satellite base station's cell, namely, the number of SSB beams contained in the target satellite base station's cell, the cell's scanning period, and the cell's SSB beam scanning time. Specifically, the scanning period of cell 1 is 20ms, which is equal to the number of SSB beams contained in cell 1 of the target satellite base station multiplied by the SSB beam scanning time of cell 1. Therefore, the source satellite base station can also determine the time when the SSB_2 beam of cell 1 of the target satellite base station scans the terminal. The time when the SSB_2 beam of cell 1 of the target satellite base station scans the terminal is the terminal's handover time.

[0172] For example, the current time is 0 day, 0 hour, 0 minute, 0 second, 0 millisecond. The source satellite base station knows that the beam number of cell 0 of the current target satellite base station is SSB_0. When the handover time arrives, the beam scanned by the target satellite base station to the terminal is SSB_2 for cell 1. If the SSB beam scanning rules for each cell of the target satellite base station are the same, the SSB beam scanning time for each cell is 2 ms. Each cell contains 10 SSB beams, which are scanned in the order of cell 0 to cell 9. The SSB beams of the cells are scanned in the order of SSB_0 to SSB_9, with a scanning period of 20 ms. The source satellite base station determines that the beam scanned by the target satellite base station to the terminal is SSB_2 for cell 1. The handover time for the terminal is 0 day, 0 hour, 0 minute, 0 second, 24 milliseconds. Therefore, the terminal receives the SSB beam signal of SSB_2 for cell 1 of the target satellite base station at 0 day, 0 hour, 0 minute, 0 second, 24 milliseconds.

[0173] S905. The terminal receives the switching time of the terminal and the SSB beam of the target neighboring cell covering the terminal sent by the source satellite base station, and when the switching time arrives, disconnects the communication connection and / or data transmission with the source satellite base station and accesses the target cell.

[0174] Specifically, in step S905, the terminal receives the switching time of the terminal and the SSB beam of the target neighboring cell covering the terminal sent by the source satellite base station, and when the switching time arrives, it disconnects the communication connection and / or data transmission with the source satellite base station. The series of process descriptions for accessing the target cell are consistent with the series of process descriptions executed by the terminal in step S805, and will not be repeated here.

[0175] Based on the handover method shown in FIG9 , where the first access network device is a first satellite base station (source satellite base station), the second access network device is a second satellite base station (target satellite base station), and the target synchronization resource (SSB beam of the target neighboring cell covering the terminal) and the handover time of the terminal are determined by the source satellite base station based on the terminal's location information, the satellite ephemeris information of the target satellite base station, and the beam scanning rule of the target satellite base station's cell, the source satellite base station sends first information to the terminal via RRC signaling. The terminal receives the first information and performs a handover process according to the instructions of the first information. The target synchronization resource is the SSB beam of the target neighboring cell covering the terminal determined by the source satellite base station. The target synchronization resource is also part of the synchronization resources corresponding to the neighboring cells of the first cell. The first cell is the cell for which the first satellite base station currently provides communication connection and / or data transmission for the terminal. Before the handover time arrives, the terminal maintains the communication connection and / or data transmission with the source satellite base station. When the handover time arrives, the terminal disconnects the communication connection and / or data transmission with the source satellite base station, measures the RSRP of the target synchronization resource, completes downlink synchronization, and then initiates initial access to the target satellite base station, accesses the target cell, and completes the cell handover. The target cell is the cell to which the SSB beam of the target satellite base station provides communication connection and / or data transmission for the terminal when the switching time arrives.

[0176] The handover method shown in Figure 9 not only has all the advantages of the handover method shown in Figure 8, but also does not require the target satellite base station to report the terminal's location information to the source satellite base station. Furthermore, the target satellite base station does not need to determine the terminal's handover time or target synchronization resource. This reduces the target satellite base station's computational overhead and further reduces signaling interactions between the target and source satellite base stations.

[0177] Although the method described in this application is proposed for the NTN system, it can also be applied to neighboring cell measurements in terrestrial 5G networks. One applicable scenario is a scenario where the SSB scanning period of the terrestrial 5G network is relatively long. Although the SSB scanning period of the current terrestrial 5G network is relatively short (generally configured to be 20ms), and the data interruption during the switching process has basically no impact on the service, future evolution may support a longer SSB scanning period of more than 100ms. The method described in this solution can be used to shorten the time of data interruption during the switching process and reduce the power consumption required by the terminal during the switching process. Another applicable scenario is a fast-moving terminal in a terrestrial 5G network (for example, a terminal in a high-speed rail scenario). Due to its fast moving speed, it will also frequently trigger cell switching. The method described in this solution can be used to estimate the target cell and switching time in advance, shorten the time of data interruption during the switching process, and reduce the power consumption required by the terminal during the switching process.

[0178] The above mainly introduces the solution provided by the embodiment of the present application from the perspective of the interaction between each node. It is understandable that each node, such as a terminal, an access network device, etc., includes a hardware structure and / or software module corresponding to the execution of each function in order to realize the above functions. Those skilled in the art should easily realize that, in combination with the algorithm steps of each example described in the embodiments disclosed herein, the present application can be implemented in the form of hardware or a combination of hardware and computer software. Whether a function is executed in a hardware or computer software driven hardware manner depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this application.

[0179] In the embodiments of the present application, functional modules of terminals, access network devices, etc. can be grouped according to the above-mentioned method examples. For example, each functional module can be grouped according 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 in the form of software functional modules. It should be noted that the grouping of modules in the embodiments of the present application is schematic and is only a logical functional grouping. In actual implementation, other grouping methods may be used.

[0180] Figure 10 shows a structural diagram of a communication device 100. The communication device 100 may be a terminal, a chip in a terminal, or a system-on-chip. The communication device 100 may be used to perform the terminal functions involved in the above embodiments. As an implementation method, the communication device 100 shown in Figure 10 includes: a receiving unit 1001, a processing unit 1002, and a sending unit 1003;

[0181] The receiving unit 1001 is configured to receive a measurement event and first information sent by a first cell. For example, the receiving unit 1001 may support the communication device 100 to execute S801 or S901.

[0182] The processing unit 1002 is configured to receive the target synchronization resource and perform synchronization measurement on the target synchronization resource when the switching time arrives, and switch from the first cell to the second cell based on the synchronization measurement result. For example, the processing unit 1002 can be configured to support the communication device 100 in executing S805 or S905.

[0183] The sending unit 1003 is configured to send the measurement event report and its own location information. For example, the sending unit 1003 may support the communication device 100 to execute S801 or S901.

[0184] For the description of the first information, target synchronization resource, and measurement event, reference may be made to that in the above embodiments.

[0185] Specifically, for a terminal that has accessed the first cell, the first cell will send a measurement event to the terminal. Accordingly, the terminal will report the measurement event and its own location information to the first cell. Subsequently, the terminal receives the first information contained in the radio resource control configuration message sent by the first cell to the terminal. According to the instructions of the first information, when the switching time arrives, the terminal receives the target synchronization resource and performs synchronization measurement on the target synchronization resource. Specifically, the terminal receives the target synchronization resource and measures the RSRP information of the target synchronization resource, completes downlink synchronization, and then initiates initial access to the target satellite base station, accesses the target cell, and completes the cell switching.

[0186] The measurement event may be at least one of the following: a location-based measurement event, a time-based measurement event, and an RRM-based measurement event; the first information is used to instruct the terminal to switch from the first cell to the second cell when the switching time arrives; the target synchronization resource may be determined by the first cell or the second cell based on the location information of the terminal, the satellite ephemeris information of the second access network device, and the scanning rule of the cell of the second access network device, and the second access network device is the access network device to which the second cell belongs. Before the switching time arrives, the terminal maintains a communication connection and / or data transmission with the first cell; when the switching time arrives, the terminal disconnects the communication connection and / or data transmission with the first cell, receives the target synchronization resource, and performs synchronization measurement on the target synchronization resource. When the switching time arrives, the terminal only needs to measure the RSRP of the target synchronization resource and complete downlink synchronization, and then initiates initial access to the target satellite base station, accesses the target cell, and completes the cell switching.

[0187] The relationship between the first cell and the second cell mentioned above can be any of the following possibilities:

[0188] (1) The first cell and the second cell belong to the same access network device;

[0189] (2) The first cell and the second cell belong to different access network devices, there is no direct communication link between the different access network devices or there is an unavailable direct communication link, and they belong to the same core network device;

[0190] (3) The first cell and the second cell belong to different access network devices, there is an available direct communication link between the different access network devices, and they belong to the same core network device;

[0191] (4) The first cell and the second cell belong to different access network devices, there is no direct communication link between the different access network devices or there is an unavailable direct communication link, and they belong to different core network devices;

[0192] (5) The first cell and the second cell belong to different access network devices, there is an available direct communication link between the different access network devices, and they belong to different core network devices;

[0193] As mentioned above, the first cell can correspond to the first satellite base station and the second cell to the second satellite base station; or the first cell can correspond to the first ground station and the second cell to the second ground station. In the case where the first cell corresponds to the first satellite base station and the second cell corresponds to the second satellite base station, the operating modes of the satellite base stations can be divided into transparent transmission mode and regenerative mode. Therefore, there are five possible relationships between the first cell and the second cell in transparent transmission mode and five possible relationships between the first cell and the second cell in regenerative mode, for a total of ten possible relationships.

[0194] As another possible implementation, the communication device 100 shown in FIG10 includes: a processing module and a communication module. The processing module is used to control and manage the operations of the communication device 100. For example, the processing module may integrate the functions of the processing unit 1002 and may be used to support the communication device 100 in executing S805 or S905 and other processes of the technology described herein. The communication module may integrate the functions of the receiving unit 1001 and the sending unit 1003 and may be used to support the communication device 100 in executing S801 or S901 and communicating with other network entities, such as communication with the functional modules or network entities shown in FIG3a. The communication device 100 may also include a storage module for storing program code and data of the communication device 100.

[0195] The processing module may be a processor or a controller. It may implement or execute the various exemplary logic blocks, modules, and circuits described in conjunction with the disclosure of this application. The processor may also be a combination that implements computing functions, such as a combination of one or more microprocessors, a combination of a DSP and a microprocessor, and so on. The communication module may be a transceiver circuit or a communication interface, and the storage module may be a memory. When the processing module is a processor, the communication module is a communication interface, and the storage module is a memory, the communication device 100 involved in the embodiment of the present application may be the terminal 30 shown in Figure 7.

[0196] Figure 11 shows a structural diagram of a communication device 110. The communication device 110 may be an access network device, or a chip or system-on-chip in the access network device. The communication device 110 may be used to perform the functions of the access network device involved in the above embodiments. As an implementation method, the communication device 110 shown in Figure 11 includes: a receiving unit 1101, a processing unit 1102, and a sending unit 1103;

[0197] The receiving unit 1101 may be designed to be used by the second network device to receive the terminal location information sent by the first network device. For example, the receiving unit 1101 may support the communication apparatus 110 to execute S802.

[0198] Another possible design is for the first network device to receive the measurement event report and the location information of the terminal reported by the terminal, or receive resource information allocated to the terminal from the second network device. For example, the receiving unit 1101 can support the communication device 110 to execute S902 or S903.

[0199] A possible design of the processing unit 1102 is to be used by the second network device to determine the target synchronization resource and the switching time. For example, the processing unit 1102 can support the communication device 110 to execute S803.

[0200] Another possible design is for the first network device to determine the target synchronization resource, the switching time, and the switching decision. For example, the processing unit 1102 can support the communication device 110 to execute S902, S904, and S802.

[0201] The sending unit 1103 may be designed to be used by the second network device to send the second information to the first network device. For example, the sending unit 1103 may support the communication apparatus 110 to execute S803.

[0202] Another possible design is for the first network device to send a measurement event, a switching time, and a target synchronization resource to the terminal; and for the first network device to send the location information of the terminal to the second network device. For example, the sending unit 1103 can support the communication device 110 to execute S801, S901, S804, S904, and S802.

[0203] Among them, the relevant descriptions of the measurement event, target synchronization resource, switching time, and second information can refer to those described in the above embodiments, and the target synchronization resource and switching time can be determined by the first access network device or the second access network device; similarly, the measurement event can be at least one of a location-based measurement event, a time-based measurement event, and an RRM-based measurement event.

[0204] In the case where the target synchronization resource and switching time are determined by the second access network device, the first access network device will make a switching decision based on the measurement event report and location information reported by the terminal, determine the second access network device to which the terminal needs to switch, and report the terminal's location information to the second access network device. The second access network device determines the SSB beam (target synchronization resource) of the target neighboring cell covering the terminal and the time when the terminal can measure the target beam (i.e., the terminal's switching time) based on the terminal's location information, its own satellite ephemeris information, and its own cell scanning rules, and transmits it to the first access network device. The first access network sends the received second information to the terminal through RRC signaling. When the switching time arrives, the terminal measures the RSRP of the SSB beam of the target neighboring cell covering the terminal, performs downlink synchronization to complete the target cell access, and then initiates initial access to the target satellite base station, accesses the target cell, and completes the cell switching. The second information includes the target synchronization resource of the second access network device and the switching time of the terminal.

[0205] When the target synchronization resource and handover time are determined by the first access network device, the first access network device will make a handover decision based on the measurement event report and location information reported by the terminal, determine the second access network device to which the terminal should handover, and complete handover preparation with the second access network device. Handover preparation involves the first access network device requesting available resource allocation from the second access network device on behalf of the terminal. The first access network device then determines the SSB beam (target synchronization resource) of the target neighboring cell covering the terminal and the time at which the terminal can measure the target beam (i.e., the terminal's handover time) based on the terminal's location information, the satellite ephemeris information of the second access network device, and the second access network device's cell scanning rules. These information is then transmitted to the terminal via RRC signaling. When the handover time arrives, the terminal measures the RSRP of the SSB beam of the target neighboring cell covering the terminal, performs downlink synchronization, and then initiates initial access to the target satellite base station and accesses the target cell, completing the cell handover. The information about the SSB beam (target synchronization resource) of the target neighboring cell covering the terminal and the time at which the terminal can measure the target beam (i.e., the terminal's handover time) transmitted by the first access network device to the terminal can also be referred to as first information.

[0206] The first access network device mentioned above can be a first satellite base station, and correspondingly, the second access network device can be a second satellite base station; or, the first access network device can be a first ground station, and correspondingly, the second access network device can be a second ground station.

[0207] Specifically, all relevant content of each step involved in the method embodiments shown in Figures 8 and 9 can be referenced in the functional description of the corresponding functional modules and will not be repeated here. The communication device 110 is used to perform the functions of the access network device in the cell handover method shown in Figures 8 or 9, thereby achieving the same effect as the above-mentioned cell handover method.

[0208] As another possible implementation, the communication device 110 shown in FIG11 includes: a processing module and a communication module. The processing module is used to control and manage the operations of the communication device 110. For example, the processing module may integrate the functions of the processing unit 1102 and may be used to support the communication device 110 in executing S902, S904, S802, S803, and other processes of the technology described herein. The communication module may integrate the functions of the receiving unit 1101 and the sending unit 1103 and may be used to support the communication device 110 in executing S801, S802, S803, S804, S901, S902, S903, or S904, as well as communicating with other network entities, such as communication with the functional modules or network entities shown in FIG3a. The communication device 110 may also include a storage module for storing program code and data of the communication device 110.

[0209] The processing module may be a processor or a controller. It may implement or execute the various exemplary logic blocks, modules, and circuits described in conjunction with the disclosure of this application. The processor may also be a combination that implements computing functions, such as a combination of one or more microprocessors, a combination of a DSP and a microprocessor, and so on. The communication module may be a transceiver circuit or a communication interface, and the storage module may be a memory. When the processing module is a processor, the communication module is a communication interface, and the storage module is a memory, the communication device 110 involved in the embodiments of this application may be the access network device 20 shown in Figure 7.

[0210] The collection, storage, use, processing, transmission, provision, and disclosure of user personal information in the technical solutions of this application comply with relevant laws and regulations and do not violate public order and good morals. For example, the processing of user personal information in the technical solutions of this application is performed with the user's authorization, which is explained here and will not be repeated here.

[0211] It should be noted that the terms "first" and "second" in the specification, claims, and drawings of this application are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units that are not listed, or may optionally include other steps or units that are inherent to these processes, methods, products, or devices.

[0212] It should be understood that in the present application, "at least one (item)" refers to one or more, "more than one" refers to two or more, "at least two (items)" refers to two or three and more than three, and "and / or" is used to describe the association relationship of associated objects, indicating that three relationships may exist. For example, "A and / or B" can mean: only A exists, only B exists, and A and B exist at the same time, where A and B can be singular or plural. The character " / " generally indicates that the previous and next associated objects are in an "or" relationship. "At least one of the following items" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, at least one of a, b or c can mean: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, c can be single or multiple.

[0213] It should be understood that in the embodiments of the present application, "B corresponding to A" means that B is associated with A. For example, B can be determined based on A. It should also be understood that determining B based on A does not mean determining B based solely on A; B can also be determined based on A and / or other information. In addition, the "connection" in the embodiments of the present application refers to various connection methods, such as direct connection and indirect connection, to achieve communication between devices, and the embodiments of the present application do not impose any limitations on this.

[0214] Unless otherwise specified, the "transmission" (transmit / transmission) appearing in the embodiments of the present application refers to bidirectional transmission, including the actions of sending and / or receiving. Specifically, the "transmission" in the embodiments of the present application includes the sending of data, the receiving of data, or the sending of data and the receiving of data. In other words, the data transmission here includes uplink and / or downlink data transmission. Data may include channels and / or signals, uplink data transmission is uplink channel and / or uplink signal transmission, and downlink data transmission is downlink channel and / or downlink signal transmission. The "network" and "system" appearing in the embodiments of the present application express the same concept, and the communication system is the communication network.

[0215] Through the description of the above implementation methods, technical personnel in the relevant field can clearly understand that for the convenience and simplicity of description, only the grouping of the above-mentioned functional modules is used as an example. In actual applications, the above-mentioned functions can be assigned to different functional modules as needed, that is, the internal structure of the device can be grouped into different functional modules to complete all or part of the functions described above.

[0216] In the several embodiments provided in this application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are merely schematic. For example, the grouping of the modules or units is merely a logical function grouping. In actual implementation, there may be other grouping methods, such as multiple units or components can be combined or integrated into another device, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0217] The units described as separate components may or may not be physically separate, and the components shown as units may be one physical unit or multiple physical units, that is, they may be located in one place or distributed in multiple different places. Some or all of the units may be selected according to actual needs to achieve the purpose of the present embodiment.

[0218] In addition, the functional units in the various embodiments of the present application may be integrated into a single processing unit, or each unit may exist physically separately, or two or more units may be integrated into a single unit. The aforementioned integrated units may be implemented in the form of hardware or software functional units.

[0219] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a readable storage medium. Based on this understanding, the technical solution of the embodiment of the present application is essentially or the part that contributes to the prior art or all or part of the technical solution can be embodied in the form of a software product, which is stored in a storage medium and includes several instructions for enabling a device, such as a single-chip microcomputer, a chip, etc., or a processor to execute all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes various media for storing program codes, such as a USB flash drive, a mobile hard disk, a ROM, a RAM, a magnetic disk, or an optical disk.

[0220] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A cell switching method, characterized in that: The method comprises: receiving first information, where the first information is used to indicate a switching time and / or a target synchronization resource for a terminal to perform a cell switching; Switch from the first cell to the second cell according to the first information.

2. The method according to claim 1, characterized in that The first information indicates the switching time and the target synchronization resource, and the switching from the first cell to the second cell according to the first information includes: When the switching time arrives, performing synchronization measurement on the target synchronization resource; Switching from the first cell to the second cell is performed based on the synchronization measurement result.

3. The method according to claim 1 or 2, characterized in that: The first information is carried in a radio resource control RRC configuration message.

4. The method according to any one of claims 1 to 3, characterized in that: The method further comprises: Before the switching time arrives, maintaining the communication connection and / or data transmission with the first cell; When the switching time arrives, the communication connection and / or data transmission with the first cell is disconnected.

5. The method according to any one of claims 1 to 4, characterized in that: The target synchronization resource is a beam, or a carrier, or a bandwidth part BWP.

6. The method according to any one of claims 1 to 5, characterized in that: The switching time is determined according to the time when the target synchronization resource arrives at the terminal; The target synchronization resource is determined based on at least one of the following information: location information of the terminal, satellite ephemeris information of the second access network device, and a beam scanning rule of a cell of the second access network device, where the second access network device corresponds to a second cell.

7. The method according to any one of claims 1 to 6, characterized in that: The first cell corresponds to a first satellite base station, and the second cell corresponds to a second satellite base station; or, The first cell corresponds to a first ground station, and the second cell corresponds to a second ground station.

8. The method according to any one of claims 1 to 7, characterized in that: The target synchronization resources are part of the synchronization resources corresponding to the neighboring cells of the first cell.

9. A cell switching method, characterized in that: The method comprises: Obtaining a switching time and / or a target synchronization resource for a terminal to perform cell switching; Sending first information, where the first information is used to indicate the switching time and / or the target synchronization resource.

10. The method according to claim 9, characterized in that The first information is carried in a radio resource control RRC configuration message.

11. The method according to claim 9 or 10, characterized in that: The method further comprises: Before the switching time arrives, maintaining the communication connection and / or data transmission with the terminal; When the switching time arrives, the communication connection and / or data transmission with the terminal is disconnected.

12. The method according to any one of claims 9 to 11, characterized in that: The target synchronization resource is a beam, or a carrier, or a bandwidth part BWP.

13. The method according to any one of claims 9 to 12, characterized in that: The switching time is determined according to the time when the target synchronization resource arrives at the terminal; The target synchronization resource is determined according to at least one of the following information: location information of the terminal, satellite ephemeris information of the second access network device, and a beam scanning rule of a cell of the second access network device.

14. The method according to claim 13, characterized in that The target synchronization resource is determined by the first access network device; or, The target synchronization resource is determined by the second access network device.

15. The method according to claim 14, characterized in that The target synchronization resource is determined by the second access network device, and the obtaining of the switching time and / or target synchronization resource for the cell switching of the terminal includes: Second information is received from the second access network device, where the second information indicates a switching time and / or a target synchronization resource for the terminal to perform cell switching.

16. The method according to any one of claims 9 to 15, characterized in that: The first access network device is a first satellite base station, and the second access network device is a second satellite base station; or, The first access network device is a first ground station, and the second access network device is a second ground station.

17. The method according to any one of claims 9 to 15, characterized in that: The target synchronization resources are part of the synchronization resources corresponding to the neighboring cells of the first cell, and the first cell is the cell where the terminal is currently located.

18. A communication device, characterized in that: The communication device comprises a processor and a communication interface, and the processor and the communication interface are used to support the communication device to execute the cell switching method according to any one of claims 1-8.

19. A communication device, characterized in that: The communication device comprises a processor and a communication interface, and the processor and the communication interface are used to support the communication device to execute the cell switching method as described in any one of claims 9 to 17.

20. A communication system, characterized in that: The communication system comprises the communication device according to claim 18, the communication device according to claim 19, and a second access network device.

21. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer instructions, and when the computer instructions are executed on a computer, the computer executes the method according to any one of claims 1 to 8, or the method according to any one of claims 9 to 17.

22. A computer program product, characterized in that The computer program product comprises computer instructions, and when the computer instructions are executed on a computer, the computer is caused to execute the method according to any one of claims 1 to 8 or the method according to any one of claims 9 to 17.

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