WO2025031200A1 - Cell handover method, apparatus and system - Google Patents

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

This application claims the priority of 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”, all contents of which are incorporated by reference in this application.

Technical Field

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

Non-terrestrial networks (NTN) include satellite communication systems, high altitude platform systems (HAPS) and air-to-ground networks. So far, the focus of the 3rd generation partnership project (3GPP) on NTN has been satellite communication networks. The integration of satellite communication networks and ground-based fifth-generation mobile communication technology (5G) networks can provide ubiquitous coverage without being restricted by topography, connecting the multi-dimensional space of air, space, land and sea to form an integrated ubiquitous access network, enabling on-demand access in all scenarios. Satellite communication equipment (or satellite) is in a state of high-speed movement compared to terminals, so the cells providing services to connected terminals will also change in a short period of time. In order to ensure the continuity of services for connected terminals, satellite communication networks will frequently trigger terminals to switch cells.

In the NTN scenario, considering the high-speed movement of satellite communication equipment, the process of cell switching by the terminal may include: after the terminal receives the radio resource control (RRC) configuration message sent by the source satellite base station, it 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 switching.

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 the system message containing synchronization information can be called an SSB beam. Currently, a terminal needs a long time 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 data transmission interruption and even terminal call drops.

Summary of the invention

The embodiments of the present application provide a cell switching method, device and system to solve the problem that during the cell switching process in the NTN scenario, after the terminal disconnects the data transmission with the source base station, when the cell switching is realized by performing synchronous measurement on the synchronous resources of all target neighboring cells, the switching time is too long, resulting in data interruption or even terminal call drop.

In order to achieve the above purpose, the embodiment of the present application adopts the following technical solution:

In a first aspect, the present application provides a cell switching method, which can be executed by a terminal and a functional module or chip in the terminal. Taking the terminal execution as an example, the method includes: the terminal receives first information for indicating a switching time and/or a target synchronization resource for the terminal to perform cell switching, and switches from a first cell to a second cell according to the first information. The terminal can be in a connected state.

Based on the method described in the first aspect, a terminal in a connected state can perform a switching time and/or target synchronization resource for 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 a 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.

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

The above switching process allows the terminal in the connected state to always maintain data transmission with the first cell before the switching time arrives, and then disconnect the data transmission with the first cell when the switching time arrives, thereby reducing the data interruption time during the switching process and further reducing The impact of low switching data interruption time on 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.

In a 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 to save signaling overhead.

In one possible design, the terminal maintains the communication connection and/or data transmission with the first cell before the switching time arrives, and disconnects the communication connection and/or data transmission with the first cell when the switching time arrives. Based on this possible design, it is avoided that the terminal in the connected state immediately disconnects the communication connection and/or data transmission with the first cell upon receiving the switching command, thereby shortening the data interruption time.

In one possible design, the target synchronization resource may be a beam, or a carrier, or a bandwidth part BWP. Specifically, when the wireless access network device needs to achieve regional coverage through beam scanning, such as 5G equipment, satellite base station equipment, etc., the target synchronization resource may be a beam. When the wireless access network device can achieve regional coverage through base station coverage, such as 4G equipment, etc., the target synchronization resource may 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 the solution can be flexibly and diversely applied to different scenarios to improve the utilization rate of the solution.

In one possible design, the switching time of the terminal switching cells is determined according to the time when the target synchronization resource arrives at the terminal, wherein the target synchronization resource can be determined according to at least one of the following information: the location information of the terminal, 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 mobile state information of the terminal and the mobile state 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, thereby reducing the signaling interaction overhead. On the other hand, the switching time of the terminal switching cells is determined according to 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.

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. Among them, the first cell can send a first information to a terminal in a 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 involved 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.

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 the target synchronization resources, for example, one or more synchronization resources in the neighboring cells can be determined as the 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 the synchronization resources (or called neighboring cell measurement).

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 first information to the terminal for indicating the switching time and/or target synchronization resources of the terminal.

Based on the method described in the second aspect, the first access network device sends the acquired 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 from 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. 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 is different from 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. Compared with the case where the switching time and/or target synchronization resource for the terminal to perform cell switching is obtained, the signaling interaction between the first access network device and the second access network device and the calculation overhead of the second access network device are reduced.

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.

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 switching time arrives, and disconnects the communication connection and/or data transmission between the first cell and the terminal when the switching time arrives. The first cell is a cell that the first access network device allocates to the terminal in the connected state to provide wireless communication services. Based on this possible design, it is avoided that the first access network device immediately stops providing communication connection and/or data transmission to the terminal after sending a switching command to the terminal, thereby shortening the time of terminal data interruption.

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.

In one possible design, the terminal switching time acquired by the first access network device is determined according to the time when the target synchronization resource arrives at the terminal, wherein the target synchronization resource can be determined according to at least one of the following information: the location information of the terminal, the satellite ephemeris information of the second access network device, and the beam scanning rule of the cell of the second access network device. Based on this possible design, the target synchronization resource acquired by the first access network device is jointly determined according to the mobile state information of the terminal, 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 to avoid unnecessary switching.

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 rule 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 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 rule 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 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.

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 the second information sent from the second access network device, wherein 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.

In one possible design, the first access network device corresponds to the first satellite base station, and the second access network device corresponds to the second satellite base station; or, the first access network device corresponds to the first ground station, and the second access network device corresponds to the 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, 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.

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 synchronization measurement of the terminal. The number of resources can be increased, the power consumption caused by the terminal measuring the synchronization resources can be reduced, and the efficiency of the synchronization resources (or neighboring cell measurement) can be improved.

In a third aspect, a communication device is provided for implementing the above-mentioned various methods. The communication device may be the terminal in the above-mentioned first aspect, or a device including the above-mentioned terminal, or a device included in the above-mentioned terminal, such as a chip; the communication device includes a module, unit, or means corresponding to the above-mentioned method, and the module, unit, or means may be implemented by hardware, software, or by executing the corresponding software implementation by hardware. The hardware or software includes one or more modules or units corresponding to the above-mentioned functions.

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 used to implement the sending and/or receiving functions in the above-mentioned first aspect and any possible implementation thereof. The transceiver module may be composed of a transceiver circuit, a transceiver, a transceiver or a communication interface. The processing module may be used to implement the processing functions in the above-mentioned first aspect and any possible implementation thereof.

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.

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.

In a fourth aspect, a communication device is provided for implementing the above-mentioned various methods. The communication device includes: a processor and a memory; the memory is used to store computer instructions, and when the processor executes the instructions, the communication device executes the method described in the first aspect. The communication device can be the terminal in the first aspect or the second aspect, or a device including the terminal, or a device included in the terminal, such as a chip.

In some possible designs, the communication device may include: a processor and a communication interface; the communication interface is used to communicate with a module outside the communication device; the processor is used to execute a computer program or instruction so that the communication device performs the method described in the first aspect above. The communication device may be the terminal in the first aspect or the second aspect above, or a device including the terminal, or a device included in the terminal, such as a chip.

In a fifth aspect, a communication device is provided for implementing the above-mentioned various methods. The communication device may be the first access network device in the above-mentioned second aspect, such as a satellite base station; or a device including the above-mentioned first access network device; or a device included in the above-mentioned first access network device, such as a chip. The communication device includes a module, unit, or means corresponding to the above-mentioned method, and the module, unit, or means may be implemented by hardware, software, or by executing the corresponding software implementation by hardware. The hardware or software includes one or more modules or units corresponding to the above-mentioned functions.

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 used to implement the sending and/or receiving functions in the above-mentioned second aspect and any possible implementation thereof. The transceiver module may be composed of a transceiver circuit, a transceiver, a transceiver or a communication interface. The processing module may be used to implement the processing functions in the above-mentioned second aspect and any possible implementation thereof.

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.

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.

In a sixth aspect, a communication device is provided for implementing the above-mentioned various methods. The communication device includes: a processor and a memory; the memory is used to store computer instructions, and when the processor executes the instructions, the communication device executes the method described in the second aspect. The communication device can be the first access network device 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.

In some possible designs, the communication device may include: a processor and a communication interface; the communication interface is used to communicate with a module outside the communication device; the processor is used to execute a computer program or instruction so that the communication device performs the method described in the second aspect above. The communication device may be the access network device in the second aspect above, or a device including the access network device, or a device included in the access network device, such as a chip.

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.

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 is caused to execute the cell switching method in the first aspect or any possible design of the first aspect, or the computer is caused to execute the cell switching method in the second aspect or any possible design of the second aspect.

In a ninth aspect, the present application provides a computer program product, which includes 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.

BRIEF DESCRIPTION OF THE DRAWINGS

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

FIG2 is a schematic diagram of a cell switching process in an existing NTN scenario;

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

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

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

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

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

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

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

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

FIG10 is a schematic diagram of the structure of a communication device provided by the present application;

FIG11 is a schematic diagram of the structure of a communication device provided in the present application.

DETAILED DESCRIPTION

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 required by the embodiments of the present application.

Non-terrestrial networks (NTN) achieve 5G communication 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 gives the height of different NTN platforms from the ground, the earth orbit information they are in, and the coverage information of the corresponding beams.

Table 1

The NTN communication system architecture is shown in Figure 1, which includes the space segment, the ground segment and the user end. Among them, the space segment mainly refers to the constellation composed of multiple satellite base stations in the sky, and the communication link (inter-satellite link, ISL, also called inter-satellite link) between satellite base stations. The ground segment mainly includes earth stations (also called gateway stations), as well as auxiliary parts such as service control, monitoring management, and time injection. Network equipment such as transmission equipment and core network equipment in the ground network can also be regarded as part of the ground segment. The user segment refers to the terminal that accesses the satellite base station, which mainly includes antennas (what we often call "pots"), equipment that processes signals and provides network access capabilities (such as routers, etc.), and terminals that access the network (mobile phones, computers, etc.). As shown in Figure 1, different satellite base stations are connected through optional inter-satellite links. The inter-satellite links can be wireless interfaces or optical interfaces, and can be defined by GPP or non-3GPP. The service link (service link) between the terminal and the satellite base station is realized through the new radio (NR). Satellite base station and gateway station The feeder link between the gateways is implemented through a 3GPP or non-3GPP wireless interface. At the same time, the satellite base station (or UAS platform) usually generates multiple beams over a given service area within its coverage area, and achieves cell coverage through the beams to provide network services to the terminal. The coverage of the satellite base station (or UAS platform) depends on the airborne antenna diagram and its minimum elevation angle. The coverage shape of the beam is usually elliptical.

There are two typical architecture modes of NTN communication system, namely transparent mode and renewable mode. In transparent mode, the satellite (or UAS platform) payload can perform frequency conversion and RF amplification in the uplink and downlink directions. In this mode, the role of the satellite is equivalent to an analog RF repeater. In renewable mode, the satellite (or UAS platform) payload will reprocess the signal received from the earth terminal. In this mode, the satellite has the same functions as a ground base station, and performs data demodulation/decoding, switching or routing, encoding/modulation, etc., which is equivalent to the satellite having 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 are used to directly realize a certain function of the satellite, such as cameras used on remote sensing satellites, communication repeaters and communication antennas used on communication satellites, etc.

Cell handover refers to the situation where a terminal moves from one cell to another while in a connected state and maintaining data transmission services, or the original service cell (source cell) can no longer provide services to the terminal due to reasons such as adjustment of wireless transmission service load, activation operation maintenance, equipment failure, etc. In order not to interrupt data transmission services and service quality, the wireless bearer system will search for 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.

The overall process of cell switching includes the following steps 1-4:

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 type and event type. 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.

Table 2

Among them, the cell quality can be measured by measuring the reference signal received power (RSRP), reference signal received 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.

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

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

Step 4, handover execution: The source base station applies for and allocates resources to the target base station, and then the source base station 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. The terminal disconnects from the source base station according to the handover command, performs uplink and downlink synchronization with the target base station, initiates initial access to the target base station, accesses the target cell, and completes the cell handover.

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

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

The source satellite base station sends a measurement event for handover to the terminal, wherein the measurement event for handover may be a measurement event based on RRM measurement. For specific measurement event information based on RRM measurement, see Table 2. The premise that the source satellite base station sends the measurement event to the terminal is that the terminal has been connected to the source satellite base station and has entered the RRC connected state.

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.

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.

S203: Switching decision.

The source satellite base station determines the target satellite base station to which the terminal switches according to the measurement report reported by the terminal.

S204: Handover preparation.

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.

S205: The source satellite base station sends a switching command to the terminal, instructing the terminal to switch from the source satellite base station to the target satellite base station.

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

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

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.

Beam scanning refers to sending or receiving beams in a pre-set manner within a specific period or time period to cover a specific spatial area. For example, beam scanning is required when the terminal starts initial access (synchronizing with the system and receiving the minimum system information broadcast). The base station transmits the beam to a specific direction at a specific time, and then changes the direction in the next time frame, and so on. Finally, the cell is covered by continuously changing the direction of the beam. Among them, initial access refers to the process of the terminal initially finding a cell when entering the system coverage area.

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

As can be seen from the above, measuring the SSB beam is the first step for the terminal to access the target cell. However, in the NTN scenario, a satellite base station (or UAS platform) includes a lot of SSB beams. Therefore, after receiving the handover command and disconnecting the data transmission with 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 situation causes the terminal to interrupt data transmission for a long time, and may even cause the terminal to drop calls. Moreover, the long-term RSRP measurement of the neighboring SSB beams by the terminal will also increase the power consumption of the terminal.

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 referred to as a source access network device) obtains the switching time and/or target synchronization resource of the terminal for cell switching, and sends 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.

In this way, a specific switching time and a specific target synchronization resource can be given to the terminal in the connected state during the cell switching process, so that the terminal can perform synchronization measurement on the target synchronization resource when the switching time arrives according to the first information indication, avoid disconnecting the data connection in advance to perform synchronization resource measurement and cell switching process, reduce data interruption delay, and/or, measure on the specified target synchronization resource, and improve the efficiency of synchronization measurement and cell switching through purposeful synchronization measurement.

The cell switching method provided in the embodiment of the present application is described below in conjunction with the accompanying drawings.

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, or 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, or a non-3GPP communication system without limitation.

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 communication (mMTC), D2D, V2X, and IoT and other communication scenarios.

The technical solution of the embodiment 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, etc., without limitation.

Referring to FIG. 3a, a communication system is provided for an embodiment of the present application, the communication system comprising 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 FIG. 3a may be a satellite base station deployed in the air. Each access network device may cover one or more cells, and the terminal may move within the cell covered by the access network device or between cells to receive network services provided by the access network device.

Taking the interaction between the first access network device and the second access network device and the terminal shown in FIG3a as an example, in the embodiment of the present application, the cell switching process is shown in FIG3b, which 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 the target synchronization resource, and sends the first information indicating the switching time and/or the target synchronization resource to the terminal. S303: The terminal receives the first information and switches from the first cell to the second cell according to the first information.

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. Switching, 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 is to switch, the first access network device interacts with the target access network device by signaling, so that the target access network device allocates available resources to the terminal.

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, until 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 range 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 range of the communication service provided by the target access network device to the terminal when the switching time arrives.

As mentioned above, the switching time is determined according to the time when the target synchronization resource reaches the terminal; the target synchronization resource is determined according to at least one of the following information: the location information of the terminal, 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 part of the synchronization resources corresponding to the neighboring cell of the first cell. Among them, 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 by the target access network device.

Specifically, the detailed process of the cell switching shown in FIG. 3 b may refer to the embodiments corresponding to FIG. 8 or FIG. 9 below.

The terminal involved in the present application may be a terminal device (terminal equipment) or a user equipment (user equipment, UE) or a mobile station (mobile station, MS) or a mobile terminal (mobile terminal, MT), etc. Specifically, the terminal may be a mobile phone, a tablet computer or a computer with a wireless transceiver function, or a virtual reality (virtual reality, VR) terminal, an augmented reality (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 may be a device that can support the terminal to realize the function, such as a chip system (such as a chip, or a processing system composed of multiple chips) or a modem. The following takes the terminal as an example to describe the cell switching method provided in the embodiment of the present application.

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), a convergence 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., and the embodiment of this application does not specifically limit this. Optionally, the base station in the embodiment of the present application may include various forms of base stations, such as: macro base stations, micro base stations (also called small stations), relay stations, access points, etc., and the embodiment of the present application does not specifically limit this.

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

As an example, in the NTN scenario, the terminal switches from the first cell to the 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 .

As an example, in the NTN scenario, the terminal switches from the first cell to the 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, the 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.

As an example, in the NTN scenario, the terminal switches from the first cell to the second cell, and the first cell belongs to satellite base station 1, and the second cell belongs to satellite base station 2. At the same time, satellite base station 1 and satellite base station 2 belong to different core networks. For example, the terminal switches from cell 1 to cell 2, and 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.

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 intersatellite link may optionally exist between satellite base station 1 and satellite base station 2.

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.

As shown in FIG. 7 , 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.

The terminal 30 includes at least one processor (in FIG. 7, the exemplary description is made by taking a processor 301 as an example) and at least one transceiver (in FIG. 7, the exemplary description is made by taking a transceiver 303 as an example). Further, the terminal 30 may also include at least one memory (in FIG. 7, the exemplary description is made by taking a memory 302 as an example), at least one output device (in FIG. 7, the exemplary description is made by taking an output device 304 as an example) and at least one input device (in FIG. 7, the exemplary description is made by taking an input device 305 as an example).

The processor 301, the memory 302 and the transceiver 303 are connected via a communication line. The communication line may include a path to transmit information between the above components.

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, processor 301 may also include multiple CPUs, and 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).

The memory 302 may be a device with 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 compressed optical disc, laser disc, optical disc, digital versatile disc, Blu-ray disc, etc.), a magnetic disk storage medium or other magnetic storage device, or any other medium that can be used to carry or store the 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 through a communication line. The memory 302 may also be integrated with the processor 301.

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.

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, and the embodiments of the present application do not specifically limit this.

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.

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

The output device 304 communicates with the processor 301 and can display information in a variety of ways. For example, the 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.

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

The access network device 20 includes at least one processor (in FIG. 7 , the exemplary description is made by taking a processor 201 as an example) and at least one transceiver (in FIG. 7 , the exemplary description is made by taking a transceiver 203 as an example). Further, the access network device 20 may also include at least one memory (in FIG. 7 , the exemplary description is made by taking a memory 202 as an example) and at least one network interface (in FIG. 7 , the exemplary description is made by taking a network interface 204 as an example). 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 a core network device via a link (for example, an S1 interface), or to connect to the network of other network devices via a wired or wireless link (for example, an X2 interface). The processor 201, the memory 202 and the transceiver 203 are connected to the network interface (not shown in FIG. 7 ), which is not specifically limited in the embodiment of the present application. In addition, the 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, which will not be repeated here.

It is 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 in the figure, or combine some components, or split some 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.

In the following, the cell switching method provided in the embodiment of the present application will be described in detail by taking the communication system (or NTN system) shown in any one of FIG. 3a or FIG. 4 to FIG. 6 as an example in conjunction with the accompanying drawings. In particular, 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, the source satellite base station and the target base station satellite have the structure of the access network device 20 shown in FIG. 7, and the terminal in the following embodiments has the structure of the terminal 30 shown in FIG. 7.

It is understandable that in the embodiments of the present application, the terminal and/or the access network device may perform some or all of the steps in the embodiments of the present application, and these steps or operations are only 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 different orders presented in the embodiments of the present application, and it is possible that not all operations in the embodiments of the present application need to be performed.

It is understandable that the access network device and terminal interaction mechanism 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 name between the various devices or the name of each parameter in the message in the following embodiments of the present application is only an example, and other names may also be used in the specific implementation, and the embodiments of the present application do not specifically limit this.

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

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

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

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 (global navigation satellite system, GNSS). The global satellite navigation system mentioned above refers to all satellite navigation systems, including the global positioning system (GPS) of the United States, the global navigation satellite system (Glonass) of Russia, the Galileo satellite navigation system (Galileo) of Europe, and the Beidou satellite navigation system of China. 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 longitude and latitude 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 wireless resource control connection state (or called a connection state).

The source satellite base station may be the first access network device in the communication system shown in FIG3a. At this time, the source satellite base station has established an RRC connection with the terminal, and the measurement event may be sent to the terminal through RRC signaling. Correspondingly, the terminal may report the measurement event report and the location information of the terminal to the source satellite base station through RRC signaling.

Specifically, the source satellite base station sends a measurement event message for switching to the terminal through radio resource control RRC signaling. The measurement event message includes the object that the terminal needs to measure, the cell list, the reporting method, the event parameters, the measurement identifier, etc. Among them, the measurement event can be at least one of the following: a time-based measurement event, a location-based measurement event, and an RRM-based measurement event. The terminal can determine the neighboring cells that meet the measurement event in the cell list based on the measurement event message, and generate a measurement event report for the neighboring cell information that meets the measurement event. Further, 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 through radio resource control RRC signaling.

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 in the cell list that meet the location measurement event based on the location measurement event, and generates a measurement event report with 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 in the cell list that meet the RRM-based measurement event based on the RRM-based measurement event, and generates a measurement event report with 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.

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, the RRM-based measurement event A4 is triggered after a certain period of time. That is, the source satellite base station sends an RRM-based A4 measurement event to the terminal, and the terminal reports the neighboring cell information whose neighboring cell level exceeds the RRM-based A4 event threshold and the latitude and longitude information provided by the global satellite navigation system (e.g., GPS system) configured by the terminal to the source satellite base station.

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.

The source satellite base station and the terminal should have the same configuration and characteristics as the source satellite base station and the terminal mentioned above, and the measurement event report and the location information of the terminal are consistent with the above description, which will not be repeated here. The target satellite base station is determined by the source satellite base station according to the measurement report information reported by the terminal and the location information of the terminal combined with the decision strategy configured by the source satellite base station.

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

When the target satellite base station is the same as the source satellite base station, the terminal performs cell switching within the same satellite base station. It can be understood that the source cell (first cell) that provides communication services to the terminal at time t1 and the target cell (second cell) that provides communication services to the terminal selected by the terminal by measuring the SSB beam of the neighboring cell after the switching time arrives belong to the same satellite base station. The above cell switching process occurs within the same satellite base station and does not involve information exchange between base stations. It is just a resource configuration between two cells within a satellite base station, and there is no need to apply to the core network to change the data transmission path.

In the case where the target satellite base station and the source satellite base station are different, the terminal performs cell switching between different satellite base stations. It can be understood that the source cell (first cell) that provides communication services to the terminal at time t1 and the target cell (second cell) that provides communication services to the terminal selected by the terminal by measuring the SSB beam of the neighboring area after the switching time arrives belong to different satellite base stations. Among them, there is an optional available intersatellite link between the target satellite base station and the source satellite base station. When there is an available intersatellite link between the target satellite base station and the source satellite base station, the satellite base stations can communicate directly through the intersatellite link.

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, and combines its own decision strategy to determine the target satellite base station. At the same time, the source satellite base station reports the obtained location information of the terminal to the target satellite base station. Among them, the decision strategy of the source satellite base station can be configured by the source satellite base station itself.

In one possible design, 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 cell in the measurement event report reported by the terminal and the movement trend of the terminal, and the signal quality of the neighboring cell in the measurement event report reported by the terminal, where the neighboring cell signal quality can be measured by the RSRP, RSRQ or SINR of the neighboring cell.

The source satellite base station and the target satellite base station prepare for handover, which means that the source satellite base station applies for and allocates resources to the target satellite base station for the terminal; the target satellite base station determines whether to allow the terminal to access resources. If the target satellite base station allows the terminal to access resources, the target satellite base station allocates air interface resources and service bearer resources to the terminal. If the handover preparation between the source satellite base station and the target satellite base station occurs in a scenario across core network devices, it is also necessary to interact with the core network side.

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. It does not need to apply to the core network to change the data transmission path. For example, the source satellite base station determines that the target cell and the source cell are the same satellite base station based on the PCI carried in the measurement report and starts the intra-station 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. Among them, 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.

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 device, and there is an available inter-satellite link between the source satellite base station and the target satellite base station. The source satellite base station sends a handover request to the base station (target satellite base station) to which the target cell belongs through 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, transmission resources, etc.

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 device, 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.

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.

S803. The target satellite base station determines the SSB beam of the terminal covered by the target neighboring cell 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 rule of the cell of the target satellite base station, and sends second information to the source satellite base station, where the second information indicates the SSB beam of the terminal covered by the target neighboring cell and the switching time of the terminal.

Among them, the target satellite base station is determined by the above-mentioned source satellite base station according to the measurement event report reported by the terminal and the location information of the terminal, combined with the self-determination strategy configured by the source satellite base station. The satellite ephemeris information of the target satellite base station includes the row number, satellite number, orbital intersection angle, orbital eccentricity, average motion and other information of the target satellite, and the mathematical relationship between the six orbital parameters of Kepler's law is used to determine the time, coordinates, orientation, speed and other parameters of the target satellite (flying body), with extremely high accuracy. The beam scanning rules of the cell of the target satellite base station include the number of SSB beams contained in the cell of the target satellite base station, the scanning period of the cell, the scanning time of the SSB beam of the cell, the characteristics of the SSB beam of the cell (for example, the angle value corresponding to the 3dB wave width of the SSB beam), and other information, which can indicate the time, range and coverage duration of the SSB beam of the cell of the target satellite base station to cover the ground area.

Among them, the location information of the terminal can be used to indicate the current location of the terminal. Specifically, the current location of the terminal can be represented by longitude and latitude or by three-dimensional spatial coordinates. In this application, the location information of the terminal can be obtained by the terminal itself and reported to the target satellite base station through the source satellite base station, for example: the terminal can obtain the current location information of the terminal through its own GNSS system.

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 beam 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.

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 the platform of the ground control target satellite base station, for example, the core network equipment to which the target satellite base station belongs. The platform of the ground control target satellite base station 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 the satellite base station or 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 of the ground control target satellite base station 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.

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 platform of the ground control 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 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 wave 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 reported by the source satellite base station and the time when the SSB beam scans the terminal.

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 scenario 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 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 target satellite base station determines through calculation that the coverage range of the SSB_1 beam of cell 0 is 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.

In the above example, it has been determined through the above process that the SSB_1 beam of cell 0 of the target satellite base station can be scanned to The terminal reported by the source satellite base station also knows the beam scanning rules of the cell of the target satellite base station, that is, the number of SSB beams contained in the cell of the target satellite base station, the scanning period of the cell, and the scanning time of the SSB beam of the cell. 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 scanning time of the SSB beam of cell 0. Therefore, the time when the SSB_1 beam of cell 0 of the target satellite base station scans to 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 to the terminal reported by the source satellite base station is the switching time of the terminal.

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

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 switching time of the terminal. 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 switching time of the terminal to the source satellite base station through radio resource control signaling.

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.

The source satellite base station receives a second message sent by the target satellite base station, the second information includes the target neighboring area transmitted by the target satellite base station covering 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 to access the target satellite base station later.

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.

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 covering the terminal in the target neighboring area and completes downlink synchronization, and then initiates initial access to the target satellite base station, accesses the target cell, and completes the cell switching.

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.

Based on the switching method shown in FIG8 , when the first access network device is the first satellite base station (source satellite base station), the second access network device is the 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 switching time of the terminal are determined by the second satellite base station according to the location information of the terminal, its own satellite ephemeris information and the beam scanning rule of its own cell, the target synchronization resource and the switching time of the terminal are transmitted to the first satellite base station (source satellite base station), and then, the first satellite base station sends the first information to the terminal through the radio resource control RRC, the terminal receives the first information, and executes the switching process according to the first information 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 resource corresponding to the neighboring cell of the first cell. The first cell is the cell for which the first satellite base station provides communication connection and/or data transmission for the terminal at the current moment. 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, measures the RSRP of the target synchronization resource and completes downlink synchronization, then initiates initial access to the target satellite base station, accesses the target cell, and completes the cell switching. The target cell is the cell to which the SSB beam for which the target satellite base station provides communication connection and/or data transmission for the terminal when the switching time arrives.

Based on the switching method shown in FIG8 , the terminal does not immediately disconnect the data transmission with the first cell after receiving the switching command, until the switching time arrives, the terminal disconnects the data transmission with the first cell, and the first cell stops the uplink and downlink scheduling with the terminal, which shortens the time. The time of data interruption 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 the 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 neighboring area SSB beam.

In the above process, the switching time received by the terminal and the SSB beam of the target neighboring area 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 area covering the terminal are determined by the source satellite base station. As shown in FIG9, a cell switching method provided in an embodiment of the present application includes the following steps:

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

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

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.

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.

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

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.

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 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, 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.

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, and the usage process and acquisition process are consistent with those described in step S803, and will not be repeated here.

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.

Among them, 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 cell of the target satellite base station is optional. One possible situation 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 cell of the target satellite base station when preparing for the above-mentioned switching. Another possible situation 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 cell of the target satellite base station.

The source satellite base station determines the SSB beam of the terminal covered by the target neighboring area and the switching time of the terminal according to 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 may 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 may determine the time, range and coverage duration of the SSB beam of the cell of the target satellite base station and the cell of the target satellite base station covering the ground area 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 SSB beam of the target satellite base station cell and the target satellite base station cell 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 scans the terminal.

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. The source satellite base station learns from the ground control platform (for example, core network equipment) of the target satellite base station that the target satellite base station contains 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 from SSB_0 to SSB_9. The scanning time of each SSB beam is 2ms, and each The 3dB width of the 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 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 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.

In the above example, after the above process, the source satellite base station has determined that the SSB_2 beam of cell 1 of the target satellite base station can scan the terminal, and the source satellite base station also knows the beam scanning rule of the cell of the target satellite base station, that is, the number of SSB beams contained in the cell of the target satellite base station, the scanning period of the cell, and the scanning time of the SSB beam of the cell. 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 scanning time of the SSB beam 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 switching time of the terminal.

For example, the current time is 0 days, 0 hours, 0 minutes, 0 seconds, and 0 milliseconds. 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 switching time arrives, the beam scanned by the target satellite base station to the terminal is cell 1 with a beam number of SSB_2. When the SSB beam scanning rules of each cell of the target satellite base station are the same, the SSB beam scanning time of each cell is 2ms, each cell contains 10 SSB beams, which are scanned in the order of cell 0-cell 9, and the SSB beams of the cells are scanned in the order of SSB_0-SSB_9, with a scanning period of 20ms. The source satellite base station determines that the beam scanned by the target satellite base station to the terminal is cell 1 with a beam number of SSB_2, and the switching time of the terminal is 0 days, 0 hours, 0 minutes, and 0 seconds 24 milliseconds. Therefore, the terminal will receive the SSB beam signal of the target satellite base station cell 1 with a beam number of SSB_2 at 0 days, 0 hours, 0 minutes, and 0 seconds 24 milliseconds.

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.

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 description of a series of processes for accessing the target cell is consistent with the description of a series of processes performed by the terminal in step S805, and will not be repeated here.

Based on the switching method shown in FIG9, when the first access network device is the first satellite base station (source satellite base station), the second access network device is the 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 switching time of the terminal are determined by the source satellite base station according to 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, the source satellite base station sends the first information to the terminal through RRC signaling, and the terminal receives the first information and performs the switching process according to the first information instruction. Among them, the target synchronization resource is the SSB beam of the target neighboring area covering the terminal determined by the source satellite base station. The target synchronization resource is also part of the synchronization resource corresponding to the neighboring area of the first cell. The first cell is the cell for which the first satellite base station provides communication connection and/or data transmission for the terminal at the current moment; before the switching time arrives, the terminal maintains the communication connection and/or data transmission with 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 measures the RSRP of the target synchronization resource and completes the downlink synchronization, and then initiates initial access to the target satellite base station, accesses the target cell, and completes the cell switching. The target cell is the cell to which the SSB beam of the target satellite base station belongs, which provides communication connection and/or data transmission for the terminal when the switching time arrives.

The switching method shown in FIG9 has all the advantages of the switching method shown in FIG8. Compared with the switching method shown in FIG8, the target satellite base station in the switching method shown in FIG9 does not need the source satellite base station to report the location information of the terminal to it, and the target satellite base station does not need to determine the switching time and target synchronization resources of the terminal. Therefore, the calculation overhead of the target satellite base station is reduced, and the signaling interaction between the target satellite base station and the source satellite base station is further reduced.

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 in which the SSB scanning cycle of the terrestrial 5G network is relatively long. Although the current SSB scanning cycle of the terrestrial 5G network is relatively short (generally configured to be 20ms), and data interruption during the switching process has basically no impact on the service, future evolution may support a longer SSB scanning cycle 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 the fast moving speed, cell switching will also be frequently triggered. 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.

The above mainly introduces the solution provided by the embodiment of the present application from the perspective of 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 each function in order to realize the above functions. It should be easily appreciated by those skilled in the art 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 the form of hardware or computer software driving hardware 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 the present application.

The embodiment of the present application can group the functional modules of the terminal, access network equipment, etc. according to the above method example. 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 integrated module 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 embodiment of the present application is schematic and is only a logical functional grouping. There may be other grouping methods in actual implementation.

FIG10 shows a structural diagram of a communication device 100, which may be a terminal, or a chip in a terminal, or a system on chip, and may be used to perform the functions of the terminal involved in the above embodiments. As an implementation method, the communication device 100 shown in FIG10 includes: a receiving unit 1001, a processing unit 1002, and a sending unit 1003;

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.

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 to execute S805 or S905.

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.

Among them, the relevant descriptions of the first information, the target synchronization resource, and the measurement event may refer to those in the above embodiments.

Specifically, for a terminal that has accessed the first cell, the first cell will send a measurement event to the terminal, and accordingly, the terminal will report the measurement event and its own location information to the first cell. Subsequently, the terminal receives the first information carried in the wireless resource control configuration message sent by the first cell to the terminal, and according to the indication of the first information, when the switching time arrives, receives the target synchronization resource and performs synchronization measurement on the target synchronization resource. Specifically, the target synchronization resource is received and the RSRP information of the target synchronization resource is measured, and downlink synchronization is completed, and then initial access is initiated to the target satellite base station, access to the target cell, and cell switching is completed.

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 indicate that the terminal switches 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 the 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 terminal arrives at the switching time, it only needs to measure the RSRP of the target synchronization resource and complete the downlink synchronization, and then initiates initial access to the target satellite base station, accesses the target cell, and completes the cell switching.

The relationship between the first cell and the second cell mentioned above may be any of the following possibilities:

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

(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;

(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;

(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;

(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;

As mentioned above, the first cell may correspond to the first satellite base station, and the second cell may correspond to the second satellite base station; or The cell corresponds to the first ground station, and the second cell corresponds 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 working mode of the satellite base station can be divided into a transparent transmission mode and a regenerative mode. Therefore, there are 5 relationships between the first cell and the second cell in the transparent transmission mode, and 5 relationships between the first cell and the second cell in the regenerative mode, for a total of 10 possibilities.

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 actions of the communication device 100. For example, the processing module can integrate the functions of the processing unit 1002, and can be used to support the communication device 100 to execute S805 or S905 and other processes of the technology described herein. The communication module can integrate the functions of the receiving unit 1001 and the sending unit 1003, and can be used to support the communication device 100 to execute S801 or S901 and communicate with other network entities, such as communication between 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.

Among them, the processing module can be a processor or a controller. It can implement or execute various exemplary logic boxes, modules and circuits described in conjunction with the disclosure of this application. The processor can also be a combination that implements computing functions, such as a combination of one or more microprocessors, a combination of DSP and microprocessors, etc. The communication module can be a transceiver circuit or a communication interface, etc. The storage module can 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 can be the terminal 30 shown in Figure 7.

FIG11 shows a structural diagram of a communication device 110, which may be an access network device, or a chip in an access network device, or a system on chip, and 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 FIG11 includes: a receiving unit 1101, a processing unit 1102, and a sending unit 1103;

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

Another possible design is to use the first network device to receive the measurement event report reported by the terminal and the location information of the terminal, or to receive the 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.

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.

Another possible design is to use 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.

A possible design of the sending unit 1103 is to be used for the second network device to send the second information to the first network device. For example, the sending unit 1103 can support the communication apparatus 110 to execute S803.

Another possible design is that the first network device sends the measurement event, the switching time and the target synchronization resource to the terminal; and the first network device sends 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.

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.

In the case where the target synchronization resource and the 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 area covering the terminal and the time when the terminal can measure the target beam (i.e., the switching time of the terminal) 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 area 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. Among them, the second information includes the target synchronization resource of the second access network device and the switching time of the terminal.

In the case where the target synchronization resource and the switching time are determined by the first 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 communicate with the second access network device. The network access device completes the handover preparation work. Among them, the handover preparation work is that the first access network device applies to the second access network device for the terminal for the available resource allocation. Then, the first access network device determines the SSB beam (target synchronization resource) of the target neighboring area covering the terminal and the time when the terminal can measure the target beam (i.e., the switching time of the terminal) according to 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 sends it to the terminal through RRC signaling. When the switching time arrives, the terminal measures the RSRP of the SSB beam of the target neighboring area covering the terminal, performs downlink synchronization, and then initiates initial access to the target satellite base station, accesses the target cell, and completes the cell switching; among them, the target neighboring area (target synchronization resource) covering the terminal and the time when the terminal can measure the target beam (i.e., the switching time of the terminal) sent by the first access network device to the terminal can also be called the first information.

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

Specifically, all relevant contents of each step involved in the method embodiments shown in FIG8 and FIG9 can be referred to the functional description of the corresponding functional module, and will not be repeated here. The communication device 110 is used to perform the function of the access network device in the cell switching method shown in FIG8 or FIG9, so the same effect as the above cell switching method can be achieved.

As another possible implementation, the communication device 110 shown in FIG. 11 includes: a processing module and a communication module. The processing module is used to control and manage the actions of the communication device 110. For example, the processing module can integrate the functions of the processing unit 1102, and can be used to support the communication device 110 to execute S902, S904, S802, S803 and other processes of the technology described herein. The communication module can integrate the functions of the receiving unit 1101 and the sending unit 1103, and can be used to support the communication device 110 to execute S801, S802, S803, S804, S901, S902, S903 or S904 and communicate with other network entities, such as communication between the functional modules or network entities shown in FIG. 3a. The communication device 110 may also include a storage module for storing program codes and data of the communication device 110.

Among them, the processing module can be a processor or a controller. It can implement or execute various exemplary logic boxes, modules and circuits described in conjunction with the disclosure of this application. The processor can also be a combination that implements computing functions, such as a combination of one or more microprocessors, a combination of DSP and microprocessors, and the like. The communication module can be a transceiver circuit or a communication interface, and the like. The storage module can 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 embodiment of the present application can be the access network device 20 shown in Figure 7.

In the technical solution of this application, the collection, storage, use, processing, transmission, provision and disclosure of user personal information involved are in compliance with relevant laws and regulations and do not violate public order and good morals. For example, in the technical solution of this application, the processing of user personal information is carried out with the authorization of the user, which is explained here uniformly and will not be repeated here.

It should be noted that the terms "first" and "second" in the specification, claims and drawings of the present 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.

It should be understood that in the present application, "at least one (item)" means one or more, "more than one" means two or more, "at least two (items)" means 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 items 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.

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 only based on A, but B can also be determined based on A and/or other information. In addition, the "connection" that appears in the embodiments of the present application refers to various connection methods such as direct connection or indirect connection to achieve communication between devices, and the embodiments of the present application do not impose any limitation on this.

Unless otherwise specified, the term "transmission" in the embodiments of the present application refers to bidirectional transmission, including the action of sending and/or receiving. Specifically, the term "transmission" in the embodiments of the present application includes the sending of data, the receiving of data, or the sending and receiving of data. In other words, the data transmission here includes uplink and/or downlink data transmission. Data can include The term "network" and "system" used in the embodiments of the present application refer to the same concept, and a communication system is a communication network.

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.

In the several embodiments provided in the present 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 only schematic. For example, the grouping of the modules or units is only a logical function grouping. There may be other grouping methods in actual implementation. For example, 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.

The units described as separate components may or may not be physically separated, 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.

In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

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, including several instructions to enable a device, such as a single-chip microcomputer, a chip, etc., or a processor (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 USB flash drives, mobile hard drives, ROM, RAM, magnetic disks or optical disks.

The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims (22)

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. The method according to claim 1, wherein 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 comprises: 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. The method according to claim 1 or 2, characterized in that The first information is carried in a radio resource control RRC configuration message. 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. 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. 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. 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. 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. 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. The method according to claim 9, characterized in that The first information is carried in a radio resource control RRC configuration message. 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. 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. 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. 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. The method according to claim 14 is 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 terminal to perform cell switching comprises: 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. 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. 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. 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 1-8. A communication device, characterized in that the communication device includes 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 9-17. A communication system, characterized in that the communication system includes the communication device as claimed in claim 18, the communication device as claimed in claim 19 and a second access network device. 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. 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 executes the method according to any one of claims 1 to 8, or the method according to any one of claims 9 to 17.