Conditional handover method, communication node, and storage medium

Abstract

The present application provides a conditional handover method, a communication node, and a storage medium. The method comprises: when it is determined that a second communication node performs conditional handover, acquiring configuration information of candidate cells; and sending a first message to the second communication node, wherein the first message comprises the configuration information of the candidate cells and an execution condition for the conditional handover, and the first message is used for instructing the second communication node to select from among the candidate cells a candidate cell, which meets the execution condition, to be used as a target cell, and to perform handover to the target cell on the basis of the configuration information. When the target cell is a non-terrestrial network cell, the execution condition comprises a reference signal condition and an execution state condition.

Description

Conditional switching method, communication node and storage medium Technical Field

[0001] The present application relates to a wireless communication network, for example, to a conditional switching method, a communication node and a storage medium. Background Art

[0002] In non-terrestrial networks (NTNs), the primary consideration for handovers is how to leverage ephemeris and terminal location information to ensure handover reliability. In terrestrial systems, radio resource management (RRM) measurements are the primary basis for handovers. However, in satellite communications, handovers rely not only on RRM measurements but also on the terminal's location and the satellite's beam movement patterns. NTN base station antennas are carried by satellites (at altitudes of 600 to 35,786 km) or high-altitude platforms (at altitudes of 8 to 20 km). Therefore, within NTN cells, the difference in Reference Signal Received Power (RSRP) or Reference Signal Received Quality (RSRQ) between the center and edge of the cell is not significant. Furthermore, because ground-to-ground signal propagation is affected by weather (such as rain and fog attenuation), the edge effects in NTN cells are even more blurred. In this scenario, it is difficult for the network to configure appropriate RSRP or RSRQ thresholds. Too high a threshold can easily lead to late triggering of measurement reports, conditional switching, and neighboring cell measurements. Conversely, too early or frequent triggering can reduce the reliability of conditional switching.

[0003] Summary of the Invention

[0004] The present application provides a conditional switching method, a communication node, and a storage medium.

[0005] An embodiment of the present application provides a conditional switching method, applied to a first communication node, including:

[0006] When it is determined that the second communication node performs conditional handover, obtaining configuration information of the candidate cell;

[0007] Sending a first message to the second communication node, where the first message includes configuration information of the candidate cell and an execution condition of conditional switching, and the first message is used to instruct the second communication node to select a candidate cell that meets the execution condition as a target cell among the candidate cells and switch to the target cell according to the configuration information;

[0008] Wherein, in the case that the target cell is a non-terrestrial network cell, the execution condition includes a reference signal condition and an execution state condition.

[0009] The embodiment of the present application further provides a conditional switching method, applied to a second communication node, comprising:

[0010] receiving a first message including configuration information of a candidate cell and an execution condition of conditional switching;

[0011] selecting a candidate cell that meets the execution condition from the candidate cells as a target cell, and switching to the target cell according to the configuration information;

[0012] Wherein, in the case that the target cell is a non-terrestrial network cell, the execution condition includes a reference signal condition and an execution state condition.

[0013] An embodiment of the present application further provides a communication node, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the above-mentioned conditional switching method when executing the program.

[0014] An embodiment of the present application further provides a computer-readable storage medium, on which a computer program is stored, and when the program is executed by a processor, the above-mentioned conditional switching method is implemented. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] FIG1 is a flow chart of a conditional switching method provided by an embodiment;

[0016] FIG2 is a flow chart of another conditional switching method provided by an embodiment;

[0017] FIG3 is a schematic diagram of a non-terrestrial network based on transparent forwarding satellites provided by an embodiment;

[0018] FIG4 is a schematic diagram of a non-terrestrial network based on a regenerative repeater satellite according to an embodiment;

[0019] FIG5 is a schematic diagram of an implementation of a conditional switching process provided by an embodiment

[0020] FIG6 is a schematic structural diagram of a conditional switching device provided by an embodiment;

[0021] FIG7 is a schematic structural diagram of another conditional switching device provided by an embodiment;

[0022] FIG8 is a schematic diagram of the hardware structure of a communication node provided by an embodiment. DETAILED DESCRIPTION

[0023] The present application is described below in conjunction with the accompanying drawings and embodiments. It will be understood that the specific embodiments described herein are merely intended to explain the present application and are not intended to limit the present application. It should be noted that, unless there is a conflict, the embodiments and features within the embodiments of the present application may be combined with each other in any manner. It should also be noted that, for ease of description, the accompanying drawings only illustrate portions relevant to the present application, not all structures.

[0024] NTN is divided into two major scenarios: transparent forwarding (also known as bent-pipe forwarding) and regenerative forwarding. In the transparent forwarding scenario, the satellite acts as an RF relay. Both the service link and feeder link use the 5G Uu interface, while the NTN ground station or gateway simply transparently transmits the New Radio (NR) Uu interface signal. Different transparent transmission satellites can connect to the same ground base station (gNB). In the regenerative scenario, the satellite acts as a satellite-based base station (gNB-DU or gNB). The service link uses the NR Uu interface. Unlike the transparent forwarding mode, the feeder link uses the satellite private radio interface (SRI). Different gNBs can connect to the same ground 5G core network.

[0025] NTN scenarios primarily involve satellite communications and low-altitude communications (from low-altitude platforms). These differ from terrestrial communications primarily in terms of high latency, wide coverage, and satellite motion. Because mobility management is crucial for network connectivity and service continuity, it is crucial to fully consider the characteristics of various networks and wireless resource constraints. In particular, the altitude and speed of satellites, along with the resulting high propagation latency and dynamic cell changes, present challenges. Achieving lossless mobility management between ground-to-space networks, minimizing service interruptions and ultimately providing a consistent user experience, is a pressing issue.

[0026] The present application provides a conditional switching method, which adopts appropriate execution conditions for conditional switching, thereby improving the reliability of conditional switching and reducing service interruptions and transmission delays during communication. The method can be implemented through interaction between a first communication node (mainly a satellite or a network device) and a second communication node (mainly a terminal device), wherein the terminal device can be a user equipment (UE) or a vehicle-mounted device, etc., and can also be understood as a module (such as a chip) in the terminal device; the satellite can be a geostationary satellite, a non-geostationary satellite, an artificial satellite, a low-orbit satellite, a medium-orbit satellite, and a high-orbit satellite, etc., and the satellite can be a transparent forwarding or regenerative forwarding satellite; network devices such as: evolved node B (eNB), radio network controller (RNC), node B (NB), basic station controller (BSC), basic transceiver station (BTS), home base station (such as Home Evolved NodeB, or Home NodeB, HNB), basic band unit (BBU), access point (AP) in a wireless fidelity (WIFI) system, wireless relay node, wireless backhaul node, transmission point (TP) A gNB can also be a transmission point (TRP) or transmission point (TP) in a 5G (e.g., NR) system, a gNB or transmission point (TRP or TP), one or a group (including multiple) antenna panels of a base station in a 5G system, or a network node that constitutes a gNB or transmission point, such as a baseband unit (BBU), distributed unit (DU), or drone. In some deployments, a gNB can include a centralized unit (CU) and a DU; it can also include a radio unit (RU).

[0027] FIG1 is a flow chart of a conditional handover method provided by an embodiment. The method can be applied to a first communication node. As shown in FIG1 , the method provided by this embodiment includes steps 110 and 120.

[0028] In step 110, when it is determined that the second communication node performs conditional switching, configuration information of the candidate cell is obtained.

[0029] In step 120, a first message is sent to the second communication node, where the first message includes the configuration information of the candidate cell and the execution conditions of the conditional switching. The first message is used to instruct the second communication node to select a candidate cell that meets the execution conditions as the target cell among the candidate cells and switch to the target cell according to the configuration information.

[0030] Wherein, in the case that the target cell is a non-terrestrial network cell, the execution condition includes a reference signal condition and an execution state condition.

[0031] In this embodiment, the first communication node may receive a measurement report from the second communication node. When the first communication node determines that the first communication node is to perform conditional switching, the first communication node obtains the configuration information of the candidate cell. The candidate cell mainly refers to a cell that can be a target of conditional switching, and there may be one or more candidate cells. After the first communication node determines that conditional switching needs to be performed, it may send a request message to an adjacent base station. The adjacent base station selects a candidate cell and sends the configuration information of the candidate cell to the first communication node. The first communication node sends a first message to the UE. The first message includes the configuration information of the candidate cell and the execution conditions of the conditional switching. On this basis, the first message can instruct the second communication node to evaluate each candidate cell according to the execution conditions. If at least one candidate cell that meets the execution conditions is found, it can be used as the target cell for conditional switching and switched to the target cell according to the configuration information of the target cell. During the CHO process, from the time the second communication node starts to synchronize with the target cell, the second communication node may no longer monitor the source cell.

[0032] The execution conditions include reference signal conditions and execution state conditions. Reference signal conditions, for example, limit the RSRP or RSRQ threshold for conditional switching; the execution state conditions can be used to limit the state of the second communication node when performing conditional switching. The execution state conditions may include location conditions, for example, the location where the second communication node can perform conditional switching or the distance between the node on the network side; the execution state conditions may also include time conditions, for example, the time condition limits the time period during which the second communication node can perform conditional switching. The reference signal condition can be configured together with the location condition, or together with the time condition. In some scenarios, the reference signal condition, location condition and time condition can also be configured together.

[0033] It should be noted that the source cell where the second communication node is located before the conditional handover can be a terrestrial network or a non-terrestrial network, and the target cell is a non-terrestrial network. The candidate cell and the source cell where the second communication node is located can be located within the same satellite coverage or within different satellite coverages.

[0034] Communication between the first communication node and the second communication node may also be achieved via a network device, the network device including at least one of the following: a ground base station and a satellite base station. The network device and the second communication node both know candidate cells and execution conditions for conditional handover. The network device may determine configuration information and execution conditions for the candidate cells and transmit the determined configuration information and execution conditions to the second communication node so that the second communication node can perform the conditional handover.

[0035] The first communication node can send a first message to each second communication node through dedicated radio resource control (RRC) signaling. After receiving the first message, each second communication node can select a target cell that meets the execution conditions according to the first message, disconnect from the source cell, and connect to the target cell through the satellite belonging to the target cell, thereby realizing conditional switching.

[0036] The first message may be sent after connection security is activated between the second communication node and the first communication node.

[0037] In this embodiment, the execution conditions and candidate cells are pre-configured before the execution conditional switching, and are not determined by real-time calculation. Therefore, the signaling overhead is relatively reduced and the processing delay is reduced. Moreover, the execution conditions are based on the characteristics of NTN communication. In addition to the reference signal conditions, the location conditions and / or the time conditions of the satellite service are also considered. On this basis, the success rate of the conditional switching can be improved, the second communication node can be prevented from switching too early or too late, frequent switching can be avoided, and the service quality can be improved.

[0038] In one embodiment, when the candidate cells satisfying the execution condition include terrestrial network candidate cells and non-terrestrial network candidate cells, the target cell is a terrestrial network candidate cell.

[0039] In this embodiment, when the candidate cells meeting the execution condition include a terrestrial network candidate cell and a non-terrestrial network candidate cell, the second communication node preferentially selects the terrestrial network candidate cell as the target cell.

[0040] In one embodiment, the terrestrial network candidate cells and the non-terrestrial network candidate cells are distinguished by fields in the cell system broadcast message; the terrestrial network candidate cells and the non-terrestrial network candidate cells correspond to different execution conditions.

[0041] In one embodiment, the method further includes: determining whether the second communication node performs conditional switching based on at least one of the following information: measurement report, capability of the second communication node, location of the second communication node, satellite ephemeris; wherein the capability of the second communication node includes the capability to support non-terrestrial network communications, and may also include the capability to support Global Navigation Satellite System (GNSS) positioning or cellular network positioning.

[0042] The capability of the second communication node primarily refers to whether the second communication node supports NTN communication. If the source cell is an NTN cell, the second communication node has NTN communication capabilities. If the source cell is a terrestrial network, the first communication node obtains the second communication node's NTN communication capabilities through RRC signaling. The location of the second communication node can refer to its geographic location information, which the second communication node can obtain through positioning, such as GNSS positioning or cellular network positioning.

[0043] Exemplarily, conditional switching can be performed when the measurement report of the second communication node shows that the adjacent cell or candidate cell is a non-terrestrial network cell; conditional switching can be performed when the second communication node has NTN capability; conditional switching can be performed when the second communication node enters a non-terrestrial network; conditional switching can be performed when the second communication node enters a satellite coverage area, etc.

[0044] In one embodiment, the execution condition can be determined based on the satellite ephemeris (the information of the satellite ephemeris can indicate the orbital parameters of the satellite. The orbits of each satellite are fixed, but the orbits of different satellites may be different) and the position of the second communication node (such as the distance from the second communication node to the cell reference point (for example, the cell center)), and combined with the reference signal condition (based on the measurement criteria of RSRP or RSRQ).

[0045] The execution conditions corresponding to different satellites may be different, and the execution conditions determined for the same satellite at different time points may also be different, which is not specifically limited in this application.

[0046] In one embodiment, the configuration information of the candidate cell includes a cell identifier and cell resource configuration information; or, the configuration information of the candidate cell includes a cell identifier, cell resource configuration information and at least one of the following: synchronization block measurement timing configuration (SS / PBCH Block Measurement Timing Configuration, SMTC), channel state information reference signal (Channel State Information Reference Signal, CSI-RS) resource location information; when the candidate cell is a non-terrestrial network cell, the synchronization block measurement timing configuration includes at least two.

[0047] In this embodiment, the candidate base station can send the configuration information of the candidate cell to the first communication node. The configuration information of the candidate cell includes at least a cell identifier and cell resource configuration information. Further, it can also include at least one of the following: SMTC, CSI-RS resource location information. Among them, the cell identifier can be used to indicate the candidate cell, the cell resource configuration information is used for the second communication node to connect to the candidate cell that meets the execution conditions, the resource configuration is a random access resource or a physical uplink shared channel (PUSCH, Physical Uplink Shared CHannel) resource configuration, and SMTC or CSI-RS is used by the second communication node to evaluate the signal quality of the candidate cell. Each candidate base station needs to send the configuration information of each candidate cell to the first communication node.

[0048] In one embodiment, the execution state condition includes at least one of a time condition and a location condition; the time condition is used to indicate a time window in which the second communication node can perform conditional switching on the candidate cell, and the length of the time window may be T. Starting from the defined time point, within a continuous time range of T, if the measurement results of the candidate cell meet the reference signal condition, the second communication node can perform conditional switching. The location condition is used to indicate a first distance threshold from the second communication node to the source cell (which may be the center position of the source cell) and a second distance threshold from the second communication node to the candidate cell (which may be the center position of the candidate cell). The second communication node can perform CHO according to the distance threshold, that is, if the distance from the second communication node to the source cell is greater than the first distance threshold, and the distance from the second communication node to the candidate cell is less than the second distance threshold, and the measurement result for the candidate cell meets the reference signal condition, then the second communication node can perform conditional switching.

[0049] In addition, the location condition can be used as a trigger event for CHO execution conditions and measurement result reporting, and the time condition can be used as a CHO execution condition, but not as a trigger event for measurement result reporting. This is because the network can configure the measurement result reporting of the second communication node according to the service stop time in the connected state.

[0050] In one embodiment, the reference signal condition is a measurement report triggering event for conditional switching.

[0051] In one embodiment, the first message is sent via RRC reconfiguration signaling.

[0052] In one embodiment, the execution condition is determined based on satellite ephemeris information, the position of the second communication node, and a reference signal reception parameter; wherein the reference signal reception parameter includes RSRP or RSRQ.

[0053] In one embodiment, the method further includes: determining a time range for the execution condition; wherein the first message is used to instruct the second communication node to switch to a target cell that meets the execution condition within the time range. In this embodiment, a candidate cell that meets the execution condition and remains valid within the time range can become the target cell.

[0054] In one embodiment, the method further includes: sending conditional handover configuration information, where the conditional handover configuration information includes satellite ephemeris information, a common timing advance (TA) parameter, a start time, and a valid time.

[0055] In one embodiment, the reference signal condition includes at least one of the following:

[0056] The reference signal quality of the neighboring cell exceeds the reference signal quality of the designated cell by a preset offset;

[0057] The reference signal quality of the neighboring cell is higher than the preset threshold;

[0058] The reference signal quality of the designated cell is lower than a first threshold, and the reference signal quality of the neighboring cell is higher than a second threshold.

[0059] The reference signal includes at least one of the following: synchronization signal block SSB, CSI-RS.

[0060] In this embodiment, the reference signal condition may include at least one of the following:

[0061] When the reference signal quality of the neighboring cell exceeds the preset offset of the designated cell (such as the serving cell), the reference signal condition is met;

[0062] The neighboring cell reference signal quality becomes better than a preset threshold, satisfying reference signal condition 4;

[0063] The designated cell reference signal quality becomes worse than a first threshold, while the neighboring cell reference signal quality becomes better than a second threshold, and the reference signal condition is met.

[0064] Reference signals include at least one of the following: Synchronization Signal Block (SSB) and Channel State Information-Reference Signal (CSI-RS). Reference signal quality includes at least one of the following: RSRP, RSRQ, Signal to Interference plus Noise Ratio (SINR), etc.

[0065] In one embodiment, the time condition or location condition can be configured together with one of the reference signal conditions. It should be noted that if the source cell is an NTN cell, the first message can also be sent directly by the satellite and not carried in the first message, but carried through other information or signaling. This application does not specifically limit the carrying method of the first message.

[0066] In one embodiment, the method further includes: sending a user plane configuration of the target cell to the second communication node, wherein the user plane configuration includes: adding a satellite-to-ground round-trip time to a user plane timer time.

[0067] In order to meet the user's service continuity requirements, a dual-active protocol stack (DAPS) switching can be introduced. That is, after receiving the switching command, the second communication node establishes a connection to the target cell while maintaining the connection to the source cell. After the second communication node successfully accesses the target cell, the connection to the source cell is released. DAPS switching ensures the continuity of user data transmission during the switching process by maintaining the dual connection between the second communication node and the source cell and the target cell and the same user plane configuration for a short period of time. In the case where both the source cell and the target cell are NTN networks, DAPS can be omitted considering the power limitation of the second communication node.

[0068] In this embodiment, NTN conditional handover can also utilize DAPS. Considering the differences between terrestrial and non-terrestrial networks, particularly the high latency between satellite and ground in NTN networks, when the source cell is a terrestrial network, the target NTN cell can utilize a different user plane configuration than the source cell. User plane configuration information can be sent from the first communication node to the second communication node before conditional handover is executed. Specifically, the round-trip time (RTT) between satellite and ground can be added to the user plane timer settings. This means that the satellite-ground latency is added to the corresponding timer (e.g., Timer + 2*RTT).

[0069] In one embodiment, the method further includes: sending status information, wherein the status information includes a Packet Data Convergence Protocol (PDCP) number, and the status information is used to indicate the sending status of uplink data and downlink data of the Uu air interface.

[0070] In this embodiment, after sending the first message to the second communication node (or after receiving the response message from the second communication node), the first communication node can forward the user plane data to the candidate base station and indicate status information. The status information is used to indicate the current uplink and downlink data sending status, including the PDCP number.

[0071] In one embodiment, the method further includes: when DAPS switching is not configured, forwarding data to the candidate base station after the second communication node successfully accesses the target base station; when DAPS switching is configured, forwarding data to the candidate base station before the switching of the second communication node is completed.

[0072] In this embodiment, if DAPS switching is not configured, the first communication node will initiate data forwarding after knowing that the second communication node has successfully accessed the target base station; if DAPS switching is configured, the first communication node will forward data to the candidate base station before the second communication node performs conditional switching.

[0073] In one embodiment, the method further comprises:

[0074] After the second communication node switches to the target cell, it sends a state migration message to the target base station and sends a switching cancellation message to the candidate base station.

[0075] The conditional handover method of this embodiment takes into account the scenario of switching from TN or NTN to NTN. The execution conditions may include: time conditions and reference signal conditions, or location conditions and reference signal conditions. That is, if the execution conditions are met, the second communication node may connect to the target cell according to the configuration information; the configuration information includes the random access resources or PUSCH uplink resources of the target cell; in addition, satellite ephemeris information and TA parameters, as well as the time window (which may include the corresponding start time and validity time) may be sent in the CHO configuration information; if the conditional handover fails, the second communication node may initiate cell selection and initiate conditional handover or RRC connection re-establishment in the selected cell according to the instructions of the first communication node; if RACH-less handover fails, the second communication node may initiate a random access process. On this basis, the reliability and success rate of conditional handover are improved, service interruption and transmission delay are comprehensively reduced, and a uniform service experience can be provided to users.

[0076] The present application also provides a conditional switching method. This method can be applied to a second communication node, primarily a terminal device, such as a UE or vehicle-mounted device, and can also be understood as a module (e.g., a chip) in the terminal device. For technical details not fully described in this embodiment, please refer to any of the above embodiments.

[0077] FIG2 is a flow chart of a conditional switching method provided by an embodiment. As shown in FIG2 , the method provided by this embodiment includes step 210 and step 220 .

[0078] In step 210, a first message is received, where the first message includes configuration information of a candidate cell and an execution condition of conditional handover.

[0079] In step 220, a candidate cell that meets the execution condition is selected from the candidate cells as a target cell, and the target cell is switched according to the configuration information.

[0080] Wherein, in the case that the target cell is a non-terrestrial network cell, the execution condition includes a reference signal condition and an execution state condition.

[0081] In this embodiment, the second communication node, based on the first message, can evaluate each candidate cell according to the execution conditions. If at least one candidate cell meeting the execution conditions is found, it can be selected as the target cell for conditional handover and handover can be made to the target cell based on the configuration information of the target cell. The execution conditions and candidate cells are pre-configured before conditional handover is performed, rather than calculated and determined in real time. This reduces signaling overhead and processing latency. Furthermore, based on the characteristics of NTN communications, the execution conditions consider not only reference signal conditions but also execution state conditions. This improves the success rate of conditional handover, prevents the second communication node from switching too early or too late, avoids frequent handovers, and improves service quality.

[0082] In one embodiment, selecting a candidate cell that meets the execution condition as a target cell from the candidate cells includes:

[0083] In a case where the candidate cells meeting the execution condition include a terrestrial network candidate cell and a non-terrestrial network candidate cell, the terrestrial network candidate cell is preferentially selected as the target cell.

[0084] In one embodiment, switching to the target cell according to the configuration information includes: switching to the target cell without a random access process according to the configuration information, and establishing an RRC connection with the target cell; when the switching without a random access process fails or the switching without a random access process is not enabled, switching to the target cell based on the random access process, wherein the random access resources are dedicated resources without conflict.

[0085] In this embodiment, in order to reduce the switching delay, a random access channel-less (RACH-less) switching method can be adopted, that is, the second communication node directly sends information through the PUSCH in the target cell, and there is no need to adopt a random access process. It is assumed that the timing advance TA of the target cell is the same as that of the source cell, and the uplink resources of the target cell are pre-configured to the second communication node through a switching command, or dynamically configured in the target cell, and uplink resources are allocated to the second communication node when the second communication node is available for scheduling in the target cell; if the RACH-less switching fails, the second communication node can adopt a RACH-based switching, for example, when the signal quality of the target cell exceeds the specified threshold, non-conflicting random access resources can be used, otherwise conflict-based random access resources are used. The above configuration information is sent by the source base station to the second communication node through a switching command.

[0086] In one embodiment, the method further comprises:

[0087] During the conditional handover process of the second communication node, upon receiving a handover command for an unconditional handover sent by the first communication node, the second communication node performs the unconditional handover.

[0088] In this embodiment, before any execution conditions are met, if the second communication node receives a non-conditional handover (HO) handover command (without CHO configuration) from the first communication node, the second communication node performs a traditional HO handover process without considering the received CHO configuration and the first message.

[0089] In one embodiment, the method further includes: starting a cell selection process when conditional handover fails; performing conditional handover again when the selected cell is a candidate cell and conditional handover enabling is attempted again when conditional handover fails; otherwise, initiating an RRC connection reestablishment process in the selected cell.

[0090] In this embodiment, if CHO execution fails, such as Radio Link Failure (RLF), the second communication node performs cell selection. If the selected cell is a candidate cell for CHO, and if the network configures the second communication node to attempt CHO after CHO fails, the second communication node attempts to perform CHO again, otherwise performs RRC connection re-establishment. In order to speed up the processing time, when the conditional switching fails, the second communication node may select a cell that has been registered and belongs to a candidate cell for CHO, or select a cell that has been registered to initiate an RRC connection reconstruction process. If the context of the second communication node cannot be retrieved, the RRC connection establishment process is performed in the selected cell. In one embodiment, switching to the target cell according to the configuration information includes: when DAPS is configured, establishing a connection with the target cell while maintaining the connection with the source cell, and releasing the connection with the source cell after successfully accessing the target cell; when DAPS is not configured, first disconnecting the connection with the source cell and then connecting to the target cell.

[0091] Figure 3 is a schematic diagram of a non-terrestrial network based on transparent relay satellites, provided by one embodiment. Figure 4 is a schematic diagram of a non-terrestrial network based on regenerative relay satellites, provided by one embodiment. As shown in Figures 3 and 4, a satellite mobile communication system includes: satellites, ground stations, terminal devices, and terrestrial network equipment. The satellites communicate with terminal devices (e.g., UE1 and UE2) via wireless signals. The satellites and ground stations are connected wirelessly, and this link is typically called a feeder link. Satellites typically form multiple beams, each similar to a cell or sector in a terrestrial mobile communication system (e.g., LTE or NR). The ground stations are connected to network equipment, such as eNBs, RNCs, NBs, BSCs, BTSs, home base stations, BBUs, access points in Wi-Fi systems, wireless relay nodes, wireless backhaul nodes, TRPs, or TPs. These equipment may also be gNBs or transmission points in 5G (e.g., NR) systems, or network nodes that constitute gNBs or transmission points, such as BBUs, DUs, and drones. In some deployments, a gNB may include a CU and a DU. The CU implements some gNB functions, while the DU implements some gNB functions. For example, the CU implements RRC and packet data convergence protocol layer functions, while the DU implements radio link control (RLC), media access control (MAC), and physical (PHY) layer functions. Because RRC layer information ultimately becomes PHY layer information (i.e., sent via the PHY layer) or is converted from PHY layer information, in this architecture, higher-layer signaling, such as RRC layer signaling or PDCP layer signaling, can also be considered to be sent by the DU, or by the DU+RU. It is understood that an access network device can be a CU node, a DU node, or a device that includes both a CU node and a DU node. Furthermore, the CU can be classified as a network device in the access network (RAN) or a network device in the core network (CN), without limitation.

[0092] The terminal device involved in the embodiments of the present application, also referred to as user equipment, is an entity on the user side for receiving / transmitting signals, used to send uplink signals to network terminal devices, or receive downlink signals from network devices. It includes devices that provide voice and / or data connectivity to users, such as handheld devices with wireless connection capabilities, or processing devices connected to wireless modems. The terminal device can communicate with the core network via the radio access network (RAN) and exchange voice and / or data with the RAN. The terminal device may include UE, V2X terminal device, wireless terminal device, mobile terminal device, device-to-device communication (D2D) terminal device, machine-to-machine / machine-type communication (M2M / MTC) terminal device, Internet of Things (IoT) terminal device, subscriber unit (Subscriber Unit), subscriber station (Subscriber Station), mobile station (Mobile Station), remote station (Remote Station), access point, remote terminal (Remote Terminal), access terminal (Access Terminal), user terminal (User Terminal), user agent (User Agent), or user equipment (User Device), wearable device, vehicle-mounted device, drone, etc., and the various terminal devices introduced above, if located on a vehicle (for example, placed in a vehicle or installed in a vehicle), can be considered as vehicle-mounted terminal devices, and vehicle-mounted terminal devices are also called vehicle-mounted units (On-Board Unit, OBU), for example.

[0093] In one embodiment, the following measurement report triggering events may be defined:

[0094] 1) Time condition T1 defines the time window when the UE can perform CHO to the candidate cell. Starting from a preset time point, the UE can perform CHO to the specific cell within the satellite service time range for the specific cell;

[0095] 2) Location condition L1, which defines two distance thresholds from the UE to the source cell and from the UE to the candidate cell, according to which the UE can perform CHO;

[0096] 3) Reference Signal Condition A3: The signal quality offset of the neighboring cell exceeds that of the designated cell. The designated cell is the primary serving cell of the Master Cell Group (MCG) or Secondary Cell Group (SCG). This event is typically used during intra-frequency or inter-frequency handover. Event A3 provides a handover triggering mechanism based on relative measurement results.

[0097] 4) Reference Signal Condition A4: The neighboring cell signal quality becomes better than a defined threshold. This event can be used for handover procedures that are independent of the serving cell's coverage. For example, in the load balancing feature, the decision to handover a UE from a serving cell may be based on load conditions rather than radio conditions. In this case, the UE only needs to verify that the target cell is better than a certain signal level threshold and can provide adequate coverage.

[0098] 5) Reference Signal Condition A5: The signal quality of a particular cell deteriorates below Threshold 1, while the signal quality of a neighboring cell deteriorates above Threshold 2. This condition is typically used in intra-frequency or inter-frequency handovers. A5 provides a handover triggering mechanism based on absolute measurement results.

[0099] The time condition or the location condition can be configured together with one of the reference signal conditions (A3, A4 or A5), such as T1+A3 / A4 / A5, or L1+A3 / A4 / A5.

[0100] FIG5 is a schematic diagram of an implementation of a conditional switching process provided by an embodiment. The conditional switching method of this embodiment can be implemented through interaction between a satellite and a terminal device. In actual application, there may be multiple terminal devices, and one terminal device is used as an example for illustrative description. As shown in FIG5 , the conditional switching process includes:

[0101] Step 201: The UE sends a measurement report, where the measurement report includes UE location information.

[0102] It should be noted that conditional handover includes two scenarios: terrestrial network to non-terrestrial network (NTN), or non-terrestrial network to non-terrestrial network. If the UE's source cell belongs to a terrestrial network, the UE sends a measurement report to the source base station where the source cell is located. The source base station selects a candidate base station, which can be connected to a satellite and belongs to a non-terrestrial network (NTN). If the source cell belongs to an NTN, that is, the source base station is connected to a satellite, the UE sends a measurement report to the satellite. The satellite / source base station selects a candidate base station, which is connected to the satellite and belongs to an NTN.

[0103] For the sake of ease of description, this application does not strictly distinguish between base stations and satellites, that is, satellites in this application can also be referred to as base stations. However, it should be noted that candidate base stations / target base stations are all connected to satellites. For transparent forwarding satellites, satellites have the ability to perform frequency conversion, signal amplification, and filtering. Signal processing is completed at a ground base station connected to the satellite. The signals sent / received by the satellite are processed by the ground base station. For regenerative forwarding satellites, if the centralized unit CU is located in the ground network, the RRC signaling is also processed by the ground network. For switching between different satellites, interaction through inter-satellite links (regenerative forwarding) or ground stations / base stations (transparent forwarding) is required. This application mainly uses service link switching (cell / satellite / base station switching) as an example for explanation. For switching involving feeder links (ground station switching), the method proposed in this application can also be used.

[0104] It should be noted that before the UE sends the measurement report, the source base station / satellite where the UE is located (or the base station where the UE is located through the corresponding satellite) sends measurement configuration information to the UE, and the UE performs measurement according to the measurement configuration and sends a measurement report; the measurement report contains the UE's location information; the satellite determines that the UE has satellite access capability through the RRC signaling reported by the UE capability, and then sends the measurement configuration to the UE. The UE determines that the current cell is a satellite cell through a system message, such as the indication of the system information block SIB19, that is, the current cell can be connected to the satellite through the Uu interface for communication. The UE receives the measurement configuration and sends the measurement report to the satellite through the satellite transceiver function module; the measurement report also includes the measurement results of the serving cell and the neighboring cell;

[0105] It should be noted that the core network element Access and Mobility Function (AMF) sends the UE context to the source base station, which contains information about roaming and access restrictions. This information is provided when the connection is established or the last Tracking Area (TA) is updated;

[0106] It should be noted that the conditional switching in this application is illustrated using the radio access network RAN ​​switching as an example, that is, the switching preparation and switching execution stages do not involve interaction with the core network. In addition, the conditional switching process of this application is mainly for the service link, that is, the link switching between the UE and the satellite, and does not include the switching process of the feeder link.

[0107] In step 202 , the source base station / satellite determines whether to adopt conditional switching. If so, the process goes to step 203 ; otherwise, the process goes to step 219 .

[0108] It should be noted that the source cell where the UE is located can be a terrestrial network TN or a non-terrestrial network NTN, and the target cells are all non-terrestrial networks. If the source cell is a terrestrial network, the source base station determines the conditional handover and selects a candidate base station. The candidate base station can be connected to the satellite, that is, it belongs to the NTN;

[0109] The source base station / satellite receives the measurement report sent by the UE and determines whether to use conditional switching based on one of the following conditions: UE location, UE capability, operator policy, and service quality (QoS) requirements. For example, if the UE is located in an area that is difficult for the terrestrial network to cover but belongs to the NTN coverage area, the UE supports NTN communication, the operator wants to offload services (such as to achieve load balancing), and / or the UE's service requires a shorter delay, the satellite determines to use conditional switching. Otherwise, the traditional switching process can be used.

[0110] Step 203: The satellite sends a request message to the candidate base station.

[0111] The satellite selects a candidate base station based on one of the following criteria: measurement reports, base station location, handover requirements, base station capabilities (e.g., connectivity to a satellite ground station). The candidate base station determines a candidate cell. The satellite sends a conditional handover request to the candidate base station. The candidate base station may be one or more. If there are multiple candidate base stations, the satellite sends a conditional handover request message to each candidate base station. The satellite and the candidate base station interact to obtain a list of candidate cells.

[0112] The request message includes at least: target cell identifier, key, Cell-Radio Network Temporary Identifier (C-RNTI) of the UE in the source base station, Radio Resource Management (RRM) configuration (including UE inactivity time), access layer configuration (including antenna information and downlink carrier frequency), QoS flow to data radio bearer (DRB) mapping rules, SIB1 from the source base station, UE's capabilities for different radio access technologies (RAT), packet data unit (PDU) session related information, and may include beam measurement information reported by the UE. PDU session related information includes slice information and QoS profile of the QoS flow.

[0113] It should be noted that a satellite may be connected to multiple ground base stations, or a base station may be connected to multiple satellites. The conditional switching can be switching base stations, switching satellites, or switching cells (the base station and satellite remain unchanged);

[0114] Step 204: The source base station / satellite obtains candidate cell configuration information.

[0115] The candidate base station first performs access control. If slice information is sent to the candidate base station, slice-related access control needs to be performed. If a PDU session is associated with an unsupported slice, the candidate base station should reject such a PDU session.

[0116] The candidate base station sends the configuration information of the candidate cell to the source base station / satellite. The configuration information includes one of the following: candidate cell identifier, cell resource configuration information, SMTC or CSI-RS resource configuration information. The cell identifier is used to indicate the candidate cell, the resource configuration information is used for the UE to connect to the candidate cell that meets the conditions, the resource configuration is a random access resource or a PUSCH resource configuration, and the SMTC / CSI-RS is used by the UE to evaluate the signal quality of the candidate cell. Each candidate base station needs to send the configuration information of each candidate cell to the source base station / satellite.

[0117] The RRM configuration may include beam measurement information related to SSB (for Layer 3 mobility) and the CSI-RS of the reporting cell, if both types of measurements are available. In addition, if carrier aggregation is configured, the RRM configuration may include a list of the best cells on each frequency where measurement information can be obtained. The RRM measurement information may also include beam measurements for cells belonging to the target base station.

[0118] The common random access channel configuration for the beam in the target cell is associated only with the SSB. The network can have a dedicated RACH configuration associated with the SSB and / or a dedicated RACH configuration associated with the CSI-RS within the cell. The target base station can only configure one of the following RACH configurations in the "Handover Command" to enable the terminal to access the target cell:

[0119] i) General RACH configuration;

[0120] ii) Common RACH configuration + dedicated RACH configuration associated with SSB;

[0121] iii) General RACH configuration + dedicated RACH configuration associated with CSI-RS.

[0122] Dedicated RACH configuration allocates RACH resources and sets quality thresholds for using these resources. When dedicated RACH resources are provided, they are prioritized by the UE. As long as the quality thresholds for these dedicated resources are met, the UE will not switch to contention-based RACH resources. The order in which dedicated RACH resources are accessed is up to the UE implementation.

[0123] Step 205: The satellite sends a first message.

[0124] The first message includes a conditional handover execution condition, including: a time condition or a location condition. The time condition defines a time window in which the UE can perform CHO on the candidate cell, that is, the UE evaluates A3 / A4 / A5 from time t1-Threshold. If the execution condition is met within a limited duration (Duration), the UE is handed over to the designated neighboring cell; the location condition defines two distance thresholds from the UE to the source cell and from the UE to the candidate cell. The UE can perform CHO according to the distance threshold. That is, when the distance from the UE to the serving cell is greater than threshold 1 and the distance from the designated neighboring cell is less than threshold 2, the UE is handed over to the designated neighboring cell.

[0125] Furthermore, the first message also includes a reference signal condition, which includes one of the following: A3, A4, or A5. Reference signal condition A3 is satisfied when the reference signal quality of the neighboring cell exceeds the offset of the designated cell (e.g., the serving cell). Reference signal condition A4 is satisfied when the reference signal quality of the neighboring cell becomes better than a defined threshold. Reference signal condition A5 is satisfied when the reference signal quality of the designated cell becomes worse than threshold 1, while the reference signal quality of the neighboring cell becomes better than threshold 2. The reference signal includes one of the following: SSB and CSI-RS. Measurement includes one of the following: RSRP, RSRQ, and SINR.

[0126] The time condition or the location condition is configured together with one of the reference signal conditions (A3, A4 or A5), that is, conditional switching requires at least two conditions to be met simultaneously.

[0127] It should be noted that the first message may also be sent directly by the satellite, not carried in the first message, and carried through other information or signaling. This application does not specifically limit the carrying method of the first message.

[0128] Step 206: The UE evaluates candidate cells and selects a target cell.

[0129] After receiving the CHO configuration, the UE maintains a connection with the source base station / satellite and begins evaluating the CHO execution conditions of candidate cells. The target cell must meet at least two conditions: time condition T1 and reference signal condition A3 / A4 / A5, or location condition L1 and reference signal condition A3 / A4 / A5. The time condition, location condition, and reference signal condition A3 / A4 / A5 are as described in step 205, where the specific parameter values ​​are sent to the UE by the source base station / satellite via RRC signaling.

[0130] If there are multiple candidate cells that meet the execution conditions, the UE may select the cell that meets one of the following conditions as the target cell: the cell with the longest time condition, the best location (such as the nearest candidate cell), or the highest quality (such as the candidate cell with the highest signal quality in A3 / A4 / A5).

[0131] Step 207: The UE disconnects from the source cell and connects to the target cell.

[0132] If at least one CHO candidate cell meets the corresponding CHO execution conditions, the UE detaches from the source base station / satellite, applies the stored resource configuration of the selected candidate cell, connects to the candidate cell, and completes the conditional handover process by sending a message to the target base station / satellite. After the handover process is successfully completed, the UE releases the stored CHO configuration. If RACH-less handover is adopted, the UE directly sends PUSCH in the target cell according to the received configuration information. Otherwise, the UE uses the conflict-free resources in the configuration information to initiate a random access process in the target cell; if RACH-less handover fails, the UE can turn to RACH-based handover or initiate a cell selection process;

[0133] In step 208 , the UE determines whether the handover is successful. If so, the process goes to step 209 ; otherwise, the process goes to step 216 .

[0134] If the UE has established an RRC connection with the target cell, the handover is successful.

[0135] Step 209: The target cell indicates that the handover is successful.

[0136] The target cell establishes an RRC connection with the UE, indicating that the handover is successful. The target cell indicates the handover success to the satellite / source base station through the target base station.

[0137] Step 210: The satellite / source base station sends a state transition message to the target base station.

[0138] For DRBs that use PDCP state preservation, the state transition message conveys the uplink PDCP sequence number (SN) receiver status and the downlink PDCP SN transmitter status. The uplink PDCP SN receiver status includes at least the PDCP SN of the first lost uplink PDCP service data unit (SDU) and may include a bit mapping of the receiver status of out-of-sequence uplink PDCP SDUs that the terminal needs to retransmit in the target cell. The downlink PDCP SN transmitter status indicates the next PDCP SN that the target base station will assign to a new PDCP SDU that does not yet have an SN.

[0139] It should be noted that, if DAPS is adopted, the relocation message may be sent before the UE is connected to the target cell.

[0140] Step 211: The satellite / source base station sends a handover cancellation message to other candidate base stations.

[0141] The handover cancel message is used to cancel the conditional handover between the UE and other base stations.

[0142] Step 212: The target base station sends a path switching request message to the core network.

[0143] Trigger the core network to switch the downlink data path to the target base station and establish an interface instance to the target base station.

[0144] Step 213: The core network switches the downlink data path to the target base station.

[0145] The core network user plane function (UPF) sends one or more "end marker" messages to the source base station on the old path of each PDU session / tunnel, and then releases the user plane / transport layer resources for the source base station.

[0146] Step 214: The core network sends a path switch request confirmation message.

[0147] Step 215: The target base station sends a UE context release message.

[0148] The context release message is used to notify the source base station / satellite that the handover is successful. The source base station / satellite can release the radio and control plane related resources associated with the UE context; any ongoing data forwarding can continue;

[0149] Step 216: The UE initiates a cell selection process.

[0150] When the initial CHO attempt fails (e.g., radio link failure, reconfiguration failure, integrity check failure, etc.), the UE performs cell selection. If the selected cell is a CHO candidate cell, and if the network configures the UE to attempt CHO after a CHO failure, the UE attempts to perform CHO once. Otherwise, it performs a connection re-establishment procedure, i.e., the UE initiates an RRC connection re-establishment procedure towards the target cell. If the UE context cannot be retrieved, it enters the RRC connection establishment procedure.

[0151] The UE first selects a target cell from cells it has registered with before;

[0152] Step 217 , whether to perform conditional switching, if yes, go to step 207 , otherwise go to step 218 .

[0153] If the cell selected by the UE belongs to the candidate CHO cell and the satellite / source base station instructs the UE to continue to try CHO once after the CHO failure, the UE attempts CHO again; otherwise, the UE performs the RRC connection reestablishment process in the selected cell.

[0154] Step 218: The UE initiates an RRC connection reestablishment process in the selected cell.

[0155] If the UE context information can be retrieved in the selected cell, the reestablishment is completed, otherwise the connection is made to the selected cell through the RRC connection procedure.

[0156] Step 219: Initiate a traditional handover process.

[0157] If the satellite determines that conditional handover is not adopted, it sends a handover command, such as an RRCReconfiguration message, to the UE to enter the traditional handover process.

[0158] The present application also provides a conditional switching device. FIG6 is a schematic diagram of the structure of a conditional switching device provided by an embodiment. As shown in FIG6, the conditional switching device includes:

[0159] The information acquisition module 310 is configured to acquire configuration information of the candidate cell when it is determined that the second communication node performs conditional handover;

[0160] a message sending module 320, configured to send a first message to the second communication node, where the first message includes configuration information of the candidate cell and an execution condition of the conditional handover, and the first message is used to instruct the second communication node to select a candidate cell that meets the execution condition as a target cell among the candidate cells and to handover to the target cell according to the configuration information;

[0161] Wherein, in the case that the target cell is a non-terrestrial network cell, the execution condition includes a reference signal condition and an execution state condition.

[0162] The conditional handover apparatus of this embodiment can instruct the second communication node, via a first message, to evaluate candidate cells based on execution conditions. If at least one candidate cell meeting the execution conditions is found, it can be selected as the target cell for conditional handover, and handover to the target cell will be performed based on the configuration information of the target cell. The execution conditions and candidate cells are preconfigured before conditional handover is performed, rather than calculated and determined in real time. This reduces signaling overhead and processing latency. Furthermore, based on the characteristics of NTN communications, the execution conditions take into account not only reference signal conditions but also location conditions or satellite service time conditions. This improves the success rate of conditional handover, prevents the second communication node from switching too early or too late, avoids frequent handovers, and improves service quality.

[0163] In one embodiment, when the candidate cells satisfying the execution condition include terrestrial network candidate cells and non-terrestrial network candidate cells, the target cell is a terrestrial network candidate cell.

[0164] In one embodiment, the terrestrial network candidate cells and the non-terrestrial network candidate cells are distinguished by fields in a cell system broadcast message; the terrestrial network candidate cells and the non-terrestrial network candidate cells correspond to different execution conditions.

[0165] In one embodiment, the apparatus further comprises:

[0166] a handover determination module, configured to determine whether the second communication node performs conditional handover based on at least one of the following information: a measurement report, a capability of the second communication node, a position of the second communication node, and satellite ephemeris;

[0167] The capabilities of the second communication node include the capability to support non-terrestrial network communications and the capability to support global navigation satellite system GNSS positioning.

[0168] In one embodiment, the configuration information of the candidate cell includes a cell identifier and cell resource configuration information;

[0169] Alternatively, the configuration information of the candidate cell includes a cell identifier, cell resource configuration information, and at least one of the following: synchronization block measurement timing configuration, channel state information reference signal CSI-RS resource location information;

[0170] In the case that the candidate cell is a non-terrestrial network cell, the synchronization block measurement timing configuration includes at least two.

[0171] In one embodiment, the execution state condition includes at least one of a time condition and a location condition; the time condition is used to indicate a time window in which the second communication node can perform conditional switching on the candidate cell;

[0172] The location condition is used to indicate a first distance threshold from the second communication node to the source cell and a second distance threshold from the second communication node to the candidate cell.

[0173] In one embodiment, the reference signal condition is a measurement report triggering event for conditional switching.

[0174] In one embodiment, the first message is sent via radio resource control (RRC) reconfiguration signaling.

[0175] In one embodiment, the execution condition is determined based on satellite ephemeris information, the position of the second communication node, and a reference signal reception parameter;

[0176] The reference signal reception parameter includes a reference signal reception strength RSRP or a reference signal reception quality RSRQ.

[0177] In one embodiment, the apparatus further comprises:

[0178] A range determination module, configured to determine a time range for the execution condition;

[0179] The first message is used to instruct the second communication node to switch to a target cell that meets the execution condition within the time range.

[0180] In one embodiment, the apparatus further comprises:

[0181] The information sending module is configured to send conditional switching configuration information, where the conditional switching configuration information includes satellite ephemeris information, a common timing advance (TA) parameter, a start time, and a valid time.

[0182] In one embodiment, the reference signal condition includes at least one of the following:

[0183] The reference signal quality of the neighboring cell exceeds the reference signal quality of the designated cell by a preset offset;

[0184] The reference signal quality of the neighboring cell is higher than the preset threshold;

[0185] The reference signal quality of the designated cell is lower than a first threshold, and the reference signal quality of the neighboring cell is higher than a second threshold.

[0186] The reference signal includes at least one of the following: synchronization signal block SSB, CSI-RS.

[0187] In one embodiment, the apparatus further comprises:

[0188] The configuration sending module is configured to send the user plane configuration of the target cell to the second communication node, where the user plane configuration includes: adding the satellite-to-ground round-trip time to the user plane timer time.

[0189] In one embodiment, the apparatus further comprises:

[0190] The status sending module is configured to send status information, wherein the status information includes a PDCP number, and the status information is used to indicate the sending status of uplink data and downlink data of the Uu air interface.

[0191] In one embodiment, the apparatus further comprises:

[0192] The forwarding module is configured to forward data to the candidate base station after the second communication node successfully accesses the target base station when DAPS switching is not configured; and forward data to the candidate base station before the second communication node switching is completed when DAPS switching is configured.

[0193] In one embodiment, the apparatus further comprises:

[0194] The sending module is configured to send a state migration message to the target base station and a switching cancellation message to the candidate base station after the second communication node switches to the target cell.

[0195] The conditional switching device proposed in this embodiment and the conditional switching method proposed in the above embodiment belong to the same inventive concept. Technical details not fully described in this embodiment can be referred to any of the above embodiments, and this embodiment has the same beneficial effects as executing the conditional switching method.

[0196] The present application also provides a conditional switching device. FIG7 is a schematic diagram of the structure of a conditional switching device provided by an embodiment. As shown in FIG7, the conditional switching device includes:

[0197] The message receiving module 410 is configured to receive a first message, where the first message includes configuration information of a candidate cell and an execution condition of conditional switching.

[0198] a handover module 420 configured to select a candidate cell that meets the execution condition from the candidate cells as a target cell, and hand over to the target cell according to the configuration information;

[0199] Wherein, in the case that the target cell is a non-terrestrial network cell, the execution condition includes a reference signal condition and an execution state condition.

[0200] The conditional handover apparatus of this embodiment can instruct the second communication node, via a first message, to evaluate candidate cells based on execution conditions. If at least one candidate cell meeting the execution conditions is found, it can be selected as the target cell for conditional handover, and handover to the target cell will be performed based on the configuration information of the target cell. The execution conditions and candidate cells are preconfigured before conditional handover is performed, rather than calculated and determined in real time. This reduces signaling overhead and processing latency. Furthermore, based on the characteristics of NTN communications, the execution conditions take into account not only reference signal conditions but also location conditions or satellite service time conditions. This improves the success rate of conditional handover, prevents the second communication node from switching too early or too late, avoids frequent handovers, and improves service quality.

[0201] In one embodiment, the switching module 420 includes:

[0202] The selection unit is configured to preferentially select the terrestrial network candidate cell as the target cell when the candidate cells meeting the execution condition include the terrestrial network candidate cell and the non-terrestrial network candidate cell.

[0203] In one embodiment, the switching module 420 includes:

[0204] A switching unit is configured to switch to the target cell in a manner without a random access process according to the configuration information, and establish an RRC connection with the target cell; when the switching without the random access process fails or the switching without the random access process is not enabled, switching to the target cell based on the random access process, wherein the random access resources are dedicated resources without conflict.

[0205] In one embodiment, the apparatus further comprises:

[0206] The unconditional switching module is configured to perform unconditional switching upon receiving a switching command for unconditional switching sent by the first communication node during the conditional switching process of the second communication node.

[0207] In one embodiment, the apparatus further comprises:

[0208] A cell selection module configured to initiate a cell selection process if conditional handover execution fails;

[0209] The re-execution module is configured to re-execute the conditional handover if the selected cell is a candidate cell and the conditional handover is enabled when the conditional handover fails; otherwise, the RRC connection re-establishment process is initiated in the selected cell.

[0210] In one embodiment, the switching module 420 includes:

[0211] The connection unit is configured to, when DAPS is configured, establish a connection with the target cell while maintaining the connection with the source cell, and release the connection with the source cell after successfully accessing the target cell; when DAPS is not configured, first disconnect the connection with the source cell and then connect to the target cell.

[0212] The conditional switching device proposed in this embodiment and the conditional switching method proposed in the above embodiment belong to the same inventive concept. Technical details not fully described in this embodiment can be referred to any of the above embodiments, and this embodiment has the same beneficial effects as executing the conditional switching method.

[0213] An embodiment of the present application also provides a communication node. Figure 8 is a schematic diagram of the hardware structure of a communication node provided by an embodiment. As shown in Figure 8, the communication node provided by the present application includes a processor 510 and a memory 520; the processor 510 in the communication node can be one or more, and Figure 8 takes one processor 510 as an example; the memory 520 is configured to store one or more programs; the one or more programs are executed by the one or more processors 510, so that the one or more processors 510 implement the conditional switching method as described in the embodiment of the present application.

[0214] The communication node further includes: a communication device 530 , an input device 540 and an output device 550 .

[0215] The processor 510, memory 520, communication device 530, input device 540 and output device 550 in the communication node may be connected via a bus or other means. FIG8 takes the bus connection as an example.

[0216] The input device 540 may be used to receive input digital or character information and generate key signal input related to user settings and function control of the communication node. The output device 550 may include a display device such as a display screen.

[0217] The communication device 530 may include a receiver and a transmitter. The communication device 530 is configured to perform information transmission and reception communication according to the control of the processor 510.

[0218] The memory 520, as a computer-readable storage medium, may be configured to store software programs, computer executable programs, and modules, such as program instructions / modules corresponding to the conditional switching method described in the embodiment of the present application (e.g., the information acquisition module 310 and the message sending module 320 in the conditional switching device). The memory 520 may include a program storage area and a data storage area, wherein the program storage area may store an operating system, an application required for at least one function; and the data storage area may store data created according to the use of the communication node. In addition, the memory 520 may include a high-speed random access memory and may further include a non-volatile memory, such as at least one disk storage device, a flash memory device, or other non-volatile solid-state storage device. In some instances, the memory 520 may further include a memory remotely arranged relative to the processor 510, and these remote memories may be connected to the communication node via a network. Examples of the above-mentioned networks include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network, and combinations thereof.

[0219] The embodiment of the present application also provides a storage medium, the storage medium stores a computer program, and the computer program, when executed by a processor, implements the conditional switching method described in any one of the embodiments of the present application. The method includes: when determining that the second communication node performs conditional switching, obtaining configuration information of the candidate cell; sending a first message to the second communication node, the first message including the configuration information of the candidate cell and the execution condition of the conditional switching, the first message being used to instruct the second communication node to select a candidate cell that meets the execution condition as the target cell in the candidate cell and switch to the target cell according to the configuration information; wherein, in the case where the target cell is a non-terrestrial network cell, the execution condition includes a reference signal condition and an execution state condition. Alternatively, the method includes: receiving a first message, the first message including the configuration information of the candidate cell and the execution condition of the conditional switching; selecting a candidate cell that meets the execution condition as the target cell in the candidate cell, and switching to the target cell according to the configuration information; wherein, in the case where the target cell is a non-terrestrial network cell, the execution condition includes a reference signal condition and an execution state condition.

[0220] The computer storage medium of the embodiment of the present application can adopt any combination of one or more computer-readable media.Computer-readable media can be computer-readable signal media or computer-readable storage media.Computer-readable storage media can be, for example, but not limited to: electrical, magnetic, optical, electromagnetic, infrared, or semiconductor systems, devices or devices, or any combination of the above.More specific examples (non-exhaustive list) of computer-readable storage media include: electrical connections with one or more wires, portable computer disks, hard disks, random access memories (RAM), read-only memories (ROM), erasable programmable read-only memories (EPROM), flash memories, optical fibers, portable CD-ROMs, optical storage devices, magnetic storage devices, or any suitable combination of the above.Computer-readable storage media can be any tangible medium containing or storing a program, which can be used by an instruction execution system, device or device or used in combination with it.

[0221] A computer-readable signal medium may include a data signal propagated in baseband or as part of a carrier wave, carrying computer-readable program code. Such a propagated data signal may take a variety of forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination thereof. A computer-readable signal medium may also be any computer-readable medium other than a computer-readable storage medium that can transmit, propagate, or transport a program for use by or in conjunction with an instruction execution system, apparatus, or device.

[0222] The program code contained on the computer-readable medium may be transmitted using any appropriate medium, including but not limited to wireless, wire, optical cable, radio frequency (RF), etc., or any suitable combination thereof.

[0223] The computer program code for performing the operations of the present application can be written in one or more programming languages ​​or a combination thereof, including object-oriented programming languages ​​such as Java, Smalltalk, C++, and conventional procedural programming languages ​​such as "C" or similar programming languages. The program code can be executed entirely on the user's computer, partially on the user's computer, as an independent software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In the case of a remote computer, the remote computer can be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or can be connected to an external computer (e.g., using an Internet service provider to connect via the Internet).

[0224] The above description is merely an exemplary embodiment of the present application and is not intended to limit the scope of protection of the present application.

[0225] It will be appreciated by those skilled in the art that the term user terminal covers any suitable type of wireless user equipment, such as a mobile phone, a portable data processing device, a portable web browser or a vehicle-mounted mobile station.

[0226] In general, various embodiments of the present application may be implemented in hardware or dedicated circuits, software, logic, or any combination thereof. For example, some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software that can be executed by a controller, microprocessor, or other computing device, although the present application is not limited thereto.

[0227] Embodiments of the present application may be implemented by executing computer program instructions by a data processor of a mobile device, for example, in a processor entity, or by hardware, or by a combination of software and hardware. The computer program instructions may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, state setting data, or source code or object code written in any combination of one or more programming languages.

[0228] The block diagram of any logic flow in the drawings of this application may represent program steps, or may represent interconnected logic circuits, modules and functions, or may represent a combination of program steps and logic circuits, modules and functions. A computer program may be stored on a memory. The memory may be of any type suitable for the local technical environment and may be implemented using any suitable data storage technology, such as but not limited to read-only memory (ROM), random access memory (RAM), optical storage devices and systems (digital versatile discs (DVD) or compact disks (CD), etc.). Computer-readable media may include non-transitory storage media. The data processor may be of any type suitable for the local technical environment, such as but not limited to a general-purpose computer, a special-purpose computer, a microprocessor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), and a processor based on a multi-core processor architecture.

[0229] The above description of exemplary embodiments of the present application has been provided by way of exemplary and non-limiting examples. However, various modifications and adaptations of the above embodiments will be apparent to those skilled in the art, when considered in conjunction with the accompanying drawings and the appended claims, without departing from the scope of the present application. Therefore, the proper scope of the present application will be determined by reference to the appended claims.

Claims

1. A conditional switching method, applied to a first communication node, comprising: When it is determined that the second communication node performs conditional switching, obtaining configuration information of the candidate cell; Sending a first message to the second communication node, the first message including configuration information of the candidate cell and an execution condition of conditional switching, the first message being used to instruct the second communication node to select a candidate cell that meets the execution condition as a target cell among the candidate cells and switch to the target cell according to the configuration information; Wherein, in the case that the target cell is a non-terrestrial network cell, the execution condition includes a reference signal condition and an execution state condition.

2. The method according to claim 1, wherein: In a case where the candidate cells satisfying the execution condition include terrestrial network candidate cells and non-terrestrial network candidate cells, the target cell is a terrestrial network candidate cell.

3. The method according to claim 2, wherein: The terrestrial network candidate cells and the non-terrestrial network candidate cells are distinguished by fields in a cell system broadcast message; The terrestrial network candidate cells and the non-terrestrial network candidate cells correspond to different execution conditions.

4. The method according to claim 1, further comprising: Determine whether the second communication node performs conditional switching according to at least one of the following information: a measurement report, a capability of the second communication node, a position of the second communication node, and satellite ephemeris; The capabilities of the second communication node include the capability of supporting non-terrestrial network communications and the capability of supporting global navigation satellite system GNSS positioning.

5. The method according to claim 1, wherein: The configuration information of the candidate cell includes a cell identifier and cell resource configuration information; Alternatively, the configuration information of the candidate cell includes a cell identifier, cell resource configuration information, and at least one of the following: synchronization block measurement timing configuration, channel state information reference signal CSI-RS resource location information; In the case that the candidate cell is a non-terrestrial network cell, the synchronization block measurement timing configuration includes at least two.

6. The method according to claim 1, wherein: The execution state condition includes at least one of a time condition and a location condition; The time condition is used to indicate a time window in which the second communication node can perform conditional switching on the candidate cell; The location condition is used to indicate a first distance threshold from the second communication node to the source cell and a second distance threshold from the second communication node to the candidate cell.

7. The method according to claim 1, wherein: The reference signal condition is a measurement report triggering event for conditional switching.

8. The method according to claim 1, wherein: The first message is sent via radio resource control RRC reconfiguration signaling.

9. The method according to claim 1, wherein: The execution condition is determined according to satellite ephemeris information, the position of the second communication node, and a reference signal reception parameter; The reference signal reception parameter includes a reference signal reception strength RSRP or a reference signal reception quality RSRQ.

10. The method according to claim 1, further comprising: Determine the time frame for the execution of the conditions; The first message is used to instruct the second communication node to switch to a target cell that meets the execution condition within the time range.

11. The method according to claim 1, further comprising: The conditional switching configuration information is sent, where the conditional switching configuration information includes satellite ephemeris information, a common timing advance TA parameter, a start time, and a valid time.

12. The method according to claim 1, wherein: The reference signal condition includes at least one of the following: The reference signal quality of the neighboring cell exceeds the reference signal quality of the designated cell by a preset offset; The reference signal quality of the neighboring cell is higher than a preset threshold; The reference signal quality of the designated cell is lower than the first threshold, and the reference signal quality of the neighboring cell is higher than The second threshold; The reference signal includes at least one of the following: synchronization signal block SSB, CSI-RS.

13. The method according to claim 1, further comprising: Sending a user plane configuration of the target cell to the second communication node, the user plane configuration comprising: adding a satellite-to-ground round-trip time to a user plane timer time.

14. The method according to claim 1, further comprising: Sending status information, the status information includes a Packet Data Convergence Protocol PDCP number, and the status information is used to indicate the sending status of Uu air interface uplink data and downlink data.

15. The method according to claim 1, further comprising: When dual-activation protocol stack DAPS switching is not configured, after the second communication node successfully accesses the target base station, forwarding data to the candidate base station; In case of configuring DAPS switching, before the second communication node switching is completed, the data is forwarded to the candidate base station.

16. The method according to claim 1, further comprising: After the second communication node switches to the target cell, it sends a state migration message to the target base station and sends a switching cancellation message to the candidate base station.

17. A conditional switching method, applied to a second communication node, comprising: receiving a first message, wherein the first message includes configuration information of a candidate cell and an execution condition of conditional switching; Selecting a candidate cell that meets the execution condition from the candidate cells as a target cell, and switching to the target cell according to the configuration information; Wherein, in the case that the target cell is a non-terrestrial network cell, the execution condition includes a reference signal condition and an execution state condition.

18. The method according to claim 17, wherein: Selecting a candidate cell that meets the execution condition from the candidate cells as a target cell includes: The candidate cells that meet the execution conditions include ground network candidate cells and non-ground network candidate cells. In this case, a ground network candidate cell is selected as the target cell.

19. The method according to claim 17, wherein: Switching to the target cell according to the configuration information includes: According to the configuration information, switching to the target cell in a manner without a random access process, and establishing a radio resource control RRC connection with the target cell; In case that the handover without random access procedure fails or the handover without random access procedure is not enabled, the handover to the target cell is based on the random access procedure, wherein the random access resources are non-conflicting dedicated resources.

20. The method of claim 17, further comprising: During the conditional switching process of the second communication node, when receiving the switching command of the unconditional switching sent by the first communication node, the unconditional switching is performed.

21. The method of claim 17, further comprising: In case of failure of conditional handover execution, the cell selection process is started; If the selected cell is a candidate cell and the conditional handover enabling is attempted again when the conditional handover execution fails, the conditional handover is performed again; otherwise, the RRC connection reestablishment process is initiated in the selected cell.

22. The method according to claim 17, wherein: Switching to the target cell according to the configuration information includes: When the dual activation protocol stack DAPS is configured, establishing a connection with the target cell while maintaining a connection with the source cell, and releasing the connection with the source cell after successfully accessing the target cell; When DAPS is not configured, the connection with the source cell is first disconnected and then connected to the target cell.

23. A communication node, comprising: at least one processor; a storage device configured to store at least one program; When the at least one program is executed by the at least one processor, the at least one processor implements the conditional switching method as described in any one of claims 1 to 22.

24. A computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the conditional switching method according to any one of claims 1 to 22.

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