Satellite switching method, communication device, storage medium and computer program product

Abstract

The invention relates to the technical field of communication, and particularly provides a satellite switching method, a communication device, a storage medium and a computer program product, and the method comprises the steps: a source satellite can determine a target group, the target group can comprise a plurality of terminals needing to execute satellite switching, the plurality of terminals can be subjected to category division, and the plurality of terminals can be subjected to category division; the group terminal is divided into a group head terminal and a group member terminal, the group head terminal is switched to a target satellite through an RACH mechanism, and the group member terminal is switched to the target satellite through an RACHless switching mechanism. Compared with the RACH switching mechanism, the RACH switching mechanism has the advantages that the operation process is simpler, the signaling overhead can be greatly reduced by controlling a large number of group members to execute RACH switching, the network congestion is reduced, and the network performance is greatly improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of communication technology, in particular to a satellite switching method, a communication device, a storage medium and a computer program product. BACKGROUND

[0002] LEO (Low Earth Orbit) satellite system refers to a system composed of a group of satellites running in a low orbit (generally not more than 2000 kilometers) from the earth's surface. The terminal located on the ground can select to access the satellite in the LEO satellite system to obtain the wireless network service provided by the satellite.

[0003] Due to the change of satellite position or user position, the terminal accessing the wireless network needs to switch satellites. When the number of users simultaneously initiating switching is large, grouping the terminals first can effectively improve the switching efficiency and reduce the switching cost.

[0004] However, even if the terminals are grouped and then the satellite switching is performed, each terminal still needs to perform the same switching signaling in the switching process, resulting in a large signaling overhead and waste of communication resources. SUMMARY

[0005] The present application is proposed in view of the above problems. The present application provides a satellite switching method, a communication device, a storage medium and a computer program product.

[0006] According to an aspect of the present application, a satellite switching method is provided, applied to a source satellite, and the method comprises:

[0007] determining a target group, the target group comprising a plurality of terminals needing to perform satellite switching;

[0008] determining a group leader terminal and a group member terminal in the target group, the group leader terminal being a terminal having the highest similarity to the switching trigger time of other terminals in the target group, and the group member terminal being a terminal other than the group leader terminal in the target group;

[0009] controlling the group leader terminal to switch to a target satellite through a RACH (Random Access Channel) switching mechanism;

[0010] controlling the group member terminal to switch to the target satellite through a RACH_less (Random Access Channel-less) switching mechanism.

[0011] According to another aspect of the present application, a communication method is provided, applied to a target satellite, comprising:

[0012] receive first indication information sent by the source satellite, the first indication information being sent by a group leader terminal after receiving a switching command sent by the source satellite, the first indication information including a random access preamble, the group leader terminal being a terminal that has the highest similarity to a switching trigger time of other terminals in a target group, the target group including a plurality of terminals that need to perform satellite switching, and a terminal in the target group other than the group leader terminal being referred to as a group terminal;

[0013] send a RAR (Random Access Response) message to the group leader terminal, the RAR message instructing the group leader terminal to perform RACH switching to switch to the target satellite, and the RAR message containing uplink TA (Timing Advance) of the target satellite;

[0014] receive a switching completion message sent by the group leader terminal, the switching completion message including uplink timing advance TA and group information of the target group, a target message identifier, and a converted PDU (Protocol Data Unit) session list;

[0015] send a first confirmation message to the source satellite, the first confirmation message being used to indicate that the group leader terminal has completed switching and instruct group member terminals to perform RACH_less switching to switch to the target satellite based on the uplink timing advance TA included in the first confirmation message.

[0016] According to still another aspect of the present application, a satellite switching method is provided, applied to a group leader terminal, and including:

[0017] receive a switching command sent by a source satellite, the switching command instructing the group leader terminal to send first indication information to a target satellite, the first indication information including a random access preamble and being used to instruct the target satellite to send a RAR message to the group leader terminal, the RAR message containing uplink timing advance TA of the target satellite;

[0018] receive a RAR message sent by the target satellite;

[0019] switch to the target satellite through a RACH switching mechanism;

[0020] send a switching completion message to the target satellite, the switching completion message including uplink timing advance TA and group information of the target group, a target message identifier, and a converted PDU session list, the switching completion message instructing the target satellite to send a first confirmation message to the source satellite, the first confirmation message being used to indicate that the group leader terminal has completed switching, the first confirmation message including the uplink timing advance TA, the uplink timing advance TA being used for group member terminals to perform RACH_less switching to switch to the target satellite, and the group leader terminal and the group member terminals belonging to the same target group.

[0021] According to another aspect of the present application, a satellite switching method is provided, which is applied to a group member terminal, and the method comprises:

[0022] receiving a broadcast message sent by a source satellite, the broadcast message comprising: uplink timing advance TA of a target satellite, group information of a target group, and switching indication information; the broadcast message is sent by the source satellite after determining that a group leader terminal has performed RACH switching to the target satellite; the group member terminal and the group leader terminal belong to the target group;

[0023] obtaining the uplink timing advance TA and the switching indication information from the broadcast message;

[0024] performing RACH_less switching by using the uplink timing advance TA according to the switching indication information, so as to switch to a target cell of the target satellite; after determining that the group member terminal is successfully accessed, the target satellite sends a second confirmation message of the group member terminal to the source satellite, and the second confirmation message indicates that the satellite switching of the group member terminal is completed.

[0025] According to another aspect of the present application, a communication device is provided, which can store a memory, a processor, and a computer program stored in the memory, and the processor executes the computer program to implement any of the above satellite switching methods. The communication device can be a terminal or a satellite, for example.

[0026] According to another aspect of the present application, a computer readable storage medium is provided, which stores a computer program / instruction, and the computer program is executed by a processor to implement the steps of any of the above satellite switching methods.

[0027] According to another aspect of the present application, a computer program product is provided, which comprises a computer program, and the computer program / instruction is executed by a processor to implement the steps of any of the above satellite switching methods.

[0028] As will be described in detail below, according to the satellite switching method of the embodiments of the present application, the source satellite can determine a target group, and the target group can include a plurality of terminals that need to perform satellite switching, and the plurality of terminals can be classified into a group leader terminal and a group member terminal. The group leader terminal is switched to the target satellite through a RACH mechanism, and the group member terminal is switched to the target satellite through a RACH_less switching mechanism. The RACH_less switching mechanism has a relatively simple operation process compared with the RACH switching mechanism, and controlling a large number of group members to perform RACH_less switching can greatly reduce signaling overhead, reduce network congestion, and greatly improve network performance.

[0029] It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the subject technology. BRIEF DESCRIPTION OF DRAWINGS

[0030] The above and other objects, features and advantages of the present application will become more apparent from the following detailed description thereof taken in conjunction with the accompanying drawings, in which:

[0031] Figure 1 is a schematic diagram illustrating a communication system to which an embodiment of the present application is applied;

[0032] Figure 2 is a flowchart illustrating a satellite handover method according to an embodiment of the present application;

[0033] Figure 3 is a flowchart illustrating a satellite handover method according to another embodiment of the present application;

[0034] Figure 4 is a flowchart illustrating a satellite handover method according to another embodiment of the present application;

[0035] Figure 5 is a flowchart illustrating a satellite handover method according to another embodiment of the present application;

[0036] Figure 6 is a signaling diagram illustrating a satellite handover method according to another embodiment of the present application;

[0037] Figure 7 is a block diagram illustrating a communication device according to an embodiment of the present application;

[0038] Figure 8 is a block diagram illustrating a communication device according to an embodiment of the present application. DETAILED DESCRIPTION

[0039] In order to make the objects, technical solutions and advantages of the present application clearer, the following will describe example embodiments according to the present application in detail with reference to the accompanying drawings. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments of the present application. It should be understood that the present application is not limited to the example embodiments described herein.

[0040] The technical solutions of the embodiments of the present application can be applied to various communication systems, for example: a wireless local area network (WLAN) communication system, a long term evolution (LTE) system, an LTE frequency division duplex (FDD) system, an LTE time division duplex (TDD), a 5th generation (5G) system or a new radio (NR), a 6th generation (6G) system, a worldwide interoperability for microwave access (WiMAX) communication system, or other evolved communication systems, and the like.

[0041] The terminal in the embodiments of the present application can also be referred to as a user equipment (UE), a mobile station (MS), a mobile terminal (MT), an access terminal, a subscriber unit, a subscriber station, a mobile station, a mobile terminal, a remote station, a remote terminal, a mobile device, a user terminal, a terminal, a wireless communication device, a user agent, or a user device, and the like.

[0042] Some examples of the terminal are: a vehicle, a mobile phone, a tablet computer, a notebook computer, a palm computer, a mobile internet device (MID), a wearable device, a virtual reality (VR) device, an augmented reality (AR) device, a wireless terminal in industrial control, a wireless terminal in self driving, a wireless terminal in remote medical surgery, a wireless terminal in a smart grid, a wireless terminal in transportation safety, a wireless terminal in a smart city, a wireless terminal in a smart home, a cellular phone, a cordless phone, a session initiation protocol (SIP) phone, a wireless local loop (WLL) station, a personal digital assistant (PDA), a handheld device with wireless communication function, a computing device or other processing device connected to a wireless modem, an in-vehicle device, a wearable device, a drone, a terminal in a 5G network, or a terminal in a future evolved public land mobile network (PLMN), etc. The embodiments of the present application are not limited thereto.

[0043] In addition, the satellite in the embodiments of the present application can be a satellite base station in a satellite communication system, can be a device of various forms in a satellite system that undertakes the function of a base station, etc. The embodiments of the present application are not limited thereto.

[0044] As shown in Figure 1 The communication system in the embodiments of the present application can include a satellite system 10 located in a low earth orbit (LEO), wherein the satellite system 10 can include a plurality of satellites 101 distributed in a link form or a mesh structure, and each satellite can provide wireless communication services for terminals in its coverage range. As shown in Figure 1 The satellite 101 in the satellite system 10 can provide wireless communication services for the terminals 201 in its coverage range 20.

[0045] In practical applications, the position of the terminal or the position of the satellite accessed by the terminal is constantly changing, so the satellite accessed by the terminal needs to be switched. With the rapid development of LEO satellite networks, the number of users and the amount of business are rapidly increasing, and the cost of switching decisions is also increasing. In particular, for groups of ground users in hot areas, users are concentrated in a fixed range, so batch users may initiate concurrent switching, resulting in a large number of request messages in the network, causing network congestion, and greatly reducing network performance.

[0046] To solve the above problems, in the embodiments of the present application, the terminals in the group are classified into group leader terminals and group member terminals, and the group leader terminals are switched to the target satellite through the RACH (Random Access Channel) mechanism, and the group member terminals are switched to the target satellite through the RACH_less switching mechanism. The RACH_less (Random Access Channel-less) switching mechanism has a relatively simple operation process compared to the RACH switching mechanism, and controlling a large number of group members to perform RACH_less switching can greatly reduce signaling overhead, reduce network congestion, and greatly improve network performance.

[0047] The two switching methods involved in the present application will be introduced as follows:

[0048] 1. RACH switching:

[0049] A1. The source base station decides that the UE needs to perform switching, sends a switching request message to the target base station, and includes the target cell identifier, UE-related information, and the like.

[0050] A2. After the target base station receives the switching request, it performs admission control, and if the switching is allowed, it prepares for switching and sends a switching request confirmation to the source base station.

[0051] A3. The source base station triggers the switching by sending an RRC (Radio Resource Control) Reconfiguration message to the UE, which includes information required for accessing the target cell, such as the target cell identifier, the selected target base station security algorithm identifier, and the like.

[0052] A4. After the UE receives the RRC Reconfiguration message, it synchronizes with the target cell and completes the RRC switching process by sending an RRC Reconfiguration Complete message to the target base station. In this process, the UE may need to use RACH resources to achieve uplink synchronization and access to the target cell.

[0053] 2. RACH-less handover

[0054] B1, Preparation phase: UE gets TA (Timing Advance) value from network side.

[0055] B2, Source base station decides to handover the UE according to measurement report and RRM (Radio Resource Management) information, and sends handover request message to target base station. After the target base station is ready for handover, the source base station triggers the handover by sending RRCReconfiguration message to the UE, which contains information required for accessing the target cell, such as target cell identity, selected target base station security algorithm identifier, etc., and can also include a set of dedicated RACH resources, association between RACH resources and SSB (Synchronization Signal Block), etc., where the TA value of the candidate cell is also indicated.

[0056] B3, After receiving the RRCReconfiguration message, the UE applies the TA value measured by itself or the TA value carried in the message, synchronizes with the target cell, and sends RRCReconfigurationComplete message on PUSCH (Physical Uplink Shared Channel) to complete the RRC (Radio Resource Control) handover process.

[0057] Compared with RACH handover, in the RACH-less handover process, there is no preamble transmission and response message or message transmission, so the handover efficiency is higher.

[0058] In order to clearly describe the technical solutions of the embodiments of the present application, in the embodiments of the present application, the same items or similar items with basically the same functions and effects are distinguished by using "first", "second", etc. For example, the first information and the second information are used to distinguish different information, and the order is not limited. Those skilled in the art can understand that "first", "second", etc. do not limit the quantity and execution order, and "first", "second", etc. also do not mean that they must be different.

[0059] It should be noted that in the present application, "exemplarily" or "for example" and the like are used to represent as an example, illustration or description. Any embodiment or design scheme described as "exemplarily" or "for example" in the present application should not be interpreted as more preferred or more advantageous than other embodiments or design schemes. In fact, the use of "exemplarily" or "for example" and the like is intended to present the relevant concept in a specific way.

[0060] Furthermore, "at least one" refers to one or more, while "more than one" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can mean: A alone, A and B simultaneously, or B alone, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one of a, b, and c can mean: a, or b, or c, or a and b, or a and c, or b and c, or a, b, and c, where a, b, and c can be single or multiple.

[0061] The various embodiments provided in this application will now be described in detail.

[0062] This application describes embodiments using terminals and network devices as examples. It should be understood that the terminal can be replaced with a device or chip capable of performing similar functions. Similarly, the network device can be replaced with a device or chip capable of performing similar functions; the names of these devices are not limited in this application. The relationship between the terminal and the network device can be one-to-one, one-to-many, many-to-one, or many-to-many. The number of terminals or network devices is not excessively limited in this application. The network composed of terminals and network devices can be a micro-domain network.

[0063] like Figure 2 The diagram shown is a flowchart of a satellite handover method provided in an embodiment of this application. This satellite handover method can be applied to a source satellite and may include the following steps:

[0064] S201. Identify the target group. The target group includes multiple terminals that require satellite handover.

[0065] Optionally, the target group can be a group determined by the source satellite from one or more groups.

[0066] One or more groups can be obtained by grouping multiple terminals by the source satellite.

[0067] Specifically, the source satellite can group terminals that meet similarity criteria into one or more groups. Therefore, a group or target group may include one or more terminals that need to perform satellite handover and meet similarity criteria.

[0068] S202. Identify the group leader terminal and group member terminals in the target group. The group leader terminal is the terminal whose handover trigger time is most similar to that of other terminals in the target group, and the group member terminals are the terminals in the group other than the group leader terminal.

[0069] Optionally, the source satellite can determine the terminal with the highest similarity as the group leader terminal and the remaining terminals as group member terminals according to the similarity of the switching trigger time of the terminal and other terminals.

[0070] The switching trigger time refers to the time when the terminal triggers the satellite to switch.

[0071] The switching trigger time of the terminal and the switching trigger time of other terminals can be compared for similarity to obtain the similarity of the terminal and other terminals, and the terminal with the highest similarity is determined as the group leader terminal.

[0072] When the other terminals include multiple terminals, the terminal can obtain multiple similarities and calculate the average similarity of the multiple similarities, and the terminal with the highest average similarity is determined as the group leader terminal.

[0073] Further, the switching trigger time of the terminal and the switching trigger time of other terminals can first calculate the difference between the two switching trigger times, and then calculate the similarity according to the difference. For example, the difference between the first value and the difference can be calculated, and then the ratio of the difference to the first value is calculated, and the ratio is determined as the similarity of the terminal and other terminals.

[0074] S203, control the group leader terminal to switch to the target satellite through the RACH switching mechanism.

[0075] S204, control the group member terminal to switch to the target satellite through the RACH-less switching mechanism.

[0076] It can be understood that RACH-less switching refers to that the group member terminal uses pre-allocated channel resources to establish a communication link with the target satellite, and adjusts the transmission time of the uplink signal through the uplink timing advance TA, and the uplink signal is transmitted through the communication link.

[0077] It can also be understood that in the case of satisfying condition 3, the source satellite can control the group member terminal to switch to the target satellite through the RACH switching mechanism.

[0078] The condition 3 may, for example, include at least one of the following: the TA is invalid when the group member terminal performs RACH-less switching; the group member terminal cannot access the target satellite when the preset timer expires; the condition 2 is not met and lasts for at least 2 measurement periods; the group member terminal fails to switch through RACH-less switching.

[0079] The timer can refer to any timer specified in the protocol (such as T304 timer) or a self-defined timer.

[0080] Optionally, the source satellite can control the group member terminal to switch to the target satellite through the RACH switching mechanism in the case that condition 2 is not met and lasts for at least 2 measurement periods. The specific content of condition 2 can be referred to the description of other embodiments, which will not be repeated here.

[0081] Optionally, the source satellite can control the group member terminal to switch to the target satellite through the RACH switching mechanism in the case that the TA is invalid when the group member terminal performs RACH-less switching.

[0082] Of course, the group member terminal can also find that the TA is invalid in the process of performing RACH-less switching, and automatically switch to the target satellite using the RACH switching mechanism, thereby improving the flexibility of switching control and ensuring the success of switching.

[0083] Optionally, the source satellite can control the group member terminal to switch to the target satellite through the RACH switching mechanism in the case that the group member terminal cannot access the target satellite when the preset timer expires.

[0084] Of course, the group member terminal can also automatically switch to the target satellite using the RACH switching mechanism in the case that the group member terminal cannot access the target satellite when the timer expires, thereby improving the flexibility of switching control and ensuring the success of switching.

[0085] Optionally, the source satellite can control the group member terminal to switch to the target satellite using the RACH switching mechanism in the case that the group member terminal fails to perform RACH-less switching.

[0086] Of course, the group member terminal can also automatically switch to the target satellite using the RACH switching mechanism in the case that the group member terminal fails to perform RACH-less switching, thereby improving the flexibility of switching control and ensuring the success of switching.

[0087] Optionally, in the case that condition 3 is met, the source satellite can send second indication information to the group member terminal, and the second indication information can be used to instruct the group member terminal to switch to the target satellite through the RACH switching mechanism.

[0088] In the embodiments of the present application, the source satellite can determine a target group, and the target group can include a plurality of terminals that need to perform satellite switching, and the plurality of terminals can be classified into a group leader terminal and a group member terminal. The group leader terminal is switched to the target satellite through the RACH mechanism, and the group member terminal is switched to the target satellite through the RACH-less switching mechanism. The RACH-less switching mechanism has a relatively simple operation process compared with the RACH switching mechanism. Controlling a large number of group members to perform RACH-less switching can greatly reduce signaling overhead, reduce network congestion, and greatly improve network performance.

[0089] In a possible design, S203 can include the following steps.

[0090] C1, sending a switching command to the group leader terminal, the switching command instructing the group leader terminal to send first indication information to the target satellite, the first indication information including a random access preamble and being used to instruct the target satellite to send a RAR message to the group leader terminal, the RAR message containing an uplink timing advance TA of the target satellite, the group leader terminal sending a switching completion message to the target satellite, the switching completion message including the uplink timing advance TA and group information of a target group, a target message identifier, and a converted PDU session list, the switching completion message instructing the target satellite to send a first confirmation message to the source satellite.

[0091] Optionally, the switching command can be RRC signaling or high-layer signaling, and the specific type of the switching command is not limited in this embodiment.

[0092] It can be understood that the uplink timing advance TA, the group information of the target group, the target message identifier, and the converted PDU session list in the switching completion message can be known. The group information can be constituted by, for example, group name and group identifier. The PDU session list can be a list formed by multiple PDU sessions, and can represent the PDU session requirement of the terminal.

[0093] C2, receiving the first confirmation message sent by the target satellite, the first confirmation message being used to instruct that the group leader terminal has completed switching, and the first confirmation message including the uplink timing advance TA.

[0094] In this embodiment, the group leader terminal can accurately acquire the uplink timing advance of the target satellite, thereby achieving accurate uplink synchronization. After acquiring the uplink timing advance TA, the group leader terminal sends a switching completion message containing the TA, the group information of the target group, the target message identifier, and the converted PDU session list to the target satellite, so as to provide more comprehensive information for the target satellite, thereby the target satellite can send a first confirmation message to the source satellite, the source satellite receives the message and the uplink timing advance TA contained in the message, so that the source satellite can explicitly know that the group leader terminal has successfully switched to the target satellite and acquire the key uplink timing information. The reliable switching message confirmation is achieved. This is very important for the management and control of group communication, and helps the target satellite to provide accurate group communication service for the group leader terminal and ensure the normal communication in the group.

[0095] In yet another possible design, S204 can include the following steps.

[0096] D1, sending a broadcast message to the group member terminal, the broadcast message comprising: uplink timing advance TA, group information of the target group, and switching indication information, the uplink timing advance TA in the broadcast message being parsed by the group member terminal to obtain, the switching indication information indicating the group member terminal to perform RACH_less switching based on the uplink timing advance TA to switch to the target cell of the target satellite, the target satellite sending a second confirmation message of the group member terminal to the source satellite after successfully accessing the group member terminal.

[0097] The broadcast message can be broadcast by the source satellite so that terminals within the coverage range of the source satellite can receive the broadcast message.

[0098] D2, receiving the second confirmation message sent by the target satellite, the second confirmation message indicating that the group member terminal completes satellite switching.

[0099] In the embodiments of the present application, the source satellite sends a broadcast message to the group member terminal, the broadcast message comprising: uplink timing advance TA, group information of the target group, and switching indication information, etc., so as to provide the information to the group member terminal, and the switching indication information indicates the group member terminal to perform RACH_less switching based on the uplink timing advance TA to switch to the target cell of the target satellite. This process can also provide more abundant switching information, thereby realizing more effective switching. By using the RACH_less switching mode, the signaling overhead and access delay caused by random access are reduced. This is of great significance to improve the overall performance and capacity of the system, especially in the case of a large number of group member terminals, which can effectively avoid random access conflicts and improve access efficiency.

[0100] As an embodiment, the source satellite in the embodiments of the present application can also be used to perform the following steps:

[0101] Receiving user messages respectively sent by a plurality of terminals, the user messages comprising at least one of the following: user identity, switching trigger time, and best access satellite;

[0102] According to the user messages respectively corresponding to the plurality of terminals, terminals satisfying a similarity condition are divided into a group, obtaining at least one group, the group comprising at least one terminal;

[0103] Determining a target group from the at least one group.

[0104] It can be understood that the user message can contain multiple user attributes, such as user identity (Identity, ID), switching trigger time, best access satellite, and group leader identity.

[0105] In the switching stage, if the terminal is not grouped, the group leader identity can be set to empty.

[0106] For example, the user message can be defined as: U n =(I n , T n , S n , G n )

[0107] wherein I n represents a user identity, T n represents a handover trigger time, S n represents an optimal access satellite, and G n represents a group leader identity, which refers to a user identity of a group leader terminal.

[0108] It can be understood that the user identity is used to distinguish different terminals. The handover trigger time refers to a time at which a terminal triggers satellite handover, and the user message can be reported at the time. The optimal access satellite refers to a target satellite with the highest communication effect or communication quality to which the terminal can join.

[0109] Optionally, the source satellite can perform similarity comparison on user messages corresponding to multiple terminals respectively, and divide users with high handover behavior similarity into a group. The similarity condition can also refer to high handover behavior similarity.

[0110] Specifically, the similarity condition can refer to identical handover attributes of user messages of the terminals, such as identical handover attributes including a satellite (such as the optimal access satellite) to be switched, a time (such as the handover trigger time) to be switched, and the like. For example, assuming that the optimal access satellite of the A terminal and the B terminal is satellite 1, and the handover trigger time of the A terminal and the B terminal is 12:00 on March 7, 2025, the A terminal and the B terminal are divided into the same group. Assuming that the optimal access satellite of the B terminal is satellite 1, and the optimal access satellite of the C terminal is satellite 2, the B terminal and the C terminal are not divided into the same group.

[0111] Optionally, for multiple terminals in the target group, the source satellite can further verify whether to retain.

[0112] In a possible design, for a terminal in the target group, the source satellite can determine whether the optimal access satellite corresponding to the terminal is the target satellite, if yes, the terminal is retained, if not, the terminal is deleted, and multiple terminals finally retained by the target group are obtained.

[0113] wherein the source satellite has received user messages of the terminals, and the user messages can include the optimal access satellite of the terminal.

[0114] In this embodiment, the source satellite receives user messages from multiple terminals, each containing at least one piece of information such as user ID, handover trigger time, and optimal access satellite. This information accurately reflects the key characteristics and status of the user terminals, providing rich and accurate foundational information for subsequent terminal grouping and management. Based on the user messages corresponding to multiple terminals, terminals meeting similarity criteria are grouped into at least one group. This allows for reasonable classification based on terminal characteristics and behavior, identifying a target group from at least one group. This enables the source satellite to focus on specific groups for further processing and operation, achieving more efficient terminal management, improving handover efficiency, optimizing resource allocation, and supporting personalized services, thus playing a positive role in improving the overall performance of the satellite communication system.

[0115] like Figure 3 The diagram shown is a flowchart of another embodiment of a communication method provided in this application. This method can be applied to a target satellite and may specifically include the following steps:

[0116] S301. Receive the first indication information sent by the source satellite. The first indication information is sent by the group head terminal after receiving the handover command sent by the source satellite. The first indication information includes a random access preamble. The group head terminal is the terminal with the highest similarity to the handover trigger time of other terminals in the target group. The target group includes multiple terminals that need to perform satellite handover. The terminals in the target group other than the group head terminal are called group terminals.

[0117] S302. Send a RAR message to the group leader terminal. The RAR message instructs the group leader terminal to perform a RACH handover to switch to the target satellite. The RAR message contains the uplink timing advance (TA) of the target satellite.

[0118] S303. Receive a handover completion message sent by the group head terminal. The handover completion message includes the uplink timing advance (TA), the group information of the target group, the target message identifier, and the list of PDU sessions that have been switched.

[0119] S304. Send a first confirmation message to the source satellite. The first confirmation message is used to indicate that the group head terminal has completed the handover and to instruct the group member terminals to perform a RACH_less handover based on the uplink timing advance (TA) included in the first confirmation message to switch to the target satellite.

[0120] In the embodiments of the present application, the source satellite can determine the target group, and the target group can include a plurality of terminals that need to perform satellite handover. The plurality of terminals can be classified into group leader terminals and group member terminals. The group leader terminals are switched to the target satellite through the RACH mechanism, and the group member terminals are switched to the target satellite through the RACH_less switching mechanism. Compared with the RACH switching mechanism, the RACH_less switching mechanism has a relatively simple operation process. Controlling a large number of group members to perform RACH_less switching can greatly reduce signaling overhead, reduce network congestion, and greatly improve network performance.

[0121] In a possible design, the target satellite can further be configured to:

[0122] receive the handover request message sent by the source satellite, the handover request message including group leader information and group member information, and the handover request message indicating that the target satellite allocates channels and wireless resources for the target group.

[0123] send a third confirmation message to the source satellite, the third confirmation message being used to indicate that the target satellite confirms to the source satellite to perform handover of the target group.

[0124] It can be understood that, after receiving the handover request message, the target satellite can start an admission control process, evaluate the current network state and resource availability, including calculating indicators such as the current load, the number of new users, and the required amount of resources, and perform admission control and resource allocation.

[0125] If the target satellite receives the target group, the target satellite allocates channels and wireless resources for the target group, encapsulates the allocated channels and wireless resources for the target group in a confirmation message, such as the third confirmation message, and sends the third confirmation message to the source satellite.

[0126] The channels and wireless resources can refer to channels that can be used by the target group and resources, such as time domain resources and / or frequency domain resources, used when performing wireless transmission through the channels. The target group can use the channels to transmit messages at a transmission opportunity corresponding to the time domain resources and / or the frequency domain resources indicated by the wireless resources.

[0127] In the embodiments of the present application, the source satellite sends a switching request message containing group leader information and group member information, and the switching request message indicates that the target satellite allocates channels and wireless resources for the target group, which helps the target satellite to prepare resources in advance. After receiving the request, the target satellite can allocate channels and wireless resources such as bandwidth and power according to the number of group leaders and group members, communication requirements and other information. This way of planning and allocating resources in advance can improve the utilization efficiency of resources, reduce resource conflicts and waste, and ensure that the target group can quickly obtain stable communication services after switching to the target satellite. The target satellite sends a third confirmation message to the source satellite to confirm the execution of the switching of the target group. This confirmation mechanism provides reliable feedback for the switching process, and the source satellite can learn in time that the target satellite has received the switching request and started the switching operation. Through this two-way information exchange, the reliability and traceability of the switching process are enhanced, which helps the source satellite to perform subsequent resource management and state updating, such as releasing unnecessary resources, and ensures the stable operation of the entire communication system.

[0128] As shown in Figure 4 Another embodiment of the communication method provided by the embodiments of the present application is a flow chart of another embodiment of the communication method, which can be applied to a group leader terminal and can specifically include the following steps:

[0129] S401, receiving a switching command sent by a source satellite, the switching command instructing the group leader terminal to send first indication information to a target satellite, the first indication information including a random access preamble and being used to instruct the target satellite to send a RAR message to the group leader terminal, the RAR message containing an uplink timing advance TA of the target satellite.

[0130] S401, receiving a RAR message sent by a target satellite.

[0131] S403, switching to the target satellite through a RACH switching mechanism.

[0132] S404, sending a switching completion message to the target satellite, the switching completion message including an uplink timing advance TA and group information of the target group, a target message identifier, and a converted PDU session list, the switching completion message instructing the target satellite to send a first confirmation message to the source satellite, the first confirmation message being used to indicate that the group leader terminal has completed switching, and the first confirmation message including the uplink timing advance TA, the uplink timing advance TA being used for a group member terminal to perform RACH_less switching to switch to the target satellite, and the group leader terminal and the group member terminal belonging to the same target group.

[0133] In the embodiments of the present application, the source satellite can determine a target group, and the target group can include a plurality of terminals that need to perform satellite handover. The plurality of terminals can be classified into a group leader terminal and a group member terminal. The group leader terminal is switched to the target satellite through the RACH mechanism, and the group member terminal is switched to the target satellite through the RACH_less switching mechanism. Compared with the RACH switching mechanism, the RACH_less switching mechanism has a relatively simple operation process. Controlling a large number of group members to perform RACH_less switching can greatly reduce signaling overhead, reduce network congestion, and greatly improve network performance.

[0134] In a possible design, the group leader terminal can perform measurement at a first period to obtain a first measurement report. The group member terminal can perform measurement at a second period to obtain a second measurement report.

[0135] Optionally, the group leader terminal sends the first measurement report to the source satellite when condition 1 and condition 2 are met.

[0136] Optionally, the group leader terminal sends the first measurement report to the source satellite when condition 1 is met and at least for 2 measurement periods.

[0137] The measurement period can be the first period, the second period, or a self-defined period. In the embodiments, the length of the self-defined period is not limited too much. For example, the length of the third period can be 30 ms.

[0138] It can be understood that, when determining whether to report the first measurement report, the measurement period of the group leader terminal can be the first period. That is, the group leader terminal sends the first measurement report to the source satellite when condition 1 is met and at least for 2 first periods.

[0139] The first measurement report refers to a report of measurement of signals of the source satellite and the target satellite by the group leader terminal according to the first period.

[0140] Specifically, the group leader terminal measures signals of the source satellite and the target satellite according to the first period to obtain the first measurement report. The first measurement report is reported to the source satellite when condition 1 and condition 2 are met, or when condition 1 is met and at least for 2 measurement periods (for example, the first period).

[0141] In another possible design, the group member terminal can send the second measurement report to the source satellite when condition 1 is met and at least for 2 measurement periods.

[0142] The second measurement report refers to a report of measurement of signal strengths of the source satellite and the target satellite by the group member terminal according to the second period.

[0143] It can be understood that when the group member terminal judges whether to report the second measurement report, the measurement period can be the second period. That is, the group member terminal sends the second measurement report to the source satellite when condition 1 is met and lasts for at least 2 second periods.

[0144] Specifically, the group member terminal can measure the signal strengths of the source satellite and the target satellite according to the second period to obtain the second measurement report. And report to the source satellite when condition 1 is met and lasts for at least 2 measurement periods (such as the second period).

[0145] Optionally, the first period can be less than the second period, or the second period is equal to the product of the first period and N, N is greater than 1. For example, the first period can be 20ms, and the second period can be 40ms. The measurement period used by the group leader terminal is higher than that of the group member terminal, which can avoid the group member terminal to perform measurement at high frequency, reduce the device overhead, reduce unnecessary measurement report sending, and achieve the purpose of saving device energy consumption.

[0146] The conditions 1 and 2 are described in detail as follows:

[0147] 1, Condition 1 refers to that the first offset is greater than the first threshold value, the first offset refers to the difference between the first RSRP and the second RSRP, the first RSRP is the RSRP obtained by the group leader terminal measuring the signal of the target satellite, and the second RSRP is the RSRP obtained by the group leader terminal measuring the signal of the source satellite.

[0148] 2, Condition 2 refers to that the difference between the first offset and the second offset is greater than the second threshold value, the second offset refers to the difference between the third RSRP and the fourth RSRP, the third RSRP is the RSRP obtained by the group member terminal measuring the signal of the target satellite, and the fourth RSRP is the RSRP obtained by the group member terminal measuring the signal of the source satellite.

[0149] The conditions 1 and 2 are represented by formulas as follows:

[0150]

[0151] Condition 1:

[0152] Condition 2:

[0153] Wherein, ue1 is the group leader terminal, ue n is the group member terminal, is the RSRP of the target satellite obtained by the group leader terminal measuring, is the RSRP of the source satellite obtained by the group leader terminal measuring, is the RSRP of the target satellite obtained by the group member terminal measuring, The RSRP of the source satellite obtained by the group member terminal is measured. TH1 is a first threshold value, and TH2 is a second threshold value.

[0154] As described above, the judgment of condition 1 and / or condition 2 requires the use of the first measurement report and the second measurement report.

[0155] Further, the judgment step of condition 1 includes P1: judging whether condition 1 is met according to the first measurement report. The judgment step of condition 2 includes P2: judging whether condition 2 is met according to the first measurement report and the second measurement report.

[0156] It can be understood that P1 can be performed by the group leader terminal or by the group member terminal. If the group member terminal performs P1, the group leader terminal needs to send the first measurement report to the group member terminal.

[0157] P2 can be performed by the group leader terminal or by the group member terminal. If the group leader terminal performs P2, the group member terminal needs to report the second measurement report to the group leader terminal. If the group member terminal performs P2, the group leader terminal needs to report the first measurement report to the group member terminal.

[0158] That is, the group leader terminal can perform P1 and / or P2, and the group member terminal can perform P1 and / or P2. Regardless of which terminal performs P1 or P2, the result needs to be reported to the other terminal.

[0159] For example, the group leader terminal can also send the judgment result of condition 1 and / or condition 2 to the group member terminal. Alternatively, the group member terminal can also send the judgment result of condition 1 and / or condition 2 to the group leader terminal.

[0160] As shown in FIG. 5, another embodiment of a communication method provided by the embodiment of the present application is shown in the form of a flow chart. The method can be applied to a group member terminal and can specifically include the following steps: Figure 5 S501, receiving a broadcast message sent by a source satellite, the broadcast message including: uplink timing advance TA of a target satellite, group information of a target group, and switching indication information; the broadcast message is sent by the source satellite after determining that a group leader terminal has performed RACH switching to the target satellite, and the group member terminal and the group leader terminal belong to the target group.

[0161] S502, obtaining the uplink timing advance TA and the switching indication information from the broadcast message.

[0162]

[0163] ​S503, performing RACH_less handover by using uplink timing advance (TA) according to the handover indication information, so as to switch to a target cell of a target satellite, and sending, by the target satellite, a second confirmation message of the group member terminal to the source satellite after the group member terminal successfully accesses, the second confirmation message indicating that the satellite handover of the group member terminal is completed.

[0164] As an embodiment, for the group member terminal, RACH handover can also be performed in case of handover failure or other cases. In case of satisfying condition 3, the RACH handover mechanism is used to switch to the target satellite.

[0165] Specifically, the group member terminal can detect whether condition 3 is satisfied, and in case of determining that condition 3 is satisfied, the RACH handover mechanism is used to switch to the target satellite.

[0166] Alternatively, the group member terminal can receive second indication information, the second indication information being used to indicate that the group member terminal switches to the target satellite by using the RACH handover mechanism.

[0167] The specific content of condition 3 can refer to the description of the related embodiments, and will not be repeated here.

[0168] In the embodiments of the present application, the source satellite can determine a target group, and the target group can include a plurality of terminals that need to perform satellite handover, and the plurality of terminals can be classified into a group leader terminal and a group member terminal. The group leader terminal switches to the target satellite by using the RACH mechanism, and the group member terminal switches to the target satellite by using the RACH_less handover mechanism. Compared with the RACH handover mechanism, the RACH_less handover mechanism has a relatively simple operation process. Controlling a large number of group members to perform RACH_less handover can greatly reduce signaling overhead, reduce network congestion, and greatly improve network performance.

[0169] As shown in FIG. 1, a satellite handover method provided by an embodiment of the present application includes the following steps: Figure 6

[0170] S601, the terminal periodically measures the RSRP of the serving satellite and the target satellite, and when the RSRP of the serving satellite is less than a fourth threshold value, sends a user message to the corresponding serving satellite.

[0171] Any serving satellite can be used as a source satellite.

[0172] ​Optionally, the fourth threshold value can be a clustering trigger threshold of the RSRP of the serving satellite, and when the RSRP of the serving satellite is less than the fourth threshold value, clustering is performed, that is, the plurality of terminals are divided into a plurality of groups. Each group contains a plurality of terminals with the same handover target. The handover target can include, for example, a source satellite, a target satellite, a handover attribute, and the like. The handover attribute can include, for example, a handover mode, a handover procedure, and the like.

[0173] It can be understood that when the RSRP of the serving satellite of the terminal is less than the fourth threshold value, the terminal triggers to send a user message to the serving satellite.

[0174] Optionally, when the terminal measures periodically, the measurement period can be the first period, the second period, or the third period.

[0175] S602, the source satellite receives a plurality of user messages respectively sent by a plurality of terminals, and the user message includes at least one of the following: a user identifier, a handover trigger time, and an optimal access satellite.

[0176] S603, the source satellite divides the terminals satisfying the similarity condition into a group according to the user messages respectively corresponding to the plurality of terminals, to obtain at least one group, and the group includes a plurality of terminals. And determine a target group from at least one group.

[0177] S604, the source satellite determines a group leader terminal and a group member terminal in the target group, the group leader terminal refers to the terminal with the highest similarity degree to the handover trigger time of other terminals in the target group, and the group member terminal refers to the terminal in the group except the group leader terminal.

[0178] As an optional implementation, the source satellite can also send a group leader confirmation message to the group leader terminal, and the group leader confirmation message is used to indicate that the terminal is determined as the group leader of the target group.

[0179] After receiving the group leader confirmation message, the group leader terminal can determine to be the group leader and continue to perform measurement to obtain a measurement report.

[0180] As an optional implementation, the source satellite can also send a member confirmation message to the group member terminal, and the member confirmation message is used to indicate that the terminal is divided into a group member.

[0181] In addition, after sending the user message, if the group member satellite does not receive the group leader confirmation message within a timing period, it directly determines itself to be a group member. The timing period can be any timer specified by the protocol or a custom timer, such as a T304 timer. In addition, the length of the custom timer can be set according to the use demand.

[0182] S605, the group leader terminal sends a first measurement report to the source satellite in the case that the condition 1 and the condition 2 are met, the first measurement report being a report of the group leader terminal measuring signals of the source satellite and the target satellite. Or, the first measurement report is sent to the source satellite in the case that the condition 1 is met and lasts for at least 2 measurement periods.

[0183] S606, the group member terminal sends a second measurement report to the source satellite in the case that the condition 1 is met and lasts for at least 2 measurement periods, the second measurement report being a report of the group member terminal measuring signal strengths of the source satellite and the target satellite.

[0184] Optionally, the group member terminal can send the second measurement report to the group leader terminal.

[0185] The group leader terminal can determine whether the condition 2 is met according to the second measurement report.

[0186] S607, the source satellite determines terminal information of the group leader terminal and group member information of the group member terminal according to the first measurement report.

[0187] The terminal information may, for example, contain group leader / group leader identification. The group member information may, for example, include group member ID.

[0188] The source satellite can encapsulate the terminal information of the group leader terminal and the group member information of the group member terminal in a handover request message.

[0189] For example, a first field in the handover request message can carry the terminal information of the group leader terminal, and a second field can carry the group member information of the group member terminal.

[0190] S608, the source satellite sends a handover request message to the target satellite, and correspondingly, the target satellite receives the handover request message sent by the source satellite.

[0191] The handover request message includes group leader information and group member information, and the handover request message instructs the target satellite to allocate channels and wireless resources for the target group.

[0192] S609, the target satellite sends a third confirmation message to the source satellite, and correspondingly, the source satellite receives the third confirmation message sent by the target satellite, the third confirmation message being used to instruct the target satellite to confirm to the source satellite that the handover of the target group is performed.

[0193] Optionally, the third confirmation message includes group information of the target group and channels and wireless resources allocated for the target group.

[0194] The group information of the target group may, for example, be group ID (such as can be named as GROUP-ID).

[0195] After the source satellite receives the third confirmation message, it can determine that the target group can perform base station switching.

[0196] The source satellite can parse the group information of the target group and the channel and wireless resources allocated for the target group from the third confirmation message.

[0197] Optionally, the source satellite parses the group information in the third confirmation message and the channel and wireless resources allocated for the target group.

[0198] S610, the source satellite sends a first notification message to the group leader terminal, and correspondingly, the group leader terminal can receive the first notification message sent by the source satellite.

[0199] The first notification message carries the wireless resources allocated for the group leader terminal and instructs the group leader terminal to start initiating satellite switching.

[0200] Optionally, the group leader terminal can parse the wireless resources allocated for the group leader terminal from the first notification message. The first notification message can instruct the group leader terminal to start initiating satellite switching.

[0201] S611, the source satellite sends a second notification message to the group member terminal, and correspondingly, the group member terminal can receive the second notification message.

[0202] The second notification message carries the wireless resources allocated for the group member terminal and instructs the group member terminal to start initiating satellite switching.

[0203] Optionally, the group member terminal can parse the wireless resources allocated for the group member terminal from the second notification message. The second notification message can instruct the group member terminal to start initiating satellite switching.

[0204] After the source satellite sends the first notification message to the group leader terminal and the second notification message to the group member terminal, it can start instructing the group leader terminal to start switching, that is, the source satellite can perform S315.

[0205] S612, the source satellite sends a switching command to the group leader terminal. Correspondingly, the group leader terminal can receive the switching command sent by the source satellite.

[0206] The switching command is used to instruct the group leader terminal to send first indication information to the target satellite.

[0207] The first indication information can be carried in a first message, which may, for example, be an RRC message, high-layer signaling, MAC-CE signaling or custom signaling. The specific type of the first message is not limited in this embodiment.

[0208] S613, the group leader terminal sends first indication information to the target satellite. Correspondingly, the target satellite receives the first indication information, and the first indication information includes a random access preamble.

[0209] S614, the target satellite sends a RAR message to the group leader terminal. Correspondingly, the group leader terminal receives the RAR message sent by the target satellite. The RAR message contains an uplink timing advance TA of the target satellite.

[0210] It can be understood that the TA can ensure that the signals of different terminals arrive at the target satellite at the same time, that is, the signals of different terminals are transmitted to the target satellite at the same time.

[0211] S615, the group leader terminal switches to the target satellite through a RACH switching mechanism.

[0212] It can be understood that the group leader terminal can perform RACH switching to the target satellite. The RACH switching mechanism is the same as the related art, and is not described here for the sake of brevity.

[0213] S616, the group leader terminal sends a handover completion message to the target satellite, and correspondingly, the target satellite receives the handover completion message sent by the group leader terminal.

[0214] The handover completion message includes an uplink timing advance TA and group information of a target group, a target message identifier, and a converted PDU session list.

[0215] The group leader terminal can encapsulate the TA and the group information in the handover completion message, and send the handover completion message to the target satellite.

[0216] In addition, the handover completion message can also encapsulate information such as a target cell identifier and a switched PDU session list.

[0217] After the target satellite receives the handover completion message, it can determine that the group leader terminal in the target group has completed switching and accessed to the local network.

[0218] S617, the target satellite sends a first confirmation message to the source satellite, and correspondingly, the source satellite can receive the first confirmation message.

[0219] The first confirmation message is used to indicate that the group leader terminal has completed switching, and includes an uplink timing advance TA.

[0220] The first confirmation message can include a TA value and group information. After the source satellite receives the first confirmation message, it can parse the TA value and the group information from the first confirmation message.

[0221] The source satellite can generate a broadcast message according to the parsed TA value and group information.

[0222] S618, the source satellite sends a broadcast message to the group member terminal, and correspondingly, the group member terminal receives the broadcast message sent by the source satellite, the broadcast message comprising: uplink timing advance TA of the target satellite, group information of the target group, and switching indication information; the broadcast message is sent by the source satellite after determining that the group leader terminal has performed RACH switching to the target satellite; the group member terminal and the group leader terminal belong to the target group.

[0223] S619, the group member terminal parses the uplink timing advance TA and the switching indication information from the broadcast message.

[0224] Optionally, the group member terminal adjusts its uplink sending time according to the uplink timing advance TA value to ensure that the signal can be correctly synchronized when reaching the target satellite, and prepares to switch to the target cell.

[0225] Optionally, the switching indication information can indicate the group member to switch.

[0226] Optionally, the source satellite can send the broadcast message on a control channel, and all group member terminals listen to the control channel to receive and parse the broadcast message.

[0227] S620, the group member terminal performs RACH-less switching according to the switching indication information and the uplink timing advance TA to switch to the target cell of the target satellite, and the target satellite sends a second confirmation message of the group member terminal to the source satellite after determining that the group member terminal is successfully accessed, the second confirmation message indicating that the group member terminal completes satellite switching.

[0228] Optionally, the group member terminal can also switch to the target satellite through the RACH switching mechanism under the condition that condition 3 is met.

[0229] Optionally, after the group member terminal completes switching, it can use the pre-allocated TA to send a switching completion message (such as RRC Connection Reconfiguration Complete) on the physical uplink shared channel (PUSCH) of the target satellite.

[0230] Further, the target satellite listens to the signal on its PUSCH channel and receives the switching completion message from the group member terminal. After receiving the switching completion message of the group member, it confirms that the switching is successful and continues to allocate uplink and downlink resources for the UE.

[0231] If the group member measures condition 2 not to be met and continues for at least 2 measurement periods during the measurement reporting stage, it means that the group leader cannot represent the group member to switch, and the group member performs traditional RACH switching, otherwise, it performs RACH-less switching.

[0232] S621, the target satellite determines that the group member terminal completes the switching, and sends a second confirmation message to the source satellite. The second confirmation message indicates that the group member terminal completes the satellite switching.

[0233] Optionally, after receiving the second confirmation message, the source satellite can confirm that the group member completes the satellite switching, release the context resources of each terminal in the target group, and clear the channels and group member information allocated for each terminal.

[0234] In the embodiments of the present application, the plurality of terminals in the target group are classified into group leader terminals and group member terminals. The group leader terminals are switched to the target satellite through the RACH mechanism, and the group member terminals are switched to the target satellite through the RACH_less switching mechanism. Compared with the RACH switching mechanism, the RACH_less switching mechanism has a relatively simple operation process. Controlling a large number of group members to perform RACH_less switching can greatly reduce signaling overhead, reduce network congestion, and greatly improve network performance.

[0235] For any terminal (such as a group member terminal or a group leader terminal), a target satellite needs to be selected for performing satellite switching. The related operation steps of the terminal are described below.

[0236] S1, a switching trigger time of the terminal is monitored. The terminal is a group member terminal or a group leader terminal.

[0237] S2, according to the distance between the terminal at the switching trigger time and each satellite, a satellite with a distance less than a fourth threshold value is determined as a candidate satellite, and at least one candidate satellite is obtained.

[0238] S3, the best access satellite that can provide the longest service time for the terminal is selected from the at least one candidate satellite.

[0239] S4, a user message is generated according to the user identifier corresponding to the terminal, the switching trigger time, and the best access satellite.

[0240] S5, the user message of the terminal is sent to the source satellite. The user message is used for group division, and one or more terminals that meet the similarity condition are divided into the same group.

[0241] It can be understood that a field carrying a group leader identifier can be set in the user message. When the group leader terminal is not determined, the field of the user message is empty. After the group leader terminal is determined, the group leader identifier can be filled into the field.

[0242] In the embodiments of the application, the switching trigger time of the terminal (group member terminal or group head terminal) is monitored, so that the time point at which the terminal may need to perform satellite switching can be accurately grasped. According to the distance between the terminal and each satellite at the switching trigger time, candidate satellites are screened out, which lays a foundation for further selection of the best access satellite, improves the efficiency and rationality of satellite selection. The best access satellite that can provide the longest service time for the terminal is selected from the candidate satellites, and the satellite with the longest service time can reduce the number of frequent switching of the terminal, reduce the signaling overhead and communication interruption risk caused by switching, and improve the stability and reliability of terminal communication. The user ID corresponding to the terminal, the switching trigger time and the best access satellite are used to generate a user message, and the generated user message provides rich and key data support for subsequent group division, so that the group division can be based on more accurate terminal characteristics and state information, and the scientificity and rationality of the group division are improved.

[0243] In a possible design, S1 can include the following steps.

[0244] S11, periodically measure the RSRP of the current serving satellite to obtain a plurality of RSRP values.

[0245] Optionally, the source satellite can periodically measure the RSRP of the current serving satellite at a first period to obtain a plurality of RSRP values. The target satellite can periodically measure the RSRP of the current serving satellite at a second period to obtain a plurality of RSRP values.

[0246] S12, use regression analysis to fit and predict the plurality of RSRP values to obtain a predicted value corresponding to the first time.

[0247] Optionally, the regression analysis can be a regression analysis algorithm, which can be used to fit and predict the plurality of RSRP values to obtain a fitting curve, where the horizontal axis of the fitting curve is time and the vertical axis is the RSRP value. According to the fitting curve, the value corresponding to the first time is determined, and the value is determined as the predicted value at the first time.

[0248] S13, if the predicted value is less than a third threshold value, the first time is determined as the switching trigger time.

[0249] Optionally, the third threshold value is a reasonable threshold value set according to actual communication requirements and system performance.

[0250] In the embodiments of the present application, the reference signal received power (RSRP) of the current serving satellite is periodically measured to obtain a plurality of RSRP values, which provides rich and time series characteristic data for subsequent analysis. The plurality of RSRP values are fitted and predicted by regression analysis to obtain a predicted value corresponding to the first time. The trend and law of signal change are fully considered, and the change of signal strength can be predicted in advance. When the predicted value is less than a third threshold value, the first time is determined as the switching trigger time. By comparing the predicted value with the threshold value, the switching operation can be triggered in time before the signal quality deteriorates to affect the communication quality, avoiding communication interruption or serious quality decline caused by sudden signal deterioration, and improving the accuracy of switching trigger time judgment.

[0251] In another possible design, at the monitoring trigger time, the distance of the terminal from the satellite is obtained as follows:

[0252] S21, determining the positions of the satellites at the switching trigger time according to the broadcast ephemeris information.

[0253] Optionally, the ephemeris information contains key data such as the running orbit and speed of the satellite, which provides a reliable basis for subsequent calculation of the distance between the satellite and the terminal, ensures the accuracy of distance calculation, and thus plays an important supporting role in switching decision and other operations in satellite communication.

[0254] S22, calculating the distances from the terminal to the satellites at the switching trigger time according to the position of the terminal and the positions of the satellites.

[0255] Specifically, the position of the terminal can refer to the position of the terminal at the switching trigger time.

[0256] Specifically, the distances from the terminal to the satellites at the switching trigger time can be calculated according to the position of the terminal at the switching trigger time and the positions of the satellites.

[0257] In the embodiments of the present application, the positions of the satellites at the switching trigger time are determined according to the broadcast ephemeris information, so that the accurate orbit parameters and other information broadcast by the satellite can be used to accurately obtain the spatial position of the satellite at a specific time. The distances from the terminal to the satellites at the switching trigger time are calculated according to the position of the terminal and the positions of the satellites, and the distance calculation is based on accurate position information. Accurate distance calculation is crucial for a satellite communication system, which can help the system to determine which satellites are closer to the terminal and the signal transmission loss is smaller, so as to select more suitable candidate satellites.

[0258] In another possible design, S3 can include the following steps:

[0259] S31. Determine the visibility time between the terminal and each candidate satellite, and obtain the visibility time corresponding to at least one candidate satellite. The visibility time refers to the duration during which the candidate satellite is within the terminal's visibility range (i.e., the elevation angle is greater than a certain threshold).

[0260] S32. Select the candidate satellite with the longest visible time as the best access satellite.

[0261] In this embodiment, by determining the line-of-sight time between the terminal and each candidate satellite, the stability of the candidate satellites can be evaluated from the perspective of the duration the satellite remains within the terminal's line-of-sight range. A longer line-of-sight time means that the communication link between the satellite and the terminal is relatively stable over a period of time, and signal transmission is less affected by the satellite entering or leaving the line-of-sight range. Selecting a satellite with a long line-of-sight time allows the terminal to maintain a connection with the same satellite for a longer period, reducing the frequency of switching and thus improving the continuity and stability of communication, optimizing the user's communication experience. Selecting the satellite with the longest line-of-sight time as the optimal access satellite helps ensure that the communication link between the terminal and the satellite remains in good condition for a longer period. A stable communication link can reduce the impact of signal fading, interference, and other problems, thereby improving communication quality and reliability.

[0262] like Figure 7 The diagram shown is a structural schematic of a communication device provided in an embodiment of this application. The communication device can be a satellite or a terminal, or a chip located in a satellite or terminal. The communication device 700 may include a processing unit 701 and a transceiver unit 702.

[0263] As one example, the communication device 700 is a source satellite or a chip located on the source satellite.

[0264] The processing unit 701 is used to: determine a target group, which includes multiple terminals requiring satellite handover; determine the group leader terminal and group member terminals within the target group, where the group leader terminal is the terminal with the highest similarity to the handover trigger time of other terminals in the target group, and group member terminals are all terminals in the group excluding the group leader terminal; control the group leader terminal to handover to the target satellite via the RACH handover mechanism; and control the group member terminals to handover to the target satellite via the RACH_less handover mechanism.

[0265] Optionally, the transceiver 702 can be configured to send a switching command to the group leader terminal, the switching command instructing the group leader terminal to send first indication information to the target satellite, the first indication information comprising a random access preamble and being used to instruct the target satellite to send a RAR message to the group leader terminal, the RAR message containing an uplink timing advance TA of the target satellite, the group leader terminal sending a switching completion message to the target satellite, the switching completion message comprising the uplink timing advance TA and group information of the target group, a target message identifier, a converted PDU session list, the switching completion message instructing the target satellite to send a first confirmation message to the source satellite; and receive the first confirmation message sent by the target satellite, the first confirmation message being used to indicate that the group leader terminal has completed switching, the first confirmation message comprising the uplink timing advance TA.

[0266] Optionally, the transceiver 702 is further configured to send a broadcast message to the group member terminal, the broadcast message comprising: an uplink timing advance TA, group information of the target group, and switching indication information, the uplink timing advance TA in the broadcast message being obtained by the group member terminal, the switching indication information instructing the group member terminal to perform RACH_less switching based on the uplink timing advance TA to switch to a target cell of the target satellite, the target satellite sending a second confirmation message of the group member terminal to the source satellite after determining that the group member terminal successfully accesses, and receive the second confirmation message sent by the target satellite, the second confirmation message indicating that the group member terminal completes satellite switching.

[0267] Optionally, the RACH_less switching refers to that the group member terminal uses a pre-allocated channel resource to establish a communication link with the target satellite, and adjusts a sending time of an uplink signal by using the uplink timing advance TA, the uplink signal being transmitted by the communication link.

[0268] Optionally, the transceiver 702 is further configured to receive a first measurement report reported by the group leader terminal, the first measurement report being reported by the group leader terminal under the condition that a condition 1 and a condition 2 are met, the first measurement report being a report of the group leader terminal measuring signals of the source satellite and the target satellite according to a first period. Alternatively, the transceiver 702 is further configured to receive a first measurement report reported by the group leader terminal and a second measurement report reported by the group member terminal, the first measurement report and the second measurement report being reported under the condition that the condition 1 is met and lasts for at least 2 measurement periods, the second measurement report being a report of the group member terminal measuring signal strengths of the source satellite and the target satellite according to a second period.

[0269] Optionally, the first period is less than the second period, or the second period is equal to a product of the first period and N, N being greater than 1.

[0270] Optionally, the condition 1 refers to that the first offset is greater than a first threshold, the first offset refers to a difference between a first RSRP and a second RSRP, the first RSRP is a RSRP obtained by the group leader terminal measuring a signal of the target satellite, and the second RSRP is a RSRP obtained by the group leader terminal measuring a signal of the source satellite.

[0271] The condition 2 refers to that a difference between the first offset and a second offset is greater than a second threshold, the second offset refers to a difference between a third RSRP and a fourth RSRP, the third RSRP is a RSRP obtained by the group member terminal measuring a signal of the target satellite, and the fourth RSRP is a RSRP obtained by the group member terminal measuring a signal of the source satellite.

[0272] Optionally, the processing unit 701 is further configured to determine group leader information of the group leader terminal and group member information of the group member terminal.

[0273] The transceiver 702 is further configured to send, to the target satellite, a handover request message, the handover request message comprising the group leader information and the group member information, the handover request message instructing the target satellite to allocate a channel and a radio resource for the target group; and receive a third confirmation message sent by the target satellite, the third confirmation message being used to instruct the target satellite to confirm, to the source satellite, performing handover of the target group.

[0274] Optionally, the third confirmation message comprises group information of the target group and the channel and the radio resource allocated for the target group.

[0275] The processing unit 701 is further configured to parse the group information in the third confirmation message and the channel and the radio resource allocated for the target group.

[0276] The transceiver 702 is further configured to send, to the group leader terminal, a first notification message carrying a radio resource allocated for the group leader terminal, to instruct the group leader terminal to start initiating satellite handover; and send, to the group member terminal, a second notification message carrying a radio resource allocated for the group member terminal, to instruct the group member terminal to start initiating satellite handover.

[0277] Optionally, the processing unit 701 is further configured to, in a case where a condition 3 is met, control the group member terminal to perform handover to the target satellite through a RACH handover mechanism.

[0278] The condition 3 is met includes at least one of the following:

[0279] TA of the RACH-less handover is invalid;

[0280] The group member terminal cannot access the target satellite when a preset timer expires;

[0281] The condition 2 is not met and lasts for at least two measurement periods;

[0282] The group member terminal fails to perform the RACH-less handover;

[0283] The condition 2 refers to a difference between the first offset and the second offset being greater than a second threshold value, the first offset refers to a difference between a first reference signal received power (RSRP) and a second RSRP, the first RSRP is obtained by the group leader terminal measuring a signal of the target satellite, and the second RSRP is obtained by the group leader terminal measuring a signal of the source satellite; the second offset refers to a difference between a third RSRP and a fourth RSRP, the third RSRP is obtained by the group member terminal measuring a signal of the target satellite, and the fourth RSRP is obtained by the group member terminal measuring a signal of the source satellite.

[0284] Optionally, the transceiver 702 is further configured to receive user messages respectively sent by the plurality of terminals, and the user messages include at least one of the following: a user identifier, a handover trigger time, and an optimal access satellite.

[0285] The processing unit 701 is further configured to divide the terminals satisfying the similarity condition into a group according to the user messages respectively corresponding to the plurality of terminals, to obtain at least one group, and the group includes at least one terminal; and determine a target group from the at least one group.

[0286] Optionally, the processing unit 701 is further configured to, for the terminals in the target group, determine whether the optimal access satellite corresponding to the terminal is the target satellite, and if yes, retain the terminal, and if not, delete the terminal, to obtain a plurality of terminals finally retained by the target group.

[0287] As an embodiment, the communication device 700 is a target satellite or a chip located in the target satellite.

[0288] The transceiver 702 can be configured to receive first indication information sent by the source satellite, the first indication information is sent by the group leader terminal after receiving a handover command sent by the source satellite, the first indication information includes a random access preamble, the group leader terminal refers to a terminal having the highest similarity with a handover trigger time of other terminals in a target group, the target group includes a plurality of terminals that need to perform satellite handover, and terminals in the target group other than the group leader terminal are referred to as group terminals; send a RAR message to the group leader terminal, the RAR message instructs the group leader terminal to perform RACH handover to switch to the target satellite, the RAR message includes an uplink timing advance (TA) of the target satellite; receive a handover completion message sent by the group leader terminal, the handover completion message includes the uplink timing advance (TA), group information of the target group, a target message identifier, and a converted PDU session list; and send a first confirmation message to the source satellite, the first confirmation message is used to indicate that the group leader terminal has completed handover, and instructs the group member terminal to perform RACH-less handover to switch to the target satellite based on the uplink timing advance (TA) included in the first confirmation message.

[0289] Optionally, the transceiver 702 is further configured to receive a switching request message sent by the source satellite, the switching request message comprising group leader information and group member information, the switching request message indicating that the target satellite allocates channels and wireless resources for the target group; and send a third confirmation message to the source satellite, the third confirmation message being used to indicate that the target satellite confirms to the source satellite to perform switching of the target group.

[0290] As an embodiment, the communication apparatus 700 is a group leader terminal or a chip located in the group leader terminal.

[0291] The transceiver 702 is configured to receive a switching command sent by the source satellite, the switching command indicating that the group leader terminal sends first indication information to the target satellite, the first indication information comprising a random access preamble and being used to indicate that the target satellite sends a RAR message to the group leader terminal, the RAR message comprising an uplink timing advance TA of the target satellite; and receive the RAR message sent by the target satellite.

[0292] The processing unit 701 is configured to switch to the target satellite through a RACH switching mechanism.

[0293] The transceiver 702 is configured to send a switching completion message to the target satellite, the switching completion message comprising the uplink timing advance TA and group information of the target group, a target message identifier, and a converted PDU session list, the switching completion message indicating that the target satellite sends a first confirmation message to the source satellite, the first confirmation message being used to indicate that the group leader terminal has completed switching, the first confirmation message comprising the uplink timing advance TA, the uplink timing advance TA being used for a group member terminal to perform RACH_less switching to switch to the target satellite, and the group leader terminal and the group member terminal belonging to the same target group.

[0294] Optionally, the transceiver 702 is further configured to send a first measurement report to the source satellite in a case where a condition 1 and a condition 2 are met, the first measurement report being a report of measurement of signals of the source satellite and the target satellite by the group leader terminal; or send the first measurement report to the source satellite in a case where the condition 1 is met and lasts for at least 2 measurement periods.

[0295] As an embodiment, the communication apparatus 700 is a group member terminal or a chip located in the group member terminal.

[0296] The transceiver 702 is configured to receive a broadcast message sent by the source satellite, the broadcast message comprising an uplink timing advance TA of the target satellite, group information of the target group, and switching indication information; the broadcast message being sent by the source satellite after determining that the group leader terminal has performed RACH switching to the target satellite, and the group member terminal and the group leader terminal belonging to the target group.

[0297] The processing unit 701 is configured to: obtain an uplink timing advance TA and switching indication information from the broadcast message; perform RACH-less switching by using the uplink timing advance TA according to the switching indication information, so as to switch to a target cell of a target satellite; and send, by the target satellite, a second confirmation message of the group member terminal to the source satellite after the group member terminal successfully accesses the target satellite, the second confirmation message indicating that the satellite switching of the group member terminal is completed.

[0298] Optionally, the processing unit 701 is further configured to: switch to the target satellite by a RACH switching mechanism in a case where a condition 3 is met.

[0299] The condition 3 includes at least one of the following:

[0300] The TA of the RACH-less switching is invalid.

[0301] The group member terminal fails to access the target satellite when a preset timer ends.

[0302] The condition 2 is not met and lasts for at least two measurement periods.

[0303] The group member terminal fails to switch by the RACH-less switching.

[0304] The condition 2 refers to a difference between a first offset and a second offset being greater than a second threshold value, the first offset refers to a difference between a first reference signal received power RSRP and a second RSRP, the first RSRP is obtained by measuring a signal of the target satellite by the group leader terminal, and the second RSRP is obtained by measuring a signal of the source satellite by the group leader terminal; and the second offset refers to a difference between a third RSRP and a fourth RSRP, the third RSRP is obtained by measuring a signal of the target satellite by the group member terminal, and the fourth RSRP is obtained by measuring a signal of the source satellite by the group member terminal.

[0305] Optionally, the transceiver 702 is further configured to: send, to the source satellite, a second measurement report in a case where the condition 1 is met and lasts for at least two measurement periods, the second measurement report being a report of measuring signal strengths of the source satellite and the target satellite by the group member terminal.

[0306] Optionally, the processing unit 701 can be configured to: monitor a handover triggering time of the terminal, the terminal being a group member terminal or a group leader terminal; determine, according to distances between the terminal and the satellites at the handover triggering time, a satellite with a distance less than a fourth threshold value as a candidate satellite, to obtain at least one candidate satellite; select, from the at least one candidate satellite, an optimal access satellite capable of providing the terminal with a longest service time; generate a user message according to a user identifier corresponding to the terminal, the handover triggering time, the optimal access satellite, and a group leader identifier; and send the user message of the terminal to a source satellite, the user message being used for group division, and one or more terminals satisfying a similarity condition being divided into a same group.

[0307] Optionally, the processing unit 701 is further configured to: periodically measure RSRP of a currently serving satellite to obtain a plurality of RSRP values; perform fitting prediction on the plurality of RSRP values using regression analysis to obtain a predicted value corresponding to a first time; and determine that the first time is the handover triggering time if the predicted value is less than a third threshold value.

[0308] And / or, the processing unit 701 is further configured to: determine positions of the satellites at the handover triggering time according to broadcast ephemeris information; and calculate distances between the terminal and the satellites at the handover triggering time according to a terminal position of the terminal and the positions of the satellites.

[0309] And / or, the processing unit 701 is further configured to: determine visible times of the terminal and each candidate satellite to obtain visible times corresponding to the at least one candidate satellite respectively, the visible time being a duration in which a candidate satellite is within a visible range of the terminal; and select a candidate satellite with a maximum visible time as the optimal access satellite of the terminal.

[0310] It should be understood that the communication apparatus herein is embodied in the form of functional units. The term "unit" herein can refer to an application specific integrated circuit (ASIC), an electronic circuit, a processor (for example, a shared processor, a dedicated processor, or a group processor and the like) and a memory for executing one or more software or firmware programs, a combination of logical circuit and / or other suitable components supporting the described functions. In an optional example, those skilled in the art can understand that the communication apparatus can be specifically the sending apparatus or the receiving apparatus in the above embodiments, and the communication apparatus can be configured to perform the respective processes and / or steps corresponding to the sending apparatus or the receiving apparatus in the above method embodiments. To avoid repetition, details are not described herein.

[0311] The communication apparatus of each of the above schemes has the function of implementing the respective steps performed by the sending apparatus or the receiving apparatus in the above method; the above function can be implemented by hardware, or by hardware executing corresponding software. The hardware or software includes one or more modules corresponding to the above functions.

[0312] In the embodiments of the present application, Figure 7 The apparatus 700 in the embodiments of the present application can also be a chip or a chip system, for example, a system on chip (SoC).

[0313] Figure 8 Another schematic block diagram of a communication apparatus 800 provided by the embodiments of the present application is shown. The apparatus 800 includes a processor 810, a transceiver 820 and a memory 830. The processor 810, the transceiver 820 and the memory 830 communicate with each other through an internal connection path. The memory 830 is configured to store instructions, and the processor 810 is configured to execute the instructions stored in the memory 830 to control the transceiver 820 to transmit and / or receive signals.

[0314] It should be understood that the communication apparatus 800 can be specifically an Internet of Things device, a terminal or a network device in the above-described embodiments, and can be used to execute each step and / or process corresponding to the terminal or the network device in the above-described method embodiments. Optionally, the memory 830 can include a read-only memory and a random access memory, and provide instructions and data for the processor. A part of the memory can also include a non-volatile random access memory. For example, the memory can also store device type information. The processor 810 can be configured to execute the instructions stored in the memory, and when the processor 810 executes the instructions stored in the memory, the processor 810 is configured to execute each step and / or process of the above-described method embodiments corresponding to the terminal or the network device. The transceiver 820 can include a transmitter and a receiver. The transmitter can be configured to implement each step and / or process corresponding to the transmitter for executing a transmitting action described above, and the receiver can be configured to implement each step and / or process corresponding to the receiver for executing a receiving action described above.

[0315] It should be understood that in the embodiments of the present application, the processor of the apparatus can be a central processing unit (CPU), and the processor can also be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field programmable gate arrays (FPGAs) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or the processor can also be any conventional processor.

[0316] In the implementation process, each step of the above method can be completed by integrated logic circuit of hardware in the processor or instruction in the form of software. The steps of the method disclosed by the embodiment of the present application can be directly embodied as hardware processor execution completion, or executed by hardware and software units in the processor. The software unit can be located in the mature storage medium in the field, such as random access memory, flash memory, read-only memory, programmable read-only memory, electrically erasable programmable memory, register, etc. The storage medium is located in the memory, and the processor executes the instruction in the memory, and combines the hardware to complete the steps of the above method. To avoid repetition, it will not be described in detail here.

[0317] The embodiment of the present application also provides a communication system, which can include the terminal and the network device in the above embodiment.

[0318] The embodiment of the present application provides a readable computer storage medium for storing a computer program, which is executed by a processor to implement the method executed by the terminal or the network device shown in various possible implementation manners in the above embodiment.

[0319] The embodiment of the present application provides a computer program product, which includes a computer program (also can be called code or instruction), when the computer program is executed by a processor, the method executed by the terminal or the network device shown in the above embodiment can be implemented.

[0320] The embodiment of the present application provides a chip system for supporting the terminal or the second device to implement the functions shown in the embodiment of the present application.

[0321] The basic principles of the present application are described above in combination with specific embodiments, but it should be pointed out that the advantages, advantages, effects and the like mentioned in the present application are only examples and cannot be considered as the must-have of each embodiment of the present application. In addition, the above-mentioned specific details are only for the purpose of example and for the purpose of understanding, and the above-mentioned details do not limit the present application to the must-use of the above-mentioned specific details.

[0322] The block diagrams of the devices, apparatuses, equipment, systems referred to in this application are merely illustrative examples and are not intended to require or imply that the connection, arrangement, configuration must be as shown in the block diagrams. These devices, apparatuses, equipment, systems can be connected, arranged, configured in any manner as will be appreciated by those skilled in the art. Words such as "include," "contain," "have," etc. are open-ended words that are to be interpreted to mean "including but not limited to," and are to be interpreted not to exclude items that do not match the description of the item that the words are to be interpreted to mean. The words "or" and "and" as used herein are to be interpreted as the word "and / or," and are to be interpreted not to exclude items that do not match the description of the item that the words are to be interpreted to mean. The word "such as" as used herein is to be interpreted as the phrase "such as but not limited to," and is to be interpreted not to exclude items that do not match the description of the item that the words are to be interpreted to mean.

[0323] Also, as used in the specification and the appended claims, the phrase "or" as used for a conjunction of at least two items indicates a disjunction of the items, such that, for example, a disjunction of "at least one of A, B, or C" means A or B or C, or AB or AC or BC, or ABC (i.e., A and B and C). In addition, the word "example" is not meant to refer to a preferred or superior example, but rather to an example example.

[0324] It is also important to note that the systems and methods of the present application can be embodied in a variety of forms without departing from the spirit or essential characteristics thereof. These and other various embodiments of the system and method of the present application are more fully described herein.

[0325] Various changes, modifications and alterations in the teachings and techniques described herein can be made without departing from the technology defined by the appended claims. In addition, the scope of the following claims is not limited to the specific embodiments described herein. Rather, the scope of the following claims includes any and all embodiments having equivalent elements, modifications, omissions, combinations (including all subcombinations) and alterations as would be practiced or embodied by one of ordinary skill in the art upon reading the preceding description. Furthermore, to the extent that there are "consisting" or "consisting essentially of" claims, it is the intention that the scope of the claims include only the features recited in the respective claim.

[0326] The above description of the disclosed aspects is given for illustrative example and not intended to limit the scope of the application. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein can be applied to other aspects without departing from the scope of the application. Thus, the present application is not intended to be limited to the aspects shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0327] The above description has been given for illustrative example and not intended to limit the embodiments of the application to the forms disclosed herein. Although a number of example aspects and embodiments have been discussed, one of skill in the art will recognize certain modifications, alternatives, changes, additions and subcombinations as can be practiced or embodied in various forms.

Claims

1. A satellite handover method, characterized in that, Applied to a source satellite, the method includes: Identify a target group, which includes multiple terminals that need to perform satellite handover; Identify the group leader terminal and group member terminals in the target group. The group leader terminal is the terminal with the highest similarity to the switching trigger time of other terminals in the target group, and the group member terminals are the terminals in the group other than the group leader terminal. The group leader terminal is controlled to switch to the target satellite through the random access channel (RACH) switching mechanism; The control group member terminals switch to the target satellite through the RACH_less handover mechanism.

2. The method according to claim 1, characterized in that, The control of the group leader terminal to switch to the target satellite via the RACH handover mechanism includes: A handover command is sent to the group leader terminal. The handover command instructs the group leader terminal to send a first indication information to the target satellite. The first indication information includes a random access preamble and is used to instruct the target satellite to send a random access response (RAR) message to the group leader terminal. The RAR message contains the uplink timing advance (TA) of the target satellite. The group leader terminal sends a handover completion message to the target satellite. The handover completion message includes the uplink timing advance (TA), the group information of the target group, the target message identifier, and the converted Protocol Data Unit (PDU) session list. The handover completion message instructs the target satellite to send a first confirmation message to the source satellite. The system receives a first confirmation message sent by the target satellite. The first confirmation message indicates that the group leader terminal has completed the handover. The first confirmation message includes the uplink timing advance (TA).

3. The method according to claim 2, characterized in that, The control of the group member terminals to switch to the target satellite via the RACH_less handover mechanism includes: A broadcast message is sent to the group member terminal. The broadcast message includes: the uplink timing advance (TA), the group information of the target group, and the handover indication information. The uplink timing advance (TA) in the broadcast message is obtained by parsing the group member terminal. The handover indication information is used to instruct the group member terminal to perform the RACH_less handover based on the uplink timing advance (TA) to switch to the target cell of the target satellite. After the target satellite determines that the group member terminal has successfully accessed the satellite, it sends a second confirmation message of the group member terminal to the source satellite. The system receives a second confirmation message sent by the target satellite, which instructs the group member terminals to complete the satellite handover.

4. The method according to claim 3, characterized in that, The RACH_less handover refers to the group member terminal using pre-allocated channel resources to establish a communication link with the target satellite, and adjusting the transmission time of the uplink signal through the uplink timing advance (TA), wherein the uplink signal is transmitted through the communication link.

5. The method according to claim 1, characterized in that, Also includes: Receive the first measurement report reported by the group leader terminal. The first measurement report is reported by the group leader terminal under the condition of satisfying condition 1 and condition 2. The first measurement report refers to the report of the group leader terminal measuring the signals of the source satellite and the target satellite according to the first cycle. Alternatively, the system may receive a first measurement report reported by the group head terminal and a second measurement report reported by the group member terminals. The first measurement report and the second measurement report are reported under the condition that condition 1 is met and the measurement lasts for at least two measurement cycles. The second measurement report is a report in which the group member terminals measure the signal strength of the source satellite and the target satellite according to the second cycle. Wherein, the first period is less than the second period, or the second period is equal to the product of the first period and N, where N is greater than 1.

6. The method according to claim 5, characterized in that, Condition 1 refers to the first offset being greater than the first threshold value. The first offset is the difference between the first reference signal received power (RSRP) and the second RSRP. The first RSRP is the RSRP obtained by the group leader terminal measuring the signal of the target satellite, and the second RSRP is the RSRP obtained by the group leader terminal measuring the signal of the source satellite. Condition 2 refers to the difference between the first offset and the second offset being greater than the second threshold value. The second offset refers to the difference between the third RSRP and the fourth RSRP. The third RSRP is the RSRP obtained by the group member terminal measuring the signal of the target satellite, and the fourth RSRP is the RSRP obtained by the group member terminal measuring the signal of the source satellite.

7. The method according to claim 1, characterized in that, Also includes: Determine the group head information of the group head terminal and the group member information of the group member terminals; A handover request message is sent to the target satellite. The handover request message includes the group head information and the group member information. The handover request message is used to instruct the target satellite to allocate channels and radio resources to the target group. The target satellite receives a third confirmation message, which instructs the target satellite to confirm with the source satellite that the target group switch will be performed.

8. The method according to claim 7, characterized in that, The third confirmation message includes the group information of the target group and the channel and radio resources allocated to the target group; Parse the group information and the channel and radio resources allocated to the target group in the third confirmation message; Send a first notification message to the group leader terminal, the first notification message carrying the radio resources allocated to the group leader terminal, to instruct the group leader terminal to start satellite handover; A second notification message is sent to the group member terminal, the second notification message carrying the radio resources allocated to the group member terminal, to instruct the group member terminal to start satellite handover.

9. The method according to claim 1, characterized in that, Also includes: Under condition 3, the group member terminals are controlled to switch to the target satellite via the RACH handover mechanism; The condition 3 includes at least one of the following: The TA is invalid when the group member terminal performs a RACH-less handover; When the preset timer expires, the group member terminals will be unable to access the target satellite; Condition 2 is not met and this condition persists for at least two measurement cycles; The group member terminal failed to switch via RACH-less; Condition 2 refers to the difference between the first offset and the second offset being greater than a second threshold value. The first offset refers to the difference between the first RSRP and the second RSRP. The first RSRP is the RSRP obtained by the group leader terminal measuring the signal of the target satellite, and the second RSRP is the RSRP obtained by the group leader terminal measuring the signal of the source satellite. The second offset refers to the difference between the third RSRP and the fourth RSRP. The third RSRP is the RSRP obtained by the group member terminal measuring the signal of the target satellite, and the fourth RSRP is the RSRP obtained by the group member terminal measuring the signal of the source satellite.

10. The method according to claim 1, characterized in that, Also includes: Receive user messages sent by multiple terminals respectively, wherein the user messages include at least one of the following: user identifier, handover trigger time, and optimal access satellite; Based on the user messages corresponding to the multiple terminals, terminals that meet the similarity criteria are grouped into one group to obtain at least one group, and the group includes at least one terminal. The target group is determined from the at least one group.

11. The method according to claim 10, characterized in that, Also includes: For a terminal in the target group, determine whether the best access satellite corresponding to the terminal is the target satellite. If yes, retain the terminal; otherwise, delete the terminal to obtain the multiple terminals that are finally retained in the target group.

12. A communication method, characterized in that, Applied to target satellites, including: The system receives a first indication message sent by the source satellite. The first indication message is sent by the group leader terminal after receiving the handover command sent by the source satellite. The first indication message includes a random access preamble. The group leader terminal is the terminal with the highest similarity to the handover trigger time of other terminals in the target group. The target group includes multiple terminals that need to perform satellite handover. The terminals in the target group other than the group leader terminal are called group terminals. A RAR message is sent to the group leader terminal, the RAR message being used to instruct the group leader terminal to perform a RACH handover to switch to the target satellite, the RAR message containing the uplink timing advance (TA) of the target satellite; Receive a handover completion message sent by the group head terminal. The handover completion message includes the uplink timing advance (TA) and the group information of the target group, the target message identifier, and the list of PDU sessions that have been switched. A first confirmation message is sent to the source satellite. The first confirmation message is used to indicate that the group leader terminal has completed the handover and to instruct group member terminals to perform a RACH_less handover based on the uplink timing advance (TA) included in the first confirmation message to switch to the target satellite.

13. A satellite handover method, characterized in that, Applied to group head terminals, including: The system receives a handover command sent by the source satellite. The handover command is used to instruct the group leader terminal to send a first indication information to the target satellite. The first indication information includes a random access preamble and is used to instruct the target satellite to send a RAR message to the group leader terminal. The RAR message contains the uplink timing advance (TA) of the target satellite. Receive the RAR message sent by the target satellite; Switch to the target satellite via the RACH handover mechanism; A handover completion message is sent to the target satellite. The handover completion message includes the uplink timing advance (TA), group information of the target group, target message identifier, and a list of PDU sessions transferred. The handover completion message instructs the target satellite to send a first confirmation message to the source satellite. The first confirmation message is used to indicate that the group leader terminal has completed the handover. The first confirmation message includes the uplink timing advance (TA). The uplink timing advance (TA) is used by group member terminals to perform RACH_less handover to switch to the target satellite. The group leader terminal and the group member terminals belong to the same target group.

14. A satellite handover method, characterized in that, Applied to group member terminals, the method includes: The system receives a broadcast message from the source satellite, which includes: the uplink timing advance (TA) of the target satellite, the group information of the target group, and the handover indication information. The broadcast message is sent by the source satellite after it determines that the group leader terminal has performed a RACH handover to the target satellite. The group member terminals and the group leader terminal belong to the target group. The uplink timing advance (TA) and the handover indication information are obtained by parsing the broadcast message. According to the handover instruction information, a RACH-less handover is performed using the uplink timing advance (TA) to switch to the target cell of the target satellite. After the target satellite determines that the group member terminal has successfully accessed the satellite, it sends a second confirmation message of the group member terminal to the source satellite. The second confirmation message instructs the group member terminal to complete the satellite handover.

15. The method according to claim 14, characterized in that, Also includes: Under condition 3, the system switches to the target satellite via the RACH switching mechanism; The condition 3 includes at least one of the following: The TA for the RACH-less switching is invalid; When the preset timer expires, the group member terminals will be unable to access the target satellite; Condition 2 is not met and this condition persists for at least two measurement cycles; The group member terminals failed to switch via RACH-less; Condition 2 refers to the difference between the first offset and the second offset being greater than the second threshold value. The first offset refers to the difference between the first RSRP and the second RSRP. The first RSRP is the RSRP obtained by the group leader terminal measuring the signal of the target satellite, and the second RSRP is the RSRP obtained by the group leader terminal measuring the signal of the source satellite. The second offset refers to the difference between the third RSRP and the fourth RSRP. The third RSRP is the RSRP obtained by the group member terminal measuring the signal of the target satellite, and the fourth RSRP is the RSRP obtained by the group member terminal measuring the signal of the source satellite.

16. The method according to claim 14 or 15, characterized in that, include: The switching trigger time of the monitoring terminal, wherein the terminal is a group member terminal or a group head terminal; Based on the distance between the terminal and each satellite at the handover trigger time, satellites with a distance less than the fourth threshold are identified as candidate satellites, thus obtaining at least one candidate satellite; Select the best access satellite from the at least one candidate satellites that can provide the longest service time for the terminal; User messages are generated based on the user identifier corresponding to the terminal, the handover trigger time, the best access satellite, and the group leader identifier; The user messages of the terminal are sent to the source satellite. The user messages are used for group division, and one or more terminals that meet the similarity conditions are divided into the same group.

17. The method according to claim 16, characterized in that, The switching trigger time of the monitoring terminal includes: The RSRP of the currently serving satellites is periodically measured to obtain multiple RSRP values; Regression analysis was used to fit and predict the multiple RSRP values ​​to obtain the predicted value corresponding to the first time step. If the predicted value is less than the third threshold, then the first moment is determined to be the handover trigger moment of the terminal.

18. The method according to claim 16, characterized in that, Also includes: Based on the broadcast ephemeris information, determine the position of each satellite at the time of the switch trigger. Based on the terminal's location and the locations of each satellite, the distance to each satellite at the time of the switchover trigger is calculated.

19. The method according to claim 16, characterized in that, The step of selecting the best access satellite from the at least one candidate satellites that can provide the longest service time for the terminal includes: The visible time between the terminal and each candidate satellite is determined to obtain the visible time corresponding to each of the at least one candidate satellite. The visible time refers to the duration of time that the candidate satellite is within the visible range of the terminal. The candidate satellite with the longest visible time was selected as the best access satellite.

20. A communication device, characterized in that, The method includes a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps of the method according to any one of claims 1-19.

21. A computer-readable storage medium having a computer program / instructions stored thereon, characterized in that, When executed by a processor, the computer program implements the steps of the method according to any one of claims 1-19.

22. A computer program product, comprising a computer program, characterized in that, When the computer program / instructions are executed by the processor, they implement the steps of the method according to any one of claims 1-19.

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