Emergency rescue ad hoc network communication system and method based on unmanned aerial vehicle cluster

Abstract

The invention relates to the technical field of emergency rescue communication, and discloses an emergency rescue ad hoc network communication method and system based on an unmanned aerial vehicle cluster. According to the method, whether a terminal is close to a cluster boundary or not is judged by monitoring a signal intensity difference value of a rescue terminal, a switching preparation process is triggered in advance, network access parameters of an adjacent cluster are obtained, and a new communication connection is established with the adjacent cluster to form a dual-connection state while connection with a current cluster is kept. And when the signal strength of the adjacent cluster exceeds that of the current cluster, disconnecting the old connection to complete switching. According to the invention, the problem of communication interruption caused by a traditional disconnection-reconnection mode is solved, the switching time delay is reduced from 8-15 seconds to less than 1 second, and the continuity of emergency rescue communication is guaranteed.

Description

Technical Field

[0001] This invention relates to the field of emergency rescue communication technology, and more specifically, to an emergency rescue ad hoc network communication method and system based on unmanned aerial vehicle (UAV) swarms. Background Technology

[0002] In large-scale emergency rescue scenarios, such as major disasters like earthquakes and floods, ground communication infrastructure suffers severe damage, creating communication gaps and causing the rescue command center to lose contact with the disaster area. Unmanned aerial vehicle (UAV) swarm self-organizing network communication systems serve as an emergency communication solution, constructing a decentralized communication network through multiple UAVs autonomously networking in the air. When the disaster area exceeds the coverage capacity of a single UAV swarm, multiple UAV swarms need to be deployed to work collaboratively, and rescue personnel carrying terminals will need to cross the coverage areas of different swarms when moving and searching within the disaster area.

[0003] Existing technologies employ a disconnect-and-reconnect switching mode, where the rescue terminal, after moving out of the coverage area of ​​the current cluster, first disconnects from the current cluster and then searches for and connects to a neighboring cluster. This traditional switching mode is based on a serial processing mechanism, requiring the terminal to disconnect the old connection before establishing a new one, and necessitating the re-execution of the entire process of scanning, authentication, and negotiation.

[0004] Existing technologies suffer from long handover interruptions, typically requiring 8 to 15 seconds to disconnect from the old connection and establish a new one, during which time the terminals are completely unable to communicate. This leads to interruptions in the transmission of emergency rescue video streams, failure to deliver emergency instructions from the command center, and security risks due to the communication blackout period for rescue teams. The root cause of this technical problem lies in the fact that traditional handover modes cannot achieve parallel transitions between old and new cluster connections, inevitably resulting in communication interruptions during the handover process. Summary of the Invention

[0005] This invention provides an emergency rescue ad hoc network communication method and system based on UAV swarms, solving the technical problem in related technologies where long switching interruption times when rescue terminals move across swarms lead to communication blackouts.

[0006] This invention discloses an emergency rescue ad hoc network communication method based on UAV swarms, comprising: acquiring the signal reception strength of the currently connected swarm and the signal reception strength of neighboring swarms received by the rescue terminal; calculating the signal strength difference between the two; when the signal strength difference is less than a boundary determination threshold, determining that the rescue terminal is approaching the swarm boundary area and generating a boundary approach alarm signal; upon receiving the boundary approach alarm signal, triggering a handover preparation process, wherein the rescue terminal sends a handover preparation request to the current swarm coordinator node, the current swarm coordinator node sends a gateway negotiation request to neighboring swarm coordinator nodes through the inter-swarm communication link, and the neighboring swarm coordinator nodes determine whether to accept the rescue terminal based on resource status. When resources are sufficient, the rescue terminal pre-allocates a network address and encryption key to the rescue terminal and returns network access parameters to the rescue terminal. After receiving the network access parameters, the rescue terminal, while maintaining its connection with the current cluster, uses the network access parameters to establish a new communication connection with the adjacent cluster, forming a dual-connection state. In the dual-connection state, the rescue terminal monitors the signal reception strength of the current cluster and the adjacent cluster. When the signal reception strength of the adjacent cluster exceeds the signal reception strength of the current cluster and the difference exceeds the handover trigger threshold, the rescue terminal sends a connection release request to the current cluster coordinator node, disconnects from the current cluster, and sets the adjacent cluster as the current connected cluster.

[0007] Further, the step of obtaining the signal reception strength of the currently connected cluster and the signal reception strength of the adjacent clusters received by the rescue terminal, and calculating the signal strength difference between the two includes: obtaining the signal reception strength indication value of the currently connected cluster received by the rescue terminal, obtaining the signal reception strength indication value of the adjacent clusters scanned by the rescue terminal; calculating the difference between the signal reception strength indication value of the currently connected cluster and the signal reception strength indication value of the adjacent clusters to obtain the signal strength difference.

[0008] Furthermore, obtaining the signal reception strength indication value of the neighboring clusters scanned by the rescue terminal includes: the rescue terminal performing a full-channel scan to obtain the network identifier and corresponding signal strength of all scanned drone clusters; identifying clusters with signal strength exceeding the reception sensitivity threshold as neighboring clusters; and identifying the neighboring cluster with the strongest signal strength as a potential handover target cluster.

[0009] Furthermore, the process by which the adjacent cluster coordinator node determines whether to accept the rescue terminal based on resource status includes: after receiving the gateway negotiation request, the adjacent cluster coordinator node reads its own resource status data, which includes the current available bandwidth and the number of currently connected terminals; it determines whether the current available bandwidth is greater than a preset minimum bandwidth threshold and whether the number of currently connected terminals is less than a preset maximum access capacity; when the current available bandwidth is greater than the minimum bandwidth threshold and the number of currently connected terminals is less than the maximum access capacity, it determines that resources are sufficient and generates an acceptance confirmation response.

[0010] Furthermore, the process of the adjacent cluster coordinator node determining whether to accept the rescue terminal based on the resource status also includes: the adjacent cluster coordinator node extracting the service type that the terminal is currently performing from the gateway negotiation request; mapping the service type to a priority value according to a preset service priority table; and when the resource status is in a critical state, if the priority value is a high priority, generating an acceptance confirmation response and triggering bandwidth limiting for low-priority services within the cluster.

[0011] Furthermore, the step of establishing a new communication connection with the neighboring cluster using the network access parameters while maintaining the connection with the current cluster includes: configuring the second logical channel of the wireless communication module of the rescue terminal; setting the working parameters of the second logical channel to the communication channel and network identifier of the neighboring cluster; and using the pre-allocated network address and encryption key in the network access parameters to complete the authentication and association process with the coordinator node of the neighboring cluster, thereby establishing a data transmission link with the neighboring cluster.

[0012] Furthermore, the dual-connection state further includes: the rescue terminal allocating the newly generated data stream to the adjacent cluster for transmission; for service streams currently being transmitted through the current cluster, continuing to transmit through the current cluster until the service stream ends or is migrated to the adjacent cluster.

[0013] Further, disconnecting from the current cluster includes: the rescue terminal sending a connection release request data packet to the current cluster coordinator node; after receiving the connection release request, the current cluster coordinator node releases the network resources allocated to the rescue terminal, deletes the routing table entry of the rescue terminal, and returns a release confirmation response to the rescue terminal; after receiving the release confirmation response, the rescue terminal disconnects from the current cluster.

[0014] Furthermore, the boundary determination threshold is dynamically adjusted based on the coverage area of ​​the drone swarm and the signal propagation environment.

[0015] This invention discloses an emergency rescue ad hoc network communication system based on unmanned aerial vehicle (UAV) swarms. The system includes a command center node, multiple UAV swarms, and rescue terminals. Each UAV swarm includes a coordinator node, a router node, and a terminal node.

[0016] This invention utilizes a cluster boundary early identification technology based on signal strength difference to trigger a handover preparation process when a rescue terminal approaches the cluster boundary. By obtaining network access parameters of adjacent clusters in advance through an inter-cluster gateway negotiation protocol, and employing a dual-connection parallel transition strategy, the rescue terminal can establish a connection with the adjacent cluster while maintaining the current connection, thus achieving a parallel transition between the old and new cluster connections. This solves the communication interruption problem caused by the traditional disconnect and reconnection mode, reducing the handover latency from 8 to 15 seconds to less than 1 second. It achieves the technical effects of eliminating communication blackout periods, ensuring continuous transmission of emergency rescue video streams, and ensuring the real-time delivery of emergency instructions from the command center. Attached Figure Description

[0017] Figure 1 This is a flowchart of the emergency rescue ad hoc network communication method based on UAV swarm of the present invention; Detailed Implementation

[0018] In large-scale emergency rescue scenarios (such as major disasters like earthquakes and floods), damage to ground communication infrastructure creates communication gaps, leading to a loss of communication between the rescue command center and the disaster area. Unmanned aerial vehicle (UAV) swarm self-organizing network communication systems serve as an emergency communication solution, constructing a decentralized communication network through multiple UAVs autonomously networking in the air. When the disaster area exceeds the coverage capacity of a single UAV swarm, multiple UAV swarms need to be deployed to work collaboratively.

[0019] The system involved in this invention includes a command center node, multiple drone swarms, and on-site rescue terminals. Each drone swarm comprises a coordinator node, router nodes, and terminal nodes, and autonomously networks via a self-organizing network protocol. Each swarm has an independent network identifier and a coordinator node. When rescue personnel carrying terminals move and search within the disaster area, they may cross the coverage areas of different swarms.

[0020] Existing technologies employ a disconnect-and-reconnect switching mode. This means that after a rescue terminal moves out of the coverage area of ​​the current cluster, it first disconnects from the current cluster and then searches for and connects to a neighboring cluster. This mode suffers from a long handover interruption time; it takes 8 to 15 seconds to disconnect the old connection and establish a new one. During this period, the terminal cannot communicate, leading to interruptions in the transmitted emergency rescue video stream, failure to deliver emergency instructions from the command center, and a communication blackout for the rescue team, posing a safety hazard. The root cause of this technical problem lies in the traditional handover mode's serial processing mechanism, which requires disconnection before establishing a new connection, making it impossible to achieve a parallel transition between old and new cluster connections.

[0021] According to an embodiment of this invention, an emergency rescue ad hoc network communication method based on unmanned aerial vehicle (UAV) swarms includes the following steps: Step 100: Obtain the real-time location coordinates and signal reception strength data sequence of the rescue terminal, determine whether the terminal is close to the cluster boundary area, and generate a boundary status identifier. Obtain the GPS coordinates of the rescue terminal and the signal strength indication value of the currently connected cluster received by the terminal (denoted as ). ), obtain the signal reception strength indication value of the neighboring clusters scanned by the terminal (denoted as ). The data acquisition cycle is 1 second.

[0022] Calculate signal strength difference : Will Compared with the preset boundary determination threshold, when When the rescue terminal is determined to be approaching the cluster boundary area, a boundary approach alarm signal is generated. The boundary determination threshold is set to 5dB in this embodiment.

[0023] It should be noted that the aforementioned boundary determination thresholds can be dynamically adjusted based on the coverage area of ​​the drone swarm and the signal propagation environment. In complex terrains such as mountainous areas, signal attenuation is rapid, so... Adjusted to 8 to 10 dB; in open plains areas, signal propagation is stable and can be... Adjust to 3 to 5 dB.

[0024] It should be noted that the identification of adjacent clusters can be based on the network identifier list scanned by the rescue terminal. Specifically, the terminal performs a full-channel scan every second to obtain the network identifiers and corresponding signal strengths of all scanned drone clusters. Clusters with signal strengths exceeding the receiver sensitivity threshold (usually -90dBm) are identified as adjacent clusters, and the adjacent cluster with the strongest signal strength is selected as the potential handover target cluster.

[0025] Step 200: Trigger the handover preparation process and obtain the network access parameters of the target cluster. When a boundary approach alarm signal is received, the rescue terminal generates a handover preparation request data packet. The data packet contains the network identifier of the adjacent cluster, signal strength data, and terminal identifier, and sends the handover preparation request data packet to the currently connected cluster coordinator node.

[0026] After receiving the handover preparation request data packet, the current cluster coordinator node extracts the network identifier of the adjacent cluster and sends a gateway negotiation request data packet to the adjacent cluster coordinator node through the inter-cluster communication link of the command center. The gateway negotiation request data packet contains the terminal identifier, the current location coordinates of the terminal, and the type of service that the terminal is currently performing.

[0027] After receiving the gateway negotiation request data packet, the adjacent cluster coordinator node reads its own resource status data, which includes the current available bandwidth and the number of currently connected terminals. It determines whether the available bandwidth is greater than the preset minimum bandwidth threshold and whether the number of currently connected terminals is less than the preset maximum access capacity. If resources are sufficient, it generates an acceptance confirmation response data packet, pre-assigns a network address and encryption key to the terminal, and sends the acceptance confirmation response data packet to the current cluster coordinator node.

[0028] After receiving the acceptance confirmation response data packet, the current cluster coordinator node extracts the network access parameters of the neighboring clusters. The network access parameters include the network identifier, communication channel, encryption key, and pre-assigned network address. The network access parameters are then sent to the rescue terminal via encrypted signaling.

[0029] It should be noted that the aforementioned inter-cluster communication links can be relayed through the command center node, or direct communication links between clusters can be pre-established during deployment. When using the command center relay method, each cluster coordinator node establishes a communication link with the command center through the UAV router node. After receiving the gateway negotiation request data packet, the command center forwards the data packet to the target cluster coordinator node based on the target cluster's network identifier. When using the direct inter-cluster communication link method, dedicated border router nodes are deployed between adjacent clusters. These border router nodes simultaneously connect to the ad hoc networks of both clusters, enabling direct data forwarding between clusters and reducing negotiation latency.

[0030] It should be noted that the above resource assessment process may also include determining the terminal service priority. Specifically, after receiving the gateway negotiation request data packet, the adjacent cluster coordinator node extracts the type of service being performed by the terminal and maps the service type to a priority value according to a preset service priority table. When the resource status is in a critical state (available bandwidth is slightly lower than the minimum bandwidth threshold), if the terminal service priority is high (such as video backhaul or voice call), an acceptance confirmation response data packet is still generated, and the bandwidth limiting mechanism for low-priority services within the cluster is triggered to reserve the necessary bandwidth for high-priority services.

[0031] Step 300: Establish dual connections between the rescue terminal and the adjacent cluster to achieve parallel communication between the old and new clusters. After receiving the network access parameters, the rescue terminal maintains its connection with the current cluster while establishing new communication connections with neighboring clusters using these parameters. Specifically, the rescue terminal configures the second logical channel of its wireless communication module, sets the operating parameters of this second logical channel to the communication channel and network identifier of the neighboring cluster, and uses a pre-allocated network address and encryption key to complete the authentication and association process with the coordinator node of the neighboring cluster, establishing a data transmission link with the neighboring cluster. At this time, the rescue terminal is simultaneously connected to two drone clusters, forming a dual-connectivity state.

[0032] In dual-connectivity mode, the rescue terminal allocates newly generated data streams to adjacent clusters for transmission. For service streams currently being transmitted through the current cluster, transmission continues within the current cluster until the service stream ends or migration is complete. For data services with lower real-time requirements (such as file transfer and image upload), the data stream can be switched from the current cluster to an adjacent cluster in dual-connectivity mode, enabling gradual migration of the service stream.

[0033] It should be noted that the duration of the dual-connection state described above is dynamically adjusted according to the progress of service migration. Once all service flows have completed their migration to the adjacent cluster, the rescue terminal sends a connection release request to the current cluster coordinator node, disconnecting from the current cluster and completing the gateway switchover process. The duration of the dual-connection state is typically 2 to 8 seconds to ensure a smooth transition of service flows.

[0034] It should be noted that the aforementioned dual-connection transmission mechanism can also be used to improve the reliability of data transmission. When the rescue terminal is located in the overlapping coverage area of ​​two clusters, critical data packets can be sent simultaneously through both clusters. After receiving the data packets, the coordinator nodes of adjacent clusters perform deduplication processing through the command center, thereby improving the success rate of transmitting critical emergency rescue information.

[0035] Step 400: Monitor signal quality changes in dual-connectivity state and trigger the final handover operation. In dual-connection mode, the rescue terminal continuously monitors the signal reception strength of the current cluster and neighboring clusters. Exceed When the difference exceeds the handover trigger threshold, or when the current cluster signal strength is lower than the minimum receiving level threshold, it is determined that the rescue terminal has moved out of the current cluster coverage area, and a final handover trigger signal is generated.

[0036] Upon receiving the final switchover trigger signal, the rescue terminal sends a connection release request data packet to the current cluster coordinator node. Upon receiving the connection release request, the current cluster coordinator node releases the network resources allocated to the terminal, deletes the terminal's routing table entry, and returns a release confirmation response to the rescue terminal. After receiving the release confirmation response, the rescue terminal disconnects from the current cluster, sets the adjacent cluster as the currently connected cluster, and completes the gateway switchover.

[0037] In the above steps, the rescue terminal triggers the handover preparation process in advance when it approaches the cluster boundary. While maintaining the connection with the current cluster, it establishes a connection with the adjacent cluster, realizing the parallel transition of the connection between the old and new clusters. This avoids the communication interruption of the traditional disconnect and reconnection mode, reduces the handover latency to less than 1 second, and ensures the continuity of emergency rescue communication.

[0038] This implementation adopts a cluster boundary identification mechanism. By comparing the difference between the current cluster signal strength received by the terminal and the signal strength of the adjacent cluster, it can detect in advance the state that the rescue terminal is about to cross the cluster boundary. This overcomes the lag defect of the traditional handover mode, which passively triggers the handover only after the terminal moves out of the coverage area. Therefore, it provides a sufficient time window for the subsequent handover preparation process.

[0039] This implementation adopts a distributed gateway negotiation protocol. Before the switchover, the current cluster coordinator node queries the resource status and negotiates parameters with the neighboring cluster coordinator node through the inter-cluster communication link. The network access parameters of the neighboring clusters are also pre-sent to the rescue terminal. This overcomes the redundant process of re-scanning, authentication, and negotiation required after the traditional switchover mode is disconnected, thus reducing the protocol interaction overhead during the switchover process.

[0040] This implementation employs a dual-connection transition transmission strategy, enabling the rescue terminal to establish connections with adjacent clusters while maintaining its connection with the current cluster. This parallel transition between old and new cluster connections overcomes the serial processing defect of traditional handover modes, which require disconnection before establishing a new connection. Therefore, it solves the communication blackout period problem caused by handover interruptions, reducing handover latency from 8-15 seconds to less than 1 second and achieving seamless cross-cluster communication. In dual-connection mode, the rescue terminal can allocate newly generated data streams to adjacent clusters for transmission, while ongoing service streams continue to be transmitted within the current cluster until migration is complete. This avoids interruptions to emergency rescue video streams and the loss of emergency commands from the command center, ensuring the continuity and reliability of emergency rescue communications.

[0041] In summary, this implementation method eliminates the communication interruption time of the traditional serial switching mode from a technical perspective by completing boundary identification, resource negotiation and parameter configuration before switching, and adopting a dual-connection mechanism to achieve parallel transition between the old and new clusters, thus solving the communication blackout period problem when rescue terminals move across clusters.

Claims

1. A method for emergency rescue ad hoc network communication based on unmanned aerial vehicle (UAV) swarms, characterized in that, Includes the following steps: The signal reception strength of the currently connected cluster and the signal reception strength of the adjacent clusters received by the rescue terminal are obtained, and the signal strength difference between the two is calculated. When the signal strength difference is less than the boundary determination threshold, it is determined that the rescue terminal is close to the cluster boundary area, and a boundary approach alarm signal is generated. Upon receiving the boundary approach alarm signal, a handover preparation process is triggered. The rescue terminal sends a handover preparation request to the current cluster coordinator node. The current cluster coordinator node sends a gateway negotiation request to the adjacent cluster coordinator node through the inter-cluster communication link. The adjacent cluster coordinator node determines whether to accept the rescue terminal based on the resource status. If resources are sufficient, it pre-allocates a network address and encryption key to the rescue terminal and returns the network access parameters to the rescue terminal. After receiving the network access parameters, the rescue terminal, while maintaining its connection with the current cluster, uses the network access parameters to establish a new communication connection with the adjacent cluster, forming a dual-connection state. In the dual-connection state, the rescue terminal monitors the signal reception strength of the current cluster and the neighboring cluster. When the signal reception strength of the neighboring cluster exceeds the signal reception strength of the current cluster and the difference exceeds the handover trigger threshold, it sends a connection release request to the current cluster coordinator node, disconnects from the current cluster, and sets the neighboring cluster as the current connected cluster.

2. The emergency rescue ad hoc network communication method based on UAV swarm as described in claim 1, characterized in that, The process of obtaining the signal reception strength of the currently connected cluster and the signal reception strength of the adjacent clusters received by the rescue terminal, and calculating the signal strength difference between the two, includes: Obtain the signal reception strength indication value of the currently connected cluster received by the rescue terminal, and obtain the signal reception strength indication value of the neighboring clusters scanned by the rescue terminal; Calculate the difference between the signal strength indication value of the currently connected cluster and the signal strength indication value of the neighboring cluster to obtain the signal strength difference.

3. The emergency rescue ad hoc network communication method based on UAV swarm as described in claim 2, characterized in that, The process of obtaining the signal reception strength indication value of the adjacent clusters scanned by the rescue terminal includes: The rescue terminal performs a full-channel scan to obtain the network identifiers and corresponding signal strengths of all scanned drone clusters. Clusters whose signal strength exceeds the receiver sensitivity threshold are identified as neighboring clusters; The neighboring cluster with the strongest signal strength is selected as the potential target cluster for handover.

4. The emergency rescue ad hoc network communication method based on UAV swarm as described in claim 1, characterized in that, The adjacent cluster coordinator node determines whether to accept the rescue terminal based on resource status, including: After receiving the gateway negotiation request, the adjacent cluster coordinator node reads its own resource status data, which includes the current available bandwidth and the current number of connected terminals. Determine whether the currently available bandwidth is greater than a preset minimum bandwidth threshold and whether the number of currently accessing terminals is less than a preset maximum access capacity; When the current available bandwidth is greater than the minimum bandwidth threshold and the number of current access terminals is less than the maximum access capacity, resources are determined to be sufficient, and an admission confirmation response is generated.

5. The emergency rescue ad hoc network communication method based on UAV swarm as described in claim 4, characterized in that, The adjacent cluster coordinator node's decision on whether to accept the rescue terminal based on resource status also includes: The adjacent cluster coordinator node extracts the type of service that the terminal is currently performing from the gateway negotiation request. The service type is mapped to a priority value according to a preset service priority table; When the resource status is in a critical state, if the priority value is high priority, an acceptance confirmation response is generated, and bandwidth limiting of low priority services within the cluster is triggered.

6. The emergency rescue ad hoc network communication method based on UAV swarm as described in claim 1, characterized in that, The step of establishing a new communication connection with the neighboring cluster using the network access parameters while maintaining the connection with the current cluster includes: The rescue terminal is configured with a second logical channel of a wireless communication module; Set the operating parameters of the second logical channel to the communication channel and network identifier of the adjacent cluster; Using the pre-assigned network address and encryption key in the network access parameters, the system completes the authentication and association process with the neighboring cluster coordinator node, establishing a data transmission link with the neighboring cluster.

7. The emergency rescue ad hoc network communication method based on UAV swarm as described in claim 1, characterized in that, The dual-connection state also includes: The rescue terminal distributes the newly generated data stream to the adjacent cluster for transmission. For service flows that are currently being transmitted through the current cluster, continue to transmit through the current cluster until the service flow ends or is migrated to the adjacent cluster.

8. The emergency rescue ad hoc network communication method based on UAV swarm as described in claim 1, characterized in that, Disconnecting from the current cluster includes: The rescue terminal sends a connection release request data packet to the current cluster coordinator node; After receiving the connection release request, the current cluster coordinator node releases the network resources allocated to the rescue terminal, deletes the routing table entry of the rescue terminal, and returns a release confirmation response to the rescue terminal. After receiving the release confirmation response, the rescue terminal disconnects from the current cluster.

9. The emergency rescue ad hoc network communication method based on UAV swarm as described in claim 1, characterized in that, The boundary determination threshold is dynamically adjusted based on the coverage area of ​​the drone swarm and the signal propagation environment.

10. An emergency rescue ad hoc network communication system based on UAV swarms, used to execute the emergency rescue ad hoc network communication method based on UAV swarms as described in any one of claims 1 to 9, characterized in that, It includes a command center node, multiple drone clusters, and rescue terminals. Each drone cluster contains a cluster coordinator node, a router node, and a terminal node. The command center node obtains the signal reception strength of the currently connected cluster and the signal reception strength of the adjacent clusters received by the rescue terminal, calculates the difference between the two signal strengths, and when the signal strength difference is less than the boundary judgment threshold, it determines that the rescue terminal is close to the cluster boundary area and generates a boundary approach alarm signal. Upon receiving the boundary approach alarm signal, a handover preparation process is triggered. The rescue terminal sends a handover preparation request to the current cluster coordinator node. The current cluster coordinator node sends a gateway negotiation request to the adjacent cluster coordinator node through the inter-cluster communication link. The adjacent cluster coordinator node determines whether to accept the rescue terminal based on the resource status. If resources are sufficient, it pre-allocates a network address and encryption key to the rescue terminal and returns the network access parameters to the rescue terminal. After receiving the network access parameters, the rescue terminal, while maintaining its connection with the current cluster, uses the network access parameters to establish a new communication connection with the adjacent cluster, forming a dual-connection state. In the dual-connection state, the rescue terminal monitors the signal reception strength of the current cluster and the neighboring cluster. When the signal reception strength of the neighboring cluster exceeds the signal reception strength of the current cluster and the difference exceeds the handover trigger threshold, it sends a connection release request to the current cluster coordinator node, disconnects from the current cluster, and sets the neighboring cluster as the current connected cluster.

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