A space-ground integrated multicast routing method for smart grid

Abstract

The present invention relates to a space-ground integrated multicast routing method for a smart grid, comprising: a source node broadcasting a beacon message to wake up selected multicast member nodes; constructing a multicast tree consisting of all multicast member nodes; for any two connected multicast member nodes in the multicast tree, if the two connected multicast member nodes cannot communicate directly, constructing the shortest routing path between the multicast member nodes as a routing link between the two multicast member nodes based on a relay node between the multicast member nodes; if the two connected multicast member nodes can communicate directly, directly constructing a routing link between the two multicast member nodes; and performing multicast routing via the routing link between the multicast member nodes. The present invention improves the reliability and efficiency of the entire smart grid communication system, ultimately ensuring the safe and stable operation of the power system.

Description

Technical Field

[0001] The present invention belongs to the field of communication technology, and in particular relates to a space-ground integrated multicast routing method for smart grids. Background Art

[0002] Smart grids, the future of modern power systems, integrate advanced information technology, communications technology, and power technology to achieve efficient, reliable, secure, and intelligent operation of power systems. As smart grids continue to expand in scale and diversify in service types, the requirements for communication networks are becoming increasingly stringent.

[0003] In smart grid communications, multicast is a crucial communication method. For example, in scenarios such as distributing real-time monitoring data of power systems and conveying power dispatch instructions, multicast can efficiently transmit information to multiple related nodes, avoiding the waste of network resources caused by repeated data transmission in unicast mode, and significantly improving information transmission efficiency.

[0004] However, smart grid communication networks present unique complexities. On the one hand, their geographical coverage is extremely broad, encompassing diverse terrains such as urban, rural, and mountainous areas. This can lead to insufficient signal coverage for traditional terrestrial communication networks in certain areas. On the other hand, smart grid communication services require extremely high real-time and reliability. Any communication failure can cause abnormal operation of the power system and even lead to safety incidents.

[0005] The emergence of integrated space-ground communication networks offers a new solution for smart grid communications. They combine the advantages of satellite and terrestrial communications. Satellite communications offer seamless coverage over large areas, complementing the limitations of terrestrial communications in remote areas or those with complex terrain. Terrestrial communications, on the other hand, offer advantages in communication capacity and transmission speed. The combination of these two technologies can provide more reliable and efficient communication services for smart grids.

[0006] However, implementing multicast routing in a space-ground integrated environment is not easy. Due to the differences between satellite and terrestrial communications, such as significant transmission latency and signal susceptibility to weather, and the geographical constraints and base station distribution of terrestrial communications, building efficient multicast routing in this complex network environment to ensure accurate and timely information transmission to all multicast member nodes has become a critical issue that needs to be addressed.

[0007] Currently, most existing multicast routing methods are designed for single network environments and are difficult to directly apply to the space-ground integrated smart grid communication scenario. Some traditional terrestrial network multicast routing algorithms cannot effectively handle latency and signal instability when faced with the unique characteristics of satellite links. Conversely, satellite network multicast routing algorithms often fail to fully consider the resource utilization and node characteristics of terrestrial networks. Therefore, a multicast routing method specifically tailored for the space-ground integrated smart grid environment is urgently needed to meet the growing communication needs of the smart grid and ensure the stable and secure operation of the power system. Summary of the Invention

[0008] In order to solve the problems existing in the background technology, the present invention provides a space-ground integrated multicast routing method for smart grid, comprising:

[0009] S1: The source node broadcasts a beacon message to wake up the selected multicast member nodes;

[0010] S2: Build a multicast tree consisting of all multicast member nodes;

[0011] S3: For any two connected multicast member nodes in the multicast tree, if the two connected multicast member nodes cannot communicate directly, the shortest routing path between the multicast member nodes is constructed based on the relay nodes between the multicast member nodes as the routing link between the two multicast member nodes; if the two connected multicast member nodes can communicate directly, a routing link is directly constructed between the two multicast member nodes; multicast routing is performed through the routing link between the multicast member nodes.

[0012] The present invention has at least the following beneficial effects

[0013] By finding relay nodes to construct the shortest routing path, the present invention can flexibly cope with such complex situations, ensuring that effective communication links can be established between multicast members in various situations, greatly enhancing the adaptability and robustness of the solution in different scenarios. It can provide a stable and efficient transmission path for various multicast communication services of the smart grid in an integrated space-ground network environment. It ensures that key information such as real-time monitoring data and dispatch instructions of the power system are accurately and timely transmitted to multiple relevant nodes, thereby improving the reliability and efficiency of the entire smart grid communication system, and ultimately ensuring the safe and stable operation of the power system. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 Schematic diagram of the method flow of the present invention;

[0015] Figure 2 Schematic diagram of the framework of the space-ground integrated network for smart grid of the present invention;

[0016] Figure 3This is a schematic diagram of the multicast tree construction and the routing link construction between multicast member nodes of the present invention. DETAILED DESCRIPTION

[0017] The following describes the embodiments of the present invention by means of specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present invention, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0018] See also Figure 1 、 Figure 2 and Figure 3 The present invention provides a space-ground integrated multicast routing method for smart grids, comprising:

[0019] S1: The source node broadcasts a beacon message to wake up the selected multicast member nodes;

[0020] Preferably, the integrated ground-ground network includes: m ground network nodes and n satellite network nodes, and all nodes are registered to the smart grid central server.

[0021] In this embodiment, the integrated space-ground smart grid includes: ground facilities (such as power plants, intelligent control and dispatching centers, transmission lines, substations, power end users, and other ground network nodes) and satellite nodes such as satellite equipment. When the ground network nodes transmit data, they can directly forward it through the ground communication link. For remote areas, they can also relay and forward it through satellite nodes.

[0022] Assume that the ground-ground integrated network consists of k nodes, including the ground network node set G = {g1, g2, ..., g m} and satellite node set S={s1,s2,...,s n}, each node is assigned a unique identifier To distinguish it from other nodes, m represents the number of ground network nodes; n represents the number of satellite nodes; α is a Boolean variable, 0 represents a satellite node and 1 represents a ground node; when a source node needs to transmit data, it will randomly select M < K receiving nodes, where M is the number of nodes participating in the multicast transmission, which is called the multicast group size.

[0023] In step S1 of this embodiment, to achieve efficient multicast routing in the integrated smart grid environment, each multicast member node is assigned a unique label to clearly indicate its specific role in the multicast tree. "S" specifically represents the source node, which initiates the message and controls the initiation of the entire multicast process. "R" represents the numerous multicast member nodes, which are the receivers of the message and are responsible for receiving and processing the relevant data sent by the source node.

[0024] During this crucial phase, the source node sends a special message containing the identifiers of all multicast member nodes. This message is like a key that unlocks the door to communication and plays a crucial role. Given the complex structure and numerous nodes of the smart grid's integrated ground-to-ground network, sending this message ensures that all nodes in the network clearly know whether they are multicast members. This is analogous to a large and complex organization using a detailed list to ensure that every member clearly understands whether they are on a specific task force. Once the nodes in the network receive this message, those that are multicast members will quickly respond. They immediately mark themselves with an "R," a clear marker on a map indicating their readiness. Simultaneously, they actively prepare and fully participate in the subsequent multicast routing process. When the source node sends this message, it also clearly identifies its location. This location information is of great significance to the entire multicast process. It is like a navigation coordinate, providing a key basis for establishing accurate and efficient communication links between subsequent multicast member nodes and the source node. This enables multicast member nodes to interact with the source node more accurately, ensuring smooth and efficient information transmission.

[0025] S2: Build a multicast tree consisting of all multicast member nodes;

[0026] Preferably, the constructing of a multicast tree consisting of all multicast member nodes includes:

[0027] S21: Connecting the satellite multicast member node to the terrestrial multicast member nodes within the coverage area;

[0028] S22: Initialize the search range of each multicast member node and calculate the Euclidean distance between each multicast member node and the source node;

[0029] S23: For each multicast member node except the source node, search for other multicast member nodes within the search range. If other multicast member nodes are found, execute step S24; otherwise, execute step S26.

[0030] S24: Determine whether the Euclidean distance between the remaining searched multicast member nodes and the source node is less than the Euclidean distance between the current multicast member node and the source node; if so, add the remaining multicast member nodes as candidate multicast member nodes to the candidate multicast member node set; then determine whether the candidate multicast member node set is empty; if so, execute step S26; otherwise, execute step S25;

[0031] S25: selecting the candidate multicast member node with the smallest Euclidean distance to the source node in the candidate multicast node set as the optimal candidate multicast member node, and connecting the multicast member node to the optimal candidate multicast member node;

[0032] S26: If the current multicast member node does not find a candidate multicast member node that meets the conditions within the search range, the search range of the current multicast member node is expanded according to a preset ratio, and steps S23 to S26 are repeatedly performed within the search range until a multicast tree consisting of all multicast member nodes is constructed.

[0033] In order to illustrate step S2 in this application in more detail, the present invention provides the following examples:

[0034] Assume that the following nodes exist in a smart grid space-ground integrated network: source node S, located at coordinates (50, 50) (two-dimensional coordinates are used here as an example; in practice, three-dimensional coordinates may be used). Satellite multicast member node S1 covers an area with radius r1 = 100, centered around itself. Terrestrial multicast member nodes G1 (coordinates 30, 40), G2 (coordinates 70, 80), G3 (coordinates 150, 180), and G4 (coordinates 220, 230), among others, are distributed at different locations. Satellite multicast member node S1 starts up and detects terrestrial multicast member nodes within its coverage area. It calculates that G3 and G4 are within S1's coverage area, so S1 establishes connections with G3 and G4, respectively. This step leverages the wide coverage of satellites to initially integrate some terrestrial nodes into the multicast network, essentially building a preliminary architecture for space-ground communications. Initialize the search range of each multicast member node (including the source node S). Assume that the initial search range is a circular area with a radius of 30 kilometers, centered on each node. Calculate the Euclidean distance between each multicast member node and the source node S. For example, for G1, its Euclidean distance to the source node S is:

[0035]

[0036] Through this calculation, each node clearly understands the spatial distance between itself and the source node, providing a quantitative basis for subsequent connection strategies. For example, G2 searches for other multicast member nodes within its initial search range. If G1 is found within this range, step S24 is executed; if not, step S26 is executed.

[0037] Step S24: G2 determines whether the Euclidean distance between G1 and the source node S is less than the Euclidean distance between G2 and the source node S. G1-S ≈22.36, Because d G1-S <d G2-S Therefore, G1 is added to the candidate multicast member node set as a candidate multicast member node. Next, the candidate multicast member node set is determined to be empty. If it is not empty, step S25 is executed. This step screens out more optimal candidate connection nodes by comparing distances, which helps optimize the multicast tree structure.

[0038] Step S25: At this point, only G1 is included in the candidate multicast node set. G1 is the candidate multicast member node with the smallest Euclidean distance to the source node. G2 is then connected to G1. This process of gradually connecting each multicast member node is like building branches, gradually forming the prototype of a multicast tree.

[0039] Step S26: If G2 does not find any eligible candidate multicast member nodes within the initial search range, the search range is expanded by a preset ratio (e.g., 1.5 times), i.e., the search range becomes a circular area with G2 as the center and a radius of 30 × 1.5 = 45. Steps S23-S26 are then repeated within the new search range until all multicast member nodes (including the source node) are connected and a complete multicast tree is constructed.

[0040] In this embodiment, step S21 utilizes the coverage of satellite multicast member nodes to connect ground multicast member nodes, giving full play to the advantages of the integrated space-ground network, expanding the coverage of the multicast network, enabling more nodes to participate in multicast communication, and meeting the widely distributed node communication needs of the smart grid. By calculating the Euclidean distance between each node and the source node and selecting the connection node based on the distance (steps S22-S25), the constructed multicast tree structure is more compact and reasonable. Shorter paths can reduce data transmission delays and signal loss, improve communication efficiency and reliability, and meet the strict requirements of the smart grid for real-time and accuracy of data transmission. The adaptive search range expansion mechanism of step S26 ensures that even in the case of uneven node distribution or complex network environment, all multicast member nodes (including source nodes) can be included in the multicast tree, enhancing the adaptability and robustness of the algorithm, and ensuring the integrity and stability of the integrated space-ground multicast communication of the smart grid.

[0041] S3: For any two connected multicast member nodes in the multicast tree, if the two connected multicast member nodes cannot communicate directly, the shortest routing path between the multicast member nodes is constructed based on the relay nodes between the multicast member nodes as the routing link between the two multicast member nodes; if the two connected multicast member nodes can communicate directly, a routing link is directly constructed between the two multicast member nodes; multicast routing is performed through the routing link between the multicast member nodes.

[0042] Preferably, the constructing the shortest routing path between the multicast member nodes according to the relay nodes between the multicast member nodes includes:

[0043] S31: For any two connected multicast member nodes in the multicast tree, one of the multicast member nodes is used as a message sending node, and the other multicast member node is used as a message receiving node;

[0044] S32: The message sending node broadcasts the request message within its communication range and receives a reply response to the request message, wherein the reply response records the propagation path of the request message and the location information of each node in the propagation path;

[0045] S33: The message sending node counts the reply responses within the timeout period set by it, and selects the propagation paths of the reply responses that include the message receiving node as a candidate path set;

[0046] S34: Filter out the shortest routing path from the message sending node to the message receiving node from the candidate path set.

[0047] In order to better illustrate step S3 of the present invention, the present application provides the following examples:

[0048] Assume that a multicast tree has been constructed in a smart grid's integrated ground-to-sky multicast network. The multicast tree contains multiple multicast member nodes, including source nodes and common member nodes. Now, consider two connected multicast member nodes, A and B, in the multicast tree to illustrate the implementation of step S3.

[0049] Case 1: Two nodes can communicate directly

[0050] If nodes A and B are within each other's communication range and the signal strength and communication quality meet the requirements for direct communication, a routing link can be directly established between them. For example, if nodes A and B are adjacent ground-based substation communication nodes, they are close together, and the communication frequency band and signal environment are good, allowing for direct data transmission and reception. In this case, a simple, direct routing link can be quickly established for multicast data transmission.

[0051] Case 2: Two nodes cannot communicate directly

[0052] If nodes A and B cannot communicate directly due to distance, obstacles, or signal interference, the shortest routing path is constructed as follows:

[0053] Step S31: Node A is used as a message sending node, and node B is used as a message receiving node.

[0054] Step S32: Node A broadcasts a request message within its communication range. Assume that there are nodes C, D, and E within the communication range of node A, and these three nodes receive the request message broadcast by node A.

[0055] Nodes C, D, and E respectively reply to the request message. Taking node C as an example, it records the propagation path of the request message as A→C in the reply response, and records the location information of nodes A and C; node D records the propagation path as A→D, and records the location information of nodes A and D; the same is true for node E.

[0056] After receiving the request message, nodes C, D, and E will continue to broadcast the request message within their respective communication ranges. Assume that nodes F and G are within the communication range of node C, node H is within the communication range of node D, and node I is within the communication range of node E. After receiving the message, these nodes will also reply and record the propagation path and location information.

[0057] Step S33: Node A sets a timeout period, such as 100 milliseconds, during which node A counts all received reply responses.

[0058] Node A removes the propagation paths of the reply response that include the propagation paths of node B and forms a set of candidate paths. Assume that after the screening, the paths A→C→F→B and A→D→H→B are obtained as candidate paths.

[0059] Step S34: Node A calculates the distance from node A to node B based on the node location information recorded for each path in the candidate path set. For example, for path A→C→F→B, the total length of the path is calculated using the geographic distance formula based on the location information of each node. The same calculation is performed for path A→D→H→B. The lengths of the paths are compared to ultimately select the shortest routing path. Assuming that the calculation finds that path A→C→F→B is shorter, this path is selected as the shortest routing path from node A to node B, and the corresponding routing link is constructed.

[0060] In this embodiment, the present invention can flexibly select the method for constructing routing links based on the actual communication conditions between multicast member nodes. For nodes that can communicate directly, links are directly constructed, which reduces unnecessary intermediate links and improves communication efficiency. For nodes that cannot communicate directly, the shortest routing path is constructed through relay nodes, which adapts to complex network environments and ensures that information can be accurately transmitted under various circumstances. By constructing the shortest routing path, the number of hops and distances in the data transmission process are reduced, and the network delay and energy consumption of data transmission are reduced. In the integrated space-ground network of the smart grid, this helps to improve the utilization of network resources and ensure the fast and accurate transmission of real-time data in the power system. By broadcasting request message packets and collecting reply responses, multiple possible routing paths can be discovered, and the shortest path can be selected as the final routing link. This multi-path search and selection mechanism increases the reliability of communication. When a path fails or is interfered with, other paths can be reselected, which improves the stability of multicast routing.

[0061] Preferably, when a multicast member node exits the multicast tree, dynamic maintenance of the multicast tree exit is performed; the dynamic maintenance of the multicast tree exit includes:

[0062] When a multicast member node in a multicast tree exits the multicast tree, the multicast member node is treated as a leaving node, and the smart grid central server deletes the leaving node and all edges connected to the leaving node from the multicast tree; when the number of edges connected to the leaving node is greater than or equal to 2, the multicast tree is divided into a source tree and one or more subtrees due to the departure of the multicast member, where the source tree is the multicast tree where the source node is located; for each subtree, the multicast member node connected to the leaving node is treated as the head node of the subtree, and the following steps are performed to perform multicast tree maintenance: for the head node of each subtree, the search range of the head node is initialized and steps S23 to S26 are performed to search for the optimal candidate multicast member node of the head node, and the head node of each subtree is connected to its optimal candidate multicast member node, completing the dynamic maintenance of the multicast tree exit.

[0063] In this example, a multicast tree has been constructed in a smart grid integrated space-ground multicast network. The multicast tree includes a source node S and multicast member nodes A, B, C, D, E, and F. The connections between these nodes are as follows: source node S connects to A and B, A connects to C and D, and B connects to E and F. Now, suppose multicast member node A wants to exit the multicast tree. The following steps are performed to dynamically maintain the multicast tree exit:

[0064] 1. Identify the leaving node and delete the related edges:

[0065] Multicast member node A is the leaving node, and the smart grid central server deletes node A and the edges connected to A from the multicast tree, namely, the edges connecting S and A, the edges connecting A and C, and the edges connecting A and D.

[0066] 2. Determine changes in the multicast tree:

[0067] Since the number of edges connected to the departing node A is 3, the multicast tree is divided into a source tree and two subtrees due to the departure of node A. The source tree is the portion of the multicast tree containing source node S. In this case, S is directly connected to node B, and node B is connected to nodes E and F. One subtree contains node C, and the other contains node D. Nodes C and D connected to the departing node A serve as the head nodes of their respective subtrees. For the subtree with C as the head node, initialize C's search range, for example, an area with radius r0 and centered around C. Then, execute step S23: C searches for other multicast member nodes within the search range. Assuming D is found within this range, execute step S24. In step S24, C determines whether the Euclidean distance between D and source node S is less than the Euclidean distance between C and the source node. Assuming that the calculated Euclidean distance between D and source node S is smaller, add D as a candidate multicast member node to the candidate multicast member node set. Determine if the candidate multicast member node set is not empty, and execute step S25.

[0068] Step S25: Because only D is included in the candidate multicast node set, D is the candidate multicast member node with the smallest Euclidean distance to the source node. Therefore, C is connected to D. Assuming that no eligible nodes are found within the initial search range for C, step S26 is executed: the search range for C is expanded by a preset ratio (e.g., 1.5 times) to an area with a radius of 1.5r0 centered on C. Steps S23-S26 are then repeated within the new search range until a suitable connection node is found. Through these steps, dynamic maintenance of the multicast tree due to the exit of node A is completed.

[0069] In this embodiment, when a multicast member node exits, the node and related edges are deleted from the multicast tree in a timely manner, avoiding invalid connections and data transmission paths, and ensuring the clarity and effectiveness of the multicast tree structure. For a multicast tree that is split due to node exit, the multicast tree can continue to maintain a complete tree structure by reconnecting the subtrees, maintaining the normal operation of multicast communication. The split subtrees are maintained, and by searching for the optimal candidate multicast member nodes and connecting them, it is ensured that each subtree can be reconnected to the multicast tree in a more reasonable manner, avoiding the situation where some nodes cannot communicate due to node exit. This dynamic maintenance mechanism can adapt to the situation where nodes in the smart grid may change at any time, improve the reliability of multicast communication, and ensure the stability of data transmission in the power system. In the process of reconnecting the subtrees, the optimal candidate multicast member nodes are selected by calculating the Euclidean distance, which helps to optimize the topological structure of the multicast tree, make the data transmission path more reasonable, reduce transmission delay and energy consumption, and improve the overall performance of the multicast tree in the smart grid ground-to-ground integrated network.

[0070] Preferably, when other non-multicast member nodes want to join the multicast tree, dynamic maintenance of multicast tree joining is performed; the dynamic maintenance of multicast tree joining includes:

[0071] When other non-multicast member nodes want to join the multicast tree, the node is used as the joining node. The smart grid central server adds the joining node from the multicast tree and performs the following steps to maintain the multicast tree: for the joining node, initialize the search range of the joining node and execute steps S23 to S26 to search for the optimal candidate multicast member node of the joining node, and connect the joining node and its optimal candidate multicast member node to complete the dynamic maintenance of the joining of the multicast tree.

[0072] In this example, a multicast tree has been constructed in a smart grid's integrated ground-to-ground multicast network. The multicast tree contains a source node S and multicast member nodes A, B, C, and D. Source node S connects to nodes A and B, node A connects to node C, and node B connects to node D. Now, a non-multicast member node E wants to join the multicast tree. The following steps are performed:

[0073] Determine the joining node: The smart grid central server identifies node E as the joining node and prepares to add it to the multicast tree.

[0074] Initialize the search range: Initialize the search range for the node E. Assume that the initial search range is a circular area with node E as the center and radius r.

[0075] Execute steps S23-S26:

[0076] Node E searches for other multicast member nodes within its initial search range. Assume that nodes A and C are found within the search range.

[0077] Node E determines whether the Euclidean distances between Node A and Node C and source node S are less than the Euclidean distance between Node E and source node S. Assuming that the Euclidean distances between Node A and Node C and source node S are both less than the Euclidean distance between Node E and source node S, Node A and Node C are added as candidate multicast member nodes to the candidate multicast member node set. Next, the candidate multicast member node set is determined to be not empty, and step S25 is executed.

[0078] Step S25: Calculate the Euclidean distances between Node A and Node C and the source node S. Assuming that the Euclidean distance between Node A and the source node S is smaller, then Node A is selected as the optimal candidate multicast member node. Node E is then connected to Node A.

[0079] Assuming that node E does not find any eligible candidate multicast member node within the initial search range, the search range of node E is expanded by a preset ratio (e.g., 1.5 times) to a circular area with a radius of 1.5r and centered at node E. Steps S23-S26 are then repeated within the new search range until a suitable optimal candidate multicast member node is found and connected.

[0080] This solution allows non-multicast member nodes to join the multicast tree, enabling the smart grid's multicast network to flexibly expand based on actual needs. As the power system develops and changes, new devices or nodes may need to join multicast communications. This dynamic maintenance mechanism can easily accommodate new nodes and meet growing communication needs. In the actual operation of a smart grid, the network topology may change frequently. The dynamic maintenance mechanism for multicast tree joining can quickly respond to new node joining requests and promptly adjust the multicast tree structure to ensure the stability and reliability of multicast communications. Even in complex and changing network environments, it ensures that newly joined nodes are smoothly integrated into the multicast network, achieving efficient data transmission. The smart grid central server uniformly manages the node joining process, completing the new node joining through fixed steps (initializing the search range, searching for the optimal candidate node, and connecting). This makes the process of node joining the multicast tree clear and simple, reducing the system's management complexity and operation and maintenance costs.

[0081] In summary, the present invention can flexibly cope with such complex situations by finding relay nodes to construct the shortest routing path, ensuring that effective communication links can be established between multicast members under various circumstances, greatly enhancing the adaptability and robustness of the solution in different scenarios. It can provide a stable and efficient transmission path for various multicast communication services of the smart grid in an integrated space-ground network environment. It ensures that key information such as real-time monitoring data and dispatch instructions of the power system are accurately and timely transmitted to multiple relevant nodes, thereby improving the reliability and efficiency of the entire smart grid communication system, and ultimately ensuring the safe and stable operation of the power system.

[0082] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions, which should all be included in the scope of the claims of the present invention.

Claims

1. A space-ground integrated multicast routing method for smart grid, characterized in that: include: S1: The source node broadcasts a beacon message to wake up the selected multicast member nodes; S2: Build a multicast tree consisting of all multicast member nodes; The ground-to-space integrated network includes: m ground network nodes and n satellite network nodes, all of which are registered to the smart grid central server; The constructing of a multicast tree consisting of all multicast member nodes includes: S21: Connecting the satellite multicast member node to the terrestrial multicast member nodes within the coverage area; S22: Initialize the search range of each multicast member node and calculate the Euclidean distance between each multicast member node and the source node; S23: For each multicast member node except the source node, search for other multicast member nodes within the search range. If other multicast member nodes are found, execute step S24; otherwise, execute step S26. S24: Determine whether the Euclidean distance between the remaining searched multicast member nodes and the source node is less than the Euclidean distance between the current multicast member node and the source node; if so, add the remaining multicast member nodes as candidate multicast member nodes to the candidate multicast member node set; then determine whether the candidate multicast member node set is empty; if so, execute step S26; otherwise, execute step S25; S25: selecting the candidate multicast member node with the smallest Euclidean distance to the source node in the candidate multicast node set as the optimal candidate multicast member node, and connecting the multicast member node to the optimal candidate multicast member node; S26: If the current multicast member node does not find a candidate multicast member node that meets the conditions within the search range, the search range of the current multicast member node is expanded according to a preset ratio, and steps S23 to S26 are repeated within the search range until a multicast tree consisting of all multicast member nodes is constructed; S3: For any two connected multicast member nodes in the multicast tree, if the two connected multicast member nodes cannot communicate directly, the shortest routing path between the multicast member nodes is constructed based on the relay nodes between the multicast member nodes as the routing link between the two multicast member nodes; if the two connected multicast member nodes can communicate directly, a routing link is directly constructed between the two multicast member nodes; multicast routing is performed through the routing link between the multicast member nodes.

2. The method for space-ground integrated multicast routing for smart grid according to claim 1, characterized in that: The constructing of the shortest routing path between the multicast member nodes according to the relay nodes between the multicast member nodes comprises: S31: For any two connected multicast member nodes in the multicast tree, one of the multicast member nodes is used as a message sending node, and the other multicast member node is used as a message receiving node; S32: The message sending node broadcasts the request message within its communication range and receives a reply response to the request message, wherein the reply response records the propagation path of the request message and the location information of each node in the propagation path; S33: The message sending node counts the reply responses within the timeout period set by it, and selects the propagation paths of the reply responses that include the message receiving node as a candidate path set; S34: Filter out the shortest routing path from the message sending node to the message receiving node from the candidate path set.

3. The method for space-ground integrated multicast routing for smart grid according to claim 2, characterized in that: When a multicast member node exits the multicast tree, dynamic maintenance of the multicast tree exit is performed; The dynamic maintenance of multicast tree exit includes: When a multicast member node in a multicast tree exits the multicast tree, the multicast member node is treated as a leaving node, and the smart grid central server deletes the leaving node and all edges connected to the leaving node from the multicast tree; when the number of edges connected to the leaving node is greater than or equal to 2, the multicast tree is divided into a source tree and one or more subtrees due to the departure of the multicast member, where the source tree is the multicast tree where the source node is located; for each subtree, the multicast member node connected to the leaving node is treated as the head node of the subtree, and the following steps are performed to perform multicast tree maintenance: for the head node of each subtree, the search range of the head node is initialized and steps S23 to S26 are performed to search for the optimal candidate multicast member node of the head node, and the head node of each subtree is connected to its optimal candidate multicast member node, completing the dynamic maintenance of the multicast tree exit.

4. The method for space-ground integrated multicast routing for smart grid according to claim 3, characterized in that: When other non-multicast member nodes want to join the multicast tree, dynamic maintenance of the multicast tree joining is performed; The dynamic maintenance of multicast tree joining includes: When other non-multicast member nodes want to join the multicast tree, the node is used as the joining node. The smart grid central server adds the joining node from the multicast tree and performs the following steps to maintain the multicast tree: for the joining node, initialize the search range of the joining node and execute steps S23 to S26 to search for the optimal candidate multicast member node of the joining node, and connect the joining node to its optimal candidate multicast member node to complete the dynamic maintenance of the joining of the multicast tree.

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