Networking protocol design method for collaborative air computing in high-level confrontation environments

Abstract

The present invention discloses a networking protocol design method for collaborative over-the-air computing in a highly hostile environment. This method primarily addresses the existing problems of poor data transmission reliability, high protocol complexity, and high control overhead in self-organizing networks. The implementation scheme comprises: designing a networking protocol frame structure comprising control time slots and service time slots, obtaining the full network topology within the control time slot; calculating the shortest path based on the full network topology; finding Y sub-shortest paths based on the shortest path calculation, and selecting m paths with the same number of hops from these Y paths as the active paths; a source node searches for time slots outside the two-hop range for all nodes; based on the found time slots outside the two-hop range, the source node finds all available time slots for relay nodes along the path using the node adjacency matrix; and filling all available time slots for all relay nodes along the path into a data packet, which is then distributed to the relay nodes. The present invention offers high reliability, low protocol complexity, and low control overhead, and can be used in the MAC layer and network layer of self-organizing networks of unmanned systems.

Description

Technical Field

[0001] The present invention belongs to the technical field of wireless communications, and in particular relates to a networking protocol design method, which can be used for the MAC layer and network layer of an unmanned system self-organizing network. Background Art

[0002] MAC layer access protocols can be divided into three categories based on their channel access mechanisms: contention-based protocols, allocation-based protocols, and hybrid protocols. Contention-based protocols include ALOHA and CSMA / CA, allocation-based protocols include TDMA and FDMA, and hybrid protocols include HTDMA.

[0003] In competitive protocols, nodes access channels in a competitive manner. Nodes actively seize channels based on their own business needs, while other nodes postpone seizing channels when they detect that the channel is busy. When multiple nodes compete for channels at the same time, conflicts may occur. To reduce the probability of conflicts, after failing to compete for channels, nodes are randomly backed off for a period of time according to the backoff strategy and adjust the time for the next channel access.

[0004] In allocation-type protocols, different partitioning methods are used to divide resources into several orthogonal sub-resources, and then these sub-resources are allocated to designated nodes for use.

[0005] In hybrid protocols, contention protocols and allocation protocols are usually combined. This type of protocol mainly adopts TDMA protocol and introduces contention mechanism in time slot allocation.

[0006] The routing protocols used in self-organizing networks are mainly divided into three categories: on-demand routing protocols, table-driven routing protocols, and hybrid routing protocols. In an on-demand routing protocol, a node will only initiate route discovery when it wants to send a data packet to its destination. In a table-driven routing protocol, all nodes maintain one or more routing tables. To ensure the real-time nature of routing information, all nodes update the routing table at regular intervals. In a hybrid routing protocol, each layer uses a table-driven routing protocol, and between layers, an on-demand routing protocol is used. Both the on-demand routing protocol and the table-driven routing protocol are flat routing protocols. The hybrid routing protocol contains both an on-demand routing protocol and a table-driven routing protocol.

[0007] Currently, the TDMA protocol is widely used in wireless ad hoc networks, particularly in scenarios like drone ad hoc networks. In TDMA, the time slot is the smallest unit, and several time slots form a time frame. The number of time slots in each time frame is called the time slot length. The time it takes for a node to transmit a data packet to a neighboring node must be less than the length of a time slot. Traditional TDMA protocols use specific allocation principles to prevent collisions between multiple user frames on the physical channel. However, over-the-air computing technology exploits this collision to achieve multi-user signal superposition and improve reliability. Therefore, it is necessary to design a reasonable time slot allocation scheme to ensure that coordinating nodes transmit information in the same time slot.

[0008] Patent document CN202310096038.2 discloses a "multi-hop TDMA time slot allocation scheme for unmanned aerial vehicle ad hoc networks." It divides each TDMA time frame into reservation subframes and data subframes in chronological order. The reservation subframe contains K reservation periods, and the data subframe contains N data time slots. It defines control short frames, service long frames, and a time slot occupancy table. A fixed reservation period is occupied based on the node ID and priority. Each node that has joined the network sends reservation application frames and reservation notification frames for the data time slots during its reserved reservation period based on current service demand and time slot occupancy. Each node that has joined the network maintains a local time slot occupancy table based on the reservation notification frames. After the reservation subframe of a TDMA time frame ends, each node communicates by sending service long frames in the reserved data time slots. This method achieves on-demand TDMA channel allocation while prioritizing the channel requirements of high-priority nodes and data timeliness. However, the scheme's drawbacks are that this access method results in high network control overhead, limited scalability as the number of nodes increases, and unsuitable for large-scale network scenarios. At the same time, the time slot allocation scheme fails to be combined with the relevant routing mechanism, which has a significant impact on the network performance of the UAV self-organizing network and the reliability cannot be guaranteed.

[0009] Patent application number CN202211415577.X discloses a "routing and time-frequency allocation method and apparatus based on an integrated air-ground ad hoc network." The method first obtains node information in the air-ground integrated ad hoc network, including available channels and edges. Based on the available channels and edges, the routing and time-frequency allocation problem model and transmission constraints for the ad hoc network are then derived. The weight of each edge corresponding to the data stream is then determined, and the minimum weight routing for the data stream is determined based on the weights and routing constraints. Finally, based on the minimum weight routing and time-frequency constraints, the routing and time-frequency allocation problem model for the ad hoc network is transformed into a slot-by-slot channel allocation optimization problem. This problem is then optimized and solved using a continuous convex approximation strategy. By simultaneously optimizing both routing and time-frequency allocation within the ad hoc network, this method improves node resource availability and reduces potential contention conflicts for candidate routing paths, thereby reducing the end-to-end latency of data stream transmission within the ad hoc network. However, because this method only optimizes end-to-end latency, it can reduce network throughput. Furthermore, the computational complexity and high hardware requirements are associated with this method. Summary of the Invention

[0010] The purpose of the present invention is to address the deficiencies of the above-mentioned existing technologies and propose a networking protocol design method for collaborative air computing in a highly hostile environment, so as to further improve network reliability, reduce protocol complexity, and reduce control overhead.

[0011] The key technologies and principles for achieving the purpose of the present invention are as follows:

[0012] The present invention realizes the design of networking protocol by coordinating air computing technology in a self-organizing network.

[0013] The above-mentioned air computing is different from the traditional communication and computing scheme of "transmit first and then calculate". Air computing aims to use the waveform superposition property of the signal during the transmission process of the wireless multi-access channel to directly demodulate the superimposed signal and obtain the calculation result. This technology can complete the calculation of an objective function while avoiding the collection of individual data through concurrent transmission of nodes. Because air computing uses the superposition of multiple access channels to realize the calculation of functions, this technology is also called multi-access channel-based computing. Air computing can combine different objective functions through the pre-processing function of the sending end, the post-processing function of the receiving end, and the linear superposition of the waveforms transmitted by multiple nodes during the transmission process to complete different computing tasks. Consider a class of objective functions with a summation structure, that is, it satisfies in the form of is the pre-processing function of the sending node, and ψ(·) is the post-processing function of the access point. Due to the summation structure of the objective function, the objective function can be calculated using the air computing architecture. It can be seen that air computing can avoid the collection of individual data and directly complete the function calculation. Regardless of the number of nodes, the objective function can be restored after a single channel usage, thereby greatly reducing the calculation delay. At the same time, the concurrent transmission of data by multiple nodes can improve the reliability of data received by the receiving end. The present invention utilizes the node concurrent transmission characteristic of air computing to realize the design of a self-organizing network networking protocol for collaborative air computing technology, including an access protocol and a routing protocol.

[0014] Based on the above principles, the technical steps for designing the networking protocol in the present invention include:

[0015] (1) Design a frame structure for a networking protocol suitable for collaborative over-the-air computing, which includes control time slots and service time slots;

[0016] (2) Construct a wireless self-organizing network scenario, including the distribution of source nodes and relay nodes, and use the designed frame structure to obtain the entire network topology within the control time slot to complete the self-organizing convergence of the network;

[0017] (3) Calculate the shortest path based on the entire network topology;

[0018] (4) Calculate the Y second shortest paths to be found based on the shortest path (Y>0, Y is an integer);

[0019] (5) Select m shortest paths from Y paths as the used paths (m <Y);

[0020] (6) Initialize the necessary parameters such as the source node, relay node set, adjacency matrix of other nodes, number of time slots, and node available time slot table;

[0021] (7) The source node searches for time slots outside the two-hop range for all nodes based on the node adjacency matrix;

[0022] (8) Based on the time slots outside the two-hop range of the node found, the source node finds a set of available time slots for the relay nodes on the path and marks them, and avoids reusing their marks when searching again;

[0023] (9) Repeat step (8) to complete the search for all available time slots of all relay nodes on the path, and fill these available time slots into the data packet and distribute it to the relay node.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] First, the present invention designs a collaborative air computing technology access protocol, which enables multiple relay nodes to complete function calculations when sending information synchronously in the same time slot, avoiding the process of the opposite node collecting individual data in turn and then performing function calculations, greatly reducing the calculation delay, and at the same time improving the reliability of the receiving end receiving data.

[0026] Second, the present invention designs a collaborative air computing technology routing protocol, so that all nodes in the network can obtain the entire network topology after two epochs, reducing control overhead. At the same time, it calculates multiple paths based on the Dijkstra algorithm, reducing the complexity of the routing protocol. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a general flow chart for realizing the present invention;

[0028] Figure 2 This is a schematic diagram of the frame structure designed in the present invention;

[0029] Figure 3 It is the multi-path query sub-flowchart in the present invention;

[0030] Figure 4 This is a sub-flowchart of time slot allocation for a single source node in the present invention. DETAILED DESCRIPTION

[0031] The present invention is further described in detail below with reference to the accompanying drawings and examples.

[0032] Reference Figure 1 , the implementation steps of this example are as follows:

[0033] Step 1: Design a frame structure for a networking protocol suitable for collaborative air computing.

[0034] like Figure 2 As shown, the frame structure of the networking protocol designed in this step includes a control time slot and a service time slot.

[0035] The control time slot includes two time elements, each time element includes M time frames, and a time frame includes N ordinary time slots, where M is the maximum number of users supported by the network, each user has a unique identification ID in [0, M-1], and N is the maximum number of relay hops supported by the network, which is used to transmit networking control information. That is, when the source information of a user node needs to be sent, the source information is sent in the 0 time slot of the time frame of the user node. After sending, the node enters a dormant state in the subsequent time slots within the current time frame period, and no longer receives, processes, or sends any information data until the next time frame period begins. When a node receives information in the nth time slot that does not belong to its own time frame, it needs to determine whether the destination node of the information is the current node: if it is the current node, it receives and processes it; otherwise, the node immediately forwards the information in the n+1th time slot within the time frame, and enters a dormant state in the subsequent time slots within the current time frame period, and wakes up at the beginning of the next time frame period.

[0036] The service time slot includes k service time slots, where the value of k depends on the length of the superframe and is a positive integer multiple of the maximum number of users M, and is used for service transmission.

[0037] Step 2: Build a wireless self-organizing network scenario, use the frame structure to obtain the entire network topology within the control time slot, and complete the self-organizing convergence of the network.

[0038] 2.1) Construct a wireless self-organizing network scenario including the distribution of source nodes and relay nodes;

[0039] 2.2) Use the frame structure designed in step 1 to obtain the topology of the wireless ad hoc network in the control time slot. This is done by each node broadcasting the unique ID of the source node and the neighbor status in the control time slot. This is achieved as follows:

[0040] 2.2.1) Send the node's unique ID in the first epoch of the control time slot. This means that a control message flood is initiated in time slot 0 of the node's time frame. This message carries the node's ID. If other nodes receive the flood in time slot 0 of time frame X, they set node X as a neighbor and the corresponding bit position in the neighbor status is set to 1.

[0041] 2.2.2) Send neighbor status in the second epoch within the control time slot. That is, initiate a control information flood containing the node ID and the neighbor status collected in the previous control time frame in the 0th time slot of the node time frame. By flooding the neighbor status across the entire network, all nodes in the network can obtain the entire network topology and complete the network's self-organizing convergence.

[0042] Step 3: Calculate the shortest path based on the entire network topology.

[0043] 3.1) Set the node, network, and array parameters, including: initializing the source node o, the destination node d, the set V of all nodes in the network topology, the set S of vertices for which the shortest path has been found, the dis array for recording the current shortest path lengths from the source node o to other vertices, and the path array for recording the predecessors of the shortest paths from the source node o to other vertices;

[0044] 3.2) Use the Dijkstra algorithm for the shortest path to find the shortest path from the source node o to the destination node d:

[0045] 3.2.1) Calculate the end point vi of the shortest path starting from the source node o from the set V - S, and add it to the set S;

[0046] 3.2.2) Modify the shortest path length from the source node o to any node vk in the set V - S that is reachable. If the distance from the source node o to vk is greater than the sum of the distance from the source node o to vi and the distance from vi to vk, then record the sum of the distance from the source node o to vi and the distance from vi to vk in the dis array, and modify the predecessor of the node vk in the path array to be vi;

[0047] 3.2.3) Repeat the operations in (3.2.1) and (3.2.2) until all vertices are included in S, and then query the shortest path from the source node o to the destination node d from the path array, and mark it as P y (y = 1), where y is the number of paths currently found.

[0048] Step 4, calculate the Y second - shortest paths to be searched according to the shortest path.

[0049] Refer to Figure 3 , the specific implementation of this step is as follows:

[0050] 4.1) Initialize the source node o, the destination node d, the number Y of shortest paths to be found, the list A of shortest paths already found, the candidate list B, and the network topology and node time - slot table these parameters;

[0051] 4.2) Compare the currently obtained number of paths y with the number of paths Y to be found:

[0052] If y < Y and there are candidate paths in the candidate list B, then execute step 4.3);

[0053] If y >= Y or there are no candidate paths in the candidate list B, then complete the path query;

[0054] 4.3) Consider each intermediate node on the P y path except the destination node d as a deviation point. Suppose there are x deviation points in total, and each deviation point is denoted as Vi , i = 1.2...x, and traverse each deviation point starting from i = 1, and find V i The shortest path to the destination node d, when finding the shortest path, pay attention to the V i The shortest path to d cannot include o to V i Any node on the path, and from V i The starting edge cannot be the same as the shortest path from V in List A. i The starting edge is the same, then P y From the starting point to V i Path + obtained V i The shortest path to the destination node d is used as the candidate path P y+1 , put it into candidate path list B;

[0055] 4.4) After traversing the deviation points, find the path with the smallest weight in list B, which is the desired P y+1 , remove the path from list B and put it into list A, and return to step 4.2).

[0056] Step 5: Select m shortest paths from the y paths as the paths to be used.

[0057] Sort the y shortest paths found according to the number of hops, and select the m shortest paths with the least hops from the y paths as the paths to be used. If the m paths with the least hops cannot be found, then select all paths that meet the requirement of the least hops.

[0058] Step 6: Initialize parameters.

[0059] The initialization parameters include the necessary parameters: source node, relay node set, adjacency matrix of other nodes, number of time slots, node available time slot table. The adjacency matrix of the initialized node is established by each node based on the connection relationship between nodes in the network topology.

[0060] In step 7, the source node searches for time slots outside the two-hop range for all nodes based on the node adjacency matrix.

[0061] Reference Figure 4 , the specific implementation of this step is as follows:

[0062] 7.1) The source node traverses its own adjacency matrix. Every time it finds a neighbor node, it records the time slot as unavailable. It then traverses the adjacency matrix of this neighbor node, finds all of its neighbors, and records the time slots of all of its neighbors as unavailable. This way, it obtains all time slots outside the two-hop range of the source node.

[0063] 7.2) The source node searches for all time slots outside the two-hop range for the relay node in the same manner as in step 7.1), and traverses all relay nodes in turn to find all time slots outside the two-hop range for the relay node.

[0064] Step 8: Based on the time slots outside the two-hop range of the node found, the source node finds a group of available time slots for the relay nodes on the path and marks them to avoid reusing their marks when searching again.

[0065] 8.1) The source node traverses its own two-hop out-of-range slot table:

[0066] If an available time slot is found, the node first records the time slot in its own to-be-used time slot table, then marks the time slot as unavailable in the time slot tables of other nodes within two hops of the node, and executes step 8.2);

[0067] If an available time slot cannot be found, the search for available time slots of all nodes on the path is completed;

[0068] 8.2) Find an available time slot for the next layer of relays based on the number of relays in the current layer of relay node set:

[0069] If there is a relay node in this layer, execute step 8.2.1);

[0070] If there are multiple relay nodes in this layer, execute step 8.2.2);

[0071] 8.2.1) Traverse the two-hop out-of-range slot table of this node:

[0072] If an available time slot is found, the node first records the time slot in its own to-be-used time slot table, then marks the time slot as unavailable in the time slot tables of all other nodes within the two-hop range of the node, and executes step 8.3);

[0073] If an available time slot cannot be found, the search for available time slots of all nodes on the path is completed;

[0074] 8.2.2) Traverse the two-hop out-of-range time slot table of all nodes in this layer in turn:

[0075] If a shared time slot can be found, the time slots of all relay nodes in this layer are first recorded in their own time slot table to be used, and then the time slot is marked as unavailable in the time slot tables of other nodes within two hops of the node, and step 8.3 is executed;

[0076] If a shared time slot cannot be found, the search for available time slots of all nodes on the path is completed;

[0077] 8.3) Determine whether the current layer is the last layer of relay:

[0078] If it is the last layer of relay, return to step 8.1);

[0079] If it is not the last relay layer, return to step 8.2).

[0080] Step 9: Fill the available time slots into the data packets and distribute them to the relay nodes.

[0081] The source node will fill all available time slots found into the data packet and distribute it to the relay node. That is, the source node first fills all the available time slot numbers of each layer into the data packet according to the layer number, and then sends it to the relay node in its first service time slot.

[0082] After receiving this data packet, the relay node forwards it until all relays receive this packet.

[0083] The above description is only a specific example of the present invention and does not constitute any limitation to the present invention. It is obvious that for professionals in this field, after understanding the content and principles of the present invention, they may make various modifications and changes in form and details without departing from the principles and structure of the present invention. However, these modifications and changes based on the ideas of the present invention are still within the scope of protection of the claims of the present invention.

[0084] It should be noted that the step numbers in the specification and claims of the present invention are only for a clear description of the embodiments of the present invention and for ease of understanding, and the order of the step numbers is not limited.

Claims

1. A networking protocol design method for collaborative air computing in a highly hostile environment, characterized by: include: (1) Design a frame structure for a networking protocol suitable for collaborative over-the-air computing, which includes control time slots and service time slots; (2) Construct a wireless self-organizing network scenario, including the distribution of source nodes and relay nodes, and use the designed frame structure to obtain the entire network topology within the control time slot to complete the self-organizing convergence of the network; (3) Calculate the shortest path based on the entire network topology; (4) Calculate the Y second shortest paths to be found based on the shortest path (Y>0, Y is an integer); (5) Select m shortest paths from Y paths as the used paths (m <Y); (6) Initialize the necessary parameters such as the source node, relay node set, adjacency matrix of other nodes, number of time slots, and node available time slot table; (7) The source node searches for time slots outside the two-hop range for all nodes based on the node adjacency matrix; (8) Based on the time slots outside the two-hop range of the node found, the source node finds a set of available time slots for the relay nodes on the path and marks them, and avoids reusing their marks when searching again; (9) Repeat step (8) to complete the search for all available time slots of all relay nodes on the path, and fill these available time slots into the data packet and distribute it to the relay node.

2. The method according to claim 1, characterized in that The control time slot and service time slot in step (1) have the following structure: The control time slot is used to transmit networking control information. It contains two time elements, each of which contains M time frames, and one time frame contains N normal time slots, where M is the maximum number of users supported by the network. Each user has a unique ID in the range [0, M-1], and N is the maximum number of relay hops supported by the network. The service time slot is used for service transmission and includes k service time slots. The value of k depends on the length of the superframe and is a positive integer multiple of the maximum number of users M.

3. The method according to claim 1, characterized in that In step (2), the designed frame structure is used to obtain the entire network topology in the control time slot. This is done by each node broadcasting source information in the control time slot. The source information includes the unique ID of the source node and the neighbor status. The implementation is as follows: The node's unique ID is sent in the first epoch within the control slot. That is, the source control information flood is sent in slot 0 of the node's time frame. The flood carries the node's ID, and the remaining bits are all 0. If other nodes receive the flood in slot 0 of time frame X, they set node X as a neighbor, and the corresponding bit position of the neighbor status is 1. The neighbor status is sent in the second epoch within the control time slot, that is, the control information containing the local node ID and the neighbor status collected in the previous control time frame period is flooded in the 0th time slot of the local node time frame. By flooding the neighbor status throughout the network, all nodes in the network can obtain the entire network topology.

4. The method according to claim 1, wherein In step (3), the shortest path is calculated based on the entire network topology, which is implemented as follows: (3a) Setting node, network, and array parameters, including: initializing the source node o, the destination node d, the set V of all nodes in the network topology, the set S of vertices for recording the shortest paths obtained, the dis array for recording the current shortest path lengths from the source point o to other vertices, and the path array for recording the shortest path predecessor nodes from the source point o to other vertices; (3b) Use the shortest path Dijkstra algorithm to find the shortest path from the source node o to the destination node d: (3b1) Select the end point vi of the shortest path starting from the source node o from the set V - S, and add it to the set S; (3b2) Modify the length of the shortest path from the source node o to any node vk in the set V - S that can be reached, record it in the dis array, and modify the predecessor node of the node vk in the path array to be vi; (3b3) Repeat (3b1) and (3b2) until all vertices are included in S. Query the shortest path from the source node o to the destination node d from the path array and mark it as P. y (y=1), y is the number of paths currently found.

5. The method according to claim 1, characterized in that Step (4) Calculate the Y second - shortest paths to be searched according to the shortest path, and the implementation is as follows: (4a) Initialize parameters such as the source node o, the destination node d, the number Y of shortest paths to be found, the list A of the shortest paths already found, the candidate list B, and the network topology and node time slot table; (4b) Compare the currently obtained number of paths y with the number of paths Y to be found: If y < Y and there are candidate paths in the candidate list B, then execute step (4c); If y >= Y or there are no candidate paths in the candidate list B, then execute step (4e); (4c) Put the y Each point on the path except the destination node d is considered as a deviation point. Suppose there are x deviation points in total, and each deviation point is recorded as V i , i=1.2...x, and traverse each deviation point starting from i=1, and find V i The shortest path to the destination node d, P y From the starting point to V i Path + obtained V i The shortest path to the destination node d is used as the candidate path P y+1 , put it into candidate path list B; (4d) After traversing the deviation points, find the path with the smallest weight in list B, which is the required P y+1 , remove the path from list B, put it into list A, and return to step (4b); (4e) Sort the y shortest paths found according to the number of hops, and select the m shortest paths with the fewest hops from the y paths as the used paths. If the m shortest paths with the fewest hops cannot be found, then select all the paths that meet the requirement of the fewest hops.

6. The method according to claim 1, wherein: In step (6), the adjacency matrix of the nodes is initialized, and each node establishes its own adjacency matrix according to the connection relationship between the nodes in the network topology.

7. The method according to claim 1, wherein: In step (7), the source node finds the time slots outside the two - hop range for all source nodes and all relay nodes according to the adjacency matrix of the nodes, and the implementation is as follows: The source node traverses its own adjacency matrix. Every time a neighbor node is found, the time slot at this time is recorded as unavailable. Then, traverse the adjacency matrix of this neighbor node, find all the neighbors of this neighbor node, and record the time slots of all the neighbor nodes of this neighbor node as unavailable, so as to obtain all the time slots outside the two - hop range of the source node; The source node uses this method to find all the time slots outside the two - hop range for the relay nodes. Traverse all the relay nodes in turn to find all the time slots outside the two - hop range for the relay nodes.

8. The method according to claim 1, characterized in that In step (8), according to the time slots outside the two - hop range of the nodes found, the source node finds a set of available time slots for the relay nodes on the path, and the implementation is as follows: (8a) The source node traverses its time slot table outside the two - hop range: If an available time slot can be found, first record this time slot in its own pending - use time slot table, and then mark this time slot as unavailable in the time slot tables outside the two - hop range of all the nodes within the two - hop range of the source node, and execute step (8b); If an available time slot cannot be found, then complete the search for available time slots for all the nodes on the path; (8b) According to the number of relays contained in the current - layer relay node set, find an available time slot for the next - layer relay: If there is one relay node in this layer, execute step (8b1); If there are multiple relay nodes in this layer, execute step (8b2); (8b1) Traverse the time slot table outside the two - hop range of this node: If an available time slot is found, the node first records the time slot in its own table of available time slots, then marks the time slot as unavailable in the time slot tables of all other nodes within the two-hop range of the node, and executes step (8c); If an available time slot cannot be found, the search for available time slots of all nodes on the path is completed; (8b2) Traverse the two-hop out-of-range time slot tables of all nodes in this layer in turn: If a shared time slot can be found, the node first records the time slots of all relay nodes in this layer into its own time slot table to be used, then marks the time slot as unavailable in the time slot tables of other nodes within two hops of the node, and executes step (8c); If a shared time slot cannot be found, the search for available time slots of all nodes on the path is completed; (8c) Determine whether the current layer is the last layer of relay: If it is the last layer of relay, return to step (8a); If it is not the last relay layer, return to step (8b).

9. The method according to claim 1, characterized in that In step (9), all available time slots found are filled into the data packet and distributed to the relay node. The source node first fills the serial numbers of all time slots available in each layer into the data packet according to the layer number, and then sends it to the relay node in its first service time slot. After receiving this data packet, the relay node forwards it until all relays receive this packet.

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