TDMA Time Slot Allocation Method for Underground and Underwater Wireless Internet of Things

Abstract

This invention discloses a low-overhead TDMA time slot allocation method for underground and underwater wireless IoT, mainly addressing the problems of excessively long time slot allocation time and high allocation overhead in existing technologies under harsh underground environments. The implementation scheme is as follows: An underground IoT network model is constructed; sensor nodes establish their own time slot table, one-hop node table, and two-hop node table at the same layer, and initialize each table entry; all nodes update their hop count information through time slot frame interaction, establishing a network hierarchical structure and updating relevant table entries; sensor nodes select their own time slot group based on their hop count; first-layer nodes have their transmission time slots uniformly assigned by the data aggregation node and do not participate in the time slot allocation process; other layer nodes negotiate and request transmission time slots by sending time slot frames to each other. This invention improves the transmission reliability of underground wireless IoT, reduces additional communication overhead, and lowers network energy consumption, and can be used for underground environmental monitoring, pipeline facility monitoring, and disaster early warning.

Description

Technical Field

[0001] This invention belongs to the field of Internet of Things (IoT) technology, and specifically relates to a Time Division Multiple Access (TDMA) time slot allocation method for IoT communication. It can be used in underground and underwater environmental monitoring, pipeline facility monitoring, and disaster early warning scenarios to avoid data transmission collisions, reduce additional communication overhead, and provide a guarantee for stable and reliable data transmission of underground and underwater IoT. Background Technology

[0002] With the rapid development of wireless communication technology, the Internet of Things (IoT) has made significant progress and is widely used in environmental monitoring, smart pipelines, disaster early warning, and many other fields, profoundly impacting all aspects of human production and life. In particular, the commercialization of 5G mobile communication technology has accelerated the arrival of the era of "Internet of Everything, full coverage," and the application areas of IoT are becoming increasingly broad, no longer limited to traditional above-ground environments. Various IoT applications for underground and underwater information collection and monitoring are emerging in large numbers. As a key technology in IoT, the time slot allocation method based on Time Division Multiple Access (TDMA) mainly solves the problem of how multiple nodes in a network can efficiently share or use physical link resources, i.e., share channel usage, reducing or even avoiding data collisions and communication failures when nodes access the same resource simultaneously. It is of great significance for reducing communication overhead, lowering network energy consumption, and ensuring transmission reliability, and is a key research focus for underground and underwater IoT.

[0003] The most unique aspect of underground and underwater IoT lies in the significant difference between the transmission medium and that in air. The special characteristics of underground or underwater environments present new challenges to the design of time slot allocation algorithms. Underground and underwater environments are characterized by high signal loss, resulting in greater signal attenuation and faster energy consumption. Furthermore, since sensor nodes operate underground and underwater, energy cannot be replenished through methods like solar power, as is possible with terrestrial networks. Therefore, the energy consumption problem is more severe in underground and underwater IoT. This necessitates that the TDMA time slot allocation algorithm completes the time slot allocation for all sensor nodes as quickly as possible, shortening the allocation time, reducing data packet interaction, and avoiding excessive overhead, thereby reducing network energy consumption. How to shorten the time slot allocation time and reduce communication overhead are the main challenges in designing time slot allocation algorithms for underground and underwater IoT.

[0004] In Jiang A, Mi Z, Dong C, et al. CF-MAC: A collision-free MAC protocol for UAVs Ad-Hoc networks [C] / / 2016IEEE Wireless Communications and Networking Conference.IEEE, 2016: 1-6, a region-labeled TDMA time slot allocation method is proposed. In this method, each sensor node maintains its own set of one-hop nodes, two-hop nodes, time slots occupied by one-hop nodes, and time slots occupied by two-hop nodes. The node obtains the time slot occupancy status within two hops by listening to time frames containing the one-hop node ID and its occupied time slot. Simultaneously, a CSMA method with random backoff time is used to avoid collisions between one-hop nodes, and collisions between two-hop nodes are avoided by marking the sensor node itself, one-hop nodes, and two-hop nodes as different regions. This method uses a distributed negotiation approach among sensor nodes to allocate time slots, making the entire time slot allocation process relatively simple. However, since collision-free transmission between sensor nodes is achieved through region marking to ensure data transmission reliability, all one-hop and two-hop nodes of the sensor node need to participate in the time slot negotiation process. This can easily lead to multiple nodes requesting the same time slot, exacerbating time slot allocation conflicts, resulting in excessively long time slot allocation time and high allocation overhead. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of the prior art by proposing a TDMA time slot allocation method for underground and underwater wireless Internet of Things, so as to shorten the time slot allocation time and reduce the time slot allocation overhead.

[0006] To achieve the above objectives, the technical solution of this invention is as follows: An underground and underwater Internet of Things (IoT) network model is established; each sensor node establishes its own time slot table, one-hop node table, and two-hop node table at the same layer; and the sink node establishes its own time slot table and one-hop node table, thus completing the initial deployment of all nodes. A network hierarchical structure is established by interactively updating the hop count information of all nodes through time slot frames, thereby updating the relevant table entries. Sensor nodes select their respective time slot groups based on their own hop counts, and all nodes complete time slot allocation.

[0007] Based on the above ideas, the technical solution of the present invention includes the following steps:

[0008] (1) Construct and initialize underground and underwater IoT models:

[0009] (1a) Construct a system comprising N sensor nodes S, each equipped with wireless communication devices and distributed in underground and underwater environments. n and a data aggregation node SSink Underground and underwater Internet of Things (IoT) models, where 1 ≤ n ≤ N;

[0010] (1b) Sensor node S n Establish your own time slot table TS n ={ID n ,HC n ,slot n}, One-hop node table TOH n ={ID i ,slot i} and the same-level two-hop node table TTH n ={ID j ,slot j},

[0011] Among them, ID n Indicates the sensor node ID number, HC n Indicates sensor node S n To data aggregation node S Sink The jump value, slot n Indicates the time slot number transmitted by the sensor node; ID i and slot i S represents n The first-hop node ID and the transmission slot number; ID j and slot j S represents n The ID number of the two hop nodes at the same layer and the transmission slot number;

[0012] (1c) Data aggregation node S Sink Establish your own time slot table TS Sink ={ID Sink ,HC sink ,slot Sink} and one-hop node table TOH Sink ={ID i ,slot i};

[0013] (1d) For sensor node S n and data aggregation node S Sink Initialize the relevant table entries;

[0014] (2) Sensor node S n Sending time-slot frames establishes a hop-count-based network hierarchy and updates node-related table entries:

[0015] (2a) Data aggregation node S Sink To other sensor nodes S in the network n Send time slot frame SF t ={IDt ,HC t ,slot t ID i ,slot i},

[0016] Among them, ID t Indicates the ID number of the sending node, HC t The slot represents the hop count of the sending node. t Indicates the timeslot number, ID, of the sending node. i The slot represents the one-hop node ID number of the sending node. i This indicates the one-hop node slot number of the sending node;

[0017] (2b) Data aggregation node S Sink Waiting to receive neighbor node S h(sink) SF slot frames h(sink) After receiving the time slot frame, SF h(sink) ID in h slot h The information is added to the one-hop node table TOH Sink middle;

[0018] (2c) Sensor node S n Waiting to receive neighbor node S h(n) SF slot frames h(n) After receiving the time slot frame, according to SF h(n) Content Update S n TS (Time Slot Table) n One-hop node table TOH n and the two-hop node table TTH at the same level n ;

[0019] (2d) Sensor node S n According to its own time slot table TS n and the one-hop node table TOH n The content is encapsulated into a new time-slot frame and sent.

[0020] (2e) Repeat steps (2c) and (2d) for all nodes until the node's own time slot table TS is reached. n The jump value information HC n One-hop node table TOH n and the two-hop node table TTH at the same level n Update complete;

[0021] (3) Sensor node S n Select a time slot group and request a transmission time slot:

[0022] (3a) Sensor node S nFrom its own time slot table TS n Read its own jump value HC n The entire TDMA time frame is divided into 3 time slot groups, and the jump value HC is... n The result is obtained by taking the modulus of the logarithm 3 (MOD). n And according to MOD n The value is selected from the corresponding time slot group;

[0023] (3b) Sensor node S n Each party requests its own transmission time slot through interactive negotiation of time slot frames.

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

[0025] First, this invention utilizes hop counts to layer the network and divides time frames into three time slot groups. Nodes in different layers avoid conflicts by joining different time slot groups. Time slot allocation is performed between nodes and nodes within two hops of the same layer through mutual negotiation. That is, only nodes within two hops of the same layer need to negotiate during the time slot allocation process, reducing the number of nodes involved in the negotiation, greatly shortening the negotiation time, and reducing the overhead of time slot allocation.

[0026] Secondly, this invention addresses the characteristic that all nodes in the first layer are two-hop nodes with no time slot reuse by having the sink node uniformly allocate time slots for the first layer nodes, thereby further shortening the time slot allocation time. Attached Figure Description

[0027] Figure 1 This is a flowchart illustrating the overall implementation of the present invention;

[0028] Figure 2 This is a schematic diagram showing the completion of the update of the three types of table entries in the node in this invention;

[0029] Figure 3 This is a schematic diagram illustrating the data transmission rules principle in this invention;

[0030] Figure 4 This is a sub-flowchart of the receiving node processing data packets in this invention;

[0031] Figure 5 This is a comparison chart of the simulation results of the residual energy ratio of the present invention and the prior art. Detailed Implementation

[0032] The embodiments and effects of the present invention will be further described in detail below with reference to the accompanying drawings.

[0033] Reference Figure 1 The implementation steps for this example are as follows:

[0034] Step 1: Build and initialize the underground and underwater IoT models.

[0035] 1.1) Construct a system comprising N sensor nodes S, each equipped with wireless communication devices and distributed in underground and underwater environments. n and a data aggregation node S Sink Underground and underwater Internet of Things (IoT) models, where 1 ≤ n ≤ N;

[0036] 1.2) Sensor node S n Create three related entries:

[0037] First, establish your own time slot table (TS). n ={ID n ,HC n ,slot n}, where ID n Indicates the sensor node ID number, HC n The slot represents the number of hops from the sensor node to the data aggregation node. n Indicates the time slot number transmitted by the sensor node;

[0038] Second, establish a one-hop node table TOH n ={ID i ,slot i}, where ID i and slot i S represents n The first-hop node ID number and the transmission timeslot number;

[0039] Third, establish a two-hop node table TTH at the same level. n ={ID j ,slot j}, where ID j and slot j S represents n The ID number of the two hop nodes at the same layer and the transmission slot number;

[0040] 1.3) Data aggregation node S Sink Create two related entries:

[0041] First, establish your own time slot table (TS). Sink ={ID Sink ,HC sink ,slot Sink}, where ID Sink Indicates the sensor node ID number, HC Sink The slot represents the number of hops from the sensor node to the data aggregation node. Sink Indicates the time slot number transmitted by the sensor node;

[0042] Second, establish a one-hop node table TOH Sink ={ID i,slot i}, where ID i and slot i S represents Sink The first-hop node ID number and the transmission timeslot number;

[0043] 1.4) Sensor node S n TS (Time Slot Table) n HC n Initially set to infinity ∞, represented by an unreachable jump value, slot n Initially empty; one-hop node table TOH n Neutralization of the same-level two-hop node table TTH n Initially empty; data aggregation node S Sink TS (Time Slot Table) Sink HC sink Initially 0, slot Sink Initially 0; one-hop node table TOH Sink Initially empty.

[0044] Step 2: The sensor node sends time slot frames to establish a network hierarchical structure based on hop count and updates the relevant table entries of the node.

[0045] 2.1) Data aggregation node S Sink Send time slot frames SF to other sensor nodes in the network t :

[0046] SF t ={ID t ,HC t ,slot t ID i ,slot i},

[0047] Among them, ID t Indicates the ID number of the sending node, HC t The slot represents the hop count of the sending node. t Indicates the timeslot number, ID, of the sending node. i The slot represents the one-hop node ID number of the sending node. i This indicates the one-hop node slot number of the sending node;

[0048] 2.2) Data aggregation node S Sink Waiting to receive neighbor node S h(sink) SF slot frames h(sink) After receiving the time slot frame, SF h(sink) ID in h slot h The information is added to the one-hop node table TOHSink middle;

[0049] 2.3) Sensor node S n Waiting to receive neighbor node S h(n) SF slot frames h(n) After receiving the time slot frame, according to SF h(n) Content Update S n TS (Time Slot Table) n One-hop node table TOH n and the two-hop node table TTH at the same level n :

[0050] 2.3.1) Parsing the time slot frame SF h(n) , will SF h(n) ID in h slot h The information is added to the one-hop node table TOH n middle;

[0051] 2.3.2) SF h(n) The jump value HC carried in h Add 1 as the new value HC new Determine HC n >HC new Is it true or false?

[0052] If true, then its own time slot table TS will be updated. n HC in n Set the value to HC new ;

[0053] Otherwise, proceed to step 2.3.3);

[0054] 2.3.3) Determining HC n =HC h Is it true or false?

[0055] If true, then SF h(n) Carrying a one-hop node ID i and the one-hop node transmit slot i Join S n TTH, a two-hop node table at the same level n middle;

[0056] Otherwise, no action will be taken;

[0057] 2.4) Sensor node S n According to its own time slot table TS n and the one-hop node table TOH n The content is encapsulated into a new time-slot frame and sent.

[0058] 2.5) Repeat steps 2.3) and 2.4) on all nodes until the node's own timeslot table TS is reached. n The jump value information HC n and the one-hop node table TOH n Two-hop node table TTH at the same level n Update complete.

[0059] The result of this example after completing network layering is as follows: Figure 2 As shown, the first layer of nodes includes nodes S1 and S2, with a hop value HC of 1; the second layer of nodes includes nodes S3, S4, and S5, with a hop value HC of 2; and the third layer of nodes includes nodes S6, S7, S8, and S9, with a hop value HC of 3. Each sensor node updates its own time slot table TS. n One-hop node table TOH n Neutralization of the same-level two-hop node table TTH n Regarding the relevant content, taking node S6 as an example, its own time slot table TS6 = {6, 3, null} indicates that S6's node ID number is 6 and its hop value is 3. Since the transmission time slot has not been allocated at this time, it is empty (null). The one-hop node table TOH6 = {(7, null)} indicates that node S7 is a one-hop node of S6. The same-layer two-hop node table TTH6 = {(8, null), (9, null)} indicates that nodes S8 and S9 are two-hop same-layer nodes of S6.

[0060] Step 3: The sensor node selects the time slot group to join based on its own jump value information.

[0061] 3.1) Divide the entire TDMA time frame into three time slot groups, denoted as time slot group A, time slot group B, and time slot group C, as shown in the figure. Figure 3 As shown, the length of the time slot group is determined based on the number of nodes in the corresponding network layer;

[0062] 3.2) Sensor node S n From its own time slot table TS n Read its own jump value HC n The jump value HC will be displayed. n The result MOD is obtained by taking the modulus of 3. n Determine MOD n Is the expression = 0 true?

[0063] If true, then sensor node S n It belongs to time slot group A;

[0064] Otherwise, proceed to step 3.3);

[0065] 3.3) Determine MOD n Is the value 1 true?

[0066] If true, then sensor node S n It belongs to time slot group C;

[0067] Otherwise, sensor node S n It belongs to time slot group B;

[0068] refer to Figure 2 and Figure 3 The first-level node hop value HC is 1, which is 1 after modulo 3, belonging to time slot group C. The first node S1 and the second node S2 select transmission time slots from time slots 11 to 15. The second-level node hop value HC is 2, which is 2 after modulo 3, belonging to time slot group B. The third node S3, the fourth node S4, and the fifth node S5 select transmission time slots from time slots 6 to 10. The third-level node hop value HC is 3, which is 0 after modulo 3, belonging to time slot group A. The sixth node S6, the seventh node S7, the eighth node S8, and the ninth node S9 select transmission time slots from time slots 1 to 5.

[0069] Step 4: Sensor nodes request their respective transmission time slots through interactive negotiation of time slot frames.

[0070] Reference Figure 4 The implementation of this step is as follows:

[0071] 4.1) Determine sensor node S n The jump value HC n Is the value 1 true?

[0072] If true, sensor node S n The transmission time slot is directly specified by the data aggregation node and does not participate in the time slot application process; steps 4.2) and 4.3) are executed.

[0073] Otherwise, proceed to step 4.4);

[0074] 4.2) Using NOH Sink The table TOH represents the one-hop node of the data aggregation node. Sink The number of intermediate nodes, and the data aggregation node is randomly selected from the time slot group to which the first-level node belongs. Sink Each time slot is used to encapsulate a time slot frame SF based on the selected time slot information. Sink And send;

[0075] 4.3) First-level node S first Received time slot frame SF Sink Then, analyze SF. Sink Get S first The corresponding transmission time slot is updated in its own time slot table TS. first middle;

[0076] 4.4) Sensor Node S n Select a node from the one-hop node table TOH within its own time slot group.n Two-hop node table TTH at the same level n An idle time slot that does not conflict with the internal node's time slot is used as a candidate time slot slot. can In the slot can Upon arrival, it will be based on its own time slot table (TS). n One-hop node table TOH n Two-hop node table TTH at the same level n Information encapsulation time slot frames SF n And send;

[0077] 4.5) Sensor Node S n Continuously monitor the channel until a candidate time slot is reached. can When it arrives for the second time, determine the one-hop node table TOH. n All slots i Time slot frames SF sent by nodes with non-empty values i Do they all carry S? n Candidate time slot application information:

[0078] If so, then sensor node S n Successfully obtained a transmission slot can , will its own time slot table TS n slot n Set the value to slot can According to its own time slot table TS n and the one-hop node table TOH n The content is encapsulated into a new time slot frame and transmitted in the time slot. can When the time slot arrives, send a time slot frame and execute 4.6);

[0079] Otherwise, re-request the transmission time slot and return to step 4.4);

[0080] 4.6) Determine the received time slot frame SF i Does the two-hop internal node transmission time slot carried in the packet conflict with its own transmission time slot?

[0081] If so, use its own time slot table TS n slot n Set to null, re-request the transmission slot, and return (4.4);

[0082] Otherwise, no action will be taken.

[0083] The technical effects of the present invention will be further explained below with reference to simulation experiments:

[0084] 1. Simulation conditions:

[0085] The simulation uses an Intel Core i5-7200U CPU with a clock speed of 2.50GHz, 8.0GB of memory, a 64-bit operating system, Microsoft Windows 10 Professional Edition, and MATLAB 2018a simulation software.

[0086] The simulation parameters are shown in Table 1. The sensor nodes are deployed in a 100m×100m area with a regular quadrilateral grid structure, and the data aggregation node S... Sink Located at the center, the maximum communication range of the sensor nodes is 15m, and there are a total of 81 nodes. The entire network is divided into 4 layers. Time slot groups A, B, and C each occupy 10 time slots. The entire time frame is divided into 30 time slots. Sensor nodes apply for time slots to send data in their respective time slot groups. Each time frame is called a cycle.

[0087] Table 1 Simulation Parameters

[0088] Simulation parameters Parameter values Network Area 100×100m Sink node position (50，50)m Node deployment structure Square grid deployment Node communication range R 15m Number of sensor nodes N 81 Network layers 4 Number of time slots in time slot group A 10 Number of time slots in time slot group B 10 Number of time slots in time slot group C 10

[0089] 2. Simulation content and results:

[0090] Under the above simulation conditions, the network time slot allocation success rates of the present invention and existing IoT distributed time slot allocation methods are calculated respectively: Where, N suc This indicates the number of nodes that have been successfully allocated a transmission time slot;

[0091] The success rate of time slot allocation for sensor nodes was statistically analyzed in both methods after 0 to 40 cycles, with the results calculated every two cycles. The simulation results are as follows: Figure 5 As shown in the figure. The horizontal axis represents the number of frames per second, and the vertical axis represents the time slot allocation success rate.

[0092] from Figure 5 It can be seen that, under different time lengths, the time slot allocation success rate of the present invention is higher than that of the prior art. The present invention achieves a 100% allocation success rate when the simulation reaches the 16th time frame, while the prior art achieves a 100% allocation success rate when the simulation reaches the 26th time frame. The time slot allocation time of the present invention is shortened by 62.5%. This is because the present invention simplifies the negotiation and application of all nodes within two hops by dividing the time slot groups into a method that only requires negotiation with nodes within two hops of the same layer, which greatly reduces the application conflict in the time slot allocation process. At the same time, the sink node uniformly assigns time slots to the first layer sensor nodes, thereby shortening the time slot allocation time and reducing the time slot allocation overhead.

Claims

1. A TDMA time slot allocation method for underground and underwater wireless Internet of Things, characterized in that, Including the following: (1) Construct underground and underwater IoT models and complete initialization: (1a) Constructing a system equipped with wireless communication devices distributed in underground and underwater environments. sensor nodes and a data aggregation node Underground and underwater IoT models, in which, ; (1b) Sensor Node Establish your own time slot table One-hop node table and the two-hop node table at the same level , in, Indicates the sensor node ID number. Represents sensor nodes To the data aggregation node The jump value, Indicates the time slot number transmitted by the sensor node; and They represent The first-hop node ID number and the transmission timeslot number; and They represent The ID number of the two hop nodes at the same layer and the transmission slot number; (1c) Data aggregation node Establish your own time slot table and one-hop node table ; (1d) For sensor nodes and data aggregation nodes Initialize the relevant table entries; (2) Sensor Node Sending time-slot frames establishes a hop-count-based network hierarchy and updates node-related table entries: (2a) Data aggregation node To other sensor nodes in the network Send time slot frames , in, Indicates the ID number of the sending node. This represents the hop count of the sending node. Indicates the timeslot number of the sending node. This represents the ID number of the first-hop node from which the sending node originates. This indicates the one-hop node slot number of the sending node; (2b) Data aggregation node Waiting to receive neighbor nodes time slot frames After receiving the time slot frame, In , The information is added to the one-hop node table. middle; (2c) Sensor node Waiting to receive neighbor nodes time slot frames After receiving the time slot frame, according to Content updates Its own time slot table One-hop node table and the two-hop node table at the same level ; (2d) Sensor Node According to its own time slot table and one-hop node table The content is encapsulated into a new time-slot frame and sent. (2e) All nodes repeat steps (2c) and (2d) until the node's own time slot table is reached. Jump value information in One-hop node table and the table of two-hop nodes at the same level Update complete; (3) Sensor Node Select a time slot group and request a transmission time slot: (3a) Sensor node From its own time slot table Read its own jump value The entire TDMA time frame is divided into 3 time slot groups, and the jump value is... The result is obtained by taking the modulus of the logarithm 3. and according to The value is selected from the corresponding time slot group; (3b) Sensor Node Each party requests its own transmission time slot through interactive negotiation of time slot frames, as follows: (3b1) Determine the sensor node jump value Is it true or false? If true, then the sensor node transmission slot Data aggregation node Directly designated, without participating in the time slot application process, executes (3b2) and (3b3); Otherwise, execute (3b4); (3b2) using Represents the one-hop node table of the Sink node. The number of nodes in the middle layer is determined by randomly selecting the sink node from the time slot group to which the first-layer node belongs. Each time slot is used to encapsulate a time slot frame based on the selected time slot information. And send; (3b3) First-level nodes Received time slot frame Then, analysis Get The corresponding transmission time slot is determined and updated in its own time slot table. middle; (3b4) Sensor Node Select from the one-hop node table within its own time slot group. Two-hop node table at the same level An idle time slot that does not conflict with the internal node's time slot is used as a candidate time slot. ,exist Upon arrival, it will display its own time slot table. One-hop node table Two-hop node table The relevant information is encapsulated into time slot frames. And send; (3b5) Sensor Node Continuously monitor the channel until a candidate time slot is available. When it arrives for the second time, check the one-hop node table. All time slot values Time slot frames sent by non-empty nodes Do they all carry sensor nodes? Candidate time slot application information: If so, then the sensor node Successfully obtained a transmission time slot , will its own time slot table In Set the value to , will its own time slot table One-hop node table and two-hop node table Encapsulate new time-slot frames within the content. and in the transmission time slot Send time slot frames when they arrive Execute (3b6); Otherwise, re-request the transmission slot and return (3b2); (3b6) Determine the received time slot frame Does the two-hop internal node transmission time slot carried in the packet conflict with its own transmission time slot? If so, then set its own time slot table. In Set to null, then return (3b2); Otherwise, no action will be taken.

2. The method according to claim 1, characterized in that, In step (1d), the sensor nodes and data aggregation nodes The relevant table entries are initialized as follows: (1d1) Sensor node Its own time slot table Mid-jump value Initially set to infinity This is represented by an unattainable jump value. Initially empty; one-hop node list Neutralizing the two-hop node table of the same level Initially empty; (1d2) Data aggregation node Its own time slot table middle Initially 0, Initially 0; one-hop node table Initially empty.

3. The method according to claim 1, characterized in that... According to step (2c) Content updates Its own time slot table One-hop node table and the two-hop node table at the same level The implementation is as follows: (2c1) Parse time slot frames ,Will In , The information is added to the one-hop node table. middle; (2c2) will The jump value carried in Add 1 as the new value ,judge Is it true or false? If true, then its own time slot table will be updated. In Set the value to ; Otherwise, execute (2c3); (2c3) Judgment Is it true or false? If true, then Carrying one-hop node ID number and the one-hop node transmission slot Join Same-level two-hop node table middle; Otherwise, no action will be taken.

4. The method according to claim 1, characterized in that, In step (3a), the jump value will be... The result is obtained by taking the modulus of 3. ,according to The value is selected from the corresponding time slot group, as follows: (3a1) Divide the entire TDMA time frame into three time slot groups, denoted as time slot group A, time slot group B, and time slot group C respectively; (3a2) will The result is obtained by taking the modulus of 3. ,judge Is it true or false? If true, then the sensor node It belongs to time slot group A; Otherwise, execute (3a3); (3a3) Judgment Is it true or false? If true, then the sensor node It belongs to time slot group C; Otherwise, the sensor node It belongs to time slot group B.

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