Local networking method for Internet of Things equipment

Abstract

The invention discloses a local networking method for Internet of Things equipment, relates to the technical field of electric power Internet of Things, and solves the technical problems that the quantity of data reported by a sensor network at the same time is limited, and the link transmission efficiency is relatively low. The method comprises the following steps of: based on a tree topology or a multi-hop topology, initiating by an access node, gradually diffusing to all network nodes, and carrying out topology establishment of network node networking; based on the scheduling of the new network node, sending a beacon and the intensity of a beacon frame signal, and selecting an existing sink node or an access node to carry out a registration request; routing configuration, static routing address updating and dynamic routing address updating of the sensor network are carried out based on the uplink routing and the downlink routing of the sensor network; and the slave node in the sensor network performs time slot synchronization according to the received BCH frame parameter of the master node, and performs local networking of the Internet of Things equipment. The sensors form a star-shaped network, the path is shortest, the number of sensors capable of being contained and reported concurrently is large, and therefore the link transmission efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of electric power Internet of Things, and in particular to a local networking method for Internet of Things devices. Background Art

[0002] The power Internet of Things is the application of the Internet of Things in smart grids. Smart cities, smart grids, etc. all integrate advanced technologies such as the Internet of Things, artificial intelligence, and big data. By effectively integrating communication infrastructure resources and power system infrastructure resources, it improves the information level of the power system, the intelligent efficiency of the distribution system, and the power supply capacity. It has the characteristics of perceptibility, intelligence, and strong connectivity.

[0003] In the power transmission and transformation scenario of the power Internet of Things, there are a large number of sensors, most of which use mesh networks. The existing wireless mesh network can only support a limited number of sensors reporting data at the same time, and the link transmission efficiency is low. There is an urgent need for a networking method that can accommodate more sensors and improve link transmission efficiency.

[0004] In the process of implementing the present invention, the inventors found that there are at least the following problems in the prior art:

[0005] The existing sensor networks have a limited amount of data that can be reported simultaneously and low link transmission efficiency, making it difficult to adapt to the development needs of the power Internet of Things. Summary of the invention

[0006] The purpose of the present invention is to provide a local networking method for IoT devices to solve the technical problems in the prior art that the number of data reported simultaneously by the sensor network is limited, the link transmission efficiency is low, and it is difficult to adapt to the development needs of the power IoT. The preferred technical solutions among the many technical solutions provided by the present invention can produce many technical effects as described below.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] The present invention provides a local networking method for Internet of Things devices. The backbone network of the sensor network includes access nodes and aggregation nodes. Each network node in the backbone network is connected to a number of 470MHz sensors to form a star network. The uplink and downlink of each network node respectively use independent hardware channels. The networking is carried out through the following steps: S100: based on a tree topology or a multi-hop topology, initiated by the access node, gradually diffused to all network nodes, and the topology of network node networking of the sensor network of the power Internet of Things is established; S200: based on the intensity of the beacon and beacon frame signal sent by the scheduling of the new network node, the existing aggregation node or access node selects to make a registration request; S300: based on the uplink routing and downlink routing of the sensor network, the routing configuration of the sensor network and the static routing address update and the dynamic routing address update are carried out; S400: the slave node in the sensor network performs time slot synchronization according to the BCH frame parameters received from the master node, and the local networking of the Internet of Things devices is carried out to obtain the sensor network.

[0009] Preferably, in the step S100, the topology establishment of the network node networking specifically includes the following steps: S110: the access node sends a beacon frame, and the adjacent aggregation node chooses to make a registration request based on the signal strength of the received beacon frame; S120: after the aggregation node registration request is successful, the access node completes the registration and sends a registration response; S130: the access node schedules the subordinate aggregation nodes to broadcast; S140: through an iterative loop, until all network node devices complete the networking; S150: for a network with multiple access nodes, the aggregation node chooses to connect to the corresponding access node based on the number of communication hops with different access nodes.

[0010] Preferably, in step S100, when the topology of the network node networking is established, when a sensor is under the jurisdiction of multiple network nodes, the sensor selects a master node to apply for network access based on the received BCH frame signal strength and the number of sensors under the jurisdiction of the master node.

[0011] Preferably, in step S200, if the parent node selected by the new network node is an access node, the access node decides whether to allow it to access the network, and sends a registration request response if it is allowed to access the network; if the parent node selected by the new network node is an aggregation node, the aggregation node forwards the registration request to the access node, and if the access node allows it to access the network, it sends a registration request response.

[0012] Preferably, in the step S300, in the uplink routing, each network node performs uplink data transmission step by step based on the master-slave relationship; in the downlink routing, each aggregation node stores the node routing table between the network nodes, and the subordinate sensor routing table, and the downlink data sent by the access node is first addressed to the last-level aggregation node through the node routing table, and then the aggregation node sends it to the corresponding sensor through the local sensor routing table.

[0013] Preferably, in the step S300, the static routing address update is initiated by the access node, and the routing update content specifically includes the following two categories: the access node initiates communication and sends its locally stored node routing table to the corresponding aggregation node; the access node initiates communication and sends its locally stored sensor routing table to the corresponding aggregation node; the dynamic routing address update is initiated by the aggregation node, and the routing update content specifically includes the following two categories: the aggregation node initiates communication and sends its subordinate node topology information or topology change information to the access node; the aggregation node initiates communication and sends its subordinate sensor topology information or topology change information to the access node.

[0014] Preferably, in step S400, the slave node performs time slot synchronization according to the parameters of the received master node BCH frame, which specifically includes the following steps: S410: the sender sends a BCH frame including a preamble, a synchronization word and a payload field, waits for the start time of its own working frame to arrive, starts sending after a delay of Ttxoffset, and the chip is ready after the conversion time, and sends out the data frames in sequence; S420: the receiver obtains the superframe configuration and frame sequence number from the payload field of the BCH frame, and obtains the millisecond timer value by detecting the time of the synchronization word; S430: the receiver records the timestamp value Ts of the synchronization word interruption time, the timestamp value Ta of the frame resolution time, and then calculates the network time of the sender at the timestamp value Ta of the frame resolution time, and completes the time synchronization with the sender.

[0015] Preferably, time slot synchronization is performed by the following formula: T1=T0+(Ta-Ts)+Tsync+Tpreamble+Tstart+Ttxoffset, wherein T1 represents the time slot moment of the receiver, T0 is the start time of the time slot of the sender, its millisecond timer value is 0, Ts represents the timestamp value of the synchronization word interruption moment, Ta represents the timestamp value of the frame parsing moment, Tsync represents the synchronization word sending time, Tpreamble represents the preamble sending time, Tstart represents the chip transceiver conversion time of the sender, and Ttxoffset represents the signal processing delay of the sender.

[0016] Preferably, the sensor network includes n layers of nodes, and the superframe structure of the sensor network includes a beacon slot, m downlink slots and m uplink slots. The slot lengths of the beacon slot, downlink slot and uplink slot are equal, and the slot of the i-th layer node lags behind that of the i-1-th layer node by one slot length.

[0017] Preferably, the sensors of the sensor network transmit data through the following steps: the sensor sends a time slot allocation request to the parent node, the parent node sends a time slot scheduling frame according to the situation, and the sensor allocated to the time slot in the time slot scheduling frame actively reports data in the next time slot.

[0018] Implementing one of the above technical solutions of the present invention has the following advantages or beneficial effects:

[0019] In this embodiment, each network node uses independent hardware channels for uplink and downlink, which improves data transmission efficiency. At the same time, each network node is connected to a number of 470MHz sensors to form a star network, ensuring that the path from the sensor to the backbone network is the shortest and can accommodate a large number of concurrent reports from sensors, thereby improving the link transmission efficiency as much as possible, thereby improving the link transmission efficiency and better adapting to the development needs of the power Internet of Things. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. It is obvious that the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0021] Figure 1 is a flow chart of a local networking method for an Internet of Things device according to an embodiment of the present invention;

[0022] Figure 2 It is a sensor network topology diagram of the local networking method of the Internet of Things device according to an embodiment of the present invention;

[0023] Figure 3 It is a flowchart of step S100 in the local networking method of the Internet of Things device according to an embodiment of the present invention;

[0024] Figure 4 It is a flowchart of step S400 in the local networking method of the Internet of Things device according to an embodiment of the present invention;

[0025] Figure 5 It is a schematic diagram of the time slot frame structure in the local networking method of the Internet of Things device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solutions and advantages of the present invention clearer, the various exemplary embodiments to be described below will refer to the corresponding drawings, which constitute a part of the exemplary embodiments, wherein various exemplary embodiments that may be used to implement the present invention are described. Unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The implementation methods described in the following exemplary embodiments do not represent all implementation methods consistent with the present disclosure. It should be understood that they are only examples of processes, methods, devices, etc. that are consistent with some aspects of the present disclosure as detailed in the attached claims, and other embodiments may also be used, or the embodiments listed herein may be modified in structure and function without departing from the scope and essence of the present invention.

[0027] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", etc. indicate the orientation or positional relationship based on the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the elements referred to must have a specific orientation, be constructed and operated in a specific orientation. The terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. The term "multiple" means two or more. The terms "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, an integral connection, a mechanical connection, an electrical connection, a communication connection, a direct connection, an indirect connection through an intermediate medium, and can be the internal connection of two elements or the interaction relationship between two elements. The term "and / or" includes any and all combinations of one or more related listed items. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0028] In order to illustrate the technical solution of the present invention, a specific embodiment is used below for description, and only the parts related to the embodiment of the present invention are shown.

[0029] Example:

[0030] The present invention provides a local networking method for Internet of Things devices, such as Figure 1 As shown in the figure, the backbone network of the sensor network includes access nodes and aggregation nodes. Each network node in the backbone network is connected to a number of 470MHz sensors to form a star network. The star network has the shortest connection transmission path, high transmission efficiency, and can accommodate a large number of concurrent sensor reports. The uplink and downlink of each network node use independent hardware channels. Specifically, the aggregation subnet and sensor subnet of the access node work on CH1 and CH2 respectively. The two subnets are synchronized at the same time, so that the access node and the aggregation node have two hardware channels. Figure 1As shown, the uplink subnet channel of the aggregation node 1 works on CH2, the downlink subnet channel works on CH3, and the sensor subnet channel works on CH4, where CH3 and CH4 are the same. This embodiment is networked through the following steps, such as Figure 2 As shown. S100: Based on tree topology or multi-hop topology (tree topology is a local area network topology similar to bus topology, which is a highly adaptable topology with a wide range of adaptability and is very suitable for hierarchical management systems with primary and secondary and hierarchical levels; in multi-hop topology, each network node is connected by wireless multi-hop through other adjacent network nodes, which has the characteristics of easy installation, flexible structure and high bandwidth), the two topological structures are easy to adapt to the needs of multiple sensors and high data transmission volume of sensor networks. They are initiated by access nodes and gradually spread to all network nodes, so as to achieve the purpose of rapid topology establishment, and the topology of network node networking of the sensor network of the power Internet of Things is established. After the topology is established, it is convenient to network the sensor network. S200: Based on the scheduling of the new network node (specifically the network node formed by the newly connected sensor) to send a beacon (sent by default in the next time slot of the beacon time slot of the parent node of the new network node) and the strength of the beacon frame signal (the signal strength information facilitates the sensor to connect to the most matching parent node), the existing aggregation node or access node selects to make a registration request to realize the access of the new network node. S300: Based on the uplink routing and downlink routing of the sensor network, the routing configuration of the sensor network and the update of the static routing address and the dynamic routing address are performed. Static routing has the advantages of simple configuration, high network security and high forwarding efficiency, but it cannot automatically adapt to network changes and is not suitable for large networks. Dynamic routing can adapt to network changes and is suitable for large networks, improve load balancing and fault tolerance, but has the problem of complex configuration and introduction of security risks. By combining static routing and dynamic routing, the advantages of the two methods can be integrated, thereby improving the efficiency and adaptability of the networking of this embodiment, thereby establishing the routing of the new network node. S400: The slave node in the sensor network performs time slot synchronization according to the BCH frame parameters received from the master node, performs local networking of the Internet of Things devices, and obtains the sensor network. In this embodiment, each network node uses independent hardware channels for uplink and downlink respectively, which improves the data transmission efficiency. At the same time, each network node is connected to a number of 470MHz sensors to form a star network, ensuring that the path from the sensor to the backbone network is the shortest, and the number of concurrent reports of sensors that can be accommodated is large, and the link transmission efficiency is improved as much as possible, thereby improving the link transmission efficiency, which can better meet the development needs of the power Internet of Things.

[0031] As an optional implementation, Figure 3 As shown, in step S100, the topology establishment of the network node group specifically includes the following steps: S110: The access node sends a beacon frame, and the adjacent sink node (i.e., the sink node directly connected to the access node, such as Figure 1 The aggregation nodes 1 and 4 in the network select the access node corresponding to the beacon frame with the strongest signal according to the received beacon frame signal strength, and select to make a registration request. S120: After the aggregation node registration request is successful, the access node completes the registration and sends a registration response, thereby realizing the networking of the aggregation node. S130: The access node schedules the subordinate aggregation nodes to broadcast, thereby establishing a network connection with all the aggregation nodes. S140: Through an iterative loop, until all network node devices complete the networking, that is, the aggregation node also realizes the networking of the network nodes corresponding to the sensors. S150: For a network with multiple access nodes, the aggregation node chooses to connect to the corresponding access node according to the number of communication hops with different access nodes, and preferably the access node corresponding to the shortest number of communication hops with the aggregation node.

[0032] As an optional implementation, in step S100, when the topology of the network node networking is established, when a sensor is under the jurisdiction of multiple network nodes, the master node with the strongest BCH frame signal is preferred based on the received BCH frame signal strength and the number of sensors under the jurisdiction of the master node. When the BCH frame signal strengths are equivalent, the master node with the least number of sensors under its jurisdiction is selected (the master node can be a aggregation node or an access node). The sensor selects a master node to apply for network access, thereby ensuring that the sensor can achieve higher quality signal transmission.

[0033] As an optional implementation, in step S200, if the parent node selected by the new network node is an access node, the access node decides whether to allow it to access the network, and sends a registration request response if it is allowed to access the network; if the parent node selected by the new network node is a convergence node, the convergence node forwards the registration request to the access node, and sends a registration request response if the access node allows it to access the network. Therefore, whether the parent node is an access node or a convergence node, the new network node can be registered for network access.

[0034] As an optional implementation, in step S300, in the network topology of this embodiment, each device can find the master device to which it belongs, and can perform uplink data transmission step by step according to the master-slave relationship. Therefore, in the uplink routing, each network node performs uplink data transmission step by step based on the master-slave relationship, which improves the efficiency and accuracy of data transmission. In the downlink routing, each aggregation node stores the node routing table between network nodes, as well as the subordinate sensor routing table. The downlink data sent by the access node is first addressed to the last-level aggregation node through the node routing table, and then the aggregation node sends it to the corresponding sensor through the local sensor routing table. If the data is for the aggregation node, the sensor communication part can be omitted. Specifically, in step S300, the static routing address update is initiated by the access node, and the routing update content specifically includes the following two categories: the access node initiates communication and sends its locally stored node routing table to the corresponding aggregation node; the access node initiates communication and sends its locally stored sensor routing table to the corresponding aggregation node; the dynamic routing address update is initiated by the aggregation node, and the routing update content specifically includes the following two categories: the aggregation node initiates communication and sends its subordinate node topology information or topology change information to the access node; the aggregation node initiates communication and sends its subordinate sensor topology information or topology change information to the access node.

[0035] As an optional implementation, Figure 4As shown, in step S400, the slave node performs time slot synchronization according to the parameters of the received master node BCH frame, which specifically includes the following steps. In the heterofrequency mode, the impact of two network nodes sending data at the same time is relatively small, and the precision requirement for the synchronization of the whole network is relatively low. Usually, as long as the synchronization between the master and slave nodes of the star network is guaranteed, of course, the error of the time slot synchronization of the whole network cannot be too large, otherwise it will affect the communication timeout judgment. The time reference of the network node comes from its clock reference circuit, and the stability of the clock reference circuit is limited by the crystal used. In order to maintain synchronization with the network, the network node needs to periodically obtain the time information in the sensor network to eliminate the deviation caused by its own crystal error. Therefore, reliable communication of the sensor network can be ensured through time slot synchronization. S410: The sender sends a BCH frame including a preamble, a synchronization word and a payload field (the receiver needs to calculate the start time of the sender's time slot based on this information), waits for the start time of its own working frame to arrive, starts sending after a delay of Ttxoffset, and the chip is ready after the conversion time, and sends the data frame in sequence. S420: The receiver obtains the superframe configuration and frame sequence number from the payload field of the BCH frame, and obtains the millisecond timer value by detecting the time of the synchronization word. The millisecond timer is the same as the sender, and synchronization is achieved. S430: The receiver records the timestamp value Ts at the time of the synchronization word interruption, the timestamp value Ta at the frame resolution time, and then calculates the network time of the sender at the time of the frame resolution time stamp value Ta, and completes the time synchronization with the sender. The time slot synchronization is performed by the following formula: T1 = T0 + (Ta-Ts) + Tsync + Tpreamble + Tstart + Ttxoffset, where T1 represents the time slot moment of the receiver, T0 is the start time of the time slot of the sender, its millisecond timer value is 0, Ts represents the timestamp value at the time of the synchronization word interruption, Ta represents the timestamp value at the frame resolution time, Tsync represents the synchronization word sending time, Tpreamble represents the preamble sending time, Tstart represents the chip transceiver conversion time of the sender, and Ttxoffset represents the signal processing delay of the sender.

[0036] As an optional implementation, Figure 5As shown, the sensor network includes n layers of nodes, and the superframe structure of the sensor network includes a beacon time slot, m downlink time slots and m uplink time slots. The time slot lengths of the beacon time slot, downlink time slot and uplink time slot are equal, that is, a superframe structure contains 2m+1 time slots, and the time slot of the i-th layer node lags behind the i-1-th layer node by one time slot length. Furthermore, in order to reduce the mutual influence between the channels inside the aggregation node 1, the uplink frame of the CH2 channel and the downlink frame of the CH3 are overlapped, so that inside the aggregation node 1, the two channels will not have the situation of sending and receiving at the same time, which will greatly reduce the influence between the internal channels. Other aggregation nodes are also considered to be set up in accordance with this, so as to reduce the influence between the internal channels. At the same time, the time slot scheduling adopts the frame-by-frame scheduling, and the node address and corresponding time slot reported in the next superframe are scheduled downlink, and the data reported by the sensor specified in the previous superframe is transmitted uplink at the same time. The uplink and downlink are almost processed in parallel, which improves the processing efficiency.

[0037] As an optional implementation, sensors in the sensor network transmit data through the following steps: the sensor sends a time slot allocation request to the parent node, the parent node sends a time slot scheduling frame according to the situation, and the sensor allocated to the time slot in the time slot scheduling frame actively reports data in the next time slot.

[0038] As an optional implementation, after the aggregation node joins the network, it sends node device status reporting frames regularly (such as every 2 minutes). After receiving the frames, the access node sends a heartbeat response frame (downlink) to complete a heartbeat process, thereby ensuring a reliable connection between the aggregation node and the access node.

[0039] The embodiment is only a specific example and does not represent only one implementation mode of the present invention.

[0040] The above description is only the preferred embodiment of the present invention. It is known to those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application belong to the protection scope of the present invention.

Claims

1. A local networking method for Internet of Things devices, characterized in that: The backbone network of the sensor network includes access nodes and aggregation nodes. Each network node in the backbone network is connected to a number of 470MHz sensors to form a star network. The uplink and downlink of each network node use independent hardware channels respectively. The network is formed through the following steps: S100: Based on a tree topology or a multi-hop topology, initiated by an access node and gradually spread to all network nodes, a topology of network node networking is established for the sensor network of the power Internet of Things; S2 00: Based on the scheduling of the new network node to send beacons and the strength of the beacon frame signal, the existing aggregation node or access node chooses to make a registration request; S300: Based on the uplink routing and downlink routing of the sensor network, perform routing configuration of the sensor network and update the static routing address and dynamic routing address; S400: The slave nodes in the sensor network perform time slot synchronization according to the BCH frame parameters received from the master node, perform local networking of the Internet of Things devices, and obtain the sensor network.

2. A method for local networking of Internet of Things devices according to claim 1, characterized in that: In the step S100, the topology establishment of the network node group specifically includes the following steps: S110: The access node sends a beacon frame, and the adjacent aggregation node selects to make a registration request based on the received beacon frame signal strength; S120: After the aggregation node registration request is successful, the access node completes the registration and sends a registration response; S130: The access node schedules the subordinate aggregation node to broadcast; S140: through iterative loops, until all network node devices complete networking; S150: For a network with multiple access nodes, the aggregation node selects to connect to a corresponding access node according to the number of communication hops with different access nodes.

3. A method for local networking of Internet of Things devices according to claim 2, characterized in that: In step S100, when the topology of the network node group is established, when a sensor is under the jurisdiction of multiple network nodes, the sensor selects a master node to apply for network access according to the received BCH frame signal strength and the number of sensors under the jurisdiction of the master node.

4. A method for local networking of Internet of Things devices according to claim 1, characterized in that: In the step S200, if the parent node selected by the new network node is an access node, the access node decides whether to allow it to access the network. If it is allowed to access the network, it sends a registration request response; if the parent node selected by the new network node is a aggregation node, the aggregation node forwards the registration request to the access node. If the access node allows it to access the network, it sends a registration request response.

5. A method for local networking of Internet of Things devices according to claim 1, characterized in that: In the step S300, in the uplink routing, each network node performs uplink data transmission step by step based on the master-slave relationship; In the downlink routing, each aggregation node stores the node routing table between network nodes and the subordinate sensor routing table. The downlink data sent by the access node is first addressed to the last-level aggregation node through the node routing table, and then the aggregation node sends it to the corresponding sensor through the local sensor routing table.

6. A method for local networking of Internet of Things devices according to claim 1, characterized in that: In the step S300, the static routing address update is initiated by the access node, and the routing update content specifically includes the following two categories: the access node initiates communication and sends its locally stored node routing table to the corresponding aggregation node; The access node initiates communication and sends its locally stored sensor routing table to the corresponding aggregation node; the dynamic routing address update is initiated by the aggregation node, and the routing update content specifically includes the following two categories: the aggregation node initiates communication and sends its subordinate node topology information or topology change information to the access node; the aggregation node initiates communication and sends its subordinate sensor topology information or topology change information to the access node.

7. A method for local networking of Internet of Things devices according to claim 1, characterized in that: In step S400, the slave node performs time slot synchronization according to the parameters of the received BCH frame of the master node, which specifically includes the following steps: S410: The sender sends a BCH frame including a preamble, a synchronization word, and a payload field, waits for the start time of its own working frame to arrive, starts sending after a delay of Ttxoffset, and after the conversion time, the chip is ready and sends out the data frames in sequence; S420: The receiver obtains the superframe configuration and frame sequence number from the payload field of the BCH frame, and obtains the millisecond timer value by detecting the time of the synchronization word; S430: The receiver records the timestamp value Ts of the synchronization word interruption time and the timestamp value Ta of the frame resolution time, and then calculates the network time of the sender at the timestamp value Ta of the frame resolution time to complete the time synchronization with the sender.

8. A method for local networking of Internet of Things devices according to claim 7, characterized in that: The time slot synchronization is performed by the following formula: T1=T0+(Ta-Ts)+Tsync+Tpreamble+Tstart+Ttxoffset, Among them, T1 represents the time slot moment of the receiver, T0 is the time slot start moment of the sender, its millisecond timer value is 0, Ts represents the timestamp value of the synchronization word interruption moment, Ta represents the timestamp value of the frame parsing moment, Tsync represents the synchronization word sending time, Tpreamble represents the preamble sending time, Tstart represents the chip transceiver conversion time of the sender, and Ttxoffset represents the signal processing delay of the sender.

9. A method for local networking of Internet of Things devices according to claim 1, characterized in that: The sensor network includes n layers of nodes, and the superframe structure of the sensor network includes a beacon time slot, m downlink time slots and m uplink time slots. The time slot lengths of the beacon time slot, the downlink time slot and the uplink time slot are equal, and the time slot of the i-th layer node lags behind that of the i-1-th layer node by one time slot length.

10. A method for local networking of Internet of Things devices according to claim 1, characterized in that: The sensors of the sensor network transmit data through the following steps: the sensor sends a time slot allocation request to the parent node, the parent node sends a time slot scheduling frame according to the situation, and the sensor allocated to the time slot in the time slot scheduling frame actively reports data in the next time slot.

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