Distributed scheduling method for external interference in real-time wireless sensor network

Abstract

According to the distributed scheduling method for the external interference in the real-time wireless sensor network, a distributed continuous data packet scheduling method is adopted, the distributed scheduling method is used for processing the external interference in the multichannel real-time wireless sensor network with space channel multiplexing in a smart factory, and meanwhile it is ensured that deadlines of all key tasks are met. According to the invention, a continuous scheduling mechanism is designed, wherein scheduling decisions made by nodes are propagated to subsequent nodes along a routing path. The mechanism ensures that local schedules generated by different nodes on the same routing path are always consistent. In order to meet the deadline requirement of a key task and at the same time, an effective heuristic algorithm is introduced and is executed locally by each node so as to determine a dynamic scheduling table, and the discarded non-key data packets are minimum when the extra workload caused by interference is processed.

Description

Technical Field

[0001] The invention relates to the technical field of communication network data flow scheduling, and in particular to a distributed scheduling method for external interference in a real-time wireless sensor network. Background Art

[0002] Smart factories represent a new trend of digitalization, automation and intelligent production in the manufacturing industry, which is of great significance to the manufacturing industry. In smart factories, industrial network technology provides technical support for automated production and intelligent management, and becomes the key to realizing the concept of smart factories. It realizes intelligent collaboration and information exchange between devices, making the production process more intelligent and efficient. As part of the industrial network, wireless networks have the advantages of flexibility, convenience, easy deployment and maintenance, and applicability to complex environments compared to wired networks. With the continuous development of wireless network technology, smart factory wireless networks are developing towards 5G network technology with higher speed, lower latency and more reliable connection.

[0003] In recent years, real-time wireless sensor networks (RTWSN) have been continuously developed and deployed in various industrial applications, especially those with strict requirements for real-time and reliable information delivery. Packet scheduling at the data link layer plays a key role in meeting these RTWSN requirements. However, RTWSNs often suffer from dynamic workload disturbances caused by unexpected interference, which is particularly serious in harsh industrial environments. Generally, unexpected interference can be divided into internal interference and external interference. Internal interference is caused by changes in the network (such as node or link failures, etc.). External interference is caused by unexpected changes in the monitoring and control environment (such as detection of an emergency, sudden increase in pressure or temperature, etc.).

[0004] There are some studies on how to deal with external interference in RTWSN in centralized methods. Hong et al. (HongS, Hu XS, Gong T, Han S. On-line data link layer scheduling in wireless networked control systems [C], Proceedings of 2015 27th Euromicro Conference on Real-Time Systems (ECRTS). IEEE, 2015, 57–66) considered the data link layer scheduling problem in wireless network control systems where external interference occurs occasionally. An online framework using a rhythmic task model, called OLS, is introduced to adjust the static schedule in response to external interference. Their method determines the duration of applying dynamic scheduling and generates a schedule of that duration to minimize the impact of network dynamics on existing network flows. Zhang et al. (Zhang T, Gong T, Gu C, JiH, Han S, Deng Q, Hu X S. Distributed dynamic packet scheduling for handling disturbances in real-time wireless networks [C], Proceedings of 2017 IEEE Real-Time and Embedded Technology and Applications Symposium (RTAS). IEEE, 2017, 261–272) proposed a dynamic packet scheduling framework called DD-PaS. DD-PaS aims to minimize the number of packet losses while ensuring that all critical events caused by interference are handled before the deadline. Gong et al. (Gong T, Zhang T, Hu XS, Deng Q, Lemmon M, Han S. Reliable dynamic packet scheduling over lossy real-time wireless networks [C], Proceedings of 31st Euromicro Conference on Real-Time Systems (ECRTS). Schloss Dagstuhl-Leibniz-Zentrum fuer Informatik, 2019) proposed a reliable dynamic packet scheduling framework called RD-PaS.RD-PaS can not only build static schedules to meet the timing and reliability requirements of end-to-end packet transmission for given periodic network traffic patterns in RTWSNs, but also quickly build new schedules to handle sudden increases in network traffic interference caused by accidents while minimizing the impact on existing network traffic. Gunatilaka et al. (Gunatilaka D, Lu C. REACT: An agile control plane for industrial wireless sensor-actuator networks [C], Proceedings of 2020 IEEE / ACM Fifth International Conference on Internet-of-Things Design and Implementation (IoTDI). IEEE, 2020, 53–65) proposed a control plane for industrial wireless sensor reaction networks (Wireless Sensor-Actuator Network, WSAN), called REACT. REACT is specifically optimized for network adaptation, significantly reducing the latency and energy cost of network reconfiguration, thereby improving the agility of WSAN in dynamic environments.

[0005] These centralized approaches rely on a central control point in the network (e.g., a gateway) to generate dynamic schedules when interference occurs. If this central control point fails, the quality of service (QoS), such as packet delivery ratio (PDR), provided by these centralized approaches will drop rapidly. In addition, as the scale of RTWSN grows, centralized approaches have the fatal disadvantage of being non-scalable. Summary of the invention

[0006] In order to solve the above technical problems, an object of the present invention is to provide a method deployed on a sensor node to cope with changes in data flow period / deadline.

[0007] The present invention provides a distributed scheduling method for external interference in a real-time wireless sensor network, comprising:

[0008] Step 1: Input parameters, including the network topology of RTWSN, the channel parameters of RTWSN and the data flow set of RTWSN;

[0009] Step 2: When the network is initialized, the device node generates a local interference information table based on the input parameters, and the gateway generates a global interference information table based on the input parameters;

[0010] Step 3: In the network non-operation phase, the gateway generates a static scheduling table within a super period according to the input parameters and the global interference information table according to the global deadline priority strategy. If all data packets within the super period can meet their deadlines in the static scheduling table, the network enters the operation phase, otherwise it returns failure;

[0011] Step 4: During the network operation phase, all device nodes follow the static schedule for transmission;

[0012] Step 5: The source node of each task determines whether there is external interference in the network by comparing the collected data with the preset threshold; if there is external interference in the network, the system enters step 6, otherwise all device nodes follow the static scheduling table for transmission;

[0013] Step 6: On the node of the task corresponding to the external interference, a local dynamic scheduling table that can ensure consistent transmission in the next cycle is generated according to the transmission update information.

[0014] Step 7: The nodes on the task path corresponding to the interference generate new transmission update information according to the dynamic scheduling table, and add the new transmission update information to the data packet;

[0015] Step 8: Determine whether the node on the task path corresponding to the interference is the destination node. If so, the system enters the next cycle. Otherwise, repeat steps 6-8 until the node on the task path corresponding to the interference is the destination node.

[0016] Step 9: Determine whether the interference event has been processed. If so, the system returns success. Otherwise, repeat steps 6-9 until the external interference event is processed.

[0017] A distributed scheduling method for external interference in a real-time wireless sensor network of the present invention has the following beneficial effects:

[0018] The distributed continuous data packet scheduling method proposed in the present invention can be used to handle external interference in a multi-channel real-time wireless sensor network with spatial channel multiplexing in a smart factory, while ensuring that the deadlines of all critical tasks are met. By generating a dynamic schedule, the scheduling method of the present invention can handle external interference events. Through the continuous scheduling mechanism, the scheduling method of the present invention ensures that inconsistent transmissions do not occur in the dynamic schedule. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The present invention is a flow chart of a distributed scheduling method for external interference in a real-time wireless sensor network. DETAILED DESCRIPTION

[0020] like Figure 1As shown, a distributed scheduling method for external interference in a real-time wireless sensor network of the present invention includes:

[0021] Step 1: Input parameters, including the network topology of RTWSN, the channel parameters of RTWSN and the data flow set of RTWSN;

[0022] (1) The network topology of RTWSN is a multi-channel multi-hop RTWSN formed by multiple device nodes and a gateway through wireless connection; the device nodes include: multiple sensor nodes, actuator nodes and relay nodes; the network is modeled as a directed graph G = (V, E), where V = {V0, V1, ...} is the set of device nodes, (V i ,V j )∈E represents the slave device node V i To device node V j reliable link.

[0023] (2) The channel parameters of RTWSN include: the number of channels, the length of time slots, and whether spatial channel multiplexing is supported. The present invention adopts a data link layer based on multi-channel time division multiple access (TDMA). The number of channels is represented by C, assuming that each device node can send or receive data on any channel within a given time, following the 15 millisecond time slot time defined in IEEE 802.15.4e. In order to increase the network capacity, the present invention adopts spatial channel multiplexing to accommodate concurrent transmissions involving different pairs of device nodes in the same time slot and the same channel. In the present invention, transmission refers to the process of sending a data packet from a sending node to its receiving node.

[0024] (3) Data flow set of RTWSN. This paper adopts the concept of task to describe the data flow from sensor nodes to actuator nodes. The system runs a fixed unicast task set T = {τ0, τ1, ..., τ N}, each task τ i (0≤i≤N) follows a specified inclusion H i The routing path of each task is τ, N is the number of tasks; a data packet is generated periodically, the source node is a sensor, passes through some relay nodes, and finally reaches an actuator. i Contains an infinite sequence of packets. τ i The kth data packet is x i,k , including the release time r i,k , deadline d i,k and completion time f i,k Packet x i,k The transfer at the hth hop is called a transmission, denoted by χ i,k (h),1≤h≤H i .

[0025] The present invention adopts a rhythm task model. Under normal conditions, each task τ i Following a given normal cycle P i and the normal relative deadline D i , D i ≤P i When interference occurs, the task τ i Enter a rhythmic state, in which, in response to disturbances, its period and relative cutoff time first decrease and then gradually recover to their normal values ​​by following a monotonically increasing pattern. and To represent τ i The period and relative end time when in the rhythm state, R represents the number of rhythm states. Once τ i Entering the rhythm state, its cycle and relative deadline are respectively adopted by and The specified value. When it starts using P again i and D i When τ i Back to normal.

[0026] The present invention assumes that at most one task is in the rhythm state at any time during network operation. To simplify terminology, the present invention refers to any task currently in the rhythm state as a rhythm task and denotes it as τ0, and denotes a task that is not currently in the rhythm state as τ i (1≤i≤N) is called a periodic task. When a task enters the rhythm state, the present invention refers to the device node on the rhythm task τ0 path as a rhythm node, and the set of rhythm nodes is represented by V rhy When a task enters the rhythmic state, the system switches to the rhythmic mode. When the interference is completely processed, usually after τ0 returns to the normal state for a period of time, the system will return to the normal mode. When the system enters the rhythmic mode, the deadline of the rhythmic task is considered to be hard, while the periodic task can tolerate occasional deadline misses. The present invention assumes that τ0 is released at the release time r of the m+1th packet. 0,m+1 Enter the rhythm state, recorded as t n→r , and at the release time r of the m+R+1th packet 0,m+R+1 Return to normal state, denoted as t r→n , m represents the index of the last data packet of the rhythm task before entering the rhythm state, τ0 is in [t n→r ,t r→n ) during the period; after the disturbance is completely processed, the system will be in the rhythm state at the end point t ep Return to normal mode at the time point; any data packet τ0 released in the rhythm mode of the system is called a rhythm data packet, and τi The data packet of a (1≤i≤N) task is called a periodic data packet.

[0027] Step 2: When the network is initialized, the device node generates a local interference information table according to the input parameters, and the gateway generates a global interference information table according to the input parameters.

[0028] The local interference information table is defined as: In order to capture the local interference information table with each device node V i According to the task set information, a local interference information table is established on each device node, and three fields are stored: input interference I In , which means that when the device node V i When it is a receiver, it will respond to V i The set of nodes that cause transmission interference; output interference I Out , which means that when the device node V i is the set of nodes that will encounter transmission interference when being a sender; HTP , which means when V i A receiver of V i The set of sender nodes whose transmission interference is caused by one of the senders of HTP stands for Hidden Terminal Interference.

[0029] A set of transmissions on the same channel does not interfere with each other if all receivers are not within the interference range of other senders, which is determined by the transmission power and distance. Each node can share its input interference with its neighbors and construct its own output interference and set of sender nodes based on the neighbors' input interference. Given I Out and I HTP , a device node can infer V i All potential interferences of any transmission sent out. Because of the memory limitation of RTWSN nodes, the present invention adopts storing local interference information table on each device node.

[0030] The global interference information is defined as: an interference information table containing all interference information obtained by the gateway by collecting the local interference information table on each device node is called a global interference information table.

[0031] Step 3: In the network non-operating stage, the gateway generates a static scheduling table within a super period according to the input parameters and the global interference information table according to the global deadline priority strategy. If all data packets within the super period can meet their deadlines in the static scheduling table, the network enters the operating stage, otherwise it returns failure.

[0032] The static scheduling table S generated in step 3 needs to ensure that all data packets are successfully transmitted; the static scheduling table S is a set of transmission-related time slot / channel allocations used in the normal mode of the system, and each time slot / channel is either idle or allocated to one or more transmissions.

[0033] In order to ensure the successful transmission of all data packets in the static scheduling table, the static scheduling table should avoid the two transmission failures of transmission conflict and transmission interference in the same time slot.

[0034] Transmission collision means that if two transmissions are allocated in the same time slot and they have the same sender or receiver, they will experience a transmission collision.

[0035] Transmission interference is when two transmissions are assigned to the same time slot and on the same channel and the signal from the first transmission interferes with the signal at the receiver of the second transmission.

[0036] Step 4: During the network operation phase, all device nodes follow the static schedule for transmission.

[0037] Step 5: The source node of each task determines whether external interference occurs in the network by comparing the collected data with the preset threshold; if external interference occurs in the network, the system enters step 6, otherwise all device nodes follow the static scheduling table for transmission.

[0038] Step 6: At the node on the task path corresponding to the external interference, a local dynamic scheduling table that can ensure consistent transmission in the next cycle is generated according to the transmission update information.

[0039] The transmission update information includes: a time slot index and a channel index and a task / data packet ID of a periodic data packet determined by a previous transmission update.

[0040] The consistent transmission means that if the sender and the receiver of the transmission allocate the same time offset and channel offset in the scheduling, the transmission is a consistent transmission.

[0041] The dynamic schedule is a set of transmission-related time slot / channel assignments for the system's cadence pattern, with each time slot / channel either idle or assigned to one or more transmissions.

[0042] The step 6 is specifically as follows:

[0043] Step 6.1: According to the transmission update information, add the transmission schedule determined when the node on the task path corresponding to the interference except the source node is used as the receiving node of the previous hop transmission to the static scheduling table in the next cycle, and obtain the transmission schedule of the node as the receiving node in the next cycle in the local dynamic scheduling table;

[0044] Step 6.2: According to the task ID and data packet ID of the discarded periodic data packet determined in the previous hop transmission in the transmission update information, remove the discarded periodic transmission in the static scheduling table in the next cycle.

[0045] Step 6.3: According to the transmission update information, determine the feasible time period in the static scheduling table for rhythmic transmission of nodes on the task path corresponding to the interference except the destination node as the sending node to meet the deadline of the data packet.

[0046] In specific implementation, according to the time slot index and channel index of the previous hop transmission in the transmission update information, it is assumed that the sending node of the h-th hop rhythmic transmission receives the time slot of the h-1-th hop rhythmic transmission as t h-1 , then the hth hop rhythmic transmission can only be in time slot t h-1 After that (ie t h-1 +1) is scheduled (if the sending node of the h-th hop transmission is the source node, that is, h = 1, then t h-1 On the other hand, in order to meet the deadline of the data packet, since each transmission after the h-th hop rhythmic transmission (h+1 hop to H0 hop) requires at least one time slot to complete, the h-th hop rhythmic transmission cannot be completed in time slot d. 0,k -(H0-h) is transmitted after that, so the feasible time period for the h-th hop rhythmic transmission is [t h-1 +1,d 0,k -(H0-h)].

[0047] Step 6.4: In a feasible time period, the number of discarded periodic data packets resulting from adding rhythmic transmission to each unit in the static scheduling table in the next cycle is calculated based on the transmission conflict and transmission interference information.

[0048] According to the definition of transmission conflict and transmission interference, rhythmic transmission and any periodic transmission with transmission conflict cannot be scheduled in the same time slot, and rhythmic transmission and any periodic transmission with transmission interference cannot be scheduled in the same unit. Assume that the h-th hop rhythmic transmission is added to a unit in the static scheduling table, the unit index is [t,c], t is the time slot index, c is the channel index, then the periodic transmission that meets any of the following two conditions needs to be discarded.

[0049] Condition 1: The periodic transmission is within the unit of time slot t and there is a transmission conflict with the rhythmic transmission.

[0050] Condition 2: The periodic transmission is within the unit [t, c] and according to the local interference information table, there is transmission interference with the rhythmic transmission.

[0051] If any periodic transmission is dropped, the corresponding periodic packet is also dropped. Since each packet can only be transmitted once in a time slot, the number of dropped periodic packets caused by adding a rhythmic transmission to a cell in the static schedule is equal to the number of dropped periodic transmissions caused by the above two conditions.

[0052] Step 6.5: Within the feasible time period, add the rhythmic transmission to the unit with the minimum number of discarded periodic data packets in the static scheduling table in the next cycle, and obtain the transmission schedule of the node as the sending node in the next cycle in the local dynamic scheduling table.

[0053] Step 7: The nodes on the task path corresponding to the interference generate new transmission update information according to the dynamic scheduling table, and add the new transmission update information to the data packet. Step 7 is specifically as follows:

[0054] Step 7.1: According to the time slot and channel where the node as a sending node transmits in the next cycle in the dynamic scheduling table, obtain the time slot index and channel index in the new transmission update information.

[0055] Step 7.2: By comparing the dynamic scheduling table and the static scheduling table in the next cycle, the task ID and the data packet ID of the discarded periodic data packet in the new transmission update information are obtained.

[0056] Step 7.3: Add the new transmission update information to the data packet within the shortest interference response time. In step 7.3:

[0057] Interference response time is used to represent the time period from when interference is detected to when the system enters rhythmic mode. What directly affects the interference response time is when the transmission update information is added to the data packet;

[0058] For a node, any idle time slot (any time slot in which a node does not send or receive a data packet is an idle time slot) can be used to add transmission update information to a data packet; if there is no such idle time slot before the node sends a data packet, then the time TxOffset before TxPacket in the MAC layer protocol of the sent data packet can be another candidate for the node to add transmission update information to the data packet;

[0059] Adding transmission update information to the data packet in the idle time slot or TxOffset before the node sends the data packet can minimize the interference response time; the shortest interference response time DRT is one cycle time of the rhythm task.

[0060] Step 8: Determine whether the node on the task path corresponding to the interference is the destination node. If so, the system enters the next cycle, otherwise repeat steps 6-8 until the node on the task path corresponding to the interference is the destination node.

[0061] Step 9: Determine whether the interference event has been processed. If so, the system returns success. Otherwise, repeat steps 6-9 until the external interference event is processed.

[0062] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A distributed scheduling method for external interference in a real-time wireless sensor network, characterized in that: include: Step 1: Input parameters, including the network topology of RTWSN, the channel parameters of RTWSN and the data flow set of RTWSN; Step 2: When the network is initialized, the device node generates a local interference information table based on the input parameters, and the gateway generates a global interference information table based on the input parameters; Step 3: In the network non-operation phase, the gateway generates a static scheduling table within a super period according to the input parameters and the global interference information table according to the global deadline priority strategy. If all data packets within the super period can meet their deadlines in the static scheduling table, the network enters the operation phase, otherwise it returns failure; Step 4: During the network operation phase, all device nodes follow the static schedule for transmission; Step 5: The source node of each task determines whether external interference occurs in the network by comparing the collected data with the preset threshold; If external interference occurs in the network, the system enters step 6, otherwise all device nodes follow the static schedule to transmit; Step 6: At the node on the task path corresponding to the interference, a local dynamic scheduling table that can ensure consistent transmission in the next cycle is generated according to the transmission update information. Step 7: The nodes on the task path corresponding to the interference generate new transmission update information according to the dynamic scheduling table, and add the new transmission update information to the data packet; Step 8: Determine whether the node on the task path corresponding to the interference is the destination node. If so, the system enters the next cycle. Otherwise, repeat steps 6-8 until the node on the task path corresponding to the interference is the destination node. Step 9: Determine whether the interference event has been processed. If so, the system returns success. Otherwise, repeat steps 6-9 until the external interference event is processed.

2. The distributed scheduling method for external interference in a real-time wireless sensor network according to claim 1, characterized in that: (1) The network topology of RTWSN is a multi-channel multi-hop RTWSN formed by multiple device nodes and a gateway through wireless connection; the device nodes include: multiple sensor nodes, actuator nodes and relay nodes; the network is modeled as a directed graph G = (V, E), where V = {V0, V1, ...} is the set of device nodes, (V i ,V j )∈E represents the slave device node V i To device node V j Reliable link; (2) The channel parameters of RTWSN include: the number of channels, the length of time slots, and whether spatial channel multiplexing is supported; a data link layer based on multi-channel time division multiple access is adopted, and the number of channels is represented by C. It is assumed that each device node can send or receive data on any channel within a given time, following the 15 millisecond time slot time defined in IEEE 802.15.4e; spatial channel multiplexing is adopted to accommodate concurrent transmissions involving different device node pairs in the same time slot and the same channel; transmission refers to the process of sending a data packet from a sending node to its receiving node; (3) Data flow set of RTWSN, using the concept of task to describe the data flow from sensor nodes to actuator nodes; the system runs a fixed unicast task set T = {τ0,τ1,…,τ N }, each task τ i (0≤i≤N) follows a specified inclusion H i The routing path of each task is τ, N is the number of tasks; a data packet is generated periodically, the source node is a sensor, passes through some relay nodes, and finally reaches an actuator; each task τ i Contains an infinite sequence of packets, τ i The kth data packet is x i,k , including the release time r i,k , deadline d i,k and completion time f i,k Packet x i,k The transfer at the hth hop is called a transmission, denoted by χ i,k (h),1≤h≤H i ; Using the rhythm task model, under normal conditions, each task τ i Following a given normal cycle P i and the normal relative deadline D i , D i ≤P i ; When interference occurs, task τ i enter a rhythmic state in which, in response to a disturbance, its period and relative deadlines first decrease and then gradually return to their normal values ​​by following a monotonically increasing pattern; Assume that at any time during the operation of the network, at most one task is in the rhythm state. Any task currently in the rhythm state is called a rhythm task and is denoted as τ0. The task that is not currently in the rhythm state is τ i (1≤i≤N) is called a periodic task; when the task enters the rhythm state, the device node on the rhythm task τ0 path is called a rhythm node, and the set of rhythm nodes is denoted by V rhy = t0; when a task enters the rhythmic state, the system switches to the rhythmic mode; when the interference is completely processed, usually after τ0 returns to the normal state for a period of time, the system will return to the normal mode; when the system enters the rhythmic mode, the deadline of the rhythmic task is considered to be hard, while the periodic task can tolerate occasional deadline misses; assuming that τ0 is released at the release time t of the m+1th packet 0,m+1 Enter the rhythm state, recorded as t n→r , and at the release time r of the m+R+1th packet 0,m+R+1 Return to normal state, denoted as t r→n , m represents the index of the last data packet of the rhythm task before entering the rhythm state, τ0 is in [t n→r ,t r→n ) during the period; after the disturbance is completely processed, the system will be in the rhythm state at the end point t ep Returns to normal mode at the time point of τ0; any data packet issued in the rhythm mode of the system is called a rhythm data packet, and τ i The data packet of a (1≤i≤N) task is called a periodic data packet.

3. The distributed scheduling method for external interference in a real-time wireless sensor network according to claim 2, characterized in that: Using vector and To represent τ i The period and relative deadline in the rhythm state, R represents the number of rhythm states; once τ i Entering the rhythm state, its cycle and relative deadline are respectively adopted by and The specified value; when it starts using P again i and D i When τ i Back to normal.

4. The distributed scheduling method for external interference in a real-time wireless sensor network according to claim 1, characterized in that: The local interference information table in step 2 is defined as: i According to the task set information, a local interference information table is established on each device node, and three fields are stored: input interference I In , which means that when the device node V i When it is a receiver, it will respond to V i The set of nodes that cause transmission interference; output interference I Out , which means that when the device node V i is the set of nodes that will encounter transmission interference when being a sender; HTP , which means when V i A receiver of V i The set of sender nodes whose transmission interference is caused by one of the senders of , HTP stands for hidden terminal interference; A set of transmissions on the same channel does not interfere with each other if all receivers are not within the interference range of other senders. The interference range is determined by the transmission power and distance. Each node can share its input interference with its neighbors and construct its own output interference and sender node set based on the neighbors' input interference. Given I Out and I HTP , a device node can infer V i any potential interference with any transmissions made; The global interference information in step 2 is defined as follows: the interference information table containing all interference information obtained by the gateway by collecting the local interference information table on each device node is called the global interference information table.

5. The distributed scheduling method for external interference in a real-time wireless sensor network according to claim 1, characterized in that: The static schedule S generated in step 3 needs to ensure that all data packets are successfully transmitted; the static schedule S is a set of time slot / channel allocations related to transmission, used in the normal mode of the system, and each time slot / channel is either idle or allocated to one or more transmissions; In order to ensure the successful transmission of all data packets in the static scheduling table, the static scheduling table should avoid the two transmission failures of transmission conflict and transmission interference in the same time slot; Transmission collision means: if two transmissions are allocated in the same time slot and they have the same sender or receiver, they experience a transmission collision; Transmission interference is when two transmissions are assigned to the same time slot and on the same channel and the signal from the first transmission interferes with the signal at the receiver of the second transmission.

6. The distributed scheduling method for external interference in a real-time wireless sensor network according to claim 1, characterized in that: The step 6 is specifically as follows: Step 6.1: According to the transmission update information, add the transmission schedule determined when the node on the task path corresponding to the interference except the source node is used as the receiving node of the previous hop transmission to the static scheduling table in the next cycle, and obtain the transmission schedule of the node as the receiving node in the next cycle in the local dynamic scheduling table; Step 6.2: According to the task ID and data packet ID of the discarded periodic data packet determined in the previous hop transmission in the transmission update information, remove the discarded periodic transmission in the static scheduling table in the next cycle. Step 6.3: According to the transmission update information, determine the feasible time period in the static scheduling table for rhythmic transmission of nodes on the task path corresponding to the interference, except the destination node, as the sending node, so as to meet the deadline of the data packet; Step 6.4: within a feasible time period, calculate the number of discarded periodic data packets generated by adding rhythmic transmission to each unit in the static scheduling table in the next cycle based on transmission conflict and transmission interference information; Step 6.5: Within the feasible time period, add the rhythmic transmission to the unit with the minimum number of discarded periodic data packets in the static scheduling table in the next cycle, and obtain the transmission schedule of the node as the sending node in the next cycle in the local dynamic scheduling table.

7. The distributed scheduling method for external interference in a real-time wireless sensor network according to claim 1, characterized in that: The transmission update information includes: a time slot index and a channel index and a task / data packet ID of a periodic data packet determined by a previous transmission update; The consistent transmission means that if the sender and the receiver of the transmission allocate the same time offset and channel offset in the scheduling, the transmission is consistent transmission; The dynamic schedule is a set of transmission-related time slot / channel assignments for the system's cadence pattern, with each time slot / channel either idle or assigned to one or more transmissions.

8. The distributed scheduling method for external interference in a real-time wireless sensor network according to claim 1, characterized in that: The step 7 is specifically as follows: Step 7.1: According to the time slot and channel where the node is used as a transmitting node for transmission in the next cycle in the dynamic scheduling table, obtain the time slot index and channel index in the new transmission update information; Step 7.2: By comparing the dynamic scheduling table and the static scheduling table in the next cycle, the task ID and the data packet ID of the discarded periodic data packet in the new transmission update information are obtained; Step 7.3: Add the new transmission update information to the data packet within the shortest interference response time.

9. The distributed scheduling method for external interference in a real-time wireless sensor network according to claim 8, characterized in that: In step 7.3: Interference response time is used to represent the time period from when interference is detected to when the system enters rhythmic mode. What directly affects the interference response time is when the transmission update information is added to the data packet; For a node, any idle time slot can be used to add transmission update information to the data packet; If there is no such idle time slot before the node sends a data packet, then the time TxOffset before TxPacket in the MAC layer protocol of sending the data packet can be another candidate for the node to add the transmission update information to the data packet; Adding transmission update information to the data packet in the idle time slot or TxOffset before the node sends the data packet can minimize the interference response time; the shortest interference response time is one cycle time of the rhythm task.

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