Wireless sensing system and self-guarding method thereof

Abstract

The present application relates to the security technology field, specifically relates to a kind of wireless sensing system and its self-guarding method.The method includes: the monitoring area is divided into several sub-regions;Based on the optimized election algorithm, periodically elect several sensing terminal nodes as the terminal node of turn in each sub-region, the rest sensing terminal nodes are as hibernate terminal node;When the terminal node of turn monitors target, based on the wireless wake-up strategy, wake up the hibernate terminal node of surrounding;The terminal node of turn and the hibernate terminal node that is woken up carry out sensing information collection to target, obtain target information and are fed back to processing center by intermediate node, then the hibernate terminal node that is woken up re-enters sleep state;Processing center carries out fusion processing to target information, obtains the linkage sensing positioning of target, and draws target moving track, obtains the visual situation awareness result of target.

Description

TECHNICAL FIELD

[0001] The present application relates to the security technology field, and in particular to a wireless sensing system and a self-guarding method thereof. BACKGROUND

[0002] Airports are important public transportation hubs, which have the characteristics of large scale, many facilities, and complex operation. Airport perimeter security, as a security barrier between the flight area and the outside world, bears the important responsibility of ensuring the safety of the flight area. Therefore, traditional airport perimeter security methods such as infrared beam method, video monitoring method, leaky cable method, and vibration cable method are usually used to contribute to social safety protection.

[0003] However, the traditional airport perimeter security method has low concealment and is not suitable for concealed monitoring. For deliberate intruders, it is relatively easy to cross and avoid. Therefore, wireless sensing systems have emerged as the times require. With the continuous development of Internet and multimedia technology, wireless technology has become a popular research topic at this stage, and wireless sensing systems are one of them. Wireless sensing systems are composed of numerous randomly distributed micro-sensors in the target monitoring area, which are connected in a wireless, multi-hop, and self-organizing manner, and have sensing, computing, and communication capabilities.

[0004] When wireless sensing systems are applied in the field of airport perimeter security, tens of thousands of wireless sensing nodes are usually arranged in the target monitoring area of the airport perimeter. The large number of nodes makes the problems of some nodes not affect the normal transmission and use of the entire network, to ensure the fault tolerance and invulnerability of the system network. However, this inevitably leads to the difficulty of balancing high accuracy, high real-time monitoring, and low energy consumption for wireless sensing systems used in airport perimeter security. Specifically: the energy of wireless sensing nodes mainly comes from batteries, so low energy consumption design is the key to prolonging its life cycle. In large places such as airports, tens of thousands of nodes need to be deployed in a wide area, and it is difficult for workers to replace the batteries, which requires each node to have extremely low energy consumption and long working life. In order to collect, process, and communicate data under low energy consumption for a large number of nodes, efficient energy management strategies and optimization algorithms are needed to ensure the overall energy efficiency of the network. Moreover, according to the different communication distances and collection efficiencies between nodes, some nodes may run out of energy in advance, causing the wireless sensing network to need to change the layout constantly, thereby increasing the difficulty of adjusting the nodes in the network. At the same time, in order to reduce energy consumption, nodes may need to reduce the frequency and amount of data transmission, which will inevitably affect the accuracy and real-time performance of monitoring. SUMMARY

[0005] In order to solve the above technical problems, the application provides a wireless sensing system and a self-guarding method thereof, aiming at overcoming the technical obstacles between the high accuracy and high real-time monitoring requirements and the low energy consumption limitations of the wireless sensing system itself, designing a safe and reliable, flexible scheduling wireless sensing system self-guarding method, effectively realizing the linkage trend perception positioning of illegal intrusion behavior, ensuring the safety of the airport perimeter, and achieving the purpose of safety protection.

[0006] In the first aspect, the application provides a wireless sensing system, comprising a plurality of sensing terminal nodes, a plurality of intermediate nodes and a processing center, the sensing terminal nodes are arranged in a monitoring area, the intermediate nodes are in wireless communication connection with the plurality of sensing terminal nodes, all the intermediate nodes are connected with the processing center, the sensing terminal node comprises an energy management unit, a sensor unit, a control processing unit, a radio frequency unit, a positioning unit, a clock unit and a storage unit, the energy management unit is used to provide energy for the whole sensing terminal node, the sensor unit is composed of a plurality of sensors, the sensor unit is used to collect different sensing information of the target, the control processing unit is used to formulate the networking strategy of the sensor unit and analyze and process the collected information, the radio frequency unit is used to transmit the processing result of the control processing unit to the intermediate node through a wireless network, the positioning unit is used to obtain the position of the sensing terminal node itself, the clock unit is used to complete the clock calibration of the sensing terminal node itself, and the storage unit is used to store the working information of the sensing terminal node within a preset period, and the energy management unit, the sensor unit, the radio frequency unit, the positioning unit, the clock unit and the storage unit are connected with the control processing unit.

[0007] Preferably, the energy management unit comprises a solar film, an energy management chip and a rechargeable lithium battery, the solar film is used to collect solar energy, the solar film is connected with the energy management chip, the energy management chip is used to collect the energy of the solar energy, and the energy management chip is connected with the rechargeable lithium battery, and the rechargeable lithium battery is used to provide energy supply for the whole sensing terminal node.

[0008] In the second aspect, the application provides a self-guarding method of a wireless sensing system, which is realized by the above wireless sensing system and comprises the following steps:

[0009] Step 102, dividing the monitoring area into a plurality of sub-areas;

[0010] Step 104, periodically electing a plurality of sensing terminal nodes as round-robin terminal nodes and the rest of the sensing terminal nodes as dormant terminal nodes in each sub-area based on an optimized election algorithm, the round-robin terminal nodes are used to take turns to guard and monitor the target;

[0011] Step 106, when the on-duty terminal node in the sub-region monitors the target, the on-duty terminal node plays a wake-up code based on a wireless wake-up strategy to wake up the dormant terminal nodes within a preset range around the on-duty terminal node;

[0012] Step 108, the on-duty terminal node and the woken-up dormant terminal nodes collect sensing information of the target to obtain target information;

[0013] Step 110, the on-duty terminal node and the woken-up dormant terminal nodes feed back the obtained target information to the processing center through the intermediate node, and then the woken-up dormant terminal nodes re-enter the dormant state;

[0014] Step 112, the processing center performs fusion processing on all the target information to obtain a joint sensing positioning of the target, and draws a target moving track based on the joint sensing positioning of the target to obtain a visual situation awareness result of the target.

[0015] As a preferred, in step 104, a number of sensing terminal nodes are periodically elected as on-duty terminal nodes in each sub-region based on an optimized election algorithm, including:

[0016] Step 202, sensing terminal node information in the current period sub-region is obtained, the sensing terminal node information including a residual energy of the node, a distance of the node to the intermediate node, and a number of adjacent nodes of the node in the sub-region;

[0017] Step 204, based on the sensing terminal node information, a probability threshold value of each sensing terminal node being elected as an on-duty terminal node is calculated;

[0018] Step 206, a random number of [0, 1] is assigned to each sensing terminal node in the sub-region, and the random number of each sensing terminal node is compared with the corresponding probability threshold value of the node, when the random number of the sensing terminal node is less than the corresponding probability threshold value of the node, the sensing terminal node is elected as an on-duty terminal node in the current period.

[0019] As a preferred, the sensing terminal node information includes the distance between adjacent nodes, then after step 206, it further includes:

[0020] Step 208, the maximum distance between adjacent nodes is taken as a distance threshold value, whether the distance between the elected on-duty terminal nodes is greater than the distance threshold value is judged, if the distance between the elected on-duty terminal nodes is greater than the distance threshold value, the elected on-duty terminal nodes are determined as the final on-duty terminal nodes in the current period, if the distance between the elected on-duty terminal nodes is less than or equal to the distance threshold value, steps 206 to 208 are re-executed.

[0021] As preferred, in step 104, based on the optimized election algorithm, a number of sensing terminal nodes in each sub-region are periodically elected as the round terminal nodes, including:

[0022] The residual energy of the round terminal nodes in the current period in each sub-region is monitored, and when the residual energy of the round terminal nodes is lower than a preset threshold, the election of the round terminal nodes in the next period is carried out based on the optimized election algorithm, and the sensing terminal nodes serving as the round terminal nodes in the current period are excluded in the election of the round terminal nodes in the next period.

[0023] As preferred, in step 204, based on the sensing terminal node information, the expression of the probability threshold of each sensing terminal node being elected as the round terminal node is calculated as:

[0024]

[0025] wherein n represents the sensing terminal node, G represents the set of sensing terminal nodes excluding the sensing terminal nodes serving as the round terminal nodes in the current period, w represents the percentage of the expected number of round terminal nodes selected in each election in the total sensing terminal nodes in the sub-region, l represents the number of the current periodic election, P(n) represents the probability threshold of the sensing terminal node belonging to the set G being elected as the round terminal node in the lth election, θ1 is a preset energy weight, E i represents the current residual energy value of the sensing terminal node, E init represents the initial energy value of the sensing terminal node, θ2 is a preset distance weight, D i represents the distance of the sensing terminal node n to the intermediate node, D max represents the farthest distance of the sensing terminal node in the sub-region to the intermediate node, θ3 is a preset proximity weight, θ1, θ2, θ3 are all > 0, and θ1+ θ2+ θ3 = 1, N i represents the number of adjacent nodes of the sensing terminal node in the sub-region.

[0026] As preferred, in step 106, when the round terminal node in the sub-region monitors the target, the round terminal node plays the wake-up code based on the wireless wake-up strategy to wake up the sleep terminal nodes within the preset range, including:

[0027] In step 302, the length of the wake-up code required by the round terminal node is calculated for the purpose that the transmission time of the wake-up code sent by the round terminal node is greater than the low-power sleep time of the sleep terminal node;

[0028] In step 304, the LoRaWAN Class B protocol is modified by using the length of the wake-up code required by the round terminal node calculated, and the modified LoRaWAN Class B protocol is used as the wireless wake-up strategy;

[0029] Step 306, when the target is monitored by the on-duty terminal node in the sub-area, the on-duty terminal node plays the wake-up code to wake up the sleep terminal node in the preset range based on the wireless wake-up strategy.

[0030] As preferred, in step 302, the expression for calculating the length of the wake-up code required by the on-duty terminal node is:

[0031]

[0032] T preamble =(n preamble +4.25)T S >T sleep

[0033] Wherein, BW represents the channel bandwidth, SF represents the spreading factor, R s represents the transmission rate of a single data packet, T s represents the transmission period of a single data packet, T preamble represents the transmission time of the wake-up code sent by the on-duty terminal node, n preamble represents the length of the wake-up code required by the on-duty terminal node, T sleep represents the low-power sleep time of the sleep terminal node.

[0034] As preferred, in step 112, the processing center performs fusion processing on all target information to obtain the joint awareness positioning of the target, including:

[0035] Step 402, time synchronization is performed on all target information, and the time-synchronized target information is associated;

[0036] Step 404, the associated target information is fused by using the Kalman filtering algorithm to obtain the target position estimation;

[0037] Step 406, the processing center re-executes steps 402-404 based on the real-time received target information to obtain the updated target position estimation, which is the joint awareness positioning of the target.

[0038] The beneficial technical effects of the present application at least include:

[0039] 1. A wireless sensing system is adopted, solar energy collection is completed through solar thin film and energy is collected through energy management chip, and rechargeable lithium battery is matched to provide energy supply for the whole sensing terminal node, the wireless sensing system provided in the application applies the solar energy supply strategy, overcomes the technical problem that the wireless sensing system of airport perimeter security is difficult to replace the battery, the energy consumption of numerous sensing terminal nodes is supplemented, the vitality of the whole system is improved, long-time self-service of large-scale wireless sensing system is realized;

[0040] 2. A self-service method of wireless sensing system is adopted, through combining optimized rotation terminal node election algorithm, wireless wake-up strategy and micro energy management of wireless sensing system, the running state of each sensing terminal node is automatically adjusted, efficient energy utilization and data transmission are realized, energy consumption of wireless sensing system is reduced, and stable and reliable self-service method of large-scale wireless sensing system is realized. Specifically:

[0041] By comprehensively considering the residual energy of the sensing terminal node, the distance from the node to the intermediate node, and the centrality of the node in the sub-area, a rotation terminal node election algorithm based on relatively fixed energy, distance and centrality is proposed. Specifically, the node with more residual energy is preferentially selected as the rotation terminal node, which can ensure that the energy consumption in the network is more balanced, prolong the service life of the whole wireless sensing network, the node close to the intermediate node can reduce the communication distance, reduce the communication delay, improve the real-time performance of data transmission, the node with high centrality is often at the center position of the sub-area, which can better collect the information of surrounding nodes, optimize the topology structure of wireless sensing monitoring network, and improve the comprehensiveness and accuracy of data collection, so as to realize the reasonable election of rotation terminal node, which can flexibly adapt to the dynamic changes in the network, such as node failure and energy depletion, and timely adjust the rotation terminal node. By comparing the random number with the probability threshold, it is ensured that all sensing terminal nodes in the network can participate in the election of rotation terminal node, avoid the premature failure of some nodes due to long-term bearing more tasks, prolong the service life of the whole network, and ensure the high accuracy and high real-time monitoring demand of wireless sensing system, which provides basic guarantee for subsequent wake-up linkage mechanism; further, distance restriction is added to the election of rotation terminal node, so that the rotation terminal node is dispersed as much as possible without selecting adjacent nodes, the coverage range of rotation terminal node in the sub-area is optimized, the low delay and low power consumption are ensured when waking up the sleep node, and the work load of each rotation terminal node is relatively balanced, thereby reducing the overall energy consumption of the system;

[0042] By evaluating the election period of each round according to the residual energy of the round terminal node, the round terminal node is prevented from being prematurely "killed" by excessive energy consumption, and a large amount of energy consumption and waste caused by frequent round terminal node election is also prevented, and at the same time, the sensing terminal node that is the round terminal node in the current period is excluded in the election process of the next period, so as to avoid the system energy imbalance caused by the node serving as the round terminal node continuously.

[0043] By creatively calculating the length of the wake-up code required by the round terminal node for the purpose of the transmission time of the wake-up code sent by the round terminal node being greater than the low-power sleep time of the sleep terminal node, the length of the wake-up code required by the round terminal node is calculated, and the length of the wake-up code required by the round terminal node is calculated on the basis of the LoRaWAN Class B protocol, so as to greatly optimize the sleep time duty cycle of the terminal node, ensure that the average power consumption of the system is lower, change the previous compromise mode of communication time and power consumption, and make the Class B protocol more suitable for the self-service scheme of the low-power wireless sensing system.

[0044] Other features and advantages of the present application will be disclosed in detail in the following specific embodiments and drawings. BRIEF DESCRIPTION OF DRAWINGS

[0045] The present application will be further described below in combination with the drawings:

[0046] Figure 1 It is a structure schematic diagram of the wireless sensing system of the embodiment of the present application.

[0047] Figure 2 It is a self-service method flow chart of the wireless sensing system of the embodiment of the present application. DETAILED DESCRIPTION

[0048] The technical solutions of the embodiments of the present application will be explained and described below in combination with the drawings of the embodiments of the present application, but the following embodiments are only preferred embodiments of the present application, not all. Based on the embodiments in the embodiments, other embodiments obtained by those skilled in the art without creative labor also belong to the protection scope of the present application.

[0049] In the following description, the appearance of terms such as "inner", "outer", "upper", "lower", "left", "right" and the like indicates the orientation or positional relationship only for the convenience of describing the embodiments and simplifying the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0050] The embodiment of the present application provides a wireless sensing system, comprising a plurality of sensing terminal nodes, a plurality of intermediate nodes and a processing center, the sensing terminal nodes are arranged in a monitoring area, the intermediate nodes are in wireless communication connection with the plurality of sensing terminal nodes, all the intermediate nodes are connected with the processing center, please refer to the accompanying drawings Figure 1 ,

[0051] The sensing terminal node comprises an energy management unit, a sensor unit, a control processing unit, a radio frequency unit, a positioning unit, a clock unit and a storage unit, and the energy management unit, the sensor unit, the radio frequency unit, the positioning unit, the clock unit and the storage unit are connected with the control processing unit, wherein the sensing terminal node has the characteristics of small volume and low power consumption, and is mainly responsible for implementing close-range sensing, detection and acquisition of related information on the target in the monitoring area, and sending the related information to the intermediate node through a wireless communication network;

[0052] The energy management unit is used for providing energy for the whole sensing terminal node;

[0053] The sensor unit is composed of a plurality of sensors, and the sensor unit is used for collecting different sensing information of the target, wherein the sensors can be sound, vibration and magnetic sensors, and the sensor unit is a signal receiving source for monitoring the target, and serves as a supplementary monitoring for the area where the line of sight cannot reach;

[0054] The control processing unit is used for formulating a networking strategy of the sensor unit and performing analysis and processing of the collected information;

[0055] The radio frequency unit is used for transmitting the processing result of the control processing unit to the intermediate node through a wireless network;

[0056] The positioning unit is used for acquiring the position of the sensing terminal node itself, and the clock unit is used for completing clock calibration of the sensing terminal node itself, thereby providing support for subsequent linkage situation awareness of the processing center;

[0057] The storage unit is used for storing the working information of the sensing terminal node within a preset period.

[0058] In one embodiment of the present application, please refer to the accompanying drawings Figure 1 The energy management unit comprises a solar film, an energy management chip and a rechargeable lithium battery, the solar film is used for collecting solar energy, the solar film is connected with the energy management chip, the energy management chip is used for collecting energy of the solar energy, the energy management chip is connected with the rechargeable lithium battery, and the rechargeable lithium battery is used for providing energy supply for the whole sensing terminal node.

[0059] It can be understood that the energy management unit as an important component of the whole sensing terminal node, is used to provide a constant source of energy for the sensing terminal node to work, and is a powerful guarantee for the long time self-service of the wireless sensing system. The working principle of the energy management unit is as follows:

[0060] (1) Solar thin film

[0061] By way of example, the solar thin film in the embodiment adopts a CIGS thin film type battery. Compared with other types of solar cells, the CIGS thin film type battery has the characteristics of strong light absorption capacity, good power generation stability, high conversion efficiency, long daytime power generation time, and high power generation capacity, and can be made flexible to meet the requirements of outdoor deployment. When the sensing terminal node has a volume of 20cm 3 (4cm×4cm×1.25cm), it can provide a utilization area of up to 16cm 2 on a single side. According to the charging characteristics of the CIGS thin film type battery, it is expected to provide a battery of 38mAh (voltage 3V) after 6 hours of effective charging per day.

[0062] (2) Energy management chip

[0063] The energy management chip in the embodiment, i.e. the micro energy collection / management chip, selects intelligent integrated energy collection and milliwatt power consumption management, is suitable for ultra-low power consumption applications with special requirements, and can collect and manage micro-watt (μW) to milliwatt (mW) level power generated by various direct current sources such as photovoltaic (solar) generators or thermoelectric generators.

[0064] Further, the energy management unit in the embodiment can also include a battery monitoring chip. The battery monitoring chip is used to detect the power state information of the rechargeable lithium battery at any time, and feed back the power state information to the control processing unit, so that each sensing terminal node can know the size level of the energy contained therein, and provide an important selection parameter basis for the selection of the subsequent shift terminal node.

[0065] One of the defects of the existing wireless sensing system is the limitation of battery power. We know that the sensor nodes of the wireless sensing system can only be small embedded devices due to the limitation of the use environment. The composition of the sensor nodes determines that only a battery with limited energy can be used for power supply. The wireless sensing system often needs to be applied in some places with harsh environment and complex area. Not only the number of nodes is large, but also it is difficult for the staff to replace the battery. Therefore, the solar energy collection is completed by the solar thin film and the energy is collected by the energy management chip in the embodiment. The rechargeable lithium battery is matched to provide energy supply for the whole sensing terminal node. The wireless sensing system provided in the embodiment overcomes the technical problem that the wireless sensing system of the airport perimeter security is difficult to replace the battery. The energy consumption of the numerous sensing terminal nodes is supplemented. The life of the whole system is improved. The long-time self-service of the large-scale wireless sensing system is realized.

[0066] On the other hand, the embodiment of the application further provides a self-service method of the wireless sensing system, which is realized by the wireless sensing system. Figure 2 , comprising the following steps:

[0067] Step 102, the monitoring area is divided into several sub-areas.

[0068] Specifically, the monitoring area is divided into N sub-areas in the embodiment. The sensing terminal nodes are controlled according to the hierarchical form topology, that is, all the sensing terminal nodes are deployed in the MxM mode, wherein M is the side length of the monitoring area.

[0069] Step 104, based on the optimized election algorithm, several sensing terminal nodes in each sub-area are periodically elected as the round terminal nodes, and the remaining sensing terminal nodes are as the sleep terminal nodes. The round terminal nodes are used for round service and monitoring of the target.

[0070] It can be understood that when the wireless sensing system works, in order to save power consumption and realize self-service, after the sensing terminal nodes complete self-positioning, most of the sensing terminal nodes will be in a sleep state. Only the radio frequency unit in the sensing terminal node works in the listening mode. These nodes are sleep terminal nodes. Only several sensing terminal nodes in each sub-area are used for round service and monitoring. These nodes are round terminal nodes.

[0071] It can be understood that in the embodiment, the round terminal nodes in the sub-area have the wake-up function. The information of each sensing terminal node can be sent to the intermediate node. The communication between the sub-areas in the system is mainly coordinated by the intermediate node. According to the concept of hierarchical management, the management is implemented step by step. This mode reduces unnecessary energy consumption on the one hand and avoids the waste of energy caused by the circulation of useless information in the whole sensing system network. At the same time, the network's anti-destroying ability is enhanced to a certain extent.

[0072] Further, in the embodiment, in step 104, the optimized election algorithm is used to periodically elect a number of sensing terminal nodes as round terminal nodes in each sub-region, including:

[0073] In step 202, the sensing terminal node information in the current period sub-region is obtained, and the sensing terminal node information includes the residual energy of the node, the distance from the node to the intermediate node, and the number of adjacent nodes of the node in the sub-region. It can be understood that the number of adjacent nodes of the node in the sub-region can represent the centrality of the node in the sub-region.

[0074] In step 204, based on the sensing terminal node information, the probability threshold of each sensing terminal node being elected as a round terminal node is calculated.

[0075] Specifically, based on the sensing terminal node information, the expression for calculating the probability threshold of each sensing terminal node being elected as a round terminal node is:

[0076]

[0077] Wherein, n represents the sensing terminal node, G represents the set of sensing terminal nodes excluding the current period as a round terminal node, w represents the percentage of the expected number of round terminal nodes selected in each election in the total number of sensing terminal nodes in the sub-region, l represents the number of the current periodic election round, P(n) represents the probability threshold of the sensing terminal node belonging to the G set being elected as a round terminal node in the lth election, θ1 is a preset energy weight, E i represents the current residual energy value of the sensing terminal node, E init represents the initial energy value of the sensing terminal node, θ2 is a preset distance weight, D i represents the distance from the sensing terminal node n to the intermediate node, D max represents the farthest distance from the sensing terminal node in the sub-region to the intermediate node, θ3 is a preset adjacent weight, θ1, θ2, θ3 are all > 0, and θ1+θ2+θ3=1, N i represents the number of adjacent nodes of the sensing terminal node in the sub-region.

[0078] In step 206, a random number in [0, 1] is assigned to each sensing terminal node in the sub-region, and the random number of each sensing terminal node is compared with the corresponding probability threshold of the node. When the random number of the sensing terminal node is less than the corresponding probability threshold of the node, the sensing terminal node is elected as a round terminal node in the current period.

[0079] It can be understood that at least one round terminal node can be elected by the embodiment. Further, in the embodiment, if the number of elected round terminal nodes is less than the number of required round terminal nodes in the current sub-region, the remaining sensing terminal nodes repeat step 206 until the required number of round terminal nodes is elected, and the repeated election mechanism is terminated.

[0080] Further, in the embodiment, the sensing terminal node information includes the distance between adjacent nodes, and after step 206, the following is further included:

[0081] Step 208: The maximum distance between adjacent nodes is taken as a distance threshold value, and it is determined whether the distance between the elected round terminal nodes is greater than the distance threshold value. If the distance between the elected round terminal nodes is greater than the distance threshold value, the elected round terminal nodes are determined as the final round terminal nodes in the current period. If the distance between the elected round terminal nodes is less than or equal to the distance threshold value, steps 206 to 208 are re-executed.

[0082] For example, taking three elected round terminal nodes as an example, when the three round terminal nodes satisfy the following conditions, the three elected round terminal nodes are determined as the final round terminal nodes in the current period:

[0083]

[0084] Wherein, (x1, y1), (x2, y2), (x3, y3) represent the coordinates of the positions of the three round terminal nodes, and R represents the maximum distance between adjacent nodes as the distance threshold value.

[0085] It can be understood that steps 202 to 208 only describe the selection method of a round terminal node in a sub-region, and the periodic selection method of a round terminal node in other sub-regions can be referred to the embodiment.

[0086] On the other hand, in the embodiment, in step 104, the optimized election algorithm is used to periodically elect a number of sensing terminal nodes as round terminal nodes in each sub-region, including:

[0087] The residual energy of the round terminal node in each sub-region in the current period is monitored. When the residual energy of the round terminal node is lower than a preset threshold value, the optimized election algorithm is used to elect the round terminal node in the next period, and the sensing terminal node serving as the round terminal node in the current period is excluded in the election process of the round terminal node in the next period.

[0088] It can be understood that the rotation of the duty terminal node in the embodiment is periodic, and the election period of each round is evaluated according to the residual energy of the duty terminal node. When the residual energy of the duty terminal node is lower than the preset threshold and is insufficient to support the subsequent duty work, the next round of duty terminal node election is started. That is, when the residual energy of one of the duty terminal nodes in the sub-area is lower than the preset threshold, all the duty terminal nodes in the current sub-area are replaced in the next round of election.

[0089] In this way, it not only avoids the premature death of the duty terminal node due to excessive energy consumption, but also prevents the large amount of energy consumption and waste caused by frequent duty terminal node elections. At the same time, the method used for the election rotation is consistent with the above-mentioned optimized election algorithm, but the sensing terminal nodes that are duty terminal nodes in the current period are excluded in the election process of the next period, so as to avoid the system energy imbalance caused by the nodes continuously serving as duty terminal nodes.

[0090] The embodiment considers the residual energy of the sensing terminal node, the distance from the node to the intermediate node, and the centrality of the node in the sub-area, and proposes a duty terminal node election algorithm based on relatively fixed energy, distance, and centrality. Specifically, the node with more residual energy is preferentially selected as the duty terminal node, which can ensure more balanced energy consumption in the network, prolong the operation life of the entire wireless sensor network, select the node close to the intermediate node to reduce the communication distance, reduce the communication delay, improve the real-time performance of data transmission, and the node with high centrality is often in the center position of the sub-area, which can better collect the information of the surrounding nodes, optimize the topology of the wireless sensor monitoring network, and improve the comprehensiveness and accuracy of data collection, so as to realize the reasonable election of the duty terminal node, adapt to the dynamic changes in the network such as node failure and energy depletion, adjust the duty terminal node in time, compare the random number with the probability threshold, ensure that all sensing terminal nodes in the network can participate in the election of the duty terminal node, avoid the premature failure of some nodes due to long-term heavier tasks, prolong the operation life of the entire network, and ensure the high accuracy and high real-time monitoring demand of the wireless sensor system, providing a basic guarantee for the subsequent wake-up linkage mechanism. Further, the election of the duty terminal node is limited by distance, so that the duty terminal nodes are as dispersed as possible and adjacent nodes are not selected, the coverage range of the duty terminal nodes in the sub-area is optimized, the low delay and low power consumption are ensured when the sleep nodes are awakened, the work load of each duty terminal node is relatively balanced, and the overall energy consumption of the system is reduced.

[0091] Step 106, when the duty terminal node in the sub-area detects the target, the duty terminal node plays the wake-up code based on the wireless wake-up strategy to wake up the sleep terminal nodes within the preset range.

[0092] According to the established rotation strategy, the rotation terminal node needs to wake up the sleep terminal node through wireless communication function. Since the energy consumption of the radio frequency unit of the sensing terminal node is quite different between the listening mode and the sleep mode, the wireless wake-up strategy of the rotation terminal node playing the wake-up code to wake up the sleep terminal node in the preset range is particularly important.

[0093] Specifically, when the rotation terminal node in the sub-area monitors the target, the rotation terminal node plays the wake-up code to wake up the sleep terminal node in the preset range based on the wireless wake-up strategy, including:

[0094] Step 302, for the purpose of the wake-up code transmission time of the rotation terminal node being greater than the low-power sleep time of the sleep terminal node, the length of the wake-up code required by the rotation terminal node is calculated.

[0095] On the other hand, in the embodiment, for the purpose of the wake-up code transmission time of the rotation terminal node being greater than the low-power sleep time of the sleep terminal node, the expression for calculating the length of the wake-up code required by the rotation terminal node is:

[0096]

[0097] T preamble =(n preamble +4.25)T S >T sleep

[0098] Wherein, BW represents the channel bandwidth, SF represents the spreading factor, R s represents the transmission rate of a single data packet, T s represents the transmission period of a single data packet, T preamble represents the wake-up code transmission time of the rotation terminal node, n preamble represents the length of the wake-up code required by the rotation terminal node, T sleep represents the low-power sleep time of the sleep terminal node.

[0099] For example, taking the low-power sleep time of the sensing terminal node as 1s, the spreading factor SF as 10, and the bandwidth BW as 125000Hz, for the purpose of the wake-up code transmission time of the rotation terminal node being greater than the low-power sleep time of the sleep terminal node, the specific implementation of calculating the length of the wake-up code required by the rotation terminal node is:

[0100]

[0101] The length of the wake-up code required by the rotation terminal node n preamble = 118, that is, the wake-up code needs to continuously send 118 times of wake-up data to ensure that the sensing terminal node is woken up in the sleep state.

[0102] Step 304, the LoRaWAN Class B protocol is modified by using the calculated length of the wake-up code required by the rotating terminal node, and the modified LoRaWAN Class B protocol is used as the wireless wake-up strategy.

[0103] Step 306, when the rotating terminal node in the sub-area monitors the target, the rotating terminal node plays the wake-up code based on the wireless wake-up strategy to wake up the sleep terminal nodes within the preset range.

[0104] Further, if the awakened sleep node can listen to the target event, the rotating terminal node can broadcast the wake-up code again to wake up more sleep nodes around it, and through the linkage triggering mechanism of waking up multiple nodes, linkage monitoring is performed to ensure the accuracy of backend identification and positioning and achieve comprehensive situation awareness.

[0105] Among them, LoRaWAN based on LoRa spread spectrum technology has three working modes, Class A, Class B and Class C.

[0106] Class A is the mainstream of the current wireless sensing system using LoRaWAN communication protocol, and is suitable for scenarios that require long running time and extremely low power consumption. Its working principle is that the node actively reports, and only opens 2 receiving information windows when sending, and is in sleep state at other times. The advantage of Class A mode is extremely low power consumption, for example, the 10-year working life of water meter application is usually based on Class A. However, if it is applied in the present embodiment, the downlink communication window of the intermediate node will only be performed after the uplink communication of the sensing terminal node occurs, which cannot meet the monitoring demand of high real-time of the wireless sensing system of airport perimeter security;

[0107] Class B is suitable for low-delay systems and can periodically open communication receiving windows. If the sensing terminal node receives the wake-up code of the node during the window period, it can receive complete downlink communication data packets. However, if it is applied in the present embodiment, the long window period will undoubtedly increase the power consumption of the wireless sensing system, thereby making it difficult to meet the low-energy consumption requirement of the wireless sensing system of airport perimeter security;

[0108] And Class C is suitable for systems that require no delay, and the downlink communication receiving window is always open, thereby ensuring that the intermediate node can communicate at any time, but it requires sufficient power and cannot meet the low-energy consumption requirement of the wireless sensing system of airport perimeter security.

[0109] To this end, the embodiment creatively calculates the length of the wake-up code required by the turn terminal node, designs and modifies the length of the wake-up code required by the turn terminal node on the basis of the LoRaWAN Class B protocol, optimizes the sleep time duty cycle of the terminal node, ensures lower average power consumption of the system, changes the previous compromise between communication time and power consumption, and makes the Class B protocol more suitable for the self-service scheme of the low-power wireless sensing system.

[0110] Next, taking the spreading factor SF as 10 and the bandwidth BW as 125000 Hz as an example, the technical effect of being able to optimize the sleep time duty cycle of the sensing terminal node while ensuring the wireless wake-up success rate is verified under the scheme of designing and modifying the length of the wake-up code required by the turn terminal node on the basis of the Class B protocol of LoRaWAN:

[0111] Under the scheme of designing and modifying the length of the wake-up code required by the turn terminal node on the basis of the Class B protocol of LoRaWAN, the wake-up code receiving time SymbolTime required by the sleep terminal node in the CAD channel activity detection mode is calculated and can be expressed as:

[0112]

[0113] At the same time, CAD is started and scanning the corresponding frequency band at most needs 480μs, so the required time is 8.448+0.48=8.928ms. Therefore, the cycle of the sensing terminal node “low-power sleep-CAD” is about 1s+8.928ms=1008.928ms, and the sleep time duty cycle of the sensing terminal node is 8.928ms÷1008.928ms×100%≈0.88%. It can be seen that the sleep time duty cycle of the sensing terminal node is greatly optimized;

[0114] Under the wireless wake-up strategy, the power consumption measurement result in the case of non-pure chip is as follows: in the deep sleep state, the node power consumption is about 2.2mA; in the case of CAD event (i.e. in the wake-up code detection state as a sleep terminal node), the power consumption is about 11.79mA±3mA, and the average power consumption per cycle is about 2.3mA. It can be seen that the wireless wake-up strategy provided by the embodiment can greatly save power consumption from the system point of view;

[0115] The feasibility of the wireless wake-up sleep terminal node work of the turn terminal node is verified through the serial port monitoring:

[0116] When the on-duty terminal node sends the wake-up code, the serial port sends the printing condition as follows:

[0117] Send unconfirme 0x01

[0118] d************************Sending Alert Message.

[0119] frame type data confirmed up

[0120] The channel value is-1

[0121] 0x00

[0122] The content size was 2

[0123] ######=====MCPS-Request====######

[0124] STATUS: OK

[0125] As can be seen from the above, the wake-up code information is sent, the channel number is-1, and the channel frequency occupied is 433MHz. The reason for using this frequency is that this frequency band is far away from the frequency section of the protocol operation, and will not produce interference to the normal protocol transmission.

[0126] When the dormant terminal node receives the wake-up code information, the serial port receives the printing condition as follows:

[0127] CaO start

[0128] The RSSI value is-121

[0129] NO detected

[0130] 0x00

[0131] Cad start

[0132] The RSSI value is-108

[0133] NO detected

[0134] 0x00

[0135] Cad start

[0136] The RSSI value is-122

[0137] NO detected

[0138] 0x00

[0139] Cad start

[0140] The RSSI value is-123

[0141] NO detected

[0142] 0x00

[0143] Cad start

[0144] The RSSI value is-113

[0145] NO detected

[0146] 0x00

[0147] Cad start

[0148] The RSSI value is-122

[0149] NO detected

[0150] 0x00

[0151] Cad start

[0152] The RSSI value is-59

[0153] Detected

[0154] 0x00

[0155] Open Rx..

[0156] RxDone State

[0157] The RSSI value is-79

[0158] RxDone

[0159] Enter process RxDone phase

[0160] Now the device will go to sleep

[0161] From this, it can be seen that when the wake-up code of the on-duty terminal node is sent, the RSSI value in the 433 channel of the dormant terminal node increases sharply, indicating that there is wake-up code information in the channel. After detecting the wake-up code information, the CAD detection is successful, the receiving window is opened to receive information, and then the control processing unit is started, and the information monitoring state is entered, which verifies that the wireless wake-up strategy provided in this embodiment can ensure the wireless wake-up success rate.

[0162] In step 108, the on-duty terminal node and the awakened dormant terminal node perform target sensing information collection to obtain target information.

[0163] The target information includes, but is not limited to, target type, quantity, sensing terminal node ID and the like.

[0164] In step 110, the on-duty terminal node and the awakened dormant terminal node feed back the target information obtained by themselves to the processing center through the intermediate node, and then the awakened dormant terminal node re-enters the dormant state.

[0165] In this embodiment, the dormant terminal node does not relay through the on-duty terminal node, but directly feeds back the obtained target information to the processing center through the intermediate node, which can reduce the delay on the one hand and save system energy on the other hand.

[0166] Further, in this embodiment, the wireless sensing system uses distributed computing to realize monitoring of the monitoring target, that is, after the on-duty terminal node and the awakened dormant terminal node complete preliminary sensing information collection, the intermediate node only transmits a small amount of identification results to the processing center to complete further positioning and situation analysis.

[0167] In step 112, the processing center performs fusion processing on all target information to obtain the joint awareness positioning of the target, and draws the target movement trajectory based on the joint awareness positioning of the target to obtain the visual situation awareness result of the target.

[0168] The position and movement trajectory of the target can be displayed based on the joint awareness positioning of the target using geographic information system (GIS) software, and the dynamic characteristics of the target can be highlighted using data visualization tools, which will not be described herein.

[0169] In one embodiment of the present specification, in step 112, the processing center performs fusion processing on all target information to obtain the joint awareness positioning of the target, including:

[0170] In step 402, time synchronization is performed on all target information, and the time-synchronized target information is associated;

[0171] It can be understood that the processing center first needs to ensure that the target position data from different terminal nodes is in the same time reference system. Moreover, due to the different clock synchronization errors of the nodes in the wireless sensor network, the processing center can use the network time protocol (NTP) or other synchronization mechanisms to synchronize the data in time.

[0172] Further, before step 402, the processing center can also take a strategy of eliminating target results deviating greatly to achieve a higher recognition rate.

[0173] Step 404: The associated target information is fused by using a Kalman filtering algorithm to obtain a target position estimate.

[0174] The data fusion method of the Kalman filtering algorithm can be used in the dynamic monitoring environment of the present application to fuse the redundant information in the sensor, making it more accurate. The evaluation of the fusion algorithm is based on different situations to introduce the concept of self-adaptation to linearly combine the estimated values of the sensor nodes, which will not be described in detail in this embodiment.

[0175] Step 406: The processing center re-executes steps 402-404 based on the real-time received target information to obtain an updated target position estimate, i.e., the target cooperative awareness positioning.

[0176] With the continuous reception of new data, the processing center needs to update the target cooperative awareness positioning in real time to provide real-time data basis for drawing the target movement trajectory based on the target cooperative awareness positioning, so as to obtain accurate target visual situation awareness results.

[0177] The above is only a preferred embodiment of the present application and a description of the technical principles used, and those skilled in the art should understand that the scope of protection involved in the present disclosure is not limited to the technical solutions formed by the specific combination of the above technical features, and also covers other technical solutions formed by any combination of the above technical features or equivalent features without departing from the disclosed concept. For example, the above features can be replaced with similar functional technical features disclosed in the present disclosure (but not limited to) to form a technical solution.

[0178] Moreover, while operations are depicted in a particular order, this should not be understood as requiring the operations to be performed in the particular order shown or in sequential order, and that some operations can be performed in parallel or in any suitably enabled order. Similarly, while several specific implementation details are included herein, they should not be taken as limitations on the scope of the disclosure. Certain features that are described in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable sub-combination.

Claims

1. A self-monitoring method for a wireless sensor system, characterized in that: The following steps are involved: Step 102, dividing the monitoring area into several sub-areas; Step 104: Periodically electing a number of sensing terminal nodes as rotating terminal nodes in each sub-area based on an optimized election algorithm, and the remaining sensing terminal nodes as dormant terminal nodes. The rotating terminal nodes are used to take turns guarding the monitoring target, including: Step 202: Acquire the sensing terminal node information in the sub-area of ​​the current cycle, wherein the sensing terminal node information includes the remaining energy of the node, the distance from the node to the intermediate node, and the number of adjacent nodes of the node in the sub-area; Step 204: Based on the sensing terminal node information, the probability threshold of each sensing terminal node being elected as a rotating terminal node is calculated, and the expression is: ， Where n represents the sensing terminal node, G represents the set of sensing terminal nodes excluding the rotating terminal nodes in the current cycle, w represents the percentage of the rotating terminal nodes expected to be selected in each round of election to all sensing terminal nodes in the sub-region, l represents the number of rounds of periodic elections currently being conducted, represents the probability threshold of the sensing terminal node belonging to the G set being elected as the rotating terminal node in the lth round of election, is the preset energy weight, Represents the current remaining energy value of the sensing terminal node, represents the initial energy value of the sensing terminal node, is the preset distance weight, Indicates the distance between the sensing terminal node n and the intermediate node, Indicates the maximum distance between the sensing terminal node and the intermediate node in the sub-area. To preset neighbor weights, Indicates the number of adjacent nodes of the sensing terminal node in the sub-area; Step 206: assign a random number between 0 and 1 to each sensing terminal node in the sub-area, compare the random number of each sensing terminal node with the probability threshold corresponding to the node, and when the random number of the sensing terminal node is less than the probability threshold of the corresponding node, select the sensing terminal node as the rotating terminal node of the current cycle; Step 106: When the rotating terminal node in the sub-area detects the target, the rotating terminal node plays a wake-up code based on the wireless wake-up strategy to wake up the dormant terminal nodes within the preset range. Step 108: The rotating terminal node and the awakened dormant terminal node collect perception information of the target to obtain target information; Step 110: The rotating terminal node and the awakened dormant terminal node feed back the acquired target information to the processing center via the intermediate node, and then the awakened dormant terminal node returns to the dormant state; In step 112, the processing center integrates all target information to obtain the target's linkage perception and positioning, and draws the target's movement trajectory based on the target's linkage perception and positioning to obtain a visual situation awareness result of the target.

2. The self-monitoring method of a wireless sensor system according to claim 1, wherein: The sensing terminal node information includes the distance between adjacent nodes, and after step 206, the following steps are further included: In step 208, the maximum distance between adjacent nodes is used as the distance threshold to determine whether the distance between the elected rotating terminal nodes is greater than the distance threshold. If the distance between the elected rotating terminal nodes is greater than the distance threshold, the elected rotating terminal node is determined as the final rotating terminal node of the current cycle. If the distance between the elected rotating terminal nodes is less than or equal to the distance threshold, steps 206 to 208 are re-executed.

3. A self-monitoring method for a wireless sensor system according to any one of claims 1 or 2, characterized in that: In step 104, a number of sensing terminal nodes are periodically elected as rotating terminal nodes in each sub-area based on an optimized election algorithm, including: Monitor the residual energy of the rotating terminal node in the current cycle in each sub-area. When the residual energy of the rotating terminal node is lower than the preset threshold, the rotating terminal node election for the next cycle is carried out based on the optimized election algorithm, and the perception terminal node of the current cycle is excluded as the rotating terminal node in the rotating terminal node election process of the next cycle.

4. The self-monitoring method of a wireless sensor system according to claim 1, wherein: In step 106, when the rotating terminal node in the sub-area detects the target, the rotating terminal node plays a wake-up code based on the wireless wake-up strategy to wake up the dormant terminal nodes within the preset range, including: Step 302 , with the goal of ensuring that the transmission time of the wake-up code sent by the rotating terminal node is longer than the low-power sleep time of the sleep terminal node, calculate the wake-up code length required by the rotating terminal node; Step 304: Modify the LoRaWAN Class B protocol using the calculated wake-up code length required by the rotating terminal node, and use the modified LoRaWAN Class B protocol as the wireless wake-up strategy; Step 306: When the rotating terminal node in the sub-area detects the target, the rotating terminal node plays a wake-up code based on the wireless wake-up strategy to wake up the dormant terminal nodes within a preset range.

5. The self-monitoring method of a wireless sensor system according to claim 4, characterized in that: In step 302, with the goal of ensuring that the wake-up code transmission time sent by the rotating terminal node is longer than the low-power sleep time of the sleep terminal node, the expression for calculating the wake-up code length required by the rotating terminal node is: ， Where BW represents the channel bandwidth, SF represents the spreading factor, Indicates the transmission rate of a single data packet. Indicates the transmission period of a single data packet, Indicates the wake-up code transmission time sent by the rotating terminal node. Indicates the wake-up code length required by the rotating terminal node. Indicates the low-power sleep time of a sleeping terminal node.

6. The self-monitoring method of a wireless sensor system according to claim 1, wherein: In step 112, the processing center integrates all target information to obtain the target's linkage perception positioning, including: Step 402: Time-synchronize all target information and associate the time-synchronized target information; Step 404: Using a Kalman filter algorithm to fuse the associated target information to obtain a target position estimate; In step 406, the processing center re-executes steps 402 to 404 based on the target information received in real time to obtain an updated target position estimate, which is the linked perception positioning of the target.

7. A wireless sensor system using the self-monitoring method of a wireless sensor system according to any one of claims 1 to 6, comprising a plurality of sensing terminal nodes, a plurality of intermediate nodes, and a processing center, wherein the sensing terminal nodes are deployed within a monitoring area, the intermediate nodes are wirelessly connected to the plurality of sensing terminal nodes, and all the intermediate nodes are connected to the processing center, characterized in that: The perception terminal node includes an energy management unit, a sensor unit, a control processing unit, a radio frequency unit, a positioning unit, a clock unit and a storage unit. The energy management unit is used to provide energy for the entire perception terminal node. The sensor unit is composed of several sensors. The sensor unit is used to collect different perception information of the target. The control processing unit is used to formulate the networking strategy of the sensor unit and analyze and process the collected information. The radio frequency unit is used to transmit the processing results of the control processing unit to the intermediate node through the wireless network. The positioning unit is used to obtain the position of the perception terminal node itself. The clock unit is used to complete the clock calibration of the perception terminal node itself. The storage unit is used to store the working information of the perception terminal node within a preset period. The energy management unit, sensor unit, radio frequency unit, positioning unit, clock unit and storage unit are all connected to the control processing unit.

8. A wireless sensing system according to claim 7, characterized in that: The energy management unit includes a solar film, an energy management chip and a rechargeable lithium battery. The solar film is used to collect solar energy, the solar film is connected to the energy management chip, the energy management chip is used to aggregate solar energy, the energy management chip is connected to the rechargeable lithium battery, and the rechargeable lithium battery is used to provide energy supply for the entire perception terminal node.

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