Apparatus, method and system for controlling power workload of edge node

Abstract

A power load balancing device of an edge node according to one embodiment may include: a control module that performs Long Range (LoRa) communication of the edge node in response to supplied power; an energy harvesting device that generates power according to a light amount corresponding to the received light in response to receiving light, and supplies the generated power to the control module as at least a portion of the supplied power; a battery connected to the control module through a switch and supplies power charged while the switch is turned on based on the light amount to the control module as at least a portion of the supplied power; and a diode coupled between the energy harvesting device and the battery in a direction that blocks the current flow from the battery to the energy harvesting device and allows power supply from the energy harvesting device to the control module.

Description

Technology Field

[0001] Below, a technology for controlling edge node power in an edge computing environment is provided. Background Technology

[0003] The development of the Internet of Things (IoT) has enabled the production of massive amounts of data. This generated data can be exchanged between different devices through various communication technologies. However, this can lead to server overload issues. To address this server overload problem, edge computing has emerged, enabling rapid processing and response near applications. An edge computing environment may include a cloud layer, which is the highest layer containing a main server. Additionally, an edge computing environment may include a fog layer containing intermediate servers. The fog layer is connected to the main server of the cloud layer and can also be connected to edge nodes (data collection devices, computing devices, or terminals, etc.) included in the edge layer. Edge nodes within the edge layer can collect data from the surrounding environment or perform data processing, and then communicate the resulting data with the fog layer. In particular, power consumption may occur when data is exchanged between edge nodes in the edge layer and intermediate servers in the fog layer. Therefore, in the operation of edge nodes in the edge layer within an edge computing environment, as the volume of processed data increases, edge node shutdowns due to excessive power consumption may occur. Since the cessation of operation adversely affects system performance, node management must be performed properly. Therefore, the following provides a technique for adjusting the workload of edge nodes by appropriately distributing the operation of edge nodes according to the power consumption of multiple edge nodes included in an edge computing environment. means of solving the problem

[0005] According to one embodiment, a power load balancing device of an edge node may include: a control module that performs Long Range (LoRa) communication of the edge node in response to supplied power; an energy harvesting device that generates power according to a light amount corresponding to the received light in response to receiving light, and supplies the generated power to the control module as at least a portion of the supplied power; a battery connected to the control module through a switch and supplies power charged while the switch is turned on based on the light amount to the control module as at least a portion of the supplied power; and a diode coupled between the energy harvesting device and the battery in a manner that blocks the current flow from the battery to the energy harvesting device and allows power supply from the energy harvesting device to the control module.

[0006] The control module may include: a switch controller that receives the amount of light corresponding to the light received from the light amount sensor and turns on the switch while the amount of light is below a threshold amount of light; and a voltage sensor controller that receives the amount of power determined based on the state of charge (SOC) of the battery collected from the voltage sensor and determines whether the edge node will perform LoRa communication or perform data backup to memory.

[0007] The above control module can control the LoRa communication according to the amount of power determined based on the state of charge (SOC) of the battery collected from the light amount corresponding to the received light and the voltage sensor.

[0008] The control module can cut off the power supplied from the battery to the control module by turning off the switch while the amount of light exceeds a predetermined threshold amount of light.

[0009] The above control module can determine the SOC of the battery based on the closed circuit voltage (CCV) of the battery.

[0010] The control module can perform LoRa communication of the edge node while the SOC of the battery is above a predetermined threshold value, and back up the data of the edge node to memory otherwise.

[0011] A power load balancing method for an edge node according to one embodiment may include: a step of generating power according to a light amount corresponding to the received light in response to an energy harvesting device receiving light, and supplying the generated power to a control module; a step of a battery connected to the control module through a switch supplying power charged while the switch is turned on based on the light amount to the control module; a step of a diode coupled between the energy harvesting device and the battery blocking the current flow from the battery to the energy harvesting device and allowing power supply from the energy harvesting device to the control module; and a step of the control module performing Long Range (LoRa) communication of the edge node in response to power supplied from the energy harvesting device and the battery, respectively.

[0012] The step of supplying the charged power to the control module may include the step of the switch controller receiving the amount of light corresponding to the light received from the light amount sensor, and turning on the switch while the amount of light is below a threshold amount of light.

[0013] The step of performing the above LoRa communication may include a step in which a voltage sensor controller receives a power amount determined based on the state of charge (SOC) of the battery collected from the voltage sensor, and determines whether the edge node will perform LoRa communication or perform data backup to memory.

[0014] The step of performing the above LoRa communication may include the step of the control module controlling the LoRa communication according to the amount of power determined based on the state of charge (SOC) of the battery collected from the light amount corresponding to the received light and the voltage sensor.

[0015] The step of supplying charged power to the control module may include the step of cutting off the power supplied from the battery to the control module by turning off the switch while the amount of light exceeds a predetermined threshold amount of light.

[0016] The step of performing Long Range (LoRa) communication of the edge node may include the step of determining the SOC of the battery based on the closed circuit voltage (CCV) of the battery.

[0017] The step of performing LoRa (Long Range, LoRa) communication of the edge node may include: performing LoRa communication of the edge node while the SOC of the battery is above a predetermined threshold value; and backing up the data of the edge node to memory when the SOC of the battery is below a predetermined threshold value.

[0018] A power load balancing system according to one embodiment comprises a plurality of edge nodes; and

[0019] An intermediate server that establishes communication with the aforementioned multiple edge nodes via LoRa communication

[0020] The apparatus comprises: a control module that performs Long Range (LoRa) communication of at least one edge node among the plurality of edge nodes in response to supplied power; an energy harvesting device that generates power according to a light intensity corresponding to the received light in response to receiving light, and supplies the generated power to the control module as at least a portion of the supplied power; and a battery connected to the control module through a switch, and supplies power charged while the switch is turned on based on the light intensity to the control module as at least a portion of the supplied power. and includes a diode coupled between the energy harvesting device and the battery in a direction that blocks the current flow from the battery to the energy harvesting device and allows power supply from the energy harvesting device to the control module, and can adjust the LoRa communication amount of the at least one edge node based on at least one of the light amount collected from adjacent edge nodes and the collected state of charge (SOC) of the battery, wherein the sensing range corresponding to an area of ​​a preset distance centered on the at least one edge node overlaps.

[0021] In a power load balancing system according to one embodiment, at least one edge node among the plurality of edge nodes can increase the amount of LoRa communication of the at least one edge node in the overlapping sensing range of the at least one edge node and the adjacent edge node while the amount of first light collected at the at least one edge node is greater than the amount of second light collected at the adjacent edge node.

[0022] In a power load balancing system according to one embodiment, at least one edge node among the plurality of edge nodes can perform LoRa communication in an overlapping sensing range where the edge node with a larger SOC of the battery among the at least one edge node and the adjacent edge node is within a threshold light amount range when the first light amount collected from the at least one edge node and the second light amount collected from the adjacent edge node are within a threshold light amount range. Brief explanation of the drawing

[0024] Figure 1 illustrates an edge computing environment. FIGS. 2 to 6 illustrate comparative embodiments of a power load balancing device for preventing edge node operation stoppage. FIG. 7 illustrates a power load balancing device of an edge node according to one embodiment. FIGS. 8 to 10 sequentially illustrate the operation of a power load balancing device according to one embodiment. Figure 11 shows a graph of the voltage and SOC sensed in a power load balancing device. Figure 12 shows a graph of the power consumption ratio according to the amount of light. FIG. 13 illustrates a graph showing the result of a power load balancing device according to one embodiment operating a switch connected to a battery based on light intensity information. FIG. 14 shows the layout of a control module included in a power load balancing device according to one embodiment. FIGS. 15 and 16 illustrate a system comprising a plurality of edge nodes and an intermediate server connected to the plurality of edge nodes to establish LoRa communication. Specific details for implementing the invention

[0025] Specific structural or functional descriptions of the embodiments are disclosed for illustrative purposes only and may be modified and implemented in various forms. Accordingly, actual implementations are not limited to the specific embodiments disclosed, and the scope of this specification includes modifications, equivalents, or substitutions included in the technical concept described by the embodiments.

[0026] Terms such as "first" or "second" may be used to describe various components, but these terms should be interpreted solely for the purpose of distinguishing one component from another. For example, the first component may be named the second component, and similarly, the second component may be named the first component.

[0027] When it is stated that a component is "connected" to another component, it should be understood that it may be directly connected to or coupled with that other component, or that there may be other components in between.

[0028] The singular expression includes the plural expression unless the context clearly indicates otherwise. In this specification, terms such as "comprising" or "having" are intended to specify the existence of the described features, numbers, steps, actions, components, parts, or combinations thereof, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0029] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this specification.

[0030] Hereinafter, embodiments will be described in detail with reference to the attached drawings. In the description with reference to the attached drawings, identical components are given the same reference numeral regardless of the drawing number, and redundant descriptions thereof will be omitted.

[0032] Figure 1 illustrates an edge computing environment.

[0033] An edge computing environment (100) may include a cloud layer, an intermediate layer called a Fog layer, and an edge layer (110). The cloud layer may include a main server, and the main server may transmit and receive data from the Fog layer. The Fog layer may include an intermediate server, and the intermediate server may transmit and receive data with the main server included in the cloud layer, while also transmitting and receiving data with the edge layer (110).

[0034] The edge layer (110) may include multiple edge nodes. For reference, the edge nodes may include a data collection device or a data processing device. For example, the edge nodes may include electronic terminals such as sensors, smartphones, antennas, on-board units, or CCTVs. This is merely an example of an edge node, and the edge nodes may include electronic devices that collect data or perform calculations on the collected data. The edge nodes included in the edge layer (110) may require high power to transmit data to the Fog layer. If the edge nodes included in the edge layer (110) require high power to transmit data to the Fog layer, the operation of the edge nodes may stop due to power consumption. For example, when transmitting data from a smartphone included in the edge layer (110) to the Fog layer, if the smartphone's power is insufficient and the data cannot be transmitted, it may have an adverse effect on the edge computing environment (100). In the following, a power load balancing device is proposed to prevent the operation of edge nodes included in the edge layer (110).

[0036] FIGS. 2 to 6 illustrate comparative embodiments of a power load balancing device for preventing edge node operation stoppage.

[0037] The comparative examples (200, 201) illustrated in FIG. 2 represent power load balancing devices implemented based on the paper “HG Lee and N. Chang, “Powering the IoT: Storage-less and converter-less energy harvesting,” The 20th Asia and South Pacific Design Automation Conference, Chiba, Japan, 2015, pp. 124-129, doi: 10.1109 / ASPDAC.2015.7058992.” The comparative examples (200, 201) directly utilize harvested energy and operate unstably by controlling the operation according to a set threshold voltage.

[0038] The comparative examples (300, 301, 302) illustrated in FIG. 3 represent power load balancing devices implemented based on the paper “Yue Xu, Hyung Gyu Lee, Yujuan Tan, Yu Wu, Xianzhang Chen, Liang Liang, Lei Qiao, and Duo Liu. 2019. Tumbler: Energy Efficient Task Scheduling for Dual-Channel Solar-Powered Sensor Nodes. In Proceedings of the 56th Annual Design Automation Conference 2019 (DAC '19). Association for Computing Machinery, New York, NY, USA, Article 172, 1-6. https: / / doi.org / 10.1145 / 3316781.3317927”. Comparative examples (300, 301, 302) may include a dual-channel solar sensor node and a scheduling algorithm in the dual-channel solar sensor node. Comparative examples (300, 301, 302) may include a power load balancing device that determines the size of the sensor node by considering the harvested energy and the energy remaining in the capacitor.

[0039] The comparative example (400) illustrated in FIG. 4 represents a power load balancing device implemented based on the paper “AJ Williams, MF Torquato, IM Cameron, AA Fahmy and J. Sienz, “Survey of Energy Harvesting Technologies for Wireless Sensor Networks,” in IEEE Access, vol. 9, pp. 77493-77510, 2021, doi: 10.1109 / ACCESS.2021.3083697.” In the comparative example (400), a battery is used as the main power source for the power load balancing device, and an energy harvesting device is used as the auxiliary power source.

[0040] The comparative example (500) illustrated in FIG. 5 represents a power load balancing device implemented based on the paper “AI Petrariu, A. Lavric, E. Coca and V. Popa, “Hybrid Power Management System for LoRa Communication Using Renewable Energy,” in IEEE Internet of Things Journal, vol. 8, no. 10, pp. 8423-8436, 15 May 15, 2021, doi: 10.1109 / JIOT.2020.3046324.” The comparative example (500) uses an energy harvesting device as the main power source and a battery as the auxiliary power source. The comparative example (500) has a problem in that an unstable energy supply is maintained from the energy harvesting device on cloudy days, and since energy is supplied by charging a capacitor, the communication cycle with an intermediate server is limited.

[0041] The comparative example (600) illustrated in FIG. 6 is based on the paper “Kang, J.; Kim, S.; Kim, J.; Sung, N.; Yoon, Y. Dynamic Offloading Model for Distributed Collaboration in Edge Computing: A Use Case on Forest Fires Management. Appl. Sci. 2020, 10, 2334. https: / / doi.org / 10.3390 / app10072334 This is an edge computing workload balancing method implemented based on ". Comparative Example (600) performs workload balancing through a distributed collaboration method in edge computing, predicts overload at edge nodes in advance, and can request collaboration with adjacent edge nodes. Unlike the comparative examples shown in FIGS. 2 to 5, Comparative Example (600) attempted to solve an optimization problem based on computer simulation.

[0042] The comparative embodiments illustrated in FIGS. 2 to 6 focus only on the communication operation itself or on the aspect of an efficient data processing method by focusing on an energy harvesting device to avoid using a battery. In other words, the comparative embodiments illustrated in FIGS. 2 to 6 have limitations, such as unstable operation, limitations on the communication cycle, and the inability to implement specific power scheduling.

[0043] Therefore, the following proposes an optimization model that considers both power and data processing methods to effectively extend the performance and lifespan of edge nodes as a power load balancing device, method, and system. The proposed invention can identify energy obtained from sunlight through light intensity information to regulate the battery consumption rate and always stably supply power to the system. In addition, it can determine the workload of the edge nodes according to the power level by recognizing the State of Charge (SoC) level of the battery.

[0045] FIG. 7 illustrates a power load balancing device of an edge node according to one embodiment.

[0046] According to one embodiment, the power load balancing device (700) of an edge node may include a device that stably supplies power so that the operation of the edge node does not stop. The power load balancing device (700) may include a control module (720), a power supply unit (710) that stably supplies power to the control module, and an application unit (730). The load balancing device (700) can achieve power load balancing of the edge node by supplying power from the power supply unit (710) to the control module (720) and determining the operation of the application unit (730) through the control module (720).

[0047] The power load balancing device (700) may include an energy harvesting device that generates power according to the amount of light corresponding to the received light in response to receiving light from the power supply unit (710), and supplies the generated power to the control module (720). For example, the energy harvesting device may include a solar panel (e.g., PV cell), but is not limited thereto. However, solar panels are mainly described below. The energy harvesting device may continuously supply power to the control module (720). Although FIG. 7 is illustrated as supplying power to the control module (720) with a single energy harvesting device, multiple energy harvesting devices may supply power to the control module (720), and the control module (720) may perform data processing of the edge node through the power supplied by the multiple energy harvesting devices. For example, the control module (720) may control a communication chip included in the edge node so that the edge node communicates with an intermediate server.

[0048] The power load balancing device (700) may include a battery that is connected to the control module (720) via a switch in the power supply unit (710) and supplies power charged to the control module (720) while the switch is turned on based on the amount of light. For example, the battery may include a lithium battery, but is not limited thereto. The switch connecting the battery and the control module (720) may include a power switch, but is not limited thereto. The battery may supply power charged in the battery to the control module (720) while the switch is turned on based on the amount of light. The switch connected to the battery may be controlled through the control module (720). For example, the control module (720) may receive additional power from the battery by turning on the switch so that sufficient power can be supplied for the edge node to operate when the amount of light is insufficient and the edge node cannot be operated by the energy harvesting device alone, that is, while the amount of light is below a critical amount of light. Accordingly, power from the energy harvesting device is continuously supplied to the control module (720), and the power consumption ratio of the battery and the power consumption ratio of the energy harvesting device may vary depending on the amount of light.

[0049] The power load balancing device (700) may include a diode coupled between the energy harvesting device and the battery in a manner that blocks the current flow from the battery to the energy harvesting device in the power supply unit (710) and allows power supply from the energy harvesting device to the control module (720). The diode can prevent reverse current from the battery to the energy harvesting device. For example, on days with insufficient sunlight, such as rainy days or cloudy days, the energy harvesting device included in the edge node cannot generate power above a certain level, so the voltage of the battery becomes higher than the voltage of the energy harvesting device, and a current flow may be generated from the battery to the energy harvesting device, but the diode can prevent the generated current flow.

[0050] The power load balancing device (700) may include a control module (720) that receives power from a power supply unit (710). The control module (720) can regulate the power supplied from the power supply unit (710) by controlling a switch connected to a battery. For example, the control module (720) may turn off the switch connected to the battery to cut off the power supplied from the battery when light quantity information is sensed such that sufficient power can be supplied solely by an energy harvesting device (e.g., a PV cell). For example, the control module (720) may include a switch controller that receives a light quantity corresponding to the light received from a light quantity sensor and turns on the switch while the light quantity is below a threshold light quantity.

[0051] For reference, the control module (720) may include a light sensor module (e.g., light sensor module), but as shown in FIG. 7, the light sensor module may be located outside the control module (720). The light sensor module may include a device that detects and measures the amount of light in the surrounding environment of an edge node (e.g., terminal, data receiving device, data processing device, etc.). For example, the light sensor module may include a photoresistor, a photodiode, a phototransistor, or a digital light sensor, but is not limited thereto.

[0052] The control module (720) can receive a light amount corresponding to the light collected from the light amount sensor module into a light amount sensor controller (e.g., a light sensor controller). The light amount sensor controller can operate a switch controller based on the light amount. For example, the control module (720) can estimate the amount of power generated by the energy harvesting device based on the light amount received by the light amount sensor controller. If the estimated amount of power is sufficient to perform LoRa communication, the control module (720) can cause the switch controller to turn off the switch connected to the battery. In another example, if the estimated amount of power generated by the energy harvesting device is insufficient to perform LoRa communication based on the light amount received by the light amount sensor controller, the control module (720) can cause the switch controller to turn on the switch.

[0053] The control module (720) may include a voltage sensor controller that receives a power amount determined based on the state of charge (SOC) of the battery collected from the voltage sensor and determines whether the edge node will perform LoRa communication or perform data backup to memory.

[0054] For reference, the voltage sensor may include, for example, a voltage sensor module (e.g., voltage sensor module). The control module (720) may include a voltage sensor module, but as shown in FIG. 7, the voltage sensor module may be located outside the control module (720). Below, the case where the voltage sensor module is located outside the control module (720) will be described with focus. The voltage sensor module corresponding to the voltage sensor can sense SOC information corresponding to the charge amount of the battery included in the power supply unit (710).

[0055] The control module (720) can receive a power amount determined based on the SOC of the power supply unit (710) battery sensed from the voltage sensor module to a voltage sensor controller (e.g., voltage sensor controller). The control module (720) can determine the operation of the application unit (730) based on the power amount received by the voltage sensor controller. For example, if the power amount determined based on the SOC is sufficient, the control module (720) can enable LoRa communication to be performed in the application unit (730) via a LoRa communication controller (e.g., LoRa Controller). As another example, if the power amount determined based on the SOC is insufficient, the control module (720) can back up the data of the edge node to the non-volatile memory (e.g., non-volatile memory) of the application unit (730) via a memory controller (e.g., memory controller). The control module (720) determines data backup to LoRa communication or memory based on the amount of power determined based on the battery's SOC, thereby preventing problems such as data loss processed or collected at the edge node when the edge node operation stops due to battery discharge, etc.

[0056] The control module (720) can perform Long Range (LoRa) communication of the edge node in response to power supplied from the power supply unit (710). For example, the control module (720) can control the power supply from the battery to the control module (720) by adjusting a switch based on the amount of light as described above, and can perform LoRa communication of the edge node in response to when the battery holds the power required for communication based on the battery's SOC. As another example, if it is determined based on the battery's SOC that the battery does not hold the power required for communication, the data of the edge node can be backed up to memory. Therefore, the control module (720) can estimate the amount of power of the battery based on the battery's SOC so that data can be backed up and restored even if the edge node dies.

[0057] The control module (720) can control the LoRa communication of the edge node according to the amount of power determined based on the amount of light corresponding to the received light and the SOC of the battery collected from the voltage sensor. For example, the control module (720) can increase or decrease the amount of communication, communication frequency, communication speed, throughput, etc. of the LoRa communication based on the power supplied from the power supply unit (710) and the SOC of the battery.

[0058] According to one embodiment, the application unit (730) included in the power load balancing device (700) may include an electronic device or memory that performs LoRa communication. For example, the application unit (730) may include a LoRa communication chip or non-volatile memory. However, this is merely an example, and the application unit (730) may include a terminal that generates or collects data as an IoT device.

[0060] FIGS. 8 to 10 sequentially illustrate the operation of a power load balancing device according to one embodiment.

[0061] FIG. 8 is a diagram relating to the operation of a power load balancing device supplying power from a power supply unit to a control module. As described in FIG. 7, the power load balancing device may include an energy harvesting device (800), a diode (810), a battery (820), and a switch (830) in the power supply unit. The power load balancing device may supply power to the control module through the energy harvesting device (800) and the battery (820). At this time, the energy harvesting device (800) may continuously supply energy harvested through sunlight to the control module. The power supplied by the energy harvesting device (800) to the control module may increase or decrease depending on the amount of light. For example, if solar energy is strong, such as on a sunny day, the ratio of power supplied to the control module by the energy harvesting device (800) may be higher than the ratio of power supplied to the battery (820). Accordingly, the power load balancing device determines the amount of power generated by the energy harvesting device (800) based on the amount of light, and if the amount of power generated by the energy harvesting device (800) based on the amount of light is insufficient to perform LoRa communication of the edge node, it can supply additional power from the battery (820) to the control module by turning on the switch (830) connected to the battery (820). In another example, if the energy harvesting device (800) generates a sufficient amount of power for the edge node to communicate based on the received light, the power load balancing device can cut off the power consumption of the battery (820) by turning off the switch (830). Through this, the power load balancing device can extend the life of the battery (820).

[0062] The power load balancing device may include a diode (810) coupled between the energy harvesting device (800) and the battery (820) in a direction that allows power supply from the energy harvesting device (800) to the control module. The power load balancing device can block the flow of current from the battery (820) toward the energy harvesting device (800) through the diode (810). For example, the diode (810) can prevent reverse current from the battery (820) toward the energy harvesting device (800) when the voltage of the battery (820) is higher than the voltage formed in the energy harvesting device (800) due to weak light.

[0063] For reference, the diode (310) may include a diode (310) having a device specification of a working voltage of 3V to 28V and a maximum working current of 15A, but the specific specifications of the diode (310) are not limited thereto.

[0065] FIG. 9 is a diagram relating to the operation of controlling the power supplied from the power supply unit to the control module based on the amount of light in the control module. The control module may include a switch controller (910) that receives a light amount corresponding to the light received from the light amount sensor (900) and turns on the switch (920) while the amount of light is below a threshold amount of light. The light amount sensor (900) may include a light amount sensor module. The light amount sensor (900) may sense the amount of light based on the light around the edge node and transmit the sensed amount of light to the control module. Based on the sensed amount of light, the control module may determine whether to turn on or turn off the switch (920) to the switch controller (910) through the light amount sensor controller (e.g., light sensor controller). For example, the control module may cut off the power supplied from the battery to the control module by turning off the switch (920) while the amount of light exceeds a predetermined threshold amount of light.

[0066] For reference, the switch (920) may include a power switch. For example, the switch (920) may include a switch element of TPS27081a. For example, the switch (920) may include a switch element that operates with specifications corresponding to an operating voltage of 0.1V to 8V, a maximum operating current of 3A, and a maximum power dissipation of 1190mW. However, this is merely an example, and the type of switch (920) is not limited thereto.

[0067] A predetermined threshold light intensity may represent the amount of light at which an edge node can perform LoRa communication. For example, the predetermined threshold light intensity may include the amount of light at which the edge node can perform LoRa communication using only the energy harvesting device. For example, the predetermined threshold light intensity may correspond to the amount of light required for the current supplied from the energy harvesting device to the control module to correspond to 120 mA. For example, the predetermined threshold light intensity may be determined to be 8,000 lux when a total of three energy harvesting devices are connected to the control module. As another example, when one energy harvesting device is connected to the control module, the threshold light intensity may be determined to be approximately 20,000 lux. The predetermined threshold light intensity may vary depending on the power generated by the energy harvesting device based on the light intensity.

[0069] FIG. 10 is a diagram illustrating a power load balancing device according to one embodiment determining the operation of an edge node through a control module based on the SOC of a battery. The power load balancing device can sense the SOC of a battery using a voltage sensor (1000). For example, the voltage sensor (1000) of the power load balancing device can sense the SOC of a battery every second. The power load balancing device can transmit the SOC of the battery sensed by the voltage sensor (1000) to a voltage sensor controller (1010) of the control module (e.g., voltage sensor controller). Based on the SOC of the battery transmitted from the voltage sensor (1000), the voltage sensor controller (1010) can generate a signal that allows the control module to determine the data processing method of the edge node. For example, when the battery's SOC is sufficient, the voltage sensor controller (1010) can cause the LoRa communication controller (e.g., LoRa controller) (1020) to generate a signal that induces LoRa communication (1040) of the edge node. As another example, when the battery's SOC is insufficient, the voltage sensor controller (1010) can cause the memory controller (1030) to store data in the edge node's non-volatile memory (1050). For example, cases where the battery's SOC is sufficient and cases where it is insufficient can be distinguished based on a predetermined threshold value of the SOC. Since the power load balancing device can determine the operation of the edge node through the control module based on the battery's SOC, the voltage sensor (1000) must be able to sense the accurate SOC. A method for accurately sensing the SOC of the power load balancing device through the voltage sensor (1000) is described below in FIG. 11.

[0070] In summary, as described in FIGS. 8 to 10, the power load balancing device can supply power to the control module through the energy harvesting device and the battery. The power-supplied control module can turn off the battery switch when sufficient power for the edge node's communication can be supplied solely by the energy harvesting device based on the amount of light. Conversely, while sufficient power for the edge node's communication cannot be supplied solely by the energy harvesting device, the control module can receive additional power from the battery by turning on the battery switch. By operating the switch, the control module can stably maintain the power supplied to the control module. The control module can determine whether to store the edge node's LoRa communication or the edge node's data in memory based on the battery's SOC.

[0072] Figure 11 shows a graph of the voltage and SOC sensed in a power load balancing device.

[0073] As described in FIG. 10 above, the power load balancing device needs to sense the accurate SOC through the voltage sensor (1000) of FIG. 10. For example, the power load balancing device can sense the battery's SOC every second. To sense the accurate SOC of the battery, it is necessary to verify it through the battery's standard open circuit voltage (OCV) or to perform a Coulomb counting method that measures the current at every moment. However, since only the closed circuit voltage (CCV) can be measured when the power load balancing device is in operation, it is necessary to estimate the OCV through the CCV and verify the SOC through the corresponding OCV.

[0074] A control module according to one embodiment can determine the state of charge (SOC) of a battery based on the closed-circuit voltage (CCV) of the battery. For example, the control module can estimate the open-circuit voltage (OCV) of the battery based on a predetermined voltage value of the CCV measured through a voltage sensor. The control module can determine the SOC corresponding to the estimated OCV as the state of charge of the battery. Table 1 below shows the measured CCV of the battery and the OCV of the battery after 24 hours of operation for a set period of time.

[0076] 1-minute exercise 10-minute exercise 30-minute exercise

[0077] Column 1 of Table 1 compares the CCV measured during 1 minute of operation of an edge node containing a power load balancing device with the OCV measured 24 hours after 1 minute of operation. Column 2 of Table 1 compares the CCV measured during 10 minutes of operation of an edge node containing a power load balancing device with the OCV measured 24 hours after 10 minutes of operation. Column 3 of Table 1 compares the CCV measured during 30 minutes of operation of an edge node containing a power load balancing device with the OCV measured 24 hours after 30 minutes of operation. Each column of Table 1 compares the voltage between the CCV and the OCV, and indicates the error value and the average error as a result of the comparison. For example, Table 1 shows that in an environment where an edge node containing a power load balancing device communicates at 1-second intervals, the difference between the CCV and the OCV corresponds to an average of about 0.1V. In addition, Table 1 shows that the average error rate in each column of CCV and OCV is approximately 2.6%. Based on this, the control module can generate a voltage graph for the battery's SOC.

[0078] FIG. 11 may include a standard OCV graph (1100) and a measured CCV graph (1110). Graphs (1100) and (1110) may include values ​​corresponding to voltage on the y-axis and the battery's SOC on the x-axis. Graphs (1100) and (1110) may be displayed at predetermined voltage value intervals based on the y-axis. For example, referring to Table 1 above, graph (1110) may be a graph shifted 0.1V downward on the y-axis compared to graph (1100). Graphs (1100) and (1110) may include a threshold line (1130) of the SOC. For example, the threshold line (1130) may be a value corresponding to the SOC determined based on the measured battery's CCV and may serve as a criterion for the battery to turn off quickly. Therefore, the power load balancing device can store data from the edge node in memory when the battery's SOC is below the value corresponding to the threshold line (1130). Although the error rate between OCV and CCV in Table 1 appears to be only 2.6%, if we refer to the box (1120) of the graph (1100), even if the voltage value at the left end and the voltage value at the right end within the box (1120) differ by only 0.1V, the SOC corresponding to the voltage value at the left end and the SOC corresponding to the voltage value at the right end can differ by up to 10%. Therefore, even if the CCV and OCV form the graph (1100) and the graph (1110) with a gap of about 0.1V, estimating the OCV through the CCV and determining the SOC based on the estimated OCV may be an accurate method for measuring SOC.

[0080] Figure 12 shows a graph of the power consumption ratio according to the amount of light.

[0081] A power load balancing device according to one embodiment can adjust the power consumption ratio according to the amount of light by controlling a switch connected to a battery based on the amount of light through a control module. A graph (1200) for the power consumption ratio according to the amount of light by the power load balancing device may include the amount of light on the x-axis and the power consumption ratio on the y-axis. For example, the graph (1200) illustrates that the power load balancing device adjusts the power supplied from the energy harvesting device (e.g., PV) and the battery, respectively, by turning on a switch connected to the battery while receiving a amount of light less than a threshold amount of light (1210). According to the graph (1200), the power load balancing device can receive power from the energy harvesting device at a rate of 100% while receiving a amount of light greater than or equal to the threshold amount of light (1210).

[0082] For example, the solar panels corresponding to the energy harvesting device may have specifications that produce 40mA at 8000 lux per unit. For example, an edge node including a power load balancing device may require 120mA of current to perform LoRa communication. If the power load balancing device included in the edge node includes a total of three solar panels, the power load balancing device can generate a total current of 120mA at 8000 lux from the energy harvesting device, so the critical light intensity (1210) in the graph (1200) may represent 8000 lux. Although the above embodiment was described assuming the case where there are three solar panels corresponding to the energy harvesting device, the number of energy harvesting devices included in the power load balancing device is not limited to this, and the critical light intensity (1210) may vary depending on the specifications and number of connections of the energy harvesting device.

[0084] FIG. 13 illustrates a graph showing the result of a power load balancing device according to one embodiment operating a switch connected to a battery based on light intensity information.

[0085] The graph (1300) shows the result of the power load balancing device controlling the operation of the battery based on the collected light intensity information. For example, if the power load balancing device receives 10,000 lux of light, the light intensity information can be replaced with a digital value. For example, 16-bit data such as 16'b0010 1010 1010 1000 can correspond to the decimal number 10920. The corresponding 16-bit data may be data representing light intensity information of approximately 10,000 lux. Through the graph (1300), the power load balancing device according to one embodiment can turn off the switch in response to a light intensity greater than or equal to the threshold light intensity (1310) among the digital light intensity information data. The graph (1300) can show the result of turning off the switch in response to a light intensity greater than or equal to the threshold light intensity (1310) among the digitized light intensity information data based on the case where there are a total of two energy harvesting devices. A power load balancing device according to one embodiment can turn off a switch by transmitting a logic low value from a control module to a switch through a GPIO in response to a light amount greater than or equal to a critical light amount (1310).

[0087] FIG. 14 shows the layout of a control module included in a power load balancing device according to one embodiment.

[0088] A control module (1400) according to one embodiment may include a switch controller (e.g., switch controller) that operates a switch of a battery, a light sensor controller (e.g., light sensor controller), a voltage sensor controller (e.g., voltage sensor controller), a LoRa communication controller (e.g., LoRa controller), and a memory controller (e.g., memory controller). For example, each component included in the control module (1400) described above may have the device specifications of Table 2 below.

[0090]

[0091] In Table 2, the switch controller included in the control module (1400) according to one embodiment may have a power consumption of 0.904 mW. The memory controller may have a power consumption of 0.489 mW. The light intensity sensor controller may have a power consumption of 0.188 mW. The voltage sensor controller may have a power consumption of 1.551 mW. The LoRa communication controller may have a power consumption of 13.021 mW. Accordingly, the control module (1400) can be implemented by synthesizing each component on chip based on the power consumption of each component indicated in Table 2.

[0092] FIGS. 15 and 16 illustrate a system comprising a plurality of edge nodes and an intermediate server connected to the plurality of edge nodes to establish LoRa communication.

[0093] In FIGS. 15 and 16, the system (1500, 1600) may include a plurality of edge nodes (1510, 1610). The plurality of edge nodes (1510, 1610) may include electronic devices that collect data or electronic devices that perform data operations. For example, the edge nodes (1510, 1610) may include smartphones, access points, sensors, CCTVs, onboard units, terminals, etc.

[0094] The system (1500, 1600) may include an intermediate server (1520, 1630) that establishes communication with a plurality of edge nodes (1510, 1610). For example, the plurality of edge nodes (1510, 1610) may establish communication with the intermediate server (1520, 1630) via LoRa communication. The plurality of edge nodes (1510, 1610) may consume power by transmitting and receiving data with the intermediate server (1520, 1630). At least one edge node among the plurality of edge nodes (1510, 1610) may include a control module that performs Long Range (LoRa) communication of at least one edge node in response to supplied power; an energy harvesting device that generates power according to the amount of light corresponding to the received light in response to receiving light, and supplies the generated power to the control module as at least a portion of the supplied power; a battery connected to the control module through a switch and supplies the power charged while the switch is turned on based on the amount of light to the control module as at least a portion of the supplied power; and a diode coupled between the energy harvesting device and the battery in a manner that blocks the current flow from the battery to the energy harvesting device and allows power supply from the energy harvesting device to the control module. Since the configuration and operation method of at least one edge node among the plurality of edge nodes (1510, 1610) have already been described in FIGS. 7 to 10, redundant content is omitted.

[0095] In FIG. 16, the system (1600) may allow at least one edge node among the included edge nodes (1610) to process data in an area (1620) of a preset distance. For example, at least one edge node among the edge nodes (1610) may be located at the center of a 9×9 grid, and the edge node may transmit and receive data collected or processed in the 9×9 grid area (1620) to an intermediate server (1630) via LoRa communication. However, the area (1620) in which the edge nodes (1610) can process data is not limited thereto, and the preset distance may vary depending on the specifications of the power load balancing device included in the edge node, such as a circular area with a radius of several km centered on the edge node.

[0096] In the system (1600), the area (1620) of an edge node may overlap with the areas of adjacent edge nodes. In the system (1600), a plurality of edge nodes (1610) may adjust the LoRa communication amount of at least one edge node based on at least one of the light amount collected from adjacent edge nodes and the collected state of charge (SOC) of the battery, where the sensing range corresponding to an area of ​​a preset distance centered on at least one edge node overlaps. The adjustment of the LoRa communication amount of an edge node in the system (1600) will be explained in detail below in FIGS. 17 and 18.

[0098] FIGS. 17 and 18 illustrate a case where edge nodes adjust the amount of LoRa communication with an intermediate server based on the amount of light collected from adjacent edge nodes and the SOC of the battery.

[0099] In FIG. 17, the system (1700) can increase the amount of LoRa communication in the overlapping sensing range (1730) of at least one edge node (1710) and an adjacent edge node (1720) while at least one edge node (1710) among a plurality of edge nodes has a first amount of light collected from at least one edge node (1710) greater than a second amount of light collected from an adjacent edge node (1720). For example, the system (1700) may include a first edge node (1710) and a second edge node (1720). The system (1700) can determine which edge node will perform LoRa communication in the first overlapping area (1730) where the sensing area of ​​the first edge node (1710) and the sensing area of ​​the second edge node (1720) overlap. For example, assuming that the second light collected from the second edge node (1720) is insufficient to perform LoRa communication with the intermediate server (1790), and at the same time the first light collected from the first edge node (1710), which is adjacent to the second edge node (1720) and whose sensing range overlaps, is sufficient to perform LoRa communication with the intermediate server (1790), the system (1700) can stop the operation of the second edge node (1720) which has insufficient light. The system (1700) can adjust the workload of the system (1700) by processing the data for the first overlapping area (1730), where the sensing range of the second edge node (1720) and the sensing range of the first edge node (1710) overlap, to increase the amount of LoRa communication at the first edge node (1710), which has a first light sufficient to communicate with the intermediate server (1790).

[0100] In another example, when the sensing area between the second edge node (1720) and another adjacent edge node overlaps, the data corresponding to the second overlapping area (1740) can perform LoRa communication with the intermediate server (1790) through the other adjacent edge node.

[0101] Accordingly, the system (1700) can adjust the power workload of the entire system (1700) by processing data in the area where the sensing range overlaps at the edge node where a large amount of light is collected, based on the amount of light collected at each adjacent edge node.

[0102] In FIG. 18, the system (1800) may enable LoRa communication in an overlapping sensing range where the edge node with a larger SOC of battery among at least one edge node and the edge node with a larger SOC is within a threshold light intensity range when the first light intensity collected from at least one edge node and the second light intensity collected from an adjacent edge node are within a threshold light intensity range. For example, the system (1800) may include a first edge node (1810), a second edge node (1820), and a third edge node (1830). The first to third edge nodes (1810, 1820, 1830) may each include a sensing area corresponding to an area of ​​a predetermined distance centered on each edge node (1810, 1820, 1830). Each of the sensing areas of each edge node (1810, 1820, 1830) may overlap with one another to form overlapping areas (1840a, 1840b, 1840c, 1850). For example, a first overlapping area (1840a) may be formed by overlapping the sensing area of ​​the first edge node (1810) and the sensing area of ​​the second edge node (1820), a second overlapping area (1840b) may be formed by overlapping the sensing area of ​​the first edge node (1810) and the sensing area of ​​the third edge node (1830), and a third overlapping area (1840c) may be formed by overlapping the sensing area of ​​the second edge node (1820) and the sensing area of ​​the third edge node (1830). Furthermore, a fourth overlapping area (1850) can be formed by overlapping each sensing area of ​​the first to third edge nodes (1810, 1820, 1830).

[0103] The system (1800) can, for example, allow the edge nodes to perform LoRa communication based on the battery SOC level of the data in the overlapping areas (1840a to 1840c, and 1850) described above when the amount of light in the edge nodes (1810, 1820, 1830) is sufficient for LoRa communication with the intermediate server (1850), and at the same time, the amount of light collected from each of the edge nodes (1810, 1820, 1830) is within a threshold light amount range (e.g., similar level). For example, when the battery SOC of the first edge node (1810) is greater than the battery SOC of the second edge node (1820), the data sensed in the first overlapping area (1840a) can establish LoRa communication with the intermediate server (1850) through the first edge node (1810). As another example, if the battery SOC of the first edge node (1810) is greater than the battery SOC of the second edge node (1820) and the battery SOC of the third edge node (1830), data sensed in the fourth overlapping area (1850) can establish LoRa communication with the intermediate server (1850) through the first edge node (1810). At this time, the system efficiency can be increased by stopping the operation of edge nodes with low battery SOCs.

[0104] Conventional IoT sensor edge node systems typically rely solely on batteries. Since batteries have a limited lifespan, large-capacity batteries must be used to build systems with a long lifespan. However, the power load balancing device according to one embodiment utilizes an energy harvesting device in addition to a battery, and can regulate communication of edge nodes according to power levels, thereby increasing the lifespan of the system. Furthermore, the proposed device, method, and system can extend the overall system lifespan by filtering nodes based on conditions using light intensity information and battery SOC information, thereby minimizing the operation of nodes under adverse conditions where power is insufficient. Additionally, since neighboring nodes collaborate in overlapping areas between adjacent edge nodes, the system's lifespan can be extended while maintaining performance.

[0105] Therefore, the present invention ensures that power is always stably supplied to the edge nodes, extending the lifespan of the entire system and facilitating long-distance communication. The present invention can be effectively applied to large-scale, widely distributed IoT sensor node systems. Furthermore, since the communication environment of the nodes can be changed according to the power consumption of the edge nodes, load balancing in edge computing environments can be achieved. The present invention can be applied to smart agriculture, smart cities, and dynamic node environments, but is not limited thereto.

[0107] The embodiments described above may be implemented as hardware components, software components, and / or combinations of hardware and software components. For example, the devices, methods, and components described in the embodiments may be implemented using a general-purpose computer or a special-purpose computer, such as, for example, a processor, a controller, an arithmetic logic unit (ALU), a digital signal processor, a microcomputer, a field programmable gate array (FPGA), a programmable logic unit (PLU), a microprocessor, or any other device capable of executing and responding to instructions. The processing unit may execute an operating system (OS) and software applications executed on said operating system. Additionally, the processing unit may access, store, manipulate, process, and generate data in response to the execution of the software. For ease of understanding, the processing unit may be described as being used as a single unit, but those skilled in the art will understand that the processing unit may include multiple processing elements and / or multiple types of processing elements. For example, the processing unit may include multiple processors or one processor and one controller. In addition, other processing configurations, such as parallel processors, are also possible.

[0108] Software may include computer programs, code, instructions, or a combination of one or more of these, and may configure a processing unit to operate as desired or command the processing unit independently or collectively. Software and / or data may be permanently or temporarily embodied in any type of machine, component, physical device, virtual equipment, or computer storage medium or device so as to be interpreted by the processing unit or to provide instructions or data to the processing unit. Software may be distributed over networked computer systems and may be stored or executed in a distributed manner. Software and data may be stored on computer-readable recording media.

[0109] The method according to the embodiment may be implemented in the form of program instructions that can be executed through various computer means and recorded on a computer-readable medium. The computer-readable medium may include program instructions, data files, data structures, etc., either alone or in combination, and the program instructions recorded on the medium may be those specifically designed and configured for the embodiment or those known and available to those skilled in the art of computer software. Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks, and magnetic tapes; optical recording media such as CD-ROMs and DVDs; magneto-optical media such as floptical disks; and hardware devices specifically configured to store and execute program instructions, such as ROM, RAM, and flash memory. Examples of program instructions include machine code, such as that generated by a compiler, as well as high-level language code that can be executed by a computer using an interpreter, etc.

[0110] The hardware device described above may be configured to operate as one or more software modules to perform the operation of the embodiment, and vice versa.

[0111] In this document, each of the phrases such as "A or B", "at least one of A and B", "at least one of A or B", "A, B or C", "at least one of A, B and C", and "at least one of A, B, or C" may include any one of the items listed together in the corresponding phrase, or all possible combinations thereof.

[0112] Although the embodiments have been described above with reference to the limited drawings, those skilled in the art can apply various technical modifications and variations based thereon. For example, suitable results may be achieved even if the described techniques are performed in a different order than described, and / or if the components of the described system, structure, device, circuit, etc. are combined or assembled in a form different from described, or replaced or substituted by other components or equivalents.

[0113] Therefore, other implementations, other embodiments, and equivalents to the claims also fall within the scope of the claims set forth below.

Claims

Claim 1 A power load balancing device for an edge node comprises: a control module that performs Long Range (LoRa) communication of the edge node in response to supplied power; an energy harvesting device that generates power according to a light intensity corresponding to the received light in response to receiving light, and supplies the generated power to the control module as at least a portion of the supplied power; a battery connected to the control module via a switch, and supplies power charged while the switch is turned on based on the light intensity as at least a portion of the supplied power; and a diode coupled between the energy harvesting device and the battery in a manner that blocks the current flow from the battery to the energy harvesting device and allows power supply from the energy harvesting device to the control module, wherein the control module receives the light intensity corresponding to the light received from a light intensity sensor and turns on the switch while the light intensity is below a threshold light intensity. A power load balancing device comprising a voltage sensor controller that receives a power amount determined based on the state of charge (SOC) of the battery collected from the voltage sensor and determines whether the edge node will perform LoRa communication or perform data backup to memory. Claim 2 delete Claim 3 A power load balancing device according to claim 1, wherein the control module controls the LoRa communication according to a power amount determined based on the state of charge (SOC) of the battery collected from a light amount corresponding to the received light and a voltage sensor. Claim 4 A power load balancing device according to claim 1, wherein the control module cuts off power supplied from the battery to the control module by turning off the switch while the amount of light exceeds a predetermined threshold amount of light. Claim 5 In claim 1, the power load balancing device wherein the control module determines the SOC of the battery based on the closed circuit voltage (CCV) of the battery. Claim 6 A power load balancing device according to claim 1, wherein the control module performs LoRa communication of the edge node while the SOC of the battery is above a predetermined threshold value, and otherwise backs up the data of the edge node to memory. Claim 7 A power load balancing method for an edge node comprises: a step of generating power according to a light amount corresponding to the received light in response to an energy harvesting device receiving light, and supplying the generated power to a control module; a step in which a battery connected to the control module through a switch supplies charged power to the control module while the switch is turned on based on the light amount; a step in which a diode coupled between the energy harvesting device and the battery blocks the current flow from the battery to the energy harvesting device and allows power supply from the energy harvesting device to the control module; and a step in which the control module performs Long Range (LoRa) communication of the edge node in response to power supplied from the energy harvesting device and the battery, respectively, wherein the step of supplying the charged power to the control module includes a step in which a switch controller receives the light amount corresponding to the light received from a light amount sensor and turns on the switch while the light amount is below a threshold light amount. Claim 8 delete Claim 9 A power load balancing method according to claim 7, wherein the step of performing LoRa communication comprises the step of a voltage sensor controller receiving a power amount determined based on the state of charge (SOC) of the battery collected from the voltage sensor and determining whether the edge node will perform LoRa communication or perform data backup to memory. Claim 10 A power load balancing method according to claim 7, wherein the step of performing LoRa communication comprises the step of the control module controlling LoRa communication according to a power amount determined based on the state of charge (SOC) of the battery collected from a light amount corresponding to the received light and a voltage sensor. Claim 11 A power load balancing method according to claim 7, wherein the step of supplying charged power to the control module includes the step of cutting off power supplied from the battery to the control module by turning off the switch while the amount of light exceeds a predetermined threshold amount of light. Claim 12 In claim 7, the step of performing Long Range (LoRa) communication of the edge node comprises the step of determining the State of Charge (SOC) of the battery based on the closed circuit voltage (CCV) of the battery, in a power load balancing method. Claim 13 A power load balancing method according to claim 7, wherein the step of performing LoRa (Long Range, LoRa) communication of the edge node comprises: performing LoRa communication of the edge node while the SOC of the battery is above a predetermined threshold value; and backing up the data of the edge node to memory when the SOC of the battery is below a predetermined threshold value. Claim 14 A computer program stored on a computer-readable recording medium in combination with hardware to execute the method of any one of claims 7 and 9 through 13. Claim 15 A plurality of edge nodes; and an intermediate server that establishes communication with the plurality of edge nodes via LoRa communication, wherein at least one edge node among the plurality of edge nodes comprises: a control module that performs LoRa (Long Range) communication of the at least one edge node in response to supplied power; an energy harvesting device that generates power according to a light intensity corresponding to the received light in response to receiving light, and supplies the generated power to the control module as at least a portion of the supplied power; and a battery connected to the control module through a switch, and supplies power charged while the switch is turned on based on the light intensity to the control module as at least a portion of the supplied power. A power load balancing system comprising a diode coupled between the energy harvesting device and the battery in a manner that blocks the current flow from the battery to the energy harvesting device and allows power supply from the energy harvesting device to the control module, and adjusting the LoRa communication amount of the at least one edge node based on at least one of the light amount collected from adjacent edge nodes and the collected state of charge (SOC) of the battery, wherein the sensing range corresponding to an area of ​​a preset distance centered on the at least one edge node overlaps. Claim 16 A power load balancing system according to claim 15, wherein at least one edge node among the plurality of edge nodes increases the LoRa communication amount of the at least one edge node in the overlapping sensing range of the at least one edge node and the adjacent edge node while the first light amount collected at the at least one edge node is greater than the second light amount collected at the adjacent edge node. Claim 17 A power load balancing system according to claim 15, wherein at least one edge node among the plurality of edge nodes performs LoRa communication in an overlapping sensing range where the edge node with a larger SOC of the battery among the at least one edge node and the adjacent edge node is within a threshold light amount range when the first light amount collected at the at least one edge node and the second light amount collected at the adjacent edge node are within a threshold light amount range.

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