Sensor network system, sink, node, data communication processing method and program

Abstract

To improve efficiency and accuracy of data collection in a sensor network system in which a single sink collects data acquired by a plurality of nodes.SOLUTION: A sensor network system comprises: a plurality of nodes for acquiring data; and a sink for collecting data from the plurality of nodes in each data collection period including a plurality of time slots. The sink comprises a first transmission controller for transmitting a beacon including information showing a channel gain threshold in each time slot to the plurality of nodes. Each node comprises: a channel gain detector for detecting channel gain between the node and the sink on the basis of the beacon; and a second transmission controller for transmitting data to the sink using a time slot satisfying a communication condition only once in a data collection period. The communication condition is satisfied when the channel gain is equal to or larger than the channel gain threshold and is satisfied when the time slot is the last time slot in the data collection period.SELECTED DRAWING: Figure 13

Description

[Technical field]

[0001] The present invention relates to a sensor network system, a sink and a node used in this sensor network system, a data communication processing method using this sensor network system, and a program used in the sink and the node. [Background technology]

[0002] There is known a sensor network system that collects and processes data acquired at multiple locations scattered in a given area. The sensor network system comprises multiple sensor node devices (hereinafter abbreviated as "nodes") and a single sink server device (hereinafter abbreviated as "sink"). The multiple nodes are arranged at multiple locations, respectively, and each node acquires data at its location and transmits it to the sink. The sink processes the multiple data collected from the multiple nodes to obtain overall data regarding the given area.

[0003] Normally, to prevent interference, the sink communicates wirelessly with one node at a time. In this case, data collection can be done digitally, but in order for the sink to collect data from all nodes, the number of time slots required is the same as the total number of nodes. In other words, as the total number of nodes increases, the time required for data collection increases.

[0004] In a system like LoRa (Long Range), which is a type of LPWA (Low Power, Wide Area), multiple nodes share the same competing communication channel to transmit to a sink, so as the number of nodes increases, not only does the data collection time increase, but the frequency of data collisions also increases.

[0005] In order for the sink to obtain overall data for a given area, it may not be necessary to know the individual data acquired by each node. For example, to find the temperature of a certain area, it is sufficient to know the average temperature acquired at multiple points. This average can be calculated by knowing the total number of nodes that successfully communicated with the sink and the sum of the data collected from these nodes.

[0006] In relation to the above, Non-Patent Document 1 (Wanchun Liu et al., "Over-the-Air Computation Systems: Optimization, Analysis and Scaling Laws," IEEE Transaction on Wireless Communications, 2020, pp. 1536-1276) discloses Over-the-Air Computation Systems (hereinafter abbreviated as "AirComp").

[0007] In AirComp, when multiple nodes transmit data to a single sink, they communicate using analog signals. All nodes transmit data at the same time, and the sink receives these data at once, allowing one data collection to be performed in a single time slot. Also, by receiving multiple analog signals at the same time, the sink can obtain the sum of these data values ​​without performing any calculations.

[0008] At this time, it is preferable that the power or field strength of the analog signal representing the data arriving from each node to the sink is proportional to the analog value of the data. However, the channel coefficient and channel gain between the node and each node differ depending on the distance between them and the communication environment. Therefore, each node appropriately adjusts the transmission power depending on the channel gain between the node and the sink. By doing so, the power or field strength of the analog signal arriving at the sink is proportional to the analog value of the data.

[0009] However, in reality, there is an upper limit to the transmission power of a node operating with limited power. When the channel gain is below a certain threshold, even if a node transmits an analog signal using the maximum transmission power, the power is not proportional to the analog value of the data. As a result, the analog data received on the multi-access channel may be distorted, and the accuracy of the sum of the analog values ​​obtained by the sink may decrease. [Prior art documents] [Non-patent literature]

[0010] [Non-Patent Document 1] Wanchun Liu et al., “Over-the-Air Computation Systems: Optimization, Analysis and Scaling Laws,” IEEE Transaction on Wireless Communications, 2020, pp. 1536–1276. Summary of the Invention [Problem to be solved by the invention]

[0011] The present invention provides a sensor network system, a sink, a node, a data communication processing method, and a program that improve the efficiency and accuracy of data collection. Other objects and novel features will become apparent from the description of this specification and the accompanying drawings. [Means for solving the problem]

[0012] The means for solving the problems will be explained below using the numbers used in the (Mode for carrying out the invention). These numbers are added to clarify the correspondence between the description in the (Claims) and the (Mode for carrying out the invention). However, these numbers should not be used to interpret the technical scope of the invention described in the (Claims).

[0013] According to one embodiment, a sensor network system (100) includes a plurality of nodes (1) and a sink (2). Each of the plurality of nodes (1) acquires data (x). The sink (2) collects the data (x) from the plurality of nodes (1) for each data collection period including a plurality of time slots. The sink (2) includes a first transmission control device (223). The first transmission control device (223) controls a channel gain threshold (g) in each of the plurality of time slots. th Each of the plurality of nodes (1) includes a channel gain detection device (122) and a second transmission control device (123). The channel gain detection device (122) detects a channel gain (g) between the node (1) and a sink (2) based on the beacon. h The second transmission control device (123) detects the channel gain (g) and transmits data (x) to the sink (2) in a time slot that satisfies a predetermined communication condition only once during the data collection period. The communication condition is h ) is the channel gain threshold (g th ) and is satisfied if the time slot is the last time slot of the data collection period.

[0014] According to one embodiment, the sink (2) includes a parameter calculation device (221), a transmission control device (223), a reception control device (224), and a post-processing device (225). The parameter calculation device (221) calculates a total number (N) of a plurality of time slots included in a data collection period based on a total number (K) of a plurality of external nodes (1), and calculates a channel gain threshold (g) based on the total number (N) of the plurality of time slots. th The transmission control device (223) calculates the total number (N) of the multiple time slots, the channel gain threshold (g thA beacon including information indicating a target value (α) of the signal amplitude and a target value of the signal amplitude is transmitted to the plurality of nodes (1). A reception control device (224) receives the plurality of data (x) transmitted from the plurality of nodes (1) in response to the beacon. A post-processing device (225) obtains the sum of the plurality of data (x) received during the data collection period.

[0015] According to one embodiment, the node (1) includes a sensing device (15), a beacon receiving device (121), a channel gain detection device (122), and a transmission control device (123). The beacon receiving device (121) detects a channel gain threshold (g) transmitted from an external sink (2) in each of a plurality of time slots included in a data collection period. th The channel gain detection device (122) receives a beacon including information representing the channel gain (g) between the sink (2) and the h The transmission control device (123) detects the channel gain (g) and transmits data (x) to the sink (2) in a time slot that satisfies a predetermined communication condition only once during the data collection period. The communication condition is h ) is the channel gain threshold (g th ) or is satisfied if the time slot is the last time slot of the data collection period.

[0016] According to one embodiment, the data communication processing method includes the steps of: each of a plurality of nodes (1) acquiring data (x) (S202); and calculating a channel gain threshold (g th The data communication processing method further includes transmitting a beacon including information representing a channel gain (g) between the sink (2) and the plurality of nodes (1) from the sink (2) (S106). The data communication processing method further includes transmitting a beacon including information representing a channel gain (g) between the sink (2) and the plurality of nodes (1) based on the beacon. h) (S208). The data communication processing method further includes each node (1) transmitting data (x) to a sink (2) in a time slot that satisfies a predetermined communication condition only once during the data collection period (S211). The data communication processing method further includes the sink (2) collecting data (x) from a plurality of nodes (1) during each data collection period (S107). The communication condition is a channel gain (g h ) is the channel gain threshold (g th ) and is satisfied if the time slot is the last time slot of the data collection period.

[0017] According to one embodiment, in a program that is executed by a calculation device (22) of a sink (2) to realize processing, the processing includes calculating (S102) a total number (N) of a plurality of time slots included in a data collection period based on a total number (K) of a plurality of external nodes (1), and calculating a channel gain threshold (g th ) and a target value (α) of the signal amplitude (S102). The process further includes calculating, for each of the plurality of time slots, a total number (N) of the plurality of time slots, a channel gain threshold (g th The process further includes transmitting a beacon including information representing the target value (α) of the signal amplitude to the plurality of nodes (1) (S106). The process further includes receiving a plurality of data (x) transmitted from the plurality of nodes (1) in response to the beacon (S107). The process further includes obtaining a sum of the plurality of data (x) received during the data collection period (S109).

[0018] According to one embodiment, in a program that is executed by a calculation device (12) of a node (1) to realize processing, the processing includes acquiring (S202) data (x) and calculating a channel gain threshold (g th) to the sink (2) based on the beacon. h The process further includes transmitting data (x) to a sink (2) in a time slot that satisfies a predetermined communication condition only once during the data collection period (S211). The communication condition is a channel gain (g h ) is the channel gain threshold (g th ) and is satisfied if the time slot is the last time slot of the data collection period. Effect of the Invention

[0019] According to one embodiment, the efficiency and accuracy of data collection can be improved. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 is a diagram showing an example of the configuration of a sensor network system according to a first related technique. [Diagram 2] FIG. 2 is a diagram showing an example of an operation of the sensor network system according to the first related technique. [Diagram 3] FIG. 3 is a diagram showing an example of an operation of the sensor network system according to the second related technique. [Figure 4] FIG. 4 is a diagram showing an example of an operation of the sensor network system according to the second related technique. [Diagram 5] FIG. 5 is a diagram showing an example of the channel gain, the transmission power, and the received power coefficient in the sensor network system according to the second related technique. [Figure 6] FIG. 6 is a diagram showing another example of the channel gain, the transmission power, and the received power coefficient in the sensor network system according to the second related technique. [Figure 7] FIG. 7 is a diagram showing an example of an operation of the sensor network system according to the fourth related technique. [Figure 8]FIG. 8 is a diagram illustrating an example of a configuration of a sensor network system according to an embodiment. [Figure 9] FIG. 9 is a diagram illustrating an example of a configuration of a node according to an embodiment. [Figure 10] FIG. 10 is a diagram illustrating an example of a configuration of a sink according to an embodiment. [Figure 11] FIG. 11 is a flowchart illustrating an example of an operation of the sink according to an embodiment. [Figure 12A] FIG. 12A is a part of a flowchart illustrating an example of an operation of a node according to an embodiment. [Figure 12B] FIG. 12B is a part of a flowchart illustrating an example of an operation of a node according to an embodiment. [Figure 13] FIG. 13 is a diagram illustrating an example of an operation of the sensor network system according to an embodiment. [Figure 14] FIG. 14 is a diagram illustrating an example of an operation of the sensor network system according to an embodiment. [Figure 15] FIG. 15 is a diagram illustrating an example of channel gain, transmission power, and reception power coefficient in the sensor network system according to an embodiment. [Figure 16] FIG. 16 is a graph comparing cumulative distribution functions of transmission power between a sensor network system according to one embodiment and a sensor network system according to a related technique. [Figure 17] FIG. 17 is a graph comparing the cumulative distribution function of the mean square error between the received power and the target power between a sensor network system according to an embodiment and a sensor network system according to a related technique. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A sensor network system, a sink, a node, a data communication processing method, and a program according to the present invention will be described below with reference to the accompanying drawings.

[0022] To better understand the embodiments, a sensor network system according to the related art will be described first.

[0023] 1 is a diagram showing an example of a configuration of a sensor network system 1000 according to a first related technique. The sensor network system 1000 includes multiple nodes 101-1 to 101-K and a sink 102. Here, the total number of nodes 101-1 to 101-K is K. When the multiple nodes 101-1 to 101-K are not differentiated from one another, they are collectively referred to as node 101-k or node 101. Here, the branch number k is any integer in the range from 1 to K.

[0024] The multiple nodes 101 are arranged at multiple positions in a predetermined area. Each node 101 acquires desired data by a sensor at the position where it is arranged. Each node 101 transmits the acquired data to a sink 102. The timing at which the multiple nodes 101 acquire data and the timing at which they transmit data to the sink 102 may be controlled based on a clock built into each node 101, or may be controlled based on a wireless signal transmitted to the node 101 from an external sink 102 or the like, for example.

[0025] 2 is a diagram showing an example of an operation of the sensor network system 1000 according to the first related art. The horizontal axis of FIG. 2 indicates time. 101 From time t 102 A process P101 is executed in which the first node 101-1 transmits the first data x1 to the sink 102. Here, at time t 101 From time t 102 The period from time t 103 From time t 104 In the second time slot up to , the process P102 is executed in which the second node 101-2 transmits the second data x2 to the sink 102. Similarly, all the nodes 101-k transmit the data x k is transmitted to the sink 102. 105 From time t106 In the K-th time slot up to the K-th time slot, the K-th node 101-K transmits the K-th data x K Then, at time t 107 From time t 108 A process P100 in which the sink 102 processes data is executed over the period of time. K When we do not distinguish between these, we call them data x k Or collectively referred to as data x.

[0026] As shown in FIG. 2, in the sensor network system 1000 of FIG. 1, the sink 102 collects data x acquired by the multiple nodes 101 by wirelessly communicating with one node 101 at a time. In this case, it is possible to prevent interference between the multiple nodes 101, and to collect the data x as a digital signal. On the other hand, in order for the sink 102 to collect the data x from all the nodes 101, the same number of time slots as the total number K of the nodes 101 are required. In other words, as the total number K of the nodes 101 increases, the time required for one data collection also increases. Depending on the total number K of the nodes 101, the time required for one data collection may become too long, making it difficult to operate the sensor network system 1000 in a practical manner.

[0027] In order for the sink 102 to obtain overall data x of a given area, there are cases where the individual data x acquired by each node 101 is not necessary. For example, to check the temperature of a certain area, it is sufficient to know the average value of temperatures acquired at multiple points. This average value can be calculated by knowing the total number K of nodes 101 and the sum of the data x collected from these nodes 101.

[0028] A sensor network system 1000 according to a second related technique that has been improved from this perspective is known. This second related technique is called Over-the-Air Computation Systems (hereinafter abbreviated as "AirComp").

[0029] A sensor network system 1000 according to the second related technique by AirComp includes a plurality of nodes 101 and a single sink 102, similar to the configuration example of the sensor network system 1000 according to the first related technique shown in FIG.

[0030] 3 is a diagram showing an example of an operation of the sensor network system 1000 according to the second related art. The first data x1 is transmitted to the sink 102 as a first analog signal generated by the first node 101-1 with a first transmission power b1. At this time, the power of the first analog signal representing the first data x1 can be expressed as b1x1. The operation of the first node 101-1 outputting the first analog signal having the power b1x1 is shown in FIG. 3 as the operation of a virtual integrator M101.

[0031] The amplitude of the first analog signal having power b1x1 is attenuated by the amplitude component of the first channel coefficient h1 while propagating through free space and being received by the sink 102. The power of the first analog signal received by the sink 102 can be expressed as h1b1x1. The operation of the free space propagating the first analog signal from the first node 101-1 to the sink 102 is shown as the operation of a virtual integrator M102 in FIG. 3. The channel coefficient h1 is expressed as a complex number including a component related to the amplitude and a component related to the phase. Of these, the component related to the amplitude can be calculated by squaring the absolute value of the channel coefficient h1, and is called a channel gain g1. The channel gain g1 is expressed as a positive real number.

[0032] Similarly, the second data x2 is generated by the second node 101-2 at the second transmission power b2 and transmitted to the sink 102 as a second analog signal having power b2x2, as shown by the operation of the virtual integrator M201. As shown by the operation of the virtual integrator M202, the amplitude of the second analog signal is attenuated by the amplitude component of the second channel coefficient h2, and is received by the sink 102 as a second analog signal having power h2b2x2. Similarly, the Kth data x Kis the K-th transmission power b K The power generated by b K x K As shown by the operation of a virtual multiplier M302, the amplitude of the Kth analog signal is multiplied by the Kth channel coefficient h K The amplitude component is attenuated by the power h K b K x K In this manner, all data x are respectively transmitted by all nodes 101 to the sink 102 as analog signals, propagate through free space, and are received by the sink 102.

[0033] FIG. 4 is a diagram showing an example of an operation of the sensor network system 1000 according to the second related art. The horizontal axis of FIG. 4 represents time. First, at time t 201 From time t 202 In the process P201, the sink 102 transmits a beacon to all the nodes 101 during the period until t 203 From time t 204 During the period up to , in process P202, the node 101 transmits data x to the sink 102 in response to the beacon, and the sink 102 receives the data x and processes the received data x.

[0034] In process P202, power b1x1, b2x2, ..., b K x K All analog signals with powers h1b1x1, h2b2x2, ..., h K b K x K At this time, the sink 102 receives all the analog signals having respective powers h1b1x1, h2b2x2, ..., h K b K x K3, the operation of obtaining this sum is shown as the operation of a virtual adder A100.

[0035] In FIG. 3, noise occurring in wireless communication from node 101 to sink 102 is shown as noise n that is added to the total power of the analog signals by adder A100.

[0036] In addition, in process P202 in Fig. 4, the sink 102 performs a predetermined post-processing on the sum of the powers of the received analog signals. As an example of the post-processing, the sink 102 may obtain an average value of the powers of the received analog signals by dividing the sum of the powers of the received analog signals by the total number of received analog signals. In Fig. 3, the post-processing by the sink 102 is shown as an operation of a virtual integrator M100 multiplying the sum of the powers of the received analog signals by a coefficient a.

[0037] Here, if the coefficient a is the reciprocal of the total number K of nodes 101, the integrator M100 calculates the power h1b1x1, h2b2x2, ..., h K b K x K The average value of the above can be calculated.

[0038] In addition, for any integer k between 1 and K, the transmission power b k and the channel coefficient h k The received power coefficient h multiplied by k b k If all of the amplitude components of the data x1 to x2 acquired by all the nodes 101 have the same constant α and the coefficient a is the inverse of the product Kα (1 / Kα) obtained by multiplying the total number K of the nodes 101 by the constant α, then the integrator M100 multiplies the data x1 to x2 acquired by all the nodes 101 by the inverse of the product Kα (1 / Kα). K The average value of the above can be calculated.

[0039] FIG. 5 shows a channel coefficient h k , transmission power b k and the received power coefficient h k b k5, the horizontal axis represents the number of the node 101 and the data x transmitted by each node 101. k The vertical axis corresponds to the received power coefficient h k b k However, strictly speaking, in Fig. 5, the received power coefficient h k b k The amplitude components are shown as the received power coefficients h k b k is the power h of the analog signal received at the sink 102 k b k x k , data x k is the quotient obtained by dividing the analog value representing the transmission power b k and the channel coefficient h k The product h k b k In each of the bars in Figure 5, the length of the lower black section is equal to the channel coefficient h k The value of the amplitude component of the channel gain g k The length of the upper white section indicates the value of the transmission power b k For ease of understanding, the horizontal axis of FIG. 5 indicates the number of the node 101 based on the channel coefficient h k are arranged from left to right in ascending order.

[0040] Each node 101-k has a channel coefficient h k Based on the constant α, the transmission power b k In this way, the transmission power b k and the channel coefficient h k The product h k b k The amplitude component of can be equal to a constant α.

[0041] However, the transmission power of node 101, b k There is an upper limit due to the physical performance of the node 101. Therefore, the channel coefficient h kIf the amplitude component of is below a predetermined threshold, the node 101-k transmits with a transmission power of b k Even if you set the transmission power to the maximum, the transmission power b k and the channel coefficient h k The product h k b k It is possible that the amplitude component of is smaller than the constant α.

[0042] FIG. 6 shows a channel coefficient h k , transmission power b k and the received power coefficient h k b k In the example of FIG. 6, the channel coefficient h k The amplitude component of is too low, so the transmission power b k Even if you set the transmission power to the maximum, the transmission power b k and the channel coefficient h k The received power coefficient h multiplied by k b k The amplitude component of is smaller than the constant α. Therefore, the received power coefficient h k b k The missing portion from the amplitude component of to the constant α appears as distortion in the calculation result of the adder A100 in Fig. 3. In other words, the greater the distortion shown in Fig. 6, the lower the accuracy of the result of the processing P202 by the sink 102.

[0043] A sensor network system 1000 according to a third related technique, which is an improvement of the second related technique from the viewpoint of suppressing the occurrence of distortion, will be described. The sensor network system 1000 according to the third related technique is also configured in the same manner as in FIG. 1. However, unlike the second related technique, its application is limited to federated learning. That is, the information transmitted from the node 101 to the sink 102 is not the data x itself acquired by each node 101, but a model obtained by machine learning for predicting data x to be acquired in the future based on a plurality of data x acquired by each node 101 in the past. Each node 101 updates its own model every time it acquires data x, and transmits the latest model to the sink 102 in response to a request from the sink 102. The sink 102 transmits to each node 101 a model obtained by averaging the models received from the plurality of nodes 101.

[0044] Here, the sink 102 does not necessarily need to receive models from all the nodes 101 every time. That is, the channel gain g k Only some of the nodes 101 for which the channel gain g between the node 101 and the sink 102 at a certain time is equal to or greater than a desired threshold may transmit the model to the sink 102. In other words, even if the positions of the node 101 and the sink 102 are fixed, the communication environment between them changes dynamically over time. This change includes, for example, a dynamic change in the channel coefficient due to the influence of channel fading. Therefore, in the sensor network system 1000 according to the third related technology, the channel gain g between the node 101 and the sink 102 at a certain time is k Only the node 101 whose model exceeds a predetermined threshold transmits the model to the sink 102 at that time. In this way, the occurrence of the distortion shown in FIG.

[0045] However, since not all nodes 101 necessarily transmit the data x to the sink 102 at the same time, this cannot be directly applied to the second related technique.

[0046] A sensor network system 1000 according to a fourth related technique, which is an improvement over the first related technique from the viewpoint of suppressing the influence of channel fading, will be described with reference to Fig. 7. Fig. 7 is a diagram showing an example of an operation of the sensor network system 1000 according to the fourth related technique. Fig. 7 includes a first graph G101, a second graph G102, and a third graph G103. The first graph G101, the second graph G102, and the third graph G103 correspond to the first node 101-1, the second node 101-2, and the third node 101-3, respectively. In each graph in Fig. 7, the horizontal axis represents time, and the vertical axis represents the channel gain g k In each graph, the black bars represent the channel gain g k The white bars represent the channel gain g k , which represents a value equal to or greater than a predetermined threshold value.

[0047] As shown in Fig. 7, in the fourth related technique, in order to suppress the influence of channel fading, the timing at which each node 101 transmits data x to the sink 102 is controlled. Basically, it is preferable to centrally control all the nodes 101 so that only one node 101 transmits at a time. However, it is difficult to completely control a large number of nodes 101, and as shown in the example of Fig. 7, a time t307 may occur at which none of the nodes 101 transmits data x. Conversely, a time t308 may occur at which multiple nodes 101 transmit data x simultaneously.

[0048] (Embodiment) In the sensor network system 100 according to an embodiment, the efficiency and accuracy of data collection are improved in consideration of the above-mentioned first related technique, second related technique, third related technique, and fourth related technique.

[0049] In terms of efficiency, the first related art requires the same number of time slots as the total number K of nodes 101 in one data collection period. On the other hand, in one embodiment, all nodes transmit to the sink in a number of time slots much smaller than the total number K of nodes 101 in one data collection period.

[0050] In terms of accuracy, in the second related technology, each node 101 has only one opportunity to transmit data x to the sink 102, so the channel gain g k If the desired communication conditions are not met, for example because the BER is too low, distortion may occur in a portion of the data x received by the sink 102. On the other hand, in one embodiment, since each node is provided with multiple opportunities to transmit data x to the sink, if the desired communication conditions are not met in a certain time slot, there is a possibility that data transmission to the sink can be performed when the desired communication conditions are met in a subsequent time slot. As a result, the probability that distortion occurs in a portion of the data x received by the sink is reduced, and the accuracy of data collection is improved.

[0051] 8 is a diagram showing an example of a configuration of a sensor network system 100 according to an embodiment. The sensor network system 100 includes multiple nodes 1-1 to 1-K and a sink 2, similar to the sensor network system 1000 of FIG. 1. Here, the total number of nodes 1-1 to 1-K is K. When the multiple nodes 1-1 to 1-K are not distinguished from one another, they are collectively referred to as node 1-k or node 1. Here, the number k is any integer in the range from 1 to K.

[0052] The multiple nodes 1 are arranged at multiple positions in a predetermined area. Each node 1 acquires predetermined data x by a sensor at the position where it is arranged. Each node 1 transmits the acquired data x to a sink 2. The timing at which the multiple nodes 1 acquire the data x may be controlled based on a clock built into each node 1, for example, or may be controlled based on a wireless signal transmitted to the node 1 from an external sink 2 or the like. The timing at which the multiple nodes 1 transmit the data x to the sink 2 is controlled based on a beacon transmitted from the sink 2, as will be described later.

[0053] 9 is a diagram showing an example of a configuration of a node 1 according to an embodiment. The node 1 includes a bus 10, a computing device 12, a memory device 13, an external storage device 14, and a sensing device 15. The node 1 further includes an antenna 112 and a power supply device (not shown). The computing device 12, the memory device 13, the external storage device 14, and the sensing device 15 are connected to each other via the bus 10.

[0054] The input / output device 11 transmits and receives data x to and from an external device such as the sink 2. The calculation device 12 executes a program stored in the memory device 13 to perform a predetermined process. The memory device 13 stores the program and data and provides them to the calculation device 12. The external storage device 14 reads out the program and data stored in a non-transitory recording medium 141 and stores them in the memory device 13. The sensing device 15 acquires predetermined data x at the position where the node 1 is located under the control of the calculation device 12.

[0055] The input / output device 11 includes a communication device 111. The communication device 111 is connected to an antenna 112. The calculation device 12 includes a beacon receiving device 121, a channel gain detection device 122, and a transmission control device 123.

[0056] The communication device 111 performs wireless communication with an external device such as a sink 2 via an antenna 112. The beacon receiving device 121 is a virtual device that receives a beacon transmitted from the sink 2 by the calculation device 12 executing a predetermined program. The channel gain detection device 122 detects a channel coefficient h k Detect the amplitude component, the channel gain g k The transmission control device 123 is a virtual device that performs an operation of controlling the communication device 111 to transmit a signal indicating the data x to the sink 2 by the calculation device 12 executing a predetermined program.

[0057] 10 is a diagram showing an example of a configuration of the sink 2 according to an embodiment. The sink 2 includes a bus 20, a computing device 22, a memory device 23, and an external storage device 24. The sink 2 further includes an antenna 212 and a power supply device (not shown). The computing device 22, the memory device 23, and the external storage device 24 are connected to each other via the bus 20.

[0058] The input / output device 21 transmits and receives data x to and from an external device such as the node 1. The arithmetic device 22 executes a program stored in the memory device 23 to perform a predetermined process. The memory device 23 stores the program and data and provides them to the arithmetic device 22. The external storage device 24 reads out the program and data stored in a non-transitory and tangible recording medium 241 and stores them in the memory device 23.

[0059] The input / output device 21 includes a communication device 211. The communication device 211 is connected to an antenna 212. The arithmetic device 22 includes a parameter calculation device 221, a beacon generation device 222, a transmission control device 223, a reception control device 224, and a post-processing device 225.

[0060] The communication device 211 performs wireless communication with an external device such as the node 1 via the antenna 212. The parameter calculation device 221 is a virtual device that performs an operation of calculating a predetermined parameter by the calculation device 22 executing a predetermined program. The beacon generation device 222 is a virtual device that performs an operation of generating a beacon by the calculation device 22 executing a predetermined program. The transmission control device 223 is a virtual device that performs an operation of controlling the communication device 211 to transmit a beacon to the node 1 by the calculation device 22 executing a predetermined program. The reception control device 224 is a virtual device that performs an operation of controlling the communication device 211 to receive a signal transmitted from the node 1 by the calculation device 22 executing a predetermined program. The post-processing device 225 is a virtual device that performs an operation of processing to consolidate signals received from the node 1 by the calculation device 22 executing a predetermined program.

[0061] Fig. 11 is a flowchart showing an example of an operation of the sink 2 according to an embodiment. Fig. 12A and Fig. 12B are each a part of a flowchart showing an example of an operation of the node 1 according to an embodiment. An example of the operation of the sensor network system 100 according to an embodiment will be described with reference to Fig. 11, Fig. 12A, and Fig. 12B.

[0062] 11, in step S101, the sink 2 starts its operation. In step S102, the parameter calculation device 221 of the sink 2 calculates parameters. The calculated parameters are the total number N of time slots included in one data collection period and the channel gain threshold g th and a target value α of the signal amplitude, where the total number N is also the maximum value N of the numbers assigned to the time slots included in one data collection period.

[0063] As an example, the parameter calculation device 221 first determines the total number N of time slots. The total number N of time slots may be selected from integers that are sufficiently smaller than the total number K of nodes 1, for example. The parameter calculation device 221 then determines the channel gain threshold g th The parameter calculation device 221 then calculates the total number of time slots N and the channel gain threshold g th A target value α of the signal amplitude is calculated based on the above.

[0064] In step S103, the sink 2 initializes the slot number of the time slot. As an example, the slot number is set to zero. In step S104, the calculation device 22 of the sink 2 increments the slot number. In step S105, the beacon generation device 222 of the sink 2 increments the slot number by one based on the total number N of time slots and the channel gain threshold g th A beacon is generated based on the total number of time slots N and the channel gain threshold g th and the target value α of the signal amplitude. The beacon may be generated to further include information indicating the current slot number. In step S106, the transmission control device 223 of the sink 2 controls the communication device 211 to transmit the beacon to the node 1.

[0065] On the other hand, in step S201 of Fig. 12A, each node 1 starts its operation. Then, in step S202, the sensing device 15 of each node 1 receives data x k The acquired data x kis stored in the memory device 13 of the node 1. In step S203, the calculation device 12 determines whether the beacon receiving device 121 has received a beacon from the sink 2. Here, if the beacon has not been received (No), step S203 is executed again. In other words, step S203 is repeated until the beacon is received. Conversely, if the beacon has been received (Yes), step S204 is executed.

[0066] In step S204, the beacon receiving device 121 acquires parameters from the received beacon. The acquired parameters include the total number N of time slots included in one data collection period and a channel gain threshold g th and a target value α of the signal amplitude. In step S205, the beacon receiving device 121 judges whether the currently received beacon is the first beacon received in the current data collection period. This judgment may be made based on, for example, information included in the beacon. In this case, the beacon generating device 222 of the sink 2 generates the beacon so that it includes information indicating whether it is the first beacon. If the currently received beacon is the first beacon (Yes), the slot number and the transmitted flag are initialized in step S206, and then step S207 in FIG. 12B is executed. Here, the initialized slot number is set to, for example, zero. Also, the initialized transmitted flag is set to "not transmitted". On the other hand, if it is not the first beacon (No), step S207 is executed without executing step S206.

[0067] In step S207 of FIG. 12B, the calculation device 12 of the node 1 increments the slot number. In step S208, the channel gain detection device 122 detects the channel coefficient h k Detect the channel gain g kFor example, information indicating the transmission power of a beacon transmitted by the sink 2 is stored in advance in the memory device 13 of the node 1, and a channel coefficient h k Calculate the channel coefficient h k The channel gain g, which is the amplitude component related to attenuation, is k By calculating the channel gain g k Detection of the above may also be performed.

[0068] In step S209, the transmission control device 123 of the node 1 determines whether the communication conditions for transmitting the data x to the sink 2 are satisfied. Specifically, the first condition that the currently transmitted flag is “not yet transmitted” is satisfied and the detected channel gain g k is the threshold g th If the second condition is met, that is, the number is equal to or greater than the maximum value N of the slot number, then it is determined that the communication condition is met.

[0069] In other words, if the current transmission flag is "transmitted", it is determined that the communication condition is not satisfied. This determination enables control so that one node 1 transmits data x to the sink 2 only once during one data collection period.

[0070] In addition, even if the current transmission flag is "not transmitted", the detected channel gain g k is the threshold g th If the time slot number is less than the maximum value N, it is determined that the communication conditions are not satisfied. k is the threshold g th If the time slot is the last time slot of the current data collection period, the transmission of data x to sink 2 is postponed to the next time slot or later. If the time slot is the last time slot of the current data collection period, even if the channel gain g k is the threshold g thEven if the received data x does not reach the set value, the data x is forcibly transmitted to the sink 2 in the current time slot.

[0071] In other words, under the precondition that the node 1 transmits the data x to the sink 2 in a time slot that satisfies a predetermined communication condition only once during the data collection period, the predetermined communication condition is a channel gain g k is the channel gain threshold g th It is satisfied if it is greater than or equal to, and is satisfied if the time slot is the last time slot of the data collection period.

[0072] If it is determined that the communication conditions are satisfied (Yes), steps S210 and S211 are executed, and then step S212 is executed. Conversely, if it is determined that the communication conditions are not satisfied (No), steps S210 and S211 are not executed, and step S212 is executed.

[0073] In step S210, the arithmetic unit 12 of the node 1 calculates the target value α of the signal amplitude and the channel coefficient h k Based on the transmission power b k Specifically, the target value α of the signal amplitude is calculated by the channel coefficient h k The quotient is calculated by dividing the power by b k In step S211, the transmission control device 123 transmits data x to the sink 2 and sets a transmission completion flag to "transmitted". k is the power b k x k The signal is transmitted to sink 2 as an analog signal having the following characteristics:

[0074] In step S212, the calculation device 12 of node 1 determines whether the current slot number is the maximum value N. If the current slot number is the maximum value N (Yes), step S213 is executed and then step S202 is executed again. If the current slot number is not the maximum value N (No), step S203 is executed again without executing step S213.

[0075] In this way, node 1 receives data x in response to the beacon sent by sink 2. k The reception control device 224 of the sink 2 generates an analog signal representing the data x by controlling the communication device 211 in step S107 of FIG. k Receive.

[0076] Here, there may be a plurality of nodes 1 that transmit analog signals to the sink 2 in response to a beacon in the same time slot. In this case, the reception control device 224 of the sink 2 receives a plurality of data x k This operation will be described with reference to FIG.

[0077] 13 is a diagram showing an example of an operation of the sensor network system 100 according to an embodiment. In step S211, the first data x1 is transmitted to the sink 2 as a first analog signal generated by the transmission control device 123 of the first node 1-1 with a first transmission power b1. At this time, the power of the first analog signal representing the first data x1 can be expressed as b1x1. In FIG. 13, the operation of the first node 1-1 outputting the first analog signal having the power b1x1 is shown as the operation of a virtual integrator M11.

[0078] The power of the first analog signal having power b1x1 is attenuated by a first channel coefficient h1 before it reaches and is received by the sink 2. The power of the first analog signal received by the sink 2 can be represented as h1b1x1. The operation of free space propagating the first analog signal from the first node 1-1 to the sink 2 is shown in FIG. 13 as the operation of a virtual integrator M12.

[0079] There is a case where another node 1 operates in the same time slot as the first node 1-1 operates as described above as the operation of the integrator M11 and the integrator M12. In this case, for example, the i-th data x iis set by the transmission control device 123 of the i-th node 1-i to the i-th transmission power b i The power generated by b i x i The i-th analog signal is transmitted to the sink 2 as the i-th analog signal having the i-th channel coefficient h i Attenuates with power h i b i x i The i-th analog signal having the signal i-th is received at the sink 2.

[0080] At this time, the sink 2 simultaneously receives two analog signals transmitted by the first node 1-1 and the i-th node 1-i through the multi-access channel. Here, the sink 2 receives the powers h1b1x1 and h i b i x i The signal may be received as a single analog signal having a power that is the sum of the powers of the analog signals. The operation of obtaining this sum is shown as the operation of a virtual adder A1 in Fig. 13. In Fig. 13, noise generated in wireless communication between the first node 1-1 and the i-th node 1-i to the sink 2 is shown as noise n1 that is added to the sum of the powers of the analog signals by the adder A1.

[0081] Although the case where two nodes 1 transmit analog signals to the sink 2 in one time slot has been described here, this is merely an example, and the number of nodes 1 may be less than or more than two. The operation of another node 1 transmitting an analog signal to the sink 2 in another time slot will be described later.

[0082] After the reception control device 224 of the sink 2 receives the data x from the node 1, in step S108 of FIG. 11, the calculation device 22 of the sink 2 determines whether the current slot number is less than the maximum value N.

[0083] If the current slot number is less than the maximum value N in step S108 (Yes), the sink 2 executes steps S104 to S107 again. At this time, the node 1 executes steps S203 in Fig. 12A to S211 in Fig. 12B again. As a result, among the nodes 1 that did not transmit the data x to the sink 2 because the communication condition was not satisfied in the same time slot as the previous time, the nodes 1 that satisfy the communication condition in the current time slot transmit the data x to the sink 2.

[0084] Here, referring again to Fig. 13, a transmission process by a virtual integrator M31 in another time slot and a reception process by a virtual integrator M32 and a virtual adder A2 will be described. That is, in the example of Fig. 13, similar to the case of the first node 1-1 and the i-th node 1-i in the past time slot, in the j-th node 1-j and the K-th node 1-K in the current time slot, the communication conditions are satisfied and the data x is transmitted to the sink 2, and the sink 2 simultaneously receives these data x. Although a case where two nodes 1 transmit analog signals to the sink 2 in the current time slot has been described, this is merely an example, and the number of nodes 1 may be less than two or more than two.

[0085] Furthermore, referring again to Fig. 13, a transmission process by the virtual integrator M21 in yet another time slot and a reception process by the virtual integrator M22 and the virtual adder A3 will be described. That is, in the example of Fig. 13, similar to the case of the first node 1-1 and the i-th node 1-i in the past time slot, and similar to the case of the j-th node 1-j and the K-th node 1-K in the other time slot described above, in the k-th node 1-k and the K-1-th node 1-(K-1) in the current time slot, the communication conditions are satisfied and the data x is transmitted to the sink 2, and the sink 2 simultaneously receives these data x. Although the case where two nodes 1 transmit analog signals to the sink 2 in the current time slot has been described, this is merely an example, and the number of nodes 1 may be less than two or more than two.

[0086] If the current slot number is not less than the maximum value N in step S108 of FIG. 11 (No), steps S109 and S110 are executed, steps S102 and S103 are executed again, and then step S104 is executed again.

[0087] In step S109, since all time slots included in the current data collection period have ended, the post-processing device 225 of the sink 2 performs post-processing to consolidate the collected data x. As an example, a case in which the average value of the data x collected from the node 1 is calculated by this post-processing will be described with reference to FIG.

[0088] The data x received for each time slot is stored in the memory device 23 as the sum of the data x received in each time slot. In the example of FIG. 13, the output value of the virtual adder A1 is h1b1x1+h i b i x i Here, as described above, the transmission powers b1 and b i and channel coefficients h1, h i is the amplitude component of h1b1 = h i b i The relationship of the amplitude component of x1 = the target value α of the signal amplitude is satisfied. Therefore, the output value of the virtual adder A1 is α(x1 + x i ).

[0089] The post-processing device 225 multiplies this output value by a coefficient a, which is set equal to 1 / (Kα). In FIG. 13, this multiplication by the post-processing device 225 is shown as post-processing by a virtual integrator M13. The output value r1 of the virtual integrator M13 is expressed as (x1+x i ) / K.

[0090] The post-processing device 225 performs similar post-processing on the sum of the data x received in all time slots. As a result, in the example of FIG. 13, the output value r2 of the virtual integrator M23 is (x j +xK ) / K is obtained, and the output value r N As (x k +x K-1 ) / K is obtained.

[0091] Further, the post-processing device 225 calculates these output values ​​r1, r2, ..., r N The sum r of the data x collected from the K nodes 1 is calculated. As a result, (1 / K)Σx is obtained as the sum r. This value is the average value of the data x collected from the K nodes 1. In the example of FIG. 13, the process of calculating this sum is shown as post-processing by a virtual adder A0.

[0092] As a modification of the configuration shown in FIG. 13, instead of the three virtual integrators M13, M23, and M33 connected in front of the virtual adder A0 in the post-processing, another virtual integrator may be placed in the rear stage of the virtual adder A0. In other words, the average value of data x can be obtained by first obtaining the sum of the outputs of the three virtual adders A1, A2, and A3, and then multiplying this sum by the coefficient a. As yet another modification, the other virtual integrator may be removed from the configuration of the above modification. In this case, the sum of data x can be obtained instead of the average value of data x.

[0093] In step S110, since all processing performed in the current data collection period has been completed, the sink 2 moves to the next data collection period and executes step S102 again.

[0094] The overall operation of the sensor network system 100 according to the embodiment described above will be described with reference to FIG.

[0095] 14 is a diagram showing an example of an operation of the sensor network system 100 according to an embodiment. The horizontal axis of FIG. 14 indicates time, and the time t 01 From time t 04 The period from time t 01 From time t 04The period from time t 01 From time t 02 A process P1 in which the sink 2 transmits a beacon to the node 1 is executed in the period until the time t 03 From time t 04 In the period up to , a process P2 is executed in which node 1 for which the communication condition is satisfied transmits data x for obtaining an output value r1 in FIG. 13 to the sink 2 in response to the beacon of process P1.

[0096] Similarly, at time t 05 From time t 08 The period until time t is the second time slot. 05 From time t 06 A process P3 in which the sink 2 transmits a beacon to the node 1 is executed until the time t 07 From time t 08 In the period up to , node 1 that has not transmitted data x to sink 2 in the first time slot and for which the communication conditions are satisfied executes process P4 in which node 1 transmits data x to sink 2 in response to the beacon of process P3 to obtain output value r2 of FIG. 13.

[0097] Similarly, at time t 09 From time t 12 The period until time t 09 From time t 10 A process P5 in which the sink 2 transmits a beacon to the node 1 is executed until the time t 11 From time t 12 In the period up to , all nodes 1 that have not transmitted data x to the sink 2 in the previous time slots will respond to the beacon of process P5 with the output value r N Then, a process P6 is executed in which data x for obtaining x is transmitted to the sink 2. Note that in the process P6, the post-processing performed in step S109 in FIG.

[0098] In this way, in the sensor network system 100 according to one embodiment, one data collection period is divided into multiple time slots, and multiple nodes 1 simultaneously transmit data x to the sink 2 in each time slot in response to the same beacon transmitted from the sink 2. Therefore, unlike the first related art, it is possible to set the total number of multiple time slots included in one data collection period to be much smaller than the total number K of nodes 1.

[0099] In the sensor network system 100 according to the embodiment, the accuracy of the data x collected by the sink 2 from the node 1 is improved. This will be described with reference to FIG. 15. FIG. 15 shows an example of the channel coefficient h k , transmission power b k and the received power coefficient h k b k 5 and 6, in FIG. 15, the horizontal axis represents the number of the node 1, and the data x transmitted by each node 1. k The vertical axis corresponds to the received power coefficient h k b k The amplitude component of is shown in logarithm.

[0100] However, the number of node 1 in FIG. 15 is independent of the number of node 1 in FIG. 13, and the channel coefficient h k The amplitude components are arranged from left to right in ascending order. Here, the length of the dashed bar graphs from the first node 1-1 to the k-th node 1-k corresponds to the channel coefficient h k In addition, for all nodes 1, the length of the black bar represents the channel coefficient h k In addition, for all nodes 1, the length of the white bar indicates the transmission power b k represents the value of

[0101] In the sensor network system 100 according to one embodiment, each node 1 is provided with multiple opportunities to transmit data x to the sink 2 in one data collection period, the number of opportunities being the same as the total number N of time slots. Therefore, the possibility that the communication condition of one node 1 will be satisfied in any of the time slots is higher than in the case of the second related art. This is illustrated in FIG. 15, where only the fourth node 1-4 out of all the nodes 1 has a channel gain g4 corresponding to the channel coefficient h4 that is greater than or equal to the threshold value g in all time slots. th 10 shows that the sink 2 transmits data x to the sink 2 using the maximum transmission power in the last N-th time slot without reaching the maximum transmission power. As a result, in the sensor network system 100 according to the embodiment, the sink 2 is more likely to collect data x from the node 1 with less distortion than in the second related art, and therefore the accuracy of the data x is improved.

[0102] Referring to FIG. 16, a comparison of the cumulative distribution functions of the transmission power of nodes 1 and 101 between a sensor network system 100 according to one embodiment, a modified example of the sensor network system 100 according to one embodiment, and a sensor network system 1000 according to a second related technology will be described.

[0103] Fig. 16 is a graph comparing cumulative distribution functions of transmission power between the sensor network system 100 according to an embodiment and the sensor network system 1000 according to a related technique. Fig. 16 includes a first graph G11 corresponding to the sensor network system 1000 according to a second related technique, a second graph G12 corresponding to the sensor network system 100 according to an embodiment, and a third graph G13 corresponding to a modified example of the sensor network system 100 according to an embodiment. In Fig. 16, the horizontal axis represents transmission power, and the vertical axis represents cumulative distribution function.

[0104] The first graph G11, the second graph G12, and the third graph G13 show the results of a computer simulation. Comparing the first graph G11, the second graph G12, and the third graph G13, the transmission power is almost the same.

[0105] With reference to FIG. 17, a comparison of the cumulative distribution function of the mean square error between the received power and the target power between the sensor network system 100 according to the embodiment and the sensor network system 1000 according to the second related art will be described.

[0106] Fig. 17 is a graph comparing the cumulative distribution function of the mean square error between the received power and the target power between the sensor network system 100 according to one embodiment and the sensor network system 1000 according to the related art. Fig. 17 includes a first graph G21 corresponding to the sensor network system 1000 according to the related art and a second graph G22 corresponding to the sensor network system 100 according to one embodiment. In Fig. 17, the horizontal axis represents the mean square error between the received power and the target power, and the vertical axis represents the cumulative distribution function. Here, the received power represents the power of the analog signal received by the sink 2, 102, and the channel gain g k is the threshold g th On the other hand, the target power may include distortion that occurs when the channel gain g k is the threshold g th , not including distortion.

[0107] The first graph G21 and the second graph G22 show the results of a computer simulation. Comparing the first graph G21 and the second graph G22, the sensor network system 100 according to the embodiment has a smaller mean square error between the received power and the target power than the sensor network system 1000 according to the second related art, that is, the distortion of the analog signal received by the sink 2 can be effectively reduced.

[0108] In this way, in the sensor network system 100 according to one embodiment, even if the accuracy of the data x received by the sink 2 is improved, the power consumed by the node 1 remains almost unchanged.

[0109] Although the invention made by the inventor has been specifically described above based on the embodiment, it goes without saying that the present invention is not limited to the above embodiment and can be modified in various ways without departing from the gist of the invention. Furthermore, the respective features described in the above embodiment can be freely combined within the scope of technical compatibility. [Explanation of symbols]

[0110] 100, 1000 Sensor Network System 1, 1-k, 1-1~1-K, 101, 101-k, 101-1~101-K nodes 10 Bus 11 Input / Output Devices 111 Communication equipment 112 Antenna 12 Arithmetic unit 121 Beacon receiving device 122 Channel Gain Detector 123 Transmission control device 13 Memory Devices 14 External storage device 141 Recording media 15 Sensing equipment 2, 102 sink 20 Bus 21 Input / Output Devices 211 Communication equipment 212 Antenna 22 Arithmetic unit 221 Parameter Calculation Device 222 Beacon Generator 223 Transmission Control Device 224 Receiving control device 225 Aftertreatment Device 23 Memory Device 24 External storage device 241 Recording media A0, A1, A2, A3, A100 Adder P1~P6, P100, P101, P102, P10K, P201, P202 Processing M100, M101, M102, M201, M202, M301, M302 integrators M11, M12, M13, M21, M22, M23, M31, M32, M33 integrators

Claims

1. Multiple nodes each of which retrieves data; a sink that collects the data from the plurality of nodes for each data collection period that includes a plurality of time slots; Equipped with The sink is a first transmission control device that transmits a beacon including information representing a channel gain threshold to the plurality of nodes in each of the plurality of time slots; Equipped with Each of the plurality of nodes a channel gain detection device for detecting a channel gain between the sink and the beacon based on the beacon; a second transmission control device that transmits the data to the sink only once during the data collection period when a predetermined communication condition is satisfied in any one of the plurality of time slots; Equipped with The communication conditions are: is satisfied if the channel gain is greater than or equal to the channel gain threshold; The time slot is filled if it is the last time slot of the data collection period. Sensor network system.

2. 2. The sensor network system according to claim 1, The sink is a parameter calculation device that calculates a total number of a plurality of time slots included in a data collection period based on a total number of a plurality of external nodes, and calculates the channel gain threshold and a target value of a signal amplitude based on the total number of the plurality of time slots; a beacon generating device for generating the beacon including information representing the total number of the plurality of time slots, the channel gain threshold, and the target value of the signal amplitude in each of the plurality of time slots; a reception control device for receiving a plurality of data transmitted from the plurality of nodes in response to the beacon; a post-processing device that obtains a sum of the plurality of pieces of data received during the data collection period; Further equipped Sensor network system.

3. 3. The sensor network system according to claim 2, The second transmission control device includes: When the channel gain is equal to or greater than the channel gain threshold, the target value of the signal amplitude is set to a transmission power based on the channel gain; when the channel gain is less than the channel gain threshold, setting the transmit power based on a maximum transmit power of the node; generating an analog signal representing the data in terms of power based on the analog value representing the data and the transmission power; Transmitting the analog signal as the data to the sink. Sensor network system.

4. 4. The sensor network system according to claim 3, The reception control device includes: an adder that simultaneously receives a plurality of the analog signals representing the plurality of data simultaneously transmitted from the plurality of nodes in each of the time slots and obtains a sum of the powers of the plurality of analog signals; Equipped Sensor network system.

5. a parameter calculation device that calculates a total number of a plurality of time slots included in a data collection period based on a total number of a plurality of external nodes, and calculates a channel gain threshold and a target value of a signal amplitude based on the total number of the plurality of time slots; a transmission control device that transmits a beacon to the plurality of nodes in each of the plurality of time slots, the beacon including information representing the total number of the plurality of time slots, the channel gain threshold, and the target value of the signal amplitude; a reception control device for receiving a plurality of data transmitted from the plurality of nodes in response to the beacon; a post-processing device that obtains a sum of the plurality of pieces of data received during the data collection period; Equipped sink.

6. A sensing device for acquiring data; a beacon receiving device that receives a beacon including information indicating a channel gain threshold, the beacon being transmitted from an external sink in each of a plurality of time slots included in a data collection period; a channel gain detection device for detecting a channel gain between the sink and the beacon based on the beacon; a transmission control device that transmits the data to the sink only once during the data collection period when a predetermined communication condition is satisfied in any one of the plurality of time slots; Equipped with The communication conditions are: is satisfied if the channel gain is greater than or equal to the channel gain threshold; The time slot is filled if it is the last time slot of the data collection period. node.

7. Each of the plurality of nodes acquires data; transmitting a beacon including information representing a channel gain threshold from a sink to the plurality of nodes in each of a plurality of time slots included in a data collection period; each of the nodes detecting a channel gain between the node and the sink based on the beacon; each of the nodes transmitting the data to the sink only once during the data collection period when a predetermined communication condition is satisfied in any one of the plurality of time slots; said sink collecting said data from said plurality of nodes for each said data collection period; Including, The communication conditions are: is satisfied if the channel gain is greater than or equal to the channel gain threshold; The time slot is filled if it is the last time slot of the data collection period. Data communication processing method.

8. A program for implementing processing by causing a sink computing device to execute the program, The process comprises: Calculating a total number of a plurality of time slots included in a data collection period based on a total number of a plurality of external nodes; calculating a channel gain threshold and a signal amplitude target value based on the total number of the plurality of time slots; transmitting a beacon to the plurality of nodes in each of the plurality of time slots, the beacon including information representative of the total number of the plurality of time slots, the channel gain threshold, and the target value of the signal amplitude; receiving a plurality of data transmitted from the plurality of nodes in response to the beacon; obtaining a sum of the plurality of data received during the data collection period; Includes program.

9. A program that realizes processing by being executed by a computing device of a node, The process comprises: Obtaining data and receiving a beacon transmitted from an external sink in each of a plurality of time slots included in a data collection period, the beacon including information representing a channel gain threshold; Detecting a channel gain between the sink and the beacon based on the beacon; transmitting the data to the sink only once during the data collection period when a predetermined communication condition is satisfied in any one of the plurality of time slots; Including, The communication conditions are: is satisfied if the channel gain is greater than or equal to the channel gain threshold; The time slot is filled if it is the last time slot of the data collection period. program.

Images