COMMUNICATION CONNECTION DETECTION METHOD, COMMUNICATION CONNECTION DETECTION DEVICE, AND SENSOR SYSTEM

Abstract

A communication connection determination method according to the present invention pertains to a method of determining communication connection between a sensor terminal (11) and a sensor accommodation terminal (12), the communication connection determination method comprising: a step for receiving a piece of first data, and storing a first timestamp; a step for determining the number of received pieces of first data; a step for calculating an average deviation reference value by using a first timestamp interval obtained from the first timestamps; a step for receiving a piece of second data, and storing a second timestamp; a step for determining the number of received pieces of second data; a step for calculating an average deviation evaluation value by using a second timestamp interval obtained from the second timestamps; and a step for determining whether or not there is a significant difference between the average deviation reference value and the average deviation evaluation value.　Thus, the present invention can provide a communication connection determination method for determining communication connection so as to avoid a buffer overflow.

Description

[Technical field]

[0001] The present invention relates to a communication connection determination method, a communication connection determination device, and a sensor system in a system that transmits and receives data acquired by a sensor. [Background technology]

[0002] In the IoT (Internet of Things), a wide variety of sensors are connected to each other via wireless communication such as the Internet, and a large amount of data is collected and analyzed. In the sensor-related technology in the IoT, as shown in Fig. 8, sensors 41_1 to 41_N and multi-connectable general-purpose sensor-containing terminals 42_1 to 42_N have been used to meet various use cases and needs, including monitoring of healthcare, structures, and the global environment (Non-Patent Document 1).

[0003] In particular, when collecting data using sensors that operate in resource-limited environments, it is necessary to understand the network connection status of the sensor to avoid power waste due to data retransmission and unintended operation. As an index for understanding this connection status, RSSI (Received Signal Strength Indicator) and the like are used, as shown in Figure 9.

[0004] When connecting a data collection terminal slave (sensor terminal) that includes a wide variety of sensors to a general-purpose sensor accommodation terminal that can be connected to the data collection terminal slave (sensor terminal), there are cases where it is not possible to guarantee a network connection with good functionality and quality of the sensor terminal.

[0005] In particular, the connection state between the sensor node and the sensor host node depends on the communication environment according to the use case. When the communication environment is unstable, packet loss occurs in any communication protocol. In this case, data is usually stored together with data retransmission.

[0006] As a result, in a connection environment where packet loss occurs frequently, the data accumulation rate exceeds the data transmission rate, causing memory congestion in the sensor node.

[0007] This situation differs from the situation where the connection between the sensor node and the sensor containing node is disconnected; although packet loss occurs, the state does not transition to a disconnected state. Therefore, unless appropriate memory management is performed, there is a possibility of buffer overflow. Since the behavior when a buffer overflow occurs is undefined and there is a possibility of serious failure occurring, it is necessary to prevent this situation from occurring.

[0008] In detail, in the timeout method conventionally used under the above circumstances, packets are received at intervals that do not exceed the timeout time, so the connection between the sensor node and the sensor containing node is not cut off. Therefore, in order to prevent failures due to buffer overflow, it is necessary to avoid situations in which packet loss occurs continuously.

[0009] Therefore, it is necessary to grasp the connection state between the sensor terminal and the sensor accommodation terminal, and appropriately determine and control whether to continue or cut off the connection depending on the connection state.

[0010] Since a wide variety of sensor terminals are connected to the sensor containing terminal, it is less costly to execute the above connection control comprehensively in the sensor containing terminal than to execute it in each sensor terminal. Also, executing the connection control comprehensively in the sensor containing terminal is more efficient because it can be implemented without updating the firmware of many sensor terminals that have already been deployed. [Prior art documents] [Non-patent literature]

[0011] [Non-Patent Document 1] Kenichi Matsunaga, Naoichi Oshima, Musa Ahmad, Toshihiko Kondo, and Hiroki Morimura, “Proposal of a Multi-Sensor Data Collection Technology Suitable for IoT,” IEICE Communications Society Conference, 2016, B-18-56, Proceedings of the IEICE Communications Conference 2, p.420. [Non-Patent Document 2] Martin Woolley, "Bluetooth CoreSpecification v5.1", ver.1.0.1, Bluetooth SIG, Inc., December 9, 2020, p.1-12. Summary of the Invention [Problem to be solved by the invention]

[0012] A disconnection in the connection between the sensor node and the sensor accommodation node can be determined by a received signal strength indicator (RSSI) which is a communication strength indicator shown in FIG.

[0013] However, since RSSI is a value obtained at the circuit level, the function must be supported in advance in the communication circuit.

[0014] Even if the information is supported, it is not necessarily accessible from the application side. This is because the information is deleted by the drivers and OS leading up to the application that the user can change, and this causes the same problem when considering the use of communication packet information, which is described below.

[0015] Bluetooth (registered trademark) Low Energy (BLE) is also a standard used for communication between sensor terminals and sensor containing terminals. In BLE, information that can be used to prevent buffer overflows is present in the communication packet. This information is a one-bit piece of information (MD flag, More Data Flag) that indicates whether there is unsent data in the header of the data channel PDU. This information can be used to determine whether there is remaining data, and can be used to prevent buffer overflows.

[0016] However, depending on the driver or OS specifications, it may be impossible to access the MD flag from the application side (Non-Patent Document 2).

[0017] Therefore, it is necessary to perform disconnection judgment to avoid buffer overflow from the sensor containing terminal by using information accessible from the application side, without using specific header information of the communication packet. [Means for solving the problem]

[0018] In order to solve the above-mentioned problems, a communication connection determination method according to the present invention is a communication connection determination method for determining a communication connection status between a sensor terminal and a sensor containing terminal, and includes a step of the sensor containing terminal receiving first data from the sensor terminal and storing a first timestamp, a step of determining whether or not the number of times the first data has been received has reached a first specified number, a step of calculating an average deviation reference value using a first timestamp interval obtained from the first timestamp when the number of times the first data has been received has reached the first specified number, a step of the sensor containing terminal receiving second data from the sensor terminal and storing a second timestamp, a step of determining whether or not the number of times the second data has been received has reached a second specified number, a step of calculating an average deviation evaluation value using a second timestamp interval obtained from the second timestamp when the number of times the second data has been received has reached the second specified number, and a step of testing whether or not there is a significant difference between the average deviation reference value and the average deviation evaluation value, and determining that a communication connection abnormality occurs when it is determined that there is a significant difference.

[0019] A communication connection determination device according to the present invention is a communication connection determination device that determines a communication connection status between a sensor terminal and a sensor containing terminal, and includes a clock unit that measures an arrival time of data from the sensor terminal, a time stamp assignment unit that acquires a time stamp based on the arrival time, a memory that stores at least one of the time stamp and a time stamp interval obtained from the time stamp, and a disconnection determination unit that statistically determines the communication connection status between the sensor terminal and the sensor containing terminal based on the time stamp interval. The disconnection determination unit includes a time stamp interval input unit to which the time stamp interval is input, an average deviation calculation unit that calculates an average deviation reference value and an average deviation evaluation value based on the time stamp interval, a storage unit that stores at least the average deviation reference value, and a test determination unit that determines whether or not to disconnect the communication connection based on the average deviation reference value and the average deviation evaluation value. do. Effect of the Invention

[0020] According to the present invention, it is possible to provide a communication connection determination method, a communication connection determination device, and a sensor system that determine a communication connection in order to avoid a buffer overflow. [Brief description of the drawings]

[0021] [Figure 1] FIG. 1 is a block diagram showing a configuration of a communication connection determination device and a sensor system according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a block diagram showing a configuration of a connection determination unit in the communication connection determination device according to the first embodiment of the present invention. [Diagram 3] FIG. 3 is a diagram for explaining the operation of the communication connection determination device and the communication connection determination method according to the first embodiment of the present invention. [Figure 4] FIG. 4 is a diagram for explaining the communication connection determination method according to the first embodiment of the present invention. [Diagram 5] FIG. 5 is a diagram for explaining the communication connection determination method according to the first embodiment of the present invention. [Figure 6] FIG. 6 is a flowchart showing a communication connection determination method according to the first embodiment of the present invention. [Figure 7] FIG. 7 is a diagram for explaining the communication connection determination method according to the first embodiment of the present invention. [Figure 8] FIG. 8 is a block diagram showing a configuration of a conventional communication connection determination device and a sensor system. [Figure 9] FIG. 9 is a diagram for explaining a conventional communication connection determination method. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] <First embodiment> A determination device and a determination method according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 7. FIG.

[0023] <Configuration of sensor system and determination device> The sensor system 1 according to this embodiment includes a sensor terminal 11 and a sensor accommodation terminal 12, as shown in FIG.

[0024] The sensor terminal 11 includes a control unit 111, a sensor circuit unit 112, a memory 113, and a wireless circuit 114, which are all connected to the control unit 111.

[0025] The control unit 111 is configured with a CPU or an MCU, and includes a sensor control unit 115 and a communication control unit 116, which control the sensor circuit unit 112 and the wireless circuit 114, respectively.

[0026] Here, since the essential function of the sensor terminal 11 is to obtain data from the sensor circuit unit 112 and transmit it to the sensor accommodation terminal 12 by wireless communication, the performance of the MPU of the control unit 111 may be low.

[0027] The sensor circuit section 112 includes a sensor and acquires data.

[0028] The wireless circuit 114 transmits the data acquired by the sensor circuit unit 112 to the sensor containing terminal 12 as a packet.

[0029] The memory 113 holds (stores) the programs and acquired data until the time of transmission.

[0030] The sensor housing terminal 12 includes a control unit 121, a clock unit 122, a memory 123, a wireless circuit 124, and a communication circuit 125, which are connected to the control unit 121, respectively.

[0031] The control unit 121 is configured with a CPU or an MCU, and includes a communication control unit 126 , a time stamp providing unit 127 , and a disconnection determination unit 128 .

[0032] Here, since the CPU or MPU in the control unit 121 of the data storage terminal 12 needs to perform calculation processing, it is desirable that the calculation capacity is high.

[0033] The communication control unit 126 controls the radio circuit 124 and the communication circuit 125 .

[0034] The wireless circuit 124 communicates with the sensor terminal 11 and receives data from the sensor terminal 11 as packets.

[0035] The communication circuit 125 communicates with the server and transmits data to the server as packets.

[0036] The clock unit 122 is configured with a precision clock, and measures the arrival time of data from the sensor terminal 11 .

[0037] The time stamp adding unit 127 obtains a time stamp based on the arrival time measured by the clock unit 122 .

[0038] The memory 123 holds (stores) the timestamps and the timestamp intervals.

[0039] The disconnection determination unit 128 acquires statistics from the time stamp interval and determines whether communication between the sensor terminal 11 and the sensor accommodation terminal 12 has been disconnected.

[0040] In this way, in the sensor system 1, the sensor terminal 11 acquires and collects data using the sensor, stores the data in a memory, and then transmits the data to the sensor containing terminal 12 wirelessly.

[0041] Meanwhile, the sensor containing terminal 12 receives the data transmitted from the sensor terminal 11, measures the arrival time of the received packet (data) using the clock unit 122, obtains a timestamp based on that time using the timestamp assignment unit 127, calculates and obtains the timestamp interval, and stores it in the memory 123.

[0042] The average deviation is calculated from the timestamp intervals and used as a reference value. Also, the average deviation is calculated from a plurality of newly obtained timestamp intervals and used as an evaluation value.

[0043] Based on the time-stamped data, disconnection determination section 128 determines whether or not the communication connection should be disconnected.

[0044] As shown in FIG. 2, the disconnection determination unit 128 includes a time stamp interval input unit 21, an average deviation calculation unit 22, a storage unit 23, and a test determination unit 24.

[0045] A time stamp interval is input to a time stamp interval input unit 21 based on the time stamp obtained from the data.

[0046] In the average deviation calculation unit 22, an average deviation reference value and an average deviation evaluation value are calculated based on the time stamp interval.

[0047] The calculated average deviation reference value and average deviation evaluation value are stored in the storage unit 23.

[0048] The test determination unit 24 determines whether or not to disconnect (or maintain) the communication connection based on the calculated average deviation reference value and average deviation evaluation value.

[0049] Here, the calculated average deviation reference value may be stored in the storage unit, and the test determination unit 24 may make a determination based on the stored average deviation reference value and the average deviation evaluation value calculated by the average deviation calculation unit.

[0050] In the sensor system 1 according to this embodiment, the determination device 10 is configured with a clock unit 122, a memory 123, a time stamp providing unit 127, and a disconnection determination unit 128.

[0051] <Judgment method> The determination method according to the present embodiment will be described with reference to FIGS.

[0052] First, a description will be given of data transmission and reception between the sensor terminal 11 and the sensor accommodation terminal 12. As shown in FIG. sendThe sensor circuit unit 112 transmits data (packet) storing the data acquired from the sensor circuit unit 112 to the sensor containing terminal 12. On the other hand, the sensor containing terminal 12 acquires a timestamp when receiving a packet from the sensor terminal 11 and stores the timestamp in the memory 123.

[0053] In this case, two consecutive timestamps T n-1 , T n Time interval d n-1 The expected value E[d n ] is expressed by equations (1) and (2).

[0054]

number

[0055]

number

[0056] where time interval d n-1 The expected value E[d n ] is the transmission period T send Matches.

[0057] In communication using the sensor system 1, when data transfer is delayed due to packet loss (e.g., dotted arrow in the figure), the timestamp interval d n-1 is T send (For example, in the figure, T p+1 ~T p+2 ) In this way, each timestamp fluctuates with respect to the expected value depending on the communication conditions.

[0058] When judging the communication status, each timestamp fluctuates randomly with respect to the expected value, but depending on the wireless communication environment, it may not follow a normal distribution. In this case, there may be more outliers than in a normal distribution, and the deviation may be large, making it difficult to monitor the communication status accurately.

[0059] In this case, the median in robust statistics is effective as an evaluation value to ensure robustness against outliers. The mean deviation is useful as a value that indicates the variation from the median, and by evaluating the median and mean deviation, it is possible to perform anomaly detection even in a communication environment with a large number of outliers. For example, as shown in Fig. 4, after initialization, the median and mean deviation are calculated as evaluation values, and when an anomaly is detected, the connection between the sensor containing terminal 12 and the sensor terminal 11 is cut off.

[0060] However, when the communication protocol is different, if the data transfer is delayed due to packet loss, the default transmission interval T send In some cases, data may be sent at intervals faster than 100ms. In this case, as shown in Figure 5, even if the communication environment deteriorates, the median reception interval may not change and only the average deviation may change.

[0061] For example, in BLE, which is a communication protocol in the sensor terminal 11, communication is performed only at a connection interval specified at the time of connection, and when an event occurs in the sensor terminal 11 that requires data transmission, transmission is attempted at the next connection interval.

[0062] This connection interval is usually the data transmission interval T send As a result, if a transmission or reception fails, retransmission is attempted at the next connection interval, so T send It is possible to record a timestamp interval shorter than

[0063] Therefore, in this embodiment, the sensor accommodation terminal 12 judges whether to connect to the sensor terminal 11 using only the average deviation, not the median, as described below.

[0064] In the determination method according to the present embodiment, the change in the representative value (average deviation) is evaluated from data in which outliers are expected and from the same population. In detail, the presence or absence of a significant difference between the reference value of the average deviation of the timestamp interval and the evaluation value is tested. Therefore, in this determination method, instead of a normal distribution, the Wilcoxon signed rank test is used, which can test the significant difference between the representative values ​​of two corresponding groups.

[0065] FIG. 6 shows a flowchart of the determination method according to this embodiment.

[0066] First, the connection between the sensor accommodation terminal 12 (parent device) and the sensor terminal (child device) 11 is initialized (step S1).

[0067] First, the sensor terminal 11 is connected to the sensor accommodation terminal 12 (step S11).

[0068] Next, the packet (data) is received and the timestamp is stored (step S12).

[0069] Subsequently, the reception of data and the storage of timestamps are repeated to obtain a predetermined number (for example, n1+1) of data and timestamps. In detail, the number of received data is counted, and it is determined whether the predetermined number has been reached, and data is received until the predetermined number is reached (step S13).

[0070] Next, by using equations (3) and (4), the n1 timestamp intervals d 1,i Using the above, the standard value is the average deviation (hereinafter referred to as the "average deviation standard value") σ stamp Calculate (step S14).

[0071]

number

[0072]

number

[0073] Next, an evaluation value is calculated (step S2).

[0074] First, data is received and the timestamp is stored (step S21).

[0075] Subsequently, the reception of data and the storage of timestamps are repeated to obtain a predetermined number (e.g., n2+1) of data and timestamps. In detail, the number of received data is counted, and it is determined whether the predetermined number has been reached, and data is received until the predetermined number is reached (step S22).

[0076] Next, by using equations (5) and (6), the n2 timestamp intervals d 1,i Using the mean deviation evaluation value σ eval Calculate (step S23).

[0077]

number

[0078]

number

[0079] Next, the presence or absence of a significant difference between the average deviation reference value and the average deviation evaluation value is determined, and disconnection is executed (step S3).

[0080] Next, the presence or absence of a significant difference between the average deviation reference value and the average deviation evaluation value is determined at a significance level α by the Wilcoxon signed rank test (step S31).

[0081] If it is determined in the Wilcoxon signed rank test that there is a significant difference, it is determined (judged) that there is a connection abnormality, and the connection between the sensor containing terminal 12 and the sensor terminal 11 is cut off (steps S32 to S33).

[0082] Moreover, if it is determined that there is no significant difference, it is determined (judged) that the connection is normal, and the connection between the sensor housing terminal 12 and the sensor terminal 11 is maintained (step S32).

[0083] The above method makes it possible to recognize the significant difference in the mean deviation between the normal state and the abnormal state in the connection between the sensor containing terminal 12 and the sensor terminal 11, and the user can arbitrarily set a level (significance level) to determine whether to disconnect the connection. Here, it is desirable to set n1 to be equal to or larger than n2 in order to make a disconnection determination with less time loss after the reference value calculation.

[0084] 7 shows a schematic diagram 31 of changes in reception intervals and a schematic diagram 32 of changes in test evaluation value in the determination method according to the present embodiment. Schematic diagram 31 shows the reception interval (dotted line), the average reception interval (solid line), and the timeout threshold (dashed line). Schematic diagram 32 shows the evaluation value (solid line) and disconnection threshold (dashed line).

[0085] In the conventional method, disconnection due to timeout is judged based on the reception interval, as shown in the outline of Figure 31, so it is necessary to set an appropriate threshold. For example, when the reception interval (dotted line) exceeds the timeout threshold (dashed line), it is judged to be a connection abnormality (black circle in the figure). As a result, if an appropriate threshold is not set, there is a possibility that the connection will not be disconnected or that disconnections will occur frequently.

[0086] In this embodiment, as shown in schematic diagram 32, a reference value is calculated in advance (initialization), and when an evaluation value (test value) exceeds a disconnection threshold, a connection abnormality is determined (white circle in the diagram).

[0087] In this way, by judging whether or not the mean deviations of two groups that do not have normal distributions are equal or not and disconnecting communication based on the evaluation value obtained, it is possible to identify instability of the communication environment from the variation in reception intervals and perform disconnection processing.

[0088] This also makes it possible to prevent abnormal operation before it occurs, and after disconnection, the connection is put into a standby state to avoid buffer overflow, allowing the sensor terminal 11 to continue operating.

[0089] As a result, the sensor containing terminal 12 can accommodate the communication specifications and design differences of the various sensor terminals 11 at low cost, and the stability of the sensor system including the sensor containing terminals and the sensor terminals can be improved.

[0090] This is particularly effective for communication protocols that perform retransmission, i.e., burst transmission, at higher speeds than the default transmission interval when there is unsent data.

[0091] Furthermore, when absolute value calculations, addition, subtraction, and averaging are used to calculate the mean deviation, fewer computational resources are required on the computer compared to variance calculations that involve accumulation such as squaring, so this is effective in reducing the amount of calculations and power consumption compared to determining anomalies using variance.

[0092] <Second embodiment> <Configuration of sensor system and determination device> While the first embodiment can operate in a configuration including a single or multiple sensor terminals, the determination method and determination device according to this embodiment can operate in a configuration including multiple sensor terminals 11. Other configurations are similar to those of the first embodiment.

[0093] <Judgment method> In the first embodiment, in the initial state of the connection between the sensor accommodation terminal and the sensor terminal, σ stamp Therefore, if the communication environment is poor immediately after the connection is started, the sensor terminal cannot receive packets from the sensor terminal (e.g., child A) at normal communication intervals, so it is necessary to calculate σ stamp cannot be obtained.

[0094] Therefore, using the data from sensor terminals other than slave A that can communicate normally, the average deviation reference value σ stamp Calculate.

[0095] Here, the communication interval of each sensor terminal T send The timestamp interval of the data received from each sensor terminal is compared with the timestamp interval of the data received from the sensor terminal, and if the timestamp intervals are equal to or less than a predetermined value, the sensor terminal is selected as a sensor terminal capable of normal communication.

[0096] Thereafter, the selected sensor terminal is used to make a determination in the same manner as in the first embodiment.

[0097] <Effects> In the determination device according to the present embodiment, there are S sensor terminals, each of which has a communication interval of T send i Let the number of data used for initialization be M. The time τ required for initialization, i.e., for obtaining the average deviation reference value, is τ when all communication intervals are the same (T send i =T send ), expressed by equation (7).

[0098]

number

[0099] Here, if the number of pieces of data M is set to a multiple of the number of sensor terminals S, it is possible to most efficiently collect the initialization data.

[0100] Moreover, the time τ when the communication intervals are different for each sensor terminal is expressed by equation (8).

[0101]

number

[0102] In this way, according to the present embodiment, the time τ is T send Since the time required for initialization, i.e., for obtaining the average deviation reference value, can be shortened, the time required for determination regarding communication disconnection can be increased, and real-time performance can be improved.

[0103] In the embodiment of the present invention, examples of the structure, dimensions, materials, etc. of each component in the configuration of the communication connection determination device and the sensor system, the determination method, etc. are shown, but the present invention is not limited to these. Anything that can exert the functions and effects of the communication connection determination device, the sensor system, and the determination method may be used. [Industrial Applicability]

[0104] The present invention can be applied to determining communication conditions in an IoT network using sensors. [Explanation of symbols]

[0105] 11 Sensor terminal 12 Sensor storage terminal

Claims

1. A communication connection determination method for determining a communication connection status between a sensor terminal and a sensor containing terminal, comprising: The sensor containing terminal receives first data from the sensor terminal and stores a first timestamp; determining whether a number of received first data has reached a first specified number; calculating an average deviation reference value using a first timestamp interval obtained from the first timestamp when the number of receptions of the first data reaches the first specified number; The sensor containing terminal receives second data from the sensor terminal and stores a second timestamp; determining whether a number of received second data has reached a second specified number; calculating an average deviation evaluation value using a second timestamp interval obtained from the second timestamp when the number of receptions of the second data reaches the second specified number; a step of testing whether there is a significant difference between the average deviation reference value and the average deviation evaluation value, and determining that a communication connection abnormality occurs when it is determined that there is a significant difference; A communication connection determination method comprising:

2. The presence or absence of the significant difference is examined by the Wilcoxon signed rank test.

2. The communication connection determination method according to claim 1.

3. The average deviation reference value satisfies formula (A) and formula (B), and the average deviation evaluation value satisfies the following formulas (C) and (D):

3. The communication connection determination method according to claim 1 or 2. [0010]

4. The sensor terminal is a plurality of terminals, selecting a sensor terminal capable of normal communication based on a communication interval of each of the plurality of sensor terminals and a timestamp interval of each of the data received from the plurality of sensor terminals; The first data is received from the selected sensor terminal. The communication connection determination method according to any one of claims 1 to 3.

5. A communication connection determination device that determines a communication connection status between a sensor terminal and a sensor accommodation terminal, A clock unit that measures the arrival time of data from the sensor terminal; a time stamp assignment unit that acquires a time stamp based on the arrival time; a memory for storing at least one of the timestamp and a timestamp interval obtained from the timestamp; a disconnection determination unit that statistically determines a communication connection status between the sensor terminal and the sensor containing terminal based on the time stamp interval; Equipped with The disconnection determination unit, a time stamp interval input unit to which the time stamp interval is input; an average deviation calculation unit that calculates an average deviation reference value and an average deviation evaluation value based on the time stamp interval; A storage unit that stores at least the average deviation reference value; a test determination unit that determines whether or not to disconnect the communication connection based on the average deviation reference value and the average deviation evaluation value.

6. The sensor terminal is a plurality of terminals, and a sensor terminal selection unit that selects a sensor terminal capable of normal communication based on a communication interval of each of the plurality of sensor terminals and a timestamp interval of each of the data received from the plurality of sensor terminals.

6. The communication connection determination device according to claim 5.

7. The sensor containing terminal is provided with the communication connection determination device according to claim 5 or 6; The sensor terminal A sensor system comprising:

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