JP6309768B2 - Wireless sensor network system - Google Patents

Description

  The present invention relates to a wireless sensor network system in which a server and a plurality of terminals communicate via a wireless network, and an information batch collection method performed using the wireless sensor network system.

  In recent years, research and development of technologies related to wireless sensor networks have been actively conducted. The wireless sensor network is a wireless network that controls a terminal including a sensor or the like via a network configured by wireless communication, and uses the terminal to collect information on a location and an environment.

  Wireless sensor networks are expected to be used in various fields such as monitoring systems and home automation. By constructing the sensor network with wireless communication, benefits such as cost reduction, expansion of sensing range, and flexibility in changing the network can be expected.

  Currently, when performing so-called ad hoc communication in a wireless sensor network, existing wireless communication systems and protocols for small-scale networks are used. In such a case, the IEEE 802.15.4 standard mainly called ZigBee (registered trademark) and other specific low-power radio systems are utilized as a de facto standard technology.

  FIG. 1 is a conceptual diagram showing the overall configuration of a wireless sensor network according to the prior art. The wireless sensor network shown in FIG. 1 includes a receiving server S that functions as a receiving server and a plurality of sensor nodes SN1 to SN5 that function as transmitting terminals.

  In such a conventional technique, each sensor node SN1-SN5 transmits information, such as observation information and observation position information, in a packet. At this time, the signals are arranged and transmitted in time series so that a plurality of signals transmitted by different sensor nodes SN1 to SN5 do not interfere with each other.

  In relation to the above, Patent Document 1 (Japanese Patent Laid-Open No. 2010-14604) discloses a description related to a vibration measurement system. This vibration measurement system includes a sensor node and a management node, and measures the vibration of the measurement object. Here, the sensor node is provided at a predetermined position of the measurement object. The management node performs wireless communication with the sensor node. The sensor node includes sensor-side detection means, sensor-side communication means, and sensor-side control means. Here, the sensor side detection means detects the degree of vibration at a predetermined position of the measurement object. The sensor side communication means performs wireless communication with the management node. The sensor-side control means controls the sensor-side detection means to execute the detection of the degree of vibration at a predetermined cycle, and the timing at which the sensor-side communication means detects the degree of vibration. The control for prohibiting wireless communication is performed.

  Patent Document 2 (Japanese Patent Laid-Open No. 2013-187552) discloses an invention relating to a wireless sensor network system. This wireless sensor network system includes a plurality of transmission terminals and a reception server. Here, the plurality of transmission terminals transmit a plurality of transmission signal groups. The receiving server receives a plurality of transmission signal groups via a wireless network. The plurality of transmission signal groups include transmission signal groups transmitted by each of the plurality of transmission terminals. Each transmission terminal includes a first circuit unit, a second circuit unit, a conversion unit, and a transmission unit. The first circuit unit generates a first information group. The second circuit unit generates a second information group. The conversion unit converts the combination of the first information group and the second information group into a combination of a transmission frequency group and a transmission time group. The receiving server includes a receiving unit and a restoring unit. The receiving unit receives a plurality of transmission signal groups. The restoration unit restores the first information group and the second information group from the transmission frequency group and the transmission time group indicated by the plurality of transmission signal groups. The invention of the present application is a further development of the invention by the inventor of Patent Document 2.

JP 2010-14604 A JP 2013-187552 A

  The conventional technique such as Patent Document 1 is effective in accurately collecting information transmitted by a small number of sensor nodes. However, if it is attempted to collect information transmitted by a large number of sensor nodes in real time, it takes too much time to collect all the information, so such a standard technique is not suitable.

  Therefore, the inventor of the present application has proposed a wireless sensor network system and a communication method thereof that place importance on efficiently collecting information transmitted from a plurality of information sources in the invention described in Patent Document 2. However, the invention described in Patent Document 2 has a trade-off relationship between the communication time compression effect and the accuracy with which the receiving server estimates the collected information, and there is room for improvement.

  In the present invention, the invention of Patent Document 2 is further developed to shorten the information collection time and improve the estimation accuracy, and the information batch collection method performed using this wireless sensor network system, I will provide a.

  The means for solving the problem will be described below using the numbers used in the (DETAILED DESCRIPTION). These numbers are added to clarify the correspondence between the description of (Claims) and (Mode for Carrying Out the Invention). However, these numbers should not be used to interpret the technical scope of the invention described in (Claims).

  The wireless sensor network system according to the present application includes a plurality of terminals (SN) and a server (S). Here, the plurality of terminals (SN) measure the observation information independently of each other. The server (S) collects the measurement results. The server (S) includes a server side transmission / reception circuit (34). Here, the server side transmission / reception circuit (34) simultaneously transmits an information transmission request signal to a plurality of terminals (SN). Each of the plurality of terminals (SN) includes a measurement unit (16, 17), a terminal side transmission / reception circuit (14), and a conversion unit (18, 19, 191). Here, a measurement part (16, 17) performs a measurement. The terminal side transmission / reception circuit (14) receives the information transmission request signal. The conversion unit (18, 19, 191) converts the measured observation information into a combination of a plurality of radio physical quantities according to the received information transmission request signal. In each terminal (SN), the terminal-side transmitting / receiving circuit (14) generates a unit signal having a frequency included in the combination at a time included in the combination and transmits the unit signal to the server (S). The server-side transmission / reception circuit (34) receives an aggregate of unit signals as a reception signal. The server (S) further includes a database (333) and a restoration circuit (37). Here, the database (333) stores the received signal received for each corresponding information transmission request signal. The restoration circuit (37) estimates the combination of the arrangement of the plurality of terminals (SN) and the measured observation information based on the plurality of reception signals stored corresponding to the plurality of information transmission request signals.

  In the information batch collection method according to the present invention, a plurality of terminals (SN) measure observation information independently of each other, and a server (S) sends an information transmission request signal to the plurality of terminals (SN). Simultaneous transmission (S1), each of a plurality of terminals (SN) receiving an information transmission request signal (S2), and each of the plurality of terminals measured according to the information transmission request signal Converting information into a combination of a plurality of radio physical quantities (S3), and transmitting a unit signal having a frequency included in the combination to a server at a time included in the combination by a plurality of terminals (SN) (S4), the server (S) receives an assembly of unit signals as a received signal (S5), and the server (S) receives the received signal for each corresponding information transmission request signal And the combination of the arrangement of the plurality of terminals (SN) and the measured observation information based on the plurality of received signals stored in correspondence with the plurality of information transmission request signals respectively by the server (S) (S10).

  According to the wireless sensor network system and the information batch collection method of the present invention, the accuracy of estimating the observation value measured by the sensor node on the receiving server side while greatly reducing the signal transmission time from a large number of sensor nodes to the receiving server. Can be improved.

FIG. 1 is a conceptual diagram showing the overall configuration of a wireless sensor network according to the prior art. FIG. 2A is a conceptual diagram illustrating an example of the overall configuration of a wireless sensor network according to the present invention. FIG. 2B is a block circuit diagram showing an example of the configuration of the sensor node according to the present invention. FIG. 2C is a block circuit diagram showing an example of the configuration of the receiving server according to the present invention. FIG. 3 is a flowchart showing the flow of processing in the information batch collection method using the wireless sensor network system of the present invention. FIG. 4 is a diagram illustrating an example of a time axis mapping process according to the present application. FIG. 5A is a diagram schematically illustrating the principle of frequency axis mapping according to the present invention. FIG. 5B is a diagram showing a specific example of frequency axis mapping according to the present invention. FIG. 6A is a diagram illustrating a first state of an example of the frequency axis shift process of the present application. FIG. 6B is a diagram illustrating a second state of the example of the frequency axis shift process of the present application. FIG. 6C is a diagram illustrating a third state regarding an example of the frequency axis shift process of the present application. FIG. 7A is a diagram illustrating an example of common subcarriers obtained from the first state illustrated in FIG. 6A. FIG. 7B is a diagram illustrating an example of the common subcarrier obtained from the second state illustrated in FIG. 6B. FIG. 7C is a diagram illustrating an example of common subcarriers obtained from the third state illustrated in FIG. 6C. FIG. 8 is a diagram illustrating the detection probability of common subcarriers according to the example illustrated in FIGS. 7A, 7B, and 7C. FIG. 9A is a diagram illustrating a state in which cells in which the detection probability illustrated in FIG. 8 has not reached the detection probability threshold are excluded from the common subcarriers illustrated in FIG. 7C. FIG. 9B is a diagram illustrating a state in which common subcarriers remaining without being excluded are extracted from FIG. 9A. FIG. 9C is a diagram illustrating an example of a result obtained by performing inverse transformation of frequency axis shift processing on the common subcarriers extracted in FIG. 9B. FIG. 9D is a diagram illustrating an example of a result obtained by performing the inverse transformation of the frequency axis mapping process on the common subcarrier illustrated in FIG. 9C. FIG. 10A is a distribution diagram illustrating an example of frequencies of a plurality of unit signals transmitted by a plurality of sensor nodes. FIG. 10B is a determination diagram illustrating a result of determination of the existence of a common subcarrier frequency performed based on the example of FIG. 10A. FIG. 10C is a comparison diagram showing a difference from FIG. 10A showing the distribution of the transmission signal in FIG. 10B showing the determination result from the reception signal. FIG. 11A is a diagram illustrating a combination of a cell corresponding to a second search and its common subcarrier frequency in a specific example illustrating a restoration method according to the fourth embodiment of the present invention. FIG. 11B is a diagram illustrating a state where there is no corresponding cell in the third search in the specific example illustrating the fourth embodiment of the present invention. FIG. 12A is a distribution diagram of subcarrier frequencies of a transmission unit signal in a specific example for explaining a restoration method according to the fifth embodiment of the present invention. FIG. 12B is a determination diagram illustrating a result of determination of the presence of a common subcarrier frequency performed based on the example of FIG. 12A in a specific example describing the restoration method according to the fifth embodiment of the present invention. FIG. 12C is a diagram illustrating a combination of a cell and a common subcarrier frequency in a state corresponding to Table 8 in a specific example describing the restoration method according to the fifth embodiment of the present invention. FIG. 12D is a diagram illustrating a combination of a cell corresponding to the second search and a subcarrier frequency serving as a single candidate in a specific example illustrating the restoration method according to the fifth embodiment of the present invention. FIG. 13A is a distribution diagram showing the arrangement of sensor nodes and subcarrier frequencies of unit signals transmitted by each sensor node in a specific example for explaining the restoration method according to the sixth embodiment of the present invention. . FIG. 13B is a determination diagram illustrating a result of determining whether there is a common subcarrier frequency in a specific example for explaining the restoration method according to the sixth embodiment of the present invention. FIG. 13C is a diagram illustrating a setting result of the estimated out-of-range area NZ in a specific example for explaining the restoration method according to the sixth embodiment of the present invention. FIG. 13D is a diagram illustrating a state in which data related to a cell for which an estimated value is obtained in the first search is deleted in a specific example for explaining the restoration method according to the sixth embodiment of the present invention. FIG. 13E is a specific example for explaining the restoration method according to the sixth embodiment of the present invention, in which there is no longer any cell in which the number of arranged sensor nodes and the number of common subcarrier frequencies match. FIG.

  With reference to the accompanying drawings, a mode for carrying out a wireless sensor network and an information batch collecting method according to the present invention will be described below.

(First embodiment)
FIG. 2A is a conceptual diagram illustrating an example of the overall configuration of a wireless sensor network according to the present invention. The components of the wireless sensor network shown in FIG. 2A will be described. In this example, the wireless sensor network includes a reception server S and a plurality of sensor nodes SN1 to SN3 that function as transmission terminals. Note that the total number of the plurality of sensor nodes SN1 to SN3 illustrated in FIG. 2A is merely an example, and does not limit the present invention.

  The positional relationship and connection relationship of the components of the wireless sensor network shown in FIG. 2A will be described. The receiving server S and the plurality of sensor nodes SN1 to SN3 communicate via a wireless network. As will be described later, the plurality of sensor nodes SN1 to SN3 may be fixed at predetermined locations or may be movable. The receiving server S is preferably fixed at a predetermined location, but this condition does not limit the present invention.

  The operation of the wireless sensor network shown in FIG. 2A will be schematically described. First, the receiving server S transmits an information transmission request signal (not shown) to all the sensor nodes SN1 to SN3. The first sensor node SN1 transmits the first unit signal TS1 in response to the information transmission request signal. Similarly, the second sensor node SN2 transmits the second signal unit TS2, and the third sensor node SN3 transmits the third unit signal TS3. The aggregate of these transmitted unit signals TS1 to TS3 is received by the reception server S as one reception signal TS0 synthesized in the radio space.

  FIG. 2B is a block circuit diagram showing an example of the configuration of the sensor node SN according to the present invention. It is assumed that the first to third sensor nodes SN1 to SN3 illustrated in FIG. 2A are configured in the same manner as the sensor node SN illustrated in FIG. 2B.

  The components of the sensor node SN shown in FIG. 2B will be described. 2B includes a bus 11, a CPU 12, a memory 13, a transmission / reception circuit 14, an antenna 15, a sensor 16, a position information acquisition circuit 17, a time axis mapping circuit 18, and a frequency axis. And a mapping circuit 19. The frequency axis mapping circuit 19 includes a frequency axis shift circuit 191. The memory 13 stores a program 131 and data 132. However, as will be described later, some or all of the position information acquisition circuit 17, the time axis mapping circuit 18, the frequency axis mapping circuit 19, and the frequency axis shift circuit 191 are included in the CPU 12, the memory 13, and the CPU 12. In some cases, the program 131 read from the memory 13 and executed can be substituted, and in this case, it can be omitted. On the contrary, in some cases, the CPU 12 and the memory 13 may be omitted, leaving the position information acquisition circuit 17, the time axis mapping circuit 18, the frequency axis mapping circuit 19, and the frequency axis shift circuit 191. The program 131 may be copied or installed from a predetermined recording medium storing the program 131 to the memory 13 and then executed by each sensor node SN. The predetermined recording medium may be a non-transitory recording medium such as a CD-ROM.

  A connection relationship of the components of the sensor node SN illustrated in FIG. 2B will be described. The antenna 15 is connected to the transmission / reception circuit 14. The bus 11 is connected to a CPU 12, a memory 13, a transmission / reception circuit 14, a sensor 16, a position information acquisition circuit 17, a time axis mapping circuit 18, and a frequency axis mapping circuit 19.

  The operation of the components of the sensor node SN shown in FIG. 2B will be schematically described. The bus 11 enables transmission and reception of signals between the connected components. The memory 13 inputs, stores, and outputs various data 132 and programs 131. The CPU 12 executes various programs 131 stored in the memory 13, performs calculations using various data 132 stored in the memory 13, and stores the calculation results in the memory 13.

  The sensor 16 performs various measurements and outputs the results as observation information. Here, as an example, the sensor 16 is a thermometer and measures temperature. However, this thermometer is merely an example of the sensor 16 and does not limit the present invention. As predetermined observation objects, other scalar quantities such as speed, humidity, rainfall, barometric pressure, concentration, etc. can be applied, and the sensor 16 can be a speedometer, hygrometer, rain gauge, barometer, densitometer, etc. Any measuring instrument may be used.

  Note that the observation target may be a vector quantity having a direction and a norm, such as velocity, in addition to a scalar quantity such as temperature. When a vector quantity is handled, the direction and its norm may be treated as two scalar quantities in a pseudo manner by quantizing each direction and its norm. After that, the scalar quantity corresponding to the direction and the scalar quantity corresponding to the norm are alternately transmitted from each sensor node SN to the receiving server S.

  The position information acquisition circuit 17 acquires position information. The position information may be obtained by measuring each time it is requested using a device such as GPS (Global Positioning System). In this example, it is assumed that the position information is biaxial coordinate information composed of latitude information and longitude information. However, this is merely an example, and the position information may be configured using another coordinate system.

  The time axis mapping circuit 18 maps position information on the time axis and outputs time information after mapping. In this example, the time axis mapping circuit 18 converts position information, which is information on two-axis coordinates, into two different times on the time axis. Similarly, the frequency axis mapping circuit 19 maps the observation information to the frequency axis and outputs the frequency information after mapping. In this example, observation information, which is a scalar quantity, is converted into one frequency on the frequency axis. These mapping operations may be performed using circuits that are physically independent from each other. Instead, a program 131 for causing the CPU 12 to execute these mapping operations is read from the memory 13 that has been stored in advance, and is read by the CPU 12. It may be done by executing.

  The transmission / reception circuit 14 and the antenna 15 receive an information transmission request signal transmitted from the reception server S and transmit a unit signal to the reception server S. This unit signal is a tone signal as an example, has a frequency included in frequency information, and is transmitted at each time included in time information.

  FIG. 2C is a block circuit diagram showing an example of the configuration of the receiving server S according to the present invention. The components of the receiving server S shown in FIG. 2C will be described. The reception server S shown in FIG. 2C includes a bus 31, a CPU 32, a memory 33, a transmission / reception circuit 34, an antenna 35, an output circuit 36, and a restoration circuit 37. The memory 33 stores a program 331, data 332, and a database 333. However, as will be described later, the restoration circuit 37 may be replaced by the CPU 32, the memory 33, and the program 331 that is read from the memory 33 and executed by the CPU 32. In this case, the restoration circuit 37 can be omitted. The program 331 may be copied or installed from a predetermined recording medium storing the program 331 to the memory 33 and then executed by the receiving server S. The predetermined recording medium may be a non-transitory recording medium such as a CD-ROM.

  The connection relationship of the components of the receiving server S shown in FIG. 2C will be described. The antenna 35 is connected to the transmission / reception circuit 34. The bus 31 is connected to a CPU 32, a memory 33, a transmission / reception circuit 34, an output circuit 36, and a restoration circuit 37.

  The operation of the components of the receiving server S shown in FIG. 2C will be schematically described. The bus 31 enables transmission / reception of signals between the connected components. The memory 33 inputs, stores, and outputs various data 332 and programs 331, and stores the received signal received from the sensor node SN in the database 333. The CPU 32 executes various programs 331 stored in the memory 33, calculates using the contents of the data 332 and the database 333 stored in the memory 33, and stores the calculation result in the data 332 or the database 333 of the memory 33. To do.

  The transmission / reception circuit 34 transmits an information transmission request signal to all the sensor nodes SN, and receives a reception signal in which unit signals transmitted from these sensor nodes SN are combined in a wireless space.

  The restoration circuit 37 analyzes the received signal and restores observation information and position information before frequency axis mapping and time axis mapping. This restoration operation may be performed using the CPU 32 and the memory 33 by recording a program 331 for causing the CPU 32 to execute the restoration operation in the memory 33 instead of the restoration circuit 37.

  The output circuit 36 outputs the restored observation information and position information. The output circuit 36 may be, for example, a display or a printing device that visually outputs the restored information. However, these are merely examples and do not limit the present invention.

  FIG. 3 is a flowchart showing the flow of processing in the information batch collection method using the wireless sensor network system of the present invention. With reference to FIG. 3, the operation of the wireless sensor network system of the present invention, that is, the information batch collecting method of the present invention will be described.

  The flowchart shown in FIG. 3 includes a first step S1 to an eleventh step S11. Hereinafter, an example of executing each step of the flowchart shown in FIG. 3 will be described.

Before executing the flowchart shown in FIG. 3, the initial state of the wireless sensor network system is prepared. In this example, the receiving server S resets the value of the information collection count _ng to 1. The information collection number _ng is a variable indicating how many times the information collection is performed. As an example, the value is increased by one each time information collection is performed. The reset information collection count _ng is stored in the memory 33. Thereafter, the receiving server S executes the first step S1.

In the first step S1, the receiving server S broadcasts an information transmission request signal to all of the plurality of terminals SN. The information transmission request signal includes, as a code number, the value of the information collection count _ng read from the memory 33 in this example. There is no particular limitation on the format in which the value of the information collection count _ng is included in the information transmission request signal. For example, it may have a format such as a waveform or frequency obtained according to an arbitrary conversion method. Further, the code number of the information transmission request signal is not limited to the number of times of information collection _ng . For example, an arbitrary number sequence whose order is previously defined in a predetermined table may be used. After the first step S1, the second step S2 is executed at the plurality of sensor nodes SN.

In the second step S2, the plurality of sensor nodes SN each receive an information transmission request signal. Each of the plurality of sensor nodes SN that have received the information transmission request signal has a frequency that the information transmission request signal has, a time at which the information transmission request signal is received, and an information collection count n as a code number included in the information transmission request signal. _g is acquired by inverse conversion of the conversion method used by the receiving server S and stored in each memory 13. In other words, the plurality of sensor nodes SN can synchronize the frequency, time, and code number by receiving the same information transmission request signal while being independent of each other. Strictly speaking, an error may occur in the timing at which each sensor node SN receives the information transmission request signal depending on the distance from the receiving server S, the radio wave condition, and the like, but it is realistic that all sensor nodes SN are distributed. Such an error can be sufficiently ignored if the range is considered.

  Note that, for various reasons including a radio wave environment, a part of the sensor node SN may not be able to receive the information transmission request signal. The sensor node SN that has not received the information transmission request signal does not perform the operation of each step thereafter, and is in a practical standby state until the subsequent information transmission request signal is received. Subsequent to the second step S2, the third step S3 is executed in the plurality of sensor nodes SN that have received the information transmission request signal.

  In the third step S3, the plurality of sensor nodes SN independently measure their own position information and a predetermined observation target, and convert a combination of these measurement results into a combination of a plurality of radio physical quantities. To do.

  The position information and the observation target are preferably measured according to the information transmission request signal. For example, the measurement may be started after receiving the information transmission request signal. Or you may employ | adopt the measurement result just before receiving an information transmission request signal, continuing a measurement regularly regularly. In this sense, various measurements by each of the plurality of sensor nodes SN may be performed at any time including the standby state strictly at a timing independent of the third step S3. In any case, the position information and the measurement result of the observation target may be temporarily stored in the memory 13 in each sensor node SN.

Each of the plurality of sensor nodes SN uses the time axis mapping circuit 18 and the frequency axis mapping circuit 19 to finally obtain the measurement result of the observation target that is a scalar quantity and the measurement result of the position information that is two-axis coordinates. Conversion to a combination of a plurality of radio physical quantities is performed according to the value of the received information collection count _ng . This conversion method is referred to herein as “radio physical quantity conversion” and will be described in detail later. In this example, a combination of one frequency and two times is obtained as a result. Here, the total number of frequencies and times obtained as a result of the radio physical quantity conversion is merely an example, does not limit the present application, and can be changed as appropriate according to the scene to be applied. After the third step S3, a fourth step S4 is executed at the plurality of sensor nodes SN.

  In the fourth step S4, each of the plurality of sensor nodes SN transmits a unit signal to the reception server S based on the radio physical quantity included in the combination obtained in the second step S2. In this example, each sensor node SN transmits a unit signal having a frequency obtained by conversion to the reception server S at two times obtained by conversion. In other words, in this example, each sensor node SN transmits a unit signal having the same frequency to the reception server S twice. After the fourth step S4, the receiving server S executes the fifth step.

In the fifth step S5, the reception server S receives a reception signal that is an aggregate in which a series of unit signals transmitted from a plurality of sensor nodes SN are combined in a wireless space, and the frequency component at each time Detect power. In addition, the reception server S stores the reception signal or the detection result of the power in the database 333 for each information collection count _ng . Subsequent to the fifth step S5, the receiving server S executes a sixth step S6.

  In the sixth step S6, the receiving server S determines a common subcarrier from the power detection result obtained in the fifth step S5. Here, the common subcarrier is intermediate data generated in order to estimate the correspondence between position information and observation information from a received signal. After the sixth step S6, the receiving server S executes a seventh step S7.

In the seventh step S7, the receiving server S determines whether the training period has been completed, that is, whether or not a sufficient number of measurement results have already been collected to calculate the common subcarrier detection probability. To do. Here, the number of collected signals used for calculating the detection probability of the common subcarrier is set as the collection frequency threshold Ng. When n _g ≧ N _g is confirmed as a result of the determination (Yes), the eighth step S8 is executed in the receiving server S after the seventh step S7. Conversely, the result of the determination, _{if n} g _{<N g} is confirmed (No), the eleventh step S11 in is executed by skipping step S10 in step S8~ tenth receiving server S in the eighth.

  In the eighth step S8, the receiving server S calculates the common subcarrier detection probability of each cell. Here, the common subcarrier detection probability is intermediate data indicating reliability for each common subcarrier, which is obtained based on past received signals accumulated in the database 333. Subsequent to the eighth step S8, the receiving server S executes a ninth step S9.

  In the ninth step S9, the reception server S selects a cell having a high common subcarrier detection probability as an estimation target. In other words, in order to improve the estimation accuracy of the overall observation information, data related to the common subcarrier with relatively low reliability is excluded from the calculation target. Following the ninth step S9, the receiving server S executes a tenth step S10.

  In the tenth step S10, the receiving server S estimates observation information of only the cell selected in the ninth step S9. Here, the receiving server S may output the result of estimating the observation information from the output circuit 36 or may store it in the memory 33. Following the tenth step S10, the receiving server S executes an eleventh step S11.

In the eleventh step S11, the receiving server S updates the value of the information collection count _ng . More specifically, in this example, the value of the information collection count _ng is increased by one, but this is only an example, and the increment may be other than 1, or the information collection count _ng May be varied according to a predetermined table. After the eleventh step S11, the receiving server S executes the first step S1 and repeats the following.

  The time axis mapping process performed in the third step S3 will be described in detail.

  FIG. 4 is a diagram illustrating an example of a time axis mapping process according to the present application. FIG. 4 includes a grid of 4 columns, 4 rows, and a total of 16 cells, and a time axis in which the first half extends in the horizontal direction from left to right and the second half in the vertical direction from bottom to top.

The grid shown in FIG. 4 indicates a region where observation information is measured in the wireless sensor network system of the present application. In this example, this area is divided into a total of 16 cells in 4 columns and 4 rows. Normally, these 16 cells are expressed by vertical and horizontal two-axis first coordinates and second coordinates. In the present application, these two-axis coordinates are converted into two times. In the example shown in FIG. 4, from left to right, the 0th column corresponds to time t ₀ , the first column corresponds to time t ₁ , the second column corresponds to time t ₂ , Associate the column with time t ₃ . Further, from bottom to top, made to correspond to zeroth row at time t _4, made to correspond to the first row at time t _5, in correspondence of the second row at time t _6, the time t ₇ the third line Make it correspond.

  The process of converting the two-axis coordinate value, which is originally two-dimensional information, into two times on the time axis, which is one-dimensional information based on such a correspondence, is referred to as a time-axis mapping process in the present application. By performing such a time axis mapping process, the total time required for transmitting signals from the plurality of sensor nodes SN to the receiving server S is reduced. In the prior art, if one sensor node is arranged in each of 16 cells, the 16 sensor nodes sequentially transmit signals, and a total of 16 unit hours are required until all transmissions are completed. In the time axis mapping process of the present application, all sensor nodes arranged in the same column simultaneously transmit signals at the time corresponding to the column, and all sensor nodes arranged in the same row Since signals are transmitted simultaneously at the time corresponding to, all transmissions can be completed within a total of 8 unit hours.

  In addition, here, for the sake of simplicity of explanation, an area of 4 columns × 4 rows = 16 cells is taken as an example, but of course, several tens columns × several tens columns = several hundred to several thousand cells or more It can be applied to any area. In such a case, the transmission time reduction rate is further improved. However, there is a tradeoff between shortening the transmission time and improving the accuracy of estimating observation information from the received signal.

  Note that the above is merely an example, and in addition, a combination of one of the coordinate values of the two axes and another observation information may be converted into two times on the time axis.

  The frequency axis mapping performed in the third step S3 and the unit signal transmission performed in the subsequent fourth step S4 will be described in detail. In the present invention, the frequency of the unit signal transmitted from each of the plurality of sensor nodes SN to the reception server S is determined based on the mapping between a plurality of observation values and frequencies prepared in advance. Assign according to. More specifically, a unit signal of a subcarrier frequency corresponding to an observed value is assigned using an OFDM (Orthogonal Frequency-Division Multiplexing) system. In the OFDM system, the signal becomes strong near the center frequency of a certain subcarrier, but the intensity is zero near the center frequency of other subcarriers, and therefore, a unit of a plurality of subcarrier frequencies received from each sensor node SN at the same time. The signal can be easily separated for each subcarrier. In the present embodiment, it is assumed that the observed value and the subcarrier frequency are associated with each other on a one-to-one basis. Therefore, at the same time timing, each sensor node SN performs conversion to one subcarrier frequency corresponding to the observed value. On the other hand, mapping may be performed so that a plurality of subcarrier frequencies are assigned to one observation value. In this case, each sensor node SN performs conversion into a plurality of subcarrier frequencies corresponding to the observed value at the same time timing.

  Such frequency axis mapping is also used, for example, in the invention relating to “wireless communication method, wireless communication device, wireless communication program, and wireless communication system” described in Table 2009-084464.

  FIG. 5A is a diagram schematically illustrating the principle of frequency axis mapping according to the present invention. FIG. 5A shows a first axis indicating the observed value and a second axis indicating the subcarrier frequency number.

First, the observation value is set as k, the minimum value of the observation range is set as K _min , the maximum value is set as K _max , and the center value is set as K _mid . Here, the observation range center value K _mid is the center value of the maximum value and the minimum value of the observation range, and is defined by the following expression.
K _mid = (K _max + K _min ) / 2

The value W that is half the width of the observation range is defined as follows.
W = (K _max −K _min ) / 2

Then, the sub-carrier frequency number placed and _{n C,} the minimum value of the sub-carrier frequency number placed and _{N min,} also the maximum value is placed and _{N max,} centered value _{N mid.} Here, the subcarrier frequency center number N _mid is a center value between the maximum value and the minimum value of the subcarrier frequency number, and is defined by the following equation.
N _mid = (N _max + N _min ) / 2

In order for such a subcarrier frequency center number N _mid to exist, the total number of subcarriers must be an odd number, and an integer A defined as follows exists.
N _max -N _min = 2W / A

A specific calculation method of frequency axis mapping will be described. If the observation value k is less than or equal to the observation range minimum value _Kmin , a subcarrier frequency minimum number _Nmin is assigned. Similarly, if the observed value k is greater than or equal to the observed range maximum value _Kmax , a subcarrier frequency maximum number _Nmax is assigned.

すなわち、観測値ｋと、観測範囲中心値Ｋ_ｍｉｄとの差を、整数２Ａの逆数で離散化し、小数点以下を切り捨てた上で、対応するサブキャリア周波数番号ｎ_Ｃと、サブキャリア周波数中心番号Ｎ_ｍｉｄとの差に置き換えることが出来る。 The observed value k is other than the above, that is, K _min <k <K _max
For allocates the sub-carrier frequency number n _C carved observations k an integer 2A. At this time, the assigned subcarrier frequency number n _C is calculated by the following equation.

That is, the difference between the observed value k and the observed range center value K _mid is discretized by the reciprocal of the integer 2A, and after the decimal point is rounded down, the corresponding subcarrier frequency number n _C and subcarrier frequency center number N It can be replaced with the difference from _mid .

FIG. 5B is a diagram showing a specific example of frequency axis mapping according to the present invention. In this example, the temperature is measured in a range of 20 to 30 ° C., and mapping is performed in a range of subcarrier frequency numbers 0 to 100. Considering FIG. 5A,
K _min = 20
K _max = 30
K _mid = 25
W = 5
N _min = 0
N _max = 100
N _mid = 50
A = 50
More specifically, the frequency axis mapping is equivalent to calculating the following expression.

表１の例において、第１のセンサノードが観測した温度は２０．０°Ｃだったので、０番のサブキャリア周波数が割り当てられる。同様に、第２のセンサノードが観測した温度は１８．９°Ｃだったので、０番のサブキャリア周波数が割り当てられる。第３のセンサノードが観測した温度は２３．４°Ｃだったので、３４番のサブキャリア周波数が割り当てられる。第４のセンサノードが観測した温度は２８．２°Ｃだったので、８２番のサブキャリア周波数が割り当てられる。第５のセンサノードが観測した温度は３０．１°Ｃだったので、１００番のサブキャリア周波数が割り当てられる。第６のセンサノードが観測した温度は３１．３°Ｃだったので、１００番のサブキャリア周波数が割り当てられる。 Table 1 shows an example in which frequency subcarrier numbers are calculated from observation information acquired by six sensor nodes using the above mapping method.

In the example of Table 1, since the temperature observed by the first sensor node was 20.0 ° C., the 0th subcarrier frequency is assigned. Similarly, since the temperature observed by the second sensor node was 18.9 ° C., the 0th subcarrier frequency is assigned. Since the temperature observed by the third sensor node was 23.4 ° C., the 34th subcarrier frequency was assigned. Since the temperature observed by the fourth sensor node was 28.2 ° C., the 82nd subcarrier frequency is assigned. Since the temperature observed by the fifth sensor node was 30.1 ° C., the subcarrier frequency of No. 100 is assigned. Since the temperature observed by the sixth sensor node was 31.3 ° C., the 100th subcarrier frequency was assigned.

Up to this point, as previously proposed in the invention described in Patent Document 2, the present invention further uses the frequency axis shift circuit 191 to determine the correspondence between the observed value before conversion and the frequency after conversion. Then, frequency axis shift processing is performed that varies according to the number of times of information collection _ng . Further, in the present embodiment, the correspondence relationship between the observation value before conversion and the frequency after conversion is also changed according to the observation position information of the sensor node SN.

The frequency axis shift process performed by the frequency axis shift circuit 191 will be described. Here, as an example, first, for each sensor node SN, a shift is performed according to one or both of the first coordinate value x and the second coordinate value y, which are observation position information, and the number of times of information collection _ng. The quantity n _shift is calculated. In this example, the following conversion formula is used using only the first coordinate value x.
n _shift = xx ( _ng- 1)

Next, the correspondence between the observed value before the conversion and the frequency after the conversion is shifted according to the calculated shift amount n _shift . In this example, the following conversion formula is used.
n ′ _car = (n _car + n _shift ) mod N _car
Here, “n ′ _car ” indicates the frequency subcarrier number after the shift, “n _car ” indicates the frequency subcarrier number before the shift, and “N _car ” indicates the total number of frequency subcarriers used for frequency axis mapping. Indicates. “Mod” is a symbol meaning modulo calculation.

  The frequency mapping process of the present application in which the frequency axis shift process described above is introduced will be described in more detail using a specific example.

  FIG. 6A is a diagram illustrating a first state of an example of the frequency axis shift process of the present application. In the example illustrated in FIG. 6A, the first sensor node A to the seventh sensor node G are arranged in a total of 16 cells of 4 columns × 4 rows. The first sensor node A is arranged in the cell in the vertical 0th column and the horizontal 3rd row, and the observed value is “1”. The second sensor node B is arranged in the cell in the second vertical column and the third horizontal row, and the observed value is “1”. The third sensor node C is arranged in a cell in the first vertical column and the second horizontal row, and the observation value is “2”. The fourth sensor node D is arranged in the cell in the vertical 0th column and the horizontal first row, and the observation value is “2”. The fifth sensor node E is arranged in the cell in the second vertical column and the first horizontal row, and the observation value is “3”. The sixth sensor node F is arranged in the cell in the second vertical column and the zeroth horizontal row, and the observation value is “4”. The seventh sensor node G is arranged in a cell in the third vertical column and the zeroth horizontal row, and the observation value is “3”.

In this example, in the first information collection, that is, when the number of times of information collection n _g = 1, the shift amount n _shift is always 0, and therefore the same result as when the frequency axis shift process is not performed is obtained. In each sensor node, frequency subcarrier numbers obtained from the observed values by frequency mapping processing are as shown in Table 2. In Table 2, the portion highlighted by the shaded line indicates the frequency component included in the actually transmitted signal.

As shown in FIG. 6A and Table 2, when the number of times of information collection n _g = 1, at time t ₀ , the first sensor node A has a unit signal having a frequency f ₁ corresponding to the observed value “1”. The fourth sensor node D transmits a unit signal having a frequency f ₂ corresponding to the observation value “2”. At time t _1, the third sensor node C transmits a unit signal having a frequency f ₂ corresponding to the observed value "2". At time t ₂ , the second sensor node B transmits a unit signal having a frequency f ₁ corresponding to the observation value “1”, and the fifth sensor node E has a frequency f ₃ corresponding to the observation value “3”. The sixth sensor node F transmits a unit signal having a frequency f ₄ corresponding to the observation value “4”. At time t ₃ , the seventh sensor node G transmits a unit signal having a frequency f ₃ corresponding to the observed value “3”.

Further, at time t ₄ , the sixth sensor node F transmits a unit signal having a frequency f ₄ corresponding to the observation value “4”, and the seventh sensor node G transmits a frequency f corresponding to the observation value “3”. A unit signal having ₃ is transmitted. At time t ₅ , the fourth sensor node D transmits a unit signal having the frequency f ₂ corresponding to the observation value “2”, and the fifth sensor node E transmits the frequency f ₃ corresponding to the observation value “3”. The unit signal which has is transmitted. At time t _6, the third sensor node C transmits a unit signal having a frequency f ₂ corresponding to the observed value "2". At time t ₇ , the first sensor node A transmits a unit signal having the frequency f ₁ corresponding to the observation value “1”, and the second sensor node B has the frequency f ₁ corresponding to the observation value “1”. The unit signal which has is transmitted.

  According to the present invention, as described above, the observation information is converted into the subcarrier frequency, the observation position information is converted into the transmission timing, and the transmission is performed, thereby, compared with the transmission method using the packet in the prior art, Very high speed transmission is possible. This is particularly noticeable when the number of sensor nodes is large. For example, if the number of sensor nodes is 2500, in the case of a transmission method compliant with the conventional ZigBee, the minimum packet size (for example, 127 bytes = 1016 bits) that can include observation information and observation position information, and the packet transmission rate is 250 kilobits. Even if an ideal environment where no collision of packets from each sensor node occurs is assumed every second, it takes about 10 seconds to transmit information of all nodes. On the other hand, in the case of the transmission method of the present invention, one slot representing one transmission timing is set to 40 microseconds with a margin of about 10 times that of a general wireless LAN, and one cell per group (that is, the above α) = 1), even if the information of each node is transmitted without being aggregated at all (that is, 2500 transmissions are performed), it is only about 100 milliseconds.

FIG. 6B is a diagram illustrating a second state of the example of the frequency axis shift process of the present application. The arrangement of the first sensor node A to the seventh sensor node G in FIG. 6B is the same as that in the case of FIG. FIG. 6B shows the case of the second information collection, that is, the number of information collection times n _g = 2. At this time, the shift amount n _shift is calculated according to the coordinate value x on the horizontal axis, and the result is as shown in Table 3. In Table 3, the portion highlighted by the shaded line indicates the frequency component included in the actually transmitted signal. As an example, since the value of the horizontal coordinate x is 2 in the second sensor node B, the frequency associated with the observed value “1” is 2 subcarriers from f ₁ to f ₃ shown in Table 2. Just shifted. Similarly, in the seventh sensor node G, since the value of the horizontal coordinate x is 3, the frequency associated with the observation value “3” is changed from f ₃ to f ₁ shown in Table 2 to −2 sub Only the carrier, ie, 3 subcarriers in modulo 5, is shifted.

As shown in FIG. 6B and Table 3, when the number of times of information collection n _g = 2, at time t ₀ , the first sensor node A has a unit signal having a frequency f ₁ corresponding to the observed value “1”. The fourth sensor node D transmits a unit signal having a frequency f ₂ corresponding to the observation value “2”. At time t _1, the third sensor node C transmits a unit signal having a frequency f ₃ corresponding to the observed value "2". At time t ₂ , the second sensor node B transmits a unit signal having a frequency f ₃ corresponding to the observation value “1”, and the fifth sensor node E has a frequency f ₅ corresponding to the observation value “3”. The sixth sensor node F transmits a unit signal having a frequency f ₁ corresponding to the observed value “4”. At time t ₃ , the seventh sensor node G transmits a unit signal having a frequency f ₁ corresponding to the observed value “3”.

Further, at time t ₄ , the sixth sensor node F transmits a unit signal having the frequency f ₁ corresponding to the observation value “4”, and the seventh sensor node G transmits the frequency f corresponding to the observation value “3”. A unit signal having ₁ is transmitted. At time t ₅ , the fourth sensor node D transmits a unit signal having a frequency f ₂ corresponding to the observation value “2”, and the fifth sensor node E has a frequency f ₅ corresponding to the observation value “3”. The unit signal which has is transmitted. At time t _6, the third sensor node C transmits a unit signal having a frequency f ₃ corresponding to the observed value "2". At time t ₇ , the first sensor node A transmits a unit signal having a frequency f ₁ corresponding to the observation value “1”, and the second sensor node B has a frequency f ₃ corresponding to the observation value “1”. The unit signal which has is transmitted.

FIG. 6C is a diagram illustrating a third state regarding an example of the frequency axis shift process of the present application. The arrangement of the first sensor node A to the seventh sensor node G in FIG. 6C is the same as in the case of FIG. 6A and FIG. 7A, and thus further detailed description is omitted. FIG. 6C shows the case of information collection for the third time, that is, the number of information collection times n _g = 3. At this time, the shift amount n _shift is calculated according to the coordinate value x on the horizontal axis, and the result is as shown in Table 4. In Table 4, the portion highlighted by the shaded line indicates the frequency component included in the actually transmitted signal. As an example, since the value of the horizontal coordinate x is 2 in the second sensor node B, the frequency associated with the observed value “1” is changed from 4 to ₅ in f ₁ to f ₅ shown in Table 2. Just shifted. Similarly, in the seventh sensor node G, since the value of the horizontal coordinate x is 3, the frequency associated with the observed value “3” is 1 subcarrier from f ₃ to f ₄ shown in Table 2. Only, ie modulo 5 and 6 subcarriers are shifted.

As shown in FIG. 6C and Table 4, when the number of information collections n _g = 3, at time t ₀ , the first sensor node A has a unit signal having a frequency f ₁ corresponding to the observed value “1”. The fourth sensor node D transmits a unit signal having a frequency f ₂ corresponding to the observation value “2”. At time t _1, the third sensor node C transmits a unit signal having a frequency f _4, corresponding to the observed value "2". At time t ₂ , the second sensor node B transmits a unit signal having a frequency f ₅ corresponding to the observation value “1”, and the fifth sensor node E has a frequency f ₂ corresponding to the observation value “3”. The sixth sensor node F transmits a unit signal having a frequency f ₃ corresponding to the observation value “4”. At time t ₃ , the seventh sensor node G transmits a unit signal having a frequency f ₄ corresponding to the observed value “3”.

Further, at time t ₄ , the sixth sensor node F transmits a unit signal having a frequency f ₃ corresponding to the observed value “4”, and the seventh sensor node G transmits a frequency f corresponding to the observed value “3”. A unit signal having ₄ is transmitted. At time t ₅ , the fourth sensor node D transmits a unit signal having a frequency f ₂ corresponding to the observation value “2”, and the fifth sensor node E has a frequency f ₂ corresponding to the observation value “3”. The unit signal which has is transmitted. At time t _6, the third sensor node C transmits a unit signal having a frequency f _4, corresponding to the observed value "2". At time t ₇ , the first sensor node A transmits a unit signal having the frequency f ₁ corresponding to the observation value “1”, and the second sensor node B has the frequency f ₅ corresponding to the observation value “1”. The unit signal which has is transmitted.

As described above, according to the frequency axis mapping process in which the frequency axis shift process according to the present invention is introduced, the value of the information collection count _ng is changed each time the information transmission request signal is transmitted. Even if the observation information at the sensor node is the same, different received signals can be generated.

  The reception of the unit signal aggregate and the power detection thereof performed in the fifth step S5 will be described in detail. The reception server S detects the power of the received unit signal for each time at which the unit signal is received and for each subcarrier frequency, compares the received unit signal with a predetermined threshold, and determines the valid unit signal, the invalid unit signal, Sort out. The unit signal selected as valid is stored in the database 333 of the receiving server S or the like.

  The determination of the common subcarrier performed in the sixth step S6 will be described in more detail.

  FIG. 7A is a diagram illustrating an example of common subcarriers obtained from the first state illustrated in FIG. 6A. FIG. 7A shows a lattice composed of four columns, four rows, and a total of 16 cells, as in FIG. 6A. The 16 cells shown in FIG. 7A indicate intermediate data generated for the reception server S to estimate observation information transmitted from the sensor node.

Of the 16 cells shown in FIG. 7A, attention is paid to the leftmost and topmost cell. As shown in FIG. 6A, time t ₀ and time t ₇ correspond to this cell. The reception server S receives a unit signal including only f ₁ and f ₂ as frequency components at time t ₀ , and receives a unit signal including only f _{1 at} time t ₇ . . From these facts, the restoration circuit 37 of the reception server S estimates that the frequency component received in common at both times, that is, f ₁ that is the common subcarrier frequency is transmitted from this cell. Actually, the first sensor node A is arranged in this cell, and the first sensor node A measures the observation value “1” converted into the frequency f ₁ . The above estimation by the restoration circuit 37 has reached correct observation information.

Next, attention is focused on the second cell from the left and the third cell from the top among the 16 cells shown in FIG. As shown in FIG. 6A, time t ₁ and time t ₅ correspond to this cell. The receiving server S, at time t ₁ has received a unit signal containing only f ₂ as a frequency component, also at time t ₅ is receiving a unit signal containing only f ₂ and f ₃ . From these facts, the restoration circuit 37 of the receiving server estimates that f ₂ that is the common subcarrier frequency is transmitted from this cell. However, actually, no sensor node is arranged in this cell, and the restoration circuit 37 of the receiving server S has detected observation information that does not exist.

Also, pay attention to the third cell from the left and the bottom cell among the 16 cells shown in FIG. 7A. As shown in FIG. 6A, time t ₂ and time t ₄ correspond to this cell. The receiving server S, at time _{t 2} has received a unit signal containing only _f 1, _{f 3} and _{f 4} as a frequency component, also at time _{t 4} units containing only _{f 3} and _{f 4} A signal is being received. From these factifications, the restoration circuit 37 of the receiving server S estimates that both the common subcarrier frequencies f ₃ and f ₄ have been transmitted from this cell. However, actually, the sixth sensor node F is arranged in this cell, and the sixth sensor node F measures only the observation value “4” converted into the frequency f ₄ . Thus, the restoration circuit 37 of the receiving server S has detected observation information that is partially correct and partially incorrect.

In the example shown in FIG. 7A, correct observation information is detected in cells indicated by thin hatched lines, and observation information that does not exist in cells indicated by dark hatched lines is detected. In the stage of the sixth step S6, regardless of whether the detected observation information is correct or incorrect, the information of the common subcarrier shown in FIG. 7A is associated with the value of the information collection count n _g = 1, and the database of the receiving server S Stored in 333.

FIG. 7B is a diagram illustrating an example of the common subcarrier obtained from the second state illustrated in FIG. 6B. In the case of the number of times of information collection n _g = 2 shown in FIG. 7B, the correct observation information is detected in the cells indicated by the thin shaded lines as in the case of the number of times of information collection n _g = 1 shown in FIG. 7A. Observation information that does not exist in the cells indicated by the dark shaded lines is detected. Here, regardless of whether the detected observation information is correct or not, the information on the common subcarrier shown in FIG. 7A is stored in the database 333 of the receiving server S in association with the value of the information collection count n _g = 2.

FIG. 7C is a diagram illustrating an example of common subcarriers obtained from the third state illustrated in FIG. 6C. Even when the number of times of information collection _ng = 3 shown in FIG. 7C, correct observation information is detected in the cells indicated by the thin shaded lines, as in the case of the number of times of information collection _ng = 1 shown in FIG. 7A. Observation information that does not exist in the cells indicated by the dark shaded lines is detected. Here, regardless of whether the detected observation information is correct or not, the information on the common subcarrier shown in FIG. 7A is stored in the database 333 of the receiving server S in association with the value of the information collection count n _g = 3.

  However, the arrangement of the cells in which the correct observation information is detected is substantially the same in FIGS. 7A, 7B, and 7C, whereas the arrangement of the cells in which the non-existent observation information is detected is as shown in FIGS. 7A and 7B. And FIG. 7C are different. This is an effect of the frequency axis shift processing according to the present application.

The calculation of the common subcarrier detection probability performed in the eighth step S8 will be described in detail. When collecting information number n _g at the seventh step S7 in has reached the collected count threshold N _g, i.e., when the intermediate data related to the common sub-carrier obtained in step S6 of the sixth is sufficiently accumulated, the receiving server The S restoration circuit 37 calculates the probability that a common subcarrier is detected for each cell. In other words, while the information collection number _ng is less than the collection number threshold value _Ng, it is a training period for improving the estimation accuracy, and the estimation operation is not started.

In this example, the value of the collection frequency threshold _Ng is set to 3. Incidentally, the present inventor has vertical 400 lines, horizontal 400 lines, even when placing the sensor nodes randomly half of the large area of the total 160,000 cells, the value of the collected count threshold N _g is about 4 practical It was confirmed that a typical estimation result was obtained.

  FIG. 8 is a diagram illustrating the detection probability of common subcarriers according to the example illustrated in FIGS. 7A, 7B, and 7C. FIG. 8 also shows a lattice composed of four columns, four rows, and a total of 16 cells. The 16 cells shown in FIG. 8 correspond to the 16 cells shown in FIGS. 6A, 6B, 6C, 7A, 7B, and 7C, respectively. For each of the 16 cells, the restoration circuit 37 of the receiving server S reads the data stored in the database 333 and calculates the probability of detection as to whether or not the common subcarrier is detected in the sixth step S6. . In this example, any of four types of 0, 1/3, 2/3, or 1 in total is calculated as the probability that a common subcarrier is detected in each cell.

  The cell selection performed in the ninth step S9 will be described in detail. In this example, the detection probability threshold is set to 1. That is, out of the 16 cells shown in FIG. 8, for cells in which the probability that a common subcarrier is detected is less than 1, it is estimated that correct observation information is not detected in the sixth step S <b> 6. Exclude from future restoration process. In the case of FIG. 8, when attention is paid to a cell having a detection probability equal to 1, it coincides with a cell in which the first sensor node A to the seventh sensor node G are actually arranged. Further, if attention is paid to a cell having a detection probability of less than 1, it matches a cell in which no sensor node is actually arranged.

  However, it is also conceivable that the detection probability of the common subcarrier does not reach 1 even in the cell where the sensor node is actually arranged due to the influence of the radio wave environment. Therefore, it is desirable to appropriately adjust the detection probability threshold according to various conditions for actually operating the wireless sensor network system and the information batch collection method of the present application. In addition, by appropriately performing such adjustment, when a part of the plurality of sensor nodes SN moves across the cell, stops the operation in the middle, or conversely starts the operation in the middle, It is possible to exclude the unit signal transmitted from such an irregular sensor node from the estimation process by the receiving server S.

The observation information estimation performed in the tenth step S10 will be described in detail. In this example, a case where the number of information collections n _g = threshold number of collections n _g = 3 will be described. Of the common subcarrier information detected in the sixth step S6 and accumulated in the database 333, attention is paid to the latest information, that is, the common subcarrier information shown in FIG. 7C. From here, cells that have not reached the detection probability threshold in the ninth step S9 are excluded.

  FIG. 9A is a diagram illustrating a state in which cells in which the detection probability illustrated in FIG. 8 has not reached the detection probability threshold are excluded from the common subcarriers illustrated in FIG. 7C. In this example, the cell in the second column from the left and the bottom row, and the cell in the rightmost column and the second row from the top are excluded. Is shown.

  FIG. 9B is a diagram illustrating a state in which common subcarriers remaining without being excluded are extracted from FIG. 9A.

Thereafter, the restoration circuit 37 of the reception server S performs the inverse transformation of the frequency axis shift process for the common subcarriers of the cells that remain without being excluded, that is, the common subcarriers estimated to be transmitted from the sensor nodes that actually exist. By doing so, the subcarrier frequency before performing the frequency axis shift process is calculated. This inversion is performed using, for example, the following inversion formula.
n _com = (n ′ _com −n _shift ) mod N _car
Here, “n _com ” indicates a common subcarrier after reverse conversion, and “n ′ _com ” indicates a common subcarrier before reverse conversion.

  FIG. 9C is a diagram illustrating an example of a result obtained by performing inverse transformation of frequency axis shift processing on the common subcarriers extracted in FIG. 9B.

Finally, inverse conversion of the frequency axis mapping process is performed on the common subcarriers obtained as a result of the inverse conversion of the frequency axis shift process, and observation information before the frequency axis mapping process is estimated. This inversion is performed using, for example, the following inversion formula.
k _est (x, y) = A × n _com −W + K _mid
Here, “k _est ” indicates a value estimated by the receiving server S from the observation value measured in the cell at the coordinates (x, y), “A” indicates the step size of the observation value, and “W” indicates the observation value. The half value of the range from the lower limit to the upper limit of the value is shown, and “K _mid ” shows the median value of the observed values. Note that the step size A, the half value W, and the median value K _mid are stored in advance in the data 332 of the receiving server S and the data 132 of each sensor node SN.

  FIG. 9D is a diagram illustrating an example of a result obtained by performing the inverse transformation of the frequency axis mapping process on the common subcarrier illustrated in FIG. 9C. In this example, it can be confirmed that the estimation result by the receiving server S matches the observation value of each cell shown in FIG. 6C.

  As described above, the wireless sensor network system according to the present invention and the information batch collection method using the same greatly increase the time required for signal transmission from the sensor node SN to the receiving server S by time axis mapping and frequency axis mapping. The estimation accuracy is improved by shifting the frequency axis and accumulating past received signals.

  In the wireless sensor network system and the information batch collection method according to the present invention, the reception server S, each of the plurality of sensor nodes SN, the total number of the plurality of sensor nodes SN up to the user, Since it is not necessary to know whether the SN is arranged, it can be said that operation with a high degree of freedom is possible.

(Second Embodiment)
In the first embodiment described above, selection of a common subcarrier with a high detection probability and estimation of observation information are performed on the assumption that at most one sensor node is arranged in each cell. However, in actual operation, there are multiple sensor nodes in the same cell, some sensor nodes move across cells, and some sensor nodes contact the receiving server in the middle of a series of information collection. Various irregularities can be considered, such as communication being interrupted. Therefore, by combining each process performed in the first embodiment with each operation such as determination, estimation, and interpolation proposed in Patent Document 2, it is possible to further improve the estimation accuracy.

  FIG. 10A is a distribution diagram illustrating an example of frequencies of a plurality of unit signals transmitted by a plurality of sensor nodes. In the present embodiment, as an example, a case will be described in which a plurality of sensor nodes are arranged in an area of 9 cells in total of 3 columns and 3 rows.

  In the present embodiment, the presence determination of a common subcarrier frequency is performed in combination with or instead of the eighth step S8 in the first embodiment. In the present embodiment, as a precondition, it is assumed that the number of sensor nodes SN arranged in one cell C is one or less, and the receiving server S does not grasp this arrangement.

FIG. 10B is a determination diagram illustrating a result of determination of the existence of a common subcarrier frequency performed based on the example of FIG. 10A. The determination diagram of FIG. 10B represents the same nine cells C as the distribution diagram of FIG. 10A, and the time t ₀ to t ₂ is assigned to the horizontal axis, and the times t ₃ to t ₅ are assigned to the vertical axis. .

Note cell C in FIG. 10B where time t ₀ and time t ₅ intersect. CPU32 of receiving server S references the table 5 summarizes the received result, a time t _0, to search for common subcarrier frequency in the time t _5. Since the common subcarrier frequencies are the first subcarrier frequency f ₁ and the second subcarrier frequency f ₂ , this result is a cell where time t ₀ and time t _{5 in} FIG. 10B intersect. It is associated with C and recorded in the memory 33 of the receiving server S.

Similarly, the common subcarrier frequencies f ₂ and f ₃ are recorded corresponding to the cell C where the time t ₁ and the time t ₅ intersect. And time t _2, the can and the time t ₅ corresponding to the cell C that intersect, the sub-carrier frequency f ₃ in common is recorded. And time t _0, corresponding to the cell C in which the time t ₄ intersect, the subcarrier frequency f ₂ that is common is recorded. The time t _1, and the time t ₄ corresponding to the cell C that intersect, the subcarrier frequency f ₂ and f ₃ common is recorded. And time t _2, the can and the time t ₄ corresponding to the cell C that intersect, the sub-carrier frequency f ₃ in common is recorded. Corresponding to the cell C where the time t ₁ and the time t ₃ intersect, a common subcarrier frequency f ₄ is recorded. And time t _2, the time and t ₃ is corresponding to the cell C that intersect, the sub-carrier frequency f ₅ in common is recorded. Note that the cell C at which the time t ₀ and the time t ₃ intersect does not have a common subcarrier frequency, so that the record remains blank.

FIG. 10C is a comparison diagram showing a difference from FIG. 10A showing the distribution of the transmission signal in FIG. 10B showing the determination result from the reception signal. In FIG. 10C, four cells C having different determination results from the actual distribution are shown as uncertain areas UZ. Here, the uncertain area UZ includes a cell C corresponding to a combination of time t ₀ and time t ₅ , a cell C corresponding to a combination of time t ₁ and time t _{5, and} a combination of time t ₁ and time t ₄ . it includes a cell C corresponding, and a cell C corresponding to the combination of the time t ₂ and time t ₄ to.

ここで、ｘ’は対象となるセルＣの横方向の座標を表し、ｙ’は対象となるセルＣの縦方向の座標を表し、ｋ_ｅｓｔは座標ｘ’，ｙ’の対象となるセルＣにおける観測情報の推定値を表し、Ｎは対象となるセルＣで候補として挙がっているサブキャリア周波数の総数を表し、Ｎ^ｉ _ｃｏｍはｉ番目の候補となるサブキャリア周波数を表す。 In this embodiment, for each cell C, the subcarrier frequency that is the determination result is inversely converted into observation information, and when a plurality of subcarrier frequencies are listed as candidates, the average value of the inversely converted values is calculated, Estimated value of observation information. This operation is generalized by the following equation.

Here, x ′ represents the horizontal coordinate of the target cell C, y ′ represents the vertical coordinate of the target cell C, and k _est represents the target cell C of the coordinates x ′ and y ′. , N represents the total number of subcarrier frequencies listed as candidates in the target cell C, and N ⁱ _com represents the i-th candidate subcarrier frequency.

When this equation is applied to FIG. 10B, the following estimation result is obtained.
k _est (t ₀ , t ₃ ) = unknown k _est (t ₀ , t ₄ ) = Af ₂ −W + K _mid
k _est (t ₀ , t ₅ ) = (1/2) {(Af ₁ −W + K _mid ) + (Af ₂ −W + K _mid )}
k _est (t ₁ , t ₃ ) = Af ₄ −W + K _mid
k _est (t ₁ , t ₄ ) = (1/2) {(Af ₂ −W + K _mid ) + (Af ₃ −W + K _mid )}
k _est (t ₁ , t ₅ ) = (1/2) {(Af ₂ −W + K _mid ) + (Af ₃ −W + K _mid )}
k _est (t ₂ , t ₃ ) = Af ₅ −W + K _mid
k _est (t ₂ , t ₄ ) = Af ₃ −W + K _mid
k _est (t ₂ , t ₅ ) = Af ₃ −W + K _mid

  At this time, for the cell C in which the estimated value remains unknown, interpolation based on the estimated value of the surrounding cell C may be performed.

More specifically, the cell C in which the estimated value is determined is detected from the cells C adjacent to the cell C whose estimated value is unknown, and the average value of the estimated values in these cells C is calculated. An unknown estimated value may be interpolated. An example of the series of procedures is shown below.
Procedure 1: Interpolate observation information of cells in which observation information of cells other than one of the adjacent cells is estimated. The average value of the estimated observation information of cells adjacent to the cell whose observation information is to be interpolated is taken as the observation information of that cell.
Procedure 2: Procedure 1 is repeated until there is no cell for which observation information of cells other than one is estimated among neighboring cells.
Procedure 3: Interpolate observation information of a cell whose estimated observation information is determined in at least one of adjacent cells. The average value of the estimated observation information of cells adjacent to the cell whose observation information is to be interpolated is taken as the observation information of that cell.
Procedure 4: Repeat steps 1 to 3 until the observation information of all cells is interpolated.
The above interpolation method is referred to as a first interpolation method for convenience.

ここで、ｋ’は補間対象セルの推定値を示し、ｋ’_ｉは推定値が確定しているｉ番目のセルの推定値を示し、ｗ_ｉはｉ番目の推定値に対応する重みを示す。 Alternatively, interpolation using an inverse distance weighting method may be performed. The inverse distance weighting method calculates the distance from the cell C whose estimated value is unknown to the cell C where the estimated value is fixed, weights the estimated value by the reciprocal of this distance, and the weighted average value is unknown. This is a method of interpolating estimated values. This calculation can be expressed by the following equation, for example.

Here, k ′ indicates the estimated value of the interpolation target cell, k ′ _i indicates the estimated value of the i-th cell for which the estimated value is fixed, and w _i indicates the weight corresponding to the i-th estimated value. .

ここで、ｄ_ｉは推定値が確定しているｉ番目のセルから補間対象セルまでの距離を示し、Ｄは逆距離加重乗数を示す。 This weight w _i can be expressed by the following equation, for example.

Here, d _i represents the distance from the i-th cell whose estimated value is fixed to the interpolation target cell, and D represents the inverse distance weighted multiplier.

  At this time, not only the cell C adjacent to the cell C whose estimated value is unknown, but also a cell C farther away may be included. In addition, the inverse distance weighting constant D used for calculating the reciprocal of the distance is not limited to 1, but other numerical values such as 2, for example, distribution characteristics of observation attributes obtained theoretically, empirically, and experimentally in advance ( You may choose suitably according to a spatial correlation etc.). The above interpolation method is called a second interpolation method for convenience.

  In the wireless sensor network communication method using the restoration method according to the present embodiment, even if an estimated value different from the information transmitted by the sensor node SN may be obtained, the difference between the estimated value and the actual value is to some extent. It is expected that the accuracy will be maintained. Even if the determination result obtained in the middle of restoration is different from the correct answer, it is expected that the error will be reduced by calculating the average value thereafter. This restoration method is particularly effective when the distribution of observation objects has a spatial correlation.

(Third embodiment)
In the present embodiment, a case where restoration can be performed with higher accuracy than in the second embodiment of the present invention will be described. Here, as a precondition, it is assumed that the observation target has a spatial correlation as in the case of the second embodiment of the present invention, and that the receiving server S knows in advance the arrangement of all the sensor nodes SN. .

In the present embodiment, since the receiving server S knows all the arrangement of the sensor node SN, the sensor node SN as a cell C corresponding to the time t ₂ and time t ₄ in the first embodiment of the present invention is If it is not arranged, the observation information can be correctly determined as “unknown”.

  After that, the same estimation method as in the first embodiment of the present invention is performed, that is, when there are a plurality of subcarrier frequency candidates in the same cell C, the respective inverse transform values are averaged.

When the estimation method according to the present embodiment is applied to FIG. 10B, the following estimation result is obtained.
k _est (t ₀ , t ₃ ) = unknown k _est (t ₀ , t ₄ ) = Af ₂ −W + K _mid
k _est (t ₀ , t ₅ ) = (1/2) {(Af ₁ −W + K _mid ) + (Af ₂ −W + K _mid )}
k _est (t ₁ , t ₃ ) = Af ₄ −W + K _mid
k _est (t ₁ , t ₄ ) = (1/2) {(Af ₂ −W + K _mid ) + (Af ₃ −W + K _mid )}
k _est (t ₁ , t ₅ ) = (1/2) {(Af ₂ −W + K _mid ) + (Af ₃ −W + K _mid )}
k _est (t ₂ , t ₃ ) = Af ₅ −W + K _mid
k _est (t ₂ , t ₄ ) = unknown k _est (t ₂ , t ₅ ) = Af ₃ −W + K _mid

  Even in the wireless sensor network communication method using the restoration method according to the present embodiment, the same effect as in the case of the first embodiment of the present invention can be obtained. That is, even if an estimated value different from the information transmitted by the sensor node SN may be obtained, it is expected that the difference between the estimated value and the actual value is maintained to a certain degree of accuracy. This restoration method is particularly effective when the distribution of observation objects has a spatial correlation.

(Fourth embodiment)
In the present embodiment, a case where restoration can be performed with higher accuracy than in the second embodiment of the present invention will be described. Here, as a precondition, as in the case of the second embodiment of the present invention, the observation target has a spatial correlation, and each cell C has at most one sensor node SN. Is guaranteed.

  In the restoration method according to the present embodiment, the subcarrier frequency of cell C having only one subcarrier frequency candidate is determined by this candidate as a pre-stage of averaging of a plurality of candidates performed in the second embodiment of the present invention. To do. The confirmed candidates are excluded from the subsequent averaging. This process is preferably repeated until there are no more definable candidates.

  The restoration method according to the present embodiment will be described in more detail using a specific example. First, consider a case where the unit signals are transmitted as shown in FIG. 10A by the plurality of sensor nodes SN, and the unit signals are received as shown in Table 5 by the receiving server S.

Next, referring to Table 5, cell C having only one subcarrier frequency candidate is searched. In the example of Table 5, the candidate of the cell C corresponding to the combination of the time t ₀ and time t ₄ it has become only the second sub-carrier frequency f _2. Similarly, the candidate of the cell C corresponding to the combination of the time t ₁ and time t ₃ has been only the fourth sub-carrier frequency f _4. The candidate for cell C corresponding to the combination of time t ₂ and time t ₃ is only the fifth subcarrier frequency f ₅ . The candidate for cell C corresponding to the combination of time t ₂ and time t ₄ is only the third subcarrier frequency f ₃ . Candidate cell C corresponding to the combination of the time t ₂ and time t ₅ has become only the third sub-carrier frequency f _3. These single candidates are determined as estimated values of observation information in each cell C.

The determined estimated value is obtained by inverse transformation using the following equation.

As a result, the estimated value of the observation information for the five cells C is determined as follows.
k _est (t ₀ , t ₄ ) = Af ₂ −W + K _mid
k _est (t ₁ , t ₃ ) = Af ₄ −W + K _mid
k _est (t ₂ , t ₃ ) = Af ₅ −W + K _mid
k _est (t ₂ , t ₄ ) = Af ₃ −W + K _mid
k _est (t ₂ , t ₅ ) = Af ₃ −W + K _mid

表６において、表５から削除されたデータは「０」で上書きしているが、これはあくまでも一例であって、本発明を限定するものではない。 Next, data related to the confirmed single candidate is deleted from Table 5. As a result, Table 6 is obtained.

In Table 6, the data deleted from Table 5 is overwritten with “0”, but this is merely an example and does not limit the present invention.

Next, referring to Table 6, the search for cell C having only one subcarrier frequency candidate is repeated. This time, the only candidate for the cell C corresponding to the combination of time t ₀ and time t ₅ is the first subcarrier frequency f ₁ . Similarly, the candidate for cell C corresponding to the combination of time t ₁ and time t ₅ is only the second subcarrier frequency f ₂ .

  FIG. 11A is a diagram illustrating a combination of a cell C corresponding to a second search and its common subcarrier frequency in a specific example illustrating a restoration method according to the fourth embodiment of the present invention. These single candidates are determined as estimated values of observation information in each cell C.

The determined estimated value is inversely transformed by the above equation and calculated as follows.
k _est (t ₀ , t ₅ ) = Af ₁ −W + K _mid
k _est (t ₁ , t ₅ ) = Af ₂ −W + K _mid

Next, when the data related to the determined single candidate is deleted from Table 6, only one piece of data remains at the intersection of the column at time t _{1 and} the row at subcarrier frequency f ₃ . Since this data is insufficient to repeat further searches, no further estimation of the estimate is performed. FIG. 11B is a diagram illustrating a state where there is no corresponding cell C in the third search in the specific example illustrating the fourth embodiment of the present invention.

At this point, the cell C corresponding to the combination of the time t ₁ and time t _4, the estimated value has not been determined. Therefore, for this cell C, the average value is obtained by the same method as in the first embodiment of the present invention.
k _est (t ₁ , t ₄ ) = (1/2) {(Af ₂ −W + K _mid ) + (Af ₃ −W + K _mid )}

In this example, the estimated value of cell C corresponding to the combination of time t ₀ and time t ₃ cannot be obtained. Therefore, for the cell C, the first or second interpolation method may be performed in the same manner as in the first embodiment using the estimated values of the surrounding cells.

  Even in the wireless sensor network communication method using the restoration method according to the present embodiment, the same effect as in the case of the first embodiment of the present invention can be obtained. That is, even if an estimated value different from the information transmitted by the sensor node SN may be obtained, it is expected that the difference between the estimated value and the actual value is maintained to a certain degree of accuracy. This restoration method is particularly effective when there is a spatial correlation in the distribution of the observation target and it is guaranteed that only one sensor node SN is arranged in each cell C at the maximum.

(Fifth embodiment)
In the present embodiment, a case will be described in which restoration can be performed with higher accuracy than in the fourth embodiment of the present invention. Here, as a precondition, as in the case of the fourth embodiment of the present invention, the observation target has a spatial correlation, and each cell C has at most one sensor node SN. Is guaranteed.

  In the restoration method according to the present embodiment, out of the subcarrier frequency candidates of each cell C, a single one in the group is searched, and this is determined as an estimated value of observation information in that cell C. This restoration method will be described in detail with reference to the drawings.

FIG. 12A is a distribution diagram of subcarrier frequencies of a transmission unit signal in a specific example for explaining a restoration method according to the fifth embodiment of the present invention. The example shown in FIG. 12A is different from the example shown in FIG. 10A in the following points. That is, in the example of FIG. 12A, the subcarrier frequency included in the unit signal transmitted from the cell C corresponding to the combination of time t ₂ and time t ₃ is not the _fifth subcarrier frequency f ₅ but the fourth subcarrier frequency. and it has a carrier frequency _{f 4.} The other cell C in FIG. 12A is the same as that in FIG. 10A, and thus further detailed description is omitted.

表７と、表５とでは、以下の点が異なる。すなわち、表５にあった第５のサブキャリア周波数ｆ_５に対応する単位信号の存在判定が表７には無く、また、表５には無かった、時刻ｔ_２の列と、第４のサブキャリア周波数ｆ_４の行との交点における単位信号の存在判定が、表７にはある。表７の、その他の部分は、表５の場合と同様であるので、さらなる詳細な説明を省略する。 In the restoration method according to the present embodiment, first, based on the distribution of unit signals shown in FIG. 12A, as in the case of the first embodiment of the present invention, the presence determination of the common subcarrier frequency is performed. 7 is obtained.

Table 7 and Table 5 differ in the following points. That is, the presence determination of the unit signal corresponding to the fifth subcarrier frequency f ₅ in Table 5 is not included in Table 7, and is not included in Table 5, the column of time t ₂ , and the fourth subcarrier frequency presence determination unit signal at the intersection of the line of the carrier frequency f ₄ is located in the Table 7. The other parts of Table 7 are the same as those in Table 5, and thus further detailed description is omitted.

FIG. 12B is a determination diagram illustrating a result of determination of the presence of a common subcarrier frequency performed based on the example of FIG. 12A in a specific example describing the restoration method according to the fifth embodiment of the present invention. The determination diagram of FIG. 12B and the determination diagram of FIG. 10B differ in the following points. That is, the common subcarrier frequency of cell C corresponding to the combination of time t ₂ and time t ₃ is fourth subcarrier frequency f ₄ in FIG. 12B. The other cell C in FIG. 12B is the same as that in FIG. 10B, and thus further detailed description is omitted.

Next, out of the subcarrier frequency candidates of each cell C, a single one in the group is searched. As a result of searching Table 7, it can be seen that the first subcarrier frequency f ₁ appears only in the cell C corresponding to the combination of time t ₀ and time t ₅ . Therefore, the subcarrier frequency of the cell C is determined to be the _first subcarrier frequency f1, and the observation information of the cell C is estimated by an inverse transformation formula.
k _est (t ₀ , t ₅ ) = Af ₁ −W + K _mid

In addition, from Table 7, data related to the first subcarrier frequency f ₁ is deleted. This state is shown in Table 8.

  Thereafter, restoration is performed in the same manner as in the third embodiment of the present invention. That is, the subcarrier frequency of cell C having only one subcarrier frequency candidate is determined by this candidate. The confirmed candidates are excluded from the subsequent averaging. This process is repeated until there are no more definable candidates.

FIG. 12C is a diagram illustrating a combination of a cell C and a common subcarrier frequency in a state corresponding to Table 8 in a specific example describing the restoration method according to the fourth embodiment of the present invention. FIG. 12C is equivalent to FIG. 12B with the following modifications. That is, the subcarrier frequency that is a candidate for cell C corresponding to the combination of time t ₀ and time t ₅ is deleted. Other cells C in FIG. 12C are the same as those in FIG. 12B, and thus further detailed description is omitted.

Referring to Table 8, when cell C having only one subcarrier frequency candidate is searched, five cells C are applicable, so that the inverse transformation formula is used for these cells C and the observation information is as follows: Presumed.
k _est (t ₀ , t ₄ ) = Af ₂ −W + K _mid
k _est (t ₁ , t ₃ ) = Af ₄ −W + K _mid
k _est (t ₂ , t ₃ ) = Af ₄ −W + K _mid
k _est (t ₂ , t ₄ ) = Af ₃ −W + K _mid
k _est (t ₂ , t ₅ ) = Af ₃ −W + K _mid

Next, when data related to the estimated single candidate is deleted from Table 8, Table 9 is obtained.

As shown in Table 9, the remaining data is the intersection of the column of time t _{1 and} the row of the second subcarrier frequency f ₂ and the intersection of the column of time t _{5 and} the row of the second subcarrier frequency f _2. If, with the column and the third row of the intersection of the subcarrier frequency f ₃ of the time t _1, only one total of three. If a cell C having only one subcarrier frequency candidate is searched again, a cell C corresponding to the combination of time t ₁ and time t ₅ is found, and the observation information is estimated by an inverse transformation equation. .
k _est (t ₁ , t ₅ ) = Af ₂ −W + K _mid
FIG. 12D is a diagram illustrating a combination of a cell C corresponding to the second search and a subcarrier frequency serving as a single candidate in a specific example illustrating the restoration method according to the fourth embodiment of the present invention.

  Next, data related to the estimated single candidate is deleted from Table 9, but since this is as described in the third embodiment of the present invention, further detailed description is omitted.

  Even in the wireless sensor network communication method using the restoration method according to the present embodiment, the same effect as in the case of the third embodiment of the present invention can be obtained. That is, even if an estimated value different from the information transmitted by the sensor node SN may be obtained, it is expected that the difference between the estimated value and the actual value is maintained to a certain degree of accuracy. This restoration method is particularly effective when there is a spatial correlation in the distribution of the observation target and it is guaranteed that only one sensor node SN is arranged in each cell C at the maximum.

(Sixth embodiment)
In the present embodiment, a restoration method when a plurality of sensor nodes SN exist in one cell C will be described using a specific example. Here, as a precondition, the spatial correlation of the observation target may be low, but it is assumed that the receiving server S knows the arrangement of the sensor nodes SN in advance.

FIG. 13A is a distribution diagram showing the arrangement of sensor nodes SN and subcarrier frequencies of unit signals transmitted by each sensor node SN in a specific example for explaining the restoration method according to the sixth embodiment of the present invention. It is. In the example illustrated in FIG. 13A, the arrangement of the sensor nodes SN and the subcarrier frequencies included in the unit signal transmitted by each sensor node SN are as follows. The cell C corresponding to the combination of the time t ₀ and the time t ₅ has a sensor node SN that transmits a unit signal having the first subcarrier frequency f ₁ and a unit signal having the second subcarrier frequency f _2. A sensor node SN for transmission is arranged. The cell C corresponding to the combination of the time t ₁ and the time t ₅ has a sensor node SN that transmits a unit signal having the second subcarrier frequency f ₂ and a unit signal having the third subcarrier frequency f _3. A sensor node SN for transmission is arranged. The cells C corresponding to the combination of the time t ₂ and time t _5, the sensor node SN for transmitting a unit signal having a third sub-carrier frequency f ₃ is arranged. The cells C corresponding to the combination of the time t ₀ and time t _4, the sensor node SN for transmitting a unit signal having a second subcarrier frequency f ₂ is disposed. The cell C corresponding to the combination of the time t ₁ and the time t ₄ has a sensor node SN that transmits a unit signal having the third subcarrier frequency f ₃ and a unit signal having the fourth subcarrier frequency f _4. A sensor node SN for transmission is arranged. The cells C corresponding to the combination of the time t ₂ and time t _4, the sensor node SN is not disposed. In the cell C corresponding to the combination of the time t ₀ and the time t ₃ , a sensor node SN that transmits a unit signal having the third subcarrier frequency f ₃ is arranged. In the cell C corresponding to the combination of the time t ₁ and the time t ₃ , the sensor node SN that transmits a unit signal having the fourth subcarrier frequency f ₄ is arranged. In the cell C corresponding to the combination of the time t ₂ and the time t ₄ , a sensor node SN that transmits a unit signal having the fourth subcarrier frequency f ₄ and a unit signal having the fifth subcarrier frequency f ₅ are provided. A sensor node SN for transmission is arranged.

すなわち、時刻ｔ_０には第１、第２および第３のサブキャリア周波数ｆ_１、ｆ_２およびｆ_３を有する単位信号が受信される。同様に、時刻ｔ_１には第２、第３および第４のサブキャリア周波数ｆ_２、ｆ_３およびｆ_４を有する単位信号が受信される。時刻ｔ_２には第３、第４および第５のサブキャリア周波数ｆ_３、ｆ_４およびｆ_５を有する単位信号が受信される。時刻ｔ_３には第３、第４および第５のサブキャリア周波数ｆ_３、ｆ_４およびｆ_５を有する単位信号が受信される。時刻ｔ_４には第２、第３および第４のサブキャリア周波数ｆ_２、ｆ_３およびｆ_４を有する単位信号が受信される。時刻ｔ_５には第１、第２および第３のサブキャリア周波数ｆ_１、ｆ_２およびｆ_３を有する単位信号が受信される。 When the sensor node SN transmits the unit signals as shown in FIG. 13A, the reception server S receives these unit signals as shown in Table 10.

That is, a unit signal having the first, second, and third subcarrier frequencies f ₁ , f _2, and f ₃ is received at time t ₀ . Similarly, a unit signal having second, third and fourth subcarrier frequencies f ₂ , f ₃ and f ₄ is received at time t ₁ . Time _t in _Paragraph 3, unit signal having a fourth and fifth sub-carrier frequency _f 3, _{f 4} and _{f 5} are received. Third time _{t 3,} the unit signal having a fourth and fifth sub-carrier frequency _f 3, _{f 4} and _{f 5} are received. The time _{t 4} the second, unit signal having a third and fourth sub-carrier frequency _f 2, _{f 3} and _{f 4} are received. The first time _{t 5,} the unit signal having a second and third sub-carrier frequencies _f 1, _{f 2} and _{f 3} are received.

  Next, referring to Table 10, when a subcarrier frequency common to each cell C is searched, FIG. 13B is obtained. FIG. 13B is a determination diagram illustrating a result of determining whether there is a common subcarrier frequency in a specific example for explaining the restoration method according to the sixth embodiment of the present invention.

The determination results obtained in FIG. 13B are as follows. That is, cell C corresponding to the combination of time t ₀ and time t ₅ has first, second, and third subcarrier frequencies f ₁ , f _2, and f ₃ as subcarrier frequency candidates. Similarly, cell C corresponding to the combination of time t ₁ and time t ₅ has second and third subcarrier frequencies f ₂ and f ₃ as candidates for subcarrier frequencies. The cells C corresponding to the combination of the time t ₂ and time t _5, as a candidate subcarrier frequency, there is a third sub-carrier frequency f _3. Cell C corresponding to the combination of time t ₀ and time t ₄ has second and third subcarrier frequencies f ₂ and f ₃ as candidate subcarrier frequencies. Cell C corresponding to the combination of time t ₁ and time t ₄ has second, third and fourth subcarrier frequencies f ₂ , f ₃ and f ₄ as candidate subcarrier frequencies. Cell C corresponding to the combination of time t ₂ and time t ₄ has third and fourth subcarrier frequencies f ₃ and f ₄ as subcarrier frequency candidates. Cell C corresponding to the combination of time t ₀ and time t ₃ has a third subcarrier frequency f ₃ as a subcarrier frequency candidate. Cell C corresponding to the combination of time t ₁ and time t ₃ has third and fourth subcarrier frequencies f ₃ and f ₄ as subcarrier frequency candidates. Cell C corresponding to the combination of time t ₂ and time t ₃ has third, fourth, and fifth subcarrier frequencies f ₃ , f _4, and f ₅ as candidate subcarrier frequencies.

Here, the cell C corresponding to the combination of the time t ₂ and time t _4, actually not arranged the sensor node SN, the receiving server S to this has been grasped in advance. Therefore, in the present embodiment, the receiving server S sets the cell C in the out-of-estimation range area NZ. FIG. 13C is a diagram illustrating a setting result of the out-of-estimation region NZ in a specific example for explaining the estimation method according to the fifth embodiment of the present invention.

In the present embodiment, next, a cell C in which the number of sensor nodes SN arranged and the number of common subcarrier frequencies coincide with each other is excluded, excluding the estimation outside region NZ. For the cell C applied by this search, the observation information by the arranged sensor node SN is estimated as the average value of the inverse transformation values of the common subcarrier frequency. In this example, the following estimated values are obtained.
k _est (t ₁ , t ₅ ) = (1/2) {(Af ₂ −W + K _mid ) + (Af ₃ −W + K _mid )}
k _est (t ₂ , t ₅ ) = Af ₃ −W + K _mid
k _est (t ₀ , t ₃ ) = Af ₃ −W + K _mid

In this embodiment, next, the cell C from which the estimated value is obtained is further excluded, and the subcarrier frequency candidates corresponding to the excluded cell C are excluded from the remaining cells C. FIG. 13D is a diagram illustrating a state in which data related to the cell C from which the estimated value is obtained in the first search is deleted in a specific example for explaining the restoration method according to the sixth embodiment of the present invention. If the same search and estimation as described above are executed again from this state, the following estimated values are additionally obtained.
k _est (t ₀ , t ₄ ) = Af ₂ −W + K _mid
k _est (t ₁ , t ₃ ) = Af ₄ −W + K _mid
k _est (t ₂ , t ₃ ) = (1/2) {(Af ₄ −W + K _mid ) + (Af ₅ −W + K _mid )}

  In the present embodiment, the cell C from which the estimated value is obtained is further excluded, and the subcarrier frequency candidates corresponding to the excluded cell C are excluded from the remaining cell C. However, this time there is no longer a cell C in which the number of arranged sensor nodes SN matches the number of common subcarrier frequencies. Therefore, thereafter, as in the case of the third or fourth embodiment of the present invention, the inverse transform values are averaged from the subcarrier frequency candidates that existed at the time of the first determination.

FIG. 13E is a specific example for explaining the restoration method according to the sixth embodiment of the present invention, and there is no longer a cell C in which the number of arranged sensor nodes SN matches the number of common subcarrier frequencies. It is a figure which shows the state which does not. The following estimated value is obtained by averaging the inverse transform values from the subcarrier frequency candidates that existed at the time of the first determination.
k _est (t ₀ , t ₅ ) = (1/3) {(Af ₁ −W + K _mid ) + (Af ₂ −W + K _mid ) + (Af ₃ −W + K _mid )}
k _est (t ₁ , t ₄ ) = (1/3) {(Af ₂ −W + K _mid ) + (Af ₃ −W + K _mid ) + (Af ₄ −W + K _mid )}

  The wireless sensor network communication method using the restoration method according to the present embodiment provides the following effects. That is, even if the spatial correlation is low in the distribution of the observation target, if the receiving server S knows the arrangement of the sensor nodes SN in advance, the difference between the estimated value and the actual value can maintain a certain degree of accuracy. There is expected.

  The wireless sensor network system of the present invention and the communication method using this system have been described above. Regarding the restoration method performed by the receiving server S, a plurality of methods have been described as the first to sixth embodiments, but it goes without saying that these methods can be freely combined within a technically consistent range. Yes. For example, for a cell for which an estimated value has not been obtained, it is desirable to use the first or second interpolation method described as the second embodiment in any embodiment.

11 Bus 12 CPU
DESCRIPTION OF SYMBOLS 13 Memory 131 Program 132 Data 14 Transmission / reception circuit 15 Antenna 16 Sensor 17 Position information acquisition circuit 18 Time axis mapping circuit 19 Frequency axis mapping circuit 191 Frequency axis shift circuit 31 Bus 32 CPU
33 memory 331 program 332 data 333 database 34 transmission / reception circuit 35 antenna 36 output circuit 37 restoration circuit C cell G, G1 to G16 cell group NZ out-of-estimation area S reception server SN, SN1 to SN5 sensor node (transmission terminal)
TS0 signal TS1 to TS3 Unit signal UZ Uncertain area

Claims (12)

A plurality of terminals that measure observation information independently of each other;
A server for collecting the measurement results,
The server includes a server-side transmission / reception circuit that simultaneously transmits an information transmission request signal to the plurality of terminals,
The information transmission request signal includes a code number that is different each time the information transmission request signal is transmitted from the server in a predetermined format that can be read by the plurality of terminals that receive the information transmission request signal.
Each of the plurality of terminals is
A measurement unit for performing the measurement;
A terminal-side transceiver circuit that receives the information transmission request signal;
A conversion unit that converts the measured observation information into a combination of a plurality of radio physical quantities, according to the received information transmission request signal and using a conversion formula according to the code number;
In each of the terminals, the terminal-side transmission / reception circuit generates a unit signal having a frequency included in the combination at a time included in the combination, and transmits the unit signal to the server.
The server-side transmitting / receiving circuit receives the aggregate of unit signals as a received signal,
The server
A database for storing the received signal received for each corresponding information transmission request signal;
Based on the plurality of received signals stored corresponding to the plurality of information transmission request signals, respectively, and using the inverse transformation formula corresponding to the code number, the arrangement of the plurality of terminals and the measured A restoration circuit for estimating a combination with observation information ;
The restoration circuit is
A wireless sensor network system for excluding, from the estimation target, the unit signal detected from coordinates in which the probability that the unit signal is detected is less than a predetermined detection probability threshold . The wireless sensor network system according to claim 1,
The observation information is
A first coordinate value and a second coordinate value indicating the position of each terminal;
Each of the terminals includes an observation value obtained by measuring a predetermined observation object at the position,
The combination of the radio physical quantities is
The first time,
The second time,
Including one frequency,
The converter is
A time-axis mapping circuit that converts the first coordinate value and the second coordinate value into the first time and the second time, respectively.
A wireless sensor network system comprising: a frequency axis mapping circuit that converts the observed value into the one frequency. The wireless sensor network system according to claim 2,
The frequency axis mapping circuit includes:
A frequency axis shift circuit that varies the correspondence between the observed value before conversion and the one frequency after conversion according to the code number;
The restoration circuit is
The wireless sensor network system which calculates the measured value before the said conversion by performing the inverse conversion of the said fluctuation | variation according to the said code number to the frequency after the said conversion. In the wireless network system according to any one of claims 1 to 3 ,
The restoration circuit is a wireless sensor network system that starts the estimation after the number of information transmission requests reaches a predetermined threshold. The wireless sensor network system according to claim 4 ,
A wireless sensor network system that uses, as the code number, an information collection count that represents the number of times the server receives the received signals from the plurality of terminals and collects information . In the wireless sensor network system according to any one of claims 1 to 5 ,
Before Kisa over Bas,
Further comprising a memory that stores in advance location information of the plurality of terminals,
The restoration circuit is a wireless sensor network system that performs the estimation with reference to the position information stored in the memory. In the wireless sensor network system according to any one of claims 1 to 6 ,
The terminal-side transmitting / receiving circuit generates and transmits the unit signal by an OFDM (Orthogonal Frequency-Division Multiplexing) scheme,
The server-side transceiver circuit receives the received signal by the OFDM method. Performing a measurement of the observation information in each plurality of terminals are independent of each other,
A step that the server broadcasts information transmission request signal to the plurality of terminals,
A step wherein each of the plurality of terminals, for receiving the information transmission request signal,
And converting each of the plurality of terminals, in response to the information transmission request signal, the observation information the measured combination of a plurality of radio physical quantity,
A step wherein the plurality of terminals, at a time that is included in the combination, a unit signal having a frequency included in the combination, transmitted to the server,
A step wherein the server, which receives the assembly of the unit signal as a reception signal,
The server, and storing the received signal received for each said corresponding information transmission request signal,
The server, based on a plurality of the received signal stored in correspondence with the plurality of the information transmission request signal, the arrangement of the plurality of terminals, and estimating a combination of the measured observation information Equipped,
The step of simultaneously transmitting the information transmission request signal,
Different code number each time of transmitting, comprising the steps <br/> included in a predetermined format to the information transmission request signal,
Receiving the information transmission request signal,
Comprising a step <br/> reading the code number from the information transmission request signal,
The converting step includes:
Comprising a step <br/> for performing the conversion using the conversion equation corresponding to the code number,
The estimating step includes:
Information Collection method comprising the steps <br/> of performing the estimation using the inverse conversion equation corresponding to the code number. The server side information batch collection program for making the said server perform each step which the said server performs among the information batch collection methods of Claim 8 . The terminal side information batch collection program for making each said terminal perform each step which said each terminal performs among the information batch collection methods of Claim 8 . A transmission / reception circuit for simultaneously transmitting an information transmission request signal to a plurality of terminals, and receiving a set of a plurality of unit signals transmitted from the plurality of terminals as a response to the information transmission request signal;
A database for storing the received signal in association with each information transmission request signal;
A restoration circuit for estimating observation information by the plurality of terminals included in the received signal,
The information transmission request signal, the transmission different code number each time it is signal includes at said plurality of terminals a predetermined format readable to receive,
The restoration circuit is configured to transmit a combination of a plurality of reception times at which a plurality of unit signals included in the reception signal are received and a plurality of frequencies respectively included in the plurality of unit signals to the information transmission corresponding to the reception signals. A server that estimates the arrangement information of the plurality of terminals and the distribution of the observation information using an inverse transformation formula corresponding to the code number included in the request signal. A measurement unit for measuring observation information;
A transmission / reception circuit for receiving an information transmission request signal including a different code number each time it is transmitted ;
A conversion unit that converts the measured observation information into a combination of a plurality of radio physical quantities, in accordance with the received information transmission request signal and using a conversion formula corresponding to the code number,
The observation information is
Including a first coordinate value and a second coordinate value indicating a position where the measurement is performed;
The transmission / reception circuit generates and transmits a first unit signal having a frequency included in the combination at a first time included in the combination,
The transmission / reception circuit generates and transmits a second unit signal having the frequency at a second time included in the combination.

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