JP2011244174A - Stability evaluation device of radio communication route, stability evaluation program, selection device of radio communication route and selection program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To evaluate stability of a communication route of a radio sensor network also including response capabilities to a future installation state, change of surrounding environment, and change of use conditions.SOLUTION: A command for transmitting test radiowave with two frequencies is output to a radio sensor terminal which functions as a data collection station among a plurality of radio sensor terminals, measurement results of received power of test radiowaves for every frequency of each of the plurality of radio sensor terminals are collected, whether or not reception levels of the test radiowaves for every frequency for every combination of the radio sensor terminals are equal to or more than the lowest threshold of the reception level is determined, whether or not difference of reception levels of the test radiowaves for every frequency for every combination of the radio sensor terminals is equal to or less than a threshold of reception level difference is determined, the combination of the radio sensor terminals whose reception level of the received power is equal to or more than the lowest threshold of the reception level and the level difference of the reception levels for every frequency is equal to or less than the threshold of the reception level difference for both of the two frequencies is selected as the radio communication route.

Description

  The present invention relates to a technique for evaluating the stability of a wireless communication route and a technique for selecting a wireless communication route. More specifically, the present invention relates to a technique for evaluating the stability of each wireless communication route in a wireless communication system in which a plurality of terminals communicate wirelessly, and a wireless communication route based on the stability evaluation of the wireless communication route. It relates to the technology to be selected.

  A wireless sensor network establishes a wireless communication network autonomously by installing multiple sensor terminals with wireless functions and relaying communication between these multiple wireless sensor terminals. Collected by each wireless sensor terminal The sensor information (data) is transmitted, and is expected to be applied to, for example, sensing / status monitoring of various facilities and labor saving / sophistication of maintenance technology.

  Regarding wireless sensor network technology, for example, international standards such as IEEE802.15 related to wireless PAN (abbreviation of personal area network) and IEEE801.11 related to wireless LAN (abbreviation of local area network) are being developed.

  Since a wireless sensor network is a system that uses radio waves, radio waves need to reach a target location in order to perform communication. Theoretically, a free space propagation loss margin can be calculated from the transmission power, the gain of the transmission antenna, the gain of the reception antenna, and the sensitivity of the receiver to obtain a communicable distance. Therefore, if the wireless sensor terminals are arranged within a range determined based on the calculated communicable distance, a plurality of wireless sensor terminals can relay communication with each other, and theoretically, a wireless communication network is established. Can be built.

  However, in reality, the place where communication is possible and the place where communication is not possible are determined depending on the surrounding environment such as the situation of the target area and facility. For this reason, for example, when a wireless sensor network is built in a place where there are many metal structures, there is a section where communication is not possible due to the effects of multiple reflections of radio waves, shielding, external noise, etc., and all sensor information (data) is stabilized. May not be collected. That is, when a small number of wireless sensor terminals are installed in a wide area, the network configuration cannot be configured in a mesh shape, and communication may concentrate on one wireless communication route. As a result, when the wireless communication route becomes impossible to communicate, there is a possibility that sensor information of a plurality of wireless sensor terminals cannot be collected.

  For this reason, it is necessary to determine whether or not communication is possible between the wireless sensor terminals. Conventionally, it is determined whether or not the test radio wave from the partner terminal has been received at a certain level (intensity). It is determined whether or not communication is possible between wireless sensor terminals by inspection (Patent Document 1).

JP 2004-341648 A

  In a conventional method for determining whether or not communication between wireless sensor terminals is possible, communication between wireless sensor terminals (that is, wireless communication route) is performed based on a result of an inspection for a specific wireless frequency scheduled to be used. It is only determined whether or not.

  However, the communication success rate between wireless sensor terminals greatly depends on the received power, and the received power varies depending on the position, and is about 1 [cm] depending on the influence of complex multiple reflection of radio waves, shielding, external noise, etc. It may change greatly depending on the position of. In such a case, even if communication is possible at the initial time point when the wireless sensor terminal is installed, if any of the positions of the transmission terminal, the reception terminal, and the reflector changes after that, communication becomes impossible. There is a fear. Specifically, the communication status may change due to the expansion of the equipment due to the temperature in addition to the inclination caused by vibration or strong wind during operation of various equipment where the wireless sensor terminal is installed. Examples that vary with period have also been reported (Hiroyuki Ozome: Basic study on wireless sensor network construction based on radio wave propagation characteristics-weak radio and IEEE 802.15.4 radio wave propagation characteristics in substations-Research of Central Research Institute of Electric Power Industry Report R05007, May 2006).

  For this reason, there is a problem that the conventional determination method cannot determine the possibility of communication in the future (in other words, the potential vulnerability) even though it can determine whether communication is possible at one time of inspection. In addition, it is difficult to say that the reliability is high because it is determined that communication is possible even with a wireless communication route with low stability in the future.

  Therefore, the present invention provides a wireless communication route stability evaluation device capable of evaluating the stability of a communication route of a wireless sensor network including the ability to cope with future changes in installation conditions, surrounding conditions, and changes in usage conditions, and The purpose is to provide a stability assessment program. Further, the present invention is a wireless communication route that can be selected based on the stability evaluation of the communication route of the wireless sensor network, including the ability to cope with changes in future installation conditions / peripheral conditions and usage conditions. An object is to provide a communication route selection device and a selection program.

  In order to achieve such an object, the wireless communication route stability evaluation apparatus according to claim 1 is directed to a command for transmitting test radio waves at two frequencies sequentially to two radio sensor terminals and a command for receiving the test radio waves. And means for collecting the measurement results of the reception power of the two radio sensor terminals for each of the two frequencies, and the reception power of the test radio wave for each of the two frequencies between the two radio sensor terminals. Means for determining whether or not the reception level is equal to or greater than the reception level minimum threshold, and whether or not the difference between the reception levels of the test radio waves for the two frequencies between the two wireless sensor terminals is equal to or less than the reception level difference threshold The reception level of the received power is equal to or higher than the reception level minimum threshold and the difference between the reception levels of the two frequencies is equal to or lower than the reception level difference threshold. The case has to have a means for evaluating the communication state between two wireless sensor nodes are stable.

  Further, the wireless communication route stability evaluation program according to claim 2 is a program for performing a process of evaluating a communication state between two wireless sensor terminals, which is sequentially performed on the two wireless sensor terminals. A process for outputting a command for transmitting a test radio wave at two frequencies and a command for receiving the test radio wave, a process for collecting measurement results of received power of the test radio wave for each of the two frequencies of the two wireless sensor terminals, and , A process for determining whether the reception level of the reception power of the test radio wave between the two wireless sensor terminals is equal to or higher than the reception level minimum threshold, and for each of the two frequencies between the two wireless sensor terminals Processing to determine whether the difference between the reception levels of the test radio waves is less than or equal to the reception level difference threshold, and the reception level of the received power is greater than or equal to the reception level minimum threshold for both of the two frequencies When the difference between the two reception levels for each frequency is equal to or less than the reception level difference threshold, the computer is caused to perform a process of evaluating that the communication state between the two wireless sensor terminals is stable. .

  According to these wireless communication route stability evaluation devices and stability evaluation programs, wireless sensor network communication routes including the ability to respond to changes in future installation conditions, surrounding conditions, and changes in usage conditions according to the principles described below. Can be evaluated.

ただし、 Ｐr：受信レベル〔dBm〕，
ｐ_r：受信電力〔mW〕，
ｚ_r：反射波の伝搬長〔ｍ〕，
φ：直接波と反射波との位相差〔radian〕，
ｆ：無線の周波数〔Hz〕，
ｃ：真空中の光の速さ〔m/s〕 をそれぞれ表す。 Here, the characteristics of fluctuations in received power (received intensity) are examined by a two-wave interference model of a direct wave and one metal reflected wave. Specifically, the distance from the straight line connecting the wireless sensor terminals to the metal surface is x [m], the distance between the wireless sensor terminals is z [m], and the direct wave is received at the distance z = 1 [m]. When the power is 1 [mW], the received power level is expressed by Equation 1.

Where Pr: reception level [dBm],
p _r : received power [mW],
z _r : propagation length of reflected wave [m],
φ: phase difference [radian] between direct wave and reflected wave,
f: Radio frequency [Hz],
c: Represents the speed of light [m / s] in vacuum.

  The third term of Equation 1-2 represents the fluctuation due to the interference between the direct wave and the reflected wave, and the reception level is changed when the phase difference φ between the direct wave and the reflected wave is (2n + 1) π (where n is an integer). A dip occurs.

Further, when z >> x, Expression 1-4 is approximately expressed as Expression 2.
(Equation 2) φ = πf / c (4x ² / z)

That is, it can be seen that the phase difference φ between the direct wave and the reflected wave depends on the distance z between the wireless sensor terminals, the distance x from the straight line connecting the wireless sensor terminals to the metal surface, and the wireless frequency f. Since the change Δφ of the phase difference φ with respect to these changes Δz, Δx, Δf is expressed by Equation 3, Δφ is determined by φ at that time and the rate of change of each variable.
(Equation 3) Δφ / φ = −Δz / z = 2Δx / x = Δf / f

  From Formula 3, it can be considered that the change Δφ in the phase difference φ due to movement is larger in the x direction than in the z direction at the point where z >> x, and the change in the reception level Pr becomes sharper. On the other hand, the place where the reception level Pr greatly changes due to the change in the phase difference φ is a point where the phase difference φ = (2n + 1) π and the intensity difference between the direct wave and the interference wave is small. That is, for example, when the change in the reception level Pr is determined only by movement in the x direction, it cannot be simplified, but on the other hand, the phase difference φ = (2n + 1) π and the point where the difference in intensity between the direct wave and the interference wave is small. Then, even if any of z, x, and f changes, reception level Pr will change a lot.

  FIG. 4 shows an example in which the direct wave reception level at f1 = 2440 [MHz], f2 = 2460 [MHz], x = 2 [m], and z = 1 [m] is set to −30 [dBm] according to Equation 1. Show. From FIG. 4 (A), there is a place where the reception level abruptly attenuates depending on the location in the case of metal reflection (different from the attenuation due to ground reflection or shielding), and if the location is moved in this vicinity, the reception level may fluctuate greatly. It is confirmed, that is, an unstable place, but this cannot be understood unless it is actually moved. On the other hand, from FIG. 4B, it can be confirmed that if the frequency is changed, it fluctuates greatly without actually moving the place.

  As described above, at the point where the fluctuation of the reception level due to the fine movement of the position of the wireless sensor terminal is large, the fluctuation of the reception level due to the fine movement of the radio wave frequency is also large. In other words, in places where the reception level fluctuates due to fine movement of the position of the wireless sensor terminal, the reception level also fluctuates due to fine movement of the frequency of the radio wave. By predicting a stable communication route and reflecting it in the evaluation of the wireless communication route, a highly stable wireless communication route can be selected. Specifically, it can be said that a communication route whose reception level fluctuates greatly when the frequency of radio waves is changed is potentially vulnerable, so by eliminating the communication route, only a highly stable wireless communication route can be obtained. Can be selected.

  Therefore, in addition to the reception level of the reception power of the test radio wave by frequency in the wireless communication route stability evaluation device and the stability evaluation program wireless sensor terminal of the present invention, the difference in the reception level of the test radio wave by frequency is used. Since the communication state between the wireless sensor terminals is evaluated, the wireless communication route is evaluated in consideration of the stability of the communication state in addition to the reception level.

  According to a third aspect of the present invention, there is provided a wireless communication route selection device that outputs a command for transmitting a test radio wave at two frequencies sequentially to a plurality of radio sensor terminals and a command for receiving the test radio wave. A means for collecting the measurement results of the test radio wave reception power for each of the plurality of wireless sensor terminals and the reception level of the test radio wave reception power for each frequency of each combination of the radio sensor terminals is the lowest reception level. Means for determining whether or not the threshold is equal to or greater than a threshold; means for determining whether or not the difference between the reception levels of the two test radio waves for each combination of wireless sensor terminals is equal to or less than a reception level difference threshold; A wireless sensor terminal in which the reception level of received power is greater than or equal to the reception level minimum threshold and the difference between the reception levels of the two frequencies is less than or equal to the reception level difference threshold for any of the two frequencies Combine so that comprises a means for selecting a radio communication route.

  A wireless communication route selection program according to claim 4 is a program for performing a process of selecting a communication route for constructing a wireless sensor network by a plurality of wireless sensor terminals. A process for outputting a command for transmitting a test radio wave at two frequencies and a command for receiving the test radio wave sequentially, and a measurement result of the received power of the test radio wave for each of a plurality of wireless sensor terminals. Processing for determining whether the reception level of the received power of the test radio wave for each frequency for each combination of wireless sensor terminals is equal to or higher than the reception level minimum threshold, and for each combination of wireless sensor terminals Either the process of determining whether the difference between the reception levels of the test radio waves for two frequencies is less than or equal to the reception level difference threshold, and the two frequencies Even if the reception level of the received power is equal to or higher than the reception level minimum threshold and the combination of the wireless sensor terminals whose difference between the reception levels of the two frequencies is equal to or less than the reception level difference threshold is selected as a wireless communication route. I try to do it.

  Therefore, according to the wireless communication route selection device and the selection program, the wireless sensor terminal uses the difference in the reception level of the test radio wave by frequency in addition to the reception level of the test radio wave reception power by frequency. Since the wireless communication route is selected by evaluating the communication state between the terminals, the wireless communication route is selected in consideration of the stability of the communication state in addition to the level of the reception level.

  According to the stability evaluation device and the stability evaluation program of the wireless communication route of the present invention, the wireless communication route is evaluated in consideration of the stability of the communication state in addition to the reception level, that is, the future installation state・ As it is possible to evaluate wireless communication routes, including the ability to respond to changes in surrounding conditions and usage conditions, even if the reception level is high at a specific frequency, the communication state is actually unstable. Thus, a potentially vulnerable wireless communication route can be detected, and the reliability of the evaluation of the wireless communication route can be improved.

  Further, according to the wireless communication route selection device and the selection program of the present invention, it is possible to select a wireless communication route in consideration of the stability of the communication state in addition to the reception level, that is, in the future installation status / periphery Since it is possible to select a wireless communication route that includes the ability to respond to changes in conditions and usage conditions, even if the reception level is high at a specific frequency, the communication state is actually unstable and latent. Therefore, it is possible to eliminate a weak wireless communication route, and it is possible to improve the reliability of selection of the wireless communication route.

It is a flowchart explaining an example of embodiment of the selection program of the radio | wireless communication route using the stability evaluation of the radio | wireless communication route of this invention. FIG. 3 is a functional block diagram of a wireless communication route selection device when selecting a wireless communication route using the wireless communication route stability evaluation of the embodiment using a program. It is a figure explaining the method of selection of the radio | wireless communication route of embodiment. It is a figure which shows the example of calculation of the characteristic of the fluctuation | variation of the reception power (reception intensity) by a two-wave interference model.

  Hereinafter, the configuration of the present invention will be described in detail based on an example of an embodiment shown in the drawings.

  FIG. 1 to FIG. 4 show an example of an embodiment of a wireless communication route selection device and a selection program using the wireless communication route stability evaluation device and the stability evaluation program of the present invention (in other words, included as a part). Show.

  In the present invention, a plurality of wireless sensor terminals are installed in advance in the target area / facility where the wireless sensor network is deployed (S0).

  In the present invention, a wireless sensor terminal having a function of switching radio frequency channels is used. In this embodiment, six wireless sensor terminals 1A, 1B,..., 1F are installed, and the wireless sensor terminal 1A is set as a data collection station and connected to the wireless communication route selection device 10 as an example. Will be described.

  In the present invention, the values of the two frequencies f1 and f2 of the test radio wave are preset. Note that the values of the frequencies f1 and f2 of the test radio wave are not limited to specific values, and appropriate frequencies are set corresponding to the frequency band scheduled for actual use. Specifically, for example, if the frequency band scheduled for actual use is 2.4 GHz band (for example, IEEE802.15.4, IEEE802.11b, etc.), 2440 [MHz] and 2460 [MHz] can be considered. In the case of a 950 MHz band (for example, IEEE802.15.4d), it is conceivable that the frequency is 951.0 [MHz] and 957.4 [MHz].

  The wireless communication route selection device includes a plurality of wireless sensor terminals 1A, 1B,..., 1F via a wireless sensor terminal 1A that functions as a data collection station among the plurality of wireless sensor terminals 1A, 1B,. , A means (11b, 11c) for sequentially outputting a command for transmitting a test radio wave at two frequencies f1, f2 and a command for receiving the test radio wave, and a plurality of wireless sensor terminals 1A, 1B,. The means (11d) for collecting the measurement result of the received power of the test radio wave for each of the two frequencies f1 and f2, and the test for each of the two frequencies f1 and f2 for each combination of the wireless sensor terminals 1A, 1B,. A means (11f) for determining whether or not the reception level of radio wave reception power is equal to or greater than the reception level minimum threshold, and a test for each of the two frequencies f1 and f2 for each combination of the wireless sensor terminals 1A, 1B,. Electric Means (11g) for determining whether or not the difference between the received levels is equal to or less than a received level difference threshold, and the received power received level is equal to or higher than the received level minimum threshold for both of the two frequencies f1 and f2. Means (11h) for selecting a combination of wireless sensor terminals 1A, 1B,..., 1F whose difference in reception level for each of the frequencies f1 and f2 is equal to or less than a reception level difference threshold as a wireless communication route.

  The wireless communication route stability evaluation device and the wireless communication route selection device described above can also be realized by executing a wireless communication route selection program including a wireless communication route stability evaluation program as a part on a computer. . In the present embodiment, a case where a wireless communication route selection program is executed on a computer will be described as an example.

  FIG. 2 shows the overall configuration of the wireless communication route selection apparatus 10 of the present embodiment for executing the wireless communication route selection program 17. The wireless communication route selection device 10 includes a control unit 11, a storage unit 12, an input unit 13, a display unit 14, and a memory 15, and is connected to each other by a signal line such as a bus. A wireless sensor terminal 1A is connected to the wireless communication route selection device 10 via a signal line such as a bus, and signals such as data and control commands are transmitted / received (ie, input / output) to / from each other via the signal line. Done.

  The control unit 11 performs control related to the overall control of the wireless communication route selection device 10 and the evaluation and selection of the stability of the wireless communication route by the wireless communication route selection program 17 stored in the storage unit 12, for example, CPU (ie central processing unit). The storage unit 12 is storage means capable of storing at least data and programs, and is, for example, a hard disk. The memory 15 serves as a memory space that is a work area when the control unit 11 executes various controls and calculations, and is, for example, a RAM (abbreviation of Random Access Memory).

  The input unit 13 is an interface for giving at least an operator's command to the control unit 11, and is, for example, a keyboard.

  The display unit 14 performs drawing / display of characters, graphics, and the like under the control of the control unit 11 and is, for example, a display.

  Then, by executing the wireless communication route selection program 17, the control unit 11 of the wireless communication route selection device 10 counts as means for controlling the count C of the test radio wave transmission for measuring the received power. .., 1F in turn for the plurality of wireless sensor terminals 1A, 1B,..., 1F via the wireless sensor terminal 1A functioning as a data collection station among the plurality of wireless sensor terminals 1A, 1B,. A frequency setting unit 11b and a test radio wave transmission command unit 11c as means for performing a process of outputting a command to transmit a test radio wave at one frequency f1, f2, and a command to receive the test radio wave, a plurality of wireless sensor terminals 1A, 1B,..., 1F, a received power collecting unit 11d as a means for collecting the measurement results of the received power of the test radio waves for each of the two frequencies f1 and f2. For each combination of the count comparison unit 11e as means for determining whether or not the value of the test radio wave transmission count C for measuring received power is a predetermined value, and the wireless sensor terminals 1A, 1B,. A reception level determination unit 11f as means for performing processing for determining whether or not the reception level of the reception power of the test radio wave for each of the two frequencies f1 and f2 is equal to or higher than the reception level minimum threshold, and the wireless sensor terminals 1A and 1B ,..., 1F, a reception level difference determination unit 11g as means for performing processing for determining whether or not the difference between the reception levels of the test radio waves for each of the two frequencies f1 and f2 is equal to or less than a reception level difference threshold. The reception level of the received power is greater than or equal to the reception level minimum threshold for both of the two frequencies f1 and f2, and the difference between the reception levels of the two frequencies f1 and f2 is less than or equal to the reception level difference threshold. Line sensor terminal 1A, 1B, ..., and the communication route selecting unit 11h is configured as a means for performing the process of selecting a combination of 1F as a wireless communication route.

  In the present embodiment, when the wireless communication route selection program 17 is executed, first, the test radio wave transmission count C = 0 for reception power measurement is set as an initial value and stored in the memory 15 (S0). ).

  In the present embodiment, the frequency f1 is set as the frequency of the test radio wave corresponding to the test radio wave transmission count C = 1, and the frequency f2 is set as the frequency of the test radio wave corresponding to the test radio wave transmission count C = 2. Thus, the wireless communication route selection program 17 (hereinafter simply referred to as the program 17) is defined.

  Then, the present invention is executed, and the count unit 11a of the control unit 11 reads the value of the test radio wave transmission count C for measuring the received power from the memory 15, and adds 1 to the C (S1). Then, the count unit 11 a stores the value of the test radio wave transmission count C in the memory 15.

  Next, the frequency setting unit 11b of the control unit 11 sets the frequency of the test radio wave transmitted for measuring the received power (S2). For example, the frequency may be a channel number of a frequency channel defined by the Radio Law.

  Specifically, the frequency setting unit 11b sets the value of the test radio wave frequency (f1 when C = 1, f2 when C = 2) associated with the value of the test radio wave transmission count C to the program 17. Read from.

  Then, the frequency setting unit 11b outputs a command for setting the frequency f1 (or f2) read from the program 17 as a communication channel for measuring received power to the wireless sensor terminal 1A functioning as a data collection station. Further, the wireless sensor terminal 1A is instructed to set the communication channel to the frequency f1 (or f2) from each wireless sensor terminal 1B,..., 1F. The command is transmitted using, for example, flooding. That is, the wireless sensor terminal 1A transmits a radio wave including data omnidirectionally, and the other wireless sensor terminals 1B,..., 1F receiving the radio wave transmit the data omnidirectionally only once.

  Next, the test radio wave transmission command unit 11c of the control unit 11 sequentially instructs each radio sensor terminal to transmit and receive test radio waves via the radio sensor terminal functioning as a data collection station (S3).

  In the present embodiment, the test radio wave transmission command unit 11c outputs a command for transmitting and receiving a test radio wave to each wireless sensor terminal via the wireless sensor terminal 1A functioning as a data collection station. In the present invention, the received power is measured for every combination of wireless sensor terminals 1A, 1B,..., 1F (hereinafter referred to as a combination of wireless sensor terminals 1).

  Specifically, first, the radio sensor terminal 1A is instructed to transmit a test radio wave, and the radio sensor terminals 1B to 1F are instructed to receive the test radio wave. Then, the wireless sensor terminal 1A floods the test radio wave (packet), and the wireless sensor terminals 1B to 1F receive the test radio wave and store all received power in association with the terminal number of the transmission source. The received power is stored in a memory included in each wireless sensor terminal.

  Next, the radio sensor terminal 1B is instructed to transmit a test radio wave, and the radio sensor terminals 1A and 1C to 1F are instructed to receive the test radio wave. Then, the wireless sensor terminal 1B floods the test radio wave, and the radio sensor terminals 1A and 1C to 1F receive the test radio wave and store all received power in association with the terminal number of the transmission source.

  Next, the radio sensor terminal 1C is instructed to transmit a test radio wave, and the radio sensor terminals 1A, 1B, 1D to 1F are instructed to receive the test radio wave. Then, the wireless sensor terminal 1C floods the test radio wave, and the radio sensor terminals 1A, 1B, 1D to 1F receive the test radio wave and store all received power in association with the terminal number of the transmission source.

  Similarly, the wireless sensor terminal 1D floods the test radio wave, and the other radio sensor terminals receive the test radio wave and store all received power in association with the terminal number of the transmission source. The other wireless sensor terminal receives the test radio wave and stores all received power in association with the terminal number of the transmission source, and the wireless sensor terminal 1F floods the test radio wave to receive another radio sensor. The terminal receives the test radio wave and stores all received power in association with the source terminal number.

  As described above, when all the wireless sensor terminals transmit test radio waves once, the bidirectional received power between all the wireless sensor terminals is measured, and the received power for each combination of the wireless sensor terminals 1 is measured. The

  Next, the received power collecting unit 11d of the control unit 11 collects the measurement results of the received power of the test radio wave of each wireless sensor terminal (S4).

  Specifically, the received power collecting unit 11d functions as a data collection station that sends a command to send a return command of the measurement result of the received power of the test radio wave to each of the wireless sensor terminals 1B, ..., 1F. The wireless sensor terminal 1A to which the command is input transmits a command for returning the measurement result of the received power to each of the wireless sensor terminals 1B,.

  Each wireless sensor terminal 1B,..., 1F transmits to the wireless sensor terminal 1A the reception power of the test radio wave flooded from the other wireless sensor terminal, which is stored in the memory during the process of S3. Then, the wireless sensor terminal 1A stores the transmitted received power data in the memory 1Aa.

  Then, the received power collecting unit 11d receives the measurement result of the received power of the test radio wave returned from each wireless sensor terminal 1B,..., 1F to the wireless sensor terminal 1A and the received power of the test radio wave of the wireless sensor terminal 1A itself. The measurement result is read from the memory 1Aa of the wireless sensor terminal 1A. Note that the measurement results returned from the wireless sensor terminals 1B,..., 1F may be directly read without being stored in the memory 1Aa of the wireless sensor terminal 1A.

  Further, the received power collection unit 11d stores the received power measurement result read from the memory 1Aa of the wireless sensor terminal in the memory 15. As a result, the measurement result of the received power for each combination of the wireless sensor terminals 1 in the case of the test radio wave frequencies f1 and f2 is accumulated in the memory 15 (in addition, since reception is impossible when reception is impossible, reception There is no data for wireless sensor terminal combinations that were impossible). Here, for example, between the wireless sensor terminals 1A and 1B, there is reception power by the terminal 1A and reception power by the terminal 1B (that is, reception power for each direction). May use the received power of only one of the terminal 1A and the terminal 1B, or may use the average of both received power.

  Next, the count comparison unit 11e of the control unit 11 determines whether or not the test radio wave transmission count C for measuring the received power is 2 (S5).

  Specifically, the count comparison unit 11e determines whether or not the value of the test radio wave transmission count C stored in the memory 15 in the process of S1 is two.

  If C ≠ 2 (actually C = 1) (S5: No), the control unit 11 returns the processing step to S1, and the processes after S1 are repeated.

  On the other hand, when C = 2 (S5: Yes), the control unit 11 advances the processing step to S6. At this time, the memory 15 stores the measurement results of the received power for each combination of the wireless sensor terminals 1 for each of the test radio wave frequencies f1 and f2 (no data when reception is impossible).

  And the reception level determination part 11f of the control part 11 determines the reception level of the reception power according to the frequency of the test radio wave for every combination of wireless sensor terminals (S6).

  In the present embodiment, the reception level is classified into three levels that combine whether or not the reception level between wireless sensor terminals is at least the required level and whether or not the reception level is sufficiently high. To do.

  First, whether or not the reception level between wireless sensor terminals is the minimum required level or more is determined by setting a reception level minimum threshold. The reception level minimum threshold is not limited to a specific value, but can be received based on the importance of information transmitted by the wireless sensor network and the situation of the target area / facility where the wireless sensor network is deployed. An appropriate value is set with reference to the extent that it cannot be said that the communication state is sufficiently good. For example, in the example shown in FIG. 4, with reference to FIG. 4A, it is conceivable to set the reception level minimum threshold to about −95 [dB]. Instead of setting the reception level minimum threshold as a specific value, it may be set based on whether or not reception is possible regardless of the reception level.

  Whether or not the reception level between the wireless sensor terminals is sufficiently high is determined using a reception level good threshold value. The reception level good threshold value is not limited to a specific value, and is based on the importance of the information transmitted by the wireless sensor network and the situation of the target area / facility where the wireless sensor network is deployed. An appropriate value is set on the basis of the degree to which the communication state can be said to be very good. For example, in the example shown in FIG. 4, it is conceivable to set the reception level good threshold to about −75 [dB] with reference to FIG. In the present embodiment, the reception level minimum threshold and the reception level good threshold are defined in the program 17.

  The reception level determination unit 11f reads the reception level minimum threshold value and the reception level good threshold value defined in the program 17 and stores them in the memory 15, and the test radio wave frequency f1 stored in the memory 15 in the process of S4. Whether each of the measurement results of the received power for each combination of the wireless sensor terminals 1 for each of f2 is equal to or higher than the reception level minimum threshold, and if it is equal to or higher than the threshold, whether or not the reception level is better than the threshold Determine whether.

  For each combination of wireless sensor terminals 1, the reception level determination unit 11 f shows that the reception power measurement result for each frequency f 1 · f 2 is 1) less than the reception level minimum threshold, 2) the reception level minimum threshold or more and the reception level is good Less than threshold value, 3) Whether the reception level is better than the threshold value (ie, whether the reception level is insufficient, low or high. No data when reception is not possible) is stored in the memory 15 Let

  FIG. 3A shows an example of the processing result of S6 for the wireless sensor terminals 1A, 1B,..., 1F (assuming the arrangement) of the present embodiment. In FIG. 3, there is no line if the reception power measurement result is unreceivable or less than the reception level minimum threshold (that is, the reception level is insufficient), a broken line if the reception level is above the minimum reception level threshold and less than the reception level good threshold (that is, the reception level is low). Above the level good threshold (that is, the reception level is high) is indicated by a solid line. For each combination of the wireless sensor terminals 1, the frequency f1 and the frequency f2 are represented by a single line, so two lines are shown at the maximum.

  Next, the reception level difference determination part 11g of the control part 11 determines the difference of the reception level according to the frequency of the test radio wave for each combination of wireless sensor terminals (S7).

  When the difference (absolute value) in the reception level for each frequency of radio waves is large, there is a high possibility that the received power will fluctuate greatly due to the fine movement of the position of the wireless sensor terminal and communication will be disabled in the future. For this reason, in the present invention, the difference in the reception level of each radio wave frequency is used as one of the evaluation indexes for the stability of the wireless communication route.

  Whether or not the communication state between wireless sensor terminals is stable (in other words, whether or not the difference in reception level by frequency of radio waves is small) is determined by setting a reception level difference threshold. To do. The reception level difference threshold is not limited to a specific value. The reception level difference may vary depending on the importance of information transmitted by the wireless sensor network and the situation of the target area / facility where the wireless sensor network is deployed. An appropriate value is set on the basis of the degree to which it can be said that the communication state is small and relatively stable. For example, in the example shown in FIG. 4, it is conceivable to set the reception level difference threshold to about 10 [dB] with reference to FIG. In the present embodiment, the reception level difference threshold is defined in the program 17.

  Here, when setting the reception level difference threshold, a reception margin that is the difference between the measured reception level and the threshold of the reception limit (in other words, the margin of how many decibels can be received) May be taken into consideration. Specifically, it is conceivable to increase the reception level difference threshold when the reception margin is large, or to decrease the reception level difference threshold when the reception margin is small.

  Also, since the antenna gain generally has frequency characteristics, the frequency characteristics of the antenna gain are measured in advance, and the actual received power is calibrated in consideration of the reception gain and transmission gain in the processes of S6 and S7. Is used.

  Then, the reception level difference determination unit 11g reads the reception level difference threshold defined in the program 17 and stores it in the memory 15 as well as the test radio frequency f1 and f2 stored in the memory 15 in the process of S4. Using the reception power measurement results for each combination of wireless sensor terminals 1, the difference (absolute value) between the reception level for frequency f1 and the reception level for frequency f2 is calculated for each combination of wireless sensor terminals 1. Whether the difference is equal to or less than the reception level difference threshold (that is, whether the communication state is stable or unstable) is stored in the memory 15. When reception is not possible and there is no reception power data, the reception level is set to an appropriate value sufficiently lower than the reception level minimum threshold, and the difference in reception level is calculated.

  Next, the communication route selection unit 11h of the control unit 11 selects a communication route for constructing the wireless sensor network (S8).

  Specifically, the communication route selection unit 11h reads the distinction between insufficient / low / high reception levels by frequency f1 / f2 for each combination of the wireless sensor terminals 1 stored in the memory 15 in the process of S6 and at S7 In the process, the distinction between the stable and unstable communication states for each combination of the wireless sensor terminals 1 stored in the memory 15 is read.

  For each combination of wireless sensor terminals 1, the communication route selection unit 11h is “the reception level of the frequency f1 is low or high”, “the reception level of the frequency f2 is low or high”, and “the communication state is stable”. In this case, the wireless communication route is selected and the result is stored in the memory 15.

  An example of the processing result of S8 for the wireless sensor terminals 1A, 1B,..., 1F of the present embodiment is shown in FIG. In FIG. 3, a solid line and a broken line representing the reception level are displayed only between the wireless sensor terminals selected as the wireless communication route.

  Referring also to FIG. 3A showing the processing result of S6, for example, between the wireless sensor terminals 1A and 1B, the reception level is high for both frequencies f1 and f2, and the communication state is stable. Selected. The wireless sensor terminals 1A to 1E are selected as communication routes because the reception level is low for both frequencies f1 and f2, but the communication state is stable.

  In addition, the wireless sensor terminals 1A-1C are not selected as a communication route because the communication level is unstable although the reception level is low or higher for both frequencies f1 and f2. That is, in the present invention, there is a case in which a terminal having a low reception level at both frequencies is given priority over a terminal having a high reception level at one frequency and a low reception level at the other frequency. . Further, the wireless sensor terminals 1A-1D are not selected as a communication route because they cannot be received at one frequency.

  And as an actual communication route as a wireless sensor network, a route with a small number of relays, for example, is adopted from the route group selected by the above-described processing for each combination of wireless sensor terminals 1. Specifically, in the example shown in FIG. 3B, in the communication from the wireless sensor terminal 1F to 1A, the wireless sensor terminal 1F → 1B → 1A, not the wireless sensor terminal 1F → 1C → 1B → 1A. Is adopted. However, other routes may be adopted as the actual communication route, and the adoption of the actual communication route as the construction of the wireless sensor network may be based on any idea.

  Then, the control unit 11 displays the processing results of S6, S7, and S8 as necessary, for example, on the display unit 14 or stores them in the storage unit 12 as a data file of the processing results (END). ).

  As a result of applying the present invention, when a wireless sensor network over the entire target area / facility cannot be constructed because a wireless communication route is not selected, or when two or more routes cannot be secured, for example, various threshold values are set. Or the position of the wireless sensor terminals 1A, 1B,..., 1F may be changed, and the processing of the present invention may be repeated until a required wireless communication route is secured.

  According to the stability evaluation device and the stability evaluation program of the wireless communication route of the present invention configured as described above, the wireless communication route is evaluated in consideration of the stability of the communication state in addition to the reception level. In other words, since it is possible to evaluate the wireless communication route including the ability to respond to changes in future installation conditions, surrounding conditions and usage conditions, even if the reception level at a specific frequency is high, the communication state is In fact, a wireless communication route that is unstable and potentially vulnerable can be detected, and the reliability of the evaluation of the wireless communication route can be improved.

  Further, according to the wireless communication route selection device and the selection program of the present invention, it is possible to select a wireless communication route in consideration of the stability of the communication state in addition to the reception level, that is, in the future installation status / periphery Since it is possible to select a wireless communication route that includes the ability to respond to changes in conditions and usage conditions, even if the reception level is high at a specific frequency, the communication state is actually unstable and latent. It is possible to eliminate vulnerable wireless communication routes and improve the reliability of wireless communication route selection.

  In addition, although the above-mentioned form is an example of the suitable form of this invention, it is not limited to this, A various deformation | transformation implementation is possible in the range which does not deviate from the summary of this invention. For example, in the present embodiment, the case where six wireless sensor terminals 1A, 1B,..., 1F are installed in the target area / facility where the wireless sensor network is deployed has been described as an example. The present invention can be applied to any number of sensor terminals as long as the number is two or more.

  Then, when it is not necessary to select a wireless communication route (in other words, to construct a communication route network as a wireless sensor network) and to simply evaluate the communication state of the wireless communication route between specific wireless sensor terminals, If the processing from S0 to S7 is performed for the wireless sensor terminal, and "the reception level of the frequency f1 is low or high", "the reception level of the frequency f2 is low or high", and "the communication state is stable", these two The communication state between the two wireless sensor terminals may be determined to be stable.

  In this embodiment, flooding is used to measure the reception power at each wireless sensor terminal, but the method for measuring the reception power is not limited to this, and reception at each wireless sensor terminal is possible. Any method can be used as long as the power can be measured.

  In this embodiment, in the determination of the reception level of the received power (S6), the reception level minimum threshold and the reception level good threshold are set to classify the reception levels into three. It is not an essential requirement of the present invention. That is, only the minimum reception level threshold is set to determine whether or not the reception level between the wireless sensor terminals is the minimum required level or more, and the wireless communication route is selected based on the determination result (S8). ), The present invention is established.

1A Wireless sensor terminal (data collection station)
DESCRIPTION OF SYMBOLS 10 Wireless communication route selection apparatus 11 Control part 12 Storage part 13 Input part 14 Display part 15 Memory 17 Wireless communication route selection program

Claims (4)

  Means for sequentially outputting a test radio wave at two frequencies and a command for receiving the test radio wave to the two wireless sensor terminals, and the two frequency sensor for each of the two frequencies. Means for collecting measurement results of test radio wave reception power, and determining whether or not the reception level of the test radio wave reception power for each of the two frequencies between the two wireless sensor terminals is equal to or higher than a reception level minimum threshold Means for determining whether or not the difference between the reception levels of the test radio waves for each of the two frequencies between the two wireless sensor terminals is equal to or less than a reception level difference threshold, and for both of the two frequencies When the reception level of the received power is equal to or greater than the reception level minimum threshold and the difference between the reception levels of the two frequencies is equal to or less than the reception level difference threshold, the two wireless sensors are received. Stability evaluation device of a wireless communication route, characterized in that it comprises a means for communication between the terminals is evaluated to be stable.   A program for performing a process for evaluating a communication state between two wireless sensor terminals, which receives a command for transmitting a test radio wave at two frequencies sequentially to the two wireless sensor terminals and the test radio wave. A process of outputting a command to perform, a process of collecting measurement results of the received power of the test radio wave for each of the two frequencies of the two wireless sensor terminals, and the two frequencies between the two wireless sensor terminals The process of determining whether the reception level of the reception power of another test radio wave is equal to or higher than the reception level minimum threshold, and the difference between the reception levels of the test radio waves for the two frequencies between the two wireless sensor terminals is received. A process for determining whether or not the difference is equal to or less than a level difference threshold, and the reception level of the reception power is greater than or equal to the minimum reception level threshold for both of the two frequencies and the two When the difference in reception level for each frequency is equal to or less than the reception level difference threshold, the computer is caused to perform a process of evaluating that the communication state between the two wireless sensor terminals is stable. Program for evaluating the stability of wireless communication routes.   Means for sequentially outputting a test radio wave at two frequencies and a command for receiving the test radio wave to a plurality of wireless sensor terminals; and It is determined whether or not the reception level of the reception power of the test radio wave for each of the two frequencies for each combination of the wireless sensor terminal and the means for collecting the test radio wave reception power measurement result is equal to or greater than the reception level minimum threshold value. Means for determining whether the difference between the reception levels of the test radio waves for each of the two frequencies for each combination of the wireless sensor terminals is equal to or less than a reception level difference threshold, and for both of the two frequencies The wireless sensor in which a reception level of received power is equal to or greater than the reception level minimum threshold and a difference between the reception levels of the two frequencies is equal to or less than the reception level difference threshold. Selection device of a wireless communication route, characterized in that it comprises a means for selecting the end of the combination as a wireless communication route.   A program for causing a plurality of wireless sensor terminals to select a communication route for constructing a wireless sensor network, and sequentially transmitting test radio waves at two frequencies to the plurality of wireless sensor terminals. A process for outputting a command and a command for receiving the test radio wave, a process for collecting measurement results of the received power of the test radio wave for each of the two frequencies of each of the plurality of radio sensor terminals, A process for determining whether the reception level of the reception power of the test radio wave for each of the two frequencies for each combination is equal to or higher than a reception level minimum threshold; and the test radio wave for each of the two frequencies for each combination of the wireless sensor terminals A process for determining whether or not the difference in reception level is equal to or less than a reception level difference threshold, and the received power for both of the two frequencies The computer performs a process of selecting a combination of the wireless sensor terminals whose reception level is equal to or higher than the reception level minimum threshold and whose difference between the reception levels of the two frequencies is equal to or less than the reception level difference threshold as a wireless communication route. A program for selecting a wireless communication route.

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