Electromagnetic noise measurement system

Abstract

To correctly understand a carrier sense operation.SOLUTION: The electromagnetic noise measurement system 100 of the present disclosure includes: a spectrum analyzer 12 for acquiring a signal level of a wireless system 200 to be measured, and the signal intensity and the bandwidth of an electromagnetic noise level from a noise source (a noise source 300 and a noise generator 11); and a server 14 for estimating a condition under which the wireless system 200 starts or stops communication, on the basis of the signal intensity and the bandwidth of the electromagnetic noise level.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a method for estimating radio quality in a wireless communication system. [Background technology]

[0002] In recent years, wireless systems have become increasingly popular in manufacturing sites and other locations, and wireless devices are increasingly being installed in close proximity to industrial machinery and other devices that generate electromagnetic noise. Such electromagnetic noise is known to interfere with the communication bandwidth of wireless communication systems. Therefore, when electromagnetic noise occurs nearby during communication between wireless devices, communication delays can increase.

[0003] To address this problem of long communication delays, wireless communication is modeled by understanding the behavior of the target communication based on a known protocol model, and future delays are predicted to guarantee the delays.

[0004] However, since communication delay time depends on the environment and implementation of the wireless system, it is necessary to appropriately reflect such conditions in the model. Therefore, as shown in Non-Patent Documents 1 and 2, studies are being conducted to customize the simulation model by combining the simulation model generated based on packet behavior etc. with the physical information of the wireless communication environment that has been measured.

[0005] In implementing a wireless communication system that stops communication when electromagnetic noise is detected, a carrier sense operation is known that stops communication at the same frequency in order to avoid wireless interference. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] Takahito Inoshita, Satoshi Ota, Natsuko Ouchi, Mizuki Kiriyama, "Delay Prediction Technology for Delay Guarantee - System Construction Using Wireless Communication Environment Measurement and System-Level Simulation -" 2022 IEICE General Conference, B-17-20 [Non-patent document 2] Natsuko Ouchi, Satoshi Ota, Takahito Inoshita, "Delay Prediction Technology for Delay Time Guarantee" - A Study on Handling Measurement Data in System-Level Simulation - 2022 IEICE General Conference, B-17-21 Summary of the Invention [Problem to be solved by the invention]

[0007] Because the carrier sense operation described above depends on the implementation, there may be a discrepancy between the model incorporated into the simulation and the actual operation. To address this issue, it is conceivable to incorporate the carrier sense operation, which affects communication delay time as described above, into the simulation model after reflecting the actual operation. However, Non-Patent Documents 1 and 2 do not make clear how to understand the carrier sense operation as a prerequisite for this. Therefore, a means for understanding the carrier sense operation has been desired.

[0008] Therefore, an object of the present disclosure is to provide an electromagnetic noise measurement system and method that can appropriately grasp carrier sense operation. [Means for solving the problem]

[0009] To achieve the above object, the electromagnetic noise measurement system and method of the present disclosure employs a technique for estimating conditions for a wireless system to stop or start communication based on the signal strength and bandwidth of the electromagnetic noise.

[0010] Specifically, the electromagnetic noise measurement system of the present disclosure includes: an analysis unit that acquires the communication signal state of the wireless system to be measured and the signal strength and bandwidth of the electromagnetic noise from the noise source; a processing unit that estimates a condition for the wireless system to start or stop communication based on the signal strength and bandwidth of the electromagnetic noise; Equipped with.

[0011] In addition, the electromagnetic noise measurement method of the present disclosure includes: Acquiring the communication signal strength of the wireless system to be measured and the signal strength and bandwidth of the electromagnetic noise from the noise source; estimating a condition for the wireless system to start or stop communication based on the signal strength and bandwidth of the electromagnetic noise; Includes.

[0012] This makes it possible to estimate the conditions under which a wireless system starts or stops communication, that is, the conditions for carrier sense operation, based on the signal strength and bandwidth of electromagnetic noise.

[0013] Further, either the analysis unit or the processing unit includes a low-pass filter that passes signals in a frequency band equal to or lower than a limited band including a center frequency of communication in the wireless system, The processing unit may estimate a condition for the wireless system to start or stop communication based on the signal strength and bandwidth of the electromagnetic noise in a limited band including the center frequency.

[0014] Here, the carrier sense operation depends on the signal strength of electromagnetic noise in a limited band including the center frequency of the communication band of the wireless system. According to the above configuration, it is possible to estimate the conditions for starting or stopping communication of the wireless system using a low-pass filter based on the signal strength and bandwidth of electromagnetic noise in the limited band including the center frequency of communication of the wireless system.

[0015] The condition may also be that the signal strength of the electromagnetic noise in a limited band including the center frequency of communication of the wireless system exceeds or falls below a predetermined threshold.

[0016] This makes it possible to grasp the carrier sense operation by checking the behavior of the signal strength of electromagnetic noise near a predetermined threshold.

[0017] The processing unit may also store the threshold value and predict the behavior of communication in the wireless system based on the threshold value.

[0018] This makes it possible to predict the behavior of communication in a wireless system based on threshold values ​​related to conditions for carrier sense operation.

[0019] The wireless communication system further includes a packet capture unit configured to acquire packets of communication data of the wireless system, The processing unit may combine the data related to the packets and the data related to the threshold value to predict communication behavior of the wireless system.

[0020] This allows the communication simulation model to be appropriately customized based on data related to packets and data related to thresholds related to conditions for carrier sense operation.

[0021] The apparatus further includes a noise generator that generates electromagnetic noise based on an instruction from the processing unit, The conditions for the wireless system to start or stop communication may be estimated based on the signal strength and bandwidth of the electromagnetic noise from the noise generator.

[0022] This allows the carrier sense operation to be grasped while changing the level of electromagnetic noise using a noise generator.

[0023] The above disclosures can be combined as much as possible. [Effects of the Invention]

[0024] According to the present disclosure, the carrier sense operation can be properly understood. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a diagram illustrating a configuration of an electromagnetic noise measurement system according to an embodiment of the present disclosure. [Figure 2] 10 is a flowchart illustrating a flow of detecting the minimum bandwidth at which a wireless LAN terminal can detect simulated noise. [Figure 3] FIG. 10 is a diagram showing the spectrum actually used in the test. [Figure 4] 10 is a flowchart illustrating a flow of detecting the maximum shift frequency at which the wireless LAN terminal can detect simulated noise. [Figure 5] FIG. 10 is a diagram illustrating verification using a noise source. [Figure 6] These are spectrograms when a wireless LAN terminal continues communication and when it stops communication. [Figure 7] 10 is a graph showing the power after passing through a 2 MHz low-pass filter when a wireless LAN terminal continues communication and when it stops communication. [Figure 8] 10 is a graph showing the power after passing through a 20 MHz low-pass filter when a wireless LAN terminal continues communication and when it stops communication. [Figure 9] FIG. 10 is a diagram illustrating carrier sense threshold estimation. [Figure 10] 10 is a flowchart illustrating a delay estimation process flow performed by the electromagnetic noise measurement system. DETAILED DESCRIPTION OF THE INVENTION

[0026] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the present disclosure is not limited to the embodiments shown below. These implementation examples are merely illustrative, and the present disclosure can be implemented in various forms with various modifications and improvements based on the knowledge of those skilled in the art. Note that components with the same reference numerals in this specification and drawings indicate the same components.

[0027] [Outline of the electromagnetic noise measurement system] 1 is a system for generating simulated electromagnetic noise and verifying the behavior of a wireless system 200. In particular, the purpose of this embodiment is to use the electromagnetic noise measurement system 100 to estimate the carrier sense operation when the wireless system 200 detects electromagnetic noise from an external device.

[0028] Here, the carrier sense operation refers to a mechanism in the wireless system 200 that checks whether another wireless station is using its own channel (the channel on which the wireless system 200 is about to start wireless transmission) before the wireless system 200 starts wireless transmission, and if another wireless station is using its own channel, it avoids transmission on the same frequency, thereby avoiding wireless interference. If a device that generates electromagnetic noise is present near the wireless system 200, the wireless system 200 may detect the electromagnetic noise and perform a carrier sense operation. Such a carrier sense operation affects the communication delay time of a wireless communication application. Therefore, in order to use a simulator to predict the delay of a wireless communication application and provide delay compensation, it is necessary to incorporate the carrier sense operation into the simulator.

[0029] Such carrier sense operation depends on the environment and implementation of the wireless system 200. Therefore, in this embodiment, a software defined radio (SDR) is used to transmit simulated electromagnetic noise near the wireless LAN terminal of the wireless system 200, thereby estimating the carrier sense operation.

[0030] Specifically, the electromagnetic noise measurement system 100 of the present disclosure includes: a spectrum analyzer 12 for acquiring the signal level of the wireless system 200 to be measured and the signal strength and bandwidth of the electromagnetic noise level from a noise source (noise source 300, noise generator 11); a server 14 that estimates conditions for the wireless system 200 to start or stop communication based on the signal strength and bandwidth of the electromagnetic noise level; Equipped with.

[0031] This makes it possible to estimate the conditions under which the wireless system 200 starts or stops communication, that is, the conditions for the carrier sense operation, based on the signal strength and bandwidth of the electromagnetic noise level.

[0032] [Wireless system configuration] The configuration of a wireless system 200 that performs communication that is the target of delay estimation (hereinafter referred to as "target communication") will be described with reference to Figure 1. The wireless system 200 is a system that performs wireless communication using a wireless LAN, and includes a wireless LAN terminal 21, a microcomputer 22, an access point 23, and a server 24.

[0033] The wireless LAN terminal 21 is configured to be able to transmit a wireless signal to the outside based on the control of the microcomputer 22. The wireless signal from the wireless LAN terminal 21 is received by the access point 23 and sent to the server 24. For example, the microcomputer 22 may be a single-board microcomputer such as Raspberry Pi (registered trademark). In this case, wireless communication (target communication) may be performed using software such as Iperf for measuring and tuning network throughput.

[0034] In this embodiment, it is assumed that the access control method used in wireless system 200 is CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance). However, the access control method is not limited to this. Furthermore, when the communication method and MCS (Modulation and Coding Scheme) are automatically controlled, the signal duration changes even when the same amount of data is transmitted. In this embodiment, however, measurements are performed after restricting MCS control.

[0035] [Configuration of electromagnetic noise measurement system] The electromagnetic noise measurement system 100 includes a noise generator 11, a spectrum analyzer 12, a packet capture device 13, and a server 14. The spectrum analyzer 12 functions as an "analysis unit." The server 14 functions as a "processing unit." The noise generator 11 functions as a "noise source."

[0036] The noise generator 11 is, for example, a software defined radio. The noise generator 11 is arranged near the wireless LAN terminal 21 and configured to generate simulated noise (electromagnetic noise). The noise generator 11 is operated by an application installed in the server 14.

[0037] The spectrum analyzer 12 acquires data relating to the frequency and level (intensity) of electromagnetic waves emitted by devices located in the vicinity thereof. Specifically, in this embodiment, the spectrum analyzer 12 acquires data relating to the frequency and level (intensity) of radio waves emitted by the wireless LAN terminal 21, and data relating to the frequency and level (intensity) of electromagnetic noise from devices located in the vicinity of the wireless system 200. The data acquired by the spectrum analyzer 12 is sent to and stored in the server 14. The spectrum analyzer 12 is operated by an application installed in the server 14. The signal level of communication by the wireless LAN terminal 21 is an example of "communication signal strength." The electromagnetic noise level generated by the noise generator 11 is an example of "electromagnetic noise signal strength."

[0038] For example, the spectrum analyzer 12 may be configured to continuously acquire IQ (In Phase / Quadrature Phase) samples of I phase (In Phase) and Q phase (Quadrature Phase).

[0039] In this embodiment, the spectrum analyzer 12 is also provided with a low-pass filter (LPF). The low-pass filter is configured to pass signals in a certain frequency band and block signals in other frequency bands. The user can arbitrarily set which frequency bands the low-pass filter will pass. When the low-pass filter is enabled, the spectrum analyzer 12 processes the signals that have passed through the low-pass filter and transmits them to the server 14. The low-pass filter may be provided in the server 14.

[0040] The packet capture 13 is configured to capture packets of communication data transmitted by the wireless LAN terminal 21. For example, the packet capture 13 may be configured to perform packet capture using tcpdump. Data related to the packets captured by the packet capture 13 is sent to and stored in the server 14. The packet capture 13 is operated by an application installed in the server 14.

[0041] The server 14 has a database that stores data from the spectrum analyzer 12 and the packet capture device 13. The server 14 also has a function for forming a network consisting of one or more wireless systems 200 and other wireless systems (radio devices) within a simulator based on the data stored in the database, and simulating the end-to-end communication quality between the target terminal and the server 14. Specifically, the simulator may be configured to have multiple nodes, and it is possible to simulate the end-to-end communication quality between the target terminal and the server 14 by assuming a network consisting of multiple wireless systems as the actual operation of the system. The simulator of the server 14 is configured to perform machine learning and statistical processing based on packet-related data to model wireless communication. For example, the server 14 may be equipped with a QualNet (registered trademark) simulator that can grasp the behavior of the wireless system 200 on a packet-by-packet basis using system-level simulation (SLS). QualNet has multiple protocol models implemented, enabling simulation of behavior on a packet-by-packet basis.

[0042] The simulator implemented in server 14 is configured to be able to predict wireless communication delay times by combining actual measurements of background traffic, such as data related to electromagnetic noise and carrier sense operation, with a packet-by-packet behavior model of wireless system 200. The simulator in server 14 is also configured to be able to implement a large number of protocols and to reproduce background traffic in the simulator using various methods.

[0043] As described above, in this embodiment, target communications for which delay estimation is desired and other background traffic (electromagnetic noise, carrier sense operation, etc.) are handled separately when modeling wireless communications of the wireless system 200. In addition, background traffic estimation data relating to background traffic is generated and used supplementarily, thereby enabling customization of the model for each site.

[0044] [Things to consider when estimating communication delay time] As described above, the CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance) method is adopted as the access control method in wireless system 200. In this case, the following two points can be pointed out as the main causes of an increase in delay time in the MAC layer. (1) When the SNR (Signal Noise Rate) on the receiving side is reduced due to electromagnetic noise or interference signals, detection and demodulation are not possible, and retransmission occurs. (2) When the transmitting side performs carrier sensing before transmission, electromagnetic noise or interference signals are detected, so the transmitter does not have an opportunity to transmit.

[0045] As a method for simulating the above problem (1), the simulator of the server 14 determines whether or not a MAC layer frame can be received as follows. (A) First, the PER (Packet Error Rate) of the target communication can be calculated from the BER (Bit Error Rate) using the following formula. PER=1-(1-BER) L L: Total number of bits of received data (B) A correspondence table between BER and SINR (Signal to Interference and Noise Ratio) for calculating the BER in the above formula is defined in advance for each modulation method, and the BER is derived from this correspondence table. (C) The physical quantity related to the SINR is calculated as follows. S: The received power of the desired signal (target communication). Since the communication method, layout, and movement are known, it is calculated from the radio wave propagation model (distance loss model such as free space loss, path loss model, fading model, etc.). L: The received power of the interference wave, calculated from the radio wave propagation model according to the communication status of the node that is the source of interference in the simulation. N: Noise is calculated taking into account thermal noise and internal circuit noise.

[0046] In this embodiment, the actual measurement value can be used by inputting the measurement result of the wireless environment as I (received power of interference waves). The actual measurement value can be, for example, the electromagnetic noise level.

[0047] On the other hand, in order to verify the above problem (2), the question arises as to what should be taken into consideration and how should actual measured values ​​of carrier sense operation, etc. be acquired. Therefore, this embodiment provides the matters to be considered when incorporating the phenomenon of cause (2) of delay extension into a simulator, and a method for acquiring the phenomenon (particularly, carrier sense operation).

[0048] First, there is electromagnetic noise, which can be broadband like impulse noise or whose frequency characteristics fluctuate over time. It is necessary to confirm the effect of fluctuations in the frequency characteristics of electromagnetic noise on communication delay time and incorporate this into the simulation model.

[0049] In addition, the methods for detecting electromagnetic noise and interference signals for carrier sense operation and for measuring their levels depend on the manufacturer's implementation. In order to verify the impact of carrier sense operation on communication delay time, it is necessary to clarify the different behavior of each wireless device and reflect this in the simulation model.

[0050] Therefore, the electromagnetic noise measurement system 100 according to this embodiment employs a method in which the actual wireless communication status of each individual wireless device is observed by the spectrum analyzer 12, and the observation results are reflected in the simulation model. Specifically, a simulated noise is generated by the noise generator 11, and the wireless communication status of the wireless system 200 is observed by the spectrum analyzer 12 while changing the bandwidth and center frequency of the simulated noise. This will be described in detail below.

[0051] [Confirmation of carrier sense operation using simulated noise] First, in this embodiment, simulated noise is emitted from the noise generator 11, and the behavior of the wireless system 200 performing the target communication is confirmed. Specifically, in this embodiment, the bandwidth and center frequency of the simulated noise generated by the noise generator 11 are changed, and it is confirmed whether the wireless LAN terminal 21 of the wireless system 200 can detect the simulated noise. In other words, it is confirmed at what bandwidth and center frequency the wireless LAN terminal 21 detects the simulated noise and performs carrier sense operation.

[0052] 2 to 4, the confirmation of carrier sense operation using simulated noise will be described in detail below. Fig. 2 shows a flow for detecting the minimum bandwidth at which the wireless LAN terminal 21 can detect simulated noise, and Fig. 4 shows a flow for detecting the maximum shift frequency at which the wireless LAN terminal 21 can detect simulated noise. The center frequency of the communication band of the target communication is set as the initial value of the center frequency of the simulated noise. The bandwidth of the simulated noise is set to CW (Continuous Wave), and the transmission power of the simulated noise is set high enough to detect a signal.

[0053] First, the noise generator 11 generates and transmits an unmodulated signal having a center frequency of the communication band of the target communication as simulated noise (step S1).

[0054] The electromagnetic noise measurement system 100 uses the spectrum analyzer 12 to determine whether the wireless LAN terminal 21 has stopped the target communication (step S2).

[0055] The electromagnetic noise measurement system 100 repeats a test to widen the bandwidth of the simulated noise while increasing the number of simulated noise signals at regular frequency intervals until the wireless LAN terminal 21 stops transmitting signals (step S2: Yes). Specifically, based on an instruction from the server 14, the noise generator 11 transmits simulated noise in which unmodulated signals with frequencies 200 kHz apart are added to both sides of the unmodulated signal generated immediately before (step S3), and repeats this process until the wireless LAN terminal 21 stops transmitting signals.

[0056] FIG. 3 shows an example of an unmodulated signal actually used in the test. In this test, even when noise generator 11 generated an unmodulated signal (three unmodulated signals) by adding an unmodulated signal spaced 200 kHz apart and an unmodulated signal spaced 400 kHz apart to the original unmodulated signal, WLAN terminal 21 continued the target communication. In other words, it was found that when there were three unmodulated signals, carrier sense operation was not performed. On the other hand, when noise generator 11 generated an unmodulated signal (five unmodulated signals) by adding an unmodulated signal spaced 600 kHz apart and an unmodulated signal spaced 800 kHz apart to the unmodulated signal, WLAN terminal 21 stopped the target communication. In other words, it was found that when there were five unmodulated signals, simulated noise was detected in WLAN terminal 21 and carrier sense operation was performed.

[0057] The frequency of the unmodulated signal to be added can be freely determined by the user. The frequency band occupied by the artificial noise can be changed by modulation.

[0058] Next, the electromagnetic noise measurement system 100 shifts the center frequency of the unmodulated signal by 0.5 MHz when the wireless LAN terminal 21 stops the target communication in the flow of Fig. 2 (step S4). Specifically, the noise generator 11 shifts the center frequency of the unmodulated signal generated immediately before by 0.5 MHz based on an instruction from the server 14.

[0059] The electromagnetic noise measurement system 100 uses the spectrum analyzer 12 to determine whether the wireless LAN terminal 21 has resumed the target communication (step S5).

[0060] The electromagnetic noise measurement system 100 repeats the test of shifting the center frequency of the simulated noise by 0.5 MHz each time until the wireless LAN terminal 21 resumes the target communication (step S5: No). Note that the amount by which the unmodulated signal is shifted is arbitrary and can be freely set by the user.

[0061] In this test, when five unmodulated signals with different bandwidths were generated, the center frequency of the simulated noise (the center frequency of the communication band of the target communication was set as the initial value) was shifted by 2.5 MHz, and the wireless LAN terminal 21 resumed communication. In other words, when the center frequency of the simulated noise was shifted by 2.5 MHz, the simulated noise was not detected by the wireless LAN terminal 21.

[0062] The above suggests that the condition under which the wireless LAN terminal 21 stops the target communication through carrier sense operation depends not on the electromagnetic noise level occupying the entire communication band, but on the electromagnetic noise level in a limited band including the center frequency of the communication band of the target communication. In the following explanation, the frequency (2.0 MHz in this embodiment) immediately before the frequency at which the wireless LAN terminal 21 resumes communication (2.5 MHz in this embodiment) when shifted from the center frequency is referred to as the "maximum shift frequency." In other words, the frequency immediately before the simulated noise is no longer detected is referred to as the "maximum shift frequency."

[0063] [Verification using actual noise sources] Next, verification using an actual noise source 300 will be described with reference to Figures 1 and 5. As shown in Figure 1, an operator installs noise source 300 near wireless system 200. Noise source 300 is, for example, a microwave oven. Noise source 300 may be provided as a component of electromagnetic noise measurement system 100, or may be provided as a separate component from electromagnetic noise measurement system 100. Note that stopping communication here also includes cases where a signal is transmitted intermittently to avoid timing when electromagnetic noise is present.

[0064] In general, it can be assumed that electromagnetic noise generated in a factory fluctuates in the frequency direction over a wide band, and that its level fluctuates in a short time period. To address such phenomena, noise source 300 is configured to generate electromagnetic noise that fluctuates in the frequency direction and that its level fluctuates in a short time period. For example, the average power of electromagnetic noise peaks at intervals of about 10 ms, and the frequency peaks move over time.

[0065] Specifically, while the noise source 300 was operating, UDP (User Datagram Protocol) communication was performed from the wireless LAN terminal 21 to the server 24. At the same time, the spectrum analyzer 12 continuously acquired IQ (In phase / Quadrature Phase) samples.

[0066] As a result of the verification using the noise source 300, as shown in FIG. 5, when the electromagnetic noise level in a limited band including the center frequency of the communication band of the target communication is relatively low, the wireless LAN terminal 21 continues the target communication even when electromagnetic noise is present. In other words, it was found that when the electromagnetic noise level in a limited band including the center frequency of the communication band of the target communication is relatively low, the carrier sense operation is not performed. On the other hand, when the electromagnetic noise level in the center frequency of the communication band of the target communication is relatively high, the wireless LAN terminal 21 transmits a signal avoiding the timing when electromagnetic noise is present. In other words, it was found that when the electromagnetic noise level in a limited band including the center frequency of the communication band of the target communication is relatively high, the carrier sense operation is performed.

[0067] This is consistent with the above suggestion that the conditions under which the carrier sense operation is performed depend on the electromagnetic noise level in a limited band including the center frequency of the communication band of the target communication.

[0068] [Verification using a low-pass filter] Next, a method for verifying carrier sense operation using a low-pass filter implemented in the spectrum analyzer 12 will be described with reference to Figures 6 to 8. In this verification, similar to the above, the verification is performed using the noise source 300. However, the scope of the present disclosure is not limited to performing the verification using the noise source 300. The verification may also be performed using the noise generator 11 while changing the simulated noise level.

[0069] Specifically, either the spectrum analyzer 12 or the server 14 is provided with a low-pass filter that passes signals in a frequency band below a limited band including the center frequency of communication of the wireless system 200, The server 14 estimates the conditions under which the wireless system 200 should start or stop communication based on the signal strength and bandwidth of the electromagnetic noise level in a limited band including the center frequency.

[0070] As described above, the carrier sense operation depends on the electromagnetic noise level in a limited band including the center frequency of the communication band of wireless system 200. According to the above configuration, a low-pass filter can be used to estimate the conditions under which wireless system 200 starts or stops communication, based on the signal strength and bandwidth of the electromagnetic noise level in the limited band including the center frequency of communication of wireless system 200.

[0071] 6 to 8 show spectrograms and signal strength data when the wireless LAN terminal 21 continues the target communication even during peaks of electromagnetic noise, while (b-1) to (b-3) of Fig. 6 to 8 show spectrograms and signal strength data when the wireless LAN terminal 21 stops the target communication during peaks of electromagnetic noise.

[0072] 7 and 8 show wireless communication conditions when different low-pass filters are applied. As described above, it is suggested that the conditions under which the carrier sense operation is performed depend on the electromagnetic noise level in a limited band including the center frequency of the communication band of the target communication. Therefore, in this embodiment, the behavior of the carrier sense operation is verified by comparing the measurement results (FIG. 7) using a low-pass filter that passes signals in a frequency band of 2 MHz or less to correspond to the maximum shift frequency with the measurement results (FIG. 8) using a low-pass filter that passes signals in a frequency band of 20 MHz or less to correspond to the entire communication band.

[0073] In Figure 7, (a-2) and (b-2) are compared. In the case of (a-2), the power due to electromagnetic noise is low and is buried in the power due to the target communication. On the other hand, in the case of (b-2), the power of the electromagnetic noise after passing through the 2 MHz low-pass filter is higher than in the case of (a-2). Furthermore, comparing (b-1) in Figure 6 with (b-2) in Figure 7, it is clear that the target communication is stopped at the timing when the power of the electromagnetic noise becomes high.

[0074] 8, the power of the electromagnetic noise after passing through the 20 MHz low-pass filter is similarly high when comparing (a-3) and (b-3). Despite this, in this embodiment, when the power of the electromagnetic noise after passing through the 2 MHz low-pass filter is high ((b-1) to (b-3)), the target communication is stopped, whereas when the power of the electromagnetic noise after passing through the 2 MHz low-pass filter is low ((a-1) to (a-3)), the target communication is continued.

[0075] In this way, it is estimated that the target communication continues when the electromagnetic noise level becomes low near the center frequency of the target communication, and stops when the electromagnetic noise level becomes high near the center frequency of the target communication. This is consistent with the above suggestion that the condition for performing carrier sense operation depends on the electromagnetic noise level in a limited band that includes the center frequency of the communication band of the target communication.

[0076] That is, the server 14 can estimate the threshold value for the electromagnetic noise level at which communication stops by performing a test in which the electromagnetic noise level is changed while applying a 2 MHz low-pass filter. In this embodiment, the model of the simulator in the server 14 can be customized using data on such electromagnetic noise levels and their threshold values.

[0077] The scope of the present disclosure is not limited to server 14 estimating the conditions under which wireless system 200 stops communication. Server 14 may estimate the electromagnetic noise level at which communication will start (restart) by performing a test in which the electromagnetic noise level is changed while applying a 2 MHz low-pass filter.

[0078] [Carrier sense threshold estimation] Next, with reference to FIG. 9, a method for estimating the carrier sense operation threshold for the electromagnetic noise level will be described. As described above, a test is performed by changing the electromagnetic noise level while applying a low-pass filter near the center frequency of the target communication. Specifically, in this embodiment, a test is performed by changing the electromagnetic noise level while applying a 2 MHz low-pass filter. In this embodiment, the test is performed while changing the electromagnetic noise level generated by the noise source 300. However, the scope of the present disclosure is not limited to performing the test using the noise source 300. The test may also be performed by changing the simulated noise level using the noise generator 11. In particular, the threshold may be estimated by gradually changing the output using an SDR (Software Defined Radio) with a high output level.

[0079] 9, the server 14 controls the noise source 300 so that the electromagnetic noise emitted by the noise source 300 gradually decreases. Then, the server 14 uses the spectrum analyzer 12 to confirm the electromagnetic noise level at which the target communication is not stopped even when electromagnetic noise from the noise source 300 is present. The server 14 estimates the electromagnetic noise level at which the target communication is not stopped (i.e., the target communication is started) as a threshold value. The threshold value is stored in the server 14.

[0080] The above-described method for estimating the threshold does not depend on the characteristics of the wireless device (wireless LAN terminal), and therefore, the above-described method can estimate the threshold for each wireless device (wireless LAN terminal) that performs the target communication.

[0081] Furthermore, in this embodiment, the electromagnetic noise level at the timing when the target communication starts (restarts) is estimated as the threshold, but the scope of the present disclosure is not limited to this. The electromagnetic noise level at the timing when the target communication stops may also be estimated as the threshold. In other words, the server 14 estimates the carrier sense operation (specifically, the carrier sense threshold) when the electromagnetic noise level in a limited band including the center frequency of the communication of the wireless system 200 exceeds or falls below a predetermined threshold. In this way, the carrier sense operation can be grasped by checking the behavior of the signal strength of the electromagnetic noise near the predetermined threshold.

[0082] [flowchart] Next, the delay prediction process flow by the electromagnetic noise measurement system 100 will be described with reference to Fig. 10. The electromagnetic noise measurement system 100 performs delay prediction based on the carrier sense operation threshold data obtained as described above and the corresponding electromagnetic noise level data, in addition to the packets of communication data acquired by the packet capture 13. Note that these data are acquired using electromagnetic noise from the noise source 300 or simulated noise from the noise generator 11.

[0083] First, in step S11, the packet capture 13 acquires packets of communication data of the target communication.

[0084] The server 14 controls the noise source 300 so that the electromagnetic noise emitted by the noise source 300 gradually decreases. Then, the server 14 uses the spectrum analyzer 12 to confirm the electromagnetic noise level at which the target communication is not stopped even if the electromagnetic noise from the noise source 300 exists.

[0085] Specifically, the spectrum analyzer 12 uses a low-pass filter to acquire actual measurements of the electromagnetic noise level in the center frequency band of the target communication, corresponding to the timing when the wireless LAN terminal 21 performs a carrier sense operation, i.e., the timing when the target communication stops. The actual measurements are transmitted to the server 14 as time-series data and stored therein.

[0086] The server 14 also estimates the electromagnetic noise level at which the target communication is no longer stopped as a threshold value. The threshold value is stored in the server 14.

[0087] In step S12, when a mixture of communication signal packets and electromagnetic noise is received, the data shaping function of the server 14 extracts only the electromagnetic noise and generates background traffic estimation data. Note that, in generating the background traffic estimation data, the communication data acquired by the packet capture 13 may be used supplementarily.

[0088] In step S13, the background traffic prediction function of the server 14 generates background traffic prediction data using the background traffic estimation data and the trained model generated in advance. Here, several approaches, such as statistical methods and machine learning methods, can be considered for generating the background traffic prediction data.

[0089] In step S14, the simulator of the server 14 predicts delays in future sections using the generated background traffic prediction data and other data required for the simulation, such as network setting data. In other words, the server 14 predicts the communication behavior of the wireless system 200 based on thresholds. This makes it possible to grasp the carrier sense operation by checking the behavior of the signal strength of electromagnetic noise near a predetermined threshold. The server 14 also combines data related to packets and data related to thresholds to predict the communication behavior of the wireless system 200. This makes it possible to appropriately customize a communication simulation model based on data related to packets and data related to thresholds related to the conditions for carrier sense operation.

[0090] In this embodiment, the above process is performed for each wireless device (wireless LAN terminal) that performs target communication, thereby making it possible to predict delays in future sections for each wireless device.

[0091] Note that step S13 or the background traffic prediction function may be omitted. In this case, instead of the future delay time, the delay time in an environment where the measured background traffic (electromagnetic noise, etc.) is present may be estimated using a simulator or the like. Then, parameters for the simulation may be adjusted in step S14 depending on the evaluation content.

[0092] Also, the process of step S14 may be omitted. In this case, assuming that the simulation will take time, the simulation may be performed in advance while changing parameters representing background traffic (reception level, frequency, etc.), and a mapping between the parameters and delay time may be obtained.

[0093] The device of the present invention can also be realized by a computer and a program, and the program can be recorded on a recording medium or provided via a network. The program of the present disclosure is a program for causing a computer to realize each function of the device according to the present disclosure, and a program for causing a computer to execute each procedure of the method executed by the device according to the present disclosure. [Explanation of symbols]

[0094] 11: Noise generator 12: Spectrum analyzer 13: Packet capture 14: Server 21: Wireless LAN terminal 22: Microcomputer 23: Access point 24: Server 100: Electromagnetic noise measurement system 200: Radio system 300: Noise source

Claims

1. an analysis unit that acquires the communication signal state of the wireless system to be measured and the signal strength and bandwidth of the electromagnetic noise from the noise source; a processing unit that estimates a condition for the wireless system to start or stop communication based on the signal strength and bandwidth of the electromagnetic noise; Equipped with Electromagnetic noise measurement system.

2. one of the analysis unit and the processing unit includes a low-pass filter that passes signals in a frequency band equal to or lower than a limited band including a center frequency of communication in the wireless system; the processing unit estimates a condition for starting or stopping communication of the wireless system based on a signal strength and a bandwidth of the electromagnetic noise in a limited band including the center frequency; The electromagnetic noise measurement system according to claim 1 .

3. the condition being that the signal strength of the electromagnetic noise in a limited band including the center frequency of communication of the wireless system exceeds or falls below a predetermined threshold; 3. The electromagnetic noise measurement system according to claim 2.

4. the processing unit stores the threshold value and predicts a behavior of communication in the wireless system based on the threshold value.

4. The electromagnetic noise measurement system according to claim 3.

5. a packet capture unit for acquiring packets of communication data of the wireless system; the processing unit combines the data related to the packet and the data related to the threshold value to predict communication behavior of the wireless system.

5. The electromagnetic noise measurement system according to claim 4.

6. further comprising a noise generator that generates electromagnetic noise based on an instruction from the processing unit; the processing unit estimates a condition for the wireless system to start or stop communication based on a signal strength and a bandwidth of the electromagnetic noise from the noise generator. The electromagnetic noise measurement system according to claim 1 .

7. Acquiring the communication signal strength of the wireless system to be measured and the signal strength and bandwidth of the electromagnetic noise from the noise source; estimating a condition for the wireless system to start or stop communication based on the signal strength and bandwidth of the electromagnetic noise; Including, Electromagnetic noise measurement methods.

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