Patent Description:
Anomaly detection device and method for electrical wiring are known as a conventional technique. For example, Patent literature <NUM> discloses anomaly detection device and method for electrical wiring, which can detect even momentary disconnection and prevent complete disconnection. Specifically, the anomaly detection device disclosed in Patent literature <NUM> is an anomaly detection device for electrical wiring that detects an anomaly in an electrical wiring based on a current signal flowing through the electrical wiring. The anomaly detection device includes a noise detection coil that is arranged in the vicinity of the electrical wiring and detects electromagnetic noise caused by disconnection of the electrical wiring. In addition, the anomaly detection device includes a resistor that converts a current generated by the electromagnetic noise detected by the noise detection coil into a voltage, and an electromagnetic noise output part that includes a waveform measurement part which measures waveform data indicating a time-series change in a voltage applied to the resistor and outputs the waveform data.

Patent literature <NUM>: Japanese Patent Laid-open "<CIT>)".

Attention is drawn to <CIT> describing systems and methods for detecting and locating ingress of an over-the-air signal into a wired communications network. Computing devices located in a plurality of different areas may be configured to identify amplitude of signals transmitted over the wired communications network as it varies by signal frequency. In one example, the system may determine expected amplitude of the over-the-air signal at the plurality of different areas. In other examples, the system may identify amplitudes received over the wired communication path at the computing devices. The system may determine a location at which the over-the-air signal has entered the wired communications network based on a comparison of the identified and expected amplitudes of the over-the-wire signal.

Attention is further drawn to <CIT> describing a method that includes retrieving key performance indicators from multi-tone signals captured by a data collector located in a cable network; identifying a fault signature based on the key performance indicators, in which the fault signature is identified based on phase domain analysis of a channel response; and accessing a data repository located in a cloud network for geographical information associated with the cable network. The method further includes determining a location of a fault in the cable network based on the fault signature and the geographical information, in which the determining further includes: determining a length of a fault cavity associated with the fault; identifying at least one segment having a length the same as the length of the fault cavity; identifying terminating devices associated with the at least one segment; and tagging the identified terminating devices as potentially faulty.

Further attention is drawn to <CIT> describing a method of managing a digital subscriber line, in particular for identifying the location of weather related faults. The method continuously measures the signal to noise (SNR) margin on the DSL line as well as measurements from weather related sensors, such as moisture and wind sensors, which each have an associated geographical location. The SNR margin measures are compared to predetermined conditions based on SNR margin characteristics associated with a population of good lines. If the SNR margin measures fail to meet the predetermined conditions, the SNR measures are also compared to the weather sensor measurements over a day or number of days. If there is a correlation between the SNR margin measures and at least one of the sensors, then location of the fault is identified as the location of the sensor having the strongest correlation with the SNR measures.

However, the above-mentioned conventional technique has a configuration for detecting disconnection of an electrical wiring, and does not have a configuration on the premise of identifying a cause of an anomaly of a signal input via an electrical wiring (cable). Therefore, in the above-mentioned conventional technique, even if there is an anomaly in the signal input via the cable, the cause cannot be identified. Therefore, there may be a problem that a user cannot take measures corresponding to the cause of the signal anomaly.

One aspect of the present invention is to realize an information processing device capable of identifying a cause of an anomaly, if any, in a signal input via a cable.

In order to solve the above-mentioned problems, an information processing device according to claim <NUM> is provided.

In addition, a control method for information processing device according to claim <NUM> is provided.

According to one aspect of the present invention, the user can take measures corresponding to the cause of the signal anomaly.

Hereinafter, an embodiment according to one aspect of the present invention (hereinafter, also referred to as "the embodiment") is described with reference to the drawings.

<FIG> is a diagram showing an example of a master-slave control system <NUM> to which a master device <NUM> (information processing device) according to the embodiment is applied. First, an outline of an application example of the master device <NUM> is described with reference to <FIG>. As shown in <FIG>, the master device <NUM> is included in the master-slave control system <NUM>.

The master device <NUM> acquires, from slave devices <NUM> included in the master-slave control system <NUM>, a signal quality of a signal input to the slave devices <NUM> via a cable. When the signal quality is poor (the signal includes noise), the master device <NUM> determines, from variations in the acquired signal quality, whether a cause of the noise included in the signal is due to a mechanical factor or is due to electrical noise. A frequency and/or a change width of variations in the signal quality differs depending on whether the cause of the noise is due to a mechanical factor or is due to electrical noise.

According to the above configuration, the master device <NUM> can determine the cause of the signal anomaly in the master-slave control system <NUM> from the variations in the signal quality of the signal. Therefore, a user can take measures according to the determined cause of the noise. That is, the user can appropriately respond to an anomaly in the signal input via the cable.

The master-slave control system <NUM> is a system that realizes automation of a manufacturing process in a factory. As an example, as shown in <FIG>, the master-slave control system <NUM> includes the slave devices <NUM>, a signal relay device <NUM>, the master device <NUM>, a display/input device <NUM>, and the like. In the master-slave control system <NUM>, data is transmitted and received between the master device <NUM> and the slave devices <NUM> by sequentially transferring data frames on a network connecting the master device <NUM> and the slave devices <NUM>. In the example shown in <FIG>, a plurality of communication paths formed by the slave devices <NUM> are branched on a communication downstream side of the signal relay device <NUM>.

<FIG> is a diagram showing another example of the master-slave control system <NUM> to which the master device <NUM> according to the embodiment is applied. In the example shown in <FIG>, the slave devices <NUM> included in the master-slave control system <NUM> establish one ring-like path on the communication downstream side of the signal relay device <NUM>.

The slave device <NUM> performs one or more functions related to the manufacturing process under the control of the master device <NUM>. The slave device <NUM> communicates with the master device <NUM> via the network and controls the drive of an external device <NUM> under the control of the master device <NUM>. The slave device <NUM> functions as a relay device for transmitting and receiving data between the master device <NUM> and the external device <NUM>.

<FIG> is a block diagram showing an example of a configuration of the slave device <NUM> according to the embodiment. As shown in <FIG>, the slave device <NUM> includes a PHY unit <NUM> and an external device control unit <NUM>.

The PHY unit <NUM> is a communication unit for communication with the slave device <NUM> on a side closer to the master device <NUM> (communication upstream side) and the slave device <NUM> on a side farther from the master device <NUM> (communication downstream side). For example, the PHY unit <NUM> is a functional block representing a function executed by an element of a physical layer that performs communication.

<FIG> is a block diagram showing an example of a configuration of the PHY unit <NUM> according to the embodiment. As shown in <FIG>, the PHY unit <NUM> includes a signal quality calculation unit <NUM>. The signal quality calculation unit <NUM> calculates a signal quality of a signal input to the PHY unit <NUM> via the cable.

The signal quality calculation unit <NUM> calculates an index representing a level of the noise included in the signal. The index is a value of a signal quality indicator (SQI). The signal quality calculation unit <NUM> outputs a signal indicating the calculated signal quality to the master device <NUM> via the other slave devices <NUM>, the signal relay device <NUM>, and the like.

The external device control unit <NUM> controls the drive of the external device <NUM> under the control of the master device <NUM>. The external device <NUM> is a machine such as a manufacturing device, an inspection device, or the like. The external device <NUM> may be input equipment such as a sensor (a temperature sensor, an optical sensor, or the like), or a switch (a push button switch, a limit switch, a pressure switch, or the like), or may be output equipment such as an actuator, a relay, a solenoid valve, or the like. In the master-slave control system <NUM>, the master device <NUM> controls an operation of the external device <NUM> and receives output data of the external device <NUM> via the slave devices <NUM>.

The signal relay device <NUM> is a relay device that relays data between an upper network and the slave devices <NUM>, the upper network including the master device <NUM> and the like. The signal relay device <NUM> is, for example, a line concentrator (hub). The signal relay device <NUM> can also be referred to as a slave device connected to the master device <NUM> via an upper bus, that is, an upper communication network.

The master device <NUM> is a control device that controls the entire master-slave control system <NUM>, and is, for example, a programmable logic controller (PLC). The master device <NUM> operates as a master device of the signal relay device <NUM> and the slave devices <NUM> in the master-slave control system <NUM>. As shown in <FIG>, the display/input device <NUM> and the like may be connected to the master device <NUM> via a connection cable or the like.

<FIG> is a block diagram showing a configuration of the master device <NUM> according to the embodiment. As shown in <FIG>, the master device <NUM> includes a communication unit <NUM>, a control unit <NUM>, and a storage unit <NUM>.

The communication unit <NUM> communicates with the slave device <NUM> via the signal relay device <NUM>. In the embodiment, in particular, a signal indicating the signal quality calculated by the slave device <NUM> is received from the slave device <NUM>. The communication unit <NUM> outputs the received signal quality to an acquisition unit <NUM>.

In addition, according to an instruction of a determination result output control unit <NUM>, the communication unit <NUM> outputs a signal indicating a result of determination performed by an anomaly determination unit <NUM> and a cause determination unit <NUM>, a signal indicating the signal quality, and the like to the display/input device <NUM>.

The control unit <NUM> includes a central processing unit (CPU), a random access memory (RAM), a read only memory (ROM), and the like, and controls each constituent element according to information processing. The control unit <NUM> includes the acquisition unit <NUM>, the anomaly determination unit <NUM>, the cause determination unit <NUM>, and the determination result output control unit <NUM>.

The acquisition unit <NUM> acquires a signal indicating the signal quality calculated by the slave device <NUM> from the communication unit <NUM>. The acquisition unit <NUM> outputs the signal indicating the signal quality to the anomaly determination unit <NUM>.

The anomaly determination unit <NUM> determines, from variations in the signal quality, whether there is an anomaly in the signal input to the slave device <NUM>.

<FIG> is a diagram showing an example of variations in the signal quality. The vertical axis shows a noise level, and the horizontal axis shows the time. (a) of <FIG> is a diagram showing an example of variations in the SQI value of a signal in a normal state. (b) of <FIG> is a diagram showing an example of variations in the SQI value of a signal including noise caused by a mechanical factor. The mechanical factor includes mechanical vibration, cable disconnection, and the like.

Here, the mechanical vibration is mechanical vibration that causes noise to be mixed into the signal in the cable when electrical connection between the cable and the equipment is incomplete.

(b) of <FIG> is a diagram showing an example of variations in the SQI value of a signal when a part of the cable is disconnected (the cable has not been completely disconnected). (c) of <FIG> is a diagram showing an example of the SQI value of a signal including noise caused by electrical noise.

The electrical noise is electrical noise that is applied to the cable and mixed into the signal in the cable. For example, the electrical noise is electromagnetic noise that propagates in the air from electronic equipment installed near the cable and is mixed into the signal in the cable. In addition, other electrical noise may include, for example, conduction noise generated from a servo mechanism and mixed into the signal in the cable. The conduction noise may be mixed into the signal in the cable and cause a malfunction in the equipment to which the signal is input. The electrical noise can also be expressed as external noise.

In the example shown in (a) of <FIG>, the SQI value does not vary from Noise level <NUM> in the signal in the normal state. The SQI value indicates the degree of noise included in the signal. When the SQI value is low, the signal includes little noise. In addition, when the SQI value is high, the signal includes a lot of noise. Moreover, the noise level in the signal in the normal state changes depending on a configuration of the master-slave control system <NUM> such as a cable length, or the like. For example, as the cable length increases, the noise level of the signal in the normal state tends to increase.

When the SQI value varies, the anomaly determination unit <NUM> determines that the signal has an anomaly. If determining that the signal has an anomaly, the anomaly determination unit <NUM> outputs a signal indicating the signal quality to the cause determination unit <NUM>.

In addition, if determining that the signal has no anomaly, the anomaly determination unit <NUM> outputs a signal indicating that there is no anomaly and a signal indicating the signal quality to the determination result output control unit.

The cause determination unit <NUM> determines, from variations in the signal quality, whether the cause of the noise included in the signal input to the slave device <NUM> is due to a mechanical factor or is due to electrical noise.

In addition, the cause determination unit <NUM> may perform the determination according to at least one of a frequency of the variations in the signal quality and an amplitude of the variations in the signal quality. For example, the cause determination unit <NUM> may perform fast Fourier transform (FFT) on time-series data of the signal quality indicated by the acquired signal to analyze a frequency component, and use the frequency component for the determination.

For example, as shown in (b) and (c) of <FIG>, the influence of a mechanical factor on the variations in the signal quality shows the following tendency compared with the influence of electrical noise on the variations in the signal quality.

The amplitude of the variations in the signal quality is described in detail. In the example shown in (b) of <FIG>, the SQI value of the signal affected by a mechanical factor varies between Noise levels <NUM> and <NUM> with Noise level <NUM> as a reference value.

In addition, in the example shown in (c) of <FIG>, the SQI value of the signal affected by electrical noise varies among Noise levels <NUM> to <NUM>. The amplitude of variations in the SQI value of the signal affected by electrical noise tends to be greater than the amplitude of variations in the SQI value of the signal affected by a mechanical factor.

For example, the cause determination unit <NUM> may determine, according to whether the amplitude of the variations in the signal quality exceeds a predetermined threshold value, whether the cause of the noise included in the signal is due to a mechanical factor or is due to electrical noise.

According to the configuration, appropriate determination can be made on whether the cause of the noise included in the signal is due to a mechanical factor or is due to electric noise.

In addition, the cause determination unit <NUM> may determine that the cause of the noise included in the signal is due to a mechanical factor when the frequency of the variations in the signal quality is equal to or lower than a predetermined value. In addition, the cause determination unit <NUM> may determine that the cause of the noise included in the signal is due to electrical noise when the frequency of the variations in the signal quality is higher than the predetermined value.

The signal quality of the signal affected by a mechanical factor varies in a time unit of several milliseconds, and the signal quality of the signal affected by electrical noise varies in a time unit of several microseconds. Therefore, the predetermined value described above may be a frequency of <NUM>, or the like.

In addition, when a predetermined noise level (for example, Noise level <NUM>) or higher continues for a predetermined period (for example, <NUM> msec) or longer, the cause determination unit <NUM> may determine that the cause of the noise included in the signal is due to a mechanical factor. Moreover, the predetermined noise level and the predetermined period described above, which serve as the criteria for the cause determination unit <NUM> to determine the cause of the noise, are values that can be appropriately set according to the configuration of the master-slave control system <NUM> such as the cable length or the like.

That is, the cause determination unit <NUM> determines that the cause of the noise included in the signal is due to a mechanical factor when the acquired signal quality varies in a unit of milliseconds. In addition, the cause determination unit <NUM> determines that the cause of the noise included in the signal is due to electrical noise when the acquired signal quality varies in a unit of microseconds.

Here, a predetermined frequency value, a predetermined noise level, and a predetermined period, which serve as the criteria for the determination, are stored in the storage unit <NUM> as determination information <NUM>.

According to the above configuration, it is possible to appropriately determine whether the cause of the noise included in the signal is due to a mechanical factor or electric noise.

In addition, the cause determination unit <NUM> may perform the determination based on a degree of similarity between the variations in the signal quality and predetermined patterns.

Here, the predetermined patterns are a variation pattern of the signal quality affected by a mechanical factor and a variation pattern of the signal quality affected by electrical noise. For example, the variation pattern is a pattern of a magnitude of a noise level, duration of a predetermined noise level, and the like. The variation pattern is stored in the storage unit <NUM> as the determination information <NUM>.

That is, according to the above configuration, the cause determination unit <NUM> obtains the degree of similarity by pattern matching between the variations in the signal quality and the predetermined patterns. The cause determination unit <NUM> can determine a cause corresponding to a similar predetermined pattern having a higher degree of similarity (more similar) as the cause of the noise.

In addition, the cause determination unit <NUM> may perform the determination with reference to a predetermined pattern corresponding to each of a plurality of causes of the noise.

For example, the plurality of causes of the noise are a mechanical factor and electrical noise.

Here, the predetermined pattern is stored in the storage unit <NUM> as the determination information <NUM>.

According to the above configuration, the cause of the noise can be determined in detail. Therefore, the user can take measures according to the determined cause of the noise.

In addition, the cause determination unit <NUM> outputs a signal indicating the determination result and a signal indicating the signal quality to the determination result output control unit.

The determination result output control unit <NUM> outputs the signal indicating the determination result of the anomaly determination unit <NUM> and the cause determination unit <NUM> and the signal indicating the signal quality to the display/input device <NUM> via the communication unit <NUM>.

The storage unit <NUM> is, for example, an auxiliary storage device such as a flash memory, a solid state drive or the like, and stores the above-mentioned determination information <NUM> and the like.

The display/input device <NUM> is, for example, a touch-panel-type display/input device. The user of the master-slave control system <NUM> can operate the master device <NUM> via the display/input device <NUM> or check an operating state of the master-slave control system <NUM> by the display/input device <NUM>. In the embodiment, in particular, the display/input device <NUM> displays the determination result of the master device <NUM>, the signal quality input to the slave device <NUM>, and the like.

Moreover, in the above embodiment, a configuration has been described in which the slave device <NUM> calculates the signal quality of the signal input via the cable and outputs the calculated signal quality to the master device <NUM>. In another configuration, for example, the signal relay device <NUM> may have the same configuration as the signal quality calculation unit <NUM> described above, and the signal relay device <NUM> may output the calculated signal quality to the master device <NUM>.

In addition, an external server device of the master-slave control system <NUM> may receive the signal indicating the signal quality and perform cause determination processing that is performed by the master device <NUM> described above on the noise included in the signal. Specifically, the external server device may be a server device connected to the master device <NUM>, or may be a cloud server device.

(a) and (b) of <FIG> are flowcharts showing an example of a flow of processing executed by the master device <NUM>. (a) of <FIG> is a flowchart showing an outline of the flow of the determination processing executed by the master device <NUM>. (b) of <FIG> is a flowchart showing an example of the flow of the cause determination processing of the noise included in the signal executed by the anomaly determination unit <NUM>. As shown in (a) of <FIG>, the acquisition unit <NUM> acquires a signal indicating the signal quality of the signal input to the slave device <NUM> (S1: acquisition step). Subsequently, the anomaly determination unit <NUM> determines whether there is an anomaly in the signal input to the slave device <NUM> (S2). When there is an anomaly in the signal input to the slave device <NUM> (YES in S2), the cause determination unit <NUM> performs the following determination. The cause determination unit <NUM> determines whether the cause of the noise included in the signal input to the slave device <NUM> is due to a mechanical factor or is due to electrical noise (S3: cause determination step). Subsequently, the determination result output control unit <NUM> outputs the determination result performed in S3 to the display/input device <NUM> (S4), and the processing ends. Moreover, when there is no anomaly in the signal input to the slave device <NUM> (NO in S2), the determination result output control unit <NUM> outputs the determination result performed in S2 to the display/input device <NUM> (S4), and the processing ends.

Next, an example of the flow of the cause determination processing (S3) of the noise included in the signal executed by the anomaly determination unit <NUM> is described with reference to (b) of <FIG>. As shown in (b) of <FIG>, the anomaly determination unit <NUM> determines whether the frequency of the variations in the acquired signal quality is equal to or lower than a predetermined value (S31). When the frequency of the variations in the acquired signal quality is equal to or lower than the predetermined value (YES in S31), the anomaly determination unit <NUM> determines that the cause of the noise included in the signal is due to a mechanical factor, and the processing continues to S4. When the frequency of the variations in the acquired signal quality exceeds the predetermined value (NO in S31), the anomaly determination unit <NUM> determines that the cause of the noise included in the signal is due to electrical noise, and the processing continues to S4.

Moreover, in the above example, an example has been described in which the anomaly determination unit <NUM> determines the cause of the noise included in the signal according to the frequency of the variations in the signal quality. As another example, the anomaly determination unit <NUM> may determine the cause of the noise included in the signal according to a magnitude of the amplitude of the variations in the signal quality, a pattern of the frequency of the variations in the signal quality and the magnitude of the amplitude of the variations in the signal quality, and the like.

A control block of the master device <NUM> (particularly the acquisition unit <NUM>, the anomaly determination unit <NUM>, the cause determination unit <NUM>, and the determination result output control unit <NUM>) and the signal quality calculation unit <NUM> of the slave device <NUM> may be implemented by a logic circuit (hardware) formed in an integrated circuit (IC chip) and the like, or may be implemented by software.

In the latter case, the master device <NUM> and the slave device <NUM> include a computer that executes commands of a program which is software for implementing each function. The computer includes, for example, one or more processors and a computer-readable recording medium that stores the program. Besides, in the computer, the processor reads the program from the recording medium and executes the program, and thereby the object of the present invention is achieved. As the processor, for example, a central processing unit (CPU) can be used. As the recording medium, in addition to a "non-temporary tangible medium" such as a read only memory (ROM) or the like, a tape, a disk, a card, a semiconductor memory, a programmable logic circuit, or the like can be used. In addition, a random access memory (RAM) or the like for expanding the program may be further included. In addition, the program may be supplied to the computer via an arbitrary transmission medium (a communication network, a broadcast wave, or the like) which is capable of transmitting the program. Furthermore, one aspect of the present invention can also be implemented in a form of a data signal embedded in a carrier wave, in which the program is embodied by electronic transmission.

The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims. Embodiments obtained by appropriately combining technical means respectively disclosed in different embodiments are also included in the technical scope of the present invention.

One aspect of the present invention can also be expressed as follows.

An information processing device according to one aspect of the present invention includes: an acquisition unit which acquires a signal quality of a signal input via a cable; and a cause determination unit which performs cause determination for determining, from variations in the signal quality, whether a cause of noise included in the signal is due to a mechanical factor or is due to electrical noise.

In addition, a control method for information processing device according to one aspect of the present invention includes: an acquisition step of acquiring a signal quality of a signal input via a cable; and a cause determination step of performing cause determination for determining, from variations in the signal quality, whether a cause of noise included in the signal is due to a mechanical factor or is due to electrical noise.

According to the above configuration, the cause of the signal anomaly can be determined from the variations in the signal quality in the input signal. Therefore, the user can take measures according to the determined cause of the noise. That is, the user can appropriately respond to an anomaly in the signal input via the cable.

In the information processing device according to one aspect of the present invention, the cause determination unit may perform the determination according to at least one of a frequency of the variations in the signal quality and an amplitude of the variations in the signal quality.

For example, the influence of a mechanical factor on the variations in the signal quality shows the following tendency compared with the influence of electrical noise on the variations in the signal quality.

Therefore, according to the configuration, it is possible to appropriately determine whether the cause of the noise included in the signal is due to a mechanical factor or is due to electrical noise.

In the information processing device according to one aspect of the present invention, the cause determination unit may determine the cause of the noise included in the signal is due to a mechanical factor when the frequency of the variations in the signal quality is equal to or lower than a predetermined value, and determine the cause of the noise included in the signal is due to electrical noise when the frequency of the variations in the signal quality is higher than the predetermined value.

Compared with the case of being affected by electrical noise as described above, the frequency of the variations in the signal quality of the signal affected by a mechanical factor is lower. Therefore, according to the above configuration, it is possible to appropriately determine whether the cause of the noise included in the signal is due to a mechanical factor or is due to electrical noise.

In the information processing device according to one aspect of the present invention, the cause determination unit may perform the determination based on a degree of similarity between the variations in the signal quality and predetermined patterns.

Here, the predetermined patterns are, for example, a variation pattern of the signal quality affected by a mechanical factor, a variation pattern of the signal quality affected by electrical noise, and the like. That is, according to the above configuration, the cause determination unit can determine a cause corresponding to a similar predetermined pattern as the cause of the noise included in the signal by the pattern matching between the variations in the signal quality and the predetermined patterns.

In the information processing device according to one aspect of the present invention, the cause determination unit may perform the determination with reference to a predetermined pattern corresponding to each of a plurality of causes of the noise.

Here, the plurality of causes of the noise are, for example, a mechanical factor and electrical noise. According to the above configuration, the cause of the noise can be determined. Therefore, the user can take measures according to the determined cause of the noise.

In the information processing device according to one aspect of the present invention, the acquisition unit may acquire an index representing a level of the noise included in the signal as the signal quality.

Here, the index representing a level of the noise included in the signal is a value of the signal quality indicator (SQI) or the like. According to the above configuration, it is possible to realize an information processing device that determines a cause of a signal anomaly from variations in the index.

In the information processing device according to one aspect of the present invention, the acquisition unit may acquire a signal quality of a signal input to a slave device in a master-slave control system.

Claim 1:
An information processing device (<NUM>), comprising:
an acquisition unit (<NUM>) which acquires a value of a signal quality indicator of a signal input via a cable; and
a cause determination unit (<NUM>) which performs cause determination for determining, from variations in the value of the signal quality indicator over time, whether a cause of noise included in the signal is due to a mechanical factor or is due to electrical noise, the mechanical factor includes mechanical vibration and cable disconnection, the electrical noise is electrical noise that is applied to the cable and mixed into the signal in the cable,
wherein the cause determination unit (<NUM>) performs the cause determination according to at least one of a frequency of the variations in the value of the signal quality indicator and an amplitude of the variations in the value of the signal quality indicator.