wlan interference identification using a convolutional

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WLAN Interference Identification Using a Convolutional Neural Network for Factory Environments Julian Webber 1,2 , Kazuto Yano 1 , Norisato Suga 1,3 , Yafei Hou 1,4 , Eiji Nii 1 , Toshihide Higashimori 1 , Abolfazl Mehbodniya 1,5 , and Yoshinori Suzuki 1 1 Wave Engineering Laboratories, Advanced Telecommunications Research Institute International (ATR), 2-2-2, Hikaridai, Soraku, Seika, Kyoto, 619-0288, Japan 2 Graduate School of Engineering Science, Osaka University, Toyonaka, Japan 3 Faculty of Engineering, Tokyo University of Science, Tokyo, Japan 4 Graduate School of Natural Science and Technology, Okayama University, Okayama City, Japan 5 Kuwait College of Science and Technology, Kuwait Email: {jwebber, kzyano, norisato.suga, yfhou, nii, higashimori, yoshinori.suzuki}@atr.jp, [email protected] AbstractFactory communication systems require highly re- liable links with predictable performance and quality of service in order to avoid outages that can damage the production-line process. Communication anomalies can be caused by narrowband interference which is difficult to identify and track from the time- domain information only. This paper describes a methodology for classifying increasing severity and types of interference in order to improve throughput prediction. Received signal strength (RSS) data is collected from both a ray-tracing simulation and a Wireless Local Area Network (WLAN) measurement campaign with a transmitter mounted on an actual automated guided vehicle (AGV). Scalogram time- frequency images are computed from the RSS signal and a convolutional neural network (CNN) is then trained to recognize the spectral features and enable the interference classification. The block random interference could be correctly classified on over 65% of the occasions in the ray- traced channel at 30 dB SNR. Index TermsWLAN, CNN, deep-learning, interference, scalogram, ray-tracing, factory communications I. INTRODUCTION Communication infrastructure in factory and industrial settings still use fixed-wire links such as Ethernet or proprietary- based technology to a considerable extent. Recently there has been a growing trend to employ wireless technology in factory systems [1] thanks to the continual improvement in data-rate, multi-user support and robustness. These systems include IEEE 802.11 wireless local area network (WLAN) [2] and wireless personal area networks such as IEEE 802.15.1 or IEEE 802.15.4 [3]. Factory communication infrastructure needs to support transmission of time critical data at sufficient rate to avoid control instability and ultimately failure. With evermore complex systems, increasingly higher Manuscript received December 15, 2020; revised June 15, 2021. This work was supported in part by the Ministry of Internal Affairs and Communications as part of the research program R&D for Expansion of Radio Wave Resources (JPJ000254). Corresponding author email: [email protected]. doi:10.12720/jcm.16.7.276-283 bandwidth signals need to be transported such as from multiple surveil-lance cameras on the production floor. Meanwhile there are many potential sources of electromagnetic interference such as wireless communication devices for wireless LAN, Blue- tooth and ZigBee, cordless phones and microwave ovens in the unregulated 2.4-2.5 GHz industrial, scientific and medical (ISM) band. There are also many physical obstructions such as workers, robots or equipment that can potentially block or degrade the communications links. In order to improve the reliability of a factory communication link, prediction of received signal strength (RSS) and throughput is required enabling advanced warning of pending anomalies. There have been a number of researches towards this goal in the literature. Future RSS samples were predicted at multiple receivers (Rx) for a transmitter (Tx) placed on an automated guided vehicle (AGV) using a probabilistic neural network (PNN) in [4]. Transmission control protocol (TCP) throughput prediction using support vector regression was made in [5]. Improvements in the quality of adaptive video using wireless traffic prediction using [Fractional] Auto- Regressive Integrated Moving Average ([F]ARIMA) time- series models were described in [6]. Recently we described methodologies to predict throughput using the PNN for time- series prediction providing optimized weights for a convolutional neural network (CNN) in [7] and for predicting anomalies in throughput using a kernel density estimation technique for multiple bandwidths in [8]. It is considered that the reliability of throughput prediction systems could be further enhanced with reliable information provided on the type and severity of the interference present. Radio frequency interference (RFI) detection using K- nearest neighbor and random forests were shown to outperform a Bayesian based detector in [9]. Sensing temporal and frequency interference characteristics was demonstrated by employing a semi-Markov chain and data with a Poisson-distribution arrival rate in [10]. A CNN was applied to detecting images generated from the FFT of the complex signal received by an astronomy Journal of Communications Vol. 16, No. 7, July 2021 ©2021 Journal of Communications 276

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Page 1: WLAN Interference Identification Using a Convolutional

WLAN Interference Identification Using a Convolutional

Neural Network for Factory Environments

Julian Webber1,2, Kazuto Yano1, Norisato Suga1,3, Yafei Hou1,4, Eiji Nii1 , Toshihide Higashimori1,

Abolfazl Mehbodniya1,5, and Yoshinori Suzuki1 1 Wave Engineering Laboratories, Advanced Telecommunications Research Institute International (ATR), 2-2-2,

Hikaridai, Soraku, Seika, Kyoto, 619-0288, Japan 2 Graduate School of Engineering Science, Osaka University, Toyonaka, Japan

3 Faculty of Engineering, Tokyo University of Science, Tokyo, Japan 4 Graduate School of Natural Science and Technology, Okayama University, Okayama City, Japan

5 Kuwait College of Science and Technology, Kuwait Email: {jwebber, kzyano, norisato.suga, yfhou, nii, higashimori, yoshinori.suzuki}@atr.jp, [email protected]

Abstract—Factory communication systems require highly re-

liable links with predictable performance and quality of service

in order to avoid outages that can damage the production-line

process. Communication anomalies can be caused by

narrowband interference which is difficult to identify and track

from the time- domain information only. This paper describes a

methodology for classifying increasing severity and types of

interference in order to improve throughput prediction.

Received signal strength (RSS) data is collected from both a

ray-tracing simulation and a Wireless Local Area Network

(WLAN) measurement campaign with a transmitter mounted on

an actual automated guided vehicle (AGV). Scalogram time-

frequency images are computed from the RSS signal and a

convolutional neural network (CNN) is then trained to

recognize the spectral features and enable the interference

classification. The block random interference could be correctly

classified on over 65% of the occasions in the ray- traced

channel at 30 dB SNR. Index Terms—WLAN, CNN, deep-learning, interference,

scalogram, ray-tracing, factory communications

I. INTRODUCTION

Communication infrastructure in factory and industrial

settings still use fixed-wire links such as Ethernet or

proprietary- based technology to a considerable extent.

Recently there has been a growing trend to employ

wireless technology in factory systems [1] thanks to the

continual improvement in data-rate, multi-user support

and robustness. These systems include IEEE 802.11

wireless local area network (WLAN) [2] and wireless

personal area networks such as IEEE 802.15.1 or IEEE

802.15.4 [3]. Factory communication infrastructure needs

to support transmission of time critical data at sufficient

rate to avoid control instability and ultimately failure.

With evermore complex systems, increasingly higher

Manuscript received December 15, 2020; revised June 15, 2021.

This work was supported in part by the Ministry of Internal Affairs

and Communications as part of the research program R&D for

Expansion of Radio Wave Resources (JPJ000254).

Corresponding author email: [email protected].

doi:10.12720/jcm.16.7.276-283

bandwidth signals need to be transported such as from

multiple surveil-lance cameras on the production floor.

Meanwhile there are many potential sources of

electromagnetic interference such as wireless

communication devices for wireless LAN, Blue- tooth

and ZigBee, cordless phones and microwave ovens in the

unregulated 2.4-2.5 GHz industrial, scientific and medical

(ISM) band. There are also many physical obstructions

such as workers, robots or equipment that can potentially

block or degrade the communications links.

In order to improve the reliability of a factory

communication link, prediction of received signal

strength (RSS) and throughput is required enabling

advanced warning of pending anomalies. There have

been a number of researches towards this goal in the

literature. Future RSS samples were predicted at multiple

receivers (Rx) for a transmitter (Tx) placed on an

automated guided vehicle (AGV) using a probabilistic

neural network (PNN) in [4]. Transmission control

protocol (TCP) throughput prediction using support

vector regression was made in [5]. Improvements in the

quality of adaptive video using wireless traffic prediction

using [Fractional] Auto- Regressive Integrated Moving

Average ([F]ARIMA) time- series models were described

in [6]. Recently we described methodologies to predict

throughput using the PNN for time- series prediction

providing optimized weights for a convolutional neural

network (CNN) in [7] and for predicting anomalies in

throughput using a kernel density estimation technique

for multiple bandwidths in [8]. It is considered that the

reliability of throughput prediction systems could be

further enhanced with reliable information provided on

the type and severity of the interference present.

Radio frequency interference (RFI) detection using K-

nearest neighbor and random forests were shown to

outperform a Bayesian based detector in [9]. Sensing

temporal and frequency interference characteristics was

demonstrated by employing a semi-Markov chain and

data with a Poisson-distribution arrival rate in [10]. A

CNN was applied to detecting images generated from

the FFT of the complex signal received by an astronomy

Journal of Communications Vol. 16, No. 7, July 2021

©2021 Journal of Communications 276

Page 2: WLAN Interference Identification Using a Convolutional

array antenna in [11]. It was shown that RFI could be

detected by the abrupt change in the amplitude of the

signal likely to appear as high intensity pixels and

distinguished from the noiseless data by the difference

in statistical distribution. A narrow-band interference

model specifically for an Orthogonal Frequency Division

Multiplexing (OFDM) communication system operating

over a power-line was described in [12]. We assume an

energy detector Rx and simple model for the received

signal after interference has been added and the

proposed system is not restricted to any modulation

scheme. Interference may appear random and

unstructured when examined solely in the time-domain.

The fast Fourier transform (FFT) is a most widely used

function for analysis of the signals in the frequency

domain. How- ever, while the short-term Fourier

transform, which divides a signal into small windows,

can provide information with either good frequency

resolution or good time resolution, it can not provide

both simultaneously with accuracy [13]. The scalogram

on the other hand simultaneously provides time-

frequency information using the wavelet transform.

There are a number of articles in which wavelets have

been applied to the classification of normal and irregular

or interfering signals using pattern matching. For

example, heartbeat irregularities have been successfully

identified using the wavelet transform by examining the

departure from regularly spaced signal pulses [14].

Epilepsy detection was demonstrated by applying deep

learning to scalograms in [15] and the wavelet transform

has also been used to identify problems in asynchronous

machines [16].

Deep-learning can be applied to recognize features

of the two-dimensional scalogram image as part of an

automated system. Examples of applications include

radiology [17] and earthquake detection [18]. It has also

been demonstrated that the CNN trained using general

images such as animals or cars for example can also

perform well at detecting features from other types of

images such as scalograms. This is because once-trained

the network is able to detect edges, areas and features

irrespective of the particular object.

In this work we employ ray-tracing to model the RSS

data variation based on the constructive and destructive

addition of multipath rays [19] and also record actual

RSS data from a WLAN measurement campaign.

Distributed and block interference is then added to the

received frequency domain signal (Fig. 1) and we study

how accurately the interference signal can be classified.

Taking inspiration from the application of wavelets to

detecting irregular features in electro-cardiogram data

[20], we investigate their use with respect to interference

in WLAN signals in factory environments.

The layout of this paper is as follows. Section II details

the ray-tracing simulation and WLAN measurement

campaign. Section III describes the spectral analysis and

feature recognition using CNN. Section IV presents and

discusses the performance evaluation results. Areas for

further work and a conclusion are drawn in Sections V

and VI respectively.

Fig. 1. Block diagram of proposed system.

II. RSS DATA-COLLECTION

We first model the RSS data in the factory through

both a deterministic ray-tracing simulation and secondly

collect real RSS data from an actual WLAN experiment.

A. Ray-tracing Simulation

A ray-tracing simulator generates RSS data variation

based on the vector addition of multipath rays [19]. The

factory room has dimensions of 20m-by-20m and two

scatterers are randomly placed within this area. AGV are

now common in warehouses such as those used by

several well-known Internet shopping companies for

collecting and transporting products to a dispatch area.

The Rx are placed at fixed positions and the Tx is

mounted on an AGV which moves along a known route

at a fixed speed of 1 m/s following the black dashed line

in Fig. 2. The simulation settings are summarized in

Table I.

TABLE I: RAY-TRACING SIMULATION SETTINGS

Fig. 2. Plan-view for ray-tracing simulation showing the Tx-mounted

AGV direction of motion, random position of scatterers and fixed Rx.

B. WLAN Measurement Campaign

A plan-view showing the layout of the experiment

environment and measurement locations is depicted in

Fig. 3. RSS measurements were recorded in an L-

shaped corridor on the 3rd floor of a Japanese office

building. The dimensions of the long corridor section

Journal of Communications Vol. 16, No. 7, July 2021

©2021 Journal of Communications 277

Page 3: WLAN Interference Identification Using a Convolutional

were 30m × 2.2 m and the short- section has

dimensions 7m × 2 m. The corridor is surrounded by

office rooms mainly comprising a metal floor and metal-

backed or concrete wall contributing to a rich multipath

scattering environment. The plasterboard ceiling was at a

height of about 2.6 m and had metallic fixings of

approximate dimensions 1m × 0.5 m containing

fluorescent strip-lights at about 3 m intervals.

Fig. 3. Plan view of the experiment environment showing location of

Tx, Rx, sniffing station and route of the AGV.

Fig. 4. Photograph of experiment environment showing (left) mobile

Tx station, and (right) AGV loaded with metallic rack and case.

The Tx was first positioned in an adjoining room

behind a door at Location-A at the top of the short-

corridor section and then sequentially moved to

measurement locations labeled A-F. A photograph of the

experiment environment showing the mobile Tx station is

shown in Fig. 4 (left). The unloaded AGV vehicle has a

relatively low-profile at 30 cm height and to simulate a

loaded vehicle a metallic trolley and suit-case were

additionally placed on top of the AGV as seen in Fig. 4

(right). The AGV moved at a speed of about 0.3 m/s.

A PC running WLAN sniffing software with modified

WLAN adapter card operating in promiscuous mode was

placed half-way along the corridor opposite to Location-

F. The Windows Media Player software was configured

to stream 4K-video from the Tx to Rx which was placed

on a chair 2.5 m from the west end of the corridor and at

a height of 0.5 m. The WLAN packet data was recorded

by the sniffing-PC over a duration of about 1 minute for

each Tx position. The sniffer data file was imported into

Matlab and 16 fields extracted including the packet

number, time-stamp, data length, signal and noise power.

As the packets arrive randomly and have different lengths

the data is irregularly sampled and we processed this to

provide estimated signal to noise ratio (SNR) at regular 1

ms intervals. The cumulative distribution function (CDF)

of the RSS SNR at locations [A, B, C, D, E] is shown in

Fig. 5. It can be seen that there was a variation of up to 30

dB in the SNR values (99% level) at the measured

locations. The locations A-D have a non line-of-sight

(NLOS) link while Location E has a line-of-sight (LOS)

link of to the Rx and WLAN sniffer. A portion of the

packets are therefore received at Location E with a higher

average SNR compared to the other locations as expected.

Fig. 5. CDF of RSS SNR for Tx at locations A-F with moving AGV.

C. Addition of Interference

Distributed or block interference is added to the

frequency domain RSS signal. For both interference types

the total number of interfered samples is steadily

increased from 50 to 1500 in steps of 50 samples. The

RSS signal together with its mean-value from the ray-

tracing simulation is depicted in Fig. 6(a). In this work

we assume that the signal at the Rx is sampled by an

energy detector and that the interference vector adds

constructively or destructively on each sample such that

the signal plus interference sums to the mean level. An

example where the block interference for the first Ns =

100 samples are set to the mean value is shown in Fig.

6(b). Similarly a case where 100 randomly distributed

samples are set to the average value is shown in Fig. 6(c).

Fig. 6. Ray-tracing RSS waveform in frequency domain showing (a)

average signal value indicated by the dashed line, (b) block

interference with first Ns = 100 samples set to the average value, (c)

100 distributed random samples set to the average value.

III. SIGNAL PROCE SSING

After generating the 2D scalogram images for each

RSS signal with increasing amounts of interference, we

first train the CNN to categorize each Red-Green-Blue

(RGB) image in the absence of receiver noise. We then

Journal of Communications Vol. 16, No. 7, July 2021

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Page 4: WLAN Interference Identification Using a Convolutional

add additive white Gaussian noise (AWGN) to the time-

domain signal and compute the accuracy to which the

CNN can correctly categorize the amount of interference

for each type.

A. Time-Frequency Analysis

The 2D scalogram decomposes the signal in order to

identify and detect periodic components. In contrast to

the Fourier transform, wavelets can be used to classify

arbitrarily small time-interval signals [21]. The

scalogram is efficiently computed using the continuous

wavelet transform (CWT) [22]. The CWT is expressed as

the product of the information signal f (t) and wavelet

function 𝜙(𝑡) as:

𝑇(𝑎, 𝑏; 𝑓(𝑡), 𝜙(𝑡)) =1

√𝑎∫ 𝑓(𝑡)𝜙 (

𝑡 − 𝑣

𝑎)𝑑𝑡

−∞

where 𝜙(𝑡) is the mother wavelet, a is a scale parameter,

and v is a translation (time) parameter. The analytic

Morse wavelet is used as CWT in the filter bank. Morse

wavelets are useful for analyzing modulated signals,

transients, and short-duration signals [23]. There are two

control parameters for Morse which allow increased

control over, for example the Morlet wavelet which uses

a single parameter.

The scalograms for increasing levels of randomly

distributed interference are plotted in Fig. 7. The red

region shows the strong time-frequency component of the

RSS signal. The abrupt change in frequency at about one-

third of the way across the time interval (x-axis)

corresponds to the change in direction of the AGV by 90

degrees as indicated in the ray-tracing layout of Fig. 2.

Increasing amounts of noise can be seen by the blurred

white areas particularly in the high frequency regions i.e.

top half of each figure. There is also progressively more

noise seen within the signal itself i.e. on the red line.

Similarly, scalograms corresponding to increasing

amounts of block interference are shown in Fig. 8. It can

be seen that as the number of interfered blocks increases

sections of the strong red signal region are progressively

removed. The distributed interference scalograms have

similar features which become relatively hard to

distinguish in noise. A block interferer on the other hand

removes a large section of the well-defined signal (red

colour) and each resulting scalogram can be easily

discerned. The structure of the non-dominant signal

(non-red) also becomes relatively stronger as seen in

sub-figure 8 of Fig. 8. The scalograms for increasing

levels of randomly distributed interference from the

WLAN trials with the Tx at location B with moving

AGV present are plotted in Fig. 9. Unlike in the ray-

tracing simulation, the AGV does not move at a

precise constant speed or course in part due to its heavy

load and, also there are many more potential scatterers

present. The walls, floor and ceiling in the trials

environment contribute to a much richer multipath

environment and together with random movement of

people walking, this contributes to a less-defined signal

with no dominant Doppler frequency present.

Fig. 7. Scalograms for increasing amounts of distributed random

interference from ray-tracing.

Fig. 8. Scalograms for increasing amounts of block interference from

ray-tracing.

B. Convolutional Neural Network

The CNN calculates weights in order to minimize a

loss function between trained and evaluation image data.

The net- work comprises three principle layers:

convolutional, pooling and fully-connected layers. A

typical convolutional layer filter has dimensions 5×5×3

for detecting small features, edges and patterns in RGB

images with 3-color depth. Pooling layers are inserted

periodically to reduce the complexity by down- sampling

the input data. Neurons in the fully-connected layer are

connected to all activations in the preceding filter: their

construction is similar to that in the convolutional layer

but they are not confined to a local region. The rectified

linear unit (ReLU) is gradually replacing use of the

sigmoid for activation function computing max(0,k)

which reduces the complexity as well as influence of low-

value or noisy input data, k.

GoogLeNet is a CNN that was trained using a subset

of everyday images from the Open Source ImageNet

database [20], [24]. It has been shown that although the

CNN is trained on generic images the developed network

structure is suit- able for classifying other input images,

for example electro- cardiograms. The scalogram has the

same dimensions as the everyday images used in the

training and is treated as a normal RGB photo image. In

this work the network settings were set as: dropout = 0.63,

and initial learning-rate = 0.001.

IV. PERFORMANCE EVALUATION

The performance is evaluated through a Monte-Carlo

soft- ware simulation comparing the accuracy between

the actual and predicted number of interfering samples. A

Journal of Communications Vol. 16, No. 7, July 2021

©2021 Journal of Communications 279

Page 5: WLAN Interference Identification Using a Convolutional

correct categorization is determined to be when the exact

number of frequency domain interfering components is

correctly estimated. For example, if the number of

samples containing interference was 200 but the CNN

classified the scalogram as having 250 interfering

samples then this was classified as an error. A

comparison of the classification accuracy for distributed

versus block interference for the ray-tracing simulation is

shown in Fig. 10. The results show that the random block

interference could be correctly classified in over 65% of

the trials at 30 dB SNR and rising to 78% in 50 dB SNR.

The block interference in which 50 or more continuous

frequency domain samples were adjacent to each other

was more often correctly categorized by the CNN. The

randomly distributed interference was more difficult to

classify with success rate between 50–60%. The

performance result for exactly classifying the size of

distributed interference on the RSS signal collected at

trials locations B, D, and E is summarized in Table II.

The system works best where there are a certain number

of strong time-frequency signature signals that could be

generated by a moving transmitter with fairly constant

speed. The categorization accuracy was observed higher

in the NLOS channels where there was a large number of

packets received by multipaths that could potentially aid

the CNN in categorizing the interference.

Fig. 9. Scalograms for increasing amounts of distributed random

interference in experiment trials.

TABLE II: PERFORMANCE ACCURACY FOR TRIALS LOCATIONS

The requirement of estimating exactly the number

of interfering samples was quite strict. As a typical

narrowband interference signal such as from competing

Wi-Fi or Bluetooth will generate a block of interference

the proposed system with near 80% success rate is

considered a suitable and promising method for its

identification. There are 30 target values of increasing

size for the interferer i.e. [50, 100, 1500] and therefore

randomly guessing the number correctly would exhibit

an average success rate of 3.33%. In this respect a 50%

accuracy rate could be considered very good and should

provide useful information to the higher layer anomaly

prediction unit. It is also possible that the anomaly

prediction unit would operate efficiently with fewer

categories of the interference such as a 5-level scale and

quantization of the interference feedback is a potential

area for further work.

Fig. 10. Comparison of the average classification accuracy for random

block versus distributed interference from ray-tracing simulation.

V. FURTHE RWORK

The intensity scale used in generation of the RGB

figure could potentially be optimized in order to use the

full dynamic range of 256 values. Removal of low-value

RSS samples by a moving-average filter prior to the

scalogram could im- prove the performance. The

current ray-tracing model could be enhanced by

increasing the number of scatterers, adding information

on the floor and wall reflectivity and include NLOS

modeling. The size of the Monte-Carlo simulation could

be enlarged by increasing the number of AGV routes,

as well as the number and bandwidth of interfering

signals. Further WLAN trials measurements could be

conducted to collect an increased range of channel

types. The study of scalograms in the presence of

multipath-rich multiple input- multiple output (MIMO)

channels is an interesting area for future research. The

scalogram block-size and sampling-rate are also

important parameters that should be optimized and may

further improve the performance of the results. The size

of the interfering blocks could be considered as a step-

wise optimization exercise considering the size of the

estimation error. Finally, the classification performance

of time-varying interferers could potentially be improved

by sampling the RSS at multiple Rx locations.

VI. CONCLUSION

We have demonstrated a machine learning based

methodology enabling the classification of distributed

and block interference of increasing severity through the

spectral decomposition of RSS data collected from both

a ray-tracing simulation and WLAN experiment. The

CNN was able to categorize the RSS signals in the

presence of block interference with higher success

compared to the equivalent amount of distributed

interference with nearly 80 percent accuracy achieved

for the ray-traced channel. The actual WLAN channel is

Journal of Communications Vol. 16, No. 7, July 2021

©2021 Journal of Communications 280

Page 6: WLAN Interference Identification Using a Convolutional

complex with many scatterers present and this

contributes to the reduced classification accuracy of 50%

in the NLOS channel. It is envisaged that the proposed

system can be utilized by a WLAN performance

predictor unit in order to improve the reliability of

pending outage prediction when in the presence of

interference.

CONFLICT OF INTEREST

There are no conflicts of interest.

AUTHOR CONTRIBUTIONS

JW measured the channel, ran simulations, and

wrote the paper. KY provided technical advice including

on interference & WLAN, NS, EN advised on

simulation, YH assisted with channel measurement, TH

advised on network issues, AM advised on wavelets

and CNN, and YS advised on system concept. All co-

authors provided input to the paper through regular

discussions. KY and YS directed the project part under

JPJ000254.

ACKNOWLEDGEMENT

This work includes results of the project entitled R&D

on Technologies to Densely and Efficiently Utilize Radio

Resources of Unlicensed Bands in Dedicated Areas,

which is supported by the Ministry of Internal Affairs and

Communications as part of the research program R&D

for Expansion of Radio Wave Resources (JPJ000254).

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Copyright © 2021 by the authors. This is an open access article

distributed under the Creative Commons Attribution License

(CC BY-NC-ND 4.0), which permits use, distribution and

reproduction in any medium, provided that the article is

properly cited, the use is non-commercial and no modifications

or adaptations are made.

Julian Webber received the M.Eng.

degree in Electronics Engineering in

1996 from Bristol University, UK. He

was then employed at Texas Instruments

and completed the Ph.D. degree in

Wireless Communications from

University of Bristol in 2004. After

working at Hokkaido University from

2007 on MIMO communications he joined Advanced

Telecommunications Research Institute International (ATR) in

2012. He is currently an assistant professor at Graduate School

of Engineering Science, Osaka University, Japan and guest

research scientist at Wave Engineering Laboratories, ATR.

Kazuto Yano received the B.E. degree

in electrical and electronic engineering,

and the M.S. and Ph.D. degrees in

communications and computer en-

gineering from Kyoto University in 2000,

2002, and 2005, respectively. In 2006, he

joined the Advanced

Telecommunications Research Institute

International (ATR). Currently, he is the head of Dept. Wireless

Communication Systems at Wave Engineering Lab- oratories,

ATR.

Norisato Suga received the Ph.D. degree

from Tokyo University of Science, Japan

and is currently an assistant professor at

faculty of engineering, Tokyo University

of Science, Japan and guest re- search

scientist at Wave Engineering

Laboratories, ATR Institute International,

Japan.

Yafei Hou received his Ph.D. degrees

from Fudan University, China and Kochi

University of Technology (KUT), Japan

in 2007. He is assistant Professor at the

Graduate School of Natural Science and

Technology, Okayama University, Japan.

He is also a guest research scientist at

Wave Engineering Laboratories, ATR

Institute International, Japan.

Eiji Nii received his B.S., M.S., and

Ph.D. degrees from Kansai University,

Osaka, Japan, in 2015, 2017, 2020,

respectively. He is currently a researcher

at Wave Engineering Laboratories of

Advanced Telecommunications Research

Institute International (ATR), Kyoto,

Japan.

Toshihide Higashimori received the

B.E. degree in economics from Kindai

University, Japan, in 1989. He joined the

Wave Engineering Laboratories, ATR

Institute International, Japan and is

engaging in development of several

simulation software.

Abolfazl Mehbodniya received his Ph.D

degree from University of Quebec,

Canada, in 2010. From 2010 to 2017 he

worked in Japan in different roles, i.e.,

JSPS research fellow, assistant professor

of electrical engineering in Tohoku

University and research scientist at ATR

international. From 2017 to 2018 he was

a Marie Curie senior research Fellow at university college

Dublin, Ireland. Since 2018, he is an associate professor and

head of electronics and communication (ECE) engineering

department at Kuwait College of science and technology. Dr.

Mehbodniya has 15+ years of experience in academia, industry

and project management. He has over 100 published papers and

patents. He is the recipient of numerous awards including JSPS

young faculty startup grant, KDDI foundation grant, Japan

Radio Communications Society (RCS) active researcher award,

European commission Marie Skodowska-Curie Fellowship and

NSERC Visiting Fellowships in Canadian Government

Laboratories. His research interests are in the areas of radio

resource management, energy- efficiency improvement,

Journal of Communications Vol. 16, No. 7, July 2021

©2021 Journal of Communications 282

Page 8: WLAN Interference Identification Using a Convolutional

interference mitigation, short-range communications, 4G/5G

design, OFDM, heterogeneous networks, artificial neural

networks, and fuzzy logic techniques with applications to

algorithm and protocol design in wireless communications. He

is a senior member of IEEE and IEICE.

Yoshinori Suzuki received the B.E.,

M.E. and Ph.D. degrees from Tohoku

University, Sendai, in 1993, 1995 and

2005 respectively. He joined NTT Wire-

less Systems Laboratories in 1995. Since

then, he engaged in researching

microwave signal processing techniques

for satellite onboard applications and

onboard multiple beam antenna feed techniques. He worked as a

part-time lecturer at Niigata University in 2012 and 2014. From

2013 to 2014, he was in charge of sales engineering of satellite

communication services in NTT Software Corporation

(currently NTT TechnoCross Corporation). Since then, he was a

research engineer in NTT Access Network Service Systems

Laboratories working on future mobile satellite communication

systems. From June 2018, he has been engaged in the research

of innovative radio communication systems at ATR Wave

Engineering Laboratories, Kyoto, Japan. He received the

Younger Engineer Award from the IEICE Japan in 2003. He is

a senior member of the IEICE.

Journal of Communications Vol. 16, No. 7, July 2021

©2021 Journal of Communications 283