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http://www.iaeme.com/IJMET/index.asp 951 [email protected]
International Journal of Mechanical Engineering and Technology (IJMET) Volume 9, Issue 13, December 2018, pp. 951–958, Article ID: IJMET_09_13_100
Available online at http://www.iaeme.com/ijmet/issues.asp?JType=IJMET&VType=9&IType=13
ISSN Print: 0976-6340 and ISSN Online: 0976-6359
© IAEME Publication Scopus Indexed
VISIBLE LIGHT COMMUNICATION USING RGB
LED FOR MACHINE-TO-MACHINE
COMMUNICATION
Tae-Kook Kim
Department of Information and Communications Engineering, Tongmyong University, Busan,
Republic of Korea
ABSTRACT
Visible light communication (VLC) is a communication technology that sends digital
signals comprising “0” and “1.” VLC uses light emitting diodes (LEDs) for both lighting
and communication functions. This study aims to investigate the wavelength
characteristics in VLC using red, green, and blue (RGB) LEDs. Furthermore, a method
for transmitting and detecting RGB signals was proposed and verified. The proposed VLC
technology can be applied to machine-to-machine communication.
Keywords: Visible Light Communication (VLC), Machine to Machine (M2M), Light
Emitting Diode (LED), Near Field Communication (NFC).
Cite this Article: Tae-Kook Kim, Visible Light Communication Using Rgb Led for
Machine-to-Machine Communication, Journal of Mechanical Engineering and
Technology, 9(13), 2018, pp. 951–958
http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=9&IType=13
1. INTRODUCTION
Visible light communication (VLC) uses visible light spectrum for transmitting information. In
VLC, an incandescent light bulb or a fluorescent lamp is replaced by a LED, which is a digital
semiconductor. The visible light spectrum is a region that is visible to the human eye with a
wavelength ranging between approximately 380 and 740 nm. The principle of VLC lays in
displaying digital signals “0” and “1” by blinking the LED that has an output wavelength in the
visible light spectrum. In this case, when the number of blinks per second is 100 or more, the
blinking of LED cannot be recognized by the human eye due to the limited perception of the
human optic nerve, allowing users to perceive that LED is continuously on, and thus, serving
both lighting and communication functions [1-5].
There are 2 types of LEDs that are used in VLC: RGB (Red, Green, Blue) LEDs that emit
white light by combining diodes that emit RGB lights and other LEDs that emit white light by
coating blue LED with a fluorescent agent. Among these LEDs, RGB LEDs have a higher
bandwidth [6], [7].
Tae-Kook Kim
http://www.iaeme.com/IJMET/index.asp 952 [email protected]
Herein, a method for transmitting signals from RGB LEDs and detecting the respective RGB
signals at the receiver is proposed and verified. This method can be applied to machine-to-
machine (M2M) communication.
2. BACKGROUND
2.1. Visible light communication
VLC is a convergence technology of digital lighting and communication that employs LED,
which is a semiconductor device. The ON/OFF function of a LED can be digitally controlled,
allowing it to blink for several million times per second [1-5].
First, VLC functions as digital lighting. When the LED is turned on, it functions as a source
of light due to the emission of light. Furthermore, the brightness of the LED can be adjusted by
changing its ON/OFF cycle. Second, VLC functions the means of communication. “High” and
“low” signals can be transmitted through the ON/OFF function of the LED. The photodetector
detects the ON/OFF function of the LED and communication can be performed by detecting high
and low signals. If the ON/OFF signal of the LED changes to 100 times or more per second,
humans do not perceive the blinking of the LED, thus recognizing that the LED is continuously
on. Therefore, the LED performs the lighting and communication functions simultaneously [8],
[9].
Figure 1 shows the visible light spectrum. Since the spectrum belongs to the visible light
band, the LED can perform both lighting and communication functions [10].
Figure 1 Visible light spectrum
2.2. Machine-to-Machine communication
M2M communication means direct communication between devices using all communication
channels, including wired and wireless channels. M2M communication can transmit sensor data
and content data between the devices without passing through infrastructure such as a base station
[11-14].
There are various communication technologies for M2M communication. A typical example
is radio frequency (RF) communication. RF wave is an electromagnetic wave with a wavelength
ranging from 1 mm to 100 km, i.e., a frequency of 3 KHz–300 GHz. Table 1 compares the VLC
Visible Light Communication Using Rgb Led for Machine-to-Machine Communication
http://www.iaeme.com/IJMET/index.asp 953 [email protected]
and RF communication. VLC has fewer compliance issues in comparison with RF
communication, as well as advantages in terms of security and electromagnetic hazards [15-18].
Table 1 Comparison between VLC and RF communication
Features VLC RF VLC advantages
Regulations on spectrum
assignment No Yes
No compatibility issues
between countries
Obstacle crossing by
signals Impossible Possible Secured
Electromagnetic hazards No Yes Ecofriendly technology
Multipath dispersion
phenomenon Yes Yes
Troubles in high speed
communication
3. VISIBLE LIGHT COMMUNICATION USING LED
Since LEDs that emit white light have a single channel, only 1 datum is transmitted at a time.
However, RGB LEDs can transmit 3 data at one time because RGB LEDs have 3 channels, i.e.,
red (R), green (G), and blue (B). In this case, if the widths of RGB channels are same during one
cycle, the colors of RGB are combined to emit white light. Herein, the wavelength band
characteristics of RGB LEDs were investigated, and a transmitter for transmitting signals
independent of RGB signals and a wavelength filter for detecting signals at the receiver were
proposed.
Figure 2 RGB signals at transmitter and receiver
3.1. Transmitter
As shown in Figure 2, the transmitter has the same widths for RGB signals during one cycle.
Thus, LEDs function as lighting by emitting white color obtained by combining the RGB colors.
Subsequently, RGB channels transmit signals independently, and the transmission is performed
by avoiding any overlapping among RGB signals, as shown in Figure 2. Each signal in the T
Tae-Kook Kim
http://www.iaeme.com/IJMET/index.asp 954 [email protected]
cycle can use Manchester coding or pulse position modulation techniques to represent “0” and
“1” signals.
3.2. Wavelength filter
RGB lights have different wavelengths. This study used IWS-S83D6-FC RGB LED
manufactured by ITSWELL to measure the wavelength. Typical RGB LEDs exhibit similar
wavelength band characteristics. ITSWELL RGB LED used in this experiment has a center
wavelength for red, green, and blue LEDs from 615 to 630 nm, 515 to 535 nm, and 455 to 475
nm, respectively, as shown in Figure 3. The filter transmits the light selectively according to the
wavelength. Thus, using a red filter that passes the red wavelength band can attenuate the green
and blue wavelengths and detect only red signal. Equation 1 represents the output voltage
according to the wavelength filter.
Vo = α VRED + β VGREEN + γ VBLUE (1)
Here, α, β, γ refer to the wavelength filter values. VRED, VGREEN, and VBLUE refer to the output
voltages of the RGB LEDs, respectively. If the red wavelength filter is used, α has a value close
to 1, and β and γ have values close to 0. This is because RGB colors have different wavelength
bands. Figure 4 shows an example of a wavelength filter.
Figure 3 RGB LED characteristics of ITSWELL product
Visible Light Communication Using Rgb Led for Machine-to-Machine Communication
http://www.iaeme.com/IJMET/index.asp 955 [email protected]
Figure 4 Wavelength filter
3.3. Dimming Controls for Lighting
To control the brightness of the light, the brightness can be adjusted by changing the ratio of the
on time of the LED to its OFF time, i.e., the brightness of the lighting is controlled by fixing one
cycle, and adjusting the widths of RGB within a fixed cycle. Equation 2 shows the output voltage
according to the width of the RGB signals.
Vo = dRED·VRED + dGREEN·VGREEN + dBLUE·VBLUE (2)
Here, dRED refers to the on duration of the red LED. VRED, VGREEN, and VBLUE refer to the
output voltages of the RGB LEDs, respectively. If the ON duration of RGB LEDs is long, dRED,
dGREEN, and dBLUE values are close to 1 and the light is bright.
4. PERFORMANCE EVALUATION
The proposed method was verified by conducting experiments. For the performance evaluation,
a transmitter and a receiver were used, and the waveform was measured using an oscilloscope.
Figure 5 shows the implemented VLC transceiver. Furthermore, Table 2 shows lists the
component used. Figure 2 shows the transmitter using RGB LED. The transmitter (TX) in Figure
5 uses the RGB signals shown in Figure 2, where only R signal is visualized, and G and B signals
in TX are not shown in the figure. The receiver (RX) used to detect the signal is a Newport 818-
BB-22 Silicon PIN Detector. The transmitter and receiver were tested at a distance of 15 cm.
Figure 6 shows the signal detection of RGB lights. The RGB signals could be detected at the
receiver, and the RGB voltage values of RX were different because the intensities of the PIN
detector and RGB LED at the receiver are different. The intensity of the Newport 818-BB-22
Silicon PIN Detector used in this experiment is shown in Figure 3.
Table 2 Experimental environment
Features Description
Transmitter RGB LED
Receiver Newport 818-BB-22 Silicon PIN Detector
Distance between
transmitter and receiver 15 cm
Tae-Kook Kim
http://www.iaeme.com/IJMET/index.asp 956 [email protected]
Figure 5 Implemented transceiver for VLC
Figure 6 Red, green, blue signal detection
Visible Light Communication Using Rgb Led for Machine-to-Machine Communication
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Figure 7 Red signal detection using red wavelength filter
Figure 7 shows red signal detection using a wavelength filter. As shown in Figure 7, it can be
seen that green and blue signals were attenuated using the red filter, and only the red signal was
detected. This experiment confirmed that RGB signals can be separately detected using a
wavelength filter which passes these signals only when they have different wavelength bands at
specific wavelengths.
5. CONCLUSION
This study investigated the wavelength characteristics of RGB LEDs. Since RGB LEDs have
different wavelengths, a filter that passes only a specific wavelength can be used to detect a signal
in each wavelength band. Moreover, the data transmission rate can be enhanced using the
proposed transmission and reception method.
The proposed VLC using the RGB LED for the M2M communication can transmit 3 signals
simultaneously and can adjust the brightness of the light. In other words, the LED can perform
the functions of lighting, brightness control of light, and communication.
The proposed VLC can be applied to data transmission and content delivery in M2M
communication.
ACKNOWLEDGMENTS
This work was supported by the National Research Foundation of Korea(NRF) grant funded by
the Korea government(MSIP : Ministry of Science, ICT & Future Planning) (No.
2017R1C1B2011285).
Tae-Kook Kim
http://www.iaeme.com/IJMET/index.asp 958 [email protected]
REFERENCES
[1] Komine, Toshihiko, and Masao Nakagawa, Fundamental analysis for visible-light
communication system using LED lights. IEEE transactions on Consumer Electronics 50(1),
2004, pp. 100-107.
[2] Rajagopal, Sridhar, Richard D. Roberts, and Sang-Kyu Lim, IEEE 802.15. 7 visible light
communication: modulation schemes and dimming support. IEEE Communications
Magazine 50(3), 2012.
[3] Jovicic, Aleksandar, Junyi Li, and Tom Richardson, Visible light communication:
opportunities, challenges and the path to market. IEEE Communications Magazine 51(12),
2013, pp. 26-32.
[4] Komine, Toshihiko, and Masao Nakagawa, Integrated system of white LED visible-light
communication and power-line communication. IEEE Transactions on Consumer Electronics
49(1), 2003, pp. 71-79.
[5] Dasari Subba Rao and Dr. N.S. Murti Sarma, Distortion Minimization with Adaptive Filter
Feedback in Visible Light Communication.
International Journal of Electronics and Communication Engineering and
Technology, 8(6), 2017, pp. 13-27.
[6] Wang, Yuanquan, et al., Demonstration of 575-Mb/s downlink and 225-Mb/s uplink bi-
directional SCM-WDM visible light communication using RGB LED and phosphor-based
LED. Optics express 21(1), 2013, pp. 1203-1208.
[7] Cossu, G., et al., 3.4 Gbit/s visible optical wireless transmission based on RGB LED. Optics
express 20(26), 2012, pp. B501-B506.
[8] Grobe, Liane, et al., High-speed visible light communication systems. IEEE communications
magazine 51(12), 2013, pp. 60-66.
[9] Pathak, Parth H., et al., Visible light communication, networking, and sensing: A survey,
potential and challenges. IEEE communications surveys & tutorials 17(4), 2015, pp. 2047-
2077.
[10] Wikipedia,Visiblelightcommunication,2018.https://en.wikipedia.org/wiki/Visible_light_co
mmunication
[11] Theoleyre, Fabrice, and Ai-Chun Pang, eds. Internet of Things and M2M Communications.
River Publishers, 2013.
[12] Hasan, Monowar, Ekram Hossain, and Dusit Niyato, Random access for machine-to-machine
communication in LTE-advanced networks: issues and approaches. IEEE communications
Magazine 51(6), 2013, pp. 86-93.
[13] Galetić, Vedran, et al., Basic principles of Machine-to-Machine communication and its
impact on telecommunications industry. MIPRO, 2011 Proceedings of the 34th International
Convention. IEEE, 2011, pp. 380-385.
[14] Wikipedia, Machine to machine, 2018. https://en.wikipedia.org/wiki/Machine_to_machine
[15] Rahaim, Michael B., Anna Maria Vegni, and Thomas DC Little. A hybrid radio frequency
and broadcast visible light communication system. GLOBECOM Workshops (GC Wkshps),
2011 IEEE. IEEE, 2011.
[16] A. Suresh and Dr. N. Somasundaram, A Study on Impact of Barcode and Radio Frequency
Identification Technology on Maximized Productivity in Manufacturing Industries at Sipcot,
Chennai. International Journal of Management, 8(1), 2017, pp. 13-20.
[17] A. Suresh and Dr. N. Somasundaram, A Study on Impact of Barcode and Radio Frequency
Identification Technology on Maximized Productivity in Manufacturing Industries at Sipcot,
Chennai. International Journal of Management, 8(1), 2017, pp. 13-20.
[18] Wikipedia, Radio frequency, 2018. https://en.wikipedia.org/wiki/Radio_frequency