implementation of speech simplex communication using...
TRANSCRIPT
Implementation of Speech Simplex Communication using Visible Light
Lita Lidyawati Electrical Engineering
National Institute of Technology Bandung, Indonesia
Lucia Jambola Electrical Engineering
National Institute of Technology Bandung, Indonesia
Arsyad Ramadhan Darlis Electrical Engineering
National Institute of Technology Bandung, Indonesia
Abstract—The visible light used by many humans as lighting only. However, in some studies have been shown that visible light can be used also for other needs that the communication system. Visible Light Communication (VLC) using white Light Emitting Diode (LED) is a promising technology for next generation communication for short range and high speed wireless transmission. In this paper, implementation of speech simplex communication using visible light is presented. Speech simplex communication using visible light needed in area where communication cannot be done easily using a technology that uses electromagnetic waves. Inexpensive transmitter and receiver of VLC system is designed and its performance is evaluated. Performance analysis is done with respect to color filter, photo sensitivity of photodiode at the receiver and the increase in distance between the transmitter and receiver. The result shows the system can receiving signal in speech frequency between 300 Hz until 3400 Hz. Test by transmitting the signal at a fixed distance results the voltage of the signal has increased almost two times that of the input signal, with the strengthening of 1.66 times. Experimental results show that the data transmission distance achieved up to 2,3 m and pair of red color filter mounted on the transmitter and the red color filter in the receiver has a voltage received relatively good compared with most other colors.
Keywords— visible light communication, light emitting diode, photodiode, color filter pair
I. INTRODUCTION
Visible light is electromagnetic radiation that is visible to the normal human eye with a wavelength of 380 to 780 nm. Infrared is electromagnetic radiation with wavelengths longer than visible light, but shorter than radio wave radiation. This infrared has a wavelength between 1 µm to 700 mm.
Visible light produced by lighting lamps have the same properties as the infrared. Today, the visible light used by humans for lighting, both indoors and outdoors. This is due to both an electromagnetic radiation, just has a different
wavelength. Therefore, if the infrared can be used in data communication, the same thing is likely to do with using visible light.
Fig. 1. Frequency Spectrum
The communication system with light media has huge potential in replacing the wireless media. This is due to human beings will not be able to work and live without their lights so that mobility and very high levels of efficiency. The technology utilizes visible light in a communication system called Visible Light Communication (VLC).
VLC is standaridized by the Institute of Electrical and Electronics Engineers (IEEE) [5]. Visible Light Communication Consortium, Japan carried out an initial research on Visible Light Communication. Now Asia, Europe, Wireless World Research Forum are also working in VLC research.
This technology will be very useful to remember that in place - a particular place, communication cannot be done easily using a technology that uses electromagnetic waves, for example in water, tunnel or in a place that cannot receive electromagnetic waves (blank spot). In addition, in these
places, conversation (speech) between people simultaneously (full duplex) using cellular technology cannot do. Full Duplex communication system is a form of communication between two parties which transmit and receive information at the same time. In this paper, we are only examining speech simplex communication using Visible Light Communication.
II. SYSTEM DESIGN OF SPEECH SIMPLEX COMMUNICATION
USING VISIBLE LIGHT COMMUNICATION
VLC system consists of: (a) transmitter using white LEDs
as a light source, (b) free space (air) as the transmission medium, and (c) photodiode at the receivers.
VLC communication has the advantages of bandwidth, low power consumption, visibility, free from Electro Magnetic Interference and radiation hazards. Fig. 2 shows the block diagram of the proposed VLC system.
Fig. 2. Block Diagram of speech simplex Visible Light Communication
A. VLC Transmitter
In this work, the input frequency of 2 kHz and voltage of 5 V is given using signal generator. Light emitting source is of phosphor based White LED of 1 Watt with the viewing angle as 180. Fig. 3 shows the schematic circuits design of the proposed VLC Transmitter.
Fig. 3. Schematic design of VLC Transmitter
B. VLC Receiver
In general, the receiving circuit consisting of a series of photo sensor (photo diode), amplifier circuit, and signal conditioner shows in Fig. 4.
Fig. 4. Schematic design of VLC Receiver
C. Integration of VLC Transmitter and Receiver Circuit
Fig. 5. Integration of VLC Transmitter and Receive Circuit
III. EXPERIMENT AND RESULT
Performance is measured from the output system that includes some testings.
A. Tests by transmitting a signal at a fixed distance
Fig. 6. Block Diagram Testing VLC system with the source of signal generator and a distance of 50 cm
Figure-6 shows the test block of the system that has been implemented. In this test signal generator generates a signal sinusoid with a frequency of 20 Hz to 20,000 Hz which is a frequency signal that can be heard by humans. The distance between the transmitter and the receiver made fixed by 50 cm.
The ouput of the system is measured by the oscilloscope are compared with the characteristics of the input signal. The test condition can be seen in Fig. 7.
Fig.7. System Testing Condition
Fig. 8 shows the input and output signals are measured with an oscilloscope system.
Fig. 8. Input (top) and output (bottom) Signal
The signal output system (bottom) experiencing a phase shift of 180 degrees of the input signal (top). This is caused by the influence of the channel transmission system is used. The phase shift can be addressed by a series of phase shifter (phase shifter) to restore the output signal to a form which should be the same as the input signal. Nevertheless, designed and implemented a system that has worked well as evidenced by the frequency of the input signal is the same as the frequency of the output signal of the system. The voltage of the signal has increased almost two times that of the input signal, with the strengthening of 1.66 time where the sample images shown in Fig. 8. The strengthening of each signal is different in each measurement and the frequency of the input signal. This is caused by environmental and measurement conditions change at any time. Results of tests performed on the system by making the input signal has a changing frequency is shown in Fig. 9.
Fig. 9. Comparison chart the frequency of the output signal to the output
voltage system with a fixed distance
In this test signal generator generates a signal sinusoid with 5 V and a frequency changed from 20 Hz to 20,000 Hz. The
frequency is the frequency of the signal that can be heard by humans. Meanwhile, if the frequency conversation (speech) has a magnitude of 300 up to 3400 Hz, so if the first test is to have good results, it means that the sound signal in the form of a conversation (speech) has a good performance. From the test results are obtained that signals can be passed to the system at a frequency of 20 Hz to 20000 Hz with the average gain was 1.41 times. This can be interpreted speech signal (300 - 3400 Hz) can be passed using this system as well.
B. Tests by transmitting a signal at a changing distance
Fig. 10. Block Diagram Testing VLC System with the source of the function generator and within a changing distance
Fig. 10 shows the block of the second testing of the system has been implemented. This test is similar to the first test, but with a changing distance until the signal cannot be received by the Rx on a system that has been implemented. The results of these tests can be seen in Fig. 11 below:
Fig. 11. Comparison chart system based on the output changing voltage range
The greater the distance between the light source or LED with receiver circuit voltage reduction occurs this proves that the greater the distance, the smaller the signal received by a receiver capable. The maximum distance that has been able to be tested by the system is 2.3 m. Distance is limited due to the need to carry on a conversation between two people about less than 2 meters. Therefore, testing is only done at a distance only.
C. Tests by transmitting a signal that is using a color filter (Red to color)
In this third test, the transmitter and receiver on the system will use a color filter on each side. This test was conducted to analyze a couple of colors to match the performance yielding a
pair of color is best. Block diagram of the test is shown in Fig. 12.
Fig. 12. Block Diagram Testing VLC system using color filters
The information signal generated from the signal generator with a frequency of conversations (300 Hz to 3400 Hz) with a voltage of 5 volts. In this test the red color filter used at the transmitter and multiple colors on a receiver. Table 1 shows the position of the color filter.
Table I. Testing VLC system with color filters (Red to Color)
Filter on Transmitter
Filter on Receiver
Red
Red
Rose
Green
Charteuse Green
Blue
Azure
Violet
Magenta
Orange
Yellow
Fig. 13. Color Filter
Fig. 14 shows a graph of test results of the system with a
color filter. In simplex communication should have the similar wavelength between transmitter and receiver that is red color. The next experiment will be used another color pairs for communication.
Fig. 14. Graph output voltage system with a red filter on the transmitter
The frequency of speech signal is similar to audio
frequency and the system should transmit and receive the signal with a good performance. The performance represented by the received voltage. Seen in Fig. 14, that the voltage signals that can be missed by the system has produced relatively good voltage above 1 Volt at a distance of 50 cm with speech frequencies (300-3400 Hz). It is proved that this system can be used as a transceiver (transmitter-receiver) Visible Light Communication (VLC). In addition, a couple of red color filters in the transmitter and receiver filters red in red color has a voltage in the receiver received a relatively greater compared to using other colors. Pair this color can be used as a basis and reference for implementing the system of full duplex speech Visible Light Communication (VLC) between colors that will not interfere with each other.
IV. CONCLUSIONS
Based on the results of research and measurements that have been made to the system using Visible Light Communication of this, it can be concluded as follows:
1. From this study, the maximum distance for data transmission from transmitter to the receiver is 2,3 m.
2. Range frequency conversation (speech) in the amount of 300 Hz to 3400 Hz has to be missed by the system, so the system has to be used to transmit voice conversations (speech) from one place to another.
3. Pair of red color filter mounted on the transmitter and the red color filter in the receiver has a voltage received relatively good compared with most other colors.
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