IMAGE TRANSFER USING LI-FI TECHNOLOGY

- Since the use of the radio-frequency (RF) portion of the electromagnetic spectrum is growing all the time, new techniques to avoid poor Internet service have become necessary, one of which is Light Fidelity (Li-Fi) technology. Li-Fi is a high-speed communication light source technology that is superior to Wi-Fi in terms of capacity, security, and accessibility. The paper is an experimental work focused on the usage of optical wireless communications (OWCs) in Li-Fi technology for transferring images of various sizes, formats, distances, and baud rates, with the results ranging from (25-280) cm, (1200- 96000) bps, and (4.7- 116) kilobytes with a time of (2.7-166) seconds.

ISSN:2222-758X e-ISSN:  microcontroller that translates data signals into binary 0's and 1's, with 0 representing OFF and 1 representing ON of the LED. The output seems constant because intensity of the LED is rapidly varied, which is undetectable by human sight [10]. The receiver consists of a photodetector that receives the transmitted signal, amplifies it to reduce noise, and then regenerates it into the required signal. The computer should be able to read the regenerated signal [11], [12]. Fig. 1 shows the block diagram of the Li-Fi full Duplex Communication system. The system architecture is comprised of two transceiver circuits, each of which comprises a transmit and receive a portion. The transceiver section on both sides can transmit and receive data simultaneously. In the transmit section the input data is translated into binary data and sent to the LED driver. It sends binary data through the ON-OFF modulation of the LED light. A solar cell serves as the receive portion which demodulates the received signal using the 1s and 0s pattern. The solar cell detects variations in light since blinking is readily detectable and the solar cell's output is analog [13]- [16]. Thus, we could identify and demodulate the communication signal conveyed by solar cells. Fig. 2 shows the schematic diagram for the proposed Li-Fi transceiver circuit. • RS-232 serial communication is used for the exchange of information between devices. It is used to interface between the laptop and the modules designed.
• MAX232 IC is mostly used to modify the logic of a signal. It converts RS-232 voltage level to TTL voltage level, this assists in signal transfer between devices.
• 74HC14 IC is an inverting buffer with Schmitt-trigger action. They can convert gradually changing input signals into clearly delineated, jitter-free output signals. This assists in noise reduction both at the sender and receiver end.
• TIP121 transistor works as a switch, to switching LED.
• White LED (1 watt) for the transmission of data.
• Polycrystalline solar cell (6 v, 150 mA, 1 watt, 110 mm 60 mm) which detect the modulated light, convert the optical signal to an electrical signal. It is used to acquire a higher area to preserve the line of sight between the transmitter and receiver for improved communication. Table I List the function of each pin for the ICs used in the circuit. Fig. 3 shows a photo of the PCB of the proposed Li-Fi transceiver circuit that is printed using Altium designer software.   proposed transceiver circuit. The VLC transceiver is connected to the computer via the DB9 connector. The USB to serial converter transfers the -15V to 15V current to the IC max232, which converts it to TTL level 5V.The output of TTL can be acquired and sent to the pin 8 of the integrated circuit 7414 (free-noise buffer), which is connected to a tip121 for a high voltage and current amplifier that serves as an LED driver. The data signal is modulated on the LED indicated by the LED's on/off state switching using the RS-232 serial data transfer protocol. To facilitate the pin reversal operation, the IC 7414 Schmitt trigger is used to provide a modulation of light that will then go through pin no. 1, which is inverted to pin 2, and again inverted to pin 3. After amplification, the signal is reduced in noise on pin 2 of IC max232 and transferred to pin 11 of IC max232, where it is converted to TTL level 5V before being passed to DB9's pin 14, which is connected to pin 2 of DB9's. The signal has been readied for processing, and it may now be read by the application VLC (LIFI).    in which the solar cell converts the optical signal to electrical signals, and the original image is recovered and displayed PC2. The inverse operation is also performed, we send data from the PC2 to the PC1. Fig. 7. b shows the application of image transmission and Fig. 7. c shows the application of image reception.

III. SOFTWARE IMPLEMENTATION
Sending visual data to the serial port was accomplished via the use of the software. The program is written in the C++ programming language for image transmission and receiving, VLC(LIFI) is employed. On both ends, the transmission and reception algorithms are set to run simultaneously, and the image to be communicated is chosen The PCs are connected to the transceiver circuits via RS232. At both the transmitter and receiver ends, the Baud rate should be the same at both transmitting and receiving sides. The serial ports are opened at the specified Baud rate. This specified baud rate can be adjusted to achieve a high-quality image. The original image is rebuilt using the ASCII values received. Fig. 7 shows the interface developed for the communication via Li-Fi. As seen in Fig. 8, the program is used to transmit images in various (2nd PC). To receive the entire image on the receiving side, the broadcast bit value must be the same as the received bit count.

IV. EXPERIMENTAL RESULTS
The following results were obtained while conducting the experiments with the two circuits. The first Table I summarizes the results of the white LED and solar cell experiments using the full-duplex system. The results of Table II are Table III, more than one type of image is transmitted at a variable baud rate. Images in PNG, BMP, and JPEG format of variable sizes with a range of baud rate from 1200 to115200. The image size starts from 6.5(PNG) kilobytes, 10.4 (JPG) kilobytes, and 15.5 KB (BMP) kilobytes were transferred without error at various baud rates, including (1200 to 115200) bps, over a distance of 60cm. Serial data transmission speed is measured in baud rates. Serial communication uses synchronous data transfer at conventional rates including 2400, 4800, 9600, and 19200 baud, etc. The ASCII value of the input data is created, then transformed to BINARY and sent to the LED. A TTL to USB converter connects the laptop with the circuit. The association between Baud rate and transmission time will be studied further. The results demonstrate that the larger the data to be delivered, the longer the time needed, but the faster the data transfer rate, the shorter the time needed. The time relies on the magnitude of the data conveyed, and the speed depends on the light and the solar cell.  image. From these data, we conclude that the greater the size of the data to be sent, the longer the time needed to receive data. These results are conducted when the distance between the transmitter and receiver is 60 cm. The experimental results depend on several factors, such as the kind, size, and intensity of the LED utilized, with a convex lens utilized. The quantity of light, as well as the intensity, affects the solar cell's reaction.
• Increasing the size of solar cell results in an increase in the receipt of data for a higher amount of light, which also results in an increase in the receipt of data and thus leads to errors in the reception of the signal.
• Additionally, the temperature increase is a negative influence on the components of the processing circuit and may harm one of its components. Data errors occur because sunlight and moisture diminish the quality of the solar cell.
Results were achieved in a lighted room at typical temperatures. Table V presents comparison of recently published references related to the current research topic and current work.
The current experimental work deals with designing a simple and low-cost communication system using LED as a transmitter, Solar cell receiver, and microcontroller unit that controls the process for transferring images in two directions between two PCs. Acceptable results were achieved by sending and receiving images of all sizes and formats successfully at different distances with baud rates ranging from 1200 to 57600 bps. The format of images that used including 6.5KB