By using Visible Light Communication (VLC), in contrast to radio waves, the secure connection can be established more efficiently since the visible light could not radiate through most solid objects. VLC has been applied for many use... more
By using Visible Light Communication (VLC), in contrast to radio waves, the secure connection can be established more efficiently since the visible light could not radiate through most solid objects. VLC has been applied for many use cases, one of them is Light-Fidelity (Li-Fi). With Li- Fi, internet access is no longer using conventional RF spectrum as employed in Wi-Fi technology but apply visible light. In this paper, we present the design and implementation of a Li-Fi on a System on Chip (SoC) with a low-cost discrete analog front end (AFE). We used ZYBO Zynq-7000 as a digital signal processing, 8 Watt yellow-colored high-brightness LED (HBLED) for downlink transmitter, and 3 Watts infrared LED (IR LED) for uplink transmitter. Our system is developed compliant with the IEEE 802.15.7 standard, i.e. PHY II.1. According to the result, our Li-Fi system makes the PC/Laptop connected to any internet sources with a maximum speed up to 500 kb/s, and the maximum optical channel distance (range between the light source and the light receptors) is about 110 cm with two lenses.
The design and implementation of visible light communication systems for transmitting digital data (texts) have been discussed in this paper. Then, two evaluations were performed also, i.e. the demonstration of streaming text through the... more
The design and implementation of visible light communication systems for transmitting digital data (texts) have been discussed in this paper. Then, two evaluations were performed also, i.e. the demonstration of streaming text through the visible light as a proof-of-concept system design. The next evaluation is a BER measurement intended to know the VLC system performance quantitatively. The value of BER against the several parameters: by the variation of distance and its reception angle. The proposed VLC system works well until the photodiode reception angle to the LEDs up to 50°. According to evaluation, our system can operate optimally within 30 – 80 cm or 50 – 130 cm of optical channel range depending on the Gain setting option. To support the reliability of noise from ambient light and interference lamps such as fluorescent lamps, the filters circuit are employed: high pass filter and DC-offset remover. Based on the BER analysis, the filters can compensate the problem of ambient light noise (DC-offset signal) and interference lamp (100-150 Hz of the carrier frequency). The speed of obtained data-rate with 1-PWM modulation and the low-cost analog component is 3.3 kbps.
The optical channel distance greatly influences the optical power received by the photodiode, the farther the distance between the receiver and the transmitter in the VLC system, the lower SNR, and the higher BER. To mitigate the mobility... more
The optical channel distance greatly influences the optical power received by the photodiode, the farther the distance between the receiver and the transmitter in the VLC system, the lower SNR, and the higher BER. To mitigate the mobility issue on the VLC system, we involve an AGC circuit put on the receiver side. Thus, the received information (signal) can adjust at specifically required voltage even though the distance and angle were changed. In this paper, the AGC circuit employs a single channel LM13700; this is commercially available as well as a low-cost Integrated Circuit (IC). The application method to design a VLC system using LM13700 configured as AGC is presented. Then the AGC performance evaluation by using two different modulations is also conducted. The results show that the weak information (signal) due to changing the optical distance and the receiver angle can be gained to a required voltage level as well. Therefore, the LM13700 can be recommended for the mobility VLC system. Our system focused on low-rate VLC applications due to bandwidth limitations within the used IC. Moreover, our system is aimed at the Line-of-Sight VLC channel.
Several factors drive the use of visible light communication systems as an alternative communication method besides RF communication, one of which is energy saving because the VLC system uses the same device for room lighting, i.e., LED.... more
Several factors drive the use of visible light communication systems as an alternative communication method besides RF communication, one of which is energy saving because the VLC system uses the same device for room lighting, i.e., LED. This study aims to model the VLC systems based on multi-carrier modulation (DCO-OFDM) by using MATLAB software. In this study, VLC the system is modeled on two parts, namely Digital Signal Processing (DSP) and optical channels. The DSP block consists of FFT, convolutional encoder, modulator-demodulator, interleaver-deinterleaver, and synchronizer. For error control coding (ECC), the Viterbi decoder algorithm is used. The results showed that DCO-OFDM frames had been successfully designed. Based on mathematical calculations through the MATLAB approach, the VLC system can work well in 5m x 5m x 3m rooms size: BER equals to zero for the minimum SNR of 10 dB has been obtained while the highest SNR value that can be achieved is ~ 30 dB.
