The cellular system goes through significant power loss due to indoor channel fading, the height of the building, wall reflections, etc. Visible Light Communication (VLC) in conjunction with the radio frequency (RF) communication can provide potential solutions to address issues wireless network is facing in the indoor environment. VLC uses existing illumination infrastructure for communication. VLC is more secure because light cannot penetrate through the wall, can offer high bandwidth and is environmentally safe green technology, unlike RF. This paper analyses and compares the RF and VLC link for indoor communication with respect to symbol-error-rate (SER) performance and power saving. The RF link path loss inside the building is modeled using WINNER-II path loss model, and VLC channel is modeled including the movement of the people. The same constellation-based modulation schemes are used in both the links for fair comparison such as binary phase shift keying (BPSK) for RF and on-o
keying (OOK) for VLC, Mthorder quadrature amplitude modulation (M-QAM) for RF and colour shift keying (M-CSK) for VLC. VLC link provides better SER performance as compared to RF link at the same signal-to-noise-ratio (SNR) for both BPSK (OOK) and 4-QAM (4-CSK) modulation schemes. There is an outstanding amount of power saving using VLC link as compared to RF link inside the room. Further, the SER gap between VLC and RF decreases as the constellation size increases.
Visible light communication (VLC) has various advantages over radio frequency (RF) communication such as ubiquity, low energy consumption, no RF radiation, and inherently secure as light does not penetrate through walls. Significant bio-medical signals including the electroencephalography (EEG) can be transferred with VLC even in places where RF is forbidden. Additionally, long-term exposure to RF radiation poses a risk to the human brain which limits the use of RF wireless wearable EEG systems. This potential advantage of VLC could help in the indoor healthcare system such as monitoring. A long-term video-EEG monitoring requires continuous monitoring by video along-with EEG signals. So, overall a significant amount of data needs to be streamed fast for real-time monitoring. A novel low-cost RF radiation-free system is proposed using VLC technology which can be integrated into a wearable EEG device. In this work, we transmit a video and multi-channel EEG signal using visible light communication. Data streams are modulated using colour shift keying (CSK) which drives the RGB LED. CSK gives double the data rate than OOK by mapping bits into a symbol. It keeps the average emitted optical colour constant during communication, thereby reduces potential human health complication related to light ashes. The proposed system aims to lower down the cost and complexity further by using single photodiode at the receiver unlike conventional CSK in IEEE 802.15.7. The receiver architecture exploits channel estimation in a better way. Computer simulations are carried out using actual raw EEG signals and video data. Simulated and theoretical SER versus SNR curves match seamlessly. The results demonstrate that at 33 dB SNR, it achieves a SER of 1x10-5. SER for different transmitter and receiver distance is also analysed. Further, the reliability and accuracy of data received at 33 dB is also discussed.
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