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Publicatie

Investigation of Visible Light Communication in a Realistic Indoor Illumination Scenario

Boek - Dissertatie

High-power white Light Emitting Diodes (LEDs) are becoming widespread in modern lighting infrastructures because of their longer lifetime and higher energy-efficiency with respect to conventional lighting. Additionally, LEDs can be switched on and off at a high pace that is impossible to be perceived by the human-eye, allowing to establish communication by means of visible light, i.e., Visible Light Communication (VLC). The presence of LEDs on one hand and the pressure on the scarce Radio Frequency (RF) spectrum due to the increasing data traffic demand on the other hand has drawn the attention towards VLC for complementing RF. VLC-based systems achieving data rates in the order of Gbit/sec have been developed and rely on the combination of Orthogonal Frequency Division Multiplexing (OFDM) with Wavelength Division Multiplexing (WDM). However, these systems barely focus on the illumination functionality of a realistic lighting infrastructure, while also requiring more advanced electronics leading to a higher implementation cost. Next to this, the LED non-linearity imposes design precautions of these VLC systems in order to avoid a deteriorated performance. In this thesis, a realistic indoor illumination scenario is considered where embedding VLC is targeted to be realized at a low-cost without requiring advanced electronics, while also prioritizing the illumination functionality and avoiding the LED non-linearity. Consequently, the focus is drawn on two power-switched modulation techniques namely Variable Pulse Position Modulation (VPPM) and the in-house developed Single Edge Position Modulation (SEPM). The spectral efficiency of both techniques is examined and also their performance is assessed by means of simulation and/or experiment over a wide range of dimming levels. Afterwards, SEPM is elaborated in an array containing co-located LEDs for improving the spectral efficiency. The adoption of a circular shift is proposed in order to produce unique waveforms at the front-end of the receiver side, allowing to retrieve the transmitted data by each LED. This developed system called Circular Shifted-SEPM (CS-SEPM) is also investigated in terms of spectral efficiency and performance. The results demonstrated that CS-SEPM can achieve an improved spectral efficiency with respect to SEPM. This improvement becomes pronounced when the number of embedded bits per waveform increases. However, the received CS-SEPM waveforms exhibit a more complicated shape and as a consequence the receiver performance rapidly degrades when Inter-Symbol Interference (ISI) starts to play a role. Moreover, 1-bit SEPM provides the best robustness against ISI and supports even under the influence of severe ISI a data rate of 10 Mbit/sec for various dimming levels. This on condition that the Signal-to-Noise Ratio (SNR) is sufficiently high, i.e., about 40 to 50 dB which is feasible for a realistic indoor VLC scenario.
Jaar van publicatie:2021
Toegankelijkheid:Open