Visible Light Communication System in Presence of Indirect Lighting and Illumination Constraints

Abstract

Visible Light Communication (VLC) systems are designed to provide illumination and data services simultaneously. To achieve this goal, LED lamps are usually deployed on the room ceilings, in order to maximize the chances of having Line-of-Sight (LoS) connectivity between the VLC transmitter and the random locations that the VLC receiver can take. In an early stage of adoption, where the cost of LED lighting fixtures enabled with VLC technology will not be suitable for ultra-dense deployments, it is expected that only one VLC transmitter is placed per room. In this situation, the use of direct illumination may have serious problems to satisfy the illumination constraints and provide a homogeneous data rate coverage. Moreover, the use of a single powerful LED lamp per room may create discomfort glare effect to users and over-exposure problems in areas of the room at which the light beam is directed. In order to address these problems, this paper studies the data rate that VLC technology can achieve with indirect illumination. That is, when the LED lamp is pointing upwards, and the VLC user receives the optical signal that is reflected back from the ceiling. Obtained simulation results show that indirect illumination provides a more homogeneous data rate coverage when compared to direct case, while simultaneously verifying the illumination constraints in most of the places that the VLC receiver may take in the room.

Effect of the Color Temperature of LED lighting on the sensing ability of Visible Light Communications

“…The LED lamp combines both Cool-White (CW) and Red-Orange (RO) chips, where P cw and P ro are the fraction of the total radiant flux emitted these LEDs. The LED lamp points directly to the white wall, similar to the indirect illumination scenarios proposed in references such as [7], [11]. In this situation, the PD receives the light that is reflected back, and the presence of color objects between the LED/PD and the white wall creates a signature on the VLC signal that influence the CSI collected in reception.…”

“…Similarly, an unsupervised learning algorithm that identifies the clusters in which the collected CSI should be divided, where each cluster is associated to a different event, was proposed in [6]. However, since Neutral-White (4000 K) [7] and Cool-White (6500 K) [6] Phosphor-Converted (PC) LEDs concentrate most of the their radiant flux in the Yellow and Blue light regions, it is challenging to distinguish different objects when there is limited contribution of the reflected optical power on the Red-Orange light region.…”

Empirical evaluation of OFDM waveforms for VLC in the presence of LED nonlinearities

“…Two USRP N200 are used to implement the software-defined processing in the VLC transmitter and receiver, using LFTX and LFRX daughterboards (0-30 MHz), respectively. The TIA gain can be adjusted in 10-dB steps, and the DC-bias and ACscaling factor that the LED driver applies to the OFDM-based waveform can be adjusted to minimize the clipping probability and control the LED non-linear distortion power [12], [16]. The effect the DC-bias has on the LED transfer function is shown in Fig.…”

Random forest learning method to identify different objects using channel estimations from VLC link

“…Since VLC systems take advantage of existing lighting infrastructure, the most common deployments rely on direct illumination, where the LED lamps are placed on the ceiling to illuminate the faced-up PDs located in beneath [15]. An indirect illumination setting has also been proposed in references such as [16], [17], where the LED lamp is pointing upwards, and the PD receives the light that is reflected back from the (white) ceiling.…”