Metameric MIMO-OOK transmission scheme using multiple RGB LEDs

In this work, we propose a novel visible light communication (VLC) scheme utilizing multiple di erent red green and blue triplets each with a di erent emission spectrum of red, green and blue for mitigating the e ect of interference due to di erent colors using spatial multiplexing. On-o keying modulation is considered and its e ect on light emission in terms of flickering, dimming and color rendering is discussed so as to demonstrate how metameric properties have been considered. At the receiver, multiple photodiodes with color filter-tuned on each transmit light emitting diode (LED) are employed. Three di erent detection mechanisms of color zero forcing, minimum mean square error estimation and minimum mean square error equalization are then proposed. The system performance of the proposed scheme is evaluated both with computer simulations and tests with an Arduino board implementatio

ASK-based spatial multiplexing RGB scheme using symbol-dependent self-interference for detection

We propose a vsible light communication scheme utilizing red, green and blue lightemitting diodes (LEDs) and three color-Tuned photodiodes. Amplitude shift keying modulation is considered, and its effect on light emission in terms of flickering, dimming, and color rendering is discussed. The presence of interference at each photodiode generated by the other two colors is used to improve detection since interference is symbol-dependent. Moreover, the capability of the photodiodes to follow the LEDs speed is considered by analyzing the possibility of equalizing the received signal, and also self-interference mitigation is proposed. The system performance is evaluated both with computer simulations and tests on an Arduino board implementation

Analysis and Demonstration of Quasi Trace Orthogonal Space Time Block Coding for Visible Light Communications

In the VLC context, pulse position modulation (PPM) and similar modulations are typically used when the overall complexity of the transmitter is required to be low or the system needs to support dimming, i.e., dynamically control the illumination level of the transmitter. However, despite the power efficiency of PPM, it is known to be bandwidth inefficient. Having known the trade-off between reliability and spectral efficiency, in this paper we propose a PPM-based space-time block coding (STBC) technique named as quasi-trace-orthogonal (QTO), derived from trace-orthogonal, to increase the spectral efficiency of PPM VLC's by limiting the reliability loss. We provide Monte-Carlo simulations for a 4×4 MIMO-VLC system and validate the results experimentally, and show that for a given signal-to-noise-ratio, the QTO-STBC based 4-PPM VLC system offers higher spectral efficiency at a cost of higher symbol error rate compared to trace-orthogonal STBC

A Comprehensive Lighting Configuration for Efficient Indoor Visible Light Communication Networks

Design of an efficient indoor visible light communication (VLC) system requires careful considerations on both illumination and communication aspects. Besides fundamental factors such as received power and signal-to-noise ratio (SNR) level, studies on mobility scenarios and link switching process must be done in order to achieve good communication link quality in such systems. In this paper, a comprehensive lighting configuration for efficient indoor VLC systems for supporting mobility and link switching with constraint on illumination, received power, and SNR is proposed. Full connectivity in mobility scenarios is required to make the system more practical. However, different from other literatures, our work highlights the significance of recognizing the main influences of field of view angle on the connectivity performance in the practical indoor scenarios. A flexible link switching initiation algorithm based on the consideration of relative received power with adaptive hysteresis margin is demonstrated. In this regard, we investigate the effect of the overlap area between two light sources with respect to the point view of the receiver on the link switching performance. The simulation results show that an indoor VLC system with sufficient illumination level and high communication link quality as well as full mobility and support link switching can be achieved using our approach

TDMA-Like infrared uplink with multi-faces photodiode access points

The Li-Fi paradigm that aims at implementing indoor communications links in indoor scenarios, paid attention to the downlink so as to grant connectivity and illumination to several users in very small cells, also known as attocells. However, few work has been done to face the problem of uplink since the use of visible light that send signals from floor to ceiling can be harmful for human eye. In this work we consider the performance offered by an infrared uplink access essentially based on TDMA. In particular we assume that the access points are characterized by the presence of multiple photodiodes on the ceiling so as to receive the signals coming from different users and directions. In this regard, we explore also the spatial dimension in order to evaluate how many users can access the network with a reasonable level of reliability and without inducing severe interference

Theoretical analysis of optical spatial multiple pulse position modulation

This paper proposes an advanced multi-pulse multi-light emitting diodes (LEDs) modulation technique to improve the efficiency for indoor visible light communication systems. The technique is referred to as spatial multiple pulse position modulation (SMPPM), and it is developed by combining a high spectral efficiency space shift keying (SSK) with a high energy efficiency multiple pulse position modulation (MPPM). During a symbol transmission, multiple active pulse slots and active LED indices are utilized as two degrees of freedom to modulate information which in turn provides the balance between the complexity, achievable spectral efficiency and energy efficiency. The analytical expression for symbol error rate (SER) of SMPPM in a multiple input multiple output system with multi-path propagation from reflection is derived theoretically using union bound technique and validated by means of Monte-Carlo simulations. Error performance of SMPPM is then evaluated extensively for different transceiver parameters and pulse configurations. Error rate distribution in a typical indoor workspace is plotted and analyzed. The SMPPM system achieves significantly higher spectral efficiency with respect to the conventional MPPM, SSK and spatial pulse position modulation (SPPM)

Mutual information of a 3x3 RGB MIMO VLC scheme based on Amplitude Shift Keying

Visible Light Communications (VLC) are a new key in the Internet access as well as, a possible enabler of Internet of Things. This kind of systems can allow, in principle, high data rate by stressing the bandwidth and also the spatial dimension. We deal in this work with a 3×3 VLC system characterized by red, green and blue LEDs at the transmitter and three photodiodes at the receiver. Each photodiode is tuned on a different color. In this paper we analyze the mutual information expression when thermal noise is present and we distinguish two different approaches. The first one considers the effect of interference of colors, while the second one aims at equalizing, from a spatial/color point of view, the channel. More, we show the numerically evaluated mutual information and the effect of some system parameters

Performance evaluation of generalized optical spatial modulation with dimming support

In this paper, we propose a modified generalized spatial modulation (MGSM) scheme with dimming support for indoor optical wireless communication (OWC) systems. The spatial indices of the active LEDs and their transmitted optical power levels are utilized to modulate data in MGSM. The key property of the signal waveforms in MGSM is that it provides the same amount of optical power emitted at any time instant that corresponds to the dimming level requested. Consequently, MGSM prevents potential health and safety concerns related to the human eye such as flickering caused by intensity modulation. The upper bound on the symbol error rate (SER) of MGSM is derived theoretically using the union bound method, which is used to verify Monte-Carlo simulations. Numerical results show that MGSM achieves a full range of dimming with sufficiently high spectral efficiency compared to conventional techniques such as multiple pulse position modulation, overlapping pulse position modulation, on-off keying and generalized spatial modulation (GSM). In terms of error performance, the SER of MGSM is compared with GSM at several dimming levels, which shows that MGSM provides an advanced and efficient modulation scheme for indoor OWC systems

Crystal structure of 4-(naphthalen-2-yl)-2-oxo-6-phenyl-1,2-dihydropyridine-3-carbonitrile

The synthesis and crystal structure of the title compound, C22H14N2O, are described. The title compound was synthesized by a three-component one-pot reaction in DMSO involving chalcone, cyanoacetamide and elemental sulfur as catalyst. The compound was characterized by spectroscopic methods and single-crystal X-ray diffraction. The structure consists of inversion-related dimers produced by N—H...O hydrogen bonding, which further interact through π–π contacts