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Optical wireless communications (OWC) has emerged as a strong candidate for wireless communications, due to the capacity limitation in the radio frequency (RF) spectrum. Especially visible light communication (VLC) has great potential for short-range outdoor vehicular communications, as vehicle LED lights also transmit data. However, outdoor VLC channels vary fast and, experience multipath scattering and reflection resulting in time domain dispersion. Outdoor VLC links are also subjected to high levels of ambient noise, especially from the sun. Orthogonal frequency-division multiplexing (OFDM), which has proven robustness to multi path fading and noise effects in RF links can also be deployed in VLC links. In this paper, optical OFDM (O-OFDM) along with adaptive modulation scheme is investigated in VLC for vehicle to vehicle (V2V) communications. A (2 x 2) multiple input multiple output (MIMO) channel, with multiple polarimetric bidirectional reflections and realistic sunlight interference is considered. Two schemes of O-OFDM; direct current biased optical OFDM (DCO-OFDM) and asymmetrically clipped optical OFDM (ACO-OFDM) are investigated. Simulation results of the proposed model show increase in data rates up to 50 Mbps along with reduced bit error rate (BER) under both line of sight (LOS) and non-LOS and high noise conditions.

Visible light communications (VLC) require III-nitride visible micro-light-emitting diodes (μLEDs) with a high-modulation bandwidth. Such μLEDs need to be driven at a high injection current density on a kA/cm2 scale, which is about 2 orders of magnitude higher than those for normal visible LED operation. μLEDs are traditionally fabricated by dry-etching techniques where dry-etching-induced damages are unavoidable, leading to both a substantial reduction in performance and a great challenge to viability at a high injection current density. Furthermore, conventional biasing (which is simply applied across a p–n junction) is good enough for normal LED operation but generates a great challenge for a single μLED, which needs to be modulated at a high injection current density and at a high frequency. In this work, we have proposed a concept for an epitaxial integration and then demonstrated a completely different method that allows us to achieve an epitaxial integration of a single μLED with a diameter of 20 μm and an AlGaN/GaN high-electron-mobility transistor (HEMT), where the emission from a single μLED is modulated by tuning the gate voltage of its HEMT. Furthermore, such a direct epitaxial approach has entirely eliminated any dry-etching-induced damages. As a result, we have demonstrated an epitaxial integration of monolithic on-chip μLED-HEMT with a record modulation bandwidth of 1.2 GHz on industry-compatible c-plane substrates.

With advances in automated and connected driving, secure communication is increasingly becoming a safety-critical function. Injection of manipulated radio messages into traffic can cause severe accidents in the foreseeable future, and can currently be achieved without having to manipulate on-board vehicle systems directly, for example by hijacking cellphones instead and using these as senders. Thereby, large-scale attacks on vehicles can be executed remotely, and target relatively vulnerable devices. To mitigate remaining vulnerabilities in current automotive security architectures, this paper proposes a secondary communication channel using vehicle head and taillights. In contrast to existing approaches, this method allows both to achieve a sufficient data rate and to extract the angular position of the sender, by means of an imaging process which only requires close-to-market, cost-efficient technology. Through this, injecting false messages by masquerading as a different sender is considerably more challenging: The receiver can verify a message’s source position with the supposed position of the sender, e.g. by using on-board sensors or communicated information. Thereby, reliably faking both the communicated messages and the position of the sender will require direct manipulation of on-board vehicle systems, raising the security level of the function accordingly, and precluding low-threshold, wide-range attacks.

Visible light communication requires III-nitride LEDs with a high modulation bandwidth but have c-plane limitations. General illumination requires green/yellow III-nitride LEDs with high optical efficiency that are difficult to achieve on c-plane substrates. Micro-LEDs with a low efficiency are used to obtain a high modulation bandwidth. This paper demonstrates a record modulation bandwidth of 540 MHz for our semipolar green LEDs with a broad area. Semipolar yellow and amber LEDs with modulation bandwidths of 350 and 140 MHz, respectively, have also been reported, and are the longest wavelength III-nitride LEDs. These results agree with differential carrier lifetime measurements.

Light bulbs have been recently explored to design Light Fidelity (LiFi) communication to battery-free tags, thus complementing Radiofrequency (RF) backscatter in the uplink. In this paper, we show that LiFi and RF backscatter are complementary and have unexplored interactions. We introduce PassiveLiFi, a battery-free system that uses LiFi to transmit RF backscatter at a meagre power budget. We address several challenges on the system design in the LiFi transmitter, the tag and the RF receiver. We design the first LiFi transmitter that implements a chirp spread spectrum (CSS) using the visible light spectrum. We use a small bank of solar cells for communication and harvesting and reconfigure them based on the amount of harvested energy and desired data rate. We further alleviate the low responsiveness of solar cells with a new low-power receiver design in the tag. Experimental results with an RF carrier of 17 dBm show that we can generate RF backscatter with a range of 80.3 meters/𝜇W consumed in the tag, which is almost double with respect to prior work. European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 814215 TRUE inpress

A software-defined networking (SDN) architecture is capable of integrating all radio frequency and optical wireless small cell networks (e.g. fifth generation (5G), long-term evolution (LTE) femtocell, wireless fidelity (WiFi), light fidelity (LiFi)) in one network domain. This paper considers a SDN-enabled heterogeneous network (HetNet) comprised of LiFi, LTE femtocell and WiFi access points (APs). The HetNet control plane maintains the state of the network topology and wireless resources, which can support the development of intelligent service provisioning and efficient data communications in x generation (xG) wireless networks. The SDN applications use the network state to provide services in the data plane. However, when the state of network and wireless resources constantly changes, the SDN applications cannot provide reliable and guaranteed services to the wireless user equipments. This paper develops a queuing theoretic framework, which provides a performance evaluation for the SDN-enabled HetNet and applications convergence. A traffic engineering (TE) scheme is developed to support dynamic agnostic downlink flows routing to APs and differentiated granular services across the HetNet. Network and user centric policies are developed to make applications aware of network resource availability on the northbound and southbound interfaces of a SDN controller. Numerical models are introduced to study the impact of the computation and communication resources of northbound and southbound interfaces on the SDN-enabled HetNet scalability and the quality-of-service (QoS) guarantee of applications. Also, simulation scenarios are conducted to evaluate the performance of the TE scheme in provisioning effective and reliable services for subscribers.

This paper proposes a new face recognition system based on combining two feature extraction techniques: the Vander Lugt correlator (VLC) and Gabor ordinal measures (GOM). The proposed system relies on the execution speed of VLC and the robustness of GOM. In this system, we applied the Tan and Triggs and retina modeling enhancement techniques, which are well suited for VLC and GOM, respectively. We evaluated our system on the standard FERET probe data sets and on extended YaleB database. The obtained results exhibited better face recognition rates in a shorter execution time compared to the GOM technique.

Visible light communication (VLC) is a short-range optical wireless communication (OWC) utilizing white light-emitting diode (LED) lighting, so that the VLC systems can provide both illumination and communication. Multiple-input multiple-output (MIMO) is an attractive technology to efficiently improve the achievable rate of VLC with multiple LED luminaries which experience a low-pass effect in practical channels. In this paper, we investigate the performance of MIMO-VLC over three general low-pass channels, including exponential, first-order and Gaussian low-pass channels. Over frequency domain, two power loading strategies for multi-subcarrier orthogonal frequency division multiplexing (OFDM) are considered, namely uniform power loading and water-filling power loading. Expressions on the achievable rate to the corresponding link power budget and bandwidth are derived. Low-pass MIMO-OFDM VLC with a matrix channel decomposition has not extensively been treated theoretically in literature, to the best of our knowledge.

International audience; This paper proposes a scheme of joint Backscatter communication (BAC) and Visible Light communication (VLC) based on Non-orthogonal Multiple Access (NOMA) for a Beyond-fifth-Generation(B5G)/Sixth-Generation (6G) ultramassive Machine-Type Communication (umMTC) system. In this proposal, a hybrid RF-VLC channel combined with NOMA supports multi-users gain data from server and sensor information from local IoT items simultaneously. Moreover, benefits from noninterference between RF-VLC channel and more time-frequency resource allocated to each user, the communication performance is improved. A simulation was implemented to verify and estimate our proposal. Results indicated that our proposal gained higher channel capacity and reach lower bit error rate (BER).

Non-orthogonal multiple access (NOMA), mulai diteliti untuk dapat digunakan sebagai teknik multiple access yang efektif pada jaringan 5G karena teknik ini dapat menghemat bandwidth modulasi. Pada penelitian ini, NOMA diterapkan untuk sistem downlink Visible Light Communivation (VLC). Kami telah melakukan analisis performansi Multi-User Detection (MUD) pada kanal propagasi Non-Line of Sight (NLOS) dengan mempertimbangkan efek reflektor dan efek bayangan (shadowing). Kami juga mempertimbangkan teknik MUD yang digunakan pada penelitian ini yaitu Succesive Interference Cancellation (SIC). Setelah simulasi yang ekstensif, kami menemukan bahwa dengan penerapan SIC sebagai MUD pada sistem NOMA-VLC lebih baik dibandingkan dengan tanpa NOMA. Selain itu, kami juga memperoleh peningkatan data rate sebesar 72 %. Kata kunci: VLC, NOMA, NLOS, MUD, Optical Wireless Communication. ABSTRACT Non-orthogonal multiple access (NOMA), began to be studied to be used as an effective multiple access technique on 5G networks because this technique can save modulation bandwidth. In this research, NOMA is applied to the Visible Light Communivation (VLC) downlink system. We have performed a Multi-User Detection (MUD) performance analysis on Non-Line of Sight (NLOS) propagation channels by considering the reflector and shadowing effects. We also consider the MUD technique used in this study, namely Successive Interference Cancellation (SIC). After extensive simulations, we found that the application of SIC as MUD to the NOMA-VLC system is better than without NOMA. In addition, we also achieve an increase in data rate of 72%. Keywords: VLC, NOMA, NLOS, MUD, Optical Wireless Communication.

In the near future, with the development of 5G NR, a massive number of IoT nodes are expected to come online. Acquiring bandwidth from an overcrowded licensed radio frequency spectrum as well as overcoming battery life constraints will become the main challenges for these IoT based devices. As a promising solution for the above challenges, this work provides a feasibility study and an implementation framework for a visible light communication-based energy-autonomous IoT node. This work proposes the use of printed electronic technology to minimize the physical characteristics and cost of the IoT node. In the future, energy-autonomous IoT nodes could be available virtually on any surface. Whenever the node is exposed to light, it will be connected to internet.

Light Fidelity (LiFi) is a new candidate for wireless networking that utilizes the visible light spectrum and exploits the existing lighting infrastructure in the form of light-emitting diodes (LEDs). It provides point-to-point and point-to-multipoint communication on a bidirectional channel at very high data rates. However, the LiFi has small coverage, and its optical gain is closely related to the receiver’s directionality vis-à-vis the transmitter, therefore it can experience frequent service outages. To provide reliable coverage, the LiFi is integrated with other networking technologies such as wireless fidelity (WiFi) thus forming a hybrid system. The hybrid LiFi/WiFi system faces many challenges including but not limited to seamless integration with the WiFi, support for mobility, handover management, resource sharing, and load balancing. The existing literature has addressed one or the other aspect of the issues facing LiFi systems. There are limited free source tools available to holistically address these challenges in a scalable manner. To this end, we have developed an open-source simulation framework based on the network simulator 3 (ns-3), which realizes critical aspects of the LiFi wireless network. Our developed ns-3 LiFi framework provides a fully functional AP equipped with the physical layer and medium access control (MAC), a mobility model for the user device, and integration between LiFi and WiFi with a handover facility. Simulation results are produced to demonstrate the mobility and handover capabilities, and the performance gains from the LiFi-WiFi hybrid system in terms of packet delay, throughput, packet drop ratio (PDR), and fairness between users. The source code of the framework is made available for the use of the research community.

International audience; The 3D indoor positioning and indoor navigation (IPIN) system is of great significance for promoting and ex- panding indoor intelligent services and applications. The rapid development of unmanned aerial vehicles (UAVs) has provided new opportunities in this field. However, in contrast to their outdoor applications, IPIN for UAVs is more challenging since the Global Positioning System (GPS) is in general inaccessible in indoor environments. In this work, we propose a UAV-enabled 3D IPIN system based on visible light communication (VLC). Firstly, a novel VLC-based indoor positioning scheme is developed using a fusion algorithm based on the dynamic time warping (DTW) method with visible light intensity sequence (VLIS) and inertial measurement unit (IMU) data. To reduce the workload of fingerprint measurements, we propose to modularize a floor site using a standard symmetric structure for VLC positioning. In this manner, the navigation can be achieved by recognizing the edge of each module. Furthermore, since the sampling frequency of IMU is much higher than that of VLIS, discrete Kalman filter (KF) is introduced to correct the location measured by IMU when VLIS is unavailable. A proof-of-concept IPIN prototype is constructed. Field experiments confirm the effectiveness of our proposed IPIN system.

In this paper, two different three-dimensional (3D) indoor visible light positioning (VLP) algorithms are experimentally assessed for an industrial environment. The Cayley–Menger determinant (CMD) and linear least square (LLS) trilateration algorithms use the received signal strength (RSS) to estimate the receiver’s 3D position without prior knowledge of its height. The unknown 3D position of the receiver is estimated by the trilateration algorithms coupled with a cost function under different realistic scenarios. The performances of the algorithms are experimentally evaluated in terms of positioning error by considering two different light-emitting diode (LED) configurations in the presence of different receiver tilt angles, and with multipath reflections. It is observed that the widespread square LED configuration results in position ambiguities while a star-shaped configuration is much more accurate. Experimental tests performed in a 4 m × 4 m × 4.1 m area with four LEDs reported a median positioning error of 10.6 and 10.5 cm using the LLS and CMD algorithms, respectively, without the presence of receiver tilt or multipath reflections. However, when a receiver tilt of 10 ∘ was added, the median error increased to 22.7 cm using the LLS algorithm and 21.6 cm using the CMD algorithm. Overall, the achieved mean and maximum values using the LLS algorithm were 13.1 and 39 cm, respectively, while they were 12.2 and 34 cm using the CMD algorithm.

International audience; In VANET networks using TDMA access it is possible to approach the full capacity of the channel when the density of vehicles increases. When this occurs, some vehicles will be unable to communicate with the rest of the network. The use of Visible Light Communication (VLC) for certain vehicles can reduce the load on the radio channel and allow all vehicles to communicate on the network. The idea of our approach is to group vehicles with VLC capacity in platoons where only the lead vehicle would use radio transmission while the other vehicles in the platoon would communicate via the VLC system. We show that if the vehicles are randomly equipped with VLC transmission capabilities (with a probability p), the gain in bandwidth is significant even without rearranging the order of the vehicles. In this paper we estimate the performance gains obtained by using VLC in terms of bandwidth and probability of collision during an initial access.

Recently, neuromorphic sensors, which convert analogue signals to spiking frequencies, have &lrm, been reported for neurorobotics. In bio-inspired systems these sensors are connected to the main neural unit to perform &lrm, post-processing of the sensor data. The performance of spiking neural networks has been &lrm, improved using optical synapses, which offer parallel communications between the distanced &lrm, neural areas but are sensitive to the intensity variations of the optical signal. For systems with &lrm, several neuromorphic sensors, which are connected optically to the main unit, the use of &lrm, optical synapses is not an advantage. To address this, in this paper we propose and &lrm, experimentally verify optical axons with synapses activated optically using digital signals. The &lrm, synaptic weights are encoded by the energy of the stimuli, which are then optically transmitted &lrm, independently. We show that the optical intensity fluctuations and link&rsquo, s misalignment result &lrm, in delay in activation of the synapses. For the proposed optical axon, we have demonstrated line of &lrm, sight transmission over a maximum link length of 190 cm with a delay of 8 &mu, s. Furthermore, we &lrm, show the axon delay as a function of the illuminance using a fitted model for which the root mean square error (RMS) &lrm, similarity is 0.95.

Plastic optical fiber (POF) is considered as an attractive candidate for next-generation networks, for fiber-to the-home or for fronthaul of wireless access points in offices. Inside such spaces, visible light communication (VLC) can be an attractive interference-free communication approach. Such system can offer high data rates with potential cost reduction compared to existing techniques. Wavelength division multiplexing (WDM) can not only increase the link capacity, but also offers the ability to share the POF media with multiple services. In VLC systems, WDM can increase capacity. However, the use of narrow emitters and narrow bandpass filters to demultiplex the WDM signals are relative costly components in such systems. This work focuses on inexpensive light emitting diodes (LEDs), to accelerate mass-market applications, and we explore the potential for relaxing the wavelength filters at the detector. In these scenarios, multiple-input multiple-output (MIMO) technology can efficiently suppress interference or automatically fall back to common signalling if the crosstalk is so large that parallel channels would be insufficiently independent. We calculate the MIMO crosstalk channel coefficients due to relatively wide LED spectra. We derive analytical expressions for the maximum achievable rate of the system and we conclude that relatively large amount of crosstalk can be tolerated without jeopardizing performance, provided that dedicated signal processing is used. We show that without such signal processing, the choice of optical filters is very critical.

The angular diversity aperture (ADA) receiver is a new form of optical wireless receiver which is made up of a number of receiving elements (REs) each consisting of a photodiode (PD) located below an aperture in an opaque screen. Previous work on the use of ADA receivers for visible light communication (VLC) analyzes only REs with round apertures and photodiodes with a limited range of parameters. This paper extends the analysis to calculate the channel gains for REs with for both round and square apertures and PDs and for more parameters. Graphs show how the gain varies as a function of the relative orientation of the transmitter and receiver for ten different designs. It is shown that the directionality of an RE depends on the offset of the PD from the aperture and that the field of view depends on the distance between the aperture and the PD. Detailed theoretical analysis and extensive simulation results demonstrate the bit error rate (BER) performance of receivers based on these ten designs in a multiple-input multiple-output (MIMO) VLC application. The round and square designs are found to have very similar BERs. It is shown that, even with high levels of shot noise, good BER results can be achieved throughout a typical scenario.

While 5G is being commercialized worldwide, research institutions around the world have started to look beyond 5G and 6G is expected to evolve into green networks, which deliver high Quality of Service and energy efficiency. To meet the demands of future applications, significant improvements need to be made in mobile network architecture. We envision 6G undergoing unprecedented breakthrough and integrating traditional terrestrial mobile networks with emerging space, aerial and underwater networks to provide anytime anywhere network access. This paper presents a detailed survey on wireless evolution towards 6G networks. In this survey, the prime focus is on the new architectural changes associated with 6G networks, characterized by ubiquitous 3D coverage, introduction of pervasive AI and enhanced network protocol stack. Along with this, we discuss related potential technologies that are helpful in forming sustainable and socially seamless networks, encompassing terahertz and visible light communication, new communication paradigm, blockchain and symbiotic radio. Our work aims to provide enlightening guidance for subsequent research of green 6G.

WOS: 000470838000028 Physical layer security (PLS) has emerged as a new concept and powerful alternative that can complement and may even replace encryption-based approaches, which entail many hurdles and practical problems for future wireless systems. The basic idea of PLS is to exploit the characteristics of the wireless channel and its impairments including noise, fading, interference, dispersion, diversity, etc. in order to ensure the ability of the intended user to successfully perform data decoding while preventing eavesdroppers from doing so. Thus, the main design goal of PLS is to increase the performance difference between the link of the legitimate receiver and that of the eavesdropper by using well-designed transmission schemes. In this survey, we propose a conceptual, generic, and expandable framework for classifying the existing PLS techniques against wireless passive eavesdropping. In this flexible framework, the security techniques that we comprehensively review in this treatise are divided into two primary approaches: signal-to-interference-plus-noise ratio-based approach and complexity-based approach. The first approach is classified into three major categories: first, secrecy channel codes-based schemes; second, security techniques based on channel adaptation; third, schemes based on injecting interfering artificial (noise/jamming) signals along with the transmitted information signals. The second approach (complexity-based), which is associated with the mechanisms of extracting secret sequences from the shared channel, is classified into two main categories based on which layer the secret sequence obtained by channel quantization is applied on. The techniques belonging to each one of these categories arc divided and classified into three main signal domains: time, frequency and space. For each one of these domains, several examples are given and illustrated along with the review of the state-of-the-art security advances in each domain. Moreover, the advantages and disadvantages of each approach alongside the lessons learned from existing research works are stated and discussed. The recent applications of PLS techniques to different emerging communication systems such as visible light communication, body area network, power line communication, Internet of Things, smart grid, mm-Wave, cognitive radio, vehicular ad-hoc network, unmanned aerial vehicle, ultra-wideband, device-to-device, radio-frequency identification, index modulation, and 5G non-orthogonal multiple access based-systems, are also reviewed and discussed. The paper is concluded with recommendations and future research directions for designing robust, efficient and strong security methods for current and future wireless systems. Scientific and Technological Research Council of Turkey (TUBITAK) [114E244] This work was supported by the Scientific and Technological Research Council of Turkey (TUBITAK) under Grant 114E244. (Corresponding author: Jehad M. Hamamreh.)

ABDULKAFI, Ayad Atiyah/0000-0002-1160-6011 WOS:000429305800022 Achieving high spectral efficiency is the key requirement of 5G and optical wireless communication systems and has recently attracted much attention, aiming to satisfy the ever increasing demand for high data rates in communications systems. In this paper, we propose a new precoding/decoding algorithm for spectral efficient optical orthogonal frequency division multiplexing (OFDM) scheme based visible light communication (VLC) systems. The proposed coded modulated optical (CMO) based OFDM system can be applied for both single input single output (SISO) and multiple input multiple-output (MIMO) architectures. Firstly, the real OFDM time domain signal is obtained through invoking the precoding/decoding algorithm without the Hermitian symmetry. After that, the positive signal is achieved either by adding a DC-bias or by using the spatial multiplexing technique. The proposed CMO-OFDM scheme efficiently improves the spectral efficiency of the VLC system as it does not require the Hermitian symmetry constraint to yield real signals. A comparison of the performance improvement of the proposed scheme with other OFDM approaches is also presented in this work. Simulation results show that the proposed CMO-OFDM scheme can not only enhance the spectral efficiency of OFDM-based VLC systems but also improve bit error rate (BER) performance compared with other optical OFDM schemes.

An organic light emitting diode (OLED) shows characteristics different from a traditional semiconductor LED when both are applied to visible light communication (VLC). This paper first experimentally characterizes its static and dynamic communication properties with varying input signals. This band-limited and power-limited light source leads to unique communication channel and noise models. Accordingly, the orthogonal frequency-division multiplexing in conjunction with offset quadrature amplitude modulation (OFDM-OQAM) is applied, and its performance is compared against the traditional dc-biased optical OFDM. To further enhance the communication performance, a bit and power loading algorithm and a proper equalization algorithm are jointly implemented to combat the channel frequency selectivity and increase the data rate. A bit-rate of 51.6 Mb/s based on a monochromic OLED is experimentally achieved through the proposed design. The rate is comparable to the multicolor OLEDs-based VLC link in the literature.

In this paper, we describe a generalized visible light communication (VLC) channel, which consists of the frequency responses of the light emitting diode (LED), the wireless optical channel, and the photo detector (PD). Based on the theoretical analysis of the generalized VLC channel, we found the response mask invariant characteristic (RMIC) under the condition of strong line of sight components, which means the shape of frequency response of generalized VLC channel is time-independent and invariant at different distances of the transceivers, different emitting angles of the LED and different incident angles of the PD. Depending on the RMIC, the shapes of received spectrum and signal-to-noise rate are also invariant. The experimental platform was set up to verify the proposed RMIC. Furthermore, a predefined VLC system with a new channel feedback method is described, both the complexity and time cost of feedback can greatly reduce through the proposed channel feedback method.

Indoor smart-farming based on artificial grow lights has gained attention in the past few years. In modern agricultural technology, the growth status is generally monitored and controlled by radio-frequency communication networks. However, it is reported that the radio frequency (RF) could negatively impact the growth rate and the health condition of the vegetables. This work proposes an energy-efficient solution replacing or augmenting the current RF system by utilizing light-emitting diodes (LEDs) as the grow lights and adopting visible light communications and optical camera communication for the smart-farming systems. In particular, in the proposed system, communication data is modulated via a 24% additional green grow LED light that is also known to be beneficial for the growth of the vegetables. Optical cameras capture the modulated green light reflected from the vegetables for the uplink connection. A combination of white ceiling LEDs and photodetectors provides the downlink, enabling an RF-free communication network as a whole. In the proposed architecture, the smart-farming units are modularized, leading to flexible mobility. Following theoretical analysis and simulations, a proof-of-concept demonstration presents the feasibility of the proposed architecture by successfully demonstrating the maximum data rates of 840 b/s (uplink) and 20 Mb/s (downlink).

A building-to-building free-space visible-light-communication link over more than 72 m link distance is presented. The link employs a dual data/clock optical channel from two 680-nm vertical-cavity surface-emitting laser laser-diodes. The receivers are implemented using custom bandwidth-enhanced avalanche photodiodes (APD) in Austria-Micro-Systems 0.35 μm complementary-metal-semiconductor-oxide technology. The APD receiver uses resistive linearization to allow for improved bias voltage control in the soft-breakdown region as well as increased signal-to-noise ratio by around 6 dB. A simple amplifier-based architecture is employed with no equalization or transimpedance-amplifier use. Measurement results show an on–off-keying data rate of 2 Gb/s and forward-error-correction-compliant bit error rate below 3.8 × 10−3.

In visible light communication (VLC) the optical digital to analog conversion (ODAC) approach was proposed as a suitable driving technique able to overcome light-emitting diode’s (LED) non-linear characteristic. This concept is analogous to an electrical digital-to-analog converter (EDAC). In other words, digital bits are binary weighted to represent an analog signal. The method supports elementary on–off based modulations able to exploit the essence of LED’s non-linear characteristic allowing simultaneous lighting and communication. In the ODAC concept the reconstruction error does not simply rely upon the converter bit depth as in case of EDAC. It rather depends on communication system set-up and geometrical relation between emitter and receiver as well. The paper describes simulation results presenting the ODAC’s error performance taking into account: the optical channel, the LED’s half power angle (HPA) and the receiver field of view (FOV). The set-up under consideration examines indoor conditions for a square room with 4 m length and 3 m height, operating with one dominant wavelength (blue) and having walls with a reflection coefficient of 0.8. The achieved results reveal that reconstruction error increases for higher data rates as a result of interference due to multipath propagation.

The paper discusses on the effect that the growth in our energy consumption as a species is having upon the planet, and how the global lighting and telecommunications industries are major contributors. We demonstrate that through the adoption of LED based lighting combined with visible light communications, substantial economical and power savings by orders of magnitude can be made over existing technologies, contributing towards a greener more sustainable future. The future of LED technology is also discussed with a focus on organic technology, promising increased savings.

Visible light communication (VLC) often suffers from line-of-sight path blockages and high levels of inter-cell interference. Thus, the analysis and design of cooperation techniques become crucial to address these key impairments. This paper studies the performance of different resource allocation schemes that are suitable for multi-cell cooperative transmission when tri- and tetra-chromatic light-emitting diodes (LEDs) and optical orthogonal frequency-division multiple access are utilized. Firstly, guidelines are derived for maintaining the same spatial distribution of the signal-to-interference-plus-noise ratio (SINR) in every sector of the multi-cell environment in case of stand-alone (non-cooperative) and cooperative transmission. Secondly, the possible resource allocation configurations for both stand-alone and cooperative transmission modes are identified for different LED types and available orthogonal resources (i.e., frequency sub-bands per color and sectors per cell). Finally, the data rate gain of the multiple resource allocation configurations are also analyzed, while verifying the illumination constraints. The obtained results confirm that the proper design of cooperative transmission configurations will be of paramount importance to provide reliable wireless link in ultra-dense VLC deployments. This work has been partially funded by the Spanish MECD FPU fellowship program granted to the author B. Genovés Guzmán, the Catalan Government under Grant 2017-SGR1479, and the Spanish Government under the national project ‘TERESA-ADA’ with ID no. TEC2017-90093-C3-2-R and TEC2017-90093-C3-1-R (MINECO/AEI/FEDER, UE).

This paper describes a vehicle-to-vehicle (V2V) communication system, employing optical camera communications (OCC). The system comprises the light emitting diode (LED)-based taillights and a raspberry camera used as the transmitter (Tx) and the receiver (Rx), respectively. The sectorized taillights (i.e., Tx) are intensity modulated at different frequencies, and a convolutional neural network (CNN) at the Rx is used for scene analysis, the region of interest (RoI) selection, and symbol detection. Results show that, the system data rates are constrained by the camera frame rate and symbol duration. The link performance is dependent on the CNN training set and we show that, the use of CNN allows a robust implementation, able to provide response under multiple situations: taillight obstruction, variable link distances, and misaligned Tx-Rx. Furthermore, CNN enables multiple input multiple output (MIMO) signal detection without the need for dedicated training. published

The ever-increasing number of vehicles on a global level signifies the need for communications between vehicles and the surrounding environment. Visible light communications (VLC) is a viable complementary technology to congested radio-frequency-based wireless systems. In order to increase the reliability of the VLC link, two novel algorithms based on (i) channel inversion (CI) and (ii) frame subtraction and CI (FSCI) schemes are proposed to successfully extract the data in a non-line-of-sight multiple-input–multiple-output spatial-division multiplexing optical camera communications system. We have adopted differential modulation and frame subtraction schemes and proposed a unique packet structure to mark the packet and the position of the footprint of transmitters (Txs) in the image frame. We show that the FSCI scheme with much simpler receiver structures can offer almost the same bit error rate performance compared with the hybrid selection/equal gain combining (HS/EGC) technique at lower transmit power (illumination) levels of 20dBm for multiple Txs. Compared with HS/EGC, CI schemes have a higher tolerance to the spacing between Txs, where the payload threshold level can be set to a fixed value of 0.5.

High speed wireless communications are highly desirable for many industrial and scientific underwater applications. Acoustic communications suffer from high latency and limited data rates, while Radio Frequency communications are severely limited by attenuation in seawater. Optical communications are a promising alternative, offering high transmission rates (up to Gb/s), while water has relatively low attenuation at visible wavelengths. Here we demonstrate the use of series-connected micro-light-emitting-diode (μLED) arrays consisting of 6 μLED pixels either 60 μm or 80 μm in diameter and operating at 450 nm. These devices increase the output power whilst maintaining relatively high modulation bandwidth. Using orthogonal frequency division multiplexing (OFDM) we demonstrate underwater wireless data transmission at rates of up to 4.92 Gb/s, 3.22 Gb/s and 3.4 Gb/s over 1.5 m, 3 m and 4.5 m, respectively, with corresponding bit error ratios (BERs) of 1.5 × 10 -3 , 1.1 × 10 -3 and 3.1 × 10 -3 , through clear tap water, and Mb/s rates through >5 attenuation lengths (ALs) in turbid waters.

Deteksi objek yang merupakan salah satu bagian utama dari sistem Smart Transportasion Network (STN) diajukan pada penelitian ini. Penelitian ini menggunakan salah satu model STN yaitu Infrastructure-to-Vehicle (I2V), dimana sistem ini bekerja dengan mendeteksi kendaraan mobil menggunakan model arsitektur RetinaNet dengan backbone Resnet101 dan FPN (Feature Pyramid Network), kemudian hasil deteksi mentrigger VLC transmitter yang terpasang di lampu penerangan jalan mengirimkan sinyal informasi menuju VLC receiver yang dipasang di mobil. Pada tahap proses training, jumlah dataset mobil yang digunakan adalah sekitar 1600 image dan 400 validation image serta pengulangan proses sebanyak 100 epoch. Berdasarkan 50 kali pengujian pada image test, diperoleh nilai precision mencapai 86%, nilai recall mencapai 85% dan f1-score mencapai 84%. Kata kunci: Object detection, RetinaNet, Resnet101, STN, VLC, I2V ABSTRACT Object detection is one of the main part in Smart Transportation Network (STN) system proposed in this research. This research used one of the STN models, namely Infrastructure-to-Vehicle (I2V), a system works by detecting car using RetinaNet architecture model with ResNet 101 and FPN (Feature Pyramid Network) as backbone, then the detection result triggers VLC transmitter set up on the street lighting to transmit information signal to the VLC receiver which set up in the car. At the training process stage, the number of car datasets is approximately 1600 images, 400 validation images and repetition of processes about 100 epochs. Based on the 50 times testing process on a image test, it is obtained 86% of a precision value, by reaching 85% of recall value, and 84% of f1-score. Keywords: Object detection, RetinaNet, Resnet101, STN, VLC, I2V

The recent, massive diffusion of LED-based illumination devices makes Visible Light Communications (VLC) a widely recognised wireless communication technology with large potential impact in many indoor and outdoor applications. In the indoor scenario, one of the most promising VLC implementations is foreseen in museums, exhibitions and cultural heritage sites. In this context, digital data can be transmitted by the specific lighting system of each artwork and received by the nearby standing visitors, allowing a complete set of dedicated services such as augmented reality (AR) and real-time indoor positioning, exploiting the directionality of the optical channel. In this work, we achieve, for the first time, VLC transmission through diffusive LED illumination of three-dimensional artworks (wooden and marble sculptures) in a real museum, exploiting the available LED illumination system, demonstrating the feasibility of VLC technology also when complex three-dimensional artworks, such as sculptures or bas-reliefs, are involved. In our experimental campaign, performed inside the Basilica of Santa Maria Novella in Florence, we perform extensive Packet Error Rate (PER) and Signal-to-Noise Ratio (SNR) tests on two important wooden and marble sculptures (Crucifix by Brunelleschi and the Holy Water Font by Bordoni, respectively), for different distances, view angles and configurations, in order to mimic a wide set of situations that visitors may encounter in a realistic scenario. We achieve successful VLC transmission for distances up to 8 m from artworks, at baud rate of 28 kBaud. We also provide detailed results on the characterization of the transmission Field of View (FoV) for our prototype, as well as the effect of side shifts of the observer’s position on the quality of VLC transmission, providing essential information for future implementations of positioning protocols and dedicated services in realistic, indoor scenarios. Our work represents an important step forward towards the deployment of VLC technology in museums and, more in general, it opens for far-reaching developments in a wide set of real indoor environments, including the cultural heritage sector, where diffusive VLC links exploiting illumination of three-dimensional objects could represent a ground-breaking innovation.

The fifth-generation of mobile network (5G) and beyond requires a radio access network (RAN) update in order to cope with the incoming increase of wireless data traffic and new applications. In this context, we propose an efficient optical-wireless architecture applied to the non-standalone (NSA) 5G new radio (NR) framework. Several distinct electrical- and optical-based fronthaul configurations combining free-space optical (FSO), wireless links, and radio over fiber (RoF) techniques were implemented and properly analyzed for selection according to network operator deployment requirements. In addition, visible light communication (VLC) was investigated as a future access network technology when immunity to electromagnetic interference is paramount. Experimental results demonstrated fourth-generation of mobile network (4G) and 5G coexistence at Gbit/s throughput and error vector magnitude (EVM) in accordance with 5G NR Release 15.

Visible Light Communication (VLC) is a short-range optical wireless communication technology that has been gaining attention due to its potential to offload heavy data traffic from the congested radio wireless spectrum. At the same time, wireless communications are becoming crucial to smart manufacturing within the scope of Industry 4.0. Industry 4.0 is a developing trend of high-speed data exchange in automation for manufacturing technologies and is referred to as the fourth industrial revolution. This trend requires fast, reliable, low-latency, and cost-effective data transmissions with fast synchronizations to ensure smooth operations for various processes. VLC is capable of providing reliable, low-latency, and secure connections that do not penetrate walls and is immune to electromagnetic interference. As such, this paper aims to show the potential of VLC for industrial wireless applications by examining the latest research work in VLC systems. This work also highlights and classifies challenges that might arise with the applicability of VLC and visible light positioning (VLP) systems in these settings. Given the previous work performed in these areas, and the major ongoing experimental projects looking into the use of VLC systems for industrial applications, the use of VLC and VLP systems for industrial applications shows promising potential.

Visible Light Communication (VLC) has been noted as an emerging technology for communications in wireless local area networks. VLC provides some distinctive features over the conventional wireless access technologies, such as Wi-Fi, Bluetooth, or ZigBee. The most prominent feature of VLC is that it can provide more exact location information, since it is based on a particular light. In addition, VLC can reduce the frequency interferences from numerous wireless channels, since it uses a completely different radio frequency channel from the conventional wireless access technologies. Thus, VLC can be used for Internet-of-Things (IoT) services. Nevertheless, up to now, not enough studies on how to provide IoT services over VLC networks have been conducted. In this paper, we propose a framework to provide IoT services in VLC networks. In particular, we will consider the unidirectional VLC network, in which the downlink channel from the VLC transmitter to the VLC receiver is given by using VLC communication, whereas the uplink channel from the VLC receiver to the VLC transmitter is implemented by using another wireless access technology, such as Wi-Fi. This is because most of the VLC receivers, such as mobile phones, cannot support the uplink VLC communication. Based on the framework of IoT services over unidirectional VLC, in this paper, we also propose the VLC&ndash, IoT protocol (VIP) which is an application layer protocol for data transport with the session management functionality that can be used to effectively provide IoT services among IoT servers, VLC transmitters and VLC receivers in the networks. The proposed VIP protocol is implemented by using the Cooja simulator. For performance analysis, the proposed scheme is compared with the existing CoAP-based scheme that does not provide the session management. From a variety of simulation experiments, we see that the proposed scheme can provide lower data transmission and handover delays, compared to the existing scheme.

A four green transverse magnetic (TM)/red transverse electric (TE) light wavelength demultiplexer device, based on multi slot-waveguide (SW) structures is demonstrated. The device aims to demultiplex wavelengths in the green/red light range with wavelengths of 530, 540, 550, and 560 nm; 630, 640, 650, and 660 nm. This means that the device functions as a 1 × 4 demultiplexer for each polarization mode (TE/TM). The controlling of the light switching between two closer segment SWs under the TM/TE polarization mode was studied by designing a suitable SW structure and setting the right segment length to fit the coupling lengths of the operating wavelengths. The device is composed of six-segment SW units and six S-bends (SB) SW. The key SW and SB parameters were optimized and determined by a full vectorial beam propagation method (FV-BPM). Results show power losses better than 0.138 dB, crosstalk better than −21.14 dB, and an optical spectrum smaller than 9.39 nm, with an overall compact size of 104.5 µm. The device can be integrated in wavelength division multiplexing (WDM) for increasing data bit rate in a visible light communication (VLC) system.

International audience; Visible Light Communication (VLC) is based on the dual use of the illumination infrastructure for wireless data communication. The major interest on this communication technology lies on its specific features to be a secure, cost-effective wireless technology. Recently, this technology has gained an important role as potential candidate for complementing traditional RF communication systems. Anyway a major issue for the VLC development is a deep comprehension of the noise and its impact on the received signal at the receiver. In this work, we present a simple but effective approach to analyze the noise and drastically reduce it through a signal processing method. In order to validate the effectiveness of this analytical approach, we have developed an USRP-based testbed. Experimental results have been carried out by evaluating the symbol error rate (SER) and show the effectiveness of the noise mitigation approach in different interference conditions and at different distance between the transmitter and the receiver.

This paper addresses dynamic nonlinear effects in the response of typical illumination Light Emitting Diodes (LEDs) to increase the reliability and data rate in Visible Light Communication (VLC) systems. These power LEDs have a limited bandwidth of only several MHz. To conceive a practical receiver, we describe the LED transient response by a nonlinear dynamic differential equation from the physical mechanisms in the Quantum Well (QW) of Double Hetero-structured (DH) LEDs. It includes the transient nonlinear relation between the input current and injection electron concentration, as governed by the dynamic rate equation. Also, we consider the static nonlinear (typically quadratic) relation between the injection electron concentration and output optical power is described by a square operator. Further we consider the static nonlinear relation between the injection current and output optical power, caused by the efficiency droop. We propose a novel post-distorter to overcome LED nonlinearities for high-speed Pulse Amplitude Modulation (PAM)-4 systems. Its performance is validated with measurements of a commercial blue LED.

Visible Light Communication (VLC) technology uses white Light Emitting Diodes (LED) for providing illumination and communication at the same time. White LEDs have excellent illumination properties but their communication properties need improvement. This article proposes a way how to evade the communication limitations of white LEDs. A part of original white LED spectrum is suppressed by an optical filter. Then the suppressed part is replaced by another LED. The correct choice of suitable LED enables to reconstruct the original spectrum. This solution removes the limitations because the white LED emits continuously. Data are carried by the communication LED only. The evaluation of reconstruction of original white light is measurement of the colour coordinates x and y. Furthermore, the communication properties of this transmitter were tested and obtained results are shown in this paper. EVM parameter was measured. Web of Science 17 1 80 74

Li-Fi technology provides the opportunity to use the spectrum of visible light to transmit information which is ways faster and safer than some other wireless technologies. This Paper presents information about complex comparative analysis between author’s prototype and other existing LiFi devices based on transmitting information using the Li-Fi technology.

Solid state lighting is nowadays widely diffused both in residential and office or industrial environment. Ambient light sensing to modulate lamp power is typical, too, but sensors inside a lamp are a challenge, due to the high flux of these sources, which easily saturates nearby light detectors. Usually, separate sensing devices must be introduced in the system, thus increasing complexity and cost. In this work, a methodology will be presented, to allow integration of a light sensing device inside a lamp, using low cost circuitry to mitigate interactions between high power LED sources and sensing photodiodes. Moreover, the same circuit allows visual light communication among sources.

The new emerging Visible Light Communication (VLC) technology has been subjected to intensive investigation, evaluation, and lately, deployed in the context of convoy-based applications for Intelligent Transportations Systems (ITS). The technology limitations were defined and supported by different solution proposals to enhance the crucial alignment and mobility limitations. In this paper, we propose to incorporate VLC technology and the Lane-Centering (LC) technique to ensure the VLC-connectivity by keeping the autonomous vehicle aligned to the lane center using vision-based lane detection in a convoy-based formation. As soon as the road lanes are detectable, the evaluated system showed stable behavior independently of the inter-vehicle distances and without the need to exchange information between vehicles. Such a combination can ensure the optical communication connectivity with a lateral error of less than 30 cm. The evaluation of the proposed system is verified using VLC prototype and an empirical result of an LC active application over 60 km on the Madrid M40 highway. Keywords: VLC, Lane-Centering, Platoon, ITS, Road safety applications.

Vehicles will soon be connected and will be interacting directly with each other and with the road infrastructure, bringing substantial benefits in terms of safety and traffic efficiency. The past decade has seen the development of different wireless access technologies for vehicle-to-everything (V2X) communications and an extensive set of related use cases have been drafted, each with its own requirements. In this paper, focusing on short-range communications, we analyze the technical and economic motivations that are driving the development of new road users' connectivity, discussing the international intentions to mandate on board devices for V2X communication. We also go in depth with the enabling wireless access technologies, from IEEE 802.11p to short-range Cellular-V2X and other complementary technologies, such as visible light communication (VLC) and millimeterWaves, up to hybrid communication and 5G. We conclude our survey with some performance comparison in urban realistic scenarios, underlying that the choice of the future enabling technology is not so easy to predict and mostly depends on mandatory laws at the international level.

Visible Light Communication (VLC) is a powerful supplement, which has gained tremendous attention recently and has become a favorable technology in short-range communication scenarios for the Fifth Generation (5G) networks. VLC possesses a number of prominent features to address the highly demanding 5G system requirements for high capacity, high data rate, high spectral efficiency, high energy efficiency, low battery consumption, and low latency. However, this prominent performance is limited by the imperfect reception, since line of sight channel condition may not always exist in practice. This paper presents and experimentally validates a SDN-assisted VLC system, which is coupled with WiFi access technology in order to improve the reliability of VLC system, reassuring zero packet loss reception quality due to misalignment or path obstructions or when the user is moving between two consecutive VLC transmitters and experience “dead coverage zones”.

Visible light communication (VLC) has become an alternative candidate in next-generation indoor wireless local area network. However, it is a great challenge for a receiver to obtain the signals from multiple LED sources that transmit different information. In this paper, we explore the BER degradation due to the overlapping of multiple LED sources in the visible light communication network. We experimentally demonstrate a Multiple Input Signal Output (MISO) VLC system utilizing space–time block coding (STBC) to overcome the signal interference due to multiple inputs. A throughput of 1.6 Gbit/s is successfully achieved, which reveals great improvement in the robustness and compatibility of LED based network system.

The light-emitting diode nonlinearity in visible light communication (VLC) systems is considered to be a major problem that deteriorates system performance. In this paper, we experimentally demonstrate a high-speed WDM CAP64 VLC system employing a Volterra series-based nonlinear equalizer to mitigate the nonlinear effect. A modified cascaded multimodulus algorithm (M-CMMA) is utilized to calculate the error function and update the weights of the nonlinear equalizer without using training symbols. An aggregate data rate of 4.5 Gb/s is successfully achieved over 2-m indoor free-space transmission with a bit error rate (BER) below the 7% forward error correction limit of 3.8 × 10-3. With the Volterra nonlinear equalizer, the Q factor of the VLC system is 1. 6 dB better than that without using the nonlinear equalizer, and the transmission distance is also increased by about 110 cm at the BER of 3.8 × 10-3. To the best of our knowledge, this is the first time that the Volterra nonlinear equalizer is utilized for high-speed carrierless amplitude and phase (CAP) modulation-based VLC systems.

In this work we present an ultra-wide coverage visible light communication (VLC) system based on a mechanical beam steering system at the transmitter terminal and a fluorescent optical concentrator at the receiver. The transmitter and receiver full field of view (FFOV) are 100° and 120°, respectively. The coverage area of the transmitter system at 2m is 12.5m2 and a data link of 300Mbps has been achieved at this range. Postprint

Visible light communications is an alternative method of indoor wireless communications that requires sensitive receivers. Ideally, single photon avalanche detectors (SPADs) could be used to create more sensitive receivers. However, the dead time, finite output pulse width, and photon detection efficiency of existing SPAD arrays limit their sensitivity and bandwidth. In this paper, an accurate equation for the impact of dead time on the sensitivity of a SPAD array is presented. In addition, the impact of the width of the output pulses on the ON-OFF keying data rate is investigated. Finally, a comparison between receivers containing an avalanche photo-diode (APD) and a large array of SPADs shows that although the receiver containing the SPAD is more sensitive in the dark, the APD-based receiver is more sensitive in a normal operating condition. However, the models that predict the performance of both receivers suggest that newer SPAD arrays will enable significant improvements in receiver sensitivity.

This work presents an effective and efficient solution (SLiFi) to the evil twin attack in wireless networks. The evil twin is a rogue Wifi Access Point (AP) that pretends to be an authentic one by using the same network configuration, including the (i) Service Set Identifier (SSID), (ii) the communication channel, and finally (iii) the MAC address of the purported AP. The evil twin is a trap set-up by an adversary willing to eavesdrop on the user's Internet traffic. The attack is relatively easy to implement, hard to detect and it can have a severe impact on a user's privacy. Many researchers focused on this attack and provided defences from different perspectives: network, access point and client side. Unfortunately, all the solutions provided so far are still not ready for mass deployment since they involve significant modifications to the 802.11 WiFi protocol. In the following, we report some of the most important ones. Gonzales et al. [1] proposed to construct a context vector containing the order of all APs detected at a particular time, with their SSID and RSSI values. This enables the client to compare its future associations with the stored context vector. Bauer et al. [2] proposed SWAT which is a request-response protocol. This approach provides a one-way AP authentication and allows the client to establish a connection to the network through a shared secret key to create a secure session based on the principle of trust-on-first-use (TOFU). Lanze et al. [3] introduced a new technique using the aircrack-ng suite. The tool airbase-ng is set up on all the devices and the beacon frames are collected from various APs. The proposed approach compares the Timing Synchronization Function (TSF) timestamps and their corresponding receiving times in order to spot anomalies due to message proxying and therefore, the presence of a malicious AP. Finally, Gangasagare et al. [4] propose a fingerprinting technique based on network traffic enabling to detect if the AP relays the traffic through another wireless connection. SLiFi does not require any changes to the already existing communication protocols and it enables the access point authentication (by the users) in a fast and reliable way. Indeed, SLiFi enables the user to authenticate the legitimate AP by exploiting a Visible Light Communication (VLC) channel. SLiFi involves two parties, i.e., the (honest) AP provided with a Wi-Fi interface and able to transmit data through a VLC channel, and an end-user, provided with a software that enables data to be read from a VLC channel, e.g., by using a webcam. SLiFi exploits four phases: AP's Public Key (PubKey) broadcast. The AP transmits its own PubKey to the end-user via an authenticated channel (VLC). The PubKey broadcast process is completely transparent to the user since each bit of the PubKey is delivered by quickly switching on and off the light of the room in which the user is. This is achieved by standard techniques of VLC: the human eye cannot perceive the fast blinking light but other devices, such as special webcams, can detect the brightness change. Subsequently, the brightness changes can be translated to a sequence of bit values. Seed generation. The end-user retrieves the public key from the VLC channel by using a webcam and transmits back to the AP a randomly generated seed encrypted with the AP's public key. The PubKey is securely delivered to the user since any other non-authorized light source can be easily spotted. Therefore, only one authorized VLC transmitter will be in place and it will deliver the PubKey of the AP. The client can now use the trusted PubKey to send back to the AP an encrypted seed to be used for the key generation. Secret key generation. The AP receives the user's encrypted seed via the Wi-Fi channel, decrypts the seed using its private key, and sends an acknowledgment message encrypted with the seed back to the end-user. This phase performs the key-agreement and both the AP and the user's device converge to a shared secret key. Encrypted communication. Any further communications between the end-user and the AP will be encrypted with the shared secret key, i.e., the seed generated by the client. SLiFi is compliant with multiple clients, indeed the AP can easily deal with concurrent communications. Moreover, from a practical perspective, SLiFi can be adopted to only generate the shared secret key and passing it to the already existing encryption algorithm, e.g., WPA2 or WPA2-Enterprise. To evaluate SliFi, we built a proof-of-concept using a (1) Raspberry Pi which emulates the AP, a (2) set of LEDs to transmit the PubKey, and (3) standard laptops to act as clients with webcams. All the software components have been implemented and tested. We performed several tests to evaluate the feasibility of our solution. To test reliability of VLC transmission, we ran various experiments to measure the Public key transmission errors as a function of the VLC bit-rate, and we observed that PubKey can reliability transmitted within a reasonable time frame. Finally, our results prove the feasibility of the solution in terms of time to establish the key and robustness to the evil-twin attack. References 1. H. Gonzales, K. Bauer, J. Lindqvist, D. McCoy, and D. Sicker. Practical Defenses for Evil Twin Attacks in 802.11. In IEEE Globecom Communications and Information Security Symposium (Globecom 2010), Miami, FL, December 2010. 2. K. Bauer, H. Gonzales, and D. McCoy. Mitigating Evil Twin Attacks in 802.11. January 2009. 3. F. Lanze, A. Panchenko, T. Engel, and I. Alcaide. Undesired Relatives: Protection Mechanisms against the Evil Twin Attack in IEEE 802.11. 4. M. Gangasagare. Active User-Side Evil Twin Access Point Detection. International Journal of Scientific & Engineering Research, May 2014.