Visible Light Communications for Indoor Applications

The field of visible light communications (VLC) has undergone a rapid development in recent years. The increased utilization of light emitting diodes (LEDs) has opened new possibilities for especially indoor services such as broadband internet connection and po- sitioning. Thus, a research within VLC is the main focus of the thesis and is divided into two main parts. At rst, the multiband carrier-less amplitude and phase (m-CAP) mod- ulation, introducing a newly adopted format for spectrally e cient VLC links, is under investigation using both theoretical and experimental approaches. The recommendations for m-CAP transmitter site design are proposed. Next, the channel modeling of indoor VLC is investigated with emphasis on the dynamically changing environments caused by moving people and non-line of sight (NLOS) propagation and new statistical models are derived.Katedra elektromagnetického pol

Mobile User Connectivity in Relay-Assisted Visible Light Communications

In this paper, we investigate relay-assisted visible light communications (VLC) where a mobile user acts as a relay and forwards data from a transmitter to the end mobile user. We analyse the utilization of the amplify-and-forward (AF) and decode-and-forward (DF) relaying schemes. The focus of the paper is on analysis of the behavior of the mobile user acting as a relay while considering a realistic locations of the receivers and transmitters on a standard mobile phone, more specifically with two photodetectors on both sides of a mobile phone and a transmitting LED array located upright. We also investigate dependency of the bit error rate (BER) performance on the azimuth and elevation angles of the mobile relay device within a typical office environment. We provide a new analytical description of BER for AF and DF-based relays in VLC. In addition we compare AF and DF-based systems and show that DF offers a marginal improvement in the coverage area with a BER < 10–3 and a data rate of 100 Mb/s. Numerical results also illustrate that relay-based systems offer a significant improvement in terms of the coverage compared to direct non-line of sight VLC links

On scaling of human body models

Abstract Human body is not an unique being, everyone is another from the point of view of anthropometry and mechanical characteristics which means that division of the human body population to categories like 5%-tile, 50%-tile and 95%-tile from the application point of view is not enough. On the other hand, the development of a particular human body model for all of us is not possible. That is why scaling and morphing algorithms has started to be developed. The current work describes the development of a tool for scaling of the human models. The idea is to have one (or couple of) standard model(s) as a base and to create other models based on these basic models. One has to choose adequate anthropometrical and biomechanical parameters that describe given group of humans to be scaled and morphed among

Varijacije tijekom sezone u izokinetičkom vršnom momentu sile kod mladih nogometaša

The aim of the study was to investigate the seasonal variation in the strength of the knee flexors and extensors in highly trained youth soccer players. The players (n=16; age 16.7±0.7) were measured at the end of the competitive season, at the beginning of the off-season and during the sixth week of a new competitive season. Isokinetic concentric peak torque was measured at 60°•s-1, 180°•s-1, 360°•s-1 in a sitting position. The testing range of motion was set from 10–90° of knee flexion. Players performed a set of six maximal repetitions for both dominant and non-dominant limb. Average values of peak torque significantly changed during the observed periods. Significant differences (p<.05) between the three measurement sessions were noted with respect to the knee flexors at all angular velocities. A post-hoc test confirmed a significant increase between the first and the second measurement for flexion in both dominant (180°•s-1; p=.033) and non-dominant legs (360°•s-1; p=.004). A significant increase was also found between the first and the third session for both limbs during knee flexion at all angular velocities. The results indicate that peak torque values of knee flexors and extensors varied differently in trained youth soccer players depending on muscle group and movement velocity with statistically significant changes in knee flexors only.Cilj je ovog istraživanja bio utvrditi varijacije tijekom sezone u snazi pregibača i opružača potkoljenice vrhunskih treniranih mladih nogometaša. Igrači (n=16; dob 16,7±0,7) su testirani na kraju natjecateljske sezone, na početku prijelaznog perioda te tijekom šestog tjedna nove natjecateljske sezone. Izokinetički koncentrični vršni moment sile mjerio se pri brzinama od 60°/s, 180°/s i 360°/s u sjedećem položaju ispitanika. Opseg pokreta se tijekom testiranja kretao od 10 do 90° fleksije koljena. Igrači su izveli seriju od šest maksimalnih ponavljanja prvo dominantnom, a onda i nedominantnom nogom. Prosječne vrijednosti vršnog momenta sile značajno su se mijenjale tijekom promatranih perioda. Značajne razlike (p<0,05) u snazi pregibača potkoljenice zabilježene su između sva tri mjerenja pri sve tri brzine izveđonja. Post hoc test je također potvrdio značajno povećanje snage pregibača potkoljenice između prvoga i drugog mjerenja za dominantnu (180°/s; p=0,033) i nedominantnu (360°/s; p=0,004) nogu. Značajno povećanje vršnog momenta sile pregibača potkoljenice obje noge pri svim brzinama također je zabilježeno između drugoga i trećeg mjerenja. Rezultati pokazuju da vršni moment sile pregibača i opružača potkoljenice različito varira kod treniranih mladih nogometaša ovisno o mišićnoj grupi i brzini pokreta, sa statističkom značajnošću promjena samo za pregibače potkoljenice

Duobinary Modulation for Visible Light Communications

The paper proposes and experimentally investigates the performance of the duobinary transmission technique for a highly bandlimited VLC system. By adding a controlled amount of inter-symbol interference (ISI) into the transmitted signals through the use of pulse shaping filters, data rate can be doubled within the same signal bandwidth. To gain full insight into duobinary signalling, the so-called modified binary scheme is also tested. Bit error rate (BER) performance of both systems is measured for a range of data rates and compared to BERs for ideal binary and traditional on-off keying non-return to zero (OOK-NRZ) formats, across the same physical link. We show the duobinary system can support higher bit rates and lower BER than OOK-NRZ while requiring half the bandwidth of the binary scheme

Performance Evaluation of Various Training Algorithms for ANN Equalization in Visible Light Communications with an Organic LED

This paper evaluates the effect of training algorithms in an artificial neural network (ANN) equalizer for a feedforward multi-layer perceptron configuration in visible light communication systems using a low bandwidth organic light source. We test the scaled conjugate-gradient, conjugate-gradient backpropagation and Levenberg-Marquardt back propagation (LM) algorithms with 5, 10, 20, 30, and 40 neurons. We show that, LM offers superior bit error rate performance in comparison to other training algorithms based on the mean square error. The training methods can be selected based on the trade-off between complexity and performance

Seasonal variation in isokinetic peak torque in youth soccer players

The aim of the study was to investigate the seasonal variation in the strength of the knee flexors and\ud extensors in highly trained youth soccer players. The players (n=16; age 16.7±0.7) were measured at the end\ud of the competitive season, at the beginning of the off-season and during the sixth week of a new competitive\ud season. Isokinetic concentric peak torque was measured at 60°·s-1, 180°·s-1, 360°·s-1 in a sitting position. The\ud testing range of motion was set from 10–90° of knee flexion. Players performed a set of six maximal repetitions\ud for both the dominant and non-dominant limb. Average values of peak torque significantly changed during\ud the observed periods. Significant differences (p<.05) between the three measurement sessions were noted\ud with respect to the knee flexors at all angular velocities. A post-hoc test confirmed a significant increase\ud between the first and the second measurement for flexion in both the dominant (180°·s-1; p=.033) and nondominant\ud legs (360°·s-1; p=.004). A significant increase was also found between the first and the third session\ud for both limbs during the knee flexion at all angular velocities. The results indicate that peak torque values\ud of knee flexors and extensors varied differently in trained youth soccer players depending on muscle group and movement velocity with statistically significant changes in knee flexors only

Non-Orthogonal Multi-band CAP for Highly Spectrally Efficient VLC Systems

In this work we propose and experimentally demonstrate a novel non-orthogonal multi-band carrier-less amplitude and phase (NM-CAP) scheme for bandlimited visible light communication systems in order to increase the spectral efficiency. We show that a bandwidth saving up to 30% can be achieved thus resulting in 44% improvement in the measured spectral efficiency with no further bit error rate performance degradation compared to the traditional m-CAP scheme. We also show that higher order systems can provide higher bandwidth compression than low order systems. Furthermore, with no additional functional blocks at the transmitter or the receiver the proposed scheme introduces no extra computational complexity.Comment: 6 pages, 5 figure

A Multi-CAP Visible-Light Communications System With 4.85-b/s/Hz Spectral Efficiency

In this paper, we experimentally demonstrate a multiband carrierless amplitude and phase modulation format for the first time in VLC. We split a conventional carrierless amplitude and phase modulated signal into m subcarriers in order to protect from the attenuation experienced at high frequencies in low-pass VLC systems. We investigate the relationship between throughput/spectral efficiency and m, where m = {10, 8, 6, 4, 2, 1} subcarriers over a fixed total signal bandwidth of 6.5 MHz. We show that transmission speeds (spectral efficiencies) of 31.53 (4.85), 30.88 (4.75), 25.40 (3.90), 23.65 (3.60), 15.78 (2.40), and 9.04 (1.40) Mb/s (b/s/Hz) can be achieved for the listed values of m, respectively