Visible Light Communications towards 5G

5G networks have to offer extremely high capacity for novel streaming applications. One of the most promising approaches is to embed large numbers of co-operating small cells into the macro-cell coverage area. Alternatively, optical wireless based technologies can be adopted as an alternative physical layer offering higher data rates. Visible light communications (VLC) is an emerging technology for future high capacity communication links (it has been accepted to 5GPP) in the visible range of the electromagnetic spectrum (~370–780 nm) utilizing light-emitting diodes (LEDs) simultaneously provide data transmission and room illumination. A major challenge in VLC is the LED modulation bandwidths, which are limited to a few MHz. However, myriad gigabit speed transmission links have already been demonstrated. Non line-of-sight (NLOS) optical wireless is resistant to blocking by people and obstacles and is capable of adapting its’ throughput according to the current channel state information. Concurrently, organic polymer LEDs (PLEDs) have become the focus of enormous attention for solid-state lighting applications due to their advantages over conventional white LEDs such as ultra-low costs, low heating temperature, mechanical flexibility and large photoactive areas when produced with wet processing methods. This paper discusses development of such VLC links with a view to implementing ubiquitous broadcasting networks featuring advanced modulation formats such as orthogonal frequency division multiplexing (OFDM) or carrier-less amplitude and phase modulation (CAP) in conjunction with equalization techniques. Finally, this paper will also summarize the results of the European project ICT COST IC1101 OPTICWISE (Optical Wireless Communications - An Emerging Technology) dealing VLC and OLEDs towards 5G networks

Tester for space micro-accelerometer

AbstractMicro-accelerometer MAC04 has been developed in order to measure very low accelerations such as those caused to satellites by atmospheric drag and other non-gravitational forces. The instrument uses a cubic proof-mass inside a small cavity. In an open loop the change of capacitance between the cube and 12 electrodes on the inner cavity surface is a measure of the applied acceleration. It is very difficult to ground test and calibrate such a device due to gravity. The tester simulates the change of capacitances (base capacitance 13,5pF, changes in a range of ±1.5pF). Complete closed loop system is presented

Experimental multi-user VLC system using non-orthogonal multi-band CAP modulation

This paper provides experimental results for a multi-user visible light communications system using multi-band carrier-less amplitude and phase (m-CAP) modulation scheme. We optimize the system performance by adapting pulse shaping filter parameters, subcarrier spacing and allocating different baud rates to individual sub-bands called allocated m-CAP (Am-CAP). We show that a maximal system data rate of ∼468 Mb/s for four users can be supported while gaining higher flexibility for optimization and the same or lower computational complexity compared with the conventional m-CAP scheme

Filter-less WDM for visible light communications using colored pulse amplitude modulation

This paper demonstrates, for the first time, a new wavelength-division multiplexing (WDM) scheme for visible light communications using multi-level coloured pulse amplitude modulation (M-CPAM). Unlike traditional WDM, no optical bandpass filters are required and only a single optical detector is used. We show that, by transmitting n independent sets of weighted on-off keying non-return-to-zero data on separate wavelengths over a line-of-sight transmission path, the resultant additive symbols can be successfully demodulated. Hence, the data rates can be aggregated for a single user or divided into individual colours for multiple user access schemes. The system is empirically tested for M = 4 and 8 using an off-the-shelf red, green and blue (RGB) chip light emitting diode (LED). We demonstrate that for M = 4, using the R and B chips a bit error rate (BER) of ≤10-6 can be achieved for each wavelength at bit rates up to 10 Mbps, limited by the LEDs under test. For M = 8 using R, G and B a BER of ≤10-6 can be achieved for each wavelength at bit rates up to 5 Mbps

Production of Poly(vinylalcohol) Nanoyarns Using a Special Saw-like Collector

This work introduces an electrospinning method for laboratory-scale production of nanofibrous materials from polyvinylalcohol (PVA) nanofibres. A procedure for the subsequent production of twisted yarns from the aligned nanofibrous strand is introduced as well. Both needle and needleless electrospinning variants were employed Mechanical properties of the nanoyarns produced were tested using a VIBRODYN 400 and their morphology was investigated by light and electron microscopy. The work also introduces a simple analysis of the field strength that causes the prevailing unidirectional fiber deposition between neighbouring lamellae of a special saw-like collector The field strength analysis was carried out both analytically and by modelling based on the software COMSOL Multiphysics.MSMT project CARSILA [ME10145]; [GACR: P208/12/0105

Demonstration of a Hybrid FSO/VLC Link for the Last Mile and Last Meter Networks

OAPA In this paper, a hybrid free-space optical and visible light communication (FSO/VLC) system was experimentally demonstrated as a solution to overcome the last mile and last meter access networks bandwidth bottleneck. We evaluate the system performance of a multiband carrier-less amplitude and phase ($\textit{m}$-CAP) modulation scheme for a range of FSO/VLC link lengths and $\textit{m}$-CAP parameters (i.e., the roll-off factor of the filters and a number of subcarriers) in terms of the data rate $R_b$ (i.e., spectral efficiency). We show that for the configuration with a 1 m VLC link the \mbox{10-CAP} offers more than a 40% improvement in the measured $R_b$ compared to 2-CAP for the same bit error rate target. The $R_b$ penalty due to the extension of a VLC link span from 1 m to 3 m reaches to 12.6 Mb/s for the \mbox{10-\text{CAP}} scheme (i.e., $\sim$39% degradation in $R_b$). To fully cover all aspects of the hybrid FSO/VLC system, we also investigate the atmospheric turbulence effect on the 500 m FSO link where $R_b$ is decreased by 30% for the refractive index structure parameter $C_n^2$ of \mbox{2.4\times10^{\minus15} m^{\minus2/3}} compared to a clear channel condition

Strategies for organic VLC: Effects of clipping on the performance of multi-band CAP modulation with polymer-based light-emitting diodes

We investigate, for the first time, the effect of signal clipping on multi-band carrier-less amplitude and phase (m-CAP) modulation in visible light communications based on PLEDs. We experimentally demonstrate a Q-factor improvement up to ~2.25 dB can be obtained with a clipping level of 50%

The Potamophylax nigricornis group (Trichoptera, Limnephilidae): resolution of phylogenetic species by fine structure analysis

Applying the phylogenetic species concept and the sexual selection theory we have reviewed some natal aspects of incipient species and their accelerated evolution. How can we recognise early stages of divergence? Which selection pressures are at work during speciation? Which pathways accelerate the speed of speciation? Which kinds of trait variabilities makes difficult to find initial split criteria? Elaborating the principles of Fine Structure Analysis (FSA) and the morphological Initial Split Criteria (ISP) it was discovered that the European spring dwelling caddisfly Potamophylax nigricornis doesn’tbelong to a single species. It represents an entire species group with seventeen peripatric species evolving on the southernperipheries of the distributional area. Four new species subgroups have been erected: Potamophylax nigricornis new species subgroup, P. elegantulus new species subgroup, P. horgos new species subgroup, P. simas new species subgroup. Eleven new species have been described: Potamophylax apados sp. nov., P. fules sp. nov., P. fureses sp. nov., P. hasas sp. novov., P. horgos sp. nov., P. kethas sp. nov., P. lemezes sp. nov., P. peremes sp. nov., P. simas sp. nov., P. tuskes sp. nov., P. ureges sp. nov. One Potamophylax sp. nov. has been differentiated and three new species status have been documented:Potamophylax elegantulus (Klapálek) stat. n., P. mista (Navás) stat. nov., P. testaceus (Zetterstedt) stat. nov