Outage Probability Analysis of RF/FSO-VLC Communication Relaying System

This paper presents an analysis of the asymmetric relaying system which provides communication between hybrid outdoor sub-system and indoor visible light communications (VLC) access points. The outdoor sub-system represents a hybrid radio-frequency (RF)/free-space optical (FSO) system, introduced to reduce the impact of weather conditions on transmission quality. Closed-form outage probability analytical expression is derived. Numerical results are presented and confirmed by Monte Carlo simulations. The effects of system and channel parameters on the outage probability performance are investigated and discussed. Greater optical transmitted power of the VLC subsystem reflects in better system performance, as well as lower indoor environment height. When the indoor room is higher, the propagation of the optical signal is longer, and there will be greater power dissipation and performance deterioration. In addition, the outage probability floor is noticed, which is important limiting factor for relaying system design.Comment: Published in: 2018 11th International Symposium on Communication Systems, Networks & Digital Signal Processing (CSNDSP

VESSELS FOR STORAGING WINE IN ANCIENT ROME AND TODAY

Wine seems to be one of the oldest beverages known to man. In order for the wine to have the required quality and not posing a danger to human health, it is necessary, as part of the production process, to be stored in appropriate vessels before reaching the consumer. The authors of this article, using the historical method and the method of analysis and comparison, will merge two different periods: Rome and today. The unusual merging of two different periods of human civilization is aimed at proving the hypothesis of this article that wine storage vessels are not a creation of today world, and their development in modern times contributes to keeping the wine quality as a food agricultural product. Also, in the article, the authors will present the way of sale and inheritance of wine in Rome, because the storage of wine in the amphorae, during the sale or inheritance then, contributed to the preservation of its quality, sale and inheritance

Mixed RF-VLC Relaying System with Radio-Access Diversity

We present a statistical analysis of a mixed radio-frequency (RF)-visible light communications (VLC) relaying system, where outdoor millimeter wave based RF links are utilized to provide backhaul connectivity for indoor VLC broadcasting. The multiple RF links are assumed to communicate with the VLC access point through decode-and-forward relay. Novel closed-form outage probability and average bit error rate expressions are derived and utilized to obtain numerical results. Monte Carlo simulations validate presented numerical results, which are further used to examine the effects of system and channel parameters on system performance.Comment: Presented at 2019 28th Wireless and Optical Communications Conference (WOCC

Performance Analysis of Industrial Cooperative Communication System in Generalized Fading Environment

This paper considers the performance analysis of M-ary phase shift keying industrial cooperative relaying system in Nakagami-m multipath fading channel with Gamma shadowing, which is known as the Generalized-K composite fading channel. Since the paper deals with the industrial environment, the communication channel is also affected by the additive Middleton\u27s Class-A impulsive noise. The bit error rate is used as a performance measure and the closed-form average bit error rate expression was derived. The influence of different fading and noise parameters on the system performance is investigated. The obtained results may be used for the improvement of the present and future industrial wireless communication systems

Performance of UV-enhanced PMMA fresnel lenses and impact on LCOE

Tiny increases in the transmittance of optical materials within a CPV module can have an important impact on the economy of a plant. This is certainly true in systems comprising multi-junction solar cells, whose high performance, based on a balanced photocurrent generation among the series-connected junctions, is very sensitive to spectrum variations. Every efficiency point gained causes not only an increase in the kilowatts hour produced, but a higher benefit on it, since the difference between electricity tariff and Levelized Cost of Electricity (LCOE) rises. This work studies the impact on the LCOE of a plant based on modules comprising PMMA lenses of two different types, standard UV blocking grade which is normally used for outdoor applications at high DNI climate and a specialty stabilized UV-enhanced transmittance acrylic (see Figure 1). Energy production will be compared for these two systems throughout the year at different sites to analyze when (season, time of the day) and where the usage of the enhanced PMMA is justified

Mixed RF-VLC Relaying Systems for Interference-Sensitive Mobile Applications

Due to their Radio-Frequency (RF) immunity, Visible Light Communications (VLC) pose as a promising technology for interference sensitive applications such as medical data networks. In this paper, we investigate mixed RF-VLC relaying systems especially suited for this type of applications that support mobility. In this system setup, the end-user, who is assumed to be on a vehicle that is in dynamic movement, is served by an indoor VLC system, while the outdoor data traffic is conveyed through multiple backhaul RF links. Furthermore, it is assumed that a single backhaul RF link is activated by the mobile relay and due to feedback delay, the RF link activation is based on outdated channel state information (CSI). The performance of this system is analyzed in terms of outage probability and bit error rate (BER), and novel closed form analytical expressions are provided. Furthermore, the analysis is extended for the case where the average SNR over the RF links and/or LED optical power is high, and approximate analytical expressions are derived which determine performance floors. Numerical results are provided which demonstrate that the utilization of multiple RF backhaul links can significantly improve overall RF-VLC system performance when outage/BER floors are avoided. This calls upon joint design of both subsystems. Additionally, the outdated CSI exploited for active RF selection can significantly degrade the quality of system performance.Comment: Published in IEEE Transactions on Vehicular Technolog

Toward a sustainable urban regeneration? Urban heritage between neoliberal forces and community preferences

The paper discusses a relationship between the neoliberal forces shaping contemporary urban transformations and the social sustainability of recent regeneration projects focused on urban heritage. Analysing two post-transitional cases, based on two different approaches, the paper will provide an insight into the dominant processes influencing both practices, as well as their anticipated/announced social sustainability and its achieved level.The first case is from Serbia - the Power Plant "Power and Light‖ - which was the first one generating alternating current in Belgrade. Located in the Dorcol area, this ex-industrial setting is situated close to the city center. Since 2005, the entire area has undergone a significant transformation into a luxurious residential and commercial complex, initiated by private investors and directed by city authorities in order to change the previous urban image.The second case, the Contemporary Art Center in Plovdiv, Bulgaria, represents different approach. Created in 1997, the center is a non-governmental organisation of public interest. In 1995 the Municipality of Plovdiv obtained the right to locate the center within the remains of the ancient baths of Rome, which were rebuilt under the Turkish Empire. As the 16th century monument, the building belonged to the municipality and in 2004, the three-year period of support started, provided by the association Art Today (the Swiss cultural program), as well as the National Heritage Fund in Bulgaria.The analysis will be based on the selected principles of social sustainability, simultaneously highlighting the problems of heritage (re)use and regeneration in a challenging global environment of uncertain financial flows and shifting local governmental priorities, which could put on hold or totally ignore the aspect of social sustainability

The Transformation of Dorćol Power Plant: Triggering a Sustainable Urban Regeneration or Selling the Heritage?

The power plant “Power and Light” (1932, Belgrade) was the first one to generate alternating current in Serbia. Situated along the Danube river, it represented a part of an industrial area positioned in the Dorćol neighborhood, close to the urban core. Since 2005, the whole area has been exposed to a significant transformation into a luxurious residential and commercial complex, triggered by the intentions of private investors and directed by the ideas of changing city authorities. Considering the unpredictable local context created by the dominant post-socialist transitional economy, the article focuses on the sensitive relationship between the social sustainability of the ongoing urban regeneration plans and the emerging neoliberal forces targeting the areas of industrial heritage. Consequently, the case of the Dorćol ex-power plant and the anticipated changes in its urban surrounding are analyzed according to the selected principles of social sustainability. Revealing numerous controversies, both on the level of preferred urban policies and their questionable application, this case addresses the problems of heritage (re)use and regeneration in an environment of fast-shifting governmental priorities and financial flows, with reduced receptivity to sustainable solutions

Wide-angle, high-concentration photovoltaics to compete with flat plate systems

A novel photovoltaic concentrator enables highly uniform irradiance on a small number of efficient solar cells. The maximum electrical power of a photovoltaic (PV) energy installation depends on three factors: the available irradiance, the size of the systems collecting sunlight, and the rate at which the device transforms light into electricity (the conversion efficiency). Developers can maximize the irradiance by carefully selecting the site and orientation of the solar facility. But they can only expand their sunlight collection systems for standard flat plate PV devices by increasing the number of solar cells, at greater cost. Here, we consider the advantages of an alternative PV system that produces more energy without increasing the number of cells used (actually, reducing it), by improving the conversion rates.We also present a new device that may enhance the commercial viability of such technologies

Primary optics for efficient high-brightness LED color mixing

In SSL general illumination, there is a clear trend to high flux packages with higher efficiency and higher CRI addressed with the use of multiple color chips and phosphors. However, such light sources require the optics provide color mixing, both in the near-field and far-field. This design problem is specially challenging for collimated luminaries, in which diffusers (which dramatically reduce the brightness) cannot be applied without enlarging the exit aperture too much. In this work we present first injection molded prototypes of a novel primary shell-shaped optics that have microlenses on both sides to provide Köhler integration. This shell is design so when it is placed on top of an inhomogeneous multichip Lambertian LED, creates a highly homogeneous virtual source (i.e, spatially and angularly mixed), also Lambertian, which is located in the same position with only small increment of the size (about 10-20%, so the average brightness is similar to the brightness of the source). This shell-mixer device is very versatile and permits now to use a lens or a reflector secondary optics to collimate the light as desired, without color separation effects. Experimental measurements have shown optical efficiency of the shell of 95%, and highly homogeneous angular intensity distribution of collimated beams, in good agreement with the ray-tracing simulations