Simulation, performance and interference analysis of multi-user visible light communication systems

The emergence of new physical media such as optical wireless, and the ability to aggregate these new media with legacy networks motivate the study of heterogeneous network performance, especially with respect to the design of protocols to best exploit the characteristics of each medium. This study considers Visible Light Communications (VLC), which is expected to coexist with legacy and future radio frequency (RF) media. While most of the research on VLC has been done on optimizing the physical medium, research on higher network layers is only beginning to gain attention, requiring new analyses and tools for performance analysis. The first part of the dissertation concerns with developing a new ns3-based VLC module that can be used to study VLC-RF heterogeneous networks via simulation. The proposed ns3 module is developed based on existing models for intensity modulated LED signals operating as lighting units transmitting to optical receivers at indoor scales (meters). These models and the corresponding simulation model are validated using a testbed implemented with a software-defined radio (SDR) system, photodetector, phosphor-converted “white” LEDs, and under PSK and QAM modulation. Two scenarios are used in the validation of the VLC module: (i) using a receiver placed right bellow the transmitter with varying range, and (ii) using a receiver with a fixed range and varying angle of acceptance. Results indicate good correspondence between the simulated and actual testbed performance. Subsequently, it demonstrates how the VLC module can be used to predict the performance of a hybrid WiFi/VLC network simulated using the ns3 environment with UDP, TCP, and combined network traffic. The second part of the dissertation focuses on modeling interference at VLC system level based on variable pulse position modulation (VPPM) and variable on-off keying (VOOK) which are used in VLC to simultaneously provide lighting with dimming control as well as communication. The bit error performance of these modulation schemes is evaluated at VLC systems consisting of multiple transmitters-receivers pairs, where co-channels interference exists. The BER is derived by providing an in depth analysis that captures the signal structure of the interference in terms of the number of transmitters. This work dispenses with the Gaussian interference model which is not suitable when the number of interferers are few and the central limit theorem (CLT) cannot be applied. The result shows that under realistic small-room scenario, the analytical results closely match with that of simulation

Riyadh Transportation History and Developing Vision

AbstractRiyadh is the capital city of the Kingdom of Saudi Arabia. It is both a rapidly moving microcosm of worldwide trends in transportation, and a unique case study. The aim of this study is to investigate the reasons behind rising car ownership and its impact on public transportation. This paper charts the historical development of the city and presents the key factors that have shaped the transport network, including governmental motivation, urban planning and financial and demographic aspects. The study reviewed the history of the Riyadh transportation system and either component during the last five decades and the factors that have made Riyadh's situation unique. From oasis to Metropolis there are many pressing issues. Resolving these requires much more than narrow technical solutions. Instead, consideration of a much broader range of factors is needed. Riyadh is presented as a city case study and the key challenges are illuminated

THE STRUCTURE OF THE CURRENT HOUSING PROVISION IN SAUDI ARABIA: AN INSTITUTIONAL PERSPECTIVE

Over the past five decades, large petroleum reserves have made Saudi Arabia one of the top twenty economies in the world. Changes to the economics and politics of the oil industry in the 1970s led to an unprecedented and rapid expansion of the country’s economy and to higher levels of internal and external migration to major Saudi cities. This has intensified the demand for housing, and particularly for affordable housing. However, despite being well-resourced, the government of Saudi Arabia has struggled to meet this increasing demand for housing. This research explores the underlying factors contributing to the Saudi housing shortage, using an innovative framework that combines insights drawn from institutional theory (which has rarely been applied to the Saudi context) with critical realism. This is used to explore qualitative data (drawn from document analysis and interviews) in order to demonstrate that institutions play a key, though sometimes contradictory, role in influencing the provision of housing in Saudi Arabia. The research focuses particularly on relationships between three sets of actors: the first set includes the state actors which are involved in the regulation process of the housing provision; the second set includes other actors who implement these regulations, this includes the financers, developers, and marketers who represent the capital interests of the Saudi housing market. Finally, the last set includes the end users of the final product represented by individual consumers. The thesis seeks to position the housing shortage at the crux of a complex series of relationships between the institutions in which these actors work, portraying a fragmented landscape in which there is a poor degree of integration and coordination between significant organizational players. Mismatches between the cultural norms, and the written and unwritten rules and regulations of different institutions, are reflected in a governance landscape where land use policy and financial mechanisms are poorly connected, and where both strategic urban planning and more quotidian types of planning permission are not joined up with individual construction projects. This disjointed institutional landscape is further complicated by the existence of competition between two governmental bodies leading to conditions of intensified capitalist land accumulation. The emergence of this fierce capitalist market has meant that development has become a source of vast surplus value, raising the price of housing and problematizing the delivery of more affordable types of dwelling

Developing the Riyadh strategic microsimulation model as a novel means of exploring policy transfer and future transport scenarios

Within just 50 years, Saudi Arabia's capital city Riyadh has developed from being a walled town to a modern metropolis of eight million people (ADA, 2015). Riyadh is a unique case study. Due to cultural and climate factors, there are good reasons why road transport dominates, with more than 93% of journeys undertaken by car. Despite substantial investment in the road network, there is severe traffic congestion caused by population growth and increased economic activity. This has made transport in and around the city time-consuming, unsafe, unhealthy and ultimately unsustainable. To address this, several high-profile projects are underway, most notably the Riyadh Metro, currently the world’s most expensive metro project, with a total value of 88 billion SAR. This research is therefore timely. It attempts to answer why Riyadh’s transport system has developed along its current lines, and whether schemes such as the Riyadh Metro will have the expected impact. To do this, the research had to operate from a strong multidisciplinary platform, linking transportation engineering, planning and urban studies to explore the issue of Policy Transfer as it applies to Riyadh. The Riyadh Metro is a paradigm case: it is a transport infrastructure that has proven successful in other (usually western) nations, and its application in Riyadh is expected to have similar benefits, despite the city’s cultural and climatic uniqueness. The research makes a substantial original contribution to knowledge by creating a strategic traffic microsimulation of Riyadh’s city core, using policy transfer insights, and unique access to Saudi Arabian stakeholder input, to develop a set of future scenarios which can be subject to a direct test in the model. This model has been created and calibrated using Riyadh traffic and mapping data, and professionally audited by the microsimulation company SIAS Ltd. One novel feature of the research is that this model is being used strategically. It enables four congestion indicators to be extracted under all network conditions, from free-flow conditions to complete saturation. These indicators are a) level of service, b) traffic flow, c) journey time and d) queue length. The values of the respective indicators will be logged and these, in turn, will represent coordinates for a so-called Overall Performance Curve (OPC). The various OPCs show how each of the indicators performs under all traffic conditions, enabling predictions about all possible future states to be explored. In other words, this research provides a scientific platform for future expectations. That’s where the policy transfer issues come in, by using the OPCs whatever the expectations, it will be on them somewhere, given that the OPC is like a formal scientific test-bed covering all scenarios and expectations. The first scenario to be explored (Scenario 1) is the ‘do nothing’ option. Current forecasts show the existing road network will be fully saturated by 2021, with a forecasted additional 40% traffic volumes in the study area. This will result in already lengthy journey times increasing by a further 90%, and queue lengths by 120%. Clearly, ‘doing nothing’ is not a viable option in light of population growth and economic development. Riyadh transportation authorities are already acutely aware of this. One further pioneering aspect of this research is its ability to survey key Riyadh stakeholders to discover what alternative scenarios are being pursued and considered, and to gauge their expected outcomes. Scenarios 2, 3 and 4 pick up on these expectations and subject them to a direct test in the strategic microsimulation model. As such, Scenario 2 embodies the current strategy involving the Riyadh Metro and examines the expected traffic reductions. According to the various OPCs, the Riyadh Metro will reduce the volume of cars on the road network by up to 43%. If these expectations arise in practice, journey times and queue lengths will be approximately halved compared with present conditions. The key, of course, is whether these expectations will in fact be met. In summary, this thesis makes a number of new contributions to theory. These include a mapping of the existing policy transfer theory to the situation pertaining to Riyadh, and an extension of existing theory to take account of unique socio-cultural and climatic factors. Solutions cannot be proven to be effective in any society unless they are tested and implemented. Thus, this research provides an opportunity for engineers, city planners, transport systems stakeholders/decision makers and beneficiaries to SEE the future in the present

Performance Assessment of Dual-Polarized 5G Waveforms and Beyond in Directly Modulated DFB-Laser using Volterra Equalizer

International audienceWe investigate the performance of 25-Gbps dual-polarized orthogonal frequency division multiplexing (OFDM)-based modulation in a directly modulated distributed feedback (DFB)-laser over 25 km of single-mode fiber. A Volterra equalizer is used to compensate for the nonlinear effects of the optical fiber. The results show that FBMC-OQAM modulation outperforms OFDM, universal filtered multicarrier (UFMC), and generalized frequency division multiplexing (GFDM) waveforms. Indeed, a target bit error rate of similar to 3.8 x 10(-3) [forward error correction (FEC) limit] for FBMC, UFMC, OFDM, and GFDM can be achieved at -30.5, -26, -16, and -14.9 dBm, respectively. The effect of the DFB laser is also investigated for UFMC, OFDM, and GFDM, and they undergo a Q penalty of 2.44, 2.77, and 4.14 dB, respectively, at their FEC limit points. For FBMC-OQAM, the signal is perfectly recovered when excluding the DFB laser at -30.5 dBm. (C) 2020 Society of Photo-Optical Instrumentation Engineers (SPIE

Pharmaceutical versus mechanical induction of labor

Labor induction is one of the most common obstetric interventions carried out in obstetric institutions. More than one fifth of labors needs induction. To date, many methods are available for labor induction with the pharmaceutical and mechanical methods being the commonest. The most common pharmaceutical agents used are prostaglandins, oxytocin, synthetic progesterone antagonists, and nitric oxide. Mechanical induction is carried out through using balloon catheters, hygroscopic dilators, artificial membrane rupture, or membrane stripping. Though pharmaceutical methods had largely replaced mechanical induction of labor, no consensus guidelines recommend their use. Studies from literature are still conflicting. However, it is generally agreed that the use of a combined approach with both pharmaceutical and mechanical methods of induction yields the best outcome. This article will review the different methods for labor induction, their effectiveness, and adverse events

Semibath Polymerization Approach for One-Pot Synthesis of Temperature- and Glucose-Responsive Core-Shell Nanogel Particles

Herein, we report a simple and easy procedure for the synthesis of core-shell structures of glucose-sensitive 3-acrylamidophenylboronic acid (APBA) and temperature-responsive P(NIPAm-AAc) shell nanogel particles using MBA as a cross-linker via free radical polymerization. The synthesized particles were approximately 100 nm and were cross-linked to one another. The shell thickness of the nanogel particles was adjusted by increasing the concentrations of NIPAm through the semibath approach during the process of polymerization. The synthesized colloidal nanogel particle shows thermoresponsive behaviors. The dynamic light scattering technique also confirmed the change in the size of particles dispersed in an aqueous solution upon increase/decrease in temperatures, which is the result of its volume phase transition temperatures (VPTT). The size and morphology of the particles were characterized by TEM, FE-SEM, and AFM. The sensitivity of these nanogel particles to temperature and glucose suggests that they have the potential for applications related to the delivery of self-regulated insulin

Methodological approach and theoretical concept for measuring hospital technical efficiency

Background: In the health care systems, efficiency measurement is considered as a key step in performing individual performance audits of production units such as, health centres and hospitals. It entails a rational framework through which resources are distributed and shared among health care facilities. Thus, there are two common approaches to measure hospital efficiency namely: non-parametric (DEA) and parametric (SFA). The article is aimed to review the articles to analyze the characteristics of these approaches and to identify the similarities, differences, strengths, and limitations related to them. Materials and Methods: The literature, which related to measuring relative efficiency of hospitals were obtained from online database involving ScienceDirect, Pubmed. The keywords used for the search terms involving hospital efficiency, healthcare efficiency, parametric approach, non-parametric approach, DEA and SFA. The review only for articles published in English language. Result: The required information about methodological approaches were obtained and summarized into the construct form. The discussion was based on approach type in term of non-parametric and parametric. Conclusion: In a nutshell, both of DEA and SFA can be applicable in healthcare setting to measure hospitals efficiency. The selection of the convenient approach is subjected to the aim of the study