A path loss model for link budget analysis of indoor visible light communications

In the context of beyond 5G indoor communication systems, visible light communications (VLC) has emerged as a viable supplement for existing radio frequency based systems and as an enabler for high data rate communications. However, the existing indoor VLC systems are limited by detrimental outages caused by fluctuations in the VLC channel gain because of user mobility. In this study, we proposed a tractable path loss model for indoor VLC that reflects the effect of room size and coating material of surfaces. We performed an extensive advanced ray tracing simulation to obtain the channel impulse responses within a room and presented a path loss model as a function of distance, room size, and coating material through curve fitting. In addition, path loss parameters such as the path loss exponent and the standard deviation of the shadowing component were determined. The simulation results indicate that path loss is a linear function of distance, path loss exponent is a function of room size and coating material, and shadowing follows a log normal distribution.Publisher's Versio

Safety mechanisms for the reliable operation of 3D vehicles

The safety and reliability of unmanned vehicles is a growing concern in our modern society. This work proposes and implements mechanisms to minimize risks in the operation of 3D vehicles. A brief analysis is performed to identify high priority risks and low complexity solutions are proposed in order to avoid or minimize their impact. To cope with critical power failures, an autonomous current monitoring system was studied and implemented after analyzing two different techniques: resistive and magnetic current sensing. Furthermore, a fall detection system capable of detecting rotational and free falls was developed and evaluated. Lastly, an obstacle detection and avoidance system relying on multiple smart sensors was proposed. Several simulation tests were performed for different velocities to obtain processing delays and stopping times and thus, the minimal safe flying distance for the avoidance of obstacles.A segurança na operação fiável de veículos não tripulados é uma preocupação crescente na nossa sociedade moderna. Este trabalho propõe e implementa mecanismos para minimizar os riscos no manuseamento destes veículos. Uma breve análise é realizada para identificar os componentes com maior risco de ocorrerem problemas e soluções de baixa complexidade são propostas a fim de evitar ou minimizar o seu impacto. Para lidar com falhas de energia críticas, um sistema de monitorização de corrente foi estudado e implementado após analisar duas técnicas diferentes: detecção de corrente resistiva e magnética. Além disso, foi desenvolvido e avaliado um sistema de detecção de quedas rotacionais e livres. Por último, foi proposto um sistema de detecção e anti-colisão de obstáculos baseado em múltiplos sensores inteligentes. Diversos testes de simulação foram realizados para obter atrasos de processamento e tempos de travagem. Deste modo foi possível calcular a distância de segurança mínima de travagem face à detecção de um obstáculo

Sensing Applications in Aircrafts Using Polymer Optical Fibres

We report on recent advances in the use of inexpensive polymer optical fibres (POFs) for sensing applications in avionics. The sensors analysed in this manuscript take advantage of the unique properties of polymers, such as high flexibility, elasticity, and sensitivity, and they range from strain, elongation, and vibration interrogators to level and temperature meters, leading to cost-effective techniques for structural health monitoring in aircraft structures. We also highlight recent power-supply methods using Power-over-POF in order to feed sensors remotely, and we discuss the constraints imposed by connectors on the performance of POF networks in aircrafts

Non-Invasive Electromagnetic Biological Microwave Testing

Blood glucose monitoring is a primary tool for the care of diabetic patients. At present, there is no noninvasive monitoring technique of blood glucose concentration that is widely accepted in the medical industry. New noninvasive measurement techniques are being investigated. This work focuses on the possibility of a monitor that noninvasively measures blood glucose levels using electromagnetic waves. The technique is based on relating a monitoring antenna’s resonant frequency to the permittivity, and conductivity of skin, which in turn, is related to the glucose levels. This becomes a hot researched field in recent years. Different types of antennas (wideband and narrowband) have been designed, constructed, and tested in free space. An analytical model for the antenna has been developed, which has been validated with simulations. Microstrip antenna is one of the most common planar antenna structures used. Extensive research development aimed at exploiting its advantages such as lightweight, low cost, conformal configurations, and compatibility with integrated circuits have been carried out. Rectangular and circular patches are the basic shapes that are the most commonly used in microstrip antennas. Ideally, the dielectric constant εr, however, and other performance requirements may dictate the use of substrate whose dielectric constant can be greater. As in our prototype blood sensor, the miniaturized size is one of the main challenges