Mehmet Baris Tabakcioglu

Improvements on Slope Diffraction for Multiple Wedges

Abstract This article proposes an improved slope uniform theory of diffraction model for fast and more accurate field prediction for multiple wedge diffractions in the transition zone. The proposed method is based on the slope uniform theory of diffraction and the Fresnel zone concept, called the slope uniform theory of diffraction with convex hull. The article also provides simulation results for the comparison of the uniform theory of diffraction based algorithms with respect to the computation time and accuracy.

Application of S-UTD-CH Model into Multiple Diffraction Scenarios

In this study, propagation prediction models based on ray tracing in coverage estimation for broadcasting systems are compared with respect to computation time and accuracy in the case of close building heights. Uniform Theory of Diffraction (UTD), Slope Diffraction (S-UTD) and Slope UTD with Convex Hull (S-UTD-CH) models are compared for computation time and propagation path loss. Moreover in this study, effects of transmitter height to relative path loss at the receiver are analyzed. Furthermore, contribution of S-UTD-CH model to UTD model increases in the transition zone. As a conclusion, S-UTD-CH model is optimum model with respect to computation time and relative path loss in transition zone.

Comparison and analyzing propagation models

This paper presents a study on a class of algorithms based on Uniform Theory of Diffraction (UTD) for multiple diffractions. S-UTD-CH model can be used for fast and more accurate field prediction for multiple diffractions in transition zone. An extensive simulation results for comparison of UTD based algorithms with respect to the computation time and accuracy was provided.

S-UTD-CH model in multiple diffractions

ABSTRACT The propagation of electromagnetic waves in empty space is an extremely simplified case. Thus, the significant question is how an electromagnetic wave propagates in an environment with obstacles such as buildings, trees or hills. Electromagnetic waves are partially reflected and partially diffracted from these obstacles. To predict the relative path loss of electromagnetic waves at the receiving position, many electromagnetic-wave propagation models have been proposed. These propagation models can be classified into models based on numerical integration and those based on ray tracing. Uniform theory of diffraction (UTD) and slope-UTD (S-UTD) models are ray-tracing-based propagation models and are briefly explained in this paper. In addition, detailed information is provided about the improved slope UTD model, which is called the S-UTD with Convex Hull (S-UTD-CH) model. The fundamentals of the S-UTD-CH model are the S-UTD, convex hull and Fresnel zone concept. In particular, the S-UTD-CH model can be applied to multiple diffraction scenarios in the transition region. Moreover, the S-UTD-CH model is considered an optimum model in terms of its accuracy and calculation or computation time. Widespread simulation results are provided to compare the models based on theoretical rays in terms of prediction accuracy and computation time. To compare these models, different operation frequencies and transmitting antenna heights are considered by using a high-performance computing technique.

Using of S-UTD-CH model in coverage mapping and comparison with FEKO software

Free space electromagnetic wave propagation is an extremely simple case. However, in the reality, there are some obstacles like hills and buildings and electromagnetic waves are diffracted and reflected form these obstacles. It is a vital problem that how an electromagnetic wave propagates in the region including multiple diffraction. Many electromagnetic wave propagation models are developed in order to map coverage and install base station in optimum number and power. S-UTD-CH model, which is an optimum models according to computation time and accuracy of prediction, can be used in coverage mapping. In this study, after giving some brief information about S-UTD-CH model, coverage map is generated by a sample scenario. Moreover, this model is compared with FEKO electromagnetic wave simulation software tool.

Relations of attention and meditation level with learning in engineering education

Neurons use electricity in order to communicate to each other. Due to numerous signals sent by neurons, there are oodles of electrical activity in the brain. Sensitive equipment like electroencephalogram (EEG) biosensor perceives the brainwaves emanated from neurons. Beta waves are responsible for problem solving or decision making and associated with attention. Alpha waves are associated with now and meditation. Neurosky EEG biosensor perceives the brainwaves and transforms these brainwaves into attention and meditation values. In this study, Neurosky EEG biosensor is used for measuring the attention and meditation levels of students. A program is developed in C# medium. The developed program records raw brainwave data, attention and meditation average while the students are studying. As the attention and meditation levels are high, the students learn the subjects in the course. If predetermined meditation and attention level are not caught, the developed program does not give permission to pass to another subject. Because of that the students have less meditation and attention average than the predetermined value; they get fewer grades in the exam.

Reducing EMI by multiple slits shielding

Electromagnetic compatibility (EMC) is vital for health and more reliable electric and electronics systems. All electronic devices have to provide EMC tests. In order to increase the quality of service of all electronic devices, a shielding mechanism has to be provided in order to eliminate electromagnetic interference (EMI). In this study a multi-slits shielding mechanism is proposed by using Uniform Theory of Diffraction and geometrical optic models. Multi-slits structure does not permit passing the direct field much and provide dominant field contribution from diffracted field. Due to using diffracted field instead of direct field, EMI is reduced.

Comparison of ray traced based models with Physical Optic model

Electromagnetic wave propagation in free space is an excessively simplified situation. Hence, the vital question is how an electromagnetic wave propagates in ambient including obstructions like mountains, trees, hills or buildings. These obstructions reflect, diffract and scatter the electromagnetic waves. UTD and S-UTD models are ray-tracing-based electromagnetic wave propagation models and shortly explained in this paper. In addition, exhaustive information is supplied about the improved slope UTD model, is called the S-UTD-CH model. Electromagnetic wave propagation models, which are UTD, S-UTD, S-UTD-CH and PO, are compared with regard to prediction accuracy and computation time among themselves. Widespread simulation results are provided to compare the models in terms of prediction accuracy and computation time. Moreover, the S-UTD-CH model is considered an optimum model in terms of its accuracy and computation time. Furthermore, how the transmitter height, the distance between buildings and the operating frequency affects the relative path loss at the receiver are analyzed.

Amplitude and slope diffraction coefficients for S-UTD-CH model

Diffraction mechanism is vital to predict the field strength and calculate the coverage in urban, rural and indoor. Diffraction occurs on the sharp surfaces like rooftop, edge, corner, and vertex. S-UTD-CH model computes three type of electromagnetic wave incidence such as direct, reflected and diffracted waves, respectively. In the case of close obstacle height, diffraction mechanism is dominant. In order to calculate the diffracted field amplitude and slope diffraction coefficient and first and second derivative of these have to derive correctly. In this paper, derivations will be made knife edge and wedge structures. Analysis about amplitude and diffraction coefficient will be made.

Medium access control protocols for wireless sensor networks with ambient energy

Wireless sensor networks (WSNs) have recently been a popular research area with a broad range of applications. One of the most significant constraints of WSNs is energy limitation of sensor nodes. Therefore, energy-efficiency has been considered as primarily design criterion in many medium access control (MAC) protocols developed. In order to solve the issue of limited-energy sources, various recent protocols have focused on energy harvesting from surrounding environment, such as solar, wind and vibration energy, resulting in providing unlimited energy source. Ambient energy exhibits a characteristic of unlimited energy source but not available always due to environmental changes. The focus is now being placed on effective utilization of the time-varying ambient energy. This study aims to provide a review of recently proposed MAC protocols for energy-harvesting WSNs describing their operating principles and underlying features.