Terahertz wireless communication

The goal of this thesis is to explore Terahertz (THz) wireless communication technology. More specifically the objective is to develop and characterize several THz communication systems and study the effect of atmosphere propagation through fog droplets and dust particles on THz communications. For demonstration, a THz continuous wave (CW) photomixing system is designed. Terahertz signals are phase encoded with both analog ramp signals and pseudorandom binary data, transmitted over a short distance, and detected. The limitation of transmission bandwidth, low single to noise ratio, vibration effects are also analyzed. In order to study and compare propagation features of THz links with infrared (IR) links under different weather conditions, a THz and IR communications lab setup with a maximum data rate of 2.5 Gb/s at 625 GHz carrier frequency and 1.5 gm wavelength, have been developed respectively. A usual non return-to-zero (NRZ) format is applied to modulate the IR channel but a duobinary coding technique is used for driving the multiplier chain-based 625 GHz source, which enables signaling at high data rate and higher output power. The bit-error rate (BER), signal-to-noise ratio (SNR) and power on the receiver side have been measured, which describe the signal performance. Since weather conditions such as fog and dust exhibit a spectral dependence in the atmospheric attenuation, the corresponding impact on THz in comparison with IR communications is not equivalent. Simulation results of attenuation by fog and dust in the millimeter and sub-millimeter waveband (from 0.1 to 1 THz) and infrared waveband (1.5 µm) are presented and compared. Experimentally, after THz and IR beams propagated through the same weather conditions (fog), performance of both channels are analyzed and compared. The attenuation levels for the IR beam are typically several orders of magnitude higher than those for the THz beam. Mie scattering theory was used to study the attenuation of THz and IR radiation due to the dust particle. Different amounts of dust are loaded in the chamber to generate a variety of concentration for beam propagation. As the dust loading becomes heavier, the measured attenuation becomes more severe. Under identical dust concentrations, IR wavelengths are strongly attenuated while THz shows almost no impact

Light sensor development for ARA platform

Some years ago Google announced the ARA initiative. This consist on a modular phone where parts of the phone, like cameras, sensors or networks can be changed. So when a new feature appears or requiered by the user it is not needed to change the mobile phone, just to buy the modules with the functionality. See https://www.youtube.com/watch?v=2pr9cV6lvws for further information. The Wireless Networks Group will receive in December a developement kit (http://projectara.com/s/ProjectAraSpiral1DeveloperHardwareManual.pdf), to start working with it on January. The PFC or MasteDuring the last years, Visible Light Communication (VLC), a novel technology that enables standard Light-Emitting-Diodes (LEDs) to transmit data, is gaining significant attention. In the near future, this technology could enable devices containing LEDs – such as car lights, city lights, screens and home appliances – to carry information or data to the end-users, using their smartphone. However, VLC is currently limited by the end-point receiver, such as a the mobile camera, or a peripheral connected through the jack input and to unleash the full potential of VLC, more advanced receiver are required. On other, few year ago, Google ATAP - the Google innovation department - announced the ARA initiative. This consist on a modular phone where parts of the phone, like cameras, sensors or networks can be changed. So when a new feature appears or required by the user it is not needed to change the mobile phone, just to buy the modules with the functionality. This Master Thesis presents the design and development of a simple module that will support communication by light (VLC) using the ARA Module Developer Kit provided by Google. It consists on building a front-end circuit, connecting a photodiode that receives the level of light and use it as data carrier, in order to receive and display data inside a custom Android application on the ARA smartphone

Support system for administration and control of FSO transceiver

Tato práce se zabývá problematikou optických bezkabelových spojů (FSO). V úvodní kapitole jsou diskutovány přednosti, základní principy a dílčí komponenty FSO spojů. Druhá kapitola se zabývá atmosférou z pohledu šířícího se optického svazku, jejím složením, základními veličinami a jevy v ní nastávajícími. V následující kapitole je popsáno několik metod ke zmírnění jevů majících negativní vliv na kvalitu spoje. Druhá část práce se zabývá návrhem podpůrného systému pro FSO, založeném na softcore mikroprocesoru MicroBlaze, návrhem jednoduchého síťového přepínače a síťového rozhraní. Závěr práce pojednává o implementaci webového serveru a tvorbě webové prezentace umožňující vzdálenou správu FSO a jeho komponent.This thesis deals with problematics of free space optical links (FSO). The first chapter discusses common benefits, essential principles and key components of a FSO link. The second chapter deals with an atmosphere in terms of beam propagation, its composition, common variables and atmospheric phenomena. Following chapter describes some methods to mitigate negative atmospheric phenonema affecting the FSO link. The second part of the thesis deals with the design of the support system for FSO, based on softcore microcontroller MicroBlaze, design of a simple network switch and a network interface for MicroBlaze. Lastly, software implementation of a web server and design of a web interface, allowing remote administration of the link and its components, are discussed.

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

NASA Tech Briefs, July 2001

Topics include: special coverage sections on Data Acquisition, and sections on electronic components and systems, software, mechanics, machinery/automation, biomedical and a special section of Photonics Tech Briefs

The Boston University Photonics Center annual report 2006-2007

This repository item contains an annual report that summarizes activities of the Boston University Photonics Center in the 2006-2007 academic year. The report provides quantitative and descriptive information regarding photonics programs in education, interdisciplinary research, business innovation, and technology development. The Boston University Photonics Center (BUPC) is an interdisciplinary hub for education, research, scholarship, innovation, and technology development associated with practical uses of light.This annual report summarizes activities of the BUPC over the period of July, 2006 through June, 2007, corresponding to the University’s fiscal year. These activities span the Center’s complementary missions in research, education, technology development, and commercialization. This reporting period included a milestone, as BUPC completed its tenth year of operation in its landmark building in the heart of the University’s Charles River Campus. Faculty research activity reached an all time high when evaluated by the usual metrics of external funding, scholarly publications, honors and awards. The Center’s educational programs were bolstered by two summer programs hosting more than 40 undergraduate interns, and by the launch of a competitive graduate fellowship program sponsoring ten BUPC graduate fellowships. In technology development, the prototype RedOwl sniper detection system pioneered by Center faculty, staff, and industry partners was fieldtested by the US Department of Defense, and has been handed off to industry partners for further pre-commercial development. Three new defense/security prototypes were developed by BUPC to address critical national defense needs in the past year and 13 faculty development projects were supported in collaboration with the Army Research Laboratory to fill the technology pipeline for our future defense-related prototyping efforts. The Center’s business incubator had a transformative year. After revising its core mission and operational strategy in the summer of 2006, the incubator generated significant demand for the intellectual environment, facilities, and expertise available to participating companies. New companies attracted by this revised value proposition now occupy all available space

Electrical and Computer Engineering Research Report 2009

Department Research Publications Enterprisehttps://digitalcommons.mtu.edu/ece-annualreports/1004/thumbnail.jp