317 research outputs found
Wireless Communication Systems for Urban Transport
This chapter describes the main features of the wireless communication systems of urban rail and related applications. The perspective will be complete: application, network and physical layers will be discussed. Moreover, to properly address some of the challenges that these systems face, we will provide a deep insight into propagation issues related to tunnels and urban areas. Finally, a detailed survey on the directions of research on all these topics will be provided
Transmission-Based Signaling Systems
In this chapter, we describe the principal communication systems applied to the transmission-based signaling (TBS) systems for railways. Typical examples are communication-based train control (CBTC), European Rail Traffic Management System (ERTMS), and distance to go (DTG). Moreover, to properly address some of the challenges that need to face these systems, we will provide a deep insight on propagation issues related to all the environments (urban, suburban, rural, tunnel, etc.). We will highlight all the communication-related issues and the operational as well. Finally, a detailed survey on the directions of research on all these topics is provided, in order to properly cover this interesting subject. In this research, hot topics like virtual coupling are explained as well
Propagation characteristic measurement and frequency reuse planning in a campus environment.
by Poon Lai Shun.Thesis (M.Phil.)--Chinese University of Hong Kong, 1994.Includes bibliographical references (leaves 59-[64]).Chapter 1 --- Introduction --- p.1Chapter 2 --- Background of Measurement in Indoor Environment --- p.7Chapter 2.1 --- Propagation loss --- p.8Chapter 2.1.1 --- Basic concepts --- p.8Chapter 2.1.2 --- Indoor propagation --- p.13Chapter 2.2 --- Multipath characteristics --- p.15Chapter 3 --- Propagation Model --- p.17Chapter 4 --- Measurement Sites and Equipment Setup --- p.21Chapter 4.1 --- Measurement sites --- p.21Chapter 4.2 --- Equipment setup --- p.22Chapter 5 --- Measurement Results --- p.27Chapter 5.1 --- Propagation loss in the same building --- p.27Chapter 5.1.1 --- Measurement in Engineering Building --- p.27Chapter 5.1.2 --- Measurement in Hostel --- p.30Chapter 5.2 --- Penetration across the atrium and neighboring building --- p.31Chapter 5.3 --- Multipath characteristics --- p.33Chapter 6 --- Frequency Reuse Planning and Limitations on Measurement --- p.50Chapter 6.1 --- Frequency reuse planning --- p.50Chapter 6.2 --- Limitations on the propagation loss measurement --- p.53Chapter 6.3 --- Limitations on multipath measurement --- p.54Chapter 7 --- Conclusions --- p.55Appendix --- p.56Chapter A --- Method of Calculating Path Loss Slope --- p.56Bibliography --- p.5
A Full Wave Electromagnetic Framework for Optimization and Uncertainty Quantification of Communication Systems in Underground Mine Environments
Wireless communication, sensing, and tracking systems in mine environments are essential for protecting miners’ safety and daily operations. The design, deployment, and post-event reconfiguration of such systems greatly benefits from electromagnetic (EM) frameworks that can statistically analyze and optimize the wireless systems in realistic mine environments. This thesis proposes such a framework by developing two fast and efficient full-wave EM simulators and coupling them with a modern optimization algorithm and an efficient uncertainty quantification (UQ) method to synthesize system configurations and produce statistical insights. The first simulator is a fast multipole method – fast Fourier transform (FMM-FFT) accelerated surface integral equation (SIE) simulator. It relies on Muller and combined fields SIEs to account for scattering from mine walls and conductors, respectively. During the iterative solution of the SIE system, the computational and memory costs are reduced by using the FMM-FFT scheme. The memory costs are further reduced by compressing large data structures via singular value and Tucker decomposition. The second simulator is a domain decomposition (DD)-based SIE simulator. It first divides the physical domain of a mine tunnel or gallery into subdomains and then characterizes EM wave propagation in each subdomain separately. Finally, the DD-based SIE simulator assembles the solutions of subdomains and solves an inter-domain system using an efficient subdomain-combining scheme. While the DD-based SIE simulator is faster and more memory-efficient than the FMM-FFT accelerated SIE simulator when characterizing EM wave propagation in electrically large mine environments, it does not apply to certain scenarios that the FMM-FFT accelerated SIE simulators can handle. The optimization algorithm and UQ method that are coupled with the EM simulators are the dividing rectangles (DIRECT) algorithm and the high dimensional model representation (HDMR)-enhanced multi-element probabilistic collocation (ME-PC) method, respectively. The DIRECT algorithm is a Lipschitzian optimization method but does not require the knowledge of the Lipschitz constant. It performs a series of moves that explore the behavior of the objective function at a set of points in the carefully picked sub-regions of the search space. The HDMR-enhanced ME-PC method permits the accurate and efficient construction of surrogate models for EM observables in high dimensions. The HDMR expansion expresses the observable as finite sums of component functions that represent independent and combined contributions of random variables to the observable and hence reduces the complexity of UQ by including only the most significant component functions to minimize the computational cost of building the surrogate model. This research numerically validated and verified the two EM simulators and demonstrated the efficiency and applicability of the EM framework via its application to optimization and UQ problems in large and realistic mine environments.PHDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/146028/1/wtsheng_1.pd
STATUS OF COMMUNICATION AND TRACKING TECHNOLOGIES IN UNDERGROUND COAL MINES
In 2006, Congress passed the MINER Act requiring mine operators to submit an emergency response plan that included post-accident communications and tracking systems to MSHA within three years of the Act. These systems were required to be designed for maximum survivability after a catastrophic event, such as a fire or explosion, and to be permissible (meets MSHA criteria for explosion-proof). At that time, no commercially available systems existed that met these standards. Several companies undertook developing new, or enhancing existing, technologies to meet these requirements. This research presents the results of a study that was conducted to determine the present day types of systems being used, along with their average annual worker hours, coal production, number of mechanized mining units, and type of communications and tracking systems installed. Furthermore, 10 mines were visited to obtain detailed information related to the various technologies. It was found the most influential parameters on system selection include MSHA district, mining method, and number of underground workers
Antennas and Propagation
This Special Issue gathers topics of utmost interest in the field of antennas and propagation, such as: new directions and challenges in antenna design and propagation; innovative antenna technologies for space applications; metamaterial, metasurface and other periodic structures; antennas for 5G; electromagnetic field measurements and remote sensing applications
Smart antennas for strategic environment
The objective of this Thesis consists in presenting in a concise and effective way the results achieved during researches and studies on satellite systems interference sources, advanced antenna arrays for satellite systems to mitigate the increasing anti-interference needs and on an innovative way to generates inhomogeneous wave in lossless media for contributing to the design of a novel type of antenna for deep penetrating lossy media
1-D broadside-radiating leaky-wave antenna based on a numerically synthesized impedance surface
A newly-developed deterministic numerical technique for the automated design of metasurface antennas is applied here for the first time to the design of a 1-D printed Leaky-Wave Antenna (LWA) for broadside radiation. The surface impedance synthesis process does not require any a priori knowledge on the impedance pattern, and starts from a mask constraint on the desired far-field and practical bounds on the unit cell impedance values. The designed reactance surface for broadside radiation exhibits a non conventional patterning; this highlights the merit of using an automated design process for a design well known to be challenging for analytical methods. The antenna is physically implemented with an array of metal strips with varying gap widths and simulation results show very good agreement with the predicted performance
Beam scanning by liquid-crystal biasing in a modified SIW structure
A fixed-frequency beam-scanning 1D antenna based on Liquid Crystals (LCs) is designed for application in 2D scanning with lateral alignment. The 2D array environment imposes full decoupling of adjacent 1D antennas, which often conflicts with the LC requirement of DC biasing: the proposed design accommodates both. The LC medium is placed inside a Substrate Integrated Waveguide (SIW) modified to work as a Groove Gap Waveguide, with radiating slots etched on the upper broad wall, that radiates as a Leaky-Wave Antenna (LWA). This allows effective application of the DC bias voltage needed for tuning the LCs. At the same time, the RF field remains laterally confined, enabling the possibility to lay several antennas in parallel and achieve 2D beam scanning. The design is validated by simulation employing the actual properties of a commercial LC medium
New feeding networks and planar antenna designs for leaky-wave systems and communication applications
The fast development in modern communication systems such as radars, medical
imaging, sensors or satellites demands efficient and compact antenna designs that
can satisfy the high data throughput and beam scanning requirements. This is
commonly achieved by different means including electromechanical or mechanical
steering, which sometimes are not the best option as additional cost, size or losses
may be introduced. However, low-cost and compact structures can be obtained
by using planar leaky-wave antennas, whose inherent high directivity and electrical
beam steering capabilities have been realised to be a solution for the issues encoun
tered by these systems.
Nevertheless, there are several limitations that these antennas still need to overcome.
One clear example is the lack of efficient and simple feeding networks for certain
types of leaky-wave antennas that can reduce their performance and compactness.
In turn, there are modern indoor applications, such as WiFi or radio frequency
identification (RFID), where selective distributed communications are required but
current leaky-wave antennas cannot efficiently provide or their use implies cost and
weight constraints.
In this thesis, planar configurations are presented to provide efficient and low profile
solutions for leaky-wave antennas using concepts such as partial reflective surfaces
or simple technologies as parallel-plate waveguides. It is also demonstrated that
novel systems for two-dimensional (2D) or wideband beam scanning can also be
obtained by the use of simple feeders including vertical electric dipoles. In addition, a
broad-beam alternative to a non-selective and expensive beam scanning performance
inside airplanes for RFID systems is introduced easing weight restrictions. These
configurations represent an advancement for the state-of-the-art and are interesting
alternatives to their non-planar counterparts. To support these designs, theoretical
analysis, full-wave simulations and measurements are provided
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