State-of-the-art in Power Line Communications: from the Applications to the Medium

In recent decades, power line communication has attracted considerable attention from the research community and industry, as well as from regulatory and standardization bodies. In this article we provide an overview of both narrowband and broadband systems, covering potential applications, regulatory and standardization efforts and recent research advancements in channel characterization, physical layer performance, medium access and higher layer specifications and evaluations. We also identify areas of current and further study that will enable the continued success of power line communication technology.Comment: 19 pages, 12 figures. Accepted for publication, IEEE Journal on Selected Areas in Communications. Special Issue on Power Line Communications and its Integration with the Networking Ecosystem. 201

Vertical Merger Enforcement Actions: 1994–April 2020

We have revised our earlier listing of vertical merger enforcement actions by the Department of Justice and Federal Trade Commission since 1994. This revised listing includes 66 vertical matters beginning in 1994 through April 2020. It includes challenges and certain proposed transactions that were abandoned in the face of Agency concerns. This listing can be treated as an Appendix to Steven C. Salop and Daniel P. Culley, Revising the Vertical Merger Guidelines: Policy Issues and an Interim Guide for Practitioners, 4 JOURNAL OF ANTITRUST ENFORCEMENT 1 (2016)

Measurement and analysis of extra propagation loss of tunnel curve

Wave propagation experiences extra loss in curved tunnels, which is highly desired for network planning. Extensive narrow-band propagation measurements are made in two types of Madrid subway tunnels (different cross sections and curvatures) with various configurations (different frequencies and polarizations). A ray tracer validated by the straight and curved parts of the measuring tunnels is employed to simulate the reference received signal power by assuming the curved tunnel to be straight. By subtracting the measured received power in the curved tunnels from the simulated reference power, the extra loss resulting from the tunnel curve is extracted. Finally, this paper presents the figures and tables quantitatively reflecting the correlations between the extra loss and radius of curvature, frequency, polarization, and cross section, respectively. The results are valuable for statistical modeling and the involvement of the extra loss in the design and network planning of communication systems in subway tunnels

Performance analysis of wireless mesh networks for underground mines

Abstract: Underground mines are harsh environments that have unique challenges that limit wireless communication. To ensure the safety and efficiency of mining operations, communication systems play a vital role. Despite the major developments in communication technologies, underground mines are still challenging environments for wireless communication, however, the advent of wireless mesh networks offers a cutting-edge solution to the mining industry and understanding the performance of this technology is fundamental to its application in dynamic areas of underground mines. This research project aims at conducting a performance analysis of wireless mesh networks by developing a prototype system set up of wireless mesh transceivers to conduct a feasibility study of data transmission on the network in underground mines. The second aspect of this study investigates network parameters, such as latency, throughput, and signal-to-noise, as a function of increasing mesh nodes on the network and internode spacing of mesh nodes. By combining theoretical models with real-time performance of the mesh system, realistic conclusions and better recommendations can be given to mining companies with regards to deploying wireless mesh systems in their underground mines.M.Ing. (Electrical and Electronic Engineering Science

The use of distributed sensor arrays in electrical and electromagnetic imaging

Electrical methods for exploring the earth, such as direct current resistivity, induced polarization and electromagnetism are used for numerous exploration, engineering and environmental applications. Common to all these applications is the desire to obtain the clearest possible image of the target. This thesis analyses and develops methods for improving signal to noise ratio for electrical methodsThe ability to recover subsurface information from electrical exploration methods is dependent on the limits of signal detection which is strongly influenced by instrumentation and the conductivity structure of the Earth. Multiple sensors can be used to collect data efficiently over a survey area. Such multi-receiver arrays can improve the signal-to-noise ratio. However, the use of multiple sensors can also be exploited to improve the signal fidelity from each sensor, which may then translate to more accurate geological models and/or greater depth of investigation. In this thesis a two step algorithm for the removal of harmonic noise and atmospheric transients is presented. The first step is the removal of harmonic noise from each sensor using a non-linear single value decomposition (SVD) inversion technique to model a modulated sinusoid to narrow band noise sources. The second step is spherics attenuation using an iterative technique of signal stripping then removing residual coherent noise across the array combined with robust statistical measures in the tacking process. I show that this approach can recover signals otherwise buried in noise and that under certain conditions, signal to noise ratio can be improved by more than 46 dB. The algorithms designed here are applicable to any type of electrical or time domain electromagnetic survey conducted with a multi-receiver array

Development and utilisation of fibre optic-based monitoring systems for underground coal mines

The continuous economic growth and depleting shallow reserves have increased the number of deeper mining operations worldwide which has made safety and productivity more challenging due to the higher stresses, heat and increased gas contents. Any major improvements in safety and productivity require a reliable and real-time monitoring system that provides more comprehensive information about various processes. The current monitoring systems suffer from lack of reliability, accuracy and high capital and operating costs. Recent advancements in fibre-optic based sensing technology have introduced unique solutions for various underground coal mine applications such as health and safety, geotechnical, ventilation, borehole, mine environment and condition monitoring. This paper presents recent research, development and utilisation of this technology by a group of researchers at the University of Queensland (UQ) and CRCMining in Australia and Shandong Academy of Science in China