Ray Launching Modeling in Curved Tunnels with Rectangular or Non Rectangular Section

International audienceSeveral methods to model radio wave propagation in tunnels have been published in the literature and will be presented in this chapter with their advantages and drawbacks. Among them, only few works are dedicated to non rectangular cross section and curved tunnels. Hence, we focus on a new method recently developed. The structure of the chapter is as follows. Section 2 presents the context of the works and why deployments of wireless telecommunication systems are needed for transport applications. Existing techniques to model radio wave propagation in tunnel are presented in section 3 with their respective advantages and drawbacks. The fourth and fifth sections are respectively devoted to the design and the evaluation of a propagation prediction model for curved tunnel with a rectangular or a circular cross section. Finally, section 6 concludes and presents some perspectives to these works

Wave Propagation

A wave is one of the basic physics phenomena observed by mankind since ancient time. The wave is also one of the most-studied physics phenomena that can be well described by mathematics. The study may be the best illustration of what is “science”, which approximates the laws of nature by using human defined symbols, operators, and languages. Having a good understanding of waves and wave propagation can help us to improve the quality of life and provide a pathway for future explorations of the nature and universe. This book introduces some exciting applications and theories to those who have general interests in waves and wave propagations, and provides insights and references to those who are specialized in the areas presented in the book

Break point analysis and modelling in subway tunnels

The time constraints in network developments inside tunnels require a characterisation of canonical tunnels in terms of propagation path losses and developing a slope model which is usually represented as a two slope model. One of the problems arisen when the canonical model tries to predict the propagation path losses inside the tunnel is to determine the distance where the slope of the propagation path losses changes. This paper analyses two of the most common approaches to determine that distance and their behaviour in different scenarios in order to clarify the radio propagation mechanisms which define the break point distance.Postprint (published version

Modelling of radio wave propagation using Finite Element Analysis.

Fourth generation (4G) wireless communication systems are intended to support high data rates which requires careful and accurate modelling of the radio environment. In this thesis, for the first time finite clement based accurate and computationally efficient models of wave propagation in different outdoor and indoor environments has been developed. Three different environments were considered: the troposphere, vegetation and tunnels and wave propagation in these environments were modelled using finite element analysis. Use of finite elements in wave propagation modelling is a novel idea although many propagation models and approaches were used in past. Coverage diagrams, path loss contours and power levels were calculated using developed models in the troposphere, vegetation and tunnels. Results obtained were compared with commercially available software Advanced Refractive Effects Prediction Software (AREPS) to validate the accuracy of the developed approach and it is shown that results were accurate with an accuracy of 3dB. The developed models were very flexible in handling complex geometries and similar analysis can be easily extended to other environments. A fully vectored finite element base propagation model was developed for straight and curved tunnels. An optimum range of values of different electrical parameters for tunnels of different shapes has been derived. The thesis delivered a novel approach to modelling radio channels that provided a fast and accurate solution of radio wave propagation in realistic environments. The results of this thesis will have a great impact in modelling and characterisation of future wireless communication systems

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

Aeronautical Engineering. A continuing bibliography with indexes, supplement 156

This bibliography lists 288 reports, articles and other documents introduced into the NASA scientific and technical information system in December 1982