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Site–specific Indoor Propagation Modeling of Ultra Wide Band Electromagnetic Waves Based on Ray Tracing

Mohtashami, Vahid | 2013

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 44959 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Shishegar, Amir Ahmad
  7. Abstract:
  8. In this dissertation, site-specific ultrawideband propagation modeling has been presented based on ray tracing. The empirical, statistical and site-specific methods are compared and the ray tracing method is selected as an efficient and accurate site-specific approach for indoor propagation modeling. The challenges of the ray tracing method in propagation modeling of ultrawideband electromagnetic waves are outlined and some solutions are presented.In order to increase the efficiency of finding the propagation paths, the modified wavefront decomposition method is presented. This method intelligently reduces the number of emitted rays and finds the exact propagation paths from the transmitter to the receiver. The simulation time reduction of several times has been achieved by using this method. Moreover, concurrent application of the modified wavefront decomposition method and boundary-volume-based acceleration techniques is shown possible.The cubic B-spline function has been incorporated in the ray tracing to reduce the computational burden of the post-processing stage. By using this function, field calculations need to be performed at a few frequency samples. Then the cubic B-spline function reconstructs the frequency response and other channel parameters in the whole bandwidth of the channel. Based on the frequency variation of the propagation mechanisms and antenna patterns, a systematic procedure for selecting the necessary and sufficient number of samples has also been presented. Simulation results show that computational efficiency of the post-processing is improved several times. The sensitivity of ray tracing results to the geometrical description of the environment is presented next. A mathematical framework based on the probability and statistics has been prepared for this purpose. A quantitative measure for evaluating the reliability of the simulation results is also presented. Simulation results show that time-domain channel parameters are almost insensitive to the lateral uncertainty of wall positions whereas the received power is more affected.The impacts of the inaccurate description of the dielectric constants of building materials on the ray tracing results are also investigated. The propagation of uncertainty in the ray tracing formulation is studied with a statistical approach. The Monte Carlo simulation is used for this pupose. For a typical office environment, the time-domain parameters are more degraded by the uncertainty of the real part of the dielectric constants. To guarantee accurate results, the dielectric constants have to be provided in the ray tracing program with a high accuracy. The received power shows little sensitivity to both real and imaginary parts of the dielectric constants except in heavily obstructed non-line-of-sight scenarios.
  9. Keywords:
  10. Sensitivity Analysis ; Ray Tracing ; Indoor Environment ; Ultra Wide Bond (UWB)Propagation ; Cubic B-Spline Function ; Modified Wavefront Decomposition Method

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