DOI: 10.5281/zenodo.10261020
title: Processing of 3-D Polygon Mesh Model and Radio Propagation Simulations in a Cave: Surface Reconstruction from Point Cloud, Simplification of the Mesh, and Ray Tracing

description: ABOUT
This repository includes mesh data from cave geometry scanning and processing, and radio propagation data from ray tracing simulations.
The geometry data is obtained with laser scanning in a cave in Slovenija.  
The geometry processing includes (i) 3-D shape reconstruction - surface reconstruction from point cloud data and (ii) simplification - reduction of the geometric complexity of the 3-D mesh model.  
The radio propagation data is obtained using CloudRT [1] ray-tracing simulator.  
The obtained propagation-related quantities include information about the propagation mechanism, interactions with the geometry, received power, delay, azimuth and elevation angles of arrival and departure, and path loss. 
 
AUTHORS
Teodora Kocevska, Andrej Hrovat, Tomaž Javornik
Department of Communication Systems
Jožef Stefan Institute, SI-1000 Ljubljana, Slovenia
teodora.kocevska@ijs.si
 
GEOMETRY PROCESSING
The cave segment used for the propagation calculations is selected from a point cloud obtained in a cave in Litia, Slovenia. The point cloud is obtained with 3-D laser scanning of the environment. The selected segment is approx. 58  m long. Several parameter configurations were considered for 3-D shape reconstruction, including Poisson surface reconstruction with octree depths of 8, 10, and 12. Geometries that represent the cave shape and have different levels of complexity were created and studied. In the simplification process, one and two-stage simplification was explored using the Quadric Edge Collapse Decimation approach. 
 
RADIO SETUP
The transmitter (Tx) is fixed at the entrance of the cave and the receiver (Rx) is moved along the cave in 40 positions with a step of 1 m.
Omnidirectional antennas at the Tx and Rx sites and vertical polarization are considered. The antenna is mounted 1.5 m above the ground.
The start frequency is 3.5 GHz, the end frequency is 3.6 GHz and the step is 10 MHz. Direct propagation and first-order reflection are considered.  
The cave geometry is represented by a triangular mesh, and the material of the cave is wet earth. The material electromagnetic properties are selected according to the specifications presented in [2].
 
FOLDER STRUCTURE
The folder structure is:
     - Polygon_Mesh_Models
          # 3-D environment models with varying levels of geometry complexity
          - Reconstruction_Segmen1_Poisson_Surface_Reconstruction
          - Simplification_Segment1_Quadric_Edge_Collapse_Decimation
     - Propagation_Data
          # Propagation quantities of all rays between a transmitter and receiver
          - AllRay_PropData
          - PathLoss
          - readme.txt
     - RayTracing_EnvironmentModel
          # Final environment model used for ray tracing simulations
          - Cave_MeshModel.json
          - Cave_MeshModel.skb
          - Cave_MeshModel.skp
     - RayTracing_MaterialProperties
          # Properties of the materials in the environment
          - materials.json
          - materials.mtl
          - readme.txt
     - Cave_Length.txt
     # Length between selected locations in the environment
     - Cave_Segment1_visual.png
     # Visualization of the environment segment used for propagation calculation
     - readme.txt
     # Overall description 
REFERENCES
[1] D. He, B. Ai, K. Guan, L. Wang, Z. Zhong, and T. Kürner, "The Design and Applications of High-Performance Ray-Tracing Simulation Platform for 5G and Beyond Wireless Communications: A Tutorial," in IEEE Communications Surveys & Tutorials, vol. 21, no. 1, pp. 10-27, First quarter 2019, doi: 10.1109/COMST.2018.2865724.
[2] R. sector of International Telecommunication Union (ITU-R), "Effects of building materials and structures on radio wave propagation above about 100 MHz," International Telecommunication Union, ITU-R Recommendation P.2040-2, 2021.
 
ACKNOWLEDGEMENT
This work was supported by the Slovenian Research Agency under grant J2-3048.