Propagation Measurements and Modelling of Natural Tropical Caves

Caves are a vital environment with an understudied propagation characteristic to date. In this paper, we investigate the propagation environments of three tourist caves in Malaysia at 900 MHz, 2.4 and 5.8 GHz. Path loss exponents are derived from measurement data for line-of-sight (LoS) and non-line-of-sight (NLoS) sections for vertical-vertical (VV) and horizontal-horizontal (HH) polarizations. Channel fading effects are subsequently analyzed. Beyond the conventional method of computing the path loss exponent values, machine learning is also incorporated into the processing of data for yielding optimum results. The findings of this work lay a good foundation towards a greater understanding of the propagation scenarios in natural tourist caves, and they help towards establishing reliable wireless communications inside such environments.