This is the published version of of A. Salam, M. C. Vuran, and S. Irmak, "A Statistical Impulse Response Model Based on Empirical Characterization of Wireless Underground Channel", to appear in IEEE Transactions on Wireless Communications, vol. 19, No. 9, 2020. DOI: 10.1109/TWC.2020.2998762

Published by IEEE with a Creative Commons Attribution 4.0 License.


Wireless underground sensor networks (WUSNs) are becoming ubiquitous in many areas. The design of robust systems requires extensive understanding of the underground (UG) channel characteristics. In this paper, an UG channel impulse response is modeled and validated via extensive experiments in indoor and field testbed settings. The three distinct types of soils are selected with sand and clay contents ranging from $13\%$ to $86\%$ and $3\%$ to $32\%$, respectively. The impacts of changes in soil texture and soil moisture are investigated with more than $1,200$ measurements in a novel UG testbed that allows flexibility in soil moisture control. Moreover, the time-domain characteristics of the channel such as the the RMS delay spread, coherence bandwidth, and multipath power gain are analyzed. The analysis of the power delay profile validates the three main components of the UG channel: direct, reflected, and lateral waves. Furthermore, it is shown that the RMS delay spread follows a log-normal distribution. The coherence bandwidth ranges between \SI{650}{kHz} and \SI{1.15}{MHz} for soil paths of up to \SI{1}{m} and decreases to \SI{418}{kHz} for distances above \SI{10}{m}. Soil moisture is shown to affect the RMS delay spread non-linearly, which provides opportunities for soil moisture-based dynamic adaptation techniques. Based on the measurements and the analysis, a statistical channel model for wireless underground channel has been developed. The statistical model shows good agreement with the measurement data. The model and analysis paves the way for tailored solutions for data harvesting, UG sub-carrier communication, and UG beamforming.


Wireless Underground Channel, Underground Communications, Internet of Underground Things

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