Path Loss Estimation for Wireless Underground Sensor Network in Agricultural Application

Path loss models are used to estimate the path loss between transmitter and receiver in applications that involve transmission of electromagnetic waves. This paper describes the wireless underground sensor networks, which communicates within the soil and is different from the terrestrial wireless sensor network. An integrated study of electromagnetic waves propagation for a wireless underground sensor network is described in this paper. Here, path loss model and signal strength are presented, because of electromagnetic waves attenuation in the soil medium. Tests were conducted at various soil volumetric water contents and node deployment depths using three different frequencies, when soil consists of 0% sands, 35% silt and 15% clay. The results showed that radio signal path loss was minimum when frequency and moisture content are low. The experimental results revealed that a 20% increase in the soil moisture content increased the path loss by more than 30%.