Exploiting soil moisture information for adaptive error control in wireless underground sensor networks

Wireless underground sensor networks (WUSNs) have recently been investigated for a wide range of applications. One challenge in wireless underground communications is its high bit error rate, especially at long distances. In WUSNs, the communication quality is substantially affected by the environment, especially the soil moisture. Thus, the underground channel quality can be effectively estimated based on local soil moisture readings. By utilizing the local soil moisture values to estimate the channel quality, adaptive error control mechanisms can be implemented for underground nodes. In this paper, two error control mechanisms, adaptive-rate forward error control and adaptive transmit power control, are considered for WUSNs. The results indicate that compared to ARQ, adaptive FEC code can increase the ranges of soil moisture values within which the network is reliable by reducing the bit error rate. In addition, adaptive transmit power control can improve energy efficiency when a wide range of transmit power levels is available. Our evaluations show that to achieve 60m communication distance in practical soil settings, the output power of the transmitter should to be adjusted in a range of 0dBm to 25dBm to improve the energy efficiency of the underground nodes.