Beamforming based signal strengthening via underground acoustics sensor networks

As the advances in sensing and wireless communication technologies, e.g., ZigBee, RFID, and WiFi, wireless sensor networks provide a promising opportunity to enhance underground environment monitoring, e.g., coal mine disaster monitoring. However, these wireless technologies suffer from signal distortion and short Non-Line-Of-Sight (NLOS). Furthermore, in underground disaster it is difficult to transmit sensing data to the ground via wireless signals. In this paper, we study beamforming based signal strengthening scheme in underground wireless sensor networks. Compare with traditional wireless signals, we use acoustic signal, which has several merits: first, it has much longer wavelength, which results to slower decay and longer propagation distance; second, it is resistant to signal distortion, which may help enhance the robustness of the underground monitoring system. Theoretical analysis is provided on both systematic and stochastic errors. Extensive simulations are carried out for theoretical verification.