Wireless Underground Sensor Network Essay

1. Introduction

Wireless underground sensor networks is a network of sensor nodes wherein both transmission and reception from the nodes both takes place underground and they do not require wired connections. These consists of number of sensors planted underground or in a cave or in a mine, to observe underground conditions. Here along with them additional sink nodes are deployed above the ground to transfer information from the sensors to the base station. These are more expensive then terrestrial WSN in all aspects starting from deployment and up to maintenance, as the equipment required need to ensure efficient communication through different mediums like soil, rocks, water etc[1].

Every node contains all the required equipment, making them more efficient than the existing alternatives of sensors underground. The

Whereas in the new technology they can be placed independent of the dataloggers and more evenly.

4. Problems in the wireless underground sensor networks

1. Extreme Path Loss

These networks often suffer from path loss caused due to absorption by material, while using EM waves in the underground network. The loss depends upon the frequency of the EM wave used and on the properties of the rock or soil through which it passes. Lower frequencies suffer from lesser path loss compared to higher frequencies. Sandy soil allows EM waves to pass through them more easily as compared to the clay soil.[8] Water content in the soil also plays a significant role in path loss calculation.

2. Reflection / Refraction

WUSN devices that are placed near the surface are able to transmit to both underground and above ground devices, therefore when the propagating EM wave reaches the ground-air interface, some of it will be reflected back into the ground and some of it will be reflected to the air[6].

3. Multipath