Multi-hop wireless sensor network for remote monitoring of soil moisture

This paper presents a case study of wireless sensor network (WSN) system for remote soil moisture monitoring. The development of this system is driven by the needs for having realtime data collection and remote monitoring access capabilities which are lacking in the conventional soil monitoring techniques. Our proposed system is developed using commercially available IRIS motes based on the IEEE 802.15.4 communications standard. The surrounding humidity, temperature and soil moisture of the crops are gathered and transmitted to a gateway for further analysis. The users will be notified when the soil moisture falls below the optimum level and they can also observe the changes in the data remotely. We validate the system and investigate its performance with respect to the types of network topology. The link quality, RSSI, network lifetime and number of packet drops are measured for both single-hop and multi-hop topologies. The finding shows that the multi-hop network offers wider area coverage with strong link quality at the expense of higher energy consumption compared to the single-hop network.

I. Introduction

Wireless Sensor Network (WSN) consists of a group of nodes in a self-organizing network that works cooperatively in performing a particular task [1]. WSNs can be utilized in many application areas such as agriculture, military, tracking and surveillance, traffic monitoring, and environmental [2]. WSN node consists of several subsystems, namely computing, communication, sensing and power unit. The computing subsystem is responsible for data processing, sensor control and communication protocol execution. Meanwhile, the communication subsystem, which comprises of a RF transceiver, provides links between the neighboring nodes and also with the outside world. The sensing subsystem includes all the required sensors that are used for sensing the corresponding physical phenomena. Lastly, the power source for the node comes from either a battery or renewable energy source [3].