Our physical world presents an incredibly rich set of observation modalities, such as heat, light, moisture, pressure, motion, etc. Recent advances in wireless sensor networks (WSNs) enable the continuous monitoring of various physical phenomena at unprecedented high spatial densities and long time durations and, hence, open new exciting opportunities for numerous scientific endeavors. Because sensor nodes are battery-powered, the most critical challenge in WSNs is minimizing the use of power, of which the most energy-consuming operation is data transmission. Given the commonly high correlations of sensed data in time and space, an analytical framework for correlation studies and new data gathering protocols is fundamentally important to reduce communication costs through lossless data compression in WSNs. This project is devoted to the fundamental investigation of exploiting temporal correlation In WSNs, for sustaining monitoring in harsh and possibly hostile environments, through an integrated theoretical and empirical approach. From this project, a novel, analytical, adaptive multimodal predictive transmission framework based on predictive coding is developed, for environmental monitoring WSN engineering, to achieve substantial energy savings and, hence, to significantly extend the lifetime of WSNs. Based on the developed framework, a new data gathering protocol suite is designed and implemented. Furthermore, a real-world environmental monitoring WSN testbed in a hilly watershed is deployed for evaluation and validation. Our interdisciplinary education plan uses the built WSN testbed and integrates our research results and new insights into education practice to provide hands-on training and experience for undergraduate and graduate students in both environmental and IT fields.
There is growing interest in the future impacts of global warming on our planet’s freshwater supplies. Liquid freshwater, making up less than one percent of the total water on Earth, is continually cycled from soil, rivers and lakes to the atmosphere and back. Plant life plays an important role because it interacts with water in the soil and atmosphere. Large root systems seek out water at various depths within the soil and thick foliage releases water vapor into the air. Therefore, to fully understand how freshwater moves through the environment, it is important to study how plants use water. This study explores the real-time monitoring of the environment for water interactions in the soil, plants and atmosphere. The methodology in this project used an innovative technology to link environmental sensors to the natural environment. The location for this study was in a nature reserve, maintained by the Audubon Society of Western Pennsylvania. A goal of this project was to provide high quality measurements of water interactions between trees and their surrounding soil without tarnishing the natural aesthetic. Wireless communications are becoming the norm with innovations such as Wi-Fi internet and Bluetooth devices. Similar technology is applied to wireless sensor networks, which allow for small, independent devices to collect and relay information over and through a variety of terrains. Applying this technology over the densely vegetated rolling hills of western Pennsylvania presented a challenge to the project, such as how to power the devices and determine the best locations for the devices. A unique aspect of this Wireless Sensor Network (WSN) deployment is the use of commercial, off-the-shelf WSN hardware and software in a long-term (more than two years) outdoor setting (at a forested nature reserve in western Pennsylvania). Included in this study is the potential influence that WSN technology has on environmental measurements. To study how water interacts in the soil, plants and atmosphere, combinations of self-made and commercial environmental sensors were installed at the nature reserve. To begin with, sap flow measurements within the trunks of trees are often used to estimate the amount of water transpired by the leaves. There are limited sap flow sensor types available that can be used in wireless network systems. Moreover, the few companies providing sap flow sensors sell them at high costs. To combat these issues, we have designed a circuit board and made our self-made sap flow sensors (e.g., $6.27 per self-made sap flow sensor versus $330 per Dynamax TDP-30 sap flow sensor). We have them integrated into our WSN testbed together with other sensors for the environmental monitoring. A novel integrated WSN network and data management system, called INDAMS (Integrated Network and Data Management System for Heterogeneous WSNs), has been developed to facilitate our real-world WSN testbed studies. This new management system, INDAMS, together with our self-built new gateway allow us not only to make real-time monitoring of our testbed now an easy task, but also to make certain type of our sensor measurements (e.g., sap flow) more accurate and to make it possible to monitor our testbed measurements in real-time. This wireless approach is important for quick identification of maintenance or system problems and also allows for access to data at any time from any location in the world as long as there is an internet access. Our testbed has provided a unique opportunity to systematically evaluate the feasibility and readiness of the state-of-the-art wireless sensing technology for conducting a potentially long-term large scale environmental monitoring and for investigating the strengths and weaknesses of the current WSN technology and its maintenance requirements for non-computer users, as it is the longest WSN in continuous operation of a similar size to the best of our knowledge. Over the course of this project, a comprehensive examination of the WSN has been conducted for environmental monitoring through the conception, design, and deployment using our WSN testbed. We have developed a new method to significantly extend mote battery lifetime. Furthermore, the real-world environmental monitoring WSN testbed in a hilly dense forested watershed in Western Pennsylvania has been used to collect important hydrologic information in a highly heterogeneous environment. Such hydrologic information is critical for hydrologists to study the interactions among soil, plant, and atmosphere system, and the role of heterogeneity plays in the interactions, and to understand how the environment and ecological system responds in the soil-plant-atmosphere system under server weather, such as server drought conditions due to climate changes. Findings of our project have also shed lights on: (1) How does the current state-of-the-art WSN technology affect environmental monitoring? and (2) How feasible is it to create a low-cost monitoring system while not sacrificing the monitoring quality?
