GreenOrbs: A Long-Term Kilo-Scale Wireless Sensor Network System in the Forest

The missions of GreenOrbs are two fold:

On one hand, GreenOrbs realizes all-year ecological surveillance in the forest, collecting various sensory data including temperature, humidity, illumination, and carbon dioxide titer. The collected information is utilized to support various significant applications, such as forest surveillance, forestry observation and research, fire risk evaluation, and succor in the wild.

On the other hand, GreenOrbs pioneers the effort in the sensor network community to build a practical system. Through the real-world experience in GreenOrbs, we expect to explore the potential design space and scientific solutions, especially addressing the research and engineering challenges for a wireless sensor network system that is deployed in the virgin forest, involves 1000+ sensor nodes, and needs to operate for over one year.

Previous website was published here: http://greenorbs.org

Wireless sensor networks (WSNs) are often deemed as appropriate solutions for environmental surveillance and real-time monitoring applications. In the past decade, WSNs have gained a lot of attention from the research and industry community. Countless research projects have been launched to study different aspects of WSNs and yielded fruitful results.

The uses of WSNs nowadays, however, are far restricted by many theoretical or practical obstacles. For examples, most WSNs adopt un-rechargeable batteries with limited power supply. The wireless links among the sensor nodes appear to be unreliable and easily affected by various environmental factors. Nevertheless, there is hardly any fundamental result on the data collection capacity of a duty-cycled WSN with unreliable wireless links. Further considering the faulty behaviors of sensor nodes and the difficulties of outdoor deployment and maintenance, a real WSN system often fails to support long-term large-scale applications with guaranteed performance.

What are the fundamental challenges in long-term large-scale WSNs? Which research and technical issues must be addressed? Where are the potential design spaces of future WSN research? The research and industrial communities are in urge need of the answers to the three questions.

Under such circumstances, we launched GreenOrbs, a WSN system of 1000+ nodes to operate in the forest for over one year. Through the experience in GreenOrbs, we gain considerable insights on the challenges and design space in long-term large-scale WSNs, such as energy consumption, scheduling and synchronization, routing efficiency, link estimation, encapsulation, deployment, diagnosis, and fault tolerance, etc.

The participation of GreenOrbs are from several organizations, including Hong Kong University of Science and Technology, Xi'an Jiao Tong University, Zhejiang Forestry University, Illinois Institute of Technology, Hangzhou Dianzi University,Tsinghua University, Beijing University of Posts and Telecommunications and Nanyang Technological University.

Principle Investigators

Name	Position	Affiliation
	Dr. Yunhao Liu	Hong Kong University of Science and Technology Tsinghua National Lab for Information Science and Technology
	Dr. Jizhong Zhao	Xi'an Jiao Tong University
	Dr. Guomo Zhou	President of Zhejiang Forestry University
	Dr. Xiangyang Li	Illinois Institute of Technology
	Dr. Guojun Dai	Hangzhou Dianzi University
	Dr. Ming Gu	School of Software, Tsinghua University
	Dr. Huadong Ma	Beijing University of Posts and Telecommunications
	Dr. Mo Li	Nanyang Technological University

Team Leaders

	Name	Position	Affiliation
	Dr. Yuan He	Postdoctoral Fellow	Hong Kong University of Science and Technology
	Lufeng Mo	Assist Professor	Zhejiang Forestry University

Team Members

	Name	Duty	Position	Affiliation
	Jiliang Wang	Protocol Design and Test	PhD student	Hong Kong University of Science and Technology
	Kebin Liu	Protocol Design and Test	Postdoctoral Fellow	Hong Kong University of Science and Technology
	Wei Dong	Protocol Design and Test	PhD student	Zhejiang University
	Ming Zhu	Hardware and RF Development	PhD Student	Dalian University of Technology
	Wei Xi	Protocol Design and Test	PhD student	Xi'an Jiao Tong University
	Zheng Yang	Theoretical Validation and Analysis	Postdoctoral Fellow	Hong Kong University of Science and Technology
	Xufei Mao	Theoretical Validation and Analysis	Assistant Professor	Beijing University of Posts and Telecommunications
	Xingfa Shen	Hardware Design and Test	Assistant professor	Hangzhou Dianzi University
	Shuo Lian	Test and System Integration	PhD student	Xi'an Jiao Tong University
	Rui Li	Test and System Integration	PhD student	Xi'an Jiao Tong University
	Tao Chen	Protocol Design and Test	PhD student	National University of Defense Technology
	Qiang Ma	Test and System Integratio	PhD student	Hong Kong University of Science and Technology
	Xin Miao	Test and System Integration	PhD student	Hong Kong University of Science and Technology
	ZhiChao Cao	Test and System Integration	PhD student	Hong Kong University of Science and Technology
	Chao Wang	Software Development	PhD student	Beijing University of Posts and Telecommunications
	Zhenge Guo	Software and Protocol Test	Mphil Student	Yanshan University
	Zhenjiang Li	Protocol Design and Test	PhD student	Hong Kong University of Science and Technology
	Tong Zhu	Protocol Design and Test	PhD student	Hong Kong University of Science and Technology
	Junliang Liu	Protocol Design and Test	PhD student	Hong Kong University of Science and Technology
	Lin Wang	Protocol Design and Test	Assistant professor	Yanshan University
	Yubo Yan	Protocol Design and Test	Mphil Student	PLA University of Science and Technology
	Jin Cui	Software and Protocol Test	Mphil Student	Northwestern Polytechnical University
	Xuan Ding	Test and System Integration	PhD student	Tsinghua University
	Danning Chen	Software Development	Mphil Student	Tsinghua University
	Lan Zhang	Protocol Design and Test	PhD student	Tsinghua University
	Shaojie Tang	Theoretical Validation and Analysis	PhD student	Illinois Institute of Technology
	Jianhui Zhang	Theoretical Validation and Analysis	Assistant Professor	Hangzhou Dianzi University

In GreenOrbs application of canopy closure estimates, we mainly address the following design issues: 

1. Generic estimation model. 
    We design a generic estimation model that works for non-vertical irradiations of sunlight and various vegetation species.

2. Sensor motes encapsulation and installation 
    We design and produce firm weatherproof sensor motes that are sustainable for very long time in the wild environments.

3. Processing of uncertain sensory data. 
    The sensor readings are often error-prone due to the complex deployment environment and diverse instrumental errors, which may lead to inaccurate      measurements.

4. Distributed cooperative node state monitoring. 
    A distributed cooperative mechanism is designed for sensors to accurately judge their statuses in a distributed manner so as to save computation and transmission cost.

From a macroscopic view, GreenOrbs is facing more research challenges towards a long-term kilo-scale WSN.

1. Light-weight network diagnosis and management

2. Online fault detection, tolerance, and correction

3. Synchronization and scheduling

4. Hardware and software reliability

5. Data collection in large-scale low duty-cycle WSNs

GreenOrbs is motivated by the need of long-term large-scale sensing for continuous environmental surveillance, precise forestry measurements and forestry research.

Canopy Closure Estimates

The first application of GreenOrbs is canopy closure estimates. Canopy closure is defined as the percentage of ground area vertically shaded by overhead foliage.

It is a widely-used indicator of the forest condition and has many significant uses in ecosystem management and disaster forecast. Previous forestry approaches of canopy closure estimates have either poor accuracy or prohibitive cost. Using WSN as a technique of quantitative measurement, GreenOrbs realizes accurate and economical canopy closure estimates of vast forest.

Fire Risk Evaluation

Another application of GreenOrbs is fire risk evaluation of forest. Traditional approaches provide only inaccurate evaluation according to the macroscopic weather forecast, including temperature, humidity, and wind force. The real fire risks, however, are in fact more related to the local status and human activities on the ground. Using sensor nodes deployed in the forest, GreenOrbs is able tomonitor the local environmental factors and act as important input elements of accurate fire rick evaluation.

Forestry Research

GreenOrbs is further designed to support forestry research through long-term large-scale observations on the forest microclimate, species interdependence, and competition among different vegetation species.

GreenOrbs is motivated by the need of long-term large-scale sensing for continuous environmental surveillance, precise forestry measurements and forestry research.

The first application of GreenOrbs is canopy closure estimates. Canopy closure is defined as the percentage of ground area vertically shaded by overhead foliage.

It is a widely-used indicator of the forest condition and has many significant uses in ecosystem management and disaster forecast. Previous forestry approaches of canopy closure estimates have either poor accuracy or prohibitive cost. Using WSN as a technique of quantitative measurement, GreenOrbs realizes accurate and economical canopy closure estimates of vast forest.

Another application of GreenOrbs is fire risk evaluation of forest. Traditional approaches provide only inaccurate evaluation according to the macroscopic weather forecast, including temperature, humidity, and wind force. The real fire risks, however, are in fact more related to the local status and human activities on the ground. Using sensor nodes deployed in the forest, GreenOrbs is able tomonitor the local environmental factors and act as important input elements of accurate fire rick evaluation.

GreenOrbs is further designed to support forestry research through long-term large-scale observations on the forest microclimate, species interdependence, and competition among different vegetation species

.