Understanding Networking Science: Understanding the science and engineering aspects of various networks (such as computer networks, social networks) has been attracting considerable research interests of scientists from different disciplines. The work conducted at Illinois Institute of Technology in the Wireless Networking Lab, led by Xiang-Yang Li, is taking on the challenge of understanding the fundamental performance behaviors of large scale wireless networking, designing and implementing more energy efficient networking technologies under the most adverse technological challenges we ever faced, implementing mobile computing systems that will fulfill practical needs, and designing wireless networking protocols that will significantly enhance the performance. Overcoming these challenges will enable a new class of energy-conscious wireless networks that deliver high throughput networking and computing in a more environmentally-responsible manner. I have been concentrating on investigating questions in various networks that have significant real world impact and that could contribute in fundamental ways to the advancement of networking science and related engineering disciplines. It involves both theoretical and empirical methods. Topics of my research projects include cyber-physical systems, wireless sensor networks, mobile computing, crowd-sourcing, and privacy issues in these networks. My research is contributing and is supported in part by the National Science Foundation, through NeTS CPS, and the EARS program.

Designing Large Scale Wireless Sensor Networks: Sensor networks, a major component in cyber-physical systems, are envisioned to consist of hundreds or thousands of inexpensive nodes that can be readily deployed to collect useful information in a robust and autonomous manner. However, several obstacles need to be overcome before this vision becomes a reality. Collaborating with researchers from several institutions, I co-lead the design and deployment of wireless sensor networks, CitySee and GreenOrbs, for environment monitoring and study. The deployed sensor network is used for air quality monitoring, motivated by fighting global warming. Global warming, i.e., the increase in the average temperature of Earth's near-surface air and oceans and its projected continuation, has enormous physical, ecological, social and economic impacts. Multi-hop large scale WSN with CO2 sensors, consisting of thousands of inexpensive nodes, can be deployed to provide real-time, comprehensive monitoring in a robust and autonomous manner. The CitySee system, collaborated by my group and research institutions from HongKong and China, is composed of more than 1200 nodes that continuously work for more than one year now. This is one of the largest sensor networking systems reported, to the best of our knowledge. A number of unique phenomena were discovered in this large system and a number of challenging questions are addressed to make it sustainable and reliable. The system and experience obtained shed light on designing sustainable, scalable, and reliable sensor networks that meet industrial standards, especially on designing sustainable sensor networking systems with limited energy, computing and communication resources available to the sensor nodes.

Security and Privacy: Increasing attentions are paid to security and privacy implications in almost every field relating the human-generated data with the advent of state of the art data analysis such as data mining or machine learning techniques. Due to different forms of the outsourcing, various user-generated digital data has formed the current big data ecosystem as well as the cloud computing environment, and the current systems involve multitudes of sensitive information from which rich personal secrets can be inferred. To utilize the current networking system with its own benefits and address the underlying security and privacy implications, Li's research group has focused on the following different security or privacy related areas: {privacy-preserving computing}, {verifiable computing and storage}, {protection of location, image and video privacy}.

Mobile and Social Networking: Online social networks are fast becoming an important communication medium amongst varied groups of people. With the advent of popular web-sites and communication tools (e.g., Facebook, Twitter), users of these sites and tools form large social networks that provide a powerful means for sharing, organizing and finding contents and contacts. Other interesting applications include political activity and political activism which have been harnessing the powers of digital social media. In this context, online social networking is a very powerful tool for many reasons. First, the broadcast nature of some social networking sites enables individuals to access a large audience, and second the network can also be used to rapidly spread the influence on others. Our research in social networking focuses on several different areas: belief propagation in social networks, relationship classification, privacy-preserving protocols in social networks, asymptotic behaviors of large scale social networks.