Contact

Prof. Xiang-Yang Li, Department of Computer Science, Illinois Institute of Technology.

Prospective Students (especially PHD students)

• Wireless Sensor Networks (WSN): 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 various aspects of WSNs and produced fruitful interesting 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 are hardly any fundamental results on the network capacity of a duty-cycled WSN with unreliable wireless links. Further considering the possible faults 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.
  
  
  Our sensor network research concentrates on platforms and methods to bridge the gaps between physical and cyber worlds. We investigate sensor and actuator network applications in environmental and energy conservation. We would like to study the following challenges:
  
  

  1. What are the fundamental challenges in implementing large-scale sustainable WSNs?
  2. Which research and technical issues must be addressed to design and implement a large-scale sustainable WSN?
  3. Where are the potential design spaces of future WSN research?
  4. How to efficiently, seamlessly, and effectively integrate the physical word, WSNs, and Internet, such that we can efficiently monitor the environment, and then derive usable knowledge?
  5. The asymptotic network capacity of large-scale wireless sensor networks under various link and network models. The optimal tradeoffs between capacity and other measurements (such as delay for mobile networks, energy consumption for WSN) of large-scale ad hoc networks.

  The research and industrial communities are in urge need of the answers to the three questions.

• Mobile Computing and Social Networking (collaboration with Tsinghua, and HangZhou DianZi University): Over the past three years, we have been developing various mechanisms to enable novel applications by bringing together multiple mobile devices. We take a people-centric approach and emphasize the key role of mobile devices in information collecting and consumption.

  Online social networking (OSN) often involves grouping specific individuals or organizations together. A number of mobile social networking services appear in the market for OSN, including Twitter, BrightKite, Loopt. Some of them offer location-based services to facilitate people's interactivity using a GPS module. Majority of systems rely on a centralized server and require communication infrastructures to provide Internet access. Further their location-based services are not offered to low-end mobile devices without GPS modules.

  To address these potential problems that could hinder OSN usage, we design and construct a multi-hop networking system named MoNet based on WiFi, and, on top of which we design and implement WiFace, a distributed privacy-aware geosocial networking service. We design a distributed content sharing protocol which can significantly shorten the relay path, reduce the conflicts and prolong the data lifetime.A role strategy is designed to encourage users to collaborate in the network.Furthermore, a key management scheme and authorization mechanism are developed to prevent some attacks and protect privacy.We conduct comprehensive experiments to evaluate performances of our mobile platform MoNet and application WiFace. The results show that MoNet is more than sufficient to support social networking, and even audio and video applications.

  Another research topic is to design and implement a multi-hop wireless ad hoc networking system using Bluetooth technology. In this work, we study a specific mobile social network that appears in local and impromptu occasions. To serve such a social network, we design and implement a relatively large-scale mobile ad hoc network, called BlueSky, using Bluetooth as a communication platform. In BlueSky, we design a virtual network layer on top of the original Bluetooth stack to provide necessary functionalities for constructing a secure and large-scale multi-hop mobile social networks. Using BlueSky, we implement one typical application, named BlueClass, for facilitating teaching needs in a class. We present findings from our real testbed studies based on which we provide the design requirements of BlueSky and BlueClass. We describe the implementation of BlueSky and BlueClass on Windows Mobile and report comprehensive usability evaluations and measurement of system performances. Our extensive evaluations demonstrate that our BlueSky and BlueClass implementation has negligible overheads, provides robust protections against attacks, and is extremely favored by students.

• Non-Cooperative and Cooperative Computing in Distributed Systems (A Microeconomic Approach to Network Ecosystems).

  We will address several system-level issues that play significant roles in designing robust and efficient network protocols with selfish participants: application layer, transport layer and medium access control layer, and network layer. Potential topics:

  1. the reputation and trust-inference for networking protocol design, and investigate free-riding detection and prevention using DiffServ and/or monetary payment;
  2. study existing transport and MAC protocols optimized for an environment with selfish users and possibly design new ones;
  3. study the impact of selfish behaviors on various routing protocols and the design of mechanisms that can detect and prevent harmful selfish behaviors and hidden action.
  4. Via a unified fashion, design network protocols thwarting selfish behaviors.
  5. Evaluate the impact of heuristics and protocols by simulation and testbed experiments.

  We need to make a great effort to explore different tradeoffs such as the communication and computation overhead and their tradeoffs, implementation cost and performance gain, etc. We anticipate that effective and efficient software tools will be developed for dealing with these problems based on solid ideas.

• Zero Pre-Configuration Secure and Dependable Communication in Tactical Mobile Ad-hoc Networks (collaboration with Kui Ren fro ECE, IIT).

  Wireless mobile ad-hoc networks have been widely applied in military tactical environments to allow mobile nodes, e.g., soldiers, tanks, battle ships, aircrafts or sensors, equipped with wireless communication devices, to exchange mission-critical information in an on-demand manner without relying on any pre-existing network infrastructure. In such applications, it is of paramount importance to ensure communication security due to the criticality of the information being exchanged and the fact that network environments can be extremely adversarial. In this research we focus on secret and dependable wireless communications in tactical mobile ad-hoc networks (T-MANET) and especially the following:

  1. Mechanisms for Zero Pre-Configuration Secret Wireless Communication
  2. Mechanisms for Zero Pre-Configuration Dependable Wireless Communication

• Other topics: We are also interested in cyber-Physical Systems, wireless networks, practical algorithms' implementation, information processing, data mining, computer graphics, and scientific computing (3D meshing for various purposes, modeling and so on).

Before Contact

• PhD thesis research represents a substantial work. You may want to read Useful Things to Know About Ph.D. Thesis Research by H.T. Kung at Harvard.
• Choosing a PhD thesis advisor is a very important decision for a graduate student. Here are some suggested readings:
  1. How to Choose a Thesis Advisor by Michael C. Loui at UIUC.
  2. How to Succeed in Graduate School from ACM Crossroads student magazine.
  3. How to Be a Good Graduate Student from the Caltech Grad Handbook.
• Before you contact me, please check out mine research interests and read through the following. This will save both your time and mine.
  1. If you are working with another faculty member in our department, please do not contact me.
  2. Research is enjoyable most of the times. Some times, however, it may not be as smooth as you thought. Please make sure you have the dedication and determination to carry out research.
  3. On average (1997--present), I work about 50-60 hours a week. You have to be prepared for this. Hard working is a necessary condition for success, but not sufficient though, :-).
  4. My research centers around better algorithms for various optimization problems in computer networks (most recently, in cyber-physical systems, wireless ad hoc networks, sensor networks, and peer-to-peer networks). In order to thrive in my group, you need to have a strong ability in algorithm design and analysis, and a broad knowledge in networks, especially wireless networks.
  5. You will also need to be able to carry out implementations effectively. Proficiency in (not just knowing) C or C++ is a must. If you do not know any one of the following programming language, you have to be prepared to learn at least one of the following simulation tools before you start the PhD program:
     • TinyOS programming and sensor network system design. (basically required)
     • NS-2: the general network simulator (basically required)
     • MATLAB: scientific computing and graphics (basically required)
     • CPLEX: for solving LP and ILP
     • LEDA: library for efficient data structures and algorithms
     • OPNET: for wireless networks and WDM networks
     For students working in WSN or CPS area, you need to be proficient in TinyOS and/or hardware design.

What is the advisor's effort?

Is it worth all the effort?

How to read technical papers in computer science?

When you read articles or reports, keep the following in mind

• What is the main contribution of the paper?
• Is this important, why?
• Is this a theoretical contribution to some fundamental problems in CS, or a protocol-like contribution, or both?
• What was the main insight in getting the result?
• What is not clear to you?
• What did the authors not do, and you regard important?
• What are the most important assumptions, are they limiting?
• What are the possible applications suggested in the paper?
• How does this relate to other things we have seen?
• What extensions does this suggest?
• Can you suggest some project idea based around the ideas in this paper?

If you read through this point and still want to work with me, please email me at xli AT cs DOT iit DOT edu with your resume (ASCII, PDF or POSTSCRIPT) and sample papers (if you do have publications). Please acknowledge that you have read this page at the beginning of your email. Otherwise, I may not spend the time to read your resume. You can also contact my current or graduated students about the research topics and styles.