My research interests lie in the area of computer network systems and applications. Specifically, I have been working on the analysis of the fundamental properties of opportunistic networks; channel modeling and performance analysis of wireless networks; bandwidth estimation in wired and wireless networks; and performance evaluation of emerging social computing systems. The primary objectives of my research are 1) to understand the fundamental properties of mobile and wireless networks; and 2) to investigate feasible solutions that facilitate more enjoyable network experience for end users. Below I briefly introduce two of my ongoing work.

• Networked Sensing Systems

  We research networked sensing systems in hostile environments, in which network contacts are intermittent, an end-to-end path between the source and the destination rarely exists, disconnection and reconnection is common, and link performance is highly variable or extreme. We tackle this problem from two directions, namely the networking and sensing sides. On the networking aspect, we perform analytical study to model network mobility and design effective schemes for data dissemination in the network; whereas, on the sensing aspect, we investigate fault-tolerant mechanisms to facilitate reliable sensing data harvesting in challenged environments and research energy efficiency mechanisms to prolong the lifespan of sensor nodes.

  In addition to theoretical study, we prototype our research results and develop real-world systems to provide networked sensing services. Specifically, we have implemented a delay-tolerant sensing system, called YushanNet, for mountaineering applications. The system employs light-weight devices with low-power short-range radio, and it exploits opportunistic hiker encounters to record and disseminate hikers’ whereabouts in the mountains. The system has been approved to be deployed on the Yushan Peak Trail, and it will soon become a regular service of the national park to provide hiker tracking, environment monitoring, and other advanced e-service to tourists.

• Social Computing Systems

  We investigate emerging social computing systems with focuses on human computation and social sensing applications. The rationale behind human computation is to outsources certain steps of the computational process to humans and solve the problems that are intuitive to humans, but computer technologies cannot solve completely by far, such as image annotation and commonsense reasoning. Among various human computation systems, we tackle `Games with a Purpose’ (GWAP) systems, which taking advantage of people’s desire to be entertained and produce useful metadata as a by-product. We argue that, in order to collect human intelligence more efficiently, GWAP systems must be designed and played with strategies. We develop a generic analysis framework to investigate intrinsic properties of GWAP systems, and conduct a set of design strategies to improve the performance of GWAP systems in terms of efficiency and quality. Moreover, we have implemented and verified the designed strategies in real-world GWAP systems; and we have released the source codes and game traces to the research community.

  In addition, we research social sensing systems, and implement the VProbe system that employs modern smart phones to collect users’ GPS information and accelerometer readings in their daily transportation. By modeling users’ behavior and inferring their energy consumption, the system not only allows users to interact with each other on social platforms (e.g., Facebook), but also provides a variety of functions that allow users to share their driving experience, compare their carbon footprint, discover the most comfortable route, and learn how to drive more eco-friendly with their friends. By integrating sensing systems and social networks, VProbe shows promises in facilitating future cyber-physical social network systems.