I have been working in the Responsive, Reliable and Real-Time (R3) Messaging project. This involved designing and building a messaging middleware to deliver messages in wide-area networks while meeting QoS requirements. There have been a lot of news coverages on this project, including New York Times, Wall Street Journal, and CNN. (See Middleware 2010, Middleware 2009 and ICSOC 2009 papers for details.)
Scalable services for cloud
I have been leading the team of researchers to develop a scalable queueing
service for cloud. Together we developed a scalable queueing service using a
DHT overlay. I also worked on experimenting different consistency
levels for a scalable cloud-based queueing service. (See ICSOC 2010.) I was
also involved in designing and developing a scalable publish/subscribe system,
built on top of Cassandra. (To appear IPDPS 2011.)
Stream processing
I worked on the Distillery project, designing the distributed version of the System S Stream Computing System. I also worked on enhancing high availability of the system. (See Middleware 2009.) I was also involved in experimenting multipath for real-time streaming applications. (See ICNP 2009.)
Mobility models and characterization
Developing mobility models is challenging. To simulate mobile users
(especially for testing wireless networks), it is important to have a realistic
mobility model. The commonly-used random waypoint model doesn't reflect real
user mobility. Based on the traces collected at Dartmouth College, I developed
a realistic model focusing on the arrival and departure rates of
hotspots. (See INFOCOM 2006.) I was also involved in developing another
model, based on the transition probabilities (at buildings and
intersections) extracted from the traces. (See MobiSys 2006.)
I also worked on discovering mobility patterns by studying real user traces. I worked on a large data set to discover interesting mobility patterns. I had fun applying Fourier transform and playing with MATLAB. (See PUC 2007, WiTMeMo 2005.)
Localization
I'm generally interested in location sensing and discovery technologies. I looked into the accuracy of the AP locations discovered through war driving or war walking. (See Pervasive 2006.)
Distributed file systems
I worked on designing and developing a distributed file system for wide-area networks.
The focus was to help mobile users to access remote files fast when they are traveling. (See Fast 2002 and NetStore 1999.)
Mobile network estimation
I worked on estimating bandwidth and latency in wireless networks. It is always interesting to adapt existing techniques (such as the Kalman filter) and find how well they address the new problems. (See MobiCom 2001)
