Joint Colloquium Distinguished Lecture Series

New Synchronization Challenges for Multi-Site Interactive Cyber-Physical Environments

Klara Nahrstedt

Wednesday, February23, 2011
306 Soda Hall (HP Auditorium)
4:00 - 5:00 pm

Klara Nahrstedt
Professor, University of Illinois at Urbana-Champaign

Downloadable pdf


Synchronization is one of the fundamental challenges in multi-site multi-sensory interactive cyber-physical environments (CPS)  due to complications such as  (a) the coexistence of highly correlated heterogeneous streams coming from multiple sensory sources at each site and capturing physical spaces such as users’ physical activities, (b) needs for multi-stream resynchronization when situation in physical spaces changes and/or users change demands (e.g., change of user views, change of user’s physical activity), (c) bounded bandwidth resources at each cyber-physical site, (d) heterogeneous end-to-end delays between sites, and (d) needs to achieve not only inter-stream synchronization, but also inter-sites synchronization capabilities.

In this talk, we discuss synchronization challenges in these new cyber-physical environments and present solutions to deal with them. Especially, we will introduce inter-stream, inter-site-sender and inter-site-receiver synchronization and resynchronization algorithms. These algorithms rely on  “timed synchronization points” , “dominant streams identification” and cooperative “bundle-based resource management” to achieve synchronized content dissemination for point-of-point and multicast-connected CPS environments under bandwidth and end-to-end delay constraints. Our smaller scale experimental results in the multi-site 3D tele-immersive cyber-physical system tesbed, called TEEVE (Teleimmersion for Everybody), and our large scale simulation results with TEEVE and Planetlab traces confirm the synchronization performance  and implementation feasibility of our solutions in supporting the multi-site interactive 3DTI system under Internet dynamics.


Klara Nahrstedt is a professor at the University  of Illinois at Urbana-Champaign,  Computer Science  Department.  Her research interests are directed towards multi-site cyber-physical systems such as power-grid and tele-immersive systems, Quality of Service (QoS) management in wired and wireless networks, Internet and overlay routing protocols, resource management in operating, distributed, and pervasive mobile systems. She is the coauthor of the widely used multimedia books `Multimedia: Computing, Communications and Applications' published by Prentice Hall, and ‘Multimedia Systems’ published by Springer Verlag. She is the recipient of the Early NSF Career Award, the Junior Xerox Award, the IEEE Communication Society Leonard Abraham Award for Research Achievements, the University Scholar Award, the Humboldt Research Award, and the Ralph and Catherine Fisher Professorship Chair. She was the editor-in-chief of ACM/Springer Multimedia Systems Journal, she was the general co-chair of ACM Multimedia 2006, the general chair of ACM NOSSDAV 2007, the general chair of IEEE Pervasive Computing and Communications (Percom) 2009, and she is currently the elected chair of ACM Special Interest Group in Multimedia (2007-2011).

Klara Nahrstedt received her Diploma degree in mathematics and numerical analysis from Humboldt University, Berlin, in 1985. She was a research scientist in the Institute for Informatik in Berlin until 1989. In 1995 she received her PhD from the University of Pennsylvania in the Department of Computer and Information Science. She is the member of ACM and IEEE Fellow.

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