Date: Wed, 15 Jan 1997 01:58:38 GMT Server: NCSA/1.4.2 Content-type: text/html Last-modified: Mon, 26 Feb 1996 19:04:04 GMT Content-length: 3304 Robert Simon's Research Interests

Robert Simon

I am interested in multimedia, real-time, CSCW, network and distributed systems research. Below are some details of my work to date, if you're interested:

Multimedia Communication Architecture
During my graduate career, I have designed and implemented a multimedia communication architecture for an Integrated Services Network. DIPCS (Distributed InterProcess Communication System) is distinguished by its use of a new distributed process group model and its ability to allow a spectrum of quality of service requirements to co-exist within a single call. DIPCS provides guaranteed support for real-time multimedia traffic through a general purpose admission control policy and a packet policing and service policy. These policies support the end-to-end delay and synchronization requirements of each connection. DIPCS provides a call model and connection management system that is scalable to a Wide Area Network.

Multimedia Routing Algorithms
Using the DIPCS call specification and network architecture I have developed both centralized and distributed multimedia routing algorithms. These algorithms are based on a mathematical model of the network and of the real-time requirements of multimedia traffic that predicts the probability of a route or set of routes being able to support the traffic specification. These algorithms have two parts. In the first part network performance is decomposed into a set of independent link evaluation problems. A link blocks if it cannot support the performance requirements of a new connection while maintaining support for existing connections. My analysis allows the link blocking problem to be determined by knowledge of only the traffic arrival rate and performance requirements.

The second part is a route assignment and optimization phase. I have explored several methods for doing the optimization. The first is similar to a classic steepest descent algorithm. The second method is by using an evolutionary computing technique. My approach encodes the problem as a tree. I define a set of genetic operators for mutation, inversion and recombination. Based on the problem instance I use domain-specific knowledge for initialization. Finally, I have developed an optimization algorithm which can be implemented in distributed or parallel fashion. This approach has produced quite encouraging results for real-time multimedia routing. Simulation results show that the blocking model coupled with an evolutionary computing approach to routing assignment optimization is very successful.

Multimedia MedNet
My research has found practical application in Multimedia MedNet. MedNet's initial goal, the development and implementation of a distributed real-time multimedia system for remote monitoring of and collaboration during neurosurgery, has been achieved in part through work that I began at Hewlett-Packard labs and continued at the University of Pittsburgh. As the lead technical person I have produced a significant amount of software, including real-time audio and call control programs that are part of the DIPCS system.