PECASE: Modeling, Analysis and Control of Subexponential Traffic Streams in Multimedia Networks

Increasing empirical evidence has demonstrated the presence of subexponential, heavy-tailed, long range dependent and self-similar statistical characteristics of traffic streams in modern multimedia networks. Examples of traffic streams with subexponential characteristics range from variable bit rate (VBNS) compressed video to various Web and Internet related applications. Traffic streams with these characteristics differ radically from conventional voice streams. The difference is not only quantitative, but qualitative as well. For example, when observed on a slow time scale voice traffic averages out and shows very little fluctuations while VBNS video traffic exhibits a dynamic statistical behavior on multiple time scales; this is often termed self-similar behavior. Furthermore, large deviations from the typical behavior of a subexponential random sequence occur in a completely different manner than with an exponential (e.g., voice) stream. Understanding these novel and intriguing statistical phenomena is of utmost importance when designing efficient and reliable wired, or wireless, multimedia communication networks.

The most common way of increasing the efficiency of communication networks is through the sharing of network resources, e.g., link capacity and buffer space. This process leads to the degradation of quality of service (QoS) that is perceived by individual network users. The design objective is to maximize the efficiency subject to the QoS constraints, e.g., delay distributions and loss probabilities. This design process naturally breaks down into the following three areas: 1) statistical data analysis and traffic modeling; 2) performance analysis and control; 3) construction of numerical and software tools for network design. These three areas of research are inherently interconnected and an effective solution used for any one of them must be based on the advances in the other two areas. Therefore, a comprehensive and integrated research agenda is suggested.

The focus of this proposal is on fundamental problems that are important for developing current technologies, e.g., Atm., TCP/IP-based and wireless data networks, as well as being potentially applicable to future network designs. The scope of the proposed research ranges from probability theory to software engineering. The impact is not only limited to multimedia communication networks, but is also important for understanding the problems in operations research, finance and insurance theory where subexponential models play an important role.

In addition to the proposed research, a curriculum that integrates theory with computing is presented. Great scientific advances have often occurred through an interplay of theory and experiment. From this perspective the researcher believes it is essential that engineers are exposed early in their careers

to theoretical and experimental knowledge in a unified fashion. This enables them to recognize the potential and limitations of both theory and experimentation and use it successfully to their advantage. This approach

also speeds up the learning process by demonstrating theoretical results on real world problems and teaches students how to abstract the essential information from the experimental observations into ever-lasting design principles.