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Delay-capacity tradeoffs for mobile wireless networks

Research Scholar

Yoora Kim, Electrical and Computer Engineering (South Korea)
Kyunghan Lee, Co-Researcher
Injong Rhee, Co-Researcher
Ness B. Shroff, Faculty Mentor


Yoora Kim received her bachelor's, master's and Ph.D. degrees in mechanical engineering, applied mathematics and mathematical sciences from Korea Advanced Institute of Science and Technology (KAIST), in 2003, 2005 and 2009, respectively. She is currently a post-doctoral research associate at The Ohio State University. Her research interests lie in modeling, design, and performance evaluation of communication systems, human mobility/delay tolerant networks, and scheduling/resource allocation problems in wireless networks under various stochastic dynamics. Her research objective is to develop fundamental foundations for wireline/wireless networks, which is thoroughly based on mathematical theories including teletraffic theory, queuing theory and probability theory.

What is the issue or problem addressed in your research?

We consider mobile wireless networks where mobiles devices are carried by humans. For the network, we deal with a problem of delay-capacity tradeoffs as the number of mobile devices increases (where delay is a time for delivering a packet to a destination, and capacity is the maximum amount of data that can be transmissible per unit time). This line of study is called scaling laws in the literature and emphasizes the scalability of a network as the network size increases. Since delay performance depends significantly on how human moves, we consider various mobility models describing human mobility patterns. We then analyze the fundamental limit on delay performance that can be achievable for a given capacity constraint.

What methodology did you use in your research?

We conduct the research through three steps (i) modeling, (ii) problem formulation, and (iii) analysis, which are based on mathematical theory and communication theory. Specifically, to model mobility patterns, we use stochastic processes and random walks, and verify the usefulness of a model by comparing it with experimentally measured data. To make the delay-capacity issue into a feasible mathematical problem, we borrow a concept of first exit time or first meeting time of a random process. To solve the problem, probability/measure theory in mathematics and diffusing phenomenon in physics are studied and used.

What are the purpose/rationale and implications of your research?

The purpose of the research is to understand the fundamental performance limit of mobile wireless networks in terms of delay and capacity. This is important for two reasons. First, it allows us to know how a network will scale in delay and capacity when the network consists of devices mainly carried by humans. Second, it helps us to know how far existing schemes can be improved, and design a scheme that can achieve the fundamental performance limit.