Project Report

Research Overview The EAPSI Fellowship brought me to the Dependable Distributed Systems and Networks (DDSN) Laboratory at National Taiwan University (NTU) in Taipei, Taiwan for 8 weeks during the summer of 2010. As my host, Professor Kuo, became more familiar with my research experience and skill set he suggested that I join a team with two of his students doing research on femtocell deployments in LTE data networks. I agreed, changing my summer research project from "Protecting Web Servers by Web Robot Detection" to "Traffic and Performance Modeling for LTE Femtocell Interference Avoidance". LTE is the newest standard in wireless networks designed specifically for highly mobile computing that is expected to supersede the current 3G standard. Major telecommunications companies across the world, including AT&T, Verizon Wireless, and China Mobile have already announced plans to convert their current EDGE and 3G networks to LTE (marketed as 4G). The technical improvements offered and level of business backing behind LTE makes it inevitable that this technology will become completely integrated into our mobile telecommunication networks. In parallel with the development of LTE, companies have begun to market private wireless base stations referred to as femtocells. A femtocell is a device that creates a small wireless voice and data signal that mobile devices can use to connect to the Internet or to make phone calls rather than using the omnipresent cellular network. The Femtocell allows wireless users to use their mobile devices to place calls and download data in areas where signal quality is traditionally very low, such as the basement of a building, a crowded city, or in a remote location. It has been found, however, that the signal interference between femtocells carrying an LTE signal and between femtocells and an LTE macrocell is a critical problem. If left unchecked, interference prevents femtocells from realizing the high quality of service they are designed to provide. The focus of my research at NTU was to develop mathematical traffic, performance, and channel interference models for an interference avoidance system being developed in the lab. The development of these models are important so that the performance of such a system can be theoretically assessed during the design phase of the research project, rather than after devoting time and resources toward implementing a simulation or even a physical test bed. Rationale, Contribution, and Outcomes The rationale to travel to Taipei, Taiwan to perform this research comes from the excellent track record of the DDSN laboratory and the high level of synergy between my skill set and the needs of the laboratory. While the researchers at the DDSN laboratory had developed a novel approach towards mitigating interference in LTE networks with Femtocells, they lacked the background necessary to develop and assess performance by a mathematical model. My research experiences in the performance and reliability modeling of distributed systems perfectly fitted the needs of the laboratory. Another reason for performing this research in Taiwan is my desire to experience performing research in an international setting. My contribution was in the development of these traffic, performance, and channel models. The models were validated through a preliminary simulation that had been developed in the laboratory. As a result of this model, we were able to identify specific aspects of the approach that reduced performance to unacceptable levels. The avoidance technique was thus adjusted and improved. The approach also introduced the use of new modeling techniques that have yet to be applied in the context of wireless networks. This new approach improved the accuracy of the model, is easily extendable, and has been iterated upon since the conclusion of the fellowship. The creation of these models is a key step in making the promise of having a high-speed, reliable LTE connection available anywhere, anytime. The personal experiences of living in Taiwan and through the relationships established between me and my counterparts at NTU are two other valuable outcomes. The day-to-day experiences of living and working in Taiwan have broadened my world-view and brought with it many life lessons, including the need to always be respectful, understanding, and open-minded, the power of cherishing ones culture and history, and the positive effects of keeping a balance between the work of research and of experiencing life. Through these lessons, I have become a more well-rounded person and more productive researcher. With aspirations to have a career in teaching and research within academia, these lessons are sure to improve my skills in mentoring students as they aspire to become well-rounded scientists. The relationship between me and the DDSN lab remain strong, and we continue to work together. This long-term, international collaboration will continue even beyond the conclusion of this research project.

National Science Foundation (NSF)
Office of International and Integrative Activities (IIA)
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Carter Kimsey
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Doran Derek E
United States
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