Performance Improvement of IEEE802.11 Wireless LAN Networks

Acknowledgment I may never have undertaken without the enthusiastic encouragement from the person who became my advisor, Prof. Yasuhiko Yasuda. He often steered me in the right direction when I wasn't certain of which path to investigate. I acknowledge his significant contribution to my PhD studies. I would like to thank Prof. Fumio Takahata, Prof. Shigeki Goto and Prof. Jiro Katto for their very significant support and guidance. Their valuable comments on this thesis based on various outlooks could lead me to the right direction. I also would like to express my gratitude to Associate Prof. Kaoru Sezaki in the University of Tokyo. He deserves special mention, not only for providing the valuable comments on my research but also for providing the opportunity for me to work on this thesis in the Sezaki Lab. in the University of Tokyo. I am also grateful to Dr. Yoshikatsu Nakagawa who is head of NRC Tokyo (Nokia Research Center Japan) and Mr. Marko Teittinen who is a Competence Area manager. They gave me an opportunity to work in NRC Tokyo as a research engineer and it has been very stimulating and rewarding to work there. And also, Mr. Toshiaki Jozawa and Mika Kasslin were often acknowledged for their significant supports and understandings on my Ph.D. studies. My working experience together with them was able to enhance this Ph.D. thesis. Other colleagues in NRC Tokyo and NRC Helsinki deserves special mention for giving me the opportunity to have valuable discussions with them. I would like to thank all of other members in Yasuda Lab. in Waseda University and in Sezaki Lab. in the University of Tokyo. Finally, I would like to appreciate my parents encouraging my interest in computer and network engineering and many sacrifices they have made for my studies.