Before the presentation of the research work, I need to thank many people who helped in this project and the development of my thesis. First of all, I owe the greatest gratitude to my supervisor, Dr. Chia Liang-Tien, Clement. He is such a nice man who always takes great pains giving me remarkable guidance. No doubt, I have learned many things and benefited a lot from him during these years. Next, I would like to express my gratitude to Dr. Deepu Rajan for his support since the beginning, and for his patience and guidance. Without their continuous