for his unconditional support, professional guidance, understanding and inspiration during my PhD study. Not only did his insights help to shape this work, but his aesthetic sense taught me what good research is truly about. The attitudes towards work I learned from him are logical, tolerant and careful, which will definitely be my valuable assets. I really appreciate his best effort to provide me a good platform for doing research. He is more than a thesis supervisor to me.It has been also a great experience to work with Associate Professor Ho Weng Khuen from the National University of Singapore. He is more like my thesis cosupervisor. I am always impressed by his expertise on pointing out the issues and on the way to solve research problems. In addition, I would like to thank Prof. Jan M. Maciejowski from University of Cambridge for his valuable suggestions in my research direction.All my friends at Nanyang Technological University made my study and life to be wonderful and memorable. In particular, I am very thankful to Zhou Dexiang, Sun Lu and Chen Xuebing, Dr. Eddy Foo, Ashok, who helped me to understand so many critical problems. I am thankful to Dr. Tri Tran for the discussions on some conference papers and report. I would like to thank my friends, Yang Cangjie,