I Introduction
With the advances in electronic and wireless communication technologies, the design and development of various novel mobile and pervasive computing applications have attracted great interests both in the industry and academic. Nowadays, people can use their smart phones easily as mini-computers to play computer games and retrieve various useful information, e.g., mapping and shopping information, through cellular or wireless networks. It can be anticipated that pervasive computing applications will become one of the cores computing applications in the coming future and more and more electronic devices will be equipped with powerful computing capability to support various novel and advanced services to mobile users.