1. Introduction
As a new computing paradigm advanced in the 1990s[1], pervasive computing emphasizes embedding computing devices in almost any kind of object imaginable in our daily life and work. Without computers being everywhere in their life, people can focus on the tasks in their life again. People almost mean the similar thing when they mention pervasive computing. However, there hasn't been any precise definition of pervasive computing so far. According to Xu Guangyou[2], pervasive computing is an integration of information space and physical space. In the integrated space people can be provided with transparent digital service anywhere and anytime.