Abstract: With the advance of ubiquitous computing and ambient intelligence, several thousands of sensors and mobile devices will collaborate each other for collecting sensing information in urban districts and providing location-aware services considering pedestrians' preference. In order for mega scale ubiquitous systems to become popular as societal systems, high reliability and robustness are required. Here, we introduce several types of ubiquitous systems used in urban districts and discuss about how we can improve their performance and reliability. |