Ever since various multimedia services based on the Internet were introduced in 1990s, traffic related to such services has been steadily increasing worldwide, usually via wired networks. However, with the introduction of new mobile devices and new multimedia services working in wireless environments, we are seeing changes in how people consume multimedia services. Users are consuming much more digital information with handheld mobile devices such as smart phones or tablet PCs. Moreover, the popularity of personal multimedia devices, such as digital cameras and camcorders, and inexpensive large-capacity personal storage media enable every single individual to perform a more active role in the circulation or distribution of multimedia information. Recent users are generating digital contents and distributing them by themselves using their smart phones via the Internet. In these days, each single user is one single source of digital information and those users are demanding new ways to manage and share their data on PCs and mobile devices more easily and quickly.