QoS adaptation methods for video delivery in pervasive environments
Morihiko Tamai · Institutional Repositories DataBase (IRDB) · 2007
In pervasive environments, mobile devices such as cell phones, PDAs and laptop PCs are connected through wired/wireless networks, and those devices are controlled based on user's context and preferences.In order to provide video streaming service in such pervasive environments, we need huge network and computational resources for encoding, delivering, decoding and drawing video contents.Thus, it is important how to achieve QoS which meets individual user requirements within various resource constraints such as network bandwidth, computational power on servers/clients, and battery amount.In this thesis, we propose application-level QoS adaptation mechanisms to provide satisfactory multimedia services to users in pervasive environments.Contributions of this study are two folds.First, we propose an energy-aware video streaming system in which the video can be played back for the specified duration within the remaining battery amount.In the system, we execute a proxy server on an intermediate node in the network.The proxy server receives the video stream from the content server, transcodes it to the video with lower quality, and forwards it to user terminals.To predict required battery amount which enables playback for the specified duration and to control battery life, we have developed a power consumption model using parameters on playback quality, playback duration, battery amount and so on.The system also allows users to play back video segments with different qualities based on the importance