Headlight Prefetching and Dynamic Chaining for Cooperative Media Streaming in Mobile Environments

摘要

Media streaming in mobile environments is becoming more and more important with the proliferation of 3G technologies and the popularity of online media services such as news clips, live sports, and hot movies. To avoid service interruptions, proper data management strategies must be taken by all parties. We propose a two-level framework and cooperative techniques for mobile media streaming. Headlight prefetching is for the cooperation of streaming access points to deal with unpredictable client movement and seamless hand-off. For each user, we maintain a virtual fan-shaped prefetching zone along the direction of movement similar to a vehicle headlight. The overlapping area and accumulated virtual illuminance of the headlight zone on a particular cell determine the degree and volume of prefetching on that cell. Dynamic chaining facilitates cooperation among users to maximize cache utilization and streaming benefit. On receiving a request from a client, the streaming access point starts a search for supplying partners before attempting to a remote media server. If a qualified partner is found, the client is chained to the partner and receives subsequent segments without server intervention. The client can itself be a supplying partner for other clients and naturally form a chain of users that are viewing and sharing the same media. Simulation results demonstrate that headlight prefetching and dynamic chaining can significantly decrease streaming disruptions, reduce bandwidth consumption, increase cache utilization and improve service response time.