A Policy-based System for Handoffs between Intermediary Content Providers in the Wireless Internet

We consider the distribution of real-time multimedia content (e.g., radio or TV broadcasts) through multiple aggregators. An aggregator is an intermediary content provider that operates a pool of proxy servers to aggregate content from sources and forward it to mobile hosts. Aggregators package content into channels (e.g., CNN or ABC) and offer them in various versions (e.g., using different encodings) that differ in quality or price. Mobile hosts receive channels via the wireless Internet, which consists of multiple types of wireless networks (e.g. 802.11 and UMTS). At specific locations, mobile hosts can connect to multiple networks simultaneously (e.g., in a hotspot) and can thus potentially receive different alternative versions of a channel from different aggregators through different interfaces. In this paper, we propose a control system that enables mobile hosts to automatically deal with these (changing) alternatives in a manner transparent to the mobile user. The system's novelty lies in the use of application-level policies. They for instance define when to look for a better version of a channel (e.g., if packet loss increases to a certain threshold) and what constitutes best based on the user's preferences. The policies thus define when and how to adapt the reception of a channel to changes in available resources or user's preferences.