Application-level Policies for Automatic Switching between Content Redistributors

We consider the distribution of live and scheduled multimedia content (e.g., radio or TV broadcasts) through multiple aggregators. An aggregator is an access-controlled redistributor that operates a pool of proxy servers to aggregate content from source content providers and forward it to mobile hosts. Aggregators package content into channels (e.g., BBC 9 o’clock news) and offer them at various quality levels (e.g., using different encodings) and prices. Mobile hosts receive channels via a ‘beyond 3G’ wireless Internet, which consists of different types of wireless networks (e.g., 802.11 and UMTS networks). In this paper, we investigate how a mobile host can switch to another aggregator and an associated quality level while it is receiving a channel. This situation can for instance occur when a mobile host roams into a (different type of) wireless network through which a new aggregator is available, or when the mobile host roams out of a network while its current aggregator is only available through that network. We use an earlier developed application-level protocol that enables mobile hosts to discover accessible aggregators and to switch to one of them. We propose a complementary control component that automatically matches the user’s preferences (e.g., regarding cost or quality) with the aggregators’ available quality levels and the capabilities of the wireless networks the mobile host can connect to. The control component uses policies to decide when to invoke the protocol to hunt for alternative aggregators, how to rate their quality levels based on the user’s preferences, and when and how to switch to another aggregator. Together, the protocol and the control component ensure service continuity without bothering the user. We present the design of the system and its prototype deployed in a small-scale test bed.