ACT has developed adaptive push/pull technology using Direct Broadcast Satellite Systems (DBS) and Unicast networks (terrestrial or wireless). In such hybrid networks, we deploy algorithms which rapidly adapt the content of the broadcast based on the "misses" obtained from the explicit (on-demand) data requests on the unicast channels. This technique has a distinctive advantage over regular scheduling algorithms which are solely dependent on a priori complete knowledge of the need. Such knowledge is often not available and even when it is, it does not cover "panic situations" during which the demand for information is growing at an exponential rate. Examples of such a panic behavior have been observed on the Internet during the Oklahoma bombing, the summer Olympic games in Atlanta, and the winter Olympic games in Japan. The demand during these situations by far surpasses the capacity of the media (server and network). In panic or high volume situations, there is no time to analyze the demand and obtain optimal or near-optimal schedules of data dissemination. Instead, rapid adaptive algorithms are necessary.
The techniques we developed take advantage of DBS for the massive data dissemination while they serve the less popular items through the unicast channels. The latter channels are,used at the same time, to adapt the broadcast content based on popularity.