Methods to improve the efficiency of IPTV services

The increasing popularity of multimedia broadband applications, beyond basic triple-play, introduces new challenges in content distribution networks. These next-generation services are not only very bandwidth-intensive and sensitive to the high delays and poor loss properties of today's Internet, they also have to support interactivity from the end user. The current trend is therefore to introduce IP-aware network elements in the aggregation networks to meet the increasing QoS requirements, offering a smooth transition from legacy ATM-based platforms towards more scalable, efficient and intelligent access networks. One of the promising services triggering this evolution is IPTV. This article presents a large scale IPTV service deployment in an IP-aware multiservice access network, supporting broadcast TV, time-shifted TV and pay-per-view services. Transparent proxy caches collaborate providing distributed network storage and user interactivity, while offering an adequate end-to-end quality of experience. As a use case, a time-shifted TV solution is introduced in more detail. We discuss a distributed caching model that makes use of a sliding window concept and calculates the optimal trade-off between bandwidth usage efficiency and storage cost. A prototype implementation of a diskless proxy cache is evaluated through performance measurements.