Multimedia proxy caching mechanism for quality adaptive streaming applications in the Internet

摘要

The Internet has witnessed a rapid growth in deployment of Web-based streaming applications during recent years. In these applications, the server should be able to perform end-to-end congestion control and quality adaptation to match the delivered stream quality to the average available bandwidth. Thus the delivered quality is limited by the bottleneck bandwidth on the path to the client. This paper proposes a proxy caching mechanism for layered-encoded multimedia streams in the Internet to maximize the delivered quality of popular streams to interested clients. The main challenge is to replay a quality-variable cached stream while performing quality adaptation effectively in response to the variations in available bandwidth. We present a prefetching mechanism to support higher quality cached streams during subsequent playbacks and improve the quality of the cached stream with its popularity. We exploit inherent properties of multimedia streams to extend the semantics of popularity and capture both level of interest among clients and usefulness of a layer in the cache. We devise a fine-grain replacement algorithm suited for layered-encoded streams. Our simulation results show that the interaction between the replacement algorithm and prefetching mechanism causes the state of the cache to converge to an efficient state such that the quality of a cached stream is proportional to its popularity, and the variations in quality of a cached stream are inversely proportional to its popularity. This implies that after serving several requests for a stream, the proxy can effectively hide low bandwidth paths to the original server from interested clients.