Hierarchical Video Caching and Transcoding for Delay-Constrained Content Delivery

Motivated by the features of video content that can have multiple versions with different qualities and be divided into several chunks, this paper proposes a caching and transcoding scheme for individual video chunks in the hierarchical wireless network. The proposed policy determines which contents, what quality, and how many chunks to be cached and transcoded depending on different cache sizes, computing resources, and communication overheads for different tiers. Considering adaptive quality selection at the transmitter end, we formulate the expected quality maximization problem, while guaranteeing delay-constrained video delivery. The proposed scheme controls tradeoffs between the following metrics: 1) transcoding and transmission time, 2) content quality and diversity of caching, and 3) caching more fractions and caching more contents. The simulation results show that the proposed scheme provides an improved content quality while guaranteeing the delay constraint, compared to traditional caching which stores the entire files only.