CooPEC: Cooperative Prefetching and Edge Caching for Adaptive 360° Video Streaming

Dynamic Adaptive Streaming over HTTP (DASH) has emerged as the de facto solution for streaming 360°videos. Viewers of 360° videos view only a fraction of each video segment, i.e., the part that corresponds to their Field of View (FoV). To facilitate FoV-adaptive streaming, a segment can be divided into multiple tiles with the FoV corresponding to a subset of tiles. Streaming each segment in its entirety from the video server to a client can incur high communication overheads both in terms of bandwidth and latency. Caching at the network edge can reduce these overheads. However, as edge cache capacity is limited, only a subset of tiles encoded at a subset of supported resolutions may be present in the cache. A viewer, depending on its FoV,may experience cache hit and low download latency for some segments, and a cache miss resulting in high download latency from video server for other segments. This can result in the DASH client unnecessarily triggering quality switches for the following reason: low (high) latency download from edge cache (server, respectively) may be misinterpreted as high (low, respectively) network throughput estimate. In this paper, we propose CooPEC (COOperative Prefetching and Edge Caching), a prefetching and complementary caching solution which uses viewers' FoV entropy to: (i) enable a bitrate oscillation-free video streaming, (ii) reduce core network bandwidth consumption, and (iii) enhance QoE for users.