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.

In this paper, we propose a taxonomy for 360° videos that categorizes videos based on moving objects and camera motion. We gathered and produced 28 videos based on the taxonomy, and recorded viewport traces from 60 participants watching the videos. In addition to the viewport traces, we provide the viewers' feedback on their experience watching the videos, and we also analyze viewport patterns on each category.

In recent years, there has been growing popularity of Virtual Reality (VR), enabled by technologies like 360° video streaming. Streaming 360° video is extremely challenging due to high bandwidth and low latency requirements. Some VR solutions employ adaptive 360° video streaming which tries to reduce bandwidth consumption by only streaming high resolution video for user's Field of View (FoV). FoV is the part of the video which is being viewed by the user at any given time. Although FoV-adaptive 360° video streaming has been helpful in reducing bandwidth requirements, streaming 360° video from distant content servers is still challenging due to network latency. Caching popular content close to the end users not only decreases network latency, but also alleviates network bandwidth demands by reducing the number of future requests that have to be sent all the way to remote content servers. In this paper, we propose a novel caching policy based on users' FoV, called FoV-aware caching policy. In FoV-aware caching policy, we learn a probabilistic model of common-FoV for each 360° video based on previous users' viewing histories to improve caching performance. Through experiments with real users' head movement dataset, we show that our proposed approach improves cache hit ratio compared to Least Frequently Used (LFU) and Least Recently Used (LRU) caching policies by at least 40% and 17%, respectively.

Virtual reality and 360-degree video streaming are growing rapidly, yet, streaming high-quality 360-degree video is still challenging due to high bandwidth requirements. Existing solutions reduce bandwidth consumption by streaming high-quality video only for the user's viewport. However, adding the spatial domain (viewport) to the video adaptation space prevents the existing solutions from buffering future video chunks for a duration longer than the interval that user's viewport is predictable. This makes playback more prone to video freezes due to rebuffering, which severely degrades the user's Quality of Experience especially under challenging network conditions. We propose a new method that alleviates the restrictions on buffer duration by utilizing scalable video coding. Our method significantly reduces the occurrence of rebuffering on links with varying bandwidth without compromising playback quality or bandwidth efficiency compared to the existing solutions. We demonstrate the efficiency of our proposed method using experimental results with real world cellular network bandwidth traces.

Virtual reality and 360-degree video streaming are growing rapidly; however, streaming 360-degree video is very challenging due to high bandwidth requirements. To address this problem, the video quality is adjusted according to the user viewport prediction. High quality video is only streamed for the user viewport, reducing the overall bandwidth consumption. Existing solutions use shallow buffers limited by the accuracy of viewport prediction. Therefore, playback is prone to video freezes which are very destructive for the Quality of Experience (QoE). We propose using layered encoding for 360-degree video to improve QoE by reducing the probability of video freezes and the latency of response to the user head movements. Moreover, this scheme reduces the storage requirements significantly and improves in-network cache performance.