| As 360-degree videos grow dramatically in popularity,more and more mobile applications begin offering 360-degree video services.However,the limited capacity and the unstable network conditions make mobile wireless networks ill-suited to the requirements of 360-degree videos(high resolution and low delay).One common approach is to take advantage of the fact that the viewer only watches a small portion of the video around the field of view(FOV).Thus,the QoS of 360-degree videos can be further optimized with a smart bandwidth allocation mechanism to prioritize the content that viewer watches.Previous efforts on 360-degree videos focus on application-level improvements where the common core idea is to adapt the encoded bitrate to optimize video quality in the time-varying FOV,relieving the problem of bandwidth.However,these works fail to directly reduce the streaming delay.This is because they use TCP transport mechanisms that rely on frequent retransmission to stream 360-degree video on highly lossy mobile wireless network.As a result,much data misses the deadline and video quality degrade heavily.This paper proposes an FOV-aware multipath transport protocol to improve 360-degree videos transmission performance on mobile wireless network,which is mainly composed of two components: an adaptive FEC(Forward Error Correction)redundancy adjusting strategy,which utilizes our proposed FOV-aware video distortion model to instruct FEC redundancy setting.With this strategy,system can allocate FEC redundancy based on how close the video content is to the FOV region,allowing more key data received integrally and timely;a packet scheduling strategy which is FOVaware and allocates the key data to the paths with smaller delay and higher bandwidth,further guaranteeing the reliability of key data.Extensive experiment results show that the proposed protocol improves video quality(PSNR)by 20% to 30% over current mainstream UDP-based video streaming protocols and 40% over TCP-based FOV-aware DASH. |
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