Partially Reliable Transport Layer for QUICker Interactive Immersive Media Delivery.

requirements such as high bandwidth (i.e., several Gbps) and low latency (i.e., five milliseconds). Today, most video-streaming applications leverage the transmission control protocol (TCP) for reliable end-to-end transmission. However, the reliability of TCP comes at the cost of additional delay due to factors such as connection establishment, head-of-line (HOL) blocking, and retransmissions under sub-optimal network conditions. Such behavior can lead to stalling events or freezes, which are highly detrimental to the user's Quality of Experience (QoE). Recently, QUIC has gained traction in the research community, as it promises to overcome the shortcomings of TCP without compromising on reliability. However, while QUIC vastly reduces the connection establishment time and HOL blocking, thus increasing interactivity, it still underperforms while delivering multimedia due to retransmissions under lossy conditions. To cope with these, QUIC offers the possibility to support unreliable delivery, like that of the user datagram protocol (UDP). While live-video streaming applications usually opt for completely unreliable protocols, such an approach is not optimal for immersive media delivery since it is not affordable to lose certain data that might affect the end user's QoE. In this paper, we propose a partially reliable QUIC-based data delivery mechanism that supports both reliable (streams) and unreliable (datagrams) delivery. To evaluate its performance, we have considered two immersive-video delivery use cases, namely tiled 360-degree video and volumetric point clouds. Our approach outperforms state-of-the-art protocols, especially in the presence of network losses and delay. Even at a packet loss ratio as high as 5%, the number of freezing events for a 120-second video is almost zero as against 120 for TCP.