Evaluating QUIC-based Downstream Transport Strategies for Low-Latency Game Streaming under Network Impairments

Sammanfattning

Background. Cloud gaming moves game simulation and rendering to a remote server, making the downstream video path part of the interactive gameplay loop. Delay, jitter, packet loss, and frame timing can therefore affect both technical stream behaviour and the gameplay experience. Objectives. This thesis evaluates how QUIC streams and QUIC datagrams affect low-latency game streaming under controlled network impairments, with WebRTC used as a clear-condition baseline. The focus is on transport behaviour, gameplay performance, and subjective post-condition ratings. Methods. A Unity-based game-streaming prototype was implemented with a WebRTC baseline and two QUIC-based downstream strategies using Rust sidecar processes. Delay, jitter, and packet loss were introduced with Linux traffic control and NetEm. Repeated objective measurement runs collected glass-to-glass latency, display jitter, missing frames, freezes, and frame timing behaviour. A user study with 19 participants connected these measurements to score, accuracy, and subjective ratings. Results. The results show an impairment-dependent trade-off. Under delay and jitter, QUIC streams suffered severe tail latency and display instability caused byreliable ordered delivery, while QUIC datagrams remained more timely. Under random packet loss, QUIC datagrams instead suffered missing frames and freezes due to loss amplification across fragmented frame chunks, while QUIC streams preserved frame continuity. Conclusions. Downstream transport design for cloud gaming must balance reliability and timeliness. Reliable delivery can preserve continuity under loss but may create harmful latency, while unreliable datagrams can remain timely but are vulnerable to frame loss. Objective transport metrics should therefore be interpretedtogether with gameplay performance and subjective post-condition ratings