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Content-aware and occupancy-based hybrid ARQ for video transmission

In this paper, an adaptive hybrid automatic repeat request (HARQ) scheme is proposed for unicast wireless video communication systems. In the proposed scheme, the receiver controls the HARQ feedback messages based on not only error detection, but also video content and playback deadline. The adaptation algorithm utilizes a delay model to estimate the transmission time of a video frame and its delivery budget time. Accordingly, the ARQ limit is adapted based on the playback buffer occupancy and importance of video packets where erroneously received packets may be falsely acknowledged to ensure continuous playback. The performance of the adaptive HARQ is evaluated with and without subpacket fragmentation. Subpacket-based HARQ outperforms packet-based HARQ in terms of delay and continuity of video playback. The adaptation algorithm improves the delay performance of both HARQ systems and eliminates buffer starvation with minimum spatial quality distortion.