Adaptive Rate Control Scheme for Video Streaming Over Wireless Channels

摘要

Providing continuous video playback with graceful quality degradation over wireless channels is fraught with challenges. Video applications require stringent delay guarantees and a relatively high throughput. Wireless channels are error prone, time varying, and bandwidth limited. To improve the reliability of the wireless link, forward error correction (FEC) and automatic repeat request (ARQ) are often used. If designed for the worst channel conditions, FEC can provide constant throughput and bounded delay. However, this causes unnecessary overhead and reduces the maximum achievable throughput when the channel is in good conditions. On the other hand, it is difficult to achieve strict delay guarantees using ARQ schemes alone, especially when the channel is in deep fading. Playback buffer occupancy plays a major role in the target video quality. The retransmission of erroneous packets and the reduction in throughput due to FEC overhead can lead to playback buffer starvation as well as transmitter buffer fullness. Therefore, it is desirable to reduce the bit rate of the transmitted video signal and increase error protection when the channel is anticipated to be bad or the receiver playback buffer starvation is predicted. In this study, we introduce a scalable and adaptive source-channel rate control scheme for video transmission over wireless packet networks. In this scheme, the level of adaptiveness is optimized to reduce the bandwidth requirement while guaranteeing delay and loss bounds. Simulation and numerical investigations are carried out to study the interactions among various key parameters and verify the adequacy of the analysis.