A rate control scheme for video streaming over wireless channels

Forward error correction (FEC) and automatic repeat request (ARQ) are typically used to improve the reliability of the wireless link. During fading periods, it is difficult to achieve strict delay guarantees using ARQ schemes alone. On the other hand, FEC can provide constant throughput and bounded delay. However, if designed for the worst channel conditions, this causes unnecessary overhead and reduces the maximum achievable throughput when the channel is in good conditions. The target video quality is greatly affected by the instantaneous playback buffer occupancy. Retransmissions of erroneous packets and the reduction in throughput due to FEC overhead can lead to playback buffer starvation. In this study, we introduce a scalable source-rate control scheme for video transmission over wireless packet networks. The scheme aims at maximizing the source bit rate at the encoder while preventing occurrences of starvation at the playback buffer. We carry out the analysis while taking into account the channel variations during video-frame transmission. We characterize the evolution of the transmission process by a finite-state Markov chain (FSMC) that facilitates the analysis. Then, we provide a time average expression that contains the key parameters of the proposed scalable scheme. In our scheme, the amount of frame scaling is optimized while guaranteeing certain 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.