A dynamic-priority based approach to streaming video over cellular network

Abstract

In a wireless cellular environment, a mobile device experiences burst error phase in which many consecutive packets are lost. This can drastically decrease the quality of the streamed video. Some researchers have proposed a time-window based Static-Prioritized approach of sending video packets, in which the video packets are reordered in every time-window from the highest priority to the lowest priority, and sent strictly in that order (high to low) till the window timer expires. This Static-Prioritized approach may yield sub-optimal quality (in terms of the total number of decodable frames received) of streamed video if the wireless channel is frequently experiencing burst error phase. This paper proposes an approach which is an improvement to the existing Static-Prioritized transmission approach and is called Dynamic-Prioritized scheme (DPS). The key idea in the proposed Dynamic-Prioritized approach (DPS) is to send the most important frame packets (e.g. 'I' frame packets) during good channel condition and the least important frame packets (e.g. 'B' frame packets) during the bad channel condition (burst error period). DPS works exactly as SPS works if there is no burst error detected. But if a burst error is detected, DPS does the following 'key' things - (1) sends least priority decodable frames till the end of burst period and (2) switches back to sending high priority frames when the burst error period is over. The proposed approach performs better, even in case when there are frequent wireless burst error phase. DPS may yield more number of total decodable frames than SPS; the reason being that the probability of less important frames ('B' frames) reaching the client during burst error period is higher (due to their small size and hence fewer number of packets needed to send a single frame) than the probability of more important frames ('I' frames) reaching the client (due to their large size and hence more number of packets needed to send a single frame).