Rate-sensitive ARQ for real-time video streaming

In this paper, we study the problem of designing an efficient ARQ algorithm for supporting real-time video streaming applications. This problem differs from traditional non-real-time error control problem in which a late arrival packet can seriously degrade the video playback quality. It is interesting to notice that if a lost packet is detected while the client buffer is running at a high position, then the probability to recover the lost packet is also high. In this paper, we present a new error control algorithm, called BREC (Buffer-controlled Retransmission-based Error Control), to dynamically control the buffer running at a specific level. By the experiments on a true VOD system in which we implement the BREC scheme, the packet loss rate can be reduced by an order of magnitude. We also show that the performance can be further improved by detecting the rate of changes in running buffer positions and use it to enhance the ability of buffer position control. Both analytical model and experimental results show that our mechanism significantly decrease packet loss and improves QoS even if a client, such as set-top box, PDA (Personal Data Assistant) or cellular phone, preserves only a limited amount of playback buffer (200K bytes of memory is used in our experiments).