A Prefetching Protocol for Continuous Media Streaming in Wireless Environments

Streaming of continuous media over wireless links is a notoriously difficult problem. This is due to the stringent Quality of Service requirements of continuous media and the unreliability of wireless links. We develop a streaming protocol for the real–time delivery of prerecorded continuous media from (to) a central base station to (from) multiple wireless clients within a wireless cell. Our protocol prefetches parts of the ongoing continuous media streams into prefetch buffers in the clients (base station). Our protocol prefetches according to a Join– the–Shortest–Queue policy. By exploiting rate adaptation techniques of wireless data packet protocols, the Join– the–Shortest–Queue policy dynamically allocates more transmission capacity to streams with small prefetched reserves. Our protocol uses channel probing to handle the location–dependent, time–varying, and bursty errors of wireless links. We evaluate our prefetching protocol through extensive simulations with VBR MPEG and H.263 encoded video traces. Our simulations indicate that for bursty VBR video with an average rate of 64 kbit/sec and typical wireless communication conditions our prefetching protocol achieves client starvation probabilities on the order of ¢¡¤£¦ ¥ and a bandwidth efficiency of 90 % with prefetch buffers of 128 kBytes