Playback delay in on-demand streaming communication with feedback

We consider a streaming communication system where the source packets must be played back sequentially at the destination and study the associated average playback delay. We assume that all the source packets are available before the start of transmission at the transmitter and consider the case of an i.i.d. erasure channel with perfect feedback. We first consider the case when the receiver buffer can be arbitrarily large, and show that the average playback delay remains bounded in the length of the stream provided that the channel bandwidth is greater than a critical threshold. Our analysis involves the application of martingale theory to study the transient behaviour of a one dimensional random walk with drift. Conversely when the channel bandwidth is smaller than the above threshold, the average playback delay increases linearly with the stream length. We also consider the finite buffer case and analyse the playback delay of a greedy dynamic bandwidth scheme. We further show through simulations that the achievable delay with a finite receiver buffer is close to the infinite buffer case for moderately large buffer values.