On prioritized coding for real-time streaming under packet erasures

We consider a real-time streaming system where high and low priority messages arrive at the source according to a periodic pattern, are transmitted over a packet erasure channel, and need to be decoded at the sink within a fixed delay. For a window-based erasure model, we show an upper bound on message sizes that can be asymptotically achieved with a proportional time-invariant intra-session code. For i.i.d. random erasures, we provide an upper bound on message sizes given probabilities of decoding the high and low priority messages respectively, and compare with the performance of our proportional coding scheme.