Scalable Video Multicast on Broadcast Channels

We propose a framework for multicasting layers of scalable video over a broadcast channel to multiple users simultaneously. The framework ensures that all users receive the content, but at differentiated levels of quality depending on channel conditions. A coding scheme well-suited to this purpose is Scalable Video Coding (SVC). In particular, we employ medium-grain scalability (MGS), which allows us to generate quality-scalable layers from a single video sequence. For transport, we assume that both the transmitter and end-users are equipped with multiple-input multiple-output (MIMO) transceivers. The transmitter employs the zero-forcing (ZF) precoding technique, which yields good performance with low complexity. With these assumptions, the scheme proposed here computes a block-diagonal ZF-precoder at fixed intervals, subject to a power constraint at the transmitter. Crucially, the algorithm assigns quality-scalable layers of video to the end-users jointly with precoder computation. The framework also ensures that delay and buffer constraints are met, which is necessary for real-time video. In terms of solution approach, the problem turns out to be a difficult mixed-integer nonlinear optimization problem.