Scalable video multicast using inter-layered superposition and network-coded cooperation over MIMO relay systems

The adoption of scalable video coding (SVC) for video multicast services is a promising solution for providing efficient streaming under channel heterogeneity, since SVC can support quality scalability with high coding efficiency. The scalability allows receivers to experience video quality according to their channel conditions. Nevertheless, the scalable video layers are inter-dependent; if a layer of the scalable video is lost, all subsequent layers that depend on the lost layer are downloaded but not rendered, which leads to a low video quality and bandwidth inefficiency. Consequently, unequal error protection among scalable video layers needs to be addressed in a bandwidth-efficient manner. This paper proposes a scalable video multicast scheme over relay-based cellular networks, consisting of two main components: inter-layered superposition in the first phase and digital network coding in the second phase. In this joint design, the proposed inter-layered superposition coding provides incremental service quality according to average channel conditions, as well as unequal error protection under channel heterogeneity. Furthermore, the network-coded cooperation, implemented by mixing all decoded signals at the relay, improves bandwidth efficiency by reducing the number of transmissions in the second phase. The proposed scheme aims to increase the number of users experiencing a maximal number of rendered video layers as well as bandwidth efficiency. We also derive the relevant channel capacities of scalable layers for performance analysis. Numerical results, consisting of a cumulative distribution function of channel capacity, achievable video data rate, and video quality measurement, confirm that our design objective can be achieved for video multicast over multiple-input and multiple-output relay-based cellular networks.