Power-Efficient Multi-Quality Multicast Beamforming based on Scalable Video Coding and Superposition Coding

In this paper, we consider multi-quality multicast of a video stream from a multi-antenna base station (BS) to multiple groups of single-antenna users requiring different qualities of the video stream, using scalable video coding (SVC). Leveraging the layered structure of SVC and exploiting superposition coding (SC) as well as successive interference cancelation (SIC), we propose a power-efficient layerbased multi-quality multicast beamforming scheme and a power-efficient quality-based multi-quality multicast beamforming scheme. For each scheme, we formulate the corresponding optimal beamforming design as a non-convex power minimization problem, and obtain a globally optimal solution in a special case as well as a locally optimal solution in the general case. Then, we show that the minimum total transmission power of the quality-based optimization problem is the same as that of the layer-based optimization problem, but the computational complexity for solving the quality-based optimization problem is lower than that for solving the layer-based optimization problem. Finally, numerical results show that the proposed solutions achieve better performance than existing solutions.