Power-Efficient Multi-Quality Multicast Beamforming Based on SVC and Superposition Coding

In this paper, we consider multi-quality multicast of a video stream from a multi-antenna base station (BS) to multiple single-antenna users requiring the video at different quality levels, 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 layer-based multi- quality multicast beamforming scheme. To reduce the computational complexity, we also propose a power- efficient quality-based multi-quality multicast beamforming scheme, which further utilizes the layered structure of SVC and quality requirements of all users. Under each scheme, for given quality requirements of all users, we formulate the corresponding beamforming design as a non-convex power minimization problem, and obtain a globally optimal solution for a class of special cases as well as a locally optimal solution for 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, although the former requires a lower computational complexity. Finally, numerical results show that the proposed solutions achieve better performance than existing solutions.