Multicast Multigroup Beamforming for Per-antenna Power Constrained Large-scale Arrays

Large in the number of transmit elements, multi-antenna arrays with per-element limitations are in the focus of the present work. In this context, physical layer multigroup multicasting under per-antenna power constrains is investigated herein. To address this complex optimization problem, low complexity alternatives to semi-definite relaxation are proposed. The goal is to optimize the per-antenna power constrained transmitter in a maximum fairness sense, which is formulated as a non-convex quadratically constrained quadratic problem. Therefore, the recently developed tool of feasible point pursuit and successive convex approximation is extended to account for practical per-antenna power constraints. Interestingly, the novel iterative method exhibits not only superior performance in terms of approaching the relaxed upper bound, but also a significant complexity reduction, as the dimensions of the optimization variables increase. Consequently, multicast multigroup beamforming for large-scale array transmitters with per-antenna dedicated amplifiers is rendered computationally efficient and accurate. A preliminary performance evaluation in large-scale systems for which the semi-definite relaxation constantly yields non rank-1 solutions is presented.

In the context of SANSA, this work employs smart antenna systems to provide point to multipoint access for terrestrial networks. The goal is to maximize the fairness in the system by managing the interference among the users. As the title suggests, such a framework suits well with multicasting scenarios considered in SANSA. More specifically, it is closely related to WP3, Tasks 3.1 and 3.2 as well as WP4, Task 4.3.