Hybrid precoding for multi-group physical layer multicasting

Next generation of wireless networks will rely on large-scale antenna systems, either in the form of massive multiple-input-multiple-output (MIMO) or millimeter wave (mmWave) systems. As digital precoders require a dedicated radio frequency (RF) chain per antenna element, the conventional fully-digital precoding schemes are not suitable for physical layer multicasting in these systems. To address this problem, in this paper we present a hybrid precoding structure for multi-group physical layer multicasting that significantly reduces the number of required RF chains. More specifically, we show that in a multi-group multicasting system with N transmit antennas, G multicasting groups, and an arbitrary number of users in each group, one can achieve the performance of any fully-digital precoder with just G radio frequency chains using the proposed hybrid multi-group multicasting structure, given N >G.