Multicast Interference Alignment in a Multi-Group Multi-Way Relaying Network

In this paper, a multi-group multi-way relaying network is considered. Multiple half-duplex nodes form a group and each node wants to share its message with all other nodes in its group via an intermediate half-duplex relay. The nodes of the whole network are equally distributed over the groups. In this paper, we propose a multicast interference alignment algorithm for a multi-group multi-way relay network, in which the minimum required number of antennas at the relay is independent of the number of nodes per group. This is an important property, because physical antenna resources are limited in general. In order to achieve this, we consider a transmission scheme with several multiple access phases and several multicast phases. In each of the multicast phases we create a MIMO interference multicast channel, by separating the antennas of the relay into clusters. Each of these clusters serves a specific group of nodes and transmits in such a way that the signals transmitted from different clusters are aligned at the non-intended multicast groups. It is shown that the proposed multicast algorithm outperforms a reference algorithm from the literature for a broad range of Signal-to-Noise Ratio (SNR) values, while still requiring less antennas at the relay.