Regenerative Multi-Group Multi-Way Relaying

We consider regenerative multi-group multi-way (MGMW) relaying. A half-duplex regenerative multi-antenna relay station (RS) assists multiple communication groups. In each group, multiple half-duplex nodes communicate with each other. The number of communication phases is defined by the maximum number of nodes among all groups. In the first phase, i.e., the multiple-access (MAC) phase, all nodes simultaneously transmit to the RS, and the RS decodes the data streams of all nodes. In the following broadcast (BC) phases, the RS transmits to the nodes. We propose three BC strategies, i.e., unicasting, multicasting, and hybrid uni/multicasting. For the multicasting strategy, either superposition or exclusive or (xor ) network coding is applied. On the one hand, we propose a transmit beamforming algorithm minimizing the RS's transmit power while guaranteeing that each node receives with a rate equal to the rate received at the RS for each particular data stream. The transmit beamforming algorithm is designed by coupling the MAC and BC phases. On the other hand, for the case where the RS's transmit power is fixed, we design low-complexity transmit beamforming algorithms: matched filter, zero forcing, minimization of mean square error, and MGMW-aware transmit beamforming. It is shown that the multicasting strategy with xor network coding improves the achievable sum rate and requires the least transmit power compared with other strategies.