A transceive strategy for regenerative multi-antenna multi-way relaying

In this paper, firstly, we introduce regenerative multi-way relaying. A half-duplex multi-antenna relay station (RS) assists multiple nodes which want to communicate to each other. Each node has a message and wants to decode the messages from all other nodes. The number of communication phases is equal to the number of nodes, N, such that when N = 2, we have the well known two-way relaying. In the first phase, multiple access (MAC) phase, all nodes transmit simultaneously to the RS and the RS decodes the data streams of all nodes. In the following (N - 1) broadcast (BC) phases, the RS transmits to each node the intended (N - 1) data streams from the other (N -1) nodes. Secondly, we propose a transceive strategy at the RS which couples the MAC and the BC phases. The strategy exploits the information about the achievable MAC signal to interference and noise ratio at the RS which enables the RS to transmit with the achievable MAC rate in each BC phase. As the strategy involves transmit beamforming at the RS, we intend to minimise the power at the RS. Since the power minimisation problem is NP-hard, we rewrite the problem into a semidefinite optimisation to solve it in reasonable time.