Non-regenerative multi-way relaying with linear beamforming

In this paper, we introduce non-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, all nodes transmit simultaneously to the RS and in the following (N-1) phases the RS applies transceive beamforming and transmits to all nodes. The achievable sum rate for asymmetric traffic and symmetric traffic cases are derived for N-phase multi-way relaying. Three low complexity linear transceive beamformers based on Zero Forcing (ZF), Minimum Mean Square Error (MMSE) and Maximisation of Signal to Noise Ratio (MSNR) criteria are designed for N-phase multi-way relaying. From sum rate analysis, MMSE outperforms the other beamformers at the expense of using feedback channel to obtain the noise variance of the nodes. If interference cancellation is performed at all nodes, MSNR achieves the highest performance gain.