Non-Regenerative Multi-Way Relaying: Space-Time Analog Network Coding and Repetition

In this letter, we investigate non-regenerative multi-way relaying when channel state information is not available at the multi-antenna relay station (RS). For stationary channels, space-time analog network coding (STANC) transmission is applied at the RS. For non-stationary channels, the RS applies repetition transmission. For both transmission schemes, in order to obtain the data streams of the other nodes, each node has to perform three receive processing operations successively: Zero Forcing (ZF) detection, back-propagated self-interference cancellation and joint detection. We assess the achievable sum rate performance of non-regenerative multi-way relaying for the proposed transmission schemes. It is shown that STANC with joint detection outperforms both benchmark transmissions, namely, ZF and Maximisation of Signal to Noise Ratio (MSNR) transceive beamforming with single stream decoding performed at each node. When the channels are non-stationary, the repetition transmission enables the multi-way communication and in medium to high SNR region, it outperforms MSNR.