MIMO Multiway Distributed-Relay Channel with Full Data Exchange: An Achievable Rate Perspective

We consider efficient communications over the multiple-input multiple-output (MIMO) multiway distributed relay channel (MDRC) with full data exchange, where each user, equipped with multiple antennas, broadcasts messages to all the other users via the help of a number of distributive relays. We propose a physical-layer network coding (PNC) based scheme involving linear precoding for channel alignment, nested lattice coding for PNC, and lattice-based precoding for interference mitigation. We show that, with the proposed scheme, distributed relaying achieves the same sum-rate as cooperative relaying in the high SNR regime. We also show that the proposed scheme achieves the asymptotic sum capacity of the MIMO MDRC within a constant gap in the high SNR regime. Numerical results demonstrate that the proposed scheme considerably outperforms the existing schemes including decodeand-forward and amplify-and-forward. Index Terms Multiway distributed relay channel (MDRC), multiple-input multiple-output (MIMO), distributed relaying, nested lattice coding X. Zhao, J. Zhang and X. Yuan are with the School of Information Science and Technology, ShanghaiTech University, Shanghai, China, email: {zhaoxiang, zhangjw1, yuanxj}@shanghaitech.edu.cn. Y. Zhang is with the the Department of Information Engineering, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, e-mail: [email protected]. The work was partially presented in IEEE International Conference on Communications in China (ICCC2016). December 28, 2016 DRAFT