Robust beamforming designs for nonregenerative multipair two-way relaying systems

Abstract

In this paper, we consider non-regenerative multipair two-way relaying systems where a relay node supports K pairs of two-way communications at the presence of imperfect channel state information (CSI). We employ a stochastic approach to model the channel uncertainties and study a robust beamforming design at the relay. It is shown that the proposed beamformer provides a reduction in the computational complexity as well as a good robustness against channel errors compared to conventional designs. To reduce the estimation overhead at the users, we also suggest an efficient downlink training method to inform the users of the channel dependent self-interference cancellation (SIC) parameters. With the training method, the additive noise may incur malfunction of the SIC. To address this issue, we develop an intelligent selection criterion which decides whether the SIC should be adopted or not. Finally, from simulation results, we demonstrate the efficiency of our proposed schemes.0018-9545 (c)

Decoupled beamforming techniques for distributed MIMO two-way multi-relay networks with imperfect CSI

“…By taking account into the channel uncertainties, the imperfect CSI scenario has been studied in [20][21][22][23][24][25]. In [20], joint relay and jammer selection and power control for physical layer security issues in two-way relay networks are studied to maximize the secrecy capacity of the network.…”

“…Particularly, the robust two-way relay precoder design for a cognitive radio network is investigated in [24], where two different types of CSI errors with corresponding robust designs are proposed. It is worth noting, in [25], the joint optimal robust beamforming designs in multipair two-way nonregenerative relaying systems, where an insightful closed form solution is obtained that is not only robust to the imperfect CSI but also adjustable to various CSI circumstances at the users and the relay.…”