Robust MIMO Relay Precoder Design for Multiple Operator One-Way Relaying with Imperfect Channel State Information

In this paper, we propose a robust relay precoder in the multiple operator relay sharing system, where multiple base stations transmit to their target user terminals simultaneously with the assistance of an amplify-and-forward relay. The base stations and the user terminals are equipped with single antennas while the relay employs multiple antennas. The channel state information at the relay is assumed to be imperfect, where the additive channel state information error is modeled as Gaussian distributed. Based on this model, we propose a robust relay precoder design that minimizes the total average relay transmit power under a signal-to-interference-plus-noise ratio constraint at each user terminal. Simulation results show that the proposed robust method outperforms the non-robust solution significantly in terms of the outage probability of the signal to interference plus noise ratio. Furthermore, we demonstrate the sharing gain achieved by this robust method via spectrum and relay sharing between multiple operators compared to the case where the spectrum and the relay are accessed exclusively by each operator.