Robust distributed beamforming design in amplify-and-forward relay systems with multiple user pairs

In this work, a signal-to-interference-plus-noise ratio (SINR)-based robust distributed beamforming scheme is proposed for one-way amplify-and-forward (AF) relay systems with multiple user pairs. The proposed scheme obtains its optimal beam vectors by utilizing convex semi-definite programming (SDP) optimization with newly derived bounds for signal and interference powers. Compared with existing works, the proposed scheme has much higher probability of obtaining the optimal solution than schemes applying approximate bounds exploiting Cauchy-Swartz (CS) inequality. In addition, in terms of transmit power consumption, the proposed scheme requires less transmit power than existing works while still satisfying the SINR constraints. Simulation results also demonstrate that the proposed SDP-based method outperforms the existing SDP-based methods.