Robust beamforming for two-user MISO broadcasting channel with delayed CSIT

Recently proposed MAT¹ scheme achieves high degrees of freedom (DoF) by exploiting delayed channel state information at transmitter side (CSIT) and the concept of interference alignment (IA), where the interference vectors of different time slots are aligned. As the starting work, MAT scheme considers no flexibility when reconstructing symbols at the third time slot, which may lead to performance degradation once the channel varies. In this paper, a probabilistic optimization problem is proposed with the assumption that the unknown channel entries follow given distribution. Instead of maximizing the sum rate directly, we strive to maximize the signal power while keeping the high probability that the interference power is lower than a pre-specified threshold. The Monte Carlo simulation results show that the proposed scheme outperforms the MAT scheme and dual SINR scheme with various channel uncertainties.