Robust leakage-based transmit beamforming with probabilistic constraint for downlink multi-user MIMO system

Multi-user multiple-input and multiple-output (MU-MIMO) wireless systems have the potential to provide a substantial gain by using transmit beamforming to allow multi-user communication in the same frequency and time slots. The main challenge for transmit beamforming design is to suppress the co-channel interference (CCI) from other users. In order to completely cancel the CCI at each user, perfect channel state information (CSI) is required at base station, which is generally not available in practice. To overcome the performance degradation caused by the imperfections, the most common approach is the worst-case method, which leads to conservative result as the extreme (but rare) conditions may occur at a very low probability. In this work, we propose a probabilistic-constrained beamforming based on signal-to-leakage ratio (SLR) criterion under consideration of inaccurate channel information. The simulation results show that the proposed beamformer achieves the lowest bit error rate (BER) and leaks the least transmit power from the desired user to all other users among the state-of-art transmit beamformers.