Improving Semi-Blind Interference Suppression on Multi-Cell Massive MIMO Systems by Multi-Antenna Users

This paper presents improved semi-blind uplink interference suppression scheme which was previously proposed. When the number of spatial multiplexing is increased in a Massive MIMO system to increase capacity, the number of orthogonal sequences required for channel estimation has an upper limit, so they are used repeatedly in each cell, resulting in inter-cell interference (ICI) caused by pilot signals so called pilot contamination. It prevents sufficient suppression of not only ICI but also inter-user interference (IUI). Our previously proposed scheme is based on intra-cell channel state information (CSI) which contains pilot contamination. Blind adaptive array (BAA) signal processing such as constant modulus algorithm (CMA) can well suppress residual interference with capturing desired signals. This paper presents interference suppression performance improvement by employing beamforming at the user terminal side. User beamforming works more effectively for semi-blind interference suppression because it can suppress ICI in advance, although it cannot suppress IUI. Computer simulations demonstrates its effectiveness.