Two New Kinds of Interference Alignment Schemes for Cellular $K$-User MIMO Downlink Networks

It is known that interference alignment (IA) plays an important role in improving the degree of freedom (DoF) multi-input and multi-output (MIMO) systems. However, most traditional IA schemes suffer from high computational complexity require global instantaneous channel state information (CSI), both which make them difficult to be extended cellular MIMO To handle these issues, two new schemes, i.e., retrospective regeneration (RIR) scheme beamforming based distributed (B-DRIA) scheme, are proposed for $K$ -user downlink networks. For RIR it adopts elimination algorithm erase redundant symbols inter-cell (ICI) signals, then uses avoid secondary interference. The obtains greater DoF gain than (RIA) but incurs performance degradation when transceiver antennas ratio (TAR) approaches 1. Therefore, B-DRIA further proposed. matrix introduced eliminate ICI, meanwhile RIA adopted align inter-user (IUI). simulation results show larger locally. Specifically, TAR 1, obtain same DoF. While 2, superior scheme.