@article{li_2021, 
  title={Two New Kinds of Interference Alignment Schemes for Cellular K-user MIMO   Downlink Networks}, 
  abstractNote={It is known that interference alignment (IA) plays an important role in
improving the degree of freedom (DoF) of multi-input and multi-output (MIMO)
systems. However, most of the traditional IA schemes suffer from the high
computational complexity and require the global and instantaneous channel state
information (CSI), both of which make them difficult to be extended to cellular
MIMO systems. To handle these issues, two new interference alignment schemes,
i.e., the retrospective interference regeneration (RIR) scheme and the
beamforming based distributed retrospective interference alignment (B-DRIA)
scheme, are proposed for cellular K-user MIMO downlink networks. For the RIR
scheme, it adopts interference elimination algorithm to erase redundant symbols
in inter-cell interference (ICI) signals, and then uses interference
regeneration algorithm to avoid secondary interference. The RIR scheme obtains
greater DoF gain than the retrospective interference alignment (RIA) scheme,
but incurs performance degradation when the transceiver antennas ratio (TAR)
approaches 1. Therefore, the B-DRIA scheme is further proposed. For the B-DRIA
scheme, the cellular beamforming matrix is introduced to eliminate the ICI, and
meanwhile distributed retrospective interference alignment algorithm is adopted
to align inter-user interference (IUI). The simulation results show that the
B-DRIA scheme obtains larger DoF than the RIR scheme locally. Specifically,
when TAR approaches 1, two schemes obtain the same DoF. While TAR approaches 2,
the DoF of the B-DRIA scheme is superior than the RIR scheme.}, 
  author={Li}, 
  year={2021}, 
  month={Jun}
  }