Semi-blind MU-MIMO based on limited features of the user multi-path intensity profiles

Downlink MU-MIMO can achieve degrees of freedom (DoF) gains without needing multi-antenna terminals. To do so, conventional MU-MIMO requires sufficiently accurate knowledge of fast-changing channel state information at the transmitter (CSIT). Recently, MU-MIMO schemes based on blind interference alignment (BIA) have been proposed that achieve DoF gains without CSIT. BIA, however, requires the use of receive antennas able to switch between multiple modes. We consider a form of MU-MIMO that can yield DoF gains without multi-mode antennas by using only knowledge of slowly-varying features of users' multipath intensity profiles. We describe the code constructions and operation of such schemes which exploit channel variations in frequency analogous to those created by antenna-mode switching over time.