Interference alignment through staggered antenna switching for MIMO BC with no CSIT

In this paper, we explore the degrees of freedom (DoF) of the broadcast channel (BC) where the transmitter is equipped with M antennas and there are K receivers, each equipped with N reconfigurable antennas capable of switching among M preset modes. Without any knowledge of the channel coefficient values but only receiver antenna switching modes at the transmitter, we propose an interference alignment scheme for this channel. We show that if N<;M, then a total of (MNK)/(M+KN-N) DoF are achievable, almost surely. The key to this interference alignment scheme is the ability of the receivers to switch between reconfigurable antenna modes to create short term channel fluctuation patterns that are exploited by the transmitter. Compared to the results we showed for MISO BC, the supersymbol of MIMO BC may have diverse structures depending M and N, and it can be determined from that of MISO BC through an iterative mapping function.