Achievable Degrees-of-Freedom of the K-user SISO Interference Channel   with Blind Interference Alignment using Staggered Antenna Switching
  In this letter, we present the first characterization for the achievable Degrees-of-Freedom (DoF) by Blind Interference Alignment (BIA) using staggered antenna switching in the $K$-user Gaussian Interference Channel. In such scheme, each transmitter is equipped with one conventional antenna and each receiver is equipped with one reconfigurable (multi-mode) antenna. Assuming that the channel is known to the receivers only, we show that BIA can achieve $\frac{2K}{K+2}$ DoF, which surpasses the sum DoF achieved by previously known interference alignment schemes with delayed channel state information at transmitters (CSIT). This result implies that the sum DoF is upper bounded by 2, which means that the best we can do with BIA is to double the DoF achieved by orthogonal multiple access schemes. Moreover, we propose an algorithm to generate the transmit beamforming vectors and the reconfigurable antenna switching patterns, and apply this algorithm to the 4-user SISO Interference Channel, showing that $\frac{4}{3}$ sum DoF is achievable. 
Ahmed M. Alaa, Mahmoud H. Ismail
cs.IT math.IT