Feedback Interference Alignment: Exact Alignment for Three Users in Two   Time Slots
  We study the three-user interference channel where each transmitter has local feedback of the signal from its targeted receiver. We show that in the important case where the channel coefficients are static, exact alignment can be achieved over two time slots using linear schemes. This is in contrast with the interference channel where no feedback is utilized, where it seems that either an infinite number of channel extensions or infinite precision is required for exact alignment. We also demonstrate, via simulations, that our scheme significantly outperforms time-sharing even at finite SNR. 
Vasilis Ntranos, Viveck R. Cadambe, Bobak Nazer, Giuseppe Caire
cs.IT math.IT