In this letter, we present the first characterization for the achievableDegrees-of-Freedom (DoF) by Blind Interference Alignment (BIA) using staggeredantenna switching in the $K$-user Gaussian Interference Channel. In suchscheme, each transmitter is equipped with one conventional antenna and eachreceiver is equipped with one reconfigurable (multi-mode) antenna. Assumingthat 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 knowninterference alignment schemes with delayed channel state information attransmitters (CSIT). This result implies that the sum DoF is upper bounded by2, which means that the best we can do with BIA is to double the DoF achievedby orthogonal multiple access schemes. Moreover, we propose an algorithm togenerate the transmit beamforming vectors and the reconfigurable antennaswitching patterns, and apply this algorithm to the 4-user SISO InterferenceChannel, showing that $\frac{4}{3}$ sum DoF is achievable.
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