Degrees of freedom for K-user SISO interference channels with blind interference alignment

We derive the degrees of freedom (DoF) for K-user single-input single-output interference channels with a reconfigurable antenna at receivers, assuming linear coding strategies without channel state information at transmitters. Our DoF converse builds upon the inherent feature that channel state's changing patterns of the links towards the same receiver are always identical. We prove the linear sum DoF is upper-bounded by n* K/K+n*(n*-1), n* where n* is the optimal number of preset modes among N. Moreover, we propose a linear scheme that achieves the upper-bound if K/n* is an integer. For the other cases, we give a guideline for the achievable scheme.