Achievable Degrees of Freedom of the $K$-User SISO Interference Channel With Blind Interference Alignment Using Staggered Antenna Switching

In this paper, we characterize the achievable (linear) degrees of freedom (DoFs) of the K-user single-input single-output (SISO) interference channel with blind interference alignment (BIA) using staggered antenna switching. In this scheme, each transmitter is equipped with one conventional antenna, and each receiver is equipped with one reconfigurable (multimode) antenna. Assuming that the channel is known to the receivers only, we show that by using linear BIA with staggered antenna switching at the receiver, a sum DoF of 2K/(K + 2) is achievable. This result implies that in using BIA, we can double the DoF achieved by orthogonal multiple-access schemes for a large number of users. Moreover, we propose a systematic algorithm to generate the transmit beamforming vectors and the reconfigurable antenna switching patterns, showing that it can achieve the 2K/(K + 2) sum DoF for any K. Finally, we apply this algorithm to the four-user SISO interference channel and demonstrate that 4/3 sum DoF is indeed achievable.