Design of ESPAR based Blind Interference Alignment for cellular systems

Recently, a technique entitled "Blind Interference Alignment (BIA)" was proposed, which allows interference to be aligned within a reduced subspace without knowledge of the channel state information at the transmitter. The key to realizing the BIA scheme is the use of a receive antenna that is capable of switching among multiple channel-states (with channel diversity) in a pre-determined way. In this paper, we exploit the ESPAR antenna, which uses only a single radio frequency chain as the receiver to provide the necessary beampattern switching for the BIA technique. Moreover, in the proposed ESPAR based BIA scheme, beam-steering of each ESPAR receiver is designed according to its position relative to the transmitter to increase the received SNR. Furthermore, we study the proposed BIA scheme by applying the ESPAR antennas to a 2-D cellular setting in order to illustrate the ESPAR beam pattern design and associated improvements in the performance of the BIA scheme. In order to keep the number of coordinating BSs at a reasonable level, we study the case where only three adjacent BSs operate the BIA scheme coordinatively. This is found to be reasonable since the other inter-cell interference is not significant due to the ESPAR beam-steering and the longer propagation distance. The simulation shows that our scheme provides comparable sum rate to that of BIA scheme operated in all cells.