  This paper investigates the achievable rate region of the multiple-input
single-output (MISO) interference channel aided by intelligent reflecting
surfaces (IRSs). We exploit the the additional design degree of freedom
provided by the coordinated IRSs to enhance the desired signal and suppress
interference so as to enlarge the achievable rate region of the interference
channel. To this end, we jointly optimize the active transmit beamforming at
the transmitters and passive reflective beamforming at the IRSs, subject to the
constant modulus constraints of reflective beamforming vectors. To address the
non-convex optimization problem, we propose an iterative algorithm to optimize
the transmit beamforming via second-order cone program (SOCP) and the
reflective beamforming via the semi-definite relaxation (SDR). Numerical
results demonstrate that the performance of the IRS-aided interference channel
with the proposed algorithm can significantly outperform the conventional
interference channel without IRS.
