Interference alignment with range expansion in a heterogeneous MIMO network

Managing smaller cells such as micro and picocells in conventional macro cellular networks is expected to provide better quality of data service. However, frequency reuse-1 operation of smaller cells with the macrocells can create additional "cell edge" area that can degrade the system performance significantly. This paper proposes an interference avoidance scheme based on interference alignment and region based zero-forcing in a heterogeneous cellular system consisting of two overlaying macro and picocells with multiple antennas. The proposed transmission strategy effectively suppresses the cross-tier interference at both macro and pico users who are in severe interference limited region, providing the benefits of coverage expansion of picoocells. Simulation results show that the proposed interference avoidance scheme provides a significant performance gain over the non-coordinated scheme in the two macro/picocells network.