Uplink interference coordination for two-tier MIMO networks

In this paper, we consider interference alignment in the two-tier network consisting of a macrocell overlaid with femtocells to enhance the coverage and the capacity of cellular network. We propose an uplink interference mitigation algorithm that simultaneously allows the interference caused by macrocell users at each femtocell base station to align into a reduced dimensional subspace while maximizing the signal-to-interference-plus-noise ratio values at the macrocell base station. We also provide the feasibility condition of our proposed algorithm and discuss the achievable degrees of freedoms. Simulation results show that the proposed algorithm considerably improves the performance of femtocell base station by maximizing the signal-to-interference-plus-noise ratio value corresponding to each macrocell user at MBS.