Interference alignment with combined receivers for heterogeneous networks

We propose a novel combined receiver which applies zero forcing (ZF) to null the dominant interferers, followed by minimum-mean-square-error (MMSE) processing to reduce the effect of the remaining interference and noise. The receiver is used in conjunction with an interference alignment (IA) scheme in a multicell environment. Simulation results considering a range of interferer profiles show that the combined receiver outperforms an MMSE receiver, due to its ability to eliminate the dominant interferers. The complete nulling of many dominant interferers in a multi-user, multicell case requires a large number of receive antennas. If the antennas are closely located in a compact array, then spatial correlation is important and its impact on the IA scheme is also considered.