System-level studies for single user and multiuser interference alignment in a heterogeneous network

In this paper we study single user and multiuser interference alignment strategies at system level. Interference alignment (IA) refers to a transmission strategy where precoders and receivers are designed cooperatively between transmission points such that interference is aligned in a smaller vector space at each receiver than it would without IA. Depending on the scheme, the receivers are not necessarily needed to align the interference. In single user interference alignment, the interference to be aligned is from the neighboring transmission points and in the multiuser case, both co-channel and interpoint interference is aligned such that own signal can be received interference free. One known problem for IA is that it is prone to external interference, that is, interfering sources that are not included in the cooperation. The performance evaluations shown in this paper are based on 3GPP LTE-Advanced compliant system level simulator. We study the single user and multiuser interference strategies with varying external interference conditions.