Interference nulling for offloaded heterogeneous users using macro generalized inverse precoder

Heterogeneous networks are a crucial paradigm that will allow future mobile networks to meet growing wireless traffic demands. An important issue in heterogeneous networks is the crosstier interference between femtocells and macrocells. In this paper, we show that a generalized inverse precoder at the macro base station can null interference to offloaded femtocell users. Under ideal conditions, the precoder can achieve perfect interference nulling, and achieve interference suppression using practical suboptimal methods under non-ideal conditions. Simulations show that even with realistic imperfect channel state information, our precoder achieves significant interference suppression while maintaining zero macro inter-user interference.