Interference mitigation in femto-macro coexistence with two-way relay channel

Motivated by the femtocell networks where cross-tier interference management is crucial to achieve higher system throughput, we consider a basic interference model consisting of a MIMO two-way relay communication network in presence of a one-way point-to-point MIMO communication link. We propose an upper-bound on the maximum degrees of freedom of this channel. Precoders using signal-space alignment strategies at the transmitter and zero-forcing (ZF) receivers are shown to achieve the maximum degrees-of-freedom. The proposed solution is particularly interesting since it allows the macro transmitter to be oblivious to the interfering two-way link, which is an important feature for obtaining distributed solutions.