Spatial Shaping and Precoding Design for Underlay MIMO Interference Channels

In this paper, we study coexistence issues between an underlay single-beam interference channel (IC) and a primary point-to-point link (PPL) that has a rate constraint. We derive spatial shaping constraints at the secondary transmitters and show that they generalize the so-called interference temperature (IT) when the PPL transmits multiple streams. We propose a successive convex approximation algorithm to compute the spatial shaping matrices that maximize the allowed transmit power of the IC while ensuring the rate constraint of the PPL. Then, we provide general interference leakage minimization (MinIL) and maximum signal-to-interference-plus-noise ratio (MaxSINR) algorithms that can incorporate both types of constraint. An additional power control step is included in the optimization procedure to further improve the sum-rate of the IC. Different numerical examples are provided to illustrate the effectiveness of the proposed techniques and to compare the performance improvement when the IC is subject to spatial shaping constraints in comparison to IT.