Robust joint signal and interference alignment for MIMO cognitive radio network

In this work, a robust joint signal and interference alignment is designed for cognitive multiple-input multiple-output (MIMO) interference channel in which single primary link coexists with multiple secondary links. Considering channel imperfections and finite signal-to-noise ratio (SNR) in practice, we propose a worst-case joint design to not only minimize the leakage of interference signals but also ensure the desired signal falling into the orthogonal complement of interference subspace. Under the assumption of the norm-bounded channel uncertainties, the underlying problem is recast to convex form via semidefinite programming (SDP), and the optimum solutions are obtained iteratively. Simulation results reveal the effectiveness of the proposed joint design, and robustness of the worst-case design against channel uncertainties.