Robust joint signal and interference alignment in cognitive radio networks with ellipsoidal channel state information uncertainties
Shuai Ma, Huiqin Du, Tharmalingam Ratnarajah, Lei Dong · IET Communications · 2013
The authors propose a distributed robust joint signal and interference alignment design for multiple‐input–multiple‐output cognitive radio (CR) networks where single primary link coexists with multiple secondary links. Considering two practical challenges of interference alignment: imperfect channel state information (CSI) and finite signal‐to‐noise ratio, the proposed scheme aims to minimise both the leakage of interference signals and that of the desired signals, while maintaining interference to the primary user below a permissible level. Under the assumption of the ellipsoidal CSI uncertainties, the joint worst‐case optimisation problem is decomposed and reformulated as semi‐definite programming form by using S ‐lemma, orthogonal relaxation and semi‐definite relaxation. Simulation results verify the effectiveness of the joint design, and robustness of the worst‐case design against channel uncertainties.