Spatial interweave for a MIMO secondary interference channel with multiple primary users

In this paper we consider a Secondary Network, modeled as a K-user Multiple-Input-Multiple-Output (MIMO) interference channel (IFC) that coexists with a set of L multi antenna Primary receivers (PRx). The objective of our investigation is to design Interference Alignment (IA) beamforming matrices at the secondary transmitters such that the interference received at the PRx is confined in a subspace of proper dimension. To solve this optimization problem we propose an iterative algorithm that is based on the algorithm described in [1]. The cognitive radio (CR) communication under investigation can take place exploiting the Spatial Domain of the complete network. For this reason it comes under the purview of Spatial Interweave CR paradigm. In addition we propose a set of feasibility conditions that the CR system should attain in order to admit an IA solution that satisfies the interference constraints on the primary users.