Opportunistic interference alignment in cognitive MIMO with finite rate feedback

Opportunistic interference alignment (OIA) and interference subspace projection techniques developed for cognitive radio networks (CRN) works when the transmitters have the perfect knowledge of the channels, which is quite unrealistic in real-time. In this paper, we investigate limited feedback precoding schemes for CRN with a primary and a cognitive MIMO links. Based on the precoding scheme used in the primary link, the primary receiver feedbacks the codebook index through a finite rate feedback, corresponding to the precoder matrix that maximizes the mutual information between the primary terminals. Subsequently, with the knowledge of free spatial directions in the primary link, the primary receiver designs a precoder matrix and quantizes its column vectors using a vector codebook and informs indices to the cognitive transmitter through a finite rate feedback. We present numerical simulation results of the date rate achieved in both the links for various system settings.