Exploiting zero forcing beamforming and TV white space band for multiuser MIMO cognitive cooperative radio networks

Cooperative Cognitive Radio Networks (CCRN) is a promising concept recently studied to enhance cellular networks. The basic idea is that a primary user (PU) transmits his traffic assisted by some selected secondary users (SUs), which transmit also their own traffics using the same channel. The existing works in the literature propose the use of the same channel by applying a time division approach, where a time slot is dedicated to secondary traffic transmission, which degrads system performance. To overcome this problem, the use of multiple antennas enables simultaneous primary and secondary transmissions. Furthermore, the integration of beam-forming techniques removes the interference generated by this simultaneous transmissions. However, for almost systems proposed so far, only the PU and one SU can transmit simultaneously. In this paper, we propose a new scheme of CCRN where SUs communicate with a fusion center (FC) over a TV White Space (TVWS) band and perform a modulation matrix that allows simultaneous transmissions of the PU and all SUs with no interferences. Finally, we prove by theoretical studies and simulations that the suggested model improves significantly the rate of secondary users yet retaining good performances for the primary link.