Spectrum Sharing Techniques for Broadcast Cognitive Radio Networks

In this paper, we consider a secondary broadcast network where a multi-antenna transmitter broadcasts the same data toward a large number of secondary receivers (SRs) in the presence of a primary communication. Thanks to its multi-antenna capabilities, the secondary transmitter (ST) uses an orthogonal beamforming technique to broadcast its data while controlling the interference perceived by the primary receiver. We develop and investigate three broadcast transmission schemes. The first one is simple and operates in underlay mode where the ST broadcasts its data simultaneously as the primary transmission. The second scheme operates in overlay mode where ST helps the primary transmission by means of cooperative diversity transmission. SRs exploit a post-transmission interference cancellation techniques to cancel the interference caused by the primary transmission. The third scheme operates also in overlay mode and the secondary network exploits also the cooperative diversity technique. The metric used to evaluate the performance of secondary broadcast network is the rate of served SRs. We compare the performances of the three schemes by simulations. Also, analytical expressions of the outage probability for the first and second schemes are provided. Simulations along with analytical results proved that our two overlay proposed schemes ensure low secondary outage probability.