Opportunistic Spectrum Sharing With Limited Feedback in Poisson Cognitive Radio Networks

In this paper, we propose two limited feedback based underlay spectrum sharing schemes in Poisson cognitive radio networks without and with primary exclusive regions, respectively. Both primary and secondary transmitters are Poisson distributed nodes with limited feedback of channel quality information from their local receivers. The primary transmitters are active if their local primary channels are above a certain threshold. In the opportunistic spectrum sharing scheme without primary exclusive region, the secondary transmitters are elected to transmit if their local channels are above the required threshold. In the opportunistic spectrum sharing scheme with a primary exclusive region, the secondary transmitters transmit if their local channels are above the threshold and they are outside the exclusive regions of the active primary receivers. For both schemes, the optimal secondary node density is analytically derived by maximizing the secondary area spectral efficiency subject to the secondary outage constraint and the primary efficiency loss constraint. Numerical results show that, for a tight secondary outage constraint, it is more beneficial to use the scheme with no primary exclusive region. For relatively loose secondary outage constraint, the scheme with primary exclusive regions is recommended.