On the Gain of Primary Exclusion Region and Vertical Cooperation in Spectrum Sharing Wireless Networks

The emerging cognitive radio (CR) technology enables the introduction of hierarchical spectrum sharing in wireless networks, where the primary users (PUs) have transmission guarantees, but the coexisting secondary users (SUs) need to be cognitive toward primary activities and adjust their transmissions to conform to the primary constraints. We consider large-scale coexisting primary and secondary networks, where concurrent primary and secondary transmissions are allowed and where the SUs control the interference at the primary receivers by tuning the probability of transmitting and by forming a primary exclusive region (PER) around each primary receiver within which all SUs have to be silent. Moreover, the primary source-destination pairs utilize vertical cooperation by selecting a nearby SU to act as a cooperative relay. We define a unified analytic framework to model cognition and cooperative transmission in large-scale networks. We characterize the achievable gains considering the transmission density region and show that both of the networks have strong incentives to participate in the collaboration.