Investigation on Multiuser Diversity in Spectrum Sharing Based Cognitive   Radio Networks
  A new form of multiuser diversity, named \emph{multiuser interference diversity}, is investigated for opportunistic communications in cognitive radio (CR) networks by exploiting the mutual interference between the CR and the existing primary radio (PR) links. The multiuser diversity gain and ergodic throughput are analyzed for different types of CR networks and compared against those in the conventional networks without the PR link. 
Rui Zhang and Ying-Chang Liang