Transmission capacity of secondary networks in hybrid overlaid/underlaid cognitive radio systems

We study the transmission capacity of the secondary (SR) network in the hybrid cognitive radio (CR) system where underlaid and overlaid access approaches are combined to improve the transmission capacity of the SR network. The transmission behavior of the primary (PR) network is characterized as a two-state (idle and busy) discrete time Markov model, and sensing performance of the SR network captured by the missed detection probability and false alarm probability is also considered. We analyze their effects on the transmission capacity of the SR network and the outage probability of the PR network. Analysis and numeric results show that hybrid mode has greater superiority than either overlaid mode or underlaid mode on the transmission capacity of the SR network, especially when the PR network has light load. The missed detection has good effect on the transmission capacity of the SR network, but increases the outage probability of the PR network, which is dispointed. The false alarm has no effect on the outage probability of the PR network, but decreases the transmission capacity of the SR network.