On Channels Activity of Opportunistic Spectrum Sharing with Homogeneous Primary Users

The availability of the spectrum opportunity to the secondary users is related to the activity of the frequency channels. In this paper, we research the activity of the channels in opportunistic spectrum sharing. A three-state continuous-time Markov chain is proposed to describe the activity of the channel. A formulation under the service traffics for the model is given and the probabilities of the channel in three states, namely it being idle, it occupied by the primary user and it occupied by the secondary user, are deduced. Furthermore, we derive the system performance metrics such as the average idle channels, the channel utilization efficiency and so on which are different from the metrics based on the activity of the users in some previous literatures. The proposed model and the metrics provide a simple but effective way to evaluate the performance of opportunistic spectrum sharing from the channels activity perspective.