Joint modelling of medium access and primary/secondary users for cognitive radios through Markov chain

The channel availability of cognitive radio is often estimated through a two-state ON/OFF model of primary users' (PUs) behaviour. The ON/OFF model estimates channel availability with respect to the presence of PUs. Multiple secondary users (SUs) may be aware of channel availability, and try to opportunistically access the channel when it becomes available. Hence, the ON/OFF model may overestimate channel capacity from the perspective of SUs, since the channel could be occupied not only by a resuming PU, but also by contending SUs. Proposed is a joint channel availability estimation through a Markov chain model which takes into account, within a single model, PU behaviour and the SU's carrier sensing with multiple access/collision avoidance contention access, without leading to the state explosion problem. Simulations performed show that the joint channel availability equation is able to estimate channel capacity with mean errors of around 2%.