Adaptive spectrum searching in cognitive radio networks

The channel sensing order in cognitive radio networks is very important and has a significant impact on the cognitive users operation. In this paper, we propose four adaptive spectrum searching schemes to determine the channel sensing order taking into consideration the primary users activities. These schemes use previous sensing results to generate a criterion to find the channel sensing sequence that guarantees the fast discovery of a free channel. Two main parameters are estimated and used to sequence the channels: the probability of a channel to be free, and how long the channel will be free. The simulation results show that the delay associated with finding free channel is reduced. Moreover, the number of triggered spectrum search processes is reduced when taking the period of the opportunity into consideration.