Channel Selection in Cognitive Radio Networks: A New Dynamic Approach

In Cognitive radio Networks unlicensed users are temporary visitors to the licensed spectrum, they may be required to vacate the spectrum when a licensed user reclaims it. This process has a large overhead for secondary users. This overhead includes the time required for sensing the spectrum and finding new channels, communication delay between secondary transmitter/receiver as well as packet loss. To decrease this overhead it is necessary to reduce the number of connection disruption in a channel as much as possible. To this end secondary users should have a proper decision about channel selection, during the spectrum handoff procedure. They have to select target channel so that the channel be available with a high probability and long idle period to avoid more disruptions. In this paper a dynamic channel selection approach is proposed to reduce connection disruption rate in cognitive radio networks. The preemptive resume priority (PRP) M/G/1 queuing network model is used to characterize the spectrum usage behaviors in secondary and primary users. Then, based on this model, a value is calculated for each channel to demonstrate how much a channel is suitable to selecting, when interrupt occurs. In this scheme the value assigned to each channel is depends on channel idle probability and average waiting time in the channel queue. Simulation results show that proposed scheme with the same data delivery rate and a slight increase in service time at the light traffics reduces the connection disruption rate of secondary users significantly.